Keywords
patellofemoral - osteoarthritis - replacement - arthroplasty - knee
Introduction
Patellofemoral (PF) osteoarthritis (OA) can be associated with anterior knee pain,
stiffness, and functional impairment.[1] Some authors report that approximately 9% of patients older than 40 years are affected
by PFOA.[2] Other authors have reported an incidence ranging from 2 to 11% in men and from 8
to 24% in women older than 55 years.[3]
[4] The higher incidence in female patients may be related to a higher incidence of
PF malalignment and dysplasia in this population.[5] Furthermore, Kobayashi et al[6] in a recent systematic review, including 32 studies, concluded that the prevalence
of PFOA was 25% in the asymptomatic population (age > 20 years) and 39% in the symptomatic
population (age > 30 years).
The development of PFOA is related to the presence of abnormal PF joint stress, which
can be due to excessive amount or inadequate dispersion of forces. The cause of these
abnormal stresses is multifactorial, including both knee- and patient-related risk
factors.[7]
Among the patient-related risk factors, increased body mass index (BMI) surely increased
the forces on the PF joint during weight-bearing activities.[8]
[9] Some authors outlined female gender and increased age to be possible risk factors
for PFOA, as well as activities involving increased load on PF joint (i.e., descending
stairs).[7] Previous trauma to the PF joint (i.e., patellar fracture or dislocation) has also
been related to the development of PFOA.[10]
[11]
Among knee-related risk factors, increased rate of PFOA has been reported in patients
who underwent anterior cruciate ligament reconstruction (ACLR), with a median prevalence
of up to 50% at 10 to 15 years after surgery.[12] Quadriceps and hip abductor weakness has also been related to PFOA, as well as ileotibial
band and hamstring contracture.[7] However, the most important knee-related risk factor is the presence of PF malalignment
or trochlear dysplasia, as well as valgus knee alignment and increased femoral anteversion.[7]
[13]
[14]
Treatment of PFOA includes nonoperative and surgical options. The nonoperative treatments
include exercise, physical therapy, taping, and injections and may result in short-term
benefit.[14] The surgical options range from joint debridement to arthroplasty. However, joint-preserving
procedures, including anterior tibial tubercle transfer or cartilage procedures, may
lead to insufficient short-term improvement. Total knee arthroplasty (TKA) with patellar
replacement is a well-established procedure to treat PFOA, but anterior knee pain
may persist in 7 to 19% of the patients.[4]
[10]
The need for replacing the PF joint while maintaining a joint kinematic closer to
that of the native knee in comparison with TKA led to the development of PF arthroplasty
(PFA).[4] PFA preserves physiologic tibiofemoral joint, thus allowing patients for a rapid
recovery with good satisfaction.[15] Although PFA is considered a valid therapeutic option to treat isolated PFOA, it
is indicated in a small and highly selected population.
The first PFA was proposed in 1955 by MacKeever. Despite the initial encouraging results,
it was quickly abandoned due to excessive wear in the trochlear groove.[16] PFA witnessed a rebirth in the 1970s, when the first generation of Richards' prostheses
(Smith & Nephew; Memphis, Tennessee, United States) was introduced and subsequently
developed later in the 1990s with the introduction of the second generation of PFA.[17]
[18] Although the clinical outcomes after PFA depend primarily on implant design and
surgical technique, careful patient selection with very strict inclusion and exclusion
criteria is mandatory for long-term survivorship and satisfactory outcomes.
The aim of the this article is to summarize the clinical features, indications and
contraindications, surgical techniques, and outcomes of PFA.
Patellofemoral Osteoarthritis
Patellofemoral Osteoarthritis
Patient History and Physical Examination
Patients with isolated PFOA report an anterior or retropatellar knee pain, usually
associated with activities that load the PF joint.[4] These activities include squatting, ascending or descending stairs, rising from
a seated position, or prolonged sitting with flexed knees.[4] Frequently, some activities, such as full squatting and kneeling, are almost impossible.
