Revision Total Knee Arthroplasty

Accomplishing a successful revision total knee
arthroplasty can be a challenging task even for the most seasoned
surgeon. Despite the added difficulties of addressing infection,
malalignment, bone loss, and instability, the primary goals of revision
surgery should remain the same as those in primary knee arthroplasty.
These goals include establishing proper alignment, balancing the
extension space in the coronal plane, and creating a flexion space that
equals the extension space. Preoperative planning allows the surgeon to
visualize these goals prior to entering the operating room and provides
the opportunity to determine what additional tools and devices will be
necessary to facilitate the revision.

Although nuclear studies, MRI, and CT scanning may be
beneficial during the assessment of the painful total knee,
conventional radiographs continue to be the most useful references for
planning a revision. Weight-bearing anteroposterior (AP), lateral, and
Merchant views offer an informative and quick method for evaluating the
prosthetic components and the surrounding bone. Previously obtained
radiographs may be available for comparison to assess progressive
changes in bone quality or component stability. Oblique flexion views
of the distal femur improve the ability to detect and estimate the size
of osteolytic lesions that may exist adjacent to the femoral
prosthesis. Fluoroscopy may also be helpful in eliminating small
degrees of obliquity seen in conventional radiographs that may obscure
radiolucent lines at component interfaces. This is particularly useful
in evaluating whether or not a cementless implant is bone ingrown.

The hip-knee-ankle radiograph allows assessment of lower
extremity alignment and is used to determine the proper femoral and
tibial mechanical axes. The distal femoral cut is made based on the
femoral mechanical axis. A line is drawn from the middle of the femoral
head to the

middle
of the knee. A perpendicular from this line at the level of the distal
femur denotes a proper distal femoral resection. The tibial mechanical
axis is defined in a similar fashion, drawing a line from the middle of
the talus to the middle of the knee. A line perpendicular to this line
at the level of the proximal tibia denotes a proper proximal tibial
resection. Deformities of the femur and tibia, such as bowing or
fracture that may compromise the position of intramedullary alignment
guides or stem insertion are detected with this radiograph. This
information allows templating of the revision distal femoral and tibial
resections to recreate a neutral lower extremity alignment and alerts
the surgeon to potential pitfalls if intramedullary alignment guides
are used.

A thoughtfully designed surgical approach is necessary
to avoid potentially devastating healing problems and to obtain
adequate access to the knee. These issues should be addressed during
the initial history and exam of the patient. Inquiries regarding
delayed wound healing, wound drainage, stiffness, or any other
complications after primary knee surgery should be made. The
examination should clearly document the location of previous skin
incisions, presence of sinus tracts, mobility of the soft tissues and
patella, active and passive range of motion, and whether an extensor
lag is present. Investigating these issues preoperatively may prevent
unexpected difficulties in the operating room.

The surgical incision must be of adequate length to
fully expose the knee joint safely without applying excessive tension
on the skin edges. It has been shown that a midline incision is less
disruptive to the anterior arterial network of the knee. However, when
multiple prior incisions are present, the most lateral skin incision
should be used. Since the blood supply to the skin over the knee comes
from medial to lateral, a medial incision in the presence of a previous
lateral incision compromises the blood flow to the skin between the
incisions. When a medial and lateral incision is encountered, the
lateral incision usually should be used and extended in both
directions. A flap is created, which must be done in the subfascial
plane to preserve the dermal plexus’ contribution to vascularity of the
flap. Frequently it is necessary to incorporate or cross a previous
incision. Any scar that must be intersected should be done in a
perpendicular fashion. Similarly, the incorporation of a previous
incision must avoid acute angles to minimize the risk of skin necrosis
and a resultant narrow bridge of skin tissue. Adherent skin must be
mobilized in the subfascial plane to identify the proper location of
the capsular incision and allow retraction of the underlying tissues.

The capsular incision is performed along the medial
border of the quadriceps tendon, the patella, and the patellar tendon
with the knee in flexion. Less invasive approaches, such as the
midvastus or subvastus incisions, generally do not provide sufficient
exposure for revision surgery. Adhesions, synovium, and scars beneath
the quadriceps tendon and throughout the medial and lateral synovial
recesses are removed with the knee extended. Care must be taken while
releasing scar over the epicondyles to prevent damage to the collateral
ligaments. The medial joint capsule is released from the underlying
tibial metaphysis, maintaining an intact sleeve around the medial
border of the proximal tibia to the posterior midline. The tibia is
externally rotated while flexing the knee until anterior subluxation of
the proximal tibia ensues. With this patellar inversion technique, no
attempt to evert the patella is made until the femoral and tibial
components have been removed. Attempts to evert the patella early risks
avulsion of the patellar tendon and should be discouraged in revision
surgery.

