Mechanical factors in electrode-induced osteogenesis.

Previous experiments have suggested that mechanical activity of electrode implants may contribute to the observed bone formation that has been attributed to the electrical currents. This was tested by implanting movable and stationary wires in the medullary canal of the rabbit femora or tibiae. The moving implants uniformly showed significant medullary bone formation at the wire, whereas the stationary ones did not. This bone persisted for as long as 8 weeks and was mostly resorbed by 12 weeks as the implants became fixed. The new trabecular bone closely resembled that typically seen at electrically active implants. Implant motion may have a more important role in electrically induced osteogenesis than previously thought.

Radiography and computerized tomography in the diagnosis of incongruity of the distal radio-ulnar joint. A prospective study.

The diagnosis of subluxation or dislocation of the distal radio-ulnar joint may be difficult to confirm by routine radiographs. We undertook a prospective evaluation of fifteen patients with acute or chronic pain in the distal radio-ulnar joint, using both standardized radiographs and computer assisted tomography. In the absence of a deformity of the distal end of the radius, a lateral radiograph made with the wrist in the neutral position accurately revealed incongruency of the distal radio-ulnar joint. When pain or cast immobilization prevented optimum positioning of the wrist for radiography, or when a deformity of the distal end of the radius was present, computer assisted tomography gave a more accurate determination of the congruency of the joint.

Conservative treatment of fractures of the thoracic and lumbar spine.

Patients with burst fractures of the thoracic and lumbar spines must receive individualized case analysis before a course of therapy can be decided. A consideration of fracture stability, degree of canal compromise, and patient evaluation becomes significant in determining operative or nonoperative treatment. In neurologically intact patients with selected fractures, nonoperative treatment can be successful in the functional rehabilitation of the patient.

Bony entrapment of the superficial peroneal nerve.

Peripheral nerve injury occasionally results from long bone fractures, but bony entrapment of a peripheral nerve occurs infrequently. Bony entrapment of a peripheral nerve is usually associated with upper extremity fractures. In a 34-year-old man bony entrapment of the superficial peroneal nerve occurred in a healed midshaft fibular fracture. The patient complained of progressive pain over the distribution of the superficial peroneal nerve after sustaining a closed displaced tibial and fibular fracture that healed in nonanatomic alignment. Exploration revealed bony entrapment of the superficial peroneal nerve in the fracture callus, with reactive neuroma formation. Excision of the neuroma resulted in complete relief of the symptoms. Persistent pain over the distal anterolateral leg and dorsal foot following a fibular and tibial fracture is usually derived from a compartment syndrome. If this has been ruled out, the differential diagnosis should include bony entrapment of the superficial peroneal nerve.

The role of radiography and computerized tomography in the diagnosis of subluxation and dislocation of the distal radioulnar joint.

The diagnosis of an isolated subluxation or dislocation of the distal radioulnar joint (DRUJ) may be extremely difficult to make from the standard radiographic examination. Radiographs and computerized tomographic (CT) scans of cadaver wrists were used to evaluate subluxation and dislocation of the DRUJ. Both subluxation and and dislocation could be accurately diagnosed from a true lateral radiographic projection of the wrist with the forearm in neutral rotation. Minimal supination or pronation of the forearm led to inaccurate diagnosis. A single CT scan through the DRUJ was diagnostic for subluxation and dislocation in all positions of forearm rotation. Wrist pain, plaster immobilization, or suboptimal wrist positioning may make it impossible to obtain a perfect lateral view of the wrist, thereby precluding the radiographic diagnosis of DRUJ subluxation and dislocation. In this instance, a single CT scan through the DRUJ is recommended.

Posterior stabilization of pelvic fractures by use of threaded compression rods. Case reports and mechanical testing.

Threaded compression rods were placed between the posterior-superior spines as a means of posterior stabilization of pelvic fractures. To document the increase in sacroiliac stability afforded by this technique, biomechanical testing was performed. Malgaigne-type fractures with sacroiliac disruptions were created in four cadaver pelvises. The fractures were stabilized with anterior frames of the Slatis or Pittsburgh type and subjected to longitudinal and torsional loading patterns on an Instron machine. The anterior fixation was then augmented with threaded compression rods placed between the posterior-superior spines to compress the disrupted sacroiliac joints, and repeat testing was conducted. Anterior frames alone were found to provide little stabilization of the disrupted sacroiliac joints with either longitudinal or torsional loading. Markedly improved stabilization in both loading modes was achieved with posterior augmentation. Two typical cases are presented to demonstrate that posterior stabilization is as efficacious in clinical practice as in the biomechanics laboratory.