Keywords
gastrocnemius muscle - tendon healing - dogs - Achilles tendon - augmentation technique
Introduction
Rupture of the Achilles tendon (AT) in dogs is mainly seen in medium-to-large breeds
and is commonly the result of acute trauma.[1] Dogs with complete AT rupture have a characteristic plantigrade stance.[1] AT injuries, involving rupture of the gastrocnemius tendon, are typically treated
surgically by primary tenorrhaphy and postoperative immobilization. The outcome of
surgical treatment is good to excellent, resulting in fewer re-ruptures, greater plantar
strength and return to normal function in 70 to 94.7% of dogs.[1]
[2]
[3]
[4] Immobilization methods include transarticular external skeletal fixator (TESF),
single-ring transarticular fixator construct, calcaneotibial bone screws, full casts
and splints.[2]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
[12] Current repair techniques involve excision of fibrous scar tissue and reattachment
of the common calcaneal tendon stumps with or without augmentation techniques.[6]
[7]
[9]
[13]
[14]
[15]
[16] Suture patterns commonly used are the locking loop (LL), three-loop pulley (3LP),
Bunnell-Mayer and Krackow.[7]
[14] The risk of gapping and suture pull-out are reduced by grasping and locking of collagen
fibres within the tendon using the LL suture pattern and by multiple divergent needle
passes using the 3LP suture pattern.[14] Gap formation greater than 3mm significantly reduces tendon strength after the repair,
leading to the deposition of scar tissue that is biomechanically inferior and prone
to re-rupture in the early postoperative period.[17] Another option, in combination with surgical repair, is the use of autogenous platelet-rich
plasma (PRP), which has been evaluated as a means of improving tendon healing in clinical
and laboratory models.[15] Augmentation techniques to strengthen the repair and shorten the postoperative immobilization
period are recommended. Methods used in dogs include autogenous tissue flaps derived
from the semitendinosus muscle, fascia lata, fibularis brevis, fibularis longus and
flexor digitorum lateralis tendons.[6]
[16]
[18]
[19]
[20]
[21] Allogeneic grafts of porcine small intestinal submucosa have also been used to augment
primary calcaneal tendon repair.[19] Synthetic implants such as polyethylene terephthalate, synthetic gastrocnemius tendon,
carbon fibre mesh and poly-4-hydroxybutyrate (P4HB) mesh, as well as application of
bone plates have been described for tendon repair.[15]
[22]
[23]
[24]
[25]
[26] In human medicine, the central gastrocnemius turnover aponeurosis flap technique
is less invasive than other methods and has been associated with a good outcome in
patients with AT rupture and gap formation.[8]
[27]
[28] Augmented repair techniques are associated with high tensile strength and a low
incidence of wound complications in human patients.[8]
[27]
[28] The use of the central gastrocnemius turnover aponeurosis flap technique has not
been described in dogs but was recently reported in one cat.[29] The aim of this case report was to describe the central gastrocnemius turnover aponeurosis
flap technique, for the treatment of subacute complete AT rupture with a moderate
residual intraoperative gap between the two tendon stumps in a dog.
Case History
A 9-year-old, 24 kg, intact male, German wirehaired pointer was referred 20 days after
the onset of left hindlimb lameness, caused by sharp force injury during a hunting
event. The dog had been treated conservatively until the time of referral. Physical
examination revealed non-weight-bearing lameness and a plantigrade stance in the left
hindlimb, which had a partially healed wound in the distal third of the caudal tibia
and swelling of the hock. The dog was sedated with intravenous dexmedetomidine (0.003 mg/kg;
Dexdomitor, Zoetis S.r.l. Rome, Italy) and methadone (0.2 mg/kg; Synthadon, Animalcare
Ltd, York, United Kingdom). Radiographic and ultrasonographic examination revealed
a complete subacute tear of the AT. Surgical repair was necessary and general anaesthesia
was induced with propofol (3 mg/kg; Propofol, Ecuphar Italia S.p.A.) and maintained
with isoflurane (IsoFlo; Aesica Queenborough Limited, Kent, United Kingdom) in oxygen.
