A Comparative Study Between Positional and Lag Screws for the Fixation of Medial Malleolar Fractures

Ankle fractures are one of the most common traumatic injuries an orthopedic surgeon encounters during their clinical practice, Hence looking into the best management of them and conducting extensive research to determine the best methods of their fixation would be justifiable. Malleolar fractures and in particular medial malleolar involve the articular surface of the ankle joint and hence a displacement beyond > 2mm requires careful anatomical restoration through open reduction and internal fixation. The medial malleolus is characterized with it's porous cancellous bone, and hence a lack of a secure fixation method is a major issue and is responsible for post-operative complication and delayed healing. The AO recommends fixation of these fractures with 4mm partially threaded lag screws. Some studies have arisen that may challenge this AO philosophy and raise the question if this actually is the best choice of treatment for medial malleolar fractures. The problem with lag screws is that they have a higher chance of unravelling. and other studies have shown that constructs fixated with fully threaded screws provide higher stability and provides higher shear resistanceand a higher pull-out strength. The other alternative to using a partially threaded lag screw would be a fully threaded lag screw of virtually the same length however it would act as a positional screw and hence the fracture displacement must be perfectly reduced with bone reduction forceps before inserting the fully threaded screws to achieve their property as positional screws.

A study conducted by parker et al. comparing the use of partially threaded and positional(fully threaded) screws of the same length found that compression force was in favor of the fully threaded screws. This could be due to threads of the fully threaded screws obtaining purchase in the dense physeal scar area while in the partially threaded screw, the threads bypass this physeal scar. Despite all this evidence and the widespread of this fracture among the population, the number of studies comparing lag vs positional screws in medial malleolar fractures is scarce and to our knowledge as of the time of the submission of this study, only a single study was made by Sayyed-Hosseinian et al., was performed as a pilot study comparing both fixation methods, due to the relatively small sample size , it indicates that further clinical trials are necessary to reach a reliable conclusion. The conduction of a clinical trial with a proper sample size should be done to assess if lag screws are actually a superior method to be considered the main recommendation, as the AO suggests, to treat medial malleolar fractures or if alternatively, positional screws are better, as some biomechanical tests mentioned prior have shown. This study will compare both methods to decide the superior fixation method in terms of achieving a better and faster quality of life post-surgery and and the least risk for potential complication for medial malleolar fractures by obtaining the AOFAS, MOXFQ and OMAS scores and comparing complications in both study groups.