Differential Diagnosis of a Sacral Stress Fracture

Differential Diagnosis of a Sacral Stress Fracture William G. Boissonnault, PT, DHSc, FAAOMPT 1 Jill M. Thein-Nissenbaum, MPT, SCS, ATC 2 Journal of ...
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Differential Diagnosis of a Sacral Stress Fracture William G. Boissonnault, PT, DHSc, FAAOMPT 1 Jill M. Thein-Nissenbaum, MPT, SCS, ATC 2

Journal of Orthopaedic & Sports Physical Therapy

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1 Assistant professor, Physical Therapy Program, University of Wisconsin at Madison, Madison, WI. 2 Faculty associate, Physical Therapy Program, University of Wisconsin at Madison, Madison, WI. Send corresponence to William G. Boissonnault, 1300 University Avenue, MSC, Room 5190, Madison, WI 53706-1532. E-mail: [email protected]

CASE

Sacral and sacroiliac (SI) joint pain, although not as common as low back pain, occurs in all age groups. The pain may be a result of muscular, ligamentous, neurological, mechanical, or bony dysfunction at or near the sacrum or SI joint. Anatomically, numerous muscles, including the sacrospinalis (erector spinae), gluteus maximus, and piriformis attach to the sacrum and could potentially present as a source of pain if strained or partially avulsed.36 Ligamentous structures that attach to the sacrum and which may cause pain if injured include the sacroiliac, iliolumbar, sacrospinous, and the sacrotuberous ligaments.26 Pain near the sacrum may also be neurological in origin, as the sacral plexus passes through the sacral foramina.36 Mechanical pain due to SI joint dysfunction may present as sacral pain and may also refer pain distally. In a study by Fortin et al,17 pain referral maps were studied in 10 subjects without SI pain by injecting contrast material into the SI joint under fluoroscopy. The study determined that the SI joint referred pain to a 3×10-cm area inferior to and over the posterior superior iliac spine (primarily to the ipsilateral side) in all subjects. As in previous studies,23,24 they found variability between subjects: 4 subjects also experienced pain to the ipsilateral medial buttock and 2 subjects experienced pain extending into the ipsilateral superior lateral thigh.17 Pain may also be referred to the sacrum from a distant structure. According to Kellgren,23,24 pain from the contralateral sacrospinalis muscle may produce pain around the sacrum,23 as may the ipsilateral L3-S2 interspinous ligaments.24 McCall et al32 documented pain referral patterns from lumbar

facet joints following saline injections and found that ipsilateral lateral sacral pain was provoked with injections at the L4-L5 facet joints. Lastly, pain in the sacral region may be of bony origin secondary to a tumor or due to a fracture. Although, primary tumors of the spine such as osteoid osteomas, chondrosarcomas, and osteosarcomas occur less frequently than metastatic disease,25 they do exist. Brat et al7 reported on a 30year-old man with a 7-month history of mild sacral pain and intermittent sciatica. Plain radiographs revealed a lesion and biopsy confirmed a chondromyxoid fibroma that was surgically removed.7 Primary breast, lung, and prostate cancers are among the most common cancers to metastasize to the axial skeleton, including the pelvic ring.16,40 Cancer metastasizing to the low back region is more common in individuals aged 50 years and older.3 The other bony source of pain seen in all age groups is fracture, including stress fracture. Two types of stress fractures exist: insufficiency fractures and fatigue fractures.9,13,14,30,35 Insufficiency fractures occur when normal muscular stress is applied to bone that is deficient in mineral content or elastic resistance.9,13,14,35 Patients who sustain insufficiency fractures often have predisposing factors, such as osteoporosis, metabolic disorders, prolonged corticosteroid use, or Paget’s disease.8,30,38 The presence of these underlying conditions should alert the clinician to the increased risk of bony lesions. In contrast, fatigue fractures are caused by the application of abnormal muscular stress or mechanical torque to a bone that has normal elasticity and mineral content.9,13,14,35 Bone, a dynamic structure, responds to the external forces placed upon it, according to Wolff’s Law. However, this response in bone may be delayed compared to muscle, as muscles typically adjust to increased demands at a faster rate than bone.9,30 Clinically, the athlete who has begun a running program, or recently increased the intensity of the program, may be ready to increase mileage or intensity from a muscular standpoint but not from a

