Experimental identifying of the corrective capabilities of the "spring" technique in the correction of multiapical deformities of the femur

Abstract

Abstract Background. The technique of multiapical deformities correction using several orthopedic hexapods (one for each apex of deformity) is accepted as “standard”. However, usage of two or more hexapods on one segment is uncomfortable for the patient, and software calculating for each of them is difficult and laborious for an orthopedic surgeon. Usage of only one orthopedic hexapod with one software calculation is the advantage of the "spring" technique (ST) correction of multiapical deformities. But its use is limited by the fact that the corrective capabilities of this technique are still unknown. Purpose of the study was to identify by the bench test the corrective capabilities of ST and compare them with the capabilities of the "standard" technique. Materials and methods. The experiment was performed using plastic models of the femur. One-ring modules were used to fix each of the bone fragments. Foam rubber discs were used to imitate soft tissues. The mobile ring was moved relative to the base one in translation, angulation, distraction and rotation. The movement was stopped if one of the struts reached a minimum or maximum length, as well as if the one of struts touched frame or "soft tissues". The Mann-Whitney U-test used for statistical analyzes. Results. The corrective capabilities of ST when using all six struts equipped with standard threaded rods are 34-96% (on average 67%) less than with "standard" technic. When replacing 3-6 (depending on the type of movement) threaded rods with longer ones, the corrective capabilities of ST increased by 36-975% (on average 315%). This provides better ST correction possibilities in translation, varus and recurvation angulation. Conclusion. The corrective capabilities of ST in most types of movements of mobile bone fragment are better than capabilities of «standard» technic if struts of the orthopedic hexapod are equipped with threaded rods of greater length.