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Objectives and questions: The management of displaced acetabular fractures in elderly patients remains a significant clinical challenge. The optimal surgical strategy, either open reduction and internal fixation or total hip arthroplasty, continues to be a matter of debate. Furthermore, postoperative weight-bearing protocols for both treatment modalities lack clear consensus. The aim of this biomechanical study was to evaluate construct stiffness as well as the magnitude of translation and angulation under load following fixation of an anterior column and posterior hemi-transverse (ACPHT) acetabular fracture. Two treatment strategies were compared: standard plate osteosynthesis using a 3.5-mm reconstruction plate (DePuy Synthes) and total hip arthroplasty using a cementless modular revision cup with an iliac peg (MRS-Titan^® maximum, Peter Brehm GmbH). All constructs were tested under full weight-bearing conditions.

Material and methods: Six composite osteoporotic pelvis models were used in this study. An ACPHT acetabular fracture, according to the Judet and Letournel classification, was created in 12 hemi-pelvic constructs. Specimens were stratified into two groups (n = 6 per group) as follows: (i) fixation of the ACPHT acetabular fracture using standard plate osteosynthesis (ORIF); and (ii) treatment of the ACPHT acetabular fracture using a cementless modular revision cup with an iliac peg (THA). All specimens underwent biomechanical testing under progressively increasing cyclic loading until failure. Interfragmentary movements were continuously monitored using a motion-tracking system.

Results: Median initial construct stiffness (N/mm)was 165.02 (IQR=9.81)for ORIF and 105.95 (IQR=80.81) for THA. Median relative translation under maximal load was comparable between groups (16,66 mm for ORIF vs. 16.30 mm for THA). THA demonstrated lower median relative rotation under maximal load (3.87° for ORIF vs. 2.78° for THA).

Discussion and conclusions: Treatment of ACPHT acetabular fractures with eitherplate osteosynthesis or usinga cementless modular revision cup with iliac pegdemonstrated encouraging results for application ofa post-surgical treatment concept with a full weight bearing approach. Further biomechanical cadavericstudies with larger sample sizeshould be initiatedfor a better understanding of acetabular fracture treatment with full weight bearing and its potential as a concept for ACPHT acetabular fracture fixation.