1.8.5 Internal fixation of lateral compression fractures (type B2)

1 Patient selection and indications

As outlined in Chapter 1.3, AO/OTA Fracture and Dislocation Classification type B2 (Young-Burgess lateral compression injury) fractures are characterized by partial disruption of the posterior arch with some degree of internal rotational instability but no vertical or posterior translational instability. Type B2 injuries result from a lateral compression force causing a unilateral internal rotation of the pelvis leading to some degree of compression or impaction of the posterior pelvic complex with an associated anterior ring injury. With posterior impaction and internal rotation directed displacement, these injuries are not likely to cause disruption of the pelvic floor ligaments and muscles, and thus, are more inherently stable and at low risk for cephalad or posterior displacements. Type B2 pelvic ring injuries encompass a broad spectrum leading to some controversy about the indications for operative treatment and the type of intervention needed. Anterior lesions include unilateral, contralateral and bilateral rami fractures, a locked symphysis, or a tilt fracture. The location of rami fractures may also be of some importance estimating the degree of displacement and the degree of fragmentation, and ultimately when choosing treatment options. Posterior lesions involve some degree of crush of the anterior sacrum or sacroiliac joint complex while maintaining an intact posterior tension band. Sacral fractures may be incomplete involving only the anterior alar cortex or a complete fracture passing through the posterior cortex [1, 2].

Lateral compression fractures are the most common type of pelvic fractures and usually can be treated nonoperatively. Unilateral B2 injuries resulting from persistent internal rotation displacement of the affected hemipelvis or continued rotational instability require operative treatment. Although some degree of internal rotation appears to be well tolerated, excessive internal rotation of the hemipelvis may cause problems with function and cosmesis. If the internal rotational deformity of the pelvis prevents a patient from rotating the lower extremity past a position of neutral rotation, a functional deficit and an abnormal gait will result. Excessive internal rotation that results in a persistent displacement of the rami fractures of 100% or more also may be an indication for operative treatment because of the possibility of a painful nonunion. Persistent internal rotation also may result in a leg-length discrepancy. Because of the normal pelvic obliquity in the sagittal plane, an apparent flexion of the hemipelvis will occur as it rotates inward on its posterior hinge resulting in a leg-length discrepancy that can be measured on an AP x-ray. This discrepancy places the ischial tuberosities at different levels making sitting unbalanced and painful. Finally, significant persistent internal rotation can lead to issues with cosmesis in thin patients. Persistent instability may cause continued pain that may be best treated by operative stabilization to allow mobilization and a more rapid return of function [3]. Ongoing pain during the nonoperative treatment phase may be a marker of persistent instability leading to a slow progression of the deformity with unacceptable alignment at the completion of treatment. Predicting which patients with B2 injuries will continue to have a progressive deformity during their treatment has been difficult. A recent study [4] assessed patients with initial nondisplaced sacral fractures resulting from a lateral compression mechanism to identify factors associated with unacceptable alignment after healing. Patients with complete sacral fractures, defined as perforation of the posterior sacral cortex, in contrast to those with only anterior sacral involvement, were more likely to have late displacement. This was also noted with patients who had bilateral rami fractures. Patients who had incomplete sacral fractures and unilateral rami fractures had no risk of further significant displacement, whereas those with a complete sacral fracture and bilateral rami fractures displaced at a rate of 68%. Obtaining stress x-rays with the patient under general anesthesia in the operating room has also been recommended to improve the diagnosis of clinical instability and the potential for further displacement of B2 injuries ( Fig 1.8.5-1 ). Another study [5] reported that 37% of patients with B2 pelvic ring injuries were treated with surgical stabilization based on instability noted during examination under anesthesia. Final indications for operative treatment include symphysis pubis injuries and the rarer special injuries: the tilt fracture and locked symphysis. The tilt fracture is an anterior injury characterized by a pubic root fracture and a symphysis disruption, in which the ramus tilts creating a prominence in the perineum that can result in dyspareunia in women [6, 7]. A locked symphysis occurs when the internal rotation causes a disruption of the symphysis instead of fractures of the pubic rami and resulting in a locked overlap of the pubic bodies [8–13] ( Table 1.8.5-1 ).

