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Winter J.D.,Hospital for Sick Children | Akens M.K.,Orthopaedic Biomechanics Laboratory | Cheng H.-L.M.,Hospital for Sick Children | Cheng H.-L.M.,University of Toronto
Physics in Medicine and Biology | Year: 2011

Magnetic resonance imaging (MRI) relaxation times provide indirect estimates of tissue O 2 for monitoring tumour oxygenation. This study provides insight into mechanisms underlying longitudinal (R 1 = 1/T 1) and transverse effective (R 2 * = 1/T 2 *) relaxation rate changes during inhalation of 100% O 2 and 3%, 6% and 9% CO 2 (balanced O 2) in a rabbit tumour model. Quantitative R 1, R 2 *, and dynamic contrast-enhanced (DCE) imaging was performed in six rabbits 12-23 days following implantation of VX2 carcinoma cells in the quadricep muscle. Invasive measurements of tissue partial pressure of O 2 (pO 2) and perfusion were also performed, which revealed elevated pO 2 levels in all tumour regions for all hyperoxic gases compared to baseline (air) and reduced perfusion for carbogen. During 100% O 2 breathing, an R 1 increase and R 2 * decrease consistent with elevated pO 2 were observed within tumours. DCE-derived blood flow was weakly correlated with R 1 changes from air to 100% O 2. Further addition of CO 2 (carbogen) did not introduce considerable changes in MR relaxation rates, but a trend towards higher R 1 relative to breathing 100% O 2 was observed, while R 2 * changes were inconsistent. This observation supports the predominance of dissolved O 2 on R 1 sensitivity and demonstrates the value of R 1 over R 2 * for tissue oxygenation measures. © 2011 Institute of Physics and Engineering in Medicine.


Kaplan K.,Jacksonville Orthopaedic Institute | Elattrache N.S.,Kerlan Jobe Orthopaedic Clinic | Vazquez O.,Orthopaedic Biomechanics Laboratory | Chen Y.-J.,Orthopaedic Biomechanics Laboratory | Lee T.,Orthopaedic Biomechanics Laboratory
Arthroscopy - Journal of Arthroscopic and Related Surgery | Year: 2011

Purpose To evaluate the effect of the addition of 2 horizontal mattress knots to the medial row of a knotless rotator cuff construct on the biomechanical properties in terms of both cyclic and failure testing parameters in an external rotation model. Methods In 8 fresh-frozen human cadaveric shoulders, a knotless transosseous repair was performed, whereas in 8 contralateral matched-pair specimens, 2 horizontal mattress knots were added to the medial-row fixation. A custom jig was used that allowed external rotation (0° to 30°) with loading. A materials testing machine was used to cyclically load repairs from 0 to 180 N for 30 cycles and then to failure. Video digitizing software was used for analysis. Data from paired specimens were compared by use of paired Student t tests. Results Ultimate load to failure was significantly higher in the modified construct (549 N v 311 N, P = .01). Linear stiffness in the first cycle, at the 30th cycle, and at failure was significantly higher (P = .02, P = .02, and P = .04, respectively) in the modified construct as well. Energy absorbed by the repaired tissue was significantly less in the modified construct at the first cycle, at the 30th cycle, and at ultimate load to failure (P = .03, P = .02, and P = .04, respectively). Significantly greater anterior gap formation occurred with the knotless technique at the first cycle (4.55 v 1.35) and 30th cycle (7.67 mm v 1.77 mm) (P = .02). Conclusions The modified construct shows improved biomechanical properties when allowing for external rotation during high-load testing. Using an additional horizontal mattress from separate sutures in the medial-row anchors helps to neutralize forces experienced by the repair. Clinical Relevance The addition of medial-row fixation to a knotless construct will enhance the stability of rotator cuff repairs with the goal of improved patient outcomes. © 2011 Arthroscopy Association of North America.


