Katy Koehler
CO 300
3/16/10
Synthetic Fibers Better than Autogenous Tissue Grafts in Tendon Replacement Surgery
The Achilles tendon is one of the largest and most worked tendons within the human
body. Connecting the gastrocnemius muscle and the soleus muscle of the calf to the calcaneus
bone of the heel, the tendon undergoes high pressures and strong forces daily. The Achilles
tendon is worked almost constantly, it is working when a person is walking, running, jumping,
walking in high heels, playing sports, going up stairs, and standing on their toes3. Due to the high
amount of use the Achilles tendon undergoes it is quite often damaged.
The usual damage done to the Achilles tendon is a common overuse injury called
Achilles tendinopathy. This can be brought on by weak calf muscles, abrupt changes in speed
and direction while running, as well as running for longer distances and overpronation of the
foot3. Tendinopathy is characterized by pain and stiffness in the Achilles tendon that intensifies
as work done by the tendon is continued. While Achilles tendinopathy is uncomfortable it can
easily be treated by exercise therapy or orthoses3. An Achilles tendon rupture is a much more
serious yet fairly common injury as well. An Achilles tendon rupture can be due to extreme
weight loads and accidental lacerations6.
Up until now, the solution to a torn tendon was a tendon replacement surgery using a
tissue graft harvested from a patient’s patellar tendon2. Because tendons will not reconnect or
heal by themselves, a surgical reconnection is the only repair option. There has recently been a
lot of discussion about the use of synthetic fibers or nanomaterials in place of a patellar tendon
tissue graft for a tendon replacement surgery2. While this topic is widely debated, relatively new
and not yet tested on humans, I believe that Achilles tendon reconstruction surgery using
synthetic fibers opposed to an autogenous tissue graft from the patellar tendon is highly
promising and will become an overall better surgical technique.
An autogenous tissue graft from the patellar tendon of a human patient to act as an
Achilles replacement tendon has multiple negative side effects. The availability of autogenous
patellar tendons for Achilles tendon reconstruction is restricted and related to withdrawal
morbidity. Firstly, autogenous tissue grafts often lead to donor site death as well as additional
pain due to the multi-tendon injury7. When completing a tendon replacement surgery, surgeons
will cut out the middle section of the patellar tendon leaving the two sides to maintain all of the
force and function of the patellar tendon. This procedure severely weakens the strength and force
the patellar tendon can withstand without rupture to itself. Autogenous tissue grafts have been
experimented on and shown to correlate with insufficient strength of the knee stabilizing
muscles. In this case, the muscles around the knee are most often stronger than the two patellar
tendon pieces and can either rupture the tendons or potentially rip the tendons off of the bone
causing an osteoporotic fracture. Also, cutting a healthy piece of tendon out of the body can
cause infection and death of the tendon7. This technique causes the patient undergoing the
surgery to then have two wound sites, one at the ankle the other at the knee, and two
inadequately functioning tendons, the Achilles tendon and the patellar tendon. These two wound
sites cause the patient more pain and discomfort than when they ruptured their Achilles tendon
alone.
Secondly, it has been proven that autogenous tissue grafts are not very durable and often
show problems regarding long term stability and immunological reactions. In this case, a second
replacement surgery is recommended. However, from the primary reconstructive surgery, the
mid-section of the patellar tendon was already removed and damaged. Therefore, when a
revision surgery is needed there is a limited availability of other suitable graft sites to choose
from within the body7. Even under the best of circumstances, tendon repairs using autogenous
tissue grafts rarely, if ever, achieve the mechanical and biological properties of the original
tendon tissue6.
On the other hand, the use of synthetic fibers as tendon reconstructive materials have
been proven to have great advantages and benefits over autogenous tissue graft replacements.
There are currently many different fibers being tested and researched on various animals and
soon to be on humans. So far, it has been scientifically proven that these synthetic fibers are
safer, stronger and more durable than autogenous tissue grafts.
In order for synthetic fibers to work correctly and replace existing tendons they must be
biologically-based, biocompatible, and have appropriate mechanical properties. Nordihydroguaiaretic acid (NDGA) is a relatively new synthetic material being used in tendon
replacements6. It acts as an adhesive between broken tendon strands. This is beneficial because
the patient is able to keep their anatomical tendon and does not need to provide a donor tendon
causing injury to their patellar region. NDGA has been proven to cause an increase in the
material properties of synthetic collagen fibers. Testing has shown that the use of NDGA results
in a 100-fold increase in strength and stiffness over untreated fibers6. Overall strength, ability to
stretch and reform, and fatigue levels all increased with the use of NDGA in tendon
replacements. The NDGA fibers also integrated with the surrounding tissue well and did not
stimulate a negative immune reaction within the body. The fibers also showed no degradation
within a six week testing period, proving them to be very durable6.
