THE EFFECT OF A NEW EXTERNAL BONE-FIXATOR ON THE TREATMENT OF FRACTURES OF LONG BONES I S. M. REZAIAN F.R.C.S. Formerly Research Fellow, Royal College of Surgeons of England*

Introduction and background history HISTOLOGICAL AND PHYSIOLOGICAL studies proved that bone healing is a repetition of bone formation. Therefore bone healing must take place under ideal conditions. The present device for external bone fixation has been designed to fulfil this aim, and the early experimental work in this field has proved encouraging. Over 5,000 papers have been published to explain in detail the complex process of bone healing. Nevertheless, many important questions about the exact mechanism of this process remain unanswered1' 3. History of treatment of fracture starts with the exhaustive investigations of the American Egyptologist, Edwin Smith3. Hippocrates (350 B.C.) described the use of bandages, while Rhazes (A.D. 860-932), a Persian physician (wrongly known as Arabian physician and author), used a mixture of lime with white matter of egg to make a firm setting cast around the fractured limb8. John Hunter was able to observe the mechanism of bone formation. Antoninus Mathijsem in 1852, a Belgian Army Surgeon, introduced the effective use of plaster of Paris bandage. The importance of this contribution cannot be over-estimated8. The history of open reduction and internal fixation virtually starts with the antiseptic technique of Lister in 1867. The influence of periosteum, endosteum and the effect of various techniques of internal fixation on bone healing have been investigated by many workers of the present century. Basic theory Nowadays, autoradiographic studies with radio-active ' Timidine', a precursor of DNA, have shown that three classic cell types in boneosteoblast, osteoclast and osteocyte-are unable to reproduce themselves. The production of them is the function of additional cell type which has been called an ' Osteoprogenitor'2, 12 Osteoprogenitor cells derive from stem cell of the host bed and, in the case of bone healing, from immediate connective granulation tissue near the fracture site. * Now Shafa Hospital, Jalleh Ave., Teheran, Iran.

(Ann. Roy. Coll. Surg. Engl. 1971, vol. 48)

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In general, granulation tissue, including stem cells, develops mainly in the vicinity of capillaries in the area of fracture, proliferating outward from the Haversian canals through the endosteal layer and the periosteal layer2' 9' 10 Present internal fixation techniques (plating-screwing and intramedullary fixation) basically interfere with osteogenic elements of bone formation. The former isolates at least one-third of the periosteum and the latter eliminates the whole endosteal layer with its important circulation; therefore, with these techniques, we deliberately produce adverse conditions for bone healing. On the other hand, leaving the infection aside, the main reasons for delayed union and non-union are lack of contact and the absence of absolute immobilization, which cannot be achieved by plaster of Paris5 7. As a result of using these inefficient techniques many complications can accompany our present-day methods of treatment. Taking as an example fractures of the shaft of the tibia, which have been treated by the above-mentioned techniques, and studying the published literature on this subject over the past 50 years, we have found that complications have been reported, varying from 7% to 75 %. These complications vary from painful joint, delayed union and non-union to eventual amputation of the leg12, 13. I have recently designed a simple external bone fixator which could be applied to all long bones. It will certainly eliminate the gap between the fragments of the fracture and produce rigid and compressed (if desirable) fixation. It neither eliminates the periosteum (as does the plate and screwing) nor strip out the endosteum (as intramedullary fixation does). Nor will it interfere with venous return and limb circulation, and it allows free movements of any joint near the site of the fracture (unlike the plaster of Paris). According to new concepts of bone formation2' 12, every somatic cell (whatever its specialization may be) apparently contains in it its full complement of DNA, a complete set of the genetic instructions which characterize the organism. But how can this mechanism allow the cell to meet the changing demands of its immediate surrounding? For instance, an osteoprogenitor knows when to produce an osteoblast or an osteoclast. There must be a factor(s) which regulates the activity of the regulatory genes themselves. It is believed this factor(s) exists in the cellular microenvironment. Therefore, what a cell can do is coded in its nucleus (DNA), but what it does depends on the signal it receives from the microenvironment and the functional state (capacity) of the cell at the time of receiving this signal. I wonder if normal physiological muscle stress would be whole (or a part of) that appropriate signal for bone induction? Everybody has seen the delayed growth of a paralysed polio limb, which is a direct result of interruption of reflex of muscle stress. Conversely, the fracture under cover of thicker muscle will unite much quicker than those which are not. Plaster of Paris cast '337

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reduces the normal physiological stress if not abolishing it as a whole. Therefore the process of decalcification and reduction of bone quality will occur in bone of a limb immobilized in plaster of Paris cast. Much more scientific work is required to prove this point. However, in summary, this new external bone fixator preserves the biological state required for bone formation (good blood supply, intact periosteum and the endosteum) and provides the normal physiological stress for bone induction (bone fragment in contact with intact muscle and joint stress). Background history with description of the present external bone fixator The idea of external fixator of fracture is not a new one6, 1O. But the great disadvantage of previous fixators is that they have all been unable to

