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Current population studies characterize idiopathic scoliosis as a single-gene disorder that follows the patterns of mendelian genetics, including variable penetrance and heterogeneity. The role of melatonin and calmodulin in the development of idiopathic scoliosis is likely secondary, with indirect effects on growth mechanisms. Reported abnormalities of connective tissue, skeletal muscle, platelets, the spinal column, and the rib cage are all thought to be secondary to the deformity itself. Although no consistent neurological abnormalities have been identified in patients with idiopathic scoliosis, it is possible that a defect in processing by the central nervous system affects the growing spine. The true etiology of idiopathic scoliosis remains unknown; however, it appears to be multifactorial.

The clinical outcome of posterolateral lumbar and lumbosacral fusions with facet screw fixation using the Boucher technique is reviewed retrospectively. The Boucher technique uses AO cortical screws that traverse the facet joint at an angle from the superior lamina, in a medial to lateral direction, to enter the respective inferior pedicle. The procedure was performed on 57 consecutive patients who had a degenerative disk disease. The pre-operative diagnosis was based on a physical examination and radiographs with myelography performed when deemed necessary. Surgery had been indicated and performed on patients with unresolved pain after 6 months of conservative therapy; radiographic signs of disk space narrowing, facet arthrosis, degenerative spondylolisthesis or instability on flexion and extension views. No prior history of spinal surgery, no involvement in any litigation or Workers Compensation process, and no detected psychiatric disturbances were also inclusion criteria for this study. Eighteen consecutive male and 39 consecutive female patients were included in the study. The average age at the time of surgery was 41.8 years. The mean active clinical follow-up (office visits) time was 5.06 months with the minimum follow-up time of 3 months. Two years after their surgery, all the patients were asked to fill out a questionnaire from which their progress was evaluated. All questionnaires were completed and returned. Postoperatively, patients were placed in either a lumbosacral corset, short rigid lumbosacral molded polypropylene brace or body cast. Overall clinical results for single level fusions showed that 91.2% of patients (31 of 34) had excellent results and 8.8% (3 of 34) had poor results. Of the multiple level fusions, 86.4% of patients (19 of 22) had excellent or good results and 9.1% (2 of 22) had poor results. Post-operative complications included only three wound infections at the iliac crest donor site. This study demonstrates that facet screw fixation using the Boucher technique has advantages. The technique not only is easy to implement by placing a small screw through a facet joint and it's respective pedicle, but produces excellent clinical results that are comparable to the other more bulky spinal instrumentation systems.

The author presents the basic biomechanical concepts linked with spine implant testing. The paper also contains the methodology of in vitro and in vivo spine implant testing. The physical and biological properties of various materials and devices commonly used in spine surgery are discussed in relation to their role in spine surgery. The paper clearly shows how all these parameters influence surgical strategy for the spine and more importantly how the choice of methods and devices influences the long term results of spinal surgery. The author also presents the biomechanical repercussions of a failed spine and his own concept of an "ideal" fusion.

At times one pedicle screw cannot be used in a posterior construct because of morphometric reasons or when the pedicle is fractured intraoperatively. It is not clear from the literature whether and to what extent a construct's stability is compromised by substituting a hook claw for one pedicle screw. A synthetic vertebra model using a hook claw in lieu of a pedicle screw in a compressive and torsional mechanical study is evaluated. Isola screw-based constructs varying in the number of pedicle screws and hook claws were used. To recreate a realistic clinical scenario, transverse connectors and a Harms cage were used as well. In compression, substituting screws with claws did not substantially change the stiffness, whereas substituting one or two pedicle screws with one or two hook claws significantly reduced torsional stiffness. We conclude that using one or two hook claws is a viable alternative for pedicle screws when the latter cannot be used in a clinical situation, especially as an adjunct when the anterior column is reconstructed.

Appropriate levels for instrumentation and fusion in scoliosis have been a matter of debate among surgeons since the introduction of operative management of this deformity. We set out to examine the hypothesis that the amount of correction achieved in all planes during surgical instrumentation of a curve should be less than, or comparable to, the degree of correction attainable at any non-instrumented adjacent curve. An algorithm was designed to facilitate preoperative planning and intraoperative performance of spinal fusion procedures in the management of scoliosis. To test the validity of the hypothesis and the proposed algorithm, measurements were taken from the preoperative radiographs of 200 patients. The dimensions of the curves were obtained from an initial set of four X-ray films: (1) standing anteroposterior film of the whole spine, (2) standing lateral film of the whole spine, (3) two properly performed side-bending films including each curve of the spine. With this data, a plan was designed using the algorithm. The results of this plan were compared with the actual results of the surgery, which were revealed only at this stage. All patients in whom actual instrumentation levels fell within those predicted by the proposed algorithm had no imbalance at follow-up. All patients whose actual instrumentation levels were short of those recommended by the algorithm showed obvious imbalance on final postoperative standing radiograph.

