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.

The external fixation has been an established method in management of musculoskeletal disorders. Various prototypes are available Majority of these have specific application in trauma specially soft tissue injuries, infections and non unions. The Illizarov fixator is probably the most versatile of these with application in majority of congenital and acquired musculoskeltal disorders. However, very few of these devices are useful in management of disorders of writ, hand, foot and ankle mainly because of their size, weight, complexities of technique and patient acceptance. This paper deals with innovative mini external fixator device which is a modular system. The device is light weight, simple to use and is modular. The technique offers static and dynamic distraction, has short learning curve, light in weight and patient friendly. The device is useful in congenital conditions like CTEV, radial club hand, ulnar club hand and lengthening of meta carpals and meta tarsals. It is also useful in acute and neglected trauma including infections in forearm, wrist, hand, ankle and foot. Its special indication extends to its application in upper tibial plateau fractures as neutralization device. The basic unit with a small clamp which off loads the deforming forces in the bone by purchase of a simple K wire 1.2 to 2.5 mm and is connected to outer rod which knurled. The device has been mechanically tested and is found to be strong ad safe for use in clinical practice. The stability of device has been tested on Instrom 6556 testing machine for pull out and crush strength proving its safety in clinical use. We have used this device in clinical practice on about 3000 patients and have found t be very useful, simple and cost effective. The paper presents the basic design, biomechanics, basic special techniques and its clinical application. The paper includes example case presentation and its application.