Biomechanical analysis of reconstructions for sternoclavicular joint instability

A variety of reconstructive methods have been described for the treatment of sternoclavicular joint instability, yet none have been analyzed in the laboratory, to our knowledge. The purpose of the present study was to evaluate three different reconstruction techniques with use of a cadaveric model: (1) intramedullary ligament reconstruction, (2) subclavius tendon reconstruction, and (3) reconstruction with use of a semitendinosus graft placed in a figure-of-eight fashion through drill-holes in the clavicle and manubrium.

Thirty-six fresh cadaveric specimens were mounted supine on a materials testing machine in a custom testing fixture and were subjected to anterior and posterior subfailure translation to determine stiffness in the intact state after preloading. One of the three reconstruction methods was performed, and the specimens were subjected to anterior or posterior translation to failure. Changes in stiffness compared with the intact state were analyzed statistically.

In the anterior direction, the stiffness of the semitendinosus figure-of-eight reconstruction was significantly greater than that of the intramedullary ligament reconstruction but was not significantly different from that of the subclavius tendon reconstruction. The peak load to failure (as defined by translation equal to the anteroposterior diameter of the medial head of the clavicle) was 230.3 +/- 146.1 N for the semitendinosus figure-of-eight reconstruction, 84.6 +/- 45.7 N for the intramedullary ligament reconstruction, and 75.6 +/- 19.0 N for the subclavius tendon reconstruction. In the posterior direction, the stiffness of the semitendinosus figure-of-eight reconstruction was significantly greater than those of both of the other reconstructions. The peak load to failure was 241.4 +/- 49.7 N for the semitendinosus figure-of-eight reconstruction, 85.0 +/- 22.8 N for the intramedullary ligament reconstruction, and 51.5 +/- 28.9 N for the subclavius tendon reconstruction.

The figure-of-eight semitendinosus reconstruction for sternoclavicular joint instability has initial biomechanical properties that are superior to those of the intramedullary ligament reconstruction and subclavius tendon reconstruction techniques.

While it is difficult to extrapolate in vitro data to the clinical situation, the figure-of-eight semitendinosus technique has superior initial biomechanical properties and may produce improved clinical outcomes in the surgical treatment of sternoclavicular joint instability.