Recently The Age / Sydney Morning Herald media outlet published an article titled “For decades, an ACL tear meant surgery. New evidence suggests that may be the wrong move.” The article highlights a recent publication in the British Journal of Sports Medicine which uses a systematic review (literature review) and a meta analysis to examine the various outcomes comparing surgery to rehabilitation following an ACL rupture. In short, the study found rehabilitation with the option for surgery performed similarly to surgery.

Surgery has been the primary treatment intervention for active individuals, especially for athletes; however rehabilitation without surgery has been a long viable option for less active individuals and in those that don’t participate in sports involving pivoting / rapid change in direction like cycling. Cadel Evans is a notable athlete who competed at a professional level without undergoing ACL reconstruction (ACLR).

What is the ACL?

The ACL or anterior cruciate ligament is one of two cruciate ligaments in the knee which provides stability to the knee. In the case of the ACL, it’s primary role is to prevent the tibia (shin bone) from sliding forward on the femur (thigh bone) which is called “anterior translation”. Additionally, it plays a role in limiting rotation at the knee, hence it is a key stabilizer of the knee especially when the knee is in a straightened position. When it is ruptured, instability of the knee during pivoting movements becomes apparent in many cases. Hence surgery is often required to reconstruct the ruptured ligament to restore stability to the knee.

Are We Wrong to Be Operating on ACL Injuries?

We need to put some context around the study The Age articles uses to support its narrative. Firstly, The Age article relies on only one study to support their claim, rather than a raft of papers indicating a similar outcome. The author correctly stated the quality of the data is low and hence the recommendations are also low quality. Secondly, on closer inspection the papers inclusion criteria include studies across all age groups, doesn’t exclude for surgery/rehab following re-ruptures, doesn’t stratify by age, sex nor surgical technique, graft type however, does includes randomized controlled trials which is a stronger methodology. Essentially though, this means we are mixing up different groups which can potentially influence the findings. This adds additional weight to suggest the findings of this study are by no means a gold standard even though the methodology was robust.

Further investigation reveals an earlier high quality systematic review which examined randomized control trials comparing surgery to conservative management. Again, the results of this review were low quality due to the high risk of bias. This study on the surface supports the articles claim that there is no difference between patient reported knee function at 2 and 5 years follow up between either group. However, when we dig deeper, we see that the most prevalent complication in the rehabilitation group was instability and by 2 years 39% went for ACLR and by 5 years this had increased to 59%. They also found that the ACLR group had higher return to sport (RTS) rates at 2 years than those in the rehabilitation group.

Return to Sport / Reinjury

The author further highlights the lower rates of RTS and risks of reinjury following surgery as additional arguments for why conservative management could be a viable alternative to surgery. It is important though, to understand what sits behind this data. A systematic review of 1342 recreational athletes found that only 59% returned to pre-injury levels of sport following ACLR, this is slightly higher than the 1/3 stated in the article but provides support for lower RTS rates post-surgery. Another systematic review and meta analysis examining 3744 patients found a similar number (61.8%) of athletes RTS following ACLR. To put context to these low RTS rates we need to consider the psychological impact such a devastating injury has on an individual. That same paper found those who RTS had higher psychological readiness, higher self-efficacy and lower kinesiophobia (movement/joint phobia) compared to those who did not RTS. Furthermore, reinjury risks for ACL ruptures include reduced psychological readiness to RTS. This highlights the importance of the psychological impact of an injury on RTS and may in part help to explain the lower rates of RTS especially in non-elite athletes, rather than associating it with a failure of surgery.

All Groups Are Not Equal

As mentioned earlier the study used to formulate the narrative for The Age article grouped all individuals together and it is known that there are specific subgroups of individuals with different risks and outcomes, males versus females, adolescent versus adults, recreational versus elite athletes etc This isn’t a critcism of the paper, as the data wasn’t available for the authors to undertake a subgroup analysis. However, in youth and adolescents a low quality systematic review and meta analysis comparing surgery to rehabiliation found 20 to 100% in the rehabilitation group experienced instability and only 6-50% in that group RTS. They found early ACLR over delayed ACLR resulted in reduced risks of meniscal tears and irreparable tears. While those in either surgical group had RTS rates of 57-100%. It is also well documented that females, especially soccer players are at greater risk of an ACL injury than males which is postulated to be due to anatomical differences (tibial slope angles).

