Calculation of the minimal clinically important difference in operated patients with adult spine deformity: advantages of the ROC method and significance of prevalence in threshold selection.

PURPOSE: The Minimal Clinically Important Difference (MCID) is crucial to evaluate management outcomes, but different thresholds have been obtained in different works. Part of this variability is due to measurement error and influence of the database, both essential for calculating the MCID. The aim of this study was to introduce the association of the ROC method in the anchor-based MCID calculation for ODI, SRS-22r, and SF-36, to objectively set the threshold for the anchor-based MCID in an adult spine deformity (ASD) population. METHODS: Multicentric study based on a prospective database of consecutively operated ASD patients. An anchor question was used to assess patients' quality of life after surgery. Different approaches were used to calculate the MCID and then compared: SEM (Standard Error of Measurement), MDC (Minimal Detectable Change), and anchor-based MCID with ROC method. RESULTS: 516 patients were included. Those who responded with 6 and 7 to the anchor question were considered improved. The MCID ranges obtained with the ROC method exhibited the lowest variability. Prediction error rates ranged from 31% (SRS-22r) to 41% (SF-36 MCS). The MCID ranges spanned between 12 and 15 for ODI, 0.6 and 0.73 for SRS-22r, 6.62 and 7.41 for SF-36 PCS, and between 2.69 and 5.63 for SF-36 MCS. CONCLUSION: The ROC method proposes an MCID range with error rate, and can objectively determine the threshold for distinguishing improved and non-improved patients. As the MCID correlates with the utilized database and error of measurement, each study should compute its own MCID for each PROM to allow comparison among different publications. LEVEL OF EVIDENCE: II.

Evaluation of "appropriate use criteria" for surgical decision-making in lumbar degenerative spondylolisthesis. A controlled, multicentre, prospective observational study.

INTRODUCTION: Selecting patients with lumbar degenerative spondylolisthesis (LDS) for surgery is difficult. Appropriate use criteria (AUC) have been developed to clarify the indications for LDS surgery but have not been evaluated in controlled studies. METHODS: This prospective, controlled, multicentre study involved 908 patients (561 surgical and 347 non-surgical controls; 69.5 ± 9.7y; 69% female), treated as per normal clinical practice. Their appropriateness for surgery was afterwards determined using the AUC. They completed the Core Outcome Measures Index (COMI) at baseline and 12 months' follow-up. Multiple regression adjusting for confounders evaluated the influence of appropriateness designation and treatment received on the 12-month COMI and achievement of MCIC (≥ 2.2-point-reduction). RESULTS: As per convention, appropriate (A) and uncertain (U) groups were combined for comparison with the inappropriate (I) group. For the adjusted 12-month COMI, the benefit of surgery relative to non-surgical care was not significantly greater for the A/U than the I group (p = 0.189). There was, however, a greater treatment effect of surgery for those with higher baseline COMI (p = 0.035). The groups' adjusted probabilities of achieving MCIC were: 83% (A/U, receiving surgery), 71% (I, receiving surgery), 50% (A/U, receiving non-surgical care), and 32% (I, receiving non-surgical care). CONCLUSIONS: A/U patients receiving surgery had the highest chances of achieving MCIC, but the AUC were not able to identify which patients had a greater treatment effect of surgery relative to non-surgical care. The identification of other characteristics that predict a greater treatment effect of surgery, in addition to baseline COMI, is required to improve decision-making.

Validation of a surgical invasiveness index in patients with lumbar spinal disorders registered in the Spine Tango registry.

