Deformity Considerations in Cervical Laminoplasty: A Narrative Review.

OBJECTIVES: We discuss the incidence of postoperative kyphosis following laminoplasty and its impact on outcomes, as well as critical radiographic parameters, intraoperative technical factors, and postoperative protocols that can be used to improve results. SUMMARY OF BACKGROUND DATA: When appropriately selected, cervical laminoplasty is a motion-sparing treatment option for cervical myelopathy and is a valid alternative to laminectomy and fusion procedures. However, like other posterior-based cervical decompression techniques, laminoplasty can cause postoperative kyphosis. METHODS: A PubMed search was performed to gather articles that focus on cervical deformity in the context of cervical laminoplasty. RESULTS: The reported conversion rates of lordotic to kyphotic cervical alignment after laminoplasty range from 5.2% to 11.3%. Kyphosis likely reduces the benefit from the operation as measured by postoperative mJOA scores. A surgeon can minimize the risk of causing a clinically significant reduction in lordosis by screening out patients with certain radiographic characteristics. Intraoperative decisions such as dissection techniques, levels chosen, and hybrid constructs can preserve the cervical tension band. Certain postoperative protocols can improve cervical posture. CONCLUSIONS: Cervical laminoplasty is an effective tool for treating degenerative cervical myelopathy. Careful radiographic screening, intraoperative decision-making, and postoperative protocols can minimize the development of postoperative cervical deformity and improve outcomes. LEVEL OF EVIDENCE: Level V.

Response to Preoperative Steroid Injections Predicts Surgical Outcomes in Patients Undergoing Fusion for Isthmic Spondylolisthesis.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: The decision to pursue operative intervention for patients with isthmic spondylolisthesis is complex. Although steroid injections are a well-accepted therapeutic modality that may delay or obviate surgery, little is known regarding their ability to predict surgical outcomes. SUMMARY OF BACKGROUND DATA: Here, we examine whether improvement after preoperative steroid injections can accurately predict clinical outcomes after surgery. METHODS: A retrospective cohort analysis was performed on adult patients undergoing primary posterolateral lumbar fusion for isthmic spondylolisthesis between 2013 and 2021. Data were stratified into a control (no preoperative injection) group and an injection group (received a preoperative diagnostic and therapeutic injection). We collected demographic data, peri-injection visual analog pain scores (VAS) pain scores, PROMIS pain interference and physical function scores, Oswestry Disability Index, and VAS pain (back and leg). Student t test was utilized to compare baseline group characteristics. Linear regression was performed comparing changes in peri-injection VAS pain scores and postoperative measures. RESULTS: Seventy-three patients did not receive a preoperative injection and were included in the control group. Fifty-nine patients were included in the injection group. Of patients who received an injection, 73% had >50% relief of their preinjection VAS pain score. Linear regression revealed a positive interaction between the injection efficacy and postoperative pain relief as measured by VAS leg scores ( P <0.05). There was also an association between injection efficacy and back pain relief, though this did not achieve statistical significance ( P =0.068). No association was found between injection efficacy and improvement in Oswestry Disability Index or PROMIS measures. CONCLUSIONS: Steroid injections are often utilized in the nonoperative therapeutic management of patients with lumbar spine disease. Here, we demonstrate the diagnostic value of steroid injections in predicting postoperative leg pain relief in patients undergoing posterolateral fusion for isthmic spondylolisthesis.

Preoperative Fluoroscopically Guided Regional Erector Spinae Plane Blocks Reduce Opioid Use, Increase Mobilization, and Reduce Length of Stay Following Lumbar Spine Fusion.

