Abstract
Introduction
Background: Primary total hip arthroplasty (THA) is performed for a variety of pathologies. Osteoarthritis (OA) is the most common indication for THA in the United States of America (USA). The study aims to establish the incidence of indications for THA in the USA as compared to India and to assess whether Avascular Necrosis (AVN) of the Hip is a more frequent indication for THA in India than in the USA.
Methods
The National Inpatient Sample database (USA) and two Indian databases (one national and one regional) were analyzed to identify all patients who underwent primary THA within the databases. The relative frequencies of each indication for THA were determined. The patients' demographics and risk factors for AVN of the hip were recorded and assessed. The data were then compared across the patients in the USA and the patients in India.
Results
225,061 primary THA patients were identified in the USA database and 20,288 in the Indian database. The proportion of primary THA performed for AVN in the American database (5.97%) was significantly lower than the proportion of THA performed for AVN in the Indian database (51.8%).
Conclusion
The relative frequency of AVN as an indication for THA is significantly higher in India than in the USA. It is important to recognize the differences in relative indications for THA between world populations, as outcomes after THA among Eastern populations of the world may not be equivalent to ones seen in their Western counterparts.
Keywords: Total hip arthroplasty, THA, Avascular necrosis, AVN, India, National inpatient sample
Highlights
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•
Avascular Necrosis is a more prominent indication for Total Hip Arthroplasty in India than in the United States.
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Osteoarthritis is the most common indication for Total Hip Arthroplasty in the United States.
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Avascular Necrosis is the most common indication in India.
1. Introduction
Avascular Necrosis (AVN) of the hip is a debilitating condition in which blood supply to the femoral head is interrupted often leading to necrosis and collapse. Risk factors include corticosteroid and alcohol exposure, trauma, autoimmune diseases, sickle cell disease, and HIV, though many cases are idiopathic.1,2 As the success of total hip arthroplasty (THA) for advanced stages of AVN has increased over time, it has now become a standard treatment in the late stages of this disease, yielding more benefit to patients as compared with conservative measures.3, 4, 5
While osteoarthritis (OA) of the hip is the most prevalent indication for primary THA in the United States of America (USA), AVN still contributes to a significant portion of surgeries. AVN is estimated to account for 5–18% of THAs in the USA.6, 7, 8 Similar estimates in Canada, Sweden, and Australia have been reported.9 Conversely, in many Asian countries (like India), AVN is more prevalent and is one of the leading indications for THA.10,11 There is a paucity of research investigating the true incidence of AVN and its indication for THA in India. India suffers a high burden of AVN that has yet to be quantified in an orthopaedic setting.12 If a dichotomy in the indications for THA exists, this would imply that areas of joint replacement research are not universally applicable to all THA patients.
The present study aims to establish the incidence of the most common indications for THA in the USA as compared to India. We further aim to compare the relative frequency of primary THA for AVN in these two populations. We hypothesize that the incidence of THA for AVN will vary significantly between the two populations.
2. Materials and methods
All data analyzed was acquired from deidentified research databases and was therefore considered exempt from internal review board approval. Databases were chosen based on availability, size, and scope; criteria for selection was the largest available databases including information on indications for THA that covered the population in the United States and the population in India as a whole. Additionally, a local tertiary referral center database was chosen to assess whether national trends would persist in an Indian subpopulation.
