Clinical treatment of osteoporotic pelvic fractures
I. Fixation of anterior pelvic ring fractures
Anterior pelvic ring fracture fixation includes external and internal fixation. External fixation through the iliac wing and above the acetabulum has some technical defects because of infection and loosening of fixation pins, etc. Currently, there are also hydroxyapatite-coated external fixation pins, which can promote bone healing and reduce loosening at the same time. Internal fixation of anterior ring fractures depends on the site of injury; injuries to the pubic symphysis are usually fixed with a bridging plate. External fixation stent combined with supraacetabular root screw and percutaneous connecting rod is another popular fixation method, but the difficulty of taking internal fixation, high incidence of heterotopic ossification and risk of lateral femoral cutaneous nerve injury are the current problems of this fixation method.
Internal fixation treatment of posterior pelvic ring injuries
Posterior pelvic ring injuries are often diverse and require extensive detailed preoperative preparation before surgery. For osteoporotic posterior pelvic ring injuries, commonly used internal fixation techniques include: iliolumbar screw fixation, sacroplasty, plate internal fixation, trans-sacral positioning rods, anterior fixation of the sacroiliac joint and the combination of various techniques.
1.Sacroiliac screw fixation
Sacroiliac screw fixation technique is commonly used in the treatment of sacral fractures and sacroiliac joint dislocation injuries in young and elderly patients, and the screws can be implanted in supine or prone position. In order to avoid rotational instability, two screws are placed in the S1 vertebral body, which are inserted and reach the midline of the sacrum. A washer is used at the nail cap and the screws are tightened with appropriate force. However, this treatment also puts the screws at high risk of loosening in osteoporotic patients, so some scholars recommend the use of cement-reinforced sacroiliac screws.
2.Sacroplasty
The treatment principle of sacroplasty is similar to that of vertebroplasty, in which a small amount of bone cement is injected into the fracture site, and the force of the injection distributes the bone cement into the cancellous bone at the fracture site, and a stable structure can be formed after the bone cement hardens. Sacroplasty can not only greatly reduce the patient’s pain, but also enable the patient to get out of bed early.
3.Plate internal fixation
Many biomechanical studies have described the advantages of internal fixators, which are now widely used in the treatment of humeral, femoral and tibial stem injuries, but this technique has not been used extensively in pelvic lesions. There are no anatomic plates specifically for pelvic ring injuries, and plates from long bones are usually bent for bridging plates for pelvic ring injuries, which are commonly used in patients with comminuted sacral fractures with vertical instability. This type of fixation provides a jointing and locking effect without exerting additional pressure on the fracture site, but this type of fixation does not completely ensure the neutralization of shear forces in bilateral iliac wing fractures. Therefore, we usually use this bridging locking plate as an additional fixation method after sacroiliac screw fixation.
4.Transsacral long screw fixation
A long threaded screw with a diameter of 6mm is passed through the dorsal side of the iliac bone, S1 vertebrae and the opposite iliac bone. Both sides of the screw are fixed with washers and nuts. Tightening the nut provides pressure to the lateral sacrum in the vertical direction of the unstable fracture plane. The amount of pressure provided by conventional screw fixation is closely related to the quality of the bone, whereas transsacral screw fixation is related to the amount of pressure of the washer placed on the dorsal iliac cortical bone. The ideal entry point is often determined intraoperatively based on the lateral view of the dorsal lateral iliac cortical bone, which is first drilled with a 2 or 8 mm drill bit and then reamed with a 4 or 5 mm drill bit after drilling to the contralateral iliac bone, and a 6 mm threaded positioning rod is placed. The indications for transsacral positioning rods are generally bilateral vertical fractures of the iliac wing combined with anterior pelvic instability, or patients with pelvic spine dislocation.
5.Sacral lumbar fixation
In a spinal-pelvic subluxation injury, the S1 or S2 vertebrae are often separated from the rest of the sacral spine and pelvis. Because of the integrity of the sacroiliac ligaments, vertical instability as in young people does not usually occur, but the patient will require bed treatment because of pain, and there is a possibility that the sacroiliac spine will protrude into the school pelvis. To prevent the progression of this instability, the sacroiliac spine is fixed to the intact dorsal pelvis, usually by placing bilateral pedicle screws on the 3rd, 4th, or 4th, or 5th vertebrae and the posterior superior dorsal iliac crest, the screws can be connected with bent screws, and the screws on each side are then connected with transverse screws. Trans-sacroiliac positioning screw fixation can also be used after iliolumbar fixation to provide interfracture pressure vertically to the fracture gap.
6.Anterior sacroiliac joint plate fusion
Some fracture instability is not located in the lateral part of the sacrum, but in the vicinity of the sacroiliac joint, and it is often difficult to achieve a satisfactory stable structure for fracture healing using sacroiliac screw fixation in osteoporotic patients. In this case, joint fusion is a better option. The skin is incised along the iliac crest, the joint is opened forward to expose the joint, the sacroiliac joint is cleared and filled with autogenous cancellous bone taken from the ipsilateral iliac crest, and two power-compression plates are fixed to the sacroiliac joint at an angle of 60 degrees. One cancellous bone screw was implanted parallel to the sacroiliac joint, and then 1-2 cortical bone screws were implanted near the medial edge of the iliac crest.
7.The combined application of various fixation techniques
Depending on the site and degree of fracture instability, it is sometimes necessary to combine several different fixation techniques to achieve strong fixation. For dorsal pelvic fixation, sacroiliac joint screws and dorsal internal fixators, or transsacroiliac joint positioning screws can be combined, while both sacroiliac joint screws and transsacroiliac joint positioning screws can be combined with the iliolumbar joint. For ventral instability, ventral plates can be combined with sacroiliac joint screws and trans-sacroiliac joint positioning screws, and in the case of multidirectional instability, the pubic isthmus can be combined with the inverted intramedullary nailing technique. The ultimate goal is to provide strong internal fixation for each type of osteoporotic pelvic ring instability.
Conclusion and outlook
The accelerated progress of an aging society is exposing surgeons to an increasing number of patients with osteoporotic and incomplete fractures. The fracture pattern in older patients differs from the high-energy injuries of younger patients, and the presence of multiple fractures and multidirectional instability is often seen. The establishment and evaluation of new fixation methods for complex osteoporotic pelvic fractures is particularly important, and more researchers are needed to further engage in clinical and biomechanical studies related to osteoporotic pelvic fractures in order to further understand the characteristics of these fractures and to better find the appropriate surgical approach and internal fixation.