In Brodsky's classical description of zones affected by diabetic neuropathic arthropathy, he described the primary areas of the foot affected to be the midfoot and rearfoot (types 1,2,3). How common is neuropathic arthropathy of the forefoot (Brodsky type 5)? This article explores the fact that Brodsky type 5 (forefoot) may be an overlooked condition in diabetes care.
Is Brodsky type 5 neuropathic arthropathy often overlooked?
In his 1986 Foot and Ankle article, Patterns of Breakdown in the Charcot Tarsus of Diabetics and Relation to Treatment, Dallas based orthopedist James Brodsky defined patterns of breakdown seen in Charcot arthropathy (also called diabetic neuropathic arthropathy or Charcot joint). He defined three primary, yet separate zones that included the midfoot or what is called Lisfranc’s joint (Type 1), Chopart’s joint and the subtalar joint (Type 2) and the ankle (Type 3A). Type 3B follows a fracture of the Calcaneal tuberosity. Brodsky describes types 4 and 5 (forefoot) as far less common. Frequencies of each type of Charcot arthropathy are seen in the chart below adapted from Ortho Bullets.
Type 1 • Involves tarsometatarsal and naviculocuneiform joints
• Collapse leads to fixed rocker-bottom foot with valgus angulation
Type 2 • Involves subtalar, talonavicular or calcaneocuboid joints
• Unstable, requires long periods of immobilization (up to 2 years)
Type 3A • Involves tibiotalar joint
• Late varus or valgus deformity produces ulceration and osteomyelitis of malleoli 20%
Type 3B • Follows fracture of calcaneal tuberosity
• Late deformity results in distal foot changes or proximal migration of the tuberosity < 10%
• Involves a combination of areas < 10%
• Occurs solely within forefoot< 10%
In my practice, I see that neuropathic arthropathy, particularly when secondary to diabetic peripheral neuropathy, often affects the forefoot. Is the prevalence of Brodsky type 5 perhaps and overlooked aspect of diabetic foot care? The two following cases show progressive neuropathy changes specific to the metatarsal phalangeal joints and digits (Brodsky type 5).
Case number one is a 57y/o female who presented to my office from our emergency department for swelling of the forefoot. She described a 23-year hx of poorly controlled type 1 diabetes. She recalled no hx of injury to the foot but states that she felt obligated to prepare food for a family reunion. The onset of symptoms occurred two months prior to her visit with us. She states that the foot became progressively worse over the week-long family reunion. The foot was warm to touch with minimal pain described with range of motion of the forefoot. Surface temperature of the forefoot was elevated by 3 degrees compared to the shin as measured by infrared temperature testing. Plain films showed the following.
Case number two shows the progressive changes within the interphalangeal joint of a 34 y/o female. She describes a 12-year hx of poorly controlled T2DM. The patient also describes a hx of opioid addiction and chronic pain management. In this case, the patient does describe a hx of trauma in that she fell down her stairs at home. Early x-rays show a marginally displaced intra-articular fracture of the distal phalanx. X-rays taken 4 weeks later show displacement of the fracture fragment, osteolysis of the fracture site with a new, longitudinal fracture of the central proximal phalanx.
These two case show progressive changes of the metatarsal phalangeal jonts and phalanges, but are they truly type 5 Charcot by the classical definition? The citation to Ortho Bullets above cites three contributing factors to Charcot arthropathy.
Mechanism and pathophysiology of Charcot arthropathy
o molecular biology
The above theories that describe the onset of neuropathic arthropathy suggest that trauma, whether repetitive micro-trauma (case 1) or abrupt trauma (case 2) contribute to the onset of Charcot arthropathy while neuropathy both aggravates and delays healing. Knowing these facts, the two cases briefly discussed above represent Brodsky type 5 neuropathic arthropathy. As foot and ankle specialists, we know to keep a high degree of suspicion for midfoot Charcot arthropathy. I think we need to have the same high degree of suspicion in our diabetic population when we see forefoot swelling suggestive of Brodsky type 5 diabetic neuropathic arthropathy.