summary Adult spinal deformity is an idiopathic or degenerative condition of the adult spine that leads to deformity in the coronal or sagittal plane Diagnosis is made with full-length spine radiographs Nonoperative treatment is a trial of NSAIDs and physical therapy. Surgical deformity correction is indicated for progressive disabling pain that has failed nonoperative management and/or progressive neurological deficits Epidemiology Demographics mean age 60 y/o males and females equally affected Anatomic location idiopathic scoliosis occurs more commonly in the thoracic spine degenerative scoliosis occurs more commonly in the lumbar spine Etiology Types coronal plane imbalance defined as lateral deviation of the normal vertical line of the spine >10° sagittal plane imbalance defined as radiographic sagittal imbalance >5 cm Pathoanatomy degenerative scoliosis results from the asymmetric degeneration of disc spaces and/or facet joints in the spine may occur in the coronal plane (scoliosis) or the sagittal plane (kyphosis/lordosis) factors contributing to loss of sagittal plane balance osteoporosis preexisting scoliosis iatrogenic instability degenerative disc disease Classification Coronal deformity can be broken down into idiopathic (residual) ASD results from untreated adolescent idiopathic scoliosis in adults degenerative (de novo) ASD defined as a progressive deformity in the adult caused by degenerative changes iatrogenic injury paralysis Idiopathic (Residual) vs. Degenerative (De Novo) ASD Idiopathic (Residual) Degenerative (De Novo) Curve pattern Follows classic curve patterns Lacks classic curve patterns Vertebral segments Involves more vertebral segments Involves fewer vertebral segments Curve location Thoracic spine Lumbar spine Curve magnitude Larger curve magnitudes Smaller curve magnitudes Presentation Symptoms low back pain (40-90%) most common symptom caused by spondylosis, micro/macroinstability, and discogenic pain more severe and recurrent than in the general population neurogenic claudication pain in lower extremities and buttocks unlike classic claudication, patients with scoliosis and stenosis do not obtain relief with sitting or forward flexion caused by spinal stenosis stenosis is located on the concave side of the curve radicular leg pain and weakness caused by foraminal and lateral recess stenosis worse in the concavity of the deformity where there is vertebral body rotation and translation Physical exam deformity with thoracic prominence seen with forward bending compensatory postural changes muscle weakness Imaging Radiographs recommended views full-length 36-inch cassette standing scoliosis radiographs in coronal (AP radiograph) and sagittal plane (lateral radiograph), with right and left bending films bending films help assess curve flexibility and the possibility of correction with surgical intervention measurements AP radiograph Cobb angle coronal balance using C7 plumb line (C7PL) and center sacral vertical line (CSVL) lateral radiograph sagittal balance C7PL T1 pelvic angle pelvic incidence pelvic incidence (PI) = sacral slope (SS) + pelvic tilt (PT) CT scan identify bony deformity, such as facet arthrosis CT myelogram most useful for assessing stenosis and bony anatomy, as rotation makes interpretation of MRI difficult better appreciation of bony anatomy and rotational deformity than MRI MRI indicated when lower extremity pain is present can identify central canal stenosis facet hypertrophy pedicle enlargement foraminal encroachment disc degeneration DEXA scan determine bone density for surgical planning Treatment Nonoperative observation with nonoperative modalities indications coronal curves <30° rarely progress modalities oral medications NSAIDs tricyclic antidepressants help with sleep disturbance physical therapy includes core strengthening (walking, cycling, swimming, and select weight lifting) corticosteroid injections and nerve root blocks diagnostic and therapeutic bracing may slow progression and increase comfort Operative surgical curve correction with instrumented fusion general indications curve >50° sagittal imbalance curve progression intractable back pain or radicular pain that has failed nonsurgical efforts cosmesis (controversial) cardiopulmonary decline thoracic curves >60° affect pulmonary function tests thoracic curves >90° affect mortality technique posterior only curve correction and instrumented fusion indications thoracic curves >50° most double structural curves >50° selection of technique is patient- and surgeon-specific combined anterior/posterior curve correction with instrumented fusion indications isolated thoracolumbar curves isolated lumbar curves extremely rigid curves requiring anterior release Techniques General goals of surgery restore spinal balance sagittal plane balance is the most reliable predictor of postoperative clinical symptoms can be measured using the C7 plumb line (C7 sagittal vertical axis) correction of sagittal plane deformity requires intense preoperative planning correct lumbar lordosis to normal anatomic range: PI = LL +/- 9° LL ≤45° - TK - PI most predictive of sagittal plane correction maintenance relieve pain obtain solid fusion worse outcomes associated with: baseline depression obesity Selecting proximal and distal fusion levels proximal extension extend to a neutral and horizontal vertebra above the main curve extend fusion to L5 indications only indicated if no pathology at L5-S1 patients with normal C7 plumb line