summary Degenerative Spondylolisthesis is a common degenerative condition characterized by subluxation of one vertebral body anterior to the adjacent inferior vertebral body with intact pars. The condition is most common in females over 40 years of age, at the L4-5 level. Diagnosis is made with lateral radiographs. Flexion and extension lateral lumbar radiographs can identify the degree of instability. MRI studies can be helpful for 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 woman Demographics more common in African Americans, diabetics, and woman over 40 years of age ~8 times more common in woman than men increase in prevalence in women postulated to be due to increased ligamentous laxity related to hormonal changes Anatomic location degenerative spondylolisthesis is 5-fold more common at L4/5 than other levels this is different that 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 vertebral body is allowed by facet joint degeneration facet joint sagittal orientation intervertebral disc degeneration ligamentous laxity (possibly from hormonal changes) degenerative cascade involves disc degeneration leads to facet capsule degeneration and instability microinstability which leads to further degeneration and eventual macroinstability and anterolithesis instability is worsening with sagittally oriented facets (congenital) that allow forward subluxation neurologic symptoms 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 foramen) caused by loss of disk height osteophytes from posterolateral corner of 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 Myerding Classification Grade I < 25% Grade II 25 to 50% Grade III 50 to 75% (Grade III and greater are rare in degenerative spondylolisthesis) Grade IV 75 to 100% Grade V Spondyloptosis (all the way off) Presentation Symptoms mechanical/ back pain most common presenting symptom usually relieved with rest and sitting neurogenic claudication & leg pain second most common symptoms defined as buttock and leg pain/discomfort caused by upright walking relieved by sitting not relieved by standing in one place (as is vascular claudication) may be unilateral or bilateral same symptoms found with spinal stenosis cauda equina syndrome (very rare) Physical exam L4 nerve root involvement (compressed in foramen with L4/5 DS) weakness to quadriceps best seen with sit to stand exam maneuver weakness to ankle dorsiflexion (cross over with L5) best seen with heel-walk exam maneuver decreased patellar reflex L5 nerve root involvement weakness to ankle dorsiflexion (cross over with L4) best seen with heel-walk exam maneuver weakness to EHL (great toe extension) weakness to gluteus medius (hip abduction) provocative walking test have patient walk prolonged distance until onset of buttock and leg pain have patient stop but remain standing upright if pain resolves this is consistent with vascular claudication have patient sit if pain resolves this is consistent with neurogenic claudication (DS) hamstring tightness commonly found in this patients, and must differentiate this from neurogenic leg pain Imaging Radiographs recommended views weight bearing lumbar AP, lateral neutral, lateral flexion, lateral extension findings slip is evident on lateral x-ray flexion-extension studies instability defined as 4 mm of translation or 10° of angulation of motion compared to adjacent motion segment MRI indications persistent leg pain that has failed nonoperative modalities best study to evaluate impingement of neural elements views T2 weighted sagittal and axial images best to look for compression of neurologic elements CT useful to identify bony pathology CT myelogram helpful in patients in which a MRI is contraindicated (pacemaker) Treatment Nonoperative physical therapy and NSAIDS indications most patients can be treated nonoperatively modalities include activity restriction NSAIDS PT epidural steroid injections indications second line of treatment if non-invasive methods fail Operative lumbar decompression with instrumented fusion, +/- interbody fusion indications most common is persistent and incapacitating pain that has failed 6 mos. 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 shows equivalent outcomes using cortical screw fixation verses pedicle screw fixation decompression often performed with a PLC perserving 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 spondylolithesis 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 most common TLIF/PLIF 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 post-op 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 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 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 about 20-29% at 10 years not all radiographic adjacent segment degeneration is symptomatic Surgical site infection (0.1-2%) treat with irrigation and debridement (usually hardware can be retained) Dural tear Positioning neuropathy LFCN seen with prone positioning due to iliac bolster ulnar nerve or brachial plexopathy from prone positioning with inappropriate position Complication rates increase with older age increased intraoperative blood loss longer operative time number of levels fused