Conditions for Preservation of Horizontal Balance of the Pelvis in Muscle Injury (Experimental Modeling of Lumbar-Pelvic Muscle Balance)
Introduction. This work deals with the study of pelvic girdle muscles functioning in violation of their function associated with pelvic trauma, ie how the muscles of the pelvic girdle provide horizontal balance of the pelvis while walking in a partial impairment of their function. Materials and Methods. To this end, condition was accepted according to which each muscle group at any time affects the system with the power proportional to the maximum possible force developed by proper muscle or group of muscles. For this purpose we have derived coefficients of proportionality for each muscle relative to the gravitational force and calculated possible efforts of corresponding muscles under their partial damage. Results of the Study. With the loss of 50 % of the power capacity of all the muscles under static hold of pelvic balance, all the muscle forces are within their physiological capabilities, while keeping about 50 % of adjustment possibilities. In the context of a larger load (1000 H) muscles are not able to cope with the task of maintaining horizontal balance of the pelvis, as maximal efforts, developed by muscles, are less than necessary. At 75% reduction in the strength of all muscle groups involved in maintaining the balance of the pelvis, the system will not be able to maintain horizontal balance of the pelvis in single-leg standing, as the maximum values, developed by the muscles, are less than effort required to maintain the balance of the pelvis. Under dynamic loads, maintaining balance of the pelvis in this case is impossible, since the magnitude of required muscular effort is much higher than the maximum possible. We can say that in this situation, the system has exhausted its possibilities of adjustment. In 50% or more decrease in strength of gluteus minimus and gluteus medius muscle, tensor fasciae latae muscle and other intact muscles, it is managed to maintain the balance of the pelvis both in a static position, and in dynamics (with weight load increased of more than twice). Although preserving the horizontal balance of the pelvis in the dynamics is possible at submaximal tension of all muscles. Additional to this decrease of the strength of optional abductor (iliopsoas muscle, quadriceps) showed that is possible to maintain the horizontal balance of the pelvis under static conditions, but it is unlikely or impossible with an increase in gravitational force by half (ie, when modeling the dynamic conditions). Conclusion. In pelvis injuries even associated with significant impairment of the function of gluteus minimus and gluteus medius muscle, and tensor fasciae latae, the restoration of function of the horizontal balance of the pelvis is possible due to other muscles of the pelvic girdle. These muscles are optional abductors, mostly it is iliopsoas muscle, anterior portion of the gluteus maximus and the direct portion of the quadriceps femoris.