Development and application of extramedullary femoral osteotomy module in total knee arthroplasty / 中华骨科杂志

ABSTRACT

Objective To investigate the outcome of a new designed extramedullary femoral osteotomy module and to compare with conventional intramedullary system in clinical study.Methods The extramedullary femoral osteotomy module was designed with the extramedullary alignment rod connecting with the T type rod at right angle,and it had a 5°-7° adjustable valgus design.The positioning module fixation screw was parallel with the epicondylar axis.The coronal plane of the distal femur bone cut was orientated by the extramedullary alignment rod pointing to the inguinal midpoint,and the sagittal plane was orientated by the extramedullary alignment rod keeping parallel with the distal femoral medullary cavity.The terminal distal femoral bone cut was conducted with suitable osteotomy after the orientation.Sixty patients who underwent unilateral total knee arthroplasty (TKA) from October 2015 to March 2016 were randomly divided into intramedullary and extramedullary group for prospective controlled study.Blood loss,drainage and the incidence of deep vein thrombosis (DVT) were evaluated at one week postoperatively.Knee valgus angle and femoral prosthesis flexion angle were analyzed at two weeks postoperatively.Moreover,the extramedullary femoral osteotomy module was used in 273 patients (78 males and 195 females) with an average age of 68.7 (range,57-82 years old) who underwent unilateral TKA from April 2016 to January 2017.Blood loss,operation duration and lower limb ultrasonography preoperatively and at one week postoperatively were recorded.Knee valgus angle and femoral prosthesis flexion angle were measured at 2 weeks postoperatively.Range of knee motion and Hospital for Special Surgery (HSS) knee score at six weeks postoperatively were also reported.Results In the randomized controlled trial,blood loss and drainage in extramedullary group was less than that in intramedullary group (t=-3.330,P=0.004).There was no significant difference in the incidence of DVT at 1 week postoperatively (x2=2.269,P=0.132) and the knee valgus angle and femoral prosthesis flexion angle at 2 weeks postoperatively within the two groups.In the clinical application,operation time was 60.13± 13.69 min,and blood loss and drainage was 109.11±70.73 ml.There were four cases of popliteal vein thrombosis,nine cases of posterior tibial vein thrombosis,and seventeen cases of muscular venous thrombosis at one week postoperatively.The incidence rate of DVT was 11.0％.There was no symptomatic pulmonary embolism at three months postoperatively.Knee valgus angle was 7.34°±0.69°,and 211 knees accounting for 77.3％ were in the range of ±3° error.Femoral prosthesis flexion angle was 6.43°±1.59°,and 273 knees were all in the range of ±10° error.Range of knee motion improved from 54.52±5.96 preoperative to 86.20±4.92 at six weeks postoperative.HSS knee score improved from 100.88°±7.51° preoperative to 110.42°±7.08° at six weeks postoperative.Conclusion The new designed extramedullary femoral osteotomy module used in distal femoral osteotomy during TKA can significantly reduce the risk of bleeding and the incidence rate of DVT postoperatively.Furthermore,patients can obtain as excellent prosthesis position and limb alignment as conventional intramedullary system.