RESIDENT’S

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BACKGROUND

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skeletal standpoint. Increasing the running mileage or the intensity of the workout will prolong the muscular pull and mechanical torque on bones that are not yet capable of accepting the added stress, putting the athlete at risk for fracture.9 Fatigue stress fractures are commonly observed in athletes as well as military recruits and account for 5% to 6% of overuse injuries.1,6,8–10,12,14,15,20,22,30,31,33–35,37,39,40 Based on an extensive review of the literature, Daffner and Pavlov9 correlated the location of various fatigue stress fractures with the causative activity (Table 1). Even though stress fractures do occur with greater frequency in the lower extremities than in the upper extremities, fatigue fractures are not thought to be common in the sacrum. In a longitudinal study by Matheson et al,31 only 1.7% (3 out of 175) stress fractures of the lower extremity were found to occur in the pelvis of female athletes. Although case reports regarding sacral stress fractures do exist,1,6,8,10,12,14,15,30,31,33,37,38 few provide a comprehensive discussion of the differential diagnostic process.10,41 Because stress fractures are a component of the very broad ‘‘overuse syndrome’’ category and can be confused with many other medical conditions, physical therapists should have a thorough understanding of the etiology, clinical manifestations, and diagnosis of stress fractures. The purpose of this resident’s case problem is to present a description of a patient referred to physical therapy with sacral pain that was subsequently diagnosed as a sacral stress fracture. The physical therapist’s differential diagnostic process for this patient is emphasized.

DIAGNOSIS History A 34-year-old homemaker and long-distance runner was referred for physical therapy with a diagnosis of right sacral pain. She was a former Division I collegiate runner and currently training for international competition. The referring physician had communicated to the primary author a concern that a stress fracture may be responsible for the symptoms, but preferred to attempt physical therapy intervention, along with cessation of running, for at least 1 to 2 weeks prior to diagnostic imaging testing. He had noted during his examination ‘‘significant asymmetry of the hip bones and suspected a sacroiliac joint injury.’’ The physician stated he had scheduled the patient for a magnetic resonance imaging (MRI) test in 10 to 14 days, but would cancel the test if the patient showed improvement with the therapeutic intervention. The sole complaints reported by the patient were a constant soreness and aching, and an intermittent ‘‘catch’’ sensation in the area of the right side of the sacrum (Figure 1). She reported that the intermittent catch was accompanied by a sensation in the right hip of being ‘‘out of place.’’ The pain had begun approximately 7 to 10 days prior to the initial physical therapy visit while the patient was running a

TABLE 1. Locations of common fatigue stress fractures as related to activity. Location Lower limb Metatarsus Navicular bone Calcaneus Tibia, proximal shaft Tibia, mid and distal shaft Fibula, distal shaft Patella Femur, shaft Femur, neck Trunk Sacrum Pelvis, obturator ring Lumbar vertebra (pars interarticularis) Upper limb Humerus, distal shaft Ulna, shaft

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Activity Marching, ballet, weight bearing after bunionectomy Marching, running Jumping Walking, running Running, leaping (basketball, aerobic dancing, ballet) Running Hurdling Ballet, running Ballet Running, aerobics Bowling, gymnastics Ballet, running, gymnastics Throwing a ball Pitching a ball, propelling a wheelchair

FIGURE 1. Location and description of symptoms at the time of the initial physical therapy visit. The X designates where the patient experienced the catch sensation and the circled area designates the area of the ache and soreness. J Orthop Sports Phys Ther • Volume 32 • Number 12 • December 2002

Impression From Patient History Based on the historical information collected, the first author was concerned about the etiology of the symptoms, as the patient had recently recovered from a stress fracture in the same general area, and that the onset of the right-side symptoms was associated with a recent return to a high level of running. The patient was aware that the referring physician had concerns about the possible presence of a stress fracture, but repeatedly stated that the physician had found asymmetry in the bony landmarks of her hip bones. Even though the patient acknowledged that the current right-side sacral pain was similar to the pain she had experienced previously on the left side, she did not believe the current pain was from a stress fracture. She frequently stated during the interview that it felt like her hip bone was out of place and that the pain was right over the sacroiliac joint. Also, during the interview, the patient expressed a concern regarding the fact that she felt she could not miss many more weeks of running without jeopardizing her long-term international competition goals. Due to concerns regarding an existing stress fracture and the origin and location of symptoms, a detailed examination of the pelvis, lumbar, and hip regions was warranted.

