What is the natural history of asymptomatic pseudotumours in metal-on-metal hip resurfacing patients?

How much does a Medical and Healthcare Products Regulatory Agency medical device alert for metal-on-metal hip arthroplasty patients really cost?

BACKGROUND

Many worldwide regulatory authorities recommend regular surveillance of metal-on-metal hip arthroplasty patients given high failure rates. However, concerns have been raised about whether such regular surveillance, which includes asymptomatic patients, is evidence-based and cost-effective. We determined: (1) the cost of implementing the 2015 MHRA surveillance in "at-risk" Birmingham Hip Resurfacing (BHR) patients; and (2) how many asymptomatic hips with adverse reactions to metal debris (ARMD) would have been missed without patient recall.

METHODS

All BHR patients eligible for the 2015 MHRA recall (all females, and males with head sizes ⩽46 mm, regardless of symptoms) at one centre were invited for review (hips = 707; patients = 593). All patients were investigated (Oxford Hip Score, radiographs, blood metal ions, and targeted cross-sectional imaging) and managed accordingly. Surveillance costs were calculated using finance department data.

RESULTS

The surveillance cost £105,921.79 (range £147.76-£257.50/patient). Radiographs (£39,598) and nurse practitioner time/assistance (£23,618) accounted for 60% of overall costs. 31 hips had ARMD on imaging (12 revised; 19 under surveillance). All revisions were symptomatic. 7 hips with ARMD under surveillance were asymptomatic and remain under regular review. The number needed to treat to avoid missing one asymptomatic ARMD case was 101 patients, representing a cost of £18,041 to avoid one asymptomatic case.

CONCLUSIONS

Implementing MHRA surveillance for "at-risk" BHR patients was extremely costly. The risk of asymptomatic ARMD was low with the BHR (1%), suggesting recommended follow-up in asymptomatic patients is not cost efficient. This raises concerns about the increasingly intensive surveillance recommended in the 2017 MHRA guidance for metal-on-metal hip patients.

The incidence of adverse local tissue reaction due to head taper corrosion after total hip arthroplasty using V40 taper and 36 mm CoCr head

AIMS

Head-taper corrosion is a cause of failure in total hip arthroplasty (THA). Recent reports have described an increasing number of V40 taper failures with adverse local tissue reaction (ALTR). However, the real incidence of V40 taper damage and its cause remain unknown. The aim of this study was to evaluate the long-term incidence of ALTR in a consecutive series of THAs using a V40 taper and identify potentially related factors.

METHODS

Between January 2006 and June 2007, a total of 121 patients underwent THA using either an uncemented (Accolade I, made of Ti₁₂Mo₆Zr₂Fe; Stryker, USA) or a cemented (ABG II, made of cobalt-chrome-molybdenum (CoCrMo); Stryker) femoral component, both with a V40 taper (Stryker). Uncemented acetabular components (Trident; Stryker) with crosslinked polyethylene liners and CoCr femoral heads of 36 mm diameter were used in all patients. At a mean folllow-up of 10.8 years (SD 1.1), 94 patients (79%) were eligible for follow-up (six patients had already undergone a revision, 15 had died, and six were lost to follow-up). A total of 85 THAs in 80 patients (mean age 61 years (24 to 75); 47 (56%) were female) underwent clinical and radiological evaluation, including the measurement of whole blood levels of cobalt and chrome. Metal artifact reduction sequence MRI scans of the hip were performed in 71 patients.

RESULTS

A total of 20 ALTRs were identified on MRI, with an incidence of 26%. Patients with ALTR had significantly higher median Co levels compared with those without ALTR (2.96 μg/l (interquartile range (IQR) 1.35 to 4.98) vs 1.44 μg/l (IQR 0.79 to 2.5); p = 0.019). Radiological evidence of osteolysis was also significantly associated with ALTR (p = 0.014). Median Cr levels were not significantly higher in those with ALTR compared with those without one (0.97 μg/l (IQR 0.72 to 1.9) v 0.67 μg/l (IQR 0.5 to 1.19; p = 0.080). BMI, sex, age, type of femoral component, head length, the inclination of the acetabular component, and heterotopic ossification formation showed no significant relationship with ALTR.

CONCLUSION

Due to the high incidence of local ALTR in our cohort after more than ten years postoperatively, we recommend regular follow-up investigation even in asymptomatic patients with V40 taper and metal heads. As cobalt levels correlate with ALTR occurrence, routine metal ion screening and consecutive MRI investigation upon elevation could be discussed. Cite this article: Bone Joint J 2022;104-B(7):852-858.

