Muscle strength and knee range of motion after femoral lengthening

Abstract

Background and purpose - Femoral lengthening may result in decrease in knee range of motion (ROM) and quadriceps and hamstring muscle weakness. We evaluated preoperative and postoperative knee ROM, hamstring muscle strength, and quadriceps muscle strength in a diverse group of patients undergoing femoral lengthening. We hypothesized that lengthening would not result in a significant change in knee ROM or muscle strength. Patients and methods - This prospective study of 48 patients (mean age 27 (9-60) years) compared ROM and muscle strength before and after femoral lengthening. Patient age, amount of lengthening, percent lengthening, level of osteotomy, fixation time, and method of lengthening were also evaluated regarding knee ROM and strength. The average length of follow-up was 2.9 (2.0-4.7) years. Results - Mean amount of lengthening was 5.2 (2.4-11.0) cm. The difference between preoperative and final knee flexion ROM was 2° for the overall group. Congenital shortening cases lost an average of 5% or 6° of terminal knee flexion, developmental cases lost an average of 3% or 4°, and posttraumatic cases regained all motion. The difference in quadriceps strength at 45° preoperatively and after lengthening was not statistically or clinically significant (2.7 Nm; p = 0.06). Age, amount of lengthening, percent lengthening, osteotomy level, fixation time, and lengthening method had no statistically significant influence on knee ROM or quadriceps strength at final follow-up. Interpretation - Most variables had no effect on ROM or strength, and higher age did not appear to be a limiting factor for femoral lengthening. Patients with congenital causes were most affected in terms of knee flexion.

Figure 1.

Mean duration of treatment with external fi xation for lengthening-over-nail (LON) technique vs. conventional Ilizarov external fi xation. The LON group had the external fi xator in place for signifi cantly less time than did patients in the conventional Ilizarov group (p < 0.001).

Figure 2.

Aggregate average knee fl exion range of motion (ROM) for the entire patient population during different stages of the lengthening process.

Figure 3.

Change in knee fl exion range of motion when patients were categorized according to the cause of limb shortening (p = 0.09).

Figure 4.

Patient age compared to percent change in muscle strength postoperatively.