Spondylolysis is a common cause of back pain in the adolescent athlete (Fig. 22.3). Many studies have investigated the incidence of spondylolysis in the adolescent athlete. Notably, Micheli and Wood reported 47 % incidence of spondylolysis in adolescent athlete presenting with back pain [22]. However, Rossi reported a much lower incidence of 15 % in a review of radiographs of adolescent athletes [33]. Additionally, Drummond et al investigated nearly 3,000 adolescent patients presenting with low back pain, diagnosing only 7.8 % of them with spondylolysis [25].

Spondylolysis is a defect in the vertebral pars interarticularis. It most commonly occurs at L5–S1 resulting from an L5 pars defect, though it may also occur at more cephalad levels. Subsequent translation of the cephalad vertebral body on the caudad vertebral body describes spondylolisthesis (Fig. 22.4) [34]. For more detail, please refer to Chap. 24 on Spondylolysis/Spondylolisthesis.

A component of the neural arch, the pedicle is also vulnerable to fracture from the cyclic loads stressing the lumbosacral spine during sports. However, pedicle stress fractures are much less common than pars stress fractures [22]. This is partly secondary to the greater intrinsic strength of the pedicles and shorter moment arm from the vertebral body. The pedicles are therefore capable of resisting greater shear forces than the pars. In a biomechanical study evaluating the mechanical strength of 74 vertebral units subject to repetitive mechanical loads, Cyron and Hutton demonstrated five pedicular stress fractures compared to 55 pars fractures [36]. Contralateral pedicular fractures have been associated with isthmic pars fractures. This phenomenon has been attributed to increased and aberrant loading of the pedicles that result from an unstable neural arch following a pars fracture [37–39]. Ulmer et al. showed a 40 % incidence of reactive changes on MRI in pedicles with contralateral spondylolysis [40].

Radiographic evaluation of pedicular fractures involves plain radiographs and CT scan. CT scan has a higher accuracy in the evaluation of these patients. When visible, hypertrophy or sclerosis is seen on the involved pedicle. Pediculolysis is clearly demonstrated as a linear lucency at the base of the involved pedicle on CT. In addition, presence of a concomitant pars defect can also be identified [39, 41]. When evaluating patients with pediculolysis, one must consider osteoid osteoma and osteoblastoma in the differential diagnosis. These entities can be differentiated from a pediculolysis by the absence of a nidus, the presence of contralateral pars defect, or the presence of a linear defect in a pedicular stress fracture. Differentiating these lesions is important because pedicle excision—a management option for symptomatic tumor—may further destabilize an already unstable neural arch [39, 42].

Early diagnosis of a pedicular stress fracture and prompt treatment is necessary to facilitate rapid return to sports. Management of pedicular stress fractures is similar to that of a pars stress fracture. Initial management is conservative and involves rest and bracing. Surgery is indicated in the setting of failed conservative treatment, though surgical treatment is rarely necessary. Techniques described in the literature include compression fixation of the defect, excision of the hypertrophic defect with lateral fusion, and bone grafting of the pars and pedicular defects with subsequent pedicle screw fixation [37, 39, 43].

Disc herniation is a rare cause of back pain in the adolescent athlete (Fig. 22.5). Only 1 % of disc herniations occur in the second decade [44]. As opposed to an incidence 48 % in the adult population, only 11 % of adolescent athletes present with symptomatic disc herniation. The most common location of herniation in the young athlete is the L4–L5 and L5–S1 level. In the skeletally immature patient, the disk may be herniated into the vertebral end plate with axial loading, demonstrating a Schmorl’s node on radiographs [29, 45].

Young athletes with disc herniations typically present with localized back pain and paraspinal muscle spasm. Impingement of the nerve roots may result in radicular symptoms. Radicular symptoms warrant an MRI evaluation. In the absence of neurological compromise, conservative management is recommended, consisting of rest and activity modification. Prolonged bed rest is discouraged. NSAIDs, muscle relaxants, and oral corticosteroids may also be beneficial. The majority of adolescents can be treated nonoperatively. However, those with progressive neurological deficits or debilitating pain that has failed conservative management are candidates for a microdiscectomy. Patients are usually able to return to full participation in sports [45, 46]. While more applicable to adult patients as it examined an adult patient population, the SPORT trial examined the effects of operative versus nonoperative management for patients with a mean age of 42 who presented with symptomatic lumbar herniated discs. This multicenter randomized controlled trial concluded that at 2 years, patients treated surgically and nonoperatively both demonstrated substantial improvement and could not make conclusions about the superiority of one treatment over the other [47].

An apophyseal ring fracture is a rare injury in the pediatric population, occurring primarily in the male adolescent athlete (Fig. 22.6) [48]. It most frequently affects L4 and L5. The incidence of apophyseal fractures may be underreported as it is frequently misdiagnosed as lumbar disc herniation [49].

In the developing lumbar spine, the superior and inferior endplates are bordered by the vertebral ring apophysis. Ossification of the apophysis commences at approximately 5 years with fusion by age 18. During the rapid adolescent growth phase, the apophysis is separated from the underlying vertebral body by a physeal zone. This area of weakness is susceptible to avulsion injuries. It has been suggested that hyperextension of the lumbar spine or rapid flexion with axial load may be the causative mechanism [48].

Clinical presentation includes low back pain with potential radicular symptoms. Neurogenic claudication, paresis, and cauda equina syndrome has also been reported. The most common finding on examination is restricted lumbar range of motion. The straight leg raise test may be positive in these patients though frank neurological deficits are usually rare [49, 50].

Radiographic evaluation involves the use of both the plain radiograph and CT scan. Bony defects can be visualized on the lateral radiograph; however, the axial CT scan images have been proven to be more sensitive [51].

Takata et al. reported on a large series of apophyseal injures, classifying these injuries into three categories based on CT findings. Type 1 fracture is a separation of the posterior rim of the vertebra body with negligible defect in the vertebra body. This type was noted primarily in patients between the ages of 11 and 13. Type 2 describes an avulsion fracture of the posterior rim of vertebra body including the posterior segment of the overlying annulus fibrosis. It is more prevalent in older patients. Type 3 fracture is a small localized fracture posterior to an irregularity in the cartilaginous endplate [49].