Neurosurg Rev DOI 10.1007/s10143-014-0565-3

REVIEW

Minimally invasive spine surgery: systematic review Péter Banczerowski & Gábor Czigléczki & Zoltán Papp & Róbert Veres & Harry Zvi Rappaport & János Vajda

Received: 20 May 2013 / Revised: 10 April 2014 / Accepted: 18 May 2014 # Springer-Verlag Berlin Heidelberg 2014

Abstract Minimally invasive procedures in spine surgery have undergone significant development in recent times. These procedures have the common aim of avoiding biomechanical complications associated with some traditional destructive methods and improving efficacy. These new techniques prevent damage to crucial posterior stabilizers and preserve the structural integrity and stability of the spine. The wide variety of reported minimally invasive methods for different pathologies necessitates a systematic classification. In the present review, authors first provide a classification system of minimally invasive techniques based on the location of the pathologic lesion to be treated, to help the surgeon in selecting the appropriate procedure. Minimally invasive techniques are then described in detail, including technical features, advantages, complications, and clinical outcomes, based on available literature. Keywords Minimally invasive . Spine surgery . Surgical approach . Endoscopic procedure . Percutaneous technique . Interspinous device . Interbody fusion

P. Banczerowski (*) : Z. Papp : R. Veres : J. Vajda National Institute of Neurosurgery, Amerikai út 57, Budapest 1145, Hungary e-mail: [email protected] P. Banczerowski e-mail: [email protected] P. Banczerowski : G. Czigléczki Department of Neurosurgery, Faculty of Medicine, Semmelweis University, Budapest, Hungary H. Z. Rappaport Department of Neurosurgery, Rabin Medical Centre, Tel Aviv University, Petah Tiqva, Israel

Abbreviations ALIF Anterior lumbar interbody fusion BLBD Bilateral laminotomy for bilateral decompression DLIF Direct lateral interbody fusion MED Microendoscopic discectomy miPLIF Minimally invasive posterior lumbar interbody fusion MISST Minimally invasive spine surgery technique miTLIF Minimally invasive transforaminal lumbar interbody fusion PED Percutaneous endoscopic discectomy PEEK Poly-Ether-Ether-Ketone PLDD Percutaneous laser disc decompression PLIF Posterior lumbar interbody fusion TLIF Transforaminal lumbar interbody fusion ULBD Unilateral laminotomy for bilateral decompression XLIF Extreme lateral interbody fusion

Introduction Various minimally invasive spine surgery techniques (MISSTs) have been developed recently with the aim of improving clinical outcomes as opposed to traditional procedures. MISSTs have no universally accepted definition, but all of these techniques aim to reduce iatrogenic complications and postoperative pain, promote faster recovery, and allow patients an earlier return to their normal daily activities. Further benefits include reduction of operative blood loss, shortening of hospital stay, reduced need for analgesics, smaller incisions, and preservation of posterior motion segments and paraspinal muscles. Several MISSTs have been introduced recently. The purpose of this article is to provide an overview of MISSTs, including technical aspects, advantages, complications, and clinical outcomes. The review is divided into two parts.

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In the first part, a classification of the different surgical methods is presented with the aim of helping the surgeon in selecting the appropriate minimally invasive procedure based on the location topography of the pathology in the spinal canal. This classification system can be applied in the daily routine of spine surgery. In the second part, individual MISSTs are defined and described, focusing on the main elements and the instrumentation of the procedures. Furthermore, clinical efficacy is analysed based on available literature.

Part 1: classification of surgical techniques A classification system [10] was introduced, which pairs various intraspinal pathologic lesions, taking into account their location topography relative to the spinal cord, with the appropriate MISST. Lesions within the spinal canal may be segmental or longitudinal to the spinal levels and axial or lateral relative to the spinal cord. Four types of lesion locations are defined in the classification system (Fig. 1): segmentallateral (e.g. meningioma or neurinoma), segmental-axial (e.g. intramedullary cavernous haemangiomas), longitudinal-axial (e.g. intramedullary astrocytoma or ependymoma), and longitudinal-lateral (e.g. metastatic epidural tumour). Table 1 summarizes these lesion location categories paired with the most appropriate surgical procedures. Surgical techniques for lesions with segmental-lateral location Hemi-semi laminectomy (partial hemilaminectomy) The technique of hemi-semi laminectomy (partial hemilaminectomy) (Fig. 2a) was developed for the removal of space-occupying lesions within the spinal canal, while preserving dorsal bone structures and the bone-muscleligament complex. The preservation of spinal integrity prevents the development of instability of the spinal column. Hemilaminectomy and hemi-semi laminectomy are mainly used to remove unilateral, intradural (e.g. meningioma, neurinoma), or extradural (e.g. epidural haematoma, abscess) pathologic lesions. Technical features [7, 130] Patients are placed in the prone position. After the determination of the spinal level with an image intensifier, a midline or paramidline incision is made according to the location of the lesion. Paraspinal muscles are dissected and retracted. The upper and lower arches of the laminae are drilled off partially. If the laminae remain intact, the method is known as hemi-semi laminectomy. If the laminae are transsected, it is known as hemilaminectomy. When needed, the hemi-semi laminectomy approach can and should be extended to a hemilaminectomy. For a wider surgical view,

the base of the spinous process and the medial parts of the articular process may be removed or the intraspinal space can be exposed by performing further adjacent fenestrations. The interspinous ligaments are left intact. In case of intradural lesions, the dura is longitudinally incised. After the removal of all pathologic tissue, the dura, fascia, and skin are closed in standard fashion. Although hemilaminectomy is considered to be a safe and effective procedure [108], hemi-semi laminectomy (partial hemilaminectomy) offers further advantages [7, 65, 130]: superior preservation of spinal integrity and fewer negative consequences in the event the level is misjudged. It is also more advantageous if re-operation becomes necessary [7]. If a segmental lesion is not explored at the right level, secondary hemi-semi laminectomies are considerably less invasive than secondary hemilaminectomies. If the need for reexploration emerges, it is considerably easier and safer to find the dural surface if part of the bony lamina remains in place. The method is suitable for the operative treatment of intra- or extradural lesions at any segment of the spine [7, 71, 95, 130], even in pregnant patients [42]. Clinical outcomes were excellent with regard to the preservation of posterior spinal structures, prevention of postoperative spinal instability or deformity, shorter hospital stay, and reduced operative blood loss [7, 130, 132]. Modifications of hemi-semi laminectomy In case of pathologies with intraforaminal components, supraforaminal burr hole modification [9] (Fig. 2b) may be performed by making an additional burr hole across the medial part of the facet joint with an average diameter of 5–7 mm. This allows complete removal of the lesion with the sparing of as much of the facet as possible. “Open-tunnel” modification [11] (Fig. 2c) may be used to remove tumours with intra- and extraforaminal components by exposing intraforaminal components from the inside of the spinal canal with hemi-semi laminectomy and from the outside with the partial removal of the lateral part of the facet joint. The outlet of the neuroforamen is opened, and tumour removal becomes possible from both ends of the opened “tunnel” while sparing most of the facet joint. Unilateral and bilateral laminotomy for bilateral decompression (ULBD or “over the top” decompression, BLBD) of lumbar spinal stenosis The standard surgical procedures used in the treatment of degenerative thoracic and lumbar spinal stenosis often resulted in the destruction or dysfunction of facet joints, disruption of the interspinous/supraspinous ligament complex, and stripping of paraspinal muscles, leading to segment instability.

Neurosurg Rev Fig. 1 Various pathologies classified according to location (see also Table 1)

ULBD (Fig. 3) and BLBD are MISSTs, which maintain the integrity and stability of the spine, provide sufficient Table 1 Classification system based on lesion location Segmental

decompression of neural structures located in the spinal canal and may be used in the lumbar and thoracic regions.

