Moderate scoliosis continues to progress at 30-year follow-up: a call for concern?

PURPOSE: This natural history study reports long-term radiographic and clinical outcomes of patients with diagnosis of AIS with curves between 30° and 50°. Our purpose was to determine if any intervention in the natural history is warranted. METHODS: This was a longitudinal descriptive study at a single institution. We reviewed patient factors, radiographic parameters, and patient-reported outcomes at 20- and 30-year follow-up. RESULTS: A total of 31 patients were included. At skeletal maturity (which was the initial point of measurement), the median age was 17 years (range 12-21), the thoracic Cobb angle was 35° ± 5° (maximum-minimum 27°-47°), and the lumbar Cobb angle was 33° ± 7° (maximum-minimum 18°-45°). The median final follow-up was 35 years (median age 52, range 32-61) when the thoracic Cobb angle was 47° ± 12° (maximum-minimum 31°-74°) and the lumbar Cobb angle was 40° ± 17° (maximum-minimum 19°-69°). At final follow-up, 9 (29%) patients had a structural curve > 50°. Ten (32%) patients had a curve from 40° to 49° and 11 (35%) patients had a curve < 40°. The thoracic Cobb angle had progressed from < 40° to > 50° in 5 patients. Thoracolumbar and lumbar Cobb angles progressed from < 40° to greater than > 50° in 1 and 3 patients, respectively. Few patients had functional limitations according to Roland-Morris, Oswestry, and SF36 scores. Pain scores were minimal at final follow-up. CONCLUSION: All AIS curves between 30° and 50° at skeletal maturity tend to progress. Thoracic curves progress more than lumbar curves during the first 20 years and then progression slows down. The opposite happens with lumbar curves. Therefore, the rate of progression decreases with thoracic curves and increases with lumbar curves. Nevertheless, few patients have functional limitations. Further follow-up is necessary to define the true long-term outcome of moderate curves at maturity.

Choose Wisely: Surgical Selection of Candidates for Outpatient Anterior Cervical Surgery Based on Early Complications Among Inpatients.

BACKGROUND: Anterior cervical discectomy and fusion (ACDF) and cervical disc arthroplasty (CDA) are attractive targets for transition to the outpatient setting. We assessed the prevalence of rapid responses and major complications in the inpatient setting following 1 or 2-level ACDFs and CDAs. We evaluated factors that may place patients at greater risk for a rapid response or a postoperative complication. METHODS: This was an institutional review board-approved, retrospective cohort study of adults undergoing 1 or 2-level ACDF or CDA at 1 hospital over a 2-year period (2018 and 2019). Data on patient demographic characteristics, surgical procedures, and comorbidities were collected. Rapid response events were identified by hospital floor staff and involved acute changes in a patient's clinical condition. Complications were events that were life-threatening, required an intervention, or led to delayed hospital discharge. RESULTS: In this study, 1,040 patients were included: 888 underwent ACDF and 152 underwent CDA. Thirty-six patients (3.5%) experienced a rapid response event; 22% occurred >24 hours after extubation. Patients having a rapid response event had a significantly higher risk of developing a complication (risk ratio, 10; p < 0.01) and had a significantly longer hospital stay. Twenty-four patients (2.3%) experienced acute complications; 71% occurred >6 hours after extubation. Patients with a complication were older and more likely to be current or former smokers, have chronic obstructive pulmonary disease, have asthma, and have an American Society of Anesthesiologists (ASA) score of >2. The length of the surgical procedure was significantly longer in patients who developed a complication. All patients who developed dysphagia had a surgical procedure involving C4-C5 or more cephalad. Patients with a rapid response event or complication were more commonly undergoing revision surgical procedures. CONCLUSIONS: Rapid response and complications are uncommon following 1 or 2-level ACDFs or CDAs but portend a longer hospital stay and increased morbidity. Revision surgical procedures place patients at higher risk for rapid responses and complications. Additionally, older patients, patients with chronic obstructive pulmonary disease or asthma, patients who are current or former smokers, and patients who have an ASA score of ≥3 are at increased risk for postoperative complications. LEVEL OF EVIDENCE: Prognostic Level III . See Instructions for Authors for a complete description of levels of evidence.

Does pelvic incidence tell us the risk of proximal junctional kyphosis in adult spinal deformity surgery?

PURPOSE: To investigate the relationship between pelvic incidence (PI) and proximal junctional kyphosis (PJK) in patients treated surgically for adult spinal deformity (ASD) with fusion from thoracolumbar junction to sacrum. METHODS: A consecutive series of ASD patients who underwent fusion from the thoracolumbar junction to the sacrum with a minimum of 2-year follow-up was studied. Patients were divided into low PI (≤ 50°) and high PI (> 50°) groups. We compared radiographic parameters and the rates of PJK, between the two groups. A sub-analysis was performed on patients with a postoperative PI minus lumbar lordosis mismatch between - 10° and 10° (i.e., ideally corrected). RESULTS: Sixty-three patients were included: 19 low PI and 44 high PI. Median follow-up was 34 months (range 24-103). Overall PJK rate was 38%. PJK was observed in 16% of low PI and 48% of high PI patients (p = 0.02). The odds ratio for developing PJK with a high PI compared to a low PI was 4.9 (p = 0.03). There were 32 ideally corrected patients. Eleven of these were in the low PI group, and 21 patients were in the high PI group. The incidence of PJK was 25% for ideally corrected patients. PJK occurred in none of these patients in the low PI group and 38% of patients in the high PI group (p = 0.03). CONCLUSION: When the upper-instrumented vertebra includes the thoracolumbar junction, patients with a PI > 50° are at a significantly higher risk of developing PJK compared to patients with a PI ≤ 50°.

