Anterior Cruciate Ligament Repair with Internal Brace Ligament Augmentation

Wilson WT, Hopper GP, Byrne PA, MacKay GM. Surg Technol Int. 2016 Oct 26;XXIX:273-278. [Link to free full text article]

This is the editor's interpretation of a paper published in the orthopaedic literature in 2016 - our attempt to make relevant medical articles accessible to lay readers. If you wish to read the original it is easy to ask your librarian to obtain a reprint for you from any medical library.


This is a case study of a patient who underwent a novel procedure of Anterior Cruciate Ligament (ACL) repair with internal bracing - that is re-constituting a torn anterior cruciate ligament rather than reconstructing it with a graft, bridging the defect with a braided suture tape and knotless bone anchors to reinforce the ligament while it healed. this was called internal brace augmentation. The patient's outcome was followed for two years.

Prior to the modern era of reconstruction of the ACL, attempts were made to repair the ligament, but results of repair were generally poor and did not appear to be much different from doing nothing. Reconstruction became the norm, using graft material obtained from the patient (autograft) or from a donor (allograft). The concern with reconstruction, though, is that the native ligament has what are called 'proprioceptive' fibres, and when the original ligament is replaced with a graft much of the proprioception - or position sense - of the knee is lost. Also problems can be experienced when grafts are taken from the same patient, with hamstring muscle weakness following harvesting of hamstrings tendon, while the alternative patellar tendon grafts can lead to anterior knee pain. Follow-up data also showed high rates of post-traumatic osteoarthritis within 20 years, despite  the ACL having been reconstructed.

During these years instrumentation improved and there have been advances in tissue engineering and regenerative medicine. Modern surgical techniques are now very focused upon restoring normal knee biomechanics to improve function and preventing long-term problems, and all of these factors has led to a re-evaluation of the older literature about repair. Some work was done to reinforce repair with bone marrow stem cells to enhance the healing of the ligament, but this required that a brace was worn over the knee to limit range of motion while the ligament healed, but this slowed rehabilitation. So Gordon Mackay, the senior author of this paper, developed a technique to repair the ACL arthroscopically (keyhole surgery) and protect the healing ligament - not via an external brace but via an internal brace ligament augmentation, which will allow faster rehabilitation. The technique uses braided suture tape and knotless bone anchors to reinforce the ligament strength and act as a secondary stabiliser after repair and on return to sports. 

 

The patient

This patient was a fit 52 year old, who had torn the ACL in her right knee while skiing, with classical mechanism of injury and clinical symptoms of a torn ACL At three weeks after her injury an outpatient appointment confirmed a lax knee with a positive anterior drawer and Lachman test indicative of a torn ACL. At four weeks after the injury she was taken to the operating theatre where the instability was confirmed under anaesthesia by a positive pivot shift test. Arthroscopy showed some softening of the joint cartilage of the femur (chondromalacia) and there was a complete tear of the ACL in its proximal part where it had avulsed from its normal attachment on the medial wall of the rounded end of the femur bone. [Ed: This tear position is important, because the review of the older literature had shown that some patient had indeed done reasonably well with repair, but that in these patients the tear was usually in the proximal part.]

 

The technique

The ACL remnant was “whip stitched”, the bone was 'picked' with a microfracture probe to stimulate bleeding, and the proximal end of the ACL was then re-approximated against the medial wall femur in its original position. A 2.5 mm braided ultra high-molecular-weight polyethylene tape was drawn in to bridge the repair from tibia to femur. This involved drilling small 3.5 mm tunnels in the tibia and femur. The upper ends of the repair and the augmentation were tensioned and fixed with a device called an ACL TightRope® and at the bottom end the braid was fixed using a device called a Swive-Lock® Suture Anchor.

 

Rehabilitation

After surgery, the patient was entered into their standard ACL rehabilitation programme, with early accelerated recovery and full weight bearing with no limitation on movement, after which she was discharged and reviewed at two weeks, five weeks, 10 weeks, and four months post-operatively. At four months, her knee was stable and she had a full range of movement with excellent muscle tone, and was back at the gym five times per week and extremely happy with her outcome. She was discharged  went on to lead the same active lifestyle that she had pre-injury, including skiing at the same level without problems. 

 

A second injury, and an opportunity for a 'second look'

At two years unfortunately she had another incident while trying to was her foot in the sink, and had twisted the same knee, which was now locked. Investigations and arthroscopy showed a sprain of the medial collateral ligament (MCL) and a torn piece of joint cartilage which was causing the locking. The ACL, however, was absolutely fine! She went on to make a full recovery and was doing well at 3 years when this article was published.

 

Conclusions

  • The authors feel that it is important that this patient presented early post-injury, and suggest that if primaryrepair is to be attempted it should be done within six weeks.

     
  • Also, this patient had a proximal ACL rupture close to the normal insertion on the femur and the type of tear which is particularly suitable for this technique.

     
  • They point out that the tunnels are only 3.5 mm, which is very small, and if there was failure of the repair then a reconstruction could be performed by simply widening these original tunnels, which is another advantage.

     
  • Inadvertantly this patient offered an opportunity to go into the knee again and confirm the integrity of the repair, proving that in her instance it was not the case that the augmentation, rather than the ligament, that was allowing such a good return to her previous sporting level.

     
  • To all this is the added benefit of retained native ACL tissue exhibiting proprioceptive qualities, with benefits in co-ordination, balance, and overall function. 

     
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