Femoral and Tibial Tunnel Diameter and Bioabsorbable Screw Findings After Double-Bundle ACL Reconstruction in 5-Year Clinical and MRI Follow-up

O iginal Resea ch Femo al and Tibial Tunnel Diame e and Bioabso bable Sc ew Findings A e Double-Bundle ACL Recons uc ion in 5-Yea Clinical and MRI Follow-up Tommi Kieka a,* † MD, PhD, An i Paakkala, † MD, PhD, Piia Suomalainen, ‡ MD, PhD, Heini Huh ala, § MSc, and Timo Ja ¨ ela ¨, || MD, PhD In es iga ion pe o med a Tampe e Uni e si y Hospi al, Tampe e, Finland Backg ound: Tunnel enla gemen is equen ly seen in sho - e m ollow-up a e an e io c ucia e ligamen econs uc ion (ACLR). Acco ding o new e idence, unnel enla gemen may be ollowed by unnel na owing, bu he long- e m e olu ion o he unnels is cu en ly unknown. Hypo hesis/Pu pose: The hypo hesis was ha unnel enla gemen is ollowed by unnel na owing caused by ossi ica ion as seen in ollow-up using magne ic esonance imaging (MRI). The pu pose o his s udy was o e alua e he ossi ica ion pa e n o he unnels, he communica ion o he 2 emo al and 2 ibial unnels, and sc ew abso p ion indings in MRI. S udy Design: Case se ies; Le el o e idence, 4. Me hods: Thi y-one pa ien s unde wen ana omic double-bundle ACLR wi h hams ing g a s and bioabso bable in e e ence sc ew ixa ion and we e ollowed wi h MRI and clinical e alua ion a 2 and 5 yea s pos ope a i ely. Resul s: The mean unnel enla gemen a 2 yea s was 58% and educed o 46% a 5 yea s. Tunnel ossi ica ion esul ed in e enly na owed unnels in 44%, in conical unnels in 48%, and ully ossi ied unnels in 8%. Tunnel communica ion inc eased om 13% o 23% in he emu and om 19% o 23% in he ibia be ween 2 and 5 yea s and was no associa ed wi h knee laxi y. A 5 yea s, 54% o he sc ews we e no isible, wi h 35% o he sc ews eplaced by a cys and 19% ully ossi ied. Tunnel cys s we e no associa ed wi h wo se pa ien - epo ed ou comes o knee laxi y. Pa ien s wi h a ibial an e omedial unnel cys had highe Lysholm sco es han pa ien s wi hou a cys (93 and 84, P¼.03). Conclusion: Tunnel enla gemen was ollowed by unnel na owing in 5-yea ollow-up a e double-bundle ACLR. Tunnel com- munica ion and unnel cys s we e equen MRI indings and no associa ed wi h ad e se clinical e alua ion esul s. Keywo ds: an e io c ucia e ligamen ; ACLR; MRI; unnel enla gemen ; unnel na owing; bioabso bable sc ew In double-bundle (DB) an e io c ucia e ligamen econ- s uc ion (ACLR), 2 emo al and 2 ibial bone unnels a e d illed a he ana omic ligamen inse ions. 10,15,18 The ape u e ixa ion o he an e omedial (AM) and pos e ola - e al (PL) hams ing g a s is done wi h ei he me al o biodeg adable in e e ence sc ews. Tunnel enla gemen a e ACLR is a common bu poo ly unde s ood pos ope a- i e phenomenon. 28,36 In a ecen s udy wi h se ial mag- ne ic esonance imaging (MRI), he bone unnels o single-bundle (SB) ACLR apidly enla ged o he i s 6 mon hs a e su ge y and he ea e slowly na owed un il 2 yea s o ollow-up. 35 In o he s udies, he unnels ha e emained cons an a e he apid enla gemen pe iod in 1- o 2-yea ollow-up. 5,14,30 Tunnel enla gemen may lead o unnel communica ion a e DB ACLR. 19 Nonsymp oma ic unnel communica ion seen on MRI has been epo ed in *Add ess co espondence o Tommi Kieka a, MD, PhD, Medical Imaging Cen e, Tampe e Uni e si y