A Three-Dimensional Comparison of Intramedullary Nail Constructs for Osteopenic Supracondylar Femur Fractures

作者：Paller David J; Frenzen Seth W; Bartlett Craig S II; Beardsley Christina L; Beynnon Bruce D^*

来源：Journal of Orthopaedic Trauma, 2013, 27(2): 93-99.

DOI：10.1097/BOT.0b013e31825199c9

• retrograde intramedullary nail
• supracondylar femur fracture
• internal fixation
• fixed angle
• locking screw
• osteoporotic bone

Objectives: This study developed a new 6 degree-of-freedom, unconstrained biomechanical model that replicated the in vivo loading environment of femoral fractures. The objective of this study was to determine whether various distal fixation strategies alter failure mechanisms and/or offer mechanical advantages when performing retrograde intramedullary nail (IMN) stabilization of supracondylar femur fractures in osteoporotic bone. %26lt;br%26gt;Methods: Forty fresh-frozen human femora were allocated into 2 groups of matched pairs: %26quot;locked%26quot; (fixed angle locking construct with both distal locking screws rigidly attached to the IMN) versus %26quot;unlocked%26quot; (conventional locking technique with 2 distal locking screws targeted through the distal locking screw holes of the IMN) and %26quot;locked%26quot; versus %26quot;washer%26quot; (fixed angle locking with the most distal screw exchanged for a bolt with condyle washers) distal fixation of a retrograde IM nails. A comminuted fracture (OTA 33-A3) was simulated with a wedge osteotomy. Bone density measurements were completed on all specimens before instrumentation. Instrumented femurs were loaded axially to failure, whereas 6 degree-of-freedom translations and angulations were measured using Roentgen stereophotogrammetric analysis. %26lt;br%26gt;Results: Mean (+/- SD) load born by %26quot;locked%26quot; specimens (1609 +/- 667 N) at clinical failure was 38.1% greater (P = 0.09) than the corresponding mean load born by %26quot;unlocked%26quot; specimens (1165 772 N). Clinical failure for the %26quot;washer%26quot; group (1738 +/- 772 N) was 29.9% greater (P = 0.07) than the corresponding mean of the %26quot;locked%26quot; counterparts (1338 +/- 822 N). Failure load was most clearly related to bone density in the %26quot;unlocked%26quot; fixation group. %26lt;br%26gt;Conclusions: Predicting failure load based on bone density using a least squares estimate suggests that the washer construct provides superior fixation to other treatment techniques. The failure mechanism for a comminuted, supracondylar fracture cannot be analyzed accurately with a 1-dimensional measurement. The most common failure mechanism in this model was medial translation and varus angulation.

• 出版日期2013-2