Joint reaction forces during femoral lengthening.

The purpose of this study was to observe the reactive force across the hip and knee joint in a cadaver study during simulated femoral lengthening. Load cells were placed in the hip and knee joints while force measurements were taken after every 1 mm of lengthening. The lengthening was performed on one side with a distal osteotomy and on the other with a proximal osteotomy to determine if the level of the osteotomy had any affect on the forces across the proximal and distal joints. The study showed that the forces at the hip and knee joints increased during lengthening. The proximal osteotomy appeared to increase the amount of force at the hip joint. The force at the knee joint was less affected by the level of the osteotomy. The relative force between the knee and the hip was approximately a 2:1 ratio with a distal corticotomy as opposed to a 1:1 ratio with a proximal osteotomy. From this study, it is suggested that if instability of the hip is a concern during femoral lengthening, then a distal osteotomy should be used.