The association between specific sports activities and sport performance following hip arthroscopy for femoroacetabular impingement syndrome: A secondary analysis of a cross-sectional cohort study including 184 athletes.

The main purpose of this secondary analysis was to compare the proportion of athletes with moderate-to-extreme difficulties in eight specific sport activities in athletes with optimal versus impaired sport performance after a hip arthroscopy for femoroacetabular impingement syndrome. Subjects were identified in a nationwide registry and invited to answer a return to sport and performance questionnaire, and the Copenhagen Hip and Groin Outcome Score Sport subscale investigating difficulties in eight specific sports activities (HAGOS sport items) as; none, mild, moderate, severe or extreme. Subjects were divided into two groups based on sport performance (optimal or impaired). The proportion of athletes with none-to-mild versus moderate-to-extreme difficulties in the eight specific sport activities was compared between groups. The association between difficulties in sport activities and sport performance were investigated using logistic regression analysis. One hundred and eighty-four athletes (31 athletes with optimal and 153 athletes with impaired sport performance) were included at a mean follow-up of 33.1 ± 16.3 months. Up to six athletes (<20%) with optimal sport performance had moderate-to-extreme difficulties in sport activities. Contrary, 43-108 athletes (28.1-70.6%) with impaired performance had moderate-to-extreme difficulties in sport activities. Furthermore, moderate-to-extreme difficulties in HAGOS sport items: 'running as fast as you can' and 'kicking, skating etc.' increased the odds (14.7 and 6.1 times, respectively) of having impaired sport performance. Many athletes with impaired sport performance reported moderate-to-extreme difficulties in sport activities, specifically moderate-to-extreme difficulties in 'running as fast as you can' and 'kicking, skating etc.' were associated with patients having impaired sport performance.

INTRODUCTION

During the last decade, hip arthroscopy has been widely adopted as a treatment for femoroacetabular impingement syndrome (FAIS) [1, 2] with several studies yielding beneficial improvements from pre-to-post surgery in hip function and pain [3, 4]. However, despite such improvements, only a small proportion may regain normal self-reported sport and physical function when compared with healthy individuals [5]. Although, most athletes seem to return to sport [6], impairments in self-reported sport function may affect the ability to return to optimal sport performance following hip arthroscopy for FAIS [7, 8]. Recent studies from Scandinavia using detailed information on return to sport and performance status, which has not previously been reported [9], have independently shown that ∼20% return to optimal sport performance following hip arthroscopy for FAIS [7, 8]. In a study evaluating 189 athletes between 18 and 30 years old, only 16.9% were engaged in their preinjury sport at preinjury level with optimal performance at a mean follow-up of 33.1 months post-hip arthroscopy for FAIS [8], Furthermore, the ability to return to optimal sport performance seemed to be driven by better post-operative hip and groin function assessed with the ‘Function in Sport and Recreation’ subscale of the Copenhagen Hip and Groin Outcome Score (HAGOS Sport subscale) [8]. However, the score of the HAGOS Sport subscale is calculated based on eight items, each representing a specific sport activity and corresponding answer scored on a 5-point Likert scale (none, mild, moderate, severe or extreme) to assess difficulty in the specific sport activity [10]. Thus, it is still unknown whether difficulties in specific sports activities from the HAGOS Sport subscale are associated with actual sport performance following a hip arthroscopy for FAIS. Thus, this secondary analysis aimed to compare the proportion of athletes with moderate-to-extreme difficulties in eight specific sport activities (HAGOS sport items) in athletes with optimal versus impaired sport performance after a hip arthroscopy for FAIS.

MATERIALS AND METHODS

Study design

This cross-sectional explorative study investigated difficulties in eight specific sport activities, measured using the HAGOS Sport subscale (Table I) [10], between athletes with optimal and impaired sport performance assessed 6 months to 6 years following hip arthroscopy for FAIS. It includes data from a previously published cohort study [8]. Participants were retrospectively recruited between 6 September 2017 and 5 October 2017. The reporting adheres to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) [11]. Approval was obtained from the Danish Ethics Committee of the Capital Region (ID: H-17016762) and the Data Agency of the Capital Region (ID: AHH-2016-053).

Table I.

