Orthopaedic injuries from snowmobile accidents: a multi-centre analysis of demographics, injury patterns, and outcomes.

PURPOSE: More than 2 million people in North America use snowmobiles, resulting in an estimated 200 fatalities and 14,000 injuries annually. The purpose of this study is to document the demographics, orthopaedic injury patterns, and short-term outcomes of patients with snowmobile-related injuries. MATERIALS AND METHODS: A retrospective review was performed at two regional trauma centres in a region where snowmobile use is prevalent. Patients who sustained snowmobile-related injuries over a 12-year period were identified from the hospitals' trauma registries using E-codes (E820-E820.9). Patient demographics were recorded, as were injury characteristics including rates of substance use, open fractures, Injury Severity Score (ISS), Abbreviated Injury Score (AIS) for the extremities, and mortality. Rates of inpatient surgery, as well as hospital and ICU length of stay (LOS), were also recorded. RESULTS: We identified 528 patients with snowmobile-related injuries. Average age was 37 years, and 418 patients (79%) were male. Eighty-eight per cent of all patients with snowmobile injuries were admitted to the hospital with an average LOS of 5.7 days. Among those admitted to the hospital, average ISS was 12.3, and 28% of these patients had ISS > 15. A total of 261 patients (56%) suffered extremity injuries (including 163 upper and 173 lower extremity fractures) with an average extremity AIS of 2.4. There were 700 total fractures (1.5 per patient), and 9% of all fractures were open. A total of 208 patients (45%) suffered head injuries, and 132 patients (28%) sustained vertebral column fractures. A total of 201 patients (43%) required inpatient surgery, and eight patients (1.7%) sustained fatal injuries. CONCLUSIONS: We present a detailed multi-centre analysis of orthopaedic injury patterns and outcomes resulting from snowmobile-related injuries. Patients injured while snowmobiling share similar injury patterns with patients injured in motorcycle and other high-energy motor vehicle accidents.

Failure of larger-diameter metal-on-metal total hip arthroplasty resulting from anterior iliopsoas impingement.

Anterior iliopsoas impingement is a recognized cause of persistent groin pain after total hip arthroplasty. We report 3 patients with failed total hip arthroplasties resulting from anterior iliopsoas and capsular impingement secondary to a metal femoral ball with a diameter larger than the native femoral head. All patients had the same implant design. Resolution of symptoms occurred in all patients after revision surgery. To our knowledge, this is the first report of this potential failure mechanism with these large-diameter implant designs and should be considered in the appropriate clinical scenario.

Case report: the nest technique for management of a periprosthetic patellar fracture with severe bone loss.

Periprosthetic patellar fracture with marked loss of bone stock presents a significant problem in total knee arthroplasty. Treatment outcomes are often unsatisfying and may lead to disruption of the extensor mechanism of the knee. We present a patient with a Type IIIb periprosthetic patellar fracture treated by a novel approach. Three Steinmann pins were used to reduce the patella and form scaffold for bone graft and a patellar button was cemented into the construct. At 7 years followup, the patient has maintained excellent range of motion, reports no knee pain, has healed the patella fracture, and has restored patellar bone stock.

In vitro analysis of anterior and posterior fixation in an experimental unstable burst fracture model.

STUDY DESIGN: A biomechanical comparison of fixation constructs in an experimental fracture model. OBJECTIVE: To determine the relative postoperative stability of anterior graft and plating with that of posterior or combined fixation constructs in an unstable thoracolumbar burst fracture model. SUMMARY OF BACKGROUND DATA: Several treatment modalities have been proposed for unstable thoracolumbar burst fractures, but the optimal technique is unclear. Previous cadaveric biomechanical studies in unstable burst fracture models have not considered the commonly used posterior (interpedicular) and anterior (plate) constructs. METHODS: Nine human spine segments (T11-L3) were potted in epoxy and scanned using dual energy x-ray absorptiometry and computed tomography. Intact specimens had baseline flexibility testing. Unstable L1 burst fractures as verified by computed tomography were created using an impulse load and posterior surgical osteoligamentous destabilization (ie, transection of the lamina, interspinous ligaments, facet capsules, and ligamentum flavum). Specimens were instrumented posteriorly with pedicle screws and rods and tested to 6 Nm in flexion-extension, lateral bending, and torsion. Corpectomy and strut grafting were then performed, and testing was repeated in varying order with posterior fixation, anterior plating and circumferential fixation. Range of motion (ROM) and neutral zone was calculated for each test and fixation groups were compared using analysis of variance. RESULTS: All specimens had AO B1.2 (unstable burst) fractures. Mean ROM for posterior-only constructs was significantly less than that of the intact in lateral bending, flexion, and extension (P<0.001). Anterior-only constructs after corpectomy and strut grafting generally resulted in a smaller ROM versus intact in flexion (NS: P=0.1) and lateral bending (P<0.001). In contrast, all anterior-only and posterior constructs had greater ROM than intact in torsion (all at P<0.05). Circumferential fixation resulted in statistically smaller ROM compared with all other constructs (P< or =0.04), and reached that of the intact specimen in torsion. Increased ROM was correlated with greater fracture comminution for posterior-only fixation (P<0.05), and was weakly correlated with lower dual energy x-ray absorptiometry score (R=0.3) for anterior-only fixation. CONCLUSIONS: Circumferential instrumentation provided the most rigid fixation, followed by posterior fixation with anterior strut grafting, posterior fixation alone, and by anterior fixation with strut grafting. These results were dependent on bone quality and the comminution severity of the fracture. These results should aid surgical decision making in addition to other factors in the overall clinical situation.

