Characterization of opioid consumption and disposal patterns after total knee arthroplasty.

AIMS: The aim of this study was to determine the general postoperative opioid consumption and rate of appropriate disposal of excess opioid prescriptions in patients undergoing primary unilateral total knee arthroplasty (TKA). PATIENTS AND METHODS: In total, 112 patients undergoing surgery with one of eight arthroplasty surgeons at a single specialty hospital were prospectively enrolled. Three patients were excluded for undergoing secondary procedures within six weeks. Daily pain levels and opioid consumption, quantity, and disposal patterns for leftover medications were collected for six weeks following surgery using a text-messaging platform. RESULTS: Overall, 103 of 109 patients (94.5%) completed the daily short message service (SMS) surveys. The mean oral morphine equivalents (OME) consumed during the six weeks post-surgery were 639.6 mg (sd 323.7; 20 to 1616) corresponding to 85.3 tablets of 5 mg oxycodone per patient. A total of 66 patients (64.1%) had stopped taking opioids within six weeks of surgery and had the mean equivalent of 18 oxycodone 5 mg tablets remaining. Only 17 patients (25.7%) appropriately disposed of leftover medications. CONCLUSION: These prospectively collected data provide a benchmark for general opioid consumption after uncomplicated primary unilateral TKA. Many patients are prescribed more opioids than they require, and leftover medication is infrequently disposed of appropriately, which increases the risk for illicit diversion. Cite this article: Bone Joint J 2019;101-B(7 Supple C):98-103.

Ultrafast Formation of a Fermi-Dirac Distributed Electron Gas.

Time- and angle-resolved photoelectron spectroscopy with 13 fs temporal resolution is used to follow the different stages in the formation of a Fermi-Dirac distributed electron gas in graphite after absorption of an intense 7 fs laser pulse. Within the first 50 fs after excitation, a sequence of time frames is resolved that are characterized by different energy and momentum exchange processes among the involved photonic, electronic, and phononic degrees of freedom. The results reveal experimentally the complexity of the transition from a nascent nonthermal towards a thermal electron distribution due to the different timescales associated with the involved interaction processes.

Microarray-based capture of novel expressed cell type-specific transfrags (CoNECT) to annotate tissue-specific transcription in Drosophila melanogaster.

Faithful annotation of tissue-specific transcript isoforms is important not only to understand how genes are organized and regulated but also to identify potential novel, unannotated exons of genes, which may be additional targets of mutation in disease states or while performing mutagenic screens. We have developed a microarray enrichment methodology followed by long-read, next-generation sequencing for identification of unannotated transcript isoforms expressed in two Drosophila tissues, the ovary and the testis. Even with limited sequencing, these studies have identified a large number of novel transcription units, including 5' exons and extensions, 3' exons and extensions, internal exons and exon extensions, gene fusions, and both germline-specific splicing events and promoters. Additionally, comparing our capture dataset with tiling array and traditional RNA-seq analysis, we demonstrate that our enrichment strategy is able to capture low-abundance transcripts that cannot readily be identified by the other strategies. Finally, we show that our methodology can help identify transcriptional signatures of minority cell types within the ovary that would otherwise be difficult to reveal without the CoNECT enrichment strategy. These studies introduce an efficient methodology for cataloging tissue-specific transcriptomes in which specific classes of genes or transcripts can be targeted for capture and sequence, thus reducing the significant sequencing depth normally required for accurate annotation. Ovary and testis isotigs over 200 bp have been deposited with the GenBank Transcriptome Shotgun Assembly Sequence Database as bioproject no.PRJNA89451 (accession nos. JV208106­JV230865).

The first case of Pasteurella canis bacteremia: a cirrhotic patient with an open leg wound.

INTRODUCTION: Severe human infections caused by the Pasteurella species are typically seen following animal bites. P. canis is a species that rarely affects humans and has never been found in systemic infections. Here, we report the first documented case of P. canis bacteremia in an infected human, thought to be caused by a dog lick to an open leg wound.

Thromboprophylaxis in patients with acute spinal injuries: an evidence-based analysis.

