Lumbar Disc Degeneration Affects the Risk of Rod Fracture Following PSO; A Finite Element Study.

STUDY DESIGN: Finite element (FE) study. OBJECTIVE: Pedicle subtraction osteotomy (PSO) is a surgical method to correct sagittal plane deformities. In this study, we aimed to investigate the biomechanical effects of lumbar disc degeneration on the instrumentation following PSO and assess the effects of using interbody spacers adjacent to the PSO level in a long instrumented spinal construct. METHODS: A spinopelvic model (T10-pelvis) with PSO at the L3 level was used to generate 3 different simplified grades of degenerated lumbar discs (mild (Pfirrmann grade III), moderate (Pfirrmann grade IV), and severe (Pfirrmann grade V)). Instrumentation included eighteen pedicle screws and bilateral primary rods. To investigate the effect of interbody spacers, the model with normal disc height was modified to accommodate 2 interbody spacers adjacent to the PSO level through a lateral approach. For the models, the rods' stress distribution, PSO site force values, and the spine range of motion (ROM) were recorded. RESULTS: The mildly, moderately, and severely degenerated models indicated approximately 10%, 26%, and 40% decrease in flexion/extension motion, respectively. Supplementing the instrumented spinopelvic PSO model using interbody spacers reduced the ROM by 22%, 21%, 4%, and 11% in flexion, extension, lateral bending, and axial rotation, respectively. The FE results illustrated lower von Mises stress on the rods and higher forces at the PSO site at higher degeneration grades and while using the interbody spacers. CONCLUSIONS: Larger and less degenerated discs adjacent to the PSO site may warrant consideration for interbody cage instrumentation to decrease the risk of rod fracture and PSO site non-union.

Biomechanical comparison of multi-rod constructs by satellite rod configurations (in-line vs. lateral) and screw types (monoaxial vs. polyaxial) spanning a lumbar pedicle subtraction osteotomy (PSO): is there an optimal configuration?

PURPOSE: Multi-rod constructs are used commonly to stabilize pedicle subtraction osteotomies (PSO). This study aimed to evaluate biomechanical properties of different satellite rod configurations and effects of screw-type spanning a PSO. METHODS: A validated 3D spinopelvic finite element model with a L3 PSO (30°) was used to evaluate 5 models: (1) Control (T10-pelvis + 2 rods); (2) lateral satellite rods connected via offsets to monoaxial screws (LatSat-Mono) or (3) polyaxial screws (LatSat-Poly); (4) in-line satellite rods connected to monoaxial screws (InSat-Mono) or (4) polyaxial screws (InSat-Poly). Global and PSO range of motions (ROM) were recorded. Rods' von Mises stresses and PSO forces were recorded and the percent differences from Control were calculated. RESULTS: All satellite rods (save InSat-Mono) increased PSO ROM and decreased primary rods' von Mises stresses at the PSO. Lateral rods increased PSO forces (LatSat-Mono:347.1 N; LatSat-Poly:348.6 N; Control:336 N) and had relatively lower stresses, while in-line rods decreased PSO forces (InSat-Mono:280.1 N; InSat-Poly:330.7 N) and had relatively higher stresses. Relative to polyaxial screws, monoaxial screws further decreased PSO ROM, increased satellite rods' stresses, and decreased PSO forces for in-line rods, but did not change PSO forces for lateral rods. CONCLUSION: Multi-rod constructs using in-line and lateral satellite rods across a PSO reduced primary rods' stresses. Subtle differences in biomechanics suggest lateral satellite rods, irrespective of screw type, increase PSO forces and lower rod stresses compared to in-line satellite rods, which had a high degree of posterior instrumentation stress shielding and lower PSO forces. Clinical studies are warranted to determine if these findings influence clinical outcomes.

The impact of age on surgical goals for spinopelvic alignment in minimally invasive surgery for adult spinal deformity.

