A variety of techniques has been described, including external fixation, internal fixation by compression plates, intramedullary fixation through the knee with a modular nail, and antegr
Trang 1Arthrodesis is one of the last options available to obtain a stable, painless knee in a patient with a damaged knee joint that is not amenable to reconstructive measures Common indications for knee arthrodesis include failed total knee arthroplasty, periarticular tumor, posttraumatic arthritis, and chronic sepsis The primary contraindications to knee fusion are bilateral involvement or an ipsilateral hip arthrodesis A variety of techniques has been described, including external fixation, internal fixation by compression plates, intramedullary fixation through the knee with
a modular nail, and antegrade nailing through the piriformis fossa Allograft or autograft may be necessary to restore lost bone stock or
to augment fusion For the carefully selected patient with realistic expectations, knee arthrodesis may relieve pain and obviate the need for additional surgery or extensive postoperative
rehabilitation
In 1958, Charnley and Lowe1 re-ported a 98.8% fusion rate in 171 adults who underwent compression arthrodesis of the knee The authors used one transfixion pin in the distal femur and another in the proximal tibia, with compression clamps placed medially and laterally (Figure 1) Most of the patients had tubercu-losis, osteoarthritis, or rheumatoid arthritis; none had a previously at-tempted knee arthroplasty
Howev-er, with the development of total knee arthroplasty (TKA), the failed TKA became an indication for knee arthrodesis.2Using Charnley clamps for the procedure, Hagemann et al3
in 1978 reported a fusion rate of only 64% in 14 patients with failed TKA
Lack of adequate bone contact and poor stability were cited as the main causes of failure
Unsatisfactory fusion rates in post-TKA patients initiated develop-ment of new techniques to improve the reliability of fusion To improve
stability and rates of fusion, both ex-ternal and inex-ternal fixation methods were attempted The external fixa-tion constructs used were unipla-nar,4modified biplanar frames with transfixion pins and half pins,5,6 or circular frames.7-9 Internal fixation devices included an anterior ten-sion-band plate,10 double plating,11 antegrade locking nail,12-14combined intramedullary rod and plate fixa-tion,15and modular intramedullary nails.16,17 No single technique has proved to be superior in all situa-tions; each has its relative
advantag-es and disadvantagadvantag-es
Indications and Contraindications
In the late 1800s and early 1900s, knee arthrodesis primarily was per-formed for sepsis, articular tubercu-losis, and instability caused by polio-myelitis.1Today, the most common indication for fusion is a failed,
unre-James H MacDonald, MD
Sanjeev Agarwal, FRCS (Orth)
Matthew P Lorei, MD
Norman A Johanson, MD
Andrew A Freiberg, MD
Dr MacDonald is in private practice in
Annapolis, MD Dr Agarwal is
Orthopaedic Surgeon, Leeds
Orthopaedic Program, Leeds General
Infirmary, Leeds, UK Dr Lorei is in
private practice in Bryn Mawr, PA Dr.
Johanson is Chair, Orthopaedic Surgery,
Drexel College of Medicine,
Philadelphia, PA Dr Freiberg is Chief,
Arthroplasty Service, Massachusetts
General Hospital, Boston, MA.
None of the following authors or the
departments with which they are
affiliated has received anything of value
from or owns stock in a commercial
company or institution related directly or
indirectly to the subject of this article:
Dr MacDonald, Dr Agarwal, Dr Lorei,
and Dr Johanson Dr Freiberg or the
department with which he is affiliated
serves as a consultant to or is an
employee of Zimmer.
Reprint requests: Dr MacDonald,
Orthopaedic and Sports Medicine
Center, 108 Forbes Street, Annapolis,
MD 21401.
J Am Acad Orthop Surg
2006;14:154-163
Copyright 2006 by the American
Academy of Orthopaedic Surgeons.