Pain is less severe when walking on level ground and in standing position with the
knee completely extended.[11] Frequently, patients affected by PFOA experience the worse pain in the early stages
of the disease.[11]
During physical examination, it is mandatory to evaluate the entire lower limb, including
muscle strength and coronal and PF malalignment (i.e., an increased Q angle). Indeed,
the presence of malalignment should be carefully evaluated because in many cases a
realignment osteotomy before or in conjunction with PFA may be required.[4] Crepitus and effusion may be reported, and the patella compression test is often
positive in the case of PFOA. The range of motion (ROM) must be investigated, and
the examiner should focus on the localization of pain and its correlation to the degree
of flexion. Normally, distal lesions (inferior pole) are painful at the first degree
of flexion, while proximal lesions are painful at higher flexion.[19] It is also mandatory to evaluate patella tracking throughout the entire knee ROM
to assess maltracking or instability (i.e., the presence of a J sign).[20]
[21] Any involvement of the tibiofemoral joint should be ruled out, as well as knee stability,
to avoid progressive tibiofemoral OA and/or instability. Furthermore, the neurovascular
status, previous scars, and hip and lumbar spine status should be carefully evaluated.[4]
Imaging
A routine series of conventional X-ray views should be obtained, including standing
anteroposterior (AP), flexed weight-bearing posterior–anterior (PA, Rosenberg), lateral,
and sunrise (Merchant) views. Both the PF and tibiofemoral joints should be carefully
evaluated on these films. Sunrise views at 30 degrees flexion allow for the best assessment,
but in some cases, it is useful to take views in various degrees of flexion to better
evaluate patellar tilt, subluxation, trochlear dysplasia, or a narrowed joint space.[22] Lateral view can reveal PF osteophytes, patella height, and joint space narrowing.
AP and PA views can reveal a medial or lateral OA. A weight-bearing, long-leg view
should also be obtained to evaluate lower limb alignment. Some authors suggest additional
computed tomography (CT) scan and/or magnetic resonance imaging (MRI) to calculate
the tibial tubercle–trochlear grove (TT–TG) distance and evaluate bone stock, rotational
malalignment, trochlear dysplasia, and intra-articular structures (articular cartilage,
menisci, and ligaments).[3]
[4]
[21]
Patellofemoral Arthroplasty: Indications and Contraindications
Patellofemoral Arthroplasty: Indications and Contraindications
A prerequisite for the success of PFA is a proper patient selection to avoid complications.[5]
[17]
[23]
[24]
[25] The most common indication for PFA is severe primary isolated PFOA that affects
daily activities without relief from conservative treatment. PFA is also indicated
in patients with posttraumatic PFOA, isolated trochlear dysplasia, patellar subluxation,
or failure of previous extensor mechanism unloading procedures, such as Fulkerson
or Maquet osteotomy.[5]
[11]
[25]
[26]
[27] Moreover, the ideal patient age ranges from 40 to 60 years.[28]
[29]
Many contraindications exist to PFA that should always be kept in mind. The presence
of tibiofemoral OA is the most common contraindication and the most common cause of
PFA failure.[5] PF malalignment, with an increased Q angle, cannot be corrected by PFA alone; so,
it has to be considered as a relative contraindication. On the contrary, mild patellar
tilt or subluxation can be corrected at the time of PFA with lateral retinacular release,
medialization of the patellar component, or partial facetectomy.[4] A PFA should preserve normal knee kinematics, joint stability with intact ligaments,
and menisci has to be considered as a fundamental prerequisite for PFA.[4] Furthermore, PFA is contraindicated in the presence of severe uncorrected coronal
plane deformity (valgus > 8 or varus > 5 degree alignment) or sagittal plane deformity
(120 degree flexion with < 10 degree flexion contracture).[4]
[11]
[28] Active infection and evidence or high suspicion of chronic regional pain syndrome
are also contraindications to PFA.[11]
[23] Quadriceps atrophy, patellar tendon scarring, patella baja, and excessive BMI (>30)
represent relative contraindications to PFA, as have been correlated to poorer outcome.[11]
[23] Hence, the ideal candidate for PFA is a middle age patient affected by isolated,
debilitating noninflammatory PFOA not responsive to conservative treatment and with
normal limb alignment.[4] The main indications and contraindications are summarized in [Table 1].
