Bryan M Armitage

Mayo Clinic - Rochester, Rochester, Minnesota, United States

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Publications (10)25.98 Total impact

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    ABSTRACT: The purpose of this study was to evaluate the maximum insertion torque of cancellous bone screws in osteoporotic proximal femurs with and without the use of washers.
    Journal of orthopaedic trauma. 06/2014;
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    ABSTRACT: The glenopolar angle assesses the rotational alignment of the glenoid and may provide prognostic information and aid the management of scapula fractures. We have analysed the effect of the anteroposterior (AP) shoulder radiograph rotational offset on the glenopolar angle in a laboratory setting and used this to assess the accuracy of shoulder imaging employed in routine clinical practice. Fluoroscopic imaging was performed on 25 non-paired scapulae tagged with 2 mm steel spheres to determine the orientation of true AP views. The glenopolar angle was measured on all the bony specimens rotated at 10° increments. The mean glenopolar angle measured on the bone specimens in rotations between 0° and 20° and thereafter was found to be significantly different (p < 0.001). We also obtained the AP radiographs of the uninjured shoulder of 30 patients treated for fractures at our centre and found that none fitted the criteria of a true AP shoulder radiograph. The mean angular offset from the true AP view was 38° (10° to 65°) for this cohort. Radiological AP shoulder views may not fully project the normal anatomy of the scapular body and the measured glenopolar angle. The absence of a true AP view may compromise the clinical management of a scapular fracture. Cite this article: Bone Joint J 2013;95-B:1114-20.
    The bone & joint journal. 08/2013; 95-B(8):1114-1120.
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    ABSTRACT: OBJECTIVES: To evaluate relative fracture stability yielded by screws placed above a lateral plate, as well as locking and non-locking screws placed through a plate in a split depression tibia plateau fracture model. METHODS: Cadaver tibia specimens (mean age 74.1 years) were randomised across 3 groups: Groups 1: raft-construct outside the plate, 2: non-locking raft screws through the plate, and 3: locking raft screws through the plate. Displacement of the depressed fragment was recorded with force values from 400N to 1600N in increasing 400N increments. The force required to elicit lateral plateau fragment displacement of 5mm, 10mm, and 15mm was also recorded. RESULTS: None of the mechanical testing results demonstrated statistical significance with p-values of <0.05. Cyclic testing of Groups 1, 2, and 3 at 400N revealed displacements of 0.54mm, 0.64mm, and 0.48mm, respectively. At 800N, displacements were 1.36mm, 1.4mm, and 1.4mm, respectively. At 1200N, displacements were 2.4mm, 1.9mm, and 2.1mm, respectively. At 1600N, displacements were 2.8mm, 2.5mm, and 2mm, respectively. Resistance to displacement data demonstrated the mean force required to displace the fracture 5mm in Groups 1, 2, and 3 were 250N, 330N, and 318N, respectively. For 10mm of displacement, forces required were 394N, 515N, and 556N, respectively. For 15mm of displacement, forces required were 681N, 853N, and 963N, respectively. Compared to combined groups using screws through the plate, Group 1 demonstrated lower displacement ≤800N, but demonstrated greater displacement >800N. Group 2 demonstrated greatest resistance to plateau displacement of 5mm compared to Group 1 or 3, while Group 3 was most resistant to greater displacement. The combined group using screws through the plate (Groups 2+3) was consistently more resistant than Group 1 at all levels of displacement. CONCLUSIONS: Designs utilising screws through the plate trended towards statistically significant improved stability against plateau displacement relative to utilising screws outside the plate. Our study also suggests that there is no significant benefit of locking screws over non-locking screws in this unicondylar tibia plateau fracture model.
    Injury 02/2013; · 1.93 Impact Factor
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    ABSTRACT: An anatomical medial knee reconstruction has not been described in the literature. Knee stability and ligamentous load distribution would be restored to the native state with an anatomical medial knee reconstruction. Controlled laboratory study. Ten nonpaired cadaveric knees were tested in the intact, superficial medial collateral ligament and posterior oblique ligament-sectioned, and anatomically reconstructed states. Each knee was tested at 0 degrees , 20 degrees , 30 degrees , 60 degrees , and 90 degrees of knee flexion with a 10-N.m valgus load, 5-N.m external and internal rotation torques, and 88-N anterior and posterior drawer loads. A 6 degrees of freedom electromagnetic motion tracking system measured angulation and displacement changes of the tibia with respect to the femur. Buckle transducers measured the loads on the intact and reconstructed proximal and distal divisions of the superficial medial collateral ligament and the posterior oblique ligament. A significant increase was found in valgus angulation and external rotation