TRIANGULAR OSTEOSYNTHESIS OF FRACTURES OF THE SACRUM IN VERTICALLY UNSTABLE PELVIC RING INJURIES

TRIANGULAR OSTEOSYNTHESIS OF FRACTURES OF THE SACRUM IN VERTICALLY UNSTABLE PELVIC RING INJURIES

Dulaev A.K., Kazhanov I.V., Presnov R.A., Mikityuk S.I.

Saint Petersburg Research Institute of Emergency Medicine named after I.I. Dzhanelidze, Saint Petersburg, Russia 

Diagnosis and treatment of the sacral fractures is still contradictable [1, 2]. Longitudinal fractures of the sacrum occur in high energy injuries in patients with polytrauma and present the component of injuries to the posterior part of the pelvic ring in 45-90 % of cases and are accompanied by spinal trauma in 20-47 % of cases [3, 4, 5]. Injuries in other anatomical fields are often more important than pelvic injury, and it influences on methods of specialized trauma care. The significance of the sacral fractures consists in both direct relation to concurrent neurological complications and the important role of the pelvic ring stabilization [1, 2, 6].
The techniques of external and internal fixation of the unstable pelvic ring have been described in the literature [3], but precise clinical recommendations and treatment protocols have not been reviewed to sufficient degree. The variety of morphology of the sacral fractures only complicates the choice of optimal surgical management, and the rate of complications and unsatisfied outcomes are still 25-60 % [5, 7]. They include posttraumatic deformation, persistent pain syndrome under physical load, and neurological complications after injuries to the roots in the lumbosacral plexus [1, 2, 8].
During the last years, the number of supporters of active surgical management for treatment of injuries to the posterior pelvic ring has increased, and some new techniques and methods for fixation of the sacral fractures have been implemented. However each way has advantages and disadvantages, and the indications for choice of one or other variant have not been presented to sufficient degree.
Objective – to evaluate the results of treatment of patients with vertically unstable pelvic injuries who underwent lumbosacral stabilization in one of the configurations (single- or double-sided) and osteosynthesis with iliosacral screws depending on the type of the longitudinal fracture of the sacrum. 

