PRIORITY PAPER EVALUATION For reprint orders, please contact: [email protected]
Cemented versus cementless total hip arthroplasty: is a hybrid the most cost effective? Evaluation of: Pennington M, Grieve R, Sekhon JS, Gregg P, Black N, van der Meulen JH. Cemented, cementless, and hybrid prostheses for total hip replacement: cost effectiveness analysis. BMJ 346, f1026 (2013). Total hip arthroplasty is an extremely successful operation by almost any measure. As the population in the developed world ages, it is also becoming a very popular operation, with nearly 500,000 replacements predicted in the USA by 2030. As more hip replacements need to be performed, the cost will become more of an issue. The debate between the effectiveness of implant types, cemented or cementless, has been ongoing for years. Although largely decided in the USA, in favor of cementless implants, the discussion in the UK continues. There are many studies arguing in favor of implants using cement and for those not using cement. Ultimately, the best implant is the one that is most comfortable in the hands of the surgeon implanting it. Financial factors must be considered, however, and the more information available, the better to help surgeons decide what is best for their patients.
Zachary D Post Department of Orthopaedic Surgery, Thomas Jefferson University, Rothman Institute, PA, USA [email protected]
KEYWORDS: cementless fixation n cost–effectiveness n hybrid hip replacement n total hip replacement
Methods & results
This paper undertakes a cost–effectiveness analysis of total hip arthroplasty (THA) components based upon the fixation method used for implantation; cemented, cementless or hybrid [1]. The authors, led by Mark Pennington from the London School of Hygiene and Tropical Medicine (London, UK), intended to improve upon previous cost evaluations of THA that show fully cemented prostheses to be the most cost effective. The previously published studies, according to Pennington et al., have ‘serious methodological shortcomings’ because of a failure to adjust for differences in preoperative quality of life and age, inconsistent use of model parameters or simply owing to being outdated. In addition, the authors note an increased usage of cementless components in the last decade and question whether this is justified from a financial perspective. Their study proposes a more thorough investigation of the cost–effectiveness of THA components including evaluation of quality-of-life parameters. The authors gathered extensive amounts of data from the National Joint Registry for England and Wales, the hospital episodes statistics and the national patientreported outcome measures program for patients undergoing surgery between July 2008 and December 2010. Exclusions included patients younger than 55 years or older than 84 years, patients who did not have a diagnosis of osteoarthritis or patients who had a nontraditional implant or approach (minimally invasive). The Oxford Hip Score and a quality-of-life tool called EQ-5D-3L measured quality of life. Quality of life was estimated at 6 months after the implantation of the prosthesis. Records were then linked between the registry and quality-of-life measures. A total of
10.2217/CER.13.43 © 2013 Future Medicine Ltd
2(4), 375–377 (2013)
part of
ISSN 2042-6305
375
PRIORITY PAPER EVALUATION Post 30,203 patients were included in the final cohort and divided according to prosthesis type. Revision data from the registry from 1997 to 2004 was assessed and applied to the cohort. Using the registry to estimate revision rates, an annual risk of revision was determined using the risk of revision for all THA patients in the first 5 postoperative years for each prosthesis type. The risk of revision was thus determined to be 1.2% for cemented, 1.8% for cementless and 1.4% for hybrid prostheses per annum. Prosthesis survival rates for 5–12 years postoperative were used to estimate revision beyond 5 years. Due to a lack of identification of hybrid prostheses in the database used to evaluate revisions, revision rates beyond 5 years for the hybrid group had to be assumed to be the same as the cemented or cementless, whichever was higher. Cost was determined by combining the cost of the implant with hospitalization and subsequent risk of revision and its associated cost. Prosthesis cost was calculated according to the price paid by the NHS provider for the most popular implants. Hospitalization costs were determined using a standard cost per day modified by the length of stay according to prosthesis type. Revision costs were then determined for each prosthesis with a factor being applied for type of revision (two-stage revisions being more costly than one stage). The quality-of-life measures were adjusted according to observed differences in the preoperative characteristics of each group. The authors used a complex statistical matching method called GenMatch to make adjustments. The cost–effectiveness model estimated lifetime revision rates and quality-adjusted life years for men and women according to age (60, 70 and 80 years). Net monetary benefit was determined from quality-adjusted life years minus the lifetime cost of each type implant. The authors found that hybrid prostheses predicted the highest postoperative quality of life for all subgroups except women aged 80 years. They also found revision rates to be highest with cementless prostheses. However, the differences were small in the 60-year-old (youngest) male group. In all groups, the initial costs were highest for the cementless prostheses and lowest for the cemented prostheses. In general, hybrid prostheses produced higher quality-adjusted life years at lower cost than cementless prostheses. In summary, they found the probability that
