Cobalt-chrome modular neck hip replacements: risk of metal-wear effects and revision surgery (DSI/2026/010)
An MHRA investigation has found increased risks of wear and corrosion associated with multiple cobalt-chrome (Co-Cr) modular neck hip stem components, including a potential increased occurrence of revision surgery due to adverse local tissue reaction (ALTR).
Summary
An MHRA investigation has found increased risks of wear and corrosion associated with multiple cobalt-chrome (Co-Cr) modular neck hip stem components, including a potential increased occurrence of revision surgery due to adverse local tissue reaction (ALTR). There is a potential increased risk of wear and corrosion associated with the presence of two interfaces on the dual taper modular neck: one between the modular neck and the modular hip stem, and another between the modular neck and modular head. MHRA recommends that patients implanted with affected devices should be invited for a virtual or face-to-face clinical review to inform them of the potential risks, assess their clinical presentation and discuss the need for continued follow-up.
Two of the systems in scope of this DSI (ABG II modular and SMF) have already been the subject of previous investigations by the manufacturers. Patients implanted with these devices may not need further follow-up if they are already undergoing monitoring based on the manufacturers’ previous recommendations.
Advice for Healthcare Professionals:
Clinical follow-up recommendation:
- trusts / hospitals should review local and national databases (e.g. the National Joint Registry) to identify patients implanted with the specified devices
- all identified patients should be contacted and invited to attend a virtual or face-to-face clinical review
- all identified patients should be informed of the risks detailed in this Device Safety Information communication
- if symptoms or clinical findings suggest an adverse soft tissue reaction or other metal-related effects, the following follow-up is recommended:
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perform a whole blood test for cobalt and chromium* using a laboratory associated with one of the following schemes:
- in England, Northern Ireland, or Wales: laboratories participating in the UK National External Quality Assessment Service (UK NEQAS)
- in Scotland: the Scottish Trace Element and Micronutrient Reference Laboratories
- conduct cross-sectional imaging using MARS MRI or ultrasound, depending on local trust or hospital policy
-
each patient should be assessed on an individual basis
-
consider revision surgery if any of the following are present:
- abnormal imaging findings
- blood metal levels that are higher than expected and/or rising.
- deterioration in hip-related clinical function or Patient Reported Outcome Measures (PROMs)
-
-
following this clinical review:
- symptomatic patients should be followed up annually while the device remains in place
- asymptomatic patients should be placed on a patient-initiated follow-up (PIFU) pathway where available and advised to return if they develop new or concerning symptoms. Where PIFU is used, the pathway should remain open for as long as the device is in situ, and patients reaching the end of a local PIFU window should be reviewed rather than automatically discharged. Where PIFU is not available, or where a patient is unlikely to be able to initiate contact reliably, they should be given written contact details for the implanting unit and their GP informed of the device and the symptoms that should prompt referral
*there is no agreed threshold value for whole blood metal levels that either predicts outcome, or mandates revision. Decisions to revise are influenced by patient factors, blood metal levels, imaging findings, and implant type and position. Other patient specific factors may need to be considered when interpreting results for blood metal levels.
Advice for Healthcare Professionals to Provide to Patients:
- the majority of patients implanted with these hip replacements have well-functioning hips and are thought to be at a low risk of developing serious problems
- a small number of patients implanted with these hips may, however, develop soft tissue reactions or other metal-related effects resulting in the need for revision surgery. Please refer to Table 1 and discuss the row for the implant system that is relevant to the patient
- patients with affected devices, who have not already been contacted, should expect to be contacted by their surgeon or implanting hospital and invited for a clinical assessment to consider and discuss whether any action is recommended. There is no need for patients to contact their surgeon or implanting hospital directly
- in the meantime, if patients experience any new or unexpected symptoms including pain, stiffness, or instability, they should speak to their implanting surgeon or the hospital where their surgery was performed in the first instance
- none of the implant systems investigated showed a higher-than-expected revision rate due to device fracture
Advice for Distributors:
- there is no advice for distributors regarding this DSI
Explanation of identified safety issue
This investigation followed on from the investigation detailed in DSI/2025/005 which found increased risks of wear and corrosion associated with the Profemur cobalt-chrome modular neck hip system, including an increased occurrence of device fracture and revision surgery.
This investigation examined all other hip replacements with a cobalt-chrome modular neck that have ever been available on the UK market. These devices were all removed from the market prior to 2019 and none remain commercially available.