MATERIALS AND METHODS

The study was conducted with approval from the bioethical committee of Saint Petersburg Research Institute of Emergency Medicine named after I.I. Dzhanelidze and corresponded to Helsinki Declare – Ethical Principles for Medical Research with Human Subjects 2000, and the Rules for clinical practice in the Russian Federation confirmed by the Order of Russian Health Ministry, June 19, 2003, No.266.
The results of treatment of 22 patients with vertical unstable injuries to the pelvic ring were analyzed. The patients were treated in Saint Petersburg Research Institute of Emergency Medicine named after I.I. Dzhanelidze in 2013-2017. The structure of pelvic injuries according to М.Е. Muller-AO/ASIF included: С1 – 19 (86.4 %), С2 – 1 (4.5 %), С3 – 2 (9.1 %) cases. The injuries to the posterior pelvis were presented by various fractures of the sacrum according to the classification by F. Denis (1988) [1]. There were 12 (54.5 %) men and 10 (45.5 %) women.
The causes of the injuries: falling from height – 12 (54.5 %), a road traffic accident – 9 (41 %), compression – 1 (4.5 %).
The study group included the patients with the following characteristics: working age (18-65), non-severe traumatic brain injury (AIS ≤ 4), a stricture of the pelvic ring injury, which allowed the use of fixation with the metal constructs in view of transpedicular lumbopelvic fixation (LPF) and sacroiliac screws. The mean age of the patients was 33.8 ± 9.8. ISS was 24.8 ± 7.9. More detailed estimation of the patients’ condition with the scheme by H.C. Pape (2005) was conducted for determination of subsequence of surgical procedures for the pelvis and other anatomical regions [9]. According to this scheme, the patients were distributed into the following groups: stable – 5 (22.7 %), borderline – 13 (59.1 %), unstable – 5 (22.7 %), critical – 1 (4.5 %) cases.
If some life-threatening conditions were identified, the urgent surgeries were carried out. These conditions were ongoing pelvic bleeding in 3 cases, intraabdominal bleeding in 6 cases, aspiration asphyxia in 1 case, tension pneumothorax in 3 cases. Two patients had the multiple pelvic injuries in view of extraabdominal rupture of the urinary bladder (1 case) and a partial detachment of the urethra in its membrane part (1 case).
Before surgery, the patients received spiral CT of the pelvis and other injured anatomical regions. The patterns of injuries to the anterior and posterior parts of the pelvic ring and to the acetabulum, and the degree of anterioposterior, vertical, external and internal rotational displacements were precised.
In all clinical cases, the primary stabilization of the longitudinal sacrum fracture was performed with sacroiliac screws, and lumbopelvic fixation was conducted with the system based on transpedicular screws (triangular osteosynthesis). The choice of one- or two-sided configuration of LPF depended on location of the sacral fracture line in relation to the articular facet of L5/S1 vertebra. One-sided LPF was used for longitudinal fractures of the sacrum going outwards from the articular facet of L5/S1. Two-sided LPF was used for longitudinal fractures of the sacrum with a fracture line going inwards or through the articular facet of L5/S1, for bilateral fractures of the sacrum, especially H- and U-shaped. LPF was performed as the second stage for additional stabilization of the sacrum fracture.
The main morphological variants of injuries to the posterior pelvic ring, which allowed its stabilization with sacroiliac screws, were: H- and U-shaped sacral fractures with residual posttraumatic kyphosis > 10°; fragmented bilateral sacral fractures along the zones of lateral masses or sacral hiatus; sacral dysostosis (absence of anatomic free space for screws in S1 and S2 vertebral bodies, so called safe zone or “passage”); fractures and fractures-dislocations of sacroiliac joints with involvement of articular surface of the sacroiliac joint (crescent injury), when the plane of the main bone fragment of the iliac wing was projected to the sacroiliac joint over insignificant square, and it did not allow selecting any adequate points for safe placement of cannulated screws and creating the normal compression. The patients with the above-mentioned morphological structures of the injuries to the posterior pelvic ring, received the final stabilization only with bilateral lumbopelvic fixation or other technique of internal osteosynthesis. Therefore, we did not include these clinical cases into the study.
Additional LPF for a longitudinal sacral fracture was used for stable general condition of the patient within 48 hours after trauma. For severe condition, LPF was the additional procedure for sacroiliac screws in the period of complete recovery of vital functions and elimination of complications (within 2-3 weeks after trauma).Transpedicular systems were installed in acute period of injury according to the low invasive technique. Opened LPF was used in case of necessary opened reposition, decompression of neural structures in the sacral region, and in late periods of traumatic disease after correction of complications and improvement in the general condition of the patient.
During surgery, multi-plane X-ray examination of the pelvis with OEC 9900 Elit C-arc (General Electric, USA) was conducted. The additional inlets and outlets of small pelvis were used.
The short term outcomes were estimated before hospital discharge. Visual Analogue Scale (VAS) was used for estimation of pain level and terms of early vertical adjustment after surgery. The long term results of the treatment were estimated for the period from 6 months to 3 years. The functional results of the treatment were estimated with the scale by S.A. Majeed [10]. The functional capabilities and life quality of the patients with vertical unstable pelvic injuries were estimated with SF-36 [11].
Microsoft Office Excel 2010 was used for creation of the database of the patients. The statistical analysis was conducted with BioStat 2009 (Analyst Soft Inc., USA). 