A cross-sectional analysis was performed using data from National Inpatient Sample (NIS) database from 2016 to 2017 (USA); the NIS is a publicly available inpatient database which does not require access permission. Data on all primary THA procedures was obtained using ICD-10-CM/PCS Procedures codes for hip replacements. The data was then categorized by diagnosis using ICD-10-CM/PCS for AVN, OA, femoral head and neck fracture, rheumatoid arthritis, ankylosing spondylitis, pathological fracture, and hip dysplasia. For patients with multiple diagnoses, the most immediate cause for surgery was considered. Therefore, priority was given to pathological fracture followed by ankylosing spondylitis, femoral head or neck fracture, AVN, rheumatoid arthritis, hip dysplasia, and OA, respectively. Patients not already classified with a code of interest and with a code for periprosthetic fracture or periprosthetic osteolysis were excluded from the dataset. All other remaining patients, including those with codes for secondary OA, were collectively included in an “other” category (Fig. 1). Finally, demographic and comorbidity information was collected on each patient including age, race, sex, corticosteroid abuse, alcohol abuse, smoking, sickle cell disease, and HIV among the categories.
Fig. 1.
Flowchart of data collection in the National Inpatient Sample (NIS)
Data on 14,294,784 from the 2016–2017 NIS database was reviewed. A final THA cohort used in analysis included 225,061 patients. “Pre-determined” diagnoses included avascular necrosis of the hip, osteoarthritis of the hip, rheumatoid arthritis, hip dysplasia, femoral head/neck fracture, ankylosing spondylitis, and pathological fracture. Patients with a THA code and either a pre-determined diagnosis or no periprosthetic fracture or osteolysis diagnosis were included in the final analysis.
The national Indian Society of Hip & Knee Surgeons (ISHKS) Joint Registry and a local tertiary referral center database from Telangana, India were assessed; the diagnoses were categorized as above. The Indian databases did not include the diagnosis of pathological fracture. The proportion of AVN was calculated for each database and compared for statistically significant differences. Risk factors for AVN were not available in the Indian registries and were therefore not analyzed.
2.1. Statistical analysis
Descriptive statistics were used to describe the incidence of each diagnosis contributing to THA. A Z-test was performed to compare the incidence of THA for AVN pairwise between the NIS and the ISHKS Joint Registry; the same analysis was used to compare the ISHKS Joint Registry and the Telangana hospital's joint replacement database. The incidences of THA for all other diagnoses were then compared in the same manner.
For the NIS database cohort, descriptive statistics were used to describe the prevalence of corticosteroid abuse, alcohol abuse, smoking status, sickle cell disease, and HIV. The proportion of each was calculated for each THA indication group. A Z-Test was then used to assess for significant differences between groups. Demographic factors age, race, and sex were determined and described. Two proportion Z-tests were used to test for differences between the AVN group and an “all other indications” group.
3. Results
Of the 14,294,784 patients in the 2016-17 NIS database, 227,354 had a code for THA. 2293 patients were excluded for diagnosis of periprosthetic fracture or periprosthetic osteolysis, leaving 225,061 patients (0.16%) under consideration in the sample (Fig. 1).
In this database, AVN was the third most common indication for primary THA, with 13,438 cases (5.97% of the THA patients). All indications for primary THA in the NIS database are seen in Fig. 2. Table 1 provides a breakdown of patients who underwent THA for each studied indication in the NIS database by sex, while Table 2 provides a similar breakdown by race. Table 3 shows the prevalence of selected risk factors across each of the indications for THA in the NIS database.
Fig. 2.
Proportion of Diagnoses Among Total Hip Arthroplasty Patients, National Inpatient Sample, Indian Joint Registry, and Telangana Hospital Databases
Osteoarthritis of the hip (OA) was the most common indication for surgery for Total Hip Arthroplasty (THA) patients in the NIS database from 2016-17. In the Indian Joint Registry (IJR) and Telangana Hospital databases, the most common indication was Avascular Necrosis of the Hip (AVN). Other diagnoses considered were Femoral Head/Neck Fracture (FHNFx), Rheumatoid Arthritis (RA), Hip Dysplasia (HD), Ankylosing Spondylitis (AS), and Other (Oth).
Table 1.
