1.    How many fractures are present?
There are obvious fractures at the left superior and inferior pubic rami.  There is mild offset or displacement of the fracture fragment.  Care should be made to assess for a possible associated fracture of the posterior pelvis.  The iliac wings appear intact.  While there is bowel gas overlying sacrum, careful evaluation of the arcuate lines suggests no obvious fracture.  Also important to note is the absence of pubic symphysis or sacroiliac joint disruption.

Note is made of left sided sacralization of L5 in the form of an enlarged left transverse process which forms an accessory articulation to the top of the sacrum.  More careful evaluation shows a vertical fracture through the enlarged left L5 transverse process that extends to that accessory articulation. A transverse process fracture in this setting is uncommon.

2.  What follow up/treatment would be appropriate?
With respect to the left acetabular fracture, while the fracture alignment appears generally well maintained with only mild offset, it should be remembered that a xray is a 2D representation and imaging such as CT with reformatted sequences would give an improved 3D representation.  Also obturator ring fractures often accompany fractures involving other areas of the pelvis, including an ipsilateral acetabular fracture, an ipsilateral or contralateral innominate fracture, or a sacral fracture. 

Isolated unilateral pubic rami/obturator ring fractures are generally considered stable and do not require surgical treatment.  However there may be occasional need for surgical reduction and fixation.  Factors that would be considered in determining the need for surgery include possible impingement of a displaced fragment on the bladder or possibly vagina or perineum.  Pubic rami fractures that are bilateral, known as a "straddle fracture", or if there was a concomitant posterior pelvic fracture are also situations where surgery would be warranted.

Isolated L5 transverse process fractures, meaning there is no involvement of the body or posterior arch, most commonly occur at the L3 and L4 vertebral levels, though any single or multiple levels may be fractured.  They are considered stable fractures and there is minimal potential for associated neurologic abnormlity or any biomechanical instability.  In this particular case, the presence of the accessory articulation would make it more likely to be biomechanically stable.  Transverse process fractures may result from direct trauma or may represent stress avulsive type fractures in cases of severe twisting.  Fractures that result from direct blunt trauma may be associated with injury to abdominal structures, including but not limited to the spleen, kidneys, and ureters.  This is especially true if the transverse process fractures involve the mid to upper lumbar vertebral levels.  CT of the abdomen should be considered in such cases.  

The presence of an L5 fracture of the makes this a more complex case.  There is strong correlation between the presence of a L5 transverse process fracture and an associated pelvic fracture.  Other studies (1,2) have found there exists a strong correlation between having an L5 transverse process fracture with having an unstable fracture of the pelvis.  While the appearance of isolated left superior and inferior pubic rami fractures in this case would suggest a stable fracture, the presence of the L5 fracture would heighten the concern for instability.  A pelvic CT in this case should be performed with further consideration for orthopedic pinning.

 

Refereneces:
1.  Starks I, Frost A, Wall P, Lim J.  Is a fracture of the transverse process of L5 a predictor of pelvic fracture instability?  J Bone Joint Surg Br. 2011 Jul;93(7):967-9.   
2.  Chmelová J1, Džupa V, Procházka B, Skála-Rosenbaum J, Báča V.  Fractures of the L5 transverse process in pelvic ring injury.  Acta Chir Orthop Traumatol Cech. 2011;78(1):46-8.