Performing high flexion activities does not seem to be crucial in developing early femoral component loosening after high-flexion TKA.

Background: It is still unclear whether high flexion (HF) activities correlated with the early loosening of the femoral component and whether HF activities are possible. We investigated what is the capability for performing various HF activities, and whether high flexion activities increase the chance of aseptic loosening after HF-TKA.

Methods: We retrospectively analysed 260 patients who underwent HF-TKA using the NexGen LPS Flex between 2001 and 2009. The mean follow-up was 6.7 years (range, 5-13). We evaluated range of motion, Knee Society scores, WOMAC, and serial radiographs for aseptic loosening. Responses to questions on individual HF activities were recorded on 5-point Likert scales based on difficulty (0-4). Patients were divided two groups based on their responses to squatting and kneeling, which were important weight-bearing HF activities in Asian population (HF group vs. non-HF group) for comparisons of aseptic loosening and clinical outcomes.

Results: More than 80 % of patients positively responded for various HF activities. The capability of HF activities showed that cross-legged sitting, squatting, and kneeling were 97.7, 51.1 and 52.7 % at the latest follow-up, respectively. Aseptic loosening was identified in two tibial components (0.8 %) but none in femoral components in non-HF group. There was no significant difference of aseptic loosening based on HF activities (0.8% vs. 0%, p = 0.063).

Conclusions: The results of this study suggest that HF activities do not seem to be associated with aseptic loosening of femoral component after HF-TKA.