The iliac pillar - Definition of an osseous fixation pathway for internal and external fixation

Oblique anterior pelvic external fixator for intraoperative reduction of rotationally unstable pelvic ring injuries

Incomplete sacroiliac joint injuries are often associated with external rotation and extension deformities on the injured hemipelvis. To appropriately correct this deformity, an oblique reduction force from caudal to cranial and lateral to medial is helpful. These injuries are often associated with traumatic disruption of the pubic symphysis. However, in injuries without traumatic disruption to the pubic symphysis, a two-pin oblique anterior external fixator can be used to obtain and maintain reduction of the sacroiliac joint, while percutaneous fixation is subsequently placed. Through a small case series and three specific patient examples, we demonstrate that the oblique anterior external fixator frame is a simple and effective strategy with the reduction and stabilization process of these multiplanar hemipelvis deformities.

Secure paediatric pelvic fracture external fixation using an intraoperative support device

Secure fixation by inserting a half-pin into the iliac crest as a pelvic external fixator is important. However, the thickness of the iliac bone depends on its location and this makes it difficult to insert a half-pin accurately. The iliac crest is especially narrow in the paediatric pelvis, making it difficult to insert the half-pin accurately compared with an adult pelvis. A case of pelvic external fixation is described for a paediatric pelvic fracture in this report, in which preoperative planning for half-pin insertion was performed accurately using a preoperative three-dimensional CT based on an intraoperative support device that uses the functional pelvic plane as a reference.

Iliac dysmorphism: defining radiographic characteristics and association with pelvic osseous corridor size

INTRODUCTION

Insertion of iliac wing implants requires understanding of the curvilinear shape of the ilium. This study serves to quantitatively identify the area of iliac inner-outer table convergence (IOTC), characterize the iliac wing osseous corridor, and define the gluteal pillar osseous corridor.

METHODS

Computed tomography scans of 100 male and 100 female hemipelves were evaluated. The iliac wing was studied using manual best-fit analysis of the bounds of the inner and outer cortices. The IOTC was defined as the location of the iliac wing with an intercortical width less than 5 mm. The shortest distance from the apex of the iliac crest to the superior border of the IOTC was defined as the iliac wing osseous corridor. Finally, the width of the gluteal pillar corridor from the gluteus medius tubercle to the ischial tuberosity was measured.

RESULTS

The IOTC is an elliptical area measuring 22.3 cm². All ilia had an area where the inner and outer cortices converged to an intercortical width of less than 5 mm; 48% converged to a single cortex. The shortest mean distance from the superior edge of the iliac crest to the beginning of the IOTC was 20.3 mm in men and 13.8 mm in women (p < 0.001). The gluteal pillar diameter averaged 5.3 mm in men and 4.3 mm in women (p < 0.001).

DISCUSSION

All ilia converge to a thin and frequently unicortical central region. A 4.5 mm iliac wing lag screw will not breach the cortex if it remains within 20 mm or 14 mm distal to the cranial aspect of the iliac crest in males and females, respectively. Not only is the gluteal pillar smaller than previously thought, in 41% of males and 73% of females, it is not be large enough for 5 mm implants.

CONCLUSION

This study quantitatively assesses the dimensions of the IOTC, the iliac crest osseous corridor, and the gluteal pillar. Overall, our findings provide improved understanding of the limits for implant use in the iliac wing as well as better appreciation of the complex osteology of the ilium. This will help surgeons to identify safe areas for implant placement and avoid inadvertent cortical penetration.

Intraperitoneal Loss of Pelvic Array Pin During Navigated Total Hip Arthroplasty

Pelvic array pin placement during navigated total hip arthroplasty has been known to cause complications; however, most of them are minor. We report a 78-year-old female who underwent a routine computer-navigated total hip replacement which was subsequently complicated by complete loss of the pelvic array pin requiring retrieval via laparotomy. No structures were injured despite the surrounding urological, vascular, and visceral anatomy. The patient recovered and subsequently underwent a total hip arthroplasty without complication 6 weeks later. This case illustrates the dangers of inserting a pelvic array pin within patients with poor bone quality and highlights necessary considerations of pin design and surgical techniques to minimize this complication.

