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Mike-Mayer A, Lam K, Morris RP, Barghouthi AA, Travascio F, Latta LL, Lindsey RW. Posterior atlantoaxial fixation of osteoporotic odontoid fracture: biomechanical analysis of the Magerl versus harms techniques in a cadaver model. Spine J 2024:S1529-9430(24)00190-6. [PMID: 38685273 DOI: 10.1016/j.spinee.2024.04.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Revised: 04/09/2024] [Accepted: 04/22/2024] [Indexed: 05/02/2024]
Abstract
BACKGROUND CONTEXT Odontoid fractures are among the most common cervical spine fractures in the elderly and are associated with increased morbidity and mortality. Clinical evidence suggests improved survival and quality of life after operative intervention compared to nonoperative treatment. PURPOSE This study seeks to examine the stability of an osteoporotic Type II odontoid fracture following posterior atlantoaxial fixation with either the Magerl transarticular fixation technique or the Harms C1 lateral mass screws C2 pedicle screw rod fixation. STUDY DESIGN Biomechanical cadaveric study. METHODS Eighteen cadaveric specimens extending from the cephalus to C7 were used in this study. Reflective marker arrays were attached to C1 and C2 and a single marker on the dens to measure movement of each during loading with C2-C3 and occiput-C1 being allowed to move freely. A biomechanical testing protocol imparted moments in flexion-extension, axial rotation, and lateral bending while a motion capture system recorded the motions of C1, C2, and the dens. The spines were instrumented with either the Harms fixation (n=9) or Magerl fixation (n=9) techniques, and a simulated Type II odontoid fracture was created. Motions of each instrumented spine were recorded for all moments, and then again after the instrumentation was removed to model the injured, non-instrumented state. RESULTS Both Harms and Magerl posterior C1-C2 fixation allowed for C1, C2, and the dens to move as a relative unit. Without fixation the dens motion was coupled with C1. No significant differences were found in X, Y, Z translation motion of the dens, C1 or C2 during neutral zone motions between the Magerl and Harms fixation techniques. There were no significant differences found in Euler angle motion between the two techniques in either flexion-extension, axial rotation, or lateral bending motion. CONCLUSIONS Our findings suggest that both Harms and Magerl fixation can significantly reduce dens motion in Type II odontoid fractures in an osteoporotic cadaveric bone model. CLINICAL SIGNIFICANCE Both Harms and Magerl posterior atlantoaxial fixation techniques allowed for C1, C2, and the dens to move as a relative unit following odontoid fracture, establishing more anatomic stability to the upper cervical spine.
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Affiliation(s)
- Austin Mike-Mayer
- The Department of Orthopedic Surgery and Rehabilitation, The University of Texas Medical Branch, 301 University Blvd., Galveston, TX, USA
| | - Kendrick Lam
- Mount Sinai Medical Center, Max Biedermann Institute for Biomechanics, 4300 Alton Rd., Miami Beach, FL, USA
| | - Randal P Morris
- The Department of Orthopedic Surgery and Rehabilitation, The University of Texas Medical Branch, 301 University Blvd., Galveston, TX, USA.
| | - Abeer Al Barghouthi
- Mount Sinai Medical Center, Max Biedermann Institute for Biomechanics, 4300 Alton Rd., Miami Beach, FL, USA
| | - Francesco Travascio
- Mount Sinai Medical Center, Max Biedermann Institute for Biomechanics, 4300 Alton Rd., Miami Beach, FL, USA; Department of Mechanical and Aerospace Engineering, University of Miami, 1251 Memorial Dr., Coral Gables, FL, USA; Department of Orthopaedics, University of Miami, 1611 NW 12th Ave #303, Miami, FL, USA
| | - Loren L Latta
- Mount Sinai Medical Center, Max Biedermann Institute for Biomechanics, 4300 Alton Rd., Miami Beach, FL, USA; Department of Orthopaedics, University of Miami, 1611 NW 12th Ave #303, Miami, FL, USA
| | - Ronald W Lindsey
- The Department of Orthopedic Surgery and Rehabilitation, The University of Texas Medical Branch, 301 University Blvd., Galveston, TX, USA
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Robbins JB, Stahel SA, Morris RP, Jupiter DC, Chen J, Panchbhavi VK. Radiographic Anatomy of the Lateral Ankle Ligament Complex: A Cadaveric Study. Foot Ankle Int 2024; 45:179-187. [PMID: 37994643 PMCID: PMC10860354 DOI: 10.1177/10711007231213355] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2023]
Abstract
BACKGROUND When lateral ankle sprains progress into chronic lateral ankle instability (CLAI), restoring precise anatomic relationships of the lateral ankle ligament complex (LALC) surgically is complex. This study quantifies the radiographic relationships between the anterior talofibular ligament (ATFL), calcaneofibular ligament (CFL), and prominent osseous landmarks visible under fluoroscopy to assist in perioperative practices for minimally invasive surgery for CLAI. METHODS Ten fresh frozen ankle specimens were dissected to expose the LALC and prepared by threading a radiopaque filament through the ligamentous footprints of the ATFL and CFL. Fluoroscopic images were digitally analyzed to define dimensional characteristics of the ATFL and CFL. Directional measurements of the ligamentous footprints relative to the lateral process of the talus and the apex of the posterior facet of the calcaneus were calculated. RESULTS Dimensional measurements of the ATFL were a mean length of 9.3 mm, fibular footprint of 9.4 mm, and talar footprint of 9.1 mm. Dimensional measurements of the CFL were a mean length of 19.4 mm, fibular footprint of 8.2 mm, and calcaneal footprint of 7.3 mm. From the radiographic apparent tip of the lateral process of the talus, the fibular attachment of the ATFL was found 13.3 mm superior and 4.4 mm posterior, whereas the talar attachment was found 11.5 mm superior and 4.8 mm anterior. From the radiographic apparent posterior apex of the posterior facet of the calcaneus, the fibular attachment of the CFL was found 0.2 mm inferior and 6.8 mm anterior, whereas the calcaneal attachment was found 14.3 mm inferior and 5.9 mm posterior. CONCLUSION The ATFL and CFL were radiographically analyzed using radiopaque filaments to outline the ligamentous footprints in their native locations. These ligaments were also localized with reference to 2 prominent osseous landmarks. These findings may assist in perioperative practices for keyhole incision placement and arthroscopic guidance. Perfect lateral ankle joint imaging with talar domes superimposed is required to be able to do this. CLINICAL RELEVANCE Radiographic evaluation of the ATFL and CFL with reference to prominent osseous landmarks identified under fluoroscopy may assist in perioperative practices for minimally invasive surgery to address CLAI for keyhole incision placement and arthroscopic guidance.
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Affiliation(s)
- Jordan B. Robbins
- John Sealy School of Medicine, The University of Texas Medical Branch, Galveston, TX, USA
| | - Shepheard A. Stahel
- John Sealy School of Medicine, The University of Texas Medical Branch, Galveston, TX, USA
| | - Randal P. Morris
- Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, TX, USA
| | - Daniel C. Jupiter
- Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, TX, USA
- Department of Biostatistics and Data Science, The University of Texas Medical Branch, Galveston, TX, USA
| | - Jie Chen
- Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, TX, USA
| | - Vinod K. Panchbhavi
- Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, TX, USA
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Garay RS, Solitro GF, Lam KC, Morris RP, Albarghouthi A, Lindsey RW, Latta LL, Travascio F. Characterization of regional variation of bone mineral density in the geriatric human cervical spine by quantitative computed tomography. PLoS One 2022; 17:e0271187. [PMID: 35802639 PMCID: PMC9269429 DOI: 10.1371/journal.pone.0271187] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Accepted: 06/24/2022] [Indexed: 11/23/2022] Open
Abstract
Background Odontoid process fractures are among the most common in elderly cervical spines. Their treatment often requires fixation, which may include use of implants anteriorly or posteriorly. Bone density can significantly affect the outcomes of these procedures. Currently, little is known about bone mineral density (BMD) distributions within cervical spine in elderly. This study documented BMD distribution across various anatomical regions of elderly cervical vertebrae. Methods and findings Twenty-three human cadaveric C1-C5 spine segments (14 males and 9 female, 74±9.3 y.o.) were imaged via quantitative CT-scan. Using an established experimental protocol, the three-dimensional shapes of the vertebrae were reconstructed from CT images and partitioned in bone regions (4 regions for C1, 14 regions for C2 and 12 regions for C3-5). The BMD was calculated from the Hounsfield units via calibration phantom. For each vertebral level, effects of gender and anatomical bone region on BMD distribution were investigated via pertinent statistical tools. Data trends suggested that BMD was higher in female vertebrae when compared to male ones. In C1, the highest BMD was found in the posterior portion of the bone. In C2, BMD at the dens was the highest, followed by lamina and spinous process, and the posterior aspect of the vertebral body. In C3-5, lateral masses, lamina, and spinous processes were characterized by the largest values of BMD, followed by the posterior vertebral body. Conclusions The higher BMD values characterizing the posterior aspects of vertebrae suggest that, in the elderly, posterior surgical approaches may offer a better fixation quality.
