Biomechanical Analysis of Stability of Posterior Antiglide Plating in Osteoporotic Pronation Abduction Ankle Fracture Model With Posterior Tibial Fragment.
BACKGROUND
We performed a biomechanical comparison of 2 methods for operative stabilization of pronation-abduction stage III ankle fractures; group 1: Anterior-posterior lag screws fixing the posterior tibial fragment and lateral fibula plating (LSLFP) versus group 2: locked plate fixation of the posterior tibial fragment and posterior antiglide plate fixation of the fibula (LPFP).


METHODS
Seven pairs of fresh-frozen osteoligamentous lower leg specimens (2 male, and 5 female donors) were used for the biomechanical testing. Bone mineral density (BMD) of each specimen was assessed by means of dual-energy x-ray absorptiometry. After open transection of the deltoid ligament, an osteotomy model of pronation abduction stage III ankle fracture was created. Specimens were systematically assigned to LSLFP (group 1, left ankles) or LPPFP (group 2, right ankles). After surgery, all specimens were evaluated via CT to verify reduction and fixation. Axial load was then applied onto each specimen using a servohydraulic testing machine starting from 0 N (Zwick/Roell, Ulm, Germany) at a speed of 10 N/s with the foot fixed in a 10 degrees pronation and 15 degrees dorsiflexion position. Construct stiffness, yield, and ultimate strength were measured and dislocation patterns were documented with a high-speed camera. The normal distribution of all data was analyzed using Shapiro-Wilk test. The group comparison was performed using paired Student t test. Statistical significance was assumed at a P value of .05.


RESULTS
All specimens had BMD values consistent with osteoporosis. BMD values did not differ between the left and right ankles of the same pair ( P = .762). The mean BMD values between feet of men (0.603 g/cm2) and women (0.329 g/cm2) were statistically different ( P = .005). The ultimate strength for LSLFP (group 1) with 1139 ± 669 N and LPPFP (group 2) with 2008 ± 943 N was statistically different ( P = .036) as well as the yield in LSLFP (group 1) 812 ± 452 N and LPPFD (group 2) 1292 ± 625 N ( P = .016). Construct stiffness trended to be higher in group 2 (179 ± 100 kNn) compared to group 1 (127 ± 73 kN/m) but this difference was not statistically significant ( P = .120). BMD correlated with bone-construct failure.


CONCLUSIONS
Fixation of the posterior tibial edge with a posterolateral locking plate resulted in higher biomechanical stability than anterior-posterior lag screw fixation in an osteoporotic pronation-abduction fracture model.


CONCLUSIONS
The clinical implication of this biomechanical study is that the posterior antiglide plating might be advantageous in patients with osteoporotic pronation abduction stage III ankle fracture.
1 University Center of Orthopaedics and Traumatology, University Medicine Carl Gustav Carus Dresden, Dresden, Germany.
Kathleen
K
Hartwich
2 Hospital Ramón y Cajal, Madrid, Spain.
Alejandro
A
Lorente Gomez
1 University Center of Orthopaedics and Traumatology, University Medicine Carl Gustav Carus Dresden, Dresden, Germany.
Jaroslaw
J
Pyrc
3 Chair and Department of Rehabilitation and Orthopaedics, Medical University of Lublin, Lublin, Poland.
Radosław
R
Gut
1 University Center of Orthopaedics and Traumatology, University Medicine Carl Gustav Carus Dresden, Dresden, Germany.
Stefan
S
Rammelt
1 University Center of Orthopaedics and Traumatology, University Medicine Carl Gustav Carus Dresden, Dresden, Germany.
René
R
Grass
D015502:Absorptiometry, Photon; D064386:Ankle Fractures / Q000150:complications / Q000503:physiopathology / Q000601:surgery*; D001696:Biomechanical Phenomena; D001860:Bone Plates; D005260:Female; D005593:Fracture Fixation, Internal / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D008297:Male; D010024:Osteoporosis / Q000150:complications / Q000000981:diagnostic imaging; D013977:Tibia
ankle fracture; biomechanical; osteoporotic bone; posterior antiglide plating; posterior tibial fragment