Developments in ACL Repair

[Stryker]

I shared this post in another forum.

Last season, one of my worst fears as a parent of a college athlete was realized as I watched my daughter land oddly after jumping to secure a soccer ball and collapse to the ground. She was diagnosed as sustaining a torn ACL and sprained MCL that required surgery. While her school helped arrange a quick surgical consult with a local surgeon for standard ACL surgery, my wife performed her own research and came across a new surgical procedure that neither the surgeon, the school's training staff or athletic department had any familiarity. The procedure is called Bridge Enhanced ACL Repair or BEAR and in simple terms allows the ends of the torn tendon re-grow together with the help of an absorbable collagen implant. Unlike standard ACL re-construction, the procedure does not require a hamstring graft or graft from a cadaver. The recovery time is similar to that of standard ACL re-construction but does require that the patient remain in a brace for a few weeks longer than the normal procedure. Preliminary studies suggest that the BEAR procedure will lead to less osteo-arthritis in the knee. It looks like the BEAR procedure may be the future of ACL repair. My daughter elected to have the BEAR procedure in November and is well on her way to full recovery and playing for her team in August.

Since most parents and physicians we have spoken to have had no knowledge of this procedure, I felt it important to share with a community of people that care about college sports and student athletes. Attached are some preliminary studies regarding the procedure.

The Bridge-Enhanced Anterior Cruciate Ligament Repair (BEAR) Procedure: An Early Feasibility Cohort Study - PubMed (nih.gov)

Bridge-Enhanced Anterior Cruciate Ligament Repair: Two-Year Results of a First-in-Human Study - PubMed (nih.gov)

[Ralph Turner]

Stryker, thanks for the post.

However, the links to the articles that you reference did not post.

If you cannot get the links to post, please Personal Message (PM) me here or email me and I will try to assist.

[Ryan Scott (Hoops Fan)]

This is good news.  I had a 90% tear of my MCL in high school and elected not to have surgery because of all the extra complications.  It healed on its own and it's good as new in terms of strength, but I definitely have more pain, etc.  This procedure seems like the best of both worlds - natural healing and some surgical repair.

Thanks for sharing.

[Stryker]

I'll try to repost the  links to the studies are below:

https://pubmed.ncbi.nlm.nih.gov/27900338/

https://pubmed.ncbi.nlm.nih.gov/30923725/

Hopefully they work.

[Ralph Turner]

I'll try to repost the  links to the studies are below:

https://pubmed.ncbi.nlm.nih.gov/27900338/

https://pubmed.ncbi.nlm.nih.gov/30923725/

Hopefully they work.

Thanks Stryker.

Both articles are Open Access, so you can click on the link and print the article to take to your orthopedist.

I first began using non-crosslinked decellularized porcine jejunum (small intestine) matrix in the early 2000's for pelvic floor repairs and had great results with it. I had no complications and believed that I got better repairs with the non-crosslinked decellularized collagen matrix, which provided a scaffold for pelvic floor repairs, than native tissue repairs or the synthetic graphs which other doctors were using. In the animal studies of the product that I used, the tritium-labeled (³H) matrix was detectable at 1% in the extirpated organ at 12 weeks. This scaffolding was removed proverbially "brick by brick" and replaced immediately with the desired tissue. It appears that this is what is happening in the ACL. I notice that the hamstring length seems longer at the 2 year follow up. This surgery makes sense to me as an improvement and may be state of the art in about 5 years. (I expect to see Dr Murray https://www.childrenshospital.org/directory/martha-murray on the lecture circuit and national television, when she  is comfortable to promote this.)

In my case, the company pulled the product from the market when the FDA sent warnings about "Mesh" for pelvic floor repairs. Even tho' this was not a mesh, they did not want to hassle with the trial lawyers who would lump this product in with the "meshes", much to my dismay.

By the way, the husband of one of my patients, who had one of my early repairs, went to the Masters in Augusta GA 6 months later and bought me a shirt. That and a few other early patients convinced me the scaffolding did with respect to the repair what meshes or other crosslinked biologics could not do. I still see a few of my repairs 15-20 years later.

