title: Magnetic resonance imaging analysis of the bioabsorbable Milagro interference screw for graft fixation in anterior cruciate ligament reconstruction.
abstract: Ligament graft fixation with bioabsorbable interference screws is a standard procedure in cruciate ligament replacement. Previous screw designs may resorb incompletely, and can cause osteolysis and sterile cysts despite being implanted for several years. The aim of this study was to examine the in vivo degradation and biocompatibility of the new Milagro interference screw (Mitek, Norderstedt, Germany). The Milagro interference screw is made of 30% ss-TCP (TriCalcium phosphate) and 70% PLGA (Poly-lactic-co-glycolic acid). In the period between June 2005 and February 2006, 38 patients underwent graft fixation with Milagro screws in our hospital. Arthroscopic ACL reconstruction was performed using hamstring tendon grafts in all the patients. MR imaging was performed on 12 randomly selected patients out of the total of 38 at 3, 6 and 12 months after surgery. During the examination, the volume loss of the screw, tunnel enlargement, presence of osteolysis, fluid lines, edema and postoperative screw replacement by bone tissue were evaluated. There was no edema or signs of inflammation around the bone tunnels. At 3, 6 and 12 months, the tibial screws showed an average volume loss of 0, 8.1% (+/-7.9%) and 82.6% (+/-17.2%, P < 0.05), respectively. The femoral screws showed volume losses of 2.5% (+/-2.1%), 31.3% (+/-21.6%) and 92.02% (+/-6.3%, P < 0.05), respectively. The femoral tunnel enlargement was 47.4% (+/-43.8%) of the original bone tunnel volume after 12 months, and the mean tunnel volume of the tibial tunnel was -9.5% (+/-58.1%) compared to the original tunnel. Bone ingrowth was observed in all the patients. In conclusion, the resorption behaviour of the Milagro screw is closely linked to the graft healing process. The screws were rapidly resorbed after 6 months and, at 12 months, only the screw remnants were detectable. Moreover, the Milagro screw is biocompatible and osteoconductive, promoting bone ingrowth during resorption. Tunnel enlargement is not prevented in the first months but is reduced by bone ingrowth after 12 months.
authors.affiliation: Department of Trauma Surgery, Plastic and Reconstructive Surgery, Georg-August-University Goettingen, Robert-Koch-Str. 40, 37075, Goettingen, Germany, khfrosch@med.uni-goettingen.de.
authors.forename: K-H
authors.initials: KH
authors.lastname: Frosch
authors.forename: T
authors.initials: T
authors.lastname: Sawallich
authors.forename: G
authors.initials: G
authors.lastname: Schütze
authors.forename: A
authors.initials: A
authors.lastname: Losch
authors.forename: T
authors.initials: T
authors.lastname: Walde
authors.forename: P
authors.initials: P
authors.lastname: Balcarek
authors.forename: F
authors.initials: F
authors.lastname: Konietschke
authors.forename: K M
authors.initials: KM
authors.lastname: Stürmer
references.citation: Arthroscopy. 1999 Jul-Aug;15(5):474-80
references.pmid: 10424550
references.citation: Arthroscopy. 2006 Nov;22(11):1204-10
references.pmid: 17084298
references.citation: Arthroscopy. 2008 Apr;24(4):441-7
references.pmid: 18375277
references.citation: J Biomed Mater Res A. 2007 Sep 1;82(3):711-22
references.pmid: 17326225
references.citation: Arthroscopy. 2002 Nov-Dec;18(9):E47
references.pmid: 12426556
references.citation: Radiol Med. 2004 Jan-Feb;107(1-2):47-57
references.pmid: 15031696
references.citation: Knee Surg Sports Traumatol Arthrosc. 2002 Mar;10(2):80-5
references.pmid: 11914764
references.citation: Arch Orthop Trauma Surg. 2007 Nov;127(9):769-75
references.pmid: 16937139
references.citation: Arthroscopy. 2000 Apr;16(3):305-21
references.pmid: 10750011
references.citation: Arthroscopy. 1999 Jul-Aug;15(5):481-8
references.pmid: 10424551
references.citation: Knee Surg Sports Traumatol Arthrosc. 2006 Dec;14(12):1245-51
references.pmid: 16710731
references.citation: Arthroscopy. 2006 Aug;22(8):820-6
references.pmid: 16904577
references.citation: Arthroscopy. 2003 Oct;19(8):E1-3
references.pmid: 14551562
references.citation: Orthopedics. 2005 Aug;28(8):779-83
references.pmid: 16119743
references.citation: Arthroscopy. 2004 Feb;20(2):122-8
references.pmid: 14760343
references.citation: Am J Sports Med. 2006 Dec;34(12):2026-37
references.pmid: 17092921
references.citation: Orthopedics. 2008 Jun;31(6):575-9
references.pmid: 18661880
references.citation: Arthroscopy. 2008 Mar;24(3):370.e1-3
references.pmid: 18308192
references.citation: Knee Surg Sports Traumatol Arthrosc. 1999;7(3):138-45
references.pmid: 10401649
references.citation: J Bone Joint Surg Br. 1990 Jul;72(4):592-6
references.pmid: 2199452
references.citation: Arthroscopy. 2000 Jul-Aug;16(5):491-8
references.pmid: 10882444
references.citation: Knee Surg Sports Traumatol Arthrosc. 1998;6(4):231-40
references.pmid: 9826805
references.citation: Radiology. 2002 Nov;225(2):541-50
references.pmid: 12409593
references.citation: Am J Sports Med. 2006 Jul;34(7):1164-9
references.pmid: 16493172
references.citation: Arthroscopy. 2006 Sep;22(9):993-9
references.pmid: 16952730
references.citation: J Biomed Mater Res A. 2007 Oct;83(1):41-51
references.pmid: 17377968
references.citation: Arthroscopy. 2005 Jun;21(6):707-10
references.pmid: 15944627