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Archive for June, 2019

ICB Lower limb biomechanics

The term Pes cavus is derived from Latin meaning ‘hollow foot’ and covers a wide spectrum of foot deformities.


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The Pes cavus foot can be hereditary or acquired and the underlying causes can be neurological, orthopaedic or neuromuscular. The condition can be wide ranging from conditions such as Chartcot-marie-tooth disease (CMT) and Fiedreich’s ataxia to the more commonly high arched supinated foot acquired from familial predisposition.
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Pes Cavus Feet - High Arch

The CMT foot symptoms are progressive and can include :

 • Ankle weakness
• High arches
• Clawed toes
• Muscle wasting
• Poor balance
• Muscle weakness in hands and feet
• Peripheral neuropathy

The Pes cavus foot

More commonly the condition is not so severe and is generally characterised by an abnormally high medial longitudinal arch, is described as a high axis foot and is most commonly associated with a high forefoot valgus deformity. Other features often include a varus (inverted) calcaneus, a plantarflexed position of the first metatarsal and adducted forefoot together with dorsal contracture of the toes or hammer toes.

Pes cavus feet will invariably be identified as supinated feet and characterised as having ‘reduced or limited pronation’.1 Population-based studies suggest that the prevalence of the cavus foot is approximately 10% 2 .The high arched cavus foot has a decreased range of motion, increased stiffness, and decreased pronatory compensation1.

Often this type of foot will exhibit increased rearfoot varus together with a higher incidence of lateral instability of the foot and ankle1.

Valmassy3 outlines 6 characteristics of a cavus foot:

1) Limited pronation

2) Rigidity

3) Uneven weight distribution

4) Digital contractures (clawing of the toes)

5) Increased tendency to lateral ankle instability with associated ankle sprains

6) Decreased ankle joint dorsiflexion(osseous block)

Inversion Sprain

Inversion Sprain

Valmassy3 states that besides the genetic predisposition or familial predisposition other causes to this condition are many and varied such as: Congenital plantarflexed 1st Ray deformity; spasm of peroneus longus; spasm of posterior tibial; weakness of peroneus brevis; weakness of peroneus longus; clubfoot deformity; metatarsus adductus. Underlying causative factors may include but not limited to: Charcot-Marie-Tooth disease, Friedreich’s ataxia, poliomyelitis, spina bifida to name a few.

Plantarflexed 1s

A study of painful Pes Cavus feet ‘indicates that custom foot orthoses are more effective than a control for reducing cavus foot pain and associated limitation in function.

The key feature of a successful orthotic device for this patient population is a contoured flexible shell moulded to the exact morphology of the foot, with a full-length cushioned top cover. Such a device has the effect of reducing and redistributing abnormal plantar pressure loading. For patients presenting to the clinician with painful cavus feet, custom foot orthoses are an effective treatment option 2.

The Pes cavus foot measure orthotics

Commonly Pes cavus feet present with Forefoot Valgus deformity (FFTVL) and it is wise in the assessment to complete a FFTVL assessment.

Biomechanical protractor

Use a forefoot valgus addition on the orthotic to reduce forefoot instability and lateral inversion of the foot by locking the 4th and 5th columns to mimic ground reaction forces.

ICB Orthotics

High arched feet do not usually require a rigid orthotic support, rather a softer accommodative device such as soft or mid density EVA materials.

ICB Orthotic

However, it is important to mould the orthotic well into the arch and use a metatarsal dome to reposition and lift the transverse arch if the toes are clawing.

ICB Orthotic

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REFERENCES
1. Steven Subotnick Sports Medicine of the Lower Extremity Edition 2 p129
2. Joshua Burns, PhD, Jack Crosbie, PhD, Robert Ouvrier, MD, Adrienne Hunt, PhD, Effective Or-thotic Therapy for the Painful Cavus Foot- A Ran-domized Controlled Trial Journal of the American Podiatric Medical Association • Vol 96 • No 3 • May/June 2006
3. VALMASSY, R.L. (1996) Pathomechanics of Lower Extremity Function. Clinical Biomechanics of the Lower Extremity, p. 61, Mosby, St Louis.

ICB Lower limb biomechanics

Leg length Inequality and the pathogenesis or the origin and development of the condition, is and will always be, a controversial subject. There is a wide variance of opinion on the significance of structural leg length and the various methods for measurement.

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Measuring of structural leg length when treating with orthotic therapy is necessary as undiagnosed structural leg length compensation will be affected when orthotics are prescribed for the patient. The natural body compensations for leg length difference can range from long leg flexion, to short leg supination amongst others as the body seeks to rebalance pelvic alignment. The most common compensation is long leg excessive pronation, accounting for around 80% of the long leg compensations. However in very large structural differences, short leg toe walking and short leg excessive pelvic drop may be taken up as compensations with inevitable upper spine outcomes such as functional scoliosis.

