解剖学的肩関節形成術における上腕骨頭再建：評価方法、オーバーラッピングの回避方法、およびその重要性

➢ Humeral head anatomy affects the tension and mechanics of the glenohumeral joint. Thus, aiming for anatomic reconstruction can help to avoid negative consequences of component malpositioning (such as "overstuffing") on soft-tissue tension and impingement-free range of motion.➢ The most common method to assess humeral head reconstruction is comparing the prosthetic humeral articular surface with the "perfect circle" incorporating the lateral cortex of the greater tuberosity, the medial greater tuberosity, and the medial calcar at the anatomic neck. Although this method is quick and helpful in assessing multiple parameters, it is important to also compare the radius of curvature, assess traditional measurements of humeral head anatomy or glenohumeral thickness, and consider that non-anatomic sizing may be used to achieve tension goals.➢ There is no consistent evidence of superior humeral head reconstruction quality with stemless, short-stem, or standard-length humeral components, suggesting that surgical technique and familiarity with an implant system remain most important.➢ Although stemless and short-stem components offer versatility in recreating pre-arthritic anatomy, their use places emphasis on having a reproducible technique for humeral neck osteotomy depth and inclination. Some techniques include careful osteophyte resection to visualize the true anatomic neck, the use of an intramedullary guide, and intraoperative assessment with fluoroscopy.➢ Although small deviations from pre-arthritic anatomy do not appear to affect clinical outcome, center-of-rotation deviations of exceeding 3 to 4 mm from the perfect circle have been associated with an inferior clinical outcome.