RESULTS AND DISCUSSION

The pelvic belt (Medplant, Russia) was used for temporary fixation of a vertical unstable injury to the pelvic ring at admission.
The patients in stable (n = 5) and borderline (n = 6) condition received the final osteosynthesis of the anterior and posterior structures of the pelvic ring upon condition of stable hemodynamics (AP > 90 mmHg) in the acute trauma period. Fixation of fractures of the anterior pelvic ring was conducted with the cannulated screws in the anterior column of the acetabulum (n = 7) and with osteosynthesis of acetabular fracture (n = 1). A pubic symphysis rupture was fixed with the reconstruction plate (n = 2) and the transpedicular system (n = 3). LPF was used for additional stabilization of the posterior pelvis: unilateral – in 8 cases, bilateral – in 3 cases. The reconstructive surgery for the injured structures of the pelvic ring was conducted immediately after admission to the trauma center in 9 cases, and for other patients – within 48 hours (the period of relative stabilization of vital functions). In 8 cases, LPF was conducted with low invasive techniques through small approaches using the specific guiding systems.
The patients in unstable (n = 4) and borderline (n = 7) state, with unstable hemodynamics (AP < 90 mmHg), received the temporary external fixation of the anterior pelvis in the anti-shock surgery room; 3 patients received stabilization of the posterior structures with C-frame (DePuy Synthes, Switzerland). One patient received the final arresting of intrapelvic bleeding with diagnostic pelvic angiography and subsequent embolization of an injured vessel. After elimination of all life-threatening consequences of the injuries, the posterior pelvic structures were stabilized with the sacroiliac screws for 4 patients, for other patients – after dismounting of C-frame. Final osteosynthesis of the anterior pelvic ring injuries in all patients, and LPF (unilateral – 7 cases, bilateral – 4 cases) were conducted in the period of full stabilization of vital functions of the body (on average, 2 weeks after trauma). The anterior pelvic structures were stabilized with the implants: the cannulated screws in the horizontal branch of the pubic bone (n = 7), the plate for pubic symphysis rupture (n = 3), external fixation device (EFD) for 2 cases with concurrent injury to the pelvic organs. Low invasive LPF was carried out for 3 clinical cases.
In the anti-shock surgery unit, one patient in critical condition received the balloon-obturator to the aorta through the femoral artery on the injury side, pelvic stabilization with C-frame and anterior EFD, with subsequent pelvic tamponade. On the second day after admission, C-frame was dismounted, and osteosynthesis of the longitudinal fracture of the sacrum was conducted with two sacroiliac screws. On the fourth day, the sponges were removed from the pelvic cavity. On 23rd day after correction of complications (the period of full stabilization of vital functions), external fixation of the anterior pelvic ring with the reconstructive plate, and bilateral LPF were conducted. Most patients received the dismounting of the transpedicular systems within 6-12 months.
There were not any lethal outcomes in the reviewed patients. In the early postsurgical period, the complications appeared in 12 (54.5 %) patients in borderline and unstable condition. The complications were associated with the concomitant injury in other anatomical regions (sepsis, pneumonia, fat embolia, thrombosis in deep veins of the lower extremities). Neurological deficiency (sciatic nerve neuropathy) was observed in three patients. According to spiral CT of the pelvis, the unsatisfactory condition of the iliosacral screws was identified in two patients, and the screws were removed. Such errors were associated with the sacrum dysmorphia in one case and with incorrect positioning of the sacroiliac screw in S2 in other case.
The mean period of hospital treatment was 34 ± 16 days. The mean value of pain syndrome was 3.1 ± 1.7 according to VAS at the moment of discharge from the trauma center. All patients could stand in 2-4 weeks after final stabilization of the posterior pelvis.
The long term results of the treatment were estimated in 13 (59.1 %) patients within the terms from 6 months to 3 years. The quantitative estimation of the pelvis was performed with the scale by S.A. Majeed and was 89.9 ± 14.7 (min. – 60, max. – 100) [10]. Excellent and good anatomical and functional results were received in 11 (84.6 %) cases, satisfactory – in 1 (7.7 %), unsatisfactory – in 1 (7.7 %). The satisfactory results of the treatment were associated with non-union of the sacral fracture that resulted in persistent pain during significant physical load. The unsatisfactory result of the treatment in one patient was associated with the concurrent complicated injury to the lumbar spine with sciatic nerve neuropathy (complete disorder of conductivity in tibial and partial (up to 80 %) in fibular portions).
One should note that the use of triangular fixation was accompanied by vertical positioning and extension of the motion mode in early terms after surgery (two weeks). The life quality was estimated with SF-36 in 13 patients with vertical unstable pelvic injuries (the table).

