Against all odds: traumatic thumb amputation following ring avulsion injury

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Ring avulsion injury of the digit is described as an injury sustained to the digit after it is pulled within a ring or a ring-like structure. It presents with a wide range of severity, from simple laceration wound to complete degloving of the digit or digit amputation. While the severity of ring avulsion injury is directly related to the amount of force involved, only minimal force is needed to result in one.

The Urbaniak classification is the most frequently used system to categorize ring avulsion injuries, dividing it into 3 classes — Class I (circulation adequate), Class II (circulation inadequate) and Class III (complete degloving or complete amputation) [1]. Certainly, the treatment strategies differ according to the severity of the injury. The choice of completion amputation and digit replantation are the common treatment juncture following Urbaniak Class III injuries. While a viable replanted digit is the main objective of digit replantation in the early days following the first human digit replantation by Komatsu and Tamai in 1968 [2], the focus is now shifted towards the return of function following replantation, with current indications for digit replantation is tailored according to findings from functional outcome studies [3].

We report a case of successful replantation of thumb following Urbaniak Class III ring avulsion injury along with the challenges it posed and its functional outcome.

Clinical case

A 10 years old boy presents at 3 hours post-trauma with Urbaniak Class III ring avulsion injury of his right thumb (Fig. 1, a), sustained in a mishap while handling a heavy sports equipment. He is right-handed and otherwise healthy. Physical examination revealed a complete amputation of the right thumb at the level of the distal aspect of the proximal phalanx. The flexor policis longus (FPL) tendon was avulsed at the musculotendinous junction and remain attached to the amputated portion (Fig. 1, b). He was subsequently pushed to the operating theatre 5 hours later (8 hours post-trauma).

 

Fig. 1. Urbaniak Class III (complete amputation) ring avulsion injury of the right thumb: a — Ryle’s tube was cannulated through the flexor tendon sheath to guide the re-insertion of the FPL; b — amputated port of the right thumb (note the differing level of injury to skin, bone, tendon); c — skin along the amputation line is loosely closed to accommodate tissue edema without compressing the digital blood vessels. Skin allograft was applied as a temporary cover

 

After stabilization with K-wires, the FPL tendon was tunneled back through its flexor sheath with its proximal end tagged with blue Prolene 4/0 suture and banked-in at Zone 5 (proximal to the wrist) for future repair. The ulnar digital artery (UDA) was explored and repaired as it has a comparatively larger caliber (0.75mm) than the radial digital artery (RDA, 0.5mm). The anastomosis was initially successful without the need for vein graft, with clinically good distal perfusion and bleeding, however, this was short-lived as it thromboses after 10 minutes. Upon further exploration of the UDA distally and proximally, an area of lucency with hourglass deformity was found distal to the injury which indicates intimal damage.

As the intimal injury of the UDA was too distal with diminishing caliber size, the RDA was subsequently explored and anastomosed. A 10 mm gap was present at the site of injury, requiring the use of vein graft which was harvested from the volar aspect of the wrist, conveniently accessed via the same incision made to bank-in the proximal end of the avulsed FPL tendon. Two venous anastomoses were performed — one at the radial aspect of the thumb (next to the artery) and another at the dorsal aspect. Reperfusion of the amputated thumb achieved after 14 hours and 30 minutes following trauma. The thumb was allowed to warm up before the digital nerves were coapted. Skin allograft was applied over the area of the open wound as temporary coverage and to facilitate tension-free closure (Fig. 1, c).

Following surgery, the child was kept sedated and paralyzed for 48 hours. Continuous intravenous heparin infusion was commenced. The circulation of the replanted thumb was closely observed. The replanted thumb demonstrated good circulation until day 5 of surgery when it became clinically congested. Duration of continuous intravenous heparin infusion was extended further, regular pinprick to exsanguinate blood was performed, followed with a local application of heparin over the pinprick site. Wound along the amputation was managed with modern dressing and allowed to heal by secondary intention. The replanted thumb remained viable and the child was subsequently discharged.

