The Hip Center Rule Can be Used to Decide if Measured Pelvic Incidence is Accurate.

STUDY DESIGN: Simulation study. OBJECTIVE: Pelvic incidence (PI) should be considered during surgical planning. The ideal patient position with both hip centers perfectly aligned for a lateral radiograph is rarely obtained. It has been suggested that a radiograph with axial and coronal rotation up to 20° is acceptable to obtain a measured PI within 6 degrees of the actual PI. We seek to: (1) evaluate the effect of variations in PI and patient malpositioning on measured vs true PI, and (2) determine whether the presence of one hip center within the bony acetabular rim of the contralateral hip can serve as a simple clinical decision rule on the accuracy of measured PI. METHODS: Published anthropometric three-dimensional pelvic landmark coordinates were used in this study. Radiographic projections were generated using linear algebra for combinations of axial and coronal rotation from -20° to +20°. True and measured PIs were compared. RESULTS: Rotation to 20° cannot be uniformly accepted as decision rule. Pelvises with higher PIs are more sensitive to malpositioning with greater PI deviation with smaller amounts of rotation. Diagnostic performance of the hip center rule demonstrated a sensitivity of 25.58% and a specificity of 100.00%. CONCLUSIONS: Rather than assessing the quality of radiographs for PI measurement by magnitude of malpositioning, we recommend clinicians use the "hip center rule." As long as at least one hip center is contained within the bony acetabular rim of the contralateral hip, there is high confidence that measured PI will be within 6° of true PI.

Calculating ex-ante Utilities From the Neck Disability Index Score: Quantifying the Value of Care For Cervical Spine Pathology.

STUDY DESIGN: General population utility valuation study. OBJECTIVE: To develop a technique for calculating utilities from the Neck Disability Index (NDI) score. METHODS: We recruited a sample of 1200 adults from a market research panel. Using an online discrete choice experiment (DCE), participants rated 10 choice sets based on NDI health states. A multi-attribute utility function was estimated using a mixed multinomial-logit regression model (MIXL). The sample was partitioned into a training set used for model fitting and validation set used for model evaluation. RESULTS: The regression model demonstrated good predictive performance on the validation set with an AUC of .77 (95% CI: .76-.78). The regression model was used to develop a utility scoring rubric for the NDI. Regression results also revealed that participants did not regard all NDI items as equally important. The rank order of importance was (in decreasing order): pain intensity = work; personal care = headache; concentration = sleeping; driving; recreation; lifting; and lastly reading. CONCLUSIONS: This study provides a simple technique for converting the NDI score to utilities and quantify the relative importance of individual NDI items. The ability to evaluate quality-adjusted life-years using these utilities for cervical spine pain and disability could facilitate economic analysis and aid in allocation of healthcare resources.

Calculating Ex-ante Utilities From the Modified Japanese Orthopedic Association Score: A Prerequisite for Quantifying the Value of Care for Cervical Myelopathy.

STUDY DESIGN: General population utility valuation study. OBJECTIVE: The aim of this study was to develop a technique for calculating utilities from the modified Japanese Orthopedic Association (mJOA) Score. SUMMARY OF BACKGROUND DATA: The ability to calculate quality-adjusted life-years (QALYs) for degenerative cervical myelopathy (DCM) would enhance treatment decision making and facilitate economic analysis. QALYs are calculated using utilities. METHODS: We recruited a sample of 760 adults from a market research panel. Using an online discrete choice experiment, participants rated eight choice sets based on mJOA health states. A multiattribute utility function was estimated using a mixed multinomial-logit regression model. The sample was partitioned into a training set used for model fitting and validation set used for model evaluation. RESULTS: The regression model demonstrated good predictive performance on the validation set with an area under the curve of 0.81 (95% confidence interval: 0.80-0.82)). The regression model was used to develop a utility scoring rubric for the mJOA. Regression results revealed that participants did not regard all mJOA domains as equally important. The rank order of importance was (in decreasing order): lower extremity motor function, upper extremity motor function, sphincter dysfunction, upper extremity sensation. CONCLUSION: This study provides a simple technique for converting the mJOA score to utilities and quantify the importance of mJOA domains. The ability to evaluate QALYs for DCM will facilitate economic analysis and patient counseling. Clinicians should heed these findings and offer treatments that maximize function in the attributes viewed most important by patients.Level of Evidence: 3.

Calculating Utilities From the Spine Oncology Study Group Outcomes Questionnaire: A Necessity for Economic and Decision Analysis.

