Progression of Osteoarthritis at Long-term Follow-up in Patients Treated for Symptomatic Femoroacetabular Impingement With Hip Arthroscopy Compared With Nonsurgically Treated Patients

Abstract

Background:

Femoroacetabular impingement (FAI) is a common cause of hip pain, especially in young patients. When left untreated, it has been demonstrated to be a risk factor for the onset or progression of osteoarthritis (OA) and has been identified as one of the main contributors leading to the need for total hip arthroplasty (THA) at a young age. While the short-term therapeutic potential of hip arthroscopy is widely recognized, little is known regarding its potential mid- to long-term preventive effect on the progression of hip OA.

Purpose:

To (1) report clinical outcomes of arthroscopically treated FAI syndrome with a minimum 5-year follow-up and compare the results to a cohort with FAI treated nonsurgically and (2) determine the influence of hip arthroscopy on the onset and progression of hip OA in patients diagnosed with FAI.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

Patients who had hip pain and were diagnosed with FAI were included. Exclusion criteria were (1) previous or concomitant hip surgery, (2) <5 years of follow-up, and (3) insufficient radiographs. Patients treated with hip arthroscopy were compared with a cohort of patients with FAI who were treated nonsurgically. Kaplan-Meier estimates of failure (defined as conversion to THA) were performed. Bivariate analysis and Cox regression were used to identify factors associated with inferior clinical and radiographic outcomes.

Results:

A total of 957 patients (650 female, 307 male; 1114 hips) (mean age, 28.03 ± 8.9 years [range, 6.5-41.0 years]) with FAI were included. A total of 132 hips underwent hip arthroscopy and 982 hips were nonoperatively treated. The mean follow-up was 12.5 ± 4.7 years (range, 5.0-23.4 years). At the final follow-up, the rate of OA progression was 26.5% in the operative group and 35.2% in the nonoperative cohort (P < .01). Conversion to THA was performed in 6.8% of the surgical patients and 10.5% of the initially nonsurgical patients (P = .19). Additionally, there was no significant difference in the risk of failure between the operatively and nonoperatively treated patients. Male sex, increased age at initial diagnosis, presence of cam morphology, and increased initial Tönnis grade were risk factors for failure (male sex: hazard ratio [HR], 2.3; P < .01; per year of increased age: HR, 1.1; P < .01; presence of cam: HR, 3.5; P < .01; per Tönnis grade: HR, 4.0; P < .01).

Conclusion:

At a mean follow-up of nearly 13 years, 7% of patients of the surgical group experienced progression to THA, compared with 11% of the nonoperative control group. While most of the operative group showed little to no OA at final follow-up, moderate OA (Tönnis grade 2) was present in 12% of the cohort compared with 22% of nonsurgical patients. Increased age at diagnosis, male sex, presence of a cam morphology, and presence of initial arthritic joint changes were found to be risk factors for failure. The results of this study demonstrated evidence for a preventive effect of hip arthroscopy on the development and progression of OA in young patients with FAI at mid- to long-term follow-up.

Keywords

femoroacetabular impingement hip arthroscopy osteoarthritis hip disease FAI

Hip pain and the associated onset and progression of hip osteoarthritis (OA) are among the most prevalent and disabling conditions affecting not only the elderly, but also young and active patients.⁵⁶ While our understanding of the etiopathogenesis of OA has advanced substantially since Ganz recognized and popularized the concept of femoroacetabular impingement (FAI) 20 years ago, the prevention of symptomatic hip OA remains an ongoing goal.^40,50,51 With the rapid and substantial recent advances in arthroscopic techniques, the use of hip arthroscopy (HA) in the diagnosis and treatment of hip pathology has increased over the past decade. HA has been demonstrated to be safe and effective and is among the fastest-growing orthopaedic procedures in the United States.⁵³ While initially used as a technique for loose-body removal and irrigation of septic arthritis, HA is currently used to treat a much wider variety of hip conditions. The recognition of FAI as a source of hip pain in young adults has rapidly expanded the clinical use of HA by applying the principles of osseous correction in a more minimally invasive manner than traditional open surgical approaches.⁷³

