A new study suggests that the current rehabilitation used for patients undergoing tendon-bone repairs such as rotator cuff repair may be partially to blame for the high rates of failed healing after surgery. Experiments in a rat model of this injury suggest that immobilising the limb for four to six weeks after surgery, rather than quickly starting physical therapy, improves healing.
“Before we did this study, we thought that delaying motion for a short period of time, seven to ten days, and then starting physical therapy would be the most beneficial to tendon healing. However, from the data in this study, it appears we should be immobilising our patients for longer periods of time,” said Scott Rodeo, M.D., of the Sports Medicine and Shoulder Service at Hospital for Special Surgery (HSS) in New York City.
To explore the timing of post-operative rehabilitation, investigators at HSS conducted experiments using a rat model of patellar tendon injury and repair. The investigators used a small metal frame to hold the joint in place and then used a specially designed motorised device to precisely apply loads of strain. One group of rats received a low load 50 times per day (analogous to a leg extension with no weight), another group received a moderate load 50 times per day and a third group had their joint immobilised for the entire study period. The researchers found that rats that had their joint immobilised had the best healing with significantly less fibrocartilage or scar tissue than rats in the other two groups. Scar tissue is weaker than original tissue, and oftentimes scar tissue forms at the interface between bone and tendon during tendon repair surgery. The rats that were immobilised also had better connective tissue organisation, higher load to failure, better bone mineral density, and fewer dead cells in the area that was operated on. During the healing and inflammatory process, there is a regeneration and remodeling of tissues, which sometimes involves cell death that can lead to inflammation.