Intramedullary pin fixation in clavicular fractures: A study comparing the use of small and large pins.

The S-shaped clavicle poses a problem for intramedullary pin fixation. Stability of fracture fixation is closely related to the length of intramedullary pin engagement. This study was carried out to determine the engagement length of intramedullary pins into clavicular fractures using a small and a large pin. Seven pairs of fresh cadaveric clavicles were prepared and arranged into Group 1 and Group 2 for paired study. A mid-third clavicular fracture was created at the junction of the two curves of the clavicle. In Group 1, a 3.2 mm diameter threaded Steinman pin was introduced into the medullary canal of the clavicle by retrograde technique and the medial fragment of the fracture was drilled until the pin perforated the bone cortex. In Group 2, a 4 mm diameter threaded Steinman pin was used in the same manner. The results showed that Group 1 had an average engagement of pin into the clavicle of 9.11 cm with a ratio to total length of the clavicle of 0.59. In Group 2, the average engagement length into the clavicle was 7.17 cm with a ratio of 0.47. The difference was significant, with the smaller pin providing better fixation. The pins in both groups perforated the lateral fragment at the posterosuperior aspect and the medial fragment at the anterior aspect of the clavicle. The angle that the pin made with the long axis of the clavicle in Group 1 was 22.43 degrees and in Group 2, 26.57 degrees. Although the 3.2 mm diameter pin was more aligned to the long axis of the clavicle than the 4 mm diameter pin, the difference was not significant.