Scaphoid Fractures and Nonunions

Epidemiology

• Account for 3-4% of all fractures.
• Second most common fracture of the upper limb after distal radius fractures.
• Most commonly missed fracture in the body.
• Highest incidence seen between 20-30 years of age.
• Male female ratio is 2:1.

Anatomy

• Got its name from the Greek word “skaphe” which means boat.
• 4 Parts
  • Tubercle
  • Distal pole
  • Waist
  • Proximal pole
• 80% covered by articular cartilage. Its implications are that 1, articular cartilage may be damaged by screw insertion, 2, Absence of periosteum results in minimal callus and 3, poor blood supply predisposes to osteonecrosis.
• Tubercle of scaphoid is overlaid by flexor carpi radialis (FCR)
• Male scaphoid is longer. Hence longer and larger screws may be required in males.
• Trabecular density is maximum at the proximal pole and thinnest at the waist. Waist is the commonest site of fracture.
• Blood vessels enter through the dorsal ridge and tuberosity. 70-80% of blood supply enters through the dorsal ridge.
• Scaphoid links the proximal and the distal carpal rows.
• There is significant intercarpal motion between scaphoid and lunate, which questions the validity of present kinematic models of carpal motion.
• Scaphocapitate and scaphotrapezial ligaments control the movements of the distal pole.

Imaging

• X-rays needed for diagnosis are PA view, Lateral view, Semipronated oblique view, Semisupinated oblique view and AP in ulnar deviation.
• Intrascaphoid angle is measured by first drawing a line connecting the widest part of proximal and distal poles, then draw lines perpendicular to it. The angle formed by their intersection is the intrascaphoid angle.
• Normal intrascaphoid angle is 40⁰ in the coronal plane and in the sagittal plane it is 30⁰.
• Intrascaphoid angle more than 35⁰ indicates humpback deformity.
• Normal height length ratio is greater than 0.65.
• Sensitivity of CT for detection of an undisplaced fracture is 89% and specificity is 91%.
• MRI is the most sensitive and specific investigation for detection of occult fractures.
• Normal scapholunate interval is 9mm at 7years of age and 3mm at 15 years of age.

Classification

Russe Classification

• Horizontal Oblique
• Transverse
• Vertical Oblique

Herbert & Fisher Classification

A. Stable Acute Fractures

A1- Tuberosity fractures

A2- Incomplete waist fractures

B. Unstable Acute Fractures

B1- Oblique fractures of distal third

B2- Displaced waist fractures

B3- Proximal pole fractures

B4- Trans-scaphoid Perilunate instability

B5- Comminuted fractures

C. Delayed union (After 6 weeks of immobilization)

D. Established nonunions

D1- Fibrous nonunions

D2- Sclerotic

Distal pole fractures can be of 2 types

1. Avulsion fractures of the volar radial lip
2. Impaction fracture of the volar half

Management

Management depends on the fracture pattern, reduction and bone quality. It also depends on the patient’s occupation and the need to return to work early. Those who need to return to work early are currently treated by percutaneous screw fixation.

General guidelines

• Undisplaced distal pole fractures are treated by 4-6 weeks of immobilization.
• Undisplaced waist fractures are treated by immobilization and percutaneous screw fixation.
• Undisplaced waist fractures are treated by 6 weeks of long arm scaphoid cast followed by 6 weeks of short arm scaphoid cast.
• Displaced fractures are treated by internal fixation by screws.

Indications for surgery

• Displaced fractures.
• Unstable fractures.
• Associated carpal injury.
• Associated distal radius fracture.
• More than 3-4 weeks delay in initial presentation.
• Undisplaced fractures in those who want early return to work. Some authors have reported high incidence of complications with percutaneous fixation.

Definition of displaced and unstable fractures

According to Cooney

• More than 1 mm displacement.
• More than 10⁰ angular displacement.
• Fracture comminution.
• Radiolunate angle more than 15⁰.
• Scapholunate angle more than 60⁰.
• Intrascaphoid angle more than 35⁰.

