Repair of large segmental bone defects: BMP-2 gene activated muscle grafts vs. autologous bone grafting.

Background: Common cell based strategies for the treatment of osseous defects require the isolation and expansion of autologous cells. Since this makes such approaches time-consuming and expensive, we developed a novel expedited technology creating gene activated muscle grafts. We have previously shown that large segmental bone defects in rats can be regenerated by implantation of muscle tissue fragments activated by BMP-2 gene transfer.

Complex distal humerus fractures-comparison of polyaxial locking and nonlocking screw configurations-a preliminary biomechanical study.

Objective: The investigation hypothesized that in current anatomical precontoured plates, angular stability plays only a minor role for the efficacy of the osteosynthesis at the distal humerus.

Methods: An AO C2.3 fracture model was simulated and osteosynthesis performed with plates positioned in parallel.

Implant material and design alter construct stiffness in distal femur locking plate fixation: a pilot study.

Background: Construct stiffness affects healing of bones fixed with locking plates. However, variable construct stiffness reported in the literature may be attributable to differing test configurations and direct comparisons may clarify these differences.

Questions/purposes: We therefore asked whether different distal femur locking plate systems and constructs will lead to different (1) axial and rotational stiffness and (2) fatigue under cyclic loading.

The impact of a distal expansion mechanism added to a standard pedicle screw on pullout resistance. A biomechanical study.

Background Context: Spinal deformity surgery in elderly patients is associated with an increased risk of implant loosening due to failure at the screw-bone interface. Several techniques can be used to increase the screw anchorage characteristics. Cement-augmented screw fixation was shown to be the most efficient method; however, this technique is associated with a risk of complications related to vertebral cement deposition and leakage.

Biomechanical evaluation of subtalar fusion: the influence of screw configuration and placement.

Common surgical procedures for subtalar fusion include joint resection, autologous bone grafting, and osteosynthesis with screws in a parallel screw configuration. Although fusion is a routine procedure, the reported rates of nonunion have been high. The present study assessed different screw configurations in terms of their rotational and bending stability in an artificial bone model and cadaver bone.

Comparison of revision strategies for failed C2-posterior cervical pedicle screws: a biomechanical study.

Study Purpose: With increasing usage within challenging biomechanical constructs, failures of C2 posterior cervical pedicle screws (C2-pCPSs) will occur. The purpose of the study was therefore to investigate the biomechanical characteristics of two revision techniques after the failure of C2-pCPSs.

Materials And Methods: Twelve human C2 vertebrae were tested in vitro in a biomechanical study to compare two strategies for revision screws after failure of C2-pCPSs.

Arthroscopic rotator cuff repair: a biomechanical comparison of the suture-bridge technique vs. a new transosseous technique using SutureButtons(®).

Background: The suture-bridge technique using anchors as established transosseous-equivalent technique in arthroscopic rotator cuff repair was compared to a modified transosseous technique suitable for arthroscopic cuff repair.

Methods: In 10 fresh-frozen matched pairs of human cadaveric shoulders (mean age 67.1, SD 8.

Biomechanical comparison of the end plate design of three vertebral body replacement systems.

Introduction: Compression fractures at the thoracolumbar junction are frequently treated by reconstruction with vertebral body replacement systems. Modern cage implants have been developed which respect the anatomy and angulation of the adjacent bony endplates. The objective of this study was to investigate the biomechanical performance of anatomic endplate design and variable endplate angulation.

Improvement of the shear fixation stability of intramedullary nailing.

Background: The healing outcome of long bone fractures is strongly influenced by the mechanical environment. High interfragmentary movement at the fracture site is detrimental to the fracture healing process. Long bone fractures stabilized with thin intramedullary nails commonly used for unreamed intramedullary nailing might be very flexible in shear direction and therefore critical for the fracture healing outcome.

Anatomical plate configuration affects mechanical performance in distal humerus fractures.

Background: Because of strong loads acting in the elbow joint, intraarticular fractures with a methaphyseal comminuted fracture site at the distal humerus demand a lot from the osteosynthetic care. Ambiguities arise concerning to the anatomic position of the implants and the resulting mechanic performance. The aim of this biomechanical study was to compare the performance of different anatomical plate configurations for fixation of comminuted distal humerus fractures within one system.

