FAI: An emerging problem in orthopedics that can have a major clinical impact
Back when I was a high-school tailback 150 lbs soaking wet the only hip problems I remember were groin pulls and hip pointers. Decades later, everything became a labral tear. Sure, dysplasia was recognized as a cause of hip pain and labral tears. But not until relatively recently has the connection between athletes, hip problems and labral tears come together with femoroacetabular impingement (FAI). It is difficult to talk about labral tears without mentioning impingement in the same breath, and vice versa.
FAI has emerged as an entity with profound clinical impact, sidelining weekend and professional athletes alike, perhaps even being the number one recognizable cause of early hip osteoarthritis. The condition and its current treatment options span hip reconstructive surgery and sports medicine.
I decided to gather two hip arthroscopic surgeons who shaped my own practice (one arthroscopically shaped my hips), a joint reconstruction surgeon with extensive expertise in open FAI surgery, and one of the foremost authorities in basic science orthopedic research, particularly as it applies to the hip. In this first of a two-part Round Table discussion, I ask these experts to teach us about the latest concepts and controversies in the management of hip labral tears and FAI.
Dean K. Matsuda, MD
Dean K. Matsuda, MD: We are hearing that isolated hip labral tears are quite uncommon. What are your thoughts?
Philip C. Noble, PhD: By isolated labral tears, I assume that we are referring to lesions of the labrum or the labro-cartilaginous junction that occur in the absence of morphologic abnormalities of the femur or the acetabulum. Naturally this statement could be completely true or completely false, depending how critically we define the morphologically normal hip.
We know that labro-cartilaginous lesions are common, especially in old age, with a prevalence of 60% to 80% reported in postmortem studies. Similarly, morphologically abnormal hips seem to have become remarkably common over the last decade with the increasing interest of musculoskeletal radiologists in FAI.
In a recent study we found that the normal femur, as conventionally defined, was relatively rare in men. Yet, in adults older than 55 years of age, the prevalence of symptomatic hip osteoarthritis (OA) is reported to be only 5% to 7%. This suggests that many individuals have silent labral pathology and silent, or clinically insignificant, bony abnormalities of the pelvis and femur. It is the connection between the two that appears to be fuzzy.
In circumstances where physical activities place abnormal loads on the labrum, usually at the extremes of the motion arc, labral pathology can be generated or exacerbated and lead to hip symptoms. If these activities are repetitive, joint degeneration may develop.
Our experiments on joint positions and labral strains show that in extension and mild flexion, large strains can develop at the anterior-superior labralchondral junction without bony impingement. This correlates nicely with McCarthys observations that labral lesions commonly occur without FAI in a population of athletic patients. Conversely, Philippon has shown that in groups of patients who routinely load the hip in a flexed position (eg, hockey goalies), labral injury is associated with chronic femoroacetabular impingement.
This concept of multiple mechanisms leading to hip OA is supported by cadaver studies of degenerated hips. We have examined a series of subjects with early degenerative joint disease (DJD) in which the majority have clear limitation of hip motion secondary to FAI, but approximately one-third of the cases have normal hip motion with labral pathology arising from some cause other than bony impingement.
Based on these observations, I believe that hip OA is a multifactorial disease which occurs when a series of risk factors coincide, including acetabular and femoral dysmorphia, soft-tissue laxity, the mechanical properties of the cartilage and labrum, the immunologic susceptibility of each patient to inflammatory mediators, and imposed loading and posture. The most important of these factors are the loads and positions imposed on the joint by functional activities.
Marc J. Philippon, MD: In our database of over 1,700 hip arthroscopies, we have no documented cases of isolated labral tears in primary hip arthroscopies. We found that 86% of all labral tears are associated with mixed cam- and pincer-type impingement, 9% were associated with isolated cam impingement, and 5% associated with isolated pincer impingement. Forty-percent of the labral tears were associated with hip instability; however, we are currently trying to identify which type of instability is associated with certain labral tears.
Thomas G. Sampson, MD: In my practice of hip arthroscopy going back to 1984 we have treated many labral tears, however, in most cases these were accompanied with other pathologies. I believe what we called labral tears were in many cases labro-cartilaginous tears of the acetabulum as well as delaminations of the articular cartilage. Isolated tears were seen in less than 10% of the patients. We saw many tears associated with DJD.
