summary Lumbar spinal stenosis is a degenerative spinal condition characterized by the narrowing of the lumbar spinal canal due to a variety of bony or soft tissue structures Diagnosis is made with MRI of the lumbar spine Treatment is a trial of nonoperative management with NSAIDs and physical therapy. Surgical laminotomy and discectomy are indicated for progressive disabling pain and/or progressive neurological deficits that have failed nonoperative management Epidemiology Incidence most common reason for lumbar spine surgery in patients >65 y/o seen in 20-25% Demographics slightly more common in males (1.5:1) average age at presentation is 65 y/o Anatomic location most commonly occurs at L4-5 (91%) Risk factors Caucasian race increased BMI congenital spine anomalies (20%) failure of posterior elements to develop, leading to short pedicles and laminae Etiology Mechanism Narrowing of the lumbar spinal canal can be due to bony structures login to view 3 more bullets soft tissue structures login to view 3 more bullets Pathophysiology cell, water, and proteoglycan content in the nucleus pulposus decrease with age degeneration of the intervertebral disk leads to diminished disk height and buckling/bulging of the annulus fibrosus anterior spinal column begins to have decreased ability to absorb stress, leading to an abnormal transfer of force to the posterior elements increased stress through the facets leads to facet joint hypertrophy, osteophyte formation, and ligamentum flavum buckling and hypertrophy combined changes lead to a narrowing of the spinal canal and compression of the neural elements Associated conditions degenerative spondylolisthesis degenerative scoliosis cauda equina syndrome rare Anatomy Osteology anterior vertebral body posterior arch formed by login to view 4 more bullets spinous process transverse process mammillary processes separate ossification centers project posteriorly from superior articular facet pars interarticularis mass of bone between superior and inferior articular facets site of spondylolysis Articulations intervertebral discs act as articulations above and below facet joint (zygapophyseal joint) formed by superior and inferior articular processes that project from junction of pedicle and lamina facet orientation login to view 1 more bullet Nerve roots nerve root exits in the foramen under same-numbered pedicle central herniations affect traversing nerve root far lateral herniations affect exiting nerve root Blood supply segmental arteries dorsal branches supply blood to the dura & posterior elements Classification Etiologic classification acquired degenerative/spondylotic changes (most common) post-surgical post-traumatic (vertebral fractures) inflammatory (ankylosing spondylitis) secondary to systemic diseases (Paget disease, acromegaly, and fluorosis) congenital short pedicles with medially placed facets can be subdivided into login to view 2 more bullets Anatomic classification central stenosis cross-sectional area <100 mm² or <10 mm anteroposterior diameter on axial CT caused by ligamentum hypertrophy directly under the lamina posteriorly and the bulging disc anteriorly results in thecal sac compression presents with symptoms of nonspecific root or lower nerve root compression (at the L4-5 level, the root of L5 is affected) lateral recess stenosis (subarticular recess) caused by facet joint arthropathy and osteophyte formation login to view 1 more bullet results in nerve root compression presents with symptoms of descending nerve root compression (at the L4-5 level, the root of L5 is affected) foraminal stenosis occurs between the medial and lateral borders of the pedicle caused by a substantial loss of disc height, foraminal disc protrusion or osteophytes, or angulation in the setting of degenerative scoliosis results in nerve root compression by the ventral cephalad overhang of the superior facet and the bulging disc presents with symptoms of exiting nerve root compression (at the L4-5 level, the root of L4 is affected) extraforaminal stenosis located lateral to the lateral edge of the pedicle caused by far lateral disc herniation presents with symptoms of exiting nerve root compression (at the L4-5 level, the root of L4 is affected) Presentation Symptoms back pain referred buttock pain leg pain often unilateral neurogenic claudication pain worse with extension (walking or standing upright) pain relieved with flexion (sitting, leaning over shopping cart, or sleeping in the fetal position) weakness bladder disturbances recurrent UTIs present in up to 10% due to autonomic sphincter dysfunction cauda equina syndrome (rare) Physical exam Kemp sign unilateral radicular pain from foraminal stenosis made worse by back extension straight leg raise (tension sign) usually negative Valsalva test radicular pain is not worsened by the Valsalva maneuver, unlike in a herniated disc normal neurologic exam patients may have no focal deficits, as exam often takes place with the patient seated and symptoms may be reproducible or exacerbated only with lumbar extension or ambulation Imaging Radiographs findings do not always correlate with clinical symptomatology standing AP and lateral nonspecific degenerative findings (disc space narrowing, osteophyte formation) degenerative scoliosis degenerative spondylolisthesis flexion/extension radiographs segmental instability and subtle degenerative spondylolisthesis myelogram plain-film myelography provides dynamic information such as degree of cut off when a patient goes into extension invasive procedure MRI imaging modality of choice findings central stenosis with a thecal sac <100 mm² obliteration of perineural fat and compression of lateral recess or foramen facet and ligamentum hypertrophy MRI findings of spinal stenosis may be found in asymptomatic patients CT myelogram more invasive than MRI findings central and lateral neural element compression bony anomalies bony facet hypertrophy Differential Important to differentiate symptoms of neurogenic claudication from those of vascular claudication flexion improves symptoms in neurogenic claudication because this posture increases the limited area available for the neural elements in the spinal canal and foramen Neurogenic Claudication vs. Vascular Claudication Neurogenic Claudication Vascular Claudication Postural changes Yes No Walking upright Causes symptoms Causes symptoms Standing stationary Causes symptoms Relieves symptoms Sitting Relieves symptoms Relieves symptoms Stair climbing Up easier (back flexed) Down easier Stationary bicycle (back flexed) Relieves symptoms Causes symptoms Pulses Normal Abnormal Hip-spine syndrome presence of coexisting hip and spine pathology must determine the primary pain generator prior to surgical treatment may require diagnostic injections to aid in diagnosis Treatment Nonoperative oral medications, physical therapy, and corticosteroid injections indications login to view 1 more bullet modalities include NSAIDs, physical therapy, weight loss, and bracing login to view 1 more bullet steroid injections (epidural and transforaminal) login to view 1 more bullet Operative wide pedicle-to-pedicle decompression indications login to view 2 more bullets outcomes login to view 1 more bullet wide pedicle-to-pedicle decompression with instrumented fusion indications login to view 4 more bullets Techniques Wide pedicle-to-pedicle decompression technique a single level decompression at L4-5 would include login to view 7 more bullets complications specific to this treatment infection dural tear epidural hematoma instability outcomes improved pain, function, and satisfaction with surgical treatment most common cause of failed surgery is recurrence of disease above or below the decompressed level comorbid conditions are the strongest predictor of clinical outcomes after decompression for lumbar spinal stenosis Wide decompression with posterolateral fusion instrumentation is controversial circumferential fusion (with PLIF or TLIF) is accepted, but no studies show its superiority Complications Complications increase with age, blood loss, and levels fused Major complications wound infection (10%) deep surgical infections are to be treated with surgical debridement and irrigation pneumonia (5%) renal failure (5%) persistent neurologic deficits (4%) Minor complications transient neurologic deficits (36%) genitofemoral nerve deficits are common following a transpsoas approach at higher lumbar levels femoral and/or obturator nerve is at risk with prolonged or excessive retraction during a transpsoas approach to the L4-L5 disc space UTI (34%) anemia requiring transfusion (27%) confusion (27%) dural tear failure of symptoms to improve