Association of 5-Year Hip Arthroscopy Outcomes with Hip Morphology and Cartilage Status at Time of Surgery: A National Registry Study With HAGOS Outcomes in 281 Patients With Femoroacetabular Impingement Syndrome

Abstract

Background:

The effects of specific bony hip morphologies, cam and dysplasia, and cartilage damage on mid- and long-term (≥5 years) patient-reported outcomes (PROs) are understudied.

Purpose:

To investigate if changes in PROs from preoperatively to 5 years after hip arthroscopy are associated with preoperative bony hip morphology and cartilage status in patients with femoroacetabular impingement syndrome.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

Patients were identified in the Danish Hip Arthroscopy Registry. Hip and groin function was assessed from preoperatively to 5 years postoperatively with the Copenhagen Hip and Groin Outcome Score (HAGOS) Activities of Daily Living (ADL) and Sports and Recreation (Sport) subscales. Morphology was defined using the anterior alpha angle (AA) and lateral center-edge angle (LCEA) as follows: mild to moderate cam (55°≤ AA < 78°), severe cam (AA ≥ 78°), pincer (LCEA > 39°), and borderline dysplasia (20°≤ LCEA < 25°). Joint space width (JSW) was defined as slightly reduced (3.1 mm ≤ JSW ≤ 4 mm) or severely reduced (2.1 mm ≤ JSW ≤ 3 mm). Acetabular cartilage status was defined by modified Beck grades 0 to 4 and femoral head cartilage status by International Cartilage Regeneration & Joint Preservation Society grades 0 to 4. Acetabular and femoral cartilage injury areas were categorized as <1, 1 to 2, or >2 cm². Multiple regression analyses assessed adjusted associations between hip morphology and cartilage injuries with improvement in HAGOS-ADL and HAGOS-Sport.

Results:

The study included 281 patients (age, 35 ± 10 years; 52.3% female). No cam and mild-to-moderate cam were associated with greater improvement in HAGOS-ADL (16 points [P = .002] and 7 points [P = .038], respectively) compared with severe cam. Normal JSW was associated with greater improvement in HAGOS-ADL (21 points; P = .026) compared with severely reduced JSW. Femoral head cartilage injury area <1 cm² was associated with greater improvements in HAGOS-ADL (17 points; P = .03) and HAGOS-Sport (21 points; P = .035) compared with femoral cartilage injury area >2 cm².

Conclusion:

Patients having no-to-moderate cam morphology, normal JSW, or femoral head cartilage injury area <1 cm² had greater improvement in PROs 5 years after hip arthroscopy compared with patients having severe cam morphology, severely reduced JSW, or femoral cartilage injury area >2 cm².

Keywords

hip arthroscopy FAIS patient-reported outcome hip morphology cartilage injury

One of the most common causes of intra-articular hip-related pain is femoroacetabular impingement syndrome (FAIS).²⁷ FAIS is defined as a motion-related dysfunction in the hip, causing a collision between the femoral head-neck junction and the anterior rim of the acetabulum as identified in radiological findings, such as cam or pincer morphology.¹¹

Surgical correction of bony hip morphology, most commonly performed arthroscopically, followed by rehabilitation, is widely used to treat FAIS.⁸ FAIS can cause damage to the intra-articular cartilage and labrum, driven by hip morphology such as cam and dysplasia.¹⁰ More specifically, Ishøi et al¹⁴ found 2 to 4 times greater odds for cartilage damage in the acetabulum in patients with mild to severe cam morphology than in those with normal cam morphology. In contrast, no association was found for pincer morphology.¹⁰

Previous studies suggest that the degree of intra-articular cartilage injury may have a short- to mid-term effect on changes in functional level in patients with FAIS before and after hip arthroscopy.^14,23 Furthermore, longitudinal studies indicate that patients with severe cam morphology are more likely to develop osteoarthritis than patients without cam morphology.^1,14 However, clear and lasting improvements in patient-reported outcomes (PROs) 5 years after hip arthroscopy have been documented for parameters such as activities of daily living, sports, quality of life (QoL), and pain.^9,16,19 Despite such improvement in PROs, the majority of patients do not reach the level of healthy controls in ADL and sports function by 1 year after surgery.^16,31

A systematic review¹⁹ from 2020 evaluated mid- to long-term PROs in patients undergoing hip arthroscopy. This review showed that osteoarthritis and older age were the most common factors associated with no improvement in PROs 5 to 20 years after hip arthroscopy.¹⁹ However, only 2 of 13 included studies used validated and recommended PROs, such as the Copenhagen Hip and Groin Outcome Score (HAGOS) or the International Hip Outcome Tool (iHOT).¹³

Bony morphology, such as cam or pincer morphology, and cartilage damage on the acetabulum or femoral head appear to be risk factors and negatively affect the outcome of postoperative functional level in patients with FAIS over a shorter follow-up time (<2 years).^18,24 Thus, further studies are needed to examine the consequences of morphology and cartilage injuries on hip and groin function measured with recommended PROs including longer follow-up times (>2 years).

In this study, we aimed to investigate if changes in patients’ functional levels (HAGOS Activities of Daily Living [ADL] and HAGOS Sports and Recreation [Sport]) from preoperatively to 5 years after hip arthroscopy were associated with preoperative bony hip morphology and/or cartilage damage in patients with FAIS.

Methods

Study Design

This registry-based cohort study investigated the association between the change in self-reported functional level from preoperatively to 5 years after arthroscopy with bony hip morphology, anterior alpha angle (AA), lateral center-edge angle (LCEA), joint space width (JSW), and hip joint cartilage damage in patients with FAIS. Self-reported hip and groin function was measured with HAGOS. All data were obtained from the Danish Hip Arthroscopy Registry (DHAR).²⁰ The reporting adheres to STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) guidelines.³³ We registered the study with the Danish Data Protection Agency of the Capital Region (ID P-2020-227). The study did not require ethics approval, as the data used were extracted from a registry.

