|SYMPOSIUM ON PELVIC TRAUMA
|Year : 2014 | Volume
| Issue : 1 | Page : 19-22
Internal fixation of pelvic injuries
Department of Orthopedics, All India Institute of Medical Sciences, Jodhpur, Rajasthan, India
|Date of Web Publication||6-Jun-2014|
Department of Orthopedics, All India Institute of Medical Sciences, Jodhpur - 342 005, Rajasthan
Source of Support: None, Conflict of Interest: None
The essence of management of pelvic fractures, a high energy injury, is multidisciplinary approach, wherein, the primary goal of treatment is hemodynamic stability. Restoration of a stable pelvic ring which allows optimum weight transmission to the limbs is the ultimate aim of any surgical procedure. Contradicting schools of thought exist between whether to fix the anterior pelvic ring first vis-a-vis the posterior ring. To some extent, the decision is guided by the operating surgeon's preference for percutaneous fixation as opposed to conventional open surgery. Anatomic reduction of the fracture remains an important goal, whether performed open or closed, as residual displacement is associated with poorer outcomes. A comprehensive literature search was conducted using the Ovid interface; 1232 English language citations relating to management of pelvic fractures were screened, out of which 34 articles were perused for surgical treatment of pelvic fractures and 21 of the above, specifically dealing with the principles and techniques and biomechanics of internal fixation of the disrupted pelvic ring, formed the basis of the present narrative.
Keywords: Internal fixation, pelvic fracture, surgical treatment
|How to cite this article:|
Elhence A. Internal fixation of pelvic injuries. J Orthop Traumatol Rehabil 2014;7:19-22
| Introduction|| |
In a sense, every patient of a pelvic ring injury merits some form of treatment or another; the spectrum of treatment, though, varies from nonsurgical care in uncomplicated stable pelvic ring injuries to formal open reduction and internal fixation for the more severe injuries. Decision making in these subtly complex situations involves patient-dependent factors (comorbidities, hemodynamic reserve, status, and quality of resuscitation), injury-dependent factors (type of pelvic ring instability), complexity of the injury (extent of soft tissue damage, time since injury), and surgeon-dependent factors (knowledge, experience, and skill of the treatment team).
Theoretically, internal fixation of the disrupted pelvic ring is indicated for an unstable fracture situation. Practically though, radiographic displacement acts as a surrogate for pelvic ring instability, thereby directing the choice of surgical intervention, ,, based on the type and extent of soft tissue damage to the stabilizing internal framework of the pelvic ring. Displacement of the posterior pelvic ring of more than 10 mm is a sign of significant posterior ring instability. Displacement of the pubic symphysis of more than 2.5 cm signifies pelvic floor disruption and displacement of the superior and inferior pubic rami of more than 1.5 cm indicates damage to the obturator-inguinal fascio-ligamentous complex.
Another important consideration for surgical treatment is deformity of the pelvic ring. Surprisingly, sometimes even "stable" pelvic ring injuries have significant rotational displacement. , On the contrary, certain undisplaced fracture situations such as the undisplaced crescent fracture or the sacral fracture are potentially unstable and can pose a significant treatment dilemma.
As the anteriorly directed force vector traverses the sacroiliac joint, which is positioned oblique to the superior-inferior axis of the sacrum, the innominate bone hinges about the sacroiliac joint, resulting in internal rotation of the pelvic ring and effecting an anterior pelvic ring disruption. Similarly, large amount of external rotation of the innominate bone is associated with a significant posterior instability. It is, however, important to remember that significant posterior instability is usually not possible without an additional break in the pelvic ring anteriorly, a potential hemodynamically destabilizing situation often requiring emergent surgical intervention in a specialist center. 
