Journal of Orthopedics & Rheumatology

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Review Article

Femoroacetabular Impingement and Labral Tear Management: Review of Current Literature and Techniques

Charles J Cogan*, John Tuttle, Vehniah K Tjong and Michael A Terry

  • Department of Orthopaedic Surgery, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
*Address for Correspondence:Charles J Cogan, Department of Orthopaedic Surgery, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA, Tel: 630-212- 0324; E-mail: Charles.cogan@northwestern.edu
Citation: Cogan CJ, Tuttle J, Tjong VK, Terry MA. Femoroacetabular Impingement and Labral Tear Management: Review of Current Literature and Techniques. JOrthopedics Rheumatol. 2017; 4(1): 6.
Journal of Orthopedics & Rheumatology | ISSN: 2334-2846 | Volume: 4, Issue: 1
 
Submission: 6 April, 2017| Accepted: 8 May, 2017 | Published: 20 May, 2017

Abstract

The incidence of hip pain in the adult is fairly common, accounting for roughly 10% of visits to sports medicine physicians annually, and the origin of the pain is often elusive. For the active patient, femoroacetabular impingement (FAI) is a common cause of hip pain, and related labral pathology further contributes to impairment. It is thought that bony overgrowth of the acetabular rim (pincer lesion) and femoral neck (CAM lesion) are responsible for impingement symptoms, which can evolve into a labral tear over time. The standard approach for treating these bony overgrowths for many years has been osteoplasty of both CAM and pincer lesions, but evidence is emerging that treatment of pincer lesions alone may be just as efficacious. Both FAI and labral pathology are treatable conditions by the orthopaedic surgeon with the goal being restoration of hip joint function, decreasing patient pain, and preventing early osteoarthritis.

