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Physical impairments in symptomatic femoroacetabular impingement: a systematic review of the evidence
  1. Matthew D Freke1,
  2. Joanne Kemp2,
  3. Ida Svege3,
  4. May Arna Risberg4,
  5. Adam Semciw5,
  6. Kay M Crossley6
  1. 1Enoggera Health Centre, Gallipoli Barracks, Enoggera, Queensland and University of Queensland, School of Health and Rehabilitation Sciences, Brisbane, Queensland, Australia
  2. 2Australian Centre for Research into Injury in Sport and its Prevention (ACRISP), Federation University Australia, Ballarat, Victoria, Australia
  3. 3Oslo University Hospital, Oslo, Norway
  4. 4Department of Orthopaedic Surgery, Oslo University Hospital, Oslo, Norway
  5. 5University of Queensland, School of Health and Rehabilitation Sciences, Brisbane, Queensland, Australia
  6. 6School of Allied Health, College of Science, Health and Engineering, La Trobe University, Melbourne, Victoria, Australia
  1. Correspondence to Matthew D Freke, Department of Physiotherapy, Enoggera Health Centre, Gallipoli Barracks, Enoggera, Brisbane, QLD 4060, Australia; matthew.freke{at}uqconnect.edu.au

Abstract

Background Femoroacetabular impingement (FAI) and accompanying pathologies are associated with pain and reduced quality of life. Physical impairments can be associated with worse symptoms and may be an important target of rehabilitation programmes in this patient group. Knowledge regarding physical impairments in individuals with symptomatic FAI is limited.

Hypothesis In adults aged 18–50 years with symptomatic FAI, to: (1) identify physical impairments in range of motion (ROM), hip muscle function and functional tasks; (2) to compare physical impairments with healthy controls; and (3) to evaluate the effects of interventions targeting physical impairments.

Study design Systematic review.

Methods A systematic review of the literature was conducted in accordance with the PRISMA statement. The modified Downs and Black checklist was used for quality appraisal. Studies of adults aged 18–50 years with symptomatic FAI that examined ROM, hip muscle function and functional tasks were included. Standardised mean differences (SMDs) were calculated where possible or best evidence synthesis and study conclusions were presented.

Results 22 studies fulfilled all inclusion criteria. Methodological quality was varied (47–82% using Downs and Black Appraisal Criteria). Hip joint ROM did not differ in individuals with symptomatic FAI compared with control participants. Individuals with symptomatic FAI demonstrated deficits in hip muscle strength and reduced dynamic balance on 1 leg when compared with control participants. For hip joint ROM, there were no significant within-group differences between preintervention and postintervention time points. Hip muscle strength improved significantly from prehip to posthip arthroscopy in a single case series. No randomised controlled trails evaluated the effect of different types of interventions for symptomatic patients with symptomatic FAI.

Conclusions Individuals with symptomatic FAI demonstrate impairments in hip muscle strength and dynamic single leg balance. This information may assist therapists in providing targeted rehabilitation programmes for individuals with FAI and associated pathology. Further research is needed to determine whether symptomatic FAI affects other aspects of functional performance; and to evaluate whether targeted interventions are effective in symptomatic FAI.

Clinical relevance This information may assist therapists in providing targeted rehabilitation programmes for individuals with symptomatic FAI.

  • Hip
  • Strength
  • Functional

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Introduction

Femoroacetabular impingement (FAI) is a recognised cause of hip pain in young and middle-aged adults, and is associated with an increased risk of end-stage radiographic hip osteoarthritis (OA) and total hip arthroplasty.1 FAI is a clinical condition, where affected patients may present with a morphological variant in hip shape on radiographs, with or without associated labral and/or chondral pathology,2 resulting in increased hip/groin pain3 and reduced activity and quality of life.1 ,4 Cam-type FAI and associated pathologies are characterised by vigorous, repetitive contact of an abnormal morphology in the femoral neck/head into the acetabulum causing soft-tissue damage to the acetabular cartilage, potentially leading to OA changes in the hip.5–8 While much speculation exists, the prevalence of cam morphology in the general population is unknown9 and the presence of a cam abnormality does not inevitably lead to symptomatic FAI.6 FAI and associated pathologies may be considered to represent early stage hip degenerative joint disease in the disease continuum.4 ,10 These pathologies will be referred to collectively as ‘symptomatic FAI’ in this systematic review.

