Iselin disease is traction apophysitis of the fifth metatarsal base and clinically presents with tenderness and pain overlying the lateral aspect of the midfoot. It was first described by a German physician Hans Iselin in 1912 . It is likely an underdiagnosed by many physicians due to lack of recognition and lack of suspicion. However, most sports medicine physicians will likely see this in their practice, though reports show it is much less common than Osgood-Schlatter’s disease and Sever’s disease.
It most commonly affects adolescents and does fall along other patterns of traction apophysitis with females being affected between ages 8 and 11 and males from 11 to 14 years old . It is often confused with a fracture at the base of the fifth metatarsal. The secondary ossification center appears as a small fleck oriented slightly oblique to the metatarsal shaft and is located on the lateral aspect of the tuberosity of the fifth metatarsal. The peroneus brevis inserts over this apophysis before skeletal maturity. There is a paucity of evidence regarding the epidemiology of Iselin’s disease due to limited studies with most data being in the form of case reports.
Iselin’s disease can be caused by repetitive minor trauma through the force of the peroneus brevis tendon acting on the apophysis. This can result in partial avulsion of the apophysis and inflammation, and excessive force can result in complete avulsion. Thus, Iselin’s disease is often associated with sporting-type activities, with all reported cases observed in athletic individuals .
Clinical presentation can vary, but most patients will present with pain over the fifth metatarsal with weight bearing activity. It does normally present similar to other traction apophysitis with pain after activity and in particular sporting activity such as running or jumping. A history of significant trauma is usually absent, although some reports show symptoms worsen after inversion events. There are usually reports of swelling over the base of the fifth metatarsal. Many will have 3-6 months of symptoms before presentation and pain over the area can be progressive .
On physical examination, there may be prominence, erythema and soft tissue edema over the base of the fifth metatarsal on inspection. There will most commonly be tenderness to palpation over this area and possibly along the peroneus brevis. Muscle strength testing is usually normal but many have discomfort with resisted eversion and possibly plantarflexion or inversion. Neurological exams are also typically normal. While observing gait, there may be an avoidance of pressure on the lateral foot and the patient may favor walking over the medial foot.
Plain radiographs are usually done and it is important to image both sides with apophyseal injuries or pain. There may be some value with the anterior-posterior view, but the apophysis is best seen on the oblique view. There may be enlargement or widening of the apophysis or fragmentation of the ossification center (Image 2). Bone scans and MRI (magnetic resonance imaging) may be done if there is still a question clinically, but sensitivity and specificity studies do not exist for Iselin’s disease (Image 3). There will likely be edema over the unfused apophysis and there may also be mild to moderate marrow edema in the adjacent fifth metatarsal. It is also important to look for any additional stress injury, response or fracture on the MRI if ordered.
Iselin disease is treated conservatively with rest and nonsteroidal anti-inflammatory drugs. Pain usually resolves within 3–6 weeks. There have been reports immobilizing the area for 2-4 weeks with a posterior splint or short leg cast depending on patient and disease severity. NSAIDs (Non-steroid anti-inflammatory drugs) are commonly prescribed for pain control and treatment of inflammation. In addition, it is important to educate the parents and child with the mechanism of injury and to avoid the activities causing the symptoms. Physical therapy appears to improve strength and coordination and may also present an opportunity to correct any foot or gait abnormalities .
There have been reports of nonunion over the apophysis and persistent widening of radiolucent lines after 3-6 months . Excision of the proximal bony fragment is recommended as long as the excised bone does not interfere with the function of the peroneus brevis tendon or stability of gait. A combination of non weight bearing and partial weight bearing can be used. Physical activity can be resumed 6-10 weeks after surgery.
The importance of highlighting Iselin’s disease is threefold. First, this will add to the differential diagnosis for children with fifth metatarsal base pain. Second, it will offer guidance in identifying these cases and reduce the incidence of mistaking them for fractures. Finally, it will increase awareness due to the limited data. This has become increasingly important owing to the increased participation of children in sports .
In conclusion, ID should be suspected in children around 10– 15 years of age who present with lateral foot pain, particularly on the tuberosity of the fifth metatarsal. A careful history, physical examination findings and a simple lateral oblique foot radiograph are usually diagnostic. Conservative treatment in the form of activity modification, rest and pain control is sufficient for most of the cases.
- Iselin H. Wachstumbeschwerden zer zeit der knockern entwicklung metatarsi quinti. Deut Z Chir 1912;117:529.
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- Ralph, Brian G., et al. “Iselin’s disease: a case presentation of nonunion and review of the differential diagnosis.” The Journal of foot and ankle surgery 38.6 (1999): 409-416.
- Gupta, Nishant, et al. “Kickboxing power hour: case report of fifth metatarsal apophysitis (Iselin disease) and its magnetic resonance imaging features.” Translational pediatrics 6.2 (2017): 98.