.r‘mm»
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`/..v;..,
`.u...
`
`r3.1%.}..JIWWLQ
`..a..i..
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`3.3...
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`Cahiers d‘enseignement de la SOFCOT
`
`Collection dirigée par J DUPARC
`
`61
`
`UNICOMPARTMENTAL
`
`KNEE ARTH ROPLASTY
`
`Ph.CARTlER M D., J A. EPINETTE, MD., G. DESCHAMPS, MD., Ph.HERNlGOU, MD.
`
`edited by
`
`Contributors
`
`ThPANDRlACCHI, J.H AUBRIOT, SA. BANKS, RM BARDEN, Th.W. BAUER, J.L. BENSADOUN,
`RABERGER G, BERGMANN, J.L, BESSE, L. BLANKEVOORT, PM BONUTI'I, Ph.CARTIER, RBCASPARI,
`J.P.CECCALD|, P.CHAMBAT, F.CHATA|N, RL.COATES, DDEJOUR, H.DEJOUR F. DELTOUR
`G. DESCHAMPS, P. DJIAN, J DUPARC, J DUPUY—PHILLON, A A. EDIDIN, J A. EPINETTE, J. FEIKES.
`A. FERREIRA, G. GACON, J O GALANTE, J.W.GOODFELLOW, GroupeGUEPAR, S. HABI. MK. HARMAN,
`Ph. HERNIGOU, Y. HIRASAWA, A.W HODGE, R HUISKES, A. IMRAN, MJIANG, M. KESTER, A. KOBAYASHI,
`T. KOSHINO, J.L. LERAT, S. LEWOLD, A. LINDSTRAND, T.W. LU, MT. MANLEY, G.D.MARKOVICH, L. MARMOR
`Ph. MAS, B MOYEN. DW. MURRAY, Ph. NEYRET, KG. NILSSON. R NIZARD, J.J. OCONNOR T. OH
`T. OHDERA,
`I. ONSTEN M D. PEYRACHE, L PIDHORZ, J ROBERTS M H. ROSAS, A.G. ROSENBERG,
`J. L. SANOUILLER R D. SCOTT, A STENSTRDM F SUSSENBACH, S. TAKAI F. TROTT, S. TSUTSUMI
`R VANAS, F. VOSS, D. R WILSON, J.WITVOET, NYOSHINO
`
`EXPANSION SCIENTIFIQUE FRANQAISE
`15, rue Saint~Benoit PARIS VIe
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`Catalo a e EIectre-Bibliographie
`.
`.
`~
`Unicongtpgrtmental knee arthroplasty/Ph Cartier, lA. Epinette,
`G Deschamps, PhHemrgou. “ Paris: Expansron screntiflque frangaise, 1997
`— (Cahiers d'enseignernent de la SOFCOT; 61)
`ISBN 2-7046-1532—2
`RAMEAU :
`
`arthroplastie
`.
`‘
`genoux artificiels
`617.2: Chirurgie et sujets connexes, Orthopedie.
`Universitaire. Professionnel, spécialiste
`
`DEWEY:
`Public concerné:
`
`© 1997 by EXpat’lSlOfl Smentiirque Frangaise All rights reserved. This book is protected
`by copyright. No part of it may be reproduced stored in a retrieval system. or transmitted,
`in any form or by any means. electronic. mechanical. photocopying, or recording, or other-
`wise, without the prior written permissron oi the publisher
`Made in France
`
`Tous droits de traduction. d‘adaptation et de reproduction par tous procédés. reserves
`pour tous pays.
`La to: du 11 mars 1957 n‘autonsant, aux termes des alinéas 2 at 3 de t‘arttcte 41. d‘une
`pert. que les .. copies on reproductions strictement réservées a l‘usage prrvé du copiste 9!
`non destinees a une utilisation collective
`el. d‘aulre part. que les analyses et Ies courtes
`citations dans un but d'excmple et d‘illustration, «toute representation on reproduction
`integrate. ou Danielle. latte sans Ie consentement de l'auteur on do sea ayants drort DU
`ayants cause. est illicite -- talinéa 1" de I'Amcle 40].
`
`Cette representation ou reproduction. par quelque procédé que ce soit. constituerait donc
`une contrelagon sanctionnée par les Articles 425 et suivants du Code penal.
