Spondylolysis and Spondylolisthesis in Immature and Adult Athletes

Rahul Basho, MD

Andre M. Jakoi, MD

Jeffrey C. Wang, MD

Dr. Wang or an immediate family member has received royalties from Aesculap/B. Braun, Amedica, Biomet, Seaspine, and Synthes; has stock or stock options held in Alphatec Spine, Amedica, Benevenue, Bone Biologics, Corespine, Electrocore, Expanding Ortho, Fziomed, Nexgen, Paradigm Spine, Pearl Diver, Promethean Spine, Surgitech, and Vertiflex; and serves as a board member, owner, officer, or committee member of AO Spine International, the Cervical Spine Research Society, the Evidence-Based Spine-Care Journal, the Global Spine Journal, Spine, the Spine Journal, the Journal of Spinal Disorders and Techniques, the North American Spine Foundation, the North American Spine Society, and the Journal of the American Academy of Orthopaedic Surgeons. Neither Dr. Basho nor any immediate family member has received anything of value from or has stock or stock options held in a commercial company or institution related directly or indirectly to the subject of this article.

Introduction

Athletes place increased demands and repetitive stresses on their musculoskeletal systems. Studies have shown that almost 30% of athletes experience low back pain referable to athletic participation.¹^,² In professional sports, lower back pain is the most common cause of lost playing time.³ Lower back injuries differ in adult and adolescent athletes; whereas nearly 70% of lumbar injuries in adolescents occur in the posterior elements of the spine, adult athletes are more likely to have muscle strains and discogenic disease.⁴

The anatomic region of the spine particularly susceptible to injury is the pars interarticularis (Figure 17-1). Also referred to as the isthmus (Greek for narrow), it is the thin region of bone that connects the superior and inferior articular processes of a vertebral body. A defect in the pars, termed spondylolysis, can result in pain and sometimes lead to instability within the spine. This instability, termed spondylolisthesis, refers to slippage of one vertebral body (spondylos in Greek) relative to another (Figure 17-2). When spondylolisthesis occurs because of a defect in the pars, it is termed isthmic spondylolisthesis.

Spondylosis has been extensively studied and is one of the few spinal conditions with follow-up data long enough to give insight into its natural history. In the early 1950s, Dr. Baker initiated a prospective study to determine the natural history of spondylolysis and spondylolisthesis. A study population of 500 children was enrolled and followed, with the last reported follow-up being at 45 years. The data showed an incidence of pars defects of 4.4% at age 6 years, which rose to 6% in adulthood.⁵ The majority of lesions occurred at the L5 level. The study also attempted to delineate the likelihood of pars defects progressing to symptomatic spondylolisthesis. Of the 30 children with pars defects, 8 had unilateral pars defects and never developed spondylolisthesis. In the 22 children with bilateral defects, all but 4 developed some degree of spondylolisthesis over their lifetimes. However, only 1 patient was found to have symptomatic slip progression in adulthood; the authors concluded that the likelihood of this occurring was 5%. Progression of the spondylolisthesis decreased with each decade of life, with the greatest progression occurring early in life. No patient developed a slip beyond 40 years. The authors stated that there was “no justification for generally advising children and adolescents with spondylolysis and low grade spondylolisthesis not to participate in competitive sports.”⁵

Although the prevalence of pars fractures in the general population is between 4% and 6%, a higher incidence is seen among athletes involved in sports requiring repetitive hyperextension, such as weight lifting, wrestling, gymnastics, and football.⁶^,⁷^,⁸ Some studies have found that up to 15% of college football players and 11% of female gymnasts have spondylolysis.⁹^,¹⁰ Different theories have been postulated in regards to the etiology of pars fractures. Among athletes, the most widely accepted is one of repetitive stress resulting in fracture. Extension of the lumbar spine results in the inferior articular process of the cranial vertebrae impacting the pars of the caudal vertebrae.¹¹ Shear stresses of 400 to 600 N caused by this motion are concentrated across the pars, an area calculated to be only 0.75 cm² at L5.¹² This repetitive stress results in a pars “stress reaction,” which if untreated can progress to a fracture.¹³ The stress reaction, microfracture, overt fracture, and spondylolisthesis are viewed as progressive stages of an overuse injury at the pars interarticularis.¹⁴

FIGURE 17-1 Depiction of the pars interarticularis. (Reprinted from Oatis CA: Kinesiology, ed 2. Philadelphia, PA, Lippincott Williams & Wilkins, 2008.)

