pattern of impact of femoroacetabular impingement upon health-related quality of life: the...

Pattern of impact of femoroacetabular impingement upon health-related quality of life: the determinant role of extra-articularfactors

Claudio Diaz-Ledezma • Paul M. Lichstein •

Mitchell Maltenfort • Camilo Restrepo •

Javad Parvizi

Accepted: 22 January 2013

� Springer Science+Business Media Dordrecht 2013

Abstract

Purpose Despite the interest in surgical treatment of

femoroacetabular impingement (FAI), its impact upon

health-related quality of life (HRQoL) has not been

established. The objectives of this study were twofold:

(a) to describe the pattern of impact of FAI on HRQoL and

(b) to assess how articular and extra-articular factors

influence HRQoL in this group of patients.

Methods A total of 108 patients [55 females (50.9 %);

age 36.0 ± 12.4 years] with intraoperatively confirmed

FAI and no evidence of secondary hip osteoarthritis were

studied. The pattern of impact on HRQoL was studied

using SF-36 V.2TM and then contrasted with other medical

conditions employing the SF-36 spydergram. The best

model explaining the influence of ‘‘articular’’ and ‘‘extra-

articular’’ factors over the SF-36 physical and mental

component scores (PCS/MCS) was selected using the

Akaike information criterion.

Results The PCS was 53.2 ± 19.2 and MCS was

68.94 ± 17.15. The SF-36 spydergram depicted an impact

pattern distinguishable from other conditions. A linear

model predicted PCS would increase by 8.9 points in male

patients and 3.7 points per point of University of California

Los Angeles score (p value \0.01; R2 0.29). For MCS,

obesity resulted in a 12.7 point reduction, psychiatric

comorbidity reduced it by 11.1; and a combined reduction

of 19 points (p value \0.01; R2 0.18). Unexpectedly, the

extent of intra-articular disease had no influence on PCS or

MCS.

Conclusions FAI impacts HRQoL with a distinguishable

pattern. In our study, the manner in which HRQoL is

affected by FAI can be explained only by patients’ char-

acteristics unrelated to the extent of intra-articular disease.

Level of evidence Prognostic Level IV.

Keywords Femoroacetabular impingement � Quality of

life � Spydergram

Introduction

Femoroacetabular impingement (FAI) is an alteration in

the hip morphology [1] associated with chondral [2–5] and

labral lesions [6, 7], and is considered one of the most

prevalent causes of hip pain in young adults [7, 8]. More

importantly, it is considered a risk factor for the develop-

ment of end-stage osteoarthritis [9, 10]. FAI is a common

indication for joint preservation surgery [6], directed to

repair labral tears, chondral lesions and to correct the

morphological hip abnormalities through different surgical

approaches [11]. In recent years, and mostly due to relative

success [12], surgical intervention for FAI has been

increasing in popularity and expanded efforts in clinical

and basic research have been invested to investigate the

disorder [13].

There are a number of previous reports in the literature

that describe improvements in physical and functional

outcomes following surgical treatment of FAI [11, 14–16].

Additionally, two previous studies reported an improve-

ment in quality of life for patients receiving surgery for

FAI [17, 18]. However, both used a debatable methodology

for such evaluation. The pattern of influence of FAI, as a

pathologic entity, on overall health-related quality of life

(HRQoL) remains unknown. Therefore, we decided to

C. Diaz-Ledezma � P. M. Lichstein (&) � M. Maltenfort �C. Restrepo � J. Parvizi

Rothman Institute, Philadelphia, PA, USA

e-mail: paul.lichstein@rothmaninstitute.com

123

Qual Life Res

DOI 10.1007/s11136-013-0359-z

conduct a study to determine which FAI factors have the

most influence on HRQoL.

This study was designed with two specific objectives.

First, we aimed to report the pattern of influence of FAI on

HRQoL using a patient-reported and validated instrument:

SF-36 V.2TM. Second, we sought to examine the influence

of: (a) clinical variables not directly related with the dis-

ease (‘‘extra-articular’’ factors) and (b) intraoperatively

confirmed grade of articular disease upon physical and

mental component scores of the SF-36.

Patients and methods

Sample

Using our institutional database, 242 primary hip-preserving

surgical procedures performed by the senior author between

February 2006 and February 2011 due to FAI were identified.

