OUTCOME FOLLOWING POLARUS NAIL FOR DISPLACED SURGICAL NECK OF HUMERUS FRACTURES: HAS A CHANGE IN IMPLANT DESIGN REDUCED HARDWARE COMPLICATIONS?

Abstract

Introduction: The Polarus nail is used in the treatment of displaced surgical neck of humerus fractures, but has been reported to have a high hardware complication rate. A recent change to 5.3 mm “non-toggling” proximal locking screws has been introduced in an attempt to minimise these complications.

The aims of this study were to determine union rates and hardware complications, and to assess whether the “non-toggle” proximal locking option prevented screw back-out.

Methods: We performed a retrospective review of case notes and radiographs of consecutive patients treated with the 150 mm length Polarus nail for acute displaced surgical neck of humerus fractures at our unit between 1st May 2002 and 29th February 2008. All patients were followed up until fracture union.

Results: Forty-nine patients were treated with the Polarus nail during the study period. Eleven patients were lost to follow-up before fracture union, so were excluded. Median age of the patients was 72 years (range: 31 to 94 years). Mean time to surgery was 10.7 days (range: two to 25 days).

Thirty-six fractures (95%) went on to unite following treatment with the Polarus nail. Of the two fractures that failed to unite one had an infective non-union and the other developed avascular necrosis with non-union of the surgical neck.

Twelve patients (32%) developed post-operative hardware complications. In nine (24%) there was backing out of the proximal locking screws, but only two patients had symptoms requiring screw removal. In five patients (13%) the nail was prominent proximally, causing impingement. In one patient (3%) the proximal screws penetrated the gleno-humeral joint, although this was asymptomatic.

There was backing-out in six of the 21 patients (29%) in which the standard 5.0 mm proximal locking screws were used. This compared with three out of 14 patients (21%) in which the 5.3 mm “non-toggling” screws were used. The difference in the rate of screw backing-out between the two groups was significant (P = 0.0474, Fisher’s Exact test). In three patients a mixture of 5.0 and 5.3 mm screws was used.

Discussion: The Polarus nail provides a stable fixation to union when used for the treatment of displaced surgical neck of humerus fractures. It is associated with a high hardware complication rate (32%), however, this is asymptomatic in the majority of cases (60%). The 5.3 mm “non-toggle” proximal locking option was found to reduce the rate of screw back-out compared with the standard 5.0 mm screw. We recommend the use of this “non-toggling” screw option for proximal locking.