and normal sacral inclination have the lowest risk of future L5-S1 disc degeneration outcomes high instrumentation failure rate when fixation does not extend to the sacrum in the presence of L5-S1 pathology extend fusion to sacrum (S1) indications extend to sacrum if any pathology at L5-S1 including L5-S1 spondylolisthesis L5-S1 spondylolysis L5-S1 facet arthrosis prior laminectomy technique may require concomitant anterior release and anterior column support (through anterior approach) for better deformity correction outcomes advantages increased stability of long fusion construct constructs less likely to fail if instrumentation extends to sacrum disadvantages increased risk of pseudoarthrosis increased surgical time increased reoperation rate increased risk of sacral insufficiency fractures altered gait postoperatively extend fusion to ilium (sacropelvic fusion) indications consider when the sacrum is included in a fusion involving >3 levels technique using iliac screws or bolts outcomes advantage increased stability of long fusion construct increased success of lumbosacral fusion disadvantage prominent hardware cement augmentation indications osteoporotic patients technique cement injection through a fenestrated tap at the end vertebra, followed by pedicle screw insertion outcomes increased fusion rates decreased deformity correction loss increased screw pull-out strength no additional complications Osteotomies overview useful to regain sagittal balance in severe angulation deformities 30°+ correction can be obtained through Smith-Petersen or pedicle subtraction osteotomies intraoperative neuromonitoring is preferred Smith-Petersen osteotomy (SPO) indications mild-to-moderate sagittal imbalance requiring correction of up to 10° per level of osteotomy prerequisites no anterior fusion at the level of the osteotomy adequate correction requires adequate disc height and mobility (correction is at the level of the disc) more correction in the lumbar spine (greater disc height and mobility) less correction in the thoracic spine (lesser disc height and mobility) pedicle subtraction osteotomy (PSO) indications severe sagittal imbalance >12 cm requiring correction of 30-35° in the lumbar spine, and 25° in the thoracic spine when anterior fusion is present (correction is at the level of the vertebral body, but not at the disc) vertebral column resection indications severe sagittal imbalance (provides more correction than PSO) requiring correction of up to 45° rigid angular thoracic spine kyphosis, such as associated with tumor, fracture, or infection severe rigid scoliosis congenital kyphosis hemivertebrae resection in thoracic/lumbar spines Anterior procedures indications large curves >70° rigid curves (no flexibility on side bending films) isolated lumbar or thoracolumbar curves anterior interbody fusion at L5-S1 when fusing to sacrum technique anterior release and fusion usually combined with posterior instrumentation and fusion staged or same day outcomes disadvantages longer surgeries if performed on the same day higher complication rates more medically stressful advantage increases stability of L5-S1 long fusion constructs helps restore and maintain sagittal and coronal balance Complications (surgical) Overall overall complication rate ~13.5% 10% major complications that often irreversibly affect the long-term health of the patient complication rates are significantly higher with osteotomies, revision procedures, and combined anterior/posterior approaches venous thromboembolism is most likely to result in poor clinical outcomes following adult spinal deformity surgery Pseudoarthrosis incidence (~5-25%) most common surgical technique resulting in pseudoarthrosis is posterior only fusion (15%) most common locations L5-S1 thoracolumbar junction risks >55 y/o kyphosis >20° positive sagittal balance >5 cm hip arthritis smoking thoracoabdominal approach incomplete lumbopelvic fixation osteoporosis Dural tear (~2.9%) Infection deep wound infection (~1.5%) superficial wound infection (~0.9%) increased risk with diabetes, smoking, increasing age, and revision surgery Implant complication instrumentation failure is more likely in bone with the lowest ratio of cortical to cancellous bone (sacrum < vertebral bodies < lumbar pedicles < thoracic pedicles) most common cause of reoperation; related to pseudoarthrosis lower rates of mechanical complications with GAP scores <3 Neurologic deficits acute neurological deficits (~1%) can occur intraoperatively after deformity correction maneuver if identified on neurophysiologic monitoring, remove instrumentation and consider a wake-up test delayed neurological deficits (~0.5%) acute neurological deficits following PSO (18%) nerve root injury screw malposition corrective maneuver Epidural hematoma (~0.2%) Pulmonary embolus (~0.2%) Deep venous thrombosis (~0.2%). Deaths (~0.3%) Prognosis Worse prognosis symptoms progress to the side of the curve convexity sagittal plane imbalance sagittal plane balance is the most reliable predictor of clinical symptoms in adults with spinal deformity Progression depends on curve type thoracic > lumbar > thoracolumbar > double major right thoracic curves (1° per year) right lumbar curves (0.5° per year) thoracolumbar curves (0.25° per year) depends on curve magnitude curves <30° rarely progress curves >50° commonly progress additional risk factors for progression increased risk when intercrestal line is below L4-5 preexisting rotational changes