Anatomical landmarks for tibial nerve block
ned according to surface anatomical landmarks (6–8).
The medication is usually injected when the needle tip
is in close contact with the targeted motor nerve cor-
responding to a (clinically evident) muscular contrac-
tion of selected muscles seen at ≤ 1.0 mA intensity and
100 µs duration of stimulation (7). Electromyography
(EMG) may also be used to help target the appropriate
motor nerve branch by monitoring the H-reflex (8).
Diagnostic nerve block (DNB) allows spastic muscle
overactivity to be differentiated from contracture, and
the respective role of different muscles in spastic over-
activity patterns to be determined (6, 7). DNB consists
of injecting a small dose of local anaesthetic near to
the nerve (motor branches) innervating spastic muscles
in order to temporarily suppress their overactivity (6).
DNB may lead to a decrease in spastic muscle overac-
tivity and clonus disappearance in the selected muscles
within a few minutes. The duration of DNB relies mainly
on the type of local anaesthetic injected (for example
lidocaine is shorter lasting than bupivacaine or ropiva-
caine) (9). On the other hand, therapeutic nerve block
(TNB) for managing spastic muscle overactivity consists
of perineural injection of phenol (in concentrations bet-
ween 5% and 7%) or alcohol (in concentrations between
45% and 100%) to obtain neurolysis (7).
Spastic muscle overactivity may lead to the deve-
lopment of changes in the muscle over time (i.e. cont-
racture, atrophy, loss of sarcomeres, accumulation of
intramuscular connective tissue, increased fat content,
degenerative changes at the myotendinous junction)
(10). These local anatomical modifications lead to a
mismatch between surface landmarks and the actual
position of the spastic muscles (11–14). Therefore, the
use of ultrasonography (US) has gained importance in
improving botulinum toxin injections for managing
some of the most frequent spastic muscle overactivity
patterns, such as equinovarus foot (13–15). On this basis,
it is plausible that the soft-tissue contracture process due
to spastic paresis may also alter the anatomical position
of some other key structures for managing spastic mus-
cle overactivity, such as motor nerve branches. Thus, the
main aim of this study was to identify, by means of US,
the anatomical landmarks of tibial motor nerve branches
to the gastrocnemii, soleus and tibialis posterior muscles
for selective motor nerve blocks in the management of
spastic equinovarus foot due to chronic stroke.
METHODS
This was a single-centre observational study. Inclusion criteria
were as follows: age > 18 years; spastic equinovarus foot conse-
quent to first-ever unilateral ischaemic or haemorrhagic stroke
(documented by a computerized tomography scan or magnetic
resonance imaging; subarachnoid haemorrhage excluded); calf
muscles spastic muscle overactivity grade of at least 1 on the
381
Modified Ashworth Scale (MAS) (16); at least 6 months since
stroke onset; no botulinum toxin injection into the affected leg
calf muscles in the 5 months before recruitment. Exclusion
criteria were as follows: participation in other trials; fixed cont-
ractures (tone grade of 4 on the MAS) or bony deformities at the
affected lower limb; previous treatment of spastic equinovarus
foot with neurolytic or surgical procedures; other neurological
or orthopaedic conditions involving the affected lower limb.
All participants were outpatients scheduled to receive selective
DNB of tibial motor nerve branches to the gastrocnemii, soleus
and tibialis posterior muscles. Written informed consent for par-
ticipation in the study was obtained from all patients. The study
was carried out accordance with the Declaration of Helsinki and
was approved by the local ethics committee.
Ultrasonographic evaluation
Patients remained in the prone position with their legs outstret-
ched during the procedure. All patients underwent real-time B-
mode US, performed using a MyLab 70 XVision system (Esaote
SpA, Genoa, Italy) interfaced with a linear probe (scanning
frequency 15–18 MHz). The examination technique consisted
of locating the tibial nerve at the terminal division of the sciatic
nerve (in the lower third of the thigh) and distally tracking its
motor nerve branches to the gastrocnemii, soleus and tibialis
posterior muscles. This, so-called “elevator technique”, enables
assessment of nerve shape, echogenicity, thickness and its rela-
tion with surrounding tissues (e.g. skin, muscles or vessels) (17).
The correct identification of tibial motor nerve branches to the
gastrocnemii, soleus and tibialis posterior muscles was checked
by means of needle (70-mm, echogenic-coated, 22-gauge needle
with length graduation) electrical stimulation (1 Hz frequency
and 100 μs duration). The tibial nerve motor branches were
located in the space (vertical, horizontal and deep) according
to the position of the fibular head (upper end) and a virtual line
extending from the middle of the popliteal fossa to the Achilles
tendon insertion (8). In addition, the spastic calf muscle echo in-
tensity was graded semiquantitatively according to the Heckmatt
scale (grade 1: normative; grade 2: increase in muscle echo in-
tensity while bone echo is still distinct; grade 3: marked increase
in muscle echo intensity and reduced bone echo; grade 4: very
high muscle echo intensity and complete loss of bone echo) (18).
Clinical evaluation
Patients remained in the supine position with their knees exten-
ded during the evaluation. The spastic ankle passive range of
motion (PROM) was measured using a handheld goniometer.
The sensitivity of the measurement was set at 5°. The dorsiflex-
ion angle was defined as positive and the plantar flexion angle
as negative, taking 0° as the neutral position of the joint (18).
The MAS is a 6-point scale grading the resistance of a relaxed
limb to rapid passive stretch (0 = no increase in muscle tone;
1 = slight increase in muscle tone at the end of the range of mo-
tion; 1+ = slight increase in muscle tone through less than half of
the range of motion; 2 = more marked increase in muscle tone
through most of the range of motion; 3 = considerable increase
in muscle tone; 4 = joint is rigid) (16). For statistical purposes, a
score of 1 was considered as 1, and a score of 1+ was considered
as 2, and so on, up to a score of 4, which was considered as 5
(19). The MAS was used to evaluate spastic calf muscles tone.
Also, the Tardieu scale (TS) was used to evaluate spastic calf
muscles tone according to the TS grade, which measured the
gain of the muscle reaction to fast stretch in dorsiflexion (0: no
resistance throughout passive movement; 1: slight resistance
throughout passive movement; 2: clear catch at a precise angle,
J Rehabil Med 51, 2019