Watch for These If You Perform Subchondroplasty of the Knee

What’s the Claim

A large case series of arthroscopically assisted subchondroplasty procedures (calcium phosphate injection into the subchondral bone) for arthritis-associated bone marrow lesions of the knee found 73% (95% CI 67% to 79%) 5-year survivorship free from conversion to TKA. Survivorship was poorer (62%) for those who already had Grade 4 chondral lesions and in particular for those older than 50 with exposed bone (59%) at the time of arthroscopy.

How’s It Stack Up?

Other studies on this topic have varied in quality, and most had a shorter duration of follow-up than did this one, but these survivorship estimates do seem in range with those published by others. An earlier study shared similarly cautionary findings about performing this procedure in patients with more advanced chondral damage. That series of 22 patients who had Grade 3 or 4 cartilage loss and bone marrow lesions did poorly, with nearly half having poor or fair Tegner scores at very short-term follow-up (median 12 months, range 6 to 24 months).

What’s Our Take?

We’re leery of this procedure — as was the commentator whose essay accompanied publication of this case series, as was a recent systematic review, which concluded that there was “insufficient evidence to recommend subchondroplasty in clinical practice.” The current study was published after that systematic review and so wasn’t included in it, but we’re not sure it’s enough to move the needle on that recommendation. Remember, survivorship estimates in a study like this must be considered a best-case estimate, since these procedures were performed by someone very experienced with the technique, some patients may have been revised elsewhere, and revision itself is a crude endpoint. The last point is important, since some patients, especially younger ones with few options, choose to live with a painful knee rather than pull the trigger on a knee replacement early in life. That said, the procedure has its passionate advocates, and this series offers good, practical guidance to those surgeons, since it identified patients who seem not to be good candidates for the procedure — those who are older than 50 and those with advanced chondral damage. Consider avoiding the procedure in those patients since, once again, the percentages shared in this study may be somewhat rosy, relative to what one might obtain in real-world practice.

Source

Wood DS, Paulson S, Nolan JR, Spanyer J, Harm RG, Heis FT. What Factors are Associated With Conversion to Knee Arthroplasty After Subchondroplasty? Clin Orthop Relat Res. Published online February 7, 2023.

Further Commentary

Ries MD. CORR Insights®: What Factors are Associated With Conversion to Knee Arthroplasty After Subchondroplasty? Clin Orthop Relat Res. Published online February 17, 2023.