Cost-Effectiveness of Bariatric Surgery Prior to Posterior Lumbar Decompression and Fusion in an Obese Population with Degenerative Spondylolisthesis.

STUDY DESIGN: Cost-effectiveness analysis. OBJECTIVE: To determine if bariatric surgery prior to posterior lumbar decompression and fusion (PLDF) for degenerative spondylolisthesis (DS) is a cost-effective strategy. SUMMARY OF BACKGROUND DATA: Obesity poses significant perioperative challenges for DS. Treated operatively, obese patients achieve worse outcomes relative to non-obese peers. Concomitantly, they fare better with surgery than with nonoperative measures. These competing facts create uncertainty in determining optimal treatment algorithms for obese patients with DS. The role of bariatric surgery merits investigation as a potentially cost-effective optimization strategy prior to PLDF. METHODS: We simulated a Markov model with two cohorts of obese individuals with DS. 10,000 patients with body mass index (BMI) more than or equal to 30 in both arms were candidates for both bariatric surgery and PLDF. Subjects were assigned either to (1) no weight loss intervention with immediate operative or nonoperative management ("traditional arm") or (2) bariatric surgery 2 years prior to entering the same management options ("combined protocol").Published costs, utilities, and transition probabilities from the literature were applied. A willingness to pay threshold of $100,000/QALY was used. Sensitivity analyses were run for all variables to assess the robustness of the model. RESULTS: Over a 10-year horizon, the combined protocol was dominant ($13,500 cheaper, 1.15 QALY more effective). Changes in utilities of operative and nonoperative treatments in non-obese patients, the obesity cost-multiplier, cost of bariatric surgery, and the probability of success of nonoperative treatment in obese patients led to decision changes. However, all thresholds occurred outside published bounds for these variables. CONCLUSION: The combined protocol was less costly and more effective than the traditional protocol. Results were robust with thresholds occurring outside published ranges. Bariatric surgery is a viable, cost-effective preoperative strategy in obese patients considering elective PLDF for DS.Level of Evidence: 3.

Lateral mass versus hybrid construct for cervical laminectomy and fusion.

Spine stabilization after C3-C7 laminectomy can be accomplished with many instrumentation options. A hybrid construct using lateral mass screws from C3 to C5 and pedicle screws at C7 can potentially maximize strength and solve the spatial constraints introduced by the placement of C6 lateral mass screws and C7 pedicle screws. Seven cadaveric cervical spines from C2 to T2 were potted in a custom testing apparatus. Differential variable reluctance transducers were placed on C6 and C7 to measure linear displacement. Specimens were loaded in flexion, extension, lateral bending, and axial torque at 1.5 Nm. A wide laminectomy was then performed, and specimens were randomized to first receive either the bilateral C3-C7 lateral mass screw construct or a hybrid construct with C3-C5 lateral mass screws and C7 pedicle screws. All specimens were tested with both constructs. Normalized deformation (mean±SD) for the lateral mass screw vs the hybrid pedicle screw constructs in the sagittal plane was 7.46%±5.48% vs 5.68%±3.67%, respectively (P=.237). Coronal deformation for lateral mass screw vs the hybrid pedicle screw constructs was 19.2%±10.9% vs 13.6%±9.53% (P=.237). Axial rotation deformation for lateral mass vs pedical screw constructs was 85.9%±83.3% vs 74.7%±58.1%, respectively (P=.868). Despite data reported in the literature indicating a higher pullout strength of pedicle screws and improved strength of hybrid pedicle screw constructs compared with lateral mass screw constructs, a hybrid construct taking spatial constraints and increased danger of pedicle screw placement above C7 into account showed no improvement in motion compared with a lateral mass screw construct.

The effect of methylprednisolone intravenous infusion on the expression of ciliary neurotrophic factor in a rat spinal cord injury model.

BACKGROUND CONTEXT: Methylprednisolone (MP) infusion after acute spinal cord injury (SCI) remains controversial despite large randomized studies, including the National Acute Spinal Cord Injury Studies (NASCIS). PURPOSE: To determine the effect of NASCIS protocol MP infusion on the expression of ciliary neurotrophic factor (CNTF), a neuroprotective cytokine, in a rat model after SCI. STUDY DESIGN: Animal laboratory study. METHODS: Thirty rats were randomized into an MP infusion group (intravenous [IV]-MP) versus normal saline (NS) control group (IV-NS) after a standardized SCI. Ciliary neurotrophic factor expression was measured by reverse transcription-polymerase chain reaction at 6, 12, 24, 48, and 72 hours post-SCI. RESULTS: Mean CNTF expression was diminished in the MP group at 12 (p=.006) and 24 (p=.008) hours postinjury compared with the control group. Expression of CNTF was not significantly different between the groups at 6, 48, and 72 hours post-SCI. CONCLUSIONS: Standardized MP infusion post-SCI reduces CNTF activation in a rat SCI model. Further study is needed to determine if this effect is seen in human SCIs.

Manipulation of carrier proteins in antibiotic biosynthesis.

Engineering biosynthetic pathways into suitable host organisms has become an attractive venue for the design, evaluation, and production of small molecule therapeutics. Polyketide (PK) and nonribosomal peptide (NRP) synthases have been of particular interest due to their modular structure, yet routine cloning and expression of these enzymes remains challenging. Here we describe a method to covalently label carrier proteins from PK and NRP synthases using the enzymatic transfer of a modified coenzyme A analog by a 4'-phosphopantetheinyltransferase. Using this method, carrier proteins can be loaded with single fluorescent or affinity reporters, providing novel entry for protein visualization, Western blot identification, and affinity purification. Application of these methods provides an ideal tool to track and quantify metabolically engineered pathways. Such techniques are valuable to measure protein expression, solubility, activity, and native posttranslational modification events in heterologous systems.