S2-Alar-iliac screw fixation for paediatric neuromuscular scoliosis: Preliminary results after two years

BACKGROUND

Correcting pelvic obliquity is among the main goals of surgery for neuromuscular scoliosis. Spino-pelvic fixation must be stable and capable of withstanding the considerable mechanical forces applied at the lumbo-sacral junction. Selection of the best anchoring option is therefore crucial. S2-alar-iliac (S2AI) screws, which are used in adults, are less often chosen in the French paediatric spinal-surgery community. The objective of this study was to report our preliminary experience with S2AI screws used in the treatment of paediatric patients with neuromuscular scoliosis.

HYPOTHESIS

Pelvic anchoring by means of S2AI screws is reliable and technically feasible in non-ambulatory children with neuromuscular scoliosis.

MATERIALS AND METHODS

Consecutive non-ambulatory patients who underwent scoliosis surgery with S2AI screw fixation to the pelvis between 2016 and 2018 were retrospectively included. The surgical procedure consisted in either posterior spinal fusion (PSF) or magnetic growing rod (MGR) implantation. In all patients, radiographs were obtained before surgery, within 3 months after surgery, and at last follow-up; and low-dose computed tomography (CT) was performed before and after surgery.

RESULTS

We included 25 patients with a mean age of 13.8±4.0 years, 18 managed by PSF and 7 by MGRs. Screw diameters ranged from 7.5 to 9.5mm and all screws were at least 60mm in length. The diameters and lengths were the same on both sides in 16 (89%) patients in the PSF group and in all patients in the MGR group. At last follow-up after a mean of 35.5±3.0 months, pelvic obliquity was corrected in all 23 patients with this abnormality before surgery. Complications consisted of lateral cortical screw breakthrough in 8 (32% of screws) patients and screw malposition in 2 (8% of screws) patients. No clinically significant complications related to the fixation material were recorded.

DISCUSSION

The results of our study demonstrate the feasibility of S2AI screw fixation in paediatric patients with neuromuscular scoliosis. Pelvic asymmetry and dysmorphism do not contra-indicate the procedure but must be evaluated before surgery. Further work is needed to assess the potential long-term consequences on pain and growth of screw passage through the sacro-iliac joints.

LEVEL OF EVIDENCE

IV, retrospective study.

Defining the iliac wing osseous fixation pathways: anatomy and implant constriction points

INTRODUCTION

Insertion of iliac wing implants requires understanding of the curvilinear shape of the ilium. This study serves to quantitatively identify the area of iliac inner-outer table convergence (IOTC), characterize the iliac wing osseous corridor, and define the gluteal pillar osseous corridor.

METHODS

Computed tomography scans of 100 male and 100 female hemipelves were evaluated. The iliac wing was studied using manual best-fit analysis of the bounds of the inner and outer cortices. The IOTC was defined as the location of the iliac wing with an intercortical width less than 5 mm. The shortest distance from the apex of the iliac crest to the superior border of the IOTC was defined as the iliac wing osseous corridor. Finally, the width of the gluteal pillar corridor from the gluteus medius tubercle to the ischial tuberosity was measured.

RESULTS

The IOTC is an elliptical area measuring 22.3 cm². All ilia had an area where the inner and outer cortices converged to an intercortical width of less than 5 mm; 48% converged to a single cortex. The shortest mean distance from the superior edge of the iliac crest to the beginning of the IOTC was 20.3 mm in men and 13.8 mm in women (p < 0.001). The gluteal pillar diameter averaged 5.3 mm in men and 4.3 mm in women (p < 0.001).

DISCUSSION

All ilia converge to a thin and frequently unicortical central region. A 4.5 mm iliac wing lag screw will not breach the cortex if it remains within 20 mm or 14 mm distal to the cranial aspect of the iliac crest in males and females, respectively. Not only is the gluteal pillar smaller than previously thought, in 41% of males and 73% of females, it is not be large enough for 5 mm implants.

CONCLUSION

This study quantitatively assesses the dimensions of the IOTC, the iliac crest osseous corridor, and the gluteal pillar. Overall, our findings provide improved understanding of the limits for implant use in the iliac wing as well as better appreciation of the complex osteology of the ilium. This will help surgeons to identify safe areas for implant placement and avoid inadvertent cortical penetration.