Outcome evaluation of new calcium titanate schanz-screws for external fixators. First clinical results and cadaver studies
- 29 Downloads
External fixators are important for correcting length discrepancies and axis deformities in pediatric or trauma orthopedic surgery. Pin loosening is a common pitfall during therapy that can lead to pain, infection, and necessary revisions. This study aims to present clinical data using calcium titanate (CaTiO3) Schanz screws and to measure the fixation strength.
Patients and methods
22 titanate screws were used for external fixators in 4 pediatric patients. Therapy was initiated to lengthen or correct axial deformities after congenital abnormalities. The maximum tightening torque was measured during implantation, and the loosening torque was measured during explantation. In addition, screws of the same type were used in a cadaver study and compared with stainless steel and hydroxyapatite-coated screws. 12 screws of each type were inserted in four tibias, and the loosening and tightening torque was documented.
The fixation index in the in vivo measurement showed a significant increase between screw insertion and extraction in three of the four patients. The pins were in situ for 91 to 150 days, and the torque increased significantly (P = 0.0004) from insertion to extraction. The cadaveric study showed lower extraction torques than insertion torques, as expected in this setting. The calculated fixation index was significantly higher in the CaTiO3 group than in the other groups (P = 0.0208 vs. HA and P < 0.0001 vs. steel) and in the HA group vs. plain steel group (P = 0.0448).
The calcium titanate screws showed favorable fixation strength compared to HA and stainless steel screws and should be considered in long-term therapy of external fixation.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
- 10.Placzek R, Ruffer M, Deuretzbacher G, Heijens E, Meiss AL. The fixation strength of hydroxyapatite-coated Schanz screws and standard stainless steel Schanz screws in lower extremity lengthening: a comparison based on a new torque value index: the fixation index. Arch Orthop Trauma Surg 2006;126:369–73.CrossRefGoogle Scholar
- 11.Checketts RG, MacEachem AG, Otterbum M. Pin track infection and the principles of pin site care. In: De Bastiani G, Apley AG, Goldberg A, (eds) Orthofix external fixation in trauma and orthopaedics. London: Springer London; 2000. http://link.springer.com/10.1007/978-1-4471-0691-3_11.CrossRefGoogle Scholar
- 26.Lethaby A, Temple J, Santy-Tomlinson J. Pin site care for preventing infections associated with external bone fixators and pins. Cochrane Database Syst Rev. 2013;12:CD004551.Google Scholar
- 31.Shirai T, Watanabe K, Matsubara H, Nomura I, Fujiwara H, Arai Y, et al. Prevention of pin tract infection with iodine-supported titanium pins, J. Orthop. Sci. J Jpn Orthop Assoc 2014;19:598–602.Google Scholar
- 32.Collinge CA, Goll G, Seligson D, Easley KJ. Pin tract infections: silver vs uncoated pins. Orthopedics. 1994;17:445–8.Google Scholar
- 37.Pettine KA, Chao EY, Kelly PJ. Analfysis of the external fixator pin-bone interface. Clin Orthop 1993;293:18–27.Google Scholar