Vet Comp Orthop Traumatol 2020; 33(03): 153-160
DOI: 10.1055/s-0039-3402518
Original Research
Georg Thieme Verlag KG Stuttgart · New York

Biomechanical and Histological Assessment of a Polyethylene Terephthalate Screw Retention Technology in an Ovine Metatarsal Fracture Model

Jeremiah Easley
1  Department of Clinical Sciences, Preclinical Surgical Research Laboratory (PSRL), Colorado State University, Fort Collins, Colorado, United States
,
Christian Puttlitz
2  Department of Mechanical Engineering, Orthopaedic Bioengineering Research Laboratory (OBRL), Colorado State University, Fort Collins, Colorado, United States
,
Cecily Broomfield
2  Department of Mechanical Engineering, Orthopaedic Bioengineering Research Laboratory (OBRL), Colorado State University, Fort Collins, Colorado, United States
,
Ross Palmer
1  Department of Clinical Sciences, Preclinical Surgical Research Laboratory (PSRL), Colorado State University, Fort Collins, Colorado, United States
,
Alexander Jones
3  Savannah, Georgia, United States
,
2  Department of Mechanical Engineering, Orthopaedic Bioengineering Research Laboratory (OBRL), Colorado State University, Fort Collins, Colorado, United States
› Author Affiliations
Funding This work was funded by a research grant to Colorado State University (Fort Collins, Colorado, United States) from Woven Orthopedic Technologies (Manchester, Connecticut, United States).
Further Information

Publication History

03 May 2019

09 November 2019

Publication Date:
23 February 2020 (online)

Abstract

Objective Screw loosening in fracture fixation poses a clinical risk which may lead to implant failure, particularly in poor bone quality. The objective of this study was to examine the effectiveness of a novel screw retention technology (SRT) for increased screw purchase in a large animal metatarsal fracture model.

Study Design This was a biomechanical, radiographic, and histological study utilizing an ovine metatarsal fracture model. Twenty-four sheep metatarsi underwent 3-mm ostectomies and were repaired with a nine-hole plate and 3.5-mm screws placed in oversized 3.5-mm holes to simulate worst case revision surgeries (i.e. no initial screw thread bone contact). Sheep were sacrificed at 3, 6 or 12 weeks (n = 6 each) post-operation. Post-sacrifice, each surgically implanted screw underwent either destructive mechanical testing or histomorphometric analyses.

Results Treated metatarsi showed improved screw retention and normal fracture healing. Significant improvement in breakout strength and pullout strength of screws treated with the SRT were found as a function of healing time. Histologically, bone ingrowth at the screw interface was also shown to significantly increase with healing time. Improvements in fracture healing, indicated by an increase in bone fraction and decrease in void space at the osteotomy, were also observed with healing time.

Conclusion The results demonstrate the effectiveness of the SRT as a method for improved screw retention in a rescue-screw type scenario.

Author's Contributions

All authors drafted, revised and approved the submitted manuscript. Jeremiah Easley, Christian Puttlitz, Cecily Broomfield, Ross Palmer and Kirk C. McGilvray contributed to conception of study, study design, acquisition of data and data analysis and interpretation. Alexander Jones contributed to conception of study, study design, and data analysis and interpretation.