Background

In the ankle, the distal tibiofibular joint is a syndesmotic articulation without articular cartilage. It is stabilized by the anterior and posterior tibiofibular ligaments, the inferior transverse ligament and the interosseous membrane.1 The fibula rotates, translates and migrates within the incisura to maintain congruence with the wedge-shaped talus through talocrural range of motion.2 Subtle motion of the fibula at this joint is important for ankle congruity to allow normal ankle motion and prevent joint degeneration.3 The ankle is a highly congruent joint, with even a 1 mm talar shift decreasing contact area by 42%.4 The osteoligamentous complex as a whole is called the "distal tibio-fibular syndesmosis" or just "the syndesmosis".

Injuries to the distal tibiofibular syndesmosis are common, occurring in 5-10% of ankle sprains and 23% of ankle fractures.2 An unstable syndesmosis leads to ankle instability and pain.2 There are various treatment strategies to stabilize the syndesmosis, varying between institutions and surgeons. Following reduction of the syndesmosis, the current most widely used treatment is placement of one or two 3.5, 4.0 or 4.5 mm diameter metal screws between the fibula and tibia at 1.5-2 cm proximal to the joint surface, penetrating three or four cortices of bone.1,2 Aftercare and weight bearing depend on fracture pattern and stability.

Practices regarding removal of metal syndesmotic screws vary. Intact syndesmotic screws limit normal fibular translation5 that may lead to screw breakage once weight bearing resumes, occurring in 7-29% of cases,2 with 3.5 mm diameter screws more likely to break than 4.0 or 4.5 mm screws.6 At 6-12 weeks postoperatively screws may be removed routinely to avoid screw breakage and allow normal motion at the syndesmosis; however, this requires further surgery, exposing the patient to further risk of complications and an economic cost to the health system.

A recent development is suture button fixation. A non-absorbable suture is passed through a drill tunnel through the tibia and fibula and secured at both ends by buttons. It is less rigid than screw fixation but allows dynamic stabilization with more normal motion and does not require routine removal.7

In addition, an advancement of the syndesmotic screw is the bioabsorbable screw. Traditional screws are made of stainless steel or titanium, while bioabsorbable screws are made of polyglycolic (PGA) or polylactic (PLA) acid. Traditional screws are weaker than metal screws, with PLA screws being stronger and slower to resorb than PGA.8 They have the benefit of not needing removal, as they eventually lose integrity to allow normal tibiofibular motion.9

In clinical practice, the question remains as to which fixation method, metal screws, bioabsorbable screws or suture button fixation, has the best outcomes. Even with the most commonly used implant (metal screws), questions remain regarding diameter, number, position and number of cortices engaged. Whether or not the screws should be removed is also unclear. With many unanswered questions about management of this common injury, there is a need to conduct a systematic review of current approaches to fixation for acute syndesmotic injury to summarize the evidence and provide guidance for clinical practice and research. A preliminary search of PubMed, the Cochrane Library and the Joanna Briggs Institute Database of Systematic Reviews and Implementation Reports found a single 2007 systematic review of syndesmotic injuries10 and no meta-analyses. The scope of the review was limited to studies on syndesmotic injury without fracture and only prospective studies. As a result, only six studies were included with only two patients who were managed with surgery. Therefore, there is a need to conduct a systematic review of current approaches to fixation for acute syndesmotic injury to summarize the evidence and provide updated guidance for clinical practice and research.

Inclusion criteria

Types of participants

The current review will consider studies that include adult patients (over 18 years) with acute syndesmotic injuries requiring surgical stabilization (with or without associated fracture). As classified by the Association for Osteosynthesis fracture classification system,11 malleolar region fractures (44-A, B and C) will be included as these are the ankle fractures most commonly associated with syndesmotic injury.

Patients with other associated ankle fractures including tibial plafond and other long bone fractures will be excluded as these patients' outcomes are likely to be affected by their other injuries. Chronic syndesmotic injuries (>6 weeks old) will be excluded as these have different management strategies and may have worse outcomes.12 Non-English studies will be excluded.

Types of interventions

The current review will consider studies that evaluate fixation of acute syndesmotic injuries with metal screws, suture button or bioabsorbable screws. The fixation should occur within six weeks of the injury in the acute hospital setting. Studies which compare two or more fixation methods will be sought preferentially, but studies with any comparator or control group will be included.

