Conservative management of femoroacetabular impingement
A case study and rationale for treatment
– Written by Joanne Kemp and Kay Crossley, Australia
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The hip joint and FAI as a cause of groin pain
In recent times the hip joint has been recognised as a significant cause of hip and groin pain in the athletic population1. It accounts for approximately 12% of soccer-related injuries2 and is the third most common injury in the Australian Football League3. Groin pain is frequently reported in those with hip pathology attending for arthroscopy, evidenced by 92% of patients with labral tears4. The most common site of pain referral in people with labral tears has been reported as the central groin region5.
Hip pain often coexists with other groin-related pathologies, including pubic and adductor symptoms, which can make definitive diagnosis and appropriate management difficult and often multi fact-orial1. Recent studies have found that 94% of athletes with long-standing adductor-related groin pain have radiological signs of femoroacetabular impingement (FAI)6,7.
FAI describes a morphological variant seen in approximately 20% of the general population8 and has been comprehensively described in recent years9-11. Three types of FAI are commonly described:
· Cam lesion which describes a reduced femoral head-neck offset, resulting in additional bone most commonly seen on the anterior, superior or antero-superior aspect of the femoral head- neck junction11.
· Pincer impingement. This refers to bony change seen in the acetabulum and can either present as a deep acetabulum which is most commonly seen anteriorly8,12 or as a retroverted acetabulum, which leads to an apparent deeper anterior acetabular wall.
· Mixed presentation where both cam and pincer lesions are seen.
Where does the pain come from?
Whilst FAI is not considered to be hip pathology, it is recognised as an anatomical variant within a normal range13,14 that may increases the risk of intra-articular hip pathology, including labral tears and chondropathy15-23 and contribute to the development of groin pain8,24. When the hip joint with FAI is placed into a position of impingement in a repetitive fashion during sporting activities, micro-trauma may occur in the hip. The presence of FAI has been shown to be associated with labral tears, most likely due to impingement of the labrum between the bony components of the hip18,21. Moreover, the presence of FAI and labral pathology may lead to an increased risk of chondropathy and ultimately hip osteoarthritis (OA)22. This increased risk is possibly due in part to the increased loads placed on the acetabular chondral surfaces when the function of the labrum is compromised25. Damage to the labrum and the acetabular chondral rim, particularly in the anterior and superior aspect of the joint, may lead to tissue breakdown and ultimately hip and groin pain.
PHYSICAL IMPAIRMENTS AND HIP JOINT LOADS IN PEOPLE WITH FAI
An understanding of the physical impairments seen in people with FAI may assist in the development of appropriate rehabilitation programmes. Hip muscle strength and hip range of motion (ROM) have been examined in people with labral pathology26 and with FAI27-29. These studies all demonstrate reductions in hip muscle strength and hip joint ROM in those with pathology. It is unclear whether this reduction in strength is associated with pain or pathology. There is limited, but emerging, evidence suggesting altered biomechanics of the hip and pelvis are present in people with FAI, which may partially explain the association between FAI and groin pain. Recent studies have demonstrated reduced pelvic30 and hip29,31 movement in the sagittal plane in people with FAI. In addition, a cadaveric study reported that rotational motion at the pubic symphysis is greater in hips with cam impingement, leading to increased opening of the anterior aspect of the pubic symphysis32. Combined, these findings may indicate that an increased load through the anterior aspect of the pelvis may be present in those with FAI, with potential to contribute to the development of groin pain.
Physical impairments such as hip muscle strength and ROM may also alter intra-articular hip loads33,34. Hip muscles, including gluteus medius, gluteus maximus, iliopsoas and the adductors contribute to forces and impulses in the anterior and superior aspects of the hip35. Strength in particular muscles may optimise loads within the joint and conversely weakness in hip muscles may load the hip in a detrimental fashion. For example, Lewis et al reported weakness in the gluteal muscles36, which contribute to hip extension, external rotation, internal rotation, adduction and abduction moment33,34,36 and weakness in iliopsoas36, which contributes to hip flexion, internal rotation and abduction moments34. Lewis et al reported that such weaknesses may increase load in the anterior aspect of the hip joint36. As muscle function is altered in the presence of pain and pathology27,37-39, resultant changes in hip joint load may increase hip pain. Suitable rehabilitation strategies may have the potential to modify hip joint loads and potentially mitigate the progression of hip and groin pain in FAI.
Similarly, ROM may impact on load within the hip. Hip flexion35,40 and hip extension36 may increase load on the anterior36,40 and superior35 regions of the hip. As the majority of FAI lesions and associated hip pathology occur in the anterior and superior regions of the hip11, loads associated with these regions of the hip requires consideration. Reduced hip internal rotation, flexion and abduction ROM have been reported in people with symptomatic FAI28. Range of motion may be limited in this group if movement at the end of range loads damaged tissue in a manner that provokes pain. Minimising loads on FAI and damaged labrum and chondral tissue in people with hip pain through the optimisation of hip muscle strength and ROM may enhance outcomes41.
