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The Effect of Stage II Posterior Tibial Tendon Dysfunction on Deep Compartment Muscle Strength: A New Strength Test.
Houck JR, Nomides C, Neville CG, Samuel Flemister A. Foot Ankle Int. 2008 Sep;29(9):895-902.
Quote:
BACKGROUND: The purpose of this study was to compare isometric subtalar inversion and forefoot adduction strength in subjects with Stage II posterior tibial tendon dysfunction (PTTD) to controls.
MATERIALS AND METHODS: Twenty four subjects with Stage II PTTD and fifteen matched controls volunteered for this study. A force transducer (Model SML-200, Interface, Scottsdale, AZ) was connected with a resistance plate and oscilloscope (TDS 410A, Tektronix, Beaverton, OR) to the foot. Via the oscilloscope, subjects were given feedback on the amount of force produced and muscle activation of the anterior tibialis (AT) muscle. Subjects were instructed to maintain a plantar flexion force while performing a maximal voluntary subtalar inversion and forefoot adduction effort. A two-way ANOVA model with the factors including, side (involved/uninvolved) and group (control/PTTD) was used.
RESULTS: The PTTD group on the involved side showed significantly decreased subtalar inversion and foot adduction strength (0.70 +/- 0.24 N/Kg) compared to the uninvolved side (0.94 +/- 0.24 N/Kg) and controls (involved side = 0.99 +/- 0.24 N/Kg, uninvolved side = 0.97 +/- 0.21 N/Kg). The average AT activation was between 11% to 17% for both groups, however, considerable variability in subjects with PTTD.
CONCLUSION: These data confirm a subtalar inversion and forefoot adduction strength deficit by 20% to 30% in subjects with Stage II PTTD. Although isolating the PT muscle is difficult, a test specific to subtalar inversion and forefoot adduction demonstrated the weakness in this population.
Re: Muscle strength and posterior tibial tendon dysfunction
Quote:
Originally Posted by NewsBot
BACKGROUND: The purpose of this study was to compare isometric subtalar inversion and forefoot adduction strength in subjects with Stage II posterior tibial tendon dysfunction (PTTD) to controls. ...MATERIALS AND METHODS: Twenty four subjects with Stage II PTTD and fifteen matched controls volunteered for this study. .....CONCLUSION: These data confirm a subtalar inversion and forefoot adduction strength deficit by 20% to 30% in subjects with Stage II PTTD. ...
What they were really doing is comparing a group of people with a medially located STJ axis (the PTTD group) to a group who probably did not have a medially located STJ axis (the control group) .... of course there will be apparent (and maybe not even real) strength deficits due to the lever arm that the posterior tibial muscle has to the STJ axis!
__________________ Craig Payne
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Re: Muscle strength and posterior tibial tendon dysfunction
Quote:
What they were really doing is comparing a group of people with a medially located STJ axis (the PTTD group) to a group who probably did not have a medially located STJ axis (the control group) .... of course there will be apparent (and maybe not even real) strength deficits due to the lever arm that the posterior tibial muscle has to the STJ axis!
Hey Craig
Good point, however isn't a large component of the cause of the medially deviated STJ axis the fact that the foot is weight bearing? ie: as the foot moves into a pronated position, the STJ axis moves medially. This is a NWB test...
I would think that the weakness is there (ie is real rather than apparent), and may be caused by the everyday poor function of the tib post for all the reasons you just mentioned.
__________________
Craig Tanner
Podiatrist ASPETAR-
Qatar Orthopaedic and Sports Medicine Hospital
Doha
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Re: Muscle strength and posterior tibial tendon dysfunction
Quote:
Originally Posted by CraigT
Hey Craig
Good point, however isn't a large component of the cause of the medially deviated STJ axis the fact that the foot is weight bearing? ie: as the foot moves into a pronated position, the STJ axis moves medially. This is a NWB test...
I would think that the weakness is there (ie is real rather than apparent), and may be caused by the everyday poor function of the tib post for all the reasons you just mentioned.
Craig and Craig:
A few things here are important to remember. First of all, any muscle strength testing protocol does not test only the ability of the muscle-tendon unit to produce a change in tensile force. Rather "muscle strength testing" is also testing the moment arm of that muscle-tendon unit relative to the joint axis that is being used to test the muscle. So, when we say we are "testing muscle strength", that is really not the case. What we are testing is "testing muscle-induced moment" about a joint axis. I think this important concept is very poorly understood in all medical disciplines, and even within the international biomechanics community.