after sectioning the medial knee structures at all tested knee flexion angles. This was restored after an anatomical medial knee reconstruction. The authors also found a significant increase in internal rotation at 0 degrees , 20 degrees , 30 degrees , and 60 degrees of knee flexion after sectioning the medial knee structures, which was restored after the reconstruction. A significant increase in anterior translation was observed after sectioning the medial knee structures at 20 degrees , 30 degrees , 60 degrees , and 90 degrees of knee flexion. This increase in anterior translation was restored following the reconstruction at 20 degrees and 30 degrees of knee flexion, but was not restored at 60 degrees and 90 degrees . A small, but significant, increase in posterior translation was found after sectioning the medial knee structures at 0 degrees and 30 degrees of knee flexion, but this was not restored after the reconstruction. Overall, there were no clinically important differences in observed load on the ligaments when comparing the intact with the reconstructed states for valgus, external and internal rotation, and anterior and posterior drawer loads. Conclusion An anatomical medial knee reconstruction restores near-normal stability to a knee with a complete superficial medial collateral ligament and posterior oblique ligament injury, while avoiding overconstraint of the reconstructed ligament grafts. This anatomical medial knee reconstruction technique provides native stability and ligament load distribution in patients with chronic or severe acute medial knee injuries.
    The American journal of sports medicine 12/2009; 38(2):339-47. · 3.61 Impact Factor
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    ABSTRACT: Fractures of the scapula involve a unique and challenging set of considerations, which must be understood to provide optimal treatment. The primary goal of this study was to create a frequency map of a series of surgically treated scapular fractures that specifically involved the scapular body and/or neck. A prospective database was used in the collection of consecutive radiographic imaging studies of patients undergoing operative treatment of scapular fractures. Scanned three-dimensional computed tomography images were superimposed and oriented to fit a model scapular template. Size dimensions were normalized by aligning specific scapular landmarks. Fracture lines were identified and traced over the combined three-dimensional computed tomography model to create a scapular fracture map. Of ninety fractures that met the criteria for inclusion, 68% involved the inferior aspect of the glenoid neck and 71% involved the superior vertebral border. Seventeen percent of the patterns included articular extension, and 22% of the fractures entered the spinoglenoid notch. Of fractures involving the inferior aspect of the glenoid neck at the lateral scapular border, 84% traversed medially to exit just inferior to the medial extent of the scapular spine, and 59% of these inferior neck fractures also had propagation to the inferior third of the vertebral border. Among the fractures involving the spinoglenoid notch, the most common pattern was demonstrated by coexisting fracture lines; 60% of the fractures of the spinoglenoid notch exited just inferior to the glenoid, 65% extended to the superior-medial vertebral border, and 45% extended to the inferior-medial vertebral border. In contrast, articular fractures did not follow predictable patterns; they demonstrated the greatest variability in trajectory, which was almost random, and there was a wide distribution of exit points along the vertebral border. Surgically treated scapular fractures display very common patterns. The most common pattern is the lateral border fracture immediately inferior to the glenoid, which extends to the superior vertebral border in more than two-thirds of cases. A smaller proportion of scapular fractures enter the spinoglenoid notch or the articular surface. There is great variation in the patterns of fractures involving the articular surface.
    The Journal of Bone and Joint Surgery 10/2009; 91(9):2222-8. · 3.23 Impact Factor
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    ABSTRACT: There is a lack of knowledge on the primary and secondary static stabilizing functions of the posterior oblique ligament (POL), the proximal and distal divisions of the superficial medial collateral ligament (sMCL), and the meniscofemoral and meniscotibial portions of the deep medial collateral ligament (MCL). Identification of the primary and secondary stabilizing functions of the individual components of the main medial knee structures will provide increased knowledge of the medial knee ligamentous stability. Descriptive laboratory study. Twenty-four cadaveric knees were equally divided into 3 groups with unique sequential sectioning sequences of the POL, sMCL (proximal and distal divisions), and deep MCL (meniscofemoral and meniscotibial portions). A 6 degree of freedom electromagnetic tracking system monitored motion after application of valgus loads (10 N.m) and internal and external rotation torques (5 N.m) at 0 degrees , 20 degrees , 30 degrees , 60 degrees , and 90 degrees of knee flexion. The primary valgus stabilizer was the proximal division of