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°.

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.

Adding Vertebral Bone Quality to the Fusion Risk Score: Does It Improve Predictions of Postoperative Complications?

STUDY DESIGN: Retrospective review of prospectively collected data. OBJECTIVE: The current study evaluates whether the addition of the Vertebral Bone Quality (VBQ) score to the Fusion Risk Score (FRS) improves its ability to predict perioperative outcomes. SUMMARY OF BACKGROUND DATA: The FRS was developed to assess preoperative risk in patients undergoing thoracic and lumbar fusions. It includes patient-derived and surgical variables, but it does not include one that directly accounts for bone health. The VBQ score allows assessment of bone quality and has been shown to correlate to DEXA-measured bone mineral density (BMD) scores. METHODS: The VBQ score was weighted based on a regression model and then added to the FRS (FRS/VBQ). The ability of the two scores to predict the outcomes was then assessed using the area under the curve (AUC). PATIENT SAMPLE: Patients undergoing elective thoracic and lumbar spinal fusion from January 2019 to June 2020 were included. OUTCOME MEASURES: The study evaluated various perioperative adverse outcomes, including major and minor adverse events, discharge other than home, extended length of stay, 90-day emergency department visits, 90-day readmission, and 90-day and 2-year reoperation rates. RESULTS: A total of 353 met the inclusion and exclusion criteria. The FRS/VBQ demonstrated improved predictive ability compared with the FRS alone when evaluating 90-day reoperation. Both scores showed fair predictive ability for any adverse event, major adverse events, minor adverse events, and 2-year reoperation rates, with AUCs ranging from 0.700 to 0.737. Both had poor predictive ability for the other outcomes. CONCLUSIONS: Adding VBQ to the FRS significantly enhances its predictive accuracy for reoperation rate. This updated risk score provides a more comprehensive understanding of a patient's preoperative risk profile, aiding both patients and physicians in assessing surgical risks and optimizing outcomes through preoperative risk stratification. LEVEL OF EVIDENCE: 3.

Removal of Spinal Instrumentation Is Not Required to Successfully Treat Postoperative Wound Infections in Most Cases.

INTRODUCTION: Controversy exists regarding whether spinal implants need to be removed to treat postoperative deep wound infections (DWIs). This retrospective study aimed to determine whether the removal or retention of implants impacts the successful treatment of a DWI after spine surgery. METHODS: Postoperative spine surgery patients presenting with signs of infection who underwent irrigation and debridement (I&D) at Twin Cities Spine Surgeons at Abbott Northwestern Hospital, Minnesota, USA, were studied. First, the persistence of infection when implants were retained or removed was assessed. Second, we analyzed the persistence of infection with respect to the number of I&D, the use of vacuum-assisted closure (VAC) treatment, pseudoarthrosis status, and functional outcomes. RESULTS: One hundred thirty-five patients were included. Treatment of infection with retention of implants occurred in 64% (87/135); of these, 7% (6/87) had a persistent infection. Of patients with implant removal (36%, 48/135), 6% (3/48) had a persistent infection. Thus, we observed no difference between treatment with implants present compared to implants removed (p = 1.0). Fifty of the 135 patients (37%) received I&D and primary wound closure, and 85 (63%) patients received I&D and VAC treatment. There was no statistical difference between primary wound closure and VAC treatment (p = 0.15) with respect to persistence. Repeat I&D with VAC (three or more times) had a significantly lower rate of recurrence than those with two I&Ds. Pseudoarthrosis and persistent infection were unrelated. At minimum one-year follow-up, achieving a minimum clinically important difference in functional outcome was independent of persistent infection status. CONCLUSION: Persistent infection was unrelated to the retention of implants. When VAC treatment was deemed necessary, more than two I&Ds resulted in a significantly better cure for infection. Those with a persistent infection were no more likely to exhibit pseudoarthrosis than those with no persistent infection. All patients showed improvement in functional outcomes at minimum one-year follow-up.

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.

Vacuum-Assisted Wound Closure Management for Posterior Lumbar Spine Infections.

