Abstract
Introduction:
In posterior cruciate ligament-retaining total knee arthroplasty (CR-TKA), a small bone block (bony island) is often preserved to protect the attachment of the posterior cruciate ligament (PCL), which might be troublesome. In contrast, we prefer to resect the tibial plateau completely to facilitate the surgical procedure. However, there is concern over the increase of the flexion gap due to partial detachment of the PCL. The purpose of the present study is to evaluate the influence of bony island resection on the flexion gap.
Methods:
The subjects were 20 consecutive patients who underwent posterior cruciate ligament-retaining total knee arthroplasty for varus osteoarthritis. There were 18 women, two men, with a mean age of 71.8 years (range, 62–82 years). All operations were performed using posterior cruciate ligament-retaining prosthesis (MERA Quest Knee System, Senko Medical Instrument Manufacturing, Tokyo) by the same senior author with a measured resection technique. The knees were exposed with a medial parapatellar approach. The distal femur was cut and the tibial plateau resection was made with preserving the bony island. The central joint gaps in 90° flexion and full extension were measured using a tensioning device (Offset Repo-Tensor, Zimmer, Warsaw, IN) at 40-lb distracting force. Then, after the resection of the bony island, the central joint gaps were measured by the same method. In addition, the posterior tilt of the tibial resection and the depth of the lateral tibial cut were measured.
Results:
The flexion gaps before and after the resection were 18.1 ± 0.4 and 18.4 ± 0.5 mm, respectively, and there was no statistical difference (p = 0.07) [Fig. 1]. Similarly, the extension gap did not increase significantly before and after the resection (20.8 ± 0.6 and 21.0 ± 0.6 mm; p = 0.81) [Fig. 2]. The mean posterior tilt was 6.0°, and the mean depth was 10.4 mm.
Discussion:
The PCL is the largest and strongest ligament among the knee ligaments. It mainly works as the first stabilizer against posterior laxity, and it has been reported to perform as the second stabilizer against valgus laxity in mid-flexion. Accordingly, we think that preserving the PCL leads to postoperative joint stability in total knee arthroplasty. However, bony island preservation, which is done in CR-TKA, often results in fractures of basal part of the island. Our procedure is comparatively easy, but it cannot avoid the problem of partial detachment of the PCL. The PCL is comprised of two bundles: the anterolateral bundle (ALB) and the posteromedial bundle (PMB). As for the attachments of the bundles, an anatomical study has reported that the locations of the centers of the ALB and PMB were 1.5 ± 0.8 and 6.0 ± 2.0 mm, respectively from the tibial plane. Therefore, considering our tibial resection, it suggests that the distal part of the ALB attachment and the most part of PMB attachment are preserved, which is supported by the results of our study.
Conclusions:
Bony island resection can be easily performed and preserve the PCL function.
