This blog (research review) is an example of what our review service looks like. Articles are sourced by industry experts and translated for clinical application. Enjoy!
The effect of open vs closed kinetic chain exercises on anterior laxity, strength and function following anterior cruciate ligament reconstruction: A systematic review and meta-analysis.
Background and objectives:
Controversy exists in the orthopaedic and physiotherapy world regarding the use of open kinetic chain (OKC) exercises during the post-operative rehab of anterior cruciate ligament reconstruction (ACLR). The often-stated reason for avoiding such as exercises is that it will stretch and damage the surgical graft. However, some trials have shown no increased tibial laxity at long term follow-up, even commencing at week 4 in a restricted ROM (45-90deg knee flexion – Fukuda et al., 2013), whereas others have (Heinje et al., 2007).
The primary objective of this review was to see if OKC exercises resulted in increased tibial laxity at short term (<3 months), medium term (3-6 months), long term (6-12 months) and very long term (12+ months) when compared to closed kinetic chain (CKC) exercises. In regards to tibial laxity, the established cut-off for clinical laxity is >2mm compared to the opposite side.
The secondary objectives were to see if there were any differences in strength, function, quality of life and adverse events when comparing the 2 types of exercises.
Mehod (what the authors did):t
Seven electronic databases were searched, looking for randomised controlled trials (RCTs) comparing OKC vs CKC exercises following ACLR up until to April 2017. Study methodological quality was assessed using the GRADE approach.
Results (what the authors found):
The authors original search strategy found 1442 articles, of which 10 studies were eligible for final review (5 patella tendon, 2 hamstrings, 2 both graft types and 1 did not specify). Of the 10 studies included in this review, they analysed 494 participants with a mean age range of 19-34yrs (74% males). The exercise protocols in these trials either compared CKC exercises to solely OKC (7 studies) or a combination of OKC and CKC (3 studies). The mean PEDro score for the articles was 5.5 with lack of participant/therapist blinding (all studies), lack of assessor blinding (5 studies) and omission of intention to treat analysis (8 studies) being the most common limitations.
For the primary outcome of tibial laxity, the results are shown below:
- Early addition of OKC (<6 weeks post-op)
- Low to moderate quality evidence from 3 studies (n=203) with no between group differences in laxity at any time points from the early addition of OKC when compared to CKC
- For all sub-groups, the between groups differences were less than the 2mm laxity threshold
- Meta-analysis demonstrates low -moderate quality evidence of no increased risk of clinical laxity regardless of intervention across all time points.
- Late addition of OKC (>6 weeks post-op)
- Limited evidence from 2 studies (n=93) showing no difference between groups in laxity at medium and long-term follow ups when adding OKC exercises later in rehab
For secondary outcomes, the results are shown below:
- Strength (early OKC)
- Low-moderate quality evidence from 2 studies (n=113) showing no between group differences in strength at any time point
- Strength (late OKC)
- Limited evidence from 3 studies (n=102) showing no between group differences at short or long-term follow-up. 1 study showed significant difference in quads strength at medium term follow up in favour of OKC exercises.
- Function (early and late OKC)
- Limited evidence from 3 studies (n=116) showing no significant differences between groups at any time point for single leg hop and triple crossover hop regardless of when OKC exercise were introduced
- Adverse events
- Four studies reported on adverse events:
- One study had no adverse events
- One reported 2 graft failures in early OKC group
- One study reported 2 graft failures in each group
- The other study was not clear in which group the adverse events occurred
- Four studies reported on adverse events:
Overall for the primary outcome measure of tibial laxity, there was low-moderate quality evidence from 3 studies that showed no between group differences at any time point when OKC exercises were introduced before 6 weeks when compared to CKC exercises. Like all good systematic reviews, the authors concluded that high-quality research on this topic is still needed before we can be more confident in the prescription of early OKC exercises and its effect on tibial laxity.
Limitations (things to keep in mind):
Although this robust systematic review and meta-analysis found that there were no significant differences between groups for tibial laxity when OKC exercises were added from at least 4 weeks post-op, it comes with a BIG BUT!
Patella grafts were found to be less vulnerable to the early introduction of OKC exercises, despite the differences in exercise protocols between the 3 trials reviewed. Hamstring grafts however showed inconsistency between studies, with the Heijne et al study showing significantly greater tibial laxity in the early OKC group, whereas Fukuda et al study showed no difference.
This inconsistency may be explained however by their use of different protocols within each study;
- Fukuda used supervised OKC exercises at 4 weeks post-op restricted in ROM from 45-90deg knee flexion until the 12-week post-op mark
- Heijne et al started OKC at 4 weeks, but progressed to full knee extension at 6 weeks post-op.
The increased ACL laxity shown in Heinje study may be explained by basic science research showing that ACL strain is 0% when OKC quad contractions are performed at 60-90deg of knee flexion and reaches its peak strain between 0-30deg of knee extension.
One must also be critical of the laxity found in this trial, with the average laxity between groups in the Heijne study being 1.4mm, which is within the clinically meaningful threshold of 2mm associated with increased ACLR graft rupture.
Clinical implications (how does this change your clinical practice):
Although the authors of this paper have still urged caution with the use of OKC exercises in the first 12 weeks post-op, it has highlighted the simple fact that OKC exercises can be used without fear of stretching the ACL graft and subsequent graft failure from 12 weeks post-op – at the very least.
Whether or not you use OKC exercises from 4 weeks post-op, and what ROM you perform them in, would be based on your own clinical judgement, the patient you have in front of you, and what makes you sleep well at night. For example, an elite athlete may use 45-90deg restricted ROM OKC exercises from 4 weeks post-op to their advantage “to get their quads back faster” to allow them to do more advanced “functional exercises” earlier. Whereas, someone with less demanding time constraints may wait until 12 weeks post-op to do full ROM knee extensions unsupervised in the gym, knowing that there is no risk in stretching the graft.
What makes me sleep well at night is supervised 45-90deg restricted ROM OKC exercises from 6 weeks post-op, with full ROM OKC exercises starting from 12 weeks post-op.