FEMORO-ACETABULAR FEMORO-ACETABULAR IMPINGEMENT SYNDROMEIMPINGEMENT SYNDROME

JAYANT SHARMAJAYANT SHARMA

M.S,D.N.B.,M.N.A.M.S.M.S,D.N.B.,M.N.A.M.S.

DEFINITIONDEFINITION

It is a condition of too much friction in the It is a condition of too much friction in the hip joint.  Basically, the femoral head and hip joint.  Basically, the femoral head and acetabulum rub abnormally creating acetabulum rub abnormally creating damage to the hip joint.  The damage can damage to the hip joint.  The damage can occur to the articular cartilage or the labral occur to the articular cartilage or the labral cartilage.cartilage.

Activities CAUSING FAIActivities CAUSING FAIIce HockeyIce HockeyHorseback RidingHorseback RidingYogaYogaFootball (American)Football (American)SoccerSoccerBallet/Dance/AcrobaticsBallet/Dance/AcrobaticsGolfGolfTennisTennisBaseballBaseballField HockeyField HockeyRugbyRugbyBike Riding/CyclingBike Riding/CyclingMartial ArtsMartial ArtsDeep squatting activities such as power liftingDeep squatting activities such as power lifting

EtiologyEtiology

Significant athletic activity before skeletal Significant athletic activity before skeletal maturity increases the risk of FAI.maturity increases the risk of FAI.

Prior Biomechanical theories suggest that Prior Biomechanical theories suggest that cartilage damage is initiated by Concentric or cartilage damage is initiated by Concentric or Eccentric overload.Eccentric overload.

- Eccentric overload - Eccentric overload                         - easily explained by                         - easily explained by

non-congruent articulations caused by non-congruent articulations caused by developmental dysplasias and post-traumatic developmental dysplasias and post-traumatic anatomy anatomy

- Concentric overload - Concentric overload                         - not as easy to explain                         - not as easy to explain

Ganz et al. CORR. 2003Ganz et al. CORR. 2003- - Summarized the concept of FAI Summarized the concept of FAI

                        - Mechanism for development of                         - Mechanism for development of osteoarthritis based on subtle aberrant bony morphology osteoarthritis based on subtle aberrant bony morphology

                                -                                 - Acetabular Retroversion / Coxa Acetabular Retroversion / Coxa Profunda Profunda                                 -                                 - Femoral Head non-sphericityFemoral Head non-sphericity                         -                         - Abnormal ContactAbnormal Contact in Normal / Near in Normal / Near Normal Appearing Hips Normal Appearing Hips                         -                         - Abutment of the Proximal FemurAbutment of the Proximal Femur on the Acetabular Rim during terminal motion of the hip on the Acetabular Rim during terminal motion of the hip leading to lesions of the labrum and/or the adjacent leading to lesions of the labrum and/or the adjacent cartilage cartilage                         -                         - Chondral and Labral lesionsChondral and Labral lesions progress progress and result in degenerative disease and result in degenerative disease

FAI FormsFAI Forms

Generally occurs as two Cam and Pincer.  Generally occurs as two Cam and Pincer.  The The Cam form (Cam comes from the (Cam comes from the Dutch word meaning “cog”) describes the Dutch word meaning “cog”) describes the femoral head and neck relationship as femoral head and neck relationship as aspherical.  aspherical. 

This loss of roundness contributes to This loss of roundness contributes to abnormal contact between the head and abnormal contact between the head and socket.  socket. 

CAM ImpingementCAM Impingement

                                - - Anatomy Anatomy                         - Abnormal Femoral Head/Neck                         - Abnormal Femoral Head/Neck junction with increased radius at the waist junction with increased radius at the waist                 - Motion                 - Motion                         - Impingement occurs primarily during                         - Impingement occurs primarily during flexion, adduction, IR flexion, adduction, IR                 -                 - Mechanics Mechanics                         - Contact between the femoral neck                         - Contact between the femoral neck and acetabular rim induces compression and acetabular rim induces compression                         - Shear stress generated at the junction                         - Shear stress generated at the junction between the labrum and the cartilage and at the between the labrum and the cartilage and at the subchondral tidemark subchondral tidemark                         - Outward avulsion of the labrum                         - Outward avulsion of the labrum and/or an inward compression of the articular cartilage and/or an inward compression of the articular cartilage at Anterosuperior Rim at Anterosuperior Rim                 -                -

