From California Technology Assessment Forum
Metal on Metal Hip Resurfacing as an Alternative to Total Hip Arthroplasty: A Technology Assessment
Introduction and Background
Introduction
The California Technology Assessment Forum (CTAF) is requested to review the scientific evidence for metal on metal (MoM) hip resurfacing as an alternative to total hip arthroplasty. This is an update to the CTAF assessment done on this same topic in 2007.[1]
Background
Disease affecting the hip joint is usually caused by osteoarthritis (OA), the most common form of joint disease.[2] OA is chiefly a disease of aging; 90% of all people have radiographic features of OA in weight-bearing joints by age 40.[3] It is characterized by changes to the structure of the entire joint, particularly degeneration of cartilage and hypertrophy of bone at the articular margins.[4] The presenting symptom of osteoarthritis of the hip is generally pain, which may be associated with a limited range of motion; though pain in the hip may be referred from other regions of the body, referred to other structures (such as the knee) or may be confused with other etiologies such as trochanteric bursitis.
Hereditary and mechanical factors may be involved in the pathogenesis of OA. Obesity is a risk factor for knee osteoarthritis and probably for the hip. Participation in competitive contact sports increases risk as do jobs requiring frequent bending and carrying; for example, farming carries a significantly increased relative risk for OA.[5]
OA of the hip joint contributes to morbidity for the individual and costs to society. Overall, OA is the sixth leading contributor worldwide to total years lost to disability, or disability adjusted life years (DALYs).[5] Individuals with hip OA may suffer from pain, stiffness and loss of function, adversely impacting their health related quality of life. The direct and indirect societal costs attributable to OA are enormous. For example, Individuals with OA are more likely to reduce work hours or take early retirement. Older adults with symptomatic arthritis report greater medical utilization and health care costs compared with people not reporting arthritis.[6]
Rheumatoid arthritis (RA), an inflammatory arthropathy, may also lead to degeneration of the hip joint, but because it is a systemic condition is unlikely to affect the hip joint alone. Involvement of the hip joint in RA occurs in ten percent to 40% of individuals.[2] Other conditions that can cause secondary OA are avascular necrosis, congenital dislocation, Paget’s disease, ankylosing spondylitis and traumatic arthritis.
Treatment for degenerative disease of the hip includes pharmacological and non-pharmacological measures, including lifestyle interventions. Analgesics such as acetaminophen and narcotics can treat the pain associated with the disease and improve function; non-steroidal anti-inflammatory medications, such as ibuprofen, can also be used and are more effective in more advanced disease but are less safe. Corticosteroid injections are a mainstay of treatment for OA and RA, though injections into the hip joint often need to be done under radiographic guidance.[7] Lifestyle interventions used to prevent or ameliorate the progression of OA include weight loss, exercise and physical therapy. Surgical interventions include arthroscopy, MoM hip resurfacing arthroplasty (HRA) and total hip arthroplasty (THA). More than 168,000 total hip arthroplasties are performed annually in the United States.[8]
In the 1950’s the concept of resurfacing the arthritic socket, as well as the femoral head, emerged, but the material used (first Teflon and then methacrylate cement) and design flaws led to numerous device failures and adverse events, such as avascular necrosis.[9] The third generation of hip resurfacing emerged in England in the 1990s, and while there are at least ten different commercially available hip resurfacing systems, to date only the Birmingham Hip Resurfacing (BHR), the Cormet 2000, and the Conserve Plus systems are FDA approved. All three of these systems use a MoM Cobalt-Chromium articulation, but they use different combinations of materials for the backing of the acetabular component. While there are differences in materials and design, all hip resurfacing devices consist of two parts: a cup shaped acetabular component and a cemented femoral cap with a stem that inserts into the femur.