All procedures were performed utilizing a muscle sparing

anterior mini-open approach of the hip [19]. A confidence

level of 95 % and margin of error of 5 % were established to

calculate a representative sample size. The prevalence of

surgically confirmed articular lesions in FAI patients =

86.5 % [20] was chosen as the response distribution, in order

to evaluate the influence of articular pathology upon

HRQoL. A representative sample size of 104 patients was

calculated. Finally, a sample of 108 patients (53 men and 55

women) with a mean age of 36.0 ± 12.4 years (15.5–62.7)

and a mean body mass index of 25.3 ± 4.6 m/kg2

(16.6–40.7) were studied. The sample was a consecutive

cases series, using a complete preoperative SF-36 survey as

inclusion criteria. All patient were diagnosed with FAI in the

context of hip pain, using the criteria of altered alpha angle

([50 degrees in frog lateral hip view; cam FAI) [21] or

presence of focal overcoverage (crossover sign in the AP

pelvis view; pincer FAI) [1], as well as a magnetic resonance

imaging or arthrogram depicting a labral tear and the

pathognomonic damage at the chondrolabral junction [22].

To guarantee that no patients with osteoarthritis were

included, both a joint space width [2 mm [23, 24] and

Tonnis grade 0 or 1 [25] were required. To avoid the inclu-

sion of patients with hip pathology misclassified as FAI [26],

as has occurred in previous studies with developmental

dysplasia of the hip [27] or neglected slipped femoral capital

epiphysis (SCFE) [28, 29], all patients presented a center

edge angle [25�, teardrop-head distance \11 mm and no

radiographic evidence of previous SCFE or Perthes’ disease.

HRQoL evaluation

The SF-36 V.2TM was used to measure HRQoL [30–32].

We elected to utilize the preoperative SF-36 V.2TM to

depict the impact of FAI over HRQoL, assuming that this

period better illustrates FAI as a pathological entity. All

patients completed the questionnaire at the time of their

first visit when they were scheduled for surgery by them-

selves without intervention from clinicians and/or research

personnel. All patients had a complete evaluation. The

scores for physical function (PF), bodily pain (BP), phys-

ical role (PR), vitality (VT), general health (GH), emo-

tional role (ER), social role (SR) and mental health (MH)

were calculated. Each domain is scored from 0 to 100 with

greater values representing increasingly normal function.

The first four domains are considered as related to physical

function and the latter four to mental health [33]. Summary

scores for both physical (PCS) and mental health function

(MCS) were also calculated. To construct a SF-36 ‘‘spy-

dergram’’ [34], the 8 domains of SF-36 V.2TM were used.

The FAI pattern was then mapped in the spydergram for

visual contrast with patterns previously described for other

medical conditions (hip osteoarthritis), as well as with the

pattern of the US general population [32, 33].

Articular and extra-articular factors

The ‘‘articular factors’’ were defined as pre- and intraop-

erative findings related to the hip joint that could have an

impact over the preoperative HRQoL. Among these factors

we included: unilateral/bilateral symptoms, duration of

symptoms (B6 months, 7–12 months and C12 months),

grade of acetabular chondral lesions (none/partial thick-

ness/full thickness), the final treatment performed for the

chondral lesion (mechanical chondroplasty vs microfrac-

ture), type of labral tears (none/intrasubstance tears/

degenerative tears), the final treatment performed for the

labral tears (repair and reinsertion vs partial or total labral

resection), and the presence of pain outside the hip area as

defined by Birrell et al. [35].

The ‘‘extra-articular’’ factors, defined as factors that do

not have a direct relationship with the hip condition, but

could potentially influence the preoperative HRQoL were

also evaluated. These factors serve to differentiate demo-

graphic and psychosocial variation in patients presenting

with symptoms related to FAI. Among these factors, we

included gender, age (using 50 years as a cutoff for ‘‘old’’

[10]), obesity (BMI C 30 kg/m2) [36], worker’s compen-

sation, psychiatric and affective comorbidities and activity

level (using the University of California Los Angeles

(UCLA) activity scale [37]), which evaluates the type and

frequency of activity level with 10 different options.

Worker’s compensation was included in the study because

of its recognized negative effect upon the outcome of

orthopedic surgery procedures [38]. Psychiatric and affec-

tive comorbidities were defined as the presence of mood

disorders that required pharmacological therapy prescribed

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123

by a psychiatrist during the last three years before the

surgery. We decided to include the latter because certain

psychological and psychiatric factors can negatively

influence the results in terms of HRQoL in patients

undergoing hip surgery [39].

Statistical evaluation

Statistical analyses were performed using the statistical

software R (version 2.14, R Foundation for Statistical

Computing, Vienna, Austria). To deal with missing data

(Table 1), multiple imputation was performed using the

MICE (Multiple Imputation by Chained Equations) [40]

add-on package for R (version 2.11; http://www.jstatsoft.

org/v45/i03) which uses a Gibbs sampler to estimate con-

ditional probabilities of missing data; 20 iterations were

used. P-values returned by pooled analysis of MICE results

assume a normal distribution of parameters.

