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A Pilot Study of the Use of an Osteochondral Scaffold Plug for Cartilage Repair in the Knee and How to Deal With Early Clinical Failures

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A Pilot Study of the Use of an Osteochondral Scaffold Plug for Cartilage Repair in the Knee and How to Deal With Early Clinical Failures
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  A Pilot Study of the Use of an Osteochondral Scaffold Plug forCartilage Repair in the Knee and How to Deal With EarlyClinical Failures Aad A. M. Dhollander, M.D., Koen Liekens, M.D., Karl F. Almqvist, M.D., Ph.D.,René Verdonk, M.D., Ph.D., Stijn Lambrecht, Ph.D., Dirk Elewaut, M.D., Ph.D.,Gust Verbruggen, M.D., Ph.D., and Peter C. M. Verdonk, M.D., Ph.D. Purpose:  To present our short-term experience with an osteochondral scaffold plug (TruFit plug;Smith & Nephew, Andover, MA) for cartilage repair in the knee and, more importantly, to discussour approach to treat early clinical failures.  Methods:  Twenty patients were consecutively treated fortheir cartilage lesions with the plug technique. These patients were prospectively clinically evaluatedat 6 and 12 months of follow-up. Magnetic resonance imaging (MRI) was used for morphologicanalysis of the cartilage repair. Biopsy samples were taken from 3 cases during revision surgery,allowing histologic assessment of the repair tissue.  Results:  The short-term clinical and MRI outcomeof this pilot study are modest. No signs of deterioration of the repair tissue were observed. Of the 15patients followed up during 1 year, 3 (20.0%) showed persistent clinical symptoms or even more clinicalsymptoms after insertion of the plug. These patients were considered as failures and therefore eligible forrevision surgery. During revision surgery, the repair tissue was carefully removed. The remainingosteochondral defect was filled with autologous bone grafts. Immediate and persistent relief of symptomswas observed in all 3 patients. Histologic assessment of biopsy specimens taken during revision surgeryshowed fibrous vascularized repair tissue with the presence of foreign-body giant cells. Conclusions: Theoverall short-term clinical and MRI outcome of the osteochondral scaffold plug for cartilage repair in theknee is modest. In this pilot study a modest clinical improvement became apparent at 12 months of follow-up. MRI data showed no deterioration of the repair tissue. Of the 15 patients, 3 (20%) hadpersistent clinical symptoms after surgery. These patients were successfully treated with removal of theosteochondral plug remnants and the application of autologous bone grafts. LevelofEvidence: Level IV,therapeutic case series. T he joint cartilage is an elastic tissue without nervesor blood or lymph vessels and varies in thicknessaccording to species. 1 Postnatal articular chondrocytesdisplayalowmitoticactivitylevel,andarticularcartilagehas a low turnover rate. The complex structure andbiomechanical function of articular cartilage make themanagement of joint surface lesions a challenge. Carti-lage lesions are believed to progress, resulting in degen-erative arthritis of the joint. 2 The ultimate aim of treat-ment is the restoration of normal knee function byregenerating hyaline cartilage in the defect and completeintegration of the regenerated cartilage with the sur-rounding cartilage and underlying bone.The use of bioabsorbable scaffolds for repair of chondral and osteochondral defects has recently beenexplored in laboratory and preclinical investigations. 