Purpose of the study: The aim of this work was to assess results after treatment by nailing of nonunion of the humeral shaft. In particular, we focused on consolidation and factors predictive of failure.

Material and method: A prospective study was conducted in 13 consecutive patients presenting aseptic nonunion of the humeral diaphysis. There were five cases after orthopedic treatment and eight cases after internal fixation. Two patients had iterative nonunions. Locked nailing was performed with three successive types of nails: the Seidel nail in four cases, the Russel Taylor nail in seven, and the ACE nail in two. Anterograde nailing was used for the first three cases and retrograde nailing for the others. All patients were followed regularly in our department. Last follow-up was one to seven years after nailing.

Results: Five nonunions (38%) did not consolidate after locked nailing. Consolidation was achieved in the other patients after four to 18 months. The anatomic result was good in these patients. Between the success and failure groups, there was no significant difference in age, gender, type of fracture, first intention treatment, delay from fracture to nailing, type or diameter of the nail, surgical access or not to the fracture site during nailing, or duration of complementary fixation. Anterograde nail insertion, used in our first three patients in this series, appeared to affect shoulder function. The retrograde route was used in other patients and did not appear to have any impact on the elbow itself or the elbow region.

Discussion: This clinical study was unable to identify clinical factors explaining failures but did provide several arguments suggesting that defective primary stability of the initial fixation could be incriminated in the failures.

Conclusion: Centromedullary locked nailing is a simple technique with potential for resolving difficult problems of nonunion. Good functional outcome can be obtained when consolidation is achieved. Rather than abandoning this technique, it would be advisable to conduct further research to determine what factors are determinant in its failures.

Purpose of the study: A clinical trial on the treatment of humeral shaft nonunions with locked nailing evidenced 5 failures among 13 cases. The circumstances leading to the nonunion, the patient’s condition, and the nailing method were not found to have a predominant effect explaining this outcome. Inversely, clinical data suggested that abnormal mobility of the nonunion appeared to result from play in the assembly. To check this hypothesis, we measured primary stability in three nailing models using cadaver bones.

Materials and methods: Three nailing models, Seidel (S), Russel-Taylor (RT) and ACE were tested, each on 5 cadaver specimens. A 1 cm segmental resection was made in the mid third of the humerus to simulate an unstable nonunion. The nailing was performed in accordance with the instructions furnished by the manufacturers. The nailed specimens were placed in a testing device which alternatively applied a rotation force around the longitudinal axis (± 0.5 Nm), an axial compression-traction force (± 20 N) and a transverse shear force applied at the level of the osteotomy (± 20 N).

Results: This study demonstrated an instability of the three nails when submitted to a rotation force or a shear force: 14 to 28° and 1.6 to 3.4 mm respectively for the RT nail; 8 to 20° and 1 to 3 mm for the S nail; 5 to 15° and 1.7 to 3.2 mm for the ACE nail. The ACE nail appeared to be more stable when submitted to compression-traction force; the S nail accepted a 0.05 to 0.65 mm play which reached 9.7 mm for the RT nail. This instability appeared to result from play in the locking systems.

Discussion: These findings would demonstrate that these nailing systems cannot, in themselves, provide satisfactory primary stability. The experimentally evidenced instability would contribute, probably in association with locally unfavorable physiological or biological conditions, to the failure rate observed when nailing is used alone.

Conclusion: The locking system for tested nails would have to be modified to eliminate play in the assembly before continuing their use for the treatment nonunion of the humeral shaft.