Keywords
reconstruction - Achilles - chronic - tendon transfer
Introduction
Chronic Lesions of Achilles Tendon
Lesions of the Achilles tendon are termed chronic if they are left untreated for more
than 4 weeks.[1] The cause of chronic Achilles tendon lesions includes neglected spontaneous ruptures
and failed repairs of the Achilles tendon. A spontaneous rupture due to Achilles tendinopathy
commonly occurs in middle-aged men who are occasionally active, and it often occurs
without any warning signs or symptoms.[2] The rupture most commonly occurs ~2 to 6 cm proximal to the insertion.[3] The patient usually feels a sharp snap with severe pain on the posterior part of
his ankle with swelling. It is immediately followed by an inability to walk or run
and a sensation of imbalance and weakness on push off. The patient usually rests the
affected part and once the signs of inflammation reduce, they slowly resume activity.
In patient with diabetes, pain may not be a predominant symptom due to neuropathy
and hence may cause the patient to ignore the acute rupture event and continue walking
on the affected leg, causing further damage. The loss of the Achilles tendon results
in a calcaneal limp[4] and this heel overload eventually causes a resistant heel ulcer in patients with
an insensate foot.[5]
The Achilles tendon is a unique feature of man and is not found in any other member
of the primate species.[6] It most probably evolved as a result of the development of bipedal gait in the primitive
Homo species. The evolution of the Homo species has been attributed to its specialized
ability for endurance running a unique feature absent in other nonhuman primate species.
The ability to run requires long spring-like tendons which reduce the energy cost
of transport by approximately 50%. The most important of these springlike ligaments
is the Achilles tendon.[7]
The Achilles tendon is formed by the fusion of the tendons of the two bellies of the
gastrocnemius which lie superficially and that of the soleus muscle which lies deeper
to the gastrocnemii. The respective tendons travel for some distance, separate from
each other, and ultimately fuse to form a single tendon known as the Achilles tendon,
the deeper fibers of which insert into the posterior part of the calcaneus and the
superficial fibers continue onto become part of the plantar fascia. In the other great
apes such as the gorilla, the gastrocnemius and soleus muscle tendons do not fuse
but insert separately and directly into the calcaneum.[6]
Developmentally the lower limb bud rotates on itself during its formation. This is
reflected in the anatomy of the Achilles tendon where the fibers of the gastrocnemius
muscles are differentially rotated over the tendon of the soleus and are preferentially
inserted onto the lateral side of the calcaneum, while the soleus fibers are inserted
into the medial side of the calcaneum. This creates a wringing action of the Achilles
tendon during contraction.[8]
The Achilles tendon inserts into the calcaneum at the Achilles tendon “enthesis organ.”
It is composed of the calcaneal periosseous fibrocartilage, the sesamoid fibrocartilage
on the inner surface of the tendon, the retrocalcaneal bursa, and the Kager's fat
pad. All these structures put together are called the Achilles tendon enthesis organ
or synovio-entheseal complex[9] and serve to dissipate the massive amount of torque transmitted through the Achilles
tendon during activities such as jumping and running. A proportion of the Achilles
tendon fibers passes on to the heel and becomes continuous with the plantar fascia
without inserting into the calcaneum. This is representative of the myofascial web
concept of Myers (Anatomy Trains)[10] which is related to the concept that tendons seldom have an isolated insertion on
to a single point of bony attachment, instead, they inset on to multiple adjacent
structures to help spread out the load transmission.
Around the region of the enthesis, the Achilles tendon is surrounded by two bursae
to reduce the friction during movement. A superficial bursa is found interposed between
the skin and tendon, while the deep retrocalcaneal bursa is found between the tendon
and the superior calcaneal tuberosity.[11]
The blood supply of the Achilles tendon can be divided into thirds. The primary vessel
supplying the Achilles tendon is the posterior tibial artery which sends branches
through a mesotenon like membrane which then expands and forms a paratenon with plexus
of vessels. The upper third is also supplied from the gastrocnemius and soleus muscle
bellies and the lower third from the periosteal plexus over the calcaneum and branches.
