results from a degradable tmc joint spacer (artelon) compared with tendon arthroplasty

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Results From a Degradable TMCJoint Spacer (Artelon) Compared

With Tendon ArthroplastyAnders Nilsson, MD, PhD, Elisabeth Liljensten, DDS, PhD,

Christina Bergström, MSc, Christer Sollerman, MD, PhD, Göteborg, Sweden

Purpose: A new spacer for the trapeziometacarpal joint (TMC) based on a biological and tissue-preserving concept for the treatment of TMC osteoarthritis (OA) has been evaluated. The purposewas to combine a spacing effect with stabilization of the TMC joint.Methods: Artelon (Artimplant AB, Sweden) TMC Spacer is synthesized of a degradable polyure-thaneurea (Artelon), which has been shown to be biocompatible over time and currently is used inligament augmentation procedures. Fibers of the polymer were woven into a T-shaped device inwhich the vertical portion separates the bone edges of the TMC joint and the horizontal portionstabilizes the joint. Fifteen patients with disabling pain and isolated TMC OA were included in thestudy. Ten patients received the spacer device and the remaining 5 (control group) were treatedwith a trapezium resection arthroplasty with abductor pollicis longus (APL) stabilization. Themedian ages of the 2 groups were 60 and 59 years, respectively. Pain, strength, stability, and rangeof motion were measured before and after surgery. Radiographic examination was performed in allpatients before and after surgery. At follow-up evaluation 3 years after surgery an unbiasedobserver evaluated all patients. Biopsy specimens were obtained from 1 patient 6 months aftersurgery.Results: All patients were stable clinically without signs of synovitis. In both groups all patientswere pain free. The median values for both key pinch and tripod pinch increased compared withbefore surgery in the spacer group but not in the APL group. The biopsy examinations showedincorporation of the device in the surface of the adjacent bone and the surrounding connectivetissue. No signs of foreign-body reaction were seen.Conclusions: This study showed significantly better pinch strength after Artelon TMC Spacerimplantation into the TMC joint compared with APL arthroplasty. (J Hand Surg 2005;30A:380–389. Copyright © 2005 by the American Society for Surgery of the Hand.)
Key words: CMC-I, degradable biomaterial, implant, OA, TMC.
Szcotra

tda

rom Artimplant AB, Göteborg, Sweden and Department of Hand Sur-ery, Sahlgrenska University Hospital, Sahlgrenska, Sweden.Received for publication December 1, 2003; accepted in revised form

ecember 1, 2004.One or more of the authors have received or will receive benefits for

ersonal or professional use from a commercial party related directly orndirectly to the subject of this article.

Reprint requests: Anders Nilsson, MD, PhD, Department of Handurgery, Sahlgrenska University Hospital, 413 19 Göteborg, Sweden.Copyright © 2005 by the American Society for Surgery of the Hand0363-5023/05/30A02-0022$30.00/0

ddoi:10.1016/j.jhsa.2004.12.001

80 The Journal of Hand Surgery

urgery often is indicated in more advanced trape-iometacarpal (TMC) osteoarthritis (OA) and in-ludes ligament reconstruction, metacarpal osteot-my, TMC arthrodesis, trapezial excision,1 soft-issue interposition2 with or without ligamenteconstruction,3–5 silicone elastomer arthroplasty,6

nd total joint arthroplasty.In TMC OA 2 common surgical procedures are

rapezial excision with tendon interposition (ten-on arthroplasty) and TMC arthrodesis.7,8 Tendonrthroplasty results in good pain relief but there are
ifferent opinions as to whether proximal migra-

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Nilsson et al / Degradable TMC Joint Spacer 381

ion of the first metacarpal bone results in de-reased pinch strength or not.9 –15 Long-term stud-es, however, have shown weak lateral pinch afterendon interposition arthroplasties.16,17 Hence itollows that tendon arthroplasty is not perceived asn optimal technique and clinically is used mainlyn elderly, less-demanding patients without heavy-abor occupations. Arthrodesis on the other handften is recommended for the relatively young,igh-demand individual who needs a strong andtable thumb, although recent studies have shownhat the pinch strength is similar to tendon arthro-lasty.12,16 Many patients with TMC arthrodesis,owever, experience problems with flattening theand and might have pain from the nearbyoints.2,9,12,16,18,19