A postoperative infection involving the tissues deep to the fascia is defined as a deep wound infection (DWI). Management of such infections after lumbar spinal surgery remains a challenge. One strategy is the use of vacuum-assisted wound closure (VAC) which applies negative pressure to the wound to improve microcirculation and to promote the formation of granulation tissue. When combined with antibiotics, VAC has been shown to successfully treat DWIs and is now a common strategy for treating deep postoperative wound infections after spinal surgery. In this article, we review the technique of VAC, its mechanism of action, indications and contraindications, and clinical outcomes in the treatment of DWIs after lumbar spinal surgery.

Provocative Discography: Diagnostic Efficacy and Safety in Symptomatic Degenerative Disk Disease.

STUDY DESIGN: This was a retrospective cohort analysis. OBJECTIVE: The objective of this study was to report the efficacy and safety profile of provocative discography. SUMMARY OF BACKGROUND DATA: It is reported that the provocative discogram as a diagnostic test for symptomatic degenerative disk disease induces disk degeneration. MATERIALS AND METHODS: Discogram cases from 1998 to 2011 were identified. A matched control group with no discogram was identified. Both had pre-magnetic resonance imaging (MRI) and post-MRI with 5 years minimum between MRI studies. Statistics were generated by group for each level and for all levels combined. RESULTS: The discogram cohort comprised 53 patients (193 disks). The control group had 51 subjects (255 disks). There were no significant demographic differences between the groups. Time intervals between the index and follow-up MRI were 11 and 8 years for the discogram and control groups, respectively. The most common injected level was L4-L5; the most painful level was L5-S1 (Visual Analog Scale=7.9); the most concordant level was L5-S1 (75%). The most deranged level as seen on discography was L5-S1 (98%). Degeneration from normal to abnormal MRI among discogram patients was 60%. For controls, the rate was 33%. The discogram and control cohorts were statistically different (P<0.01). Among discogram patients, 58% had a fusion surgery between MRI studies. Comparing the discogram group without interval fusion to controls, the degeneration rate was not different at a 5 years' minimum follow-up. CONCLUSIONS: The L5-S1 intervertebral disk level was the most painful, concordant, and deranged level as seen on discogram. Patients who underwent a provocative discogram and interval fusion had a higher rate of subsequent degeneration than similar low back pain sufferers with no discogram. Degeneration rates were comparable at 5 years' minimum follow-up between discogram patients without interval spine fusion and patients without discogram exposure. The provocative discogram did not accelerate degeneration among these patients.

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.

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.

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.

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).

Subaxial cervical pedicle screw insertion with newly defined entry point and trajectory: accuracy evaluation in cadavers.

Successful placement of cervical pedicle screws requires accurate identification of both entry point and trajectory. However, literature has not provided consistent recommendations regarding the direction of pedicle screw insertion and entry point location. The objective of this study was to define a guideline regarding the optimal entry point and trajectory in placing subaxial cervical pedicle screws and to evaluate the screw accuracy in cadaver cervical spines. The guideline for entry point and trajectory for each vertebra was established based on the recently published morphometric data. Six fresh frozen cervical spines (C3-C7) were used. There were two men and four women. After posterior exposure, the entry point was determined and the cortical bone of the entry point was removed using a 2-mm burr. Pilot holes were created with a cervical probe based on the guideline using fluoroscopy. After tapping, 3.5-mm screws with appropriate length were inserted. After screw insertion, every vertebra was dissected and inspected for pedicle breach. The pedicle width, height, pedicle transverse angulation and actual screw insertion angle were measured. A total of 60 pedicle screws were inserted. No statistical difference in pedicle width and height was found between the left and right sides for each level. The overall accuracy of pedicle screws was 83.3%. The remaining 13.3% screws had noncritical breach, and 3.3% had critical breach. The critical breach was not caused by the guideline. There was no statistical difference between the pedicle transverse angulation and the actual screw trajectory created using the guideline. There was statistical difference in pedicle width between the breach and non-breach screws. In conclusion, high success rate of subaxial cervical pedicle screw placement can be achieved using the recently proposed operative guideline and oblique views of fluoroscopy. However, careful preoperative planning and good surgical skills are still required to ensure screw placement accuracy and to reduce the risk of neural and vascular injury.

