# CIM Case: Charcot Foot ## Clinical Scenario **Patient:** 60-year-old female **Presentation:** Right foot swelling and redness developing over 1 week, minimal pain, has been walking on it, noticed "warm feeling" in foot **Relevant history:** Type 2 diabetes for 15 years, on oral hypoglycaemics and insulin, HbA1c 9.2% (poorly controlled), peripheral neuropathy diagnosed 5 years ago, bilateral cataracts (diabetic retinopathy), previous left foot ulcer healed with conservative treatment **Examination findings:** - Right midfoot significantly swollen and erythematous - Increased warmth compared to left foot (>2°C difference by infrared thermometer) - Loss of medial longitudinal arch (early rocker-bottom deformity) - Peripheral pulses palpable bilaterally (dorsalis pedis, posterior tibial) - Absent protective sensation (10g monofilament negative at all sites) - Absent ankle reflexes bilaterally - No open wounds or ulceration - No purulent discharge - Probe to bone not applicable (no wound) - Able to weight-bear but with antalgic gait - Left foot shows healed plantar ulcer scar --- ## Investigations Provided ### Laboratory Results | Test | Result | Normal Range | Interpretation | |------|--------|--------------|----------------| | Hb | 118 g/L | 115-160 g/L | Normal | | WCC | 8.2 ×10⁹/L | 4-11 ×10⁹/L | Normal (argues against infection) | | Platelets | 245 ×10⁹/L | 150-400 ×10⁹/L | Normal | | ESR | 18 mm/hr | <20 mm/hr | Normal | | CRP | 12 mg/L | <5 mg/L | Mildly elevated (can occur in acute Charcot) | | HbA1c | 9.2% | <6.5% | Poorly controlled diabetes | | Fasting glucose | 11.2 mmol/L | 3.5-5.5 mmol/L | Elevated | | Creatinine | 145 μmol/L | 60-110 μmol/L | Mildly elevated (diabetic nephropathy) | | eGFR | 48 mL/min | >90 mL/min | Stage 3a CKD | | Uric acid | 0.38 mmol/L | 0.15-0.45 mmol/L | Normal (excludes gout) | | Procalcitonin | 0.1 ng/mL | <0.5 ng/mL | Normal (argues against bacterial infection) | ### Imaging **Image 1: Weight-bearing AP and Lateral Foot Radiographs** **Radiological features:** - Fragmentation of the tarsometatarsal (Lisfranc) joints - Subluxation at tarsometatarsal articulation - Subchondral sclerosis and bone debris - Joint effusion with soft tissue swelling - Early collapse of medial longitudinal arch - No sequestrum or involucrum (favours Charcot over osteomyelitis) - No gas in soft tissues **Anatomical location:** Midfoot (Brodsky Type 1, Sanders/Frykberg Pattern II) **Image 2: MRI Foot with Gadolinium (if obtained)** **MRI findings:** - Bone marrow oedema in navicular, cuneiforms, and metatarsal bases - Periarticular soft tissue oedema - Joint effusions at Lisfranc joints - No rim-enhancing fluid collection (argues against abscess) - No sinus tract - Subchondral bone changes without cortical destruction pattern typical of osteomyelitis - Ghost sign negative (intact cortex) ## Questions & Model Answers **Differential Diagnosis of Acute Hot Swollen Foot in Diabetic:** | Diagnosis | For | Against (This Patient) | |-----------|-----|------------------------| | **Charcot neuroarthropathy** | Neuropathy, diabetic, midfoot involvement, intact skin, normal WCC | Relatively acute presentation | | **Osteomyelitis** | Swelling, diabetes, previous ulcer | No wound, normal WCC, no fever | | **Cellulitis** | Erythema, swelling | No portal of entry, no systemic features | | **Septic arthritis** | Swelling, joint involvement | No fever, normal WCC | | **DVT** | Swelling, immobility | Erythema extends to midfoot, no calf tenderness | | **Gout** | Acute red swollen joint | Normal uric acid, midfoot not typical site | | **Fracture** | Swelling | No trauma, neuropathy (may miss minor trauma) | **Distinguishing Charcot from Osteomyelitis:** | Feature | Charcot | Osteomyelitis | |---------|---------|---------------| | **Intact skin** | Usually | Usually ulcer/wound | | **Probe to bone** | N/A | Positive (89% PPV if ulcer) | | **WCC/CRP** | Often normal or mildly elevated | Usually elevated | | **Procalcitonin** | Normal | Elevated | | **Temperature difference** | >2°C warmer | May be warm | | **X-ray pattern** | Fragmentation, subluxation, debris | Periosteal reaction, sequestrum | | **MRI pattern** | Bone marrow oedema, subchondral | Cortical destruction, sinus tract, abscess | | **WBC scan** | May show uptake | Increased uptake | **Key Clinical Clues in This Patient:** - **Intact skin** - argues strongly against osteomyelitis - **Normal WCC** - infection less likely - **Profound neuropathy** - substrate for Charcot - **Midfoot involvement** - classic Charcot location **Diagnosis: Acute Charcot Neuroarthropathy** (Eichenholtz Stage 1) > **Consultant Tip:** The absence of an ulcer or wound makes osteomyelitis very unlikely. Charcot typically has intact skin. Always probe to bone if there is a wound. **Classification Systems:** **1. Eichenholtz Classification (Temporal Staging):** | Stage | Name | Radiographic Features | Clinical Features | |-------|------|----------------------|-------------------| | **0** | Prodromal | Normal X-ray | Warmth, swelling (MRI may show oedema) | | **1** | Development (Fragmentation) | Bone fragmentation, joint debris, subluxation | Hot, swollen, erythematous - "acute phase" | | **2** | Coalescence | Absorption of debris, fusion of fragments, sclerosis | Decreasing warmth and swelling | | **3** | Reconstruction (Remodelling) | Consolidation, ankylosis, rounded bone ends | Cool, stable, may have fixed deformity | **This Patient:** **Stage 1 (Fragmentation)** - acute presentation with fragmentation visible on X-ray. **2. Anatomical Classification (Brodsky/Sanders-Frykberg):** | Type | Anatomical Location | Frequency | Prognosis | |------|---------------------|-----------|-----------| | **Type 1 (Pattern II)** | Tarsometatarsal (Lisfranc) | 60% | Most common, rocker-bottom | | **Type 2 (Pattern I)** | Forefoot (MTP/IP joints) | 15% | Better prognosis | | **Type 3A (Pattern III)** | Midtarsal (Chopart) | 10% | Significant instability | | **Type 3B (Pattern IV)** | Ankle joint | 10% | Worst prognosis, high amputation | | **Type 4 (Pattern V)** | Calcaneus | 5% | Heel ulceration risk | **This Patient:** **Type 1 (Lisfranc/tarsometatarsal)** - most common location, classic rocker-bottom deformity. **3. Schon Classification (Deformity-Based):** | Stage | Description | |-------|-------------| | **I** | Early, no deformity | | **II** | Bony prominences without ulcer | | **III** | Bony prominences with ulcer | | **IV** | Osteomyelitis complicating Charcot | > **Consultant Tip:** Know Eichenholtz for staging (guides treatment) and Brodsky for anatomical location (predicts outcome). Midfoot (Type 1) is most common. **Pathophysiology - Two Main Theories:** **1. Neurotraumatic Theory (French-German):** | Component | Mechanism | |-----------|-----------| | **Sensory neuropathy** | Loss of protective sensation | | **Repetitive microtrauma** | Continued weight-bearing despite injury | | **Unrecognised fractures** | Patient unaware of bone injury | | **Progressive destruction** | Ongoing damage without protective behaviour | **2. Neurovascular Theory (More Current):** | Component | Mechanism | |-----------|-----------| | **Autonomic neuropathy** | Loss of sympathetic vascular tone | | **Arteriovenous shunting** | Blood bypasses capillary beds | | **Increased blood flow** | Hyperaemia to bone | | **Bone resorption** | RANKL upregulation, osteoclast activation | | **Weakened bone** | Fractures with minimal trauma | **RANKL/OPG Axis:** | Factor | Role in