STUDY DESIGN: General population utility valuation study. OBJECTIVE: The aim of this study was to develop a technique for calculating utilities from the Spine Oncology Study Group Outcomes Questionnaire v2.0 (SOSGOQ2.0). SUMMARY OF BACKGROUND DATA: The ability to calculate quality-adjusted life-years (QALYs) for metastatic spine disease would enhance treatment decision-making and facilitate economic analysis. QALYs are calculated using utilities. METHODS: Using a hybrid concept-retention and factorial analysis shortening approach, we first shortened the SOSGOQ2.0 to eight items (SOSGOQ-8D). This was done to lessen the cognitive burden of the utility valuation exercise. A general population sample of 2730 adults was then asked to evaluate 12 choice sets based on SOSGOQ-8D health states in a Discrete Choice Experiment. A utility scoring rubric was then developed using a mixed multinomial-logit regression model. RESULTS: We were able to reduce the SOSGOQ2.0 to an SOSGOQ-8D with a mean error of 0.003 and mean absolute error of 3.078 compared to the full questionnaire. The regression model demonstrated good predictive performance and was used to develop a utility scoring rubric. Regression results revealed that participants did not regard all SOSGOQ-8D items as equally important. CONCLUSION: We provide a simple technique for converting the SOSGOQ2.0 to utilities. The ability to evaluate QALYs in metastatic spine disease will facilitate economic analysis and patient counseling. We also quantify the importance of individual SOSGOQ-8D items. Clinicians should heed these findings and offer treatments that maximize function in the most important items.Level of Evidence: 3.

Rotational Anatomy of the Radius and Ulna: Surgical Implications.

PURPOSE: The rotational anatomy of the forearm bones is not well defined. This study aims to further the understanding of the torsion of the radius and ulna to better guide treatment. METHODS: Computed tomography images of 98 cadaveric forearms were obtained and 3-dimensional models of the radius and ulna were generated and analyzed. The rotation of the radius was evaluated by comparing the orientation of the distal radius central axis (DRCA) with the volar cortex of the distal radius (DR) and biceps tuberosity (BT). The rotation of the ulna was evaluated by assessing the orientation of the ulnar head with respect to the proximal ulna. RESULTS: The DR volar cortex pronates from distal to proximal. The BT was 43.8° ± 16.9° supinated from the DRCA (range, 2.7°-86.5°). The mean difference in rotation between contralateral biceps tuberosities was 7.0° ± 7.1°. The volar cortex of the DR was 12.6° ± 5.4° supinated compared with the DRCA. The ulnar head was pronated 8.4° ± 14.9° with respect to the greater sigmoid notch (range, 50.3° pronation-22.0° supination). CONCLUSIONS: The BT has a variable orientation relative to the DR, but it is generally located anteromedially in a supinated arm or 136° opposite the radial styloid. Understanding the rotational anatomy of the radius and ulna can play an important role in surgical planning and implant design. The rotational anatomy of the radius and ulna varies significantly between individuals, but is similar in contralateral limbs. CLINICAL RELEVANCE: Distal radius volar cortex rotational anatomy can help guide treatment of DR fractures and malunions as well as assist in positioning of wrist arthroplasty implants, particularly in the presence of bone loss. The side-to-side similarities demonstrated in this study should be helpful in managing patients with segmental bone loss or fracture malunion and those requiring joint reconstruction.

A technique for approximating transition rates from published survival analyses.

BACKGROUND: Quality-adjusted-life-years (QALYs) are used to concurrently quantify morbidity and mortality within a single parameter. For this reason, QALYs can facilitate the discussion of risks and benefits during patient counseling regarding treatment options. QALYs are often calculated using partitioned-survival modelling. Alternatively, QALYs can be calculated using more flexible and informative state-transition models populated with transition rates estimated using multistate modelling (MSM) techniques. Unfortunately the latter approach is considered not possible when only progression-free survival (PFS) and overall survival (OS) analyses are reported. METHODS: We have developed a method that can be used to estimate approximate transition rates from published PFS and OS analyses (we will refer to transition rates estimated using full multistate methods as true transition rates). RESULTS: The approximation method is more accurate for estimating the transition rates out of health than the transition rate out of illness. The method tends to under-estimate true transition rates as censoring increases. CONCLUSIONS: In this article we present the basis for and use of the transition rate approximation method. We then apply the method to a case study and evaluate the method in a simulation study.

A General Population Utility Valuation Study for Metastatic Epidural Spinal Cord Compression Health States.

