Keywords
open knee injury - traumatic loss of extensor mechanism - transplantation of extensor
mechanism - allograft - patella
Medical History
An 18-year-old female suffered a serious motorcycle injury in 2021 when she collided
with a oncoming vehicle at high speed out of town. Among other injuries, the motorcyclist
sustained a severe type 3 extremity trauma (Gustilo-Anderson type IIIB) on the left
side from the accident which included a multi-fragment femoral shaft fracture, open
knee joint injury with the loss of anteromedial soft-tissue coverage of the joint,
subtotal loss of the knee extensor mechanism with partial loss of the quadriceps and
patellar tendons, parts of the patella and anterior tibial head fracture. After receiving
initial care in another hospital including placement of a VAC device and an external
fixation device extending beyond the knee joint, a second-look procedure was carried
out prior to the necessary reconstruction surgery, which also confirmed multibacterial
wound infection (Bacillus cereus, Enterococcus faecalis, Kluyvera intermedia). The
patient was then transferred to our department for
further treatment.
Findings
On transfer to our department, examination showed pronounced ventral soft-tissue defect
of about 25 × 15 cm in the area of the anteromedial thigh and knee covered by a vacuum-assisted
wound dressing, previously confirmed trauma-related knee joint infection, and an external
fixation device extending beyond the knee joint (s. [Fig. 1]). Imaging confirmed the diagnosed bony defects mentioned above. Duplex sonography
and CT angiography performed in the context of emergency vascular surgery found no
further accident-related vascular damage except for complete left popliteal vein thrombosis.
There were no peripheral sensorimotor losses with the exception of defect-related
failures.
Fig. 1 Clinical (a, b) and radiological (c, d, e) images following transfer of the patient to our department.
Treatment and Course
The interdisciplinary extremity board of our institution decided to start treatment
by resolving the infection and repairing the soft-tissue defect by carrying out a
free latissimus dorsi flap-plasty together with a split-thickness skin graft. This
would then be followed by temporary reconstruction of the extensor mechanism by performing
hamstring tendon plasty.
During the third-look operation (s. [Fig. 2]), foreign bodies still present in the wound were entirely removed, and local antibiotics
were administered after repeat debridement and the taking of bony and soft-tissue
samples. The above-described flap reconstruction with screw osteosynthesis of the
tibial head and reconstruction of the extensor mechanism using a semitendinosus tendon
was carried out 9 days after transfer of the patient to our department. Surgery was
done under antibiotic therapy consisting of piperacillin/tazobactam to combat antibiotic-resistant
bacteria and with repeat temporary placement of a vacuum-assisted wound closure system.
Macroscopic examination showed no signs of infection and preservation of the cranial
superior pole of the patella. This subsequently healed well, allowing the remaining
superficial skin defects to be covered with split skin grafts. Treatment of the femoral
fracture was changed from an
external fixation device to osteosynthesis surgery with placement of an antegrade
intramedullary femoral locking nail. As healing continued to progress well and partial
loading of the left lower extremity became possible, the patient was discharged home
on crutches with oral antibiotic therapy consisting of amoxicillin/clavulanic acid
at 5 weeks after admission to our department.
Fig. 2 Clinical (a) and radiological (b, c) images taken during third-look surgery following osteosynthesis of the accompanying
femoral fracture.
A wound healing disorder with prolonged wound secretions developed around the area
of the knee joint covered by the flap, making repeat revision surgery necessary at
3 weeks after discharge. Massive re-infection of the knee was detected after lifting
of the knee flap, with fracture-associated infection of the tibial head accompanied
by septic arthritis of the knee. Treatment necessitated carrying out extensive debridement
of the knee joint and complete resection of the bony remnant of the patella and the
remnants of the quadriceps and patellar tendons including the semitendinosus plasty
and the removal of both screws at the tibial head (s. [Fig. 2]). Antibiotic-loaded ceramic bone replacement material was inserted. No microorganisms
were detectable while the patient was still taking antibiotics and she received further
antibiotics administered intravenously. The complete loss of the knee extensor mechanism
including the patella and
its adjoining quadriceps and patellar tendons made it necessary to decide on the further
approach to treat the knee joint in this young female patient. In consultation with
the patient, the decision was made in the interdisciplinary extremity conference to
implant a fresh frozen extensor mechanism allograft which included a patella with
adherent quadriceps and patellar tendons and a tibial tuberosity bone block after
controlling for infection.
