The American Joint Replacement Registry (AJRR) is the largest registry of total hip and knee arthroplasty (THA and TKA) procedures performed in the U.S. The National (Nationwide) Inpatient Sample (NIS) is a public database containing demographic estimates based on more than seven million hospitalizations annually. The purpose of this study was to analyze whether AJRR data is representative of the national experience with TJA as represented in NIS Cohen's d effect sizes were computed to ascertain the magnitude of differences in demographics, hospital volume (in 50 patient increments), and geographic characteristics between the AJRR and NIS databases.Introduction
Methods
Component malposition in total hip arthroplasty (THA) contributes to wear, dislocation, and leg length discrepancy (LLD). Robotic assisted total hip arthroplasty (rTHA) utilises computer-assisted haptically guided bone preparation and implant insertion to improve accuracy. The goal of this study is to compare accuracy and clinical outcome with manual THA (mTHA) and rTHA at minimum 1 year follow-up interval. Consecutive primary THA performed by one fellowship trained surgeon included: the first 100 mTHAs in his clinical practice (Group1- year 2000), the last 100 mTHAs before rTHA use (Group2- year 2010), and the first 100 rTHA (Group3- year 2011). All THAs utilised cementless implants, cross-linked polyethylene, and a posterior approach. Comparisons included age, sex, diagnosis, implant head size, blood loss (EBL), operative time, LLD, early dislocation and infection. Acetabular abduction (AAB), anteversion (AAV), and LLD were measured using validated software (Martell Hip Analysis Suite). The Lewinnek safe zone defined accuracy (AAB- 30°-50°, AAV- 5°-25°). Statistical analysis included ANOVA, Chi squared, and Fisher tests. Power analysis demonstrated adequate sample sizes. No differences were noted regarding group demographics. Average operative times varied: Group 1, 2, and 3- (160, 129, and 143 minutes, respectively). No deep infections occurred in any group. LLD greater than 1.5 cm varied: Groups 1, 2, and 3 (9%, 1%, 1%, respectively). Dislocation rates varied: Groups 1, 2, and 3- (5%, 3%, and 0%, respectively). EBL was less with rTHA than mTHA (Groups 1, 2, 3: 533cc, 437cc, 357cc, respectively). Average implant head size increased comparing Groups 1, 2, and 3 (31mm, 34.6mm, and 35.2mm, respectively). AAB accuracy varied: Groups 1, 2, and 3 (66%, 91%, and 98%, respectively). AAB greater than 55 degrees varied: Groups 1, 2, and 3 (15%, 1%, and 0%, respectively). There was a 3% fractured acetabular liner rate in Group 1, all cases occurred with AAB > 55 degrees, and AAB greater than 55 degrees correlated with increased acetabular liner fracture rate (20% vs. 0%, P < 0.05). No cases of fractured acetabular liners occurred in Group 2 or 3. rTHA improved AAV accuracy compared with mTHA (Group 2- 48%, Group 3- 75%; p<0.0001). Improved acetabular component accuracy with rTHA correlated with lower dislocation rates compared with mTHA (p<0.001). Total hip arthroplasty performed with traditional manual techniques has demonstrated excellent clinical outcomes in the majority of patients with many THA designs if components are placed accurately. Limitations in mTHA remain that alter results if accurate component placement is not achieved. In our study, clinical experience over 10 years improved AAB accuracy with mTHA, but AAV remained problematic. rTHA improved AAB and AAV accuracy compared with mTHA and demonstrated reduced early dislocation rates, improved rate of LLD, and reduced acetabular liner fracture risk compared with mTHA (p<0.05). Average rTHA operative times were 14 minutes longer than mTHA (Group 2), but this was not associated with increased EBL or infection rates. Further study is needed to evaluate whether the short term clinical and radiographic advantages noted with rTHA compared with mTHA will be maintained at longer follow up intervals.
