Efficacy Comparison of Three Kinds of Distal Tibial Hemiepiphyseal Implants in the Treatment of Postoperative Ankle Valgus of Congenital Pseudarthrosis of the Tibia

Background: Congenital pseudarthrosis of the tibia is a complex and serious disease in orthopedics which often requires multiple operations for treatment. Postoperative ankle valgus deformity is easily seen after the operation of congenital pseudarthrosis of the tibia. The aim of this study is to retrospectively evaluate the safety of three different implants for treating postoperative ankle valgus after congenital pseudarthrosis of the tibia.Methods: A total of 41 patients with postoperative ankle valgus after congenital pseudarthrosis of the tibia from December 2010 to July 2019 were selected. Out of these 41 patients, 23 patients were treated with “U”-shaped tension screw, 10 patients were treated with hollow screw and 8 patients were treated with cortical bone screw. The evaluation index was tibiotalar angle. The general data, preoperative, postoperative and final follow-up imaging data were recorded, and the deformity correction rate and complications were compared. Results: all the patients were performed with postoperative follow-up visit for at least 12 months (31 months on average). In the “U”-shaped tension screw group, the preoperative tibiotalar angle was (74.8±4.8°), the tibiotalar angle was (85.8±4.5°) when the internal fixation was removed; in the hollow screw group, the average preoperative tibiotalar angle was (72.2±6.1°), the average tibiotalar angle was (88.4±5.1°) when the internal fixation was removed; in the cortical bone screw group, the average preoperative tibiotalar angle was (75.1±4.2°), the average tibiotalar angle was (88.4±5.1°) when the internal fixation was removed. The correction effect of the “U”-shaped tension screw group was better than that of the other two groups, but the difference was not significant (the correction rate of the “U”-shaped tension screw group was 0.71°/month, with that of in the hollow screw group and cortical bone screw group being 0.64°/month and 0.61°/month respectively, P＞0.05). One case of internal fixation complication was reported in the hollow screw group; two cases of missing correction effect were reported, one in cortical bone screw group and one in hollow screw group; and two cases showing symptom of wound pain were reported in the “U”-shaped screw group. Conclusion: Ankle valgus is a common postoperative complication of congenital tibial pseudarthrosis. Temporary hemiepiphyseal is an effective treatment for postoperative ankle valgus deformity of congenital pseudarthrosis of the tibia in children. Through comparison, the "U"-shaped tension screw provides relatively better orthopedic results and has a lower rate of internal fixation complications.

Evaluation and Comparison of Stress Patterns and Teeth Displacement with Intrusion of Maxillary Posterior Segment by Skeletal Anchorage System (Infrazygomatic Crestal Bone Screw) and High Pull Headgear: A 3D Finite Element Study

Introduction: In the last decades the application of the Finite Element Methodology (FEM) has become popular. It can calculate stresses and displacement in complex structures and can anticipate the tissue responses to orthodontic mechanics applied for treating different malocclusions. This study evaluated and compared the stress patterns and teeth displacement with application of 450g of intrusive force bilaterally on maxillary posterior segment utilizing a conventional old method, High-Pull Headgear (HPHG) and a newer method, Infrazygomatic Crestal Bone Screw (IZC-BS) using 3D-FEM. Method: A 3D-FEM model of the craniomaxillary segment with maxillary teeth was reconstructed from the Cone Beam Computed Tomographic image of a patient with class II div I malocclusion on class II skeletal base with anterior open bite and 450g of intrusive force was applied bilaterally on maxillary posterior segment utilizing HPHG and IZC-BS and stress patterns and teeth displacement were studied and compared. Result: Von Mises stresses on Zygomaticomaxillary, Zygomaticotemporal and Pterygomaxillary sutures and surface landmarks on maxillary, zygomatic, temporal and sphenoid bones were more pronounced and generalized for HPHG group. Intrusion, expansion and sagittal displacement of maxillary posterior segment were also more pronounced with HPHG group. Stresses weren’t present at the apical root areas of the maxillary posterior teeth for both the groups. Conclusion: On applying equal amount of intrusive force bilaterally to the maxillary posterior segment, stress patterns and teeth displacement were more pronounced and effective for HPHG group however; apical root areas of the maxillary posterior teeth in both the groups didn’t show any stresses.

