Throw the Baby Out with the Bath Water? Challenging the Paradigm of Root Biomechanics

Transcription

1 Throw the Baby Out with the Bath Water? Challenging the Paradigm of Root Biomechanics

2 Faculty Jarrod Shapiro, DPM, FACFAS, FACFAOM Associate Professor Western University of Health Sciences College of Podiatric Medicine Program Director, Chino Valley Medical Center Chino, California

3 Faculty Disclosures Dr. Shapiro has disclosed no relevant financial relationships with any commercial interests.

4 Learning Objectives 1) Appreciate the role of Root biomechanics in modern day practice 2) Explain the evidence supporting other major biomechanical theories 3) Apply new biomechanical theories to nonsurgical and surgical lower extremity therapies

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6 Your Current Options: Alphabet Soup Root system Subtalar Axis Location and Rotational Equilibrium (SALRE) Tissue stress Rotational equilibrium Sagittal facilitation Maximal Arch Supination Stabilization (MASS) Neoteric biomechanics Best evidence should determine the parts. What is the evidence behind the major theories? Should parts be modified/discarded?

7 State of the Biomechanical Union Sagittal facilitation MASS theory These are NOT Root mutually exclusive! Tissue stress Rotational equilibrium

8 Root Biomechanics

9 Root Gets the Credit (and the Blame) Codified a system of foot biomechanics Created a systematic examination and classification based on morphology Methodology for consistent foot orthosis manufacture Did not create most of the concepts

10 Root ML. JAPA. 1964;54(2): Root ML, et al. In: Biomechanical Examination of the Foot. Volume Root ML, et al. In: Clinical Biomechanics Volume II: Normal and Abnormal Function of the Foot What Root Principles Are We Talking About? Joint axes, foot function Subtalar neutral position The normal foot Compensation for abnormal joint motion Examination techniques

11 STJ Historical STJ Today Closed kinetic chain function Hinge-like motion of joints Determined axes STJ center of focus Closed kinetic chain confirmed Helical motion Axes move w/bones, not hinges All joints involved in pronation/ supination TNJ more important than STJ STJ = subtalar joint; TNJ = talonavicular joint. Manter J. The Anat Record. 1941;80(4): Hicks JH. J Anat. 1953;87(4): Root ML, et al. J Am Podiatr Med Assoc. 1966;56(4): Elftman H. Clin Orthop. 1960;16: Van Langelaan EJ. Acta Orthop Scand. 1983;54(suppl 204):S135-S229. Benick RJ, Acta Orthop Scand. 1983;56(suppl 215). Lundberg A, et al. Foot Ankle. 1989;9(5): Lundberg A, et al. The Foot. 1993;3(2): Nester C, et al. J Am Podiatr Med Assoc. 2001;91(2):68-73.

12 MTJ Historical Oblique and longitudinal MTJ axes Divergent axes = control of MTJ MTJ controls forefoot MTJ Today 1 vs 2 MTJ axis All joints involved in pronation/ supination MTJ motion along TNJ Locking by CCJ Most FF:RF motion at lesser tarsus MTJ = midtarsal joint; CCJ = calcaneocuboid joint; FF = forefoot; RF = rearfoot. Manter J. The Anat Record. 1941;80(4): Hicks JH. J Anat. 1953;87(4): Root ML, et al. J Am Podiatr Med Assoc. 1966;56(4): Elftman H. Clin Orthop. 1960;16: Van Langelaan EJ. Acta Orthop Scand. 1983;54(suppl 204):S135-S229. Lundberg A, et al. The Foot. 1993;3(2): Nester C, et al. J Am Podiatr Med Assoc. 2001;91(2): Nester C, et al. J Am Podiatr Med Assoc. 2002;(92)2: Ouzounian TJ, et al. Foot Ankle. 1989;10(3): Foot and Lower Extremity Biomechanics II. Precision Intricast, Inc; Bojsen-Moller F. J Anat. 1979;129(1):

13 Midtarsal Joint Locking Mechanism Elftman H. Clin Orthop. 1960;16: Sarrafian s Anatomy of the Foot and Ankle. 3rd ed. LW&W; Bojsen-Moller F. J Anat. 1979;129(1):

14 What About STJ Neutral Position?...the rearfoot position is pronated during the first onehalf of stance, is neutral just before heel lift and is supinated during propulsion. Root ML, et al. In: Clinical Biomechanics Volume II: Normal and Abnormal Function of the Foot. 1977:139.

