Modified retrograde tendon flap technique for reconstructing the extensor tendon defect in zone Ⅱ of a finger

doi:10.21203/rs.3.rs-19899/v1

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Modified retrograde tendon flap technique for reconstructing the extensor tendon defect in zone Ⅱ of a finger

https://doi.org/10.21203/rs.3.rs-19899/v1

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Purpose: To evaluate the effect of the modified retrograde tendon flap technique for reconstructing the extensor tendon defect in zone Ⅱ of a finger.

Methods: 12 patients with the extensor tendon defect in zone Ⅱ were investigated retrospectively. They were all treated surgically by the modified retrograde tendon flap technique, featuring the creation of a new terminal slip to bridge the extensor tendon defect using extensor tendon inner lateral bands. At the final follow-up, the range of motion at each joint of the injured finger was recorded.

Results: Average follow-up was 18 months (ranging from 11 to 26 mos). Eight patients achieved full active DIPJ extension, whereas one patient had an extensor lag of 10° and three had a lag of 5°. All patients achieved normal active flexion ranges and full passive motion ranges of DIPJ compared with their uninjured side. All the involved finger joints were clinically stable, with no tenderness, pain, nail deformity, or limitation using their hands for daily life.

Conclusions: The modified retrograde tendon flap technique, which is easy to operate and popularize, may be the procedure of choice in patients with a gap deficiency in Zone Ⅱ of the extensor tendon of a finger.

Orthopedic Surgery

Extensor tendon injury

Tendon segmental defect

Zones Ⅱ

Tendon reconstruction

Tendon flap

Tendon lengthening

Extensor tendon injury is a common problem in hand surgery, because the extensor tendons of the hand are located in a superficial position on the dorsal aspect of the hand and are highly vulnerable to injury.^[1]^[2][3][4]^[5]Most often, these injuries can be primarily repaired. On occasion, however, the injury may involve tendon loss or gap in the extensor tendon, precluding primary approximation of the cut ends. Such injuries that lead to the actual substance loss in the extensor tendons require specialised attention and can be some of the most challenging to repair, as extensor tendons have less excursion than flexor tendons.^[⁶^] In such injuries with loss of tendon substance, operation using a free tendon graft or tendon transfer techniques may be employed for reconstruction of complex extensor tendon lacerations or gaps.^[⁷^][⁸^][⁹^][¹⁰^][¹¹^][¹²^][¹³^][¹⁴^][¹⁵^][¹⁶^][¹⁷^]

From September 2014 to December 2018, we used the modified retrograde tendon flap technique to treat 12 patients with extensor tendon gap in zone Ⅱ. And all patients had a good result with an average motion arc of 56 degrees. Traditional free tendon graft technique requires a multistage procedure: primary debridement ＆ suture, and secondary transplantation. However, the modified retrograde tendon flap technique, using the inner hemilateral bands of the same injured finger to bridge the extensor tendon gap and create a new terminal slip, has the advantage of being a single stage procedure. And in addition, it avoids the need to use a free tendon graft, thus avoiding the injury of tendon donor site. Even if the result was unsatisfactory, the patient could still be treated by the second-stage tendon transplantation.

From Sep, 2014 to Dec, 2018, 12 fingers of 12 patients (10 men and 2 women) with open injuries of extensor tendon at the level of zone Ⅱ^[18] were operated on using a modified retrograde tendon flap. At the time of the operation, patients were aged 24 to 55 years (mean, 40 years). All the 12 patients had sustained type Ⅲ injuries as per Doyle classification (Table 1)^[¹⁹^] and the average length of extensor tendon defects was 6 mm (4 to 8 mm). The left hand was involved in 8 cases and the right in 4. The mechanisms of injury included friction (n=5), crush (n=3), slash (n=2) and avulsion (n=2). All patients were treated with emergency surgery by the same surgeon under interphalangeal nerve block anesthesia within a mean time of 5.5 hours (3.5 to 7.0 h) after injury. Mean operative time was 55 minutes (45 to 60 min) and the mean finger root tourniquet time during surgery was 35 minutes (25 to 40 min). Table 2 lists clinical demographics of the patients.

The ethical committee of our hospital approved the study protocol. Written informed consents were obtained from all patients. All investigations were conducted according to the principles expressed in the Declaration of Helsinki.

Surgical Technique

The operation was carried out under interphalangeal nerve block anesthesia with the aid of finger root tourniquet control. The patient was placed in the supine position with the upper extremity abducted.

