Aims

Elevated blood cobalt levels secondary to metal-on-metal (MoM) hip arthroplasties are a suggested risk factor for developing cardiovascular complications including cardiomyopathy. Clinical studies assessing patients with MoM hips using left ventricular ejection fraction (LVEF) have found conflicting evidence of cobalt-induced cardiomyopathy. Global longitudinal strain (GLS) is an echocardiography measurement known to be more sensitive than LVEF when diagnosing early cardiomyopathies. The extent of cardiovascular injury, as measured by GLS, in patients with elevated blood cobalt levels has not previously been examined.

Elevated blood cobalt secondary to metal-on-metal (MoM) hip arthroplasties has been shown to be a risk factor for developing cardiovascular complications including cardiomyopathy. Published case reports document cardiomyopathy in patients with blood cobalt levels as low as 13µg/l. Clinical studies have found conflicting evidence of cobalt-induced cardiomyopathy in patients with MoM hips. The extent of cardiovascular injury, measured by global longitudinal strain (GLS), in patients with elevated blood cobalt levels has not previously been examined.

Sixteen patients with prospectively collected blood cobalt ion levels above 13µg/l were identified and matched with eight patients awaiting hip arthroplasty with no history of cobalt implants. Patients underwent echocardiogram assessment including GLS.

Patients with MoM hip arthroplasties had a mean blood cobalt level of 29µg/l compared to 0.01µg/l in the control group. There was no difference or correlation in EF, left ventricular (LV) end systolic dimension, LV end diastolic dimension, fractional shortening, ventricular wall thickness or E/e’ ratio. However, GLS was significantly reduced in patients with MoM hip arthroplasties compared to those without (−15.2% v −18%, (MoM v control) p= 0.0125). Pearson correlation demonstrated that GLS is significantly correlated with blood cobalt level (r= 0.8742, p=0.0009).

For the first time, this study has demonstrated reduced cardiac function in the presence of normal EF as assessed by GLS in patients with elevated cobalt above 13µg/l. As GLS is a more sensitive measure of systolic function than EF, routine echocardiogram assessment including GLS should be performed in all patients with MoM hip arthroplasties and elevated blood cobalt.

Elevated blood cobalt secondary to metal-on-metal (MoM) hip arthroplasties has been shown to be a risk factor for developing cardiovascular complications including cardiomyopathy. Published case reports document cardiomyopathy in patients with blood cobalt levels as low as 13µg/l (13ppb, 221nmol/l). Clinical studies have found conflicting evidence of cobalt-induced cardiomyopathy in patients with MoM hips. Global longitudinal strain (GLS) is an echocardiography measurement known to be more sensitive than ejection fraction at diagnosing early cardiomyopathies. The extent of cardiovascular injury, as measured by GLS, in patients with elevated blood cobalt levels has not previously been examined.

Sixteen patients with documented blood cobalt ion levels above 13µg/l were identified from a regional arthroplasty database. They were matched with eight patients awaiting hip arthroplasty with no history of cobalt implants. All patients underwent electrocardiogram and echocardiogram assessment for signs of cardiomyopathy including GLS.

Patients with MoM hip arthroplasties had a mean blood cobalt level of 29µg/l (495nmol/l) compared to 0.01µg/l (0.2nmol/l) in the control group. There was no difference or correlation in ejection fraction (EF), left ventricular (LV) end systolic dimension, LV end diastolic dimension, fractional shortening, ventricular wall thickness or E/e’ ratio. However, GLS was significantly reduced in patients with MoM hip arthroplasties compared to those without (−15.2% v −18%, (MoM v control) p= 0.0125). Pearson correlation demonstrated that GLS is significantly correlated with blood cobalt level (r= 0.8742, p=0.0009).

For the first time, this study has demonstrated reduced cardiac function in the presence of normal EF as assessed by GLS in patients with elevated cobalt above 13µg/l. As GLS is a more sensitive measure of systolic function than EF, routine echocardiogram assessment including GLS should be performed in all patients with MoM hip arthroplasties and elevated blood cobalt above 13µg/l. Further work is recommended to assess if these cardiac changes are present in patients with elevated blood cobalt levels below 13µg/l.