Symptomatic FAI can have a significant impact on pain, function and quality of life outcomes in the young and middle aged4 ,11 that may ultimately reduce their capacity to lead active and productive lives. Identifying potentially modifiable impairments in patients with symptomatic FAI is important. If they can be identified when hip degenerative disease is in its early stages, it may be possible to design rehabilitation interventions to slow the symptomatic progression of symptomatic FAI. Arthroscopic surgery of the hip to reshape impingement lesions and salvage acetabular labarum and chondral surfaces is the most common treatment at present.12 Postsurgical rehabilitation programmes have been described in detail.13 ,14 High-quality evidence to support the effect of either surgical, non-surgical or postsurgical interventions for patients with symptomatic FAI is currently lacking. At present the impairments and disabilities of patients with symptomatic FAI are poorly understood.15 A greater understanding may lead to the development of effective interventions (both non-operative and postoperative) that can reduce pain, improve activity and enhance quality of life in affected individuals.

The physical impairments and activity limitations of individuals with all forms of FAI (cam, pincer and mixed) has been previously systematically reviewed;15 however, that study combined clinical and laboratory-based biomechanical data and did not provide standardised effect size (ES) measures to facilitate comparisons between studies. Moreover, a large number of studies have been published since the search date of the previous review. The goal of this review was to examine physical impairments that can be measured in the clinical setting and encompasses much of the rapidly expanding knowledge and available literature in the area of physical impairments in individuals with symptomatic FAI.

The aim of this review was to systematically appraise the literature to:1 identify physical impairments in adults aged 18–50 years with symptomatic FAI;2 compare physical impairments in individuals with symptomatic FAI to healthy controls; and3 to evaluate the effects of interventions targeting physical impairments in patients with symptomatic FAI.

Methods

The systematic review protocol was developed in accordance with the PRISMA statement16 and registered online at http://www.crd.york.ac.uk/PROSPERO/display_record.asp?ID=CRD42014014605. Literature search criteria and methods were proposed and agreed on by two authors and were established a priori to minimise selection bias.

Search strategy

A comprehensive, reproducible search strategy was performed on the following databases for dates of publication between 1 January 1990 and 22 August 2015: Scopus, MEDLINE, CINAHL, PubMed, Ausport, SportsDiscus, PEDro, PsychINFO and Google Scholar. January 1990 was selected as the earliest retrieval record due to the paucity of literature on FAI prior to this date.12 Reference lists of appropriate studies were manually searched for relevant papers. The search strategy used the PICO format, and included

  • . P=human adults with symptomatic FAI, diagnosed by MRI or at arthroscopy [‘femoracetabular impingement’, ‘labr*’, ‘chondr*’, ‘pathology’, ‘osteoarthritis’, ‘arthritis’, ‘pain’, ‘hip joint’];

  • . I=surgical and non-surgical interventions [‘arthroscop*’, ‘physiotherapy’, ‘physical therapy’, ‘exercise’, ‘therapy’]; C=people without FAI, labral or chondral pathology [‘control’, ‘healthy’, ‘asymptomatic’];

  • . O=physical impairments of the hip. This may include hip joint range of motion (ROM), hip muscle strength, measures of functional performance, electromyography (EMG), gait analysis [‘hip’, ‘muscle strength’, ‘range of motion’, ‘range of movement’ ‘range’, ‘movement’, ‘EMG’, ‘impairment’, ‘musculoskeletal’, ‘proprioception’, ‘balance’, ‘motor control’, ‘gait’, ‘kinematic’. ‘stiffness’, ‘weakness’, ‘function*’, ‘performance’].

The strategy was modified for each database. Titles and abstracts were screened for relevant studies by two independent reviewers (JK and IS). Any disagreements regarding inclusion were resolved by an independent arbitrator (KMC). All potential references were imported into Endnote X6 (Thomson Reuters, Carlsbad, California, USA) and duplicates were removed. Full-text versions of identified papers were then retrieved for final eligibility screening by a single reviewer (JK).

