Lumbar Facet Orientation
BM (Back, Medial) in sagittal plane; permits flexion/ext, prevents rotation
Psoas Syndrome Key Sign
Pelvic shift to OPPOSITE side; positive Thomas test on affected side
Scotty Dog Defect
Fracture of pars interarticularis = Spondylolysis (collar on dog)
Disc vs Stenosis
Disc herniation worsens with flexion; Stenosis improves with flexion (shopping cart)
Psoas Syndrome: Anatomy & Clinical Presentation
The iliopsoas originates from T12–L5 vertebrae and inserts onto the lesser trochanter of the femur. Hypertonicity of the psoas creates a characteristic diagnostic cluster:
Clinical Picture
Patient presents stooped forward (flexed) and tilted toward the dysfunctional side. Difficulty standing fully erect.
Pelvic Shift & Sacral Torsion
Pelvic shift occurs to the CONTRALATERAL (opposite) side. Causes a non-neutral backward sacral torsion with the axis on the same side.
Key Segmental Somatic Dysfunction
L1 or L2 is flexed, sidebent, and rotated to the same side as the hypertonic psoas (e.g., L1 F SRRR for right psoas spasm). Contralateral piriformis spasm frequently develops compensatorily.
Thomas Test
Patient lies supine and pulls one knee to chest. If the opposite leg lifts off the table, the test is positive for ipsilateral psoas contracture.
Spondylolisthesis, Spondylolysis & Spondylosis
Board questions constantly challenge differentiation between the three 'spondylos':
| Condition | Pathology & Anatomy | Key Imaging Finding | High-Yield Board Pearls |
|---|---|---|---|
| Spondylosis | Degenerative osteoarthritis of spine | Osteophytes, disc narrowing, facet hypertrophy | Age > 50; worse with extension; morning stiffness |
| Spondylolysis | Fracture of pars interarticularis without slippage | Oblique X-ray shows collar on Scotty dog | Repetitive hyperextension (gymnasts, football linemen); most common at L5 |
| Spondylolisthesis | Anterior slippage of one vertebral body over another | Lateral X-ray: Meyerding grading I (0-25%) to IV (75-100%) | Grade III/IV requires surgical fusion; HVLA strictly contraindicated! |
Herniated Nucleus Pulposus vs. Lumbar Spinal Stenosis
Differential diagnosis of low back pain with lower extremity radiculopathy:
| Feature | Herniated Disc (HNP) | Lumbar Spinal Stenosis |
|---|---|---|
| Typical Age | Young to middle-aged adults (30–50) | Elderly (> 65 years) |
| Pain Quality | Sharp, shooting radicular pain down dermatome | Pseudoclaudication (bilateral leg aching/heaviness with walking) |
| Positional Trigger | Worsens with flexion, sitting, coughing (Valsalva) | Worsens with extension / standing erect |
| Relieving Factors | Improves with lying flat or extension | Improves with flexion (shopping cart sign, leaning forward) |
| Physical Exam | Positive Straight Leg Raise (30–70°), dermatomal sensory/motor deficit | Normal pulses (rules out vascular claudication); wide-based gait |
COMLEX / OMM Integration
NBOME High-Yield Correlate
L5-Sacrum Diagnostic Rules
- Rule 1 (Rotation): L5 rotates in the opposite direction of sacral rotation.
- Rule 2 (Sidebending): L5 sidebends to the same side as the sacral oblique axis.
- Example: Right-on-Right forward sacral torsion (Right axis, Right rotation) → L5 is sidebent Right and rotated Left (
- Rule 2 (Sidebending): L5 sidebends to the same side as the sacral oblique axis.
- Example: Right-on-Right forward sacral torsion (Right axis, Right rotation) → L5 is sidebent Right and rotated Left (
L5 N SRRL).
Board Traps & Common Distractors
- Cauda Equina Syndrome (Emergency): Bilateral sciatica, saddle anesthesia, urinary retention or overflow incontinence, and decreased anal sphincter tone. Requires emergent surgical MRI and decompression within 24–48 hours to avoid permanent paralysis.
- HVLA Contraindication: Never perform HVLA over active spondylolisthesis (especially Grade II or higher) or acute radicular disc herniation.