VS. THE OLD ROOT THEORY

Transcription

1 THE NEW BIOMECHANICS VS. THE OLD ROOT THEORY Sponsor Paris Orthotics NEW YORK Podiatric Clinical Conference DOUGLAS H. RICHIE JR., DPM SEAL BEACH, CA OBJECTIVES 1. Review pertinent clinical concepts of Root Theory 2. Present new, conflicting experimental evidence 3. Propose clinical applications of these new insights Criticisms of the Root Theory It behooves the podiatry profession to first of all establish a common nomenclature which is specific in its meaning so that knowledge can be accurately transmitted. Secondly, the foot must be classified as to its various functional and structural types, with specific clinical methods for measurement and evaluation so that one foot type at a time can be given detailed study to further our knowledge of the problems we face. Merton L. Root, Reliability of clinical measurements 2. Dynamic subtalar joint position 3. Criteria for normalcy 4. Single axis model 5. Frontal plane rearfoot motion significance 6. Kinematic patterns of RF motion 7. Static measures = dynamic function McPoil and Hunt 1995, Michaud 1997, Keenan 1997, Levitz and Sobel 1997, 1998, Payne 1997,

2 Criteria for a Normal Foot In the individual with normal lower extremities, the following conditions exist during normal static stance upon a level surfac e (ground). I. The legs in the sagittal bisection of the calcanei are perpendicular to the ground (vertical) and parallel to each other in both extremities. II. Thesubtalar joints of both feet are positioned at their neutral positions. III. The midtarsal joints are locked in their fully pronated positions. IV. The full plantar surface of the forefoot of each foot rests upon the ground, all metatarsals bear weight, and the plantar surface of the forefoot parallels the plantar surface of the heel. Root, ML, Orien, WP, Weed, JH: Clinical Biomechanics: Normal and Abnormal Function of the Foot, Vol 2. Los Angeles, Clinical Biomechanics Corp, KINETICS Forces acting on a body part There is also no evidence that the posterior bisection of the calcaneus is perpendicular to the plantar surface of the calcaneus, which is used as the reference plane for the frontal-plane forefoot deformity. KINEMATICS Timing and movement of a body part Payne CB: The past, present, and future of podiatric biomechanics. JAPMA 88:53, 1998 Kinematics of Rearfoot Motion 2

3 As the midstanceperiod begins, the leg begins to externally rotate and the subtalar joint begins to supinate. Just before the end of the midstanceperiod, subtalar joint supinationmoves the foot into a slightly supinated position. Pronation of the foot is abnormal if the amount of pronation, during any period of locomotion, becomes excessive or if any pronation occurs at a time when the foot should be supinating. When treating the foot, the objective of functional orthopedic therapy is to reestablish normal motion and position of the foot during the stance phase of gait. Root, ML, Orien, WP, Weed, JH: Clinical Biomechanics: Normal and Abnormal Function of the Foot, Vol 2. Los Angeles, Clinical Biomechanics Corp, Abnormal compensatory pronation of the foot is the most common cause of pathology within the foot. Abnormal pronation of the foot is defined as abnormal pronation of the entire foot which occurs at the subtalar joint. Abnormal pronation of the foot usually refers only to abnormal subtalar joint pronation, but, rarely, abnormal ankle joint pronation may also be included. Root, ML, Orien, WP, Weed, JH: Clinical Biomechanics: Normal and Abnormal Function of the Foot, Vol 2. Los Angeles, Clinical Biomechanics Corp, Normal Rearfoot Motion Should We Control Calcaneal Eversion? 2 opposing views 1. Achieves neutral position before heel off Root, et al CONTROVERSIES When does STJ achieve neutral? Rearfoot angle vs RCSP 2. Remains at resting position until heel off McPoil & Cornwall, 1994 Pierrynowski & Smith, 1996 Mosseley, 1996 Liu, 1997 Controversy Root et al.: RCSP & NCSP calcaneus to ground Others: Rearfoot angle calcaneus to leg Figure A & B: The resting calcaneal stance position is determined by measuring the posterior biscetion line of the heel to the ground with the foot relaxed. 3

4 NCSP RCSP Fig. 3. A plot of the mean pattern of rearfoot motion as well as the mean angles for RSFP and SJNP for the 100 feet. The two unmarked lines represent plus or minus on standard deviation from the mean pattern of rearfoot motion. Subtalar Neutral = Normal? Nine subjects Three dimensional treadmill analysis Max eversion at 44% of gait cycle Neutral STJ position at 66% and 74% of gait cycle Pierrynowski, M.R., Smith, S.B.: Rear foot inversion/eversion during gait relative to the subtalar joint neutral position. Foot and Ankle 17: 406, 1996 Subtalar Joint When does pronation end and supination begin? 36% of gait cycle 44% of gait cycle What initiates supination? McPoil and Cornwall 1994 Pierrynowski, 1996 Independent Joints Independent Axes A B Figure A, B. The subtalar joint is moved to its end range of inversion (A) and eversion. (B) Motion and excursion values are recorded. 4