Validation, reliability, and complications of a tethering scoliosis model in the rabbit.

This study was conducted to refine a small animal model of scoliosis, and to quantify the deformities throughout its growth period. Subcutaneous scapula-to-contralateral pelvis tethering surgery was selected due to its minimally invasive nature and potential applicability for a large animal model. The procedure was performed in 7-week-old New Zealand white rabbits. Group A animals (n=9) underwent the tethering procedure with a suture that spontaneously released. Group B animals (n=17) had the identical procedure with a robust tether and pelvic fixation, which was maintained for 2 months during growth. All animals developed immediate post-operative scoliosis with a Cobb angle of 23 degrees (range, 6-39 degrees) in group A and 59 degrees (range, 24-90 degrees) in group B animals. During the 2 month post-tethering, group A animals lost their tether and scoliosis resolved, whereas all animals in group B maintained their tether until scheduled release at which time the mean scoliosis was 62 degrees. Immediately after tether release, group B scoliosis decreased to a mean 53 degrees. Over the following 4 months of adolescent growth, the scoliosis decreased to a mean of 43 degrees at skeletal maturity; the decrease usually occurred in animals with less than 45 degrees curves at tether release. Radiographs revealed apical vertebral wedging (mean 19 degrees ) in all group B animals. Sagittal spinal alignment was also assessed, and for group B animals, the scoliotic segment developed mild to moderate kyphosis (mean 28 degrees) and torsional deformity, but the kyphosis resolved by 4 months after tether-release. Complications specific to this technique included a high rate of transient scapulothoracic dissociation and cases of cor pulmonale. In conclusion, this tethering technique in immature rabbits consistently produced scoliosis with vertebral wedging when the tether was intact through the first 2 months of the protocol. The transient exaggeration of kyphosis suggests that the production of scoliosis is not necessarily dependent on lordosis in this model. Because this technique does not violate thoracic or spinal tissues, it may be useful in the investigation of secondary physiologic effects of mechanically-induced scoliosis, and may be scalable to larger animal species.

Measurement of in vivo intradiscal pressure in healthy thoracic intervertebral discs.

STUDY DESIGN: In vivo pressures were measured in radiologically healthy middle and lower thoracic discs in 6 adult volunteers. OBJECTIVES: To quantify and compare intradiscal pressures from the middle and lower thoracic spine during various body positions and maneuvers, and to investigate the potential variation of these pressures with orientation of the measurement transducer. SUMMARY OF BACKGROUND DATA: In vivo intradiscal pressures have been reported for the lumbar spine; however, the authors are unaware of any studies presenting intradiscal pressures in the thoracic spine. METHODS: A specially constructed pressure-sensing needle was inserted into the nucleus pulposa, and pressures were recorded during a variety of body positions and maneuvers in middle and lower thoracic discs in 6 study participants. In three of the body positions, pressures were measured with the needle in both vertical and horizontal orientations to investigate whether the measured pressures were directionally dependent. RESULTS: Intradiscal pressure varied significantly with body position and maneuver, with pressures being greatest in positions where study participants held 10-kg weights in each hand. Disc level and orientation of the pressure needle did not significantly influence intradiscal pressure. In some body positions, thoracic intradiscal pressures were significantly different from previously reported pressures from the lumbar spine. CONCLUSIONS: Thoracic intradiscal pressure was significantly influenced by body position and maneuver but not disc level. Intradiscal pressures are useful for gaining greater insight into the biomechanics of the thoracic spine.