3 From the Department of Orthopaedic Surgery and Traumatol-ogy (A.A.M.D., K.L., K.F.A., R.V., P.C.M.V.) and Laboratory of Connective Tissue Biology, Department of Rheumatology (A.A.M.D.,S.L., D.E., G.V.), Ghent University Hospital, Ghent; and Department of Orthopaedic Surgery and Traumatology, Stedelijk Ziekenhuis Ro-eselare (P.C.M.V.), Roeselare, Belgium. A.A.M.D. and K.L. have contributed equally to this article and share first authorship. The authors report no conflict of interest. Received January 12, 2011; accepted July 27, 2011. Address correspondence to Aad A.M. Dhollander, M.D., Depart-ment of Orthopaedic Surgery and Traumatology, Ghent University Hospital, De Pintelaan 185 (P5), 9000 Ghent, Belgium. E-mail:aad.dhollander@ugent.be© 2012 by the Arthroscopy Association of North America0749-8063/1135/$36.00doi:10.1016/j.arthro.2011.07.017  225  Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 28, No 2 (February), 2012: pp 225-233  Such matrix scaffolds, implanted alone or in combi-nation with cells, allow immediate filling of the defectand support local migration of chondrogenic and os-teogenic cells that synthesize new ground substance.The osteochondral scaffold plugs (TruFit plug; Smith& Nephew, Andover, MA) are acellular synthetic poly-mer scaffolds that are inserted into the osteochondralbone to provide a stable scaffold that in theory couldencourage the regeneration of a full thickness of articularcartilage to repair chondral defects. 4 Conflicting clinicaloutcomes have been reported recently with the use of these plugs for cartilage repair in the knee. 5,6 The pur-poses of this pilot study are to present our short-termexperience with the osteochondral scaffold plug for car-tilagerepairinthekneeand,moreimportantly,todiscussour approach to treat early clinical failures, because atotal joint replacement or a wait-and-see period of 2years are the only published alternatives in the litera-ture. 4-6 It was hypothesized that all patients treated withthis osteochondral plug technique for a cartilage lesion inthe knee would improve clinically and that all plugswould fill the cartilage defects completely with tissuewith a signal similar to cartilage on magnetic resonanceimaging (MRI). METHODSStudy Population Patients with 1 focal cartilage defect involving thefemoral condyle, patella, or trochlea that could betreated preferably with 1 plug or a maximum of 2plugs and with clinical symptoms (  1 of the follow-ing symptoms: pain, swelling, locking, and “givingaway”) were eligible for treatment. There was noinitial trial of nonoperative management. Smokers andWorkers’ Compensation cases were also included. Weexcluded cartilage defects with a size greater than 2cm 2 . Therefore an MRI scan or arthro–computed to-mography scan was performed preoperatively to confirmour clinical suspicion of a cartilage defect. On the basisof the defect size observed on these investigations, weconsidered the patients eligible for treatment with theplug device and they were included in this pilot study.Other exclusion criteria were age under 16 years or over55 years, body mass index greater than 32, and thepresence of multiple focal cartilage defects, untreatedtibiofemoral or patellofemoral malalignment or instabil-ity, diffuse osteoarthritis or bipolar “kissing” lesions,major meniscal deficiency, and other general medicalconditions such as diabetes or rheumatoid arthritis. Clin-ical experimentation was approved by the hospital’s eth-ics committee, and informed consent to participate in thestudy and to comply with the postoperative regimen wasobtained from all patients. The patients included in thispilot study were treated between October 2008 and No-vember 2010.In total, 20 patients (8 male and 12 female patients)were treated consecutively and followed up for 12months. The right side–to–left side ratio was 10:10.The lesions were focal in all cases. Of the cartilagedefects, 8 were located on the medial femoral condyle,4 on the lateral femoral condyle, 5 on the patella, and3 on the trochlea. All lesions were International Car-tilage Repair Society grade III or IV 7 and had a meansize of 0.83 cm 2 (range, 0.38 to 1.58 cm 2 ). The causeof injury was traumatic in 7 cases, focal nontraumatic(focal degenerative lesions) in 9 cases, and osteochon-dritis dissecans in 4 cases. The mean age of thepatients was 31.65 years (range, 17 to 53 years). Themean duration of symptoms before surgery was 26.30months (range, 2 to 122 months).Previous surgery in 10 of the patients included 4partial meniscectomies, 4 anterior cruciate ligamentreconstructions, 1 case of meniscal suture, and 3 car-tilage repair procedures, such as autologous chondro-cyte implantation (n  1) or microfracturing (n  2)of chondral lesions.Associated procedures were performed in 5 pa-tients: 2 Fulkerson osteotomies, 1 lateral release, 1suturing of a medial meniscus tear, and 1 lateral allo-geneic meniscal transplantation. 