INTRODUCTION: Being able to quantify the invasiveness of a surgical procedure is important to weigh up its associated risks, since invasiveness governs the blood loss, operative time and likelihood of complications. Mirza et al. (Spine (Phila Pa 1976) 33:2651-2661, 2008) published an invasiveness index for spinal surgery. We evaluated the validity of a modified version of the Mirza invasiveness index (mMII), adapted for use with registry data. METHODS: A cross-sectional analysis was performed with data acquired from the Spine Tango registry including 21,634 patients. The mMII was calculated as the sum of six possible interventions on each vertebral level: decompression, fusion and stabilization either on anterior or posterior structures. The association between the mMII and blood loss, operative time and complications was evaluated using multiple regression, adjusting for possible confounders. RESULTS: The mean (± SD) mMII was 3.9 ± 5.0 (range 0-40). A 1-point increase in the mMII was associated with an additional blood loss of 12.8% (95% CI 12.6-13.0; p < 0.001) and an increase of operative time of 10.4 min (95% CI 10.20-10.53; p < 0.001). The R2 for the blood loss model was of 43% and for operative time, 47%. The mean mMII was significantly (p < 0.001) higher in patients with surgical complications (4.5 ± 5.6) and general medical complications (6.5 ± 7.0) compared to those without (3.8 ± 4.9). Our results were comparable to those reported in the original publication of Mirza et al. CONCLUSION: The mMII appeared to be a valid measure of surgical invasiveness in our study population. It can be used in predictor models and to adjust for surgical case-mix when comparing outcomes in different studies or different hospitals/surgeons in a registry.

The impact of deep surgical site infection on surgical outcomes after posterior adult spinal deformity surgery: a matched control study.

PURPOSE: The impact of deep surgical site infection (SSI) on surgical outcomes after adult spinal deformity (ASD) surgery is still unclear. We aimed to study the morbidity of SSI in ASD and its impact on deformity correction and functional outcome. METHODS: Prospective multicenter matched-cohort study including consecutively enrolled ASD patients. Patients developing SSI were matched to similar controls in terms of age, gender, ASA, primary or revision, extent of fusion, and use of tri-columnar osteotomies. Preoperative parameters, surgical variables, and complications were recorded. Deformity parameters and Health Related Quality of Life (HRQoL) scores were obtained preoperatively and at 6, 12, and 24 months. Independent t test and Fischer's exact test were used for comparisons. RESULTS: 444 surgical ASD patients with more than 2 years of follow-up were identified. 20 sustained an acute SSI and 60 controls were accordingly matched. No differences were observed between groups in preoperative radiological and HRQoL variables confirming comparable groups. SSI patients had longer hospital stay and more mechanical complications including proximal junctional kyphosis. Infection was associated with more unrelated complications and revisions. Deformity correction was maintained equally at the different time intervals. One death was related to SSI. SSI patients had worse overall HRQoL status at 1 year and were less likely to experience improvement. However, no significant differences were recorded thereafter. CONCLUSION: SSI significantly affects the first postoperative year after posterior ASD surgery. It is associated with more complications, unrelated revisions, and worst quality of life. However it's negative impact seems to be diluted by the second postoperative year as differences in HRQoL scores between the two groups decrease. These slides can be retrieved under Electronic Supplementary material.

The Impact of Unplanned Reoperation Following Adult Spinal Deformity Surgery: A Prospective Longitudinal Cohort Study with 5-Year Follow-up.

BACKGROUND: The long-term impact of reoperations following adult spinal deformity (ASD) surgery is still poorly understood. Our aim was to identify the relationship between unplanned reoperation and health-related quality of life (HRQoL) gain at 2 and 5 years of follow-up. METHODS: We included patients enrolled in a prospective ASD database who underwent surgery ≥5 years prior to the start of the study and who had 2 years of follow-up data. Adverse events (AEs) leading to an unplanned reoperation, the time of reoperation occurrence, invasiveness (blood loss, surgical time, hospital stay), and AE resolution were assessed. HRQoL was measured with use of the Oswestry Disability Index, Scoliosis Research Society-22, and Short Form-36. Linear models controlling for baseline data and index surgery characteristics were utilized to assess the relationships between HRQoL gain at 2 and 5-year follow-up and the number and invasiveness of reoperations. The association between 5-year HRQoL gain and the time of occurrence of the unplanned reoperation and that between 5-year HRQoL gain and AE resolution were also investigated. RESULTS: Of 361 eligible patients, 316 (87.5%) with 2-year follow-up data met the inclusion criteria and 258 (71.5%) had 5-year follow-up data. At the 2-year follow-up, 96 patients (30.4%) had a total of 165 unplanned reoperations (1.72 per patient). At the 5-year follow-up, 73 patients (28.3%) had a total of 117 unplanned reoperations (1.60 per patient). The most common cause of reoperations was mechanical complications (64.9%), followed by surgical site infections (15.7%). At the 5-year follow-up, the AE that led to reoperation was resolved in 67 patients (91.8%). Reoperation invasiveness was not associated with 5-year HRQoL scores. The number of reoperations was associated with lesser HRQoL gain at 5 years for all HRQoL measures. The mean associated reduction in HRQoL gain per unplanned reoperation was 41% (range, 19% to 66%). Reoperations resulting in no resolution of the AE or resolution with sequelae had a greater impact on 5-year follow-up HRQoL scores than reoperations resulting in resolution of the AE. CONCLUSIONS: A postoperative, unplanned reoperation following ASD surgery was associated with lesser gain in HRQoL at 5 years of follow-up. The association did not diminish over time and was affected by the number, but not the magnitude, of reoperations. Resolution of the associated AE reduced the impact of the unplanned reoperation. LEVEL OF EVIDENCE: Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Ratings of global outcome at the first post-operative assessment after spinal surgery: how often do the surgeon and patient agree?

