Page 245 - Advances in Biomechanics and Tissue Regeneration

P. 245

CHA PTE R

Biomechanical Study in the Calcaneus Bone

After an Autologous Bone Harvest

†
Javier Bayod Lo ´pez*, Ricardo Becerro de Bengoa Vallejo , and
Marta E. Losa Iglesias ‡
*Group Applied Mechanics and Bioengineering, School of Engineering and Architecture, University of Saragossa, Zaragoza,
†
Spain Department of Nursing, School of Nursing, Physiotherapy and Podiatry, Complutense University, Madrid, Spain
‡
Faculty of Health Sciences, Rey Juan Carlos University, Madrid, Spain

12.1 INTRODUCTION

The extraction of bone stock for autologous graft is a technique performed routinely in foot and ankle surgery [1–3].
Autologous bone grafts in the foot are performed in procedures such as distraction osteotomies, revision surgeries,
nonunion fractures, and joint fusion [3, 4]. The iliac crest is a common donor site, but it is associated with complication
rates from 10% to 49% [3, 5, 6], including potential visceral injury, chronic pain, numbness, bruising, infection, and
delayed healing [7–14]. Other donor sites, including the proximal and distal tibia, fibular, distal radius, and greater
trochanter, have fewer relative complications, but generally less bone can be harvested [3, 4].
In foot and ankle surgery, the calcaneus provides an optimal site to procure an autologous bone graft. Using ankle-
block anesthesia and small incisions, the bone can be successfully harvested and surgically implanted using the same
operative field [7]. Importantly, only minor complications are associated with calcaneus bone harvest. A 2-year out-
come study of 17 patients who had undergone foot surgery and calcaneal bone harvest reported minor incisional
symptoms in three patients. Medial heel pain was reported in five cases, including three ascribed to plantar fasciitis,
and one with pain prior to the surgical procedure caused by a clubfoot deformity [7]. This study demonstrated that the
calcaneus is a safe option for donor grafts in foot and ankle surgical procedures, rather than the proximal tibia, distal
tibia, or iliac crest that are traditionally used [7].
Heel fracture represents one significant complication that can occur with calcaneal bone harvest. One study eval-
uated the clinical outcomes of 19 patients who had foot surgery using autogenous, tricortical bone grafts harvested
from the calcaneus [4]. Allogenic cubes were used in 1 cohort (9 patients) to fill the defect, and the remaining 10 patients
received no tissue replacement. After 6months, two patients succumbed to a heel fracture. One fracture, in a patient
from the first cohort, was inferior to the graft site, and a patient from the second cohort experienced a fracture posterior
to the graft site [4]. Unfortunately, it was unclear if the fractures resulted from the size of the graft, emphasizing the
importance of future investigations to establish the maximum graft size for safe extraction.
Based on this the objective of the current study was to determine the effects on the mechanical properties of the
foot due to progressive calcaneus bone removal. To address this, a three-dimensional (3-D) finite element (FE) model
was developed. With this approach, we evaluated six conditions of principal stress. One variable was the intact foot,
and the remaining five conditions included a model where a piece of bone of variable depth (maximum 7.5mm)
had been removed. Because of potential increases in mechanical stress in the calcaneus secondary to contraction
of the Achilles tendon, we also evaluated mechanical properties of the foot with increasing traction forces assigned
to the Achilles.

240 241 242 243 244 245 246 247 248 249 250