Artificial ligament

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Artificial ligaments are devices used to replace damaged ligaments. Today, the most common use of artificial ligaments is in anterior cruciate ligament reconstruction. [1] Although autotransplantation remains the most common method of ligament reconstruction, numerous materials and structures were developed to optimize the artificial ligament since its creation in the World War I era. [2] Many modern artificial ligaments are made of synthetic polymers, such as polyethylene terephthalate. [3] Various coatings have been added to improve the biocompatibility of the synthetic polymers. [3] Early artificial ligaments developed in the 1980s were ineffective due to material deterioration. [4] Currently, the Ligament Advanced Reinforcement System (LARS) artificial ligament has been utilized extensively in clinical applications. [5] Tissue engineering is a growing area of research which aims to regenerate and restore ligament function. [2]

Contents

History

Artificial ligament research began in the World War I era. [2] In the first documented case of an artificial ligament in 1914, Dr. Corner utilized a piece of silver filament as synthetic graft to reconstruct a ruptured anterior cruciate ligament (ACL). [2] A ligament made of silk was used to replace an ACL in 1918. [2]

In the early 1980s, technological progress in chemistry and materials science promoted the development of medically suitable materials. Doctors utilized these synthetic materials in clinical applications. The Food and Drug Administration (FDA) approved an artificial ligament made of Gore-Tex for use in ACL reconstruction in 1986. [6]

The design of artificial ligaments in the 1980s consisted of two major parts: a relatively stiff cable or tape, and silicone rubber cylinders on one or both ends. [2] The cable or tape was usually made of polyethylene, nylon or carbon fiber. The silicone rubber cylinder varied in size to fit different sized patients. [2] [7] [1] Theoretically, the flexibility of the silicone rubber would allow some deformation under relatively low loads, and the artificial ligament would stiffen to maintain its shape under higher loads. [7] [1] Practically, this design never achieved its goal to mimic the property of a natural ligament. [8] The mechanical performance of the artificial ligaments was inadequate for widespread clinical application. In the long term, performance loss, complications, and failure occurred. [8]

Material deterioration contributed to the ineffectiveness of early artificial ligaments. [4] Issues would occur in the months and years following treatment. [2] [4] J.E. Paulos indicated in a report about Gore-Tex usage in ACL reconstruction: "Early results of the Gore-Tex prosthesis used for ACL reconstruction showed low rates of failure. Unfortunately, with extended follow-up, our rate of complications continues to increase. Mechanical failure, effusions, and infections continue to occur". [2] At the time, the materials used in artificial ligaments could not sustain adequate mechanical performance. [2] [4] For many of these materials, their mechanical performance diminished in the long-term. [1] [8] [4]

Current design

The primary usage of modern artificial ligaments is in anterior cruciate ligament reconstruction. Many artificial ligaments seek to mimic or exceed the performance of the native ACL. [5] The mechanical performance of an artificial ligament can be characterized by abrasion resistance, withstanding flexural and rotational fatigue, [2] and preventing graft slippage or rupture. [9] Biocompatibility is important to the performance of the artificial ligament in vivo. [3] Biocompatibility is related to new tissue ingrowth, [10] fibroblast migration, osseointegration of bone, reduction of inflammation, preventing scar tissue infiltration, and improving hydrophilicity. [3] Tissue ingrowth and fibroblast migration have been shown to improve the mechanical strength of the artificial ligament, [10] and osseointegration with the surrounding bone can reduce the likelihood of graft slippage. [9] Many artificial ligaments are designed to minimize inflammation and scar tissue infiltration because they can hinder the mechanical strength and can cause graft rupture. [3] Artificial ligament design strives to improve hydrophilicity because hydrophobicity can trigger the host's natural response to foreign bodies. [3]

