With time, the plastic in the cup side of the total hip replacement becomes worn out. In that process tiny plastic particles are produced to which the surrounding tissues react. This reaction leads to the bone getting gradually eaten away (lysis) leading to loosening of the hip replacement. The hip becomes painful. Pain can be present in the hip in the region of the groin or it can present as thigh pain. Sometimes the loosening may be relatively asymptomatic for a long time and becomes only very symptomatic when there is large amount of bone destruction which makes the revision procedure even more complex. This is one of the reasons for regularly following the hip replacement patients with x-rays through their lifetime.

The ball of the total hip replacement may come out of the socket. This can occur at an early stage or at a late stage. There are a number of reasons for dislocation to occur. Usually it would be possible to put the hip back into the joint (often will need an anaesthetic). If the dislocation keeps recurring, it would be appropriate to consider revision procedure. Mr. Ganapathi was involved in a study analysing the financial aspect and functional improvement following in patients with first time dislocation of the hip. On a conservative estimate, the financial cost in subsequent management of 100 first time dislocating hips was over £500000 and the functional improvement was less than optimal. One of the reason for dislocation is the fact that the ball of the total hip replacement is much smaller than the native ball of the hip joint. This compromise was taken as the properties of the materials available in the past did not suit larger size heads. However, there are various modern material available (like metal, ceramic and special plastics) which allow a bigger size ball to be used during the hip replacement. Studies have shown that the there is less dislocation rates as the ball size increases. The UK national registry also shows that there is an increasing trend among the hip surgeons to use relatively larger ball in the recent years.

Infection following hip replacement is a very rare complication. It can occur soon after surgery (early infection) or many years after the hip replacement (late infection). Early infection can be superficial or deep. While the former may respond to antibiotics, the deep infection will need further surgery in the form of washout or revision procedure. Late infection can occur at anytime throughout the lifetime due to bacteria (bugs) entering the blood stream from infection in other parts of the body. If this happens, the hip replacement gradually gets loose and the hip becomes painful. Although it is a challenging problem, majority of the patients could be treated by revision surgery. This usually is a two stage procedure with the first stage being removal of the infected hip replacement and insertion of temporary spacer and treatment with antibiotics followed by second stage with a definitive hip replacement (when the infection has settled – usually after 3 months).

This is a rare complication following hip replacement. The bone fractures (breaks) around the vicinity of the hip replacement. Depending on the type of fracture, this may be treated by internal fixation or by further revision surgery with a complex hip replacement.

This can occur in some cases of uncemented implants if there is not enough host bone contact with the implants (usually in the acetabular component) or if there is not enough vascularity for the bone growth to occur. Special materials like trabecular metal (made of tantallum) are now available which have a porous structure similar to cancellous bone and has better osteointegration properties than conventional titanium implants and hence being increasingly used in revision hip replacement.

This is quite a challenging problem and more commonly associated with lateral approach. Often the failure is due to the fact that the abductor muscle is quite weak and is not able to hold the sutures. This can give an abnormal gait and in addition, this can also be a factor resulting in recurrent dislocation. Revision surgery often involves some form of constrained/captured device to hold the ball in place. While it may be possible to reattach the abductor muscle, it is not always successful.

Scientific Literature

The following are some relevant selected scientific references:

1. Trends in the number of knee and hip arthroplasties: considerably more knee and hip prostheses due to osteoarthritis in 2030.

Ned Tijdschr Geneeskd. 2010;154(20):A1534.
Otten R, van Roermund PM, Picavet HS.
Rijksinstituut voor Volksgezondheid en Milieu, Centrum voor Preventie- en zorgonderzoek, Bilthoven, the Netherlands.

Abstract: OBJECTIVE: To predict the future number of knee and hip arthroplasties due to osteoarthritis (OA) in the Netherlands based on historical trends and demographic projections.

DESIGN: Data analysis and model calculations.

METHOD: Two future projections were based on age and sex-specific number of hospital admissions for the placement of total knee or hip prostheses due to OA between 1995 and 2005; data were obtained from the Dutch National Medical Registration (LMR). The demographical projection was based on the incidence of arthroplasty in 2005 combined with demographic predictions from Statistics Netherlands regarding the time period between 2005 and 2030. The trend projection used the trend in the age and sex-specific incidence of surgery between 1995 and 2005.

RESULTS: Between 1995 and 2005, the annual number of knee arthroplasties in patients with a primary diagnose of OA increased from 4,916 to 14,565, an increase of 196%. The total number of hip arthroplasties increased from 13,785 to 20,715, an increase of 50%. The demographical projection suggests that the number of total hip arthroplasties will increase to 31,731 by 2030, an increase of 53%, and the number of knee arthroplasties to 22,183. The trend projection suggests that the numbers may increase to 51,680 for the hip (+149%) and to 57,893 for the knee (+297%).

CONCLUSION: The increase in the number of knee and hip arthroplasties due to OA will probably continue in the coming 20 years. The following developments will probably contribute to this: demographical changes, the increase in overweight, improved long-term outcomes of arthroplasty, more active lifestyle of the elderly and the increasing number of orthopaedic surgeons.

 

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2. Changes in surgical loads and economic burden of hip and knee replacements in the US: 1997-2004.

Arthritis Rheum. 2008 Apr 15;59(4):481-8.
Kim S.
Robert Stempel School of Public Health, Florida International University, Miami, FL 33199, USA.

Abstract: OBJECTIVE: A major component of the economic burden associated with the treatment of arthritis relates to surgical joint replacements of the hips/knees. The purpose of this study was to describe the recent trend of hip/knee replacements and the associated economic burden.

METHODS: The Nationwide Inpatient Survey from 1997 to 2004 was analyzed. The International Classification of Diseases, Ninth Revision, Clinical Modification procedure coding was used to identify joint replacement cases.

