Introduction to Biomechanical Evaluation Qualitative Biomechanics Peter G. Guy B.Sc., D.Ch.

Introduction to Biomechanical Evaluation Qualitative Biomechanics Peter G. Guy B.Sc., D.Ch. During the course of a biomechanical evaluation the findings are recorded in either a qualitative or quantitative method of recording. Each of these recording methods has advantages and disadvantages. Both qualitative and quantitative biomechanics can benefit from the bisection of the posterior aspects of the tibia and the calcaneus. In qualitative biomechanics, the observed angles are placed into categories. With experience the tibial and calcaneal bisections are not required when using qualitative methods. In quantitative biomechanics, the observed angles are measured using various measurement devices. Bisection of the Tibia and the Calcaneus It is important to remember at all times that the lines used are designed to represent the osseous structures underlying and thus where tissue movement occurs it must be minimised where possible. To maximise the visualisation of the posterior aspect of the tibia and calcaneus: 1. Place the patient in the prone position with one leg flexed at the knee and placed over the opposite leg so that number 4 is formed. (Figure 1) 2. The foot to be examined should be aligned so the second digit is pointing towards the ground. This will aid the visualisation of the tibia to the calcaneus in neutral and the forefoot to rearfoot relationship. Figure 1 3. The area of motion needs to be located between lower leg and calcaneus. This area represents the soft tissue overlying the subtalar joint space. In this area the skin surface moves so much that a line drawn here would create too much confusing distortion, thus it is avoided. The area of motion is located by placing the middle of the thumb at the level of the middle of the lateral malleoli. The thumb is placed on Area of Motion Peter G. Guy B.Sc., D.Ch. 2007 1

the posterior aspect of the talus. Lines are drawn above and below the thumb (Figure 1a). These lines provide the upper and lower margins of the area of motion. 4. The first line of reference to be drawn is the bisection of the tibia. Bisection of the lower 1/3 of the tibia will produce a line long enough to offer a suitable section to measure yet not so long as to minimise any deformity present (see Figure 2). The upper bisection is normally 1/3 from the bottom of the tibia and can be visualised or measured with a ruler. (The bisection of the tibia is actually the bisection of the lower 1/3 of the leg that includes the tibia and fibula.) Lower 1/3 of the tibia Lower ½ of the tibia Figure 2 5. The lower bisection of the tibia is located at the upper margin of the "area of motion". In all but those cases of extreme structural deformity or trauma a bisection of the Achilles tendon at this point should suffice. The bisection of the Achilles tendon should coincide with the mid point between the medial and lateral malleoli on the posterior aspect of the lower leg. The lower bisection of the tibia should be marked with the ankle joint at 90. The two points are then carefully joined together without disturbing the tissue with the ankle joint at 90. 6. The final bisection to be drawn is the calcaneus bisection. The upper bisection is located at the lower boundary of the "area of motion". To create this, the tibial bisection is marked where it would cross the lower boundary if extended. The upper bisection of the calcaneus should be done with the STJ in neutral and the ankle joint at 90. 7. The lower bisection of the calcaneus is located by finding the plantar posterior aspect of the calcaneus at the point where the plantar fat pad begins. Place the STJ in neutral and with the thumb and index finger of one hand tightly bind down the skin of the posterior aspect of the calcaneus. Visually bisect the lower margin of the calcaneus with the other hand. With the skin tightly bound and the STJ in neutral carefully join the two points and extend the line onto the plantar surface. (Figure 3). 8. When measuring the tibia to calcaneus relationships the middle of the tractograph can be placed at the lower border of the area of motion. Figure 3 Figures 1 to 3 were drawn by Mark Bradley D. Pod.M. Peter G. Guy B.Sc., D.Ch. 2007 2