This factor is especially important at the subtalar joint (STJ) axis where there are such small moment arms and also such a large variation in STJ moment arms for the invertors and evertors. Take, for example, the posterior tibial muscle. In the patient that has a medially deviated STJ axis, the moment arm during weightbearing for producing STJ supination moment may be in the order of 5 mm whereas, in the normal shaped foot the supination moment arm is in the order of 20 mm and in the laterally deviated STJ axis, the supination moment arm is in the order of 30 mm. In other words, for a given absolute muscle-tendon contractile tensile force, the medially deviated STJ axis could have a six-fold decrease in "posterior tibial muscle strength" when compared to a laterally deviated STJ axis.
I challenge anyone to describe to me any other muscle-joint combination in the human body that can have such large relative changes in muscle moment arm lengths from one individual to another. This is one of the reasons why the concept of understanding STJ axis location is so significant and so important for the health professional that treats foot and lower extremity mechanically-based pathology.
__________________
Sincerely,
Kevin
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
Re: Muscle strength and posterior tibial tendon dysfunction
Kevin wrote "I challenge anyone to describe to me any other muscle-joint combination in the human body that can have such large relative changes in muscle moment arm lengths from one individual to another."
How about the piriformis in subjects with substantial leg length difference and pelvic rotation. Another would be the VMO (quad) in subjects with genu varum, and/or genu valgum. Rather high changes in moment arms result in these muscles with the anatomical variations across different patients.
There are many factors which can subject some to decreased strength in the posterior tibial muscle. Kevin is clearly correct with respect to muscle moments and STJ axis deviation....but this is just not the only reason why dysfunction occurs. In fact, I have seen several cases of PTTD in which the posterior tibial muscle exhibits normal strength, while the peroneals are markedly inhibited. Change peroneal strength improves heel lift function, and can decrease stress to the posterior tibial.
Re: Muscle strength and posterior tibial tendon dysfunction
Quote:
Originally Posted by Dananberg
Kevin wrote "I challenge anyone to describe to me any other muscle-joint combination in the human body that can have such large relative changes in muscle moment arm lengths from one individual to another."
How about the piriformis in subjects with substantial leg length difference and pelvic rotation. Another would be the VMO (quad) in subjects with genu varum, and/or genu valgum. Rather high changes in moment arms result in these muscles with the anatomical variations across different patients.
There are many factors which can subject some to decreased strength in the posterior tibial muscle. Kevin is clearly correct with respect to muscle moments and STJ axis deviation....but this is just not the only reason why dysfunction occurs. In fact, I have seen several cases of PTTD in which the posterior tibial muscle exhibits normal strength, while the peroneals are markedly inhibited. Change peroneal strength improves heel lift function, and can decrease stress to the posterior tibial.
Howard
Howard:
I don't think that there are as significant changes in hip joint axis moment arm for the piriformis or as significant changes in knee joint axis moment arm for the vastus medialis obliquus (VMO) as there are for the subtalar joint (STJ) axis for the posterior tibial tendon. The posterior tibial tendon can have a moment arm for supination that is as much as (if not more) 6 times longer in the foot that has a laterally deviated axis than the moment arm for supination is in the medially deviated STJ axis foot. I don't think the piriformis or VMO have magnitudes of change in muscle moment arm lengths that are even close the posterior tibial tendon for their respective joint axes. This large change in PT tendon supination moment arm length to the STJ axis is caused by the insertion of posterior tibial tendon being on the navicular and the wide range of possible range of adduction/abduction motion of the navicular relative to the talar head, where the STJ axis passes superiorly out of.
__________________
Sincerely,
Kevin
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
Re: Muscle strength and posterior tibial tendon dysfunction
Kevin,
I guess that even in these tough economic times, its good to know there are some things that remain reliable. The nature of our conversations are like they have never changed.
I was really thinking about the effect of the piriformis on the sacroiliac (SIJ) joint, and not the hip. If the rotation of the pelvis is forward, and guarding pain via hip flexion is the gait style, then the effective difference is highly significant, and can disable many with lower back pain. Prehaps you are correct, that the PT/STJ is greater, its really splitting hairs. What's far more important is the reason why the PT muscle weakened itself to begin with. This is a discussion for another day.
As far as the VMO goes, patients with terrible knee pain often walk with a large component of midstep flexion at the knee during weight bearing. When the
30-40 degree flexion stress is added to the varus/valgus equation, then one could argue that the moment arm stress point may be close to that of the PT/STJ as well.
I do accept your point though, that the stress on the PT tendon in a foot with a medial deviation is far greater than without, and the greater the deviation, the more stressful it is for the tendon.
