Critical factors in cut-out complication after Gamma Nail treatment of proximal femoral fractures

Abstract

Background: The most common mechanical failure in the internal fixation of trochanteric hip fractures is the cut-out of the sliding screw through the femoral head. Several factors that influence this complication have been suggested, but there is no consensus as to the relative importance of each factor. The purpose of this study was to analyse the cut-out complication with respect to the following variables: patients' age, fracture type, fracture reduction, implant positioning and implant design.

Methods: 3066 consecutive patients were treated for trochanteric fractures with Gamma Nails between 1990 and 2002 at the Centre de Traumatologie et de l'Orthopedie (CTO), Strasbourg, France. Cut-out complications were identified by reviewing all available case notes and radiographs. Subsequently, the data were analysed by a single reviewer (AJB) with focus on the studied factors.

Results: Seventy-one cut-out complications were found (2.3%) of the 3066 trochanteric fractures. Cut-out failure associated with avascular head necrosis, pathologic fracture, deep infection or secondary to prior failure of other implants were excluded from the study (14 cases). The remaining 57 cases (1.85%, median age 82.6, 79% females) were believed to have a biomechanical explanation for the cut-out failure. 41 patients had a basicervical or complex fracture type. A majority of cut-outs (43 hips, 75%) had a combination of the critical factors studied; non-anatomical reduction, non-optimal lag screw position and the characteristic fracture pattern found.

Conclusions: The primary cut-out rate of 1.85% was low compared with the literature. A typical cut-out complication in our study is represented by an unstable fracture involving the trochanteric and cervical regions or the combination of both, non-anatomical reduction and non-optimal screw position. Surgeons confronted with proximal femoral fractures should carefully scrutinize preoperative radiographs to assess the primary fracture geometry and fracture classification. To reduce the risk of a cut-out it is important to achieve both anatomical reduction and optimal lag screw position as these are the only two factors that can be controlled by the surgeon.

Figure 1

Assessment of lag screw positioning in the femoral head. a. the eleven-zone template of the head; b. the sagittal plane of the head, in which the screw position was recorded.

Figure 2

Cut-out patterns (two-dimensional interpretation). Primary position of the lag screw in the femoral head (points in the zone template), direction of migration and approximate penetration point of the lag screw (arrows). Red arrows: 31-B2.1 (basicervical) fractures, green arrows: 31-A3.3 fractures, black arrows : other fractures; 43 cases, central cut-out has not been considered.

Figure 3

Yearly distribution of cut-out complication. Red arrow: introduction of the Trochaneric Gamma Nail.

Figure 4

Comparison of relative frequency of patient age groups for the non-cut-out group (n= 3009), and cut-out group (n= 57).

Figure 5

Comparison of the fracture types for proximal femur (AO 31) between non-cut-out and cut-out group. * statistically significant overrepresentation (p<0.001).

Figure 6

Frequency of lag screw cut-out in relation to the position in the femoral head. Total number of screws in each zone is represented by the numerator (n = 2610), and the number of screws that cut-out in each zone is represented by the denominator (n = 55).

Figure 7

Venn diagram: interrelations between critical cut-out factors. The figures represent number of cases in each category.