Keywords metallosis - hip synovitis - periprosthetic hip infection - fracture of ceramic acetabular
liner
Introduction
Ceramic component fracture is a well-described complication of ceramic-on-ceramic
hip arthroplasty. Even if it is rare, a rapid identification and treatment is essential
to avoid severe complication[1 ]; the persistence of ceramic debris, can lead to more severe systemic complication,
due to release of metallic ions.[2 ] Symptoms of metal intoxication vary with blood level of metal ions and can lead
to patient's death in very severe cases.[3 ]
We described the unusual clinical presentation, diagnostic, and surgical management
of this unique case of hip metallosis presenting as a periprosthetic infection.
Case Presentation
In March 2014, a 72-year-old Caucasian immune-competent man was referred to our hospital
with a suspected diagnosis of periprosthetic hip infection. The patient underwent
in 2010, a primary ceramic-on-ceramic total hip arthroplasty, and 3 years after revision
surgery was performed for fracture of ceramic liner with a metal-on-polyethylene bearing
surface. The patient presented to our observation with persistent hyperthermia (39.0–39.5°C),
local pain, and swelling of the hip and groin. The range of joint motion was slightly
limited and little painful. A periprosthetic hip infection was then suspected. An
empiric antibiotic therapy was administered for 1 week without improvement.
Preoperative Assessment
Laboratory examinations revealed increased level of C-reactive protein (325.2 mg/L),
erythrocyte sedimentation rate 79 mm/h, white blood cell count (12,000/µL), neutrophils
count (8,730/µL), and high level of acute-phase inflammatory proteins. Fever persisted
high despite antibiotics. Hip radiographs showed a typical feature of severe metallosis,
the “bubble sign” surrounding the prosthesis ([Fig. 1 ]).[4 ] Computed tomography scan of the pelvis revealed a large pseudotumor of the hip (11 cm × 4 cm;
[Fig. 2 ]). Black synovial fluid of 250 cc was aspirated and sent for laboratory evaluation.
Microbiological cultures were negative in all five samples, while synovial fluid showed
high level of leukocytes (22,000 cell/mm3 ) and metals ions (titanium, 379,100 µg/L; cobalt, 63 µg/L; chrome, 1,379,000 µg/L;
molybdenum, 160,400 µg/L; vanadium, 17,180 µg/L; and manganese, 265,500 µg/L). A severe
metallosis was than hypothesized and surgical revision was planned.
Fig. 1 (A, B ) Preoperative radiographs of the right hip showing the bubble sign.
Fig. 2 Preoperative CT scan showing pseudotumor with radiopaque level of synovial fluid.
CT, computed tomography.
Surgical Treatment
A large pseudotumor of the hip was isolated and removed. The soft tissues were black
stained and it contained black synovial fluid due to metal debris. After soft tissue
debridement and irrigation, the acetabular cup, polyethylene liner, and femoral head
were removed. All components showed macroscopic wear ([Figs. 3 ] and [4 ]). Some ceramic fragments were identified and removed. A ceramic-on-ceramic bearing
surface was then restored after residual ceramic fragments removal.
Fig. 3 Removed implant showing ceramic debris and sign of metallosis.
Fig. 4 (A, B ) Retrieved acetabular shell and femoral head with macroscopic metal wear.
Postoperative Course
Body temperature returned within normal limits in few days. Hip pain disappeared and
the patient followed a standard rehabilitation protocol. Blood and urinary concentrations
of metal ions were examined during postoperative course. Metal ions concentrations
were followed at the time of surgery (T0), 2 weeks (T1), and 4 weeks (T2) after operation.
Blood levels of chrome (T0 = 5.07 µg/L; T1 = 4.62 µg/L; and T2 = 3.6 µg/L) and cobalt
(T0 = 0.41 µg/L; T1 = 0.62 µg/L; and T2 = 1.02 µg/L) were slightly increased than
normal threshold values. During the first 2 months, the patient reported dysgeusia
with a persistent metallic taste that progressively disappeared. In 2 months he returned
to daily life activities without limitations.
Regular clinical and radiologic follow-up was observed during subsequent years, with
no sign of loosening or wear at 3 years of follow-up with an Harris' hip score of
82 ([Fig. 5 ]). The patient was fully satisfied of clinical results and perceived quality of life.
Fig. 5 (A, B ) 3-years follow-up radiographs of the right hip with regular appearance.
Discussion
Fracture of ceramic components may cause catastrophic consequences.[5 ]
[6 ]
[7 ]
[8 ]
[9 ]
[10 ] Revision surgery should be performed promptly with accurate synoviectomy and joint
irrigation to remove ceramic debris and preserve hip implants from abrasive effects.[5 ] Some authors reported that revision should be performed with ceramic-on-ceramic
implants because early damage and failure of metal and polyethylene may occur because
of residual ceramic fragments.[6 ]
Patients with severe metallosis suffered from serious neurological and cardiac complications
which in a case leaded to patient death.[11 ]
None of reported cases presented with clinical features simulating periprosthetic
infection that were observed in our report. Also initial laboratory examinations supported
this hypothesis.
Periprosthetic infection associated with component fracture was already reported in
literature but in these cases local and systemic symptoms of inflammation were associated
with positive cultures.[12 ]
[13 ] In our case, all symptoms were related to inflammatory response against metal particles
and, to the best of our knowledge, this is the first case of severe metallosis simulating
a periprosthetic infection.
This report confirms that all patients sustaining a revision hip arthroplasty after
fracture of a ceramic component should be carefully controlled with clinical and radiological
follow-up and informed about the possibility of future complications related to residual
ceramic fragments. A careful investigation must always be performed to correctly and
properly reach the correct diagnosis.
