Bearing selection for total hip arthroplasty in young patients is important because of the likely long service life of the implant. Careful consideration of the next operation is recommended when choosing components. No prospective, randomized studies exist that document the clear superiority of any bearing couple in young, active patients. Modern metals, ceramics, and polyethylenes all hold promise. Further long-term data on modern bearings are needed to determine the clinical performance of these bearings. This article summarizes the available data on various bearing couples in patients aged younger than 50 years.
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Consider the next operation (revisability) of any implant in young, active patients.
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Hard-on-hard bearings have generally not resulted in significantly lower wear and less reoperations (survivorship) in young, active patients. Squeaking, sensitivity to component position, and adverse reactions to debris remain concerning.
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Modern ceramic or metal on modern polyethylenes probably represent the most predictable bearing choices for young, active patients in 2012; however, long-term data are needed to properly support this assumption.
Introduction
Over the past few decades, various procedures have been introduced to preserve the native hip joint in young patients. Concerns about wear-related premature failure of arthroplasty in young patients remain. Despite our best efforts, in some situations, arthroplasty is the only remaining reasonable reconstructive option. Few patients are willing to accept arthrodesis of the hip when presented with the alternative of hip arthroplasty. Modern advances in uncemented technology have essentially solved the problem of long-term fixation of the acetabular and femoral components. Various studies have documented the long-term durability of various ingrowth surfaces and various stem geometries. The preference of component selection will vary by surgeon, bone quality, and anatomy. Cemented fixation in young active patients has generally fallen out of favor in North America. Most surgeons would choose uncemented components for total hip arthroplasty (THA) in young patients. Practically speaking, therefore, the more challenging decision making surrounds the choice of bearing surface. The purpose of this article is to review various bearing surface choices, their pros and cons, and to summarize the available published long-term data on the performance of various bearing couples, specifically in patients aged younger than age 50.
Component selection in young patients
When a THA is implanted in a young patient, it is safe to assume that the most likely long-term problem that patient will face in the future is osteolysis from bearing-related wear debris. Every arthroplasty will eventually fail and require revision. With this in mind, it is important, in the authors’ opinion, to consider the revisability of any implanted components. For example, a modular, uncemented, acetabular component offers the ease of later liner exchange. Future improvements in bearing surface (ie, next-generation polyethylenes) may be available to further improve the durability of the construct. Such an option is not available on a monoblock, all-metal, acetabular component designed to articulate with a large metal head. Many studies support such lesional treatment of osteolytic defects with retention of well-fixed acetabular components. Additionally, modularity offers the insertion of liners with various lipped elevations and offsets and various head sizes to optimize hip stability. Such a need to plan for the future revision is important in patients aged younger than 50 years.
The recent problems with metal-on-metal bearings have caused some concern among surgeons that considered such monoblock, large-head, metal-on-metal articulations as a potential benefit for young, active patients. There is a growing body of knowledge on adverse reactions to metal-on-metal devices, and the true scope of the problem has not yet been defined. Many of these constructs used monoblock, screwless, uncemented, acetabular components that essentially require the revision of a well-fixed cup (with associated bone loss) to perform a bearing exchange. This example has led the authors to abandon any monoblock, single-bearing acetabular components. The authors routinely choose modular, uncemented, acetabular components, which facilitate later bearing exchange and allow multiple bearing options.
Component selection in young patients
When a THA is implanted in a young patient, it is safe to assume that the most likely long-term problem that patient will face in the future is osteolysis from bearing-related wear debris. Every arthroplasty will eventually fail and require revision. With this in mind, it is important, in the authors’ opinion, to consider the revisability of any implanted components. For example, a modular, uncemented, acetabular component offers the ease of later liner exchange. Future improvements in bearing surface (ie, next-generation polyethylenes) may be available to further improve the durability of the construct. Such an option is not available on a monoblock, all-metal, acetabular component designed to articulate with a large metal head. Many studies support such lesional treatment of osteolytic defects with retention of well-fixed acetabular components. Additionally, modularity offers the insertion of liners with various lipped elevations and offsets and various head sizes to optimize hip stability. Such a need to plan for the future revision is important in patients aged younger than 50 years.
