Revisiting the concept of talar shift in ankle fractures.
BACKGROUND
In 1976, Ramsey and Hamilton published a classic experiment investigating the biomechanical effects of talar shift in a simple ankle fracture model. Their finding was that 1 mm of talar shift resulted in a 42% decrease in tibiotalar contact surface area. Based on this conclusion, 1 mm of talar shift became the recognized indication for operative fixation.


METHODS
Twelve cadaver ankles were dissected and the distal tibia coated with carbon powder. A 70-kg load was applied to the distal tibia that resulted in transference of the carbon onto the talus. The contact surface area was determined at 0, 1, 2, 4 and 6 mm of talar shift using spacers fixed in the medial gutter. Tracing paper was used to mark the outline of the contact area and measured using graph paper.


RESULTS
Our results were similar to Ramsey and Hamilton's original experiment. One millimeter of lateral talar shift resulted in 40% loss of contact surface area compared with 42% in the original experiment. A large variance was seen in talar contact surface area depending on the morphology of the ankle joint.


CONCLUSIONS
Ramsey and Hamilton's original experiment was valid.
Lloyd
John
J
4 Victoria Drive West, Salisbury District Hospital, Wiltshire, SP2 8QX United Kingdom. jelloyd1@btopenworld.com
Elsayed
Sherief
S
Hariharan
Kartik
K
Tanaka
Hiro
H
D016512:Ankle Injuries / Q000473:pathology* / Q000503:physiopathology; D001696:Biomechanical Phenomena; D002102:Cadaver; D002244:Carbon; D004396:Coloring Agents; D005592:Fracture Fixation / Q000379:methods; D006801:Humans; D015203:Reproducibility of Results; D013628:Talus / Q000473:pathology* / Q000503:physiopathology; D013977:Tibia / Q000473:pathology / Q000503:physiopathology; D013978:Tibial Fractures / Q000473:pathology* / Q000503:physiopathology; D016474:Weight-Bearing / Q000502:physiology
D004396:Coloring Agents; D002244:Carbon