While the indications for the use of HA continue to expand, the technique is primarily used to treat symptomatic labral tears and FAI. The purpose of these procedures is the correction of bony abnormalities and associated soft tissue pathologies to reduce and eliminate hip pain, improve joint range of motion, and ultimately prevent or delay the development and progression of symptomatic OA.⁶² Previous studies have demonstrated that early-stage surgical interventions in young patients with symptomatic FAI may increase the longevity of articular cartilage and prevent the cascade of joint degeneration.²² In contrast, HA performed in patients with advanced stages of OA is often associated with unsatisfying and contradictory results.^1,44 While the procedure is generally efficacious, the most common reoperation after HA remains conversion to total hip arthroplasty (THA), especially when HA is performed in patients with preexisting degenerative hip changes.^18,32,36

Given these findings, there remains a substantial clinical need to identify patients preoperatively who will benefit from HA and to distinguish them from patients likely to progress to severe OA and THA regardless of intervention. Improving this understanding will allow treating surgeons to more accurately counsel patients with symptomatic FAI. Therefore, the purposes of this study were to (1) report clinical outcomes of arthroscopically treated FAI syndrome with a minimum 5-year follow-up and compare the results with a cohort with FAI treated nonsurgically and (2) determine the influence of HA on the onset and progression of hip OA in patients diagnosed with FAI.

Methods

Study Population and Design

Data on patients undergoing HA between 1998 and 2015 after the failure of comprehensive nonoperative management were prospectively collected and identified using an HA database at a high-volume academic hip preservation center (Mayo Clinic, Rochester, Minnesota, USA). All patients provided written informed consent for research participation. Patient data were collected preoperatively, intraoperatively, and throughout follow-up for the purpose of outcome research.

All data were collected following approval of the Mayo Clinic Institutional Review Board (No. 17-004959). Inclusion criteria were as follows: (1) patients diagnosed with FAI syndrome evaluated with hip pain, (2) a minimum of 5 years of follow-up, and (3) the presence of sufficient radiographic studies (anteroposterior [AP] view of the pelvis and cross-table lateral hip radiographs).^59,75 Patients were excluded if they had (1) previous unrelated hip conditions (including avascular necrosis, ankylosing spondylitis, Legg-Calve-Perthes disease, pigmented villonodular synovitis, and slipped femoral epiphysis) or (2) concomitant surgery (including periacetabular osteotomy). Patients who underwent bilateral HA, both simultaneously and staged, were included in the database. A total of 201 patients were identified for evaluation in the surgical group, with 129 patients (64%), comprising 45 men (34.9%) and 84 women (65.1%), eligible based on study criteria (Figure 1). Of note, the overall majority of female patients observed was consistent with previously published series on HA.^35,52 A total of 1364 patients were evaluated for inclusion in the nonsurgical group, with 957 patients (70%) eligible based on study criteria. This included 307 men (32%) and 650 women (68%).

Nonsurgically treated patients were drawn from the population-based Rochester Epidemiology Project (REP) database in Olmsted County, Minnesota, USA, which had a population of 144,260 in 2010.⁵⁷ Briefly, the REP is a medical record linkage system that provides access to the complete medical records for all residents of Olmsted County, regardless of the medical facility in which the care was delivered.¹⁹ The REP was used to identify all patients in a geographic area who were evaluated by a physician with an International Classification of Diseases, 9th or 10th Revision, diagnostic code of FAI (M24.851, M24.852, M76.20) between January 2000 and January 2016. The database contains complete diagnostic and procedural information from all applicable medical centers until December 1, 2020, to ensure sufficient follow-up to determine the natural history after FAI diagnosis. Clinical notes, radiographic images, and operative notes related to the injury were manually reviewed in detail. Patients with a concomitant history of avascular necrosis, neuromuscular disorder, trochanteric bursitis, hip fracture, pelvic fracture, previous hip surgery, and/or hip dislocation were excluded. Patients were only included if (1) their symptoms, as documented in the chart, were consistent with FAI as defined by the Warwick Agreement, “The primary symptom of FAI syndrome is motion-related or position-related pain in the hip or groin. Pain may also be felt in the back, buttock, or thigh,” and (2) they had radiographic findings consistent with FAI.²⁷

For all patients, time from the first clinically documented episode of hip pain to final follow-up was calculated. Time from initial evaluation to development of hip OA and progression to THA was recorded.