Lateral

Axial

• Hemi-semi laminectomy

• Hemi-semi laminectomy

• Supraforaminal burr hole technique

• [Split laminotomy]

• “Open-tunnel” technique

• Unilateral and bilateral laminotomy for bilateral decompression

• Unilateral and bilateral laminotomy for bilateral decompression • Posterior foraminotomy with tubular retractor assistance

Longitudinal

• Transuncal and transcorporeal anterior microforaminotomy • Multilevel hemi-semi laminectomy

• Split laminotomy (+ “archbone” technique) • Para-split laminotomy

Neurosurg Rev Fig. 2 Pathologies with segmental-lateral location (and foraminal or extraforaminal spreading) and appropriate surgical approaches. A Hemisemi laminectomy (partial hemilaminectomy, interlaminar fenestration). B Supraforaminal burr hole approach. C “Opentunnel” (partial lateral facetectomy) approach

Technical features [6, 115, 116] Patients are placed in the prone position. Unilateral approach is used from the side with the more pronounced stenosis. Decompression is achieved by the partial medial resection of adjacent facets and of the small medial portion of the base of the spinous process, the partial resection of the upper and lower part of the laminar arch, and the complete removal of the ligamentum flavum. The contralateral ligamentum flavum and the medial portion of the

Fig. 3 Postoperative threedimensional reconstruction and axial CT scans showing unilateral laminotomy for bilateral decompression of lumbar spinal stenosis

contralateral facet are also removed for contralateral decompression. This process allows visualization of the contralateral nerve root and foramen. If necessary, discectomy and foraminotomy may also be performed. Bilateral approach can be used in case of a complicated anatomical situation or if bilateral decompression cannot be achieved via a unilateral approach. The surgical steps are similar to those described above, with the exception of the bilateral approach [34].

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ULBD is a safe technique with long-term effectiveness for the treatment of spinal stenosis [24, 88], even in highrisk patients with multilevel stenosis [93]. Complications are few and include dural tear, nerve root injury, and the necessity of re-operation [27]. This approach demonstrates the extent of navigation possible within the spinal canal; it is even adaptable to the resection of extramedullaryintradural spinal tumours [40]. To fulfil the requirements of a MISST, bilateral decompression via unilateral approach exists in a full-endoscopic setup as well, which offers benefits in terms of complications, traumatization, and rehabilitation [67]. When comparing ULBD to BLBD, operative time was significantly shorter and operative blood loss and the rate of postoperative radiographic instability were lower [44]. On the other hand, some studies revealed the advantage of BLBD over ULBD in outcome parameters [120]. Other clinical and radiologic findings showed no difference between the two surgical procedures, and neither approach was associated with an increased dynamic slip during flexion-extension motion [87]. However, an increase in the risk of slippage was observed in patients who demonstrated sagittal motion associated with spondylolisthesis and who were treated via the unilateral approach [50]. Despite these controversies, both techniques led to the marked improvement of symptoms and quality of life [27, 120]. Posterior foraminotomy with tubular retractor assistance Posterior foraminotomy is an alternative surgical approach for the treatment of lateral disc herniation, spinal stenosis, and radiculopathy [49, 63, 127]. MISST with tubular retractor assistance preserves spinal stability and may avoid the need of prosthesis implantation [127]. It is used mainly in the cervical region, but it may also be applied for thoracic and lumbar surgery. Posterior approach prevents complications associated with anterior procedures, such as vessel injury, nerve root injury, oesophageal penetration, and adjacent segment disease [25, 63, 127]. Technical features [29, 63, 84, 127] Patients are placed in the prone position, and a midline or paramidline incision is made after determination of spinal level. Paraspinal muscles and tissues are carefully dilated to allow for the placement of tubular dilators. The tubular retractor is placed over the dilators and may be fixed (if required) over the lamina-facet junction with a tablemounted flexible arm. After removing the dilators, the lateral mass of the lamina and the medial facet joint are drilled off to create a surgical route for the removal of the pathologic lesion with the aid of a surgical microscope. The extent of resection depends on the size of pathology. In case of spinal stenosis or disc herniation,

bony decompression or discectomy may be performed through the foramen. Closure is made in standard fashion. The most common reported complications are dural tear, cerebrospinal fluid leak, and postoperative neck discomfort with painful muscular spasms [54, 127]. The complications of tubular-assisted foraminotomy originate from the inability to obtain adequate visualization, which may lead to inadequate decompression or nerve injury [84]. Precise lesion location can be determined and complications can be avoided with three-dimensional visualization under the microscope [43]. Compared to traditional open procedures, no statistically significant difference was found in intervention time or complications, but analgesic need, hospital stay, blood loss, skin incision size, and muscle injury were reduced as opposed to standard procedures [63, 127]. Long-term outcomes showed complete recovery and no instability in the operated cervical segment [49, 129]. The keyhole approach offers an effective treatment option and improves quality of life [49, 128, 129]. Transuncal and transcorporeal anterior microforaminotomy Transuncal foraminotomy was developed as a new MISST for the treatment of cervical radiculopathies. To relieve a compressed nerve root by removing the disc fragment, a hole is drilled through the base of the uncinate process without disturbing most of the disc tissue in the intervertebral space. The functional anatomy of the motion segment remains preserved, and the adjacent level disease followed by interbody fusion is prevented [51, 73]. As a modification, the transcorporeal foraminotomy is performed by drilling a hole through the inferolateral part of the upper vertebral body to the lateral direction and downwards ending at the foraminal level of the disc below [52]. The method may be suitable to preserve the lower end plate and the medial wall of the transverse foramen [20]. The short-term and long-term outcomes are also favourable, and there were no major complications during the follow-up periods [19, 20]. Comparing the preserved disc height, spinal stability, length of hospital stay, and patient satisfaction revealed that the transcorporeal approach is more effective than the transuncal approach [45]. Surgical techniques for lesions with an axial-longitudinal location Split laminotomy and the “archbone” technique The multilevel spinous process splitting and distracting laminotomy (Fig. 4) for the surgery of multilevel lesions located in the spinal canal was developed for adults to explore primarily intramedullary spinal pathologies with the aim of

Neurosurg Rev Fig. 4 Intraoperative photograph and illustrations showing the appropriate approaches for pathologies with longitudinalaxial location. A Split laminotomy approach. B “Para-split” laminotomy approach, as a rescue technique for split laminotomy

preservation of posterior structures and spine stability. The technique is a slight modification of the multilevel split laminotomy developed for children [13]. This method leaves the muscle attachment intact and reduces postoperative complications. It may be applied in the cervical region and in the thoracic and lumbar regions as well. Furthermore, it may be used in patients of all ages and the number of vertebral segments involved in this surgical process is theoretically unlimited. Technical features [5, 8, 13] Patients are placed in the prone position. In midline posterior approach, the skin, fascia, and interspinous ligaments are incised. The interspinous ligaments are dissected longitudinally, then the ligamentum flavum is removed at the middle part to expose the midline epidural space. The spinous processes are split in the midline with an oscillating saw or craniotome and are then separated and distracted with Cloward-type retractors. The retractors are positioned precisely to the inner cortex of the vertebral arch above the dura in the epidural space. It is important to use gentle force when opening the retractor in order to prevent fracture of the spinous process. After gradual distraction of the bones, the dura space is exposed and intramedullary spaceoccupying lesions located mainly in the midline can be removed. The dura is sutured directly or, if necessary, duraplasty is carried out with a liodural patch and fibrin glue. After removal of the retractors, the spinous processes are also sutured directly to each other. If total resection of an intramedullary tumour is not possible because of the lack of recognizable cleavage (i.e. diffusely infiltrative tumours), intraspinal space occupation can only be alleviated

temporarily. In this case, with the aim of moderate enlargement of the spinal canal, bony decompression is achieved by placing a tricortical iliac bone graft between the bony parts facing each other. Data in the literature indicate that tricortical iliac grafts may lead to complications such as pain at the donor site and infections. To reduce complications and surgery time (graft removal), PEEK (Poly-Ether-Ether-Ketone, Solis Cervical Cage, Stryker Spine SAS, Z.I. de Marticot, 33610, Cestas, France) cages can also be applied (Fig. 5). In all cases, precise insertion and continuous visual control are important to avoid penetration of the grafts into the spinal canal. The technique is similar to the placement of an “archstone” into the arch of a vault in architecture, and thus, it was borrowed and changed to “archbone” in surgery. Banczerowski et al. [8] used the multilevel spinous process splitting and distracting laminotomy technique with or without complementary bone grafting in 19 adult patients with various pathologies located in the spinal canal. The approach used did not affect the extent of resection or neurological outcome. No sign of spinal instability or deformation was observed during follow-up. Papp et al. [94] also operated on 38 patients (including the previous cohort of patients) with this method. The incidence of postoperative local pain was lower and early mobilization was possible resulting in shorter hospital stay. Spinal instability was not observed in the follow-up period. Para-split laminotomy [92] (Fig. 4b) is a modification of split laminotomy, where the opening of the spinal canal is in the parasagittal plane. It is used in complicated anatomical situations (thin, immature, or osteoporotic spinous processes), where midline splitting and opening of spinal canal is not feasible.

