1.1 Patient selection and indications

The pubic symphysis is a nonsynovial amphiarthrodial joint that is formed at the junction of the two innominate bones anteriorly. The joint comprises a fibrocartilaginous disc that is stabilized by the anterior capsular and ligamentous structures. The pelvis is a stable unit when the intact symphysis is combined with the posterior ligamento-capsular structures stabilizing the sacroiliac joints ( Fig 1.8.4-1 ). Therefore, by definition, a traumatic injury to the pubic symphysis that results in widening is associated with some posterior soft-tissue injury if the innominate bones remain intact. The typical mechanism of injury for an open book (B1) pelvic ring injury is due to a force directed from anterior to posterior, such as that seen in a motorcycle crash or an equestrian injury ( Fig 1.8.4-2a ). Another mechanism of injury is an external rotation or abduction force applied to either or both legs ( Fig 1.8.4-2b ).

In most open book injuries, the pubic symphysis is disrupted without any associated anterior ring fractures [1] ( Fig 1.8.4 3 ). If anterior fractures occur in conjunction with a pubic symphysis dislocation, these are typically located in the pubic body near the midline (parasymphyseal fractures) or at the junction of the pubis and superior pubic ramus. Fractures of the ramus involving the obturator ring occur but are uncommon in open book injury patterns. In most cases fractures of the pubic ramus do not require internal fixation, as there is little tendency for increasing gap formation or further displacement to occur (assuming the pubic symphysis and any associated relevant posterior ring injuries have been stabilized) [1, 2]. The associated soft tissues that limit further displacement of pubic ramus fractures include the pectineal ligament (of Cooper), the inguinal ligament (of Poupart), and the pectineal muscle. This has been confirmed clinically in rotationally unstable patterns [1, 2]. Of 29 patients with open book injuries, the anterior lesion was a pure pubic symphysis dislocation in 23 cases, a pubic symphysis dislocation associated with a ramus fracture in four cases, and a ramus fracture with an acetabular fracture in two cases [1]. In a larger series of pelvic ring injuries not limited to open book patterns, only 17 (16%) of 105 obturator ring fractures in 127 patients required internal fixation. Of the 88 ramus fractures not fixed, none required delayed fixation for instability, loss of reduction, or nonunion [2].

Wide displacement (exceeding 20 mm) is probably the only indication for consideration of operative fixation of ramus fractures associated with open book pelvic injuries [2]. However, pubis or parasymphyseal fractures have limited soft-tissue constraints and require fixation more frequently when associated with an open book pelvis injury pattern and a pubic symphysis disruption. In these patterns, the plate length for pubic symphyseal fixation can be extended to support the pubis fracture with good results expected.

Controversy continues regarding the definition of a pubic symphysis dislocation that requires operative stabilization. The original recommendation was an absolute widening of 2.5 cm consistent with a significant injury of the anterior sacroiliac ligaments [3–5]. Open book injuries with less than 2.5 cm of separation of the pubic symphysis have traditionally been considered stable and are amenable to nonoperative treatment. However, many orthopedic trauma surgeons have taken a much more aggressive approach to the treatment of pubic symphysis dislocations. This is based on a more thorough appreciation of the injury as demonstrated on computed tomographic (CT) scans, combined with their clinical experience. It is fallacious to apply a single static measurement of symphyseal widening to all pelvic ring injuries given the following:

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  The actual size of the pelvis varies significantly, and thus a widening of the anterior ring will affect the injury to the posterior ring.

  
  
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  Radiographic measurements are notoriously inaccurate.

  
  
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  Significant variable “recoil” occurs following injury. This may mask more significant associated posterior ring lesions that have occurred despite a smaller measurement of the symphyseal separation.

  
  
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  Oftentimes, binders, sheets, or simple repositioning of the lower extremities may have occurred at the time of the AP pelvis x-ray and a partial reduction may be present.

Circumferential sheeting has been shown to effectively and partially reduce the rotationally unstable pelvis, and this may lead to a gross underestimation of the extent of the injury to the anterior pelvis [6]. In fact, static x-rays may lead to underestimation of the actual injury, even if no pelvic manipulation has occurred. Stress x-rays were performed on a series of 22 patients with a symphyseal diastasis between 1 and 2.5 cm to determine the extent of pelvic ring instability. Interestingly, despite an injury, radiographic measurement of an average diastasis of 1.8 cm, the average diastasis with applied stress was 2.5 cm. This intraoperative stress examination has led to a change in the treatment plan in more than 25% of patients [7].

