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The long-term results of patello-fermoral arthroplasty
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mainly in the primary osteoarthritis etiologic
group. Despite the absence of statistical group-
to-group comparison, which may constitute one
of the limitations of this study, we think our
best results were seen in patients with a pre
operative diagnosis of instability and corrected
alignment of the extensor mechanism. The
clinical evaluation presented in this study also
confirmed that PFA can provide a significant
improvement in knee function for patients
affected by isolated patellofemoral arthritis.
This long-term study of 12 to 20 years showed
that 29 out of 66 patients implanted with PFA
required conversion to TKA. In the only
available study with a comparative long-term
follow-up published by Kooijman
et al.
, the
authors also concluded that patellofemoral
unicompartmental arthroplasty has a high
revision rate. In that study of 45 knees with an
average follow-up of 15.6 years the authors
noted seven revisions related to the arthroplasty
and 12 revisions for tibiofemoral osteoarthritis
progression. Authors of both studies show that
progressive osteoarthritis in the unreplaced
tibiofemoral compartment was the major cause
of failure in knees implanted with PFA.
Progression of osteoarthritis in the unreplaced
femorotibial compartment also was also noted.
In our study we did try to identify the etiology
of the patello-femoral degeneration and we
found that this progression of osteoarthritis
occurred mainly in the group of primary
patellofemoral arthritis. Patients with a history
of patellar instability or patellar fracture did not
tend to have progressive osteoarthritis changes
in the tibiofemoral joint. In patients with
primary patellofemoral osteoarthritis, careful
preoperative radiographs should determine
whether there is tibiofemoral malalignment. If
significant frontal plane malalignment is
present, this should either be corrected or be
considered a relative contraindication to PFA.
In this study, we think our best results were
seen in patients with a neutral or slightly valgus
mechanical axis and none of the patients with
concomitant osteotomy had revision for
tibiofemoral degeneration. The need for lateral
retinacular release or realignment of the
extensor mechanism at the time of PFA also
has been noted in the studies of Tauro
et al.
and
Krajca-Radcliffe and Coker. Cartier
et al.
and
Mertl
et al.
used the elevation of the anterior
tibial tubercle as part of the procedure. We
think that this not required for most of the
patient and the problem is most of the time on
the femoral side and this issue can be addressed
without any action on the anterior tibial
tuberosity, specially with the new generation of
implants. During surgery the importance of
precise alignment of the femoral component,
avoiding flexion and internal rotation, may also
contribute to achieve correct patella tracking as
noted previously.
Regarding the number of secondary procedures
after PFA compared with the outcome after
TKAfor the treatment of isolated patellofemoral
osteoarthritis, we favor TKA as the first option
in older patients. Laskin
et al.
and Parvizi
et al.
reported good results after TKA for isolated
patellofemoral arthritis in patients averaging
67 or 70 years old, but they also noted a high
incidence of lateral retinacular release or
extensor mechanism realignment procedures
and the number of patients with postoperative
patellar tilt found in this group of patients.
Mont
et al.
noted only one poor result after
30 cases of TKA done for patellofemoral
arthritis in patients averaging 73 years old.
Despite the high rate of conversion to TKA at a
12- to-20 year followup presented in this study
we consider PFA to be a valuable option for
middle-aged carefully selected patients. The
ideal candidate should have a knee with isolated
patellofemoral arthritis and no important frontal
tibiofemoral deformity. When the arthritis is
secondary to patellofemoral instability, atten
tion should be taken to obtain a correct
alignment of the extensor mechanism. For
patients younger than 60 years, we think PFA
can be a useful “temporary” procedure that
easily can be converted to TKA if needed. We
believe all the components of the PFA should
be cemented and the PE patellar button should
be compatible with conventional TKA designs.
Additionally, it is not irreversible like patel
lectomy and it is a more nonoperative option
for younger patients than TKA.