When revision surgery is performed on a stiff knee, more
extensile exposures may on occasion be necessary. The quadriceps snip
is the most commonly used method to relax the extensor mechanism. It is
accomplished by completely incising the quadriceps tendon at a
45-degree angle from distal medial to proximal lateral in line with the
fibers of the vastus lateralis 4 to 6 cm above the patella. The
quadriceps V-Y turndown is typically reserved for the near ankylosed
knee. This technique divides the quadriceps tendon at its junction with
the rectus muscle, at a 45-degree angle, in a distal and lateral
direction. Although effective for exposure, this approach is frequently
accompanied by extensor lag postoperatively. A tibial tubercle
osteotomy provides excellent exposure and is preferable to the V-Y
turndown in extremely stiff knees. However, persistent anterior knee
pain and nonunion have been described with this technique. The routine
use of extensile exposure is unnecessary and should be discouraged.
More than 90% of revisions can be performed with the patellar inversion
technique previously described.

Depending on the stability and type of fixation, the
removal of total knee components can be a time-consuming and
frustrating process. However, the benefits of a safe and orderly
extraction must be considered. Avoidance of condylar bone loss or
fracture can greatly facilitate a successful reconstruction.
Familiarity with implant removal instruments and their proper use
assists in making this step more efficient and less complex.

The order in which the implants are removed decreases
the risk of complications and enhances the ability to remove the next
component. The tibial polyethylene insert is removed first. Knowledge
of implant-specific removal instruments for modular inserts is
necessary. Most modular inserts can be removed with an osteotome that
will disengage the plastic from the underlying tibial tray. Initial
removal of the tibial insert will increase space in the knee that is
needed to remove the other components.

The femoral component is generally removed second. The
implant/cement interface for cemented implants is disrupted with thin
osteotomes or ultrasonic devices. Working at this interface from both
the medial and lateral sides limits bone loss. The implant/bone
interface for cementless implants is most easily divided with thin
osteotomes, power saws, or thin high-speed cutting burrs. The anterior
condylar, distal, and chamfer interfaces are usually

readily
accessible. The posterior condylar interface is more difficult to reach
and may require angled osteotomes or a Gigli saw for disruption if this
portion of the component is well fixed. Once loosened, the femoral
implant can be removed by gently tapping the anterior flange with a
metal punch and mallet in a distal direction. Vigorous disimpaction
should be discouraged as this indicates that the fixation has not been
sufficiently disrupted to proceed with removal.

Removal of the femoral component provides access to the
tibial tray. The same instruments used to disrupt the femoral
interfaces are also used here. However, cemented implants with a
roughened surface may require a saw or ultrasonic device to separate
the cement from the implant. After the component is loosened, the knee
is hyperflexed and the tibia is anteriorly translated. Osteotomes can
then be stacked under the tray to elevate it out of the proximal tibia.

Uncemented stems without biologic fixation typically are
removed with their respective implant during the extraction process
outlined above. However, well-fixed cemented stems and roughened stems
secured biologically to bone can be very difficult to remove. If the
stems cannot be disimpacted with the attached implant, the condylar
portion should be disengaged or cut away from the stem. This provides
direct access to the stem. Cemented stems can then be removed by
breaking the cement/stem interface with a high-speed burr or ultrasonic
device. Biologically fixed stems can be removed with trephines designed
to remove cementless total hip arthroplasty femoral stems or a narrow
high-speed burr. Rarely a femoral window or tibial tubercle osteotomy
is required for the removal of well-fixed cemented or cementless stems.

Extraction of failed components is an often overlooked
step of the revision. Use of proper tools and patience is warranted to
avoid making the surgery more complex by removing excessive bone or
initiating fractures.

With the failed components removed, adequate space
should be available within the joint to observe bone quality and
deficiency and begin preparing the femur and tibia for reimplantation.
The hip-knee-ankle radiograph may be reassessed to determine whether an
intramedullary guide may be used and to review the resection level and
angle for the distal femoral and proximal tibial resections.