After switching to ampicillin/sulbactam, antibiotic therapy was changed again to oral
therapy with amoxicillin/clavulanic acid. The infection was fully resolved after a
total of 14 weeks of antibiotic therapy with only partial loading of the leg permitted
and the knee joint immobilized with a thigh splint.
During follow-up, lab tests for infection parameters were unremarkable; wound and
skin lesions continued to heal as expected, the flapplasty healed, and joint puncture
found no suspiction of infection, even after antibiotic therapy was discontinued.
These positive developments meant that finally, 5 months after the accident, the planned
reconstruction of the extensor mechanism using a previously carefully measured fresh
frozen extensor mechanism allograft (Cells + Tissuebank Austria, CTBA, Krems an der
Donau, Austria; s. [Fig. 3]) could be carried out. During the procedure, the flap was raised again and the knee
joint was inspected. The site was found to be free of infection, whereupon the extensor
mechanism allograft was implanted. As a prophylaxis against infection, the allograft
was soaked with vancomycin solution, similar to the procedure recommended for allogeneic
tendon allografts. The patella was then positioned under X-ray
control at the correct level compared to the contralateral side to match the Insall-Salvati
ratio of the opposite leg, and a bony bed was created at the tibial tuberosity for
press-fit implantation of the tuberosity bone graft at the transplant using an oscillating
saw. The bone graft was positioned in an anatomically correct position and additionally
fixed with 2 parallel 3.5-mm cortical screws using the lag screw technique. This was
then followed by careful alignment of the patella to the femoral trochlear groove
with the knee joint in an extended position, and stitching of the quadriceps tendon
into the remnant of the quadriceps tendon stump or the distal muscular part of the
quadriceps muscle was carried out using the onlay technique and slow-resorption sutures.
The operation was completed by primary wound closure which included the raised edges
of the flap. The knee joint was immobilized again with a dorsal splint. Postoperative
X-ray images show correct positioning of the
patellofemoral joint with anatomical repositioning of the tibial bone graft in the
region of the tibial tuberosity using screw osteosynthesis.
Fig. 3 Standard X-ray images of the allograft before (a after additional coating with vancomycin powder), during (b, c) and after transplantation (d, e).
After an uneventful course in hospital (s. [Fig. 4]) which included 14-day prophylactic i.v. antibiotic coverage with ampicillin/sulbactam,
prophylactic antibiotic therapy was switched to oral amoxicillin/clavulanic acid after
intraoperative samples were found to be negative. The patient was discharged home
with instructions to keep the operated extemity immobile for 4 weeks and for partial
loading not to exceed 20 kg.
Fig. 4 Clinical image (a, b) 14 days after latissimus dorsi flap-plasty.
At regular follow-up visits, the patient was gradually approved for increased loading
and movement: 6 weeks of passive loading and movement were followed by a further 4
weeks of active loading and movement. Antibiotic therapy was discontinued after a
total of 12 weeks of prophylactic antibiotic therapy following transplantation of
the allograft. Active mobility of the left knee joint was now 0–5–45° (max. extension/flexion).
After the patient successfully returned to work as a bank clerk and continued physiotherapeutic
exercise, her mobility increased to 0–0–65° (extension/flexion). The patient was now
fully mobile and no longer required crutches, the knee was fully weight-bearing and
only a slight limp was still apparent. Control X-ray imaging after 4 months showed
continued correct positioning of the patellofemoral joint and implanted extensor mechanism
allograft, and good centering of the patella on axial imaging of the patella at 30°
flexion with good bony integration of the tibial bone block in the proximal tibial
metaphysis (s. [Fig. 5]).
Fig. 5 Control X-ray imaging carried out 4 months after transplantation with adequate integration
of the tibial bone graft (a, b) and good centering of the patella (c).
14 days after her last presentation as an outpatient and just 15 weeks after transplantation
of the extensor mechanism allograft, the patient participated in a car race as a co-driver
on part of the race circuit. During a collision she sustained a proximal lower leg
fracture near the bony bed of the implanted tibial bone block. Surgical treatment
of the fracture consisted of closed repositioning and LISS plate osteosynthesis using
a minimally invasive technique and prophylactic antibiotic therapy (s. [Fig. 6]).
Fig. 6 Conventional X-ray imaging before (a, b) and after (c, d) surgical treatment of a traumatic peri-implant proximal tibial fracture.
Axial alignment with good bony consolidation of the fracture were already present
3 months after carrying out osteosynthesis. Active mobility of the left knee joint
at the time was already 0–0–60° (extension/flexion).
