In view of the current level of knowledge and the numerous treatment possibilities, none of the existing classification systems of thoracic and lumbar injuries is completely satisfactory As a result of more than a decade of consideration of the subject matter and a review of 1445 consecutive thoracolumbar injuries, a comprehensive classification of thoracic and lumbar injuries is proposed The classification is primarily based on pathomorphological criteria Categories are established according to the main mechanism of injury, pathomorphological uniformity, and in consideration of prognostic aspects regarding healing potential The classification reflects a progressive scale of morphological damage by which the degree of instability is determined The severity of the injury in terms of instability is expressed by its ranking within the classification system A simple grid, the 3-3-3 scheme of the AO fracture classification, was used in grouping the injuries This grid consists of three types: A, B, and C Every type has three groups, each of which contains three subgroups with specifications The types have a fundamental injury pattern which is determined by the three most important mechanisms acting on the spine: compression, distraction, and axial torque Type A (vertebral body compression) focuses on injury patterns of the vertebral body Type B injuries (anterior and posterior element injuries with distraction) are characterized by transverse disruption either anteriorly or posteriorly Type C lesions (anterior and posterior element injuries with rotation) describe injury patterns resulting from axial torque The latter are most often superimposed on either type A or type B lesions Morphological criteria are predominantly used for further subdivision of the injuries Severity progresses from type A through type C as well as within the types, groups, and further subdivisions The 1445 cases were analyzed with regard to the level of the main injury, the frequency of types and groups, and the incidence of neurological deficit Most injuries occurred around the thoracolumbar junction The upper and lower end of the thoracolumbar spine and the T 10 level were most infrequently injured Type A fractures were found in 661 %, type B in 145%, and type C in 194% of the cases Stable type Al fractures accounted for 347% of the total Some injury patterns are typical for certain sections of the thoracolumbar spine and others for age groups The neurological deficit, ranging from complete paraplegia to a single root lesion, was evaluated in 1212 cases The overall incidence was 22% and increased significantly from type to type: neurological deficit was present in 14% of type A, 32% of type B, and 55% of type C lesions Only 2% of the Al and 4% of the A2 fractures showed any neurological deficit The classification is comprehensive as almost any injury can be itemized according to easily recognizable and consistent radiographic and clinical findings Every injury can be defined alphanumerically or by a descriptive name The classification can, however, also be used in an abbreviated form without impairment of the information most important for clinical practice Identification of the fundamental nature of an injury is facilitated by a simple algorithm Recognizing the nature of the injury, its degree of instability, and prognostic aspects are decisive for the choice of the most appropriate treatment Experience has shown that the new classification is especially useful in this respect

A comprehensive classification of thoracic and lumbar injuries

collected in the literature. Most of the descriptions of sarcomas in fibrous dysplasia that are in the literature are single case reports or reports of a few case^.^-'^ The largest series, which includes 15 cases, is that from Memorial Sloan-Kettering Cancer Center, New York.2,20 In 1988, Yabut and coworkers' reported a new case and found 83 cases in a careful review of the literature. The most common of the malignancies was osteosarcoma, followed by fibrosarcoma and chondrosarcoma. The possibility of sarcomatous change in fibrous dysplasia without prior irradiation seems well established, as verified by several reports of documented case~.~~~~'' The role of radiation therapy in the occurrence of sarcoma in fibrous dysplasia is still c~ntroversial.'~~~~' In Huvos' series," only 1 of 15 patients with sarcomas in fibrous dysplasia had received radiation therapy. In the review of the literature by Yabut and coworker^,^ 23 patients had received radiation therapy, 46 had not had prior irradiation, and 14 did not have information available. The purpose of the current study was to review and report our experience with malignancies in fibrous dysplasia. Materials and Methods

Malignancies in fibrous dysplasia.

Ilizarov embarked on his remarkable medical career as a general practitioner in the small industrial town of Kurgan, Siberia, after World War II69,75,96 Antibiotics were scarce, and chronic osteomyelitis associated with loss of bone, non-unions, and skeletal deformities were so common that Ilizarov found himself practicing orthopaedics although he had had no formal training in that specialty With the use of modular-ring external fixators and transosseous wires attached to the rings under tension to stabilize the bone fragments, he introduced the concept of induction of local bone formation with a minimally invasive procedure69,75,96 Ilizarov coined the term distraction osteogenesis to describe the induction of new-bone formation between osseous surfaces that are gradually pulled apart9 His clinical successes in the salvage of limbs that would otherwise have been amputated and in the return of disabled patients to productive levels of activity eventually spread by word of mouth throughout the Communist bloc of countries69,75 By 1981, a group of Italian orthopaedic surgeons had learned of his technique9 More recently, the method was introduced in North America, where it has been adopted primarily for limb-lengthening12,49,120,125 and the correction of limb deformities as well as the treatment of non-unions and bone loss secondary to trauma, infection, or tumor39,41,43,46,76,78,99,114,124,135,142

Ilizarov practiced in an isolated area of the world without access to the many technological and medical advances that took place during the four decades after World War II As a result, he relied on distraction osteogenesis to treat a variety of musculoskeletal conditions The reconstruction of …

Limb-lengthening, skeletal reconstruction, and bone transport with the Ilizarov method.