Copenhagen Hip and Groin Outcome Score (HAGOS), function, sports and recreational subscale [10]

Instruction: The following questions concern your physical function when participating in higher-level activities. Answer every question by ticking the appropriate box. If a question does not pertain to you or you have not experienced it in the past week please make your ‘best guess’ as to which response would be the most accurate. The questions should be answered considering what degree of difficulty you have experienced during the following activities in the past week due to problems with your hip and/or groin.
SP1 Squatting
None	Mild	Moderate	Severe	Extreme
□	□	□	□	□
SP2 Running
None	Mild	Moderate	Severe	Extreme
□	□	□	□	□
SP3 Twisting/pivoting on a weight bearing leg
None	Mild	Moderate	Severe	Extreme
□	□	□	□	□
SP4 Walking on an uneven surface
None	Mild	Moderate	Severe	Extreme
□	□	□	□	□
SP5 Running as fast as you can
None	Mild	Moderate	Severe	Extreme
□	□	□	□	□
SP6 Bringing the leg forcefully forward and/or out to the side, such as in kicking, skating etc.
None	Mild	Moderate	Severe	Extreme
□	□	□	□	□
SP7 Sudden explosive movements that involve quick footwork, such as accelerations, decelerations, change of directions etc.
None	Mild	Moderate	Severe	Extreme
□	□	□	□	□
SP8 Situations where the leg is stretched into an outer position (such as when the leg is placed as far away from the body as possible)
None	Mild	Moderate	Severe	Extreme
□	□	□	□	□

Participants

Three hundred and fifty eligible participants were identified in the Danish Hip Arthroscopy Registry [12] based on the following inclusion and exclusion criteria. Inclusion criteria were: age of 18–30 years at the time of surgery and ≤35 years at the time of follow-up; pre-surgery cam morphology on plain radiograph (Alpha Angle ≥55°) [13]; surgical procedure consisting of at least cam resection and acetabular labral surgery performed during the preceding 6 months to 6 years as these are the two most common FAIS procedures performed in Denmark [14]. Exclusion criteria were: pre-surgery joint space width <3 mm [15]; grade 4 on Becks and/or ICRS cartilage classification identified during surgery [16]; any of the following surgical procedures at any time: extra articular surgery of the hip joint (except capsular closure), microfracture in the hip joint, periacetabular osteotomy and surgery to the ligamentum teres; previous hip arthroscopy in the same hip joint; previous hip pathology such as Perthes’ disease, slipped capital femoral epiphysis, hip dysplasia (lateral center edge angle (Wiberg) <25°) and/or avascular necrosis of the femoral head; any rheumatoid disease in the hip joint such as synovial chondromatosis. Eligible participants were invited to answer a web-based survey delivered using the Research Electronic Data Capture (REDCap) tool (v. 7.1.1, Vanderbilt University) hosted at the Capital Region of Denmark [17]. The survey consisted of (i) a return to sport questionnaire collecting information on preinjury and present sport participation, including type of sport and self-reported performance [8] and (ii) assessment of self-reported hip and groin function using the HAGOS [10, 18]. Subjects were included if they reported participation in sport prior to onset of initial hip and groin pain, an intention to return to preinjury sport at preinjury level following hip arthroscopy, and completed the HAGOS Sport subscale (Table I). Informed consent was provided by the participants by responding to the survey.

Outcome measures

The outcome measures were: (i) the between-group difference in the proportion of athletes with none-to-mild versus moderate-to-extreme difficulties in eight specific sport activities (HAGOS Sport subscale items; Table I) based on sport performance (optimal versus impaired); (ii) the association between difficulties (none-to-mild versus moderate-to-extreme) in HAGOS Sport subscale items and sport performance (optimal versus impaired); (iii) the between-group difference in the proportion of athletes with none-to-mild versus moderate-to-extreme difficulties in HAGOS Sport subscale items based on type of sport (contact, pivoting versus non-contact, pivoting versus non-contact, non-pivoting) and acetabular cartilage status identified during surgery (Beck grade 0–1 versus Beck grade 2 versus Beck grade 3).

