Carpal Fractures (including Malunion and Nonunion) Flashcards
(45 cards)
What is the most common mechanism of injury for scaphoid fractures?
Forceful wrist extension, ulnar deviation, and intercarpal supination. This typically occurs during high-energy impacts such as motor vehicle accidents, falls from height, or contact sports.
What is the unique blood supply pattern of the scaphoid, and how does it affect healing potential?
The scaphoid has a retrograde blood supply, with vessels entering primarily at the distal pole. Approximately 70-80% of blood supply to the proximal pole comes through intraosseous vessels traversing the waist, making proximal pole fractures particularly susceptible to avascular necrosis and nonunion.
Which imaging modality is most reliable for confirming healing of scaphoid fractures, and when should it be used?
CT scan with 1-mm cuts in coronal and lateral planes is most reliable for evaluating bridging bone at the fracture site. Standard radiographs at 3 months are unreliable for determining healing. CT should be performed at 6-12 weeks post-treatment to assess for bridging bone.
In Slade and Geissler’s revised classification of scaphoid nonunions, what characterizes Grade III nonunions and what is their treatment approach?
Grade III nonunions have minimal bone resorption of the anterior cortical bone and minimal fracture sclerosis (≤2 mm) confirmed by CT scan. These nonunions can be treated with rigid fixation without correction of deformity if alignment is adequate, and may not require bone grafting.
What is the ‘humpback deformity’ in scaphoid malunion, and why is it clinically significant?
The humpback deformity is a flexion deformity of the scaphoid that results in a foreshortened scaphoid length and DISI (dorsal intercalated segment instability) pattern. It is significant because it alters normal carpal kinematics, leading to abnormal radiocarpal loading patterns and eventual degenerative arthritis if uncorrected.
When performing percutaneous scaphoid fixation, what is the optimal central axis screw position and why is it important?
The optimal position is along the central axis of the scaphoid (central third on all radiographic views). This position provides maximal biomechanical stability, maximal thread purchase, minimizes risk of articular penetration, and avoids eccentric loading that can lead to fragment displacement or fixation failure.
How is SNAC (Scaphoid Nonunion Advanced Collapse) wrist classified, and what is the surgical approach for each stage?
- Stage I: Radial styloid arthrosis - scaphoid reconstruction;
- Stage II: Radioscaphoid arthrosis - scaphoid reconstruction or radial styloidectomy with scaphoid reconstruction;
- Stage III: Capitolunate arthrosis - four-corner fusion or proximal row carpectomy;
- Stage IV: Pantrapezial arthrosis - complete wrist fusion or arthroplasty.
Describe Geissler’s arthroscopic technique for scaphoid nonunion fixation. What is the key advantage of this approach?
Geissler’s technique involves:
* Wrist suspension in traction tower with 30° flexion;
* Arthroscope placed in 6R portal;
* Entry point identified at SLIL-scaphoid junction;
* Guide wire placed down central axis;
* Compression screw inserted;
* Bone graft/matrix introduced through cannula.
The key advantage is direct visualization of the starting point for guide wire placement, allowing optimal screw positioning.
In vascularized bone grafting for scaphoid nonunion with AVN, what is the 1,2 ICSRA technique and what are its key anatomical landmarks?
The 1,2 ICSRA (first, second intercompartmental supraretinacular artery) technique harvests a vascularized bone graft from the dorsal distal radius. Key landmarks: the vessel lies between the first and second extensor compartments, approximately 1.5 cm proximal to the radial styloid. The pedicle is mobilized while keeping the vascular attachment, and a corticocancellous graft is elevated with the vessel and inserted into the scaphoid defect.
What clinical and radiographic parameters determine when to consider vascularized bone grafting versus conventional bone grafting for scaphoid nonunion?
Vascularized bone grafting should be considered when:
1) Proximal pole AVN is present (confirmed by MRI or absence of punctate bleeding intraoperatively);
2) Previous failed conventional bone grafting;
3) Long-standing nonunion (>1 year);
4) Proximal pole sclerosis >2mm on CT;
5) Absence of arthritic changes.
Conventional grafting is sufficient for well-perfused fragments.
What is the ‘sandwich technique’ for proximal pole scaphoid nonunion fixation and when is it indicated?
The sandwich technique involves compressing the small proximal fragment between the lunate and the distal scaphoid fragment with two headless compression screws - one from scaphoid to lunate and one standard intramedullary scaphoid screw. It’s indicated for very small proximal pole fractures where standard fixation provides insufficient stability due to minimal thread purchase and high cantilever bending forces.
How does treatment approach differ for scaphoid nonunion with substantial bone loss (Grade IV-VI in Slade-Geissler classification) compared to those without substantial bone loss (Grade I-III)?
Grade I-III (without substantial loss): Rigid fixation alone may be sufficient if well-perfused. Grade IV-VI (with substantial loss): Requires bone grafting in addition to fixation. Grade IV (2-5mm loss) and Grade V (5-10mm loss) need structural grafting. Grade VI (synovial pseudarthrosis) requires open débridement and corticocancellous structural graft.
What are the key steps in the arthroscopic management of scaphoid nonunion, and what technical factors determine success?
