Evaluation of Results after Flexor Digitorum Superficialis Tendon Transfer to Provide Fingers and Thumb Extension in Radial Nerve Lesions

INTRODUCTION
Tendon transfers follow a basic concept that
nothing new is created but functional parts are
rearranged into the best possible working combination
so it is the relocation of a tendon from a
functioning muscle to replace an injured or nonfunctional
muscle-tendon unit [1].
Several factors are considered when choosing
an appropriate tendon transfer to restore hand
muscle function: The tendon transfer route and the
tendon insertion site. Other factors such as tissue
equilibrium, timing of the tendon transfer, joint
mobility, the relative power and amplitude of the
transferred muscle tendon unit, and synergism.
Principles and rules must be followed in tendon
transfer [2].
The aim of this study is to evaluate the results
after the use of flexor digitorum superficialis in
tendon transfer after radial nerve palsy.
PATIENTS AND METHODS
Ten patients were included in this study. Those
patients presented to the outpatient clinics of plastic
surgery at Al-Azhar University (Al-Hussin and
Bab Al-Sheeryia) Hospitals. They initially presented
during the period starting May 2014 to May 2017.
Ten patients with radial nerve palsy were included
in the study, of which three patients had
posterior interosseous nerve (PIN) affection, leading
to loss of thumb and fingers extension.
The other seven patients had high radial nerve
affection, leading to wrist drop in addition to the
lost extension of the thumb and fingers. The loss
of wrist extension in those patients further impaired
the thumb and fingers function, due to frailer
flexion; and thus weakened the hand power grip.
Six patients were injured in their right hand (dominant),
while four were injured in their left hand
(all non-dominant). patients were assessed by the
range of motion of wrist, thumb, and Fingers (Tables
1,2).
Table (1): Criteria for range of motion of wrist, thumb, and
fingers [3].
Wrist extension
Finger extension
Thumb extension
Wrist flexion
Excellent
0-80
0-10
100-80
Full
0
0
80-60
0-20
Good Fair
45 extension
lag
45 extension
lag
60-30
0
Poor
70 extension
lag
90 extension
lag
30-0
Dorsiflexion
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Objective evaluation:
Subjective evaluation:
Post-operative management and rehabilitation:
The splint was removed after 4-5 weeks postoperatively,
Physiotherapy program was carried
out by a therapist experienced in hand therapy.
Range of motion exercises started at 5-6 weeks
post-operatively. All exercises were passive at first,
and then attempts for active motion started about
two weeks later. Reeducation exercises started
concomitantly for the FDS powered transfers,
Vol. 42, No. 2 / Evaluation of Results after Flexor Digitorum Superficialis Tendon
patients were taught to fire the transfer by trying
to independently flex his ring and middle fingers.
RESULTS
This series included ten patients with radial
palsy transfers; seven of whom suffered from high
radial palsy, while the other three suffered from
posterior interossious nerve (PIN) palsy, Table (3).
• 8 patients (out of 10) yielded 'Excellent to good'
results:
Patients who underwent tendon transfers with
'early' timing obtained 'excellent to good'' results.
These patients showed marked improvement
to the motor power scoring M4-M5 on the MRC
grading system, i.e. they obtained full range of
thumb extension with reasonable power against
resistance.
• 2 patients (out of 10) yielded 'Fair' results:
These patients showed moderate improvement
to the motor power scoring M3 on the MRC grading
system, i.e. they obtained some thumb extension
against gravity.
Table (3): Data about ten patients with radial palsy transfers.
1
2
3
4
5
6
7
8
9
10
Level of
injury
High radial
High radial
PIN
High radial
High radial
PIN
High radial
High radial
PIN
High radial
Conventional
Early
Conventional
Early
Early
Conventional
Early
Early
Conventional
Conventional
Timing of
surgery
3
4
5
4
4
5
4
5
5
2
Subjective
evaluation
scale
Fair
Good
Excellent
Excellent
Good
Excellent
Excellent
Good
Excellent
Fair
Objective
evaluation
Mode of trauma
Cut wound
Cut wound
Cut wound
Cut wound
Fracture mid-shaft humerus
Radial head dislocation
Cut wound
Cut wound
Cut wound
Bullet injury
Case
Table (2): Subjective evaluation scale [4].
