Diabetic Foot Conditions Quiz

Neuropathic Bone Disease Overview

• Neuropathic bone disease, specifically Charcot foot, is a progressive condition.
• It's characterized by joint dislocation, pathological fractures, and severe pedal architectural destruction.
• The "6 D's" of Charcot foot include destruction, debris, dislocation, distention, disorganization, and increased density (subchondral sclerosis).

Etiologies

• Diabetes is the most common cause.
• Other etiologies include spinal disorders (MS, CMT), paraneoplasms, transplant (kidney, kidney-pancreas), leprosy, tabes dorsalis, syringomyelia, steroids, alcoholism, and pernicious anemia.

Prevalence and Statistics

• Charcot neuroarthropathy is reported in 0.1-7.5% of the general diabetic population.
• Up to 35% of diabetic patients with neuropathy may have this condition.
• Patients typically have diabetes mellitus (DM) for 10 years or more before onset.
• Bilateral occurrences are reported anywhere from 9% to 75%.
• The average age of onset is 50.3 years.

Pathophysiology

• Neurotraumatic theory: Exaggerated overuse injury coupled with loss of protective sensation.
• Repetitive microtrauma: Can initiate the condition.
• Lack of sensation: Allows continued tissue destruction, resulting in fractures and dislocations.
• Neurovascular theory: Vasomotor neuropathy in patients with intact blood flow, arteriovenous shunting leads to bone resorption and weakening that exacerbates fractures and dislocations through continued weightbearing.
• Increased inflammatory response: Osteoclast-osteoblast imbalance is present with increased osteoclasts. Osteoclasts cause bone lysis leading to more inflammation that causes bone and joint destruction.
• RANKL: Elevated RANKL leads to osteoclast activation and bone destruction.
• Histology: Bone and cartilage debris embedded in synovium. Replacement of cartilage by fibro-osseous tissue.

Clinical Features

• Red, hot, and swollen feet usually with a temperature difference of >2 degrees Celsius compared to the unaffected limb.
• Edematous feet are common.
• Sensory neuropathy is typically present.
• Pain may be present but doesn't necessarily correlate with the extent of damage.
• Bilateral involvement is observed in 9-30% of cases.

Differential Diagnosis

• Conditions that can mimic Charcot arthropathy include infection, rheumatoid arthritis, osteoarthritis, gout, and osteomyelitis.

Diagnosis

• Diagnosis is primarily based on a combination of clinical features.
• Key diagnostic features include redness, heat, edema, and a greater than two-degree difference in temperature compared to other limbs.
• Radiographic findings are essential: these include cortical fractures, periosteal reactions, joint debris, deformity, dislocation, and the rocker-bottom deformity.
• Lack of a break in the skin is also important.

Imaging Considerations

• MRI: T1 images reveal decreased signal intensity, and T2 images show increased signal intensity. Moreover, STIR images demonstrate prominent marrow edema.
• MRI Considerations: Bone marrow edema may be present around ulcers or in tracts, potentially suggesting a bone infection. Charcot-related edema frequently manifests in peri-articular regions.
• X-rays: Standard X-rays are important but sometimes require further imaging like CT scans or MRIs to ascertain the extent of damage.

Nuclear Medicine

• Three-phase Tc99m-MDP scan is generally 85% sensitive but 55% specific due to other causes of bone remodeling.

• Ga67 shows high false-positive rates; In111 shows high sensitivity rates in detecting osteomyelitis in the neuropathic foot.

• A combined scan (Tc99m-MDP and Tc99m-HMPAO (Ceretec)) offers 94% sensitivity and 91% specificity.

• Combined Scan: A combination of Tc99m-MDP and In11 scans provide 86% sensitivity and 94% specificity

• Other Scans: Tc99m-Sulfur Colloid and In111 have demonstrated efficacy in more recent studies.

• WBC scan in conjunction with nuclear medicine scans: helps differentiate osteomyelitis and Charcot, cellulitis, and possible absence of osteomyelitis or an active form of Charcot.

Probing to Bone

• Ability to probe to bone using a metallic instrument positively predicts osteomyelitis and negatively predicts osteomyelitis. The positive predictive value for osteomyelitis is 89% for positive results and 96-98% for negative results.
• Importance of probing: helpful in determining whether the condition is osteomyelitis.

Bone Biopsy

• Bone biopsy with culture is considered the gold standard for differentiating Charcot from osteomyelitis.
• Findings of bone and cartilage fragments embedded in synovium support diagnosis.

Sequelae (Complications)

• Foot and ankle deformity are prominent complications.
• Increased pressure, ulceration, soft-tissue and bone infections, partial amputation, limb loss, potentially increased risk of contralateral Charcot development.
• Death is a potential complication in severe cases.

Treatment

• Stage I: Non-weight-bearing (NWB) and temperature stabilization. Total contact cast or boot are primarily used. Time to healing can span 9-11 months, depending on the response to treatment.
• Stage II: Protected weight bearing with specific devices to manage the condition. Foot support is crucial, and orthotic devices including custom molded shoes or pressure-relieving orthotics might be useful.
• Stage III: Conservative care in combination with custom orthotics or braces may be required for management. Ultimately, more tailored approaches might be required.
• Conservative care: Extra-depth or custom-molded shoes and pressure-relieving orthotics are considered. Appropriate footwear is crucial. Severely deformed feet might require surgical correction.
• Surgical treatment: Exostectomy (removal of bone spurs) and arthrodesis (fusion of bones) are common surgical methods. Realignment osteotomy and various fixation approaches (e.g., external or internal fixation, including a combination of both) may be part of the surgical intervention. Management of infections is critical. This may lead to partial and more extensive foot amputations in severe cases (below knee, or above the knee).
• Extensive medical workup is needed before surgical intervention.
• NWB or partial weight bearing is typically required. Optimizing vascular status is crucial.
• Renal or cardiac status poses significant implications for the outcomes of treatment. Cardiac function is also a significant factor.

Brodsky Classification

• Anatomic classification of Charcot foot, with different foot regions affected. Type 1 is tarsometatarsal, type 2 is Chopart's/subtalar, type 3A and 3B are ankle and calcaneus; Sequential, type 4 is multiple regions, and type 5 is forefoot.

Eichenholtz Classification

• Stages of Charcot arthropathy's natural history describe its progression from development to fragmentation, coalescence, and reconstruction-consolidation.

Test your knowledge on the diagnosis and treatment of diabetic foot conditions. This quiz covers important aspects such as bone biopsies, negative predictive values, and potential complications. Challenge yourself with questions that are crucial for understanding diabetic foot management.