Endoprosthetic replacement of the TMC joint haseen used, either as TMC implants with preservationf the trapezium or as an interposition after trape-ium resection. Both implant designs are associatedith subluxation, material fatigue, and occurrence ofear debris causing adverse tissue reactions.6,20 In a

ecent report regarding the cemented surface replace-ent trapeziometacarpal prosthesis (SR; Avanta Or-

hopaedics, San Diego, CA), only 40% of the patientsaintained an excellent/good result 33 months after

urgery.21

A new T-shaped TMC device made of a degrad-ble polycaprolactone-based polyurethaneurea (Arte-on; Artimplant AB, Sweden) has been developed.he device has 2 modes of action: to resurface theistal part of the trapezium and to stabilize the TMCoint by augmentation of the joint capsule.

The choice of a degradable biomaterial for theMC spacer device is based on a biological ap-roach to support the local tissue repair. The pur-ose of the biomaterial is to prevent bony impinge-ent but also to provide a scaffold for tissue

ngrowth. The biomaterial undergoes a slow andontrolled degradation to allow the body to formrganized tissue; with time a new articular surfaces formed. The rationale for the horizontal wings iso offer initial stabilization of the joint capsule asell as provide a scaffold function. With degrada-

ion of the biomaterial an increasing amount ofechanical load may be transferred from the de-

ice to the remodeling joint capsule.The treatment of TMC OA with the Artelon spacer

as evaluated in an open, controlled, prospectiveilot study. The control group consisted of patientsho had trapezium excision and abductor pollicis

ongus (APL) tendon interposition. The results from s

re-examination an average of 3 years after surgeryre presented.

aterials and Methodshe Implanthe biomaterial (Artelon) used in the TMC device ispolycaprolactone-based polyurethaneurea that de-

rades by hydrolysis.22 The complete hydrolysis ofrtelon takes approximately 6 years, as shown by in

itro degradation studies. The polymer has been usedn other medical applications and both in vitro and inivo studies have shown the safety and biocompat-bility of the material.23,24 The T-shaped device wasoven from Artelon fibers that were processed by aet spinning procedure and it has a dry weight of.3 g.22 The vertical spacer part of the device servess an interposition in the TMC joint, preventing theetacarpal base to abut onto the trapezium bone

Fig. 1). The horizontal wings augment the dorsaloint capsule and thus prevent dorsoradial migrationf the proximal metacarpal.

atientsn open, controlled, prospective pilot study, which

ollowed the Declaration of Helsinki, was performed.nformed consent was obtained from all patients be-ore inclusion into the study. The study protocol waseviewed and approved by the Sahlgrenska Academythics Committee.Fifteen patients with radiographically verified, iso-

ated TMC OA stage 3 according to Eaton andlickel25 were included in the study. Indication for

igure 1. Artelon TMC Spacer in the TMC joint in a skeleton.ar � 10 mm.

urgery was disabling pain for at least 2 years before

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382 The Journal of Hand Surgery / Vol. 30A No. 2 March 2005

urgery and failure of conservative treatment withplints and steroid injections.

Exclusion criteria were diabetes mellitus, kidneynsufficiency, OA in the STT joint, ongoing cortisonereatment, or malignancy within the past 10 years.he patients were included consecutively in the clin-

cal study and had surgery between September 1999nd February 2001.

The first 5 patients received the Artelon TMCpacer anchored to bone with osteosutures, theext 5 patients were treated with APL tendonrthroplasty, and the remaining 5 patients receivedhe Artelon TMC Spacer anchored with titaniumcrews. There were 9 women and 1 man with anverage age of 60 years (range, 22– 66 years) in thepacer group and 5 women with an average age of9 years (range, 51–72 years) in the APL group.ix patients had surgery on the dominant hand in

he study group compared with 3 patients in thePL group.Two patients (1 man, 1 woman) in the spacer

roup had a previous history of trauma; the remain-ng patients suffered from OA.

All patients were examined by the surgeon before

Table 1. Patients and Study Results

Patient Group GenderDominant

HandOperated

Hand

1 Spacer F R R2 Spacer F R R3 Spacer F R L4 Spacer F R R5 Spacer M R R6 Spacer F R R7 Spacer F R L8 Spacer F R L9 Spacer F L R10 Spacer F R R11 APL F R L12 APL F R L13 APL F R R14 APL F R R15 APL F R R

Spacer Median

Minimum/maximum

APL MedianMinimum/maximum

urgery for baseline measurements and at all fol- t

ow-up visits. In addition an independent observerho did not know which treatment group the patientad received examined all patients at the 3-yearollow-up examination. The clinical examination in-luded both subjective and objective tests.