Physical Examination

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Observation revealed that the patient was of an ectomorphic body build. The physician’s report noted she was 170.2 cm tall and weighed 50.8 kg. During the standing postural assessment, a slight decrease in the lumbosacral junction lordotic curve was noted. Palpation over the right sacral base provoked moderate tenderness, with the patient stating, ‘‘that is where my pain is.’’ No other area of the pelvis, hips, or lumbar spine was painful or tender to palpation. The right iliac crest, right posterior superior iliac spine, right anterior superior iliac spine, and the right greater trochanter appeared to be elevated compared to the corresponding bony landmarks on the left side. The sacral pain did not increase or decrease during trunk active forward, backward, and side-bending range of motion (ROM), or passive overpressures (of the same movements done actively) in standing. The only active ROM deficit was a slight decrease in backward bending at the lumbosacral junction. At the end of the trunk backward bending motion, the patient noted a slight pressure sensation at the midline of the lumbosacral junction. Central and unilateral posterior-anterior (PA) pressures of the lumbar spine and sacrum, as described by Maitland,29 did not alter the patient’s symptoms.

CASE

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her family history (first-degree relatives) was negative for serious illness.

RESIDENT’S

series of hills as part of her training regimen. The pain came on suddenly and was intense (6 on a scale of 0 to 10, 0 representing no pain and 10 the worst pain imaginable). Within 24 hours of the onset of symptoms, the patient received chiropractic treatment consisting of chiropractic adjustments and ice, but this intervention did not decrease the patient’s symptoms. Although the pain intensity had diminished since the onset, the pain still prevented her from running, which was the patient’s sole rehabilitation goal. The patient reported that she had not previously experienced right sacral pain, but had experienced similar pain on the left side of the sacrum approximately 5 months prior to this initial visit. At that time, she had been diagnosed as having a stress fracture on the left side of the sacrum. At the initial visit, the patient rated the right sacral pain intensity between a 1 (feeling her best) and a 4 (feeling her worst) on a scale of 0 to 10. Although she always experienced some discomfort, the sacral soreness and aching was most intense when the patient tried to run, walked more than a mile, or stood for more than 30 minutes. She experienced the catch sensation while riding a stationary bike, which she had been doing since she was told to refrain from running. The patient reported that since the physician visit she had tried shallow water running in the pool, but had to discontinue the activity due to intense right sacral pain. The sacral pain did not wake her from sleep, but a low-intensity ache was always present. The patient reported that her overall health was very good and denied having any other symptoms, including numbness, tingling, weakness, fatigue, nausea, fever, chills, sweats, or unexplained weight change. She also denied having any symptoms associated with the review of systems checklists for the gastrointestinal and urogenital systems.4 The patient’s medical history included a report of hypothyroidism (duration of approximately 12 months), for which she was taking synthroid. She also reported taking Advil (approximately 800 mg per day), daily calcium and iron supplements, and oral contraceptives. She denied tobacco and alcohol use, and reported that she avoided drinking beverages containing caffeine. The patient’s surgical history was negative and the 2 prior hospitalizations were associated with the births of her children (2 and 4 years old). Her only report of significant personal injury was the left sacral stress fracture, confirmed by MRI, sustained approximately 5 months prior to the onset of the right sacral pain. The patient reported that she was unable to run for approximately 6 to 7 weeks after the left sacral stress fracture was diagnosed. She gradually returned to her running program and reported that during the 4 to 6 weeks prior to the onset of the right sacral pain, her training program had been very intense. Lastly,

