The learning curve for minimally invasive Oxford phase 3 unicompartmental knee arthroplasty: cumulative summation test for learning curve (LC-CUSUM)

Abstract

BackgroundThe minimally invasive Oxford unicompartmental knee arthroplasty (UKA) is a demanding procedure but has many advantages compared with total knee arthroplasty (TKA). The aim of this observational study was to investigate the learning curve of one experienced surgeon introducing minimally invasive Oxford phase 3 UKA into his routine clinical practice.MethodsThe first 50 consecutive cases of minimally invasive Oxford phase 3 UKA performed by one surgeon were evaluated to determine whether there was an association between outcomes and the cumulative number of cases performed, indicating the presence of learning curve. The cohort was divided into two groups: group A comprised the first 25 cases and group B cases 26–50. Duration of surgery, blood loss, Hospital for Special Surgery score, range of motion, complications, and the radiographical position of the implant were compared between the groups. The cumulative summation test for learning curve (LC-CUSUM) was then used to further analyze the learning curve.ResultsThe mean age and follow-up were 64.4 years and 50.9 months, respectively. The duration of surgery and blood loss were significantly more favorable in group B. The length of incision gradually reduced from 9.7 ± 1.3 to 8.5 ± 1.1 cm. Failures were identified in nine patients (18%). Two revisions and two dislocations were encountered in group A; one revision was performed 4 years after surgery for a patient in group B because of a fracture. One case of lateral compartment osteoarthritis was identified in group A. Two patients in each group reported continuing unexplained pains. CUSUM analysis showed that failure rates diminished rapidly after 16 cases and reached an acceptable rate after 29 cases.ConclusionsMinimally invasive Oxford phase 3 UKA for anteromedial osteoarthritis is a demanding procedure, but satisfactory outcomes can be achieved after approximately 25 cases.

Patterns of Compartment Involvement in End‐stage Knee Osteoarthritis in a Chinese Orthopedic Center: Implications for Implant Choice

“…report how well Chinese arthroplasty surgeons have adapted to handling the minimally invasive Oxford phase 3 medial UKA. They found that failure rates diminished rapidly after 16 cases, and satisfactory outcomes were achieved after approximately 25 cases. In addition, good results can be expected when using UKA for more than 20% of overall knee arthroplasty, and the optional proportion was 40% to 60%.…”

Patient-Specific Instrument Can Improve Functional and Radiographic Results during Learning Curve for Oxford Unicompartmental Knee Arthroplasty

“…By contrast, there are previous studies reporting a 3.5-fold greater revision rate during as compared with after the learning curve. 8 In a series of 445 consecutive UKAs performed by four surgeons, Hamilton et al 26 noted two-fold greater revision rates in surgeons with no experience. This appears to suggest that PSI instrumentation may help to compensate partly the lack of experience.…”

“…However, the purpose of the study was to see the effect of use of the PSI system by a surgeon during the UKA learning curve. Such curve was defined as the first 25 cases by Zhang et al, 8 who considered case 16 as the inflection point of such results. Second, the follow-up time was 2 years.…”

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

“…Malposition increases the risk of bearing dislocation in mobile UKA, a serious complication that usually requires revision surgery [9][10][11]. Incorrect alignment in the coronal plane can also influence the outcome of UKA [12,13]. Overcorrection causes contralateral compartmental overload and failure in arthritis progression.…”