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Relevant traumatic injury of the knee joint—MRI follow-up after 7–10 years
European Journal of Radiology 72 (2009) 473–479
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European Journal of Radiology journal homepage: www.elsevier.com/locate/ejrad
Relevant traumatic injury of the knee joint—MRI follow-up after 7–10 years Michel D. Crema a,∗ , Monica D. Marra a,1 , A. Guermazi a,2 , Klaus Bohndorf b,3 , Frank W. Roemer a,b,4 a b
Department of Radiology, Boston Medical Center, Boston University Medical School, FGH Building, 3rd floor, 820 Harrison Avenue, Boston, MA 02118, United States Department of Radiology, Klinikum Augsburg, Stenglinstr. 2, 86156 Augsburg, Germany
a r t i c l e
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Article history: Received 15 April 2008 Received in revised form 29 July 2008 Accepted 6 August 2008 Keywords: MRI Knee Trauma Meniscal tear
a b s t r a c t Objective: To evaluate prospectively the history of relevant traumatic knee injuries at least 7 years after trauma by MRI focusing on the development of degenerative changes. Materials and methods: Seventeen patients without baseline degenerative changes had a follow-up knee MRI several years after relevant knee injury (interval baseline—follow-up was 9.1 years, S.D. ±1.3 years). Relevant knee injury was defined as complete cruciate or collateral ligament rupture, traumatic meniscal tear or osteochondral injury. Baseline MRI examinations were evaluated for traumatic ligamentous, chondral, meniscal and osseous lesions. Follow-up MRIs were evaluated for ligamentous and meniscal status, articular surface and incidence of degenerative changes such as cartilage loss, osteophytes and bone marrow lesions. Results: Among the 11 patients who had a complete rupture of the ACL at baseline, 3 (27.3%) presented with cartilage loss. Among the eight patients who had suffered a post-traumatic meniscal tear at baseline, four (50%) presented with cartilage loss at follow-up. Among the five patients who had an osteochondral fracture at baseline, two (40%) presented with cartilage loss at follow-up imaging. Cartilage loss in all cases was observed adjacent to the subregions where meniscal damage and/or osteochondral incongruence was/were present at follow-up imaging. Conclusion: We hypothesize that the post-traumatic or postsurgical meniscal damage and the persistence of an irregular articular surface may have played a role in the subsequent loss of cartilage in our patient population. Published by Elsevier Ireland Ltd.
1. Introduction Knee trauma is very common, especially among the young population, with a yearly incidence of 1.1% [1]. Knee injury is associated with an increased risk for post-traumatic degenerative changes [2–6]. The majority of prospective longitudinal studies have assessed the development of degenerative changes after acute knee trauma using plain film radiographs of the knee [6–8]. Although osteoarthritis is defined by radiographic features such as presence of osteophytosis and joint space narrowing, magnetic resonance imaging (MRI) has a higher sensitivity and specificity for
∗ Corresponding author. Tel.: +1 617 414 4957; fax: +1 617 638 6616. E-mail addresses: [email protected] (M.D. Crema), monica [email protected] (M.D. Marra), [email protected] (A. Guermazi), [email protected] (K. Bohndorf), [email protected] (F.W. Roemer). 1 Tel.: +1 617 414 4959; fax: +1 617 638 6616. 2 Tel.: +1 617 414 3893; fax: +1 617 638 6616. 3 Tel.: +49 821 400 2441; fax: +49 821 400 3312. 4 Tel.: +1 617 414 4954; fax: +1 617 638 6616. 0720-048X/$ – see front matter. Published by Elsevier Ireland Ltd. doi:10.1016/j.ejrad.2008.08.001
