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British Medical Books Health Issues Computerized Tomography

Fractures of the Femoral Neck

Importance

  • unsolved #
  • affect the elderly – preceded by OP
  • 250.000 hip #s in USA / yr
    • increase as society more geriatric
  • socio-economical burden

Anatomy

Intracapsular femoral neck / head

  • #-healing different
  • no cambium layer in its fibrous covering
    • no peripheral callus formation –> healing endosteal union alone

Trabecular system (Ward)

  • bone deposition along stress lines
  • calcar femorale - dense bone that reinforces femoral neck postero-inferiorly
  • trabeculae disappear with OP – Singh index (VI – I)

Blood supply special

  • extracapsular arterial ring at base of femoral neck
    • posteriorly large branch of MFCA (med. fem. circumflex)
    • anteriorly by smaller branches of LFCA
    • superior & inf. gluteal artery -> minor contributions
  • ascending cervical branches - retinacular arteries
    • pass under synovium on the neck
    • risk of injury at #
  • subsynovial intracapsular ring (Hunter)
    • second ring at margin of cartilage
    • lateral epiphyseal arteries as penetrate the head
  • artery of ligamentum teres
    • derived from obturator or MFCA
    • medial epiphyseal arteries
    • inadequate to supply femoral head with displaced #s

Epiphyseal Blood Supply

  • lateral epiphyseal vessels (retinacular vessels) enter head postero-superiorly -> main blood supply
  • medial epiphyseal vessels entering thru ligamentum teres -> supply area around fovea
  • intraosseous cervical vessels from marrow

NOF

  • intraosseous vessels disrupted -> nutrition of head depends on remaining retinacular vessels & vessels in lig.teres
  • position at reduction NB in development of AVN
    • valgus reduction -> kinking of lat.epiphyseal vessels & tethering of med.epiphyseal vessels in lig.teres

AVN following # NOF

  • risk of AVN ~ degree of initial displacement of fracture
  • minimally displaced # -> low risk < 10%
  • displaced # -> AVN may be > 80%
    • most retinacular vessels disrupted -> femoral head nutrition dependent on remaining retinacular vessels & vessels in ligamentum teres

Aseptic necrosis - AVN

  • avascular segment early after #NOF, reduction, pinning
  • revascularization occurs from
    • remaining blood supply
    • vascular ingrowth at #-site

X-ray - increased density from

    • new bone laid down
    • relative increase in density compare to OP around
    • calcification in marrow (decreased blood wash out)
  • early detection - MRI

Late segmental collapse

  • if no repair of necrotic bone or process slow
  • x-ray - flattening of head & # of subchondral bone (crescent sign)

Prevention

  • position achieved at reduction NB
    • valgus & rotatory malposition -> affect blood supply
    • screws in superior or lateral position -> interrupt lateral epiphyseal vessels
  • early fixation of # -> decrease risk of AVN
  • hip joint capsulotomy/aspiration << AVN – controversial

Mechanism of injury

  • fall producing a direct blow to GT
  • lateral rotation of extremity
  • major trauma in young patients

Classification

Anatomic location

  • subcapital – beneath articular surface of head
  • transcervical - # across neck between head & GT
  • base of neck – extracapsular -> not included in NOF#

Pauwels classification

  • based on # angle
    • Type I – fracture line 30° from horizontal
    • Type II - line 50°
    • Type III - line > 70° from horizontal
  • little difference between nonunion & AVN rates of type II & III #s -> not good prognosticator

Garden classification

  • based on degree of displacement
  • garden I-II & Garden III-IV treated similarly

Garden I

  • incomplete or impacted fracture
  • trabeculae of inferior neck still intact
  • includes “abducted impaction fracture”
  • AVN develops in 10-40% with or without internal fixation
    • extreme valgus position -> kinking of vessels
  • risk of non-union low

Garden II

  • complete frx without displacement
  • wt bearing trabeculae interrupted by #line across entire neck
  • slight varus -> not impacted -> no bony stability -> displacement occur unless fixed internally
  • risk of non-union
    • transverse #line heal well
    • vertical configuration -> >> nonunion rate

