Robert McGuire

Early Failure of Long Segment Anterior Cervical Plate Fixation

A retrospective, multicenter study was undertaken to evaluate the early postoperative failure rate of long segment anterior cervical fusion and plating to stabilize the cervical spine after a two- or three-level corpectomy for degenerative, traumatic, and neoplastic diseases of the cervical spine. Patient demographic factors as well as technical factors such as bone graft placement, plate and screw position, and postoperative brace immobilization were analyzed. During the early postoperative period, the graft/plate construct dislodged in 3 of 33 patients with a two-level corpectomy and fusion (9%) compared with 6 of 12 patients with a three-level corpectomy and fusion (50%). The difference in failure rates after a three- versus two-level corpectomy and fusion was statistically significant (p < 0.05). A higher early failure rate was also seen with failure to correctly lock the screws to the plate and the use of a peg-in-hole type bone grafting technique, although these differences were not statistically significant. Although several technical and patient-specific factors may contribute to this, anterior cervical plating and bone grafting alone after a three-level cervical corpectomy for various spinal disorders appears to afford inadequate stability in the early postoperative period, regardless of immobilization methods.

Electocatalytic Water Oxidation by Cobalt(III) Hangman β-Octafluoro Corroles

Cobalt hangman corrole, bearing β-octafluoro and meso-pentafluorophenyl substituents, is an active water splitting catalyst. When immobilized in Nafion films, the turnover frequencies for the 4e(-)/4H(+) process at the single cobalt center of the hangman platform approach 1 s(-1). The pH dependence of the water splitting reaction suggests a proton-coupled electron transfer (PCET) catalytic mechanism.

Electrocatalytic Activity Studies of Select Metal Surfaces and Implications in Li-Air Batteries

Rechargeable lithium-air batteries have the potential to provide ≈3 times higher specific energy of fully packaged batteries than conventional lithium rechargeable batteries. However, very little is known about the oxygen reduction reaction (ORR) and oxygen evolution in the presence of lithium ions in aprotic electrolytes, which hinders the improvement of low round-trip efficiencies of current lithium-air batteries. We report the intrinsic ORR activity on glassy carbon (GC) as well as polycrystalline Au and Pt electrodes, where Au is the most active with an activity trend of Au ≫ GC > Pt. Rotating disk electrode (RDE) measurements were used to obtain the kinetic current of the ORR and the reaction order with respect to oxygen partial pressure in 1 M LiClO 4 propylene carbonate: 1,2-dimethoxyethane (1:2 v/v). In addition, air electrodes with Vulcan carbon or Au or Pt nanoparticles supported on Vulcan were examined in Li-O 2 single cells, where the observed discharge cell voltages follow the catalytic trend established by RDE measurements. The ORR mechanism and the rate-determining steps were discussed and contrasted with the ORR activity trend in acid and alkaline solutions.

The use of primary internal fixation in spondylolisthesis.

A prospective randomized study was designed to examine differences in the primary fusion rate between two surgically treated groups of patients with spondylolisthesis, Twenty-seven patients under want L5 laminectomy (Gill prodedur) and L5 nerve root decompression. Fourteen patients (group I) underwent in-situ posterolateral fusion, thirteen patients (group II) received internal stabilization with the Steffee plate and screw system. All patients were followed for a minimum of two years. Ten of fourteen (72%) patients treated with non-instrumented fusion went on to union. Ten of thirteen (78%) patients treated with internal fixation achieved union. No statistically significant increase in the primary fusion rate occurred with addition of internal fixation compared to non-instrumented posterolateral grafting alone.

Two-year fusion rate equivalency between Grafton DBM gel and autograft in posterolateral spine fusion: a prospective controlled trial employing a side-by-side comparison in the same patient.