Keywords

Hip pain; Femoroacetabular impingement; CAM; Pincer; Labrum; Arthroscopy; Repair

Introduction

Hip and groin pain encompass a wide variety of pathology, including both intra and extra-articular injury of the intra-articular injuries FAI, labral tear, and osteoarthritis are amongst the most common in physically active patients, accounting for roughly 40, 33, and 24 percent of hip pain, respectively [1]. Annually, roughly 10 percent of patient seeking care with a sports medicine physician present with hip or groin pain [2]. Furthermore, even with the exclusion of osteoarthritis, nearly 14 percent of patients over age 60 report significant hip pain on a weekly basis [3]. Despite their common incidence and frequency these injuries can be easily misdiagnosed or overlooked. One study demonstrated that patients with intra-articular hip pathology saw on average 3.3 healthcare providers, defined in this study as physicians, chiropractors, physical therapists, and nurse practitioners, before definitive diagnosis, thus making recognition and triage of patients with suspected hip joint pathology important for providers who may be encountering this problem [4].
The labrum is a fibrocartilaginous ring of tissue along the circumferential edge of the acetabulum, and it functions to provide stability to the joint by deepening the acetabular socket and creating a negative pressure seal keeping the femoral head in articulation with the acetabulum [5,6]. FAI is a clinical entity characterized by bony overgrowth of the femoral neck (CAM lesion) and/or acetabular rim (pincer lesion), which leads to pain with range of motion at the hip and eventual osteoarthritis development [7]. The relationship of FAI, labral tear, and osteoarthritis is thought to progress along a spectrum, with FAI contributing to an eventual labral tear, and an unstable, injured labrum paving the way for premature osteoarthritis [8]. Thus the treatment of these diseases is centered around not only improving hip joint function and decreasing pain, but also preventing the premature development of osteoarthritis. Over the last decade, the paradigm of treatment has shifted from the once gold standard of open repair to the less invasive modality of arthroscopic surgery, which has aided in providing symptomatic relief of anatomical abnormalities and prevention of premature OA while minimizing complications from surgery. The purpose of this article is to further discuss the evolution and pathophysiology of damage to the hip joint from FAI as well as to elucidate current trends and strategies in arthroscopic treatment.
Femoroacetabular Impingement
FAI is the clinical syndrome resulting from abnormal articulation of the anterior femoral neck and the acetabular rim, often leading to compression of the acetabular labrum. This process occurs as a result of bony overgrowth on either the femoral neck or the acetabulum. There are three types of impingement lesions: pincer, CAM, or mixed. The underlying etiology of the osseous deformities contributing to FAI remains unclear, but both genetic and acquired causes have been proposed in recent literature [9-13]. The basis for the genetic investigation of a cause for FAI stems from studies that have shown a much larger propensity for white as compared to Asian populations to develop osteoarthritis [14-16]. A variety of genetic studies exist analyzing single nucleotide polymorphisms related to hip development and morphology [9,10] however, a recent review by Packer and Safran suggests that insufficient evidence exists to confirm the genetic influence of developing FAI, and the primary cause, particularly for CAM type lesions, seems to be related to an acquired risk from high level athletic participation from a young age [13]. One study by Kapron et al. examined radiographs of 134 hips in Division I NCAA football players and found that 95 percent of hips had evidence of FAI [17]. Similar studies have identified a high prevalence of CAM type lesions for athletes participating in ice hockey, basketball, and soccer [12,18,19]. Based upon these and similar other studies,Packer and Safran suggest CAM lesions development during physeal development throughout adolescence [13].
CAM impingement results from a non-spherical articulation of the femoral head with the acetabulum, most often due to bony abnormality at the femoral head-neck junction [20]. In CAM impingement, there is articulation of an abnormal femoral headneck junction with the anterior superior portion of the acetabular rim causing symptoms of impingement, particularly in flexion and internal rotation [21,22]. Damage to the labrum occurs in a distinct pattern in CAM impingement. Shearing forces of the non-spherical femoral head abutting against the chondrolabral junction lead to separation of the labrum from the acetabular cartilage, while the labrum remains grossly unharmed [23]. Certain radiographic signs can also clue the clinician in to CAM lesions in a suspecting case of FAI. Reduced femoral head-neck offset, defined as the maximal. anterior radius of the femoral head compared to that of the adjacent femoral neck, is a hallmark of CAM type impingement, best seen on frog-leg lateral views (Figure 1) [24,25]. This reduced offset is classically measuredwith the “alpha angle”, which is defined as the angle between the femoral neck axis and a line from the center of the femoral head through the point along the femoral head where asphericity of the head-neck junction begins (Figure 1) [22]. A normal “alpha angle” has been considered between 55 and 60degrees, though a cut-off of 55 degrees is more commonly accepted [26]. Another common finding in CAM impingement, known as the “pistol-grip deformity” can best be seen on AP view, which is due to the reduced femoral head-neck offset resembling the smooth handle of a pistol (Figure 2) [25].
JOR-2334-2846-04-0030_fig1
Figure 1: CAM impingement with a measured alpha angle on frog-leg lateral radiograph.
JOR-2334-2846-04-0030_fig2
Figure 2: Pistol grip deformity shown by green arrows.