Pain was evaluated with a visual analogue scale inhich 10 represented the highest degree of pain

xperienced and 0 represented no pain. The visualnalog scale measurements were recorded at maxi-al loading in the key pinch.Strength was measured for 3 different handgrips:

he key pinch (lateral pinch), the tripod pinch, and theransverse volar grip. Measurements were performedith the patient sitting in a chair with the elbow

esting on a table. The values of the key pinch andripod pinch were recorded using a pinch gaugeNorth Coast Medical, Inc) and the transverse volarrip was recorded with a dynamometer (Jamar; Sam-ons Preston Inc, Bolingbrook, IL).Radial and palmar thumb abduction were mea-

ured by a goniometer and were recorded betweenhe first and second metacarpals. To evaluate thebility to flatten the hand, the range of retropositionas measured as the distance (cm) between the

Follow-Up Time Age

Pain (Visual AnalogScale)

Pre-operative

Post-operative

3 y 3 mo 22 6.0 1.03 y 8 mo 56 4.0 03 y 6 mo 65 8.0 03 y 4 mo 56 7.0 03 y 4 mo 48 1.0 02 y 8 mo 65 5.0 02 y 7 mo 63 8.0 02 y 8 mo 66 2.0 02 y 8 mo 59 0 3.02 y 8 mo 61 8.0 03 y 2 mo 72 5.0 0

1 y 10 mo 58 3.0 4.03 y 1 mo 51 3.0 03 y 2 mo 72 5.0 0

3 y 59 8.0 2.0

3 y 60 5.5 0

y 7 mo/3 y 8 mo 22/66 0/8.0 0/3.0

3 y 1 mo 59 5.0 0y 10 mo/3 y 2 mo 51/72 3.0/8.0 0/4.0

— —

2

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humb and table underneath the hand when the dor-

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um of the hand was pressed against the table. Thealmar abduction, that is, the distance (cm) betweenhe thumbnail and the nail of the index finger duringaximal opening, was measured. Maximal extension

nd flexion in the metacarpophalangeal and interpha-angeal joints were measured using a flexible rod andransferred to a paper chart from which the angle ofexion or extension was measured.Grip function was measured by the Sollerman

and function test consisting of 20 different activitiesf daily life in which the main handgrips are used tohe same extent as in daily life.26 The testing of theatients was performed by an occupational therapist.he time to return to presurgical occupation was

egistered. The patients’ subjective assessments ofhe treatment result measured at 3-year follow-upvaluation were recorded using a Likert scale (1 �oor; 5 � excellent). All patients were examinedadiographically before surgery and at follow-upvaluation.

urgical Techniquehe APL arthroplasty was performed according toigfusson and Lundborg.5 In brief, a longitudinalurved dorsoradial incision over the trapezium was

Table 1. Continued

Key pinch (kg) Tripod pinch (kg)Transve

Pre-operative

Post-operative

Pre-operative

Post-operative

Pre-operativ

7.0 8.5 6.5 7.0 16.07.5 8.0 6.0 10.0 14.05.0 6.0 4.0 7.5 33.02.5 8.0 3.0 10.0 12.0

12.0 10.5 10.0 8.0 50.07.0 8.0 7.0 9.0 29.05.5 6.0 6.0 6.0 22.07.5 8.0 6.0 6.0 22.04.0 2.0 4.0 2.0 14.04.0 8.0 4.0 8.0 24.04.5 6.0 4.0 4.0 22.02.5 3.5 3.5 2.0 18.09.0 7.0 9.0 8.0 28.06.0 5.0 5.0 4.0 30.07.0 5.0 6.5 4.0 22.06.2 8.0 6.0 7.8 22.0

2.5/12.0 2.0/10.5 3.0/10.0 2.0/10.0 12.0/50.6.0 5.0 5.0 4.0 22.0

2.5/9.0 3.5/7.0 3.5/9.0 2.0/8.0 18.0/30.— p � .05 — p � .05 —

Pain (visual analogue scale) was recorded at maximal loading of k

ade. A distally based fascia-capsule flap was raised

o expose the first carpometacarpal joint and then therapezium was excised. A distally based strip, 6- to-cm long, of the most radial part of the APL wasrepared. The strip was inserted through the radialart of the capsule and then through a cut in theexor carpi radialis tendon, and then was pulled upnd around one of the remaining parts of the APLendon, twisting the flexor carpi radialis and the APLogether.

