SCAPHOID FRACTURE

INTRODUCTION- 

Views of scaphoid --> X - rotational (pronation/supination);  Y -sagittal  (flexion/extension);  Z - coronal  (radial/ulnar).

•The  treatment  of  scaphoid  fractures  requires  knowledge  of  the blood  supply, surgical  approaches, and  effects  that  fractures  and nonunions  of  the  scaphoid  have  on  carpal  kinematics,  stability, and  arthritis.

• New methods  of  scaphoid  repair have  been  developed  to  minimize  additional  surgical  trauma and  optimize  stabilization  until  healing. 

GENERAL CONSIDERATIONS 

INCIDENCE- 

• Scaphoid is  the  “keystone”  of  the  carpus.

•The  scaphoid  is  not  only  important  but  it  is  the  most  commonly  fractured  carpal  bone.  Scaphoid  fractures  account  for 60%  to  70%  of  all  carpal  fractures  and  are  second  in  frequency of  wrist  fractures  only  to  distal  radius  fractures.

• The  majority of  injuries  are  low-energy  injuries,  either  from  a  sporting  event (59%)  or  from  a  fall  onto  an  outstretched  wrist  (35%);  the remainder  result  from  high-energy  trauma  such  as  a  fall  from a  height  or  a  motor  vehicle  injury. 

• incidence more common in Males than females .

ANATOMY  OF  THE  SCAPHOID

• Skaphos in Greek means Boat, so its a boat shaped bone . Other terms like twisted peanut, as bean shaped are also used to describe this bone.

•Approximately  80%  of  the  scaphoid  is  covered  by  cartilage,  limiting  ligamentous  attachment  and  vascular  supply .

• The  scaphoid  is  divided  into  three  regions: proximal  pole,  waist,  and  distal  pole  (tubercle).

•The  scaphoid  is  oriented  in  the  carpus  with  an  intrascaphoid  angle  averaging  40  ±  3  degrees  in  the  coronal  plane and  32  ±  5  degrees  in  the  sagittal  plane.

☆intrascaphoid angle increases in scaphoid fracture.  

•The  scaphoid  is  the  only  carpal  bone  that  bridges  the  proximal  and distal  carpal  rows  and  acts  as  a  tie-rod.

•carpal  rows are  supported  by  stout  intrinsic  ligaments  and  reinforced  by  a volar and dorsal extrinsic ligaments. 

• The  scapholunate  interosseous  ligament  (SLIL)  is  a  stout ligament  connecting  the  scaphoid  to  the  lunate  and  is  the primary  stabilizer. The  dorsal  region of this ligament  resists palmar-dorsal  translation  and  gap  due to transverse collagen fibres arrangement,  whereas  the  volar  portion resists  rotation due to oblique collagen fibers arrangement.

•Radioscaphocapitate  (RSC)  ligament - 

It acts as fulcrum around which scaphoid rotates , scaphoid can also fracture around this fulcrum from Waist .

• Scaphocapitate and Scaphotrapezial ligaments  function as primary restraints of the distal pole .

•Vascular  Anatomy-  

• The  blood  supply  of  the  scaphoid  bone  is  predominantly  retrograde.  The  major blood  supply  to  the  scaphoid  is  via  the  radial  artery:  70  to  80%  of  the  intraosseous  and  proximal  pole  vascular supply  is  from  branches  of  the  radial  artery  entering  distally through  the  dorsal  ridge  of  the  scaphoid  between  the  proximal and  distal  articular  surfaces.  The  radial  artery  or  the  superficial palmar  arch  also  give  volar  branches  that  enter  in  the  region  of the  tubercle  and  provide  the  blood  supply  to  20%  to  30%  of  the bone  in  the  region  of  the  distal  pole.

• The  proximal  pole  also  gets  blood  supply  from  the  radioscapholunate ligament  (ligament  of  Testut,  a  neurovascular  conduit)  and directs  scapholunate  branches  from  the  palmar  and  dorsal transverse  carpal  arches.

•The  more  proximal  the  fracture,  the  more  likely  the  bone  is to  be  dysvascular  and  the  higher  the  risk  of  nonunion. Proximal pole  fractures  have  been  reported  to  have  an  incidence  of  avascular  necrosis  (AVN)  of  13%  to  50%.

•Combined  palmar  and  dorsal  approaches  taking  off the  soft  tissue  at  the  tubercle  and  the  dorsal  ridge  would  not  be advisable , majority of vessels enter  from these landmarks, to be left intact. 