The model was further pruned to eliminate variables not

affecting PCS or MCS by using backward stepwise

regression based on the Akaike information criterion

(AIC) [41].

Results

HRQoL evaluation and comparison

The mean ± SD for the eight domains of the SF-36 V.2TM

and for the two summary scores are presented in Table 2.

Patients with FAI had higher scores for PCS and MCS

when compared with patients with hip arthritis undergoing

hip arthroplasty. However, in most of the SF-36 V.2TM

domains, FAI patients had lower means than the general

US population. The pattern of presentation for FAI was

established and visually compared using the ‘‘spydergram’’

[34] (Fig. 1).

Influence of articular and extra-articular factors

over HRQoL

Workers’ compensation status and UCLA score were found

to be major factors influencing PCS. However, analysis of

the pooled results showed that only gender [no missing

values (0 %); p = 0.027] and UCLA score [14 missing

values (13.0 %); p = 0.006] were statistically significant

factors affecting PCS (Fig. 2). A linear model based on

gender and UCLA scores (no interactions) predicted that

PCS increases 8.9 points in male patients [standard error

(SE) 3.5; p = 0.012] and 3.7 points per point of UCLA

score (SE 0.69; p = 0.001). The overall model fit had a

p value of 0.001 and the adjusted R2 was 0.29.

The same process was performed for MCS, returning an

initial model that emphasized obesity, psychiatric comor-

bidity and labral resection, with a borderline dependence

upon workers’ compensation. Pooled results from multiple

imputation showed a dependence on obesity [one missing

value (0.9 %); p = 0.004] and a borderline dependence on

psychiatric comorbidity [17 missing values (15.7 %);

p = 0.058]. The overall average amount of missing data

was 9 values (8.2 %). Exploration of those model param-

eters suggested obesity and psychiatric comorbidity com-

bined were worse than the sum of their individual effects

and so an interaction term was added to this model. With

this model, obesity reduced MCS by 12.7 points [SE 5.3;

p = 0.018], psychiatric comorbidity reduced it by 11.1

points [SE 4.3; p = 0.013]; and their combination (present

in two cases) by a further 19 points [SE 12.8; p = 0.114].

The p value of the model fit was 0.0001 and the adjusted

R2 value was 0.18.

Discussion

This study demonstrates that FAI generates a distinguish-

able pattern of impact on HRQoL when evaluated with SF-

36 V.2TM. We have demonstrated the crucial importance of

patient demographics and psychosocial characteristics on

the perception of decreased QoL in FAI.

The pattern of impact displayed a profound compromise

in PF, BP and RP that may be explained by the fact that

FAI is a musculoskeletal condition whose main manifes-

tation is hip pain. The practically inexistent difference

between FAI patients and the general population for ER,

MH and GH may be a reflection of the fact that this con-

dition is primarily observed in young and relatively healthy

adults. The decrement noticed in VT and SF may reflect the

dissatisfaction that FAI population had with respect to their

functional status, considering that they are a relatively

active population.

As a pathological condition affecting PCS, FAI had a

larger impact in women and in those patients with the

highest activity level. Regarding gender differences, it is

known that women display a higher prevalence and

severity of self-reported musculoskeletal pain, with a var-

iation in impact on HRQoL (SF-36 V.2TM) [42]. Addi-

tionally, the consequences of musculoskeletal pain are

different in men and women. Women with musculoskeletal

pain report more healthcare use than men, while men report

more work disability [43]. Although some biological fac-

tors could explain the differences, the main explanation is

presumably gender disparities in work, economy, daily

living, social life and expectations between women and

men [42]. In an evaluation of activity level as a factor

explaining lower HRQoL, our data demonstrate a more

Qual Life Res

123

profound impact on PCS for the most active patients

(UCLA 9 and above), who feel that their physical health is

the same as sedentary patients (UCLA 5). We speculate

that this observation could be explained by the fact that the

most active patients (who may also be classified as ath-

letes) [19] feel that the practice of sports and related

activities is a crucial component of their lives. Patients

without the ability to participate in sports and activities

with the frequency or quality they wish (because of the FAI

symptoms) may translate their frustration into a decreased

HRQoL.

