Recently, the use of metal-on-metal articulations
in total hip arthroplasty (THA) has led to an increase in adverse
events owing to local soft-tissue reactions from metal ions and
wear debris. While the majority of these implants perform well,
it has been increasingly recognised that a small proportion of patients
may develop complications secondary to systemic cobalt toxicity
when these implants fail. However, distinguishing true toxicity
from benign elevations in cobalt ion levels can be challenging. The purpose of this two part series is to review the use of cobalt
alloys in THA and to highlight the following related topics of interest:
mechanisms of cobalt ion release and their measurement, definitions
of pathological cobalt ion levels, and the pathophysiology, risk factors
and treatment of cobalt toxicity. Historically, these metal-on-metal
arthroplasties are composed of a chromium-cobalt articulation. The release of cobalt is due to the mechanical and oxidative
stresses placed on the prosthetic joint. It exerts its pathological
effects through direct cellular toxicity. This manuscript will highlight the pathophysiology of cobalt
toxicity in patients with metal-on-metal hip arthroplasties. Take home message: Patients with new or evolving hip symptoms
with a prior history of THA warrant orthopaedic surgical evaluation.
Increased awareness of the range of systemic symptoms associated
with cobalt toxicity, coupled with prompt orthopaedic intervention, may
forestall the development of further complications. Cite this article:
As adverse events related to metal on metal hip
arthroplasty have been better understood, there has been increased
interest in toxicity related to the high circulating levels of cobalt ions.
However, distinguishing true toxicity from benign elevations in
cobalt levels can be challenging. The purpose of this review is
to examine the use of cobalt alloys in total hip arthroplasty, to
review the methods of measuring circulating cobalt levels, to define
a level of cobalt which is considered pathological and to review
the pathophysiology, risk factors and treatment of cobalt toxicity.
To the best of our knowledge, there are 18 published cases where
cobalt metal ion toxicity has been attributed to the use of cobalt-chromium
alloys in hip arthroplasty. Of these cases, the great majority reported
systemic toxic reactions at serum cobalt levels more than 100 μg/L.
This review highlights some of the clinical features of cobalt toxicity,
with the goal that early awareness may decrease the risk factors
for the development of cobalt toxicity and/or reduce its severity. Take home message: Severe adverse events can arise from the release
of cobalt from metal-on-metal arthroplasties, and as such, orthopaedic
surgeons should not only be aware of the presenting problems, but
also have the knowledge to treat appropriately. Cite this article:
The aim of this review is to address controversies
in the management of dislocations of the acromioclavicular joint. Current
evidence suggests that operative rather than non-operative treatment
of Rockwood grade III dislocations results in better cosmetic and
radiological results, similar functional outcomes and longer time
off work. Early surgery results in better functional and radiological
outcomes with a reduced risk of infection and loss of reduction compared
with delayed surgery. Surgical options include acromioclavicular fixation, coracoclavicular
fixation and coracoclavicular ligament reconstruction. Although
non-controlled studies report promising results for arthroscopic
coracoclavicular fixation, there are no comparative studies with
open techniques to draw conclusions about the best surgical approach.
Non-rigid coracoclavicular fixation with tendon graft or synthetic
materials, or rigid acromioclavicular fixation with a hook plate,
is preferable to fixation with coracoclavicular screws owing to
significant risks of loosening and breakage. The evidence, although limited, also suggests that anatomical
ligament reconstruction with autograft or certain synthetic grafts
may have better outcomes than non-anatomical transfer of the coracoacromial
ligament. It has been suggested that this is due to better restoration
horizontal and vertical stability of the joint. Despite the large number of recently published studies, there
remains a lack of high-quality evidence, making it difficult to
draw firm conclusions regarding these controversial issues. Cite this article:
Down’s syndrome is associated with a number of
musculoskeletal abnormalities, some of which predispose patients
to early symptomatic arthritis of the hip. The purpose of the present
study was to review the general and hip-specific factors potentially
compromising total hip replacement (THR) in patients with Down’s
syndrome, as well as to summarise both the surgical techniques that
may anticipate the potential adverse impact of these factors and
the clinical results reported to date. A search of the literature
was performed, and the findings further informed by the authors’
clinical experience, as well as that of the hip replacement in Down
Syndrome study group. The general factors identified include a high
incidence of ligamentous laxity, as well as associated muscle hypotonia
and gait abnormalities. Hip-specific factors include: a high incidence
of hip dysplasia, as well as a number of other acetabular, femoral
and combined femoroacetabular anatomical variations. Four studies
encompassing 42 hips, which reported the clinical outcomes of THR
in patients with Down’s syndrome, were identified. All patients
were successfully treated with standard acetabular and femoral components.
The use of supplementary acetabular screw fixation to enhance component
stability was frequently reported. The use of constrained liners
to treat intra-operative instability occurred in eight hips. Survival
rates of between 81% and 100% at a mean follow-up of 105 months
(6 to 292) are encouraging. Overall, while THR in patients with
Down’s syndrome does present some unique challenges, the overall
clinical results are good, providing these patients with reliable
pain relief and good function. Cite this article:
Symptomatic cobalt toxicity from a failed total
hip replacement is a rare but devastating complication. It has been reported
following revision of fractured ceramic components, as well as in
patients with failed metal-on-metal articulations. Potential clinical
findings include fatigue, weakness, hypothyroidism, cardiomyopathy,
polycythaemia, visual and hearing impairment, cognitive dysfunction,
and neuropathy. We report a case of an otherwise healthy 46-year-old
patient, who developed progressively worsening symptoms of cobalt
toxicity beginning approximately six months following synovectomy
and revision of a fractured ceramic-on-ceramic total hip replacement
to a metal-on-polyethylene bearing. The whole blood cobalt levels
peaked at 6521 µg/l. The patient died from cobalt-induced cardiomyopathy.
Implant retrieval analysis confirmed a loss of 28.3 g mass of the
cobalt–chromium femoral head as a result of severe abrasive wear
by ceramic particles embedded in the revision polyethylene liner.
Autopsy findings were consistent with heavy metal-induced cardiomyopathy. We recommend using new ceramics at revision to minimise the risk
of wear-related cobalt toxicity following breakage of ceramic components. Cite this article:
