Progressive chondrocyte death after impact injury indicates a need for chondroprotective therapy.
BACKGROUND
Impact injury to articular cartilage can lead to posttraumatic osteoarthritis.


OBJECTIVE
This study tests the hypotheses that (1) chondrocyte injury occurs after impact at energies insufficient to fracture the cartilage surface, and that (2) cartilage injury patterns vary with impact energy, time after injury, and cartilage thickness.


METHODS
Controlled laboratory study.


METHODS
Fresh bovine osteochondral cores were randomly divided into 5 groups: (1) control, (2) 0.35 J, (3) 0.71 J, (4) 1.07 J, and (5) 1.43 J impact energies. Cores were subjected to computer-controlled impact loading and full-thickness sections were then prepared and incubated in Dulbecco's Modified Eagle's Medium/F12 at 37 degrees C. Adjacent sections were harvested 1 and 4 days after impact for viability staining and fluorescent imaging. The area of dead and living chondrocytes was quantified using custom image analysis software and reported as a percentage of total cartilage area.


RESULTS
The highest impact energy fractured the cartilage in all cores (1.43 J, n = 17). Seventy-three percent and 64% of the osteochondral cores remained intact after lower energy impacts of 0.71 J and 1.07 J, respectively. At lower energy levels, fractured cores were thinner (P <.01) than those remaining intact. In cores remaining intact after impact injury, chondrocyte death increased with increasing impact energy (P <.05) and with greater time after impact (P <.05). A progressive increase in dead cells near the bone/cartilage interface and at the articular surface was observed.


CONCLUSIONS
These data showing progressive chondrocyte death after impact injury at energies insufficient to fracture the cartilage surface demonstrate a potential need for early chondroprotective therapy.


CONCLUSIONS
These data show that efforts to reduce chondrocyte morbidity after joint injury may be a useful strategy to delay or prevent the onset of posttraumatic osteoarthritis.
Cartilage Restoration Center, Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, PA 15261, USA.
Michal
M
Szczodry
Christian H
CH
Coyle
Scott J
SJ
Kramer
Patrick
P
Smolinski
Constance R
CR
Chu
D000818:Animals; D002358:Cartilage, Articular / Q000293:injuries*; D002417:Cattle; D019902:Chondrocytes / Q000473:pathology*; D018450:Disease Progression; D009336:Necrosis / Q000517:prevention & control; D010003:Osteoarthritis / Q000503:physiopathology; D011897:Random Allocation; D014947:Wounds and Injuries / Q000473:pathology*