Musculoskeletal · Spine Pathology
The facts most likely to be tested
Isthmic spondylolisthesis is caused by a pars interarticularis stress fracture and is most common in adolescent athletes involved in repetitive hyperextension.
Degenerative spondylolisthesis occurs due to facet joint arthropathy and is most common in older adults at the L4-L5 level.
The Scotty dog sign with a collar on the neck is the classic radiographic finding of spondylolysis on an oblique lumbar spine radiograph.
Patients typically present with chronic low back pain that is exacerbated by lumbar extension and relieved by rest.
Physical examination often reveals a palpable step-off deformity at the level of the affected vertebrae due to anterior slippage.
Lateral lumbar radiographs are the gold standard for diagnosing and grading the severity of the vertebral displacement.
Initial management for symptomatic patients involves activity modification, physical therapy for core strengthening, and NSAIDs.
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A 15-year-old male gymnast presents with a 3-month history of chronic low back pain that worsens during training, particularly when performing back handsprings. On physical examination, he has tight hamstrings and a palpable step-off at the lumbosacral junction. Neurological examination is intact with no focal deficits. A lateral lumbar radiograph demonstrates anterior slippage of L5 on S1.
What is the most likely diagnosis?
Isthmic spondylolisthesis
The patient's age, history of repetitive hyperextension, and the classic finding of a palpable step-off on physical exam are diagnostic of isthmic spondylolisthesis, which is confirmed by the anterior slippage seen on lateral radiographs.
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Etiology / Epidemiology
Common in adolescent athletes (hyperextension) and elderly patients (degenerative).
Clinical Manifestations
Lower back pain with step-off deformity; radiculopathy if nerve root compression occurs.
Diagnosis
Lateral radiograph is the gold standard to measure Meyerding grade slippage.
Treatment
Physical therapy and core strengthening; avoid hyperextension in acute phases.
Prognosis
Most are stable; Grade III-V often require surgical stabilization.
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Epidemiology & Etiology
Isthmic type results from spondylolysis (pars interarticularis stress fracture) common in gymnasts and football linemen. Degenerative type occurs due to facet joint arthropathy and disc degeneration in patients >50. Congenital forms are rare but present with sacral dysgenesis.
Pertinent Anatomy
The pars interarticularis is the thin bone segment connecting the superior and inferior facets. Slippage typically occurs at L5-S1 (isthmic) or L4-L5 (degenerative).
Pathophysiology
Repetitive hyperextension causes a stress fracture of the pars interarticularis, leading to anterior vertebral body translation. This instability causes mechanical back pain and potential foraminal stenosis. Chronic slippage leads to compensatory hyperlordosis.
Clinical Manifestations
Patients present with localized low back pain exacerbated by extension. Physical exam reveals a palpable step-off deformity at the spinous process. Cauda equina syndrome (bowel/bladder incontinence, saddle anesthesia) is a rare but critical red flag requiring emergent imaging.
Diagnosis
The lateral radiograph is the gold standard for diagnosis and grading. The Meyerding classification grades slippage from I (<25%) to V (spondyloptosis, >100%). MRI is indicated if there is evidence of neurologic deficit.
Treatment
Initial management is conservative with NSAIDs and physical therapy focusing on core stabilization. Avoid hyperextension activities during the acute phase. Surgical intervention (decompression and fusion) is reserved for Grade III+ or patients failing 6 months of conservative therapy.
Prognosis
Most low-grade slips remain stable with conservative care. Grade III-V slippage carries a high risk of progressive neurologic deficit and requires long-term orthopedic monitoring.
Differential Diagnosis
Spondylolysis: Pars defect without vertebral slippage
Herniated Nucleus Pulposus: Radiculopathy without step-off deformity
Lumbar Spinal Stenosis: Pain relieved by flexion, not extension
Ankylosing Spondylitis: Morning stiffness and sacroiliitis
Vertebral Compression Fracture: History of osteoporosis or trauma