The Ligament Advanced Reinforcement (LARS) is a leading artificial ligament in ACL repair surgery. They are made of polyethylene terephthalate (PET). [3] They consist of an intraosseous and an intra-articular portion. The intraosseous section consists of longitudinal fibers bounded by a knitted transverse structure. This knitted structure can help prevent deformation and abrasion. [5] [11] The intra-articular portion is made of longitudinal fibers pretwisted at a 90 degree angle. This section is designed to resist fatigue and promote tissue ingrowth. [5] Leeds Keio ligaments consist of a polyester mesh structure. It seeks to mimic the mechanical properties of the native ACL. The porous nature of the ligament can promote tissue ingrowth which has been shown to improve mechanical properties. [5] The PGA Dacron artificial graft consists of 75% braided biodegradable polyglycolic acid and 25% permanent Dacron thread. [11] The Kennedy LAD artificial ligament is made of polypropylene ribbons. It is designed to promote tissue ingrowth and the progressive transfer of load onto the new ligament. [10]

Ligament Advanced Reinforcement System (LARS) artificial ligament. The two end sections are the intraosseous portions and center portion is the intra-articular region. LARS artificial ligament.png
Ligament Advanced Reinforcement System (LARS) artificial ligament. The two end sections are the intraosseous portions and center portion is the intra-articular region.

The native ACL of a human has a tensile strength on the order of kilonewtons, [3] and an elongation at failure of approximately 10%. [10] The mechanical properties of the native ACL vary throughout the human population. The strength of a child's ACL tends to be greater than that of an adult. [10] PGA Dacron artificial ligaments have an ultimate tensile strength near 3500 N and a mean ultimate elongation of approximately 20%. [10] Kennedy LAD ligaments have a tensile strength at failure of approximately 1500 N and an approximate stiffness of 50 N/mm. [10] Leeds-Keio artificial ligaments have an ultimate tensile strength near 2000 N and a stiffness around 250 N/mm after tissue ingrowth. [10] LARS artificial ligaments have varying mechanical properties depending on the amount of fibers used. A higher gauged ligament will have a greater tensile strength. During testing, a 60 gauge LARS ligament exhibited an ultimate tensile strength of 2500 N while a 120 gauge ligament exhibited a tensile strength of 5600 N. [5] [12] The ingrown tissue has been shown to improve viscoelastic properties and reduce friction. [5]

PET artificial ligament coated with hyaluronic acid coating. Collagen tissue infiltration is evident. PET Hyaluronic Acid Tissue.png
PET artificial ligament coated with hyaluronic acid coating. Collagen tissue infiltration is evident.

Coatings have been added to artificial ligaments to improve their biocompatibility. 58S bioglass and hydroxyapatite coatings have been shown to improve osseointegration and cellular activity in vitro and in animal studies [3] when deposited onto PET ligaments using the soaking method. [2] [3] Hydroxypropyl cellulose surface treatments have been shown to improve osseointegration for PET ligaments in animal studies. [2] Uncoated PET is hydrophobic, so coatings are designed to improve hydrophilicity. [3] Hyaluronic acid coatings can reduce hydrophobicity and have been shown to reduce scar tissue formation and inflammation in vivo. [3] Hyaluronic acid and chitosan composite coatings can be deposited onto artificial ligament surfaces by the layer-by-layer technique, and they have been shown to enhance new bone formation at the ligament interface in mice. [9] The chitosan is used to reduce hydrophobicity and improve osseointegration and mineral deposition, while the hyaluronic acid promotes cell differentiation and growth. [9] Poly(sodium styrene sulfonate) coatings have been shown in animal studies to improve knee functionality and mimicry of the native ACL. [2] [13]

Clinical application

The anterior cruciate ligament (ACL) is a frequently injured human body structure that may cause secondary damages to the knees, such as meniscal tears and articular cartilage degeneration, without medical treatment. ACL reconstruction is a commonly practiced technique for ACL injury, conducted on 30% of patients, which manages to restore stability to the knee structure. [2] [14] Traditional ACL reconstructions uses autografts or allografts which demand a long rehabilitation time and in most cases, develop donor morbidity in the long term. [11]