Indications for Primary THA by Sex, Mean Age, 2016-17 NIS database.
| OA | FHNFx | AVN | RA | HD | Path Fx | AS | Oth | TOTAL | |
|---|---|---|---|---|---|---|---|---|---|
| Male | 44.7% | 31.5% | 53.9% | 25.8% | 29.0% | 34.8% | 53.9% | 45.5% | 42.0% |
| (N = 94399) | |||||||||
| Female | 55.3% |
68.5% |
46.1% |
74.2% |
71.0% |
65.2% |
46.1% |
54.5% |
58.0% |
| (N = 130615) | |||||||||
| Mean Age | 66.2 | 79.0 | 57.9 | 65.1 | 53.6 | 70.3 | 63.3 | 66.8 | 68.1 |
Note. Not all patients in the database had age and/or sex listed. Patients without a listed age and/or sex were omitted from this table.
NIS- National Inpatient Sample; OA- Osteoarthritis; FHNFx- Femoral Head and Neck Fracture; AVN- Avascular Necrosis; RA- Rheumatoid Arthritis; HD- Hip Dysplasia; Path Fx-Pathological Fracture; AS- Ankylosing Spondylitis; Oth- Other.
Table 2.
Indications for Primary THA by NIS Race, 2016-17 NIS database.
| NIS Race | OA (N = 134407) | FHNFx (N = 43248) | AVN (N = 12882) | RA (N = 4903) | HD (N = 2985) | Path Fx (N = 1241) | AS (N = 368) | Oth (N = 14853) | TOTAL (N = 214877) |
|---|---|---|---|---|---|---|---|---|---|
| White (N = 184121) | 86.8% | 86.8% | 75.7% | 80.0% | 81.4% | 79.9% | 74.7% | 84.7% | 85.7% |
| Black (N = 15593) | 7.3% | 4.5% | 14.9% | 10.0% | 6.1% | 8.9% | 14.7% | 7.5% | 7.3% |
| Hispanic (N = 8403) | 3.3% | 4.8% | 5.0% | 6.4% | 6.9% | 5.6% | 7.1% | 4.4% | 3.9% |
| Asian/Pacific Islander (N = 2379) | 0.8% | 1.9% | 1.6% | 1.2% | 2.5% | 2.1% | 0.5% | 0.9% | 1.1% |
| Native American (N = 640) | 0.2% | 0.3% | 0.5% | 0.5% | 0.5% | 0.6% | 0.3% | 0.4% | 0.3% |
| Other (N = 3751) | 1.6% | 1.7% | 2.3% | 1.9% | 2.5% | 2.9% | 2.7% | 2.0% | 1.7% |
Note. Not all patients in the database had race listed. Patients without a listed race were omitted from this table. Columns may not add to 100% due to rounding.
NIS- National Inpatient Sample; OA- Osteoarthritis; FHNFx- Femoral Head and Neck Fracture; AVN- Avascular Necrosis; RA- Rheumatoid Arthritis; HD- Hip Dysplasia; Path Fx- Pathological Fracture; AS- Ankylosing Spondylitis; Oth- Other.
Table 3.
Prevalence of Selected Risk Factors in Cases of Primary THA, 2016-17 NIS database.
| Risk Factor | OA (N = 141028) | FHNFx (N = 44859) | AVN (N = 13438) | RA (N = 5122) | HD (N = 3193) | Path Fx (N = 1286) | AS (N = 380) | Oth (N = 15755)T | TOTAL (N = 225061) |
|---|---|---|---|---|---|---|---|---|---|
| Sickle Cell Disease (N = 423) | 0.1% | <0.1% | 1.6% | 0.2% | 0.2% | 0.2% | 0.5% | 0.2% | 0.2% |
| Smoking (N = 22158) | 8.6% | 10.2% | 19.6% | 9.4% | 10.2% | 12.0% | 10.0% | 11.5% | 9.8% |
| Alcohol Abuse (N = 4508) | 1.2% | 3.6% | 4.9% | 1.0% | 0.8% | 2.6% | 1.3% | 2.3% | 2.0% |
| Corticosteroid Abuse (N = 4538) | 1.4% | 2.7% | 4.2% | 10.3% | 1.4% | 4.9% | 1.3% | 0.9% | 2.0% |
| HIV (N = 306) | 0.1% | 0.1% | 1.0% | <0.1% | 0.1% | 0.5% | 0% | 0.2% | 0.1% |
Note. Not all patients in the database had one of the listed risk factors. Patients with more than one risk factor are listed multiple times.