Do Preoperative Nasal Antiseptic Swabs Reduce the Rate of Surgical Site Infections After Adult Thoracolumbar Spine Surgery?

INTRODUCTION: Surgical site infection (SSI) remains a major complication after adult spinal surgery. We investigated whether adding preoperative nasal decontamination by antiseptic swab (skin and nasal antiseptic povidone-iodine, SNA-PI) to our antimicrobial protocol reduces the SSI rate among our patients undergoing thoracolumbar spinal surgery. METHODS: We retrospectively reviewed all adult thoracolumbar spinal surgeries performed between June 2015 and May 2017 at a single hospital. Patients were divided into those who received nasal decontamination (SNA-PI+) and those who did not (SNA-PI-). SSI rates and responsible pathogens were compared between the cohorts. RESULTS: A total of 1,555 surgeries with nasal decontamination (SNA-PI+) and 1,423 surgeries without (SNA-PI-) were included. The SSI rate in the SNA-PI+ group was 13 of 1,555 (0.8%) versus 10 of 1,423 (0.7%) for SNA-PI- group (P = 0.68). The infection rate was the highest among posterior instrumented fusions in the SNA-PI+ group (1.4%). Methicillin-sensitive Staphylococcus aureus was responsible for 70% of infections in the SNA-PI- group and 38% in the SNA-PI+ group (P = 0.13). CONCLUSIONS: Routine nasal antiseptic swab before spine surgery did not affect the overall rate of SSI in thoracolumbar spinal surgeries. The incidence of methicillin-sensitive S aureus was lower in patients who received nasal decontamination (5/1,555, 0.3%) compared with those who did not (7/1,423, 0.5%); however, this result was not statistically significant (P = 0.57).

Posterolateral Versus Transforaminal Interbody L4/5 Fusion: Correlation With Subsequent Surgery.

STUDY DESIGN: This is a retrospective cohort study. OBJECTIVE: To compare posterolateral versus transforaminal interbody fusion (PLF vs. PLF+TLIF) of the L4/5 segment regarding rates of subsequent surgery, clinical and radiographic parameters, and patient satisfaction. SUMMARY OF BACKGROUND DATA: Surgical treatment of lumbar stenosis, decompression with or without fusion, is an efficacious treatment in select patients. Reoperation is thought to be a problem after lumbar fusion. Despite multiple studies, the fusion method that minimizes the need for subsequent surgery has yet to be determined. MATERIALS AND METHODS: A retrospective cohort study was conducted on 89 patients who had an isolated L4/5 decompression and fusion, from January 2006 to 2012. All patients had stenosis and degenerative spondylolisthesis at the L4/5 level. All surgeries were performed at a single center, using either PLF (31 patients) or PLF+TLIF (58 patients) techniques. Preoperative and postoperative patient-reported outcome measures (Oswestry disability index, visual analog scale back pain, visual analog scale leg pain) and radiographic parameters (L4/5 lordosis and overall lumbar lordosis) were measured. Patient satisfaction was acquired via a questionnaire. Chart reviews and patient questionnaires were used to determine the incidence of subsequent lumbar surgery over a minimum follow-up of 5 years. RESULTS: At an average of 8.7 years follow-up, 2 of 31 patients in the PLF group had subsequent lumbar surgery, compared with 16 of 58 patients in the PLF+TLIF group (6% vs. 28%; P=0.02). There were no significant differences between groups with respect to sex, age, body mass index, tobacco, perioperative measures, patient-reported outcomes, or radiographic parameters (P>0.05). CONCLUSIONS: Both PLF and PLF+TLIF are effective fusion methods for L4/5 stenosis and spondylolisthesis. In this study, patients treated with PLF were less likely to undergo a subsequent lumbar surgery. More research is needed to determine which factors influence whether PLF or PLF+TLIF should be used in these patients. LEVEL OF EVIDENCE: Level III.

Validation of the Fusion Risk Score for Thoracic and Lumbar Spine Fusion Procedures.

