The effect of angled osteochondral grafting on contact pressure: a biomechanical study.
BACKGROUND
Flush osteochondral plugs can reduce contact pressure compared with an empty defect in the articular cartilage. However, incongruities such as graft angulation have an unknown effect.


OBJECTIVE
Incongruity of the articular cartilage after osteochondral transplantation affects articular surface contact pressure.


METHODS
Controlled laboratory study.


METHODS
An 80-N load was applied with a material testing system for 120 seconds to the femoral condyles of 50 fresh swine knees. Contact pressures were measured using Prescale super low film. Five conditions were tested: (1) intact articular surface; (2) surface with 4.5-mm-diameter circular defect; (3) defect grafted with a flush 4.5-mm-diameter plug from the contralateral condyle; (4) defect grafted with a 30 degrees angled 4.5-mm-diameter plug, with lower edge flush (tip elevated with respect to the adjacent surface); and (5) defect grafted with a 30 degrees plug, with tip flush to the adjacent surface (lower edge sunk). Angled grafts were obtained using a rotational bearing vise aligned with a 30 degrees fixed-angle track. The film was digitally scanned and analyzed, and standard statistical tests were performed.


RESULTS
Mean peak pressures of intact cartilage (8.57 kg/cm2), flush graft (9.81 kg/cm2), and sunk and angled graft (9.15 kg/cm2) were not significantly different (P < .5). The mean pressures for defects (12.01 kg/cm2) and the elevated angled graft (14.50 kg/cm2) were significantly (P < .05) higher than that of intact cartilage.


CONCLUSIONS
Slightly sunk grafts were still able to reduce elevated contact pressures to normal levels. However, elevated angled grafts increased contact pressure. These results suggest that it is preferable to leave an edge slightly sunk rather than elevated.
Koh
Jason Lee
JL
Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA. kohj1@hotmail.com
Kowalski
Adam
A
Lautenschlager
Eugene
E
D000818:Animals; D001696:Biomechanical Phenomena; D002358:Cartilage, Articular / Q000637:transplantation*; D007719:Knee Joint / Q000601:surgery*; D013552:Swine; D014481:United States; D016474:Weight-Bearing