MANAGEMENT OF FAI
Cam-type FAI is now commonly treated by femoral osteoplasty via either hip arthroscopy or an open surgical approach42. Outcomes for hip arthroscopy with femoral osteoplasty appear to be favourable for up to 3 years post arthroscopy42. However, most studies examining outcomes for hip arthroscopy are case-series evidence only42. In addition, no studies to date have compared the effectiveness of hip arthroscopy vs conservative management. Furthermore, there is limited evidence as to what constitutes the most effective conservative management for FAI43. Current strategies for the conservative management of FAI are based on the knowledge of physical impairments in people with FAI. To date, rehabilitation programmes have been reported in the literature as clinical protocols only, therefore the programme described in this article is an expert opinion based on clinical experience and in interpretation of the literature in this field. Generally, rehabilitation programmes focus on modifying adverse hip joint forces, created by abnormal hip morphology and pathology. This can be achieved by modifying both hip muscle function and external joint loads, as well as providing appropriate education and advice. Figure 2 outlines the relationship between these factors.
Hip muscle function
Modifiable physical impairments such as hip muscle strength may alter hip joint loads, impacting on pain, function and disease progression. Improving hip muscle strength appears to be an important treatment goal in order to optimise hip joint loads. A number of studies have suggested exercises to activate the hip abductors44,45, hip extensors45,46 and rotators47 in healthy people without pain. It has been suggested that improving muscle strength in hip muscles in people with hip pathology may reduce hip joint loads and subsequent progression of hip OA41. No studies have directly measured the effect of hip strengthening interventions on outcomes in people with hip pathology such as labral pathology or FAI or following hip arthroscopic surgery.
Recent studies have described the roles of hip muscles, with respect to muscle morphology, primary action of joint movement and lines of pull in relation to the axis of joint movement33,34,48. Importantly, these studies have described differing roles, with some muscles having greater capacity to generate torque over larger ranges of motion (prime movers), while other muscles are better placed to act as joint stabilisers. These concepts are based on sound principles of kinesiology, examining muscle physiological cross-sectional area in relation to muscle fibre length and lines of pull in relation to the axis of joint movement33,34,48. The primary stabilisers of the hip are thought to provide a posterior, medial and inferior force on the femur, ensuring the head of the femur is located in a position within the acetabulum to minimise stress on potentially vulnerable structures such as the anterosuperior acetabular labrum and the anterosuperior acetabular rim, while maximising the neuromotor control of the hip41. The primary stabilisers of the hip include iliopsoas, gluteus medius, gluteus maximus, quadratus femoris, obturator internus, inferior and superior gemelli and adductor brevis and pectineus41.
Once adequate control of the deep hip stabilisers has been attained, a staged hip strengthening programme can be undertaken. Generalised hip strengthening exercises should initially be undertaken with specific activation of the deep stabilisers prior to completing the exercise. This ensures that the athlete has adequate control of the hip prior to placing it under load, which will assist in protecting vulnerable or damaged structures within the hip. Generalised hip strengthening exercises should be undertaken based on clinical assessment. Hand-held dynamometry can be used to reliably assess hip muscle strength49,50. Exercises are frequently commenced in prone (to ensure specificity and isolation of muscle activations) and then progressed into functional/weight-bearing positions. Strengthening exercises need to be targeted to the needs of the individual, progressed according to patient responses and targeted to the sporting/physical requirements51.
There is minimal evidence directly examining the influence of type or volume of activity on hip joint loads. However the type of activity undertaken may influence hip joint loads, partially due to the intensity of activity9, but also possibly due to hip ROM undertaken during certain activity. Lewis et al reported an increase in anterior hip joint forces when the hip joint extended beyond 10° of ROM36. This force increased when weakness in the gluteal muscles or iliopsoas was present. Therefore it appears that hip joint loads can be modulated by the type as well as the amount of activity. The influence of amount of activity undertaken by people with hip pain and pathology on hip joint loads has not been directly measured. However, a greater volume of high impact activity is associated with an increased risk of hip OA52. This may indirectly reflect a progression in hip joint degeneration associated with increased hip joint loads53. Rehabilitation programmes for people with symptomatic FAI should include strategies to address the volume and intensity of activity undertaken. Moreover, extremes of hip rotation, particularly in combination with hip extension or hip flexion should be reduced in order to minimise potentially pain-inducing loads.
In conclusion, the evidence supporting the best conservative management for FAI is limited. Given the rapid increase in interest in this condition, knowledge of appropriate rehabilitation programmes will most likely grow in the coming years. Conservative management of symptomatic FAI focuses on decreasing adverse hip loads through the implementation of hip muscle strength programmes and modification of external joint loads. This may result in a lessening of symptoms associated with this condition.
Acknowledgements: The authors would like to acknowledge Bodysystem Hobart Australia for permission to use the images contained in this article.
Joanne Kemp M.Sports Physio., B.App.Sc.(Physio) ,Ph.D.
Kay Crossley B.App.Sc.(physio), Ph.D.
School of Health and Rehabilitation Sciences
University of Queensland
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Image via Jos Dielis