Qualitative Biomechanics This method of recording results occurs by placing an observed angle into one of two or more categories. The practitioner must be able to perform qualitative recordings before quantitative recordings can be performed. The following non- weight bearing and weight bearing biomechanical examinations can be categorised: 1. The calcaneus to tibia in neutral 2. The forefoot to rearfoot relationship 3. The 1 st ray position 4. The STJ axis deviation 5. The tibia to ground in neutral 6. The neutral calcaneal stance position (NCSP) 7. The tibia to calcaneus neutral and relaxed 8. The relaxed calcaneal stance position (RCSP) 9. The supination resistance test 10. The maximum pronation test 11. The Hubscher manoeuvre 12. The Scherer foot classification. Dr. Merton Root DPM established most of the standard podiatric biomechanical terminology for motions, positions, and structural deformity. Root terminology allows the practitioner to place observations into categories. Root established and outlined the protocol to examine the foot and lower extremities. Root devised the neutral position of the STJ. The neutral position of the STJ is used as reference point when performing certain biomechanical examinations of the foot and lower extremity 1. Calcaneus to Tibia in STJ neutral The relationship between the calcaneus and the tibia can be either inverted, or parallel, or everted when the STJ is held in the neutral position and the MTJ is the fully pronated position. (Figure 4) An inverted calcaneus to tibia in neutral is termed calaneal varum. An everted calcaneus to tibia in neutral is termed calcaneal valgum. Calcaneal varum is a cause of rearfoot varus. Calcaneal valgus is a cause of forefoot valgus. Figure 4 Peter G. Guy B.Sc., D.Ch. 2007 3

Forefoot to Rearfoot Relationship Plantar plane of the forefoot in relationship to the calcaneal bisection (Figure 5 a, b, c) An inverted forefoot to rearfoot relationship is termed forefoot varus. This assuming there is no soft tissue component to the inverted forefoot to rearfoot relationship (forefoot supinatus). An everted forefoot to rearfoot relationship is termed a forefoot valgus. Forefoot varus and valgus are boney deformities. When a STJ neutral cast is taken of the foot, the forefoot to rearfoot relationship is captured in the negative cast. The positive cast is balanced so the cast remains perpendicular to the supporting surface. The resulting orthosis will bring the ground up to the forefoot. The balanced orthotic device will prevent the STJ from compensating for the forefoot to rearfoot deformity. Fig 5a Fig 5b Fig 5c Inverted Perpendicular Everted Reduced Forefoot to Rearfoot Relationship Press on the navicular to remove forefoot supinatus. The reduced forefoot to forefoot to rearfoot relationship represents the removal of a soft tissue frontal plane deformity. Any remaining inverted forefoot to rearfoot angulation represents a forefoot varus, which is a boney deformity. (Figure 6) Forefoot Supinatus Supinatus It is the difference between an inverted forefoot to rearfoot relationship and a less inverted or Figure 6 perpendicular reduced forefoot to rearfoot relationship (Figure 6). If the forefoot supinatus is not removed it will result in a greater amount of erroneous forefoot varus. If the positive cast is balanced with the forefoot supinatus present, the resulting orthosis will prevent proper functioning of the 1 st ray and 1 st MPJ. Peter G. Guy B.Sc., D.Ch. 2007 4

Effect Of Plantarflexed 1 st Ray on the Forefoot to Rearfoot Relationship Mobile Plantarflexed First Ray When observing the forefoot to rearfoot relationship the presence of a mobile plantar flexed first ray can minimise the actual inverted forefoot to rearfoot deformity. (Figure 7) To observe the actual forefoot to rearfoot relationship, dorsiflex the 1 st metatarsal until it is in line with the 2 nd 5 th metatarsal heads to reveal the actual inverted forefoot to rearfoot deformity. Figure 7 Evaluation of the 1 st Ray Position Figure 8a Figure 8b Figure 8c The relative amount of movement of the 1 st ray above and below the 2 nd through 5 th metatarsal heads reference point is used to categorise the 1 st ray as plantarflexed or dorsiflexed. The mobile plantar flexed 1 st ray as described above has more movement below the 2 nd through 5 th metatarsal heads reference point. However the 1 st ray can move above the 2 nd through 5 th metatarsal heads reference point. Therefore, this is reason it is considered mobile. When ground reaction force is applied to the 1 st metatarsal head it is push into a position above the 2 nd through 5 th metatarsal heads reference point. The diagram to the left demonstrates the procedure to evaluate the position of the 1 st ray. The 2 nd through 5 th metatarsal heads are grasped with the index finger and thumb of one hand. The 1 st ray is grasped with the index finger and thumb of the other hand. (Figure 8b) Using the 2 nd through 5 th metatarsal heads reference point the 1 st ray is elevated or depressed to the end range of movement. In a normal situation there should be an equal amount of movement above and below the 2nd through 5 th metatarsal heads reference point. (Figure 8a,c) A rigid plantar flexed 1 st ray occurs when there is no movement above the 2 nd through 5 th metatarsal heads reference point. In fact the 1 st ray cannot be place even with the 2 nd through 5 th metatarsal heads reference point. 2 Figure 8. a-c from page 49 & 50 of Root et al. Normal and Abnormal Function of the Foot. Clinical Biomechanics Corp., Los Angeles., 1977. Peter G. Guy B.Sc., D.Ch. 2007 5