In most cases, the revision distal femoral cut may be
referenced from an intramedullary rod that is secured within the
diaphyseal cortex. If the femoral canal is not amenable to an
intramedullary guide, an extramedullary guide or computer assistance
may be used. The former is less accurate than intramedullary guidance,
and the latter adds complexity to the case. Regardless, a flat cut is
made with an oscillating saw through the cutting guide at an angle
perpendicular to the mechanical axis. The amount of bone removed should
be minimal to prevent elevating the joint line excessively. Exceptions
to this include a significant preoperative flexion contracture from an
inadequate primary distal femoral resection or if nonsupportive bone is
encountered that will eventually require augmentation. The estimated
level of the joint line is 2 to 2.5 cm distal to the epicondyles, 1 cm
distal to the inferior pole of the patella with the knee in extension
or more simply when the patella rests in the proper position in the
trochlear groove in full extension.

The proximal tibial resection provides the foundation on
which the revision is built. Therefore, the importance of creating an
accurate cut that is perpendicular to the mechanical axis cannot be
overstated. This resection can be referenced from intramedullary or
extramedullary alignment guides. Intramedullary guides may be
influenced by bowing within the proximal tibia or by the presence of
sclerotic bone within the intramedullary canal.

Although several techniques exist, we prefer using the
classic method of balancing the knee if the collateral ligaments are
not attenuated. After the components are provisionally sized, a
coronally symmetric extension gap is created with the appropriate
medial and lateral releases. The height of this gap is measured with
the knee in extension. The knee is then flexed and the flexion gap is
measured and then tensioned. The appropriate AP cut guide is placed on
the distal femur and is rotated until parallel with the tibial cut. A
stylus is used anteriorly to prevent notching the distal femur. The
size of the AP cutting block can then be manipulated to match the
height of the flexion gap with the previously measured extension gap.
Other methods used to establish rotation of the femoral component, such
as the posterior condylar axis or trochlear axis, are difficult to
reference in the revision situation because of previous bony resections
and bone loss. While we prefer to use the classic method described
above to set femoral rotation and balance the flexion gap, the
epicondylar axis can be used to assess femoral rotation when collateral
ligaments are severely attenuated.

After the flexion and extension gaps are balanced, the
femoral box and chamfer cuts are made. If the use of augments has been
calculated into the gap balancing, augments should be added to the
femoral cutting blocks to avoid unnecessary bone resection. The
necessity of stems, augments, and degree of articular constraint can
now be determined.

Some degree of bone loss is to be expected when
performing a revision total knee replacement. Significant deficiencies
may be seen when aseptically loosened components have been neglected or
the primary total knee failed owing to osteolysis or infection.
Although bone deficiencies cannot be comprehensively evaluated before
the failed components have been removed, assessment of the preoperative
radiographs should alert the surgeon to existing defects and allow
preparation of a surgical strategy to manage these defects. Bone loss
can be categorized into cavitary defects, which have an intact
surrounding cortical rim, or segmental defects, with no surrounding
cortex. Depending on the severity of the bone loss, cement, cement and
screws, bone graft, modular metallic augments, and custom implants can
be used to fill the deficiencies and recreate the joint line.

Cement is frequently used to fill small contained defects of both the femur and the tibia. When cement is used to

fill more significant defects, screws partially embedded in host bone
can be added to strengthen the cement construct. This technique can be
extremely effective in moderate-sized deficiencies, especially in older
patients.

Bone graft has been used to address a wide variety of
osseous deficiencies around the knee from small cavitary lesions to
extensive segmental defects. Because autograft is usually in short
supply, allograft bone is generally used in revision total knee
arthroplasty. Although a thorough discussion of bone graft basic
science is beyond the scope of this chapter, familiarity with the types
of allograft, sterilization methods, storage process, disease
transmission, and incorporation with the host is required before its
use.

Particulate allograft is typically used to fill
contained cavitary defects when sufficient host bone is present to
provide structural support for the revision components. If healthy host
bone is encountered at the base of the lesion, vascularization of the
allograft and replenishment of bone stock can be expected.

Structural allografts are most commonly used to manage
segmental defects that are too large to be managed with metallic
augments. This scenario is commonly seen in cases of advanced
osteolysis or infection. Femoral head allografts have been used
successfully to fill large cavitary defects of both the distal femur
and proximal tibia in these situations and provide a structurally sound
surface on which stemmed cemented revision components are used.

