Morphometric Analysis of the Sacrum and its Surgical Implications

Abstract

Introduction: The predisposition of the human sacrum to a wide range of traumatic, degenerative and metastatic ailments demands frequent surgical interventions. For effective surgical management of these conditions, a comprehensive anatomical knowledge of the sacrum is mandatory but variability in morphometric dimensions exists amongst different population and precludes the standardisation of measurements. Aim: To present a morphometric reference database for sacral instrumentation in Indian population and enable comparisons with other populations. Materials and Methods: The study was performed on 108 adult human sacra. Linear measurements of the sacra were taken with the help of digital Vernier’s calliper and angular parameters were determined with a goniometer. Results: The morphometric analysis of the sacra of Indian population demonstrated that height and width of the first Anterior Sacral Foramina (ASF) were 12.97 mm and 12.23 mm respectively while height and width of the first Posterior Sacral Foramina (PSF) were 10.36 mm and 7.66 mm respectively. The height and width of the second ASF were 12.85 mm and 13.13 mm respectively but the height and width of the second PSF were 7.05 mm and 7.30 mm respectively. Further, the anterior and posterior pedicle height were observed to be 20.74 mm and 20.18 mm respectively. Anteromedial and anterolateral screw trajectory distance were noted to be 45.67 mm and 44.60 mm respectively. The S1 pedicle depth was 23.48 mm but the S1 wing depth was 44.09 mm. Furthermore, there existed a highly significant difference (p<0.001) between the angular parameters of the right and left sides. Conclusion: The height and width of the sacral foramina along with transverse distances between them were less in Indian sacra. Anterior pedicle height was observed to be greater in Indian sacra. However, posterior pedicle height was found to be lower than the values reported by other population. Additionally, the screw trajectory distances also displayed lower values in Indian population. Hence, present study signifies the application of screws of shorter length during sacral instrumentation as the morphometric dimensions are of lesser value in Indian population.

Keywords

• implants
• instrumentation
• screw trajectory angle
• screw trajectory distance