LIVRE JDG 2012

M. Nelitz, H. Reichel, S. Lippacher

Deie

et al.

have [12] described good results

after non anatomic MPFL reconstruction in

children between 6 and 10 years. They have

chosen the posterior one-third of the proximal

attachment of the MCL as the site for pulley.

Brown

et al.

[6] described a technique with

combined medial patellofemoral ligament and

medial patellotibial ligament reconstruction

leaving the insertion of the semitendinosus

tendon intact. They sutured the free limb to the

MCL as proximal as possible. Both techniques

can produce an inadvertent distalisation of the

patella, even if it is not needed.

Sillanpää

et al.

[24] described a technique

using a free graft wrapped around the adductor

magnus tendon.

None of the described techniques is strictly

anatomical, as they use the femoral insertion of

the MCL or of the adductor magnus tendon as

a reference for the femoral insertion of the

MPFL. Adetailed anatomical study by Baldwin

[3] has shown that the adductor tubercle

provides exclusive attachment for the adductor

magnus tendon and the medial epicondyle

provides exclusive attachment for the MCL,

whereas the insertion of the MPFL is found in

a groove between these two landmarks. Using

these non anatomical techniques it is

furthermore difficult to control the accurate

tension of the graft during fixation.

The need for an anatomical reconstruction is

now widely accepted. If the femoral origin is

placed too proximally tightening of the MPFL

in knee flexion with concomitant increased

contact stress can occur [13, 25, 26]. Camp

al.

[8] found the failure to restore the anatomical

femoral insertion to be a main risk factor for

the failure of MPFL reconstruction.

Several studies have shown that the insertion

of the MPFL is typically distal to the femoral

physis [3, 14, 15, 16, 18]. On MRI scan, Kepler

et al.

[14] measured the distance between the

MPFL insertion onto the distal femur and the

medial distal femoral growth plate or physeal

scar. The femoral MPFL insertion averaged

5mm distal to the femoral growth plate. A

radiographic study using the radiographic

landmarks desribed by Schöttle

et al.

[22]

confirmed the results of Kepler

et al.

[14]. The

authors have shown that the median origin of

the MPFL as seen on the AP view averaged

6.4mm (2.9-8.5mm) distal to the femoral

physis [18].

For patients with open physis this means that

an insertion proximal to the physis has to be

strictly avoided as it can create increased

medial patellofemoral pressure [13].

In summary the technique described in this

study has two major advantages. First it

reconstructs the anatomy of the MPFL and at

the same time it is respecting the distal femoral

physis. To avoid injury of the physis the femoral

insertion as well as the direction of the blind

hole have to be checked radiographically on

lateral and AP view. As the femoral insertion of

the MPFL is distal to the physis the bone tunnel

has to be strictly in the epiphysis. Secondly the

technique desribed in the present study

technique uses a sling through the proximal

half of the patella, which recreates the double-

bundle structure of the MPFL and decreases

patellar rotation compared to single-point

fixation [2, 23].

Conclusion

This is the first report of a minimal invasive

procedure for anatomical reconstruction of the

MPFL in children with open growth-plates.

This technique considers the fact that the

femoral insertion of the MPFL is distal to

femoral physis. As a too proximal insertion of

the graft proximal to the physis can cause

unintentional tightening of the MPFL in knee

flexion this has to be considered during the

reconstruction of the MPFL in skeletally

immature patients.

Abstract

Recurrent lateral patellar dislocation is a

common knee injury in the skeletally immature

adolescent. In adults anatomical reconstruction

of the MPFL is recommended, but due to the