3) One potential explanation includes the direct force provided by the wide and broad insertion of the Achilles tendon in these individuals and may result in an increased risk of avulsion fractures. We hypothesize that individuals that possess extensive insertion are at increased risk for potential avulsion fractures. In our study, extensive insertion was found in fifteen out of a total of twenty cases of avulsed calcaneal fractures. Although the true prevalence of extensive insertion of the Achilles tendon is not well established, a recent study by Lowy 6) demonstrated this anatomical variant in two of ten dissected specimens. We examined this problem by examining the anatomical variations of the Achilles tendon insertion and the different mechanisms of injury. 9, 10) However, this description can only account for the classification of type I fractures within our study and cannot explain the other fracture patterns detected in young male patients. 7, 8) These fractures have also been observed with increased frequency in diabetic patients due to insufficiency fractures associated with peripheral neuropathy. Several studies have suggested that avulsion fractures of the calcaneal tuberosity have an osteoporotic origin. 6) Therefore, anatomical variances of the Achilles tendon were divided into the infrabursal insertion, which is the usual anatomy and more extensive insertion or higher than what is normally described. Anatomical variances of the Achilles tendon were previously described as differences in the level of insertion (more or less extensive) of the Achilles tendon into the calcaneus.
The mechanism of injury was recorded and defined as tripping, falling or a direct blow. Other data included demographic information, the specific mechanism of injury and the anatomical variance of the Achilles tendon according to the findings of both the MRI and surgery. Adequate X-rays and clinical notes were available for each patient included in the study. All patients had an observable avulsed bony fragment on the heel.
Twenty patients with an avulsed calcaneal tuberosity out of a total of 764 cases of calcaneal fractures (2.6%) were identified including fourteen men and six women.
Patient information was obtained over a six year period from 20 and included a description of the specific trauma episodes, surgical records, X-rays and MRI of all patients with avulsion fracture of calcaneal tuberosity. The classification scheme defines the four types of avulsion fracture of the calcaneal tuberosity through features including age, gender, the anatomical variances of the Achilles tendon, the fibers involved, and finally the mechanism of injury. Through this report, we propose a novel modified classification system that corresponds to the magnetic resonance imaging (MRI) and surgical findings. 3 - 5) Due to this variability, a modified classification is required according to each type of fracture pattern. Because the Achilles tendon has the following criteria including 1) a broad based insertion on the calcaneus, 2) a braided and coiled anatomical pattern with 90° rotated collagen fibers, and 3) a variable and sudden distribution of force on each avulsion, the resulting patterns of avulsion fracture are as diverse as the potential patient treatment options. 1, 2) Due to the low percentage of incidence, little has been reported regarding these types of fractures.Īvulsion fractures of the calcaneal tuberosity are usually caused by sudden muscular contraction of the Achilles tendon when the heel is flat on the ground. Recent studies on the epidemiology of these specific fractures have demonstrated that avulsed calcaneal fractures account for 1.3% to 2.7% of all calcaneal fractures. Avulsion fractures of the calcaneal tuberosity are rare and infrequent injuries.
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