The patellar tendon bone-tendon-bone graft has been the "gold standard" graft choice for ACL reconstructions since it became common practice in the mid-1980. It has been used extensively by surgeons since that time and still remains the graft of choice for a high number of orthopedists who perform this surgery regularly. The patellar tendon 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 incision based just along the medial border of the tendon... The middle third of the tendon 10-11 mm wide is then removed along with 2-2.5 cm long bone blocks still apart of the tendon at each end of the graft from the tibial tubercle and the outer surface of the patella. This gives a composite bone-tendon-bone graft that has very strong insertion points of the tendon soft tissue into bone. The tensile strength of this graft has been measured by Noyes (1984) to be about 2950 Newton’s to failure, versus the strength of an intact ACL at 2160 N. What happens to the remaining patellar tendon after a third of it has been removed? Over 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. Surgeons have even been able to re-harvest another patellar tendon graft from the original tendon once enough time has passed for tendon reconstitution (although there's now evidence that this repaired tissue may not be as strong as normal patellar tendon tissue). 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. 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 inserted next to the bone plug (like 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 "gold standard" graft isn't perfect, however. There may be more pain associated with this donor site than from any of the other graft choices. As a result there is sometimes 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 patellar tendon ruptures, as well as fracturing the patella both intraoperative 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 and sensitivity that can occur at the incision site and should probably consider an alternative graft choice. One of the bigger issues with patellar tendon grafts that recently has a number of orthopedists switching to alternative grafts is the incidence of anterior knee pain when patients try to resume athletic activities. Specifically there are some studies5 showing an increased rate of patellofemoral pain and/or...
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