Biomechanics of the proximal interphalangeal joint after total joint replacement

Abstract

Introduction Small joints arthroplasty of the hand including the proximal interphalangeal joint (PIPJ) is associated with the need to create anatomically adapted structures using optimal materials. Introduction of a new medical device requires comprehensive preclinical testing.The objective was to determine a range of loads allowed for the proximal interphalangeal joint after arthroplasty through analyzing the biomechanics to prevent critical conditions and complications.Methods A full-ceramic non-constrained anatomically adapted proximal interphalangeal joint implant was developed between 2016 and 2021 using an integrated approach with preclinical trials and a clinical study of 42 patients (25 males, 17 females) with PIPJ arthritis. A digital endoprosthesis was created with 3D-modelling. Critical conditions for the digital model imitating typical joint movements were explored with the use of finite element method and the findings to be employed in clinical practice.Results A stable biomechanical construct was intact with loads of 5 kilograms and a motion ranging from 0 to 60 degrees, with loads of 20 kilograms and a motion ranging between 0 and 30 degrees. Cortical bone could sustain loads up to 20 kilograms with a motion ranging between 0 and 60 degrees. Discussion Load capacity of the implant was explored considering the strength of bone tissue and zirconium ceramics as a material. The study set a vector for the development of the optimal mode of motor activity early after surgery and indicated the optimal range of motion to be applied after PIPJ arthroplasty.Conclusion The load up to 5 kg was optimal for the patient to be applied early after surgery with the range of flexion measuring less that 90°. The patient could use a load of 5 to 20 kg with flexion in the proximal interphalangeal joint measuring less than 30°. Endoprosthetic components were likely to get dislocated with a load of 20 kg and flexion angle of greater than 30°. Periprosthetic fracture could occur with flexion angle of greater than 60°.