Treatment of chronic mallet finger with swan neck deformity using a modified Spiral Oblique Retinacular Ligament (SORL) reconstruction procedure: A case series and technical note

Abstract

Introduction and importance

Chronic terminal extensor tendon injury produces mallet deformity and secondary swan neck deformity. It can be found in neglect cases and in a failed cases after conservative treatment or primary surgical repair. Surgery is considered in cases with extensor lag of more than 30° and functional deficit. Reconstruction of the spiral oblique retinacular ligament (SORL) has been reported in literatures to correct swan neck deformity by a dynamic mechanical basis.

Case presentation

Three cases of chronic mallet finger associated with swan neck deformity were treated by the modified technique of SORL reconstruction. Range of motion (ROM) of distal interphalangeal (DIP) joints and proximal interphalangeal (PIP) joints were measured along with the complications. The clinical outcome was reported using the Crawford's criteria.

Clinical discussion

All patients had an average age of 34 years (20–54). Average time to surgery was 16.67 months (2–24) and average of DIP extension lag was 66.67°. All patient gave excellent Crawford criteria at the latest follow up (average 15.3 months). The average PIP joint ROM were −1.6⁰ (0⁰ to −5⁰) of extension and 110⁰ (100⁰−120⁰) of flexion for the PIP joint and −1.6⁰ (0⁰ to −5⁰) of extension and 83.33⁰ (80⁰–85⁰) of flexion for the DIP joint.

Conclusion

We present our technique to manage chronic mallet injury which only utilized two skin incisions and one button at the distal phalanx to minimize risk of skin necrosis and patient discomfort. This procedure can be considered as one of the options for the treatment of chronic mallet finger deformity associated with swan neck deformity.

Highlights

• •Chronic terminal extensor tendon injury often leads to secondary swan neck deformity
• •Swan neck deformity can be treated surgically by spiral oblique retinacular ligament (SORL) reconstruction
• •We modified the standard SORL reconstruction technique with a more minimal invasive manner.

1. Introduction

The term chronic is designated for a more than 4-weeks-old mallet injury. Splinting is the most common initial treatment method for soft tissue or bony mallet finger that is present within 8 weeks after injury without a fixed deformity. Another initial treatment that has been proposed was the temporary fixation with k-wire. Regardless of the treatment option, slight extensor lag and dorsal prominent bump were common as a sequelae. Failure of initial treatment, extensor lag of 40° or more, secondary deformity, and functional deficit were indications of surgery [1]^, [2].

Many techniques for the treatment of chronic mallet finger have been described: Fowler's central slip tenotomy, spiral oblique retinacular ligament (SORL) reconstruction, wire insertion, arthrodesis, chondrodesis, among others [3]. The presence of extension lag of more than 45°, secondary swan neck deformity, or chronic cases with no sufficient tendon substance around its foot print, were the indication for SORL reconstruction [4]. Differ from the swan neck because of primary proximal interphalangeal (PIP) joint laxity (proven by the distal Bouvier-type maneuver), the surgery aims in secondary swan neck is not only to prevent PIP hyperextension but also to increase the extension force at distal interphalangeal (DIP) joint [2]. Thompson were firstly introduced SORL reconstruction technique on 1978 [5]. This technique requires two buttons or metal clips for proximal and distal attachment of the tendon graft on the distal phalanx and laterally on the proximal phalanx [5]. Thereafter, several modifications were reported for this reconstruction method. However, pullout suture technique risk for subsequent skin necrosis due to the prolonged pressure to the underlying skin. In the attempt to avoid that risk, we developed a technique of SORL reconstruction with only utilized two skin incisions and one button at the distal phalanx. The work has been reported in line with the SCARE guideline [6]^, [7].

2. Presentation of case

There were two male and one female patients with chronic mallet injury (mean DIP extension lag of 66.6^o) with secondary swan neck deformity that treated with SORL reconstruction procedure in our center. Two patients were neglected cases who never sought medical treatment for the injury. One patient had recurrent mallet deformity after tendon plication and wiring. Average time to surgery was 16.67 months (2–24 months). The average age was 34 years (20–54 year). All patients were right-handed. Pre-operative radiological examination confirmed no significant joint subluxation, joint arthrosis, or synostosis of interphalangeal joints. Patients were followed up with an average of 15.3 months (9–24 months). Informed consent has been taken from all patient and this study has been approved by the ethics committee in our institution.

2.1. Approach

The procedure was done under the axillary block by experienced surgeon. Skin incision was made with dorsal lazy S incision over the DIP joint. A skin flap was carefully raised including the dorsal vein to prevent skin necrosis. The underlying tendo-ligamentous structure was exposed and inspected for the quality of any tendinous remnant. The second incision was made with mid axial approach over the proximal phalanx. The position of the incision can be determined by the direction of pull that we want to create in the presence of additional angulation deformity of the distal phalanx (Fig. 1). To overcome the radial angulation of the distal phalanx, the graft is pulled ulnarly, then passed to the proximal skin incision at the radial side of the proximal phalanx, and vice versa. If the mallet deformity was not complicated by radial or ulnar angulation of the distal phalanx, no particular protocol to place the proximal skin incision. The proximal skin incision was made at the proximal end of the volar soft tissue tunnel, at the opposite side of the proximal limb of the lazy s incision over the distal phalanx. We avoided making incisions at the pinching surface of the index finger and the touching surface of the little finger to avoid pain or discomfort over the scarred area.