Outcomes

The current review will consider studies that include the following outcome measures: compound functional scores, range of motion (as measured clinically or with a goniometer), pain as measured by visual analog scale or other metrics, radiological measurements of the syndesmosis (clear space and tibiofibular overlap) and complications. Compound functional scores such as the Olerud-Molander,13 the American Orthopedic Foot and Ankle Society ankle-hindfoot score and the American Academy of Orthopedic Surgeons foot and ankle score14 will be sought where reported.

Types of studies

The current review will consider both experimental and epidemiological study designs including randomized controlled trials and non-randomized controlled trials. In the absence of higher level studies, this review will also consider quasi-experimental, before and after studies, prospective and retrospective cohort studies, case-control studies, analytical cross-sectional studies, descriptive epidemiological study designs including case series, individual case reports and descriptive cross-sectional studies with or without a control group for inclusion.

Search strategy

A comprehensive and exhaustive literature search will be performed. The search strategy aims to find both published and unpublished studies. A three-step search strategy will be utilized in this review. An initial limited search of MEDLINE and CINAHL will be undertaken followed by analysis of the text words contained in the title and abstract, and of the index terms. A second search, using all identified keywords and index terms, will then be undertaken across all included databases. Third, the reference list of all identified reports and articles will be searched for additional studies. Studies published in English will be considered for inclusion in this review. There is no time limit for this review.

The databases to be searched include PubMed, Embase, Scopus, The Cochrane Central Register of Controlled Trials, Web of Science and CINAHL.

The search for unpublished studies will include Mednar, ProQuest Theses and Dissertations, Open Grey and Libraries Australia.

Initial search strategy keywords to be used will be syndesmos^*[tw] OR syndesmot^*[tw] OR (tibiofibular[tw] AND distal[tw]) OR (tibio-fibular[tw] AND distal[tw]) OR (diastasis[tw] AND ankle[tw]) OR ("high ankle"[tw] AND sprain[tw]) OR (high-ankle[tw] AND sprain[tw]) OR AITFL[tw] OR PITFL[tw] OR "anterior inferior tibiofibular ligament"[tw] OR "posterior inferior tibiofibular ligament"[tw] OR "anterior inferior tibio-fibular ligament"[tw] OR "posterior inferior tibio-fibular ligament"[tw].

Assessment of methodological quality

Papers selected for retrieval will be assessed by two independent reviewers for methodological validity prior to inclusion in the review using standardized critical appraisal instruments from the Joanna Briggs Institute Meta Analysis of Statistics Assessment and Review Instrument (JBI-MAStARI) (Appendix I). Any disagreements that arise between the reviewers will be resolved through discussion or with a third reviewer.

Data extraction

Data will be extracted from papers included in the review using the standardized data extraction tool from JBI-MAStARI (Appendix II). The data extracted will include specific details about the interventions, populations, study methods and outcomes of significance to the review question and specific objectives. Attempts will be made to contact authors of primary studies for missing information or to clarify unclear data.

Data synthesis

Quantitative data will, where possible, be pooled in statistical meta-analysis using JBI-MAStARI or RevMan where appropriate. All results will be subject to double data entry. Effect sizes expressed as odds ratio (for categorical data) and weighted mean differences (for continuous data) and their 95% confidence intervals will be calculated for analysis. Heterogeneity will be assessed statistically using the standard Chi-square and I² and also explored using subgroup analyses based on the different study designs included in this review. Where statistical pooling is not possible, the findings will be presented in narrative form including tables and figures to aid in data presentation where appropriate. Forest plots and a GRADE Summary of Findings table will aid in the presentation of results.

If sufficient quality data is extracted, subgroup analysis will be performed for metal screws evaluating screw diameter, number of screws, number of cortices engaged, location relative to syndesmosis and screw removal versus retention.

Acknowledgments

The current review is to contribute toward a Masters of Clinical Science through the Joanna Briggs Institute based at the University of Adelaide for the main author.

Appendix I: Appraisal instruments

MAStARI appraisal instrument

Appendix II: Data extraction instruments

MAStARI data extraction instrument

References