Image: Sampson TG
Prior to 2001, we did not scrutinize X-rays as we do today looking for the elements of FAI. Today, labral tear is the most common diagnosis on MRIs in my referred patients. Many MRIs are of inadequate quality and have to be repeated; however, most often I spent a great deal of time showing the patient that what they really have is a labral-cartilage junctional tear or degeneration form of FAI and not an isolated labral tear. MRA with gadolinium may be helpful, but I prefer to see an MRI so I can determine if the painful side has an effusion.
Regarding the relationship of developmental dysplasia of the hip and FAI, remember that plain X-rays may show a narrow center-edge angle or false profile, however, the impinging rim is anterior where it is difficult to image. At surgery, whether I have or have not imaged the rim osteophyte with X-rays, CT or MRI, I will always look for an anterior rim lesion and have found it more often than not even if it was not seen with imaging.
Robert T. Trousdale, MD: We feel that the majority of labral tears are secondary to structural problems about the hip joint and have some data published in the orthopedic literature that support this fact. We retrospectively looked at all the labral tears at the Mayo Clinic over a period of time and found that more than eight out of 10 patients had concurrent structural problems. One can easily envision both impingement problems and dysplasia putting more stress on the labrum and leading to labral pathology.
Matsuda: What is the relevant basic science to support or refute labral preservation surgery?
Noble: The hip labrum plays a critical role in keeping the head of the femur reduced within the acetabulum, in maintaining lubrication of the joint and in serving as a soft bumper at the limits of motion. Nerves within the labrum also provide potential for proprioception.
As in the shoulder, venting of the labrum greatly reduces the resistance to distraction and frank dislocation. The mechanism of labral stabilization has been demonstrated in our experiments and in several elegant studies by Ferguson and Ganz. They show that labrum forms a seal for joint fluid through contact against the femoral head, and the effectiveness of this sealing function is reflected in the force needed to displace the head within the socket.
As the labral seal keeps synovial fluid between the articulating surfaces, a healthy labrum increases the hydrodynamic component of lubrication which keeps friction to a minimum. It also protects against overload of the chondral surface and the underlying bone during episodes of sudden impact as larger instantaneous loads can be supported before fluid is displaced from the zone of articulation.
Our experiments have shown that the labrum also undergoes significant strain during activities involving abduction and external rotation around the neutral position. Once the labrum is vented and torn, micro-instability ensues with 1-mm to 1.5-mm increased anterior displacement of the femoral head within the acetabulum. This change in the mechanical environment may directly lead to cartilage overload and the onset of DJD, although the relationship between micro-instability and cartilage health is not well understood.
These observations and the clinical results of Beck and Espinosa support the conclusion that labral excision is undesirable and should be regarded as the meniscectomy of the hip. However, from a basic science perspective, labral reattachment poses some unique challenges because of the lack of vascularity, the frequency of secondary hip deformities and the different patterns of labral pathology.
Studies of labral vascularity report differing conclusions; however, all authors agree that the more central (articular) two-thirds of the cross-section of the labrum are avascular. Whether the remainder of the labrum has any vascularity is a subject of debate; however, it is agreed that the fibrous tissue covering the capsular surface is a potential source of blood supply after refixation.
Given this situation, it is conceivable that reattachment of the labrum will only occur along the capsular edge of the tissue and that the strength of the reattachment will be determined primarily by the sutures rather than the bridging tissue. Although Phillipon has reported encouraging results in professional athletes in the short term, the properties of the labral reconstruction remain unknown.
Another question which will only be answered with long-term follow-up is the fate of the joint after labral reattachment. Espinoza and Leunig have shown that hip symptoms and function dramatically improve with labral preservation. It is unknown whether this beneficial outcome arises from increased stability of the joint, or improvements in lubrication and the distribution of articular pressures. An even more important question is whether it can be assumed that these symptomatic improvements necessarily indicate that the onset of OA has been significantly delayed and, if so, for how long?
One explanation of the connection between labral pathology and chondral degeneration is that separation of the labral-chondral junction provides access for joint fluid to the subchondral boundary which serves as a breach of the protective outer layer of the cartilage. This often leads to chondral delamination and rapid development of an unsalvageable joint. If the key event in this scenario is access of fluid to the chondro-labral junction, formation of a mechanically stable labral reconstruction may be sufficient to minimize mechanical symptoms but may not block the progression of joint degeneration.