Study Participants

Participants were identified in DHAR,²⁰ which was established in 2012 and since then has collected hip arthroscopy data from 14 hospitals in Denmark. Patients who undergo hip arthroscopy are invited to complete PROs preoperatively and again postoperatively after 1, 2, 5, and 10 years. This study identified all patients in the registry who had fulfilled PROs both before surgery and 5 years after hip arthroscopy. The inclusion criteria were patients between the ages of 15 and 50 years with signs of FAIS that included at least 1 of the following radiological changes: cam deformity (AA > 55°), pincer deformity (LCEA > 39°), and/or borderline hip dysplasia (20° < LCEA < 25°). Exclusion criteria were as follows: severely reduced JSW (<2.1 mm), previous surgery in the same hip joint regardless of procedure, previous hip pathology or injury such as ligamentum teres rupture, Legg-Calvé-Perthes disease, slipped capital femoral epiphysis, hip dislocation, femoral neck fracture, or avascular necrosis. Patients were also excluded if they had hip dysplasia (LCEA < 20°) and any rheumatologic diseases involving the hip joint, including synovial chondromatosis.

Outcomes

Self-Reported Hip and Groin Function

We used the HAGOS to measure the changes in patients from preoperatively to 5 years after hip arthroscopy. The HAGOS is a validated and recommended¹³ self-reported questionnaire with 37 items which was developed for physically active young to middle-aged adults with longstanding hip and/or groin pain. It is divided into 6 subscales: Pain, Symptoms, ADL, Sport, Physical Activity, and QoL. Each item is answered on a 5-point scale from 0 to 4, and each subscale has a possible score from 0 to 100, with 0 being extreme symptoms and 100 indicating no symptoms.³⁰

Predictor Variables

The predictor variables were selected based on previous studies showing that bony hip morphology and cartilage damage may affect the functional level in patients with FAIS up to 5 years after hip arthroscopy.^2,3,20-25,28

Hip Morphology

Hip morphology, reported by the operating surgeon, was obtained with plain radiographs and included AA and LCEA.²⁰ The AA was used to measure the presence of cam morphology and was obtained, as recommended by the Warwick Agreement,¹¹ as either a cross-table lateral or a Dunn or frog-leg lateral. The AA was categorized as normal (AA < 55°), mild to moderate cam deformity (55°≤ AA < 78°), and severe cam deformity (AA ≥ 78°).^11,14 LCEA was used to measure the presence of pincer morphology and borderline dysplasia on a weightbearing anteroposterior pelvic view and was categorized as borderline dysplasia (20°≤ LCEA < 25°), normal (25°≤ LCEA ≤ 39°), and pincer deformity (LCEA > 39°).^2,11,12,14

Cartilage Status Radiological Cartilage Status

JSW was measured on plain weightbearing radiographs at the lateral end of the sourcil.²⁰ JSW was divided into 3 categories: normal (JSW > 4 mm), slightly reduced (3.1 mm ≤ JSW ≤ 4 mm), and severely reduced (2.1 mm ≤ JSW ≤ 3 mm), in line with previous studies.^14,20

Perioperative Cartilage Status

The cartilage status was divided into injuries of the femoral head and the acetabulum and was assessed during hip arthroscopy by the operating surgeon. The cartilage status on the femoral head was measured using the International Cartilage Regeneration & Joint Preservation Society³² (ICRS) classification: normal cartilage (grade 0), near-normal cartilage (grade 1), abnormal cartilage (grade 2), partial loss of cartilage (grade 3), or exposed bone (grade 4). The acetabular cartilage status was assessed according to the modified Beck classification⁴: normal cartilage (grade 0), fibrillation (grade 1), wave sign (grade 2), gap between the acetabular bone and cartilage (grade 3), or exposed bone (grade 4). For the statistical analysis, the ICRS and Beck classifications were dichotomized into none to minimal cartilage injury (grade 0 or 1) and moderate to severe cartilage injury (grades 2-4), in line with previous studies.^14,21,22,29 In addition, the cartilage injury area of the femoral head and the acetabulum were measured individually. Each injury area was then divided into 3 categories: <1 cm², 1 to 2 cm², and >2 cm².

Sample Size

As this study was a registry study, the sample size was determined by the number of eligible patients in the DHAR. Sample size calculation was made to ensure that we could detect a potential association between PRO and the predictive variables. A sample of 153 patients was needed to detect a medium effect size of the association between bony hip morphology and cartilage damage and improvements in HAGOS-ADL and HAGOS-Sport subscales, including a statistical significance level of .05 with a power of 0.8.

Statistical Analysis

Continuous patient characteristics and outcome measures were presented as mean with standard deviation, and categorical data were presented as number of events with percentage. The comparison between preoperative and 5-year follow-up for all PROs was performed using the paired t test, with effect sizes calculated from the t test using the Cohen d formula: t/√N. A descriptive analysis was performed to explore how many patients achieved the 95% reference intervals (RIs) for all HAGOS subscales, based on the values achieved by healthy control hips from the study by Thorborg et al.³¹ In addition, the percentage of patients who achieved the Patient Acceptable Symptom State (PASS) for the HAGOS subscales was calculated, with cutoff PASS scores from Ishøi et al.¹⁵ A linear mixed model was used to observe the changes in HAGOS-ADL and HAGOS-Sport subscale items between preoperative and 1-, 2-, and 5-year follow-up data. Missing data from patients during the 1- and 2-year follow-ups were assumed to be missing at random.