`
`© Expansion Scientifique Frangaise, 1997
`Adresse postale : 31, boulevard de Latour-Maubourg, 75343 PARIS CEDEX 07 (France).
`
`ISBN 2-7046—1532-2
`lSSN 0338-3849
`
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`

`Unicompartmental Knee Arthroplasty:
`a US Experience
`
`RM. BONUTTI, M.D., M.A. KESTER, PhD.
`
`Treatment of unicompartmental arthritis of the knee is
`a difficult challenge. There are a number of treatment
`alternatives which must be individualized for each
`
`patient. Conservative treatment options include anti—
`intlammatories, bracing, weight reduction and activity
`modifications. Surgical options
`include arthroscopy
`and
`debridetnent.
`abrasion
`arthroplasty.
`biologic
`resurfacing.
`osteotomy. Unicompartmental Knee
`Arthroplasty (UKA) or Total Knee Arthroplasty (TKA).
`In the United States in 1995, approximately 250.000
`knee arthroplasties were performed of which less than
`5% were UKA [102]. This contrasts with Sweden
`studies which look at a large series ofknee arthroplasties.
`Multiple Swedish authors have identified the utilization
`of UKA ranging from 40% to 90% of all patients with
`osteoarthritis undergoing knee arthroplasty [64, 202.
`270]. This utilization ofUKA differs markedly from the
`US experience. There are many factors which relate to
`the US experience in utilizations.
`Current indications and contradictions for UKA in the
`
`United States have evolved (Figs 1 and 2). Indications
`include 1) patients greater than 60 years of age with a
`sedentary life
`style, 2) osteoarthritis
`in
`a
`single
`compartment, 3) range of motion must be greater than
`150 to 900, 4) deformity ofless than 10 ° of varus or 15°
`of val gus. One cannot correct severe contracture angu-
`larmalalignmentwith UKAimplantforfearofdamaging
`critical
`ligamentous structures during the balancing
`process [123]. Contra-indications to UKA include: 1)
`significant bicompartmental disease, 2) symptomatic
`patellofemoral compartment. 3) obesity — greater than
`200 pounds. 4) deformity greater than 20°, 5) ruptured
`ligaments — ACL, PCL or MCL, and 6) inflammatory
`arthritis.
`In the US, Stern and lnsall, et al. using most
`rigid criteria identified that only 6% of patients in the
`United States meet their strict criteria for UKA [293].
`Evaluation of UKA suggests variable long term
`results. Some studies suggestlong term UKA results are
`inferior to TKA results. However. these studies often
`evaluate first generation UKA designs and compare
`them to second or third generation TKA designs with
`difference
`in
`instrumentation.
`surgeon
`technique.
`cement technique. patient criteria and implant design.
`
`For example, Marmor notes in his first generation
`implant design, a 70% survivorship at 10 to 13 year
`follow—up [221]. Contrast this with Scott’s. et al. more
`recent study describing a second generation design with
`a 90% survivorship at 9 year follow—up [274]. There is
`no question that the UKA is a very surgeon and technique
`dependent procedure. There are marked variation in the
`implants and instrumentation. Instrumentation is very
`similar to TKA instrumentation, however. UKA is
`markedly different with preservation of the ACL, PCL.
`contralateral compartment, as well as the patellofemoral
`joint. Clearly it is difficult to achieve the ACL and PCL
`isometry while maintaining the
`balance
`in
`the
`contralateral compartment and the patellofemoral joint
`with traditional implant instrumentation.
`The US experience in knee arthroplasty differs
`markedly from the European experience. Christensen’s
`study with 575 UKA at 9 year follow—up identified a96%
`survivorship
`[64]. A more
`extensive
`study
`by
`Lindstrand. et al. evaluating 3.777 UKA at 8 year follow-
`up showed a 15% revision rate for PCA and 7% revision
`rate for St. Georg and a 5% revision rate for Marmor
`implants [202]. He notes survivorship for UKA appears
`very implant and design specific. Likewise studios
`identified, for example that PCA TKA has a much lower
`survivorship than other contemporary TKA [306]. The
`following table compares the long term US survivorship
`of contemporary UKA (Table I).