the sMCL. The primary external rotation stabilizer was the distal division of the sMCL at 30 degrees of knee flexion. The primary internal rotation stabilizers were the POL and the distal division of the sMCL at all tested knee flexion angles, the meniscofemoral portion of the deep MCL at 20 degrees , 60 degrees , and 90 degrees of knee flexion, and the meniscotibial portion of the deep MCL at 0 degrees and 30 degrees of knee flexion. An intricate relationship exists among the main medial knee structures and their individual components for static function to applied loads. Interpretation of clinical knee motion testing following medial knee injuries will improve with the information in this study. Significant increases in external rotation at 30 degrees of knee flexion were found with all medial knee structures sectioned, which indicates that a positive dial test may be found not only for posterolateral knee injuries but also for medial knee injuries.
    The American journal of sports medicine 08/2009; 37(9):1762-70. · 3.61 Impact Factor
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    ABSTRACT: There is limited information regarding directly measured load responses of the posterior oblique and superficial medial collateral ligaments in isolated and multiple medial knee ligament injury states. Tensile load responses from both the superficial medial collateral ligament and the posterior oblique ligament would be measurable and reproducible, and the native load-sharing relationships between these ligaments would be altered after sectioning of medial knee structures. Descriptive laboratory study. Twenty-four nonpaired, fresh-frozen adult cadaveric knees were distributed into 3 sequential sectioning sequences. Buckle transducers were applied to the posterior oblique ligament and the proximal and distal divisions of the superficial medial collateral ligament; 10 N.m valgus moments and 5 N.m internal and external rotation torques were applied at 0 degrees , 20 degrees , 30 degrees , 60 degrees , and 90 degrees of knee flexion. With an applied valgus and external rotation moment, there was a significant load increase on the posterior oblique ligament compared with the intact state after sectioning all other medial knee structures. With an applied external rotation torque, there was a significant load decrease on the proximal division of the superficial medial collateral ligament from the intact state after sectioning all other medial knee structures. With an applied external rotation torque, the distal division of the superficial medial collateral ligament experienced a significant load increase from the intact state after sectioning the posterior oblique ligament and the meniscofemoral division of the deep medial collateral ligament. This study found alterations in the native load-sharing relationships of the medial knee structures after injury. Sectioning both the primary and secondary restraints to valgus and internal/external rotation of the knee alters the intricate load-sharing relationships that exist between the medial knee structures. In cases in which surgical repair or reconstruction is indicated, consideration should be placed on repairing or reconstructing all injured medial knee structures to restore the native load-sharing relationships among these medial knee structures.
    The American journal of sports medicine 08/2009; 37(9):1771-6. · 3.61 Impact Factor
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    ABSTRACT: Double-bundle anterior cruciate ligament (ACL) reconstructions involve drilling 2 tibial tunnels separated by a narrow 2-mm bone bridge. The sequence of reaming and drilling the tibial tunnels for double-bundle ACL reconstructions has not been defined. Fixing a graft in the posterolateral ACL tibial tunnel before reaming the anteromedial tibial tunnel will reduce the number of complications, as compared with drilling both the anteromedial and posterolateral tunnels before graft fixation, when performing double-bundle ACL reconstructions. Controlled laboratory study. Twelve porcine tibias were divided into 2 groups of 6 specimens. Fresh bovine extensor tendons grafts were fixed in 7-mm tunnels reamed using an inside-out method. Grafts were fixed in a retrograde fashion with 7-mm bioabsorbable retrograde screws. The tibias in group 1 were reconstructed by reaming and reconstructing the posterolateral tunnel before reaming and securing the graft for the anteromedial tunnel (ie, 1:1 method), whereas those in the second group were reconstructed by reaming both tunnels before graft fixation in either (ie, the 2:2 method). The specimens were biomechanically tested with cyclic and load-to-failure parameters. Cyclic testing revealed no significant difference between the 2 methods in displacement or stiffness. In load-to-failure testing, the 1:1 group withstood significantly higher initial failure loads and ultimate loads. Pullout displacement was significantly higher for the 1:1 group. Whereas no tibias in the 1:1 group sustained fractures, 4 from the 2:2 group demonstrated a bone bridge fracture. Soft tissue ACL grafts fixed in the tibia with the 1:1 method withstood significantly higher initial and ultimate failure loads and were stiffer than the grafts fixed with the 2:2 method. Tibias fixed with the 1:1 method were also less susceptible to bone bridge fracture. The potential for a lower complication rate and greater pullout strength seen with the 1:1 method may prove useful to surgeons performing anatomic double-bundle ACL reconstructions, in addition to other procedures involving reconstructing 2 closely positioned tunnels, including anatomic posterolateral corner and medial collateral reconstructions.
