Sustentaculum tali in Chinese population: anatomy and clinical significance.

BACKGROUND: Previous studies lacked adequate quantitative data on sustentaculum tali (ST), especially in Chinese population. The aims of this study are to explore the quantitative morphology of ST in dried bone specimens, and to discuss its implications related to ST screw fixation, talar articular facet variation, as well as subtalar coalitions. METHODS: A total of 965 dried intact calcanei from Chinese adult donors were evaluated. All linear parameters were measured by two observers with a digital sliding vernier caliper. RESULTS: Most parts of ST body can accommodate a commonly-used 4-mm-diameter screw, but the minimum height of anterior ST is only 4.02 mm. The shapes of the STs are slightly affected by left-right, subtalar facet, but the subtalar coalition may potentially increase the sizes of STs. The incidence of tarsal coalition is 14.09%. Among the osseous connection, there are 58.8% of type A articular surface and 76.5% of middle and posterior talar facet (MTF and PTF) involvement. ROC curve shows that subtalar coalition will be detected when ST length is greater than 16.815 mm. CONCLUSIONS: Theoretically, all the STs can accommodate 4 mm diameter screw, but a 3.5 mm diameter screw is recommended to be placed in the middle or posterior of the small ST for safety. The shapes of the STs are greatly influenced by the subtalar coalition, while they are less affected by left-right, subtalar facet. The osseous connection is common in type A articular surface and always involved in the MTF and PTF. The cut-off value of the length of STs was confirmed as 16.815 mm for predicting subtalar coalition.

Anatomical parameters of sustentaculum Tali screw placement in the Asian population: A retrospective radio-anatomical study.

Purpose: This study aimed to determine the anatomical parameters of successful Sustentaculum Tali (ST) screw placement in the Asian population. Method: CT scans of unilateral feet of 110 participants were reviewed, retrospectively. The 3 D reconstruction of the calcaneus and morphometric measurements were performed by Mimics Research 19.0 and 3-Matic Research 11.0. Finally, six cadaveric feet were used for verification of the accuracy of the measurements. Results: We discovered a method to help place ST screw successfully: (1) The entry point located at the middle section of the lateral wall of posterior talar articular surface (PTAS), and the perpendicular distance from the entry point to the lateral edge of PTAS (PDEL) was 10.78 mm, (2) Screw was perpendicular to the z-axis, 66.98° to the y-axis (the longitudinal axis of the foot), (3) The length of the ST screw should be approximately 44.74 mm in male and 41.14 mm in female, and (4) The diameter of the ST screw should be approximately 4.0 mm in male and 3.5 mm in female. With this new method, all screws in six cadaveric feet were placed successfully into the middle of ST. Conclusions: In this study, we discovered a general approach to safely place ST screws in the Asian population, which may potentially help surgeons improve their success rate in surgical practice.

Morphological Characteristics of the Spinous Process of Axis: Clinical Implications for Cervical Spine Manipulation.

OBJECTIVE: The purpose of this study was to evaluate the osseous variation of the axis spinous process as it may relate to palpation by clinicians. METHODS: Morphologies of the bifid spinous process in the intact dry axis of 121 Chinese adult were investigated and classified. The angular deflection of the spinous processes, the bifid spinous processes (the bifid portions of the spinous processes), and the length of the bifid spinous processes were observed and measured. RESULTS: The bifid spinous process morphologies were classified into 4 types: inverted-V shape (n = 49), inverted-U shape (n = 50), M shape (n = 18), and nonbifid spinous processes (n = 4). The direction of the spinous processes and bifid spinous processes were consistent because they depended on each other's direction of deviation. When the correlation between angular deflection of spinous processes and bifid spinous processes was analyzed, the right deviations of spinous process specimens (29 cases) showed that angular deflections of spinous processes were equal to bifid spinous processes and there was no statistically significant difference seen between them (t = 0.286, P > .05), whereas in the left deviations of spinous process specimens (49 cases), the angular deflection of spinous processes were not equal in length, but bigger than the bifid spinous processes, which was statistically significant (t = -3.079, P = .003 < .05). CONCLUSION: The anatomical structure of the spinous processes and the bifid spinous processes vary from one another, but they exhibit some regularity. In clinical spinal manipulation practice, the anatomical characteristic of the axis should be taken into account during cervical static palpation, diagnostic imaging, and treatment.