`
`TABLE 1
`
`
`
`Author
`Patients
`Followup ] Surviwn‘s/zip
`Heck
`294
`10 YRS
`91 %
`l
`Swank
`82
`8.5 YRS
`81%
`2
`Capra
`52
`10 YRS
`93%
`3
`Rougraff
`I20
`10 YRS
`93%
`4
`
`5
`Scott
`100
`9 YRS
`90%
`
`l
`
`The poorest long term UKA results, that ofSwank and
`Stulberg. et al. should be evaluated critically [301]
`These implants were PCA and Microloc UKA.
`If one
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`UNICOMPARTMENTAL KNEEARTHROI’IASTY. A US EXPERIENCE
`
`2M
`
`Fig. l.
`A) Pre-operative AP X-ray. Isolated medial compartment 0A.
`B) Pre-operative lateral X-ray.
`
`
`
`C) Post-Operative UKA. Merchant view.
`
`Fig. 2.
`A) Post-operative UKA. AP view.
`B) Post-operative lateral X-ray.
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`
`l’..\7 l)’(i5\’(.’7"l I. 111/),111 l KESTER. PI] 1).
`
`'I'KA. one will Iind similar poor results. Therefore. one
`n 1th compare comparable implants. cot nparahlc designs
`and patient criteria. Therefore, just like TKA desrgns
`which have \m'iable success rate. UKA implants also
`have a variable success rate and poor results ofUKA may
`be attributable to implant designs or techniques.
`lfone contrasts UKA long term studies with those of
`long term studies of TKA.
`there is also a marked
`variation. Evaluate the following table ofc<mtemporary
`TKA designs (Table II).
`
`TABLE II
`
`
`|
`
`
`[
`[ Author
`Patients Follow-up[ Sit/‘t'i'vw‘sltip' Implant
`j
`Insall
`139
`9 YRS
`‘
`94%
`1B.
`1
`2 Rorabeck
`344
`3 YRS
`91%
`‘ MB.
`3 Rand
`7200
`10 YRS
`79%
`Multiple I
`TSAO 80
`
`4
`6 YRS
`80%
`[ PCA
`
`If one contrasts UKA long term survivorship with
`those long terms studies of TKA, obviously the best
`studies quoted are those of lnsall’s, et a1. classic paper
`which notes a 94% survivorship in 9 to 12 year follow—
`up [291]. However, as Lindstrand, et al. identifies UKA
`survivorship
`is
`very
`implant
`dependent. TKA
`survivorship is also very implant dependent [202].
`If
`one looks critically at comparable series, one finds for
`example, Tsao, et al. using a PCA TKA implant reports
`a 6 year follow—up with only an 80% survivorship and
`20% re—operation
`rate
`[306]. Contrast
`this with
`Swank's, et al. study at 8.5 year follow—up of PCA UKA’s
`with
`an
`81% survivorship
`[301]. One
`can
`see
`is
`comparable survivorship and again this
`implant
`related. Clearly with similar implant designs, one sees
`comparable results.
`Looking closer at Rand’s study at a long term follow—
`up of a large series of implants, he reported a 79%
`survivorship at 10 year follow—up [257]. Although.
`many physicians quote Insall’s, et al. paper, it is unlikely
`that most orthopedic surgeons in the US can compare
`their results and technique to lnsall‘s [291]. Perhaps we
`should use Rand’s long term series as a true barometer of
`long term survivorship because his series included
`multiple surgeons, a large series and more objective
`analysis as a surgeon designer who was not evaluating
`patients.
`1t is clearly comparable to literature published
`on UKA survivorship.
`Furthermore, to compare UKA to TKA. one must
`evaluate
`implant’s
`surgical
`technique
`and
`instrumentation. UKA in the United States has been
`
`suggested to have inferior results to TKA. However,
`failure appears
`to be
`related to implant design,
`polyethylene wear, subsidence and progressive disease
`in the contralateral compartment.
`In TKA. the ACL is
`sacrificed and with increasing frequency the PCL is
`sacrificed. the opposite compartment is removed. and the
`patellofemoral
`joint
`is usually replaced.
`[it UKA,
`instrumentation is
`similar or deri\ed from TKA
`
`instrumentation. However. UKA requires more precise
`soft tissue balancing. joint balancing and alignment is
`
`more critical. The ACL and PCL are maintained and
`ligament balancing \vitlt isoittetry should be considered.
