Samuel R. Ward: Associate professor in the Departments of Radiology, Orthopaedic Surgery and Bioengineering at the University of California, San Diego.
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1) Muscle undergoes significant structural and physiological adaptations after tendon rupture including radial and longitudinal muscle fiber atrophy, increased muscle fibrosis, and changes in passive muscle mechanics and stiffness. 2) Chronic rotator cuff tears result in retraction of the muscle from the bone, fatty infiltration of the muscle, and difficulty repairing the tendon. The muscle becomes insensitive to rehabilitation after chronic tearing. 3) Evidence suggests that after chronic tears, muscle function does not recover its normal relationship to structure. Changes in the extracellular matrix may underlie increased muscle stiffness observed after tearing.
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Samuel R. Ward: Associate professor in the Departments of Radiology, Orthopaedic Surgery and Bioengineering at the University of California, San Diego.
- 1. 10/10/13 Physiological and Mechanical Adaptations of Muscle to Tendon Rupture Samuel R. Ward, PT, PhD Associate Professor Muscle Physiology Lab Departments of Radiology, Orthopaedic Surgery, and Bioengineering University of California San Diego VA Medical Center San Diego MuscleTech Network, Barcelona, Oct 15, 2013 Background • Cuff injuries effect ~30% of people over 60 1 • 20-50% of repairs will fail 2 • Chronic tears – Muscle retraction, fatty atrophy and fibrosis 3 – Nerve injury 4 – Difficult to repair 5 – High re-tear rates 2 – Insensitive to rehabilitation 6 Healthy 1 Lehman et al, Bull Hosp Jt Dis, 1995 Harryman et al, JBJS 1991 Gerber et al, JBJS, 2004 4 Costouros et al, Arthroscopy, 2007 5 Peterson, et al JSES 2011 6 Gerber et al, JBJS, 2000 2 3 Severe Tear 1
- 2. 10/10/13 Skeletal Muscle Hierarchy Lieber, Skeletal Muscle Structure and Function, 2010 Muscle Force Structure-Function Relationships Muscle Length Winters et al, J Biomech, 2012 Powell et al, J Appl Physiol, 1984 Bodine et al, J Neurophysiol , 1982 2
- 3. 10/10/13 Normal Architecture Ward, et al Clin Orthop, 2006 30.0 PCSA (cm2) 25.0 Deltoid Subscapularis 20.0 15.0 Infraspinatus 10.0 Supraspinatus 5.0 teres minor 0.0 0.0 2.0 4.0 6.0 8.0 Fiber Length (cm) 10.0 12.0 Ward, et al Clin Orthop 2006 Altobelli, et al, Submitted J Biomech 2013 3
- 4. 10/10/13 Pathology Normal Tear 47.72 mm 30.47mm Anterior Biceps tendon SS tendon attached to Infraspinatus and anterior capsule Muscle Area Changes with Tear and Age (Human) Barry et al, JSES 2012 4
- 5. 10/10/13 Muscle Structural Changes After Tear (Sheep) Fat Muscle Gerber C, et al JBJS 2004 Muscle Fiber Length Changes After Tear (Human) 80 No Tear Tear Fiber Length (mm) 70 60 50 40 30 20 10 0 1 Tomioka et al, JSES 2009 5
- 6. 10/10/13 Architectural Adaptations to Tear and Nerve Injury Relative Muscle Tension" Sato, et al, In Submission JBJS 100" 80" 60" 40" 20" 0" 0.5" 1.0" 1.5" 2.0" 2.5" 3.0" 3.5" 4.0" Sarcomere Length (µm) " 6
- 7. 10/10/13 Whole Supraspinatus Muscle Stiffness Gerber et al, JSES, 1998- Human Safran, et al, JBJS 2005- Dog Gerber et al, JBJS 2004- Sheep Human Passive Mechanics Injured Cuff Elastic Modulus (kPa) 700 600 500 Supraspinatus Infraspinatus Control * 400 300 200 100 0 Single Fiber Fiber Bundle Silldorff, Submitted JBJS 7
- 8. 10/10/13 Tissue Adaptations to Tear and Nerve Injury (rat) Sato, et al, In Submission JBJS Structural Change- Summary Muscle Force Healthy Tear Muscle Length 8
- 9. 10/10/13 Rabbit Lower Extremity Tenotomy C: TA T: TA 10 mm C: ED L T: EDL 10 mm C: EDI I T: EDI I 10 mm Active & Passive Mechanics In Vivo Mechanical Testing Tenotomy & Length-Tension Curve Muscle Architecture Fiber Area Muscle Tension Control 100 µm Muscle Length 9
- 10. 10/10/13 Tenotomy Alters LT Relationship Stress After Repair Normalized Fiber Length [mm] 40 300 Control Tenotomy Control Tenotomy * * 250 30 200 * * 20 150 TA * * 100 10 50 0 0 TA TA EDL EDL EDII EDII EDL EDII * = p < 0.05 4000 250 * Control Tenotomy 6000 * * TA 200 Stress [kPa] Passive Stiffness [kPa] Tentomy Alters Passive Stiffness 2000 150 100 50 0 Control Tenotomy 0 TA 250 EDL 0 EDII EDL 40 Fiber Length [mm] 60 80 EDII 250 200 20 Stress [kPa] Stress [kPa] 200 150 100 50 Control Tenotomy 0 0 5 10 15 20 Fiber Length [mm] 25 30 150 100 50 Control Tenotomy 0 0 5 10 Fiber Length [mm] 15 20 10
- 11. 10/10/13 ECM Remodeling Control Tenotomy TA 50 µm EDL Winters, et al, In Progress 50 µm 50 µm 50 µm EDII 50 µm 50 µm New Histology Methods H&E Wheat Germ Agglutinin Picro-sirius Red KI67 αSMA Trichrome Reticulin pCEβ Winters, Buck et al, In Progress 11
- 12. 10/10/13 Human Muscle Gene Expression Choo, McCarthy et al, In Progress JBJS Summary • Structural Changes – Radial and longitudinal atrophy • Physiological Changes – After chronic tears, function does not follow structure – Evidence for ECM changes leading to muscle stiffness • Rehabilitation – Massive tears in the shoulder don’t appear to recover 12
- 13. 10/10/13 Faculty Doug Chang, MD- UCSD Adam Engler, PhD- UCSD Don Fithian, MD – Kaiser Larry Frank, PhD- UCSD Jan Fridén, MD- Göteborg, Sweden Christian Gerber, MD- Balgrist, Switzerland Eric Hentzen, MD, PhD- UCSD John Lane, MD- Coast Surgery Center Rick Lieber, PhD- UCSD Hiro Okuno, MDJoseph Sarver, PhD- Penn Simon Schenk, PhD- UCSD Lou Soslowsky, PhD- Penn Andrea Taylor, PhD- Duke Steve Thomopoulos, PhD- Wash U Students Grant Altobelli, MD – Tufts Geoff Abrams, MD- Stanford Alex Choo, MD- UCSD Carolyn Eng, BS- Harvard Ki Lee, MD- Yonsei Meagan McCarthy, MD- UCSD Randy McKnight- UCSD Morgan Silldorff, MD- UCSD Gretchen Meyer, PhD- UCSD Eugene Sato, BS- UCSD Ana Rodriguez-Soto, BS- UCSD 13