Other studies have also identified that the Achilles tendon is supplied by two arteries,
the middle third supplied by the peroneal artery, and the proximal and distal thirds
being supplied by the posterior tibial artery.[12]
Diagnosis
A chronic Achilles tendon injury may present with an obvious sign of rupture with
a palpable or visible defect in the continuity of the Achilles tendon ([Fig. 1]). Clinical tests for testing the integrity of the Achilles tendon include the Simmond's
or Thompson's calf squeeze test, Matle's test, O'Brien's needle test, and the Copeland's
sphygmomanometer Test.
Fig. 1 Step like deformity visible on the lateral view. If a scar bridges the defect, such
a dip may not be visualized.
The calf squeeze test described by Simmond[13] about 5 years before Thompson[14] involves squeezing of the calf muscles in a patient lying prone with his feet overhanging
the edge of the examination couch. The examiner squeezes calf causing the feet to
plantarflex indicating the integrity of the tendon. In the Matle's test,[15] the patient lies prone with his knees flexed to 90 degrees and ankles let loose.
In a patient with a ruptured Achilles tendon, the involved ankle falls into dorsiflexed
or neutral position, while the normal ankle stays in plantarflexion due to the tone
of the triceps surae ([Fig. 2]).
Fig. 2 Matle's test: The involved ankle in the foreground is more dorsiflexed compared with
the uninvolved foot in the back ground which remains plantarflexed due to the tone
of the triceps surae.
In the O'Brien's needle test,[16] a needle is inserted into the substance of the Achilles tendon ~10 cm proximal to
the insertion and just medial to the midline and the patient is asked to dorsiflex
and plantarflex his ankle. The tip of the needle tilts distally and hub proximally
with dorsiflexion if the substance of the tendon distal to the needle is intact. In
the Copeland's sphygmomanometer test,[17] a cuff is tied around the patient's midleg flexed at the knee in a prone position
with the foot plantarflexed and is inflated to 100 mm Hg. The patient's foot is then
passively dorsiflexed and the quantum of the rise in the sphygmomanometer is noted.
In individuals with an intact Achilles tendon, the pressure will rise to ~140 mm Hg.[17] A point to remember, however, is that the test was originally described using a
mercury manometer which is a rarity nowadays.
During clinical testing, it must be kept in mind that a false positive result may
occur due to the formation of a bridging scar in between the cut ends of the Achilles
tendon. Patients are also able to perform an active ankle flexion the presence of
a ruptured Achilles tendon due to the action of the intact secondary flexors of the
ankle joint such as the flexor hallucis longus (FHL), flexor digitorum longus, peroneus
longus, and tibialis posterior muscles. This can be unmasked by the relative weakness
of the affected side when compared with the normal side.
Imaging
A plain X-ray taken in an individual shows the soft tissue outline of the Achilles
tendon inserting into the calcaneum ([Fig. 3]). The maximum anteroposterior width of the Achilles tendon in the lateral view radiograph
has been found to be 8 mm and anything more than that signifies a pathology of the
Achilles tendon.[18] A translucent area just beneath the Achilles tendon represents the fat pad and it
dips ~2 mm below the superior most border of the calcaneus. In inflammatory conditions
of the Achilles tendon, this inverted triangle bordered by the calcaneum anteriorly,
the enthesis posteriorly and continuous with the Kager's fat pad superiorly, gets
obliterated.
Fig. 3 The X-ray shows the soft tissue outline of the normal Achilles tendon with a lucent
area deep to it representing the Kager fat pad (*) and fatty tissue deep to the Achilles
tendon.
