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Acetabular labral tear

Introduction

Historically, hip surgery is has been limited by the need for an arthrotomy. Therefore advanced disease processes have been a criteria for surgery.

With the advent of arthroscopy ,the previous unrecognized & untreated disease process have become mainstream.Labral pathology is common.(McCarthy - 93% (54 hips) , Seldes et al - cadavers 96% (53 of 55),Byers et al - 365 cadavers 88% > 30 years old) Hip arthroscopy was introduced by Dr Burman in 1931. It gained 'popularity' in 1977 with Dr Gross.

Anatomy

The labrum is a fibrocartilagenous structure attached to the acetabular rim. It runs circumferentially and is usually continuous with the transverse acetabular ligament.

The labrum is triangular with a recess between the capsule and labrum. A tongue of bony acetabulum extends into the substance of the labrum.

Histology of Labral Tears

There are two types of labral tears. One is detachment through the transition zone (89%) while the other is cleavage planes through labral substance.

Vascular Anatomy

Dr Kelly et al injected 12 cadaver hips with India ink. The obturator, superior gluteal, & inferior gluteal arteries supply the labrum. Blood supply enters peripherally, via the capsular side. There are no regions of hypovascularity moreover all tears exhibited hypervascularization within the labral tear.

Labral Function

The exact role unclear . Dr Konrath et al observed that the labrum does not increase contact area, distribute load, or reduce contact stresses in the hip. Dr Tan et al note the labrum increased surface area 28% & deepened the cup 5 mm. Dr Ferguson et al found the labrum sealed the hip to limit fluid expression & improved stability

Pathophysiology of Tears

Labral tears are symptomatic. Dr Ferguson et al noted the absence of a labrum increased cartilage surface consolidation.

Dr Seldes et al found that degenerative changes are associated with labral tears.

Etiology

Labral tears result from trauma, femoroacetabular impingement, capsular laxity/hip hypermobility, dysplasia, degenerative

Trauma
There are two types of trauma: minimal trauma and dislocation. The posterior labral tear is associated with disloctation while the anterior labral tear is asssociated with minimal trauma (aka hyperextension with external rotation and abduction)

Femoroacetabular Impingement

This is repetitive microtrauma  from neck abutment against the acetabular rim. This mechanism causes increased shear to the labrum & articular cartilage. There are two varieties: incer. Impingement results from a non-spherical femoral headabuting in flexion and mild internal rotation. This basically isdecreased femoral head-neck offset vs. "pistol-grip" Pincer Impingement results from abnormal anterior overcoverage. This is the linear contact between the acetabular rim and the head-neck junction (acetabular retroversion).

Hypermobility

This results from an underlying collagen disorders or hormonal hypermobility causes rotational instability. The instability allows the head to impinge on the labrum.

Dysplasia

Labral tears are associated with dysplastic conditions; DDH, SCFE, LCP. The anterior labrum often hypertrophied. Impingement occurs between the head and the anterior acetabulum.

Degenerative

Tears are associated with degenerative changes. Inflammatory arthritides are of note. These tears involve more than one labral region most likely representing end-stage disease.

History

Patients will complain of groin pain +/- radiation to the knee or diffuse trochanteric or buttock pain. The pain is associated with activity. Most people will reporta a history of twisting injury, trip, or fall.

Mechanical symptoms: A clicking/catching sensation and or a locking sensation is noted.

Physical Exam

Patients present with gait abnormalities (Trendelenberg gait) and decreased step length. There is rarely tenderness to palpation. Range of motion is limitied by painful flexion, abduction, & internal rotation. Mechanical symptoms present with resisted ipsilateral straight leg raise and forced internal rotation with an axial load. TheMcCarthy Sign is pain with hip extension. DrFitzgerald proposedAnterior is flexion, external rotation, & ab*duction. ? extension, *internal. rotation, & *ad*duction while<FONT size=3>Posterior is internal rotation, and adduction ? extension, external rotation,

Imaging

Modalities include X-Ray, bone scan, CT, Ultrasound, MRI vs. MRA

MRA (MR Arthrography)

Capsular distention with contrast outlines labrum and fills tears. Tears manifest as linear extension of contrast or labral blunting. DrCzerny et al found the sensitivity to be 95% vs. 80%. DrToomayan et al found sensitivity: 92% vs. 25%

X-Ray

Measurements of dysplasia are key. The Center Edge Angle < 20 is dysplasia. TheAcetabular Index  > 10 is dysplasia. The femoral Neck-Shaft Angle > 140 is dysplasia. Acetabular version is measured by tracing the acetabular walls. Figure-of-8 sign is noted along with pincer impingement.Normal femoral neck shows concave appearance. The absence of concavity indicates a decreased offsest. C impingement is also apparent. Decreased offset on a lateral x-ray with a ratio < 0.152 equates to cam impingement.

Treatment

Nonoperative 

The data lacking. A reasonable regimen isPWB for 2-4 weeks,NSAID's,P.T./ROM.

Arthroscopy

Indications are a positive historym physical exam,and failed non-op measures. Steroid injections are also considered.Contraindications to arthroscopy includeExtra-articular sources of pain, skin issues, sepsis/abscess, conditions that limit distraction, e.g. HO/protrusio, moderate/severe dysplasia, relative - obesity. The technique is done in the supine or lateral position. A special distractor is used with an extra wide peroneal post. Place thehip in abduction and traction. 8-10 mm of distraction ideal with 25-50 lbs.Last place thehip in adduction with gentle countertraction.

Portal Placement

Anterior paratrochanteric portal: 1-2 cm. anterior to & superior to tip of greater trochanter. Visualizes anterior femoral head, neck, and labrum, ligamentum teres, & most of acetabulum. There is risk to femoral neurovascular structures.

Anterior portal: Anterior portal is used to visualize the anterior triangle. Its location is the intersection of vertical from ASIS & horizontal from anterior paratrochanteric portal. Risk to the lateral femoral cutaneous nerve & the ascending branch of the lateral femoral circumflex artery. Visualization of the anterior joint is possible.

Proximal trochanteric portal: Proximal trochanteric portal is locacted 2-3 cm proximal to tip of greater trochanter. Next advance medially and slightly superiorly. Visualizes the labrum, femoral head, and fovea.There is risk to femoral neurovascular bundle.

Posterior Paratrochanteric Portal: Posterior paratrochanteric portal is located 2-3 cm posterior to greater troch at the level of anterior paratrochanteric portal. There is risk to thesciatic nerve, especially if foot externally rotated. Visualization of the posterior joint is possible.

Debridement shows good short term results. Long-term results dependent on degenerative changes. Debridement alters labral function.

Labral repairs are designed to avoid degenerative changes. The outcomes are promissing. Techniques include suture anchor vs. cerclage. The distal lateral accessory portal is utilized. The total complication rate is 1.34 - 6%. These include direct injury to neurovascular structures, neuropraxia of sciatic; femoral; pudendal; or lateral femoral cutaneous nerve, pressure necrosis, fluid extravasation, chondral scuffing, broken instruments, and avascular necrosis of the femoral head.

Summary

  • Labral tears are common and sypmtomatic
  • Anterior groin pain with mechanical symptoms vs. dull butt/trochanter pain
  • Decreased ROM with mechanical symptom
  • Arthroscopic debridement vs. repair

Selected References

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