Entrapment of Digital Nerves due to an Embedded Ring: A Case Report

Chronic embedded ring injury, which has a very dramatic appearance, is very rare, with only approximately 20 cases previously reported in the English literature.[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] In most of the reported cases, the ring was simply removed with a ring cutter in the emergency setting, and few surgical interventions were required. There have been only a few reports of sensory disturbance of the finger with an embedded ring.[2] [4] [8] However, the appearances of the digital nerves have never been confirmed with a surgical procedure when the ring was removed. This is the first case report of a chronic embedded ring injury in which severe constriction of the digital nerves by the embedded ring was demonstrated on surgical exploration, and atraumatic neurolysis of the digital nerves was required.

A 73-year-old woman presented with an embedded ring in her right ring finger, with swelling and foul discharge after a blow. She had been wearing the ring for more than 20 years, and the ring had been embedded for 10 years. She had previously received psychotherapy and had taken orally antianxiety agents for few years, but she was on no drugs at the time of presentation. The patient reported that she had gained weight from 38 kg early in life to 62 kg recently. On examination, only the dorsal part of the ring could be seen above the skin dorsally, and an intact bridge of skin overlaid the volar aspect of the ring ([Fig. 1]). The ring finger was swollen with foul discharge, but the distal circulation was satisfactory. The range of motion was limited to moderate flexion. On neurological examination, although there was no numbness, sensation distal to the buried ring was diminished: Semmes Weinstein monofilament values were 4.56 on the ulnar side and 4.31 on the radial side; static two-point discrimination values were 10 mm on the ulnar side and 8 mm on the radial side. Plain radiographs of the ring finger showed the completely buried ring within the volar soft tissue, but bone scalloping was not appreciable in the proximal phalanx ([Fig. 2]).

Fig. 1 The appearance of the embedded ring on the ring finger. About two-thirds of the ring is embedded into the soft tissue of the proximal phalanx. The volar skin is intact.

Fig. 2 Plain radiograph of the ring finger. The volar part of the ring is completely buried.

Surgical exploration was performed under brachial plexus anesthesia to avoid damaging the neurovascular bundles during removal of the ring. A Brunner zigzag incision was made on the volar aspect of the ring finger. The neurovascular bundles, especially the digital nerves, were extremely entrapped between the ring and the proximal phalanx ([Fig. 3]), and the flexor digitorum profundus tendon was ruptured. The neurovascular bundles were released carefully, and then the ring was removed safely after opening the stems of the ring without using a ring cutter because of the divided original design of the bottom of the ring ([Fig. 4]). The hypertrophic granulation tissue at the entrance wounds was debrided, and the skin was primarily closed.

Fig. 3 Intraoperative view of the ring finger showing the entrapment of the neurovascular bundle under the embedded ring (arrow).

Fig. 4 The digital nerves becoming thinner (arrow) after neurolysis and removal of the ring.

The wound healed uneventfully with oral antibiotic coverage. About 1 year and 7 months after the surgery, the sensory disturbance of the finger improved without numbness; Semmes Weinstein monofilament values were 3.61 on the ulnar side and 2.83 on the radial side, and static two-point discrimination values were 7 mm on the ulnar side and 6 mm on the radial side. Although we recommended additional tendon reconstruction of the flexor digitorum profundus, she refused it and was left with restricted flexion of the distal interphalangeal joint.

In the early stage of the embedded ring, the digital skin is still intact, although minor abrasion can occur, and the ring is very tight and barely mobile.[6] As the condition progresses, the skin and subcutaneous tissue are eroded with low-grade infection, and then part of the volar skin starts healing. As time goes by, the ring becomes gradually embedded into the finger with only the dorsal surface exposed. In the final stage, the soft tissue, flexor and extensor tendons, digital nerves, and phalangeal bone become involved. Because the digital circulation is usually maintained with the slowly progressive nature of this injury, ischemia has never happened even in the advanced stage, and few cases require surgical intervention.[2] [5] [6] Awan et al identified the intact and formed digital arteries and nerves over the embedded ring on surgical exploration.[1] In contrast, the neurovascular bundles, especially the digital nerves, were severely constricted between the ring and the proximal phalangeal bone in the present case. This is the first report confirming entrapment of the digital nerves due to an embedded ring, and it appears that aggressive surgical intervention including atraumatic neurolysis is needed to prevent damage to the digital nerves whenever the ring is removed in severe cases of embedded ring injury.

The term “embedded ring syndrome” is recognized and stresses the absolute association noted between the embedded ring injury and mental or cognitive impairment.[2] [3] [5] [6] Leung and Ip reported that mental illness, female sex, poor social support, poor mental function, and a timid personality were risk factors for embedded ring injury.[6] They also mentioned that most patients refused further reconstruction such as tenolysis and the function of the finger did not improve after removal of the ring, especially in advanced cases, and these might have been related to the patients' mental condition, poor compliance, and loss to follow-up.[6] In this case, the patient was a woman with a history of psychosomatic disorder, and she refused further secondary tendon reconstruction with tendon grafting, did not perform rehabilitation, and was lost to follow-up. These coincide with the features of embedded ring syndrome.[2] [6]

If individuals with psychiatric illness or loss of cognitive function have a tight ring, it should be considered as a risk factor for embedded ring injury, and the ring should be removed before becoming embedded. In severe cases of embedded ring injury, when the ring is removed, surgical exploration is needed to detect and release entrapment of the digital nerves, preventing damage to the neurovascular bundles. A favorable preoperative psychiatric assessment is also important for a good postoperative result.

• References

• 1 Awan B, Samargandi OA, Aljaaly HA, Makhdom AM. Single patent vessel over an embedded ring: a case report. Hand Surg 2013; 18 (1) 125-128
• 2 Witt PD. Uncommon features of an uncommon problem: embedded ring syndrome in a child. Plast Reconstr Surg 2007; 119 (5) 1631-1632
• 3 Zeng BW, Guo YJ, Huang CC. Embedded ring injury of the middle finger in an amphetamine abuser. J Chin Med Assoc 2006; 69 (2) 95-97
• 4 Sleilati F, Claude O, Werther JR, Ebelin M, Doursounian L. Chronic finger constriction by completely embedded rings: one ring may hide another. Plast Reconstr Surg 2004; 114 (6) 1674-1676
• 5 Deshmukh NV, Stothard JS. The embedded ring injury - case report and review of literature. Hand Surg 2003; 8 (1) 103-105
• 6 Leung YF, Ip SP. Chronic erosion injury of a digit by a ring: epidemiology, staging, treatment and prognosis. Br J Plast Surg 2002; 55 (4) 353-355
• 7 Bennett KG, Brou JA, Levine NS. Completely embedded ring in the finger of a growing child. Ann Plast Surg 1995; 34 (1) 76-77
• 8 Kuschner SH, Gellman H, Hume M. Embedded ring injuries. Clin Orthop Relat Res 1992; (276) 192-193
• 9 Drake DA, Lewis F, Newmeyer WL, Kilgore Jr ES. An unusual ring injury. J Hand Surg Am 1977; 2 (2) 111-112
• 10 Freedman BJ. Ulceration of wedding-ring into phalanx. BMJ 1947; 2 (4538) 1034