Ligament Augmentation and Reconstruction System (LARS)

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Introduction[edit | edit source]

The Ligament Augmentation and Reconstruction System or Ligament Advanced Reinforcement System (LARS) is an artificial ligament used as a synthetic graft for ACL and PCL reconstructions as well as knee extensor, ankle ligament, and shoulder and hip tendon reconstructions [1].

In ACL injuries, the LARS ligament can only be used to bind the stumps of the ruptured ACL together[1], therefore if there are no tissue remnants at one or both of the ligament sites, the LARS ligament can only be used as a scaffold to augment an autograft or allograft reconstruction. However, by making use of the remaining tissue, the LARS ligament is able to promote a faster healing process and earlier restoration of proprioception as well as encourage the ingrowth of native tissue into the synthetic ligament.

ACL injury presentation slideshow title.png

The LARS device is made from polyethylene terephthalate (PET) that is treated post-manufacture to remove a fat emulsion necessary in the processing phase but that can cause reactive synovitis and immune-responses in the human body if not removed[2].

It consists of two sections,

  • the intra-articular section.
  • the intra-osseous section.

Previous synthetic ligaments have struggled with high occurrences of synovitis as a result of wear on the ligament releasing microparticles into the joint. The new LARS system attempts to overcome this by combining two bundles of free longitudinal fibres in the intra-articular section and inverse warp knitted fibres in the intra-osseous section[1]. The longitudinal fibres are rotated 90° and orientated clockwise or anticlockwise for right or left knee ACL reconstructions respectively to replicate the native ACL and help it resist torsion and shearing forces that have been hypothesised to cause the wear that leads to synovitis in earlier designs [3]. Furthermore, the free orientation of the longitudinal fibres is meant to promote the ingrowth of osteoblast and fibroblast cells and to resist fatigue during flexion and extension. The fibres are also porous to allow for further fibroblastic ingrowth with the intention that newly formed collagen will eventually overtake the synthetic ligament [3][4].

The LARS ligament comes in many different sizes and designs depending on the intended use and the surgical technique used to implant the device. The traditional LARS ligament can withstand forces between 3500N to 5000N, while the short ligament can withstand forces of 3000N and the suspensory fixation ligament can withstand forces between 2700N and 4720N [1].

It is important to note that although the LARS ligament has been commercially available since 1992, it has not been granted approval in all countries, including the USA. However, it is available in the UK, France, Germany, Canada, China, and Australia. Many studies have been done on the use of LARS in China, with high levels of success reported with older populations[4]. It is also particularly well known in Australia, gaining national attention because of its frequent use by high-level sports athletes. However, it has recently gained some level of notoriety and many surgeons have become wary of the risk of failure and the resulting synovitis and premature arthritis [5].

Advantages of LARS[edit | edit source]

  • No impaired function or morbidity of the donor site used in autografts
  • Shorter return to function
  • Mimics natural ACL structure and orientation
  • Reduces shearing forces on the implant
  • Porosity encourages tissue ingrowth
  • Low cases of synovitis reported

Disadvantages[edit | edit source]

  • Residual post-operative laxity still present
  • Requires tissue remnants of the ACL to be used in reconstruction
  • Lack of long-term studies and mixed results on the current base of knowledge [6][7]

Surgical Procedure[edit | edit source]

Unlike an autograft which can replace the whole ligament, the LARS system can only be used when there are tissue remnants of the original ligament.[1]After it has been decided to use the LARS ligament for the reconstruction pre-operative planning must take place,

First, imaging techniques are used to confirm the clinical diagnosis, identify the anatomic femoral and tibial landmarks that will be used to orientate the surgeon and to determine whether a notch plasty is required [1].

There are four LARS device insertion techniques:

  • The traditional technique.
  • The independent AM portal technique.
  • The short ligament technique which aims to reduce damage to the quadriceps by not requiring the LARS ligament to be pulled through the femoral tunnel into the soft tissue.
  • The suspensory fixation technique which is an alternative to the normal screw fixation and relies on endobutton and cross-pin type suspensory femoral fixations [1].

A detailed explanation of the different surgical procedures can be found here:

The LARS ligament can also be used to augment autograft or allograft reconstructions. This is useful when harvested grafts are weak and/or undersized. The synthetic ligament acts a central core over which the biological ligament is looped. The combined ligament can then be fixed using either interference screws or suspensory fixations[1].