5 Figure 1-33: From the neutral subtalar joint position this foot inverts 20 when the subtalar joint is fully supinated and everts 10 when the subtalar joint is fully pronated. This foot has a normal rearfoot, and its full range of subtalar joint motion, measured in a frontal plane, is 30. Clinical Measurement Calcaneal Inversion - Eversion 15 cadaveric legs Unlocked vs locked tibiotalar joint Manual vs radiographic measurments Taylor, K.F., Bojescul, J.A., Howard, R.S., Mizel, M.S., McHale, K.A., Measurement of Isolated Subtalar Range of Motion: A Cadaver Study. Foot and Ankle Intl 22: , 2001 Clinical Measurement Calcaneal Inversion - Eversion This study demonstrates that the clinical measurements of calcaneal eversion and inversion did not correlate well with radiographic measurements. The contribution of the tibiotalar joint to apparent subtalar motion, as measured clinically and radiographically, was found to be one-third of the arc of motion. Axis of Motion of the Pedal Joints Fact vs. Fiction Taylor, K.F., Bojescul, J.A., Howard, R.S., Mizel, M.S., McHale, K.A., Measurement of Isolated Subtalar Range of Motion: A Cadaver Study. Foot and Ankle Intl 22: , 2001 In this model, the subtalar and midtarsal joints have been described as dual screws connected to the talonavicular joint in opposite directions. This model introduced the concept of the position of the subtalar joint. The range of motion of the midtarsal joint is controlled by subtalar joint position. In a pronated subtalar joint, the two axes of the midtarsal joint are in a more parallel orientation, increasing the range of motion. In a supinatedsubtalar joint, the two axes of the midtarsal joint are in a more oblique orientation, decreasing the range of motion. - Justin Wernick - Russell G. Volpe Valmassy, R: Clinical Biomechanics of the Lower Extremities. St. Louis, Mosby-Year Book, Inc

6 Bi-axial Model of MTJ Refuted by: Van Langelaan (1983) Benink (1985) Lundberg (1989) Should We Control Calcaneal Eversion? CONTROVERSIES When does STJ achieve neutral? Rearfoot angle vs RCSP Independence vs Interdependence of joint movements The tarsal bones together form an articulated ring of bones. The talus articulates with the calcaneus, the calcaneus with the cuboid, the cuboid with the navicular, and the navicular with the talus: a socalled kinematic chain with only 1 kinematic degree of freedom. Under weightbearing conditions, this kinematic chain acts as a mechanism in engineering terms, if a motion is imposed upon one of the links, the other links are also forced to move. Huson A: Biomechanics of the tarsal mechanism. A key to the function of the normal human foot. JAPMA 90:12, Figure 1. An osteoligamentous dissected specimen of the foot exarticulated at the ankle joint. The dorsal capsules of the talonavicular and calcaneocuboid joints have been removed. The foot is held in the neutral position corresponding with upright standing. Figure 2. The talus has been moved as it does in supination of the foot while the calcaneus, cuboid, and navicular are kept immobile. The talar head has left the navicular socket laterally, creating a wide gap at the medial side of the talonavicular joint. Because of the complex mechanical relationships between the tarsal motions and between these and other complex motions in the tarso-metatarsal joints, the use of axes of rotation as tools for a reliable quantitative clinical evaluation of foot function has no firm basis so far. Huson A: Biomechanics of the tarsal mechanism. A key to the function of the normal human foot. JAPMA 90:12,

7 HINGE AXIS? VanLangelaan E.J. A Kinematical Analysis of the Tarsal Joints. Acta Orthop Scand 54: 204, 1983 Lundberg et al. Kinematics of the Ankle / Foot Complex: Plantarflexion and Dorsiflexion. Foot and Ankle 9: 194, 1989 Six cadaver specimens Axis-finder rod LED path photography MRI serial cuts Single axis, at tips of malleoli Singh A.K. : Kinematrics of the Ankle : A Hinje Axis Model. Foot & Ankle 13:439,

