Heterotopic Ossicfication of hip post THA

This procedure has me stumped...any advice would be great! The physician states the patient has a heterotopic ossification s/p THA and he did an excision of the ossification with a femoral head exchange. I come up with 728.13 for the dx but didn't know if I should code a complication also...on the CPT® side I am stumped because to me it sounds like he did a 27036 but I wasn't sure what to do about the femoral head exchange...I've included the op note so you can see what I mean. PLEASE HELP!!!!



OPERATIVE PROCEDURE: The patient was brought to the OR by general anesthesia staff after spinal anesthesia
was placed in the preoperative holding area. He was positioned supine on the operating table and a Foley catheter
was placed without difficulty. He was then positioned into the left lateral decubitus position and held in place with
Stahlberg hip positioning system maintaining strict cervical alignment over an axillary roll. His right leg was then
examined flexion to approximately 80 degrees and 20 degrees loss of full extension. His abduction is limited to
approximately 10 degrees. His right hip was then prepped and draped in the normal, strict sterile fashion. At this
point we drew out his old incision and lengthened this both proximally and distally. A skin incision was made with
a 10-blade scalpel and we looked at his old incision taking full thickness skin in the process. We then brought this
down in a standard posterior lateral hip approach to the IT band. The IT band was in good condition and well
healed. We split this inline with the femur up to the greater trochanteric prominence and curved posterior
superiorly. At this point a Charnley retractor was placed. We were essentially looking at a femur that was 2-3 times
as wide as normal. There was no bursa present. This extra femoral width was secondary to heterotopic ossification.
We began chipping away at this especially the posterior region with an osteotome trying to get back to normal tissue
and staying close the original femur so that we would not get anywhere close to the sciatic nerve. Numerous large
pieces of bone were removed. We took this dissection down to lesser trochanter in the gluteus maximus insertion
region. We utilized a Bovie anytime we were removing bone to let us know when we were close to the sciatic
nerve. We essentially removed this large piece of bone off the posterior femur. This seemed to track superiorly up
into the piriformis region and extended up toward the sciatic notch. We did remove this large section of posterior
bone which also involved a very small portion of the posterior gluteus medius. The majority of the gluteus medius
was intact after removal of this posterior bone. We then turned our attention to the deeper bone which was in the
capsule region surrounding the hip. The hip was essentially surrounded with bone. We used a rongeur to take away
some of this bone so that we could visualized some of the underlying capsule. We then split this inline with the
femoral neck taking care not to injure the acetabular of the polyethylene. We then essentially had a calcified inferior
and superior capsule. Both of these capsular sections were removed. We carefully removed this superior capsule
making sure not to remove any additional abductor muscle. Once the superior capsule was removed we were able to
dislocate the femur and the ceramic head was removed. We used a rongeur to remove any of the anterior bone in the
anterior capsule region. At this point all the visible extra bone was removed. We then turned our attention to the
bone that was seen in the anterior hip capsular region and anterior soft tissues on lateral proximal femur x-ray. We
could palpate this coming from the anterior aspect of the hip when dissecting underneath the gluteus medius with
fingertip dissection and a cob. The remaining anterior bone seemed to be a small amount and in a good position
where it would not cause any impingements or problems. We placed a trial 36+ 5 mm femoral head and looked at
our extension. We could get him extended back to neutral but not much past this. We then stepped down one head
size after dislocating the hip and trialed a 36 + 1.5 mm head and our extension was mildly improved. However our
stability decreased significantly to where at 90 degrees flexion we could only internally rotate to approximately 40
degrees before there was lift off of the femoral head. We went back and looked at some of the anterior bone and it
seemed we were pinching anteriorly. We were able to remove some of this anterior bone with a rongeur. At this
point the1.5 mm head seemed to be much more stable. We inspected the polyethylene component and it did not appear that we needed to do a liner exchange given that it had
only been 6 months. We went ahead and placed a revision 36 mm + 1.5 ceramic head over a clean trunnion and
reduced the hip. At this point we were taking it through a stability test and it just did not seem as stable as we would
like with internal rotation only to 50 degrees at 90 degrees flexion. There also seemed to be an excessive shuck.
We could extend it back to approximately 20 degrees however I had concerns that he would have instability when
sitting and going from sitting to standing. We elected to go ahead and dislocate the hip a final time, remove this
head and place a final 36 mm plus 5 revision DePuy ceramic femoral head over a clean trunnion. We reduced the
hip a final time. Again we could get him back to 0 degrees flexion if not a few degrees of extension. The hip was
stable to internal rotation to approximately 65 degrees at 90 degrees flexion. We then irrigated the wound out
copiously with pulse lavage. We were unable to close the capsule since it was mostly removed. The piriformis was
also not present since it had ossified and had been removed. We went ahead and closed the IT band over a drain
with 0-Vicryl figure-of-eight sutures interrupted fashion followed by 2-0 Vicryl in the subcutaneous layer and
staples in the skin. The patient was placed in a sterile dressing, abduction pillow awakened and transferred to the
recovery room without complication.