Charcot's Joint (Neuropathic Arthropathy)

Etiology / Causes

Syphilis is an infrequent but increasingly recognized cause because inadequate treatment of primary/secondary syphilis or antibiotic exposure for unrelated infections can mask classic signs - a high index of suspicion and appropriate serologic testing are required.

Pathogenesis

Joint Distribution

• Diabetes: Preferentially involves the small joints of the foot - especially the tarsometatarsal (Lisfranc) joints. Unlike syphilitic Charcot, the large weight-bearing joints are less commonly affected.
• Syphilis/tabes dorsalis: Classically affects large weight-bearing joints - knee (most common in tabes), hip, ankle.
• Syringomyelia: Typically affects upper limb joints (shoulder, elbow).

Anatomic Classification (Brodsky - Foot & Ankle)

The medial column of the foot fails before the lateral column due to the pull of the posterior tibial tendon. Sagittal plane deformities are more likely to cause ulceration than transverse plane abnormalities.

Eichenholtz Staging (Disease Stage Classification)

Some authors have questioned the validity of the Eichenholtz classification and prefer MRI or PET/CT-based systems to detect Stage 0 changes missed on plain radiographs.

Clinical Features

• The classic presentation is a warm, swollen, erythematous foot in a diabetic patient - often mistaken for cellulitis or gout
• Pain is typically disproportionately mild relative to the degree of destruction due to sensory neuropathy
• The patient may continue weight-bearing, accelerating destruction
• Skin temperature difference >2°C between feet is a clinical clue
• Associated foot ulcers and autonomic impairment are common

Diagnosis

• Clinical: Warm, swollen, relatively painless foot in a neuropathic patient
• Plain radiographs: Fragmentation, subluxation, debris - but may be normal in Stage 0
• MRI: Best for early detection (Stage 0) - periarticular edema, occult fractures
• Bone scan (Tc-99m): Increased uptake; used when MRI contraindicated
• PET/CT: Useful for early stages and differentiating from osteomyelitis
• Serology: If syphilis suspected (RPR/VDRL, confirmatory FTA-ABS)
• Histology: Osteochondral fragments in synovium is diagnostic

Treatment

Nonoperative (Eichenholtz-guided)

• Stage 1 (Active/Fragmentation): Total contact cast (TCC) or orthosis - offloads the region and maintains alignment through healing. This is the cornerstone of management.
• Stage 2 (Coalescence): Transition to prefabricated boot or custom-molded ankle-foot orthosis (AFO) as radiographic signs of healing appear.
• Stage 3 (Consolidation): Accommodative shoe with molded orthosis once swelling completely resolves.

• Glycemic optimization (poor glucose control worsens bone quality)
• Vitamin D supplementation (hypovitaminosis D is common in diabetic patients and plays a role in pathogenesis)
• Bisphosphonates and calcitonin have shown limited effectiveness and are not current standard of care
• Patients should be counseled that up to 50% may still require surgical intervention despite intensive conservative treatment

Operative

• Instability with soft-tissue compromise
• Ulceration that cannot be off-loaded
• Failed conservative management (particularly Type 3A ankle involvement)
• Limb-threatening deformity

Key Points for Exams

Sickle Cell Anemia in Orthopaedics

Pathophysiological Basis

Complete Orthopaedic Manifestations of Sickle Cell Disease

1. Sickle Cell Dactylitis (Hand-Foot Syndrome)

• Age: Children under 5 years; rarely seen after age 5
• Pathology: Infarction of bone marrow and cortical bone of the small tubular bones → periostitis and soft tissue swelling
• Clinical: Diffuse, painful swelling, tenderness and warmth of the hands and feet lasting 1-3 weeks
• Radiographs: Periosteal elevation, subperiosteal new bone formation, areas of radiolucency and increased density in metacarpals, metatarsals, and proximal phalanges - "moth-eaten" appearance

• Prognosis: Resolves in weeks with little or no residual damage; also seen in sickle cell thalassemia

2. Bone Infarction (Vaso-occlusive Crisis)

• Mechanism: Sickling of red cells → vascular occlusion → sterile infarction of bone cortex and marrow
• Presentation: Periarticular and long bone pain; warm tender joints; knees and elbows most often affected; joint effusions (usually non-inflammatory unless synovial infarction occurs)
• Radiographic features: Periosteal elevation, irregular cortical thickening, bone marrow lysis → fibrosis → new bone formation
• Special variant - Vertebral infarction: Infarction of vertebral end plates → central depression of the endplate while periphery remains elevated = "H-shaped" or "cod-fish" vertebrae - pathognomonic of sickle cell disease
• Children: Epiphyseal growth plate infarction can cause growth disturbance and limb length discrepancy

