Synovial Membrane Microarthroscopy of the Equine Midcarpal Joint:Technique Application and Evaluation of Four Vital Stains

Abstract

The objectives of this study were to evaluate the feasibility of microarthroscopy in the equine midcarpal joint using the vital stains methylene blue, trypan blue, neutral red, and Janus green B, to describe the components of the lamina propria, vascular architecture, and types of synoviocytes of the synovium. Microarthroscopy of both left and right midcarpal joints of ten horses was performed, with and without vital staining of the synovium. Four vital stains (methylene blue, trypan blue, neutral red, and Janus green B) were evaluated, with each stain randomly placed in five joints. Biopsy specimens of synovium were harvested from the dorso-medial and the dorso-lateral aspects of the joint prior to completion of the procedure. Horses were recovered from anesthesia. All dyes were biocompatible. At 60x without vital staining, the surface topography, vascular network, and translucency of the synovium were observed. Intra-articular vital dyes improved the evaluation of the surface topography of the synovium. At magnification of 150x with vital staining, individual synoviocytes were identified clearly with all dyes, except with neutral red. Methylene blue provided the best in vivo microscopic differentiation of the structure of the intima. Trypan blue had superior retention in formalin processed biopsies. Methylene blue, trypan blue, neutral red, and Janus green B stains can be used safely for microarthroscopy. Good visualization of cells and vascular network can be obtained by microarthroscopy. Microarthroscopic evaluation of the synovium compares favorably with conventional histological evaluation of biopsy specimens. Microarthroscopy is a valuable tool for both research and clinical diagnoses of equine articular diseases.