Keywords
knee - dislocation - chronic - neglected - neurovascular - treatment
Introduction
Traumatic knee dislocation is a severe although rare injury, evaluated by 0.02% to
the skeletal trauma, albeit the true incidence is unknown as often reduction of the
dislocation is performed at the scene of the trauma. It is often caused by a severe
trauma, although rare cases have been described due to nonsevere traumas, such as
hyperextension.
Knee dislocation is an orthopaedic emergency because of the possible capsular ligamentous,
neurovascular injuries, compartment syndrome, or open lesions. The incidence of neurovascular
damage is estimated by 20% of cases. Femoral nerve palsy and popliteal artery early
disruption are the most frequent early complications with a variable incidence of
10 and 25%, respectively. The most common late complications are instability and limping.[1]
Knee dislocation is classified, according to tibial displacement, as posterior, medial,
and lateral, with a rotatory and anterior component as the most frequent complication.[2] It requires an emergency treatment to achieve immediate and stable reduction and
to treat any associated injury, especially neurovascular ones. Surgical treatment
is necessary in irreducible dislocations, in open injuries, and when the neurovascular
structures are compromised.
Rare cases of inveterate and chronic dislocation of the knee have been described;
these are difficult to classify because of the variability of lesion patterns and/or
of the associated injuries.[3] The case that we describe herein shows many peculiarities concerning the etiology,
the pathologic features, and the absence of neurovascular injuries caused by the injury
itself, but with progressive adaptation of the neurovascular bundle to the pathological
condition without additional late damage.
Case Report
This is the case of a 69-year-old woman, weighing 130 kg, wearing a knee brace on
her right lower limb, due to deformation, instability, and load-dependent pain. She
had an ambulatory range limited to a few steps and therefore made use of a wheelchair.
She accidentally fell at home and hurt her right knee, with a reported trauma in hyperextension.
X-rays revealed a subluxation with articular diastasis and a concomitant detachment
of the apex of the fibular head. This was the only lesion identified and treated by
the orthopaedic surgeon at the time of the first visit.
Her leg was placed into a knee plaster cast with no weight bearing for 30 days. Once
the cast was removed, X-rays revealed the persistence of an articular diastasis and
severe anterior subluxation of the tibia. She was prescribed an articulated brace,
rehabilitation, and progressive recover of weight bearing. Doppler ultrasound of the
lower limbs was negative, and magnetic resonance (MR) revealed no conditions worthy
of urgent treatment. No surgical treatment was suggested and the patient was left
with her articular disease, to which she adapted without any further complications
([Fig. 1]). She came to our attention 3 years after the trauma, with an X-ray that showed
a total and inveterate dislocation of her right knee. MR exam documented severe alterations
of the soft tissues, although there was no apparent discontinuity of extensor apparatus.
Computed tomography angiography with contrast medium was highly significant and showed
the unexpected adaptation of the neurovascular structures to the total dislocation
([Fig. 2]).
Fig. 1 Imaging after the plaster has been removed. (A) Persistent joint diastasis and onset of a posterior subluxation of the femur can
be seen on X-rays. (B) Magnetic resonance image shows integrity of the extensor mechanism.
Fig. 2 Imaging at 2-year follow-up. (A) X-ray shows complete anterior dislocation of the tibia. (B) Computed tomography angiography documents the dislocation and the kinking of the
popliteal vascular fascia in absence of significant distal stenosis.
At the clinical exam, the knee showed a severe multidirectional instability; the dislocation
was irreducible, but the patient showed 90 degrees of knee flexion and full active
extension, which confirmed the integrity of the extensor apparatus. There was tolerable
pain, only during active extension.
The arterial pulse was well perceivable at a popliteal level and distally at the level
of the dorsalis pedis and anterior tibial artery, with no sensory–motor impairment.
We proposed placing the limb in traction and performing a total joint arthroplasty
(TKA) subsequently. However, the patient refused the suggested treatment.
Discussion
Knee dislocation is a rare pathological condition that can be underestimated during
the emergency assessment; therefore, X-rays, examination of vascular and neurological
conditions, as well as a complete balance of articular injuries should be performed.
The immediate and stable closed reduction can lead to a remission of the neurovascular
compression. However, dislocation, or subluxation of the knee, can be undiagnosed
because of a diagnostic mistake at the time of the trauma, particularly in the absence
of neurovascular injuries, which usually lead to surgical treatment.
Taylor et al[4] reported good results with nonsurgical treatment. Conversely, Ríos et al[1] recently demonstrated better functional results with surgical approach. Nonoperative
treatment was associated with unsatisfactory results in 100% of the cases.
Chronic knee subluxation–dislocation is rare, as the severity of the injury always
leads to an early diagnosis and to appropriate treatment during the acute phase. Sisto
and Warren[5] described a single case of chronic knee dislocation, treated 24 weeks after the
acute injury with a reduction, and fixation with Steinmann crossed wires and pins.
The 2-year follow-up showed a pain-free stable and rigid knee (range of motion: 5–40
degrees).
In the case described herein, the mechanism of knee dislocation mechanism was quite
peculiar, as it was not caused by a violent trauma but by the acceleration of the
substantial body mass during the fall. Therefore, there was no real joint dislocation
at the time of trauma but a joint diastase with no immediate neurovascular injury.
The detachment of the apex of the fibula's head attracted the attention of physicians
that provided first aid, who neglected the more severe joint injury.
Also, unusual was the treatment both during emergency and follow-up; in fact, once
the plaster was removed, the radiographic examination showed a worsening of the joint
condition and no surgical solution was suggested.
Over the years, the load on the knee dramatically led to the dislocation becoming
chronic and at the same time, it determined a slow adaptation of the popliteal neurovascular
bundle, with an adaptive elongation that guaranteed adequate vascular supply to the
leg, without any ruptures or occlusions.
The treatment of neglected knee dislocation may be performed by arthrodesis or arthroplasty.[6] In this case, given the age of the patient (69 years), the compromised general health
status and the modest functional needs, implanting a hinged TKA after a gradual reduction
of the dislocation with the Ilizarov's apparatus appeared to be appropriate. Arthrodesis
is not indicated in this case, whereas it is instead necessary in the presence of
severe instability, paralysis, neuropathy, infections after TKA, and damage to the
extensor mechanism. Although arthrodesis is a valid option, it can cause persistent
knee pain, lower back pain, and difficulty in driving, with considerable limitations
in resuming working activities.[5]
Unfortunately, the patient refused to undergo two surgeries, and therefore, this case
is described as having no surgical solution.
