Gait and function after intra-articular arthrodesis of the hip in adolescents.

BACKGROUND: Patients who have had a hip arthrodesis have been reported to have pain in the back and the knee due to an altered gait. There is little information about the specific compensatory mechanisms that are adopted when walking. The purpose of this study was to objectively define gait adaptations after an arthrodesis of the hip and to correlate the kinematic findings with pain and other patient outcomes. METHODS: Nine patients who had had an arthrodesis of the hip at an average age of thirteen years and five months (range, ten years and nine months to sixteen years and eleven months) were evaluated with gait analysis and muscle strength-testing and completed a questionnaire related to pain and function. The average duration of follow-up was eight years and ten months (range, two years and one month to thirteen years and ten months). The frequency of the postoperative visits varied. Seven patients were adults at the time of the study and were called back specifically for the study. RESULTS: All patients had decreased cadence and step lengths. The kinematic findings included decreased dorsiflexion of the ipsilateral ankle, hyperextension of the ipsilateral knee during the stance phase, and a tendency toward increased genu valgum during gait. In normal gait, there is no genu varum or valgum during the stance phase. The patients had an average (and standard deviation) of 7 +/- 4 degrees of genu valgum. Pelvic and lumbar motion in the sagittal plane was excessive in all patients. Strength-testing revealed clinically relevant weakness in the ipsilateral quadriceps in all patients, with a difference of more than 20 percent between the two extremities in six patients. The gastrocnemius. soleus muscle was stronger on the side with the fused hip in six patients. The questionnaire, designed by Harris in 1969 and completed by the patients at the time of the gait analysis, revealed back pain in seven patients. The questionnaire was administered only once. The functional outcome as measured with use of the same questionnaire worsened as the duration of follow-up increased. CONCLUSIONS: The gait analysis showed excessive motion in the lumbar spine and the ipsilateral knee in all nine patients. This abnormal motion led to pain as the duration of follow-up increased, and all patients who had been followed for four or more years after the arthrodesis complained of back pain. We hypothesized that excessive motion for an extended duration can lead to back pain. The preferred position of the hip for the arthrodesis was 20 to 25 degrees of flexion, neutral abduction-adduction, and neutral rotation.

Radiographic evaluation of the position of implants in the medial malleolus in relation to the ankle joint space: anteroposterior compared with mortise radiographs.

BACKGROUND: Displaced transverse fractures of the medial malleolus are commonly treated with open reduction and internal fixation with two screws or wires. A mortise radiograph is often used to verify the position of the implants relative to the joint space. However, because the medial and lateral talomalleolar spaces are normally not parallel, the mortise projection (which is colinear with the lateral space) does not provide an accurate radiograph of the medial joint space. METHODS: In ten cadaveric ankles, two wires were inserted into the medial malleolus, as is done for fixation of a fracture, and the distance of the wires from the joint space was measured on an anteroposterior radiograph, on mortise radiographs made with the foot in 15 and 30 degrees of internal rotation, and on anatomical cross section. RESULTS: The measurement on the anteroposterior radiograph exceeded the anatomical measurement in only two specimens, and the discrepancy was 0.5 millimeter in both instances. Measurement of the osseous thickness between the joint surface and the posterior wire on the mortise radiographs always revealed a lower value than the measurements on the anteroposterior radiograph and the anatomical cross section of the same specimen. There was a false appearance of intra-articular placement of the posterior wire on the 15-degree mortise radiographs of four specimens and on the 30-degree mortise radiographs of eight specimens. CONCLUSIONS: These findings demonstrate that the mortise projection provides an oblique radiograph of the medial joint space that can inaccurately reflect the true position of fixation implants in the medial malleolus. Because an anteroposterior radiograph is made with the articular surface of the medial malleolus tangential to the beam, it provides a more accurate representation of implants in the medial malleolus.

The role of the interosseous membrane and triangular fibrocartilage complex in forearm stability.

This study investigated the relative roles of the interosseous membrane (IOM) and triangular fibrocartilage complex (TFCC) in the transmission of force from the hand to the humerus. Our findings suggest a spectrum of forearm destabilizing injuries. The intact radius abutting the capitellum provides the primary restraint to proximal migration of the radius. After radial head excision, up to 7 mm of proximal radial migration can occur under axial compression. If the TFCC or the IOM alone is disrupted, little alteration in load or displacement is evident. When both the midportion of the IOM and TFCC are incompetent, however, further proximal radial migration occurs, the radial stump abuts the humerus, and load is shifted back to the radial column. These data suggest that the central portion of the IOM is the crucial structural subdivision within the IOM acting as a restraint to proximal radial migration. The TFCC also resists proximal radial migration and participates in load transfer. We propose that clinical migration of the radius under an axial load greater than 7 mm implies disruption of both the midportion of the IOM and TFCC.