376
J. Compar. Effect. Res. (2013) 2(4)
hybrid prostheses were the most cost effective to be 75% for men and 70% for women with the probability that the cementless prostheses were the most cost effective to be approximately 1% for both sexes. Discussion
The overall effectiveness of THA to relieve pain and dysfunction for patients suffering from degenerative hip disease was demonstrated long ago [2,3]. Sir John Charnley was actively involved in the development of hip replacement and the improvement of the cementing technique. However, aseptic loosening eventually developed of both the femoral and acetabular components of early hip replacements. What would eventually be known as osteolysis was initially thought to be related to the cement. Bill Harris et al. described the phenomenon as ‘cement disease’ [4]. The concerns regarding cement, in combination with a desire for a more dynamic fixation for younger patients, ultimately led to the development of the cementless components in widespread use today. Press fit femoral components have been used for nearly 30 years and large, long-term studies have demonstrated their effectiveness, with 20-year survivor rates estimated at greater than 99% [5]. The success of cementless components has been so profound that their adoption has been near universal in the USA. In fact, the use of hybrid or cemented techniques has become limited or rare at most institutions. The article by Pennington et al., is a detailed, extensively researched attempt to demonstrate the superior cost–effectiveness of hybrid implants. That cemented stems are successful in the hands of talented surgeons who are familiar with their use is not in contention. However, there are a few assumptions in the Pennington article that place the outcome of their approach in question. First is the author’s decision to restrict their evaluation to patients over the age of 55 years. This oversight introduces bias as many healthy, young patients, those who potentially would benefit from cementless fixation, are excluded. The technique for estimating the failure of the implants is also flawed. There are many studies providing long-term survival rates of both cemented and cementless stems, yet the authors chose to limit their model to a yearly rate determined by the revision rate at 5 years. This approach favors the cemented stems for
future science group
Cemented versus cementless total hip arthroplasty
cementless constructs are likely to maintain a low revision rate while that of cemented constructs is likely to increase [5,6]. The main limitation of this study is its lack of applicability to markets outside of the UK. Most institutions and surgeons in the USA are so unfamiliar with using cement for THA that results associated with doing so would certainly be compromised. In the same vein, to suggest that revision rates for cementless components implanted by surgeons more familiar with cementing are interchangeable with those achieved by surgeons exclusively implanting cementeless components is unsound. The efficiency of implanting cementless stems in the USA also has a cost saving factor that is not considered in the current study. There are many, many factors that contribute to a successful outcome after THA. Many, but not all, are addressed here. Surgical approach and surgeon experience are just two that are not evaluated in the current study. The cost associated with THA is also multifactorial. The main driver of increased cost associated with THA using cementless components in this study was the initial cost of the implant. More widespread use of cementless components would certainly decrease this cost.
PRIORITY PAPER EVALUATION
Future perspective
The success of THA, even at 20 years post-op, is indisputable. The discussion of how to improve the success rate has evolved to a few percentiles of patients who still fail to achieve long-term success. Costs associated with THA, however, remain high and must continue to decrease. This study contributes to that discussion. A similar study evaluating patients in the USA, with a few minor changes, would be insightful. It is unlikely that the outcome would be the same for the reasons discussed above. However, such a study would help in the understanding of what drives the cost associated with THA and what parameters are truly critical to maintaining the high success rate we have achieved for the vast majority of patients needing THA. Financial & competing interests disclosure The author has no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties. No writing assistance was utilized in the production of this manuscript.
