Keywords
tendon injuries - early active mobilization - flexor digitorum superficialis - tendon
transfer - wide-awake approach
Introduction
Closed ruptures of the flexor digitorum profundus (FDP) tendons are rare and often
require surgical treatment. Free tendon grafting is the standard clinical practice;
however, it is not suitable when the muscle amplitude of the ruptured FDP is insufficient.[1] The flexor digitorum superficialis (FDS) of the other finger is used as an available
motor for the ruptured FDP tendon in this situation. FDS tendon transfer is not a
new operative procedure. Mayer introduced this technique, which he called “the pedunculated
graft.”[2]Although this tendon transfer procedure has been reported to be useful, some surgeons
do not prefer this method, because it may be difficult to determine the appropriate
tension of the transferred tendon.[3]
-
[5] Recently, the wide-awake approach for hand surgery has become widespread. The simplicity,
safety, and convenience of this technique provides benefits for surgeons and patients.[6] Of all the operations performed with the wide-awake approach, flexor tendon surgery
has been the most improved. The wide-awake approach is useful for flexor tendon surgery,
because it allows surgeons to adjust the tension of the transferred tendon during
active movement, in order to confirm that the transfer is not overly tight or loose
before skin closure.[7]
The purpose of the study was to evaluate the outcomes of the FDS transfer that used
the wide-awake approach, followed by early active mobilization, for closed rupture
of the FDP tendon.
Materials and Methods
This study was a retrospective review of a case series. The potential participants
were identified by searching our institutional billing records from January 2012 to
October 2019 for International Classification of Disease 10 code M66.3 that describes
the diagnosis as “spontaneous rupture of flexor tendons.” The following inclusion
criteria were applied: (1) a closed rupture of the FDP tendon of the little finger,
with or without a concomitant FDS tendon rupture in zone 3 or 4; (2) use of the FDS
tendon of the ring finger for tendon transfer; (3) operation under local anesthesia
or wrist block; and (4) rehabilitation with early active mobilization. Patients with
multiple tendon ruptures were excluded. The clinical characteristics and injury details
of the study participants were retrieved from the medical and operative records, which
included simple sketches of the surgical procedures. All participants provided written
informed consent before their participation in the study. This study was approved
by the Ethics Committee of the Niigata Hand Surgery Foundation (hospital approval
number: R2–1). The study was conducted according to the principles of the World Medical
Association Declaration of Helsinki.
Surgical Procedure Selection
When the proper maximum amplitude of the proximal ruptured FDP tendon stumps was 15
mm or more, we figured that the ruptured tendon could serve as a motor for the graft,
and a free tendon graft using the palmaris longus tendon was performed.[1]When the proper maximum amplitude of the ruptured FDP tendons stumps was less than
15 mm, either a tendon transfer with the FDS tendon of the ring finger or an end-to-side
tendon transfer with the FDP of the ring finger was performed based on the surgeon’s
preference.
Surgical Technique
All operations were performed under the wide-awake approach. Each patient received
an injection of 10 to 25 mL in total of 1% lidocaine with 1:100,000 epinephrine delivered
to the skin-incision region (
[Fig. 1]
). Wrist blocks were also used in some patients, based on the surgeon’s preference.
We usually used a pneumatic tourniquet to control bleeding for the first 20 to 30
minutes of surgery until an adequate epinephrine effect was obtained. A zig-zag skin
incision was made around the ruptured site in the palm, which was identified by the
three-dimensional (3D) images of the tendon (
[Fig. 2]
). This image was created using volume rendering of the CT scans, which were created
preoperatively by the radiologists.[8] The distal and proximal stumps of the ruptured FDP tendon were exposed. The proximal
stump was grasped gently and pulled distally. We confirmed that the proper maximum
amplitude of the proximal stump of the ruptured tendon was less than 15 mm. Then,
the ring finger FDS tendon was severed distally as much as possible and was passed
behind the intervening common palmer digital artery and nerve. The proximal stump
of the FDS tendon was sutured into the distal stump of the FDP tendon, using a single
fine nonabsorbable suture. The tension of the transferred tendon was considerably
tight when the flexion angle of the proximal interphalangeal (PIP) joint was approximately
80° and the wrist was in the neutral position (
[Fig. 3]
). The surgeons confirmed that the patients could actively flex and fully extend their
digits. After the appropriate tension was obtained, the proximal stump of the FDS
tendon was weaved through the distal stump of the FDP tendon, and then perpendicular
to the previous pass, for a total of two or three passes. The tendons were secured
with figure-of-eight sutures at each pass and at both ends. If the tension of the
transferred tendon was not appropriate, then it could be adjusted until the proper
tension was achieved. Finally, the incision was closed.
