Spinal cord injury models in non human primates: are lesions created by sharp instruments relevant to human injuries?

The worldwide incidence of traumatic spinal cord injury (SCI) is approximated at 180,000 new cases per year. Experiments using nonhuman primates (NHP) are often used to replicate the human condition in order to advance the understanding of SCI and to assist in the development of new treatments. Experimental spinal cord lesions in NHP have been created by a number of methods including blunt trauma, epidural balloons, circumferential cuffs, and dropping a precision weight over the spinal cord. As well, experimental lesions have been created with sharp instruments after opening the dura mater. However, spinal cord lesions that are created with a sharp instrument in NHP experiments may not replicate the clinical and pathological features of human spinal cord injury. Researchers should recognize the challenges associated with making clinical inferences in human SCIs based on NHP experiments that created experimental lesions with a sharp surgical instrument.

Acute traumatic spinal cord injury induces glial activation in the cynomolgus macaque (Macaca fascicularis).

BACKGROUND: Traumatic spinal cord injury leads to direct myelin and axonal damage and leads to the recruitment of inflammatory cells to site of injury. Although rodent models have provided the greatest insight into the genesis of traumatic spinal cord injury (TSCI), recent studies have attempted to develop an appropriate non-human primate model. METHODS: We explored TSCI in a cynomolgus macaque model using a balloon catheter to mimic external trauma to further evaluate the underlying mechanisms of acute TSCI. RESULTS: Following 1hour of spinal cord trauma, there were focal areas of hemorrhage and necrosis at the site of trauma. Additionally, there was a marked increased expression of macrophage-related protein 8, MMP9, IBA-1, and inducible nitric oxide synthase in macrophages and microglia at the site of injury. CONCLUSIONS: This data indicate that acute TSCI in the cynomolgus macaque is an appropriate model and that the earliest immunohistochemical changes noted are within macrophage and microglia populations.

The acetabular blood supply: implications for periacetabular osteotomies.

As the popularity of juxta-acetabular osteotomies in adults increases, concern arises that such a procedure will potentially cause avascular necrosis of the acetabular fragment. In order to verify the remaining vascularization after a Bernese periacetabular osteotomy, an injection study with colored latex was performed. The vascularity of the outside of the periacetabular bone was studied in 16 hips after injection of colored latex into the abdominal aorta and the inside in four hips. To confirm the conclusions drawn from the anatomic study, a Bernese periacetabular osteotomy was performed in two additional hips after latex injection. This study demonstrated that through a modified Smith-Peterson approach and with execution of the osteotomies from the inside of the pelvis the acetabular fragment remains vascularized by the supra-acetabular and acetabular branches of the superior gluteal artery, the obturator artery and the inferior gluteal artery. Some uncertainty remains about how much correction is tolerated by the smaller blood vessels.

Irreducible dislocations of the cervical spine with a prolapsed disc: preliminary results from a treatment technique.

STUDY DESIGN: The preliminary results from a treatment technique for irreducible dislocations of the cervical spine with prolapsed disk are reported. OBJECTIVE: To report the success of a technique for grafting and instrumentation of the anterior cervical spine before reduction. This technique is useful in cervical fracture-dislocations irreducible through the anterior approach that must be approached first from the front because of a prolapsed disc. SUMMARY OF BACKGROUND DATA: In the treatment of cervical facet dislocations, a third anterior procedure often is necessary to accomplish the anterior instrumentation and fusion. The reported technique describes a method that eliminates this third procedure by using a cervical buttress plate. METHODS: Between August of 1996 and October 1998, four patients had dislocation of the cervical spine with a prolapsed disc that could not be reduced using the anterior approach. After discectomy and endplate preparation, a tricortical bone graft was harvested from the iliac crest, placed in the interspace, and held with a buttress plate screwed in two places into the superior vertebral body. The anterior wound then was closed. The posterior elements were exposed and the facets reduced by flexing the neck and posteriorly translating the superior segment. Fluoroscopy was used during the reduction to ensure that the graft was pulled into the interspace, that the screws in the buttress plate did not pull out of the superior vertebral body, and that the reduced graft did not impinge on the spinal cord. A posterior fusion was performed and the posterior wound closed. RESULTS: All the patients had consolidation of both anterior and posterior fusions. No cases of instrument failure occurred, either anteriorly or posteriorly. No cases of neurologic deterioration occurred, and no complications were attributable to the use of this technique. CONCLUSION: The reported technique was used successfully in the treatment of four patients with irreducible dislocations of the cervical spine.

Use of magnetic resonance imaging in evaluating injuries to the pediatric thoracolumbar spine.