The compromise that FAI produces in MCS was

accentuated in patients with obesity and in those with

current or past psychiatric comorbidity. It is known that

Table 1 Intra- and extra-articular variables among FAI patients

Intra-articular factors Frequency % Valid % Extra-articular factors Frequency % Valid %

Bilateral pain Gender

No 78 72.22 73.58 Male 53 49.10 49.10

Yes 28 25.93 26.42 Female 55 50.90 50.90

Lost 2 1.85 Lost 0 0.00 0.00

Total 108 100.00 100.00 Total 108 100.00 100.00

Duration of symptoms C50 years old

6 months or less 26 24.07 25.74 Yes 15 13.89 13.89

7–12 months 25 23.15 24.75 No 93 86.11 86.11

More than 12 months 50 46.30 49.50 Lost 0 0.00 0.00

Lost 7 6.48

Total 108 100.00 100.00 Total 108 100.00 100.00

Acetabular chondral lesion Psychiatric comorbidity

No 6 5.56 7.32 No 73 67.59 80.22

Partial thickness 46 42.59 56.10 Yes 18 16.67 19.78

Full thickness 30 27.78 36.59 Lost 17 15.74

Lost 26 24.07

Total 108 100.00 100.00 Total 108 100.00 100.00

Treatment chondral lesion Obesity

Mechanic chondroplasty 81 75.00 82.65 No 92 85.19 85.98

Microfracture 17 15.74 17.35 Yes 15 13.89 14.02

Lost 10 9.26 Lost 1 0.93

Total 108 100.00 100.00 Total 108 100.00 100.00

Labrum lesion UCLA

Intrasubstance lesion 29 26.85 26.85 Mean 5.7

Labral detachment 47 43.52 43.52 SD 2.7

Degenerative lesion 31 28.70 28.70 Min 2

No labral lesion 1 0.93 0.93 Max 10

Total 108 100.00 100.00 Lost 14

Labrum treatment Workers’ compensation

Labral repair/reinsertion 85 78.70 83.33 No 91 84.26 91.00

Partial/total labral resection 17 15.74 16.67 Yes 9 8.33 9.00

Lost 6 5.56 Lost 8 7.41

Total 108 100.00 100.00 Total 108 100.00 100.00

Pain outside of the hip area

No 58 53.70 69.05

Yes 26 24.07 30.95

Lost 24 22.22

Total 108 100.00 100.00

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123

obese patients are more prone to present self-reported,

work-restricting musculoskeletal pain than non-obese

controls [44]. Additionally, the presence of psychiatric

comorbidity is expected to compromise MCS. Considering

previous studies focused on orthopedic patients reported a

lower preoperative MCS independently predicted patient

dissatisfaction after surgery [45], we believe that our data

provide important information regarding patients under-

going surgical management for FAI. Based on our data,

FAI patients with obesity or psychiatric comorbidity could

be at risk for potential dissatisfaction following FAI

surgery.

Interestingly, in our study, the intrinsic articular factors

such as the status of articular cartilage and labral pathology

had no impact on physical health. This observation could

be explained by four potential causes: (a) the extent of

articular cartilage and labral involvement may have been

underestimated due to limitations in surgical visualization

[46] with the utilized surgical approach. Although it is

possible some articular lesions may have been located in

the blinded area for the anterior mini-open approach, the

vast majority of the articular lesions observed in FAI are

located in the accessible area [47]. (b) The use of other

methods to classify articular cartilage and labral pathology

[3, 48] could have led to a different result with regard to the

influence of articular and labral pathology on HRQoL in

this cohort. We decided to use the presented classification

because it is closely related to our intraoperative decision

making. (c) Due to the retrospective nature of this study,

some of the data points were missing. We utilized the

multiple imputation model to account for this shortfall.

This model is an accepted advanced statistical method to

deal with missing data [49–51], which is being used with

more frequency in the medical literature. Therefore, we

feel that this shortcoming has been addressed appropri-

ately. (d) Because patients were operated on by a single

surgeon at a single institution, it is possible that the find-

ings of the study may not be applicable to all patients with

FAI. (e) The observation that articular factors did not

appear to affect physical function may be due to a lack of

sensitivity of the SF-36 to detect subtle changes in physical

function associated with articular factors.

The vast majority of the reports on surgical treatment for

FAI concentrate on functional results, without a clear

statement of impact on HRQoL [11, 15, 16, 52–54]. To our

knowledge, only two studies have evaluated HRQoL as part

of the outcomes following surgical intervention. Bea

ule et al. examined the impact of surgical hip dislocation

using the Western Ontario McMaster Osteoarthritis score

(WOMAC) score [17]. A preoperative mean score of

61.2 ± 20 increased to 81.4 ± 16 postoperatively

(p \ 0.001), and it was concluded surgical treatment

improved the HRQoL. The findings of the latter study are

difficult to interpret because WOMAC was reported as a

single value instead of the accepted standard consisting of

separate scores for function, stiffness and pain.

