Biomedical subjects

Richard D Peindl

Publications and source records attributed to Richard D Peindl.

8 recordsLinked to original sources

PubMed2006

Textile analysis of heavy weight, mid-weight, and light weight polypropylene mesh in a porcine ventral hernia model.

BACKGROUND: The purpose of this study was to assess the burst strength and stiffness of heavy weight (HW), mid-weight (MW), and light weight (LW) polypropylene mesh pre-implantation and 5 months post-implantation in a porcine ventral hernia model. MATERIALS AND METHODS: HW (95 g/cm2), MW (45 g/cm2), and LW (28 g/cm2) polypropylene were tested as dry samples (n = 8/mesh) before implantation using a stamp strain machine. Three weeks after creating four hernia defects in each mini-pig (n = 18), the polypropylene meshes (8 x 10 cm; 24/mesh type) were implanted in the preperitoneal space, ensuring 2 cm overlap circumferentially. At 5 months, the mesh was harvested en bloc with the abdominal wall. Testing of burst strength and stiffness was repeated on the ex vivo specimens. RESULTS: After implantation in the pig for 5 months, the mean burst strength and stiffness of HW and MW meshes remains the same. LW mesh with an absorbable monofilament in its weave has significant reductions in mean burst strength (P = 0.01) and mean stiffness (P < 0.0001). The burst strength for all meshes tested was much higher than measured for the abdominal wall fascia alone. The degree of shrinkage of the various weight meshes did not differ. CONCLUSION: A reduction in mean burst strength and stiffness occurs after 5 months implantation of LW polypropylene mesh with an absorbable monofilament. All meshes exhibited burst strengths that were much greater than the burst strength of the abdominal wall fascia alone. After tissue incorporation, the LW polypropylene mesh maintains mean burst strength comparable to MW polypropylene mesh, while becoming less stiff than HW mesh. Long-term, this may contribute to more physiological abdominal wall compliance after LW polypropylene mesh implantation.

Animals↗

PubMed2006

Acetabular component deformation with press-fit fixation.

Acetabular component deformation secondary to forces encountered during insertion is a potential consequence of the press-fit technique. This study characterized the stiffness of Pinnacle 100 cups (DePuy, Warsaw, Ind) via mechanical testing and used this information with intraoperative measurements of cup deformation to calculate the in vivo forces acting on cups inserted during hip arthroplasty in 21 patients. We found that 90.5% of cups had measurable compression deformity, averaging 0.16 +/- 0.16 mm. The corresponding forces acting on these cups averaged 414 +/- 421 N. For hard-on-hard bearing surfaces, such in vivo deformation of acetabular shells may result in negative clinical consequences such as equatorial loading with increased wear and potential seizing of components, chipping of ceramic inserts, or locking mechanism damage.

Acetabulum↗

PubMed2006

Biomechanical analysis of blade plate versus locking plate fixation for a proximal humerus fracture: comparison using cadaveric and synthetic humeri.

OBJECTIVE: To compare the mechanical stability of a fixed-angle blade plate with that of a locking plate in a cadaveric proximal humerus fracture-fixation model subjected to cyclic loading. A secondary objective was to evaluate whether the use of synthetic humerus specimens would replicate significant differences found during cadaveric tests. DESIGN: Mechanical evaluation of constructs in bending and torsion. SETTING: Biomechanical laboratory in an academic medical center. METHODS: Simulated humeral neck fractures (Orthopaedic Trauma Association (OTA) classification 11A3), in matched-pair cadaveric and synthetic specimens underwent fixation using either a 3.5-mm, 90-degree cannulated LC-Angled Blade Plate or a 3.5-mm LCP Proximal Humerus Locking Plate. Cadaveric specimen constructs were cyclically loaded in bending and torsion; synthetic specimens were tested in torsion. MAIN OUTCOME MEASURE: Humeral shaft-bending displacements and angular rotations for respective cyclic bending loads and axial torques were recorded and compared at repeated cyclic intervals to evaluate construct loosening. RESULTS: Locking-plate constructs exhibited significantly less loosening than blade-plate constructs for torsional loading in cadaveric specimens (P = 0.036). The two types of constructs performed similarly for torsional loading in synthetic specimens (P = 0.100). Under cyclic, closed-bending load conditions in which the plates served as tension members, both types of constructs performed similarly in cadaveric specimens (P = 0.079). CONCLUSIONS: For simulated humeral neck fractures subjected to cyclic loading, locking-plate constructs demonstrated significantly greater torsional stability and similar bending stability to blade plates in a cadaveric specimen model. In contrast, these same constructs performed similarly with torsional loading when using synthetic humerus specimens. These results indicate potential advantages for locking-plate fixation. They also indicate that the synthetic specimens tested may not be appropriate for evaluating fixation stability in the humeral head, where cancellous bone fixation predominates.

