artrosis unicompartamental

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COPYRIGHT 2003 BY THE JOURNALOF BONEAND JOINT SURGERY, I NCORPORATED

Cur r ent Concept s Review

Unicompar t ment alAr t h r it is of t h e Knee

BY RICHARD IORIO, MD, AND WILLIAM L. HEALY, MD

Investi gati on performed at the Department of Ort hopaedic Surgery, Lahey Clinic Medical Center,

Bur li ngton, Massachusetts, and Boston Medical Center, Boston, M assachusetts

Unicompartmental arthritis of the knee is a degenerative condition characterized by abnormal articular cartilagein the medial or lateral part of the tibiofemoral joint, which may be associated with meniscal disruption, ligamen-tous instability, and limb malalignment.

Nonoperative treatments for unicompartmental degenerative arthritis of the knee include oral and injectablemedications, weight loss, exercise, physical therapy, canes, crutches, braces, and orthoses.

Arthroscopy for unicompartmental arthritis of the knee can provide a clinical benefit in terms of reduced painand improved function for patients with mechanical symptoms, mild degenerative disease, and minimal or nomalalignment. Meniscal tears, loose bodies, osteophytic spurs, or chondral flaps can cause mechanical symp-toms, which can be treated successfully with arthroscopy.

Proximal tibial valgus osteotomy and distal femoral varus osteotomy for treatment of unicompartmental arthritisof the knee can realign a deformed limb, reduce pain, and improve function for active, high-demand patientswith a projected life expectancy of twenty years or more.

As a patients life expectancy and expectations for activity decrease as a result of age and disease, unicompart-mental and total knee arthroplasty provide predictably successful surgical options for the treatment of unicom-partmental arthritis of the knee.

Arthritis of the knee is a common clinical problem: 2% of theUnited States population older than seventeen years of age and10% of Americans over sixty-five years of age have clinicallyrelevant arthri tis of the knee1. Arthritis of the knee causes painand restricts activity, and patients with arthritis are twice aslikely to seek medical care as are their peers without arthritis2.

Unicompartmental arthritis of the knee is defined as acondition characterized by degenerative articular cartilage inthe medial or lateral aspect of the tibiofemoral joint, which

may be associated with meniscal disruption, ligamentous in-stability, and malalignment1-3. The most common symptom ofunicompartmental arthritis of the knee is pain confined tothe affected compartment, which may be associated withswelli ng, effusion, instability, impingement, crepitus, stiffness,and malalignment. Radiographic findings of unicompartmen-tal arthritis of the knee may include joint space narrowing,squaring of the femoral condyle, subchondral sclerosis, inter-condylar spurring, joint line osteophytes, and varus or valgusmalalignment of the affected limb3,4.

We will review the natural history of unicompartmentalarthritis of the knee in adults and discuss nonoperative and

operative treatments. Isolated patellofemoral osteoarthritisand inflammatory arthritides will not be discussed. We believethat early diagnosis and early treatment may improve thefunctional well-being and long-term outcome in patients withunicompartmental arthri ti s of the knee.

Natural History of DegenerativeArthrit is of the KneeThe specific cause of degenerative arthritis of the knee is not

clear, but when it occurs in an active patient, it is generallyprogressive5,6. Trauma is frequently a cause of the degenerativeprocess, which results in deterioration of articular cartilageand symptomatic degenerative arthritis7-12. The degenerativeprocess may include articular cartilage damage (chondrocytesand matr ix), meniscal damage, ligament damage, and joint in-congruity. Angular malalignment may contribute to the devel-opment and progression of unicompartmental arthritis of theknee by overloading the medial or lateral aspect of a tibiofem-oral joint with abnormal articular cartilage.

The spectrum of articular cartilage damage can rangefrom minimal to severe. Small, superficial, focal defects of ar-


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TH E JOURNALOF BON E & JOINT SURGERY JBJS.ORG

VOLUME 85-A NUMBER 7 JULY 2003

UNICOMPARTMENTAL ARTHRITISOFTH E KNEE

ticular cartilage that are not associated with symptoms shouldbe distinguished from extensive, full-thickness cartilage de-fects associated with symptomatic degenerative arthritis13-15.The location and size of articular cartilage defects determinethe severity of symptoms and the need for treatment 15. Whenan articular cartilage lesion is less than 2 to 3 cm 2 in area, or alesion has good peripheral cartilage support (shoulders), itmay take several years before degenerative arthritis develops13-

15 (Table I). Minas and Nehrer15 suggested that articular carti-lage defects in which the exposed subchondral bone is notsupported by a peripheral cartilage border are often symp-tomatic and deteriorate more quickly. Symptomatic lesions ofarticular cartilage often progress with age, and treatment ofisolated chondral or osteochondral defects may decrease orminimize the development of degenerative arthr itis13,15-18.

Evaluation of Unicompartment alArthrit is of the KneeThe history and physical examination can provide useful in-formation concerning joint line tenderness, meniscal damage,ligamentous instability, and malalignment associated with

unicompartmental arthri tis of the knee. Dynamic gait analysiscan provide additional information about ligamentous insuf-ficiency and malalignment. Before a specific treatment is se-lected, inflammatory arthritides should be excluded as a causeof unicompartmental arthrit is.

