Changes in Achilles tendon moment arm from rest to maximum isometric plantarflexion:in vivoobservations in man

Category: Ankle; Ankle Arthritis Introduction/Purpose: Deficits in ankle joint kinetics following total ankle arthroplasty (TAA) may be attributed to a reduction in the force-generating capacity of ankle joint muscles, but it is also important to consider the alterations to joint structure that may accompany this procedure. One key parameter indicative of joint structure with the potential to be influenced by TAA is the plantarflexion moment arm of the Achilles tendon (ATma). ATma is an indicator of the potential for the tendon force to produce plantarflexion moment that is determined by the three-dimensional line of action of the tendon relative to the ankle joint axis. The purpose of this study was to assess pre-to-post TAA changes in ATma; we hypothesized that pre- and post-TAA moment arms would not be different. Methods: We tested 10 TAA patients (age at surgery: 62.86 +- 9.72 y; height: 1.72 +- 0.08 m; body mass: 97.81 +- 20.89 kg) at pre-operative (˜ 1 mo pre) and post-operative (˜6 mo post) visits. All procedures involving testing of human subjects were approved by the Penn State Hershey Medical Center Institutional Review Board. ATma were measured using a method that combined ultrasound imaging of the tendon with 3D motion tracking of both the ultrasound probe and the ankle joint. The tendon and joint axis were located during trials in which the patients were seated with the knee extended while the ankle joint was voluntarily rotated in the sagittal plane. We also examined sagittal-plane weightbearing radiographs (pre- and post-op) to determine the AP distance from the center of the talar dome to the posterior margin of the calcaneus. Pre- and post-op ATma were compared using a paired t-test and regression. Results: No significant mean differences were found between post-op ATma and pre-op ATma (p = 0.360). Despite this, some patients were found to have large differences between pre- and postoperative ATma. For example, participants 1, 3, and 8 exhibited changes of -54.22%, +64.14% and +123.98% (pre-to-post) respectively (Figure 1). A moderate correlation between pre- and post-op ATma was found (r2 = 0.461, p = 0.031), indicating that only 46.1% of the variance in post-op ATma was explained by pre-op ATma (Figure 1). The normalized AP distance measured from the radiographs did not significantly change on average pre- to post-TAA (p = 0.561), and we found the change in this distance to correlate with the change in ATma (r2 = 0.370, p = 0.062). Conclusion: This is the first investigation of whether TAA alters ATma. Our results supported our hypothesis that pre-operative ATma predicts post-operative ATma. However, our hypothesis is supported only when the mean differences are considered, as there were sizeable differences for individuals. Despite a non-significant average change in ATma following TAA, at the individual level substantial changes in ATma were observed in seven of the 10 patients. Change in ATma was only partly explained by change in the AP position of the talar dome. Change in ATma has potential consequences for function in terms of ankle plantarflexor strength and walking velocity.

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Letter to the editor regarding: Effects of cerebral palsy on Achilles tendon moment arm length – Do children with CP have larger or smaller moment arms than typically developing children? Commentary on: Alexander et al.

Journal of Biomechanics ◽

10.1016/j.jbiomech.2019.03.039 ◽

2019 ◽

Vol 92 ◽

pp. 175-177

Author(s):

B.M. Kalkman ◽

C.N. Maganaris ◽

L. Bar-On ◽

T.D. O'Brien

Keyword(s):

Cerebral Palsy ◽

Achilles Tendon ◽

Typically Developing ◽

Moment Arm ◽

Typically Developing Children ◽

Moment Arms ◽

Letter To The Editor

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In vivo physiological cross-sectional area and specific force are reduced in the gastrocnemius of elderly men

Journal of Applied Physiology ◽

10.1152/japplphysiol.01186.2004 ◽

2005 ◽

Vol 99 (3) ◽

pp. 1050-1055 ◽

Cited By ~ 138

Author(s):

Christopher I. Morse ◽

Jeanette M. Thom ◽

Neil D. Reeves ◽

Karen M. Birch ◽

Marco V. Narici

Keyword(s):

