Purpose: The impact of altering a patient’s hip offset during total hip arthroplasty (THA) on periprosthetic fracture risk is unknown. The purpose of this study was to compare periprosthetic fracture risk in patients where THA offset was “matched” to their contralateral native hip versus those where offset was mismatched. Materials and Methods: We reviewed 50 patients with Vancouver B periprosthetic fractures at a single academic institution between 2012 and 2019 and compared them with a matched cohort. By utilizing a validated technique, two reviewers calculated combined hip offset from anteroposterior pelvis radiographs. Offsets of the operative side and the native hip were measured and denoted as either as a “match” if values were within 5 mm of the contralateral, native hip, or a “mismatch” if the prosthetic horizontal hip offset differed more than 5 mm from the native side. Independent sample t-tests and chi square analyses were used for data comparison. Relative risk (RR) with a 95% confidence interval (CI) was then calculated. Results: Unmatched offset was associated with increased risk of periprosthetic fracture (P<0.001). This finding was true for cases where offset was increased relative to the native hip (P<0.001) and where implant offset was decreased relative to the native hip (RR=3.0, 95% CI 1.3-7.6, P=0.015). Conclusion Failure to restore a patient’s offset during THA is associated with increased rates of periprosthetic fracture. Although restoration of native hip anatomy is an important technical consideration of this procedure, alterations in the hip lever arm may predispose patients to periprosthetic fracture.

Purpose: Use of dual mobility (DM) articulations can reduce the risk of instability in both primary and revision total hip arthroplasty (THA). Knowledge regarding the impact of this design on patient-reported outcome measures (PROMs) is limited. This study aims to compare clinical outcomes between DM and fixed bearing (FB) prostheses following primary THA. Materials and Methods: All patients who underwent primary THA between 2011-2021 were reviewed retrospectively. Patients were separated into three cohorts: FB vs monoblock-D vs modular-DM. An evaluation of PROMs including HOOS, JR, and FJS-12, as well as discharge-disposition, 90-day readmissions, and revisions rates was performed. Propensity-score matching was performed to limit significant demographic differences, while ANOVA and chi-squared test were used for comparison of outcomes. Results: Of the 15,184 patients identified, 14,652 patients (96.5%) had a FB, 185 patients (1.2%) had a monoblock-DM, and 347 patients (2.3%) had a modular-DM prosthesis. After propensity-score matching, a total of 447 patients were matched comparison. There was no statistical difference in the 90-day readmission (P=0.584), revision rate (P=0.265), and 90-day readmission (P=0.365) and revision rate due to dislocation (P=0.365) between the cohorts. Discharge disposition was also non-significant (P=0.124). There was no statistical difference in FJS-12 scores at 3-months (P=0.820), 1-year (P=0.982), and 2-years (P=0.608) between the groups. Conclusion DM bearings yield PROMs similar to those of FB implants in patients undergoing primary THA.Although DM implants are utilized more often in patients at higher-risk for instability, we suggest that similar patient satisfaction may be attained while achieving similar dislocation rates.