PHYSICIAN UPDATE: Hop-Testing Asymmetry: Frontal & Transverse Plane (Oct. 2018)

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Peak Performance Physical Therapy & Sports Training EVIDENCE-BASED PRACTICE UPDATE October 2018 Hop-Testing Asymmetry: Frontal & Transverse Plane   CURRENT EVIDENCE Wren TA, Mueske NM, et al. Hop Distance Symmetry Does NOT indicate normal landing biomechanics in adolescent athletes with recent ACL reconstruction. JOSPT. 2018; 48(8): 622-629.   by Mike Napierala, PT, SCS, CSCS, FAFS NOTE:  This is a Part II following last month’s review by Karen Napierala, PT, ATC, MS, CAFS in which she focused mainly on the sagittal plane findings, which are the majority and main focus of Wren et al’s study. You can review Karen’s update HERE. Background: This study’s purpose was to compare operative limb single-leg hop biomechanics following ACLR to both the contralateral non-operative limb and a normal knee control group. They wanted to determine whether the gold standard of 90% hop distance symmetry should be used for return-to-sport readiness following ACLR surgeries in adolescents, and if it is associated with normalized biomechanics. Method: Forty-six 12-to-18-year-old patients along with 38 age-matched contralateral controls participated. ACLR patients were at a mean of 7.2 months post-op. Single Anterior Hop test (best of three) along with 3-D motion-analysis data were recorded at initial contact and between initial foot contact and maximum weight-bearing limb knee flexion on landing. Thirty-eight controls of the same age, who participated in 3/week sporting activities, with no injury history, were tested to provide normative data. Patients were grouped for data analysis based on limb symmetry index (LSI) as symmetric (> 90%) or asymmetric (< 90%). The control group was pared down to 24 of the 38 based on those exhibiting 90% LSI(72% of group), since relative symmetry is considered a target for normal function.  Results: Here I’ll focus on the frontal/transverse plane findings.  The authors reported that both symmetric and asymmetric patients had lower average external knee adduction moments, reaching statistical significance for both limbs for symmetric patients and the operative limb of asymmetric patients.  Additionally, the authors later indicated that “only minor differences were noted in the frontal/transverse plane” regarding symmetric patients.  No comments were made regarding the asymmetric patients group.  In the Discussion they do caution that the Vicon plug-in gait model has been shown to have high intersubject variance.” I’ll expand below on some of the findings Wren et al failed to emphasize.   Maximum hip adduction angle was 4.10 for controls, 5.20 for symmetric/operative limb and 4.90 for asymmetric/operative side while only 1.90 and 1.40 for non-operative symmetric and asymmetric sides respectively – not apparently reaching statistical significance.  Minimum knee adduction angle was 1.50 for controls, but 0.40 and 0.20 respectively for symmetric non-op and operative limbs while asymmetric limbs were -0.60 and -0.90 respectively for non-op and operative limbs – again, apparently not reaching statistical significance.  Average external knee adduction moment was lower for symmetric and asymmetric patients and was significantly less vs controls (0.098 units) for symmetric patients both non-operative (0.071) and operative side (0.056), and for asymmetric operative limbs (0.06). Conclusion: Symmetric patients achieved symmetry by, in part, hopping shorter on the non-operative opposite leg. Both symmetric and asymmetric patients off loaded their operative side.  Hop distance symmetry may not be an adequate indicator of single leg function or return to sport readiness. The authors neglected to address frontal plane findings in their conclusion statement.  I would add that there were small but statistically significant differences with a trending toward knee abd moments for both knees of symmetric patients and the operative limb of asymmetric patients, with both limbs of the operative limb trending toward knee abd angles. THE PEAK PERFORMANCE PERSPECTIVE Karen covered many pertinent concepts regarding this article’s overall kinetic chain implications in terms of compensatory tendencies noted, the inadequacy of post-operative limb symmetry index scoring as a valid comparison to normal pre-injury function (due to subsequent decline of non-operative limb performance also), and the sagittal plane dominant perspectives regarding hip, knee, and ankle loading. We advocate for return to play (RTP) functional testing that demands authentic activity stressors rather than focusing solely on the more easily measured and observed exclusive sagittal plane traditional power indicators, which too often happen to the mutual exclusion of the quality and quantity measures of frontal and transverse plane dynamic stability.  