patient-specific implants for focal cartilage lesions in

IIn the quest for increased surgical precision and improved joint kinematics, Computer-Assisted OrthopedicSurgery (CAOS) shows promising results for both total and partial joint replacement. In the knee, comput-

er-assisted joint design can now be applied to the treatment of younger patients suffering pain and restric-

tion of activity due to focal defects in their femoral articular cartilage. By taking MRI scans of the affected

knee and digitally segmenting these scans, we can identify and map focal defects in cartilage and bone.

Metallic implants matched to the defect can be fabricated, and guide instrumentation to ensure proper

implant alignment and depth of recession in the surrounding cartilage can be designed from segmented MRI

scans.

Beginning in 2012, a series of 682 patient-specific implants were designed based on MRI analysis of femoral

cartilage focal defects, and implanted in 612 knees. A Kaplan-Meier analysis found a cumulative survivorship

of 96% at 7-year follow-up from the first implantation. Fourteen (2.3%) of these implants required revision

due to disease progression, incorrect implant positioning, and inadequate lesion coverage at the time of

surgery.

These survivorship data compare favorably with all other modes of treatment for femoral focal cartilage

lesions and support the use of patient-specific implants designed from segmented MRI scans in these cases.

Patient-Specific Implants for Focal Cartilage Lesions in The Knee:

Implant Survivorship Analysis up to Seven Years Post-Implantation

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#1384 Ryd FINAL

ABSTRACT

LEIF RYD, MDSENIOR MEDICAL CONSULTANT

EPISURF MEDICALSTOCKHOLM, SWEDEN

KATARINA FLODSTRÖM, PHDCHIEF SCIENTIFIC OFFICER

EPISURF MEDICALSTOCKHOLM, SWEDEN

Copyright © 2020 Surgical Technology International™

MICHAEL T. MANLEY, FRSA, PHDCONSULTANT IN ORTHOPAEDIC SCIENCESMICHAEL T. MANLEY FRSA, PHD, LLC

NAPLES, FL, USA

Orthopaedic SurgerySURGICAL TECHNOLOGY INTERNATIONAL Volume 38

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Sophisticated computerized methodsof implant design and placement havebecome increasingly common in the fieldof orthopedics. Computer-Assisted

Orthopedic Surgery (CAOS) has beenshown to be effective in reducing thenumber of outliers that occur with tradi-tional methods of knee alignment andcomponent placement following totalknee arthroplasty (TKA).1-3 In advanced

systems, computer models of the dis-eased knee are produced pre-operativelyfrom MRI or CT scans and used todevelop a specific pre-operative plan.During surgery, stereo cameras monitorthe movement of the patient and instru-

#1384 Ryd FINAL

Patient-Specific Implants for Focal Cartilage Lesions in The Knee: Implant Survivorship Analysis up to Seven Years Post-ImplantationRYD/FLODSTRÖM/MANLEY

INTRODUCTION

Figure 1. A Damage Marking Report (DMR) showing a partial-depth cartilage lesion (pink), a full-depth cartilage lesion (red), and an underlying bone marrowlesion (blue). The two MR images correspond to the lesions described in the DMR.

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ments so that the pre-operative plan canbe followed with precision. In some sys-tems, patient-specific guide saw blocksdeveloped from pre-operative kneeimages, so-called PSI-TKA technology,show improved component alignmentcompared to alignment with traditionalcutting guides.4,5 In an extended applica-tion of CAOS, patient-specific total kneeimplants, developed pre-operativelyfrom MR images, have been suggested tobe a way to completely individualizeknee surgery. Superior component fitand alignment6,7 and excellent clinicalperformance have been reported.8Younger patients with focal lesions in

the femoral articular cartilage of the kneeare not usually regarded as candidates forTKA, even though they may suffer pain,restricted range of motion, and difficultyparticipating in sports or other activities.9If left untreated, focal lesions are regardedas a precursor to severe knee osteoarthri-tis (OA).10-14 Methods for treating focaldefects include microfracture of the bonebed underlying the lesion to generatefibrocartilage,15 restoration of normalhyaline cartilage in the lesion by chondro-cyte implantation,16-18 and filling ofthe defect by cartilage resurfacingimplants.15,19 Results obtained with auto-genous chondrocyte implantation (ACI),developed in the 1990s by Brittberg andcoworkers,17 suggest that cell implanta-tion successfully relieves pain and restoresfunction in patients up to age 35-40years.20-23 Microfracture has been shownto be effective in younger patients withsmall lesions.24 A disadvantage with bothmicrofracture and chondrocyte implanta-tion is that extensive periods of restrictedweight-bearing following surgery arerequired to protect the repair.25 Also,these biological methods do less well inpatients older than 30-35 years.26-29Small metallic implants, developed in

