Acetabular Labrum

Femoral Head Arthritis

FIGURE 2.3. A 20-year-old man with a 3-month history of acute left hip pain. (A) AP radiograph demonstrates findings consistent with old Legg-Calve-Perthes disease. (B) Lateral view defines the presence of intraarticular loose bodies (arrows). (C) CT scan substantiates the intraarticular location of the fragments (arrows). (D) Arthroscopic view medially demonstrates the loose bodies.

FIGURE 2.3. A 20-year-old man with a 3-month history of acute left hip pain. (A) AP radiograph demonstrates findings consistent with old Legg-Calve-Perthes disease. (B) Lateral view defines the presence of intraarticular loose bodies (arrows). (C) CT scan substantiates the intraarticular location of the fragments (arrows). (D) Arthroscopic view medially demonstrates the loose bodies.

(E) Viewing anteriorly, the anterior capsular incision is enlarged with an arthroscopic knife to facilitate removal of the fragments.

(F) One of the fragments is being retrieved. (G) Loose bodies can be removed whole. (E and F, JWT Byrd. Arthroscopy, December 2003, with permission.)

and natural history. This may partly explain why the results of surgical intervention, although often good, are not uniformly successful.

Labral tears were first reported in the literature as a detachment associated with posterior dislocation of the hip, serving as a block to reduction or source of recurrent instability.13-15 Altenberg, in 1977, was the first to report on labral pathology as a cause of hip pain in absence of a dislocation episode.16 He described two cases treated with open debridement.

The labrum is a fibrocartilaginous rim that encompasses the circumference of the acetabulum, effectively deepening the socket (Figure 2.4). The ring is incomplete inferiorly where the labrum ends at the anterior and posterior margins of the inferior aspect of the acetabular fossa, becoming confluent with the transverse acetabular ligament. The acetabular labrum has not been studied as extensively as has its counterpart, the glenoid labrum of the shoulder. Functionally, it may not be quite as complex, but it is susceptible to acute tearing and degeneration.17,18

The constrained ball-and-socket bony architecture of the hip provides much more inherent stability than the glenohumeral joint. Although the acetabular labrum may not be as critical to this stability, it undoubtedly has an important role in the distribution of forces across the articular surfaces of the joint.17 Additionally, a normally positioned labrum is critical to normal acetabular development, as animal studies have shown that aberrant positioning of the labrum leads to dysplasia and osteoarthritis.19

Seldes et al. reported in detail the anatomy, histo-logic features, and vascularity of the adult acetabular labrum.20 They described that the capsule attaches directly to the bony rim of the acetabulum with a distinct separation from the labrum (Figure 2.5). Thus, integrity of the labrum does not appear to be as critical to stability of the hip as compared with the cap-sulolabral complex in the shoulder. It is likely that the labrum still has a role as a fluid seal, creating a vacuum effect to enhance stability, but labral lesions do not appear to be as synonymous with instability of the hip as compared with the shoulder. These authors also observed that labral degeneration occurs as part of the aging process and identified microvascular proliferation in conjunction with tears, suggesting some capacity for healing.

McCarthy et al. correlated their clinical observations on labral tears with an anatomic study and made the following observations.21 Tears begin at the articular labral junction, an area that they term the watershed region. They observed that the labrum receives its blood supply from the obturator, superior gluteal, and inferior gluteal arteries. These vessels en-

Artritic Femoral Head
FIGURE 2.4. Acetabulum and the fibrocartilaginous labrum.
Femopral Head Articular Cartilage Cover
FIGURE 2.5. Relationship of the acetabular labrum and capsule as described by Seldes, including the bone of the acetabulum (B), labrum (L), articular cartilage (A), the tide mark (TM), and capsule (C).

ter through the synovium at the reflection of the capsule onto the peripheral surface of the labrum, penetrating only the outermost layer of the labrum on its capsular side. They also observed that labral lesions are almost uniformly present in elderly cadaver specimens.

Arthroscopy has defined considerable morphologic variation of the labrum. Sometimes it is thin and hypoplastic and other times robust in size. This variation is most evident in the presence of acetabular dys-plasia in which the labrum is markedly enlarged, assuming a weight-bearing role and importance in stability of the joint.

The greatest variability of the labrum is found lateral and anterior. The posterior labrum exhibits the most consistent morphology and is the least often damaged. Early arthroscopic literature from Japan reported a propensity for posterior labral tears.22-24 However, this observation has not been supported by more recent literature in which most tears have been observed laterally and anteriorly.23-25 This discrepancy may reflect unique aspects of the population or may simply be aberrant because of the small study groups reported.

Villar et al. have developed a classification system for labral tears categorized according to etiology (traumatic, degenerative, idiopathic, congenital, or dysplastic), morphology (radial flap, radial fibrillated, longitudinal, peripheral, or unstable), and location (anterior, posterior, or superior).25 However, regardless of the tear pattern, these lesions uniformly occur at the articular labral junction. Accompanying articular damage has variously been reported to be present in 50% of the cases by Glick, 48% of the cases by Villar, 55% of cases by Byrd, and 73% of cases by McCarthy.12,21,26,27 McCarthy also found that only 6% of articular lesions did not have accompanying labral pathology.

