A novel extramedullary technique to guide femoral bone preparation in mobile unicompartmental knee arthroplasty based on tibial cut and overall alignment

Abstract

Background: The mobile Oxford unicompartmental knee arthroplasty (UKA) implant has been widely used with an intramedullary guide for femoral preparation. We modified the femoral guide technique based on the tibial cut first and spacer block technique. This study was performed to determine the radiographic accuracy and early clinical outcomes of the extramedullary method. Methods: We retrospectively evaluated 50 consecutive patients who underwent UKA using the extramedullary technique. An equal number of patients who underwent UKA with the conventional technique were matched as the control group. Clinical outcomes were evaluated in terms of the operating time, blood loss, range of motion, and Hospital for Special Surgery score. Radiographic accuracy was evaluated by the implant position and alignment in the coronal and sagittal planes. Results: The mean follow-up period was 39.76 ± 5.77 months. There were no differences in the postoperative Hospital for Special Surgery score, range of motion, or hip-knee-ankle angle between the two groups. The operating time in the extramedullary group was shorter than that in the conventional group (54.78 ± 7.95 vs. 59.14 ± 10.91 min, respectively; p = 0.025). The drop in hemoglobin after 3 days was only 12.34 ± 4.98 g/L in the extramedullary group which was less than that in the conventional group (p = 0.001). No significant differences were found in the postoperative coronal and sagittal angles between the two groups. Acceptable radiographic accuracy of the implant alignment and position was achieved in 92% of patients in the extramedullary group and 96% of patients in the conventional group. Conclusions: The radiographic and clinical results of the extramedullary technique were comparable with those of the conventional technique with the advantage of no intramedullary interruption, less blood loss, a shorter operating time, and more rapid recovery. As the technique depends on the accurate tibial cut and overall alignment, we do not recommend it to surgeons without high volume experiences. Trial registration: Retrospectively registered

Trajectory of Bearing Movement During Oxford Mobile-bearing Unicompartmental Knee Arthroplasty Using Kinematic Alignment Technique: a Retrospective Analysis

“…Therefore, this method could also be called the extramedullary technique. Our past research showed that UKA performed using this technique can be as reliable and accurate as the conventional technique in terms of the prosthesis position but that it has a shorter operating time, less blood loss, and more rapid recovery without intramedullary interruption [10]. Moreover, the results of the present study showed that this method can improve the bearing movement trajectory, which is another advantage.…”

“…In 2020, we introduced a kinematic alignment technique and con rmed that the prothesis position using this method was similar to that using traditional MP devices [10]. The present study was performed to determine whether this technique can improve the bearing movement trajectory.…”

“…The surgeries were performed using the kinematic alignment technique introduced by Zhang et al in 2020 [10] and were all performed by the same senior surgeon using an Oxford Phase 3 MB unicompartmental knee prosthesis. After precise resection of the tibial plateau, a feeler gauge was inserted into the exion joint gap to con rm that the ligament tension was restored and that the relationship between the tibial plateau surface and lower limb anatomical axis was normal.…”

Evidence-based surgical technique for medial unicompartmental knee arthroplasty

“…A spacer block preferably of 9 mm is inserted with an alignment guide to check the requisite coronal alignment, tibial slope, and the tightness in 5-10°of flexion. It is recommended to use a 9-mm spacer block instead of an 8-mm spacer block as a 9-mm spacer allows the surgeon intraoperative flexibility of ± 1 mm [47]. The thickness is correct when the 9-mm spacer block can slide easily in and out.…”

The Swing Angle of the Intramedullary Rod in the Canal During Medial Mobile-bearing Unicompartmental Knee Arthroplasty: a Finite Element Analysis Study

“…There is ongoing debate regarding the IM rod with respect to its usefulness. [19] In this study, a three-dimensional (3D) model of the femur and IM rods of different lengths were established using computed tomography (CT). The positioning errors for different rod lengths were obtained through nite element analysis, and correlations between the mathematical model of the femur and swing angle of the rods were evaluated.…”