High-frequency ultrasonogram can also be used to identify the continuity of the Achilles
tendon, its dimensions, and its vascularity.[19] The gold standard imaging test is a magnetic resonance imaging (MRI) scan of the
involved area. T1-weighted images show a good anatomical delineation of the tendon,
whereas T2-weighted images demonstrate fluid accumulation, a sign of tendon pathology,
well.[20] The normal average thickness of the Achilles tendon on an MR is ~6 mm.[21] The normal retrocalcaneal bursa measures ~ 6 mm superoinferiorly, 3 mm mediolaterally,
and 2 mm anteroposteriorly.[11]
Pedobarogram
A pedobarogram is a dynamic recording of the pressures that act on the sole of the
foot during the stance phase of the gait cycle. Information like peak pressures, force,
area in contact with the ground, and the duration of the stance phase can be gathered
from a pedobarogram. Force plate testing has not been described as a diagnostic modality
of Achilles tendon injuries; however, it has been an established method to diagnose
gait disturbances in patients with neuropathic ulcers and orthopaedic problems.[22]
[23]
[24]
[25]
We have noticed in our series of patients that the pedobarogram is effective at indirectly
diagnosing an inefficiency of the muscle-Achilles tendon-calcaneum, midfoot, and forefoot
axis integrity by documenting the increase in calcaneal loading and the associated
calcaneal gait that occurs with Achilles tendon insufficiency[26] even when clinical testing is inconclusive because of fibrous bridging of the gap.
Serial pedobarograms at regular intervals after surgical repair of a ruptured Achilles
tendon documented the return of function evidenced by the progressive increase in
forefoot loading ([Fig. 4]).
Fig. 4 Serial pedobarogram in a young girl after direct repair of an acute Achilles tendon
injury. Image (A) showing only calcaneal loading with little or no forefoot loading. Images (B–D) showing the gradual return of forefoot function with a concomitant reduction in
heel pressures.
Management Protocols
Reconstruction of the chronic Achilles tendon injury primarily depends on the age
of the injury and the magnitude of the gap that exists between the proximal tendon
that has undergone adaptive shortening and the distal healthy tendon. The length of
the final gap is determined after debridement of the fibrotic and degenerate areas
of the ruptured tendon ends. Most protocols for repair of chronic Achilles tendon
injuries take into consideration the size of the defect as the lone criterion. More
recent publications have stressed the need to take the age of the injury, the status
of the tendon ends, and other factors into consideration.
The Myerson protocol[27] divides chronic Achilles tendon injuries based on the size of the defect. Lesions
with a gap of less than 2 cm are directly repaired. A gap of 2 to 5 cm are treated
by a V -Y advancement with an occasional tendon transfer for augmentation if required.
Gaps of greater than 5 cm are primarily treated with a tendon transfer with a combination
of a V -Y lengthening if required.
The Kuwada protocol[28] divides the lesions into four types. Type I consists of partial thickness injuries
which were treated conservatively. Type II consists of defects up to 3 cm and are
treated with an end-to-end repair. Type III lesions, those with gaps of 3 to 6cm between
the ends of debrided tendon, require a tendon graft flap possibly strengthened with
a synthetic graft. Type IV lesions with greater than 6 cm were treated with a gastrocnemius
recession and free tendon graft or synthetic graft.
Maffulli et al[29] gave no specific protocol based on the size of the defect. They suggested that the
primary end-to-end repair whenever possible was the best choice and a tendon transfer
was to be done for defects that could not be repaired primarily. The first choice
for a transfer was a peroneus brevis followed by the flexor digitorum longus muscle
with tendon for larger defects. In cases where the tear was larger than 6.5 cm, a
nonvascularized gracilis tendon graft or semitendinosus graft was preferred.
Other protocols that have been published for the treatment of chronic Achilles tendon
lesions based on the size of the include those by Bevialcqua,[30] Den Hartog,[31] and Krahe and Berlet.[32]
Recently, Buda et al[33] have published a protocol which considers other factors like the extent of injury,
time since injury, the presence of MRI signs of tendinopathy like paratenonitis, tendinosis
of the ruptured ends, and presence of insertional tendinopathy apart from the size
of the defect. They suggested an end-to-end repair of full-thickness defects of 1
to 2 cm in size. For defects > 2cm up to 5 cm, they suggested a turndown flap or V–Y
advancement repair. One or two tendon transfers with a V–Y tendinous flap and the
use of an allograft were recommended in gaps larger than 5cm.