At 24 and 19 months, respectively, after implantation of the extensor mechanism allograft
and osteosynthesis of the proximal tibial fracture, active mobility (extension/flexion)
was 0–0–80°. Contrast-enhanced ultrasonography carried out 2 years after transplantation
of the extensor mechanism implant showed periostal perfusion of the bony components
of the allograft (s. [Fig. 7]). The patient currently has no symptoms and is very satisfied with the functional
and clinical results (s. [Fig. 4], []). Her KOOS symptom score (KOOS: Knee Osteoarthritis Outcome Score) is 68, KOOS pain
score is 83, and KOOS-ADL score (Activities of Daily Living) is 91. Her EQ-5D quality
of life score is 0.788 and her IKDC score is 56.3% (IKDC: International Knee Documentation
Committee). The patient was also advised to request extended antibiotic prophylaxis
if
she had any dental or other surgical procedures.
Fig. 7 Clinical imaging (a, b) and sonographic confirmation of the integration (c) of the tibial implant 24 months after transplantation. Lateral X-ray shows no signs
of patellar necrosis (d).
Gait two years after transplantation of the allograft.Video
Discussion
The case history presented here shows a special reconstruction procedure in a patient
with complete loss of the extensor mechanism following initial severe soft-tissue
trauma followed by infection. Initial treatment required coverage of the soft-tissue
defect and control of the infection. To manage such complex cases as well as bone
and joint infections and bony defect situations, our institution set up an interdisciplinary
“muskuloskeletal board” in which both periprosthetic [1] and fracture-associated infections [2] are discussed.
After successful soft-tissue coverage and elimination of the infection, the question
arose about the further treatment options due to the loss of the extensor mechanism.
Leaving the situation “as is” without a further surgical intervention as would be
the case for a “classic” patellectomy was not appropriate in this case, as the additional
loss of the quadriceps and patellar tendons meant that the patient would have no extensor
function in that knee, which would probably result in gait instability. The alternatives
were arthrodesis of the knee or implantation of an extensor mechanism allograft. In
view of the young age of the patient who was just 18 years old, her high level of
compliance, and her wish for knee mobility, we decided to attempt an individual curative
approach and carry out extensor mechanism allograft surgery using a fresh frozen transplant.
There are only a few descriptions of extensor mechanism allograft implantations in
the literature, usually presented in the context of case reports or individual case-control
studies [3]
[4]
[5]
[6]
[7]. Transplantation of an entire extensor mechanism is a known procedure primarily
carried out in the context of managing complications of knee endoprosthesis surgery
[3]
[4]
[5] and performed as a last resort in cases where other reconstruction options have
either been exhausted or are otherwise no longer possible. There are some known, small,
very much
location-dependent case series in the field of tumor orthopedics [6].
Even though the reported satisfaction rates are adequate, a decreased range of movement,
muscular weakness, and restricted activities of daily life are often present, even
in cases where healing proceeds as expected. Complication rates of up to 50% have
been reported with follow-up periods of more than 5 years in some cases [3]
[6]. Combined extensor and flexor deficits often coincide with limitations in the total
range of movement of about 80°, although better clinical results have been observed
for knee joint prostheses [3]
[4]. There are no data on quality-of-life scores for these patients.
In our case, the clinical result after a follow-up of 24 months was very satisfactory
for the patient, despite her sustaining another traumatic fracture of the proximal
tibia after transplantation following a car accident on a race track. Overall, integration
and healing of the transplant without infection was remarkable; it followed implementation
of appropriate measures such as excluding persistent infection by carrying out joint
puncture shortly before implanting the extensor mechanism allograft and repeat postoperative
antibiotic therapy for several weeks. Good bony integration of the bony tibial allografts
was observed in the metaphyseal tibial area after just 3 months. The subsequent fracture
occurred in the context of direct violent impact trauma and should therefore not be
classed as a “pathological” fracture or a typical complication of allograft surgery.
The relatively young age of the patient and her good state of health certainly contributed
to the currently very
positive result of treatment. Nevertheless, potential re-infection of the graft, graft
necrosis and cartilage lesions in the femoral sulcus with subsequent arthrosis may
develop at a later stage. Immunosuppression, which is used for classic organ donations,
was and is not necessary as HLA sensitization has not been reported in the context
of fresh frozen allograft transplantations. This is because the manner by which fresh
frozen allografts are prepared prevents HLA sensitization and includes different chemical
wash steps to clean cancellous bone and mechanical preparation of the tendinous parts
of the transplant to free them from extra-tendinous components prior to cryopreservation,
as was done to the allograft used in this patient.
