Total volume of cam deformity alone predicts outcome in arthroscopy for femoroacetabular impingement

  • Sarah H. EllisEmail author
  • Diana M. Perriman
  • Alexander W. R. Burns
  • Teresa M. Neeman
  • Joseph T. Lynch
  • Paul N. Smith



Rates for arthroscopic surgery for femoroacetabular impingement (FAI) are rising and there is growing concern related to the effectiveness and costs associated with this treatment. There is a general lack of consensus as to the criteria for surgical selection of patients. The purpose of this study was to determine whether patient outcome following arthroscopic surgery for FAI could be predicted based on the size and location of deformity. The specific questions were: (1) what is the morphology of FAI in terms of size and location of deformity in a cohort of patients selected for surgery? (2) Do morphological factors predict postoperative improvement in hip scores? (3) Do morphological factors predict preoperative hip scores? (4) Are there clusters of morphological factors which explain postsurgical improvement in hip scores?

Materials and methods

Computer tomography (CT) surgical plans of 90 hips in 79 patients who had undergone primary hip arthroscopy for FAI were retrospectively reviewed. Four parameters for the femur and acetabulum were created: total depth of deformity, maximal depth, extent and the position of maximal deformity. This data were compared with prospectively acquired preoperative and postoperative patient outcome data using generalised linear models.


The cohort comprised 33 males and 46 females aged 37.9 (18–61). The majority (74%) had mixed morphology, 23% isolated cam, and 3% isolated pincer. Overall, the bone depth was greatest and more extensive on the femur. Increased total additional cam deformity alone predicted poorer postoperative outcome (p = 0.045). None of the morphological factors were related to preoperative scores and there was no association between the meta-variables and postoperative outcome.


The results of this study indicate that a greater total volume of cam deformity led to poorer postoperative patient outcome scores at 1 year. This information provides the surgeon with more accurate patient-specific data for prediction of expected outcomes.

Level of evidence

Level III diagnostic.


FAI Hip Impingement Acetabulum Morphology Arthroscopy 



Femoroacetabular impingement


Computer tomography

Dyonics PLAN

Dyonics PLAN Hip Impingement Planning System


International Hip Outcome Tool


Minimal clinical important difference


Author contributions

SE conducted the research, analysed the images, and conducted the analysis and was primarily responsible for the manuscript preparation. DP conceived the research idea, devised, and supervised the research plan, assisted with the analysis and the manuscript preparation. AB contributed to the research plan, advised and supervised the image measurement and contributed to the manuscript preparation. JL contributed to the research plan, analysis, and the manuscript preparation. TN devised the analysis plan and supervised the analysis. PN contributed to the research plan and manuscript preparation. All authors read and approved the final manuscript.


There was no funding recieved for this study.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical approval

Ethics approval for this study was obtained through the Australian Capital Territory Health and Australian National University Human Ethics Committees (ETHLR.13.044 and Human Ethics Protocol 2015/070, respectively).


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Copyright information

© European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA) 2019

Authors and Affiliations

  1. 1.Australian National University Medical School, College of Health and MedicineAustralian National UniversityActonAustralia
  2. 2.Trauma and Orthopaedic Research UnitCanberra HospitalGarranAustralia
  3. 3.Statistical Consulting UnitAustralian National UniversityActonAustralia

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