Study Design. Multicenter, prospective equivalency trial with each patient serving as his/her own control. Objectives. To compare the effectiveness of a Grafton® DBM gel composite with iliac crest autograft in posterolateral spine fusion. Summary of Background Data. While autograft remains the preferred graft material to facilitate spine fusion, the supply is limited and harvesting produces undesirable clinical consequences. Methods. A total of 120 patients underwent posterolateral spine fusion with pedicle screw fixation and bone grafting. Iliac crest autograft was implanted on one side of the spine and a Grafton® DBM/autograft composite was implanted on the contralateral side in the same patient. An independent, blinded reviewer evaluated anteroposterior and lateral flexion-extension radiographs. The fusion mass lateral to the instrumentation on each side was judged fused or not, and the mineralization of the graft was rated absent, mild, moderate, or extensive. The degree of correspondence in outcomes between sides was estimated by computing the percentage agreement and kappa statistic. Results. Nearly 70% of patients (81 of 120) provided complete 24-month radiographic studies. The bone graft mass was fused in 42 cases (52%) on the Grafton® DBMside and in 44 cases (54%) on the autograft side. The overall percentage agreement for fusion status between sides was approximately 75% (61 of 81), indicating moderately strong statistical correspondence (kappa = 0.51, P < 0.0001). Bone mineralization ratings also were similar between treated sides. Perfect agreement was realized in almost 60% of patients (48 of 81) with moderate statistical correspondence (weighted kappa = 0.54, P < 0.0001). Conclusions. Grafton® DBM can extend a smaller quantity of autograft than is normally required to achieve a solid spinal arthrodesis. Consequently, a reduced amount of harvested autograft may be required, potentially diminishing the risk and severity of donor site complications.

Hangman Corroles: Efficient Synthesis and Oxygen Reaction Chemistry

The construction of a new class of compounds--the hangman corroles--is provided efficiently by the modification of macrocyclic forming reactions from bilanes. Hangman cobalt corroles are furnished in good yields from a one-pot condensation of dipyrromethane with the aldehyde of a xanthene spacer followed by metal insertion using microwave irradiation. In high oxidation states, X-band EPR spectra and DFT calculations of cobalt corrole axially ligated by chloride are consistent with the description of a Co(III) center residing in the one-electron oxidized corrole macrocycle. These high oxidation states are likely accessed in the activation of O-O bonds. Along these lines, we show that the proton-donating group of the hangman platform works in concert with the redox properties of the corrole to enhance the catalytic activity of O-O bond activation. The hangman corroles show enhanced activity for the selective reduction of oxygen to water as compared to their unmodified counterparts. The oxygen adduct, prior to oxygen reduction, is characterized by EPR and absorption spectroscopy.

Oxygen reduction reactivity of cobalt(II) hangman porphyrins

Cobalt(II) hangman porphyrins are delivered from easily available starting materials, in two steps, in good yields, and with abbreviated reaction times. Selected compounds from a library of Co(II) hangman porphyrins immobilized on multiwall carbon nanotubes establish that the four-electron four-proton catalytic reduction of oxygen to water in aqueous solution can be achieved at the single cobalt center of the hangman platform. Reaction trends within the library reveal that the selective reduction of O2 to H2O occurs at electron deficient hangman porphyrin platforms possessing a distal group that is capable of proton transfer.

Unstable thoracolumbar burst fractures: anterior-only versus short-segment posterior fixation.

Operative management of a thoracolumbar burst fracture varies according to many factors. Fracture morphology, neurologic status, and surgeon preference play major roles in deciding upon anterior, posterior, or combined approaches. Optimizing neural decompression while providing stable internal fixation over the least number of spinal segments is the goal. Short-segment constructs via a single-stage approach (anterior versus posterior) have become viable options with advances in instrumentation and techniques. This study compares anterior-only fixation utilizing a corpectomy strut graft and a modern thoracolumbar plating system with a posterior-only construct using pedicle screws and load sharing hooks for the treatment of unstable burst fractures. Functional outcome and sagittal plane restoration and maintenance of sagittal plane alignment were evaluated. Fifty-three patients with unstable burst fractures were assessed with 40 undergoing an anterior-only construct and 13 having a short-segment posterior-only construct. The posterior-only group had no hardware failures; however, the loss of sagittal plane correction averaged 8.1 degrees, whereas the anterior-only group averaged only a 1.8-degree increase in sagittal plane kyphosis. Both techniques resulted in statistically significant initial improvement in sagittal alignment; however, the posterior short-segment group lost this statistical significance at follow-up whereas the anterior-only group continued to demonstrate statistically significant improvement in sagittal alignment at follow-up compared to preoperative measurements.

Blood Loss in Major Spine Surgery : Are There Effective Measures to Decrease Massive Hemorrhage in Major Spine Fusion Surgery?

