Impingement in the
Hip – Cam, Pincer or
is it a Mixed Bag?
SCOTT BISSELL, MD
CONNECTICUT ORTHOPEDIC ASSOCIATES
AUGUST 4, 2015
Overview
Anatomy
Terminology
Cam impingement
Pincer impingement
Pathophysiology
FAI and OA
Prevalence of FAI
Diagnosis
Treatment Options
Questions
Basic Hip Anatomy
Background
Femoroacetabular Impingement (FAI) first
described in the early 1990’s
Increasingly recognized as a source of hip
pain and dysfunction
Pathomechanics
Work by Ganz et al
FAI caused by repetitive abutment of a morphologically abnormal
proximal femur and/or acetabulum during terminal range of motion of
the hip
This process eventually leads to damage of the acetabular labrum and
cartilage dependent on the location of the osseous abnormality
Two most common osseous abnormalities
Abnormal femoral head-neck offset
Acetabular over-coverage
Third described type as “mixed” or “combined”
Cam Impingement
Most common form of isolated FAI
Typically seen in young adult males (age 20-30)
Loss of normal femoral head-neck contour may
be due to:
Abnormal extension of the proximal femoral
epiphysis
Short or long femoral neck
Varus femoral neck
Perthes
Slipped capital femoral epiphysis (SCFE)
Cam Impingement
The non-spherical portion of the anterolateral
femoral head produces a shear force on the
chondrolabral junction as it enters the acetabulum
in hip flexion
Over time, repetitive shear force results in
Chondrolabral separation
Acetabular chondral delamination
Labral detachment
Pincer Impingement
Most commonly seen in women ages 30-40
Acetabular overcoverage
Focal overcoverage at the anterior superior
rim
Relative anterior overcoverage (acetabular
retroversion)
Global overcoverage
Protrusio acetabuli
Coxa profunda
Pincer Impingement
Acetabular overcoverage results in crushing of
the labrum against the normal femoral neck in
hip flexion and internal rotation
Continued abutment results in
Labral degeneration
Chondral injury
Possible ossification of the rim
Contracoup mechanism can result in damage
to the posterior femoral head and acetabulum
as the femoral head levers anteriorly
Combined Impingement
Most common type of FAI (72% - 86%)
Components of both cam and pincer
impingement although typically one is
the dominant component
FAI and its Role in the Development
of Osteoarthritis
Morphological
abnormalities of the
femoral head
and/or acetabulum
Abnormal contact
between the
femoral head and
acetabular margin
Supraphysiologic
stress resulting in
tearing of the
labrum and avulsion
of underlying
cartilage
Further deterioration
and wear –
eventual onset of
OA
FAI and OA Questions
Is FAI the cause or the effect of
OA?
Are the deformities seen in FAI
developmental or congenital or
possibly a reaction to the OA
(analogy osteophyte formation)?
Future directions
Identify which patients with FAIrelated morphologic abnormalities
are at greatest risk for developing
hip OA, especially at a young age
Should we intervene in the
asymptomatic hip with FAI to
hopefully prevent OA in the future?
Prevalence of FAI
Ochoa et al reviewed x-rays of 155
patients (age 18-50) presenting
with hip pain
87% had one findings consistent
with FAI
81% had two findings consistent
with FAI
Reichenbach et al reported on 1080
symptomatic military recruits in Switzerland
430 selected randomly and 244 had MRI
scans
Mean age 19 years
Prevalence of CAM deformity was 24%
Prevalence of FAI
Hack et al studied 200
asymptomatic volunteers using
MRI
Mean age 29.4 years
α- angle measured at two positions
53% had evidence of CAM
morphology (α- angle >50.5°)
What does this mean?
Highlights the importance of clinical
correlation during the diagnostic
work-up for FAI
Diagnosis of FAI
Patient history
Physical exam
Selective intra-articular injections
Radiology
Plain radiographs
CT scan
MRI and MRA (magnetic resonance arthrography)
Patient History
Trauma
Childhood hip disease
SCFE
Perthes
Developmental dysplasia
Symptoms
Pain
What positions?
What activities?