It has still to be demonstrated that current methods of labral reattachment restore the original fluid barrier formed by the junction between the labrum and the articular surface, thereby protecting the subchondral boundary from ingress of pressurized joint fluid.
Matsuda: What is the relevant clinical science to support or refute labral preservation surgery?
Philippon: The literature continues to grow to support labral preservation. Ferguson and colleagues showed that contact stresses in acetabular cartilage increase with time, and are up to 92% higher in the absence of the labrum.
Another study shows labral disruption and DJD of the hip were related. Espinosa and colleagues showed that labral repair resulted in 80% excellent outcomes, while debridement only had excellent outcomes in 28%.
Image: Matsuda DK
Labral debridement was compared to refixation in patients with FAI in a recent study by Larson and colleagues who found good to excellent results in 66.7% of the patients in the labral debridement group vs. 89.7% in the labral refixation group. They concluded based on their early results, labral refixation resulted in better outcomes.
We recently completed a study on 112 patients with FAI and labral pathology at a minimum of 2 years postoperative. Their preoperative modified Harris Hip score (MHHS) was 58. Fifty-eight patients underwent labral repair and 54 underwent debridement. The labral repair group had a postoperative MHHS score of 87 compared to 81 in the labral debridement group. Labral repair was identified as an independent predictor of improved MHHS in this group. The median patient satisfaction in this cohort was nine on a scale of 1 to 10 with 10 being very satisfied.
As new studies show the importance of labral tissue, we have set a threshold of 7 mm of labral width that needs to be present for a repair. As the width of the labral tissue decreases (due to previous debridement or degeneration), so do the changes in the joint and treatment options. On these data, we think it is critical to preserve the native labrum using repair techniques when possible.
Trousdale: The relative clinical data to support labral preservation vs. labral debridement is actually quite scant. There are some retrospective data with relatively small numbers that suggest labral preservation is better than labral debridement, but we really do not have good long-term outcome studies to support the fact that labral refixation is better than labral debridement.
Yet, from a theoretical sense it is a good judgment to try to preserve the labrum when possible. The labrum serves an important function including deepening the socket and preserving the fluid seal in the hip joint which is probably important for long-term cartilage viability. Certainly in young active patients it is reasonable to consider trying to save the labrum whenever possible.
Matsuda: How do you diagnose labral tears and FAI?
Philippon: We perform a standard physical exam, range of motion and specific tests to diagnose labral tears and FAI. Tests for FAI include: the anterior impingement test, posterior impingement test, and the Faber distance examination a measurement of the distance from the lateral genicular line in the knee to the exam table. These are complemented by radiographs: cross-table lateral radiographs to assess the anterior femoral head-neck offset (alpha angle) and AP pelvis radiographs to evaluate the acetabulum for the amount of coverage of the femoral head and the degree of version.
Classifications of cam- and pincer-type impingement are based on radiographic images and MRI. Acetabular retroversion or coxa profunda indicate pincer-type impingement and an alpha angle of greater than 42º is considered positive for cam impingement.
Joint space is measured preoperatively on an AP pelvis radiograph at three locations: the lateral, center and medial edge of the sourcil. This is a crucial step in the evaluation process. Joint space of less than 2 mm is considered a relative contraindication for most hip arthroscopies. In our study, those with joint space less than 2 mm were 39 times more likely to progress to total hip arthroplasty.
A special sequence alpha angle MRI is also completed to further document the alpha test. Our research has shown that the MRI alpha angle is more accurate than radiographs. Currently we use a 3T MRI and are determining the sensitivity and specificity of this instrument for the diagnosis of labral tears.
We also use a pain test, where lidocaine is injected into the hip joint to determine if symptoms are intra-articular or extra-articular. A functional sports test is performed before and after surgery to see if symptoms affect performance and function.
Sampson: I diagnose labral tears and FAI by first listening to the patients history of insidious onset of groin pain, which may or may not have some related old sprain. Usually the patient will have positional pain, mostly with sitting, that is relieved with hip extension. He or she may have an unpredictable pop on occasion and little pain with walking; however, when performing sports that involve twisting and flexing, the hip becomes painful.