Standardized variables collected in the HA database used for this study included patient characteristics, clinical history, radiographic data, and rate of conversion to THA, if applicable. Values captured included age, sex, laterality, lateral center-edge angle (LCEA), Tönnis angle, alpha angle, crossover sign, and posterior wall sign. Radiographic measurements were performed on standing AP pelvis radiographs obtained both preoperatively and throughout the follow-up period.⁶⁴ In the event of conversion to THA, the last radiographs obtained before surgery were analyzed. Radiographic features were graded according to the Tönnis classification. In brief, grade 0 indicates that no signs of OA were detectable. Grade 1 indicates slight narrowing of the joint space, slight lipping at the joint margin, and slight sclerosis of the femoral head or acetabulum. Grade 2 indicates the presence of small bony cysts, further narrowing of the joint space, and moderate loss of femoral head sphericity. Grade 3 is the most severe and indicates large cysts, severe narrowing of the joint space, severe femoral head deformity, and avascular necrosis.⁴⁶

Radiographs were obtained as part of the routine clinical evaluation as determined necessary by the evaluating physician. No radiographs were obtained strictly for the purpose of this study. All included patients had radiographs at initial physician evaluation and at follow-up. The time points of subsequent radiographs were at the discretion of the evaluating physician.

A cam deformity was defined as an alpha angle >55° as described in previous literature.⁴⁵ Frank et al²⁰ concluded that an alpha angle >50° to 55° defined a cam deformity. The higher of these was chosen in this study to increase specificity.

FAI syndrome was diagnosed according to the 2016 Warwick Agreement based on the presence of a triad of symptoms, clinical signs, and imaging findings.²⁷ Because of the retrospective nature of this study, we were unable to confirm examination findings consistent with FAI in all cases. Physician understanding of FAI has increased since first described in 1999, but knowledge and documentation of physical examination techniques were limited in the early years of this study.⁷⁴ In this study, patients were only included if they had symptoms and diagnostic imaging consistent with FAI as defined by the Warwick Agreement.²⁷ Once it was confirmed that the symptoms and radiographic findings were consistent with FAI, patients were followed by chart and radiographic review to determine whether they developed symptomatic hip OA.³¹ Failure was defined as any patient undergoing conversion to THA.

A thorough chart and radiographic review was performed on all patients. All radiographic reviews were performed by a fellowship-trained orthopaedic surgeon (M.H.). We evaluated for a pistol-grip deformity on a standard AP pelvic view and measured the alpha angle on a lateral view (cross-table, frog-leg, or 45° Dunn view). A best-fit circle was used to define the femoral head contour, and alpha angles were measured between the bisection of the femoral neck axis and a line connecting the center of the femoral head to the point of the beginning of asphericity.⁷⁹ Radiographic parameters were standardized based on the parameters outlined by Clohisy et al.¹⁶ If radiographs were not compliant with these parameters, they were not used for measurements.⁷⁹

Assessment of Risk Factors for Failure and Worse Clinical Outcome

Preoperative radiographs were retrospectively reviewed for evidence of FAI consisting of the presence of relative acetabular retroversion on a true AP plain pelvic radiograph, as indicated by a crossover sign and prominent ischial spine sign, acetabular protrusion, or a pincer divot at the femoral head-neck junction.¹⁶ Cam impingement was defined as an alpha angle >55° on an oblique radiograph (Table 1).¹⁶ In addition, the presence of labral tear/pathology was required on magnetic resonance imaging (MRI). The MRI was also reviewed for the presence of subchondral cysts or edema.

Table 1

Radiographic Findings Associated With Each FAI Type^a

FAI Type	Radiographic Findings
Cam type	Typical pistol-grip deformity and/or Alpha angle >55°^3,7
Pincer type	Crossover sign (COS)^7,16,47,75 and/or Coxa profunda or acetabular protusion^{3,16,47,75,77} and/or Lateral center-edge angle (LCEA) ≥40°^47,75,77 and/or Tönnis angle <0°¹⁶
Mixed type	Both cam and pincer-type features

FAI, femoroacetabular impingement.

