OBJECTIVE: To evaluate possible changes in patellar height after total knee arthroplasties with and without preservation of the posterior cruciate ligament (PCL). METHOD: Analysis was made of pre- and post-operative X-rays of 120 patients submitted to total knee arthroplasties at the National Institute of Traumatology and Orthopedics between January 2003 and January 2005, with Johnson-type rotary platform implants. The sample was divided into two groups, group I corresponding to radiographic exams before and after total knee arthroplasty with preservation of the PCL (n = 60), and group II corresponding to radiographic exams before and after arthroplasties without preservation of the PCL (n = 60). To measure the values before and after surgery, the authors used the Blackburne Peel method, whose normal value is equal to 0.8 (± 0.2), therefore varying between 0.6 and 1. RESULTS: The mean pre-operative patellar ratio in group I was equal to 0.874, and in group II the mean was equal to 0.857. The mean post-operative patellar height ratio in group I was equal to 0.849, varying between 0.54 and 1.03. In group II, the lower ratio was equal to 0.48, and the highest, equal to 0.94, the mean rate being equal to 0.79. The comparison of post-operative value between the groups presented a statistically significant difference (p < 0.05). CONCLUSIONS: A tendency towards decreased patellar height was seen in both groups studied, but it was more evident in the group in which the PCL was not preserved.
Posterior cruciate ligament; Patella; Arthroplasty, replacement, knee
