University of Utah, Department of Orthopaedics, Salt Lake City, UT, USA.
Department of Orthopedic Surgery, Cooper Health, Cherry Hill, NJ, USA.
J Shoulder Elbow Surg. 2022 Aug;31(8):1674-1681. doi: 10.1016/j.jse.2022.03.022. Epub 2022 May 7.
Variable neck-shaft angle (NSA) stemmed humeral components have been incorporated into certain implant designs to better re-create normal anatomy in total shoulder arthroplasty (TSA). The purpose of this study was to determine if premorbid glenohumeral joint anatomy is better restored with a fixed- vs. variable-NSA prosthesis.
A randomized controlled trial was performed including 50 patients with osteoarthritis indicated for primary anatomic TSA. Patients were randomized preoperatively to receive either a variable- (n = 26) or fixed-NSA (n = 24) prosthesis. Humeral neck cut in the variable-NSA group matched the patient's anatomic neck, with prosthetic NSA of 127.5°, 132.5°, and 137.5° available. Fixed-NSA cuts were made with an intramedullary guide of 132.5°. Preoperative and postoperative radiographs were evaluated for specific radiographic anatomic variables: NSA, head thickness, tuberosity-to-head height, head offset, articular arc, greater tuberosity offset, and center of rotation (COR). Postoperative radiographic criteria were compared between groups.
No differences were found between groups in demographics or preoperative radiographic measures. When comparing average difference in preoperative and postoperative measurements in the fixed-NSA group, the humeral head offset from the humeral shaft axis significantly decreased by 1.4 mm (P = .046), and the COR moved superiorly (3.0 mm, P = .002) without significant medialization or lateralization. In the variable angle group, humeral head offset decreased but did not reach significance (1.2 mm, P = .091), and the COR also moved superiorly (2.9 mm, P < .001) without significant medialization or lateralization. All remaining radiographic parameters did not significantly change from pre- to postoperative imaging. In comparing the fixed- and variable-NSA groups' net change from the premorbid measurements, no significant differences were found in tuberosity-to-head height, head offset, or COR position in both the horizontal and vertical planes.
Both fixed- and variable-NSA anatomic TSA humeral components demonstrate adequate restoration of premorbid anatomy radiographically.
可变颈干角（NSA）肱骨头假体已应用于某些假体设计中，以更好地重建全肩关节置换术（TSA）中的正常解剖结构。本研究旨在确定在固定 NSA 与可变 NSA 假体中，哪种假体更能恢复术前盂肱关节解剖结构。
这是一项随机对照试验，共纳入 50 例拟行初次解剖型 TSA 的骨关节炎患者。患者术前随机分为可变 NSA 组（n=26）和固定 NSA 组（n=24）。可变 NSA 组的肱骨头颈切割与患者解剖颈匹配，假体 NSA 角度为 127.5°、132.5°和 137.5°。固定 NSA 组采用髓内导板切割，角度为 132.5°。术前和术后的 X 线片用于评估特定的影像学解剖学变量：NSA、头厚、结节-头高度、头偏移、关节弧、大结节偏移和中心旋转（COR）。比较两组术后的影像学结果。
两组在人口统计学或术前影像学测量方面无差异。在固定 NSA 组中，与术前相比，术后平均测量的差异中，肱骨头相对于肱骨干轴线的偏移显著减少了 1.4mm（P=0.046），COR 向上移动（3.0mm，P=0.002），但没有明显的内侧或外侧移位。在可变角度组中，肱骨头偏移减少，但无统计学意义（1.2mm，P=0.091），COR 也向上移动（2.9mm，P<0.001），但无明显的内侧或外侧移位。所有其余影像学参数在术前和术后影像学检查中均无显著变化。比较固定 NSA 和可变 NSA 组从术前测量的净变化，在水平和垂直平面上，结节-头高度、头偏移或 COR 位置均无显著差异。
固定 NSA 和可变 NSA 解剖型 TSA 肱骨假体在影像学上均能充分恢复术前解剖结构。
