A new lesser metatarsophalangeal joint replacement arthroplasty design - in vitro and cadaver studies

Background Isolated degenerative joint disease and/or Freiberg’s infraction of the lesser metatarsophalangeal joint, although not frequent may become debilitating in the younger individual. Currently, once conservative management fails, the mainstay of treatment is debridement and excision-interposition arthroplasty. Replacement arthroplasty has been ineffective in the long term as the joints are subject to severe repetitive fatigue loading over small articulating surfaces through a wide range of motion. This is an in vitro and cadaver study of a new design replacement arthroplasty developed by the senior author. The aim of this study is to evaluate this novel replacement arthroplasty of the lesser metatarsophalangeal joint in a laboratory setting and cadaver implantation. Methods This three-component mobile bearing device is made of titanium and high density polyethylene which evolved over 4 years. It was subjected to 5,000,000 cycles in a laboratory under physiological and excessive forces to assess resistance to fatigue failure and wear pattern of the polyethylene liner. Following these tests, it was implanted in 15 fresh frozen cadavers at various stages of its development, during which the surgical technique was perfected. Range of motion and stability was tested using custom made instrumentation in four cadavers. The implant was inserted in a further two cadavers by an independent foot and ankle surgeon to check reproducibility. Results The device showed almost no signs of wear or surface deformation under physiological forces. The surgical technique was found to be simple and reproducible in the cadaver trial. The average dorsiflexion was 28.5° and 28.9° pre- and post-implant respectively. The average plantar flexion was 33.8° and 20.8° pre- and post- implant respectively. The joints were stable both pre- and post-operatively. Post-operative stability was objectively assessed for dorsal displacement and dorsiflexion using a 5 kgf (49 N) and was found to be excellent. Conclusion This novel lesser metatarsophalangeal joint replacement arthroplasty has been developed as an option in the surgical treatment of symptomatic degenerative joint disease and/or Freiberg’s infraction resistant to conservative treatment. The implant was found to be durable and resistant to wear in the laboratory testing. The cadaver studies have shown it to require minimal specialized instrumentation with good surgical reproducibility. This proof of concept study is the basis for clinical trials.

Patient Outcomes Following Polyvinyl Alcohol Hydrogel Implant of the Lesser Metatarsals

Category: Lesser Toes; Other Introduction/Purpose: Lesser toe metatarsal phalangeal (MTP) joint pathology presents a challenge for surgical treatment. Recently, synthetic cartilage implants have been shown to be safe and efficacious in treating hallux ridigus, offering pain relief while preserving motion at the MTP joint. At our institution, metatarsophalangeal joint arthroplasty using a polyvinyl alcohol (PVA) hydrogel implant has been utilized in the 2nd and 3rd MTP joints for advanced arthritis, failed management of Freiberg’s infraction, and osteochondral defects. We present a case series describing the clinical outcomes of 12 patients following PVA implantation of the 2nd or 3rd MTP. Methods: We retrospectively identified 12 consecutive patients (13 joints) who underwent PVA hydrogel implantation of the 2nd (n=12) or 3rd (n=1) metatarsal head between 2017 and 2019. PVA implant was indicated for advanced arthritis in 6 patients (7 joints), Freiberg’s infraction in 4 patients, and osteochondral defect in 2 patients. Average age was 51 years (range, 20-67), with 100% females. Patient-reported outcomes measurement information system (PROMIS) scores were collected preoperatively and at latest follow-up, with an average follow-up of 20.4 months (range, 8.3 to 29.2). Retrospective chart review was performed to evaluate postoperative complications, including need for revision, implant removal, and persistent pain. Results: Overall, patients demonstrated mean improvement in all PROMIS domains, with a significant improvement in Pain Intensity of 11.9 points (p=0.03) postoperatively. A total of 4 postoperative complications occurred in the 12 patients: one case of AVN at 2 years postoperatively, one revision with removal of the implant and bone grafting of the second metatarsal head at 1 year postoperatively, one periprosthetic fracture at 9 months postoperatively, and one recurrence of pain requiring ultrasound- guided injection at 7 months postoperatively. Three additional patients reported persistent pain postoperatively. Conclusion: This study represents the largest case series to date evaluating the use of PVA hydrogel implant in the surgical correction of lesser toe MTP joint pathology. While the PVA implant presents a viable option in the setting of advanced arthritis, Freiberg’s infraction, and certain osteochondral defects, it is not without complications. The specific indications for use of the PVA implant should be carefully considered before implantation.

Outcomes of Polyvinyl Alcohol Hydrogel Implant of the Lesser Metatarsals

Background: Lesser toe metatarsophalangeal (MTP) joint pathology presents a challenge for surgical treatment. At our institution, arthroplasty using a polyvinyl alcohol (PVA) hydrogel implant has been utilized in the second and third MTP joints for advanced arthritis, failed management of Freiberg’s infraction, and osteochondral defects. We present a case series describing the clinical outcomes of 13 patients following PVA implantation of the second or third MTP. Methods: We retrospectively identified 13 patients (14 joints) who underwent PVA hydrogel implantation of the second ( n = 12) or third ( n = 2) metatarsal between 2017 and 2019. The average age was 49 (range, 20-67) years, with 100% females. Patient-Reported Outcomes Measurement Information System (PROMIS) scores were collected preoperatively and at an average of 21.1 (range, 8.3-29.2) months postoperatively. Clinical outcomes were also evaluated. The average time to clinical follow-up was 24.7 (range, 7-35.8) months. Results: On average, patients demonstrated pre- to postoperative improvement in all PROMIS domains, with significant improvements in Pain Intensity ( P = .01) and Pain Interference ( P = .01). Five postoperative complications were observed: 1 case of persistent avascular necrosis, 1 revision with implant removal and bone grafting, 1 periprosthetic fracture, and 2 recurrences of pain requiring ultrasound-guided injection. Conclusion: This study represents the largest case series to date evaluating the use of PVA implant in the surgical correction of lesser toe MTP joint pathology. While the PVA implant presents a viable option in the setting of advanced arthritis, Freiberg’s infraction, and certain osteochondral defects, it is not without complications. The specific indications for use of the PVA implant should be carefully considered. Level of Evidence: Level IV, case series.