Cefazolin (22mg/kg; Cefazolina Dorom, Teva Pharma, Milano, Italy) was administered
prophylactically before surgery. The dog was placed in sternal recumbency with the
tarsocrural joint in complete extension, and the affected hindlimb was aseptically
prepared. The skin was incised caudolaterally to expose the complete tendon rupture
located ∼ 2 cm from the calcaneal insertion. The proximal and distal portions of the
common calcaneal tendon stumps were debrided to remove fibrous tissue, resulting in
a 2.4 cm gap between the two stumps of the tendon. The gap was reduced to 7 mm by
combining a 3LP suture pattern with a LL suture pattern using 2 metric polypropylene
(Prolene, Ethicon Inc., Somerville, New Jersey, United States) suture material. The
skin incision was extended proximally to ∼ 2cm from the stifle joint. A combination
of blunt and sharp dissection was used to free a 3 cm (length) × 1.5cm (width) section
of the proximal part of the gastrocnemius aponeurosis that was folded 2.5 cm distally
to cover the tenorrhaphy and sutured using 3 metric polydioxanone (Polydioxanone PDS
Somerville, New Jersey, United States) suture material in a simple interrupted pattern.
The desmotomy in the proximal section of the gastrocnemius tendon, where the flap
was obtained, was repaired with the same suture material (3 metric PDS) in a simple
continuous suture pattern[8]
[27]
[28] ([Fig. 1]). The subcutaneous tissues and skin were closed routinely. A type II free-form methyl
methacrylate TESF was placed with the tarsus in extension at 145 degrees.[10] Five positive-profile centre-threaded pins (Alcyon Italia S.p.A., Cuneo, Italy)
were placed through the tibia in a proximal to distal direction and extended through
the tarsal bone and proximal metatarsal bones. The pins were bent to a 90-degree angle
and were secured with orthopaedic cerclage wire (IMEX Veterinary, Inc., Texas, United
States) and methyl methacrylate connections (Acrylx, IMEX Veterinary, Inc.). The dog
was discharged 1 day postoperatively and the owner was instructed to restrict the
activity of the dog. Postoperative treatment included amoxicillin and clavulanic acid
(12.5 mg/kg, q12h; Synulox, Pfizer, Rome, Italy) for 7 days and meloxicam (0.1 mg/kg,
q24h; Metacam, Boehringer Ingelheim, Germany) for 14 days, as well as cleaning (q12h)
of the TESF pins. Re-evaluations were done at 14, 45 and 55 days and 6 and 12 months
postoperatively. Ultrasonographic examination of the large haematoma seen at the time
of presentation ([Fig. 2A]) showed gradual organisation from 45 days onward ([Fig. 2B–D]). Gradual healing of the sutured tendon ends was also seen via ultrasonography.
The TESF was removed 45 days after surgery, but the activity level of the dog was
restricted for another 10 days. There was mild lameness that persisted until 55 days
after surgery, but no major complications were reported. Minor complications were
swelling and skin irritation associated with the TESF. Six months after surgery, the
dog was in good general health and ultrasonography showed further improvement in the
organisation of the AT as evidenced by changes in its echotexture. Re-evaluation 6
and 12 months after surgery revealed no signs of lameness, and the dog had returned
to its previous use as a hunting dog 6 months postoperatively.
Fig. 1 Intraoperative technique description. Caudolateral incision. (A) Exposure of the Achilles tendon stumps. (B) Primary tendon repair (after debridement) using three-loop pulley and locking loop
suture patterns with a residual gap. (C) Identification and isolation of the gastrocnemius tendon aponeurosis section. (D) The free aponeurosis of the tendon was folded over the defect distally (E) and sutured in a simple interrupted suture pattern to cover the tenorrhaphy (thin
arrows) (F). The desmotomy in the proximal part of the gastrocnemius tendon, where the flap
was obtained, and was closed with the same suture material in a simple continuous
suture pattern (thick arrows) (G).
