A noninvasive method of assessing the motion of the subtalar joint was developed for use in clinical and research settings. Anatomical reference frames for the calcaneus and talus were produced using a marker placement model utilizing 14 markers. An asymptomatic individual was tested during barefoot walking with a CODA MPX30 system. Intertrial variability and motion patterns, in all three planes, of the calcaneus with respect to the talus were analyzed as part of a validation study. The observed patterns in all three planes were found to have good face validity with published literature as well as good consistency during stance. The findings of this study support the further use of this model in both clinical and research settings, allowing investigation of the motion patterns of a larger cohort than has hitherto been possible.
The considerable variation in subtalar joint structure and function shown by studies indicates the importance of developing a noninvasive in vivo technique for assessing subtalar joint movement. This article reports the in vitro testing of the CODA MPX30, an active infrared marker motion analysis system. This work represents the first stage in the development of a noninvasive in vivo method for measuring subtalar joint motion during walking.
The in vitro repeatability of the CODA MPX30 system’s measurements of marker position, simple and intermarker set angles, was tested. Angular orientations of markers representing the position of the talus and the calcaneus were measured using a purpose-designed marker placement model.
Marker location measurements were shown to vary by less than 1.0 mm in all of the planes. The measurement of a 90° angle was also found to be repeatable in all of the planes, although measurements made in the yz plane were shown to be consistently inaccurate (mean, 92.47°). Estimation of segmental orientation was found to be repeatable. Estimations of marker set orientations were shown to increase in variability after a coordinate transform was performed (maximum SD, 1.14°).
The CODA MPX30 was shown to produce repeatable estimations of marker position. Levels of variation in segmental orientation estimates were shown to increase subsequent to coordinate transforms. The combination of the CODA MPX30 and an appropriate marker placement model offers the basis of an in vivo measurement strategy of subtalar joint movement, an important development in the understanding of the function of the joint during gait. (J Am Podiatr Med Assoc 101(5): 400–406, 2011)
Quantifying subtalar joint kinematics during locomotion is a major challenge but is critical to understanding foot function. The difficulty of modeling the subtalar joint is demonstrated by the plethora of three-dimensional multisegment foot models lacking specific consideration of the subtalar joint. Scientific attempts to develop an adequate method of quantifying subtalar joint kinematics should include investigation of the movement of skin-mounted markers. This study reports on a single-subject investigation into this topic.
Radiopaque markers were attached to the skin overlying the medial and lateral malleoli and the medial and lateral talar heads of a single subject. Frontal, sagittal, and transverse plane radiographs were taken with the foot in the fully pronated and fully supinated positions. Parallax corrected measurements were taken of the displacement of the markers from the bony landmarks. Measurements were also taken of the effect of these displacements on angular calculations.
Skin movement at the four anatomical locations was not uniform, with displacements varying from 0.61 to 22.18 mm. Movement of the malleolar markers was found to be less than that of the talar head markers. The distortion of angular measurements caused by movement of the skin markers relative to the bony landmarks was found to be only 1° in the sagittal and transverse planes and 5° in the frontal plane.
For this subject, skin-mounted markers could be used to assess subtalar joint motion. Further studies are necessary to investigate the implications of these findings to the wider population. (J Am Podiatr Med Assoc 101(6): 497–504, 2011)
The subtalar joint allows complex motion of the foot relative to the leg, the analysis of which has presented a major challenge for researchers. The considerable interpatient variation in structure and function of the subtalar joint highlights the importance of developing a protocol to assess the kinematics in individuals rather than developing an overarching description of function. The use of skin-mounted markers is, therefore, preferable, allowing the noninvasive collection of data. We sought to assess the face validity of a skin-mounted marker–based protocol to measure the in vivo kinematics of the subtalar joint.
Thirty participants were recruited using minimal exclusion criteria. A previously tested skin-mounted marker placement protocol was used in conjunction with two CODA MPX 30 sensors to capture data during walking. The data produced were compared with those from previous studies that used bone-mounted markers.
The results in all three planes represented feasible outcomes compared with those of previous studies, the data falling within the ranges published. Patterns of movement demonstrated are similar to, although not the same as, those shown by previous investigations.
This study did not produce patterns of movement that exactly matched those of previous investigations. The results were, however, within the ranges previously published, and the patterns of movement shown were feasible. The results suggest the face validity of the method as a means of assessing the in vivo kinematics of the subtalar joint during the stance phase of gait.
The determination of anatomical reference frames in the rearfoot during three-dimensional multisegment foot modeling has been hindered by a variety of factors. One of these factors is related to the difficulty in palpating, or the absence of, anatomical landmarks. A novel device (the Calcaneal Marker Device) aimed at standardizing marker placement at the calcaneus was, therefore, developed and evaluated for its reliability.
Throughout a random repeated-measures design, the repeatability of calcaneal marker placement was evaluated for two techniques: manual placement and placement using the Calcaneal Marker Device. Translational changes after marker placement and the clinical effect on intersegment angle calculation were quantified.
Intraobserver variability was greater in therapist 2 (<5.3 mm) compared with therapist 1 (<2.9 mm). Intraobserver variability was also found to be less than 1.6 mm throughout use of the device. Interobserver variability was found to be significantly higher for the position of markers placed manually (5.8 mm), whereas with the Calcaneal Marker Device, the variability remained lower (<1.3 mm). The effect on the computed intersegment angles followed a similar trend, with variability of 0.4° to 4.0° and 1.0° to 8.7° for CMD and manual placement, respectively.
These findings suggest that variations in marker placement are considerably reduced when the novel Calcaneal Marker Device is used, possibly toward the limits dictated by the fine motor skills of therapists and tissue artifacts.
Clinical and cadaver studies have reported that supernumerary muscles could be the etiology of a variety of pathologic disorders, such as posterior impingement syndrome, tarsal tunnel syndrome (TTS), and flexor hallucis longus tenosynovitis. We describe a unique variant of the flexor digitorum accessorius longus (FDAL) muscle as an apparent cause of TTS, functioning as an independent flexor of the second toe, which has not been described in the literature. In addition to this case report, a systematic review was performed of TTS caused by the FDAL muscle.
A targeted search of PubMed, the Cochrane Library, the Cumulative Index to Nursing and Allied Health Literature, and Web of Science identified full-text papers that fulfilled the inclusion and exclusion criteria.
Twenty-nine papers were identified for inclusion in the systematic review: 12 clinical papers of TTS caused by the FDAL muscle and 17 cadaver-based papers.
Clinicians often do not include the FDAL muscle in the differential diagnosis of TTS. This literature review suggests that the FDAL is an important muscle in terms of its functional and clinical significance. Knowledge of this muscle, its anatomical location and variations, and its magnetic resonance imaging characteristics may help clinicians make an accurate differential diagnosis.