Objectives: To investigate the potential role of a commercially available preparation of micronized Amniotic Membrane Allograft (AMA) (Amniofix, MiMedx, USA) in the biological augmentation of an in vitro model of rotator cuff repair with respect to cellular pro- liferation, collagen content and mechanical properties of the bone- tendon interface.
Methods: The in vitro model consisted of artificial bone-tendon constructs (BTC). These were manufactured using a brushite anchor. (bone substitute) and a chick tendon fibroblast-seeded fibrin gel (tendon substitute). BTC were maintained with supplemented culture medium. The treatment group received 26 ll of AMA every 2–3 days. This dose was calculated on a 1 vial per rotator cuff strategy, using published data on the area of the rotator cuff footprint and adjusted for the surface area of the BTC interface. Bone-tendon interface strength was tested at 4 weeks using an Instron microtester. The collagen content of the BTC and cellular proliferation of fibroblasts were assessed using colorimetric assays.
Results: No significant effect on cellular proliferation was noted with the addition of AMA to fibroblasts in culture (p = 0.7). There was no significant difference between the mean maximum loads to failure of the bone-tendon interface in the control group (0.33 N (± 0.24)) and the AMA group (0.23 N (± 0.10)) (p = 0.371). There was no sig- nificant difference in the mean quantity of hydroxyproline per milligram of tissue in the control group (31.7 lg/mg) and the treat- ment group (35.8 lg/mg) (p = 0.72).
Conclusions: Biological augmentation of cuff repair in order to improve clinical outcomes is currently highly topical. Evaluation of the efficacy of proposed agents in an in vitro model is convenient and allows assessment of the mechanical properties of the bone-tendon interface as well as the effect on fibroblast proliferation and collagen content of the tissue.
The use of AMA in this in vitro study has not shown any benefit that would support its potential in improving the biology of cuff repair.