15.2 Lumbar Spine Pathology: Disc Herniation, Stenosis, and Spondylolisthesis

Lumbar Spine Pathology: Disc Herniation, Stenosis, and Spondylolisthesis

A lumbar scan may describe disc material outside the disc space, narrowing around neural structures or translation between vertebrae. Each finding answers a different anatomical question. Match its location to the examination and symptom behavior before selecting rehabilitation or referral.

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Lumbar Disc Morphology

The lumbar disc has a hydrated central nucleus pulposus surrounded by layers of annulus fibrosus. In the joint spine and radiology societies' nomenclature, a disc bulge is a broader extension of the disc contour. A herniation is localized displaced disc material beyond the disc space. The convention uses less than a quarter of the circumference on an axial image for localized displacement.

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• Protrusion: Compare the widest displaced portion with its base at the edge of the disc space in the same plane. The base is wider in each plane. This shape can occur with or without containment.
• Extrusion: The displaced material is wider than its base in at least one plane, or continuity with the parent disc has been lost. For example, a displaced portion that is 7 mm wide at a 4 mm base in one sagittal plane meets the shape criterion, even if the axial slice appears broad-based.
• Sequestration: A subtype of extrusion in which the fragment is fully detached. Migration describes movement away from the site of extrusion and can occur with a connected or detached fragment.

Containment describes whether intact outer annulus or posterior longitudinal ligament fibers enclose the displaced material. The covering may be difficult to establish on routine imaging. These terms describe morphology and location. Symptom severity and the need for treatment depend on the clinical assessment. In serial MRI studies, migrated herniations sometimes became smaller or disappeared during nonsurgical care. Follow pain, function and neurological status as distinct outcomes.

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Mechanical Diagnosis and Therapy (MDT / McKenzie Classification)

MDT evaluates symptoms and function during repeated movements and sustained positions. The three named mechanical syndromes describe clinical responses. MDT also recognizes presentations outside these syndromes, including conditions needing medical assessment.

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• Derangement: A directional preference, often with movement loss. Symptom improvement during and after loading is often accompanied by better movement or function. Centralization is common in spinal presentations, but the response does not show a disc fragment moving or a specific annular condition.
• Dysfunction: Familiar symptoms occur consistently only at a limited end range in the spinal presentation. Consider graded loading when appropriate to the findings and tissue tolerance.
• Postural: Symptoms occur only during prolonged static loading. Assess whether changing position or changing the duration of the task helps.

Centralization is progressive retreat and abolition of distal symptoms that remains after the tested movement or sustained position. Peripheralization is a maintained distal spread. An improvement with extension, flexion or a lateral movement can guide a loading trial. Recheck its effect over visits. For example, if repeated extension abolishes thigh pain and the improvement is maintained, extension is a candidate direction. If extension produces sustained distal symptoms or worsening neurological findings, reassess before continuing. Directional preference does not require centralization.

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Lumbar Spinal Stenosis by Location

Lumbar spinal stenosis describes narrowing in the central canal, lateral recess or neural foramen. Disc and facet degeneration, osteophytes and ligamentum flavum thickening or buckling can contribute. More than one region can be involved at the same level.

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Interpret imaging with the history and examination. A canal diameter alone cannot establish symptomatic stenosis or cauda equina syndrome. The Saudi guideline for adult low back pain and sciatica advises selecting imaging when red flags are present or the result could change management. Severe radiating low back pain with new bladder, bowel or sexual dysfunction, or new perineal numbness, warrants immediate assessment through the local cauda equina pathway.

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Neurogenic vs. Vascular Claudication: Differential Diagnosis

In the historical bicycle test of van Gelderen, symptom behavior differs between upright and flexed cycling in a patient with neurogenic claudication. When an exercise comparison is safe, later onset in flexion can support posture-dependent symptoms. Cycling position and symptom timing do not establish the cause. The 2024 ACC/AHA peripheral artery disease guideline recommends exercise treadmill ABI for suspected chronic symptomatic PAD despite normal or borderline resting ABI. Use the appropriate vascular assessment pathway when the history supports it.

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Spondylolysis and Spondylolisthesis

Spondylolysis is a defect in the pars interarticularis, the bone between a vertebra's superior and inferior articular processes. Consider an active pars bone stress injury in a young athlete with persistent activity-related back pain, particularly in a sport involving repeated extension or rotation. Extension-related pain can raise suspicion, but a single-leg extension test cannot confirm or exclude active spondylolysis.

A pars defect can appear as a collar on the neck of the traditional Scotty dog image on an oblique radiograph. Adding oblique views did not improve accuracy in a study of adolescents compared with standard two-view films. Plain radiographs can miss early stress injury. If suspicion remains, medical assessment and appropriately selected imaging, such as MRI for active bone stress, can clarify the diagnosis.

Spondylolisthesis means that one vertebra has translated relative to the segment beneath it. In isthmic spondylolisthesis, the slip is associated with a pars lesion. A pars defect can exist without a slip. In degenerative spondylolisthesis, disc and facet changes can permit anterior translation with an intact pars.

Measuring an anterior slip

On a standing lateral radiograph, divide the anterior translation by the anteroposterior length of the upper endplate of the vertebra below and multiply by 100. For L5 on S1, the denominator is the length of the upper sacral endplate. A translation of 14 mm over a 40 mm endplate is 35%, which is Meyerding grade II.

Rehabilitation decisions

The slip grade describes translation. Use symptoms, neurological status, progression and the medical assessment to guide activity and referral. For a young athlete with a confirmed active pars injury and medical clearance, reduce sport loads that reproduce pain and begin exercise within tolerance. Early options include trunk control, hip and lower-limb strengthening and conditioning that the athlete can perform without provoking symptoms. Progress toward the required extension, rotation and impact as symptoms and sport-task performance allow. In a randomized trial in adolescent athletes with MRI-confirmed active spondylolysis, starting supervised physiotherapy promptly improved early pain and function and shortened time to return to sport compared with resting before starting therapy.

Adult degenerative slips have a different rehabilitation context. A trial in adults older than 50 found similar changes in pain and disability with flexion and stabilization exercises. Choose a starting position the person tolerates and assess how exercise changes the activities that matter, such as standing or walking. Refer a symptomatic high-grade slip for specialist assessment. Escalate a progressive motor deficit urgently and suspected cauda equina syndrome immediately.

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Clinical Case Scenario

A 68-year-old retired postal worker presents with a 9-month history of bilateral aching pain and heaviness in his buttocks and calves that begins after walking approximately 150 meters. The pain forces him to sit down, resolving within 10 minutes. He notes that he can walk through a grocery store for over an hour without discomfort if he leans forward onto the shopping cart. Lumbar range of motion reveals pain-free flexion with severe buttock aching provoked by lumbar extension. Lower extremity pedal pulses (dorsalis pedis and posterior tibial) are 2+ bilaterally. Ankle-brachial index (ABI) is 1.05 bilaterally. On the Bicycle Test of van Gelderen, he can pedal for only 4 minutes in an upright posture before leg heaviness forces him to stop, but he pedals for 20 minutes without symptoms when leaning forward in trunk flexion.

• Diagnostic Assessment: The symptom pattern supports neurogenic claudication. Check vascular risk, examination and course before settling on the explanation. The resting ABI of 1.05 and palpable pulses do not exclude PAD if exertional suspicion persists.
• Physical Therapy Plan: After safety screening, agree on a walking goal and start with education, pacing, and graded exercise. Try stationary cycling or short walking intervals with planned rests if tolerated. Track walking distance and recovery time under comparable conditions. Reassess the differential if the response changes or the examination shows new neurological or vascular findings.