The recent problems with metal-on-metal bearings have caused some concern among surgeons that considered such monoblock, large-head, metal-on-metal articulations as a potential benefit for young, active patients. There is a growing body of knowledge on adverse reactions to metal-on-metal devices, and the true scope of the problem has not yet been defined. Many of these constructs used monoblock, screwless, uncemented, acetabular components that essentially require the revision of a well-fixed cup (with associated bone loss) to perform a bearing exchange. This example has led the authors to abandon any monoblock, single-bearing acetabular components. The authors routinely choose modular, uncemented, acetabular components, which facilitate later bearing exchange and allow multiple bearing options.
Hard-on-hard bearings
Theoretically, these bearings offered the potential benefit of low wear rates and potentially lower rates of clinically problematic osteolysis. Ceramic-on-ceramic and metal-on-metal bearings enjoyed periods of popularity in the last few decades. Unfortunately, further follow-up demonstrated that these surfaces were sensitive to component positioning. For example, a slightly vertical cup placement could cause stripe wear and increased debris generation. Ceramic-on-ceramic bearings also occasionally demonstrated the unique but uncommon problem of squeaking. Good results have been reported, but a clear clinical benefit (ie, lower revision rate) has not been demonstrated to date.
Metal-on-metal bearings offered the potential benefit of large femoral head diameters that would optimize range of motion and hip stability. Additionally, the initial impressions were that debris from these bearing couples would be ionic and, therefore, cleared by the kidneys, potentially minimizing the local tissue response to wear debris. Obviously, recent data have demonstrated a concerning rate of local tissue reactions to metal wear debris. Pseudotumors and painful fluid collections continue to occur. The true scope of the problem has not yet been elucidated. The previous concerns have led many North American surgeons to abandon hard-on-hard bearings. It is important to realize that data exist that document reasonable survivorship of metal-on-metal and ceramic-on-ceramic bearings. All designs are not alike, making direct comparisons nearly impossible.
Ceramic-on-polyethylene bearings
Reasonable data exist to demonstrate improved wear performance of ceramic-on-polyethylene bearings when compared with metal-on-polyethylene bearings; however, a clear clinical benefit to these decreased wear rates (ie, greater survivorship) has not been clearly documented. Advances in modern ceramic heads have decreased but not eliminated concerns about fracture, even in young, active patients. Many surgeons currently consider ceramic-on-cross-linked polyethylene bearings as the bearings of choice for young, active patients; however, considerable controversy still exists. Only longer-term follow-up will provide further information on the best bearing choice.
Newer-generation polyethylenes
An ever-increasing body of data continues to support the improved performance of cross-linked polyethylenes with modern sterilization and packaging processes. The wear rates have improved based on penetration studies; generally, revisions for osteolysis with a modern bearing are rare in the absence of cup malposition. Again, a clear increase in survivorship has not been demonstrated; however, it is probably reasonable to assume that improved wear rates will translate into lower rates of revision for osteolysis. Various manufacturers are adding antioxidant additives to minimize in vivo oxidation. Long-term data supporting this improvement are not yet available. The clinical performance of these newer polyethylenes has also driven surgeons back to polyethylene and away from hard-on-hard bearing couples. Polyethylene liners also offer various offsets, head-size options, and elevated lips that cannot be used in hard-on-hard bearings. Reasonably large femoral heads can now safely be used with modern polyethylenes with a low reported rate of liner fractures. It is clear that metal- or ceramic-on-polyethylene bearings will generate debris and eventually lead to osteolysis; however, this is a problem that can effectively be treated with bearing exchange with or without grafting of osteolytic lesions. Essentially, we know how these bearing couples will fail and how to treat them when they do. The same cannot be said for wear-related problems with hard-on-hard bearing couples.
