Is Hyperflexion Possible with the Solitary Use of High-Flexion Insert in Knee Replacement Preserving the Posterior Cruciate Ligament? (Mid-term Results)

Abstract

Objective: For evaluating the early midterm results of our patients who underwent total knee replacement allowing for hyperflexion and for identifying the factors affecting the range of flexion in particular. Methods: A total of 150 knees of 95 patients who underwent total knee replacement using a high-flexion cruciate retaining insert were evaluated. The patients were followed up for a mean of 8.5 (3.5-11) years. The knee joints were assessed pre- and postoperatively and at the final follow-up using the Knee Society Scoring System and their ranges of motion were recorded. The component survival was also investigated. Results: The mean preoperative knee score was 49.1 +/- 12.0, the mean functional score was 48.9 +/- 14.1 and the mean range of flexion was 119.3 +/- 18.9 degrees. The same values of the follow-up improved on 92.9 +/- 8.2 (p<0.0001), 90.7 +/- 10.6 (p<0.0001) and 128.0 +/- 11.5 degrees (p<0.0001), respectively. A moderate correlation was detected between the preoperative and postoperative ranges of flexion (r=0.623, p<0.0001). There was an insert revision of one knee (0.6\%) because of early infection. No revision was required owing to aseptic loosening. Analysis using the ROC revealed the probability of postoperative hyperflexion of 130 degrees and above in knees that had a preoperative range of flexion of 115 degrees and above. Conclusion: The postoperative range of flexion was found to correlate with the preoperative range of flexion. The results of our study showed that a higher range of flexion is not possible with the solitary use of high-flex Cruciate Retaining insert and the preoperative range of flexion is an important factor in attaining hyperflexion even with the use of such inserts.