To determine the net contribution of a spinal construct to stability, and whether extending the construct to another level in situations in which a defective pedicle cannot have a screw inserted, we performed biomechanical tests in which we evaluated three-, four-, and five-level synthetic spinal constructs in which the location and number of pedicle screws were varied above and below a vertebrectomy defect. We subjected all constructs to axial, compression, lateral bending, flexion, extension, and torsional forces with the use of an Instron biaxial machine. Left-right symmetrical constructs were more stable than asymmetrical ones. Three-level constructs were statistically stiffer than the longer ones in compression, left bending, and flexion. Torsional stability, however, was greater in the longer constructs. Five-level constructs with both end screws in place had greater torsional stiffness than when they were missing a screw. In vertebrectomy defects, if four screws cannot be placed across it, then the engagement of two screws is indicated. The stability provided by a single screw at a spinal level is minimal. Additional screws augment the purchase of the construct in the bone; however, they do not afford further protection to the defect.

Familial dysautonomia (FD) is a rare autosomal recessive disease occurring in Jews of Ashkenazi descent, with only some 500 recognized cases. The causative gene was identified on chromosome 9. FD is of considerable orthopedic interest, because of the prevalence of skeletal deformity. About 90% of surviving dysautonomic children will develop a spinal curvature, commonly a scoliosis. The scoliotic curve is usually kyphotic rather than lordotic, and appears during the first decade of life. Fifty-one of the 90 reported cases of familial dysautonomia in Israel involved patients who were seen at the scoliosis clinic for assessment and treatment of their spinal deformities. Most of the patients presented with a scoliotic deformity associated in 37 cases with an increased thoracic kyphosis. In our series orthotic treatment and physiotherapy were found to be minimally successful at best. Surgical treatment of the spine was performed in 13 of 51 patients in this series. A retrospective review of these patients' charts and radiographs was carried out. Six years of follow-up are reported. The primary indication for surgery was progression of the spinal curve. Only posterior spinal fusions were performed. Anterior transthoracic procedures were avoided in spite of the significance of the kyphotic deformity, because of the frequency of pulmonary complications. Harrington distraction and compression instrumentation was used. Three-millimeter compression rods were used in a distraction mode in thin, young children. "Harri-Luque" segmental sublaminar wiring technique and Wisconsin spinous process segmental wiring was used in some. In all cases, the spine fusion was supplemented by bank bone only, to avoid the additional trauma of graft removal. We believe that surgical intervention is advantageous, if done early in the evolution of spinal deformity. Greater technical difficulties and a higher complication rate were encountered in this series relative to the problems usually seen after spinal deformity surgery in children; this is all the more important in a disease in which general anesthesia is an additional major complicating factor. It is hoped that the improved physical condition now seen after early gastrostomy and fundoplication will aid in reducing this high complication rate. Only a small degree (about 25%) of correction was achieved in the majority of patients. Some of this apparent rigidity derived from the inability to apply sufficient instrumental corrective force because of the friable osteoporotic bone. After surgery, there was a marked decrease in the frequency of pneumonia and an improvement in the degree of ataxia, for reasons not understood, which led to an obvious improvement in the quality of life.

Biomechanical studies have shown hooks to be superior to pedicle screws in pull-out, especially in osteoporosis. This study evaluates the possible increase in stiffness of pedicle screws provided by laminar hooks while applying non-destructive forces to a vertebrectomy model assembled with Compact Cotrel Dubousset (CCD) instrumentation. Synthetic vertebrae were employed in a three-level vertebrectomy model. CCD screw-based three-level constructs with and without sublaminar hooks in the caudal element were tested in flexion, extension, compression, lateral bending, and torsion. There was no statistically significant advantage in adding inferior laminar hooks to a caudal end vertebra that had bilateral pedicle screws in any of the testing modes. Torsional stability, however, was augmented, but not significantly. Torsional instability and osteoporotic bone may be the clinical justifications for adding laminar hooks below screws in the caudal end vertebra.