Patient-orientated questionnaires are becoming increasingly popular in the assessment of outcome and are considered to provide a less biased assessment of the surgical result than traditional surgeon-based ratings. The present study sought to quantify the level of agreement between patients' and doctors' global outcome ratings after spine surgery. 1,113 German-speaking patients (59.0 +/- 16.6 years; 643 F, 470 M) who had undergone spine surgery rated the global outcome of the operation 3 months later, using a 5-point scale: operation helped a lot, helped, helped only little, didn't help, made things worse. They also rated pain, function, quality-of-life and disability, using the Core Outcome Measures Index (COMI), and their satisfaction with treatment (5-point scale). The surgeon completed a SSE Spine Tango Follow-up form, blind to the patient's evaluation, rating the outcome with the McNab criteria as excellent, good, fair, and poor. The data were compared, in terms of (1) the correlation between surgeons' and patients' ratings and (2) the proportions of identical ratings, where the doctor's "excellent" was considered equivalent to the patient's "operation helped a lot", "good" to "operation helped", "fair" to "operation helped only little" and "poor" to "operation didn't help/made things worse". There was a significant correlation (Spearman Rho = 0.57, p < 0.0001) between the surgeons' and patients' ratings. Their ratings were identical in 51.2% of the cases; the surgeon gave better ratings than the patient ("overrated") in 25.6% cases and worse ratings ("underrated") in 23.2% cases. There were significant differences between the six surgeons in the degree to which their ratings matched those of the patients, with senior surgeons "overrating" significantly more often than junior surgeons (p < 0.001). "Overrating" was significantly more prevalent for patients with a poor self-rated outcome (measured as global outcome, COMI score, or satisfaction with treatment; each p < 0.001). In a multivariate model controlling for age and gender, "low satisfaction with treatment" and "being a senior surgeon" were the most significant unique predictors of surgeon "overrating" (p < 0.0001; adjusted R (2) = 0.21). Factors with no unique significant influence included comorbidity (ASA score), first time versus repeat surgery, one-level versus multilevel surgery. In conclusion, approximately half of the patient's perceptions of outcome after spine surgery were identical to those of the surgeon. Generally, where discrepancies arose, there was a tendency for the surgeon to be slightly more optimistic than the patient, and more so in relation to patients who themselves declared a poor outcome. This highlights the potential bias in outcome studies that rely solely on surgeon ratings of outcome and indicates the importance of collecting data from both the patient and the surgeon, in order to provide a balanced view of the outcome of spine surgery.

Stability analysis of craniovertebral junction fixation techniques.