3. Osteomyelitis

• Incidence: Significantly elevated due to functional asplenia (splenic infarction → impaired opsonization of encapsulated organisms)
• Most common organism: Salmonella species - isolated in up to 70% of cases in sickle cell osteomyelitis; this is the classic high-yield exam fact (contrast with the general population where Staphylococcus aureus is most common)
• S. aureus and Streptococcus also occur
• Most common site: Diaphysis of long tubular bones (unlike typical haematogenous osteomyelitis which preferentially affects metaphysis)
• Radiographs: Periosteal elevation → cortical disruption

Critical diagnostic challenge: The clinical and radiological features of osteomyelitis and bone infarction in sickle cell disease are nearly identical - both cause pain, swelling, fever, elevated inflammatory markers, and periosteal changes. No single test reliably differentiates them. The presence of a cortical break or periosteal collection favors infection. Empiric antibiotic therapy should be started when diagnosis is uncertain.

4. Avascular Necrosis (Osteonecrosis)

• Incidence: ~5% of patients develop AVN of the femoral head; significantly higher in HbSS + HbS-alpha thalassemia
• Sites affected (in order of frequency):
  1. Femoral head (most common)
  2. Humeral head
  3. Distal femur
  4. Tibial condyles
  5. Vertebral bodies, distal radius, other juxtaarticular sites
• Mechanism: Vaso-occlusion → ischaemia of subchondral bone → death of bone → subchondral collapse

Ficat & Arlet Staging (Femoral Head)

The crescent sign represents a subchondral fracture with separation of articular cartilage from necrotic bone - pathognomonic of Stage 3 AVN.

• Natural history: The vast majority of untreated patients with AVN progress to femoral head collapse within 5 years; symptoms nearly always precede collapse
• Imaging: MRI is far more sensitive than plain radiograph for early detection

Treatment of AVN in Sickle Cell Disease

• Associated with higher rates of orthopaedic and medical complications in most studies
• Early prosthetic loosening is a recognized complication - mechanism is extended bone infarct disease causing poor bone stock
• Higher risk of periprosthetic joint infection (PJI) due to underlying immunodeficiency
• Structural bone disease makes joint replacement technically challenging
• Pre-operative exchange transfusion to raise HbA levels and reduce HbS <30% is generally recommended perioperatively

5. Septic Arthritis

• Prevalence: ~3% of adults with sickle cell disease develop septic arthritis
• Most commonly affected joint: Hip (36/59 infections in one large series)
• Organisms: S. aureus and gram-negative organisms most common; Salmonella less commonly causes septic arthritis than osteomyelitis
• Diagnosis triggers: WBC >15,000/mm³, ESR >24 mm/hr, CRP >20 mg/L in context of fever and joint pain
• Source: More often distant osteomyelitis via bacteraemia rather than contiguous spread
• When epiphysis is infarcted during crisis, joint effusion develops that is clinically indistinguishable from septic arthritis → diagnostic arthrocentesis is mandatory

6. Bone Changes from Marrow Hyperplasia

• Widening of medullary cavities with thinning of cortices
• Coarse trabeculations throughout skeleton
• Central cupping of vertebral bodies
• In normal individuals red marrow is in the axial skeleton; in sickle cell disease it extends to long bones, tarsals, and carpals
• Vertebral compression → dorsal kyphosis
• Protrusio acetabuli from softening of the acetabulum
• In the skull: widening of diploic spaces (though less dramatic than thalassaemia)

7. Osteopenia and Osteoporosis

• Common in HbSS, especially as marrow hyperplasia competes with normal bone remodeling
• Lumbar spine is the most commonly affected site
• Low BMI and low vitamin D levels are consistent correlates
• Delayed skeletal maturation and puberty (by 12-24 months) in children

8. Growth Disturbance

• Majority of children with sickle cell disease show growth declines vs. peers
• Epiphyseal infarction in children can cause leg length discrepancy
• Delayed puberty and skeletal maturation are common

9. Gouty Arthritis

• Up to 40% of sickle cell patients are hyperuricaemic - due to increased urate generation from haemolysis + interstitial renal disease
• Attacks may be polyarticular
• Diagnostic arthrocentesis required to distinguish from septic arthritis or synovial infarction

Key Radiological Features Summary

Perioperative Considerations in Sickle Cell Disease

High-Yield Summary for Exams

Undisplaced Acetabular Fractures - Assessment & Nonoperative Management

Background

1. Whether the weight-bearing dome is involved
2. The degree of articular displacement (threshold: <2 mm = acceptable)
3. Whether the hip is stable and congruent

