SYMPOSIUM: COMPLEX KNEE LIGAMENT SURGERY
Articulated External Fixator for Treatment of Complex Knee Dislocation
Maurilio Marcacci MD, Stefano Zaffagnini MD,
Tommaso Bonanzinga MD, Andrea Pizzoli MD,
Mario Manca MD, Enzo Caiaffa MD
Published online: 12 October 2011
? The Association of Bone and Joint Surgeons1 2011
uncommon injury caused by violent trauma that can result
in long-term complications, such as arthrofibrosis, stiffness,
instability, and pain. Perhaps owing in part to its rarity,
treatment of this injury is controversial. We therefore
Knee dislocation is a severe but relatively
describe a treatment approach for these complex cases
involving a novel dynamic knee external fixator.
Description of Technique
reconstruction when possible and/or repair of other asso-
ciated lesions. At the end of the surgical procedure, the
surgeon applied an external fixator that reproduced normal
knee kinematics, allowing early motion exercises and
reducing the risk of joint stiffness while protecting the
bony and soft tissue structures involved in the repair during
the first healing phase.
Patients and Methods
We retrospectively reviewed eight
patients treated with this approach, four of whom had the
PCL reconstructed and four of whom had only associated
injuries reconstructed. We evaluated all patients with
clinical scores (subjective International Knee Documenta-
tion Committee form, Lysholm score, and Tegner level),
physical examination (objective International Knee Docu-
mentation Committee form), and KT-1000TMarthrometer
for AP laxity. Minimum followup was 10 months (mean,
26 months; range, 10–45 months).
One patient had manipulation under anesthesia.
The median Lysholm score was 76, Tegner level was 4,
and subjective International Knee Documentation Com-
mittee was 73. All patients recovered to their preinjury
work activity, except one unemployed patient. Stability
was normal or nearly normal in five patients; the mean
side-to-side difference in AP displacement with manual
maximum force was 2.9 mm.
This approach with an external fixator
allowed staged reconstruction and early motion and pro-
vided reasonable stability, ROM, and activity level at
followup in patients with complex injuries.
Level of Evidence
Level IV, therapeutic study. See
Guidelines for Authors for a complete description of levels
We performed open PCL
One of the authors certifies that he (MM) has designed a device used
in this study and a member of his immediate family has or may
receive payments or benefits, in any 1 year, of less than $10,000 from
a commercial entity (Citieffe, Calderara di Reno, BO, Italy) related to
Each author certifies that his or her institution approved the human
protocol for this investigation, that all investigations were conducted
in conformity with ethical principles of research, and that informed
consent for participation in the study was obtained.
This work was performed at the Rizzoli Orthopaedic Institute,
M. Marcacci, S. Zaffagnini (&), T. Bonanzinga
3rd Orthopaedics and Traumatologic Clinic, Rizzoli Orthopaedic
Institute, Via Pupilli 1, 40136 Bologna, Italy
M. Marcacci, S. Zaffagnini, T. Bonanzinga
Biomechanics and Technologic Innovation Laboratory,
Codivilla-Putti Research Center, Bologna University,
Via di Barbiano 1/10, 40136 Bologna, Italy
Department of Orthopaedics, C Poma Hospital, Mantova, Italy
Department of Orthopaedics, Versilia Hospital USL12,
Viareggio Toscana, Italy
Department of Orthopaedics, Taranto Hospital, Taranto, Italy
Clin Orthop Relat Res (2012) 470:869–876
and Related Research®
A Publication of The Association of Bone and Joint Surgeons®
A knee dislocation is a severe injury caused by violent
trauma and can result in long-term adverse effects that
impair the patient’s ability to return to physical work or
recreational activities. The incidence of this injury is quite
low, comprising less than 0.2% of orthopaedic injuries .
Recently, the Knee Dislocation Study Group defined this
type of injury as a traumatic lesion resulting in the rupture
of at least three of the four major ligaments of the knee and
leading to a substantial degree of functional instability .
However, associated injuries, such as knee fractures and
vascular and neurologic injuries, make it challenging to
define the wide spectrum of knee dislocations.
Strategies for the management of knee dislocation are
varied and controversial [18, 19, 40]. Nonoperative treat-
ment generally results in stiff knees with limited ROM and
low functional scores [1, 16, 27, 37]. Many surgeons
therefore recommend surgery to repair or reconstruct all of
the involved stabilizing structures [2, 8, 9, 13, 14, 16, 20–
22, 25, 31, 32]. However, even after surgery, some residual
impairment of function is still expected, with an incidence
of complications, such as stiffness or failure of some
reconstructed structures, between 21% and 61% .
