Perspective

MRI abnormalities not always indicative of ankle ACI results

Researchers found mean AOFAS scores improved 39.4 points from preoperative to postoperative.

After patients underwent ankle autologous chondrocyte implantation, they had clinical improvements despite the presence of abnormalities on their MRIs.

“While MRI is an important tool in the postoperative assessments of [autologous chondrocyte implantation] ACI grafts, the various MRI abnormalities we see must be interpreted with caution because they do not always correlate to how well the patient is doing,” Richard D. Ferkel, MD, told Orthopedics Today.

Ferkel and colleagues compared the appearance of 24 grafts at a mean of 65.8 months after ACI performed for osteochondral talus lesions with preoperative MRI to evaluate the lesions for fill, surface regularity, signal pattern, bone marrow edema, subchondral plate irregularity and the presence of cystic lesions. Researchers measured clinical outcomes with the American Orthopaedic Foot and Ankle Society clinical outcome score.

Results showed more than 75% defect fill in 92% of the grafts and 75% and 25% of the grafts had a mildly irregular or moderately irregular articular surface, respectively. In addition, 96% of graft repair tissue had a heterogenous signal pattern, of which 58% were layered and 38% were mottled.

“One of the things we did see was 58% of the patients had decreased bone marrow edema or decreased swelling in the bone, so 21% or five patients still had some increase in the bone marrow edema,” Ferkel said. “We had hoped ... everybody would have no bone marrow edema, but some did.”

An abnormal subchondral bone plate was found in most grafts. Results showed 10 grafts had focal defects, seven grafts had slight depressions and five grafts had both focal defects and slight depressions. The investigation showed an increase in cystic lesions in seven grafts and no change, a decrease in cysts or no cysts in the other grafts.

The mean postoperative AOFAS score was 87.5 points. Mean improvement was 39.4 points. – by Casey Tingle

Disclosure: Ferkel reports no relevant financial disclosures.

After patients underwent ankle autologous chondrocyte implantation, they had clinical improvements despite the presence of abnormalities on their MRIs.

“While MRI is an important tool in the postoperative assessments of [autologous chondrocyte implantation] ACI grafts, the various MRI abnormalities we see must be interpreted with caution because they do not always correlate to how well the patient is doing,” Richard D. Ferkel, MD, told Orthopedics Today.

Ferkel and colleagues compared the appearance of 24 grafts at a mean of 65.8 months after ACI performed for osteochondral talus lesions with preoperative MRI to evaluate the lesions for fill, surface regularity, signal pattern, bone marrow edema, subchondral plate irregularity and the presence of cystic lesions. Researchers measured clinical outcomes with the American Orthopaedic Foot and Ankle Society clinical outcome score.

Results showed more than 75% defect fill in 92% of the grafts and 75% and 25% of the grafts had a mildly irregular or moderately irregular articular surface, respectively. In addition, 96% of graft repair tissue had a heterogenous signal pattern, of which 58% were layered and 38% were mottled.

“One of the things we did see was 58% of the patients had decreased bone marrow edema or decreased swelling in the bone, so 21% or five patients still had some increase in the bone marrow edema,” Ferkel said. “We had hoped ... everybody would have no bone marrow edema, but some did.”

An abnormal subchondral bone plate was found in most grafts. Results showed 10 grafts had focal defects, seven grafts had slight depressions and five grafts had both focal defects and slight depressions. The investigation showed an increase in cystic lesions in seven grafts and no change, a decrease in cysts or no cysts in the other grafts.

The mean postoperative AOFAS score was 87.5 points. Mean improvement was 39.4 points. – by Casey Tingle

Disclosure: Ferkel reports no relevant financial disclosures.

    Perspective
    Hollis G. Potter

    Hollis G. Potter

    The investigators demonstrated a variable [magnetic resonance] MR appearance despite good clinical results, thus suggesting the MRI results must be interpreted with caution. The benefit of MRI following cartilage repair is to provide an objective assessment of the biologic integration of the tissue, as well as any host-mediated response. It is not uncommon that objective outcome variables do not correlate with more subjective patient-reported outcome measures (PROMs). The discordance between clinical (subjective) and imaging (objective) results is often a function of individuals who report good function and limited symptoms despite the presence of suboptimal graft appearance on imaging. Such findings are common when correlating clinical PROMs to imaging in osteoarthritis of the ankle, knee or hip. Limitations of the study include a single-point long-term follow-up and the lack of parametric mapping techniques, which provide a noninvasive assessment of implant biochemistry. Cell-based techniques, such as ACI, characteristically have better fill compared to microfracture, particularly in the ankle, and this finding is corroborated by the authors results. MRI remains an important objective assessment of any cartilage repair procedure.

    • Hollis G. Potter, MD
    • Chair, department of radiology and imaging Hospital for Special Surgery New York

    Disclosures: Potter reports no relevant financial disclosures.