Radiographic evaluation is an essential component ofthe diagnosis of unicompartmental arthritis of the knee. Ra-diographs made in the anteroposterior plane with the patientbearing weight19 as well as lateral, tangential patellofemoral,and tunnel views20 allow objective evaluation of the three com-partments of the knee (Table II). However, these radiographsmay not accurately predict the status of the articular cartilageas seen at arthroscopy21,22. Radiographic sensitivity with re-

gard to showing deterioration of the art icular cart ilage may beimproved by making posteroanterior views with the patientbearing weight and with the knee flexed 40 to evaluate theposterior aspects of the femoral condyles and tibial plateau,especially in the lateral compartment17,19. Radiographs of thehip, knee, and ankle made on one long film with the patientstanding allow calculation of the static mechanical axis andidentification of any angular deformity of the involved limb.The patient must be able to place full weight on the affectedlimb for a true measurement of limb deformity to be ob-tained. The mechanical axis is determined by a line drawnfrom the center of the femoral head to the center of the knee

joint and a line drawn from the center of the knee jointthrough the center of the ankle joint19,23. A mechanical axis of0 to 3 of varus is considered to be within normal limits19,23.Generally, a varus or valgus deviation of 10 is associatedwith symptoms of unicompartmental arthrit is19.

Nonoperative M anagement ofUnicompartm ental Osteoart hritis of the KneeOral Medicati ons, Nutr it ional

Supplements, and Topical Analgesics

Analgesic medications without anti-inflammatory properties,such as acetaminophen, are the initial medications used totreat degenerative arthritis of the knee. These medications areeffective in relieving pain, they are associated with a low inci-dence of side effects, and they are inexpensive24-26. Nonsteroi-dal anti-inflammatory medications are the most commonlyused drugs for treatment of degenerative arthritis of the kneeand other joints25-28. These drugs, which inhibit cyclooxygenase

1 and 2, have analgesic and anti-inflammatory properties, butthey can be associated with gastrointestinal and other side ef-fects. In a short-term clinical trial in which acetaminophenand ibuprofen, in analgesic and anti-inflammatory doses, werecompared as treatments for symptomatic arthritis of the knee,the efficacy of the two drugs was equivalent24. When nonste-roidal anti-inflammatory drugs are used chronically, it is im-portant for patients to have medical monitoring of hepatic,renal, and gastrointestinal systems28. Specifi c cyclooxygenase-2inhibitors have demonstrated clinical efficacy in the treatmentof symptomatic arthritis of the knee, with decreased gas-trointestinal and renal side effects. However, specific cyclooxy-genase-2 inhibitors are more expensive, and risk-benefit and

cost-benefi t analyses must be completed to better define the roleof these agents26,28.

Nutri tional supplements (so-called nutr iceuticals), suchas glucosamine and chondroitin sulfate, have been touted aschondroprotective agents. Double-blind, placebo-controlled,randomized trials have shown that glucosamine is mildly ef-fective for relieving pain associated with degenerativearthritis26,29-32. In a study by Reginster et al.33, 212 patients withosteoarthritis of the knee were randomized to a glucosamineor a placebo treatment group. After three years of treatment,the glucosamine group had less joint-space narrowing andimproved WOMAC (Western Ontario and McMaster Univer-

TABLE I Outerbridge54 Grading System for Carti laginous

Degeneration

Stage I Soft discolored superficial fibrillation

Stage II Fragmentation 1.3 cm2

Stage IV Erosion to subchondral bone (eburnation)

TABLE II Ahlbck 3 Grading System for Degenerative

Arthr i t is

Stage I Joint space narrowing

Stage II Joint space obliteration

Stage III Minor bone attrition

Stage IV Moderate bone attrition

Stage V Severe bone attrition

Stage VI Subluxation


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sity Osteoarthritis Index) scores when compared with the pla-cebo group. However, we are not aware of any long-termstudies demonstrating beneficial effects of glucosamine on thearticular cartilage of an arthritic joint26,29. Some patients withunicompartmental arthritis of the knee report improvementwith use of topical analgesics (e.g., methyl salicylate, capsaicin,and nonsteroidal creams) as either adjunctive treatment ormonotherapy34.

