Abstract
0.9% Saline and Hartmann’s are commonly used joint irrigating solutions during articular surgery. The objective of the study was to determine whether the osmolarity of these solutions affects chondrocyte death in mechanically injured articular cartilage.
The osmolarity of 0.9% Saline (285 mOsm) and Hartmann’s (255 mOsm) solutions was varied from 100–600 mOsm by the addition of distilled water or sucrose. Osteochondral explants (rectangular blocks, n=72) harvested from the metacarpophalangeal joints of six different three-year old cows were exposed to prepared solutions of different osmolarity for 2 minutes to allow in situ chondrocytes (cells embedded within their native extracellular matrix) to respond to the altered osmotic environment. Explants were then mechanically injured through the full thickness of articular cartilage with a fresh scalpel and incubated in the same solution for 2.5 hours. Using confocal laser scanning microscopy (CLSM) and fluorescent probes to determine cell viability, percentage cell death (PCD, 100 × number of dead cells/number of dead and live cells) was quantified within the full thickness of mechanically injured articular cartilage as a function of solution osmolarity.
Cell death was localised to the superficial zone (first 100 microns from the articular surface) of injured cartilage for explants exposed to the control 0.9% Saline (285 mOsm) and Hartmann’s (255 mOsm) solutions, with relative sparing of the middle and deep zones (analysis of variance (ANOVA), p< 0.05). Compared to the control explants exposed to 0.9% Saline, PCD in the superficial zone was greatest for the low osmolarity (100 mOsm) saline solution and least for the high osmolarity (600 mOsm) saline solution (ANOVA, p=0.04). PCD in the superficial zone significantly decreased for explants exposed to 600 mOsm solutions of 0.9% Saline and Hartmann’s, compared to their respective control solutions (p< 0.05 for paired comparisons). There was no significant difference in the PCD between 600 mOsm solutions of 0.9% Saline and Hartmann’s (p=0.5).
Increasing the osmolarity of 0.9% Saline and Hartmann’s solutions is chondroprotective in a surgically relevant model of mechanical cartilage injury. These experiments have important clinical relevance for the design of irrigation solutions during arthroscopic and open articular surgery.
Correspondence should be addressed to Dr Roger Bayston, Division of Orthopaedic and Accident Surgery, Queen’s Medical Centre, Nottingham, NG7 2UH, England.
