Spondylolysis

Spondylolysis, a stress fracture of the pars interarticularis (the part of the lamina located between the superior and inferior articular processes of the vertebrae), is one of the most common conditions associated with lower back pain in adolescent athletes [35]. In the adolescent athlete population, the fracture of the pars interarticularis occurs at a time of spinal growth in the posterior elements, as well as anterior elements of the attached growth plate [36]. A recent study at Children's Hospital Boston [37] examined 100 athletic patients under the age of 18 who had back pain and found spondylolysis present in 47 of these patients. Spondylolysis caused by overuse injuries is increasingly being diagnosed in younger patients between 5 and 10 years of age [7,37-39]. These findings demonstrate the high occurrence of spondylolysis in the adolescent athletic population and the increasing importance of physician vigilance in its early detection.

In a prospective study by Beutler and colleagues [40], 500 first-grade students were examined for spondylolysis and were followed for 45 years. Over the 45-year period, the authors found spondylolysis in 6% of the subjects; 4.4% of the total population had developed spondylolysis by the age of 6; and an additional 1.6% of the subjects had developed the condition by the age of 14. Studies such as these suggest that the onset of spondylolysis in the general population may be a preadolescent condition [36].

Cause

The cause of spondylolysis is controversial. The precipitating factor in the condition is considered to be mechanical, arising from fatigue failure [30,31]. This notion has been demonstrated in biomechanical studies. In a study by Cyron and colleagues [30,31], the inferior articular facets of lumbar vertebrae were subjected to various loading patterns. Results indicate that the lumbar neural arch at the pars interarticularis is vulnerable to mechanical fatigue. This is

Fig. 1. Lysis of one or both of the pars interarticularis in the posterior elements of the lumbar spine may result from repetitive extension or rotation of the lower spine. G, LS vertebral body; R, LS spinous process.

further supported in a study by Merbs [41] in which Alaskan Eskimos crouch in positions for long periods of time, subjecting them to unusual stresses becoming concentrated in the lower back. Other proposed origins of spondylolysis include trauma, genetics, and developmental defects (Fig. 1) [5].

Epidemiology

In the general population the prevalence of spondylolysis is 4% to 6% [7,36]. Bilateral spondylolysis is more common than unilateral spondylolysis, and L5 is the most commonly affected level of the vertebrae [40,42-44].

In the athletic population, females may be at an increased risk for spondylolysis. This is in contrast to the general population in which males are twice as likely to develop the condition. This gender difference may be attributed to a wide range of factors that include hormonal abnormalities and nutritional factors [5,45,46].

The recent increase in female sports participation also may play a role [45,46]. The number of female athletes participating at the high school, collegiate, and elite levels has increased nearly 10-fold since the passage of Title IX [46]. Title IX requires that all schools that receive federal funding must provide equal opportunities for men and women. As with all other stress fractures, a thorough medical history of a female athlete is important to rule out amenorrhea and low mineral bone density, which are prevalent in female athletes and may put them for increased risk of stress fractures [4,9].

The general athletic population is not necessarily at a higher risk than the general population for developing spondylolysis; however, athletes in certain sports with repetitive hyperextension, extension, and rotational movements of the back show an increase in the incidence of a spondylolytic cause [4-8]. Examples of such sports are ballet, gymnastics, diving, and soccer [4-8,37,39]. In a study by Ciullo and Jackson [47], there was an 11% incidence of spondylolysis in female gymnasts, approximately four times the anticipated rate in North America.

Clinical Presentation

Spondylolysis in the athletic population is commonly symptomatic [6,7,37,48]. The adolescent athlete presents with lower back pain, which becomes worse with activity. A thorough history of the onset of back pain is important, including gradual or acute onset, associated factors such as growth spurt or increased training, and the presence of systemic symptoms or night pain [4,7].

On physical examination, there may be tenderness to palpation at the affected vertebral level. Range of motion may be limited or painful in flexion and extension but is usually more compromised in extension. Hamstrings are typically tight on popliteal angle testing as well as straight leg raises. Eighty percent of patients are noted to have tight hamstrings on physical examination [49]. Single leg lumbar extension will often reproduce the pain on the ipsilateral side [47]. To establish the diagnosis of spondylolysis, certain diagnostic imaging modalities can be helpful.