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9 Traditional Biomechanical Exam Static Measurements Open Kinetic Chain Calcaneus is Point of Reference The assessment of the range of motion of the subtalar joint is done in a non-weightbearing position, but there is a difference between the weightbearing and nonweightbearing range of excursion of the calcaneus in the frontal plane, indicating motion in the joint. Static measurements are used as part of the biomechanical assessment of patients, but in light of these reports and other work on the reliability of the measurements, their usefulness must be reconsidered. Payne CB: The past, present, and future of podiatric biomechanics. JAPMA 88:53, 1998 A Figure A: With the patient standing in the angle and base of gait and the subtalar joint held in its neutral position, the angle of the bisection of the lower leg relative to the ground determines the tibial position. Figure A & B: The resting calcaneal stance position is determined by measuring the posterior biscetion line of the heel to the ground with the foot relaxed. 9

10 PT Tendon removed Spring ligament removed CKC Universal Joint Rotation PT Tendon removed Spring ligament removed Torsion Transmission Tibia: Dominant Lever The Myth of the Subtalar Joint Should We Control Calcaneal Eversion? CONTROVERSIES When does STJ achieve neutral? Rearfoot angle vs RCSP Independence vs Interdependence of joint movements Importance of STJ control of LE 10

11 3 Myths of Podiatric Biomechanics Calcaneus = Subtalar Joint = Foot 1. The calcaneus controls the subtalar joint 2. The subtalar joint controls the foot 3. The foot controls the leg Frontal plane movement of the calcaneus has been the primary indicator for measurement of foot pronation in studies on foot orthoses, while control of excessive foot pronation has been the primary objective in the prescription of functional foot orthoses. - William R. Olson Valmassy, R: Clinical Biomechanics of the Lower Extremities. St. Louis, Mosby-Year Book, Inc Figure 1-44: Closed chain pronation of the subtalar joint. Pronation of the subtalar joint in the weight bearing foot results in eversion of the calcaneus, and the talus adducts and plantarflexes relative to the calcaneus. The leg follows the talus in a transverse plane and internally rotates. In a sagittal plane, the leg also moves to some extent with the talus. As the talus plantarflexes, the proximal aspect of the tibia moves forward to flex the knee slightly. One method of estimation of correction for the severe pronator is the 5-to-1 rule Five degrees of plaster correction produces 1º of calcaneal inversion (rearfoot change). Measurement of the patient presents with an RCSP of 10º everted on the involved left side. Utilizing the 5 to 1 rule in an attempt to bring the rearfoot back to a vertical position, a 50 degree inverted orthotic correction should be ordered. - Richard Blake Valmassy, R: Clinical Biomechanics of the Lower Extremities. St. Louis, Mosby-Year Book, Inc

12 Controlling Calcaneal Eversion Effects of Functional Foot Orthoses AUTHOR Clarke et al. Cavanagh Rogers et al Smith et al Taunton et al Sims DECREASED EVERSION 2.5º 2º per 6mm wedge 1-2º 1.2º 1-2º 2º Simms and Cavanagh noted that although studies have claimed that foot and ankle symptoms are usually dramatically decreased with the use of foot orthoses, the objective improvement in rearfoot motion is considerably more modest, suggesting that therapeutic success is not necessarily due to restoring the foot to what is functionally considered normal. This raises the possibility that foot orthoses are effective for reasons that are not entirely clear. Payne CB: The past, present, and future of podiatric biomechanics. JAPMA 88:53, 1998 Variation in the spatial location of the subtalar joint axis affected the overall biomechanics of the foot during weight bearing activities. Therefore, during many weightbearing motions, the foot may approximate a relatively rigid unit with all the bones of the foot rotating around the central pivot of the talus at the subtalar joint axis. Kirby KA: Subtalar joint axis location and rotational equilibrium theory of foot function. Journal Am Pod Med Assoc 91:465, 2001 Kirby KA: Subtalar joint axis location and rotational equilibrium theory of foot function. Journal Am Pod Med Assoc 91:465, 2001 Finally, Huson s theory on the constraint mechanism of the human tarsus, which has been supported by the tarsal kinematic research of Cornwall and McPoil, and the roentgen stereophotogrammetry studies done by Van Langelaan, Benink, and Lundberg and Svensson are all consistent with the current author s theory that the subtalar joint axis is the primary inversion/eversion axis of the foot. STJ: Pivitol Joint? The authors believe that the finding that the magnitude of navicular (midfoot) movement is greater than that of calcaneus (rearfoot) illustrates the importance of the midfoot for typical foot function during walking. Kirby KA: Subtalar joint axis location and rotational equilibrium theory of foot function. Journal Am Pod Med Assoc 91:465, 2001 Cornwall MW, McPoil TG: Three-dimensional movement of the foot during the stance phase of walking. JAPMA 89:56,

