# Proximal tibiofibular joint dislocation is rare in knee dislocations type Schenck III or higher

## TL;DR

This study found that dislocation of the proximal tibiofibular joint is rare in severe knee dislocations, with only 5.4% of cases showing full dislocation.

## Contribution

The study introduces two new CT-based parameters to assess proximal tibiofibular joint dislocation in knee injuries.

## Key findings

- Complete PTFJ dislocation was observed in 5.4% of knee dislocation cases, all in type IV injuries.
- Fibula lateralisation and posterior fibula area are suitable parameters for assessing anterolateral dislocation of the proximal fibula.
- No PTFJ dislocations were found in the uninjured contralateral knee group.

## Abstract

The purpose of the study was to determine the prevalence of proximal tibiofibular joint (PTFJ) dislocations in knee dislocations classified as Schenck type ≥III and to compare with uninjured contralateral knees, which served as control cohort.

Patients treated at Cologne Merheim Medical Center with knee dislocation ≥III between 2015 and 2022 were included, while one control group consisted of uninjured contralateral knees. In addition to established PTFJ‐specific parameters, two novel computed tomography‐based PTFJ parameters were implemented on scans obtained a mean of 5 days post‐trauma. The fibula lateralisation quantifies the lateral shift of the proximal fibula joint line in relation to the tibial PTFJ joint line. The posterior fibula area quantifies the fibula position in the sagittal plane with reference to the posterior tibial margin.

A total of 107 knee joints were included, comprising 40 with knee dislocation ≥III, 24 uninjured contralateral knees and 43 chronically isolated anterior cruciate ligament insufficient knees. The overall cohort had a median posterior fibula area of 92.7% and a fibula lateralisation of 0.0%. Complete PTFJ dislocation was observed in 5.4% of knee dislocation cases, all in type IV injuries. Fibula lateralisation analysis indicated PTFJ subluxation in an additional 21.6% of cases. No PTFJ dislocations were present in the contralateral knee group. The knee dislocation group differed significantly from the matched contralateral knee group with regard to fibula lateralisation (r = 0.43; p = 0.007), whereas no differences were observed for inclination‐horizontal (p = 0.620), inclination‐fibular axis (p = 0.082) and obliquity (p = 0.602).

This study demonstrates a 5.4% prevalence of PTFJ dislocation in knee dislocations ≥III, which is lower than previously reported. The incidence of PTFJ dislocation in knee dislocations type IV is high at 33.3%. Fibula lateralisation and posterior fibula area are suitable parameters for assessing anterolateral dislocation of the proximal fibula. Inclination‐horizontal, inclination‐fibular axis and obliquity show no relevant side‐to‐side differences in individuals.

Level III.