Fig. 1 The image shows the locations of the injections (blue dots) for flexor digitorum
superficialis (FDS) tendon transfer. The surgeon injects 10 to 25 mL of local anesthetic
under the incision (red line). The nerves are indicated with a yellow line.
Fig. 2 A three-dimensional image of the tendon using volume rendering of the CT scans that
is created preoperatively. The distal stump of the ruptured flexor digitorum profundus
(FDP) tendon of the little finger is indicated with a yellow arrow. .
Fig. 3 Clinical images of a 78-year-old woman who sustained a zone 4 closed rupture of the
flexor digitorum profundus (FDP) tendon to the little finger of her left hand. (A, B) Active and passive flexion before surgery. (C) The proximal stump of the FDP of the little finger (asterisk) and severed flexor
digitorum superficialis (FDS) of the ring finger after being passed behind the intervening
neurovascular bundle (arrow). (D) The transferred tendon illustrating that tension was considerably tight with an
approximately 80 ° flexion angle of the proximal interphalangeal joint (PIP) joint.
(E, F) Active extension and flexion immediately after tendon transfer. (G, H) Postoperative flexion and extension 27 weeks after surgery.
Postoperative Treatment
A dorsal protective splint was used to immobilize the hand, with the wrist in a neutral
position, the metacarpophalangeal (MP) joints at 30 to 60° of flexion, and the interphalangeal
(IP) joints fully extended. All patients were hospitalized for at least 4 weeks after
surgery for postoperative treatment and received instruction and supervision from
the hand therapists every day. This hospitalization, which included rehabilitation,
was covered by either industry injury insurance or personal health insurance. On the
first postoperative day, mobilization began after the surgeon had removed the bulky
dressing and applied a new thin dressing. The patient was instructed to hold the fingers
in a gentle and active manner for a few seconds while flexing the IP joints passively
into the palm as much as possible. Subsequently, the MP and IP joints were permitted
active full extension. This active mobilization was performed three to four times
per day. After the second postoperative day, unassisted active flexion exercises were
allowed. In addition, controlled passive extension according to Duran’s method was
performed to prevent IP joint contracture.[9] The dorsal protective splint was applied when the patient was not performing exercise.
At night, the little finger was flexed, and the other digits were extended, to remove
tension from the suture site of the tendon. The dorsal block splint was completely
removed at 6 weeks after surgery.
Outcome Measurements
At the final evaluation, the surgeon or therapist used a goniometer to measure the
active motion of the three joints of the finger, that is, metacarpophalangeal (MCP),
PIP, and distal interphalangeal (DIP) joints. The clinical results were evaluated
with the total active motion (TAM) of the little finger, the %TAM, the grip strength
of both arms, and a functional evaluation according to Strickland and Glogovac’s criteria.[10] The Quick Disability of the Arm, Shoulder, Hand-Japanese version (Quick DASH-JSSH)
scores were recorded for patient-rated outcomes.[11] Intraoperative findings and complications, which included grafted tendon rupture,
phlegmon, or wound dehiscence after tendon grafting, were noted at the monthly visit.
Results
Number of Patients and Injured Fingers
Thirty-four patients were diagnosed with a closed rupture of the FDP tendon of the
little finger in zone 3 or 4 between January 2012 and October 2019. A total of six
fingers from six patients met the criteria and were reviewed in this study. [Table 1] shows the injury-related data. The operations were performed by three surgeons who
had the following levels of expertise[12]: level 4 (highly experienced specialist), n = 2 (operated on five patients); and level 2 (less experienced specialist), n = 1 (operated on one patient).
