Scapular pressure distribution and its association with upper limb function in breast cancer survivors following modified radical mastectomy: a cross-sectional study

Abstract

Upper limb dysfunction remains a frequent challenge for breast cancer survivors following modified radical mastectomy (MRM) with axillary lymph node dissection (ALND). Although alterations in scapular function may be relevant to postoperative shoulder impairment, scapular-region loading patterns and their relationships with upper limb function remain insufficiently understood. This exploratory cross-sectional study examined the associations between scapular-region pressure distribution and upper limb function during shoulder flexion in this population. Twenty-six female breast cancer survivors (mean age, 49.2 ± 11.0 years) who had undergone MRM with ALND and achieved at least 120° of active shoulder flexion were included in this cross-sectional study. A body pressure sensor system recorded scapular-region pressure distribution bilaterally at 0°, 30°, 60°, 90°, and 120° of shoulder flexion under standardized supine conditions. Key variables included the maximum pressure value (MPV), number of peak pressure values (NPPV), and the horizontal distance of the MPV from the center of pressure (HDSMC). Shoulder range of motion, Disabilities of the Arm, Shoulder, and Hand (DASH) scores, and scapular positioning were also assessed. Side-to-side differences in scapular-region pressure distribution and scapular position were observed. In separate stepwise regression analyses, active shoulder flexion was associated with the DASH score (adjusted R² = 0.190), DIASS at 90° of shoulder flexion (adjusted R² = 0.186), NPPV at 30° (adjusted R² = 0.119), and HDSMC at 90° (adjusted R² = 0.206). However, the association with NPPV30° was not statistically significant in a Spearman sensitivity analysis. Simple linear regression analysis showed that the surgical-to-non-surgical side ratio of MPV at 120° of shoulder flexion was associated with the DASH score (adjusted R² = 0.245). Altered and asymmetric scapular-region pressure-distribution patterns were associated with shoulder mobility and self-reported upper limb disability in this exploratory sample of breast cancer survivors following MRM with ALND. Given the small sample size, cross-sectional design, absence of a healthy control group, and lack of direct measurements of scapular kinematics, these findings should be considered preliminary. Larger prospective controlled studies are needed to validate these pressure-derived measures and determine their clinical relevance.