Surgical Technique

Arthroscopic hip surgeries were performed by experienced, sports medicine fellowship-trained arthroscopic surgeons (A.J.K., B.A.L.) at a high-volume hip preservation center. Positioning and surgical approach have been described previously in detail.^9,37,60 In brief, patients were positioned in the modified supine position, and 2 or more arthroscopic portals were used, including the anterolateral and midanterior portals. Diagnostic arthroscopy was performed to directly evaluate the labrum and articular surfaces. Cam and pincer lesions were corrected if present.^13,14 All patients then underwent labral repair or debridement, as indicated, using previously published standard techniques.^15,17 In the setting of clinically painful iliopsoas snapping reproducible on physical examination, fractional lengthening of the psoas tendon was performed. Capsular repair was performed at the discretion of the operating surgeon, being more commonly used in young patients performing high-demand activities, patients with dysplastic radiographic features, and patients with hip or generalized laxity resulting in easy translation of the femoral head under traction. Capsular repair was performed using a standard, previously published technique at 40° of hip flexion with the interportal capsulotomy closed in a medial to lateral fashion.^11,12

Statistical Analysis

Patient comorbidities, characteristics, and radiographic measurements and their associated standard deviations and percentages of the population were reported for descriptive statistical purposes. Time to event was calculated as the date of event or last follow-up date minus the date of hip pain onset. Kaplan-Meier analysis was used to determine the rate of failure and OA development. Kaplan-Meier analyses were then subanalyzed by treatment modality and sex using a Wilcoxon test. Data were censored by OA event. Wilcoxon rank-sum tests were used to compare ordinal variables such as preoperative and postoperative Tönnis scores. P values <.05 were considered significant. All analyses were conducted in Microsoft Excel (Version 16.48) and IBM SPSS (Version 26; IBM Corp).

Results

A total of 957 patients (650 female; 307 male, 1114 total hips, mean age, 28.03 ± 8.9 years) were included in this study, with a mean follow-up of 12.5 ± 4.7 years. Patient characteristics are shown in Table 2, and radiographic findings are displayed in Tables 3 and 4.

Table 2

Hip Characteristics^a

	Surgical Group (n = 132)	Nonsurgical Group (n = 982)	P Value
Age at onset of pain, y	28.2 ± 7.9 (12.5-41.0)	28.1 ± 9.0 (6.5-39.07)	.9
Sex
Male	47 (35.6)	303 (30.9)	.27
Female	85 (64.4)	679 (69.1)
Laterality
Left	57 (43.2)	463 (47.1)	.39
Right	75 (56.8)	519 (52.9)
Follow-up time, y	10.6 ± 4.0 (5.2-23.4)	12.79 ± 4.7 (5.0-23.33)	.12

Values are presented as mean ± SD (range) or n (% of cohort).

Table 3

Radiographic Findings^a

	Surgical Group (n = 132)	Nonsurgical Group (n = 982)
Initial Tönnis grade
0	43 (32.6)	350 (35.6)
1	86 (65.2)	570 (58.0)
2	3 (2.3)	56 (5.7)
3	0	6 (0.6)
Measurements
Tönnis angle, deg	2.4 ± 5.6 (–16.1 to 18.4)	4.2 ± 6.6 (–16 to 32)
Alpha angle, deg	63.9 ± 13.6 (31.6 to 97.8)	61.9 ± 14.5 (28.9 to 99.6)
LCEA angle, deg	33.7 ± 5.4 (20.6 to 45.2)	32.6 ± 7.2 (4.2 to 60.6)
Positive signs
Crossover sign	112 (84.8)	757 (77.1)
Ischial spine sign	87 (65.9)	556 (56.6)
Acetabular profunda	78 (59.1)	606 (61.7)
Acetabular protrusion	0	5 (0.5)
Posterior wall sign	86 (65.2)	581 (59.2)

Values are presented as mean ± SD (range) or n (% of cohort). LCEA, lateral center-edge angle.

Table 4

Initial and Final Follow-up Tönnis Grades^a

Initial Grades				Follow-up Grades
Tönnis Grade	Surgical	Nonsurgical	P Value	Tönnis Grade	Surgical	Nonsurgical	P Value
0	43 (32.6)	350 (35.6)	.588	0	27 (20.5)	209 (21.3)	.866
1	86 (65.2)	570 (58.0)	.318	1	81 (61.4)	507 (51.6)	.153
2	3 (2.3)	56 (5.7)	.107	2	16 (12.1)	215 (21.9)	.014
3	0	6 (0.6)	.369	3	8 (6.1)	51 (5.2)	.661

Values are presented as n (% of cohort).