RESULTS: During 2004, approximately 225,900 (95% confidence interval [95% CI] 201,782-250,018) primary hip replacements and 431,485 (95% CI 397,454-465,516) primary knee replacements were performed. This was a 37% increase in primary hip replacements and a 53% increase in primary knee replacements compared with 2000. The number of primary replacement procedures increased equally for males and females; however, the number of procedures increased excessively among persons age 45-64 years. While Medicare remained the major source of payment (55.4% for primary hip replacements, 59.3% for primary knee replacements), private insurance payment experienced a steeper increase. In 2004, the national bill of hospital charges for hip/knee replacements was $26.0 billion, the hospital cost was $9.1 billion, and the amount of reimbursement was $7.2 billion (28% of hospital charges or 79% of hospital cost). Nearly 600,000 hip replacements and 1.4 million knee replacements will be performed in the year 2015.CONCLUSION: The number of joint replacement procedures performed is growing faster than ever. The health care community should consider and prepare for this upcoming demand of surgical loads and its associated economical burden.

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3. Prevalence of primary and revision total hip and knee arthroplasty in the United States from 1990 through 2002.

J Bone Joint Surg Am. 2005 Jul;87(7):1487-97.
Kurtz S, Mowat F, Ong K, Chan N, Lau E, Halpern M.
Exponent Inc., 3401 Market Street, Suite 300, Philadelphia, PA 19104, USA.

Abstract: BACKGROUND: The purpose of this study was to quantify the procedural rate and revision burden of total hip and knee arthroplasty in the United States and to determine if the age or gender-based procedural rates and overall revision burden are changing over time.

METHODS: The National Hospital Discharge Survey (NHDS) for 1990 through 2002 was used in conjunction with United States Census data to quantify the rates of primary and revision arthroplasty as a function of age and gender within the United States with use of methodology published by the American Academy of Orthopaedic Surgeons. Poisson regression analysis was used to evaluate the procedural rate and to determine year-to-year trends in primary and revision arthroplasty rates as a function of both age and gender.

RESULTS: Both the number and the rate of total hip and knee arthroplasties (particularly knee arthroplasties) increased steadily between 1990 and 2002. Over the thirteen years, the rate of primary total hip arthroplasties per 100,000 persons increased by approximately 50%, whereas the corresponding rate of primary total knee arthroplasties almost tripled. The rate of revision total hip arthroplasties increased by 3.7 procedures per 100,000 persons per decade, and that of revision total knee arthroplasties, by 5.4 procedures per 100,000 persons per decade. However, the mean revision burden of 17.5% for total hip arthroplasty was more than twice that for total knee arthroplasty (8.2%), and this did not change substantially over time.

CONCLUSIONS: The number and prevalence of primary hip and knee replacements increased substantially in the United States between 1990 and 2002, but the trend was considerably more pronounced for primary total knee arthroplasty.

CLINICAL RELEVANCE: The reported prevalence trends have important ramifications with regard to the number of joint replacements expected to be performed by orthopaedic surgeons in the future. Because the revision burden has been relatively constant over time, we can expect that a greater number of primary replacements will result in a greater number of revisions unless some limiting mechanism can be successfully implemented to reduce the future revision burden.

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4. Total hip arthroplasty in Denmark: incidence of primary operations and revisions during 1996-2002 and estimated future demands.

Acta Orthop. 2005 Apr;76(2):182-9.
Pedersen AB, Johnsen SP, Overgaard S, Søballe K, Sørensen HT, Lucht U.
Department of Orthopaedics, Aarhus University Hospital, Denmark.

Abstract: BACKGROUND: The annual number of total hip arthroplasties (THA) has increased in Denmark over the past 15 years. There is, however, limited detailed data available on the incidence of THAs.

METHODS: We calculated the incidence rates (IR) of primary THA and revision in Denmark between 1996 and 2002 and estimated the demands for primary THA in Denmark until 2020. We used data from the Danish Hip Arthroplasty Registry, a nationwide and population-based clinical database, to identify patients who had undergone primary THA (n = 37,144) or revision arthroplasties (n = 6446). Age and sex-specific data on the Danish population were obtained from the StatBank Denmark. All IRs were standardized according to two standards, i.e. the Danish population in 1996 and the European standard population (18 age groups). The future demands for primary THA were estimated using the age and sex-specific incidence of primary THA for 2002 as a reference, and taking into account the expected changes in the age distribution of the population and the trend in IRs seen in Denmark between 1996 and 2002.

RESULTS: The annual overall standardized IRs of primary THAs and revisions increased from 101 (95% confidence interval (CI): 97.6-104) to 134 (CI: 131-138) and from 19.2 (CI: 17.9-20.5) to 21.1 (CI: 19.8-22.4) per 100,000 inhabitants from 1996 to 2002, respectively (IRs adjusted to the Danish population in 1996). The IRs of primary THAs and revisions increased by 30% and 10% during this period. The relative increase in IRs of primary THAs was found to be similar in both women and men. The increase was higher among patients aged 50-59 years, however. Furthermore, a decrease in IRs was seen in patients who underwent primary THA due to rheumatoid arthritis. IRs of primary THAs have been estimated to increase by 22% in 2020 compared with 2002, based only on the expected changes in the age distribution of the population. However, assuming that the annual age and sex-independent increase in the IRs seen in the period 1996-2002 will continue, the IR of primary THA is estimated to increase by as much as 210% in 2020.

INTERPRETATION: The overall annual standardized IRs of primary THAs and revisions in Denmark increased during the period from 1996 to 2002. Moreover, the demands for THA procedures in the coming decades may exceed the current capacity due to the ageing population and a continued age and sex-independent increase in surgical activity.