Abstract

A study was done to test the strength of various configurations of tension band wiring (TBW) and we report clinical results of ‘Horizontal Figure of Eight TBW’ (H – 8 TBW).

In an experimental lab, a model of the fractured patella was mounted on a Nene tensile testing machine and various configurations of TBWs were tested in different positions of Kirschner wires. The strength of TBW and various knots securing the ends of wires were analysed on load/displacement graphs. The experimental results were compared with the theoretical results using trigonometry and mathematical equations. Since 1986, H – 8 TBW (Sonanis and Bhende modification) was used clinically in 42 patients (40 fractured patella, and 2 greater trochanteric osteotomies) in 26 males and 16 females and all patients were followed up to average 18 months.

Experimentally H – 8 TBW (0.8mm wire) could resist maximum distraction force of 700 N and achieved maximum compression. Placement of the two Kirschner wires at the mid way between centre and edge of patella at the level of fracture site achieved optimum rotational stability and compression. Crimping method of gripping the ends of wires was the most secured method (120 N). Clinically bony union using H-8 TBW was achieved in all 41 patients. Complications seen were wire discomfort in 3 patients and one death.

We conclude that H – 8 TBW achieved maximum compression, optimum K wire placement was at the 1/4th distance from the edge of the patella, and crimping the ends of wire secured best fixation.