STUDY DESIGN: This is a retrospective cohort study. OBJECTIVE: This study aimed to determine whether the Fusion Risk Score (FRS) is valid for perioperative complications. SUMMARY OF BACKGROUND DATA: The FRS was previously formulated from a retrospective review of 364 fusion surgeries in patients over age 65. Patient demographics, comorbidities, surgical approach, levels, and osteotomies are incorporated in a weighted manner. This score correlated well with the risk of perioperative complications, operative time, estimated blood loss during surgery, and length of hospital stay. MATERIALS AND METHODS: A new cohort of patients was studied. Subjects were 65 years old or older and had undergone routine elective thoracic or lumbar fusion surgery. The FRS was calculated for each subject to estimate risk (low, medium, or high) for perioperative complications. Actual incidences of major complications in the first 90 days after the surgery were noted and statistically compared with the predicted risk. The FRS was compared with intensive care unit admittance, estimated blood loss, operative time, and hospital length of stay to determine whether the score was predictive. RESULTS: In total, 51% of our patients were at low risk (FRS, 1-3) for perioperative complications; 43% were at medium risk (FRS, 4-9); and 7% were at high risk (FRS, over 9). A total of 8% in the low-risk group, 23% in the medium-risk group, and 67% in the high-risk group actually developed significant perioperative complications. Medium-risk and high-risk patients experienced proportionally more perioperative complications than did low-risk patients; the difference was highly statistically significant. CONCLUSIONS: This study validated the association between the FRS and complications in the first 90 days after thoracolumbar spinal fusion surgery on the basis of patient and surgery characteristics. It also predicts the risk of intensive care unit admission, operative time, blood loss, and hospital length of stay.

Recurrent Surgical Site Infections in the Spine After Treatment With the Vacuum-assisted Closure (VAC) System.

STUDY DESIGN: This study retrospectively reviewed recurrences of surgical site infections (SSI) in spinal patients treated with vacuum-assisted closure (VAC) technology. OBJECTIVE: Identify patient and treatment factors associated with recurrence of SSI after VAC treatment. SUMMARY OF BACKGROUND DATA: Patients treated with VAC can achieve healing of deep spine wound infections; however, some patients develop a recurrent infection. Risk factors associated with a recurrence have not been identified. MATERIALS AND METHODS: One hundred and eleven patients with SSI after spine surgery from 2002 to 2010 were studied. They had been treated with irrigation and debridement, placement of VAC, and IV antibiotics. They subsequently were taken to surgery for primary closure of their wound. Patients with SSI who healed after the initial infection treatment were compared with patients who experienced recurrence. Patient and treatment factors that were studied included smoking status, body mass index, obesity status, diagnosis of diabetes, fusion surgery, methicillin-resistant Staphylococcus aureus, or polybacteria infection, number of irrigation and debridement treatments before closure, duration of IV antibiotic treatment, and duration of treatment time with VAC. Patients with SSI who healed after the initial treatment were compared with patients who experienced recurrence. RESULTS: Fourteen patients had at least one recurrence of wound infection. None of the patient or treatment factors was associated with the recurrence of a SSI. CONCLUSIONS: Among spine surgery patients with a SSI treated with the VAC system, those factors which predispose a patient to develop a recurrent SSI remain unknown. LEVEL OF STUDY: Level IV.

Prediction of health status based on postoperative radiographic variables in adult scoliosis.

OBJECTIVE: To evaluate the effect of surgical treatment on health related quality of life (HRQOL) and radiographic variables in patients with adult scoliosis. METHODS: Sixty-eight patients with adult spinal deformities underwent radiographic analysis. The enrollment criteria were as follows: age older than 18 years, adult degenerative or progressive idiopathic scoliosis (Cobb angle >10°), and surgical treatment within one year before this study was undertaken. The following variables were measured: curve type, apical level, curve magnitude, coronal and sagittal balance using a C7 plumb line (C7 PL) and gravity line, lateral intervertebral olisthesis, lumbar lordosis, sacral slope and pelvic tilt. HRQOL was assessed by the Oswestry Disability Index (ODI). Both preoperative and postoperative data were collected and changes in radiographically assessed variables and ODI scores attributable to surgery calculated; correlations between these changes were then assessed. The radiographically assessed variables and ODI scores were analyzed with SigmaStat (SPSS, Chicago, IL, USA). The level of statistical significance was set at P < 0.05. RESULTS: Surgical treatment resulted in improvements in ODI scores and several radiographically assessed variables, including sagittal balance, lumbar lordosis, lateral olisthesis and coronal Cobb angle. Only sagittal balance expressed as C7 PL was correlated to both preoperative and postoperative ODI. Gravity line, an alternative measurement of spinal balance, did not provide better correlations with HRQOL than C7 PL. CONCLUSIONS: Spinal balance assessed by gravity line did not provide a better correlation with HRQOL than C7 PL. Loss of sacral slope and retroverted pelvis are commonly seen in adult scoliosis and are not significantly changed by surgical treatment, including restoration of lumbar lordosis and sagittal balance.