STUDY DESIGN: Retrospective review. OBJECTIVE: To determine the effectiveness of erector spinae plane (ESP) blocks at improving perioperative pain control and function following lumbar spine fusions. METHODS: A retrospective analysis was performed on patients undergoing < 3 level posterolateral lumbar fusions. Data was stratified into a control group and a block group. We collected postop MED (morphine equivalent dosages), physical therapy ambulation, and length of stay. PROMIS pain interference (PI) and physical function (PF) scores, ODI, and VAS were collected preop and at the first postop visit. Chi-square and student's t-test (P = .05) were used for analysis. We also validated a novel fluoroscopic technique for ESP block delivery. RESULTS: There were 37 in the block group and 39 in the control group. There was no difference in preoperative opioid use (P = .22). On postop day 1, MED was reduced in the block group (32 vs 51, P < .05), and more patients in the block group did not utilize any opioids (22% vs 5%, P < .05). The block group ambulated further on postop day 1 (312 ft vs 204 ft, P < .05), and had reduced length of stay (2.4 vs 3.2 days, P < .05). The block group showed better PROMIS PI scores postoperatively (58 vs 63, P < .05). The novel delivery technique was validated and successful in targeting the correct level and plane. CONCLUSIONS: ESP blocks significantly reduced postop opioid use following lumbar fusion. Block patients ambulated further with PT, had reduced length of stay, and had improved PROMIS PI postoperatively. Validation of the block demonstrated the effectiveness of a novel fluoroscopic delivery technique. ESP blocks represent an underutilized method of reducing opioid consumption, improving postoperative mobilization and reducing length of stay following lumbar spine fusion.

Potential Selection Bias in Observational Studies Comparing Cervical Disc Arthroplasty to Anterior Cervical Discectomy and Fusion.

STUDY DESIGN: Retrospective study using a national administrative database. OBJECTIVE: To define the cohort differences in patient characteristics between patients undergoing cervical disc arthroplasty (CDA) and anterior cervical discectomy and fusion (ACDF) in a large national sample, and to describe the impact of those baseline patient characteristics on analyses of costs and complications. SUMMARY OF BACKGROUND DATA: CDA was initially studied in high quality, randomized trials with strict inclusion criteria. Recently a number of non-randomized, observational studies have been published an attempt to expand CDA indications. These trials are predisposed to falsely attributing differences in outcomes to an intervention due to selection bias. METHODS: Adults undergoing ACDF or CDA between 2004 and 2014 were identified using International Classification of Diseases, 9, Clinical Modification (ICD-9-CM) diagnosis and procedure codes. Perioperative demographics, comorbidities, complications, and costs were queried. Patient characteristics were compared via chi-square and t tests. Cost, mortality, and complications were compared between ACDF and CDA cohorts using models that adjusted for demographics and comorbidities, as well as "naïve" models that did not. RESULTS: A total of 290,419 procedures, 98.2% ACDF and 1.8% CDA, were included in the sample. Compared with ACDF patients, CDA patients were younger, healthier as evidenced by number of comorbidities, and had an improved socioeconomic status as measured by income and insurance. The naïve logistic regression model showed that hospital costs for CDA were $549 lower than ACDF. In the fully specified model, CDA was $574 more expensive. The naïve model for medical complications suggests a protective advantage for CDA over ACDF, odds ratio of 0.627, P < 0.01. No statistically significant difference was found in the fully specified model in terms of complications. CONCLUSION: Patients undergoing CDA were younger and healthier with higher socioeconomic statuses compared with ACDF patients. Accounting for these baseline differences significantly attenuated the apparent benefit for CDR on costs and medical complications. LEVEL OF EVIDENCE: 3.

Mobile messaging and smartphone apps for patient communication and engagement in spine surgery.

Mobile health (mHealth) applications are rapidly becoming increasingly available to patients. These interventions utilize simple mobile messaging (SMS) and software applications on mobile devices for a variety of purposes. In the surgical population mHealth applications have shown promise in increasing medication and protocol adherence, monitoring patients after surgery, and helping modify behaviors associated with poor surgical outcomes. There is a paucity of spine specific applications at this time. Further development and study of efficacy of spine specific mHealth applications is needed.

Defining Instability in Degenerative Spondylolisthesis: Surgeon Views.