Таблица. Шкала качества жизни SF-36, n = 13
Table. Life quality scales-36, n = 13

Main parameters of life quality

Mean score

Physical functioning, PF

80.9 ± 25.8

 Role-Physical Functioning, RP

70.4 ± 38.8

Bodily pain, BP

84.8 ± 20.4

General Health, GH

89.0 ± 3.1

Vitality, VT

65.0 ± 15.8

Social functioning, SF

50.2 ± 16.0

RERole-Emotional, RE

73.2 ± 39.3

Mental Health, MH

69.8 ± 17.9

PH (physical health)

49.2 ± 8.3

MH (mental health)

44.7 ± 8.8

The patients gave their written consent for publishing the clinical case. 

Clinical case

The patient S., age of 34, was admitted one and half hour after catatrauma. Glasgow Coma Scale was 15, AP – 130 and 80 mmHg, HR – 100 per min. The examination showed the clinical signs of a vertical unstable injury to the pelvic ring. The pelvic belt (Medplan, Russia) was applied. Pelvic SCT identified a pubic symphysis rupture, fractures of left pubic and ischial bones, a fragmented median fracture of the sacrum with anterioposterior and vertical displacement (Fig. 1).

Figure 1. Presurgical pelvic SCT: a) axial plane; b) frontal plane; c) sagittal plane; d) 3D reconstruction

        

The line of the median sacral fracture in the superior regions located outwards from the articular facet of L5/S1 vertebra. The fracture was classified as type 1 according to B. Isler (1990) [6]. The general severity was 34 according to ISS. The patient was categorized as “borderline” state with stable hemodynamics. In the anti-shock surgical room, osteosynthesis of a fracture of lateral sacrum and the left pubic bone with the cannulated screws was carried out, and the pubic symphysis rupture was fixed with the low-invasive transpedicular system (Fig. 2).

Figure 2. Intrasurgical X-ray images: a) fractures of anterior and posterior parts of pelvis fixed with cannulated screws; b) fixation of pubic symphysis with transpedicular system

    

Next day after the trauma, left-sided low-invasive lumbopelvic fixation with the transpedicular system was conducted for additional stabilization of the pelvic ring (Fig. 3).

Figure 3. Low invasive lumbopelvic fixation: a) guiding tubs during introduction of transpedicular screws; b) appearance of surgical wound

   

The figure 4 shows the SCT image of the pelvis in the postsurgical period.

Figure 4. Postsurgical pelvic SCT (3D reconstruction): a) frontal view; b) lateral view

   

