Case report 246. Osteolysis of the ilium associated with a loose acetabular cup following total hip arthroplasty, secondary to foreign body reaction to polyethylene and methyl methacrylate

Focal osteolysis in total hip replacement: CT findings

OBJECTIVE

To describe the CT findings of focal osteolysis following total hip replacement (THR).

DESIGN AND PATIENTS

CT imaging features of 30 THRs with focal osteolysis visualized on follow-up radiographs and undertaken revision surgery were reviewed. On CT scans, the shape and anatomic location of osteolytic lesions was recorded, as well as their size and number. The presence of cortical disruption or expansion, liner wear, metallosis, and heterotopic ossification was also noted. In each case, surgical and histologic findings were correlated with imaging features.

RESULTS

Focal osteolysis was common in the superior part of acetabular and femoral components. CT features of focal osteolysis were multiple, expansile, oval, or round radiolucencies, which were conglomerated into multilobular shape. The cortex adjacent to the osteolytic lesions revealed irregular thinning and discontinuity (29/30, 97%) accompanied by a few tiny fragments. Liner wear was common (27/30, 90%), and metallosis was frequent (8/30, 26.7%). Pathologic results were foreign body reaction in 20 patients, chronic inflammation in eight, and fibrosis in two.

CONCLUSION

CT appearances of focal osteolysis following THR are multilobulated lucent areas with expansile periosteal reaction and cortical abnormalities, mimicking infection or tumor. We consider that CT is useful for the prediction and assessment of the nature and extent of focal osteolysis.

Compatibility of the totally replaced hip. Reduction of wear by amorphous diamond coating

Particulate wear debris in totally replaced hips causes adverse local host reactions. The extreme form of such a reaction, aggressive granulomatosis, was found to be a distinct condition and different from simple aseptic loosening. Reactive and adaptive tissues around the totally replaced hip were made of proliferation of local fibroblast like cells and activated macrophages. Methylmethacrylate and high-molecular-weight polyethylene were shown to be essentially immunologically inert implant materials, but in small particulate form functioned as cellular irritants initiating local biological reactions leading to loosening of the implants. Chromium-cobalt-molybdenum is the most popular metallic implant material; it is hard and tough, and the bearings of this metal are partially self-polishing. In total hip implants, prerequisites for longevity of the replaced hip are good biocompatibility of the materials and sufficient tribological properties of the bearings. The third key issue is that the bearing must minimize frictional shear at the prosthetic bone-implant interface to be compatible with long-term survival. Some of the approaches to meet these demands are alumina-on-alumina and metal-on-metal designs, as well as the use of highly crosslinked polyethylene for the acetabular component. In order to avoid the wear-based deleterious properties of the conventional total hip prosthesis materials or coatings, the present work included biological and tribological testing of amorphous diamond. Previous experiments had demonstrated that a high adhesion of tetrahedral amorphous carbon coatings to a substrate can be achieved by using mixing layers or interlayers. Amorphous diamond was found to be biologically inert, and simulator testing indicated excellent wear properties for conventional total hip prostheses, in which either the ball or both bearing surfaces were coated with hydrogen-free tetrahedral amorphous diamond films. Simulator testing with such total hip prostheses showed no measurable wear or detectable delamination after 15,000,000 test cycles corresponding to 15 years of clinical use. The present work clearly shows that wear is one of the basic problems with totally replaced hips. Diamond coating of the bearing surfaces appears to be an attractive solution to improve longevity of the totally replaced hip.

Aggressive granulomatous lesion presenting as tumor in cementless long stem total hip arthroplasty

We describe a patient with an aggressive granulomatous lesion around a cementless total hip prosthesis, which simulated a tumor. The granuloma showed a uniform histopathology, which included mononuclear cells and metal wear particles. Aggressive granulomatous lesions in replaced hips are a distinct condition, different from simple loosening or infection; the lesions may grow rapidly, so that revision surgery is indicated soon after diagnosis.

Pathologic supracondylar fracture due to osteolytic pseudotumor of knee following cementless total knee replacement

Wear debris of polyethylene, polymethylmethacrylate, and metal have been recognized to be associated with foreign body reactions, osteolysis, and aseptic prosthetic loosening after joint replacement arthroplasty. Further, foreign body reaction due to the presence of extensive wear debris can cause aggressive granulomatous lesions and pathologic fracture. To our knowledge, there has been no previous report of pathologic fracture of the femur due to an agressive pseudotumor. This report describes a case of pathologic supracondylar fracture of the femur 6 years and 5 months after cementless total knee replacement arthroplasty. The fracture occurred through an aggressive expanding soft tissue mass that was a tumorlike lesion secondary to polyethylene wear debris. The lesion was associated with massive osteolysis around the femoral component of the total knee prosthesis.

