# Custom-made acetabular implants for revision total hip arthroplasty: postoperative evaluation of the accuracy of implant positioning

## TL;DR

This study evaluates how accurately custom-made acetabular implants are placed during hip revision surgery and their clinical outcomes.

## Contribution

The study introduces a method for assessing implant positioning accuracy using plain AP radiographs in revision hip arthroplasty.

## Key findings

- 87.1% of implants were positioned within or on the border of Lewinnek’s safe zone for anteversion and inclination.
- Implant survival was 96.7% over a median follow-up of 43 months with low mechanical complications.
- Accurate planning is crucial for achieving proper implant position and osseous integration.

## Abstract

The increasing need for revision total hip arthroplasty due to complications such as bone defects following implant loosening has – among others – led to the development of custom-made acetabular implants. This study evaluated the accuracy of implant positioning measured on AP radiographs and the respective clinical outcomes.

A retrospective analysis of 31 cases involving severe acetabular bone loss (Paprosky type IIIa/ IIIb) was conducted. Preoperative planning was based on CT scans, and postoperative evaluation was performed via AP radiographs, focusing on Lewinnek’s safe zone for anteversion (AV) and inclination (INCL).

Results showed that 87.1% of the implants were positioned within or on the border of Lewinnek’s safe zone for AV and INCL. Mean AV (SD) was 13.9° (8.7°), mean INCL (SD) 46.9° (6.1°). Mean deviations between planning and postoperative results were 7.4° for AV (SD) (5.5°; p = 0.704) and 3.7° for INCL (SD) (5.2°; p = 0.068). Implant survival was 96.7% over a median follow-up (IQR) of 43.0 months (65.0).

Correct positioning of customized acetabular implants could be achieved via assessment on plain AP radiographs using a superimposition method. The results were further emphasized by the low rate of mechanical complications and high implant survival. Lewinnek’s safe zone is a good guideline for proper cup positioning but should not be prioritized over primary stability of the implant. Accurate planning is key to achieving both a satisfying position and sufficient osseous integration. Further research involving higher case numbers through a multi-center approach is needed to draw definitive conclusions.