Medial Displacement Calcaneal Osteotomy: Loss of Correction with Varying Drilling Techniques

CATEGORY: Hindfoot INTRODUCTION/PURPOSE: Surgical correction of Stage 2 posterior tibial tendon dysfunction typically involves a combination of soft tissue and bony corrections, often including a medial displacement calcaneal osteotomy (MDCO). This osteotomy is often fixated utilizing two parallel screws; however, it remains unknown how much correction is lost based on various accepted drilling techniques for common fixation of this osteotomy. Our cadaveric study compares three different surgical drilling techniques, using two parallel cannulated screws for fixation, to best maintain desired translation of the MDCO. METHODS: Fifteen above knee, fresh-frozen, matched pair cadaveric specimens (30 limbs) were randomized equally into three groups. Calcanealosteotomies were performed, followed by manual 10 mm medial translation of the tuberosity. Two parallel 2.5mm guide wires were advanced across the osteotomy site under fluoroscopy. The first group involved a ‘staggered’ drilling technique in which one guide wire was over drilled to the osteotomy site with a 4.5mm cannulated drill and then a 7.0 mm cannulated screw was placed across the osteotomy, followed by a second screw in similar fashion. The second, ‘simultaneous’ group consisted of over drilling both guide wires sequentially followed by placement of both screws. The third control group involved simultaneously over drilling only the near cortex, followed by placement of the 2 screws. Following screw fixation, the calcaneal tuberosity was manually translated in a lateral direction. The loss of correction was then marked and measured in millimeters. RESULTS: All thirty cadaveric specimens underwent standard medializing calcaneal displacement osteotomy without significant variation, or complication. Loss of medialization was measured in millimeters following a manual lateral displacing force after the screw fixation of the osteotomy. The ‘simultaneous’ drilling group experienced the greatest loss of medial displacement with the mean loss of correction being 2.6 mm (range 1.37 - 3.48 mm) following manual lateral translation. The ‘staggered’ group showed an average loss of 1.16 mm (range 0.36 - 2.67 mm). The control group, that simply involved drilling of the near cortex, demonstrated the greatest maintenance of medial displacement with a mean loss of only 0.036 mm (range 0.01 - 0.06 mm). CONCLUSION: Our cadaveric study comparing three different drilling techniques for maintaining the intended correction following MDCO demonstrates that simultaneous over drilling of only the tuberosity near cortex prior to screw fixation was the most resistant to loss of medial displacement; whereas mean loss of correction with simultaneous drilling of both wires to the osteotomy resulted in the greatest loss of correction at an average of 26%.