Rationing for Total Hip and Knee Arthroplasty Using the New Zealand Orthopaedic Association Score: Effectiveness and Comparison With Patient-Reported Scores

BackgroundThere is increasing interest in scoring systems to prioritize patients for hip and knee arthroplasty. The purpose of this study was to determine the effectiveness of the New Zealand Orthopaedic Association (NZOA) score and compare it with patient-reported scores of patients listed for hip and knee arthroplasty.MethodsOver a 1-year period, all patients listed for primary hip and knee arthroplasty were scored by a prioritization nurse. The NZOA score, outcome, preoperative Oxford hip or knee score (OHKS) and reduced Western Ontario McMaster osteoarthritis index (WOMAC) score (RWS) were collected.ResultsOverall, 608 patients were listed for hip (319) or knee (289) arthroplasty. The mean scores for knees were all better than hips (P < .001). On initial scoring, 324 patients (53%) were given certainty (mean NZOA, 80.5; OHKS, 10.0; RWS, 35.1), 90 (15%) given clinical over-ride (NZOA, 69.6; OHKS, 12.0; RWS, 33.2), and 194 (32%) returned to general practitioner (NZOA, 64; OHKS, 14.2; RWS, 30.8). Knees (38%) were more likely to be returned than hips (26%; P = .002). Fifty (26%) were re-referred during the study period (mean, 5 months) and given certainty or over-ride. The difference at final outcome between patients with certainty and clinical over-ride was NZOA, 10.3 points; Oxford, 1.6 points; and RWS, 1.4 points. The difference between clinical over-ride and returned to general practitioner was NZOA, 7.2; Oxford, 4.4; RWS, 5.3.ConclusionThe NZOA score is an effective tool for rationing for joint arthroplasty. Patients around the threshold score of 70 may not have a clinically important difference compared with those above threshold.