Fate of the Patellar Tendon after ACL SurgeryIf you tear the anterior cruciate ligament (ACL) in your knee, chances are the doctor will use part of your patellar tendon as a graft to repair it. The patellar tendon is located between the kneecap and the lower leg bone. The middle third portion is taken out and used to replace the torn ACL.
What happens to the patellar tendon? Does it grow back? This study takes a long-term look using repeated MRIs of the donor site in 19 patients over a period of six years. They report on the thickness, width, and appearance of the middle portion of the patellar tendon. The donor site was compared to the patellar tendon on the healthy knee.
The researchers thought they would see a normal donor site six years after healing. Other studies have not shown a normalization of the site in the short-run. Longer studies show the tendon increases in thickness up to two years later.
The authors report that the tendon tries to adapt by getting wider and thicker on either side of the gap. The size of the hole gets smaller starting as early as six weeks after surgery. At six years there's still some thinning in the center of the tendon. The thickness on the sides returned to normal at nearly six years. The extra width stayed the same, and the center was still thinner than on the normal side.
The authors conclude that a harvested patellar tendon doesn't return to normal. It does remodel itself even after two years, but the tissue quality is lower than normal. If the patient ruptures the repaired ACL, tissue to repair it again should come from someplace else (such as the hamstring tendons behind the knee). It's not advised to take more tissue from the first donor site.
Michael Svensson, MD, et al. Does the Patellar Tendon Normalize after Harvesting Its Central Third? A Prospective Long-Term MRI Study. In The American Journal of Sports Medicine. January/February 2004. Vol. 32. No. 1. Pp. 34-38.
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