Classification - Letournel System (The International Standard)

5 Elementary Types

5 Associated Types

Imaging Assessment

Radiographic Views

1. AP pelvis - standard; gives overview; measures medial roof arc
2. Judet views (45° obliques):
   • Iliac oblique - shows posterior column and anterior wall; measures posterior roof arc
   • Obturator oblique - shows anterior column and posterior wall; measures anterior roof arc
3. CT scan - mandatory once acetabular fracture is diagnosed:
   • Defines fracture pattern precisely
   • Identifies articular impaction
   • Detects intraarticular fragments
   • Assesses displacement at the weight-bearing dome (superior 10 mm of acetabular articular surface)
   • Guides treatment decision

The Weight-Bearing Dome - Key Prognostic Concept

Core principle: Fractures that do NOT involve the weight-bearing dome can be considered for nonoperative management if the hip is stable and congruent. Fractures that DO involve the dome require a decision based on the degree of displacement.

Criteria for Nonoperative (Conservative) Management

Absolute Indications for Nonoperative Treatment

1. Undisplaced fractures (or displacement <2 mm) - including those involving the weight-bearing dome
2. Displaced fractures in regions NOT involving the weight-bearing dome - confirmed by roof arc measurements >45° (or revised criteria - see below)
3. Both-column fractures with secondary congruence (see below)
4. Wall fractures that do not compromise hip stability (confirmed by dynamic stress examination)
5. Patients unable to withstand surgery - significant medical comorbidities

The Roof Arc Measurement (Matta)

If the roof arc exceeds these values on all three views, the weight-bearing dome is intact and nonoperative management is appropriate regardless of displacement below the dome.

Note (Rockwood & Green 2025): The classic 45° value has been questioned. Subsequent biomechanical studies produced different criteria (45° medial, 25° anterior, 70° posterior). Even newer sit-to-stand loading studies suggest significantly higher critical angles may be needed, though clinical implications remain uncertain.

Roof arc is NOT applicable to: both-column fractures (no intact acetabulum to measure) or posterior wall fractures.

Special Situations

Both-Column Fractures with "Secondary Congruence"

• Parallelism between femoral head and acetabular articular surface in all three radiographic views (AP and both Judet views), without traction
• Fragment displacement and medial joint displacement not so excessive as to limit motion
• Limb shortening must be acceptable

Secondary congruence is necessary but not sufficient for nonsurgical treatment. These fractures do not have as good a prognosis as anatomically reduced fractures, but outcomes are acceptable in appropriate patients.

Posterior Wall Fractures

• Cannot be assessed by roof arc measurements
• May only be treated nonoperatively if the hip is completely stable
• Previously thought that <20% posterior wall involvement (on axial CT) was stable - but hip instability can still occur in some cases
• Mandatory dynamic stress examination under anaesthesia is the only reliable way to determine hip stability in posterior wall fractures - assumed unstable until proved otherwise
• Special hazard - cranial/peripheral posterior wall fragments: occur after falls from height with hip in extension; maximal instability in extension and adduction (walking position); even small fragments carry high complication rates

Nonoperative Treatment Protocol (Campbell's Operative Orthopaedics 2026)

Stage 1 - Acute Phase

Stage 2 - Transition (Weeks 6-12)

• When radiographic and clinical signs suggest healing - begin progressive weight bearing
• Typically partial weight bearing from ~6 weeks if no displacement on serial X-rays
• Full weight bearing usually by 10-12 weeks when fracture consolidated

Stage 3 - Rehabilitation

• Gait training, hip strengthening exercises
• Return to activities as tolerated

Indications for URGENT/EMERGENCY Surgery (i.e., cannot be managed conservatively)

Outcomes of Nonoperative Treatment

• Best outcomes: No dome involvement; secondary congruence in both-column; stable posterior wall; fractures below the weight-bearing dome
• Displacement <2 mm (even at the dome): acceptable outcomes with nonoperative treatment
• Main risk of nonoperative treatment: Secondary displacement - hence mandatory serial radiographic follow-up

Follow-Up Protocol (Summary)

Day 0     → AP pelvis + Judet views + CT; establish diagnosis and displacement
Week 0-2  → Skeletal traction if needed; non-weight bearing
Week 2-6  → Serial AP pelvis radiographs (every 1-2 weeks)
First mobilization → Immediate AP pelvis post-mobilization
Week 6    → Radiograph + clinical review; consider partial weight bearing
Week 10-12 → Full weight bearing if healed
Month 6   → Final radiograph; assess for post-traumatic arthritis / AVN
Year 1-2  → Long-term surveillance (post-traumatic OA develops in 10-25%)

Key Points for Exams