Segmental defects that extend proximal to the collateral
insertions on the femoral epicondyles impair ligamentous stability as
well as component stability. This situation may be encountered with a
comminuted supracondylar periprosthetic fracture or severe cases of
osteolysis. Partial or full distal femoral allografts (depending on the
bone defect location), may be cemented to stemmed revision components
using a back table technique. The allograft-prosthetic composite is
then secured to the host femur using a diaphyseal engaging stem.
Another alternative in this situation is a salvage system or tumor
prosthesis which uses a rotating hinge device. This is particularly
useful in the elderly, limited-demand population.

Concerns regarding structural allograft resorption,
nonunion, fracture, and disease transmission have encouraged the use of
metallic devices to fill segmental osseous defects. Modular metallic
augments use the predictable properties of metal to manage segmental
deficiencies adjacent to both tibial and femoral revision prostheses.
These devices allow the surgeon to re-establish the joint line, assist
in component alignment, and adjust soft tissue balance to improve knee
kinematics. The augments are available in various sizes and shapes,
with corresponding trials, creating a versatile system that has greatly
reduced the necessity for structural bone grafts and custom implants.

Tibial augmentation devices are available in full wedge,
hemiwedge, and block geometries, depending on the manufacturer. They
usually are applied to fill segmental medial, lateral, or combined
defects of 5 to 20 mm in depth. The location and size of the defect
determines which type of augment is appropriate to preserve supportive
host bone. Although joint line elevation may be accomplished with the
use of a thicker insert, this has the disadvantage of placing
increasing stress on the locking mechanism of the tibial insert to the
baseplate. Combined medial and lateral block augments will elevate the
joint line without applying undue stress on the locking mechanism. A
longer stem should be considered in this situation, as the augments
will effectively shorten stem penetration into host tibia.

Femoral modular augments are available in the block
geometry in various thicknesses and may be applied to the medial and/or
lateral condyles distally and posteriorly. Distal augments fill
segmental defects below the epicondyles or depress the joint line to
its anatomic location. As in the tibia, a longer stem may be required
to effectively engage the host femur when distal augmentation is
employed. Posterior augments are beneficial in decreasing the flexion
gap, which is usually greater than the extension gap in the revision
situation. Laterally placed posterior augmentation assists patellar
tracking by externally rotating the femoral component when
posterolateral bone is deficient.

Significant bony anatomic deficiencies occasionally
require tumor prostheses or custom implants. Modern tumor prostheses
may have cemented or press-fit intramedullary fixation to the host bone
and are equipped with modular diaphyseal segments. These features
provide a versatile implant that has intraoperative flexibility.
However, most tumor prostheses use a rotating hinge articulation that
increases stresses placed on the bone/implant interface and may not be
ideal for more active patients.

As previously discussed, some degree of bone loss is to
be expected when performing a revision total knee replacement. The use
of stems on revision components is designed to transfer stress away
from the damaged periarticular bone to the shaft. Contemporary revision
total knee systems are equipped with numerous stem options: variable
length stems designed to engage the metaphyseal or diaphyseal bone,
cemented or press-fit interfaces, and straight or offset stems.
Although the use of stems in revision total knee arthroplasty is
routine, the appropriate use of the stem options available remains
controversial.

Several biomechanical studies comparing cemented versus
noncemented stems in cadaveric tibias reveal significantly less tibial
tray micromotion in the cemented group. Similarly, retrospective
clinical studies consistently show higher rates of radiolucent lines
adjacent to noncemented stems at 18 months to five years postop. The
only retrospective comparison revealed significantly greater
radiographic stability when cemented stems were used.

Uncemented diaphyseal engaging stems have become popular
because they are simple to use and help guarantee acceptable implant
alignment in most circumstances. However, in some cases, diaphyseal
stem engagement may compromise tibial component position owing to the
limitations of a canal-filling stem. An unrecognized valgus tibial bow
will malalign the tibial component into valgus when a canal-filling
diaphyseal engaging stem is used. Also, the frequent anteromedial
location of the shaft in reference to the plateau will cause the
baseplate to overhang medially when a canal-filling stem is used.
Although an offset tibial stem may decrease such malposition, a
relatively narrow

metaphyseal
engaging cemented straight or offset stem may be adjusted within the
cement mantle to fully accommodate these anatomic variants.

Canal-filling stems can have a similar negative effect
on the alignment of the femoral prosthesis. Because of the anterior
femoral bow, a diaphyseal engaging stem may contact the anterior
endosteal surface of the canal, causing flexion of the component.
Alternatively, if the canal-filling stem slides past the anterior
endosteal surface, the femoral component may translate anteriorly, both
overstuffing the patellofemoral joint and increasing the flexion gap.
As in the tibia, a narrow metaphyseal engaging cemented stem may be
positioned more posteriorly within the cement mantle of the distal
femur to decrease the flexion gap without being biased by the femoral
bow.

