Pelvic Ring External Fixation

Indication. Temporary — and occasionally definitive — external fixation of an unstable pelvic ring, used most often as damage control in the haemodynamically unstable polytrauma patient. The frame reduces pelvic volume, tamponades venous bleeding and holds the ring while the patient is resuscitated and before definitive internal fixation. Absolute indications - Haemodynamically unstable patient with an APC II-III or vertical shear pelvic ring injury and persistent hypotension despite a pelvic binder and resuscitation

• Open pelvic fracture with massive haemorrhage requiring immediate volume reduction and tamponade
• Damage-control orthopaedics in the polytrauma patient with the lethal triad (acidosis, hypothermia, coagulopathy)
• Unstable pelvic ring with an associated bladder or rectal injury requiring urgent laparotomy and simultaneous pelvic stabilisation Relative indications - APC II or LC III injury with borderline haemodynamics (a transient responder) as a bridge to definitive fixation
• Vertically unstable pelvis requiring posterior C-clamp supplementation when sacroiliac screw placement is delayed by the patient's physiology
• Open-book pelvis with greater than 2.5 cm of symphyseal diastasis and an ongoing transfusion requirement despite a binder
• A patient requiring prolonged transport or transfer to a definitive trauma centre Contraindications. Absolute: a stable pelvic ring pattern (APC I, LC I, isolated pubic ramus fractures) where a frame adds morbidity without benefit; an isolated acetabular fracture without pelvic ring instability; and a patient in cardiac arrest with no return of spontaneous circulation after 15 minutes of resuscitation. Relative: severe osteoporosis or an iliac wing fracture precluding adequate pin purchase; local soft-tissue contamination or a Morel-Lavallée lesion at the planned pin sites (use an alternative corridor); and a stable patient in whom definitive internal fixation within 24 hours is realistic (proceed straight to ORIF). The one decision that matters. Every anterior frame is damage control — a bridge, not the final operation. The choice the operator actually makes at the bedside is which pin corridor to use:

Consent specifically for LFCN injury (up to 30 percent), pin-site infection (10-25 percent), malreduction or loss of reduction, and the near-certain need for later definitive internal fixation. Setup. Supine on a radiolucent flat-top or fracture table, with the abdomen and pelvis widely prepped for possible laparotomy and both legs prepped free if reduction manoeuvres or traction are anticipated. The pelvic binder stays in place until the frame is tightened. Position the C-arm so that AP, inlet, outlet, obturator oblique and iliac oblique views are all obtainable without repositioning. General anaesthesia with invasive arterial monitoring; avoid induction hypotension and have the massive transfusion protocol and blood products immediately available.

The goal is to reduce and stabilise the unstable pelvic ring with an anterior frame while protecting the lateral femoral cutaneous nerve, the sciatic notch contents, the hip joint and the inner table — then to add posterior control for vertically unstable patterns. The supra-acetabular exposure is laid out step by step below, with the corridor and its danger structures described inline where they are encountered.

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Immediate post-operative care (day 0-3). Continue resuscitation and monitoring in ICU or HDU. Check haemoglobin, lactate, base deficit and coagulation every 6 hours until stable. Pin-site care is daily chlorhexidine cleaning with sterile dressings. Start DVT prophylaxis — mechanical sequential compression plus LMWH once the bleeding risk permits. Maintain frame stability: no early mobilisation or weight-bearing. Transition to definitive internal fixation. External fixation is a bridge, not the definitive treatment. Plan conversion within 5-7 days once the patient is physiologically stable. Prerequisites: lactate less than 2 mmol/L and base deficit less than 4 mEq/L, haemoglobin stable without transfusion for 24 hours, coagulation normalised, no active infection or pin-site sepsis, and CT confirming pin position and residual displacement. Definitive fixation options depend on the residual injury: symphyseal plating for residual symphyseal diastasis greater than 2.5 cm; percutaneous sacroiliac screws for the posterior ring (most common); open reduction and internal fixation for complex sacral fractures or associated acetabular fractures; and combined anterior and posterior constructs for vertically unstable patterns. Remove the pins in theatre at the time of definitive fixation, debride and culture the sites if there is any sign of infection, close them with absorbable sutures or allow secondary healing, and continue antibiotics for 48 hours post-removal if the sites were clean. Rehabilitation after definitive fixation. Touch or partial weight-bearing (about 20 kg) for 6-12 weeks depending on posterior ring stability, progressing guided by radiographic healing. Hip abductor strengthening and core stabilisation from week 6. Return to work is around 3-6 months for desk-based roles and 6-12 months for manual labour, with long-term follow-up for post-traumatic arthritis, leg-length discrepancy and chronic pain.

Biomechanical rationale. External fixation of the unstable pelvic ring reduces pelvic volume by 10-15 percent and increases stiffness by 50-70 percent, providing tamponade of the low-pressure venous bleeding that accounts for 80-90 percent of pelvic haemorrhage. The anterior frame alone provides rotational stability but insufficient vertical control in type C injuries, which is why posterior supplementation is required for vertically unstable patterns. Classification context — the Young-Burgess force vectors. Indications and stability hinge on the mechanism. The patterns referenced throughout this operation map onto the standard Young-Burgess classification:

In the Tile mechanical classification these correspond directly: type A patterns are stable, type B (including open-book APC II and lateral compression) are rotationally unstable but vertically stable, and type C (APC III and vertical shear) are completely unstable in both planes — the group that always needs posterior control alongside the anterior frame. Damage-control timing and mortality. Application of external fixation within 30-60 minutes of arrival in the haemodynamically unstable patient is associated with reduced transfusion requirements and improved survival; delay beyond 90 minutes correlates with increased mortality from exsanguination. The combination of a pelvic binder, external fixation and selective angioembolisation forms the modern resuscitation algorithm. Supra-acetabular versus iliac crest pins. Supra-acetabular pins give superior biomechanical stability and lower loosening rates than iliac crest pins, and their corridor allows connection to a posterior C-clamp for vertical shear. Iliac crest pins are faster to insert but have higher infection and loosening rates (greater than 30 percent by 3 weeks) and are reserved for rapid damage-control situations. Transition to definitive fixation. External fixation is a temporary measure. Conversion to internal fixation within 5-7 days minimises pin-site infection and allows definitive reduction and stabilisation. Prolonged external fixation (greater than 3 weeks) is associated with pin-site infection rates exceeding 25 percent and loss of reduction in vertically unstable patterns.