How to Read an AP Pelvis

I saw the Quick Guide to reading a Chest X-ray over at ScrubNotes, and decided to publish the ortho version: How to read an AP Radiograph of the Pelvis. As with the CXR, it is important to evaluate the AP radiograph of the pelvis using a systematic approach. Here is that approach that I have been taught.

There are six lines that one should evaluate when looking at an AP radiograph of the Pelvis.

1. The iliopectional line to evaluate the anterior column.

2. The ilioischial line to evaluate the posterior column.

3. The dome of the acetabulums.

4. The 'tear drop' to evaluate the anteroinferior portion of the acetabular fossa.

5. The anterior rim of the acetabulum.

6. The posterior rim of the acetabulum.

It is also, of course, important to evaluate the rest of the bony structures visible on the radiograph, including the pubic rami, the SI joints, the neck of each femur, the visualized lumbar spine and sacrum, and the pubic symphysis.

Fractures in the pelvis can be difficult to visualize and if there is doubt, one can order additional views, including inlet and outlet views to further evaluate for rami fractures. The inlet view will allow for evaluation of the superior rami for fractures and the pelvis for anterior-posterior displacement of the pelvis. Outlet views will allow for evaluation of the inferior rami for fractures and for determination of superior-inferior displacement of the pelvis. Judet views are one additional study that can be ordered to evaluate the acetabulum. These views are shot at a 45 degree angle to the pelvis. The obturator oblique radiograph will allow for evaluation of the anterior column and the posterior wall of the acetabulum. The iliac oblique, conversely, will allow for evaluation of the posterior column and the anterior wall of the acetabulum.

If there continues to be doubt, it is appropriate to order a CT scan of the pelvis with 2.5mm (MSK) cuts. A normal CT of the pelvis will take 5mm cuts, which may lead one to miss subtle fractures. The MSK pelvis will allow for full and detailed evaluation of all of the osseous structures of the pelvis and assist in the determination of what pathology is present, if any. It is important to remember, however, that all classification systems for pelvis fractures are based on plain radiographs, and as such, are necessary for operative planning.

I want to start posting about different fracture classification systems soon - sort of like the "For my own Edification" posts at Trauma Bay. The first will be a post about pelvic fractures, and I hope to get it up in the next few days. I'm an action sort of learner. I learn by doing - and so, as I go over these things, I'm going to start keeping my notes here.

Image Source: KUMC Radiographic Anatomy

The Good Medical Student

The first few months of the year are prime time for 4th year medical students who are interested in matching in orthopaedic surgery. A couple of groups of medical students have rotated with our service by this point, and overall, there is an interesting dichotomy of students. Some of the students are too aggressive, and they end up coming across as a real jerk. Others are quieter than a church mouse. They stand in the corner and you'd never even know that they were there. Not too many, frankly, have been in between.

I thought I would write this post, because I remember doing my first ortho rotation and not really know what to do, especially in the OR. Here are some tips on how to be a stand-up student (especially if you are going to do an away rotation) and increase your chances of matching.

1. In the OR, always help move the patient to and from the bed. If the nurse is standing by the patient, ready to help move the patient, ask him/her if they would like you to take their place. The circulator has a lot of stuff to do, and if you do this job, they will greatly appreciate you.

2. When you walk into the room, introduce yourself to the circulator and the scrub. Put on gloves and get ready to help move and position the patient. Stand by the patient and assist the anesthesia folks if they need anything.

3. Learn where things are kept in the room. If someone needs something, offer to go and get it. You have no idea how helpful this can be!

4. If the patient needs a foley to get the case started, volunteer to put the foley in. If you need help, ask one of your residents to watch you. I know you are on an orthopaedic surgery rotation, but nothing says you can't to do this simple/quick procedure to help move the room along. I do foleys all the time as an intern, and I will continue to do them if they need to be done. The goal is to minimize delay and keep the day in the OR moving. The faster the OR is over, the faster you (and your resident/attending) get to go home!

5. Make sure the scrub has gloves and a gown for you.

6. Ask the circulator if they need help prepping the patient and do so before you scrub for the case.

7. If the attending/resident has a piece of suture, you should have a suture scissor in your hand. The worst thing that can happen is the attending/resident takes the scissors from you because you are not in a good position to cut suture.

8. Pay attention to what is going on in the case. If an attending/resident is drilling a hole in bone, ask the circulator for the depth gauge. If you show that you are paying attention during the case, you'll get more opportunity to do things.

9. Look at the approach for the case and LEARN YOUR ANATOMY. If you answer one question correctly, you'll likely not be asked many more questions - and you'll get rewarded with more opportunities to participate in the case.

10. Watch the closure. When you get an opportunity to suture, give it a go, work to do it correctly. You can practice at home with pig's feet, oranges, bananas, and pretty much anything else that has an outer skin. Ask the scrub to give you any extra, unused suture that might be left over at the end of the case.

11. Offer to write notes. I know that this seems like busy work, but it is VERY helpful, and it actually does have some educational value. When I write a neurovascular exam of the lower extremity, I have been asked what the nerve/muscle abbreviations are - many times. It's OK to ask if you don't know. It's amazing how little orthopaedic surgery is taught in medical school - and because of this, there's a ton to learn.

12. Don't be afraid to ask questions, but know the appropriate time to do so.

13. Be the first person in the door and the last one to go home.

14. Be part of the team and don't ever complain!!!!

15. Nothing listed above is scut! These are all jobs someone on the team needs to do and if you volunteer to do some of the less fun jobs, somewhere along the way, you'll get an opportunity to do some of the more fun stuff!

I am very careful to attempt to get students to participate, but not all residents are that way, not even with me as the intern. Unless you put yourself in a position to be helpful, you're not going to get invited to the party. This is your education we're talking about - and you're paying for it. Not to sound to schizophrenic, but you also have to be patient. You'll get opportunities, but there are dues to be paid first. We all have to do it.