34th Annual Scientific Meeting proceedings

Objectives:

The stability of implant fixation directly impacts surgical outcome in patients implanted with interlocking nails. Bone compaction has been shown to enhance initial implant stability, and the strategic placement of distal bolts can influence construct rigidity and load distribution. However, the relative contributions of bone preparation technique and bolt configuration to overall construct stability remain unclear, particularly across different bone densities.

The aim of our study was to evaluate the mechanical impact of bolt placement in compacted and non-compacted foam models of differing densities. We hypothesized that cancellous compaction will improve bone/nail interface stability regardless of bone density while bolt configurations would not have a significant effect.

Methods:

10-, 12.5-, 15-, and 20-PCF polyurethane foams simulated the distal femur of a mid-sized dog. To fit a 7mm I-Loc nail, 4-cm long central tunnels were created through either line-to-line reaming (7mm) or sequential compaction with custom mandrels (4mm to 7mm). Bolts (positions 3, 4, or 3+4) were inserted and 4 constructs/group were tested for medio-lateral bending under displacement control. Stiffness (2-4 mm) and maximum load were compared using two-way ANOVA with post-hoc Tukey (p<0.05)

Results:

Dual-bolting consistently provided higher stiffness and maximum load compared to single bolt configurations in both reamed and compacted specimens (p<0.0001). Bolt 4 showed marginally higher values than bolt 3.

Conclusions:

This study suggests that compaction techniques and strategic bolt placement enhance the immediate stability of an I-Loc nail. Further clinical validation is warranted, but this study indicates the potential for improving surgical techniques in distal femoral correction procedures.