Ferreira L M, Knowles N K, Richmond D N, Athwal G S
Roth|Mcfarlane Hand and Upper Limb Centre, Surgical Mechatronics Laboratory, St. Josephs Health Care, London, ON, Canada; Department of Mechanical and Materials Engineering, University of Western University, London, ON, Canada; Schulich School of Medicine and Dentistry, University of Western University, London, ON, Canada.
Roth|Mcfarlane Hand and Upper Limb Centre, Surgical Mechatronics Laboratory, St. Josephs Health Care, London, ON, Canada; Department of Mechanical and Materials Engineering, University of Western University, London, ON, Canada.
Orthop Traumatol Surg Res. 2015 Jun;101(4):427-30. doi: 10.1016/j.otsr.2015.03.010. Epub 2015 Apr 25.
Glenoid bone grafting is often used in cases of reverse shoulder arthroplasty (RSA) with glenoid deficiency. Additionally, bony increased-offset RSA (BIO-RSA) uses a cylindrical bonegraft harvested from the humeral head and is positioned beneath the glenoid baseplate to increase lateralization. Postoperative computed tomography (CT) has been used to detect glenoid bonegraft resorption, which is typically identified by a gap between the bonegraft and baseplate; however, CT images are often degraded by implant metal artifact. The purpose of this CT imaging study was to determine if a simulated bonegraft resorption gap is detectable following RSA with glenoid bone grafting.
CT is unable to detect bone graft resorption following reverse shoulder arthroplasty conducted with bone grafting beneath the glenoid baseplate.
RSA with glenoid bone grafting was performed on four cadaver shoulders. Glenoid bonegraft resorption gaps were simulated by fixing the implant at six different gap widths (0, 1, 2, 4, 6 and 8mm). Clinical CT scans were acquired for each gap resulting in 6 scans per specimen. Two experienced observers (blinded) analyzed DICOM images in the axial and coronal directions, and measured gap widths using Mimics(®) software. Each observer had access to approximately 200 images per condition per specimen.
The sensitivity of CT imaging to positively identify bonegraft resorption was 38%, with an accuracy of 46%. Inter-observer agreement was 92%. Observers tended to visualize no-gap for most conditions. Resorption gap width measurements were consistently underestimated.
Metal artifact prevented identification of simulated bonegraft resorption gaps and observers most often determined that there was bonegraft-to-implant "healing" on CT, when in fact a gap was clinically present. This study illustrates the need for more effective imaging techniques to determine if bonegraft resorption has occurred following RSA.
肩胛盂植骨常用于肩胛盂缺损的反肩关节置换术（RSA）。此外，骨增加偏移量反肩关节置换术（BIO-RSA）使用从肱骨头获取的圆柱形骨移植块，并将其置于肩胛盂基板下方以增加外展。术后计算机断层扫描（CT）已用于检测肩胛盂植骨吸收，其通常通过植骨与基板之间的间隙来识别；然而，CT图像常因植入物金属伪影而退化。本CT成像研究的目的是确定在进行肩胛盂植骨的RSA术后，模拟的植骨吸收间隙是否可被检测到。
在肩胛盂基板下方进行植骨的反肩关节置换术后，CT无法检测到植骨吸收。
对四具尸体肩部进行肩胛盂植骨的RSA手术。通过将植入物固定在六种不同的间隙宽度（0、1、2、4、6和8毫米）来模拟肩胛盂植骨吸收间隙。针对每个间隙进行临床CT扫描，每个标本共扫描6次。两名经验丰富的观察者（不知情）在轴向和冠状方向分析DICOM图像，并使用Mimics（®）软件测量间隙宽度。每个观察者每种情况每个标本可获取约200张图像。
CT成像对阳性识别植骨吸收的敏感度为38%，准确率为46%。观察者间一致性为92%。在大多数情况下，观察者倾向于将间隙视为无间隙。吸收间隙宽度测量结果一直被低估。
金属伪影妨碍了对模拟植骨吸收间隙的识别，观察者在CT上大多判定植骨与植入物“愈合”，而实际上临床上存在间隙。本研究表明需要更有效的成像技术来确定RSA术后是否发生了植骨吸收。