Neurosurg Rev Fig. 5 Intraoperative photograph and illustration showing the “archbone” technique. Distracted spinous process and complementary PEEK cage between the facing bony parts resulting in moderate enlargement of the spinal canal

Kota Watanabe et al. [125] described a variation of the spinous process splitting laminotomy technique for the treatment of lumbar canal stenosis where the L4 spinous process is split longitudinally in the midline and then divided from the L4 posterior arch, leaving the paraspinal muscles attached to the bony elements. A randomized controlled study showed that acute postoperative wound pain was decreased and postoperative muscle atrophy was prevented by this procedure compared with conventional laminectomy [126]. Kim K. et al. [62] examined the effect of spinous process splitting methods on postoperative paraspinal muscle damage and found it less invasive compared to the technique of bilateral decompression via hemilaminectomy. As another variation of the spinous process splitting laminotomy technique, the “Marmot operation” was introduced for the treatment of degenerative lumbar spinal stenosis. With this procedure, muscular trauma is also minimized, spinal stability is preserved, and hospital stay is shortened [18].

splitting laminotomy for non-degenerative pathologies of the segmental-axial location is more complicated and time-consuming. Surgical steps of these methods are described above in detail. Surgical techniques for lesions with a lateral-longitudinal location If the pathologic lesion is located in lateral-longitudinal or dorsolateral-longitudinal positions with expansion involving several segments, multiple hemi-semi laminectomy (partial hemilaminectomy) may be the appropriate technique (Figs. 2 and 6). It provides better visualization of the lateral space of the spinal canal, but the technique requires more surgical routine. Surgical steps are described above in detail.

Part 2: minimally invasive instrumented techniques Endoscopic techniques

Surgical techniques for lesions with a segmental-axial location Hemi-semi laminectomy (partial hemilaminectomy) can be recommended when the intramedullar pathology is positioned in one segment and close to the interlaminar fenestration (e.g. intramedullary cavernous haemangioma). Surgical exploration allows visualization of the dorsal and dorsolateral parts of the spinal cord and easy removal of the pathologic lesion. Spinous process splitting laminotomy, the Watanabe and Marmot technique in degenerative cases, and unilateral and bilateral laminotomy for bilateral decompression (ULBD, BLBD) may also be appropriate MISSTs for the treatment of lesions with a segmental-axial location. The spinous process

Microendoscopic discectomy (MED) and METRx system As an early endoscopic technique, MED (Fig. 7) was introduced in 1997 [38, 98] as a MISST. Although this method was successfully used for the treatment of disc herniation, there were limitations such as a non-reusable endoscope, inconsistent image quality, and limited working space. To address these limitations, the METRx system (Medtronic Sofamor Danek, Memphis, TN, USA) was developed, with the benefits of threedimensional visualization, improvement of image quality, smaller endoscopic diameter, and larger surgical space [90]. The method is adaptable to perform discectomy or

Neurosurg Rev Fig. 6 Intraoperative photograph and illustration showing the appropriate approaches for pathologies with longitudinallateral location: multilevel hemisemi laminectomy (partial hemilaminectomy, interlaminar fenestration)

decompression in the cervical [57], thoracic [113], and lumbar regions [98] of the spine. Technical features [38, 90, 98] Patients are placed in the prone position with flexed spine. Incision length is matched to the diameter of the respective tubular retractor. The guide wire is gently docked onto the bone under fluoroscopic guidance to avoid inadequate positioning. The initial dilators are placed on the lamina under fluoroscopy to dilate the paraspinal musculature. The working channel is placed over the final dilator and is fixed with a table-mounted flexible arm.

Fig. 7 Microendoscopic discectomy (MED) technique

The endoscope is inserted into the working channel. After achieving appropriate visualization on the video monitor, microdiscectomy or bony decompression can be performed. Closure is made in standard fashion. The advantages [35, 98] of endoscopic procedures over open techniques include reduced tissue trauma, operative time, recovery time, and risk of complications. Furthermore, these methods allow better, direct visualization of the lesion, which is an element of successful treatment; however, these procedures have a learning curve [98, 107]. Long-term clinical outcomes are satisfactory and significantly better than those achieved with traditional methods [15, 124]. Reported complications are rare [38, 98, 107] and include dural tear, neurological damage, infection, and instrument malfunction. Several MISSTs have a full-endoscopic variant [106, 122]. PED (percutaneous endoscopic discectomy) technique As a full-endoscopic variant, percutaneous endoscopic discectomy is considered to be a minimally invasive technique for the treatment of disc herniation, especially in the lumbar spine [82]. The procedure may be performed via transforaminal, extraforaminal, and interlaminar approaches [21, 22, 75] and under local or general anaesthesia. Its advantages over open methods are similar to those mentioned before [35, 98]. Reported complications [1, 118] include dural tear, postoperative dysaesthesia, haematoma, and visceral and S1 nerve injury.

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To avoid S1 nerve root injury, a new technique known as sMED (small-incision microendoscopic discectomy) was introduced. It mimics microendoscopic discectomy and is a variation of PED. The S1 nerve root is safely retracted medially and caudally, which allows treatment of disc herniation without nerve root complication [31, 66]. If the herniated nucleus pulposus has migrated into the hidden zone, traditional PED approaches cannot be used. In these cases, PETA (percutaneous endoscopic translaminar approach) can be applied, which is also a variation of PED. In PETA, a bone hole is made above the hidden zone with a high-speed drill and through this hole the pathologic disc can be removed [30]. PLDD (percutaneous laser disc decompression) The procedure is a treatment option for patients with different stage of disc degeneration. Although it may be applied for all regions of the spine, it is primarily used for the treatment of lumbar lesions. Technical features [23, 24, 39] Patients are placed in the prone position with semiflexed spine under local anaesthesia. The entry point and the correct pathway are determined with CT or fluoroscopy. After creating a satisfactory pathway with a needle, an optical fibre is inserted into the disc under fluoroscopic or CT guidance. Discectomy is performed with laser energy to vaporize the disc area. Due to heat generation or hyperpressure caused by gas accumulation in the disc, pain may occur during the procedure, so patients have to be able to communicate and respond to pain [39]. Reducing pressure with aspiration or increasing the interval between pulses may alleviate the pain. At the end of the procedure, closure is made in standard fashion. The most common complications [39, 99] of PLDD include infection, postoperative back pain, or necessity of reoperation, but these occur rarely. Its advantages [23, 24, 39] are similar to those mentioned with other endoscopic procedures. The percutaneous approach, instrumented guidance, and performance under local anaesthesia contribute to the safety and long-term efficacy of this technique [24]. A systematic review is available from Singh et al., which evaluates the clinical effectiveness of percutaneous laser discectomies [112].

percutaneous pedicle screw instrumentation methods were developed to minimize muscle damage and to provide sufficient fixation. These methods include, but are not limited to, the Luxor, Mantis (Stryker Medical), and Sextant techniques. In the present review, the arc-based system called Sextant (Medtronic Sofamor Danek, Memphis, TN) is discussed in detail [36] (Fig. 8). Technical features of the Sextant technique [36, 90] Patients are placed in the prone position, and small incisions are made to place guiding wires and tubular retractors. After the placement of screws, screw towers are coupled and an arc system with a measuring device is connected to them. The distal end of the arc system with a perforating tip is used to make the subcutaneous pathway. The required rod size is measured and then passed through the pathway made previously to finish fixation. Closure is performed in standard fashion. Other percutaneous pedicle screw stabilization methods follow more or less the similar surgical steps as the Sextant technique by using standard instruments. Advantages [37, 86, 103] of percutaneous pedicle screw fixation techniques include reduced operation time, muscular trauma and blood loss, quick recovery, favourable aesthetic outcome with small incisions, and sparing of posterior elements with effective posterior stabilization of the thoracic and lumbar spine. However, the use of these equipments has a learning curve [86]. The Sextant technique is also a safe procedure for posterior fixation, shares the same advantages mentioned above, and fulfils the requirements of MISSTs [36, 37]. Interspinous devices and X-STOP technique Although a discussion on interspinous devices should be included in a review of MISSTs, their use remains controversial. The most common indication of interspinous devices is

Percutaneous pedicle screw fixation and the Sextant technique The long-lasting procedures and forceful retraction of paraspinal muscles often resulted in ischemic necrosis, which may have contributed to chronic back pain in postlaminectomy syndrome [90]. Minimally invasive