Haemorrhagic Pseudotumour Following Metal-on-Metal Hip Replacement

We present a unique report of a spontaneous haemorrhage into a pseudotumour five years following revision surgery for failed metal-on-metal hip arthroplasty. The patient sustained no trauma, was not taking anticoagulants and had no bleeding disorder. Rapid progression in the size of the pseudotumour caused significant symptoms and functional impairment. Surgical excision was recommended by a national specialist centre, but with conservative management, significant regression of the pseudotumour was noted, with complete resolution of symptoms. This case is the first report of haemorrhage into a pseudotumour, which is an important differential and can be managed non-operatively.

Study to Assess the Rate of Adverse Reaction to Metal Debris in Hip Resurfacing at a Minimum 13-year Follow-up

BACKGROUND

Hip Resurfacing (HR), although reducing in popularity, is still used in the younger male population. Excellent medium-term results have been published; however, the use of metal on metal has reduced with increased awareness of adverse reactions to metal debris (ARMD). ARMD has been shown to often be clinically "silent" following large Head MoM total hip replacement (THR). The purpose of our study was to report the incidence of ARMD following HR with a minimum follow-up of 13 years.

METHODS

We performed a retrospective study of a consecutive series of patients who underwent HR between January 1, 2000 and August 1, 2005. All patients were entered into our hospital MoM hip replacement surveillance program database. Patients were reviewed yearly for symptoms and blood ion levels. Patients had Magnetic Resonance (MR) imaging to assess for ARMD.

RESULTS

A total of 102 patients with 123 hip replacements were included in the study. Eight hips in 7 patients were revised: two for fracture, one for avascular necrosis, and five for ARMD. A best-case scenario of 109 (93.2%) resurfacings were surviving at 13 years. With regard to the radiological analysis, 34% were found to have ARMD on MR.

CONCLUSION

While the implant survivorship in our series is acceptable, we found a high incidence of ARMD. Surgeons and patients with or considering a HR should be aware of the risk of ARMD developing. This allows an informed choice as to the best implant for their personal requirement and informs of the potential modes of failure and need for long-term screening.

Follow-up of Metal-on-Metal Hip Replacements at a Large District Hospital and the Implementation of Medicines and Healthcare Products Regulatory Agency Guidelines: A Review of 297 Patients

Background

Medicines and Healthcare products Regulatory Agency (MHRA) guidance for patients with metal-on-metal (MoM) hip replacements was provided in 2012 and updated in 2017 to assist in the early detection of soft-tissue reactions due to metal wear debris. A large number of MoM hip replacements were undertaken at our hospital trust. A program of recall for all patients with MoM hip replacements was undertaken and MHRA guidelines were implemented. In this study, we aimed to investigate the effectiveness of the revised MHRA guidelines in the detection of early adverse reactions to metal debris and to re-evaluate the indications for metal artifact reduction sequence magnetic resonance imaging (MARS-MRI) and revision surgery.

Methods

Identification and recall of all patients with MoM hip replacements from 2001 were conducted by using theatre logs, patient records, clinical coding information, and consultant logbooks. Two senior arthroplasty consultants reviewed X-rays and patient records. Postal questionnaires were forwarded to patients, together with requests for general practitioners to complete cobalt and chromium blood tests. The two consultant-led review of MOM replacements was undertaken with further radiological investigations (X-rays, MARS-MRI) performed according to the 2017 guidance with support of consultant radiologists.

Results

Of 674 identified patients, 297 were available for review: 26 patients did not have MoM implants, 36 were untraceable, 59 refused follow-up, 87 moved out of area, 147 had died, and 22 already had revision. Of 297 patients, 126 were women and 171 were men; age range was 39 to 95 years (mean age, 69 years); 126 had resurfacing and 171 had MoM replacements. Twenty-six patients had elevated metal ions. Thirty-three patients underwent MARS-MRI: MARS-MRI results were positive in 17 and negative in 16. Of 17 patients with positive MARS-MRI, 10 patients were asymptomatic and seven were waiting revision.

Conclusions

Positive MARS-MRI can often occur in the absence of elevated metal ion levels; elevated blood metal ion levels do not mean MARS-MRI will be positive. All patients with MoM replacements were at risk. It is imperative to assess patients regularly for symptoms that may raise clinical suspicion and maintain a low threshold to performing MARS-MRI.

Physical Activity Is Associated With the Level of Chromium but Not With Changes in Pseudotumor Size in Patients With Metal-on-Metal Hip Arthroplasty

BACKGROUND

Metal-on-metal (MoM) total hip arthroplasty (THA) and resurfacing hip arthroplasty (RHA) were previously considered an excellent option for young and physically active patients. However, the relationship between MoM THA/RHA patients' daily physical activity (PA), metal ion measurements of chromium and cobalt, and pseudotumor dynamic is insufficiently explored.