Fig. 1. (a) External fixator, and fixation equipment. (b) Immediately after fixation.

produce rigid fixation, which is nowadays a popular theory for bone healing. A new design of external bone fixator, which is more elegant than other similar devices, is now presented (Fig. la). Furthermore, it is the only external fixatoT. which will provide rigid fixation without the necessity of providing *dditional means, e.g. plaster of Paris, for complete immobilization'. It has the following possibilities: 1. Fixation of nearly all types of fractures, especially those near to the ankle or knee joint which are not suitable for plating and screwing or

intra-medullary fixation. 2. It would appear ideal for the fixation of compound fractures as it provides a good rigid fixation and gives the opportunity for frequent observation of the condition of the wound. 3. It may equally be suitable for lengthening the leg if destruction exceeds 21 inche's and still remain rigidly fixed. 338

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This external fixator consists of a series of stainless steel pins which pass at right angles through the bone by special drill direction parallel to each other. Each pin has a threaded section in the centre of the shaft which provides an adequate grip on the bone. The ends of the pins are held fast in metal axes in both sides by grub screws (Fig. Ib). A minimum of four pins is used, but provision has been made for more pins if required. Both axes have a threaded sleeve in their middle third and, by twisting the sleeves, the proximal and distal part of the axes (and the fragments of the bone if fractured) are brought together, closing the gap between bone edges. The frame may also be used to distract the fragment by up to 2 inches if required with the fragments remaining still firmly fixed in the apparatus. (This apparatus has been patented by N.R.D.C. and is made by Chas. F. Thackray Ltd., 69 Weymouth Street, London, W.1, in two sizes; the standard size for the fixation of fracture of human tibia, and half-standard size for the purpose ofexperimental work on the dog's tibia.)

Material and method In order to find out the practical effect of this external bone fixator we carried out a series of experimental work as follows: A. Choice of animal After the monkey the dog has a metabolism of bone most closely analogous to that of men4. Therefore we selected 12 mature Boxer dogs, weight 22-28 Kg. (average 25 Kg.), aged between 2.5 and 3 years. They were kept free in separate cages and were fed postoperatively on ordinary commercial food. B. Technique of operation Each dog was anaesthetized by intravenous Nembutal (j ml./Kg.). The left leg was shaved and surgically cleaned. Operations were carried out under sterile conditions with a 1-inch incision over the anteromedial shaft of the tibia, the shaft of which was divided transversely between tibial tubercle and medial malleolus using an electric oscillating saw. The fracture was manipulated under direct vision and fixed either with external fixator or Hicks type of plate and screws. When using the external bone fixator the fracture was first manipulated and then a special drill director held against the medial side of the tibia and two pins were passed transversely through the distal fragment. Again checking the position of the fracture, the fragments w :educed and two pins were then passed through the proximal fragi -.t. Next, the external axes of the apparatus were applied and the position of the drill director changed in order to provide the possibility for twisting the threaded part of the pin into the tibia. Having done this and getting enough grip in the bone so as to avoid sliding of the pins, the drill director is replaced with the other axes of the apparatus (Fig. lb). The middle 339

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sleeve of the axes is then twisted until both fragments contact each other and eliminate the fracture gap. The position of the fracture is checked by radiography before the skin is closed with black silk and some ordinary dressing spray (e.g. Nubecutane) is poured over the incision and entrance of the pin. The projecting extra ends of the pins are cut off, using an iron saw. The dog is transferred to a recovery room, and later moved to its cage. In another group of dogs the fracture was fixed with a Hicks type plate (as used for the human radius) and screwing in the usual way. C. Result Results of this series of experiments were checked by: Clinical observation Simple radiography Gross angiography Microangiography 5. Naked-eye examination of specimen 6. History 7. Tensometry. 1. 2. 3. 4.

