This is the editor's interpretation of a paper published in the orthopaedic literature in 2017 - our attempt to make relevant medical articles accessible to lay readers. If you wish to read the original it is easy to ask your librarian to obtain a reprint for you from any medical library.

This publication gives the outcomes of a group of patients over 35 years of age with isolated, full thickness defects of the femoral condyle roughly half of whom were treated with biological methods to encourage joint cartilage restoration while the other half were managed with a focal metallic resurfacing implant. The biological methods included microfracture, osteochondral autograft transplantation, osteochondral allograft, and autologous chondrocyte implantation. The two groups were matched according to treatment location, defect grade and size, and age profile, and the outcomes followed for an average of 2.6 years in the biological group and 2.0 years in the implant group.


Why the study was undertaken

In young people like this an isolated full-thickness cartilage defect poses a dilemma. Despite the limited defect size, the symptoms suffered by these patients can match those who are scheduled for knee replacement, but the patients are not in the age group where a partial knee replacement or a total knee replacement would be considered. If left alone, however, such focal lesions tend to progress and eventually become arthritis, so the study was undertaken to see to what degree current biological methods reduce symptoms when compared to the small metal resurfacing implants that are currently available.



The patients in the study were very carefully selected to avoid including any individuals where there were other factors that might compromise the issue at question - so for example if there was more than one defect, any alignment problem with the leg (eg varus or valgus) or any medical or metabolic problem that might interfere with the outcomes.



In the biological group (30 patients) the surgeons were all experienced in biological interventions of this sort, and all the patients had their surgery in the same institution and the procedures were recorded in the institutional cartilage registry. In each patient only one biological intervention was performed for each person - microfracture in fifteen individuals, osteochondral autograft transplantation [OAT] in two, debridement in two, autologous chondrocyte implantation [ACI] in one, and osteochondral allograft in ten. However 63% had had some prior procedure in the knee. This group had a significantly greater body mass index than the implant group, but in other respects they were well matched.

In the implant group (32) patients were treated with the HemiCAP focal femoral condyle resurfacing prosthesis. The procedures were performed in 8 US centres by 12 surgeons. 84% had had some prior procedure in the knee.

Patients were scored according to their outcomes, and the authors note that  "(p)atients were considered a success if they improved by at least 20% in the Western Ontario and McMaster Osteoarthritis Index (WOMAC) pain and function subdomains in the study knee and did not undergo any subsequent defect or implant-related procedures during the course of a 2-year follow-up period."



The authors conclude that - "(t)he study showed that focal metallic resurfacing resulted in similar clinical outcomes when compared with biologic procedures for the treatment of focal chondral lesions of the femoral condyle in a matched group of patients." What is interesting is that the implant goup showed "significantly better clinical success and required fewer subsequent procedures."


Limitations of the study

The study had some limitations. Most of the patients had had prior work on their relevant knee. for example, the biological techniques themselves were not really comparable, and patients in the OAT group did better than the other biological procedures. However, it remains an interesting study.