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Anatomical double bundle mpfl reconstruction
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neither the patella nor the femoral insertion can
be reconstructed at its anatomical insertion,
and the graft used is always a single bundle
graft despite the fact that the MPFL consists of
a proximal and a distal bundle [3]. This also
includes a single point fixation at the patellar
side, increasing the rotational moment of the
patella in flexion extension movement. In terms
of the fixation itself, some techniques fix the
graft to the surrounding soft tissue [13] and not
to the patellar and/or femoral bone even though
a ligament is a structure in between bones, and
recent studies have proven the high resistance
to failure of tendon-bone interfaces.
Since tendon to bone healing showed excellent
results in ACL reconstruction with hamstring
tendon grafts, the same tendon-to-bone fixation
is used at both, the femoral and the patellar side
in our technique.
While tendon-to-bone tunnel healing is created
on the femoral side using a biodegradable
screw for fixing the graft loop, the free graft
ends are now fixed directly and anatomically
into the patella using a biotenodesis device.
This technique seems to provide a higher load
to failure strength than an earlier described
technique, where a laminar attachment of the
graft was performed at the patellar side using
two suture anchors [6], which may result in
loosening of the knot during full range of
motion testing; or, the patellar bone may be too
soft for a secure anchoring. Knotting the free
graft ends to each other at the patellar edge [8]
are comparable to a non-aperture indirect
fixation in ACL surgery. With the suture anchor
technique, a secure graft to bone healing can
not be provided in every case and loosening of
the graft could occur.
Another technique, looping the graft through
the patella provides a very high initial fixation
strength and preliminary results are promising
[9]. However, if micromotion in the patellar
tunnels develops, it may lead to a slackening of
the graft at later follow up. However, if the
graft is very short, the femoral insertion can not
be reached and an overly anterior fixation has
to be accepted, leading eventually to an
increased patellofemoral pressure or loss of
fexion.
The use of a free autograft in the above
described technique allows us to place the graft
at the anatomical insertion with a sufficient
length and to recreate the double bundle
structure of the MPFL as it was described in an
anatomical study by Amis [3]. This provides a
higher stability, as the proximal bundle seems
to stabilise in extension, while the distal bundle
stabilises in flexion. Furthermore, the double
bundle reconstruction decreases patellar
rotation in contrast to techniques where only a
single point fixation is performed or the middle
part of the quadriceps tendon is flipped medially
[4]. Reproducing the anatomy of the native
MPFL enables the reconstructed ligament to
have an isometric function, and therefore
avoids increased patellofemoral pressure in
higher degrees of knee flexion [6]. We also
estimate that in long-term follow up, slackening
of the graft will not occur due to an improved
tendon to bone healing by using direct fixation
at the femoral as well as at the patellar
insertion.
References
[1] SM Desio, RT Burks, KN Bachus Soft tissue
restraints to lateral patellar translation in the human knee.
Am J Sports Med 1 (1998) (26):59-65.
[2] E Nomura, M Inoue Surgical technique and rationale
for medial patellofemoral ligament reconstruction for recurrent
patellar dislocation.
Arthroscopy 5 (2003) (19): E47.
[3]AAAmis, PFirer, J Mountney, WSenavongse,
NP Thomas Anatomy and biomechanics of the medial
patellofemoral ligament.
Knee 3 (2003) (10): 215-20.
[4] RN Steensen, RM Dopirak, WG McDonald,
3
rd
The anatomy and isometry of the medial patellofemoral
ligament: implications for reconstruction.
Am J Sports Med 6
(2004) (32): 1509-13.
[5] PB Schottle, A Schmeling, N Rosenstiel, A
Weiler Radiographic landmarks for femoral tunnel
placement in medial patellofemoral ligament reconstruction.
Am J Sports Med 5 (2007) (35): 801-4.