Table 1
Indications and contraindications for PFA
|
Indications
|
Contraindications
|
|
Advanced primary isolated PFOA
|
Absolute contraindications
|
|
Posttraumatic PFOA
|
Tibiofemoral OA
|
|
Trochlear dysplasia
|
PF malalignment
|
|
Patellar subluxation or mild patellar tilt
|
Knee instability (ligaments and/or menisci injuries)
|
|
Failed extensor mechanism unloading procedures
|
Limb malalignment (Valgus deformity > 8 degrees or varus deformity > 5 degrees)
|
|
Age > 40 years
|
Acute infection or CRPS
|
|
Relative contraindications
|
|
Quadriceps atrophy
|
|
Patella baja
|
|
BMI > 30
|
Abbreviations: BMI, body mass index; CRPS, complex regional pain syndrome; OA, osteoarthritis; PF, patellofemoral; PFA, patellofemoral arthroplasty; PFOA,
patellofemoral osteoarthritis.
Implant Design
The first PFA design was an isolated resurfacing of the patella with a screw-on Vitallium
patellar shell. Despite initial encouraging results, it was quickly abandoned due
to excessive wear in the trochlear groove.[16]
[30]
The first generation of complete PFA (both sides) only replaced the trochlear cartilage
leaving the subchondral bone intact (inlay design); so, the position of the PFA was
related to the anatomy of the native trochlea. Furthermore, the trochlear component
was positioned flush with the surrounding cartilage, the rotational alignment was
parallel to the trochlear inclination, the mediolateral coverage was limited, and
the surgical technique was mainly free hand.[31] First-generation PFA was successful in the short-term period, providing early pain
relief, but the results were not maintained over time and more than 50% of the implants
failed in the mid- to long-term follow-up with high reoperation rate.[32]
The second-generation PFA was designed to improve clinical outcomes and address the
limitations of the previous design, mainly related to maltracking and instability.[31] These implants used the same anterior femoral cuts as in TKA and completely replaced
the anterior compartment of the knee (onlay design). Furthermore, these were characterized
by a broad trochlear flange that narrowed distally,[18] a valgus tracking angle and a good congruity throughout the entire ROM, avoiding
catching, snapping, or popping.[4]
Both generations include symmetric and asymmetric implants. The second-generation
designs can be used in all patients, regardless of anatomic variations, and are therefore
more versatile and suitable.[21]
The PF implants can also be sorted according to the morphology of each component.
The patellar button can be shaped with facets or as a dome and can be symmetric or
asymmetric. It is advisable that patellar button design match the trochlear shape
of TKAs to allow for retention of the component, if a PFA revision is required.[33]
Nevertheless, the evolution of PFA is mostly based on the design of the trochlear
component. The sagittal radius of curvature, the mediolateral width, the distal–proximal
extension, and the grade of constrain are the most important features of the trochlear
design.[34] A less constrained design allows the patella for more freedom but may increase the
risk of patellar instability. On the contrary, a more constrained design (deep trochlear
groove) allows less patellar movement causing an increase in PF loads and a high risk
of early loosening.[33] Consequently, the goal of implant design is to reproduce as close as possible the
normal anatomy, thereby allowing smooth patellar tracking and minimizing the risk
of subluxation or dislocation.[34]
[35]
[36] The sagittal radius of curvature and the proximal extension of the implant determine
the point of engagement of the patellar button with the trochlear component.[37] These parameters can significantly influence patellar tracking. Furthermore, the
point at which the patellar button engages the trochlear component is also influenced
by the distal coverage of the implant.[33]
Nowadays, inlay implants have been mostly abandoned and onlay implants are mainly
used worldwide.
Surgical Technique (Onlay Design)
Surgical Technique (Onlay Design)
After a midline incision (from 1 cm proximal to the patella to just proximal to the
tibial tubercle), the arthrotomy can be performed using surgeon's choice between medial
parapatellar, midvastus, or subvastus approach. Care must be taken to avoid damaging
the menisci, ligaments, or tibiofemoral articular cartilage. The patella can be either
laterally dislocated or left in place and gently and partially everted. At this point,
the surgeon should inspect the entire knee to confirm that the tibiofemoral joint
is not involved and there are no ligamentous injuries.