Many authors advocate the use of aggressive rehabili-
tation to avoid postoperative stiffness despite the risk of
placing excessive force on the graft tissue [5, 12, 13, 24,
36]. In recent papers, high subjective scores, reasonable
stability, and a return to activities were achieved by per-
forming simultaneous reconstruction of the ACL and PCL,
as well as medial or lateral structures, followed by an
aggressive rehabilitation protocol [5, 12, 13].
neurovascular injuries or fractures, there is no agreement on
treatment,and given the infrequentand variednatureofthese
injuries, it is difficult to standardize a treatment algorithm. In
these complex cases, reconstruction of all of the ligaments
combined with other additional surgery may be performed,
but sometimes a staged procedure is recommended.
We describe a treatment approach for these complex
cases that involves combining open surgery with a novel
dynamic knee external fixator (EF) (Fig. 1A) that repro-
duces the normal kinematics of the knee. This device
allowed forstagedreconstruction andearlymotionexercise.
It also reduced the risk of joint stiffness while protecting the
graft andotherbonyandsofttissuestructuresduringthe first
healing phase. We report eight patients with complex, high-
energy dislocations treated with our protocol.
This approach was for complex knee dislocation where all
of the four major ligaments of the knee were injured or
where associated lesions, such as knee fractures or neuro-
vascular injuries, coexisted. At the time of admission, all
patients had a history, physical examination, standard
radiographic evaluation, and MRI performed. The status of
the ligaments was documented and graded according to the
classification made by Schenck  and modified by others
[35, 39], which assessed the injury pattern and presence or
absence of associated knee fractures. Knee dislocations
without both cruciates involved are considered KD-I, with
both cruciates only KD-II, with both cruciates and medial
or lateral structures KD-III, with both cruciates and both
lateral and medial structures KD-IV, and if associated
fractures occur KD-V. Four knees were KD-V and four
were KD-IV. A complete examination of the neurovascular
status of the involved leg was also performed.
Fig. 1A–C (A) A photograph shows the novel dynamic EF. Diagrams show (B) how the EF reproduces the four-bar linkage model of the
cruciate ligaments and (C) the four-bar linkage model of the cruciate ligaments in a normal knee.
870Marcacci et al. Clinical Orthopaedics and Related Research1
Patients underwent an open reduction surgery with the
standard medial parapatellar arthrotomy and, when possi-
ble, a single-bundle PCL reconstruction using hamstrings
tendons. Concurrently, we reconstructed or repaired the
lateral and the medial structures if they were severely
damaged and internally fixed any associated fractures.
After PCL reconstruction and/or caring of the other asso-
ciated lesions, a dynamic EF (Citieffe, Calderara di Reno,
BO, Italy) designed by one of the authors (MM) was
applied using the following procedure (Fig. 2).
In certain patients, we modified this protocol because
associated lesions contraindicated the PCL reconstruction
and medial or lateral reconstruction/repair. These injuries
included associated tibial or femoral fractures compromising
the ability to perform the tunnels, wide knee exposure
increasing the risk of infection, and severe vascular injury.
In these patients, we surgically treated the associated
lesions but not the PCL or medial or lateral structures and
delayed the reconstruction of the injured ligaments.
The EF was designed to replicate motion based on a
four-bar linkage model of the knee . The hinge was
designed with a central body made of radiotransparent
material and a shaft and distraction ring nuts made of a
light titanium alloy. As per the four-bar linkage model, the
crossed position of the cruciate ligaments provided pos-
terior rollback of femoral condyle during knee flexion. The
device allowed knee flexion-extension motion and poster-
ior rollback, as in a normal knee with a rotational axis that
changes during flexion (Fig.1B–C). Internal-external rota-
tions that normally occur along the longitudinal axis were
fixed. The knee was allowed to move only in the sagittal
plane with a reduced ROM (0?–100?). The normal flexion-
extension axis of the knee is nearly parallel to the transe-
picondylar axis [4, 34]. In a preliminary in vitro study of a
cadaveric knee, we performed a kinematic evaluation of
the same knee without and with the EF applied and aligned
with the epicondylar axis. The data suggested, through the
ROM, the EF did not affect the tibial movement with
respect to the femur when compared with a normal knee
(Fig. 3). We did not, however, perform any studies with
incorrect EF placement. Therefore, we believed it impor-
tant to align the fixator axis with the knee flexion-extension
axis to reproduce the natural knee motion and avoid plac-
ing aberrant forces on the joint. This step was demanding
Fig. 2A–D (A) AP and (B) lateral radiographs show the knee
dislocation in Patient 3. (C) AP and (D) lateral radiographs show the
same knee after PCL reconstruction and the EF implant.
