Patients with femoroacetabular impingement syndrome (FAI) can experience lasting clinical improvement after arthroscopic osteoplasty and labral repair or débridement [4, 18, 23]. Hip arthroscopy can treat the pain associated with FAI; however, some patients will still eventually undergo early conversion to THA due to unresolved symptoms and progression of arthritis [9, 16, 22, 24, 26]. Older age, obesity, concurrent acetabular microfracture, labral débridement rather than repair, and preoperative joint space narrowing less than 2 mm may all be associated with an increased risk of conversion to THA after hip arthroscopy [16, 17, 25].
However, our knowledge of these risk factors is limited and incomplete, because most prior research on the topic comes from single-center studies [4, 7, 16], and has not focused on particular arthroscopic indications (such as arthroscopic osteoplasty for FAI). As hip arthroscopy is an approach that could be used to treat many kinds of hip pathology, analyses focused on particular indications is needed. Usage of hip arthroscopy for FAI is rising, therefore, identifying additional patient characteristics associated with conversion to THA could help guide preoperative patient selection counseling and selection to allow for more effective care [20, 25]. We therefore wished to evaluate current trends and patient characteristics associated with early conversion to THA after hip arthroscopy performed specifically for FAI.
Using a large healthcare claims database over a 5-year period (2011 to 2016), we therefore asked (1) What is the survivorship free from THA after arthroscopic osteoplasty performed for FAI? (2) What identifiable demographic factors and patient characteristics are associated with early conversion to THA after hip arthroscopy for FAI?
Patients and Methods
Study Design and Setting
The Truven Health MarketScan Commercial Claims and Encounters databases (Truven Health Analytics, Ann Arbor, MI, USA) is one of the largest commercial claim databases in the United States containing more than 240 million unique workers and their dependents who are covered by employer-sponsored health insurance . This database only contains employer-sponsored claims; therefore, workers compensation patients, self-insured individuals, as well as Medicaid and Medicare patients are excluded. The MarketScan claims database contains individual-level data regarding healthcare claims, laboratory results, discharge information, procedures, diagnoses, and pharmacy dispensing.
We used the MarketScan claims database to identify all patients with a hip arthroscopy claim between January 1, 2011 and December 31, 2014. Inclusion criteria were a minimum of 3 months of continuous enrollment before surgery, age between 12 years to 63 years, a Current Procedural Terminology (CPT) surgical code of either 29914 or 29915 to indicate osteoplasty, and continuous prescription drug data over the follow-up period. We started with the year 2011 as this is when CPT coding changed for hip arthroscopy to specify femoral (29914) or acetabular (29915) osteoplasty to address the impingement morphology of FAI. We ended with 2014 so as to have 2 years of complete follow-up data within the database. Exclusion criteria were patients older than 63 years due to potential overlap with Medicare insurance, those who did not meet follow-up criteria, those with prior hip arthroscopy within a 1-year window, and those with missing prescription drug data. As this is an employer-based database, a small subset of employers opted not to provide prescription data. The age, sex, underlying diagnosis, number of arthroscopic surgeries, Charlson comorbidity codes, region, and year were collected, using ICD-9, Clinical Modification (ICD-9-CM), and ICD-10-CM. As there is variable enrollment in MarketScan, we were unable to definitively capture all prior hip arthroscopic procedures for each patient. For example, some patients may have undergone hip arthroscopy before enrollment in this database. Therefore, for patients with multiple hip arthroscopy codes, we limited survivorship analysis to survivorship after the most recent hip arthroscopy event.
Patients were classified into diagnostic categories based on ICD codes associated with surgery. Diagnoses were classified as FAI, osteoarthritis, inflammation, dysplasia, or soft tissue diagnoses (see Appendix 1; Supplemental Digital Content 1, http://links.lww.com/CORR/A389). The most frequent inflammation diagnostic codes included avascular necrosis, pigmented villonodular synovitis, and rheumatoid arthritis. Although we assumed all patients had a diagnosis of FAI to have had an osteoplasty, we acknowledged that patients could also carry other diagnoses at the time of surgery.