the last decade,26-28, 30 may be a way totreat patients who are too old for biolog-ical treatment and too young for TKA,the so-called GAP-age.31 Metallicimplants have the benefit that the defectis filled immediately and the surroundinghealthy cartilage receives structural sup-port to prevent defect enlargement.32Patient rehabilitation is thus much short-er than with biologic treatments. Onecaveat learned from animal studies is thatexact sizing and placement of a metallicimplant is important. The fit of the pros-thetic articular surface with the sur-rounding healthy cartilage mustminimize synovial fluid intrusion into the

interface between the implant and sub-chondral bone to protect fixation.17 Inaddition, the metallic articular surfacemust be slightly recessed below the sur-rounding healthy femoral cartilage tominimize wear of the opposing (tibia orpatella) cartilage counterface.33A first-generation metallic focal defect

implant (HemiCAP/UniCAP, Arthrosur-face, Boston, MA, USA) featured a libraryof different articular surface shapes in anattempt to provide a “best-fit” to a focallesion during surgery. Pain relief andrestoration of function were reported forpatients with implants sized and implant-ed properly. When implants were mis-placed or left proud of the cartilagesurrounding the defect, erosion of theopposing articular surfaces was seen.34,35A more recent development (Episeal-

er, Episurf Medical, Stockholm, Sweden)uses the CAOS approach in the design ofpatient-specific focal defect-fillingimplants and associated instrumentation.This technology uses segmented MRimages for lesion analysis, 3D-reconstruc-tion of the knee in computer modelsdeveloped from the segmented images,and computer-aided design and manufac-turing for the implant and associatedinstruments.36,37 Patient rehabilitationtime to full weight-bearing has beenshown to be about 6 to 8 weeks, withexcellent short-term pain relief and sur-vivorship.38,39 An important measure ofthe success of this approach is implant sur-vivorship, since the return of pain willnormally lead to implant removal. Wereport here a survivorship analysis of thefirst 612 knees (682 patient-specificimplants) treated with this technologyover the first eight years of clinical use.We also report all complications found.

Material and Methods

For each patient who was a candidatefor the Episealer technology, a three-

dimensional MRI sequence of the dam-aged knee was taken and uploaded to themanufacturer. The MRI images wereanonymized in the uploading process andonly patient age and gender were includ-ed as a coarse identity safeguard. A radi-ologist reviewed all MRI scans to ensurethat the knee was a candidate for focaldefect-filling, and the scan was segment-ed digitally. A three-dimensional modelof the knee with defects and surroundingcartilage was produced (Fig. 1). A Dam-age Marking Report (DMR) describingthe knee pathology was generated and acustom plan with details of the implantdesign and the implant position requiredto fill the defect was developed. Possiblecontraindications for the procedure, suchas excessive cartilage wear in the femuror wear of the opposing cartilage on thetibia and/or patella, as well as severeosteo-arthritis were identified at thisstage and integrated in the DMR (Fig. 1).The entire DMR was uploaded forapproval by the treating surgeon. If thesurgeon approved the patient treatmentplan, the implant and instruments weremanufactured.Implant design parameters included a

patient-matched articulating surface, aswell as full coverage of the defect toensure contact between the implant andsurrounding cartilage. Implants weremanufactured from cobalt-chromiumalloy to provide an articulation that isresistant to wear. For the fixation inter-face, the alloy was coated with titaniumand hydroxyapatite to encourage biologicfixation in subchondral bone. To ensurethe necessary precision at surgery, eachimplant was matched with individualizedguide instruments to ensure proper posi-tioning of the implant and its recessionbelow the surrounding cartilage.For the surgical procedure, the implant

was delivered with a visualization guidethat showed details of the final design andits required surgical placement (Fig. 2).37

#1384 Ryd FINAL


Figure 2. Examples from a “Final Design”. The shape and position of the MRI-based individualized 3D-printed guide instrument are shown.