0

10

20

30

40

50

60

70

80

90

100PF

RP

BP

GH

VT

SF

ER

MH

Mean US population [32]

Pre-operative FAI Population

Pre-Total hip artrhoplasty [33]

Fig. 1 SF-36 ‘‘spydergram’’

depicting the pattern of

compromise that FAI produces

on HRQoL. As point of

comparison, the mean US

population as well as a large

sample of patients with end-

stage hip osteoarthritis (pre total

hip arthroplasty) are presented

Qual Life Res

123

Furthermore, when WOMAC is appropriately utilized,

higher scores indicate more functional impairment [55, 56].

Thus, the methodology as well as the representation of the

pre- and postoperative HRQoL is questionable. The second

study illustrated the HRQoL of a large series of patients who

underwent hip arthroscopy using an instrument called Rosser

index matrix, which is composed by 7 different categories for

disability and 4 for distress, generating 29 possible health

states [57]. The authors, as they have presented in the past

[57–59], used modified Harris hip scores to generate the

Rosser index matrix, demonstrating a positive impact of hip

arthroscopy on HRQoL in FAI patients. As a limitation, the

investigation did not evaluate HRQoL directly, but derived

the information from an organ-specific score. This approach

has been questioned by Byrd and Jones, especially for

patients who do not undergo arthroplasty [16]. Additionally,

literature generated using this method of HRQoL evaluation

is scarce and presents a difficulty when endeavoring to

compare results with those of other medical conditions. For

the aforementioned reasons, we felt that there was a need to

fully evaluate the impact of FAI on HRQoL and to establish

its pattern of disease. The SF-36 V.2TM was chosen because

of its acceptance in the orthopaedic literature [31], as well as

its application in a multidimensional portrayal of HRQoL.

We believe that our findings have particular relevance in

clinical practice, since we can predict outcomes based on

obesity, level of activity, and mental health despite any

degree of intra-articular damage.

Table 2 Preoperative SF-36 scores among patients undergoing femoroacetabular impingement surgery (current study), total hip replacement

[33] and the mean US population [32]

FAI sample characteristics (n = 108) Pre-THA Sample

(n = 2,223) [33]

FAI versus pre-THA Mean US population

(n = 2,474) [32]

FAI versus mean

US population

SF-36 dimension Mean SD Min Max Mean SD p value Mean SD p value

PF 56.67 25.92 0.00 100.00 24.5 NA – 84.2 23.3 \0.01

RP 43.75 41.03 0.00 100.00 13.5 NA – 80.9 34.0 \0.01

BP 38.98 19.52 0.00 90.00 31.4 NA – 75.2 23.7 \0.01

GH 74.49 16.02 30.00 100.00 62.9 NA – 71.9 20.3 0.19

VT 52.55 20.91 5.00 100.00 43.3 NA – 60.9 20.9 \0.01

SF 62.73 30.47 0.00 100.00 57.1 NA – 83.3 22.7 \0.01

RE 80.56 34.14 0.00 100.00 63.8 NA – 81.3 33.0 0.81

MH 74.37 15.01 32.00 100.00 65.5 NA – 74.7 18.1 0.85

PCS 53.29 19.20 16.00 98.00 28.0* 7.8* \0.01 50.0 10.0 \0.01

MCS 68.94 17.15 27.50 100.00 28.7* 12.1* \0.01 50.0 10.0 \0.01

* Ref. [33] disclosed a reduced sample size for calculation of PCS (1,629 patients) and MCS (1,193 patients)

Femoroacetabular impingement (FAI), total hip arthroplasty (THA), United States (US), sample size (n), standard deviation (SD), minimum

(Min), maximum (Max), physical function (PF), bodily pain (BP), physical role (PR), vitality (VT), general health (GH), emotional role (ER),

social role (SR), mental health (MH), physical component summary (PCS), mental component summary (MCS) and non-available (NA)

Fig. 2 Correlation between

PCS and UCLA activity scale

among FAI patients

Qual Life Res

123

In conclusion, FAI displays a distinct pattern of impact

on HRQoL. In our series, the impact of FAI, considered as

a pathological entity, is dependent upon differences

between individual patients and not on the extent of the

identified articular damage.

References

1. Parvizi, J., Leunig, M., & Ganz, R. (2007). Femoroacetabular

impingement. The Journal of the American Academy of Ortho-paedic Surgeons, 15(9), 561–570.

2. Anderson, L. A., Peters, C. L., Park, B. B., Stoddard, G. J.,

Erickson, J. A., & Crim, J. R. (2009). Acetabular cartilage

delamination in femoroacetabular impingement. Risk factors and

magnetic resonance imaging diagnosis. The Journal of Bone andJoint Surgery. American, 91(2), 305–313.

