SLR - October 2014 - Erin Younce

Posterior Malleolus Fracture
 
Reference: Irwin, TA, Lien JL, Kadakia AR.  Posterior Malleolus Fracture.  Journal of American Academy Orthopedic Surgery  21:32-40; 2013.

Scientific Literature Review
 
Reviewed By: Erin Younce, DPM
Residency Program: St. Vincent Charity Medical Center
 
Podiatric Relevance: In dealing with ankle fractures, the presence of a posterior malleolus fracture negatively affects prognosis. The integrity and ligamentous attachment is important for load transfer, posterior talar stability, and rotary ankle stability. There is variation among surgeons regarding the decision for fixation of this fragment. This article’s purpose is to review current literature on the topic for the consideration of both orthopedists and podiatrists alike.
 
Methods: Anatomy, biomechanics, and clinical decision making is reviewed. Posterior malleolus fractures occur in 7-44 percent of all ankle fractures, most in the setting of rotational ankle fractures. Harris’ cadaver study demonstrated that the PITFL provides 42 percent of syndesmotic stability. Macko’s and Hartford’s cadaveric studies demonstrated that at 33 percent fragment size, only 87 percent contact area remained. Fitzpatrick showed that with a simulated posterior malleolus fracture, the location of contact stress redistributes anteromedially during dynamic range of motion. Raasch concluded that the fibula and the AITFL are the primary restraint to posterior translation of the talus because posterior subluxation of the talus in simulated fractures involving >30 percent of the posterior malleolus occurred only after disruption of the fibula and AITFL.

Results: Various literature regarding fixation of the posterior malleolar fragment is reviewed, however, is limited by the lack of standardization in examining functional outcomes, relatively small patient populations, and varied treatment protocols by the investigators. It is generally understood that with anatomic reduction of the lateral malleolus fracture, the posterior malleolus is often reduced via ligamentotaxis of the PITFL and if there is residual displacement of the posterior fragment, it should be corrected; however, no consensus exists regarding the minimal size of a posterior malleolus fracture fragment requiring fixation regardless of displacement. Several authors recommend surgical fixation of posterior malleolus fractures involving >25 percent of the articular surface; in contrast, high-level data in the literature are insufficient to support the use of this number as a threshold. Langenhuijsen concluded that joint congruity should be achieved for all posterior malleolus fractures involving > or equal to 10 percent of the articular surface with or without internal fixation; fixation was reserved for fragments > or equal to 10 percent of the articular surface. Jaskulka noted that even small posterior tibial rim fractures may be assosicated with poorer prognosis; significantly better long-term results in posterior fragments involving >5 percent of the articular surface treated surgically compared with those treated nonsurgically. Heim recommended surgical fixation of all posterior malleolar fragments except posterior lip avulsions. Gardner demonstrated that posterior malleolus fixation restored 70 percent of syndesmotic stiffness compared with 40 percent with syndesmotic screw fixation. Miller found that posterior malleolar reconstruction more accurately restored the syndesmotic articulation than did syndesmotic screw fixation. No study to date has been performed comparing surgical fixation of the posterior malleolus to the use of syndesmotic screws alone
 
Conclusions: The author does not follow a strict size threshold for management of the posterior fragment, in general. In the case of any significant displacement, regardless of fragment size, the author treats the posterior malleolus fracture with open reduction and internal fixation through a posterior lateral approach with the patient in the prone position. The postoperative course involves six weeks of nonweightbearing, followed by three-six weeks of weightbearing in boot immobilization. In the author’s experience, syndesmotic screws are rarely required when the posterior malleolus is fixed primarily; however thorough evaluation of the integrity of the anterior tibiofibular joint should be performed this including CT scan. Posterior lip avulsion fractures, as well as small, completely nondisplaced posterior fragments are usually managed conservatively. 

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