Osteochondroses and Apophyseal Injuries of the Foot in the Young Athlete

Abstract

With an increase in involvement in sports activities by children and adolescents, there has been a concomitant increase in both acute and overuse injuries. The pediatric skeleton lends itself to injuries unique to the young athlete, including various apophysites and osteochondroses. It is important for primary care and sports physicians treating the athlete to be aware of normal and abnormal variations in the pediatric skeleton, as well as common sites of injury in the pediatric foot. This article provides an overview of some of the most common skeletal foot injuries in the pediatric athlete, including Freiberg's infraction, Sever's disease, Kohler's disease, os navicularis, and Iselin's disease.

INTRODUCTION

With an increase in involvement in sports activities by children and adolescents, there has been a concomitant increase in both acute and overuse injuries. Among athletic injuries, the foot is the third most common cause of time lost in sport, with the ankle and knee being more common (³). Overall, foot and ankle injuries are the second most frequent reason for a visit to the primary care physician in young athletes (¹).

The pediatric skeleton lends itself to injuries unique to the young athlete, including various apophysites and osteochondroses. Primary care and sports medicine physicians treating the athlete need to be aware of normal and abnormal variations in the pediatric skeleton, as well as common sites of injury in the pediatric foot. An understanding of the pathophysiology, clinical presentation, diagnosis, and treatment of common foot complaints will allow for the best care of the young athlete and the safest, most timely return to sports.

The majority of athletic injuries are classified as either acute or overuse. Keys to diagnosis include a detailed history, understanding of the mechanism of injury, focused physical exam, and appropriate imaging. Understanding of normal foot development and proper interpretation of imaging results is vital to the appropriate diagnosis and management, especially in skeletally immature athletes.

During growth, there is tremendous change in the muscles and bones of the foot as the physis of long bones and cartilage models in small bones make them prone to acute and repetitive stress injuries (¹). Additionally, congenital abnormalities that may remain asymptomatic and often undiagnosed in inactive children can become symptomatic and painful in active children as increased stress is placed on the bone or joint.

Osteochondroses and apophysitis are two conditions common in the young athlete. Osteochondroses, "bone-cartilage conditions," are a heterogeneous group of injuries to the epiphyses, physes, and apophyses of children. This group of disorders of unknown origin results from a disturbance in endochondral ossification, and these disorders, in general, are self-limited. Proposed etiologies include rapid growth, heredity, anatomic characteristics, trauma, dietary factors, and a defect in vascular supply (^2,12,16).

Osteochondroses follow a unique series of events beginning with necrosis of bone and cartilage. This is followed by revascularization, reorganization with granulation tissue formation and invasion, osteoclast resorption of necrotic segments, and finally osteoid replacement and formation of mature lamellar bone.

Apophysites are a subset of osteochondroses occurring at the bony attachment sites of musculotendinous units. An apophysis develops as an accessory ossification center and is evident on plain films. Irritation at this attachment site and protuberance is called apophysitis.

The following is an overview of Freiberg's infraction, Sever's disease, Kohler's disease, os navicularis, and Iselin's disease, which are some of the most common skeletal foot problems encountered in the pediatric athlete. Although all of these conditions can be found in sedentary children, increased activity and involvement in competitive sports increases the likelihood that the condition will become symptomatic and clinically relevant.

FREIBERG'S INFRACTION

Freiberg's infraction first was described in 1914 (⁵) and generally is thought to be an osteochondroses of the metatarsal head. The second metatarsal head is the most commonly affected, followed by the third metatarsal.

There currently is debate in the literature as to the true etiology of the disease, which presents as forefoot pain and focal tenderness over the affected metatarsal head. Possible etiologies include osteonecrosis of the metatarsal head, acute or repetitive trauma, stress overloading, avascular necrosis following acute trauma, and even tuberculosis. Freiberg's is most prevalent in athletic adolescent females.