Charcot | |--------|-----------------| | **RANKL** | Increased - promotes osteoclastogenesis | | **OPG** | Decreased - loses inhibition of osteoclasts | | **RANK** | Receptor on osteoclast precursors | | **Result** | Unchecked bone resorption | **Triggering Event:** | Potential Triggers | |-------------------| | Minor trauma (often unnoticed) | | Surgery (including foot surgery) | | Infection | | Renal transplant (immunosuppression) | **Inflammatory Cascade:** | Stage | Events | |-------|--------| | **Trigger** | Minor trauma/fracture | | **Inflammation** | TNF-α, IL-1, IL-6 release | | **RANKL upregulation** | Increased osteoclast activity | | **Bone destruction** | Fragmentation and collapse | | **Deformity** | If not offloaded during healing | **Prerequisites for Charcot:** 1. **Neuropathy** - loss of protective sensation (essential) 2. **Adequate blood supply** - needs perfusion for inflammatory response 3. **Weight-bearing** - mechanical stress drives destruction > **Consultant Tip:** Charcot requires BOTH neuropathy AND adequate blood supply. Pure ischaemic feet rarely develop Charcot - they develop dry gangrene instead. **Acute Phase Management (Stage 1 - Fragmentation):** **Principle: OFFLOADING is Critical** Continued weight-bearing leads to progressive collapse and deformity. **Step 1: Immediate Measures** | Action | Details | |--------|---------| | **Strict non-weight-bearing** | Essential in acute phase | | **Total Contact Cast (TCC)** | Gold standard for offloading | | **OR removable walker** | CROW boot (Charcot Restraint Orthotic Walker) | | **Duration** | Until transition to Stage 2 (coalescence) | **Step 2: Monitoring** | Parameter | Target | |-----------|--------| | **Temperature difference** | <2°C compared to contralateral foot | | **Swelling** | Resolved | | **Serial X-rays** | Every 4-6 weeks | | **Clinical review** | Every 2-4 weeks for cast changes | **Total Contact Cast Technique:** | Feature | Purpose | |---------|---------| | **Minimal padding** | Total contact with skin | | **Moulded to contour** | Even pressure distribution | | **Non-removable** | Enforces compliance | | **Changed regularly** | Every 1-2 weeks initially (oedema decreases) | **Duration of Treatment:** | Phase | Duration | |-------|----------| | **Non-weight-bearing** | 3-6 months (until consolidation) | | **Protected weight-bearing** | Additional 3-6 months | | **Transition to footwear** | Custom accommodative footwear | **Adjunctive Medical Management:** | Treatment | Evidence | Role | |-----------|----------|------| | **Bisphosphonates** | Limited evidence | May reduce bone turnover (theoretical) | | **Vitamin D/Calcium** | Standard | Ensure bone health | | **Glycaemic control** | Essential | Optimise HbA1c | **For This Patient:** 1. Apply TCC today 2. Non-weight-bearing with crutches/wheelchair 3. Optimise diabetes (endocrine referral) 4. Serial X-rays 4-weekly 5. Monitor temperature difference 6. TCC changes every 2 weeks initially > **Consultant Tip:** The key to preventing deformity is early diagnosis and aggressive offloading. A missed acute Charcot that continues to weight-bear develops rocker-bottom deformity. **Chronic Charcot with Deformity and Ulceration:** This represents failed conservative management or late presentation with: - Fixed midfoot collapse (rocker-bottom) - Bony prominence plantarly - Recurrent ulceration over prominence - Risk of osteomyelitis through ulcer **Indications for Surgery:** | Indication | Rationale | |------------|-----------| | **Recurrent ulceration** | Bony prominence causes pressure | | **Unstable deformity** | Cannot be braced | | **Impending ulceration** | Prominent bone, thin skin | | **Osteomyelitis** | May require resection | | **Unbraceable