Trang 2visable TKA, which may be
second-ary to persistent infection, massive
bone or soft-tissue loss, or
irrepara-ble damage to the extensor
mecha-nism.18Septic arthritis and
osteomy-elitis are the next most common
indications after failed TKA for knee
arthrodesis
An uncommon complication
fol-lowing TKA is loss of the extensor
mechanism A number of techniques
have been described for
reconstruc-tion, including extensor allograft,
which achieves variable results.19
Knee fusion may be considered as a
salvage method for this condition,
particularly when extensor
mecha-nism reconstruction has failed
Patients with highly aggressive or
malignant periarticular tumors may
also be treated by fusion after
resec-tion when allograft, metal
prosthe-ses, or rotationplasty are not
appro-priate Fusion is most commonly
considered after tumor resection
when the extensor mechanism is
lost or in the presence of infection.20
Occasionally, knee arthrodesis is
indicated for young patients with
unilateral posttraumatic
degenera-tive joint disease who maintain jobs
that require heavy manual
la-bor.12,21 Rarely seen indications are
painful ankylosis, paralytic
condi-tions with severe deformities, and
neuropathic joints Despite
exten-sive soft-tissue release, a
chronical-ly painful and stiff knee is unlikechronical-ly
to regain useful range of motion
fol-lowing total knee replacement In
patients with neuropathic joints,
ar-throplasty may fail because of
asep-tic loosening or a poor functional
re-sult In these circumstances, fusion
may be indicated for salvage.22
Pa-tients who experience significant
disability from instability also are
candidates for elective arthrodesis
The primary contraindications to
knee fusion are bilateral
involve-ment or an ipsilateral hip
arthrode-sis.2When planning surgery, it is
im-portant to check the ipsilateral hip
for arthritis; a fused knee will
trans-fer more stress to the hip and ankle
The decision to proceed with a knee arthrodesis should be individu-alized, dependent on the clinical sit-uation and the expectations of the patient The functional limitations imposed by arthrodesis should be fully understood preoperatively by the patient
Alternatives to Knee Arthrodesis
When primary TKA or revision TKA are not good options, resection ar-throplasty may be considered as an alternative to knee arthrodesis in some patients This procedure in-volves removal of all components and cement when an arthroplasty is
in place as well as thorough débride-ment The bone ends are shaped to provide maximum contact in exten-sion; however, no attempt is made to achieve fusion Postoperative sup-port is provided by a cast followed by bracing, when required, and patients are encouraged to flex and extend the knee as is comfortable
In one report of 26 patients, 28
knees with failed, infected TKA were managed by resection arthroplasty.23 Systemic signs of infection were eliminated in all knees; local signs of infection were eliminated in 89% of the knees After surgery, 58% of the patients (15/26) were able to ambu-late without assistance, 3 knees had spontaneous fusion, and 6 were later converted to an arthrodesis because
of instability In the successful group, the average postoperative range of motion was 36° The authors con-cluded that patients’ degree of satis-faction following a resection arthro-plasty is directly related to their degree of preoperative disability Transfemoral amputation is an option for the severely damaged knee not suitable for primary or revision TKA, resection arthroplasty, or fu-sion
General Principles
Systemic problems, such as diabetes mellitus, rheumatoid arthritis, chronic renal failure, peripheral
vas-Figure 1
Charnley compression clamp (Adapted with permission from Nelson CL, Evarts
CM: Arthroplasty and arthrodesis of the knee joint Orthop Clin North Am
1971;2:245-264.)
