TECHNICAL TRICK The Subcristal Pelvic External Fixator: Technique, Results, and Rationale Lucian B. Solomon, MD, PhD, FRACS, Anthony P. Pohl, MD, MB BCh, FRACS, Atul Sukthankar, MD, and Mellick J. Chehade, MBBS, PhD, FRACS Summary: We report a new technique for pelvic external fixation that we have developed as an alternative to the anterosuperior (Sla ¨tis) and the anteroinferior (supra-acetabular) type pelvic external fixator configurations. The method principally differs from the other techniques by virtue of the subcristal positioning of the pins and offers advantages in terms of easier pin placement, less skin irritation, less pin tract infection and loosening, and less interference with hip flexion, while allowing dressing, sitting, and walking. Between 1992 and 2006, we successfully used subcristal pelvic external fixators as the definitive fixation device for 20 patients with pelvic ring disruptions. The only complications encountered were superficial pin tract infections in 4 patients (20%) who were successfully treated with wound care and antibiotics. Key Words: pelvic ring, injury, external fixation (J Orthop Trauma 2009;23:365–369) INTRODUCTION Pelvic external fixators can be built in different grades of complexity starting from 3 basic frames (Fig. 1): (a) anterosuperior, 1,2 with pins inserted perpendicular to the iliac crest in a superior to inferior direction (as in the Sla ¨tis frame 3 ); (b) anteroinferior, 1,2 with supra-acetabular pins inserted in an anterior to posterior direction 4 ; and (c) subcristal, 2 with pins inserted from the anterior superior iliac spine (ASIS) in the subcortical bone of the iliac crest and parallel with the crest. External fixation of the pelvis is one of the few pelvic operations occasionally performed by surgeons who do not specialize in acetabular and pelvic ring fixations. The superficial location of the iliac crest can easily mislead the less-experienced surgeon who is attempting to use the anterosuperior configuration to control the pelvic volume in emergency situations, such that the pins are incorrectly placed. In our clinical practice, we have observed this predominantly for patients who have had their initial assessment and treatment at peripheral health care centers. Others authors have also acknowledged this problem. 5 Most complications associated with pelvic external fixators are related to the failure to correctly place the pin between the inner and outer tables of the ilium, interference of the pins with anatomic structures located between skin and the bone entry point, or injury at sites where bone penetration occurs. After being faced with the complications and/or incon- venience to the patients associated with the use of pelvic external fixators built on anterosuperior and anteroinferior pin placement, we carefully analyzed the human pelvis anatomy and concluded that pin placement subcortical to the anterior one fourth to one third of the iliac crest from the ASIS provided us with the best possible approach. We report on 20 patients where we used subcristal positioning of pins to provide pelvic ring fixation (Figs. 2, 3). OPERATIVE TECHNIQUE The patient is positioned supine on the operating table. The ASIS and the anterior aspect of the iliac crest’s contour are marked on the skin. A skin incision of approximately 2 cm is made in line with the iliac crest starting at the ASIS down toward the subinguinal region (Fig. 4). Blunt dissection is used to expose the anterior aspect of the ASIS superficial to the insertion of the inguinal ligament. A trocar–cannula set (trochar/drill sleeve/pin sleeve) is rolled mediolaterally and superoinferiorly over the ASIS to define the entry point. Because of the overhang of the iliac crest, the entry point lies medial to the center of the palpable ASIS and allows place- ment of the threaded pin just lateral to the inner cortex of the ilium. After defining the entry point, the trocar is removed with one hand, whereas the other hand stabilizes the drill sleeve. The external cortex is opened with a 4.0-mm drill orientated parallel with the superior aspect of the iliac crest toward the iliac tuberosity (IT), whereas the contralateral hand guides the direction by palpating the iliac crest between the thumb and index fingers. While maintaining the pin sleeve in place, the drill is removed and a 5-mm threaded pin (150–180 mm in length) is inserted until all the threads of the pin are intra- osseous. The pin is directed toward the IT between the 2 cortices of the iliac crest. This is done at a low speed with the power drill in the screw mode so that the blunt pin finds its way between the 2 iliac cortices, without perforating them, before the change in direction of the iliac crest that occurs at the IT. The position of the pin can be checked with an image intensifier (Fig. 5) and then the procedure is repeated on the Accepted for publication February 24, 2009. From the Department of Orthopaedics, Royal Adelaide Hospital and University of Adelaide, Adelaide, Australia. The authors did not receive grants or outside funding in support of their research or preparation of this manuscript. Reprints: Lucian B. Solomon, MD, PhD, FRACS, Department of Orthopaedics, Royal Adelaide Hospital and University of Adelaide, Level 4 Bice Bldg, RAH, North Terrace, Adelaide, SA 5000, Australia (e-mail: bogdansolomon@mac.com). Copyright Ó 2009 by Lippincott Williams & Wilkins J Orthop Trauma  Volume 23, Number 5, May/June 2009 www.jorthotrauma.com | 365