The postsurgical period was without abnormalities. The walking with crutches and 20 % load to the left lower extremity was allowed. The patient was discharged in satisfactory condition on 25th day. He was examined after six months. The examination did not show any complaints and shortening of the lower extremities. He could walk without additional support. The motion in the hip joints was full and painless. During estimation of the long term results, the quantitative value of the total index of S.A. Majeed’s score (1989) [10] was 95 that corresponds to excellent functional results of the treatment.
Currently, the various techniques of fixation of the injured posterior structures of the pelvic ring are used. One of the most common techniques is EFD. This technique is characterized by relative simplicity, fast mounting and low invasiveness. It is especially important for treatment of patients with severe associated injury in acute period of traumatic disease. Therefore, EFD on the basis of rods is used more often for unstable pelvic injuries in comparison with other methods [5, 7]. The mounting of the device in the anterior pelvic ring does not require high surgical skills and obligatory intrasurgical X-ray control. The disadvantages include low stability of fixation (especially for posterior pelvic structures), bulkiness of the constructs, decreasing life quality and high rate of local infectious complications. Moreover, a quite difficult task is achievement of sufficient reposition of vertical displacements in the posterior pelvic ring that requires more composite constructions. Each fixation technique is often used as the first stage and subsequently can be replaced by internal metal constructs.
The literature includes some reports on fixation of the posterior pelvis with compression transsacral or sacroiliac screwed connection. In transsacral conduction, the connection is located transversely in S1 vertebral body; in sacroiliac variant – the connection goes through the posterior spines of the iliac bones [12]. The difference in location of the connection consists in creation of different support points and derivation of various effects from the compression. Such variant of fixation is similar with placement of the iliosacral screws. The difference consists in achievement of high compression of the fracture zone in the connection. It significantly increases the stability, and placement of the iliosacral connection sometimes removes the pelvic deformations of “closed book” type. The indications for use of such construct are only sacral fractures in the zone 1 according to Denis and ruptures of the sacroiliac joint. Otherwise, the risk of compression of spinal roots inside the sacral hiatus or the sacral canal increases significantly.
There is a method for fixation of sacral fractures with the plates for small bone fragments in different configurations. It includes the use of pre-modelled reconstructive plates with angle stability or 1/3 tubular plates and short sacroiliac plates [2]. For more traumatic approach, relatively low stability of fixation and high risk of infectious complications due to hypodynamia, bed rest and difficult nursing care, it remains the method of choice in treatment of sacral fractures relating to neurological deficiency or necessary decompression of neural structures. Higher traumatic potential of the approach is compensated by wide possibility for reposition in displacement of fragments that is especially helpful for delayed or late surgical interventions.
There is a method for stabilizing the injured posterior pelvis with the transiliac plate, which is installed behind the sacrum and is fixed with screws to the posterior iliac spines. This way of internal fixation promotes quite high stability of fixation with possibility of opened reposition and decompression of the sacral canal. The negative moments are traumatic potential of the surgical approach and high risk of infectious complications [3].
Sacroplasty (introduction of bone cement into the sacral vertebral bodies and lateral masses of the sacrum) is mainly used for fatigue osteoporotic abnormal fractures in older persons and is technically identical to vertebral plastics. It has the same advantages and disadvantages and has very limited indications for using [13].
Posterior bridge-like transiliac transverse fixation means the introduction of transpedicular screws into the posterior iliac spines with rod connection. The low invasive way of use of this system is difficult to use for evident vertical displacement of sacral fractures [14].
Osteosynthesis with iliosacral screws is one of the low invasive surgical interventions. This type of surgical management uses the skin punctures in the gluteal region. Spongious screws of different diameter are placed through the iliac bone and the sacroiliac joint into S1 and/or S2 vertebral body. Low massiveness of the construct and low degree of fixation of screw thread in the spongious bone do not provide sufficient stability, and limited capabilities of closed reposition in vertical displacement make this method inapplicable for vertically unstable pelvic fractures with significant displacement of sacral fragments.
In lumbopelvic fixation, the transpedicular screws are placed according to the standard technique into L4 and L5 vertebral bodies and S1/S5 or into the iliac crests. Fixation can be uni- or bilateral, depending on morphology of sacral fracture. The transpedicular systems give the high stability of fixation. The negative moments of the technique are difficulty in placement of the transpedicular screws in the sacrum and difficult modelling of the connecting rod during its subcutaneous guiding. The high profile of the heads of the standard transpedicular screws determines the high risk of bedsores in the places of the constructs.
During triangular osteosynthesis, lumbopelvic fixation with the transpedicular systems is combined with placement of the iliosacral screws. The axial load in the upper half of the human body (F1 force) goes through the spinal column to S1 body and the spinal process of L5-S1 bodies and lateral masses of the sacrum. F2 force vector is applied through the lower extremity, the femoral heads and the acetabulum to the posterior parts of the pelvic ring. Location and length of the iliosacral screw are determined on the basis of calculation of the shortest distance (L1 and L2) from the force lines (F1 and F2) in supposed vertical load by body weight to the spinning axis, which goes through the zone of a transverse sacral fracture, to balance the force moments (M1 and M2) or vector physical values characterizing the rotational action of these forces (Fig. 5).

