Innovations

Treatment Options for ArticularCartilage Defects of the Knee

Alvin J. Detterline ^ Steven Goldberg ^ Bernard R. Bach, Jr. '^ Brian J. Cole

The treatment of symptomatic articular cartilage defects of theknee has evolved tremendously in the past decade. Previously,there were limited treatment options available to patients whosuffered from either partial-thickness or full-thickness cartilagelesions. Because articular cartilage has a limited capacity forhealing, patients were often treated symptomatically untilthey became candidates for osteotomy or total joint replace-ment. Recently, both reparative and restorative procedureshave been developed to address this significant source ofmorbidity in young active patients. Microfracture is a repara-tive technique that induces a healing response to occur in anarea of articular cartilage damage, Osteochondral autograftsand allografts in addition to autologous chondrocyte implan-tation are restorative techniques aimed at recreating a morenormal articular surface. Both types of procedures have beendeveloped to alleviate the symptoms associated with focalchondral defects, as well as limit their potential to progress toa diffuse degenerative arthritis. Treatment can vary depend-ing on both cartilage defect and patient factors. This articlesummarizes the various treatment options that have recentlybecome available.

When articular cartilage is traumatically injured orhas tmdergone degenerative changes resulting trom

arthritis, it is unable to heal the damaged cartilage withnormal articular cartilage. Its lack of vascularity and rela-tive absence of cells capable of becoming matuie caitilagecells, or chondfocytes. make partial-thickness cartilageinjuries incapable of healing or forming a new, smootharticular surface. Thus, partial-thickness caitilage injuries,without surgical inteT"V'ention will either remain injuredor progressively worsen with time. Pieces of articular car-tilage may become elevated flaps and irritate the synoviallining of the knee causing swelling (effusion) and mechan-ical symptoms of catching. If the flap of cartilage becomesdetached, it can become a loose body, causing locking ofthe knee so that it does not bend or straighten fully. Full-thickness cartilage injuries that also penetrate the sub-chondral bone are capable of limited healing with fibro-

cartilage, a type of cartilage that is different from normalarticular cartilage and does not function as well or havethe durability of normal cartilage. Patients with sympto-matic cartilage defects previously were treated with anti-inflammatoi"y medications, intraarticular steroid injec-tions, intraarticular viscosupplements (hyaluronic acid),nutraceuticals (glucosamine or chondroitin sulfate). physi-cal therapy, or activity modifications to alleviate theirsymptoms. Unfortunately, none of these treatment modali-ties lesults in cartilage healing. They may only decreasethe associated pain or swelling. When quality of life isdiminished despite the above treatments, osteotomies ortotal knee replacements were historically the major sur-gical options, but neither of these facilitated cartilagehealing.

Over the past decade, surgical procedures have beendeveloped to directly treat the cartilage injury by eitherreparative or restorative measures, Reparative proceduresare designed to allow the cartilage lesion to heal with adifferent type of cartilage called fibrocartilage. This typeof caitilage does not have the same mechanical propertiesas noi mal aiticular cartilage, hyaline cartilage, but doesprovide a covering over the othen.vise exposed imderlyingbone, which can alleviate symptoms of pain and swelling.Restorative procedures are designed to allow the cartilagelesion to heal with a type of cartilage that is more like nor-mal hyaline cartilage,

W EvaluationSymptomatic cartilage lesions can present as localized ordiffuse knee pain. The knee joint can be viewed as threeentities: the medial tibiofemoral, lateral tibiofemoral, andanterior patellofemoral compartments. It is important forthe surgeon to localize the patient's symptoms to one ormore compartments. With tibiofemoral disease, the pain

'!' Alvin J. Detterline, MD, Rush University Medical Center, Chicago, IL,

'f Steven Goldberg, MD, Rush University Medical Center, Chicago, IL.

r Bernard R. Bach, Jr., MD, Rush University Medical Center, Chicago, IL,

f Brian L Cole, MD, MBA, Rush University Medical Center. Chicago, IL.

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is often worse \vi(li weight-bearing activities and locatedeither medial or lateral to the midline, along the tibio-[emoral joint line. When the patcllofemoral region is in-volved, patients often complain of anterior knee pain thatworsens with activities, such as descending stairs, arisingfrom a chair, or squatting. Recurrent swelling, catching,or locking can also he suggestive of focal chondral defects(Freedman, Fox, & Cole, 2004).

