Authors:

Prem N Ramkumar, MD, Riley J Williams, MD

Abstract:

The authors and Cartiheal Ltd – the implant developer and study funding source – should be applauded for achieving what so many aspire to perform but so few meaningfully execute: a prospective, randomized multicenter international clinical trial. Moreover, doing so with 97% follow-up over a two-year span should be lauded as well, particularly since the outcome metrics include heterogeneous elements: multiple patient-reported outcome instruments (KOOS, IKDC), advanced imaging (MRI), and reoperation rates (treatment failures). Additionally, the design and development of an off-the-shelf implant from a derivative of coral exoskeleton warrants unique appreciation. Repurposing a natural element to deliver a “farm-to-table” solution for what attempts to solve the greatest quandary in orthopaedics – articular cartilage loss – is, at worst daringly clever and, at best, the holy grail.

The lofty goals of this novel biphasic, porous implant lend to a unique clinical context that trickles down to unique strengths and limitations. It is important to recognize that this implant is not attempting to only address focal articular cartilage lesions. Rather, this study and this implant are attempting to address femoral cartilage loss both focally (i.e. Kellgren-Lawrence 0 or 1) – and geographically (i.e. Kellgren-Lawrence 2 or 3) – in the condyles and/or trochlea for adults from a broad range of ages (21 to 75) and lesion size (>3cm2 or <3cm2). Herein lies the dilemma. There exists no consensus “surgical standard of care” for a patient population with this broad a range of cartilage pathology. In the setting of osteoarthritis where there exist multiple femoral foci, one could argue the “surgical standard of care” is a partial or total knee arthroplasty. For focal articular cartilage lesions, the “surgical standard of care” has been well-demonstrated to be osteochondral autograft transfer (i.e. OATS, mosaicplasty),2 with ample room to include consideration of osteochondral allograft or autologous chondrocyte implantation. However, the surgical standard of care in either scenario is certainly not microfracture – especially for lesions > 3cm2.1 Despite the accessibility and cost-effectiveness of microfracture, this operation has predictably rapid deterioration in clinical results at the timepoint the study concludes (2 years postoperatively).3 Thus, clinical superiority is unsurprising and overstates the implant impact. A more appropriate comparison would be to stratify patients by age and lesion characteristics, then compare the PROMs of the novel implant to the appropriate comparison procedure: osteochondral autograft or arthroplasty. Additionally, two details warrant scrutiny: (1) the inclusion criteria clearly restricts patients up to 3 chondral lesions yet Figure 1 illustrates a knee with 4 scaffold implants; (2) 8 of the 12 authors possess financial conflicts with the implant designer that funded the study, which introduces notable bias.

Agili-C represents an exciting, unique, and ambitious solution attempting to mitigate focal and geographic chondral lesions, but the jury remains out on its clinical effectiveness in the absence of no comparison to osteochondral autograft or arthroplasty. Regardless, comparison to a predictably flawed surgical option in microfracture is no real comparison at all.

You can order the original study here:

In Knee-Joint Surface Lesions, an Aragonite-Based Scaffold Improved Clinical and Radiographic Outcomes at 24 Months Versus Microfracture and Debridement