8 Surgical ProcedureImplant Technique:  A mini-arthrotomy in atourniquet-controlled bloodless surgical field was per-formed to allow access to the defect. The lesion wasmeasured after the bottom of the cartilage defect wasfreshened, and the edges of the defect were trimmedback to stable walls of healthy cartilage. As describedby Melton et al., 9 the decision as whether to use 1 plugor multiple plugs is made at this stage, based on thecharacteristics of the lesion. Then, a single cylindricalhole (or multiple holes for multiple plugs) of 8 to 12mm in depth is drilled through a drill sleeve into thedefect. The drill hole size will be matched to the size of the defect and the planned implant diameter. A plugprepared to the same depth is introduced into the defectunder direct vision. The implant then needs to be“tamped” down with a punch until the surface of theimplant is continuous with the surrounding articular car-tilage (Fig 1). This tamping is inherent to the technique and in accordance with the device manual. In our expe-rience, we did not observe that this tamping caused any226  A. A. M. DHOLLANDER ET AL.  damage to the plugs. If more than 1 plug is required, abridgeof1to2mmshouldbeleftifpossible.Finally,theimplant is probed to ensure that the implant is stable andthat the edges of the implant are congruent with thesurrounding chondral surfaces. 9 In 17 of the 20 patients, only 1 plug was inserted. In7 patients a plug of 9 mm was used, in 2 patients aplug of 7 mm was used, and in 8 patients a plug of 11mm was inserted. In the remaining 3 patients, 2 plugswere implanted. In 1 patient 2 plugs of 9 mm wereused, in 1 patient a plug of 9 mm and a plug of 7 mmwere used, and finally, in 1 patient a plug of 9 mm anda plug of 11 mm were implanted.The postoperative regimen was as follows. The pa-tients were non–weight bearing for 4 weeks. Achieving anormal gait pattern was advised at 10 weeks postopera-tively. Maximum active flexion did not exceed 90° forthe first 4 weeks of rehabilitation. Full range of motionwas allowed 8 weeks postoperatively. Isometric quadri-ceps training, straight length raising, and hamstringisometrics were advised after the first 2 weeks. Returnto low-impact sports was allowed 12 months aftersurgery. 10 Revision Surgery:  The indications for revisionsurgery were persistent clinical symptoms or evenmore clinical symptoms after the insertion of a plugfor a minimal period of 9 months. During revisionsurgery, the remnants of the plug were carefully re-moved. The remaining osteochondral defect was filledwith autologous bone grafts harvested from the iliaccrest (Fig 2). Clinical Evaluation All 20 patients were clinically prospectively evalu-ated with use of the Knee Injury and OsteoarthritisOutcome Score (KOOS), 11-13 the Tegner activity F IGURE  2.  Sagittal 3D fast low-angleshot spoiled gradient echo MR imageswith water excitation. (A) MR imageof a synthetic osteochondral plug in-serted into the medial femoral condyle6 months after surgery. (B) MR imageof the same patient 6 months afterrevision surgery with autologous bonegrafts for a failed plug repair. F IGURE  1.  One of the 2 planned plugs (11 mm and 9 mm) insertedinto the predrilled cylindrical holes in the medial femoral condyle. 