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.
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
Related Posts:
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
Stephen,
I am always on the fence when interpreting the results found within a study conducted on animals however having read this article I found some positive relief.
Though I have not used LIPUS following a rotator cuff repair, let alone at all, I am still fascinated by what it brings to the table.
Based on the results I am more willing to try LIPUS as a preoperative and postoperative measure. I understand that there were no reported cases of infection or tendon avulsion however I am interested about the negative effects that have been produced as a result of LIPUS application, in humans or animals. I believe results like that could help shed light on whether the application of LIPUS is higher reward than risk so to speak.
In addition, aside from the statistics showing improvement as a result of the LIPUS treatment these results were based on growth and repair. The study did not assess biomechanical progression. I would like to see a study conducted over a longer period of time that includes strength and ROM as well as a comparison to a control group that did not receive LIPUS. Hopefully a study like that could shed some light on further aspects of rehabilitation down the road beyond a month post op (possibly with humans as well).
The authors concluded that LIPUS is a “simple, feasible, noninvasive yet an economical treatment…” to my knowledge I’m drawing a blank as to what other noninvasive treatment, if there is one, it is being compared to. I am also interested in comparing the efficacy of LIPUS to that treatment as well as the risks associated with them.
All in all I found this study to be interesting and informative causing possible clinical application conclusions to be drawn.
What is your experience with LIPUS, outcomes and general thoughts on the modality?
William thanks for the comment. To my knowledge there are not real risks associated with LIPUS which is a huge advantage. Knowing that it cant do any harm makes it attractive in the clinic.
I agree more research is clearly needed in both animals and humans. Biomechanical data of the tendon would be very interesting. Based on the improvements in the bone I would guess that the tendons mechanical properties were improved since it has been shown that poor bone footprint properties result in repair failure of the rotator cuff.
Personally I have not used it previously with rotator cuff repair patients but I would be will to try it in the future.