Cobalt-chrome dual taper modular neck hip replacements were introduced to the market with the intention of allowing better alignment of hip stems to the anatomy of the patient and restoring more natural biomechanics compared to non-modular systems, due to the option for intraoperative decision making.
The potential benefits of this design have been considered alongside the potential increased risk of wear and corrosion associated with the presence of two interfaces: one between the modular neck and the modular hip stem, and another between the modular neck and modular head.
The individual benefits and risks of each device were also considered, given the differences in device design, indications, stated benefits, population of use, number of implants used and available data.
The investigation found that the rate of revision due to metal-related effects (such as ALTR) varied between different implant systems. Table 1 shows a breakdown of usage and outcomes for these devices based on data from the UK National Joint Registry (NJR) extracted in June 2026.
Table 1: Cobalt-chrome modular neck usage and outcomes, based on UK NJR data.
‘Material not specified’ indicates the device was either cobalt-chrome or titanium.
| Year of last implantation | Devices implanted | Devices revised | Devices revised due to ALTR | |
|---|---|---|---|---|
| Aesculap AG (Metha modular) | 2012 | 59 (+ 23 material not specified) | 7* (+ <5 material not specified) | <5* |
| LimaCorporate (H-Max-M) | 2014 | 139 (+ 33 material not specified) | 13 (+ <5 material not specified) | <5 |
| Smith and Nephew (SMF) | 2012 | 12 | 0 | 0 |
| Stryker (ABG II modular) | 2012 | 63 | 17 | <5 |
| Symbios (HARMONY modular) | 2015 | 49 (+7 material not specified) | 10 (+ <5 material not specified) | 0 |
| Symbios (SPS modular) | 2018 | 597 (+ 25 material not specified) | 38 (+ <5 material not specified) | 12 |
*Note that this includes revisions in cases where the Metha modular necks were used off-label in combination with metal-on-metal hip replacements.
None of the implant systems investigated showed a higher-than-expected revision rate due to device fracture, which is different to the findings in DSI/2025/005.
One implant system (SPS modular) was found to have a revision rate due to ALTR approximately twice as high as expected based on statistical analysis and has recently been the subject of a field safety notice because of this investigation.
Three implant systems (Metha modular, H-Max-M, ABG II modular) had limited evidence of revision surgery due to ALTR and two implant systems (SMF and HARMONY modular) had no confirmed evidence of revision surgery due to ALTR at the time of writing in June 2026. Of these systems, ABG II modular and SMF have already been subject to related field safety notices which were initiated in 2012 and 2016 respectively.
The Metha modular, H-Max-M, ABG II, SMF and HARMONY modular systems were not widely adopted in the UK, resulting in a relatively low number of implanted devices. This means that credible conclusions cannot be drawn from statistical analysis of these smaller data sets.
Even where there is limited or no confirmed evidence of increased risks of wear and corrosion, the same design feature (a cobalt-chrome dual taper modular neck) exists across all these devices. This introduces an additional interface between the modular neck and the modular hip stem where wear and corrosion can occur. This is documented in literature for each of these devices [1- 9] except for the HARMONY modular.
Based on the available evidence, including global sales and complaints data, and a review of associated literature, the investigation concluded that follow-up is warranted for all patients with the affected devices.
Three implant systems (ABG II modular, SMF and SPS modular) have associated manufacturer-issued field safety corrective actions as detailed in the next section. For the remaining systems (Metha modular, H-Max-M and HARMONY modular), the manufacturer has not issued a field safety corrective action based on the information available to them. As a precautionary measure, the MHRA recommends applying the same approach to these systems to help make sure that all patients implanted with these types of devices are informed and receive appropriate and consistent follow-up where necessary.
Most of these devices were implanted over 10 years ago and may be approaching the end of their expected lifetime. MHRA’s clinical orthopaedic experts and the Interim Devices Working Group consider that the recommended actions are appropriate since earlier detection of any ALTR should give a better revision outcome should this become necessary.
Previous Field Safety Corrective Action (FSCA)
The ABG II and SMF modular neck ranges were previously subject to the following related field safety corrective actions:
- 05 July 2012 (Manufacturer Reference: RA 2012-067 EXT): Product recall for ABG II modular stems and ABG II modular necks due to variability in adverse local tissue reaction rates among sites. Further information was made available in ‘‘Product Field Action RA 2012-067 EXT ’ in January 2013 and ‘Product Field Action RA 2012-067 EXT 2’ in July 2014.
- 15 November 2016 (Manufacturer Reference: R-2016-48): Voluntary market removal for SMF modular due to a higher than anticipated complaint and adverse event trend.