The surgical procedure was divided into the following four steps. ①Debridement: The wound (Fig. 1) was appropriately debrided, taking care not to excise too much of the extensor apparatus. After the debridement, the length of extensor tendon zone Ⅱ defect was assessed. Z-shaped prolonged incision was made to expose the surgical area fully. (Fig. 2) ②Fixation: An appropriately sized K-wire (φ1.0~1.5mm) was used to fix the distal interphalangeal joint (DIPJ) in a slightly hyperextended position (5°~10°). (Fig. 3) While achieving the requirement of extensor tendon anastomosis, the hyperextended position could also overcome a certain degree of skin defect. ③Cut and turnover: According to the defect length of extensor tendon, the inner halves of the two lateral bands of the proximal tendon stump were cut in U-shape to make a flap, leaving the most distal portion intact. The width of the U-shape incision was about half of the width of the tendon, and the length was about 2-3 mm longer than the tendon gap. (Fig. 4) The tendinous flap was then flipped over to bridge the tendon gap. (Fig. 5) ④Suture: The two lateral bands donor sites were stitched longitudinally to each other with 4-0 nonabsorbable sutures. A ’rip-stop’ suture was used at the point where the tendinous flap was flipped to prevent detachment of the tendinous flap from the tendon donor. Once these had been done, the tendinous flap was sutured to the remaining stump of the distal tendon with 4-0 nonabsorbable sutures intermittently and without tension. (Fig. 6) Then, the skin defect could be sutured directly, benefiting from the fixation of DIPJ.

Postoperative Management

Postoperatively, a palmar forearm plaster splint with wrist neutral and finger extension was used to protect the fix effect and antibiotics to prevent infection. 4 weeks after the surgery, K-wire was removed. The splint was used for an additional 2 weeks, and the immediate to early motion was made actively and passively with the aid of a physiotherapist for each individual patient.

All the patients were followed in clinic till they were discharged from our care. This averaged 18 months (11 to 26 mos). At the final follow-up, flexion and extension of the involved finger joints were recorded using a goniometer. The clinical results were evaluated according to Crawford criteria (Table 3)^[20]. In addition the patients were examined for tenderness, pain, nail deformity, and limitation in daily life.

There were no instances of pin tract or wound infection nor did any patient have skin or scar problems attributable to the surgical technique. At the final follow-up, eight patients achieved full active DIPJ extension, whereas one patient had an extensor lag of 10° and three had a lag of 5°. (Table 2) All patients achieved normal active flexion ranges and full passive motion ranges of DIPJ compared with their uninjured side. The active and passive motions of proximal interphalangeal joint (PIPJ) and metacarpophalangeal joint (MPJ) in all the involved fingers were normal. According to the Crawford criteria (Table 3)^[20], all patients were graded at least ‘good’. All the involved finger joints were clinically stable, with no tenderness, pain, nail deformity, or limitation using their hands for daily life.

Injuries to extensor tendon are a common problem seen by hand surgeons. With a reported incidence rate of 14 cases per 100,000 person-years^[21], more than half of acute tendon traumas consist of extensor tendon injuries. The problem of addressing an injury of the terminal slip becomes even more challenging when there is substance loss with a resultant gap between the cut ends, because even a 1 mm tendon gap in those zones may cause 20° extension loss, or shortening of the extensor tendon by as little as 1 mm may cause decreased finger flexion.^[22][23]There are three chief techniques for reconstruction of the extensor tendons: (a) free tendon graft reconstruction^[⁷^]^[12][13][16], (b) tendon transfer surgery^[11], or (c) free composite tissue flaps^{[8][9][10][14][15][17]}. However, each technique is associated with unique challenges, e.g. donor site morbidity, prolonged treatment^[10] and grafting may produce more adhesions than direct repair.^[24]These procedures require a second incision for harvesting a donor graft and use tendons that may not be morphologically similar to the reconstructed extensor tendon.^[²³^]Due to the possibility of the absence^[25] or variation^[26][27] of the donor tendon, the techniques might not even be realized.

In an effort to solve these problems, many techniques of using local tendon flap have been reported in theory^[²³^] and practice^{[24][28][29][30][31][32]}. As tendon lacerations under 50-60% of the crosssectional area do not require repair unless complete or partial entrapment of the tendon is observed, so decreasing the tendon cross-sectional diameter by 50% is biomechanically safe and in keeping with current literature.^[5][33][34]Our investigation is conducted to apply theories to practice, and has the advantage of providing an easy solution to bridge gaps in the terminal slip. The principle of our technique involves the use of extensor tendon inner lateral bands to creat a local retrograde tendon flap, so as to repair the gap resulting after extensor tendon injury with substance loss. It is important to correctly measure the gap so that an appropriate length of retrograde tendon flap can be designed.^[³¹^]