Re: Muscle strength and posterior tibial tendon dysfunction
Quote:
Originally Posted by Dananberg
Kevin,
I guess that even in these tough economic times, its good to know there are some things that remain reliable. The nature of our conversations are like they have never changed.
Howard:
I don't have much fun discussing things with people that are always in agreement with me. I'm sure we will be having discussions for many years to come.
__________________
Sincerely,
Kevin
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
Re: Muscle strength and posterior tibial tendon dysfunction
Quote:
Originally Posted by Kevin Kirby
I challenge anyone to describe to me any other muscle-joint combination in the human body that can have such large relative changes in muscle moment arm lengths from one individual to another. This is one of the reasons why the concept of understanding STJ axis location is so significant and so important for the health professional that treats foot and lower extremity mechanically-based pathology.
I don't know how to measure relative lever arms but here are a couple of things to think about.
The interossei muscles can turn from plantar flexors to dorsiflexors depending on position of the toes. A non reducible dorsiflexion contracture of the MPJ could keep these muscles as dorsiflexors.
Also the anterior tibial can change from a pronator to a supinator of the STJ depending on STJ position and STJ axis position. Although the anterior tibial will still maintain its function of a dorsiflexion of the ankle regardless.
Re: Muscle strength and posterior tibial tendon dysfunction
Quote:
Originally Posted by efuller
I don't know how to measure relative lever arms but here are a couple of things to think about.
The interossei muscles can turn from plantar flexors to dorsiflexors depending on position of the toes. A non reducible dorsiflexion contracture of the MPJ could keep these muscles as dorsiflexors.
Also the anterior tibial can change from a pronator to a supinator of the STJ depending on STJ position and STJ axis position. Although the anterior tibial will still maintain its function of a dorsiflexion of the ankle regardless.
Cheers,
Eric
The anterior tibial tendon to subtalar joint (STJ) axis relationship certainly rivals that of the posterior tibial tendon to STJ axis. But since the STJ axis is involved in both of these muscle to joint axis changes, then my point remains the same....the STJ axis displays some pretty impressive changes in muscle moment arms from one individual to another and throughout its normal range of motion......much more than any other joint in the body that I know of.
I'm not too impressed about the range of movement of the interossei across the metatarso-phalangeal joint axis....even though it there is definitely some changes that occur.
__________________
Sincerely,
Kevin
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
Re: Muscle strength and posterior tibial tendon dysfunction
I appreciate Kevin’s comments regarding the medial/lateral location of the subtalar joint axis with regard to the posterior tibialis tendon muscle strength, and in reference to his article in 2001 about the subtalar joint equilibrium theory. So what really is being discussed is not so much an element of muscle strength as it is a discussion about mechanical advantage. A medially located subtalar axis would have a decreased mechanical advantage for the posterior tibialis, thus requiring it to work harder to do the same amount of work that a more laterally (or as you call it “normal”) located axis would require.
However, one concept that I feel really escapes the discussion is not so much about muscle strength, which usually is describing a muscle action, which is usually describing a NWB test. What the discussion and research really needs to start focusing on is what the muscles FUNCTION is. In this example of the posterior tibialis one primary element of the muscle test used was inversion. However, the posterior tibialis primarily functions in WB as a decelerator (i.e. eccentric) controller of eversion and dorsiflexion. Reber (1993) started a discussion about this with the posterior muscles of the calf (rather than them being called the plantar flexors).
Clinically, a discussion of mechanical advantage is relevant to the function of the posterior tibialis. However a discussion that focuses on a non-WB test that encourages non-functional muscle contractions is really not that relevant.
Re: Muscle strength and posterior tibial tendon dysfunction
Effect of eccentric exercise program for early tibialis posterior tendinopathy.
Kulig K, Lederhaus ES, Reischl S, Arya S, Bashford G. Foot Ankle Int. 2009 Sep;30(9):877-85.
Quote:
BACKGROUND: Morphology and vascularization of painful tibialis posterior (TP) tendons before and after an intervention targeting the degenerated tendon were examined. Functional status and pain level were also assessed.
MATERIALS AND METHODS: A10-week twice daily, progressive eccentric tendon loading, calf stretching program with orthoses was implemented with ten, early stage TP tendinopathy subjects. TP tendons were imaged by grayscale and Doppler ultrasound at INITIAL and POST evaluations to assess the tendon's morphology and signs of neovascularization. The Foot Functional Index (FFI), Physical Activity Scale (PAS), 5-Minute Walk Test, and single heel raise (SHR) test were completed at INITIAL and POST evaluations. The Global Rating Scale (GRS) was completed at 6 months followup. One-way ANOVA was used to compare the FFI at INITIAL, POST, and 6-MONTH time points. Paired t-tests were used to compare means between the remaining variables. The level of significance was p = 0.05.
