Ultrasound Evaluation of Elbow After Cartilage Transplantation for Osteochondritis Dissecans
Athletes involved in overhead throwing sports are at risk for a problem at the elbow called osteochondritis dissecans (OCD). Baseball pitchers and racket-sport players are affected most often. Sometimes gymnasts who put weight through the arms develop this condition, too. It can be very disabling. Treatment that enables them to return to full participation in their sport is a challenge.
The forceful and repeated actions of these sports can strain the surface of the elbow. Specifically, the capitellum is affected. The capitellum is a knob at the end of the humerus (upper arm bone). It forms the upper part of the elbow that fits into the cup-shaped depression on the head (top) of the radius bone. The radius runs from the outer edge of the elbow down the forearm to the thumb-side of the wrist. The joint formed by the connection of these two bones is called the humeroradial joint.
With repetitive shearing and compressive force on the capitellum, the bone under the joint surface weakens and becomes injured. This, in turn, damages the blood vessels going to the bone. Without blood flow, the small section of bone dies. The injured bone cracks. It may actually break off. The result is osteochondritis dissecans (OCD).
If the condition isn't treated or if treatment fails, the humeroradial joint can become unstable. The articular surface of the radial head is made of stiffer cartilage than the cartilage of the capitellum. Some experts say that's why the capitellum side of the joint is affected rather than the radial head side. However, as the capitellum breaks down, the humeroradial joint can shift and even dislocate.
The two main goals in treatment are to regain pain free elbow motion and function (short-term goal) and prevent osteoarthritis from developing later (long-term goal). Conservative (nonoperative) care isn't always successful meeting the first goal. Despite a long period of rest from throwing or weight-bearing, very few patients make it back to their sports activities.
And even with surgery to remove or reattach the broken pieces, very few athletes are able to return to full sports participation. For this reason, newer methods of treatment are being explored. Autologous osteochondral mosaicplasty is one approach that may help athlete regain full function again.
In the mosaicplasty procedure, the surgeon takes plugs of bone and cartilage from the patient's knee and transfers it to the elbow. The word autologous refers to the fact that the graft comes from the patient (not from a donor). This method sounds good in theory. But there are some questions about using cartilage from one joint to help heal cartilage in another joint. Is the knee cartilage the same stiffness as the elbow cartilage? Will it hold up under repetitive force?
In this study, ultrasound is used to assess the tissue quality of the plugs before and after grafting. This may be the first study evaluating the material properties of autologous osteochondral plugs transplanted in humans (a fairly uncommon procedure). Material properties refer to stiffness or roughness of the cartilage.
The advantage of ultrasound imaging is that it can measure cartilage stiffness, roughness, and thickness. Degeneration of the articular cartilage can be determined from the signal intensity, duration, and interval. For example, decreased signal intensity and prolonged signal duration are two indicators of cartilage degeneration.
Ten young (ages 10-19) male baseball players were tested. They all had been diagnosed with osteochondritis dissecans and treated with autologous osteochondral mosaicplasty. Various ultrasound measures of cartilage were taken. The researchers tested the healthy cartilage of the capitellum, the OCD lesion, the radial head, the donor site in the knee, and the osteochondral plug after grafting.
Here's what they found:
The authors conclude that ultrasound evaluation of OCD can help identify areas of degeneration before they can be seen with X-rays. Although ultrasound shows the mechanical properties of cartilage (stiffness, thickness, roughness), it must be done during surgery when the surgeon has access to the cartilage and plug grafts.
The invasive nature of this type of testing may help identify treatment methods that are successful but probably won't be used to diagnose the problem. Finding ways to speed up diagnosis and get treatment started sooner is still a valuable goal. The end result may be faster and more complete recovery. Long-term follow-up of mosaicplasty using plugs from the knee placed in the patient's own elbow will be the next step in this study. The authors plan to report their findings at a later date.
References: Kohei Nishitani, MD, et al. Intraoperative Acoustic Evaluation of Living Human Cartilage of the Elbow and Knee During Mosaicplasty for Osteochondritis Dissecans of the Elbow. An In Vivo Study. In The American Journal of Sports Medicine. December 2008. Vol. 36. No. 12. Pp. 2345-2353.Back