Published data
The available data are heterogeneous, with various femoral and acetabular components, various approaches, and multiple surgeons involved. Table 1 summarizes published data on THA in young patients and delineates the bearing type and survivorship results. Keep in mind that this data cover many decades, and improvements in bearing couples may not allow extrapolation of older gamma-in-air sterilized polyethylene results to the expected performance of modern polyethylenes. It is nearly impossible to make any direct comparisons from the available literature. It is possible, however, to evaluate the larger studies, with contemporary implants and modern sterilization techniques, and to discern some trends in bearing performance. Prospective randomized studies with modern bearings and reasonable lengths of follow-up (at least 15 years) are not available to allow the surgeon to determine which bearing surface is best for a particular patient. A good understanding of the pros and cons of every bearing couple is important, therefore, to guide patients and surgeons alike.
| Reference | Bearing Surface | Number of Patients | Mean Age | Mean Follow-Up (mo) | Survivorship |
|---|---|---|---|---|---|
| Mont et al, 1993 | Metal on PE Uncemented | 42 | 36 | 54.0 | 1 revision because of aseptic loosening (2%) |
| Berger et al, 1997 | Metal on PE Uncemented | 57 | 37 | 106.0 | 98.8% survivorship at 10 y (acetabular component only) |
| Dowdy et al, 1997 | Metal on PE Uncemented | 36 | 42 | 63.6 | 3 of 41 hips (7.3%) revised because of aseptic loosening or osteolysis of acetabular component No revisions for femoral component |
| Kronick et al, 1997 | Metal on PE Uncemented | 154 | 37.6 | 99.6 | 2 (1.2%) femoral revisions 5 (3.4%) acetabular revisions for failure |
| McLaughlin and Lee, 2000 | Metal on PE Uncemented | 82 | 37 | 122.4 | No femoral component required revision for aseptic loosening 98% chance of survival of femoral component at 12 y |
| McLaughlin and Lee, 2011 | Metal on PE Uncemented | 79 | 36 | 192.0 | Survival of femoral component (revision for aseptic loosening as endpoint) was 100% at 18 y Survival of femoral component (revision for any reason as endpoint) was 97% at 18 y |
| D’Antonio et al, 1997 | Metal on PE Uncemented (hydroxyapatite) | 136 | 38.4 | 81.6 | No stem revised for aseptic loosening and femoral component mechanical failure rate was 0% |
| Chiu et al, 2001 | Metal on PE Uncemented | 45 | 33 | 91.2 | 98% survivorship at 5 and 10 y (revision for aseptic loosening as endpoint) |
| Capello et al, 2003 | Metal on PE Uncemented (hydroxyapatite) | 91 | 39 | 135.0 | Femoral component showed 99.1% survivorship at minimum follow-up of 10 y (1 stem revised because of aseptic loosening) |
| Singh et al, 2004 | Metal on PE Ceramic on PE Cemented and uncemented cups | 33 | 42 | 120.0 | Uncemented stem 100% at 12 y Uncemented cup 96% at 10 y Cemented cup 90.5% at 12 y |
| Hartley et al, 2000 | Metal on PE Uncemented | 39 | 31 | 112.0 | 12.5% required revision for osteolysis and PE wear (none because of femoral side) |
| Dunkley et al, 2000 | Metal on PE Uncemented | 50 | 41 | 84.0 | No acetabular components revised for loosening 10.9% acetabular liners replaced for excessive PE wear |
| Duffy et al, 2001 | Metal on PE Uncemented | 72 | 32 | 123.6 | Estimated survival-free revision for aseptic loosening or osteolysis 97.5% (5 y) and 80.1% (10 y) |