Pincer type impingement results from either a focal or global over-coverage of acetabular rim over the femoral head, which results in abutment (Figure 3) [8]. In a pincer type lesion, the labrum itself is not spared because it is being compressed between the femoral neck and the acetabular overhang, especially at extremes of movement. Multiple studies have shown that eventual ossification of the labrum can ensue as a result of such repeated microtrauma, which further contributes to the acetabular over-coverage [23,27,28]. Chronic impingement of the femoral neck with the anterosuperior acetabular rim, especially when ranged through forceful flexion, classically leads to a ‘countre-coup’ chondral lesion at the posteroinferior acetabulum [8]. As impingement occurs over time, the femoral head begins to sublux posteriorly, increasing pressure between the posteromedial femoral head and the posteroinferior acetabulum [23]. The combination of these forces, primarily the compressive force at the anterosuperior labrum, ultimately lead to labral tearing and damage (Figure 4). Radiographic evidence of pincer type lesions can also support the diagnosis. The “crossover sign” can be seen in pincer type impingement. This is when tracing the anterior and posterior edges of the acetabulum shows an intersection prior to the superiormost aspect of the acetabular rim (Figure 5). The degree of acetabular overcoverage is typically measured by the lateral center-edge angle, first described by Wiberg in 1939, which is the angle between avertical line and a line connecting the center of the femoral head to the lateral edge of acetabular rim from an AP radiograph [29]. A center edge angle less than 25 degrees is considered dysplastic, whereas a center edge angle greater than 39 degrees is suspicious for acetabular overcoverage [29].
JOR-2334-2846-04-0030_fig3
Figure 3: Pincer impingement seen on AP radiograph. Bony overgrowth highlighted with green arrow.
JOR-2334-2846-04-0030_fig4
Figure 4: Intraoperative picture of anterior labrum tear. Green arrows mark labral tear. Labrum (L), acetabulum (Ac), femoral head (FH).
JOR-2334-2846-04-0030_fig5
Figure 5: Normal hip on left. Crossover sign on right. Blue line is anterior wall, red line is posterior wall.
Although studies have shown distinct radiographic and anatomic differences between CAM and pincer lesions, the majority of patients present with a mixed scenario. One study that examined 302 hips showed only 26 with an isolated CAM lesion and 16 with an isolated pincer lesion [23]. The mixed presentation offers a unique challenge to the orthopaedic surgeon as they plan to offer the greatest surgical benefit with as little intervention as necessary. Recent evidence supports the notion that fixing the pincer lesion along with a labralrepair while leaving the CAM lesion alone can offer an equal surgical outcome with less associated morbidity. One study of 106 hips with combined-type FAI showed that at 2 year follow-up, patients who received acetabuloplasty and labral repair alone were equivalent to outcomes in the literature for acetabuloplasty and femoroplasty with labral repair [30]. The advantage of an isolated acetabuloplasty for combined-type FAI includes potential avoidance of complications such as avascular necrosis, heterotopic ossification, and femoral neck fractures.
Labral Tear
While FAI is the underlying disease process in patients presenting to clinic, acetabular labral tears are the likely cause of patient pain due to the presence of abundant free nerve endings. Labral tears are the most common indication for arthroscopic surgery [8,31,32]. Much like in the shoulder, the primary function of the acetabular labrum is to stabilize the hip joint. Not only does the labrum deepens the socket for the femoral head to articulate with the acetabulum, but it also functions to create a negative pressure seal, which keeps synovial fluid in the intra-articular space [23,33]. Much like a meniscus in the knee, the labrum also functions as a shock absorber, decreasing stress on the joint itself [34]. Although plain radiographs are routinely obtained when acetabular labral pathology is suspected, the most accurate diagnostic tool remains MR arthrogram [35,36]. One study that compared pre-operative MR arthrogram findings to intraoperative surgical findings showed 92% accuracy for labral lesions and 89-94% accuracy for acetabular chondral lesions [37]. When faced with ambiguous symptomatology, MR arthrogram offers the opportunity to inject the hip with local anesthetic for additional diagnostic assistance (Figure 6).
JOR-2334-2846-04-0030_fig6
Figure 6: MR arthrogram showing tear of the superior labrum.
Management
Initial management of a suspected labral tear resulting from FAI is typically physical therapy, anti-inflammatory medications, and activity modification. However, for many patients this does not adequately treat the problem. A recent cost effective analysis has shown that hip arthroscopy is a more cost effective option for 94.5% of patients with an acetabular labral tear, and their risk to develop symptomatic osteoarthritis or require a total hip arthroplasty is cut in half [38]. While the gold-standard of treatment was once open repair, the paradigm over the last decade has shifted to arthroscopic repair. There is still debate about exactly what type of arthroscopic procedures are most effective, but they often involve addressing both the labral tear and the bony abnormalities. Treatment of the labral tear initially mimicked treatment of torn menisci in the knee, including some combination of debridement or repair. However, recent evidence supports moving away from debridement alone and moving toward repair of the labrum to the acetabular rim; this leads to improved patient reported outcome measures and decreased conversion to total hip arthroplasty [7,8,39]. Some studies have shown that addressing the labral pathology alone would lead to failure rates of up to 92% if the underlying bony abnormalities causing impingement are not corrected [40,41]. Many treating physicians will debride both the CAM and pincer lesions, but recent evidence shows that debridement of the pincer lesion alone provides equal benefit without the added possiblemorbidity of femoral osteoplasty, including avascula necrosis, heterotopic ossification, and femoral neck fractures [30].