Degenerative changes in the spine, specifically disc degeneration and facet arthrosis, and osteoporosis are conditions that primarily affect the elderly and may significantly impact the quality of life. The relationship between osteoporosis and degenerative changes in the hip joint has been studied, but their correlation in the spine is not entirely clear. Two hundred ninety-four subjects older than 50 years of age were retrospectively studied for the existence of lumbar spinal degeneration and osteoporosis through radiologic examination for 3 clinical manifestations: (1) disc degeneration, (2) facet joint arthrosis, and (3) lumbar osteoporosis. Peripheral osteoporosis in the distal radius of the nondominant hand was measured using a single-photon bone absorptiometer. Results indicated that subjects with severe osteoporosis in the distal radius also had severe degenerative changes in the discs and the facets; those with mild osteoporosis in the distal radius showed a tendency to have a lesser degree of degenerative changes than the subjects without osteoporosis.

When introduced, the Wisconsin segmental spine instrumentation (WSSI) and the Cotrel Dubousset instrumentation (CDI) were promoted as technical advances for the correction of spinal deformities. Both systems provide acceptable correction and greatly reduce the need for postoperative immobilization. A retrospective study of a homogeneous group of 53 adolescent patients with idiopathic scoliosis with King Type II curves who had reached skeletal maturity at follow-up was conducted to compare and analyze the results of these two systems. Thirty-six of these patients had been operated on using WSSI and 17 had been operated on using CDI. CDI and WSSI were found to be equally effective in treating King Type II curves. No difference was found between the two groups in the fusion rates, spinal balance, time required for surgery, or amount of curve correction. The answer to the question of which system is "better" depends on the surgeon's experience and familiarity with the equipment.

During the 10-year period 1981-1990, 59 patients suffering from spinal cord or cauda equina compression underwent anterior spinal decompression and in most cases spinal restabilization with methylmethacrylate cement and/or instrumentation. Follow-up in 55 patients showed that 75% were improved neurologically by the procedure, one-third of these showing complete recovery from the spinal cord compression. The results in younger female patients suffering from metastatic breast cancer were considerably better than those of older men with prostatic metastases. Other genitourinary system tumors also had a relatively poorer prognosis. There was a significantly better result for metastatic lesions of the thoracic or thoracolumbar spine than for lesions in the lumbar spine causing cauda equina paralysis.

Two cases are reported of avascular necrosis of the femoral head occurring as a late complication of an intertrochanteric fracture. The cases are presented to emphasize the importance of including this condition in the differential diagnosis of any late clinical deterioration following such an injury.

Three patients with ankle fractures are presented to demonstrate poor results due to improper application of a syndesmotic screw. In these cases failure of surgical treatment caused accelerated disruption of the ankle mortise with cartilage wear, or instability and joint distraction. Simple internal fixation with a single screw requires strict awareness of the potential harm that can be inflicted on the joint. The syndesmotic screw has to be inserted with a proper understanding of the biomechanics of ankle joint structures.

As the patient population grows, strategies for preventing osteoporosis and for improving its management are urgently needed. Coordinating the efforts of existing hospital programs may help to meet these goals.

Spinal imaging has rapidly evolved into a complex diagnostic field requiring specialized expertise. While many imaging modalities reveal portions of a topographic map of the spine necessary for surgery, only magnetic resonance imaging emerges as the imaging modality of widest and most efficacious first choice. With the increasing high-technology sophistication of modern imaging modalities, the spine surgeon must become completely conversant with the radiologic data produced by these imaging techniques. The authors present a logical approach to spinal imaging--an algorithm--based on etiologic classification and aimed at conserving medical resources and developing an optimal diagnostic pathway for spine injury and disease. Spine surgeons are urged to incorporate the interpretative insights of radiologists into the diagnostic process.

A modified form of judo training was practiced by a class of 7 blind, mentally retarded children with associated neuropsychiatric disturbances. The biweekly training program lasted for 6 months. Analysis indicated improvements in physical fitness, motor skills, and psychosocial attitude. The authors concluded that a modified form of judo can be used as a therapeutic, educational, and recreational tool for multiply handicapped children.

