Focus On
Patellofemoral Joint Replacement
Introduction
There has been renewed interest in patellofemoral joint (PFJ)
replacement in recent years, following the development of
second-generation prostheses and the publication of good midterm results1-4. Young patients with isolated patellofemoral
arthritis represent a difficult clinical problem and the availability
of proven alternatives to total joint replacement is an important
surgical advance. However, in the older population, it is not clear
whether isolated PFJ replacement offers any advantage over
total knee replacement (TKR).
PFJ arthritis occurs in isolation in approximately 10% of
patients with arthritis of the knee. The patients tend to be
younger, with a preponderance of females5. When non-operative
measures are no longer effective, there are various operative
interventions available, including: arthroscopic debridement,
lateral release, re-alignment, partial lateral patellar facetectomy,
microfracture, mosaicplasty/autologous chondrocyte implantation, patellectomy, patellofemoral replacement, and TKR.
Patients with patellofemoral pathology have often had multiple surgical interventions before undergoing joint replacement,
a fact that reflects the difficulty in treating this condition in the
younger patient.1-4,6-7 Isolated lesions in specific locations in the
patellofemoral articulation may be amenable to re-alignment
procedures, chondrocyte implantation, microfracture or partial
lateral facetectomy. However, once the disease process involves
both sides of the joint and is more extensive, the results of such
procedures are less predictable.6,8 It is for these patients that
joint replacement may be indicated.
Patellofemoral replacement has existed since the 1950s
when McKeever reported a series of 40 patients with patellar
resurfacing using a Vitallium prosthesis screwed onto the
patella.9 In the 1970s, Blazina et al10 and Lubinus11 introduced
femoral components combined with the resurfaced patella.
However, results were mixed, with high rates of revision, complications and progression of arthritis, requiring revision to TKR.
Second generation PFJ replacements have existed since the
1990s with an evolved design rationale.12 The femoral component has a broad, symmetrical trochlear flange that narrows distally, ensuring that the patella engages during flexion but is
relatively unconstrained in extension. The majority of literature
concerning this type of patellofemoral replacement relates to
the Avon implant (Stryker, Howmedica Osteonics, New Jersey)
and there exist several published series, both from the originating centre in Bristol and also several independent centres. The
Femoro Patella Vialli (FPV) (Wright Medical, UK) has a similar
design concept.
The ideal patient for PFJ replacement is one with severe signs
and symptoms of isolated patellofemoral disease. These correlate with radiologically proven arthritis, best demonstrated on
tangential views of the patellofemoral joint. Nicol et al1 found
the lowest rates of progression of femorotibial arthritis in
patients with pre-existing trochlear dysplasia as an underlying
cause for their patellofemoral arthritis, defined as sulcus angle
of greater than 145° over three readings. In addition, CT and
MRI can aid in the assessment of both the patellofemoral articulation and the femorotibial compartments. There should be no
fixed flexion deformity or malalignment. Prior arthroscopy and
direct inspection of the knee joint at the time of surgery also
have a role in assessing the suitability of partial rather than full
joint replacement. There have been case reports in the literature
suggesting that PFJ replacement can be combined with chondrocyte grafting of isolated lesions found at the time of surgery, in
cases where the patient was thought to be otherwise suitable for
PFJ replacement.13
Results of patellofemoral joint replacement
Early reports regarding PFJ replacement have been mixed. Kooijman, Driessen and van Horn14 reported the outcome of 56 first
generation PFJ replacements in 51 patients at a mean of 15
years. They found an early re-operation rate of 18% and a revision rate of 15.5% for complications relating to the prosthesis. A
further 30% were ultimately revised because of progression of
femorotibial arthritis at a mean of 15.6 years. In those knees
that were not revised, functional results were reported to be
good or excellent in 86% and durable during the follow-up
period. Other mid- to long-term follow up studies of first-generation PFJ replacements have also revealed high rates of re-operation (26% to 63%) and revision (19% to 51%).16,17
The longest follow-up for PFJ replacements in the literature
using the Avon PFJ replacement (Stryker, Mahwah, New Jersey)
is from Ackroyd et al4 in 2007. They reported on 109 consecutive
patients with a 4.2% rate of failure in the first five years, and an
80% rate of success based on Bristol knee scores at five years.