    The American journal of sports medicine 06/2009; 37(8):1539-47. · 3.61 Impact Factor
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    ABSTRACT: Anatomic studies have described areas where there is no direct threat of inadvertent suprascapular nerve injury; however, these studies did not describe danger zones during open reduction and internal fixation of the fractured scapula. We therefore sought to define the topographic distribution in which these vulnerable structures most commonly are found, thus establishing danger zones. Twenty-four nonpaired cadaveric specimens were dissected. The infraspinatus and teres minor musculature were elevated off the posterior scapula body to reveal critical areas where the suprascapular neurovasculature and circumflex scapular artery were vulnerable to injury. We established radial coordinates to determine this relation to osseous landmarks. The mean distance from the spinoglenoid notch to the inferior border of the danger zone was 2.4 cm (range, 1.2-3.8 cm). The mean distance from the medial extent of the scapular spine to the medial border of the danger zone was 4.3 cm (range, 3.0-6.7 cm). The entry of the ascending branch of the circumflex scapular artery was located at the lateral border 5.6 cm (range, 4.5-7.0 cm) inferior to the spinoglenoid notch. These danger zones can aid the surgeon in determining the risk for suprascapular nerve injury, specifically with scapula fractures involving the spinoglenoid notch and/or lateral border.
    Clinical Orthopaedics and Related Research 01/2009; 467(8):2011-7. · 2.79 Impact Factor
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    ABSTRACT: There is limited information regarding load responses of the posterior oblique and superficial medial collateral ligaments to applied loads. The degree of knee flexion affects loads experienced by the posterior oblique ligament and both divisions of the superficial medial collateral ligament. The posterior oblique ligament provides significant resistance to valgus and internal rotation forces near knee extension. Different load responses are experienced by proximal and distal divisions of the superficial medial collateral ligament. Descriptive laboratory study. Twenty-four nonpaired, fresh-frozen cadaveric knees were tested. Buckle transducers were applied to the proximal and distal divisions of the superficial medial collateral and posterior oblique ligaments. Applied loads at 0 degrees, 20 degrees, 30 degrees, 60 degrees, and 90 degrees of knee flexion consisted of 10 N m valgus loads, 5 N.m internal and external rotation torques, and 88 N anterior and posterior drawer loads. External rotation torques produced a significantly higher load response on the distal superficial medial collateral ligament than did internal rotation torques at all flexion angles with the largest difference at 90 degrees (96.6 vs 22.5 N). For an applied valgus load at 60 degrees of knee flexion, loads on the superficial medial collateral ligament were significantly higher in the distal division (103.5 N) than the proximal division (71.9 N). The valgus load response of the posterior oblique ligament at 0 degrees of flexion (19.1 N) was significantly higher than at 30 degrees (10.6 N), 60 degrees (7.8 N), and 90 degrees (6.8 N) of flexion. At 0 degrees of knee flexion, the load response to internal rotation on the posterior oblique ligament (45.8 N) was significantly larger than was the response on both divisions of the superficial medial collateral ligament (20 N for both divisions). At 90 degrees of flexion, the load response to internal rotation torques reciprocated between these structures with a significantly higher response in the distal superficial medial collateral ligament division (22.5 N) than the posterior oblique ligament (9.1 N). The superficial medial collateral ligament experienced the largest load response to applied valgus and external rotation torques; the posterior oblique ligament observed the highest load response to internal rotation near extension. This study provides new knowledge of the individual biomechanical function of the main medial knee structures in an intact knee and will assist in the interpretation of clinical knee motion testing and provide evidence for techniques involving repair or reconstruction of the posterior oblique ligament and both divisions of the superficial medial collateral ligament.
    The American journal of sports medicine 09/2008; 37(1):140-8. · 3.61 Impact Factor

Publication Stats

136 Citations
25.98 Total Impact Points

Institutions

  • 2013
    • Mayo Clinic - Rochester
      • Division of Orthopaedic Surgery
      Rochester, Minnesota, United States
  • 2008–2009
    • University of Minnesota Twin Cities
      • Department of Orthopaedic Surgery
      Minneapolis, MN, United States
    • University of Oslo
      Kristiania (historical), Oslo County, Norway