OBJECTIVEAchieving appropriate spinopelvic alignment in deformity surgery has been correlated with improvement in pain and disability. Minimally invasive surgery (MIS) techniques have been used to treat adult spinal deformity (ASD); however, there is concern for inadequate sagittal plane correction. Because age can influence the degree of sagittal correction required, the purpose of this study was to analyze whether obtaining optimal spinopelvic alignment is required in the elderly to obtain clinical improvement.METHODSA multicenter database of ASD patients was queried. Inclusion criteria were age ≥ 18 years; an MIS component as part of the index procedure; at least one of the following: pelvic tilt (PT) > 20°, sagittal vertical axis (SVA) > 50 mm, pelvic incidence to lumbar lordosis (PI-LL) mismatch > 10°, or coronal curve > 20°; and minimum follow-up of 2 years. Patients were stratified into younger (< 65 years) and older (≥ 65 years) cohorts. Within each cohort, patients were categorized into aligned (AL) or mal-aligned (MAL) subgroups based on postoperative radiographic measurements. Mal-alignment was defined as a PI-LL > 10° or SVA > 50 mm. Pre- and postoperative radiographic and clinical outcomes were compared.RESULTSOf the 185 patients, 107 were in the younger cohort and 78 in the older cohort. Based on postoperative radiographs, 36 (33.6%) of the younger patients were in the AL subgroup and 71 (66.4%) were in the MAL subgroup. The older patients were divided into 2 subgroups based on alignment; there were 26 (33.3%) patients in the AL and 52 (66.7%) in the MAL subgroups. Overall, patients within both younger and older cohorts significantly improved with regard to postoperative visual analog scale (VAS) scores for back and leg pain and Oswestry Disability Index (ODI) scores. In the younger cohort, there were no significant differences in postoperative VAS back and leg pain scores between the AL and MAL subgroups. However, the postoperative ODI score of 37.9 in the MAL subgroup was significantly worse than the ODI score of 28.5 in the AL subgroup (p = 0.019). In the older cohort, there were no significant differences in postoperative VAS back and leg pain score or ODI between the AL and MAL subgroups.CONCLUSIONSMIS techniques did not achieve optimal spinopelvic alignment in most cases. However, age appears to impact the degree of sagittal correction required. In older patients, optimal spinopelvic alignment thresholds did not need to be achieved to obtain similar symptomatic improvement. Conversely, in younger patients stricter adherence to optimal spinopelvic alignment thresholds may be needed.https://thejns.org/doi/abs/10.3171/2018.4.SPINE171153.

Curve Laterality for Lateral Lumbar Interbody Fusion in Adult Scoliosis Surgery: The Concave Versus Convex Controversy.

BACKGROUND: Minimally invasive lateral lumbar interbody fusion (LLIF) is an effective adjunct in adult degenerative scoliosis (ADS) surgery. LLIF approaches performed from the concavity or convexity have inherent approach-related risks and benefits. OBJECTIVE: To analyze LLIF approach-related complications and radiographic and clinical outcomes in patients with ADS. METHODS: A multicenter retrospective review of a minimally invasive adult spinal deformity database was queried with a minimum of 2-yr follow-up. Patients were divided into 2 groups as determined by the side of the curve from which the LLIF was performed: concave or convex. RESULTS: No differences between groups were noted in demographic, and preoperative or postoperative radiographic parameters (all P > .05). There were 8 total complications in the convex group (34.8%) and 21 complications in the concave group (52.5%; P = .17). A subgroup analysis was performed in 49 patients in whom L4-5 was in the primary curve and not in the fractional curve. In this subset of patients, there were 6 complications in the convex group (31.6%) compared to 19 in the concave group (63.3%; P < .05) and both groups experienced significant improvements in coronal Cobb angle, Oswestry Disability Index, and Visual Analog Scale score with no difference between groups. CONCLUSION: Patients undergoing LLIF for ADS had no statistically significant clinical or operative complication rates regardless of a concave or convex approach to the curve. Clinical outcomes and coronal plane deformity improved regardless of approach side. However, in cases wherein L4-5 is in the primary curve, approaching the fractional curve at L4-5 from the concavity may be associated with a higher complication rate compared to a convex approach.

