Christopher Neville

The Relationship Between Ankle, Hindfoot, and Forefoot Position and Posterior Tibial Muscle Excursion

Background: The purpose of this study was to examine the relationship of forefoot position in the transverse plane (abduction/adduction), hindfoot position in the frontal plane (eversion/inversion), and ankle position in the sagittal plane (plantarflexion/dorsiflexion) with posterior tibialis (PT) muscle excursion using an in vitro cadaver model. Methods: Seven fresh-frozen cadaver specimens were potted and mounted on a frame. The PT tendon was dissected 15 cm proximal to the medial malleolus, and a 5-kg weight was sutured to the tendon. A six-camera motion analysis system (Optotrak, Northern Digital, Inc.) was used to track three-dimensional (3D) motion of the tibia, calcaneus (hindfoot) and first metatarsal (forefoot) using bone pins. The ankle, hindfoot, and forefoot were manually placed in 24 different ankle and foot positions. A stepwise regression analysis was used to examine the relationship among ankle, hindfoot, and forefoot kinematics and PT muscle excursion. Results: Hindfoot eversion/inversion and forefoot abduction/adduction accounted for 77% of the variance in PT muscle excursion, with small contributions from ankle plantarflexion/dorsiflexion (5.7%) and forefoot plantarflexion/dorsiflexion (1.9%). A combined regression equation applied to individual specimens resulted in average errors of less than 2.5 mm. Conclusions: This study supports the hypothesis that PT muscle excursion can be estimated using specific foot and ankle kinematic variables. Further, these data suggest that hindfoot eversion and forefoot abduction account for most of the variance in PT muscle excursion and are theorized to be important to control clinically altering the length of the posterior tibial muscle.

Comparison of Changes in Posterior Tibialis Muscle Length Between Subjects With Posterior Tibial Tendon Dysfunction and Healthy Controls During Walking

STUDY DESIGN Case control study. OBJECTIVE To compare posterior tibialis (PT) length between subjects with stage II posterior tibial tendon dysfunction (PTTD) and healthy controls during the stance phase of gait. BACKGROUND The abnormal kinematics demonstrated by subjects with stage II PTTD are presumed to be associated with a lengthened PT musculotendon, but this relationship has not been fully explored. METHODS Seventeen subjects with stage II PTTD and 10 healthy controls volunteered for this study. Subject-specific foot kinematics were collected using 3-D motion analysis techniques for input into a general model of PT musculotendon length (PTLength). The kinematic inputs included hindfoot eversion/inversion (HF Ev/lnv), forefoot abduction/adduction (FF Ab/Add), forefoot plantar flexion/dorsiflexion (FF Pf/Df), and ankle plantar flexion/dorsiflexion (Ankle Pf/Df). To estimate the change in PTLength from neutral the following model was used: PTLength = 0.401(HF Ev/lnv) + 0,270(FF Ab/Add) + 0.137(FF Pf/Df) + 0.057(Ankle Pf/Df). Positive values indicated lengthening from the subtalar neutral (STN) position, while negative values indicated shortening relative to the STN position. A 2-way analysis of variance (ANOVA) model was used to compare PTLength between groups across the stance phases of walking (loading response, midstance, terminal stance, and preswing). Also, a 2-way ANOVA was used to assess the foot kinematics that contributed to alterations in PTLength. The Short Musculoskeletal Functional Assessment Index and Mobility subscale were used to compare function and mobility. RESULTS PTLength was significantly greater (lengthened) relative to the STN position in the PTTD group compared to the control group across all phases of stance, with the greatest between-group difference in PTLength occurring during preswing. The greater PTLength in subjects with PTTD compared to controls was principally attributed to significantly greater HF Ev/lnv during loading response (P = .014) and midstance (P = .015). During terminal stance and preswing, each kinematic input to estimate PTLength contributed to lengthening (main effect, P = .03 and P = .01, respectively). Subjects with PTTD with abnormally greater PTLength reported significantly lower function (P = .04) and mobility (P = .03) compared to subjects with PTTD with normal PTLength during walking. CONCLUSIONS The greater PTLength, as determined from foot kinematics, suggests that the PT musculotendon is lengthened in subjects with stage II PTTD, compared to healthy controls. The amount of lengthening is not dependent on the phase of gait; however, different foot kinematics contribute to PTLength across the stance phase. Targeting these foot kinematics may limit lengthening of the PT musculotendon. Subjects with excessive PT lengthening experience a decrease in function.

