Abstract
Purpose
The purpose of our study was to evaluate the usefulness of magnetic resonance imaging (MRI) in the follow-up of patients treated with collagen meniscus implant (CMI) and to identify MRI patterns suitable for defining its evolution.
Materials and methods
Between March 2001 and June 2003, CMI was performed on 40 patients (27 men and 13 women, age 23–58 years, median 41 years) affected by irreparable medial meniscal lesions. All patients underwent MRI follow-up at 6 months and 1 year and 16 patients 2 years after the operation; 12 patients underwent second-look arthroscopy with implant biopsy. All MRI examinations were performed with a 1.5-T unit using GE T2*, spin-echo (SE) T1, and FatSat fast spin-echo (FSE) DP and T2-weighted sequences, with different orientations. At 24 months, MR arthrography was also performed. Implant evolution was assessed on the basis of MRI direct and indirect criteria. Direct criteria were morphology and signal intensity of the collagen meniscus/residual meniscus complex. Based on these characteristics, three pattern were identified and classified from 1 to 3, where a higher score corresponded to characteristics approaching those of the normal meniscus. Indirect criteria were chondral surface and subchondral bone marrow oedema at implant site and associated synovial pathology.
Results
MRI follow-up at 6 months showed CMI shape and size to be normal (type 3) in 35/40 patients and type 2 in 5/40 patients. CMI signal intensity was type 1 in 32/40 patients and type 2 in 8/40. An interface between prosthetic and native meniscus was identified in 27/40 patients. Chondral lesions were present in 3/40 cases and subchondral bone marrow oedema in 8/40 cases. Reactive synovial effusion was seen in 2/40 patients. MRI follow-up at 12 months showed CMI shape and size to be normal (type 3) in 33/40 patients and type 2 in 7/40. Signal intensity was type 1 in 14/40 patients and type 2 in 26/40 patients. The interface was seen in 19/40 patients. The associated chondral lesions were unchanged, whereas subchondral bone marrow oedema was present in 3/40 patients. No synovial reaction was detected. At 24 months, CMI size was type 3 in 9/16 patients, type 2 in 6/16, and type 1 in one patient in whom the implant could not be identified, as it had been totally resorbed. CMI signal intensity was type 2 in 11/15 and type 3 in 4/16. The interface was identified in seven patients. MR arthrography depicted two additional chondral lesions and enabled correct grading of all lesions. Subchondral bone marrow oedema was present in two patients only.
Conclusions
MRI enables morphological and structural changes of CMI to be monitored over time. Follow-up can be extended beyond 2 years, until the CMI has stabilised and subchondral bone marrow oedema has completely resolved. In the single case with a poor CMI outcome, no related direct or indirect signs were identified.
Riassunto
Obiettivo
Scopo del nostro lavoro è valutare l’utilità della RM nel follow-up di pazienti sottoposti ad impianto di menisco collagenico bovino (CMI) e individuare patterns RM idonei a definirne l’evoluzione.
Materiali e metodi
Quaranta pazienti, 27 maschi e 13 femmine (di età compresa tra 23 e 58 anni, età mediana: 41 anni), sottoposti a impianto di menisco protesico mediale per via artroscopica, hanno eseguito follow-up con RM a 6 mesi e a 1 anno e solo 16 pazienti a 2 anni dall’intervento; in 12 casi è stato eseguito second look artroscopico con prelievo bioptico dell’impianto. Le indagini RM sono state eseguite con tomografo da 1,5 T, il protocollo di studio prevedeva sequenze Ge T2*, SE T1 e FSE FATSAT DP/T2 variamente orientate in tutti i controlli, a 24 mesi si eseguiva anche esame artro-RM. Per la valutazione dell’evoluzione dell’impianto all’indagine RM sono stati considerati criteri diretti: le dimensioni e l’intensità di segnale del complesso menisco collagenico-menisco residuo (in base a queste caratteristiche abbiamo individuato tre tipi di patterns che abbiamo classificato da 1 a 3, con valore tanto più alto quanto più queste si avvicinano alle caratteristiche del menisco normale) e criteri indiretti: superfici condrali e spongiosa ossea sottocondrale in sede di impianto e patologia sinoviale associata.
Risultati
Nel controllo RM a 6 mesi in 35/40 pazienti le dimensioni del CMI erano di tipo 3, in 5/40 di tipo 2. L’intensità di segnale del CMI era di tipo 1 in 32/40 pazienti, di tipo 2 in 8/40. L’interfaccia menisco protesico-menisco nativo era identificabile in 27/40 pazienti. In 3/40 casi è stata evidenziata patologia condrale e in 8/40 casi sofferenza dell’osso subcondrale. In 2/40 pazienti vi era versamento reattivo sinoviale. Nel controllo a 12 mesi la morfologia e le dimensioni dell’impianto erano normali (tipo 3) in 33/40 pazienti, mentre erano di tipo 2 in 7/40. L’intensità di segnale del complesso era di tipo 1 in 14/40 pazienti, di tipo 2 in 26/40 pazienti. L’interfaccia era presente 19/40 pazienti. Le lesioni condrali associate mantenevano aspetto invariato, mentre la sofferenza della spongiosa ossea subcondrale era presente solo in 3/40 pazienti. Non vi era alcuna reazione sinoviale. Nel controllo a 24 mesi in 9/16 pazienti le dimensioni del CMI erano di tipo 3, in 6/16 di tipo 2; in 1 pazienti l’impianto non risultava identificabile, totalmente riassorbito (tipo 1). In 11/15 pazienti l’intensità di segnale del CMI era di tipo 2, mentre in 4/15 era sovrapponibile al menisco normale, di tipo 3. In 7 pazienti l’interfaccia risultava riconoscibile. Con artro-RM è stato possibile rilevare 2 nuovi casi di patologia condrale e definire il corretto grading di tutte le lesioni; solo in 2 pazienti vi era sofferenza della spongiosa ossea subcondrale.
Conclusioni
La RM consente di monitorare nel tempo le variazioni morfologiche e strutturali del CMI, riteniamo che il follow-up possa essere prolungato altre i 2 anni, fino alla “stabilizzazione” del CMI e alla completa risoluzione delle aree di edema della spongiosa ossea subcondrale. Nell’unico caso di evoluzione sfavorevole del CMI non si sono individuati segni diretti o indiretti correlabili.
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Genovese, E., Angeretti, M.G., Ronga, M. et al. Follow-up of collagen meniscus implants by MRI. Radiol med 112, 1036–1048 (2007). https://doi.org/10.1007/s11547-007-0204-y
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DOI: https://doi.org/10.1007/s11547-007-0204-y