The literature relating to internal fixation of pelvic fractures is divided between two distinct thought processes relating to reduction and fixation of the completely unstable pelvic ring injury. The advocates of open surgery viz. Letournel,  Matta and Tornetta,  begin with reduction and fixation of the posterior pelvic ring as the preliminary surgical construct. The anterior ring lesion is then assessed for need of fixation, if required. Routt et al.,  and Griffin et al.,  on the contrary emphasize anterior surgical stabilization of the unstable pelvic ring as the initial building block upon which percutaneous-closed reduction and fixation of the posterior pelvic ring is performed wherever possible. There is also substantial difference of opinion on the preferred approach for the fixation of the posterior pelvic ring, between the two schools. Wherein, Matta and Tornetta  prefer to use open surgical reduction and fixation techniques, citing ease of reduction of the vertically displaced posterior pelvic ring in completely unstable situations, Shuler et al.  and Barei et al.  prefer the percutaneous iliosacral fixation technique in supine position for stabilization of the ipsilateral sacroiliac joint and sometimes even the contralateral sacroiliac joint (the transiliac transsacral screw fixation).  The supine position according to these authors is less damaging to an already hemodynamically compromised pelvic injury patient. Our philosophy for treatment of these injuries essentially revolves around two distinct thought processes; one is that the posterior pelvic ring contributes about 60% of the overall pelvic ring stability and needs to be addressed first; the other, as has also been professed by Letournel,  is that once the posterior pelvic ring disruption is reduced, the anterior ring displacement falls back in place by itself and only requires to be stabilized by plates and screws, if at all.
Fixation techniques, inter alia, require to be tailored to the patient's medical condition, hemodynamic status, injury pattern, anatomic variants, and surgeon's training and experience.  A detailed discussion of the individual techniques is beyond the scope of this text, as such, these would be discussed as broad groups of percutaneous techniques and open reduction and fixation techniques for anterior and posterior ring lesions.
Percutaneous fixation essentially comprises of external fixation and percutaneous screw fixation. External fixation has its primary role in urgent stabilization of the pelvic injury patient; however, it is a useful modality of definitive treatment for certain open book or external rotation injuries; to close a displaced anterior pelvic ring fracture and also to distract a significantly internally rotated injury to its normal reduced position. , The two most common percutaneous screw fixation techniques practiced for fixation of pelvic ring disruption are the Iliosacral screw fixation and the pubic ramus screw fixation. , Screw placement can be performed in association with open or closed reduction; the challenge, however, for the pelvic surgeon, is to obtain a stable closed reduction.
The Iliosacral screw placement entails a very clear understanding of the three-dimensional geometry of the sacrum. The screw placement is performed from a posteroinferior to anterosuperior position. The screw starts from the Ilium and ends in the body of the sacrum for ipsilateral sacroiliac joint stabilization. Routt et al.,  have also used Iliosacral screws to fix bilateral sacroiliac instability. Iliosacral screw placement is as much an art as it is science as it involves the surgeon's tactile sense of perceiving continued bony resistance while drilling in combination with continuous fluoroscopic guidance to obtain an accurate screw placement along the safe corridor. Templeman et al.,  have demonstrated that even a 5° change in the trajectory of screw placement can lead to an unsafe screw placement. Variation in sacral morphology further decreases the safe corridor for placement of this lag screw. The two prerequisites for an accurate placement of the iliosacral screw are accurate radiologic imaging and correct positioning of the patient on a wide radiolucent table top with a wide excursion of the intraoperative imaging equipment. The use of anteroposterior, cephalad, and caudad views peroperatively is extremely important to ensure the accurate and safe placement of the iliosacral screw.  Iliosacral screws can be placed in prone or supine position. The 6.5 or 7.0 mm partially threaded plain cancellous or cannulated cancellous screws are the preferred size used for this fixation. It is useful for pelviacetabular surgeons to tutor themselves in the art of screw placement in the supine position, as it enables management of the often polytraumatized patient with minimum destabilizing movement. Neurologic monitoring and navigation have been described as aids to safe screw placement but are dependent upon the resources available to each institution. ,,
The retrograde transpubic screw is another useful technique to stabilize the superior pubic ramus, low anterior column fractures. This technique is often used to address unilateral or bilateral transpubic instability.  The screw finds entry in the anterior cortex of the pubic body just inferior to the pubic tubercle. The 4.5 mm partially threaded cancellous screws are usually most appropriate to effect this fixation. It is imperative that drilling and subsequent screw placement be done under constant image intensifier control to avoid perforation of the femoral neurovascular bundle or the acetabular socket. A combination of the obturator view along with the cephalad and caudad views provides the best view for safe and accurate placement of this intramedullary splintage. Displaced fractures are best reduced using the modified Stoppa exposure or the medial part of the Ilio-inguinal approach,  wherein the pulp of the finger also acts as a guide to direct the drilling and subsequent placement of the transpubic screw. The technique is largely advocated to be pursued and practiced under supervision or by experienced surgeons to avoid disastrous complications. In our practice, we tend to use the retrograde superior pubic ramus screw only in situations where following the fixation of the posterior pelvic ring, the displaced anterior ring, even if reduced, raises some concern about potential instability.
