Injury to the acetabular labrum is a very common cause of chronic, persistent hip pain in young and older patients alike. It is seen mainly in people with intense sporting activity involving a large range of movement at the hip joint, such as martial arts, dance and ballet, but also football and basketball. It is very often associated with the condition of femoroacetabular impingement, in which the abnormal shape of the femoral head or of the acetabulum creates an abnormal pattern of hip movement and an accompanying overuse syndrome.
In the early stages of the condition the treatment is conservative, with painkillers, anti-inflammatory drugs and physiotherapy. When the symptoms are not controlled, however, the most effective treatment for the problem is hip arthroscopy. Arthroscopic treatment of a labral tear not only relieves the symptoms but also has a protective effect, preventing further wear of the joint, that is to say osteoarthritis.
The labrum of the acetabulum has attracted a great deal of interest from hip surgeons in recent years, as it has been shown to be closely linked with the overall health of the joint and with the onset of the first osteoarthritic lesions.1 Its important role in the biomechanics of the joint is now generally accepted, and for this reason great emphasis has been placed in the international literature on the concept of its surgical preservation (preserving surgery) which usually means arthroscopic selective partial excision (partial labrectomy) or repair and stabilisation (labral repair). 2
(1: capsular surface of the labrum, 2: peri-acetabular groove,
3: acetabular bone, 4: articular cartilage,
5: body of the labrum, 6: articular surface of the labrum).
Structure and biomechanical characteristics
If the acetabular labrum is examined under magnification, it can be seen that it is essentially the anatomical continuation of the articular cartilage (Figure 1). The articular cartilage – labrum complex therefore acts as a single surface, providing correct congruity between the femoral head and the acetabulum. For this reason, any damage to the labrum also affects the structure of the articular cartilage and, secondarily, the overall function of the joint.
In vertical cross-section the labrum appears triangular in shape, its base attaching to the bony rim of the acetabulum and to the articular cartilage, while its apex lies free. In many cases part of the bony attachment extends deep into the substance of the labrum. It has two surfaces: the articular surface, which is in continuous contact with the femoral head, and the capsular surface, which together with one side of the capsule forms the peri-acetabular groove.3
The labrum is fibrocartilaginous in composition. Studies have shown that it consists of dense bundles of collagen fibres, resembling a ligament histologically. Chondrocytes have been observed on the articular surface, and fibrocytes within its substance.4
The boundary between the articular surface of the labrum and the articular cartilage, the so-called transitional zone, is the most vulnerable point on the inner surface of the acetabulum, and for that reason it sustains injury perhaps more than any other area.5
Its arthroscopic appearance varies from person to person, both in its dimensions and in its shape. The anterior labrum, however, always differs in basic morphology from the posterior labrum, being broader and thicker, and it is also more vulnerable to tears (Figures 2 and 3).
fairly thick and broader.
In most cases it cannot be distinguished
macroscopically from the articular cartilage
(ΕΧ: labrum, ΑΥ: synovium, ΜΚ: femoral head).
of small thickness, and is clearly distinguished from the acetabular articular cartilage
(ΜΚ: femoral head, ΑΥ: synovium, ΕΧ: labrum).
The biomechanical importance of the acetabular labrum has been described extensively in the literature.6 It appears to contribute to the stability of the joint by providing a seal (sealing effect), creating negative pressure within the joint, maintaining a continuous layer of synovial fluid and distributing loads over a larger surface.
Tears of the acetabular labrum
The recognised causes of a labral tear are femoroacetabular impingement of the cam or pincer type, microinstability of the hip, injury (a single traumatic episode with no underlying abnormal anatomy) and generalised degeneration of the joint. 7
The topography of the micro-anatomy in tears of the acetabular labrum is of particular interest. According to one classification, tears are divided into Type I, in which the articular cartilage separates from the labrum, and Type II, which are found at the free edge of the labrum (Figures 4A, 4B, 5A, 5B, 5C and 5D).8 Tears of the first category have been shown to be more serious, that is those occurring in the labrum – articular cartilage transitional zone, since they extend deeply as far as the subchondral bone and secondarily also cause delamination of the adjacent cartilage flap of the acetabulum.
the tear has occurred in the transitional zone
between the labrum and the acetabular articular cartilage.
involves multiple planes
within the substance of the free edge
of the acetabular labrum
involving the whole substance of the labrum.
with complete disorganisation of the structure of the labrum.
Type I tears are the ones that over time produce progressive damage to the hip joint, as the areas of delamination usually extend further, denuding wider areas of subchondral bone (Figures 6A, 6B, 7A and 7B).
has widened and delamination
of the labrum and the articular cartilage
from the subchondral bone has begun.
the delaminated articular cartilage (ΑΑΧ),
which has not, however, displaced,
appears darker in colour.
both the labrum and the articular cartilage
have delaminated over a large area,
leaving an uncovered surface of subchondral bone.
grade IV chondral lesion on the Outerbridge scale.
