Brant Jason, Roberts Michael, Nelms Nathaniel, Schottel Patrick, Haimes Mark, Blankstein Michael
Department of Orthopaedics and Rehabilitation, University of Vermont, Burlington, Vermont.
JB JS Open Access. 2025 Sep 8;10(3). doi: 10.2106/JBJS.OA.25.00182. eCollection 2025 Jul-Sep.
In robotic-assisted total knee arthroplasty (RA-TKA), the femoral prosthesis is positioned independent of the intramedullary canal and frequently in flexion for function optimization. Femoral prosthesis flexion displaces retrograde intramedullary nail (rIMN) start point posteriorly potentially exacerbating hyperextension deformity in periprosthetic fracture (PPFx) fixation. The aim of this study was to determine the relationship between RA-TKA femoral component flexion with rIMN sagittal trajectory angulation. We hypothesized flexion of the femoral component increases nail sagittal angle.
This is a single-center academic observational study including adult patients undergoing primary RA-TKA by 3 fellowship-trained arthroplasty surgeons between August 2023 and February 2024. Final femoral implant characteristics after knee gap balancing were obtained from intraoperative computerized tomography screenshots. Sagittal angle measurements of rIMN trajectory based on distal femoral nail start point and center of femoral shaft were measured using ImageJ software and compared with several variables with a focus on femoral component flexion for 10-mm and 12-mm nail sizes.
A total of 111 patients (61 female and 50 male) with a mean age of 67 years (SD 10) and height 168 cm (SD 11) were included. The mean femoral component flexion was 5.87° (SD 2.13), and the mean nail sagittal trajectory angle was 9.83° (SD 2.79) and 11.43° (SD 2.88) for the 10-mm and 12-mm nails, respectively. There was a significant linear correlation of a 0.50° increase in the mean sagittal angle for every 1.0° increase in femoral component flexion for both nail sizes (p < 0.001).
There is a linear correlation between femoral component flexion and rIMN sagittal trajectory angle. The mean sagittal angulation was approximately 10°, and the mean component flexion was 6°. As number of RA-TKAs performed nationally is expected to increase, a rIMN with a distal bend designed to compensate for femoral component flexion could be considered to limit hyperextension deformity in distal femur PPFx fixation.
Level IV. See Instructions for Authors for a complete description of levels of evidence.
在机器人辅助全膝关节置换术（RA-TKA）中，股骨假体的定位独立于髓内管，并且经常处于屈曲位以优化功能。股骨假体的屈曲会使逆行髓内钉（rIMN）起始点向后移位，这可能会加重假体周围骨折（PPFx）固定时的过伸畸形。本研究的目的是确定RA-TKA股骨组件屈曲与rIMN矢状轨迹角度之间的关系。我们假设股骨组件的屈曲会增加髓内钉的矢状角。
这是一项单中心学术观察性研究，纳入了2023年8月至2024年2月期间由3名接受过 fellowship 培训的关节置换外科医生进行初次RA-TKA的成年患者。膝关节间隙平衡后最终的股骨植入物特征从术中计算机断层扫描截图中获取。使用ImageJ软件测量基于股骨远端髓内钉起始点和股骨干中心的rIMN轨迹的矢状角，并与几个变量进行比较，重点关注10毫米和12毫米髓内钉尺寸的股骨组件屈曲情况。
共纳入111例患者（61例女性和50例男性），平均年龄67岁（标准差10），身高168厘米（标准差11）。股骨组件的平均屈曲角度为5.87°（标准差2.13），10毫米和12毫米髓内钉的平均髓内钉矢状轨迹角度分别为9.83°（标准差2.79）和11.43°（标准差2.88）。两种髓内钉尺寸中，股骨组件屈曲每增加1.0°，平均矢状角均显著线性增加0.50°（p < 0.001）。
股骨组件屈曲与rIMN矢状轨迹角度之间存在线性相关性。平均矢状角约为10°，平均组件屈曲角度为6°。由于预计全国范围内进行的RA-TKA数量会增加，可考虑设计一种带有远端弯曲以补偿股骨组件屈曲的rIMN来限制股骨远端PPFx固定时的过伸畸形。
IV级。有关证据水平的完整描述，请参阅作者指南。
