OMM Review — Lumbar Spine

Lumbar Anatomy and Key Landmarks

The lumbar spine consists of five large vertebrae (L1-L5) designed for weight-bearing and mobility. Their vertebral bodies are larger than those in the cervical or thoracic regions, and they possess stout transverse and spinous processes. Key anatomical landmarks help guide palpatory diagnosis and treatment in this region.

• Superior aspect of the iliac crests: Corresponds to the level of the L4 vertebral body or the L4-L5 intervertebral disc space. This is a crucial landmark for palpating lumbar segments.
• PSIS (Posterior Superior Iliac Spine): Located at the level of the S2 segment of the sacrum.
• Tuffier's Line (Intercristal Line): An imaginary line connecting the tops of the iliac crests, which typically crosses the L4 spinous process or L4/L5 interspace. This is a common injection landmark.

Lumbar Mechanics and Somatic Dysfunction

The lumbar spine primarily adheres to Fryette's Type II mechanics (non-neutral), particularly for individual segments (L1-L5) when initiating motion from a flexed or extended position. This means that if a segment is already in flexion or extension, sidebending and rotation will occur to the same side. However, when the lumbar spine is in a neutral position (Type I), sidebending and rotation occur to opposite sides.

When diagnosing lumbar somatic dysfunction, consider the patient's posture and the regional curve. A common example of a Type II dysfunction is an L3 vertebra that is flexed, rotated right, and sidebent right (L3 F RSbR). This indicates that the segment is stuck in a position of flexion, and its rotation and sidebending are coupled to the same side of the rotation.

Lumbosacral Angle (Angle of Ferguson)

The lumbosacral angle, also known as the angle of Ferguson, is formed by the intersection of a horizontal line and a line drawn along the superior endplate of S1. A normal angle is approximately 25-35 degrees. An increased lumbosacral angle often correlates with increased lumbar lordosis and can lead to increased shear forces at the L5-S1 junction, potentially contributing to low back pain or spondylolisthesis.

Low Back Pain Differentials and OMM Concepts

Low back pain is a pervasive complaint with a broad differential. Osteopathic evaluation emphasizes identifying musculoskeletal causes and somatic dysfunctions while screening for serious conditions that require urgent referral.

• Psoas Syndrome: Often caused by a unilateral spasm of the psoas major muscle, leading to an ipsilateral flexion contracture of the hip. This typically results in a compensatory lumbar somatic dysfunction, usually at L1 or L2, characterized by flexion, rotation, and sidebending to the side of the psoas spasm. Patients may exhibit a positive Thomas test and have difficulty standing upright.
• Iliolumbar Ligament Strain: This ligament connects the L4 and L5 transverse processes to the ilium. Strain or sprain typically causes localized tenderness and pain near the iliac crest, especially during lumbar motion. It is common during pregnancy or after trauma.
• Herniated Nucleus Pulposus (HNP): Most common at L4-L5 or L5-S1, often due to posterolateral herniation compressing nerve roots. Presents with radicular pain, numbness, weakness in a dermatomal/myotomal distribution. Positive Straight Leg Raise test (pain reproduced below the knee at 30-70 degrees of hip flexion).
• Spinal Stenosis: Narrowing of the spinal canal or intervertebral foramina, typically due to degenerative changes (osteophytes, ligamentum flavum hypertrophy). Causes neurogenic claudication (pain, numbness, weakness in legs that is worse with extension and relieved with flexion, e.g., 'shopping cart sign').
• Spondylolysis: A stress fracture or defect in the pars interarticularis, most commonly at L5. Often seen in young athletes involved in repetitive extension and rotation. Pain is unilateral and worse with extension. On oblique X-ray, it appears as a 'Scotty dog' with a collar.
• Spondylolisthesis: Anterior slippage of one vertebral body over another, most commonly L5 over S1. Often a consequence of bilateral spondylolysis. Can cause palpable 'step-off' deformity, low back pain, and radicular symptoms.
• Cauda Equina Syndrome: A medical emergency! Compression of the cauda equina nerve roots, typically presenting with saddle anesthesia (numbness in buttocks/perineum), new-onset bowel or bladder dysfunction (incontinence/retention), and bilateral lower extremity weakness/sensory loss. Requires immediate surgical consultation.