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Affiliation(s)
- Ryan S. Garay
- Department of Mechanical and Aerospace Engineering, University of Miami, Coral Gables, Florida, United States of America
| | - Giovanni F. Solitro
- Louisiana State University Health-Shreveport, Shreveport, Louisiana, United States of America
| | - Kenrick C. Lam
- University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Randal P. Morris
- University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Abeer Albarghouthi
- Max Biedermann Institute for Biomechanics, Mount Sinai Medical Center, Miami Beach, Florida, United States of America
| | - Ronald W. Lindsey
- University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Loren L. Latta
- Max Biedermann Institute for Biomechanics, Mount Sinai Medical Center, Miami Beach, Florida, United States of America
- Department of Orthopaedic Surgery, University of Miami, Miami, Florida, United States of America
| | - Francesco Travascio
- Department of Mechanical and Aerospace Engineering, University of Miami, Coral Gables, Florida, United States of America
- Max Biedermann Institute for Biomechanics, Mount Sinai Medical Center, Miami Beach, Florida, United States of America
- Department of Orthopaedic Surgery, University of Miami, Miami, Florida, United States of America
- Department of Industrial Engineering, University of Miami, Coral Gables, Florida, United States of America
- * E-mail:
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McChesney GR, Morris RP, Al Barghouthi A, Travascio F, Latta LL, Lindsey RW. Relationship to drill bit diameter and residual fracture resistance of the distal tibia. Clin Biomech (Bristol, Avon) 2022; 97:105686. [PMID: 35679746 DOI: 10.1016/j.clinbiomech.2022.105686] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Revised: 05/17/2022] [Accepted: 05/24/2022] [Indexed: 02/07/2023]
Abstract
BACKGROUND The etiology of bone refractures after screw removal can be attributed to residual drill hole defects. This biomechanical study compared the torsional strength of bones containing various sized cortical drill defects in a tibia model. METHODS Bicortical drill hole defects of 3 mm, 4 mm, and 5 mm diameters were tested in 26 composite tibias versus intact controls without a drill defect. Each tibia was secured in alignment with the rotational axis of a materials testing system and the proximal end rotated internally at a rate of 1 deg./s until mechanical failure. FINDINGS All defect test groups were significantly lower (P < 0.01) in torque-to-failure than the intact group (82.80 ± 3.70 Nm). The 4 mm drill hole group was characterized by a significantly lower (P = 0.021) torque-to-failure (51.00 ± 3.27 Nm) when compared to the 3 mm drill hole (59.00 ± 5.48 Nm) group, but not different than the 5 mm hole group (55.71 ± 5.71 Nm). All bones failed through spiral fractures, bones with defects also exhibited posterior butterfly fragments. INTERPRETATION All the tested drill hole sizes in this study significantly reduced the torque-to-failure from intact by a range of 28.4% to 38.4%, in agreement with previous similar studies. The 5 mm drill hole represented a 22.7% diameter defect, the 4 mm drill hole a 18.2% diameter defect, and the 3 mm drill hole a 13.6% diameter defect. Clinicians should be cognizant of this diminution of long bone strength after a residual bone defect in their creation and management of patient rehabilitation programs.
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Affiliation(s)
- Grant R McChesney
- The Department of Orthopedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, TX, USA
| | - Randal P Morris
- The Department of Orthopedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, TX, USA.
| | - Abeer Al Barghouthi
- Max Biedermann Institute for Biomechanics, Mount Sinai Medical Center, Miami Beach, FL, USA
| | - Francesco Travascio
- Max Biedermann Institute for Biomechanics, Mount Sinai Medical Center, Miami Beach, FL, USA; Department of Mechanical and Aerospace Engineering, Department of Orthopaedic Surgery, Department of Industrial Engineering, University of Miami, Coral Gables, FL, USA
| | - Loren L Latta
- Max Biedermann Institute for Biomechanics, Mount Sinai Medical Center, Miami Beach, FL, USA
| | - Ronald W Lindsey
- The Department of Orthopedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, TX, USA
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Khalid MA, Morris RP, Black N, Maassen NH. Biomechanical Evaluation of Humerus Fracture After Subpectoral Biceps Tenodesis With Interference Screw Versus Unicortical Button. Arthroscopy 2020; 36:1253-1260. [PMID: 31973991 DOI: 10.1016/j.arthro.2019.10.034] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Revised: 10/23/2019] [Accepted: 10/27/2019] [Indexed: 02/02/2023]
Abstract
PURPOSE To compare the torsional failure strength of the humerus after subpectoral biceps tenodesis with an interference screw versus a unicortical button in a human cadaveric model. METHODS Thirteen matched pairs of fresh-frozen human cadaveric upper extremities were randomized to receive either 2.6 × 12 mm unicortical button or 6.25-mm interference screw subpectoral biceps tenodesis. After the procedure, the humeri were loaded into a materials testing machine. The humeri were loaded in external rotation with respect to the elbow at 1.0°/s until failure. Rotation angle to failure, failure torque, energy absorbed, and stiffness were compared by paired t-tests with alpha set at 0.05. RESULTS Humeri that were fixed with unicortical buttons showed statistically significant higher rotation to failure (26.87 ± 5.83 vs 19.04 ± 3.86°, P < .001), failure torque (54.11 ± 22.01 vs 44.95 ± 17.47 Nm, P < .001), and energy absorbed (883.93 ± 582.28 vs 451.40 ± 216.19 Nm-Deg, P = .002) than humeri fixed with interference screws. CONCLUSIONS In a cadaveric biomechanical model, at time 0, the use of a 2.7 × 12-mm unicortical button fixation in biceps tenodesis resulted in higher loads required to fracture the humerus when compared with a 6.25-mm interference screw fixation in a torsion model. CLINICAL RELEVANCE This study demonstrates a significant biomechanical difference with regards to fracture of the humerus, between 2 commonly used fixations methods and implant sizes, interference screw, and unicortical button. The results of this study can aid surgeons in implant selection as well as help to improve patient education prior to surgery.
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Affiliation(s)
- Mohammed A Khalid
- Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, Texas, U.S.A
| | - Randal P Morris
- Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, Texas, U.S.A
| | - Natalie Black
- Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, Texas, U.S.A
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Namm JD, Morris RP, Speck FL, Lindsey RW. The Impact of Eccentric Diaphyseal Plate and Screw Placement on the Risk of Peri-Implant Fracture. J Bone Joint Surg Am 2018; 100:1765-1770. [PMID: 30334887 DOI: 10.2106/jbjs.18.00024] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
BACKGROUND The objective of this study was to determine the impact of the type and orientation of peripheral screw placement in an eccentrically positioned locking plate on the structural integrity of the plate-diaphyseal bone interface. We hypothesized that central placement of the screw at the end of the plate in this setting is more important than screw type (locking versus nonlocking) to limiting the risk of subsequent fracture. METHODS Twenty osteoporotic fourth-generation composite left humeri were divided into 4 groups and plated with stainless-steel 6-hole locking plates and 4.5-mm screws. Group 1 (control group) consisted of a centrally positioned plate with a centrally placed non-locking end screw at the sixth, most-proximal hole. Group 2 consisted of an eccentrically positioned plate with a non-locking proximal end screw placed through the center of the bone. Group 3 consisted of an eccentrically positioned plate with a locking proximal end screw placed perpendicular to the plate and eccentrically across the cortex. Group 4 consisted of an eccentrically positioned plate with a non-locking proximal end screw placed perpendicular to the plate and eccentrically across the cortex. Each group was tested with a single load to failure in torsion at a rate of 1°/second. RESULTS The control group (Group 1) failed at significantly higher peak torque values (51.62 ± 7.35 Nm) than Group 2 (38.98 ± 6.78 Nm; p = 0.006), Group 3 (34.75 ± 1.81 Nm; p < 0.001), and Group 4 (31.55 ± 1.23 Nm; p < 0.001). Failure energy absorbed in Group 1 (2,591.49 ± 819.63 Nm/degree) was significantly higher than Group 3 (1,430.51 ± 449.99 Nm/degree; p = 0.04) and Group 4 (952.49 ± 123.52 Nm/degree; p = 0.004), but not significantly higher than Group 2 (1,847.73 ± 827.35 Nm/degree; p = 0.27). CONCLUSIONS Eccentrically placed plating of humeral shaft fractures significantly increases the risk of peri-implant fracture compared with a centrally placed plate. Directing the proximal-end screw centrally in an eccentrically placed plate may help to mitigate this risk at the proximal end. CLINICAL RELEVANCE When possible, care should be taken to place the plate centrally on the bone to avoid increased risk of peri-implant fracture at the proximal plate-bone interface.
