Higher rates of hemiarthroplasty dislocation observed in patients with preoperative CEA less than 38.5 & ADWR less than 34.5

Hip hemiarthroplasty dislocation is a devastating complication. Among other preoperative risk factors, acetabular morphology has been rarely studied. Luigi Zanna et al conducted a study to evaluate the influence of preoperative native acetabular morphology on hemiarthroplasty dislocation. The study was conducted at Department of Orthopaedic Surgery, Aou Careggi, University Hospital of Florence, Florence, Italy. It has been published in “The Journal of Arthroplasty.”

The authors retrospectively reviewed 867 patients who underwent hip hemiarthroplasty for femoral neck fracture. The 380 included patients were treated with an anterior-based muscle-sparing approach. The central-edge angle (CEA) and acetabular depth-to-width ratio (ADWR) of the fractured hip were measured preoperatively on the anteroposterior pelvic view. Receiver operating characteristic curves were performed to analyze the optimal cutoff for CEA and ADWR. Hemiarthroplasty dislocation occurred in 18 patients (4.7%), and the remaining 362 patients were used as the control group.

Key findings of the study were:

• No significant differences in terms of sex, age, dementia, neuromuscular disease, and body mass index were found between the 2 groups.

• Eighteen patients (4.7%) sustained a hip dislocation during the study period, 14 (77.8%) were anterior and 4 (22.2%) were posterior.

• The 18 patients who had a hip dislocation had significantly smaller mean CEA than the control group (P = .0001) (mean 36.1 ± 7.5 and 43.2 ± 5.6 , respectively) as well as ADWR (mean 34 ± 6 versus 37 ± 4, respectively) (P = .001).

• Patients who had neurological comorbidities such as dementia (P = .967) and neuromuscular diseases (P = .382) did not show a higher rate of dislocation.

• Using the receiver operating characteristic analysis, we report significant cutoffs of 38.5 for CEA (P = .0001) and 34.5 for the ADWR (P = .017)

The authors commented – “In conclusion, excluding the dislocation risk factor related to the surgical approach, we advise measuring the CEA and ADWR on preoperative radiographs. In cases of either a CEA smaller than 38.5 or an ADWR smaller than 34.5 or a combination of both, changing the native acetabular morphology implanting a THA might help reduce the risk of dislocation and prevent further operations in an elderly and frail patient. However, when addressing elderly patients who have multiple comorbidities and a short life expectancy, even when they possess preoperative morphological risk factors for a hemiarthroplasty dislocation, the decision to perform a THA instead of a hemiarthroplasty needs to be a multi disciplinary decision.”

Further reading:

Acetabular Morphology Predicts the Risk of Dislocation Following Hemiarthroplasty for Femoral Neck Fractures in the Elderly

Luigi Zanna, Matteo Innocenti et al

The Journal of Arthroplasty 2023

https://doi.org/10.1016/j.arth.2023.02.042