We used administrative codes to identify comorbidities used in the Charlson Comorbidity Index . The Deyo adaption for the Charlson Comorbidity Index was used for each patient . We subclassified comorbidities into peripheral vascular disease, cardiovascular disease, cerebrovascular/neurodegenerative disease, pulmonary diseases, malignancies, renal disease, liver disease, gastrointestinal diseases, and AIDS. Using administrative codes, we also identified those patients with lower back pain and depression diagnoses within 3 months of hip arthroscopy (see Appendix 1; Supplemental Digital Content 1, http://links.lww.com/CORR/A389). Patients were considered to have a depression diagnosis if they had both a depression diagnostic code and had filled a mood stabilizing medication within 3 months of that diagnosis (Appendix 1; supplemental materials are available with the online version of CORR®). Patients were identified as having a history of preoperative opioid use if they filled one or more prescriptions for opioids before the month before hip arthroscopy. By doing so, we excluded patients who might have filled an opioid prescription solely related to their hip arthroscopy procedure.
We then identified all patients in our cohort who underwent THA (CPT codes 27130 and 27132). Our primary outcome was hip arthroscopy survival as defined by conversion to THA.
Patient Cohort, Trends, and Univariate Analysis
A total of 15,548 patients underwent hip arthroscopy with osteoplasty in the MarketScan database from 2011 to 2014. There were 4730 patients who had at least 2 years of follow-up and met all inclusion criteria (Fig. 1). We found that the annual incidence of hip arthroscopic osteoplasty claims in the MarketScan claims database increased over the time period of the study (Fig. 2). In 2011, the incidence of hip arthroscopy was 1.2 persons per 100,000. However, by 2014, the incidence of hip arthroscopy had grown to 2.1 persons per 100,000. Within this cohort, 7% (338 of 4730) underwent conversion to THA within 2 years of hip arthroscopy for FAI. Univariate tests of associations between THA and patient factors were performed using t-tests for continuous variables and chi-square tests for categorical variables. In a univariate, unadjusted analysis, we found that compared with patients who did not convert to THA, those who went on to THA were older (50 ± 8 years versus 37 ± 13 years; p < 0.001) and more likely to have a history of obesity (6% versus 4%; p = 0.03), depression (8% versus 6%; p = 0.04), smoking (6% versus 3%; p = 0.04), or opioid use (42% versus 20%; p < 0.001). Diagnoses of osteoarthritis (71% versus 40%; p < 0.001) and inflammation (7% versus 4%; p < 0.001) were more common in the THA conversion group (see Appendix 2; Supplemental Digital Content 2, http://links.lww.com/CORR/A390). These data were then used for a logistic regression with findings as described in results, below.
To assess any potential bias related to lack of information on laterality in ICD-9 coding, a parallel hold-out sample with hip arthroscopies from October 2015 to December 2016 using ICD-10 coding was extracted along with 1 year of follow-up to estimate the proportion of patients who might be misclassified as THA conversion when using ICD-9 coding. Of the 340 observed THAs during the follow-up of patients with a FAI related hip arthroscopy claim after October 2015, 329 (97%) were on the same hip or a bilateral THA while 11 (3%) were on the opposite hip.
Survivorship Analysis and Statistical Analysis
Our primary analyses were performed by logistic regression and then confirmed with a Cox regression survival model, lifting the requirement of 2 years of continuous, postoperative enrollment to ensure our models were not potentially biased by a “healthy-worker” effect. We used a Kaplan-Meier survival analysis to estimate the proportion of patients with a THA within 2 years of follow-up. We selected variables based on our univariate analysis and previously described risk factors for conversion to THA. Kaplan-Meier survival curves, stratified by factors associated with THA, were obtained to assess the time-to-event. All statistical tests were two-sided with a p value less than 0.05 indicating statistical significance. STATA 14 (StataCorp, College Station, TX, USA) was used for all analyses. With an expected sample size of 12,000 patients undergoing arthroscopic surgery during the study period and an expected conversion to THA proportion as high as 10% and low as 5%, the study had 80% power to detect a relative risk as small as RR = 1.5 for a dichotomous exposure variable as small as 5% (n = 600) of the total sample.