MATERIALS AND METHODS

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Implantation was performed using thepatient-specific instrumentation guide(Fig. 3). A drill guide located on the carti-lage surrounding the defect and a depthgauge allowed fine-tuning of the drilldepth in increments of 200 µm. Therequired recession of the implant articula-tion was checked using a dummy toensure that the articular surface of theimplant was approximately 0.5 mmbelow the surrounding healthy cartilage(Fig. 4).For the survival analysis reported

here, we examined all post market sur-veillance records from all patients in thedatabase held by the manufacturer with-out any exclusions. This analysis includedall implants that required revision for anycause. Patients treated from December2012 (first implantation) to the end ofJune 2020 were included in the analysis.Revisions were tabulated and the reasonsfor revision were recorded in the adverseevent analysis file. The cause of revisionwas analyzed for each case, and the origi-nal DMR and treatment plan were

reviewed.Survivorship was calculated using a

Kaplan-Meier analysis.40 To calculate thecumulative revision rate (CRR), thenumber of knees “at risk” of revision atthe beginning of each year of follow-upwas determined. The number of revi-sions during each year of follow-up wasregistered and divided by the numbers“at risk” during that period andexpressed as a percentage. These yearlypercentages were added together to givea cumulative revision rate.

#1384 Ryd FINAL


Figure 3. Patient-specific alignment guide to ensure accurate positioning of theimplant.

Figure 4. A patient-specific implant placed with custom instrumentation. Notethe recession of the implant beneath the level of the surrounding cartilage.(Courtesy T. Spalding, MD)

Table IRevisions Reported at 7-year Follow-Up

Case FU at revision(months)

Age(at index

op)Site

Implanttype

Revision Cause

1234567891011121314

6781115161928283028293030

3944654345613252525250554238

TrochleaTrochlea

Med condyleMed condyleMed condyleMed condyleMed condyleLat condyleMed condyleMed condyleTrochlea

Med condyleTrochleaTrochlea

SoloSoloTwinTwinTwinSoloTwinSoloTwinSoloTwinTwinSoloSolo

Other pain (fem-tib OA)Trauma 3 weeks post-opDisease progression, possibly related to technical error at operationUnknown pain. Metal allergy, unknown relevancePain, several lesions in the knee.Borderline indication. Tibial cartilage wearPain, proud implantInfectionUnknown, revised by another surgeonLesion was too large, not fully covered by the implantOther pain (fem-tib OA)Pain. Other lesions in the knee at the time of surgery, occurred after the DMR.Additional HTO failedImplant was too small, lesion not fully covered. Progression of lesionafter surgery

OA, osteoarthritis; DMR, Damage Marking Report; HTO, high tibial osteotomy

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Results

During the evaluation period, a totalof 682 Episealer implants were implant-ed in 612 knees. The patient age atsurgery ranged from 27 to 72 years,with a mean value of 48.6 years. Onepatient operated upon in 2018 diedfrom unrelated causes in 2019, but hasbeen included in the calculations. At the time of this writing, 14 of the

612 operated knees have been revised.This corresponds to a crude revisionrate of 2.3%. The revisions and the rea-sons for each are shown in Table I.Revisions were due to various caus-

es, that included disease progression,incorrect implant positioning, inade-quate lesion coverage and causes unre-lated to the implant. In three revisedcases, the pre-operative indicationswere poor as there were additionallesions in these knees that were nottreated. In one case, there was a techni-cal error at implantation and in threecases manufacture of the implant wasslightly different than that described inthe DMR. There was one case of infec-tion. Revisions included eight implantsplaced in the medial condyle, one in thelateral condyle and five in the trochleaarea. For knees receiving multipleimplants, there were no revisions with-in the study period. A Kaplan-Meiersurvivorship analysis of the patients atrisk at the beginning of each year of fol-low-up is shown in Table II. Kaplan-Meier survivorship at six years offollow-up was 96.3% (Fig. 5). Thisvalue includes revision due to all caus-es.

Discussion

Computer-Assisted OrthopedicSurgery (CAOS) for joint replacement inthe knee has included precision monitor-ing of cutting angles through the moni-toring of saw and patient movement1,41 aswell as patient-specific cutting blocks andpatient-specific total knee implants.5-7 Ithas been suggested that these systemscome with a learning curve, add time tothe operative procedure, and are not yetfully accepted.2,3,42. From a technologicalperspective, proponents claim improvedaccuracy of implantation 4,6,7,43 and better

functionality in the mid-term follow-up.8However, a recent Cochrane analysisreported no difference in accuracy withsome of these approaches compared tostandard implantation systems.44 Thejury is still out on the use of CAOS fortotal knee replacement.Accurate resurfacing of focal defects

in the articular cartilage in the femoralknee can only be attempted with com-puter-aided design and manufacture.Each defect is unique with respect to sizeand extent, while accurate implant place-ment is crucial to procedural effective-ness. Excellent clinical results in terms of