Eligibility criteria

Studies were eligible for inclusion if they were reported in English; report level IV evidence or above; contained human participants with symptomatic FAI assessed using preoperative diagnostic imaging techniques or hip arthroscopy; had at least five participants; and examined physical impairments of the hip or functional performance. Symptomatic FAI was defined as the presence of an impingement variant at the head–neck junction, and/or associated impingement-type pathologies (such as chondral or labral pathology). Physical impairments included hip joint range of motion (measured using goniometry, inclinometers, electronic or imaging devices), hip muscle function (measured using isometric or isokinetic testing devices and measures of muscular activity collected as EMG, motor control; balance or proprioception) and functional task performance (including squatting, walking and other activities of daily living). Studies specifically examining biomechanics during gait were excluded.

All quantitative study designs were considered, including randomised controlled trials (RCTs), prospective or retrospective approaches.17 Studies were excluded if they were case series with <5 participants, published abstracts, non-peer reviewed or in a language other than English.

Quality evaluation

The Downs and Black checklist was used to appraise the methodological quality of included studies.18 This has adequate reliability and validity for assessing non-randomised studies. The original 27 items was modified to 17 items following the exclusion of criteria 4, 13, 14, 15, 17, 19, 22, 23, 24 and 27. There were no RCTs found; therefore, only criteria that were applicable for non-randomised studies were evaluated. Included studies were rated by two independent reviewers (IS and MDF). A third reviewer audited the ratings of a random selection of included studies (JK). Any disagreements between reviewers were discussed and consensus determined by an independent arbitrator (JK). Studies were considered high quality with a score of more than 60% (10 points or more out of 17).19

Statistical analyses

All statistical analyses were performed by a single author (JK) using SPSS V.21.0 software (SPSS Inc, Chicago, Illinois, USA). Eligible papers were grouped where possible based on (1) type of physical impairment or functional performance task reported; and (2) whether a between-group comparison (symptomatic FAI vs healthy controls) or within-group comparison (preintervention to postintervention) was undertaken. Inter-rater agreement on the included Downs and Black criteria was evaluated using the κ statistic, where 0.01–0.20 represents slight agreement; 0.21–0.40 represents fair agreement; 0.41–0.60 represents moderate agreement; 0.61–0.80 represents substantial agreement and 0.81–1.0 represents almost perfect agreement.17 ,20

Data management

Data from included studies were extracted by two reviewers (JK and IS). Authors of included studies were contacted for additional data where reported data were inadequate for standardised mean difference (SMD) calculation. Findings were summarised in tables. Population characteristics (age, gender, type and description of hip OA, duration of symptoms), details of level of evidence, outcome measures, length of follow-up and any intervention undertaken were collated. SMDs were calculated to determine the magnitude of differences in impairments between groups; and was calculated as the mean difference between groups (between-group), divided by the patient group SD. Standardised paired differences (SPDs) were calculated to determine the magnitude of the effect between time points in the patient group (within-group); divided by the preintervention SD. SMD or SPD magnitude was interpreted as: ≥0.8 large effect; 0.5–0.79 moderate effect; and 0.2–0.49 weak effect. 95% CIs for SMDs were calculated as 1.96×SE of each measure, where the SE=SD/√number of participants. Where SMDs or SPDs could not be calculated, study conclusions were presented. Meta-analysis was undertaken where study homogeneity and available data allowed. A best evidence synthesis21 was conducted where pooling of data was not possible for each of hip joint ROM, hip muscle function and functional task performance. Evidence was categorised as ‘strong’ if there were multiple high-quality cohort studies; ‘moderate’ if there was either one high-quality cohort study and more than two high-quality case–control studies, or more than three high-quality case–control studies; ‘limited’ if there were either one or two case–control studies, or multiple cross-sectional studies; and ‘insufficient’ if there was not more than one cross-sectional study. Evidence was summarised as ‘conflicting’ if findings in <75% of the studies were inconsistent, taking into account the participants, interventions, controls, outcomes and methodological quality of the original studies. These classifications were based on the recommendations of van Tulder et al.21

Results

Search strategy

Results of the search strategy are contained in figure 1. One hundred and eighteen full texts were screened; however, 96 papers did not meet inclusion criteria, leaving 22 papers in the final analyses.

