At the conclusion of last week's discussion, this led us to the question, are we focusing too much on biomechanics? As rehab professionals, are we not addressing this as a part of our rehabilitation and negating any faulty biomechanics? In a study byKing et al Am J Sport Medicine 2019, the authors attempted to investigate this.
Purpose: To identify if differences in the magnitude of asymmetry of biomechanical and performance variables exist between ACLR athletes at the end of rehabilitation and healthy cohorts.
Methods: 156 male multidirectional field sports athletes who suffered an ACL rupture and who intended to return to the same level of sports participation after surgery were recruited for this study. Athletes were between the ages of 18 to 35 years old, underwent a primary ACLR and were tested approximately 9 months post operatively. All of the athletes in the ACLR group had a none patellar tendon bone graft from the ipsilateral side during surgery.
Rehabilitation Program: All the athletes in the ACLR group underwent an accelerated rehabilitation protocol with weight-bearing as tolerated on crutches for 2 weeks, followed by progressive strengthening and neuromuscular control program. Program progressed to include power and plyometric drills. As competency improved the athlete was progressed to linear running and change of direction (CoD) drills.
All athletes, cohort and ACLR athletes, underwent 3D movement (via Vicon system) analysis while the athlete performed three maximal efforts on the following tests:
- Double leg drop jump test from 30 cm step
- Single leg drop jump test from 20 cm step
- Single leg hop for distance test
- 90 degree planned and unplanned CoD test.
Results: There were differences in asymmetry of biomechanical variables across all jump and CoD tests, with greater asymmetries in the ACLR group. The majority of differences between groups were in the sagittal and frontal planes with notable differences in the magnitude of motion in the frontal plane and control of speed of motion. There were greater differences noted in the jump tests compared to the CoD tests. The single-legged drop jump demonstrated large differences in performance asymmetry.
Discussion: One challenge with this study is we don't know enough details related to the rehabilitation protocol. One thing I can say from experience, is that all too often I see rehab professionals so worried about progressing the athlete to the next phase that they will let technique suffer as a result. You train what you get and get what you train. In other words, if they are doing plyometrics and allowing the athlete to perform the exercise while allowing the knee to fall into a valgus position with each rep, then how can we expect when we do functional or biomechanical testing that this will change? Secondly, are we training to the testing protocol. As easy as this sounds and as much as we think this is would skew the results, why would we not do that? We know that if you do a single leg squat or single leg multidirectional hop that if your knee goes into a valgus position this puts you at risk. So why would we not train to improve that. Yes, it is a part of the testing protocol but it is a part of the testing protocol because we know if you do that during that movement, then you are at a greater risk.
This whole series we have presented a lot of research which has lead us to some logical conclusions.
- In our RTPlay testing:
- We need to do single limb testing. Sports is single limb in nature and therefore we must measure stability in single limb performance.
- We need to include some measure of biomechanics when assessing limb symmetry index (LSI). Don't simply take the ability to perform the test as passing criteria but how are they controlling the magnitude of motion and speed of motion?
- If we have the ability to look at baseline data (contralateral limb prior to sugery), we should use this to measure against for determining LSI (Rohman et al - Absolute LSI). This helps to account for any disuse atrophy of the non-surgical leg.