Patellar Tendon Graft

The patellar tendon bone-tendon-bone graft has consistently demonstrated excellent surgical outcomes with a 90-95% success rate in terms of returning to pre-injury level of sports. A patellar tendon graft is harvested through a 3-4" long vertical incision based just along the medial (inside) border of the tendon. This procedure begins by harvesting through two shorter horizontal incisions centered over each end of the tendon. The middle third of the tendon 10-11 mm wide is then removed longitudinally along with 2-2.5 cm long bone blocks in continuity at each end of the graft from the tibial tubercle and the outer surface of the patella respectively. This yields a composite bone-tendon-bone graft that has very strong insertion points of the tendon soft tissue into bone.

Advantages

One of the advantages of this construct is that because the bone-tendon interface is quite strong, the surgeon only has to fix the block of bone in the bone tunnel rather than trying to fix the soft tissue itself. A headless screw is simply inserted next to the bone plug (think of it as a square peg in a round hole) to interference fit and locks the bone in place. The patellar tendon fibers are thereby immediately secured and are stable enough to begin motion and weight bearing when tolerated. The ends of the graft heal bone-to-bone in around 6-8 weeks, which appears to be quicker than the healing process for soft tissue-to-bone. Interference screws are now available in a bioresorbable material that actually dissolves within the bone over 2 to 3 years.

The course of three to four months after surgery the tendon regenerates or “grows back.” Initially it seems to overgrow into a thick, large tendon that then remodels back to a more normal contour by 12-18 months postoperatively. Hence patellar tendon ruptures at the donor site are unlikely after the first few months post-op. Patellar tendon ruptures can and do occur however during the initial 6-8 weeks after surgery if the remaining tendon is stressed too hard.

Disadvantages

There is apparently more pain associated with this donor site than from any of the other graft choices, particularly compared to the hamstring tendons. As a result there is typically a greater initial atrophy or wasting response of the quadriceps muscle compared to say either a hamstring or cadaver allograft. This can require more prolonged physical therapy to recover from and could possibly delay the initial return to sports. The incision (scar) is bigger, and almost all patients end up with a permanent loss of sensation 2-3" in size just lateral to the incision. There is a risk of fracturing the patella both intraoperatively as well as postoperatively, although bone grafting the defect in the patella at the time of surgery has reduced the incidence of the latter. Patients who kneel a lot for a living are often unhappy with the patellar tenderness that can persist for up to two years and should probably consider an alternative graft choice. One of the bigger issues is that there is an increased rate of patellofemoral pain and/or tendonitis of the patellar tendon with stairs, jumping, skiing and other such activities 6-12 months out from surgery. Ultimately these are often treatable with continued strengthening, rest from sports, and time, but these symptoms can delay the expected time of return to sports.