Introduction
Composition of ...
Main Chemicals, Compounds, Components
Proteins are Platelet-rich plasma (PRP). It is a fraction of plasma that is produced by centrifugal separation of whole blood. It is a useful delivery system for growth factors important in tissue engineering. PRP contains plasma proteins which are known to act as cell adhesion molecules important for osteoblast, fibroblast, and epithelial cell migration and viability. These proteins allow a graft to be put in the place of the previous ACL and form to the body and its functions. As the graft is placed in as the ACL the body takes over and breaks it down, so cells from the body can begin to rebuild the ligament for strength.
The patellar tendon is a thick and strong band of connective tissue on the front of the knee. It starts at the bottom of the patella to just below the knee to the front of the tibia, called the tibial tubercle. When using the patellar tendon as an ACL graft, surgeons remove a strip from the middle of it. The graft includes the bone attachments from the bottom of the patella and the tibial tubercle. The connection it has with both bones allows your knee to straighten. The bending and straightening motion stretches and contracts your muscle which is also interacts with the elastin in your knee. Elastin is in connective tissues like the patellar tendon. It allows things to return back to their normal position, and therefore is a big factor in the recovery in the ACL.
Chemistry's Role
All of the compounds of the ACL are not man-made, you have the option of using an autograft or an allograft. The autograft is bone or tissue from your own body, where an allograft is used from a donor. The proteins and tendons of your knee are made and strengthened by your body even after a new one is placed in the spot of the torn ACL. There is a period where your body breaks down the foreign ligament after surgery, and rebuilds it for future strength.
Background Research
The ACL provides 85% of total restraining force of anterior translation. It has a structure of ⅔ water, ⅓ solid components- proteoglycans, elastin, proteins and glycoproteins. It has a specialized enzyme called lysyl-oxidase, and promotes cross link formation. The ligament itself has a length of 38mm, and a width of 10mm. Lysyl is a healing protein in the knee. Another tendon is brought to replace the torn ACL, so the Lysyl-oxidase will not heal the ACL itself, it will help rebuild the “new” ACL. The Patellar Tendon is commonly used as the graft replacement for the ACL. The patellar tendon, Bone Tendon Bone (BTB), graft has consistently shown excellent surgical outcomes with 90-95% success rates in allowing athletes to return to playing sports post surgery. Because of the bone on each side the patellar tendon holds in place and prevents the tibia from moving too far forward. After surgery, the body develops network of blood vessels in the new graft called revascularization, this takes about 12 weeks. At this time the graft is at its weakest, which means it has a greater chance of stretching or tearing. A stretched or torn graft can occur if you push yourself too hard during this period of recovery. When revascularization is complete, strength in the graft gradually builds. A second surgery may be needed to replace the graft if it is stretched or torn. Post surgery many will be on crutches from 2-4 weeks. Gradually you will be able to put weight on the injured leg and start walking while still in a brace. Most choose to go to a physical therapist. After about 6 months athletes should be cleared to resume their sports or activities. The new graft will eventually allow complete range of motion and many will not be able to notice the prior injury.
Resources
http://orthoinfo.aaos.org/topic.cfm?topic=a00549
The ACL - Anterior Cruciate Ligament
Anatomy- The femur, tibia, and patella meet to form the knee joint. The kneecap is there for protection in front of the joint. These bones are connected by four ligaments- the lateral collateral, posterior cruciate, medial collateral, and the anterior cruciate (ACL).
Causes of tears- Changing direction rapidly, stopping suddenly, slowing down while running, landing from a jump, direct contact or collision, or hyperextension.
http://www.sportsandortho.com/minneapolis/anterior-cruciate-ligament-ACL-injury.htm
Made of- tough fibrous material that connects bone to a bone.
There are over 250,000 ACL injuries per year in the U.S.
http://www.physio-pedia.com/Anterior_Cruciate_Ligament_%28ACL%29
Composition- The ACL is a band of connective dense tissue that goes from the the femur to the tibia.
It receives nerve fibers from the posterior articular branches of the tibial nerve.
The ACL provides 85% of total restraining force of anterior translation.
http://www.ismni.org/jmni/pdf/16/21FRANK.pdf?q=ligament
⅔ water
⅓ solid components- proteoglycans, elastin, proteins and glycoproteins.
specialized enzyme called lysyl-oxidase, promotes cross link formation.
http://www.cryst.bbk.ac.uk/pps97/assignments/projects/emilia/Proteoglycans.HTM
Proteoglycans- D glucuronate + GlcNAc
http://www.rsc.org/Education/Teachers/Resources/cfb/proteins.htm
Proteins- NH2CHRCOOH (aq) + H (aq) = NH3CHRCOOH (aq)
http://www.chemistryexplained.com/Ge-Hy/Glycoprotein.html
Glycoproteins-N-linked- endoplasmic reticulum and Golgi apparatus.
Addition of amino acids = polypeptide (C4H8N2O3)
O-linked- addition of sugar residues to the hydroxyl side chain of serine or threonine residues in polypeptides in the Golgi apparatus.
http://en.wikipedia.org/wiki/Actin#In_smooth_muscle
Actin amino acid sequence is a highly conserved protein as it has little charge over its course of evolution.
http://www.wheelessonline.com/ortho/anatomy_of_acl
Length of 38mm
width of 10mm
Small anteromedial band- tight in flexion (crossed)
Larger bulky posterolateral- tight in extension (both are parallel)
http://www.sciencedirect.com/science/article/pii/S0020138312003579
Lysyl is a healing protein in the knee.
Although another tendon is brought to replace the torn ACL, so the Lysyl-oxidase will not heal the ACL itself, it will help rebuild the “new” ACL
http://en.wikipedia.org/wiki/Elastin
Highly elastic protein in connective tissue
Allows tissues to resume shape after stretching or contracting
ELN gene encodes a protein that is 1 of the 2 components of elastic protein.
http://en.wikipedia.org/wiki/Proline
Hydrophobic amino acid (glycine & proline)
(EtO2C)2+CH2=CH.CN------>(EtO2CH2)2 CH.CH2 CH2 CN
Tropoelastin is another name for elastin
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2952126/
Healing of the ACL post surgery
http://www.methodistorthopedics.com/patellar-tendon-graft-reconstruction-of-the-acl
http://www.orthoassociates.com/SP11B35/
Patellar tendon common replacement for a torn ACL.
About the Author
Jeanann Lemelin is a Junior at Billings Senior. She has been a three sport varsity athlete for three years. She has been apart of two state championship volleyball teams, and a third place finish at state basketball. Her basketball season was cut short in the 2014-15 season as a junior due to the tearing of her ACL. She has since gone through surgery and now enduring the challenges that come with her recovery and physical therapy. Along with sports Jeanann is involved in Student Council, Senior Advocates, National Honors Society, Billings Youth Leadership, and STEM Society while keeping a 4.0 gpa.