Clicking, popping, catching
Stiffness
Distribution of pain
Typically groin pain (83%)
May occasionally radiate to L/S
spine, lateral hip
Typical patient is young and
active participating in activities
requiring repetitive hip flexion
Physical Exam
Often patients indicate deep interior
hip pain with the “C-sign”
Radiographic Evaluation
Plain radiographs
AP pelvis
45 degree Dunn view
Lateral
False profile
CT scan
MRI or MRA
Plain Radiographs
AP pelvis
45 degree Dunn view
Plain Radiographs
Frog Lateral View
False Profile View
Alpha angle
Measure of the degree of asphericity and cam impingement
at the anterior head-neck junction
Noltzi et al: FAI patients (74°) and
normal controls (42°)
Findings Associated with CAM
Impingement
Fibrocystic change at the headneck junction
CAM lesion
Moving to the Acetabular Side
Acetabular Version
Acetabular Version
Anteverted Acetabulum
Retroverted Acetabulum
Findings Associated with Pincer
Impingement
Coxa Profunda
Acetabular Protrusio
Lateral Center Edge Angle
Above 40° may indicate overcoverage
Below 25° may indicate dysplasia –
structural instability
Acetabular Dysplasia
Dysplasia or undercoverage
Normal for comparison
MRI/MRA Imaging of the Labrum
Normal Hip Labrum
Chondrolabral Separation
Clinical Summary
Management Options for FAI
Non-operative
Operative
Arthroscopic
Open
Combined Arthroscopic and Open
Non-Operative Management
Activity modification
Anti-inflammatory medication
Injections
Intra-articular
Extra-articular
Iliopsoas
Trochanteric
Physical therapy
Core strength
Flexibility (though increased hip ROM
SHOULD NOT be the goal of
treatment)
Data suggests that symptomatic patients
with mild deformity may improve with
nonsurgical management
Emara et al reported on 37 patients with αangle <60° treated with PT and activity
modification followed at 2 years
11% chose surgical management
16% experienced recurrent symptoms
89% had significant improvement in mean
Harris hip score
Surgical Management
Goals
Improve pain
Improve range of motion
Improve function
Perhaps decrease the risk of future
progression to the OA – concept of
“hip preservation”
Address the pathology
Reshape the acetabular rim
Recontour the femoral head-neck
junction
Debride, repair, or reconstruct the
labrum
Address articular cartilage lesions
Surgical Planning – Open vs
Arthroscopic Approaches
Patient characteristics
Disease pattern
Location and extent of CAM
Complex proximal femoral
deformities
Surgeon preference and comfort
Surgical Approaches
Open Surgical Dislocation
Initial description by Ganz et al
Protects the vascular supply from the medial circumflex artery and its lateral retinacular branches
Requires a trochanteric osteotomy preserving the abductor attachments
Hip is dislocated anteriorly allowing access to the acetabulum and proximal femur
Outcomes of Surgical Dislocation
Ganz et al and Beck et al
Peters and Erickson reported on 30
hips
Mean 4.7 years follow-up
Good to excellent in 13 of 19
hips(68%)
Mean 2.7 years follow-up
HHS improved
Presence of Tonnis grade 2 or
greater changes increased risk of
failure
13.3% conversion rate to THA
More recent data (not this study)
suggests THA rate now 0-5%
Espinosa et al
28% rate of excellent outcomes
with labral debridement
(combined good/excellent 76%)
80% rate of excellent outcomes
with labral repair (combined
good/excellent 94%)
Complications of Surgical
Dislocation
Osteonecrosis (although reports
are lacking to support this)
Nonunion of trochanteric
osteotomy (0-3%)
Trochanteric pain (46% of all
patients and 74% of female
patients in one study)
Intra-articular adhesions (up to 6%
of cases)
Sink et al
Multicenter cohort of 334 hips
undergoing surgical hip dislocation
Overall complication rate of 9%
Hip Arthroscopy
Introduced in the late 1970s and
initially was used to manage labral
tears and loose bodies
Specialized equipment
Distraction table
Fluoroscopy
Long instrumentation
Access central and peripheral
compartments via small “portal”
incisions
Hip Arthroscopy
Hip Arthroscopy
Outcomes – Hip Arthroscopy
Multiple studies
Success rate of 67% to 90%
Rates of conversion to THA 0-9%
Retrospective studies
Larson et al compared outcomes of
rim trimming with labral debridement
(LD) vs labral repair (LR)
67% good/excellent with LD
90% good/excellent with LR
Nepple et al found that treatment of
the bony deformity was associated
with significantly greater
improvement and decreased failure
rates
Complications of Arthroscopic Hip
Surgery
Complication rate 1% to 6%
Persistent pain
Iatrogenic labral and articular
cartilage damage
Instability
Extravasation of fluid into adjacent
spaces (ex. retroperitoneal)
Heterotopic ossification (may be
up to 8% in untreated patients)
Fracture
Nerve damage
Adhesions
Avascular necrosis
Combined Arthroscopic and Open
Approach
Can allow for address of complex
deformities that may not be
completely accessible via
arthroscopy
Complex deformities or structural
instability may require open
procedures
Dysplasia
Abnormal femoral anteversion
Trochanteric impingement
Summary
CAM impingement on the femoral
side
Some patients may be treated without
surgery
Pincer impingement on the
acetabular side
Surgical options include:
Most cases of FAI are combined
CAM and pincer
Radiographic findings of CAM and
pincer impingement exist in the
normal asymptomatic population
Arthroscopic intervention
Open surgical dislocation
Combined approach
Surgery - regardless of approach - offers
reliable good/excellent outcomes in
properly selected patients with a low
complication rate
Thank You
Journal of the AAOS 2013;
Vol 21, Supplement 1
0