NIS- National Inpatient Sample; OA- Osteoarthritis; FHNFx- Femoral Head and Neck Fracture.
AVN- Avascular Necrosis; RA- Rheumatoid Arthritis; HD- Hip Dysplasia; Path Fx- Pathological Fracture; AS- Ankylosing Spondylitis; Oth- Other.
All 20,288 patients from the Indian Joint Registry underwent primary THA. 10,509 (51.8%) had a diagnosis of AVN. The proportion of patients who had a primary THA for AVN in the NIS database (5.97%) was significantly lower than in the Indian Joint Registry (z = 210.66, p < .001). All the indications for primary THA in the ISHKS database (Fig. 2) and a comparison of the indications for primary THA between the NIS database and the Indian Joint Registry are provided in Table 4.
Table 4.
Selected Proportion of Diagnoses Among Total Hip Arthroplasty Patients, 2016-17 NIS Database vs 2006-21 ISHKS Indian Joint Registry (IJR).
| Database | OA | FHNFx | AVN | RA | HD | AS |
|---|---|---|---|---|---|---|
| NIS (N = 225061) | 62.7% | 19.9% | 6.0% | 2.8% | 1.4% | 0.2% |
| IJR (N = 20288) | 10.1% | 2.6% | 51.8% | 6.2% | 2.1% | 5.6% |
| Z |
145.44 |
60.9 |
210.66 |
33.64 |
7.71 |
94.54 |
| P-Value | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 |
Note. Rows will not add to 100% as not all indications for Primary THA are listed in both databases, and therefore were excluded.
ISHKS- Indian Society of Hip and Knee Surgeons; OA- Osteoarthritis; FHNFx- Femoral Head and Neck Fracture; AVN- Avascular Necrosis; RA- Rheumatoid Arthritis; HD- Hip Dysplasia.
AS- Ankylosing Spondylitis.
776 patients were reviewed from the Telangana Hospital database. Three were excluded for periprosthetic fracture diagnosis leaving 773 for consideration in our analysis. There was no significant difference between the proportion of patients who had a primary THA for AVN in the ISHKS Joint Registry (51.8%) and in the Telangana hospital database (52.0%), (z = 0.11, p = .911). All the indications for primary THA in the Telangana Hospital database (Fig. 2) and a comparison of the indications for primary THA between the National Indian Joint Registry and the Telangana Hospital database can be seen in Table 5.
Table 5.
Selected Proportion of Diagnoses Among Total Hip Arthroplasty Patients, 2006-21 ISHKS Indian Joint Registry (IJR) vs Telangana, India Hospital Database (THD).
| Database | OA | FHNFx | AVN | RA | HD | AS |
|---|---|---|---|---|---|---|
| IJR (N = 20288) | 10.1% | 2.6% | 51.8% | 6.2% | 2.1% | 5.6% |
| THD (N = 773) | 16.8% | 12.9% | 52.0% | 6.2% | 1.4% | 1.0% |
| Z |
6.02 |
16.59 |
0.11 |
0.01 |
1.3 |
5.5 |
| P-Value | <0.001 | <0.001 | 0.911 | 0.991 | 0.195 | <0.001 |
Note. Rows will not add to 100% as not all indications for Primary THA are listed in both databases, and therefore were excluded.
ISHKS- Indian Society of Hip and Knee Surgeons; OA- Osteoarthritis; FHNFx- Femoral Head and Neck Fracture; AVN- Avascular Necrosis; RA- Rheumatoid Arthritis; HD- Hip Dysplasia; AS- Ankylosing Spondylitis.