Per the University of Washington Institutional Review Board, this study was exempt from review.
Two-year Survivorship After Hip Arthroscopy for FAI
Within the cohort of 4730 patients, 7% (338) underwent conversion to THA within 2 years of hip arthroscopy for FAI. In our sensitivity analysis we used the larger cohort (11,323 patients) with partial follow-up and found the Kaplan-Meier estimated conversion to THA was similar at 6.7% (95% CI 6.1 to 7.3). In this model the median time of follow-up was 517 days (1.6 years) with 4625 (41%) censored at 2 years. When categorizing by age, the proportion of patients going on to THA within 2 years after hip arthroscopy increased by decade, with more than 18% of those older than 55 years converting to THA (Table 1). We found no statistically significant changes in the age distribution of patients undergoing hip arthroscopy over time or the proportion of patients converting to THA per year from 2011 to 2014.
Table 1. -
Age and temporal trends for conversion to THA within 2 years after hip arthroscopy for FAI (n = 4730)
||No THA, % (n)
||THA, % (n)
|By age category, years
||p < 0.001a
|By year of surgery
||p = 0.154 a
ap values based on chi-square test for linear trend.
Among this cohort, 7% (338 patients) underwent conversion to THA while 93% (4392 patients) did not.
Factors Associated with 2-Year Conversion to THA after Hip Arthroscopy for FAI
After controlling for confounding variables such as sex, obesity, and depression, we found that older age, diagnoses of osteoarthritis or joint inflammation, and opioid use were all independently associated with increased odds of conversion to THA (Table 2). A Kaplan-Meier survival analysis (n = 11,323) similarly revealed increased proportion of conversion to THA among older patients (Fig. 3A), those with diagnoses of osteoarthritis and/or joint inflammation (Fig. 3B), those with preoperative opioid use (Fig. 3C), and smokers (Table 3).
Table 2. -
The logistic regression analysis demonstrates odds of undergoing THA after hip arthroscopy for FAI within 2 years (n = 4730; pseudo R2
||Odds ratio (95% CI)
||1.08 (1.07 to 1.10)
||1.09 (0.49 to 1.39)
||2.91 (2.27 to 3.77)
||1.89 (1.16 to 3.09)
||1.22 (0.65 to 2.33)
||0.76 (0.54 to 1.08)
|Lower back pain
||0.78 (0.57 to 1.06)
||1.29 (0.76 to 2.19)
|Charlson Comorbidity index
||0.92 (0.77 to 1.11)
||1.39 (0.83 to 2.32)
||2.17 (1.69 to 2.79)
||1.44 (0.92 to 2.24)
aIndicates statistical significance.
Table 3. -
The Cox regression survival analysis with hazard ratios demonstrates the factors associated with conversion to THA after arthroscopic hip surgery for FAI, for total available follow-up (n = 11,323)
||Hazard ratio (95% CI)
||1.08 (1.07 to 1.09)
||1.12 (0.95 to 1.31)
||2.53 (2.13 to 3.01)
||1.53 (1.10 to 2.11)
||1.27 (0.83 to 1.92)
||0.94 (0.76 to 1.17)
|Lower back pain
||0.86 (0.71 to 1.05)
||1.55 (1.14 to 2.11)
|Charlson Comorbidity index
||0.95 (0.84 to 1.06)
||1.21 (0.87 to 1.67)
||2.02 (1.71 to 2.38)
||1.15 (0.85 to 1.55)
aIndicates statistical significance.
