In vivo biomechanical evaluation of nail-plate fixation of femoral neck fractures of rehabilitated patients.

A major advantage of internal fixation of intertrochanteric fractures is that it can normally be followed by early and fast rehabilitation of the patient, finding expression in weight bearing and locomotion abilities of the patients. Complications which nevertheless occur, are mostly of mechanical origin. The purpose of our study was to evaluate the biomechanical performance of rehabilitated patients treated with four different types of nail-plates. Forty nine patients (12 men and 37 women) with walking ability, and with an average age of 70.5 years, were tested on a 10 m walkway, instrumented for the monitoring of the time distance parameters of the stride. This method of evaluation is especially suitable for pathological gait, free or supported, as it does not impose any constraints on the natural and individual walking trend of the patient. The average time elapsed between the actual fracture and the locomotor test was 764 days, implying that the investigated patients formed a homogeneous, well-rehabilitated group. The main average stride results were as follows: contact time 1.25 sec, double contact time 0.41 sec, stride length 68.2 cm, velocity 51.39 cm/sec and symmetry 0.51. No significant differences were found in these parameters between the subgroups of patients using different nail-plates. These results show that while the biomechanical performance of the patients with their implants was satisfactory (good walking symmetry) this group can be characterized by its smaller stride and slower gait, compared to those of a healthy population of the same age.