Pyrocarbon Radial Head Arthroplasty offers satisfactory clinical and radiological outcomes with low Revision Rate: A Systematic Review

Abstract

Introduction: Pyrocarbon promises to be an optimal material choice for radial head arthroplasty (RHA) due to an elastic modulus comparable to the radial diaphysis and thus providing higher biocompatibility. Primary objective was to determine the complications and revision rates related to the usage of these prostheses. The secondary objective was to assess the clinical and radiological outcomes of Pyrocarbon RHAs.

Hypothesis: Pyrocarbon RHAs have good clinical and radiological outcomes with low complications and revisions.

Methods: Ovid MEDLINE and Embase databases were used to search for studies on outcomes and complications of the RHAs using Pyrocarbon radial head prostheses. The systematic review was designed in accordance with the PRISMA guidelines and included studies were appraised using the MINORS tool. Complications and RHA revision rates were assessed. Functional outcomes were reviewed using PROMs (like MEPI, DASH and BMS), post-op range of motion (using goniometer) and grip-strength (using the dynamometer). Post-operative radiological outcomes like peri-prosthetic lucency, radial neck osteolysis, radio-capitellar congruence, capitellar erosion, overstuffing/understuffing and osteoarthritis were reported using radiographs.

Results: A total of 12 studies cumulatively reporting 353 patients who underwent Pyrocarbon RHAs were included in the review. The mean age of patients across the studies ranged from 47 years to 54 years of which 50.5% were males. The majority of radial head replacements were done for acute trauma (87.5%) with the remainder done for arthritis (1.7%) and trauma sequelae (10.8%). Mean follow-up period in the selected studies ranged from 18 months to 110 months with minimum follow-up across all studies being 12 months. MoPyC (Modular Pyrocarbon, Tornier™) was the implant of choice in ten studies while two studies used the Ascension Pyrocarbon radial head (Ascension Orthopaedics™). Ten studies demonstrated mean MEPI ranging from 75.5 to 96. Mean extension deficit ranged from 6 to 19 degrees, mean flexion from 120 degrees to 140 degrees, mean pronation from 71 to 87 degrees and mean supination from 63 to 85 degrees. Relative grip strength ranged from 69% to 96% of the contralateral limb. Revisions due to implant-related reasons (intra-prosthetic dissociation, prosthetic fracture, peri-prosthetic loosening, radio-capitellar subluxation and under-stuffed/over-stuffed elbow) was 6.4% (24/353). Radial stress shielding and peri-prosthetic lucency was reported in 10% to 100% of patients across different studies but symptomatic implant loosening leading to revision remained rare (2%, 7/353). Radio-capitellar congruence was reported in 81% to 100% cases while capitellar erosion ranged from 0% to 89%. Pyrocarbon implants specific complications included head-neck intra-prosthetic de-coupling (1.1%) and pyrocarbon head fractures (0.9%). 4.2% cases underwent re-surgery due to non-RHA related reasons.

Discussion: The pyrocarbon RHA shows good functional outcome, range of motion and low revision rates. This aligns with the working hypothesis of this review. However, pyrocarbon radial head implants have implant-specific complications like pyrocarbon radial head fractures and intra-prosthetic decoupling between stem and head. Despite promising in-vitro biomechanical properties, capitellar wear is still a common finding with a pyrocarbon RHAs. Despite these factors, pyrocarbon radial head implants are a viable alternative for radial head arthroplasty.