OUTCOMES AFTER FIRST METATARSOPHALANGEAL JOINT FUSION FOLLOWING FAILURE OF CARTIVA HEMIARTHROPLASTY

Arthritis of the great toe metatarsophalangeal joint (MTPJ) remains the commonest arthritic condition of the foot with significant impact on patients lives. Arthrodesis has remained the mainstay of surgical treatment of this condition. However, Polyvinyl Alcohol (PVA) hydrogel arthroplasty of the 1st metatarsophalangeal joint has become a valid and mainstream means of surgical treatment of hallux rigidus. However, the literature outlines concerns regarding the conversion to arthrodesis with other hemiarthroplasty and total 1st MTPJ arthroplasty implants due to the increased complexity of arthrodesis with regards to bone loss and the need for bone grafting. The primary aim of this study is to to determine the outcomes of patients who had subsequent revision surgery to fusion for failure of this implant. Secondarily, we aim to document the medium to long term survivorship of 1st MTPJ Cartiva arthroplasty in a single foot and ankle unit at an academic centre. We retrospectively reviewed all MTPJ arthroplasty procedures performed by our unit since the commencement of Cartiva hemiarthroplasty in 2009 to June 2021. From a total of 197 identified, 173 cases were included in the study. A full chart review was conducted to determine if conversion to fusion had taken place during follow up. For the subset of patients who went on to an arthrodesis, we calculated the time to revision surgery, fixation method and use of bone graft or graft substitute. The X-rays at last follow up were reviewed to determine whether union has been achieved. The pre Cartiva, pre revision and post revision X-rays were reviewed to measure the length of the 1st metatarsal and ray. Visual analogue scale for pain, Foot and Ankle Ability Measure (FAAM) - sport and activities of living (ADL) sub scales along with short form 36 physical functioning score (SF-36 PFS) were collected to determine functional outcomes. We noted a 10 year revision free survivorship of 82.3%. Of the 16 patients who underwent revision to fusion, 4 (26.6%) patients developed a non union, all of whom were symptomatic and required revision. All these patients went on to fusion after re-revision. The Cartiva procedure resulted in no significant loss of the metatarsal length with an average loss of height of 0.88 mm. The average SF-36 PCS was 39.5 at latest follow up, with a FAAM ADL score of 77.2, and a FAAM SDL of 59.4. The average VAS pain score following 1st MTPJ fusion for failed Cartiva hemiarthroplasty was 3.3. Although we noted no significant loss of metatarsal length or complexity of surgery converting a failed Cartiva to fusion, we noted a higher non union rate and worse functional outcomes compared to primary arthrodesis of the 1st MTPJ.