gms | German Medical Science

Objectives: The increasing prevalence of hip joint arthritic changes and advancements in technical treatment options have led to a rising number of total hip arthroplasties (THA) worldwide. Despite the high success rates, a relevant proportion develop complications such as aseptic loosening or periprosthetic joint infection. The use of custom-made acetabular implants has emerged as a viable option for complex cases. However, ensuring accurate intraoperative positioning of these implants remains a significant challenge.

This study aimed to contribute to the existing knowledge on the accuracy of intraoperative positioning of custom acetabular implants by utilizing postoperative plain a.p. radiographs as the primary imaging modality. The research focused on complex revision cases with large osseous defects, and evaluated the success of implant positioning in terms of inclination (INCL), anteversion (AV), and leg length discrepancy (LLD).

Methods: The study included 31 cases of acetabular revision for osseous defects classified as Paprosky type IIIa and IIIb following THA, performed between 2013 and 2018. A detailed clinical algorithm was employed to assess and plan custom implantation. Radiographs were taken at 6 weeks postoperatively serving as the basis for accuracy assessment. The Lewinnek safe zone for INCL and AV was utilized as a reference to determine successful implantation. Mean follow-up was 30 months.

Statistical analysis was performed using IBM SPSS Statistics for Windows, version 27.0 (Armonk, New York: IBM Corporation).

Fisher’s exact test was performed for all dichotomous variables. Mann-Whitney-U test was performed for all continuous variables.

Results and conclusion: Mean age was 66.2 years, with indications for acetabular restoration being periprosthetic joint infections, aseptic loosening, or tumour resections. Implant survival was 96.7% with one case of aseptic loosening after eight years. Mean AV was 13.9°, with most implants positioned within or at the border of the Lewinnek safe zone (87%). Mean INCL was 46.9°, with 87% of cases within or at the border of the proposed range. The study identified a mean difference between planning and postoperative results for AV of 7.4° (p = 0,704), INCL of 3.7° (p = 0,068), and leg length discrepancy of 4.5 mm (p = 0,002).

Overall, 70% of cases were within or at the border of Lewinnek safe zone.

This study demonstrates that accurate positioning of individual acetabular components for revision of THA with severe osseous defects can be achieved and assessed primarily through postoperative a.p. radiographs. The majority of implants were placed within or at the border of the Lewinnek safe zone, despite the complexity of these cases.