The implantation of the Artelon TMC Spacer waserformed through a dorsal approach with a curvedkin incision over the TMC joint. The radial arteryas identified and carefully was mobilized proxi-ally and protected. The periosteum of the dorsal

rapezium and the capsule of the TMC joint werelevated distally. With traction placed on the thumbhe TMC joint was inspected and the articular surfacelong with the most distal part (2 mm) of the trape-ium was removed with an osteotome. The dorsalortex of both the trapezium and the proximal meta-arpal were removed to allow the wings of the deviceo be in close contact with the trabecular bone andeveled with cortical bone surface. Any bone cystsere filled with excised bone.

lar grip Radial Range ofMotion (°)

Volar Range ofMotion (°)

Post-erative

Pre-operative

Post-operative

Pre-operative

Post-operative

40.0 25 30 30 2030.0 20 10 20 631.0 35 35 60 2030.0 50 20 35 1050.0 45 35 30 2030.0 20 25 12 2028.0 30 32 30 2026.0 18 30 20 308.0 20 40 20 20

31.0 20 18 18 2020.0 15 15 40 1420.0 40 20 30 1533.5 22 35 20 2027.5 30 25 42 2520.0 20 25 20 1530 22.5 30 25 20.0/50.0 18/50 10/40 12/60 6/3020.0 22 25 30 15.0/33.5 15/40 15/35 20/42 14/25— — — — —

. Patient 9 displayed pain only in tripod pinch (5.0).

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The device was anchored to bone with either non-

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esorbable coated braided polyester osteosutures (3-0iCrone Davis & Geck, Nepean, Canada) or titaniumcrews (screw diameter, 1.6 mm; Medicon, Tuttin-en, Germany). Bone canals were prepared for thesteosutures with a 1.1-mm–diameter AO hand burr.hus one wing was anchored to the first metacarpalnd the other wing was anchored to the trapezium. Inll cases the periostal flap including the dorsal cap-ule was relocated and sutured with a resorbableuture covering the wings. After surgery the thumbas immobilized in a spica cast for 5 weeks in bothroups.

istologyt 6 months after surgery biopsy specimens were

aken from 1 patient (Table 1, patient 9) when 1 ofhe titanium screws was removed owing to discom-ort. The biopsy specimens (�2 � 2 mm) wereaken from the distal wing of the spacer close tohe metacarpal. After removal the biopsy speci-

ens were immersed immediately in buffered for-alin (4%) for 24 hours. The tissue then was

ehydrated, embedded in paraffin, and sectionedith a conventional microtome (section thickness,4 –5 �m). In addition the hard tissue of the

iopsy specimen was decalcified in 12% ethyl-nediaminetetraacetic acid for 2 weeks (shakennd changed daily). The sections were preparedonsecutively longitudinally from the surface ofhe biopsy specimen through the entire biopsypecimen. The majority of the sections (both bonend soft tissue) were stained with toluidine blueecause this is one of few stains that adequatelytains the biomaterial. Light microscopic analysisas performed.

tatisticsescriptive statistics was used for presentation of the

esults. A Wilcoxon rank sum test was used to com-are grip strength in the different treatment groups. Aignificance level of .05 was regarded as statisticallyignificant.

esultshe results in all patients are summarized in Table 1.ll spacer patients and 4 APL patients were followedp for 3 years. One APL patient was followed up foryears because the patient did not respond to the

epeated calls. Except for 2 spacer patients with aransient inflammatory reaction with moderate localwelling and tenderness at 2 weeks after surgery
Table 1, patients 7 and 9), no other postsurgical r
omplications were detected. Routine blood analysisesults were normal and the tissue reaction subsidedithin the following 2 weeks. X-ray examination

howed a distance between the trapezium and theetacarpal (Fig. 2). At re-examination all patientsere examined with an x-ray and reported major pain

elief without any differences between the spacer andhe APL group (Fig. 3). Grip and pinch strength,

