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December 14, 2018
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An 81-year-old woman with acute groin pain 6 weeks after THA revision surgery

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An 81-year-old woman presented to our clinic with a chief complaint of left hip pain and inability to bear weight. She had undergone left total hip arthroplasty revision surgery 6 weeks previously to address polyethylene wear of her index THA performed 20 years prior to presentation. The patient was noted to have a protrusio prior to her revision surgery with violation of the medial wall, however her revision surgeon was able to perform an appropriate acetabular revision by using a multi-hole shell. During her rehabilitation from that surgery, the patient sustained a fall and subsequently developed severe left hip pain with any attempt at weight-bearing. She was subsequently referred to our practice for further evaluation and management.

Her past medical history was significant for prior myocardial infarction status post-coronary artery bypass grafting, paroxysmal atrial fibrillation status post-pacemaker placement and associated congestive heart failure. She is managed by a pulmonologist for chronic obstructive pulmonary disease and requires home oxygen. Her past surgical history included the aforementioned CABG and pacemaker placement, as well as left THA 20 years prior to presentation and left hip revision THA 6 weeks prior to presentation. She also underwent cervical and lumbar fusions, and abdominal hernia repair. Home medications included home oxygen (4L every night), albuterol nebulizer/inhaler, montelukast, fluticasone-vilanterol inhaler, tiotropium, baby aspirin, losartan, metoprolol succinate XL, furosemide, pantoprazole and oxycodone. She had documented anaphylactic allergies to penicillins, iodinated contrast, barbiturates and bees. She is a former smoker with a 45-year pack-year history who quit smoking 25 years ago. She denied alcohol and illicit drug use.

On physical examination in the clinic, the patient was afebrile with normal vital signs and in no acute distress. Her BMI was noted to be 27.3 kg/m2 Her prior posterolateral hip incision was well-healed without evidence of erythema or drainage. Range of motion at the left hip was limited secondary to pain, but was otherwise normal in the other joints of the ipsilateral and contralateral lower extremities. The patient was intact on motor and sensory examination and had palpable pedal pulses bilaterally.

Postoperative anteroposterior (AP) and lateral plain radiographs obtained after her left hip revision THA (Figure 1) were compared to new films taken after her fall (Figure 2).

 Postoperative and new radiographs
Figure 1. Postoperative radiographs were obtained after the patient’s initial left hip revision THA that were AP (a) and lateral (b) views.
Figure 2. New AP (a) and lateral (b) radiographs of the patient were obtained after her fall.

Source: P. Maxwell Courtney, MD

What is your diagnosis?

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Acetabular fracture with acute pelvic discontinuity following revision THA

The patient is a medically complex 81-year-old woman who fell 6 weeks after a revision left THA and sustained an acetabular fracture with acute pelvic discontinuity. As demonstrated in her post-fall plain radiographs (Figure 2), the acute pelvic discontinuity with fracture of the acetabulum resulted in migration of the acetabular component into the pelvis. Given the complexity of her injury, as well as her medical history, a substantial discussion was had regarding the various treatment options, such as open reduction internal fixation (ORIF) with revision arthroplasty or girdlestone procedure. The medical and surgical risks, benefits, postoperative protocols and alternatives were thoroughly discussed with the patient, who desired to proceed with fracture fixation and reconstruction. She was advised to be non-weight-bearing on the left lower extremity prior to surgery. She was scheduled for expedient ORIF and reconstruction. Per standard revision guidelines, bloodwork was obtained to rule out the presence of concomitant infection with elevation in the patient’s erythrocyte sedimentation rate and C-reactive protein. Further investigation was deferred until the OR with the plan being to obtain joint fluid and tissue cultures for definitive diagnosis. Given the patient’s substantial comorbidities, preoperative medical clearance and optimization were performed by her own cardiologist and pulmonologist. With this in mind, her surgery was scheduled at our associated level-1 tertiary/quaternary care institution to provide the full spectrum of care.

After optimization was complete and clearance obtained, the patient was taken to the OR to undergo ORIF and reconstruction. Given her elevated preoperative inflammatory markers, fluid was aspirated from the hip, which had a cell count of 1,800 white blood cells. Additionally, a synovial biopsy was performed, sent for pathologic analysis prior to proceeding with implantation, and it was interpreted as negative for acute inflammation. Three additional tissue cultures were sent for analysis during the procedure. Using the patient’s old posterolateral incision in a lateral decubitus position, we extended the dissection proximally into a Kocher-Langenbeck approach to the acetabulum. We identified the sciatic nerve proximally, placed the hip into extension with the knee in flexion over a padded Mayo stand to relax tension on the nerve. We removed the acetabular component and its screws. The femoral component was found to be well-fixed and well-aligned. We did send three synovial tissue specimens and a frozen section to rule out periprosthetic joint infection.

Attention was first turned toward fixation of the transverse acetabular fracture and acute pelvic discontinuity. Treatments options for chronic pelvic discontinuity include a cup-cage construct, a custom acetabular triflange component or acetabular distraction. For acute discontinuities with appropriate acetabular bone stock, ORIF with plate osteosynthesis is the preferred treatment. Using a 5.0mm Schanz pin in the ischium, we derotated the posterior column and used a series of point-to-point clamps to achieve our reduction. We placed a nine-hole, 3.5mm reconstruction plate along the posterior column and secured it with three bicortical screws proximal and three screws distal to the transverse fracture.