demonstrating acute traumatic lesions within the knee and early post-traumatic degenerative changes [9–11]. The aim of this study is to describe the history of relevant traumatic knee injuries 7–10 years after acute knee trauma using MRI and to focus on the development of degenerative changes. To our knowledge there are only few reports in the literature on this particular subject [12–14]. 2. Materials and methods We performed a retrospective review of all written MRI reports of patients who had been referred for an examination of the knee in our institution between January 1995 and March 1999. Of 904 patients who underwent a knee MRI during this period, 253 were referred for assessment of acute knee trauma. All of these patients were examined within 14 days after the trauma. According to several previous reports in the literature, we defined a “relevant” traumatic injury as a traumatic lesion within the knee that may increase the risk of developing premature degenerative changes [12,15–18]: a complete anterior cruciate ligament (ACL) or posterior cruciate ligament (PCL) rupture, complete (grade III) collateral ligament rupture, disruptions of the articular surface including
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chondral or osteochondral fractures and acute traumatic meniscal tears. Patients who reported prevalent degenerative changes such as non-traumatic cartilage loss, osteophytosis and prior meniscectomy were excluded. Eighty patients fulfilled the criteria of having suffered a relevant traumatic knee injury as defined above according to the written radiology report. None of the MRI reports mentioned additional degenerative changes. The study design was approved by the local institutional review board. 2.1. Subjects We were able to contact 42 patients. Nineteen (23.8%) patients agreed to participate in the follow-up examination. The follow-up MRI was offered free of charge, but we could not reimburse the costs of travel or time spent for the examination. Patients gave several reasons for not participating: a convenient examination appointment could not be found, no reimbursement for travel or time could be offered, unwillingness to participate in any clinical studies, patients were symptom-free and not interested, or they had had a pacemaker implantation since the baseline exam. All patients were informed about the possible risks of MRI and signed a consent form prior to the examination. Two patients were excluded from this study after we analyzed baseline and follow-up examinations. One was excluded due to the presence of pre-existing degenerative changes at the baseline examination that were not noted in the original report. The other was excluded due to a partial rupture of the ACL at baseline instead of a complete rupture as described in the initial report. A baseline partial ACL disruption was not considered a relevant traumatic lesion for inclusion in this study. Thus, altogether baseline and follow-up MRI examinations of 17 patients were available for analysis. 2.2. MR imaging Baseline imaging was performed with a 1.5 T MRI (Philips ACSNT, Eindhoven, NL), using a standard knee coil. The sequence protocol at baseline imaging included short tau inversion recovery (STIR) sequences in the sagittal, coronal and axial planes (TR 2580 ms, TE 12 ms, TI 160 ms, 4 mm slice thickness, 0.8 interslice gap, 20 slices, 256 × 203 matrix, 4 numbers of excitations (NEX), 160 mm2 field of view (FOV), echo train length 8); a sagittal T1w sequence (TR 450 ms, TE 15 ms, 4 mm slice thickness, 0.4 interslice gap, 20 slices, 256 × 204 matrix, 2 NEX, 160 mm2 FOV, echo train length 5); and a sagittal T2w sequence (TR 2250 ms, TE 108 ms, 4 mm slice thickness, 0.4 interslice gap, 20 slices, 512 × 256 matrix, 3 NEX, 160 mm2 FOV, echo train length 13). Additional coronal and sagittal T2w 3D gradient echo sequences were acquired for some patients for better visualization of the cartilage (TR 700 ms/TE 18 ms, flip angle 30◦ , 3 mm slice thickness, 0 interslice gap, 28 slices, 512 × 256 matrix, 4 NEX, 160 mm2 FOV). Follow-up examinations were performed with a dedicated 1.0 T open MRI system (OrthOneTM , ONI Medical Systems, Wilmington, MA) with a 160 mm diameter circumferential extremity coil. The sequence protocol at the follow-up examination included triplanar proton density-weighted fat-suppressed (PDFS) sequences (TR 4800 ms, TE 35 ms, 3 mm slice thickness, 0 mm interslice gap, 32 slices, 288 × 192 matrix, 2 NEX, 140 mm2 FOV, echo train length 8) and a sagittal T1w spin echo sequence (TR 660 ms, TE 15 ms, 4 mm slice thickness, 0 mm). In case of marked postsurgical susceptibility artifacts, the PDFS sequences were replaced by STIR sequences (TR 6650 ms, TE 15 ms, TI 100 ms, 3 mm slice thickness, 0 mm interslice gap, 28 slices, 256 × 192 matrix, 2 NEX, 140 mm2 FOV, echo train length 8).