Biomechanical Phenomena↗

PubMed2006

Prospective evaluation of adhesion formation and shrinkage of intra-abdominal prosthetics in a rabbit model.

Laparoscopic ventral hernia repair requires an intraperitoneal prosthetic; however, these materials are not without consequences. We evaluated host reaction to intraperitoneal placement of various prosthetics and the functional outcomes in an animal model. Mesh (n = 15 per mesh type) was implanted on intact peritoneum in New Zealand white rabbits. The mesh types included ePTFE (DualMesh), ePTFE and polypropylene (Composix), polypropylene and oxidized regenerated cellulose (Proceed), and polypropylene (Marlex). Adhesion formation was evaluated at 1, 4, 8, and 16 weeks using 2-mm mini-laparoscopy. Adhesion area, adhesion tenacity, prosthetic shrinkage, and compliance were evaluated after mesh explantation at 16 weeks. DualMesh had significantly less adhesions than Proceed, Composix, or Marlex at 1, 4, 8, and 16 weeks (P < 0.0001). Marlex had significantly more adhesions than other meshes at each time point (P < 0.0001). There were no statistically significant differences in adhesions between Proceed and Composix meshes. After mesh explantation, the mean area of adhesions for Proceed (4.6%) was less than for Marlex (21.7%; P = 0.001). The adhesions to Marlex were statistically more tenacious than the DualMesh and Composix groups. Overall prosthetic shrinkage was statistically greater for DualMesh (34.7%) than for the remaining mesh types (P < 0.01). Mesh compliance was similar between the groups. Prosthetic materials demonstrate a wide variety of characteristics when placed inside the abdomen. Marlex formed more adhesions with greater tenacity than the other mesh types. DualMesh resulted in minimal adhesions, but it shrank more than the other mesh types. Each prosthetic generates a varied host reaction. Better understanding of these reactions can allow a suitable prosthetic to be chosen for a given patient in clinical practice.

Animals↗

PubMed2005

Arthroscopic knot tying: the role of instrumentation in achieving knot security.

PURPOSE: To determine the role of arthroscopic knot-tying instrumentation in achieving knot security. TYPE OF STUDY: Biomechanical study. METHODS: The security achieved by 3 different commercially available knot-tying instruments using No. 2 braided suture and a standardized knot configuration was compared. Instrumentation included (1) a single-hole knot pusher, (2) a cannulated double-diameter knot pusher, and (3) a mechanical end-splitting knot tightener. Hand-tied knots served as controls. Testing included both cyclic loading and load to failure parameters using the Bionix 858 (MTS Inc, Eden Prairie, MN) and Instron Mini 44 (Instron, Canton, MA) materials testing systems, respectively. An experienced arthroscopic shoulder surgeon and a less experienced junior-level orthopaedic resident surgeon performed tying. RESULTS: Knot displacement after cyclic loading was smallest for the mechanical end-splitting knot tightener (average, 0.054 mm) and did not differ statistically from hand-tied knots (average, 0.058 mm). Knots tied with this device also withstood the greatest load to failure (average, 126.0 N) and were statistically similar to hand-tied knots (average, 134.1 N). The single-hole pusher had an average cyclic loading displacement of 0.095 mm and failed at 108.6 N. The cannulated double-diameter pushers had an average cyclic loading displacement of 0.106 mm and failed at 93.1 N. Both were statistically less secure than hand-tied knots or those tied with the end-splitting tightener. Investigator experience did not affect knot security with those tied by the mechanical end-splitting tightener or hand-tied knots. CONCLUSIONS: The end-splitting tightener provided the most secure arthroscopic knots that were statistically as secure as those tied by hand for both investigators. The knot-tying instrument used in arthroscopic shoulder surgery may be an important consideration with potential clinical implications based on knot security. CLINICAL RELEVANCE: The specific knot tying instrument that is selected for use in arthroscopic shoulder surgery may play an important role in the degree of ultimate knot security achieved in suture repair.