Key steps: 1) Diagnostic arthroscopy to assess cartilage status and SLIL; 2) Central axis guide wire placement; 3) Fracture site débridement and reaming; 4) Percutaneous bone graft harvesting (distal radius); 5) Graft delivery through cannula; 6) Headless compression screw fixation. Success depends on: proper patient selection (minimal deformity), confirmed fibrous tissue at nonunion site (to contain graft), and anatomic reduction of fragments.
Describe the optimal approach to diagnose and treat Trans-scaphoid Perilunate Fracture-Dislocations.
Diagnosis: AP/lateral radiographs, CT scan to evaluate fracture pattern. Treatment: 1) Urgent closed reduction to decompress median nerve; 2) Definitive treatment via combined dorsal and volar approaches; 3) Dorsal - reduce and repair scapholunate ligament; 4) Volar - repair volar capsule and lunate-triquetral ligament; 5) Scaphoid fracture fixation with compression screw; 6) K-wire stabilization of carpal joints; 7) 8-12 weeks immobilization followed by rehabilitation.
What are the most common complications following scaphoid fracture fixation, and how can they be prevented?
Common complications:
screw malposition (10-16%),
nonunion (5-15%),
hardware-related issues (5-8%), and
AVN (varies by fracture location).
Prevention: 1) Use fluoroscopy in multiple planes or arthroscopic guidance for accurate screw placement; 2) Optimize biology with appropriate grafting for at-risk nonunions; 3) Use central axis placement of implant; 4) Consider vascularized grafting for proximal pole or delayed presentations with AVN risk.
What features differentiate pediatric scaphoid fractures from adult patterns, and how does treatment approach differ?
Pediatric differences: 1) Most commonly involve distal scaphoid (vs. waist in adults); 2) Higher healing potential; 3) Presentation pattern shifting toward adult pattern near skeletal maturity. Treatment: Nondisplaced fractures typically heal with casting alone (3-5 months); Nonunions in skeletally immature may heal with prolonged casting, but most surgeons favor screw fixation with bone grafting for established nonunions in adolescents.
What is the evidence regarding cost-effectiveness of surgical versus nonsurgical treatment of nondisplaced scaphoid waist fractures?
Studies by Arora and Davis demonstrated that surgical fixation of nondisplaced scaphoid waist fractures is cost-effective despite higher initial costs. Patients return to work 5-7 weeks earlier than with casting, and when considering productivity costs, surgery is less expensive than casting.
How do you diagnose and treat hook of hamate fractures, and what are the potential complications of untreated fractures?
Diagnosis: Carpal tunnel view radiographs, CT scan, point tenderness over hook. Treatment: Nondisplaced acute fractures may heal with immobilization; displaced/chronic fractures typically require excision. Complications of untreated fractures include: 1) Flexor digitorum profundus/superficialis rupture to ring/small fingers; 2) Ulnar nerve irritation; 3) Hamato-metacarpal arthritis.
What is the pathomechanics of scaphoid nonunion progression to SNAC wrist, and what are the radiographic features at each stage?
Pathomechanics: Altered carpal mechanics → radial styloid impingement → progressive articular degeneration. Stage I: Radial styloid-distal scaphoid arthrosis; Stage II: Complete radioscaphoid arthrosis; Stage III: Capitolunate arthrosis due to DISI deformity; Stage IV: Pantrapezial arthrosis.
In the setting of a scaphoid nonunion with punctate bleeding observed during surgery from the proximal fragment, what prognostic information does this provide and how does it influence treatment?
Punctate bleeding indicates viable bone with preserved vascularity. This is a positive prognostic sign suggesting: 1) Conventional (non-vascularized) bone grafting will likely be successful; 2) Lower risk of post-fixation AVN; 3) Higher union rates.
What are the biomechanical advantages of headless compression screws over K-wire fixation for scaphoid fractures and nonunions?
Advantages include: 1) Greater compression across fracture/nonunion site; 2) Resistance to rotational forces; 3) Allowance for earlier wrist mobilization; 4) No hardware removal required; 5) Decreased risk of wire migration/breakage; 6) Better stability under physiologic loading.
What is the Fernandez technique for correcting scaphoid malunion with a humpback deformity, and what are the expected outcomes?
Technique: 1) Volar approach through FCR; 2) Osteotomy at malunion site; 3) Insertion of a wedge-shaped tricortical iliac crest graft; 4) Compression screw fixation. Outcomes: 80-90% union rates, significant improvement in radiocarpal mechanics, correction of carpal alignment and DISI deformity.
What is the role of bone morphogenetic proteins and other biologics in the treatment of scaphoid nonunions?
Current evidence is limited and experimental. Case reports and small series using BMP show: 1) Enhanced healing of proximal pole nonunions; 2) Reduced radiographic healing time; 3) Potential to avoid conventional bone grafting in selected cases.
What factors guide the choice between proximal row carpectomy (PRC) and four-corner fusion (4CF) for SNAC wrist?
Factors include: 1) Age and activity demands (PRC better for older, less demanding wrists); 2) Capitate head status (must be preserved for PRC); 3) Stage of disease (both applicable for stage II-III); 4) Lunate status (lunate fossa preservation needed for PRC); 5) Motion requirements (PRC preserves more motion, 60-70% vs 50-60% for 4CF); 6) Grip strength expectations (both achieve ~70-80% of normal); 7) Anticipated longevity (4CF may have better long-term durability but higher complications). Both reliably provide pain relief.
