Accuracy of total knee arthroplasty using the modified gap technique based on the bone gap: an evaluation of the bone gap with a distal femoral trial component

Abstract

Background In total knee arthroplasty (TKA) using the modified gap technique, the soft-tissue balance is measured after osteotomy of the distal femur and proximal tibia (conventional bone gap). However, after osteotomy, the flexion gap size during 90° knee flexion may be larger than that observed after implantation. The tension of the lateral compartment during 90° flexion may also be reduced after osteotomy of the distal femur. We manufactured a distal femoral trial component to reproduce the condition after implantation and prior to posterior condyle osteotomy. This study aimed to evaluate the effect of the trial component on the flexion gap. Methods This prospective study included 21 consecutive patients aged 78 years with medial osteoarthritis who underwent cruciate-retaining TKA between February 2017 and March 2018. The postoperative flexion gap size and inclination during 90° flexion were compared between cases with and without the trial component. Results The mean joint gap size with the trial component (13.4 ± 0.80 mm) was significantly smaller than that without the trial component (14.7 ± 0.84 mm). The mean gap inclination angle with the trial component (3.7° ± 0.62°) was significantly smaller than that without the trial component (5.5° ± 0.78°). Conclusions In the present study, the joint gap size and medial tension were significantly reduced after the trial component had been set. Accurate measurement of the soft-tissue balance is an important factor in the modified gap technique, and this method using a distal femoral trial component can offer better outcomes than those achieved with conventional methods.

Evaluation of the flexion gap with a distal femoral trial component in posterior-stabilized total knee arthroplasty

“…The condition after final femoral component setting should be re-created using the distal femoral trial component when the flexion gap was measured in order to establish a precise soft tissue balance. It was reported previously that the joint gap size and medial tension were significantly reduced after setting the distal femoral trial component in CR TKA [10]. Since the modified gap technique has usually been performed for PS-TKA, it was essential to evaluate the effect of the distal femoral trial component with the PCL dissected.…”

“…The flexion gap size and inclination during 90° flexion were measured using a JDK offset tensor before and after setting the distal femoral trial component, as well as the final femoral trial component after cutting the posterior condyle (Fig. 2) [10,11]. Referring to the flexion gap size and inclination with and without the distal femoral trial component, the rotational and anteroposterior positions were determined so that the gap size in the final femoral trial component was approximately 2 mm larger than the extension gap size and the inclination in the final trial component was approximately 3°.…”

“…Bone gap was measured after conventional cutting of distal femur and proximal tibia, revealing an increase in flexion gap as compared with that after setting the implant. The distal femoral trial component (Zimmer-Biomet, Warsaw, Indiana, USA) was constructed, and the effect of distal femoral resection on the flexion gap with or without the distal femoral trial component was evaluated in cruciate-retaining (CR) TKA so that there was no influence of posterior cruciate ligament resection [10]. The joint gap size and medial tension were significantly reduced after setting the trial component in CR-TKA.…”

Constitutional alignment predicts medial ligament balancing in mechanically aligned total knee arthroplasty for varus knees

“…When assessing gaps intraoperatively, various studies have reported on the difference in gap size with and without trial components [8][9][10]. This is because with the trial implants in place, the flexion and extension gaps as well as medial tension change due to the effect of the femur component on the surrounding soft tissues [17,23].…”

Increased Posterior Condylar Offset Decreases the Extension Gap in Cases With Flexion Contracture in Modified Gap Technique Total Knee Arthroplasty

“…The association between the gap difference and preoperative flexion contracture is also examined because preoperative flexion contracture is a factor affecting the intraoperative and postoperative extension gap [ 8 ]. No research has yet compared the changes in PCO and extension gap, evaluated before the resection of the posterior condyle with the distal femoral trial and after the resection of the posterior condyle with the placement of the femoral trial component [ 9 , 10 ]. The purpose of this study was to elucidate the relationship between the change in medial and lateral PCO and the extension gap using a TKA modified-gap technique.…”