Measuring Large Leg Length

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Managing a treatment protocol to assist in minimising issues can be difficult especially if the spine is fixed, that is, the spine (or spinal segment) is not mobile or correctable by conservative means. This is often referred to as a Fixed Sagittal Imbalance (FSI) and conservative treatment looks to make the patient as comfortable as possible when surgical intervention is not undertaken.

In this newsletter we will focus on conservative treatment methods that can be adopted when the osseous structure is mobile.

Assessment for structural leg length difference as part of the initial assessment will avoid removal of undiagnosed compensations and provide an understanding of the size and extent of the leg length difference .

Using Orthotics treating large leg length

There are many ways to measure leg length, tape measure, x-ray, physical assessment of the limbs such as Palpation for Supine Medial Malleoli Asymmetry Technique 1

ICB provides both 10mm and 15mm extended heel lifts which can be used when the patient has custom made orthopaedic shoes or is wearing boots or the shoe has extra depth in the heel cup as they can be accommodated inside the shoe wear.

ICB orthotics heel lift

The extended heel lift is designed with a longer profile to support the mid foot and eliminate any mid foot collapse which can occur in Heel lift Larger than 8mm high. ICB regular heel lifts are available in S/M/L heel 4/6/8mm and the extended model is available in 10 &15mm.

Generally leather dress shoes can cope with a heel lift up to 6- 8mm (depending upon heel cup height) when added to the orthotic, higher than that the patient may complain that their heel is slipping out of the shoe.

Using Orthotics on large leg length

Therefore, alternate shoe styles or modifications need to be considered to accommodate for large structural differences. When recommending shoes with orthotics a deep heel cup is an advantage.

Cross trainers and boots are able to accommodate a larger amount of heel lift in the heel cup, however this may limit the patient to a smaller selection of fashion shoe styles. A solution may be to add maximum amount to the orthotic and then modify the patient’s shoe to achieve the best result. (see below)

Treating leg length with orthotics 2

To incorporate an intrinsic lift, the sole of the shoe should not contain gel, air cushion pockets and have a base that is flat with no arch cut out. A boot maker can cut the EVA sole with a band saw, finishing behind the breakpoint or 1st MTPJ when the heel lift is less than 30mm. This will enable a normal walking pattern and toe off to occur.

Shoe for treating large leg length

Once the intrinsic heel lift in the shoe sole is over 30mm the cut in the sole must extend to the sulcus behind the phalanges and if a greater amount, to the end of the foot in a thicker ‘ramp’ like adjustment.

The patient featured presented with a condition that could be treated with orthotics , an additional heel lift or raise was recommended to be placed into the heel of the shoe by a boot maker or shoe repairer.

A temporary Heel Lift was used to validate the treatment suggestion note the RIGHT shoe with temporary extrinsic addition which successfully corrected the functional
Shoe For Treating Large Leg Length

Extrinsic Heel Lift under shoe heel (above)

scoliosis, this is the amount that should be added into the shoe sole.

Refer :The Orthotic Solution book p45 

Note: It is recommended that both left and right feet are fitted with an orthotic, in addition to any heel lift requirements, to ensure the foundation of the body is balanced.

Generally most footwear will accommodate an orthotic with a 6-8mm heel lift addition (depending upon heel cup height). If a larger heel lift is required(10mm +), extra depth footwear or boots may be required – or alternatively, adjustments to the footwear to incorporate a partial lift into the sole of the footwear can assist.

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Reference: 1. Gary Fryer 2005 : Factors affecting the intra-examiner and inter-examiner reliability of palpation for supine medial malleoli asymmetry .

ICB Superior Biomechanics

Tibial torsion has been defined as torsion of tibia bone along its longitudinal axis1, which produces a change in alignment of the planes of motion of the proximal and distal articulations, it is a twist in the osseous structure.

 
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This definition draws a distinction between both Tibial Torsion (twist in the bone) and Tibial rotation.

Tibial Torsion (twist in the bone) and Tibial rotation.

Tibial Rotation occurs when the tibia internally or externally rotates along its axis as a functional outcome of biomechanical forces such as supination and pronation.

Pronation and Supination

Tibial rotation is the rotation of the entire tibial shaft (bone) which takes place in gait as the foot pronates and supinates. The Tibia can exhibit both torsion and rotation and this makes this subject both interesting and somewhat difficult.

Tibial torsion occurs where the tibia exhibits a twist in the actual bone and is apparent from birth.

The biomechanical condition can be treated prior to skeletal maturity using foot orthotic devices which work to un torsion the tibia (see Fig 1) .