A multiple linear regression analysis was performed to assess the association between radiological and perioperative findings and changes in all HAGOS subscale scores. Assumptions for conducting multiple linear regression analyses were satisfied, including no indication of multicollinearity between independent variables. The crude and adjusted β coefficients were estimated for each potential variable. The adjusted β coefficients in each variable were made for all other variables, including age and sex. Possible variables for the change in PRO were AA (classified into 3 categories), in which severe cam morphology was selected as the reference group; LCEA (classified into 3 categories), in which pincer morphology was set as the reference group; and JSW (classified into 3 categories), in which severely reduced JSW was selected as the reference group. For the ICRS and Beck classifications (classified into 2 categories), grades 2 to 4 were selected as the reference group, and >2-cm² cartilage injury area in both the acetabulum and femoral head (classified into 3 size categories) was set as the reference group. The statistical analyses were performed in SPSS (Version 26; IBM Corp) with the significance level set at P < .05.

Results

Data from 281 patients operated on for FAIS from the DHAR between August 2014 and May 2015 could be included for the descriptive analysis. The mean age at the time of the surgery was 35.5 ± 10.1 years, and 52.3% of patients were female. Of the included 281 patients, 58 were excluded from the analysis for changes from preoperatively to 1, 2, and 5 years postoperatively because of missing HAGOS outcomes at the 1- and 2-year follow-ups (Figure 1). A total of 47 patients could not be included in the multiple regression analysis because they had ≥1 missing value on AA, LCEA, and cartilage status; therefore, the final analysis included 234 patients (Figure 1). A detailed overview of patient characteristics, radiological data, operative data, and preoperative PRO scores is shown in Table 1.

Figure 1.

Flowchart of patient inclusion in the study. AA, alpha angle; HAGOS, Copenhagen Hip and Groin Outcome Score; LCEA, lateral center-edge angle.

Table 1

Descriptive, Radiographic, Operative, and Preoperative Self-Reported Hip and Groin Outcome Data on Included Patients (N = 281)^a

Characteristic	Value
Age at surgery, y	35.53 ± 10.1
Female sex	147 (52.3)
Radiological entities (n = 234)
Pure cam morphology	185 (79.1)
Pure pincer morphology	5 (2.1)
Mixed (cam and pincer morphology)	22 (9.4)
Cam morphology and borderline dysplasia	22 (9.4)
Radiological data
AA, deg (n = 233)	69.82 ± 12.2
Normal (AA < 55°)	34 (14.6)
Mild to moderate cam (55°≤ AA < 78°)	138 (59.2)
Severe cam (AA ≥ 78°)	61 (26.2)
LCEA, deg (n = 233)	31.18 ± 5.2
Normal (25°≤ LCEA ≤ 39°)	185 (79.4)
Borderline dysplasia (20°≤ LCEA < 25°)	27 (11.6)
Pincer (LCEA > 39°)	21 (9.0)
JSW, mm (n = 281)	3.63 ± 0.6
Normal (JSW > 4 mm)	186 (66.2)
Slightly reduced (3.1 mm ≤ JSW ≤ 4 mm)	87 (31.0)
Severely reduced (2.1 mm ≤ JSW ≤ 3 mm)	8 (2.8)
Operative data
ICRS classification (n = 255)
Grades 0-1	223 (87.5)
Grades 2-4	32 (12.5)
Cartilage injury area, femoral head, cm² (n = 255)	1.19 ± 0.52
<1	221 (86.7)
1-2	19 (7.5)
>2	15 (5.9)
Beck classification (n = 255)
Grades 0 and 1	26 (10.2)
Grades 2-4	229 (89.8)
Cartilage injury area, acetabulum, cm² (n = 255)	1.84 ± 0.64
<1	75 (29.4)
1-2	145 (56.9)
>2	35 (13.7)
Preoperative PRO scores (n = 281)
HAGOS subscales (0-100)
Pain	55.1 ± 19.4
Symptoms	52.5 ± 17.4
ADL	57.3 ± 23,2
Sport	40.4 ± 23.4
PA	22.9 ± 24.4
QoL	32.6 ± 16.4
HSAS (0-8)	2.8 ± 2.1
EQ-5D (0-1)	0.7 ± 0.1

Data are reported as mean ± SD or n (%). AA, alpha angle; ADL, Activities of Daily Living; EQ-5D, EuroQol-5 Dimensions; HAGOS, Copenhagen Hip and Groin Outcome Score; HSAS, Hip Sports Activity Scale; ICRS, International Cartilage Regeneration & Joint Preservation Society; JSW, joint space width; LCEA lateral center-edge angle; PA, Physical Activity; PRO, patient-reported outcome; QoL, Quality of Life; Sport, Sports and Recreation.

Pre- to Postoperative Changes in Hip and Groin Function

Overall, pre- to postoperative changes in self-reported hip and groin function showed improvements for both HAGOS-ADL and HAGOS-Sport. Improvements were found in all PROs from presurgery to 1, 2, and 5 years after surgery; however, improvements in all PROs from baseline to 1 year postsurgery remained stable at 2 and 5 years postoperatively (Table 2 and Figure 2).