Upon outpatient follow-up one-month post-trauma, the extensor policis longus tendon was noted to be exposed as a result of skin edge necrosis distal to the amputation line with an area of 2x1.5 cm. The child was subsequently brought to the operating theatre at which the first dorsal metacarpal artery flap (FDMA flap) was raised to cover the exposed tendon. Recovery was uneventful following the surgery (Fig. 2). At 2 months following trauma, the FPL tendon was transferred to the FDS of the ring finger with the aim to restore thumb flexion with the repair performed at Zone 5 (proximal to the transverse carpal ligament). Early active movement and rehabilitation were commenced following tendon transfer. He has good ROM at the CMCJ with good apposition however has stiffness over the IPJ with delayed union of the fracture site. He is fully satisfied with the functional and esthetic outcome of the surgeries (Fig. 3).

 

Fig. 2. The design (a) of FDMA flap to provide soft-tissue cover to the exposed extensor tendon (1 month following trauma) (b); FTSG is utilized to cover the donor site defect (c)

 

Fig. 3. Functional outcome 10 months post surgery

 

Discussion

Despite the technical challenges and the potential risks, a little argument can be made against thumb replantation in a child. The importance of the function of the thumb was well described by John Napier by his statement “The hand without a thumb is at worst nothing but an animated spatula and at best a pair of forceps whose points don’t meet properly” [4]. Replantation in young patients has a higher success rate, leveraging upon their enhanced wound healing capabilities [5]. Children can easily adapt to functional limitations, fully maximizing the remaining function following replantation.

As demonstrated by the case above, digit amputation by ring avulsion poses various challenges to successful replantation. Unlike guillotine type amputation, avulsion amputation presents with differing levels of injury to the bone, tendon, vessels, nerve, and skin. To achieve a good functional outcome, each of these structures must be repaired or reconstructed and require extensive surgical exploration and dissection beyond the initial wound.

Intimal separation often extends far beyond the blood vessel rupture point following avulsion injury[6]. Intimal separation may expose the highly thrombogenic tunica media and thus causes thrombosis following anastomosis. This was seen in our case when the initial anastomosis was unsuccessful. Despite considerable dissection of the vessel done initially, a section of intimal damage was missed as it occurs even further distal from the transected point. Therefore, to achieve good patency rate, there must be a thorough exploration and complete removal of the injured vessel, and at which the anastomosis is done away from the zone of injury. An interposition vein graft may be required to bridge the gap following removal of injured vessel, however, the vein graft by itself may contribute to thrombosis as it lacks elastic lamina that allows for expansion during systole and contraction during diastole which causes turbulent flow [6].

The usage of heparin has been revealed to decrease thrombosis rate in micro anastomosis [7]. While there is no consensus regarding the risk-benefit of continuous intravenous heparin infusion following digit replantation [8], it was commenced in our case in view of multiple risk factors that contribute to thrombosis. This, however, came at a price as the child developed multiple bleeding episodes through the wound requiring blood transfusion, which, in itself carries risks. No less than a day following discontinuation of continuous heparin infusion and normalization of the activated partial thromboplastin time (aPTT) at day 5 post replantation, the replanted thumb became clinically congested, suggesting of venous thrombosis. This underscores the role of continuous heparin infusion in a complex digit replantation in preventing thrombosis.

Late-onset venous congestion following replantation poses another dilemma for the microsurgeon. Surgical exploration and re-anastomosis may compromise the healing arterial anastomosis. Inflammation following prior surgery may not yet settle, presenting with fragile, leaky vessels which makes re-anastomosis even more challenging. While “arterial-only” replantation reportedly can lead to a successful replantation [9], means to provide temporary venous outflow must be made while effective peripheral circulation is established. In our case, pinprick at regular intervals at the nailbed, followed by local application of heparin proved adequate in exsanguinating congested blood.

