Patient satisfaction after total knee arthroplasty is better in patients with pre-operative complete joint space collapse

Aim of the studyTo determine if pre-operative radiologic minimal joint space width (mJSW) is related to the outcome of total knee arthroplasty (TKA) (primary hypothesis). Likewise, the aim was to test if pre-operative mJSW is related to prosthesis survival (secondary hypothesis).MethodsA retrospective comparative analysis was performed. Group 1 was comprised of patients with pre-operative mJSW 0-1mm. Group 2 were patients with pre-operative mJSW >= 2mm. The clinical outcome was determined with the Western Ontario and MacMaster Universities Osteoarthritis Index (WOMAC) score pre-operatively and one year after TKA. Only patients with pre-operative weight-bearing radiographs and complete WOMAC score data were accepted.ResultsAvailable for analysis were 377 patients, of whom 188 were allocated to Group 1 (118 female, 70 male, age 7011years) and 189 to Group 2 (118 female, 71 male, age 7013years). Pre-operative WOMAC total and WOMAC subscores showed no significant differences between groups. Post-operatively, the WOMAC total was significantly better in Group 1 than in Group 2, 10 +/- 22 and 19 +/- 31, respectively (p<0.001, Power 97.5%). Similarly, the WOMAC subscores for pain, stiffness, and function were also significantly better in Group 1 than in Group 2. Five-year prosthesis survival was 94.2 and 91.6% in Groups 1 and 2, respectively (p=0.07, Power 71%).Discussion Patients with pre-operative complete joint space collapse (0 to 1mm mJSW) achieve a significantly better WOMAC result from TKA than do those with a mJSW equal to or greater than 2mm. From our findings, it is recommended that complete joint space collapse especially be used as an indication for TKA surgery.Conclusion Our study was underpowered to sufficiently show an effect of pre-operative mJSW on prosthesis survival.