The precise technique of implantation varies with the implant used. As a general rule,
the trochlea is prepared with an anterior cutting guide, taking care not to damage
the anterior cortex of the femur.[33]
Evaluation of the correct rotational alignment is mandatory to obtain good outcomes,
and it can be achieved using an intramedullary femoral guide, navigation, or robotic
devices.[38]
[39]
The anterior femoral cut can be either performed in an “anatomical” or “functional”
fashion. The “anatomical” anterior femoral cut is performed perpendicular to the AP
axis (Whiteside's line) or parallel to the transepicondylar axis and then the patella
is recentered by freeing up the lateral retinaculum. Alternatively, the “functional”
femoral cut can be performed with more external rotation relative to the patellar
plane and can be combined with lateral translation of the femoral component to avoid
additional procedures on the extensor mechanism.[33]
Once the appropriate rotation is obtained, the anterior cut is performed and the appropriate
size of the trochlear component is selected. The presence of the “grand piano” is
the sign of a good external rotation of the component. The sign is an image, resembling
a grand piano, that results on the anterior cut of the femur as a consequence of the
asymmetric anterior cut.[11] To avoid maltracking, the cutting guide and then the definitive implant, should
be placed slightly lateral. Once the femur has been prepared, the trial component
is impacted to make sure there is no ACL impingement and no stepoff with the condylar
cartilage.
The patellar cut is performed as in the standard TKA. It is important to leave at
least 14 mm of bone thickness, and care must be taken to avoid asymmetric cut and
overstuffed component. If it is not possible to leave an adequate amount of bone stock,
a bone graft, and cement or patella augmentation button are viable solutions.[40] To prevent maltracking, the patellar component should be medialized and the lateral
osteophytes should be removed to avoid bony impingement.[11]
The patella tracking should be carefully checked with trial components. If it is not
adequate, a lateral release can be performed. In case of more severe malalignment,
advancement of the vastus medialis or tibial tubercle transfer can be performed. However,
these procedures should be carefully planned preoperatively, and worse outcomes can
be expected.[33]
[40] When the correct size and position of the implant are achieved, the trial components
are removed and the definitive components are cemented. Surgeons should be careful
to avoid thermal damage to the adjacent cartilage during cementation ([Fig. 1]).
Fig. 1 Anteroposterior and lateral X-ray view after left PFA implants. PFA, patellofemoral
arthroplasty.
Postoperative Rehabilitation
Postoperative care follows the same indications as in the TKA. Full weight bearing
is immediately allowed as tolerated. Rehabilitation focuses on active and passive
ROM exercises along with gait training. In case of additional procedures, such as
advancement of the vastus medialis oblique or tibial tubercle transfer, a slower and
more cautious rehabilitation may be required.[11]
[40]
Complications and Failure
Complications and Failure
PFA shares most of the complications with the TKA, such as polyethylene wear, arthrofibrosis,
and persistent pain. Early complications, such as persistent anterior knee pain, patellar
catching or snapping, intraoperative fracture, and extensor mechanism failure are
more frequent in PFA than in TKA and are mostly related to malpositioning.[41]
[42] Conversely, loosening and infection occur at a lower rate compared with TKA.[43]
[44] However, there are some specific early complications related to PFA that should
be mentioned. One specific complication is a lateral swelling due to a hematoma after
bleeding in the lateral compartment when a lateral release during PFA is performed.
Another common complication is patellar maltracking or patellar instability due to
failure of a medial ligament repair or an inadequate tracking correction during surgery.
Furthermore, peripatellar pain due to “overstuffing” of the patellar component can
occur. Another specific complication is lateral catching due to wrong realignment
of the extensor mechanism, or more frequently, to poor trochlear component placement,
frequently related to a rotational malposition.[45]
Late complications requiring revision usually occur in the setting of a well-functioning
PFA. The most common cause of late PFA failure is progression of tibiofemoral OA,
accounting for approximately 25% of the revision at 15 years of follow-up.[46]
[47] Some authors reported that tibiofemoral OA progression is more frequent in obese
patients and when the indication is primary PFOA compared with those affected by trochlear
dysplasia.[10]
[46]
[47]
[48]
[49]
[50] Aseptic loosening is another possible cause of revision and is more frequent in
cementless PFA.[10] Van der List et al[42] published a systematic review, including 39 studies evaluating failures after PFA.
The authors concluded that the first cause of failure was tibiofemoral OA progression
(38%), pain (16%), aseptic loosening (14%), and patellar maltracking (10%). Furthermore,
pain was recognized as the first cause (31%) of early failures (within 5 years), while
OA progression was more common in late failures (46%).