Rigid Plantarflexed 1 st Ray During the evaluation of the 1 st ray position, the 1 st ray will not be allowed to elevated to the 2 nd through 5 th metatarsal heads reference point. This results in the forefoot to rearfoot relationship being everted. The 2 nd through 5 th metatarsal heads are perpendicular to the calcaneal bisection. However, a line drawn from the 5 th metatarsal head to the 1 st metatarsal head results in the everted position in relation to the calcaneal bisection. (Figure9) Figure 9 Mapping STJ Axis Location Figure 10 Mapping the STJ axis is non-weight bearing clinical examination technique developed by Kevin Kirby DPM 3. During the 1950 s and 1960 s Drs. Merton Root, Bill Orien, and John Weed developed most of the commonly used podiatric biomechanical examination techniques. Figure 10 from page 50 of Foot and Lower Extremity Biomechanics: A Ten Year Collection of Precision Intricast Newsletters. Precision Intricast, Inc., Payson, Arizona, 1997. Drs. Root, Orien, and Weed suggested that if the deformity had been identified (forefoot varus, forefoot valgus, rearfoot varus, plantarflexed 1 st ray, etc), then the patient s biomechanical compensations could predicted during gait. Dr. Kevin Kirby observed that there was a poor correlation between dynamic foot function and the observations/measurements made during a standard biomechanical examination. Kirby developed a heel pushing technique to observe how patients responded to plantar heel pressure. In individuals with normal feet, the thumb pressure on the centre of the heel caused STJ supination to occur. In individuals with a maximally pronated STJ and significant MLA flattening during stance and gait, thumb pressure on the centre of the heel caused no STJ supination. Supination did not occur until pressure was applied medial to the centre of the heel. These observations lead Kirby to develop the technique for mapping the STJ axis position on the plantar aspect of the foot. Peter G. Guy B.Sc., D.Ch. 2007 6

When plantar pressure is applied to the point of no rotation in the heel area the foot neither pronates nor supinates (figure 10). Kirby was able to map the STJ axis on the plantar aspect of the foot by applying thumb pressure at 1cm increments on the points of no rotation distal to Figure 11 the heel. These points of no rotation were marked and connected resulting in a line representing the STJ axis. (Figure 11) Plantar pressure medial to the axis causes the STJ supination. Plantar pressure lateral to the axis causes STJ pronation. Kirby observed that feet with the most medially deviated STJ axis had the following features: 1. the flattest MLA s; 2. maximally pronated STJ; 3. a convex shape on the medial border of the foot while standing; 4. difficult to supinate from the maximally pronated position; 5. difficult to control with a standard Root orthotic. Feet with the most laterally deviated STJ axis had the following features: 1. the highest MLA s; 2. concave medial border of the foot while standing ; 3. supination instability with a tonic spasm of the peroneus brevis. Figure 11 from Kirby, K A.: Methods for Determination of Positional Variations in the Subtalar Joint Axis, JAPMA., 77:228-234, May 1987 Weight Bearing Observations Angle and Base of Gait Weight bearing neutral and relaxed measurements is observed in the angle and base of gait. The base of gait is determined by having the patient walk and observing the distance between the two heels. The angle of gait is determined by having the patient walk and observing the angle that the midline of the foot makes with the line of progression. The tibia to ground neutral, the neutral calcaneal stance position, the tibia to calcaneus angle neutral, the tibia to calcaneus relaxed, the relaxed calcaneal stance position, the maximum pronation test, and the supination resistance test are observed in the angle and base of gait Figure 12 Tibia to Ground Neutral (Figure12) The foot is held in STJ neutral and the angulation of the bisection of the tibia is observed in relation to the ground. An inverted tibial bisection represents a tibial varum. Tibial varum is a cause of rearfoot varus. Neutral Calcaneal Stance Position (NCSP) (Figure12) The foot is held in STJ neutral position and the angulation of the bisection of the calcaneus is observed in relation to the ground. An inverted NCSP is indicative of rearfoot varus condition. The NCSP is a combination of the NWB tibia to calcaneus neutral and the tibia to ground neutral. Inverted Tibia to ground Inverted NCSP Medial Inverted Tibia to Calcaneus Angle Neutral Peter G. Guy B.Sc., D.Ch. 2007 7

