Unstable sacral/pelvic or acetabular fracture are severe high energy fractures Surgical intervention are necessary after patient's conditions are stable. The complexity of local anatomical structure, the nearby major vessels, organ and visceral structures make the operations difficult and in high risks.

The surgical principles are concluded as:

1. Sacrum fracture with rotational instability: close reduction and iliosacral screw fixation

2. Sacrum fracture with vertical shearing instability: open reduction and ipsilateral riangular osteosynthesis with /without neurological decompression

3. Spinopelvic dissociation: open reduction and bilateral triangular osteosynthesis with

   /without neurological decompression

4. Iliac fracture with sacroiliac joint(SI) joint dislocation: close reduction with iliosacral screw fixation (for SI joint dislocation), anterior open reduction with double plates fixation (for iliac fracture)

5. Anterior acetabular/ pubic fracture: close /open reduction with plates/screw fixation.

6. Symphysis dislocation: open reduction with double plates

7. Acetabulum fracture: posterior open reduction with double plates anterior open /minimally invasive reduction with plates/screw fixation. The implementation of anterior column screw under C-arm X-ray transillumination for pubic fractures was first report in the literature in 1995, and we had this surgical method in our hospital since 2011. The first report of minimally invasive internal fixation in pelvic or acetabular in the literature was reported in 2013, and we had such minimally invasive surgical approach in our hospital since 2014. We would like to retrospectively and prospectively collect the final outcome of these patients and the comparative analysis of different surgical methods in our institution.

AO foundation published an updated fracture and dislocation classification compendium in 2018. Pelvic ring fracture is classified into ABC three type according to intact, incomplete/complete disruption of the posterior arch. Each type of injury is further divided into groups regarding of severity. The old Young Burgess classification of pelvic ring injury has been integrated into this classification. This retrospective study aim to re-classify patients who sustained unstable pelvic fracture and underwent surgery in CMUH under Dr. Tsai since 2009 according to the new system.

The investigators adopted Majeed Pelvic Score for functional outcome and EQ-5D for quality of life evaluation. A telephone survey will be conducted for all patients. Multiple logistic and linear regression analyses will be used for statistical assessment with the MPS and the EQ-5D. This will provide the investigators with the insight of the correlation between injury severity and functional/QOL outcome. Also, the investigators' study aims to determine the prognostic factors relate to poor outcome. Age, mechanism of injury, sex, ISS score, associated injury, surgical method, bladder or neurologic complication, radiologic outcome,unity of fracture will be recorded from medical chart. Statistical analysis will be conducted to identify the correlation between each factor that influence the functional and QOL outcome.

Inclusion Criteria:

1. 18 years old and above with the appropriate informed consent
2. traumatic pelvic or acetabular fracture with 2018 AO/OTA classification
3. a minimum of 48 months postoperative follow-ups

Exclusion Criteria:

1. pelvic or acetabular fractures that were pathological or non-traumatic in nature
2. patients with incomplete follow-up details
3. patients who denied surgical management
4. patients who received external fixation as part of their treatment strategy

sacral/pelvic or acetabular fracture patients