On exam, there is tenderness over the second (or third) metatarsal head and occasional shortening of the second ray. Diagnostic radiographs show widening of the metatarsal phalangeal (MTP) joint followed by collapse and sclerosis of the metatarsal head. The irregularity and flattening of the metatarsal head also may include spurring dorsally. Loose body formation and secondary thickening of the metatarsal shaft also can occur (¹⁵).

Treatment of Freiberg's is symptomatic. Standard treatment includes rest and avoidance of activities that load the foot, especially high-impact running. A short period of immobilization often is indicated for symptom and pain control. Although casting for 6 to 12 wk can be used to decrease symptoms, there is no evidence that this shortens the disease course. Metatarsal bar orthosis and stiff-soled shoes that help decrease the stress on the affected metatarsal head and limit mobility of the MTP joint also can be utilized. As symptoms subside, there should be a gradual return to weight-bearing activities. In general, reossification and signs of radiographic healing takes between 2 and 3 yr.

Animal research has shown a strong association between nonsteroidal antiinflammatory drug (NSAID) use and delayed bone healing (^8,13,14). Although there is less research to support definitive delay in bone healing in human models (^4,6), the author prefers to use acetaminophen over NSAID for analgesia and symptom control in pediatric and adolescent athletes with acute injuries of the bone and cartilage.

Although the vast majority of cases can be managed nonoperatively, for those cases recalcitrant to conservative management, surgery is an option. Surgical options include joint debridement, synovectomy, and removal of loose bodies. Bone grafting and rotational osteotomies also have been used to decrease pain (¹). Sproul retrospectively studied 11 operative cases of Freiberg's in which most cases had failed nonoperative treatment. Operative cases showed good short-term success and relief of symptoms with debridement; however, late results were not well documented, and there is a theoretic risk of increase in arthritic changes (¹⁵).

SEVER'S DISEASE

Calcaneal apophysitis, or Sever's disease, is a common overuse injury found in the pediatric athlete. Sever's is most common in children between the ages of 8 and 12 yr and accounts for more than 8% of the overuse injuries in children and adolescents (¹⁰). Overuse is the most often cited etiology; however, poor shoewear and contracture of the Achilles tendon also may play a role.

Commonly thought to be a traction apophysitis, newer evidence has indicated that Sever's actually may result from repetitive compression to the actively remodeling metaphysis (⁹). Ogden et al. studied 14 active children with heel pain unresponsive to previous interventions (including heelcord stretching, orthotics, NSAID, and activity modification). They found evidence of metaphyseal stress fractures via magnetic resonance imaging (MRI), which resolved with a limited period of partial or nonweight-bearing, with or without immobilization. The pre- and posttreatment MRI showed resolution of the metaphyseal edema but persistence of the normal increased signal in the apophysis (secondary ossification center) with treatment. With evident microfailure, hemorrhage, and edema on MRI, they concluded that Sever's disease actually is a chronic repetitive injury (compression) to the actively remodeling trabecular metaphyseal bone rather than a traction injury to the apophysis (⁹).

Patients with Sever's typically present with heel pain that increases with activity, specifically running and jumping. On exam, there is tenderness over the posterior heel at the insertion of the Achilles tendon on the calcaneus with frequent heel-cord tightness and weak dorsiflexion. Tenderness on the medial and lateral calcaneal body also is common and may be more indicative of metaphyseal injury.

Plain radiographs can be useful to rule out an acute fracture and may show fragmentation and sclerosis of the calcaneal apophysis. They rarely are helpful for a definitive diagnosis as the apophysis commonly is fragmented in most children even without symptoms; therefore, most children should be treated based on their clinical exam. In recalcitrant cases, an MRI may be useful potentially to document more significant bony edema (stress reaction), which may require a more prolonged period of rest or immobilization.

Treatment for Sever's is symptomatic with relative rest, an occasional short period of immobilization or restricted weight-bearing, ice, and analgesics as necessary. Stretching and strengthening of the calf musculature aid in rehabilitation. Shoe inserts such as heel cups, pads, and lifts also can be used for symptom relief. A short course of physical therapy with gastrocnemius and soleus stretching and strengthening is recommended by many authors (¹⁰).