BACKGROUND: The increased risk for venous thromboembolic events following spinal trauma is well established. The purpose of the present study was to examine the literature in order to determine the optimum thromboprophylaxis regimen for patients with acute spinal injuries with or without spinal cord injury. METHODS: EMBASE, MEDLINE, and Cochrane databases were searched from the earliest available date to April 2008 for clinical trials comparing different methods of thromboprophylaxis in adult patients following acute spinal injuries (with or without spinal cord injury). Outcome measures included the prevalences of deep-vein thrombosis and pulmonary embolism and treatment-related adverse events. RESULTS: The search yielded 489 studies, but only twenty-one of them fulfilled the inclusion criteria. The prevalence of deep-vein thrombosis was significantly lower in patients without spinal cord injury as compared with patients with spinal cord injury (odds ratio = 6.0; 95% confidence interval = 2.9 to 12.7). Patients with an acute spinal cord injury who were receiving oral anticoagulants had significantly fewer episodes of pulmonary embolism (odds ratio = 0.1; 95% confidence interval = 0.01 to 0.63) than those who were not receiving oral anticoagulants (either untreated controls or patients managed with low-molecular-weight heparin). The start of thromboprophylaxis within the first two weeks after the injury resulted in significantly fewer deep-vein-thrombosis events than delayed initiation did (odds ratio = 0.2; 95% confidence interval = 0.1 to 0.4). With regard to heparin-based pharmacoprophylaxis in patients with spinal trauma, low-molecular-weight heparin significantly reduced the rates of deep-vein thrombosis and bleeding episodes in comparison with the findings in patients who received unfractionated heparin, with odds ratios of 2.6 (95% confidence interval = 1.2 to 5.6) and 7.5 (95% confidence interval = 1.0 to 58.4) for deep-vein thrombosis and bleeding, respectively. CONCLUSIONS: The prevalence of deep-vein thrombosis following a spine injury is higher among patients who have a spinal cord injury than among those who do not have a spinal cord injury. Therefore, thromboprophylaxis in these patients should start as early as possible once it is deemed safe in terms of potential bleeding complications. Within this population, low-molecular-weight heparin is more effective for the prevention of deep-vein thrombosis, with fewer bleeding complications, than unfractionated heparin is. The use of vitamin K antagonists appeared to be effective for the prevention of pulmonary embolism.

Spinal injuries after falls from hunting tree stands.

BACKGROUND CONTEXT: Spinal injuries are common sequelae of falls from hunting tree stands. Significant neurological injury is not uncommon and can result in significant morbidity as well as enormous expenditure of health care dollars. Recent literature on the subject is limited. PURPOSE: The purpose of this study was to identify precipitating causes, characterize the spectrum of spinal injury, and determine potential interventional safety and prevention recommendations. STUDY DESIGN: A retrospective study. METHODS: Medical record review of 22 patients admitted either directly or via referral to a level I spinal cord injury referral center over a 10-year period (1995-2005) after a fall from a hunting tree stand. RESULTS: All patients were men with a mean age of 46 years (range, 27-80 years). Initial acute care hospitalization averaged 10 days (range, 2-28 days). The average height of fall was 18 feet (range, 10-30 feet). Four of 19 falls (21%) occurred during the morning hours, 2 of 19 falls occurred during the afternoon, and 13 of 19 falls (68%) occurred during the evening hours. Time lapse from injury to presentation to an emergency department ranged from 30 minutes to 14 hours. Alcohol use was a factor in 2 of 20 falls (10%). Hypothermia complicated 3 of 21 cases (14%). Associated injuries were present in 12 of 21 patients (57%) and included fractures to the axial and appendicular skeleton, pneumothoraces, a retroperitoneal bleed, and a brachial plexopathy. Eight of 22 patients (37%) sustained injury to the cervical spine. Five of these 8 patients (63%) had neurological deficits (3 complete and 2 incomplete spinal cord injuries). Thirteen of 22 (59%) patients sustained injury to the thoracic or lumbar spine. Ten of these 13 (77%) had neurologic deficits (3 complete and 7 incomplete). Nine of 22 (41%) patients were treated nonoperatively; the remaining 13 (59%) underwent operative intervention. CONCLUSIONS: Falls from hunting tree stands remain a significant cause of spinal injury and subsequent disability. The best intervention for these injuries is prevention. There is a continued need for hunter safety education to reduce the incidence of these injuries with emphasis on safety harness usage, proper installation and annual inspection of tree stands, hunting in groups with periodic contact, the use of communication devices, and abstinence from alcohol consumption while hunting.

