Langerhans cell histiocytosis (LCH), formerly called "eosinophilic granuloma," is a benign bone neoplasm that is rare in adults. It is a cellular lesion with histiocytes, plasma cells, small lymphocytes, neutrophils, giant cells, foam cells, and eosinophilic leukocytes1. The disease typically presents during childhood, with >90% of cases occurring between the ages of five and fifteen years. LCH typically presents as a lytic medullary lesion with sharply defined margins, most commonly in the skull and in the diaphyses of long bones. The pelvis is affected in 5% to 17% of reported cases2,3.
We report an unusual case of LCH presenting in the femur of a healthy young adult man following primary total hip arthroplasty for presumed idiopathic osteonecrosis. Inspection of the joint at the time of the initial surgery demonstrated no findings that were thought to warrant formal histological investigation of bone at the arthroplasty site. One year later, repeat radiographs demonstrated changes mimicking a periprosthetic infection. The prosthesis was removed, and histological examination of tissue curetted from the lytic lesions adjacent to the prosthetic femoral stem demonstrated findings consistent with a diagnosis of LCH. Cultures of curetted tissue from the same site revealed no bacterial, mycobacterial, or fungal growth. The patient, treated initially as if he had an infection at the site of the arthroplasty, underwent placement of an antibiotic cement spacer followed by revision total hip arthroplasty. At the most recent follow-up evaluation, there had been no recurrence of the LCH and the hip prosthesis was functioning well. In retrospect, LCH, which was present at revision, could have been present at the primary operation and could have been diagnosed if tissue specimens had been submitted for histological examination. This experience underscores the importance of maintaining a high index of suspicion for unexpected diagnoses in cases where less common findings, such as large cystic lesions, are noted in otherwise routine hip arthroplasty procedures. The patient was informed that data concerning the case would be submitted for publication, and he provided his consent.
A twenty-five-year-old man presented with progressively increasing left hip pain following a motor-vehicle accident that had taken place three years previously. No fracture was sustained during that accident. At the time of presentation, pain was present in the buttock and groin, and was worse with weight-bearing activities. The patient derived little benefit from ibuprofen or use of a cane. Because nonoperative treatment was unsuccessful, he requested consideration of surgical treatment.
On examination, the patient's height was 178 cm, and he weighed 84 kg. Left hip motion included flexion of 125°, abduction of 35°, external rotation of 40°, and internal rotation of 10°. Pain was present with all planes of motion except flexion. He had an antalgic gait, but the remainder of the physical examination revealed negative findings. Laboratory findings included a white blood-cell count (WBC) of 6.2 × 109/L (normal, 3.4 to 10 × 109/L), a rheumatoid factor of <7 units/mL (normal, <14 units/mL), a negative result on testing for the human leukocyte antigen B27 (HLA-B27), and negative chlamydia and gonococcal DNA probe tests. The erythrocyte sedimentation rate (ESR) was slightly elevated at 23 mm/hr (normal, 0 to 10 mm/hr).
Radiographs of the left hip showed osteoarthrosis with juxta-articular cysts in the femoral head and the acetabulum (Fig. 1). A computed tomography (CT) scan and T1-weighted and T2-weighted magnetic resonance images (MRI) of the left hip had been obtained prior to referral. The CT scan confirmed the presence of subchondral cysts. The MRI scan demonstrated extensive cystic areas in both the femoral head and the acetabulum (Fig. 2). Edema in the proximal part of the femur extended throughout the neck into the greater trochanter, and there was a large joint effusion.
The patient underwent an uncomplicated cementless total hip arthroplasty with a ceramic-on-ceramic bearing (Duraloc and Replica; DePuy, Warsaw, Indiana). Inspection of the femoral head and the acetabulum during surgery demonstrated findings that were thought to be consistent with osteonecrosis and secondary osteoarthritis. Hypertrophic, inflamed synovium was present. A large acetabular cyst was curetted and packed with a mixture of morselized femoral head autograft and demineralized bone. The postoperative course was uncomplicated.
Routine radiographs obtained ten months postoperatively revealed a lytic defect in the endosteal bone adjacent to the middle third of the femoral component. Three months later, the defect had increased in size (Figs. 3 and 4). The patient reported no fever, chills, or local wound changes, but he did report occasional hip and proximal thigh pain. Physical examination revealed no wound erythema, swelling, or skin breakdown. Laboratory studies showed a WBC of 7.5 × 109/L, an ESR of 7 mm/hr, and a C-reactive protein (CRP) level of 6.6 mg/L (normal, <6.3 mg/L). A technetium-99 bone scan revealed diffuse uptake surrounding the prosthesis on the delayed phase imaging. An attempted hip aspiration yielded no fluid for culture.
Infection was thought to be the most likely cause of the progressive radiographic changes, and it was decided to remove the implant, obtain tissue for culture, and, after appropriate antibiotic therapy, implant a new prosthesis. The well-fixed femoral component was removed through an extended trochanteric osteotomy. A large, lytic, transcortical defect containing hypovascular tan-pink granulation tissue was found in the proximal part of the femur. Multiple culture and pathology samples were obtained. A methylmethacrylate spacer impregnated with vancomycin was placed. Local suction-instillation antibiotic treatment with intracapsular tubes was begun with a solution of 0.1% gentamicin and 0.1% polymyxin B. Intravenous vancomycin treatment was also administered. Local and systemic antibiotic therapy was discontinued eight days later, after the final cultures of the intraoperative specimens showed no bacterial growth. Subsequently, fungal cultures were reported as negative at four weeks and cultures for acid-fast bacilli were negative at seven weeks.
Histological examination of the curetted tissue obtained at surgery revealed LCH on multiple sections. These findings included focal aggregates of eosinophils admixed with Langerhans cells (Fig. 5-A). The inflammatory infiltrate included plasma cells, lymphocytes, neutrophils, and eosinophils. The identity of the Langerhans cells was confirmed by strongly positive immunohistochemical staining for S100 and CD1a (Fig. 5-B).
Because all of the cystic lesions had been removed by thorough curettage, neither radiation therapy nor additional surgical treatment was recommended for the tumor. Six weeks following the debridement and after final cultures and histological reports were obtained, the patient underwent removal of the antibiotic spacer and revision arthroplasty with an uncemented implant and a metal-on-metal bearing articulation (Pinnacle and AML; DePuy). There were no postoperative complications, and the patient was able to return to his previous profession as a bartender. The most recent radiographs of the left hip, obtained thirty-eight months after revision, showed no recurrence of the lesion.