Total hip arthroplasty (THA) has been shown to successfully and predictably relieve pain and improve function in patients with symptomatic coxarthrosis. As a direct result of its success, hip replacement surgery is increasingly being considered for the management of younger patients with symptomatic osteoarthritis of the hip. These patients have higher functional demands and greater life expectancy 1-3 than traditional THA patients, posing a challenge to arthroplasty surgeons.
The conventional approach to treating this younger group of patients has been THA with cemented or uncemented components, or a combination of these components, with good results reported for the combination. Likewise, good results have been reported with two alternative surgical options: custom Computer Assisted Design - Computer Assisted Manufacture (CAD CAM) THA 4-6 and metal on metal hip resurfacing arthroplasty (MoM HR), although a great deal of controversy surrounds routine use of MoM prostheses. This brief review focuses on primary custom CAD CAM prostheses as well as MoM HR.
These components are designed based on endosteal geometry in order to optimise fit and fill of the patient’s proximal femur with removal of as little bone as possible.4 Information on the shape of the proximal femur is provided by plain X-ray 4 or computed tomography images.5 The rationale behind the use of these implants lies with the notion that by conforming the shape and design of the prosthesis to the existing proximal femur, one could recreate a hip joint that is biomechanically and physiologically as close as possible to the patient’s normal hip. Specifically for uncemented total hip replacement designs, optimal results rely on obtaining initial stability, contact over the entire ingrowth surface, and uniform stress transfer to the proximal femur.7 Custom prostheses have produced excellent long-term results in young, active patients in the primary setting and good long-term results when used for revision THA.8
The medium- to long-term results of uncemented custom femoral components have been encouraging:
- Muirhead-Allwood et al 4 recently reported a worst-case survival of 98.2% at 13.2 years for a cohort of 112 CAD CAM femoral components in patients with a mean age of 46.2 years.
- Flecher et al 5 described improved function at up to 15 years, but survival of the femoral component was only 87%.
- Akbar et al 6 reported no femoral failures at a mean of 14 years postoperatively in a population of patients younger than 40 years.
- Benum et al 9 reported promising medium-term clinical results and a revision rate for the femoral component of 1.1% at 7 years in a cohort of 191 femurs of normal and abnormal shape and dimension.
- Similarly, encouraging results have been reported in patients with osteoarthritis secondary to hip dysplasia.10-12
While these results are encouraging, the outcome measures and design processes have varied among papers, and not all authors measured activity levels. This makes comparison difficult. It is important to also note that these results are comparable to the best published results for conventional components with any method of fixation.
First attempts at hip resurfacing with Teflon components by Charnley in the 1960s and Wagner in the 1970s led to catastrophic failures. Gerard and Muller 13 pioneered MoM HR in the 1970s with only limited success. These failures were mainly due to poor engineering and material choice.
The modern era was heralded by McMinn in the mid-1980s after he recognised the low long-term wear and clinical success of the Ring and McKee Farrar prostheses in his region (Derek McMinn, personal communication). He re-introduced the concept of MoM HR using third-generation implants that consisted of a cemented metal femoral component and a press-fit metal acetabular component (designs varied among manufacturers).14 Proposed advantages of modern MoM HR include:
- Conservation of femoral bone stock
- Low wear rates
- Improved proprioception and stability,
- Increased range of motion
- Relative ease of revision (particularly on the femoral side)
These advantages have made MoM implants attractive for use with younger, high-demand patients.15-17
Few subjects, however, are as controversial as contemporary MoM HR in current orthopaedic literature. Results are varied and seem to be design related. This has led to at least one prosthesis being withdrawn.18
Numerous case series have reported results of modern resurfacing implants.15-17 Recent reviews have also addressed the evidence for the surgical technique, outcomes, complications and modes of failure of the hip resurfacing prostheses.19-20 Furthermore, van der Wegen et al 21 recently demonstrated that none of the hip resurfacing implants used to date meets the full 10-year National Institute of Clinical Excellence (NICE) benchmark for choosing a primary total hip replacement, which is a survival rate of at least 90% at a 10-year follow up.
While good short-term results have been reported,17 potentially serious complications have also emerged including elevated metal ion levels, aseptic lymphocytic vasculitis associated lesions (ALVAL), and soft tissue destructive lesions (pseudotumors).22
Unfortunately, there is a paucity of literature on the subject of hip resurfaces versus custom prostheses, with many authors focusing on the outcome between conventional THA and hip resurfacing. A recent review 23 found that while some authors report earlier return to sporting activities, functional results and patient satisfaction levels are comparable between the two groups.
Sandiford et al 24 recently reported results of a prospective study comparing two well-matched cohorts of young patients treated with hip resurfacing and custom uncemented (CAD CAM) prostheses. They found no significant clinical difference or difference in level of function between the two groups in the short term. To the authors' knowledge, this is the only study directly comparing these groups of patients.
The recent publication of the 7th annual report of the National Joint Registry revealed an overall revision rate of 2.9% at 5 years following primary hip replacement. The revision rates varied according to the type of prosthesis. The 5-year revision rate was lowest in patients who received a cemented prosthesis (2.0%). Patients who received a resurfacing prosthesis had a 5-year revision rate of 6.3%, worse than cemented, cementless, and hybrid prostheses.
Furthermore, the impact of prosthesis type depended on the age and gender of the patient:
- In men younger than age 55 years, the 5-year revision rates were lowest in those with hybrid prostheses (2.6%) and as high as 5.6% in those with hip resurfacing.
