Load imbalances existed as determined by a sensor after conventional gap balancing with a tensiometer in total knee arth
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KNEE
Load imbalances existed as determined by a sensor after conventional gap balancing with a tensiometer in total knee arthroplasty Sang Jun Song1 · Hyun Woo Lee1 · Kang Il Kim1 · Cheol Hee Park2 Received: 6 June 2019 / Accepted: 27 August 2019 © European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA) 2019
Abstract Purpose To evaluate intercompartmental load intraoperatively with a sensor after conventional gap balancing with a tensiometer during total knee arthroplasty (TKA). Methods Fifty sensor-assisted TKA procedures were performed prospectively between August and September 2018 with a cruciate-retaining prosthesis. After applying a modified measured resection technique, conventional balancing between resected surfaces was achieved. The equal and rectangular flexion–extension gaps were confirmed using a tensiometer at 90° and 5°–7° (due to posterior tibial slope) of knee flexion. Then, the load distribution was evaluated intraoperatively with a sensor placed on trial implants in the positions of knee flexion (90° flexion) and extension (10° flexion). Results The proportion of coronal load imbalance (medial load − lateral load ≥ ± 15 lb) was 56% in extension and 32% in flexion (p = 0.023). The proportion of sagittal load imbalance (extension load − flexion load ≥ ± 15 lb) was 36% in the medial compartment and 4% in the lateral compartment (p 20°);
Knee Surgery, Sports Traumatology, Arthroscopy
and/or severe flexion contracture (> 20°). The preoperative demographics and deformities are presented in Table 1.
Methods All primary CR TKA procedures were performed with a modified measured resection technique with patellar resurfacing. A medial parapatellar approach was used with a midline skin incision. All osteophytes were removed from the femur and tibia. An intramedullary guide was used for distal femoral resection, and the transepicondylar axis was used for femoral component rotation. The size of the femoral component was selected using the anterior-referencing method. An extramedullary guide was used for tibial resection. The tibial slope was usually set to 5°–7° of posterior slope in the sagittal plane. The reference line for tibial rotation was accurately aimed at a line passing through the medial third of the tibial tubercle and the second metatarsal or middle of the talus. The posterior cruciate ligament (PCL) was preserved and protected during tibial resection by vertical sawing in front of the PCL insertion site [35]. Following resection, soft tissue balancing was performed using a conventional method. The flexion and extension gaps were assessed at 90° and 5°–7° (the degree of extension was influenced by the posterior tibial slope) of knee flexion with a force-controlled tensiometer system (B. Braun Aesculap, Tuttlingenm, Germany) to assess an equal rectangular flexion–extension gap [38]. An absolute distraction force of 120–150 N was applied [14, 38]. The tensiometer consisted of an instrument showing gap size (mm) and a distractor (Fig. 2a). The medialized offset tensio
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