4. Discussion
The common indications for THA include OA, AVN, congenital hip disorder, and inflammatory arthritis,13,14 with OA being the most common indication for THA in the USA.15 Studies have shown that OA accounts for up to 85% of THA in the USA, whereas AVN accounts for 5–12% of THA cases.15, 16, 17, 18, 19 However, most of these metrics were first described over two decades ago and are still cited in current literature, despite changing patient demographics in the USA.20 Our aim was to provide an update on the rates of the most common indication for THA in the USA and to compare these rates with those seen in the Indian population. To the author's knowledge, this is the first study to compare these rates between two separate national databases and the first one to show the high incidence of AVN in an Indian population using a national registry.
The data from the NIS database demonstrates that the most common indications for THA are significantly different between the USA and India. Using national registries, we found that OA accounted for nearly 63% of THAs in the USA and 10.1% in India. AVN was an indication for THA in 5.97% of the cases in the USA, which is consistent with previous estimates.6, 7, 8 In India, THA for AVN was significantly higher on both a national and regional level (51.8% and 52.0%, respectively) and accounted for the majority of procedures.
Smaller studies from India have previously reported AVN in up to 42% of total hip replacements, followed by OA (14.4%) and inflammatory arthritis (12.7%).21 Similar studies in Korea and Sub-Saharan Africa have demonstrated that roughly 50% of THAs are performed for AVN of the femoral head.11,22 Conversely, other developed countries including Australia, Canada, and Sweden have demonstrated that AVN accounts for smaller numbers (2.8–6.0%) of all THA.9
Most outcome data on THA is from Western countries, with a markedly different socio-economic profile, where rates of THA for AVN are declining.23 With such large discrepancies in the rates of indications for THA, we can question the generalizability of THA research from developed countries to the countries with differing ethnic populations and socio-economic conditions; this may also be true for micro-populations within a specific country. It is known that patients undergoing THA for AVN have inferior outcomes compared to those undergoing THA for primary OA. Patients with osteonecrosis of the femoral head have higher incidence of 90-day mortality, surgical site infection, unplanned readmission, and revision surgery.24 Having a higher frequency of AVN, the Indian population likely shares the associated poor outcomes and Western research may be less applicable in this scenario.
The cause of these disparities is currently unknown. We speculate that the large portion of AVN in these countries is associated with individual risk factors. Our USA population data shows that Sickle Cell Disease (SCD) was 17.2 times more prevalent among patients with THA for AVN than patients who underwent THA for another cause. HIV was 12 times more prevalent; alcohol abuse was 2.7 times more prevalent, corticosteroid use 2.2 times, and smoking 2.1 times. Still, many cases are considered to be idiopathic in nature.25
Other causes for the discrepancy may be economic or cultural in nature. In India, the poverty rate is higher than in the USA, with figures varying based on definition of poverty. Poverty is associated with four of the five risk factors among AVN patients: HIV, SCD, Smoking, and Alcohol Abuse.26, 27, 28, 29 While SCD itself is a genetically inherited condition, patients with more severe genotypes are more likely to live in poverty.27 It is likely the rates of the disease are much higher in India than in the USA, though it is largely undocumented in the arthroplasty literature.30 Smoking rates are also much higher in India than in the USA (34.6% vs 14%, respectively).31,32 Furthermore, India has a recognized pattern of over-prescription of steroids and alcohol use.33,34 Poverty may also affect the rates of disease for sub-populations within a country. For example, we found Asian-Americans have a higher proportion of THAs for AVN (8.7%) than White Americans (5.3%); Asian-Americans, and especially senior Asian-Americans, the ones who would be most likely to undergo THA, have higher poverty rates.35 More research is needed to determine if poverty is an independent risk factor for THA for AVN of the femoral head, or if it is simply associated with the known risk factors for the disease.