Impact of case type, length of stay, institution type, and comorbidities on Medicare diagnosis-related group reimbursement for adult spinal deformity surgery.

OBJECTIVE The aim of this study was to educate medical professionals about potential financial impacts of improper diagnosis-related group (DRG) coding in adult spinal deformity (ASD) surgery. METHODS Medicare's Inpatient Prospective Payment System PC Pricer database was used to collect 2015 reimbursement data for ASD procedures from 12 hospitals. Case type, hospital type/location, number of operative levels, proper coding, length of stay, and complications/comorbidities (CCs) were analyzed for effects on reimbursement. DRGs were used to categorize cases into 3 types: 1) anterior or posterior only fusion, 2) anterior fusion with posterior percutaneous fixation with no dorsal fusion, and 3) combined anterior and posterior fixation and fusion. RESULTS Pooling institutions, cases were reimbursed the same for single-level and multilevel ASD surgery. Longer stay, from 3 to 8 days, resulted in an additional $1400 per stay. Posterior fusion was an additional $6588, while CCs increased reimbursement by approximately $13,000. Academic institutions received higher reimbursement than private institutions, i.e., approximately $14,000 (Case Types 1 and 2) and approximately $16,000 (Case Type 3). Urban institutions received higher reimbursement than suburban institutions, i.e., approximately $3000 (Case Types 1 and 2) and approximately $3500 (Case Type 3). Longer stay, from 3 to 8 days, increased reimbursement between $208 and $494 for private institutions and between $1397 and $1879 for academic institutions per stay. CONCLUSIONS Reimbursement is based on many factors not controlled by surgeons or hospitals, but proper DRG coding can significantly impact the financial health of hospitals and availability of quality patient care.

Does Spanning a Lateral Lumbar Interbody Cage Across the Vertebral Ring Apophysis Increase Loads Required for Failure and Mitigate Endplate Violation.

STUDY DESIGN: Randomized Biomechanical Cadaveric Study-Level II. OBJECTIVE: We aimed to elucidate that placing lateral lumbar interbody cages that span the stronger ring apophysis will require increasing loads for failure, decreasing rates of subsidence, regardless of bone density or endplate integrity. SUMMARY OF BACKGROUND DATA: There are several reports regarding the rates and grades of cage subsidence when utilizing the lateral lumbar interbody fusion technique. However, there is limited data on how spanning the lateral cage across the ring apophysis can prevent it. METHODS: Eight fresh-frozen human spines (L1-L5) were utilized. Each vertebra was placed with their endplates horizontal in an MTS actuator. A total of 40 specimens were randomized into Groups:Load displacement data was collected at 5 Hz until failure. RESULTS: Longer cages spanning the ring apophysis provided more strength in compression with less subsidence relative to shorter cages, regardless of endplate integrity.Longer cages, spanning the ring apophysis, resting on intact endplates (G2) had a significant (P < 0.05) increase in strength and less subsidence when compared with the smaller cage group resting on intact endplates (G1) (P = 0.003).Longer cages spanning the ring apophysis of intact endplates (G2) showed a significant (P < 0.05) increase in strength and resistance to subsidence when compared with similar length cages resting on decorticated endplates (G4) (P = 0.028). CONCLUSION: Spanning the ring apophysis increased the load to failure by 40% with intact endplates and by 30% with decorticated endplates in this osteoporotic cadaveric model. Larger cages that span the endplate ring apophysis could improve the compressive strength and decrease subsidence at the operative level despite endplate violation or osteoporosis. LEVEL OF EVIDENCE: 2.

Cardiac Emboli Documented by Intraoperative Transesophageal Echocardiogram During Administration of a Topical Hemostatic Agent Prior to Pedicle Subtraction Osteotomy.

