SLR - August 2013 - Joanna Wyman
Reference: Manegold S, Haas N, Tsitsilonis S, Springer A, Mardian S, Schaser K. J Bone Joint Surg Am. 2013;95:815-20
Scientific Literature Review
Reviewed by: Joanna Wyman, DPM
Residency Program: INOVA Fairfax Hospital, Falls Church VA
Podiatric Relevance: Total ankle replacement has gained increasing popularity over the last 10 years and remains the only motion-preserving option for ankle arthritis. With improvements in implant design and surgeon experience, total ankle replacement is becoming an effective and reliable alternative to ankle arthrodesis in some patients. The recent expansion in the use of total ankle replacements in combination with improved implant survival, increased patient life expectancy, and therefore increased functional demands on the implant, results in potentially more complications. Periprosthetic ankle fractures are one of the complications that are anticipated to increase. The aim of this work was to introduce a classification system of periprosthetic ankle fractures that could be employed in a treatment algorithm to guide the timing and method of fracture treatment and to assist in decision-making regarding revision arthroplasty.
Methods: A total of 503 patients who underwent either primary or revisional total ankle arthroplasty over a 13-year period were examined. Both S.T.A.R. and Hintegra prostheses were used. All patients had standard radiographs which were examined by blinded orthopaedic surgeons and a radiologist. In cases where periprosthetic fractures occurred, a CT scan was obtained to evaluate prosthetic stability. The proposed classification is based on three parameters which are sequentially assessed: the apparent fracture cause, the fracture location, and the stability of the prothesis. The first parameter (cause) is classified as intraoperative (Type 1), postoperative traumatic (Type 2), or postoperative stress fracture (Type 3). The second parameter (location) has four possible values: medial malleolus (A), lateral malleolus (B), tibia (C), and talus (D). Lastly, the third parameter (stability of prosthesis) is classified as either stable (S) or unstable (U). If there is no clinical or radiographic sign of implant loosening or the fracture does not extend to the prosthesis, the implant is considered stable. If there is periprosthetic osteolysis or fracture-related implant loosening, the prosthesis is classified as unstable.
Results: Twenty-one patients with periprosthetic fractures were identified, yielding a 4.2 percent fracture rate in the 503 patients analyzed. Eleven of the fractures (2.2 percent) occurred intraoperatively (type 1) and the remaining ten (2.0 percent) occurred postoperatively. Of the postoperative fractures, two (0.4 percent) were traumatic and eight (1.6 percent) were due to postoperative stress. Two-thirds (14) of the 21 fractures were located in the medial malleolus. After primary total ankle replacement, the rate of periprosthetic fracture was 3.9 percent and increased to 7.9 percent after revision arthroplasty, although this was not a statistically significant difference. All intraoperative fractures (type 1) and all postoperative traumatic fractures (type 2) were treated according to AO principles. A more varied treatment plan was followed for postoperative stress fractures (type 3). Five non-displaced fractures without prosthesis loosening were treated non-operatively. The three others were treated operatively, two required osteosynthesis and in one of these cases the total ankle replacement was later converted to an ankle arthrodesis. In the third case, a medial malleolar stress fracture caused varus malpositioning of the tibial component and was treated with a supramalleolar corrective osteotomy.
Conclusions: Periprosthetic fractures following total ankle replacements are uncommon with a prevalence of 4.2 percent in this study. In the case of intraoperative fractures, most are iatrogenic and are caused by the use of an oscillating saw or by oversizing the prosthesis and are located in the medial or lateral malleolus. The rate of intraoperative fractures is reduced with increasing surgical experience. These types of fractures should be treated according to AO principles with an aim to achieve sufficient bone stability for prosthesis anchorage and uncomplicated osseous integration of the prosthesis. Postoperative type 2 fractures that are stable should be treated according to AO principles. Fractures deemed unstable should be treated to achieve stability of both the fracture and the prosthesis. This may require revision, staged revision in the case of infection, or fusion. Type 3 stress fractures in this study occurred in the medial malleolus and likely occurred due to varus malpositioning during implantation leading to increased mechanical load. In stable fractures a supramalleolar osteotomy aimed at restoring the biomechanics axis of the leg should be performed. Conservative non-operative treatment may be indicated for some stable fractures. Unstable Type 3 fractures will typically require revision arthroplasty. A full periprosthetic fracture decision-making algorithm can be found in Figure 2. In conclusion, this study presents a novel, systematic, practical classification of periprosthetic fractures following total ankle replacements which provides straightforward planning of subsequent operative or non-operative treatment based on fracture classification.