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General Recommendations for Orthopaedic Surgeons BEFORE Metal-on-Metal Hip Resurfacing Surgery
Consider your patient's individual characteristics. Each implant has a unique set of benefits and risks which will result in different outcomes in different patient populations.
Select a metal-on-metal (MoM) hip resurfacing implant for your patient only after determining that the benefits of using a MoM hip resurfacing implant outweigh the risks, in comparison to using alternative total hip systems (metal-on-polyethylene, ceramic-on-polyethylene, ceramic-on-ceramic or ceramic-on-metal).
Members of the FDA's Orthopaedic and Rehabilitation Devices Advisory Panel identified young males with larger femoral heads as the best candidates for MoM hip resurfacing systems.
Get adequate training in the technical aspects of each individual implant and the surgical instruments needed.
The success of MoM hip systems is highly dependent on correct placement and implantation.
Contact the manufacturer for device specific information on proper placement.
Thoroughly review the most recent version of approved manufacturer labeling to determine the contraindications, warnings, and precautions of the device being implanted.
Do not implant MoM hip systems in:
Patients with known moderate to severe renal insufficiency
Patients with known metal sensitivity (e.g. cobalt, chromium, nickel)
Patients with suppressed immune systems
Patients currently receiving high doses of corticosteroids
Females of childbearing age
When discussing the implant and procedure with the patient, make sure the patient understands:
There are hip implants available with different bearing surfaces and each type of hip implant has unique benefits and risks.
All hip implants will need to be replaced eventually, and implant longevity is influenced by a patient's age, sex, weight, height, activity level, anatomy, cause of hip pain, and other medical conditions (e.g., overall health, allergies, bone quality, comorbidities). The potential risks associated with MoM hip implants include, but are not limited to:
Infection
Loosening
Dislocation
Osteolysis
Bone or device fracture
Elevated metal ion levels in the joint and blood
Transplacental transport of metal ions
Development of local inflammatory reactions and lesions including soft tissue masses and tissue necrosis
Development of potential systemic events related to elevated metal ion levels
Revision surgery
Femoral neck fracture (for hip resurfacing)
Certain patients have an increased risk for greater wear of the device or for an adverse local tissue reaction (ALTR) and require closer follow-up. These patients may include:
Patients with bilateral implants
Patients with resurfacing systems with small femoral heads (less than or equal to 44 mm). Some manufacturers have recalled resurfacing femoral heads of less than or equal to 46 mm.
Female patients
Patients receiving high doses of corticosteroids
Patients with evidence renal insufficiency
Patients with suppressed immune systems
Patients with suboptimal alignment of device components
Patients with suspected metal sensitivity (e.g. cobalt, chromium, nickel)
Patients who are severely overweight (BMI >40)
Patients with high levels of physical activity
Previously implanted hardware at or near the hip joint may increase wear of the device or the amount of metal exposure to the patient who receives a MoM implant or revision.
There is currently no evidence to support the use of pre-operative skin patch testing or other tests to predict implant sensitivity prior to surgery.
General Recommendations for Orthopaedic Surgeons DURING Metal-on-Metal Hip Resurfacing Surgery
Be aware that suboptimal placement may cause excess wear and early failure.
Pay particular attention to the angles of inclination and anteversion of the acetabular cup.
For resurfacing systems, make sure of appropriate orientation of the femoral stem-shaft angle before cementing into place (all resurfacing femoral heads are intended for cemented use only).
Do not mix components from different hip implant systems. Each hip implant system has different metallurgy and design specifications and it is imperative that all implanted components and their associated instruments be from the SAME manufacturer's marketed hip implant system.
General Recommendations for Orthopaedic Surgeons AFTER Metal-on-Metal Hip Replacement and Resurfacing Surgery (Follow-up)
At the time of hospital discharge, schedule the patient for routine office follow-up.
At the time of hospital discharge, review with the patient or caregiver the signs/symptoms of adverse events.
The FDA recommends routine long-term follow-up of patients with metal-on-metal (MoM) hip implants, typically to occur every 1 to 2 years.