Table 2

Self-Reported PROs Before and 1, 2, and 5 Years After Surgery^a

PRO	Before Surgery (n = 281)	1 Y After Surgery (n = 223)	2 Y After Surgery (n = 223)	5 Y After Surgery (n = 281)	MD (95% CI), Before to 5 Y After Surgery (n = 281)	Effect Size^b	P
HAGOS (0-100)
Pain	55.1 ± 19.3	75 ± 21.2	74.4 ± 21.6	74.4 ± 22.4	19.2 (16.8-21.7)	0.91	<.001
Symptoms	52.5 ± 17.4	69.5 ± 20.1	69.2 ± 20.5	68.1 ± 21.3	15.6 (13.3-17.9)	0.78	<.001
ADL	57.3 ± 23.2	77.6 ± 21.9	77.6 ± 22.7	76.4 ± 23.5	19.1 (16.3-21.9)	0.79	<.001
Sport	40.4 ± 23.4	63 ± 27.9	63.9 ± 27.7	62.9 ± 29.5	22.5 (19.1-25.9)	0.77	<.001
PA	22.9 ± 24.4	47.3 ± 33.4	50.6 ± 33.1	53.5 ± 35.1	30.6 (26.1-35.2)	0.79	<.001
QoL	32.6 ± 16.4	56.6 ± 26.1	58.3 ± 25.5	59.8 ± 26.3	27.3 (24.1-30.4)	1.01	<.001
HSAS (0-8)	2.8 ± 2.1	3.1 ± 1.8	3.4 ± 1.8	3.2 ± 1.7	0.4 (0.1-0.7)	0.18	.002
EQ-5D (0-1)	0.7 ± 0.1	0.8 ± 0.2	0.8 ± 0.2	0.8 ± 0.2	0.1 (0.1-0.13)	0.59	<.001

Data are reported as mean ± SD unless otherwise indicated. Boldface P values indicate a statistically significant difference between groups (P < .05). ADL, Activities of Daily Living; EQ-5D, EuroQol-5 Dimensions; HAGOS, Copenhagen Hip and Groin Outcome Score; HSAS, Hip Sports Activity Scale; MD, mean difference; PA, Physical Activity; PRO, patient-reported outcome; QoL, Quality of Life; Sport, Sports and Recreation.

Cohen d.

Figure 2.

Copenhagen Hip and Groin Outcome Score (HAGOS) Activities of Daily Living (ADL) and Sports and Recreation (Sport) subscale scores (mean with error bars indicating 95% CI) before surgery (Pre) and at 1, 2, and 5 years after surgery.

Furthermore, the percentages of patients who reached the 95% RI for HAGOS-ADL and HAGOS-Sport were 37% (95% RI, 94.75-100) and 28% (95% RI, 87.5-100), respectively. In addition, 49% and 57% of patients reached the PASS for HAGOS-ADL and HAGOS-Sport (Table 3).

Table 3

Patients Who Were Within the 95% RIs of Healthy Matched Controls or Who Achieved PASS on HAGOS Subscales at 5 Years After Surgery^a

HAGOS Subscale	Before Surgery (n = 281)	1 Y After Surgery (n = 223)	2 Y After Surgery (n = 223)	5 Y After Surgery (n = 281)
HAGOS-Pain (95% RI, 90-100)	55.1 ± 19.3	75 ± 21.2	74.4 ± 21.6	74.4 ± 22.4
>90	13 (5)	71 (32)	76 (34)	97 (35)
<90	268 (95)	152 (68)	147 (66)	184 (65)
Achieved PASS (cutoff, >68.75)	—	151 (68)	144 (65)	177 (63)
HAGOS-Symptoms (95% RI, 78.57-100)	52.5 ± 17.4	69.5 ± 20.1	69.2 ± 20.5	68.1 ± 21.3
>78.57	25 (9)	99 (44)	98 (44)	118 (42)
<78.57	256 (91)	124 (56)	125 (56)	163 (58)
Achieved PASS (cutoff, >62.5)	—	148 (66)	145 (65)	180 (64)
HAGOS-ADL (95% RI, 94.75-100)	57.3 ± 23.2	77.6 ± 21.9	77.6 ± 22.7	76.4 ± 23.5
>94.75	20 (7)	66 (30)	83 (37)	104 (37)
<94.75	261 (93)	157 (70)	140 (63)	177 (63)
Achieved PASS (cutoff, >82.5)	—	126 (57)	118 (53)	138 (49)
HAGOS-Sport (95% RI, 87.5-100)	40.4 ± 23.4	63 ± 27.9	63.9 ± 27.7	62.9 ± 29.5
>87.5	10 (4)	55 (25)	56 (25)	79 (28)
<87.5	271 (96)	168 (75)	167 (75)	202 (72)
Achieved PASS (cutoff, >60.94)	—	132 (59)	137 (61)	161 (57)
HAGOS-PA (95% RI, 75-100)	22.9 ± 24.4	47.3 ± 33.4	50.6 ± 33.1	53.5 ± 35.1
>75	16 (6)	73 (33)	78 (35)	121 (43)
<75	265 (94)	150 (67)	145 (65)	160 (57)
Achieved PASS (cutoff, >43.75)	—	122 (55)	126 (57)	171 (61)
HAGOS-QoL (95% RI, 85-100)	32.6 ± 16.4	56.6 ± 26.1	58.3 ± 25.5	59.8 ± 26.3
>85	2 (1)	44 (20)	48 (22)	72 (26)
<85	279 (99)	179 (80)	175 (78)	209 (74)
Achieved PASS (cutoff, >42.5)	—	147 (66)	153 (69)	202 (72)

Data are reported as mean ± SD or n (%). 95% RIs are from Thorborg et al³¹; PASS cutoffs are from Ishøi et al.¹⁵ Dashes indicate areas not applicable. ADL, Activities of Daily Living; HAGOS, Copenhagen Hip and Groin Outcome Score; PA, Physical Activity; PASS, Patient Acceptable Symptom State; QoL, Quality of Life; RI, reference interval; Sport, Sports and Recreation.

