The «gull sign» in acetabular fractures revisited: is it predictive for failure after osteosynthesis in older adults?

Abstract

The gull sign was described as a radiographic marker of superomedial dome impaction in acetabular fractures and was considered predictive of failure after osteosynthesis in older patients (≥ 60 years). To determine whether the radiographic gull sign is associated with higher conversion rates to total hip arthroplasty (THA) within 24 months after open reduction and internal fixation (ORIF) for displaced acetabular fractures in patients aged ≥ 60 years. In this retrospective cohort study, 126 patients aged ≥ 60 years (mean 76 years, range 60.1-93.6) underwent ORIF for displaced acetabular fractures via the Pararectus approach between 2009 and 2020. Preoperative pelvic radiographs were assessed for the presence of the gull sign, and CT scans were evaluated for dome impaction. Failure was defined as conversion to total hip arthroplasty (THA) within 24 months after ORIF. Kaplan-Meier analyses with log-rank tests were performed on the entire cohort, and diagnostic performance was analysed in the subset with complete two-year follow-up (n = 93). At two years, 20 of 93 patients (22 %) had undergone THA, occurring on average 12.1 months after the index surgery (range 2-45 months). A radiographic gull sign was identified in 21 patients (23 %). The subsequent THA conversion rate was similar between those with and without the sign (5/21 [24 %] vs 15/72 [21 %]; p = 0.99). Concordance between radiographs and CT was limited: only 12 of 21 gull-positive patients (57 %) showed a true dome impaction on CT, while CT nevertheless revealed impaction in 21 of 72 gull-negative patients (29 %). Among patients with CT-confirmed impaction, 8 of 33 (24 %) underwent THA within 24 months, compared with 12 of 60 (20 %) without impaction (p = 0.79). Kaplan-Meier analysis of the entire cohort (n = 126) likewise showed no difference in THA-free survival between groups. Neither a radiographic gull sign nor CT-confirmed dome impaction predicted early conversion in our series of acetabular fractures managed via Pararectus approach; overall conversion rates were acceptable. Accordingly, the gull sign is not a harbinger per se for failure of osteosynthesis in older adults.