| Crowther et al, 2002 | Metal on PE Uncemented | 44 | 37 | 132.0 | 98% survival of acetabular component at 10 y Average wear rate: 0.15 mm/y |
| Kim et al, 2003 | Metal on PE Uncemented | 80 | 46.8 | 117.6 | No aseptic loosening at latest follow-up 10-y survival with revision as endpoint is 99% for acetabular and femoral components With loosening as endpoint, 10-y survival is 100% Average wear rate: 0.12 mm/y |
| McAuley et al, 2004 | Metal on PE Uncemented | 488 | 40 | 83.0 | Survivorship of THA (with revision of cup or stem excluding PE exchange as endpoint): 98.4% (5 y), 93.2% (10 y), 79.0% (15 y) Survival of stem (any stem revision as endpoint): 99.0% (5 y), 98.2% (10 y), 95.0% (15 y) Survival of cup (any cup revision as endpoint): 97.4% (5 y), 87.6% (10 y), 53.8% (15 y) |
| Kearns et al, 2006 | Metal on PE Uncemented | 221 | 41.1 | 100.8 | Overall survival: 81.2% (10 y) and 46.8% (15 y) 21 revisions (30% of all revisions) because of aseptic loosening Femoral stem survival: 99.3% (5 y), 98.9% (10 y), 96.8% (15 y) Acetabular survival: 98.7% (5 y), 84.6% (10 y), 52.5% (15 y) |
| Collis, 1991 | Metal on PE Cemented | 25 | <50 | 178.8 | 15-y survival rate (need for revision as endpoint) 69% |
| Barrack et al, 1992 | Metal on PE Cemented | 44 | 40.9 | 144.0 | No femoral component revised for aseptic loosening 11 (22%) cemented acetabular components revised for aseptic loosening |
| Joshi et al, 1993 | Metal on PE Cemented | 103 | 32 | 192.0 | Probability of implant survival at 20 y was 75% Overall probability of cup survival at 20 y was 84% Overall probability of femoral component survival at 20 y was 86% |
| Ballard et al, 1994 | Metal on PE Cemented | 36 | 41 | 132.0 | With aseptic loosening that would lead to revision as endpoint, 10-y survival was 83% for acetabular component and 95% for femoral component 10 hips revised (all because of aseptic loosening of acetabular component): femoral component loose in 2 of the 10 |
| Devitt et al, 1997 | Metal on PE Cemented | 77 | 42 | 217.2 | 27 hips revised (20.4%): 77% of revisions because of aseptic loosening Overall probability of implant survival at 20 y 75% |
| Sullivan et al, 1994 | Metal on PE Cemented | 57 | 42 | 216.0 | 13% revision rate for aseptic loosening of acetabular component 2% revision rate for aseptic loosening of femoral component 22-y survival (revision because of aseptic failure) of acetabular component 76% 22-y survival (revision because of aseptic failure as endpoint) of femoral component 92% |
| Smith et al, 2000 | Metal on PE Cemented | 40 | 41 | 190.8 | Survival at 18 y (revision for aseptic loosening as endpoint) was 71% for acetabular component and 95% for femoral component |
| Dorr et al, 1994 | Metal on PE Cemented | 39 | 31 | 194.4 | 33 of 49 hips revised for aseptic failure (67%) Revision rates: 12% (4.5 y), 33% (9.2 y), and 67% (16.2 y) |
| Torchia et al, 1996 | Metal on PE Cemented | 50 | 17 | 151.2 | 29 of 63 hips (46%) failed Failure rate 27% at 10 y, 45% at 15 y |
| Mulroy and Harris, 1997 | Metal on PE Cemented | 40 | 41 | 183.6 | Revision rate for aseptic loosening of femoral component 2% (1 of 51) 10 of 47 (21%) acetabular components were revised for aseptic loosening |
| Callaghan et al, 1998 | Metal on PE Cemented | 69 | 42 | 279.6 | 21 of 93 hips (23%) revised because of aseptic loosening (27 total revisions) 18 acetabular components (19%) and 5 (5%) femoral components revised because of aseptic loosening |