15 Smith-Oricchio K, et al. J Orthop Sports Phys Ther. 1990;12(1): What About STJ Neutral in Stance? Only 3 of 20 subjects (15%) stood in STJ neutral Most people do not stand in STJ neutral

16 What About Neutral Position During Gait?...the rearfoot position is pronated during the first onehalf of stance, is neutral just before heel lift and is supinated during propulsion. Root ML, et al. In: Clinical Biomechanics Volume II: Normal and Abnormal Function of the Foot. 1977:139.

17 Root Based Ideas about Normal Walking and Neutral Position on a Study by Wright et al, 1964 but Wright used a potentiometer to find joint motion patterns in only 2 subjects Reached neutral position at 60% to 75% of stance phase BUT: Wright s definition of neutral was Relaxed stance with knees extended Arms at sides Feet 6 inches apart Comfortable out-toeing More like RCSP than NCSP RCSP = resting calcaneal stance position; NCSP = neutral calcaneal stance position. Wright DG, et al. J Bone Joint Surg Am. 1964;46-A(2):

18 50 healthy subjects gait Two-dimensional videography over 12 m walkway x 3 for each extremity Also filmed in RCSP and NCSP and digitized Typical gait pattern RF slight inversion prior to heel strike RF eversion from heel strike to foot flat RF inversion started after 50% of stance and continued until toe-off Neutral position was in RCSP, NOT NCSP Experimental results invalidate neutral McPoil T, et al. Foot Ankle Int. 1994;15(3):

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20 Root ML, et al. Biomechanical Examination of the Foot. Volume Biophysical Criteria for Normalcy Distal one-third leg is vertical Posterior calcaneal bisection vertical Knee, ankle, STJ parallel w/ floor (in transverse plane) Plantar FF parallels plantar RF, both parallel with ground Metatarsals 2, 3, 4 dorsiflexed position, all parallel with ground Metatarsal heads 1, 5 in same plane as heads of 2, 3, 4

21 McPoil TG, et al. J Orthop Sports Phys Ther. 1988;9(12): healthy females (116 feet) surveyed Forefoot varus 8.6% Forefoot valgus 44.8% Plantarflexed 1st ray 14.7% Subtalar varus 83.6% Tibial varum 98.3% Normal alignment 17% Most humans do NOT fit the biophysical criteria of normalcy

22 Surveyed prevalence of FF varus, FF valgus, neutral position in healthy population 120 subjects (234 measured feet) Goniometer measurement Position Population Varus 86.67% Valgus 8.75% Neutral 4.56% Neutral FF:RF rare Varus most common Garbalosa JC, et al. J Orthop Sports Phys Ther. 1994;20(4):

23 What About the Orthometric Examination? Subtitle

24 Examined reliability of STJ neutral and ROM examinations 42 patients, 14 examiners Measurement ROM = range of motion. Intraclass Correlation Interclass Correlation Coefficient STJ neutral STJ inversion STJ eversion Intratester reliability high Intertester reliability low

25 WB = weight bearing. Smith-Oricchio K, et al. J Orthop Sports Phys Ther. 1990;12(1): Measurement Calcaneal inversion prone Calcaneal eversion prone Interrater Correlation STJ neutral by palpation.60 Calcaneal eversion WB.75 Poor reliability of STJ ROM and STJ neutral examinations Higher reliability when WB

26 Several Concepts Need Updating Lower extremity mechanics has changed Neutral is IDEAL, not NORMAL Examination is inaccurate

27 McCormack AP, et al. Foot Ankle Clin. 2001;6(1): Don t Throw the Baby Out with the Bathwater Has not been debunked Other theories have limited research also Replace Root with what? Wording may change, but the idea is the same

28 Adapted from McPoil TG, et al. J Orthop Sports Phys Ther. 1995;21(6): Tissue Stress Theory Looks for tissues under stress rather than measuring anomalies Help body cope with that stress Step 1: Determine specific injured anatomy Step 2: ID force causing stress Step 3: Determine structural or functional characteristics causing stress Step 4: Design a plan