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Affiliation(s)
- Joshua D Namm
- Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, Texas
| | - Randal P Morris
- Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, Texas
| | - Fred L Speck
- Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, Texas
| | - Ronald W Lindsey
- Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, Texas
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Weiss WM, Saucedo RP, Robinson JD, Lo CCJ, Morris RP, Panchbhavi VK. The Effect of Suture Anchor Insertion Angle on Calcaneus Pullout Strength: Challenging the Deadman's Angle. Foot Ankle Spec 2017; 10:411-414. [PMID: 27881831 DOI: 10.1177/1938640016679705] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Refractory cases of Achilles tendinopathy amenable to surgery may include reattachment of the tendon using suture anchors. However, there is paucity of information describing the optimal insertion angle to maximize the tendon footprint and anchor stability in the calcaneus. The purpose of this investigation is to compare the fixation strength of suture anchors inserted at 90° and 45° (the Deadman's angle) relative to the primary compressive trabeculae of the calcaneus. METHODS A total of 12 matched pairs of adult cadaveric calcanei were excised and potted to approximate their alignment in vivo. Each pair was implanted with 5.5-mm bioabsorbable suture anchors placed either perpendicular (90°) or oblique (45°) to the primary compressive trabeculae. A tensile load was applied until failure of anchor fixation. Differences in failure load and stiffness between anchor fixation angles were determined by paired t-tests. RESULTS No significant differences were detected between perpendicular and oblique suture anchor insertion relative to primary compressive trabeculae in terms of load to failure or stiffness. CONCLUSION This investigation suggests that the fixation strength of suture anchors inserted perpendicular to the primary compression trabeculae and at the Deadman's angle are possibly comparable. LEVELS OF EVIDENCE Biomechanical comparison study.
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Affiliation(s)
- William M Weiss
- Department of Orthopedic Surgery and Rehabilitation, Texas Tech University Health Sciences Center Foster School of Medicine, El Paso, Texas (WMW).,Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, Texas (RPS, JDR, RPM, VKP).,Texas A&M Health Science Center College of Medicine-Scott & White, Temple, Texas (C-CJL)
| | - Ramon P Saucedo
- Department of Orthopedic Surgery and Rehabilitation, Texas Tech University Health Sciences Center Foster School of Medicine, El Paso, Texas (WMW).,Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, Texas (RPS, JDR, RPM, VKP).,Texas A&M Health Science Center College of Medicine-Scott & White, Temple, Texas (C-CJL)
| | - John D Robinson
- Department of Orthopedic Surgery and Rehabilitation, Texas Tech University Health Sciences Center Foster School of Medicine, El Paso, Texas (WMW).,Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, Texas (RPS, JDR, RPM, VKP).,Texas A&M Health Science Center College of Medicine-Scott & White, Temple, Texas (C-CJL)
| | - Chung-Chieh Jason Lo
- Department of Orthopedic Surgery and Rehabilitation, Texas Tech University Health Sciences Center Foster School of Medicine, El Paso, Texas (WMW).,Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, Texas (RPS, JDR, RPM, VKP).,Texas A&M Health Science Center College of Medicine-Scott & White, Temple, Texas (C-CJL)
| | - Randal P Morris
- Department of Orthopedic Surgery and Rehabilitation, Texas Tech University Health Sciences Center Foster School of Medicine, El Paso, Texas (WMW).,Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, Texas (RPS, JDR, RPM, VKP).,Texas A&M Health Science Center College of Medicine-Scott & White, Temple, Texas (C-CJL)
| | - Vinod K Panchbhavi
- Department of Orthopedic Surgery and Rehabilitation, Texas Tech University Health Sciences Center Foster School of Medicine, El Paso, Texas (WMW).,Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, Texas (RPS, JDR, RPM, VKP).,Texas A&M Health Science Center College of Medicine-Scott & White, Temple, Texas (C-CJL)
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Speck FL, Morris RP, Lindsey RW. Effect of Plate in Close Proximity to Empty External-Fixation Pin Site on Long-Bone Torsional Strength. Am J Orthop (Belle Mead NJ) 2017; 46:E108-E111. [PMID: 28437504] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Complex tibia fractures are often provisionally stabilized with external fixation prior to definitive fracture fixation. Bicortical defects, such as those left after removal of a fixator pin, can decrease the torsional strength of long bone. Evaluating the effect of subsequent plate fixation in close proximity to a defect on the torsional strength of the tibia is the purpose of this study. Eight groups of 5 fourth-generation left composite tibias were tested to failure in torsion. The experimental plated groups consisted of bicortical defects at 3 cm, 2 cm, and 1 cm distal to the plate end, with 1 plated group without a defect. The control groups consisted of equivalent defects in the same distal longitudinal locations, without plates attached, as well as an unplated group without a defect. There were no statistical differences in torsional stiffness or failure torque between any of the groups. The mode of failure for all specimens with bicortical defects was a spiral fracture that bisected the axis of the defect. Based on the results of this composite tibia study, varying the proximity of a bicortical defect to a plate does not affect the torsional stiffness or torsional failure strength of the bone.
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Affiliation(s)
| | - Randal P Morris
- Department of Orthopaedic Surgery and Rehabilitation, University of Texas Medical Branch, Galveston, TX.
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Casagrande DJ, Morris RP, Carayannopoulos NL, Buford WL. Relationship Between Ulnar Variance, Cortical Bone Density, and Load to Failure in the Distal Radius at the Typical Site of Fracture Initiation. J Hand Surg Am 2016; 41:e461-e468. [PMID: 27707565 DOI: 10.1016/j.jhsa.2016.08.021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Revised: 08/24/2016] [Accepted: 08/28/2016] [Indexed: 02/02/2023]
Abstract
PURPOSE Increased ulnar variance has been shown to lead to diminished load borne by the distal radius. The purpose of this study was to determine the correlations among ulnar variance, bone mineral density, and load to failure at the distal radius. METHODS Posteroanterior radiographs and computed tomographic scans were taken of 12 cadaveric forearms in neutral rotation. Ulnar variance was measured for each wrist by the method of perpendiculars. Measurements of cortical, trabecular, and combined bone density were made at the distal radius. We performed linear regression analysis and correlation analysis to determine the relationship between bone densities and ulnar variance measurements. Next, we loaded the 12 cadaveric radii to failure under axial compression. Linear regression analysis and correlation analysis were then performed to determine the relationship between load to failure and both ulnar variance and cortical density. RESULTS Increased ulnar variance was significantly correlated with decreased cortical bone density at the distal radius and both were correlated with decreased load to failure. We found no correlation between ulnar variance and trabecular density or combined trabecular and cortical bone density at the distal radius. CONCLUSIONS Our study found that increased ulnar variance and decreased cortical bone mineral density correlates with decreased load to failure under axial compression. CLINICAL RELEVANCE Ulnar variance is linked to both bone quality and load to failure at the distal radius.