Magnetic resonance imaging (MRI) of acute thoracolumbar spinal injuries allows excellent evaluation of the neurologic and soft tissue structures. Owing to recent advances in imaging techniques that permit greater spatial resolution and more detailed imaging of tissue, MRI now affords effective visualization of injury to the ligaments, intervertebral disk, bones, and spinal cord after spine trauma. Cord changes have been classified into three patterns that are predictive of clinical outcomes in adults with cord injuries. The value of MRI in evaluating pediatric patients with thoracolumbar injuries or in predicting their clinical outcome has not been assessed. After retrospectively reviewing 19 pediatric thoracolumbar fractures associated with neurologic deficits from three level 1 trauma centers, we conclude that MRI is the imaging modality of choice in these patients because it can accurately classify injury to bones and ligaments and because the cord patterns as determined by MRI have predictive value.

The anatomy and function of the gluteus minimus muscle.

In order to investigate the functional anatomy of gluteus minimus we dissected 16 hips in fresh cadavers. The muscle originates from the external aspect of the ilium, between the anterior and inferior gluteal lines, and also at the sciatic notch from the inside of the pelvis where it protects the superior gluteal nerve and artery. It inserts anterosuperiorly into the capsule of the hip and continues to its main insertion on the greater trochanter. Based on these anatomical findings, a model was developed using plastic bones. A study of its mechanics showed that gluteus minimus acts as a flexor, an abductor and an internal or external rotator, depending on the position of the femur and which part of the muscle is active. It follows that one of its functions is to stabilise the head of the femur in the acetabulum by tightening the capsule and applying pressure on the head. Careful preservation or reattachment of the tendon of gluteus minimus during surgery on the hip is strongly recommended.

The management of severe acetabular bone loss using structural allograft and acetabular reinforcement devices.

The cases of 37 acetabular reconstructions in 35 patients with major structural pelvic bone loss were reviewed. At an average follow-up of 7.1 years, patients rated their results as excellent in 12 cases (32.4%), good in 22 (59.5%), fair in 2 (5.4%), and poor in 1 (2.7%). Thirty-four cases (91.9%) were classified as a clinical success. Thirty-six allografts (97.3%) had radiographic evidence of full incorporation. Of the unrevised hips, 1 (2.7%) was classified as definitely loose, 2 (5.4%) as probably loose, and 4 (10.8%) as possibly loose. One revision of an acetabular component was required because of late sepsis. This is the first reported series on the use of acetabular reinforcement devices with solid bulk allograft covering more than 50% of the socket. The allograft is protected in the early postoperative period, superior migration of the cup is virtually eliminated as a complication, and the incidence of aseptic loosening is greatly diminished.

Lateral insufficiency fractures of the femur caused by osteopenia and varus angulation: a complication of total hip arthroplasty.

Lateral femoral insufficiency fractures in total hip arthroplasty occur due to osteopenia and varus positioning of the femoral component, the femur itself, or both. The presentation of these fractures can be unclear but usually involves the insidious onset of unexplained thigh or groin pain. The patients are likely to have significant comorbidities as well. Characteristic radiographic findings may be present, depending on when the patient presents. The insufficiency fractures generally occur at the level of the femoral stem tip on the lateral cortex of the femur. If left untreated, pain and loss of function continue. Eventually an insufficiency fracture can progress to a displaced periprosthetic fracture. Nonsurgical treatment is not successful. Recommended treatment involves revision to a long-stem femoral component. The risk of postoperative complications is significant.

Treatment of thoracolumbar burst fractures without neurologic deficit by indirect reduction and posterior instrumentation: bisegmental stabilization with monosegmental fusion.

This study retrospectively reviews 20 sequential patients with thoracolumbar burst fractures without neurologic deficit. All patients were treated by indirect reduction, bisegmental posterior transpedicular instrumentation and monosegmental fusion. Clinical and radiological outcome was analyzed after an average follow-up of 6.4 years. Re-kyphosis of the entire segment including the cephaled disc was significant with loss of the entire postoperative correction over time. This did not influence the generally benign clinical outcome. Compared to its normal height the fused cephalad disc was reduced by 70% and the temporarily spanned caudal disc by 40%. Motion at the temporarily spanned segment could be detected in 11 patients at follow-up, with no relation to the clinical result. Posterior instrumentation of thoracolumbar burst fractures can initially reduce the segmental kyphosis completely. The loss of correction within the fractured vertebral body is small. However, disc space collapse leads to eventual complete loss of segmental reduction. Therefore, posterolateral fusion alone does not prevent disc space collapse. Nevertheless, clinical long-term results are favorable. However, if disc space collapse has to prevented, an interbody disc clearance and fusion is recommended.

