Applications of endoscopic surgery of the foot and ankle are expanding and
include plantar
fasciotomy1-7,
release of the transverse metatarsal
ligament8, incision
of the posterior tibial tendon
sheath9,
calcaneoplasty10,11,
decompression of the retrocalcaneal
bursa12, suture of
a torn Achilles
tendon13,14,
release of the Achilles
peritenon15, and
endoscopic gastrocnemius
recession16. There
are, however, relatively few reports of complications following endoscopic
foot
surgery2,17-19.
Even in a recent review dealing with complications of arthroscopy of the foot,
there was no mention of inadvertent injury to the plantar plate or flexor
tendons20. To our
knowledge, no reports of complications following attempted release of the
transverse metatarsal ligament for treatment of interdigital neuroma have been
published.
We present the case of a patient who had a complication of attempted
endoscopic release of the transverse intermetatarsal ligament that resulted in
damage to the plantar plate of the metatarsophalangeal joint of the fourth toe
and transection of the flexor digitorum longus tendon with subsequent
instability of the metatarsophalangeal joint.
Afifty-two-year-old woman had been diagnosed as having an interdigital
neuroma of the third web space of the right foot. The symptoms included
tingling and a burning sensation in the third web space, without pain,
swelling, or a reduction in the range of motion of the lesser
metatarsophalangeal joints. Surgical intervention for removal of the neuroma
was recommended at that time, and the patient underwent an attempt to
endoscopically release the transverse metatarsal ligament of the third web
space to decompress the neuroma. Immediately after the operation, the patient
noticed that the fourth toe was markedly elevated and that it overlapped the
adjacent fifth toe. She later reported that the pain was exacerbated when she
wore closed-toed shoes. She also experienced a painful clicking of the
metatarsophalangeal joint along with episodes during which she felt as if the
toe was locked in extension. These episodes required her to manually plantar
flex the metatarsophalangeal joint of the fourth toe to relieve the locking
sensation.
Six months after the endoscopic surgery, the patient presented to our
clinic. Physical examination revealed hyperextension of the digit and a valgus
deformity at the metatarsophalangeal joint of the fourth toe, with pressure
against the adjacent fifth toe (Fig.
1). Stiffness and a fixed flexion deformity were present at the
proximal interphalangeal joint of the fourth toe. Dorsal-plantar instability
was easily demonstrable at the metatarsophalangeal joint, which was resting in
dorsal subluxation. This subluxation was painful, and a palpable clunk was
produced when the toe was passively flexed at the metatarsophalangeal joint.
Active range of motion was limited to minimal flexion at the
metatarsophalangeal joint and no demonstrable flexion at the proximal or
distal interphalangeal joint of that toe. Conservative treatment, including
taping of the toe and the use of a custom orthosis with a metatarsal bar, was
initiated but had no appreciable benefit.
After an additional six months, reconstructive surgery was performed in an
attempt to correct the position of the toe and address the metatarsophalangeal
instability. A dorsal incision in the interspace between the third and fourth
toes was used to explore that web space and to perform a capsulotomy of the
metatarsophalangeal joint along with lengthening of the extensor tendon. The
two ends of the transected flexor digitorum longus tendon were located through
this approach. Primary repair was impossible because of extensive retraction
of the tendon (Fig. 2). A
resection arthroplasty of the proximal interphalangeal joint was performed to
straighten the fixed flexion deformity of the toe. Through a plantar incision,
the plantar plate was noted to be attenuated, and most of its proximal
insertion was seen to be detached. The plantar plate was reinforced and was
reattached to the metatarsal neck. Drill holes in the medial and lateral sides
of the plantar aspect of the metatarsal neck were made. To reinforce the
distal stump, we passed 2-0 Vicryl sutures through the corresponding sides of
the plantar plate and through the drill holes in the corresponding plantar
aspect of the metatarsal neck. The site of the proximal interphalangeal
resection arthroplasty was pinned with a 0.045-in (0.114-cm) wire. With the
ankle and metatarsophalangeal joints held in neutral position, the pin was
passed across the metatarsophalangeal joint to protect the reconstruction. The
pin was removed four weeks after the surgery.
The postoperative course was unremarkable except for swelling that was slow
to resolve and a concomitant vague aching, both of which had resolved by the
time of the one-year follow-up evaluation. At the most recent follow-up visit,
four years following the reconstructive surgery, the patient reported no
symptoms of instability and was satisfied with the position of the toe. On
physical examination of the foot, there was no residual extension at the
metatarsophalangeal joint, and the toe was noted to be well aligned with the
other digits in the sagittal plane (Fig.
3). There was still a very mild but persistent valgus deformity at
the metatarsophalangeal joint that was causing the fourth toe to touch the
fifth, thus increasing the space between the third and the fourth toes.
Persistent mild discomfort under the fourth metatarsal head was managed
satisfactorily by the intermittent use of a metatarsal pad insert within the
shoe.
In our patient, an endoscopic procedure that was intended to release the
transverse intermetatarsal ligament resulted in extensive injury to the
plantar plate of the metatarsophalangeal joint of the fourth toe and
transection of the flexor digitorum longus tendon. This produced a
hyperextension deformity and painful instability of the metatarsophalangeal
joint. Although surgery to reconstruct the deformity was successful, the
patient had a prolonged course of treatment and substantial morbidity as a
result of these complications.
Barrett and
Pignetti8 reported
on a series of seventeen patients who underwent endoscopic decompression for
intermetatarsal nerve entrapment and for whom the duration of follow-up was
nine months to one year. In that study, none of the patients had complications
except for one patient in whom a traditional open neurectomy was subsequently
required. Their report also included the results of a cadaver study in which
an endoscopic decompression of the nerve in both the second and the third
interspace was performed in fifteen fresh-frozen specimens. In the course of
completing those thirty procedures, the investigators accidentally transected
four lumbrical tendons during an attempt to release the transverse
intermetatarsal ligament. There was no mention of the vulnerability of either
the plantar plate or the flexor tendon with this technique. The authors stated
in that 1994 report that, because of the need for follow-up of a larger
patient population, they had initiated a prospective study of all patients
undergoing endoscopic surgery for treatment of a neuroma. After a careful
search of the literature, however, we were unable to find a follow-up study
published by those authors.
A symptomatic interdigital neuroma is most commonly addressed with an open
surgical technique, which includes release of the intermetatarsal ligament,
usually through a dorsal incision, and is widely considered to be associated
with low morbidity. When this technique has included resection of the nerve,
the patient satisfaction rates have been reported to be 80% to 85% throughout
the
years21,22.
This case report highlights the inherent hazards of poor visualization and
difficult manipulation that can occur with the use of endoscopic surgical
techniques in the soft tissues of the foot. The outcome in our patient
demonstrates the need for the surgeon not only to be meticulous in the
identification of anatomic structures and cautious with regard to the surgical
technique, but also to adequately inform patients of the risks of the
procedure. The relative risk compared with the benefit of both the open and
the endoscopic technique is a legitimate concern for the surgeon as well as
for the patient who wishes to make an educated decision regarding treatment of
an interdigital neuroma.