Second, I notice that the exam is mostly normal except for loss of internal rotation and abduction compared to the opposite hip. The patient may have a positive impingement sign with flexed internal rotation. Those with a partial delamination defect may also have pain in the same location when bringing the leg up from extension, internal rotation to flexion external rotation.
Imagine when doing the impingement test that the acetabulum is like the face of a clock. In a right hip, if directly lateral from the tip of the trochanter is 12 oclock, the clock face from 1 oclock to 4 oclock may be zones 1 and 2 where most delaminations are seen. If the delamination is attached at 4 oclock, then with clockwise rotation the cam bump will catch it, cause pain and snap. On the other hand, counterclockwise rotation may cause pain but no snap will occur.
Along with these findings, plain radiographs including a proper AP pelvis X-ray including hip-to-below-the-lesser-trochanters with the coccyx 1 cm to 2 cm from the pubis symphysis, and frog and cross-table laterals should give clues to the cam and pincer morphology.
CT scans are great, but involve a lot of radiation. They help map out the lesions. I like a high-quality MRI of the affected hip only not a pelvis MRI, which is essentially worthless. I order MRAs if the hip has no effusion to act as contrast.
I do an injection test if I am not clear as to whether the pain is from the hip. If a patient has a gadolinium MRA with anesthetic and says he or she had no relief from the test, you need to follow up with the right question Did you have any relief of the hip pain at the time of the MRA or directly afterwards? Also, it needs to be determined if a long-acting, instead of short-acting, anesthetic agent was used.
Trousdale: The role of history, physical examination, and appropriate imaging studies, all are important. In general, the history and physical examination are relatively nonsensitive and nonspecific tests. Catching, locking, groin pain, pain with flexion and internal rotation, and pain with apprehension of the hip all indicate potential labral problems, impingement problems, or dysplasia and are relatively nonspecific findings.
The plain radiographs, which in our center include a good AP pelvic, a true lateral, an oblique, and a false-profile view, are the gold standard for diagnosing bony abnormalities.
For labral and chondral pathology, the best test in our minds is an MRI with intra-articular gadolinium. There are centers that are looking at the sensitivity and specificity of MRI without intra-articular gadolinium. In the future with appropriate software technology, this may become very reliable. Presently we get both sagittal, coronal, and radial MRI views of the hip joint which is probably the most sensitive and specific for labral and chondral pathology.
A note from the editor:
Part 2 of this Round Table discussion will appear in the July issue.
For more information:
- Dean K. Matsuda, MD, can be reached at Southern California Permanente Medical Group, Kaiser West Los Angeles Medical Center, 6041 Cadillac Ave., Los Angeles, CA; 323-857-4477; e-mail: email@example.com. He has intellectual property rights with ArthroCare.
- Philip C. Noble, PhD, can be reached at Institute of Orthopedic Research & Education, 6550 Fannin-Smith Tower, Ste. 2512, Houston, Texas 77030; 713-441-3010; e-mail: firstname.lastname@example.org. He receives royalties from Smith & Nephew, Stryker and Zimmer; is a paid consultant or employee of, and receives research or institutional support from Smith & Nephew and Zimmer; and receives miscellaneous non-income support from Biomet, Smith & Nephew and Zimmer.
- Marc J. Philippon, MD, can be reached at 181 W Meadow Drive, Ste. 400, Vail, CO 81657; 970-476-1100; e-mail: email@example.com. He receives royalties from Smith & Nephew and Bledsoe; is on the speakers bureau and is a paid or unpaid consultant for and receives non-income support from Smith & Nephew and receives institutional or research support from Smith & Nephew and Ossur.
- Thomas G. Sampson, MD, can be reached at Post Street Orthopaedics and Sports Medicine, 2299 Post St., Suite 107, San Francisco, California 94115-3443; 415-345-9400; ew-mail: firstname.lastname@example.org. He receives royalties from Smith & Nephew.
- Robert T. Trousdale, MD, can be reached at Mayo Clinic, 200 First St. SW E14B, Rochester, MN 55905; 507-284-3663; e-mail: email@example.com. He receives research or institutional support, miscellaneous funding and royalties from and is a consultant to DePuy and he is a consultant to Wright Medical Technology.