Table 1
Data for the six patients who underwent FDS tendon transfer using the wide-awake approach
|
Case
|
Age (years)
|
Sex
|
Zone of injury
|
FDS rupture
|
Mechanism of injury
|
|
Abbreviations: FDS, flexor digitorum superficialis; FDP, flexor digitorum profundus;
SD, standard deviation.
|
|
1
|
78
|
Female
|
4
|
None
|
Pisotriquetral osteoarthritis
|
|
2
|
74
|
Female
|
4
|
None
|
Pisotriquetral osteoarthritis
|
|
3
|
69
|
Male
|
4
|
None
|
Unknown
|
|
4
|
78
|
Female
|
4
|
None
|
Pisotriquetral osteoarthritis
|
|
5
|
79
|
Female
|
3
|
None
|
Variation of the FDP tendon
|
|
6
|
55
|
Male
|
4
|
None
|
Nonunion of the hook of hamate
|
|
Average
|
72.2 (SD 8.4)
|
|
|
|
|
Intraoperative Findings and Complications
The cause of the injury was not revealed for one patient. FDP rupture of the little
finger was caused by pisotriquetral osteoarthritis in three patients. An abrasive
surface that resulted from nonunion of the hook of hamate caused an FDP rupture of
the little finger in one patient. The lack of interdependence between the FDP tendons
of the ring and little finger was found as the cause of rupture in another patient.
No wound complications or infections were noted. There were no ruptures of the transferred
tendons and no fingers that required tenolysis. There were no complaints about the
ring finger.
Recovery and Range of Active Digital Motion
[Table 2] shows the clinical results related to FDS tendon transfer. The mean follow-up period
was 40.3 weeks (range: 27–56 weeks). The average TAM and %TAM at the final evaluation
were 201.8° (range: 85–248°) and 75.4% (range: 30.4–88.1%), respectively. At the final
visit, the grip strength was, on average, 17.0 kg (range: 3.0–39.0 kg) in the affected
arm and 23.5 kg (range: 11.9–46.0 kg) on the unaffected side. According to the Strickland
and Glogovac criteria, outcomes were excellent for two, good for three, and poor for
one patient. Of the six patients, only one, a 78-year-old woman, experienced a poor
outcome. The patient had maintained a good range of motion during her hospital stay;
however, the range of motion restriction gradually progressed after discharge, and
the TAM at the final follow-up was 85°. The main cause of the poor TAM was the loss
of extension of the PIP joint. The mean Quick DASH-JSSH score for the disability/symptom
module was 14.6 (range: 0–32.5).
Table 2
Clinical assessment related to FDS tendon transfer
|
Case
|
Timing of surgery (weeks)
|
Final follow-up
(weeks)
|
Grip strength of the affected arm (kg)
|
Grip strength of the unaffected arm (kg)
|
TAM
(degrees)
|
%TAM
|
Functional evaluation a
|
|
Abbreviations: FDS, flexor digitorum superficialis; TAM, total active motion.
a The Strickland and Glogovac criteria.
|
|
1
|
9
|
27
|
9.9
|
22.1
|
244
|
84.1
|
Excellent
|
|
2
|
7
|
28
|
9.0
|
13.0
|
229
|
88.1
|
Good
|
|
3
|
28
|
44
|
27.3
|
31.3
|
172
|
79.3
|
Good
|
|
4
|
9
|
52
|
13.8
|
16.7
|
233
|
87.3
|
Excellent
|
|
5
|
Unknown
|
35
|
3.0
|
11.9
|
85
|
30.4
|
Poor
|
|
6
|
26
|
56
|
39.0
|
46.0
|
248
|
83.2
|
Good
|
Discussion
The current study showed satisfactory outcomes for the FDS tendon transfer, using
the wide-awake approach, followed by early active mobilization for the closed rupture
of the FDP tendon. The average TAM and Quick DASH-JSSH scores were relatively good,
and no major complications were noted, although grip strength in some patients had
not recovered sufficiently. There were no complaints regarding the donor site. We
believe that using the wide-awake approach and early active mobilization may contribute
to good clinical outcomes after the FDS tendon transfer.