Elevated levels of circulating cobalt ions have been linked with a wide range of systemic complications including neurological, endocrine, and cardiovascular symptoms. Case reports of patients with elevated blood cobalt ions have described significant cardiovascular complications including cardiomyopathy. However, correlation between the actual level of circulating cobalt and extent of cardiovascular injury has not previously been performed. This review examines evidence from the literature for a link between elevated blood cobalt levels secondary to metal-on-metal (MoM) hip arthroplasties and cardiomyopathy. Correlation between low, moderate, and high blood cobalt with cardiovascular complications has been considered. Elevated blood cobalt at levels over 250 µg/l have been shown to be a risk factor for developing systemic complications and published case reports document cardiomyopathy, cardiac transplantation, and death in patients with severely elevated blood cobalt ions. However, it is not clear that there is a hard cut-off value and cardiac dysfunction may occur at lower levels. Clinical and laboratory research has found conflicting evidence of cobalt-induced cardiomyopathy in patients with MoM hips. Further work needs to be done to clarify the link between severely elevated blood cobalt ions and cardiomyopathy.

Cite this article: Bone Joint Res 2021;10(6):340–347.

Introduction: Intra-articular injection (IAJ) with cortico-steroid and local anaesthetic has been used as both diagnostic and therapeutic intervention in osteoarthritis of the hip. Doubt remains about its efficacy in confirming the source of symptoms in patients with both hip and spinal arthritis. There are also concerns about the introduction of infection for patients undergoing surgery.

Methods: All patients undergoing Hip IAJ for osteoarthritis within a 6-month period in 2007 were reviewed for three surgeons at one institution retrospectively. Data was collated and analysed using a set protocol allowing 18 months follow-up period.

Results: 41 procedures (38 patients) had injections within the study period. Male: Female ratio was 17:24. Average age was 52 years. There were 54% right-sided procedures.

25/41 patients had full response to the injection. 80% were listed for surgery as a result (documented reasons in those not listed). 6/41 patients had a partial response to the injection – 66% were managed conservatively (due to co-morbidities elicited at review, or spinal pathology). 10/41 patients had no benefit – 3 were offered surgery (one after MRI confirmation, one after prolonged physiotherapy and one after discussion about diagnostic overlap).

Hip replacement completely reduced symptoms in 19/21 (90%) and partially in 2/21 (10%) (1 had undergone a successful pre-operative IAJ).

There were no deep infections in patients undergoing surgery after injection. 1 patient had a superficial infection (resolved at review).

Discussion: Diagnostic IAJ can be of value in patients when there are concerns whether the origin of symptoms is truly ascribable to the hip. Patients where injections are successful go on to undergo successful surgery without an increased risk of infection.

Aims: In recent years, volar locking plates have increased in popularity for the treatment of displaced distal radial fractures. The angular stability of the screws help maintain reduction permitting early mobilisation. The aim of this study was to assess functional outcome using both subjective and objective methods.

Methods: The study was a prospective cohort study. Over a 2 year period 110 patients with closed, displaced distal radial fractures were considered suitable for treatment with the distal radius volar locking plate. Of these, 51 patients were followed up for a full 12 months. One year post-operatively all patients were reviewed and both subjective and objective measurements made:

Subjective:

Pain – visual analogue scale (VAS) (0 = no pain, 10 = worst pain ever).

For the purpose of this analysis, the fractures were divided into intra- and extra-articular fracture patterns based on the initial pre-operative X-rays.

Results: The mean age was 55 years (28 – 83), 36 were female and 15 male. Of the fractures, 26 were extra-articular and 25 intra-articular. 28 of the 51 patients had a period of physiotherapy post-operatively. 23 patients were either not referred to physiotherapy or failed to attend.

Subjectively 75% of patients had an excellent result with a pain VAS score of 0–1/10 (mean 0.9 for extra-articular and 1.2 for intra-articular) and an overall function VAS score of 9–10/10 (mean 92% for extra-articular and 86% for intra-articular).

Objective outcome measures were also very good. The results for the extra-articular group showed a mean grip strength of 85%, a mean pinch grip of 91%, a mean flexion of 82%, a mean extension of 88%, a mean pronation of 98% and a mean supination of 98%. The results for intra-articular fractures showed a mean grip strength of 80%, a mean pinch grip of 88%, a mean flexion of 78%, a mean extension of 83%, a mean pronation of 94% and a mean supination of 93%.

Conclusions: Overall patients made an excellent recovery. The majority of patients had little or no pain and almost complete return to function at 12 months post-operatively. Interestingly, individual patient demographics (age, sex, fracture type, physiotherapy) did not make a statistically significant difference to the outcome measures.

This study confirmed excellent functional results comparable with other methods of fixation for extra-articular fractures, but it also showed good results with the more complex intra-articular fractures.