The association of comorbidity indices and minimal clinically important difference in a population undergoing shoulder arthroplasty

BackgroundShoulder arthroplasty (SA) procedures are increasingly common. The Charlson and Elixhauser indices are ICD-10 based measures used in large databases to describe the patient case mix in terms of secondary medical conditions. There is a paucity of data on the relationship between these indices and patient-reported outcome measures (PROMs) after shoulder arthroplasty.MethodsPatients undergoing SA from 2016-2018 were identified in the electronic medical records. Charlson and Elixhauser comorbidities were used to calculate comorbidity scores according to established algorithms (eg Elixhauser-Walraven). Patient shoulder-specific (American Shoulder and Elbow Surgeons (ASES) score and Shoulder Activity Scale (SAS)) and general health scales (SF-12 Mental Component Score (MCS) and Physical Component Score (PCS) and Patient-Reported Outcomes Measurement Information System-Pain Interference (PROMIS-PI)) PROMs were obtained from our institution’s shoulder registry. Linear regression models adjusting for age and sex evaluated associations between comorbidity scores and PROMs. Receiver operating characteristic (ROC) curves determined optimal cutoffs, maximizing sensitivity and specificity to identify patients likely to fail to meet minimal clinically important difference (MCID) values.ResultsA total of 1817 SA procedures were identified. Higher Charlson and Elixhauser-Walraven scores were significantly associated with lower baseline SAS and SF-12 PCS. Patients with higher Charlson scores had lower baseline ASES (P = .003) and lower baseline (P = .0002) and 2-year (P = .02) SF-12 MCS. No significant associations were found for PROMIS-PI with either index. The Charlson score better predicted the failure to meet MCID for SF-12 PCS with an AUC of 0.64, compared to 0.55 for Elixhauser-Walraven. Conversely, Elixhauser-Walraven better predicted PROMIS-PI with an AUC of 0.66, compared to 0.53 for Charlson. Moderate AUCs were observed for the remaining PROMs, ranging from 0.57-0.64, with little difference between index scores.ConclusionHigher Charlson and Elixhauser-Walraven scores were associated with lower baseline scores on most PROMs. Generally, the Charlson score performed better than the Elixhauser-Walraven score in predicting worse outcomes at 2 years. Comorbidity indices may be useful as a decision aid to provide appropriate expectations of outcomes for patients undergoing SA.