Pulsed carbon dioxide laser for cartilage vaporization and subchondral bone perforation in horses. Part II: Morphologic and histochemical reactions.

This research investigated the use of a pulsed carbon dioxide laser to vaporize cartilage and perforate subchondral bone in horses and observed the subsequent morphological and chemical changes. It found that vaporizing cartilage resulted in rapid regrowth, with minimal impact on surrounding tissues, whereas drilling into subchondral bone led to poor penetration and significant damage.

Experimental Procedures

• Eight horses were used for this experiment, with articular cartilage vaporized in four and both cartilage and subchondral bone perforated in the other four.
• Intercarpal joints were arthroscopically examined, with a 1cm cartilage crater or a series of holes created in the third carpal bone of one joint, while the contralateral carpus acted as control.
• Following euthanasia at week eight, the treated and control joints were examined for gross changes and samples of cartilage and subchondral bone, synovial membrane, and peripheral lymph nodes were studied histologically.
• The depletion of glycosaminoglycan, a substance crucial for the cartilage matrix, was assessed through safranin-O histochemical staining.

Findings

• The results showed that cartilage removal via laser vaporization resulted in quick regrowth, producing fibrous and fibrovascular tissues and occasional regions of fibrocartilage at the end of eight weeks.
• The surrounding structures – the subchondral bone, synovial membrane, and draining lymph nodes – appeared to be essentially unaffected by the laser-induced vaporization procedure, indicating both the precision and the minimal collateral damage of the technique.
• In contrast to vaporization, carbon dioxide laser drilling of subchondral bone resulted in poor penetration and extensive thermal necrosis – tissue death due to heat.
• Significant secondary damage was also noticed on the apposing articular surface of the radial carpal bone due to the laser drilling procedure, emphasizing the unsuitability of the procedure for penetrating bone structures.

Conclusions

• This research demonstrates the potential use of pulsed carbon dioxide lasers for cartilage vaporization with minimal side effects and fast recovery.
• At the same time, it highlights the disadvantage and potential risks associated with using the same method for penetrating into subchondral bone, due to its poor penetration and extensive tissue damage.
• The finding emphasizes the importance of considering the specificity of different tissues’ physical and biological properties when designing novel medical procedures.