Musculoskeletal · Spine Pathology
The facts most likely to be tested
Spondylolysis is a stress fracture of the pars interarticularis, most commonly occurring at the L5-S1 level.
The classic clinical presentation is activity-related low back pain that is exacerbated by lumbar hyperextension.
The pathognomonic radiographic finding on an oblique lumbar spine view is the scotty dog sign, where the collar represents the fracture.
Spondylolysis is most frequently seen in adolescent athletes participating in sports requiring repetitive hyperextension and rotation, such as gymnastics or football.
Physical examination often reveals tight hamstrings and a positive one-legged hyperextension test (Stork test).
Initial diagnostic imaging of choice is plain film radiography, but MRI is the gold standard for detecting early-stage stress reactions or bone marrow edema.
First-line management for symptomatic patients is conservative therapy, consisting of activity modification, physical therapy, and a lumbar brace.
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A 15-year-old male competitive gymnast presents to the clinic with a 3-month history of dull, aching low back pain that worsens during training. He denies any radicular symptoms, bowel or bladder incontinence, or trauma. On physical examination, he has limited lumbar flexion and tight hamstrings bilaterally. He experiences reproducible pain when standing on one leg and performing lumbar hyperextension. Radiographs of the lumbar spine show a lucency across the pars interarticularis of the L5 vertebra.
What is the most likely diagnosis?
Spondylolysis
The patient's presentation of activity-related back pain in a young athlete, combined with the classic finding of a pars interarticularis defect (scotty dog sign), is diagnostic for spondylolysis.
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Etiology / Epidemiology
Common in adolescent athletes involved in repetitive hyperextension (gymnasts, linemen).
Clinical Manifestations
Low back pain exacerbated by lumbar extension; Scotty dog sign on imaging.
Diagnosis
Oblique lumbar radiographs are initial; CT scan is the gold standard for defect visualization.
Treatment
Activity restriction and physical therapy (core stabilization) are first-line; avoid contact sports until asymptomatic.
Prognosis
Most heal with conservative management; progression to spondylolisthesis is the primary long-term risk.
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Epidemiology & Etiology
Occurs primarily in adolescents due to repetitive stress on the immature skeleton. High-risk activities include gymnastics, football, and weightlifting involving chronic lumbar hyperextension. It is the most common cause of low back pain in this demographic.
Pertinent Anatomy
The defect occurs at the pars interarticularis, the bridge of bone between the superior and inferior articular facets. This region is the weakest point of the vertebral arch and is susceptible to stress fractures.
Pathophysiology
Repetitive microtrauma leads to a stress fracture of the pars interarticularis. If the defect remains unhealed, it can lead to instability of the vertebral body. This instability may result in anterior slippage of one vertebra over another, known as spondylolisthesis.
Clinical Manifestations
Patients present with localized low back pain that worsens with lumbar extension and improves with rest. Physical exam may reveal tight hamstrings and a limited range of motion. Red flags include bowel/bladder incontinence or saddle anesthesia, which suggest cauda equina syndrome.
Diagnosis
Initial evaluation includes oblique lumbar radiographs to identify the Scotty dog sign, where the 'collar' represents the pars defect. A CT scan is the gold standard for definitive diagnosis and assessment of fracture healing. MRI is indicated if there is suspicion of nerve root impingement or disc pathology.
Treatment
Initial management is conservative, consisting of activity restriction and physical therapy focusing on core and abdominal strengthening. A thoracolumbosacral orthosis (TLSO) brace may be used for pain control. Avoid contact sports until the patient is pain-free and demonstrates full range of motion.
Prognosis
Most patients achieve bony union or fibrous stability with conservative management. The primary complication is progression to spondylolisthesis, which requires serial lateral radiographs to monitor for slippage. Surgical intervention is reserved for refractory cases.
Differential Diagnosis
Spondylolisthesis: anterior slippage of the vertebral body
Herniated nucleus pulposus: radicular pain and positive straight leg raise
Scheuermann's kyphosis: rigid thoracic kyphosis in adolescents
Lumbar strain: pain typically improves with rest and lacks bony defect
Infection/Tumor: systemic symptoms like fever or night pain