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With a stable acetabular socket after ORIF, we needed to manage the Paprosky 3B acetabular deficit. Using porous metal acetabular augments, we began to reconstruct the acetabulum. We used two augments fastened together with screws to fill the superior medial defect, which Wayne G. Paprosky, MD, FACS, described as the “dome technique.” After unitizing the augments to the acetabular component with cement, we impacted a multihole cup into place and secured it with four additional screws, two on each side of the transverse fracture. Because of cup overhang and inadequate fixation, we chose to place a buttress augment and unitized this to the cup with cement, as well. Finally we used a dual-mobility bearing articulation to help minimize the patient’s risk of dislocation. Excellent stability was achieved with clinically equivalent leg lengths noted intraoperatively. Intraoperative photographs (Figure 3) and postoperative plain radiographs (Figure 4) show the patient’s surgery and radiographic result. Postoperatively, the patient was made toe-touch weight-bearing in anticipation of 2 to 3 months for osteointegration to occur prior to advancement to full weight-bearing.

reconstruction for pelvic discontinuity
Figure 3. Intraoperative photographs taken during reconstruction for pelvic discontinuity show porous metal augments used medial to the acetabular component which had the discontinuity (a), the augments in situ (b) and the acetabular component in place after implantation (c).
Figure 4. Shown are the patient’s final postoperative AP (a) and lateral (b) radiographs.

Discussion

An active, aging population is associated with an increase in the prevalence of primary and revision joint arthroplasty surgery. Pelvic discontinuities, in which the ilium superiorly is separated from the ischiopubic segment inferiorly, have been estimated to be present in 1% to 5% of revisions. Although pelvic discontinuities are typically chronic in nature due to bone loss, infection or non-united stress fractures, they may also occur acutely secondary to trauma or during surgery as a result of over-reaming of the acetabulum and/or impaction of press-fit components. Reported risk factors for discontinuities include female gender, as well as rheumatoid arthritis and history of prior local radiation.

In revision hip arthroplasty, history-taking in patients with pelvic discontinuity should focus on all previous procedures and treatments, such as radiation, the onset of symptoms and any traumatic etiology. Symptoms consistent with concomitant infection should be explored. Meanwhile, physical examination should be comprehensive, but certainly include evaluation of neuromotor function, integrity of the soft tissue envelope, function of the abductor complex and the presence/location of prior surgical incisions.

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Laboratory studies

In revisions settings, we recommend obtaining routine laboratory studies to assess the presence of infection. Laboratory analysis should include complete blood count, ESR rate and CRP. If elevations are noted, we may obtain a preoperative aspiration or obtain aspiration/frozen section/cultures at the time of surgery.

Plain radiographs should be obtained in all patients, including a minimum of AP pelvis, AP hip, and lateral hip views. Judet views can be valuable to further assess the anterior and posterior columns. When possible, films should be compared to postoperative radiographs from the patient’s prior procedure to assess component positions and to help elucidate bony changes. The surgeon should be particularly vigilant for the presence and location of fracture lines, asymmetry of the obturator ring and medial migration of the inferior hemipelvis relative to the proximal segment with resultant disruption of Kohler’s line. Additional investigation is often performed with CT in these complex cases, particularly with suppression and thin cuts. Some management options require a well-performed thin-cut CT. On the basis of these findings, pelvic discontinuities can be described using the American Academy of Orthopaedic Surgeons acetabular bone deficiency classification or the Paprosky classification of acetabular bone loss.

Management often requires detailed knowledge of pelvic and acetabular anatomy, as well as both arthroplasty and trauma reconstruction techniques. Adult reconstruction surgeons should work closely with their trauma colleagues to address these complex cases. An extensive posterior approach is necessary to visualize the anatomy of the acetabulum and achieve access to the posterior column. A number of management options exist for performing revision arthroplasty in the setting of pelvic discontinuity. Regardless of technique, the goals of surgery are a well-fixed acetabular component and a unitized hemipelvis. The hemipelvis may be unitized by healing the discontinuity or by becoming well fixed to the superior and inferior aspects of the acetabular component. Acute pelvic discontinuity with adequate bone stock can best be managed with plate osteosynthesis with good results. Chronic pelvic discontinuity with associated Paprosky 3B acetabular defects have three treatment options. Although cup-cage constructs have reasonable outcomes in large bone defects, they have high failure rates in the setting of pelvic discontinuity. A custom triflange acetabular component is an option, with reasonable success rates in some smaller series, however it can take several months and up to 1 year to process and manufacture the custom device. Recently, acetabular distraction has been described to manage chronic discontinuity with early success, as well, and is the senior author’s preferred treatment for these difficult cases. In our patient, we achieved a stable column fit for our acetabular component with a pelvic reconstruction plate and adequate fixation on each side of the fracture. It is important that screw fixation of the acetabular component also includes screws into both the posterior and anterior column. The porous metal cup in this case also acts as an “internal plate” while it promotes biologic ingrowth as the discontinuity heals.

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Pelvic discontinuities, acute or chronic, represent a challenge for any surgeon who performs revision THA, however, this case report can guide surgeons in their stepwise management of a difficult problem in revision THA.

Disclosures: Ciccotti and Courtney report no relevant financial disclosures.