Foot Kinematics During a Bilateral Heel Rise Test in Participants With Stage II Posterior Tibial Tendon Dysfunction

STUDY DESIGN Experimental laboratory study using a cross-sectional design. OBJECTIVES To compare foot kinematics, using 3-dimensional tracking methods, during a bilateral heel rise between participants with posterior tibial tendon dysfunction (PTTD) and participants with a normal medial longitudinal arch (MLA). BACKGROUND The bilateral heel rise test is commonly used to assess patients with PTTD; however, information about foot kinematics during the test is lacking. METHODS Forty-five individuals volunteered to participate, including 30 patients diagnosed with unilateral stage II PTTD (mean +/- SD age, 59.8 +/- 11.1 years; body mass index, 29.9 +/- 4.8 kg/m2) and 15 controls (mean +/- SD age, 56.5 +/- 7.7 years; body mass index, 30.6 +/- 3.6 kg/m2). Foot kinematic data were collected during a bilateral heel rise task from the calcaneus (hindfoot), first metatarsal, and hallux, using an Optotrak motion analysis system and Motion Monitor software. A 2-way mixed-effects analysis of variance model, with normalized heel height as a covariate, was used to test for significant differences between the normal MLA and PTTD groups. RESULTS The patients in the PTTD group exhibited significantly greater ankle plantar flexion (mean difference between groups, 7.3 degrees ; 95% confidence interval [CI]: 5.1 degrees to 9.5 degrees ), greater first metatarsal dorsiflexion (mean difference between groups, 9.0 degrees ; 95% CI: 3.7 degrees to 14.4 degrees ), and less hallux dorsiflexion (mean difference, 6.7 degrees ; 95% CI: 1.7 degrees to 11.8 degrees ) compared to controls. At peak heel rise, hindfoot inversion was similar (P = .130) between the PTTD and control groups. CONCLUSION Except for hindfoot eversion/inversion, the differences in foot kinematics in participants with stage II PTTD, when compared to the control group, mainly occur as an offset, not an alteration in shape, of the kinematic patterns.

Effects of the Airlift PTTD Brace on Foot Kinematics in Subjects With Stage II Posterior Tibial Tendon Dysfunction

STUDY DESIGN Experimental laboratory study. OBJECTIVES To investigate the effect of inflation of the air bladder component of the AirLift PTTD brace on relative foot kinematics in subjects with stage II posterior tibial tendon dysfunction (PTTD). BACKGROUND Orthotic devices are commonly recommended in the conservative management of stage II PTTD to improve foot kinematics. METHODS AND MEASURES Ten female subjects with stage II PTTD walked in the laboratory wearing the AirLift PTTD brace during 3 testing conditions (air bladder inflation to 0, 4, and 7 PSI [SI equivalent: 0, 27,579, and 48,263 Pa]). Kinematics were recorded from the tibia, calcaneus (hindfoot), and first metatarsal (forefoot), using an Optotrak motion analysis system. Comparisons were made between air bladder inflation and the 0-PSI condition for each of the dependent kinematic variables (hindfoot eversion, forefoot abduction, and forefoot dorsiflexion). RESULTS Greater hindfoot inversion was observed with air bladder inflation during the second rocker (mean, 1.7 degrees; range, -0.7 degrees to 6.1 degrees). Less consistent changes in forefoot plantar flexion and forefoot adduction occurred with air bladder inflation. The greatest change toward forefoot plantar flexion was observed during the third rocker (mean, 1.4 degrees; range, -3.8 degrees to 3.9 degrees). The greatest change towards adduction was observed during the third rocker (mean, 2.3 degrees; range, -3.4 degrees to 6.5 degrees). CONCLUSIONS On average, the air bladder component of the AirLift PTTD brace was successful in reducing the amount of hindfoot eversion observed in subjects with stage II PTTD; however, the effect on forefoot motion was more variable. Some subjects tested had marked improvement in foot kinematics, while 2 subjects demonstrated negative results. Specific foot characteristics are hypothesized to explain these varied results.