- In women younger than age 55 years, the lowest 5-year rates were seen in those with a cemented prosthesis (3.6%), whilst it was up to 8.3% in those with resurfacing.
- A similar pattern was found for patients aged 55 to 64 years, with 5-year revision rates being consistently worse for patients with resurfacing prostheses.
- Kim YH, Oh SH, Kim JS. Primary total hip arthroplasty with a second-generation cementless total prosthesis in patients younger than fifty years of age. J Bone Joint Surg. 2003;85:109-114.
- Langdon IJ, Bannister GC. Cemented hip replacements in patients younger than 50 years: 16-24 year results. Hip International. 1999;9:151-153.
- Fisher J, Ingham E, Stone MH. Alternative bearing couples in total hip replacements. Solutions for young patients. Hip International. 2003;13:531-535.
- Muirhead-Allwood SK, Sandiford N, Skinner JA, Hua J, Kabir C, Walker PS. Uncemented custom computer-assisted design and manufacture of hydroxyapatite-coated femoral components: survival at 10 to 17 years. J Bone Joint Surg Br. 2010 Aug;92(8):1079-84.
- Flecher X, Pearce O, Parratte S, Aubaniac JM, Argenson JN. Custom cementless stem improves hip function in young patients at 15-year followup. Clin Orthop Relat Res. 2010 Mar;468(3):747-55.
- Akbar M, Aldinger G, Krahmer K, Bruckner T, Aldinger PR. Custom stems for femoral deformity in patients less than 40 years of age: 70 hips followed for an average of 14 years. Acta Orthop. 2009 Aug;80(4):420-5.
- Bargar WL. Shape the implant to the patient: a rationale for the use of custom-fit cementless total hip replacements. Clin Orthop. 1989;249:73-78.
- Muirhead-Allwood S, Sandiford NA, Skinner JA, Hua J, Muirhead W, Kabir C, Walker PS. Uncemented computer-assisted design-computer-assisted manufacture femoral components in revision total hip replacement: a minimum follow-up of ten years. J Bone Joint Surg Br. 2010 Oct;92(10):1370-5.
- Benum P, Aamodt A. Uncemented custom femoral components in hip arthroplasty. A prospective clinical study of 191 hips followed for at least 7 years. Acta Orthop. 2010;81:427-435.
- Sakai T, Sugano N, Ohzono K, Lee SB, Nishii T. The custom femoral component is an effective option for congenital hip dysplasia. Clin Orthop. 2006;451:146-153.
- Flecher X, Parratte S, Aubaniac JM, Argenson JN. Three-dimensional custom-designed cementless femoral stem for osteoarthritis secondary to congenital dislocation of the hip. J Bone Joint Surg [Br]. 2007;89:1586-1591.
- Kawate K, Ohneda Y, Ohmura T, Yajima H, Sugimoto K, Takakura Y. Computed tomography-based custom-made stem for dysplastic hips in Japanese patients. J Arthroplasty. 2009;24:65-70.
- Gerard Y. Hip arthroplasty by matching cups. Clin Orthop Relat Res. 1978 Jul-Aug;(134):25-35
- Grigoris P, Roberts P, Panousis K, Bosch H. The evolution of hip resurfacing arthroplasty. Orthop Clin North Am. 2005;36:125-134.
- Amstutz HC, Ball ST, Le Duff MJ, Dorey FJ. Resurfacing THA for patients younger than 50 years: results of 2- to 9-year followup. Clin Orthop. 2007;460:159-164.
- Steffen RT, Pandit HP, Palan J, et al. The five-year results of the Birmingham Hip Resurfacing arthroplasty: an independent series. J Bone Joint Surg [Br]. 2008;90:436-441.
- Daniel J, Pynsent PB, McMin DJ. Metal-on-metal resurfacing of the hip in patients under the age of 55 years with osteoarthritis. J Bone Joint Surg [Br]. 2004;86:177-184.
- Shimmin AJ, Walter WL, Esposito C. The influence of the size of the component on the outcome of resurfacing arthroplasty of the hip: a review of the literature. J Bone Joint Surg [Br]. 2010;92:469-476.
- Amanatullah DF, Cheung Y, Di Cesare PE. Hip resurfacing arthroplasty: a review of the evidence for surgical technique, outcome and complications. Orthop Clin North Am. 2010;41:263-272.
- van der Weegen W, Hoekstra HJ, Sijbesma T, Bos E, Schemitch EH, Poolman RW. Survival of metal-on-metal hip resurfacing arthroplasty. A systematic review of the literature. J Bone Joint Surg [Br]. 2011;93:298-306.
- Pandit H, Glyn-Jones S, McLardy-Smith P, Gundle R, Whitwell D, Gibbons CL, Ostlere S, Athanasou N, Gill HS, Murray DW. Pseudotumours associated with metal-on-metal hip resurfacings. J Bone Joint Surg Br. 2008 Jul;90(7):847-51.
- Shimmin AJ, Baré JV. Comparison of functional results of hip resurfacing and total hip replacement: a review of the literature. Orthop Clin North Am. 2011 Apr;42(2):143-51, vii. Review.
- Sandiford NA, Muirhead-Allwood SK, Skinner JA, Hua J. Metal on metal hip resurfacing versus uncemented custom total hip replacement-early results. J Orthop Surg Res. 2010;18:5-8