A BIOMECHANICAL COMPARISON OF MATCHED FOUR-STRAND AND FIVE-STRAND SEMITENDINOSUS-GRACILIS GRAFTS

ABSTRACT Introduction: Recent studies have shown that the likelihood of semitendinosus-gracilis graft rupture is inversely correlated to its diameter. A graft can be prepared in a five-strand or four-strand fashion to increase its diameter. However, the biomechanical superiority of five-strand semitendinosus-gracilis grafts is still under debate. Objective: This study aimed to evaluate the biomechanical characteristics of matched four-strand and five-strand human semitendinosus-gracilis grafts. Methods: We evaluated semitendinosus-gracilis tendons harvested from ten fresh human male and female cadavers, aged 18-60 years. Four-strand or five-strand grafts were prepared with the tendons and fixed to wooden tunnels with interference screws. Each graft was submitted to axial traction at 20 mm/min until rupture; the tests were donor matched. Data were recorded in real time and included the analysis of the area, diameter, force, maximum deformation and stiffness of the grafts. Results: The diameter, area and tunnel size were significantly greater in the five-strand grafts than in the four-strand grafts. There were no significant differences in biomechanical properties. The area and diameter of the graft were positively correlated to stiffness, and inversely correlated to elasticity. There was no significant correlation between graft size and maximum force at failure, maximum deformation or maximum tension. Conclusion: Five-strand hamstring grafts have greater area, diameter and tunnel size than four-strand grafts. There were no significant differences in biomechanical properties. In this model using interference screw fixation, the increases in area and diameter were correlated with an increase in stiffness and a decrease in elasticity. Level of evidence V; biomechanical study.

Computed Tomography Imaging of BioComposite Interference Screw After ACL Reconstruction With Bone–Patellar Tendon–Bone Graft

Background: Bioabsorbable interference screws tend to have high resorption rates after anterior cruciate ligament (ACL) reconstruction; however, no studies have examined screws composed of 30% biphasic calcium phosphate and 70% poly-d-lactide (30% BCP/70% PLDLA). Purpose: To evaluate femoral and tibial tunnel widening and resorption of 30% BCP/70% PLDLA interference screws and replacement with bone at 2 to 5 years after ACL reconstruction using bone–patellar tendon–bone (BTB) autograft. Study Design: Case series; Level of evidence, 4. Methods: Included were 20 patients who had undergone ACL reconstruction using BTB autograft and were reevaluated 2 to 5 years after surgery using computed tomography scans. Tunnel measurements were obtained from computed tomography scans in the sagittal and coronal planes and were compared with known tunnel measurements based on operative reports. These images and measurements were used to assess tunnel widening, resorption of the 30% BCP/70% PLDLA screw, its replacement with bone, and possible cyst formation. Paired t tests were used to compare initial and final femoral and tibial tunnel measurements. Results: The cross-sectional area of the femoral tunnel decreased at the aperture ( P = .03), middle ( P = .0002), and exit ( P < .0001) of the tunnel compared with the initial femoral tunnel size, and the tibial tunnel cross-sectional area decreased at the aperture ( P < .0001) and exit ( P = .01) of the tunnel compared with the initial tibial tunnel size. Bone formation was observed in 100% of femoral tunnels and 94.7% of tibial tunnels. Screw resorption was 100% in the femur and 94.7% in the tibia at the final follow-up. Cysts were noted around the femoral tunnel in 2 patients (5.1%). Conclusion: The 30% BCP/70% PLDLA interference screws used for ACL reconstruction using BTB autograft had high rates of resorption and replacement with bone, and there were no increases in tunnel size at 2 to 5 years postoperatively. The authors observed a low rate of cyst formation and no other adverse events stemming from the use of this specific biointerference screw, suggesting that this type of screw is a reasonable option for graft fixation with minimal unfavorable events and a reliable resorption profile.