1. Clinical observation: After general anaesthesia with Nembutal, the dog normally slept for 4-6 hours and was drowsy for another 8-12 hours before starting to move. First, all dogs tried unsuccessfully to take off the external bone fixator from their legs. As this was not successful, it seemed that they accepted the apparatus. All our dogs, generally, have been able to stand on their operated leg within 1-2 days. They moved around the cage freely at the end of the first week, some of of them even sooner. They were able to walk, to run and to jump free of trouble from the second week. We already know that the quadruped animals, especially the dog, can stand and walk upon three sound limbs. Should a leg hurt it would be impossible to persuade the dog to put it to the ground. In our dog, however, in the second week after the operation, not only was it able to walk, run, sit and lie down, but even to stand on its hind operated leg (Fig. 2a). The result of clinical observation is that this apparatus produces a rigid fixation in the fracture site and allows free painless movement to the joint nearby. It was well tolerated by the dog, and theoretically there would be little doubt why it would not be well tolerated in the human, which will allow him to use his joint from the day after the operation. 2. Radiological result: Whatever the mechanism of bone healing may be, there is no doubt that the elimination of the fracture gap is the most effective factor leading to union in the shortest period of time. Naturally, two fragments with practically no space between them will join together much sooner than when there is a gap. Our external fixator, fortunately, has the unique effect of eliminating the fracture gap. 340

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The radiological examination three weeks after operation (Fig. 2b) confirms that fixation is absolutely rigid and that union is taking place. There is no periosteal reaction which is a definite sign of persistence of movement. Microangiography Technique: The dog is anaesthetized and killed with a double dose of intravenous Nembutal. Before it gets cold the femoral artery is

(a)

(b)

Fig. 2. (a) Ability of the animal to stand on hind legs, with external fixator in position. (b) Three weeks after operation.

catheterized and the arterial trees filled with standard red micro-opaque (made by Damancy and Co. Ltd., Ware, Herts., England). No pressure for the injection is used. The arterial tree in the leg is filled with an average of 250 ml. of micro-opaque. An X-ray film is taken for studies of gross angiography and the result is seen as described below. Then a string is tightened around the root of the limb and the whole limb is removed and placed in 10% formalin for 5 days. After that, the limb is dissected and the portion of bone including the fracture site (about 5 cm.) is removed. The specimen is frozen in a cold medium, consisting 341

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I

Fig.

3.

after plate fixation. (Arrow Microangiogram of fracture threeofweeks plate.) indicates site

of spirit and solid carbon dioxide. The frozen specimen is then sliced by an electric saw. The slide of 2 mm. diameter is X-rayed and the film enlarged (Fig. 3). This picture shows that the periosteal reaction in the site of the plate is nil and consequently there is no sign of bone healing, whereas in the opposite side of the plate there is a good blood supply, with considerable periosteal reaction and the fracture gap is filling well. On the other hand (Fig. 4), where a bone has been fixed with the external fixator, periosteal reaction is much more complete and during a similar period of time complete bone healing has taken place. Summary Radiological results and microangiography once again confirm that the result of our external fixator in treatment of long bones is far better than by other means, e.g. rigid fixation with plate and screw. It clearly shows that healing process by this technique of external fixation will

Fig. 4. Microangibgram of fracture fixed with external fixator.

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accelerate to such a degree that cortical fracture of the tibia will heal completely in four weeks, after which the apparatus can be removed and the fractured limb is sound both clinically and radiologically. ACKNOWLEDGEMENT

I would like to thank the Council of the Royal College of Surgeons of England for permission to work in the Department of Physiology and at the Buckston Browne Establishment at Downe, anid for a grant from the Laming Evans Research Fund for this research project. I am deeply grateful to Professor D. Slome, who offered me all the facilities available in his department, and also for his constant encouragement. I am also indebted to Mr. Norman Capener for his criticism and valuable advice and also for taking the trouble to correct this paper. I wish also to thank the staff at Buckston Browne Research Laboratory and photographic dept. R.C.S. for their help. REFERENCES 1. ANDERSON, R. (1945) J. Bone Jt. Surg. 27, 37. 2. BASSETr, A. L. (1962) J. Bone Jt. Surg. 44-A, 1217. 3. BICK, E. M. (1948) Sourcebook of orthopaedics, 2nd edit. Baltimore, Williams and Wilkins, p. 102. 4. CHARNLEY, J. C. (1948) J. Bone Jt. Surg. 30-B, 478. 5. ELLIS, H. (1958) J. Bone Jt. Surg. 40-B, 190. 6. GROVES, E. W. H. (1922) On modern methods of treating fractures, 2nd edit. New York, Wood. 7. HIcKS, J. (1963) Lancet, 2, 272. 8. KELLY, P. J. (1968) J. Bone Jt. Surg. 50-A, 766. 9. LETrIN, A. F. (1969) J. Bone Jt. Surg. 51-B, 177. 10. MULLER, M. (1963) Proc. Roy. Soc. Med. 56, 455. 11. NADEN, J. R. (1949) J. Bone Jt. Surg. 31-A, 586. 12. RHINELANDER, F. W., and BARAGRY, R. A. (1962) J. Bone Jt. Surg. 44-A, 1273. 13. URIST, M. R. (1965) Science, 150, 893. 14. WATSON-JONES, R., and COLTART, W. D. (1943) J. Bone Jt. Surg. 39, 260.

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