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Affiliation(s)
- Danielle J Casagrande
- Department of Orthopaedic Surgery and Rehabilitation, University of Texas Medical Branch, Galveston, TX.
| | - Randal P Morris
- Department of Orthopaedic Surgery and Rehabilitation, University of Texas Medical Branch, Galveston, TX
| | | | - William L Buford
- Department of Orthopaedic Surgery and Rehabilitation, University of Texas Medical Branch, Galveston, TX
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Wilson WK, Morris RP, Ward AJ, Carayannopoulos NL, Panchbhavi VK. Torsional Failure of Carbon Fiber Composite Plates Versus Stainless Steel Plates for Comminuted Distal Fibula Fractures. Foot Ankle Int 2016; 37:548-53. [PMID: 26755535 DOI: 10.1177/1071100715625291] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
BACKGROUND Carbon fiber composite implants are gaining popularity in orthopedics, but with few independent studies of their failure characteristics under supra-physiologic loads. The objective of this cadaveric study was to compare torsional failure properties of bridge plating a comminuted distal fibula fracture with carbon fiber polyetheretherketone (PEEK) composite and stainless steel one-third tubular plates. METHODS Comminuted fractures were simulated in 12 matched pairs of fresh-frozen human fibulas with 2-mm osteotomies located 3 cm proximal to the tibiotalar joint. Each fibula pair was randomized for fixation and implanted with carbon fiber and stainless steel 5-hole one-third tubular plates. The constructs were loaded in external rotation at a rate of 1-degree/sec until failure with a materials testing system. Torsional stiffness and mode of failure, as well as displacement, torque, and energy absorption for the first instance of failure and peak failure, were determined. Statistical analysis was performed with paired t tests and chi-square. RESULTS There were no significant differences among the 12 pairs for torsional stiffness, first failure torque, peak failure displacement, peak failure torque, or peak failure energy. Stainless steel plates exhibited significantly higher displacement (P < .001) and energy absorption (P = .001) at the first indication of failure than the carbon fiber plates. Stainless steel plates permanently deformed significantly more often than the carbon fiber plates (P = .035). Carbon fiber plates exhibited no plastic deformation with delamination of the composite, and brittle catastrophic failure in 1 specimen. CONCLUSIONS In a comminuted human fibula fracture fixation model, carbon fiber implants exhibited multiple pre-peak failures at significantly lower angles than the first failure for the stainless steel implants, with some delamination of composite layers and brittle catastrophic failure rather than plastic deformation. CLINICAL RELEVANCE The torsional failure properties of carbon fiber composite one-third tubular plates determined in this independent study provide novel in vitro data for this alternative implant material.
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Affiliation(s)
- William K Wilson
- Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, TX, USA
| | - Randal P Morris
- Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, TX, USA
| | - Adam J Ward
- Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, TX, USA
| | - Nikoletta L Carayannopoulos
- Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, TX, USA
| | - Vinod K Panchbhavi
- Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, TX, USA
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Alexander J, Morris RP, Kaimrajh D, Milne E, Latta L, Flink A, Lindsey RW. Biomechanical evaluation of periprosthetic refractures following distal femur locking plate fixation. Injury 2015; 46:2368-73. [PMID: 26553428 DOI: 10.1016/j.injury.2015.09.033] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Revised: 08/20/2015] [Accepted: 09/29/2015] [Indexed: 02/02/2023]
Abstract
INTRODUCTION Distal femur fractures proximal to total knee femoral component constitutes the most prevalent type of periprosthetic fracture, and plate fixation treatment is associated with a 7.7% incidence of refracture proximal to the plate. The primary objective of this study was to compare proximal fixation techniques of a periprosthetic distal femur fracture plate in an osteoporotic bone model. The secondary objective was to determine the subsequent periprosthetic plate fracture pattern and/or complexity associated with each proximal plate fixation configuration. MATERIALS AND METHODS A segmental defect was created in 21 synthetic osteoporotic adult femurs 6 cm proximal to the distal femur and all specimens were stabilised with a 246 mm locking femur plate. Fixation in the most proximal hole was varied by use of either a cerclage cable, unicortical locking screw, or a bicortical locking screw. Specimens were tested to failure in simultaneous eccentric compression and torsion. RESULTS Proximal cerclage fixation demonstrated higher mean maximum axial force at failure (4142.67±178.71 N, p<0.001), stiffness (443.8±61.64 N/mm), and maximum torque (20.9±0.93 N m, p<0.001). Unicortical and bicortical screw refractures occurred at the screw, cerclage wire refractures occurred at the first proximal screw distal to the cerclage. CONCLUSIONS In periprosthetic distal femur fracture locking plate fixation, proximal hole stabilization with a cerclage wire tolerates significantly higher failure forces while distributing forces distal to the area within the plate fixation. Cerclage wiring may be an option in distal femur periprosthetic fractures to alleviate stress risers in vulnerable bone.
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Affiliation(s)
- Jamie Alexander
- The University of Texas Medical Branch, 301 University Boulevard, Route 0165, Galveston, TX 77555, United States.
| | - Randal P Morris
- The University of Texas Medical Branch, 301 University Boulevard, Route 0165, Galveston, TX 77555, United States.
| | - David Kaimrajh
- Max Biedermann Institute for Biomechanics, Mount Sinai Medical Center, Department of Research, 4300 Alton Road, Miami Beach, FL 33140, United States.
| | - Edward Milne
- Max Biedermann Institute for Biomechanics, Mount Sinai Medical Center, Department of Research, 4300 Alton Road, Miami Beach, FL 33140, United States.
| | - Loren Latta
- Max Biedermann Institute for Biomechanics, Mount Sinai Medical Center, Department of Research, 4300 Alton Road, Miami Beach, FL 33140, United States.
| | - Adam Flink
- The University of Texas Medical Branch, 301 University Boulevard, Route 0165, Galveston, TX 77555, United States.
| | - Ronald W Lindsey
- The University of Texas Medical Branch, 301 University Boulevard, Route 0165, Galveston, TX 77555, United States.
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LeBa TB, Carmichael KD, Patton AG, Morris RP, Swischuk LE. Ultrasound for Infants at Risk for Developmental Dysplasia of the Hip. Orthopedics 2015; 38:e722-6. [PMID: 26270760 DOI: 10.3928/01477447-20150804-61] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Accepted: 11/14/2014] [Indexed: 02/03/2023]
Abstract
The best screening method for developmental dysplasia of the hip is controversial. Ultrasonography is sensitive, but cost-effectiveness may limit its use. This study assessed whether ultrasound screening would increase in effectiveness if targeted toward infants with established risk factors for developmental dysplasia of the hip and normal findings on physical examination. All ultrasound scans performed at the authors' institution from January 2007 through January 2011 to screen for developmental dysplasia of the hip were reviewed. Infants with risk factors for developmental dysplasia of the hip and normal findings on physical examination by orthopedic faculty or a pediatrician were selected. Of the 530 cases that were reviewed, 217 had risk factors for developmental dysplasia of the hip and normal findings on physical examination. Mean age of the 217 selected patients was 6.9 weeks. Of the patients, 83% were female, 77% had breech presentation, 30% were firstborn children, 13% had intrauterine packaging abnormalities, and 3% had a family history of developmental dysplasia of the hip. Of the 217 infants, 44 had 1 risk factor, 121 had 2 risk factors, 46 had 3 risk factors, and 6 had 4 risk factors. Dynamic ultrasound evaluation showed instability in 17 patients, for a 7.8% incidence of developmental dysplasia of the hip. All 17 patients were treated with a Pavlik harness. The results suggested that selective ultrasound screening may be effective in infants with risk factors and normal findings on physical examination. Selective ultrasound screening changed treatment management in almost 8% of patients and clinical follow-up in 6.5%. Analysis of the cost-effectiveness of screening is needed.
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Abstract
UNLABELLED For Lisfranc injuries, screw fixation of the medial and middle columns is currently the standard of treatment. The purpose of this study was to biomechanically evaluate the use of allograft for a severed Lisfranc ligament compared to standard screw fixation and the intact condition. Six pairs of fresh-frozen cadaveric lower extremities were prepared with reflective marker arrays and cyclically loaded to simulate partial weight bearing under 4 sequential testing conditions: (1) intact ligament, (2) disrupted ligament, (3) tendon allograft reconstructed ligament, and (4) rigid screw fixation. The relative displacement between the medial cuneiform and the second metatarsal was assessed via motion analysis. A mixed model analysis of variance was used to determine the significance (α = .05) of displacement differences. Mean displacements and 95% confidence intervals for each condition were as follows: (1) intact 9.1 (7.1-11.2) mm, (2) cut ligament 9.4 (7.4-11.5) mm, (3) allograft fixation 8.8 (6.8-10.9) mm, and (4) screw fixation 8.2 (6.2-10.3) mm. There were no significant differences among the specimens according to condition. Allograft fixation provided adequate strength and stability and did not differ significantly compared to intact or screw fixation. LEVELS OF EVIDENCE Level V: Bench testing.
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Abstract
BACKGROUND The purpose of this prospective study was to determine whether gravity versus manual external rotation stress testing effectively detects widening of the medial clear space in isolated ankle fractures when compared with the uninjured contralateral side. METHODS Manual external rotation stress and gravity stress tests were performed on injured and uninjured ankles of ankle fracture patients in a clinic setting. Medial clear space measurements were recorded and differences between gravity and manual stress views were determined. RESULTS Twenty consecutive patients with ankle injury were enrolled in the study. When compared with the uninjured side, gravity stress views showed a statistically significant (P = .017) increase in medial clear space widening (1.85 ± 1.07 mm) compared with manual stress view widening (1.35 ± 1.04 mm). CONCLUSIONS This study suggests that gravity stress views are as effective as manual external rotation stress views in detecting medial clear space widening in isolated fibular fractures. LEVEL OF EVIDENCE Diagnostic, Level II: Prospective, comparative trial.
