Effect of force tightening on cable tension and displacement in greater trochanter reattachment

Abstract

The purpose of this study was to evaluate cable tension during installation, and during loading similar to walking in a cable grip type greater trochanter (GT), reattachment system. A 4th generation Sawbones composite femur with osteotomised GT was reattached with four Cable-Ready® systems (Zimmer, Warsaw, IN). Cables were tightened at 3 different target installation forces (178, 356 and 534 N) and retightened once as recommended by the manufacturer. Cables tension was continuously monitored using in-situ load cells. To simulate walking, a custom frame was used to apply quasi static load on the head of a femoral stem implant (2340 N) and abductor pull (667 N) on the GT. GT displacement (gap and sliding) relative to the femur was measured using a 3D camera system. During installation, a drop in cable tension was observed when tightening subsequent cables: an average 40+12.2% and 11 ± 5.9% tension loss was measured in the first and second cable. Therefore, retightening the cables, as recommended by the manufacturer, is important. During simulated walking, the second cable additionally lost up to 12.2+3.6% of tension. No difference was observed between the GT-femur gaps measured with cables tightened at different installation forces (p=0.32). The GT sliding however was significantly greater (0.9 ± 0.3 mm) when target installation force was set to only 178 N compared to 356 N (0.2 ± 0.1 mm); p<0.001. There were no significant changes when initial tightening force was increased to 534 N (0.3 ± 0.1 mm); p=0.11. In conclusion, the cable tightening force should be as close as possible to that recommended by the manufacturer, because reducing it compromises the stability of the GT fragment, whereas increasing it does not improve this stability, but could lead to cable breakage.

The Relationship Between Arthroplasty Surgeons’ Experience Level and Optimal Cable Tensioning in the Fixation of Extended Trochanteric Osteotomy

“…This was thought to be associated with the tension not being able to be checked. In a study by Canet et al, 6 trochanteric osteotomy was performed on a synthetic femur model; re-fixation of the osteotomized fragment was made with plate and cables after placement of the prosthesis, and a model was created that mimicked walking. The tension applied to the cables was at 50%, 100%, and 150% of the value recommended by the manufacturer.…”

“… 3 , 4 Of them, while plate and cable combinations have been recounted to allow less migration and offer better stability than the horizontal cerclage wire and cable methods; studies reporting bursitis, pain, and abductor failure due to the combined use of plates and cables also exist. 1 , 2 , 4 - 6 On the other hand, some studies reported that successful clinical and radiological results have been obtained with isolated cable fixations which require less soft tissue dissection and aim at minimizing the blood supply in the osteotomized fragment. 1 , 2 , 7 …”

“…In another study conducted with artificial bone models, it was reported that less tightening of the cables during fixation after ETO would cause instability in the greater trochanter, while overtightening may lead to fractures in the cable or the bone. 6 In order to avoid these complications, manufacturers have introduced a tensioning device with a calibrated tension gauge. 9 However, many of the cables currently available in the market do not have calibrated tension gauges in their tensioning devices, and manufacturers recommend adjusting the tension in line with the surgeon’s experience.…”

“…3,4 Of them, while plate and cable combinations have been recounted to allow less migration and offer better stability than the horizontal cerclage wire and cable methods; studies reporting bursitis, pain, and abductor failure due to the combined use of plates and cables also exist. 1,2,[4][5][6] On the other hand, some studies reported that successful clinical and radiological results have been obtained with isolated cable fixations which require less soft tissue dissection and aim at minimizing the blood supply in the osteotomized fragment. 1,2,7 Although some researchers suggested that there is a decreased risk of bursitis with fixation through the use of cables after ETO, and that the circulation of the bone fragment is less affected with less soft tissue dissection, complications with the use of cables were also reported.…”

Sensor and Instrumentation for Cable Tension Quantification

“…F. Canet et al [1] analyzed the effect of force tightening and simulated walking on cable tension and displacement in trochanter reattachment with an experimental set-up. Dynamic cable load will decrease if the trochanter fracture heals.…”