If the patient experiences any pain or decreased hip function approximately 3 or more months after surgery, instruct the patient to contact you for a follow-up exam.
Patient follow-up visits should include:
Physical exam with functional assessment, including careful assessment for hip abduction strength to rule out abductor damage
Check for asymptomatic local swelling or masses; and
Assessment of organs and systems for changes including systemic adverse events in cardiovascular, nervous, endocrine (especially thyroid) and renal systems.
Appropriate radiographs to check for implant positioning and osteolysis
Schedule certain patients with increased risk of device wear or adverse reaction to metal debris (ARMD) for closer follow-up. These may include:
Patients with bilateral implants
Patients with resurfacing systems with small femoral heads (less than or equal to 44 mm)
Female patients
Patients receiving high doses of corticosteroids
Patients with evidence of renal insufficiency
Patients with suppressed immune systems
Patients with suboptimal alignment of device components
Patients with suspected metal sensitivity (e.g. cobalt, chromium, nickel)
Patients who are severely overweight (BMI >40)
Patients with high levels of physical activity
Pay close attention to signs of the following local and systemic symptoms or complications associated with metal-on-metal (MoM) hip implants:
Local symptoms or complications:
Hypersensitivity (allergic type reaction)
Loosening
Infection
Osteolysis (bone loss)
Soft tissue mass or pseudotumor (fluid-filled or solid soft tissue mass around the replaced joint that is diagnosed radiologically)
Femoral neck fracture (for resurfacing systems)
Systemic symptoms or complications:
General hypersensitivity reaction (skin rash)
Cardiomyopathy
Neurological changes including sensory changes (auditory, or visual impairments)
Psychological status change (including depression or cognitive impairment)
Renal function impairment
Thyroid dysfunction (including neck discomfort, fatigue, weight gain or feeling cold
Follow-Up for Asymptomatic Patients Clinical Evaluation
If a patient with a metal-on-metal (MoM) hip implant is asymptomatic and has a well-functioning hip, follow-up should occur periodically (typically 1 to 2 years), as with any hip arthroplasty.
Be aware the following patients may experience increased wear of the implant and/or adverse reaction to metal debris and require closer monitoring. They include:
Patients with bilateral implants
Patients with resurfacing systems with small femoral heads (less than or equal to 44mm)
Female patients
Patients receiving high doses of corticosteroids
Patients with evidence of renal insufficiency
Patients with suppressed immune systems
Patients with suboptimal alignment of device components
Patients with suspected metal sensitivity (e.g. cobalt, chromium, nickel)
Patients who are severely overweight (BMI >40)
Patients with high levels of physical activity
Patient follow-up visits should include:
Physical exam with functional assessment; with attention to abductor strength and Trendelenburg test to rule out abductor damage
Checking for asymptomatic local swelling or masses; and
Assessment for possible systemic adverse events in cardiovascular, nervous, endocrine (especially thyroid) and renal systems.
Appropriate radiographs to evaluate for osteolysis or loosening.
Additional Testing for Asymptomatic Patients
If clinical and imaging data support that the hip prosthesis is functioning properly and the patient is asymptomatic, the FDA is not aware of data which supports the need to routinely check blood metal ion levels or perform soft tissue imaging.
Findings of lesions on soft tissue imaging, or of elevated blood metal ion levels in the absence of symptoms have been reported in a limited number of research studies for some MoM hip implant patients. These studies are difficult to interpret because:
The exact incidence or prevalence of asymptomatic lesions and their natural history is not known.
The correlation between elevated blood metal ion levels in isolation and development of potential local or systemic adverse reactions is not well established
If the orthopaedic surgeon determines it is in the best interest of the patient to conduct soft tissue imaging, please review the FDA's recommendations.
If the orthopaedic surgeon determines it is in the best interest of the patient to test metal ion levels, please review the FDA's recommendations.