**Table 1.8.5-1** Indications for operative treatment.
Excessive deformity Inability to rotate limb past neutral Complete 100% displacement of the rami Resultant unacceptable limb-length discrepancy Unacceptable cosmetic appearance
Persistent instability Continued pain Progression of deformity on subsequent x-rays
Symphyseal disruption
Special injuries Tilt fracture Locked symphysis

2 Nonoperative treatment

Most lateral compression type B2 fractures can be treated without surgery. Patients may be mobilized early with protected weight bearing of the limb ipsilateral to the posterior lesion. In patients with an incomplete sacral fracture and no significant initial displacement, early weight bearing as tolerated is allowed with minimal risk of further displacement. Serial x-rays should be obtained after mobilization weekly for the first 3–4 weeks to ensure that alignment remains unchanged. Displacement should be measured on these x-rays, and if any progression is detected operative stabilization should be considered because early intervention yields results far superior to those obtained for late malunion surgery.

**Fig 1.8.5-1a–d** Type B2 pelvic ring injury with an ipsilateral sacral fracture and superior and inferior rami fractures. a AP pelvic x-ray. b Computed tomographic scan showing the sacral fracture. c Intraoperative C-arm image with no stress. d Intraoperative C-arm image with lateral stress demonstrating internal rotation of the hemipelvis suggestive of rotational instability and consideration of operative stabilization. (X-rays courtesy of HC Sagi, MD. Florida Orthopedic Institute).

3 Preoperative planning

Definitive surgical treatment with internal fixation is indicated when the patient is adequately resuscitated and all other major injuries have been identified and addressed. The soft tissues surrounding the pelvis should be carefully assessed, and abrasions, lacerations, and degloving injuries must be resolved prior to internal fixation. Because intraoperative image intensification is often needed, the surgical team should ensure that adequate visualization is not limited due to abdominal distention secondary to air in the gastrointestinal tract or contrast used for previous imaging studies that has not yet cleared. High-quality preoperative x-rays including an AP, inlet, and outlet views of the pelvis and a thin-cut computed tomography (CT) are mandatory. In case of any concerns about urological injury, a retrograde urethrogram and cystogram should be performed (see Chapter 1.13). The surgical plan should be based on a comprehensive review of the x-rays to identify all pelvic ring injuries and to understand the directions and degree of displacement. With this understanding a plan for reduction and fixation can be completed.

4 Surgical technique

4.1 Reduction

By definition these injuries are partially unstable with an internal rotation deformity; therefore, reduction and stabilization of the anterior ring is needed. Posterior ring stabilization is more controversial but may be done to provide additional stabilization of a complete sacral fracture, if late displacement is a concern or as an adjunct to support the anterior fixation.