Executive summary The debate over the best way to implant a total hip replacement, cemented or cementless, has been contested for decades. The reviewed study utilizes complex statistical analysis of the National Joint Registry to demonstrate the cost–effectiveness of each method. ■■ Although the reviewed study finds the hybrid cement technique to be the most cost effective, the authors make assumptions that may not be valid and the results are not applicable to other parts of the world. ■■ ■■
References Papers of special note have been highlighted as: of interest n
1
Pennington M, Grieve R, Sekhon JS, Gregg P, Black N, van der Meulen JH. Cemented, cementless, and hybrid prostheses for total hip replacement: cost effectiveness analysis. BMJ 346, f1026 (2013).
2
O’Shea K, Bale E, Murray P. Cost analysis of primary THA. Ir. Med. J. 95(6), 177–180 (2002).
3
Sochart DH, Porter ML. The long-term results of Charnley low-friction arthroplasty in young patients who have congenital dislocation, degenerative osteoarthrosis, or
future science group
rheumatoid arthritis. J. Bone Joint Surg. Am. 79(11), 1599–1617 (1997). 4
n
5
Harris WH, Schiller AL, Scholler JM, Freiberg RA, Scott R. Extensive localized bone resorption in the femur following total hip replacement. J. Bone Joint Surg. Am. 58, 612–618 (1976).
n
6
Early description of erosion of the bone surrounding cemented hip replacement implants, thought to be due to an adverse reaction to the cement. Lombardi AV Jr, Berend KR, Mallory TH, Skeels MD, Adams JB. Survivorship of 2000 tapered titanium porous plasma-sprayed femoral components. Clin. Orthop. Relat. Res. 467(1), 146–154 (2009).
www.futuremedicine.com
n
Study of 1866 patients treated with cementless femoral stems with a follow-up of 2–20 years. The Kaplan–Meier survival rate for the cementless stems at 20 years was 99.3%. Berry DJ, Harmsen WS, Cabanela ME, Morrey BF. Twenty-five-year survivorship of two thousand consecutive primary Charnley total hip replacements: factors affecting survivorship of acetabular and femoral components. J. Bone Joint Surg. Am. 84-A(2), 171–177 (2002). Study showing greater than 80% survivorship at 25 years of follow-up of cemented Charnley low-friction arthroplasty implants.
377
Cemented versus cementless total hip arthroplasty: is a hybrid the most cost effective? Evaluation of: Pennington M, Grieve R, Sekhon JS, Gregg P, Black N, van der Meulen JH. Cemented, cementless, and hybrid prostheses for total hip replacement: cost effectiveness analysis. BMJ 346, f1026 (2013). Total hip arthroplasty is an extremely successful operation by almost any measure. As the population in the developed world ages, it is also becoming a very popular operation, with nearly 500,000 replacements predicted in the USA by 2030. As more hip replacements need to be performed, the cost will become more of an issue. The debate between the effectiveness of implant types, cemented or cementless, has been ongoing for years. Although largely decided in the USA, in favor of cementless implants, the discussion in the UK continues. There are many studies arguing in favor of implants using cement and for those not using cement. Ultimately, the best implant is the one that is most comfortable in the hands of the surgeon implanting it. Financial factors must be considered, however, and the more information available, the better to help surgeons decide what is best for their patients.
