PEMF is currently approved by the FDA for adjunctive treatment of lumbar/cervical spine fusion and for treatment of long-bone non-unions. Soft tissues are a potential new therapeutic application for PEMF due to pre-clinical studies showing a reduction of inflammatory markers following PEMF exposure. The aim was therefore to investigate the structural/functional effects of PEMFs on tendon-to-bone and tendon-to-tendon healing in a rotator-cuff (RC) and Achilles tendon (AT) repair model, respectively. RC study: Adult male rats (n=280), underwent bi-lateral supraspinatus tendon transections with immediate repair followed by cage activity until sacrifice (4, 8, and 16 weeks). Non-controls received PEMF for 1, 3, or 6 hours daily. AT study: Male rats underwent acute, complete transection and repair of the Achilles tendon (FULL, n=144) or full thickness, partial width injury (PART, n=160) followed by immobilization for 1 week. Sacrifice was at 1, 3, and 6 weeks. Outcome measures included passive joint mechanics, gait analysis, biomechanical assessments, histological analysis of the repair site and mCT (humerus) assessment (FULL only). RC study: Significant increases in modulus, stiffness, bone mineral content and improved collagen organization was observed for the PEMF groups. No differences in joint mechanics and ambulation were observed. AT study: A decrease in stiffness and limb-loading rate was observed for the PEMF groups for the FULL groups, whereas an increase in stiffness with no change in range-of-motion was seen for the PART groups. The combined studies show that PEMF can be effective for soft tissue repair but is dependent on the location of application.
Rotator cuff tears are common injuries which often require surgical repair. Unfortunately, repairs often fail [1] and improved repair strength is essential. P2 Porous titanium (DJO Surgical, Austin TX) has been shown to promote osseointegration [2,3] and subdermal integration [4]. However, the ability of P2Porous titanium to aid in supraspinatus tendon-to-bone repair has not been evaluated. Therefore, the purpose of this study was to investigate P2 implants used to augment supraspinatus tendon-to-bone repair in a rat model [5]. We hypothesized that supraspinatus tendon-to-bone repairs with P2 implants would allow for ingrowth and increased repair strength when compared to standard repair alone. Thirty-four adult male Sprague-Dawley rats were used (IACUC approved). Rats received bilateral supraspinatus detachment and repair with one limb receiving P2 implant. Animals were sacrificed at time 0 (n=3), 2 weeks (n=8), 4 weeks (n=9) and 12 weeks (n=14). Limbs were either dissected for histological and SEM analysis or mechanical testing as described previously [5]. Specimens for histology and SEM were embedded in PMMA for tissue-implant interface analysis. Specimens were first viewed in SEM under BSE to detect bony ingrowth, then stained with Sanderson's Rapid Bone Stain and viewed under transmitted and polarized light for tissue ingrowth. Comparisons were made using Student's t-tests with significance at p≤0.05.INTRODUCTION
METHODS