The surgical cohort consisted of 132 hips with a mean age of 28.2 ± 7.9 years. There were 10 patients who underwent bilateral procedures; hence, the final cohort included 47 male hips (35.6%) and 85 female hips (64.4%) with a mean follow-up of 10.6 ± 4.0 years. A total of 43 hips (32.6%) were initially graded with a preoperative Tönnis grade of 0; 86 (65.2%) grade 1; 3 (2.3%) grade 2; and 0 hips grade 3 (Table 3).

The nonsurgical cohort consisted of 835 patients with a mean age of 28.1 ± 9.0 years. This included 303 male (30.9%) and 679 female (69.1%) hips with a mean follow-up of 12.79 ± 4.7 years. In this group, 350 hips (35.6%) were initially graded with a Tönnis grade of 0 at the initial time of evaluation; 570 (58.0%) grade 1; 56 (5.7%) grade 2; and 6 hips (0.6%) grade 3 (Table 3).

At the time of inclusion, the mean LCEA was 33.7°± 5.4° in the operative group and 32.6°± 7.2° in the nonoperative group (P = .09) (Table 3). The Tönnis angles were 2.4°± 5.6° and 4.2°± 6.6°, respectively (P < .01), and the alpha angles were 63.9°± 13.6° and 61.9°± 14.5°, respectively (P = .13).

Rate of Hip OA

Of the 1114 FAI hips analyzed, 878 (78.8%) were diagnosed with OA at the final follow-up. Severe OA (Tönnis grades 2 and 3) was found in 290 (26%) hips. Of hips with OA, 112 (10.1%) were subject to conversion surgery to THA. The mean survival time to severe OA after FAI diagnosis was 12.73 ± 4.7 years.

At the final follow-up, the rate of OA progression was 26.5% (n = 35) in the operative group and 35.2% (n = 346) in the nonoperative cohort (P < .01).

Survival Based on Treatment

Kaplan-Meier survival curves were used to compare time-dependent survival of surgically versus nonsurgically treated hips (Appendix Figure S1, available in the online version of this article). Failure occurred in 103 nonoperatively treated hips (10.5%) and 9 hips (6.8%) treated with HA (P = .19). For the patients who underwent HA, survival free from revision was 100% at 5 years after surgery, 100% at 10 years, and 97% at 15 years. Nonoperatively treated patients had survival rates of 100%, 99%, and 98% at 5, 10, and 15 years, respectively (P = .69). The combined survival rates were 100%, 99.2%, and 96.3% at 5, 10, and 15 years, respectively. In the univariate Cox proportional hazards model for treatment modality, there was no significant difference in the risk of failure between the operatively and nonoperatively treated groups (risk ratio, 0.86; 95% CI, 0.41-1.8; P = .69).

Risk Factors for Hip OA and Failure

Because of differences in treatment type (operative vs nonoperative) and preoperative OA status (Tönnis grade 0 vs Tönnis grade ≥1), Kaplan-Meier analysis was conducted to assess survival by these characteristics in the overall group (Appendix Figures S1 and S2, available online) along with intergroup differences in survival within each group (surgical and nonsurgical groups).

In the group overall, there was no difference in survival by treatment type (operative, 93.2%; nonoperative, 89.5%; P = .69) (Appendix Figure S1, available online), but patients who showed no signs of OA at initial evaluation had a significantly better survival rate than patients with Tönnis grade ≥1 (Tönnis grade 99.3%; Tönnis grade ≥1, 93.2%; P < .01) (Appendix Figure S2, available online). In the subgroup analysis, the initial arthritis grade (Tönnis grade 0, 7%; Tönnis grade ≥1, 6.8%; P = .01) was not significant for survival at the final follow-up in the surgical cohort. Conversely, in the nonoperatively managed group, arthritis grade at the time of diagnosis (Tönnis grade 0, 4.6%; Tönnis grade ≥1, 13.6%; P < .01) was significant for survival within the group.