The judicious use of offset stems may limit component
malposition when canal-filling stems are used. However, the
intraoperative flexibility, as well as biomechanical and radiographic
comparisons, prompts some surgeons to continue to use cemented
metaphyseal engaging stems in most cases.

Articular constraint refers to the degree of stability
afforded to the knee joint by prosthetic design. Additional constraint
must be supplied by the implants if the soft tissues around the knee
are insufficient to maintain joint stability. In the revision
situation, the choices of constraint include posterior stabilized
articulations, nonlinked constrained prostheses, and rotating hinge
constrained designs. Because increased levels of constraint generate
larger stresses on the implant/bone interface, the least amount of
constraint that provides a stable joint should be selected. Although a
thorough preoperative examination may alert the surgeon to potential
instability issues, a final decision regarding the degree of articular
constraint often cannot be made until bone defects are addressed and
ligament balancing has been accomplished.

Most revision total knee replacements can be
accomplished with posterior stabilized implants. These prostheses
provide minimal constraint through a congruent tibiofemoral articular
surface and a spine and cam mechanism that promotes femoral rollback
and prevents posterior displacement of the tibia in flexion. This
design requires functional collateral ligament support for varus and
valgus stability in flexion and extension. Equalizing the flexion and
extension gaps is necessary to prevent the spine from dislocating
posterior to the cam if an excessive flexion space exists.

Nonlinked constrained implants are used when one or both
collateral ligaments are insufficient, creating varus or valgus laxity
or an excessive flexion gap that cannot be balanced with the extension
gap. This design is equipped with a taller and thicker polyethylene
spine or post that may be reinforced with an underlying metal pin. The
post closely approximates the intercondylar box providing rotational,
translational, and varus/valgus support to the knee joint. Stems should
be used to dissipate forces transmitted to the implant/bone interface.

Rotating hinge constrained components are generally
reserved for cases of severe bone loss or global instability where the
flexion gap is so excessive that the condylar post of a nonlinked
constrained device will be unable to prevent posterior displacement of
the tibia under the femur. Because rotating hinge devices do not
constrain rotation, less stress may be placed on the implant/bone
interface than with nonlinked constrained devices. Generally, the use
of rotating hinge constrained components is discouraged except in
elderly patients with global instability, severe bone loss, and low
functional demands because the large osseous resection necessary for
implantation limits salvage options (including arthrodesis).

Infection is the cause of failure in approximately 1% to
2% of total knee replacements. Therefore a high index of suspicion for
infection is warranted during the evaluation of all failed total knees.
Prompt diagnosis not only may decrease the risk of morbidity and
mortality but also increases the available treatment options.

An investigation for infection should occur during the
evaluation of every patient with a painful total knee. Unfortunately,
the presentation varies considerably depending on the length of time
since surgery, the duration of the infection, the virulence of the
offending organism, the host status, and use of antibiotics.
Nevertheless, a history of continuous knee pain, swelling, warmth,
problems with postoperative wound healing, drainage, or an active
infection in another area of the body prompts further scrutiny.
Radiographs are valuable for assessing the components and periarticular
bone quality but rarely distinguish infectious from aseptic failures.

Because of inaccuracies of diagnostic tests, none can be
used in isolation to reliably predict the presence of infection, but
when used in concert, they allow detection of approximately 90% of
infections. Serologic tests including white cell count, sedimentation
rate, and C-reactive protein are sensitive but relatively nonspecific
screening tests. Routine use of various radioisotope scans appears
impractical owing to their low sensitivity. Aspiration of the knee may
provide the most useful preoperative information if there is clinical
suspicion for infection and the patient has not received antibiotics
within 2 weeks. Although the sensitivity of culture results after
aspiration is limited, analysis of the synovial fluid revealing
>2,500 white blood count (WBC)/mm and >90% polymorphonuclear
(PMN; leucocytes) is highly sensitive and specific for infection in the
prosthetic knee joint. If an infectious cause for total knee failure
remains questionable intraoperatively, frozen histologic analysis by an
experienced pathologist should be performed with tissue taken from
multiple sites in search of evidence of acute inflammation. Despite
clinical scenarios, such as the presence of inflammatory arthropathies
or indolent organisms, that continue to impair our ability to
distinguish septic from aseptic failures, the judicious use of
diagnostic tests improves the ability to identify infected total knee
replacements.

