Twenty-one children, ranging in age from eight to fifteen years,
with bilateral functional flexible flatfoot were included in the
study. The diagnosis of functional flexible flatfoot was made by
clinical examination, radiographic examination, and, in doubtful
cases, gait analysis in order to confirm functional impairment.
Clinical diagnosis was based on restriction of dorsiflexion of the
ankle joint after manual correction of the deformity, increased
heel valgus at rest and during the tiptoe standing test, footprint
enlargement at rest and during the Jack test, and the presence of
discomfort (slight pain and fatigue).
These parameters were measured before surgery and four years
after it. Preoperative and postoperative data were compared by statistical
analysis with the Student t test and the chi-square test (level
of significance, p < 0.001). Standard lateral and dorsoplantar
radiographs were made before surgery and at the time of follow-up.
Meary’s line was measured in all cases. Gait analysis consisted
of kinematic, kinetic, and electromyographic measurements. All patients
were followed for four years.
Surgical treatment is performed under general anesthesia. A tourniquet
is applied proximally to the lower limbs. Patients are placed in
a supine position with the foot internally rotated. A 1-cm incision over
the sinus tarsi is performed. The extensor retinaculum is opened
to the cuboid bone with use of curved scissors. By turning the tip
of the scissors upward and pushing in a medial direction toward the
internal malleolus, the tip of the scissors can be felt going into
the deepest region of the sinus tarsi (Figs. 2 and 3).
A 6-mm rod is introduced in the same direction, followed by an
8-mm rod until correction is obtained. The skin and the fibers of
the retinaculum are retracted with two small separators to introduce the
reabsorbable implant with its positioner (Figs. 4 and 5).
The reabsorbable screw is inserted to open and stabilize the
implant, and it is tightened until the characteristic "squeaking" is
heard from the material. The retinaculum is sutured with one 3-0
reabsorbable suture, and the skin is sutured with another stitch.
This is the only surgical step available for correction. The operation
is performed bilaterally when the deformity involves both feet (Figs. 6, 7, 7, 8, and 9).
After the foot is corrected by insertion of the implant, the
dorsiflexion of the foot is checked with the knee in extension.
In this series, it was not possible to dorsiflex six feet to a right
angle. In these cases, the Achilles tendon was lengthened subcutaneously
with two, three, or four alternate hemisections and forcing of the
foot dorsally to stretch the tendon until 10° of dorsiflexion was
achieved (Fig. 10).
In twelve feet with an accessory navicular, a prominent painful
navicular bone, or interruption of Meary’s line at the
naviculocuneiform joint with an angle of >10°, a medial
procedure was also performed. Through a 3-cm incision over the navicular prominence,
the navicular bone and the posterior tibial tendon are exposed.
The periosteum and the posterior tibial tendon are detached from
the navicular, with maintenance of the metatarsal expansion and
the fibers directed toward the navicular. After tangential resection
of the navicular prominence and the removal of the accessory navicular,
the posterior tibial tendon is put under tension with use of a 2-0
reabsorbable Bunnell suture and the suture is passed from plantar
to dorsal through the spongy part of the navicular bone (Figs. 11 and 12).
By the surgeon pulling the two ends of the suture, the tendon
is advanced distally to lie under the navicular bone. The suture
is reinforced with another cross stitch with 2-0 suture. The sheath
of the posterior tibialis is sutured with 3-0 suture (Figs. 13 and 14).
When only the implant was inserted, a walking boot is worn for
two weeks in order to avoid any pain during walking and to permit
an earlier return to normal daily life. When the combined procedure was
done, the period of immobility with a boot is five weeks: three
weeks without weight-bearing and two weeks with weight-bearing.
In both cases, when the boot is removed, normal footwear is worn and
cycling and swimming are advised.
No significant differences were found between preoperative and
postoperative plantar flexion, supination, and pronation. Dorsiflexion
measured with the subtalar joint in neutral position was 11.4° ±
6.3° before surgery and 17.7° ± 3.6° at the time
of follow-up (p < 0.0001) (Figs. 15 and 16). Discomfort
was present in only 5% of the children at the time of follow-up,
whereas it had been present in 81% of the children before
surgery (p < 0.0001) (Fig. 17).
The mean heel valgus deviation at rest was 11.4° ±
4.2° preoperatively and 5.8° ± 3° at the time of
follow-up (p < 0.0001) (Figs. 18, 19, and 20).
The mean heel valgus correction during the tiptoe standing test
was —1.9° ± 4.9° preoperatively and —6.3° ±
3.4° at the time of follow-up (p < 0.0001) (Figs. 21, 22, and 23).
The footprint grade at rest was 2.6 ± 1.3 preoperatively
and 0.8 ± 1.2 at the time of follow-up (Figs. 24 and 25). The
footprint grade during the Jack test was 1.8 ± 1.4
preoperatively and 0.5 ± 1.1 at the time of follow-up
(Figs. 26 and 27).
With the site of angulation at the level of the talonavicular
joint, the mean angulation of Meary’s line was 164° ±
10° preoperatively and 174° ± 5° at the time of
follow-up (p < 0.0001) (Figs. 28, 29, 30).
Only two complications were observed in our series: small fragments
of the implant impinged against the shoes at one and two years.
These problems spontaneously resolved with resorption of the material.
Magnetic resonance imaging performed from three months to five
years after surgery did not show sinus formation or any osseous
alterations in the sinus tarsi. The implant began to change six
months after surgery (Fig. 31). At one year, fragmentation of
the implant could be seen but the overall structure was still intact
(Fig. 32).
Structural integrity disappeared at eighteen months, and fragmentation
of the implant became more evident (Fig. 33). At three years, the implant had
almost completely disappeared and edema in the sinus tarsi could
be seen (Fig. 34).
At four years, the implant was completely absorbed (Fig. 35).
Extra-articular arthroereisis with use of a bioreabsorbable implant
in the sinus tarsi was simple and effective in correcting functional
flexible flatfoot. Surgery performed during growth provides an optimal
and lasting correction of the deformity, restoring the talocalcaneal
alignment with remodeling of the subtalar joint. This correction
improves the biomechanics to prevent problems caused by persistent pronation
of the foot. The bioreabsorbable implant proved to be virtually
complication-free and did not need to be removed.