Trang 3cular disease, and corticosteroid use,
are evaluated preoperatively because
of their potential effect on wound
healing In addition, a complete
pe-ripheral neurologic examination is
performed and any flexion
deformi-ty, malalignment of the limb, and
loss of range of motion are noted
The examination includes standard
anteroposterior and lateral knee
ra-diographs along with standing
hip-to-ankle radiographs for assessing
limb alignment and position of
ex-isting implants
Assessment of existing scars is
important; a solitary longitudinal
scar can be used for the surgical
inci-sion in knee arthrodesis Because
most of the blood supply to the skin
overlying the knee is derived from
fascial perforators from the medial
side, the surgical approach should
use the most lateral longitudinal
parapatellar incision when previous
multiple incisions are present.24
An existing transverse scar can be
crossed perpendicularly without
compromise of the skin flaps;
how-ever, plastic surgery consultation is
recommended when the viability of
the overlying skin is in question
A preoperative trial period in a
knee immobilizer or a cylinder cast,
simulating a knee fusion, will
dem-onstrate for the patient potentially
problematic activities, such as the
use of public transportation and the
increased energy required for
ambu-lation
Surgical Technique
At surgery, previous incisions are
clearly marked before application of
sterile adhesive drapes Skin flaps
should not be undermined more than
necessary and should be handled
with care to minimize damage to
cu-taneous circulation by forceps or
forceful retraction Stiffness may be
a problem when removal of a knee
prosthesis is required at the time of
débridement or fusion Many
exten-sile approaches have been described
and may be used to gain adequate ex-posure.25
The application of sound fracture fixation principles can improve the likelihood of successful arthrodesis
The elements needed to achieve bony union are good viable bone contact, adequate blood supply, and rigid fixation
The cruciate ligaments and me-niscal remnants are removed, as are prosthetic components and any bone cement The final position for knee fusion should be in the “neutral range”: 7° ± 5° of valgus and 15° ± 5°
of flexion.26TKA cutting guides may
be used to achieve this alignment
To maintain limb length, minimal bone resection is performed when the fusion is being done after TKA
Bone graft is required when there is marked loss of bone stock from the distal femur or the proximal tibia
Large bone defects can be managed
by use of a vascularized fibular rota-tory graft In a series of 13 patients so treated, fusion was achieved in 12 (mean follow-up, 51 months).27The patella may be left alone, used as a graft to fill defects, excised to relieve tension on the incision, or fused to the trochlear groove Good apposi-tion of the bone ends is critical to achieving fusion Careful attention
to hemostasis helps to reduce the in-cidence of wound hematoma and breakdown
A slightly foreshortened, fused leg allows easier clearance during the swing phase of gait When the leg is too short, a shoe lift may be used
The presence of active sepsis may decrease the fusion rate; therefore, it
is necessary to eradicate infection before the arthrodesis procedure
Conventional External Fixation
The advantages of external fixa-tion compared with internal include limited exposure and decreased blood loss during application Exter-nal fixation does not involve perma-nent hardware that could act as a po-tential nidus for infection, and there
is no risk of spreading an indolent in-fection in the knee farther into the tibial or femoral canal as there is with internal rod or plate fixation External fixation provides intraoper-ative flexibility, allowing alignment
of the fusion site into a position of mild flexion and valgus, compared with intramedullary fixation
Final-ly, when repeated débridements are required, the fixator frame can be disconnected from the pins during the procedure and then reassem-bled
Disadvantages of external fixa-tion include the risk of ptract in-fection and pin loosening before suc-cessful fusion In addition, a risk of neurovascular injury during pin in-sertion exists The apparatus is more cumbersome postoperatively com-pared with internal fixation Further, weight bearing cannot advance as quickly, and there is a risk of stress fracture through the pin sites
Final-ly, in some series, a lower fusion rate
is reported for external fixation com-pared with intramedullary fixation after failed TKA (Table 1)
External fixation is preferred, however, for patients with good bone stock in whom pseudarthrosis is less likely, for those in whom blood loss
or fat emboli associated with in-tramedullary nailing would not be well tolerated, and for those at par-ticularly high risk for infection with the use of internal fixation devices
In a comparative study of 26 patients undergoing knee fusion, all
13 with intramedullary nailing achieved fusion, whereas 6 of 13 with an external fixator required re-vision surgery and intramedullary nailing for successful fusion.12 How-ever, the study groups were not ran-domized, and the external fixation group had a higher percentage of vir-ulent organisms
The surgical technique used for all fixators follows similar princi-ples: a longitudinal incision is made, and the bone is cut from the distal femur and proximal tibia perpendic-ular to the longitudinal axis of the
Trang 4limb prior to fixator application.
