Department of Orthopaedic Surgery, Hospital for Special Surgery, 535 East 70th Street, New York, NY, 10021, USA.
Department of Biomechanics, Hospital for Special Surgery, 535 East 70th Street, New York, NY, 10021, USA.
Knee Surg Sports Traumatol Arthrosc. 2019 Jul;27(7):2140-2144. doi: 10.1007/s00167-019-05422-5. Epub 2019 Feb 28.
The purpose of this study was to evaluate the thickness of medial and lateral posterior femoral condylar bone resected with five implant systems using posterior referencing jigs set at 3° of external rotation. The hypothesis was that posterior condylar resection thickness on the medial side would be equal to the thickness of the femoral implant posteriorly, regardless of implant system.
Posterior referencing femoral sizers were used on right femur sawbones models for five different implant systems. Each sawbones model was sized using a femoral sizer for the specific implant system. Sizing guides were set at 3° of external rotation for the right femur. Each system's 4-in-1 cutting block was then used to make posterior condylar cuts. The thicknesses of the cut bones were measured using a manual calliper.
The amount of bone resected from both medial (P = 0.0004) and lateral (P < 0.0001) posterior condyles differed significantly across the five implant systems. The mean thickness of bone resected from the posteromedial femoral condyle ranged from 9.4 ± 0.5 to 12.4 ± 0.9 mm. The mean thickness of the posterolateral condyle cut ranged from 6.7 ± 0.6 to 10.2 ± 0.3 mm. The difference in thicknesses between the bone resection from the posteromedial condyle and the implant thickness of the posterior condyles ranged from 0.6 to 2.9 mm.
The thickness of bone removed from the posterior femoral condyles varied by up to 3 mm across the five TKA implant systems. For each system, the posteromedial condyle resection was larger than the thickness of the posterior condyle of the actual implant. As the difference between the posterior bone resection and the implant thickness increases, the flexion gap will likely loosen and should be accounted for during gap balancing. In commonly used knee implant systems, resected bone is greater than implant thickness and may lead to flexion instability.
本研究旨在评估使用设置为 3°外旋的后参考夹具的五种植入物系统切除的股骨内、外侧后髁的厚度。假设是内侧后髁切除的厚度将与股骨后植入物的厚度相等，而与植入物系统无关。
使用五个不同植入物系统的后参考股骨定标器对右股骨锯骨模型进行测量。每个锯骨模型都使用特定植入物系统的股骨定标器进行定标。对于右股骨，定标器设置为 3°外旋。然后，使用每个系统的 4-in-1 切割块进行后髁切割。使用手动卡尺测量切割骨的厚度。
五个植入物系统之间，内侧（P=0.0004）和外侧（P<0.0001）后髁切除的骨量有显著差异。从股骨后内侧髁切除的骨平均厚度范围为 9.4±0.5 至 12.4±0.9mm。后外侧髁切割的平均厚度范围为 6.7±0.6 至 10.2±0.3mm。从股骨后内侧髁切除的厚度与后髁植入物厚度之间的差异范围为 0.6 至 2.9mm。
在五个 TKA 植入物系统中，从股骨后髁切除的骨厚度相差可达 3mm。对于每个系统，后内侧髁切除的量大于实际植入物后髁的厚度。随着后骨切除与植入物厚度之间的差异增加，屈曲间隙可能会松动，在间隙平衡过程中应予以考虑。在常用的膝关节植入物系统中，切除的骨比植入物厚度大，可能导致屈曲不稳定。