227 OSTEOCHONDRAL SCAFFOLD PLUG  scale, 14 and a visual analog scale (VAS) 15,16 for painpreoperatively and at 6 and 12 months of follow-up. MRI Technique All MRI examinations at 6 and 12 months of follow-up were performed on a 1.5-T or 3-T magneticresonance(MR)unit(MagnetomAvanto,MagnetomSym-phony Tim, or Magnetom Trio; Siemens Medical Solu-tions, Erlangen, Germany). Of the 20 patients, 19 had con-sentedtofollowthepostoperativeMRIevaluationprotocol.We performed a standard knee MRI protocol includingproton density–weighted with high sampling efficiency(SPACE) and T2-weighted turbo spin echo acquisitionsusing a dedicated send-receive 8-channel knee coil. Imag-ing parameters of the sequences were as follows: ●  Sagittal proton density–weighted and T2-weightedturbo spin echo images (echo time [TE], 24/96milliseconds on 1.5-T MR unit and 22/101 milli-seconds on 3-T MR unit; repetition time [TR],4,000 milliseconds on 1.5-T MR unit and 4,662milliseconds on 3-T MR unit; slice thickness, 3 mmwith a 0.3-mm intersection gap; field of view(FOV), 180 mm; matrix size, 512    307 on 1.5-TMR unit and 448  246 on 3-T MR unit) ●  Coronal proton density–weighted images with fatsaturation (TE, 43 milliseconds on 1.5-T MR unitand 44 milliseconds on 3-T MR unit; TR, 4,400milliseconds on 1.5-T MR unit and 3,140 millisec-onds on 3-T MR unit; slice thickness, 3 mm; FOV,180 mm; matrix size, 512  240 on 1.5 T MR unitand 448  218 on 3-T MR unit) ●  Transverse 3-dimensional (3D) dual echo steady-state images with gradient echo sequence (TE, 5.5milliseconds; TR, 19 milliseconds; flip angle, 25°;slice thickness, 3 mm; FOV, 160 mm; matrix size,256  156) ●  Sagittal 3D fast low-angle shot images with waterexcitation images (only on 1.5-T MR unit) withspoiled gradient echo (TE, 27.0 milliseconds; TR,13.7 milliseconds; flip angle, 30°; slice thickness, 1mm consecutively; FOV, 180 mm; matrix size,512    240) ●  Sagittal 3D proton density SPACE images with fatsaturation (only on 3-T MR unit) (TE, 43 millisec-onds;TR,1,100milliseconds;slicethickness,0.6mm;FOV, 160 mm; matrix size, 320  269) (Fig 2). Original and Modified MOCART System For the description of the repair tissue, we used thesrcinal Magnetic Resonance Observation of CartilageRepair Tissue (MOCART) system previously pub-lished by Marlovits et al. 17,18 Nine variables were usedto describe the morphology and signal intensity of therepair tissue compared with the adjacent native carti-lage. Besides the srcinal MOCART system, we alsoused a modification of this system previously pub-lished by Dhollander et al. 19,20 Both morphologic MRIclassification systems were applied to the MR imagestaken at 6 and 12 months of follow-up. All MR imageswere evaluated by an independent reviewer. Both theoriginal and modified MOCART scores were ex-pressed as a percentage of the maximum score (100%is the maximum score). 19,20 Histologic Analysis Biopsy specimens of 3 patients were taken from thearea of implantation during revision surgery, allowinghistologic assessment of the repair tissue. Biopsyspecimens measuring 2 mm in diameter were har-vested from the medial femoral condyle in 2 patientsand from the patella in 1 patient. The specimens wereprocessed for standard histologic evaluation. Paraffin-embedded (5-  m-thick) sections of repair tissue werestained with H&E. All cartilage samples were stainedwith H&E for general histology. 21 Different parame-ters were used to describe the type of repair tissue, aspreviously published. 