Etiology of CAM ImpingementEtiology of CAM Impingement                         - Elliptical Femoral Head                         - Elliptical Femoral Head                         - Slipped Capital Femoral                         - Slipped Capital Femoral Epiphysis - Epiphysis - SCFESCFE                        -                         - Legg Calve PerthesLegg Calve Perthes                         -                         - Adult OsteonecrosisAdult Osteonecrosis                        - Malunited Femoral Neck                         - Malunited Femoral Neck Fractures Fractures

The Pincer FormThe Pincer Form

Pincer comes from the French word meaning “to Pincer comes from the French word meaning “to pinch” pinch” describes the situation where the socket or describes the situation where the socket or acetabulum has too much coverage of femoral acetabulum has too much coverage of femoral head.  head.  This over-coverage typically exists along the This over-coverage typically exists along the front-top rim of the acetabulum,front-top rim of the acetabulum,results in the labral cartilage being “pinched” results in the labral cartilage being “pinched” between the rim and the anterior femoral head-between the rim and the anterior femoral head-neck junction. neck junction. 

Pincer form of the ImpingementPincer form of the Impingement

Secondary to “retroversion”, or “profunda”,Secondary to “retroversion”, or “profunda”,

Most of the time, the Cam and Pincer Most of the time, the Cam and Pincer forms exist together. forms exist together.

Pincer ImpingementPincer Impingement                                - - AnatomyAnatomy

                        - Excessive Acetabular Coverage                         - Excessive Acetabular Coverage                 - Motion                 - Motion                         - Dependent on acetabular morphology                         - Dependent on acetabular morphology     -     - MechanicsMechanics                         - Linear Contact between the labrum and femoral                         - Linear Contact between the labrum and femoral head/neck junction head/neck junction                                 - Anterior = Acetabular Retroversion                                 - Anterior = Acetabular Retroversion

                                                                - Circumferential = Coxa Profunda - Circumferential = Coxa Profunda

                                                - Force from the femoral neck is transferred through the - Force from the femoral neck is transferred through the labrum to the acetabular cartilage labrum to the acetabular cartilage Results is chronic degeneration of Results is chronic degeneration of anterior labrum and subsequent ossificationanterior labrum and subsequent ossification Further deepens the Further deepens the cup.cup.

                                                Resultant leverage of head in acetabulum with excessive Resultant leverage of head in acetabulum with excessive ROM can result in contre-coup lesion in posteroinferior acetabulum ROM can result in contre-coup lesion in posteroinferior acetabulum and posteromedial femoral head and posteromedial femoral head

                                                                - Leading to Circumferential involvement - Leading to Circumferential involvement                                

Etiology Etiology                         - Acetabular Retroversion                         - Acetabular Retroversion                         - Coxa Profunda                         - Coxa Profunda                         - Protrusio Acetabuli                         - Protrusio Acetabuli                         - Iatrogenic overcorrection                         - Iatrogenic overcorrection for retroversion/dysplasia for retroversion/dysplasia                         - Coxa Vara                        - Coxa Vara                        - Os Acetabuli                         - Os Acetabuli

ASSOCIATED CARTILAGEASSOCIATED CARTILAGE

FAI is associated with cartilage damage, FAI is associated with cartilage damage, labral tears, labral tears,

early hip arthritis, early hip arthritis,

hyperlaxity, hyperlaxity,

sports hernias, and sports hernias, and

low back pain.low back pain.

FAI is common in high level athletes, but FAI is common in high level athletes, but also occurs in active individualsalso occurs in active individuals

DiagnosisDiagnosis

Most patients can be diagnosed with a Most patients can be diagnosed with a good history,good history,

A A patient’s historypatient’s history .  . 

The The physical examphysical exam

The The plain x-rayplain x-ray films films

EXAMINATIONEXAMINATION

Gait should be closely scrutinized looking for Gait should be closely scrutinized looking for

an abductor lurch,an abductor lurch,

a shortened stance phase,a shortened stance phase,

circumduction, or steppage.  circumduction, or steppage. 

Leg lengths should be measured using accurate Leg lengths should be measured using accurate methods.  methods. 