`As in the sports medicine literature. clearly if the ACL
`and PCL are not in isometric position. an increase in the
`rate of failure can occur. If the ACL is sacrificed, one
`clearly identifies a greater rate of failure in UKA. Also,
`the patellofemoral joint, as well as the contralateral tibia
`femoral
`compartment
`are
`spared. Instrumentation
`should take this into account, however. existing implants
`and instrumentation rely significantly on surgeon’s
`technical ability to balance the compartments, and
`instrumentation has not been developed to adequately
`measure tension and isometry for the ACL and PCL
`ligaments as well as the contralateral compartment.
`UKA has been documented to have a greater rate of
`failure than TKA. This may be related to implant design,
`polyethylene wear, subsidence and progressive disease
`in the contralateral compartment. The classic paper on
`UKA design, that of Hodge and Chandler. identify that
`with a constrained implant,
`there was a 70% 5 year
`survivorship with a 27% reoperation rate
`[142].
`However. using an unconstrained UKA implant relying
`on
`ligaments
`and contralateral
`compartment
`for
`stabilization, there was a 92%, 5 year survivorship and
`only 8% incidence of re-operation. This article clearly
`identifies that in UKA, the implant should not constrain
`or stabilize thejoint. The stability should be imparted by
`ligaments — ACL and PCL, as well as the opposite
`compartment and patellofemoral joint.
`Comparing TKA to UKA, Callahan, et al. identifies,
`“Patient outcome appears to be worse for TKA than
`UKA.” He concludes that UKA may afford better patient
`outcomes than TKA [54]. There are very few papers in
`the US literature comparing UKA to TKA. Rougraff, et
`a1. performed a retrospective study comparing UKA
`versus TKA in similar patient populations
`[270]
`(Figs 3A, 3B, 3C and Table III).
`
`TABLE III
`
`TKA
`
`
`
`81
`Number
`11% (9)
`Revision
`20% (1 1)
`Reop
`98°
`ROM
`Knee Score
`90
`85
`
`TransFusion
`1%
`67%
`
`
`
`significant
`statistically
`identified
`authors
`The
`findings in the UKA versus TKA population were UKA
`had: 1) lower revision rate, 2) lower re—operation rate.
`3) improved range of motion, 4) higher knee score.
`5) lower transfusion rate.
`In another comparable study by Laurencin, et al. a
`majority 01 the patients preferred UKA over TKA. The
`UKA had better range of motion and more normal gait
`pattern [194].
`Chassin. et al. identified that 70% of patients with
`UKA have a normal biphasic gait pattern. This contrasts
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`prevalence of quadriceps avoidance gait in UKA which
`appears to be associated with the retention of the ACL.
`This study fttrther suggests that U KA patients have better
`gait patterns and function better than comparable TKA
`patients loll.
`It appears that UKA patients function
`better than TKA patients. and if a patient is a candidate
`for l‘KA. UKA notild provide better functional results.
`
`In one of the best studies 7 the only prospective .irmfr
`comparing UKA \ersus TKA versus High Tibial
`Osteotomy lHTOi.
`if) patients
`\tcre e\aluatcd by
`Jefferson and Whittle IISB].
`'l'l'tcy found that UK.-’-\
`have: /I better ROM. 2) better function. 3’) superior gait
`pattern in terms of cadence.
`t-elocity. stride length. 4)
`tnore predictable results than l-l'l'(,). When compared to
`TKA. UKA had: / i better correction of deformity and 3)
`better functional and gait pattern. This was a prospective
`study and ()hjc’ClH'L‘l} looked at the functional results and
`identified that UKA functionally out performed both
`HTO and TKA.
`
`HTO may btty ti the for the younger tnore active obese
`patient or the cruciate deficient patient. However. there
`is significant evidence for disease progression over time.
`Results of llTO arc iuehly variable with long term
`success ranging from 26% to 7792 success rate [69. 226.
`295].
`In a L'ttlllt‘ttlftllh'c‘ study ofUKA vs. HTO. Kozinn
`and Scott identified that the UKA has better quadriceps
`
`Fig. 3. — TKA Failure. Design and implant related.
`A) AP X-ray.
`B) Lateral X-ray.
`C) Merchant view.
`
`increased
`stance.
`leg
`single
`increased
`strength.