BACKGROUND: Craniovertebral arthrodesis in the upper cervical spine is challenging because of the high degree of mobility afforded by this region. A novel method for achieving atlantoaxial fixation with use of polyaxial screws inserted bilaterally into the lateral masses of C1 and transpedicularly into C2 with longitudinal rod connection has recently been introduced. The question remains as to whether this technique provides adequate stability when extended cephalad to include the occiput. The purpose of this study was to determine the primary stability afforded by this novel construct and compare its stability with the current standard of bilateral longitudinal plates combined with C1-C2 transarticular screws. METHODS: We used ten fresh-frozen human cadaveric cervical spines (C0-C4). Pure moment loads were applied to the occiput, and C4 was constrained during the testing protocol. We evaluated four conditions: (1) intact, (2) destabilized by means of complete odontoidectomy, (3) stabilization with longitudinal plates with C1-C2 transarticular screw fixation, and (4) stabilization with a posterior rod system with C1 lateral mass screws and C2 pedicle screws. Rigid-body three-dimensional rotations were detected by stereophotogrammetry by means of a three-camera system with use of marker triads. The range of motion data (C0-C2) for each fixation scenario was calculated, and a statistical analysis was performed. RESULTS: Destabilization of the specimen significantly increased C0-C2 motion in both flexion-extension and lateral bending (p < 0.05). Both fixation constructs significantly reduced motion in the destabilized spine by over 90% for all motions tested (p < 0.05). No significant differences were detected between the two constructs in any of the three rotational planes. CONCLUSIONS: Both hardware systems provide equivalent construct stability in the immediate postoperative period when it is critical for the eventual success of a craniovertebral arthrodesis. On the basis of this work, we believe that the decision to use either construct should be determined by clinical rather than biomechanical concerns.

The assessment of complications after spine surgery: time for a paradigm shift?

BACKGROUND CONTEXT: Recent years have witnessed a shift in the assessment of spine surgical outcomes with a greater focus on the patient's perspective. However, this approach has not been widely extended to the assessment of complications. PURPOSE: The present study sought to quantify the patient-rated impact/severity of complications of spine surgery and directly compare the incidences of surgeon-rated and patient-reported complications. STUDY DESIGN: Prospective study of patients undergoing surgery for painful degenerative lumbar disorders, being operated in the Spine Center of an orthopedic hospital. PATIENT SAMPLE: A total of 2,303 patients (mean [standard deviation] age, 61.9 [15.1] years; 1,136 [49.3%] women and 1,167 [50.7%] men). PATIENTS: Core Outcome Measures Index, self-rated complications, bothersomeness of complications, global treatment outcome, and satisfaction. Surgeons: Spine Tango surgery and follow-up documentation forms registering surgical details and complications. METHODS: PATIENTS completed questionnaires before and 3 months after surgery. Surgeons documented complications before discharge and at the first postoperative follow-up, 6 to 12 weeks after surgery. RESULTS: In total, 615 out of 2,303 (27%) patients reported complications, with "bothersomeness" ratings of 1%, not at all; 22%, slightly; 26%, moderately; 34%, very; and 17%, extremely bothersome. PATIENTS most commonly reported sensory disturbances (35% of those reporting a complication) or ongoing/new pain (27%) followed by wound healing problems (11%) and motor disturbances (8%). The surgeons documented complications in 19% of patients. There was a minimal overlap regarding the presence or absence of complications in any given patient. CONCLUSIONS: Most complications reported by the patient are perceived to be at least moderately bothersome and are, hence, not inconsequential. Surgeons reported lower complication rates than the patients did, and there was only moderate agreement between the ratings of the two. As with treatment outcome, complications and their severity should be assessed from both the patient's and the surgeon's perspectives.

Comparison of patient and surgeon ratings of outcome 12 months after spine surgery: presented at the 2009 Joint Spine Section Meeting.

