Diagnosis of femoroacetabular impingement (FAI) has increased significantly over the past decade. There are three types of hip impingement, including Cam, Pincer, and mixed or combined type.
Cam impingement is an abnormality whereby the femoral neck is aspherical, and the lack of roundness in the neck inhibits normal ranges of motion in the hip joint, causing a larger bone lesion to form, abutting against the acetabulum. Cam lesions can be congenital, but in adolescent athletes, this may represent a previously undiagnosed slipped capital femoral epiphysis (SCFE) with posterior displacement due to high pressures from intense activity before the age of 14.
SCFE is most often “silent” in the adolescent athletic population, as the diagnosis often comes historically from the diagnosis of a Cam deformity and/or lumbopelvic/hip dysfunction many years later.1-2
Pincer impingement is an abnormality whereby the acetabulum overhangs, causing an abutment of the acetabulum on the otherwise normal femoral neck. This abutment creates a bony lesion that decreases ranges of motion and inhibits normal mechanics around the hip joint.1-2
Mixed or combined-type FAI is the most common type of hip impingement, a mix of both Cam and Pincer lesions in varying degrees on a case-by-case basis. FAI can be unilateral or bilateral and is three times more common in males.1-2
Common Symptoms
The history of symptoms in a patient with FAI can vary greatly. Common hip symptoms can include, but are not restricted to, decreased range of motion (with internal rotation being the most limited), anterior hip pain with deep hip flexion or repetitive motions, pain in the “C” cup distribution around the hip joint, a deep ache within the hip joint after activity, or a groin strain. Intra-articular-related lesions are often reported as sharp and stabbing with loaded rotational movements such as cutting and pivoting.
Most commonly, a patient with FAI will present with concurrent disorders that are compensatory and often include low back pain, dysfunction and repetitive strain and stress injuries of the gluteal musculature, repetitive groin strain, trochanteric bursitis, sacroiliac joint dysfunction, and osteitis pubis. Femoroacetabular impingement is often associated with an increased pelvic incidence angle.1
Low back pain may be the patient’s chief complaint; they are often unaware that hip dysfunction is the root cause of their pain.
Appropriate Diagnosis
History, physical examination and imaging are valuable in diagnosing FAI appropriately. Orthopedic testing can include the log test and anterior impingement test. An anteroposterior pelvis and Dunn view radiographs can be obtained to evaluate for FAI. The Dunn view evaluates the aspherical Cam lesion, although it has limitations depending on the location of the Cam lesion.
High-resolution magnetic resonance imaging (MRI) can also be used to diagnose FAI lesions and other intra-articular lesions, including labrum tears. 3T MRI scans are very sensitive and allow for evaluation of the labrum when magnetic resonance arthrography (MRA) is unavailable.1-3
Individuals with FAI are at an increased risk for both labral tears and early-onset osteoarthritis within the hip joint.1,3,4 Asymmetrical forces on the articular cartilage of the hip joint can cause early osteoarthritic changes, like the asymmetrical forces on the anterosuperior labrum, causing premature degeneration and tearing due to the pathomechanics of FAI.
Hip-Spine Syndrome
“Hip-spine syndrome” was coined in the 1980s and describes a condition whereby a deformity at the hip creates an environment for increased pelvic incidence angle and hyperlordosis of the lumbar spine. An anteverted acetabulum creates an overhang of the acetabulum on the femur. It reinforces an increased pelvic tilt to avoid the abutment at the leading edge of the joint complex and, thus, avoid hip pain.
Increased pelvic incidence angle directly correlates to increased lumbar hyperlordosis, directly impacting the comorbidities associated with lumbar spine hyperlordosis.4 Prolonged neuropatterning of this posture can create adaptive shortening of the anterior hip capsule and posterior ligaments of the spine, and increased forces on the lumbar facet joints.
Hyperpronation of the Foot
With the collapse of the medial longitudinal arch of the foot, increased tension is placed on the plantar fascia and tibialis posterior during hyperextension. The compensatory imbalance of the lateral structures of the lower leg leads to hyperpronation of the foot, an altered biomechanical movement that has implications along the entire kinetic chain.5
In three-dimensional gait studies of individuals with FAI, data supports an increase in hindfoot varus position at heel strike and a reduction in maximum hindfoot eversion during the stance phase, leading to hyperpronation of the subtalar joint.6
In a recent study, the pelvic angle of women with subtalar hyperpronation was measured before and after wearing functional foot orthoses. The study supported that by decreasing the distance of medial longitudinal arch collapse with functional foot orthoses, the pelvic angle was decreased.5
The Link / Treatment
FAI, hip-spine syndrome, and foot hyperpronation can be difficult conditions to treat. FAI can lead to premature osteoarthritis, which has an enormous economic impact. Individuals with FAI often have significant low back pain related to increased pelvic angle and hyperpronation of the subtalar joint.3
Custom foot orthoses in individuals with subtalar hyperpronation demonstrate a decrease in the pelvic angle, which can positively influence low back pain and hip pathomechanics. Treatment of FAI, hip-spine syndrome, and hyperpronation of the subtalar joint should include, but is not limited to, a trial of soft-tissue mobilization, spinal and extraspinal manipulative therapies, and rehabilitative exercise prescription.
Custom flexible orthotics should be considered in the early management of these conditions to improve function and decrease pain, while increasing the efficacy of other interventions.
References
- Byrd JW. Femoroacetabular impingement in athletes: current concepts. Am J Sports Med, 2014 Mar;42(3):737-51.
- Siebenrock KA, Ferner F, Noble PC, et al. The Cam-type deformity of the proximal femur arises in childhood in response to vigorous sporting activity. Clin Orthop Relat Res, 2011 Nov;469(11):3229-40.
- Harris-Hayes M, Royer NK. Relationship of acetabular dysplasia and femoroacetabular impingement to hip osteoarthritis: a focused review. PM R, 2011 Nov;3(11):1055-1067.e1.
- Okuzu Y, Goto K, Okutani Y, et al. Hip-spine syndrome: acetabular anteversion angle is associated with anterior pelvic tilt and lumbar hyperlordosis in patients with acetabular dysplasia: a retrospective study. JBJS Open Access, 2019 Jan 29;4(1):e0025.
- Park K. Effects of wearing functional foot orthotics on pelvic angle among college students in their 20s with flatfoot. J Phys Ther Sci, 2017 Mar;29(3):438-441.
- Hetsroni I, Funk S, Ben-Sira D, et al. Femoroacetabular impingement syndrome is associated with alterations in hindfoot mechanics: a three-dimensional gait analysis study. Clin Biomech, 2015 Dec;30(10):1189-93.