Hospi al, FIN-33521, Tampe e, Finland (email: [email p o ec ed]). † Medical Imaging Cen e, Tampe e Uni e si y Hospi al, Tampe e, Finland. ‡ Di ision o O hopaedics and T auma ology, Depa men o T auma, Musculoskele al Su ge y and Rehabili a ion, Tampe e Uni e si y Hospi al, Tampe e, Finland. § School o Heal h Sciences, Uni e si y o Tampe e, Tampe e, Finland. || A h oscopic and Spo s Medicine Cen e Omasai aala, Helsinki, Finland. The au ho s decla ed ha hey ha e no con lic s o in e es in he au ho ship and publica ion o his con ibu ion. E hical app o al o his s udy was ob ained om he E hical Commi ee o Tampe e Uni e si y Hospi al. The O hopaedic Jou nal o Spo s Medicine, 5(2), 2325967116685525 DOI: 10.1177/2325967116685525 ªThe Au ho (s) 2017 1 This open-access a icle is published and dis ibu ed unde he C ea i e Commons A ibu ion - NonComme cial - No De i a i es License (h p://c ea i ecommons.o g/ licenses/by-nc-nd/3.0/), which pe mi s he noncomme cial use, dis ibu ion, and ep oduc ion o he a icle in any medium, p o ided he o iginal au ho and sou ce a e c edi ed. You may no al e , ans o m, o build upon his a icle wi hou he pe mission o he Au ho (s). Fo ep in s and pe mission que ies, please isi SAGE’s websi e a h p://www.sagepub.com/jou nalsPe missions.na . 10% o 19%o pa ien s in he emu and in 24% o 29%o pa ien s in he ibia in 1- o 2-yea ollow-up. 19,20,30 The long- e m consequences o unnel communica ion a e unknown, bu knee ins abili y has been hypo hesized o occu . 6,12,26 Bioabso bable sc ews ha a e used o g a ixa ion ha e been manu ac u ed using a leas 7 di e en polyme combina ions. 22 The abso p ion and ossi ica ion o he bioabso bable sc ews ha e been e alua ed using compu ed omog aphy (CT) and MRI. 2,3,8 In addi ion o sc ew abso p- ion and ossi ica ion, small nonsymp oma ic cys s inside and nea he pa ially eso bed sc ews ha e been epo ed. 2,4,7,27,31,33 I was claimed ha he widely used poly-L-lac ic acid (PLLA) sc ews would eso b in 2 yea s. Howe e , his claim was la e shown o be alse. In ollow-up s udies, comple e abso p ion o he sc ews has been shown o ake as long as 10 yea s. 27,31,33,34 L-lac ide, D-lac ide, and ime hylene ca bona e sc ews we e also claimed o eso b in 2 yea s, bu 78%o he sc ews we e s ill pa ially isible in MRI 2 yea s a e su ge y. 24 The pu pose o his s udy was o examine he bone unnel diame e s and biodeg adable L-lac ide, D-lac ide, and i- me hylene ca bona e sc ew indings in 5-yea clinical and MRI ollow-up a e DB ACLR. Ou hypo hesis was ha unnel enla gemen is ollowed by unnel na owing caused by ossi ica ion, as seen on MRI ollow-up. The ossi ica ion pa e ns o he unnels, unnel communica ion, and sc ew abso p ion MRI indings we e e alua ed in his s udy. METHODS Pa ien s W i en consen was equi ed om all pa ien s. The inclu- sion c i e ia we e an ACL inju y equi ing econs uc ion and closed g ow h pla es. The exclusion c i e ia we e p e- ious ACLR, mul iligamen inju y o he index knee, o inju y o he con ala e al knee. Su gical Technique All pa ien s unde wen DB ACLR by he same su geon using he same ana omic echnique wi h hams ing au o- g a s as desc ibed p e iously in de ail. 15 In b ie , he ibial unnels we e c ea ed o he ana omic oo p in wi h a guide. The ibial AM unnel was loca ed in