The potential advantage of MoM hip resurfacing over THA is that it allows for most of the femoral head to be preserved and only replaces the surface of the joint; this maintains the femoral canal and can make revision surgery, if necessary, less complex.[10] Thus, MoM hip resurfacing has been promoted for younger patients with end-stage OA of the hip or RA, traumatic arthritis, hip dysplasia or avascular necrosis for whom conventional THA is not expected to last their lifetime. Other potential advantages of hip resurfacing over THA include earlier return to function and less restriction on function compared to THA. However, one expert points out that the posterior approach favored in resurfacing devascularizes the femoral head, possibly permanently, potentially leading to avascular necrosis over time.[11] Hip resurfacing is considered by most to be a more challenging operation for the surgeon than THA and requires specialized training and a significant learning curve.[12-14]
The 2007 CTAF assessment concluded that the peer-reviewed literature had not kept pace with changes in hip resurfacing technology; most of the published literature consisted of case series from single surgeons, and there were no randomized controlled trials of FDA approved hip resurfacing devices.[1] We undertake the current assessment to review the peer-reviewed literature of the three FDA approved MoM hip resurfacing systems published since the 2007 assessment, with a particular focus on randomized controlled trials (RCT) and comparative study (level 1-4) evidence.
Technology Assessment (TA)
TA Criterion 1: The technology must have final approval from the appropriate government regulatory bodies.
The Birmingham Hip Resurfacing (BHR) system (Smith & Nephew Inc., Memphis, TN, USA) received FDA PMA approval in 2006.
The Cormet 2000 Hip Resurfacing System (Corin USA, Tampa, FL, USA) received FDA PMA approval in July 2007.
Wright Medical Technologies (Arlington, TX, USA) CONSERVE Plus Hip System received FDA PMA approval in November 2009.
There are several other hip resurfacing devices which have been developed but which have not received FDA clearance at this time.
TA Criterion 1 is met.
TA Criterion 2: The scientific evidence must permit conclusions concerning the effectiveness of the technology regarding health outcomes.
The Medline, Embase, and Cochrane clinical trials database, Cochrane reviews database and the Database of Abstracts of Reviews of Effects (DARE) were searched for relevant references through April 2010. While the majority of the search results were published case studies, there were four RCTs, two since the 2007 CTAF assessment and none of which studied an FDA approved device.[15-18] One of these RCTs resulted in multiple publications.[18-22] There was a final publication which presented the study protocol for a planned RCT comparing MoM hip resurfacing to THA, but didn’t state which MoM would be studied.[23] In addition, there were nine publications reporting on six non-randomized comparison studies.[24-32]
Level of Evidence: 3,4,5
TA Criterion 2 is met.
TA Criterion 3: The technology must improve net health outcomes.
Randomized Controlled Trials
As noted above, there are three published RCT’s of MoM hip resurfacing compared with total hip arthroplasty, none of which studied an FDA approved device. As noted in the 2007 CTAF assessment, the first, by Howie et al, was stopped early due to early failures in the MoM hip resurfacing group.[17] The second, by Venditolli et al, found no difference in satisfaction or complication rates, but the MoM hip resurfacing group had better postoperative functional performance.[18] The third, by Garbuz et al, compared a non-FDA approved device to large diameter MoM total hip arthroplasty and while they found no difference in quality of life (QoL) outcomes, they noted increased serum cobalt and chromium ion levels in both groups, but highest in MoM large head total hip arthroplasty, demonstrating that circulating metal ions are a concern for all MoM hip devices.[16] The final trial, by Lavigne et al, compared a non-FDA approved device to large diameter total hip arthroplasty and found no difference in gait speed, postural balance, and clinical scores; both groups achieved similar function to a healthy control group by three months.[15]
Non-Randomized Comparative Studies
Again, as noted above, our search turned up nine publications reporting on six non-randomized comparison studies. ( Table 1 .) All of these studies had small sample sizes and for many of them their comparator groups were either recruited selectively or were historical controls. Only one study – Brennan et al – reported on the BHR and they compared the weight of acetabular reamings for BHR patients to differentially selected un-cemented THA patients and found the weights to be similar; this is at best a surrogate marker for potential adverse outcome of a femoral neck fracture.[24]
Of the six publications reporting on the Conserve Plus hip resurfacing system, three reported slightly different comparisons and/or outcomes for overlapping patient populations,[27, 28, 32] and a fourth may well also be from an overlapping population given that the authors are also overlapping.[29] These were retrospective analyses comparing MoM hip resurfacing patients to historical control patients with ‘conventional’ THA from a separate registry; taken together they found no difference in Harris Hip Score – a measure of pain, function, satisfaction, or range of motion. There was a difference in activity level; however, activity level was different in the two groups at baseline and no adjustments were made for this, possibly because of the small sample sizes. A fifth study had similar findings and similar limitations.[25] The sixth study of Conserve Plus was a retrospective study in which patients acted as their own controls – they assessed range of motion in those patients in their registry who had MoM hip resurfacing on one side and THA on the other, some of which were revisions from prior resurfacing procedures.[26] These authors found no difference by type of replacement, including no difference in the subset of patients with revisions and no difference when stratified by size of implant. Of note, the study was underpowered for these subanalyses.
