The Biology of ACL Reconstruction and Regeneration

One of the best examples of the wonders of modern medicine is Anterior Cruciate Ligament reconstruction.  Because the body is unable to heal the ACL on its own, it requires reconstruction in order to restore normal function to the knee.  The process of ACL regeneration relies heavily on the biology of your knee.

When I reconstruct your ACL, I take a tendon, either from an organ donor or from a different part of your body, then place it where I want a ligament to grow.  Your body uses this tendon as a scaffolding to regenerate a new anterior cruciate ligament.  This process occurs and 3 phases.  The initial phase is characterized by necrosis or cell death.  During the first 4 weeks after surgery, your body tears down all of the living cells in the graft, leaving only nonliving tissue as a blueprint for the final ligament.  The second portion of the regeneration process is called the proliferation phase.  This usually occurs in the second and third month after surgery.  This is characterized by influx in your own body’s cells into the remaining scaffolding.  The scaffolding also undergoes changes that cause significant weakness in the graft.  6-8 weeks after surgery is typically thought of as the weakest point and the time where of the structure of the graft needs the most protection.  The final phase, the ligamentization phase begins about 3 months after surgery.  During this time, the graft is slowly and steadily getting stronger and becoming more like the original ACL.  There is no clear end point however there is plenty of evidence suggesting that the graft will continue to mature over the following year.

I am a 43 year old Athlete and I tore my ACL, now what?

The short answer is, you don't need it.  As a sports medicine surgeon, I live to get people "back in the game", be that Eathampton HS football or the over 40 soccer leage at Allsports.  However, most of life does not require an ACL.  So why can I ski bumps without an ACL, but my kid's babysitter should have it reconstructed?  The answer lies with age.  In the over 40 population, it has long been thought that there are 3 groups of people who tear their ACLs: Copers, Adapters, and non-Copers.

If you are a Coper, with some dedicated rehab and a brace, you can return to all of the dumb things you were doing before you tore your ACL.  If you are an Adapter, with some good rehab and a whiff of mortality, you get back to life and many of the things you were doing before, but you take a less aggressive approach to athletics.  You limit the cutting, twisting, pivoting sports, but can remain active in athletics that are less "ACL Dependant".  If you are a non-Coper, you knee feels unstable inspite of dedicated rehab and a brace, and you are unwilling to accept the limitations that this injury has foisted on you.  In this case, there is decent evidence that an ACL reconstruction will help you stabilize your knee and get you "Back in the Game".  For most middle aged athletes, life is busy and they don't have the time to jump right into the 6-9 month rehab that an ACL recontruction requires, so the most common recommendation is to try non-surgical management of the ACL tear and see how it goes.

Sports Medicine Lecture Series Kicks Off!

This May, the physicians at HampOrtho successfully kicked off a Sports Medicine lecture series at CDH.   Drs. Fallon and McBride lead a fun and informative discussion on the Anatomy of Athletic Knee Injuries at the Cooley-Dickinson OR while giving a cadaveric demonstration of ACL reconstructions.  It gave the participants the chance to see first hand the surgical anatomy of the knee and try their hand at arthroscopic surgery on a cadaver.  Similar events are planned for this summer.  It is designed as a free service to our local Athletic Trainers, so if you are an AT-C and interested, please contact our office manager and we will put you on the list.