The early interests in artificial ligaments led to the implementation of non-human tissue, such as Proplast ligaments made of Teflon and carbon fibers and Polyflex made of polypropylene. [10] [15] The results demonstrated poor resistance to torsion forces. [11] Approved by FDA in 1986 and adopted in clinics later, Gore-Tex cruciate ligament prosthesis demonstrated low rates of mechanical failure but high rates of rupture in follow-up. [16] Gore-Tex was then abandoned in ACL surgery and Leeds-Keio (LK) ligament was then adopted. In the later long term follow-up research, LK ligament demonstrated promising performance at first but still showed low stability rates in 2 years and increased degenerative changes compared with their opposite joint in one decade. [17] [18] In the 21st century, the Ligament Advanced Reinforcement (LARS) ligament became the most popular artificial ligament on the market. LARS ligaments not only provide satisfactory outcomes initially but also do not perform differently in at least 2 years. [19] LARS ligaments demonstrate higher stability and lower morbidity rate compared to autograft in short-term research and in a 9-year study, LARS ligament showed a 100% survival rate. [5] Synthetic ACL grafts always develop creep, fatigue and failure so the demand for synthetic grafts with sufficient supply, satisfactory mechanical properties, and low morbidity rate is essentially high. [5] Currently, the LARS ligament is the most comparable to both autografts and other synthetic grafts. [5]

Rate of knee injury among patients with failed ligament augmentation and reconstruction system Rate of knee injury among patients with failed ligament augmentation and reconstruction system.png
Rate of knee injury among patients with failed ligament augmentation and reconstruction system

Complications that commonly occur in the artificial ligaments after the first ten years are breakage, wear debris, synovitis, recurrent instability, osteolysis and chronic effusions. [10] Complications do not commonly surface right after the surgery or after a relatively short term, and in a few cases, start to show up after the first ten years. Follow-up research is required to study the performance of certain synthetic materials for artificial ligament and to monitor the health of patients. [10] Rupture rates are usually recorded in 2 to 5 years. [10]

Tissue engineering

While the future of artificial ligaments is unknown, leading researchers in tissue engineering aim to regenerate and repair the ligament to restore normal function. [2]   ACL tissue engineering will be based on the healing of the medial collateral ligament (MCL), since the ACL does not heal naturally. [2]  A seed cell will be used in tissue engineering for the repair of ACL ligaments. The seed cell must have qualifications such as: easily available, potent to proliferate, and efficient in elaborating a mature extracellular matrix.  Stem cells such as bone marrow-derived mesenchymal stem cells, adipose-derived stem cells, perivascular stem cells, and human foreskin fibroblasts are commonly used in tissue engineering. [2]

Related Research Articles

A ligament is the fibrous connective tissue that connects bones to other bones. It is also known as articular ligament, articular larua, fibrous ligament, or true ligament. Other ligaments in the body include the:

<span class="mw-page-title-main">Knee</span> Leg joint in primates

In humans and other primates, the knee joins the thigh with the leg and consists of two joints: one between the femur and tibia, and one between the femur and patella. It is the largest joint in the human body. The knee is a modified hinge joint, which permits flexion and extension as well as slight internal and external rotation. The knee is vulnerable to injury and to the development of osteoarthritis.

<span class="mw-page-title-main">Posterior cruciate ligament</span> One of four major ligaments of the knee

The posterior cruciate ligament (PCL) is a ligament in each knee of humans and various other animals. It works as a counterpart to the anterior cruciate ligament (ACL). It connects the posterior intercondylar area of the tibia to the medial condyle of the femur. This configuration allows the PCL to resist forces pushing the tibia posteriorly relative to the femur.

<span class="mw-page-title-main">Anterior cruciate ligament</span> Type of cruciate ligament in the human knee

The anterior cruciate ligament (ACL) is one of a pair of cruciate ligaments in the human knee. The two ligaments are also called "cruciform" ligaments, as they are arranged in a crossed formation. In the quadruped stifle joint, based on its anatomical position, it is also referred to as the cranial cruciate ligament. The term cruciate translates to cross. This name is fitting because the ACL crosses the posterior cruciate ligament to form an “X”. It is composed of strong, fibrous material and assists in controlling excessive motion. This is done by limiting mobility of the joint. The anterior cruciate ligament is one of the four main ligaments of the knee, providing 85% of the restraining force to anterior tibial displacement at 30 and 90° of knee flexion. The ACL is the most injured ligament of the four located in the knee.