Saltzman C.L.,University of Utah | Hillis S.L.,Cadre Inc | Stolley M.P.,University of Iowa | Anderson D.D.,Orthopaedic Biomechanics Laboratory | Amendola A.,University of Iowa
Journal of Bone and Joint Surgery - Series A | Year: 2012

Background: Initial reports have shown the efficacy of fixed distraction for the treatment of ankle osteoarthritis. We hypothesized that allowing ankle motion during distraction would result in significant improvements in outcomes compared with distraction without ankle motion. Methods: We conducted a prospective randomized controlled trial comparing the outcomes for patients with advanced ankle osteoarthritis who were managed with anterior osteophyte removal and either (1) fixed ankle distraction or (2) ankle distraction permitting joint motion. Thirty-six patients were randomized to treatment with either fixed distraction or distraction with motion. The patients were followed for twenty-four months after frame removal. The Ankle Osteoarthritis Scale (AOS) was the main outcome variable. Results: Two years after frame removal, subjects in both groups showed significant improvement compared with the status before treatment (p < 0.02 for both groups). The motion-distraction group had significantly better AOS scores than the fixed-distraction group at twenty-six, fifty-two, and 104 weeks after frame removal (p < 0.01 at each time point). At 104 weeks, the motion-distraction group had an overall mean improvement of 56.6% in the AOS score, whereas the fixed-distraction group had a mean improvement of 22.9% (p < 0.01). Conclusion: Distraction improved the patient-reported outcomes of treatment of ankle osteoarthritis. Adding ankle motion to distraction showed an early and sustained beneficial effect on outcome. Level of Evidence: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence. Copyright © 2012 by The Journal of Bone and Joint Surgery, Incorporated.


Oh J.H.,Seoul National University | Shin S.-J.,Ewha Womans University | McGarry M.H.,Orthopaedic Biomechanics Laboratory | Scott J.H.,Orthopaedic Biomechanics Laboratory | And 2 more authors.
Journal of Shoulder and Elbow Surgery | Year: 2014

Background: The variability in functional outcomes and the occurrence of scapular notching and instability after reverse total shoulder arthroplasty remain problems. The objectives of this study were to measure the effect of reverse humeral component neck-shaft angle on impingement-free range of motion, abduction moment, and anterior dislocation force and to evaluate the effect of subscapularis loading on dislocation force. Methods: Six cadaveric shoulders were tested with 155°, 145°, and 135° reverse shoulder humeral neck-shaft angles. The adduction angle at which bone contact occurred and the internal and external rotational impingement-free range of motion angles were measured. Glenohumeral abduction moment was measured at 0° and 30° of abduction, and anterior dislocation forces were measured at 30° of internal rotation, 0°, and 30° of external rotation with and without subscapularis loading. Results: Adduction deficit angles for 155°, 145°, and 135° neck-shaft angle were 2° ± 5° of abduction, 7° ± 4° of adduction, and 12° ± 2° of adduction (P < .05). Impingement-free angles of humeral rotation and abduction moments were not statistically different between the neck-shaft angles. The anterior dislocation force was significantly higher for the 135° neck-shaft angle at 30° of external rotation and significantly higher for the 155° neck-shaft angle at 30° of internal rotation (P < .01). The anterior dislocation forces were significantly higher when the subscapularis was loaded (P < .01). Conclusions: The 155° neck-shaft angle was more prone to scapular bone contact during adduction but was more stable at the internally rotated position, which was the least stable humeral rotation position. Subscapularis loading gave further anterior stability with all neck-shaft angles at all positions. © 2014.


