METHODS: Vancomycin at various concentrations was added to JectOS and polymethyl methacrylate (PMMA). Then, the cement was molded into standardized dimensions for in vitro testing. Cylindrical vancomycin-JectOS samples were subjected to compressive strength. The results obtained were compared to PMMA-vancomycin compressive strength data attained from historical controls. The zone of inhibition was carried out using vancomycin-JectOS and vancomycin-PMMA disk on methicillin-resistant strain culture agar.
RESULTS: With the addition of 2.5%, 5%, and 10% vancomycin, the average compressive strengths reduced to 8.01 ± 0.95 MPa (24.6%), 7.52 ± 0.71 MPa (29.2%), and 7.23 ± 1.34 MPa (31.9%). Addition of vancomycin significantly weakened biomechanical properties of JectOS, but there was no significant difference in the compressive strength at increasing concentrations. The average diameters of zone of inhibition for JectOS-vancomycin were 24.7 ± 1.44 (2.5%) mm, 25.9 ± 0.85 mm (5%), and 26.8 ± 1.81 mm (10%), which outperformed PMMA.
CONCLUSION: JectOS has poor mechanical performance but superior elution property. JectOS-vancomycin cement is suitable as a void filler delivering high local concentration of vancomycin. We recommended using it for contained bone defects that do not require mechanical strength.
METHODS: Six porcine lumbar spines (L2-L5) were separated into 12 functional spine units. Bilateral total facetectomies and interlaminar decompression were performed for all specimens. Non-destructive loading to assess stiffness in lateral bending, flexion and extension as well as axial rotation was performed using a universal material testing machine.
RESULTS: PS and CS constructs were significantly stiffer than the intact spine except in axial rotation. Using the normalized ratio to the intact spine, there is no significant difference between the stiffness of PS and CS: flexion (1.41 ± 0.27, 1.55 ± 0.32), extension (1.98 ± 0.49, 2.25 ± 0.44), right lateral flexion (1.93 ± 0.57, 1.55 ± 0.30), left lateral flexion (2.00 ± 0.73, 2.16 ± 0.20), right axial rotation (0.99 ± 0.21, 0.83 ± 0.26) and left axial rotation (0.96 ± 0.22, 0.92 ± 0.25).
CONCLUSION: The CS-rod TLIF construct provided comparable construct stiffness to a traditional PS-rod TLIF construct in a 'standardized' porcine lumbar spine model.
METHODS: This study involved 70 consecutive Lenke 1 and 2 AIS patients who underwent scoliosis correction with alternate-level pedicle screw instrumentation. Preoperative parameters that were measured included main thoracic (MT) Cobb angle, proximal thoracic (PT) Cobb angle, lumbar Cobb angle as well as thoracic kyphosis. Side-bending flexibility (SBF) and fulcrum-bending flexibility (FBF) were derived from the measurements. Preoperative height and post-operative height increment was measured by an independent observer using a standardized method.
RESULTS: MT Cobb angle and FB Cobb angle were significant predictors ( p < 0.001) of height increment from multiple linear regression analysis ( R = 0.784, R2 = 0.615). PT Cobb angle, lumbar, SB Cobb angle, preoperative height and number of fused segment were not significant predictors for the height increment based on the multivariable analysis. Increase in post-operative height could be calculated by the formula: Increase in height (cm) = (0.09 × preoperative MT Cobb angle) - (0.04 x FB Cobb angle) - 0.5.
CONCLUSION: The proposed formula of increase in height (cm) = (0.09 × preoperative MT Cobb angle) - (0.04 × FB Cobb angle) - 0.5 could predict post-operative height gain to within 5 mm accuracy in 51% of patients, within 10 mm in 70% and within 15 mm in 86% of patients.