Abstract
Introduction: Total knee replacement (TKR) is an established and successful treatment option for symptomatic osteoarthritis of the knee. Arthroplasty surgeons, however, continue to debate the merits of posterior cruciate ligament (PCL) preservation or resection. Published literature on this subject has not demonstrated a significant clinical difference in outcome in matched subjects. Deliberate PCL resection during non-posterior stabilised TKR has also been shown to have similar outcomes.
The aims of this study were to map the tibial PCL footplate using MRI in patients undergoing TKR and more importantly, to document the percentage disruption of this footplate as a result of the tibial cut.
Patients and Methods: Patients awaiting TKR were prospectively enrolled into this study. Plain radiographs and an MRI scan of the knee were performed. Using coronal and sagittal images and the available software, the cross sectional area of the tibial PCL footplate was determined along with its location relative to the tip of the fibular head. Plain x-rays of the knee were performed postoperatively. Using a number of pre-determined markers we estimated the impact of the operative tibial cut on the PCL footplate.
Results: Twenty-five patients were enrolled into this study. There were 7 male and 18 female patients, mean age: 69 years. The vast majority of implants were AMK (80%), with a mean posterior slope cut of 3.6 degrees (range 0–7) and mean spacer height 11.4 mm (range 8–16).
From MRI analysis, the tibial PCL footplate had a mean surface area of 83 mm2 (range: 49 – 142), and there was a significant difference between male and female patients [Male: 104 mm2versus Females: 75 mm2; t-test, p < 0.005]. The inferior most aspect of the PCL footplate was located on average 1 mm above the superior most aspect of the fibular head (range: 10 mm below to 7 mm above).
Analysis of post-operative radiographs showed that the average tibial cut extended to 4 mm above the tip of the fibular head (range 2 mm below to 14 mm above). Over one third of patients had tibial cuts extending below the inferior most aspect of their PCL footplate (complete removal) and a further one third had cuts which extended into their PCL footplate (partial removal).
Conclusions We have found a wide variation in the size and location of the tibial PCL footplate when referenced against the fibular head.
Proximal tibial cuts using conventional jigs resulted in the removal of a significant portion if not all of the PCL footplate in the majority of patients.
Our findings suggest that when performing PCL retaining TKR’s, we commonly do not actually preserve the PCL.
The abstracts were prepared by Emer Agnew, Secretary to the IOA. Correspondence should be addressed to him at Irish Orthopaedic Association Secretariat, c/o Cappagh National Orthopaedic Hospital, Finglas, Dublin 11, Ireland.