BIOMECHANICS OF SCAPHOID FRACTURES 

• Hyperextension  past  95  degrees   is  the  usual  position  of  injury,  but  other  mechanisms  such  as  axial  loading  have also  been  postulated  to  produce  scaphoid  fractures. 

• Hyperextension mechanism usually causes Volar waist fractures, whereas Proximal scaphoid fractures occur due to dorsal subluxation  during  forced  hyperextension. 

• Nonunion  occurs in  10%  to  15%  of  all  scaphoid  fractures. 

 The  risk  of  nonunion increases  with: 

1.  Delay  of  treatment  for  more  than  4  weeks 

2.  Proximal  pole  fractures 

3.  Fracture  displacement  greater  than  1  mm 

4.  Osteonecrosis 

5.  Tobacco  use 

6.  Associated  carpal  instability  (DISI  =  dorsal  intercalated segmental  instability  with  a  scapholunate  angle  >  60 degrees  and  a  capitolunate  angle  >  15  degrees)  secondary to  humpback  (flexed  with  intrascaphoid  angle  >  45 degrees;  the  normal  intrascaphoid  angle  is  24  degrees) scaphoid  positioning. 

• For  nondisplaced  waist  fractures  treated  with  casting,  nonunion  rates  are  5%  to  12%. Nonunion  rates  for  displaced scaphoid  fractures  treated  nonoperatively  are  higher,  reaching 50%. 

•Untreated  displaced  fractures  of  the  waist  are  subject  to varying  degrees  of  these  forces  and  will  usually  angulate  as  the volar  bone  is  reabsorbed,  yielding  a  “humpback”  of  flexion  deformity of scaphoid. 

• Extension of lunate with its attachment to triquetrum  results  in  a  DISI deformity.  Ultimate  treatment  of  a  humpback  scaphoid  nonunion  with  DISI  requires  both  restitution  of  scaphoid  anatomy and  reversal  of  the  secondary  changes  in  carpal  kinematics.

• Untreated  scaphoid nonunion  progesses to scaphoid nonunion advance collapse (SNAC) and ultimately Pancarpal Arthritis. 

CLINICAL PRESENTATION- 

• pain and swelling  on  the  radial  side  of  the wrist .

• history  of  trauma,  such  as  falling  on  an  outstretched hand,  collision  of  the  wrist  against  a  person  or  heavy  obstacle, or  possibly  a  direct  blow  against  an  object.

 PHYSICAL EXAMINATION-

• On visual  INSPECTION , Wrists  with acute  fractures  may  have  swelling  and  bruising  in  the  radial aspect.

•“Snuffbox tenderness " which  applies  predominantly  to  waist  fractures,  represent  70%  of  scaphoid  fractures. 

•The  second most  common  type  of  scaphoid  fracture  is  proximal  pole  fracture,  at  20%. The  least  common is distal  pole  fracture, at  10%.

PALPATION - 

•To  palpate  the  anatomic snuffbox  for  the  waist  examination, palpate  just  distal  to  the  radial  styloid  in  the  “soft  spot.”

•Distal  pole  should  be  palpated  at  the  scaphoid  tubercle  on  the palmar  aspect  of  the  wrist  just distal to anatomic snuffbox .

•The  proximal  pole  is  palpated  dorsally  in  line  with  the second  ray  just  distal  to  the  dorsal  radius lip. 

☆  Scaphoid Shift Test / Watson test - 

- In  normal  wrists,  the scaphoid  cannot  flex  because  of  the  external  pressure  by  the  examiner’s  thumb. This  may  produce  pain  on  the  dorsal  aspect  of  the  scapholunate  (SL)  interval  owing to  synovial  irritation. 

- A  “positive”  test  is  seen  in  a  patient  with  an  SL  tear  or  in  a patient  with  a  lax  wrist;  the  scaphoid  is  no  longer  constrained  proximally  and subluxes  out  of  the  scaphoid  fossa  (straight  arrow).  When  pressure  on  the  scaphoid is  removed,  it  goes  back  into  position  and  typically  a  clunk  occurs. 

- Scaphoid shift test has  low specificity,  in  local  problems  inducing  local  synovitis  (e.g., occult  ganglion  or  dorsal  RS  impingement),  this  test  may  also provoke  sharp  pain  making  it  difficult  to  discern  whether  there is  an  abnormally  subluxable  proximal  scaphoid. 

DIAGNOSTIC IMAGING -

Radiography.