Primary Outcomes

Association Between Improvements in HAGOS-ADL and Bony Hip Morphology and Cartilage Status

Greater improvements in HAGOS-ADL from preoperatively to 5 years postsurgery were associated with no cam morphology (15.9 [95% CI, 5.9-25.8], P = .002) and mild to moderate cam morphology (6.9 [95% CI, 0.4-13.5], P = .038), compared with severe cam morphology. The same applied for normal JSW (20.7 [95% CI, 2.5-39.0], P = .026) compared with severely reduced JSW. For perioperative cartilage injuries, femoral head cartilage injury area <1 cm² was associated with greater improvements in HAGOS-ADL (17.3 [95% CI, 1.7-33.0], P = .03) compared with femoral head cartilage injury area >2 cm². No associations were found for LCEA, ICRS classification, Beck classification, and acetabulum cartilage injury area on improvements in HAGOS-ADL (Table 4).

Table 4

Multiple Linear Regression Results of Association Between Radiological and Operative Data and HAGOS-ADL^a

Variable	Crude β (95%CI)	SE	P	Adjusted β (95% CI)^b	SE	P
Morphology
AA
Normal (AA < 55°)	12.4 (3.9 to 21.6)	4.5	.005	15.9 (5.9 to 25.8)	5.1	.002
Mild to moderate cam (55°≤ AA < 78°)	5.7 (−0.6 to 12.0)	3.2	.073	6.9 (0.4 to 13.5)	3.3	.038
Severe cam (AA ≥ 78°)	Reference			Reference
LCEA
Normal (25°≤ LCEA ≤ 39°)	1.9 (−6.6 to 10.3)	4.3	.659	2.0 (−6.8 to 10.8)	4.5	.652
Borderline dysplasia (20°≤ LCEA < 25°)	−6.4 (−17.5 to 4.8)	5.7	.262	−4.0 (−15.9 to 8.0)	6.2	.515
Pincer (LCEA > 39°)	Reference			Reference
Cartilage status
JSW
Normal (JSW > 4 mm)	22.4 (5.5 to 39.4)	8.6	.010	20.7 (2.5 to 39.0)	9.3	.026
Slightly reduced (3.1 mm ≤ JSW ≤ 4 mm)	19.9 (2.5 to 37.2)	8.8	.025	18.1 (−0.3 to 36.6)	9.4	.054
Severely reduced (2.1 mm ≤ JSW ≤ 3 mm)	Reference			Reference
Cartilage injury status
ICRS classification
Grades 0 and 1	1.7 (−5.3 to 8.7)	3.6	.628	−9.8 (−22.8 to 3.2)	6.6	.138
Grades 2-4	Reference			Reference
Cartilage injury area, femoral head
<1 cm²	8.4 (−4.2 to 21.0)	6.4	.189	17.3 (1.7 to 33.0)	7.9	.03
1-2 cm²	−4.4 (−20.8 to 11.9)	8.3	.593	−0.5 (−17.1 to 16.0)	8.4	.949
>2 cm²	Reference			Reference
Beck classification
Grades 0-1	7.7 (−2.0 to 17.5)	5.0	.119	8.1 (−2.1 to 18.2)	5.1	.119
Grades 2 and 4	Reference			Reference
Cartilage injury area, acetabulum
<1 cm²	4.7 (−5.1 to 14.5)	5.0	.345	0.3 (−10.4 to 11.0)	5.4	.961
1-2 cm²	2.6 (−6.4 to 11.6)	4.6	.564	−0.2 (−9.8 to 9.5)	4.9	.975
>2 cm²	Reference			Reference

Boldface P values indicate statistical significance (P < .05). AA, alpha angle; ADL, Activities of Daily Living; HAGOS, Copenhagen Hip and Groin Outcome Score; ICRS, International Cartilage Regeneration & Joint Preservation Society; JSW, joint space width; LCEA, lateral center-edge angle.

Adjusted for all other variables including age and sex.

Association Between Improvements in HAGOS-Sport and Bony Hip Morphology and Cartilage Status

Greater improvements in HAGOS-Sport were associated with a femoral head cartilage injury area <1 cm² (21.3 [95% CI, 1.6-40.8], P = .035) than with a femoral head cartilage injury area >2 cm². No associations were found for AA, LCEA, JSW, ICRS classification, Beck classification, or acetabulum cartilage injury area in improvements in HAGOS-Sport (Table 5).

Table 5

Multiple Linear Regression Results of Association Between Radiological and Operative Data and HAGOS-Sport^a

Variable	Crude β (95% CI)	SE	P	Adjusted β (95% CI)^b	SE	P
Morphology
AA
Normal (AA < 55°)	7.7 (−3.2 to 18.5)	5.5	.164	10.5 (−2.0 to 22.9)	6.3	.10
Mild to moderate cam (55°≤ AA < 78°)	6.5 (−1.2 to 14.2)	3.9	.096	6.1 (−2.1 to 14.4)	4.2	.143
Severe cam (AA ≥ 78°)	Reference			Reference
LCEA
Normal (25°≤ LCEA ≤ 39°)	3.6 (−6.7 to 13.8)	5.2	.495	0.7 (−10.3 to 11.7)	5.6	.897
Borderline dysplasia (20°≤ LCEA < 25°)	−6.6 (−20.2 to 6.9)	6.9	.34	−6.4 (−21.4 to 8.6)	7.6	.40
Pincer (LCEA > 39°)	Reference			Reference
Cartilage status
JSW
Normal (JSW > 4 mm)	27.2 (6.6 to 47.8)	10.5	.010	19.9 (−2.9 to 42.9)	11.6	.086
Slightly reduced (3.1 mm ≤ JSW ≤ 4 mm)	21 (−0.1 to 42)	10.7	.051	15.0 (−8.2 to 38.1)	11.7	.204
Severely reduced (2.1 mm ≤ JSW ≤ 3 mm)	Reference			Reference
Cartilage injury status
ICRS classification
Grades 0-1	4.3 (−4.2 to 12.9)	4.3	.316	−7.0 (−23.3 to 9.3)	8.3	.397
Grades 2 and 4	Reference			Reference
Cartilage injury area, femoral head
<1 cm²	15.9 (0.6 to 31.2)	7.8	.042	21.3 (1.6 to 40.8)	9.9	.035
1-2 cm²	−0.2 (−20 to 19.7)	10	.98	4.8 (−16 to 25.6)	10.6	.651
>2 cm²	Reference			Reference
Beck classification
Grades 0-1	7.8 (−4.1 to 19.6)	6	.199	9.9 (−2.9 to 22.6)	6.5	.128
Grades 2 and 4	Reference			Reference
Cartilage injury area, acetabulum
<1 cm²	11.5 (−0.4 to 23.4)	6	.058	4.4 (−9.1 to 17.9)	6.8	.520
1-2 cm²	6.5 (−4.4 to 17.5)	5.6	.242	1.4 (−10.8 to 13.5)	6.2	.821
>2 cm²	Reference			Reference