The patient's posture should be noted, including The patient's posture should be noted, including examination of the back for scoliosis. examination of the back for scoliosis.

Anterior femoral-acetabular Anterior femoral-acetabular impingementimpingement

the affected hip is flexed to ninty degrees and the leg is the affected hip is flexed to ninty degrees and the leg is internally rotated and adducted. internally rotated and adducted. If there is abnormal contact between the anterior-If there is abnormal contact between the anterior-superior acetabular rim and femoral neck, pain may be superior acetabular rim and femoral neck, pain may be elicited.  elicited.  Posterior impingement may be tested by having the Posterior impingement may be tested by having the patient dangle their legs off the end of an examination patient dangle their legs off the end of an examination table, table, with the affected leg externally rotated by the examiner, with the affected leg externally rotated by the examiner, and the opposite limb held flexed by the patient.  In a and the opposite limb held flexed by the patient.  In a positive exam, the femur contacts the posterior positive exam, the femur contacts the posterior acetabular rim eliciting pain. acetabular rim eliciting pain.

EXAMINATIONEXAMINATION

The range of motionThe range of motion A decreased range of motion of the hip, A decreased range of motion of the hip, especially in cases of an external rotation especially in cases of an external rotation contracture, can point to an intra-articular cause contracture, can point to an intra-articular cause of the pain.  of the pain.  Patients with hip pathology often also develop a Patients with hip pathology often also develop a flexion contracture. The Thomas test is a helpful flexion contracture. The Thomas test is a helpful maneuver.  maneuver.  A thorough neurovascular exam should be A thorough neurovascular exam should be conducted to rule out spine and other neural conducted to rule out spine and other neural causes of the patient's pain. causes of the patient's pain.

RADIOLOGYRADIOLOGY

The AP pelvis X-ray must be well centered The AP pelvis X-ray must be well centered and well developed as to show a clear and well developed as to show a clear outline of the acetabulum.  outline of the acetabulum.  The coccyx should point toward the The coccyx should point toward the symphysis pubis, and there should be symphysis pubis, and there should be about 1-2 cm between them. about 1-2 cm between them. The anterior and posterior walls, the tear The anterior and posterior walls, the tear drop and the lateral edge of the drop and the lateral edge of the acetabulum should be noted. acetabulum should be noted.

MeasurementsMeasurements

may be taken to evaluate for hip dysplasia may be taken to evaluate for hip dysplasia including the including the Tönnis angleTönnis angle (abnormal < 10 (abnormal < 10 degrees),degrees), the lateral center-edge angle of Wibergthe lateral center-edge angle of Wiberg (abnormal < 25 degrees), and (abnormal < 25 degrees), and the the Anterior center-edge angle of LequesneAnterior center-edge angle of Lequesne (abnormal < 25 degrees) as measured on a (abnormal < 25 degrees) as measured on a false-profile radiograph. false-profile radiograph. The neck shaft angleThe neck shaft angle of the proximal femur is of the proximal femur is considered normal between 120 and 140 considered normal between 120 and 140 degrees.degrees.

Coxa ProfundaCoxa ProfundaWhen the floor of the acetabular fossa is in When the floor of the acetabular fossa is in line with the ilioischial line; line with the ilioischial line; Protrusio is present when the medial most Protrusio is present when the medial most femoral head overlaps the ilioischial line. femoral head overlaps the ilioischial line. The crossover signThe crossover sign is a sensitive and specific is a sensitive and specific indicator of native acetabular version.   indicator of native acetabular version.   On an On an AP pelvis radiographAP pelvis radiograph, the outlines of , the outlines of the edges of the anterior and posterior walls the edges of the anterior and posterior walls of the acetabulum should meet superiorly of the acetabulum should meet superiorly and laterally.  and laterally. 