Standard radiographs are the initial imaging modal-ity used for evaluation. They include a weight-bearingposteroanterior image with the knee in full extension, a45-degree-nexion weight-bearing posteroanterioi" image,a non-wcight-bearing 4.S-degree-nexion lateral view, andan axial view (also called sunrise or Merchant) of thepatellofemoral joint. These views are used to Identity jointspace narrowing within a single compartment that maybe indicative of a focal cartilage lesion or narrowing inmultiple compartments, sugge.sting a more global degen-erative arthritic process. Limb alignment and the pres-ence of loose bodies and osteochondral fi'acturcs are alsoassessed. Cartilage is not well visualized on X-ray imagingbecause it lacks the mineralization ol hone, and thus, manyfocal chondral injuiics will have noiTnal plain radiographs.Therefore, if a patient has persistent knee symptoms de-spite consei-x'ative treatment, referral to an orthopaedicsurgeon is recommended. Fui'thcr testing, such as mag-netic resonance imaging (MRI), can be useful to bettervisualize the extent and location of articular cartilagelesions. However, special articular cartilage settings andtechnique for the MRI are needed, making it more usefulfor an orthopaedic surgeon to order the study rather thana primary care physician. MRI is not always requii'ed, es-pecially because it is nol sensitive when looking for localcartilage injuiy When the clinical histoiy and symptomsare consistent with a focal cartilage injuiy, after plain

radiographs are obtained, arthroscopy may he the nextindicated step.

Nonoperative treatment of chondral lesions is usuallyresened for incidental asymptomatic defects (Freedmanet al., 2004). When the lesions become symptomatic,nonoperative treatment is less likely to be successful andoperative intei"vention is warranted (Figure 1).

W Surgical Treatment OptionsNonreparative, NonrestorativeDebridement and LavageDebridement and lavage is typically reserved for lower de-mand older patients with small lesions (<2 to 3 cm^) andlimited symptoms who would have difficulty with activ-ity or weight-bearing restrictions postoperatively (Bert& Maschka, 1989; Federico & Reider, 1997; Freedmanet al., 2004; Noyes, Bassett, Grood, & Butler, 1980; Owens,Stickles, Balikian, & Busconi, 2002; Rand, 1991). It entailsarthroscopic surgeiy where two to three small incisionsare placed about the knee to place a small camera and in-stmments inside the joint to evaluate and treat the lesions.Loose chondral flaps that can cause mechanical symptomsare removed. Relief from this type of procedure may be in-complete or temporal^' because no attempt has been madeto restore or repaii- the cartilage lesion. Current rcseaichdemonstrates that the best candidates for debridemenland lavage ai e those who suffer from mechanical symp-toms (such as a catching or locking sensation when at-tempting to bend or straighten the knee), which can becaused by a torn meniscus or loose body (Moseley et al.,2002). The recoveiT time from this type of procedure isI'clatively short, with immediate full weight-bearing andunrestricted activities.

Lesion Location

Femoral Condyle|

Size

< 2-3cm' >2-3cm2

Mlcrofrscture • •OC AutOQraft * *ACIOC Altograft

ACIOCAIIognn

Patellofemoral

Size

< 2-3cm^ >2-3cm2

• / •

• •

••Low O«mand

liMlcrofrachireACtOC AirtograftOC flilograi

[AOh0CAfk>Jg3«

* 4• ; •

« t

•

FIGURE 1. The general treat-ment algorithm which is fol-lowed for determining whichreparative or restorative tech-nique might be utilized for aspecific cartilage lesion.

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Reparotive

MicrofracturePaticnls with small to moderate-sized lesions (1 to 5 cm- )and moderate demands may be treated with marrow-stimulating techniques, such as microlracttirc. The basisof tliis ti"eatment option is to stimulate fibrocartilage in-giowth into the chondral defect to eover the underlyingbone (Freedman et al., 2004; Gill & MacGillivray, 2001;Steadman et al., 2003). The procedure is done aithi'oscop-ieally and involves fuil-lhickness eanilage removal downto bone with well-defined sharp boundaries of normalcartilage to prevent injury propagation. An awl is used tocreate a bed of small holes in the stibchondral bone tocreate bleeding within the bone, allowing cells from thebone marrow to enter the avascular cartilage defect, dif-ferentiate into fibrocartilage pi-oducing cells, and fill thedefect with fibrocartilage (Figures 2A and B). This proce-dure can be done aftei' failed debridement and lavage orother cartilage-specific surgical procedures.