Operative Management and the Authors’ Preferred Techniques
Operative Management and the Authors’ Preferred Techniques
Primary Repair
Primary repair with or without a gastrocsoleus lengthening is the preferred procedure
when the gap between healthy tendon ends after debridement is less than 2 cm and the
distal insertion of the Achilles tendon on to the calcaneum is intact. The operation
is usually done under spinal anesthesia and the patient is positioned in a semiprone
position turned to the involved side which brings the operative site upward and gives
unrestricted access to the posterior, medial, and lateral sides. The leg is placed
on a foam pad with mild flexion at the knee to allow relaxation of the gastrocnemii
muscles. The Achilles tendon is approached through a curved incision raising a medially
based flap and extended proximally and distally in the midline giving good access
to the proximal and distal stumps and enthesis. The most commonly studied suture techniques
include the double-stranded Kessler, double-stranded Bunnell, and Krackow repairs.
The Krackow technique has shown a greater tendency to gap formation.[34] The actual strength of the repairs has been shown to depend on the number of suture
strands crossing the repair site rather than the suture technique as such.[35] We prefer the double-stranded Kessler repair with a thick monofilament 1 Prolene
(NW 843- Ethicon), though newer materials like Ethibond (Ethicon) and Fiberwire (Arthrex)
have been shown to have greater tensile strength in recent studies.[34]
When the enthesis is grossly destroyed by degenerative changes and the gap is lesser
than 2 cm, the proximal tendon end is fixed on to the decorticated surface of the
posterior part of the calcaneus with the help of a suture anchor. This repair may
or may not be strengthened with a tendon transfer depending upon the tension in the
repair.
Occasionally, a V–Y lengthening or gastrocsoleus lengthening may be required to bring
down the proximal tendon to enable a primary repair. We prefer a transverse Vulpius
gastrocsoleus recession[36] done just below the insertion of the gastrocnemii. A transverse incision is made
along the gastrocsoleus leaving the soleus muscles intact to fractionally lengthen
the tendon by ~1 to 2 cm. The division of the midline raphe of the soleus helps to
gain a few millimeters. The same release made in the form of a V can be reapproximated
in the form of a Y to get a V–Y lengthening.
Peroneus Brevis Transfer
Some patients with an intact distal stump may require an augmentation of the primary
repair with a tendon transfer. The peroneus brevis tendon transfer is the transfer
of choice for augmentation of a primary repair. The tendon is harvested through an
incision at the base of the fifth metatarsal and taken out through the surgical wound
behind the fibula. The peroneus longus tendon lying superficial to the brevis tendon
is left intact. The tendon length is relatively short but is enough to be inserted
into the calcaneum in a dorsoplantar direction using an interference screw and can
also be also hitched to the distal stump of the tendoachilles.[37] Considering the shorter tendon length and need for an interference screw, we prefer
to use the peroneus brevis as a distally based flap for cover of an incomplete Achilles
tendon injury rather than a proximally based donor for transfer.
Flexor Hallucis Longus Transfer
This is our preferred technique for tendon transfers for both substitution and augmentation
of Achilles tendon repairs. FHL tendon transfer for Achilles tendon reconstruction
was first described by Wapner et al.[38] In patients with an enthesis loss and proximal tendon of insufficient length to
reach the calcaneum, the FHL transfer is a preferred procedure to both create a new
insertion and bridge the gap in the Achilles tendon ([Fig. 5]). The FHL tendon harvested at the base of the great toe (double incision) is an
ideal choice for transfer in this situation. Some authors prefer to use the single
incision technique to harvest the FHL proximal to the Henry knot to preserve great
toe function at the cost of donor tendon length. The muscle is synergistic and the
strongest of all available transfers.[39] The FHL muscle and tendon have been proven to hypertrophy following transfer and
achieve a concentric and eccentric contraction strength comparable to that of the
uninjured side.[40]
Fig. 5 Transfer of the flexor hallucis longus tendon to bridge a gap of the Tendo Achilles.
The tendon is harvested from the base of the toe using a two-incision technique (A) and routed through the calcaneus and woven into the proximal Tendo Achilles stump
(B–D). Skin is closed over a drain (E).
The FHL is first isolated at the base of the great toe and at the midfoot through
separate incisions. The distal end is cut and retrieved at the midfoot. The proximal
part of the muscle belly with its tendinous origin lies in the midline just anterior
to the ruptured ends of the Achilles tendon. The deep fascia separating the deep compartment
from the Achilles tendon is incised longitudinally to identify the FHL and which is
then isolated. The tendon is again retrieved behind the ankle after dividing the Henry
knot. The tendon is then routed through a transosseous tunnel in the calcaneum and
sutured onto itself in a Pulvertaft weave with the ankle in ~45 degrees of flexion.
