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Background Dislocation is one of the most prominent and challenging complications following the revision of total hip arthroplasty (THA). Dual-mobility cups are an option to address this problem. There is, however, little data on the outcomes of modern modular dual-mobility (MDM) cups in the revision of THA. In this study, the clinical and radiological outcomes following the revision of THA with an MDM cup using the direct anterior approach (DAA) were evaluated. Methodology We retrospectively reviewed patients who underwent a revision of THA between March 2017 and July 2019. The inclusion criteria were a revision of THA using an MDM cup through the DAA. A uniform acetabular implant was used in each revision. Outcome measures were assessed radiographically and clinically. The clinical outcome measures consisted of dislocation, infection, and re-revision. Functional assessment was performed using the Harris Hip Score preoperatively and at the last clinical examination in our department. Results This study retrospectively identified a cohort of 26 patients who underwent a revision of THA. Two patients were excluded due to incomplete follow-up because they died. Finally, 24 patients were included. A total of 17 isolated acetabular revisions and seven complete revisions were performed with a mean follow-up of 39 months (range = 29-59). No dislocations or deep infections were observed in our population to date. Except for one case of early aseptic loosening of the acetabular component, we observed no other signs of loosening, osteolysis, migration, or intraprosthetic dislocation. Conclusions THA revision through the DAA using an MDM cup is a safe and effective procedure. We observed no dislocation in a high-risk population undergoing THA revision surgery during a minimal follow-up of two years.
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INTRODUCTION: Currently there are no accepted international guidelines for the correct placement of reconstruction prostheses in the axial plane of the femur after en bloc resection. The most accepted method is based on the linea aspera as an intraoperative landmark, indicating posterior. This study was conducted to address the reliability of the linea aspera as a landmark for rotational alignment. MATERIAL AND METHODS: 50 CT angiographies of the right limb were used for this purpose. These 2D images were reconstructed into 3D models using proprietary software (materialize NV, Leuven, Belgium). The posterior condylar line was used as a reference axis. The orientation of the linea aspera was described as the angle between the perpendicular line to the PCL, through the center of the diaphysis, and the lateral (α) and medial labium (ß). RESULTS: The linear mixed model shows that the α- and ß-angles are significantly associated with the distance from the joint line (p<0.001) and vary significantly between subjects (p<0.001). The α-angle has the lowest variance and approximates more closely true posterior, while the median ß-angle never overlaps true posterior. DISCUSSION: When a surgeon would blindly rely on the linea aspera as a posterior landmark roughly 78% of the femoral implants would exceed the accepted ±3° deviation around the surgical transepicondylar axis (sTEA) as defined in total knee replacement. The linea aspera is not a reliable landmark for axial rotation of femoral implants. The position is highly dependent on the osteotomy height and in addition differs between individual patients. Preoperative assessment of the linea aspera is advocated in order to reduce the risk of malrotation. As the height of the osteotomy cannot always be determined correctly preoperatively, a table was designed as a guideline for how much a deviation from the planned resection height will affect the rotation of the implant.