he an e io pa o he oo p in and he ibial PL unnel in he pos e io pa o he oo p in . The emo al unnels we e c ea ed ia an an e omedial po al wi h eehand echnique o he ana- omic inse ions o he AM and PL bundles o he ACL. The bony wall be ween he emo al unnel ape u es was a leas 1 o 2 mm. The g a s we e ixed wi h bioabso bable in e e ence sc ews (L-lac ide, D-lac ide, and ime hylene ca bona e; Hexalon, Inion Co) using an ou side-in ech- nique in he ibia and an inside-ou echnique in he emu . Rehabili a ion Full weigh bea ing was allowed immedia ely in he pos op- e a i e ehabili a ion p og am. No b ace was used. C u ches we e used o 3 o 4 weeks, and closed kine ic chain exe cises we e s a ed immedia ely a e su ge y. Cycling was pe mi ed on an e gome e a 4 weeks. I ull unc ional s abili y was achie ed, unning was pe mi ed a 3 mon hs and pi o ing spo s a 6 mon hs. MRI E alua ion Pa ien s unde wen MRI scans a 2 and 5 yea s a e su - ge y. The esul s o he 2-yea MRI e alua ion o 66 pa ien s ha e been published p e iously. 19,20 In he 2-yea e alua- ion, a 1.5-T MRI (Signa Exci e HD image ; GE Heal hca e) was used. The 1.5-T imaging p o ocol included sagi al T1- weigh ed images wi h a epe i ion ime/echo ime o 2800/ 19 ms and a slice hickness/gap o 4.0/1.0 mm, sagi al p o- on densi y (PD)–weigh ed images (2320/24 ms and 4.0/1.0 mm), sagi al T2-weigh ed images (3740/78 ms and 4.0/1.0 mm), co onal T1-weigh ed images (500/16 ms and 4.0/1.0 mm), co onal a -supp essed (FS) images (3300/74 ms and 4.0/1.0 mm), axial FS PD-weigh ed images (1940/40 ms and 4.0/1.0 mm), and oblique sagi al and co onal T1-weigh ed images along he AM g a plane (660/16 ms and 3.0/0.3 mm). The 5-yea e alua ions we e done using 3 T MRI (MAGNETOM T io 3T; Siemens Heal hca e Sec o ) and 8-channel knee coil. The 3-T imaging p o ocol included sagi al PD-weigh ed images (2800/19 ms and 3.0/0.3 mm), sagi al FS T2-weigh ed images (5100/80 ms and 3.0/0.3 mm), co onal T1-weigh ed images (1150/18 ms and 3.0/0.3 mm), co onal FS T2-weigh ed images (4600/85 ms and 3.0/0.3 mm), axial FS PD images (3650/36 ms and 3.0/0.3 mm), and oblique sagi al and co onal PD-weigh ed images along he AM g a plane (2800/19 ms and 2.5/0.25 mm). The images we e e alua ed by 2 musculoskele al adi- ologis s using a PACS (pic u e a chi ing and communi- ca ion sys em) wo ks a ion (Ca es eam VuePacs 11.14). Tunnel wid h was measu ed independen ly, and he pa e n o bone unnel ossi ica ion and he indings o unnel communica ion and sc ew abso p ion we e e alu- a ed in consensus. The wid h o he emo al and ibial unnels was measu ed in an e opos e io (AP) and mediola e al (ML) di ec ions a he la ges pa o he unnels, and he means o he measu emen s we e used as he maximum unnel wid h (Figu e 1). 20 In cases o unnel communica ion, he common ape u e was mea- su ed and used o bo h unnels (Figu es 2 and 3). Tunnel wid h was compa ed wi h he diame e o he d ill used. 20 The ossi ica ion pa e n o he unnels was di ided in o 3 g oups: e enly na owed ( emaining unnel o app oxi- ma ely cons an diame e ) (Figu e 4), conical ( emaining unnel conical wi h p onounced na owing o he dis al unnel) (Figu e 4), and ully ossi ied (Figu e 1). Tunnel communica ion was e alua ed a he unnel ape u e and up o 1 cm dis al om he join line. 30 The biodeg adable sc ews we e e alua ed and g aded as comple ely isible (Figu e 5), pa ially isible(Figu es3and4),andno isible (Figu es 1 and 6). 