foot** | Failed accommodative footwear | **Surgical Options:** **1. Exostectomy (Simple Bony Resection):** | Feature | Details | |---------|---------| | **Indication** | Prominent bone causing ulcer, stable foot | | **Technique** | Remove bony prominence, close skin | | **Advantage** | Lower morbidity | | **Disadvantage** | Does not correct deformity | **2. Realignment Arthrodesis (Reconstruction):** | Feature | Details | |---------|---------| | **Indication** | Unstable deformity, failed exostectomy | | **Technique** | Midfoot osteotomy, realignment, fusion | | **Fixation** | Locking plates, intramedullary bolts, external fixation | | **Super construct principle** | Extend fusion beyond zone of injury, use strongest fixation | **Super Construct Principles:** | Principle | Application | |-----------|-------------| | **Fusion extends beyond injury zone** | Include adjacent joints | | **Strongest fixation possible** | Locking plates, bolts | | **Multiple fixation points** | Spread load | | **Bone resection to reduce tension** | Shorten column if needed | | **Plantigrade position** | Must achieve braceable foot | **3. Amputation:** | Indication | Level | |------------|-------| | **Uncontrollable infection** | Below-knee or higher | | **Unsalvageable deformity** | Syme's or transtibial | | **Poor vascular status** | Appropriate level by vascular assessment | | **Patient preference** | After informed discussion | **Postoperative Management:** | Phase | Duration | Management | |-------|----------|------------| | **Non-weight-bearing** | 3-6 months | Longer than standard fusion | | **Protected weight-bearing** | 3-6 months | CROW boot | | **Final footwear** | Lifelong | Custom accommodative | > **Consultant Tip:** Charcot reconstruction has high complication rates (30-40%). The goal is a plantigrade braceable foot, not a normal foot. Sometimes amputation provides better function. **Prognosis:** **Natural History (Untreated or Late-Treated):** | Outcome | Frequency | |---------|-----------| | Rocker-bottom deformity | 60-70% | | Recurrent ulceration | 40-50% | | Osteomyelitis through ulcer | 20-30% | | Major amputation | 10-15% | **With Early Adequate Treatment:** | Outcome | Frequency | |---------|-----------| | Stable braceable foot | 60-70% | | Minor deformity manageable with footwear | 20-25% | | Major deformity requiring surgery | 10-15% | | Amputation | <5% | **Risk Factors for Poor Outcome:** | Factor | Impact | |--------|--------| | **Late diagnosis** | More deformity at presentation | | **Poor compliance** | Continued weight-bearing | | **Ankle involvement** | Highest amputation rate | | **Bilateral disease** | 25-30% develop contralateral Charcot | | **Poor glycaemic control** | Impaired healing | | **Nephropathy** | Impaired bone healing | **Long-Term Requirements:** | Requirement | Rationale | |-------------|-----------| | **Lifelong footwear modification** | Protect foot from recurrence | | **Regular podiatry** | Ulcer prevention | | **Diabetes optimisation** | Reduce complication risk | | **Contralateral foot surveillance** | High risk of bilateral disease | **Counselling Points for This Patient:** 1. **Disease explanation:** - "This is not an infection but your bones are fragile due to nerve damage" - "We need to stop you walking on it to prevent collapse" 2. **Treatment duration:** - "Expect 6-12 months in casts/boots" - "Lifelong special footwear after that" 3. **Potential outcomes:** - Best case: stable foot in accommodative footwear - Worst case: amputation (explain risk is low with compliance) 4. **Compliance is critical:** - "If you weight-bear during acute phase, the foot will collapse" - "Every step causes more damage" 5. **Contralateral foot:** - "25-30% chance the other