[Gregory Sager]

I'll try to repost the  links to the studies are below:

https://pubmed.ncbi.nlm.nih.gov/27900338/

https://pubmed.ncbi.nlm.nih.gov/30923725/

Hopefully they work.

Thanks Stryker.

Both articles are Open Access, so you can click on the link and print the article to take to your orthopedist.

I first began using non-crosslinked decellularized porcine jejunum (small intestine) matrix in the early 2000's for pelvic floor repairs and had great results with it.

Translated into Texan as, "Ma'am, let's jus' boil us up some chitlins and we'll use it to fix up your lady parts good and proper!"

(Seriously, though, Ralph, this is impressive work, and I learned a ton about modern surgical replacement techniques for ligaments in your response. Thanks!)

In my case, the company pulled the product from the market when the FDA sent warnings about "Mesh" for pelvic floor repairs. Even tho' this was not a mesh, they did not want to hassle with the trial lawyers who would lump this product in with the "meshes", much to my dismay.

By the way, the husband of one of my patients, who had one of my early repairs, went to the Masters in Augusta GA 6 months later and bought me a shirt. That and a few other early patients convinced me the scaffolding did with respect to the repair what meshes or other crosslinked biologics could not do. I still see a few of my repairs 15-20 years later.

Y'know, I never thought of it this way before, Ralph, but it occurs to me that a lot of the perquisites that come with your chosen profession must consist of tangible rewards from grateful husbands.

[Ralph Turner]

Proverbially, it is extremely gratifying to give a woman back her life with pelvic floor reconstruction. I have the most wonderful patients in the world. I am so grateful for them.

[Stryker]

So happy this board has returned. Figured I'd update you all with a link to an article published in April 2023 providing the first meta-analysis comparing the BEAR and the ACLR techniques in the management of ACL tears.

https://pubmed.ncbi.nlm.nih.gov/37042698/

The study compares the results of BEAR ACL surgery to ACL reconstruction using a hamstring graft. The authors note that the analysis may be different for ACL reconstruction using a patellar graft since the patellar tendon is stronger.

The study confirms that "compared to the ACLR technique, the BEAR surgery showed no differences in muscle strength (quadriceps and hip abductors) knee joint laxity, and postoperative knee scores. However, it showed better hamstring strength. Earlier resolutions of symptoms and return to activities were also seen in the BEAR group. These results prove that this primary repair technique is a reliable and efficacious technique for the treatment of ACL ruptures, however, further randomized clinical studies will be needed to compare both of these techniques."

I'll share further studies as they are published.

[Stryker]

At least 2 of the BEAR trials should be reporting new data sometime this year as the participants in the respective studies reach the 2 yr and 6 year post-op stages. In the interim, I figured I'd share
some interesting articles with implications for advances in ACL repair. The first is:
New understanding of avian eggshell attachment -- implications for medical procedures and egg industry
https://www.sciencedaily.com/releases/2024/02/240214122613.htm


This new understanding could someday allow doctors to use nanospikes to attach the ligament or replacement graft to the bone rather than placing a screw into the bone to serve as the anchor.

The second is:
Females less likely to heal from ACL injuries than males | ScienceDaily
https://www.sciencedaily.com/releases/2023/10/231018115125.htm


While not earth-shattering, the data gives some insight into a cause for the disparate rate of ACL injuries between male and female athletes and may eventually lead to changes that could reduce the occurrence of ACL injuries for female athletes.

[DriftlessDuhawk]

So happy this board has returned. Figured I'd update you all with a link to an article published in April 2023 providing the first meta-analysis comparing the BEAR and the ACLR techniques in the management of ACL tears.

https://pubmed.ncbi.nlm.nih.gov/37042698/

The study compares the results of BEAR ACL surgery to ACL reconstruction using a hamstring graft. The authors note that the analysis may be different for ACL reconstruction using a patellar graft since the patellar tendon is stronger.