STUDY DESIGN: Surgeon survey. OBJECTIVE: To examine factors influencing surgeons' definition of instability in grade 1 degenerative spondylolisthesis (DS) and assess treatment preferences for both stable and unstable DS. SUMMARY OF BACKGROUND DATA: DS treatment options are broadly classified as decompression with or without fusion. In surgical decision-making, "instability" is frequently considered as a key factor. However, no consensus on the definition of instability exists. METHODS: A survey was conducted to ascertain the minimum amounts of static translation, dynamic translation, and angulation change that surgeons considered significant for determining instability. The importance of other clinical and radiographic features were also assessed, and respondents' standard treatment for stable and unstable DS. RESULTS: Out of 226 respondents, 99% deemed dynamic translation moderately to extremely influential for determining instability, whereas only 55% found static translation as important. The most prevalent cut-off values for dynamic (57%) and static translation (32%) were at least 2-4 mm and for angulation change at least 10-15 degrees (43%). Facet angulation was considered moderately to extremely important to determine instability by 69% of the surgeons, disk height by 67%, patient age by 64%, severity of stenosis by 55%, severity of back pain by 50%, patient-reported function by 49%, pelvic incidence by 47%, and severity of neurogenic claudication by 42%.Decompression with fusion was the preferred treatment method for unstable DS in 99% of the respondents. For stable DS, 40% would still perform fusion, whereas 60% preferred treatment with decompression-alone. Those who preferred fusion for stable DS reported significantly lower thresholds for static (P<0.001) and dynamic translation (P=0.004) for their determination of instability. CONCLUSIONS: Clear consensus regarding the definition of instability does not exist. Dynamic translation is the most agreed-upon parameter of influence. Treatment preferences vary for stable DS, but for unstable cases there is broad consensus to perform fusion. LEVEL OF EVIDENCE: Level II.

Software-Based Postoperative Communication With Patients Undergoing Spine Surgery.

STUDY DESIGN: Observational study. OBJECTIVES: Perioperative patient anxiety is a major concern in orthopedic surgery. Mobile messaging applications have been used in a number of healthcare settings. The goal of this project is to develop a novel mobile messaging application aimed at decreasing perioperative patient anxiety in spine surgery patients. METHODS: Postoperative recovery journals were collected from patients undergoing spine surgery. Journals were used as a framework to develop a software-messaging library. A subsequent cohort of patients received daily text messages with educational material regarding their recovery for 14 days after discharge from their operative admission. Patients ranked the usefulness of the survey on day 14; further feedback was obtained via interviews. RESULTS: Nineteen postoperative recovery journals were collected and analyzed. Content regarding postoperative recovery was compiled. The pilot group consisted of 21 patients. Average rating of the application on a 1 to 5 scale with 5 being "very useful" was 4.57. Of the 12 patients available for postoperative interviews, 11 felt the content of the messages was relevant. Nine of 12 patients felt the application made it less likely for them to call clinic. CONCLUSIONS: The study presents a unique mobile phone messaging tool to offer patients support in the 2 weeks following spine surgery. The tool was felt to be useful by nearly all patients, had a high degree of patient engagement, and made the majority of patients less likely to call clinic.

Lumbar Interbody Fusions for Degenerative Spondylolisthesis: Review of Techniques, Indications, and Outcomes.

STUDY DESIGN: Broad narrative review. OBJECTIVES: To review and summarize the current literature on the outcomes, techniques, and indications of lumbar interbody fusion in degenerative spondylolisthesis. METHODS: A thorough review of peer-reviewed literature was performed on the outcomes, techniques, and indications of lumbar interbody fusions in degenerative spondylolisthesis. RESULTS: A number of studies have found similar results between interbody fusions and posterolateral fusion in the setting of degenerative spondylolisthesis. There is some evidence that suggests that interbody fusion may be a useful adjunct in the setting of unstable degenerative spondylolisthesis. The number of options for interbody fusions has quickly expanded. Initially, interbody fusions were accomplished via an anterior approach. Posterior and transforaminal interbody fusions are 2 options that accomplish an interbody fusion without the morbidity of an anterior approach. Over the past decade, minimally invasive options including extreme lateral, oblique, and minimally invasive transforaminal interbody fusions have gained popularity. CONCLUSIONS: Lumbar interbody fusion can be a useful tool in the setting of unstable degenerative spondylolisthesis. A number of technique options, both open and minimally invasive, are available to accomplish an interbody fusion. The literature to this date does not support a clear benefit of one technique over others in the setting of degenerative spondylolisthesis.