Fig. 3 A graph shows the movement of the tibia with respect to the
femur of a normal knee (NK) and of the same knee with our external
fixator (EF). This movement was evaluated by means of a navigation
system considering the anteroposterior (AP) and the proximodistal
(PD) displacement between the two bones during the ROM.
Volume 470, Number 3, March 2012External Fixator for Knee Dislocation871
because identifying the epicondyles was difficult .
Once we identified the lateral epicondyle by palpating the
lateral aspect of the knee, we marked it with a sterile
surgical marker. Then, we implanted a Kirschner guidewire
through the marked point under fluoroscopic control to
reproduce the transepicondylar axis. This Kirschner wire
was used as a reference for positioning the hinge. A hole in
the center of the EF allowed us to position the system
according to the transepicondylar axis as confirmed by the
implanted guidewire. We then inserted the first pin in the
lateral aspect of the femoral diaphysis with the knee flexed
at 90?. Flexion-extension movements of the knee were
performed to check whether the EF alignment allowed
unconstrained joint motion. Once the position was
checked, and depending on any possible associated lesion
of the tibia, we inserted a tibial pin on the medial side by
means of a half ring or directly on the lateral side to avoid
further damage to the involved leg, We then inserted two
more pins parallel to the previous one to gain additional
stability. The system also allowed joint distraction to pro-
tect from coexisting internally fixed or nondisplaced
Postoperative rehabilitation was started the day after
surgery with continuous passive motion from 0? to 100? for
the first week (Fig. 4). For the next 3 weeks, we allowed
patients active ROM with no motion restriction. Patients
weightbearing and isometric exercises the day after sur-
gery. This was true even for patients with fractures, as the
EF provided some distraction force to the joint. For
patients with associated fractures, we allowed partial
weightbearing at 30% of total body weight.
We removed the EF under epidural anesthesia 1 month
after surgery and tested the ROM and stability of the knee.
All patient presented knee flexion of at least 100? without
any extension deficit. In one patient, we performed further
ligament reconstruction not performed at the initial surgery.
The rehabilitation program was continued to achieve full
ROM and allow complete healing of the soft tissues
involved in the injury and open surgery. The program
included active knee mobilization, cycling, swimming, and
concentric exercises. Duration and intensity of the program
were customized according to the specific needs of the
patients. Fullweightbearing wasallowed 15or30 daysafter
EF removal depending on the associated fracture status.
Patients and Materials
We retrospectively reviewed the records of eight patients
with complex, high-energy dislocation treated with our
protocol (Table 1). Every patient sustained a dislocation as
a result of high-energy trauma and no patients sustained
bilateral knee dislocations. The mechanism of injury
involved a motorcycle crash, pedestrian struck by a vehi-
cle, pedestrian struck by a motorcycle, or an automobile
crash. No sports-related knee dislocations were included in
this study group. Minimum followup was 10 months
(mean, 26 months; range, 10–45 months).
In three patients, we observed and treated a unicondylar
tibial plateau fracture. These patients underwent internal
fixation with a gentle distraction obtained by the EF to
allow partial weightbearing. A patient who presented with
a combined patella fracture underwent the tension band
wiring technique, and in another, we treated a popliteal
artery lesion with bypass (Table 1).
We did not reconstruct the PCL in four patients. This
treatment strategy was necessary because fractures made
the PCL reconstruction impracticable due to structural
impairments (one), open injury with high risk of infection
Fig. 4A–B Photographs show postoperative rehabilitation with continuous passive motion starting from (A) extension to (B) about 100? of knee
872 Marcacci et al. Clinical Orthopaedics and Related Research1
(two), or severe injury of the popliteal artery (one). In these
patients, we treated the severe associated lesions during the
None of these four patients underwent further ligament
reconstruction before the followup evaluation as they had
reasonable knee stability. Of the four patients who under-
went PCL reconstruction at the time of EF application, one
underwent manipulation under anesthesia 2 months before
followup because of flexion limitation at 65?, and one
patient underwent an ACL reconstruction 5 months after EF
The patients underwent postoperative controls (1 and
3 months after EF removal) to check whether supplemen-
tary surgery was necessary. The final followup consisted of
clinical evaluation and a series of self-administered ques-
tionnaires, including the subjective International Knee
Documentation Committee (IKDC) form , Lysholm
score, and Tegner level . The patients were also asked
whether they had recovered their preinjury work activity.