Alignment of pedicle screws with pilot holes: can tapping improve screw trajectory in thoracic spines?

Pedicle screws are placed using pilot holes. The trajectory of pilot holes can be verified by pedicle sounding or radiographs. However, a pilot hole alone does not insure that the screw will follow the pilot hole. No studies have characterized the risk of misalignment of a pedicle screw with respect to its pilot hole trajectory. The objective of this study was to measure the misalignment angles between pedicle screws and pilot holes with or without tapping. Six human cadaveric thoracic spines were used. One hundred and forty pilot holes were created with a straight probe. Steel wires were temporarily inserted and their positions were recorded with CT scans. The left pedicles were tapped with 4.5 mm fluted tap and the right pedicles remained untapped. Pedicle screws (5.5 mm) were inserted into the tapped and untapped pedicles followed by CT scans. The trajectories of pilot holes and screws were calculated using three-dimensional vector analysis. A total of 133 pilot holes (95%) were inside pedicles. For the untapped side, 14 out of 68 (20%) screws did not follow the pilot holes and were outside the pedicles. For the tapped side, 2 out of 65 (3%) did not follow and breached the pedicles. The average misalignment angles between the screw and pilot hole trajectory were 7.7 degrees +/- 6.5 degrees and 5.6 degrees +/- 3.2 degrees for the untapped side and tapped side, respectively (P < 0.05). Most pedicle screws had lateral screw breach (13 out of 16) whereas most pilot holes had medial pedicle breach (6 out of 7). Tapping of pilot holes (1 mm undertap) helps align pedicle screws and reduces the risk of screw malposition. Although most pedicle screws had lateral breach, the risk of medial pedicle breach of the pilot holes must be recognized.

Biomechanical comparison of transpedicular versus extrapedicular vertebroplasty using polymethylmethacrylate.

STUDY DESIGN: An in vitro biomechanical study using osteoporotic cadaveric vertebrae. OBJECTIVE: To compare the biomechanics of transpedicular and extrapedicular approaches in polymethylmethacrylate vertebroplasty in terms of height restoration, strength, and stiffness. SUMMARY BACKGROUND DATA: Cement is typically injected through a transpedicular approach in both vertebroplasty and kyphoplasty procedures. Previous biomechanical studies were primarily focused on the transpedicular approach. Extrapedicular approach has been recently developed to provide more symmetric cement filling and has good clinical results. However, no biomechanical data are available to compare these 2 techniques. METHODS: Twenty-four osteoporotic vertebral bodies were randomly divided into 2 groups for either transpedicular or extrapedicular vertebroplasty. Six lumbar and 6 thoracic vertebrae were used for each group. Each vertebral body was compressed by 25% of its original height and its strength and stiffness were measured. The vertebral bodies were treated with polymethylmethacrylate using either transpedicular or extrapedicular approach. The height restoration was measured before the treated vertebrae were recompressed to determine posttreatment strength and stiffness. RESULTS: Both techniques increased vertebral strength by approximately 50% of the intact strength. There was no statistical difference in posttreatment strength between these 2 techniques. However, the transpedicular technique had higher stiffness recovery (70% to 80%) from the intact stiffness than the extrapedicular technique (60%). The extrapedicular approach achieved greater height restoration in thoracic vertebrae. CONCLUSIONS: Both extrapedicular and transpedicular techniques increased strength but reduced stiffness compared with the intact condition. The extrapedicular technique achieved greater height restoration possibly attributed to its easier access to the fracture site. These biomechanical data provide useful information when selecting an approach for cement injection in vertebroplasty procedures.

Symptomatic pseudarthrosis requiring revision surgery after 1- or 2-level ACDF with plating: peek versus allograft.