Results: Literature Review
Results: Literature Review
The outcomes for PFA were quite variable, mainly because of the improvement in surgical
technique, patient selection, and implant design.[51] A recent systematic review published by van der List et al[42] concluded that the survivorship of PFA at 5-, 10-, 15-, and 20-year follow-up was
91.7, 83.3, 74.9, and 66.6%, respectively. There were few studies comparing inlay
and onlay PFA. Van der List et al[42] found that studies published before 2010 reported a higher annual revision rate
when compared with more recently published studies (2.33 vs. 1.93). Furthermore, the
authors reported good to excellent results in 87.3% of the patients 5 years after
surgery. Similar to other studies, the authors concluded that better long-term outcomes
and survivorship could be expected with second-generation implants.[42]
[44]
Dy et al[44] performed a meta-analysis to compare complication, reoperation, and revision rate
following first- and second-generation PFA and between PFA versus TKA for PFOA. The
authors concluded that there was a higher risk of reoperation (OR: 4.33) and revision
(OR: 4.93) in first generation compared with second-generation PFA.[44]
Inlay PFA
Tauro et al[32] reviewed 66 inlay PFAs with 65% of survivorship rate at 8-year follow-up and only
45% of good or excellent results. The most frequent cause of revision was patellar
maltracking and progression of tibiofemoral OA. Argenson et al[10] reported 58% survival at 16-year follow-up, while Van Jonbergen et al[27] reported 69% survivorship at 20-year follow-up. However, also in these studies,
the main reasons for revision were progression of tibiofemoral OA and patellofemoral
complications. Other authors described an incidence of patellar maltracking after
inlay PFA ranged between 17 and 36%.[17]
[32]
[35]
[52] The Australian National Joint Replacement Registry reported that more than 20% of
the implants needed a revision at 5-year follow-up.[53] All the studies are summarized in [Table 2]. In summary, results with the first generation of PFA have been disappointing, with
high complication and failure rates.[33]
Table 2
PFA inlay design results
|
Author
|
N cases (mean age)
|
Prosthesis design
|
Follow-up (y)
|
Revision rate (%)
|
Good or excellent results (%)
|
|
Blazina et al[17]
|
57 (39)
|
Richards I & II
|
2
|
35
|
N/A
|
|
Arciero et al[24]
|
25 (62)
|
Richards IICFS-Wright
|
5.3
|
28
|
85
|
|
Cartier et al[72]
|
72 (65)
|
Richards I & II
|
4
|
7
|
85
|
|
Argenson et al[10]
|
66 (57)
|
Autocentric
|
5.5
|
15
|
84
|
|
Krajca-Radcliffe and Coker[46]
|
16 (64)
|
Richards I & II
|
5.8
|
6
|
88
|
|
Mertl et al[73]
|
51 (60)
|
Spherocentric
|
3
|
6
|
82
|
|
Arnbjörnsson and Ryd[74]
|
113 (56)
|
Multiple
|
7
|
22
|
75
|
|
De Cloedt et al[75]
|
45 (51)
|
Autocentric
|
6
|
18
|
63
|
|
de Winter et al[52]
|
26 (59)
|
Richards II
|
11
|
19
|
76
|
|
Tauro et al[32]
|
62 (66)
|
Lubinus
|
7.5
|
28
|
45
|
|
Smith et al[76]
|
45 (72)
|
Lubinus
|
4
|
19
|
64
|
|
Kooijman et al[47]
|
45 (50)
|
Richards II
|
17
|
22
|
86
|
|
Board et al[77]
|
17 (66)
|
Lubinus
|
1.5
|
35
|
53
|
|
Lonner[35]
|
30 (38)
|
Lubinus
|
4
|
33
|
84
|
|
Merchant[78]
|
16 (47)
|
LCS
|
4.5
|
0
|
94
|
|
Argenson et al[79]
|
66 (57)
|
Autocentric
|
16.2
|
42
|
84
|
|
Cartier et al[36]
|
79 (60)
|
Richards II & III
|
10
|
25
|
77
|
|
Sisto and Sarin[57]
|
25 (45)
|
Kinematch
|
6
|
0
|
100
|
|
Jørgensen et al[80]
|
31(N/A)
|
Richards II
|
7.7
|
3
|
65
|
|
Gadeyne et al[81]
|
43(67)
|
Autocentric
|
6
|
24
|
72
|
|
van Wagenberg et al[48]
|
24 (64)
|
Autocentric
|
4.8
|
29
|
30
|
|
van Jonbergen et al[27]
|
185 (52)
|
Richards II
|
13.3
|
25
|
84
|
|
Charalambous et al[82]
|
51 (64)
|
LCS
|
2
|
33
|
33
|
|
Hoogervorst et al[83]
|
33 (47)
|
Richards II
|
9.7
|
21
|
90
|
Abbreviations: LCS, low contact stress; N, number; PFA, patellofemoral arthroplasty;
N/A, not available.
