Keywords
acetabulum - femur head - fractures, bone - hip dislocation
Introduction
Post-traumatic posterior hip dislocation is usually caused by high-energy trauma in
young individuals involved in road traffic accidents (RTAs). The mechanism of injury
is usually a dashboard injury in which there is an axially directed force from the
knee in a flexed hip and, depending on the magnitude of force and position of the
hip at the time of injury, several other associated injuries can occur, such as osteochondral
avulsion, posterior wall fracture, and transverse fracture with posterior wall involvement.[1] Reduction of hip dislocation should be done on an emergency basis within 12 hours
to decrease the risk of avascular necrosis of the hip. Nonconcentric reduction or
persistent instability after reduction are usually caused by intra-articular loose
bodies, an incarcerated fragment, or posterior osteolabral avulsion.[2] Addressing these injuries is of paramount importance to achieve a stable and concentric
reduction to decrease the risk of subsequent redislocation of the hip, osteoarthritis,
and avascular necrosis (AVN) of the hip and allow early mobilization. Small osteolabral
avulsions can be easily missed, and postreduction stress testing and computed tomography
(CT) scan of the hip should be done to look for these injuries.[3] The usual modality of treatment of these unstable osteolabral avulsions is suture
anchors, Herbert screws, or spring plates.[4] But when the bony avuslion is small, the use of these implants becomes a tedious
job. We present a novel technique of fixing small osteochondral avuslion fractures
not amenable to fixation using screws or spring plates.
Method
Our study was a retrospective analysis of 57 cases who underwent open reduction and
internal fixation for posterior fracture dislocation of acetabulum by a single surgeon
at a tertiary level trauma center in north India from 2012 to 2018. Approval was obtained
from the ethical committee of the institution and informed written consents were obtained
from all patients for inclusion in the study and publishing of data in a scientific
journal without any disclosure of personal details.
Six cases with a small posterior labral osteochondral fragment leading to instability
were identified and were fixed using a novel method. All 6 patients were male, with
a mean age of 36.1 years old (range 21–54 years old), and the right side was involved
in 5 out of 6 patients. The mechanism of injury in all six patients was RTA and all
of them had a concurrent posterior dislocation at the time of injury. Three patients
had a transverse acetabular fracture with associated posterior osteolabral fracture
and the other three had only osteochondral fragments associated with posterior dislocation.
In the latter three patients, posterior dislocation was reduced in the emergency department
under sedation, but they had persistent dynamic instability. So, they were planned
for surgery and dynamic instability was confirmed by stress testing in the operation
theatre under C-arm in obturator view of the hip. The patients with an associated
transverse fracture were planned for open reduction according to the criteria of Matta
[5] and the osteochondral fragment was addressed when persistent posterior instability
was noted after fixing the transverse fracture.
All patients were operated using the Kocher Langenbeck approach. Surgical dislocation
of the hip was not performed in any case. Trochanteric flip osteotomy was performed
in two transverse fractures and in one posterior wall injury. The osteochondral fragments
were so small in all these cases that they could not be fixed using routine methods
such as screw or spring plate ([Figures 1] and [2]). The fragments were stabilized using Kirschner wires with the lateral ends bent
over the retroacetabular area and a buttress plate (3.5 mm reconstruction plate) was
applied over the bent and cut hair pin loop of the Kirschner wires to secure the fixation
([Figure 3]). Intraoperative movements were assessed immediately after fixation and the concentricity
of the reduction was checked under imaging after dynamic stress testing in all views.
All six hips were stable and reduced while the osteochondral fragments were also securely
fixed throughout the complete range of motion of the hip.
Fig. 1 Anteroposterior view of the preoperative X ray of the left hip of a patient with
small osteochondral avulsion of the posterior wall after reduction of hip dislocation.
Fig. 2 Postreduction axial images from the preoperative computed tomography scan of the
affected hip.
Fig. 3 Immediate anteroposterior view of the postoperative X ray of the hip of the same
patient.
Isometric quadriceps strengthening exercises were started immediately postoperatively.
The patients were kept on toe-touch weight bearing mobilization with a walker frame
for ∼ 4 weeks followed by a gradual increase in weight bearing according to the tolerance
of the patient at ∼ 8 to 10 weeks after surgery, depending on the degree of radiographic
consolidation of the fracture. The clinical outcome was evaluated using the Harris
Hip Score at 6 weeks, 3 months, 6 months, 1 year, and at final follow-up. The quality
of articular reduction and joint congruency was evaluated by postoperative plain radiographs
using the Matta classification (anatomic/imperfect/poor)[5] and supplemented with 3-D CT scans. The radiological evaluation at the final follow-up
was performed based on the criteria of Matta[5]: Excellent (a normal appearing hip joint); good (mild changes with minimal sclerosis
and joint narrowing < 1 mm); fair (intermediate changes with moderate sclerosis and
joint narrowing < 50%); and poor (advanced osteoarthritis changes). All patients were
followed-up for a minimum of 2 years (mean 44 weeks; range: 24–66 weeks). There were
no surgical site infections, sciatic nerve injuries, loss of reduction, or nonunion
at the trochanteric osteotomy site. All acetabular fractures were united at the final follow-up and the mean time to
union was 6.4 months (range: 4–10 months). The mean Harris Hip Score at the final
follow-up was 92.5 (range: 90.4–95.8). No patient developed features suggestive of
AVN hip. The radiological outcome at the final follow-up was deemed excellent in four
and good in two patients.
Final Comments
Posterior dislocation of the hip with associated wall fracture is a common injury
in high energy RTAs. Persistent instability after reduction of the dislocation or
fixation of the fracture should divert the attention of the orthopedist to look for
any posterior osteolabral tears. Identification of a small acetabular ‘fleck sign’
in an X ray of the hip in oblique view near the posterior wall in the absence of any
major acetabular fracture is a marker of posterior labral avuslion and should be assessed
thoroughly by stress testing under imaging to look for any dynamic instabilities.[6] The choice of method of fixation in avulsions with small bony fragments remains
arguable due to the fragment being not amenable to fixation with anchors, screws,
or plates and lack of stability when fixed with Kirschner wires alone. In the present
study, we described a novel technique of fixing these small osteochondral labral injuries
using Kirschner wires and buttress plates over the bent wire ends. The buttress plates
increased the stability of the Kirscnher wire fixation and prevented pullout of the
wires. The hips remained stable after fixation on dynamic stress testing in the operation
theatre under imaging and at all follow-ups. Our technique is a simple, cost-effective,
and reliable way of fixing such avulsions with satisfactory outcomes.