Reduction of type B2 injuries is based on the degree of initial displacement. The initial alignment is sometimes so minimal that internal fixation is performed without reduction because of concerns for potential late deformity, secondary to perceived fracture instability. Reduction maneuvers should be performed for displaced fractures. Internal rotational displacement of the pelvis tends to occur with the hinge posteriorly at the sacral fracture or crushing at the sacroiliac joint area; thus, reduction maneuvers are easier to perform from the anterior ring away from the hinge. External rotation and abduction of the lower extremities may assist in the reduction and may be all that is necessary with minimal deformity. Additional external rotation force may be applied with the use of Schanz pins placed in the affected hemipelvis as a joystick to directly maneuver that portion of the pelvis. These pins most commonly are placed in the supraacetabular area but also may be useful in the iliac crest. A universal distractor can also be used over the Schanz pins and with a careful understanding of the deformity the correct vector can be obtained to complete the reduction. A reduction tool attached to the pins in the supraacetabular area on both sides of the pelvis often can be used to reduce the internal rotational deformity with distraction. In patients who have a significant flexion component of the hemipelvis, a vector can be created to correct the internal rotation and flexion by placing one pin on the stable side of the pelvis in the iliac crest and a second pin in the supraacetabualar region on the displaced side to create an oblique vector [14] ( Fig 1.8.5-2 ). Displacement in the posterior ring in this type of fracture usually is minimal and impacted; however, in some instances posterior reduction will be needed. Posterior reduction usually can be accomplished by closed techniques in these injuries. Traction on the lower extremity of the affected side is usually adequate and can be optimized by stabilization of the contralateral hemipelvis. Stabilization of the uninvolved hemipelvis can be accomplished by placing a Schanz pin into the iliac wing and proximal femur and using external fixation bars to connect the pins to a clamp on the bed or with the use of special frames [15] ( Fig 1.8.5-3 ). Traction through a distal femoral pin on the involved side can then be applied with maximal efficiency. Open reduction of the posterior ring is rarely needed in type B2 fractures because there is an intact posterior arch. So after anterior ring reduction, the alignment of the posterior ring usually is adequate. Open reduction of the posterior ring rarely is needed and these techniques are described in Chapter 1.8.6.

Although type B2 pelvic ring disruptions are among the most common types of pelvic injuries, the need for fixation and the type of fixation needed is controversial. Because the deformity is in internal rotation, the fixation should maintain alignment and resist any further displacement into internal rotation. Rotational forces about the pelvis are most simply and effectively addressed by anterior ring fixation often with external fixation, anterior subcutaneous internal fixator, ramus screws, or plate and screw constructs. The need for posterior fixation is unclear but when needed it is usually done with iliosacral screws. Each of these techniques is discussed further.

Standard external fixation is commonly used to stabilize the anterior pelvic ring in these injuries and is effective with minimal complications. Anterior subcutaneous internal fixation is a newer variant of this technique developed from experience with anterior external fixation using supraacetabular pins [16, 17]. It was developed to address the problems of pin-site infection and patient comfort issues associated with external fixation, especially in obese patients.

**Fig 1.8.5-2** Universal distractor applied with an oblique vector to correct the deformity often seen with type B2 pelvic injuries. The pin on the uninjured side is in the iliac crest and the pin on the injured side is in the supraacetabular region.

**Fig 1.8.5-3a–b** a Pelvic-stabilizing clamp attached through external fixation bars to the uninjured side of the pelvis and proximal femur to allow application of traction on the contralateral injured side of the pelvis. It is most effective to stabilize the uninjured side of the pelvis to the bed make traction on the injured side effective. b Starr frame used for closed reduction of pelvis.

The anterior subcutaneous internal fixation system uses pedicle screws placed in the supraacetabular region and a subcutaneous connection rod. A description of the technique and some early results has been published ( Fig 1.8.5-4 ). The obturator oblique C-arm image is obtained to visualize the portal for placement of the supraacetabular pedicle screw and a 2–3 cm longitudinal incision is made, centered over the area of the anterior inferior iliac spine. The starting point for screw placement, which is just proximal to the tendon origin of the rectus femoris and screw orientation, can be defined with the obturator outlet and iliac oblique C-arm images. A screw that is 15–50 mm proud of the anterior inferior iliac spine should be chosen and should have at least 60 mm intraosseous. At least 15–50 mm of the screw must be left outside of the bone so that the connection rod can be attached to the screw and passed superficial to the sartorius muscle. Once the screws have been placed on both sides of the pelvis, the appropriate connection bar can be contoured with an anterior bow and tunneled subcutaneously from one side to the other. The tunnel is located just under the skin and above the sartorius muscle. The rod is then attached to the screw on both sides and distraction can be performed to achieve reduction using appropriate tools through the rod. The pedicle screw caps are then tightened and any excess rod lateral to the screws removed with a rod cutter. The advantages of this type of fixation compared with external fixation include improved comfort and tolerance with ability to sit, stand, and roll to the sides, easier nursing care, decreased risk of infection, and maintenance of reduction with ability to serve as definitive anterior fixation. Complications reported [18] in a series of 91 patients included asymptomatic heterotopic ossification around the implants in 35% of patients, irritation of the lateral femoral cutaneous nerve in 30% (which resolved in all but one patient), a wound infection rate of 3.3%, and surgical revision due to technical error in 6.7%. Potential disadvantages compared with standard external fixation include the need for special instruments and implants and the need for a second surgery for removal.

