The role of pectoralis major and latissimus dorsi muscles in a biomechanical model of massive rotator cuff tear.

Background: Superior migration of the humeral head after massive rotator cuff tear (mRCT) is thought to lead to cuff tear arthropathy. Previous biomechanical studies have demonstrated the ability of the pectoralis major and latissimus dorsi (PM/LD) muscles to resist this migration. This study examined the role of PM/LD muscles on glenohumeral joint forces and acromiohumeral contact pressures in a mRCT model.

Irradiation does not modify mechanical properties of cancellous bone under compression.

Background: Gamma radiation sterilization can make cortical bone allograft more brittle, but whether it influences mechanical properties and propensity to form microscopic cracks in structurally intact cancellous bone allograft is unknown.

Questions/purposes: We therefore determined the effects of gamma radiation sterilization on structurally intact cancellous bone mechanical properties and damage formation in both low- and high-density femoral cancellous bone (volume fraction 9%-44%).

Methods: We studied 26 cancellous bone cores from the proximal and distal femurs of 10 human female cadavers (49-82 years of age) submitted to a single compressive load beyond yield.