Lattice gas dynamics: application to driven vortices in two dimensional superconductors.

A continuous time Monte Carlo lattice gas dynamics is developed to model driven steady states of vortices in two dimensional superconducting networks. Dramatic differences are found when compared to a simpler Metropolis dynamics. Subtle finite size effects are found at low temperature, with a moving smectic that becomes unstable to an anisotropic liquid on sufficiently large length scales.

A comparison of three screw types for unicortical fixation in the lateral mass of the cervical spine.

STUDY DESIGN: In vitro comparison of three different screws for unicortical fixation in lateral masses of the cervical spine. OBJECTIVES: To compare the axial load-to-failure of cervical lateral mass screws and their revision screws in a cadaveric model. SUMMARY OF BACKGROUND DATA: Lateral mass screws are used for posterior fixation of the cervical spine. Risks to neurovascular structures have led many surgeons to advocate unicortical application of these screws, although fixation strength may vary with screw design. METHODS: Screws from three posterior cervical fixation systems were used: Axis, Starlock/Cervifix, and Summit. Tested were 3.5-mm cancellous screws, along with revision screws for each system. The C3-C6 vertebrae from three cadaveric specimens were fixed with screws inserted into the lateral masses at a depth of 10 mm with 30 degrees cephalad and 20 degrees lateral angulation. Coaxial pullout force was recorded for each primary and revision screw. RESULTS: Axial load-to-failure (mean +/- SD) of the screws was 459 +/- 60 N for Axis screws, 423 +/- 78 N for Starlock screws, and 319 +/- 97 N for Summit screws. The Axis and Starlock screws were significantly stronger than Summit screws (P = 0.017 and P = 0.067, respectively). The load-to-failure of revision screws was much lower than that of primary screws (Axis 54%, Starlock 56%, Summit 63% of the primary screw), without significant difference between screw types. CONCLUSIONS: The Axis and Starlock screws resisted significantly greater axial load-to-failure than did the Summit screws. For all three systems, the revision screws could not restore the load-to-failure of the primary screw in this model. The tested unicortical screws had a consistently higher load-to-failure than those previously tested under similar conditions, suggesting that currently available screws may be superior to those previously tested.

Magnetic resonance imaging analysis of soft tissue disruption after flexion-distraction injuries of the subaxial cervical spine.

STUDY DESIGN: A retrospective study was performed with the use of magnetic resonance imaging to evaluate the type and degree of soft tissue disruption associated with flexion-distraction injuries of the subaxial spine. OBJECTIVE: To determine what soft tissue structures are injured in flexion-distraction injuries of the subaxial spine. SUMMARY OF BACKGROUND DATA: Prior published reports of unilateral and bilateral cervical facet dislocations have described the analyzed mechanisms and biomechanics of this injury subtype. No retrospective magnetic resonance imaging analysis of associated soft tissue disruption has been documented. METHODS: Magnetic resonance imaging evaluations of the cervical spine were obtained for all patients with a flexion-distraction injury, Stages 2 (unilateral facet dislocation) and 3 (bilateral facet dislocation), between September 1994 and May 1998. Two neuroradiologists, blinded to both clinical and radiographic findings, graded all the soft tissue structures for evidence of attenuation or disruption. The soft tissue structures were graded on a scale of 1 (intact), 2 (indeterminate), or 3 (disrupted). RESULTS: For this study, 48 patients satisfied the inclusion criteria: 25 with unilateral facet dislocation and 23 with bilateral facet dislocation. Disruption to the posterior musculature, interspinous ligament, supraspinous ligament, facet capsule, ligamentum flavum, and posterior and anterior longitudinal ligaments was found in a statistically significant number of patients with bilateral facet dislocation. For most of these structures, disruption was found to be statistically significant in patients with a unilateral facet dislocation, except for the posterior longitudinal ligament, in which significance was not consistently demonstrated using 95% confidence intervals in the binomial testing. In a comparison between unilateral and bilateral facet dislocations using a two-sided Fisher's exact test, it was found that disruption to the anterior and posterior longitudinal ligaments and the left facet capsule were statistically significant, with all three more prominent in bilateral facet dislocation. A multivariate analysis between unilateral and bilateral facet dislocations showed that disruption to the anterior longitudinal ligament was associated significantly with a bilateral facet dislocation. Disc disruption was found to be associated significantly with both injury types, but was more common in bilateral facet dislocation, although this difference in intergroup comparisons was not statistically significant. CONCLUSIONS: Unilateral and bilateral facet dislocations of the subaxial spine are associated with damage to numerous soft tissue structures that provide stability to the lower cervical spine. Damage to the posterior longitudinal ligament did not occur consistently in unilateral facet dislocations. Bilateral facet dislocations were associated significantly with disruption to the posterior and anterior longitudinal ligaments and left facet capsule, as compared with unilateral facet dislocations. Magnetic resonance imaging allows visualization of these disruptions.