Zachary D Post Department of Orthopaedic Surgery, Thomas Jefferson University, Rothman Institute, PA, USA [email protected]
KEYWORDS: cementless fixation n cost–effectiveness n hybrid hip replacement n total hip replacement
Methods & results
This paper undertakes a cost–effectiveness analysis of total hip arthroplasty (THA) components based upon the fixation method used for implantation; cemented, cementless or hybrid [1]. The authors, led by Mark Pennington from the London School of Hygiene and Tropical Medicine (London, UK), intended to improve upon previous cost evaluations of THA that show fully cemented prostheses to be the most cost effective. The previously published studies, according to Pennington et al., have ‘serious methodological shortcomings’ because of a failure to adjust for differences in preoperative quality of life and age, inconsistent use of model parameters or simply owing to being outdated. In addition, the authors note an increased usage of cementless components in the last decade and question whether this is justified from a financial perspective. Their study proposes a more thorough investigation of the cost–effectiveness of THA components including evaluation of quality-of-life parameters. The authors gathered extensive amounts of data from the National Joint Registry for England and Wales, the hospital episodes statistics and the national patientreported outcome measures program for patients undergoing surgery between July 2008 and December 2010. Exclusions included patients younger than 55 years or older than 84 years, patients who did not have a diagnosis of osteoarthritis or patients who had a nontraditional implant or approach (minimally invasive). The Oxford Hip Score and a quality-of-life tool called EQ-5D-3L measured quality of life. Quality of life was estimated at 6 months after the implantation of the prosthesis. Records were then linked between the registry and quality-of-life measures. A total of
10.2217/CER.13.43 © 2013 Future Medicine Ltd
2(4), 375–377 (2013)
part of
ISSN 2042-6305
375
PRIORITY PAPER EVALUATION Post 30,203 patients were included in the final cohort and divided according to prosthesis type. Revision data from the registry from 1997 to 2004 was assessed and applied to the cohort. Using the registry to estimate revision rates, an annual risk of revision was determined using the risk of revision for all THA patients in the first 5 postoperative years for each prosthesis type. The risk of revision was thus determined to be 1.2% for cemented, 1.8% for cementless and 1.4% for hybrid prostheses per annum. Prosthesis survival rates for 5–12 years postoperative were used to estimate revision beyond 5 years. Due to a lack of identification of hybrid prostheses in the database used to evaluate revisions, revision rates beyond 5 years for the hybrid group had to be assumed to be the same as the cemented or cementless, whichever was higher. Cost was determined by combining the cost of the implant with hospitalization and subsequent risk of revision and its associated cost. Prosthesis cost was calculated according to the price paid by the NHS provider for the most popular implants. Hospitalization costs were determined using a standard cost per day modified by the length of stay according to prosthesis type. Revision costs were then determined for each prosthesis with a factor being applied for type of revision (two-stage revisions being more costly than one stage). The quality-of-life measures were adjusted according to observed differences in the preoperative characteristics of each group. The authors used a complex statistical matching method called GenMatch to make adjustments. The cost–effectiveness model estimated lifetime revision rates and quality-adjusted life years for men and women according to age (60, 70 and 80 years). Net monetary benefit was determined from quality-adjusted life years minus the lifetime cost of each type implant. The authors found that hybrid prostheses predicted the highest postoperative quality of life for all subgroups except women aged 80 years. They also found revision rates to be highest with cementless prostheses. However, the differences were small in the 60-year-old (youngest) male group. In all groups, the initial costs were highest for the cementless prostheses and lowest for the cemented prostheses. In general, hybrid prostheses produced higher quality-adjusted life years at lower cost than cementless prostheses. In summary, they found the probability that
376
J. Compar. Effect. Res. (2013) 2(4)
hybrid prostheses were the most cost effective to be 75% for men and 70% for women with the probability that the cementless prostheses were the most cost effective to be approximately 1% for both sexes. Discussion
The overall effectiveness of THA to relieve pain and dysfunction for patients suffering from degenerative hip disease was demonstrated long ago [2,3]. Sir John Charnley was actively involved in the development of hip replacement and the improvement of the cementing technique. However, aseptic loosening eventually developed of both the femoral and acetabular components of early hip replacements. What would eventually be known as osteolysis was initially thought to be related to the cement. Bill Harris et al. described the phenomenon as ‘cement disease’ [4]. The concerns regarding cement, in combination with a desire for a more dynamic fixation for younger patients, ultimately led to the development of the cementless components in widespread use today. Press fit femoral components have been used for nearly 30 years and large, long-term studies have demonstrated their effectiveness, with 20-year survivor rates estimated at greater than 99% [5]. The success of cementless components has been so profound that their adoption has been near universal in the USA. In fact, the use of hybrid or cemented techniques has become limited or rare at most institutions. The article by Pennington et al., is a detailed, extensively researched attempt to demonstrate the superior cost–effectiveness of hybrid implants. That cemented stems are successful in the hands of talented surgeons who are familiar with their use is not in contention. However, there are a few assumptions in the Pennington article that place the outcome of their approach in question. First is the author’s decision to restrict their evaluation to patients over the age of 55 years. This oversight introduces bias as many healthy, young patients, those who potentially would benefit from cementless fixation, are excluded. The technique for estimating the failure of the implants is also flawed. There are many studies providing long-term survival rates of both cemented and cementless stems, yet the authors chose to limit their model to a yearly rate determined by the revision rate at 5 years. This approach favors the cemented stems for
future science group
Cemented versus cementless total hip arthroplasty
cementless constructs are likely to maintain a low revision rate while that of cemented constructs is likely to increase [5,6]. The main limitation of this study is its lack of applicability to markets outside of the UK. Most institutions and surgeons in the USA are so unfamiliar with using cement for THA that results associated with doing so would certainly be compromised. In the same vein, to suggest that revision rates for cementless components implanted by surgeons more familiar with cementing are interchangeable with those achieved by surgeons exclusively implanting cementeless components is unsound. The efficiency of implanting cementless stems in the USA also has a cost saving factor that is not considered in the current study. There are many, many factors that contribute to a successful outcome after THA. Many, but not all, are addressed here. Surgical approach and surgeon experience are just two that are not evaluated in the current study. The cost associated with THA is also multifactorial. The main driver of increased cost associated with THA using cementless components in this study was the initial cost of the implant. More widespread use of cementless components would certainly decrease this cost.