The study confirms that "compared to the ACLR technique, the BEAR surgery showed no differences in muscle strength (quadriceps and hip abductors) knee joint laxity, and postoperative knee scores. However, it showed better hamstring strength. Earlier resolutions of symptoms and return to activities were also seen in the BEAR group. These results prove that this primary repair technique is a reliable and efficacious technique for the treatment of ACL ruptures, however, further randomized clinical studies will be needed to compare both of these techniques."

I'll share further studies as they are published.

Super interesting stuff. As a physical therapist, I have heard about BEAR, myself and many of my colleagues are in the wait-and-see period on it. I have heard one negative review from a PT who saw a patient with a BEAR implant and stated that the patient was having nervous system issues following the surgery...

Hopefully, the technology will keep progressing and we can get to the point where they have the kinks ironed out. The benefit of having a brand new ACL vs a different ligament in the place of an ACL is huge. Due to the uniqueness of the ACL the fiber direction is different than that of every other tendon and ligament in the body. Being able to have a new ligament in place that has the same fiber direction as an ACL will allow it to perform in the best possible way.

[Stryker]

Hopefully, this is not getting too technical but the below linked article provides a meta-analysis of the reported clinical outcomes of autograft ACL reconstruction compared to augmented ACL repair procedures.

https://journals.sagepub.com/doi/full/10.1177/23259671231223743#bibr1-23259671231223743

The article concludes that autograft ACL reconstruction remains the gold standard for ACL injuries. The authors note that, as a group, augmented ACL repair was associated with higher rates of reoperation, hardware removal, and failure compared with autograft ACL reconstruction in studies with minimum 2-year follow-up data. While also noting that augmented ACL repair had higher Lysholm scores and hamstring strength versus autograft ACL reconstruction, they suggest that these advantages are short-lived. "It seems that, compared with ACL reconstruction, ACL repair has a better return to activity, knee function, and quality of life during early follow-up, but, when regarding the longer follow-up time, no significant difference was found. A randomized clinical trial by Barnett et al5 with a maximum follow-up time of 2 years showed that patients undergoing the BEAR procedure had a higher IKDC score and Knee injury and Osteoarthritis Outcome Score (KOOS) as well as better hamstring muscle strength than patients undergoing ACL reconstruction at early timepoints postoperatively. However, the gap between BEAR and ACL reconstruction in IKDC score and KOOS narrowed over time, whereas significant differences in hamstring strength persisted until the 2-year follow-up."

This study has some limitations, especially as it applied to the BEAR procedure. First, the data on some new procedures, like BEAR, is not long enough to be conclusive since post-op data on reported clinical outcomes has yet to reach beyond the five year point. While the two year data on BEAR has been released,  the six year post-op data on the first BEAR Study is only now expected to be released later this year. As such, their conclusions, as it applies to BEAR procedures, may have to be re-visited.

 Second, the authors did not conduct a subgroup analysis. Instead, they included a variety of arthroscopic ACL repair techniques under the category of augmented ACL repair. Those techniques include suture anchor repair (SAR), suture augmentation repair, repair with dynamic intraligamentary stabilization (DIS), bridge-enhanced ACL repair (BEAR), and internal brace ligament augmentation (IBLA). A high negative rate relative to only one such technique could skew the conclusions as to the entire group.  For example, the ACL repair group showed a significantly higher hardware removal rate. As the authors note, this is probably because most of their included studies used a DIS augmentation technique, in which the monobloc spring-screw is much bulkier than that used in ACL reconstruction, leading to a frequent removal of hardware. Review of the studies indicated that most reoperations were caused by hardware removal, scar tissue, range of motion deficits, and arthrofibrosis, which might be caused by the additional spring device that is implanted in the tibia during repair, especially repair with dynamic augmentation. Since such hardware in not included in the BEAR  procedure, the negative rates for hardware rate and re-operations are likely not applicable to the BEAR procedures and  may be misleading to a patient considering BEAR.