#1384 Ryd FINAL


Table IICumulative revision of 612 Episealer (Episurf Medical, Stockholm, Sweden)

knees at 7-year follow-up

Time(months)

Number atRisk

CumulativeNumber at

Risk

Failure Survival

Estimate 95% LB 95% UB Estimate 95% LB 95% UB

0

12

24

36

48

60

72

84

612

478

327

191

97

42

15

4

--

4

7

14

14

14

14

14

--

0.75%

1.43%

4.05%

4.05%

4.05%

4.05%

4.05%

--

0.28%

0.68%

2.36%

2.36%

2.36%

2.36%

2.36%

--

1.99%

2.99%

6.92%

6.92%

6.92%

6.92%

6.92%

--

99.25%

98.57%

95.95%

95.95%

95.95%

95.95%

95.95%

--

98.02%

97.01%

93.08%

93.08%

93.08%

93.08%

93.08%

--

99.72%

99.32%

97.64%

97.64%

97.64%

97.64%

97.64%

Figure 5. Cumulative survival graph of 612 patients receiving 682 patient-specific focal defect resurfacingimplants.

RESULTS DISCUSSION

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patient-reported outcome measures(PROMs) have recently been reportedfor patient-specific focal defect kneeimplants at two years post-implanta-tion.29,38 The procedure was reported tobe simple and reproducible and goodrelief of pain was achieved.38 In a seriesof 80 implants, 2.5 % had been revisedat 24-months follow-up. We have shownhere, in a larger series of 682 implants,that survivorship at 7-years follow-upwas better than 96%. There were 14revisions out of the 682 implants placed,with a crude revision rate of 2.5%.These survival results are superior to

those reported for other surgicalapproaches to this type of lesion; survivaldata for microfracture, non-custommetal implants and ACI indicate a sur-vival rate of about 75% at 6 years afterimplantation.45-47Joint replacement registries are an

increasingly important source of sur-vivorship data. Large numbers ofentries provide statistical power, butnecessitate the use of simple analysissuch as survival statistics.48 For reasonsof statistical power, we chose survivaldata as the dependent variable in ourreport. Recent survival analyses of focaldefect resurfacing implants available inthe Australian Joint Arthroplasty Reg-istry show a 6-year survival of about75% and an 11-year survival of 54% for244 first-generation metal resurfacingdevices implanted.34 The AustralianRegistry reported that the most com-mon mode of failure for a metal defectresurfacing implant was “progression ofthe joint disease”, perhaps anosteoarthritic process, an ill-fittingdevice and/or liberal preoperative indi-cations. By comparison, the survivor-ship of 96% found in our analysismimics the best TKA survivorshipreported in national registries, albeit forolder, less-active patients.34,49Perhaps it is reasonable to assume

that the superior results we report hereare due to the patient-specificity ofimplants and instruments. In animalstudies, an implant that is designed toaccurately fill the defect was shown toprotect the integrity of fixation fromdamage due to synovial fluid intrusioninto the supporting subchondral bone.The titanium/hydroxyapatite coating ofthe implant also promotes adherence ofcar tilage, so-called chondro-integration,50 further protecting fixa-tion. For longevity of the articulation, ametallic implant must not protrude

above the surrounding cartilage or itwill severely damage the opposing carti-lage counterface.33,51. The incrementalfine-tuning allowed during drilling bythe patient-specific alignment guidesensures that implants are neither tiltednor inserted in a too-shallow position.Human cartilage compresses asymptoti-cally upon weight-bearing by about20%,52 corresponding to about 0.5 mmin the normal knee. For patients withthese metallic implants, activities such aswalking or running will compress thejoint space and cause the opposing carti-lage to meet metal. The key to survivalis proper implant positioning so that,during joint compression, the opposingcartilage does not meet a metal edge. Acontraindication for this procedure isalready-compromised opposing tibialcartilage found at the time of the pre-operative DMR.46 Thus, for the Episeal-er technology, opposing cartilage ICRSstage III-IV is a contraindication andsuch patients are usually not acceptedfor surgery.Of the 14 revisions in this report,

three (patients 2, 3 and 8 in Table I)were caused by factors that could not beattributed to the index surgery.In two cases (patients 10 and 14), the