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But unilateral pressures over the right side of L5 and of the sacrum revealed slight hypomobility (grade 2 on a scale of 0 to 6 [0 = ankylosed, 3 = normal, and 6 = unstable]) as defined by Gonnella and Paris.18 The patient reported local tenderness (‘‘that is where my pain is’’) during the PA pressures over the right side of the sacrum, but the aching did not increase during this maneuver. It should be noted that good intertester reliability has been demonstrated for PA pressures of the lumbar spine regarding pain provocation, but poor reliability has been noted regarding accessory motion testing.28 With the patient in a prone position, palpation over the sacral base (SB), right and left sides, and the inferior lateral angles (ILA) of the sacrum revealed a slightly right rotated position of the sacrum (the right SB and ILA appeared more posterior relative to the left SB and ILA). With the patient in a prone-on-elbows position, palpation over the same landmarks again revealed a right-rotated position of the sacrum, but with significantly increased asymmetry of the landmarks as compared to that revealed in prone. The right ILA with the patient in a prone-on-elbows position also appeared to be slightly inferior to the left ILA. Lastly, with the patient seated and in a forward-flexed position of the trunk, palpation over the same landmarks did not reveal a rotated position of the sacrum. The ilial shear test, as described by Magee,27 did not alter the patient’s symptoms and the end feel was symmetric. Hip active and passive ROM testing, including the flexion, abduction, and external rotation (FABER) test and the hip scour test, did not alter the patient’s symptoms, and revealed symmetric normal mobility (per Magee27) with the exception of the combined movement of right-hip flexion, medial rotation, and adduction. With the hip flexed to 90° and in full medial rotation, adduction of the right hip was limited to 25° compared to that of the left hip, which was limited to 40°. During this maneuver, the patient experienced an intense deep ‘‘stretch’’ sensation in the right buttock, compared to a very mild stretch sensation noted in the left buttock when testing the left hip. A neurologic screening of the lower extremities, including sensory, myotome testing, and testing of the quadriceps and Achilles tendon reflexes did not reveal any deficits. Lower extremity pulses were easily found and symmetric when comparing extremities. Lastly, the straight leg raise test was negative bilaterally.

Impression From the Physical Examination The physical examination findings supported the physician’s conclusion that the right sacral pain was local pain and not referred from another area. Symptoms were not altered during the assessment of the lumbar spine (palpation, active ROM, overpressures, PA pressures), nor during the assessment of 616

the hip regions (palpation, active ROM, overpressures, FABER, and scour testing). Only palpation and pressure directly over the right sacral base area provoked any discomfort. Although the palpation and the PA pressures over the right sacral base did not make the patient’s pain worse, the patient reported tenderness. In addition, the most significant impairments noted were the right sacroiliac joint hypomobility and the right hip adduction ROM deficit observed with the hip internally rotated and flexed to 90°. (It should be noted that poor interrater reliability has been shown regarding the use of the PA techniques for mobility assessment, and that reliability assessment has not been done regarding palpation of sacral bony landmarks to compare position change with the patient prone, prone on elbows, and in seated-trunk flexion.) The asymmetric height of the ilial bony landmarks and greater trochanters suggested a possible leg length discrepancy. This may have precipitated the sacroiliac joint injury while running on hills and the decreased mobility noted at the right hip could have developed secondary to the injury. The primary author’s one nagging concern was the inability to increase or decrease the patient’s pain during the physical examination. If the pain had been of muscular origin, the patient’s pain would have likely been reproduced with local palpation, passive stretching, or active contraction of the tissue. Ligamentous or joint pain would have likely been reproduced with stressing of the tissues during local palpation, active movements, overpressures, or the special tests such as the hip FABER test, scour test, and ilial shear test. The neurological exam was negative. Considering that the pain was severe enough to prevent running of any intensity, and that the patient experienced a painful catch with biking, the first author expected to be able to alter the patient’s symptoms at some point during the examination. This led to the question of whether the pain was truly associated with the right sacroiliac joint dysfunction and the decreased right hip flexibility or, considering the patient’s history, with a stress fracture.

Course of Intervention During the initial visit, manual therapy interventions were utilized to treat the right sacroiliac joint and the L5 dysfunction. These techniques were followed by passively stretching the right hip into flexion, medial rotation, and adduction. Following these interventions, reassessment of the sacral position with the patient positioned prone and prone on elbows revealed symmetric sacral bony landmarks (SB and ILA). In addition, PA pressures over the right sacral base, although still eliciting tenderness, did not reveal the hypomobility noted earlier in the examination. Right hip adduction, measured with the

J Orthop Sports Phys Ther • Volume 32 • Number 12 • December 2002

FIGURE 3. Follow-up magnetic resonance axial image of the sacrum. The 4 arrows identify the lesion of the right sacral ala. The high-signal intensity zone represents an increase in the degree of edema compared to that noted in Figure 2 with the central area of decreased signal revealing a more visible fracture line than that noted in Figure 2.