Inj ectable In tra-Art icular Medicati ons

Acute exacerbations of degenerative arthritis of the knee pre-senting with pain, swelling, and effusion can be treated with as-piration of the knee joint and intra-articular injection of acorticosteroid preparation. Corticosteroid injections are fre-quently combined with a local anesthetic medication, and theseinjections can provide short-term symptomatic relief. How-ever, corticosteroid injections can increase the risk of damage tothe articular carti lage of the injected knee joint, and they should

not be repeated more than three or four times a year35.Intra-articular injection of hyaluronan is intended to pro-

vide so-called viscosupplementation or restoration of the rheo-logical properties of synovial fluid in the arthritic knee. Thesehigh-molecular-weight solutions are expected to supplementthe reduced concentration of hyaluronan in arthritic knees. Ithas also been suggested that hyaluronan therapy may alter theprogression of arthritis of the knee and may decrease inflamma-tion of the synovial membrane compared with that associatedwith corticosteroid injections17,36. Short-term studies17,37,38 havesuggested that there is no advantage of hyaluronic acid visco-supplementation over nonsteroidal anti-inflammatory drugs inthe treatment of an arthritic knee. When hyaluronan injection

was compared with corticosteroid injection for treatment of ar-thritis of the knee, the effects of hyaluronic acid viscosupple-mentation were found to be slower in onset, the treatment wasmore expensive, and it was associated with a higher risk of alocal inflammatory response39. However, the use of hyaluronicacid viscosupplementation in patients who were older than theage of sixty years and had severe disease provided longer-lastingrelief of symptoms than did intra-articular corticosteroidinjections34,39,40. More information on the appropriate use of thistreatment is expected from prospective, double-blind, placebo-controlled studies.

Weight Loss

The reduction of joint reaction forces and symptoms of de-generative arthritis by a decrease in body mass is a fundamen-tal concept in the management of arthritic joints34. Obesity isan independent risk factor for the development of osteoarthri -tis in the knee41, and this association is higher for women thanfor men42. Women over the age of fifty with malalignmenthave a higher prevalence of degenerative arthritis of the kneethan do age-matched control subjects in the general, nonaf-fected population43. Weight loss by obese women decreases therisk of the development of degenerative arthritis. A weight lossof 5.1 kg over ten years has been shown to decrease the risk ofdegenerative arthritis by >50%44.

Exercise and Physical Therapy

Exercise, as an adjunct to weight reduction, has value in thetreatment of an arthritic knee. Stretching to prevent contrac-ture, maintain range of motion, increase muscle strength, andincrease dynamic stability of the knee can reduce symptomsassociated with an arthritic knee17. Quadriceps muscle weak-ness is common among patients with degenerative arthritis ofthe knee and may be a risk factor for this disease. Patient edu-cation programs and supervised fitness and walking sessionshave been shown to improve functional status without wors-ening the symptoms of osteoarthritis of the knee45. Physicaltherapy modalities, such as cold treatments, hydrotherapy, ul-trasonography, iontophoresis, and massage, can help to re-duce swelling and stiffness during a period of exacerbation ofsymptoms. Heat treatments can be used to decrease morningstiffness, reduce start-up discomfort, and serve as a warm-upfor exercise24,39.

Ambulatory Support Devices

During a period of acute exacerbation of symptoms in a kneewith degenerative arthritis, ambulatory support devices canhelp a patient to remain active in the presence of a painful,swollen knee17,26,39. A cane in the hand contralateral to a kneewith arthritis can decrease the weight-bearing load on the de-generated knee joint by 30% to 60%34,46. One or two crutchescan further decrease the load.

Braces

Three types of knee braces are commercially available fortreatment of a knee with degenerative arthritis: compressionknee sleeves, supportive knee braces, and unloading knee

braces. Polypropylene, neoprene, or elasticized knee sleevesmay minimize swelling and provide a feeling of increased sup-port and warmth about the knee without changing limb align-ment, joint stability, or mechanical function. Some patientsreport a feeling of security with a knee sleeve, possibly becauseof enhanced proprioceptive feedback17. Supportive knee bracesinclude hinged braces (for varus-valgus instability), anteriorcruciate insufficiency braces (for anteroposterior and rotatoryinstability), and patellofemoral braces (for patellofemoralmalalignment or instability). Unloading braces are designedto apply a varus or valgus force at the knee and relieve painduring activity by distracting the joint space of the involvedcompartment during weight-bearing and activity47. A fluoro-

scopic gait study48

demonstrated that condylar separation ofthe medial tibiofemoral joint space can be achieved with anunloading knee brace in patients with medial unicompart-mental arthritis. All patients (twelve of fifteen) in whomcondylar separation was achieved dur ing gait in that study hada decrease in symptoms. Failure of the unloading knee bracewas associated with obesity and a poor fit of the brace. Otherstudies42,49,50 have demonstrated similar efficacy of unloadingknee braces. However, patient compliance and high cost havebeen mentioned as problems with unloading knee braces.They are difficult to wear for extended periods of time becauseof their size and because of the degree of force imparted to the


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limb to alter alignment51. The use of these devices on valgusknees with lateral compartment arthritis has not been re-ported, to our knowledge.

Footwear Modification and Or thoti cs

Well-padded, energy-absorbing shoe soles or orthotic devicescan decrease the load across the knee joint during heel strike.Deformity of the ankle, hindfoot, or midfoot leading to limbmalalignment can exacerbate tibiofemoral arthritic symp-toms. Orthotic correction and supportive, adaptive footwearwith a medial longitudinal arch support, a calcaneal cushion,and a rigid last can improve alignment of the foot. An ankle-foot orthosis may be necessary for severe ankle deformity,which can aggravate preexisting degenerative arthritis of theknee17,26.

