X-ray imaging judgment of the safety zone in screw fixation surgery for posterior ankle fracture

Abstract

ObjectiveTo propose a method based on intraoperative ankle acupoint X-ray fluoroscopy to determine the safe area of screw fixation surgery for posterior ankle fractures using the posteromedial vertical syndesmotic line(PVSL). MethodsA retrospective analysis was conducted on the clinical data of 21 cases of Lauge-Hansen type Ⅲ-Ⅳ posterior malleolar fractures fixed with hollow screws in Danyang peoples Hospital from October 2019 to June 2021. During the operation, the radiological safety area was determined the screw which located within 1-2 mm of the tibia side of PVSL under ankle acupoint fluoroscopy of C-arm X-ray machine, and the quality of screw placement was evaluated by three-dimensional reconstruction of multi-slice spiral CT scan after operation. ResultsUnder intraoperative X-ray fluoroscopy, the posterior ankle screw was inserted within 1-2mm of the tibial side of the PVSL, and no screw entered the lower tibiofibular joint. The posterior ankle fracture block was effectively fixed. The follow-up time was 12-18(15.24 ±4.37） months. Among 21 patients, there were no complication such as sural nerve injury, abnormal hallux flexion, and all incisions healed in grade A. There was no re-displacement, delayed union, or non union of the fractures. One year after surgery, the ankle joint AOFAS score was(86.74 ± 10.84), and the excellent and good rate was 95.2%. ConclusionUnder intraoperatiue X-ray fluoroscopy, the placement of posterior ankle screws within 1-2mm of the tibial side of PVSL can improve the accuracy of screw placement and avoid injury caused by screw entry into the lower tibiofibular joint. PVSL can provide an imaging reference for the safe range of implant placement in posterior ankle fractures.

Keywords

• ankle joint fracture
• posterior ankle fracture
• hollow screw
• safe zone
• x-ray fluoroscopy examination
• the posteromedial vertical syndesmotic line