Physical function computer adaptive test outcomes in diabetic lumbar spine surgical patients.

BACKGROUND CONTEXT: Diabetes is a highly prevalent comorbid condition among patients undergoing spine surgery. Several studies have used legacy patient-reported outcome measures to implicate diabetes as a predictor of increased disability, pain, and decreased physical function and quality of life following spine surgery. The effect of diabetes on postoperative physical function has not yet been studied using the PROMIS Physical Function Computer Adaptive Test (PF CAT). PURPOSE: To understand the effect of diabetes on physical function outcomes among patients undergoing lumbar spine surgery, as reported by the PF CAT. STUDY DESIGN/SETTING: A retrospective cohort study was performed at a single university-based spine clinic. PATIENT SAMPLE: Patients who underwent lumbar spine surgery between October 1, 2013 and April 26, 2018 with both PF CAT and Oswestry Disability Index (ODI) scores available for review. OUTCOME MEASURES: PROMIS PF CAT. Secondary measures of disability included the ODI. METHODS: PF CAT and ODI questionnaires were administered to patients via electronic tablets. Data from these questionnaires were collected prospectively, and retrieved from a university database. Wilcox tests, Exact Wilcox tests, linear regression models, and descriptive analytics were applied. RESULTS: Patients meeting inclusion criteria included 233 nondiabetic patients and 65 diabetic patients. Mean PF CAT scores among diabetics were lower than those of nondiabetics at all time-points from preoperative through 12 months postoperative, with significance found at both 6 months (p=.035) and 12 months (p=.039) postoperative. Mean ODI scores among diabetics were significantly higher than those of nondiabetics at 3 months (p=.018) and 12 months (p=.027) postoperative. By 12 months postoperative, a smaller proportion of diabetics reached PF CAT and ODI minimum clinically important difference thresholds when compared to nondiabetics. CONCLUSIONS: Diabetes is associated with lower PF CAT scores up to one year following lumbar spine surgery. However, many of these patients achieve meaningful improvement in physical function during this time. The PF CAT is consistent with legacy outcome measures in assessing outcomes in diabetic patients undergoing lumbar spine surgery, with an added benefit of decreased patient burden.

Evidence of an Inherited Predisposition for Spinal Cord Tumors.

STUDY DESIGN: Retrospective study. OBJECTIVES: To determine familial clustering of primary spinal cord tumors using a statewide genealogy database. METHODS: The Utah Population Database (UPDB) was queried using ICD-Oncology (International Classification of Diseases for Oncology) codes for primary spinal cord tumors. The hypothesis of disproportionate familial clustering was tested using the Genealogical Index of Familiality (GIF). The relative risks (RRs) in relatives were calculated using the ratio of observed spinal cord tumors to expected spinal cord tumors in relatives using estimated rates from the UPDB. The related clusters of spinal cord cancer cases with a significant excess number of spinal cord cancer cases descending from a common founder pair were identified using internal UPDB rates. RESULTS: The analysis of the GIF for individual with tumors of the spinal cord showed excess close and distant relatedness (case GIF = 3.82; control mean GIF = 2.68; P = .068). Excess relatedness for spinal cord cancers was observed when only more distant relationships were considered (P = .019). The RRs for spinal cord tumors were elevated in second- and third-degree relatives but this did not reach statistical significance (RR = 2.9, P = .15, and RR = 2.0, P = .14). Multiple extended pedigrees with a significant excess of spinal cord cancer cases among the descendants were identified. CONCLUSIONS: The excess relatedness of tumor cases over controls in distant relationships, the higher RRs to distant relatives, and the discovery of high-risk pedigrees all suggest a familial predisposition to the development of spinal cord tumors.

Failure of facet replacement system with metal-on-metal bearing surface and subsequent discovery of cobalt allergy: report of 2 cases.