Heel and sole wedges can realign the foot 5 to 10 ineither the varus or the valgus plane. With a lateral wedge andinsole, the shift in alignment reduces medial joint-space

loading52. Keating et al.53 evaluated 121 knees with medial uni-compartmental arthritis in eighty-five patients who weretreated with a lateral heel and sole wedge. Sixty-one of the 121knees had a good or excellent result after four to twenty-fourmonths of treatment. Knees with all grades of arthritic in-volvement showed improvement. Patients with stage-II dis-ease according to the modified Outerbridge classification54 hadthe most improvement. The use of heel and sole wedges forpatients with arthritis of the lateral compartment of the kneehas not been reported, to our knowledge.

Operat ive Management ofUnicompart mental Art hritis of the Knee

ArthroscopyArthroscopy of a painful arthritic knee permits a surgeon todefine the extent of degenerative disease, formulate a treat-ment plan based on those findings, and correct mechanicalproblems that are amenable to arthroscopic treatment55-57. I thas been difficult to correlate the definition of the size andcharacter (shape, depth, and integrity of the border) of art icu-lar cartilage lesions with the extent and degree of success of ar-throscopic intervention by comparing studies of arthroscopictreatment of knees with degenerative arthritis. However, sub-optimal outcomes following arthroscopic surgery of the kneehave been associated with greater arthritic deterioration onpreoperative radiographs, limb malalignment, and calcium

pyrophosphate deposition58,59

.The use of arthroscopy of the knee to treat unicompart-mental arthritis is controversial because the procedure cannotalter the natural history of the disease60,61. Arthroscopic lavageof the knee without dbridement may mitigate symptoms inthe short term by dilut ion of inflammatory cytokines17,58,62, andthere have been several retrospective studies of arthroscopictreatment of degenerative arthritis of the knee, with bothfavorable57,58,63-66 and unfavorable60,67-69 results. Moseley et al.70

questioned the benefit of arthroscopic surgery as a treatmentfor arthritis of the knee in a study in which they compared aplacebo group with a group t reated with arthroscopic joint la-

vage and another group treated with arthroscopic dbride-ment. All three treatment groups had a decrease in symptomsup to two years after intervention. This study was confined toolder men in a Veterans Administration Hospital. The extentof the arthritic involvement of the knee (in one, two, or threecompartments) was not documented. The patients were notstratified according to the degree of malalignment, bodyweight, or type of symptoms. The authors concluded that ar-throscopy of a knee with degenerative arthritis may not be in-dicated when there is only pain in the absence of othersymptoms (such as catching, clicking, locking, or giving-way).Furthermore, they suggested that a decrease in symptoms af-ter arthroscopy may be associated with a placebo effect.

Arthroscopic dbridement for isolated unicompartmen-tal arthritis of the knee has been reported to be beneficial forpatients with mild degenerative disease, normal alignment,and an unstable meniscal tear59,66,71-73. Varus malalignment is amore negative prognostic factor than is valgus malalignment

when predicting whether arthroscopic dbridement will besuccessful for the treatment of unicompartmental arthritis ofthe knee66.

Operat ive Treatment of Damaged Art icular Car ti lage

Focal defects of articular cartilage secondary to trauma or os-teochondritis dissecans have limited capacity for repair andoften progress to osteoarthritis with symptoms of pain, swell-ing, and stiffness13,15,74. The Pridie operationwhich involvesan arthrotomy; dbridement of osteophytes, loose bodies, me-niscal fragments, and ligamentous debris; and drilling of ex-posed subchondral bone to encourage a fibrocartilaginousrepairhas a success rate similar to that of other fibrocartilag-

inous stimulation techniques75

. In one series75

, forty-six ofsixty patients were satisfied with the result of this operationand thought that it was a success and five patients believedthat they were worse off than they had been preoperatively.

With the arthroscopic microfracture technique, an awl isused to crack exposed or eburnated condylar bone, create sub-chondral bleeding, and stimulate development of fibrocar-tilage76,77. Arthroscopic abrasion arthroplasty78 is an arthroscopicmodification of open dbridement75,79-81. With that procedure,arthroscopic tools are used to dbride the joint and a rotatoryinstrument is employed to abrade sclerotic bone and stimulatefibrocartilage formation. Lesions >2 cm2 are more likely toprogress to arthritis because of the inability of fibrocartilage to

effectively replace hyaline cartilage in these defects13-15

.In patients with focal defects of articular cartilage inwhom arthroscopic dbridement is not successful and micro-fracture or abrasion arthroplasty is not likely to succeed, im-plantation or transplantation of articular cartilage may be areasonable treatment option. Three methods of implantationof articular cartilage are available at this time: (1) autologousosteochondral plug transfer, (2) autologous chondrocyte im-plantation, and (3) osteochondral allograft transplanta-tion13,15,82-98. To our knowledge, a comparison of the long-termresults of these procedures has not been publ ished. We are alsonot aware of any studies on the use of these techniques in the


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treatment of unicompartmental arthritis; their role remains tobe defined.