Rx (Garden I & II)

  • closed reduction & IF with cannulated screws or pins - emergency

Garden III

  • complete fracture with partial displacement
  • if it needs a reduction, then its a type III fracture
  • femoral & acetabular trabeculae do not align
  • retinacular vessels of Weitbrecht remain attached
  • risk of non union - >> with vertical #line

Garden IV

  • complete fracture with total displacement
  • no continuity between proximal and distal fragments
  • trabeculae in head line up with acetabular lines

Rx (Garden III & IV)

  • cannulated screws in young
  • hemiarthroplasty or THR

Signs & Symptoms

Stress & impacted

  • Hx of fall
  • pain in groin or along medial side of knee
  • tenderness over GT
  • fair ROM (active – passive)
  • may be able to walk
  • X-rays

      • normal initially
      • tomograms may help
  • bone scan –> uptake after 72 hrs (slow turnover d/t OP)
  • MRI – prompt

Displaced

  • pain in hip region
  • leg in ER, abD & shortened -> traction for pain relief & protect remaining vascular supply
  • X-ray

      • confirms
      • true AP & lateral

Radiology of the Hip

AP view

  • with foot IR 15° - best views of femoral neck

Lateral view

  • patient supine & opposite hip flexed & abD
  • shows posterior comminution

Frogleg Lateral View

  • do not order in any pt.suspected hip # or dislocation
  • patient supine with knees flexed, soles together & thighs abducted
  • central beam directed vertically just above symphysis

Radiographic Features

  • femoral head & neck produces an S or reversed S curve outline on all projections used to assess reduction
  • posterior comminution - most evident on lateral view
    • higher prevalence of non-union

Non-displaced

  • if plain radiographs N -> MRI- immediate interpretation
  • bone scan after 48-72 hrs
  • pubic ramus # common - tenderness over symphysis

Garden’s Alignment Index

  • angle of compression trabeculae on AP & lateral view
    • should be 160° on AP
    • 180° on lateral
  • to assess reduction
    • acceptable reduction within range of 155-180° on both views -> minimizes non-union and AVN

Lowell’s Alignment Theory

  • radiographic outline of femoral head & neck junction have a convex outline -> S or reversed S curve
  • if outline reveals an unbroken C curve -> # not reduced

Differential Diagnosis

  • with hip pain and no apparent

Pubic ramus fracture

  • commonly seen in the elderly
  • tenderness over the pubic bone

Treatment

Impacted or incomplete fractures – Garden I

  • valgus & abD position
  • femoral neck cortex impacted into cancellous head -> stability

Non-operative Rx

  • spica cast -> risk of disimpaction
  • only if # several weeks old & pt.walks without pain
  • immobilisation -> fatal pulmonary complications

Operative

  • do not disimpact #
  • internal fixation with multiple pins
    • Knowles pins, cannulated screws, Muller screws
  • larger implants (as compression hip screws) may disimpact #

Complete undisplaced – Garden II

  • no impaction – likely to displace if not fixed

Non-operative

  • historical

Operative

  • closed reduction & internal fixation
    • multiple screws (cannulated, Muller)
    • DHS + screw above to prevent rotation

Displaced Fractures – Garden III / IV

Non-operative Rx

  • historical
  • high rate of deformity, non-union

Operative

  • goal – anatomical reduction & stable fixation
  • as an emergency in younger patients
    • << AVN if # reduced w/in 12 hrs
    • skin traction while preparing pt.-> >> blood flow!
    • quick resuscitation if necessary (rehydration, basic bloods etc.)

