ACL Reconstruction with the LARS Ligament

Posted on 21. Oct, 2010 by The Sports Physiotherapist

 

LACKING APPROPRIATE RESEARCH SUPPORT OR THE NEXT GOLD STANDARD?

It must be the hottest debate in knee surgery at the moment. Should ACL reconstructions be performed using the LARS (Ligament Augmentation and Reconstruction System) or should orthopaedic surgeons continue to use the more traditional four strand hamstring (4HS) or bone patella tendon bone (BPTB) grafts? It is a good question. Obviously for us as sports physiotherapists the choice is not ours to make, but, invariably the injured athlete will ask our professional opinion.

So how do you reply when they say – “What do you think I should do?”. The easiest thing to do is give them some facts.

THE LARS SURGERY

The latest LARS is composed of polyethylene terephthalate – an industrial-strength polyester fibre. It can only be used in a population that has a well vascularised ACL stump, ideally in acute settings. The theory is that the LARS pulls the two ends of the ACL together and allow for fibroblastic ingrowth.  Check out the video below for a sweet animation of the surgery – drilling tunnels, fixation etc.

OUTCOMES

The unfortunate thing about the ‘new’ LARS ligament is that there are no long-term follow-ups, as widespread use of the new ligaments has not been around. This is the biggest issue many orthopaedic specialists have, will it stand up to the test of time? You know what, only time will tell. Until then, the best research has approximately 5 year follow-ups. Therefore, the outcomes discussed below are within that time-frame.

DONOR SITE MORBIDITY

This is a benefit of the LARS graft option. Having no donor site means that there is no donor site morbidity. Roe et al. (2005) showed at 7 year follow up 14% of 4HS and 38% of BPTB patients had some donor site symptoms (tenderness, irritation or numbness). This is definitely a tick in the LARS box.

RTP TIME-FRAMES

Optimal management of a LARS reconstruction can result in RTP at the 3 month mark, which many would suggest is the main draw-card of the LARS. This is particularly given that it is widely accepted that appropriate RTP time-frames for 4HS and BPTB grafts are 6 – 12 months. The traditional graft choices mean that an ACL rupture is season ending whichever way you look at it. Another win for the LARS crew.

KNEE STABILITY

The studies widely examine knee stability utilising the KT1000, and a good level of stability is a side-to-side difference in anterior translation of less than 3mm. At four year follow-up, 73.9% of 4HS and 95.8% of LARS had less than 3mm of translation (Liu et al. 2010). Roe et al. (2005) showed that 82% of BPTB grafts had less than 3mm of translation at 5 year followup. This suggests that in the short term LARS offers increased knee stability.

ACTIVITY LEVELS

Generally measured using the Lysholm Knee Scale and Tegner Score. Liu et al. (2010) found no significant differences between LARS and 4HS grafts at 4 year follow up. Roe et al. (2005) found no significant differences between 4HS and BPTB at 5 and 7 year follow up.

COMPLICATION RATES

In the short term window i.e. 5 year follow up, there does not seem to be a major difference in failure rates. Gao et al (2010) showed a complication rate of approximately 6% at 5 years. Roe et al. (2005) suggests that there is no significant difference between BPTB and 4HS failure rates at 7 year followup – about 20% for both. Interestingly, the study found those with patellar tendon grafts were more likely to rupture their contralateral ACL (18%) than ipsilateral (4%), whilst for 4HS grafts there was approximately even risk (10%) between legs. Either way you can tell your athlete they have a one in five chance of ending up with another ACL rupture.

SUMMARY

Information overload? In summary, this evidence suggests at 4 year follow up the LARS show improved outcomes of:

  • Donor Site Morbidity
  • RTP Timeframes
  • Knee Stability

CONCLUSIONS

You know what, I was surprised by these results. One thing has been made clear to me:

The LARS Ligament can be used as a short-term short-rehab solution for ACL ruptures.

Other than that, I could not in good conscience recommend the LARS ligament to athletes. If you are pushing for one more season, one more Olympic Games or one more contract signing in the short term then the LARS may be the appropriate decision. However, there is no long-term data to display what the longer term outcome is going to be.

 

REFERENCES

Roe J, Pinczewski LA,  Russell VJ, Salmon L, Kawamata T and Chew M. A 7-Year Follow-up of Patellar Tendon and Hamstring Tendon Grafts for Arthroscopic Anterior Cruciate Ligament Reconstruction : Differences and Similarities. Am J Sports Med 2005 33: 1337

Gao K, Chen S, Wang L, Zhang W, Kang Y, Dong Q, Zhou H, Li L. Anterior Cruciate Ligament Reconstruction With LARS Artificial Ligament: A Multicenter Study With 3- to 5-Year Follow-up.
Arthroscopy – Journal of Arthroscopic and Related Surgery (2010) 26 (4), pp. 515-523

Liu Z, Zhang X, Jiang Y, Zeng B. Four-strand hamstring tendon autograft versus LARS artificial ligament for anterior cruciate ligament reconstruction. International Orthopaedics (SICOT) (2010) 34:45–49

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