In an attempt to explain the increased frequency of pathological fractures found in thalassemia major patients, we examined noninvasively several properties of bones in 17 patients. We found a significant decrease in the bone mineral content (BMC) and the bone density (BD) of both trabecular (34% and 4% diminution, respectively) and cortical bone (24% and 3% diminution, respectively), as compared with normal controls. We also found that metacarpal cortical indices (CI) were significantly lower in thalassemic patients as compared with normal controls (36% diminution). As expected, upper limb fractures were more frequent in those patients with greater bone diminution. Furthermore, the degree of bone diminution was greater in patients receiving fewer blood transfusions and shorter courses of desferrioxamine. Bone densitometry should probably be included in the comprehensive evaluation of thalassemia patients in order to help guide overall treatment.

The incidental occurrence of lumbar spine fractures in individuals with preexisting first degree lumbosacral isthmic spondylolisthesis may be looked upon as a simulated in vivo biomechanical experiment testing the stability of the lumbosacral subluxation. Among 200 patients with thoracolumbar spine fractures managed at the author's institution during the period of 1980-1989, five such cases were collected. All patients had a grade I isthmic spondylolisthesis at the L5-S1 level, and all sustained a burst fracture of the lumbar spine. In two patients, there was a previous history of low back pain and lumbosacral spondylolisthesis. In the other three patients, the olisthesis was judged to be old by a negative 99mTc-MDP bone scan, whereas the fractured vertebra showed intense uptake and/or by the negative operative findings at L5-S1 level during surgery. It was found that the incidence of lumbosacral spondylolisthesis in patients with thoracolumbar fractures was smaller than in the general population but the difference was not statistically significant (p = 0.213). In addition, it is concluded that mild lumbosacral spondylolisthesis can absorb considerable axial loading without an ascertainable evidence of damage.

This study examines the relation between the nature of acoustic emission signals emitted from cancellous bone under compression and the mechanical properties of the tissue. The examined bone specimens were taken from 12 normal, 31 osteoporotic and six osteoarthritic femoral heads. The mechanical behaviour of the osteoporotic bone specimens was found to be significantly different from that of the normal specimens both in the pre-yield and post-yield ranges. In the osteoarthritic bones only the elastic behaviour was significantly different. The rates of acoustic events before yield and beyond it were found to be significantly higher both in the osteoporotic and osteoarthritic bone specimens. The average peak amplitude of the signals was also significantly higher in the diseased bones. Stepwise regression analysis showed that a combination of the acoustic emission parameters could significantly predict some mechanical properties of the bone. The energy absorbed during compression and the ultimate compressive stress of the specimens could be estimated from the rate of pre-yield acoustic events, the average amplitude of the signals and the rate of post-yield events. However, the explanation power of the acoustic emission parameters was only moderate. The nature of acoustic emission signals was thus demonstrated to be a potential tool for assessing bone quality.

Thirty three fresh femora from 18 cadavera were loaded to fracture at a deformation rate of 5 mm/min to study the effect of density of the cancellous core in fracture initiation of the femoral neck. The neck of the femur was modelled as a composite beam subjected to bending and the ultimate strength of the bone at the superior aspect of the neck was calculated from the model, which was fed by the mechanical tests and geometry measurements. The area porosity of the cancellous core was introduced into the beam model after measuring the apparent density of dry fat-free bone for each specimen. The results showed a strong dependence between the ultimate strength obtained and the cancellous bone density, the latter previously measured for each specimen by the non-invasive Compton scattering technique. Area porosity of the femoral neck was found to have little effect on the results obtained, permitting the use of an average value for this parameter in calculating the ultimate strength of the neck of the femur.

Disseminated intravascular coagulopathy is a serious complication of numerous pathological conditions, particularly metastatic cancer. It is rarely encountered in orthopaedic surgery. Prompt recognition and treatment is required to prevent death. We describe two patients with pathological fractures of the proximal femur due to metastatic disease who died from disseminated intravascular coagulation after operation. A high index of suspicion, careful monitoring of the clotting mechanism and prompt treatment are required.

Thirty-four femoral necks from human cadavers were measured by techniques assessing bone density and bone mineral density, and by the Singh index. These methods are based on photon interaction with biological components and can be applied noninvasively for clinical evaluation of changes in skeletal status. Trabecular bone volume, mineralized bone volume, and relative osteoid volume were evaluated histomorphometrically using undecalcified histologic sections obtained from the same samples. The trabecular and mineralized bone volumes showed significant correlations with the bone density and mineral density. These results enhance the validity of recently developed photon-interaction techniques for evaluating bone properties.