STUDY DESIGN: General population utility valuation study. OBJECTIVE: This study obtained utility valuations from a Canadian general population perspective for 31 unique metastatic epidural spinal cord compression (MESCC) health states and determined the relative importance of MESCC-related consequences on quality-of-life. SUMMARY OF BACKGROUND DATA: Few prospective studies on the treatment of MESCC have collected quality-adjusted-life-year weights (termed "utilities"). Utilities are an important summative measure which distills health outcomes to a single number that can assist healthcare providers, patients, and policy makers in decision making. METHODS: We recruited a sample of 1138 adult Canadians using a market research company. Quota sampling was used to ensure that the participants were representative of the Canadian population in terms of age, sex, and province of residence. Using the validated MESCC module for the "Self-administered Online Assessment of Preferences" (SOAP) tool, participants were asked to rate six of the 31 MESCC health states, each of which presented varying severities of five MESCC-related dysfunctions (dependent; non-ambulatory; incontinent; pain; other symptoms). RESULTS: Participants equally valued all MESCC-related dysfunctions which followed a pattern of diminishing marginal disutility (each additional consequence resulted in a smaller incremental decrease in utility than the previous). These results demonstrate that the general population values physical function equal to other facets of quality-of-life. CONCLUSION: We provide a comprehensive set of ex ante utility estimates for MESCC health states that can be used to help inform decision making. This is the first study reporting direct utility valuation for a spinal disorder. Our methodology offers a feasible solution for obtaining quality-of-life data without collecting generic health status questionnaire responses from patients. LEVEL OF EVIDENCE: 4.

Back to Bayesian: A strategy to enhance prognostication of metastatic spine disease.

AIMS: Clinicians must consider prognosis when offering treatment to patients with spine metastases. Although several prognostic indices have been developed and validated for this purpose, they may not be applicable in the current era of targeted systemic therapies. Even before the introduction of targeted therapies, these prognostic indices should not have been directly used for individual patient decision making without contextualising with other sources of data. By contextualising, we mean that prognostic estimates should not be based on these scores alone and formally incorporate clinically relevant factors not part of prognostic indices. Contextualisation requires the use of Bayesian statistics which may be unfamiliar to many readers. In this paper we show readers how to correctly apply prognostic scores to individual patients using Bayesian statistics. Through Bayesian analysis, we explore the impact of new targeted therapies on prognostic estimates obtained using the Tokuhashi score. METHODS: We provide a worked calculation for the probability of a patient surviving up to 6 months using dichotomous prognostication. We then demonstrate how to calculate a patient's expected survival using continuous prognostication. Sensitivity of the posterior distribution to prior assumptions is illustrated through effective sample size adjustment. RESULTS: When the predicted prognosis from the Tokuhashi score is contextualised with data on contemporary systemic treatments, patients previously deemed non-surgical candidates may be eligible for surgery. CONCLUSIONS: Bayesian prognostication generates intuitive results and allows multiple data points to be synthesised transparently. These techniques can extend the usefulness of existing prognostic scores in the era of targeted systemic therapies.

Adverse events and their risk factors 90 days after cervical spine surgery: analysis from the Michigan Spine Surgery Improvement Collaborative.

OBJECTIVEThe Michigan Spine Surgery Improvement Collaborative (MSSIC) is a statewide, multicenter quality improvement initiative. Using MSSIC data, the authors sought to identify 90-day adverse events and their associated risk factors (RFs) after cervical spine surgery.METHODSA total of 8236 cervical spine surgery cases were analyzed. Multivariable generalized estimating equation regression models were constructed to identify RFs for adverse events; variables tested included age, sex, diabetes mellitus, disc herniation, foraminal stenosis, central stenosis, American Society of Anesthesiologists Physical Classification System (ASA) class > II, myelopathy, private insurance, anterior versus posterior approach, revision procedures, number of surgical levels, length of procedure, blood loss, preoperative ambulation, ambulation day of surgery, length of hospital stay, and discharge disposition.RESULTSNinety days after cervical spine surgery, adverse events identified included radicular findings (11.6%), readmission (7.7%), dysphagia requiring dietary modification (feeding tube or nothing by mouth [NPO]) (6.4%), urinary retention (4.7%), urinary tract infection (2.2%), surgical site hematoma (1.1%), surgical site infection (0.9%), deep vein thrombosis (0.7%), pulmonary embolism (0.5%), neurogenic bowel/bladder (0.4%), myelopathy (0.4%), myocardial infarction (0.4%), wound dehiscence (0.2%), claudication (0.2%), and ileus (0.2%). RFs for dysphagia included anterior approach (p < 0.001), fusion procedures (p = 0.030), multiple-level surgery when considering anterior procedures only (p = 0.037), and surgery duration (p = 0.002). RFs for readmission included ASA class > II (p < 0.001), while preoperative ambulation (p = 0.001) and private insurance (p < 0.001) were protective. RFs for urinary retention included increasing age (p < 0.001) and male sex (p < 0.001), while anterior-approach surgery (p < 0.001), preoperative ambulation (p = 0.001), and ambulation day of surgery (p = 0.001) were protective. Preoperative ambulation (p = 0.010) and anterior approach (p = 0.002) were protective of radicular findings.CONCLUSIONSA multivariate analysis from a large, multicenter, prospective database identified the common adverse events after cervical spine surgery, along with their associated RFs. This information can lead to more informed surgeons and patients. The authors found that early mobilization after cervical spine surgery has the potential to significantly decrease adverse events.