Boldface P value indicates statistical significance (P < .05). AA, alpha angle; HAGOS, Copenhagen Hip and Groin Outcome Score; ICRS, International Cartilage Regeneration & Joint Preservation Society; JSW, joint space width; LCEA, lateral center-edge angle; Sport, Sports and Recreation.

Adjusted for all other variables including age and sex.

Discussion

We found that patients with FAIS with either no cam or mild-to-moderate cam morphology showed a greater improvement in self-reported activities of daily living than those with severe cam morphology. In addition, normal JSW and a cartilage injury area <1 cm² on the femoral head were associated with greater improvements than severely reduced JSW and femoral head cartilage injury area >2 cm². Furthermore, we found greater HAGOS-Sport improvement when the cartilage injury area was <1 cm² on the femoral head compared with a cartilage injury area >2 cm².

Association Between Improved HAGOS-ADL and HAGOS-Sport and Morphological Findings

Patients with radiographs showing no cam and those with mild-to-moderate cam morphology before surgery improved 16 points and 7 points, respectively, in HAGOS-ADL compared with patients with severe cam morphology at 5 years of follow-up. These findings align with a scoping review¹⁸ that found that the larger the cam deformity, the less improvement in PROs after hip arthroscopy. These findings are interesting because a study from Casartelli et al⁷ showed that severe cam, although reported as a mean AA of 73°, is also associated with worse outcome in patients undergoing nonsurgical treatment. Thus, it seems that severe cam may be related to a poorer prognosis, irrespective of whether patients receive surgery or not. One explanation related to poorer prognosis might be, as Ishøi et al¹⁴ from our group has found, that patients with mild-to-moderate cam were at greater risk of having cartilage damage than patients with no cam lesion.

We did not find any associations between pincer morphology and change in HAGOS-ADL or HAGOS-Sport, which is in line with previous studies^2,14,17 reporting that pincer morphology did not affect self-reported hip and groin function or result in increased cartilage damage. The present study found no association between borderline dysplasia and self-reported hip and groin function. However, a scoping review¹⁸ showed that borderline dysplasia could result in poorer improvement in PROs after surgery. In addition, Ishøi et al¹⁴ found an increased risk (OR, 3.08) of having cartilage injury on the femoral head (ICRS grades 3 and 4) in patients with borderline dysplasia. The missing association in the present study is most likely related to a small number of patients with borderline dysplasia (11%).

Association Between Improved HAGOS-ADL and HAGOS-Sport and Cartilage Status

We found that patients with JSW >4 mm improved by 21 points more than those with JSW ≤3 mm on the HAGOS-ADL from preoperatively to 5 years after surgery. These findings align with results from a systematic review²⁹ in which normal JSW was associated with better Hip Outcome Score–ADL values 2 years after hip arthroscopy. At the 5-year follow-up, Domb et al⁹ found an association between body mass index, age, and lateral JSW and Non-Arthritic Hip Score and modified Harris Hip Score. Both PROs are, however, not recommended for evaluation after hip arthroscopy, and these findings should be investigated for replication using better-suited PROs for FAIS, such as HAGOS or iHOT.

In the present study, we found that having a cartilage damage area <1 cm² on the femoral head was associated with preoperative to 5-year postoperative improvement in HAGOS-ADL and HAGOS-Sport (17.3 points and 21.3 points, respectively), compared with a cartilage damage area >2 cm². To our knowledge, there are currently no studies that have investigated if the size of cartilage damage in patients with FAIS is associated with improved self-reported functional level. These findings indicate that the extent of cartilage damage on the femoral head may suggest who will benefit most from hip arthroscopy. However, this should be interpreted with caution, as the prevalence of severe cartilage injury area on the femoral head (>2 cm²) was only 6% in the present study. In addition, the prevalence of severe cartilage injuries on the femoral head measured with ICRS (grades 2-4) was lower (13%) when compared with the acetabulum (90%; Beck classification grades 2-4). A previous study⁵ showed similar distribution of cartilage damage on the femoral head and in the acetabulum (24% vs 76%). Although the frequency of cartilage damage on the femoral head was relatively low, this might indicate a decreased likelihood of resuming previous activity levels. Furthermore, some patients with cam morphology might also have borderline dysplasia, increasing the risk of cartilage injury on the femoral head⁶ and to general intra-articular hip health after hip arthroscopy.

