Biomechanical comparison of 4.0-mm short-threaded cannulated screws and 4.0-mm short-threaded cancellous screws in a canine humeral condylar fracture model.

Objective: To compare biomechanical properties of a humeral condylar fracture model stabilized either with a 4.0-mm short-threaded cancellous screw (CCS) or with a 4.0-mm short-threaded cannulated screw (CNS).

Study Design: In vitro biomechanical study.

Sample Population: Bilateral cadaveric canine humeri (n = 20).

Methods: Fractures of the lateral portion of the humeral condyle were simulated by standardized osteotomies; 10 condyles were each stabilized with CCS and 10 with CNS. Axial compression load was applied to each specimen until failure and force-displacement curves generated. Testing data for each construct were determined and compared using either a Student's paired t-test (quantitative data) or a χ(2) test (qualitative data) with statistical significance set at P < .05.

Results: Yield load (elastic limit), ultimate load at failure, and displacements at loads corresponding to walk and trot were determined from each curve. Mean ± SD ultimate load at failure was significantly higher (P = .01) for CCS constructs (1261 ± 261 N) than for CNS constructs (1078 ± 231 N). Yield loads were not significantly different (P = .10) between construct types, and exceeded all expected loads supported by the humeral condyle at walk. The risk of having a yield load below the expected physiologic load at trot was not statistically higher with a CNS construct compared with a CCS construct (P = .26).

Conclusion: Humeral condylar fracture repaired either by a 4.0-mm cannulated screw or a 4.0-mm cancellous screw have comparable stability in this condylar fracture model.