Three-dimensional cartilage formation by bone marrow-derived cells seeded in polylactide/alginate amalgam.

Bone marrow-derived cells are considered as candidate cells for cartilage tissue engineering by virtue of their ability to undergo chondrogenesis in vitro when cultured in high density or when embedded within a three-dimensional matrix in the presence of growth factors. This study evaluated the potential of human bone marrow-derived cells for cartilage tissue engineering by examining their chondrogenic properties within a three-dimensional amalgam scaffold consisting of the biodegradable polymer, poly-L-lactic acid (PLA) alone, and with the polysaccharide gel, alginate. Cells were suspended either in alginate or medium and loaded into porous PLA blocks. Alginate was used to improve cell loading and retention within the construct, whereas the PLA polymeric scaffold provided appropriate mechanical support and stability to the composite culture. Cells seeded in the PLA/alginate amalgams and the plain PLA constructs were treated with different concentrations of recombinant human transforming growth factor-beta1 (TGF-beta 1) either continuously (10 ng/mL) or only for the initial 3 days of culture (50 ng/mL). Chondrogenesis was assessed at weekly intervals with cultures maintained for up to 3 weeks. Histological and immunohistochemical analysis of the TGF-beta 1-treated PLA/alginate amalgam and PLA constructs showed development of a cartilaginous phenotype from day 7 to day 21 as demonstrated by colocalization of Alcian blue staining with collagen type II and cartilage proteoglycan link protein. Expression of cartilage specific genes, including collagen types II and IX, and aggrecan, was detected in TGF-beta 1-treated cultures by reverse transcription-polymerase chain reaction analysis. The initiation and progression of chondrogenic differentiation within the polymeric macrostructure occurred with both continuous and the initial 3-day TGF-beta 1 treatment regimens, suggesting that key regulatory events of chondrogenesis take place during the early period of cell growth and proliferation. Scanning electron microscopy revealed abundant cells with a rounded morphology in the PLA/alginate amalgam. These findings suggest that the three-dimensional PLA/alginate amalgam is a potential candidate bioactive scaffold for cartilage tissue engineering applications.

Distraction extension injuries of the cervical spine.

Twenty-four consecutive patients with cervical distraction extension injuries were retrospectively reviewed to study the safety and efficacy of various treatment protocols in this type of cervical spine injury. Sixteen of 24 patients with cervical distraction extension injuries underwent surgical stabilization. All patients undergoing surgical stabilization were noted to have a stable fusion at their latest follow-up. There were three instances of surgically related neurologic deterioration as a result of over-distraction of the anterior column interspace at the time of graft placement. The overall mortality rate was 42% in this aged patient population. Anterior reconstruction of the cervical spine with an anterior cervical graft and plate acting as a tension band is the ideal treatment method for stabilization of acute distraction extension injuries involving primarily the soft tissue structures (anterior longitudinal ligament and intervertebral disc). Type 2 injuries, depending on the degree of displacement and the adequacy of closed reduction, may need to be approached initially posteriorly to obtain adequate alignment, followed by an anterior reconstructive procedure. Great care should be taken during anterior graft placement to avoid over-distraction of the spine. If nonsurgical intervention is selected, close regular radiographic follow-up is necessary to detect early vertebral malalignment, which may predispose to spinal cord dysfunction. Older patients sustaining this injury have a high mortality rate.