implant did not cover the entire carti-lage lesion. Often, lesions are extremelyirregular in shape, with “corners” stick-ing out some distance from the corelesion. To accommodate such corners, alarger implant is needed, with excessivehealthy cartilage excised. The DMRshows the shape of the lesion, and thesurgeon must decide how best to bal-ance implant size, placement, and lesioncoverage. A smaller implant may meanthat a portion of the cartilage lesion isleft uncovered. It is known that smallcartilage lesions can heal with time53 butfurther work is required to analyzelesions that are not fully covered becauseof shape or due to their position close tothe edges of the knee. Revision case 10is an example of an edge lesion. The lit-erature suggests that lesion size isinversely related to implant longevity,35and a longitudinal (A-P) size of 30-35mm has been suggested as a contraindi-cation for this approach. Somewhat sur-prisingly, we found that none of thelarger Episealer implants with a lengthof 35mm were revised at the time of thisanalysis. One Episealer implant that wasmalplaced above the cartilage surfacewas revised for pain. Another threepatients reported pain, and their

implants were also revised. Pain as acomplication is found following surgeryof the knee and other joints. For focaldefect implants, pain may be related toimplant malposition or may be due tounknown cartilage conditions that arenot resolved by these implants.The use of MRI to evaluate a carti-

lage defect means that, as part of pre-operative planning, both the cartilageand the subchondral bone can beassessed, visualized and used in estab-lishing the indication for the procedure.Insufficient bone stock to support theimplant and signs of severe progressiveosteoarthritis are contraindications fortreating the defect in isolation. MRIplays an important role in identifyingand quantifying bone marrow lesions(BML).54,55 Cartilage does not containnerve-endings, but subchondral bonedoes. With patient-specific implants,BMLs can be identified and treated byexcision and a corresponding thickeningof the implant, with good relief frompain.28In the treatment of full-thickness

focal defects in the articular cartilage ofthe knee, microfracture and treatmentby implantation of chondrocytes bothshow satisfactory results in the relief ofpain and restoration of function. For ayounger adult with a focal lesion, one ofthe primary patient needs is a shortperiod of rehabilitation and a rapidreturn to full function. Neithermicrofracture nor a biologic approachmeet this criterion as tissue growth andmaturation may extend beyond 18months post-surgery.56,57 Metallic andpolymeric implants that are used to fillcartilage defects do not require longperiods of rehabilitation and a recoveryof three months or so is often adequatefor full functional activity to begin.56,57The literature shows that, with properdesign, implantation technique andalignment, metallic implants can providesatisfactory clinical results and goodpatient satisfaction with a focal defectresurfacing procedure.26-29,58

Conclusion

In this follow-up of 612 consecutivepatients (682 implants) receiving focaldefect resurfacing implants for painfulfemoral cartilage defects, we have showna 96% implant survivorship at 7 yearspost-implantation. Although survivor-ship by itself does not imply patient satis-faction with the procedure, these results

#1384 Ryd FINAL


CONCLUSION

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are superior to those reported in the lit-erature for other focal defect-filling tech-nologies. Of the 14 identified revisionsin this analysis, none were due to a failingimplant and most were due to improperpatient selection. Review of the MRIscans of the implants that failed showsthat, in some cases, the cartilage lesionwas too large in both size and depth forresurfacing to be successful. The pres-ence of osteophytes or adverse changesin bone density that may affect implantstability are now also known to be a con-traindication for resurfacing. The carefulassessment of the pathology of each indi-vidual patient should be considered whenoffering patient-specific implants as asolution to a painful femoral cartilagedefect. However, for patients who satisfythe selection criteria, this technologyoffers a short rehabilitation time and thepotential for long-term relief of pain andreturn of function in what would other-wise be a painful knee.

Authors’ Disclosure

Dr Ryd is the Senior Medical Consul-tant to Episurf Medical AB (Stockholm,Sweden) and is compensated by the com-pany for his work with them. Dr Flod-strom is Chief Scientific Officer ofEpisurf Medical AB and is an Episurfemployee. Dr Manley is a consultant toEpisurf Medical, Stryker Orthopaedics(Kalamazoo, MI) and other companies asneed arises.