For cartilage implantation or transplantation to be suc-cessful, as defined by reduced pain, improved function, and asatisfied patient, the limb must be well aligned and the kneemust be stable. If the mechanical axis of the limb passes throughthe compartment with the damaged articular cartilage, align-ment must be shifted to relieve the stress on that compartment.Realignment can be achieved with osteotomy99,100. Instabilitysecondary to ligamentous or meniscal pathology can be associ-ated with progression of chondral damage, and instability mustbe corrected to minimize force transmission to the surgically al-tered articular cartilage16,17,101.

Patients with low-grade unicompartmental arthritis ofthe knee (Outerbridge stage II or lower) and a previous menis-cectomy have been reported to have had good results at a maxi-mum of five years after meniscal transplantation17,102-105. Meniscalallografts may not be useful in patients with advanced osteoar-

thritis, instability, or deformity. Short-term follow-up of pa-tients treated with meniscal allograft transplantation combinedwith osteotomy and/or anterior cruciate ligament reconstruc-tion has shown promising results106.

Osteotomy

Limb malalignment can accentuate stress on damaged articularcartilage, leading to pain, progressive loss of articular cartilage,and increasing angular deformity of the knee. The goal of os-teotomy in the treatment of unicompartmental arthritis of theknee is to realign the limb and shift weight-bearing force fromthe degenerated tibiofemoral compartment to the healthiercompartment. As long as overcorrection is avoided, corrective

osteotomy of the knee is associated with biological improve-ment of damaged articular cartilage with maintenance of artic-ular cartilage in the less degenerated compartment107-109.

Patient selection is critical to the success of kneeosteotomy100, which may be considered for patients with ahigh-demand, active lifestyle whose life expectancy exceedsthe expected survival of a knee prosthesis. Stabili ty of the kneeand a functional range of motion are generally required for asuccessful osteotomy, and inflammatory arthritis and kneestiffness are generally contraindications17,19. Instability due toanterior cruciate ligament insufficiency can be corrected withreconstruction of that ligament. The reconstruction can becombined with osteotomy, as staged or simultaneous proce-

dures, in order to unload an arthritic compartment and re-store stability of the knee101.Correction of deformity is critical to the success of a

knee osteotomy. The normal mechanical axis of the limb, de-fined as a line from the center of the hip joint to the center ofthe ankle joint, should pass through or just medial to the cen-ter of the knee joint. Angular deformity of the limb can bemeasured as the angle subtended at the knee by a line throughthe center of the femoral head and the center of the knee, andextended to the floor, and a line from the center of the knee tothe center of the ankle. An angle of 0 to 3 of varus is consid-ered normal19,23. The angle of correction of an osteotomy is

determined by adding to the deformity of the limb an overcor-rection of 2 to 4 to ensure a shift of the weight-bearing forceto the uninvolved compartment110.

Varus Unicompartmental Art hri ti s

A stable knee with arthritis of the medial compartment associ-ated with a varus deformity, without subluxation or lateralthrust, and with an arc of motion of 90 may be treated with aproximal tibial valgus osteotomy17,19,110,111. Mild-to-moderatepatellofemoral arthritis is not a contraindication to a success-ful outcome of a high tibial osteotomy112. Several surgical tech-niques to correct varus deformities at the knee, includinglateral closing-wedge osteotomy, medial opening-wedge os-teotomy, and dome osteotomy of the proximal part of thetibia, have been described.

The most common technique for proximal tibial valgusosteotomy is creation of a lateral closing wedge, which can bestabilized with internal fixation (staples, plate, screws, or ten-

sion band), external fixation, or a cast. Billings et al.113 de-scribed a technique involving plate-and-screw fixation thatprovided reproducible angular correction, created stability atthe osteotomy site, allowed early motion of the knee, and pro-vided predictably successful results. Other methods of per-forming proximal tibial valgus osteotomy include a dome cut(which permits greater angular correction without shorteningthe limb114), an interlocking-wedge osteotomy (which can ad-vance the tibial tubercle anteriorly115), and proximal tibial val-gus osteotomy combined with tibial tubercle elevationosteotomy (which permits a more distal wedge cut) 110.

Proximal tibial valgus osteotomy can also be performedwith a medial opening-wedge osteotomy in the proximal part

of the tibia. Methods of fixation for medial opening-wedgeosteotomy include plate-and-screw fixation with or withoutautogenous or allogeneic bone graft116, a hemicallotasis tech-nique with external fixation117, and small-wire external fixa-tion. The potential advantages of medial opening-wedgeosteotomies fixed with plates and screws include a simple re-producible bone cut, no disruption of the proximal tibiofibu-lar joint, minimized risk of peroneal nerve injury, avoidanceof patella infera, and prevention of contracture of the patellartendon due to its resultant redundancy116.