**Fig 1.8.5-4a–g** Operative stabilization of the image shown in **Fig 1.8.5-1** . a Incisions for placement of screws to be used for the anterior subcutaneous internal fixator. **b–c** Intraoperative teardrop image obtained on the obturator outlet view to define the corridor for screw placement into the sciatic buttress. c Figure relating anatomy to C-arm image seen in **Fig 1.8.5-4b** . d Iliac oblique view to visualize starting point for screw placement and direction above the greater sciatic notch. **e–f** Images with subcutaneous internal fixator in place to stabilize pelvis. g Postoperative clinical pictures show the patient′s ability to sit upright. (Images courtesy of HC Sagi, MD. Florida Orthopedic Institute).

Anterior internal fixation also may be performed with plate and screw fixation. This technique provides reliable stable fixation with little risk of loss of reduction or fixation [19]. Plate fixation has been recommended for injuries with symphysis pubis displacement and also for pubic rami fractures also. Plate fixation of rami fractures is less commonly used, thus, other fixation methods or no fixation is more commonly considered. Symphyseal injuries can be plated through a Pfannenstiel approach with a 4- or 6-hole plate. In a patient with a symphyseal injury and a rami fracture it may be possible to plate only the symphysis, if the ramus is minimally displaced due to the strong soft-tissue attachments. If the ramus is significantly displaced or displacement occurs with manipulation of the symphysis, fixation of the ramus also is indicated ( Fig 1.8.5-5 ). Plate fixation of the ramus may be performed through the Pfannenstiel incision. If more lateral access is needed, the approach must be extended into an ilioinguinal or a modified ilioinguinal approach with only the first and third windows developed to allow the plate to be passed and screws placed safely outside of the hip joint. A Stoppa approach may also be suitable for this use. Alternatively, plate fixation of the symphysis with a medullary pubic ramus screw for fixation of the ramus has been described [20].

Medullary superior pubic ramus screws placed retrograde or antegrade also have been used to stabilize pubic rami fractures in these injuries. For the fracture mechanism in type B2 injuries, the screw will act as a strut to maintain alignment of the ramus and prevent internal rotation [20]. When placing the retrograde screws, the surgeon must stand on the side of the table opposite the ramus to be instrumented and use adequate intraoperative imaging. The inlet and the obturator outlet views are essential to confirm the proper starting point and orientation of the screw ( Fig 1.8.5-6 ). The skin incision is made at the contralateral pubic tubercle adjacent to the base of the penis or mons pubis. The starting point for the drill is just inferior to the pubic tubercle on the injured side. With C-arm image intensification, the orientation of the drill bit and eventual screw is directed within the superior ramus across the fracture and cephalad to the hip joint ( Fig 1.8.5-5 ). Antegrade screws may be used with fractures more lateral in the ramus. The same C-arm views are used to assist with the direction of the screw placement. The starting point is approximately 4 cm cephalad to the superior portion of the hip joint in the anterior pillar of the pelvis and courses toward the inferior aspect of the ipsilateral pubic tubercle. These screws are identical but just placed from opposite ends. Correct placement of these screws is technically demanding but has been successful in maintaining alignment of rami fractures with low morbidity. In a more recent review [21] of 112 patients who underwent percutaneous fixation of 145 pubic rami fractures, loss of reduction occurred in 15% of the fractures and was most commonly due to collapse of the ramus over the screw with recurrence of the internal rotational deformity. Factors associated with loss of reduction included age (elderly), gender (female) and patients with retrograde placed ramus screws [21] (see Chapter 1.8.3).