# Adjustment of Acetabular Cup Inclination Assisted by Smartphone during Revision Total Hip Arthroplasty: Surgical Technique and Report of Four Cases

## TL;DR

This paper introduces a smartphone-assisted method to adjust acetabular cup inclination during hip revision surgery, showing successful outcomes in four cases.

## Contribution

A novel smartphone-based technique for acetabular cup placement during revision hip surgery, accounting for pelvic tilt.

## Key findings

- All four patients had successful cup placements within the Lewinnek safe zone with no complications.
- The smartphone-assisted method proved effective in adjusting cup inclination while considering pelvic tilt.
- Functional outcomes were excellent for all patients, with follow-up periods of 17 to 24 months.

## Abstract

We herein present a smartphone-assisted technique for acetabular cup placement during revision total hip arthroplasty (rTHA). Four patients were operated on: three were submitted to second-stage rTHA after infection, and one underwent surgery due to aseptic loosening. The technique entails three main steps: evaluation of the amount of lateral pelvic tilt (either clinically or radiographically); setting a supracetabular rod using the smartphone app as a reference for inclination adjustment; and acetabulum preparation and final cup placement using the smartphone to guide the inclination angle after considering the amount of pelvic tilt. Cup anteversion was adjusted according to the transverse acetabulum ligament. All 4 cases underwent a follow-up that ranged from 17 to 24 months. None of the patients required further revision, and no complications (intraoperative, early, or late postoperative) were observed. All cups were within the Lewinnek safe zone for inclination (42°, 43°, 47°, and 41°). The functional outcome per the Harris Hip Score was excellent for all patients. Smartphones are cheap tools that can assist physicians in the adjustment of acetabular cup inclination during rTHA; however, assessing the possible lateral pelvic tilt and considering it while placing the cup are crucial.

Apresentamos Uma Técnica Assistida Por
Smartphone
Para A Colocação De Cúpula Acetabular Durante A Revisão De Artroplastia Total De Quadril (Ratq). Quatro Pacientes Foram Submetidos À Cirurgia; Três à rATQ de segundo estágio após infecção e um devido a afrouxamento asséptico. A técnica tem três etapas principais: avaliação (clínica ou radiográfica) da inclinação pélvica lateral; colocação de uma haste supra-acetabular usando o aplicativo do
smartphone
como referência para o ajuste da inclinação; e preparação do acetábulo e colocação final da cúpula utilizando o
smartphone
para a orientação do ângulo de inclinação após considerar a inclinação pélvica. A anteversão da cúpula foi ajustada de acordo com o ligamento acetabular transverso. Todos os quatro casos foram acompanhados por 17 a 24 meses; nenhum paciente precisou de outra cirurgia de revisão ou apresentou complicações (intraoperatórias pós-operatórias precoces ou tardias). Todas as cúpulas estavam dentro da zona segura de Lewinnek de inclinação (42° 43° 47° e 41°). O resultado funcional de acordo com o Harris Hip Score foi excelente em todos os pacientes. Os
smartphones
são ferramentas baratas que podem auxiliar os médicos no ajuste da inclinação da cúpula acetabular durante a rATQ; no entanto é crucial avaliar a possível inclinação pélvica lateral e considerá-la ao posicionar a cúpula.