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Diagnosing And Addressing Unilateral Ainhum In The Lower Extremity
While ainhum is a rare condition, it can have devastating and painful consequences. With this in mind, the authors discuss the progression of ainhum and keys to the diagnostic workup in the case of a patient who presented with significant pain and swelling of his fifth toe.
Originally described by da Silva Lima in 1880, ainhum is a rare pathological hyperkeratotic narrowing or constriction band that forms around the proximal aspect of the fifth toe, which often leads to auto-amputation. While the true cause of ainhum (also known as dactylolysis spontanea) remains unclear, it appears that predisposing factors include race and genetics. The condition is likely triggered by some sort of trauma.1,2
Although there has not been any clinical evidence that this condition is hereditary, in some studies, patients did report one of their parents experiencing similar pathological processes.3 It is very likely that the prevalence of this condition is higher as it may be underdiagnosed. In addition, if this condition is left untreated, it can lead to ulceration or infection at the affected digit.4
Most reports of ainhum are in males of African descent at a ratio of 2:1 in comparison to female cohorts. These patients usually live in tropical areas such as South America and India although South America has the highest overall reported incidence.5,6 Of that subset, those affected are typically between 20 and 50 years old (with an average age of 38 years) with youngest documented patient being seven years old.6
The natural progression of ainhum reportedly occurs in four stages ranging from a fissure in the plantar surface of the fifth toe to complete auto-amputation.
Stage 1: Development of a clavus, which progresses to an annular fissure around the toe.
Stage 2: The digit becomes globular distal to the constriction band at the groove, which is associated with bone resorption and arterial stenosis.
Stage 3: The involved bone become symptomatically painful, separating at the joint with hypermobility of the digit.
Stage 4: A bloodless auto-amputation of the toe occurs.3
Ainhum is primarily a clinical diagnosis, which consists of soft tissue constriction with bulbous enlargement of the toe, thinning of phalangeal bone and phalangeal lysis.7 Radiographic findings of documented cases of ainhum typically consist of a radiolucent ring constricting at the base of the affected digit with bone resorption or osteolysis at the distal and middle phalanges with a tapering appearance.8 Previous histological reports of ainhum have revealed a thickened stratum corneum near the fibrous annular band, hyperkeratosis or acanthosis of the epidermis, and the presence of lymphocytes and fibroblasts within the dermis due to an increased inflammatory response caused by tissue damage.9
Early-stage treatment protocols can involve Z-plasty whereas late-stage cases only end in surgical or auto-amputation.10 In addition, there are reported non-operative treatments with utilization of either topical or injectable salicylates, injectable corticosteroids or retinoids with symptomatic relief and/or partial resolution of the condition.9,11,12 The goal of this case report is to present a true ainhum case outside of the typical geographic area of presentation as they are rare and little documentation is available.9
When A 65-Year-Old Male Presents With Significant Pain And Swelling to His Fifth Digit
A 65-year-old Haitian American male with no significant past medical history presented to our hospital’s emergency department from home for evaluation of significant pain and swelling to his left fifth digit (see top two photos above). The patient first noticed a small hair-like band around the left fifth digit approximately four months prior to his initial presentation. The patient did not recall any traumatic injury to that area or a prior infectious process. He complained of abnormal gait with worsening pain since onset, which increased when wearing closed toe shoes. The patient preferentially wore open toe sandals to avoid any shoe wear from rubbing or touching the area of concern. There was no related family history of ainhum on the maternal or paternal sides of the patient's family.
Upon the physical examination, the patient presented with a constriction band of the left fifth digit proximally at the proximal phalanx with edema to the distal aspect of the digit with hyperpigmentation. There were no signs of infection present to the digit or lymphangitis present in the lower leg. However, the digit was ischemic in appearance with sluggish capillary refill time (less than three seconds) to the distal tuft of the involved digit. The patient had palpable dorsalis pedis and posterior tibial pulses. We noted his skin temperature from the proximal tibial tuberosity to the distal foot to be warm bilaterally. Although he did not exhibit hair growth to the bilateral lower extremities, examination revealed intact gross sensation.
Radiographic imaging studies of the left foot showed deformity of the left fifth proximal phalanx with thinning of the shaft and head with smooth margins (see last image above). After extensive review of the findings and treatment options with the patient, he elected to proceed with non-operative management of the ischemic digit. We instructed the patient to keep the digit dry by painting the area with betadine and avoiding trauma to the area. Due perhaps to the patient’s travel distance from his home to our office location, he subsequently failed to keep any follow-up appointments.
Final Thoughts
Typically, in these cases, clinicians employ conservative management, which results in auto-amputation of the affected digit. In this particular case, the patient elected for continued conservative management versus elective amputation after a lengthy discussion. Although we were not involved in the patient’s definitive treatment, this is a unique case presentation of ainhum in an adult male. This case reveals the necessity for health-care providers, specifically podiatrists, to be able to promptly diagnose this condition with the aim of preserving the involved digit, thus preventing deformities, psychological and emotional trauma, and possible ulceration infection or surgical site infections leading to increased morbidity.6 To our knowledge, this was the first documented and reported case of ainhum in the South Florida area.
Dr. Johnson is currently a Podiatric Medicine and Surgery Clinical Research Fellow at University of Pennsylvania-Penn Presbyterian Medical Center in Philadelphia and a former podiatric surgical resident at the Aventura Hospital and Medical Center in Aventura, Fla.
Dr. Venero is a first-year Podiatric Medicine and Surgery Resident at the Department of Veteran Affairs-Orlando VA Medical Center in Orlando, Fla. and former medical student extern at the Aventura Hospital and Medical Center in Aventura, Fla.
Dr. Holewinski is the Clinical Director of the Aventura Hospital and Medical Center Podiatry Residency Program in Aventura, Fla.
Dr. Williams is the Podiatry Residency Program Director at the Aventura Hospital and Medical Center in Aventura, Fla.
The authors disclose that this research was supported (in whole or in part) by HCA Healthcare and/or an HCA Healthcare affiliated entity. The views expressed in this publication represent those of the authors and do not necessarily represent the official views of HCA Healthcare or any of its affiliated entities.
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