Mismatch analysis of humeral nailing: antegrade versus retrograde insertion.

Abstract

Closed humeral nailing is now considered an alternative treatment for humeral-shaft fracture. The nail can be inserted with either the antegrade or retrograde method. We investigated and compared the problem of geometric mismatch of the humeral nail to the humerus between the two methods of insertion. The study was performed using virtual simulation based on computed tomography (CT) data of 76 Thai cadaveric humeri and the commonly used Russell-Taylor humeral nail 8 mm in diameter and 220 mm long. Mismatch of the nail to the intact humerus was analyzed and compared between the antegrade and retrograde nailing approaches. The results showed: (1) the diameter of the medullary canal averaged 7.9-13.8 mm; (2) the minimal reaming diameter to accommodate virtual nail insertion averaged 8.8-14.8 mm for the antegrade and 8.8-29.3 mm for the retrograde approach; (3) the minimal reaming thickness of the inner cortex averaged 0.1-1.5 mm for the antegrade and 0.1-9.9 mm for the retrograde approach; (4) the percentages of cortical bone removed prior to nail insertion were 3.8-107.1% and 3.8-1,287.6% for the antegrade and retrograde approaches, respectively; (5) the eccentricity of the nail-medullary canal center were 0.4-3.4 and 0.4-10.6 mm for the antegrade and retrograde approaches, respectively. Less mismatching occurred with antegrade nailing than with the retrograde approach. Retrograde nailing requires excessive reaming at the distal part of the humerus to accommodate nail insertion. This may create bone weakness and the risk of supracondylar fracture.