Cadaveric Biomechanical Comparison of Prepectoral and Submuscular Implant-based Breast Reconstruction

Decreased postoperative pain and functional impact have been associated with prepectoral breast implant placement versus submuscular placement; yet no mechanical analyses have quantified this difference. Using 1 postmortem human subject, a 3-dimensional biomechanical tracking system was used to determine the impact of pocket placement on shoulder girdle dynamics for submuscular acellular dermal matrix (ADM)-assisted and prepectoral implants. Smooth silicone breast implants were placed bilaterally-one in the prepectoral plane with anterior ADM coverage and the other in the submuscular ADM-assisted plane. Using tracking nodes at the sternum, clavicles, scapulae, and humeri, each shoulder was tested through serial standardized trials of extension, flexion, lateral extension/flexion, oblique extension/flexion, and abduction using manual manipulations of the shoulder and a counter-weight apparatus before and after implant placement. Bone kinematics (bony displacement and rotation) and kinetics (joint force and moment) were recorded. To achieve equal shoulder extension and flexion maneuvers, submuscular placement was associated with increased scapular, humeral, and clavicular displacement as well as increased scapular and humeral rotation compared with preoperative measurements, whereas prepectoral placement showed no difference. Increased scapular and clavicular rotation with extension and decreased rotation with abduction were noted with both pockets. This cadaveric biomechanical model shows that submuscular implant placement is associated with compensatory increases in bony displacements and rotation required to complete standardized movements consistent with activities of daily living. Further replication of this protocol with varying cadaveric body types and implant sizes would generate predicted postoperative shoulder movement models for implant-based breast reconstruction in different pocket locations.