Each patient underwent a physical examination by one of
the authors, who graded the results according to the
guidelines of the objective IKDC knee ligament standard
evaluation form . ROM of both knees was determined
with a goniometer and loss of flexion and extension was
determined relative to the uninvolved side. AP laxity was
determined with the KT-1000TMarthrometer (MEDmetric
Corp, San Diego, CA, USA) using the manual maximum
test, a reportedly discriminating and reliable test to evalu-
ate the side-to-side differences in AP laxity between the
knees [3, 15, 26].
At last followup, the median Lysholm score was 77, Teg-
ner level was 4, and subjective IKDC was 73. All patients
recovered their preinjury work activity except Patient 3,
who was unemployed before the trauma. Of these seven
patients, two were heavy workers while five were involved
in sedentary work activity (Table 2).
Based on the objective IKDC assessment, stability was
normal in one patient (Patient 5 who underwent a delayed
ACL reconstruction), nearly normal in four patients, and
abnormalinthreepatients. Ofthesethreepatients, Patients2
and 4 had abnormal AP laxity but had not undergone ACL
reconstruction. Patient 2 had a high body mass index (41.9),
and Patient 4 decided not to undergo surgery because of his
observed no loss of extension in these patients, while the
mean loss of flexion was 11.9? comparedto the contralateral
knee. The instrumented evaluation of the mean side-to-side
difference in AP displacement with manual maximum force
normal stability with respect to the IKDC evaluation and
KT-1000TMand a 5? loss of knee motion (Table 2).
We observed no infections related to the pins or to the
Strategies for treating knee dislocations havebeen varied and
controversial [18, 19, 40]. Several authors have reported
Table 1. Patient characteristics
Patient Sex Age at
Injured ligaments Associated
with EF implant
1Male 4745 32.2No ACL + PCL + MCL
NoNo PCL + MCL repair
2 Male42 33 41.9No ACL + PCL + MCL
NoPCL + PLC repair
+ internal fixation
3 Male20 10 22.4Yes ACL + PCL + MCL
No NoPCL + MCL repair
4 Male1818 20.9No ACL + PCL + MCL
5 Male 1826 21.3 NoACL + PCL Tibial
NoPCL + internal
6Male 27 2228.8 Yes ACL + PCL + MCL
7 Female45 20 27.5 NoACL + PCL + MCL
8 Male 20 3421.5Yes ACL + PCL + MCLPatella NoPatella TBW
EF = external fixator; MCL = medial collateral ligament; LCL = lateral collateral ligament; PLC = posterolateral corner; TBW = tension
Volume 470, Number 3, March 2012External Fixator for Knee Dislocation 873
and high subjective scores with single-stage surgery of
all involved stabilizing structures. However, these studies
knee dislocations and excluded open dislocations and
patients with vascular lesions and associated fractures. To
our knowledge, there is a lack of papers focused on complex
high-energy knee dislocations [16, 27]. We therefore
developed a treatment approach for these complex cases
involving a novel dynamic knee external fixator that repro-
duced closely the features of normal knee kinematics; the
device allowed staged reconstruction and early motion
exercise, reducing the risk of joint stiffness while protecting
the graft and other bony and soft tissue structures during the
first healing phase. We described the followup observations
of eight patients with complex, high-energy dislocations
treated with our approach.
This study had some limitations. First, we had a small
number of patients; however, knee dislocations are rela-
tively uncommon, and out of this wide spectrum of
injuries, we included only patients with complex knee
dislocations caused by high-energy traumas, which are
even rarer. However, our primary purpose was to describe
the approach. Second, because ours was a retrospective
review, we had no standard protocol for evaluation and
treatment before this study. Third, since we had no control
group of patients treated in another way, we compared our
results to the available literature, and owing to variability
in patient selection and methods, such a comparison was
only an approximation. Fourth, this system presented a risk
of infection related to the use of pins implanted close to the
reconstructed structures. However, we did not observe, in
our small series, any infection either related to the pin itself
or to the reconstruction procedure.
Table 2. Clinical results
ROM Loss of
at MMT (mm)
2 71 683C4
6 76 694B2
7 75 734B3
IKDC = International Knee Documentation Committee; MMT = manual maximum test (side-to-side difference).
Table 3. Literature comparison
Ohkoshi et al.
8 (9 knees) KD-III: 100%40.1 ± 16B: 77.8% Active: 0?–127?