24 In addi ion, he eplacemen o sc ews by bone o a luid- illed cys was also e alua ed (Figu es 1 and 6). 2Kieka a e al The O hopaedic Jou nal o Spo s Medicine Clinical E alua ion The 2- and 5-yea pos ope a i e clinical e alua ions we e done by 2 senio o hopaedic esiden s. The e alua ions included In e na ional Knee Documen a ion Commi ee (IKDC) and Lysholm knee sco es. In he IKDC e alua ion, he an e io s abili y and side- o-side di e ence o bo h knees was es ed using a KT-1000 a h ome e (MED- me ic Co p). S a is ical Me hods The da a we e analyzed using IBM SPSS S a is ics, e - sion 19.0 so wa e (IBM Co p). The s a is ical signi i- cance o he esul s was calcula ed using a 2- ailed es wi h hesigni icancele else o<.05.Bland- Al man in e obse e ag eemen s be ween he unnel measu emen s we e calcula ed using S a a 8.2 so wa e (S a aCo p LP). Figu e 1. Measu emen o he emo al an e omedial unnel diame e using a co onal T1-weigh ed magne ic esonance image. The a ow indica es he ully ossi ied pos e ola e al emo al unnel and sc ew. Figu e 2. Measu emen o he common ape u e o he com- munica ing emo al unnels using a sagi al p o on densi y– weigh ed magne ic esonance image. Figu e 4. A conical emo al an e omedial (AM) unnel and an e enly na owed ibial AM unnel in an oblique co onal p o on densi y–weigh ed magne ic esonance image. The a ow indi- ca es a pa ially isible sc ew. Figu e 3. Measu emen o he common ape u e o he com- munica ing ibial unnels using a sagi al p o on densi y– weigh ed magne ic esonance image. The a ow indica es a pa ially isible an e omedial unnel sc ew. The O hopaedic Jou nal o Spo s Medicine Tunnel and Sc ew Findings A e DB ACLR 3 RESULTS Be ween he yea s 2004 and 2008, 75 pa ien s we e p o- spec i ely en olled in o he s udy. Du ing he i s 2 yea s o ollow-up, 8 pa ien s we e los due o long a el dis- ances, and 1 pa ien su e ed a new inju y and needed e ision su ge y. In o al, 66 pa ien s we e a ailable o MRI and 61 pa ien s o clinical e alua ion a 2-yea e alua ion. The mean ollow-up ime om su ge y o 2- yea MRI was 23 mon hs ( ange, 17-30 mon hs). The mean ime in e al om 2-yea MRI o 2-yea clinical e alua ion was 151 days ( ange, 10-424 days). The 5-yea e alua ion was i s es ic ed o a andom sample o 40 pa ien s due o MRI a ailabili y, bu inally, only 31 pa ien s we e a ailable o MRI and 29 pa ien s o clinical e alua ion due o long a el dis ances. The mean ollow-up ime om su ge y o 5-yea MRI was 67 mon hs ( ange, 46-89 mon hs). The mean ime in e al om 5-yea MRI o 5-yea clinical e alua ion was 40 days ( ange, 5-123 days). The mean ime in e al om 2-yea MRI o 5-yea MRI was 44 mon hs ( ange, 25-63 mon hs). Tunnel Enla gemen and Na owing The mean na owing o he 4 unnels was in o al 12% be ween 2 and 5 yea s (Table 1). In Bland-Al man compa - isons, he mean di e ence be ween he 2 adiologis s an- ged om 0.9 o 1.8 mm in he 2-dimensional measu emen s o he 4 unnels. Pa e n o Tunnel Ossi ica ion A he 2-yea MRI, all unnels we e enla ged, wi h no signs o ossi ica ion. A he 5-yea MRI, 44%o he unnels we e e enly na owed, 48%we e conical, and 8%we e ully