Tibia to Calcaneus Angle Neutral (Figure12) This angle should be similar to the non weight-bearing tibia to calcaneus angle; however, because of skin movement they will probably be different. The difference between the tibia to calcaneus neutral and relaxed represents static pronation. Relaxed Position Everted Relaxed Tibia To Calc. Angle Everted RCSP Figure 13 Medial Tibia to Calcaneal Angle Relaxed (Figure 13) This weight-bearing angle is useful when compared to the weight bearing neutral tibia to calcaneus angle. This angle can be inverted, parallel or everted. Relaxed Calcaneal Stance Position (RCSP) (Figure 13) This angle represents the calcaneal bisection in relation to the ground. This angle can be inverted, perpendicular, or everted. The RCSP observation can be combined with the forefoot to rearfoot relationship observation. This produces one of the nine foot types in the Scherer Foot Classification. Kirby K. JAMPA 91(9): 465, 2001 RCSP Supinated Pronated Supination Resistance Test The determination of the subtalar joint (STJ) axis location in relation to the plantar foot is an important clinical examination technique that allows appreciation of the pronation and supination moments acting across the STJ axis. Once this examination technique is mastered, it will be noted that patients with medially deviated STJ axes tend to have a maximally pronated STJ in relaxed calcaneal stance position Peter G. Guy B.Sc., D.Ch. 2007 8

(RCSP). Patients with laterally deviated STJ axes tend to have the STJ neutral or slightly supinated from neutral while standing in RCSP. Kevin Kirby developed the supination resistance test. 4 The supination resistance test is performed with the patient standing in their angle and base of gait, in RCSP. Figure 14 from the Precision Intricast website The patient should also be instructed to relax their feet during the test so that no extrinsic muscular contraction occurs. In other words, the patient should not try to either pronate or supinate their STJ while the test is being performed or the test will give unreliable results. Once the patient is standing in RCSP, the examiner places Figure 14 the tips of two of their fingers directly plantar to the medial aspect of the navicular in the medial longitudinal arch of the foot. Pull directly superiorly on the medial navicular parallel to the long axis of the tibia (Fig. 14). When the examiner starts to pull superiorly on the medial navicular, it should be noted how the patient s foot responds to this force. In addition, the examiner should note the magnitude of the force that is required to supinate the STJ from its resting position. Care must be taken while performing the test that the patient does not feel as if they are being pushed out of balance since this will make the patient use alternate muscles than what they normally would use while standing in RCSP. In general, if the test is performed as outlined above, the patient will not feel as if they are being pushed out of balance. In a foot that has a normal STJ axis location (i.e. passing posteriorly through the posterior-lateral calcaneus and anteriorly through the first intermetatarsal space area), the examiner will only have to exert a few pounds of digital force to cause STJ supination. As the STJ axis becomes more laterally located, a lesser magnitude of digital force is required to produce STJ supination. As the STJ axis becomes more medially located, a greater magnitude of force is required to produce STJ supination. If the STJ axis is severely medially deviated, so that the STJ axis passes directly over the medial aspect of the navicular, the examiner will not be able to supinate the STJ using the supination resistance test. The biomechanical principles behind the supination resistance test are relatively simple. The more lateral the location of the STJ axis while in RCSP, then the longer is the lever arm (i.e. moment arm) for the examiner to produce supination moment across the STJ axis by pulling superiorly on the medial navicular. The more medial the location of the STJ axis while in RCSP, then the shorter is the moment arm for the examiner to produce supination moment across the STJ axis by pulling superiorly on the navicular. If the STJ axis is so severely medially deviated that the STJ axis passes directly over the medial aspect of the navicular, there will be no moment arm for the examiner to produce supination moment across the STJ axis and the examiner will not be able to supinate the STJ even with a very large amount of digital force on the medial navicular. In these cases you may be able to supinate the STJ by moving your fingers proximally and repeat the test. The supination resistance test illustrates how body weight has less effect on the amount of digital force required to supinate the STJ than the position of the STJ axis. The supination resistance test allows the examiner to feel the forces acting on the foot during weightbearing activities which would normally be difficult to measure and appreciate.. Peter G. Guy B.Sc., D.Ch. 2007 9