Cutting, change of direction, unexpected twisting/bending, either based on sport reactions or contact from another player, all require control of frontal and transverse plane forces.  The ability to powerfully hop in just one direction is valuable but very limited.  For example, two functional hop tests we utilize are a frontal plane single leg timed side-side hop and also a timed rotational (450 up to 1200 depending on pt status and goal activity ).  Both provide useful insights into more authentic demands on the ACLR knee (and a host of other LE injuries as well). In turn, the rehabilitation progression of proprioception, dynamic stability, strength and power training, and agility all reflect that understanding.  Too often patients, especially athletes, exercise in sagittal plane restricted motions despite their ultimate goal activity containing substantial amounts of frontal and transverse plane deceleration/acceleration requirements.  Exercises aimed at training muscle groups like the hip ER’s and abd’s or Tib Posterior or gluteals/hamstrings must be consistent enough with typical use for the body to quickly apply this newfound ability directly into functional tasks. An example would be the common “clamshell” exercise…generally designed to stimulate the hip abductors/ER’s.  Regardless of the loading used, which typically is body weight alone or ankle/cuff wts, the disconnect for the body we’d propose has more to do with proprioceptive inconsistencies – the fact that those muscles never see substantial loading for NWB actions but rather are loaded in ADL and athletics by superincumbent body weight via gravity and inertial loading. The “leap of faith” if you will, that must occur for a clamshell trained hip to then perform with excellence in a hop landing or a cutting move are seemingly massive.  The post-operative ACLR hop tests most commonly referenced in the literature are a 3x Anterior Hop, a 3x Anterior Crossover Hop, and a 6m Timed Anterior Hop.  While these tests remain sagittal plane dominant they do at minimum require multiple acceleration-deceleration efforts.  An advantage of the Crossover hop is the hybrid demand of decelerating forward momentum with simultaneous frontal plane stresses into both genu varum (knee adduction) or genu valgum (knee abduction).  Dynamic valgus has been identified in numerous studies over the past decade or more as a key risk factor for ACL injury.  Knees collapsing into valgus during landing events have greater risk of subsequent ACL injury.  Knee abduction is a natural kinetic chain extension of the lower extremity landing mechanics that begin with foot pronation.  Subtalar joint pronation, via talus adduction contributes to kinetic chain proximal tibial IR, knee abduction, femoral IR, hip adduction/flexion.  This is one means of producing dynamic valgus.  Landing with the foot ER’d can also cause the proximal knee segment to drive medially into valgus/abduction as well.  Proximally driven “top-down” mechanics ot a trunk/pelvis segment turning away from the landing limb may also produce dynamic valgus. Wren et al did attempt to examine frontal plane knee biomechanics but they oddly chose to measure “knee adduction” angles and external moments, directly in contrast to the other lower extremity measures taken, which, as noted above, are collectively consistent with the pattern of dynamic valgus that is a known ACL risk indicator. Their data does indicate (-) knee adduction angle values for asymmetric patients both non-operative and operative knees….ie, knee abduction.  Both knees of symmetric ACLR patients and the operative side of asymmetric ACLR patients also had statistically significant reductions of knee adduction moment, or in other terms – trending toward knee abduction moments.  It remains to be seen why Wren et al’s study did not demonstrate the same dynamic valgus in either controls or ACLR patients that have been noted in other studies.  They do indicate that the gait model they used tends to result in high intersubject variance of frontal plane variables.  Based on the known dynamic valgus concerns  for landing/hopping mechanics it appears Wren et al missed an important opportunity to gather accurate valuable data to help us better understand differences in this kinematic variable for symmetric and asymmetric hoppers. Finally, the Wren et al group use control group data for comparison.   