External fixation apparatus for the treatment of pelvic ring injuries: a general concept

According to domestic and foreign authors, the number of pelvic injuries has doubled in the last decade and the situation is expected to worsen. Accordingly, pelvic surgery is developing both in terms of tactics for providing specialized medical care and in terms of surgical intervention techniques.

We divided all pelvic injuries into two groups, the treatment of which is fundamentally different. The first group includes fractures of the anterior and posterior pelvic half-rings, ruptures of the pubic symphysis and sacroiliac joint (vertical injuries and fractures). According to our data, these fractures account for 77% of all injuries. The second group includes fractures and fracture-dislocations of the acetabulum (23% of all pelvic injuries).

The stabilization of the pelvic ring involves the sacroiliac joints, which have a special anatomical configuration, the ligaments and muscles of the pelvic girdle, as well as variable intra-abdominal pressure, which determines the degree of tension in the pelvic floor, transmitted to the bones involved in the formation of the outlet from the pelvis.

The pelvic girdle together with the sacrum is based on a spherical vault, constructed on the basis of general architectural laws. To dampen loads, the vault is "separated by elastic layers". Accordingly, the posterior part of the pelvis and two lateral parts are distinguished. An impression of the frontal section of the pelvic girdle of a corpse showed a spherical vault, which is located vertically, and the spinal column rests on its top.

The arch passes through the junction of the spine with the sacrum and the centers of the hip joints. In the initial position of the pelvic girdle, the centers of the hip joints and the support point of the spine on the sacrum lie in the same frontal plane. Farabeuf showed that after separating the articular parts of the sacrum by sawing, installing it back and connecting the pubic bones in the initial position of the pelvis, the separated part did not fall out. Thus, the sacrum is the key of the arch. Moreover, P.F. Lesgaft showed that the sacrum in the area of the articular surface has the shape of a wedge, narrowed downwards and forwards. Consequently, the body with its weight cannot shift the sacrum forwards and downwards. Thus, the bone geometry of the sacroiliac joints provides rigid stabilization of the pelvic ring.

With alternating loads, the ligamentous apparatus of the pelvis plays a major role in stabilizing. The spinosacral and tuberosacral ligaments serve as ties of the pillars of the pelvic ring vault. Muscle fibers are embedded in their thickness, ensuring the maintenance of their taut state. These ligaments represent a group of relatively rigid stabilizers of the pelvis. The ligaments of the pubic symphysis are also included in this group. The muscles of the pelvic girdle also participate in stabilizing the pelvis and are dynamic stabilizers.

Thus, the pelvic girdle is a complex multi-component spatial structure. In case of vertical damage to the pelvic ring, as a rule, there is a violation of the relationship of the key of the vault - the sacrum with the pillars - the innominate bones. It follows from this that in case of vertical damage to the pelvic ring, it is fundamentally important to restore the vault and reliably stabilize it.

The sacroiliac joint is a true joint with articular cartilages, synovial membrane and capsule, supported by the anterior and posterior sacroiliac ligaments. The joints are variable, often asymmetrical and incongruent: on the iliac bones, their surfaces are longer and narrower than on the sacrum. The latter can make small (up to 5 mm) rotational movements around the frontal axis below the second sacral segment, where, corresponding to the protrusions of the sacrum, there are depressions in the articular surfaces of the iliac bones. Above this axis, the sacrum narrows in a wedge-shaped manner not only in the caudal but also dorsal directions. Such a mechanism normally ensures rotational mobility of the joint, as well as spring force during walking.

Thus, the axis of extremely limited rotation in the frontal plane of the hemipelvis relative to the sacrum is at the level of the second to third sacral vertebrae. It is in this zone that the moments of forces acting on the pelvic ring in the cranial and caudal directions are balanced. The introduction of intraosseous rods into the iliac bones through the crest to a depth of 5-7 cm in the zones located around the axis of rotation (at the level of the axis, above and below it) of the sacroiliac joints ensures minimal mechanical impact on the ilium during repositioning of the hemipelvis, which allows avoiding additional damage to the iliac bones and achieving repositioning of the pelvic bones with minimal effort, as well as minimizing the load on the external fixation apparatus with the pelvis balanced after repositioning.

The external fixation device must have a wide range of repositioning capabilities and ensure reliable fixation of the pelvis. The developed external fixation device for the treatment of pelvic ring injuries with displacement meets these requirements. Its peculiarity lies in the formation of support on the iliac bones, with 2 rods installed in the supraacetabular region, in the projection of the lower pole of the sacroiliac joint. 2 rods are installed in the iliac crests. In case of fresh injuries and fractures, 3 rods correctly installed through the iliac crest are sufficient. The rods are attached to the support assembled from the components of the Ilizarov apparatus. After this, the pelvis is repositioned and stabilized in the device. In this case, along with other pelvic ring injuries, the reconstructed pelvic vault is also stabilized.

An external fixation device applied to the damaged pelvis in compliance with the general concept ensures repositioning, reliable stabilization, early activation with loading on both limbs, and improved treatment outcomes.

Candidate of Medical Sciences, Head of the Research Department Khabibyanov Ravil Yarkhamovich. External fixation device for the treatment of pelvic ring injuries: general concept // Practical Medicine. 8 (64) December 2012 / Volume 1

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