The significance of thoracolumbar spinal canal size in spinal cord injury patients.

STUDY DESIGN: A prospective, consecutive case series. OBJECTIVES: To determine the relation between spinal canal dimensions and Injury Severity Score and their association with neurologic sequelae after thoracolumbar junction burst fracture. SUMMARY OF BACKGROUND DATA: There is a relation in the cervical spine between spinal canal dimension and its association with neurologic sequelae after trauma. A similar relation at the thoracolumbar junction has not been conclusively established. METHODS: Forty-three patients with thoracolumbar junction burst fractures (T12-L2),13 with and 30 without neurologic deficit, were included. Computed tomographic scans were used to measure the sagittal and transverse diameters and the surface area of the spinal canal at the level of injury, as well as one level above and one level below the fracture level. Injury severity score was calculated for both groups. Statistical analysis comparing those with a neurologic deficit to those without was performed by Student's t test. RESULTS: The ratio of sagittal-to-transverse diameter at the level of injury was significantly smaller in patients with a neurologic deficit than in those without a neurologic deficit (P < 0.05). The mean transverse diameter at the level of injury was significantly larger in patients with neurologic deficit than in the neurologically intact patients (P < 0.05). The surface area of the canal at the level below the injury was significantly larger in the patients with a neurologic deficit than in those without a deficit (P < 0.05). Patients with a neurologic deficit had a statistically higher Injury Severity Score when admitted than those without a neurologic deficit (P < 0.0001), although the difference became insignificant after the neurologic component of the scoring system was eliminated. CONCLUSION: There are no anatomic factors at the thoracolumbar junction that predispose to neurologic injury after burst fracture. The shape of the canal after injury, however, as determined by the sagittal-to-transverse diameter ratio, was predictive of neurologic deficit.

The risk of foraminal violation and nerve root impingement after anterior placement of lumbar interbody fusion cages.

STUDY DESIGN: Three groups of six embalmed cadaver spines underwent placement of lumbar interbody fusion cages centered either at midline, 10% lateral of midline, or 20% lateral of midline. The spines were evaluated for evidence of neuroforamen violation or nerve root impingement. OBJECTIVES: To determine the potential for foraminal violation or nerve root impingement after correct placement and lateral misplacement of lumbar interbody fusion cages. SUMMARY OF BACKGROUND DATA: Radicular symptoms after anterior cage placement have raised some concern about the potential for inadvertent device-related foraminal violation not adequately appreciated by intraoperative fluoroscopy. METHODS: Preoperative computed tomography scanning and plain radiography was used to measure endplate dimensions at L4-L5 and to template the appropriately sized interbody fusion cages. The cadaveric specimens were randomly divided into three groups of six (Groups I-III) and instrumented at L4-L5 either at midline (I) or 10% (II) or 20% (III) lateral of midline. Postoperative computed tomography and plain radiography was evaluated for evidence of neuroforamen violation, followed by dissection of the specimens. RESULTS: Foraminal violation occurred in one of six spines in group II (10% off midline) and in three of six spines in group III (20% off midline). Two of the three cadavers in group III with foraminal violation also were noted to have nerve root abutment on computed tomography scans and spinal dissection. CONCLUSIONS: Excessive lateral placement of lumbar interbody fusion cages may result in foraminal violation and possible nerve encroachment. The "safe zone" for centering the cages extends approximately 5 mm on either side of midline.

Internet resources for spine surgeons.