In the nonsurgical group, the presence of preoperative OA conferred a 6-fold increase in the odds of failure over nonarthritic joints (odds ratio, 6; 95% CI, 4.1-9.2; P < .001) (Figure 2). A multivariate Cox proportional hazards model was used to evaluate the interaction between surgery and presence of preoperative OA. Treatment modality did not significantly affect the failure rate (hazard ratio [HR], 1.1; 95% CI, 0.5-2.2; P = .93) (Figure 3). Patients with preoperative evidence of OA were 4 times more likely to experience failure (HR, 4; 95% CI, 2.9-5.4; P < .01) in the overall cohort. Male hips were 2.4 times more likely to fail than female hips (HR, 2.4; 95% CI, 1.6-3.5; P < .01), and the presence of a cam morphology was associated with an increased risk of 3.5 for failure (HR, 3.5; 95% CI, 1.5-8; P < .01) (Appendix Figure S3, available online). Otherwise, there was no significant change in the risk of failure in the overall group based on laterality (HR, 1.1; 95% CI, 0.8-1.6; P = .8), alpha angle (HR, 1; 95% CI, 1-1.1; P = .25), Tönnis angle (HR, 1; 95% CI, 0.9-1.1; P = .16), LCEA (HR, 1; 95% CI, 0.9-1; P = .1), presence of a posterior wall sign (HR, 0.8; 95% CI, 0.5-1.2; P = .26), a crossover sign (HR, 0.7; 95% CI, 0.4-1.2; P = .2), an ischial spine sign (HR, 1.5; 95% CI, 0.9-2.3; P = .1), an acetabular profunda (HR, 0.7; 95% CI, 0.5-1.1; P = .14), or an os acetabuli (HR, 1.3; 95% CI, 0.8-2.2; P = .29). Kaplan-Meier survival curves for surgical and nonsurgical patients were also constructed by initial Tönnis grade as noted in Appendix Figure S4 (available online). In both groups, joints that showed signs of arthrosis at the time of initial diagnosis were associated with significantly worse survivorship when compared with initially nonarthritic joints (HR, 1.4; 95% CI, 1.1-1.7; P < .001). Hips that progressed in Tönnis grade had a significantly higher rate of failure than hips with no change in Tönnis grade (HR, 1.7; 95% CI, 1.4-2.2; P < .01).

Of note, female hips showed a significantly better survival than male hips (P < .0001) (Figure S2).

In the overall cohort, the risk of failure increased with initial Tönnis grade. Furthermore, risk of failure was increased per year of increased patient age at the time of initial evaluation (HR, 1.1; 95% CI, 1-1.1; P < .01).

Subgroup Analysis Surgical Cohort

A total of 132 hips were treated with HA. In these patients, resection of a cam lesion of the femoral neck was the most frequently carried out procedure (n = 124; 93.94%), followed by a labral repair (n = 120), pincer resection (n = 107), labral debridement (n = 79), and capsular closure (n = 60). In 60 hips (45.45%), a capsular repair was performed at the end of the procedure.

Post Hoc Power Analysis

A post hoc power analysis was performed to determine the sample size through use of a 2-sided hypothesis test at an alpha level of .05, a power of 0.8, and a sample proportion of 9:1 in the matched cohorts. With 103 hip failures observed in the nonsurgical group, there was 80% power to detect hazard ratios of at least 1.75, 1.77, and 2.01 for risk factors with prevalence rates of 50%, 60%, and 80%, respectively.

Discussion

The purposes of this study were to (1) report clinical outcomes of arthroscopically treated FAI syndrome with a minimum 5-year follow-up and compare the results to a cohort with FAI treated nonsurgically and (2) determine the influence of HA on the onset and progression of hip OA in patients diagnosed with FAI. The main finding of our present study is that arthroscopic treatment of FAI may delay the onset and progression of OA in comparison with nonsurgical treatment. While operatively and nonoperatively managed patients demonstrated similar Tönnis grades at the time of study inclusion, 12% of operative patients demonstrated Tönnis grade 2 changes at the final follow-up compared with 22% in the nonoperatively managed cohort. This finding suggests a potential preventive effect of arthroscopic treatment over nonoperative therapy in terms of OA progression. Furthermore, the conversion to THA at a mean follow-up of 13 years was 7% in patients who underwent HA compared with 11% in nonoperatively managed patients, indicating a potential preventive effect of HA; however, this was not statistically significant at the time of the final follow-up (P = .19). While HA for FAI has been previously established to be safe and efficacious in relieving hip symptoms, our findings are clinically relevant in that they suggest that early operative intervention for FAI may alter the natural history of FAI and slow the progression of degenerative changes and conversion to arthroplasty.