3. Beck, M., Leunig, M., Parvizi, J., Boutier, V., Wyss, D., & Ganz,

R. (2004). Anterior femoroacetabular impingement: Part II.

Midterm results of surgical treatment. Clinical Orthopaedics andRelated Research, 418, 67–73.

4. McCarthy, J. C., & Lee, J.-A. (2011). History of hip arthroscopy:

Challenges and opportunities. Clinics in Sports Medicine, 30(2),

217–224.

5. Sampson, T. G. (2011). Arthroscopic treatment for chondral

lesions of the hip. Clinics in Sports Medicine, 30(2), 331–348.

6. Clohisy, J. C., St John, L. C., & Schutz, A. L. (2010). Surgical

treatment of femoroacetabular impingement: A systematic review

of the literature. Clinical Orthopaedics and Related Research,468(2), 555–564.

7. Jaberi, F. M., & Parvizi, J. (2007). Hip pain in young adults:

Femoroacetabular impingement. The Journal of Arthroplasty,22(7 Suppl 3), 37–42.

8. Plante, M., Wallace, R., & Busconi, B. D. (2011). Clinical

diagnosis of hip pain. Clinics in Sports Medicine, 30(2), 225–238.

9. Ganz, R., Parvizi, J., Beck, M., Leunig, M., Notzli, H., & Sie-

benrock, K. A. (2003). Femoroacetabular impingement: A cause

for osteoarthritis of the hip. Clinical Orthopaedics and RelatedResearch, 417, 112–120.

10. Clohisy, J. C., Dobson, M. A., Robison, J. F., Warth, L. C.,

Zheng, J., Liu, S. S., Yehyawi, T. M., & Callaghan, J. J. (2011).

Radiographic structural abnormalities associated with premature,

natural hip-joint failure. The Journal of Bone and Joint SurgeryAmerican, 93 (Suppl 2), 3–9.

11. Botser, I. B., Smith, T. W. Jr, Nasser, R., & Domb, B. G.

(2011). Open surgical dislocation versus arthroscopy for femo-

roacetabular impingement: A comparison of clinical outcomes.

Arthroscopy: The Journal Of Arthroscopic and Related Surgery:Official Publication of the Arthroscopy Association of NorthAmerica and the International Arthroscopy Association, 27(2),

270–278.

12. Impellizzeri, F. M., Mannion, A. F., Naal, F. D., Hersche, O., &

Leunig, M. (2012). The early outcome of surgical treatment for

femoroacetabular impingement: Success depends on how you

measure it. Osteoarthritis and cartilage/OARS, OsteoarthritisResearch Society, 20(7), 638–645.

13. Haviv, B., Burg, A., Velkes, S., Salai, M., & Dudkiewicz, I.

(2011). Trends in femoroacetabular impingement research over

11 years. Orthopedics, 34(5), 353.

14. Stevens, M. S., Legay, D. A., Glazebrook, M. A., & Amirault, D.

(2010). The evidence for hip arthroscopy: Grading the current

indications. Arthroscopy: The Journal of Arthroscopic andRelated Surgery: Official Publication of the Arthroscopy

Association of North America and the International ArthroscopyAssociation, 26(10), 1370–1383.

15. Byrd, J. W., & Jones, K. S. (2000). Prospective analysis of hip

arthroscopy with 2-year follow-up. Arthroscopy: The Journal ofArthroscopic & Related Surgery: Official Publication of theArthroscopy Association of North America and the InternationalArthroscopy Association, 16(6), 578–587.

16. Byrd, J. W. T., & Jones, K. S. (2010). Prospective analysis of hip

arthroscopy with 10-year followup. Clinical Orthopaedics andRelated Research, 468(3), 741–746.

17. Beaule, P. E., Le Duff, M. J., & Zaragoza, E. (2007). Quality of

life following femoral head-neck osteochondroplasty for femo-

roacetabular impingement. The Journal of bone and joint surgery,89 (4), 773–779.

18. Malviya, A., Stafford, G. H., & Villar, R. N. (2012). Impact of

arthroscopy of the hip for femoroacetabular impingement on

quality of life at a mean follow-up of 3.2 years. The Journal ofBone and Joint Surgery, 94 (4), 466–470.

19. Cohen, S. B., Huang, R., Ciccotti, M. G., Dodson, C. C., &

Parvizi, J. (2012). Treatment of femoroacetabular impingement in

athletes using a mini-direct anterior approach. The Americanjournal of sports medicine, 40(7), 1620–1627.

20. Meermans, G., Konan, S., Haddad, F. S., & Witt, J. D. (2010).

Prevalence of acetabular cartilage lesions and labral tears in

femoroacetabular impingement. Acta Orthopaedica Belgica,76(2), 181–188.