Ground Stability Analysis in Non-Open-Cut Tunneling Method Using Small-Diameter Steel Pipe Piles

The non-open-cut method is used for constructing tunnels under existing roads without blocking traffic. Various non-open-cut methods use pipe roofs made of medium- and large-diameter steel pipe piles. However, the risk of ground settlement or heave is involved during the application of such piles. Therefore, research is conducted through model tests and numerical analysis on the non-open-cut method to investigate these problems using small-diameter piles. The progress of tunnel construction is divided into two repetitive steps. The first step (Stage 1) involves pulling back the pressure panel, and the second step involves propelling the precast structure (Stage 2). The behaviors of the pipe piles and ground displacement are analyzed according to the cover depth, tunnel size, existence and nonexistence of the shoe structure, and progress of tunnel construction. Small-diameter piles reduce the displacement during both stages. With a decrease in cover depth, the stress acting on the pile decreases during Stage 1 and increases during Stage 2. The presence of the shoe structure reduces the stress on the pile during both stages. The ground behavior based on the construction progress indicates that the ground settlement increases during Stage 1; however, no correlation is observed during Stage 2 at low depth.

Glenoid Reaction to Biocomposite and PEEK Suture Anchors Following Arthroscopic Labral Repairs

Objectives: Biocomposite and all-suture suture anchors have been shown to cause reactive changes in the humerus and glenoid when used for arthroscopic rotator cuff and glenoid labrum repairs. The purpose of this study was to quantify glenoid anchor widening using biocomposite or PEEK suture anchors for arthroscopic shoulder stabilization. Our hypothesis was that biocomposite and PEEK anchors would lead to significant reactive changes in the glenoid as evidenced by a difference in postoperative tunnel size compared to suture anchor diameter. Methods: We searched the Military Data Repository for all patients with a history of a glenoid labrum repair who underwent a postoperative CT scan of the affected shoulder in our hospital market region. CT scans were measured using organic IMPAX tools to calculate the width and length of bone tunnels as described by Tompane et al. Bone mineral density was calculated by measuring the average Hounsfield Units through four axial segments of the glenoid neck in a best fit circle of cancellous bone. Tunnel widening was defined as an increase in width greater than 0.1mm compared to the drill size for each implant. Measurements were made by two independent observers blinded to other patient factors. Patient charts were also reviewed to obtain anchor data, injury, and surgical variables. Univariate analysis was performed to compare differences between tunnel widths and anchor sizes Results: We analyzed 146 bone tunnels in 37 shoulders that met inclusion criteria. The mean age was 23 (18-45), with 126 male and 20 females. The average time to CT scan from labrum repair was 782 days (159-2210). The majority of CT scans (33) were obtained after recurrent instability events, 2 were obtained for preoperative planning prior to shoulder arthroplasty, and 2 were obtained to evaluate the glenoid prior to military commissioning. The average number of anchors used per shoulder was 5. There were 17 PEEK and 129 biocomposite anchors included. There were 113 Arthrex, 28 Mitek, and 3 Zimmer Biomet anchors included in the data. There were 81 anchors in the anterior inferior quadrant, 21 anterior superior, 37 posterior inferior, and 6 in the posterior superior quadrant of the glenoid. The mean difference between tunnel and anchor width was 0.002mm across the data set. Fifty-five biocomposite anchors (43.6%) showed an increased tunnel diameter of greater than 0.1mm compared to anchor size. 7 PEEK anchors (41%) demonstrated an increased tunnel diameter greater than 0.1mm. Additionally, 14 tunnels demonstrated an increased width greater than 1mm compared to anchor size and all were biocomposite anchors. There was no difference in tunnel widening between biocomposite and PEEK anchors (p=0.34). The average change in width across widened tunnels was 0.07mm. The average change in tunnel size across all anchors was 0.02mm. On univariate analysis, bone mineral density, anchor size, anchor position, time to CT scan, composition, and age were not shown to have a statistically significant correlation. Conclusion: At short term 2 year follow-up there was no difference in tunnel widening between PEEK and biocomposite suture anchors. Although the majority of bone tunnels did not demonstrate significant widening compared to the implant size, 43.6% of biocomposite and 41% PEEK anchors generated reactive changes greater than 0.1mm. There were no clear trends in anchor type or location that clearly contributed to tunnel widening.