The treatment of an infected total knee depends on the
timing and duration of the infection, the virulence of the organism,
and the patient’s overall health. Fluid and tissue cultures must be
obtained to guide antibiotic therapy. Acute infections, whether in the
early postoperative period or hematogenous in origin, are typically
managed with attempted prosthetic retention. Open surgical debridement,
radical synovectomy, and tibial insert exchange followed by a short
period of intravenous (IV) antibiotics and chronic suppression are
recommended in the proper situations. Required criteria include the
following: no evidence of osteomyelitis, component loosening, or sinus
tract formation; an organism of low virulence that is susceptible to
antibiotics; and symptoms that have been present for a short period of
time (i.e., <4 weeks postop or within 48 hours of a hematogenous
infection). The presence of resistant organisms or an immunocompromised
host appear to provide less favorable results with prosthetic retention.

Exchange arthroplasty is the preferred treatment for
infections that have been present for >4 weeks or involve more
virulent organisms. This process involves resection of the infected
components, a thorough joint debridement, and prosthetic reimplantation.

Delayed exchange arthroplasty has been preferred by most
surgeons in North America. Eradication of infection consistently
approaches 90% in the literature with a two-stage approach. During the
first stage, after component removal and debridement, a cement spacer
that is impregnated with heat-stable antibiotics is used to discourage
soft tissue contracture while delivering high local doses of
antibiotics to the infected knee. Some surgeons currently fashion an
articulating spacer to minimize bone loss and knee stiffness while
improving patient function between stages. This technique also
facilitates exposure at reimplantation without any apparent increase in
reinfection rates. Systemic antibiotics usually are discontinued about
6 weeks after the spacer is placed. An aspiration prior to
reimplantation may be performed and serologic tests for inflammation
(erythrocyte sedimentation rate [ESR], C-reactive protein [CRP]) are
followed for a gradual return to normalcy prior to reimplantation.
Reimplantation usually is performed 2 to 3 months after the first
stage. If serologic tests do not normalize, or if frozen section
analysis at the time of reimplantation suggests continued active
infection, a repeat debridement with articulating spacer exchange is
performed and reimplantation is delayed.

Functional results after revision TKA for infection have
improved with more rapid diagnosis and the availability of modern
revision systems. However, results have been tempered by increasing
rates of bacterial antibiotic resistance as well as more
immunocompromised hosts. Failure to eradicate total knee infections
after repeated attempts at reimplantation leaves the surgeon with few
options. Resection arthroplasty is reserved for patients with poor
baseline functional requirements. Arthrodesis remains a viable option
in patients with irreparable extensor mechanism disruption, multiple
recurrent infections, or an inadequate soft tissue envelope provided
the contralateral limb and ipsilateral ankle and hip are functional.
Above-knee amputation is generally reserved for situations where other
reconstructive or salvage efforts are deemed futile.

Based on the Mayo Clinic Joint Registry, the prevalence
of periprosthetic fractures adjacent to primary TKAs is 2.3% and rises
to 6.3% after revision TKAs. The number of patients with this problem
appears to be increasing as the volume of total knees being implanted
climbs and patients live longer and more active lives. Distal femur
fractures are seen more frequently than patellar or proximal tibia
fractures. Issues relevant to the treatment of these periprosthetic
fractures include the anatomic location, bone quality, functional
requirements of the patient, and whether the fracture occurred
intraoperatively or postoperatively.

Intraoperative distal femur fractures typically involve
the condyles and occur during removal of failed components or during
the insertion of a posterior stabilized implant into an incompletely
prepared intercondylar box. Although screws may provide sufficient
fixation for a nondisplaced fracture, transferring stress away from the
condyle to the shaft through the use of a stemmed component is
warranted when fractures are unstable.

Most postoperative fractures of the distal femur are
traumatic in origin. Previous notching of the distal femur may
contribute to torsional failure. Treatment is based on fracture
displacement and component stability. Nonoperative treatment using a
cast or brace should be considered for nondisplaced fractures when the
femoral component remains stable, especially while treating a patient
with low functional demands. Close radiographic follow-up is required
to ensure that the fracture remains well aligned.