Figure 1

Summary of search strategy results. FAI, femoral acetabular impingement.

Methodological quality

Initial agreement between the two raters was substantial (κ=0.626). Agreement was reached on 328 items out of 381 items in total (81%; see online supplementary appendix 1). Consensus was obtained on the quality rating for the remaining 77 items. The methodological quality scores ranged from 14 points out of 17 (82%)22 ,23 to 8 points out of 17 (47%).3 ,24–26 The overall mean (SD) rating was 10.69 (1.89) points out of 17 (63%).

Participants

The 22 included studies contained 819 patients with FAI in total, with sample sizes ranging from 724 to 112 patients.23 Sixteen studies included age-matched healthy control groups (12 non-surgery, 1 presurgery, 3 postsurgery), and 5 within-group studies investigated the change in outcome preintervention and postintervention. One study contained men only.24 The remaining 21 studies contained both men and women. The mean (SD) ages for patients in the included studies ranged from 245 ,24 to 3712 ,27 years. All studies included participants based on a diagnosis of FAI and associated labral and/or chondral pathology. The method of diagnoses ranged from arthroscopic findings,22 ,23 ,27 ,28 to positive clinical signs on physical examination,24 ,26 ,29–33 to radiographic, CT or MRI diagnosis.3 ,24–26 ,29–32 ,34–38

Outcomes measured

Physical impairment outcomes reported included hip joint ROM;3 ,22 ,23 ,25 ,27 ,33 ,34 ,36 ,37 ,39–42 hip muscle function;22 ,26 ,29 ,30 ,31 ,33 simulated hip joint ROM using three-dimensional CT or three-dimensional kinematics;24 ,28 ,32 ,34 ,38 ,43 hip muscle volume;31 hip muscle EMG;29 ,30 and functional performance tasks such as single leg balance,27 squat depth and pelvic ROM,44 and number of strides per day.35 The reliability of physical impairment outcomes measured was reported in 7 out of the 23 studies. Reported intraclass correlations ranged from 0.7227 to 1.0.31

Main findings

Owing to study heterogeneity, it was not possible to conduct meta-analyses, and therefore a best evidence synthesis was conducted. The results for hip joint ROM, hip muscle function and functional task performance are outlined below. There were no RCTs or non-randomised trials found examining the effect of different types of interventions for patients with FAI on physical impairments. All papers included were case–control or case-series studies only, and SMDs and SPDs have been reported for these studies where able.

Hip joint range of motion

Between-group comparison of hip range of motion in symptomatic FAI to pain-free controls.

Twelve studies examined hip joint ROM in individuals with FAI using goniometers,3 ,22 ,23 ,25 ,27 ,33 ,34 ,36 ,37 ,39–41 while simulated hip joint ROM was reported in five studies (table 1).24 ,28 ,32 ,34 ,38 Between-group SMD data for case–control studies examining hip muscle ROM are contained in figure 2. SMDs were able to be calculated for eight case–control studies,3 ,22 ,25 ,28 ,32–34 ,36 ,37 with seven studies demonstrating no difference for all measures of hip ROM. In studies where SMD were not able to be calculated, results were conflicting. Ross et al40 reported no difference in ROM, except flexion (p=0.03) between hockey goalies with greater α angles and femoral retroversion, compared with positional players. In contrast, Philippon et al23 compared the painful to non-painful leg in individuals with symptomatic FAI prior to hip arthroscopy, and reported reduced ROM in all planes of movement (p=0.001 to p<0.001).

Table 1

Summary of included between-group case–control studies evaluating effect of FAI and associated pathologies on hip range of movement

Figure 2

(A–F) Between-group SMDs for hip ROM (based on only case–control studies, no RCTs were found). ER, external rotation; EST, electromagnetic tracking system; FAI, femoral acetabular impingement; IR, internal rotation; RCT, randomised controlled trial; ROM, range of movement; SMD, standardised mean difference.