The Bürch-Schneider anti-protrusio cage in revision total hip arthroplasty: indications, principles and long-term results.

Patients who had a revision total hip arthroplasty using the Bürch-Schneider anti-protrusio cage (APC) by a single surgeon have been reviewed after a minimum of five years. There were 63 operations in 58 patients with an average age of 63 years (41 to 83) at the time of revision. At an average follow-up of 8.5 years (5 to 18), 15 patients (25.9%) rated their results as excellent, 38 (65.5%) as good, and five (8.6%) as fair. Five further revisions of the acetabular prosthesis were required, three due to aseptic loosening, one for recurrent dislocation and one due to sepsis. Of the remainder, one was definitely loose, two probably loose, and 12 possibly so. Impressive augmentation of bone stock can be achieved with the anti-protrusio cage, while enabling the hip to be centred in its anatomical position.

Intraoperative assessment of femoral head vascularity after femoral neck fracture.

OBJECTIVES: To develop an intraoperative technique to predict the development of avascular necrosis after internal fixation of femoral neck fractures. DESIGN: Prospective study. SETTING: All patients were treated at the same hospital. PATIENTS/PARTICIPANTS: Sixty-four patients who presented for internal fixation of a femoral neck fracture were enrolled in the study. INTERVENTION: A 2.0-millimeter drill was used to assess the presence and character of bleeding from the femoral head at open reduction and internal fixation of a femoral neck fracture. MAIN OUTCOME MEASUREMENTS: Patients were evaluated postoperatively by history, examination, and roentgenography for the development of avascular necrosis of the femoral head fragment. A minimum two-year follow-up with radiography was required for entry into the study, with an average follow-up of 3.2 years. RESULTS: None of the fifty-six patients with bleeding from the drill holes in the femoral head fragment developed avascular necrosis. Eight of eight patients with no bleeding after reduction developed avascular necrosis. There were no infections or nonunions. CONCLUSIONS: Intraoperative drilling of the femoral head is a highly sensitive and specific predictor for the development of avascular necrosis after femoral neck fractures.

Total hip arthroplasty with use of an acetabular reinforcement ring in patients who have congenital dysplasia of the hip. Results at five to fifteen years.

The purpose of our study was to examine the clinical and technical problems associated with reconstruction of the hip in patients who had congenital dysplasia and to offer recommendations for their solution. We reviewed the records on 123 consecutive total hip arthroplasties that had been performed by one of us (M. E. M.), between 1981 and 1986, for the treatment of coxarthrosis due to congenital dysplasia of the hip. A minimum of five years of follow-up was required for inclusion in the study. The study group consisted of seventy patients who had had a total of eighty-seven reconstructions. According to the classification of Crowe et al., eleven hips had type-IV acetabular dysplasia; sixty-five, type-II; and eleven, type-II. Acetabular reconstruction was performed with use of the Müller acetabular roof-reinforcement ring and a polyethylene cup, which was inserted with cement. Autologous graft from the femoral head was used in forty-two hips. Femoral reconstruction was performed with use of the Müller straight-stem component for congenital dysplasia of the hip in eighty hips and with use of a standard Müller straight-stem component in seven hips. At an average of 9.4 years (range, five to fifteen years) postoperatively, the result was described as excellent for sixty hips (69 per cent), as good for twenty-three (26 per cent), as fair for two (2 per cent), and as poor for two. Nine (10 per cent) of the hips had been revised. One revision had been performed because of aseptic loosening of the acetabular component; one, because of aseptic loosening of the femoral component; one, because of aseptic loosening of both components; and six, because of infection. Of the unrevised hips, three had had superior migration of the acetabular component of less than five millimeters, and mild protrusion had developed in one. Two hips had a continuous radiolucent line around the acetabular construct. Two hips had had subsidence of the femoral stem of less than three millimeters; one had a complete, non-progressive radiolucent line at the bone-cement interface; and four had a radiolucent line at the proximal part of the bone-cement interface. Six hips had evidence of endosteal osteolysis. Six hips had grade-III or IV heterotopic ossification according to the system of Brooker et al. These results compare favorably with others in the literature. We recommend restoration of the anatomical hip center with the use of an acetabular roof-reinforcement ring and a polyethylene cup inserted with cement for the reconstruction of a deficient acetabulum. The acetabular reinforcement ring prevents resorption of bone graft and migration of the cup, which are major causes of failure of the cup in patients who have had a reconstruction of a deficient acetabulum. Bone graft should be used medially and superiorly as needed to augment bone stock notably. Cement should not be used to fill acetabular defects as we believe that it contributes to aseptic loosening.