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worsened and the fracture line was more visible compared to the first MRI. The patient admitted to a trial of land-based running during the period of time between the 2 MRI studies. The patient was instructed by the physician to continue with her current program of lap swimming and weight training without progressing either activity, and to avoid running of any type. Lastly, computed tomography (CT) was ordered 3 to 4 weeks following the second MRI (7 to 8 weeks after the original MRI). These films (Figure 4) revealed a linear sclerosis with a faint cen-

CASE

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FIGURE 2. Magnetic resonance axial image of the sacrum. The 4 arrows identify the lesion of the right sacral ala. The high-signal intensity zone represents edema around the central area of decreased signal. This is consistent with an incomplete right sacral ala fracture.

RESIDENT’S

hip flexed to 90° and medially rotated, had improved to 35°. The patient stated that her right hip generally felt much more flexible after the interventions and that walking was less painful. The apparent leg length discrepancy was discussed with the patient, and she reported that she had been given a heel lift for her left shoe after the diagnosis of a left sacral stress fracture. She stated that she never used the lift, even when she had resumed running. The patient was instructed to bring the heel lift to the next physical therapy visit and to continue refraining from running. Lastly, she was instructed in a home exercise program to stretch the right hip. The patient made an appointment to see the primary author 4 days after the initial visit. At that time she reported that her swimming and weight lifting were improving, and that she was able to increase the intensity of her workouts without an increase in pain. She also noted that there was still pain with running in shallow water, but the pain was not quite as intense. She stated she had entertained the thought of land-based running, but the catch in her right hip stopped her. She reported that at the start of this second visit, her right hip bone felt out of place and she was concerned as to how that might have happened. She was unaware of what may have precipitated the sensation. The physical examination again revealed moderate tenderness with palpation over the right sacral base area, but trunk backward bending was no longer limited at the lumbosacral junction, and only a very slight right-rotated sacral position was noted in the prone-on-elbows position. In addition, as occurred following the initial intervention, the right L5 and right sacral base hypomobility was not noted with the PA pressures. Lastly, the right-hip ROM deficit was significantly reduced, and very little difference existed between the right- and left-hip combination of flexion, medial rotation, and adduction ROM. The primary author expressed concern to the patient regarding the persistent catch in her hip, the continued pain with running in the pool (albeit reportedly less intense), and the moderate right sacral tenderness, despite the fact that there was apparent improvement in the impairments noted during the initial visit. The patient agreed to keep the MRI appointment, which was scheduled for the next day, and to halt the physical therapy until the MRI results were known. The following day the referring physician contacted the primary author and reported that the MRI revealed an abnormality in the right ala of the sacrum. The resultant diagnosis was an incomplete right sacral ala fracture (Figure 2). He stated that the patient would continue to swim (laps only, no running), and participate in weight training at a clinic closer to her home for a month, after which a follow-up MRI would be done. The follow-up MRI (Figure 3) revealed that the amount of edema had

FIGURE 4. Follow-up computed tomography scan of the bony pelvis, axial image. The 2 arrows identify an area in the right sacral ala of linear sclerosis with a faint central lucency, consistent with a healing stress fracture.

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tral lucency, consistent with a healing sacral stress fracture.

DISCUSSION Sacral stress fractures present with numerous screening, diagnostic, and management challenges to the clinician. First, the development of stress fractures appears to be associated with a wide range of extrinsic and intrinsic risk factors. Second, multiple conditions, including soft tissue strain, lumbar disk disease, SI joint sprain, sciatica, bony injury, metastasis, osteogenic sarcoma, and Ewing’s tumor can mimic the clinical presentation of stress fractures.9,30,33,38 Third, several published case reports of sacral stress fractures describe a wide range of symptoms and signs (Table 2), many of which manifest inconsistently and could be considered nonspecific.

Lastly, there is disagreement within the literature as to the recommended sequence of diagnostic imaging modalities. To meet this challenge, a detailed history and thorough physical examination are essential for the development of an accurate diagnosis. However, as this case illustrates, the patient response to treatment can also be an important factor that guides the practitioner’s clinical decision making. The literature suggests that the cause of stress fractures is multifactorial and that athletes in particular can present with both extrinsic and intrinsic risk factors. Intrinsic factors, including gender, decreased aerobic fitness level, leg length discrepancy, and diminished muscle strength, may play a role in the incidence of stress fractures. Women have a higher incidence of stress fractures compared to men, which is most likely due to a multitude of factors, including menstrual irregularities, lower bone mineral density, and narrower bone width.41 Extrinsic risk factors associated with stress fractures include a sudden change in the training regimen, improper footwear, and alterations in the training surface.1,12,15,19,41 This patient presented with both intrinsic and extrinsic risk factors, which included female sex, a recent rapid increase in training intensity, and questionable footwear, as she wasn’t wearing the recommended sole insert in her left shoe. In addition, she had just recently recovered from a stress fracture in the same area, albeit in the opposite side. Pain originating from a sacral stress fracture will typically be described by patients as low back pain, which is the most frequently reported complaint by patients seeking outpatient physical therapy services.2,5,11,21 Physical therapy intervention is provided for many of the conditions listed above (soft tissue strains, lumbar disk disease, sciatica, and SI joint sprains), all of which can mimic the clinical presentation of sacral stress fractures. When any bony lesion is suspected, therapists must also be vigilant for warn-