Best evidence synthesis for between-group differences in individuals with symptomatic FAI compared with case–controls was limited and conflicting, as one high-quality case–control study22 reported no between-group differences between hips and controls, while the other high-quality case–control study23 reported significant between-leg differences in individuals with painful symptomatic FAI prior to hip arthroscopy. The other included studies were of moderate or low quality, but consistently reported no difference between groups.

Within-group comparison of effect of intervention on hip range of motion

Within-group SPD data for studies examining hip joint ROM are contained in figure 3 and table 2. There was no significant difference in precompared to posthip arthroscopy for all ranges of movement. This appears to be regardless of how ROM was measured. This is in contrast to the study conducted by Emara et al,25 who compared pre-post physiotherapy intervention ROM. Best evidence synthesis for within-group differences in ROM was limited. One high-quality case series34 and one moderate-quality case series32 had SPDs for change in hip ROM that were not significant when prehip to posthip arthroscopy were compared. In contrast, one low-quality case series demonstrated large significant SPDs comparing prephysiotherapy to postphysiotherapy treatment for FAI.25

Table 2

Summary of included studies evaluating within-group effect of FAI and associated pathologies on hip range of movement, strength and functional performance between preintervention and postintervention time points

Figure 3

Within-group SMDs for hip ROM. Abd, abduction; Add, adduction; ER, external rotation; FAI, femoral acetabular impingement; Flex, flexion; IR, internal rotation; ROM, range of movement; SMD, standardised mean difference.

Hip muscle function

Hip muscle function (including strength, electrical activity and muscle volume) was examined in six studies.22 ,26 ,29 ,30 ,31 ,33 Results are contained in tables 2 and 3. Between-group SMD data for case–control studies examining hip muscle function are contained in figure 4 and table 4, and within-group SPDs in figure 5 and table 2. Hip muscle strength was measured and reported in all six studies,22 ,26 ,29–31 ,33 in addition hip muscle cross-sectional area was examined in one study31 and two studies reported on hip muscle EMG activity.29 ,30 SMDs for hip muscle strength were able to be calculated for all six studies22 ,26 ,29–31 ,33 and indicated that with few exceptions, there were significant differences in all hip strength measures in all studies (table 4), favouring controls in between-group comparisons. This was regardless of the sex of participants or whether individuals with FAI had undergone hip arthroscopy surgery. The exceptions were hip extension strength, where no significant effects were noted comparing individuals with FAI to controls.30 Studies of hip flexor size and strength reported conflicting results; SMD calculations for Mendis et al31 revealed no significant differences in hip flexor cross-sectional area between individuals with FAI and controls. In contrast, there was a significant moderate between-group effect (ES (95% CI) 0.59 (0.36 to 0.83)) when comparing hip flexor strength in individuals with FAI to controls29 during sustained submaximal isometric contraction. For muscle size, only one significant SMD was noted, where tensor fascia latae (TFL) was significantly larger in the non-injured leg of the person with FAI compared with healthy controls (ES (95% CI) 1.50 (0.26 to 2.74)). Otherwise there were no significant muscle size differences between the injured leg with FAI, the non-injured leg and healthy case–controls. Hip muscle EMG amplitude was reported in two studies, and SMDs were able to be calculated for both studies.29 ,30 There were no significant between-group effects for rectus femoris or TFL EMG activity when comparing individuals with FAI to controls during a resisted hip flexion exercise task in standing.30 For within-group effects, one study compared hip muscle strength prehip arthroscopy to 2.5 years posthip arthroscopy.26 Calculation of SPDs revealed significant moderate-to-large within-group change favouring the postoperative time point for all muscle strength measures except hip abduction.

Table 3

Summary of included case–control studies evaluating effect of FAI and associated pathologies on functional tasks

Table 4

Summary of included between-group case–control studies evaluating effect of FAI and associated pathologies on hip muscle function

Figure 4

(A–C) Between-group SMDs for hip muscle strength (based on only case–control studies, no RCTs were found). FAI, femoral acetabular impingement; RCT, randomised controlled trial; SMD, standardised mean difference.

Figure 5

Within-group SMDs for hip muscle strength. Abd, abduction; Add, adduction; ER, external rotation; FAI, femoral acetabular impingement; Flex, flexion; IR, internal rotation SMD, standardised mean difference.