Two papers reported on the Cormet 2000 hip resurfacing system in the same patient population.[30, 31] The earlier report concludes that the resurfacing patients had equal overall clinical success with the ceramic-on-ceramic THA patients in terms of a composite score including Harris Hip Score, ‘radiographic evidence of success’, absence of device related complications and absence of revision; however, the MoM hip resurfacing group had substantially more revisions (7.1% vs. 1.9%) in a shorter follow-up time frame.[31] Revisions were primarily due to femoral neck fractures and femoral component loosening. The THA group was the historical control. The later report assessed the Harris Hip Score at specific time-points over two-year follow-up in the same two groups of patients, concluding that while there were differences early on, with the THA group doing better at six weeks and the MoM hip resurfacing group doing better at six months, there was no difference at 12 or 24 months with >90% of both groups scoring in the excellent range.[30]
Studies Focused on Adverse Outcomes or Side Effects
Our search found eight publications since the 2007 CTAF assessment which specifically focus on adverse events associated with FDA approved hip resurfacing device systems, four reporting on early failure[33-36] and four reporting on blood metal ion levels.[37-40] Of the four studies focused on early failure and revision rates, three were case series and one was a meta-analysis.[36] The case series with the longest follow-up period (mean five years) included patients with varying MoM hip resurfacing devices in place, but most were BHR, and reported a 5.2% failure rate with pain being the predominant reason for revision and loosening of the femoral component the next most common cause.[33] The other study of BHR had a much lower revision rate (2.8%) with a shorter mean follow-up time of 3.5 years, and pain was also the predominant cause, followed by femoral neck fracture.[35] At time of revision, these authors found evidence of metallosis (immune reaction to metal) and necrosis. The meta-analysis included multiple devices for both MoM hip resurfacing and the comparator THA patients, although all of the THA had cementless femoral components, and all of the included studies had a young patient population (mean age <55).[36] These authors found a higher overall failure rate for THA when failure was defined as all reasons, including after revision and asymptomatic radiographic failure. The THA patients had approximately double the follow-up time as the hip resurfacing patients (8.5 years vs. 3.9 years). When the authors defined failure more narrowly to focus on the greatest risk with MoM hip resurfacing as ‘femoral failure due to mechanical failure’, the hip resurfacing group had about double the rate of failure.
There has been increasing concern in the literature about blood metal ion levels as a result of wear from metal on metal hip replacements, in both hip resurfacing and THA. While there is no safe or toxic level of chromium and cobalt in the blood, the concern about increased levels ranges from local tissue toxicity, to chromosomal damage and malignant cellular transformation.[41-44] The four publications that focused on this topic all studied patients with BHR. One found that both hip resurfacing and metal-on-metal THA patients with small diameter (28mm) heads had similar chromium and cobalt levels, both higher than healthy controls without metal implants.[40]Another study compared unilateral MoM BHR, bilateral MoM BHR with metal-on-polyethylene THA and ceramic-on-ceramic THA.[37] They report the highest chromium and cobalt ion levels with both types of MoM hip replacement, smaller elevation for the metal-on-polyethylene group, and negligible levels for the ceramic-on-ceramic group. A third study again reported increased ion levels for patients with MoM hip resurfacing implants; however, they found that as the femoral component size increased, ion levels decreased, implying that with less friction and wear there is less release of ions.[39] The fourth study found enhanced lymphocyte activity for nickel, but not for chromium and cobalt; there was no difference for patients with and without pseudotumors (a cystic or solid mass relating to resurfaced hip), although the pseudotumor group was very small (n=10).[38]
TA Criterion 3 is met.