TABLE 2. Patient’s signs and symptoms associated, or not associated, with sacral stress fractures as reported by various authors. Signs and Symptoms Localized pain Antalgic gait Tenderness with palpation Normal ROM* of hip Normal neurovascular status Positive Patrick Test Groin pain Normal lumbar spine ROM Pelvic tilt Pain with SLR† to 60°–70° Leg length discrepancy Previous stress fracture at the same site Decreased bone mineral density Ischial tuberosity pain

References Finding an Association With Stress Fracture 1,10,14,19,39 1,10,33 1,6,8,12,14,15,19,33 1,6,12,14,19 1,12,33 1 1,39 1,6,10,12,14,19,39 6,14 8 6,8 12 6,12 15

References Finding No Association With Stress Fracture 33 1,10 37,39 10,33 10

10

* Range of motion. † Straight leg raise. 618

J Orthop Sports Phys Ther • Volume 32 • Number 12 • December 2002

• • • • • • • •

Female sex Recent history of stress fracture in same area as the current chief complaint* Rapid increase in training intensity (running) prior to the onset of symptoms* Localized pain complaint Marked tenderness with local palpation Apparent leg length discrepancy No provocation of symptoms with anything but local palpation* Improvement of lumbar, sacroiliac joint, and hip dysfunctions with lack of symptom improvement*

* Findings most concerning to the first author regarding the source of the patient’s symptoms.

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imaging modalities as part of the differential diagnostic process. Any abnormality in the CBC requires further diagnostic testing; the CBC is found to be normal in patients with stress fractures.1,10,37,39 Diagnostic imaging modalities are not always conclusive when a stress fracture is suspected. In fact, of the case reports reviewed, many subjects with a stress fracture were found to have normal findings on plain radiographs.1,6,8,10,12,14,15,19,33,39 Although plain film radiography is the initial test for most patients with low back pain, the sacrum is a challenge to image definitively on plain films secondary to the overlying soft tissues and bowel gas.12,33 Plain films detecting a stress fracture are also dependant upon the time frame between injury and the imaging examination.9 Holtzhausen19 suggested a lag period of 2 to 12 weeks from the onset of pain to the presence of positive findings on plain radiographs. Considering this potential lag time, if the initial plain films are read as normal, taking follow-up radiographs 1 to 2 weeks later may be recommended.9 However, oftentimes due to the urgency to formulate a diagnosis in athletes, follow-up diagnostic testing, such as radionuclide bone imaging, is recommended. Bone scans, once considered the gold standard for diagnosing stress fractures, have been identified as the recommended follow-up diagnostic examination tool in many case reports.1,6,8,10,12,15,19,30,33,34,37,39 Bone scans prove to be highly sensitive, nearing 100%, and may show abnormalities early in the course of a stress fracture (as early as 6 to 72 hours after the onset of symptoms).13,19,31,35 However, Eller et al12 reported that the image resulting from the increased radioactive tracer uptake is fairly nonspecific in identifying anatomic detail. Fanciullo and Bell13 suggested using computed tomography (CT) scanning to enhance specificity. CT scanning has been utilized in many published case reports of sacral stress fractures.1,8,10,12,30,33,39 As with bone and CT scans, MRI is commonly used for patients with suspected stress fractures,9,12,14 but there is disagreement among authors regarding

CASE

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TABLE 3. A summary of examination findings that led to the concern about a bony lesion being associated with the patient’s chief complaint.

