Teres minor muscle hypertrophy is a negative predictor of outcomes after reverse total shoulder arthroplasty: an evaluation of preoperative magnetic resonance imaging and postoperative implant position.

BACKGROUND: Predictors of outcomes after reverse total shoulder arthroplasty (rTSA) remain unclear. The purpose of this study was to analyze the impact of preoperative muscle quality and postoperative implant positioning on patient-reported outcomes following rTSA. METHODS: We evaluated 88 shoulders treated with rTSA in which preoperative magnetic resonance imaging was available. Preoperative muscle quality was evaluated, including fatty infiltration, rotator cuff muscle volume, and total tear size. Postoperative implant position was determined radiographically. The correlation between imaging parameters and the 2-year postoperative American Shoulder and Elbow Surgeons (ASES) score was examined. Multivariate analyses were performed to adjust for confounding factors including patient demographic characteristics and implant position. RESULTS: Univariate analysis showed that the ASES score was significantly lower in patients with teres minor muscle hypertrophy relative to those with normal muscle (73.3 ± 22.8 vs. 84.2 ± 16.9, P = .02). The functional subscore was significantly lower in patients with grade 2 fatty infiltration of the deltoid muscle relative to those with grade 0 fatty infiltration (26.1 ± 14.6 vs. 34.8 ± 11.6, P = .03). Older age was associated with a higher pain subscore (ρ = 0.32, P = .002). Multivariate analysis demonstrated that teres minor muscle hypertrophy remained a significant independent predictor of the ASES score (ß coefficient = 91.3, P = .03). CONCLUSION: Teres minor muscle hypertrophy is an independent negative predictor of patient-reported outcomes after rTSA.

Meniscus Form and Function.

The menisci are 2 fibrocartilaginous crescents anchored via bony and ligamentous attachments to surrounding structures. Their biochemical composition and multilayered structure make them ideal for converting compressive forces to tensile forces in addition to improving joint congruity and providing shock absorption to weight bearing. The medial meniscus maintains more attachments at both the horns and the midbody than the lateral meniscus, making it more susceptible to injury. Understanding of the gross anatomy, vascular anatomy, biochemical composition, and microstructure is key to understanding causes of meniscal pathology as well as treatment options for restoring its primary functions.

The Influence of Tibial and Femoral Bone Morphology on Knee Kinematics in the Anterior Cruciate Ligament Injured Knee.

Bone morphology is one feature that contributes to knee kinematics. The geometry of the tibia and femur vary across individuals, and these differences can influence the risk of anterior cruciate ligament (ACL) injury and of failure after isolated ACL reconstruction. There has been renewed interest in lateral extra-articular stabilization procedures to supplement an ACL reconstruction, although which patients benefit most from these procedures remains unclear. This article reviews the impact of bone morphology on knee kinematics, including tibial slope, depth of the medial tibial plateau, intercondylar notch shape, tibial eminence volume, and sphericity of the femoral condyles.