The Gamma nail is frequently used in unstable
peri-trochanteric hip fractures. We hypothesised that mechanical failure
of the Gamma nail was associated with inadequate proximal three-point
fixation. We identified a consecutive series of 299 Gamma nails
implanted in 299 patients over a five-year period, 223 of whom fulfilled
our inclusion criteria for investigation. The series included 61
men and 162 women with a mean age of 81 years (20 to 101). Their fractures
were classified according to the Modified Evans’ classification
and the quality of fracture reduction was graded. The technical
adequacy of three points of proximal fixation was recorded from
intra-operative fluoroscopic images, and technical inadequacy for
each point was defined. All patients were followed to final follow-up
and mechanical failures were identified. A multivariate statistical
analysis was performed, adjusting for confounders. A total of 16
failures (7.2%) were identified. The position of the lag screw relative
to the lateral cortex was the most important point of proximal fixation,
and when inadequate the failure rate was 25.8% (eight of 31: odds
ratio 7.5 (95% confidence interval 2.5 to 22.7), p <
0.001). Mechanical failure of the Gamma nail in peri-trochanteric femoral
fractures is rare (<
1%) when three-point proximal fixation is
achieved. However, when proximal fixation is inadequate, failure
rates increase. The strongest predictor of failure is positioning
the lateral end of the lag screw short of the lateral cortex. Adherence
to simple technical points minimises the risk of fixation failure
in this vulnerable patient group. Cite this article:
