Comparison of Hip and Knee Arthroplasty Rates of Individuals With and Without Prader-Willi Syndrome

Prader-Willi syndrome (PWS) is a complex genetic condition, affecting between 1:10,000 and 1:30,000. The prevalence of hip dysplasia in children with PWS is reportedly between 8% and 30%, but the long-term consequences of residual hip dysplasia remain largely unknown in this population. The purpose of this study was to comparatively estimate the number of total hip arthroplasty (THA) and total knee arthroplasty (TKA) procedures performed on adults with and without PWS, using a national hospital discharge database, in an effort to elucidate long-term outcomes and guide clinicians treating orthopaedic concerns in younger individuals with PWS.

Methods: 

The National Inpatient Sample of the Healthcare Cost and Utilization Project is the largest all-payer inpatient care database, containing annual data from >7 million hospital stays; sampling weights and stratification variables are provided for producing estimates of >35 million hospitalizations nationwide. THA and TKA procedures were identified, then stratified by whether or not the patient had a diagnosis of PWS. The ages of the 2 groups and sex mix were compared, as was the length of stay for the procedure, and discharge status.

Results: 

From 2004 to 2014, 9.4 million patients nationwide, by weighted estimate, underwent THA (3.1 million) or TKA (6.3 million). Sixty-five patients were identified as having the diagnosis of PWS (39 with THA, 26 with TKA); 7 patients per million having hip or knee arthroplasties had PWS. Sixty-eight percent of those with PWS were younger than 50 years, compared with only 7% of those without PWS (P<0.001). The female:male prevalence was 47:53 for patients with PWS and 60:40 for the total group. The mean length of stay was similar, but patients with PWS were more likely to be transferred to another facility after surgery (77% vs. 36%; P=0.008).

Conclusions: 

Hip dysplasia prevalence is higher in persons with PWS, but the rate of late treatment with THA is much lower than in the general population. We recommend only active observation for stable and improving hips in young children with PWS, as the consequences of overtreatment can be serious, including further delaying their neuromuscular development, and exposure to possibly unnecessary perioperative risks.