In patients who have an avulsion fracture of the patellar pole
(Fig. 1), the extensor
mechanism is disrupted and should be repaired. Preservation of the inferior
patellar pole and osteosynthesis maintain the patellar height and the normal
anatomic and biomechanical relationships of the patellofemoral joint and thus
can provide better clinical results compared with those of excision of the
patellar pole fragments combined with patellar tendon repair. In the present
report, we describe a new technique of fixation with a basket plate that
provides stable fixation and preserves the patellar pole even in patients with
comminuted avulsion fractures.
The procedure is performed with the patient under spinal block or general
anesthesia. The patient is placed in the supine position. A thigh tourniquet
is applied. The leg is draped in a manner that will allow free movement of the
knee. The knee is supported in a slightly flexed position with use of a
bolster (Fig. 2).
A straight midline incision, approximately 12 cm in length, is made in the
skin. It starts about two fingerbreadths proximal to the displaced proximal
fragment of the patella and runs distally over the pole fragment to the tibial
tuberosity (Fig. 3).
Full-thickness skin flaps are raised medially and laterally to expose the
transversely ruptured retinaculum on either side of the fracture, both
fragments, and the patellar tendon (Fig.
4).
CRITICAL CONCEPTSINDICATIONS:Avulsion fractures of the apex of the patella, including comminuted
fracturesCONTRAINDICATIONS:Open fracturesActive infection at or near the operative siteSleeve avulsionsPathologic fracturesSeverely osteopenic boneAn unreliable, noncompliant patientPITFALLS:An anteriorly tilted plate leads to a less-than-optimal direction of the
pulling force on the four posterior hooks. These hooks can bend, allowing the
distal fragments to displace.Positioning the parallel screws too far anteriorly prevents positioning of
the oblique screws.If the proximal fragment is less than half of the patellar length, the
fixation may be insufficient.Not placing the interwoven suture during the treatment of a comminuted
fracture, or piercing the patellar tendon with the hooks of the basket plate
proximal to the suture, may lead to slippage of the fragments between the
hooks of the plate and redisplacement.Excessively aggressive rehabilitation in the first three weeks
postoperatively may lead to mechanical failure.AUTHOR UPDATE:Although severely osteopenic bone is still regarded as a relative
contraindication, the age of the patient is not a limitation of the
procedure.The indications of the technique have been extended to include comminuted
fractures of the distal pole of the patella, provided that the proximal, solid
fragment constitutes more than half of the patellar length.
CRITICAL CONCEPTS
INDICATIONS:
Avulsion fractures of the apex of the patella, including comminuted
fractures
Avulsion fractures of the apex of the patella, including comminuted
fractures
CONTRAINDICATIONS:
Open fracturesActive infection at or near the operative siteSleeve avulsionsPathologic fracturesSeverely osteopenic boneAn unreliable, noncompliant patient
Open fractures
Active infection at or near the operative site
Sleeve avulsions
Pathologic fractures
Severely osteopenic bone
An unreliable, noncompliant patient
PITFALLS:
An anteriorly tilted plate leads to a less-than-optimal direction of the
pulling force on the four posterior hooks. These hooks can bend, allowing the
distal fragments to displace.Positioning the parallel screws too far anteriorly prevents positioning of
the oblique screws.If the proximal fragment is less than half of the patellar length, the
fixation may be insufficient.Not placing the interwoven suture during the treatment of a comminuted
fracture, or piercing the patellar tendon with the hooks of the basket plate
proximal to the suture, may lead to slippage of the fragments between the
hooks of the plate and redisplacement.Excessively aggressive rehabilitation in the first three weeks
postoperatively may lead to mechanical failure.
An anteriorly tilted plate leads to a less-than-optimal direction of the
pulling force on the four posterior hooks. These hooks can bend, allowing the
distal fragments to displace.
Positioning the parallel screws too far anteriorly prevents positioning of
the oblique screws.
If the proximal fragment is less than half of the patellar length, the
fixation may be insufficient.
Not placing the interwoven suture during the treatment of a comminuted
fracture, or piercing the patellar tendon with the hooks of the basket plate
proximal to the suture, may lead to slippage of the fragments between the
hooks of the plate and redisplacement.
Excessively aggressive rehabilitation in the first three weeks
postoperatively may lead to mechanical failure.
