Comparison between two computer-assisted total knee arthroplasty: gap-balancing versus measured resection technique

Abstract

Two surgical strategies are possible in total knee arthroplasty (TKA): a measured resection technique, in which bone landmarks are used to guide resections equal to the distal and posterior thickness of the femoral component, or a gap-balancing approach, in which equal collateral ligament tension in flexion and extension is sought before and as a guide to final bone cuts. In this study performed with computer assisted system, we compared the 2 different methods in 126 patients followed prospectively in order to analyze the effect of both the techniques on joint-line (JL) maintenance, axial limb restoration and components position. The gap technique showed a statistical increase in the post-operative value when compared with the measured resection technique, (P = 0.008). When comparing the two groups regarding to the pre-operative deformity, we have found a statistical difference (P = 0.001) in case of moderate pre-operative deformity (less than 10 degrees), and the measured resection technique showed a slight superiority in preserving a joint line more faithful to the pre-operative. We found an ideal alignment for the mechanical axis (180 degrees ± 3 degrees) (95% of cases). In six cases (5%), the mean post-operative value exceeded (varus or valgus) the ideal value by more than 3 degrees. In the frontal plane, a good alignment was observed for both femoral and tibial components without a significant difference between the two techniques. In the sagittal plane was found more alignment variability due to the different implants used and their ideal starting slope, from 7 degrees to 3 degrees. Finally, the surgeon can use the approach with which he has more confidence; however, as the measured resection technique causes less reduction in the post-operative joint-line position, in case of shortening of patellar tendon or patella infera, this technique is preferable.

Influence of tibial slope on extension and flexion gaps in total knee arthroplasty: increasing the tibial slope affects both gaps

“…At 0°slope, the tibial cuts consisted only of the amount of bone necessary to allow prosthetic components to fill the space under load [27]. These gaps are differentiated from the typical extension and flexion gaps, which are defined under distraction of the knee joint [6,7].…”

“…The mean gap size of all 20 specimens averaged 19.3 mm, with the accompanying standard deviation of (± 2.9 mm) reflecting basically the varying cartilage thicknesses present. This can be explained because of the resection technique as described by Tigani et al [27], in which bony reference points were used. A total knee prosthesis that is symmetric in the area of the contact points would thus exactly fill in this osseous resection gap, and distraction of the knee in this state would, neglecting changes in the capsule/ligaments caused by the resection itself, lead to the typical extension and flexion gaps.…”

Soft-tissue balancing in total knee arthroplasty: cruciate-retaining versus posterior-stabilised, and measured-resection versus gap technique

“…However, the same pattern was found in the gap technique in our study. The advantage of the measured-resection technique involves preservation of the joint line by avoiding excessive release of medial structures [27,28]. To this end, in procedures using measured resection, residual lateral ligament laxity tends to be allowed [29][30][31].…”

“…To this end, in procedures using measured resection, residual lateral ligament laxity tends to be allowed [29][30][31]. In contrast, focusing on the adjustment of varus/valgus ligament balance in the gap technique sometimes results in excessive release of medial structures to equalise lateral laxity and requires the use of a thicker polyethylene insert [27,28]. Recognising this, in this study, even with the gap technique, a larger flexion gap of up to 5 mm and residual lateral laxity up to 3°were accepted in the soft-tissue-balancing procedure, especially in PS.…”

Soft Tissue Balance in Total Knee Arthroplasty

“…Under such debate, several surgeons recently reported more consistent equalization of extension and flexion gaps with the use of computer-assisted gap balancing technique, compared with conventional measured resection technique [119,120]. In contrast, in the comparison between the navigation-assisted measured resection and navigationassisted gap balancing technique, some surgeons reported a better restoration of the joint line position in the navigation-assisted measured resection technique despite no differences in short-term clinical outcomes [120,121]. Using the offset type tensor, which can be used in the gap technique [123], we performed soft tissue balance assessment during CR TKA using the tibia first gap technique with navigation system.…”