Survivorship free of THA after hip arthroscopy for FAI remains incompletely characterized. In this large-database analysis of more than 11,000 patients who underwent hip arthroscopy, the overall conversion to THA within 2 years after arthroscopy was 7% and for patients younger than 35 years, it was less than 1%. We found that older age, preoperative diagnoses of osteoarthritis or inflammation, opioid use, and smoking were all independently associated with conversion to THA after hip arthroscopy for FAI. This study focused only on patients undergoing hip arthroscopy with osteoplasty for FAI. Previous database analyses have combined FAI with other indications for hip arthroscopy [2, 3, 11, 13, 14, 25]. However, hip arthroscopy is a tool, not an operation, so it is important that studies (like this one) focus on what is done through the arthroscope, rather than simply that an arthroscope was used.
There are several potential limitations to this study mostly related to the use of an administrative database. Firstly, as this is a claims-based study, it is not possible to obtain radiographic variables, highly detailed clinical data, or clinical outcome data such as physical exam findings and patient-reported outcomes. Instead, we relied upon administrative codes, and we were unable to further stratify the severity of diagnoses such as obesity, osteoarthritis, or psychiatric symptoms. We were also unable to reliably capture other important factors such as dysplasia or instability. These conditions are not always captured reliably with diagnostic codes. Due to the inconsistency of diagnosis coding for FAI, we chose to use CPT coding to identify patients that underwent osteoplasty as this is a procedure which would only be done for FAI, and not for other hip diagnoses. We were unable to identify the proportion of patients with a suboptimal clinical outcome (such as persistent pain or disability) as we did not have patient satisfaction or other clinical outcome data. There may be a higher percentage of patients who did not benefit from surgery compared with the percentage who converted to THA. Also, ICD-9-CM codes do not provide laterality. Our above-described laterality analysis suggests that our primary analysis over-estimated the proportion of THA conversion by a minimal amount as only 3% of THA were on the contralateral hip. Furthermore, we excluded patients who had a previous hip arthroscopy code within 1 year before the hip arthroscopy event used for our analysis. Therefore, we may have excluded patients who are not revisions because of laterality. And we may have missed some revisions or conversions because of enrollment issues within the database. Due to limitations of follow-up and enrollment in this database, it was not feasible to investigate the effect of revision arthroscopy on conversion to hip replacement. Additionally, the MarketScan database has additional sources of selection bias. It is an insurance-based claims database and, therefore, does not capture uninsured patients, Medicare patients, workers compensation patients, self-insured patients, or patients insured with a company not part of this database. Analysis of overall demographics of MarketScan shows that this cohort tends to be a younger, healthier group that can maintain employment and therefore employer health benefits. Also, hip arthroscopy is typically performed in younger people and such individuals may be more likely to change jobs. As this database is employer-based, there is notable censoring due to patients dropping out of the sample because of employment changes or aging. For these reasons, our patient population is not fully representative of the US population at large. Further investigation of other national databases may provide more insight into overall national trends. As noted above, there is substantial loss of follow-up in this database because changes in people’s insurance can affect inclusion in this database. Lastly, we did not stratify for surgeon experience; it is possible that outcomes may be different based upon the experience of the operative surgeon. Therefore, our findings should be interpreted considering these limitations.