STUDY DESIGN: This is a case report. OBJECTIVE: Describe the occurrence of cardiac emboli recorded on transesophageal echocardiogram (TEE) after the injection of a topical hemostatic agent into a vertebra prior to performing a pedicle subtraction osteotomy (PSO). SUMMARY OF BACKGROUND DATA: Hemostasis during spinal surgery is critical for adequate visualization and to reduce the risk of perioperative complications. Adult spinal deformity surgery can involve performing PSOs which are useful in cases of fixed spinal deformities and are associated with increased blood loss secondary to epidural and cancellous bleeding. Prior to performing a PSO, a topical hemostatic agent can be injected into the vertebra through the pedicle screw pilot holes in an attempt to decrease cancellous bleeding. Injected hemostatic agents can pressurize the vertebral body similar to cementation in vertebroplasty and during fracture reaming and prosthetic implantation in the femur. Patients with cardiac defects such as patent foramen ovale or atrial septal defect may be more prone to systemic embolic events resulting in morbidity or mortality. METHODS: We injected a topical hemostatic matrix agent through the pedicle screw pilot holes into the L1 vertebral body prior to performing a PSO while simultaneously recording with TEE. RESULTS: The TEE recorded large visible emboli traveling through the heart into the pulmonary vasculature. The patient remained stable throughout the remainder of the case and a postoperative spiral computed tomography (CT) scan was negative for filling defects. The patient had an uneventful hospital course. CONCLUSION: Questions remain about the exact consistency of these emboli, when they are most likely to occur, how much cardiopulmonary insult can be tolerated without resulting in complications, or how to prevent their occurrence. Patients undergoing spinal surgery with the plan to inject hemostatic matrix agents into the vertebral body may benefit from a preoperative TEE to reduce the risk of complications associated with embolic events, especially in patients with undiagnosed patent foramen ovale or atrial septal defect. LEVEL OF EVIDENCE: 5.

Comparison of Ocular Radiation Exposure Utilizing Three Types of Leaded Glasses.

STUDY DESIGN: Anthropomorphic phantoms were used to measure radiation exposure to the surgeon phantom's eye. Groups analyzed were: Group 1-no glasses (None); Group 2-leaded lenses without lead sides (WOLS); Group 3-leaded lenses with lead sides (WLS); and Group 4-sport wraparound leaded glasses (Sport). Glasses were 0.75 mm lead equivalent. OBJECTIVE: To evaluate the efficacy of three types of leaded eyeglasses at reducing radiation exposure to the lens during typical views of minimally invasive spine surgery. SUMMARY OF BACKGROUND DATA: Minimally invasive spine surgery relies upon fluoroscopic x-ray. Ocular radiation exposure is associated with cataract formation. Leaded glasses can reduce ocular radiation exposure. METHODS: Fifteen individual 20-second exposures with the fluoroscopic C-arm in the anteroposterior (AP) and lateral positions, with phantom head positioned at 0, 45, and 90 degrees to the fluoroscope were performed. Radiation was measured using a solid-state dosimeter. Student t test was used to calculate significance. RESULTS: All glasses (WOLS, WLS, and Sport) had significant reductions in ocular radiation versus no glasses, at all individual head positions (P ≤ 1.31 × 10). Sport had significantly lower ocular radiation dose than WLS at all head positions except at 90 degrees AP (P = 0.001). WOLS had significantly lower ocular radiation dose than Sport in three out of six cases including phantom head at 0 degrees AP (P = 0.0003), 90 degrees AP (P = 4.46 × 10), and 90 degrees lateral (P = 7.38 × 10). WOLS had significantly lower radiation dosage at all head positions than WLS except at 45 degrees AP (P = 0.303). All glasses resulted in a significant reduction in total radiation dose from all head positions over no glasses (P ≤ 8.37 × 10). CONCLUSION: We demonstrate a significant reduction in ocular radiation exposure with all three types of leaded glasses. Lead glasses, WOLS and Sport, were the most effective at reducing ocular radiation. LEVEL OF EVIDENCE: 3.

