KEY WORDS Electrical burn - patellar ligament - semitendinosus tendon graft
INTRODUCTION
Injury to patellar ligament is one of the most common forms of tendon injury around
knee joint. The resultant extension disability from patellar ligament rupture poses
a significant surgical challenge to the surgeon. Rupture of patellar ligament may
be acute, which is commonly seen amongst young athletes, whereas chronic rupture is
seen in cases of systemic diseases such as rheumatoid arthritis, systemic lupus erythematosus,
chronic renal failure, hyperparathyroidism and diabetes mellitus.[1 ]
[2 ] Patellar ligament injury due to electrical burns is very rare, and we did not find
a single case of severe and bilateral injury after extensive literature search. Here,
we describe such a case and its unique mode of one-stage reconstruction, the first
of its kind described in literature.
CASE REPORT
An 8-year-old boy was admitted in the burn unit of our hospital with the history of
electrical burn injury to both of his knees when his lower limbs were entangled in
a live electric wire. On examination, there was third-degree burn on both knees anteriorly
with near full-thickness destruction of patellar ligament on both sides. The patient
was initially managed conservatively. After multiple debridements over next 4 weeks,
resultant defects on left side consisted of complete loss of patellar ligament, loss
of some part of the upper end of tibia due to osteomyelitis and exposure of the joint
space. On the right side also, patellar ligament was destroyed, tubercle of tibia
and lower pole of patella were exposed, but the joint cavity seemed to be intact [Figure 1 ].
Figure 1: Clinical presentation before surgery
At this point of time, as both patellar ligaments were destroyed, the young boy was
unable to extend his knees actively, thus he became wheelchair bound for locomotion.
Hence, to give the boy an opportunity to walk, reconstruction of patellar ligament,
at least on one side, became essential. For the right knee, reconstruction of patellar
tendon was done with an ipsilateral and looped semitendinosus tendon graft, and for
the grossly destroyed left knee joint, arthrodesis was done.
Both the joints were operated in the same sitting by two teams simultaneously. The
patient was operated in supine position under general anaesthesia. On the left-sided
knee joint, infected and necrotic cartilages and bone of the articular surfaces of
tibia and femur were removed; the bone ends were made raw and the exposed bones were
covered with ipsilateral pedicled medial gastrocnemius muscle flap with skin graft
over it.
On the right side, patellar tendon was reconstructed. Incision was made at pes anserinus.
Semitendinosus tendon was identified and divided at musculotendinous junction. Proximal
end of the divided distal part was delivered distally at incision site keeping the
insertion intact. Mid pole of the patella and the tibial tuberosity were drilled separately
to make a tunnel with a cannulated burr over a K-wire. Great care was taken so as
not to damage the articular surface of the patella. Thereafter, the semitendinosus
tendon was passed through patella from medial to lateral side and then passed in reverse
direction through the tibial tunnel and fixed to distal intact insertion of semitendinosus,
thus forming a loop; the tension of the reconstructed tendon was adjusted by sutured
in 30° of flexion of knee joint [Figure 2a and b ]. The whole reconstruction was covered with medial gastrocnemius musculocutaneous
flap.
Figure 2: (a and b) Reconstruction patellar tendon by semitendinosus tendon
On the left side, physiotherapy for hip and ankle joint was started on the 4th post-operative day. On the right side, knee joint was subjected to physiotherapy
from 2nd week onwards; he was given passive motion training, gradually increasing the range
of motion and later active movements from second post-operative week to subsequent
12 weeks. For both sides, gradual weightbearing such as standing with help was started
after 6 weeks postoperatively and walking with assistance started on 8th post-operative week.