Compression of the apposed bone
surfaces is applied both during
sur-gery and in the postoperative period
The patient is instructed to remain
in partial weight bearing until
evi-dence of early healing is seen on follow-up radiographs; then is al-lowed to proceed to full weight bear-ing No additional support other than the external fixator is needed
After frame removal, a lightweight
cast may be applied for 6 to 8 weeks until union is achieved
Uniplanar External Fixation
A variety of external fixator con-structs is used to achieve successful
Table 1
Modes of Fixation and Rates of Knee Fusion*
Study
No of Cases
Predominant Indication for Fusion Mode of Fixation Fusion Rate†(%) External fixators
Charnley and
Figgie et al26 27 All post-TKA, all rheumatoid,
22 septic
16 ex fix, 2 dual plating,
1 IM nail, 8 casts
70 Rand et al7 28 All post-TKA, 25 septic Ace-Fischer fixator (DePuy,
Warsaw, Indiana)
71 Hak et al6 36 22 septic TKA, 9 loose TKA,
3 posttraumatic OA, 1 Charcot neuropathy, 1 TB
19 single plane ex fix,
17 biplanar
58 single plane,
65 biplanar Knutson et al28 91 All post-TKA, 66 septic,
25 aseptic mechanical failures
49 Hoffmann frames,
40 Charnley clamps; also
IM nails, staples, Rush pins
50
Plating
Pritchett et al10 26 9 posttrauma, 6 post-TKA, 5 DJD,
2 neuropathic, 4 unstable
Tension-band plating 100
IM nails
Vlasak et al12 32 All post-TKA, 18 septic, 8 loose
aseptic, 6 nails post-ex fix failure
19 IM nail, 13 ex fix 100 IM nail,
38 ex fix Enneking and
Shirley13 20 All posttumor resection IM nail with cortical struts 80
Donley et al14 20 8 septic TKA, 1 loose, 3 giant cell,
2 failed ex fix, 4 unstable
Puranen et al29 33 15 TKA, 5 unstable, 4
post-trauma, 2 septic, 2 TB, 5 fusion nonunion
Modular nails
Waldman et al16 21 All post-TKA, septic Modular IM nail (Neff nail) 95
Arroyo et al17 21 16 tumors, 5 failed TKA Modular IM nail (Neff nail) 90
Combined modalities
Knutson et al30 20 All post-TKA, 15 septic, 4 loose,
1 unstable
10 IM nails, 10 ex fix 85 Fahmy et al31 20 10 failed Charnley clamp,
5 post-TKA, 2 posttrauma,
3 neuropathic joints
Charnley clamp with IM nail
100
* Studies reporting on a minimum of 20 cases.
† The fusion rate indicated is the initial fusion rate and does not include knees that required other procedures (eg, bone grafting)
to achieve union.
DJD = degenerative joint disease, ex fix = external fixation, IM = intramedullary, OA = osteoarthritis,
TB = tuberculosis, TKA = total knee arthroplasty
Trang 5arthrodesis Cunningham et al4
re-ported on uniplanar unilateral frame
use in 10 patients; successful union
was achieved in 9 Because anterior
placement increases rigidity, the
fix-ator is applied anteromedially or
anterolaterally, depending on the
position of the skin incision Two or
three 6-mm Schanz pins are used on
either side Although the uniplanar
external fixator provides the
bend-ing stiffness and the compression
re-quired for fusion, medial-lateral
sta-bility is less optimal
Biplanar External Fixation
Biplanar fixators use transfixion
pins in the femur and tibia,
supple-mented by additional Schanz pins
placed anteriorly (Figure 2) The
an-terior pins may be placed through
the arthrodesis incision or through
separate incisions.5In one series,
bi-planar fixators used in 17 patients achieved a fusion rate similar to that obtained with uniplanar fixators in
19 patients.6 However, complica-tions with the biplanar fixator in-cluded a 39% primary nonunion rate (reduced to 25% after revision sur-gery), a 17% infection rate at pin site, one stress fracture through a pin site, and one persistent infection, re-sulting in above-knee amputation
Circular External Fixation
Circular frames increasingly are used in knee arthrodesis because of ease of application, excellent stabil-ity, and versatility in terms of limb alignment and ability to bear weight
in the early postoperative period
Advantages include continuous
axi-al compression and the ability to easily make adjustments for align-ment These frames can be applied
in the presence of active infection, and bone grafting is not required.32 The main disadvantage of the circu-lar external fixator is the bulkiness
of the frame
Typically, two rings each are used for the tibia and femur;
alternative-ly, one ring and one arch may be used for the femur instead of two rings The rings are connected by threaded rods, which can be used to provide compression across the fu-sion site Preoperatively, the frame is assembled and sterilized The posi-tion of the rings is planned based
on radiographic assessment A gap of
10 cm between the distal femoral ring and the proximal tibial ring al-lows access to the wound when needed During surgery, compres-sion can be applied by the fixator across the fusion site and the amount of compression can be ad-justed postoperatively Weight bear-ing as tolerated is allowed immedi-ately after surgery