Progression of disease was noted in 28% of patients, and reoperation occurred in eight knees, including four revisions to
TKR: there were a further 11 revisions after five years. In 2010,
Odumenya et al2 reported on 50 Avon PFJ replacements with
100% survival at five years. Radiological progression of disease
©2010 British Editorial Society of Bone and Joint Surgery
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MATTHEW PR WILKINSON, FARES S HADDAD
occurred in 22% and three patients had revisions performed
after the five-year mark. In 2009, Starks, Roberts and White3
reported on 37 Avon PFJ replacements with two-year follow-up
demonstrating high post-operative functional knee scores, two
re-operations and no revisions. In the same year, Leadbetter et
al7 reported on a multicentre trial involving the Avon prosthesis
in 79 knees. The mean age was 58 years and there had been 81
previous operations. A Knee Society Score (KSS) of more than
80 was achieved in 84% of patients, and there were six revisions
to TKR with a mean follow-up of three years.
With respect to other patellofemoral implants, in 2008
Mohammed et al17 reported on a series of 101 arthroplasties
using the Lubinus, Avon and FPV systems with a mean follow-up
of four years. They reported on 35 re-operations and four revisions to TKR. All of the revisions and 43% of the re-operations
were in patients who had undergone joint replacement using the
Lubinus implant.
From the Australian joint registry, the best performing PFJ
replacement is the Avon with a five-year rate of revision of
9.9%,18 compared with the overall rate of revision rate all PFJ
replacements of almost 15%. By comparison, the five-year rate
of revision for unicompartmental knee replacements (UKR) is
8.8%, and for TKR is 3.8%. In younger patients, who are a more
comparative population, the rate of revision for UKR in patients
less than 65 years old is 10.8%, and for TKR is 5.62%.
TKR for isolated patellofemoral joint arthritis remains the gold
standard and several series have been reported in the literature.
In 2002, Mont et al19 reported on a series of 30 TKRs in 27
patients, with a mean age of 73 years, and reported no re-operations or revisions. All but one case had excellent or good results
with a KSS of more than 80. In 2007, Meding et al20 reported on
a series of 33 TKRs in patients aged less than 60 years (mean
52 years) and isolated PFJ arthritis. Follow-up at a mean of 6.2
years demonstrated no re-operations or revisions and a mean
KSS of 88. Interestingly, Thompson et al21 in 2001, presented a
series of 33 patients with isolated patellofemoral arthritis, with a
mean age of 73 years, who underwent TKR without patellar
resurfacing with good-to-excellent results and no revisions at a
mean follow-up of 20 months. An important additional finding in
these studies was the high rate of lateral release required and
that extra care was required to optimise patellofemoral tracking
including distal realignment in some cases.22,23 TKR appears to
be a reliable procedure in this patient group but these studies
did not address the implications of TKR in the younger patient
and the problems of subsequent revision.
In 2006, Lonner, Jasko and Booth23 reported on a series of
12 patients who underwent revision of patellofemoral replacement to TKR. In all patients, a primary knee replacement could
be performed without stems or augments: the patellar component was retained and the outcome scores were not compromised when compared with primary TKRs.
As well as ease of revision, there are some other theoretical
advantages of PFJ replacement as it is less invasive, and is associated with a shorter operating time and a quicker rehabilitation.
The preservation of the femorotibial compartments and cruciate
ligaments results in improved gait and knee kinematics.6 The
implication is that a PFJ replacement may provide a more functional knee in the younger, higher demand patient.
Summary
It is clear from a review of the literature that PFJ replacement is
associated with a higher revision rate than TKR, although it is
comparable to unicompartmental knee replacement. However,
patients having PFJ replacement are often younger than those
undergoing TKR and may have had multiple surgical procedures
before joint replacement. Dissatisfaction with TKR is known to
occur in approximately 10% to 20% of patients where no relatively simple revision procedure can generally be offered.25
Therefore, it is conceivable that rates of revision of PFJ replacement may also be increased because of the availability of a relatively straightforward secondary procedure for dissatisfied patients.
The currently published short- and mid-term series on secondgeneration patellofemoral prosthesis are encouraging, with high
retention of prosthesis and good functional results. It is unclear
whether offering a PFJ replacement in an older patient offers any
functional advantage when the revision rates are likely to be
higher. In the younger patient, when the risks of offering TKR outweigh the benefits, PFJ replacement is a reasonable option.
Matthew PR Wilkinson, FRACS (Orth), Clinical Fellow
Fares S Haddad, FRCS (Orth), Consultant Orthopaedic Surgeon
Department of Orthopaedics,
University College Hospital, London, UK
References
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THE JOURNAL OF BONE AND JOINT SURGERY
FOCUS ON... PATELLOFEMORAL JOINT REPLACEMENT
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