FAI is characterized by an abnormal hip morphology and is recognized as an important cause of hip pain, contributing to early degeneration of the hip joint in young adults.^{23,26,33,37,42,54} The radiographic findings associated with FAI are well defined.¹⁶ Multiple studies have reported the prevalence of radiographic structural deformity in asymptomatic individuals.^20,29,43 The underlying pathology is likely caused by an anatomic predisposition in combination with a distinct activity level and repetitive eliciting movement of the hip joint.^5,19,23,78 Because of increased stresses being placed on the joint, FAI is considered a risk factor for the development of degenerative joint disease and the resulting need for THA, while morphological specifications of the joint can be quantified by radiographic studies, allowing for investigation of association with progressive OA.^{21,41,48,63,66,72,76} Initial treatment focuses on nonoperative measures, which include activity modification and physical therapy and can be followed by surgical intervention, if symptoms remain.² Favorable intermediate results of open or arthroscopic techniques have been reported in previous studies.^24,28,55 However, there has been a paucity of evidence regarding long-term clinical outcomes and failure rates of FAI treatment in the literature. The current study aims to provide guidance regarding expected outcomes by presenting a population-based analysis of patients with FAI who underwent arthroscopic surgical treatment or nonsurgical therapy.

One of the main goals of every joint preservation surgery, besides reduction or elimination of clinical and biomechanical symptoms, is to prevent or delay the need for THA. For this reason, conversion to THA is a generally accepted definition of failure, which has been used in many other previous studies investigating hip preservation procedures.^{6,24,58,70,78} Conversion to THA after HA has been reported at wide-ranging rates of 4% to 34%, with varying times of follow-up strongly influencing the reported rates.^58,61,65,67 Increased patient age and higher Tönnis grade at onset of pain are typically associated with an elevated rate of OA (18% for patients >40 years, 23% for >50 years, and 25% for >60 years) and conversion to THA.^{6,30,39,68,69} Patients in our study group averaged 28 years at the time of index surgery and had a 7% conversion rate at the time of the final follow-up. The low conversion rate might be partially attributed to the low mean age of our patient group and constitutes a promising result, especially in consideration of the long follow-up time frame. Factors associated with conversion to THA in our study were increased patient age, male sex, early signs of OA, and the presence of a cam lesion. Of note, despite our relatively young cohort, the median age of patients who underwent conversion to THA was 41 years at the time of their primary HA and 50 years at the time of their conversion to THA, suggesting that not all chronologically young patients may be good candidates for HA and that not all patients have alterable natural history. This agrees with results of other studies reporting that the indication for hip preservation surgery in patients >40 years of age with signs of OA is highly individual and should be decided carefully.^{10,24,25,58,71}

In the present study, index surgery was performed at a relatively young patient age, likely leading to a strong preventive effect of the procedure in terms of onset and progression of OA. The rate of Tönnis grade 3 OA was 6% in the HA group, which is low compared with other studies.^8,37,38 Remarkably, the Tönnis grade 3 OA rate was only 6% in the non-HA group at the time of follow-up. The lack of a significant difference in the development of high-grade OA between the groups may be attributable to the young age of patients at the time of inclusion and a natural history that plays out over decades of follow-up. Certainly, patients with substantial hip dysplasia from childhood often do not experience considerable degeneration and undergo conversion to hip arthritis until their 40s and 50s. This is highlighted by the fact that the mean age at follow-up was 37 years, which is relatively young for the development of severe OA, even in the presence of substantial FAI.

In terms of risk factors for failure after HA during the follow-up period evaluated, Haviv and O’Donnell³⁴ reported their findings after arthroscopic treatment of FAI in 564 hips with OA stages between Tönnis grades 1 and 3. They reported that up to 50% of patients treated with arthroscopy had to undergo THA at a mean of 1.5 years after index surgery.³⁴ Risk factors considered to be responsible for poor clinical outcomes of HA described in this study were elevated patient age and advanced OA at the time of the index surgery (Tönnis grade 3), in agreement with our results.⁵⁶ We would therefore expect the rate of failure to increase with progression of age. These factors associated with failure of HA treatment are not limited to arthroscopic treatment only but are relevant for other joint-preserving procedures of the hip, including femoral and acetabular osteotomies.^4,49 This study provides baseline data for hip OA progression and failure after nonsurgical and arthroscopic treatment in young patients with hip pain and will allow for future comparison with patients who undergo these treatment modalities.

