Adult spinal deformity refers to abnormal curvatures of the spine in patients who have completed their growth.
Recent evidence has revealed sagittal plane malalignment to be a key driver of pain and disability in this population and has led to a significant shift toward a more evidence-based management paradigm.
ASD is increasing in prevalence in North America due to an aging population and demographic shifts.
They are typically seen in males and females over the age of eighteen. The age range of patients seeking treatment for adult scoliosis and other deformities varies widely, however. It is not unusual for patients who are well into their sixties, seventies or even eighties present with symptoms of pain and functional limitations. With increasing life expectancy along with more active lifestyles, the number of older adults requiring treatment has also gone up. Unlike the younger or adolescent patient with a spinal deformity, the older adult presents with a completely different set of problems and challenges to the treating physician.
Adult spinal deformity (ASD) surgery is increasing in the spinal neurosurgeon's practice.
A survey of neurosurgeon AANS membership assessed the deformity knowledge base and impact of current training, education, and practice experience to identify opportunities for improved education. Eleven questions developed and agreed upon by experienced spinal deformity surgeons tested ASD knowledge and were subgrouped into 5 categories:
1) radiology/spinopelvic alignment
2) health-related quality of life
3) surgical indications
4) operative technique
5) clinical evaluation.
Chi-square analysis was used to compare differences based on participant demographic characteristics (years of practice, spinal surgery fellowship training, percentage of practice comprising spinal surgery).
Responses were received from 1456 neurosurgeons. Of these respondents, 57% had practiced less than 10 years, 20% had completed a spine fellowship, and 32% devoted more than 75% of their practice to spine. The overall correct answer percentage was 42%. Radiology/spinal pelvic alignment questions had the lowest percentage of correct answers (38%), while clinical evaluation and surgical indications questions had the highest percentage (44%). More than 10 years in practice, completion of a spine fellowship, and more than 75% spine practice were associated with greater overall percentage correct (p < 0.001). More than 10 years in practice was significantly associated with increased percentage of correct answers in 4 of 5 categories. Spine fellowship and more than 75% spine practice were significantly associated with increased percentage correct in all categories. Interestingly, the highest error was seen in risk for postoperative coronal imbalance, with a very low rate of correct responses (15%) and not significantly improved with fellowship (18%, p = 0.08).
The results of this survey suggest that ASD knowledge could be improved in neurosurgery. Knowledge may be augmented with neurosurgical experience, spinal surgery fellowships, and spinal specialization.
It results from cumulative degenerative changes focused in the intervertebral discs and facet joints that occur asymmetrically to produce deformity.
There are many different causes of spinal deformity in the adult. The most common varieties include idiopathic scoliosis that was present during adolescence (teenage years) and then became worse during adulthood, deformity that began in adulthood due to degenerative (wear and tear) changes in the spine and deformity that developed later in life after previous surgery during teenage years. Other less frequent causes include curvatures due to osteoporosis (brittle bones), previous fractures of the spine due to an accident, spondylolisthesis (slipped vertebrae) and rarely, infections and tumors of the spine. Adult idiopathic scoliosis: This is a slow increase in curvature that began during teenage years in an otherwise healthy individual and progressed during adult life. Some of these patients may have had brace treatment during adolescence while others may have never sought treatment during their teenage years. This can occur in the thoracic (upper) and lumbar (lower) spine and has the same basic appearance as that seen in teenagers. They include shoulder asymmetry, a rib hump or a prominence of the lower back on the convex side of the curvature. These curves can get worse in the older patient due to degeneration of the discs which results in settling of the vertebrae (spinal segments). Additionally, arthritis sets in the joints of the spine (facets) which leads to the formation of bone spurs. This can result in pain and stiffness of the back. In more severe cases, patients may also develop shooting pain and numbness down the legs due to pinched nerves.
Post-surgical deformity: This type is seen in patients who had previously undergone spinal surgery either for scoliosis or for degenerative low back conditions. These patients develop a condition called “Flat Back Syndrome” where the lower back has lost its normal inward curvature or lordosis. As a result, patients with this condition are unable to stand upright and are usually “pitched forward”. They are typically seen in patients who have had long fusions of the spine in the past. Another category of post-surgical deformity is “Junctional Kyphosis” which is an angular deformity (kyphosis) that develops just above or below a previous spinal fusion. Both these conditions result in an imbalance of the spine from the side (sagittal imbalance) and lead to progressive low back pain and stiffness.
ASD is characterized by malalignment in the sagittal and/or coronal plane and, in adults, presents with pain and disability.
