The Journal of Bone and Joint Surgery (American) 84:1782-1787 (2002)
© 2002 The Journal of Bone and Joint Surgery, Inc.
A Biomechanical Analysis of Four Different Methods of Harvesting Bone-Patellar Tendon-Bone Graft in Porcine Knees
Kirti Moholkar, MS, FRSCI,
David Taylor, PhD,
Myra O'Reagan, MSc, PhD and
Gary Fenelon, FRCSI
Investigation performed at the Department of Orthopaedics, St. James's Hospital, and the Departments of Mechanical and Manufacturing Engineering and Statistics, Trinity College, Dublin, Ireland
Kirti Moholkar, MS, FRCSI
Gary Fenelon, FRCSI
Department of Orthopaedics, St. James's Hospital, James Street, Dublin 8, Ireland. E-mail address for K. Moholkar: kmoholkar{at}hotmail.com Please address requests for reprints to K. Moholkar.
David Taylor, PhD
Myra O'Reagan, MSc, PhD
Departments of Mechanical and Manufacturing Engineering (D.T.) and Statistics (M.O'R.), Trinity College, Dublin, Ireland
The authors did not receive grants or outside funding in support of their research or preparation of this manuscript. They did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.
Background: Anterior cruciate ligament reconstruction with use of bone-patellar tendon-bone graft is commonly performed to treat functional instability of the knee after injury of the anterior cruciate ligament. Patellar fracture is an underreported complication of this procedure, yet it may be a career-ending injury for a professional athlete. The purpose of this study was to design a new technique to procure the patellar bone plug when reconstructing the cruciate ligament with use of patellar tendon.
Methods: Fifty-eight knees were harvested from eighteen to twenty-four-month-old pigs. Bone plugs of four geometrical shapes were cored out of the patellae from forty knees (four plug shapes for each of ten knees). Ten knees had no graft removed. Fifty knees were tested for the effects of a single impact. Eight knees (two plug shapes for each of four knees) were tested for the effects of repeated impacts. Data were analyzed statistically with use of an ordinal logistic model. The probability of impact failure of the patella at different energy levels was calculated.
Results: Impact energy has been shown to have a significant effect on the outcome (p < 0.001). When controlling for energy level, there was a significant difference between the sharp and round corners (p < 0.01). The ordinal logistic model was found to be very good for predicting the outcome of impact testing. The impact energy required to create a 1% probability of complete fracture was 7 J for a patella with a sharp-cornered plug defect, 17 J for a patella with a trapezoidal plug, 22 J for a patella with a sharp-cornered defect with a drill-hole at the corner, 40 J for a patella with a round-cornered defect, and about 49 J for a normal patella. Repeat impact testing substantially damaged the patellae with sharp-cornered defects, as they failed earlier at a lower energy and after a lower number of impacts than did the patellae with round-cornered defects.
Conclusions: We propose the use of the round-cornered patellar bone plug when bone-patellar tendon-bone graft is harvested for anterior cruciate ligament reconstruction, to further reduce the small likelihood of a patellar fracture occurring intraoperatively or in the early postoperative rehabilitation phase.

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