Guillain-Barré syndrome after pelvic fracture fixation: a rare cause of postoperative paralysis.

STUDY DESIGN: Case report. OBJECTIVE: To describe the important epidemiology, clinical presentation, and pathophysiology of Guillain-Barré syndrome (GBS) after orthopedic surgery in a trauma patient. SUMMARY OF BACKGROUND DATA: Little in the orthopedic literature describes trauma as an etiology of GBS. We report a case of post-traumatic GBS in a 52-year-old male who developed ascending weakness after experiencing pelvic trauma that required 2 separate orthopedic procedures for pelvic stabilization after a fall from a height of 12 ft. After the index operative procedure, the patient complained of left S1 numbness. Computed tomographic scan demonstrated the pelvic screw approximating the left S1 neuroforamen and correlated with the patient's immediate postoperative symptoms. A secondary procedure to reposition the screw alleviated the patient's left S1 numbness. Two weeks postoperatively, the patient developed profound ascending lower extremity weakness. This case highlights the importance of considering all etiologies, no matter how uncommon, in the differential diagnosis of lower extremity weakness. METHODS: Case report with literature search on GBS in orthopedic trauma patient. RESULTS: We propose that direct neural trauma from poorly positioned hardware resulting in clinical neurological symptoms may have been the inciting event that caused GBS in this trauma patient. CONCLUSION: Post-traumatic GBS is a rare, potentially life-threatening cause of weakness. Once mechanical causes are ruled out with appropriate imaging, all etiologies in the differential diagnosis must be explored. If the image findings cannot explain the clinical examination, other biologic causes of weakness, including GBS, must be explored. The causes of GBS in the postoperative trauma patient include infection, trauma, surgery, or direct neural injury. LEVEL OF EVIDENCE: 4.

Disease severity and treatment in adolescent idiopathic scoliosis: the impact of race and economic status.

BACKGROUND CONTEXT: Ethnic disparities have been documented in the incidence and treatment of many diseases. Additionally, race and socioeconomic status (SES) have been shown to affect disease severity and access to care in the recent orthopedic literature. PURPOSE: To assess the role, if any, that race, SES, and health insurance type play in disease severity and treatment decisions in patients with adolescent idiopathic scoliosis. STUDY DESIGN: Retrospective chart review. PATIENT SAMPLE: Pediatric patients seen in a single surgeon's practice over 6 years (2004-2009). OUTCOME MEASURES: Treatment modality (observation, bracing, or surgery). METHODS: Data were obtained from 403 patients seen over 6 years (2004-2009). A patient-reported questionnaire was used to collect race, age, family income, and parent marital status data. Race was self-reported as "Asian," "black or African American," "Hispanic or Latino," "white or Caucasian," or "Other." Socioeconomic status was determined using family income and type of health insurance as indicators. Major curve magnitude and prescribed initial treatment (observation, brace, or surgery) were assessed from physician records. An independent sample t test was used to detect differences in curve magnitude of the different racial groups. A Pearson chi-square analysis was used to detect group differences for curves in surgical patients, defined as curves greater than 40°, and their initial treatment. RESULTS: Patients self-identified with one of the following racial groups: white (N=219), black (N=86), Hispanic (N=44), Asian (N=37), or Other (N=17). Mean curve magnitude was greater in black than in white patients (33° vs. 28°, p<.05). Black patients were more likely to present with curves in the surgical range (34% vs. 24%, p<.05) and were more likely to have surgery as their initial treatment than white patients (34% vs. 19%, p<.05). Black patients had more limited health care plans and lower incomes compared with whites (p<.001). Patients with higher access insurance plans presented at a younger age than patients with more limited access plans, irrespective of race (13.6 vs. 14.1, p<.05). There was no difference in Cobb angle at presentation by income or type of insurance. CONCLUSIONS: Curve magnitude and percentage of patients with curves in the surgical range were greater in black than in white patients. There was no difference in age on presentation or treatment offered across all racial groups. Black patients were more likely to have surgery as their initial treatment than white patients. While race did have an impact on disease severity in this single surgeon's practice, SES did not.