Approaches to scaphoid fixation

• The approach to fix may be dorsal or volar.
• These approaches may be open, mini-open or percutaneous.
• Proximal pole fractures need dorsal approach and distal third fractures are approached volar.
• Waist fractures may be approached dorsal or volar.
• Volar approaches need osteotomy of the volar radial lip of trapezium to expose the entry point; hence dorsal approach is becoming more popular.
• Dorsal approaches carry the risk of damage to blood supply entering the scaphoid through the dorsal ridge.
• Current best practice for the treatment of displaced acute scaphoid fractures is by percutaneous approach

Indications for open approach

• Scaphoid nonunions
• Irreducible fractures
• Comminuted fractures.

Volar open approach

• Incision from a point 2 cm proximal to the scaphoid tuberosity in line with FCR and distally in line with thumb metacarpal.
• Open the sheath of FCR and retract the tendon medially.
• Avoid dissection on the ulnar side of FCR to avoid injury to palmar branch of median nerve.
• Incise the dorsal sheath of FCR.
• Superficial branch of radial artery may need cauterization.
• Incise the capsule between long Radiolunate ligament and radioscaphocapitate ligaments.
• Avoid dissection on the radial side of scaphoid.

Volar percutaneous approach (Haddad and Goddard)

• Supine position with thumb suspended in Chinese finger trap.
• Under C Arm identify and mark scaphotrapeziotrapezoid (STT) joint.
• Reduce the fracture under C arm control.
• Make a longitudinal stab incision 1 cm distal to STT joint.
• Put the guide wire towards the centre of proximal pole and aim towards the Lister’s tubercle

Dorsal open approach

• 3-4 cm incision proximally and distally in line with the III metacarpal.
• Plane of dissection is between 3^rd and 4^th extensor compartments.
• Retract Extensor pollicis longus (EPL), Extensor carpi radialis longus (ECRL) and Extensor carpi radialis brevis (ECRB) radially and extensor digitorum communis (EDC) medially.
• T shaped capsulotomy done. Transverse limb at the dorsal edge of distal radius and vertical limb radial to the dorsal intercarpal ligament.
• Avoid accidental injury to the dorsal part of scapholunate interosseous ligament (SLIL).
• Avoid injury to blood vessels entering the scaphoid through the dorsal ridge.

Dorsal percutaneous approach (Slade technique)

• Supine position with the hand on a hand table with C Arm.
• Reduce the fracture.
• Forearm pronated.
• With image guidance mark scapholunate interval.
• Pronate and flex the wrist to 45⁰ till the scaphoid is seen as a circle with overlap of proximal and distal poles.
• Make a stab incision oven the centre of the circle.
• Bluntly dissect with a haemostat up to the bone.
• Use a 14G IV cannula as a tissue protector during guide wire insertion.
• Drive the K wire through the centre of the circle.
• Starting point is 3 mm radial to the attachment of proximal membranous portion of the SLIL.
• Aim towards a point 5 mm distal to the scaphoid tuberosity.
• Withdraw the K wire through the volar exit point till the tip of the K wire is at the radiocarpal joint. This is to prevent breakage of wire during imaging to confirm central position of the K wire.
• Confirm position by AP, lateral and 30⁰ pronated lateral views.
• Once position is confirmed, drive back the wire out through the dorsal skin so that part of the guide wire is outside both on the volar and dorsal side. This is to have control on both ends of the guide wire in case of breakage.

Dorsal Mini-open Technique

• 1 cm long incision just to the Lister’s tubercle.
• Open the sheath of both EPL and EDC.
• Retract EPL radially and EDC medially.
• Open the capsule and identify the starting point for guide wire.
• Prevents injury to extensor tendons and other soft tissue.

Reduction of displaced fractures.

• Longitudinal traction is given over the index and middle fingers to distract the fracture site and reduce.
• Percutaneously K wires may be inserted into the proximal and distal fragments to act as joysticks.
• To achieve reduction, use the joysticks to flex the proximal pole and the distal pole is extended and supinated.