The labrum is preserved,
but is completely detached at its base.
These extensive areas of delamination are in effect the first lesions of degeneration of the joint, that is of osteoarthritis of the hip, which may not be visible on radiographs or even on MRI, other than as mild early osteoarthritic changes (the appearance of small subchondral cysts, focal thinning of the articular cartilage).
The treatment of a labral tear
Conservative treatment with anti-inflammatory drugs, rest and physiotherapy always has a place, particularly in the early stages when symptoms first appear. 9 It has been shown, however, particularly in the athletic population, that returning to the level of sporting activity before the tear causes the symptoms to recur. In these cases, where conservative treatment has failed, surgical treatment is recommended.
The modern method of choice for surgical treatment is the arthroscopic technique, by which selective partial excision of the labrum, repair and stabilisation, or reconstruction is carried out. 10 The traditional technique of selective partial excision has shown good results at ten years. 11 With the rise of the concept of hip-preserving surgery, however, the international trend is now to try to preserve the torn labrum wherever this is possible, by repairing and stabilising it with bone suture anchors (Figures 8A and 8B). The aim is to retain this valuable anatomical structure of the labrum, with the ultimate goal of slowing the wear of the joint.
in the bony rim of the acetabulum,
and through the loop of the suture
the labrum is secured.
with a bone anchor and sutures.
In cases with large areas of delamination and chondral defects, it is recommended that the technique of microfracture be used, either to attempt to stabilise the existing cartilage flap or for the potential production of fibrocartilage from the subchondral bone (Figures 9A and 9B).
the microfracture technique is carried out,
aiming to release multipotent blood cells
that will help the cartilage flap to reattach.
the microfracture technique is used
to produce fibrocartilage.
In recent years reconstruction has emerged as an alternative surgical treatment in patients in whom the labrum is absent or extensively destroyed, and when it cannot be repaired. Grafts of iliotibial band, gracilis tendon and ligamentum teres have been used for reconstruction. The early results of the technique appear encouraging. 12
Conclusions
The acetabular labrum has been recognised as a structure of great importance to the hip joint, both for its proper function and for the prevention of early wear. Tears of the labrum may represent the first stage of further structural damage to the joint. The most recent data in the current literature suggest that the view that every effort should be made to preserve it, whether by repair or by reconstruction, is gaining ground.
References
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McCarthy JC, Noble PC, Schuck MR, Wright J, Lee J. The Otto E. Aufranc Award: The role of labral lesions to development of early degenerative hip disease. Clin Orthop Relat Res. 2001 Dec;(393):25-37.Bsat S, Frei H, Beaulé PE. The acetabular labrum: a review of its function. Bone Joint J. 2016 Jun;98-B(6):730-5.
- Seldes RM, Tan V, Hunt J, Katz M, Winiarsky R, Fitzgerald RH Jr. Anatomy,histologic features, and vascularity of the adult acetabular labrum. Clin Orthop Relat Res. 2001 Jan;(382):232-40.
- Walker JM. Histological study of the fetal development of the human acetabulumand labrum: significance in congenital hip disease. Yale J Biol Med. 1981 Jul-Aug;54(4):255-63.
- cCarthy JC, Noble PC, Schuck MR, Wright J, Lee J. The watershed labral lesion: its relationship to early arthritis of the hip. J Arthroplasty. 2001 Dec;16(8 Suppl 1):81-7.
- Tzaveas A, Villar R: Acetabular Labral and Chondral Pathology. The Open Sports Medicine Journal. 2010 Volume 4, pp 64-74.
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Lage LA, Patel JV, Villar RN. The acetabular labral tear: an arthroscopic classification. Arthroscopy. 1996 Jun;12(3):269-72. -
Seldes RM, Tan V, Hunt J, Katz M, Winiarsky R, Fitzgerald RH Jr. Anatomy, histologic features, and vascularity of the adult acetabular labrum. Clin Orthop Relat Res. 2001 Jan;(382):232-40. - Bsat S, Frei H, Beaulé PE. The acetabular labrum: a review of its function. Bone Joint J. 2016 Jun;98-B(6):730-5. doi: 10.1302/0301-620X.98B6.37099. Review.
- Harris JD. Hip labral repair: options and outcomes. Curr Rev Musculoskelet Med. 2016 Dec;9(4):361-367. Review.
- Byrd JW, Jones KS. Hip arthroscopy for labral pathology: prospective analysis with 10-year follow-up. Arthroscopy. 2009 Apr;25(4):365-8.
- Ayeni OR, Alradwan H, de Sa D, Philippon MJ. The hip labrum reconstruction: indications and outcomes--a systematic review. Knee Surg Sports Traumatol Arthrosc. 2014 Apr;22(4):737-43.