`maximum gait. and increased fttnction over HTU | |8l l.
`'l‘herefore.
`if
`one
`critically
`analyzes
`functional
`improvement. UKA appears to prmide better clinical.
`functional results than HTU.
`
`Weale et all. identified that with a long term follow—up
`of [2 to I? years only 2099;: L1 KA had pain Vt here as 57"}?
`of HTO had significant pain [32 . ’l‘herefore. at
`long
`term. greater than l2 year follow-up l ”(A has better pain
`relief than HTO.
`
`In another comparative study 01 UKA versus HTO,
`Stewart, et al. reported that with HTO there was a 60%
`evidence of disease progression in the contralateral
`compartment at 5 year follow-up and 83% ofprogression
`of disease at 9 year follow—up in the contralateral
`compartment [295].
`there have been very different
`[n UKA. however.
`studies on disease progression with Hodge and Chandler
`identifying a 13‘7“?
`incidence of disease progression in
`the contralateral compartment
`at ntinitmtm 5 year
`follow-up [l-lll. The greatest exidencc of disease
`progression (Surtani's. et al. stud} of lateral cottipouent
`UKA only] identified a 23‘} progression ol‘diseasc in the
`contralatcral compartment UK.) at 3 year lollonsup
`DWI.
`l-lotrever.
`onl_\
`.‘~ i't
`ol
`patients
`nerc
`symptomatic enough at H )L‘tlt
`follou—up to require
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`264
`
`I’M [HI/V1177]
`
`\1 I)
`
`l!
`
`l
`
`It'll‘STE/t’. FUD
`
`
`
`osteoarthritis may
`This
`suggests
`that
`progress
`radiographically, however, the necessity to revise UKA
`patients to TKA for progressive osteoarthritis is small.
`Klemme, et al. used bone scans to analyze progressive
`disease in UKA and found that there was no radiographic
`evidence for progressive arthrosis in their unreplaced
`compartments.
`
`replaced
`concluded disease progression in
`He
`compartments was unusual after contemporary UKA,
`and concluded that most failures and poor results are
`from mechanical inadequacies and were attributable to
`surgical
`technique and design considerations [I73].
`Disease progression in the contralaleral compartment
`UKA is uncommon with appropriate implants and with
`appropriate surgical
`techniques. This confirms many
`other studies which suggest a low rate of progressive
`osteoarthritis in the contralateral compartment of UKA.
`In the US. several studies have suggested significant
`difficulty in revising l lKA to TKA.
`lnsall identified that
`the revision of UKA may be difficult. However. in all
`l9 of his patient which nere early generation UKA.
`designs.
`all were
`revised to prirnar‘r TKA. None
`
`
`
`Fig. 4. — TKA to TKA revision.
`A) Stemmed revision implants with wedges and bone
`graft.
`B) Lateral X-ray.
`C) Patella. Merchant view.
`
`litany
`r‘eVision implants. however.
`required special
`required hone gralting to hurld up tihial hon) detects.
`This again. is altrihutahle to early implant designs and
`early cement
`techniques which remmed significant
`trhirrl hone stock and has made revision more difficult.
`Yet. 89% of his UKA revisions were satisfied at follow-
`up [253].
`In a comparative study, Insall, et al. compared revision
`ofHTO to TKA and found that only 80% ofpatients were
`satisfied [154]. Jackson, et al.
`in another US series
`studied 43 patients: 23 revisions from UKA t0 TKA and
`20 revisions from HTO t0 TKA [l57]. The two groups
`were similar, however. 30% of the HTO’S which revised
`to TKA suffered serious post operative complications
`and were classified as poor results.
`Munk. et a1. studied revision of HTO to TKA in
`(i? palienls and found that 3?"; ol patients had I'airtopoor
`results
`lhe range ol motion post
`l'K.\ \\;I\ lllb‘
`\xith 2
`l'i'v rernperalinn rate at
`i}e;rr tollmt-rrp.
`In a parallel
`study. he irlcntilietl El—l'lt success rate \\ iIh prrrnar} TKA.
`'l‘lrrs suggests fetish)” from [H i.) to TKA ma} he more
`7|
`..