The following video is an animation of an ACL reconstruction using a LARS ligament

Clinically Relevant Anatomy[edit | edit source]

See:

Anterior Cruciate Ligament (ACL)

Anterior Cruciate Ligament (ACL) - Structure and Biomechanical Properties

Rehabilitation[edit | edit source]

As with other forms of ACL reconstruction, rehabilitation depends on other pathologies of the knee as well as the individual characteristics and requirements of the patient. However, research suggests that those with a LARS ligament reconstruction can return to sport at a much earlier date than those with other forms of reconstruction [3] [7][8]

There is limited available information on rehabilitation programmes with these details often missing from studies into the LARS ligament [9]. The following protocol has been suggested:[1]

  • No post-op bracing or immobilisation.
  • Full weight-bearing with mobilisation and isometric quadriceps exercises to be started the day after surgery to recover full extension.
  • 90° of flexion should be obtained after 7-10 days.
  • Return to driving should be at the patient’s and surgeon’s discretion.
  • Return to work will depend on the type of work and the individual patient’s recovery time.
  • A patient can usually commence jogging 6-9 weeks post-surgery.
  • Participation in competitive sport is dependent on the patient’s individual recovery and should only be recommended once the patient has regained full proprioception. Generally, this is possible after 3-4 months.      

Another study by Hamido et al, compared four-strand hamstring grafts (4-SHG) and 4-SHG augmented with LARS ligaments in ACL reconstructions and used the same rehabilitation protocol for both groups. They listed the following schedule in their study.[10]

  • Quadriceps isometric closed kinetic-chain exercises and straight leg raises were initiated as early as possible.
  • Knee flexion began from 45° and increased gradually to complete flexion and extension within the first week.
  • Crutches were used for 3 weeks.
  • Static stepping for balance was allowed for the first few weeks followed by full weight-bearing after 4 weeks postoperative.
  • Cycling was permitted 4–5 weeks postoperatively.
  • Patients usually returned to normal daily activity and allowed to participate in non-competitive sports, which did not include pivoting sports or recreational skiing in four months and returned to sports activity after six months.

Evidence from Research[edit | edit source]

Historically, synthetic ligaments have always failed when compared to biological replacements, so surgeons have been reluctant to suggest this new generation of treatment. This has resulted in a shallow base of research on the outcomes of the LARS ligament and even fewer studies have focused on long-term follow-ups. Even after analysing the available data, it is hard to come to a definitive decision on the validity of the LARS ligament since studies find it either a solid replacement in many situations or a device that still fails to live up to its biological alternatives with high rates of failure and joint synovitis.

The following is a summary of many of the available studies and includes some systematic reviews of multiple studies.

  • A study by Norsworthy[11] examined the results of 54 patients of an average age of 36.5 who underwent a LARS ligament reconstruction at their own request or because they required a rapid return to activity. After a minimum 5-year follow up, 17 patients had a surgically confirmed failure of their LARS ligament, a rate of 31.5%. They found that in all the failures, less than 50% of the LARS ligament had native tissue ingrowth and seven patients had visible evidence of synovitis. In the patients that did not have a failed device, an average IKDC (International Knee Documentation Committee) score of 86.2 and no statistically significant differences in ROM and anterior laxity in side-to-side comparisons was recorded.
  • In a comparative study between the LARS ligament and another synthetic ligament called ABC Purely Polyester Ligament, Iliadis et al[12], found a rupture rate of 31% for the LARS ligament after a mean follow-up of 9.5 years. More than 80% of the ruptures were caused by a further knee injury, with 68% occurring during sports activity. However, for those with an intact ligament, the study reported average Lysholm scores of 90, a mean IKDC score of 90 and positive scores on other measurement scales. The study also reported that 60% of these patients returned to their preinjury level of activity. The average age of participants in this study was 26.1 and all participants were male.
  • Mascarenhas and MacDonald [13] discuss the benefits and outcomes of a variety of synthetic ligaments and use a study by Lavoie et al. among others to examine the LARS ligament. Lavoie examined 47 patients who underwent ACL reconstructions using the LARS ligament. After a mean time of 21.9 months, a follow-up revealed that 38 patients had suffered from chronic ruptures of their ACL and a further 9 presented with acute or subacute ruptures.
  • Two studies by Parchi et al[14], examined the outcomes of the LARS ligament with long-term follow-ups. The first study recorded a global positive result in 92.3% of cases with only one graft failure (1/26) and no cases of knee synovitis or infection. The study concluded that the LARS ligament was suitable for older patients that required a fast functional recovery (9). In the second study, the 26 patients were all aged over 30 and required a quick return to sport. The patients returned to their activity in an average of four months and reported overall positive results. Four (4/26) graft failures were recorded and a majority of patients scored ‘good’ or ‘excellent’ on ROM, knee laxity, KOOS (Knee injury Osteoarthritis Outcome Score) and the Cincinnati knee rating scale[14]. Parchi suggested one reason for the variation in results of studies into LARS could be the difference in methods of graft fixation. However, they also noted that research is being conducted on improving the fixation methods using nanotechnologies.[14]
  • A systematic review by Newman et al,[3] examined the results of nine studies into ACL reconstructions using the LARS ligament. They found a failure rate of just 2.5% in 675 LARS uses and that many of the failures were attributed to a technical error in bone tunnel placement. They also found that a successful return to sport occurred between two and six months after surgery. Furthermore, only two cases of synovitis were recorded. However, it is important to note that Newman determined that the methodological quality of the studies in their review was poor, so this should be kept in mind when analysing the results.
  • A six-week follow-up study by Krupa et al,[15] compared the preoperative and postoperative results of the Lachman test, anterior drawer test and the pivot-shift test on 20 males who underwent a LARS ACL reconstruction. Most recorded normal postoperative results for both the Lachman and anterior drawer test and negative pivot-shift tests. They also found that in general there was no difference in ROM between the involved and uninvolved knees (14). This study is, however, limited by the very short-term nature of the follow-up.
  • Finally, two studies by Hamido et al,[10][16] examined the use of the LARS ligament in conjunction with short or under-sized hamstring tendons compared with autologous four-strand hamstring graft (4-SHG) ACL reconstructions. The first study in 2011 that was conducted at the end of a 5-year follow up found the combination to be ‘useful, safe and satisfactory… especially when an early return to high levels of sports activity is needed’[16]. The second study [10] also found the augmented ACL reconstruction to be superior to the use of just the 4-SHG, again after a 5-year follow-up. The IKDC, KOOS, Lysholm and Tegner scores favoured the LARS augmentation and they also found significantly less anterior displacement than the 4-SHG.[17]

