The Short-term Clinical Outcome Of Minimally Invasive Unicompartmental Knee Arthroplasty For Spontaneous Osteonecrosis Of The Knee

Objective: Safety and effective minimally invasive unicompartmental knee arthroplasty(UKA)in osteoarthritis(OA)of the medial compartment of the knee has been validated to in large patient series.Nevertheless,the literature reports limited data on clinical outcomes of UKAs performed for spontaneous osteonecrosis of the knee.In our study,to analyze the short-term outcome of minimally invasive unicompartmental knee arthroplasty(UKA)for spontaneous osteonecrosis of the knee(SONK)by case retrospective study.Materials and Method: From July 2013 to May 2015,6 cases with spontaneous osteonecrosis of the knee treated by unicompartmental knee arthroplasty,in the Department of Joint Surgery,the Second Affiliated Hospital of Dalian Medical University,were reviewed retrospectively.1 male and 5 females were included,with the mean age was(70.3 ± 9.3)years,the mean body mass index(BMI):(27.5 ± 4.1)kg /m2.5 cases of necrotic lesions in the right medial femoral condyle,1 case in the left.According to the radiographic staging system of Mont,4 cases were grade Ⅲ,2 cases were grade Ⅳ.All patients were diagnosed by preoperative X-ray and MRI examination.The size of necrosis lesions,tibiofemoral angle,range of motion(ROM),VAS score,HSS score of the knees were evaluated before the operation,and recorded.All UKA procedures were performed by a mobile Oxford medial UKA(Biomet,United States)was used in all patients.All patients were asked to follow up 1,3,6,12 months after surgery and thereafter once a year.Outpatient follow-up patients were asked about the satisfaction for the surgery,examined by radiologic assessments,VAS score andHSS score.The short-come clinical outcome was evaluated by comparing the VAS score,the HSS score,range of motion(ROM),and the tibiofemoral angle between the preoperation and the last follow-up.Results:All of the patients were followed up for a mean time of 14.8 ± 5.4 months(9~24 months).All patients can passive buck the knee to 90 ° after 1 week and painless active full flexion within 2 postoperation months.The width of necrotic lesions accounted for 28.67% ~ 47.28% of the femoral condyle,an average ratio(36.10 ±6.20)%.The score of HSS knee was increased from(63.17 ± 6.56)to(91.33 ± 4.41)at the time of the final follow-up,P <0.05,which was statistically significant.The pain VAS score was reduced from preoperative(5.67 ± 0.816)points to(1.17 ± 1.169)points,P <0.05,the difference was statistically significant.The mean postoperation full flexion was 116.67 ± 7.53 °(105 ~ 125 °),which was not statistically significant compared with that preoperation.The tibiofemoral angle improved from preoperative 180.17 ±1.95 ° to 176.09 ± 1.91 °,P <0.05,the difference was statistically significant.In our follow-up,83.3% of the patients were very satisfied with the outcome of the operation,16.7% were satisfied.All patients’ HSS score ≥85 points,excellent rate of 100%.All cases without deep vein thrombosis and pulmonary embolism occurred after the operation,no operative death cases.There were no complications such as implant loosening,dislocation of the meniscal bearing,periprosthetic infection,prosthetic sagging,progression of arthrosis inthe lateral tibiofemoral compartment,osteolysis and so on.Conclusion:The pain was obvious relieved,and the function of the knee was improved obviously after the operation.There was no obvious complication during follow-up.The short-term clinical outcome of minimally invasive unicompartmental knee arthroplasty(UKA)for spontaneous osteonecrosis of the knee is reliable.