Bearing Surface Considerations for Total Hip Arthroplasty in Young Patients




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.








  • Consider the next operation (revisability) of any implant in young, active patients.



  • 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.



  • 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.



Key Points


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.



Table 1

Summary of published data on various bearing couples in patients aged younger than 50 years
























































































































































































































































































































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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Feb 23, 2017 | Posted by in ORTHOPEDIC | Comments Off on Bearing Surface Considerations for Total Hip Arthroplasty in Young Patients
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