Effect of mediolateral gap difference on postoperative outcomes in navigation-assisted total knee arthroplasty using an ultracongruent insert and the medial stabilising technique

Abstract

PurposeThis study was aimed to compare the clinical, functional, and radiographic outcomes between symmetric and asymmetric extension and mediolateral gap balance after navigation‐assisted (NA) total knee arthroplasty (TKA) using ultracongruent (UC) insets and the medial stabilising technique (MST). MethodsIn all, 363 knees of 275 patients who underwent mechanical alignment‐target NA TKA with MST between January 2015 and December 2017 were analysed. Patients were divided into balanced (extension mediolateral gap difference ≤ 2 mm) and tight medial (difference ≥ 3 mm) groups. Pre‐ and postoperative clinical, functional (range of motion, Western Ontario and McMaster University Osteoarthritis [WOMAC] index, Knee Society Knee Score [KSKS], and Knee Society Function Score [KSFS]) and radiographic (hip–knee–ankle [HKA] angle, femoral condylar offset, extension angle [a minus indicates hyperextension], and joint line distance) outcomes were compared between the groups. Student’s t‐ or Chi‐squared test was used to compare the outcomes. ResultsAmong the 363 knees analysed, 279 (77%) were assigned to the balanced group and 84 (23%) to the tight medial group. The preoperative HKA angle was significantly greater in the tight medial group than in the balanced group (9.7° ± 4.1° vs 14.3° ± 4.7°, P < 0.001). The postoperative WOMAC index, KSKS, and KSFS were similar between the groups. The change in the joint line distance was not significantly different (1.5 ± 3.7 vs 2.0 ± 3.3; n.s). ConclusionThe clinical, functional, and radiographic outcomes, including joint line distance, were comparable between the tight medial and balanced group after mechanical alignment‐targeted UC TKA with MST. Level of evidenceLevel III, retrospective comparative study.

Role and Results of Constrained Insert in Computer-Assisted Primary Total Knee Arthroplasty: A Propensity-Matched Study

“…The average follow-up in group CP was 44 ± 9.9 months (range 37-61) and in group PS was 42.7 ± 5.5 months (range 36-43) ( P = .06). The average insert thickness in the CP group was 10.7 ± 2.1 mm [ 3 , [9] , [10] , [11] , [12] , [13] , [14] , [15] , [16] , [17] ], while in PS group it was 10.4 ± 1.6 mm [ 3 , [8] , [9] , [10] , [11] , [12] , [13] , [14] ] (range 9-15) ( P = .36) ( Table 3 ).…”

“…A CP insert with primary femoral component is also effectively used in valgus knees where medial laxity persists in extension and flexion after valgus deformity is corrected to ±2 degree with the help of computer assisted surgery (CAS) [ 15 ]. Similar to varus knees, CP insert is not a substitute for inadequate soft tissue balancing in a valgus knee but only an adjunct to achieve more stability and maintain M-L gap difference between ≤2 mm throughout the arc of motion ( Figure 6 , Figure 7 , Figure 8 ) [ 16 , 17 ].…”

The Effect of Severe Varus Deformity on Clinical and Radiographic Outcomes in Mechanical Aligned Total Knee Arthroplasty with Medial Stabilizing Technique

“…A previous study demonstrated that the severity of the preoperative varus alignment was closely related to the mediolateral gap difference [ 11 ]. One major concern in allowing for lateral laxity is the possibility of hyperextension after TKA.…”

“…The deep MCL was released to create a space for implantation. Other medial soft tissue releases were not performed and lateral physiological laxity was allowed to avoid excessive medial release, as in previous studies [ 5 , 11 ]. Distal femoral and proximal tibial cuttings were performed in a plane perpendicular to the mechanical axes of the femur and tibia, respectively.…”