Study Design. Systematic review. Objective. To determine the definition and incidence of significant hemorrhage in adult spine fusion surgery, and to assess whether measures to decrease hemorrhage are effective. Summary of Background Data. Significant hemorrhage and associated comorbidities in spine fusion surgery have not yet been clearly identified. Several preoperative and intraoperative techniques are currently available to reduce blood loss and transfusion requirements such as cell saver (CS), recombinant factor VIIa, and perioperative antifibrinolytic agents, such as aprotinin, tranexamic acid, and &egr;-aminocaproic acid. Their effectiveness and safety in spine surgery is uncertain. Methods. A systematic review of the English-language literature was undertaken for articles published between January 1990 and April 2009. Electronic databases and reference lists of key articles were searched to identify published studies examining blood loss in major spine surgery. Two independent reviewers assessed the quality of the literature using the Grading of Recommendations Assessment, Development, and Evaluation criteria. Disagreements were resolved by consensus. Results. A total of 90 articles were initially screened, and 17 ultimately met the predetermined inclusion criteria. No studies were found that attempted to define significant hemorrhage in adult spine surgery. We found that there is a high level of evidence that antifibrinolytic agents reduce blood loss and the need of transfusion in adult spine surgery; however, the safety profile of these agents is unclear. There is very low evidence to support the use of CS, recombinant factor VIIa, activated growth factor platelet gel, or normovolemic hemodilution as a method to prevent massive hemorrhage in spine fusion surgery. Conclusion. There is no consensus definition of significant hemorrhage in adult spine fusion surgery. However, definition in the anesthesiology literature of massive blood loss is somewhat arbitrary but is commonly accepted to entail loss of 1 volume of the patients total blood (60 mL/kg in adults) in <24 hours. On the basis of the current literature, there is little support for routine use of CS during elective spinal surgery. Concerns related to the use of aprotinin were such that our panel of experts unanimously recommended against its use in spine surgery on the basis of the reports of increased complications. With respect to the antifibrinolytics of the lysine analog class (tranexamic acid and aminocaproic acid), on the basis of the available efficacy and safety data, we recommend that they be considered as possible agents to help reduce major hemorrhage in adult spine surgery.

Anterior-only stabilization of three-column thoracolumbar injuries

Objective: The optimal treatment of “unstable” thoracolumbar injuries remains controversial. Studies have shown the advantages of direct anterior decompression of thoracolumbar injuries along with supplemental posterior instrumentation as a combined or staged procedure. Others have also shown success in decompression as a single-stage anterior procedure, largely limited to two-column (anterior and middle) injuries. A retrospective review of all available clinical and radiographic data was used to classify unstable three-column thoracolumbar fractures according to the Association for the Study of Internal Fixation (AO) classification system. This was conducted to evaluate the efficacy of stand-alone anterior decompression and reconstruction of unstable three-column thoracolumbar injuries, utilizing current-generation anterior spinal instrumentation. Methods: Between 1992 and 1998, 40 patients underwent anterior decompression and two-segment anteriorly instrumented reconstruction for three-column thoracolumbar fractures. Retrospective review of all available clinical and radiographic data was used to classify these unstable injuries according to the AO classification system, evaluating for neurologic changes, spinal canal compromise, preoperative and postoperative segmental angulation, and arthrodesis rate. Results: According to the AO classification system, there were 24 (60%) type B1.2, 10 (25%) type B2.3, 5 (12.5%) type C1.3, and 1 (2.5%) type C2.1 three-column injuries. Preoperative canal compromise averaged 68.5% and vertebral height loss averaged 44.5%. There were no cases of neurologic deterioration, and 30 (91%) patients with incomplete neurologic deficits improved by at least one modified Frankel grade. Mean preoperative segmental kyphosis of 22.7° was improved to an early mean of 7.4° (P < 0.0001). At latest follow-up, angulation had increased by an average 2.1° but maintained significant improvement from preoperative measurements (P < 0.0001). There was one early construct failure due to technical error. Thirty-seven of the remaining patients (95%) went on to apparently stable arthrodesis. Conclusions: Current types of anterior spinal instrumentation and reconstruction techniques can allow some types of unstable three-column thoracolumbar injuries to be treated in an anterior stand-alone fashion. This allows direct anterior decompression of neural elements, improvement in segmental angulation, and acceptable rates of arthrodesis without the need for supplemental posterior instrumentation.