Outcome differences between conversion to THA for traumatic ONFH after failed internal fixation and primary THA for nontraumatic ONFH in patients under 55: a retrospective case-control study.

OBJECTIVES

The aim of this study was to compare outcomes of Conversion to Total Hip Arthroplasty (CTHA) for Traumatic Osteonecrosis of the Femoral Head (ONFH) after failed internal fixation with Primary THA for Nontraumatic ONFH, and to provide insights into CTHA for Patients Under 55 among these individuals.

METHODS

This retrospective study analyzed 292 patients aged 18–55 between January 2013 and August 2022. Patients who underwent Conversion to THA (CTHA) for secondary ONFH after failed internal fixation of femoral neck fractures (n = 146) and those who underwent Primary THA for Nontraumatic ONFH (n = 146) were compared regarding complications, survival rates, perioperative parameters, Harris Hip Scores, acetabular anteversion and abduction angles over a mean 5.5-year follow-up.

RESULTS

The conversion group exhibited a significantly higher incidence of intraoperative periprosthetic fractures compared to the primary group (5.5% vs. 0.7%, P = 0.039). In the conversion group, routine postoperative secretion cultures yielded a 6.8% bacterial positivity rate. Regarding perioperative parameters, conversion procedures required significantly longer operative time (1.3 ± 0.47 vs. 1.0 ± 0.24 h, P < 0.001) and resulted in greater blood loss (143.2 ± 135.2 vs. 112.7 ± 41.1 mL, P = 0.007). Despite these surgical challenges, both groups demonstrated comparable clinical outcomes. There were no significant differences in the final Harris Hip Scores (90.4 ± 4.5 vs. 89.7 ± 3.6, P = 0.134) or mid-to-long-term implant survival rates (> 93% for both, P = 0.607). Radiographic assessment also showed comparable acetabular anteversion (P = 0.255) and abduction angles (P = 0.948) between the two groups.

CONCLUSIONS

CTHA for traumatic ONFH after failed internal fixation in patients under 55 years of age presented mid-to-long-term implant survival rates and hip functional outcomes comparable to primary THA for nontraumatic ONFH. However, CTHA is associated with a higher incidence of intraoperative periprosthetic fractures and a potential risk of postoperative infection. Notably, given the risk of occult infection, we recommend routine tissue or secretion cultures during implant removal and subsequent arthroplasty for all THA patients with retained implants in situ to ensure early detection and targeted management of potential prosthetic joint infections.