BACKGROUND: Polyetheretherketone (PEEK) and machined allograft interbody spacers are among devices used as fusion adjuncts in anterior cervical discectomy and fusion (ACDF). Most results are good to excellent but some patients develop pseudarthrosis. We compared the reoperation rates for pseudarthrosis following 1- or 2-level ACDF with PEEK or allograft cages. METHODS: This was a retrospective cohort study. We reviewed patients who underwent 1- or 2-level ACDF. The rate of subsequent surgery for pseudarthrosis was calculated for cases confirmed by computerized tomography. Patient-reported outcomes were collected at post-index surgery follow-up and post-revision ACDF follow-up. Radiographic parameters were assessed at a minimum of 1-year post-op on all patients. RESULTS: Two hundred and nine patients were included: 167 received allograft and 42 received PEEK. Subsidence was demonstrated in 31% of allograft and 29% of PEEK patients. There were no significant differences in clinical outcomes between allograft and PEEK groups. Clinical outcomes were not adversely affected by subsidence. Reoperation for pseudarthrosis was performed in 8% of allograft patients and 14% of PEEK patients (not statistically different). Improvement in patient-reported outcome was significantly better for patients without symptomatic post-operative pseudarthrosis. CONCLUSIONS: Both allograft and PEEK spacers are acceptable options for ACDF surgery. Similar clinical outcomes and rates of radiographic subsidence were found. Subsidence was not a factor in clinical outcomes. Reoperation for pseudarthrosis was associated with poor outcomes. A higher incidence of revision for symptomatic pseudarthrosis occurred in the PEEK group, but this was not statistically significant.

Biomechanical evaluation of a new AxiaLIF technique for two-level lumbar fusion.

Single level axial lumbar interbody fusion (AxiaLIF) using a transsacral rod through a paracoccygeal approach has been developed with promising early clinical results and biomechanical stability. Recently, the transsacral rod has been extended to perform a two-level fusion at both L4-L5 and L5-S1 levels (AxiaLIF II). No biomechanical studies have been conducted on multilevel fusion using the AxiaLIF technique. In this study, the biomechanics of L4-S1 motion segments instrumented with the AxiaLIF II transsacral rod was evaluated. Six human cadaveric lumbosacral spine segments from L4 to S1 were used (age ranges 46-74 years). Unconstrained and non-destructive pure moments in axial torsion, lateral bending, and flexion extension were applied to each specimen following intact, standalone AxiaLIF II, and AxiaLIF II with two posterior fixation options: facet screws and pedicle screws with rods. Range of motion was calculated from the raw data collected with an optical motion tracking system. The two-level transsacral rod was successfully inserted in all the specimens. At L4-L5 level in axial torsion (AT) and flexion extension (FE), none of the surgical treatments showed statistically significant difference between the procedures (all P > 0.05) although facet screws and pedicle screws had higher stability on average. In lateral bending (LB), the two posterior fixation techniques had significantly higher construct stability (P < 0.05) than the standalone rod. No significant difference was found between facet screws and pedicle screws (P = 0.821). At L5-S1 level in AT and LB, none of the surgical treatments were found to be statistically significant (all P > 0.05). In FE, standalone two-level transsacral rod had significantly higher range of motion (ROM) compared with the posterior fixation techniques (P < 0.05). In conclusion, the standalone rod reduced intact ROM significantly. Supplementary fixations including facet screws and pedicle screws are required to achieve higher construct stability for successful fusion. Further clinical studies are essential to evaluate the practical success of this technique.

Clinical and radiological outcome of anterior-posterior fusion versus transforaminal lumbar interbody fusion for symptomatic disc degeneration: a retrospective comparative study of 133 patients.

Abundant data are available for direct anterior/posterior spine fusion (APF) and some for transforaminal lumbar interbody fusion (TLIF), but only few studies from one institution compares the two techniques. One-hundred and thirty-three patients were retrospectively analyzed, 68 having APF and 65 having TLIF. All patients had symptomatic disc degeneration of the lumbar spine. Only those with one or two-level surgeries were included. Clinical chart and radiologic reviews were done, fusion solidity assessed, and functional outcomes determined by pre- and postoperative SF-36 and postoperative Oswestry Disability Index (ODI), and a satisfaction questionnaire. The minimum follow-up was 24 months. The mean operating room time and hospital length of stay were less in the TLIF group. The blood loss was slightly less in the TLIF group (409 vs. 480 cc.). Intra-operative complications were higher in the APF group, mostly due to vein lacerations in the anterior retroperitoneal approach. Postoperative complications were higher in the TLIF group due to graft material extruding against the nerve root or wound drainage. The pseudarthrosis rate was statistically equal (APF 17.6% and TLIF 23.1%) and was higher than most published reports. Significant improvements were noted in both groups for the SF-36 questionnaires. The mean ODI scores at follow-up were 33.5 for the APF and 39.5 for the TLIF group. The patient satisfaction rate was equal for the two groups.

