Contemporary Outcomes of Highly Porous Metaphyseal Cones in Revision Total Knee Arthroplasty: A Systematic Review and Meta-Analysis.

Abstract

Metaphyseal bone loss represents a major reconstructive challenge in revision total knee arthroplasty (RTKA). Highly porous metaphyseal cones have potential for osseointegration and durable fixation. While early evidence was limited to tantalum cones, newer designs, such as three-dimensional-printed titanium cones, have been introduced by multiple manufacturers, necessitating an updated synthesis of the literature. PubMed, Scopus, and Cochrane databases were searched from inception through October 1, 2024. Eligible studies included randomized controlled trials and observational cohorts reporting clinical or radiological outcomes of metaphyseal cones in RTKA with a minimum 1-year follow-up. Demographics, implant characteristics, functional scores, survivorship, cone removal rates, and radiographic outcomes were recorded. Pooled analyses were performed using random-effects models, with subgroup analyses by cone material and fixation type. There were 63 studies comprising 4,433 patients and 5,435 cones that were included, with 79.9% of femora and 75.4% of tibiae involving Anderson Orthopaedic Research Institute Type 2B or 3 defects. Significant improvements in function were observed, with pooled Knee Society Score Knee and Function scores of 77.4 (95% confidence interval [CI], 70.6 to 84.3) and 67.5 (95% CI, 58.4 to 76.6), respectively. The pooled all-cause re-revision rate at a weighted mean follow-up of 49.7 months was 13.5% (95% CI, 11.0 to 16.2%), most commonly due to infection, while cone removal occurred in 3.6% (95% CI, 2.2 to 5.2%), with aseptic loosening accounting for only 0.7%. Radiographic osseointegration was achieved in 96.0% (95% CI, 92.5 to 98.5%). Subgroup analyses demonstrated no significant difference in survivorship between tantalum versus titanium cones (3.7% versus 2.2%, P = 0.199), or cemented versus hybrid fixation (4.7 versus 1.9%, P = 0.274). Modern metaphyseal cones have high osseointegration rates and implant survivorship in RTKA. Failure due to aseptic loosening is exceedingly rare, with infection being the predominant cause of cone revision. These findings support metaphyseal cones as a reliable solution for managing severe bone loss in RTKA, with comparable outcomes noted across different cone materials and fixation strategies.