Fusion risk score: evaluating baseline risk in thoracic and lumbar fusion surgery.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: The fusion risk score (FRS) is introduced to assess baseline risk of spine fusion surgery preoperatively. An objective method of stratifying risk allows the surgeon to control risk through tailoring intervention and explain differences in complication profile in high-complexity practice. SUMMARY OF BACKGROUND DATA: Research has identified an elevated risk of serious complications in performing spine fusion surgery in the elderly, yet the rate of such surgery continues to increase. A range of comorbidities and the surgical factors are demonstrated predictors of perioperative risk. METHODS: Retrospective review was made of 364 consecutive fusion surgical procedures in patients older than 65 years in an 18-month period. Logistic regression analysis was performed to identify factors predictive for the occurrence of perioperative events. The predictive variables were incorporated in a weighted fashion into the FRS scaled from 1 to 20. Patient demographics and comorbidities were incorporated into the FRS patient score (maximum 10) and surgical approach, levels, and osteotomies into the FRS procedure score (maximum 10). RESULTS: Multivariate analysis demonstrated chronic kidney disease (odds ratio [OR] = 5.3, 95% confidence interval [CI]: 1.5-18.6, P = 0.008), chronic obstructive pulmonary disease (OR = 5.3, 95% CI: 2.0-14.2, P < 0.001), ischemic heart disease (OR = 4.1, 95% CI: 2.0-8.4, P < 0.001), an open anterior approach (OR = 3.6, 95% CI: 1.4-9.3, P = 0.010), diabetes (OR = 3.0, 95% CI: 1.4-6.4, P = 0.004), previous spinal surgery at the same site (OR = 2.6, 95% CI: 1.3-4.9, P = 0.005), age (OR = 1.07, 95% CI: 1.01-1.13, P = 0.019), and the number of motion segments fused (P = 0.049) to be predictive of perioperative events. When applied, the FRS was highly predictive of perioperative events, intensive care unit admission, operative time, blood loss, and length of stay (all P < 0.0001). A score over threshold 9 carries a greater than 50% risk of perioperative events. CONCLUSION: The FRS predicts the risk of complications after spine fusion surgery on the basis of patient and surgery characteristics. It also predicts the risk of intensive care unit admission and correlates with operative time, blood loss, and postoperative length of stay. By balancing the FRS procedure score to the individual FRS patient score, the surgeon can quantify and control perioperative risk.

MRI measurement of neuroforaminal dimension at the index and supradjacent levels after anterior lumbar interbody fusion: a prospective study.

BACKGROUND: Anterior interbody fusion has previously been demonstrated to increase neuroforaminal height in a cadaveric model using cages. No prior study has prospectively assessed the relative change in magnetic resonance imaging (MRI) demonstrated neuroforaminal dimensions at the index and supradjacent levels, after anterior interbody fusion with a corticocancellous allograft in a series of patients without posterior decompression. The objective of this study was to determine how much foraminal dimension can be increased with indirect foraminal decompression alone via anterior interbody fusion, and to determine the effect of anterior lumbar interbody fusion on the dimensions of the supradjacent neuroforamina. METHODS: A prospective study comparing pre- and postoperative neuroforaminal dimensions on MRI scan among 26 consecutive patients undergoing anterior lumbar interbody fusion without posterior decompression was performed. We studies 26 consecutive patients (50 index levels) that had undergone anterior interbody fusion followed by posterior pedicle screw fixation without distraction or foraminotomy. We used preoperative and postoperative MRI imaging to assess the foraminal dimensions at each operated level on which the lumbar spine had been operated. The relative indirect foraminal decompression achieved was calculated. The foraminal dimension of the 26 supradjacent untreated levels was measured pre- and postoperatively to serve as a control and to determine any effects after anterior interbody fusion. RESULTS: In this study, 8 patients underwent 1 level fusion (L5-S1), 12 patients had 2 levels (L4-S1) and 6 patients had 3 levels (L3-S1). The average increase in foraminal dimension was 43.3% (p < 0.05)-19.2% for L3-4, 57.1% for L4-5, and 40.1% for L5-S1. Mean pre- and postoperative supradjacent neuroforaminal dimension measurements were 125.84 mm(2) and 124.89 mm(2), respectively. No significant difference was noted (p > 0.05). CONCLUSIONS: Anterior interbody fusion with a coriticocancellous allograft can significantly increase neuroforaminal dimension even in the absence of formal posterior distraction or foraminotomy; anterior interbody fusion with a coriticocancellous allograft has little effect on supradjacent neuroforaminal dimensions.

Spinal cord injury from electrocautery: observations in a porcine model using electromyography and motor evoked potentials.