Foot in Podiatry Tibial torsion

Once skeletal maturity has occurred, the soft tissue structures are engaged within the body to correct and adjust by tightening and or elongating as the means of correction or repositioning of the foot structure. In both instances knowledge of tibial torsion and tibial rotation will be invaluable to practitioners, in the design and implementation of treatments for their patients.

The broad parameters for identifying Tibial torsion have been outlined by Dr Merton Root 2 and Ronald L. Valmassy DPM3 and others, in which it is stated that torsion of the tibia be undertaken by measurement of the position of the medial and lateral malleoli apexes, (see Fig 2) a technique known as the Malleoli Position. (M.P.) This method imagines a pin bisecting medial and lateral malleoli apexes whilst the knee joint is maintained in the neutral position.

Malleoli Position

Several tibial torsion measurement techniques have been used or recommended by researchers; radiological methods and arthropometric methods, such as gravity goniometers. The method of measurement generally used in clinical practice is either by eye or by use of a gravity goniometer to measure malleoli positioning. (see Fig 3)

By Eye assessment

By Eye assessment

Gravity goniometer

Gravity Goniometer

Root and Valmassey reported that the average normal position of the normal malleolar position M.P. was 13° – 18° 2, or slight out toed position.

The malleolar position is determined by observing the bisection of apex of the medial and lateral malleolar whilst the knee joint remained in the neutral position and the patient in the supine position.

Due to the occurrence of displacement of the patella it should be noted that research groups stipulate the position of the knee joint not patella as neutral in the sagittal plane. The positioning of the knee joint was achieved by the using of the knee condyles and lifting in the sagittal plane, ensuring that no lateral or medial deviation is observed.

There are believed to be several causes of the Tibial Torsion condition such as :

a) Acquired: due to injury / trauma such as a broken tibia which is re-positioned and takes on a post-operative internal or external position.

b) Genetics: congenital which is inherited from the mother, father or their genetic lines.

c) Acquired or caused by the environment, especially the uterine environment such as positioning in the womb – the tibia can form in an internal or external torsion position.

When treating in the field of paediatrics it should be noted that Tibial Torsion can effect the gait pattern which, if left untreated may have considerable affect upon the child as it grows to maturity. The outcome may leave the child’s biomechanical structure compromised, leading to other pathologies as the body seeks to compensate for these changes.

Traditionally paediatric biomechanical foot problems were given a low priority, with the result that manageable cases were left untreated and secondary features related to structural pathologies developed. Michaud comments that – ‘Early recognition and management, of actual foot problems in the young would go a long way to the reduction of issues later in life’ 4.

‘Gait plate’ orthotic treatment is a simple and effective method of restoring the lower limb to the ‘normal Malleoli Positioning range of 13° to 18° for children over the age of 6 years.

The gait plate orthotic device is manufactured to provide an extension under the 5th phalange for in-toe or under the hallux for out-toe. In gait the gait plate extension is identified by the proprioception system in the body and the brain instructs the body to reposition the foot in an automated response pattern, gently working on removing the bone torsion in an attempt to reposition to the 13-18° position.

ICB Orthotic

The method is gentle and persuasive and has measurable results , however it appears to be most effective during ‘growth spurts’ in children.

If left untreated the body will naturally attempt to correct by using soft tissues to cosmetically correct the in toed or out toed position. Abnormal foot positioning, i.e. that which is opposed to what is accepted as ‘ideal’ or normal, encourages the body to use soft tissue to en-gage compensatory mechanisms.

Some studies have actually concluded that tight rotators and adductors have a compensatory repositioning function, as in the case of out toe and in toe positioning, relating to tibial torsion. 5,6,7,8, Again it must be stated that this is not strictly the case in every situation, and as such a small number of patients may present with tibial torsion without exhibiting hip compensations. The reasons for a lack of compensatory muscle tightness are unknown. These compensatory mechanisms can move joints in the body outside the normal range of motion and in the pro-cess may lead to so called ‘idiopathic’ soft tissue tight-ness such as Tight Abductors & Adductors or alternatively joint soreness during the compensation process.

 

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References:

1. MULLAJI Arun B, SHARMA Amit K,1 MARAWAR Satyajit V, and KOHLI AF. Tibial Torsion in Non-Arthritic Indian Adults: A Computer Tomography Study of 100 Limbs.