Screw fixation of scaphoid

• The key to success in screw fixation is placement of the guide wire in the central axis of scaphoid.
• The guide wire should be in the middle third of the proximal pole in the AP and lateral views.
• Central placement of the screw provides greater stiffness, greater resistance to displacement and greater load to failure.
• Another wire should be inserted to prevent rotation during screw insertion in such a way that it will not interfere with the screw placement.
• Screw should be 2-3 mm below the articular surface.
• Screw should be 4 mm less than the measured length of scaphoid.
• Guide wire should be adequately reamed to prevent distraction during screw insertion.
• Reaming should stop 2 mm from the articular surface.
• If central screw placement doesn’t provide adequate stability, then it should be augmented with a K wire.

Scaphoid Nonunions

• Incidence of nonunion range from 5-10% in waist fractures.
• Scaphoid compression test is done by axial compression of thumb, pain is suggestive of injury.
• Union is indicated by progressive obliteration of fracture site and also by the development of trabeculae that cross the fracture site on serial x-rays. In case of doubt regarding union, CT scan may be useful.

Predisposing factors for nonunion.

• Displacement more than 1 mm
• Fracture of proximal pole
• Vertical oblique pattern
• Comminuted fractures
• Associated carpal injuries
• Delayed diagnosis
• Inadequate immobilization
• Osteonecrosis
• Smoking

Bone defects in nonunion.

• Proximal fractures have small crescentric defects
• Distal nonunions have large triangular defects with humpback deformity
• Humpback deformity is flexion of the distal fragment and extension of proximal fragment with associated shortening of scaphoid.
• Extension of proximal fragment leads to extension of lunate leading to dorsal intercalated segment instability.
• Its development depends on the position of fracture line in relation to the apex of the dorsal ridge of scaphoid.
• Dorsal component of SLIL and dorsal intercarpal ligament are attached to the dorsal ridge
• If the fracture is distal to the dorsal ridge; humpback deformity may occur. If proximal; attaché ligaments prevent humpback deformity.
• Humpback deformity needs volar approach and corticocancellous wedge graft to correct the shortening and deformity. ( Fernadez technique)
• Problem with Fernandez technique is the difficulty in screw insertion with the graft in situ.
• Stark technique is volar approach, forceful dorsiflexion to correct the humpback deformity, cancellous grafting to maintain the correction and K wire fixation.

Geissler and Slade classification of scaphoid nonunions.

i. 4-12 week delayed presentation

ii. Fibrous union – Minimal gap, no cyst, no sclerosis

iii. Minimal sclerosis with <1 mm bone resorption

iv. Cyst formation and sclerosis with 1-5 mm bone resorption, no deformity

v. Deformity and/or cyst formation, > 5 mm bone resorption, cyst formation

vi. With radiocarpal and/or midcarpal arthritis

Special circumstances

• Proximal pole nonunion
• Osteonecrosis
• Associated carpal instability

Management of nonunion depends on the duration, carpal alignment, bone loss, presence or absence of humpback deformity, carpal collapse, osteonecrosis and previous surgery.

Matte-Russe technique- Creation of a egg shaped cavity in the proximal and distal fragments and filling with cancellous graft.

Modified Matte- Russe technique- Creation of a trough and placement of two corticocancellous graft with their cortical surface facing each other.

Vascularised bone graft (VBG)

Indications

• Proximal pole osteonecrosis
• Displaced acute proximal pole fractures
• Failed nonvascularised bone graft

Contraindications

• Radiocarpal and midcarpal arthritis.
• Damage to radial artery, I dorsal metacarpal artery or dorsal carpal arch.
• Previous surgery on the dorsum of wrist.
• Smokers.

Types of VBG

Pedicled based on

• 1,2 intercompartmental supraretinacular artery (Zaidemberg).
• Volar carpal artery (Kuhlmann).
• Capsular VBG based on 4^th extrracompartmental artery of dorsal carpal arch.
• Vascularised thumb metacarpal graft (Bertelli).

Free VBG

• Free iliac crest
• Free fibula

Copyright -Dr Rajesh Purushothaman, Associate Professor of Orthopaedics, Kozhikode, Kerala, India.
Contact me at learning.orthopaedics@gmail.com