History

Pars defects account for a much larger percentage of lumbar spine injuries in skeletally immature athletes compared with adults.¹⁵ Hunter et al showed that 47% of patients younger than the age of 18 presenting to a sports medicine clinic with back pain had spondylolysis compared with 5% of adults older than the age of 21 years presenting with similar symptoms.¹⁶ Skeletally immature athlete typically describes a history of activity related pain and 40% will recall a specific inciting even.¹⁷ Adult athletes usually complain of lower limb pain greater than back pain.¹⁸

FIGURE 17-2 Progressive displacement of a pars interarticularis fracture. (Reprinted from Egol K, Koval KJ, Zuckerman JD: Handbook of Fractures, ed 4. Philadelphia, PA, Lippincott Williams & Wilkins, 2010.)

Physical Examination

A gait examination and detailed neurologic examination should be performed. The typical presentation is one of back pain exacerbated by extension. Hyperlordosis and hamstring tightness can be present. Radicular symptoms are usually not present but can occur secondary to nerve root irritation from fibrocartilaginous tissue overgrowth at the defect narrowing the foramen. Younger patients with higher grade subluxations can present with a palpable step-off. The only “pathognomonic” finding in the literature is the stork test, in which the patient extends his or her lumbar spine while in a single-limb stance; re-creation of pain in the lumbar region is indicative of a pars lesion (Figure 17-3). This test, however, has been shown to have a low sensitivity and specificity.¹⁹^,²⁰

Imaging Studies

Plain Radiography

Imaging studies are used to diagnose spondylolysis, differentiate acute and chronic lesions, guide treatment, and assess healing. Initial imaging studies have traditionally consisted of six views (anteroposterior, lateral, flexion, extension, and oblique views of the lumbar spine). On oblique views, the pars appears as the neck of the “Scotty dog,” and visualized fractures show a radiolucency through this region. Whereas acute fractures typically present as narrow and irregular, chronic fractures are smooth and rounded.¹^,²²

FIGURE 17-3 Depiction of the stork test. (Reprinted from Anderson MK: Foundations of Athletic Training. Philadelphia, PA: Wolters Kluwer, 2017.)

Amato et al demonstrated that the single best view for detecting spondylosis was the collimated lateral view; 84% of cases were diagnosed with this view alone.²³ However, 19% of the cases were only visible on the oblique view. In a review of 1743 soldiers, Libson et al demonstrated that 20% of all cases of spondylolysis were visible only on oblique views.²⁴ Based on these studies, 45° oblique views have been long regarded as necessary when screening for a pars defect. However, they can be insensitive because the pars is obliquely oriented to all three orthogonal planes.²¹ Fractures are only well visualized when the radiographic beam is tangential to the plane of the fracture. This fact, coupled with increasing concerns about radiation exposure, have called into question the utility of the oblique view as a screening modality for spondylosis. Beck et al demonstrated no significant difference between the sensitivity and specificity of two-view versus four view radiographs in detecting a pars defect in the pediatric population.²⁵ They emphasized that the addition of oblique views increased the radiation dose to the patient by 75%, from 0.72 mSV for a two-view study to 1.26 mSV for a four-view study. Although the authors thought that oblique views did add some diagnostic value in patients with unilateral pars defects, they concluded that “the increased radiation and costs associated with the use of oblique views are not outweighed by their diagnostic value.” It is important that the clinician consolidate findings from both the history and physical examination before ordering oblique films on adolescent patients. If two view studies do not show evidence of a pars defect and it is clinically suspected, advanced imaging is warranted.

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