Data collection

Difficulties in specific sport activities were assessed using the eight individual items, defined as a question and corresponding answer, from the HAGOS Sport subscale (Table I). From here referred to as: SP1 (‘squatting’); SP2 (‘running’); SP3 (‘twisting/pivoting’); SP4 (‘walking on an uneven surface’); SP5 (‘running as fast as you can’), SP6 (‘kicking, skating etc.’); SP7 (‘explosive movements’); SP8 (‘stretched into an outer hip position’) (Table I) [10]. Each question, representing a specific sport activity, is scored on a 5-point Likert scale ranging from no to extreme hip and groin difficulties (none; mild; moderate; severe; extreme). Difficulties in the specific sport activities were divided into ‘none-to-mild’ or ‘moderate-to-extreme’ based on normative responses from athletes with no hip and pain [19].

The type of sport and self-reported sport performance were collected using a self-report return to sport questionnaire described in detail in Ishoi et al. [8]. In brief, athletes were instructed to indicate if they were engaged in their preinjury sport at preinjury level at the time of follow-up. Athletes who were engaged in their preinjury sport at preinjury level were asked to state their current sport performance and participation as: (i) optimal sports performance including full sports participation, (ii) impaired sports performance but full sports participation and (iii) impaired sports performance including restricted sports participation [20]. Athletes who reported optimal sport performance including full participation were defined as athletes with ‘optimal sport performance’, whereas athletes with impaired performance, restricted participation or athletes not engaged in their preinjury sport at preinjury level were defined as athletes with ‘impaired sport performance’.

Acetabular cartilage status identified during surgery was extracted from the Danish Hip Arthroscopy Registry [12].

Statistical methods

The proportion of athletes with none-to-mild and moderate-to-extreme difficulties in each of the eight specific sport activities (HAGOS Sport subscale items, Table I) were calculated by use of percentages with corresponding 95% confidence interval (95% CI). A chi-square test of homogeneity was used to assess the following outcome measures: (i) differences in the proportion of none-to-mild versus moderate-to-extreme difficulties in each HAGOS Sport subscale item (dependent variable) based on the independent variables of either sport performance (optimal versus impaired), type of sport (contact, pivoting versus non-contact, pivoting versus non-contact, non-pivoting) and acetabular cartilage status (Beck grade 0–1 versus Beck grade 2 versus Beck grade 3). The association between sport performance (optimal versus impaired) and difficulties (none-to-mild versus moderate-to-extreme) in HAGOS Sport subscale items was assessed using a logistic regression with backward selection of variables with sport performance as the dependent variable and difficulties in HAGOS Sport subscale items as independent variables. All statistical analyses were performed in SPSS (v. 23, IBM Corporation, New York, USA) with significance set at P < 0.05.

RESULTS

A total of 184 athletes were included (age at follow-up: 26.8 ± 3.4 years; male: 50%) at a mean follow-up of 33.1 ± 16.3 months (range: 6.3–67.8 months) (Fig. 1). Thirty-one athletes [16.8%; 95% CI (11.8; 22.3)] were classified with optimal sport performance, whereas 153 athletes [83.2%; CI 95% (77.1; 88.1)] were classified with impaired sport performance. A detailed overview of demographic, radiographic and operative findings is provided in Table II. An overview of sports participation is provided in Table III.

Fig. 1.

Flow of participants.

Table II.

Demographic, radiographic and operative data of included athletes

	Included athletes (n = 184)
Demographic data
Follow-up, months (SD), range	33.1 (16.3), 6.3–67.8
Gender, no. males (%)	92 (50.0)
Level of sport
Elite/professional, no. (%)	32 (17.4)
Competitive, no. (%)	75 (40.8)
Recreational, no. (%)	77 (41.8)
Mean age at surgery, years (SD)	23.5 (3.3)
Mean age at follow-up, years (SD)	26.8 (3.4)
Radiographic data
Alpha Angle, ° (SD)	72.8 (10.9)
Lateral center edge angle, ° (SD)	32.2 (4.9)
Joint space width, no. >4.0 mm (%)	154 (83.7)
Operative data
Bilateral operation, no. (%)	23 (12.5)
Becks classification
Normal cartilage, no. (%)	3 (1.6)
Fibrillation, no. (%)	45 (24.5)
Wave sign, no. (%)	78 (42.4)
Cleavage tear between labrum and articular cartilage, no (%)	58 (31.5)
ICRS classification
Normal cartilage, no. (%)	138 (75.0)

Table III.