ossi- ied (Table 2). The pa ien s wi h e enly na owed emo al PL unnels had a be e ange o mo ion in knee lexion han he pa ien s wi h conical PL unnels (149and 140, Figu e 6. The same pa ien as in Figu e 5 a 5-yea magne ic esonance imaging. The pos e ola e al emo al unnel sc ew is no isible. The a ow indica es a luid- illed cys in he loca ion o he eso bed sc ew in a co onal T2-weigh ed a - supp essed magne ic esonance image. Figu e 5. The a ow indica es he comple ely isible sc ew in he pos e ola e al emo al unnel in a co onal T2-weigh ed a - supp essed magne ic esonance image a 2-yea e alua ion. TABLE 1 Tunnel Diame e s a Tunnel Mean D ill Diame e , mm Tunnel Diame e , mm P b 2y Enla gemen , %5y Na owing, % Femo al AM 6.2 10.1 63 8.9 12 .000 Femo al PL 5.9 9.2 58 7.9 14 .000 Tibial AM 6.6 10.3 57 9.3 10 .001 Tibial PL 6.0 9.1 52 8.2 10 .001 All unnels 6.2 9.7 58 8.6 12 .001 a AM, an e omedial; PL, pos e ola e al. b Two- ailed es . TABLE 2 Di e en Pa e ns o Tunnel Ossi ica ion a 5-Yea Magne ic Resonance Imaging a Tunnel E enly Na owed, %Conical, %Fully Ossi ied, % Femo al AM 36 61 3 Femo al PL 26 52 22 Tibial AM 71 29 0 Tibial PL 45 52 3 All unnels 44 48 8 a AM, an e omedial; PL, pos e ola e al. 4Kieka a e al The O hopaedic Jou nal o Spo s Medicine espec i ely, P¼.02). The o he di e ences in clinical e a- lua ions we e small and no s a is ically signi ican . Tunnel Communica ion Femo al unnel communica ion inc eased om 13% o 23% o pa ien s be ween 2- and 5-yea MRIs. Tibial unnel com- munica ion inc eased om 19% o 23%o pa ien s du ing he same pe iod. In 5-yea e alua ion, he pa ien s wi h unnel communica ion in MRI had less laxi y in ins umen- ed an e io s abili y measu emen (side- o-side di e ence 1.9 mm wi h and 2.8 mm wi hou emo al unnel commu- nica ion [P¼.35] and 1.5 and 2.8 mm wi h and wi hou ibial unnel communica ion [P¼.20]) and highe Lysholm sco es (91 and 88 on he emo al side [P¼.59] and 93 and 88 on he ibial side [P¼.38]). Bu he di e ences we e no s a is ically signi ican . Simila ly, he di e ences in o he clinical e alua ions we e small and s a is ically no signi ican . Sc ew Findings The MRI indings o he sc ews a e shown in Table 3. In cases whe e sc ews we e no isible, a luid- illed cys in he p e ious sc ew posi ion was seen in 60%o pa ien s in he emo al AM unnels, in 47%o pa ien s in he emo al PL unnels, in 88%o pa ien s in he ibial AM unnels, and in 63%o he pa ien s in he ibial PL unnels. The emaining 40%,53%,12%, and 37%o non isible sc ews we e eplaced by bony ing ow h. Pa ien s wi h a ibial AM unnel cys had highe Lysholm sco es han pa ien s wi hou a cys (93 and 84, espec i ely; P¼.03). The e we e no o he s a is ically signi ican associa ions wi h unnel cys s ound wi h o he unnels o clinical es s. DISCUSSION This s udy showed ha he maximum diame e s o he 4 bone unnels o DB ACLR na owed be ween 2- and 5-yea pos ope a i e MRIs. Thus, ou hypo hesis was con i med. The unnel ossi ica ion pa e n was desc ibed as e enly na owed, conical, o ully ossi ied. Despi e unnel na ow- ing, unnel communica ion inc eased du ing ollow-up. Nea ly hal o he bioabso bable L-lac ide, D-lac ide, and ime hylene ca bona e sc ews we e pa ially isible a 5 yea s. Those sc ews ha we e no isible we e eplaced by luid- illed cys s and bone. The enla gemen o he bone unnels has been seen in many s udies 1 o 2 yea s a e ACLR. { The causes o unnel enla gemen a e unknown and p obably mul i- ac o ial, wi h p oposed mechanical and biochemical causes. 