Achilles Tendon ◽

Voluntary Contraction ◽

Pennation Angle ◽

Specific Force ◽

Plantar Flexor ◽

Moment Arm ◽

Plantar Flexors ◽

Elderly Men ◽

Cross Sectional

Sarcopenia and muscle weakness are well-known consequences of aging. The aim of the present study was to ascertain whether a decrease in fascicle force (Ff) could be accounted for entirely by muscle atrophy. In vivo physiological cross-sectional area (PCSA) and specific force (Ff/PCSA) of the lateral head of the gastrocnemius (GL) muscle were assessed in a group of elderly men [EM, aged 73.8 yr (SD 3.5), height 173.4 cm (SD 4.4), weight 78.4 kg (SD 8.3); means (SD)] and for comparison in a group of young men [YM, aged 25.3 yr (SD 4.4), height 176.4 cm (SD 7.7), weight 79.1 kg (SD 11.9)]. GL muscle volume (Vol) and Achilles tendon moment arm length were evaluated using magnetic resonance imaging. Pennation angle and fiber fascicle length (Lf) were measured using B-mode ultrasonography during isometric maximum voluntary contraction of the plantar flexors. PCSA was estimated as Vol/Lf. GL Ff was calculated by dividing Achilles tendon force by the cosine of θ, during the interpolation of a supramaximal doublet, and accounting for antagonist activation level (assessed using EMG), Achilles tendon moment arm length, and the relative PCSA of the GL within the plantar flexor group. Voluntary activation of the plantar flexors was lower in the EM than in the YM (86 vs. 98%, respectively, P < 0.05). Compared with the YM, plantar flexor maximal voluntary contraction torque and Ff of the EM were lower by 47 and 40%, respectively ( P < 0.01). Both Vol and PCSA were smaller in the EM by 28% ( P < 0.01) and 16% ( P < 0.05), respectively. Also, pennation angle was 12% smaller in the EM, whereas there was no significant difference in Lf between the YM and EM. After accounting for differences in agonists and antagonists activation, the Ff/PCSA of the EM was 30% lower than that of the YM ( P < 0.01). These findings demonstrate that the loss of muscle strength with aging may be explained not only by a reduction in voluntary drive to the muscle, but mostly by a decrease in intrinsic muscle force. This phenomenon may possibly be due to a reduction in single-fiber specific tension.

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Achilles Tendon Moment Arms Computed Using Ultrasound and Motion Analysis: In Vivo Estimates for Male Subjects

ASME 2008 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2008-193155 ◽

2008 ◽

Author(s):

Justin D. Cowder ◽

Thomas S. Buchanan ◽

Kurt T. Manal

Keyword(s):

Achilles Tendon ◽

Motion Capture ◽

Hybrid Method ◽

Lower Limb ◽

Muscle Force ◽

Average Weight ◽

Moment Arm ◽

Moment Arms ◽

Male Subjects

Accurate estimates for Achilles tendon moment arm (MA) are essential when computing gastroc-soleus force from the net plantarflexion moment. Errors in approximating the Achilles tendon MA will adversely affect the muscle force estimate. We have noted that Achilles tendon MAs reported by Maganaris [1] and others are significantly greater (> 1 cm) than values used by Delp et al. computed using SIMM [2]. It is important to note that the stature of Delp’s lower limb model was almost identical to the average weight and height of the subjects in a study by Maganaris. This led us to question which MA profiles were more anatomically meaningful. To address this, we calculated Achilles tendon MAs for 10 male subjects using a previously described method. The method combines ultrasound and video-based motion capture, and referred to as the hybrid method. Subjects in our study were chosen to ensure they were of a similar stature to those tested by Maganaris, thereby minimizing confounding effects of subject anthropometrics.

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Effects of Achilles Tendon Moment Arm Length on Insertional Achilles Tendinopathy

Applied Sciences ◽

10.3390/app10196631 ◽

2020 ◽

Vol 10 (19) ◽

pp. 6631

Author(s):

Takuma Miyamoto ◽

Yasushi Shinohara ◽

Tomohiro Matsui ◽

Hiroaki Kurokawa ◽

Akira Taniguchi ◽

...