Displaced fractures with stable implants are treated
with rigid internal fixation or intramedullary nails. Although several
types of plates have adequate reported results, fixed-angle devices
with proximal and distal locking screws are an attractive option.
Fixation in the osteopenic bone that is frequently encountered is
improved significantly when locking screws are used. The precontoured
distal femoral plate may also assist with indirect reduction of the
fracture and can be placed through a smaller incision to produce
minimal disturbance to the fracture hematoma. Modern retrograde
intramedullary nails also provide rigid fixation. However, distal
fixation can be a problem in some fracture patterns. The ability of a
specific posterior stabilized femoral component to accept a retrograde
nail must be investigated preoperatively. Occasionally bone grafting or
cement augmentation is required to enhance distal fixation when
extensive comminution or osteopenia is present.

Distal femur fractures with loose femoral components
require component revision in addition to fracture fixation. A stemmed
component with adjuvant fixation is used. However, if comminution is
severe, a rotating hinge tumor prosthesis can be used to reconstruct
the knee.

Periprosthetic fractures of the tibia plateau that occur
intraoperatively may be secured with cancellous screws or a low-profile
plate. A longer tibial stem is recommended to protect the fractured
plateau. Metaphyseal fractures that occur adjacent to the stem are
usually nondisplaced and vertical in orientation. They often occur
during removal of a failed tibial component. When recognized, they
should also be treated with a longer stem to bypass the defect.
Nondisplaced intraoperative fractures that are distal to the

stem
have been successfully treated with a brace or cast and limited weight
bearing. However, displaced fractures distal to the stem require
internal fixation for stability.

Postoperative periprosthetic fractures of the tibia
plateau commonly lead to tibial implant failure. Prosthetic
malalignment, osteopenia, osteolysis, and osseous necrosis have been
implicated as predisposing factors. Revision of the tibial component
with a stemmed implant and managing the bone loss with modular augments
or bone graft are recommended.

Postoperative fractures adjacent to the stem of a stable
tibial prosthesis are generally caused by a traumatic mechanism. These
fractures are often nondisplaced and may be treated in a long-leg cast.
Displaced fractures are best managed with a plate and screw construct.
Metaphyseal fractures with an unstable prosthesis require revision to a
longer stemmed prosthesis. Stable tibial components with a
postoperative fracture distal to the stem often can be treated
nonoperatively in a long-leg cast with protected weight bearing. If the
tibial prosthesis is loose, revision surgery is indicated. However,
delayed reconstruction after the fracture has healed in a cast may
simplify the surgery.

Tibial tubercle fractures that occur in the
postoperative setting may be the result of trauma or owing to the
nonunion of a tubercle osteotomy. Nondisplaced fractures are amenable
to casting in extension. Displaced fractures require reduction and
internal fixation with screws or wires.

Intraoperative periprosthetic patella fractures usually
occur during the removal of a failed patellar implant with deficient
underlying bone. Postoperative fractures generally are the consequence
of direct impact onto the knee or the result of indirect trauma from a
forceful quadriceps contraction. Increased vulnerability to patella
fractures occurs after excessive bone resection, overstuffing of the
patellofemoral joint, or eccentric position of the component. The
method of periprosthetic patella fracture management is controversial
and depends on the location, extensor mechanism function, stability of
the implant, and medical status of the patient.

Patella fractures with a stable implant and a functional
extensor mechanism generally are treated nonoperatively with a brace or
cast keeping the knee in extension while allowing full weight bearing.
Occasionally a nonunited marginal fracture fragment may require
excision for continued pain. Surgical repair is recommended for
fractures associated with a significant extensor lag. When fractures
with an intact extensor mechanism are accompanied by a loose implant,
the decision to simply remove the component versus attempted revision
should be based on the remaining patellar bone stock.

Difficulties with obtaining adequate knee motion after
TKA can be a frustrating experience for the patient as well as the
surgeon. Although the normal knee range of motion is approximately 0 to
140 degrees, most functional activities can be accomplished with 95 to
100 degrees of flexion. Less excursion of the knee makes walking, stair
use, and sitting problematic.

Arthrofibrosis is the most commonly identified cause of
limited motion after a technically sound total knee replacement has
been performed. Dense adhesions develop within the joint, resulting in
limited flexion and extension. Aggressive range of motion protocols
have been instituted at most hospitals to prevent prolonged
immobilization, which can exacerbate this condition. However, it is
difficult to predict which patients will require further intervention
to maintain motion. A careful manipulation under general or regional
anesthesia may restore knee motion to near its observed intraoperative
level if performed prior to the maturation of adhesions in the first 6
weeks postoperatively. Once scar has matured, arthroscopic lysis of
adhesions has been used effectively to disrupt fibrous bands around the
fat pad and superior pole of the patella. Arthroscopic release of the
posterior cruciate ligament also has provided significant improvements
in motion when a cruciate-retaining prosthesis presents with a stiff
knee.