Best evidence synthesis for hip muscle strength is limited, with one high-quality case–control study22 and no RCTs. The remaining studies were moderate or low in quality. The limited evidence suggests significant between-group differences in hip muscle size, strength and activity between individuals with symptomatic FAI compared with case–controls favouring the controls, and significant improvement in hip muscle strength posthip arthroscopy compared with prearthroscopy.

Functional tasks (squat depth, pelvic ROM, single leg balance, number of strides)

A number of different clinical measures of functional tasks were reported. SMD data for case–control studies examining hip functional tasks are contained in figure 6. These included squat depth, pelvic ROM, single leg balance and number of strides.27 ,29–31 ,35 ,44 There were no significant between-group effects for squat depth44 pelvic ROM,44 or total number of daily strides35 between individuals with FAI and controls. In addition, when assessing static balance on one leg with eyes closed, no differences were seen in individuals posthip arthroscopy compared with controls.27 However, when individuals posthip arthroscopy undertook a dynamic single leg squat task, significant moderate between-group effects were noted compared with controls, where patients demonstrated increased medial–lateral sway (ES (95% CI) −0.57 (−0.76 to −0.38)) and worse anterior–posterior control (−0.45 (−0.57 to −0.34)),27 both indicators of reduced dynamic balance.

Figure 6

SMDs for functional tasks (based on only case–control studies, no RCTs were found). RCT, randomised controlled trial; ROM, range of movement; SMD, standardised mean difference.

Best evidence synthesis for functional tasks provided varying evidence depending on the challenges of the activity. One high-quality case–control study27 reported significant between-group SMDs for a dynamic balance task, while the other high-quality case–control study44 reported no significant between-group SMDs for squat depth or pelvic ROM. The remaining study was of moderate quality.35

Discussion

This systematic review included 22 studies (16 case–control studies—level III evidence, 1 cross-sectional comparison—level IV evidence, 5 case series—level IV evidence) to establish whether individuals with symptomatic FAI demonstrated physical impairments and/or functional limitations compared with individuals without symptomatic FAI. No RCTs were found. Four of the studies evaluated the ‘within-group’ effects of surgical and conservative intervention on ROM (three studies) and muscle strength (one study). This review found limited evidence that individuals with symptomatic FAI have significant differences in hip muscle function in ‘between-group’ (favouring the control group) and ‘within-group’ (favouring postintervention) studies. There was limited, conflicting evidence to suggest ROM and functional deficits exist when compared with individuals without symptomatic FAI or for postintervention using ‘within-group’ comparisons.

Reduced hip ROM into flexion, internal rotation and adduction3 ,23 ,32 ,34 ,36 ,47–51 is commonly reported in FAI research. In the current review, these restrictions were only significant in low-quality study,25 where reduced ROM was observed in all directions compared with the unaffected limb in a population of male and female athletic patients with high α angles. The conclusions of this paper should be treated with some caution as it suffered a high risk of bias due to a low-quality score and lacked description of measuring methodology, intervention compliance and treatment content. The five between-group studies with sufficient data for SMD calculations3 ,22 ,28 ,32 ,33 ,34 ,36 ,37 consistently demonstrated no significant differences for all measures of hip ROM. This suggests that while cam abnormalities may create increased bony impingement/abutment that can result in soft tissue damage,52 symptomatic FAI does not appear to be associated with lower hip ROM. Recent studies investigating the effect of FAI-related bony deformities in athletic populations have also reported a non-significant influence of cam on hip rotation ROM53 ,54 and all other directions of movement.54 It is possible that computer simulations or X-ray studies that rely on direct bone contact to predict impingement may be unrealistic.45 It might also reflect that some studies evaluated participants postsurgery, which may have influenced the results. Surgical interventions had no significant effect on hip ROM. Evaluation of ‘within-group’ studies describing surgical intervention to remove the cam abnormality32 ,34 indicated no significant changes to ROM. Surgery to restore hip ROM should be questioned in light of these findings. Thus, while further high-quality studies are clearly needed, the best available evidence suggests that ROM is not impaired in individuals with symptomatic FAI and should not be the primary target for treatment regimes.

