SLR - June 2016 - Innjea S. Park

“A to P” Screw Versus Posterolateral Plate for Posterior Malleolus Fixation in Trimalleolar Ankle Fractures 

Reference: O'Connor, Timothy J. MD, Mueller, Benjamin MD, PhD, Ly, Thuan V. MD, Jacobson, Aaron R. DC, Nelson, Eric R. MD, Cole, Peter A. MD. “A to P” Screw Versus Posterolateral Plate for Posterior Malleolus Fixation in Trimalleolar Ankle Fractures. Journal of Orthopaedic Trauma. 29(4):e151–e156, April 2015.

Scientific Literature Review

Reviewed By: Innjea S. Park, DPM
Residency Program: Wyckoff Height Medical Center

Podiatric Relevance: Fractures of the posterior malleolus are commonly found in rotational ankle fractures (7 to 44 percent). Although a surgical indication for fractures involving more than 25 percent articular surface is still regarded as norm, surgical indications for posterior malleolus fractures have expanded over the years in terms of ankle stability. It is generally acknowledged that the fixation of posterior malleolus fracture is done either with anterior to posterior (AP) screws percutaneously or through a posterolateral (PL) approach using screws or a buttress plate. However, the authors emphasized the fact that a posterior malleolar fragment is an AO type B articular injury, which is normally fixated with buttress plating in other parts of the body. Despite the fact that ankle fractures involving posterior malleolus fracture often accompany more detrimental outcomes, there is a lack of comparative studies regarding the two most common surgical approaches. Therefore, to seek for more optimal surgical technique, authors set a hypothesis that for posterior malleolus fracture, PL buttress plating allows direct access for fixation, which is more advantageous than the AP percutaneous screw.

Methods: This retrospective study was performed at a single level I trauma center. Authors identified all patients with Current Procedural Terminology codes specific to ankle fracture from January 2002 to December 2010. Overall, 37 patients were filtered to meet inclusion criteria: 1) age 18 years or older at the time of surgery, 2) ankle fracture that underwent surgical stabilization of all three malleolar fragments and 3) posterior malleolus was surgically fixed with either anterior to posterior lag screws (AP screw) or PL plate fixation. Patients were excluded if they had 1) additional ipsilateral or contralateral lower extremity injury, 2) pilon-type trimalleolar fracture (AO-OTA 43 C Type) and/or 3) history of a lower-extremity fracture. Twenty-one received PL plate fixation, and 16 patients received AP screw fixation. All 37 surgeries were performed by five attending surgeons who had either trauma or foot and ankle fellowship training. This study examined all patients via goniometric motion assessment, self-administered Short Musculoskeletal Function Assessment (SMFA) 5 and radiographic analysis. The degree of arthritis was evaluated on final follow-up x-rays by Bargon 6 reference criteria; Bargon grades 0 and 1 were combined representing no or mild arthritis, whereas grades 2 and 3 were combined representing more significant arthritis. In terms of statistical analyses, Mann-Whitney U test and Fischer Exact were incorporated to identify statistically significant differences between the two groups.  

Results: Twenty-seven out of eligible 37 patients chose to participate in the study. Sixteen patients underwent posterior buttress plating, and 11 underwent AP screw fixation with mean follow-up times of 54.9 and 32 months, respectively. Demographic information was similar between groups. The posterolateral plating group demonstrated superior postoperative SMFA scores compared with the AP screw group with statistically significant differences in the SMFA bother index (26.7 vs. 9.2, P = 0.03). Although it was not statically significant, there was also improved outcomes for the PL plate group in the SMFA functional index (P = 0.08) as well as in the mobility (28.3 vs. 12.9, P = 0.08). However, there were no significant differences in the range of motion or the development of ankle arthritis over time. Furthermore, radiographic evaluation revealed no significant differences in the amount of residual articular gap or steps between the two groups.  

Conclusions: Authors concluded that patients with trimalleolar ankle fractures when the posterior malleolus was treated with posterolateral buttress plating had superior clinical outcomes at follow-up compared with those treated with AP screws. Although the authors acknowledged that ORIF through PL approach can impose technical challenges, PL buttress plating offers superior biomechanical stability and strength compared with AP screw fixation. This is possible because PL approach enables the fracture to be directly addressed so that more desirable anatomic reduction can be achieved. Furthermore, more recent studies have emphasized the importance of posterior malleolar fixation in providing syndesmotic stability in relation to the posterior inferior tib-fib ligament, which is the strongest stabilizer of the syndesmosis; therefore, any left unfixed injuries involving posterior malleolus would result in complete syndesmotic disruption and instability. For this reason, this particular comparative study on posterior malleolus fixation method will give more guidance to any podiatric surgeon performing ORIF of tirmallolar ankle fractures in achieving optimal results.  

Educational Opportunities