13 Figure 1. An osteoligamentous dissected specimen of the foot exarticulated at the ankle joint. The dorsal capsules of the talonavicular and calcaneocuboid joints have been removed. The foot is held in the neutral position corresponding with upright standing. Figure 2. The talus has been moved as it does in supination of the foot while the calcaneus, cuboid, and navicular are kept immobile. The talar head has left the navicular socket laterally, creating a wide gap at the medial side of the talonavicular joint. The tibiofibular talar unit does not function independently of the subtalar or midtarsal joint but acts cooperatively in closed-kinetic chain performance. The complex movement pattern known as supination and pronation of the foot must occur in concert with talar movement in the ankle housing unless spontaneous or surgical ankylosis has occurred in the ankle Vogler HW, Bojsen-Moller F: Tarsal functions, movement and stabilization mechanisms in foot, ankle and leg performance. JAPMA 90:112, Talar positioning on top of the calcaneus is determined by ankle movement and midtarsal joint motions and varies depending on whether these are open- or closed-kinetic-chain events. Changes in any one of these joints alter the position and function of the others to varying degrees. Vogler HW, Bojsen-Moller F: Tarsal functions, movement and stabilization mechanisms in foot, ankle and leg performance. JAPMA 90:112, Two Lever Theory The subtalar joint provides most of the transverse plane motion which is necessary at the distal extremity to allow internal and external leg rotation during the stance phase of gait. The subtalar joint pronates to allow internal leg rotation and supinates to allow external leg rotation. Root, ML, Orien, WP, Weed, JH: Clinical Biomechanics: Normal and Abnormal Function of the Foot, Vol 2. Los Angeles, Clinical Biomechanics Corp, The ankle connects two unequal levers, the leg and the foot. The longer lever contains only a pair of bones, the tibia and fibula. The more massive tibia conveys most of the body weight directly on the talus and acts as a solid lever in ankle injuries. The foot, on the other hand, is composed of numerous small bones intercepted by joints, which weaken it as a lever. Kelikian,

14 Two Lever Theory Between these two unequal levers (unequal in bulk, length and strength) lies the talus. When the foot is dorsiflexed at the ankle, the talus becomes firmly lodged in the tibiofibular socket and serves as part of the proximal lever or the leg Kelikian, 1985 Transverse Plane Internal rotation of tibia = Internal rotation of talus Tibial Rotation During Stance 25 Subjects External markers 3-D motion of foot and shank Tibial Rotation During Stance Max velocity of tib internal rotation = 7% of gait cycle Max velocity of tib external rotation = at toe off Max amount rotation of tibia = 12º internal Total range rotation of tibia = 17º Nester CJ., Hutchins S., Bowker P., Shank rotation: A measure of rearfoot motion during normal walking. Foot and Ankle 21: , 2000 Nester CJ., Hutchins S., Bowker P., Shank rotation: A measure of rearfoot motion during normal walking. Foot and Ankle 21: ,

15 Angle (Deg) degrees Ang 1 Ang 2 Angular displacement Ang 4 Ang 5 time (one gait cycle) Ang 3 Toe off Nester CJ., Hutchins S., Bowker P., Shank rotation: A measure of rearfoot motion during normal walking. Foot and Ankle 21: , 2000 We found that external rotation of the shank (indicating supination) began much earlier, at around 16% of the gait cycle. This is most likely a consequence of the fact that motion of the shank in the transverse plane can occur at the ankle and mid-tarsal joints without any change in the angle between the heel and shank in the frontal plane. Nester CJ, Hutcdhins S, Bowker P: Shank rotation: A measure of rearfoot motion during normal walking. Foot and Ankle International 21:578, Rearfoot Tibia When does External Rotation of the Tibia begin? Percent of Walking Cycle 17% Avg. Internal Rotation 7 Authors Levens et al % 7 Reinschmidt et al % 7 Nester Stance Phase Duration (%) Cornwall W., McPoil G., Footwear & Foot Orthotic Effectiveness Research: A New Approach. Foot/Ankle 21: Movement Coupling 1. Inversion of heel begins at 50-55% of gait cycle Kepple (1990) Mannon etal (1997) McPoil & Cornwall (1994) Pierrynowski and Smith (1996) 2. External rotation of shank begins at 16% of gait cycle Levens et al (1948) Cornwall & McPoil (1995) Reinschmidt et al (1997) Nester (2000) Movement Coupling How can the tibia externally rotate while the calcaneus remains everted (does not move)? Tibia can internally rotate on talus Rearfoot complex can internally rotate as one unit on the forefoot (transverse plane MTJ motion) 15