Grafting refers to a surgical procedure to move tissue from one site to another on the body, or from another creature, without bringing its own blood supply with it. Instead, a new blood supply grows in after it is placed. A similar technique where tissue is transferred with the blood supply intact is called a flap. In some instances, a graft can be an artificially manufactured device. Examples of this are a tube to carry blood flow across a defect or from an artery to a vein for use in hemodialysis.

Allotransplant is the transplantation of cells, tissues, or organs to a recipient from a genetically non-identical donor of the same species. The transplant is called an allograft, allogeneic transplant, or homograft. Most human tissue and organ transplants are allografts.

<span class="mw-page-title-main">Segond fracture</span> Avulsion fracture of the lateral tibial condyle of the knee

The Segond fracture is a type of avulsion fracture from the lateral tibial plateau of the knee, immediately below the articular surface of the tibia.

<span class="mw-page-title-main">Anterior cruciate ligament reconstruction</span> Surgical process

Anterior cruciate ligament reconstruction is a surgical tissue graft replacement of the anterior cruciate ligament, located in the knee, to restore its function after an injury. The torn ligament can either be removed from the knee, or preserved before reconstruction through an arthroscopic procedure. ACL repair is also a surgical option. This involves repairing the ACL by re-attaching it, instead of performing a reconstruction. Theoretical advantages of repair include faster recovery and a lack of donor site morbidity, but randomised controlled trials and long-term data regarding re-rupture rates using contemporary surgical techniques are lacking.

<span class="mw-page-title-main">Arthrodesis</span>

Arthrodesis, also known as artificial ankylosis or syndesis, is the artificial induction of joint ossification between two bones by surgery. This is done to relieve intractable pain in a joint which cannot be managed by pain medication, splints, or other normally indicated treatments. The typical causes of such pain are fractures which disrupt the joint, severe sprains, and arthritis. It is most commonly performed on joints in the spine, hand, ankle, and foot. Historically, knee and hip arthrodeses were also performed as pain-relieving procedures, but with the great successes achieved in hip and knee arthroplasty, arthrodesis of these large joints has fallen out of favour as a primary procedure, and now is only used as a procedure of last resort in some failed arthroplasties.

<span class="mw-page-title-main">Semitendinosus muscle</span> One of the hamstring muscles; posterior part of the thigh

The semitendinosus is a long superficial muscle in the back of the thigh. It is so named because it has a very long tendon of insertion. It lies posteromedially in the thigh, superficial to the semimembranosus.

<span class="mw-page-title-main">Cruciate ligament</span> Type of ligament shaped like an X

Cruciate ligaments are pairs of ligaments arranged like a letter X. They occur in several joints of the body, such as the knee joint, wrist joint and the atlanto-axial joint. In a fashion similar to the cords in a toy Jacob's ladder, the crossed ligaments stabilize the joint while allowing a very large range of motion.

<span class="mw-page-title-main">Anterior cruciate ligament injury</span> Ligament injury near the knee

An anterior cruciate ligament injury occurs when the anterior cruciate ligament (ACL) is either stretched, partially torn, or completely torn. The most common injury is a complete tear. Symptoms include pain, an audible cracking sound during injury, instability of the knee, and joint swelling. Swelling generally appears within a couple of hours. In approximately 50% of cases, other structures of the knee such as surrounding ligaments, cartilage, or meniscus are damaged.

<span class="mw-page-title-main">Patellar tendon</span> Tendon in the human knee

The patellar tendon is the distal portion of the common tendon of the quadriceps femoris, which is continued from the patella to the tibial tuberosity. It is also sometimes called the patellar ligament as it forms a bone to bone connection when the patella is fully ossified.

<span class="mw-page-title-main">Unhappy triad</span> Medical condition of the knee

The unhappy triad, also known as a blown knee among other names, is an injury to the anterior cruciate ligament, medial collateral ligament, and meniscus. Analysis during the 1990s indicated that this 'classic' O'Donoghue triad is actually an unusual clinical entity among athletes with knee injuries. Some authors mistakenly believe that in this type of injury, "combined anterior cruciate and medial collateral ligament disruptions that were incurred during athletic endeavors" always present with concomitant medial meniscus injury. However, the 1990 analysis showed that lateral meniscus tears are more common than medial meniscus tears in conjunction with sprains of the ACL.

