A Cohort Study of Bioabsorbable Screws for Syndesmosis Fixation Fixation in Ankle Fracture

Overview

The investigators aim to evaluate the fixation of the ankle syndesmosis in appropriate ankle fractures with bioabsorbable screws. Ankle fractures are common, and a proportion of them involve both fracture of the bone and also disruption of the syndesmosis, a strong ligamentous complex connecting the distal fibula and tibia. If left without fixation this causes a high incidence of pain and early arthritis. The most common technique for fixation of this syndesmosis involves the use of the same type of metal screws used to fix the fractured bones. As the syndesmosis permits small degrees of movement in normal subjects, fixation of this with metal usually leads to screw breakage and, or pain. It is common practice to remove these screws after a period of time once the syndesmosis has healed in the correct position. Bioabsorbable screws have the advantage of allowing small increments of movement, and also resorb naturally therefore do not have to be removed with a second surgical procedure. They are used in other centres worldwide, and the investigators therefore seek to evaluate syndesmosis fixation with them in their unit. The investigators would aim to recruit patients who have a syndesmotic injury requiring fixation, and who can consent to participating. They would undergo an identical surgical procedure to the standard current practice, apart from using a bioabsorbable screw in exchange for the metallic screw for syndesmosis fixation. All other components would remain unchanged, as would post operative protocol and management. To evaluate the fixation the investigators would use a limited CT scan (equivalent of about 3 months background radiation) after the time of fixation and at one year. This will help to assess the maintenance of reduction of the syndesmosis with time. The investigators would also assess patient reported outcome measures and pain scores, length of procedure and intraoperative radiation levels, weight bearing distribution tests, as well as any complication that may arise.

Surgical Technique The operation requires the patient positioned supine with a sandbag beneath the ipsilateral buttock to internally rotate the leg to permit the ankle and foot to sit in neutral. Appropriate antibiotics as per local guidelines should be administered prior to insufflation of a tourniquet. Fluoroscopy is required throughout the procedure and should be positioned on the contralateral side to the injured limb to improve the access for the surgical team. Depending on the injury type the fibula may or may not require fixation (maissoneuve or weber B/C type injury). This will be performed if necessary via a direct lateral approach to the fibula, and fixation as per surgeon preference appropriate for the fracture configuration. Typically a lag screw and one-third tubular neutralisation plate is used. Plates should be applied to the posterolateral surface of the fibula to permit passage of the syndesmosis screw through the plate and for increased mechanical stability. Following this the syndesmosis will be reduced with the foot plantigrade using large pointed reduction forceps with or without a K-wire. Medial malleolar fixation, if required, is performed after fibula fixation. Bio-absorbable screw fixation A single 4.5 mm fully threaded ActivascrewTM (2094913CE01) is placed through four cortices if the fibula fracture is being fixed, through the plate if feasible. Two are used in the case of high fibula or maissoneuve injuries. These will all be through four cortices. A countersink may be used. The screws should be placed parallel to the tibial plafond, 2-4cm proximal to the tibio-talar joint and 30° from posterior to anterior. In the case of fibula fixation this should be though the plate if feasible. The reduction of the syndesmosis and appropriate placement of the positioning screw(s) should be checked intra-operatively with fluoroscopy. The syndesmosis is reduced, using reduction forceps. A hole is drilled with the 3.5mm drill, then tapped with the 4.5mm tap and measured. The ActivascrewTM holder and screwdriver are used to pick up and insert the desired screw. Once the screw is in position the insertion adapter is removed and discarded. Standardised rehabilitation protocol Post operatively the patient remains non weight-bearing in a Plaster for a total of 6 weeks with a cast change, wound check and removal of sutures at 2 weeks. Following this the patient would then remain partial weight bearing in a protective boot for a further 6 weeks. The patients should be prescribed 6 weeks of Low Molecular Weight Heparin for venous thromboembolic prophylaxis as per local protocol. Sample size considerations A total number of 40 patients should be sufficient to assess the outcome of fixation using this device. Patients selection and enrolment Patients will be thoroughly screened to assess their suitability for the study and must fit the inclusion and exclusion criteria.