PRIORITY PAPER EVALUATION
Future perspective
The success of THA, even at 20 years post-op, is indisputable. The discussion of how to improve the success rate has evolved to a few percentiles of patients who still fail to achieve long-term success. Costs associated with THA, however, remain high and must continue to decrease. This study contributes to that discussion. A similar study evaluating patients in the USA, with a few minor changes, would be insightful. It is unlikely that the outcome would be the same for the reasons discussed above. However, such a study would help in the understanding of what drives the cost associated with THA and what parameters are truly critical to maintaining the high success rate we have achieved for the vast majority of patients needing THA. Financial & competing interests disclosure The author has no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties. No writing assistance was utilized in the production of this manuscript.
Executive summary The debate over the best way to implant a total hip replacement, cemented or cementless, has been contested for decades. The reviewed study utilizes complex statistical analysis of the National Joint Registry to demonstrate the cost–effectiveness of each method. ■■ Although the reviewed study finds the hybrid cement technique to be the most cost effective, the authors make assumptions that may not be valid and the results are not applicable to other parts of the world. ■■ ■■
References Papers of special note have been highlighted as: of interest n
1
Pennington M, Grieve R, Sekhon JS, Gregg P, Black N, van der Meulen JH. Cemented, cementless, and hybrid prostheses for total hip replacement: cost effectiveness analysis. BMJ 346, f1026 (2013).
2
O’Shea K, Bale E, Murray P. Cost analysis of primary THA. Ir. Med. J. 95(6), 177–180 (2002).
3
Sochart DH, Porter ML. The long-term results of Charnley low-friction arthroplasty in young patients who have congenital dislocation, degenerative osteoarthrosis, or
future science group
rheumatoid arthritis. J. Bone Joint Surg. Am. 79(11), 1599–1617 (1997). 4
n
5
Harris WH, Schiller AL, Scholler JM, Freiberg RA, Scott R. Extensive localized bone resorption in the femur following total hip replacement. J. Bone Joint Surg. Am. 58, 612–618 (1976).
n
6
Early description of erosion of the bone surrounding cemented hip replacement implants, thought to be due to an adverse reaction to the cement. Lombardi AV Jr, Berend KR, Mallory TH, Skeels MD, Adams JB. Survivorship of 2000 tapered titanium porous plasma-sprayed femoral components. Clin. Orthop. Relat. Res. 467(1), 146–154 (2009).
www.futuremedicine.com
n
Study of 1866 patients treated with cementless femoral stems with a follow-up of 2–20 years. The Kaplan–Meier survival rate for the cementless stems at 20 years was 99.3%. Berry DJ, Harmsen WS, Cabanela ME, Morrey BF. Twenty-five-year survivorship of two thousand consecutive primary Charnley total hip replacements: factors affecting survivorship of acetabular and femoral components. J. Bone Joint Surg. Am. 84-A(2), 171–177 (2002). Study showing greater than 80% survivorship at 25 years of follow-up of cemented Charnley low-friction arthroplasty implants.
377