Thoracic Epidural Abscesses: A Systematic Review.

STUDY DESIGN: Systematic review. OBJECTIVES: Past research has demonstrated increased speed and severity of progression for spinal epidural abscesses (SEAs) of the thoracic level, specifically, when compared with SEAs of other spinal cord levels. Untreated, this infection can result in permanent neurological sequelae with eventual progression to death if inadequately managed. Despite the seriousness of this disease, no articles have focused on the presentation, diagnosis, and treatment of SEAs of the thoracic level. For this reason, specific focus on SEAs of the thoracic level occurred when researchers designed and implemented the following systematic review. METHODS: A query of Ovid-Medline and EMBASE, Cochrane Central, and additional review sources was conducted. Search criteria focused on articles specific to thoracic epidural abscesses. RESULTS: Twenty-five articles met inclusion criteria. The most commonly reported symptoms present on admission included back pain, paraparesis/paraplegia, fever, and loss of bowel/bladder control. Significant risk factors included diabetes, intravenous drug use, and advanced age (P = .001). Patients were most often treated surgically with either laminectomy, hemilaminectomy, or radical decompression with debridement. Patients who presented with neurological deficits and had delayed surgical intervention following a failed antibiotic course tended to do worse compared with their immediate surgical management counterparts (P < .005). CONCLUSIONS: For the first time researchers have focused specifically on SEAs of the thoracic level, as opposed to previously published general analysis of SEAs as a whole. Based on the results, investigators recommend early magnetic resonance imaging of the spine, laboratory workup (sedimentation rate/C-reactive protein, complete blood count), abscess culture followed by empiric antibiotics, and immediate surgical decompression when neurological deficits are present.

Virtual fracture carving improves understanding of a complex fracture: a randomized controlled study.

BACKGROUND: The visual overlay technique for surgical planning is difficult to apply to spatially complex fractures. Virtual reality can be applied by virtual fracture carving to adapt the visual overlay technique to three-dimensional (3D) images. In this study, we evaluated whether virtual fracture carving is a useful exercise by performing two experiments comparing trainees' understanding of a complex fracture with the application of either current preoperative techniques or the use of the Virtual-Fracture-Carving Simulator. METHODS: Forty-eight participants-senior medical students and residents in postgraduate year 1 (PGY1)-were asked to learn the anatomy of an associated both-column acetabular fracture. The participants were randomized into three groups: control, Sawbones, and virtual (Virtual-Fracture-Carving Simulator). The randomization protocol was stratified for sex and visuospatial ability. The measure of learning was a fracture line-drawing task evaluated for nineteen anatomic relationships. RESULTS: The virtual group performed better than both the control and the Sawbones group, with an absolute difference in score of 22.7% (p = 0.0001) and 17.8% (p = 0.0026), respectively. There was no significant difference between the control and Sawbones groups. The virtual group drew fracture characteristics requiring a higher level of spatial understanding with greater accuracy. CONCLUSIONS: The results of this study validate the concept behind the visual overlay planning technique-i.e., that thoughtful play promotes understanding of fracture anatomy. These results objectively demonstrate that the use of a Virtual-Fracture-Carving Simulator is feasible, and superior to conventional preoperative planning strategies in terms of quantity and quality of understanding of a spatially complex fracture.

Biometric morphing: a novel technique for the analysis of morphologic outcomes after facial surgery.

The results of facial surgery are intuitively judged in terms of the visible changes in facial features or proportions. However, describing these morphologic outcomes objectively remains a challenge. Biometric morphing addresses this issue by merging statistical shape analysis and image processing. This study describes the implementation of biometric morphing in describing the average morphologic result of facial surgery. The biometric morphing protocol was applied to pre- and postoperative images of the following: (1) 40 dorsal hump reduction rhinoplasties and (2) 20 unilateral enophthalmos repairs. Pre- and postoperative average images (average morphs) were generated. The average morphs provided an objective rendering of nasal and periorbital morphology, which summarized the average features and extent of deformity in a population of patients. Subtle alterations in morphology after surgery, which would otherwise be difficult to identify or demonstrate, were clearly illustrated. Biometric morphing is an effective instrument for describing average facial morphology in a population of patients.