AUTHOR UPDATE:
Although severely osteopenic bone is still regarded as a relative
contraindication, the age of the patient is not a limitation of the
procedure.The indications of the technique have been extended to include comminuted
fractures of the distal pole of the patella, provided that the proximal, solid
fragment constitutes more than half of the patellar length.
Although severely osteopenic bone is still regarded as a relative
contraindication, the age of the patient is not a limitation of the
procedure.
The indications of the technique have been extended to include comminuted
fractures of the distal pole of the patella, provided that the proximal, solid
fragment constitutes more than half of the patellar length.
The blood clot is removed, the knee joint is irrigated, and the fracture
fragments are cleaned of debris to allow exact reconstruction. The articular
surface of the femoral condyles is examined to identify any cartilage lesions.
The distal fragment or fragments are prepared for fixation with the basket
plate designed by
Smiljani1. The plate
has the shape of a basket with four posterior and three anterior hooks that
can be bent to fit the shape of the inferior patellar pole. The four posterior
hooks are thrust through the patellar tendon to embrace the posterior surface
of the patellar pole while the anterior hooks embrace the patellar pole
ventrally (Fig. 5).
In patients with comminution of the patellar pole, a number-1 absorbable
interwoven suture is placed transversely through the patellar tendon and
circumferentially just distal to the pole fragments and is used to tie the
fragments into a
bundle2 (Figs.
5 and
6). This suture prevents
slippage of the multiple tiny fragments between the hooks of the basket plate.
The four posterior hooks of the basket plate are then thrust through the
patellar tendon, just distal to the suture line, so that the pulling force of
the extensor mechanism is transferred to the patellar pole fragments mainly by
the interwoven suture. In patients with one solid fragment, the suture is not
needed and the hooks of the plate are thrust through the tendon just distal to
the fragment. The hooks are curved to fit the shape of the posterior surface
of the patella so that the pole fragments are embraced by the basket
(Fig. 7). It is acceptable for
the tips of the posterior hooks to touch the articular surface of the
posterior surface of the patella.
A 2.0-mm Kirschner wire is then drilled through one of the central plate
holes and through the patellar pole as posteriorly as possible so that, after
reduction, it will lie in the posterior aspect of the main fragment, parallel
with the articular surface (Fig.
8).
The pole fragments within the plate are then reduced and temporarily held
to the main fragment with two large, pointed reduction forceps. The Kirschner
wire is then drilled across the fracture line into the proximal fragment
(Fig. 9). One of the large,
pointed reduction forceps is then removed from the plate hole distally and is
placed around the apex of the metal basket to compress the plate to the main
proximal fragment (Fig. 10).
The three anterior plate hooks are then curved to fit the shape of the
anterior patellar surface. Correct positioning of the Kirschner wire must be
checked on the image intensifier at this point.
The plate is then fixed to the main patellar fragment with two 4.0-mm
cancellous-bone screws. The first is placed through the free central hole of
the plate, and then the second is placed after the Kirschner wire has been
removed (Fig. 10). These two
lag screws must be parallel to provide interfragmentary compression, and they
should be placed as posteriorly as possible to provide the optimal position of
the reduced patellar tendon with its pole fragments
(Figs. 11-A and 11-B). Another
two small cancellous-bone screws are then positioned obliquely and ventrally
into the proximal patellar fragment to increase resistance against distraction
forces (Fig. 12).
The prominence of the tips of the four posterior hooks that might impinge
against the articular surface of the femoral groove should be identified by
palpation with the tip of the finger through the retinacular gap on either
side of the patella. If they are prominent, they should be bent further toward
the patellar surface. A suction drain is placed into the joint, and the
retinaculum is repaired with use of number-0 absorbable sutures
(Fig. 13). At the end of the
procedure, the knee is fully flexed to test the stability of the fixation
(Fig. 14). Postoperative
radiographs are made routinely to check the reduction of the fracture and the
position of the patella (Fig.
15).
A standard wound closure is performed in layers with use of number-2
absorbable sutures for the subcutaneous tissue and a subcuticular stitch for
the skin.
Postoperatively, knee immobilization is not necessary. Patients start
passive motion exercises on the first postoperative day and are encouraged to
perform active flexion exercises of the knee in the prone position. Active
extension exercises are allowed after the third postoperative week. Patients
are encouraged to start bearing weight during level walking on the second
postoperative day and full weight-bearing without limitation is encouraged at
six weeks.