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 FAI-related 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 angleMeasure 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 head-neck junction

CAM lesion

Moving to the Acetabular Side

Acetabular Version

Acetabular Version

Anteverted AcetabulumRetroverted 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 α- angle <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

Mean 4.7 years follow-up

Good to excellent in 13 of 19 hips(68%)

Presence of Tonnis grade 2 or greater changes increased risk of failure

Peters and Erickson reported on 30 hips

Mean 2.7 years follow-up

HHS improved

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%

Iatrogenic labral and articular cartilage damage

Heterotopic ossification (may be up to 8% in untreated patients)

Fracture

Nerve damage

Adhesions

Avascular necrosis

Persistent pain

Instability

Extravasation of fluid into adjacent spaces (ex. retroperitoneal)

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

Pincer impingement on the acetabular side

Most cases of FAI are combined CAM and pincer

Radiographic findings of CAM and pincer impingement exist in the normal asymptomatic population

Some patients may be treated without surgery

Surgical options include:

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