Fig. 8 Percutaneous pedicle screw fixation and Sextant technique

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back pain and neurogenic claudication caused by foraminal stenosis. X-STOP, StenoFix (DePuy Synthes), DIAM and APERIUS (Medtronic Sofamor Danek) and Coflex (Paradigm Spine) are some of the known interspinous devices. T h e X - STO P te ch n i q u e ( S t . F r a n ce s Me d i ca l Technologies, Inc.) was approved for the treatment of the lumbar region in elderly patients who are not candidates for traditional surgical treatment due to comorbidities. Patient selection is performed according to a criterion system [17, 68, 69, 90]. Advantages of the X-STOP technique include shorter operation time, improved sagittal balance of the spine [109], increased foraminal diameter [102, 111], and the possibility of implant removal in the event of complications [90]. The most common reported complications are device dislodgement and spinous process fracture [14, 58, 90], which occur mainly in patients with spondylolisthesis or osteoporosis [58]. With optimal patient selection, the X-STOP technique may constitute a clinically effective and radiologically viable method and can improve quality of life [17, 48, 68]. On the other hand, Epstein [32] reviewed the literature of interspinous devices and found high rates of complications and reoperations, poor outcomes, and high costs in patients over the age of 50 years. Based on these data, the author questioned the safety and effectiveness of interspinous devices and recommended a re-evaluation of their use. Interbody fusion techniques Laparoscopic anterior lumbar interbody fusion (laparoscopic ALIF) Minimally invasive laparoscopic ALIF is an appropriate option for the treatment of degenerative diseases [80, 96, 134]. The technique is performed via a transperitoneal approach while maintaining pneumoperitoneum and using an endoscope to enable adequate visualization [80, 134]. Several types of cages are available to create fusions, stabilize motion segments, and reconstruct the anatomy of operated areas [133]. Reported complications include vascular, nerve, retroperitoneal, and peritoneal injury; chyloperitoneum; ileus; pseudoarthrosis; and adjacent segment disease [80, 96, 119, 134]. Long-term clinical outcomes are satisfactory; however, low incidence of adjacent segment disease has been reported [59]. After a long learning curve, complications are reduced and laparoscopic ALIF becomes a useful surgical alternative even for the treatment of elderly patients, particularly if additional percutaneous fixation is used [59, 80, 96, 134]. When comparing transforaminal lumbar interbody fusion (TLIF) with ALIF, TLIF shows biomechanical advantages over ALIF; on the other hand, blood loss, operative time, and costs are less with ALIF [47, 53, 61]. Comparing ALIF to posterior lumbar interbody fusion (PLIF), clinical outcomes are similar, but ALIF may be preferable in the prevention of adjacent segment disease [85] (Fig. 9).

Minimally invasive posterior lumbar interbody fusion (miPLIF) The main indications [16, 56, 77] of the miPLIF procedure include degenerative disc diseases and spondylolisthesis. In this procedure [26, 56], the lateral extent of the disc space is exposed using a tubular retractor system (described at the METRx system). Decompression, discectomy, and interbody fusion with cages are carried out through the working channel. Finally, a percutaneous pedicle screw system (described at the Sextant technique) can be placed to stabilize the segments. Advantages [16, 26, 56, 77] of this technique include biomechanical advantages, shorter hospital stay, and faster recovery rate. The most common complications [16, 26, 56, 89] are nerve injury, instability, pseudoarthrosis, and adjacent segment disease. Longterm outcomes are maintained and comparable with open PLIF procedures; thus, miPLIF is considered to be an effective alternative surgical option [16] (Fig. 9). Minimally invasive transforaminal lumbar interbody fusion (miTLIF) The miTLIF was introduced with the goal of reducing complications of other interbody fusion techniques and may be also adaptable for the treatment of lumbar pathologies [70, 110]. The surgical procedure [26, 70, 110] is similar to miPLIF, but with this method, the lateral aspect of the spinous process, the lamina, and the facet joint are exposed. In addition to biomechanical advantages, reduced operative blood loss, shorter hospital stay, faster rehabilitation, and cost-effectiveness have been described [26, 41, 97, 123]. Main complications are durotomy and infection, but no increased risk was observed in elderly patients [70, 74, 110]. With respect to long-term clinical outcomes [60, 105], miTLIF may become a treatment option as effective as open approaches, but the technique has a learning curve [72]. The comparison [4, 26] of TLIF and PLIF techniques shows similar effectiveness of the two surgical alternatives. However, posterior integrity is better preserved and radiological results are superior with the TLIF procedure (Fig. 9). Lateral transpsoas approach: direct lateral interbody fusion (DLIF) or extreme lateral interbody fusion (XLIF) Spondylolisthesis, degenerative disc diseases, and foraminal stenosis are considered to be the main indications of the lateral transpsoas approach [2, 78, 81, 83, 91]. Lumbarized sacrum is a relative contraindication of this method [114]. In lateral patient positioning, the procedure is performed through the retroperitoneum and psoas muscle under fluoroscopy guidance, using tubular retractors [2, 78, 81, 83]. Neural monitoring is required during surgery to prevent lumbosacral plexus injury, which is the main complication of this method [46, 55].

Neurosurg Rev Fig. 9 Axial view of lumbar interbody fusion techniques and directions of approaches

Additional reported complications are postoperative radiculopathy, vessel injury, and pseudoarthrosis [2, 104]. A “safe corridor” was defined to avoid iatrogenic injuries [101], and this improved the safety of this technique. The lateral transpsoas approach shares the same advantages as other interbody fusion techniques [2, 78, 81, 83, 131] (Fig. 9). Long-term clinical and radiological outcomes and fusion rates are satisfactory [131] and render interbody fusion via a lateral transpsoas approach an effective and popular surgical option [2, 78, 81, 83]. The axial or presacral approach, axiaLIF system The axiaLIF system (TranS1, Inc.) is an alternative surgical option in cases where traditional approaches are contraindicated [3, 28, 100]. The procedure may be applied for the treatment of degenerative disc diseases, scoliosis, spinal stenosis, and spondylolisthesis at the L4–S1 level [12, 28, 100]. After a small perianal incision, the dissector and the tubular retractor are docked to the base of the sacrum through the avascular presacral space, which is followed by the surgery of pathology and screw insertion. Additional posterior fixation can be applied with pedicle or facet screws to stabilize the L4–S1 segments [28, 100]. Biomechanical and anatomical advantages include sparing of neurovascular and posterior structures [33, 100]. The main complications are pseudoarthrosis and superficial infection [76, 100], but satisfactory midterm clinical outcomes prove the effectiveness of the axiaLIF system [79, 121].

Discussion Laminectomy remains the most common procedure for removing spinal pathologic lesions [64, 117]. Multilevel laminectomies that cause destruction of dorsal bony elements, joints, and posterior ligaments may lead to spinal instability, deformation, and other complications. The derangement of normal anatomy and biomechanical structure and the damage to paraspinal muscle attachments may both contribute to the development of instability of posterior motion segments. In order to prevent biomechanical and surgical complications, the need for less invasive surgical techniques emerged worldwide. These techniques aim to minimize derangement of the normal spinal structure and to preserve as much bony elements and bone-muscle units as possible. The development of minimally invasive procedures has accelerated during the last two decades, characterized by technical advances in illumination, magnification, and instrumentation. Due to varying surgical results and differences in reported methods, it is difficult to define the exact place of each procedure and to state whether a given technique is suitable for use in daily routine. The purpose of this review was to provide a summary of minimally invasive procedures within the framework of a classification system and to describe individual techniques, including detailed technical aspects. In part 1, surgical methods are presented within the framework of a classification system based on the location of pathologic lesions (Table 1, Fig. 1). Hemi-semi laminectomy (partial hemilaminectomy) and its variants are appropriate

Neurosurg Rev

methods for the removal of various types of segmental-laterallocated pathologies with preservation of dorsal spinal stability. Both unilateral and bilateral laminotomy for bilateral decompression can be used for the treatment of spinal stenosis, with good clinical outcomes. Foraminotomies with or without modifications are alternative surgical approaches for the treatment of disc herniations and tumours and for bony decompression. Split laminotomy and its variant, para-split laminotomy are mainly recommended for the removal of longitudinal-axial located intraspinal lesions. Its “archbone” modification enables the moderate enlargement of the spinal canal. In part 2, MISSTs involving different instruments are discussed. Providing improved visualization and sufficient surgical space, endoscopic techniques are appropriate methods to perform discectomy or decompression at any level of the spine. Percutaneous pedicle screw fixation (e.g. Sextant) techniques minimize muscle damage and enable sufficient stabilization of the spine. The use of interspinous devices still remains controversial. Various minimally invasive interbody fusion methods are commonly used in the treatment of degenerative diseases. None of them is proved to be superior to each other; however, some of them results in better outcomes in some aspects. In general, benefits of instrumented methods are reduction of tissue trauma, recovery time, and blood loss. Further benefits include low rate of complications, favourable aesthetic outcome with small incisions, and sparing of posterior elements with effective posterior stabilization of the spine. In summary, sufficient evidence is available for each MISST to be used as a clinically effective treatment option. In addition, MISSTs fulfil the basic principle of surgery: “leaving the smallest footprint”. Acknowledgments The authors are indebted to Zsófia Perjés M.D. for the excellent illustrations. Conflict of interest The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

