Primary repair by direct suture of the torn medial soft-tissue stabilizers
following an acute patellar dislocation in pediatric patients does not improve
long-term subjective or functional results. Therefore, acute patellar
dislocation is treated nonoperatively in our hospital except in patients with
an osteochondral fracture requiring surgical repair (Figs.
1-A, 1-B,
1-C). Surgical treatment is
considered in patients with recurrent patellar dislocation, and reconstruction
of the medial patellofemoral and patellotibial ligaments is our preferred
technique.
Preoperative Evaluation
The physical examination includes an assessment of thigh muscle atrophy,
range of knee motion, and stability of the knee. Patellar tracking and the Q
angle are observed. The rotational profile and axial alignment of the lower
extremities are documented, and general joint laxity is assessed. The
radiographic examination includes plain anteroposterior and lateral
radiographs of the affected knee and tangential radiographs of both patellae
with the knee in 20° of
flexion1. Magnetic
resonance imaging is not routinely acquired.
Selection of Surgical Procedure
Reconstruction of the patellofemoral and patellotibial ligaments with a
semitendinosus tendon graft (Fig.
2) constitutes the anatomical basis of the
operation2. Lateral
release is performed only when tightness of the lateral retinaculum does not
allow congruent tracking of the patella. In skeletally mature patients, a
tibial tubercle transfer is also performed if the Q angle is >20°.
Trochleoplasty should be considered in patients with a flat or convex femoral
sulcus3.
Procedure
The patient is placed supine on a standard operating-room table. General
anesthesia is induced, and examination of both knees, including an assessment
of patellofemoral tracking, is accomplished before sterile preparation and
draping of the limb. A thigh tourniquet is used with a pressure of 250 mm Hg.
First, arthroscopy of the affected knee is performed through standard portals
mainly to evaluate patellar tracking, the depth of the femoral trochlea, and
the condition of the patellofemoral joint surfaces—this additional
information is used in the selection of the surgical technique. Second, loose
bodies are sought and removed if found.
A longitudinal 4-cm skin incision is made medial to the tibial tubercle.
The semitendinosus is identified, and its tendon is harvested proximally with
a tendon stripper while its distal insertion site is maintained intact
(Fig. 3). A running 2-0 Vicryl
crisscross suture (polyglactin; Ethicon, Somerville, New Jersey) is then
placed in the proximal end of the tendon. Two additional 2-cm incisions are
made at the inferomedial and superomedial borders of the patella. A
longitudinal intraosseous tunnel is created with a 3.2-mm cannulated drill in
the medial quadrant of the patella (Fig.
4) and then is widened with a 4-mm drill. A subfascial tunnel is
created between the semitendinosus insertion and the inferomedial patellar
incision. The tendon graft is then passed through this tunnel and through the
patella from distal to proximal, exiting from its superomedial pole
(Fig. 5). From its exit at the
superior aspect of the patella, the tendon graft is tunneled in a subfascial
plane to the adductor tubercle, where a 3-cm incision is made. The graft is
tensioned maximally with the knee in 30° to 45° of flexion while
making sure that the patella is sitting well in the trochlea. The tension is
checked in full knee extension (the graft should allow little lateral movement
of the patella, only up to one-fourth of the patellar width). Proper tension
of the graft also allows congruent smooth tracking of the patella. Patellar
tracking and stability are tested throughout the range of knee motion. A 7-mm
hole is then drilled at the adductor tubercle, and the graft is secured with
an absorbable 8 × 23-mm Biotenodesis screw (Arthrex, Naples, Florida)
(Fig. 6). The tourniquet is
released, and the incisions are closed. In skeletally immature patients, a
Biotenodesis screw cannot be used—rather, the graft is passed around the
adductor magnus tendon and is sutured to this tendon and to itself with 0
Vicryl.
A lateral retinacular release in selected patients (when tightness of the
lateral retinaculum does not allow congruent tracking of the patella) is
performed through an extended anterolateral arthroscopic portal to allow
45° of rotation of the patella above the horizontal. In skeletally mature
patients with a Q angle of >20°, the tibial tubercle is transferred 8
to 12 mm medially and is fixed with two 6.5-mm lag screws.
Postoperative Care
Weight-bearing and active range-of-motion exercises are allowed immediately
and are initiated as tolerated. A return to sports is allowed after four
months; however, patients who have had a tibial tubercle transfer walk with
only partial weight-bearing on crutches for the first six weeks.
CRITICAL CONCEPTSINDICATIONS:Recurrent patellar dislocation in patients with functional disabilityRELATIVE INDICATIONS:High-demand athletes with a primary patellar dislocationPatellar dislocation with large femoral osteochondral fractures requiring
fixationCONTRAINDICATIONS:Active infectionAnterior cruciate ligament reconstruction with a patellar tendon graftPatellar fracturePITFALLS:Failure in tendon harvesting resulting in amputation of the graft or a
hematomaPatellar fractureJoint surface damageImproper tensioning of the graftAUTHOR UPDATE:Our original study showed that primary repair of the torn medial
stabilizing soft-tissue structures by direct suture in a dysplastic
patellofemoral joint does not improve patellar stability. The procedure
described in the present report was developed after the preliminary results of
the primary repair study were available.
CRITICAL CONCEPTS
INDICATIONS:
Recurrent patellar dislocation in patients with functional disability
Recurrent patellar dislocation in patients with functional disability
RELATIVE INDICATIONS:
High-demand athletes with a primary patellar dislocationPatellar dislocation with large femoral osteochondral fractures requiring
fixation
High-demand athletes with a primary patellar dislocation
Patellar dislocation with large femoral osteochondral fractures requiring
fixation
CONTRAINDICATIONS:
Active infectionAnterior cruciate ligament reconstruction with a patellar tendon graftPatellar fracture
Active infection
Anterior cruciate ligament reconstruction with a patellar tendon graft
Patellar fracture
PITFALLS:
Failure in tendon harvesting resulting in amputation of the graft or a
hematomaPatellar fractureJoint surface damageImproper tensioning of the graft
Failure in tendon harvesting resulting in amputation of the graft or a
hematoma
Patellar fracture
Joint surface damage
Improper tensioning of the graft
AUTHOR UPDATE:
Our original study showed that primary repair of the torn medial
stabilizing soft-tissue structures by direct suture in a dysplastic
patellofemoral joint does not improve patellar stability. The procedure
described in the present report was developed after the preliminary results of
the primary repair study were available.