OBJECT: The contemporary assessment of spine surgical outcome primarily relies on patient-centered reports of symptoms and function. Such measures are considered to reduce bias compared with traditional surgeon-based outcome ratings. This study examined the agreement between patients' and surgeons' ratings of outcome 1 year after spine surgery. METHODS: The study involved 404 patients (mean age 56.6 +/- 16.4 years; 259 women, 145 men) and their treating surgeons. At baseline and 12 months postoperatively patients completed the Core Outcome Measures Index (COMI) rating pain, function, quality of life, and disability. At 12 months postoperatively, they also rated the global outcome of surgery and their satisfaction with treatment. The surgeon, blinded to the patient's evaluation, rated the global outcome of surgery as excellent, good, fair, or poor. RESULTS: Seventy-six percent of the patients who were considered by the surgeon to have an excellent or good outcome achieved the minimum clinically important difference (MCID) of a 2.2-point reduction on the COMI; 24% achieved less than the MCID. There was a significant correlation between the surgeons' and patients' global outcome ratings (Spearman rho = 0.56; p < 0.0001). The degree of absolute agreement between them was significantly influenced by surgeon seniority: senior surgeons "overrated" the outcome in 24.5% of cases (compared with patients' ratings) and "underrated" it in 17.5% of cases. Junior surgeons overrated in 7.8% of cases and underrated in 43.8% of cases (p < 0.0001). Surgeon overrating occurred significantly more frequently for patients with a poor self-rated outcome (measured as global outcome, COMI score, or satisfaction with treatment). In a multivariate model, the independent variables "senior surgeon" and "patient dissatisfaction with care" were the most significant unique predictors of surgeon overrating of the global outcome (p < 0.0001; adjusted R(2) for the model = 0.16). CONCLUSIONS: Overall, agreement between surgeon and patient was reasonably good. The majority of patients who were rated as excellent/good by the surgeons had achieved the MCID in the prospectively measured COMI score. Discrepancies in outcome ratings were influenced by surgeon seniority and patient satisfaction. For a balanced view of the surgical result, outcomes should be assessed from the perspectives of both the patient and the surgeon.

Use of allograft femoral rings for spinal deformity in adults.

Anterior structural support plays an important role in spinal deformity surgery. Femoral ring allografts have been widely used for this purpose despite numerous alternative implants such as cages. The literature and the authors' experience support the use of femoral ring allograft as a structural and biologic compatible implant to reconstruct anterior column defects. Pseudarthrosis rates and the rate of subsidence and loss of correction are low. No long-term studies exist that show that cages are superior in correction of deformity. Femoral ring allograft remains a viable, cost-effective, and biologic sound alternative.

Biomechanical testing of posterior atlantoaxial fixation techniques.

STUDY DESIGN: An in vitro biomechanical study of C1-C2 posterior fusion techniques was conducted using a cadaveric model. OBJECTIVE: To investigate and compare the acute stability afforded by a novel rod-based construct that uses direct polyaxial screw fixation to C1 and C2 with contemporary transarticular screw and wire techniques. SUMMARY AND BACKGROUND DATA: Acute stability of the atlantoaxial complex is required to achieve bony consolidation. Various forms of posterior wiring were the first standardized procedures advocated to achieve C1-C2 fixation, but because of insufficient construct stability, these techniques have been coupled with transarticular screw fixation. Significant technical difficulties, however, including the possibility of neurovascular compromise during implantation are associated with transarticular screw placement. A novel technique that uses direct polyaxial screw fixation to C1 and C2 and bilateral longitudinal rods was developed recently. However, there are no published reports detailing the biomechanical characteristics of this new construct. METHODS: In this study, 10 fresh-frozen human cadaveric cervical spines with occiput (C0-C4) were used. Osteoligamentous specimens were tested in their intact condition after destabilization via odontoidectomy, and after two different Gallie wiring techniques. Each specimen was assigned to one of the two screw fixation groups. Five specimens were implanted with the polyaxial screw-rod construct and tested. The remaining five specimens were tested after application of bilateral C1-C2 transarticular screws with Gallie wiring (Magerl-Gallie technique). Pure-moment loading, up to 1.5 Nm in flexion and extension, right and left lateral bending and right and left axial rotation, was applied to the occiput, and relative intervertebral rotations were determined using stereophotogrammetry (motion analysis system). Range of motion data for all fixation scenarios were normalized to the destabilized case, and statistical analysis was performed using one-way analysis of variance with Fisher's least significant difference PLSD post hoc test for multiple comparisons. RESULTS: The data indicate that destabilization via odontoidectomy significantly increased C1-C2 motion. Both screw techniques significantly decreased motion, as compared with both Gallie wiring methods in lateral bending and axial rotation (P < 0.02 for all) and tended toward reduced motion in flexion-extension. There was no statistically significant difference between the two screw techniques. CONCLUSIONS: The results clearly indicate the screw-rod system's equivalence in reducing relative atlantoaxial motion in a severely destabilized upper cervical spine, as compared with the transarticular screw-wiring construct. These findings mirror the previously reported clinical results attained using this new screw-rod construct. Thus, the decision to use either screw construct should be based on safety considerations rather than acute stability.

