Transcript of "Blood supply & fractures of scaphoid"
Blood supply & Fracture of Scaphoid
Blood Supply of Wrist and Carpus Radial Ulnar Anterior interosseous arteries Deep palmar arch
Anastomotic network three dorsal & three palmar arches connected longitudinally at their medial and lateral borders by radial & ulnar arteries dorsal to palmar interconnections b/w dorsal and palmar branches of anterior interosseous artery
Intrinsic blood Supply The scaphoid, capitate & 20% of lunate supplied by a single vessel - at risk for osteonecrosis. The trapezium, triquetrum, pisiform & 80% of lunate receive nutrient arteries through two nonarticular surfaces consistent intraosseous anastomoses. ON is rare. The trapezoid and hamate lack an intraosseous anastomosis and after fracture, can have avascular fragments.
Scaphoid Anatomy skaphos (Greek) – boat Cashew shaped within the wrist joint more than 80% of its surface(except tubercle) - covered by articular cartilage
Scaphoid - blood supply two major vascular pedicles1.Volar branch enters the scaphoid tubercle and supplies its distal 20% to 30%2. Dorsal scaphoid branch of the radial artery. Enter through numerous small foramina along the spiral groove and dorsal ridge. (80% of the blood supply).
No vascular supply (13%) or only a single perforator (20%) proximal to the waist of scaphoid. Unusual retrograde vascular supply - high risk of nonunion and ON after fracture.
Scaphoid Fracture Most commonly fractured carpal bone 68% of carpal fractures Fall on outstretched hand – forced dorsiflexion of hand & radial deviation
When fractured, proximal pole - extend with attached lunate distal pole - remains flexed, creating -hump-back deformity.
Classification Russe -1)Horizontal oblique - compressive forces across fracture site.2)Transverse –combination of compressive & shear forces.3)Vertical oblique – 5% , shear forces across fracture site.
Herbert classification- stability and delayed & nonunion of fractures. Type A fractures- stableType A1- fracture of tubercleType A2 – incomplete fractures through waist
Type B –Acute and Unstable fractures Type B1- Distal oblique fractures Type B2- Complete fractures through waistType B3- Proximal pole fracturesType B4- Transscaphoid & Perilunate dislocations of carpusType B5-Comminuted
Type C fractures – Delayed unions Type D fractures – established Nonunions
Prosser classification Classification of Distal pole fractures Type 1 – Tuberosity fracture. Type 2 - Distal intra-articular fracture. Type 3 – Osteochondral fracture.
Diagnosis Wrist pain Tenderness & fullness in anatomic snuffbox. Axial compression of thumb elicits pain Forced ulnar deviation of pronated wrist also elicits pain
Even if initial radiographs –ve, immobilise in wrist splint/shortarm thumb cast Rpt after 10- 14 days If still –ve and suspecting #,take MRI/ CT Scan Fast,convenient, sensitive and specific.
Associated Injuries Fractures of the distal radius Perilunate dislocation and Transscaphoid perilunate fracture dislocations Joint and ligament damage that inevitably accompanies this injury (x-ray never reveals the true degree of injury)
Cast Immobilization Undisplaced Stable Fractures A1 - 4 weeks A2 - 8 to 12 weeks until radiographic union. decision for conservative Mx - CT scan shows no displacement. patient reviewed 6 weeks after cast removal for clinical and radiological examination and then every 3 months until the outcome is clear. Patients should be seen for a final check up after 1 year.
Cast Immobilization Position of wrist has no affect over healing. No difference b/w longarm & short arm cast. Needs to be continued till fracture has healed. Proximal pole fractures-12 weeks or longer
Surgery - indication Displaced fracture Proximal pole fractures regardless of displacement Associated perilunate injuries Open fractures Polytrauma pts
Percutaneous Fixation Guidewire placed percutaneously along central axis of scaphoid to use cannulated screw system. Main key is to achieve most centrally placed screw while holding fracture in compression
Risk of open procedures can be Avoided. Healing time found to be same as cast immobilization Bond etal reported average healing time to be 7 weeks in these pts,compared to 12 weeks Rx in cast No functional difference after 2 yrs
Volar percutaneous approach – distal scaphoid used as entry point. Preferred for distal pole fractures. Use 16 gauge needle to find entry point of guidewire. Proximal cartilaginous surface of scaphoid preserved.
Dorsal percutaneous approach: Proximal pole is entry point Wrist in flexion & ulnar deviation
Arthroscopic Allows assessment of intraarticular injuries like ligamentous structures Many choices for percutaneous fixation-Herbert screw-Herbert-whipple screw-Acutrak screw
Open-Palmar Classic Russe approach For stable and unstable non union Advantages --Excellent visualization-Less risk of vascular injury
Disadvantages-potential for scarring-limitation of wrist extension-injury to volar radiocarpal ligament-inability to assess and address dorsal scapholunate ligament.
Open - Dorsal Centered over Lister’s tubercle Transverse incision over prox.scaphoid Do not disturb dorsal ridge Excellent visualization of prox.pole,esp with in maximum flexion Prefered open approac for prox. Pole fracture.
Disadvantages of immobilization Frequent visits to check cast fit. Frequent radiographs to check alignment. Potential skin breakdown Prolonged immobilization till complete healing Stiffness of immobilized joints
Disadvantages of Surgery Potential for infection Wound complications Injury to nerves,ligaments or tendons Injury to vascular supply to scaphoid Hardware failure or need for its removal Associated aneasthesia complications.
Complications Non Union Malunion Osteonecrosis – Preiser’s disease Management – arthroscopic debridement and drilling of the lesion, rest, splintage, and electrical stimulation vascularized bone graft harvesting a pronator quadratus graft.
Pearls Occult scaphoid fractures are easily detected by MRI scans. Percutaneous stabilization of scaphoid fractures significantly reduces the rate of nonunion, as well as reducing the time lost from work and sports. Proximal pole fractures can also be stabilized percutaneously by a dorsal approach.
Pitfalls Scaphoid fractures are easily missed in children. This can result in nonunion and serious problems. Malalignment of scaphoid fractures is often undiagnosed. CT scans are helpful. Conservative treatment often ends in delayed healing. An aggressive operative approach is recommended.
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