The Rate of Subsequent Hallux Interphalangeal Joint Fusion after First Metatarsophalangeal Fusion: A Large-Scale National Database Study

Category: Midfoot/Forefoot; Other Introduction/Purpose: The development of adjacent joint arthritis following arthrodesis is a universal concern in orthopaedic surgery. Arthrodesis of the hallux metatarsophalangeal (MTP) joint is an effective and commonly performed treatment for first MTP arthritis and other conditions. Despite its widespread use, the risk of symptomatic degeneration at the interphalangeal joint remains undetermined and is a common question from patients considering the procedure. This study investigated the rate of subsequent hallux interphalangeal joint (IPJ) fusion following arthrodesis of the first MTP joint using a large commercial database. Methods: Patients who underwent hallux interphalangeal arthrodesis after hallux metatarsophalangeal arthrodesis were identified from a large national commercial insurance database using CPT code identification (PearlDiver). The Kaplan-Meier curve for survivorship free of subsequent interphalangeal fusion was generated covering 10 years from the index operation. Results: Of 87,890 patients who had first metatarsophalangeal arthrodesis, 808 patients (0.91%) subsequently underwent subsequent hallux interphalangeal joint arthrodesis within 10 years. Because CPT codes were reported without laterality, it is possible that a small subset of patients may have undergone a subsequent contralateral IP fusion, and therefore this result should be regarded as an upper limit of the possible rate. Conclusion: This is the first large-scale data to address the common patient concern of subsequent degeneration of the interphalangeal joint following metatarsophalangeal fusion. The rate of subsequent fusion is less than 1%, a result that highlights the durability of the clinical result of the first MTP fusion and should reassure patients and surgeons considering the procedure relative to motion-sparing alternatives.