On follow-up after 10 months, the functional outcome was evaluated using Insall modification
of Knee scoring (1993) system on the right side where the patellar tendon reconstruction
was done. We found no flexion contracture, no pain, no extension lag, normal alignment
(no varus or valgus deformity) of knee and total range of motion was 120°; with no
anteroposterior or mediolateral instability. Thus, total Knee Society score was 72
out of 100. The patient thus achieved a good range of motion of the right knee joint
[Figure 3a and b ] and walking without any assistance [Video 1].
Figure 3: (a) Full extension of the left knee. (b) 90° flexion of the left knee
DISCUSSION
Movement of knee joint is an integral part of human locomotion, and the patellar ligament
has a major contribution to it. Patellar ligament is a strong tendon to hold the patella
with the tibia so as to transmit the extensor force which provides the mechanism and
strength of the extensor mechanism of knee. For normal bipedal locomotion, at least
one knee joint has to be functional, without which it is not possible to walk unsupported.
In most instances of acute patellar ligament rupture, where the quality of tendon
is good, primary repair can be done. However, for chronic cases, where primary repair
is not possible, various different reconstruction techniques have been described such
as autologous semitendinosus alone[3 ] or with the gracilis graft,[4 ] allograft using the tendoachiles[5 ] or a contralateral bone-patellar-tendon-bone graft[6 ] and synthetic materials.[2 ] Although in our case, the injury was an acute one, primary repair was impossible
because there was a complete loss of patellar ligament which had to be reconstructed,
preferably with autologous tissue in view of the infected condition. As there was
wide area of soft tissue loss around the both knees, coverage of the knee was also
a great concern. As the left knee joint cavity was partially destroyed, extensor apparatus
reconstruction was not attempted in view of the possibility that pain-free full range
of movement, the joint might not be achieved. Furthermore, the upper end of tibia
was osteomyelitic, precluding the option of primary joint replacement.
As the right knee joint cavity was intact but with a completely destructed patellar
ligament, we attempted to reconstruct the right-sided patellar tendon so that there
is at least one well-functioning knee joint to give the boy a chance to walk. We used
an ipsilateral semitendinosus tendon graft because it is a robust tissue which can
restore the strength and stability of the extensor mechanism of the knee joint and
it has minimum donor site morbidity.[7 ] Furthermore, being an autograft, the ipsilateral semitendinosus tendon graft can
be used safely in infected condition such as in this case. There are essentially two
steps, harvesting and fixation. After dividing through the musculotendinous junction,
some authors also prefer to cut the distal insertion and harvest it as a free tendon
graft, which is then passed through the osseous tunnel made through the patella and
the tibial tuberosity, and sometimes, the tibial passage is additionally strengthened
using a bioabsorbable interference screw.[8 ] However, we followed the alternative method[9 ] where the distal insertion of the semitendinosus tendon was kept intact, and the
proximal cut end was tunnelled through the patella and tibial tuberosity making a
loop and sutured with itself. In view of existing infection, we used no metallic screw/wire
to fix the tendon with the patella or tibia. We believe that the intact insertion
of semitendinosus tendon with tibia is sufficient to hold it and preservation of distal
insertion can facilitate the healing process.[4 ]
Our case is unique in its presentation and management. No such case of bilateral destruction
of patellar tendon with extensive soft tissue injury around knee joints due to electrical
burn has been described in the literature. Neither has been described previously,
the reconstruction of patellar ligament in acute injury along with soft tissue coverage.
Here, the semitendinosus loop was used to re-establish the extensor mechanism of one
knee, along with gastrocnemius flap coverage to provide a one-stage reconstruction
of the knee joint to give the boy a chance to walk.
CONCLUSION
To conclude, bilateral patellar tendon injury by electrical burn is very rare. In
such cases, at least one patellar tendon needs to be reconstructed to achieve bipedal
locomotion. An autologous looped semitendinosus graft for reconstruction of patellar
ligament is a noble method, in such situations, which can restore the strength and
stability and function of knee joint. This procedure has minimal morbidity, achieves
full range of motions and develops enough strength for weightbearing so that patient
can walk without assistance.
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