Lumbar Stenosis : Wheeless' Textbook of Orthopaedics

- Discussion:
- spinal stensosis is a narrowing of the lumbar spinal canal and/or neural foramina;
- results in compression of the cauda equina and lumbar nerve roots, producing neural root ischemia and neurogenic claudication;
- compression of neural structures also compresses vascular supply of nerves so that symptoms are predominately those of neural ischemia;
- because both neural canal and the neural foramen are narrowed w/ spine in extension & opened in flexion, neural compression is most often temporary;
- pain induces patients to change position and relieve nerve pressure before permanent neurologic damage is done;
- although degenerative spondylolisthesis is common cause of stenosis, 10% of adults > 65 yrs may have this finding & many are asymptomatic;

- pathoanatomy:
- central stenosis:

- refers to narrowing and compression within the lumbar spinal canal.

- lateral recess stenosis:

- refers to narrowing and compression within the subarticlar region which is lateral to the dura and medial to the pedicle;

           - foramenal stenosis:
                   - refers to narrowing and compression at the entrance and within the neural foramen formed by the cephalad and caudal pedicles,
                              facet joints dorsally and vertebral body and discs ventrally.

- contributing causes:
- achondroplasia

- degenerative disc disease and facet joint arthropathy

- degenerative spondylolisthesis

- fractures

- levels adjacent to surgical fusion

- epidural lipomatosis

- ligamentum flavum hypertrophy

- synovial cysts

- iatrogenic

- references:
- The natural course of lumbar spinal stenosis.

- Clinical Findings:

- patients with LSS experience neurogenic claudication characterized by pain, numbness and weakness in the lower extremities while at
rest and standing;

    - patients are usually 50 years or older;
    - radicular symptoms may be unilateral or bilateral with or without back pain
    - pain occurs when the patient is upright and particularly when walking;
    - standing and walking up inclines increase pain;
    - sitting and lying on side with the hips and knees flexed relieve pain as does leaning over a shopping cart.

- extension of the lumbar spine is not well tolerated and aggravates radicular pain, where as flexion of the lumbar spine is well tolerated and
relieves pain

- in contrast to patients with claudication caused by vascular disease patients with LSS can ride an exercise bicycle w/o experiencing leg pain.

- typical symptom is leg pain, numbness, and weakness developing after patient walks a predictable distance;
- patient seeks relief by sitting, leaning forward to "relieve pressure" putting his foot on a raised rest, or lying down;
- common denominator is changing the position of the spine from extension to flexion;
- dx of spinal stenosis is made by eliciting h/o of pseudoclaudocation, positive spinal Phalen test, and imaging confirming stenosis;
- patients may present with bizarre neurologic complaints

- sensory, motor and reflex changes may be minimal to none

- bowel and bladder sphincter dysfunction may be seen
- EMG is helpful in evaluation the nerve roots affected and in ruling out other causes of neuropathy;

- Phalen test may be specific;
- this test attempts to reproduce symptoms of leg pain, weakness, or numbness by causing neural ischemia;
- w/ pt upright, bend the patient into extension for a full minute;
- this should accentuate the spinal stenosis;
- positive test will produce a crescendo of leg symptoms followed by rapid relief of these symptoms when the patient flexes forward,
places his hands on examination table, and places one foot on stool;

- Radiographs:
    - AP and lateral radiographs including flexion and extension laterals are helpful.
    - disk space narrowing is a poor predictor of symptoms;
- instability:
- normal anterior and posterior translation from L1 to L5 is about 8% of length of vertebral body or about 4 mm;
- note that the typical degenerative changes of osteophyte formation, decrease in disc height, and ligament calcification will serve to limit motion;
- Myelogram:
- myelogram with the patient in extension may offer the best information on location of stenotic areas;
- CT scan:
           - coronal and sagittal CT reconstructions are quite helpful
           - evaluate for lateral stenosis & central stenosis;
- cross-sectional dural areas of < 100 mm2 denote stenosis;
- clinical syndrome of lumbar stenosis correlates more closely w/ anteroposterior diameter of the dural sac;
- dural sac w/ AP diameter of < ten millimeters is consistent w/ clinical syndrome of lumbar stenosis;
- MRI:
           - MRI delineates very accurately the compressive elements of LSS
    - references:
           - Role of computed tomography and myelography in the diagnosis of central spinal stenosis.
           - Radiologic diagnosis of degenerative lumbar spinal instability.

- Non Operative Treatment:
    - high percentage of patients will have little change in their symptoms without treatment;
    - physical therapy and aquatic exercises which avoid extension may be helpful.
    - image guided intralaminal epidural and transforaminal nerve root steroid injections may provide relief for variable periods of time.

- Operative Treatment:
    - decompression by laminectomy and partial facetectomy is effective.
    - indications for fusion:
            - fusion with instrumentation in addition to decompression may be necessary in patients with degenerative spondylolisthesis,
                     degenerative scoliosis, post laminectomy, and those with adjacent segment stenosis following a fusion;
            - w/ no segmental instability, arthrodesis may not be required, (assumming that posterior elements have not been destabilized);
- degenerative spondylolisthesis;
- positioning:
   - be particularly certain that there is no pressure on abdomen which would compress the vertebral venous plexus;
- decompression:
       - laminae are minimally trimmed for exposure;
     - includes widening of lateral recess;
    - removal of medial rim of facets;
- postero-lateral fusion:
- see: fusion of the spine