The Effect of Stage II Posterior Tibial Tendon Dysfunction on Deep Compartment Muscle Strength: A New Strength Test

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.

Ankle and foot kinematics associated with stage II PTTD during stance.

Background: Subjects with stage II posterior tibial tendon dysfunction (PTTD) exhibit abnormal foot kinematics; however, how individual segment kinematics (hindfoot (HF) or first metatarsal (first MET) segments) influence global foot kinematics is unclear. The purpose of this study was to compare foot and ankle kinematics and sagittal plane HF and first MET segment kinematics between stage II PTTD and controls. Materials and Methods: Thirty patients with stage II PTTD and 15 healthy controls were evaluated. Kinematic data from the tibia, calcaneus, and first MET were collected during walking using three dimensional motion analysis techniques. A three-segment foot model (HF, calcaneus; first MET, first metatarsal, and tibia) was used to calculate relative angles (ankle, HF relative to tibia; midfoot, first MET relative to HF) and segment angles (HF and first MET relative to the global). A mixed effect ANOVA model was utilized to compare angles between groups for each variable. Results: Patients with PTTD showed greater ankle plantarflexion (p = 0.02) by 6.8 degrees to 8.4 degrees prior to or at 74% of stance; greater HF eversion (p < 0.01) across stance (mean difference = 4.5 degrees); and greater first MET dorsiflexion (p < 0.01) across stance (mean difference = 8.8 degrees). HF and first MET segment angles revealed greater HF dorsiflexion (p = 0.01) during early stance and greater first MET dorsiflexion (p = 0.001) across stance. Conclusion: Abnormal HF and first MET segment kinematics separately influence both ankle and midfoot movement during walking in subjects with stage II PTTD. Clinical Relevance: These abnormal kinematics may serve as another measure of response to clinical treatment and/or guide for clinical strategies (exercise, orthotics, and surgery) seeking to improve foot kinematics.

An Ankle-Foot Orthosis With a Lateral Extension Reduces Forefoot Abduction in Subjects With Stage II Posterior Tibial Tendon Dysfunction

STUDY DESIGN Controlled laboratory, repeated measures. BACKGROUND Posterior tibial tendon dysfunction is a common musculoskeletal problem that includes tendon degeneration and collapse of the medial arch of the foot (flatfoot deformity). Ankle-foot orthoses (AFOs) typically are used to correct flatfoot deformity. Correction of flatfoot deformity involves increasing forefoot adduction, forefoot plantar flexion, and hindfoot inversion. OBJECTIVES To test whether a foot orthosis with a lateral extension reduces forefoot abduction in patients with stage II posterior tibial tendon dysfunction while walking. METHODS The gait of 15 participants with stage II posterior tibial tendon dysfunction was evaluated under 3 conditions: a standard AFO, an AFO with a lateral extension, and a shoe-only control condition. Kinematic variables of interest were evaluated at designated time points in the gait cycle and included hindfoot inversion/eversion, forefoot plantar flexion/dorsiflexion, and forefoot abduction/adduction. A 3-by-4, repeated-measures analysis of variance (brace condition by gait phase) was used to compare variables across conditions. RESULTS The AFO with a lateral extension resulted in a significantly greater change in forefoot adduction compared to the standard AFO (2.6°, P = .02) and shoe-only conditions (4.1°, P<.01) across all phases of stance. Forefoot plantar flexion was significantly increased when comparing the standard AFO and AFO with a lateral extension to the shoe-only condition. The AFO with the lateral extension also demonstrated significantly increased hindfoot inversion during the loading response and terminal stance phases. CONCLUSION Off-the-shelf and standard AFOs have been shown to improve forefoot plantar flexion and hindfoot eversion, but not forefoot adduction. A lateral extension added to a standard AFO along the forefoot significantly improved forefoot adduction in participants with posterior tibial tendon dysfunction while walking.