Number of athletes participating in different sports

Type of sport	n (%)
Non-contact, pivoting (n = 37)
Dancing	12 (32.4)
Gymnastic	11 (29.7)
Badminton	5 (13.5)
Tennis	3 (8.1)
Golf	2 (5.4)
Volleyball	2 (5.4)
Cross-fit	1 (2.7)
Skateboarding	1 (2.7)
Non-contact, non-pivoting (n = 65)
Running	27 (41.5)
Horse riding	12 (18.5)
Fitness/strength training	11 (16.9)
Cycling	5 (7.7)
Athletics	3 (4.6)
Swimming	3 (4.6)
Triathlon	3 (4.6)
Motocross	1 (1.5)
Contact, pivoting (n = 82)
Football (soccer)	48 (58.5)
Handball (team)	19 (23.2)
Basketball	6 (7.3)
Martial art	6 (7.3)
Ice hockey	2 (2.4)
Boxing	1 (1.2)

Athletes with optimal sport performance versus impaired sport performance

The proportion of athletes reporting moderate-to-extreme difficulties in specific sport activities (HAGOS Sport subscale items) was significantly higher in athletes with impaired sport performance compared with athletes with optimal sport performance (28.1–70.6% versus 0–19.4%, P ≤ 0.001) (Table IV). For athletes with impaired sport performance, moderate-to-extreme difficulties in sport activities were most pronounced in the following HAGOS Sport subscale items; SP8 (‘stretched into an outer hip position’) [70.6%; 95% CI (62.9; 77.2)], SP5 (‘running as fast as you can’) [64.1%; 95% CI (56.2; 71.2)], SP7 (‘explosive movements’) [61.1%; 95% CI (52.2; 67.6)], and SP6 (‘kicking, skating etc.’) and SP2 (‘running’) [58.8%; 95% CI (50.6; 66.6)]. An overview of HAGOS scores are provided in Supplementary Table 1.

Table IV.

Proportion of athletes with none-to-mild versus moderate-to-extreme difficulties in specific sport activities (HAGOS sport items) based on sport performance

Sport activities	Optimal sport performance (n = 31a)		Impaired sport performance (n = 153)		Chi-square test of homogeneity
	Difficulties, no. (%)		Difficulties, no. (%)
	Yes	No	Yes	No
SP1 (‘squatting’)	3 (9.7)	28 (90.3)	64 (41.8)	89 (58.2)	P = 0.001
SP2 (‘running’)	2 (6.5)	29 (93.5)	90 (58.8)	63 (41.2)	P < 0.001
SP 3 (‘twisting/pivoting’)	1 (3.3)	29 (96.7)	61 (39.9)	92 (60.1)	P < 0.001
SP4 (‘walking on an uneven surface’)	0 (0)	31 (100)	43 (28.1)	110 (71.9)	P = 0.001
SP5 (‘running as fast as you can’)	2 (6.5)	29 (93.5)	98 (64.1)	55 (35.9)	P < 0.001
SP6 (‘kicking, skating etc.’)	3 (9.7)	28 (90.3)	90 (58.8)	63 (41.2)	P < 0.001
SP7 (‘explosive movements’)	4 (12.9)	27 (87.1)	92 (60.1)	61 (39.9)	P < 0.001
SP8 (‘stretched in an outer hip position’)	6 (19.4)	25 (80.6)	108 (70.6)	45 (29.4)	P < 0.001

aThirty athletes in twisting/pivoting. Difficulties are based on the HAGOS Sport/recreational subscale and dichotomized as ‘Yes’ (moderate-to-extreme) and ‘No’ (none-to-mild).

The association between sport performance and difficulties in HAGOS Sport subscale items were found to be significant (P < 0.001) with adequate goodness of fit (Hosmer and Lemeshow test, χ2 (2) = 0.503, P = 0.0.778). Moderate-to-extreme difficulties in SP5 (‘running as fast as you can fast’) and SP6 (‘kicking, skating etc.’) were significantly associated with impaired sport performance, corresponding to an odds ratio (OR) of 14.7 [95% CI (3.3; 66.3)] and 6.1 [95% CI (1.7; 22.3)], respectively (Supplementary Table 2A–C).