Biomechanics of cervical laminoplasty: kinetic studies comparing different surgical techniques, temporal effects and the degree of level involvement.

Laminoplasty is a common surgical technique used to treat cervical myelopathy. Both voids and contradictory information exist in the literature with regard to the initial and long-term biomechanical consequences of cervical laminoplasty. In order to clarify the existing literature, as well as provide clinically useful information, we identified three specific aims: (1) to measure the long-term differences in kinetics between the open door laminoplasty (ODL) and French door laminoplasty (FDL) techniques; (2) to delineate differences in primary and long-term cervical motion after laminoplasty; and (3) to determine whether inclusion of additional levels in the laminoplasty procedure results in a change in immediate cervical biomechanics. The study design involved both an animal (caprine) model and in vitro surgical simulation. We kinematically evaluated the cervical spine specimens (C2-C7) by applying pure bending moment loads to the cephalad vertebra (C2), while constraining the caudal vertebra (C7). Resultant intervertebral rotations (C3-C6) were determined via stereophotogrammetry. Overall, the data indicate that both FDL and ODL significantly reduce range of motion 6 months postoperatively, compared with the un-operated spine. There were no significant differences between the two techniques after 6 months. We also showed that ODL produces a significant reduction in motion 6 months postoperatively compared with the immediate postoperative condition. Finally, the data indicated that extending the laminoplasty from two to four levels did not significantly change range of motion. The choice of technique should be based upon the surgeon's experience with these technically demanding procedures. In addition, initial stability considerations should not affect the decision to extend the laminoplasty to adjacent levels. Finally, the data also suggest that early changes in biomechanics should not be a major factor when considering whether immobilization of the cervical spine is necessary after laminoplasty. In fact, our temporal study, as well as previously reported clinical data, indicates that one should expect significantly decreased intervertebral motion 6 months after laminoplasty. Therefore, early physical therapy should be considered to preserve a more physiologic pattern of cervical range of motion.

Temperature and thermal dose distributions during intradiscal electrothermal therapy in the cadaveric lumbar spine.

STUDY DESIGN: Human cadaveric lumbar spines were used to assess the temperature and thermal dose distribution during intradiscal electrothermal therapy in vitro. OBJECTIVES: To determine whether intradiscal electrothermal therapy produces adequate tissue temperatures to denature annular collagen or ablate nerve cells. SUMMARY OF BACKGROUND DATA: Several hypothesized mechanisms for the effect of intradiscal electrothermal therapy have been suggested and include: 1) shrinkage of the nucleus and/or the annulus fibrosus by contraction of collagen fibers; and 2) thermal ablation of sensitive nerve fibers in the outer annulus. METHODS: Intradiscal electrothermal therapy was performed using the standard clinical protocol on 12 lumbar specimens in a 37.0 degrees C water bath using the SpineCath by Oratec. Temperatures were recorded simultaneously at 40 different locations in the disc. Thermal dose (Equivalent Minutes 43.0 degrees C) was calculated at each temperature point. RESULTS: The highest temperature measured (out of 520 points) was 64.0 degrees C and was within 1 mm of the heating coil. Temperatures in excess of 60 degrees C were all within 1 to 2 mm of the intradiscal electrothermal therapy catheter surface, the 50 to 60 degrees C range extended approximately 6 mm, above 48 degrees C extended approximately 7 mm, and above 45 degrees C extended to approximately 10 mm. Less than 2% of points achieved temperatures sufficient for collagen denaturation (>60 degrees C). On average, 42.5% of points accumulated >250 Equivalent Minutes 43.0 degrees C, a conservative common dose threshold for thermal necrosis of cells. The time history of thermal measurements demonstrated that the disc temperature had not reached steady state by the end of the heating protocol (16.5 minutes). CONCLUSIONS: Except for a very limited margin (1-2 mm) around the catheter, the temperature necessary to induce collagen shrinkage was not observed within the disc. Temperatures sufficient to ablate nerves were developed in some areas but were not reliably produced in clinically relevant regions, such as the posterior annulus. These results suggest that beneficial clinical outcomes may be critically dependent on probe placement or other factors unknown.