21. Clohisy, J. C., Nunley, R. M., Otto, R. J., & Schoenecker, P. L.

(2007). The frog-leg lateral radiograph accurately visualized hip

cam impingement abnormalities. Clinical Orthopaedics andRelated Research, 462, 115–121.

22. Werlen, S., Leunig, M., & Ganz, R. (2005). Magnetic resonance

arthrography of the hip in femoroacetabular impingement: Technique

and findings. Operative Techniques in Orthopaedics, 15(3), 191–203.

23. Jacobsen, S. (2006). Adult hip dysplasia and osteoarthritis.

Studies in radiology and clinical epidemiology. Acta Orthopae-dica, 77(324), 1–37.

24. Arden, N. K., Lane, N. E., Parimi, N., Javaid, K. M., Lui,

L.-Y., Hochberg, M. C., et al. (2009). Defining incident radio-

graphic hip osteoarthritis for epidemiologic studies in women.

Arthritis and Rheumatism, 60(4), 1052–1059.

25. Tonnis, D., & Heinecke, A. (1999). Acetabular and femoral

anteversion: Relationship with osteoarthritis of the hip. TheJournal of Bone and Joint Surgery, 81(12), 1747–1770.

26. Ng, V. Y., & Ellis, T. J. (2012). Cam morphology in the human

hip. Orthopedics, 35(4), 320–327.

27. Paliobeis, C. P., & Villar, R. N. (2011). The prevalence of dys-

plasia in femoroacetabular impingement. Hip International: TheJournal of Clinical and Experimental Research on Hip Pathologyand Therapy, 21(2), 141–145.

28. Millis, M. B., & Novais, E. N. (2011). In situ fixation for slipped

capital femoral epiphysis: Perspectives in 2011. The Journal ofBone and Joint Surgery, 93(Suppl 2), 46–51.

29. Kuzyk, P. R. T., Kim, Y.-J., & Millis, M. B. (2011). Surgical

management of healed slipped capital femoral epiphysis. TheJournal of the American Academy of Orthopaedic Surgeons,19(11), 667–677.

30. Ware, J. E., Jr, & Sherbourne, C. D. (1992). The MOS 36-item

short-form health survey (SF-36). I. Conceptual framework and

item selection. Medical Care, 30(6), 473–483.

31. Patel, A. A., Donegan, D., & Albert, T. (2007). The 36-item short

form. The Journal of the American Academy of OrthopaedicSurgeons, 15(2), 126–134.

32. Ware, J. E., Jr. (2000). SF-36 health survey update. Spine, 25(24),

3130–3139.

33. Anderson, P. A., Puschak, T. J., & Sasso, R. C. (2009). Com-

parison of short-term SF-36 results between total joint

Qual Life Res

123

arthroplasty and cervical spine decompression and fusion or

arthroplasty. Spine, 34(2), 176–183.

34. Strand, V., Crawford, B., Singh, J., Choy, E., Smolen, J. S., &

Khanna, D. (2009). Use of ‘‘spydergrams’’ to present and inter-

pret SF-36 health-related quality of life data across rheumatic

diseases. Annals of the Rheumatic Diseases, 68(12), 1800–1804.

35. Birrell, F., Lunt, M., Macfarlane, G. J., & Silman, A. J. (2005).

Defining hip pain for population studies. Annals of the RheumaticDiseases, 64(1), 95–98.

36. World Health Organization Technical Report Series (2000).

Obesity: Preventing and managing the global epidemic. Report of

a WHO consultation. World Health Organization technical report

series, 894 i–xii, 1–253.

37. Zahiri, C. A., Schmalzried, T. P., Szuszczewicz, E. S., & Am-

stutz, H. C. (1998). Assessing activity in joint replacement

patients. The Journal of arthroplasty, 13(8), 890–895.

38. De Moraes, V. Y., Godin, K., Tamaoki, M. J. S., Faloppa, F.,

Bhandari, M., & Belloti, J. C. (2012). Workers’ compensation

status: Does it affect orthopaedic surgery outcomes? A meta-

analysis. PLoS ONE, 7(12), e50251.

39. Badura-Brzoza, K., Zajac, P., Brzoza, Z., Kasperska-Zajac, A.,

Matysiakiewicz, J., Piegza, M., et al. (2009). Psychological and

psychiatric factors related to health-related quality of life after

total hip replacement—preliminary report. European Psychiatry:The Journal of the Association of European Psychiatrists, 24(2),

119–124.

40. Azur, M. J., Stuart, E. A., Frangakis, C., & Leaf, P. J. (2011).

Multiple imputation by chained equations: What is it and how

does it work? International Journal of Methods in PsychiatricResearch, 20(1), 40–49.