In a previous report, adjustment of the tension of the transferred tendon was performed
by observing the cascade of increasing flexion of the fingers when proceeding from
the index to the small finger.[3] However, the appropriate tension is difficult to determine during FDS tendon transfer
because the characteristics of the muscle contraction differ between the FDP and FDS.
Several reports have shown that the FDS mainly works at a later phase of grip motion
and is recruited during active power grip.[13]
[14] If there is insufficient tension of the transferred FDS tendon, then during grip
motion, the little finger is not flexed simultaneously with the other fingers that
are mobilized by the FDP. We believe that tension of the transferred FDS tendon should
be considerably increased to obtain sufficient flexion of the little finger with a
slight grip motion. The considerably tight tension applied a strain to the FDS and
encouraged gliding. However, there is a concern that limitation of extension remains
in this situation, because surgeons cannot confirm whether full extension is possible
when the patient is under a brachial plexus block or general anesthesia.
The wide-awake approach can allay this concern. Wide-awake tendon surgery has an important
advantage, in that surgeons can easily determine the tension of the tendon and observe
active movement of the tendon during surgery.[7] Another advantage is that patients can recognize the recovery of their hand function
during surgery. Moreover, the wide-awake approach could minimize the differences in
outcomes that are affected by the surgeons’ experiences. Thus, wide-awake surgery
is particularly useful in FDS tendon transfer, in which it is difficult to determine
the tension of the transferred tendon. However, considering that we used a pneumatic
tourniquet for the first 20 to 30 minutes of surgery, the anesthesia technique used
in this study was simple “wide-awake surgery” and not the “wide-awake local anesthesia
no tourniquet” approach.[6]
In Japan, a prolonged hospital stay for rehabilitation after surgery is common. We
ensure that patients with closed ruptures of the flexor tendon are admitted to the
hospital for at least 4 weeks for postoperative treatment, because safe and controlled
early active mobilization following FDS tendon transfer is also a key factor that
contributes to a satisfactory outcome. The hand surgeon and therapist monitor the
condition of patient’s hand every day. Schneider and Wehbe reported that 25% of patients
require tenolysis after FDS tendon transfer to the FDP, because active motion begins
3 to 4 weeks postoperatively.[3] Koda et al suggested that the modified Kleinert method after FDP tendon transfer
may contribute to a poor outcome.[4] Early active mobilization can reduce the risk of developing adhesions and result
in improved functional outcomes after tendon surgery; thus, this protocol has been
used widely for tendon transfers such as the extensor indicis proprius to extensor
pollicis longus tendon transfer.[15]
[16] Although we employed early active mobilization after the FDS tendon transfer and
achieved good outcomes, there was a patient with a poor outcome due to loss of extension
of the PIP joint. This patient had maintained a good range of motion during the 4
weeks of hospitalization. Thus, for this surgical procedure, we believe that patients
should undergo strict extension exercises for more than 4 weeks, which is especially
important for elderly patients. Moreover, it might be better to continue extension
exercises for 12 weeks, because this is the timeframe in which the scar tissue matures.[17]
Our study has some limitations. The major limitation was that this was a small retrospective
study with no comparison group. To confirm our proposed theory, a larger case-control
study is warranted. However, we believe that this might be difficult, due to the idiosyncrasies
of the disease and the surgical procedure. Second, selection bias could not be excluded,
because the surgical procedure was selected based on the surgeon’s preference; when
the proper maximum amplitude of the proximal stumps of the ruptured FDP tendon was
less than 15 mm, either tendon transfer, using the ring finger FDS tendon, or an end-to-side
tendon transfer using the ring finger FDP was performed. Finally, the mean follow-up
period was short (mean 40.3 weeks). A longer time of observation is necessary, considering
that the tendon healing maturation phase continues for up to 1 year.[18]
Conclusion
We recommend the FDS tendon transfer of the ring finger, as the first-line tendon
transfer within the available surgical options, when the muscle amplitude of the ruptured
FDP of the little finger is insufficient. Although the FDS tendon transfer is technically
challenging, the wide-awake approach is helpful to determine the tension during surgery,
and postoperative early active motion exercise is also useful to obtain a satisfactory
outcome.
