Anatomy of the ilium for bone marrow aspiration: map of sectors and implication for safe trocar placement

Abstract

Purpose: The bony anatomy of the human ilium has been well described from a qualitative perspective; however, there are little quantitative data to help the surgeon to perform bone marrow aspiration from the iliac crest in the thickest part of the ilium. The minimum thickness of the spongiousus bone in an iliac wing (transverse thickness between the two tables) is an important factor in ensuring the safe placement of a trocar between the two tables of the iliac wing. For example, with an 8-gauge (3.26 mm) trocar, one can consider that if the transverse thickness of the spongiousus bone of the iliac wing is <3 mm, it will be difficult to insert the trocar safely between the two tables.

Methods: For this study, we measured spongiousus bone thickness on 48 iliac wings to map the ilium in six sectors, which were defined by drawing lines from equidistant points spaced along the rim of the iliac crest to the centre of the hip. These sectors can be transposed in the same manner to any patient. To evaluate the risks to reach vascular or neurologic structures, 410 trocars were introduced in the different sectors of 20 iliac bones of ten cadavers.

Results: A map was constructed indicating the thickness of the spongiousus bone in each sector. The thickness data was used to create a map that identifies the sites where bone marrow can be obtained with a trocar of 3-mm diameter according to the thickness of the spongiousus bone. Sectors 2, 3 and 6 appear to be more favourable for accommodating a 3-mm diameter trocar. Sectors 1, 4 and 5 comprise the areas with the thinnest parts of the iliac crest, with some areas being thinner than the trocar diameter. The sector system reliably predicted safe and unsafe areas for trocar placement. In cadavers, dissection demonstrated nine vascular or neurologic lesions created when trocars were introduced into sectors 1, 5 and 6.

Conclusion: Using the sector system, trocars can be directed away from neural and vascular structures and towards zones that are likely to contain larger bone marrow stock.