To achieve optimal results, a strict adherence to post-operative protocol is required. The protocol includes aperiod of non-weight bearing (4 to 6 weeks) and use of acontinuous passive motion (CPM) machine that puts theknee tln'ough a specified i"ange of motion without weightbeating. The benefit of CPM is that it prevents aithrofibro-sis (or knee stiffness) while the treated cartilage defect isallowed to heat without the stress of weight bcai'ing.

Restorative

Osteochondral Autograft TransplantationThe symptomatic chondral lesion is debrided of cartilageand a small portion of underlying bone to determine thesize and shape of the osteochondral autograft that willbe needed, Osteochondral aulografts arc round cylindersof fiill-thickness cartilage attached to a plug ol its underly-ing bone. These osteochondral autografts are harvestedailhroscopically h"om non-weight-beaiing areas of the kneewhere the articular cartilage and underlying bone can beremoved without causing new symptoms or loss of func-tion. The donor graft is inserted using a press-fit technique(Figures 3A and B).

These osteochondral autograft plugs are most com-monly transplanted to symptomatic lesions involving thefemoral condyles. The lesions should be small to medium-sized (0.5 to 3 cm-) because the amount of donor tissueavailable is limited (Freedman el al., 2004; Hangody,Feczko, Bartha, Bodo, & Kish. 2001; Kish & Hangody,2004), Oecasionaily, a small incision may be necessai>' forhai'vest. For larger lesions, a technique of using multipleplugs called "mosaicplasty" can be employed (Kish, Modis,& Hangody, 1999).

The advantage of osteochondral autografts is that thetissue is autogenous and has normal living hyaline carti-lage. Thus, this technique results in cartilage that is mostsimilar to the cartilage that was injured. The disadvantagesinclude donor site morbidity (pain and new cartilagedefect), technical difficulty in matching the contour ofthe defective articular surface to the donor plug, residualgaps between cartilage plugs, and the risk for cartilage orbone collapse. Postoperative recovery requires a period ofnon-weight bearing and the use of a CPM machine for upto 6 weeks.

FIGURE 2. (A) The arthroscope is used to visualize a sympto-matic focal cartilage lesion involving the femoral condyle beforemicrofracture. (B) The femoral condylar lesion has been treatedusing microfracture technique where vertical boundary wallshave been created and small holes have been made to stimu-late bleeding and the reparative response.

Osteochondral Allograft TransplantationFresh osteochondral allograft transplantation entails theimplantation of a cadaveiic osteoehondral graft into thecartilage defect (Aubin, Cheah, Davis, &. Gross, 2001;Bugbee, 2000; Garrett, 1994; Ghazavi, Pdtzker, Davis &iGross, 1997; Gross, 1997; Meyers, Akeson & Convery,1989). A small ailhrotomy is made to expose the cartilagedefect. An osteochondi'al allograft plug is han'ested tomatch the defect's size and contour and then press fit toachieve stability (Figures 4A and B).

This procedure is used for mediimi to large articularcartilage defects (3 cm^ up to an entire hemicondyle) inolder high-demand patients who may have associated boneloss (>6 to 8 mm). Most commonly used for defects involv-ing the femoral condyles, osteochondrai allografts may alsobe used for patella, trochlea, or tibial plateau lesions.

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FIGURE 3. (A) The arthroscope is used to visualize a focal carti-lage lesion involving the femoral condyle prior to osteochondralautograft transplantation. (B) The articular cartilage defect hasbeen debrided, and a portion of the patient's own articular car-tilage has been harvested from a non-weight bearing portion ofthe same knee to fill the defect

The major advantage of osteochondral allograits isthe ability to replace large osteochondial defects in asingle-stage procedure. Additionally, the articular caililagedefect is replaced with articular cartilage rather than fihro-caitilage. The disadvantages include graft availability,technical difficulty, cost, and possible disease transmis-sion. Postoperative rehabilitation includes the patient toremain non-weight bearing for 6 to 8 weeks and the use ofa CPM machine.