Medial opening-wedge osteotomy of the proximal partof the tibia with use of porous hydroxyapatite to treat osteoar-thritis of the medial compartment of the knee was successful

in a series of twenty-one knees in eighteen patients followedfor an average of 78.6 months (range, thirty-eight to 114months)118. All patients had pain relief and improvement inwalking ability. No patient required conversion to total kneearthroplasty or had graft collapse. External fixation methodscan be associated with pin track infection, nonunion, anddeep venous thrombosis. In addition, an external frame is re-quired for an average of seven weeks.

A nine-year survivorship analysis of 113 knees treatedwith proximal tibial valgus osteotomy demonstrated a ten-dency for recurrence of varus alignment of >5 (in 18% of theknees), progression of lateral compartment arthritis (in 60%),


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and progression of medial compartment arthritis (in 93%)119.The probability of progression of the arthritis was much higherthan was the probability of recurrence of varus malalignment.

The Mayo Clinic has a forty-year experience with proxi-mal tibial osteotomy for treatment of medial tibiofemoralarthritis and varus deformity of the knee. Prior to the popu-larization of total and unicompartmental knee arthroplasty,Coventry et al.120 reported the results of eighty-seven osteoto-mies in seventy-three patients followed for a median of tenyears. With failure defined as the performance of a total kneearthroplasty after the osteotomy, the survivorship was 89% atfive years and 75% at ten years. If, at one year after the opera-tion, the valgus angulation of the anatomic axis (femorotibialangle) was


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and medial thrust (low adductor moment) can cause dynamicdeformity and failure of an osteotomy unless it is corrected atthe time of the osteotomy132,133.

Proximal tibial varus osteotomy can be used to treatlateral unicompartmental arthritis in patients with a tibiofem-oral angular deformity of12 of valgus and a predicted joint-line obliquity of1017,72,100,132. Coventry132 performed a closing-wedge varus osteotomy of the medial aspect of the proximalpart of the tibia in thirty-one knees in twenty-eight patientswho had painful unicompartmental arthritis of the lateral

compartment. The patients were followed for an average of9.4 years (range, two to seventeen years). Six knees requiredtotal knee arthroplasty at an average of 9.8 years after the os-teotomy. Twenty-four knees had either no pain or mild pain atthe last evaluation. Mart i et al.134 performed an opening-wedgevarus osteotomy of the lateral aspect of the proximal part ofthe tibia in thirty-six patients with an average valgus defor-mity of 11.6. They reported thirty good or excellent results atan average of eleven years, with the best results obtained in pa-tients with isolated lateral arthritis who had undergone a

Fig. 1-A

Posteroanterior standing radiograph

made with the knee in 40 of flexion of

a thirty-eight-year-old woman with de-

generative arthritis of the lateral com-

partment and valgus malalignment of

the right knee.

Fig. 1-B

Fig. 1-B Anteroposterior standing radiograph made after distal femoral varus osteotomy. Fig. 1-C Eight-year follow-up anteroposterior stand-

ing radiograph made after implant removal, showing maintenance of the lateral joint space.

Fig. 1-C


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proximal lateral opening-wedge varus osteotomy.Distal femoral varus osteotomy can be used to treat lat-

eral tibiofemoral arthritis in patients with a preoperative ti-biofemoral angle of >12 or a predicted joint-line obliquity of>10 after osteotomy72,99,135-137 (Figs. 1-A, 1-B, and 1-C). Healyet al.99 reported the results of twenty-three distal femoral varusosteotomies in twenty-one patients followed for an average offour years (range, two to nine years). Nineteen of the twenty-three knees had a good or excellent result as rated with TheHospital for Special Surgery knee score. Fifteen of sixteenknees with lateral tibiofemoral arthritis and valgus deformity

had a good or excellent result. Rheumatoid arthritis and inad-equate preoperative motion were associated with poor results.Intermediate-term results reported by other authors135-137 con-firmed these findings. In a long-term evaluation of twenty-one patients treated with distal femoral varus osteotomy forlateral unicompartmental arthritis, Finkelstein et al.138 found aten-year survivorship of 64%, with conversion to total kneearthroplasty as the end point. In patients with severe valgusdeformity in whom a single osteotomy will result in excessivebone loss or joint line obliquity, a distal femoral varus osteot-omy can be combined with a proximal tibial medial osteot-omy to obtain correction72.

Unicompartmental Knee Art hroplasty

Arthroplasty is considered for treatment of painful unicompart-mental arthritis when restoration of the articular cartilage and os-teotomy are not indicated. The choice of unicompartmental ortotal knee arthroplasty depends on the patient, the knee, and thesurgeon. The ideal candidate for unicompartmental knee arthro-plasty has low activity demands, a stable knee with


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mand have been associated with poorer results141,145. In patientswith medial unicompartmental arthritis, the best results are ob-tained when the postoperative mechanical axis is in the centeror slightly medial to the center of the knee. Overcorrection andsevere undercorrection have been associated with early failure146.In patients with lateral unicompartmental arthritis, the cor-rected mechanical axis should be in the lateral compartment,

medial to the preoperative mechanical axis143,147,148

. Poor resultshave been reported as a result of technical problems such as in-adequate implant fixation, poorly designed articulating surfaces(nonconforming articulations), and insufficient polyethylenethickness143,145,148-154.