foot develops this too" - "Inspect both feet daily" 6. **Multidisciplinary care:** - Diabetologist, podiatrist, orthotist, nurse specialist - Lifelong surveillance > **Consultant Tip:** Charcot is a chronic condition requiring lifelong management. The acute phase treatment is just the beginning. Emphasise compliance - every unauthorised weight-bearing step can cause irreversible damage. --- ## Key Teaching Points ### Pattern Recognition **This pattern suggests Charcot Neuroarthropathy:** - Diabetic patient with peripheral neuropathy - Warm, swollen, erythematous foot - Relatively painless (neuropathy) - Intact skin (no ulcer or wound) - Midfoot involvement - Normal or only mildly elevated inflammatory markers - Radiographic fragmentation without sequestrum **Distinguish from Osteomyelitis:** | Feature | Charcot | Osteomyelitis | |---------|---------|---------------| | Skin integrity | Usually intact | Usually wound/ulcer | | Probe to bone | N/A | Positive | | WCC | Normal | Elevated | | Procalcitonin | Normal | Elevated | | Location | Midfoot most common | Under ulcer | ### Critical Management Points 1. **Early diagnosis is key** - before significant collapse occurs 2. **Offloading is the mainstay** - TCC or non-removable walker 3. **Don't confuse with infection** - both can have warmth and erythema 4. **Long treatment duration** - 6-12 months offloading 5. **Lifelong surveillance** - contralateral foot at risk 6. **Surgery for deformity/ulceration** - not primary treatment --- ## Common Examiner Follow-ups **Q: "How do you monitor response to treatment?"** Monitoring parameters: - **Temperature difference:** Should decrease to <2°C - **Swelling:** Progressive reduction - **Serial X-rays:** Transition from fragmentation to coalescence - **Clinical examination:** Resolution of acute signs Transition to Stage 2 (coalescence) typically takes 3-6 months. This is when gradual weight-bearing can begin. --- **Q: "What is the evidence for bisphosphonates in Charcot?"** Evidence for bisphosphonates: - **Theoretical rationale:** Reduce osteoclast activity, prevent bone resorption - **Jude et al. (2001):** Pamidronate reduced bone turnover markers - **Recent trials:** Mixed results, no clear clinical benefit demonstrated - **Current practice:** Not routinely used, consider in refractory cases The mainstay of treatment remains offloading. Bisphosphonates are not standard of care. --- **Q: "What if MRI shows changes consistent with both Charcot and osteomyelitis?"** This is challenging - "overlap" cases: - **Charcot with secondary osteomyelitis:** Can occur if ulcer develops - **Ghost sign:** Absent bone marrow on T1 with absent cortex suggests osteomyelitis - **Sinus tract:** Strongly suggests osteomyelitis - **Response to offloading:** Charcot improves; osteomyelitis progresses If doubt: - Bone biopsy for culture and histology - Consider tagged WBC scan - Trial of offloading with close monitoring - Multidisciplinary discussion --- **Q: "How does Charcot affect surgical planning for foot and ankle procedures?"** Considerations: - **Higher non-union rate** - impaired bone healing - **Higher infection rate** - diabetic microvasculature - **Need for super constructs** - extend fixation, use stronger implants - **Longer healing times** - extended non-weight-bearing - **Risk of triggering Charcot** - any surgery can trigger acute Charcot in at-risk feet Prophylactic measures: - Optimise glycaemic control preoperatively - Prolonged non-weight-bearing - Close monitoring post-surgery - Consider protected weight-bearing longer than standard protocols --- ## Related Topics - Diabetic Foot Ulcers - Osteomyelitis - Midfoot Arthrodesis - Peripheral Neuropathy - Total Contact Casting - Diabetic Foot Infections