Hip muscle function was impaired in those with FAI. The six studies where SMD could be calculated22 ,26 ,29–31 ,33 indicated that with the exception of hip extension strength in two studies26 ,30 and hip flexion strength in one study,31 there were significant between-group differences in all hip muscle strength measures favouring the control group. Why hip flexion and extension were exempt from strength changes in these papers remains to be identified. One study showed significant difference in hip flexor EMG activity in individuals with FAI compared with controls.30 However, the EMG amplitude in this study was not normalised to a submaximal or maximal contraction reference value and the validity of comparing raw EMG signals between groups is not considered valid because it can be affected by factors such as adiposity, position of electrodes and skin impedance.55 Another study showed significant increase in TFL cross-sectional area of the non-injured leg.31 The impingement pain induced by symptomatic FAI3 ,48 may play a role in inhibiting muscle contraction around the hip. Studies have shown experimentally induced knee joint pain reduces flexion and extension muscle strength by 5–15% compared with the control conditions56 and patients suffering with knee OA reported 20–40% less quadriceps strength than healthy controls.57 For sufferers of knee OA, resistance training may increase strength by 5%–71%57 and has been shown to be beneficial for sufferers of hip OA.58 The strength deficits noted in this study suggest that programmes to improve strength may provide a positive rehabilitation intervention for both presurgical and postsurgical symptomatic FAI sufferers. There are no studies comparing temporal EMG measures such as muscle contraction onset, offset and duration. Further studies are required to investigate strength and muscle activity in individuals with symptomatic FAI across all movement directions and should include asymptomatic control groups that have been imaged to ensure absence of cam abnormalities. These studies may include measuring preoperative muscle strength and progress to follow muscle strength changes through postoperative rehabilitation programmes.

Functional task performance was not impaired in individuals with symptomatic FAI. While there was no difference in static balance on one leg with eyes closed between individuals posthip arthroscopy compared with controls, the same patients demonstrated reduced balance via increased medial–lateral sway and worse anterior–posterior control during a dynamic single-leg squat task.27 The control groups used were only age, sex and physical activity matched for one study.27 One study had low numbers of controls significantly older than the symptomatic group and defined only by age,35 the remaining study matched only by age and body mass.44 A lack of consistency in the control groups makes it difficult to have confidence in the validity of between-group differences reported. These findings are similar to those in a recent study by Charlton et al59 that reported patients' posthip arthroscopy having increased frontal plane hip adduction and knee valgus compared with controls. The authors suggested that this may perpetuate impingement load in the hip during single leg functional tasks and called for targeted rehabilitation programmes to improve lower limb control during these tasks.59 Biomechanically, some studies suggest that symptomatic FAI affects walking by reducing speed60 and limiting ROM in the sagittal and frontal planes46 ,60 ,61 as well as reducing peak hip extension, abduction,46 ,61 adduction and internal rotation during the stance phase of gait.60 These findings contradict the conclusions of this review where no significant difference was noted in ROM between individuals with symptomatic FAI and normal controls. It should also be noted that normal gait does not require hip joint motion to end of range, so non-significant ROM reductions should not affect gait by restricting movement. More studies are required in functional limitations in individuals with symptomatic FAI.

This review enhances the body of literature examining the physical impairments and functional limitations within sufferers of symptomatic FAI. When reviewing the physical impairments and activity limitations in individuals with FAI impingement, Diamond et al15 reported decreased ROM into directions of hip joint impingement, altered sagittal and frontal plane hip ROM during gait, altered sagittal plane hip ROM during stair climbing, and decreased hip adductor and flexor muscle strength. The conclusions of this paper differed. While 9 out of the 14 papers cited by the Diamond study were included in this review, five were excluded as not having clinically used measures of strength and ROM. The current review included evidence gained from an additional 13 papers; these data resulted in a different conclusion regarding the effect of symptomatic FAI on ROM and function. The use of ES measures has allowed an unbiased appraisal of existing literature to clarify physical examination findings that can be expected during the objective assessment of individuals presenting with symptomatic FAI. These important findings can be used to develop rehabilitation programmes for conservative management and postsurgical rehabilitation. Emara et al25 suggest modifications to those activities of daily living that may be exacerbated by FAI and maintaining function within ‘safe range of movement’ as a means of improving function and reducing symptoms. Other modifiable impairments such as greater hip flexion range and adduction strength have been associated with higher quality-of-life patient-reported outcome scores in patients with chondrolabral pathology 12–24 months posthip arthroscopy.11 Programmes targeted at improving these specific impairments as well as other strength and functional movement patterns around the hip may help improve functional outcomes for those with symptomatic FAI.