We have previously investigated electromyographic (EMG) and transcranial motor evoked potential (MEP) abnormalities after mechanical spinal cord injury. We now report thermally generated porcine spinal cord injury, characterized by spinal cord generated hindlimb EMG injury activity and spinal cord motor conduction block (MEP loss). Electrocautery (EC) was delivered to thoracic level dural root sleeves within 6-8 mm of the spinal cord (n = 6). Temperature recordings were made near the spinal cord. EMG and MEP were recorded by multiple gluteobiceps intramuscular electrodes before, during, and after EC. Duration of EC was titrated to an end-point of spinal motor conduction block (MEP loss). In 5/6 roots, ipsilateral EMG injury activity was induced by EC. In 4/5 roots, EMG injury activity was identified before MEP loss. In all roots, a minimum of 20 s EC and a temperature maximum of at least 57 °C at the dural root sleeve were required to induce MEP loss. Unexpectedly, conduction block was preceded by an enhanced MEP in 4/6 trials. EMG injury activity, preceding MEP loss, can be seen during near spinal cord EC. Depolarization and facilitation of lumbar motor neurons by thermally excited descending spinal tracts likely explains both hindlimb EMG and an enhanced MEP signal (seen before conduction block) respectively. A thermal mechanism may play a role in some unexplained MEP losses during intraoperative monitoring. EMG recordings might help to detect abnormal discharges and forewarn the monitorist during both mechanical and thermal injury to the spinal cord.

Mechanical Load Study of Lumbar Center of Rotation and Lordosis and Its Potential Relationship to Formation of Rotatory Olisthesis.

INTRODUCTION: Rotatory olisthesis is a common finding of adult degenerative scoliosis. An in vitro model of rotatory olisthesis of the lumbar spine and its correlation with the center of rotation (COR) and lumbosacral lordosis (L3-S1) are presented. METHODS: Different centers of rotation and various angles of lumbosacral lordosis were tested for the production of rotatory olisthesis. The radiological finding of rotatory scoliosis was excacerbated with the center of rotation lying in the posterior column and with a normolordotic or hyperlordotic lumbosacral spine. Twenty-one synthetic models of L3-sacrum with simulation of certain anatomic restraints (ligaments and capsules) and disc disruption at L4-L5 were used. The COR was reproduced at the anterior, middle, or posterior column. A combination of a constant axial load at the lateral side of the upper vertebra and a similar size contralateral-side horizontal axial rotation force at the level of L4 vertebral body were applied to produce a rotatory olisthesis. The loaded specimens were immobilized at the end of the dynamic procedure and were imaged in two planes by fluoroscopy. The lateral and anteroposterior olisthesis at L4-L5 levels as well as L3-L5 scoliotic, L3-S1 lordotic Cobb angles and L4-L5 intervertebral rotation were measured. RESULTS: The radiologic finding of rotatory olisthesis (translation ≥ 1mm with rotation) appeared in the spinal units with the COR in the posterior column, although olisthesis was less than 1mm in specimens with the COR in the anterior or middle column. With COR in the posterior column and 40° to 60° of L3-S1 lordosis, rotatory olisthesis at the L4-L5 level was produced with anteroposterior olisthesis as the main component (p < .05). In specimens with 20° to 40° lordosis, lateral olisthesis was the main component of rotatory olisthesis (p < .05), and in less than 20° lordosis, rotatory olisthesis was minimum (translation less than 1 mm). CONCLUSION: During an in vitro study for the appearance of rotatory olisthesis in the lumbar spine, the COR has been identified to lie in the posterior elements. The main component of rotatory olisthesis is anteroposterior olisthesis and lateral olisthesis in normolordotic and hypolordotic lumbosacral spine, respectively. The described model of rotatory olisthesis in the lumbar spine may serve as a guide for the formation of this deformity and can be the base for future research in the treatment of rotatory olisthesis in degenerative lumbar scoliosis.

Supervised exercise, spinal manipulation, and home exercise for chronic low back pain: a randomized clinical trial.

BACKGROUND CONTEXT: Several conservative therapies have been shown to be beneficial in the treatment of chronic low back pain (CLBP), including different forms of exercise and spinal manipulative therapy (SMT). The efficacy of less time-consuming and less costly self-care interventions, for example, home exercise, remains inconclusive in CLBP populations. PURPOSE: The purpose of this study was to assess the relative efficacy of supervised exercise, spinal manipulation, and home exercise for the treatment of CLBP. STUDY DESIGN/SETTING: An observer-blinded and mixed-method randomized clinical trial conducted in a university research clinic in Bloomington, MN, USA. PATIENT SAMPLE: Individuals, 18 to 65 years of age, who had a primary complaint of mechanical LBP of at least 6-week duration with or without radiating pain to the lower extremity were included in this trial. OUTCOME MEASURES: Patient-rated outcomes were pain, disability, general health status, medication use, global improvement, and satisfaction. Trunk muscle endurance and strength were assessed by blinded examiners, and qualitative interviews were performed at the end of the 12-week treatment phase. METHODS: This prospective randomized clinical trial examined the short- (12 weeks) and long-term (52 weeks) relative efficacy of high-dose, supervised low-tech trunk exercise, chiropractic SMT, and a short course of home exercise and self-care advice for the treatment of LBP of at least 6-week duration. The study was approved by local institutional review boards. RESULTS: A total of 301 individuals were included in this trial. For all three treatment groups, outcomes improved during the 12 weeks of treatment. Those who received supervised trunk exercise were most satisfied with care and experienced the greatest gains in trunk muscle endurance and strength, but they did not significantly differ from those receiving chiropractic spinal manipulation or home exercise in terms of pain and other patient-rated individual outcomes, in both the short- and long-term. CONCLUSIONS: For CLBP, supervised exercise was significantly better than chiropractic spinal manipulation and home exercise in terms of satisfaction with treatment and trunk muscle endurance and strength. Although the short- and long-term differences between groups in patient-rated pain, disability, improvement, general health status, and medication use consistently favored the supervised exercise group, the differences were relatively small and not statistically significant for these individual outcomes.