RESULTS: There was a significant difference in FFI total, pain, and disability at the three time-points. Post-hoc paired t-tests revealed that the FFI scores were lower for the total score and pain and disability subcategories when comparing from INITIAL to POST and INITIAL to 6-MONTH evaluations (p < 0.05 for all). The number of SHR increased significantly on the involved side from INITIAL to POST evaluation (p = 0.041). The GRS demonstrated minimum clinically important differences for improvements in symptoms at 6-MONTH. Tendon morphology and vascularization remained abnormal following the intervention.
CONCLUSION: A 10-week tendon specific eccentric program resulted in improvements in symptoms and function without changes in tendon morphology or neovascularization.
Re: Muscle strength and posterior tibial tendon dysfunction
Deep Posterior Compartment Strength and Foot Kinematics in Subjects With Stage II Posterior Tibial Tendon Dysfunction.
Neville C, Flemister AS, Houck JR. Foot Ankle Int. 2010 Apr;31(4):320-8.
Quote:
BACKGROUND: Tibialis posterior muscle weakness has been documented in subjects with Stage II posterior tibial tendon dysfunction (PTTD) but the effect of weakness on foot structure remains unclear. The association between strength and flatfoot kinematics may guide treatment such as the use of strengthening programs targeting the tibialis posterior muscle.
MATERIALS AND METHODS: Thirty Stage II PTTD subjects (age; 58.1 +/- 10.5 years, BMI 30.6 +/- 5.4) and 15 matched controls (age; 56.5 +/- 7.7 years, BMI 30.6 +/- 3.6) volunteered for this study. Deep Posterior Compartment strength was measured from both legs of each subject and the strength ratio was used to compare each subject's involved side to their uninvolved side. A 20% deficit was defined, a priori, to define two groups of subjects with PTTD. The strength ratio for each group averaged; 1.06 +/- 0.1 (range 0.87 to 1.36) for controls, 1.06 +/- 0.1 (range, 0.89 to 1.25), for the PTTD strong group, and 0.64 +/- 0.2 (range 0.42 to 0.76) for the PTTD weak group. Across four phases of stance, kinematic measures of flatfoot were compared between the three groups using a two-way mixed effect ANOVA model repeated for each kinematic variable.
RESULTS: Subjects with PTTD regardless of group demonstrated significantly greater hindfoot eversion compared to controls. Subjects with PTTD who were weak demonstrated greater hindfoot eversion compared to subjects with PTTD who were strong. For forefoot abduction and MLA angles the differences between groups depended on the phase of stance with significant differences between each group observed at the pre-swing phase of stance.
CONCLUSION: Strength was associated with the degree of flatfoot deformity observed during walking, however, flatfoot deformity may also occur without strength deficits.
CLINICAL RELEVANCE: Strengthening programs may only partially correct flatfoot kinematics while other clinical interventions such as bracing or surgery may also be indicated.
Re: Muscle strength and posterior tibial tendon dysfunction
Modified strength testing protocol for use in subjects with posterior tibial tendon dysfunction
Cady, J., Noffey, J., Neville, C. Abstract
Quote:
Purpose:
To examine the reliability of a modified ankle and hip isometric and isokinetic strength testing protocol using a isokinetic testing unit. The modified protocol was designed to be used in an ongoing clinical trial of patients with Posterior Tibial Tendon Dysfunction (PTTD) who are typically older (50-80years), overweight (BMI ~ 30), and experiencing pain.
Methods:
Seven healthy subjects were recruited to perform hip flexion, extension, abduction, and adduction in modified standing positions. Additionally, ankle plantar flexion and dorsiflexion was tested. All motions were performed isometrically and isokinetically to be analyzed for their level of test-re-test agreement.
Results:
Intraclass correlation coefficients and standard error of the measurement (SEM) for a select data set were used as cut-off points to describe pilot data from 10 subjects with PTTD and are included in Table 1.
Reliability (test, re-test) of selected lower extremity muscle groups. All isometric data are tested in the neutral position while isokinetic data are tested at 60 degrees per second. ICC Model (3,1). PF – plantar flexion.
Conclusion:
Test-re-test reliability was good to excellent and used to interpret the clinical trial data. Preliminary findings suggest that an increase in muscle strength, that exceeded the SEM reliability values, were associated with improved self reported function (Foot Function Index-Revised) in subjects who wore a jointed ankle brace.
Muscle strength and posterior tibial tendon dysfunction
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