•five radiographic  views  for  the  assessment  of  scaphoid  fractures: wrist  posteroanterior  (PA),  lateral,  and  oblique  views;  scaphoid view;  and  clenched  pencil  view.

•true scaphoid  pisiform  capitate  (SPC)  lateral  radiograph taken for carpal alignment assessment. 

Scaphoid View

Clenched pencil view 

Computed  Tomography.

•Computed  tomography  (CT)  scanning is  helpful to delineate  scaphoid  fracture  displacement,  bony  morphologic  findings,  gapping,  sclerosis,  cysts,  and  evidence  of  healing(usually preferred to take at 3 months) . CT is  particularly  helpful  in  addressing  nonunions.  It  is  important  that  CT  scans  are  taken  with  overlapping  1-mm  cuts  along the  long  axis  of  the  scaphoid  and  with  coronal  and  sagittal reconstructions. 

•evaluating  the  vascularity  of  the  proximal pole  of  the  scaphoid.

Magnetic  Resonance  Imaging.  

•Magnetic  resonance  imaging (MRI)  is  best  to  determine  whether  there  is  occult  scaphoid fracture.  Specificity  is  90%  and  sensitivity  is  between  90%  and 100%,as  opposed  to  bone  scintigraphy,  which  is  92%  to  95% sensitive  and  60%  to  95%  specific.

•MRI  with  or  without contrast  enhancement  might  be  helpful  in  assessing  the  vascularity  of  the  bone,  but the  patient  history  and  CT  imaging must be taken into account. 

SCAPHOID FRACTURE CLASSIFICATION- 

•Scaphoid  fractures  have  been  classified  by  fracture  location (proximal,  waist,  or  distal),  plane  (transverse  or  oblique),  and stability  (stable  or  unstable). 

• fracture  classification  helps in management  of  injuries,for  rapid healing  with  minimal  complications  and  rapid  return  to  routine activities .

•following classification are used- 

1)Russe classification - 

The Russe classification predicts instability according to the inclination of the fracture line; for example, vertical oblique fractures. 

2)AO classification -  The AO classification breaks the fracture down into simple anatomic location (distal pole, waist, proximal pole) and comminution.

3)Herbert and Fisher classification -proposed a classification intended to identify those fractures most applicable for operative fixation and is commonly used throughout the literature .

Herbert  and  Fisher  classified  scaphoid  fractures according  to  their  stability.

4) Mayo classification- 

criteria for instability according to mayo is as follows: 

• >1 mm of fracture displacement

• A lateral intrascaphoid angle of  >35 degrees 

•Bone loss or comminution 

•Fracture malalignment 

•Proximal pole fractures 

•DISI deformity 

•Perilunate fracture-dislocation.

NOTE- 

* Displaced fracture --> displacement  is  defined  as  DISI  malalignment  of  1  mm [DISI  =  dorsal  intercalated  instability  with  scapholunate angle  >  60  degrees  and  capitolunate  angle  >15  degrees].

SCAPHOID NONUNION CLASSIFICATION 

1) Slade and Geissler Classification 

2) Lichtman Classification 

3) Alnot Classification 

MANAGEMENT OF SCAPHOID FRACTURES -

 •Up to 25% of scaphoid fractures are not visible on initial radio-graphs.

•All clinically suspected scaphoid fractures are treated as fractures with short-arm thumb spica cast immobilization until the cause of the symptoms is clarified since failure to treat a stable scaphoid fracture within 4 weeks increases the nonunion rate.

• Follow-up clinical examination and radiograph are taken at 2 weeks .

• MRI is done for diagnosing occult and acute fractures and is generally diagnostic within 24hrs of injury . 

SCAPHOID CAST - 

• position of immobilization- wrist slightly extended, and the proximal phalanx of the thumb included in a position of slight opposition (“scaphoid cast”).

☆ See here for Scaphoid Surgical Methods .

Mechanics  of  Fracture  Fixation - 

• Since  majority  of  the  scaphoid  is  covered  with  cartilage, fracture  callus  is  not  produced,  so  primary  bone  healing  is entirely  dependent  on  rigid  stabilization  of  the  fracture  fragments  until  healing.

•The  mechanical  effectiveness  of  internal  fixation  is  determined  by  the  bone  quality,  fracture  geometry,  fracture  reduction,  choice  of  implant,  and  implant  placement.

•Fracture  reduction  and  placement  of  the implant in the biomechanically  ideal  position  are  the  most important of  the five variables.

•screws  centrally  placed  in  the  proximal  fragment  of  the scaphoid  had  superior  results  compared  with  screws  placed  in an  eccentric  position. 