The effect on the pullout strength by the timing of pedicle screw insertion after calcium phosphate cement injection.

STUDY DESIGN: Biomechanical Cadaveric Study. OBJECTIVE: To characterize the pullout strength of calcium phosphate cement augmented screws between 0 and 6 minutes after cement injection. SUMMARY OF BACKGROUND DATA: Earlier studies with calcium phosphate cement on pedicle screws inserted into a metal mold or sawbone have shown that the augmentation strength can be affected by the time between cement injection and screw insertion. However, these studies only compared soft cement to completely hardened cement with extended waiting times. These extended waiting times are impractical in live spinal surgeries. METHODS: Twenty-four pedicle screws were inserted and pulled out axially from cadaveric bone to make revision models. The 24 screw holes were randomly divided into 4 groups, with each group having 6 holes. For each group, identical pedicle screws were inserted at 0, 2, 4, and 6 minutes after injection with bioresorbable calcium phosphate cement (CPC). After 24 hours, the augmented screws were pulled out axially and their pullout strengths were compared. RESULTS: The difference between secondary pullout strength and primary pullout strength increased up to 4 minutes after cement injection but decreased after 6 minutes but without statistical difference among the 4 time settings (P>0.3). CONCLUSIONS: The augmented screws had similar fixation strength regardless of the time between cement mixture and screw insertion as long as they are inserted within 6 minutes. Augmentation power tends to increase up to 4 minutes after cement injection but decreases after 6 minutes.

Is it safe to back out pedicle screws after augmentation with polymethyl methacrylate or calcium phosphate cement? A biomechanical study.

STUDY DESIGN: Biomechanical cadaveric study. OBJECTIVE: To determine the torque required to remove pedicle screws augmented with polymethyl methacrylate (PMMA) or calcium phosphate cement (CPC); thus, proving the safety of back out of augmented screws in the osteopotoric model, which would be a more dangerous setting than the nonosteoporotic model. SUMMARY OF BACKGROUND DATA: To our knowledge, no earlier study has characterized the safety of backing out pedicle screw augmented with PMMA or CPC. METHODS: Pedicle screws were inserted in 24 osteoporotic vertebrae (48 pedicles). The maximal insertion torque and pullout strength of each screw were recorded. After pullout of the pedicle screws, the vertebrae were then randomized into 2 groups of 12 (24 pedicles) each. PMMA was injected into the pedicles in the first group and CPC was injected into the second group after which the pedicle screws were inserted. The pedicle screws were inserted into the pedicle holes augmented with PMMA or CPC, respectively. Finally, all augmented screws were backed out and the maximal removal torque was recorded using a digital torque wrench. RESULTS: Throughout the study, no incidence of pedicle or lamina fractures was observed. The average insertion torque was 0.5±0.27 and 0.45±0.29 N·m for groups 1 and 2, respectively (P=0.724). The average pullout strength was 723.1±391.7 and 671.2±383.0 N (P=0.950). After cement augmentation, the average removal torque was 0.77±0.31 and 0.81±0.26 N·m for PMMA and CPC, respectively (P=0.494). CONCLUSIONS: The results of this study showed that pedicle screws can be easily and safely backed out after augmentation with PMMA or CPC. The result of CPC, however, may only be valid before any bony ingrowth.

Radiculopathy in degenerative lumbar scoliosis: correlation of stenosis with relief from selective nerve root steroid injections.

OBJECTIVE: The purpose is to define the origin of radiculopathy of patients with degenerative lumbar scoliosis-stenosis and to assess the correlation between percentage of initial radicular leg pain relief with selective nerve root injections and lateral canal dimensions. DESIGN: Retrospective clinical study. SETTING AND PATIENTS: Thirty-six consecutive patients (average age 72) from Twin Cities Spine Center with degenerative lumbar scoliosis (average major curve 25°) and radicular symptoms were studied. INTERVENTIONS: Patients underwent 46 selective steroid injections of nerve roots concordant with clinical symptomatology. OUTCOME MEASURES: Radiographic measurements included major and lumbosacral curve Cobb angle. Computerized measurements of magnetic resonance imaging (MRI) included minimum subarticular height and foramen cross-sectional area of the nerve roots that were injected. Initial response from the nerve root injections was also rated. RESULTS: Twenty-five percent of nerve root symptoms were coming from the major curve, 72.2% from the lumbosacral hemicurve and 2.8% from both (P<0.001). The affected nerve roots were more frequently the L4 (34.8%) and L5 (28.3%) nerve roots. A total of 71.7% of radicular symptoms were originating from the concavity of the curve and 28.7% from the convexity (P<0.001). The relief from injections was more than 50% in 75% of the patients at 15 days postinjection. There was no statistical significant correlation (P>0.05) between the lateral canal dimensions and the initial response to injection of anesthetic plus steroid injection. CONCLUSIONS: In degenerative lumbar scoliotic curves, radicular symptoms are attributed mainly to nerve roots exiting from the concavity of the lumbosacral hemicurve. No evidence was found that the rate of initial relief from selective nerve root injections correlates with the degree of stenosis noted in the MRI.