Type of sport

No between-group differences were observed in the proportion of athletes with moderate-to-extreme difficulties in specific sport activities (HAGOS Sport subscale items) (P ≥ 0.148) (Table V). An overview of HAGOS scores are provided in Supplementary Table 3.

Table V.

Proportion of athletes with none-to-mild versus moderate-to-extreme difficulties in specific sport activities (HAGOS sport items) based on type of sport

Sport activities	Non-contact, pivoting sport (n = 37a)		Non-contact, non-pivoting sport (n = 65)		Contact, pivoting sport (n = 82)		Chi-square test of homogeneity
	Difficulties, no. (%)		Difficulties, no. (%)		Difficulties, no. (%)
	Yes	No	Yes	No	Yes	No
SP1 (‘squatting’)	12 (32.4)	25 (67.6)	23 (35.4)	42 (64.6)	32 (39.0)	50 (61.0)	P = 0.769
SP2 (‘running’)	20 (54.1)	17 (45.9)	35 (53.8)	30 (46.2)	37 (45.1)	45 (54.9)	P = 0.495
SP 3 (‘twisting/pivoting’)	11 (30.6)	25 (69.4)	22 (33.8)	43 (66.2)	29 (35.4)	53 (64.6)	P = 0.879
SP4 (‘walking on an uneven surface’)	13 (35.1)	24 (64.9)	12 (18.5)	53 (81.5)	18 (22.0)	64 (78.0)	P = 0.148
SP5 (‘running as fast as you can’)	22 (59.5)	15 (40.5)	36 (55.4)	29 (44.6)	42 (51.2)	40 (48.8)	P = 0.690
SP6 (‘kicking, skating etc.’)	18 (48.6)	19 (51.4)	30 (46.2)	35 (53.8)	45 (54.9)	37 (45.1)	P = 0.557
SP7 (‘explosive movements’)	19 (51.4)	18 (48.6)	31 (47.7)	34 (52.3)	46 (56.1)	36 (43.9)	P = 0.595
SP8 (‘stretched in an outer hip position’)	25 (67.6)	12 (32.4)	37 (56.9)	28 (43.1)	52 (63.4)	30 (36.6)	P = 0.531

aThirty-six athletes in twisting/pivoting. Difficulties are based on the HAGOS Sport/recreational subscale and dichotomized as ‘Yes’ (moderate-to-extreme) and ‘No’ (none-to-mild).

Acetabular cartilage status

No between-group differences were observed the proportion of athletes with moderate-to-extreme difficulties in specific sport activities (HAGOS Sport subscale items) (P ≥ 0.069) (Table VI). An overview of HAGOS scores are provided in Supplementary Table 4.

Table VI.

Proportion of athletes with none-to-mild versus moderate-to-extreme difficulties in specific sport activities (HAGOS sport items) based on acetabular cartilage status

Athletic movement	Beck grade 0–1 (n = 48)b		Beck grade 2 (n = 78)		Beck grade 3 (n = 58a)		Chi-square test of homogeneity
	Difficulties, no. (%)		Difficulties, no. (%)		Difficulties, no. (%)
	Yes	No	Yes	No	Yes	No
SP1 (‘squatting’)	19 (39.6)	29 (60.4)	32 (41.0)	46 (59.0)	16 (27.6)	42 (72.4)	P = 0.237
SP2 (‘running’)	23 (47.9)	25 (52.1)	45 (57.7)	33 (42.3)	24 (41.4)	34 (58.6)	P = 0.161
SP 3 (‘twisting/pivoting’)	22 (45.8)	26 (54.2)	25 (32.1)	53 (67.9)	15 (26.3)	42 (73.7)	P = 0.099
SP4 (‘walking on an uneven surface’)	11 (22.9)	37 (77.1)	24 (30.8)	54 (69.2)	8 (13.8)	50 (86.2)	P = 0.069
SP5 (‘running as fast as you can’)	24 (50.0)	24 (50.0)	48 (61.5)	30 (38.5)	28 (48.3)	30 (51.7)	P = 0.240
SP6 (‘kicking, skating etc.’)	26 (54.2)	22 (45.8)	38 (48.7)	40 (51.3)	29 (50.0)	29 (50.0)	P = 0.834
SP7 (‘explosive movements’)	26 (54.2)	22 (45.8)	42 (53.8)	36 (46.2)	28 (48.3)	30 (51.7)	P = 0.772
SP8 (‘stretched in an outer hip position’)	29 (60.4)	19 (39.6)	50 (64.1)	28 (35.9)	35 (60.3)	23 (39.7)	P = 0.876