Autologous Chondrocyte ImplantationThe procedure is a two-stage technique where during thefirst surgetT -, a small piece of cartilage (about the size ofa raisin) is hai"vested arthroscopically from a non-weight-bearing portion of the patient's knee. This cartilage is thensent to a company that processes the cartilage cells. The

FIGURE 4. ^A) A small arthrotomy has been made to expose thearticular cartilage defect before osteochondral allograft transplan-tation. (B) The chondral defect has been debrided, and an osteo-chondral allograft has been inserted to fill the defect.

chondrocytes are isolated and grown in tissue culture toallow them to multiply for several weeks. This results inmillions of autologous cartilage cells that are suspended insolution and shipped back to the surgeon for reimplanta-tion. The second stage of the procedure involves a secondsurgery, an open arthrotomy to expose the lesion, which isdebrided, so that the defect has circumferential verticalwalls ()! normal articular cartilage. A periosteal patch ishaiTested from the ipsilateral tibial shaft to provide a cov-

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erage cap over ihe defect. The patch is sewn in place andsealed with fibrin glue. The chondrocyte-conlaining solu-tion is then injected into the sealed pouch {Figures 5Aand B). The repair tissue that results from this procedureis durable, mechanically litTn, and hyaline-like in histology(Peterson, Brittbcrg, Kiviranta. Akcilund & Lindahl, 2002).

Autologous chondrocyte implantation (ACI) is used forinteimediate to high-demand patients who have failedarthroscopic debridement or microfracture. The techniqueis used for larger (2 to !0 cm^) symptomatic lesions involv-ing both the femoral condyles and trochlea and ihe patella(Brittberg et al., 1994; Chu, Conveiy, Akeson, Meyers &

B

FIGURE 5. (A) An arthrotomy has been performed to expose thefocal chondrai defect on the trochlea prior to autologous chon-drocyte implantation. (B) The chondral defect on the trochlea hasbeen debrided, a periosteal patch has been harvested from thetibial shaft and sewn in place, and the chondrocytes have beeninjected inside the created pouch.

Amiel, 1999; Gillogly, Voight, & Blackburn, 1998; Micheliel al., 2001; Minas, 2001; Peterson et al., 2002; Petersonet al., 2000). An intact bone bed is required, making carti-lage lesions associated with bone loss better treated byosteochondral grafting.

The postoperative course foi" this procedure involvesnon-weight bearing in addition to range-of-motion exer-cises with the use of a CPM machine for 6 weeks. However,because this involves two surgeries, one of which is alarger open arthrotomy, pain relief and restoration of func-tion may take as long as 12 to 18 months.

• I Concomitant ProceduresAlong with focal chondial lesions, there may be associatedinjuries or presence of limb malalignment that may alsoneed to be addressed surgically. The most common injuriesare ligament and meniscus tears. The meniscus fimc-tions as a shock absorber during loading but also dis-tributes force during axial loading. Chondral injuriesmay occur as a result of a torn meniscus, or a highly irregu-lar chondral suiface may predispose a patient to a menis-cal tear {Freedman et al., 2004; Messner & Maletius,1996; Rangger, Klestil, Gloet/.er, Kemmler. & Benedetto,1995; Schimmer, Brulhart. Duff, & Glinz, 1998). If achondi'al defect is present in a meniscal-deficient knee, itis paramount that the meniscal deficiency be addressedwith a procedure such as a meniscal allograft transplanta-tion (Freedman et al., 2004). In addition, any ligamentousinstability must be addressed to restore stability to protectthe articular cartilage from excessive shear forces.

If vaiTis malalignment exists with a medial condyle de-fect, a valgus-producing high-tibial osteotomy shouldbe performed to unload the medial compartment fromexcessive forces during weight bearing. Similarly, valgusmalalignment should be treated with a vaRis-producingdistal femoral osteotomy. In ihe presence of patellar ortrochlear lesions, distal realignment with anteromedial-ization of the libial tubercle may be performed primarilyto unload the patellofemoral compartment and protectthe cartilage repair site (Freedman et al., 2004).

• ConclusionThere have been many recent advancements in the treat-ment of articular cartilage defects of the knee. Reparativeprocedures, such as microfracture, can provide signifi-cant relief of .symptoms but do not attempt to recreate thenoiTnal articular cartilage. Restorative procedures, suchas osteochondral autographs or allografts and autologouschondi ocyte implantation, have been developed to recre-ate the normal articular caitilage surface. The most appro-priate option depends on many variables, including bothcartilage-specific and patient-specific factors. Thus, a thor-ough discussion between physician and patient is requiredto elicit which ti eatment option is most advisable for eachindividual.

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