Lower Limbs Alignment in Patients with a Unilateral Completely Dislocated Hip

BACKGROUND Severe hip osteoarthritis is known to lead to secondary osteoarthritis of the knee joint. It is not clear whether contracture or a leg length discrepancy is more important in determining the knee alignment. METHODS In this study, 48 hips in 48 patients with a unilateral completely dislocated hip (Crowe IV) were recruited. The patients were divided into two groups (Crowe IVa and IVb). The Crowe IVa group had completely dislocation with psudo-articulation, and the Crowe IVb group had completely dislocation without psudo-articulation. The lower limb alignment was divided into three patterns according to the femorotibial angle; varus (≥176 degrees), neutral(170 to 175 degrees) and valgus(≤169 degrees). RESULTS The combination of valgus alignment on the affected side and varus alignment on the unaffected side, so-called "windswept deformity" was observed in 12.5% of the patients; this included 18.2% and 7.7%, in the Crowe IVa and Crowe IVb groups, respectively. The valgus alignment on the unaffected side, namely "long leg arthropathy," was found to have occurred in 6.3% of the patients, including 13.6% of the patients in the Crowe IVa group; there were no cases of long "leg arthropathy" in the Crowe IVb group. CONCLUSION The lower limb alignment on the unaffected side had a tendency to be varus in the Crowe IV patients. The "windswept deformity" was observed in each of the groups; however, "long leg arthropathy" was only found in the Crowe IVa group.