David et al8reported solid fusion
at a mean of 28 weeks in all 13 pa-tients in whom the Ilizarov external fixator was used for failed knee ar-throplasty Patients were treated for
an average of 19 weeks in the fixator, followed by 9 weeks in a plaster cyl-inder cast Recurvatum deformity was corrected in one patient by add-ing a hadd-inge, a modification that exemplifies the versatility of the sys-tem Oostenbroek and van Roer-mund32 reported on 15 infected TKAs treated with arthrodesis using the Ilizarov ring fixator; union was achieved in all but one patient Aver-age patient Aver-age was 75 years, averAver-age time in the frame was 28 weeks, and mean leg-length discrepancy as a re-sult of bone loss was 4 cm The com-plications reported were osteitis in two patients, frame instability in two, nonunion in one, and, as a re-sult of poor bone stock, fracture of the femur and tibia after frame re-moval in one In another study, a hy-brid frame was used successfully in two patients with an infected knee arthroplasty after a single-stage
Figure 2
Biplanar fixator (Adapted with permission from Brooker AF, Hansen NM Jr: The
biplane frame: Modified compression arthrodesis of the knee Clin Orthop
1980;60:163-167.)
Trang 6débridement and fixator
applica-tion Average time to union was
10 weeks.33
However, 19 patients treated by a
ring fixator had a fusion rate of only
68% after an average of 4.5 months
and an overall complication rate of
84%.9The problems included
super-ficial pin-tract infection in 55% and
nonunion in 32% Despite the high
rate of pin-tract infection, no actual
pin loosening was observed It is
im-portant to note that a circular or
uni-lateral fixator is preferable to
inter-nal fixation in the presence of highly
virulent or polymicrobial
infec-tion.34
Plate Fixation
Compression plate
osteosynthe-sis, used for stabilization of the knee
fusion, can also achieve rigid
fixa-tion of the fusion mass
Compres-sion between the distal femur and
proximal tibia may be obtained,
en-hancing the potential for successful
fusion and subsequent alignment of
the lower extremity In the early
postoperative period, external
im-mobilization typically is not
re-quired, and partial weight bearing
may be started A drawback to
inter-nal plate fixation is that recurrent or
new infection following plate
osteo-synthesis may be difficult to
man-age In these cases, removal of
hard-ware is required, followed by an
alternative means of stabilization to
gain a solid knee fusion
Pritchett et al10reported on 26
pa-tients whose knee arthrodeses were
managed by a single tension-band
plate technique The plate was
ap-plied on the anterior aspect across
the fusion site; by positioning the
knee in slight flexion, the plate
ab-sorbed the tension stress while the
compressive forces were transmitted
through the bone Six patients had a
failed prior TKA Three other
pa-tients had an active infection in the
joint, with drainage and
inflamma-tion; serial débridement had been
used to manage the patients with
in-fected TKA before arthrodesis Bone
graft and external support were not used An anterior midline approach was used for the arthrodesis and the plating, resulting in fusion
clinical-ly in 6 to 12 weeks and
radiological-ly by 16 weeks, without major com-plications Patients were allowed immediate partial weight bearing
In another report, dual plates were used in 11 patients after failed TKA.11One plate was applied on the medial and the lateral side, and each was contoured to approximate the anteromedial and anterolateral sur-face of the tibia, respectively Two patients had bone grafting, with the patella either fixed to the trochlear notch or used as bone graft A cylin-der cast was applied with weight bearing as tolerated until healing was evident on radiographs All pa-tients had fusion at an average of
5.6 months, although one patient had a femoral stress fracture and an-other, persistent infection
Intramedullary Fixation With a Long Nail
Since it provides rigid fixation, an intramedullary nail can be used to stabilize the fusion site until bone union This is accomplished best with insertion of an interlocking nail antegrade from the piriformis fossa, down the length of the femur, across the knee joint and into the distal tibia
Intramedullary nailing (Figure 3) produced a fusion rate of 95% com-pared with 64% for external fixation
in one series.35Intramedullary nail-ing also is advantageous because it is
a surgical technique familiar to many surgeons Nailing is especially
Figure 3
Anteroposterior (A) and lateral (B) views of a long antegrade intramedullary nail.