KOHLER'S DISEASE

Kohler's disease, also known as Kohler's syndrome, is an osteochondroses of the tarsal navicular. Kohler's occurs in children between the ages of 4 and 9 yr, with a higher prevalence in boys. The characteristic fragmentation of the navicular bone in the midfoot is bilateral in up to one fourth of cases. The syndrome is thought to be congenital and is not always symptomatic. Kohler's can be an incidental finding on radiographs with no focal tenderness or pain.

Kohler's disease presents as midfoot pain with a characteristic limp. Symptoms increase with weight-bearing, and the child favors walking on the lateral aspect of the affected foot. The clinical history may involve an acute injury or be insidious and vague with no specific inciting event.

Physical exam reveals diffuse pain along the medial border of the midfoot. Localized tenderness also may be accompanied by swelling and erythema.

Plain radiographs are diagnostic, revealing sclerosis and narrowing/flattening of the tarsal navicular (Fig. 1). Radiographs can help to differentiate Kohler's from acute or stress navicular fractures. Although Kohler's can present bilaterally, contralateral radiographs usually are helpful for comparison.

Figure 1: Radiograph revealing sclerosis and narrowing/flattening of the tarsal navicular consistent with Kohler's disease.

Basic treatment includes rest, ice, and analgesics. Most symptomatic cases benefit from immobilization in a short leg walking cast (SLWC) for 4 to 6 wk. The author's preferred method of treatment includes a SLWC for 3 wk, reevaluation, and subsequent casting for an additional 3 wk if indicated.

Kohler's disease often has a prolonged course of mild pain, but over time the majority heal without long term sequelae. Subsequent radiographs reveal reorganization of the tarsal navicular, with a small percentage of cases resulting in chronic deformation of the bone after healing, most often asymptomatic.

OS NAVICULARIS

The differential diagnosis of medial foot pain includes os navicularis (accessory navicular). Usually presenting in a slightly older age group compared with Kohler's, an os navicularis is an accessory ossicle at the posterior tibialis muscle insertion. The accessory navicular generally does not ossify until 9 yr of age. The overall prevalence of this ossicle is approximately 2% to 12%. In about half of the cases, the accessory ossicle will go on to fuse to the navicular.

The os navicularis has been associated with flat feet (¹). The insertion of the major portion of the tibialis posterior tendon into the accessory bone can displace the tendon and allow the foot to deviate into a valgus position.

Patients present with pain on the medial border of foot. Prominence of the navicular can lead to shoewear problems and callous formation. The condition may present insidiously or become exacerbated by acute trauma to the foot and ankle. The mechanism of injury may mimic an acute medial ankle sprain with abnormal traction on the posterior tibialis tendon. A valgus stress injury may fracture the attachment of the ossicle to the navicular, resulting in abnormal motion and result in flatfoot with prominence of the accessory bone and navicular.

On physical exam there can be palpable movement of the accessory ossicle and definite tenderness over the medial border of the navicular. Passive, forced eversion, and resisted inversion reproduce symptoms.

Plain radiographs reveal a well-ossified ossicle off of the proximal medial border of the navicular.

The presence of an accessory navicular can not only be symptomatic locally but also can predispose the posterior tibialis tendon to injury. Fibers of the posterior tibialis tendon generally insert onto both the navicular and accessory ossicle. This abnormal insertion can predispose certain athletes to acute tendon injury. Athletes presenting with chronic medial ankle pain may show edema within the accessory navicular on MRI, indicating chronic stress (³).

Treatment of accessory navicular ossicles is symptomatic. Doughnuts over the prominent navicular to prevent repetitive pressure and irritation and orthotics to correct pes valgus can be helpful. Occasionally, a short period of immobilization, 3 to 6 wk in a SLWC, can help relieve symptoms. Although rare, severe cases require surgery for excision of the ossicle and advancement of the posterior tibialis tendon to decrease symptoms (¹).