Figure 15 Maximum Pronation Test Kevin Kirby described the maximum pronation test 5. The maximum pronation test starts from the relaxed calcaneal stance position (RCSP) with the patient in their angle and base of gait. The patient is instructed to, lift the lateral side of their forefeet off the ground while keeping their knees extended (figure 15). The patient will use their peroneus brevis to maximally pronate their subtalar joint. If the feet are already maximally pronated then the calcaneus will evert less than 2 degrees. If this occurs, special anti-pronation features have to be added to the orthoses such as the Kirby medial skive. If the calcaneus everts more than 5 degrees, then the STJ is close to the neutral position in RCSP. This situation does not require any special anti pronation features added to the orthosis. Figure 15 from page 47 of Foot and Lower Extremity Biomechanics: A Ten Year Collection of Precision Intricast Newsletters. Precision Intricast, Inc., Payson, Arizona, 1997. The Hubscher Maneuver The Hubscher maneuver is a weight bearing test in which the attempt is made to dorsiflex the hallux. This will initiate the windlass mechanism as described by Hicks in the 1950 s 7 8 9 10. If the hallux is pulled even slightly upward into dorsiflexion, tension force is increased within the medial band of the plantar fascia (MBPF). Figure 16 Figure 17 Peter G. Guy B.Sc., D.Ch. 2007 10

Figures 16 & 17 from page 143 of Foot and Lower Extremity Biomechanics: A Ten Year Collection of Precision Intricast Newsletters. Precision Intricast, Inc., Payson, Arizona, 1997. The increase in posterior pull on the proximal phalanx of the hallux causes an equal an opposite posteriorly directed force on the 1 st metatarsal head (figure 16). The Hubscher manoeuvre causes increase tension in the MBPF causing the talo-navicular, navicularfirst cuneiform, and the first cunieform first metatarsal joints to buckle into a high arched foot. The result is a plantarflexed forefoot on the rearfoot (figure 17). STJ supination occurs with the Hubscher maneuver because of the plantarflexion of the 1 st ray that causes an increased supination force on the forefoot and rearfoot. Supination of the STJ will also occur because of the increased interosseous compression force within the medial aspect of the bones of the medial arch (figure 17). When the windlass mechanism is activated, coupling occurs between the foot and leg. As the foot supinates ligamentous coupling causes the tibia to externally rotate. If this does not occur this signifies a significant loss of ligamentous integrity in the rearfoot and mid foot. Feet that have a medially deviate STJ axis and low arch will result in no STJ supination during the Hubscher maneuver. A failed Hubscher maneuver is also suggestive of functional hallux limitus, especially if the 1 st MPJ has a normal non- weight bearing range of motion. Single Leg Raise The single leg raise begins with the patient standing on one leg. The patient is asked to raise their heel off the ground. On the affected side, there will be an inability of the patient to raise their heel of the ground standing on one leg due to lack of leverage and pain. If the PTT is weak or ruptured the MTJ will be very unstable. The MTJ cannot maintain a rigid lever during heel lift. The gastroc-soleus plantarflexes the rearfoot instead of the forefoot at the MPJs. The lack of leverage & pain inhibits heel lift. Peter G. Guy B.Sc., D.Ch. 2007 11