A biomechanical rationale for C1-ring osteosynthesis as treatment for displaced Jefferson burst fractures with incompetency of the transverse atlantal ligament.

Nonsurgical treatment of Jefferson burst fractures (JBF) confers increased rates of C1-2 malunion with potential for cranial settling and neurologic sequels. Hence, fusion C1-2 was recognized as the superior treatment for displaced JBF, but sacrifies C1-2 motion. Ruf et al.

The repair of critical-sized bone defects using expedited, autologous BMP-2 gene-activated fat implants.

The repair of bone defects can be induced experimentally with bone morphogenetic protein-2 (BMP-2) producing fat-derived stem cells, but this ex vivo tissue engineering method requires the isolation and long-term culture of autologous cells. To develop an expedited bone repair strategy, we transferred BMP-2 cDNA directly to autologous fat tissue fragments that were held in culture for only 24 h before implantation. We evaluated the ability of such gene-activated fat grafts to regenerate large segmental bone defects in rats.

Healing of large segmental bone defects induced by expedited bone morphogenetic protein-2 gene-activated, syngeneic muscle grafts.

Numerous preclinical studies have shown that osseous defects can be repaired by implanting bone morphogenetic protein (BMP)-2-transduced muscle cells. However, the drawback of this treatment modality is that it requires the isolation and long-term (approximately 3 weeks) culture of transduced autologous cells, which makes this approach cumbersome, time-consuming, and expensive. Therefore, we transferred BMP-2 cDNA directly to muscle tissue fragments that were held in culture for only 24 hr before implantation.

Influence of intramedullary nail diameter and locking mode on the stability of tibial shaft fracture fixation.

Background: Fracture healing is affected by the type and the magnitude of movements at the fracture site. Mechanical conditions will be a function of the type of fracture management, the distance between the fracture fragments, and the loading of the fracture site. The hypothesis to be tested was that the use of a larger-diameter intramedullary nail, together with compressed interlocking, would enhance the primary stiffness and reduce fracture site movements, especially those engendered by shearing forces.

Influence of thread design on pedicle screw fixation. Laboratory investigation.

Object: The authors conducted a study to determine the thread properties that provide optimal screw fixation in cancellous bone, when screws of the same external screw diameter are used.

Methods: Three compliance engineering-certified screws in clinical use, all of the same external diameter and length, were compared in an axial pullout experiment with respect to advantageous thread properties. As test material, standardized Sawbone blocks with 3 different densities (0.

Validation of a femoral critical size defect model for orthotopic evaluation of bone healing: a biomechanical, veterinary and trauma surgical perspective.

Numerous in vivo studies have been conducted to investigate bone regeneration in orthotopic defect models, but a reliably standardized critical-size defect (CSD) model in small animals is still lacking in tissue-engineering research. Utilizing the expertise of trauma surgeons, veterinary surgeons, and engineers, we evaluated the optimal fixation strategy for in vivo application in terms of surgical suitability and conducted biomechanical studies for 3 fixation devices. Fixation strategies were an external fixation device made of polymethylmethacrylate, widely used in animal care; a self-constructed external clamp-fixation device, designed and manufactured using rapid prototyping techniques; and commercially available 1.

Cervical anterior transpedicular screw fixation (ATPS)--Part II. Accuracy of manual insertion and pull-out strength of ATPS.

Reconstruction after multilevel decompression of the cervical spine, especially in the weakened osteoporotic, neoplastic or infectious spine often requires circumferential stabilization and fusion. To avoid the additional posterior surgery in these cases while increasing rigidity of anterior-only screw-plate constructs, the authors introduce the concept of anterior transpedicular screw (ATPS) fixation. We demonstrated its morphological feasibility as well as its indications in a previous study in Part I of our project.

Interfragmentary movement in diaphyseal tibia fractures fixed with locked intramedullary nails.

Objectives: Biomechanical study on cadaveric bones using physiological loading conditions to quantify interfragmentary movements in a tibial shaft fracture model fixed by intramedullary nailing.

Methods: Six fresh frozen human cadaveric tibiae were sequentially tested in axial, torsional, 4-point bending, and shear loading configurations. Tests were performed in intact specimens and osteotomized specimens equipped with interlocked intramedullary nails.