Parity, menopausal timing, and spinopelvic mismatch: a moderated mediation analysis of low back pain in postmenopausal women.

PURPOSE: To evaluate the association of parity and menopausal timing with spinopelvic alignment in postmenopausal women and whether pelvic incidence-lumbar lordosis (PI-LL) difference statistically mediates the association between parity and low back pain.

METHODS

This single-centre cross-sectional study included 239 postmenopausal women aged ≥ 45 years. Standardised standing lumbosacral radiographs were used to measure pelvic incidence, sacral slope, pelvic tilt, lumbar lordosis, and PI-LL difference. PI-LL mismatch was defined as ≥ 10°. Pain severity was assessed using a visual analogue scale. Multivariable regression and mediation analyses were performed.

RESULTS

Higher parity was associated with greater pelvic incidence, sacral slope, and PI-LL difference. Pelvic incidence differed significantly across parity groups (nulliparous, 1-2 deliveries, and ≥ 3 deliveries) (H(2) = 30.163, p < 0.001), with median values of 43.80° (40.30-47.50) in nulliparous women and 48.35° (44.80-51.30) in women with ≥ 3 deliveries. Earlier menopausal age was associated with greater PI-LL difference. PI-LL mismatch was present in 25.5% of women and was associated with higher pain severity (p < 0.001).

CONCLUSION

Higher parity and earlier menopausal age were associated with differences in measured spinopelvic parameters, particularly PI-LL difference. Reproductive history and menopausal timing may be clinically relevant when interpreting low back pain in postmenopausal women.

LEVEL OF EVIDENCE: IV.