Stephenson D.R.,University of Southern California | Oh J.H.,Seoul National University | Oh J.H.,Orthopaedic Biomechanics Laboratory | McGarry M.H.,Seoul National University | And 2 more authors.
Journal of Shoulder and Elbow Surgery | Year: 2011

Hypothesis: Reverse shoulder arthroplasty is growing in popularity for patients with deficient rotator cuffs; however, the phenomenon of scapular notching continues to be a concern. This study examined the effects of humeral component version in the Aequalis Reversed Shoulder Prosthesis (Tornier, Edina, MN) on impingement of the humeral prosthesis against the scapula to test the hypothesis that the mechanical contact of the humeral component with the scapular neck is influenced by the version of the humeral component. Materials and methods: Seven shoulders from deceased donors were tested after the Aequalis Reversed Shoulder was implanted. The deltoid, pectoralis major, and latissimus dorsi were loaded based on physiologic cross-sectional area. The degree of internal and external rotation when impingement, subluxation, or dislocation occurred was measured at 0°, 30°, and 60 ° glenohumeral abduction in the scapular plane. Testing was performed with the humeral component placed in 20 ° of anteversion, neutral version, 20 ° of retroversion, and 40 ° of retroversion. Results: Maximum external rotation at 0° abduction was -1° ± 4° at 20° anteversion, 15° ± 3° at neutral, 28° ± 4° at 20° retroversion, and 44° ± 5° at 40° retroversion (P < .05). Maximum internal rotation at 0° abduction was 128° ± 9° at 20° anteversion, 112° ± 9° at neutral, 99° ± 8° at 20° retroversion, and 83° ± 8° at 40° retroversion (P < .05). Maximum external rotation at 30° abduction was 70° ± 6° at 20° anteversion, 84° ± 7° at neutral, 97° ± 6° at 20° retroversion, and 110° ± 5° at 40° retroversion (P < .05). There was no limitation to internal rotation at 30° abduction. No impingement occurred at 60° abduction. Discussion: Version of the humeral component plays a role in range of motion and impingement in reverse total shoulder arthroplasty. Anteversion can significantly decrease the amount of external rotation achievable after reverse total shoulder surgery. Conclusion: Placing the Aequalis Reversed Shoulder humeral component at between 20° and 40° of retroversion more closely restores a functional arc of motion without impingement. © 2011.


Uggen C.,Kerlan Jobe Orthopaedic Clinic | Dines J.,Hospital for Special Surgery | McGarry M.,Orthopaedic Biomechanics Laboratory | Grande D.,North Shore Medical Center | And 2 more authors.
Arthroscopy - Journal of Arthroscopic and Related Surgery | Year: 2010

Purpose: The purpose of this study was to determine whether suture could be coated with recombinant human platelet-derived growth factor BB (rhPDGF-BB) and whether the coated suture would improve histologic scores and biomechanical strength of sheep rotator cuff repairs. Methods: FiberWire sutures (Arthrex, Naples, FL) were dip coated in a collagenrhPDGF-BB solution. Coating was confirmed by use of enzyme-linked immunosorbent assay. Rotator cuff tears were created in 18 sheep. The tendons were wrapped in Gortex (Gore Medical, Flagstaff, AZ) and allowed to scar for 2 weeks. Tendons were then repaired to bone by use of standard anchors loaded with either rhPDGF-BBcoated sutures or uncoated sutures. Gross examination, histologic analysis, and biomechanical testing were performed 6 weeks after repair. Results: Enzyme-linked immunosorbent assay confirmed successful loading of the growth factor onto the sutures. Gross examination showed well-healed tendon-to-bone interfaces in both rhPDGF-BBaugmented repairs and controls. Histologic analysis using a semiquantitative rating scale showed improved tendon-to-bone healing in the rhPDGF-BBaugmented repairs. There was no significant difference in the ultimate load to failure of rhPDGF-BBaugmented rotator cuff repairs compared with standard suture repairs at 6 weeks after repair. Conclusions: We were able to coat No. 2 FiberWire with rhPDGF-BB. At short-term follow-up, rhPDGF-BBcoated sutures enhanced histologic scores of sheep rotator cuff repairs; however, ultimate load to failure was equivalent to standard suture repairs. Clinical Relevance: rhPDGF-BBcoated sutures seem to produce a more histologically normal tendon insertion. © 2010 Arthroscopy Association of North America.