To classify web sites on common spinal disorders as to their utility for the spine surgeon and patient. Five common spinal disorders were used to generate lists of relevant sites. These sites were categorized as to their relevance for patients and surgeons, their sponsoring organization, and their comprehensiveness. A total of 56,249 web sites were found using the five key words on five search engines. Using the "And" operator, a total of 227 web sites were generated. The majority of sites were patient oriented. Physician- or organization-sponsored sites were the most common. Ten sites were found to have comprehensive information for both patients and spine surgeons. Many web sites exist that discuss disorders of the spine. Currently there is not any one web site that contains comprehensive information for both the spine surgeon and patient.

Injuries of the thoracolumbar spine associated with restraint use in head-on motor vehicle accidents.

Many authors have described spinal and bodily injuries associated with seat belt use. However, most reports have focused primarily on lap seat belts and resultant flexion-distraction injuries. This retrospective chart review studies the relation between the specific type of restraint or air bag and the resultant thoracolumbar spinal injury subtype and associated bodily injuries. The charts of 221 patients who had sustained thoracolumbar fractures in motor vehicle accidents during a 10-year period were reviewed, and 37 patients were identified whose accidents were clearly described as a frontal collision and whose specific form of restraint was recorded. Among the 15 patients who used a shoulder strap and lap belt device (three-point restraint), 12 patients sustained burst fractures (80%) compared with 4 of the 14 patients (28.6%) restrained with lap seat belts alone. Life-threatening intraabdominal injuries occurred in 57.1% of lap-belted victims and in 26.7% of patients who used three-point restraints, and the character of these injuries also differed. No patients in an automobile in which an air bag deployed sustained major associated bodily injuries. Among restrained occupants of head-on motor vehicle accidents who have sustained a thoracolumbar fracture, patients using lap belts are more likely to sustain the classic flexion-distraction injury patterns, whereas patients using three-point restraints may sustain a higher incidence of burst fractures. In addition, three-point restraints are associated with a decreased risk of intraabdominal injury compared with lap seat belts.

A plate-rod device for treatment of cervicothoracic disorders: comparison of mechanical testing with established cervical spine in vitro load testing data.

Posterior cervical internal fixation has long been accomplished using wires, hooks, and rods. More recently, the cervical lateral mass screw and plate or rod systems have been used effectively in unstable lower cervical spine disorders. Each form of fixation has its advantages and disadvantages. Interspinous wiring and lateral mass screw placement obviate canal penetration in the cervical region but are associated with a potential neurologic risk as a result of canal encroachment. Minor canal intrusion by laminar hooks in the thoracic spine pose a lesser neurologic risk than in the cervical region. To exploit the benefits and safety features of spinal instrumentation, a combination plate rod construct (PRC) has been developed that obviates canal penetration in the cervical region by way of lateral mass and cervical pedicle screw fixation and hooks or wires in the thoracic spine. A biomechanical analysis of the PRC device was performed and compared with the in vivo maximal load data of the cervical spine and established maximal load data of the Roy-Camille posterior cervical fixation system. The PRC has greater strength and resistance to failure than is necessary to sustain maximal in vivo cervical spine loads, and it has also compared favorably with the parameters of the Roy-Camille system. The PRC device, or variations on it, is an excellent option for spinal fixation across the cervicothoracic junction because of its superior biomechanical qualities and versatility in stabilizing a complex anatomic junction of the spine.

SmMAK16, the Schistosoma mansoni homologue of MAK16 from yeast, targets protein transport to the nucleolus.

The SmMAK16 gene from Schistosoma mansoni was cloned by chance when an adult worm cDNA library was probed with antiserum to affinity-purified S. mansoni GSH S-transferases. SmMAK16 encodes a hydrophilic protein of 259 amino acids with a molecular mass of 31 kDa. The protein shares 43% sequence identity and 66% similarity to the nuclear protein MAK16 of Saccharomyces cerevisiae that has been implicated both in cell cycle progression and biogenesis of 60S ribosomal subunits. Both proteins display a similar degree of sequence similar to the hypothetical protein CeMAK16 from Caenorhabditis elegans. These proteins share a number of apparent protein motifs, including two nuclear localization signals (NLS), multiple sites for phosphorylation by protein kinase CK2 and four conserved cysteine residues that resemble a zinc binding domain. SmMAK16 mRNA is more highly expressed in adult female worm than males. Recombinant SmMAK16 was phosphorylated by human protein kinase CK2. When chimeric constructs containing SmMAK16 fused the green fluorescent protein (GFP) were transiently transfected into COS-7s cells, the reporter was localized not in nuclei, but exclusively in nucleoli. The yeast and nematode homologues were likewise able to direct nucleolar accumulation of the fluorescent reporter. The high degree of sequence conservation together with the ability to direct nucleolar protein transport supports the hypothesis that MAK16 proteins play a key role in the biogenesis of 60S subunits.