2. ROOT ML, ORIEN WP, WEED JH, HUGHES R, Biomechanical Ex-amination of the Foot The Orthotic Solution I 67 Vol 1. p34, 1971

3. VALMASSY R.L., (1996) Clinical Biomechanics of the Lower Ex-tremeties. p255

4. MICHAUD, T.C (1997): Foot Orthoses and Other Forms of Conserva-tive Foot Care. Sydney: Williams & Wilkins, p168.

5. STAHELI, LT. In-toeing and Out-toeing in Children. Journal Family Practice. May 1983;16(5):1005-11.

6. STAHELI LT, CORBETT M, WYSS C, KING H. Lower Extremity Rota-tional Problems in Children. Normal Values to Guide Management. American Journal Bone Joint Surgery Jan 1985;67(1):39-47.

7.DAVIDS JR, DAVIS RB. Tibial Torsion: Significance and Measure-ment. Gait Posture. Jul 2007;26(2):169-71.

ICB Lower limb biomechanics

Posterior tibial tendon dysfunction (PTTD) is a condition that results in inflammation or tearing of the posterior tibial tendon.


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The Tibialis Posterior is an inverter and plantar flexor of the foot1. The Posterior Tibial Tendon is the major dynamic stabiliser of the foot in pre-venting rearfoot eversion or pronation and is subject to repetitive overuse injury such as, peritendinitis, inflammation of the tendon sheath, and rupture2. Often the early stages of the condition can be overlooked or misdiagnosed3.

PTTD can be experienced bilaterally and or unilaterally, typically beginning with a paratenonitis of the tendon which may lead to synovitis, intrasubstance tearing and tendinosis4. ‘Recent literature has reported a higher prevalence of PTTD in women than in men, but with no explanation for this discrepancy5.

It is suggested that there are numerous underlying causative factors such as: excessive pronation, trauma, anatomical anomalies (eg. leg length discrepancy), inflammatory joint diseases, acute evulsion, iatrogenic events to name a few.

Many commentators state that PTTD is an overuse condition as the symptoms usually occur after activities that involve stress on the tendon, such as running, walking, hiking or climbing stairs.

The condition has often been categorised as ‘adult acquired flatfoot’ and research concludes that PTTD results in loss of medial arch structure and abduction of the forefoot, resulting in a change of gait4, accompanied by ensuing upper structure issues.

PTTD is categorised as having 3 stages of progression, the duration and severity can move rapidly from acute phase to subacute phase and ultimately chronic. The symptoms of PTTD can include pain and swelling. As PTTD advances, eversion of the calcaneus occurs and the arch often flattens, shifting pain to the lateral aspect of the foot (below the ankle). As the tendon deteriorates arthritis often develops in the foot. In more severe cases, arthritis may also develop in the ankle.

A recent study of PTTD Phase 2 patients suggest that non-surgical treatments to consider include reducing Posterior Tendon activity using arch supports/foot orthotics4 and inverting the rearfoot using an orthotic device with an Increased rearfoot varus angle. Inverting the entire orthotic device using an ‘inversion ramp’ can significantly reduce strain on the tibialis tendon.

Inversion Ramp to Invert Orthotic Device

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ICB Full Length orthotic fitted with inversion ramp.
The ICB ramps are available in 4°,6°,8° and are 32cm in length.

Inversion ramp on full length orthotic.

Conservative Treatments
Immobilisation: short-leg cast or ‘moon boot’ to allow the tendon to recover.
Ultrasound therapy and exercises may help rehabilitate the tendon and reduce inflammation.
Nonsteroidal Anti-Inflammatory Drugs (NSAIDs) to reduce the pain and inflammation.
Foot Orthotic Devices: to reduce calcaneal eversion/pronation are effective in stages 1-3. The addition of a medial flange to the dorsal arch of the orthotic can provide extra support to the navicular.

Medial Flange to control Navicular

Medial Flange on Orthotic

Footwear: Shoes that are designed with a flat base that provide good mid foot control and heel cup support can reduce arch collapse. In cases of PTTD that have progressed substantially or have failed to improve with non-surgical intervention, surgery may be required.

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References:

1. Merriman’s Assessment of the Lower Limb (2008), 3rd Edition. Churchill Livingstone. p264 2. Plattner PF (1989) Tendon problems of the foot and ankle. Postgraduate Medicine 86(3):155-170 3. Wassef S., Mikhail M., (2008) Ankle, tibilais posterior tendon injuries. Available at: http:// emedi-cine.medscape.com/article/ 386322-overview 4. S.I. Ringleb, S.J. Kavros, B.R. Kotajarvi, D.K. Han-sen, H.B. Kitaoka, K.R. Kaufman Changes in gait associated with acute stage II posterior tibial tendon dys-function Gait & Posture 25 (2007) 555–564 Biomechanics Laboratory, Division of Orthopedic Research, Mayo Clinic College of Medicine. 5. Gehrig Laura MD, Posterior Tibial Tendon Dysfunction: More Prevalent in Women, AAOS Now, Issue: March 2009

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