Peltier K.E.,University of Southern California | McGarry M.H.,Orthopaedic Biomechanics Laboratory | Tibone J.E.,University of Southern California | Lee T.Q.,Orthopaedic Biomechanics Laboratory
Journal of Shoulder and Elbow Surgery | Year: 2012

Background: Arthroscopic repair techniques for anterior instability most commonly address only the anterior band of the inferior glenohumeral ligament. This study quantitatively evaluated and compared the combined anterior and posterior arthroscopic plication by repairing both the anterior and posterior bands of the inferior glenohumeral ligament with the anterior arthroscopic plication alone. Materials and methods: Six cadaveric shoulders were tested in 60° of glenohumeral abduction with 22 N of compressive force in the coronal plane for intact, after anterior capsular stretching, after anterior repair, and after posterior arthroscopic repair. Range of motion, glenohumeral translation, and glenohumeral kinematics throughout the rotational range of motion were measured with a MicroScribe 3DLX (Immersion, San Jose, CA, USA). Glenohumeral contact pressure and area were measured with a pressure measurement system (Tekscan Inc, South Boston, MA, USA). Results: Stretching the anterior capsule significantly increased external rotation and anterior translation (P <.05). After anterior plication, external rotation was restored to the intact condition, and anterior translation was significantly decreased compared with stretched condition (P <.05). The combined anterior and posterior plication significantly decreased internal rotation compared with the intact condition. The anterior plication shifted the humeral head posterior in external rotation, whereas the combined anterior and posterior plication shifted the humeral head anterior in internal rotation (P <.05). Both repairs led to a decrease in glenohumeral contact area at 45° external rotation (P <.07). Conclusions: The addition of a posterior plication to anterior plication for anterior instability has no biomechanical advantage over a typical arthroscopic anterior repair for anterior glenohumeral instability. © 2012.


Mihata T.,Orthopaedic Biomechanics Laboratory | Mihata T.,Osaka Medical College | McGarry M.H.,Orthopaedic Biomechanics Laboratory | Kinoshita M.,Osaka Medical College | Lee T.Q.,Orthopaedic Biomechanics Laboratory
American Journal of Sports Medicine | Year: 2010

Background: The objective of this study was to determine the effects of increased horizontal abduction with maximum external rotation, as occurs during the late cocking phase of throwing motion, on shoulder internal impingement. Hypothesis: An increase in glenohumeral horizontal abduction will cause overlap of the rotator cuff insertion with respect to the glenoid and increase pressure between the supraspinatus and infraspinatus tendon insertions on the greater tuberosity and the glenoid. Study Design: Controlled laboratory study. Methods: Eight cadaveric shoulders were tested with a custom shoulder testing system with the specimens in 60° of glenohumeral abduction and maximum external rotation. The amount of internal impingement was evaluated by assessing the location of the supraspinatus and infraspinatus articular insertions on the greater tuberosity relative to the glenoid using a MicroScribe 3DLX. Pressure in the posterior-superior quadrant of the glenoid was measured using Fuji prescale film. Data were obtained with the humerus in the scapular plane and 15°, 30°, and 45° of horizontal abduction from the scapular plane. Results: At 30° and 45° of horizontal abduction, the articular margin of the supraspinatus and infraspinatus tendons was anterior to the posterior edge of the glenoid and less than 2 mm from the glenoid rim in the lateral direction; the contact pressure was also greater than that found in the scapular plane and 15° of horizontal abduction. Conclusion: Horizontal abduction beyond the coronal plane increased the amount of overlap and contact pressure between the supraspinatus and infraspinatus tendons and glenoid. Clinical Relevance: Excessive glenohumeral horizontal abduction beyond the coronal plane may cause internal impingement, which may lead to rotator cuff tears and superior labral anterior to posterior (SLAP) lesions.