29 Subtalar Axis Location Rotational Equilibrium Theory (SALRE) 1. When rotational forces (moment) around a joint are same, then equilibrium à no motion 2. Excessive forces cause pathology/stress 3. Treatment by adjusting rotational forces on foot

30 Wait Just a Moment! Kirby KA. J Am Podiatr Med Assoc. 2001;91(9):

31 Muscle/Tendon Action Depends on Axis Location

32 Plantar Parallel Examination Kirby K. J Am Podiatr Med Assoc. 1987;77(5):

33 Van Alsenoy KK, et al. J Am Podiatr Med Assoc. 2014;104(4): Is It Valid? Intrarater reliability: Improves with experience Interrater reliability:

34 Foot and Lower Extremity Biomechanics II: Precision Intricast Newsletters, nd ed. Precision Intricast, Inc; Rotational Equilibrium Method of Orthoses Use orthoses to alter orthotic reaction force medial or lateral to STJ axis as needed Adjust the supinatory moment medial to STJ axis when STJ axis is medially deviated Reduce strain/stress to affected structures

35 Medial Heel Skive Typical orthosis Medial heel skive Applies increased supinatory moment (orthosis reaction force) medial to the STJ axis at the heel Kirby K. J Am Podiatr Med Assoc. 1992;82(4):

36 Medial Oblique Shell Inclination (MOSI) Technique Harradine P, et al. J Am Podiatr Med Assoc. 2011;101(6):

37 State of the Biomechanical Union Sagittal facilitation MASS theory These are NOT Root mutually exclusive! Tissue stress Rotational equilibrium

38 If Not These Other Theories, Then What? A Hybrid Approach

39 Applying a Unified Approach Harradine P, et al. J Am Podiatric Med Assoc. 2009;99(4):

40 Hybrid Approach to AAF Root Measure the abnormalities (FF supinatus, RF varus, etc) Attain more normal anatomic structure Support deformity/decrease compensation Tissue Stress/SALRE ID PT tendon, medial column strain Create supinatory torque across STJ axis Sag Facilitation Others Facilitate motion at ankle rocker (equinus) and forefoot rocker (1st MTPJ limitation). Increase arch height.

41 Kogler GF, et al. J Bone Joint Surg. 1999;81-A(10): Tissue Stress Orthosis for Plantar Fasciitis Wedge under the lateral forefoot decreased plantar fascial strain Wedge under the medial forefoot increased strain Wedges under the hindfoot did not affect strain Forefoot valgus wedging for patients with plantar fasciitis

42 Hybrid Nonsurgical AAF Approach Orthosis Rx components Rigid shell Minimal cast fill Deep heel cup Medial heel skive Medial flange RF varus extrinsic post 1st ray cut-out +/- heel lift Rigid shoe, Thomas heel, rocker sole Ankle-foot orthotic brace PT: Eccentric strengthening

43 Where Does Surgery Fit? Subtitle

44 Surgery Similar Endpoints to Root Many surgical studies looking at deformity correction use a Rootian endpoint Example: Flatfoot recon previously looked at kinematics Planal dominance purely kinematic

45 Looked at Evans cadaveric model Decrease 1st met load Increase TNJ moment Looked at stresses on tissues, kinetics in a cadaver flatfoot model 10 mm MDCO decreased 1st met head load, TNJ moment, increases lateral column load FDL transfer had little effect Cadaver kinetic study 6 mm arthroereisis decreases load on medial arch, moments about the TNJ MDCO = medial displacement calcaneal osteotomy. TNJ= talonavicular joint; FDL = flexor digitorum longus. Arangio GA, et al. Clin Biomech (Bristol, Avon). 2007;22(4): Arangio GA, et al. Clin Biomech (Bristol, Avon). 2009;24(4): Arangio GA, et al. Clin Biomech (Bristol, Avon). 2004;19(8):

46 Performed MDCO (5, 10 mm translation) +/- FTT Modeled effects radiographically, plantar force, soft tissue, and joint strain Results: Largest improvement with 10 mm MDCO, decreased medial strain, joint contact forces Showed use of kinetic data to help with decisions Spratley EM, et al. Ann Biomed Engin. 2015;43(8):

47 Conclusions Root has issues Consider the strengths of a hybrid approach More kinetic and kinematic research needed Clinical research to demonstrate improved patient outcomes Newer theories require direct validation New research methods on the horizon

48 Thank You!

49 Subtitle Q & A