Computer Simulation of Pectoralis Major Muscle Strain to Guide Exercise Protocols for Patients After Breast Cancer Surgery

Abstract

Early detection and successful cancer treatments have increased the number of long-term breast cancer survivors, 3,5 making optimal recovery and quality of life a primary goal. 8 Up to 50% of survivors have a loss of shoulder motion after completion of their treatments, 28,46 which often extends into a long-term impairment. 33,48 This loss of motion has been found to be predictive of reduced capability to perform functional activities 28 and has been shown to be related to depressive symptoms in a group of 183 older women. 13T T STUDY DESIGN: Descriptive study. T T OBJECTIVES:To quantify and rank the order of strain (length change in proportion to the resting length) of 3 portions of the pectoralis major (PM) muscle during various exercises. T T BACKGROUND:A biomechanical foundation on which to base exercise prescriptions for patients after breast cancer surgery is lacking. T T METHODS: An interactive, 3-D, computergraphic simulation system, developed to study biomechanical properties of the musculoskeletal system, was used to simulate movements of the glenohumeral, scapulothoracic, and scapuloclavicular joints of the shoulder, and to estimate strain in 3 portions of the pectoralis major (PM) muscle throughout the motions. The computed tomography scans of 2 male cadavers and literature review formed the basis for the estimations used in the model. Strains in the clavicular, midsternum, and abdominal regions of the PM were expressed as percent strain: [(change in muscle length/resting length) × 100]. Exercise motions were based on PM muscle anatomy and published breast cancer rehabilitation protocols. T T RESULTS:Strains of the PM regions ranged from -21% shortening of the clavicular region during flexion to 55% lengthening of the abdominal region during the overhead stretch. Strain between adjacent regions was most uniform for the movement of abduction with external rotation, and least uniform with flexion. T T CONCLUSION: PM muscle lengtheningestimates were not linearly proportioned to shoulder joint motions, and varied for 3 portions of the PM. This information may help clinicians and researchers to estimate lengthening of PM portions throughout measurable shoulder motions.

Reliability and validity of active and passive pectoralis minor muscle length measures

“… 12 While the pectoralis minor muscle is lengthened during the corner stretch, lengthening of the pectoralis major muscle also likely occurs during this stretch. 27 This may explain why the muscle length change reported by Borstad and Ludewig 12 is smaller than our active and passive muscle length changes. As reported previously, our procedures for lengthening the pectoralis minor muscle were based on a cadaveric study by Muraki et al 22 In their study, displacement sensors were directly attached to the pectoralis minor muscles in nine cadaveric specimens.…”

Upper‐body morbidity after breast cancer

“…Early assessment and intervention postsurgery, by way of education and shoulder exercises, are important to correct subtle treatment‐related changes in scapulae position and stability that left untreated may lead to upper‐body symptoms and impairments, and also to correct muscle recruitment imbalance 95, 101. Ongoing assessment and education is necessary to determine whether tissue changes that may occur during and beyond the adjuvant treatment period, such as shortening of the pectoralis major, perpetuate existing, or lead to the development of, upper‐body morbidity 102. Range of motion exercises play a particularly important role during and after radiation treatment to enhance tissue extensibility and promote normal movement patterns101 and should be encouraged indefinitely to avoid tissue contracture and concomitant alterations to the joint mechanics of the shoulder.…”

“…95,101 Ongoing assessment and education is necessary to determine whether tissue changes that may occur during and beyond the adjuvant treatment period, such as shortening of the pectoralis major, perpetuate existing, or lead to the development of, upper-body morbidity. 102 Range of motion exercises play a particularly important role during and after radiation treatment to enhance tissue extensibility and promote normal movement patterns 101 and should be encouraged indefinitely to avoid tissue contracture and concomitant alterations to the joint mechanics of the shoulder. Furthermore, manual techniques such as myofascial release have also been considered useful in improving tissue extensibility and enhancing mobility.…”

Efficacy of Complementary Therapies in the Quality of Life of Breast Cancer Survivors

“…Gentle articular movements and stretching, during and after treatments, promotes joint mobility and restores muscle flexibility ( 89 , 90 ), prevents muscle contractures, and alters shoulder mechanics ( 91 ). Resistance exercise prevents musculoskeletal injury, improves muscular strength, improves ROM, and reduces body fat as well as systemic inflammation levels ( 75 ).…”