A concomitant posterior approach improves fusion rates but not overall reoperation rates in multilevel cervical fusion for spondylosis.

STUDY DESIGN: Retrospective comparative study of 2 approaches to multilevel fusion for cervical spondylosis in consecutive patients at a single institution. OBJECTIVE: To provide justification for a concomitant posterior approach in multilevel cervical fusion for spondylosis by demonstrating decreased pseudarthrosis and reoperation rates. SUMMARY OF BACKGROUND DATA: Among the factors that affect cervical rates is the number of levels, such that increasing the number of levels leads to lower fusion rates. Because of this, modifications have been sought to improve union in multilevel procedures. One option is an antero-posterior (AP) approach or circumferential arthrodesis. METHODS: Seventy-eight consecutive patients who underwent multilevel cervical fusion at a single institution and with minimum 2-year follow-up data were divided into an anterior-only group (anterior: n=55), and an AP group (AP: n=23). Union was assessed by surgical exploration, computerized tomography scan, and flexion-extension radiographs. The groups were compared in terms of pseudarthrosis rates and reoperation rates. RESULTS: Using chi(2) analysis, there was a significant difference in pseudarthrosis rates (anterior 38% vs. AP 0%; P<0.001), and reoperation rate for pseudarthrosis (anterior 22% vs. AP 0%; P=0.01). There were no differences in overall (anterior 36% vs. AP 30%; P=0.62) and early (anterior 15% vs. AP 26%; P=0.13) reoperation rates, but late reoperations were increased in the anterior group (24% vs. AP 4%; P=0.043). CONCLUSIONS: A concomitant posterior fusion significantly reduced the incidence of pseudarthrosis (0% vs. 38%) and pseudarthrosis-related reoperations (0% vs. 22%) compared with traditional anterior-only fusion. However, this did not translate to a difference in overall reoperation rates. The majority of reoperations in the AP group (86%) were performed within 6 months, whereas those in the anterior-only group (65%) were performed later, which was generally when a pseudarthrosis became evident.

Treatment of degenerative spondylolisthesis by instrumented posterolateral versus instrumented posterolateral with transforaminal lumbar interbody single-level fusion.

BACKGROUND: The purpose of this study was to compare outcomes of patients with degenerative spondylolisthesis treated by posterolateral lumbar fusion (PLF) versus PLF with transforaminal lumbar interbody fusion (PLF + TLIF). Studies of PLF versus PLF + TLIF have shown either equivalence or support for PLF + TLIF in lumbar spine surgery. Many are heterogeneous in the conditions treated, with few considering only spondylolisthesis of degenerative origin. Radiographic outcomes tend to favor PLF + TLIF, but this has not translated into better clinical outcomes. METHODS: This was a retrospective cohort study. Forty-nine patients undergoing single-level PLF and seventy patients undergoing single-level PLF + TLIF with two-year follow-up were retrospectively reviewed. Demographics, Oswestry Disability Index (ODI), implant cost, surgical data, and complications were analyzed. RESULTS: There was no difference in ODI improvement at two-year follow-up between the cohorts (P=0.97). Dural tears were more common in the PLF cohort (P<0.01), but otherwise complication and reoperation rates were similar. Implant cost (P<0.01) and operative time (P=0.01) were higher in the PLF + TLIF cohort. CONCLUSIONS: The addition of a TLIF to a PLF did not result in a functional improvement in the treatment of degenerative spondylolisthesis as measured by the ODI.