(Adapted with permission from Windsor RE: Knee arthrodesis, in Insall JN, Scott
WN [eds]: Surgery of the Knee, ed 3 New York, NY: Churchill Livingstone, 2000,
pp 1103-1116.)
Trang 7useful in patients with substantial
bone loss because intercalary bone
graft can easily be placed alongside
the rod Internal fixation allows
pa-tients to more easily mobilize
post-operatively, and the strength of the
construct allows early weight
bear-ing
Disadvantages of intramedullary
nailing include prolonged surgical
time and increased blood loss.14
An-other limitation is that the
compres-sion exerted across the fucompres-sion site
can be applied only with weight
bearing When the canal diameters
of the femur and tibia are different,
achieving optimum fixation with a
uniform diameter device may be
dif-ficult, although custom implants
with dual diameters can be designed
Contraindications to intramedullary
nailing include the presence of an
ip-silateral hip replacement prosthesis,
malunited femoral shaft fracture,
gross deformity of the femoral shaft,
and active infection
Persistent infection following
nailing is a potential hazard, but
many studies have shown a low risk
of infection after intramedullary
nailing for knee arthrodesis.29,36,37
Control of infection is important
before nailing In a series of 20
pa-tients (8 failed TKAs), the average
time necessary to clear infection
after prosthesis removal was 12
months.14
For antegrade nail insertion with
an interlocking nail, the patient is
positioned supine, and the
ipsilater-al hip is elevated for easier exposure
The desired length of nail is
deter-mined preoperatively from
long-standing anteroposterior radiographs
of the extremity Adequate
débride-ment and preparation of the distal
fe-mur and proximal tibia is performed
Because the tibial canal is narrower
than the femoral canal, the tibial
ca-nal may be reamed first to judge the
best nail diameter The piriformis
fossa is entered, and a ball-tipped
guide wire is inserted, as is done in
antegrade femoral nailing for
femo-ral fracture Following reaming, the
nail is inserted with the bow of the nail kept anteromedial to provide valgus and flexion at the knee The nail is advanced to within 2 cm of the ankle joint, with locking screws used to prevent proximal migration
or rotation of the nail
A study of 33 patients (15 failed TKAs) treated by an antegrade long nail reported union in 29 patients at
3 to 4 months;2917 of these patients required less assistance in walking than previously after arthrodesis In addition, intramedullary nailing may be used as a salvage procedure after failed external fixation.12The average time between removal of the fixator and insertion of the nail in the series of Vlasak et al12 was 26 weeks, and no patient developed an infection from the previous pin sites
Following nailing, the axis of
tib-ia and femur coincide, and, despite positioning the curvature of the nail, there is loss of normal knee valgus
However, the shortening resulting from bone loss after knee prosthesis removal may obviate the need for flexion Therefore, a position of full extension is recommended for fu-sion following failed TKA; this posi-tion is thought to provide a more nearly normal gait.38 As a result of the altered mechanical axis of the limb, a possibility of increasing stress on the ankle joint exists, but this has not been found to be a prob-lem
Potential complications of in-tramedullary fixation include migra-tion and breakage of the intramedul-lary device, neurovascular injury, tibial fracture during insertion, and delayed union.35In addition, fracture
of the tibia distal to the nail has been reported Complications specific to a long intramedullary nail include glu-teal pain and proximal migration of the nail.39
Vascularized Fibular Graft and Allograft
In cases that involve large bone defects or segments of avascular
bone, vascularized fibular grafts have been used with femoral nailing for knee arthrodesis.27Management op-tions include shortening the extrem-ity or using allografts, vascular bone grafting, or amputation
The nail is inserted first The ip-silateral fibula is harvested next, ei-ther on a pedicle or as a free graft, and is used to bridge the defect Fem-oral defects≥10 cm usually need free transfer of fibula, whereas smaller femoral defects and most tibial de-fects can be managed by fibular graft
on a pedicle.27 The fibular graft is used as an onlay graft, or is placed in
a trough proximally and distally, and
is fixed with a proximal and distal plate and/or screws