Proposal for an Adaptive Bone Screw Design Based on FEA Studies Exemplified by Pedicle Screw

This paper presents a proposal for a density-adaptive design of bone screws using pedicle screws for spinal fixations as an example. The basis is the analysis and categorization of currently available variants of bone screws, which differ in principle in their thread design because of different application areas (cortical or cancellous bone). These screw variants are investigated in FEA simulations for pullout and bending with regard to occurring stresses. A corresponding simulation model is presented for this purpose. The precise design models for these screws are generated in a CAD system using a self-developed configuration tool. Based on the FEA evaluation, the proposal for a new pedicle screw design, consisting of several thread types merged into each other, is described in detail. By integrating different thread types over the shaft, the respective properties of the bone can thus be optimally utilized.

Concave or convex rod translation first in adolescent idiopathic scoliosis instrumentation with differential rod contouring?

The objective was to assess deformity correction and bone-screw force associated respectively with concave manipulation first, convex manipulation first, and different differential rod contouring configurations. Instrumentation scenarios were computationally simulated for 10 AIS cases with mean thoracic Cobb angle (MT) of 54±8°, apical vertebral rotation (AVR) of 19±2° and thoracic kyphosis of 21±9°. Instrumentations with major correction maneuvers using the concave side rod were first simulated; instrumentations with major correction maneuvers using the convex side rod were then simulated. Simulated correction maneuvers were concave/convex rod translation followed by apical vertebral derotation and then convex/concave rod translation. There were no significant differences in deformity corrections and bone-screw forces between concave rod translation first and convex rod translation first with differential rod contouring. Increasing differential rod contouring angle and concave rod diameter improved AVR correction and increased the TK and bone-screw forces; the effect on the MT Cobb angle was not clinically significant.

Can the body slope of interference screw affect initial stability of reconstructed anterior cruciate ligament?: An in-vitro investigation

Background Superior biomechanical performance of tapered interference screws, compared with non-tapered screws, with reference to the anterior cruciate ligament (ACL) reconstruction process, has been reported in the literature. However, the effect of tapered interference screw’s body slope on the initial stability of ACL is poorly understood. Thus, the main goal of this study was to investigate the effect of the interference screw’s body slope on the initial stability of the reconstructed ACL. Methods Based on the best screw-bone tunnel diameter ratios in non-tapered screws, two different tapered interference screws were designed and fabricated. The diameters of both screws were equal to bone tunnel diameter in one-third of their length from screw tip, then they were gradually increased by 1mm, in the lower slope (LSTIS), and 2 mm, in the higher slope (HSTIS) screws. To simulate the ACL reconstruction, sixteen soft tissue grafts were fixed, using HSTIS and LSTIS, in synthetic bone blocks. Through applying sub-failure cyclic incremental tensile load, graft-bone-screw construct’s stiffness and graft laxity in each cycle, also through applying subsequent step of loading graft to the failure, maximum load to failure, and graft’s mode of failure were determined. Accordingly, the performance of the fabricated interference screws was compared with each other. Results HSTIS provides a greater graft-bone-screw construct stiffness, and a lower graft laxity, compared to LSTIS. Moreover, transverse rupture of graft fibers for LSTIS, and necking of graft in the HSTIS group were the major types of grafts’ failure. Conclusions HSTIS better replicates the intact ACL’s behavior, compared to LSTIS, by causing less damage in graft’s fibers; reducing graft laxity; and increasing fixation stability. Nonetheless, finding the optimal slope remains as an unknown and can be the subject of future studies.

The application of an allogeneic bone screw for osteosynthesis in hand and foot surgery: a case series

Introduction The allogeneic bone screw transplant is a new osteosynthesis device making the use of foreign fixation material obsolete for various kinds of indications. Moreover, it is integrated into the recipient bone by natural bone remodeling without harming the surrounding tissue. The aim of this study was to determine the efficacy and safety of the transplant for osteotomy and arthrodesis in hand and foot surgery and to evaluate the clinical importance of the device. Materials and methods A single-surgeon case series of 32 patients who had undergone hand or foot surgery with the application of an allogeneic bone screw with an average follow-up time of 1 year is reported. Clinical data were reviewed to evaluate the pain levels and satisfaction of the patients and the frequency and type of complications occurring during the healing process. Routine radiography and computed tomography were reviewed to determine the fusion rate, the ingrowth behavior of the transplant and the possible occurrence of transplant failure. Results High patient satisfaction was paired with low postoperative pain levels and a low complication rate. 97% of the patients were free of pain at the timepoint of the second follow-up examination, the mean time of recovery of full mobility was 50.1 ± 26.1 days after surgery. Wound healing disturbance occurred only in two cases. Bony consolidation of the osteotomy or arthrodesis gap as well as osseointegration of the transplant was seen in all cases. No transplant failure or transplant loosening occurred. Conclusions The application of the allogeneic bone screw resulted in a 100% fusion rate while the patient burden was low. The transplant is safe and suited for various kinds of osteosynthesis in hand and foot surgery.