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Affiliation(s)
- Thu-Ba LeBa
- Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, Texas
| | - Zbigniew Gugala
- Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, Texas
| | - Randal P Morris
- Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, Texas
| | - Vinod K Panchbhavi
- Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, Texas
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Abstract
BACKGROUND The purpose of this prospective study was to determine whether gravity versus manual external rotation stress testing effectively detects widening of the medial clear space in isolated ankle fractures when compared with the uninjured contralateral side. METHODS Manual external rotation stress and gravity stress tests were performed on injured and uninjured ankles of ankle fracture patients in a clinic setting. Medial clear space measurements were recorded and differences between gravity and manual stress views were determined. RESULTS Twenty consecutive patients with ankle injury were enrolled in the study. When compared with the uninjured side, gravity stress views showed a statistically significant (P = .017) increase in medial clear space widening (1.85 ± 1.07 mm) compared with manual stress view widening (1.35 ± 1.04 mm). CONCLUSIONS This study suggests that gravity stress views are as effective as manual external rotation stress views in detecting medial clear space widening in isolated fibular fractures. LEVEL OF EVIDENCE Diagnostic, Level II: Prospective, comparative trial.
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Affiliation(s)
- Thu-Ba LeBa
- Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, Texas
| | - Zbigniew Gugala
- Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, Texas
| | - Randal P Morris
- Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, Texas
| | - Vinod K Panchbhavi
- Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, Texas
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Chronister JE, Morris RP, Andersen CR, Buford WL, Bennett JM, Mehlhoff TL. A biomechanical comparison of 2 hybrid techniques for elbow ulnar collateral ligament reconstruction. J Hand Surg Am 2014; 39:2033-40. [PMID: 25194771 DOI: 10.1016/j.jhsa.2014.07.040] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Revised: 07/17/2014] [Accepted: 07/21/2014] [Indexed: 02/02/2023]
Abstract
PURPOSE To compare the valgus laxity and fixation strength of 2 hybrid techniques for elbow ulnar collateral ligament reconstructions. METHODS Reflective markers were placed near the ligament attachments of the ulnar collateral ligament on the humerus and ulna of 12 fresh-frozen cadaveric upper extremities for tracking displacement with 4 motion analysis cameras. Valgus laxity testing was performed on the intact, disrupted ligament, and reconstructed elbows by applying a 3.0 Nm moment across the joint at 15° intervals throughout elbow motion from 0° to 120°. Two hybrid techniques for ulnar collateral ligament reconstruction were performed: a proximal docking method and a single-point distal fixation method. Failure testing was performed with the elbow at 90° by applying a cyclic valgus load 12 cm distal to the joint that we increased in 10-N intervals. RESULTS Valgus laxity testing revealed no difference in ligament displacements between the 2 techniques over the entire range of elbow motion. Ligament displacement for the proximal docking hybrid technique was significantly higher than the intact at 0° and 15° of elbow flexion. Failure testing revealed no differences in ligament displacements or failure load between the 2 techniques. CONCLUSIONS Both the proximal docking and the single-point fixation hybrid reconstructions provided sufficient joint stability and strength compared to the intact elbows, with the exception of the proximal docking method at low flexion angles. The reconstructions were not significantly different with respect to valgus laxity or graft fixation displacement at failure. CLINICAL RELEVANCE The proximal docking and single-point fixation hybrids tested here are both viable surgical options with sufficient strength and valgus laxity mechanics, warranting clinical evaluation.
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Affiliation(s)
- Justin E Chronister
- Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, TX; Fondren Orthopaedic Group, LLP, Houston, TX
| | - Randal P Morris
- Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, TX; Fondren Orthopaedic Group, LLP, Houston, TX.
| | - Clark R Andersen
- Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, TX; Fondren Orthopaedic Group, LLP, Houston, TX
| | - William L Buford
- Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, TX; Fondren Orthopaedic Group, LLP, Houston, TX
| | - J Michael Bennett
- Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, TX; Fondren Orthopaedic Group, LLP, Houston, TX
| | - Thomas L Mehlhoff
- Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, TX; Fondren Orthopaedic Group, LLP, Houston, TX
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Abstract
BACKGROUND Knotless barbed sutures are seeing more common use in wound closures and small tendon repairs. The purpose of this study was to evaluate the strength and resistance to gap formation of these sutures in larger tendons, such as the Achilles, compared with conventional repair. METHODS Six matched pairs of fresh-frozen human cadaver Achilles tendons were transected to simulate a rupture. Six tendons were repaired using a double Bunnell over-the-top technique with Fiberwire, and the matched pairs were repaired using a double Bunnell knotless technique with barbed suture. The tendons were tested to failure and stiffness, peak failure load, percentage elongation, load at initial gap and load at 5-mm gap (clinical failure) were compared. RESULTS The mean peak failure load for the Fiberwire group (459 N) was significantly higher (P = .029) compared with the barbed suture group (184 N). Percentage elongation at peak load was significantly lower in the barbed suture group (P = .014), as was percentage elongation at initial gapping (P = .007) and percent elongation at 5 mm of gapping (P = .004). CONCLUSION While the knotless barbed suture is attractive for its design and resistance to gap formation, low failure loads compared with conventional suture are concerning for large tendon repairs. LEVELS OF EVIDENCE Therapeutic, Level IV: Bench testing.
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Affiliation(s)
- Brian N Kanz
- CHRISTUS Santa Rosa Medical Group, Westover Hills Orthopaedics, San Antonio, Texas (BNK)
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Lucas KJ, Morris RP, Buford WL, Panchbhavi VK. Biomechanical comparison of first metatarsophalangeal joint arthrodeses using triple-threaded headless screws versus partially threaded lag screws. Foot Ankle Surg 2014; 20:144-8. [PMID: 24796836 DOI: 10.1016/j.fas.2014.02.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/16/2013] [Revised: 02/21/2014] [Accepted: 02/26/2014] [Indexed: 02/04/2023]
Abstract
BACKGROUND Triple-threaded, cannulated headless screws of varying thread diameters and pitch are designed to maintain thread length across the arthrodesis plane, provide joint compression, and reduce countersinking. This study tested the biomechanical fixation strength of conventional partially threaded lag screws compared to triple-threaded headless screws in first metatarsophalangeal joint arthrodesis. METHODS First metatarsophalangeal joint arthrodesis using a crossed screw technique was performed on 11 paired, preserved cadaver first rays with two 4.0-mm triple-threaded, cannulated headless screws or two 4.0-mm partially threaded, cannulated lag screws. The constructs were tested to failure through dorsally directed cantilever bending. RESULTS The triple-threaded, cannulated headless screws displayed significantly greater bending stiffness (p=0.017) and failure load (p=0.040) during load-to-failure testing compared to the partially threaded, cannulated lag screws. CONCLUSIONS Triple-threaded, cannulated headless screws may be a viable alternative to partially threaded lag screws in first metatarsophalangeal arthrodesis.
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Affiliation(s)
- Kurt J Lucas
- Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555-0165, United States
| | - Randal P Morris
- Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555-0165, United States
| | - William L Buford
- Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555-0165, United States
| | - Vinod K Panchbhavi
- Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555-0165, United States.
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Capelle JH, Couch CG, Wells KM, Morris RP, Buford WL, Merriman DJ, Panchbhavi VK. Fixation strength of anteriorly inserted headless screws for talar neck fractures. Foot Ankle Int 2013; 34:1012-6. [PMID: 23456083 DOI: 10.1177/1071100713479586] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
BACKGROUND For noncomminuted talar neck fractures, traditional fixation is with small fragment screws or cannulated screws. Newer screw systems on the market allow placement of cannulated headless screws, which provide compression by virtue of a variable-pitch thread. The headless construct has an inherent advantage, particularly for the talus, when the screws must be countersunk to prevent wear of the joint articular surfaces. This study tested the biomechanical fixation strength of cannulated headless variable-pitch screws compared with conventional cannulated screws, both placed in an anterior to posterior direction. METHODS A reproducible talar neck fracture was created in nine paired, preserved, cadaver talar necks using a materials testing machine. Talar head fixation was then performed with two cannulated headless variable-pitch 4/5 screws or two 4.0-mm conventional cannulated screws. The specimens were tested to failure and the fixations were normalized to their intact pairs and compared. RESULTS The headless variable-pitch screw fixation had significantly lower failure displacement than the conventional screw fixation. No significant differences were found between the two fixations for failure stiffness, load at failure or energy absorbed. CONCLUSIONS Cannulated headless variable-pitch screws significantly improved failure displacement when compared to conventional cannulated screws in a cadaveric model, and may be a viable option for talus fracture fixation. CLINICAL RELEVANCE Headless, fully threaded, variable-pitch screws have inherent advantages over conventional screws in that they may be less damaging to the articular surface and can compress the fracture for improved reduction. This study demonstrates these screws are also biomechanically similar to conventional screws.