Summary[edit | edit source]

The LARS ligament can function as both an independent synthetic ligament if there are enough tissue remnants of the ruptured ACL or as a scaffold to augment the use of other kinds of ligament graft. It is one of a growing number of synthetic ligaments that are attempting to improve on the failures of past artificial devices. There are multiple iterations of the LARS device to suit many different scenarios in ACL reconstruction, but they all attempt to promote faster healing, a quicker return of proprioception and the ingrowth of native tissue into the reconstruction.

There are multiple reconstructions and augmentation techniques based on the type of LARS ligament used and the requirements of the patient.

Rehabilitation programmes for LARS reconstructions are similar to those for autograft and allograft surgeries but boast an accelerated return to function. However, other joint and connective tissue pathologies must be taken into account when designing and prescribing recovery and rehabilitation schedules.

The research into the reliability and validity of the LARS ligament has produced extremely varied data, with many studies producing contrary results. Researchers who have conducted systematic reviews have often cautioned on the methodological quality and the scarcity of high-quality, long-term follow-up studies when making a judgement on the use of the LARS ligament in ACL injuries.

References[edit | edit source]

  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 Corin Group. ACL Augmentation and Reinforcement Surgical technique LARS ACLTM Contents [Internet]. Corin P; 2013 [cited 2020 Sep 11]. Available from: https://www.coringroup.com/assets/product-resources/LARS/Resources-Product-Literature-LARS-ACL-Surgical-Technique.pdf
  2. Corin Group. LARS TM ACL [Internet]. Corin P; 2010 [cited 2020 Sep 12]. Available from: https://www.coringroup.com/assets/product-resources/LARS/Resources-Product-Literature-LARS-ACL-Your-Questions-Answered.pdf
  3. 3.0 3.1 3.2 3.3 Newman SDS, Atkinson HDE, Willis-Owen CA. Anterior cruciate ligament reconstruction with the ligament augmentation and reconstruction system: A systematic review [Internet]. Vol. 37, International Orthopaedics. Springer; 2013 [cited 2020 Sep 11]. p. 321–6. Available from: /pmc/articles/PMC3560896/?report=abstract
  4. 4.0 4.1 Chen S, Chen T, Wan F, Jiang J, Feller JA. Synthetic ligaments for ACL reconstruction. In: Controversies in the Technical Aspects of ACL Reconstruction: An Evidence-Based Medicine Approach [Internet]. Springer Berlin Heidelberg; 2017 [cited 2020 Sep 13]. p. 333–41. Available from: https://link.springer.com/chapter/10.1007/978-3-662-52742-9_31
  5. Whatever happened to LARS? The miracle ACL surgery that was too good to be true - ABC News [Internet]. [cited 2020 Sep 11]. Available from: https://www.abc.net.au/news/2018-08-17/whatever-happened-to-lars-acl-the-miracle-cure-that-was-too-good/10129102
  6. Iliadis DP, Bourlos DN, Mastrokalos DS, Chronopoulos E, Babis GC. LARS Artificial Ligament Versus ABC Purely Polyester Ligament for Anterior Cruciate Ligament Reconstruction. Orthop J Sport Med [Internet]. 2016 Jun 23 [cited 2020 Sep 11];4(6):2325967116653359. Available from: http://www.ncbi.nlm.nih.gov/pubmed/27453894
  7. 7.0 7.1 Parchi PD, Gianluca C, Dolfi L, Baluganti A, Piolanti N, Chiellini F, et al. Anterior cruciate ligament reconstruction with LARSTM artificial ligament results at a mean follow-up of eight years. Int Orthop [Internet]. 2013 Aug 1 [cited 2020 Sep 12];37(8):1567–74. Available from: https://pubmed.ncbi.nlm.nih.gov/23812539/
