What is a malum perforans?

What is Mal Perforans (Malum Perforans Pedis)?

Mal perforans, also known as malum perforans pedis or "perforating ulcer," is a chronic, deep plantar foot ulcer that occurs predominantly in diabetic patients with peripheral neuropathy, typically located at pressure points on the sole of the foot, most commonly under the metatarsal heads. 1

Pathophysiology and Underlying Causes

The condition develops through a specific mechanism related to loss of protective sensation:

• Peripheral neuropathy is the central pathophysiologic factor, causing loss of protective sensation that allows repetitive trauma to go unnoticed 2
• Motor neuropathy contributes by causing foot deformities and creating abnormal pressure points that concentrate mechanical stress 2
• Autonomic neuropathy results in dry, cracking skin due to reduced sweating, compromising the protective skin barrier 2
• The ulcer typically begins after a break in the protective skin envelope at sites of trauma or pressure 2

Less Common Etiologies

While diabetes is the predominant cause, mal perforans can also result from:

• Spinal canal stenosis with spondylolisthesis causing radicular nerve damage 3
• Spina bifida and lipo-meningocele in pediatric cases, where severe radicular lesions lead to neurotropic ulceration 4

Clinical Characteristics

The ulcer presents with distinctive features:

• Chronic, painless plantar ulceration at pressure-bearing sites, most commonly under metatarsal heads 1
• Deep penetration that can extend to bone, hence the term "perforating" 1
• High recurrence rate even after initial healing with conservative measures 1
• Risk of spreading infection and serious tissue destruction if inadequately treated 1

Treatment Approach

Conservative Management (First-Line)

• Pressure offloading is essential, though many ulcers will respond initially to conservative measures 1
• Specialized footwear designed to remove pressure from healing areas and potential new pressure points 1
• Local DMSO (dimethylsulfoxide) application showed complete healing in 70% of patients (14/20) within 4-15 weeks in one study, compared to only 10% (2/20) with conventional treatment 5

Surgical Management (Definitive Treatment)

Surgical excision is indicated to achieve long-term healing when conservative measures fail or recurrence is frequent: 1

• Excision of the distal metatarsal head (dorsal approach) is the primary surgical technique 1, 6
• Primary closure of the plantar ulcer with secondary healing of the dorsal incision 6
• Excision of distal metatarsal plus first toe amputation may be required in more extensive cases 1

Surgical Outcomes in Diabetics with Arterial Insufficiency

This radical surgical approach is effective even in patients with significant arterial insufficiency: 6

• 100% primary healing rate of plantar wounds in 40 diabetic patients, including 38% without palpable pedal pulses 6
• No amputations or readmissions for forefoot sepsis during mean 38.5-month follow-up 6
• Minimum toe pressure of 60 mmHg is required for successful healing 6
• Recurrence was associated with noncompliance with orthotic follow-up care, not with perfusion indexes 6

Critical Management Pitfalls

• Do not confuse with bowel perforation: The term "perforans" refers to the ulcer penetrating through the plantar skin/soft tissue, not intestinal perforation 1
• Recognize non-diabetic causes: In cases not responding to standard diabetic foot care, investigate for spinal pathology, especially in younger patients 3, 4
• Address underlying neurologic disease: When mal perforans results from spinal lesions, surgical treatment of the spinal pathology is essential for ulcer healing 4
• Ensure orthotic compliance: Post-surgical recurrence is primarily related to inadequate pressure offloading, not vascular status 6