Size and shape of biomaterial wear debris

A literature review of wear debris is presented. Included are debris retrieved at revision of total joint replacement and at autopsy, as well as debris produced in vitro in wear testers and joint simulators or otherwise fabricated for biological experiments. Observations of wear debris in vivo and in vitro are classified in tabular form according to material type, origin, size, shape and color. Polymer particles, most commonly ultra-high molecular weight polyethylene (UHMWPE), exhibit the largest size range and appear as granules, splinters or flakes, while ceramic particles possess the smallest size range and have a granular structure. Metal particles seen in vivo and in vitro, whether from cobalt-chromium alloys or, less frequently, other alloys, form granular or needle-like shapes and generally are smaller than polymer particles but larger than ceramic particles. Particles generated in joint simulators resemble the size and shape of in vivo wear particles from total joint replacement (TJR) retrieved at revision or autopsy. However, particles prepared in vitro, whether in simulators or by other means, do not consistently resemble wear debris particles from TJR.

Evaluation of wear in an all-polymer total knee replacement. Part 2: clinical evaluation of wear in a polyethylene on polyacetal total knee

In an effort to improve the long-term result of total joint replacement arthroplasty, we have investigated the use of a polymer-on-polymer articular replacement arthroplasty. Because of their known biocompatibility and previous use in orthopedic surgery, polyethylene and polyacetal (copolymer, Hoechst) were selected. Polyethylene served in its usual role as the concave member of the articulation; polyacetal formed the convex number. Formal wear testing using a multi-channel hip simulator demonstrated superior wear characteristics of the polymer-on-polymer configuration compared to a conventional chrome-cobalt versus polymer (polyethylene) configuration. A clinical series of relatively high-activity patients having a minimum five-year follow-up (N = 26) showed no specific unfavorable reaction to this material combination in a total knee replacement. Given certain potential advantages of polymeric materials, as well as some theoretical disadvantages of metallic materials, a polymer-on-polymer design for a large joint replacement may have some merit.

Histological patterns of bone and articular tissues after orthopaedic reconstructive surgery (artificial joint implants)

Revision surgery after failures of joint replacements leads to histological studies on joint and bone tissues close to the implanted material. Aspectic loosening is the main complication. The surgical pathologist has to identify wear debris (metal, polyethylene, polymethylmethacrylate, chiefly) which promotes a histiocytic granuloma. Some surgical procedures such as cup or resurfacing arthroplasties create a new articular surface and a bone remodeling or necrosis. Cemented joint prostheses show various membrane structures between bone and the cement mantle while there is an association of bone resorption and formation. Non-cemented, porous-coated joint prostheses induce little bone ingrowth, even in satisfactory clinical results. Mechanical factors are predominant in massive limb prostheses. For silicone elastomer implants or artificial ligaments, wear of material promotes many tissular reactions. Often used bone grafts show little creeping substitution process in case of homografts, even well-incorporated on X-rays. More retrieval specimen studies are necessary to delineate precise topographical histological lesions, including non-loosened joint implants.

Revision of aggressive granulomatous lesions in hip arthroplasty

Fourteen patients had revision arthroplasty for aggressive granulomatosis in 16 previously replaced cemented total hips. The revision was performed on average 8 years (range, 6-13 years) after the primary arthroplasty. Twelve patients had multifocal granulomatous lesions. Pain was the first clinical sign of the aggressive granulomatosis, beginning on average 1.7 years (range, 0.8-3.8 years) after the primary operation. One patient had a fracture of the femur due to large granulomas while waiting for revision. The patients were under follow-up evaluation for an average of 5.4 years (range, 4-7 years) after revision. Two patients had recurrence of aggressive granulomatosis at the original sites 4.5 and 6.5 years after revision. Eleven patients had good or excellent results of revision.

Granulomatous pseudotumors in total joint replacement

Fourteen patients (15 joints) developed a foreign body reaction to methylmethacrylate, polyethylene, or metal adjacent to a total joint implant, a condition we would like to term granulomatous pseudotumors. There were eight male and six female patients. Their average age was 61 years. The hip was involved in 14 joints (femoral component 11 times, acetabulum 7, and greater trochanter once). One patient presented with granulomatous pseudotumors of the knee. The principal findings included increasing pain and radiographic evidence of loosening occurring on average 2.7 years following the implant. This was followed by a characteristic and gradually developing radiographic pattern of discrete rounded lucencies. These developed into large ovoid lytic areas, destroying both methylmethacrylate and bone. Histologically, the appearances were characterized by histiocytic infiltration and the presence of multiple foreign body giant cells. Foreign material was identified in 9 of 11 cases. The pathogenesis is unknown but appears related to micromovement or loosening of the implant.