Total Hip Arthroplasty: Leg Length Discrepancy Affects Functional Outcomes and Patient's Gait

Our study was targeted to investigate the relationship between postoperative leg length discrepancy (LLD) and the outcomes of total hip arthroplasty (THA) including gait, hip function, and lower back pain (LBP). Ninety-two patients who underwent primary THA during Jan 2009 to Apr 2011 in our medical center were enrolled in this study. We measured postoperative LLD of the patients both directly and from the leg radiographs. Six months after the surgery, we evaluated the hip function with Harris Hip Score (HHS), analyzed the gait, and recorded the degree of LBP. Patients with LLD between 10 and 20 mm were given the block footbeds to correct the difference in the leg length. Then 1 year after the surgery, the above-mentioned parameters were evaluated again. (1) LLD: Patients were divided into three groups according to the magnitude: less than 10 mm were grouped as A, those between 10 and 20 mm as B, and more than 20 mm as C. (2) Gait analysis: patients with larger LLD showed slower gait speed (t = 6.527; p < 0.01), longer single support time (t = -2.665; p = 0.01), and shorter foot-off time (t = -8.502; p < 0.01). After half a year of the surgery, Group B patients showed recovery and their functional performance was not significantly different from that of the patients in Group A (t = -0.686; p = 0.49). (3) HHS: In the first half of the follow-up year, patients with smaller LLD showed an improved function (t = 6.56; p < 0.01). At the end of year one, the HHS of Group B patients was not significantly different from that of Group A (t = 1.4; p = 0.16), suggesting a good recovery, however, Group C patients showed no improvement in HHS scores. (4) LBP: Initially, Group B patients suffered from more severe LBP than Group A patients, however, the examination conducted in the end of year 1 exhibited no difference in the LBP levels of the two groups (t = 0.683; p = 0.01, t = -0.85; p = 0.40). After THA surgery, the outcome was found to be significantly associated with the degree of different length of lower limbs. The use of block such as footbed could partly relieve the symptoms of hip dysfunction and LBP. However, the recovery was less significant in patients with leg length difference more than 20 mm.