2.3. MR assessment 2.3.1. Baseline Baseline images were interpreted in consensus by three musculoskeletal radiologists (FWR, MDC, and MDM). We did not evaluate the patellofemoral compartment as none of the subjects included in this study presented with patellofemoral injury at baseline. The cruciate ligaments, collateral ligaments, menisci, bone marrow and cartilage of the tibiofemoral compartments were assessed for traumatic injury at baseline using the following grading scheme. The cruciate ligaments were evaluated as either of normal signal and morphology, as a partial rupture or a complete rupture. The collateral ligaments were graded as normal, as a grade I lesion (fluid-equivalent signal surrounding a normal ligament), as a grade II lesion (abnormal signal within the ligament) or as a grade III lesion (complete rupture). The menisci were evaluated by region (anterior horn, body, and posterior horn) as presenting with a normal aspect, intrameniscal degenerative signal change, a single tear, a complex tear, or a displaced tear. Articular surface lesions were subdivided into categories: subchondral impaction, osteochondral depression, osteochondral indentation, detached chondral fracture, or detached osteochondral fracture [19]. Associated subchondral bone contusions were also noted, but not scored for volume. 2.3.2. Follow-up Follow-up images were interpreted in consensus by the same readers. For those patients who underwent knee surgery after baseline imaging, all surgical reports were available. For the cruciate ligaments and collateral ligaments, the presence of a surgical repair was evaluated. If surgical repair was obvious, we evaluated the graft (cruciate) or the ligament (collateral) as presenting with a normal aspect, as of abnormal signal intensity in a continuous graft/ligament or a complete rupture. If surgical repair was absent, we evaluated the ligament as being continuous or ruptured. For the menisci, we evaluated the persistence or absence of baseline tears and the presence of mucoid degeneration, partial meniscectomy and complete meniscectomy. In the cases of baseline disruption of the articular surface, at follow-up the surfaces were graded as being either intact or with persistent osteochondral disruption. Finally, we evaluated the presence of degenerative changes in the tibiofemoral compartments, which included cartilage loss, presence of osteophytes, and presence of degenerative bone marrow lesions (edema and subchondral cysts). These compartments were subdivided into four regions: medial weight-bearing femur, lateral weight-bearing femur, medial tibia, and lateral tibia. The weight-bearing femur was subdivided into central (region covering the menisci) and posterior, and the tibial plateau was divided into the anterior (below the anterior horn of menisci), central (between the horns of menisci), and posterior (below the posterior horn of menisci) subregions. We did not evaluate the femoral trochlear region (anterior) because it is part of the patellofemoral compartment. Cartilage thickness loss was evaluated with the following classification scheme: 0—none, 1—partial thickness loss or 2—full thickness loss. The area of cartilage thickness loss was obtained with measurements in sagittal and coronal planes. Osteophytes and degenerative bone marrow lesions were evaluated with the following classification: 0—none, 1—mild, 2—moderate or 3—large. 3. Results Among the 17 patients, there were 11 men and 6 women. The average patient age at baseline was 33.9 ± 11.9 standard deviation (S.D.) years (range 20–54), and the mean time interval between
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Table 1 Overview of patient demographics, inclusion criteria and follow-up findings Patient
Age (BL)
Gender
Interval BL–FU
Lesions (inclusion criteria)
Degenerative changes at the FU
1 2
33 23
M M
7Y1M 9Y2M
ACL (complete rupture)/MM (single tear) ACL (complete rupture)/MM (single tear)
3 4
29 25
F M
7Y1M 10Y5M
ACL (complete rupture)/MM (single tear) LM (displaced tear)/OCF (osteochondral indentation)
5
35
F
10Y6M
ACL (complete rupture)/MM (complex tear)
