Department of Orthopaedic Surgery, University of Arizona College of Medicine, Phoenix, AZ, USA.
Lawson Health Research Institute, London, ON, Canada.
J Shoulder Elbow Surg. 2021 Jun;30(6):1273-1281. doi: 10.1016/j.jse.2020.09.023. Epub 2020 Oct 16.
In reverse shoulder arthroplasty, Inferior tilt was originally promoted to decrease rates of baseplate failure. However, the literature is conflicting regarding the effect of tilt on scapular neck impingement, which has been associated with an increased risk of notching, increased risk of impingement-related instability, and decreased range of motion. We hypothesized that inferior tilt of -10° would lead to increased medialization and increased scapular neck impingement compared with 0° of tilt.
Twenty patients without glenoid bone loss undergoing reverse shoulder arthroplasty (RSA) at a single institution underwent computed tomography scans of the entire scapula and proximal humerus for preoperative planning. For each patient, we digitally implanted a 25-mm glenoid baseplate flush with the inferior rim of the glenoid. We then simulated impingement-free range of motion with 16 different implant configurations: glenoid tilt (0° vs. -10°), baseplate lateralization (0 mm vs. +6 mm), glenosphere size (36 mm vs. 42 mm), and neck-shaft angle (135° vs. 145°). The primary endpoint was external rotation with the arm at the side (ERS), which is the primary mode of both notching and impingement-related instability, and the secondary endpoint was adduction (ADD). We recorded the RSA angle, preoperative scapular neck length (SNL), and postoperative SNL. Data were compared by paired t tests and a multivariable regression analysis.
In every simulation, inferior tilt led to more impingement on the scapular neck. Inferior tilt of the glenoid component was associated with a mean 27% decrease in impingement-free external rotation (P < .01 in all cases) and a mean 32% decrease in impingement-free ADD (P < .01 in all cases). Inferior tilt removed 3.2 mm of additional SNL (P < .001). Multivariable regression analysis showed that lateralization had the most impact on impingement-free external rotation and ADD (P < .001), followed by glenosphere size (P < .001), neck-shaft angle (P < .001), postoperative SNL (P < .001), glenoid tilt (P = .001), inclination (P < .001), and RSA angle (P = .023 for ERS and P = .025 for ADD).
Relative to 0° of tilt of the baseplate, inferior tilt of -10° was associated with increased scapular neck impingement in ERS and ADD, likely a result of the increased medialization necessary to seat an inferiorly tilted implant, which shortens the scapular neck and brings the humerus closer to the scapula. This scapular neck impingement increases the risk of notching and impingement-related instability.
在反肩置换术中，最初提倡下倾斜以降低底板失效的发生率。然而，关于倾斜对肩胛颈撞击的影响，文献存在矛盾，肩胛颈撞击与切迹形成的风险增加、撞击相关不稳定的风险增加以及活动范围减小有关。我们假设与 0°倾斜相比，-10°的下倾斜会导致内侧化增加和肩胛颈撞击增加。
在一家机构中，20 名无肩胛盂骨丢失的反肩置换术（RSA）患者接受了整个肩胛和近端肱骨的计算机断层扫描，用于术前规划。对于每位患者，我们数字化植入了一个 25 毫米的肩胛盂底板，使其与肩胛盂下缘平齐。然后，我们用 16 种不同的植入物配置模拟了无撞击的活动范围：肩胛盂倾斜（0°与-10°）、底板外侧化（0 毫米与+6 毫米）、关节盂假体大小（36 毫米与 42 毫米）和颈干角（135°与 145°）。主要终点是手臂在侧方的外旋（ERS），这是切迹形成和撞击相关不稳定的主要模式，次要终点是内收（ADD）。我们记录 RSA 角、术前肩胛颈长度（SNL）和术后 SNL。通过配对 t 检验和多变量回归分析比较数据。
在每种模拟中，下倾斜都会导致肩胛颈撞击增加。肩胛盂组件的下倾斜与无撞击的外旋（所有情况下均<.01）和无撞击的 ADD（所有情况下均<.01）减少了 27%有关。下倾斜去除了 3.2 毫米的额外 SNL（<.001）。多变量回归分析显示，外侧化对无撞击的外旋和 ADD 影响最大（<.001），其次是关节盂假体大小（<.001）、颈干角（<.001）、术后 SNL（<.001）、肩胛盂倾斜（P=.001）、倾斜（<.001）和 RSA 角（ERS 的 P=.023，ADD 的 P=.025）。
与 0°的底板倾斜相比，-10°的下倾斜与 ERS 和 ADD 中的肩胛颈撞击增加有关，这可能是由于为了安置下倾斜的植入物而需要更大的内侧化，从而缩短了肩胛颈并使肱骨更靠近肩胛。这种肩胛颈撞击增加了切迹形成和撞击相关不稳定的风险。
