The influence of reconstruction choice and inclusion of radiation therapy on functional shoulder biomechanics in women undergoing mastectomy for breast cancer

Abstract

Purpose: The functional implications of reconstructing the breast mound with a latissimus dorsi (LD) flap or placing an implant under the pectoralis major (PM) muscle is complicated by potential comorbidities from disinserting these muscles and adjuvant radiotherapy. We utilized novel robot-assisted measures of shoulder stiffness and strength to dissociate how breast reconstruction choice and inclusion of radiation therapy impact shoulder morbidity in post-mastectomy reconstruction patients. Methods: Shoulder strength and stiffness were collected from 10 irradiated LD flap breast reconstruction patients, 14 two-stage subpectoral implant reconstruction patients (subpectoral), and 10 irradiated deep inferior epigastric perforator (DIEP) flap patients an average of 659 days post-reconstruction. Univariate ANOVAs examined surgical group differences in strength and stiffness. Results: There were main effects of surgical group on vertical adduction, vertical abduction, and internal rotation strength. The LD flap group was significantly weaker than the subpectoral group in all measures and significantly weaker than the DIEP group during vertical adduction. There was also a main effect of surgical group on vertical adduction stiffness, where the LD group exhibited significantly reduced stiffness while producing vertical adduction torque. No significant differences between the subpectoral and DIEP groups existed for any measure of shoulder strength or stiffness. Conclusions: Disinsertion of the LD, not the disinsertion of the PM or radiotherapy, contributes to strength deficits following LD flap breast reconstructions. The combined disinsertion of the PM and LD compromises shoulder stability in the vertical plane. Shoulder function should be a focal point of the surgical decision-making process and postsurgical care.