Closed reduction

  • on fracture table
  • in extension – traction, then IR & abD (Whitman)
  • in flexion – hip flexed to 90°, traction in line of femur, IR, then abD & bring down to extension
  • (Leadbetter)

  • assessed with image or x-rays
    • garden’s alignement index
    • lowell’s alignement curves
    • assess infero-medial apposition – calcar line
    • assess posterior comminution – risk of loss of reduction later
  • acceptable reduction
    • neck-shaft angle between 130-150°
    • valgus reduction - increase stability
      • excessive valgus(>185°) >> rate of AVN (tethering vessels)
      • can be reduced by decreasing traction
    • varus reduction
      • increased non-union rate
      • more traction applied, & GT pushed medially
    • angulation (anteversion)
      • should be between 0-15° of anteversion
  • stability of reduction
    • evaluate posterior comminution on lateral view
      • risk of loss of reduction & non-union
  • gentle manipulation max. 2-3x
  • if no success -> open reduction or hemiarthroplasty

Open reduction

  • if closed reduction unacceptable -> >> risk of AVN or non-union
  • difficult procedure
  • anterior or anterolateral approach (Watson-Jones, Hardinge’s)
  • use posterior approach for pedicle bone grafting
    • if posterior comminution

Methods of fixation

Goals

  • anatomical reduction
    • closed or open if necessary
    • open reduction thru’ Watson-Jones approach
      • may be difficult on traction table
  • rigid fixation & impaction at site
  • proper placement of fixation device

Multiple pins & screws

    • Knowles pins, Muller screws, cannulated screws etc.
    • can be performed under local
    • ideal in impacted #s
    • 3 or 4 pins inserted parallel
    • do not penetrate head

Fixed-angle nails

    • Smith-Petersen nail, Jewett nail
    • Historical

Sliding compression screw

    • Richards screw, DHS
    • improved fixation strength
    • if danger of rotating head -> accessory pin above screw

Pin placement

    • inferior on AP view
    • slightly posterior or central on lateral view
    • depth - tip within 1cm from subchondral bone
    • ideally 135° angle to femoral shaft

Postoperative treatment

  • if stable fixation - PWB with walker on D2 for 6-8/52
  • gradually FWB as callus formation allows
  • if unstable # or unco-operative pt.-> mobilize in bed & sitting
  • follow up with serial x-rays until union
    • check for possible AVN also

Hemiarthroplasty

Indications

    • physiologic age > 75 yrs – life expectancy < 5 yrs
    • poor general health would prevent a second operation
    • pathologic hip fractures
    • Parkinson’s dx, hemiplegia, or other neurological dx
    • severe OP with loss of primary trabeclae in femoral head
    • inadequate closed reduction in old pt.
    • displaced (Garden 3 & 4)
    • pre-existing hip dx (DJD, RA, AVN)-> THR rather

Contraindications

    • pre-existing sepsis
    • young patient (< 75 yr) -> THR
    • preexisting dx of the acetabulum -> THR
      • RA, OA or Parkinson’s dx

Advantage

    • allows immediate weight bearing – cemented
    • eliminates AVN or non-union -> no need for second op

Austin Moore Prosthesis

    • only true calcar support prosthesis
    • if 1/2 to 3/4 inches of remaining femoral neck above LT
    • fenestration in stem ->“self locking” & bony ingrowth
    • new design -> solid-stem - interference fit
    • surgery shorter – no cementing

Thompson Prosthesis

    • for pts with limited femoral neck above LT
    • if poor bone stock
    • cemented
    • can be modular
    • should be used rather than A-M

Pre Op Planning

  • correctly size prosthesis for the femoral head
    • if too large - tight joint with decreased motion & pain
    • if too small - erosion, superomedial migration & pain
    • neck length also critical
  • ideally inserted prostheses should restore anatomical distance between superior aspect of LT & acetabulum -> restore length of abductor mechanism
    • inserted into medullary canal in neutral or slight valgus position

Surgical Approaches

  • Anterolateral Approach - Watson Jones
  • Lateral Approach – Hardinge
  • Posterior Approach

Complications

Mortality

  • pts. older & more debilitated - 10 to 40%
  • small difference from pts. with ORIF

Fracture of femur

  • 4.5%
  • when surgeon attempts to reduce prosthesis
  • consider cement combined with a long stem prosthesis

Dislocation

  • less than 10%
  • avoid dislocation during bed to bed transfers
  • more common with too much anteversion or retroversion
  • use abduction pillow

Sepsis

  • 2% to 20%
  • more common with posterior surgical approach
  • may be superficial or deep, acute, subacute or chronic

Pain (loosening or subsidence)