TA Criterion 4: The technology must be as beneficial as any established alternatives.
The primary established alternative is total hip arthroplasty. While there are no RCTs of the FDA approved hip resurfacing devices comparing to current conventional THA devices, the comparison studies cited above all report results showing equivalent functional results after MoM hip resurfacing and THA. While there is concern about early failure requiring revision after MoM hip resurfacing, THA presents other concerns particularly for younger, more active patients who have risk of shattering their femur in the event of trauma and who will undoubtedly require repeat THA with less and less available bone over time. Concern about metal ions exists for both resurfacing and THA (metal-on-metal).
TA Criterion 4 is met.
TA Criterion 5: The improvement must be attainable outside of the investigational setting.
MoM hip resurfacing has been used broadly outside of investigational settings. Each device requires training and given a considerable learning curve – and adverse events including early failure associated with inexperienced surgeons – hip resurfacing should only be performed after appropriate training and early cases should be supervised by experienced surgeons.
Conclusion
While there are more published studies comparing hip resurfacing with THA than at the time of the CTAF 2007 assessment, all of which suggest equivalent results for resurfacing and THA, some of the same questions that were of concern at that time remain and we reiterate them here: What is the long term durability of the resurfaced hip compared with THA? What will be the short and long term results when this generation of younger patients who have undergone hip resurfacing are eventually converted to THA? Will there be unforeseen long term complications that will make this revision more problematic than anticipated? What are the long term health consequences of increased low levels of circulating metal ions produced by MoM hip resurfacing? It is incumbent upon the hip resurfacing community to continue to investigate these questions and assure that metal-on-metal hip resurfacing continues to be a viable and safe option for young active patients with degenerative hip disease.
Despite these remaining questions, after considerable discussion and expert testimony regarding the existing data on both benefits and harms, the forum supported approval of metal-on-metal hip resurfacing as an alternative to total hip arthroplasty.
Recommendation
It is recommended that metal on metal hip resurfacing by surgeons who have completed training using FDA-approved devices meets CTAF criteria 1 through 5 as an intervention for degenerative hip disease in appropriate patients younger or <65 who have an active life expectancy of more than 10 to 15 years.
June 2, 2010
This is the second assessment of this technology.
The CTAF panel voted in favor of the recommendation as noted above.
Recommendations of Others
Blue Cross Blue Shield Association (BCBSA)
A June 2007 assessment by the BCBSA Technology Evaluation Center found that “use of an FDA-approved metal-on-metal total hip resurfacing device as an alternative to THA in patients who are likely to outlive the 10 years or more functional lifespan of a traditional MoM prosthesis meets the TEC criteria.”
Centers for Medicare and Medicaid Services (CMS)
Neither a National Coverage Decision nor a Local Coverage Decision was found through a search of the CMS Coverage database.
California Orthopaedic Association (COA)
The COA was invited to have a representative attend the meeting and to provide an opinion on this technology.
Alliance for Orthopedic Solutions
The Alliance for Orthopedic Solutions provided an opinion and attended the meeting to provide testimony.
National Institute for Health and Clinical Excellence (NICE)
In 2002 NICE issued a guidance document which states (in part):
"MoM hip resurfacing is recommended as an option for people with advanced hip disease who would otherwise receive a conventional primary total hip replacement (THR) and are likely to live longer than the device is likely to last." This document is available at: http://guidance.nice.org.uk/TA44.
"MoM hip resurfacing is recommended as an option for people with advanced hip disease who would otherwise receive a conventional primary total hip replacement (THR) and are likely to live longer than the device is likely to last." This document is available at: http://guidance.nice.org.uk/TA44.
Canadian Coordinating Office for Health Technology Assessment (CCOHTA)
In March 2005 the CCOHTA published a document on Minimally Invasive Hip Resurfacing. This is the most current document as of March 2010. The CCOHTA notes: “Outcome-based research and long-term follow-up are necessary to assess the clinical and economic impact of a minimally invasive approach to hip resurfacing. There is also a need for defined criteria to determine which patients might benefit from this surgical approach”.
No hay comentarios:
Publicar un comentario