What Happens to the Patellar Tendon Gap After ACL Harvest?…and other common ACL questions.

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A common question regarding ACL reconstructions is,  “does the patellar tendon gap heal after the central third is harvested for an ACL graft? This is a great question because as you can see in the photos below one of the patellar tendons appears normal when the quad is on tension, while the other has an obvious gap.  Before I get into answering this question let me explain the difference between the appearance of these knees.  The first photo is of a Right knee that is approximately 2 years post-op and the central third was harvested using two horizontal incisions at the ends of the patellar tendon, the second photo is of a Left knee that is approximately 7 months post-op using a traditional vertical incision, both girls are high school soccer players.  Upon physical examination the Right knee feels normal, while the Left knee has a palpable gap.

Knee ACL patellar tendon 3
Knee ACL patellar tendon

 The consensus in the research (1,2,3,4,5,6,7) is that the tendon gap will gradually fill in with tendon-like tissue and be nearly healed between 2 & 3 years.  Tendon healing begins as soon as 6 weeks to 6 months and may include some scar tissue. Cerullo 1995, and Adriani 1995, both found early signs of scarring on the gap at 1 year or less. Kartus 1999, measured the gap via MRI and found it to be 9mm at 6 weeks, 5mm at 6 months and 2mm at 2 years.  However the same author also concluded in a later study that at 2 years the tendon is still showing signs of active healing but has not healed enough for reharvestSvensson 2004, also agreed that reharvesting the same tendon is not recommended even at 6 years, as the tendon is still in the process of healing.

What about suturing the tendon?  Brandsson 1998, found that there is no benefit to closing the gap in terms of post-op morbidity, functional outcomes or patellofemoral pain.  In the prior mentioned study by Cerullo 1995, sutured harvest sites developed scarring of the entire patellar tendon at 6 months, which can reduce the biomechanical properties of the tendon.  The group of subjects that had the gap left open only developed localized scarring on the central third and demonstrated greater quad strength on isokinetic testing.  Even though the tendon is without its central third there is a very low incidence of tendon rupture 0.06% & 0.08% as reported by Lee 2008, and Milankov Ziva 2008, respectively.

Is there anything that can speed the healing process?   Platelet Rich Plasma (PRP) has a growing presence among the sports medicine field but is still in need of further high level and high volume research.  To my knowledge it is not covered by insurance, but it’s positive results on tendon injuries may help it to become an option in the forseable future.  A study by de Almeida 2012, found that PRP to the harvested patellar tendon showed improved gap healing and less post-op pain at 6 months compared to subjects without the PRP injection.

Why is the lateral side of my lower leg numb?  When the Surgeon makes their incisions for surgery and harvest of the patellar tendon the Infrapatellar branches of the Saphenous nerve get disrupted, below is a great photo from Kartus 2000, to illustrate this.  Nerve regrowth is possible but sometimes sensation remains muted or slightly abnormal.

knee nerve 2







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