`‘IliilLllii than l'r.‘\'l\lt¥ll ol l‘l\':\ It:
`l'li,‘~.|34.‘.lrl‘igs 1'»
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`Lr'..\/l(“(.)rllP.lRTl/ENT/ll. KNEE ARTHRU/‘L/lST)’: :\ U 8' EXPERIENCE
`
`26)
`
`Therefore. after reviewing current literature in the US.
`UKA appears to have comparable long term survivorship
`to TKA. UKA appears to show better functional results
`than TKA, however. is still an underutilized procedure
`in
`the United
`States. The
`reasons
`for
`this
`underutilization may be multifactorial.
`
`First. the US population appears to be different than
`the Swedish or European population. The biggest single
`difference appears to be the greater incidence of obesity
`in the US population which may limit the number of
`patients which are candidates for UKA. A study by the
`National Center for Health Statistics, a Division of the
`United States Department of Health and Human Services
`identified that 59% of American men and 49% of
`American Women are significantly overweight. This
`study also suggests that Americans over the last decade
`progressively are increasing in weight and this trend is
`worsening [196]. Therefore. on the basis of weight
`alone, over half the potential candidates in the US for
`UKA are eliminated.
`
`to be a surgeon’s
`there also appears
`Second,
`preference in the US for implantation ofTKA over UKA.
`In residency training programs, there is the perception
`that
`the TKA obtains better results and have more
`
`reproducible results than UKA. As we have previously
`discussed, surgical technique for UKA is much more
`surgeon dependent because of balancing the ligaments,
`contralateral compartment and patellofemoral
`joint.
`UKA may be more difficult to teach in the US residency
`training systems. and therefore. more physicians leaving
`US training programs
`are unfamiliar with UKA
`instrumentation and implantation; and therefore, lean
`toward performing TKA.
`
`An excellent study performed by Lavemia and
`Guzman, evaluated knee arthroplasties in Florida.
`Lavemia found that
`in Florida over 62% of all knee
`
`arthroplasties were implanted by surgeons who perform
`less than 10 joint replacements a year. For revision
`arthroplasties. 90% of
`revision arthroplasty were
`performed by surgeons who do 10 or less revisions per
`year [ I 93]. If one extrapolates Insall ’s, et al. criteria that
`less than 6% of patients in the US quality for UKA and
`if the average US surgeon performs l0 or less joint
`replacements per year. the average US surgeon would
`therefore find less tltan | patient who is a candidate for
`UKA per-year [293]. Based on this relative unfamiliarity
`with UKA, many
`surgeons would lean
`toward
`performing TKA.
`There are over 20.000 orthopaedic surgeons in the
`United States, and as evidenced by Lavernia’s, et al.
`study.
`the majority of knee arthroplasties in the US
`appear to he performed by surgeons who have fairly
`limited experience with UKA HUS]. This suggests a
`relative lack of familiarity and \\‘Utlltl make surgeons less
`likely to place an implant or perform techniques where
`they have limited indications arid \\ hich requires greater
`technical skill.
`
`In the US.
`Another reported issue is reimbursement.
`a UKA requires comparable. if not a greater amount of
`time for a surgeon technically to implant. However. the
`reimbursement in the US fora UKA is significantly less
`
`than that for TKA ~ approximately 4( 9’0 less. TKA has
`the perception in the US as having better fttrrctional
`results and has a significant higher reimbursement ratio.
`Therefore, surgeons may subjectively lean to this
`treatment option.
`Implant manufacturers in the US receive a greater
`reimbursement for the TKA irrrplant over the UKA
`implant. UKA implants can range from $800 to $3.000
`where TKA implants can range from $1,500 to as much
`as $6.000 or more. These marketing issues may have
`significant
`impact
`on
`implant manufactures
`and
`surgeons.
`In the US. company representatives routinely
`are in the operating theater advising surgeons during a
`surgery.
`Finally, there appears to be less research and money
`invested for UKA implants. Companies are reluctant to
`invest millions of dollars to develop implants with new
`instrumentation for a perceived limited market with
`redttced reimbursements. All of these factors appear to
`place some overall perceived preference of the surgeons,
`of the US. for the utilization ofTKA over UKA. Some
`studies such as Scott, et al. suggest that after 10 years
`there may be a progressive deterioration results for UKA.
`Survivorship in Scott’s
`study
`shows
`that
`95%
`survivorship at 9 years, 85% at 10 years, 82% at 11 years.