  • main late complication
  • usually from loosening or migration of prosthesis
    • presence of a radiolucent zone around prosthesis
    • if clinical signs & symptoms -> revision to THR
  • less with cemented prosthesis

Bipolar prosthesis

  • femoral stem + double jointed head component ->> acetabular friction
  • cost factor

Total hip arthroplasty

Indications

  • pre-existing hip dx. – OA, RA, Paget’s, pathological etc.
  • active, mobile elderly pt. with displaced #NOF
  • failure after ORIF of #NOF
  • if hemiarthroplasty indicated, but have dx. of contralateral hip

Results

  • inferior to THR in OA & RA

Stress Fractures of Femoral Neck

  • relatively uncommon injuries - military recruits & athletes
  • normal bone undergoing repeated submaximal stresses or diseased bone undergoing repeated minimal stresses
  • classified as either tension or compression

Radiographs

  • initial radiographs often normal
  • bone scan or MRI

Non-surgical Treatment

  • serial radiographs to detect changes in pattern or displacement
  • compression occur on the inferior aspect of NOF -> more stable & can be treated without surgery
  • initially with bed rest followed by protected wt bearing

Surgical Treatment

  • fractures of both cortices -> immediate internal fixation - cannulated screws

Pathologic Hip Fractures

Hyperparathyroidism

  • incidence of hip frx is about 10%
  • in younger pts with good bone stock - ORIF
  • in elderly pts consider primary THR
  • renal failure -> high risk of infection

Metastatic Dx

  • common – 30-50% around hip
  • consider cemented solid stem hemiarthroplasty or THR
  • X-Ray - acetabulum & distal femoral shaft involvement

Pagets disease

  • NOF << intertrochanteric or subtrochanteric
  • non displaced fractures - ORIF
  • often do not heal during sclerotic phase
  • heal rapidly during the vascular phase
  • possibility of excessive bleeding
  • displaced fractures -> prosthetic replacement
  • x-ray of femoral shaft to determine excessive bowing

Parkinson’s Disease

  • 6 month mortality of 60%
  • osteoporosis & contractures
  • consider primary prosthetic replacement (hemi or THR)
    • depends on age, activity, life expectancy

Spastic Hemiplegia/Stroke

  • up to 10% have #NOF
  • usually on hemiplegic side -> varying degrees of flexion & adduction contracture associated with spasticity
  • if ORIF planned -> tenotomy before reduction
  • if marked spastic hemiplegia -> hemiarthroplasty
  • also consider tenotomy of hip contractures

Complications

Mortality

  • 10-40%
  • highest in 1st 6 months
  • higher in pts.from nursing homes

Thrombo-embolic dx

  • leading cause of death
  • incidence of DVT ~40% after hip surgery

Prophylaxis

  • dextran
  • aspirin
  • low-dose warfarin
  • heparin
  • low-molecular-weight heparin
    • 40 mg Clexane sc. daily

Infection

  • 1%
  • superficial or deep
  • acute, subacute or chronic

Prophylaxis

  • iv. AB – Kefzol 1g 8hrly 3 doses
  • aseptic technique

Non-union

  • improved fixation devices -> < 5%
  • pain in groin or buttock
  • some varus angulation
  • if no evidence of healing by 6-12 months after
  • comminution, especially posterior -> >> risk
    • posterior muscle pedicle graft (quadratus femoris) enhance # stability & union, >> blood supply femoral head

Rx

  • determine viability of femoral head, degree of OP & neck resorption
    • Tc scan, SPECT scan

Salvage femoral head

  • refixation with BG & valgus OT
    • << sharing force at site
    • produce valgus -> shortens lever arm of abDs from GT to femoral head-> >> P°, AVN & early OA of head
    • use cane after OT
    • McMurray displacement OT
    • Schanz angulation OT
  • arthrodesis

Arthroplasty (hemi- or THR) if head collapsed

Avascular necrosis

  • major long term complication
  • early anatomical reduction & stable fixation may prevent
  • presents ~ 6 months on X-ray
  • MRI – early detection
    • disturbed by metallic implants

Rx

  • symptomatic - core decompression, osteotomies
  • arthroplasty