Establishing a role for vancomycin powder application for prosthetic joint infection prevention-results of a wear simulation study.

Topical vancomycin powder (VP) has shown efficacy and safety in decreasing post-operative spine infections. VP use in arthroplasty has not been established. Concerns remain for third-body wear with the addition of crystalline substrate at the implant interface. The study's purpose was to compare wear behavior of CoCr on UHMWPE to identical wear couples with VP. A six-station wear simulator was utilized and cyclic articulations were run for 10 million cycles (Mc). UHMWPE wear was measured using photography, stereomicroscopy, and gravimetric measurement. There were no differences in wear mark length (P = 0.43), width (P = 0.49), or gravimetric wear at 10 Mc (P = 0.98). VP and control groups lost 0.32 and 0.33 mg, respectively. VP may have a role in PJI prevention. A well-designed clinical study is needed.

Novel concepts in the evaluation and treatment of high-dysplastic spondylolisthesis.

The classification system of spondylolisthesis proposed by Marchetti and Bartolozzi is the most practical regarding prognosis and treatment and includes the description of both low- and high-dysplastic developmental spondylolisthesis (HDDS). Unfortunately, it does not provide strict criteria on how to differentiate between these two subtypes. The accepted treatment for HDDS is surgical. However, there is no consensus on how to surgically stabilize this subtype of spondylolisthesis, and although the concept of reducing spinal deformity before fusion is attractive, the issue of surgical reduction versus in situ fusion remains controversial, especially for HDDS (Meyerding Grades III and IV). The purpose of this study was (1) to describe the severity index (SI) as a simple method that can be used in the identification of low-dysplastic developmental spondylolisthesis from HDDS allowing earlier surgical stabilization to prevent slip progression, (2) to provide guidelines for using the unstable zone for the inclusion of L4 in stabilization, and (3) to describe a surgical technique in the reduction and stabilization of this challenging surgical entity in an attempt to decrease the risk of iatrogenic L5 neurologic injury. The concepts of SI and unstable zone in the evaluation and treatment of HDDS are relatively new. In our study, patients with an SI value >20% were classified as having HDDS and surgical stabilization was offered. In addition, all vertebrae that were contained in the defined unstable zone were surgically instrumented and fused with attempts at anatomic reduction. This case series involved the retrospective radiological review of 25 consecutive patients surgically treated for HDDS between April 2000 and September 2004 by two senior surgeons. All 25 patients had a minimum 3-year follow-up. Reduction of slip, lumbosacral kyphosis, sacral inclination, fusion rate, maintenance of reduction, and iatrogenic L5 neurologic injury were evaluated. Twenty-two patients underwent a single-level L5-S1 fusion. Three patients had extension of the L5-S1 fusion to include L4 because it fell into the unstable zone. Slip improved from 67.2 to 13.6%, focal L5-S1 kyphosis improved from +17.5 degrees to -6.4 degrees . There were no pseudoarthroses and all patients had radiographic evidence of solid bony fusion at latest follow-up. To date, there have been no re-operations secondary to progression of deformity or loss of fixation. Two re-operations were performed, one for a superficial wound infection, the other for further laparoscopic decompression for continued L5 nerve root symptoms after the index surgery. One patient developed an iatrogenic L5 radiculopathy with dysaesthesiae 3 days postoperatively which completely resolved over 6 weeks. HDDS is best treated surgically. Early identification and stabilization of this challenging surgical entity could prevent the progression of slip and deformity making the index surgery less technically demanding. Vertebrae that are contained in the unstable zone can be instrumented and stabilized so that progression of the deformity and re-operation might be avoided. The authors suggested surgical technique can provide a way to restore sagittal balance, provide an environment for successful fusion, and decrease the risk of iatrogenic L5 neurologic injury.