Characterization of the biomechanical properties of canine trachea using a customized 3D-printed apparatus.

OBJECTIVES: The canine trachea is considered to be an excellent preclinical model for tracheal research due to its similar mechanical and dimensional characteristics to the human trachea. However, normative biomechanical properties have yet to be defined and it is one of the main reasons tracheal reconstruction has not succeeded in animal models at large scale. Variation and inaccurate measurement due to a lack of proper apparatus for mechanical tests further prevent determination of normative mechanical data of the trachea. The goal of this study was to overcome these shortcomings by designing the measuring apparatus using 3D-printing technology. Using this apparatus, we determined the normative biomechanical properties of the canine trachea. METHODS: Whole tracheas were obtained from thirteen mongrel dogs. Biomechanical measurements were performed to determine the radial compressive strength and tensile strength of the intact trachea, and the elastic modulus of the tracheal cartilage. RESULTS: Structural parameter data indicated the canine trachea to have inner-diameters similar to those of the human trachea and other widely used animal models. The compressive strength was 4.24N while the tensile strength was 29.96N. The elastic modulus of the cartilage portion of the trachea was 1.58N without showing a significant difference in value based on the location of the trachea. CONCLUSIONS: This study delineates a comprehensive and foundational characterization of the biomechanical properties of both the intact and cartilage portion of the canine trachea. The parameters were in agreement with those of the human trachea, confirming the canine trachea to be an excellent preclinical model for tracheal research.

Patients with idiopathic trigeminal neuralgia have a sharper-than-normal trigeminal-pontine angle and trigeminal nerve atrophy.

BACKGROUND: Trigeminal neuralgia (TN) is primarily diagnosed by symptoms and patient history. Magnetic resonance (MR) imaging can be helpful in visualizing the neurovascular compression of the trigeminal nerve in TN patients, but the current parameters used as diagnostic markers for TN are less than optimal. The aim of this study is to assess whether the angle between the trigeminal nerve and the pons (the trigeminal-pontine angle) on the affected side of patients with idiopathic TN differs from that of the unaffected side and that found in controls without TN. METHODS: A case-control study of 30 clinically diagnosed idiopathic TN patients aged 30 to 79 years and 30 age- and sex-matched controls was conducted. We compared the trigeminal-pontine angle and trigeminal nerve atrophy via fast-imaging employing steady-state acquisition (FIESTA) MR imaging. RESULTS: A sharp trigeminal-pontine angle was observed in 25 patients (25/30) on the affected side. As such, the mean angle of the trigeminal nerve on the affected side (40.17) was significantly smaller than that on the unaffected side (48.91, p = 0.001) and that in the control group (52.02, p < 0.001). CONCLUSIONS: A sharp trigeminal-pontine angle on the affected side was found in idiopathic TN patients by FIESTA imaging. This suggests that a sharp trigeminal-pontine angle increases the chance of neurovascular compression on the medial side of the trigeminal nerve.

Toward more useful pressure-controlled discography: in vitro evaluation of injection speed, sensor location, and tube length.

OBJECTIVE: Pressure-controlled manometric discography is used by clinicians to evaluate discogenic pain. However, some would improve diagnostic accuracy. The goal of this study was to investigate potential confounding factors that might affect discographic results. Pressure differences depending on different speed of injection, lengths of connecting tubing and locations of sensors were evaluated using an in vitro model system. METHODS: Two sets of automated discography devices were arranged to record post-syringeal pressure pressures (PSPs) and intradiscal pressures (IDPs) in an "air chamber disk model" representing intradiscal pressure. PSPs and IDPs were measured simultaneously while varying injection speeds, and using intrasyringeal and extrasyringeal pressure sensors and contrast medium-filled tubing of different lengths. All pressure/volume curves were collected and viewed dynamically, and stored for further analysis. RESULTS: At injection speed of 0.1 cc/second, the mean pressure difference (mean ΔP) between PSP and IDP was 38.1 psi. As injection speed was reduced, mean ΔP was proportionally decreased. Mean ΔP was 5.3 psi at injection speed of 0.01 cc/second and 0.7 psi at 0.005 cc/second. Mean ΔP values were significantly higher when pressures were recorded using intrasyringeal sensor: at injection speed of 0.1 cc/second, PSP and IDP values were 82.9 and 30.1 psi, respectively, compared with 50.6 and 12.5 psi measured by extrasyringeal sensor. Mean ΔP due to increased length of tubing was not significant. CONCLUSION: Discography can be better performed with low speed injection (≤0.01 cc/second), using an extrasyringeal sensor. Difference of length of connecting tubings did not cause significant pressure differences. These data suggest that automated discography is a helpful adjunct to improve diagnostic accuracy, due to extrasyringeal location of pressure sensor and greater control of injection speed.