We must remember that this group may or may not reflect our ideal physically.  It is unknown which people in the control group are actually an at risk group based on other factors – such as dynamic valgus landing mechanics or strength profiles or balance function.  Wren et al also chose to define “control” only as the 62% who were within 10% between L-R for Anterior Hop Test performance.  It is worth noting that over 1/3 of all “normals” in fact had > 10% asymmetry in hop testing, and that was evenly split between their pre-defined “dominant” and “nondominant” side being superior. The case study below demonstrates some of the hop testing utilized at Peak Performance for a patient who underwent ACLR. THE PEAK PERFORMANCE EXPERIENCE Becca stated: “My ACL and meniscus tears had me sitting out all the activities I love--mountain biking, swing dancing, and hiking--now I am ready to start racing and performing again with full confidence.” History:  25 yr old female swing dancer and mountain biker had non-contact twisting mechanism to (L) knee while kicking a ball at recreational league soccer practice.  MRI was (+) for torn ACL and MM tear.  Underwent ACLR + PMM and began outpatient PT three days later. Subjective: Pt reported 2/10 pain max at post-op PT evaluation.  Was using Toradol and Percocet post op.  IKDC was 30%.  Pt employed as engineer.  Goals were returning to competitive mountain biking and swing dance. Objective:  TEST Eval 4 mo Re-eval DC @ 7mo Knee ROM PROM: Ext 10hyper, flex 570 AROM:  0-1360 1-1400 Quad 600 isometric NT 37.7kg (78%) 49.8 kg (88%) Hams 200 isometric NT 24.6kg (95%) 27.0kg (116%) SLB rotational “no touch” test 20sec NT  14x (88%) 20x (120%)     (excellent decel Dyn Valg/Pron) Quads Ant Stepdown NT 5.25” 12lb wts  64% 5.25” 20lb wts 89% 3x Ant Hop NT Submax 1x Ant = Fair 103% Side-side 10sec hops NT NT 100% 900  Rotational Hops NT NT 80% Outcome:  At DC re-eval Pt reported max 1/10 sx only after hours of mountain biking or heavy wt lifting.  She self-reported 99% function and IKDC was 89%.  She also resumed swing dancing but felt she was not quite fully WNL yet with all dance moves. Treatment:  Exercise: After early post-op care phase once pt FWB she was advanced through functional exercise approach with primarily WB based strengthening focusing on quadriceps, hamstrings/gluteals, plantarflexors and as healing time passed increasingly including especially supinators and hip abductors and ERs .  Proprioception/Dynamic Stability: Early simple single-leg balancing (SLB) progressed with visual challenges (dominant and both eye closed) along with plane-based challenges using both upper and contralateral lower limbs to promote deceleration toward right rotation and knee abduction stresses (dynamic valgus). Vibration platform was utilized for increased neuromuscular stimulus.  Impact based demands were later included. Manual therapy: Ankle joint mobilization to restore dorsiflexion. Functional Training: Impact progression drills beginning with stabilization landings and explosive push offs into (B) landings were initiated.  Over time she progressed into multidirectional leaping and single leg hopping drills along with agility stepping/change of direction work to prepare for her swing dance demands. You can trust the Physical Therapists at PEAK PERFORMANCE to do a thorough evaluation, to search for related but underlying contributing factors to kinetic chain dysfunction, and to design exercise progressions that both respect tissue healing and creatively use biomechanics principles to prevent symptoms and optimize carryover to your patients' functional goals. Call us at 218-0240 to discuss your patient's specific needs.   Mike Napierala, PT, SCS, CSCS, FAFS Peak Performance is just minutes away from your patients in Penfield, Fairport, Pittsford, Brighton, Rochester and, of course, East Rochester.   We promise Individualized, hands-on and biomechanically appropriate Physical Therapy for your patients.  No "one-size-fits-all" approaches. We WILL go the extra mile and "dig deeper" to discover underlying causes for injury risk and delayed recovery using the most advanced Evidence Based methods available and, we’re able to make unique adjustments to exercise prescriptions to speed the return to function and to minimize or prevent symptoms from interfering.    No surprises. No hassles. Confident your patient is in the right place.    COME VISIT US AT 161 E Commercial St Just 1 mile off 490 exit (585) 218-0240 www.PeakPTRochester.com