The aim of this study was to report on 2 patients in whom metal-on-metal (MOM) facet replacements failed, with subsequent positive findings on allergy testing. Motion-preserving devices have been used with limited success when instrumentation is indicated in the mobile spine. MOM-bearing surfaces in orthopedics were developed to increase implant longevity, yet have been associated with numerous adverse outcomes, including local tissue reactions, pseudotumors, metallosis, and the need for revision surgery. Five patients with spinal stenosis and low-grade spondylolisthesis were randomized to undergo facet replacement surgery with the ACADIA facet replacement system at the authors' institution. Two patients experienced a return of neurological symptoms after a pain-free interval (< 2 years) with development of local tissue reaction and positive findings on allergy testing to cobalt, the metal in the MOM-bearing surface. Both patients underwent successful removal of the implant and revision to titanium posterior spinal fusion and interbody fusion without further complication. Motion-preserving devices have been designed and trialed for specific indications in the mobile spine. Given the adverse results from MOM devices in hip arthroplasty and now the early reports with MOM facet replacements, caution is warranted when moving forward with any MOM joint-bearing surface. Both patients presented here had an unusual tissue reaction locally and subsequent positive allergy testing results to cobalt. These 2 patients appear to have developed a delayed hypersensitivity reaction to the metal, likely from fine debris at the MOM interface.

The utility of preoperative laboratories in predicting postoperative complications following posterolateral lumbar fusion.

BACKGROUND CONTEXT: Several studies have suggested that laboratory results have minimal impact on clinical decision making in surgery. Despite the widespread use of preoperative testing in spine surgery and the large volume of posterolateral lumbar fusions (PLFs) being performed each year, no study has assessed the ability of preoperative laboratories to predict adverse events following PLF. PURPOSE: The purpose of this study was to explore the relationship between commonly obtained preoperative laboratory results and postoperative complications following one- to two-level PLF. STUDY DESIGN: This is a retrospective study of prospectively collected data. PATIENT SAMPLE: The 2006-2013 American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database was employed to identify all patients who underwent one- to two-level PLF. OUTCOME MEASURES: The outcome variables of interest were 30-day postoperative complications, which were assessed as major complications, minor adverse events, and total complications. MATERIALS AND METHODS: Demographics, comorbidities, and perioperative characteristics were collected for each patient. Preoperative laboratories included sodium, blood urea nitrogen, creatinine, albumin, bilirubin, serum glutamic oxaloacetic transaminase, alkaline phosphatase, white blood cell count, hematocrit, platelet count, prothrombin time, international normalized ratio, and partial thromboplastin time. Bivariate analysis and multivariate logistic regression modeling were used to explore the relationship between abnormal preoperative laboratories and the incidence of postoperative complications. RESULTS: After controlling for age, ASA score, length of surgery, and all significant comorbidities, abnormal sodium (odds ratio [OR]=2.47, 95% confidence interval [CI]: 1.45-4.19, p=.001) and abnormal INR (OR=2.33, 95% CI: 1.09-4.98, p=.029) were significantly associated with the development of any complication. Sodium (OR=1.61, 95% CI: 1.01-2.54, p=.04) and platelets (OR=1.58, 95% CI: 1.02-2.44, p=.04) were associated with minor complications. Meanwhile, creatinine (OR=1.74, 95% CI: 1.02-2.99, p=.04) and platelets (OR=1.71, 95% CI: 1.02-2.89, p=.04) were significant predictors of major adverse events. CONCLUSIONS: This study represents the first attempt to assess the utility of preoperative laboratories in predicting postoperative complications in PLF. Although the majority of laboratories were not significantly associated with adverse events, abnormal sodium values, INR, creatinine, and platelets were shown to be predictive of various complications.

Optimal Entry Point and Trajectory for Anterior C1 Lateral Mass Screw.

