Total hip arthroplasty: leg length inequality impairs functional outcomes and patient satisfaction.
BACKGROUND
Leg length inequality (LLI) was identified as a problem of total hip arthroplasty soon after its introduction. Leg lengthening is the most common form of LLI. Possible consequences are limping, neuronal dysfunction and aseptic component loosening. LLI can result in an increased strain both on the contralateral hip joint and on the abductor muscles. We assessed the influence of leg lengthening and shortening on walking capacity, hip pain, limping and patient satisfaction at 2-year follow-up.


METHODS
478 cases with postoperative lengthening and 275 with shortening were identified, and matched with three controls each. Rigorous adjustment for potential differences in baseline patient characteristics was performed by propensity-score matching of covariates. The arbitrarily defined desired outcomes were a walking capacity >60 minutes, no hip pain, no limping, and excellent patient satisfaction. Differences in not achieving the desired outcomes between the groups were expressed as odds ratios.


RESULTS
In the lengthened case group, the odds ratio for not being able to walk for an hour was 1.70 (95% CI 1.28-2.26) for cases compared to controls, and the odds ratio for having hip pain at follow-up was 1.13 (95% CI 0.78-1.64). The odds ratio for limping was 2.08 (95% CI 1.55-2.80). The odds ratio for not achieving excellent patient satisfaction was 1.67 (95% CI 1.23-2.28). In the shortening case group, the odds ratio for not being able to walk for an hour was 1.23 (95% CI 0.84-1.81), and the odds ratio for having hip pain at follow-up was 1.60 (95% CI 1.05-2.44). The odds ratio for limping for cases was 2.61 (95% CI 1.78-3.21). The odds ratio for not achieving excellent patient satisfaction was 2.15 (95% CI 1.44-3.21).


CONCLUSIONS
Walking capacity, limping and patient satisfaction were all significantly associated with leg lengthening, whereas pain alleviation was not. In contrast, hip pain, limping and patient satisfaction were all significantly associated with leg shortening, whereas walking capacity was not.
Institute for Evaluative Research in Orthopaedics, University of Bern, Stauffacherstrasse 78, 3014, Bern, Switzerland.
Christoph
C
Röder
Raphael
R
Vogel
Lukas
L
Burri
Daniel
D
Dietrich
Lukas P
LP
Staub
D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects*; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D004185:Disability Evaluation; D005060:Europe; D005260:Female; D006621:Hip Joint / Q000503:physiopathology / Q000601:surgery*; D006801:Humans; D007870:Leg Length Inequality / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology / Q000523:psychology; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D016017:Odds Ratio; D015207:Osteoarthritis, Hip / Q000503:physiopathology / Q000601:surgery*; D010149:Postoperative Pain / Q000209:etiology; D017060:Patient Satisfaction; D057216:Propensity Score; D011446:Prospective Studies; D012042:Registries; D013997:Time Factors; D016896:Treatment Outcome; D016138:Walking