biological augmentation of rotator cuff tears

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  1. 1. An Evaluation Of Amniotic Membrane Allograft As A Potential Agent For Biological Augmentation Of Rotator Cuff Repair Adnan Saithna1, Jennifer Z. Paxton2, Uchena Wudebwe2, Liam M. Grover2 and Martyn Snow1 1The Royal Orthopaedic Hospital 2School of Chemical Engineering, The University of Birmingham
  2. 2. AMA and tendon repair Reduction of peri-tendinous adhesions (Ozgenel at al 2004 & Demirkan et al 2002) Favourable influence on collagen deposition (Yang et al 2010) Improved mechanical properties (Yang et al 2010, Ozbuluk et al 2010, He at al 2002, Ozgenel et al 2001)
  3. 3. Micronised AMA
  4. 4. Cellular Proliferation Study
  5. 5. 0% SerumLow A.M. High A.M. Images taken on Day 7
  6. 6. Manufacture and Maintenance of Bone-Tendon Constructs Manufacture: - 35mm Sylgard coated Petri dish - Brushite anchor (Bone substitute) - Fibrin Gel (soft tissue substitute) - Seeded with 100,000 Chick Tendon Fibroblastss - DMEM + 10% FBS, 2.4% L-glutamine, 2.4% HEPES - 1% penicillin/streptomycin Maintenance: - Incubated at 37C, 5% CO2 - Fed with s-DMEM every 2-3 days Ascorbic acid (250M) and proline (50M) were added on day 7 onwards, along with AMA (13l/ml DMEM) in the treatment group.
  7. 7. Typical sequence of maturation
  8. 8. AMA Dosing Cost prohibitive One vial per cuff strategy Calculation based on previous work on surface area of soft tissue attachment to the brushite anchor (Paxton et al, Ann Biomed Eng, 2010) Rotator cuff footprint area (Mochizuki et al, JBJSAm 2009) 13uL per ml of DMEM
  9. 9. Fibrin Gel Contraction Constructs photographed daily and image J analysis software was used to assess area and rate of contraction. No significant difference was demonstrated between control and treatment groups -200 0 200 400 600 800 1000 1200 DAY 0 3 5 7 10 15 27 Area of construct mm2 Day of Culture A B C
  10. 10. Mechanical Testing Instron Microtester 37oC Water Bath 10N Load Cell Load applied at 0.4mm/sec Load/Extension and mode of failure recorded
  11. 11. Mechanical Testing - Results The mean maximum load to failure of the hard/soft interface in the control group was 0.33N (+/-0.24) and 0.23N (+/-0.10) in the AMA group. No statistically significant difference was demonstrated between groups (p=0.371). 0 0.1 0.2 0.3 0.4 Control AMA MaximumLoad(N) Treatment
  12. 12. Collagen content There was no difference between groups with respect to ug of hydroxyproline per mg of tissue Control 35.76ug +-10.19, AMA 31.7ug +/- 8.49, p=0.72 0 5 10 15 20 25 30 35 40 45 group D group E ughyppermgoftissue
  13. 13. Discussion AMA had no significant effect on cellular proliferation , collagen content, or on the mechanical properties of the interface. In contrast to previous work. However these animal studies used human amniotic fluid or membrane rather than a micronized preparation and also investigated mid-substance tendon healing rather than the specifically investigating the bone/tendon interface.
  14. 14. Limitations Dose of AMA restricted by cost In vitro study so not the whole picture Model only evaluates fibroblasts No inflammatory component
  15. 15. Future Directions Localised AMA delivery - Anchor encased in 150uL of fibrin containing a single dose of 26uL of AMA
  16. 16. Mechanical Testing - Localised AMA A trend towards increased maximum load to failure was seen in the AMA group but this was not significant (control 0.20N (+/- 0.13), fibrin 0.21N (+/-0.02), fibrin + AMA 0.29N (+/-0.02) 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 Control Fibrin Fibrin+AMA MaximumLoad(N) Treatment
  17. 17. Conclusions No benefit of AMA at a maximum cost effective dose for clinical application. Model allows easy in vitro assessment of potentially therapeutic agents but has some limitations.

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