easured for key pinch, tripod pinch, and transverseolar grip, increased in the spacer group comparedith presurgical values in contrast to the APL group,

n which no improvement was recorded (Figs. 4–6,able 1). At 3 years the spacer patients were signif-

cantly stronger as recorded by both the surgeon andhe independent observer in tripod pinch (p � .05)ompared with the APL group. The results also re-ealed a significant difference in key pinch betweenhe 2 groups (p � .05) when recorded by the inde-endent observer. There was no difference in rangef motion in the metacarpophalangeal or interphalan-eal joints between the groups. The range of motion

igure 2. An x-ray 3 years after surgery showing the ArtelonMC Spacer in the TMC joint of the left thumb.

egarding palmar and radial abduction of the thumb,

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s well as the retroposition (Table 1), the palmarbduction, and the ability to flatten the hand, were theame in both groups. The palmar abduction (theistance in cm between the thumb and index finger)as 15.0 before surgery and 13.8 after surgery in the

igure 3. Pain according to the visual analog scale beforeurgery and at follow-up examinations. Results presented foratients treated with Artelon TMC Spacer (Spacer) and pa-

ients treated with trapezium excision and APL tendon inter-osition (APL). �, Spacer; , APL.

igure 4. Strength in key pinch (pinch gauge) before and 3ears after surgery. Results presented for patients treated withrtelon TMC Spacer (Spacer) and patients treated with tra-ezium excision and APL tendon interposition (APL). At 3ears values are given for both the surgeon (3 y) and thendependent observer (3 y_io). Statistically significant differ-

bnces are marked. �, Spacer; , APL.

pacer group compared with 15.2 and 14.5, respec-ively, in the APL group. The ability to flatten theand (the distance between the thumb and the table)as 1.0 cm before surgery and 0.8 cm after surgery

n the spacer group compared with 1.2 cm and 1.3m, respectively, in the APL group. Comparableesults in the 2 groups were seen in the Sollermanand function test.Four patients in the spacer group were working

efore surgery and at the 3-year follow-up evaluationll had returned to their previous occupations. In thePL group only 1 patient was working before sur-ery but was retired at the re-examination.Except for 1 patient (Table 1, patient 9) the

atients in both the spacer and APL groups wereatisfied with the treatment. Median values on theikert scale were 4.8 and 5.0 in the spacer andPL groups, respectively. Radiographic examina-

ion showed no dislocation or any adverse hostissue response.

istologyhe decalcified sections containing bone showed alose contact between Artelon fibers and boneithout intervening structures. The bone adjacent

o the Artelon fibers and at a distance from the

igure 5. Strength in tripod pinch (pinch gauge) before and 3ears after surgery. Results presented for patients treated withrtelon TMC Spacer (Spacer) and patients treated with tra-ezium excision and APL tendon interposition (APL). At 3ears values are given for both the surgeon (3 y) and thendependent observer (3 y_io). Statistically significant differ-nces are marked. �, Spacer; , APL.

iomaterial had a mature lamellar appearance (Fig.

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). Sections with connective tissue in close contactith Artelon showed tissue in-growth into the wo-en structure (Fig. 8). There were no chronic in-ammatory cells or any foreign-body response in

he vicinity of Artelon.

igure 6. Strength in transverse volar grip (Jamar) before andyears after surgery. Results presented for patients treatedith Artelon TMC Spacer (Spacer) and patients treated with

rapezium excision and APL tendon interposition (APL). At 3ears values are given for both the surgeon (3 y) and thendependent observer (3 y_io). �, Spacer; , APL.

igure 7. Light micrograph from a patient with an Artelon TMight turquoise areas incorporated in the host bone. The bone
ontact (I: interface) with the biomaterial without signs of adverse
iscussionhe use of a degradable spacer with capsule augmen-

ation might be indicated in patients with isolated OAf the TMC joint with high demands on grip functionnd pinch strength. These patients often are badandidates for excision of the trapezium, which forany years has been the benchmark arthroplasty.27

esection of the trapezium results in a grossly alterednatomy with subsequent shortening of the thumbnd decreased pinch strength.16,17,27 By preservinghe trapezium and the surrounding ligaments ArtelonMC Spacer offers the possibility to combine 2ell-documented methods of restoration of degener-

ted OA joints by joint capsule augmentation (by theorizontal portion of the device) and resurfacing ofhe articular surface (vertical portion of the device).