The labrum is also susceptible to abnormal variations such as inverted position entrapped within the joint. Inversion can occur with or without accompanying acetabular dysplasia. The exact mechanism by which the labrum becomes inverted is unclear, whether it is congenital or acquired in early life. By the time symptoms occur as a result of tearing of the inverted portion, it is noted to be a long-standing process. However, we have also observed this as an acute phenomenon in which an intact labrum became trapped and was treated by simple arthroscopic reduction.

Dorrell and Catterall28 have documented an increased incidence of inverted acetabular labra associated with severe hip dysplasia. We have found that lesser degrees of labral inversion and subsequent tearing may be associated with lesser degrees of dyspla-sia. This concept has been furthered by Klaue et al.,29 who also reported labral tearing associated with milder degrees of hip dysplasia. However, they described treatment by periacetabular osteotomy. We suspect that arthroscopic debridement could be equally effective in alleviating symptoms with considerably less morbidity. Arthroscopic debridement in the presence of dysplasia should be performed in a conservative fashion. Excessive debridement could potentiate instability and accelerate secondary degenerative wear. However, debridement of the damaged portion can result in significant symptomatic improvement with results comparable with those seen in nondysplastic hips.

Harris et al. reported the presence of an inverted acetabular labrum as a source for subsequent development of osteoarthritis.30 More recently, we have defined clinical and radiographic features characteristic of osteoarthritis due to an inverted labrum.31 This condition may occur with or without accompanying radiographic evidence of acetabular dysplasia. Once os-teoarthritis has developed, the results of arthroscopy are no better in the presence of an inverted labrum than for other forms of degenerative arthritis. It is an intriguing concept that perhaps early arthroscopic intervention for the inverted labrum could delay the subsequent development of osteoarthritis; however, currently no data support that earlier intervention appreciably alters the natural course of this degenerative process. Debridement may improve the symptoms, but will not necessarily change the long-term outlook.

Detachment of the acetabular labrum has been reported in the literature. Nishina et al. described this by arthrography in a series of patients undergoing

Chiari pelvic osteotomy.32 Klaue et al. observed this in a series of periacetabular osteotomies performed for acetabular rim syndrome, and Fitzgerald reported on this in his 20-year experience of acetabular lesions treated by both arthrotomy and arthroscopy.29,33 However, we have observed a labral cleft to occur as a common normal variant (Figure 2.6).34 The separation of the labrum and acetabulum can be deep without representing a pathologic lesion. It is important not to misinterpret this normal variant as a traumatic detachment.

The pathomechanics of acute labral tears are incompletely understood but are most commonly attributed to a twisting injury. Acute tearing of a healthy labrum seems to represent a minority of cases; thus, underlying degeneration should be suspected with most cases. Degeneration may be present even in relatively young adults. The ability of magnetic resonance imaging (MRI) and gadolinium arthrography with magnetic resonance imaging (MRA) to detect labral pathology is improving, with sensitivities greater than 90%. However, the specificity is more suspect, with false-positive interpretations as high as 20% among MRAs in our series. Additionally, the study by Lecouvet et al. demonstrated MRI evidence of labral pathology in asymptomatic volunteers, and the incidence increased with age.35 Tanabe has shown by electron microscopy that the labrum is susceptible to senile degenerative changes associated with the aging process, which is consistent with the work of Seldes et al. and McCarthy et al., who, in separate cadaveric studies, each demonstrated 96% prevalence of labral lesions in specimens averaging 78 years of age.17,20,21 Also of note, although MRIs are improving

Normal Anterior Labral Cleft Hip
FIGURE 2.6. Example of a normal labral cleft. Viewing the right hip from the anterior portal, the probe has been placed in the separation between the labrum (L) and lateral aspect of the bony ac-etabulum (A).

at showing labral tears, they remain poor at detecting any accompanying articular damage. Subtle radiographic findings, such as slight joint space narrowing, are often a harbinger of advanced articular wear.

The results of labral debridement (partial labrec-tomy) are often gratifying but are not uniformly successful even among experienced surgeons. Glick reported only 46% good results at an average 34-month follow-up, but the presence of radiographic evidence of arthritis was a significant influencing variable.26 In the absence of arthritis, there were 71% good results, and only 21% when arthritis was present. Villar reported 67% patient satisfaction at an average 3.5 years follow-up with this procedure.27 Moderate chondral damage was present in 48% of cases, but in his series this did not influence the results. We reported an average 20-point improvement (modified Harris hip score) among patients with 5-year follow-up.12 Fifty-five percent had associated chondral lesions. No statistical difference was identified between those with and without chondral damage, but the power of the study may have been insufficient to detect a difference.

Arthritis Joint Pain

Arthritis Joint Pain

Arthritis is a general term which is commonly associated with a number of painful conditions affecting the joints and bones. The term arthritis literally translates to joint inflammation.

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Responses

  • gaudenzia marchesi
    What is an acetabular labrum?
    4 years ago
  • negassi
    Where is the labral chondral junction in the hip?
    3 years ago
  • mohamed
    Where is the anterosuperior labral?
    12 months ago

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