Percutaneous Harvest of Calcaneal Bone Autograft: Quantification of Volume and Definition of Anatomical Safe Zone

Bone grafting is commonly used in reconstructive foot and ankle surgery. The calcaneus provides an excellent site for graft harvest due to its rich vascularity and access to corticocancellous or strictly cancellous bone. The relatively thin soft tissue envelope makes dissection easy compared to more proximal autograft sites. In this investigation we quantified cancellous autograft volume from the calcaneus while simultaneously defining anatomical safe zones and identifying anatomical structures at risk. Nine matched-pair (18 total) fresh-frozen cadaveric below-knee limbs were utilized. All limbs were thawed at room temperature prior to the procedure. Calcaneal autograft was harvested following the senior author's (D.J.E.) technique. Bone graft was packed and quantified by podiatric medical students (B.R. and J.T.). An independent investigator (K.S.) meticulously dissected the lateral calcaneal soft tissue envelope to determine rates of neurovascular compromise. Anatomical safe zones were defined by measurements of the harvest site compared to vital anatomical structures. Cancellous autograft averaging 0.85 cc was obtained through an average cortical opening of 0.77 cm. The stab incision is approximately 2.2 cm anterior to the posterior aspect of the calcaneus and 1.6 cm superior to the inferior aspect of the calcaneus. This incision is an average 1.8 cm from the main branch of the sural nerve. No neurovascular damage was found. This study details percutaneous harvest of calcaneal autograft for use in forefoot or midfoot surgeries with an emphasis on feasibility of this additional procedure. The technique proposed is valuable based on simplicity, wide anatomic safe zone, and potential improvement of surgical outcomes.