[Effect of femoral offset change on pain and function after total hip arthroplasty].

OBJECTIVE: To investigate the effects of altering the femoral offset after total hip arthroplasty on postoperative pain and function.

METHODS: A total of 162 patients undergoing single total hip arthroplasty between March 2009 and December 2011 met the inclusion criteria. According to difference of femoral offset between operative side and contralateral side, the patients were divided into 3 groups: decreased offset group (< 5 mm, 30 cases), normal offset group (-5-5 mm, 87 cases), and increased offset group (> 5 mm, 45 cases). There was no significant difference in gender, age, and disease duration among 3 groups (P > 0.05). The types of femoral stem and head prosthesis were compared among 3 groups. Short Form 12 Health Survey (SF-12) score, Western Ontario and McMaster University Osteoarthritis Index (WOMAC) score, and Harris score were used to evaluate the clinical outcomes.

RESULTS: Standard offset femoral prosthesis was most used, followed by increased offset femoral prosthesis, and decreased offset femoral prosthesis was least in 3 groups. The types of femoral stem and head prosthesis showed no significant difference among 3 groups (P > 0.05). The patients were followed up 12-33 months (mean, 25 months). There was no significant difference in SF-12 score among 3 groups at 1 year after operation (P > 0.05); there was no significant difference in WOMAC pain and stiffness scores among 3 groups (P > 0.05) except WOMAC body function score (P < 0.05). According to Harris scoring criteria, the results were excellent in 13 cases, good in 8 cases, fair in 7 cases, and poor in 2 cases in decreased offset group; the results were excellent in 42 cases, good in 34 cases, fair in 9 cases, and poor in 2 cases in normal offset group; the results were excellent in 31 cases, good in 12 cases, and fair in 2 cases in increased offset group; and significant difference was found among 3 groups (Z= -3.152, P=0.008).

CONCLUSION: Increased offset is more conducive to joint functional recovery and pain relief; decreased offset may lead to joint function deterioration and pain aggravation.