Previous analyses of hip arthroscopy trends have shown that the annual incidence of hip arthroscopy has increased and is projected to rise further [2, 3, 14, 25]. As this procedure becomes more common, the number of patients interested in hip arthroscopy may also increase. We demonstrated growth in the incidence of arthroscopic hip osteoplasty for FAI in this cohort. Encouragingly, THA conversion after arthroscopy for FAI was found to decrease in this dataset over the time of our study. However, better risk stratification of patients regarding THA conversion risk is still needed to ensure more clinically efficacious and cost-effective care. Most early series on outcomes after hip arthroscopy were focused on younger, healthier patients [19, 22, 23]. As indications for and attitudes towards hip arthroscopy have evolved, however, hip arthroscopy in older patients for a variety of indications has become more common. Patients in their 50s and older have been shown in previous studies to have increased risk of conversion to THA within the short-term (up to 20%) when compared with patients in their 30s [7, 13, 15, 21, 22, 25]. Our dataset echoes these findings with a 18% conversion to THA in patients older than 55 years. When temporal age patterns in our cohort were analyzed, we found that the absolute incidence of hip arthroscopy in older patients continued to increase over time. However, the proportion of hip arthroscopy that is being performed in older patients decreased and started to stabilize over time. These findings suggest that practice patterns may still need to catch up with current evidence regarding outcomes in older individuals, although this conclusion must be interpreted within the confines of this database. Nevertheless, the role of age should be understood as highly complex. Although age is clearly associated with conversion risk, many middle-aged patients can still experience meaningful clinical benefit . It is likely that age is a proxy for findings such as osteoarthritis or other conditions that are associated with hip survival [16, 21]. Middle-aged and older patients had a higher risk of THA conversion. However, these conclusions are limited by the dataset, and there may still be a potential benefit for hip arthroscopy in carefully selected individuals without radiographic osteoarthritis and these patients should not be excluded solely based on age. Rather, imaging and other clinical factors should be considered as well.
In addition to age, we found preoperative diagnoses of osteoarthritis and inflammation, as well as opioid use and smoking, to have a negative association with THA-free hip survival. Systematic reviews have largely recommended against hip arthroscopy in mild or worse osteoarthritis [6, 27]. Around three quarters of the patients who underwent a THA conversion in our series had an osteoarthritis code. Our findings are further confirmation that hip arthroscopy likely does not provide a lasting benefit to prevent THA in patients with osteoarthritis and FAI. Hip arthroscopy for FAI in patients with osteoarthritis should be carefully considered. Similarly, joint inflammation diagnostic codes were also associated with a higher risk of THA conversion. Pigmented villonodular synovitis and rheumatoid arthritis were the most frequent joint inflammation codes. For patients with these conditions, progression to THA may be part of their natural history. This natural history was likely not substantially modifiable with hip arthroscopy in this dataset. Preoperative opioid use was also strongly associated with higher likelihood of conversion to THA in our series. Westermann et al.  recently reported that preoperative opioid use was associated with worse functional outcomes before hip arthroscopy. Also, Anciano Granadillo et al.  recently reported that preoperative opioid use was associated with an increased rate of conversion to THA after hip arthroscopy. It may be that patients with chronic pain and opioid use do not find relief with hip arthroscopy and thus seek further surgical treatment to address their pain. Notably, evidence from arthroplasty studies has shown a higher risk of revision THA after primary THA for patients with higher perioperative opioid use [6, 27, 28, 30]. The relationship between preoperative opioid use and outcomes in hip arthroscopy has been less well characterized and must be further studied. Our cohort was predominately female, and previous studies have demonstrated that women are more likely to undergo conversion to THA after hip arthroscopy . Our analysis did not demonstrate this, although this may be because we focused on FAI only. Likewise, we did not demonstrate a relationship between lower back pain and depression in our cohort. Factors such as mood, psychiatric disorders, or lower back pain have already been shown to affect hip pain and function [10, 12]. These conditions may further confound clinical evaluation as they can simulate or magnify existing hip pathology. Further investigation into the effects of these factors in hip arthroscopy for FAI is needed.
In summary, we used a large commercial database to determine that the overall conversion of hip arthroscopy for FAI to THA within 2 years is 7%. Although the findings of this study are limited and should not be taken in isolation, FAI patients who are older age, carry diagnoses of inflammatory or degenerative articular disease, or who use opioids or smoke should be counseled about a potentially increased risk of undergoing early conversion to THA after hip arthroscopy. Future investigation should focus on further characterizing mid- and long-term hip survival after arthroscopy for FAI, with more detailed cost analyses and investigations into the relationships of conversion risk and clinical data not captured in medical codes.
The authors would like to thank Ellie Brewer and the University of Washington Surgical Outcomes Research Center for their help with this project.
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