The distal free end is then woven mediolaterally into the proximal end of the Achilles
tendon. Each weave is anchored with 3–0 Prolene (Ethicon) sutures. Once the repair
is complete, the skin flap is sutured over a tube drain. The foot is dressed, and
the ankle position is maintained with an anterior below knee slab for ~2 weeks.
Postoperative Protocols
After suture removal, the repair was protected in a below knee equinus cast for ~2
weeks and a neutral cast for ~8 weeks. The patients are allowed protected full weight
bearing with a below knee cast on the operated leg 8 weeks after surgery and unprotected
full weight bearing is allowed at 12 weeks post-surgery in footwear with a heel raise.
The patients are cautioned not to attempt isolated forefoot weight bearing particularly
when climbing stairs. Ankle plantar flexion strengthening exercises are started and
the patient reviewed once in 2 months. The serial pedobarographic evaluation showed
the return of forefoot loading in ~11 to 13 months in patients who underwent an FHL
transfer. Other tendons transfers reported in the literature include the flexor digitorum
longus muscle transfer. On comparison of the FHL and the peroneus brevis muscles in
cadaveric studies, Sebastian et al concluded that the mechanical properties both muscles
were similar.[41]
Free Tendon Graft
Few patients have very large gaps due to loss of tendon substance which is not amenable
for repair by tendon flaps. They may be reconstructed with free tendon grafts. Commonly
used free tendon grafts include the semitendinosus tendon, gracilis tendon,[42] FHL tendon graft, and fascia lata. We prefer to use the fascia lata ([Fig. 6]). It can be rolled into a thick cord like graft and then woven into the proximal
and distal ends of the Achilles tendon using a Pulvertaft weave. The use of allograft
tendon[43] alone or in combination with a xenograft[44] has also been described in the repair of large gaps, but this procedure is not commonly
described in the literature and its use is an exception.
Fig. 6 In very large gaps, a fascia lata graft (A) is used to bridge the gap (B). In cases with concomitant soft tissue loss, a free gracilis muscle flap is used
to provide cover (C).
Achilles Tendon Gap with Overlying Soft Tissue Loss
Sometimes a chronic lesion occurs because of a failed primary repair of an acute Achilles
tendon repair. Such lesions usually present with loss of the overlying skin and soft
tissue. In such cases, we prefer to do a debridement of the sloughed tissues till
healthy bleeding edges. The bed and enthesis are debrided to healthy tissue and all
calcific degenerate tendon tissues are removed. The wound is managed by moist dressing
till a healthy clean bed is achieved. In the next stage, a tendon reconstruction is
done with a tendon graft or FHL tendon transfer with wound closure by a microvascular
gracilis muscle flap cover which is the flap of choice in our unit ([Fig. 6]). The muscle is covered with a split-thickness skin graft. Other flaps that have
been described for use in chronic Achilles tendon lesions with soft tissue loss include
a local reverse sural pedicled flap, perforator based propeller flaps[45] ([Fig. 7]), reverse peroneus brevis flaps,[46] and the microvascular free anterolateral thigh flap and latissimus dorsi flap.[47]
[48]
[49] In a rare case with infected complex defect, reconstruction with a free gracilis
flap alone has been found to bridge the gap and function as an effective interposition
graft.[50]
Fig. 7 Propeller flap based on the posterior tibial perforator used to cover a post debridement
defect following a failed reconstruction of a chronic Tendo Achilles injury.
Overview
Repair and reconstruction of this biomechanically important tendon depend upon multiple
factors which need to be taken into consideration. Following one of the multiple protocols
([Fig. 8]) which best suits the reconstructing surgeon and the clinical scenario with adherence
to principles of tendon repair and reconstruction, namely a good debridement, gentle
appropriate technique and ensuring that the repair is covered by healthy soft tissue
should ensure good results.
Fig. 8 Flowchart of the authors protocol of management of chronic Achilles tendon Injuries.
FHL, flexor hallucis longus.