References 1. Ahn Y (2012) Transforaminal percutaneous endoscopic lumbar discectomy: technical tips to prevent complications. Expert Rev Med Devices 9(4):361–366 2. Arnold PM, Anderson KK, McGuire RA Jr (2012) The lateral transpsoas approach to the lumbar and thoracic spine: a review far lateral approaches (XLIF) in adult scoliosis. Surg Neurol Int 3(Suppl 3):S198–S215 3. Aryan HE, Newman CB, Gold JJ, Acosta FL Jr, Coover C, Ames CP (2008) Percutaneous axial lumbar interbody fusion (AxiaLIF) of the L5-S1 segment: initial clinical and radiographic experience. Minim Invasive Neurosurg 51(4):225–230

4. Audat Z, Moutasem O, Yousef K, Mohammad B (2012) Comparison of clinical and radiological results of posterolateral fusion, posterior lumbar interbody fusion and transforaminal lumbar interbody fusion techniques in the treatment of degenerative lumbar spine. Singap Med J 53(3):183–187 5. Banczerowski P, Bognar L, Rappaport ZH, Veres R, Vajda J (2014) Novel surgical approach in the management of longitudinal pathologies within the spinal canal: the split laminotomy and “archbone” technique. Adv Tech Stand Neurosurg 41:47–70 6. Banczerowski P, Lipóth L, Veres R (2007) [Bilateral “over the top” decompression through unilateral laminotomy for lumbar and thoracic spinal canal stenosis]. Ideggyogy Sz 60(11–12):467–473, Article in Hungarian 7. Banczerowski P, Vajda J, Veres R (2008) Removal of intraspinal space-occupying lesions through unilateral partial approach, the “hemi-semi laminectomy”. Ideggyogy Sz 61(3–4):114–122, Article in Hungarian 8. Banczerowski P, Vajda J, Veres R (2008) Exploration and decompression of the spinal canal using split laminotomy and its modification, the “archbone” technique. Neurosurgery 62(5 Suppl 2): ONS432–ONS440 9. Banczerowski P, Veres R, Vajda J (2009) Modified minimally invasive surgical approach to cervical neuromas with intraforaminal components: hemi-semi-laminectomy and supraforaminal burr hole (modified foraminotomy) technique. Minim Invasive Neurosurg 52(1):56–58 10. Banczerowski P, Veres R, Vajda J (2012) New minimally invasive surgical techniques in spinal surgery. Ideggyogy Sz 65(5–6):169– 180, Article in Hungarian 11. Banczerowski P, Veres R, Vajda J (2014) Modified surgical approach to cervical neuromas with intraforaminal components: minimal invasive facet joint sparing “open-tunnel” technique. J Neurol Surg A Cent Eur Neurosurg 75(1):16–19 12. Boachie-Adjei O, Cho W, King AB (2013) Axial lumbar interbody fusion (AxiaLIF) approach for adult scoliosis. Eur Spine J 22(Suppl 2):S225–S231 13. Bognár L, Madarassy G, Vajda J (2004) Split laminotomy in pediatric neurosurgery. Childs Nerv Syst 20(2):110–113 14. Bowers C, Amini A, Dailey AT, Schmidt MH (2010) Dynamic interspinous process stabilization: review of complications associated with the X-Stop device. Neurosurg Focus 28(6):E8 15. Casal-Moro R, Castro-Menéndez M, Hernández-Blanco M, BravoRicoy JA, Jorge-Barreiro FJ (2011) Long-term outcome after microendoscopic diskectomy for lumbar disk herniation: a prospective clinical study with a 5-year follow-up. Neurosurgery 68(6): 1568–1575 16. Cheung NK, Ferch RD, Ghahreman A, Bogduk N (2013) Longterm follow-up of minimal-access and open posterior lumbar interbody fusion for spondylolisthesis. Neurosurgery 72(3): 443–451 17. Chiu JC (2006) Interspinous process decompression (IPD) system (X-STOP) for the treatment of lumbar spinal stenosis. Surg Technol Int 15:265–275 18. Cho DY, Lin HL, Lee WY, Lee HC (2007) Split-spinous process laminotomy and discectomy for degenerative lumbar spinal stenosis: a preliminary report. J Neurosurg Spine 6(3):229–239 19. Choi G, Arbatti NJ, Modi HN, Prada N, Kim JS, Kim HJ et al (2010) Transcorporeal tunnel approach for unilateral cervical radiculopathy: a 2-year follow-up review and results. Minim Invasive Neurosurg 53(3):127–131 20. Choi G, Lee SH, Bhanot A, Chae YS, Jung B, Lee S (2007) Modified transcorporeal anterior cervical microforaminotomy for cervical radiculopathy: a technical note and early results. Eur Spine J 16(9):1387–1393 21. Choi G, Lee SH, Bhanot A, Raiturker PP, Chae YS (2007) Percutaneous endoscopic discectomy for extraforaminal lumbar

Neurosurg Rev disc herniations: extraforaminal targeted fragmentectomy technique using working channel endoscope. Spine (Phila Pa 1976) 32(2): E93–E99 22. Choi G, Lee SH, Raiturker PP, Lee S, Chae YS (2006) Percutaneous endoscopic interlaminar discectomy for intracanalicular disc herniations at L5-S1 using a rigid working channel endoscope. Neurosurgery 58(1 Suppl):ONS59–ONS68 23. Choy DS (1991) PLDD offers advantages of safety, simplicity, speed. Clin Laser Mon 9(3):39–41 24. Choy DS (1995) Clinical experience and results with 389 PLDD procedures with the Nd:YAG laser, 1986 to 1995. J Clin Laser Med Surg 13(3):209–213 25. Clarke MJ, Ecker RD, Krauss WE, McClelland RL, Dekutoski MB (2007) Same-segment and adjacent-segment disease following posterior cervical foraminotomy. J Neurosurg Spine 6(1):5–9 26. Cole CD, McCall TD, Schmidt MH, Dailey AT (2009) Comparison of low back fusion techniques: transforaminal lumbar interbody fusion (TLIF) or posterior lumbar interbody fusion (PLIF) approaches. Curr Rev Musculoskelet Med 2(2):118–126 27. Costa F, Sassi M, Cardia A, Ortolina A, De Santis A, Luccarell G et al (2007) Degenerative lumbar spinal stenosis: analysis of results in a series of 374 patients treated with unilateral laminotomy for bilateral microdecompression. J Neurosurg Spine 7(6):579–586 28. Cragg A, Carl A, Casteneda F, Dickman C, Guterman L, Oliveira C (2004) New percutaneous access method for minimally invasive anterior lumbosacral surgery. J Spinal Disord Tech 17:21–28 29. Curto DD, Kim JS, Lee SH (2013) Minimally invasive posterior cervical microforaminotomy in the lower cervical spine and C-T junction assisted by O-arm-based navigation. Comput Aided Surg 18(3–4):76–83 30. Dezawa A, Mikami H, Sairyo K (2012) Percutaneous endoscopic translaminar approach for herniated nucleus pulposus in the hidden zone of the lumbar spine. Asian J Endosc Surg 5(4):200–203 31. Dezawa A, Sairyo K (2011) New minimally invasive discectomy technique through the interlaminar space using a percutaneous endoscope. Asian J Endosc Surg 4(2):94–98 32. Epstein NE (2012) A review of interspinous fusion devices: high complication, reoperation rates, and costs with poor outcomes. Surg Neurol Int 3:7 33. Erkan S, Wu C, Mehbod AA, Hsu B, Pahl DW, Transfeldt EE (2009) Biomechanical evaluation of a new AxiaLIF technique for two-level lumbar fusion. Eur Spine J 18(6):807–814 34. Eule JM, Breeze R, Kindt GW (1999) Bilateral partial laminectomy: a treatment for lumbar spinal stenosis and midline disc herniation. Surg Neurol 52(4):329–337 35. Fessler RG, Khoo LT (2002) Minimally invasive cervical microendoscopic foraminotomy: an initial clinical experience. Neurosurgery 51(5 Suppl):S37–S45 36. Foley KT, Gupta SK, Justis JR, Sherman MC (2001) Percutaneous pedicle screw fixation of the lumbar spine. Neurosurg Focus 10(4):E10 37. Foley KT, Gupta SK (2002) Percutaneous pedicle screw fixation of the lumbar spine: preliminary clinical results. J Neurosurg 97(1 Suppl):7–12 38. Foley KT, Smith MM (1997) Microendoscopic discectomy. Tech Neurosurg 3:301–307 39. Gangi A, Dietemann JL, Ide C, Brunner P, Klinkert A, Warter JM (1996) Percutaneous laser disk decompression under CT and fluoroscopic guidance: indications, techniques, and clinical experience. Radiographics 16(1):89–96 40. González-Martínez EL, García-Cosamalón PJ, FernándezFernández JJ, Ibáñez-Plágaro FJ, Alvarez B (2012) Minimally invasive approach of extramedullary intradural spinal tumours. Review of 30 cases. Neurocirugia (Astur) 23(5):175–181, Article in Spanish