STUDY DESIGN: A radiographic analysis of the anatomy of the C1 lateral mass using computed tomography (CT) scans and Mimics software. OBJECTIVE: To define the anatomy of the C1 lateral mass and make recommendations for optimal entry point and trajectory for anterior C1 lateral mass screws. SUMMARY OF BACKGROUND DATA: Although various posterior insertion angles and entry points for screw insertion have been proposed for posterior C1 lateral mass screws, no large series have been performed to assess the ideal entry point and optimal trajectory for anterior C1 lateral mass screw placement. MATERIALS AND METHODS: The C1 lateral mass was evaluated using CT scans and a 3-dimensional imaging application (Mimics software). Measuring the space available for the anterior C1 lateral mass screw (SAS) at different camber angles from 0 to 30 degrees (5-degree intervals) was performed to identify the ideal camber angle of insertion. Measuring the range of sagittal angles was performed to calculate the ideal sagittal angle. Other measurements involving the height of the C1 lateral mass were also made. RESULTS: The optimal screw entry point was found to be located on the anterior surface of the atlas 12.88 mm (±1.10 mm) lateral to the center of the anterior tubercle. This optimal entry point was found to be 6.81 mm (±0.59 mm) superior to the anterior edge of the atlas inferior articulating process. The mean ideal camber angle was 20.92 degrees laterally and the mean ideal sagittal angle was 5.80 degrees downward. CONCLUSIONS: These measurements define the optimal entry point and trajectory for anterior C1 lateral mass screws and facilitate anterior C1 lateral mass screw placement. A thorough understanding of the local anatomy may decrease the risk of injury to the spinal cord, vertebral artery, and internal carotid artery. Delineating the anatomy in each case with preoperative 3D CT evaluation is recommended.

Patient Satisfaction is Not Associated With Self-reported Disability in a Spine Patient Population.

STUDY DESIGN: This is a retrospective review. OBJECTIVE: To evaluate the relationship between patient functional status and self-assessment of disability as measured by 3 commonly used clinical assessment instruments-the Oswestry Disability Index (ODI), the Neck Disability Index (NDI), and the EuroQol (EQ)-5D and patient satisfaction scores in a spine surgery clinic population. SUMMARY OF BACKGROUND DATA: Patient satisfaction surveys, which measure the "patient experience of care" are becoming an increasingly important measure of the quality of medical care. Despite the widespread use of patient satisfaction surveys, little is known about the relationship between patient satisfaction and patient functional status or self-assessed level of disability. MATERIALS AND METHODS: We retrospectively reviewed records of 231 consecutive patients presenting to a single academic spine surgery center between February 2011 and October 2013 who completed both a patient satisfaction survey as well as one or more patient-reported outcome questionnaires (NDI, ODI, and/or EQ-5D) for a single clinical encounter. Statistical analysis was performed to determine if an association exists between the overall patient satisfaction score and each patient-reported outcome score. RESULTS: Spearman correlation coefficients demonstrated no correlation between any patient-reported outcome score and the patient satisfaction score [NDI=-0.113 (-0.409 to 0.207) P=0.489] [ODI=-0.008 (-0.149 to 0.133) P=0.912] [EQ-5D=0.011 (-0.119 to 0.140) P=0.872] for a single clinical encounter. CONCLUSIONS: These results provide evidence against an association between patient-reported functional status or self-assessed level of disability and patient satisfaction in a spine patient population.

PROMIS PF CAT Outperforms the ODI and SF-36 Physical Function Domain in Spine Patients.