2.3 ± 1.9
24–12091 (70–100)5.3 (3–7)2.6 (0.0–9.0)
et al. 
64 (24–108)83 (15–100)5 (0–9) 2.7 ± 3.7
et al. 
37Group A: 12
24 (14–41)A: 3?–118?
Group B: 25 B: 2?–120?
Marcacci et al.8 KD-IV: 50%
26 (10–45) 77 (62–96) 4 (3–7)A: 12.5%
* Values are expressed as mean or mean ± SD, with range in parentheses; IKDC = International Knee Documentation Committee.
874Marcacci et al.Clinical Orthopaedics and Related Research1
Comparing our findings with those of other studies was
difficult since the study populations often differed due to
the heterogeneity of this type injury (Table 3). Ohkoshi
et al.  reported on a series of eight patients (KD-III)
who underwent staged reconstruction: early PCL followed
by delayed ACL reconstruction. They gained full passive
ROM (0?–139.5?) in all knees. Those authors concluded
staged reconstruction minimized postoperative stiffness.
Their results confirmed the risk of arthrofibrosis and stiff-
ness was higher when both cruciate ligaments were
reconstructed at the same time [6, 7, 16, 17, 29, 30]. This
aspect was even more important when associated lesions,
such as neurovascular injuries, or fractures occurred.
Fanelli and Edson  reviewed a series of 35 patients,
including six with KD-IV dislocations. They reported
variable results: the Tegner score ranged from 3 to 7 and
the Lysholm score ranged from 70 to 100. They concluded
multiligament reconstruction did not require staged surgery
but suggested their procedure was less reliable for PCL
reconstruction, possibly owing to the placement of too
much stress on the graft during the rehabilitation phase.
Engebretsen et al.  evaluated 85 consecutive patients
treated with simultaneous reconstruction of the ACL and
PCL, repair of medial or lateral structures, and early
aggressive rehabilitation protocol. They also performed a
subanalysis based on high- (51%) and low-energy (49%)
trauma, acute and chronic surgery, and KD-IV (12%)
versus KD-II–III (88%). They concluded their procedure
provided worse outcomes, especially concerning subjective
scores and one-leg hop tests, in patients with high-energy
or KD-IV knee dislocations compared to those with low-
energy or lower-grade knee dislocations. Stannard et al.
 presented the Compass knee hinge (CKH) external
fixator (Smith and Nephew, Memphis, TN, USA) in caring
for knee dislocations. This device was designed to allow
early ROM without overstressing the graft tissues. In their
series, they performed staged surgery in 12 patients using
the CKH in the initial surgery, followed by aggressive
rehabilitation. Twenty-seven patients treated without the
CKH formed the control group. They found a higher rate of
PCL failures in the control group and concluded their
device allowed for the healing of reconstructed structures
and other secondary restraints during rehabilitation, leading
to good joint mobility without a sacrifice in stability.
However, the CKH does not allow for femoral posterior
rollback during knee flexion, which is a distinctive feature
of knee ROM; our device more closely reproduces the
kinematics of the normal knee, allowing not just flexion-
extension movement but also reproducing the posterior
rollback. This feature reduces the stress on repaired soft
tissue structures, such as the reconstructed grafts and the
capsule, and presumably would allow them to heal under
more physiologic stress.
All seven of the employed patients in our study returned
to their preinjury work activity. Stability was normal
in the one patient who underwent the delayed ACL recon-
struction, nearly normal in four patients, and not normal in
three patients (Table 2). Of these latter three patients, two
had abnormal AP laxity but did not undergo ACL recon-
struction: one was precluded because of his high body mass
index (41.9) and the other decided not to undergo further
surgery because of his high level of activity. The third
patient (Patient 3) had abnormal varus laxity. This patient
was the only one who failed because of stiffness, for which
we performed manipulation under anesthesia.
Our observations show this surgical approach to com-
plex high-energy knee dislocations resulted in more than
60% of normal or nearly normal knees. These data are
similar to those reported in the literature [16, 27]. More-
over, the opportunity to stage surgery while protecting soft
tissues and limiting the risk of knee stiffness allowed for
later ligament reconstruction to be performed, similar to
that performed for isolated ligament injuries.
the drawings and Costanza Musiani for helping with the references.
Three of the eight patients came from the Rizzoli Orthopaedic
Institute, two from the C Poma Hospital, two from the Versilia
Hospital, and one from the Taranto Hospital.
The authors thank Silvia Bassini for preparing
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