Unlike teenagers with spinal deformity who rarely complain of pain, adult patients with deformity present with a variety of symptoms. Low back pain and stiffness are the two most common symptoms. In addition, numbness and cramping in the legs and shooting leg pain due to pinched nerves can occur. These symptoms are due to degeneration of the discs and joints leading to narrowing of the openings for the spinal sac and nerves (spinal stenosis). Loss of sagittal balance causes the patients to compensate by bending their hips and knees to try and maintain an upright posture. This puts greater strain on the muscles of the lower back and legs causing the patients to fatigue early. There is a gradual loss of function and a decrease in the activities of daily living.
Full length standing radiographs in both the coronal and sagittal plane that include all segments of the spine as well as the pelvis and hips are essential in the diagnostic evaluation of adults with spinal deformity. From such radiographs the segmental alignment, regional curvatures and global balance can be measured. Pelvic parameters such as pelvic incidence and pelvic tilt will also help define compensatory mechanisms of deformity. Focal imaging studies may be necessary to assess for instability (flexion-extension radiographs). Advanced imaging studies (i.e. MRI or CT myelography) may be needed to assess patients with lower extremity symptoms or other neurologic signs or symptoms.
Coronal deformity is usually less symptomatic than a sagittal deformity because there is less expenditure of energy and hence less effort to maintain upright posture. However, nerve root compression at the fractional curve or at the concave side of the main curve can give rise to debilitating radiculopathy.
Findings demonstrate significant variability in health-related quality-of-life measures and radiographic parameters between North American and Japanese patients, supporting the need for population-adjusted sagittal modifiers to more accurately classify deformity 2).
Nonoperative management is recommended for patients with mild, nonprogressive symptoms; however, evidence of its efficacy is limited. Surgery aims to restore global spinal alignment, decompress neural elements, and achieve fusion with minimal complications. The surgical approach should balance the desired correction with the increased risk of more aggressive maneuvers. In well-selected patients, surgery yields excellent outcomes 3).
Not every adult with a spinal deformity requires treatment. In fact, the vast majority of adults with deformity do not have disabling symptoms and can be managed with simple measures such as periodic observation, over the counter pain relievers and exercise. The exercises are aimed at strengthening the core muscles of the abdomen and back and improving flexibility. Some patients may benefit from short term use of braces to get pain relief. Braces do not have any long term effect on the degree of the deformity. For persistent leg pain and other symptoms due to arthritis and pinched nerves, injections such as epidurals, nerve blocks or facet injections may provide temporary relief. These are usually performed by a pain management physician who may also prescribe stronger medications. Unfortunately, stronger pain medications can also be habit forming and have to be used with caution.
Is reserved for a small subset of patients who have failed all reasonable conservative (non-operative) measures. They generally have disabling back and/or leg pain and spinal imbalance. Their functional activities are severely restricted and their overall quality of life has reduced substantially.
The goals of surgery are to restore spinal balance and reduce pain and discomfort by relieving pressure off the nerves (decompression) and maintaining corrected alignment by fusing and stabilizing the spinal segments. Surgical stabilization involves anchoring hooks, wires or screws to the spinal segments and using metal rods to link the anchors together. They act as a tether and allow the spine to fuse in the corrected position. Fusion is performed by using the patient’s own bone or using cadaver or synthetic bone substitutes. In more severe cases, spinal segments have to be cut and realigned (osteotomy) or entire segments may have to be removed prior to realigning the spine (vertebral column resection). There are many different types of surgical procedures designed to treat adult spinal deformities. A detailed description of each is beyond the scope of this discussion.
It is important to note that surgery in the adult deformity population is riskier than in the adolescent teenager. The complication rate is significantly higher and the recovery, a lot slower. Therefore, surgery should only be undertaken as a last resort and only after the patient has a clear understanding of the risks and benefits. All reasonable non-surgical measures should be attempted first. At the same time, when patients are carefully chosen and are mentally well-prepared for the surgery, excellent functional outcomes can be obtained which at times can be a positive life changing experience for a given individual patient.
Recent advances in surgical techniques include less invasive approaches by making smaller incisions as well as using biologic substances to accelerate the fusion process. Use of computer-assisted navigation systems and various forms of spinal cord and nerve monitoring may help in improving surgical precision and accuracy. Although promising, longer follow-ups are needed before one can conclude that they are superior to existing time-honored methods.
Minimally invasive surgery (MIS) techniques are increasingly used to treat adult spinal deformity. However, standard minimally invasive spinal deformity techniques have a more limited ability to restore sagittal balance and match the pelvic incidence-lumbar lordosis (PI-LL) than traditional open surgery.