Diagnostic Imaging

The initial diagnostic workup consists of plain radiographs, which include anterior and posterior views of the lumbar spine [4,5,36]. A sign suggestive of spondylolysis on the anteroposterior (AP) view is lateral deviation of the spinous process caused by associated rotation of the spinous process toward the shorter of the laminae [35]. Plain radiographs have a low sensitivity for diagnosing spondylolysis, and early radiographic changes may not be detected [50]. They are, however, more helpful in detecting spondylolisthesis, the slipping of all or part of the vertebrae forward over one another. In addition, the presence of spina bifida occulta on plain films increases the likelihood of spondylolysis (Fig. 2) [47]. SPECT bone scans are more sensitive at detecting spondylolysis than initial radiographs or planar bone scans [47,51]. Single photon emission-computed tomography (SPECT) bone scans are used to identify areas of bone turnover at the pars interarticularis in patients with spondylolysis and are

Spina Bifida Occulta Pain
Fig. 2. Spina bifida occulta, as observed on standard AP radiographs of the lumbosacral spine, increases the likelihood of spondylolysis as a cause of lower back pain in adolescents.

advantageous because they can remain positive for 6 to 9 months, even when the patient is asymptomatic [35].

CT scans have become the accepted method of characterizing fractures [13,52]. They are currently the gold standard for detailing bony morphology and depicting osseous pathoanatomy (Fig. 3) [13].

Recently, many physicians and researchers have put more emphasis on the use of the advanced multiplanar cross-sectional imaging modality of MRI [53-55] in the diagnosis and evaluation of spondylolysis [6]. As Lim and colleagues [13] have espoused, MRI could potentially offer a more streamlined way to evaluate spondylolysis because it can demonstrate both bony anatomy and bony edema and inflammation in one single test, as opposed to combining the complementary modalities of CT and SPECT imaging, which currently serve as adjuncts to each other. A recent investigation by Campbell and colleagues [56] has shown good correlation between MRI with CT and with SPECT imaging. In the future, MRI may prove useful in the follow-up examination of these fractures.

Treatment

Treatment for spondylolysis varies and reflects a lack of consensus among practitioners. At Children's Hospital Boston, an athlete with spondylolysis is taken out from sports and treated initially with a 0°-extension Boston overlapping brace, which is worn for 23 hours per day. The primary goal of bracing is to decrease the lumbar lordosis, rendering the sagittal alignment of the pars more vertical, thus reducing shear forces, while also promoting healing of the lesion [7,36]. In addition, a physical therapy regimen that initiates both peripelvic flexibility and antilordotic strengthening is prescribed. Activity is restricted to physical therapy, the stationary bike, and swimming (excluding the butterfly stroke and breaststroke). All hyperextension maneuvers of the spine are avoided.

After a period of 4 to 6 weeks, the athlete is reexamined. If the athlete is pain-free, particularly on extension, he or she is returned to sports, while continuing bracing, provided that he or she remains asymptomatic and continues with physical therapy. The initial goal of physical therapy is spinal stabilization. If the athlete continues to experience pain, wearing the brace and physical therapy (antilordotic and peripelvic flexibility exercises) are continued until he or she is pain-free.

At the 4-month mark of treatment, a CT scan is performed to assess healing. The patient is clinically assessed. The optimal goal of the treatment is a pain-free bony union. Patients who exhibit bony union or a persistent pain-free nonunion at the site of the lysis (fibrous union) are allowed to fully return to activities at this point and are weaned from the brace. Therefore, the clinical status of the patient predominates radiographic healing [7]. According to one study, 78% of patients with symptomatic spondylolysis who were treated with a Boston overlapping brace demonstrated good or excellent results with full return to sports [5].

Electrical stimulation is considered in patients who exhibit a painful nonunion at the 4-month mark. This technology has been used successfully in an attempt to heal established nonunions in long bone fractures [57]. It is believed that electrical stimulation mimics the negative potential created by the body's electrical impulses at the fracture site. Research is currently underway at the present authors' institution and several others to determine the effectiveness of electrical stimulation in healing patients with spondylolysis (Fig. 4) [36].

Surgical stabilization may be considered in patients who have failed conservative treatment and have persistent pain with sports and activities of daily living. The typical form of treatment is a posterolateral transverse process fusion [7]. After surgery, the patient is immobilized in a cast or brace for 3 to 6 months [7]. Sports activities are not permitted until 12 months after fusion occurs. A return to contact sports must be individualized after lumbar fusion [58,59].

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Back Pain Revealed

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