The reason why inner hemilateral band is used instead of outer ones^[³¹^] is to make the tendon flap as a whole, which is more similar to the anatomical structure of defective tendons, two lateral bands on the outside and a complete aponeurosis in the middle. (Fig. 7) Leaving behind a sufficient amount of the lateral band is also important to prevent loss of intrinsic activity. Otherwise, a Boutonniere deformity may be caused.^[⁴^] Care must be taken to ensure that a ’rip-stop’ suture is used at the point where the tendinous flap is flipped to strengthen the intensity between the flap and the tendon. Failing to do so may result in a distal extension of the incision in the lateral band leading to a complete detachment of the hemilateral band from the extensor hood.^[31] In these cases, figure-of-eight sutures were used for reconstruction. No specific study has shown an advantage of one type of repair over another. However, as different suturing techniques may result in different tensile loads, we can try other suture methods in the future to try to improve the therapeutic effect.^[³⁵^] In addition, the immediate to early motion should be paid more attention.^[36] So that adhesion formation may be minimised and better outcomes may be obtained.^[³⁵^][³⁷^] As choosing the best rehabilitation program for each individual patient based on the characteristics of his injury is crucial^[3], the surgeon-therapist in-depth communication is essential to clarify details of the injury and repair, and safe motion parameters.^[36]

In terms of treatment time, the modified retrograde tendon flap technique has the distinct advantage of being a single stage procedure in the emergency surgery to avoid the secondary operation. In terms of surgical region, it has the obvious advantage of using locally available tissue to avoid the need for harvesting a graft from another location.^[²³^] In these cases, not only the function of DIPJ was good, but also the functions of PIPJ and MPJ were not affected. This shows that the modified retrograde tendon flap technique may not cause donor functional deficits, and this may due to harvesting half of each lateral band. Besides, the technique is easy to operate and popularize, yet does not compromise salvage by tendon graft and/or two-stage reconstruction in cases of failure.^[24]

However, this technique can not repair too large defects and the defect is currently controlled within 8mm. Another limitation to the current investigation is the relatively small patient population. Thus, no statistical analysis is possible. It is difficult to get a more definite conclusion from limited clinical data, although all of the twelve patients in this study did have good final results without complications. The outcomes may vary in other, larger cohorts. In the follow-up work, we will continue to increase the number of cases in order to reach a more definite result.

The modified retrograde tendon flap technique with good therapeutic effect, which is easy to operate and popularize, may be an effective method for reconstructing a gap deficiency in the terminal slip of the extensor tendon of a finger. Further clinical and biomechanical studies are needed to evaluate the clinical effectiveness of this technique.^[³⁵^]

DIPJ: distal interphalangeal joint; PIPJ: proximal interphalangeal joint; MPJ: metacarpophalangeal joint

Ethics approval and consent to participate

All procedures were part of the standard medical care. As this study has a retrospective design, the need for informed consent was waived by the Institutional Review Board.

Consent for publication

Not applicable.

Availability of data and material

All data generated or analyzed during this study are included in this published article.

Competing interests

The authors declare that they have no competing interests.

Funding

No funding was obtained for this study.

Authors’ contributions

LW and JYZ drafted the article and drew illustrations. LW and GYY performed the operation. LW and LJF undertook patient rehabilitation. All authors read and approved the final manuscript.

Acknowledgements

Not applicable.

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Table 1 Doyle Classification of Mallet Finger Type Injuries
Type I:	Closed, with or without avulsion fracture.
Type Ⅱ:	Laceration at or proximal to the distal interphalangeal joint with loss of tendon continuity.
Type Ⅲ:	Deep abrasion with loss of skin, subcutaneous cover, and tendon substance.
Type Ⅳ:	(A) Transepiphyseal plate fracture in children.
	(B) Hyperflexion injury with fracture of the articular surface of 20% to 50%
	(C) Hyperextension injury with fracture of the articular surface usually greater than 50% and with early or late palmar subluxation of the distal phalanx

Table 2 Clinical Demographics of 12 Patients

Patient	Gender	Age at Surgery	Injured Finger	Mechanism of Injury	Tendon gap (mm)	Follow-up (month)	Range of Motion (degrees) (DIPJ of Injured Finger)
Patient	Gender	Age at Surgery	Injured Finger	Mechanism of Injury	Tendon gap (mm)	Follow-up (month)	Flexion	Extension
1	M	29	Index/L	Slash	7	11	0	65
2	M	53	Ring/L	Avulsion	6	22	-5	45
3	F	41	Index/R	Friction	4	18	0	70
4	M	49	Ring/R	Friction	5	18	0	60
5	M	44	Middle/L	Avulsion	5	18	0	70
6	M	38	Middle/R	Crush	6	15	-5	55
7	M	47	Ring/L	Crush	7	20	-10	50
8	F	32	Little/L	Friction	5	16	0	65
9	M	55	Ring/L	Crush	4	26	0	55
10	M	24	Middle/R	Slash	8	16	0	50
11	M	36	Index/L	Friction	6	18	0	60
12	M	35	Ring/L	Friction	8	14	-5	55

Table 3 Crawford Evaluation Criteria
Grade	Description
Excellent	Full distal interphalangeal joint extension, full flexion, no pain
Good	0-10 degrees of extension deficit, full flexion, no pain
Fair	10-25 degrees of extension deficit, any flexion loss, no pain
Poor	More than 25 degrees of extension deficit or persistent pain

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Modified retrograde tendon flap technique for reconstructing the extensor tendon defect in zone Ⅱ of a finger

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