•Biomechanically,  the  longer  the  screw,  the  more  rigid  the  fixation,  because  longer  screws  reduce  forces  at  the  fracture  site and  bending  forces  are  spread  along  the  screws.

• Augmentation with K wires or mini headless screw necessary when central screw placement alone cannot provide rigid fixation. 

Techniques  for  Rigid  Fixation 

Implants  for  Rigid  Fixation  of  Scaphoid  Fractures -

•Implants  used  included  Kirschner  wires,  AO  compression screws,  headless  compression  screws,  plates,  and  bioabsorbable implants. 

SCREWS 

☆The  difference  in  pitch  between  the  leading  thread  (P1)  and  the trailing  thread  (P2)  of  the  Herbert  screw  governs  the  rate  of  “take-up,”  or  drawing together,  of  the  two  bone  fragments  to  produce  compression.

SURGICAL METHODS- 

•Click here for SCAPHOID SURGICAL METHODS 

1) Scaphoid  Open  Reduction  and  Internal  Fixation  From  the  Dorsal Approach/Mini-Open  Approach.

2) Scaphoid Mini-Open  Screw  From  the  Palmar  Approach - 

Technical points- 

•  Place  the  guidewire  as  centrally  as  possible  in  the  scaphoid. 

•  Consider  using  an  antirotation  wire. 

•  Common  error  is  using  a  screw  that  is  too  long. 

•  Subtract  at  least  4  mm  from  the  measured  distance. 

•  A  common  screw  length  for  an  adult  male  is  20  mm. 

•  Do  not  ream  past  the  far  cortex .

•  If  feeling  a  lot  of  resistance  (especially  when  reaming  over  wire),  stop  and look.  The  wire  may  be  bent  and  break  or  the  drill  bit  may  break .  

•  Beware  of  hoop  stresses.  Use  countersinking  to  avoid  excessive  hoop stresses  that  can  fracture  the  near  fragment. 

•  Consider  the  use  of  joysticks  to  gain  reduction. 

•  If  needed,  reduce  and  pin  the  lunate  in  neutral  (out  of  DISI) 

•  Consider  supplemental  fixation  for  more  stability.

Delayed presentation of Scaphoid waist fractures  - 

•Surgery  is  generally  indicated  for  delayed  presentation  of  a scaphoid fracture 4 to 6 weeks or more following injury. 

• patients with delayed presentation have a higher rate of non union .

COMPLEX SCAPHOID FRACTURES 

1)Combined fractures of Scaphoid and distal radius - 

• Early Surgery is planned in these patients with ORIF of distal radius fracture and mini open approach and fixation for Scaphoid fractures. 

2) Transscaphoid  Perilunate  Fracture-Dislocations 

•Perilunate fracture-dislocations  represent  approximately  5%  of  wrist  fractures  and  are  about  twice as  common  as  pure  ligamentous  dislocations.  •Transscaphoid perilunate  fracture-dislocation  is  the  most  common  type  of complex  carpal  dislocation.

• ORIF (via  Dorsal approach  or Palmar  or Proximal row carpectomy ) of these injuries have a good prognosis. 

Technical Consideration-

•It  is  imperative  during  reduction  to  restore  Gilula’s  lines  in  coronal  plane and  attain  neutral  radiolunate  and  capitolunate  alignment  in  the  sagittal plane.

COMPLICATIONS   of  Scaphoid  Fracture  Treatment - 

•The  most  common  complications are -

 1)delayed  union, 

 2) nonunion, 

 3) arthritis,  

 4) reduced  wrist  motion, and 

 5) loss  of  strength etc . 

MANAGEMENT OF SCAPHOID NONUNION- 

☆ Scaphoid Nonunion criteria 

failure  of  union  following  cast immobilization  or  surgical  treatment  of  6  months’  duration.

Evaluation  of  Scaphoid  Nonunion - 

•following things to be considered-

1.  Site  of  nonunion , At  the  waist  or  at  the  proximal pole? - more  proximal  the  fracture,  the  more  likely the  proximal  bone  will  be  dysvascular.

2.  Is  the  nonunion  displaced ?

3.  Is  there  a  humpback  deformity?

4. Is  DISI  present? 

- If  there is  humpback  deformity  and  carpal  malalignment,  they  may have  to  be  corrected  at  the  time  of  bone  grafting  and  fixation.