41. Habib A, Smith ZA, Lawton CD, Fessler RG (2012) Minimally invasive transforaminal lumbar interbody fusion: a perspective on current evidence and clinical knowledge. Minim Invasive Surg 2012:657342 42. Han IH, Kuh SU, Kim JH, Chin DK, Kim KS, Yoon YS et al (2008) Clinical approach and surgical strategy for spinal diseases in pregnant women: a report of ten cases. Spine (Phila Pa 1976) 33(17): E614–E619 43. Hilton DL Jr (2007) Minimally invasive tubular access for posterior cervical foraminotomy with three-dimensional microscopic visualization and localization with anterior/posterior imaging. Spine J 7(2):154–158 44. Hong SW, Choi KY, Ahn Y, Baek OK, Wang JC, Lee SH et al (2011) A comparison of unilateral and bilateral laminotomies for decompression of L4-L5 spinal stenosis. Spine (Phila Pa 1976) 36(3):E172–E178 45. Hong WJ, Kim WK, Park CW, Lee SG, Yoo CJ, Kim YB et al (2006) Comparison between transuncal approach and upper vertebral transcorporeal approach for unilateral cervical radiculopathy— a preliminary report. Minim Invasive Neurosurg 49(5):296–301 46. Houten JK, Alexandre LC, Nasser R, Wollowick AL (2011) Nerve injury during the transpsoas approach for lumbar fusion. J Neurosurg Spine 15(3):280–284 47. Hsieh PC, Koski TR, O’Shaughnessy BA, Sugrue P, Salehi S, Ondra S et al (2007) Anterior lumbar interbody fusion in comparison with transforaminal lumbar interbody fusion: implications for the restoration of foraminal height, local disc angle, lumbar lordosis, and sagittal balance. J Neurosurg Spine 7(4):379–386 48. Hsu KY, Zuchermann JF, Hartjen CA, Mehalic TF, Implicito DA, Martin MJ et al (2006) Quality of life of lumbar stenosis-treated patients in whom the X STOP interspinous device was implanted. J Neurosurg Spine 5:500–507 49. Jagannathan J, Sherman JH, Szabo T, Shaffrey CI, Jane JA (2009) The posterior cervical foraminotomy in the treatment of cervical disc/osteophyte disease: a single-surgeon experience with a minimum of 5 years’ clinical and radiographic follow-up. J Neurosurg Spine 10(4):347–356 50. Jang JW, Park JH, Hyun SJ, Rhim SC (2012) Clinical outcomes and radiologic changes following microsurgical bilateral decompression via a unilateral approach in patients with lumbar canal stenosis and grade I degenerative spondylolisthesis with a minimum 3-year follow-up. J Spinal Disord Tech 51. Jho HD (1996) Microsurgical anterior cervical foraminotomy. A new approach to cervical disc herniation. J Neurosurg 84(2): 155–160 52. Jho HD, Kim WK, Kim MH (2002) Anterior microforaminotomy for treatment of cervical radiculopathy: part 1—disc preserving “functional cervical disc surgery”. Neurosurgery 51(5 Suppl): S46–53 53. Jiang SD, Chen JW, Jiang LS (2012) Which procedure is better for lumbar interbody fusion: anterior lumbar interbody fusion or transforaminal lumbar interbody fusion? Arch Orthop Trauma Surg 132(9):1259–1266 54. Jödicke A, Daentzer D, Kästner S, Asamoto S, Böker DK (2003) Risk factors for outcome and complications of dorsal foraminotomy in cervical disc herniation. Surg Neurol 60(2):124–129, discussion 129–30 55. Kepler CK, Bogner EA, Herzog RJ, Huang RC (2011) Anatomy of the psoas muscle and lumbar plexus with respect to the surgical approach for lateral transpsoas interbody fusion. Eur Spine J 20: 550–556 56. Khoo LT, Palmer S, Laich DT, Fessler RG (2002) Minimally invasive percutaneous posterior lumbar interbody fusion. Neurosurgery 51(5 Suppl):S166–1 57. Khoo LT, Perez-Cruet MJ, Laich DT, Fessler RG (2002) Posterior cervical microendoscopic foraminotomy. In: Perez-Cruet MJ,

Neurosurg Rev

58.

59.

60.

61.

62.

63.

64.

65.

66.

67.

68.

69.

70.

71.

72.

73.

74.

Fessler RG (eds) Outpatient spinal surgery. Quality Medical Publishing, Inc., St. Louis, pp 71–93 Kim DH, Shanti N, Tantorski ME, Shaw JD, Li L, Martha JF et al (2012) Association between degenerative spondylolisthesis and spinous process fracture after interspinous process spacer surgery. Spine J 12(6):466–472 Kim JS, Choi WG, Lee SH (2010) Minimally invasive anterior lumbar interbody fusion followed by percutaneous pedicle screw fixation for isthmic spondylolisthesis: minimum 5-year follow-up. Spine J 10(5):404–409 Kim JS, Jung B, Lee SH (2012) Instrumented minimally invasive spinal-transforaminal lumbar interbody fusion (MIS-TLIF); minimum 5-years follow-up with clinical and radiologic outcomes. J Spinal Disord Tech. doi:10.1097/BSD.0b013e31827415cd Kim JS, Kang BU, Lee SH, Jung B, Choi YG, Jeon SH et al (2009) Mini-transforaminal lumbar interbody fusion versus anterior lumbar interbody fusion augmented by percutaneous pedicle screw fixation: a comparison of surgical outcomes in adult low-grade isthmic spondylolisthesis. J Spinal Disord Tech 22(2):114–121 Kim K, Isu T, Sugawara A, Matsumoto R, Isobe M (2008) Comparison of the effect of 3 different approaches to the lumbar spinal canal on postoperative paraspinal muscle damage. Surg Neurol 69(2):109–113 Kim KT, Kim YB (2009) Comparison between open procedure and tubular retractor assisted procedure for cervical radiculopathy: results of a randomized controlled study. J Korean Med Sci 24(4): 649–653 Kishan A, Gropper MR (2006) Thoracic laminectomy. In: Fessler RG, Sekhar L (eds) Atlas of neurosurgical techniques: spine and peripheral nerves. Thieme, Inc., New York, pp 448–451 Koch-Wiewrodt D, Wagner W, Perneczky A (2007) Unilateral multilevel interlaminar fenestration instead of laminectomy or hemilaminectomy: an alternative surgical approach to intraspinal space occupying lesions. J Neurosurg Spine 6:485–492 Koga S, Sairyo K, Shibuya I, Kanamori Y, Kosugi T, Matsumoto H et al (2012) Minimally invasive removal of a recurrent lumbar herniated nucleus pulposus by the small incised microendoscopic discectomy interlaminar approach. Asian J Endosc Surg 5(1):34–37 Komp M, Hahn P, Merk H, Godolias G, Ruetten S (2011) Bilateral operation of lumbar degenerative central spinal stenosis in fullendoscopic interlaminar technique with unilateral approach: prospective 2-year results of 74 patients. J Spinal Disord Tech 24(5):281 Kondrashov DG, Hannibal M, Hsu KY, Zucherman JF (2006) Interspinous process decompression with the X-STOP device for lumbar spinal stenosis. A 4-year follow-up study. J Spinal Disord Tech 19:323–327 Lauryssen C (2007) Appropriate selection of patients with lumbar spinal stenosis for interspinous decompression with the XSTOP device. Neurosurg Focus 22(1):E5 Lawton CD, Smith ZA, Barnawi A, Fessler RG (2011) The surgical technique of minimally invasive transforaminal lumbar interbody fusion. J Neurosurg Sci 55(3):259–264 Lee CH, Hyun SJ, Kim KJ, Jahng TA, Kim HJ (2012) What is a reasonable surgical procedure for spinal extradural arachnoid cysts: is cyst removal mandatory? Eight consecutive cases and a review of the literature. Acta Neurochir (Wien) 154(7):1219–1227 Lee JC, Jang HD, Shin BJ (2012) Learning curve and clinical outcomes of minimally invasive transforaminal lumbar interbody fusion: our experience in 86 consecutive cases. Spine (Phila Pa 1976) 37(18):1548–1557 Lee JY, Löhr M, Impekoven P, Koebke J, Ernestus RI, Ebel H et al (2006) Small keyhole transuncal foraminotomy for unilateral cervical radiculopathy. Acta Neurochir (Wien) 148(9):951–958 Lee P, Fessler RG (2012) Perioperative and postoperative complications of single-level minimally invasive transforaminal lumbar interbody fusion in elderly adults. J Clin Neurosci 19(1):111–114