A retrospective review of minimally invasive spinal deformity surgery cases was performed to identify parameters in the 20% of patients who had the greatest improvement in Oswestry Disability Index (ODI) scores versus those in the 20% of patients who had the least improvement in ODI scores at 2 years' follow-up.
One hundred four patients met the inclusion criteria, and the top 20% of patients in terms of ODI improvement at 2 years (best group, 22 patients) were compared with the bottom 20% (worst group, 21 patients). There were no statistically significant differences in age, body mass index, pre- and postoperative Cobb angles, pelvic tilt, pelvic incidence, levels fused, operating room time, and blood loss between the best and worst groups. However, the mean preoperative ODI score was significantly higher (worse disability) at baseline in the group that had the greatest improvement in ODI score (58.2 vs 39.7, p < 0.001). There was no difference in preoperative PI-LL mismatch (12.8° best vs 19.5° worst, p = 0.298). The best group had significantly less postoperative sagittal vertical axis (SVA; 3.4 vs 6.9 cm, p = 0.043) and postoperative PI-LL mismatch (10.4° vs 19.4°, p = 0.027) than the worst group. The best group also had better postoperative visual analog scale back and leg pain scores (p = 0.001 and p = 0.046, respectively).
The authors recommend that spinal deformity surgeons using MIS techniques focus on correcting a patient's PI-LL mismatch to within 10° and restoring SVA to < 5 cm. Restoration of these parameters seems to impact which patients will attain the greatest degree of improvement in ODI outcomes, while the spines of patients who do the worst are not appropriately corrected and may be fused into a fixed sagittal plane deformity 4).
Both hybrid (HYB) surgical approach and circumferential MIS (cMIS) approach approaches resulted in clinical improvement, as evidenced by decreased Oswestry Disability Index ODI and VAS pain scores. While there was no significant difference in degree of radiographic correction between groups, the HYB group had greater absolute improvement in degree of lumbar coronal Cobb angle correction, increased lumbar lordosis LL, decreased sagittal vertical axis SVA, and decreased LL-Pelvic incidence PI. The complication rate, however, was higher with the HYB approach than with the cMIS approach 5).
For successful multilevel correction and stabilization of degenerative spinal deformities, a rigid basal construct to the sacrum is indispensable.
The surgical treatment of multilevel degenerative spine disease carries a significant risk for pseudarthrosis and screw loosening, mandating a rigid sacropelvic fixation. The use of an iliosacral plate resulted in an inferior surgical and clinical outcome when compared to iliac screws 6).
The surgical management of adult spinal deformity (ASD) is rapidly growing despite the high costs and frequent complications associated with these procedures.
Although multiple reports have documented significant benefit from surgical treatment of adult spinal deformity (ASD), these procedures can have high complication rates. Previously reported complications rates associated with ASD surgery are limited by retrospective design, single-surgeon or single-center cohorts, lack of rigorous data on complications, and/or limited follow-up. Accurate definition of complications associated with ASD surgery is important and may serve as a resource for patient counseling and efforts to improve the safety of patient care.
From 2002 to 2007, the rate of complex fusion procedures in the Medicare population increased 15-fold and was accompanied by a 5.6% incidence of life-threatening complications and a 30-day readmission rate of 13% 7) 8).
A high prevalence of residual cervical deformity (CD) has been identified following surgical treatment of adult spinal deformity (ASD). Development of new onset CD is less understood and its clinical impact unclear.
More than 47% (47.7%) of patients without preop cervical deformity develop new postop cervical deformity after ASD surgery. Independent predictors of new onset CD at 2 years include diabetes, higher preop TS-CL, and ending instrumentation above T4. Significant improvements in HRQL scores occurred despite the development of postoperative CD 9).
The reintubation rate after ASD surgery is approximately 1.8%. Patients with a history of chronic lung disease and patients undergoing fusion of 8 or more segments may be at an increased risk for reintubation; other associated factors included acute respiratory failure, sepsis, and deep vein thrombosis. Patients who required postoperative airway management after ASD surgery were 9.8 times more likely to die during their hospital stay compared with controls 10).
The growth of these complex deformity procedures is partially driven by the poor ability of nonoperative management of ASD to improve pain and function. A recent study of adult patients with scoliosis treated using non- operative techniques found that there were no significant improvements in any of the health-related quality of life (HRQOL) outcome measures over the evaluation period 11).