Fig. 2 Preoperative and postoperative ultrasonographic examinations. (A) Time of presentation: The gap between the tendon stumps is visible as a large, hypoechoic
and well-marginated area in the Achilles tendon (blue arrowhead). There is a clear
focal disruption of the fibre pattern at the level of the lesion. A more normal fibre
pattern is visible in the stump ends. (B) Forty-five days postoperatively: The hypoechoic lesion is smaller (blue arrowhead),
and a more structured fibre pattern is evident in the gastrocnemius tendon (G) and
common calcaneal tendon (CCT). (C) Six-month re-evaluation: The fibre pattern of the calcaneal tendon (CT)(*) is slightly
more homogeneous and the hypoechoic lesion is less well defined and more echogenic
(blue arrowhead); a hypoechoic portion is still evident proximally (#). (D) Twelve-month re-evaluation: The lesion is smaller and has increased in echogenicity
(blue arrowhead) with poorly defined margins, but the overall fibre pattern of the
CT (*) is still moderately abnormal. Pr: proximal part of tendon; Ds: distal part
of tendon.
Discussion
The prognosis of surgical repair of AT rupture in dogs is generally considered good
to excellent.[2]
[5]
[7] However, the prognosis for return to work or to vigorous athletic activity is fair
to poor[18]; only one report found that the majority (71%) of working dogs returned to full
or substantial levels of work after surgical repair,[4] which was in agreement with the outcome of the present case. Although many techniques
have been used successfully, no single technique has been shown to significantly reduce
complications or shorten the time to optimal limb function.[5]
[7]
[8] Surgical repair is aimed at providing sufficient strength to resist gap formation
at the anastomosis site and support the tendon during the healing process.[5]
[7]
[13] The 3LP and the LL suture patterns have both been advocated for the repair of transected
round or semi-round tendons in dogs.[7]
[13]
[16]
[17] In one study, a modified 3LP suture pattern was found to be superior to the LL technique
for reattaching canine tendon to bone and for reducing gap formation.[13] Barbed polypropylene suture material did not appear to provide a major benefit when
used in a modified 3LP suture pattern.[22] An in vitro canine gastrocnemius avulsion model showed that two Krackow sutures were better able
to resist 3mm gap formation and load to failure than the 3LP suture pattern.[14] Schulz and et al described the use of a loop-suture tenorrhaphy for treating common
calcanean tendon injuries in dogs. That procedure used autogenous leukoreduced PRP,
injected into the site of tendon repair or delivered in a collagen sponge soaked with
PRP, when a gap remained in addition to augmentation using a GalaFLEX P4HB mesh.[15] The fibre loop was chosen in that case series for its biomechanical properties and
ease of application, although the braided nature of the material may increase the
risk of infection.[15] The efficacy of PRP in surgical repair of AT injuries in humans and dogs is not
clear and further studies are needed. In the present case, the use of the 3LP and
LL suture patterns did not completely eliminate the gap between the tendon stumps.