Effect of number of fusion levels on S1 screws in long fusion construct in a calf spine model.

STUDY DESIGN: In vitro biomechanical study evaluating the effect of fusion levels on simulated S1 screws on calf spines. OBJECTIVE: To measure the stresses of simulated S1 screws as a function of increasing fusion levels in long-fusion construct. SUMMARY OF BACKGROUND DATA: Extension of long fusion to sacrum remains a difficult clinical challenge despite the recent knowledge and technology. Several biomechanical studies have evaluated the bending moment on sacral screw of various fixation techniques. The high risk of sacral screw failure has been primarily attributed to the long lever arm of instrumentation and pullout force on S1 screw. However, none of these studies characterized how the number of fusion levels affected the sacral screw stresses. Because the number of fusion levels is an important factor in considering additional fixation options to protect the sacral screws, the effect of fusion levels on sacral screw stresses must be understood. METHODS: Eight calf spines (T13-L5) were used in this study (L5 is simulated as S1). Twelve pedicle screws were inserted. A combination of strain gages were attached to the spinal rods located between L4 and L5. Pure flexion moment (7.5 Nm) was applied to the partially fused construct as the level of fusion varied between 1 and 5 levels. The number of fusion levels increased from lower vertebrae to upper vertebrae. The pullout force, bending moment, and transverse force acting on the S1 screw were calculated from the strain gage signals. One way repeated measure ANOVA was used to analyze the pullout force, bending moment, and transverse force data. RESULTS: The pullout force and transverse load had significant difference between single and multilevel fusion. However, no difference was found among multilevel fusion procedures (all P > 0.05). The mean pullout force was 29 ± 8 and mean transverse force was 139 ± 18 N. For bending moment, there was no statistical difference among all fusion levels. The average bending moment was 1.02 ± 0.34. Addition of anterior interbody cages at lower levels (L3-L4 and L4-L5) reduced the stresses on the simulated S1 screw by approximately 20% with P < 0.05. CONCLUSION: All three stresses, flexion moment, transverse load, and screw pullout force, must be considered in studying the biomechanics of long-fusion construct. There was no significant increase in sacral screw loading with increasing fusion levels when the same flexion moment was applied. It is postulated that the higher load present in long-fusion construct may lead to the premature failure of the lumbosacral fixation.

Biomechanical evaluation of an expandable meshed bag augmented with pedicle or facet screws for percutaneous lumbar interbody fusion.

OBJECTIVE: To evaluate the biomechanics of lumbar motion segments instrumented with stand-alone OptiMesh system augmented with posterior fixation using facet or pedicle screws and the efficacy of discectomy and disc distraction. BACKGROUND CONTEXT: OptiMesh bone graft containment system has been used for vertebral compression fractures and percutaneous lumbar interbody fusion. The filled mesh bag serves as the interbody device providing structural support to the motion segment being fused. No biomechanical data of this new device are available in the literature. METHODS: Twenty-four fresh human cadaveric lumbar motion segments were divided into two groups. In the control group, multidirectional flexibility testing was conducted after an intact condition and standard transforaminal lumbar interbody fusion (TLIF) procedure. In the OptiMesh group, testing was performed following intact, stand-alone OptiMesh procedure, OptiMesh with facet screws (placed using the transfacet approach), and OptiMesh with pedicle screws and rods. Range of motion (ROM) was calculated for each surgical treatment. The lordosis and disc height change of intact and instrumented specimens were measured in the lateral radiographs to evaluate the disc space distraction. In the OptiMesh group, cyclic loading in flexion extension (FE) was applied to measure cage subsidence or collapse (10,000 cycles at 6 Nm). After biomechanical testing, all the specimens were dissected to inspect the discectomy and end plate preparation. The area of discectomy was measured. RESULTS: The mean ROM of the intact specimens was 2.7°, 7.4°, and 7.2° in axial torsion (AT), lateral bending (LB), and FE, respectively. There was no difference between the control group and OptiMesh group. The mean ROM of the stand-alone OptiMesh system decreased to 2.4°, 5.1°, and 4.3° in AT, LB, and FE. The ROM decreased to 0.9° in AT, 2.2° in LB, and 0.9° in FE with OptiMesh system and facet screws. On average, OptiMesh system with pedicle screws and rods reduced the ROM to 1.3° in AT, 1.6° in LB, and 1.1° in FE. Compared with the intact condition and stand-alone OptiMesh system, both posterior fixation options had significant statistical difference (p<.001). In AT, ROM of facet screws was lower than that of pedicle screws (p < .05). There was no statistical difference between the facet and pedicle screws in LB and FE (p > .05). The mean volume of bone graft packed into each bag was 8.3 ± 1.5 cc. The average increase of lordosis was 0.6° ± 1.0° after meshed bag was deployed. The average distraction achieved by the OptiMesh system was 1.0 ± 0.6 mm. The average prepared area of discectomy was 42% of the total disc. The disc height change after cyclic loading was 0.2 mm. No subsidence or collapse was noticed. CONCLUSIONS: The OptiMesh system offers large volume of bone graft in the disc space with small access portals. The OptiMesh system had similar construct stability to that of standard TLIF procedure when posterior fixation was applied. However, the amount of distraction was limited without additional distraction tools. With the anterior support provided by the expandable meshed bag, facet screws had comparable construct stability to that of pedicle screws. Slightly higher stability was observed in facet screws in AT.

