SLR - April 2019 - Natalia Cardona

Persistent Postoperative Step-Off of the Posterior Malleolus Leads to Higher Incidence of Posttraumatic Osteoarthritis in Trimalleolar Fractures

Reference: Verhage, SM, Krijnen P, Schipper IB, & Hoogendoorn JM. Perisistent postoperative step-off of the posterior malleolus leads to higher incidence of posttraumatic osteoarthritis in trimalleolar fractures. Arch Orthop Trauma Surg. 2019 Mar; 139(3):323–329.

Scientific Literature Review

Reviewed By: Natalia Cardona, DPM
Residency Program: Northwest Medical Center, Margate, FL

Podiatric Relevance:
The posterior malleolus fracture of an ankle may many times be overlooked, even though it is an important component of an ankle fracture. Decisions regarding management require an understanding of the ligaments, bony architecture and components of the injury. Traditionally, the size of the posterior fragment is considered the most important indicator of whether or not the posterior malleolus fragment should be fixated. Factors contributing to poor functional and radiologic outcomes are still unclear. This study was designed to determine predictors for the development of posttraumatic osteoarthritis and worse functional outcomes in trimalleolar fractures.   

Methods: This is a retrospective cohort study, which evaluated 169 patient outcomes following trimalleolar fracture, treated between 1996 and 2013 in the Netherlands with a mean follow-up of six years. Originally, patients were treated in an anterior-to-posterior approach to the posterior malleolus fragment, but after 2011, the authors changed their operative strategy to open reduction and internal fixation via posterolateral approach. The average fragment size was 17 percent of the inta-articular surface. Twenty patients had a posterior fragment smaller than 5 percent of the intra-articular surface, 119 patients a fragment of 5–25 percent and 30 patients a posterior fragment larger than 25 percent. In total, 39 patients (23 percent) underwent fixation of the posterior fragment. Anatomic reduction was defined as a step-off or gap of 1 mm or less.  

Results: The authors noted clinical union in all 169 patients. Anatomical reduction of the posterior malleolus fracture fragment was achieved in 23 out of 39 patients while clinical union was noted in all 169 patients. According to the study, osteoarthritis was present in 49 (30 percent) of the patients. The median AOFAS score after follow-up was 93, and the median AAOS score was 92. A persistent postoperative step-off larger than 1 mm was found in 65 patients (39 percent). Significant risk factors for the development of osteoarthritis was a higher age and postoperative step-off > 1 mm.  Osteoarthritis and BMI were noted to be significant risk factors for worse functional outcome.

Conclusion: The authors of this study concluded it is advisable to correct intra-articular step-off of posterior malleolar fragments to reduce the risk of developing osteoarthritis and, consequently, the risk of worse functional outcomes after long-term follow-up. What was very interesting in this study, was that neither size of the posterior malleolar fragment, or type of fixation, was associated with the development of osteoarthritis or with a poor functional outcome. Therefore, they determined that it would be beneficial to the patient to anatomically reduce and fixate all intra-articular posterior malleolar fracture fragments regardless of size.

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