Taylor Castagna
MANE 6963 – Friction and Wear of Materials
Function of the Labrum and Management of Labral Pathology – Ranawat, Kelly

Labral Anatomy, Function and Basic Science Review
1. Runs circumferentially around the acetabular perimeter to the base of the fovea.
Attached to the transverse acetabular ligament posteriorly and anteriorly. Thinner in
the anterior inferior section and thicker and slightly rounded in appearance posteriorly.
Inferior recess is present in the posterior superior portion of the acetabulum.
2. The recess b/w the acetabular labrum and the hip extends circumferentially around the
labrum. Free nerve endings have been identified within Labral tissue, potentially
explaining the pain pathway in a patient with a Labral tear.
3. Vascular pattern of labrums is distinct, majority of the vascular supply to the labrum
comes from capsular contributions (capsular vessels from surrounding hip capsule). The
articular surface of the labrum has decreased vascularity and has limited synovial
covering. Arthroscopic visualization of injured labral tissue has shown more extensive
penetration of the vascular tissue throughout the entire substance of the labrum,
suggesting an improved healing potential than has been previously believed. Greatest
healing potential is at the peripheral capsulolabral junction
Blood supply to the labrum is from the obturator artery, with contributions from the inferior
and superior gluteal vessels. They form a vascular network that supplies the peripheral area of
the capsulolabral junction
4. Peterson and coworkers confirmed that vascular penetration into the labrum is from the
adjacent joint capsule and are greatest at the peripheral one third of the labrum.
Labrum has 2 distinct types of tissue:
 Fibrocartilage – near the articular surface transition zone, Peterson states this
area developed this type of tissue due to shear and compressive forces present
Taylor Castagna
MANE 6963 – Friction and Wear of Materials
Function of the Labrum and Management of Labral Pathology – Ranawat, Kelly

Dense connective tissue – outer or external circumference, tissue type an
adaptation to tensional stress.
 Work supports the importance of location regarding the pathogenesis and
healing of labral tears based on vascularity
5. Seldes and coworkers defined a transition zone between the fibrocartilage in the labrum
and the acetabular articular cartilage. Also identified a bony projection from the
acetabulum into the substance of the labrum that is attached via a zone of calcified
cartilage and serves as an anchor from labrum to acetabulum
Cross section of acetabular labrum. (A) labral attachment, on the nonarticular side of the bone,
the labrum attaches directly to the acetabulum. On the articular side, the labrum attaches
indirectly through a zone of calcified cartilage and by merging with the articular hyaline cartilage
through a transition zone. (B) labral width and thicknee. In the anterior region of the
acetabulum, the labrum is wider and thinner, and in the posterior region it is thicker
6. Speculation on function
 Enhance stabiulity by maintaining negative intra-articular pressure in the hip
joint.
 Acts as a tension band to limit expansion during motion between the anterior
and posterior columns during loading in the gait cycle (walking/running)
 Studies by Ferguson and coworkers using a poroelastic finite element model
have shown that the intact labrum appears to have an important sealing
function in the hip joint by limiting fluid expression from the joint space and
protecting the cartilage layers of the hip. In the absence of the sealing
mechanism, strains with the cartilage matrix are significantly higher resulting in
increased cartilage surface consolidation as well as contact pressure of the
femoral head against the acetabulum.
 Ferguson and co also identified a stabilizing role of the labrum using the
poroelastic model. Showed that the labrum provides structural resistance to
lateral and vertical motion of the head within the acetabulum.
 Because the labrum appears to enhance joint stability there is specific
concern of rotational instability or hypermobility of a hip associated
Taylor Castagna
MANE 6963 – Friction and Wear of Materials
Function of the Labrum and Management of Labral Pathology – Ranawat, Kelly


with a deficient labrum. This is a draw back in excision of labral tissue as
a method to remove the pain associated with a torn labrum. Labral
repair and preservation will maximize the labrums ability as a sealing
mechanism and joint stabilizer enabling the joints ability to take
compressive forces.
Epidemiology and diagnosis
1. Injuries to labrum most common source of hip pain. 300 cases labral tears were present
in 90 percent.
2. Patients present with mechanical symptoms (catching and painful clicking) as well as
restricted ROM.
3. Dynamic forces acting across the injured hip will result in hip pain, decreased athletic
performance, and limitations on daily living.
4. Magnetic resonance imaging (gadolinium-enhanced as a contrast medium) for patients
present with pain to determine if a labral tear is present, physical findings is essential for
proper treatment due to no imaging technique as entirely sensitive for picking up tears.
Etiology and Classification
1. Underlying cause of the labral injury must be identified to properly treat patients.
Following four causes
 Trauma
 Laxity/hypermobility (loose ligaments)
 Bony impingement
 Dysplasia
2. Femoroacetabular impingement is the most common cause for labral injury and was the
cause in 55% of the 300 cases.
 Bony impingement can result from decreased femoral head neck junction offset
(cam effect) shown below by asphericity of the femoral head
Taylor Castagna
MANE 6963 – Friction and Wear of Materials
Function of the Labrum and Management of Labral Pathology – Ranawat, Kelly





Overhang of the anterior superior acetabular rim (pincer lesion)
Tears associated with acetabular rim cartilage wear adjacent to the tear (ALAD –
acetabular labrum articular disruption).
 ALAD 1 – softening of the adjacent cartilage
 ALAD 2 – early peel back of cartilage
 ALAD 3 – large flap of cartilage worn
 ALAD 4 – complete loss of cartilage
 Capsular laxity or hypermobility probably second most comment cause of labral
injury 23% of 300 cases. Iliofemoral ligament is the tissue with the greatest
laxity in the anterior capsule. This results in abnormal loading of the anterior
superior labrum. Labrum is found to be bruised because it gets pinched by
anteriorly translated femoral head.
 Repair of labral tears without evaluation of underlying causes will likely result in
poor outcomes. Factors must be identified preop and treated appropriately at
the time of surgery.
Nonarthroscopic Management of Labral Tears
1. Do not address underlying mechanical problems
2. Patients for surgery are held to attempted rehabilitation with no success and with the
clearly identifiable pathology based on clinical exams and radiographic studies.
Arthroscopic Management of Labral Tears
1. Consists of debridement and repair
 Debridement attempts to relieve pain by removing the unstable flap tear that
causes the observed hip discomfort.
 Repair
Conclusion
Taylor Castagna
MANE 6963 – Friction and Wear of Materials
Function of the Labrum and Management of Labral Pathology – Ranawat, Kelly
1. Must work still is to be done with regards to labral preservation
2. Work by Konrath suggests removal of the labrum does not significantly increase the
pressure or load in the acetabulum and thus conclude that labral excision may not
predispose the hip to premature OA. Many surgeons believe labral tears should be
handled by excision based on this
3. Patients may experience pain relief with debridement, Kelly believes the excision will
compromise its function. New skills should improve patient outcomes by preserving
labral tissue and ultimately the entire hip joint.