Gap formation can significantly delay tendon healing, leading to disorganized and
non-uniform collagen fibril alignment at the repair site with deposition of mechanically
inferior scar tissue.[13]
[17] One study showed that the addition of a continuous epitendinous suture pattern to
the 3LP and LL suture patterns eliminated small gaps between the tendon ends and increased
failure loads of both repair methods more than twofold.[16] To our knowledge, those techniques have not been used in cases with a wide, non-reducible
gap, such as the 7 mm gap in the present case. Further studies are required to determine
healing times as well as acquisition of adequate strength of the AT repair in cases
with a wide gap. It is possible that the additional suture passes of the epitendinous
pattern could interfere with the blood supply to the tendon.[16] We instead chose an augmentation technique to strengthen and support the repair,
to reduce the risk of adhesions, to shorten the postoperative immobilization period
and to decrease the risk of a revision surgery. Free allogenous and autogenous grafts
undergo rapid degradation and acquisition of adequate tendon strength depends on ingrowth
of host tissue.[19] The use of an autogenous flap from the semitendinosus muscle, fascia lata or fibularis
brevis, fibularis longus, or flexor digitorum lateralis tendons[6]
[18]
[19]
[20]
[21] provides mechanical protection as well as a good blood supply but increases the
invasiveness of the surgical procedure by necessitating a large surgical field. Synthetic
implants and application of bone plates have been described which provide the best
tensile resistance but may incite foreign body reactions and increase the risk of
infection, adhesions, migration and possible revision surgery.[15]
[23]
[24]
[26] All these techniques yielded good clinical results in dogs when used for repair
of tendon lesions greater than 2 cm in length and associated with extensive tissue
trauma. A central gastrocnemius turnover aponeurosis flap technique was shown to be
a useful adjunct to conventional suture repair of large defects in humans and in a
cat with AT rupture.[8]
[27]
[28]
[29] After conventional primary repair, a central aponeurotic tendon flap is isolated
proximally, folded distally to cover the defect and extends ∼ 2.5 cm beyond the rupture
site. This tendon flap technique improves mechanical strength and biomechanical stability
of the primary repair, reducing the risk of adhesions and re-rupture.[27]
[28] This technique has been used in human medicine for repair of mid-tendon lacerations
of less than 2.5cm in length, which are covered with the freed aponeurosis of the
tendon.[8] The same procedure was chosen in the present case because we felt it provided a
more durable support to the repair compared with free allogenous and autogenous grafts
that undergo rapid degradation.[19] It is also less invasive than autogenous flaps despite having a less robust vascular
supply compared with the flexor digitorum lateralis tendon and semitendinosus muscle,[18] and the risk of foreign body reaction, adhesion formation and revision surgery was
considered low.[15]
[23]
[24]
[25]
[26] For 2 to 3 weeks after surgery, the repair is entirely dependent on the suture when
augmentation is not done.[5]
[17] Postoperative immobilization is recommended during this time to prevent suture failure
or pull-out and to promote collagen deposition and fibril alignment,[5]
[7] which impart strength to the repair site.[7] Different methods of immobilization have been described but no method has been shown
to be superior with respect to complication rate, duration of immobilization, recovery
time and functional outcome.[2]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
[12] A minimum of 6 to 10 weeks of immobilization is recommended to facilitate healing
of the AT. However, this time should not be exceeded because of the risk of complications
associated with the method of immobilization.[4]
[5] Prolonged recovery is often associated with major complications, including re-rupture
of the tendon.[4]
[5] A type II free-form methyl methacrylate TESF was chosen for tarsocrural joint immobilization
in the present case. It was removed 6 weeks postoperatively to avoid major complications
associated with swelling and skin irritation around the most proximal pin in the tibia.
The activity level of the dog was restricted until the third postoperative examination,
at which time a gradual increase was allowed based on the results of ultrasonography.
Long-term clinical and ultrasonographic re-evaluations, 6 months postoperatively,
showed normal gait and a return to the previous activity level as well as good healing
of the AT with no adhesion formation. However, the echogenicity and echotexture of
the fibrillary pattern of the injured tendon were still abnormal 6 and 12 months after
surgery. Restoration of the normal homogeneity of collagen fibres may take several
years.[30] In conclusion, a central gastrocnemius turnover aponeurosis flap repair can be used
in dogs with complete AT rupture with or without a mid-tendon residual gap. Further
studies are required to determine whether this procedure is suitable on a larger scale
for the repair of common calcaneal tendon rupture in dogs of varying weight, age and
activity level as well as in injuries with large gaps.