RESIDENT’S

ing signs of the other more serious diseases, including bony metastasis, osteosarcoma, and Ewing’s tumor. Although one can never be certain that cancer doesn’t exist based solely on a history and physical examination, this patient did not present with any of the classic findings associated with cancer of the musculoskeletal system3 (no previous personal history of cancer, no family history of cancer, age [34 years] falling between 20 and 50 years, no worsening of sacral pain with assumption of a supine position, no complaints of night pain). The patient described in this case report had apparent right SI joint and L5-S1 dysfunctions that could possibly have been responsible for her pain complaints. This fact clouded the clinical decisionmaking process, preventing a definitive diagnosis during the initial examination. However, this hypothesis was rendered less likely upon follow-up examination; trunk and pelvis examination procedures did not alter the patient’s complaints, and the originally noted impairments were improved without a concurrent reduction in the patient’s chief complaint. Table 2 summarizes the symptoms and signs reported in published sacral stress fracture case reports. Of those noted, only localized pain,1,10,14,19,39 tenderness with palpation,1,6,8,12,14,15,19,33 normal lumbar spine ROM,1,6,10,12,14,19,39 normal hip ROM,1,6,12,14,19 and a normal neurovascular status1,12,33 were consistently reported in these cases. The patient in this resident’s case problem complained of localized sacral pain and tenderness over the area with palpation. She had a normal neurovascular examination. She had a slight decrease in backward bending at the lumbosacral junction, which may have been associated with the noted sacral and L5-S1 dysfunctions and not secondary to the stress fracture. The patient also presented with diminished right hip ROM, which may or may not have been directly associated with the sacral stress fracture. Examining the patient only after onset of symptoms precludes the first author from comparing examination findings prior to and after the onset of pain. Ruling out the hip as the source of symptoms was important, because this case could have been an atypical presentation of a femoral neck stress fracture. The diagnosis of a femoral neck stress fracture carries a sense of urgency because this lesion could progress to a devastating fracture and require immediate surgical pinning. Based on the noted intrinsic and extrinsic factors and the above information, the first author was concerned foremost about the presence of a bony lesion of the sacrum. See Table 3 for a summary of the examination findings that lead to the concern about the patient’s chief complaint being associated with a bony lesion and with stress fracture being of greatest concern. When a bony lesion is suspected, physicians will order a complete blood count (CBC) and diagnostic

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the level of specificity of the MRI findings. Several authors stated that even though plain radiographs and bone scans have served as the primary modalities for imaging suspected stress fractures, MRI provided for a more specific initial or follow-up diagnosis.12,13,35 Eller et al12 believed MRI to be valuable, as it resulted in the localization of the involved area and enabled a clear distinction from other common problems, such as SI joint dysfunction. According to Daffner and Pavlov,9 the MRI image of a stress fracture will show low signal on the T1-weighted image and increased signal on the T2-weighted images with injection of gadopentetate dimeglumine. The authors also believed the results to be nonspecific and were concerned that the findings may be confused with osteoporosis or infection. Several other authors felt that signal alterations due to edema or hemorrhage on MRI may be misleading, or may be interpreted as neoplasia.13,14 The diagnostic imaging sequence for this patient included 2 successive MRI scans (4 weeks apart), followed by a CT scan approximately 7 weeks after the initial MRI. All 3 tests were done without contrast.

CONCLUSION Determining whether a patient’s symptoms are associated with a condition for which physical therapy intervention is indicated is one of the important questions physical therapists attempt to answer during an initial patient visit. As this resident’s case problem illustrates, the answer to this question may not be clear until subsequent patient visits occur. Sacral stress fractures, although relatively uncommon, are a potential source of back pain, which is a common complaint in patients seeking physical therapy outpatient services. Because bony lesions can be associated with serious medical conditions, such as cancers and fractures, early detection and an accurate diagnosis is paramount to appropriate care. An important element in screening for such conditions is recognizing patients with the relevant risk factors. The presence of the risk factors associated with insufficiency and fatigue fractures, as described in this case, should alert the therapist to scrutinize symptoms and signs suggestive of a bony lesion thoroughly. As described, there is an unfortunate degree of overlap of symptoms and signs for many of the conditions causing back pain and those of sacral stress fractures. Another important element of this screening process is establishing a prognosis that carries expectations of patient progression, both from a subjective and a physical examination standpoint.5 If these expectations are not met, the therapist must reconsider the original diagnosis, and, as in this case, insure that the patient is referred for physician 620

follow-up and the recommended appropriate diagnostic workup.

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RESIDENT’S

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