STUDY DESIGN: The Oswestry Disability Index v2.0 (ODI), SF36 Physical Function Domain (SF-36 PFD), and PROMIS Physical Function CAT v1.2 (PF CAT) questionnaires were prospectively collected from 1607 patients complaining of back or leg pain, visiting a university-based spine clinic. All questionnaires were collected electronically, using a tablet computer. OBJECTIVE: The aim of this study was to compare the psychometric properties of the PROMIS PF CAT with the ODI and SF36 Physical Function Domain in the same patient population. SUMMARY OF BACKGROUND DATA: Evidence-based decision-making is improved by using high-quality patient-reported outcomes measures. Prior studies have revealed the shortcomings of the ODI and SF36, commonly used in spine patients. The PROMIS Network has developed measures with excellent psychometric properties. The Physical Function domain, delivered by Computerized Adaptive Testing (PF CAT), performs well in the spine patient population, though to-date direct comparisons with common measures have not been performed. METHODS: Standard Rasch analysis was performed to directly compare the psychometrics of the PF CAT, ODI, and SF36 PFD. Spearman correlations were computed to examine the correlations of the three instruments. Time required for administration was also recorded. RESULTS: One thousand six hundred seven patients were administered all assessments. The time required to answer all items in the PF CAT, ODI, and SF-36 PFD was 44, 169, and 99 seconds. The ceiling and floor effects were excellent for the PF CAT (0.81%, 3.86%), while the ceiling effects were marginal and floor effects quite poor for the ODI (6.91% and 44.24%) and SF-36 PFD (5.97% and 23.65%). All instruments significantly correlated with each other. CONCLUSION: The PROMIS PF CAT outperforms the ODI and SF-36 PFD in the spine patient population and is highly correlated. It has better coverage, while taking less time to administer with fewer questions to answer. LEVEL OF EVIDENCE: 2.

A comparative study on the accuracy of pedicle screw placement assisted by personalized rapid prototyping template between pre- and post-operation in patients with relatively normal mid-upper thoracic spine.

PURPOSE: The aim of this study was to assess the accuracy of rapid prototyping drill template technique for placing pedicle screws in the mid-upper thoracic vertebrae in clinics. METHODS: 151 consecutive patients underwent thoracic instrumentation and fusion for a total of 582 pedicle screws placed in the mid-upper thoracic vertebrae. Using computer software, the authors constructed drill templates that fit onto the posterior elements of the mid-upper thoracic vertebrae with drill guides designed to instrument the pedicles. The start point and three dimensional location of the planned and inserted screws were measured and compared. RESULTS: Grading of the CT scans revealed 559 (96.1 %) out of 582 screws completely within the desired pedicle. The direction of pedicle violation included 5 medial, 2 airball, and 16 lateral. The paired t test suggested that these results were statistically significant in more than half of the locations (T1-left-TA(P = 0.024), T2-left-SA(P = 0.031), T3-left-SA(P = 0.014), T4-left-TA(P = 0.004), T5-left-TA(P = 0.034), T7-left-TA(P = 0.000). T1-right-TA(P = 0.049), T2-right-TA(P = 0.044), T3-right-TA(P = 0.014), T5-right-TA(P = 0.013)). The paired t-test suggested that these results were statistically significant at several locations (T4-left-Δy(P = 0.041), T5-left-Δx(P = 0.016), T3-right-Δy(P = 0.015)). CONCLUSION: Use of a rapid prototyping drill template to assist in the placement of mid and upper thoracic pedicle screws may lead to increased accuracy. This patient specific technology must be combined with an understanding of the patients' anatomy and carefully secured to the posterior elements intraoperatively to avoid nerve or vascular complications.

Geographic variations in the cost of spine surgery.

STUDY DESIGN: Retrospective review. OBJECTIVE: To define the geographic variation in costs of anterior cervical discectomy and fusion (ACDF) and posterolateral fusion (PLF). SUMMARY OF BACKGROUND DATA: ACDF and lumbar PLF are common procedures that are used in the treatment of spinal pathologies. To optimize value, both the benefits and costs of an intervention must be quantified. Data on costs are scarce in comparison with data on total charges. This study aims at defining the costs of ACDF and PLF and describing the geographic variation within the United States. METHODS: Medicare Provider Utilization and Payment data were used to investigate the costs associated with ACDF, PLF, and total knee arthroplasty (TKA). Average total costs of the procedures were compared by state and geographic region. RESULTS: Combined professional and facility costs for a single-level ACDF had a national mean of $13,899. Total costs for a single-level PLF had a mean of $25,858. Total costs for a primary TKA had a national mean of $13,039. The cost increased to an average of $22,138 for TKA with major comorbidities. Analysis of geographic trends showed statistically significant differences in total costs of PLF, TKA, and TKA, with major complications or comorbidities between geographic regions (P < 0.01 for all). CONCLUSION: Three of the 4 procedures (PLF, TKA, and TKA with major complications or comorbidities) showed statistically significant variation in cost between geographic regions. The Midwest provided the lowest cost for all procedures. Similar geographic trends in the cost of spinal fusions and TKAs suggest that these trends may not be limited to spine-related procedures. Surgical costs were found to correlate with cost of living but were not associated with the population of the state. These data shed light on the actual cost of common surgical procedures throughout the United States and will allow further progress toward the development of cost-effective, value-driven care. LEVEL OF EVIDENCE: 3.