22 The general features, extracel-lular matrix, and cell types of the repair tissue wereexamined. Statistical Analysis All clinical data were expressed in terms of mean  standard deviation of the mean. The Wilcoxon testwas used to analyze statistical differences betweenpreoperative and follow-up KOOS values, Tegnerscores, and VAS pain scores. For all tests,  P    .05was considered significant. The Bonferroni methodwas performed as a post hoc test. All statistical anal-yses were performed by use of PASW Statistics, ver-sion 18 (SPSS, Chicago, IL). RESULTSClinical Outcome There was a modest improvement in VAS scores forpain indicated by the patients. Preoperatively, the meanVAS score was 64.84    24.75 mm (N    20); at 6months of follow-up, it was 53.22    30.75 mm(n    19); and at 1 year of follow-up, it was 29.85   27.09 mm (n  15). The differences between the preop-228  A. A. M. DHOLLANDER ET AL.  erative and postoperative (12-month) values were statis-tically significant ( P  .006). According to the Tegneractivity scale, no obvious differences were observed dur-ing the 12-month follow-up period. Before the operation,the mean Tegner score was 3.78  2.51 (N  20); at 6months after surgery, it was 2.41  2.12 (n  19); andat 12 months of follow-up, it was 3.15  2.51 (n  15).Total KOOS and all KOOS subdomain scores (activ-ities of daily living, pain, symptoms/stiffness, quality of life, and sports and recreational activities) improved sig-nificantly when preoperative and postoperative valueswere compared (Table 1). No infections occurred in the postoperative period.Of the 15 patients, 3 (20.0%) showed persistentsymptoms or even more symptoms immediately afterthe implantation of the synthetic plug (Table 2). The symptoms did not improve over time. These patientswere not treated for their cartilage lesions previouslyand were considered as clinical failures and thereforeeligible for revision surgery. Two patients underwentrevision at 9 months after the initial procedure. Onepatient underwent revision at 12 months of follow-up.The last patient had already undergone a mobilizationunder anesthesia because of a limited range of motionat 3 months of follow-up due to arthrofibrosis. The 3revised patients were carefully clinically followed upafter revision surgery, with a median follow-up timeof 6 months (range, 3 to 12 months). Immediate andpersistent relief of symptoms was observed in all 3patients (Table 2). MRI OutcomeTwelve-Month Longitudinal Follow-up of Re-pair Tissue With Original and Modified MOCARTSystem:  At the 12-month follow-up, it was shownthat the srcinal MOCART score remained approxi-mately stable over time (mean at 6 months of follow-up, 69.61%  11.28%; mean at 12 months of follow-up, 66.32%  7.16%). As with the srcinal MOCARTsystem, a higher modified MOCART system scoresignified a more cartilage-like aspect of the repairtissue on MRI and a more complete filling of thedefect, without it being overfilled. These percentagesalso remained relatively stable over time (mean at 6months of follow-up, 69.28%  10.59%; mean at 12months of follow-up, 65.76%  8.68%). MRI Data Evaluated With Original MOCARTSystem at 6 and 12 Months of Follow-up:  At 6 and12 months after the insertion of the plug, the MRIdata were analyzed according to the original T ABLE  1.  Total KOOS and Individual KOOS Subdomains Preoperatively (N   20) and at 6 Months (n  19) and 12 Months (n  15) After Surgery and   P  Values for Comparisons Between Preoperative Scores and Scores at Follow-up Preoperative 6 mo 12 moTotal KOOS 214.16  92.47 263.94  139.09 ( P  .151) 358.69  112.37 ( P  .019)KOOS SubdomainsPain 51.32  20.07 63.33  32.14 ( P  .120) 79.85  19.38 ( P  .011)Symptoms/stiffness 52.74  16.73 63.50  29.32 ( P  .148) 78.15  22.21 ( P  .021)Activities of daily living 56.26  23.22 66.67  31.32 ( P  .067) 83.54  17.49 ( P  .013)Sports and recreational activities 22.89  24.40 30.00  30.86 ( P  .495) 58.85  34.35 ( P  .050)Quality of life 30.95  18.22 40.44  25.20 ( P  .107) 58.31  25.27 ( P  .008) T ABLE  2.  Overview of Individual Total KOOS and VAS Scores of 3 Patients Considered as Clinical Failures Evolution After Scaffold Plug Evolution After Revision SurgeryPreoperative 6 mo 9 mo 12 mo 1 mo 3 mo 4 mo 6 mo 12 moTotalKOOSPatient 1 262 79 101 127 189 314 314 332Patient 2 96 104 101 171 171 219 322 372Patient 3 60 52 52 114 135VAS scorePatient 1 38 83 80 72 61 21 18 15Patient 2 76 88 87 72 60 35 3 12Patient 3 80 85 83 65 50 229 OSTEOCHONDRAL SCAFFOLD PLUG
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