Influence of Tunneling in Cohesionless Soil for Different Tunnel Geometry and Volume Loss under Greenfield Condition

This paper presents the numerical analysis of settlement to profile the vulnerable zone or influence zone due to tunneling activities in cohesionless deposits for free field or Greenfield conditions. The analysis considers the factors like saturated density (γsat), unsaturated density (γunsat), angle of shearing resistance (φ), deformation modulus (ES), volume loss (VL), and the support pressure of the shield head at the tunnel face. The obtained results using a finite element program (FEM) PLAXIS 3D are compared with measured and predicted surface settlement using field measuring instruments, and analytical and empirical solution show a reasonable agreement and are found to be conservative. From literature, for Greenfield condition the ground settlement equal to 10 mm is taken as the minimum value to map the influencing zone considering the fact that the structure which lies beyond this zone would undergo negligible settlement. Settlement trough and 10 mm settlement contour characteristics are presented for different tunnel sizes placed at the same depth and the same tunnel size placed at different depths, respectively. Various influencing zones are arrived for the sandy grounds of different denseness based on the parametrical studies involving parameters such as tunnel size “D,” tunnel axis depth “z,” and volume loss “VL.”

A Rescue-Assistance Navigation Method by Using the Underground Location of WSN after Disasters

A challenging rescue task for the underground disaster is to guide survivors in getting away from the dangerous area quickly. To address the issue, an escape guidance path developing method is proposed based on anisotropic underground wireless sensor networks under the condition of sparse anchor nodes. Firstly, a hybrid channel model was constructed to reflect the relationship between distance and receiving signal strength, which incorporates the underground complex communication characteristics, including the analytical ray wave guide model, the Shadowing effect, the tunnel size, and the penetration effect of obstacles. Secondly, a trustable anchor node selection algorithm with node movement detection is proposed, which solves the problem of high-precision node location in anisotropic networks with sparse anchor nodes after the disaster. Consequently, according to the node location and the obstacles, the optimal guidance path is developed by using the modified minimum spanning tree algorithm. Finally, the simulations in the 3D scene are conducted to verify the performance of the proposed method on the localization accuracy, guidance path effectiveness, and scalability.

Research on Influence of Road Tunnels with Different Lanes on Surrounding Rock Characteristic Curve

Convergence confinement method is an important guidance method for tunnel construction and support design. Numerical simulation method was used to comparatively analyze the ground reaction curve and the plastic zone under different rock grade and roadway tunnel size. The results show that the change of tunnel size has different effects on the maximum deformation of the tunnel arch crown, the ground reaction curve and the plastic zone range. Finally, some suggestions were put forward for the construction and optimization of the large span arch tunnel support structure. The research results may provide some guidance for related engineering

A numerical study of surface-wave-based tunnel detection at the Black Diamond Mines Regional Preserve, California

Detecting underground voids, such as old mine workings, solution cavities in karst terrain, or unknown tunnels such as illicit cross-border tunnels, is a challenging problem for geophysics and an important concern for geotechnical design, public safety, and domestic security. Seismic surface-wave-based detection methods have become increasingly popular for detecting relatively shallow and small targets; however, the theoretical limitations of these methods have thus far remained unclear. We use a suite of 3D numerical simulations inspired by a tunnel detection experiment carried out at the Black Diamond Mines Regional Preserve (BDM) in northern California. The geophysical anomalies predicted by our numerical simulations at BDM agree with field observations, and our estimates for the location of the primary tunnel target agree with historical records in the area. Using our calibrated numerical model, we perform a parametric study to determine the effect of tunnel size, depth of burial, filling material, and source characteristics to determine the range over which surface-wave backscattering and attenuation-based methods are effective. In addition, we perform a regression analysis to determine a relationship for the maximum depth at which a tunnel may be detected via these approaches, given the target diameter, wavelength of interest, and the signal-to-noise ratio.