11,36 The de elopmen o unnel changes has been ollowed in 2 p e ious s udies using se ial c oss-sec ional imaging. 9,35 In he s udy wi h se ial CT ollow-up, he SB ACLRs we e comple ed using he ans ibial echnique, and he bone–pa ella endon–bone (BPTB) g a was ixed wi h i anium in e e ence sc ews. 9 In he s udy wi h se ial MRI ollow-up, he SB ACLRs we e also com- ple ed using he ans ibial echnique, and bo h BPTB g a s and hams ing endon g a s we e used wi h bioab- so bable L-lac ide, D-lac ide, and ime hylene ca bona e sc ews. 35 Despi e he simila i ies in he ope a i e echni- ques, he CT s udy showed inc easing unnel enla gemen up o 2 yea s o ollow-up, bu he MRI s udy showed ha unnels enla ge du ing he i s 6 mon hs and hen s a o na ow un il 2 yea s o ollow-up. 9,35 In s udies on unnel enla gemen a e DB ACLR, he ollow-up imes ha e anged om 8 o 26 mon hs, and enla gemen o he 4 unnels inc eased up o 50%. 1,16,20,23,29,30 We a e no awa e o p e ious s udies ha ha e compa ed 2- and 5-yea pos ope a i e MRI unnel measu emen s a e DB ACLR. Ou esul o unnel na - owing be ween 2- and 5-yea MRIs is simila o he only p e iously published inding o unnel na owing a e SB ACLR wi h sho e ollow-up. 35 In cases wi h conical un- nels in ou s udy, he maximum diame e was measu ed a he la ge unnel ape u e, al hough mos o he ossi ica ion was seen in he na owed dis al pa o he unnel. The me hod o maximum diame e measu emen was chosen ins ead o unnel olume calcula ion o be e ep oducibil- i y and use ulness in clinical wo k. In addi ion, in cases wi h unnel communica ion, he diame e o he common ape u e was used o bo h unnels. Thus, ou esul o unnel na owing unde es ima es he o al amoun o ossi- ica ion. Based on p e ious s udies and ou esul s, a e ACLR, he bone unnels i s enla ge un il 6 mon hs and he ea e slowly na ow be ween 6 mon hs and 2 yea s, and he na owing con inues o a leas 5 yea s a e su ge y. 35 In e es ingly, in ano he s udy wi h 5-yea pos ope a i e MRI, no all unnels we e enla ged, which migh , in ou opinion, e lec ea ly unnel enla gemen and subsequen na owing, esul ing in a nea ly o iginal d ill diame e a 5 yea s. 21 In a p e ious DB ACLR s udy, some unnels we e ully ossi ied as ea ly as 2 yea s a e su ge y, bu in ou indings, he unnels we e enla ged 2 yea s pos ope a- i ely, and only a ew we e ully ossi ied a 5 yea s. 23 Ou conical unnel ossi ica ion pa e n inding is simila o a ecen SB ACLR s udy ha used he same bioabso bable L-lac ide, D-lac ide, and ime hylene ca bon- a e sc ew. 35 Conical unnel shape means ha unnel ape - u es a e he las pa o ossi y. A e DB ACLR, unnel communica ion a he unnel ape u es has been p e iously seen in 10% o 19%o pa ien s in he emu and in 24% o TABLE 3 Biodeg adable Sc ews in Magne ic Resonance Imaging 2y,%5y,% Comple ely isible 100 0 Pa ially isible 0 46 No isible 0 54 Tunnel cys 2 36 Sc ew ossi ica ion 0 19 { Re e ences 1, 13, 16, 20, 21, 23, 30, 32, 35. The O hopaedic Jou nal o Spo s Medicine Tunnel and Sc ew Findings A e DB ACLR 5 29%o pa ien s in he ibia. 19,20,30 In ou s