Changes in PROs From Preoperatively to 5 Years Postoperatively

We found improvements on all HAGOS subscales from before surgery to 1 year after surgery. The improvements achieved in PROs at 1 year remained stable 2 and 5 years after surgery. These findings align with studies from Kierkegaard et al,¹⁶Öhlin et al,²³ and Domb et al,⁹ indicating that improvements seem to remain stable 5 years after surgery for FAIS.

Despite improvements across PROs, only 26% to 43% of the patients achieved the 95% RI level of healthy controls on the HAGOS subscales (Table 3). These findings are comparable to those of Thorborg et al,³¹ who found that only 20% to 38% of patients reached a score within the 95% RI at 1 year of follow-up. We also found that the PRO scores from 1 to 5 years postoperatively were stable, with no further improvement or deterioration occurring. This trend applied to all subscales except for the HAGOS–Physical Activity, which measures participation in preferred physical activities, as the percentage of patients who achieved the 95% RI increased from 33% to 43% from 1 to 5 years postoperatively.

Results from the present study showed that the PASS was achieved in 49% of patients on the HAGOS-ADL and 72% of patients on the HAGOS-QoL at 5 years after hip surgery. These findings are somewhat higher than the numbers from Ishøi et al,¹⁵ in which 46% of patients achieved the PASS when asked a single PASS question (“Taking into account your hip and groin function and pain and how it affects your daily life including your ability to participate in sports and social activities, do you consider that your current state is acceptable if it remained like that for the rest of your life?”) at 1 to 2 years after surgery. The reason for the differences in PASS in the present study may be because PASS was derived as a cutoff score from the HAGOS subscales as opposed to the single question that was used by Ishøi et al.¹⁵ PASS rates seemed to be fairly consistent from 1 to 5 years after surgery.

Methodological Considerations

The strength of the present study was the use of data from a nationwide hip arthroscopy registry, which increases the study’s external validity and conclusion about the population outside of this study. In addition, the DHAR contains data from 14 hospitals with several surgeons included and variations in age, sex, activity levels, and radiological findings, all of which contribute to an increase in the external validity, as selection bias is minimized compared with a single-center study and specific patient characteristics.

However, the study also has some limitations. Multiple surgeons could have different surgical techniques and may have affected the PROs differently. First, the study did not include data on cam and labrum status postoperatively, as the main focus was hip morphology and cartilage injury status preoperatively, as well as their associations with PROs. However, cam and labrum status postoperatively may influence PROs, and further studies are needed to investigate this. Second, the present study included a small portion of patients from DHAR who answered HAGOS both preoperatively and at 5 years postsurgery, which may result in selection bias. However, as the main aim of the present study was to investigate the association between hip morphology and cartilage damage and the HAGOS, missing responses are less of an issue. We have no reason to believe that this type of association is linked to whether a patient chose to complete the questionnaire or not. As only a fraction of the patients registered in DHAR had completed HAGOS at all time points, one has to be cautious when trying to generalize from 1-, 2-, and 5-year results. The results align with previous reports on HAGOS at 1, 2, and 5 years.^9,16,23 Furthermore, Poulsen et al²⁶ only found differences in age and sex and no major difference in HAGOS before surgery in the DHAR, between responders and nonresponders, which suggests that missing responses in DHAR are likely missing at random.

Conclusion

Patients having no-to-moderate cam morphology, normal JSW, or femoral head cartilage injury area <1 cm² had greater improvements in PROs 5 years after hip arthroscopy than patients with severe cam morphology, severely reduced JSW, or femoral cartilage injury area >2 cm².

Footnotes

Acknowledgements

The authors thank the Steering Committee of the DHAR for allowing access to registry data.

Final revision submitted September 3, 2023; accepted September 7, 2023.

The authors declared that they have no conflicts of interest in the authorship and publication of this contribution. 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.

Ethical approval was not sought for the present study.

References

Agricola

Heijboer

Bierma-Zeinstra

, et al. Cam impingement causes osteoarthritis of the hip: a nationwide prospective cohort study (CHECK). Ann Rheum Dis. 2013;72(6):918-923.

Agricola

Heijboer

Roze

, et al. Pincer deformity does not lead to osteoarthritis of the hip whereas acetabular dysplasia does: acetabular coverage and development of osteoarthritis in a nationwide prospective cohort study (CHECK). Osteoarthritis Cartilage. 2013;21(10):1514-1521.

Agricola

Waarsing

Arden

, et al. Cam impingement of the hip: a risk factor for hip osteoarthritis. Nat Rev Rheumatol. 2013;9(10):630-634.

Beck

Kalhor

Leunig

Ganz

Hip morphology influences the pattern of damage to the acetabular cartilage: femoroacetabular impingement as a cause of early osteoarthritis of the hip. J Bone Jt Surg Br. 2005;87(7):1012-1018.

Bhatia

Nowak

Briggs

Patterson

Philippon

MJ.

Outerbridge grade IV cartilage lesions in the hip identified at arthroscopy. Arthroscopy. 2016;32(5):814-819.

Bolia

Briggs

Locks

, et al. Prevalence of high-grade cartilage defects in patients with borderline dysplasia with femoroacetabular impingement: a comparative cohort study. Arthroscopy. 2018;34(8):2347-2352.

Casartelli

Bizzini

Maffiuletti

, et al. Exercise therapy for the management of femoroacetabular impingement syndrome: preliminary results of clinical responsiveness. Arthritis Care Res (Hoboken). 2019;71(8):1074-1083.

de Sa

Holmich

Phillips

, et al. Athletic groin pain: a systematic review of surgical diagnoses, investigations and treatment. Br J Sports Med. 2016;50(19):1181-1186.

Domb

Chen

, et al. Predictors of clinical outcomes after hip arthroscopy: 5-year follow-up analysis of 1038 patients. Am J Sports Med. 2021;49(1):112-120.

10.

