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Iliac wing insufficiency fractures as unusual postoperative complication following total hip arthroplasty: a case report.

Insufficiency fractures (IF) occur when normal stresses are applied to bone weakened by osteoporosis. In the elderly, the pelvis is the most common location for these fractures, typically involving the parasymphyseal pubis or the sacral ala. (1-3) The ilium is rarely involved. (1) We report a case of bilateral iliac wing insufficiency fractures identified following unilateral total hip arthroplasty. To our knowledge, this complication has not been reported in the literature.

Case Report

An 87-year-old female presented 2 weeks following primary left total hip arthroplasty (THA) with acute exacerbation of persistent bilateral hip pain since surgery. Her past medical history is notable for mild Alzheimer's dementia, hypothyroidism, cervical and breast cancer treated with radiation and mastectomy and total abdominal hysterectomy, and bilateral salpingo-oophorectomy, 25 years ago, respectively. Prior to surgery, the patient was ambulatory without assistive devices and had a history of osteoporosis, which had been treated with Alendronate, vitamin D, and calcium for a prolonged period of time (Fig. 1). Family history was negative for osteoporosis. The patient did not previously undergo a DEXA bone density scan.

The patient initially underwent THA for osteoarthritis exacerbated by a medial acetabular wall IF in the absence of a known injury (Fig. 2). On the third postoperative day, the patient was discharged home with a home health aide. At that time, she was able to ambulate with a walker. Two weeks postoperatively, the patient developed bilateral hip pain after an episode in which she fell backwards onto her bed as her legs slipped out from under her, landing on her buttocks. Clinical findings and imaging studies revealed bilateral iliac wing fractures, as well as an anterior and superior dislocation of the left THA (Fig. 3). Computer tomography images are presented showing the iliac insufficiency fractures (Fig. 4). Furthermore, a change in the position of the acetabular component, periprosthetic femur fracture, and a nondisplaced left inferior pubic ramus fracture were noted. The patient was admitted for a complex revision of left THA using cup and cage reconstruction of the acetabulum and a modular femoral component with a trochanteric grip plate augmented by cerclage wires (Fig. 5). It was decided that the iliac wing fractures did not require operative management. Postoperatively, the patient's course was remarkable only for acute postoperative anemia, which responded well to blood transfusion. The patient was discharged from the orthopaedic service to a rehabilitation facility on postoperative day 5 where she continued an uneventful recovery. At her 9 month follow-up, the patient was ambulating with a cane and was living in an assisted living environment. Her follow up x-ray showed well-positioned implants and healed bilateral iliac wing fragility fractures (Fig. 6).

Discussion

Though the exact etiology of this unusual presentation of iliac wing IFs after THA is not known, the patient's hyperextension injury 2 weeks after the primary surgery resulting in a dislocation is the likely cause. During such an injury, the muscular attachments at the iliac wings including the iliacus anteriorly and gluteals posteriorly may have exerted sufficient force to create these fractures, which were not observed on the postoperative images (Fig. 2). Since the episode described was clearly low impact (landing on a soft bed from a height of less than 12 inches), it is reasonable to conclude that osteoporosis was an important predisposing factor.

In a study by Labuda and coworkers, the prevalence of osteoporosis in osteoarthritic patients who underwent total joint arthroplasty was equal to the general age matched population. (4) A retrospective review by Soubrier and colleagues examined 60 cases of IF, as defined by a newly documented fracture occurring spontaneously or resulting from moderate pressure; fractures were confirmed by radiography, scintography, CT, and MRI over a 9-year period. They revealed 91 of these fracture types, only one of which involved the ilium. (1)

Only two other reports of iliac wing insufficiency fractures were found in the English literature. (5), (6) Chary-Valckenaere and associates reported 14 cases of iliac wing insufficiency fractures. They reported that initial images in all patients were interpreted as negative; they concluded that radionuclide testing and MRI had a high rate of fracture detection compared to standard x-ray and CT images. (5)

Clinically, iliac wing insufficiency fractures may be asymptomatic or present with mechanical pain and should especially be considered in postmenopausal women with one or more osteoporosis risk factors. These fractures are generally managed by limiting weightbearing, although a few cases have been reported in which percutaneouse injection of cement has been utilized. (7) These procedures are technically challenging given the curvilinear pelvic anatomy, relative lack of cancellous bone, difficult access to fracture sites, and the proximity of visceral structures. (7, 8)

