Result of posteromedial capsule and superficial medial collateral ligament release on gap and alignment in total knee arthroplasty in varusknee deformity by computer assisted surgery measurement: a retrospective stud
Authors: Chaiyakit Pruk , Onklin Ittiwat , Ampunpong Weeranate 
Published: May 2020

Soft tissue release and gap balancing in total knee arthroplasty (TKA) are important issue and lack of conclusive result. We performed posteromedial capsule (PMC) and superficial medial collateral ligament (sMCL) release by preservation of anterior attachment of pes anserine. Gaps and alignment were recorded by computer assisted surgery measurement.

Results:

T: The mean correction of varus deformity after PMC release and sMCL release were 4.88 ± 2.82° and 3.39 ± 1.7 respectively with the mean FC after PMC and sMCL release correction of 5.57 ± 3.5 and 1.34 ± 2.9° respectively. The mean medial gap changes on full extension after PMC and sMCL release was 1.83 ± 1.39 and 1.67 ± 1.04 mm. respectively with the mean medial gaps at 90 degree flexion after PMC and sMCL release changes of 0.73 ± 0.9 and 5.14 ± 2.11 mm. respectively. The mean lateral gap changes on extension after PMC and sMCL release were -1.3 ± 1.83 and -1.1 ± 1.6 mm. respectively with the mean lateral gaps at 90 degree flexion after PMC and sMCL release changes of -0.19 ± 1.03 and 0.06 ± 1.75 mm. here were 21 patients (16 female and 5 male) with mean age of 68 (48-78) years. The mean body mass index was 28.49 (20.70 – 39.95) kg/m2. The mean preoperative hip-knee-ankle angle was varus 8.12 (3.5-16.0) degrees with mean flexion contracture of 11.3 (3.5-16.0) degrees. Sixteen knees were implanted with Fixed bearing knee prosthesis and five knees were implanted with Mobile bearing knee prosthesis (Table.1). We performed PMC release in all patients, and combined PMC and sMCL release in fourteen patients. The mean correction of varus deformity after PM release and sMCL release were 4.88 ± 2.82 and 3.39 ± 1.7 degrees respectively. While the mean correction of flexion contracture after PMC release and sMCL release were 5.57 ± 3.5 and 1.34 ± 2.9 degrees respectively (Fig.8). The mean medial gaps change on extension after PMC and sMCL release were 1.83 ± 1.39 and 1.67 ± 1.04 mm. respectively. The mean medial gaps change at 90 degree flexion after PMC and sMCL release were 0.73 ± 0.9 and 5.14 ± 2.11 mm. respectively (Fig.9). The mean lateral gaps change on extension after PMC and sMCL release were 1.3 ± 1.83 and -1.1 ± 1.6 mm. respectively. The mean lateral gaps change at 90 degree flexion after PMC and sMCL release were -0.19 ± 1.03 and 0.06 ± 1.75 mm. (Fig.9). There is no instability of knee after PMC and sMCL release.

Materials and Methods:

Twenty one patient had been operated on. TKA with computer assisted surgery was performed using PMC and sMCL release by preservation of anterior attachment of pes anserine. Alignment, medial and lateral gaps were measured by computer assisted surgery. The mean age was 68 (48-78) years with the mean preoperative hip-kneeankle angle of 8.12 (3.5-16.0) degrees and the mean flexion contracture (FC) of 11.3 (3.516.0) degrees.

Conclusion:

We believe that sMCL release with preservation of anterior attachment of pes anserinus in total knee arthroplasty has additional effect on varus knee correction after PMC release without creation of knee instability.