summary Degenerative spondylolisthesis is a common degenerative condition characterized by subluxation of one vertebral body anterior to the adjacent inferior vertebral body with an intact pars interarticularis The condition most commonly occurs in females >40 y/o and most commonly at the L4-5 level Diagnosis is typically made with lateral radiographs. Flexion and extension lateral lumbar radiographs can identify the degree of instability. MRI studies can be helpful for determining central or foraminal stenosis Treatment is a trial of nonoperative management with NSAIDs and physical therapy. Surgical management is indicated for progressive disabling pain that has failed nonoperative management and/or progressive neurological deficits Epidemiology Prevalence ~5% in men ~9% in women Demographics more common in African Americans, diabetics, and women >40 y/o ~8x more common in women than men increased prevalence in women is postulated to be due to increased ligamentous laxity related to hormonal changes Anatomic location degenerative spondylolisthesis is 5x more common at L4-5 than other levels differs from isthmic spondylolisthesis, which is most commonly seen at L5-S1 Risk factors sacralization of L5 (transitional L5 vertebrae) sagittally oriented facet joints Etiology Pathoanatomy forward subluxation (intersegmental instability) of the vertebral body occurs due to facet joint degeneration facet joint sagittal orientation intervertebral disc degeneration ligamentous laxity (possibly from hormonal changes) degenerative cascade involves disc degeneration leading to facet capsule degeneration and instability microinstability, which leads to further degeneration and eventual macroinstability and anterolithesis this instability is worsened by sagittally oriented facets (congenital) that allow forward subluxation neurologic symptoms are caused by central and lateral recess stenosis a degenerative slip at L4-5 will affect the descending L5 nerve root in the lateral recess caused by slippage, hypertrophy of ligamentum flavum, and encroachment into the spinal canal of osteophytes from facet arthrosis foraminal stenosis a degenerative slip at L4-5 will affect the L4 nerve root as it is compressed in the foramen vertical foraminal stenosis (loss of height of the foramen) caused by loss of disc height osteophytes from the posterolateral corner of the vertebral body pushing the nerve root up against the inferior surface of the pedicle anteroposterior foraminal stenosis (loss of anterior to posterior area) caused by degenerative changes of the superior articular facet and posterior vertebral body Classification Meyerding Classification Grade I <25% Grade II 25-50% Grade III 50-75% (grade III and higher are rare in degenerative spondylolisthesis) Grade IV 75-100% Grade V Spondyloptosis (>100%) Presentation Symptoms mechanical/back pain most common presenting symptom usually relieved with rest and sitting neurogenic claudication and leg pain second most common symptom defined as buttock and leg pain/discomfort caused by walking upright relieved by sitting not relieved by standing in one place (as in vascular claudication) may be unilateral or bilateral same symptoms are found with spinal stenosis cauda equina syndrome (very rare) Physical exam L4 nerve root involvement (compressed in foramen with L4-5 degenerative spondylolisthesis) weakness of quadriceps best seen with sit-to-stand exam maneuver weakness of ankle dorsiflexion (crossover with L5) best seen with heel-walk exam maneuver decreased patellar reflex L5 nerve root involvement weakness of ankle dorsiflexion (crossover with L4) best seen with heel-walk exam maneuver weakness of EHL (great toe extension) weakness of gluteus medius (hip abduction) provocative walking test have the patient walk a prolonged distance until onset of buttock and leg pain have the patient stop but remain standing upright if pain resolves, consistent with vascular claudication have the patient sit if pain resolves, consistent with neurogenic claudication hamstring tightness commonly found in these patients and must be differentiated from neurogenic leg pain Imaging Radiographs recommended views weight-bearing lumbar spine views (AP, lateral, flexion, and extension) findings slip is evident on the lateral view flexion/extension views instability defined as 4 mm of translation or 10° of angulation compared to adjacent segment MRI indications persistent leg pain that has failed nonoperative modalities best study to evaluate neural element impingement views T2-weighted sagittal and axial images are best to look for compression of neurologic elements CT useful to identify bony pathology CT myelogram helpful in patients in whom an MRI is contraindicated (pacemaker) Treatment Nonoperative physical therapy and NSAIDs indications most patients modalities include activity restriction NSAIDs physical therapy epidural steroid injections indications second-line if noninvasive methods fail Operative lumbar decompression with instrumented fusion, +/- interbody fusion indications most common indication is persistent and incapacitating pain that has failed 6 months of nonoperative management and epidural steroid injections progressive motor deficit cauda equina syndrome technique often combined with a posterior lumbar interbody fusion or transforaminal interbody fusion new data show equivalent outcomes using cortical vs. pedicle screw fixation decompression is often performed with a PLC-preserving unilateral (undercutting) approach navigation and MIS techniques are widely used outcomes ~79% have satisfactory outcomes improved fusion rates shown with pedicle screws improved outcomes with successful arthrodesis worse outcomes found in smokers smokers should undergo smoking cessation prior to surgery posterior lumbar decompression alone indications usually not indicated due to instability associated with spondylolisthesis only indicated in medically frail patients who cannot tolerate the increased surgical time of performing a fusion outcomes ~69% treated with decompression alone are satisfied ~31% have progressive instability anterior lumbar interbody fusion (ALIF) indications reserved for revision cases with pseudoarthrosis outcomes injury to superior hypogastric plexus can cause retrograde ejaculation Techniques Posterior decompression and posterolateral fusion (+/- instrumentation) approach posterior midline approach multiple parasagittal incisions for minimally invasive approaches decompression usually done with laminectomy, wide decompression, and foraminotomy fusion posterolateral fusion with instrumentation is most common TLIF/PLIF are growing in popularity and may increase fusion rates and decrease risk of postoperative slip progression reduction of listhesis limited role in adults cost in degenerative spondylolisthesis, adding an interbody cage increases hospital costs without increasing fusion rates Cortical bone trajectory screw designed to decrease the amount of lateral exposure for obtaining screw starting points lower intraoperative blood loss, smaller skin incision, and decreased pain scores at 1-week postoperatively fusion rates and functional outcomes similar to conventional pedicle screw fixation some studies suggest conventional pedicle screw fixation may be more stable other studies have demonstrated greater screw pullout strength given cortical contact of the screw mostly described in combination with interbody fusion (PLIF or TLIF) starting point is more medial and caudal than traditional pedicle screws trajectory is more cephalad and lateral than a traditional screw cortical trajectory screws are generally smaller than traditional pedicle screws Complications Pseudoarthrosis (5-30%) CT scan is more reliable than MRI for identifying failed arthrodesis Adjacent segment disease (30-40%) risk of adjacent segment degeneration requiring surgery is ~20-29% at 10 years not all radiographic adjacent segment degeneration is symptomatic Surgical site infection (0.1-2%) treated with irrigation and debridement usually, hardware can be retained Dural tear Positioning neuropathy LFCN seen with prone positioning due to an iliac bolster ulnar nerve or brachial plexopathy from prone position with improper positioning Complication rates increase with older age increased intraoperative blood loss longer operative time number of levels fused