`To date, other studies have not identified this [181].
`Meta—analysis performed by Callahan, et al. of 2,391
`UKA in the US literature at 6 year mean follow-up
`identify an [8% complication rate and a revision rate of
`9.2%. UKA implanted studies after 1987, however,
`showed significant better outcomes. However. for TKA
`patients at 3.6 year follow-up identified a complication
`rate of 30%. revision rate of 7.2% and a lower global
`rating score for TKA [54]. This may be due to the fact
`that TKA patients were worse
`pre—operatively.
`However. better outcomes were obtained in UKA
`
`patients and may be due to better patient selection. Yet
`patient outcomes were clearly worse for TKA than for
`UKA in this study. UKA currently uses a formal
`arthrotomy similar in scope to TKA. Future trends
`suggest
`that
`a possible limited incision or mini-
`arthrotom y approach without everting the patella may be
`of value in placing the UKA as intermediate treatment
`options. Litwin.
`et
`al.
`studied
`2-4 patients who
`underwent UKA under arthroscopic guidance. He
`utilized a 3" to 4" L—shaped incision. Patients were
`discharged at 24 to 48 hottrs. and at l2 month follow—up.
`3 of the 24 required revision. However. 2] of 24 were
`satisfied [204]. This short term study with a limited
`incision procedure suggests that UKA may have fast
`recovery and reduced pain. This
`is not
`a
`true
`arthroscopic procedure, however,
`as
`a 3"
`to 4"
`arthrotomy incision was performed. However,
`there
`was fairly rapid discharge from the hospital and fairly
`rapid return to function.
`(‘aspari reported the first seriesofo patients implanted
`\t ith a arthroscopic assistance. All (.1 patients at greater
`than | year follow—up were doing well. The procedure
`nus
`technical]; difficult
`and required fairly long
`operative times # greater than 3 hours. ('aspari notes that
`all patients arc doing well at lidlmvttp and lime not
`S&N EXHIBIT 1035
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`266
`
`P, M. BONUTTI. M.l).. MA. KESTER. PILD.
`
`
`
`
`
`Fig. 5.—Standing AP X-ray. Isolated medial compart-
`ment disease. Osteonecrosis.
`
`Fig. 6. — Stanting AP UKA. 2 yr post-operative.
`
`The future holds promise for UKA in the United
`States.
`lmproved instrumentation which would allow
`the surgeon to more precisely balance the ACL and PCL
`for isometry. as well as balance the patellol‘emoral joint
`and contralateral compartment may improve function
`and pre\ent progression of disease. Possibly a limited
`incision vi ithout ewrting the patella will allow for l'asler
`recovery time as less exposure is required for a single
`compartment.
`Implant
`fixation
`is
`an
`issue
`and
`improvements in implant stability, with implants that
`may have larger surface area for bone ingrowth. or for
`cement fixation need to be evaluated. Further studies on
`
`bearing surfaces with issues of wear appear to be critical
`for long term follow—up of these implants.
`Recently, in the US literature, Grelsamer in a review
`article for US J BJS stated that in patients more than 7() yezu‘s
`of age. UKA is a more cost-el'tective implant. He
`concluded that in terms of function and durability. a TKA
`will probably provide an excellent result. however. he
`
`states."UKAwouldbeprel‘erredintheappropriatematched
`patients over the age ot‘7tl"| [33]. This appears to override
`current philosophy and practice in the l lS.
`l lowever. based
`on his extensive study of literature he suggests that UKA is
`air under-utilized procedure in the US.
`In conclusion. UKA is a highly successful procedure
`and with appropriate indications may be the preferred
`treatment
`option
`for
`patients
`with
`isolated
`unicompartmental knee arthritis.
`In the 118. studies
`suggest that only a small percentage ot‘ patients may
`qualify l'or UKA. and this population may be limited due
`to weight. deformity. activity level. and severity ol‘
`disease. However. in appropriate patients. UKA clearly
`out performs TKA (Figs 5 & (1). Questions arise that in
`long tenn results greater than IO years for UKA whether
`results will deteriorate. This
`issue still has
`to be
`
`in the appropriate patient. UKA
`answered. however.
`clearly has superior results and excellent
`long term
`results.
`
`S&N EXHIBIT 1035
`S&N v. BSI
`IPR2013-00629
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