What About Knee OA?

The author makes a claim that ACLR reduces the risks of osteoarthritis (OA), a claim which they provide no evidence to support. Again, this falls back into all things are not equal and so we cannot group everyone together. It is possible to rupture an ACL and preserve the meniscus. Furthermore, injuries can involve one or both meniscus, as well as the articular cartilage and damage to meniscus and/or cartilage are going to be relevant factors in whether an individual is likely to develop OA. A recent lower quality systematic review and meta analysis examining clinical outcomes and OA 22 years post ACLR found satisfactory outcomes but noted high levels of OA (2.8x compared to the individuals well knee) particularly in those with concomitant meniscal and or cartilage injuries, adding further weight to the argument that cartilage/meniscus injury may play a role in OA development following ACL ruptures.

Furthermore, knee OA following ACLR is a multifactorial process potentially involving factors associated with surgery like an incorrect femoral/tibial alignment but also factors not associated with surgery such as early return to sport, altered lower limb strength and balance. In that follow up study 12.8% had severe OA and only 1.1% went on for a total knee replacement. Melbourne sports chiropractor Dr. Shannon has spent time with orthopaedic knee surgeons in clinical practice and surgery in the US and it is their opinion based on personal experience that the risk of OA increases in patients who delay or do not undergo reconstruction due to the higher likelihood of cartilage injuries.

Where Are We Then?

The narrative for the article is that we have been potentially wrong to operate on those with ACL injuries and perhaps we need to look at alternatives. As has been clearly illustrated in this blog, strong, consistent data is clearly lacking to support a view that we shouldn’t be operating on ACL injuries especially in those active individuals. Injury management options are always weighed up and made based on the circumstances surrounding the individual. Does that mean operating on all individuals with an ACL injury? No. Should the current approach start shifting towards conservative management over surgery? No. More consistent and higher quality data is warranted to make that shift, as has been the case for Achilles tendon ruptures.

You can find out more information about Dr. Shannon and The Shannon Clinic here. If you would like to book an appointment to have your knee assessed, our Melbourne CBD chiropractic practice is centrally located on the corner of Collins Street and Swanston Street, opposite the Melbourne Town Hall in the Manchester Unity building.

Anterior cruciate ligament (ACL) knee injuries are devastating injuries that can significantly impact an athlete’s career including ending their ability to return to high level competitive sport. Individuals who suffer an ACL injury have lower self-reported knee function, quality of life and a greater risk of long-term joint morbidity including early osteoarthritis (1,2). Whilst those who undergo reconstructive surgery have lower return to sport rates with relatively high reinjury rates up to 24%, with the greatest risk being in the first 7 months (1,3).

The mean time to return to sport following ACL reconstructive surgery (ACLR) is approximately 7 months with accelerated rehabilitation program as short as 6 months (4,5). However, it has been established that when athletes return to sport following an ACLR they continue to exhibit neuromuscular and biomechanical alterations including quadriceps strength deficits resulting in altered landing patterns (1,6). These deficits may potentially result in higher risks of reinjury to the grafted and/or contralateral knee, all indicating that potentially we are returning our athletes too quickly to play following ACLR.

Reviewing Return to Play Findings Following ACLR

To investigate further Melbourne city chiropractor Dr. Shannon critically review the Read et.al article “Lower Limb Kinematic Asymmetries in Professional Soccer Players With and Without Anterior Cruciate Ligament Reconstruction: Nine Months is Not Enough Time to Restore “Functional” Symmetry or Return to Performance” in the April 2020 issue of the American Journal of Sports Medicine.