Placement of pedicle screws in the human cadaveric cervical spine: comparative accuracy of three techniques.

STUDY DESIGN: This investigation was conducted in two parts. In the first part, a morphometric analysis of critical cervical pedicle dimensions were measured to create guidelines for cervical pedicle screw fixation based on posterior cervical topography. In the second part of the study, a human cadaver model was used to assess the accuracy and safety of transpedicular screw placement in the subaxial spine using three different surgical techniques: 1) using surface landmarks established in the first part of the study, 2) using supplemental visual and tactile cues provided by performing laminoforaminotomies, and 3) using a computer-assisted surgical guidance system. OBJECTIVE: To assess the accuracy of transpedicular screw placement in the cervical spine using three surgical techniques. SUMMARY OF BACKGROUND DATA: A three-column fixation device implanted to secure an unstable cervical spine can be a valuable tool with a biomechanical advantage in the spine surgeon's armamentarium. Despite this advantage, concerns over surgical neurovascular complications have surfaced. Cadaver-based morphometric measurements used to guide the surgeon in the placement of a pedicle screw show significant variability, raising legitimate concerns as to whether transpedicular fixation can be applied safely. METHODS: Precise measurements of 14 human cadaveric cervical spines were made by two independent examiners of pedicle dimensions, angulation, and offset relative to the lateral mass boundaries. On the basis of this analysis, guidelines for pedicle screw placement relative to posterior cervical topography were derived. In the second part of the study, 12 human cadaveric cervical spines were instrumented with 3.5-mm screws placed in the pedicles C3-C7 according to one of three techniques. Cortical integrity and neurovascular injury were then assessed by obtaining postoperative computed tomography scans (1-mm cuts) of each specimen. Cortical breaches were classified into critical or noncritical breaches. RESULTS: Linear measurements of pedicle dimensions had a wide range of values with only fair interobservercorrelation. Angular measurements showed similarangulation in the transverse plane (40 degrees ) at each level. With respect to the sagittal plane, both C3 and C4 pedicles were oriented superiorly relative to the axis of the lateral mass, whereas the C6 and C7 pedicles were oriented inferiorly. The dorsal entry point of the pedicle on the lateral mass defined by transverse and sagittal offset had similar mean values with wide ranges, although there often was excellent correlation between observers. There were no significant interlevel, right/left, or male/female differences noted with respect to offset. Using one of three techniques, 120 pedicles were instrumented. In group 1 (morphometric data): 12.5% of the screws were placed entirely within the pedicle; 21.9% had a noncritical breach; and 65. 5% had a critical breach. In group 2 (laminoforaminotomy), 45% of the screws were within the pedicle; 15.4% had a noncritical breach; and 39.6% had a critical breach. In group 3 (computer-assisted surgical guidance system), 76% of the screws were entirely within the pedicle; 13.4% had a noncritical breach; and 10.6% had a critical breach. Regardless of the technique used, the vertebral artery was the structure most likely to be injured. CONCLUSIONS: On the basis of the morphometric data, guidelines for cervical spine pedicle screw placement at each subaxial level were derived. Although a statistical analysis of cadaveric morphometric data obtained from the cervical spine could provide guidelines for transpedicular screw placement based on topographic landmarks, sufficient variation exists to preclude safe instrumentation without additional anatomic data. Insufficient correlation between different surgeons' assessments of surface landmarks attests to the inadequacy of screw insertion techniques in the cervical spine based on such specific topographic guide