The Use of PS or CR Models is not Sufficient to Explain the Differences in the Results of Total Knee Arthroplasty. Study of Interactions

Abstract

Aim: The study of results of Total Knee Arthroplasty based exclusively on the use of models Posterior stabilized (PS) or Cruciate retaining (CR) may be insufficient if we do not analyse other factors. Our objective is to analyse the interaction of certain factors as age, sex, BMI, prior deformity and use of navigation  on the  follow-up. Materials and Methods: Multicenter study of 415 Total Knee Arthroplasty (TKA). In 298 cases, the CR model was implanted and the PS in 117. The results were evaluated with the scales WOMAC, AKS and SF-12 v2. The average age of the series was 71 years (SD 7.8). The mean BMI was 31.7 (SD 4). In 294 cases, the frontal deformity of the mechanical axis of the knee was greater than 3°, particularly varus. Surgical navigation was used in 38.5% of patients as a helper in the implant of arthroplasty. Results: PS implanted joints demonstrated better results in all subscales than CR implanted joints. However,the study of the interaction between type of technique and preoperative deformity, sex, age, and BMI, showed that prior deformity and BMI influenced more on results than the use of one model or another. Navigation improved the results in the three scales, although these cases started with lower scores. Conclusion: Analysis of results of TKAs based exclusively on the use of PS or CR models is insufficient. Characteristics of the patient, previous deformity and navigation aid influence more on the results than using one model or another.