Fibula head is a useful landmark to predict the location of posterior cruciate ligament footprint prior to total knee arthroplasty.

PURPOSE

The hypothesis of our study is that a routine tibial cut during cruciate retaining TKA may result in a partial or a total removal of the PCL footprint. Therefore providing a reliable landmark is essential to estimate the probability of PCL damage with a tibial cut and to enable the surgeon to decide pre-operatively whether a cruciate retaining implant design is suitable.

METHODS

In a case series of 175 cruciate retaining TKA, the routinely made standing postoperative AP-view radiographs were evaluated to determine the distance between fibula head and tibial cutting plane. In a second case series knee MRI of 223 subjects were consecutively used to measure the vertical distance between tibial attachment of PCL and fibula head. The probability of partial or total PCL damage was calculated for different vertical distances between tibial cut and fibula head.

RESULTS

The vertical distance between the tibial cut and the most proximal point of the fibula head averaged 6.1 mm ±4.8 mm. The mean vertical distance from fibula head to proximal and to distal PCL footprint revealed to be 11.4 mm ±3.7 mm and 5.4 mm ±2.9 mm, respectively. The location of the insertion was not significantly different between subgroups such as age (<50 or >50 years), gender and side. Based on our results 11 (7%) knees were considered at high risk of an entire PCL removal after implantation of a cruciate retaining TKA design.

CONCLUSIONS

Currently available routine tibial preparation techniques result in partial or total posterior cruciate ligament detachment. Fibula head as a landmark aids to predict the PCL location and to estimate its disruption pre- and postoperatively on AP-view radiographs.