This review was able to use 22 articles in an area of rapidly expanding research, some with conflicting observations. Studies were eligible for inclusion if they contained human participants with symptomatic FAI assessed using preoperative diagnostic imaging techniques or hip arthroscopy; had at least five participants and examined physical impairments of the hip. In an effort to make this paper clinically relevant, only papers including measures of ROM and strength were reviewed. Despite meeting these criteria, some of the inclusions may have suffered from relatively small sample sizes and poorly described methodology. As 15–29% of the population62–65 have asymptomatic cam-type abnormalities, their potential inclusion within the control group may have affected results. When examining the evidence for the effect of symptomatic FAI, all papers containing ‘impingement-related pathology’ were included. Restricting searches to the English language may have potentially omitted studies that could have been included in this review and the findings should be interpreted in light of these limitations. It is recommended that future populations studied need more specific diagnostic labelling to be able to examine the differences between specific patient groups. There is an urgent need for RCT designs to address questions related to differences between groups for different types of interventions. Future research should also examine the relationship between symptoms and impairments in symptomatic FAI.

The strengths of this review include using a thorough search strategy, comprehensive evaluation of multiple databases and usage of the Downs and Black checklist to appraise the methodological quality of included studies.18 This has adequate reliability and validity for assessing non-randomised studies. This review also included the calculation of SMDs, ensuring an unbiased evaluation of ESs, taking into account sample sizes and variability of data within individual studies. The authors acknowledge the limitations of the use of ESs only based on case–control studies, not based on RCTs (as there are no RCTs within this topic). Any systematic review is limited by the quality of the studies included in the review. While the studies in this manuscript scored reasonably well on the quality appraisal tool, all studies included were only case–control and case-series studies. As stated in the recent editorial by Weir et al,66 this limits the overall confidence in the findings presented. Areas for future research should aim at providing a better understanding of the ROM, strength and functional limitations encountered by sufferers of symptomatic FAI. These studies should include age, weight, sex and activity matching of controls and participants as well as radiographic screening to prevent the inclusion of asymptomatic cam abnormalities among the controls which may potentially compromise the normal data.

Conclusion

Individuals with symptomatic FAI demonstrate deficits in hip muscle strength when compared with the normal population and pre/post treatment interventions, as well as reduced dynamic balance on one leg. However, no RCTs have evaluated the effect of different types of interventions for symptomatic patients with symptomatic FAI. Limiting this review to measures of movement, with exclusion of kinematics in gait, the authors found hip joint ROM did not appear to be altered in individuals with symptomatic FAI compared with control participants. This differs from previously published findings that incorporated laboratory measures of ROM. In the papers assessed, there was no other compromise of function in squatting, total daily strides or static balance. Further research is needed to determine whether symptomatic FAI affect other aspects of functional performance; and to evaluate whether targeted strength training or skill acquisition interventions can improve hip muscle strength and physical function in symptomatic FAI.

What are the findings?

  • Femoroacetabular impingement (FAI) is associated with pain and reduced quality of life. Physical impairments can be associated with worse symptoms and may be an important target of rehabilitation programmes in this patient group. Knowledge regarding physical impairments in individuals with symptomatic FAI is limited.

How might it impact on clinical practice in the future?

  • Individuals with symptomatic FAI demonstrate impairments in hip muscle strength and dynamic single leg balance. This information may assist therapists in providing targeted rehabilitation programmes for individuals with symptomatic FAI.

Acknowledgments

Kate Croft (Queensland and School of Health and Rehabilitation Sciences, University of Queensland, Australia) assisted in reviewing the quality of papers included in this manuscript.

References

View Abstract

Footnotes

  • Twitter Follow Joanne Kemp at @JoanneLKemp and Adam Semciw at @ASemciw

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement All the data used in this paper were sourced from the publications included in the References section and is available online.

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