Subtalar Joint Axis Research Articles

Clinical determination of the linear equation for the subtalar joint axis.

The authors present a methodology to measure the frontal plane angular and linear displacement and the transverse plane angular displacement of subtalar joint movement. This method is combined with a modification of the Kirby method for determining the transverse plane projection of the subtalar joint axis onto the plantar foot. A mathematical model is then used to construct the subtalar joint axis into a three-dimensional linear equation. Data are obtained from an in vivo series of 62 feet that indicates that within acceptable clinical errors of measurement the subtalar joint is a ginglymus type of joint that moves around a single fixed axis. Results also indicate that the subtalar joint axis is more superior and lateral to the neutral foot than any previous studies on cadaver feet have shown. Finally, the authors show that once the subtalar joint axis can be accurately located, the torque on the joint axis produced by ground reactive forces and muscular forces can be computed.

Rotational equilibrium across the subtalar joint axis.

A review of the rotational forces, or moments, acting across the subtalar joint axis during relaxed bipedal stance is presented. The concept of rotational equilibrium about the subtalar joint axis is used to explain some of the biomechanical differences between feet that stand in the neutral and maximally pronated subtalar joint positions. In addition, the mechanical basis of treatment of sinus tarsi syndrome with foot orthoses using the concepts of subtalar joint axis moments rotational equilibrium of the subtalar joint is presented.

Methods for determination of positional variations in the subtalar joint axis.

Methods for determination of positional variations in the subtalar joint axis.

Variations in the Human Subtalar Joint

Clinical observations reveal that high-arched cavus feet are rigid while low-arched planus feet are hypermobile. One reason may be osseous variations in the human subtalar joint (STJ). This article reviews STJ anatomy, biomechanics, and pathomechanics and describes STJ variations found in 32 adult human calcanei. In the sample, 20 bones had two STJ facets and 12 bones had three STJ facets. A oneway Student t-test showed that the bones with two STJ facets had significantly greater (t = 2.23) facet surface area than the bones with three STJ facets. A second finding concerned three sagittal plane approximations of arch height and STJ axis angle. Calcanei with two STJ facets had significantly lower angles (tA = -1.99, tB = -1.82, and tC = -2.18) than three STJ facet calcanei. To the extent that osseous factors represent joint range of motion, this study shows that STJ facet number is a factor in foot mobility. J Orthop Sports Phy Ther 1987;8(10):489-494.

Use of trichlorethylene inhalations during physiotherapy.

<h3>Background</h3> There are many possible predisposing factors for Achilles tendon disorders suggested in the literature but their pathogenetic relevance is not proven in most cases. The asymmetric mechanical load distribution within the Achilles tendon during locomotion is frequently addressed as a major risk factor for Achilles tendon disorders. The spatial orientation of the subtalar joint axis (STA) may influence the Achilles tendon loading possibly leading to overload injuries. <h3>Hypothesis</h3> There is a significant difference between the orientation of the STA in subjects with and without Achilles tendon pathologies. <h3>Materials and methods</h3> 614 subtalar joint axes determined in 307 long-distance runners with and without Achilles tendon disorders were included. Achilles tendon disorders were defined as any Achilles tendon–related pain during or following running, existing for more than 2 weeks in the past. Motion analysis of the foot was performed using an ultrasonic pulse-echo-based measurement system. The orientation of the STA was expressed by two angles. <h3>Results</h3> The mean inclination angle was 42±16° and the mean deviation angle was 11±23°. There was a significant difference (p=0.002) between the mean deviation angle measured in subjects with Achilles tendon pathologies (18±23°) and those without (10±23°). <h3>Conclusions</h3> The results demonstrate a wide interindividual variability of the spatial orientation of the STA. In addition, the mean deviation angle in people with Achilles tendon pathologies is significantly more oblique than in people without. This finding indicates that the spatial orientation of the STA is related to the incidence of overuse injuries of the Achilles tendon in the investigated sample.