Objective—To determine the critical temperature that reduces chondrocyte viability and evaluate the ability of chondrocytes to recover after exposure to the critical temperature.
Sample Population—Cartilage explants obtained from the humeral heads of 30 sheep.
Procedures—In a randomized block design, 318 full-thickness cartilage explants were collected from 30 humeral heads of sheep and cultured for up to 14 days. On the first day of culture (day 0), explants were subjected to temperatures of 37°, 45°, 50°, 55°, 60°, or 65°C for 5 minutes by heating culture tubes in a warming block. The ability for chondrocytes to recover after exposure to the critical temperature was determined by evaluating viability at days 0, 1, 3, 7, and 14 days after heating. Images were analyzed by use of confocal laser microscopy.
Results—Analysis of images revealed a significant decrease in live cells and a significant increase in dead cells as temperature increased. Additionally, the deepest layer of cartilage had a significantly lower percentage of live cells, compared with values for the 3 most superficial layers. Chondrocytes did have some ability to recover temporarily after the initial thermal insult.
Conclusions and Clinical Relevance—A strong relationship exists between increasing temperature and cell death, with a sharp increase in chondrocyte death between 50° and 55°C. Chondrocytes in the deepest cartilage layer are most susceptible to thermal injury. The threshold of chondrocyte recovery from thermal injury is much lower than temperatures reached during chondroplasty by use of most radiofrequency energy devices.
Objective—To evaluate the use of hydrothermal ablation
of articular cartilage for arthrodesis in horses
through investigation of the effects of joint lavage
with physiologic saline (0.9% NaCl) solution (80°C) for
various treatment times on chondrocyte viability in
the articular cartilage of the metacarpophalangeal and
metatarsophalangeal joints of cadaveric horse limbs.
Sample Population—7 pairs of metacarpophalangeal
and 8 pairs of metatarsophalangeal joints
from 8 Thoroughbreds.
Procedure—The horses were euthanatized for reasons
unrelated to musculoskeletal disease. On a random
basis, 1 joint of each pair underwent intra-articular
lavage for 5, 10, or 15 minutes with heated saline
solution (80°C); the other joint underwent sham treatment
of similar duration with saline solution at 22°C
(control). Cartilage samples from the distal articular
surface of metacarpus III (or metatarsus III), the proximal
surface of the proximal phalanx, and the lateral
and medial proximal sesamoid bones were assessed
for chondrocyte viability via confocal microscopy and
viability staining following enzymatic digestion.
Results—Compared with the control joints, findings
of both viability assays indicated that the percentage
of sites containing viable chondrocytes in heat-treated
joints was decreased. Treatment hazard ratios of 0.048
(confocal microscopy) and 0.2 (digestion assay) were
estimated. Histologically, periarticular soft tissues had
minimal detrimental effects after heat treatment.
Conclusions and Clinical Relevance—Ex vivo intraarticular
lavage with saline solution at 80°C resulted in
the death of almost all articular chondrocytes in the
joint. This technique may be a satisfactory method for
extensive cartilage ablation when performing
arthrodesis by minimally invasive techniques. (Am J Vet Res 2005;66:36–42)