Ganz

Parvizi

Beck

, et al. Femoroacetabular impingement: a cause for osteoarthritis of the hip. Clin Orthop Relat Res. 2003;417:112-120.

11.

Griffin

Dickenson

O’Donnell

, et al. The Warwick Agreement on femoroacetabular impingement syndrome (FAI syndrome): an international consensus statement. Br J Sports Med. 2016;50(19):1169-1176.

12.

Griffin

Dickenson

Wall

PDH

, et al. Hip arthroscopy versus best conservative care for the treatment of femoroacetabular impingement syndrome (UK FASHIoN): a multicentre randomised controlled trial. Lancet. 2018;391(10136):2225-2235.

13.

Impellizzeri

Jones

Griffin

, et al. Patient-reported outcome measures for hip-related pain: a review of the available evidence and a consensus statement from the International Hip-related Pain Research Network, Zurich 2018. Br J Sports Med. 2020;54(14):848-857.

14.

Ishøi

Thorborg

Kraemer

, et al. Demographic and radiographic factors associated with intra-articular hip cartilage injury: a cross-sectional study of 1511 hip arthroscopy procedures. Am J Sports Med. 2019;47(11):2617-2625.

15.

Ishøi

Thorborg

Ørum

, et al. How many patients achieve an acceptable symptom state after hip arthroscopy for femoroacetabular impingement syndrome? A cross-sectional study including PASS cutoff values for the HAGOS and iHOT-33. Orthop J Sports Med. 2021;9(4):2325967121995267.

16.

Kierkegaard

Mechlenburg

Dalgas

Lund

Five-year follow-up after hip arthroscopic surgery in the Horsens-Aarhus Femoroacetabular Impingement (HAFAI) cohort. Orthop J Sports Med. 2022;10(3):23259671221075653.

17.

Kopec

Qian

Cibere

, et al. Relationship between hip morphology and hip-related patient-reported outcomes in young and middle-aged individuals: a population-based study. Arthritis Care Res (Hoboken). 2019;71(9):1202-1208.

18.

Kuroda

Saito

Çınar

Norrish

Khanduja

Patient-related risk factors associated with less favourable outcomes following hip arthroscopy. Bone Joint J. 2020;102(7):822-831.

19.

Kyin

Maldonado

Shapira

Lall

Domb

BG.

Mid- to long-term outcomes of hip arthroscopy: a systematic review. Arthroscopy. 2021;37(3):1011-1025.

20.

Lund

Mygind-Klavsen

Gronbech Nielsen

, et al. Danish Hip Arthroscopy Registry (DHAR): the outcome of patients with femoroacetabular impingement (FAI). J Hip Preserv Surg. 2017;4(2):170-177.

21.

Lund

Nielsen

Lind

Cartilage status in FAI patients—results from the Danish Hip Arthroscopy Registry (DHAR). Sicot J. 2017;3:44.

22.

Mygind-Klavsen

Lund

Nielsen

, et al. Danish Hip Arthroscopy Registry: predictors of outcome in patients with femoroacetabular impingement (FAI). Knee Surg Sports Traumatol Arthrosc. 2019;27(10):3110-3120.

23.

Öhlin

Ahlden

Lindman

, et al. Good 5-year outcomes after arthroscopic treatment for femoroacetabular impingement syndrome. Knee Surg Sports Traumatol Arthrosc. 2020;28(4):1311-1316.

24.

Öhlin

Sansone

Ayeni

, et al. Predictors of outcome at 2-year follow-up after arthroscopic treatment of femoro-acetabular impingement. J Hip Preserv Surg. 2017;4(3):224-230.

25.

Olach

Gerhard

Giesinger

Lampert

Erhardt

JB.

Clinical and radiological outcome at mean follow-up of 11 years after hip arthroscopy. Arch Orthop Trauma Surg. 2019;139(1):1-6.

26.

Poulsen

Lund

Roos

EM.

The Danish Hip Arthroscopy Registry: registration completeness and patient characteristics between responders and non-responders. Clin Epidemiol. 2020;12:825-833.

27.

Reiman

Agricola

Kemp

, et al. Consensus recommendations on the classification, definition and diagnostic criteria of hip-related pain in young and middle-aged active adults from the International Hip-related Pain Research Network, Zurich 2018. Br J Sports Med. 2020;54(11):631-641.

28.

Roling

Mathijssen

Bloem

RM.

Incidence of symptomatic femoroacetabular impingement in the general population: a prospective registration study. J Hip Preserv Surg. 2016;3(3):203-207.

29.

Sogbein

Shah

Kay

, et al. Predictors of outcomes after hip arthroscopic surgery for femoroacetabular impingement: a systematic review. Orthop J Sports Med. 2019;7(6):2325967119848982.

30.

Thorborg

Holmich

Christensen

Petersen

Roos

EM.

The Copenhagen Hip and Groin Outcome Score (HAGOS): development and validation according to the COSMIN checklist. Br J Sports Med. 2011;45(6):478-491.

31.

Thorborg

Kraemer

Madsen

Holmich

Patient-reported outcomes within the first year after hip arthroscopy and rehabilitation for femoroacetabular impingement and/or labral injury: the difference between getting better and getting back to normal. Am J Sports Med. 2018;46(11):2607-2614.

32.

van den Borne

Raijmakers

Vanlauwe

, et al. International Cartilage Repair Society (ICRS) and Oswestry macroscopic cartilage evaluation scores validated for use in autologous chondrocyte implantation (ACI) and microfracture. Osteoarthritis Cartilage. 2007;15(12):1397-1402.

33.

von Elm

Altman

Egger

, et al. The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement: guidelines for reporting observational studies. PLoS Med. 2007;4(10):e296.