Fig. 1.

A. Swan neck deformity of the middle finger secondary to neglected bony mallet injury. B. Skin incision design over the DIP joint to expose terminal extensor tendon. The proximal limb of the lazy s incision was made at the ulnar side to accommodate the direction of pull of the graft ulnarly to overcome the radial angulation of the distal phalanx. C. Mid-axial incision at the ulnar side of the proximal phalanx. Red line: incision line. Yellow dots, axis of the phalanges. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

2.2. Graft preparation

A palmaris longus tendon graft was harvested and prepared for reconstruction by removing all non-tendinous substance. The graft can be divided to adjust the tunnel diameter and the finger in general to prevent bulkiness. One edge was trimmed and sutured by Krackow technique to smoothened the edge for passing it through the distal bone tunnel on the terminal extensor footprint. We used heavy suture by braided non-absorbable suture material. The length of both threads was made equal and an additional needle was put so that both ends had needles attached.

2.3. Distal bone tunnel

The footprint was drilled with a 2.0 k-wire perpendicularly to the bone surface to create a bone tunnel. The tendon graft was secured to the base of the distal phalanx through the bone tunnel by passing both needles to the tunnel and penetrate the pulp, the volar skin, and lastly through the button's hole over the finger pulp. After that, threads were tied to each other. A soft padding between skin and button has to be placed adequately to prevent necrosis while ensuring a secure fixation of distal end of the graft to the button.

2.4. Proximal bone tunnel

Through the proximal limb of the S incision at the dorsal DIP joint, the graft was passed volarly and proximally through a soft tissue tunnel towards the second skin incision on the mid-axial proximal phalanx on the contralateral side. A bone tunnel was made on the base of the proximal phalanx. Before entering the proximal bone tunnel, the graft was divided. One-half of the graft entered the bone tunnel and then went under the extensor mechanism back to the mid-axial opening. Both halves were sutured together with pulvertaft technique or side-to-side technique after proper tensioning of the graft (Fig. 2).

Fig. 2.

A. The prepared graft is inserted into bone tunnel at the terminal extensor tendon footprint at the base of the distal phalanx and fixed to a sterile button. The proximal limb is passed volarly and proximally to the contralateral side. B. at the proximal skin opening, the graft was divided. One part of the proximal limb is passed through the proximal bone tunnel at the proximal phalanx and then passed back through the soft tissue tunnel to be sutured back to another part.

2.5. Tensioning the graft

Adjustment was made until DIP neutral extension to overcome future extension lag due to graft lengthening. The PIP joint was made in neutral position (10–20 degree of flexion) (Fig. 3). After tensioning, we confirmed the correct tension by passively flexed the PIP joint which should be accompanied by passive flexion of the DIP joint. Post operatively, we applied a bulky dressing without any rigid immobilization to allow the patient for early active ROM as tolerated. The pull-out suture was removed at 6 weeks.

Fig. 3.

Proper tensioning is made in DIP neutral extension and the PIP joint was made in neutral flexion position (10–20°) A. Schematic position of the final construct. B. The post-operative finger position.

All of the patient had an uneventful post operative period. No post operative paresthesia or infection was noted during the immediate post operative follow-up. The average PIP joint ROMs at the latest follow-up were −1.6 degrees (range; 0 to −5) of extension and 110 degrees (range; 100 to 120) of flexion for the PIP joint and −1.6 degrees (range; 0 to −5) of extension and 83.33 degrees (range; 80 to 85) of flexion for the DIP joint. Swan-neck deformities were completely corrected in all cases. Patients were followed up for an average of 15.3 months (9–24 months). No boutonniere deformity, nail deformity, skin dimple, and further extension lag were present on the latest follow-up. Outcome assessment by the Crawford criteria revealed that all patients were categorized as excellent. Patient's characteristics and outcomes were summarized on Table 1.

Table 1.

Summary of patient characteristic and outcome.

No	Sex	Hand-dominance	Age	Side	Injury	Finger	Onset (month)	Conservative	Primary surgery	Pre-operative			Post-operative (last FU)			FU (month)
										Swan neck deformity	DIP extension lag	PIP hyper-extension	DIP ROM post	PIP ROM post	Complication
1	M	Right	20	Left	Open	Middle	2	No	No	Yes	75	20	-5/85	0/110	No	6
2	M	Right	28	Left	Closed	Little	24	No	Plication pinning	Yes	80	20	0/80	0/100	No	42
3	F	Right	54	Right	Closed	Little	24	No	No	Yes	45	15	0/85	-5/120	No	29

3. Discussion

Various methods have been proposed for the surgical treatment of chronic mallet deformity include tendon plication, tendon repair with tendon graft, threading of a strip of the lateral band into the distal phalanx, tenodermodesis [2]^, [8]^, [9]. These surgeries aim to reconstruct the disrupted extensor mechanism and correcting the mallet deformity [8]. However, they often result in restricted DIP flexion and even boutonniere deformity due to the overtightened DIP. Moreover, valuable PIP joint flexion may also be restricted by increased tension on the extensor mechanism or adherence of the extensor mechanism over the middle phalanx [10].