  8. Mascarenhas R, MacDonald PB. Anterior cruciate ligament reconstruction: A look at prosthetics - Past, present and possible future [Internet]. Vol. 11, McGill Journal of Medicine. McGill University; 2008 [cited 2020 Sep 12]. p. 29–37. Available from: /pmc/articles/PMC2322926/?report=abstract
  9. Machotka Z, Scarborough I, Duncan W, Kumar S, Perraton L. Anterior cruciate ligament repair with LARS (ligament advanced reinforcement system): A systematic review [Internet]. Vol. 2, Sports Medicine, Arthroscopy, Rehabilitation, Therapy and Technology. BioMed Central; 2010 [cited 2020 Sep 12]. p. 1–10. Available from: https://link.springer.com/articles/10.1186/1758-2555-2-29
  10. 10.0 10.1 10.2 Hamido F, Al Harran H, Al Misfer AR, El Khadrawe T, Morsy MG, Talaat A, et al. Augmented short undersized hamstring tendon graft with LARS® artificial ligament versus four-strand hamstring tendon in anterior cruciate ligament reconstruction: Preliminary results. Orthop Traumatol Surg Res. 2015 Sep 1;101(5):535–8.
  11. Norsworthy CJ, Tulloch SJ, Devitt BM, Porter TJ, Hartwig TR, Klemm HJ. My experience with the LARS ACL device at minimum 5 year follow up. 2017 ISAKOS Congress, 7 June 2017 [cited 2020 Sep 11]. Available from: https://www.isakos.com/data/abstractpresentations/GenSes/2017-06-07/1530-SectionID1214/1550-Norsworthy/OUTLINE_EVENT_10096_MEMBER_ID_74440.pdf
  12. Iliadis DP, Bourlos DN, Mastrokalos DS, Chronopoulos E, Babis GC. LARS Artificial Ligament Versus ABC Purely Polyester Ligament for Anterior Cruciate Ligament Reconstruction. Orthop J Sport Med [Internet]. 2016 Jun 23 [cited 2020 Sep 11];4(6):2325967116653359. Available from: http://www.ncbi.nlm.nih.gov/pubmed/27453894
  13. Mascarenhas R, MacDonald PB. Anterior cruciate ligament reconstruction: A look at prosthetics - Past, present and possible future [Internet]. Vol. 11, McGill Journal of Medicine. McGill University; 2008 [cited 2020 Sep 12]. p. 29–37. Available from: /pmc/articles/PMC2322926/?report=abstract
  14. 14.0 14.1 14.2 Parchi PD, Ciapini G, Paglialunga C, Giuntoli M, Picece C, Chiellini F, et al. Anterior cruciate ligament reconstruction with LARS artificial ligament—clinical results after a long-term follow-up. Joints [Internet]. 2018 Jun 1 [cited 2020 Sep 12];6(2):75–9. Available from: /pmc/articles/PMC6059861/?report=abstract
  15. Krupa S, Królikowska A, Reichert P. Postoperative Knee Joint Stability Following Anterior Cruciate Ligament Reconstruction Using the Ligament Advanced Reinforcement System. Polim Med [Internet]. 2016 Jul 1 [cited 2020 Sep 12];46(2):155–61. Available from: https://pubmed.ncbi.nlm.nih.gov/28397456/
  16. 16.0 16.1 Hamido F, Misfer AK, Al Harran H, Khadrawe TA, Soliman A, Talaat A, et al. The use of the LARS artificial ligament to augment a short or undersized ACL hamstrings tendon graft. Knee [Internet]. 2011 Dec 1 [cited 2020 Oct 20];18(6):373–8. Available from: http://www.thekneejournal.com/article/S0968016010001754/fulltext
  17. Wang XM, Ji G, Wang XM, Kang HJ, Wang F. Biological and Biomechanical Evaluation of Autologous Tendon Combined with Ligament Advanced Reinforcement System Artificial Ligament in a Rabbit Model of Anterior Cruciate Ligament Reconstruction. Orthop Surg. 2018 May 1 [cited 2020 Oct 20];10(2):144–51. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6594536/