Physical examination and radiographs of the knee may
reveal technical problems with the primary surgery that may impede
motion. Retained osteophytes, implant malalignment, improper component
sizing, and imbalance of flexion and extension gaps can mechanically
limit motion. Unlike arthrofibrosis, diminished motion was most likely
present at the completion of the primary surgery in these situations.
Manipulation and arthroscopic releases are rarely helpful under these
circumstances. Revision surgery is necessary to improve these motion
limitations. Since significant complications may accompany revision
TKA, careful consideration must be taken before embarking on this
effort to re-establish motion.

Retained osteophytes located on the posterior femoral
condyles can impair both flexion and extension. A mechanical block
caused by impingement of the osteophyte on the posterior tibia may
limit flexion. Extension is impaired by the mass of the osteophyte,
tenting the posterior capsule. Removal of the tibial insert is required
to access the posterior knee prior to the cautious removal of the
osteophytes with an osteotome.

Component malalignment can also limit motion,
particularly concerning the slope of the tibia baseplate in the
sagittal plane. Excessive posterior slope may limit full extension and
cause flexion instability. Anterior slope of the baseplate may cause
hyperextension of the knee and limit flexion. Knowledge of the required
slope for the specific implant in question is needed prior to its
revision.

Improper femoral component sizing and the mismatch of
flexion and extension gaps are closely related. A common error is
underresection of the distal femur. This produces a tight extension gap
and a resultant flexion contracture. Similarly, an insufficient
posterior femoral resection will lead to oversizing the femoral
component and create a tight flexion space. Flexion of the knee may
also be impaired if insufficient patellar bone is resected, creating an
“overstuffed” patellofemoral joint.

Surgical management of a stiff total knee should be
undertaken cautiously because several mechanisms are not amenable to
operative repair. A thorough evaluation is necessary to determine the
appropriate treatment. Although surgical intervention has provided
statistically significant improvements in motion, functional
improvements are not consistently realized.

Modern ultra–high-molecular-weight polyethylene provides
a low-friction surface intended to articulate with a polished femoral
component. However, even with a highly congruent articulation, small
polyethylene particles are released from the tibial insert owing to the
complex shearing and rotational motions of the knee joint, even during
the normal gait cycle. Furthermore, tibial locking mechanisms in
modular components allow some degree of insert micromotion, producing
backside polyethylene wear. Several additional variables have been
implicated in accelerating particle release: abrasive wear, method of
polyethylene sterilization and shelf life, coronal alignment of
implants, congruency of prosthetic articulations, patient size, and
activity levels. Polyethylene wear produces various total knee problems
ranging from aseptic synovitis to osteolytic defects that can impair
component fixation and complicate reconstructive efforts. As total knee
replacements are now implanted in young, active patients, long-term
survivorship may become increasingly impaired by material limitations.

The clinical triad of effusion, pain, and progressive
changes in coronal alignment of the knee characterizes accelerated
polyethylene wear. The effusion is related to the inflammatory reaction
induced by macrophage engulfment of the shed particles creating a boggy
synovitis that may be accompanied by pain. The asymmetric wear may
produce symptomatic instability. If neglected at this point,
progressive osteolysis will ensue. Therefore, it is important to revise
the patient presenting with these symptoms promptly.

Management of osteolysis depends on the extent and
location of the lesions as well as component stability. Preoperative
radiographs, including oblique flexion views, should alert the surgeon
to loose components and allow an estimation of bone loss. Revision
components with alternate levels of articular constraint, stems,
modular augments, and allograft may be necessary to facilitate
reconstruction. The damaged tibial insert is removed and a full
synovectomy is performed. All components should be stressed to ensure
stability. If stable, consideration of filling defects with particulate
allograft or cement is warranted. Unstable components are removed and
revised as described in the section above.

The continuum of problems associated with polyethylene
wear highlights the need for routine postoperative surveillance of
total knee patients. It has also led to innovative devices intended to
reduce backside wear, which appears to correlate with osteolysis.
All-polyethylene, nonmodular metal-backed, and rotating-platform tibial
components are currently being investigated to determine their ability
to limit osteolysis.