The First Metatarsal Rise Sign Hittermann first described this test for PTTD 11. Patients sit on the end of the table with their feet partially weightbearing on the floor and knees flexed to 90. The examiner externally rotates the leg or inverts the heel of the affected foot. If the 1st metatarsal rises off the supporting surface, the patient has PTTD and a loss of ligamentous integrity. If the ligamentous integrity is intact the arch will raise while supinating the foot. The1st metatarsal will plantarflex and maintain contact with the ground due to ligamentous tension. If positive you can determine if the forefoot supinatus is reducible Functional Hallux Limitus Test In this nonweightbearing test, the examiner holds the foot of the subject in the subtalar joint neutral position. One hand is used to hold the first ray in a dorsiflexed position by loading the first metatarsal head. The other hand is used to dorsiflex the proximal phalanx of the hallux. The test result for functional hallux limitus is considered positive if there is immediate plantarflexion of the first metatarsal Peter G. Guy B.Sc., D.Ch. 2007 12

and negative if there is a delay in plantarflexion or a range of motion of the proximal phalanx on the first metatarsal before plantarflexion of the first ray occurred. Payne demonstrated that the functional hallux limitus test had good sensitivity (0.72) and specificity (0.66) to predict excessive midtarsal joint pronation during the late stance phase as the heel begins to lift 12. Clinicians should consider the possibility of functional hallux limitus when a late midstance collapse of the midtarsal joint is noted during gait and should include the clinical test for functional hallux limitus in the routine assessment of a patient s biomechanical function. Manual Muscle Testing Evaluating tibialis posterior muscle strength and tendon integrity Plantarflex the ankle to 45. Using your right palm press on the medialplantar aspect of the distal 1st met. Your left fingers palpate the PTT. Ask your patient to supinate their foot. Flexion of the hallux indicates assistance form the FHL and/or FDL. Note the amount of force required to prevent supination of the foot. Note the palpable tension within the PTT. Evaluating peroneus longus strength Peroneal muscle strength can be evaluated by placing the forefoot area in a supinated position and asking the patient to resist the force. Peter G. Guy B.Sc., D.Ch. 2007 13

Scherer Foot Classification 1. In RF Ev FF Rigid Valgus/ Pes Cavus High lateral arch STJ motion mostly Abd-Add Limited joint motion No MTJ motion NWB Calc inverted at midstance Trigger toe Check for Anterior Cavus 1.6 mm navicular drop Lat. STJ axis? 4. Pp RF Ev FF High arch foot NWB MTJLA supination during propulsion will compensate for Ev FF. Abrupt loud heel contact Moderate Bunion 6 mm navicular drop Check for Anterior cavus 7. Ev RF Ev FF FFVAL that collapses Mobile NWB MTJ motion Severe supinatus Severe bunion Radiograhic features of pronated foot Med. STJ axis? 13.2 mm navicular drop 2. In RF Pp FF UC RFVAR Limited joint motion Full 1st MPJ ROM Lateral column dorsiflexes Medial column plantarflexes Short 1st Metatarsal 3 mm navicular drop Lat. STJ axis? 5. Pp RF Pp FF Normal foot based on Root Criteria 7 mm navicular drop 8. Ev RF Pp FF Asymptomatic flatfoot Abduction of FF on RF Mobile foot Moderate Bunion Post tib syndrome Max pronation at heel contact Med. STJ axis? 13.5 mm navicular drop 3. In RF In FF UC RFVAR and FFVAR Very abducted gait Lateral shoe wear Limited motion Very rare foot Dramatic lateral shoe wear 8 mm navicular drop Lat. STJ axis? 6. Pp RF In FF UC FFVAR Abducted gait Limited joint motion H.molle 4/5 space Extensor substitution Wide forefoot on normal foot 6.5 mm navicular drop 9. Ev RF In FF Flexible flatfoot STJ motion mostly Ev -In Heel contact everted Mobile foot Moderate Bunion Severely propulsive Med. STJ axis? 14.8 mm navicular drop In-inverted; Ev-everted; RF-rearfoot in relaxed calcaneal stance); FF-forefoot to rearfoot relationship in STJ neutral; FFVAR-forefoot varus; FFVAL-forefoot valgus; UC-uncompensated; Pp-perpendicular This classification uses the non-weight bearing forefoot to rearfoot relationship and the weight- bearing relaxed calcaneal stance position 13. Each one of these observations can either be inverted, perpendicular, or everted. For example, if you have you have an everted forefoot to rearfoot relationship and an inverted RCSP the resultant category is category number one, which is a highly arched foot type. The Scherer classification system use Root forefoot and rearfoot structural deformities and assigns various pathologies to each of the categories in an effort to aid the understanding of how static structural problems behave in a dynamic situation. In 1998, Parker and Infanti reported that the RCSP had moderate to good intra-rater reliability and the forefoot to rearfoot relationship had poor to moderate intra-rater reliability. Overall the Scherer classification had moderate intra-rater reliability 14. Scherer did not discuss navicular drop or STJ axis position in the original paper on this classification system. The possible sagittal plane deviations of STJ axis have been included in the Scherer classification. In 1999, Vivekanand reported values for navicular drop in each Scherer category 15. Navicular drop is the only Peter G. Guy B.Sc., D.Ch. 2007 14