Another aspect of surgical management that has been debated recently in the literature is the outcomes of older patients undergoing hip arthroscopy. Traditionally studies have shown that older age was an independent risk factor for conversion to total hip arthroplasty [42,43]. Recent studies, however, are suggesting that osteoarthritis might be a confounding variable in this prior conclusion, as older patients with minimal or no arthritic changes have demonstrated similar improvements to younger patients after hip arthroscopy [44-47]. Minimal arthritic change is often identified as Tönnis grades 0 to 1 or joint space measurement of greater than 2 millimeters. A recent study examining the outcomes of patients with Tönnis grade 2 showed odds ratio of conversion to total hip arthroplasty of 7.73 as compared to Tönnis grade 0 and 4.36 as compared to Tönnis grade 1 [48]. This data clearly demonstrates the limited role of hip arthroscopy as a joint preservation procedure in patients with Tönnis grade 2 arthritis. Ultimately it seems to be the degree of osteoarthritic joint damage, and not the age of the patient, that determines outcomes from hip arthroscopy.
Arthroscopic Surgical Technique
Patient positioning and setup is an important first step in arthroscopic hip surgery. Patients are typically positioned supine or lateral positioning, and traction is applied to the ipsilateral leg in order to distract the femoral head from the acetabulum (Figure 7). Often general anesthesia is required for the relaxation needed to obtain enough distraction to properly visualize the articular surface. Adequate visualization is obtained with 25 to 50 pounds of traction [49]. Once positioned, proper portal placement is important for visualization and access to the intra-articular space. Three standard portals are used in hip arthroscopy: anterolateral, anterior, and distal anterolateral accessory [50]. The anterolateral portal is primarily used as a viewing portal throughout the procedure, and its placement is in reference to the greater trochanter-1 to 2 cm anterior and 1 to 2 cm superior to the tip of the greater trochanter. The second portal created is the anterior portal, which allows for visualization of the posteriorsuperior labrum and capsule and tends to be the working portal. The location of the anterior portal is placed at the intersection of a line extending horizontally from the anterolateral portal and a vertical line from the anterior superior iliac spine. It is important that this portal be placed bluntly because of the nearby proximity of the lateral femoral cutaneous nerve [50]. The final portal established is the distal anterolateral accessory portal, which is often used for decompression of bony abnormalities in CAM type impingement but also allows for an appropriate angle for acetabular anchor placement.
JOR-2334-2846-04-0030_fig7
Figure 7: Preoperative positioning showing hip traction.
After establishing proper distraction of the femoral head from the acetabulum, the anterolateral portal is established-often under fluoroscopic guidance. Confirmation of proper anterolateral portal placement can be achieved by visualization of the anterior triangle, which is the anterior capsule, labrum, and femoral head [50]. Subsequently, the anterior portal can be placed under direct visual guidance through the anterior capsule.
Treatment of an acetabular labral tear is the most common indication for arthroscopic hip surgery, and is a primary target of intervention for pain relief and improved hip function [8]. Following a standard diagnostic arthroscopy of the hip joint, the labral tear should be addressed by first defining the extent of the tear. Depending on the type of impingement occurring, the labrum may still be attached at the chondral junction. If so, the labrum should be released carefully from the articular cartilage sharply. At this point, in the case of a mixed or pincer lesion, acetabular decompression may be carried out. While removal of the anterolateral edge is important, the concept of volumetric decompression is perhaps more so, thus allowing for unimpeded deep hip flexion while avoiding labral impingement [30]. There is good evidence that labral repair is preferred over debridement whenever possible [7,8,39]. Repair of the labrum is achieved with insertion of suture anchors into the capsular side of the acetabular rim (Figure 8). Anchor position is important to monitor. If the anchor is too proximal, the labrum will be fixed away from the articular surface and may not be optimally functional. If the angle is too steep, the articular cartilage may be damaged or the anchor may be subchondral, leading to articular damage even to the femoral head. If the angle is too shallow, the anchor may not get good bony purchase. Anchors are typically 5-10 mm apart. Multiple suture techniques have been described for labral repair, including looped versus pierced sutures, but recent evidence shows no difference in patient reported outcomes, failure, or revision rates between these different techniques [51].
JOR-2334-2846-04-0030_fig8
Figure 8: Intraoperative photo of anterosuperior labral repair. Labrum (L), Acetabulum (Ac), Femoral Head (FH).

Conclusion

FAI remains a common cause of pain and impaired function for the adult population. While further research is needed to elucidate the underlying etiology of FAI, understanding of its role as a precursor to osteoarthritis has made appropriate and timely management a key to treatment. A growing familiarity with clinical presentation, radiographic features, and intraoperative findings, along with improved surgical techniques over the last decade has made arthroscopic management of FAI and labral tears a safe, effective, and reliable procedure.

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