Patients with these devices who have already been told about the potential risks linked to their hip implant during the previous FSCA may not need further follow-up if they are already undergoing monitoring. These systems are included in this information to help make sure all affected patients have been identified and informed.
The Symbios CoCr modular necks combined with SPS modular stems have recently been subject to the following related field safety corrective action because of this investigation:
- 18 June 2026 (Manufacturer Reference: FA 2026-01): Symbios Cobalt-Chrome Modular Necks assembled with SPS cementless anatomical Modular Stems
Note: This safety communication does not apply to any fixed-neck hip stem products.
Reporting advice
Healthcare professionals should report incidents involving medical devices:
- in England and Wales to the Yellow Card website or via the Yellow Card app
- in Scotland to Incident Reporting & Investigation Centre (IRIC) and their local incident recording system
- in Northern Ireland to the Yellow Card website in accordance with your organisation’s medical device policies and procedures
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Additional information
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For any enquiries, please contact info@mhra.gov.uk
Stakeholder engagement:
- British Orthopaedic Association
- British Hip Society
- UK National Joint Registry
- Interim Devices Working Group
- NHS England National Patient Safety team
- Incident Reporting & Investigation Centre (IRIC) for Scotland
- Welsh Government
- Medical Device and Estates Safety (MDES) within the Department of Health Northern Ireland
An advance copy for review was sent to all the devolved administrations for stakeholder engagement.
References
[1] Grupp TM, Baxmann M, Jansson V, Windhagen H, Heller K-D, Morlock MM, Knaebel H-P. How to Proceed with Asymptomatic Modular Dual Taper Hip Stems in the Case of Acetabular Revision. Materials. 13(5), 1098 (2020). https://doi.org/10.3390/ma13051098.
[2] López, RE, Pelayo de Tomás, JM, Morales Suárez Varela, M. et al. Comparison of chromium and cobalt serum levels between a modular neck stem and its monoblock counterpart in primary total hip arthroplasty. Eur J Orthop Surg Traumatol 33, 3403–3409 (2023). https://doi.org/10.1007/s00590-023-03567-1.
[3] López RE, Pelayo de Tomás JM, Morales Suárez Varela M, Rodrigo Pérez JL. Evolution of chromium and cobalt serum levels after the use of a modular neck stem in primary total hip arthroplasty. Rev Esp Cir Ortop Traumatol. 68(1), 26-34 (2024). https://doi.org/10.1016/j.recot.2023.11.010.
[4] Beauchamp J-E, Vendittoli P-A, Barry J, Pelet S, Belzile EL, Catastrophic failure of femoral stem modular junction when combined with metal-on-metal bearing in comparison to ceramic-on-ceramic: A retrospective cohort study, Orthopaedics & Traumatology: Surgery & Research, 107, 1 (2021) https://doi.org/10.1016/j.otsr.2020.102749.
[5] Gkagkalis G, Mettraux P, Omoumi P, Mischler S, Rüdiger HA. Adverse tissue reaction to corrosion at the neck-stem junction after modular primary total hip arthroplasty. Orthop Traumatol Surg Res. 101(1), 123-6 (2015). https://doi.org/10.1016/j.otsr.2014.11.003.
[6] Laurençon J, Augsburger M, Faouzi M, Becce F, Hassani H, Rüdiger HA. Systemic Metal Ion Levels in Patients With Modular-Neck Stems: A Prospective Cohort Study. The Journal of Arthroplasty, 31(8), 1750-1755 (2016) https://doi.org/10.1016/j.arth.2016.01.030.
[7] Cannella A, Greco T, Polichetti C, De Martino I, Mascio A, Maccauro G, Perisano C. A Rare Case of Adverse Reaction to Metal Debris in a Ceramic-on-Ceramic Total Hip Replacement. J Funct Biomater. 13(3), 145 (2022) https://doi.org/10.3390/jfb13030145.
[8] Inoue D, Restrepo C, Nourie B, Restrepo S, Hozack WJ. Patients With Modular-Neck Total Hip Arthroplasty: A Brief Five-Year Follow-Up Study. J Arthroplasty. 35(6S), S268-S272 (2020). https://doi.org/10.1016/j.arth.2020.02.059.
[9] Kouyoumdjian, P., Mansour, J., Bauzou, F., Michaud, J., & Coulomb, R. (2025). Dual-taper modular stems: aseptic lymphocytic vasculitis-associated lesions (ALVAL): revision rates and outcome in a single hospital series. HIP International, 35(6), 598 - 606. https://doi.org/10.1177/11207000251356413.