In early 2019 Cristiani et al published an article showing < 20% of patients met rehabilitation goals of having > 90% limb symmetry in strength (isokinetic quads and hamstrings at 90deg/sec) and single hop for distance tests at 6 months post-op.
This study had a very large sample size (4093 patients), comprising 45.7% females, with a mean age of 28 years (+/-10 years). 86.5% of participants completed the full test battery at 6 months post-op.
Factors that were significantly correlated with not achieving limb symmetry in all 3 tests at 6 months were - medial meniscal repair or resection and being older than 30 years. Positive predictive factors for achieving limb symmetry were hamstring tendon autograft compared to bone-patella tendon-bone autograft.
Study specifics
Concurrent ACL + meniscal repair patients were had restricted ROM in a hinged brace and were non weight-bearing in the first 6 weeks post-op.
Rehab was standardised to ROM, strength, balance and control with closed chain exercises for the quadriceps until 3 months post-op. Open chain quad strength training was permitted after 12weeks post-op.
Isokinetic testing was conducted at 90deg / sec with appropriate warm up, trials and rest. Single leg hop testing included verbal cues, warm up and 3 attempts per leg requiring the participant to stick the landing. The quality of the movement was not scored. Patients who hadn’t completed jumping/hopping in their rehab or weren’t confident didn’t complete hop testing.
Isokinetic Quads:
35.7% of participants achieved LSI of >90% quadriceps strength. Natural limb dominance was not factored in.
Females, those aged > 30 years, and those with concomitant medial or lateral meniscal repair had reduced odds of meeting LSI criteria. People with a hamstring autograft had increased odds of meeting quad strength LSI.
Unsurprisingly, patients with ACLR + meniscal repair were less likely to achieve strength symmetry due to their 6 week period of non weight-bearing and restricted ROM which likely exacerbated their limb deconditioning.
Isokinetic Hamstrings:
47.5% of participants achieved LSI of >90% hamstring strength (not factoring in natural limb dominance).
Factors increasing the odds of not meeting LSI criteria were: Age > 30 years, hamstring autograft and cartilage injury (non-specified grade/location), and surgery > 3 months from time of injury.
Anecdotally, in our clinical ACL population we have certainly found hamstring strength more difficult to fully regain than quads strength in a hamstring graft population (especially at isokinetic speeds >90deg/sec). Rehab needs to be individualised to graft type and patient, and is assisted by objective strength testing throughout the rehab period to identify areas in need of greater focus.
With regards to delayed surgery leading to delays in regaining hamstring strength post-operatively, this reinforces the importance of a patient undertaking a comprehensive prehabilitation program to optimise strength (all muscle groups) and settle the knee pre-operatively.
Single leg hop:
67.9% of people meet the hop criteria of > 90% LSI. This highlights the importance of a test battery as the single leg hop for distance test in isolation is the easiest to achieve and can hide persistent muscle strength deficits. It’s important to note, the quality of the movement and landing was not factored in.
Factors that decreased the odds of meeting this criteria were female gender, age > 30 years, delayed ACLR, medial meniscal repair or resection and cartilage injury.
Interestingly a high pre-injury Teger score of > 6 was a predictive factor as to who would do well with this test as was HS autograft which makes sense as a single leg hop is a quad/glut dominant exercise and less impacted upon by the greater quad strength deficits seen with BPTB grafts.
Overall clinical relevance….
-It is very likely that a large number of patients are being given complex rehab drills, or are returning to sports specific training at 6months post-op without having the required strength and power. This exposes them to a greater risk of re-injury.
-We strongly suggest that all ACLR patients are strength tested at 6 months post-op using validated strength measures to assess their limb symmetry and pure strength. We also recommend patients have their neuromuscular control assessed at 6 months. This helps determine whether they are ready to progress onto more complex rehab and running drills, and to allow them to re-set their gym priorities. Patients generally appreciate these objective measures which allow them to see where they’re at, see the outcome of their long-slog rehab work and motivate them to persist.
Please see our contact page if you would like to refer your patients for evidence based strength and control testing using our specialised equipment. Several surgeons use this service as part of their rehab protocol at 6 months which also includes a detailed report back to you the treating therapist.