METHODS

One hundred eleven patients with 148 hip articulations, 77 MoM THA/RHA and 71 MoP THA, participated in a prospective cohort study, with 5 cross-sectional analyses during a 1-year follow-up. Baseline follow-up was at mean 7.1 (range: 0.2-21.5) years postoperative. At baseline and every 3 months thereafter, patients' daily PA was monitored during a 2-week period using a triaxial accelerometer, and next metal artifact reducing sequence magnetic resonance imaging scans, metal ion measurements of chromium and cobalt, and the Copenhagen Hip and Groin Outcome Score questionnaire were completed.

RESULTS

We found a statistically significant relationship between daily PA and metal ion measurements of chromium at all follow-ups in MoM THA/RHA patients (P ≤ .03) but not in MoP THA patients (P > .35). Patients' daily PA was not related to changes in pseudotumor size at any follow-up (P > .30). Ten of 26 (38%) pseudotumors in MoM THA/RHA and 8 of 29 (28%) pseudotumors in MoP THA changed classification according to the Anderson grading. No pseudotumors transformed in appearance or changed anatomical location.

CONCLUSION

The daily PA of MoM THA/RHA patients is associated with metal ion measurements of chromium but not with changes in pseudotumor size. This is new and important knowledge, which may be useful for hip surgeons in recommendation and monitoration of the consequences of PA in active patients with MoM THA/RHA.

Higher Prevalence of Mixed or Solid Pseudotumors in Metal-on-Polyethylene Total Hip Arthroplasty Compared With Metal-on-Metal Total Hip Arthroplasty and Resurfacing Hip Arthroplasty

BACKGROUND

Pseudotumors are a common finding in metal-on-metal (MoM) total hip arthroplasty (THA) and resurfacing hip arthroplasty (RHA). However, information on pseudotumors in metal-on-polyethylene (MoP) THA is limited.

METHODS

One hundred eleven patients with 148 hip articulations-30 MoM THA, 47 MoM RHA, and 71 MoP THA-participated in a cross-sectional study at mean 7.1 (range: 0.2-21.5) years postoperatively. Patients were evaluated with metal artifact reducing sequence magnetic resonance imaging, measurements of metal ions, clinical scores of Harris Hip Score, Oxford Hip Score, the Copenhagen Hip and Groin Outcome Score, and conventional radiographs.

RESULTS

Pseudotumors were present in 13 of 30 (43%) MoM THA, 13 of 47 (28%) MoM RHA, and 29 of 71 (41%) MoP THA patients, which was a similar prevalence (P = .10). The prevalence of mixed or solid pseudotumors was significantly higher in patients with MoP THA (n = 10) compared to MoM THA (n = 3) and MoM THA (n = 0), (P = .01). Hips with a mixed or solid pseudotumor had significantly poorer scores of Harris Hip Score (P = .01) and OHS (P = .002) and higher metal ion levels of cobalt (P = .0009) compared to hips without a pseudotumor or with a cystic pseudotumor.

CONCLUSION

Pseudotumors have primarily been associated with MoM hip articulations, but we found a similar pseudotumor prevalence in MoP THA, which is the most common bearing worldwide. Mixed or solid pseudotumors were more often seen in MoP THA compared with MoM hip articulations, and patients with a mixed or solid pseudotumor had poorer clinical scores and higher metal ion levels than patients without a pseudotumor or with a cystic pseudotumor.

Metal-on-metal surface hip arthroplasties. Is annual monitoring of blood metal levels necessary?

INTRODUCTION

Blood cobalt (Co) and chromium (Cr) ion levels have been used as surveillance tools for adverse reaction to metal debris in metal-on-metal (MoM) hip arthroplasty. The aim of our study was to present serial 7-13 year blood Co and Cr levels in a cohort of MoM total hip arthroplasties in asymptomatic patients.

MATERIAL AND METHODS

A total of 52 MoM surface total hip arthroplasties were included in this study with data collected prospectively. Annual follow-up with blood Co and Cr measurements was performed. Revision surgery was necessary for 16 patients and therefore they dropped out of the study. The metal ion levels were analyzed separately in 31 asymptomatic patients.

RESULTS

High Cr or Co levels were not found continuously in any of the asymptomatic patients. The median Cr in blood was maintained between 1.3 and 5.4μg/L and that of Co between 0.5 and 1.2μg/L. After 7 years, there was no significant change in Co and Cr values.

CONCLUSION

In the medium term and in asymptomatic patients, the metallic blood levels remained unchanged; therefore, it does not seem appropriate to repeat these tests on a permanent basis in annual controls.

