Biomechanical evaluation of an intramedullary clavicle screw in simple oblique and butterfly wedge fractures.

This biomechanical study evaluates the performance of a solid titanium-alloy intra-medullary (IM) clavicular screw in torsion and cantilever bending in cadaveric clavicle specimens with simulated simple oblique and butterfly wedge midshaft fractures. Thirty-two fresh-frozen male clavicles were sorted into six experimental groups: Torsion Control, Torsion Simple Oblique Fracture, Torsion Butterfly Wedge Fracture, Bending Control, Bending Simple Oblique Fracture, and Bending Butterfly Wedge Fracture. The experimental groups were controlled for density, length, diameter, and laterality. All other samples were osteotomy-induced and implanted with a single 90 mm × 3 mm clavicle screw. All groups were tested to physiologically relevant cutoff points in torsion or bending. There were no statistically significant differences in the performance of the oblique and butterfly wedge fracture models for any torsion or bend testing measures, including maximum torsional resistance (p = 0.66), torsional stiffness (p = 0.51), maximum bending moment (p = 0.43), or bending stiffness (p = 0.73). Torsional testing of samples in the direction of thread tightening tended to be stronger than samples tested in loosening, with all groups either approaching or achieving statistical significance. There were no significant differences between the simple oblique or the butterfly-wedge fracture groups for any of the tested parameters, suggesting that there is no difference in the gross biomechanical properties of the bone-implant construct when the IM clavicle screw is used in either a simple midshaft fracture pattern or a more complex butterfly wedge fracture pattern.

Is There a Preoperative Morphine Equianalgesic Dose that Predicts Ability to Achieve a Clinically Meaningful Improvement Following Spine Surgery?

BACKGROUND: Preoperative opioid use is widespread and associated with worse patient-reported outcomes following spine surgery. OBJECTIVE: To calculate a threshold preoperative morphine equianalgesic (MEA) dose beyond which patients are less likely to achieve the minimum clinically important difference (MCID) following elective surgery for degenerative spine disease. METHODS: The study included 543 cervical and 1293 lumbar patients. Neck Disability Index and Oswestry Disability Index scores were collected at baseline and 12 mo postoperatively. Preoperative MEA doses were calculated retrospectively. Multivariate logistic regression was then performed to determine the relationship between MEA dose and the odds of achieving MCID. As a part of this regression, Bayesian inference and Markov Chain Monte Carlo methods were used to estimate the values of inflection points (or "thresholds") in MEA. RESULTS: Overall, 1020 (55.5%) patients used preoperative opioids. A total of 50.3% of cervical and 61.9% of lumbar patients achieved MCID. The final logistic regression model demonstrated that MCID achievement decreased significantly when mean preoperative MEA dose exceeded 47.8 mg/d, with a 95% credible interval of 29.0 to 60.0 mg/d. CONCLUSION: Minimum and maximum MEA doses exist, between which increasing opioid dose is associated with decreased ability to achieve clinically meaningful improvement following spine surgery. Patients with preoperative MEA dose exceeding 29 mg/d, the lower limit of the 95% credible interval for the mean MEA dose above which patients exhibit significantly decreased achievement of MCID, may be considered for preoperative opioid weaning.