Limitations

Our study has several important limitations. First is the retrospective nature of the study. While our study is the first of its kind to compare the natural history of operative and nonoperative management of FAI at long-term follow-up, it must be acknowledged that the understanding of FAI has increased since its first description in the literature and that we do not, to date, have prospective or randomized evidence for this recently recognized diagnosis and associated interventions. Of note, the prospective manner in which the REP follows patients through their care on a populational level does substantially add to the granularity and completeness of the data presented. Further, we do not know precisely why some patients elected nonsurgical treatment, so there is a possibility of selection bias influencing the results. Patients electing nonsurgical treatment may have been more averse to surgery, and this could depress the rate of conversion to THA as well. Second, we included patients with mild or borderline acetabular dysplasia in the present study, which is known to increase the risk of OA and therefore might be a confounder leading to an elevated OA rate than expected in a nondysplastic FAI cohort. Additionally, the included surgical patients were deemed to be arthroscopic candidates without periacetabular osteotomy, thus comprising a general, nonbiased population of patients undergoing HA. A further limitation is the unavailability of patient-reported outcomes, so differences in symptoms and disability cannot be evaluated. Finally, larger sample sizes and extended follow-up as these patients reach their 50s, 60s, and beyond will provide valuable information of the natural history of postarthroscopy FAI. Patients in the present study had a mean age of 40.6 years at the final follow-up, which might still be too young to see more frequent progression to high-grade OA. This constellation might explain why a preventive effect of HA for the progression to midgrade OA was present, but none for high-grade OA or the conversion to THA. Despite these limitations, we believe our findings will prove helpful in counseling young patients with FAI and will provide a reference to set expectations of surgical and nonsurgical treatment of the disorder.

Conclusion

At a mean follow-up of nearly 13 years, 7% of patients in the surgical group experienced progression to THA, compared with 11% of the nonoperative control group. While most of the operative group showed little to no OA at the final follow-up, moderate OA (Tönnis grade 2) was present in 12% of the cohort compared with 22% of nonsurgical patients. Increased age at diagnosis, male sex, presence of a cam morphology, and presence of initial arthritic joint changes were found to be risk factors for failure. The results of this study demonstrated evidence for a preventive effect of HA on the development and progression of OA in young patients with FAI at mid- to long-term follow-up.

Supplemental Material

sj-pdf-1-ajs-10.1177_03635465231188114 – Supplemental material for Progression of Osteoarthritis at Long-term Follow-up in Patients Treated for Symptomatic Femoroacetabular Impingement With Hip Arthroscopy Compared With Nonsurgically Treated Patients

Supplemental material, sj-pdf-1-ajs-10.1177_03635465231188114 for Progression of Osteoarthritis at Long-term Follow-up in Patients Treated for Symptomatic Femoroacetabular Impingement With Hip Arthroscopy Compared With Nonsurgically Treated Patients by Martin Husen, Devin P. Leland, Heath P. Melugin, Keshav Poudel, Mario Hevesi, Bruce A. Levy and Aaron J. Krych in The American Journal of Sports Medicine

Footnotes

Submitted November 1, 2022; accepted May 25, 2023.

One or more of the authors has declared the following potential conflict of interest or source of funding: M.H. was funded by Deutsche Forschungsgemeinschaft (DFG; German Research Foundation)–Projektnummer 466023693. B.A.L. has received consulting fees and royalties from Arthrex Inc. A.J.K. has received research support from Aesculap/B.Braun, Arthrex Inc, Ceterix, Arthritis Foundation, and Histogenics; consulting fees from Arthrex, JRF Ortho, Vericel, and Responsive Arthroscopy; royalties from Arthrex and Responsive Arthroscopy; honoraria from Joint Restoration Foundation, Vericel Corporation, and Musculoskeletal Transplant Foundation; a grant from DJO; and personal fees from Gemini Mountain Medical and Smith & Nephew. The authors acknowledge support from the Foderaro-Quattrone Musculoskeletal-Orthopaedic Surgery Research Innovation Fund. This study was partially funded by the National Institute of Arthritis and Musculoskeletal and Skin Diseases for the Musculoskeletal Research Training Program (T32AR56950). AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.

ORCID iDs

Martin Husen

Aaron J. Krych

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