5.  Is  there  comminution,  cyst  formation,  or  cavitation? 

 • If  the  nonunion  is stable  and  well  aligned  and  bone  loss  is  minimal,  limited opening  in  the  nonunion  site,  curetting  as  necessary,  and cancellous  bone  grafting  may  be  appropriate,  followed  by  internal  fixation  by  a  headless  compression  screw. 

6.  Was  there  previous  surgery? 

-Any  previous  surgical  or  other  treatments should  be  taken  into  account  because  they  would  make  further treatment  more  complex.

7.  Does  the  proximal  pole  look  dysvascular?   

-In cases of diminished vascularity bone grafting have to be considered. 

- According  to  Green,  vascularity  was  best  determined  by punctate  bleeding.  MRI also helpful .

8.  Is  there  arthritis  (SNAC  wrist)?  If  so,  at  what  stage? 

- if  early  arthritis  (SNAC  I)  is  confined  to  the  radial  styloid,  radial  styloidectomy  and  scaphoid  bone  grafting  could  be  considered. 

- In advanced  arthritis with mild symptoms,  nonoperative  management  is  considered .  

- In arthritis  with severe symptoms ,  other  options may  include  partial  denervation  or  salvage  procedures  such  as scaphoid  excision  and  four-bone  fusion,  proximal  row  carpectomy,  total  wrist  fusion,  hemiwrist  arthroplasty,  and  total  wrist arthroplasty.

9.  Is  the  scaphoid  deformed  or  salvageable?

- sometimes the proximal or distal pole has fragmented and is not usable .

Treatment algorithm- 

HYBRID RUSSE PROCEDURE- 

The  hybrid  Russe  procedure  is  advantageous  because  it  is  effective  for  humpback  scaphoid  nonunions  with  DISI.

Steps - 

• Exposure of nonunion site 

• uptake of bone graft 

• Packing of Graft into the Nonunion site 

• Internal fixation with headless screw 

VASCULARIZED BONE GRAFTING 

Common choices are - 

1. 1,2  intercompartmental  supraretinacular  artery  (ICSRA) pedicle  (Zaidemberg)

2.  Pedicled  on  the  volar  carpal  artery  (Mathoulin) 

3.  Dorsal  capsular  pedicle  (Sotereanos) 

4.  Free  medial  femoral  condyle  graft  (Doi,  Bishop  and  Shin, Higgins 

Surgical  Fixation  of  Scaphoid  Nonunion  With Nonvascularized  Bone  Graft  (Distant)  Wedge  Graft 

Fernandez-Fisk  wedge  graft. - 

• This procedure is use to treat scaphoid nonunion with carpal instability. 

STEPS - 

(1)preoperative  calculation  of  the exact  scaphoid  length  and  form  based  on  comparative  radiographs  of  the  opposite  wrist,  (2)  the  use  of  a  palmar  approach, (3)  the  insertion  of  a  wedge-shaped  corticocancellous  graft from  the  iliac  crest  after  resection  of  the  pseudarthrosis,  and  (4) the  use  of  internal  fixation. 

Anterior Wedge Grafting - 

Unsalvageable Scaphoid Proximal Pole Nonunion  - 

Rib osteochondral autograft reconstruction of the proximal pole. 

Salvage  Procedures  for  Scaphoid  Nonunion   Advanced  Collapse

1) Radial Styloidectomy . - good for  stage  I  SNAC  arthritis  when  combined  with  procedures  to heal  scaphoid  nonunions.

2) Distal  Scaphoid  Resection  Arthroplasty.

•Indicated in waist fracture  nonunion  with  SNAC  I  styloscaphoid  arthritis  with significant  loss  of  wrist  dorsiflexion  and  radial  deviation  and pain  on  wrist  loading,  gripping,  and  range  of  motion.

3) Proximal  Row  Carpectomy .

• it is a simple motion preserving salvage operation done ideally in  a relatively  low-demand  patient  older  than  40  years  with  stage II  or  III  SNAC  with  no  to  minimal  capitolunate  degenerative disease. 

• removal of proximal row starts with Scaphoid then Lunate and then Triquetrum  with taking care not  to  damage  the  articular surface  of  the  head  of  the  capitate.

• Avoid injury to RSC ligament that prevents postoperative Ulnar translocation of the carpus. 

4) Intercarpal  Fusion.- Fourbone  (capitate-lunate-hamate-triquetrum)  fusion  with  scaphoid  excision  satisfactorily  treats  degenerative  SNAC  arthritis affecting  the  radioscaphoid  and  midcarpal  joints  while  preserving  an  anatomically  congruous  radiolunate  joint.

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