Op treatment for ASD can provide significant improvement of HRQL measures at min 2-year follow-up. In contrast, nonop treatment appears to at best maintain presenting levels of pain and disability 12).
Poor HRQOL uniformly determined operative treatment for ASD. Spinal deformities differed between age groups. Younger OP had larger scoliosis but similar spinopelvic alignment (SPA) and sagittal vertical axis (SVA) than nonoperatively (NON). Older OP had similar scoliosis but worse SVA than NON. Age associated differences for poor HRQOL must be considered when evaluating ASD patients 13).
High prevalence of residual cervical spine deformity (CD) has been identified after surgical treatment of adult spinal deformity. Development of new onset CD is less understood and its clinical impact unclear.
A total of 47.7% of patients without preoperative CD developed new onset postoperative CD after thoracolumbar surgery. Independent predictors of new onset CD at 2 years included diabetes, higher preoperative T1 slope minus cervical lordosis, and ending instrumentation above T4. Significant improvements in health-related quality of life scores occurred despite the development of postoperative CD 14).
For elderly patients with ASD, osteoporosis increases the risk of revision surgery, while BMP use decreases the risk. Other comorbidities were not found to be significant predictors of long-term revision rates. It is expected that within 5 years following the index procedure, over 30% of patients will require revision surgery 15).
The PearlDiver database (2005-2012) was used to determine revision rates in elderly ASD patients treated with a primary thoracolumbar posterolateral fusion of 8 or more levels. Analyzed risk factors included demographics, comorbid conditions, and surgical factors. Significant univariate predictors were further analyzed with multivariate analysis. The causes of revision at each year of follow-up were determined.
A total of 2293 patients who had been treated with posterolateral fusion of 8 or more levels were identified. At the 1-year follow-up, 241 (10.5%) patients had been treated with revision surgery, while 424 (18.5%) had revision surgery within 5 years. On univariate analysis, obesity was found to be a significant predictor of revision surgery at 1 year, while bone morphogenetic protein (BMP) use was found to significantly decrease revision surgery at 4 and 5 years of followup. Diabetes mellitus, osteoporosis, and smoking history were all significant univariate predictors of increased revision risk at multiple years of follow-up. Multivariate analysis at 5 years of follow-up revealed that osteoporosis (OR 1.98, 95% CI 1.60-2.46, p < 0.0001) and BMP use (OR 0.70, 95% CI 0.56-0.88, p = 0.002) were significantly associated with an increased and decreased revision risk, respectively. Smoking history trended toward significance (OR 1.37, 95% CI 1.10-1.70, p = 0.005). Instrument failure was consistently the most commonly cited reason for revision. Five years following surgery, it was estimated that the cohort had 68.8% survivorship.
For elderly patients with ASD, osteoporosis increases the risk of revision surgery, while BMP use decreases the risk. Other comorbidities were not found to be significant predictors of long-term revision rates. It is expected that within 5 years following the index procedure, over 30% of patients will require revision surgery 16).
A retrospective analysis of a prospective multicenter database of 365 adult spinal deformity (ASD) patients who had undergone surgical treatment was performed. Health-related QOL variables were examined preoperatively and at the 2-year postoperative follow-up. Patients were grouped by their 36-Item Short Form Health Survey mental component summary (MCS) and physical component summary (PCS) scores. Both groups had PCS scores ≤ 25th percentile for matched norms; however, the low mental health (LMH) group consisted of patients with an MCS score ≤ 25th percentile, and the high mental health (HMH) group included patients with an MCS score ≥ 75th percentile. RESULTS Of the 264 patients (72.3%) with a 2-year follow-up, 104 (28.5%) met the inclusion criteria for LMH and 40 patients (11.0%) met those for HMH. The LMH group had a significantly higher overall rate of comorbidities, specifically leg weakness, depression, hypertension, and self-reported neurological and psychiatric disease processes, and were more likely to be unemployed as compared with the HMH group (p < 0.05 for all). The 2 groups had similar 2-year postoperative improvements in HRQOL (p > 0.05) except for the greater improvements in the MCS and the Scoliosis Research Society-22r questionnaire (SRS-22r) mental domain (p < 0.05) in the LMH group and greater improvements in PCS and SRS-22r satisfaction and back pain domains (p < 0.05) in the HMH group. The LMH group had a higher rate of reaching a minimal clinically important difference (MCID) on the SRS-22r mental domain (p < 0.01), and the HMH group had a higher rate of reaching an MCID on the PCS and SRS-22r activity domain (p < 0.05). On multivariable logistic regression, having LMH was a significant independent predictor of failure to reach an MCID on the PCS (p < 0.05). At the 2-year postoperative follow-up, 14 LMH patients (15.1%) were categorized as HMH. Two LMH patients (2.2%), and 3 HMH patients (7.7%) transitioned to a PCS score ≥ 75th percentile for age- and sex-matched US norms (p < 0.01). CONCLUSIONS While patients with poor mental and physical health, according to their MCS and PCS scores, have higher medical comorbidity and unemployment rates, they still demonstrate significant improvements in HRQOL measurements postoperatively. Both LMH and HMH patient groups demonstrated similar improvements in most HRQOL domains, except that the LMH patients had difficulties in obtaining improvements in the PCS domain 17).