Onlay PFA
The second-generation PFA demonstrated significantly improved short- and mid-term
outcomes due to a careful patient selection. The Australian National Joint Replacement
Registry reported less than 10% revision rates for onlay PFAs.[53] The onlay design could reduce the incidence of patellar maltracking to 1% after
PFA.[49]
[54]
[55]
[56] Therefore, when patellar tracking was satisfactory after PFA, revisions due to patellofemoral
issues were reduced, leaving progression of tibiofemoral OA as the first cause of
failure. Excellent results were reported by Ackroyd et al[54] with a 5-year survivorship of 96%. Sisto et al,[57] in a series of custom-made implants, reported 100% survivorship at 6 years with
good to excellent results in all the patients. Also, Butler et al,[58] in a smaller series of custom-made implants, reported 91% survivorship at 5-year
follow-up. Leadbetter et al,[49] in a series of 79 onlay PFAs, reported 94% survivorship at a mean 3-year follow-up
with 84% good to excellent results. Similar results were reported by other authors
at 5-year follow-up despite a 26% reoperation rate for lateral release, debridement,
tibial tubercle transfer, or arthroscopic assessment.[59] All the studies are summarized in [Table 3].
Table 3
PFA onlay design results
|
Author
|
N cases (mean age)
|
Prosthesis design
|
Follow-up (y)
|
Revision rate (%)
|
Good or excellent results (%)
|
|
Lonner[35]
|
25 (44)
|
Avon
|
0.5
|
0
|
96
|
|
Ackroyd and Chir[18]
|
306 (62)
|
Avon
|
2
|
3.6
|
80
|
|
Cossey and Spriggins[39]
|
4 (52)
|
Avon (Navigation)
|
1
|
0
|
100
|
|
Nicol et al[50]
|
103 (68)
|
Avon
|
7.1
|
14
|
N/A
|
|
Ackroyd et al[54]
|
109 (68)
|
Avon
|
5.2
|
15
|
80
|
|
Mohammed et al[59]
|
101 (57)
|
Multiple
|
4
|
4
|
72
|
|
Butler and Shannon[58]
|
22 (49)
|
Performa
|
5
|
14
|
N/A
|
|
Leadbetter et al[49]
|
79 (58)
|
Avon
|
3
|
16
|
84
|
|
Starks et al[55]
|
37 (66)
|
Avon
|
2
|
0
|
86
|
|
Odumenya et al[37]
|
50 (66)
|
Avon
|
5.3
|
4
|
94
|
|
Gao et al[84]
|
11 (54)
|
Avon
|
2
|
0
|
100
|
|
Sarda et al[85]
|
44 (62)
|
Avon
|
4.5
|
5
|
85
|
|
Mont et al[56]
|
43 (49)
|
Avon
|
7
|
12
|
N/A
|
|
Beitzel et al[86]
|
22 (46)
|
Journey
|
2
|
0
|
N/A
|
|
Yadav et al[87]
|
51 (54)
|
LCS
|
4.2
|
20
|
N/A
|
|
Davies et al[88]
|
52 (61)
|
FPV
|
2
|
13
|
79
|
|
Hofmann et al[89]
|
40 (61)
|
Natural Knee II
|
2.5
|
10
|
95
|
|
Morris et al[90]
|
31 (55)
|
Multiple
|
2.5
|
3
|
N/A
|
|
Williams et al[91]
|
48 (63)
|
FPV
|
2
|
15
|
N/A
|
|
Al-Hadity et al[92]
|
53 (62)
|
FPV
|
3
|
3
|
97
|
|
Benazzo et al[93]
|
25 (67)
|
Multiple
|
4.7
|
12
|
N/A
|
|
Dahm et al[94]
|
59 (56)
|
Avon
|
4
|
3
|
N/A
|
|
Fink et al[95]
|
53 (61)
|
Vanguard
|
3.7
|
6
|
N/A
|
|
Hernigou et al[96]
|
85 (71)
|
Hermes
|
12
|
5
|
82
|
|
Akhbari et al[97]
|
61 (66)
|
Avon
|
5
|
7
|
80
|
|
Liow et al[98]
|
51 (53)
|
Sigma
|
4
|
8
|
76
|
Abbreviations: FPV, Femoro Patella Vialla; LCS, low contact stress; N, number; PFA,
patellofemoral arthroplasty; N/A, not available.
