Adverse local tissue reaction arising from corrosion at the femoral neck-body junction in a dual-taper stem with a cobalt-chromium modular neck

Abstract

Background: Femoral stems with dual-taper modularity were introduced to allow additional options for hip-center restoration independent of femoral fixation in total hip arthroplasty. Despite the increasing availability and use of these femoral stems, concerns exist about potential complications arising from the modular neck-body junction.

Methods: This was a multicenter retrospective case series of twelve hips (eleven patients) with adverse local tissue reactions secondary to corrosion at the modular neck-body junction. The cohort included eight women and three men who together had an average age of 60.1 years (range, forty-three to seventy-seven years); all hips were implanted with a titanium-alloy stem and cobalt-chromium-alloy neck. Patients presented with new-onset and increasing pain at a mean of 7.9 months (range, five to thirteen months) following total hip arthroplasty. After serum metal-ion studies and metal artifact reduction sequence (MARS) magnetic resonance imaging (MRI) revealed abnormal results, the patients underwent hip revision at a mean of 15.2 months (range, ten to twenty-three months). Tissue specimens were examined by a single histopathologist, and the retrieved implants were studied with use of light and scanning electron microscopy.

Results: Serum metal levels demonstrated greater elevation of cobalt (mean, 6.0 ng/mL) than chromium (mean, 0.6 ng/mL) or titanium (mean, 3.4 ng/mL). MRI with use of MARS demonstrated adverse tissue reactions in eight of nine patients in which it was performed. All hips showed large soft-tissue masses and surrounding tissue damage with visible corrosion at the modular femoral neck-body junction. Available histology demonstrated large areas of tissue necrosis in seven of ten cases, while remaining viable capsular tissue showed a dense lymphocytic infiltrate. Microscopic analysis was consistent with fretting and crevice corrosion at the modular neck-body interface.

Conclusions: Corrosion at the modular neck-body junction in dual-tapered stems with a modular cobalt-chromium-alloy femoral neck can lead to release of metal ions and debris resulting in local soft-tissue destruction. Adverse local tissue reaction should be considered as a potential cause for new-onset pain in patients with these components, and early revision should be considered given the potentially destructive nature of these reactions. A workup including serologic studies (erythrocyte sedimentation rate and C-reactive protein), serum metal levels, and MARS MRI can be helpful in establishing this diagnosis.

Fig. 1

Fig. 1 Coronal short tau inversion recovery (STIR) magnetic resonance image acquired with use of metal artifact reduction sequence (MARS), demonstrating a large pseudotumor (arrows) surrounding the prosthetic hip joint, approximately twenty-one months following total hip arthroplasty (Case 3). As a reference, the greater trochanter (GT), modular prosthetic femoral neck (N), and modular femoral head (H) are labeled.

Fig. 2

Fig. 2 Posterior (left) and medial (right) light microscopic images of modular femoral neck that was retrieved after approximately sixteen months in vivo (Case 2). Surface damage, consisting of fretting, corrosion, and black debris, was apparent on all retrieved cobalt-chromium modular femoral neck-body junctions.

Fig. 3

Fig. 3 Scanning electron microscope image (×3500) demonstrating fretting and corrosion (left and center) as well as a thick deposit of fretting-corrosion debris (right) on the lateral aspect of a damaged neck-body junction that had been in vivo for approximately twenty months (Case 1). Similar findings were seen in all ten retrieved implants.

Fig. 4

Fig. 4 Scanning electron microscope image (×1500) of a femoral head-neck junction that had been in vivo for sixteen months, demonstrating marked pitting corrosion of a cobalt-chromium femoral neck that was mated with a ceramic head (Case 6). Femoral head-neck corrosion was found in six of the ten implants analyzed (five with ceramic heads, and one with a metal head).

Fig. 5

Fig. 5 Histological surgical specimen obtained 12.6 months following hip arthroplasty (Case 4), demonstrating abundant diffuse and perivascular lymphocytes in the joint pseudocapsule. The synovial lining is absent, and a layer of organizing fibrin exudate (*) covers the inner surface of the capsule (hematoxylin and eosin stain, ×25 magnification).

Fig. 6

Fig. 6 Histological specimen obtained during revision surgery after 12.5 months in vivo (Case 5). A broad layer of the joint pseudocapsule is necrotic (N) and covered by a surface layer of fibrin (*). Diffuse lymphocytes and a lesser number of eosinophils form a distinct layer (hematoxylin and eosin stain, ×25 magnification).

Fig. 7

Histological specimen removed during revision surgery (Case 1). The majority of the specimen was necrotic, but viable areas of pseudocapsule showed chronic inflammation dominated by diffuse lymphocytes and scattered eosinophils (hematoxylin and eosin stain, ×200 magnification).

Fig. 8

An energy-dispersive x-ray spectrum (Case 5) reveals the elemental composition of particles rich in chromium (Cr) and consistent with chromium phosphate corrosion product. Traces of cobalt (Co) and titanium (Ti) are also present, the latter suggesting that these particles were generated by corrosion at the junction between the cobalt-chromium modular femoral neck and the titanium alloy stem. The particles (inset) lie in necrotic fibrous tissue of the joint pseudocapsule (backscattered electron micrograph, ×200). O = oxygen, Mg = magnesium, P = phosphorus, S = sulfur, and Ca = calcium.