Femoroacetabular Impingement Flashcards
Femoroacetabular impingement (FAI) syndrome is a …
…motion-related clinical disorder of the hip involving premature contact between the acetabulum and the proximal femur and which results in particular symptoms, clinical signs and imaging findings. Degenerative changes and osteoarthritis may develop in the long-term as a result of this abnormal contact.
Mechanism of Injury / Pathological Process
FAI syndrome is associated with certain variations in the morphology of the hip joint. Cam morphology describes a flattening or convexity of the femoral head neck junction.This morphology is more common in men
Pincer morphology describes “overcoverage” of the femoral head by the acetabulum in which the acetabular rim is extended beyond the typical amount, either in one focal area or more generally across the acetabular rim.This morphology is more common in women.
It is important to note that these morphologies are thought to be fairly common (around 30% of the general population), including in people without hip symptoms. Raveendran et al (2018) found that 25% of men and 10% of women had evidence of cam morphology in at least one hip while 6-7% of men and 10% of women demonstrated pincer morphology in their longitudinal cohort study.[5] Thus the isolated presence of either cam or pincer morphology is insufficient for a diagnosis of FAI syndrome
Both types of morphology can lead to damage to the articular cartilage and the labrum due to impingement between the acetabular rim and the femoral head during movement, hence causing the symptoms of FAI syndrome. Metabolic analysis of tissue samples by Chinzei et al (2016) suggested that articular cartilage may be the main site of inflammation and degeneration in hips with FAI and that if OA progresses, metabolic activity spreads to the labrum and synovium and labrum.
Given that cam and pincer morphologies can be present in asymptomatic individuals, Casartelli et al (2016) propose that other factors outwith the bony structures may be involved with FAI syndrome. Weakness of deep hip muscles could not only compromise hip stability but also lead to overload of secondary movers of the hip, thus causing an anterior glide of the femoral head into the acetabulum and increased joint loading. Repeated loading of the labrum in this may could lead to upregulation of nociceptive receptors in that structure through the production of neurotransmitters such as substance P
Etiology (possible Influencing Factors)
Intrinsic factors, given 1) radiological findings of FAI-associated morphologies among subjects those with affected siblings and 2) higher instances of cam morphology in men and pincer morphology in women
Exposure to repetitive and often supraphysiologic hip rotation and hip flexion during development in childhood and adolescence (e.g. hockey, basketball or football).
Repeated stress of this type may trigger adaptive remodeling and eventually development of FAI-associated morphologies and symptoms
History of childhood hip disease (e.g. slipped capital femoral epiphysis (SCFE) or Legge-Calve-Perthes disease) which may have altered the shape of the femoral head
Malunion following femoral neck fractures which may have altered the contour of the femoral head/neck
Surgical over-correction of conditions such as hip dysplasia may lead to the pincer morphology
Clinical Presentation
Patients with suspected FAI syndrome typically report stiffness and pain in the hip and/or groin. Heterogeneity of diagnostic criteria in past research has meant that it has been difficult to ascertain the full scope of physical impairments stemming from FAI.
However, pain from FAI is commonly held to be aggravated with acceleration sports as well as squatting, climbing stairs and prolonged sitting. With FAI that may have advanced to hip osteoarthritis, signs and symptoms more typical of this condition may be identified.
In the Warwick Agreement on FAI syndrome published in 2016, the authors noted that a particular triad of symptoms, clinical findings and imaging findings are required for a diagnosis of FAI
Clinical Findings
Various pain-provocation hip impingement tests are used clinically but flexion adduction internal rotation (FADIR) is the most commonly used test and is sensitive but not specific.The FADIR position of provocation is associated with impingement at the anterior rim of the acetabulum.
Pain associated with the posterior rim can be provoked by passively bringing the hip from flexion to extension while maintaining a position of hip abduction and external rotation with the leg hanging off the examination table.
Hip ROM is often restricted, most commonly internal rotation with the hip flexed.[2] However, Diamond et al (2015) noted that in some studies, controls were not imaged for asymptomatic FAI thus caution is needed with generalizing these results and further research will help clarify the impact of FAI on hip ROM.
Frangiamore et al (2017) recommended assessing the single limb squat to identify hip abductor weakness as well as reproduction of pain with hip flexion (which could be FAI or other intra-articular pathology).
Similarly, they recommended assessing stair ascending and descending since this this requires greater hip flexion than walking on a flat surface.
Differential Diagnosis
Acute hip pain due to tumour, infection, septic arthritis, osteomyelitis, fracture and avascular necrosis are red flag conditions that should be ruled out. In athletes, other causes of hip pain include inguinal pathology, adductor pathology and athletic pubalgia.
Management / Interventions
To date, hip arthroscopy has commonly been utilized but early reports tended to be limited to cohort-level, typically showed only short-term benefits and were usually authored by surgeons, thus introducing the possibility of population bias
n addition, Peters et al (2017) stated that they found heterogeneity in the surgical criteria reported in the literature leading them to question whether the same condition was in fact being treated in all studies.They found that only 56% of the reviewed studies included at least one surgical criterion from each of the three categories recommended in the Warwick Agreement.
As well, the vast majority of the studies (92%) included diagnostic imaging as a criterion, yet there is currently no consensus on specific imaging modalities or cut-off values to determine when surgery is indicated.Failed conservative treatment was found to be an infrequent surgical criterion in this review.The issue of heterogeneity of diagnostic and surgical criteria in the research has been raised by multiple authors.
Reiman and Thorburg (2015) likened the rapid increase in surgical correction for FAI to the rise in shoulder arthroscopies between 2000 and 2010 which was not based on quality evidence. They summarized the state of research on FAI as follows: “clinical impressions of improvement from treatment often appear favourable, but these impressions can be deceiving when valid outcome measures, spontaneous recovery and/or placebo effects are not accounted for
Thus, these various issues should be considered when trying to determine the best course of action for a patient with FAI syndrome. As per the Warwick Agreement on FAI syndrome (2016), the authors stated that “[t]here is currently no high-level evidence to support the choice of a definitive treatment for FAI syndrome” therefore all options should be considered for each patient and an approach should be selected based on a shared decision-making process. In the meantime, high quality research should be conducted to clarify the effectiveness of surgical versus on-surgical treatment of FAI and also to determine if corrective surgery can prevent OA as is proposed
Conservative Management
Casertelli et al (2016) suggest that improving neuromuscular function of the hip should be a goal of conservative protocols for FAI syndrome due to weakness of deep hip musculature and an expected subsequent reduction in dynamic stability of the hip joint.These authors recommend including hip-specific and functional lower limb strengthening, core stability and postural balance exercises.
To improve dynamic stability of the hip, there should be a focus on strengthening the deep hip external rotators, abductors and flexors in the transverse, frontal and sagittal planes.With this approach, the authors propose that for at least some patients with symptomatic FAI, loading of the labrum could be reduced which would then facilitate downregulation of nociceptive neurotransmitters in the labrum.
As well, strengthening could help with more generalized inflammation in the hip joint that is commong with FAI syndrome