aFifty-seven athletes in twisting/pivoting. Difficulties are based on the HAGOS Sport/recreational subscale and dichotomized as ‘Yes’ (moderate-to-extreme) and ‘No’ (none-to-mild).

bThree athletes had Beck grade 0.

DISCUSSION

Optimal sport performance versus impaired sport performance

The main finding of this explorative analysis was that a large proportion of athletes with impaired sports performance had moderate-to-extreme difficulties in the following HAGOS Sport subscale items; SP8 (‘stretched into an outer range hip position’), SP5 (‘running as fast as you can’), SP7 (‘explosive movements’), SP6 (‘kicking, skating etc.’), and SP2 (‘running’), all being high joint load activities. In contrast, difficulties in SP1 (‘squatting’), SP3 (‘twisting/pivoting’) and SP4 (‘walking on an uneven surface’) were reported by a minority of athletes, indicating that these activities may only provide little stress to the joint hip following hip arthroscopy for FAIS, and thus are not important for optimal sport performance. In line with this, Domb et al. [21] observed that athletes who returned to sport were better able to perform high-load sport activities. Furthermore, Naal et al. [22] noted a shift from high-impact sports (soccer, jogging, indoor sports) to lower impact activities (cycling, Nordic walking, fitness/weight training) following open surgery for FAIS, indicating that the hip joint was less able to tolerate high loads.

Moderate-to-extreme difficulties with SP8 (‘stretched into an outer hip position’) were reported by 70.6% of athletes with impaired sport performance. Interestingly, a systematic review reported no differences in isolated passive hip range of motion between patients with FAIS and healthy controls [23], indicating that other factors are responsible for difficulties in SP8 (‘stretched into an outer hip position’). As outer range hip positions are associated with large lever arms, such activities likely result in considerable hip joint moments (force acting across the hip joint) and contact forces in the hip joint [24]. Additionally, a systematic review observed a lower peak hip extension angle during walking in patients with FAIS compared with healthy controls, which may reduce anterior hip joint forces [25]. Collectively, these observations suggest that difficulties in SP8 (‘stretched into an outer hip position’) may be due to inability to tolerate load rather than reduced isolated hip range of motion per se [23, 25, 26].

Moderate-to-extreme difficulties in the high-load HAGOS Sport subscale items; SP2 (‘running’), SP5 (‘running as fast as you can’), SP6 (‘kicking, skating etc.’) and SP7 (‘explosive movements’) were reported by most athletes with impaired sport performance (≥58.8%). These findings are not surprising since large forces are distributed across the hip joint during these activities [24, 27–29]. During running, vertical ground reaction forces easily exceed three times body weight [30] whereas the peak magnitude of the resultant hip joint contact forces (forces measured in the hip joint) can reach 11 times body weight for a running pace of 3.47 m s−1 [24]. As the hip joint contact forces are primarily influenced by the activity of the hip muscles [24], even higher hip joint contact forces are likely to occur during high-speed running due to large increases in hip muscle peak forces with increasing speed [24, 27]. Additionally, explosive activities such as running acceleration are associated with significant increased hip joint work compared with steady state running [28], whereas single-leg landing, an activity often present in various sports, is associated with vertical ground reaction forces up to 5.30 times body weight [29]. The ability of the hip joint to tolerate and attenuate ground reaction forces during high load sport activities are not yet clear in athletes who have had a hip arthroscopy for FAIS [25]. However, 1–2 years following hip arthroscopy for intra-articular hip pathology subjects demonstrate increased hip adduction and knee valgus angle during single-leg squatting [31]. Interestingly, such movement pattern is associated with less hip joint loading [32], indicating a compensatory movement pattern. Supporting this, patients with FAIS show reduced hip joint contact forces during walking indicative of a protective mechanism [26].