COXA PROFUNDACOXA PROFUNDA

In cases of In cases of acetabular retroversionacetabular retroversion, this , this crossover of the anterior and posterior crossover of the anterior and posterior acetabular wall outlines is more distal. acetabular wall outlines is more distal. Changes in the acetabular rim may also Changes in the acetabular rim may also be noted. be noted.  A A 'double line'double line' is seen in labral ' is seen in labral ossification. ossification.  An An os acetabulios acetabuli may also be an indicator may also be an indicator of pathology of pathology

Alterations of the proximal femoral anatomy, such as Alterations of the proximal femoral anatomy, such as head neck offset and bump formation can be observed in head neck offset and bump formation can be observed in addition to acetabular and labral pathology.addition to acetabular and labral pathology. A pistol grip deformity of the femoral head is often seen A pistol grip deformity of the femoral head is often seen in Cam Type impingement.  in Cam Type impingement.  In this situation the superior-lateral head neck junction is In this situation the superior-lateral head neck junction is convex instead of concave. convex instead of concave.  A high fovea can also indicate asphericity of the femoral A high fovea can also indicate asphericity of the femoral head that is not able to be appreciated on the AP films.head that is not able to be appreciated on the AP films. A cross table lateral may show an abnormality in the A cross table lateral may show an abnormality in the anterior head neck junction in cases of impingement.  anterior head neck junction in cases of impingement.  

The Alpha AngleThe Alpha Angle

Drawn on the AP pelvis radiograph, is formed Drawn on the AP pelvis radiograph, is formed by a line drawn from the center of the femoral by a line drawn from the center of the femoral head through the center of the femoral neck,head through the center of the femoral neck, A line from the center of the femoral head to A line from the center of the femoral head to the femoral head/neck junction, found by the the femoral head/neck junction, found by the point by which the femoral neck diverges from a point by which the femoral neck diverges from a circle drawn around the femoral head. circle drawn around the femoral head.   A normal patients' alpha angle is around 45 A normal patients' alpha angle is around 45 degrees, degrees, whereas patients with whereas patients with Femoroacetabular Femoroacetabular impingement may be around 70 degrees.impingement may be around 70 degrees.

ALPHA ANGLEALPHA ANGLE

TONNIS ANGLE

LCA

CROSSOVER

PROFUNDA

ACEA

MRIMRI

Often an MRI of the hip is used to confirm Often an MRI of the hip is used to confirm a labral tear or damage to the joint a labral tear or damage to the joint surface.  surface. 

The MRI is most helpful in eliminating The MRI is most helpful in eliminating certain causes of non FAI hip pain certain causes of non FAI hip pain including avascular necrosis (dead bone) including avascular necrosis (dead bone) and tumors.and tumors.

DIFFRENTIAL DIAGNOSISDIFFRENTIAL DIAGNOSIS

Hip Dysplasia (Adult Form)Hip Dysplasia (Adult Form)Lumbar Spine Pain (Low Back Pain)Lumbar Spine Pain (Low Back Pain)Lumbar Radiculopathy Low Back Facet Disease)Lumbar Radiculopathy Low Back Facet Disease)Sacroiliitis Sacroiliitis Trochanteric BursitisTrochanteric BursitisPiriformis SyndromePiriformis SyndromePsychosomatic Pain DisorderPsychosomatic Pain DisorderIliopsoas Tendinitis/Tendonitis/TendinosisIliopsoas Tendinitis/Tendonitis/TendinosisGroin Pull Groin Pull Sports Hernia (abdominal muscle strain)Sports Hernia (abdominal muscle strain)Iliac ApophysitisIliac ApophysitisQuadriceps Hernia/Strain Chronic Pain Syndromes  Quadriceps Hernia/Strain Chronic Pain Syndromes 

TreatmentTreatmentNon-operativeNon-operative

A course of non-operative treatment for A course of non-operative treatment for most hip pathology may be tried first. most hip pathology may be tried first. Patients presenting with femoroacetabular Patients presenting with femoroacetabular impingement or labral disease may try impingement or labral disease may try modification of activity modification of activity avoiding excessive hip movement avoiding excessive hip movement regular non-steroidal anti-inflammatory regular non-steroidal anti-inflammatory medicationmedication

ArthroscopyArthroscopy

Arthroscopic assessment of the hip can include Arthroscopic assessment of the hip can include examination of both the central and peripheral examination of both the central and peripheral compartments. compartments. The central compartment includes the labrum and all The central compartment includes the labrum and all structures located further medially. structures located further medially. Tearing of the labrum anterolaterally and damage to the Tearing of the labrum anterolaterally and damage to the acetabular cartilage is characteristic. acetabular cartilage is characteristic. The lesions of the labrum and any areas of chondral The lesions of the labrum and any areas of chondral damage are debrided. damage are debrided. Labral repair may be possible for specific tears. Labral repair may be possible for specific tears. For areas of exposed subchondral bone a microfracture For areas of exposed subchondral bone a microfracture technique may be performed.technique may be performed.