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Conner CS, Perez BA, Morris RP, Buckner JW, Buford WL, Ivey FM. Three femoral fixation devices for anterior cruciate ligament reconstruction: comparison of fixation on the lateral cortex versus the anterior cortex. Arthroscopy 2010; 26:796-807. [PMID: 20511038 DOI: 10.1016/j.arthro.2009.10.015] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/23/2009] [Revised: 10/30/2009] [Accepted: 10/30/2009] [Indexed: 02/02/2023]
Abstract
PURPOSE To evaluate the biomechanical properties of 3 anterior cruciate ligament (ACL) reconstruction femoral fixation devices in a porcine model with implantation on both the lateral femoral cortex and the anterior femoral cortex. METHODS ACL reconstructions with an 8-mm porcine tendon graft were performed on 48 porcine femurs with the EndoButton CL (Smith & Nephew, Andover, MA), ToggleLoc with ZipLoop technology (Biomet Sports Medicine, Warsaw, IN), or EZLoc (Biomet Sports Medicine). In 8 specimens for each implant, the femoral tunnel was drilled from the 10:30 surgical position out the lateral cortex. In another 8 specimens for each implant, the tunnel was drilled from the 10:30 position to a standardized anterior femoral surface. Cyclic testing was performed on an MTS testing machine (MTS, Eden Prairie, MN) from 50 N to 450 N for 2,000 cycles, followed by load-to-failure testing in specimens that survived. The cortical thickness and location of the implant exit were recorded. RESULTS In the lateral femur group, 0 of the EZLoc devices, 2 of the ToggleLoc devices, and 3 of the EndoButtons completed cyclic testing. In the anterior femur group, 1 of the EZLoc devices, 5 of the ToggleLoc devices, and 5 of the EndoButtons completed cyclic testing (P = .012). In the anterior femur group, the ToggleLoc exhibited higher 2,000-cycle elongation (5.46 +/- 1 mm) than the EndoButton (3.55 +/- 0.6 mm) (P = .005). The EndoButton showed a higher first failure load (1,190.9 +/- 150.0 N) than the ToggleLoc (912.6 +/- 82.4 N) (P = .007). The anterior cortex (1.4 mm) was thinner than the lateral cortex (1.7 mm) (P = .0002). CONCLUSIONS The EndoButton provided the strongest ACL femoral fixation with significantly less graft-implant elongation and significantly higher failure loads. It was also shown in a porcine model that implants on the anterior cortical surface perform better than those on the lateral surface. Increased cortical thickness, in the range tested, was not associated with improved implant performance in the porcine model. CLINICAL RELEVANCE The EndoButton provided the best ACL femoral fixation of the devices tested.
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Affiliation(s)
- Chad S Conner
- Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, 301 University Blvd., Galveston, TX 77555-0165, U.S.A.
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Bartek IL, Rutherford R, Gruppo V, Morton RA, Morris RP, Klein MR, Visconti KC, Ryan GJ, Schoolnik GK, Lenaerts A, Voskuil MI. The DosR regulon of M. tuberculosis and antibacterial tolerance. Tuberculosis (Edinb) 2009; 89:310-6. [PMID: 19577518 DOI: 10.1016/j.tube.2009.06.001] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2008] [Revised: 05/22/2009] [Accepted: 06/01/2009] [Indexed: 10/20/2022]
Abstract
Adaptation of Mycobacterium tuberculosis to an anaerobic dormant state that is tolerant to several antibacterials is mediated largely by a set of highly expressed genes controlled by DosR. A DosR mutant was constructed to investigate whether the DosR regulon is involved in antibacterial tolerance. We demonstrate that induction of the regulon is not required for drug tolerance either in vivo during a mouse infection or in vitro during anaerobic dormancy. Thus, drug tolerance observed in these models is due to other mechanisms such as the bacilli simply being in a non-replicating or low metabolic state. Our data also demonstrate that the DosR regulon is not essential for virulence during chronic murine infection. However, decreased lung pathology was observed in the DosR mutant. We also show that the DosR regulon genes are more highly conserved in environmental mycobacteria, than in pathogenic mycobacteria lacking a latent phase or environmental reservoir. It is possible that the DosR regulon could contribute to drug tolerance in human infections; however, it is not the only mechanism and not the primary mechanism for tolerance during a mouse infection. These data suggest that the regulon evolved not for pathogenesis or drug tolerance but for adaptation to anaerobic conditions in the environment and has been adapted by M. tuberculosis for survival during latent infection.
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Affiliation(s)
- I L Bartek
- Department of Microbiology, School of Medicine, University of Colorado Denver, P18-9115, 12800 East 19th Avenue, PO Box 6511, Aurora, CO 80045, USA
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Alemohammad AM, Yazaki N, Morris RP, Buford WL, Viegas SF. Thumb interphalangeal joint extension by the extensor pollicis brevis: association with a subcompartment and de Quervain's disease. J Hand Surg Am 2009; 34:719-23. [PMID: 19345877 DOI: 10.1016/j.jhsa.2008.12.015] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2008] [Revised: 11/18/2008] [Accepted: 12/10/2008] [Indexed: 02/02/2023]
Abstract
PURPOSE First dorsal compartment anatomy was analyzed for the presence of a separate compartment for the extensor pollicis brevis (EPB) tendon and the ability of the EPB to extend the thumb interphalangeal (IP) joint in order to determine if these characteristics were associated with each other, and with de Quervain's disease. METHODS Two groups were studied: (1) 90 cadaver wrists, 28 to 89 years, 38 male and 52 female specimens; and (2) 143 patient wrists, 21 to 82 years, 18 men and 125 women, in which the first dorsal compartment was released for treatment of de Quervain's disease. RESULTS The EPB was in a separate compartment in 102 of 143 of the surgical group and 18 of 90 of the cadaver group. The EPB was able to extend the IP joint in 56 of 143 of the surgical group and 19 of 90 of the cadaver group. When the EPB was able to extend the IP joint, it was in a subcompartment in 49 of 56 of the surgical group and 9 of 19 of the cadaver group. When the EPB was able to produce IP extension in the cadaver group, it was inserted on the distal phalanx or the extensor hood. CONCLUSIONS In a substantial number of people undergoing surgery for de Quervain's disease and in cadavers, the EPB can extend the thumb IP joint. When it does, particularly in patients with de Quervain's disease, it is likely to reside in a subcompartment of the first dorsal compartment. The incidences of a subcompartment for the EPB and the ability of the EPB to extend the thumb IP joint were higher in the de Quervain's patient population than in the cadaver group.
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Conner CS, Morris RP, Vallurupalli S, Buford WL, Ivey FM. Tensioning of anterior cruciate ligament hamstring grafts: comparing equal tension versus equal stress. Arthroscopy 2008; 24:1323-9. [PMID: 19038701 DOI: 10.1016/j.arthro.2008.07.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/25/2008] [Revised: 05/20/2008] [Accepted: 07/05/2008] [Indexed: 02/02/2023]
Abstract
PURPOSE A biomechanical study was undertaken to determine whether equal-stress or equal-tension tensioning of anterior cruciate ligament 4-stranded semitendinosus and gracilis grafts provides a stronger graft construct when testing to ultimate failure. METHODS Eighteen fresh-frozen cadaveric semitendinosus and gracilis tendons were each positioned over a cylinder rod/cryo-clamp connected to an MTS machine (MTS Systems, Eden Prairie, MN) by another cryo-clamp. In the equal-tension group the 4 strands were equally tensioned by weights. In the equal-stress group a tensioning device applied equal stress based on the cross-sectional areas of the tendons. The tendons were preconditioned with 10 cycles and then tested to failure. Graft creep during the preconditioning cycle was determined by MTS measurement of the change in clamp distance. RESULTS The maximum loads of 4-stranded semitendinosus and gracilis grafts tensioned by equal stress were found to be similar to those of the grafts tensioned by equal tension (2,803 +/- 431 N and 2,772 +/- 461 N, respectively). The loads at first failure were 2,640 +/- 468 N and 2,452 +/- 461 N, respectively (P = .17). The preconditioning cycles showed that the equal-stress group resisted graft creep significantly better (P = .0003). CONCLUSIONS The strength of the 4-stranded hamstring graft when equally tensioned or equally stressed was equivalent when tested to failure. After 10 preconditioning cycles, equal stress resisted graft creep significantly better. Equal-stress tensioning offers an alternative tensioning method for 4-stranded hamstring grafts. CLINICAL RELEVANCE Equal-stress tensioning offers an alternative tensioning method for 4-stranded hamstring grafts.