An anatomic study to determine the optimal entry point, medial angles, and effective length for safe fixation using posterior C1 lateral mass screws.

STUDY DESIGN: Anatomic study of the C1 lateral mass using fine-cut computed tomographic scans and Mimics software. OBJECTIVE: To investigate the optimal entry point, medial angles, and effective length for safe fixation using posterior C1 lateral mass screws. SUMMARY OF BACKGROUND DATA: Placing posterior C1 lateral mass screws is technically demanding, and a misplaced screw can result in injury to the vertebral artery, spinal cord, or internal carotid artery. Although various insertion angles have been proposed for posterior C1 lateral mass screw, no clear consensus has been reached on the ideal medial angle of the C1 lateral mass. METHODS: The C1 lateral masses were evaluated using computed tomographic scans and Mimics software in 70 patients. The effective width and effective screw length of posterior C1 lateral mass screws were measured at different medial angulations relative to the midline sagittal plane. The height (H) for screw entry point on the posterior surface of C1 lateral mass and the distance (D) between screw entry point and the intersection of the midline sagittal plane and the posterior arch of the atlas were also measured. RESULTS: The mean height (H) for screw entry on the posterior surface of the lateral mass was 4.25 mm, the mean distance (D) between screw entry point and the intersection of the midsagittal plane and the posterior arch of the atlas was 27.62 mm. The optimal medial angle was 20.86° with a corresponding effective width of 10.56 mm and effective screw length of 21.87 mm. CONCLUSION: This study helps to define the specific anatomy related to C1 posterior lateral mass screw placement in an effort to facilitate instrumentation. However, variation is seen in lateral mass anatomy, and this study must be combined with customized surgical planning that includes advanced imaging for safe and effective instrumentation. LEVEL OF EVIDENCE: 1.

Deviation analysis of C2 translaminar screw placement assisted by a novel rapid prototyping drill template: a cadaveric study.

PURPOSE: The goal of this study is to evaluate the accuracy of patient-specific CT-based rapid prototype drill templates for C2 translaminar screw insertion. METHODS: Volumetric CT scanning was performed in 32 cadaveric cervical spines. Using computer software, the authors constructed drill templates that fit onto the posterior surface of the C2 vertebrae with drill guides to match the slope of the patient's lamina. Thirty-two physical templates were created from the computer models using a rapid prototyping machine. The drill templates were used to guide drilling of the lamina and post-operative CT images were obtained. The entry point and direction of the planned and inserted screws were measured and compared. RESULTS: Sixty-four C2 translaminar screws were placed without violating the cortical bone of a single lamina. The bilateral average transverse angle of intended and actual screw for C2TLS was 56.60 ± 2.22°, 56.38 ± 2.51°, 56.65 ± 2.24°, 56.39 ± 2.45°. The bilateral mean coronal angle of the planned and actual screw for C2TLS was 0°, 0°, -0.07 ± 0.32°, 0.12 ± 0.57°. The average displacement of the entry point of the superior and inferior C2TLS in the x, y, z axis was 0.27 ± 0.85, 0.49 ± 1.46, -0.28 ± 0.69, 0.43 ± 0.88, 0.38 ± 1.51, 0.23 ± 0.64 mm. CONCLUSION: The small deviations seen are likely due to human error in the form of small variations in the surgical technique and use of software to design the prototype. This technology improves the safety profile of this fixation technique and should be further studied in clinical applications.