Racial predisposition may also play a role in the increased prevalence of AVN in India. For example, the rates of SCD are much higher among people of Indian, Arabian, and African descent.36 Conversely, White Americans are more likely to undergo elective surgery for THA than other races, when controlling for age, access to insurance, and prevalence of OA.36 Although, there may be a genetic component contributing to the disparity in THA indications, socioeconomic and cultural differences are also likely significant contributors.
4.1. Risk factor for AVN
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A)Known causes:
-
-Alcohol
-
-Steroids
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-Smoking
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-SCD
-
-HIV
-
-
-
B)Suggested causes:
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-Poverty
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-Genetic/Racial predisposition
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Irrespective of the causes for the alarmingly high rates of AVN leading to THA in the Indian population, it is important to recognize this fact based on the data highlighted in this study. The increased rate of complications that are known to occur after THA for AVN could lead to worse outcomes in Indian and other Eastern populations as compared to their Western counterparts. A majority of the long-term outcome and survival analyses in the world wide THA literature is based on analysis performed on Western populations; the same outcome and survival rates might not apply to Indian or other Asian populations. Therefore, it is crucial to understand this discrepancy, especially when counseling patients for THA. This highlights the need for long term outcomes analysis from the Indian subcontinent, and from other Asian countries at large.
There are limitations to our current study. Using the NIS and ISHKS Joint Registry limits our ability to gather granular details about the patients, allowing for potential misclassifications to occur. This is a known limitation of large database studies, which may cause variability in reported diagnoses.37 Comorbid medical conditions and risk factors are also typically under-coded in large database studies.38 Other potential limitations with large third-party database studies include external validity, selection bias, and confounding; these are known complications and are thought to not significantly affect the impact of such a study.38 Additionally, with large cohort studies, small variations may prove statistically significant. There was also a large mismatch in cohort size between our Indian and USA populations making statistical comparison between the two cohorts inexact; however, both databases had an adequately large number of subjects, making this the largest study of its kind available in the literature. The stark difference between the proportions of AVN between the two populations was very evident regardless of the sample sizes. Furthermore, the databases compared were not entirely from the same time periods: the NIS database used to represent the USA was from 2016-17, while the ISHKS Indian Joint Registry included data from 2006 to 2021. In the United States, the proportion of THAs performed for AVN is estimated to have decreased by 38% from 2008-2015.23 While this is hardly an insignificant change, it is very unlikely to explain the 863% difference seen between the proportion of THA for AVN in the Indian and American databases. Lastly, national datasets are not inherently representative of a country's entire population, though they do have a role in creating general impressions of national trends.
5. Conclusion
The most common indications for THA in the USA and India vary significantly, with OA being the most common in the USA (up to 64%) and AVN being the most common indication in India (around 52%). The indications for THA may vary significantly based on cultural habits, race, and income. It is important to recognize the differences in relative indication for THA between differing world populations, as outcomes after THA may not be equivalent and cannot be compared.
Funding/sponsorship
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
Institutional ethical committee approval
This is an observational study. All data analyzed was acquired from deidentified research databases and was therefore considered exempt from internal review board approval; no ethical approval is required.
CRediT authorship contribution statement
Ramakanth R. Yakkanti: Conceptualization, Methodology, Supervision, Writing – review & editing. Sagie Haziza: Conceptualization, Writing – review & editing, Writing – original draft. Nathan A. Wasserman: Conceptualization, Methodology, Writing – original draft, Writing – review & editing, Formal analysis, Data curation. Adarsh Annapareddy: Conceptualization, Resources, Data curation. V. Ratnakar: Resources, Data curation. S.R. Karri: Resources, Data curation. Victor H. Hernandez: Conceptualization, Methodology, Supervision. A.V. Gurava Reddy: Conceptualization, Resources. Raju Vaishya: Writing – review & editing.
Declaration of competing interest
None.
Acknowledgements
None.
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