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Affiliation(s)
- Chad S Conner
- Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, TX 77555-0165, USA.
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Yazaki N, Burns ST, Morris RP, Andersen CR, Patterson RM, Viegas SF. Variations of capitate morphology in the wrist. J Hand Surg Am 2008; 33:660-6. [PMID: 18590848 DOI: 10.1016/j.jhsa.2008.02.002] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/11/2007] [Revised: 02/01/2008] [Accepted: 02/04/2008] [Indexed: 02/02/2023]
Abstract
PURPOSE This anatomical study details and categorizes variations in capitate morphology and associated structures in the human cadaveric wrist. METHODS We dissected 107 cadaveric wrists. Capitate morphology, the presence of capitate and hamate ridges, the lunate types, and the width of the medial hamate facet of type II lunates and 4th carpometacarpal joint types were recorded. RESULTS Three types of capitate were identified. The flat type (69/107, or 65%) was characterized by a horizontally oriented (radio-ulnar) lunate-capitate articulation and a longitudinally oriented (proximal-distal) scaphoid-capitate articulation. The flat type was associated with type I lunates or type II lunates with a smaller facet. The spherical type (23/107, or 22%) was associated with a concave articulation formed by the scaphoid and lunate articulations, with an indistinct border between the scaphoid and lunate facets. The width of the medial hamate facet of type II lunates in wrists with a spherical-type capitate was <or=4 mm. The V-shaped type (15/107, or 14%) was characterized by separate lunate and scaphoid facets that converge, forming a V-shape. All the V-shaped capitates had a type II lunate with a large facet. CONCLUSIONS A relationship was found between the 3 capitate types and both the lunate types and the width of the medial hamate facet of the type II lunates. Further study is warranted to determine if these differences in capitate morphology influence the development or progression of various wrist pathologic conditions, such as Kienböck's disease and post-traumatic arthritis associated with scapholunate dissociation and scaphoid nonunion, and the outcome of certain surgical procedures, such as a proximal row carpectomy.
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Affiliation(s)
- Naoya Yazaki
- Department of Hand Surgery, Nagoya University Graduate School of Medicine, Nagoya, Aichi, Japan
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Koh S, Morris RP, Andersen CL, Jones EA, Viegas SF. Ultrasonographic examination of the synovial fold of the radiohumeral joint. J Shoulder Elbow Surg 2007; 16:609-15. [PMID: 17507252 DOI: 10.1016/j.jse.2006.10.019] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2005] [Revised: 06/14/2006] [Accepted: 10/28/2006] [Indexed: 02/01/2023]
Abstract
This report describes the anatomy of the synovial fold of the radiohumeral joint and assesses its visibility by ultrasonography. Forty-nine fresh cadaver radiohumeral joints were examined by ultrasonography before and after intraarticular saline injection and then dissected. Digital photos were taken before and after the joint capsule was excised. The relative coverage of the radial head by the fold was calculated. Synovial folds were observed in all specimens. Forty-three had anterior and posterior lobes. The synovial fold covered an average of 28% of the radiocapitellar joint surface of the radial head. The sensitivity of the ultrasonography was 81%, 46%, and 85% from the anterior, lateral, and posterior aspects of the radiohumeral joint, respectively. Intraarticular saline injection improved the sensitivity to 96%, 67%, and 94%, respectively. The synovial fold is a consistent anatomic structure, and ultrasonography can be a useful preoperative diagnostic tool.
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Affiliation(s)
- Shukuki Koh
- The Department of Hand Surgery, Nagoya University School of Medicine, Nagoya, Japan
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Battle J, Carmichael KD, Morris RP. Biomechanical comparison of flexible intramedullary nailing versus crossed Kirschner wire fixation in a canine model of pediatric forearm fractures. J Pediatr Orthop B 2006; 15:370-5. [PMID: 16891966 DOI: 10.1097/01202412-200609000-00012] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Abstract
This study compares the biomechanical properties of crossed Kirschner wires with those of flexible intramedullary nails in a canine model. The Kirschner wire groups had greater anteroposterior, lateral, and torsional stiffness and force to failure rates in most of the bones tested. Bones fixated with flexible intramedullary nails could bend and recoil during failure testing. The bones fixated with Kirschner wires failed at smaller levels of displacement and frequently had hardware cut-out during failure testing. Flexible intramedullary nails have more recoil and do not induce new fracture lines, which may explain their clinical superiority to Kirschner wires despite providing less rigid fixation.
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Affiliation(s)
- Jacob Battle
- Department of Orthopaedic Surgery and Rehabilitation, The University of Texas Medical Branch, Galveston, Texas 77555-0165, USA
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Iwamoto A, Morris RP, Andersen C, Patterson RM, Viegas SF. An anatomic and biomechanic study of the wrist extensor retinaculum septa and tendon compartments. J Hand Surg Am 2006; 31:896-903. [PMID: 16843147 DOI: 10.1016/j.jhsa.2006.02.026] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/22/2005] [Revised: 02/26/2006] [Accepted: 02/27/2006] [Indexed: 02/02/2023]
Abstract
PURPOSE The anatomy of the extensor retinaculum of the wrist has been described previously; the purpose of this study was to describe the specific anatomy of the septal attachments on the radius and to investigate the mechanical strength of each septal attachment on the radius and each of the 6 compartments of the extensor retinaculum. METHODS Thirty-four wrists from 24 fresh-frozen and 10 embalmed cadavers were used. First, anatomic measurements of the individual extensor retinaculum septums were performed with calipers and a 3-dimensional digitizer. Next each extensor retinaculum septum was excised as a bone-retinaculum-bone autograft and was tested in tension to failure with a materials testing machine. Finally the 6 extensor retinaculum compartments were tested to failure. RESULTS Septum 1/2 had the largest radial surface area and septum 3/4 had the smallest. Septum 1/2 also was found to have the highest failure strength at 51.3 +/- 15.3 N. In compartment testing, compartments 1 and 2 had the highest overall resistance to failure and compartment 5 had the lowest. Compartment 6, which was thought to be the weakest because of clinically observed subluxation of the extensor carpi ulnaris tendon, had stronger failure data than expected. CONCLUSIONS This study offers detailed analysis of the extensor retinaculum compartments and 3-dimensional anatomy of the septal attachments. Clinically this study lends insight to the strength of bone-retinaculum-bone autografts and the etiology of extensor carpi ulnaris subluxation.
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Affiliation(s)
- Akira Iwamoto
- Department of Orthopaedic Surgery, Dokkyo University School of Medicine, Tochigi, Japan
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Koh S, Morris RP, Patterson RM, Kearney JP, Buford WL, Viegas SF. Volar fixation for dorsally angulated extra-articular fractures of the distal radius: a biomechanical study. J Hand Surg Am 2006; 31:771-9. [PMID: 16713841 DOI: 10.1016/j.jhsa.2006.02.015] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/21/2005] [Revised: 02/09/2006] [Accepted: 02/09/2006] [Indexed: 02/02/2023]
Abstract
PURPOSE To compare the biomechanical properties of 10 volar plate-fixation designs in 2 fracture models (dorsal wedge osteotomy, segmental resection osteotomy models). METHODS Forty-eight radiuses were used in this study including 8 pairs. In 40 specimens a 15-mm dorsally based wedge osteotomy was performed and the volar cortex was fractured manually. They were arranged into 10 fixation groups with 5 different fixation designs (test 1). In the contralateral specimens of 8 paired radiuses a 10-mm segment of bone was excised (test 2). Four of the 10 fixation systems were chosen for these specimens. Cadaver hands and the proximal radiuses were potted in polymethylmethacrylate and tested with a servohydraulic materials testing machine with 300 N of axial compression load at 1 N/s initially and after each 1,000 cycles up to 5,000 cycles. After cyclic loading the specimens were loaded to failure in axial compression at 2 mm/min. The stiffness, failure peak load, and failure mode of each specimen were recorded. RESULTS In test 1 in the wedge osteotomy specimens the T plate was the stiffest and the Synthes titanium plate was the least stiff; however, all specimens completed the 5,000 cycles of loading with no failures. There was no significant difference between the 10 fixation groups in failure peak load and only 7 of 40 failed at the distal portion of the hardware in the final load to failure testing. In test 2 the resection osteotomy specimens were less stiff and failed at a lower failure peak load compared with the wedge osteotomy specimens. Failure at the distal portion of the fixation system was seen in 7 of 8 specimens; nonlocking screws loosened and tines compressed the surrounding bone, resulting in tine-hole enlargement. CONCLUSIONS All of the plate-fixation systems delivered sufficient stability to permit the simulated postoperative regimen of 1 week of immobilization followed by 5 weeks of early mobilization until expected union at 6 weeks after surgery. Based on these results a preferable volar fixation system would appear to benefit from the following: (1) sufficient plate strength to support the distal fragment from the volar side, (2) a locking system with sufficient strength to remain locked during the healing process, and (3) a distal design that does not affect the bone adversely. The anatomic reduction of the volar cortex in the wedge osteotomy specimens added stability to the construct.