ISELIN'S DISEASE

Iselin's disease, first described in 1912 by Iselin, is a traction apophysitis at the base of the fifth metatarsal. It is thought to be a stress reaction in the insertional apophysis with microfractures about the tendon's Sharpey fibers. As in Osgood Schlatter disease, actual ossicles can rupture free and cause a fragmented appearance to the apophysis with bony overgrowth.

Iselin's occurs during a period of rapid growth and is more common in children engaged in sports involving repetitive traction. The timing of ossification varies with the mean appearance between the ages of 12 and 13 yr, but it can be seen as early as 10 yr in boys and 8 yr in girls. Fusion is usually complete by 17 to 18 yr.

Patients with Iselin's disease typically present with lateral foot pain with weight-bearing and swelling around the base of the fifth metatarsal. The apophysis can enlarge and become symptomatic from direct shoewear pressure. Iselin's may be insidious or an acute or chronic sequelae of a simple inversion ankle injury (⁷). Pertinent physical exam findings include tenderness to palpation and soft tissue swelling around the fifth metatarsal tuberosity and pain with resisted eversion. Extreme dorsiflexion and plantar flexion with inversion also can increase the pain (¹⁰).

Plain radiographs should be obtained to rule out other causes of pain (tumor, infection, stress fracture). In skeletally immature athletes, the main differential diagnosis includes acute avulsion fracture, os vesalianum (sesamoid adjacent to insertion of peroneas brevis tendon), and acute fracture at the metaphyseal-diaphyseal junction (commonly known as a Jones fracture).

The apophysis at the base of the fifth metatarsal is a shell-shaped bone fleck lying parallel to the long axis of metatarsal at the lateral plantar aspect of the tuberosity (Fig. 2). The apophysis may be enlarged compared with the opposite side with disordered ossification and/or a slight separation of the chondro-osseuos junction.

Figure 2: The apophysis at the base of the fifth metatarsal is a shell-shaped bone fleck lying parallel to the long axis of metatarsal at the lateral plantar aspect of the tuberosity.

Plain radiographs can help to differentiate apophyseal injuries from acute avulsions as typical intraarticular avulsion fractures are transverse in nature from traction from the peroneus brevis or lateral plantar aponeurposis (¹¹) as opposed to the parallel nature of the apophysis.

Contralateral radiographs are useful for comparison in questionable diagnoses and repeat radiographs at 7 to 10 d can be helpful if there is a concern for an occult fracture, as bony sclerotic changes then may be evident.

In patients presenting with pain at the base of the fifth metatarsal but no radiographic signs of acute fracture, the author's preferred method of treatment includes immobilization in a SLWC or boot if the patient is deemed to be compliant for 2 wk. This brief period of immobilization is followed by repeat examination and x-rays. If there are no radiographic signs of acute fracture (avulsion) and the patient is symptom-free, immobilization can be discontinued; however, most patients require an average of 4 wk of immobilization for acute apophysitis symptom control.

Modified activity, cryotherapy, and a home exercise program should be used once the patient can ambulate without pain. A gradual progression of activity should be guided by the lack of pain and limping. A typical home exercise program for acute ankle sprains with an emphasis on strengthening, stretching and proprioception (stabilization and coordination skills) of the foot and ankle can be utilized. Iselin's may last several months to years, but it always resolves when ossification is complete.

CONCLUSION

Injuries to the foot are extremely common in the pediatric athlete. Familiarity with the developing pediatric skeleton is essential for the accurate diagnosis and treatment of young athletes. Proper diagnosis, symptom control, immobilization, activity modification, and appropriate rehabilitation all play key roles in safe and timely return to sport. Unfortunately there is little supporting evidence in the literature for the treatment of skeletal foot problems in children. Recommendations are based mainly on opinion and tradition, leaving great opportunities for future research and discovery in our active pediatric population.