udy, unnel communica ion was also seen, and i inc eased om he 2- o 5-yea e alua ion bu was no associa ed wi h knee laxi y. This inding is simila o a p e ious DB ACLR s udy and con a y o hypo hesized inc eased ins abili y. 6,12,19,26 The abso p ion a e o di e en biodeg adable sc ews is a iable and depends, among o he ac o s, on he ma e ial cons uc and he deg eeo c ys alliza ion. 22,33 In long- e m ollow-up, PLLA sc ews ha e aken 10 o 16 yea s o ully abso b and ossi y, and cys o ma ion has been e- quen bu no associa ed wi h ad e se ou come. 31,33,34 In 5-yea ollow-up, PLLA-hyd oxyapa i e (PLLA-HA) sc ews we e pa ially abso bed and incomple ely ossi ied. 2 In s ud- ies o b- icalsium phospha e PLLA (b-TCP-PLLA) sc ews, almos comple e ossi ica ion was seen 3 o 4 yea s pos op- e a i ely. 3,25 In 2- o 4-yea ollow-up, b-TCP polylac ic-co- glycolic acid (b-TCP-PLGA) sc ews we e pa ially abso bed and no ossi ied. 4,7 In a p e ious s udy o he same L-lac ide, D-lac ide, and ime hylene ca bona e sc ew as used in ou s udy, 78%o he sc ews we e pa ially isible and 15%o pa ien s had a ibial unnel cys in 2-yea ollow- up. 24 In ou s udy, all sc ews we e comple ely isible a 2 yea s and hal o he sc ews we e pa ially isible a 5 yea s. Thus, he abso p ion a e was slowe when com- pa ed wi h he only p e ious s udy on his sc ew bu on he same le el wi h he o he ypes o biodeg adable sc ews. 2-4,7,22,24,25,31,33,34 The sc ews we e equen ly eplaced by a luid- illed cys , bu in ou s udy, hese small cys s we e no associa ed wi h wo se pa ien - epo ed ou comes o ins abili y. The commonly used PLLA sc ews ha e shown a simila 30% o 50%non- symp oma ic cys o ma ion a e in MRI s udies. 31,33 Howe e , in p e ious e ision cases, he L-lac ide, D-lac ide, and ime hylene ca bona e sc ews we e ound o ha e so ened 8 mon hs a e su ge y and o ally abso bed a e 18 mon hs. 17 A leas in he case o his sc ew ype, MRI may unde es ima e he sc ew abso p ion a e, and u he alida ion o MRI indings wi h su gical con i - ma ion is wa an ed. The limi a ions o ou s udy include he mean ime o 44 mon hs be ween he MRI s udies ha p e en ed a mo e de ailed analysis o he changes in he unnels and he sc ews be ween 2 and 5 yea s pos ope a i ely. The o al ollow-up ime also a ied om 46 o 89 mon hs, which inc eased he possibili y ha di e en unnel shapes and sc ew abso p ion indings may e lec di e - en s ages o hese slow p ocesses. The hi d and mos impo an limi a ion is he possible pa ien selec ion bias, as we we e able o e alua e only 31 o 66 pa ien s in 5-yea ollow-up. The emaining pa ien s we e los due o noncom- pliance and geog aphical es ain s. The s eng hs o he s udy a e long ollow-up ime, p ospec i e s udy se ing, and he good image quali y o he 3-T MRI used in he 5-yea e alua ions. CONCLUSION Ou s udy is he i s o use MRI o e alua e unnel changes 5 yea s a e DB ACLR. Tunnel na owing caused by bony ing ow h p og essed slowly be ween 2 and 5 yea s a e su ge y and esul ed in bo h e enly na owed and coni- cal unnels. The biodeg adable in e e ence sc ews, once abso bed, we e eplaced by luid- illed cys s and bone. The MRI indings o unnel communica ion and unnel cys s we e equen bu no associa ed wi h a wo se clin- ical ou come. 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