The effects of Low-intensity Pulsed Ultrasound on tendon-bone healing in a transosseous-equivalent sheep rotator cuff model

Lovric V, Ledger M, Goldberg J, Harper W, Bertollo N, Pelletier MH, Oliver RA, Yu Y, Walsh WR.  Knee Surg Sports Traumatol Arthrosc. 2012 Mar 31. [Epub ahead of print]

Rotator cuff tears occur frequently and have a high rate of re-tears.  It has been very difficult to achieve effective rotator cuff healing not to mention reestablish the native tendon-bone interface following a cuff repair.  There has been attempts at optimizing the rehabilitation following cuff repair to improve success, however, no study has examined the application of low-intensity pulsed ultrasound (LIPUS) following cuff repair.  Therefore, the objective of this study was to examine the effects of LIPUS on the early phases of tendon-bone healing in a sheep model.
Eight sheep underwent detachment and immediate reattach of the infraspinatus tendon.  The infraspinatus tendon in sheep is similar to the supraspinatus in humans.  Half (n = 4) of the animals were given LIPUS and the other half (n = 4) did not receive any treatment.  The LIPUS treatment was started the day following surgery and was administered 5 days a week for a duration of 20 minutes per day.  The LIPUS was delivered at 30 mW/cm2 in 200-µs bursts of sine waves at a frequency of 1.5MHz and a 0.2 duty cycle during each treatment.  Twenty-eight days post-surgery micro-CT, histology, and immunohistochemistry were performed on all animals.  They found increased bone mineral density at the rotator cuff footprint in the LIPUS group compared to the control group. They also found that the LIPUS group had an improved histological appearance compared to the control group.  They observed thicker regions of woven bone and increased osteoblast activity.  There was also more established Sharpey’s fibers in the transition region of tendon to bone.  The immunohistochemistry results found an increased amount of vascular endothelial growth factor (VEGF), RUNX2, and Smad4 in the LIPUS group.  Each of these proteins have been associated with improved bone healing. 

This is an interesting study that examines the use of LIPUS to improve rotator cuff tendon to bone healing following surgical repair.  LIPUS is a modality that has been seen frequently in sports medicine.  It has seemed to be most effective treating bone fractures but has been used to treat soft tissue injuries as well.  The rotator cuff insertion site is a unique location that incorporates soft tissue and bone.  These unique characteristics may optimize both the soft tissue and bone effects of the LIPUS to improve rotator cuff healing.  In addition, there are several studies demonstrating signs of degeneration in both the torn tendon and the bone of the rotator cuff footprint in chronically torn rotator cuff tendons.  This further suggests that LIPUS may have the potential to improve healing by increasing cell proliferation of both the bone and tendon.  Although it wasn’t examined in this study, the use of LIPUS preoperatively may be warranted in chronically torn tendons that undergo severe degeneration and have a poor prognosis.  However, due to the small sample size and the short time point of 28 days following surgery, there is clearly more research that needs to be done to fully understand the mechanisms through which LIPUS leads to improved rotator cuff healing.  Have you used LIPUS following rotator cuff repair?  Have you had success? 

Written by:  Stephen Thomas
Reviewed by:  Kyle Harris

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Lovric, V., Ledger, M., Goldberg, J., Harper, W., Bertollo, N., Pelletier, M., Oliver, R., Yu, Y., & Walsh, W. (2012). The effects of Low-intensity Pulsed Ultrasound on tendon-bone healing in a transosseous-equivalent sheep rotator cuff model Knee Surgery, Sports Traumatology, Arthroscopy DOI: 10.1007/s00167-012-1972-z