External ring fixation versus screw fixation for ankle arthrodesis: a biomechanical comparison.
BACKGROUND
The use of external ring fixation for ankle arthrodesis offers an alternative to internal screw fixation when bone quality is suboptimal, when complex ankle pathology is present, and as a salvage procedure for complicated cases. Additionally, it permits earlier weightbearing and postoperative adjustment of bone alignment and joint compression. This study was designed to determine whether there are differences in initial ankle joint fixation integrity between these two techniques.


METHODS
Ten fresh-frozen cadaveric lower extremities underwent ankle arthrodesis with a hybrid ring fixator, and the bending and torsional stiffness of each arthrodesed joint was quantified. Stiffness was calculated from angulation measured at the tibiotalar joint using electronic clinometers attached to those bones. The external fixators were then removed and ankle arthrodesis performed using 6.5-mm cannulated screws: three across the ankle joint, one fixing the fibula to the tibia, and one fixing the fibula to the talus. Stiffness testing was then repeated.


RESULTS
No statistically significant difference in bending stiffness, torsional stiffness, or joint rotation under torsional load was demonstrable between the two techniques.


CONCLUSIONS
The similarity in ankle fusion site stability achieved with external ring fixation and an optimized screw fixation technique under the described testing conditions indicates that, in cases in which suboptimal bone quality or complex ankle pathology preclude the use of internal fixation, an external fixator is a viable option.


CONCLUSIONS
Establishing that the primary stability of external ring fixation is comparable to that of screw fixation provides a basis for its use in cases in which screw fixation may be problematic.
Ogut
Tahir
T
Istanbul University Cerrahpasa Medical Faculty, Department of Orthopaedics and Traumatology, Istanbul Turkey.
Glisson
Richard R
RR
Chuckpaiwong
Bavornrit
B
Le
Ian L D
IL
Easley
Mark E
ME
D000843:Ankle Joint; D001174:Arthrodesis / Q000295:instrumentation*; D001696:Biomechanical Phenomena; D001863:Bone Screws; D002102:Cadaver; D019544:Equipment Failure Analysis; D016267:External Fixators; D006801:Humans; D016059:Range of Motion, Articular; D016474:Weight-Bearing