The effect of intense physical training on the bone-mineral content of young adults who are unaccustomed to physical activity has not yet been established. In this study, 268 male recruits, eighteen to twenty-one years old, were evaluated before and after fourteen weeks of strenuous physical training. The bone-mineral content of both legs at the level of the distal third of the tibia in each individual was measured using single-beam photon absorptiometry. The subjects started their training with equal values for bone-mineral content in both legs. During the training period, the average bone-mineral content of the left leg increased by 11.1 per cent and that of the right leg, by 5.2 per cent. In the group of subjects who did not complete the training course, mainly because they incurred stress fractures, the increase in bone-mineral content was significantly less than the increase in those who completed the program. This study indicated that in young adults a high level of loading of bone results in either a stress fracture or a rapid increase in bone-mineral content.

The bone density, mineral content and average shear stress in bending at failure were measured in vitro in 33 femoral necks of women and men of different ages. The correlations between these three parameters as well as their correlation with the Singh index were carefully analyzed and found to show that the Singh index is of no clinical value. The best correlation exists between bone density and shear stress at failure. Practically no correlation is found between the breaking stress and Singh index. The breaking stress decreases with age much faster than the bone density or bone mineral content. The correlation between the work to fracture and the bone density or its mineral content is only moderate. The bone density is best indicator for the compressive bone strength. The changes of bone strength are apparently influenced by factors other than the bone density and mineral content, although the possibility that small changes in bone density or mineral content cause large changes in bone strength cannot be excluded.

Four patients sustaining tarsal navicular body fractures are presented. Analysis based on these cases and on 36 patients suffering from identical fractures reported in the literature led to a new mechanical assumption: the axial compression on the foot, as a result of falling from height, causes impaction of the talus into the body of the navicular bone. The clinical followup results reported are usually disappointing. Favorable results are obtained in a vertical two-part fracture, by an open reduction and internal fixation of the tarsal navicular body fracture. In highly comminuted fractures, talo-navicular-cuneiform arthrodesis can be carried out.

Epidural methadone analgesia was initiated soon after admission to emergency room in elderly patients who sustained osteoporotic proximal femoral fracture and who were considered to be high surgical risks. The severe pain was significantly reduced, enabling early mobilization of the patients. The analgesia was discontinued only when nonnarcotic analgesia sufficed. The treatment lasted for about 3.5 weeks. One minor complication was observed during the treatment period. We concluded that patients who have femoral neck fracture who are at high risk for operation and have to be observed and stabilized before operation can be managed by continuous epidural methadone analgesia.

Six patients with spinal cord compression as the presenting symptom of malignant lymphoma are described. These patients suffered from back pain for several months and were diagnosed after sudden paraparesis appeared. Five patients were treated by operative decompression followed by local irradiation, and all regained their motor function. A sixth patient presented with a more insidious paraparesis. A bone marrow aspiration established the diagnosis of malignant lymphoma, and this patient recovered with radiation and steroids alone. Thus, we recommend considering malignant lymphoma as a possible cause of acute cord compression, attempting to establish the diagnosis on an emergency basis within several hours, and attempting to achieve decompression with local radiotherapy and intravenous dexamethasone.

A group of 223 military recruits aged 18-21 years underwent strenuous physical training for a period of 14 weeks. The absolute bone density of the distal tibia in both lower limbs was measured before the training period and at its end. The density was determined by the Compton scattering technique, which has been developed in our laboratory; this method provides the bone mass of all bone constituents per unit volume. The distribution curve of the bone density in both tibiae shifted to higher values at the end of the training period. The mean bone density in the right and left tibia increased significantly by 7.5%. This study indicates that following an intensive physical exercise regime, a significant increase in the mass density of bone can be obtained in young adults within a short period.

The density of the distal radius in the non-dominant forearm was measured non-invasively by Compton spectrometry in 234 post-menopausal women. The density of the trabecular tissue was determined almost independently from that of cortical tissue by horizontal and vertical scanning of the bone. It was found that the lower the density of the trabecular bone, the greater the difference between the density of the cortical and trabecular bone. As osteoporosis progresses, trabecular bone density in the distal radius seems to decrease faster than that of compact bone. Hence the severity of the disease is best determined by measuring the density of trabecular bone.