Figure 5. Biomechanics of fixation with iliosacral screws: a) fixation with short iliosacral screw without vertical load from body weight (L1 < L2, F1 = F2, F1xL1 = F2xL2, М1 = М2); b) fixation with short iliosacral screw with load from body weight (F1 < F2; L1 < L2, F1xL1 < F2xL2, М1 < М2); c) fixation with long iliosacral screw with vertical load from body weight (F1 < F2; L1 > L2, F1xL1 ≤F2xL2, М1 ≤ М2); d) a combination of iliosacral and lumbosacral fixation (F1 < F2; L1 > L2, F2xL2 – F3x(L1 + L2) ≤ F1xL1, М2 – М3 ≤ М1)

     

Owing to biomechanical schemes, the nearer the sacral fracture line to its middle line, the higher the length of the screw (L1 + L2), and it is placed to bigger surface (L1) in an uninjured part of the sacrum. Longer iliosacral screws provides better fixation, because they have higher resistance to rotation and vertical shearing. The stability of fracture fixation is achieved by means of the force, which is proportional to the value created by interfragment compression. However in Denis 2-3 sacral fractures, creation of compression in the fracture zone is contraindicated owing to the risk of sacral roots compression. Triangular synthesis combines the advantages of both methods, resulting in significant increase in fixation stability without increasing the negative moments [4]. Lumbopelvic fixation redirects the point of application of the gravitational vector F1 to the head of the transpedicular screw in the posterior parts of the iliac bone, resulting in decrease in rotational load to the iliosacral screw, alignment of force moments F1 and F2, and providing the stability in the region of the transverse sacral fracture.
The analysis of the literature data allows separating the main causes of poor functional results of treatment of transverse sacral fractures with use of the triangular system: slow consolidation and the false joint; a fracture of the metal construct; pain syndrome in the plane of positioning the metal construct; incorrect union; iatrogenic injury to L5 neural root; evident inclination of L5 after distraction in the junction of L5-S1 on the side of fixation (in unilateral configuration of lumbopelvic fixation) [15]. Our clinical observations showed only one case of sacral fracture non-union, without other complications. For prevention of L5 inclination in the frontal plane, the transpedicular system was removed within the terms from 6 months to one year. The good and excellent functional outcomes (84.6 %) show the biomechanically substantiated reliability of this fixation technique for transverse sacral fixation. 

CONCLUSION

1. Transverse sacral fractures, which are the component of the unstable injury to the pelvic ring or are accompanied by lumbopelvic dislocation and increasing neurological symptoms, require the surgical management.
2. The high variety of morphological variants of the injury to the posterior structures requires for proper selection of an implant or combination of implants.
3. Stabilization of transverse sacral fractures is better to perform in early terms of traumatic disease, when indirect reposition with full recovery of the pelvic ring anatomy is possible, resulting in promotion of good anatomical and functional results. Triangular osteosynthesis on the basis of sacroiliac screws and transpedicular systems provides reliable fixation of the posterior pelvic ring. It allows early vertical positioning and rehabilitation. It can be actively used for patients in acute period of trauma. Low invasive techniques are preferable.

Information about financing and conflict of interests

The study was conducted without sponsorship.
The authors declare the absence clear and potential conflicts of interests relating to publication of this article.

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