Unicompartmental knee arthroplasty has several poten-tial advantages over total knee arthroplasty. The surgical ap-proach and surgical dissection can be considerably less extensivefor unicompartmental knee arthroplasty155. Patellar resurfacingis avoided. Requirements for perioperative blood transfusionare diminished156. The range of motion following unicompart-mental knee arthroplasty is generally greater156-158. Properly se-

lected patients have a shorter postoperative recovery time, andthey return to work or to preoperative activities faster. Further-more, revision of a unicompartmental arthroplasty is less diffi-cult than is revision of a total knee arthroplasty156.

More recent intermediate and long-term follow-upstudies of unicompartmental knee arthroplasty performedwith a well-designed implant in properly selected patientshave demonstrated predictably good results comparable withthose of total knee arthroplasty during the first postoperativedecade145,147. In a study of 100 unicompartmental arthroplastiesfollowed for eight to twelve years, in patients with a mean ageof seventy-one years at the time of the operation, Scott et al. 147

reported an 85% survivorship at ten years, with the end pointdefined as revision arthroplasty. Thirteen patients underwentrevision. Stockelman and Pohl159 reported forty-three satisfac-tory results and four revision operations at an average of 7.4years (range, five to twelve years) after forty-seven unicom-partmental knee arthroplasties. In a study of sixty-two uni-

compartmental knee arthroplasties in patients with an average

Fig. 2-C

Posteroanterior standing radiograph made with the knee in

40 of flexion, demonstrating osteoarthritis in the lateral

compartment.

Fig. 2-D

Postoperative anteroposterior standing radiograph made

five years after a unicompartmental knee arthroplasty. The

mechanical axis is now in the center of the knee joint.


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age of sixty-eight years (range, fifty-one to eighty-four years),Berger et al.160 reported a 98% survivorship at ten years, withrevision to total knee arthroplasty as the end point. Onepatient required revision to a total knee arthroplasty at eighty-seven months. Christensen161 reported that seven of 575 uni-compartmental prostheses required revision to a total kneearthroplasty at two to eleven years. Squire et al.162 reported thatfourteen of 140 cemented unicompartmental knee prosthesesin patients with an average age of seventy years required revi-sion to a total knee arthroplasty after fifteen to twenty-twoyears of follow-up. In a study of 143 medial Oxford unicom-partmental knee arthroplasties followed for a mean of 7.6years, the survivorship was 98% at ten years163. Five knees re-quired revision to a total knee arthroplasty.

Revision of a failed unicompartmental knee arthroplastyto a total knee arthroplasty can be accomplished successfullybut may be associated with technical difficulties. Barrett andScott164 reported a good or excellent result in thirteen of twenty-

nine patients at an average of 4.6 years after they had undergonea revision to a total knee arthroplasty. Treatment of osseous in-sufficiency requiring augmentation with bone graft or bone ce-ment and use of long-stem implants was necessary in 50% ofthese revision operations. The authors suggested that the tech-nique of the original operation determines the technical diffi-culty of the revision surgery. When minimal bone was resectedduring the unicompartmental knee arthroplasty, and primarytotal knee arthroplasty implants can be used during the revisionsurgery without bone augmentation, stems, or constrained im-plants, revision to a total knee arthroplasty following unicom-partmental knee arthroplasty can be as successful as primarytotal knee arthroplasty164.

Unicompartmental knee arthroplasty and high tibial os-teotomy have been used to treat unicompartmental arthritis insimilar patients. Broughton et al.165 compared the results offorty-two unicompartmental knee arthroplasties with those offorty-nine high tibial osteotomies after an intermediate five toten-year follow-up. A good result was reported after thirty-twoof the forty-two unicompartmental knee arthroplasties at anaverage of 5.8 years and after twenty-one of the forty-nine hightibial osteotomies at an average of 7.8 years. The authors con-cluded that the results of unicompartmental knee arthroplastywere better than those of osteotomy, and the knees had less latedeterioration. Ivarsson and Gillquist166 reported that patientswho had had unicompartmental knee arthroplasty demon-

strated better gait velocity and superior muscle strength com-pared with those who had had an osteotomy.Schai et al.154 evaluated the results two to six years after

twenty-eight unicompartmental knee arthroplasties performedin patients with an average age of fifty-two years. Twenty-fivepatients had satisfactory pain relief, and two patients requiredrevision to a total knee arthroplasty. The conclusion of the studywas that, at two to six years, unicompartmental knee arthro-plasty in middle-aged patients yields results (with revision con-sidered the end point) that are competitive with those ofosteotomy but inferior to those of total knee arthroplasty.

