Large diameter femoral heads

Cooper, H. John; Valle, Craig J. Della

doi:10.1302/0301-620x.96b11.34342

Cited by 88 publications

(30 citation statements)

References 40 publications

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“…Increasing the head size results in an increase of the head-to-neck ratio, improvement of the range of motion to impingement, and an increase in the amount of displacement required before the head dislocates. 57 This has led to an increasing use of large diameter prosthetic heads over the last decade. 58 Multiple studies have emphasised the benefit of large heads in reducing dislocation rates.…”

Section: Large Diameter Headsmentioning

confidence: 99%

Constrained liners, dual mobility or large diameter heads to avoid dislocation in THA

Guyen

2016

EFORT Open Reviews

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Dislocation remains a common cause of failure after total hip arthroplasty. The limitations of existing approaches to address instability have led to the development of powerfull options: constrained liners, dual mobility and large heads. These implant-related options have proven to be very efficient, but have raised concerns.With constrained liners, restricted range of motion (ROM) is responsible for impingement leading to high likelihood of failure, depending on the design, with various failure modes.Improvements of the bearing materials have addressed some of the concerns about increased volumetric wear of conventional polyethylene and offer an option to reduce instability: large diameter heads have the advantage of increased ROM before impingement, increased head-neck ratio, and jump distance. Highly cross-linked polyethylene helps address the risk for increased wear, and also large heads provide improved stability without the risk of mechanical failures observed with constrained liners. However, the increase of the head size remains limited as reducing the thickness of the liner may lead to fractures. In addition, the jump distance decreases as the cup abduction increases.The dual mobility concept simultaneously attempts to address head-neck ratio, constraint, and jump distance. Despite the need for longer follow-up, concerns raised about potential increased wear and intra-prosthetic dislocation with first generation implants have been addressed with modern designs.With a dramatic increase of the head-neck ratio whilst reducing the risk of mechanical failure or excessive wear, dual mobility THA outperforms large diameter heads and constrained liners at 10 years follow-up. For these reasons, dual mobility continues to gain interest worldwide and is becoming the most popular option to manage instability.Cite this article: Guyen O. Constrained liners, dual mobility or large diameter heads to avoid dislocation in THA. EFORT Open Rev 2016;1:197-204. DOI: 10.1302/2058-5241.1.000054.

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Section: Large Diameter Headsmentioning

confidence: 99%

Constrained liners, dual mobility or large diameter heads to avoid dislocation in THA

Guyen

2016

EFORT Open Reviews

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“…The development and deterioration of MACC are associated with taper design, metal-alloy mismatch (Galvanic corrosion), implant positioning, implantation time, joint loading magnitude, numbers of loading cycles, frictional torque at the bearing surface, patient and surgical factors (tissue inter-positioning, failure to achieve initial engagement) and others. Particulate debris and metal ions are released through mechanical and corrosive mechanisms, and these may lead to several adverse tissue reactions and even mechanical failure at the taper junction in the worse cases 27 28 29 30 31 32 33 34) . The use of larger head sizes increases frictional torque, and increased frictional torque elevates stress at the taper junction, thus causing an increase in bending moment with increased offset between the head center and trunnion interface center of pressure ( Fig.…”

Section: Wear On Trunnion-bore Interfacementioning

confidence: 99%

Current Concepts of Using Large Femoral Heads in Total Hip Arthroplasty

2016

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Instability and dislocation after total hip arthroplasty are the most common causes of revisions and major complications for failure of inserted prostheses, leading to a reduction in quality of life. Because the use of artificial femoral head sizes smaller than patient's own size is the important cause for dislocation, the use of large femoral head have increased. Femoral head sizes greater than 32 mm offer multiple advantages in physical function and activity levels of patients by improving hip stability, decreasing dislocation rate and increasing range of motion. However, various concerns are encountered including wear debris generation at the trunnion-bore interface and increases in frictional torque and stress over the component-bone interface when using larger head sizes. So, the use of femoral head sizes less than 40 mm is recommended.

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“…6,18,25,28-30 For example, greater assembly forces have been shown to increase the contact area at the head-trunnion interface 31 and reduce the rate of corrosion. 32 No studies, however, have considered the effect of assembly force in relation to head size.…”

Section: Introductionmentioning

confidence: 99%

Large-diameter total hip arthroplasty modular heads require greater assembly forces for initial stability

MacLeod

Sullivan

Whitehouse

et al. 2016

Bone & Joint Research

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ObjectivesModular junctions are ubiquitous in contemporary hip arthroplasty. The head-trunnion junction is implicated in the failure of large diameter metal-on-metal (MoM) hips which are the currently the topic of one the largest legal actions in the history of orthopaedics (estimated costs are stated to exceed $4 billion). Several factors are known to influence the strength of these press-fit modular connections. However, the influence of different head sizes has not previously been investigated. The aim of the study was to establish whether the choice of head size influences the initial strength of the trunnion-head connection.Materials and MethodsTi-6Al-4V trunnions (n = 60) and two different sizes of cobalt-chromium (Co-Cr) heads (28 mm and 36 mm; 30 of each size) were used in the study. Three different levels of assembly force were considered: 4 kN; 5 kN; and 6 kN (n = 10 each). The strength of the press-fit connection was subsequently evaluated by measuring the pull-off force required to break the connection. The statistical differences in pull-off force were examined using a Kruskal–Wallis test and two-sample Mann–Whitney U test. Finite element and analytical models were developed to understand the reasons for the experimentally observed differences.Results36 mm diameter heads had significantly lower pull-off forces than 28 mm heads when impacted at 4 kN and 5 kN (p < 0.001; p < 0.001), but not at 6 kN (p = 0.21). Mean pull-off forces at 4 kN and 5 kN impaction forces were approximately 20% larger for 28 mm heads compared with 36 mm heads. Finite element and analytical models demonstrate that the differences in pull-off strength can be explained by differences in structural rigidity and the resulting interface pressures.ConclusionThis is the first study to show that 36 mm Co-Cr heads have up to 20% lower pull-off connection strength compared with 28 mm heads for equivalent assembly forces. This effect is likely to play a role in the high failure rates of large diameter MoM hips.Cite this article: A. R. MacLeod, N. P. T. Sullivan, M. R. Whitehouse, H. S. Gill. Large-diameter total hip arthroplasty modular heads require greater assembly forces for initial stability. Bone Joint Res 2016;5:338–346. DOI: 10.1302/2046-3758.58.BJR-2016-0044.R1.

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Large diameter femoral heads

Cited by 88 publications

References 40 publications

Constrained liners, dual mobility or large diameter heads to avoid dislocation in THA

Constrained liners, dual mobility or large diameter heads to avoid dislocation in THA

Current Concepts of Using Large Femoral Heads in Total Hip Arthroplasty

Large-diameter total hip arthroplasty modular heads require greater assembly forces for initial stability

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