Arthroscopy↗

PubMed2004

Unstable proximal extraarticular tibia fractures: a biomechanical evaluation of four methods of fixation.

OBJECTIVE: To compare the biomechanical stability of extraarticular proximal tibia fractures reconstructed using a double-plate construct, locking plate system, hybrid external fixator, and single lateral periarticular plate, all from the same manufacturer. DESIGN: Standardized proximal tibial fractures (AO classification 41-A3.2 and A3.3) in synthetic tibiae were stabilized using one of the four constructs. Load versus proximal fragment translation and rotation were monitored in each case. Fixation was evaluated for moderately unstable and completely unstable fractures simulated by wedge and gap osteotomies of the proximal femur. SETTING: Academic medical center biomechanical engineering laboratory. MAIN OUTCOME MEASUREMENTS: Proximal fragment axial displacement, varus rotation, and posterior rotation versus applied load for each of the constructs. RESULTS: The double-plate construct was significantly stiffer than all other constructs with regard to resistance to axial displacement, varus rotation, and posterior rotation for both types of unstable fractures. With regard to axial stiffness, the double-plate construct was statistically similar to an intact tibia for moderately stable fractures. The locking plate and the external fixator were similar for stabilization of moderately unstable fractures, whereas the locking plate and the periarticular plate were significantly stiffer than the external fixator construct for completely unstable fractures. CONCLUSION: For axial load applied to a wedge or gap osteotomy of the proximal tibia, the double-plate construct provided significantly more rigidity than the other constructs. The locking plate, periarticular plate, and hybrid external fixator tested provided similar rigidity for the wedge osteotomy, but for the gap osteotomy the external fixator could not support 600N without complete closure of the gap.

Biomechanical Phenomena↗

PubMed2003

Biomechanical effects of processing bulk allograft bone with negative-pressure washing.

The best method for processing allograft bone to prevent disease transmission without compromising its biomechanical function is not yet determined. We evaluated the biomechanical effects of processing bulk allograft bone segments with negative-pressure washing. Specimens were prepared from matched pairs of adult cadaveric femurs. The experimental femur underwent routine processing, followed by negative-pressure washing, whereas its matched control underwent routine processing only. Each specimen was tested to failure, and maximal stress values were determined. No differences were found in yield stress comparisons between groups for the following specimens and tests: compression of machined femoral heads, screw push-out testing in cortical bone, and 4-point bending of cortical beams. Compression testing of diaphyseal ring struts provided varied results. Negative-pressure-washed half-ring strut grafts were statistically stronger (9.6%) than their matched controls (P = 0.018). Negative-pressure-washed full-ring strut grafts were statistically less strong (-12.2%) than their control counterparts (P = 0.003). We studied 5 different allograft types (designed with clinically relevant geometries) subjected to 3 modes of testing (representative of loading in typical clinical situations). Our data show that processing of large, essentially intact allograft bone segments with negative-pressure washing had little, if any, biomechanical effect relative to frozen controls.

Biomechanical Phenomena↗

PubMed2002

Biomechanical testing of cadaveric specimens: importance of bone mineral density assessment.

The bone density of cadaveric specimens is highly variable and has a significant effect on the results of biomechanical testing but it is not often assessed before testing is performed in the lab. Bone mineral density (BMD) tests such as dual X-ray absorptiometry (DXA) are widely available, easy to perform and correlate highly and significantly with bone strength in many modes of failure. We present the results of two different studies performed on cadaveric foot and ankle specimens. In these studies the results vary significantly according to BMD, and this effect is not always eliminated with the use of matched pairs of cadaveric specimens.

Ankle Joint↗