RESUMEN
Purpose: This study aims to compare the compressive and tensile strengths of bone cement mixed with various concentrations of vancomycin, tobramycin, and combinations of the two. Methods: 12 mm × 6 mm antibiotic bone cement samples were created by vacuum mixing 0-4 g of vancomycin, tobramycin, and combinations of the two in 0.5 g increments per one pouch (40 g) of Palacos LV cement. An Instron 3369 Universal Testing System was used to determine the compressive and tensile strengths. Results: Compressive and tensile strengths of the bone cement without antibiotics were 118 ± 4 MPa and 30.3 ± 12 MPa, respectively. 4 g of vancomycin alone decreased the compressive strength to 108 ± 4 MPa (p-value 0.001) and decreased the tensile strength beginning at 2 g which yielded a strength of 28.1 ± 12 MPa (p-value 0.016). Tobramycin alone decreased the tensile strength beginning at 1.5 g yielding a strength of 27.7 ± 7 MPa (p-value 0.003). Although it decreased compressive strength at 1 g to 117 ± 7 MPa (p-value 0.002), it demonstrated variable effects with increasing concentrations. A combination of vancomycin and tobramycin decreased both the compressive (111 ± 5 MPa, p-value 0.014) and tensile (27.9 ± 8 MPa, p-value 0.007) strengths beginning at 1 g each. Conclusions: Various combinations of vancomycin and tobramycin affect the compressive and tensile strengths of bone cement. Clinicians should be diligent when mixing these antibiotics in bone cement to prevent possible failure of the constructs.
RESUMEN
BACKGROUND: The Latarjet procedure reduces recurrent glenohumeral instability but has potential hardware and graft complications. The procedure has been modified to use various screw types as well as suture buttons. Biomechanical studies have evaluated the effect of these implants on construct strength. With varying results it is unclear whether there is an optimal implant to use. METHODS: We conducted a systematic review of human cadaveric biomechanical studies evaluating Latarjet ultimate failure load. Two independent reviewers screened articles and included them after full text review. Additional factors including implants used, graft orientation, cortices engaged, drill diameter, and screw characteristics were recorded. Meta-regression was performed on the 145 specimens from eight studies that met inclusion criteria. RESULTS: Screw fixation resulted in a 396.8 N (95% CI, 149.8-643.7) N higher ultimate failure load against shear stresses than suture buttons (p = 0.002). There were no differences between implants for ultimate failure load against tensile forces. Tensile strength was significantly affected by drill diameter with each millimeter of increase reducing the mean ultimate failure load by 127.4 N (95% CI, 41.2-213.6) N (p = 0.004). CONCLUSIONS: These results suggest that using screw fixation and minimizing drill diameter can obtain the maximum ultimate failure load against both shear and tensile forces in a Latarjet construct.