In a series of 13 patients, 8 with tu-mor resection, 4 with failed infected TKA, and 1 with severe complicated rheumatoid arthritis, 12 had a suc-cessful fusion.27One patient had an amputation for persistent infection This procedure is important to con-sider in cases with large bone defects but is technically demanding, with an average operating time of 8.3 hours and an average blood loss >2 L.27 Intercalary allograft is a recon-struction option for large defects, such as those following tumor resec-tion In a study of 39 patients, the graft was stabilized after placing it in the defect with an intramedullary nail passed in a retrograde tech-nique.40To create rotational stability, two patients had an additional plate fixation at the graft-host junction Union was obtained on both ends of the graft in 32 patients, and 5 non-unions healed following bone graft-ing Three patients had above-knee amputation—two for chronic non-union and one for local recurrence
Intramedullary Fixation With Modular and Nonmodular Nails
Two categories of nails can be in-serted through the knee: modular and nonmodular Examples of mod-ular intramedullary nails (Figures 4 and 5) include the Wichita and the
Trang 8Neff.17A single incision is used
Fol-lowing bone preparation, the
femo-ral part of the nail is inserted
retro-grade into the femoral canal, and the
tibial half of the nail is inserted
an-tegrade into the tibial canal The two
ends are then connected at the level
of the knee joint by a conical couple
and secured with locking screws
Different types of modular nails
are available, and it is critical that
surgeons become familiar with the
details specific to each before
inser-tion Modularity of femoral and
tib-ial components improves fit in
situ-ations in which a discrepancy
between the canal diameters exists
A curved femoral rod allows
place-ment of the knee in slight valgus,
when desired When there is no
ma-jor bone loss, patients are allowed to
bear weight as tolerated
immediate-ly after surgery In cases of major
bone defects, weight bearing is
de-layed until radiographic signs of
healing are evident
In a series of 21 patients (6 with
failed TKA) treated with a modular
nail, fusion was achieved in 90% at
an average of 8.4 months.17The
au-thors reported a 38% complication
rate, which included three stress
fractures, three peroneal nerve
pal-sies, one wound infection, and one
reflex sympathetic dystrophy For
extensive bone loss around the knee,
2- and 4-cm spacers are available,
and bone grafting can be done at the
same time Another series reported
successful fusion using a modular
nail in 20 of 21 patients at a mean of
6.3 months.16
An example of a nonmodular nail
is the Huckstep intramedullary nail,
a solid titanium nail with a
quadrilat-eral cross-section design and
multi-ple locking holes throughout its
en-tire length.41The required length is
measured and cut preoperatively
Be-cause of the ability to use multiple
locking screws, a shorter length of
nail provides adequate stability It is
possible to position the knee in slight
valgus and flexion with this device
In addition, the nail can be used in
the presence of the femoral stem of
an ipsilateral hip replacement
The nail is inserted retrograde into the femur and guided antegrade into the tibia, using the screw holes for purchase When the middle of the nail is at the level of the knee joint, tibial interlocking is done, using the visible screws to align the jig Then the apposing ends of the femur and tibia are impacted together, and fem-oral interlocking is done using the jig.41Four to six screws are inserted
in both the femur and the tibia Be-cause the nail fits loosely in the fe-mur, it is possible to position the
knee in slight valgus No external support is required postoperatively, and weight bearing as tolerated is al-lowed
In one series of 31 patients with infected TKA and 2 with Charcot joints, union was achieved in 30 of
33 knees (91%), with an average time to union of 5.2 months.41 Prob-lems associated with the nail in-clude screw backing out, screw breakage, and nail breakage, the lat-ter reported in 4 of 22 patients
treat-ed with the Huckstep nail.42 Regardless whether a modular or nonmodular nail is chosen, the
ad-Figure 4
Modular nail (Adapted with permission from Arroyo JS, Garvin KL, Heff JR:
Arthrodesis of the knee with a modular titanium intramedullary nail J Bone Joint Surg Am 1997;79:26-35.)
Figure 5
Anteroposterior (A) and lateral (B) radiographs demonstrating the Neff nail in situ.