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5-year results of focal articular prosthetic resurfacing forthe treatment of full-thickness articular cartilage defectsin the knee. Arch Orthop Trauma Surg 2011;131(8):1135-43.27. Bollars P, Bosquet M, Vandekerckhove B, Harde-man F, Bellemans J. Prosthetic inlay resurfacing for thetreatment of focal, full thickness cartilage defects of thefemoral condyle: a bridge between biologics and con-ventional arthroplasty. Knee Surg Sports TraumatolArthrosc 2012;20(9):1753-9.28. Nathwani D, McNicholas M, Hart A, Miles J, BobicV. Partial resurfacing of the knee with the BioPolyImplant: Interim report at 2 years. JB JS Open Access2017;2(2):e0011.29. Stålman A, Sköldenberg O, Martinez-Carranza N,Roberts D, Högström M, Ryd L. No implant migrationand good subjective outcomne of a novel customizedfemroal resurfacing metal implant for focal chondrallesions. Knee Surg Sports Traumatol Arthrosc2018;26(7):2196-204.30. Brennan SA, Devitt BM, O’Neill CJ, Nicholson P.Focal femoral condyle resurfacing. Bone Joint J2013;95-B(3):301-4.31. Li CS, Karlsson J, Winemaker M, Sancheti P, Bhan-dari M. Orthopedic surgeons feel that there is a treat-ment gap in management of early OA: internationalsurvey. Knee Surg Sports Traumatol Arthrosc2014;22:363-78.32. Bergfeld JA. Articular cartilage injury: filling pot-holes. Orthopedics 2004;27(9):973-4.33. Martinez-Carranza N, Berg HE, Hultenby K,Nurmi-Sandh H, Ryd L, Lagerstedt AS. Focal kneeresurfacing and effects of surgical precision on opposingcartilage. A pilot study on 12 sheep. Osteoarthritis Car-tilage 2013;21(5):739-45.34. Australian Orthopaedic Association National JointReplacement Registry (AOANJRR). Hip, Knee &Shoulder Arthroplasty: 2019 Annual Report. Adelaide,South Australia: AOA; 2019:190.35. Laursen JO. Treatment of full-thickness cartilagelesions and early OA using large condyle resurfacingprosthesis: UniCAP(®). Knee Surg Sports TraumatolArthrosc 2016;24(5):1695-701.36. Martinez-Carranza N, Berg HA, Lagerstedt AS,Nurmi-Sandh H, Schupbach P, Ryd L. Fixation of a dou-ble-coated titanium-hydroxiapatite focal knee resurfac-ing implant A 12-month study in sheep. OsteoarthritisCartilage. 2014(Jun; 22(6)):836-44.37. Ryd L. The Mini-Metal concept for treating focallesions and its possible application in athletes. AspetarSports Med J 2016;10:292-5.38. Holz J, Spalding T, Boutefnouchet T, et al. Patientspecific metal implants for focal chondral lesions in theknee - Excellent clinical results at 2 years. Knee SurgSports Traumatol Arthrosc 2020 Oct 6. doi:10.1007/s00167-020-06289-7.39. Martinez-Carranza N, Rockborn P, Roberts D,Högström M, Stålman A. Successful treatment offemoral chondral lesions with a novel customizedmetal implant at midterm follow.up. Cartilage2020 Oct 27;1947603520967064. doi: 10.1177/1947603520967064.40. Ranstam J, Cook JA. Kaplan-Meier curve. Br J Surg2017;104(4):442.41. Jenny JY, Saragaglia D, Bercovy M, et al. Navigationimproves the survival rate of mobile-bearing total kneearthroplasty by severe preoperative coronal deformity:A propensity matched case-control comparative study. JKnee Surg 2020 Feb 19. doi: 10.1055/s-0040-1701441.42. Callaghan JJ, Liu SS, Warth LC. Computer-assistedsurgery: a wine before its time: in the affirmative. JArthroplasty 2006;21(4 Suppl 1):27-8.43. Renson L, Poilvache P, Van den Wyngaert H.Improved alignment and operating room efficiency withpatient-specific instrumentation for TKA. Knee2014;21(6):1216-20.44. Woon JTK, Zeng ISL, Calliess T, et al. Outcome ofkinematic alignment using patient-specific instrumenta-tion versus mechanical alignment in TKA: a meta-analy-sis and subgroup analysis of randomised trials. ArchOrthop Trauma Surg 2018;138(9):1293-303.45. Knutsen G, Drogset JO, Engebretsen L, et al. Arandomized multicenter trial comparing autologouschondrocyte implantation with microfracture: long-term follow-up at 14 to 15 years. J Bone Joint Surg Am

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