Biplanar radiography in femoroacetabular impingement syndrome (FAIS): abetween- and within-participants case-control study

Presenter’s name (Last, First): Murphy, Nicholas

Qualifications: MBBS, BA, BMedSc

Affiliations: 1) Kolling Institute of Medical Research, Sydney Musculoskeletal Health, University of Sydney. 2) Department of Orthopaedic Surgery, John Hunter Hospital, Newcastle.

Other authors:
Jillian Eyles PhD, Venkatesha Venkatesha PhD,James M Linklater FRANZCR, Sonika Virk MSc(Hons)Biochemistry, Libby Spiers BSc(Phty), JohnO’Donnell FRACS, Peter Wilson FRACS, David J Hunter PhD


Background / Introduction:

Radiologic measurements of femoroacetabular impingement syndrome (FAIS) poorly discriminate those with symptoms from those without. Biplanar radiography (EOS) enables measurement of spinopelvic and version parameters in functionally relevant postures, which may better discriminate.


Questions: (i) In people with FAI morphology, which parameters measured on standing EOS scans distinguish symptomatic cases from asymptomatic controls? (ii) In people without FAI morphology, which parameters distinguish those with symptomatic acetabular labral tears (ALT) from asymptomatic controls? (iii) Which parameters distinguish the symptomatic from asymptomatic hip in patients with unilateral FAIS/ALT? (iv) In patients with FAIS/ALT, how does pelvic tilt change with hip flexion, and which bony pelvic morphology measures are associated?

Patients / Methods:

This unmatched case-control study compared 3D EOS measurements between patients with FAIS/ALT (cases) and asymptomatic controls. All participants had standing biplanar EOS radiographs, and cases had additional radiographs in 90° hip flexion and modified Dunn view. Logistic regression determined parameters distinguishing (i) symptomatic from asymptomatic participants with FAI morphology, (ii) symptomatic from asymptomatic participants with no FAI morphology. Paired samples t-tests compared the symptomatic and asymptomatic hips for cases with unilateral symptoms. Linear regression investigated associations between pelvic bony morphology and change in pelvic tilt with hip flexion


The 97 participants (age:45.5±15.9;67% female), comprised 35 cases and 62 controls. In participants with FAI morphology, increased standing pelvic tilt distinguished symptomatic from asymptomatic participants (OR:1.22;95%CI:1.04,1.44;p=0.015). In participants without FAI morphology, decreased standing sacral slope distinguished symptomatic from asymptomatic participants (OR:0.83;95%CI:0.71,0.97;p=0.022). No differences were detected between symptomatic and asymptomatic hips in cases with unilateral symptoms. Fourteen of 32 (44%) cases anteriorly tilted their pelvis with symptomatic hip flexion. Cases with larger pelvic incidence (beta coefficient=-0.19;95%CI:-0.31,-0.07;p=0.004) and greater acetabular anteversion (beta coefficient=-0.64;95%CI:-1.28,-0.01;p=0.046) tended to anteriorly tilt the pelvis with hip flexion.

Standing pelvic tilt and sacral slope distinguished cases from
asymptomatic controls more accurately than bony morphology measures such as anteroposterior alpha angle. Anterior pelvic tilt with hip flexion was observed in 44% of FAIS/ALT patients, a maladaptive movement pattern promoting bony femoroacetabular conflict.

Level of Evidence & Study type: 3 Case-control

Declarations of Conflict: DJH is a consultant to Pfizer, Lilly, TLC Bio and Merck Serono and is supported by an NHMRC Investigator Fellowship. The remaining authors have no conflicts of interest to declare.