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    Is a Synthetic Cartilage Implant an Appropriate Treatment Option for Patients with Hallux Rigidus?

    A recently published retrospective study evaluated early outcomes and complications of the CARTIVA hydrogel synthetic cartilage implant in the treatment of hallux rigidus for patients in the US.

    Authors

    John F. Dankert, MD, PhD; Yoshiharu Shimozono, MD; and John G. Kennedy, MD, MCh, MMSc, FFSEM, FRCS(Orth)

    Article

    Cassinelli SP, Chen S, Charlton TP, and Thordarson DB. Early outcomes and complications of synthetic cartilage implant for treatment of hallux rigidus in the United States. Foot Ankle Int. 2019 Oct; 40(10): 1140-1148.

    Summary

    A hydrogel-based synthetic cartilage implant (CARTIVA SCI, Wright Medical Group; Memphis, Tennessee) was approved as a treatment option for hallux rigidus by the US Food and Drug Administration in July 2016.

    This decision was based on findings from a prospective randomized controlled non-inferiority study performed by Baumhauer et al [1] involving patients at institutions in the United Kingdom and Canada. The study authors found that the synthetic cartilage implant provided pain relief and functional outcomes equivalent to those of first metatarsophalangeal arthrodesis with safety events.

    A recently published study by Cassinelli et al sought to evaluate patient experience with the synthetic cartilage implant in the US. This single-center, single-surgeon study identified a cohort of 60 patients (52 female and 8 male) who had received a total of 64 synthetic cartilage implants between August 2016 and August 2018.

    Exclusion criteria for the study were a hallux valgus angle of more than 20° and concomitant bunion correction. The mean follow-up time was 18.5 months (range 12 to 30 months). Patient-reported Outcomes Measurement Information Scores (PROMIS) for physical function and for pain interference were available for 66% (42/64) and 63% (40/64) of patients, respectively, for their most recent follow-up appointments.

    Outcomes of this study were less impressive than the original Level I prospective clinical trial:

    • 14% (9/64) of patients were very satisfied
    • 28% (18/64) were satisfied
    • 20% (13/64) were neutral
    • 11% (7/64) were unsatisfied
    • 11% (17/64) were very unsatisfied

    PROMIS physical function scores averaged 42 at 15.2 months of follow-up, equating to “mild dysfunction,” and PROMIS pain interference averaged 60 at 15 months of follow-up, equating to “mild pain.”

    Postoperative treatments were also reported in this retrospective study:

    • 52% (33/64) of patients had at least 1 corticosteroid injection for ongoing pain after surgery
    • 20% (13/64) of patients underwent a reoperation with implant removal
    • 8% (5/64) of patients underwent arthrodesis

    One patient was noted to have a subsided implant with bony contact between the proximal phalanx and metatarsal head. A second patient was noted to have a subsided and damaged implant with pathology demonstrating a foreign body giant cell reaction and neovascularization.

    Clinical Relevance

    Growing evidence indicates that a hydrogel-based synthetic cartilage implant may not function well in all patients with hallux rigidus and that it may lead to early implant subsidence, osteolysis of the surrounding bone, continued inflammation, and ongoing pain. These implant-related complications were not reported in the original Level I prospective clinical trial, but they have been found in other studies such as the recently published article by Cassinelli et al, which is among the first to evaluate the synthetic cartilage implant in a US patient population.

    Limitations noted in the study by Cassinelli et al include its retrospective nature, short follow-up, single-surgeon cohort, and multiple concurrent procedures as confounding factors in select patients. Preoperative PROMIS level of function scores also were not collected until midway through the study. Furthermore, in preoperative counseling, the study authors advised patients that they would have a 90% chance of having a good result while maintaining motion. More modest preoperative counseling may have led to a higher postoperative satisfaction level.

    In conclusion, although the synthetic cartilage implant had promising early results in a Level 1 prospective trial in the treatment of hallux rigidus, more-recent literature is describing less-favorable outcomes, with catastrophic failure of the implant in many patients.

    This literature, coupled with our own experience with the implant system, has led us to take meticulous care in patients selection for using the synthetic cartilage implant in the treatment of hallux rigidus. Additional animal-based and long-term follow-up studies are necessary to determine which patients can safely receive this synthetic cartilage implant.

    Author Information

    John F. Dankert, MD, PhD, is an orthopaedic surgery resident in the Department of Orthopaedic Surgery at NYU Langone Health, New York, New York. Yoshiharu Shimozono, MD, is an attending foot and ankle orthopaedic surgeon in Japan and research fellow working with Dr. John Kennedy at NYU Langone Health. John G. Kennedy, MD, MCh, MMSc, FFSEM, FRCS(Orth), is a Professor in the Department of Orthopaedic Surgery at NYU Langone Health. He is also the Chief of the Division of Foot and Ankle Surgery at NYU Langone Health.

    Disclosures: The authors have no disclosures relevant to this article.

    Reference

    1. Baumhauer JF, Singh D, Glazebrook M, Blundell C, De Vries G, Le IL, Nielsen D, Pedersen ME, Sakellariou A, Solan M, Wansbrough G, Younger AS, Daniels T; for and on behalf of the CARTIVA Motion Study Group. Prospective, randomized, multi-centered clinical trial assessing safety and efficacy of a synthetic cartilage implant versus first metatarsophalangeal arthrodesis in advanced hallux rigidus. Foot Ankle Int. 2016; 37(5):457-469.