The results of this study show that the pain-reliev-ng effect of Artelon TMC Spacer implantation wasquivalent to that after a tendon arthroplasty, but theinch strength was considerably better comparedith both presurgical values and the APL group.ange of motion was comparable after both proce-ures despite the ligament reinforcement producing arm fixation between the metacarpal base and trape-ium. There was no difference between the groupsegarding palmar adduction and abduction or regard-ng retroposition of the thumb; thus flattening of theand was not a problem.

acer 6 months after implantation. Artelon (A) can be seen assteocytes (OC) is surrounding the material and show a close

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Previous efforts to replace the TMC joint withmplants made from materials such as silicone, ex-anded polytetrafluoroethylene, polypropylene, andollagen have been associated with some disadvan-ages.

The use of silicone trapezial implants was previ-usly a common procedure but wear and deformationf the implant has been shown to cause foreign-bodyeactions characterized by multinucleated giant cellsontaining small particles of silicone.28 Pellegrinind Burton29 found a 25% failure rate with siliconemplants and a high rate of revision surgery causedy subluxed implants and marked silicone synovitis.his can be associated with erosion of adjacent bone,nd 56% cyst formation has been reported.30

Reactions after implantation of expanded polytet-afluoroethylene implants also have been reported.reenberg et al31 observed osteolytic changes around

he Gore-Tex implants in 80% of their patients andistologic examination of 1 retrieved implant showedrayed graft material and giant cells. Muermans andoenen32 compared the use of Gore-Tex andolypropylene (Marlex) implants with the interposi-ion of a strip of extensor carpi radialis longus tendonfter trapeziectomy. Marlex was well tolerated buthey reported a 30% incidence of synovitis charac-erized by pain and osteolysis in patients with Gore-

igure 8. Light micrograph from 1 patient with an Artelon TMrom an ongoing multicenter study). Artelon (A) is stained turqhe interface between Artelon and connective tissue (I) show

ex implants. Belcher and Zic33 compared trapezi-

ctomy alone with interposition of porcine dermalollagen xenograft (Permacol) in 26 patients withA of the TMC joint. The study was terminatedrematurely because of adverse reactions to the im-lant in 6 of 13 patients. Three implants were exam-ned histologically, all showing foreign-body reac-ions with numerous multinucleated giant cells.atients with Permacol implants reported signifi-antly more pain after surgery than control patients.

previous effort to replace the trapezium with aolid polyurethane implant showed encouraging re-ults with no adverse tissue reaction from the poly-rethane but also a similar frequency of implantislocations as seen after silicone implants.34

During the degradation of Artelon, which takeslace by hydrolysis, the mechanical properties andhe weight of the material decrease, as does the molarass of the polymer. It is important to emphasize

hat when the hydrolysis is completed, part of theegraded material (approximately 50% of the initialeight) will remain incorporated at the site of im-lantation.The tissues adjacent to the Artelon devices, how-

ver, show a normal vascularization and a very lim-ted amount of plasma and giant cells, which nor-ally is a fairly common event in tissues surrounding

ifferent implants.35

cer 12 months after implantation (biopsy specimen obtainedand is surrounded by connective tissue with fibroblasts (FB).sign of foreign-body reaction. Bar � 100 �m.

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The degradation rate is an inherent property of the

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iomaterial and in the case of Artelon it takes ap-roximately 6 years before the material is hydro-yzed. It may be argued that the entire degradationeeds to be followed up before any conclusions cane drawn. With the new degradable and woven TMCevice, however, we aim to obtain formation of aew functional surface. Such a tissue formation isossible to study as early as 6 months after surgery.n fact this study shows that the patients have a goodutcome after implantation of the spacer and theiopsy specimens show that a host tissue is present inhe device.

The results show a noteworthy and clinically sig-ificant postsurgical increase of key pinch and tripodinch in the spacer group compared with the APLroup. As this pilot study proceeds more data of bothong-term clinical and radiographic results will bebtained.

Scott McDonald is gratefully acknowledged for skillful occupationalherapy. Professor Bengt Edberg, Pia Roy, and Rolf Nilsson are acknowl-dged for textile development and manufacturing, and Karin Darle Ols-on is acknowledged for technical assistance.

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results from a degradable tmc joint spacer (artelon) compared with tendon arthroplasty

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