Study population
This retrospective study was approved by our institutional review board. All methods were carried out in accordance with relevant guidelines and regulations. We investigated the medical records and radiographs of 158 skeletally mature patients who underwent open reduction and internal fixation (ORIF) for an acetabular fracture at a level 1 trauma center between March 2014 and March 2019. Patients with an acetabular fracture including a transverse fracture with or without a PW and/or T-component fracture were eligible for inclusion. The exclusion criteria were having another type acetabular fracture, participation in less than 12 months of follow-up (except for early conversion to total hip arthroplasty [THA]), incomplete medical records or radiographs, periprosthetic fracture, preexisting hip disease, and open pelvic fracture.
Surgical procedure and postoperative protocol
All surgeries were performed by a single surgeon trained in the field of orthopaedic trauma. Surgical timing was determined based on the patient’s condition and associated injuries. An anterior intrapelvic approach with or without the lateral window of the ilioinguinal approach in the supine position and/or the Kocher-Langenbeck approach in the lateral decubitus position was chosen as the surgical approach based on the configuration of the fracture, the site where the main displacement was involved, and consideration of the associated pelvic ring injury (PRI). Whether to fix the single-column or the double-column, how to perform fixation, and the sequence of reduction and fixation were determined at the discretion of the surgeon based on the fracture configuration, the site of the major fracture, reduction quality, associated PRI, and surgical approach. All implants used for fixation were 3.5 reconstruction plates (titanium; DePuy Synthes, Oberdorf, Switzerland) and/or 3.5 low-profile pelvic plates (stainless steel; DePuy Synthes).
Serial radiographs including pelvic series (anteroposterior, iliac/obturator oblique, and inlet/outlet views) were obtained immediately after surgery and periodically during follow-up. After the drain was removed within 48 to 72 hours after surgery, computed tomography (CT) scans including axial, coronal, and sagittal views were obtained to evaluate the reduction quality and position of the implants in all study participants. Passive or active range of motion exercises were encouraged as tolerated within the first two to three days after surgery. Partial weight-bearing with crutches or a walker and full weight-bearing were allowed at six to eight weeks and 12 weeks after surgery, respectively, depending on the patient’s general condition and associated injuries.
Assessment of measurements
Measurements of demographic data, fracture configurations, and surgical factors and outcomes were recorded. Demographic data included age, sex, body mass index (BMI), American Society of Anesthesiologists (ASA) classification, diabetes mellitus (DM), smoking history, injury mechanism, injury severity score (ISS), and injury side (right or left). Fracture configurations included the plane of the transverse fracture (infratectal, juxtatectal, or transtectal), dome impaction, PW involvement, PW comminution, PW impaction, associated fracture of the T-component, femoral head injury, hip dislocation at the time of the initial injury, and association of the displaced PRI. Surgical factors included the surgical approach, single-column or double-column fixation, postoperative residual gap and step, and classification of reduction quality according to Matta’s criteria.4 Surgical outcomes included time to union, osteoarthritis (OA), osteonecrosis of the femoral head (ONFH), and conversion to THA.
The plane of the transverse fracture was classified as follows: infratectal, the main fracture line was oriented across the acetabular fossa; juxtatectal, at the transition of the acetabular fossa to the cranial/superior joint surface; and transtectal, across the superior dome of the acetabulum. PW comminution was defined as a fracture with three or more separate articular fragments. Fracture union was defined as the absence of a fracture line and/or bridging callus across fracture sites on the follow-up radiographs of the pelvic series and the ability to perform full weight-bearing ambulation without joint pain and progressive loss of reduction.
Two orthopaedic surgeons who did not participate in surgery and were blinded to the surgical outcomes independently measured the postoperative residual gap and step using a standardized CT-based method on a picture archiving and communication system.8,9 The averages of each value were used for analyses. Reduction quality was classified as anatomical (≤1 mm), imperfect (1–3 mm), or poor (>3 mm). The other demographic data, fracture configurations, surgical factors, and surgical outcomes were assessed and documented by one of the authors.
Demographic data, fracture configurations, and surgical factors and outcomes were verified. Additionally, OA and/or ONFH considered poor according to Matta’s grading system4 and required conversion to THA indicated poor outcomes. Risk factors for the outcomes and cutoff points of related variables were statistically analyzed.
Statistical analysis
Interobserver reliability of the residual gap and step measurements was evaluated by the intraclass correlation coefficient (ICC). Univariate and multivariate logistic regression tests were performed to determine risk factors for postoperative OA. A receiver-operating characteristic (ROC) curve analysis was used to identify cutoff points for factors that affect OA. MedCalc software (version 18.11; MedCalc Software, Ostend, Belgium) was used for the ROC curve analysis and SPSS software (version 22.0; SPSS Inc, Chicago, IL, USA) was used for the other statistical analyses. Statistical significance was set at P<0.05.