| Keener et al, 2003 | Metal on PE Cemented | 43 | <50 | 300.0 | Survivorship with revision of either component because of aseptic loosening as endpoint at 30 y was 69% Survivorship at 30 y (revision because of aseptic loosening as endpoint) of acetabular component was 72% Survivorship at 30 y (revision because of aseptic loosening as endpoint) of femoral component was 93% |
| Burston et al, 2010 | Metal on PE Cemented | 47 | 39 | 144.0 | 10 hips (19%) required revision for mechanical failure of acetabular component Survivorship of cup (revision of cup for cup failure as endpoint) was 81.1% at average of 12 y Survivorship of stem (aseptic loosening or osteolysis as endpoint) was 100% at average of 12 y |
| Kerboull et al, 2004 | Metal on PE Cemented | 222 | 40.1 | 174.0 | Cumulative survivorship at 20 y was 85.4% Survival at 20 years with radiologic definite or probable aseptic loosening as endpoint was 94.8% for acetabular component and 93.1% for femoral component |
| Fye et al, 1998 | Ceramic on ceramic Ceramic on PE Uncemented | 58 | 37 | 84.0 | Probability of survival (revision as endpoint) for series was 96.9% at 11 y Mechanical failure rate was 7.6% for cups and 6% for stems Revision rate was 1.5% for cups and 1.5% for stems |
| Sedel et al, 1994 | Ceramic on ceramic Cemented uncemented | 113 | 41 | 63.0 | 96% femoral component survival at 10 y 90.3% acetabular component survival at 10 y |
| Bizot et al, 2000 | Ceramic on ceramic Cemented uncemented | 104 | 32.3 | 92.4 | 9.3% required revision for acetabular aseptic loosening Survival rates at 10 and 15 y were 84.6% and 80% (revision for mechanical failure as endpoint) Survival rates of femoral component at 10 and 15 y were 94.8% and 84.8% |
| Ha et al, 2007 | Ceramic on ceramic Uncemented | 64 | 37 | 66.0 | No acetabular or femoral components revised at latest follow-up Wear of ceramic components was undetectable |
| Fenollosa et al, 2000 | Ceramic on ceramic Uncemented, cemented, and hybrid | 74 | 38.1 | 111.6 | Survival at 177 mo Cemented: 80% Hybrid: 45% Cementless: 95.74% |
| Baek and Kim, 2008 | Ceramic on ceramic Uncemented | 60 | 39.1 | 85.2 | No hips showed evidence of aseptic loosening No hips revised for any reason |
| Finkbone et al, 2012 | Ceramic on ceramic Uncemented (2 cemented stems) | 19 | 16.4 | 52.0 | 1 revision for loose acetabular component 96% survival (revision any reason as endpoint) No ceramic implant fractures |
| Migaud et al, 2011 | Metal on metal Ceramic on PE | 78 | <50 | 151.0 | No hips revised in metal-on metal group 12-y survival (revision as endpoint) was 100% 11 (28%) hips revised in ceramic-PE group because of wear or osteolysis 12-y survival (revision as endpoint) 70% |
| Delaunay et al, 2008 | Metal on metal Uncemented | 73 | 40.7 | 87.6 | 10-y survival (revision as endpoint) was 100% 10-y survival (reoperation for any cause) was 96.4% |
| Kim et al, 2004 | Metal on metal Uncemented | 60 | 37 | 84.0 | No femoral or acetabular component revised because of aseptic loosening |
| Girard et al, 2010 | Metal on metal Uncemented | 34 | 25 | 108.0 | 1 of 47 hips (2.1%) revised for acetabular osteolysis Survival rate of femoral component at 10 y 100% Combined survival at 10 y 94.5% |
| Hwang et al, 2011 | Metal on metal Uncemented | 70 | 39.8 | 148.8 | Survivorship at average of 12.4 y (revision for any reason as endpoint) was 98.7% 2 hips (2.5%) had a progressive osteolytic lesion 1 hip revised because of osteolysis possibly secondary to hypersensitivity |
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