SAFE Surgical Hip Dislocation- SAFE Surgical Hip Dislocation- OsteoplastyOsteoplasty

Surgical dislocation of the hip has been described.  Surgical dislocation of the hip has been described.  A posterior incision (Kocher-Langenbeck) as this approach A posterior incision (Kocher-Langenbeck) as this approach usually provides better access to posterior parts of the joint usually provides better access to posterior parts of the joint after the hip is dislocated. after the hip is dislocated. A trochanteric flip osteotomy is performed. The trochanter is A trochanteric flip osteotomy is performed. The trochanter is osteotomized from a posterior to anterior direction, the cut osteotomized from a posterior to anterior direction, the cut exits superficial to the piriformis fossa superiorly and at the exits superficial to the piriformis fossa superiorly and at the vastus ridge inferiorly. vastus ridge inferiorly. The gluteus minimus muscle is dissected carefully off the The gluteus minimus muscle is dissected carefully off the capsule starting at the piriformis interval. capsule starting at the piriformis interval. The capsulotomy is Z-shaped (for the right hip), with the The capsulotomy is Z-shaped (for the right hip), with the superior limb located along the posterior acetabular rim, and superior limb located along the posterior acetabular rim, and the inferior limb located at the level of the anteromedial the inferior limb located at the level of the anteromedial femoral neckfemoral neck

After dislocation of the hip, the acetabular labrum and After dislocation of the hip, the acetabular labrum and the adjacent articular cartilage are assessed, and the the adjacent articular cartilage are assessed, and the identified lesions are tested for partial or complete identified lesions are tested for partial or complete avulsions from the acetabular rim. avulsions from the acetabular rim. The severity, extent, and location of these lesions should The severity, extent, and location of these lesions should be defined, and their association with FAI should be be defined, and their association with FAI should be confirmed by provocative maneuvers in flexion and confirmed by provocative maneuvers in flexion and internal rotation with the head relocated.  internal rotation with the head relocated.  The combination of anterior over coverage and the The combination of anterior over coverage and the status of the labrum and the acetabular articular cartilage status of the labrum and the acetabular articular cartilage will determine the type of treatment of the acetabular rim.will determine the type of treatment of the acetabular rim. In cases of anterior over coverage contributing to FAI, In cases of anterior over coverage contributing to FAI, as is frequent with acetabular retroversion, a resection as is frequent with acetabular retroversion, a resection osteoplasty of the anterosuperior rim is done.  osteoplasty of the anterosuperior rim is done. 

Periacetabular OsteotomyPeriacetabular Osteotomy

Reorientation of the articulating surfaces of the Reorientation of the articulating surfaces of the hip joint is an attractive procedure in the patient hip joint is an attractive procedure in the patient with hip dysplasia.with hip dysplasia.Increased joint congruity after reorientation of Increased joint congruity after reorientation of the osteotomized fragment allows load the osteotomized fragment allows load transmission through a broader area subjected transmission through a broader area subjected to less pressure. to less pressure. These changes can be expected to reduce pain These changes can be expected to reduce pain and possibly protect the articular cartilage from and possibly protect the articular cartilage from degenerative changesdegenerative changes

Pelvic OsteotomyPelvic Osteotomy

Corrects the major anatomic abnormality Corrects the major anatomic abnormality and has the further advantage over and has the further advantage over femoral osteotomy of not creating a femoral osteotomy of not creating a secondary femoral deformity. secondary femoral deformity.

Femoral osteotomy may be added to Femoral osteotomy may be added to pelvic osteotomy when coexistent femoral pelvic osteotomy when coexistent femoral anatomic abnormalities are significant. anatomic abnormalities are significant.

Bernese Periacetabular OsteotomyBernese Periacetabular Osteotomy

The is indicated for patients with hip The is indicated for patients with hip symptoms of mechanical overload, symptoms of mechanical overload, impingement, or hip instability as a result impingement, or hip instability as a result of insufficient acetabular coverage. of insufficient acetabular coverage.