Sternotomy Closure With a Unique Iso-Elastic™ Polymer Cable System

Introduction
Sternal fixation with a plain wire has several known limitations, including “cut-through” into the sternum, wire breakage, untwisting of wires when loaded, and imperfect conformance of the wires to the shape of the sternum. Any one of these limitations, or a combination of several, can lead to poor stability and motion in the sternal halves, resulting in delayed or failed bone healing, increased short- and long-term pain and disability, increased risk of infection, and increased treatment costs.

The novel Iso-Elastic™ TM polymer cable system (SuperCable®, Kinamed®, Inc.) has a well-established clinical history in high-load orthopedic applications (1,2), such as in the hip, and has recently been applied to sternotomy fixation. The high strength elasticity of these cables offers much greater sternal stability as a result of the compressive force applied by the tensioned cable, while also functioning as a “shock absorber” on the construct, neutralizing loads from coughing, sneezing, and patient movement (3). The cable is made from nylon and gel-spun ultra-high-molecular-weight polyethylene (UHMWPE), with a titanium alloy locking clasp.

Surgical Technique
The closure technique is similar to the wire in that the cables are passed parasternally with a blunt passer. Tightening is accomplished with a dedicated tensioning instrument with a torque gauge that provides feedback for consistent tensioning. Four of the polymer cables are placed along the body of the sternum, with one conventional wire placed transosseously though the manubrium. An optional second wire may be placed parasternally in the body of the sternum simply to speed initial approximation of the sternum.

Summary
Surgical time is similar to that with the use of traditional 7 to 8 pass wire fixation. Initial stability achieved with the cables as assessed by manipulation of the sternal halves is much greater in all planes. The locking clasp bridges over the osteotomy and buttresses the sternum against A-P displacement, and the significant compression applied by the elastic cables provides rostral-caudal stability. If re-entry into the chest is required, the polymer cables can be readily cut with a scalpel for rapid access. Additional study should be conducted to formally assess the clinical benefits of this system.

The author finds the SuperCable for sternum closure effective and reliable, and has not seen any sternum dehiscence in about 150 cases in the past two years.

References

1. Ting NT, Wera GD, Levine BR, Della Valle CJ. Early experience with a novel nonmetallic cable in reconstructive hip surgery. Clin Orthop Relat Res. 2010 Sep;468(9):2382-2386.
2. Edwards TB, Stuart KD, Trappey GJ, O’Connor DP, Sarin VK. Utility of polymer cerclage cables in revision shoulder arthroplasty. Orthopedics. 2011 April;34(4).
3. Sternotomy Closure Force Under Cyclic Lateral Distraction: Comparison of Three Closure Techniques (2017). Data on file at Kinamed Inc.