Anatomy and classification neck femur in young adult

Dr.Rajesh Kumar RajnishDept. of Orthopaedics,

UCMS & GTB hospital, Delhi

Introduction

• Fractures of hip have been described as an orthopaedic epidemic

• Estimated global incidence-1.66 million fractures(1990).

• Expected to increase to 6.26 million fractures by 2050.

• Approx. 50% of these-intracapsular fractures.

Hip joint

• Ball-and-socket joint composed of head of femur and acetabulum

AnatomyProximal femur

The outline of the proximal end of the femur is characterised by almost spherical head, slightly flattened neck and two trochanters with communicating intertrochanteric ridge

• Physeal closure age 16yrs

• Neck-shaft angle 130°-135° <Coxa vera > Coxa valga

Anteversion (Medial femoral torsion)

• Angle subtended by femoral neck to the transcondylar axis of the knee joint.

15°- 25°

Calcar Femorale• Dense vertical palte of bone

from Posteromedial femoral shaft under LT to GT

• Reinforcing posterinferior femoral neck

Trabecular patterns

• Principal Compressive Group

• Principal Tensile Group • Greater Trochanteric

Group• Secondary Compressive

Group• Secondary Tensile Group• Ward's Triangle

Blood supply

Crock described three major groups of vessels

• Extracapsular arterial ring• Ascending cervical branches of arterial

ring • Artery of ligamentum teres

• Formed at base of femoral neck at level of capsular attachment

• Posteriorly – branch of medial circumflex femoral artery

• Anteriorly – ring is completed by branches of lateral circumflex femoral artery

• Minor contributions Superior and inferior gluteal arteries

Extracapsular ring

Medial circumflex femoral artery

It is a branch of• profunda femoral artery • femoral artery (rarely) • Participates in formation of extracapsular ring• Major contributor in extracapsular ring

Medial circumflex femoral artery

Gives of various branches – Medial ascending cervical arteries (inferior

retinacular, medial metaphyseal)– Posterior ascending cervical arteries– Arterial branches to superior gluteal artery– Branches to greater trochanter

Lateral ascending cervical artery– Terminal branch– Gives off metaphyseal branches to neck &

continues as lateral epiphyseal artery, a prominent vessel, for femoral head

– Provides most of blood supply to femoral head in children 3 to 10 years of age

Lateral circumflex femoral artery

It is a branch of• Profunda femoral artery • Femoral artery (rarely)• Participates in formation of extracapsular ring• Gives anterior ascending cervical arteries to

neck and femoral head

Ascending cervical arteries

• Also known as retinacular arteries (Within the capsule), described initially by Weitbrecht

• Derived from extracapsular arterial ring • Enters capsule at base of neck • Subsynovial course • Supplies metaphysis and epiphysis

• Ascend on surface of femoral neck in four groups:– Anterior– Posterior– Medial– Lateral

• Lateral group most important- largest contributor to femoral head. If damaged More chances of AVN

Subsynovial intra-articular arterial ring

• At the articular margin of femoral head

• Formed by vessels that penetrate the head (epiphyseal arteries)

• Lateral epiphyseal vessels supplying lateral weight-bearing portion most important

• Joined by vessels from ligamentum teres.

Artery of ligamentum teres

• Branch of Obturator artery or Medial circumflex femoral

artery• Gives blood supply to a small area of head of

the femur• Contribute little blood supply to femoral head

until age 8 and then only about 20% as an adult .

• Not sufficient to maintain blood supply of feoral head.

Blood supply of metaphysis

• Extracapsular arterial ring • Anastomoses with intramedullary branches of

the superior nutrient artery system• Branches of the ascending cervical arteries• Subsynovial intra-articular ring (descending

metaphyseal arteries)

Significance Blood supply of metaphysis

• Excellent vascular supply to metaphysis explains the absence of avascular changes in the femoral neck as opposed to the head.

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CLASSIFICATION

ANATOMICAL LOCATION • Subcapital• Transcervical• Basicervical (base of the neck fracture)

Classification

Pauwels Classification

• Based on the angle of the fracture line across the femoral neck.

• Relates to biomechanical stability• Predictive of more fixation failure and

nonunion with increasing angle • More vertical fracture has more shear force

Classification

• Pauwels – Angle describes vertical shear vector

Garden Classification

• Based on the degree of displacement of the fracture noted on pre-reduction antero-posterior x-rays in relation to trabecular line in femoral head to those in acetabulum

• Most frequently used• Four groups

Garden Classification

I Valgus impacted or incomplete

II Complete Non-displaced

III Complete Partial displacement

IV Complete Full displacement

Garden Classification

• Poor interobserver and intraobserver reliability.• Outcome of undispalced and displaced

fractures are independent of grade assinged.• Modified to:– Non-displaced

• Garden I (valgus impacted)• Garden II (non-displaced)

– Displaced• Garden III and IV

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Orthopaedic Trauma Association (OTA) Classification

• Alphanumeric fracture classification• Femoral neck fractures are designated type 31B• 31 is the proximal femur group and B the

femoral neck subgroup• Its complexity limits its usefulness in routine

clinical practice• Mainly used for research purposes• Neither useful in selecting treatment option nor

in predicting outcome.

• B1 group fracture is undisplaced to minimally displaced subcapital fracture

• B2 group includes transcervical fractures through the middle or base of the neck

• B3 group includes all displaced non-impacted subcapital fractures

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Singh Index

• Based on the pattern of proximal femoral trabecular line

• A method of estimating degree of osteoporosis• Six separate categories

Grade VI:• All normal trabecular groups are visible• Upper end of femur seems to be completely occupied by

cancellous bone

Grade V:• Principal tensile & principal compressive trabeculae is

accentuated• Ward's triangle appears prominent

Grade IV:• Principal tensile trabeculae are markedly reduced but can still

be traced from lateral cortex to upper part of the femoral neck         

• Grade III:

• A break in the continuity of the principal tensile trabeculae opposite the greater trochanter

• this grade indicates definite osteoporosis

Grade II:• Only principal compressive trabeculae stand out

prominently     

Grade I:• principal compressive trabeculae are markedly reduced

in number and are no longer prominent

Limitations

• Little practical value.• Poor interobserver and intraobserver leves of

agreement• Does not correlate with bone density as

measured.

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Imaging and other Diagnostic Studies

Radiography •Preferred initial modality in evaluating femoral neck fractures•AP and Lateral views•Lateral view gives idea regarding dispalcement

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Limitations

 • Spiral fractures are difficult to assess on a

single view.• Comminution is not easily demonstrated• Some stress fractures are simply not visible on

plain images.

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COMPUTED TOMOGRAPHY• Because of its superior resolution, cross-sectional

capabilities, and amenability to image reconstruction in the coronal and saggittal planes,

• Useful for assessing fracture comminution preoperatively and in determining the extent of union (or lack there of) postoperatively.

 

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MRI

• In cases of doubtful diagnosis MRI may be useful additional modality. 

• Can also show soft tissue problems associated with hip pain in absence of fracture.

Limitations • Relative lack of widespread availability• Its higher costs• Exclusion of patients with cardiac pacemakers

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Nuclear Medicine

• In past technititium bone scan was used in situations when plane radiography not able to show fracture.

• Usually show positive result in fracture neck femur.

• False negative results in osteopenic bone if carried out within 48-72 hrs of injury.

• Sensitive but not specific • CT scan is more accurate