0
1
2
3
4
5
Not improved in comparison to pre-operative state.
Slightly improved; does not help in everyday activities.
Slightly improved; helps in everyday activities, but cannot
tolerate work load.
Moderately improved; can be burdened with workload for
1-2 hours.
Greatly improved; can be burdened with workload for more
than 2 hours.
Greatly improved; uses hand normally in all muscular
activities with usual intensity; does not notice weakness.
Fig. (1): The flexor digitorum superficialis to middle and ring,
pronator teres are harvested and identified.
Fig. (2): Demonstration of the interossius tunnel.
Surgical techniques:
Egypt, J. Plast. Reconstr. Surg., July 2018 365
Fig. (3): A Pulvertaft weave of the flexor digitorum superficialis
of the ring and middle to extensor digitorum and
extensor policis respectively.
Fig.(4): Nerve grafting and tendon transfer done simultaneously.
Fig. (5): Pre-operative wrist and fingers drop of right hand
after radial nerve injury.
Fig. (6): Post-operative result with restoration of wrist and
fingers extension.
Fig. (7): Pre-operative wrist and fingers drop of left hand
after radial nerve injury.
Fig. (8): Post-operative result with restoration of wrist and
fingers extension 1 year later.
DISCUSSION
Non-cooperative, non-compliant patients or
those who did not accept the labor-intensive preand
post-operative physiotherapy program were
not considered candidates for tendon transfer procedures.
The selection of patients indicated for tendon
transfers, and the decision of the timing of their
surgeries, were very meticulously done. It is always
borne in mind that a tendon transfer reconstructs
a lost function at the expense of a donor motor
unit.
Interosseous tunnel make a physiological, biomechanical
vector of pull. If this is done, a large
window should be created in the interosseous
membrane to prevent constriction or tethering of
the transfer [5].
Choosing to perform a delayed nerve repair or
graft, that was of a clearly poor prognosis from
the start, rather than a tendon transfer, would mean
wasting 6 more months for the patient, waiting for
an unwarranted result.
The FDS transfer set was primarily employed;
as it provides thumb extension independent from
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the fingers and wrist extension, because the FDS
control for each finger is independent from the
other fingers, as advocated by Boyes [5].
The FDS of the middle finger was preferred as
a motor for the EPL. When the FDS is used as a
motor, it provides 7cm of excursion, while the
FCR provides only 3cm; therefore, the FDS is
more efficient, noting that the EPL normally provides
5cm excursion. The FDS also provides more
powerful contraction than that of the PL [7,8].
The FDS tendon was harvested proximal to
their bifurcation through a window between the
A1 and A2 pulleys as originally recommended by
North & Littler, to avoid injury to the vincula or
to the flexor sheath, and to leave behind a 3-cm
length of superficialis tendon that glides freely
within the flexor sheath. Using this method, we
did not encounter any case of PIP joint flexion
contracture in the donor digit, or any swan neck
deformities as in the study conducted by Altintas
et al., [9].
89% of patients with radial palsy were able to
resume working after tendon transfer. In the study
by Gousheh and Arasteh 92% of the patients reintegrated
into working life. In the study by Moussavi,
et al., 95% of the patients experienced functional
improvement [3-10].
The 3-6 months timing for return to work or
resumption of everyday life activities achieved by
radial palsy patients in this study, is also consistent
with the literature [8].
Communication among physician, therapist,
and patient is necessary to maximize the outcome
and prevent untoward complications.
Vol. 42, No. 2 / Evaluation of Results after Flexor Digitorum Superficialis Tendon