Long-term survivorship analysis comparing the results of

unicompartmental knee arthroplasty in well-selected patientswith those of total knee arthroplasty are not available, to ourknowledge. In a short-term (six-month to four-year) studycomparing the results of thirty-one unicompartmental knee ar-throplasties with those of 133 total knee arthroplasties, Weale etal.167 reported that the patient-perceived outcomes, pain scores,and functional results were equivalent in the two groups. Lau-rencin et al.168 compared the results in twenty-three patientswho had had a unicompartmental knee arthroplasty on oneside and a total knee arthroplasty on the other; ten patients pre-ferred the side with the unicompartmental procedure, threepreferred the side with the total knee arthroplasty, and tenfound no difference. Comparison studies157,158 have shown thatpatients with unicompartmental knee arthroplasty have a betterrange of motion (flexion of >120) and walk faster than dothose treated with total knee arthroplasty.

Recently developed minimally invasive techniques forunicompartmental knee arthroplasty have emphasized smaller

skin and capsular incisions, limited quadriceps disruption, anddecreased rehabilitation time. Long-term follow-up studies onthese techniques are not available, to our knowledge. Peer-reviewed results have been reported for only 136 elderly patients(average age, sixty-six years) followed for an average of eightyears; eleven patients required revision to a total knee arthro-plasty155. Minimally invasive unicompartmental knee arthro-plasty is an attractive surgical treatment option for elderlypatients with unicompartmental arthritis, and it may be pre-ferred over osteotomy or total knee arthroplasty in these pa-tients. Minimally invasive unicompartmental knee arthroplastyhas been described as a so-called pre-total knee arthroplasty op-eration for patients of all ages155; however, this recommendation

requires fur ther investigation and scientific support.

Total Knee Arthroplasty

Total knee arthroplasty is an accepted surgical treatment forpainful unicompartmental osteoarthritis of the knee in olderpatients, and the prevalence of total knee arthroplasty isincreasing169-173. Total knee arthroplasty has also performed wellin younger patients174-178. When patients of any age with uni-compartmental osteoarthritis and with any diagnosis are poorcandidates for other types of nonoperative and operative treat-ment, total knee arthroplasty is an option. To our knowledge,the results of total knee arthroplasty in patients with unicom-partmental arthritis of the knee are no different than those in

patients with bicompartmental or tricompartmental degenera-tive arthritis.

Authors Opinion and ConclusionsAt the beginning of the twenty-first century, unicompartmen-tal arthritis of the knee is a common clinical problem in theUnited States, and many diverse nonoperative and operativetreatments are available. Oral and injectable medications,weight loss, exercise, physical therapy, canes, crutches, braces,orthotics, arthroscopy, cartilage resurfacing, osteotomy, andarthroplasty offer patients and surgeons a wide spectrum ofsuccessful treatment options.


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Arthroscopic surgery for unicompartmental arthritis ofthe knee should be reserved for patients with mechanicalsymptoms (catching, clicking, locking, instability, or giving-way) that are consistent with loose meniscal fragments, chon-dral articular flaps, loose bodies, and/or impinging intercon-dylar spurs. When arthroscopy of the knee is performed formechanical symptoms, the outcome is predictably successful.However, in sharp contrast, arthroscopic surgery performedmerely for a painful arthritic knee without mechanical symp-toms may not have a lasting benefit 63. Future studies are war-ranted to determine whether arthroscopic surgery can benefitpatients who have primary mechanical symptoms with con-comitant arthritic symptoms179.

When unicompartmental arthritis has developed in aknee, consideration should be given to an attempt to delay orameliorate the degenerative process with biological treat-ments. Historically, this advice was proposed for younger,high-demand patients. However, as patients with arthritic

knees now live longer and desire active lifestyles, treatmentoptions for unicompartmental osteoarthritis should be con-sidered in light of life expectancy and a patients desire for ac-tivity. Osteotomy is an attractive surgical option for activepatients with unicompartmental arthrit is and limb deformitywho are expected to live twenty years or more.

As a patients life expectancy and expectations for activ-ity decrease as a result of age or disease, unicompartmentalknee arthroplasty and total knee arthroplasty become moreattractive options for the surgical treatment of unicompart-mental arthritis of the knee. Unicompartmental knee arthro-plasty can be a successful option, with enduring results, forunicompartmental, noninflammatory arthritis. When patient

selection, surgical technique, and implant utilization are opti-

mized, unicompartmental knee arthroplasty can offer patientsa knee that is functionally superior to a total knee prosthesis,and conversion to total knee arthroplasty can be performedwithout substantial surgical difficulty. Minimally invasive uni-compartmental knee arthroplasty may offer advantages withregard to short-term rehabilitation over traditional arthro-plasty approaches.

Total knee arthroplasty is a predictably successful treat-ment for unicompartmental arthri tis in the older population.The surgical technique of total knee arthroplasty is more com-monly mastered by general orthopaedic surgeons than arealternative operations such as osteotomy and unicompart-mental knee arthroplasty. Wear of bearing surfaces and im-plant loosening are concerns in young active patients treatedwith total knee arthroplasty; however, a well-performed totalknee arthroplasty in this population will provide an excellentfunctional outcome for many years. Surgeons must considersurgical skill and patient demands when choosing a surgical

treatment for unicompartmental arthritis of the knee.

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