Surgical Fixation of Calcaneal Beak Fractures—Biomechanical Analysis of Different Osteosynthesis Techniques

Abstract

The calcaneal beak fracture is a rare avulsion fracture of the tuber calcanei characterized by a solid bony fragment at the Achilles tendon insertion. Treatment usually requires osteosynthesis. However, lack of biomechanical understanding of the ideal fixation technique persists. A beak fracture was simulated in synthetic bones and assigned to five different groups of fixation: A) 6.5-mm partial threaded cannulated screws, B) 4.0-mm partial threaded cannulated screws, C) 5.0-mm headless cannulated compression screws, D) 2.3-mm locking plate, and E) 2.8-mm locking plate. Different traction force levels were applied through an Achilles tendon surrogate in a material-testing machine on all stabilized synthetic bones. Outcome measures were peak-to-peak displacement, total displacement, plastic deformation, stiffness, visual-fracture-line displacement, and mode of implant failure. The 2.3- and 2.8-mm plating groups showed a high drop-out rate at 100 N tension force and failed under higher tension levels of 200 N. The fracture fixation using 4.0-mm partial threaded screws showed a significantly higher repair strength and was able to withhold cyclic loading up to 300 N. The lowest peak-to-peak displacement and the highest load-to-failure and stiffness were provided by fracture fixation using 6.5-mm partial threaded cannulated screws or 5.0-mm headless cannulated compression screws. As anticipated, large 6.5-mm screw diameters provide the best biomechanical fixation. Surprisingly, the 5.0-mm headless cannulated compression screws yield reliable stability despite the absent screw head and washer. When such large screws cannot be applied, 4.0-mm screws also allow reasonable fixation strength. Plate fixation should be implemented with precaution and in combination with a restrictive postoperative motion protocol. Finally, clinical cases about the surgical application and recovery are included.

Analysis of Calcaneal Avulsion Fractures Treated Surgically and Nonsurgically

“…In this study, 2 cannulated cancellous screws were inserted in 92.9% of the cases treated with CCS fixation, and, similar to the opinion of Doany et al 11 , it is preferable to use multiple cannulated cancellous screws in cases in which the bone fragments are large enough 4,10-12,20,22 . A 1:2 screw-to-bone ratio was recommended for prevention of fragmentation of the fracture in a biomechanical study by Jordan et al 22 . The present results suggest that 2 cannulated cancellous screws should be inserted if possible.…”

“…Since there was no difference in the results among the different types of augmentation (although the study population was relatively small), a washer may be selected as the first choice because it involves small additional incisions 12 . In this study, 2 cannulated cancellous screws were inserted in 92.9% of the cases treated with CCS fixation, and, similar to the opinion of Doany et al 11 , it is preferable to use multiple cannulated cancellous screws in cases in which the bone fragments are large enough 4,10-12,20,22 . A 1:2 screw-to-bone ratio was recommended for prevention of fragmentation of the fracture in a biomechanical study by Jordan et al 22 .…”

“…Early intervention was desirable because one of the causes was thought to be persistent pressure on the skin by bone fragments 2 . In order to minimize the incidence of postoperative complications, it is necessary to pay attention to factors related to surgical interventions, such as early and minimally invasive surgery, assurance of the fixation strength, and prolonged immobilization in the equinus position 4,[8][9][10][11][12]19,20,22,26 .…”

“…After surgery, all patients were made non-weight-bearing with immobilization by a cast in the equinus position for 2 to 6 weeks. Physical therapy was then initiated, and the patient’s weight-bearing was gradually increased 3 , 4 , 22 , 24 .…”

“…All screws used were partially threaded and ranged from 3.5 to 6.5 mm in diameter. All screws utilized the plantar cortex for fixation 3,4,8,11,12,[20][21][22] . A washer, suture anchor, tension-band wiring, or Steinmann pin was also used for augmentation.…”