Review Question - QID 216271

This patient sustained an intraoperative medial malleolus fracture during total ankle arthroplasty (TAA). Prophylactic intraoperative pinning of the medial malleolus prior to the osteotomy helps prevent intraoperative medial malleolar fractures.

Periprosthetic fractures of the medial malleolus are more common than lateral fractures. Known risk factors for intraoperative fracture include uncontrolled saw blade excursion, excessively medial or lateral placement of the tibia prosthesis, use of an oversized tibial prosthesis, or over-distraction from an external fixator. Prophylactic K-wire (or screw) insertion through the medial malleolus prior to the osteotomy has been shown to reduce the risk of intraoperative fractures.

Manegold et al. reviewed 503 total ankle replacements performed over 13 years. They report a 4% periprosthetic fracture risk (2% intraoperative and 2% postoperative). Moreover, 66% of these fractures occurred in the medial malleolus. They proposed a classification system (Illustration A) and treatment algorithm (Illustration B).

McGarvey et al. retrospectively reviewed TAA performed by 2 surgeons. They report 9 fractures with use of two different TAA designs. They concluded that the vast majority of these fractures occurred intraoperatively and the medial malleolus was more commonly involved.

Figure A shows a chronic medial malleolar fracture. Illustration A shows the Manegold classification system. It is based on 3 parameters: fracture cause/timing, anatomic location and stability of implants. Illustration B shows the Manegold algorithm for treatment of TAR periprosthetic fractures. Illustration C shows prophylactic pinning of the medial malleolus prior to the osteotomy with the jig in place.

Incorrect Answers:
Answer 1: Overdistraction of the joint site and early external fixator removal before final implantation can create sudden episodic bending moments about the malleoli increasing the risk of fracture
Answer 2: An oversized tibial tray creates high compressive loads on the medial malleolus and increases fracture risk of fracture
Answer 3: Making a more medially-based plafond cut increases the risk of a medial malleolus fracture
Answer 4: Making a more proximal tibial cut increases the risk of a medial malleolus fracture as the bone bridge between the ankle joint and the outer cortex of the tibia narrows