Another useful synthetic fiber in Achilles tendon reconstruction surgery is expanded
polytetrafluoroethylene (e-PTFE) grafts5. The e-PTFE again acts as a glue and holds broken
tendon pieces together. In tests completed on chicken tendons, e-PTFE showed no infection or
post-operative complications5. Initial functional recovery using the e-PTFE graft was a little slow
but over a period of three months the two tendon stumps and the e-PTFE grew completely
together. Histological reports state that the e-PTFE segment was colonized by the original
connective tissue cells and within six months no discernable difference could be found between
the two tissues. Within that time period the tendon showed a 100% recovery in both strength and
stiffness levels5. While e-PTFE takes slightly longer to heal than other grafts it heals stronger
than autogenous tissue grafts. It also is less invasive and an overall simple operation. The use of
e-PTFE grafts will be great for Achilles tendon ruptures that would otherwise need multiple
autogenous tissue grafts from the patellar tendon to heal5.
In a similar experiment done by Xiaoron Li on rats, synthetic nanomaterials were used to
reattach ruptured tendons directly to the bone1. It was discovered that the nanomaterials could
almost perfectly imitate natural tendon and mimicked the mineral properties as well as the
mechanical and biochemical properties of in-vivo tendons. The synthetic fibers also imitated the
natural mineral gradients of the tissues and proved to be another strong and efficient replacement
for autogenous tissue replacement grafts1.
Along the same lines of synthetic tendon replacement materials, there are a number of
ideas pointing towards using synthetic fibers to “grow” completely new tendons. The main fiber
type being used for the re-growth of tendons is bioceramics. Bioceramics are porous synthetic
fibers and provide areas for tendon tissue ingrowth to occur4. Not only are bioceramics very
biocompatible with the body but they literally grow into the body and disappear as it fully heals
itself. Bioceramics are formed from calcium orthophosphates, a synthetic yet bioresorbable and
bioactive compound4. Bioceramics can be used to create a direct physical bond between bone to
bone, tendon to tendon, or tendon to bone. In doing so, bioceramics are very practical and will be
an excellent way to rejoin ruptured tendons such as the Achilles.
In conclusion, I believe that reconstruction surgery of the Achilles tendon should be done
using synthetic fibers opposed to an autogenous tissue graft from the patellar tendon of the
human patient. Not only can an autogenous patellar donor tendon lead to weakness of the knee
joint, morbidity of the tendon and increased pain in the patient but chances are that the
replacement itself will need to be replaced within a matter of time. Synthetic fibers on the other
hand have been proven to be more durable, less invasive, and stronger. The pros of using
synthetic fibers for an Achilles tendon replacement surgery greatly outweigh the cons of using
the patellar tendon for the replacement surgery. Overall, I believe that as science continues to
advance, synthetic fibers will become a better tendon replacement material than autogenous
tissue grafts taken from the patellar tendon in Achilles tendon replacement surgery.
Works Cited
1. A. A. R. Nanomaterial for Joining Tendon and Bone. Chemical & Engineering News
[serial online]. June 29, 2009;87(26):27. Available from: Academic Search Premier,
Ipswich, MA. Accessed March 5, 2010.
2. Catherine Saint L. Looking for Alternatives to Ligament Replacement Surgery. New York
Times [serial online]. April 20, 2006:6. Available from: Academic Search Premier,
Ipswich, MA. Accessed March 5, 2010.
3. Chang H, Burke A, Glass R. Achilles Tendinopathy. JAMA: Journal of the American
Medical Association [serial online]. January 13, 2010; 303(2):188. Available from:
Academic Search Premier, Ipswich, MA. Accessed March 5, 2010.
4. Dorozhkin S. Bioceramics of Calcium Orthophosphates. Biomaterials [serial online].
March 2010;31(7):1465-1485. Available from: Academic Search Premier, Ipswich, MA.
Accessed March 5, 2010.
5. Giorgetti M, Giannessi E, Ricciardi M. Expanded Polytetrafluoroethylene as Tendon
Replacement: An Experimental Study in Chickens. Scandinavian Journal of Plastic &
Reconstructive Surgery & Hand Surgery [serial online]. February 2001;35(1):23-27.
Available from: Academic Search Premier, Ipswich, MA. Accessed March 5, 2010.
6. Koob T. Biomimetic Approaches to Tendon Repair. Comparative Biochemistry &
Physiology Part A: Molecular & Integrative Physiology [serial online]. December
2002;133(4):1171. Available from: Academic Search Premier, Ipswich, MA. Accessed
March 5, 2010.
7. Tischer T, Vogt S, Aryee S, et al. Tissue Engineering of the Anterior Cruciate
Ligament: A New Method Using Acellularized Tendon Allografts and Autologous
Fibroblasts. Archives of Orthopedic & Trauma Surgery [serial online]. November
2007;127(9):735-741. Available from: Academic Search Premier, Ipswich, MA.
Accessed March 5, 2010.