Shoulder Service, Florida Orthopaedic Institute, Tampa, FL, USA.
Department of Translational Research, Foundation for Orthopaedic Research and Education, Tampa, FL, USA.
J Shoulder Elbow Surg. 2022 Jun;31(6S):S136-S142. doi: 10.1016/j.jse.2022.01.131. Epub 2022 Feb 16.
Severe glenoid bone loss (SGBL) poses significant technical challenges. Adequate fixation of glenoid implants may require the use of alternative screw placement. Although bone volumes for the spine and lateral pillars have previously been defined, insufficient evidence exists regarding the distribution of screw placement for fixation in such regions for cases with SGBL. The purpose of this study is to evaluate the variability of screw placement. We hypothesize that determining this variability and establishing common patterns of glenoid bone loss will allow for recommendations for preoperative planning, and implant design and selection.
An internal registry of 2 high-volume shoulder and elbow surgeons was queried, and 65 three-dimensional scapulae models exhibiting SGBL were identified. A fellowship-trained shoulder and elbow surgeon simulated the placement of two 3.5 mm × 30 mm screws, one in the scapular spine (CS) bone volume and one in the inferior column (IS) bone volume. Three orthogonal reference planes were created using anatomic reference points: the scapula trigonum, estimated glenoid center, and inferior pole. Screw positions were mapped, and deviations from the reference planes were calculated. Mutual positions of the IS to CS were also computed. Intraobserver reliability was assessed using 10 randomly selected samples. Median and 25th and 75th percentiles were reported for screw orientation distributions. Means and standard deviations were reported for screw head positions.
We demonstrated excellent intraobserver reliability (intraclass correlation coefficients, 0.90-0.98). Fifty percent of CS were oriented 10° ± 5° of retroversion from the scapula plane, with 5° ± 5° of inclination. For IS, 50% were positioned 0° ± 4° from the scapula plane, with -33° ± 7° of inclination. The relationship of the IS with the CS was medial and posterior in 49% of cases, lateral and posterior in 45%, and lateral and anterior in 6% of cases. On average, the distance between the CS and IS heads was 25 mm ± 4 mm.
For SGBL, adequate fixation of glenoid implants can be achieved by placing screws in the spine and lateral columns, with excellent reproducibility. Future implant designs should accommodate CS positioned -16° to -5° from the scapula plane, with 0° to 12° of inclination, and IS positioned -6° to 4° from the scapula plane, with -40° to -25° of inclination. Moreover, mutual screw positions suggested bone loss distributions anteriorly and inferiorly. Future implant designs should consider the potential benefits of augmentation to accommodate interscrew distances of 21-29 mm and anatomic locations of the IS relative to the CS.
严重的肩胛盂骨缺损（SGBL）带来了重大的技术挑战。为了充分固定肩胛盂植入物，可能需要使用替代的螺钉放置方式。虽然先前已经定义了脊柱和侧柱的骨量，但对于 SGBL 病例中用于固定的这些区域的螺钉放置分布，仍缺乏足够的证据。本研究的目的是评估螺钉放置的可变性。我们假设，确定这种可变性并建立常见的肩胛盂骨丢失模式，将有助于术前规划、植入物设计和选择的推荐。
查询了 2 位高容量肩肘外科医生的内部登记处，确定了 65 个存在 SGBL 的三维肩胛模型。一位经过 fellowship 培训的肩肘外科医生模拟了两个 3.5mm×30mm 螺钉的放置，一个在肩胛脊柱（CS）骨量中，一个在下柱（IS）骨量中。使用解剖参考点创建了三个正交参考平面：肩胛三角，估计的肩胛盂中心和下极。映射螺钉位置，并计算与参考平面的偏差。还计算了 IS 与 CS 的相互位置。使用 10 个随机选择的样本评估观察者内可靠性。报告螺钉取向分布的中位数和 25 百分位和 75 百分位。报告螺钉头位置的平均值和标准差。
我们证明了观察者内可靠性非常好（组内相关系数，0.90-0.98）。50%的 CS 从肩胛平面向后旋转 10°±5°，倾斜 5°±5°。对于 IS，50%的位置与肩胛平面相差 0°±4°，倾斜 -33°±7°。IS 与 CS 的关系在 49%的病例中是内侧和后部，在 45%的病例中是外侧和后部，在 6%的病例中是外侧和前部。平均而言，CS 和 IS 头部之间的距离为 25mm±4mm。
对于 SGBL，可以通过在脊柱和侧柱中放置螺钉来实现肩胛盂植入物的充分固定，具有良好的可重复性。未来的植入物设计应考虑 CS 从肩胛平面向后倾斜 -16°至-5°，倾斜 0°至 12°，IS 从肩胛平面向前倾斜 -6°至 4°，倾斜 -40°至-25°。此外，相互的螺钉位置表明骨丢失分布在前部和下部。未来的植入物设计应考虑到骨增量的潜在益处，以适应 21-29mm 之间的螺钉间距和 IS 相对于 CS 的解剖位置。