Reduced force absorption capacity may be due to degradation of the hip cartilage properties [33]. Thus, FAIS patients with cam morphology undergoing surgery have markedly reduced proteoglycan content in the acetabular cartilage including a 70% reduced compressive stiffness of the cartilage [33]. Such degeneration is likely to shift the load imposed on the hip joint during sport activities to the acetabular subchondral bone, leading to increased bone plate stiffness and further increases in cartilage tensile stresses over time [33, 34]. Impaired hip and lower limb muscle function, often observed in FAIS patients [23], may also contribute to reduced force absorption capacity [35] and low self-reported hip function [36, 37]. However, as muscle force production is a major contributor to hip joint contact forces [24], the ability to produce high muscles forces could mimic an increased ability to tolerate load across the hip joint rather than an effect of muscle strength per se.

The proportion of athletes with moderate-to-extreme difficulties in HAGOS Sport subscale items were not different based on type of sport. In line with this, several reports suggest that athletes in different sports can expect to obtain a similar sporting ability post-hip arthroscopy [38, 39], although positional differences have been observed [40]. In relation to this, Menge et al. [40] noted a lower return to sport rate in offensive linemen compared with other positions in a cohort of elite American Football players. Offensive linemen were characterized by the largest body mass index and all had cartilage injuries; furthermore, they push off forcefully from the line with the hip in flexion, and thus create a large hip extension moment which may cause difficulties/pain in the anterior superior aspect of the acetabulum [40].

The proportion of athletes with moderate-to-extreme difficulties in HAGOS Sport subscale items was not different based on acetabular cartilage status. This is surprising since damaged cartilage may reduce the force absorption capacity of the hip joint [41] leading to increased impact forces acting on the subchondral bone [42]. However, 98.4% of athletes had an acetabular cartilage lesion (≥Becks grade 1), and it could be speculated whether having a cartilage lesion or not is more important for post-surgery sport performance rather than the severity. Furthermore, resection of a cam deformity may alleviate excessive stress on the acetabular cartilage potentially lowering hip pain during specific sport activities for some athletes [43-45].

Clinical relevance

Current rehabilitation strategies following hip arthroscopy for FAIS are based on expert opinions [46, 47] and physical impairments such as information on hip muscle strength and range of motion [48, 49] including biomechanical analyses of low-load activities such as walking [25]. However, information on which factors contribute to optimal sport performance in athletes is uncertain but could further guide rehabilitation and return to sport strategies of athletes with an intention to return to optimal sport performance. The present findings suggest the ability to perform sport activities such as SP5 (‘running as fast as you can’) and SP6 (‘kicking, skating etc.’) without difficulties are important for obtaining optimal sport performance following hip arthroscopy for FAIS. Since these activities are associated with considerable load distributed across the hip joint, focusing on improving intra-articular load bearing capacity as an adjunct to hip muscle strengthening may be an important component in rehabilitation after hip arthroscopy for FAIS.

Methodological considerations and limitations

The present study is not without limitation. A cross-sectional design was used; thus, it remains to be investigated if rehabilitation targeting the specific sport activities with moderate-to-extreme difficulties will result in a higher return to optimal sport performance rate following hip arthroscopy for FAIS. Furthermore, as subjects were identified retrospectively 6.3–67.8 months following hip arthroscopy for FAIS it is possible that some athletes may not have been fully rehabilitated at the time of inclusion. However, the decision to include athletes from 6 months was based on recommendations from high-volume hip arthroscopy centers [46]. Finally, although the HAGOS is recommended as a reliable and valid patient-reported outcome in patients with FAIS [18], the reliability of the specific items is unknown.

CONCLUSION

Following hip arthroscopy for FAIS most athletes with impaired performance have moderate-to-extreme difficulties in HAGOS Sport subscale items such as SP8 (‘stretched into an outer hip position’), SP5 (‘running as fast as you can’), SP7 (‘explosive movements’) SP2 (‘running’) and SP6 (‘kicking, skating etc.’). Furthermore, moderate-to-extreme difficulties in ‘running as fast as you can’ and ‘kicking, skating etc.’ were associated with increased odds of reporting impaired sport performance.

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