Internal fixation of cervical trauma following corpectomy and reconstruction. The effects of posterior element injury.

Although biomechanical data indicates that anterior fixation alone in unstable cervical injuries may not provide adequate stability, reports of clinical series indicate general success with this method of treatment. The specific contribution of posterior column injury to overall stability following reconstruction has not been evaluated. This study examined the biomechanical stability of anterior and/or posterior plate fixation following anterior corpectomy and reconstruction for unstable cervical injuries with varying degrees of posterior element injury. The C4-C6 motion segments of ten fresh frozen bovine cervical spines were used. After mounting, nondestructive mechanical testing in axial compression, torsion, flexion, extension, and lateral bending was done as an intact control. A C5 corpectomy with reconstruction using a synthetic bone graft was performed and the posterior ligaments sectioned at the C5-C6 level. Each specimen was sequentially instrumented with anterior and posterior plating alone and in combination and each construct was mechanically retested. The specimens were then further destabilized by bilateral facetectomies at C5-C6 and again tested with the same instrumentation combinations. In comparison to the controls, the spines with a C5 corpectomy/bone graft and posterior ligament rupture with anterior plating demonstrated significantly increased stiffness in flexion, extension, and lateral bending; posterior plating increased stiffness in only flexion and lateral bending. In axial compression and torsion, anterior or posterior plating demonstrated stiffness similar to the controls. Further destabilization by facetectomy significantly decreased stiffness of the instrumented construct (less than control) in torsion with anterior or posterior plate fixation alone. Combined plating showed increased stability compared to controls in all loading conditions for both patterns of instability. Anterior plating alone was able to restore the stability of the cervical spines with posterior ligamentous injury after corpectomy, but it failed to do so with the addition of bilateral facetectomies. For the unstable cervical spine with significant bilateral loss of posterior bony contact, anterior or posterior plating alone may not provide sufficient stabilization in the absence of any additional external immobilization. Combined plating should be considered, which may obviate the need for external immobilization.

A new technique for complex fibula fracture fixation in the elderly: a clinical and biomechanical evaluation.

OBJECTIVE: To determine whether intramedullary fixation could augment plate fixation strength in comminuted and osteopenic fibula fractures. STUDY DESIGN: Retrospective clinical study and biomechanical laboratory study. METHODS: Twenty comminuted or osteopenic fibula fractures in twenty patients age fifty years or older were stabilized using plate fixation augmented with intramedullary Kirschner wires. Nineteen patients were available for follow-up which averaged 15.4 months (range, 6-43 months). In conjunction with this clinical series, a biomechanical evaluation was performed comparing fixation of mildly osteopenic fibulas using this technique to plate and screws alone. The fibulas were first tested non destructively in bending, and then destructively in torsion to determine stability and ultimate strength of the fixation. RESULTS: All nineteen fractures united without loss of reduction: seventeen of nineteen patients (89%) had either no pain, slight or mild pain. Biomechanical testing demonstrated that the resistance to bending of the plated fibulas augmented with Kirschner wires was 81% greater than the fibulas stabilized with a plate alone (p < .05). In torsional testing, the augmented group had twice the resistance to motion than the plate group (p < .002). CONCLUSION: This clinical series and biomechanical study support the use of plate fixation augmented with intramedullary Kirschner wires for the treatment of comminuted and osteopenic fibula fractures in the elderly.

Distal femoral fixation: a laboratory comparison of the 95 degrees plate, antegrade and retrograde inserted reamed intramedullary nails.

A biomechanical cadaver study was performed to compare the stability of three standard distal femoral fixation techniques. Eighteen mildly osteoporotic femurs were selected, based on a dual-energy x-ray absorption scanning bone density of 0.3-0.5 g/cm2 and a Singh index of III-IV. After initial mechanical characterization of these intact femurs, a distal femoral osteotomy was created, reduced, and stabilized under compression using random assignment to one of three methods of fixation: (a) six-hole 95 degrees supracondylar plate, (b) retrograde inserted statically locked supracondylar intramedullary nail, and (c) antegrade inserted statically locked Russell-Taylor nail. The instrumented femurs were mechanically tested, a 1-cm gap created, and the femurs retested. The specimens were finally loaded to failure in A-P three-point bending. The 95 degrees plate provided significantly stiffer fixation than the supracondylar intramedullary nail or Russell-Taylor nail in both a compressed transverse and gap distal femoral osteotomy model. The Russell-Taylor nail provided the least rigid fixation. The 95 degrees plate and Russell-Taylor nail had statistically significant greater loads to failure than the supracondylar intramedullary nail. These results support the use of a 95 degrees plate when maximum rigidity of fixation or maximum compression is desired.