75. Lew SM, Mehalic TF, Fagone KL (2001) Transforaminal percutaneous endoscopic discectomy in the treatment of far-lateral and foraminal lumbar disc herniations. J Neurosurg 94(2 Suppl):216–220 76. Lindley EM, McCullough MA, Burger EL, Brown CW, Patel VV (2011) Complications of axial lumbar interbody fusion. J Neurosurg Spine 15(3):273–279 77. Logroscino CA, Proietti L, Pola E, Scaramuzzo L, Tamburrelli FC (2011) A minimally invasive posterior lumbar interbody fusion for degenerative lumbar spine instabilities. Eur Spine J 20(Suppl 1): S41–S45 78. Marchi L, Oliveira L, Amaral R, Castro C, Coutinho T, Coutinho E et al (2012) Lateral interbody fusion for treatment of discogenic low back pain: minimally invasive surgical techniques. Adv Orthop 2012:282068 79. Marchi L, Oliveira L, Coutinho E, Pimenta L (2012) Results and complications after 2-level axial lumbar interbody fusion with a minimum 2-year follow-up. J Neurosurg Spine 17(3): 187–192 80. Mathews HH, Evans MT, Molligan HJ, Long BH (1995) Laparoscopic discectomy with anterior lumbar interbody fusion: a preliminary review. Spine (Phila Pa 1976) 20(16):1797–1802 81. Mayer HM (1997) A new technique of minimally invasive anterior lumbar spine fusion. Spine 22:691–699 82. Mayer HM, Brock M (1993) Percutaneous endoscopic discectomy: surgical technique and preliminary results compared to microsurgical discectomy. J Neurosurg 78(2):216–225 83. McAfee PC, Regan JJ, Geis WP, Fedder IL (1998) Minimally invasive anterior retroperitoneal approach to the lumbar spine. Emphasis on the lateral BAK. Spine 23:1476–1484 84. Mikhael MM, Celestre PC, Wolf CF, Mroz TE, Wang JC (2012) Minimally invasive cervical spine foraminotomy and lateral mass screw placement. Spine (Phila Pa 1976) 37(5):E318–E322 85. Min JH, Jang JS, Lee SH (2007) Comparison of anterior- and posterior-approach instrumented lumbar interbody fusion for spondylolisthesis. J Neurosurg Spine 7(1):21–26 86. Mobbs RJ, Sivabalan P, Li J (2011) Technique, challenges and indications for percutaneous pedicle screw fixation. J Clin Neurosci 18(6):741–749 87. Nakanishi K, Tanaka N, Fujimoto Y, Okuda T, Kamei N, Nakamae T et al (2013) Medium-term clinical results of microsurgical lumbar flavectomy that preserves facet joints in cases of lumbar degenerative spondylolisthesis: comparison of bilateral laminotomy with bilateral decompression by a unilateral approach. J Spinal Disord Tech 26(7):351–358 88. Oertel MF, Ryang YM, Korinth MC, Gilsbach JM, Rohde V (2006) Long-term results of microsurgical treatment of lumbar spinal stenosis by unilateral laminotomy for bilateral decompression. Neurosurgery 59(6):1264–1269, discussion 1269–70 89. Okuda S, Iwasaki M, Miyauchi A, Aono H, Morita M, Yamamoto T (2004) Risk factors for adjacent segment degeneration after PLIF. Spine (Phila Pa 1976) 29(14):1535–1540 90. Oppenheimer JH, DeCastro I, McDonnell DE (2009) Minimally invasive spine technology and minimally invasive spine surgery: a historical review. Neurosurg Focus 27(3):E9 91. Ozgur BM, Aryan HE, Pimenta L, Taylor WR (2006) Extreme lateral interbody fusion (XLIF): a novel surgical technique for anterior lumbar interbody fusion. Spine J 6(4):435–443 92. Padanyi C, Vajda J, Banczerowski P (2014) Para-split laminotomy: a rescue technique for split laminotomy approach in exploring intramedullary midline located pathologies. J Neurol Surg A Cent Eur Neurosurg. 75(4):310–316 93. Papavero L, Thiel M, Fritzsche E, Kunze C, Westphal M, Kothe R (2009) Lumbar spinal stenosis: prognostic factors for bilateral microsurgical decompression using a unilateral approach. Neurosurgery 65(6 Suppl):182–187

Neurosurg Rev 94. Papp Z, Vajda J, Veres R, Banczerowski P (2010) Minimal invasive surgical techniques for the treatment of pathologic lesions, situated in the midline of the spinal canal. Biomech Hung 3(1):189–200 95. Papp Z (2009) Removal of multiple thoracic dumbbell tumours through combined hemi-semi laminectomy and minimal invasive paraspinal approach. Ideggyogy Sz 62(7–8):265–270, Article in Hungarian 96. Park SH, Park WM, Park CW, Kang KS, Lee YK, Lim SR (2009) Minimally invasive anterior lumbar interbody fusion followed by percutaneous translaminar facet screw fixation in elderly patients. J Neurosurg Spine 10(6):610–616 97. Parker SL, Mendenhall SK, Shau DN, Zuckerman SL, Godil SS, Cheng JS et al (2013) Minimally invasive versus open transforaminal lumbar interbody fusion (TLIF) for degenerative spondylolisthesis: comparative effectiveness and cost-utility analysis. World Neurosurg. doi:10.1016/j.wneu.2013.01.041 98. Perez-Cruet MJ, Foley KT, Isaacs RE, Rice-Wyllie L, Wellington R, Smith MM et al (2002) Microendoscopic lumbar discectomy: technical note. Neurosurgery 51(5 Suppl):S129–S136 99. Plancarte R, Calvillo O (1997) Complex regional pain syndrome type 2 (causalgia) after automated laser discectomy. A case report. Spine 22:459–461 100. Rapp SM, Miller LE, Block JE (2011) AxiaLIF system: minimally invasive device for presacral lumbar interbody spinal fusion. Med Devices (Auckl) 4:125–131 101. Regev GJ, Chen L, Dhawan M, Lee YP, Garfin SR, Kim CW (2009) Morphometric analysis of the ventral nerve roots and retroperitoneal vessels with respect to the minimally invasive lateral approach in normal and deformed spines. Spine 34:1330–1335 102. Richards JC, Majumdar S, Lindsey DP, Beaupre GS, Yerby SA (2005) The treatment mechanism of an interspinous process implant for lumbar neurogenic claudication. Spine 30:744–749 103. Ringel F, Stoffel M, Stüer C, Meyer B (2006) Minimally invasive transmuscular pedicle screw fixation of the thoracic and lumbar spine. Neurosurgery 59(4 Suppl 2):ONS361–ONS366 104. Rodgers WB, Gerber EJ, Patterson J (2011) Intraoperative and early postoperative complications in extreme lateral interbody fusion: an analysis of 600 cases. Spine (Phila Pa 1976) 36(1):26–32 105. Rouben D, Casnellie M, Ferguson M (2011) Long-term durability of minimal invasive posterior transforaminal lumbar interbody fusion: a clinical and radiographic follow-up. J Spinal Disord Tech 24(5):288–296 106. Ruetten S, Komp M, Merk H, Godolias G (2008) Full-endoscopic cervical posterior foraminotomy for the operation of lateral disc herniations using 5.9-mm endoscopes: a prospective, randomized, controlled study. Spine (Phila Pa 1976) 33(9):940–948 107. Sairyo K, Sakai T, Higashino K, Inoue M, Yasui N, Dezawa A (2010) Complications of endoscopic lumbar decompression surgery. Minim Invasive Neurosurg 53(4):175–178 108. Sario-glu AC, Hanci M, Bozkuş H, Kaynar MY, Kafadar A (1997) Unilateral hemilaminectomy for the removal of the spinal spaceoccupying lesions. Minim Invasive Neurosurg 40(2):74–77 109. Schulte LM, O’Brien JR, Matteini LE, Yu WD (2011) Change in sagittal balance with placement of an interspinous spacer. Spine (Phila Pa 1976) 36(20):E1302–E1305 110. Schwender JD, Holly L, Rouben D, Foley K (2005) Minimally invasive transforaminal lumbar interbody fusion (TLIF): technical feasibility and initial results. J Spinal Disord Tech 18:1–6 111. Siddiqui M, Karadimas E, Nicol M, Smith FW, Wardlaw D (2006) Influence of X Stop on neural foraminal and spinal canal area in spinal stenosis. Spine 31:2958–2962 112. Singh V, Manchikanti L, Benyamin RM, Helm S, Hirsch JA (2009) Percutaneous lumbar laser disc decompression: a systematic review of current evidence. Pain Physician 12(3):573–588 113. Smith JS, Eichholz KM, Shafizadeh S, Ogden AT, O’Toole JE, Fessler RG (2013) Minimally invasive thoracic microendoscopic