Patellofemoral Arthroplasty versus Total Knee Arthroplasty
Several studies reported successful results after TKA for isolated PFOA with good
mid-term results in approximately 90% of patients. However, almost 19% of the patients
still experienced anterior knee pain after surgery.[60]
[61]
[62] Dahm et al[41] compared 33 patients who underwent PFA versus 22 patients who underwent TKA for
isolated PFOA with 2.5-year follow-up. The group reported similar functional and pain
scores but higher activity scores in the PFA group. Furthermore, PFA group had fewer
complications, shorter postoperative hospital stays, less blood loss, and a better
postoperative flexion (127 vs. 118 degrees). Dy et al,[44] in a meta-analysis, compared the mid-term results and complications of PFA (inlay
and onlay) versus TKA. The authors concluded higher reoperation and revision rates
(odds ratio [OR] = 8.06 and 8.11, respectively) for PFA compared with TKA. However,
when first- and second-generation PFA were grouped separately, first-generation PFA
demonstrated a higher reoperation and revision rate (OR = 4.33 and 4.39, respectively)
compared with second-generation PFA, and there were no differences between second-generation
PFA and TKA regarding reoperation or revision rate, pain, or mechanical complications.[44] Lonner et al[63] and van Jonbergen et al[64] compared the outcomes of TKA after failed PFA to primary TKA. The studies reported
similar outcomes in both the groups, and no significant technical problems were described
in TKA after PFA. These findings were also confirmed by other studies. Several authors
confirmed that PFA could potentially delay TKA, by 10 to 15 years in up to 80% of
the patients, and revision to TKA can be performed without difficulty.[15]
[41]
[50]
[54]
[63]
[64]
[65]
Patellofemoral Arthroplasty and Unicompartmental Knee Arthroplasty
Currently, the association of PFA and UKA is one of the most debated topics. Traditionally,
PFA was contraindicated in patients with evidence of tibiofemoral OA. Nowadays, with
recent implant design and improvement in surgical techniques, combined PFA and medial
or lateral tibiofemoral UKA can be performed with good results.[66]
[67] Furthermore, the possibility to perform a UKA in cases of failure of PFA due to
medial or lateral tibiofemoral OA progression may avoid the revision to TKA.[33] Indeed, the association between PFA and UKA allows for retaining of the medial pivot,
with consequent better knee kinematic.[68] This procedure can be performed in young patients or in elderly patients with severe
comorbidities because of the less invasiveness of the surgery compared with TKA.[23] Some authors have described promising results for PFA associated to UKA. Argenson
et al[67] reported optimal ROM and no postoperative pain in 17 patients treated with unlinked
PFA and UKA. Heyse et al[69] reported a 100% survivorship at 12-year follow-up in nine patients treated with
UKA and PFA. Kamath et al[70] described an improvement in all 21 patients treated with PFA and UKA at 2-year follow-up
and reported only one significant complication (knee instability). Parratte et al[71] reported a 54% survivorship at 17-year follow-up in 77 knees with a good satisfaction
rate. Also, Sabatini et al[23] reported an improvement in functional and clinical scores at 18-month follow-up
in a case series of six knees treated with isolated PFA and nine knees treated with
combined PFA and UKA. However, few studies are available that have evaluated the association
of PFA and UKA, with small numbers and short follow-ups.
Conclusion
PFA has shown to be a viable option for the treatment of isolated PFOA. The ideal
candidate for a PFA is a middle-aged female with PFOA not responsive to the conservative
treatment and without significant malalignment or tibiofemoral OA. Modern PFA design
onlay style, strict patient selection, and improvement in surgical techniques have
produced satisfactory results in the past decades in short- to mid-term follow-up,
with 10-years of survivorship of almost 90%. The main cause of failure of second-generation
PFA is progression of tibiofemoral OA. However, the introduction of the association
of PFA and UKA may reduce the need for revision to TKA due to tibiofemoral OA progression.
Despite the good mid-term outcomes after PFA, future research is warranted to evaluate
the long-term results of the second-generation PFA, and eventually, the efficacy of
combination of PFA and UKA in comparison with TKA.