Revision surgery of metal-on-metal hip arthroplasties for adverse reactions to metal debris

Background and purpose - The initial outcomes following metal-on-metal hip arthroplasty (MoMHA) revision surgery performed for adverse reactions to metal debris (ARMD) were poor. Furthermore, robust thresholds for performing ARMD revision are lacking. This article is the second of 2. The first article considered the various investigative modalities used during MoMHA patient surveillance (Matharu et al. 2018a ). The present article aims to provide a clinical update regarding ARMD revision surgery in MoMHA patients (hip resurfacing and large-diameter MoM total hip arthroplasty), with specific focus on the threshold for performing ARMD revision, the surgical strategy, and the outcomes following revision. Results and interpretation - The outcomes following ARMD revision surgery appear to have improved with time for several reasons, among them the introduction of regular patient surveillance and lowering of the threshold for performing revision. Furthermore, registry data suggest that outcomes following ARMD revision are influenced by modifiable factors (type of revision procedure and bearing surface implanted), meaning surgeons could potentially reduce failure rates. However, additional large multi-center studies are needed to develop robust thresholds for performing ARMD revision surgery, which will guide surgeons' treatment of MoMHA patients. The long-term systemic effects of metal ion exposure in patients with these implants must also be investigated, which will help establish whether there are any systemic reasons to recommend revision of MoMHAs.

What is appropriate surveillance for metal-on-metal hip arthroplasty patients?

The unexpected high revision rates of large-diameter (femoral head sizes of 36 mm or greater) metal-on-metal hip arthroplasties (MoMHAs) have led to worldwide regulatory authorities recommending regular surveillance, even for asymptomatic individuals. However, these recommendations are not evidence-based and are very costly. The rapidly evolving evidence base requires an update regarding the investigation and management of MoMHA patients. This article is the first of 2 (the second article in this series will consider the threshold for performing revision, and the outcomes following ARMD revision surgery: Matharu et al., Revision surgery of metal-on-metal hip arthroplasties for adverse reactions to metal debris: A clinical update. Acta Orthop 2018; in press), and considers the various investigative modalities used during surveillance, with specific focus on blood metal ion sampling and cross-sectional imaging. No single investigation can universally be used during MoMHA patient surveillance. Recent studies have now provided important information on interpreting blood metal ions (effective in identifying patients at low risk of problems), clarifying the roles of cross-sectional imaging (reserve combined ultrasound and MARS-MRI for complex cases), and providing parameters to safely exclude many asymptomatic patients from regular surveillance. This information will be useful when designing future surveillance protocols for MoMHA patients.

PET/CT to detect adverse reactions to metal debris in patients with metal-on-metal hip arthroplasty: an exploratory prospective study

Metal-on-metal (MoM) bearings in total hip arthroplasties and hip resurfacing arthroplasties have recently shown a new type of complication: adverse reactions to metal debris (ARMD). ARMD is characterized by local severe inflammation and tissue necrosis leading to implant failures. The gluteal muscle region is important for the patient outcome after revision surgery. This prospective positron emission tomography/computed tomography (PET/CT) study was undertaken to evaluate the characteristics of 2-deoxy-2-[¹⁸ F]fluoro-d-glucose ([¹⁸ F]FDG) and [⁶⁸ Ga]Gallium citrate ([⁶⁸ Ga]Citrate) PET/CT in ARMD patients. [¹⁸ F]FDG and [⁶⁸ Ga]Citrate PET/CT were performed in 18 hip arthroplasty patients: 12 ARMD patients (with 16 MoM hips) and six arthroplasty controls without ARMD. Tracer uptake was evaluated visually, and maximum standardized uptake (SUV_max ) was measured in the gluteal muscle region. ARMD severity was graded by metal artefact reduction sequence-magnetic resonance imaging (MARS-MRI). Periprosthetic [¹⁸ F]FDG uptake was observed in 15 of 16 hips, [⁶⁸ Ga]Citrate uptake in three of 16 hips, respectively. The distribution of tracer uptake resembled infection in three hips. In the gluteal muscle region, the SUV_max of [¹⁸ F]FDG was significantly greater in hips with moderate and severe ARMD compared with the controls (P = 0·009 for [¹⁸ F]FDG and P = 0·217 for [⁶⁸ Ga]Citrate). In patients who needed revision surgery, an intraoperative finding of gluteal muscle necrosis was associated with increased local SUV_max as detected by preoperative [¹⁸ F]FDG (P = 0·039), but not by [⁶⁸ Ga]Citrate (P = 0·301). In conclusion, the inflammatory reaction to metal debris in hip arthroplasty patients is best visualized with [¹⁸ F]FDG.