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Affiliation(s)
- Shukuki Koh
- Department of Hand Surgery, Nagoya University School of Medicine, Nagoya, Japan
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Abstract
PURPOSE To compare the biomechanical properties of 6 dorsal and volar fracture fixation plate designs in a cadaver model. METHOD Six different plating techniques were used on surgically simulated, unstable, extra-articular distal radius fractures in fresh-frozen cadavers. Specimens were tested to failure in axial compression with the Materials Testing System machine, and were analyzed with a motion analysis system. The 6 different fixation systems studied included an AO stainless steel Pi plate (group 1), an AO titanium Pi plate (group 2), a Forte plate (group 3), a dorsally placed Symmetry plate (group 4), a volarly placed Symmetry plate (group 5), and a volarly placed SCS/V plate (group 6). RESULTS All dorsal plates (groups 1, 2, 3, 4) failed in apex dorsal angulation and all volar plates (groups 5, 6) failed in apex volar angulation. No group developed an average angular deformity greater than 5 degrees with a load of 100 N, which compares with the physiologic loads expected with active wrist motion. Only the volarly placed SCS/V plated specimens (group 6) resisted deformation of 5 degrees or more at loads up to 250 N, which compares with the physiologic loads expected with active finger motion, and was significantly stronger and more rigid than the other 5 plate groups. CONCLUSIONS The SCS/V plate fixation system is the most rigid of the systems tested and may offer adequate stability for the treatment of the distal radius fracture in which the anterior and/or posterior metaphyseal cortex is comminuted severely.
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Affiliation(s)
- Denju Osada
- Division of Research, Department of Orthopaedic Surgery and Rehabilitation, University of Texas Medical Branch, Galveston, TX 77555, USA
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Folcher M, Morris RP, Dale G, Salah-Bey-Hocini K, Viollier PH, Thompson CJ. A transcriptional regulator of a pristinamycin resistance gene in Streptomyces coelicolor. J Biol Chem 2001; 276:1479-85. [PMID: 11050092 DOI: 10.1074/jbc.m007690200] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Pip is a pristinamycin-induced transcriptional regulator protein detected in many Streptomyces species by its ability to specifically bind sequence motifs within the promoter of a Streptomyces pristinaespiralis multidrug resistance gene (ptr). To investigate the possible role of Pip in regulating multidrug resistance, it was purified from a genetically characterized species, Streptomyces coelicolor, utilizing an affinity matrix of the ptr promoter conjugated to magnetic beads. Reverse genetics identified the corresponding locus and confirmed that it encoded Pip, a protein belonging to the TetR family of procaryotic transcriptional repressors. Pip binding motifs were located upstream of the adjacent gene pep, encoding a major facilitator antiporter homologous to ptr. In vivo analysis of antibiotic susceptibility profiles demonstrated that pep conferred elevated levels of resistance only to pristinamycin I (PI), a streptogramin B antibiotic having clinical importance. Purified recombinant Pip was a dimer (in the presence or absence of PI) and displayed a high affinity for its palindromic binding motifs within the ptr promoter and the upstream region of pep. The Pip/ptr promoter complex was dissociated by PI but not by any of the other nonstreptogramin antibiotics that were described previously as transcriptional inducers. These procaryotic regulatory elements served as the basis for the development of systems allowing repression or induction of cloned genes in mammalian and plant cells in response to streptogramin antibiotics (including pristinamycin, virginiamycin, and Synercid(R)).
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Affiliation(s)
- M Folcher
- Biozentrum, University of Basel, Department of Microbiology, Klingelbergstrasse 70, CH-4056 Basel, Switzerland
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Fussenegger M, Morris RP, Fux C, Rimann M, von Stockar B, Thompson CJ, Bailey JE. Streptogramin-based gene regulation systems for mammalian cells. Nat Biotechnol 2000; 18:1203-8. [PMID: 11062442 DOI: 10.1038/81208] [Citation(s) in RCA: 239] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Here we describe repressible (PipOFF) as well as inducible (PipON) systems for regulated gene expression in mammalian cells, based on the repressor Pip (pristinamycin-induced protein), which is encoded by the streptogramin resistance operon of Streptomyces coelicolor. Expression of genes placed under control of these systems was responsive to clinically approved antibiotics belonging to the streptogramin group (pristinamycin, virginiamycin, and Synercid). The versatility of these systems was demonstrated by streptogramin-regulated expression of mouse erythropoietin (EPO), human placental secreted alkaline phosphatase (SEAP), or green fluorescent protein (GFP) in diverse cell lines (BHK, CHO, HeLa, and mouse myoblasts). Analysis of isogenic constructs in CHO cells demonstrated the PipOFF system gave lower background and higher induction ratios than the widely used tetracycline-repressible (TetOFF) expression systems. The streptogramin-based expression technology was functionally compatible with the TetOFF system, thus enabling the selective use of different antibiotics to independently control two different gene activities in the same cell.
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Affiliation(s)
- M Fussenegger
- Institute of Biotechnology, Swiss Federal Institute of Technology, ETH Zurich, CH-8093 Zurich, Switzerland.
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Grecula MJ, Morris RP, Laughlin JC, Buford WL, Patterson RM. Femoral surface strain in intact composite femurs: a custom computer analysis of the photoelastic coating technique. IEEE Trans Biomed Eng 2000; 47:926-33. [PMID: 10916264 DOI: 10.1109/10.846687] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Understanding how forces are distributed through the proximal femur has many clinical applications for surgeons, researchers, and prosthetic designers. A new system for two-dimensional analysis of femoral surface strain was developed and applied to intact composite femurs. The photoelastic coating method was used to resolve the surface strain under axial loading, and strain analysis was performed using digital imaging of the strain patterns and original computer programs. The technique provides qualitative and quantitative data that describes overall femoral surface strains more completely than previous point analysis and strain gauge techniques. Results from repeated testing found the photoelastic process, computer imaging and computer analysis of strain areas to be statistically repeatable.
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Affiliation(s)
- M J Grecula
- Department of Orthopaedic Surgery and Rehabilitation, University of Texas Medical Branch, Galveston 77555-0892, USA.
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Stright PA, Morris RP, Hale JR. Insearch of continuing competency. Interview by Dr. Milton Eger. Am J Nurs 1979; 79:666-9. [PMID: 255052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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Morris RP, Hale JR. In search of continuing competency. Interview by Dr. Milton Eger. J Am Optom Assoc 1978; 49:1405-7. [PMID: 748415] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Morris RP. The optometric recognition award program--an option for self assessment. J Am Optom Assoc 1977; 48:803-8. [PMID: 915184] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
This discussion addresses itself to the need for all optometrists to continue recognizing their professional responsibility to maintain continuing competency through meaningful optometric education experiences; and to work toward this goal by participation in the Optometric Recognition Award Program. The ORA Program is structured to enable the participant to design, record and fulfill his personal continuing optometric education needs. Fullfillment of the award requirements, 150 hours of C.O.E. in three years, results in recognition by the AOA in the form of a recognition plaque.
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Fullmer CD, Morris RP. Primary cytodiagnosis of unsuspected mediastinal Hodgkin's disease. (Report of a case). Acta Cytol 1972; 16:77-81. [PMID: 4501878] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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