static indicator that can predict dynamic rearfoot motion 16. Navicular drop values have been included for each one of the categories. Modified Romberg s Test The patient is asked to perform tasks of increasing difficulty. Observe the response to standing on one leg, loss of vision and then displacement. The patient starts off with eyes open standing on one leg with arms crossed. The patient should be able to maintain balance for at least 20-30 seconds without much shoulder sway occurring. The next part of the test is with the patient eyes closed standing one leg. The goal is 30 seconds with eyes closed. Ask the patient, do you feel steady? You can test displacement by a light nudge on the sternum. These tests allow a rough estimate of balance and can help some causative factors such as osteoarthritis, neuropathy, foot problems, muscle weakness, pain, or contractures. You can test with and without orthoses. Patients who present with pes planus and pes cavus usually have difficulty with this testing. Patients with a history of lateral ankle instability should be asked to perform this test. References 1 Root, ML, Orien, WP, Weed JH, and Hughes RJ. Biomechanical Examination of the Foot. Clinical Biomechanics Corp., Los Angeles, 1971 2 Root, M., Orien, W., Weed, J. Normal and Abnormal Function of the Foot. Clinical Biomechanics Corp., Los Angeles. P.49-50, 1977. 3 Kirby K. Methods for Determination of Positional Variations in the Subtalar Joint Axis. JAPMA. 1987; 77:228-234 4 Precision Intricast website 5 Kirby, K A. : Foot and Lower Extremity Biomechanics: A Ten Year Collection of Precision Intricast Newsletters. Precision Intricast, Inc., Payson, Arizona, 1997 7 Hicks JH. The mechanics of the foot. J. Anat 1953; 87:345-357 8 Hicks JH. The mechanics of the foot. II. Plantar aponeurosis and the arch. J. Anat 1954; 88:25-30 9 Hicks JH. The foot as a support. Acta Anat. 1955; 25:34-45 10 Hicks JH, The mechanics of the foot. IV. The action of the muscles on the foot in standing. Acta Anat. 1957; 27:180-192 11 Hintermann B, Gachter A. The first metatarsal sign: A simple sensitive sign of tibialis posterior tendon dysfunction. Foot Ankle 1996, 17:237 12 Payne C, Chuter V, Miller K, Sensitivity and Specificity of the Functional Hallux Limitus Test to Predict Foot Function J Am Podiatr Med Assoc 92(5): 269-271, 2002) 13 Scherer PR and Morris JL: the Classification of Human Foot Types, Abnormal Foot Function, and Pathology, in Clinical Biomechanics of the Lower Extremities ed. by RL Valmassy. CV Mosby,St Louis,1996 14 Infante AM and Parker S. The Inter-rater and Intra-rater Agreement of the Scherer and Morris Foot Classification System among Physical Therapists, Chiropractors, Chiropodists, and Family Physicians. 3rd year thesis, Ontario Chiropody Program.1998 15 Vivekanand, B. Investigation into the Relationship of Navicular Height Difference and Foot Classification According to Morphology. 3rd year thesis, Ontario Chiropody Program. 1999 16 McPhoil, TG, Cornwall, MW. The relationship between static lower extremity measurements and rearfoot motion during walking. J Orthop.Sports Phys Ther 1996:24:309 Peter G. Guy B.Sc., D.Ch. 2007 15