Kaplan’s lesions are defined as open wounds with the metacarpal head exposed in the palms, accompanied by complex dorsal dislocation of the metacarpophalangeal joint (MCPJ). Kaplan’s lesions are clinically rare because the volar side of the MCPJ is anatomically supported and reinforced by a stronger adjacent structure. Moreover, lesions in the little finger are very rarely reported because most Kaplan’s lesions occur in the index finger. The reduction of lesions and restoration of joint stability is difficult when Kaplan’s lesions occur. Various methods have been currently introduced in the treatment of Kaplan’s lesions; however, no standardized treatment has been established because of the rarity of this disease. This paper reports a case of Kaplan’s lesion of the left little finger without fracture after a fall; the case was successfully treated with open reduction using a volar approach.
Kaplan’s lesions are defined as open wounds of metacarpal head buttonholes exposed into the palms, accompanied by complex dorsal dislocation of the metacarpophalangeal joint (MCPJ) [
When a Kaplan’s lesion occurs, it is easy to assume that it can be treated with closed reduction alone followed by skin closure; however, in reality closed reduction is difficult and nearly impossible [
This study reports a case of Kaplan’s lesion of the little finger treated with open reduction using the volar approach. The study was approved by the Institutional Review Board of the Konkuk University Chungju Hospital (IRB No. KUCH 2021-01-001). The patient provided written informed consent for the publication and use of his images.
A 61-year-old male with a history of stroke presented to the emergency room after a fall from a height of 2 m at work. The patient was diagnosed with an L2 spine compression fracture on lumbar computed tomography, and a 4-cm horizontal laceration was observed on the volar side of the MCPJ of the little finger of his left hand (
An extended horizontal incision and an additional vertical incision, both 2 cm long, were made on the head of the metacarpal bone within the horizontal open wound (
Upon assessment of the left fifth MCPJ on postoperative day 5, smooth flexion and extension movement were observed. To avoid possible damage to the operative site, the range of motion (ROM) of the finger was not evaluated. At the second postoperative week, no dysesthesia of the left little finger was observed. The ROM of the repaired MCPJ was evaluated on follow-up 6 months postoperatively. The flexion and extension angles of the MCPJ were 82° and −4°, respectively. This indicated that more than 70% of the normal value of ROM as per the American Medical Association criteria was recovered (
Kaplan’s lesions are caused by the rupture of the volar plate, comprised of thick and sturdy tissue, in a hyperextended MCPJ, making such lesions rare. Approximately 50% of all Kaplan’s lesions are accompanied with a fracture of the metacarpophalangeal head [
The volar plate plays a role in the stability and rigid support of the MCPJ on the palm surface. Moreover, the flexor tendon and A1 pulley are located on the volar side of the volar plate, providing additional stability to the MCPJ [
The noose theory suggests that closed reduction is difficult to perform in cases with Kaplan’s lesions. It is hypothesized that the head of the metacarpal bone, which is dislocated and observed within the open wound, is noosed by adjacent structures (e.g., the natatory ligament, superficial transverse metacarpal ligament, flexor tendons, pretendinous band, and lumbricals) [
When planning treatment for Kaplan’s lesions, the surgeon should aim at the restoration of the patient’s MCPJ motion and perform the reduction and repair of the volar plate and surrounding soft tissues. In case of excessive closed reduction, the interposition of the volar plate and articular capsule occurs on both the volar and dorsal sides. According to previous studies, few cases of successful closed reduction exist because the volar plate, capsule joint, and collateral ligaments imposing on the joint are entrapped in the joint and thus interfere with the reduction [
The most important point of the surgical treatment of Kaplan’s lesions is to remove the imposing structures in the dislocated space and release the metacarpal head from the noose formed by the adjacent structures. The preferred method for this surgical treatment has changed over time. The dorsal approach was first introduced in 1876, enabling easy access to associated osteochondral fractures and entrapped volar plates as well as decreasing the risk of neurovascular injury. However, the anatomical restoration of the entrapped volar plate and damaged adjacent structures is difficult using this method, and MCPJ instability remains [
In this case, the authors confidently used the volar approach for the following reasons: first, the traumatic wound was not accompanied by a fracture; second, the open wound was already large enough to approach, and third, the anatomical location of the sesamoid bone was clearly visible on the preoperative X-ray. This made it easy to access the lesion and thereby provided good results, including recovery of motor function. If the sesamoid bone is not clearly visible in the preoperative X-ray view, or if the positional relationship between the bones is inaccurate due to fractures, preoperative computed tomography is recommended [
Standard treatment for Kaplan’s lesion has not yet been established as such lesions are rare; however, various approaches can be applied depending on the traumatic condition of the lesion and the surgeon’s preference. Based on anatomical differences, the surgeon should consider the restoration of the ruptured volar plate and adjacent structures as well as the reduction of the complex dorsal dislocation of the MCPJ of the little finger.
No potential conflict of interest relevant to this article was reported.
A patient presented with dislocation of the left little finger. Clinical photographs before surgery; (A) palmar view and (B) focus view. Preoperative X-ray; (C) anteroposterior view and (D) lateral view. Yellow arrow is the sesamoid bone.
Open reduction by a volar approach was performed. (A, B) Intraoperative findings; palmar view.
No redislocation was noted after reduction on the postoperative X-ray. (A) Anteroposterior view and (B) lateral view.
The range of motion was evaluated at postoperative month 6. Clinical photographs 6 months later; (A) flexion, (B) extension, and (C) a scar.
Illustration of Kaplan’s lesion of the little finger; palmar view.