ObjectiveTo study the experimental biomechanics of acetabular posterior wall fractures so as to provide theoretical basis for its clinical treatment. MethodsSix formalin-preserved cadaveric pelvises were divided into groups A and B (n=3). The fracture models of superior-posterior wall and inferior-posterior wall of the acetabulum were created on both hips in group A;fractures were fixed with two interfragmentary screws and a locking reconstruction plate. The fracture models of superior-posterior wall of acetabulum were created on both hips in group B;fractures were fixed with two interfragmentary screws and a locking reconstruction plate at one side, and with acetabular tridimensional memory fixation system (ATMFS) at the other side. The biomechanical testing machine was used to load to 1 500 N at 10 mm/min speed for 30 seconds. The displacement of superior and inferior fracture sites was analyzed with the digital image correlation technology. ResultsNo fracture or internal fixation breakage occurred during loading and measuring;the displacement valuess of the upper and lower fracture lines were below 2 mm (the clinically tolerable maximum value) in 2 groups. In group A, the displacement values of the upper and lower fracture lines at superior-posterior wall fracture site were significantly higher than those at inferior-posterior wall fracture site (P<0.01), and the displacement values of the upper fracture line were significantly higher than those of lower fracture line (P<0.01) in two fracture types. In group B, the displacement values of the upper and lower fracture lines at the side fixed with screws and a locking reconstruction plate were similar to the values at the side fixed with ATMFS, all being close to 2 mm;the displacement values of the upper fracture line were significantly higher than those of lower fracture line (P<0.05) in two fixation types. ConclusionThe actual biomechanical effect of the superior-posterior wall of acetabulum is much greater than that of the inferior-posterior wall of acetabulum and they should be discriminated, which might be the reasons of reduction loss, femoral head subluxation, and traumatic arthritis during follow-up.