Follow-Up for Symptomatic Patients
Clinical Evaluation
If a patient experiences local symptoms (i.e. pain or swelling at or near the hip, a change in walking ability such as development of Trendelenburg gait, or a noise from the hip joint) more than three months after metal-on-metal (MoM) hip implant surgery, conduct a thorough evaluation, with attention to abductor weakness or Trendelenburg sign to identify abductor damage.
Follow-up of symptomatic patients with MoM hip implants should occur at least every six months.
Guide your clinical evaluation by the symptoms and physical findings, including an assessment for well-known and more common emergent complications including joint infection, implant loosening, peri-prosthetic facture and dislocation.
Recognize that localized lesions associated with reactions to metal debris may also present with pain or a variety signs and symptoms including:
Local nerve palsy
Palpable mass
Local swelling
Joint dislocation or subluxation
Abductor weakness
Additional Testing for Symptomatic Patients
In some patients with symptoms, plain radiograph findings (e.g. osteolysis, femoral neck narrowing, component suboptimal positioning, fracture), in conjunction with other non-imaging information, are sufficient to indicate a need for revision surgery.
In other symptomatic patients, cross-sectional imaging should be considered to diagnose and assess soft tissue findings surrounding an implant.
Patients with MoM hip implants who develop any symptoms or physical findings that indicate their device may not be functioning properly, should be considered for metal ion testing. (Link to Important Considerations for Metal Ion Testing). It is important to note that at the current time, there is insufficient evidence in the U.S. demonstrating a correlation between a metal ion level in isolation and the presence of localized lesions, clinical outcomes and/or the need for revision surgery.
Assessment for Systemic Effects
Evaluate patients with new systemic symptoms in collaboration with their primary medical physicians or specialists to determine the cause of their symptoms or findings.
Patients with evidence of excessive device wear or a localized adverse local tissue reaction (ALTR) should be assessed for potential systemic effects of exposure to metal ions.
A thorough physical examination should be performed by the patient's health care team, which include primary medical physicians and/or specialists, with particular focus on cardiovascular, neurological, endocrinological (especially thyroid), and renal systems.
Because metal ions are cleared through the kidneys, a patient who has renal insufficiency may be at higher risk for systemic adverse events. Blood urea nitrogen (BUN) and creatinine levels may be measured to evaluate a patient's renal function.
Device Revisions
At this time, there is not enough evidence to provide a science-based recommendation for a threshold value of metal ion levels in the blood that would serve as a trigger for revision.
The decision to revise a patient's metal-on-metal (MoM) hip implant should be made in response to the overall clinical scenario and results of diagnostic testing.
In extreme cases, adverse local tissue reactions (ALTR) may significantly damage periprosthetic bone, muscle, and nerves. Therefore patients with progressing ALTR, may be considered for earlier revision to prevent extensive damage.
If you recommend revision, advise patients of the surgical risks of revision as well as the expected outcomes, including:
Revision procedures are complicated and may not fully resolve a patient's pain nor restore complete function;
In case of ALTR, revision of a MoM hip may have a worse prognosis than revision of other types of bearing surfaces especially for subsequent hip dislocation.
Possible need for an additional revision procedure in the future; and
Metal ion levels should be expected to decrease after revision.
In selecting components for revision:
Check the specific device labeling for compatibility of device components.
Consider the benefits and risks of all bearing surfaces for each patient.
If a patient is suspected to have developed metal sensitivity, carefully select the materials of the revision components (potentially avoiding materials with nickel or chromium).
In order to better understand the performance of these devices and causes of failure, a retrieval analysis is recommended, especially in cases where there is no obvious cause for implant failure such as suboptimal positioning.
Talk to the patient about returning the implant for retrieval analysis. A retrieval analysis is a vital part of a manufacturer's quality system allowing them to assess manufacturing and quality processes through their Corrective and Preventative Action (CAPA) system.
If the patient agrees, contact the manufacturer prior to revision surgery for instructions on returning the implant for analysis.
Along with the implant, provide non-identifying information about the patient, the date of procedure, observations from the revision surgery and the histopathology report from any tissue sent to the hospital pathologist.