Post-operatively, a young child may become restless — being in an unfamiliar environment compounded by inherent fear towards healthcare staff. Despite the best effort for stabilization and protection, restlessness may compromise a newly replanted digit. Our patient was kept sedated and paralyzed for 48 hours following surgery, necessitating intensive care. Following extubation, the child heavily guards his right hand and becomes agitated whenever inspection is made to his replanted thumb even with the gentlest approach. We overcome this by constructing a heavy POP backslab with a protective hooded space for his right hand to protect against accidental trauma to the replanted thumb.

Secondary procedures commonly ensue following successful digit replantation, either to treat secondary defects or to allow the return of a function [10]. In our case, the child has undergone two procedures following replantation. The first was to provide tissue cover to the exposed extensor tendon, in which the surrounding wound was initially left to heal secondarily. The first dorsal metatarsal artery (FDMA) flap was utilized, giving a “like to like” tissue cover to the dorsal aspect of the amputation line. We then performed tendon transfer (FDS of the ring finger to FPL). One month following tendon transfer (3 months following trauma), the child demonstrated good thumb flexion with intensive physiotherapy.

Conclusion

The journey through replantation of an amputated digit following avulsion injury poses various challenges both to the microsurgeon and patient. The success of digit replantation is assessed by the return of function and not merely a viable replanted digit, hence multiple surgeries may be required to achieve a successful outcome.

Additional information

Source of funding. This study did not receive any funding.

Conflict of interests. The authors declare no obvious or potential conflicts of interest related to the publication of this article.

Ethical statement. Informed consent for the patient has been obtained.

Author contributions

M.I. Hamzan, M.J. Jeffrey — the primary author and was involved with writing, editing and submitting this work.

A.S. Halim, A.Z. Mat Saad — involved in the design, writing and editing, reviewing and approving the final version of the manuscript.

All authors made a significant contribution in the research and preparation of the article. Additionally, all the authors read and approved the final version before publication.

Acknowledgements. We appreciate the journal for the opportunity to work with them.

About the authors

Muhammad Izzuddin Hamzan

Reconstructive Science Unit, School of Medical Sciences, Universiti Sains Malaysia; Hospital Universiti Sains Malaysia, Health Campus, Universiti Sains Malaysia

Email: drmizzud@gmail.com
ORCID iD: 0000-0002-2143-3740

MD, trainee surgeon of Plastic & Reconstructive Surgery Reconstructive Science Unit

Malaysia, Kelantan

Mohamad J. Jeffrey

Reconstructive Science Unit, School of Medical Sciences, Universiti Sains Malaysia; Hospital Universiti Sains Malaysia, Health Campus, Universiti Sains Malaysia

Email: jeremijeffrey@gmail.com
ORCID iD: 0000-0002-2401-9262

MBBS, MRCS, trainee surgeon of Plastic & Reconstructive Surgery Reconstructive Science Unit

Malaysia, Kelantan

Ahmad S. Halim

Reconstructive Science Unit, School of Medical Sciences, Universiti Sains Malaysia; Hospital Universiti Sains Malaysia, Health Campus, Universiti Sains Malaysia

Author for correspondence.
Email: ashalim@usm.my
ORCID iD: 0000-0001-8999-6403

BSc, MD, Med Spec, FCCP, Professor, Senior Consultant of Plastic & Reconstructive Surgery Reconstructive Science Unit

Malaysia, Kelantan

Arman Z. Mat Saad

Management and Science University Medical Centre

Email: armanzaharil@gmail.com
ORCID iD: 0000-0002-4003-6783

MBBCh, BAO, AFRCS, MS, Professor, Senior Consultant of Plastic & Reconstructive Surgery Reconstructive Science Unit, School of Medical Sciences, Hospital Universiti Sains Malaysia, Health Campus, Universiti Sains Malaysia, Kelantan, and Head of Department of Plastic and Reconstructive Surgery Unit, Management and Science University Medical Centre

Malaysia, Shah Alam

References

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