The other reconstructive procedures are Fowler central slip tenotomy, and the spiral oblique retinacular ligament (SOLR) reconstruction. The central slip release allows the entire extensor mechanism to glide proximally and balancing the forces. Thus, it will improve the DIP extension while decreasing PIP hyperextension. The limitation of this procedure is that it usually not effective for a severe extension lag (more than 36°) [3].

The SORL reconstruction procedure as firstly described by Thompson in 1978 simultaneously corrects the DIP extension lag and PIP hyperextension without any alteration or scarring of the extensor mechanism or restriction of DIP and PIP joint flexion [5]. The dynamic concept by inserting the graft in a spiral fashion and fix it to the bone tunnel coordinating the motion of the PIP and DIP joint and provides a tenodesis effect as PIP extension tightened the SORL and produce DIP joint extension [5].

Some literatures have reported the outcomes of Thompson procedure for chronic mallet deformities [4]. In the original publication of this technique, Thompson reported the DIP deformity correction in 5 patients to an average of 5° (range 0–15°) of extension post-operatively [5]. In other study by Kanaya et al. in 7 patients, they were able to correct the DIP joint to a final average of 5° (range, 10°–0°) of extension and an average of 63° (range, 45°–80°) of flexion. This result suggested that the Thompson procedure not only afford improvement of extensor lag of the DIP joint but also maintain the DIP joint flexion [4].

Our technique modified the classic Thompson by utilizing only two skin incisions. We found that the preferred the inner fixation of the proximal tendon attachment instead of fixing the graft with a pull-out suture will reduce the risk of skin dimpling or infection because lesser incision and number of pull-out sutures. The blood supply to the skin has to be preserved especially on the dorsal incision where the soft tissue is very thin. The skin flap must be raised along with the underlying dorsal vein to prevent dorsal skin necrosis. Volarly, a padding has to placed adequately to prevent necrosis while ensuring a secure fixation of distal end of the graft to the button.

The Crawford criteria is one of the most commonly used classification system for chronic mallet surgery based on extension/flexion loss of the DIP joint and pain with high clinical relevance [11]. Although we have not able to compare the strength to classic Thompson in this small series, the excellent outcome in this report showed that a good strength of fixation has been achieved because both ends of the graft were fixed to bone tunnels. The proximal end was looped and sutured to itself after passing the proximal bone tunnel made an interlocking system that will not easily break.

Finally, tension adjustment is a critical point of the procedure. Since the concept of the SORL reconstruction is to produce DIP extension through a tenodesis effect, over tensioning of the graft will cause a premature extension of DIP before PIP joint extension. Thus, it will further create a boutonniere deformity. Thompson used the neutral extension of PIP and DIP joint as an end-point tensioning [5]. While Immamura et al. suggested a maneuver that showed a slight extensor lag of DIP when the PIP is passively extended fully and a fully flexed PIP which accompanied by a fully flexed DIP [2]^, [10]. We used a neutral resting PIP slight flexion (10–20°) and just a neutral extension of DIP. Hyperextension of DIP is not suggested as it can interfere with grip strength. Moreover, an extension lag of 10° is generally acceptable [3]. We did not use Kirschner wire fixation to maintain the tension as in our experience the wire usually gave false stability.

The limitation of this study is we did not compare with the standard SORL technique and small sample size. A potential drawback of this technique is mid-axial bulky mass as the result of tendon ends that are sutured together which may produce discomfort during finger adduction or hand grip. However, in our study, none reported difficulties or discomfort with gripping or doing other hand functions. Further studies with larger sample are needed to prove this possible disadvantage and to compare this technique to the previously established SORL reconstruction technique.

4. Conclusion

This is the preliminary report of three cases with excellent result by correcting the mallet and swan neck deformities while preserving both PIP and DIP joint flexion which are functionally needed to perform a grip. We believe that this technique will potentially give less skin and wound problems over the standard technique.

Patients' consent

Written informed consent was obtained from the three patients for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal on request.

Disclaimer

No patient or author details are included in the figures.

Funding

N/A.

Ethical approval

None. Because this paper is retrospectively reporting cases and not considered as human research. Thus, ethical approval is exempt/waived at our institution.

Consent for publication

The patient provided informed consent for the case details and accompanying images to be published.

CRediT authorship contribution statement

Heri Suroto: Conceptualization, methodology, validation, resources, supervision.

Dina Aprilya: Formal analysis, investigation, writing and editing.

Tabita Prajasari: Software, data curation, review and editing.

Andre Bayu Nugraha: Project administration, data curation, visualization.

Declaration of competing interest

N/A.