gms | German Medical Science

Objectives: To determine whether preoperative radiologic joint space width (JSW) is related to the outcome of medial unicondylar knee arthroplasty (UKA) (primary hypothesis). The aim was to investigate whether preoperative JSW is related to prosthesis survival (secondary hypothesis).

Methods: A retrospective comparative analysis was performed. One group was comprised of UKA patients with preoperative JSW 0 - 1 mm. Another group was formed by patients with preoperative JSW bigger 2 mm. Value was taken from preoperative weight-bearing Schuss-view radiographs. The clinical outcome was determined with the Western Ontario and MacMaster Universities Osteoarthritis Index (WOMAC) score preoperatively and one year after medial UKA. Implant survival data were obtained from the state's arthroplasty registry.

Results: There were 80 patients with a preoperative JSW 0-1mm (age 66, BMI 27.8) and 70 patients with a preoperative JSW bigger 2mm (age 64, IQR 15, BMI 28.1). WOMAC total was 10 ±10 in patients with 0-1mm JSW and 25 ±47 in patients with more than 2mm JSW at one year postoperative (p=0.052). WOMAC pain was 7 ±16 in patients with 0-1mm JSW and 18 ±46 in patients with more than 2mm JSW one year postoperative (p = 0.047). WOMAC function was 10 ±9 in patients with 0-1mm JSW and 17 ±51 in patients with more than 2mm JSW at one year postoperative (p=0.048, Table 2). In patients with 0-1mm JSW 5-year prosthesis survival was 92.3% and in patients with more than 2mm JSW it was 81.1% (p=0.016).

Conclusion: In patients with preoperative complete joint space collapse (0 to 1mm JSW) clinical outcome was superior to that of patients with incomplete joint space collapse. This was true for both 1-year postoperative WOMAC pain and WOMAC function and for 5-year implant survival rates. On the basis of our findings it is recommended that 'complete joint space collapse' especially be used as indication for medial UKA surgery.