Important Factors Affecting Outcomes of OAT Treatment for the Heel
Holes referred to as "defects" in cartilage and bone can be treated with a technique called osteochondral autograft transfer or OAT. Efforts are being made to identify factors that might predict a good or favorable result.
Osteochondral lesions refer to damage or defects to the joint cartilage (chondral) that go all the way down to the first layers of bone (osteo). Holes in the osteochondral layer and/or loose fragments of bone and cartilage in the joint can cause pain, locking of the joint, and eventually osteoarthritis.
Osteochondral autograft transfer (OAT) involves removing a plug of cartilage and bone from a healthy area (in this case from a non-weight bearing area of the knee) and transferring it into the osteochondral lesion (i.e., hole in the surface of the same patient's joint). The word "autograft" refers to the fact that the patient donates his or her own tissue for the procedure.
In this study from Korea, surgeons used a second arthroscopic examination a year later to evaluate the results of this procedure used on the talus (ankle bone). It is rare that a second-look arthroscopic exam is possible so the results of this study are important. Quality of bone and cartilage graft were evaluated using the second arthroscopy instead of MRI in order to get a better look at the results.
Using an analysis of many patient variables, the researchers were able to determine the most important factors affecting the final results. They investigated the role of age, gender, body mass index (BMI), duration of symptoms, severity (depth and size) and location of lesion, and presence of bone cysts as predictive factors of outcomes. They also looked at results based on patient satisfaction, pain, function, and activity level.
So what did they find? Ninety-five per cent (95%) of the group reported good-to-excellent outcomes. The most important factor in the result of the OAT procedure was actually a surgical effect. The surgeon must restore the joint surface smoothly, evenly, and anatomically accurately.
Impingement (pinching) of the surrounding soft tissues must be avoided. The graft shape and size must match the defect as closely as possible. And the graft must be covered over carefully with a patch to prevent "uncovered" areas. It seems that any gaps or uncovered spots quickly fill in with fibrous cartilage. The result is an unstable defect area.
Although a second-look arthroscopy is an invasive procedure, it does provide an opportunity to treat any problems present, especially mismatching of the joint surfaces. Fibrous adhesions causing impingement can be removed. And any uneven margins can be smoothed over. Any gaps where the graft meets the defect can be filled in.
The authors suggest longer-term studies (beyond the one-year mark) in order to evaluate changes and look for influencing factors that might not show up in the first 12-months. They also commented that their study was fairly small in terms of number of patients (52 ankles). Therefore the study should be repeated with a larger number of subjects before accepting these results as the final word on the subject.
Yong Sang Kim, MD, et al. Factors Associated with the Clinical Outcomes of the Osteochondral Autograft Transfer System in Osteochondral Lesions of the Talus. Second-Look Arthroscopic Evaluation. In The American Journal of Sports Medicine. December 2012. Vol. 40. No. 12. Pp. 2709-2719.