Incidence of transcortical tibial fractures with self-tapping and non-self-tapping screws in a canine TPLO model.

Abstract

OBJECTIVE: To compare the incidence of radiographically apparent transcortical diaphyseal tibial fractures between self-tapping screws (STS) and non-self-tapping screws (NSTS) in a canine tibial plateau leveling osteotomy (TPLO) model. STUDY DESIGN: Case series. ANIMALS: Dogs (n = 106) that had TPLO. METHODS: NSTS (n = 107), STS titanium (n = 104), or STS stainless steel (n = 105) screws were used for TPLO. Effect of STS and NSTS were compared by reviewing postoperative craniocaudal and lateral radiographic projections taken immediately after TPLO. Three screws distal to the tibial osteotomy served as the in vivo model for canine cortical bone. A transcortical fracture was defined as the presence of a saucer-shaped radiolucent defect on the periosteal surface of the trans-cortex surrounding the screw and the presence of radiopaque material (bone) separate from the transcortical periosteal surface. The effect of screw type and STS material (stainless steel or titanium) on the incidence of transcortical fractures was evaluated. RESULTS: STS had a significantly higher (P = .006) incidence of transcortical fractures (18.0%) compared with NSTS (0.8%). The effect of STS material on the incidence of transcortical fractures was not significant (P = .485). No cis-cortical factures were identified. CONCLUSIONS: We suspect the increased incidence of transcortical fractures with STS is because of the shorter cutting flutes as compared with those of a tap used with a NSTS.