Relationship of early postoperative perceived leg length discrepancy to the progression of osteoarthritis in the contralateral hip after unilateral total hip arthroplasty-a retrospective cohort study using propensity score matching.
Yuji Kawabata, Mitsuhiro Kimura
PMID 37020827WHAT IT FOUND
Patients who felt their operated leg was longer 3 weeks after one-sided hip replacement had more joint space narrowing in the opposite hip at 1 year when similar patients were matched (1.00 mm vs 0.22 mm).
Without matching, the difference was not clear enough.
Key findings
01Thirteen of 65 analysed patients had a more than 2-mm perceived leg length discrepancy 3 weeks after surgery.
02In propensity-matched groups, change in contralateral hip minimum joint space width was 1.00 ± 0.66 mm with perceived leg length discrepancy and 0.22 ± 0.51 mm without, a significant difference with effect size r=0.57.
03Before matching, the difference in change in minimum joint space width was not significant (1.00 ± 0.66 mm with perceived leg length discrepancy and 0.57 ± 0.96 mm without, p=0.25).
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The analysis used only 65 patients, and the matched comparison used 13 patients in each group. The difference in joint space width was not significant before matching (p=0.25), so the positive result depends on the matched analysis. This was an observational cohort, not a treatment study, so it cannot show that perceived leg length discrepancy caused osteoarthritis progression. Patients with preoperative contralateral minimum joint space width less than 2.0 mm were excluded, so the finding does not apply to severe preoperative osteoarthritis. Perceived leg length discrepancy was assessed only at 3 weeks, and its later course was not measured. Physical activity and spinal mobility were not included as covariates, so residual confounding is possible.
Declared interests
None of the authors has any conflict of interest to disclose.
The easy way to misread this
Do not conclude that correcting perceived leg length discrepancy will prevent contralateral hip osteoarthritis. This was an observational study, the pre-matched comparison was not significant, and the authors state that observational studies cannot establish a causal relationship.