Biomechanical analysis of iliac crest loading following cortico-cancellous bone harvesting

Abstract

Background: Iliac crest bone harvesting is a frequently performed surgical procedure widely used to treat bone defects. The objective of this study is to assess the biomechanical quantities related to risk for pelvic fracture after harvesting an autologous bone graft at the anterior iliac crest.

Methods: Finite element models with a simulated harvest site (sized 15 × 20 mm, 15 × 35 mm, 30 × 20 mm and 30 × 35 mm) in the iliac wing are created. The relevant loading case is when the ipsilateral leg is lifted off the ground. Musculoskeletal analysis is utilized to compute the muscle and joint forces involved in this motion. These forces are used as boundary conditions for the finite element analyses. Bone tissue stress is analyzed.

Results: Critical stress peaks are located between the anterior superior iliac spine (ASIS) and the anterior edge of the harvest site. Irrespective of the graft size, the iliac wing does not show any significant stress peaks with the harvest site being 20 to 25 mm posterior to the ASIS. The harvest area itself inhibits the distribution of the forces applied on the ASIS to extend to the posterior iliac wing. This leads to a lack of stress posterior to the harvest site. A balanced stress distribution with no stress peaks appears when the bone graft is taken below the iliac crest.

Conclusion: A harvest site located at least 20 to 25 mm posterior to the ASIS should be preferred to minimize the risk of iliac fatigue fracture.

Keywords: ASIS; Autologous bone graft; Biomechanical investigation; Bone harvesting; FEA; Fatigue fracture; Iliac crest; Pelvis.

Fig. 1

a Fatigue fracture of the ASIS following bone graft harvesting at the anterior iliac crest. 1 = ASIS, 2 = location of bone graft harvesting. The arrow shows the fracture side. b The 76-year-old patient needed a plate osteosynthesis for pain relieve and to get mobilized

Fig. 2

Exemplary grayscale values of the ilium from the CT scan

Fig. 3

Right iliac bone: 1 = anterior superior iliac spine (ASIS), 2 = anterior inferior iliac spine, 3 = acetabulum, 4 = sciatic notch, 5 = posterior inferior iliac spine. Bone graft harvest site of 15 × 20 mm (a, black rectangle) and 15 × 35 mm (b, red rectangle). Dotted lines and dotted rectangles = the position of the harvest side was drafted beginning 5 mm posterior to the ASIS along the iliac wing. c Bone graft harvest site of 30 × 20 mm (red dashed rectangle) and 30 × 35 mm (red rectangle) 5 mm posterior to the ASIS. Black dashed rectangle = cavity of 15 × 20 mm was taken 5 mm below the iliac crest and 10 mm posterior to the ASIS

Fig. 4

MRI of a pelvis and the hip joint in T2 sagittal reconstruction: 1 = ASIS, 2 = iliac crest, 3 = femoral head, 4 = sartorius muscle, 5 = femoral rectus muscle, 6–8 = minor, medium, and greater gluteal muscles, 9 = abdominal muscle, 10 = location of bone graft harvesting. The arrows show the traction of muscle forces that provoke a fatigue fracture of the ASIS [13]

Fig. 5

a Right iliac wing without bone graft harvest. b–d Right iliac wing with simulated bone graft harvest site of 15 × 35 mm with the cutout 5 mm (b), 15 mm (c), and 35 mm (d) posterior to the ASIS. e Right iliac wing with 15 × 20 mm cutout 10 mm posterior to the ASIS and 5 mm below the iliac crest

Fig. 6

a X-ray (right pelvis ala-view) of a 73-year-old patient 8 years after bone harvesting (vascularized iliac crest) and simultaneous plate osteosynthesis to prevent a fatigue fracture. b Anatomically shaped low profile small fragment plates and cortical screws (optionally angular stable) that can be used to reconstruct the iliac crest following bone graft harvesting