Tendon Morphology in Stage II Tibialis Posterior Tendon Dysfunction Is Associated with a Clinical Measure of Deep Posterior Compartment Strength

Category: Ankle Introduction/Purpose: Tibialis Posterior Tendon Dysfunction (TPTD) is thought to be a primary cause of acquired flatfoot and a result of tendon degeneration. High-frequency ultrasound has been used to measure the morphological changes associated with tendon degeneration while clinical measures of foot deformity and strength are used to identify and stage the condition. However, limited data on tendon morphology in subjects with TPTD are available to guide clinical decision making. It was hypothesized that within a group of subjects with Stage II TPTD there would be large differences in tendon cross-sectional area and these differences would be associated with clinical measures of strength. Findings from this study could be used to guide clinical examination and refine future classification schemes. Methods: Thirty-four participants (Age x?x; Sex X Female) diagnosed with unilateral stage II TPTD were included. Measures of tendon cross-sectional area were captured at the level of the medial malleolus using a Sonosite M-Turbo ultrasound unit with a 6-MHz to 13-MHz 45-mm linear transducer (Sonosite Inc. Bothell, WA). Measures of tendon cross-sectional area were completed using ImageJ software. Subjects involved and uninvolved sides were compared for both tendon area and deep posterior compartment strength. Strength was measured using a custom strength testing device to measure plantar-flexion and inversion strength of the deep posterior compartment. All subjects completed self-report measures of function (Foot and Ankle Ability Measure (FAAM)) and self-reported pain on a numerical rating scale. Group comparisons were made with a one-way ANONA comparing groups with an alpha level maintained at 0.05. Results: Tibialis Posterior Tendon cross sectional area for the group of 34 subjects averaged 31.9% larger on the involved compared to the uninvolved side consistent with signs of degeneration. However, values ranged from 110% larger on the involved side to 43% smaller on the involved side across the group. Due to the observed variance, the group was divided into an enlarged tendon group (n=16) and an average size group (n=18). The enlarged group had an average tendon cross-sectional area of 62.6%(22.2%) larger on the involved side while the average size group averaged 2.9%(22.2%) (p<0.001). Comparing the deep posterior compartment strength between groups, the enlarged group was 34.6%(32.7%) weaker on the involved side while the average tendon area group was 11.4%(34.4%) weaker on the involved side (p=0.04). Conclusion: Tendon cross sectional area varies widely despite a classification of stage II TPTD and self-report of similar pain and function across patients. Subjects tested who had greater tendon cross-sectional area, indicating more degeneration, also demonstrate greater weakness. No differences in self-reported pain, leg strength, or function were found between groups. Deep posterior compartment weakness and tendon morphology may help to inform classification systems and predict outcomes for subjects with TPTD.

Ultrasound Assessment of the Tibialis Posterior Tendon

The patient was a 52-year-old woman with a chief complaint of left medial foot and ankle pain for the past 12 months that was of an insidious nature and on a worsening trend. High-frequency ultrasound was used to measure and assess the integrity of the tibialis posterior tendon and potentially provide further insight into the source of the symptoms. Examination of the left involved tibialis posterior tendon revealed gross abnormality with tendon enlargement, disruption in tendon structure, and fluid surrounding the tendon. The patient was subsequently diagnosed with left stage II (flexible flatfoot deformity) posterior tibial tendon dysfunction. The initial intervention included the use of an orthotic device designed, in theory, to address both the inflammatory and degenerative processes by unloading the tibialis posterior tendon and applying compression to the ankle. The goal, following a decrease in pain and acute inflammation, was to encourage tibialis posterior tendon loading through targeted progress...