Historically, because of the problems involved in initial limb salvage and the subsequent difficulty of reconstructing large skeletal defects many fractures with significant bone loss were treated by primary amputation. Modern techniques of fracture stabilisation and soft-tissue reconstruction mean

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The management of fractures with bone loss

Transplantation of marrow-derived mesenchymal stem cells and platelet-rich plasma during distraction osteogenesis--a preliminary result of three cases.

We used an experimental rabbit model of leg lengthening to study the morphology and function of muscle after different distraction rates. Lengthening was in twice-daily increments from 0.4 to 4 mm per day. New contractile tissue formed during lengthening, but some damage to the muscle fibres was seen even at rates of less than 1 mm per day; abnormalities increased with larger rates of lengthening. There was proliferation of fibrous tissue between the muscle fibres at distraction rates of over 1 mm per day. Active muscle function showed adaptation when the rate was 1.0 mm per day or less, but muscle compliance was normal only after rates of 0.4 mm per day. Muscle responded more favourably at rates of distraction slower than those shown to lead to the most prolific bone formation. At present the rate of distraction in clinical practice is determined mainly by factors which enhance osteogenesis. Our study suggests that it may be advisable to use a slower rate of elongation in patients with poor muscle compliance associated with the underlying pathology; this will allow better accommodation by the contractile and connective tissues of the muscles.

The response of muscle to leg lengthening

Distraction osteogenesis is widely used for leg lengthening, but often requires a long period of external fixation which carries risks of pin-track sepsis, malalignment, stiffness of the joint and late fracture of the regenerate. We present the results of 20 cases in which, in an attempt to reduce the rate of complications, a combination of external fixation and intramedullary nailing was used. The mean gain in length was 4.7 cm (2 to 8.6). The mean time of external fixation was 20 days per centimetre gain in length. All distracted segments healed spontaneously without refracture or malalignment. There were three cases of deep infection, two of which occurred in patients who had had previous open fractures of the bone which was being lengthened. All resolved with appropriate treatment. This method allows early rehabilitation, with a rapid return of knee movement. There is a lower rate of complications than occurs when external fixation is used on its own. The time of external fixation is shorter than in other methods of leg lengthening. The high risk of infection calls for caution.

Leg lengthening over an intramedullary nail

Abundant implant-derived biomaterial wear particles are generated in aseptic loosening and are deposited in periprosthetic tissues in which they are phagocytosed by mononuclear and multinucleated macrophage-like cells. It has been stated that the multinucleated cells which contain wear particles are not bone-resorbing osteoclasts. To investigate the validity of this claim we isolated human osteoclasts from giant-cell tumours of bone and rat osteoclasts from long bones. These were cultured on glass coverslips and on cortical bone slices in the presence of particles of latex, PMMA and titanium. Osteoclast phagocytosis of these particle types was shown by light microscopy, energy-dispersive X-ray analysis and SEM. Giant cells containing phagocytosed particles were seen to be associated with the formation of resorption lacunae. Osteoclasts containing particles were also calcitonin-receptor-positive and showed an inhibitory response to calcitonin. Our findings demonstrate that osteoclasts are capable of phagocytosing particles of a wide range of size, including particles of polymeric and metallic biomaterials found in periprosthetic tissues, and that after particle phagocytosis, they remain fully functional, hormone-responsive, bone-resorbing cells.

Biomaterial particle phagocytosis by bone-resorbing osteoclasts

We reviewed 173 patients undergoing distraction osteogenesis to determine the incidence, location and timing of fractures occurring as a complication of the procedure.

There were 17 fractures in 180 lengthened segments giving an overall rate of fracture of 9.4%. Unexpectedly, the pattern and location of the fractures were very variable; six were within the regenerate itself, six at the junction between the regenerate and the original bone and five at distant sites in the limb. Of those occurring in the regenerate, five were noted to be associated with compression and partial collapse of the regenerate. In three patients collapse and deformity developed gradually in the distracted segment over the six months after removal of the frame.

The method of treatment of these fractures should be chosen to take into account multiple factors, which are additional and often different from those to be considered during management of acute traumatic injuries. Internal fixation appears to be most appropriate for displaced fractures, although in small children, or in those in whom there has been, or is, infection of the screw tracks, a new period of treatment using external fixation may be needed. Fixation by intramedullary nailing was associated with a risk of infection, even if screw tracks were assessed as healthy at the time of insertion of the nail. Internal fixation with the use of plates is safe for displaced, unstable fractures in children.

A. H. R. W. Simpson

Papers

The response of muscle to leg lengthening

Leg lengthening over an intramedullary nail

Biomaterial particle phagocytosis by bone-resorbing osteoclasts

Leg lengthening over an intramedullary nail

Fracture after distraction osteogenesis