Open reduction of the anterior pelvic ring typically entails use of the transverse Pfannensteil incision. The exposure is used to split the recti on both sides, enter the retropubic space of Retzius, sweep the recti on both sides, exposing the superior pubic ramus on both sides of the symphysis, extending up to the span of the intended length of the plate and screw device.
Once the symphysis and the rami are exposed, reduction of the symphysis or the fractured segment is the main objective. The most significant practical tip, according to our experience, at this stage of the operation, is that the reduction of the symphysis is a staged process as opposed to a one time reduction using a reduction clamp. The symphysis is reduced bit by bit using two tenaculum forceps, thereby guarding against crushing of the thin plate of bone between the symphysis and the ischial ramus. An alternative reduction technique is to obtain reduction using two unicortical screws and gradual reduction using a Jungbluth clamp. 
Once reduced, fixation of the anterior pelvic ring is achieved by plate fixation. Tile and Kellam  have advocated the use of double plating, but this is hardly ever required today, with significant improvement in the pullout strength of the plates being used nowadays.
Posterior pelvic ring fixation is traditionally associated with vertically unstable fractures. These injuries are associated with a substantial risk of retroperitoneal hemorrhage,  presence of the Morel-Lavallee lesion (internal degloving) and 25% incidence of skin breakdown following internal fixation of these fractures. , Sacroiliac joint dislocation, transiliac fracture dislocations (crescent fractures)m and iliac wing fractures can be fixed by anterior internal iliac approach (the first window of the Ilioinguinal approach). This is a preferred exposure when there is extensive soft tissue degloving of the posterior soft tissues.
Perhaps, the most important step in fixation of the above injuries is reduction of the fracture. Various methods have been described for reduction viz. Schanz pin in the iliac wing used as joysticks, screws placed in the ilium and sacrum and reduction effected by Jungbluth clamps, two tined reduction clamps placed over inferior aspect of the sacral ala and the apex of the iliac crest. Anterior fixation is usually in the form of osteosynthesis using the workhorse 3.5 mm reconstruction plate; two plates are used usually at an angle of 70° to one another. The sacral ala is the recipient of a single screw and this form of treatment is usually contraindicated in the presence of comminution of the sacral ala due to a higher risk of fixation failure. 
Posterior gateway to the pelvic ring is provided by two exposures; one through the posterior midline and the other 2.5 cm lateral to the posterior superior iliac spine.  Reduction is achieved by one of two methods; direct compression across the sacroiliac joint using a short oblique clamp through the greater sciatic notch, and deployment of the specialized Weber tenaculum forceps across the posterior arch to correct superior-inferior displacement.
Postreduction fixation techniques include Iliosacral screws, transiliac bars, and posterior tension band plates. Unstable zones 2 and 3 sacral fractures are complicated by late displacement in the superior inferior direction which might require lumbopelvic fixation. We, feel that the pelviacetabular surgeon, should train himself in the various techniques of both anterior and posterior pelvic fixation, as certain clinical scenario, as eluded to earlier in the text, obviate the usage of one technique over another; however, as is true for most surgical decisions, surgeons prefer to use the approach and technique which they are most well-versed with, which is a reasonable choice as long as the surgical stabilization allows for optimal healing and stable weight transfer across the pelvis to the lower extremities.
No narrative on pelvic internal fixation is complete without a mention of the biomechanics of fixation. Yinger et al.,  studied stiffness of various constructs individually and in combination vis-a-vis the mediolateral translation and rotation at the sacroiliac joint. These researchers reported that two Iliosacral screws or one ilio-sacral screw and one tension band plate have the most stiff and stable construct. The wide variability in the mechanical testing mechanisms justify the continued use of different fixation devices in various combinations.
In conclusion, the use of two or more points of fixation across the posterior pelvic ring, result in a stiffer construct than a single point of fixation. The experienced pelvic surgeon, though, is still the best judge on the types of fixation devices to be used; whether to use them anteriorly or posteriorly or both simultaneously, based on the personality of the fracture complex; especially in the light of the fact that surgical stabilization in most clinical studies, has not shown improved functional outcomes, rather it has demonstrated, only a lower incidence of pain and more pain free outcomes, which is a reasonable treatment objective, considering the devastating nature of the injury.
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