diskectomy: surgical technique and case series. World Neurosurg 80(3–4):421–427 114. Smith WD, Youssef JA, Christian G, Serrano S, Hyde JA (2011) Lumbarized sacrum as a relative contraindication for lateral transpsoas interbody fusion at L5-6. J Spinal Disord Tech 26:156–165 115. Spetzger U, Bertalanffy H, Naujokat C, von Keyserlingk DG, Gilsbach JM (1997) Unilateral laminotomy for bilateral decompression of lumbar spinal stenosis. Part I: anatomical and surgical considerations. Acta Neurochir (Wien) 139(5):392–396 116. Spetzger U, Bertalanffy H, Reinges MH, Gilsbach JM (1997) Unilateral laminotomy for bilateral decompression of lumbar spinal stenosis. Part II: clinical experiences. Acta Neurochir (Wien) 139(5):397–403 117. Tandon N, Vollmer DG (2006) Cervical laminectomy. In: Fessler RG, Sekhar L (eds) Atlas of neurosurgical techniques: spine and peripheral nerves. Thieme, Inc, New York, pp 233–238 118. Tenenbaum S, Arzi H, Herman A, Friedlander A, Levinkopf M, Arnold PM et al (2011) Percutaneous posterolateral transforaminal endoscopic discectomy: clinical outcome, complications, and learning curve evaluation. Surg Technol Int XXI:278–283 119. Than KD, Wang AC, Rahman SU, Wilson TJ, Valdivia JM, Park P et al (2011) Complication avoidance and management in anterior lumbar interbody fusion. Neurosurg Focus 31(4):E6 120. Thomé C, Zevgaridis D, Leheta O, Bäzner H, Pöckler-Schöniger C, Wöhrle J et al (2005) Outcome after less-invasive decompression of lumbar spinal stenosis: randomized comparison of unilateral laminotomy, bilateral laminotomy and laminectomy. J Neurosurg Spine 3:129–141 121. Tobler WD, Gerszten PC, Bradley WD, Raley TJ, Nasca RJ, Block JE (2011) Minimally invasive axial presacral L5-S1 interbody fusion: two-year clinical and radiographic outcomes. Spine (Phila Pa 1976) 36(20):E1296–E1301 122. Wang B, Lü G, Patel AA, Ren P, Cheng I (2011) An evaluation of the learning curve for a complex surgical technique: the full endoscopic interlaminar approach for lumbar disc herniations. Spine J 11(2):122–130 123. Wang J, Zhou Y, Feng Zhang Z, Qing Li C, Jie Zheng W, Liu J (2012) Comparison of clinical outcome in overweight or obese patients after minimally invasive versus open transforaminal lumbar interbody fusion. J Spinal Disord Tech 27(4):202–206 124. Wang M, Zhou Y, Wang J, Zhang Z, Li C (2012) A 10-year followup study on long-term clinical outcomes of lumbar microendoscopic discectomy. J Neurol Surg A Cent Eur Neurosurg 73(4):195–198 125. Watanabe K, Hosoya T, Shiraishi T, Matsumoto M, Chiba K, Toyama Y (2005) Lumbar spinous process-splitting laminectomy for lumbar canal stenosis. Technical note. J Neurosurg Spine 3(5): 405–408 126. Watanabe K, Matsumoto M, Ikegami T, Nishiwaki Y, Tsuji T, Ishii K et al (2011) Reduced postoperative wound pain after lumbar spinous process-splitting laminectomy for lumbar canal stenosis: a randomized controlled study. J Neurosurg Spine 14(1):51–58 127. Winder MJ, Thomas KC (2011) Minimally invasive versus open approach for cervical laminoforaminotomy. Can J Neurol Sci 38(2): 262–267 128. Witzmann A, Hejazi N, Krasznai L (2000) Posterior cervical foraminotomy. A follow-up study of 67 surgically treated patients with compressive radiculopathy. Neurosurg Rev 23(4):213–217 129. Woertgen C, Rothoerl RD, Henkel J, Brawanski A (2000) Long term outcome after cervical foraminotomy. J Clin Neurosci 7(4): 312–315 130. Yaşargil MG, Tranmer BI, Adamson TE, Roth P (1991) Unilateral partial hemi-laminectomy for the removal of extra- and intramedullary tumours and AVMs. Adv Tech Stand Neurosurg 18:113–132 131. Youssef JA, McAfee PC, Patty CA, Raley E, DeBauche S, Shucosky E et al (2010) Minimally invasive surgery: lateral

Neurosurg Rev approach interbody fusion: results and review. Spine (Phila Pa 1976) 35(26 Suppl):S302–S311 132. Yu Y, Zhang X, Hu F, Xie T, Gu Y (2011) Minimally invasive microsurgical treatment of cervical intraspinal extramedullary tumors. J Clin Neurosci 18(9):1168–1173 133. Zdeblick TA, Phillips FM (2003) Interbody cage devices. Spine (Phila Pa 1976) 28(15 Suppl):S2–S7 134. Zucherman JF, Zdeblick TA, Bailey SA, Mahvi D, Hsu KY, Kohrs D (1995) Instrumented laparoscopic spinal fusion. Preliminary results. Spine (Phila Pa 1976) 20(18):2029–2034

Comments Tamas Doczi, Pecs, Hungary The goals of minimally invasive spine surgery are (1) to avoid biomechanical complications inherent in traditional destructive techniques and (2) to improve the efficacy of surgical management of various spinal diseases. The purpose is aimed to be achieved by avoiding structural damage to crucial posterior stabilizing elements and by preserving both anatomical integrity and stability of the spine. The aim of this manuscript is to formulate a systematic classification of various minimally invasive methods previously reported that were applied for different pathologies. The authors also claim that the manuscript shall help spinal surgeons in the selection of the appropriate approach or procedure. To achieve these goals, minimally invasive techniques have been described in details including technical features, advantages, complications, and clinical outcomes based on personal experience and available literature. As an overview, it is not an original study in terms of setting first a

hypothesis then trying to prove or disprove the concept with facts and figures that are based on either own data or on those collected from literature search. It is a description of available surgical techniques and creation of a system according to the authors’ personal view. It is rather questionable whether the manuscript can really help spinal surgeons in the selection of the appropriate procedure in an individual case. As a trial of setting a nomenclature for spinal surgeons in the field of minimally invasive surgery, this manuscript well deserves publication. Sandro M. Krieg, Bernhard Meyer, Munich, Germany Nowadays, spine surgeons have a large armamentarium of procedures and treatment options at hand, which also include various minimally invasive procedures. It is therefore highly welcomed that the present review offers not only an overview but also the recommendation for a classification system of minimally invasive techniques. The targets of this article are two different types of surgeons: experienced spine surgeons who might get another view on some of their own surgical approaches and junior surgeons who need a structured overview for daily decisionmaking processes. However, a very wide variety of approaches is presented and some quantification concerning the frequency of use or applicability as well as actual percentages of treatment success or complications seem desirable. Moreover, the characterization and choice of references concerning endoscopic techniques are highly biased and do not mirror daily routine or the current state of evidence. This accords also to laser techniques. More critical statements from an evidence-based point of view would increase the value of this article. Moreover, in the age of increasing use of posterior dynamic stabilization by screw-rod systems, this option deserves at least some notice in a systematic overview.