We performed isokinetic knee testing to assess thigh muscle function in ten patients (12 legs) before and after mid-shaft femoral shortening averaging 46 mm (27 to 70). Tests were at angular velocities of 60 degrees/sec and 180 degrees/sec, and were performed preoperatively and after 3, 6, 12 and 24 months. Isokinetic tests at two years showed a significant reduction in muscle function in both quadriceps and hamstrings, but recovery of function was significantly better for the hamstrings. There was a linear relationship with correlation of r2 = 0.31 to 0.86 between loss of muscle force at two years and the magnitude of shortening. Long-term loss of muscle force should be expected after a mid-shaft shortening of the femur of more than 10%.

We performed bilateral femoral shortening operations on 15 skeletally mature patients (11 women and four men). Their mean height pre-operatively was 193.5 cm and they were shortened by 5 to 9 cm. We used a subtrochanteric Z-osteotomy with an AO condylar plate in 11 patients, and mid-diaphyseal osteotomy with an intramedullary locking nail in four. After an average follow-up of 8.1 years, isokinetic muscle testing showed that muscle strength was reduced bilaterally in five patients. The strength ratio between hamstrings and quadriceps muscles was normal in all those treated by subtrochanteric shortening; in those shortened at the mid-shaft the quadriceps was relatively weaker. The result was rated as excellent by 11 patients, very good by three, and good by one.