Moreover, the authors recognized that certain procedures are limited to certain patient populations and different rupture locations. For example, a BEAR procedure is generally limited to ruptures with frayed ends and must be conducted within the first 90 days following injury. Different qualifiers apply to other procedures.  Whether the results will be sustained at long-time follow-up is still unknown because there are too few long-term comparative studies focusing on different surgical techniques and patient populations to conduct subgroup analysis. Some potential confounders, such as age and preoperative activity level, were not corrected, which might cause risk of bias because younger age and (pursuit of) higher activity level have been reported to negatively influence the outcomes of both modern ACL repair and ACL reconstruction. In other words, younger patients may have different results than older patients.

My takeaway from the report is that it is still too early to determine whether the BEAR procedure is more or less effective than ACL reconstruction.

[Stryker]

As expected, the 6 yr followup results of the BEAR I trial were published three days ago.

https://journals.sagepub.com/doi/full/10.1177/23259671241260632

The purpose of this study was to compare the 6-year follow-up outcomes of patients who underwent the BEAR procedure compared with those of a nonrandomized concurrent control group receiving autograft ACL reconstruction (ACLR). Since this was the first trial of its kind, the number of patients involved was small, consisting of only 10 patients in each group. We still await the results of subsequent BEAR II trial that evaluated a larger group of patients. Still, the results of the preliminary trial remain promising.

The 2-year follow-up data from the first 2 BEAR trials determined that the BEAR implant was safe, that the clinical and patient-reported outcomes of the BEAR procedure were equal to or greater than those of ACLR procedures and that those having the BEAR procedure had greater hamstring function than those patients receiving the ACLR procedure, However, long-term assessments were needed to determine if the 2-year results of BEAR would be maintained. This study provides the clinical and patient-reported outcomes 6 years after the date of surgery.

The most important finding of this study was that patients who underwent the BEAR procedure had outcomes no worse than those after ACLR with a hamstring tendon autograft at the 6-year follow-up. While the outcome in certain categories for both groups were comparable, there were several categories where the BEAR procedure exceeded the outcomes for the ACLR group.

As suspected, the study showed that the isometric hamstring strength of patients remained significantly greater in the BEAR group compared with the ACLR group, as was the case at the 2-year follow-up. IKDC physical examination grades for BEAR were also superior to those after ACLR, another finding that was present at the 2-year follow-up. Approximately two-thirds of patients in each group had ligament or graft tissue with low signal intensity (indicating a stronger ligament) on the 6-year MRI scans. Instrumented anterior laxity values for BEAR and ACLR were similar at the 2- and 6-year follow-ups. It is interesting to note that the 2-year results of the BEAR I trial were similar to those reported in the 2-year follow-up of the larger BEAR II trial (NCT02664545), in which patients were randomized to receive BEAR or ACLR. It will be interesting to see if the 6-year BEAR II results will follow suit when those data become available.

It is also interesting to note that at the 2-year follow-up, there were no ipsilateral ACL reinjuries within either group in the BEAR I trial. Since the 2-year follow-up, an additional patient in each group underwent another knee surgery: a partial meniscectomy in the ACLR group and hardware removal in the BEAR group.So there appears to be no difference in reported re-injuries between the 2 groups in this study.

Quadriceps and hamstring muscle weakness after ACLR surgery has been well documented. In an adolescent population, it was reported that patients receiving hamstring tendon grafts have a 32% deficit in hamstring muscle strength at the 6- to 9-month follow-up. Morphological and strength deficits of the hamstring muscles after hamstring tendon reconstruction in adults are present at 2-year follow-up. In the current study, patients receiving BEAR did not exhibit significant muscle strength deficits at 6 years, while those in the ACLR group, all of whom received a hamstring tendon graft, had a significant reduction in isometric hamstring strength.

In short, the data in this small study continue to support the position that the BEAR procedure is at least as good as ACLR and exceeds ACLR in several key categories. However, more data is needed. Studies are underway to identify which patients will do better with BEAR. Animal studies suggest that the post-traumatic osteoarthritis after BEAR is less than that seen after ACLR. It will be interesting to see if these findings translate to humans.