Prevalence of dysmorphic sacral features in the general population.

Area of Science:

• Orthopedic Surgery
• Radiology
• Anatomy

Background:

• Posterior pelvic ring injuries are increasingly common and require internal fixation for instability.
• Sacroiliac (SI) screw placement necessitates detailed knowledge of pelvic anatomy.
• Sacral dysmorphism prevalence in the general population is not well-defined.

Purpose of the Study:

• To determine the prevalence of individual sacral dysmorphic features.
• To investigate associations between sacral dysmorphism and demographic factors.

Main Methods:

• Retrospective review of 1000 adult trauma patient pelvic CT scans.
• Identification and recording of specific sacral dysmorphic features.
• Calculation of feature prevalence and statistical analysis of demographic associations.

Main Results:

• Over 96% of subjects exhibited at least one dysmorphic feature, averaging 2.7 per person.
• Residual S1 discs (72.2%) and tongue-in-groove (TIG) SI joints (7.7%) were most and least prevalent, respectively.
• TIG SI joints were linked to more concurrent dysmorphic features and were more common in women, as were S1 discs and colinear upper sacra.

Conclusions:

• Completely normal sacral morphology is rare (<4% prevalence).
• Sacral anatomy exists on a spectrum, with dysmorphism being the norm.
• TIG SI joints may indicate higher dysmorphism, potentially complicating transiliac-transsacral screw fixation.