Keyword(s):

Achilles Tendon ◽

Achilles Tendinopathy ◽

Control Group ◽

Moment Arm ◽

Healthy Individuals ◽

Suture Bridge ◽

Significant Difference ◽

The Moment ◽

Insertional Achilles Tendinopathy ◽

Suture Bridge Technique

Insertional Achilles tendinopathy (IAT) is caused by traction force of the tendon. The effectiveness of the suture bridge technique in correcting it is unknown. We examined the moment arm in patients with IAT before and after surgery using the suture bridge technique, in comparison to that of healthy individuals. We hypothesized that the suture bridge method influences the moment arm length. An IAT group comprising 10 feet belonging to 8 patients requiring surgical treatment for IAT were followed up postoperatively and compared with a control group comprising 15 feet of 15 healthy individuals with no ankle complaints or history of trauma or surgery. The ratio of the moment arm (MA) length/foot length was found to be statistically significant between the control group, the IAT group preoperatively and the IAT group postoperatively (p < 0.01). Despite no significant difference in the force between the control and preoperative IAT groups, a significantly higher force to the Achilles tendon was observed in the IAT group postoperatively compared to the other groups (p < 0.05). This study demonstrates that a long moment arm may be one of the causes of IAT, and the suture bridge technique may reduce the Achilles tendon moment arm.

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The effect of foot type on the Achilles tendon moment arm and biomechanics

The Foot ◽

10.1016/j.foot.2018.10.003 ◽

2019 ◽

Vol 38 ◽

pp. 91-94 ◽

Cited By ~ 1

Author(s):

Manja Deforth ◽

Lukas Zwicky ◽

Tamara Horn ◽

Beat Hintermann

Keyword(s):

Achilles Tendon ◽

Moment Arm

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Considerations on the human Achilles tendon moment arm for in vivo triceps surae muscle–tendon unit force estimates

Scientific Reports ◽

10.1038/s41598-020-76625-x ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Denis Holzer ◽

Florian Kurt Paternoster ◽

Daniel Hahn ◽

Tobias Siebert ◽

Wolfgang Seiberl

Keyword(s):

Achilles Tendon ◽

Triceps Surae ◽

Muscle Forces ◽

Moment Arm ◽

Unit Force ◽

Plateau Region ◽

Triceps Muscle ◽

Triceps Surae Muscle ◽

The Individual

Abstract Moment arm-angle functions (MA-a-functions) are commonly used to estimate in vivo muscle forces in humans. However, different MA-a-functions might not only influence the magnitude of the estimated muscle forces but also change the shape of the muscle’s estimated force-angle relationship (F-a-r). Therefore, we investigated the influence of different literature based Achilles tendon MA-a-functions on the triceps surae muscle–tendon unit F-a-r. The individual in vivo triceps torque–angle relationship was determined in 14 participants performing maximum voluntary fixed-end plantarflexion contractions from 18.3° ± 3.2° plantarflexion to 24.2° ± 5.1° dorsiflexion on a dynamometer. The resulting F-a-r were calculated using 15 literature-based in vivo Achilles tendon MA-a-functions. MA-a-functions affected the F-a-r shape and magnitude of estimated peak active triceps muscle–tendon unit force. Depending on the MA-a-function used, the triceps was solely operating on the ascending limb (n = 2), on the ascending limb and plateau region (n = 12), or on the ascending limb, plateau region and descending limb of the F-a-r (n = 1). According to our findings, the estimated triceps muscle–tendon unit forces and the shape of the F-a-r are highly dependent on the MA-a-function used. As these functions are affected by many variables, we recommend using individual Achilles tendon MA-a-functions, ideally accounting for contraction intensity-related changes in moment arm magnitude.

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In vivo measurement-based estimations of the human Achilles tendon moment arm

European Journal of Applied Physiology ◽

10.1007/s004210000247 ◽

2000 ◽

Vol 83 (4-5) ◽

pp. 363-369 ◽

Cited By ~ 75

Author(s):

Constantinos N. Maganaris ◽

Vasilios Baltzopoulos ◽

Anthony J. Sargeant

Keyword(s):

Achilles Tendon ◽

Moment Arm ◽

In Vivo Measurement

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