Diagnosis of iliac wing fragility fractures may be challenging, as radiographs can be negative at symptom onset and healing callus may be misdiagnosed as metastatic foci. (9) Cooper and coworkers defined diagnostic criteria for IF on CT findings which include the presence of a fracture line, with or without adjacent sclerosis, and without destructive osteolysis. (10) Soubrier and colleagues recommend scintography as the study of choice in defining IF, CT to demonstrate fracture lines, and MR to show fracture lines, especially if uncertainty exists regarding malignant lesions. (1)

In summary, the unusual postoperative complication of bilateral iliac wing IF after total hip arthroplasty presented here highlights the gravity that osteoporosis carries and the difficulty diagnosing these injuries radiographically and as a differential diagnosis for postoperative continued hip pain. Special care must be taken when treating patients with osteoporosis especially during intraoperative and postoperative care.

Caption: Figure 1 Anteroposterior pelvis radiograph before the patient underwent total hip arthroplasty; acetabular protrusion is seen on the left.

Caption: Figure 2 Anteroposterior pelvis radiograph, status post left total hip arthroplasty.

Caption: Figure 3 Anteroposterior pelvis radiograph after the patient sustained a low energy trauma demonstrating bilateral iliac wing insufficiency fracture and left total hip arthroplasty dislocation.

Caption: Figure 4 Computer tomography axial image of the pelvis demonstrating bilateral iliac wing fragility fractures. Disclosure Statement

None of the authors have a financial or proprietary interest in the subject matter or materials discussed, including, but not limited to, employment, consultancies, stock ownership, honoraria, and paid expert testimony.

References

(1.) Soubrier M, Dubost JJ, Boisgard S, et al. Insufficiency fracture. A survey of 60 cases and review of the literature. Joint Bone Spine. 2003 Jun; 70(3):209-18.

(2.) Melton LJ III. Epidem of spinal osteoporosis. Spine. 1997 Dec 15;22(24 Suppl):2S-11S.

(3.) Daffner RH, Pavlov H. Stress fractures: current concepts. Am J Roent. 1992; 159:242-5.

(4.) Labuda A, Papaioannou A, Pritchard J, et al. Prevalence of osteoporosis in osteoarthritic patients undergoing total hip or total knee arthroplasty. Arch Phys Med Rehabil. 2008 Dec; 89(12):2373-4.

(5.) Chary-Valckenaere I, Blum A, Pere P, et al. Insufficiency fractures of the ilium. Rev Rhum Engl Ed. 1997 Oct; 64(10):542-8.

(6.) Franjon C, Monteiro I, Rannou F, et al. Stress fracture of the iliac wing due to bone insufficiency. Report of a case. Rev Rhum Engl Ed. 1998 Oct; 65(10):598-600.

(7.) Douglas BP, Datir A, D'Souza SL, D'Souza LS, et al. Percutaneous treatment of insufficiency fractures: Principles, technique and review of literature. Skeletal Radiol. 2010;39(2):117-30.

(8.) Davies AM, Bradley SA. Iliac insufficiency fractures. Br J Radiol. 1991 Apr; 64(760):305-9.

(9.) Peh WC, Khong PL, Yin Y, et al. Imaging of pelvic insufficiency fractures. Radiographics. 1996 Mar; 16(2):335-48.

(10.) Cooper KL, Beabout JW, Swee RG. Insufficiency fractures of the sacrum. Radiology. 1985 Jul; 156(1):15-20.

Omri Ayalon, M.D., Ran Schwarzkopf, M.D., M.Sc., Scott E Marwin, M.D., and Joseph D. Zuckerman, M.D.

Omri Ayalon, M.D., Scott E, Marwin, M.D., and Joseph D. Zuckerman, M.D., are in the Department of Orthopaedic Surgery, NYU Hospital for Joint Diseases, New York, New York. Ran Schwarzkopf, M.D., M.Sc., is in the Department of Orthopaedic Surgery, University of California Irvine Medical Center, Orange, California. The first two authors contributed equally to this work.

Correspondence: Ran Schwarzkopf, M.D., 101 The City Drive South, Orange, California 92868; schwarzk@gmail.com.

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Article Details
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Author:Ayalon, Omri; Schwarzkopf, Ran; Marwin, Scott E.; Zuckerman, Joseph D.
Publication:Bulletin of the NYU Hospital for Joint Diseases
Article Type:Clinical report
Geographic Code:1USA
Date:Oct 1, 2013
Words:1361
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