The number of ACL reconstructions (ACLR) being performed in Australia, particularly in young people, has risen significantly in recent years. One study has shown that the number of ACLRs being performed in under 25yr-olds has increased by 74% (Zbrojkiewicz, Vertullo, & Grayson, 2018). This increasing trend has also been recently observed in New Zealand (Sutherland, Clatworthy, Fulcher, Chang, & Young, 2019).
ACLR is a very common recommendation for ACL injury, with one study showing that 98% of paediatric patients in Australia were recommended ACLR (Shaw & Finch, 2017). However, not all ACLR are the same. Depending on the age of the patient and the number of previous ACLRs the patient has had; the surgeon may perform an autograft ACLR (using the patient’s own tissue - bone-patella tendon-bone, hamstring or quadriceps) or an allograft ACLR (using donor or cadaver tissue; most common Achilles tendon).
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While these two types of ACLR are both treatment options for the ACL injured athlete, they can both fail, with allografts more likely to fail than autografts in younger athletes. In a prospective, randomised controlled trial (RCT) on highly active military personnel (mean age 26yrs) Bottoni et al., (2015) reported an allograft failure rate of 26% versus autograft failure rate of 8% at 10-year follow-up. Wasserstein, Sheth, Cabrera, & Spindler (2015) found similar numbers in their systematic review on autograft and allograft failure rates in athletes aged under 25yrs. When looking at these ACLR treatment options, autografts have been shown to be more cost-effective than allografts (Mistry et al., 2019).
Despite ACLR being a very common treatment for ACL injury, it is not the only treatment option. A prospective RCT by Frobell et al (2013) - the only one of its kind published to date – found that exercise rehabilitation-alone was equally as effective as ACLR at 2-year and 5-year follow-up in a cohort of ACL injured adults in many outcome measures (to be discussed in more detail throughout this paper).
A common goal for the ACL injured patient is to return to their pre-injury level of sport, and there is a widely held belief that the patient requires an ACLR to do so. Unfortunately, ACLR does not guarantee a return to pre-injury level of sport, with Ardern, Taylor, Feller, & Webster (2014) showing that only 65% of non-elite ACLR athletes will return to pre-injury level of sport (time taken to return to pre-injury level of sport unclear). This is in contrast to professional athletes, with 83% returning to pre-injury level of sport no later than 13 months post-op ACLR (Lai, Ardern, Feller, & Webster, 2018).
There is also an assumption that an ACLR is required to preserve the articular cartilage and meniscus from further injury upon return to sport and to prevent osteoarthritis (OA) changes over time. This assumption has not been shown to be entirely true, as observed by the outcomes in the studies from Frobell et al (2013) and Hurd, Axe, & Snyder-Mackler (2008). Poulsen et al (2019) show that OA change is 4-6x more likely to happen over at least 10 years following ACL injury regardless of treatment choice. There is some evidence however that does show worsening meniscus and cartilage lesions with delayed ACLR (Sanders et al., 2016), but as Filbay (2019) points out in her recent review, high-quality strengthening and neuromuscular training is not accounted for in these studies.
These two pertinent topics to the ACL injured patient (return to pre-injury level of sport and OA risk) will be discussed in more detail.
Return to pre-injury sport
Frobell et al (2013) randomly allocated 120 ACL injured patients (mean age 26 years) to two separate groups; Group One was offered an early ACLR (either hamstring or bone-patella tendon-bone autografts), whilst Group Two was offered structured rehabilitation with the option of having a delayed ACLR whenever they chose to do so. The authors then followed both groups for 2 years and 5 years, and at these 2 time points they had a sub-group of participants from Group Two who were managing well with rehabilitation-alone (these participants formed Group Three).
The authors found that after 2 years, 38% of delayed ACLR group (Group Two) had elected to have a delayed ACLR. At 5 years, 51% of Group Two had elected to have a delayed ACLR, leaving 49% of Group Two still managing without an ACLR (including returning back to pre-injury levels of activity). This remaining 49% were considered Group Three (rehabilitation-alone).
At 5 year follow-up, there was no statistically significant differences between groups in regards to pain, symptoms, function in ADLs, function in sports, knee-related QOL, general physical/mental health, current physical activity level, return to pre-injury activity level, radiographic OA or the number of meniscus surgeries performed between those treated with early ACLR and those given the option of having a delayed ACLR or those performing rehabilitation-alone.
Despite showing no differences between groups with returning to pre-injury levels of sport, the authors did show that only 20% of the participants in each of the treatment groups were still participating in their pre-injury levels of sport at 5-year follow-up. Considering the average age of the participants at the time of injury was 26, and 5 years later being 31 years of age, it’s possible that personal circumstance at this stage of life (focus on career and family rather than sport), may have influenced this decline in pre-injury levels of sport. Another RCT of this type in a younger population would be interesting to see if this trend is different between the three treatment groups.
Nevertheless, the assumption that one must have an ACLR to ensure a return to pre-injury level of sport was not supported in this well conducted trial. Nor was it observed in a case study of elite European handball players, where it was shown that 82% of a group of ACL injured patients successfully return to pre-injury levels with rehabilitation alone. These athletes also went on to participate at their pre-injury level of sport for a further 4.1years. This is in contrast to 58% of a group of players who returned to pre-injury levels of sport following ACLR, who went on to play for a further 3.8 years at pre-injury level of sport (Myklebust, Holm, Maehlum, Engebretsen, & Bahr, 2003). Similar to Frobell et al (2013), Myklebust et al (2003) showed no significant differences between either ACLR and rehab-alone groups when looking at radiographic OA changes and patient reported outcome measures at long term follow-up. Furthermore, a professional English Premier League soccer player was observed to make a successful return to pre-injury level of sport without ACLR, just 8 weeks after rupturing his ACL injury in a game, and was able to manage a further 2 years at EPL standard of play without re-injury (Weiler, Monte-Colombo, Mitchell, & Haddad, 2015).
Both of these examples are not as strong as the evidence provided in the Frobell et al (2013) paper, but it does further highlight that ACLR is not the only treatment choice for ACL injured athletes, even elite athletes.
Given the above evidence that ACL injuries can be managed successfully with rehabilitation-alone, it should be acknowledged that the ACL injured patients from the Frobel et al (2013) study were excluded from the RCT if they had high grade concomitant injuries to the knee (full PCL, MCL, LCL ruptures, posterior-lateral corner injuries, full thickness chondral lesions and complex meniscus injuries). Therefore, care must be taken when discussing the findings of this paper with patients, and applying these findings in a clinical environment.
The challenge for the clinician is to identify those who can potentially cope without an ACL, including returning to pre-injury levels of sport. Hurd et al (2008) used a screening test to identify “potential copers” that could be considered by clinicians. The screening test consisted of the KOS-ADLs, the Global Rating of Knee Scale (GRS), 6m timed hop test and the number of instability episodes the patient has had since injury. To be considered a “potential coper” one must pass ALL of the following criteria:
Hurd et al (2008) screened 345 ACL injured athletes (mean age 27) and identified 42% as “potential copers”. 72% of the “potential copers” returned to pre-injury levels of sport without ACLR. Furthermore, none of the 72% sustained further chondral or meniscal injuries during the 10-year follow-up period, and none of those who elected to have a delayed ACLR due to instability worsened their knee. At 10-year follow-up, 40% of the original “potential copers” were still classified as such, whilst 57% elected to have a delayed ACLR at some time point during the 10 years. Extending on this, Thoma et al., (2019) showed that 45% of ACL-injured patients identified early after their injury as a “non-copers” can change their coping status to “potential cope