<span class="mw-page-title-main">Meniscus tear</span> Rupturing of the fibrocartilage strips in the knee called menisci

A tear of a meniscus is a rupturing of one or more of the fibrocartilage strips in the knee called menisci. When doctors and patients refer to "torn cartilage" in the knee, they actually may be referring to an injury to a meniscus at the top of one of the tibiae. Menisci can be torn during innocuous activities such as walking or squatting. They can also be torn by traumatic force encountered in sports or other forms of physical exertion. The traumatic action is most often a twisting movement at the knee while the leg is bent. In older adults, the meniscus can be damaged following prolonged 'wear and tear'. Especially acute injuries can lead to displaced tears which can cause mechanical symptoms such as clicking, catching, or locking during motion of the joint. The joint will be in pain when in use, but when there is no load, the pain goes away.

Kevin Robert Stone is an American physician, orthopedic surgeon, clinician, researcher, and company founder of The Stone Clinic and the Stone Research Foundation in San Francisco.

Posterolateral corner injuries of the knee are injuries to a complex area formed by the interaction of multiple structures. Injuries to the posterolateral corner can be debilitating to the person and require recognition and treatment to avoid long term consequences. Injuries to the PLC often occur in combination with other ligamentous injuries to the knee; most commonly the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL). As with any injury, an understanding of the anatomy and functional interactions of the posterolateral corner is important to diagnosing and treating the injury.

<span class="mw-page-title-main">Medial knee injuries</span> Medical condition

Medial knee injuries are the most common type of knee injury. The medial ligament complex of the knee consists of:

<span class="mw-page-title-main">Posterior cruciate ligament injury</span> Medical condition

The function of the posterior cruciate ligament (PCL) is to prevent the femur from sliding off the anterior edge of the tibia and to prevent the tibia from displacing posterior to the femur. Common causes of PCL injuries are direct blows to the flexed knee, such as the knee hitting the dashboard in a car accident or falling hard on the knee, both instances displacing the tibia posterior to the femur.

Movement assessment is the practice of analysing movement performance during functional tasks to determine the kinematics of individual joints and their effect on the kinetic chain. Three-dimensional or two-dimensional analysis of the biomechanics involved in sporting tasks can assist in prevention of injury and enhancing athletic performance. Identification of abnormal movement mechanics provides physical therapists and Athletic trainers the ability to prescribe more accurate corrective exercise programs to prevent injury and improve exercise rehabilitation and progression following injury and assist in determining readiness to return to sport.