Trang 9vantage of the nails inserted through
the knee is the ability to gain
tramedullary fixation without an
in-cision near the hip and without
plac-ing the hip at risk should sepsis
occur The major problem with
these nails is the difficulty in
remov-al, which may require an anterior
cortical window and burrs in order
to cut the nail into multiple pieces
Results of Knee Fusion
Fusion rates in knee arthrodesis
range from 38% to 100%, depending
on the method used (Table 1)
In-tramedullary nail fixation typically
has a higher fusion rate, especially
after failed TKA, whereas infected
knees have a lower fusion rate, as do
knees with rheumatoid arthritis
The fusion rate after TKA is lower
than that of knees that have not
un-dergone TKA; this lower rate most
likely is a result of increased bone
loss, poorer bone apposition,
persis-tent infection, or limb shortening.9
A Swedish study that included
mul-tiple surgeons with mulmul-tiple
tech-niques treating 91 failed TKAs,
dem-onstrated that the fusion rate in
community practice may not be as
high as that reported by some
cen-ters Of 91 knees, fusion occurred in
the 10 in which an intramedullary
rod was used, whereas external
fixa-tion for failed TKA had a failure rate
≥50%.28
Complications and
Disadvantages
The most frequent complication of
arthrodesis is pain resulting from
nonunion Causes of nonunion
in-clude deficient bone stock,
inade-quate fixation, persistent infection,
and lack of solid osseous contact.17
Established nonunions should be
treated as in fracture care: atrophic
nonunions with iliac crest bone graft
or vascularized fibula graft,
hyper-trophic nonunions with more rigid
fixation A failed external fixator
may be converted to an
intramedul-lary rod; however, this conversion should occur in two stages to avoid spreading pin-tract contamination through the medullary canal Other complications, regardless of the method of immobilization chosen, include intraoperative fracture, deep vein thrombosis, continued drainage from infection, new infection, wound dehiscence, and peroneal nerve palsy Supracondylar fractures have been reported in above-knee fu-sion; these fractures can be managed with antegrade locking nails A po-tential long-term complication of knee arthrodesis is a biomechanical effect on the hip, spine, and ankle as
a result of an altered gait
Conversion to TKA
Patients should understand preoper-atively that, in most cases, a knee ar-throdesis cannot be converted to TKA at a later date Many authors have reported high complication rates associated with converting a fusion to TKA Henkel et al43 de-scribed seven cases of TKA after formal knee fusion; two patients un-derwent secondary refusion for in-fection and ligamentous instability, respectively, six of seven underwent revision surgery—for arthrolysis (three patients), a regional soft-tissue flap for skin necrosis (two), and neurolysis of peroneal nerve (one)
The mean range of motion
achiev-ed was 74° at a mean follow-up of
56 months, and the mean Hospital for Special Surgery (HSS) score im-proved from 54 to 68
A similar report of 30 patients showed final flexion achieved was 75.8°, with an average extensor lag of 9°.44 There were no revisions for loosening at 5.3 years mean follow-up; 53% of patients had skin edge necrosis The HSS score improved from 60 to 73 Hu45reported a 53%
complication rate in 17 cases of TKA following formal knee fusion; two patients were converted back to fu-sion for patellar tendon loss and in-fection, respectively The mean
range of flexion achieved was 84° However, a recent study of 36 pa-tients undergoing a posterior stabi-lized knee prosthesis at an average of 24.5 years after knee fusion showed
an improvement in HSS knee score from a mean of 60 to 83.2.46The av-erage patient age was 39.2 years; the average follow-up was 7.7 years
Summary
Techniques for obtaining stability for knee fusion have evolved to meet
a challenging common indication, the failed TKA Studies demonstrate good results with intramedullary fix-ation, either with a long antegrade nail through the piriformis fossa or with a coupled nail inserted through the knee Circular fixators also are gaining popularity as experience with these devices increases Causes
of fusion failure include persistent infection, inadequate bone contact, insufficient immobilization, or inad-equate bone stock Multiple tech-niques are available for knee arthro-desis, each with its own advantages and disadvantages The treating sur-geon should be well versed in the ad-vantages and disadad-vantages of these techniques before selecting the ap-propriate method
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