THE NATURAL HISTORY OF TYPE VII ALL INTRA-EPIPHYSEAL FRACTURES OF THE LATERAL MALLEOLUS

Abstract

Background: Inversion-type ankle injuries are common in pediatric athletes, often resulting in lateral malleolar fractures (1). Ogden described the Type VII lateral malleolar physeal fracture as an injury in which the fracture line is totally within the secondary ossification center of the distal fibular epiphysis (2). The purpose of this paper is to report on the outcomes of 31 children participating in various types of sports activities who had sustained a Type VII fracture of the lateral malleolus. Methods: Here we report the results of an IRB approved prospective (longitudinal) cohort study carried out at a tertiary care pediatric hospital from March 2012 to December 2017. Eligible patients were those with a type VII (all epiphyseal) fracture of the lateral malleolus, either treated initially or seen in follow-up by the senior author. Exclusion criteria included those patients with all other lateral malleolar injuries and those with negative radiographs. Thirty-one children were enrolled during the study interval. Type VII fractures were classified as either transverse, oblique, or tip avulsion, depending on the trajectory and location of the fracture line within the secondary center of ossification of the lateral malleolus. We recorded the following demographic data: sex of the patient, age at the time of injury, mechanism of injury, sport involved, weight bearing status at the time of injury, treatment of the injury, and time from injury to release to sports activity. Children were permitted to return to sports when they had no discomfort on palpation and an ankle range of motion was equal to the uninvolved side. The primary outcome focus was radiographic status of the fracture at the time of the last clinical evaluation. Results: Thirty-one children with a Type VII fracture of the lateral malleolus were enrolled during the study interval. There were 8 girls and 23 boys. The average age at the time of injury was 107 months (˜9 years.) All the children had sustained a supination inversion-type injury while participating in a full spectrum of sports activities. Twenty-five children were initially unable to bear weight, and 6 could walk but with a limp. Twenty-six children were treated with a weight-bearing cast and crutches, and five of those who could bear weight were treated with a cast boot. Four fractures were oblique, 8 were transverse, and 19 were tip avulsions. All the children were asymptomatic and had a negative drawer test when cleared for sports participation at an average time of 3.5 months (range 2.5 to 4) after injury. Eighteen children had radiographs showing uneventful healing of the fractures (Figure 1) when released to full activity, but 13 (31%) healed with formation of a discrete os subfibulare (Figure 2.) The 18 fractures that healed uneventfully were located above the distal third of the fibular epiphysis. All of the 13 that healed with an os subfibulare were located either at the distal tip of the fibula (4) or at the anterior distal aspect of the tip (9) corresponding to the area of attachment of the ATFL. Conclusions: All of children sustaining a Type VII fracture of the lateral malleolus were able to return to full sports activities. Eighteen of the 31 Type VII fractures (58%) healed uneventfully. However, 13 (42%), healed with the formation of an os subfibulare. Since the presence of an os subfibulare has been associated with recurrent ankle instability and pain (3), it may be prudent to observe and even recommend ankle rehabilitation exercises for these children to help prevent long-term problems. [Figure: see text][Figure: see text] Su AW, Larson AN. Pediatric Ankle Fractures: Concepts and Treatment Principles. Foot Ankle Clin. 2015;20(4):705-719.26589088. Ogden JA. Injury to the growth mechanisms of the immature skeleton. Skeletal Radiol. 1981;6(4):237-253.7292021. Pill SG, Hatch M, Linton JM, Davidson RS. J Bone Joint Surg Am. 2013;95: e115(1-6) d http://dx.doi.org/10.2106/JBJS.L.00847 .