References

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  2. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Chen T, Jiang J, Chen S (January 2015). "Status and headway of the clinical application of artificial ligaments". Asia-Pacific Journal of Sports Medicine, Arthroscopy, Rehabilitation and Technology. 2 (1): 15–26. doi:10.1016/j.asmart.2014.11.001. PMC   5730644 . PMID   29264235.
  3. 1 2 3 4 5 6 7 8 9 10 11 12 Li H, Chen S (February 2015). "Biomedical coatings on polyethylene terephthalate artificial ligaments". Journal of Biomedical Materials Research. Part A. 103 (2): 839–45. doi:10.1002/jbm.a.35218. PMID   24825100.
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  5. 1 2 3 4 5 6 7 8 9 10 Iliadis DP, Bourlos DN, Mastrokalos DS, Chronopoulos E, Babis GC (June 2016). "LARS Artificial Ligament Versus ABC Purely Polyester Ligament for Anterior Cruciate Ligament Reconstruction". Orthopaedic Journal of Sports Medicine. 4 (6): 2325967116653359. doi:10.1177/2325967116653359. PMC   4933937 . PMID   27453894.
  6. ↑ US-FDA. "Guidance Document for the Preparation of Investigational Device Exemptions and Premarket Approval Applications for Intra-Articular Prosthetic Knee Ligament Devices" (PDF). Food and Drug Administration .
  7. 1 2 Jenkins DH, McKibbin B (November 1980). "The role of flexible carbon-fibre implants as tendon and ligament substitutes in clinical practice. A preliminary report". The Journal of Bone and Joint Surgery. British Volume. 62-B (4): 497–9. doi: 10.1302/0301-620X.62B4.7430232 . PMID   7430232.
  8. 1 2 3 Cuppone M, Seedhom BB (2001). "Effect of implant lengthening and mode of fixation on knee laxity after ACL reconstruction with an artificial ligament: a cadaveric study". Journal of Orthopaedic Science. 6 (3): 253–61. doi:10.1007/s007760100044. PMID   11484120. S2CID   6272767.
  9. 1 2 3 4 Li H, Ge Y, Zhang P, Wu L, Chen S (November 2011). "The effect of layer-by-layer chitosan-hyaluronic acid coating on graft-to-bone healing of a poly(ethylene terephthalate) artificial ligament". Journal of Biomaterials Science. Polymer Edition. 23 (1–4): 425–38. doi:10.1163/092050610X551989. PMID   21255485. S2CID   42571974.
  10. 1 2 3 4 5 6 7 8 9 10 11 12 Legnani C, Ventura A, Terzaghi C, Borgo E, Albisetti W (April 2010). "Anterior cruciate ligament reconstruction with synthetic grafts. A review of literature". International Orthopaedics. 34 (4): 465–71. doi:10.1007/s00264-010-0963-2. PMC   2903133 . PMID   20157811.
  11. 1 2 3 4 Jia ZY, Zhang C, Cao SQ, Xue CC, Liu TZ, Huang X, Xu WD (July 2017). "Comparison of artificial graft versus autograft in anterior cruciate ligament reconstruction: a meta-analysis". BMC Musculoskeletal Disorders. 18 (1): 309. doi:10.1186/s12891-017-1672-4. PMC   5517802 . PMID   28724372.
  12. ↑ Liu ZT, Zhang XL, Jiang Y, Zeng BF (February 2010). "Four-strand hamstring tendon autograft versus LARS artificial ligament for anterior cruciate ligament reconstruction". International Orthopaedics. 34 (1): 45–9. doi:10.1007/s00264-009-0768-3. PMC   2899266 . PMID   19396441.
  13. ↑ Halim S (2019-11-29). "Developing bioactive and biodegradable synthetic ligaments". SciTech Europa. Retrieved 2020-04-02.[ permanent dead link ]
  14. ↑ Cimino F, Volk BS, Setter D (October 2010). "Anterior cruciate ligament injury: diagnosis, management, and prevention". American Family Physician. 82 (8): 917–22. PMID   20949884.
  15. ↑ Dandy DJ, Flanagan JP, Steenmeyer V (July 1982). "Arthroscopy and the management of the ruptured anterior cruciate ligament". Clinical Orthopaedics and Related Research (167): 43–9. PMID   6896483.
  16. ↑ Wredmark T, Engström B (1993-06-01). "Five-year results of anterior cruciate ligament reconstruction with the Stryker Dacron high-strength ligament". Knee Surgery, Sports Traumatology, Arthroscopy. 1 (2): 71–5. doi:10.1007/BF01565455. PMID   8536011. S2CID   12856081.
  17. ↑ Rading J, Peterson L (1995-05-01). "Clinical experience with the Leeds-Keio artificial ligament in anterior cruciate ligament reconstruction. A prospective two-year follow-up study". The American Journal of Sports Medicine. 23 (3): 316–9. doi:10.1177/036354659502300311. PMID   7661259. S2CID   28416792.
  18. ↑ Murray AW, Macnicol MF (February 2004). "10-16 year results of Leeds-Keio anterior cruciate ligament reconstruction". The Knee. 11 (1): 9–14. doi:10.1016/S0968-0160(03)00076-0. PMID   14967321.
  19. ↑ Nau T, Lavoie P, Duval N (April 2002). "A new generation of artificial ligaments in reconstruction of the anterior cruciate ligament. Two-year follow-up of a randomised trial". The Journal of Bone and Joint Surgery. British Volume. 84 (3): 356–60. doi: 10.1302/0301-620x.84b3.12400 . PMID   12002492.
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