41. Lindsey, J. K., & Jones, B. (1998). Choosing among generalized

linear models applied to medical data. Statistics in Medicine,17(1), 59–68.

42. Bingefors, K., & Isacson, D. (2004). Epidemiology, co-morbid-

ity, and impact on health-related quality of life of self-reported

headache and musculoskeletal pain–a gender perspective. Euro-pean Journal of Pain (London, England), 8(5), 435–450.

43. Wijnhoven, H. A. H., De Vet, H. C. W., & Picavet, H. S. J.

(2007). Sex differences in consequences of musculoskeletal pain.

Spine, 32(12), 1360–1367.

44. Peltonen, M., Lindroos, A. K., & Torgerson, J. S. (2003).

Musculoskeletal pain in the obese: A comparison with a general

population and long-term changes after conventional and surgical

obesity treatment. Pain, 104(3), 549–557.

45. Gandhi, R., Davey, J. R., & Mahomed, N. N. (2008). Predicting

patient dissatisfaction following joint replacement surgery. TheJournal of Rheumatology, 35(12), 2415–2418.

46. Malik, A. K., Chou, D. T. S., & Witt, J. D. (2010). Anterior

approaches to the hip for the treatment of femoro-acetabular

impingement: A cadaveric study. Hip International: The Journalof Clinical and Experimental Research on Hip Pathology andTherapy, 20(4), 482–488.

47. Tannast, M., Goricki, D., Beck, M., Murphy, S. B., & Siebenrock,

K. A. (2008). Hip damage occurs at the zone of femoroacetabular

impingement. Clinical Orthopaedics and Related Research,466(2), 273–280.

48. Konan, S., Rayan, F., Meermans, G., Witt, J., & Haddad, F. S.

(2011). Validation of the classification system for acetabular

chondral lesions identified at arthroscopy in patients with femo-

roacetabular impingement. The Journal of Bone and JointSurgery, 93(3), 332–336.

49. Mackinnon, A. (2010). The use and reporting of multiple impu-

tation in medical research—a review. Journal of Internal Medi-cine, 268(6), 586–593.

50. Klebanoff, M. A., & Cole, S. R. (2008). Use of multiple impu-

tation in the epidemiologic literature. American Journal ofEpidemiology, 168(4), 355–357.

51. Harel, O., & Zhou, X.-H. (2007). Multiple imputation: Review of

theory, implementation and software. Statistics in Medicine,26(16), 3057–3077.

52. Sekiya, J. K., Martin, R. L., & Lesniak, B. P. (2009). Arthro-

scopic repair of delaminated acetabular articular cartilage in

femoroacetabular impingement. Orthopedics, 32(9).

53. Philippon, M. J., Schroder E Souza, B. G., & Briggs, K. K.

(2012). Hip arthroscopy for femoroacetabular impingement in

patients aged 50 years or older. Arthroscopy: The Journal OfArthroscopic & Related Surgery: Official Publication of theArthroscopy Association of North America and the InternationalArthroscopy Association, 28(1), 59–65.

54. Peters, C. L., Schabel, K., Anderson, L., & Erickson, J. (2010).

Open treatment of femoroacetabular impingement is associated

with clinical improvement and low complication rate at short-

term followup. Clinical Orthopaedics and Related Research,468(2), 504–510.

55. Tubach, F., Ravaud, P., Baron, G., Falissard, B., Logeart, I.,

Bellamy, N., et al. (2005). Evaluation of clinically relevant states

in patient reported outcomes in knee and hip osteoarthritis: The

patient acceptable symptom state. Annals of the RheumaticDiseases, 64(1), 34–37.

56. Bellamy, N., Buchanan, W. W., Goldsmith, C. H., Campbell, J.,

& Stitt, L. W. (1988). Validation study of WOMAC: A health

status instrument for measuring clinically important patient rel-

evant outcomes to antirheumatic drug therapy in patients with

osteoarthritis of the hip or knee. The Journal of Rheumatology,15(12), 1833–1840.

57. Norman-Taylor, F. H., Palmer, C. R., & Villar, R. N. (1996).

Quality-of-life improvement compared after hip and knee

replacement. The Journal of Bone and Joint Surgery, 78(1), 74–77.

58. Chan, C. L., & Villar, R. N. (1996). Obesity and quality of life

after primary hip arthroplasty. The Journal of Bone and JointSurgery, 78(1), 78–81.

59. Norman-Taylor, F. H., & Villar, R. N. (1997). Hybrid hip

arthroplasty in the younger patient. Quality of life. The Journal ofArthroplasty, 12(6), 646–650.

Qual Life Res

123