Healos graft carrier with bone marrow aspirate instead of allograft as adjunct to local autograft for posterolateral fusion in degenerative lumbar scoliosis: a minimum 2-year follow-up study.

OBJECT: The objective of this study was to examine the efficacy and safety of Healos graft carrier with bone marrow aspirate and local autograft compared with the results of allograft in patients with lumbar degenerative scoliosis undergoing posterolateral fusion. METHODS: Twenty-eight patients with degenerative scoliosis underwent posterolateral instrumented fusion and decompression. Patients were grouped according to the graft used. Group A consisted of 12 cases in which the authors used a Healos graft carrier, bone marrow aspirate, and local autograft, and Group B consisted of 16 cases in which the authors used cancellous allograft and local autograft. Patients were followed for a minimum of 2 years postoperatively in terms of pain (visual analog scale), function (Oswestry Disability Index), curve magnitude (Cobb angle), and fusion status (plain and dynamic radiographs). The 2 groups did not differ statistically significantly (p > 0.05) in age, sex, smoking habits, magnitude of preoperative visual analog scale score, Oswestry Disability Index score, Cobb angle, or number of levels requiring decompression and fusion. RESULTS: The groups had similar (p > 0.05) results in terms of pain, function, curve progression, and fusion rates at the 2-year follow-up examination. Radiographic fusion was achieved in all but 2 cases, 1 in each group, in which the patients were asymptomatic. Patients in the allograft group (Group B) showed evidence of fusion earlier than in the Healos group (p < 0.05). No toxicity from Healos graft was recorded. CONCLUSIONS: The combination of Healos hydroxyapatite sponge and bone marrow aspirate plus local allograft had significantly slower fusion rates but equal clinical outcomes compared with cancellous allograft plus local autograft when used for posterolateral fusion in patients with degenerative lumbar scoliosis.

Surgical outcomes of decompression, decompression with limited fusion, and decompression with full curve fusion for degenerative scoliosis with radiculopathy.

STUDY DESIGN: A retrospective clinical cohort study at a single spine center of patients with degenerative scoliosis and radiculopathy severe enough to require surgery. OBJECTIVE: To evaluate the functional outcomes of 3 surgeries for degenerative scoliosis with radiculopathy; decompression alone, decompression and limited fusion, and decompression and full curve fusion. SUMMARY OF BACKGROUND DATA: Although these 3 surgical treatments have all been described for this problem, there exists little information as to what outcomes to expect. METHODS: The study cohort consisted of 85 patients who met the inclusion criteria of degenerative scoliosis and radiculopathy, who had undergone 1 of the above 3 surgeries, who had not had any previous lumbar spine surgery, who had a minimum follow-up of at least 2 years, and who had filled out preoperative and postoperative functional evaluation forms including SF-36, Oswestry Disability Index, Roland Morris Scores, and a satisfaction questionnaire. Logistic regression analysis was conducted to predict the likelihood of success as related to decompression alone of rotatory olisthetic segments, extent of fusion, and postoperative sagittal balance. Patient demographics including curve magnitude, operative blood loss, length of hospital stay, complications, and need for revision surgeries were analyzed. The patients having decompression alone had the highest mean age (76.4 years) compared to decompression and limited fusion (70.4), and decompression and full curve fusion (62.5). RESULTS: Cobb scoliosis angles remained unchanged in the 2 groups not having full curve fusion, while the full curve fusion group changed from a mean 39° before surgery to 19° at follow-up. The complication rate was highest (56%) in the full fusion group, was 40% in the limited fusion group, and 10% in the decompression alone group. The overall SF-36 analysis showed significant improvement in bodily pain, social function, role emotional, mental health, and mental composite domains. Oswestry Disability Indexes improved significantly in the decompression alone and limited fusion groups, but not in the full fusion group. In contrast, the satisfaction questionnaire showed the highest success to be in the full-curve fusion group and the lowest in the decompression-only group.Regression analysis revealed that sacrum to curve apex fusions and positive postoperative sagittal imbalance were associated with poor outcomes. CONCLUSION: Both good and poor results were seen with each of the 3 procedures.