Background

This study examines professional soccer players specifically looking at kinetics, focusing on asymmetries during a counter movement jump (CMJ). The framework for this article is an analytical observational cross-sectional design and although it is not the most robust design format, it enables a cohort to be observed and compared at certain time points across the study. It executes this by dividing athletes into 4 groups, those who are 3-6 months, 6-9 months, >9 months into their ACLR rehabilitation and a control group. Strengths to this observational study are the use of the CMJ as an assessment measurement tool provided the risk of errors is minimized, as well as the use of a control group. Some questions are raised over the participation inclusion criteria as there is no mention of; any current or prior ankle injuries which are prevalent in soccer and can effect landing mechanics (7,8,9,10), which knee was injured dominant or non-dominant leg, if strength asymmetries were present prior to the injury, whether all ACLR participants followed a standardised rehabilitation program, were any players involved with ACL injury prevention programs and the cohort is specific to professional soccer players.

Counter Movement Jump

Findings

The study found that jump height (which is linked to an ability to complete tasks at a high level in soccer such as sprinting and change of direction) increased in the first 3-6 months however, it plateaued at 6-9 months and remained well below (3-4cm) the control group after 9 months. Whilst peak power, as measured by dual force plates followed a similar pattern and remained well below (3-4W/kg) the control group after 9 months. There were also significant interlimb asymmetries in the ACLR group during the eccentric (preload and deceleration phases) and concentric (jump phase) which decreased the further out from surgery the participants were, yet significant differences remained after 9 months. Indicating ACLR players were employing an offloading strategy to protect the injured knee. Furthermore, the uninjured limb was the dominant force producer. Both findings are consistent with other similar research indicating the changes occur due to altered nervous system function, strength deficits, reduced range of motion and fear of reinjury. The over reliance on the dominant limb for peak force production is important as it results in greater torque and stress loading of the knee and if the musculature is unable to dissipate the force effectively during a jump landing it may contribute to higher risk of injury, it may also lead to fatigue and potential injury of the uninjured knee.

Results

The results suggest that even after 9 months soccer players who have undergone ACLR are showing power, strength, and asymmetries between limbs with lower power and jump height figures compared to healthy controls. Knowing that strength deficits are associated with reinjury rates in a variety of lower limb injuries, it would suggest that potentially players are being returned to play before they are ready, increasing their risk of reinjury (11,12).

Although this study has its weaknesses the results are consistent with those in similar studies looking a landing patterns in participants following ACLR helping to build on the available evidence that limb kinetic asymmetries exist in ACLR patients up to and greater than 9 months (1,6,13). These findings together suggest that longer recovery times are warranted, and individuals should only be returned to play following ACLR when they have limb asymmetries within a tolerable limit. Read et.al recommend benchmark goals such as, a jump height of 33-35cm and a concentric impulse asymmetry of no more than 2.5-3.1%. They also provide quartile figures, enabling clinicians to establish whether an individual is progressing quickly or slowly with their rehabilitation based on the CMJ metrics. They also point out that inter limb differences are task, variable and physical quality specific, meaning limb differences will occur across different tests and variables in the same task therefore using one asymmetry metric such as a single leg hop test with a <10% asymmetry isn’t an appropriate guide to determine progression and return to play status. A combination of tasks should be used including single leg hop, isokinetic strength, CMJ analysing the different variables in the task ie. height, power etc.

Concluding Thoughts

ACL injuries are devastating knee injuries and it is paramount to reduce the risks of reinjury that athletes are not rushed back prematurely, furthermore evidence shows a 50% reduction in reinjury rates for every month return to sport is delayed up to 9 months post-surgery (5). Focusing on reducing lower limb strength asymmetry, especially improving quadriceps strength is vitally important in helping to monitor an athletes ACLR progress and in determining when they are ready to return safely to sport. Consideration should also be given to ACL injury prevention programs which have been shown to reduce the risk of ACL injures by 53%, with any program consisting of strength, plyometrics, agility, balance and flexibility exercises (2).

For more interested blog articles check out the Shannon Clinic blog page.

With evidence particularly in soccer showing a high rate of reinjuries it is important that athletes are not rushed back into their sport. Melbourne ciry chiropractor Dr. Shannon is well placed to help you navigate your injury assessment, rehabilitation and return to sport. To make an appointment to see sports chiropractor Dr. Shannon or remedial massage therapist Paula Pena click below. You will find our chiropractic clinic centrally located on Collins Street in the CBD of Melbourne.