16 Tibiotalar Delay The talus does not immediately follow internal / external rotation of the tibia. Ant. Talo-Fib and Sup Deltoid have to tighten before talar motion is observed. Lateral rotation of the lower leg in the stance phase of gait allows a slight delay in transmitting this transverse plane rotation to the foot. This action is believed to be related to that of the horizontally aligned ligament fibers that surround the ankle and talus that must absorb these forces before transmitting them Huson A, VanLangelaan EJ, Spoor CW: Tibiotalar delay and tarsal gearing. J Anat 149: , 1986 Vogler HW, Bojsen-Moller F: Tarsal functions, movement and stabilization mechanisms in foot, ankle and leg performance. JAPMA 90:112, Transverse Plane Movements In Gait Ankle Midtarsal 10.6 McCullough, Burge Nester Nester 16

17 Ankle vs STJ Transformation of leg rotation into calcaneal eversion-inversion, and vice versa, has been suggested to occur mainly at the subtalar joint. When this is true, subtalar joint fusion must result in a significant loss of movement transferred between calcaneus eversioninversion and tibial rotation. However, as shown previously, it did not. Hintermann B., Nigg BM: Influence of arthrodeses on kinematics of the axially loaded ankle complex during dorsiflexion/plantarflexion. Foot & Ankle 16:633, 1995 Foot & Ankle International/Vol.21, No. 3/March 2000 Fig. 5 Movement coupling between calcaneal eversion-inversion and tibial rotation for the five test subjects (mean curves of three repetitions). The dashed line represents a theoretical 1:1 coupling from the calcaneus to the tibia. HS (heel strike); MS (midstance); TO (takeoff); SD (mean standard deviation in the horizontal (x) and vertical (y) direction) Stacoff, Nigg, Reinschmidt, 2000 Considering motion at only one of the three, i.e. the subtalar joint, is unlikely to describe the eventual motion which results from all three in combination since it does not account for factors affecting the other joints. Nester, 1997 Ankle, Subtalar and Mid-tarsal joints Rear foot Complex Downing, 1978 Nester, 1997 Tarsal Mechanism Huson, 1991 Ankle Joint Complex Hintermann, Nigg, 1994 Ankle Joint Complex 3 Segments: tibia, talus and calcaneus 2 Joints: ankle, subtalar Universal Joint: inversion of calcaneus = external rotation of tibia eversion of calcaneus = internal rotation of tibia 17

18 CKC Universal Joint Rotation Torsion Transmission Tibia: Dominant Lever 18

19 Functional Foot Orthoses 1.Do not change skeletal alignment 2.Change input signal to CNS 3.Modulates muscle activity Nigg, Benno: Foot Orthoses Do They Align the Skeleton? Prescription Foot Orthotic Laboratory Association, International Conference Foot Biomechanics and Orthotic Therapy. Nov

20 Shin Muscle Activity On Various Sport Surfaces: An EMG Study By: DOUGLAS H. RICHIE, D.P.M. HERBERT A. DeVRIES, Ph.D. CLIFFORD K. ENDO, D.P.M. JOURNAL AMERICAN PODIATRIC MEDICAL ASSOCIATION VOL 83, No. 4, APRIL., 1993 ECCENTRIC vs. CONCENTRIC PHASES - Two separate counters - Kistler accelerometer triggers timing circuit - Concentric phase begins at g Max through mid-swing - Eccentric phase begins at mid-swing through contact and g Max 20

21 Stationary Run Eccentric Phase Leg flexors lengthen immediately after foot touchdown Concentric Phase Leg flexors shorten immediately after g Max during propulsion 21

22 Conclusion As the surface becomes harder and impact increases, the overall eccentric activity in the posterior musculature of the lower leg increases. This may be partly due to pre-activation of these muscles prior to foot touchdown. Prior to footstrike a pre-innervation phase of muscular contraction occurs allowing stiffness and elasticity to the leg. As vertical impact increases, preactivation of the muscles increases. Gollhofer et al. Int J Sports Med, :19 22

23 Where Do We Go From Here? 1. Re-design podiatric biomechanics curriculum 2. Emphasize importance of joint interdependence and foot-leg interdependence 3. Prioritize clinical & laboratory research 4. Beliefs must be based upon sound scientific methodology Where Do We Go From Here? The field of foot orthopedics, and to some degree foot surgery, is a conglomeration of theory, techniques of treatment, and treatment modalities that are too frequently not based upon scientific fact. Merton L. Root, It is o.k. to say: I don t know 23