Anatomical analysis of different helical plate designs for distal femoral fracture fixation.

Purpose: Helical plates potentially avoid the medial neurovascular structures of the thigh. Two implant designs for additional medial 90° helical plate in double plate constructs for geriatric patients and 180° helical plate for single plating in young patients are potential alternatives to widely used standard straight plates.

Aims: (1) assess the distances to adjacent anatomical structures being at risk when applying medial 90° and 180° helical plates with MIPO technique to the femur, (2) compare these distances with medial straight plates, and (3) correlate measurements performed during surgical dissection with CT angiography.

Methods: MIPO was performed in ten human cadaveric femoral pairs using either a 90° helical 14-hole LCP (Group 1) or a 180° helical 15-hole LCP-DF (Group 2). Using CT angiography, distances between femoral arteries and plates as well as distances between plates and perforating vessels were evaluated. Following, specimens were dissected and distances determined again. All plates were removed and measurements were repeated with straight medial plates (Group 3).

Results: Overall closest distances between plates and femoral arteries were 14.5 mm (11-19 mm) in Group 1, 21.6 mm (15-24 mm) in Group 2 and 6.5 mm (5-8 mm) in Group 3, with significant differences between Group 3 and both other groups (p < 0.001). Distances to the nearest perforating vessels were 22.4 mm (15-30 mm) in Group 1 and 1.2 mm (1-2 mm) in Group 2. Measurement techniques (visual after surgical disection and CT angiography) demonstrated a strong correlation (p < 0.010).

Conclusions: Inserting 90° and 180° helical plates with MIPO technique is safe, however, attention must be paid to the medial neurovascular structures with 90° helical plates and to the proximal perforating vessels with 180° helical plates. Helical plates can avoid irritation of medial neurovascular structures - compared with straight plates - although care must be taken during their distal insertion. Measurements during surgical dissection correlate with CT angiography.