Department of Orthopaedic and Traumatology Surgery, Louis Caty hospital, Epicura Baudour, Saint-Ghislain, Belgium.
Department of Orthopaedics, School of Medicine, Free university of Brussels, Brussels, Belgium.
Int Orthop. 2018 Dec;42(12):2797-2806. doi: 10.1007/s00264-018-3856-4. Epub 2018 Mar 3.
Lateralized tibial tubercle is a cause of patellar instability. Before proceeding with reduction of the tibial tubercle-trochlear groove (TT-TG) distance, surgeons prefer to know whether this distance is pathologic. However, the pathological value remains discussed and may vary with the size of the knee.
We sought to determine variability in the traditional TT-TG distance versus the anthropometric knee size, using dimensions of the distal part of the femur and proximal part of the tibia of 85 CT scans of the knees in two groups of knees, one normal group without history of patellofemoral instability and one pathologic group with history of instability.
The average TT-TG distance measured 13 mm in normal knees and 16.4 mm in pathologic knees. The variability in measurements between normal and pathologic knees varied respectively between ± 5 and ± 15 mm, with as consequence absence of threshold value between normal and pathologic knees. These measurements were supplemented by an analysis of a size ratio coefficient. In the normal group without history of instability, linear regression analysis showed that patients with larger knees tended to have higher TT-TG distances and that the values are associated with the mean ML femoro-tibial width (p = 0.014; Pearson coefficient = 0.4). The knees with history of instability also keep proportional increase of TT-TG with the size of the knee as the knees without history of instability. We developed a nomogram to more appropriately represent the normal values for a given size of the knee. Application of the nomographic model on the CT scan TT-TG data of the patients who have knee instability allows the orthopaedic surgeon to associate the TT-TG distance with the knee size and to evaluate the medial transfer corresponding to the knee size.
The average TT-TG distances in normal and pathologic knees were not identical for each size of the knees.
外侧胫骨结节是髌股关节不稳定的原因之一。在进行胫骨结节-滑车沟（TT-TG）距离的复位之前，外科医生更倾向于了解该距离是否异常。然而，异常的 TT-TG 距离的临界值仍存在争议，并且可能因膝关节大小的不同而变化。
我们旨在确定传统 TT-TG 距离与下肢解剖学尺寸的变异性，使用了股骨远端和胫骨近端的尺寸，纳入了 85 例 CT 膝关节扫描的两个膝关节组，一组为无髌股关节不稳定病史的正常组，另一组为有不稳定病史的病理组。
正常膝关节的 TT-TG 平均距离为 13mm，病理膝关节为 16.4mm。正常和病理膝关节之间的测量值的变异性分别在±5mm 和±15mm 之间，因此正常和病理膝关节之间不存在临界值。这些测量值补充了大小比系数的分析。在无不稳定病史的正常组中，线性回归分析显示，膝关节较大的患者 TT-TG 距离较高，并且与股骨-胫骨的平均 ML 宽度相关（p=0.014；皮尔逊系数=0.4）。有不稳定病史的膝关节也随着膝关节的大小呈现 TT-TG 的比例增加，与无不稳定病史的膝关节相同。我们制定了一个列线图，以更适当地表示给定膝关节大小的正常值。将列线图模型应用于有膝关节不稳定的患者的 CT 扫描 TT-TG 数据，可以让矫形外科医生将 TT-TG 距离与膝关节大小相关联，并评估与膝关节大小对应的内侧转移。
对于每个膝关节大小，正常和病理膝关节的平均 TT-TG 距离并不相同。