Smith et al conducted a study to prospectively assess the rates of complications associated with ASD surgery with a minimum 2-year follow-up based on a multicenter study design that incorporated standardized data-collection forms, on-site study coordinators, and regular auditing of data to help ensure complete and accurate reporting of complications. In addition, they report age stratification of complication rates and provide a general assessment of factors that may be associated with the occurrence of complications.
As part of a prospective, multicenter ASD database, standardized forms were used to collect data on surgery-related complications. On-site coordinators and central auditing helped ensure complete capture of complication data. Inclusion criteria were age older than 18 years, ASD, and plan for operative treatment. Complications were classified as perioperative (within 6 weeks of surgery) or delayed (between 6 weeks after surgery and time of last follow-up), and as minor or major. The primary focus for analyses was on patients who reached a minimum follow-up of 2 years.
Of 346 patients who met the inclusion criteria, 291 (84%) had a minimum 2-year follow-up (mean 2.1 years); their mean age was 56.2 years. The vast majority (99%) had treatment including a posterior procedure, 25% had an anterior procedure, and 19% had a 3-column osteotomy. At least 1 revision was required in 82 patients (28.2%). A total of 270 perioperative complications (145 minor; 125 major) were reported, with 152 patients (52.2%) affected, and a total of 199 delayed complications (62 minor; 137 major) were reported, with 124 patients (42.6%) affected. Overall, 469 complications (207 minor; 262 major) were documented, with 203 patients (69.8%) affected. The most common complication categories included implant related, radiographic, neurological, operative, cardiopulmonary, and infection. Higher complication rates were associated with older age (p = 0.009), greater body mass index (p ≤ 0.031), increased comorbidities (p ≤ 0.007), previous spine fusion (p = 0.029), and 3-column osteotomies (p = 0.036). Cases in which 2-year follow-up was not achieved included 2 perioperative mortalities (pulmonary embolus and inferior vena cava injury).
This study provides an assessment of complications associated with ASD surgery based on a prospective, multicenter design and with a minimum 2-year follow-up. Although the overall complication rates were high, in interpreting these findings, it is important to recognize that not all complications are equally impactful. This study represents one of the most complete and detailed reports of perioperative and delayed complications associated with ASD surgery to date. These findings may prove useful for treatment planning, patient counseling, benchmarking of complication rates, and efforts to improve the safety and cost-effectiveness of patient care 18).
The Nationwide Inpatient Sample was used to identify surgical patients with adult spinal deformity (ASD) between 2002 and 2011. Only patients > 21 years old and elective cases were included. Patient characteristics, inpatient morbidity, and inpatient mortality were compared between teaching hospital and nonteaching hospitals. A multivariable logistic regression analysis was performed to examine the effect of hospital teaching status on surgical outcomes.
A total of 7603 patients were identified, with 61.2% (n = 4650) in the teaching hospital group and 38.8% (n = 2953) in the nonteaching hospital group. The proportion of patients undergoing revision procedures was significantly different between groups (5.2% in teaching hospitals vs 3.9% in nonteaching hospitals, p = 0.008). Likewise, complex procedures (defined as fusion of 8 or more segments and/or osteotomy) were more common in teaching hospitals (27.3% vs 21.7%, p < 0.001). Crude overall complication rates were similar in teaching hospitals (47.9%) compared with nonteaching hospitals (49.8%, p = 0.114). After controlling for patient characteristics, case complexity, and revision status, patients treated at teaching hospitals were significantly less likely to develop a complication when compared with patients treated at a nonteaching hospital (OR 0.89; 95% CI 0.82-0.98). The mortality rate was 0.4% in teaching hospitals and < 0.4% in nonteaching hospitals (p = 0.210).
Patients who undergo surgery for ASD at a teaching hospital may have significantly lower odds of complication development compared with patients treated at a nonteaching hospital 19).