Hammond G.,Long Beach Orthopaedic Surgical and Medical Group | Tibone J.E.,University of Southern California | McGarry M.H.,Orthopaedic Biomechanics Laboratory | Jun B.-J.,Orthopaedic Biomechanics Laboratory | Lee T.Q.,Orthopaedic Biomechanics Laboratory
Journal of Bone and Joint Surgery - Series A | Year: 2012

Background: Resurfacing of the humeral head has gained interest as an alternative to traditional hemiarthroplasty because it preserves bone stock and respects the native geometry of the glenohumeral articulation. The purpose of this study was to compare the biomechanics of the intact glenohumeral joint with those following humeral head resurfacing and following hemiarthroplasty. Methods: Seven fresh-frozen cadaveric shoulders were tested with the rotator cuff, pectoralis major, and latissimus dorsi musculature loadedwith 20N and the deltoidmuscle loadedwith 40N in a custom shoulder testing system. Each specimen was tested in 20°, 40°, 60°, and 80° of vertical abduction. The articular surfaces of the humeral head and the glenoid were digitized to calculate the positions of the geometric center and apex of the humeral head relative to the geometric center of the glenoid at each testing position. The contact area and contact pressures were also measured with use of a Tekscan pressure sensor. Results: The geometric center of the humeral head shifted by a mean (and standard error) of 2.2 ± 0.3 mm following humeral resurfacing and 4.7 ± 0.3mmfollowing hemiarthroplasty (p < 0.0002). The apex of the humeral head was shifted superiorly at all abduction angles following hemiarthroplasty (p < 0.03). Both humeral resurfacing and hemiarthroplasty decreased the glenohumeral contact area and increased the peak pressure. Conclusions: Resurfacing more closely restored the geometric center of the humeral head than hemiarthroplasty did, with less eccentric loading of the glenoid. Clinical Relevance: Compared with hemiarthroplasty, humeral resurfacing may limit eccentric glenoid wear and permit better function because the glenohumeral joint biomechanics and the moment arms of the rotator cuff and the deltoid muscle are restored more closely to those of the intact condition. Copyright © 2012 by the Journal of Bone and Joint Surgery, Incorporated.


Shin S.J.,Orthopaedic Biomechanics Laboratory
Arthroscopy : the journal of arthroscopic & related surgery : official publication of the Arthroscopy Association of North America and the International Arthroscopy Association | Year: 2013

Our purpose was to investigate the effect of supraspinatus tendon tear combined with anterior capsulolabral injury on glenohumeral joint biomechanics and to identify which structures should be repaired when both pathologic conditions are present. Eight cadaveric shoulders were tested on a custom system. Five conditions were tested: intact supraspinatus full-thickness tear, supraspinatus tear combined with Bankart lesion, supraspinatus repair, and supraspinatus repair combined with Bankart repair. Rotational range of motion, glenohumeral kinematics, and the force required for anteroinferior dislocation were measured at 30° and 60° of glenohumeral abduction. Repeated-measures analysis of variance with Tukey post hoc test was used for statistical analysis. Bankart lesions combined with supraspinatus tears significantly increased total rotational range of motion (7.6° ± 6.3° at 30° of glenohumeral abduction and 14.1° ± 10.3° at 60° of glenohumeral abduction; P < .05). Bankart lesions combined with supraspinatus tears also significantly decreased the force required for dislocation normalized to range of motion (26.6% ± 21.0% at 60° of abduction) compared with intact shoulders (P = .04). Bankart repair combined with supraspinatus repair restored range of motion and the force required for dislocation; however, Bankart repair combined with supraspinatus repair shifted the humeral head posteriorly at the midrange of rotation in 30° and 60° of abduction (P < .05). Supraspinatus tendon tears combined with Bankart lesions increased humeral rotational range of motion and decreased the force required for dislocation. Repair of both pathologic conditions successfully restored range of motion and increased the force required for dislocation. Both supraspinatus tendon and anterior labral repair are suggested for patients with combined Bankart lesions and supraspinatus tears to restore shoulder function and possibly prevent recurrent dislocation. However, when repairing both pathologic conditions, care should be taken not to overtighten the joint, which may lead to stiffness or osteoarthritis. Published by Elsevier Inc.

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