Results of a recent biomechanical study [8] evaluating the symphyseal widening that occurred with an externally applied load has further complicated the application of a single numerical value to identify pelvic ring injuries requiring operative treatment. In this study, both constrained (external rotation only) and unconstrained (also allowing flexion and extension) testing was performed. The average pubic symphysis separation at the time of anterior sacroiliac joint failure was 2.2 cm overall; this is strikingly similar to the value of 2.5 cm that is so frequently used. However, only 20% of the 20 specimens failed in the range of 2–3 cm (range of values, 1–4.5 cm). In the unconstrained testing, the sacrospinous and sacrotuberous ligaments remained intact in all specimens, indicating that these ligaments may not be torn at the time of anterior sacroiliac ligament injury associated with pubic symphyseal dislocation [8].

Summarizing the indications for internal fixation of open book injuries is difficult, given the paucity of definitive clinical studies that correlate well with existing anatomical and biomechanical studies. It is often difficult to determine pelvic instability and associated ligamentous injuries from a single static AP pelvic x-ray. The indications for stress x-rays are unclear, and it is uncertain what value should be used as gold standard to indicate injury to the ligaments of the posterior pelvis and the need for operative stabilization. Although the value of 2.5 cm is a good place to start, there is incredible variability in the degree of pubic symphyseal separation that results in presumed pelvic instability requiring fixation. Certainly, injuries with greater than 2.5 cm of diastasis require fixation but the indications likely extend to many injuries with much less symphyseal separation.

The timing of definitive surgical stabilization depends on the hemodynamic stability of the patient (discussed below), the management priorities of any associated injuries, and the characteristics of the patient. Open book pelvic injuries occur in people of all age groups but are more frequently observed in patients with good bone quality. The associated pelvic ring injuries will determine the need for augmentative pelvic fixation as well as the order of fixation ( Table 1.8.4-1 ).

1.2 Acute stabilization

Most anterior pelvic ring injury stabilization procedures can be performed after a thoughtful evaluation, preoperative planning, and prioritization of other injuries. However, in certain circumstances, urgent or emergent stabilization is necessary. In the hemodynamically unstable patient who is undergoing a laparotomy for an associated abdominal or pelvic visceral injury, acute stabilization is often warranted. Pubic symphyseal stabilization provides pelvic stability, facilitates patient management, and may limit ongoing blood loss in the pelvis. Internal fixation obviates the need for any anterior external fixator devices, which may be cumbersome or may limit patient positioning for other procedures. In unstable patterns (type C), acute anterior pelvic internal fixation of the symphysis will often help to reduce the posterior pelvis until definitive fixation can be performed. Pubic symphyseal disruptions with an open traumatic wound in the perineum will often be associated with rectal injury, fecal contamination, and/or the need for a diverting colostomy. In these instances, internal fixation may allow for pelvic stabilization and facilitate wound care in the perineal region. An associated urological injury that requires acute repair may also benefit from simultaneous pubic symphysis stabilization and internal fixation. The presence of a suprapubic catheter is not a contraindication for internal fixation of the pubic symphysis. Although the risk of infection is likely increased due to the presence of an associated urethral or bladder injury, symphyseal plating has been performed with success and infection remains unlikely. In one small series [9] reviewing a multidisciplinary approach to operative fixation of pelvic ring disruptions associated with bladder or urethral injuries, the pelvic ring injury and the urological injury were both repaired acutely with an overall infection rate of less than 5%.

4.1 Access

The surgical approach to the pubic symphysis has been described previously (see Chapter 1.6). In most circumstances the Pfannenstiel approach is used for exposure, reduction, clamp application, and plate placement ( Fig 1.8.4-5 ). In circumstances where a previous or simultaneous midline laparotomy incision has extended too far distally (into the region of the proposed Pfannenstiel approach), the laparotomy incision can be used for access and fixation of the pubic symphysis; however, this is not optimal or recommended. A separate surgical approach for the anterior pelvic fixation is preferable whenever possible.

If peripheral access is necessary (for reduction of associated parasymphyseal or medial rami fractures), the midline rectus split can be extended proximally to enhance exposure and allow clamp applications and/or implant placement. This can usually be accomplished without extending the skin incision. Instead, dissection of the subcutaneous fat from the anterior rectus fascia proximally will typically allow a more proximal rectus split. Associated anterior column acetabular fractures or peripheral ramus fractures that require fixation often necessitate more extensive surgical approaches. The development of the Stoppa approach allows for dissection along the pelvic brim and allows access for reduction and implant placements [13, 14]. On occasion, the lateral window of the ilioinguinal approach or the entire ilioinguinal approach may be necessary to allow adequate visualization, reduction, and implant placement for some associated ramus or anterior column acetabular fracture patterns.