Improvement in Gait Parameters After Lengthening for the Treatment of Limb-Length Discrepancy.

Bhave A, Paley D, Herzenberg JE (Maryland Center for Limb Lengthening and Reconstruction, The James Lawrence Kernan Hospital, Baltimore, Md), J Bone Joint Surg Am. 1999;81:529-534.

Limb-length discrepancy leads to a characteristic limp and possible low back pain. Although compensatory mechanisms are used during walking, they lead to an asymmetrical gait between the shorter and longer limb. The purpose of this prospective study was to compare objective gait parameters for the shorter and longer limb before and after limb-lengthening to determine if the correction produced a normalization of gait as measured by ground reaction force vectors. These findings were also compared to subjects without limb-length discrepancies to determine if the resulting gait parameters fell within the "normal" range.

The subjects were 18 patients (mean age=24 years; range= 11-42 years) who underwent limb lengthening. Limblength discrepancy was measured on full-length radiographs using appropriate lifts. The mean limb-length discrepancy was 4.9 centimeters with a range of 3.5 to 11.0 centimeters. Before their operations, 11 patients reported low back pain. The methods of limb lengthening used included the Ilizarov apparatus (7 patients), a nail and an external fixator (6 patients), and a nail and an Ilizarov apparatus (5 patients).

For gait analysis, patients were videotaped while walking at the following times: preoperatively and at an average of 12 months after the operation. Preoperative analysis showed that all patients with limb-length discrepancies compensated by holding the foot in varying degrees of equinus. For comparison, 20 subjects without limb-length discrepancies (mean age=21 years; range= 16-32 years)were analyzed. The study used dual forceplates where previous studies used a single forceplate. All subjects walked over the forceplates, making contact with each at their preferred rate several times. Five ground reaction force vectors were collected for each limb.

Stance time and the second peak of the vertical ground reaction force vector were measured for both limbs. The rate of loading from time of foot contact to the first peak of the vertical ground reaction force vector was also measured for both sides. Stance-time difference between the 2 limbs was normalized and expressed as a percent reduction for the shorter limb compared to the longer limb. The second peak of the ground reaction force vector was expressed as a percentage of body weight. Rate of loading was expressed as the product of body weight per second.

In patients who had had tibial Lengthening, plantar-flexor strength was measured using the maximum number of single heel-rises possible on a forceplate. The results were expressed as a percentage of body weight. A paired t test was used to evaluate for significance of all paired variables pre- and postoperatively. Regression analysis was performed to compare the effect of limb-length discrepancy on the variables; significance was set at [Alpha]=.05.

The change in mean stance time between the 2 limbs of patients with limb-length discrepancies wits significant. Before lengthening, the mean stance time between limbs differed by 12%, whereas after lengthening, it differed by 2.4%. The mean stance time between limbs in people with out leg-length discrepancies was 2%. The difference between patients with leg-length discrepancies and people without leg-length discrepancies was statistically significant before lengthening, but this difference was removed after the limb-lengthening procedure. Measurement of the second peak of the vertical ground reaction force vector demonstrated a significant difference between the 2 limbs of people with limb-length discrepancies preoperatively but not postoperatively. No significant change in muscle strength was found after lengthening. The mean loading rate for the shorter limb showed a significant change from a rate of 5.7 times body weight per second before the operation to 4.7 times body weight per second after the operation. The mean loading rate for the subjects without limb-length discrepancies was 3.9 times body weight per second. Of the 11 patients with preoperative low back pain, none had pain at the postoperative follow-up.

According to the authors, this study documented measurable and significant stance-time asymmetry in the gait of patients with moderate limb-length discrepancy. The lengthening of the shorter limb resulted in a normalization of stance and the elimination of low back pain. They noted that critical factors for normalization of gait after lengthening depended on correction of the length to within 1 cm, adequate range of motion and strength, and the absence of pain in the lengthened limb.

Byron E Russell, PT
Hardin-Simmons University
Abilene, Tex