6 7 8
23 23 54
M M M
10Y9M 7Y8M 8Y8M
MCL (grade III)/OCF (osteochondral depression) MCL (grade III) ACL (complete rupture)/OCF (osteochondral depression)
9 10 11 12 13 14 15 16 17
32 20 54 45 27 26 28 51 49
F F F M M F M M F
9Y3M 10Y10M 10Y1M 10Y3M 9Y11M 10Y3M 7Y10M 7Y3M 8Y8M
ACL (complete rupture)/PCL (complete rupture)/MCL (grade III) ACL (complete rupture) ACL (complete rupture)/MCL (grade III) LM (single tear)/OCF (osteochondral depression) ACL (complete rupture) ACL (complete rupture) PCL (complete rupture) ACL (complete rupture)/MM (single tear)/OCF (osteochondral depression) LM (complex tear)
Osteophyte (MF—grade 1) Cartilage loss (MT—grade 1), osteophyte (MF—grade 1) – Cartilage loss (LT—grade 1, LF—grade 2), osteophyte (LF—grade 1), bone marrow lesion (LT, LF—grade 1) Cartilage loss (MT, MF—grade 1), osteophyte (MT, MF, LF—grade 1), bone marrow lesion (MT—grade 1) Bone marrow lesion (LT—grade 1) Osteophyte (MT—grade 1) Cartilage loss (LF—grade 1), osteophyte (MF—grade 1) Osteophyte (MF—grade 1) Osteophyte (LT, LF—grade 1) – Osteophyte (LF—grade 1) – – – Osteophyte (MF—grade 1) Cartilage loss (LT—grade 2, LF—grade 1), osteophyte (MF—grade 2, LT, LF—grade 1), bone marrow lesion (LT, LF—grade 1)
Interval between baseline (BL) and follow-up (FU) MRI studies, relevant lesions present at baseline, and degenerative changes detected at follow-up. M: male; F: female; Y: years; M: months; ACL: anterior cruciate ligament; PCL: posterior cruciate ligament; MCL: medial collateral ligament; MM: medial meniscus; LM: lateral meniscus; OCF: osteochondral fracture; MF: medial femur; MT: medial tibia; LF: lateral femur; LT: lateral tibia; (–): no degenerative changes detected.
baseline and follow-up studies was 9 years (Y) and 2 months (M) (range 7Y1M–10Y10M, S.D. ±1Y4M). We will present only findings concerning relevant traumatic lesions in our patient population. All associated partial ligamentary ruptures and bone contusions observed at baseline, which were considered as non-relevant lesions in this study, demonstrated complete resolution at followup. 3.1. Baseline findings Table 1 gives an overview of the patient population, the MRI findings of relevant lesions at baseline and the findings of degenerative changes at follow-up. Eleven patients (64.7%) had a complete rupture of the ACL, two (11.7%) had a complete rupture of the PCL, four (23.5%) had a grade III lesion of the medial collateral ligament (MCL), five (29.4%) had a traumatic tear of the medial meniscus, three (17.6%) had a traumatic tear of the lateral meniscus and five (29.4%) had suffered an osteochondral fracture (one with an osteochondral indentation and four with osteochondral depression fractures). Nine patients (52.9%) had two relevant traumatic findings and two (11.8%) had three relevant traumatic findings at baseline. 3.2. Follow-up findings 3.2.1. Ligaments At follow-up, among the 11 patients who had suffered a complete rupture of the ACL, 10 had undergone surgical repair (8 presented with a normal aspect of the graft, and 2 presented with a continuous graft with abnormal signal intensity). One patient still had a complete rupture of the ligament, with no surgical repair. Both patients who had a complete rupture of the PCL underwent surgical repair, with a normal aspect of the graft at the follow-up examination. All four patients who had a grade III lesion of the MCL
had surgical repair. A continuous ligament with normal signal was observed at follow-up imaging. 3.2.2. Menisci Two of five patients who had a traumatic tear of the medial meniscus and two of three patients who had a traumatic tear of the lateral meniscus had undergone partial meniscectomy (Fig. 1). The remaining four meniscal tears did not change from baseline to follow-up. 3.2.3. Articular surface Among the five patients who had suffered an osteochondral fracture at baseline, one patient showed persistence of an osteochondral indentation (Fig. 2), and another patient showed persistence of an osteochondral depression fracture at follow-up. All other patients who had baseline osteochondral fractures or subchondral impactions had intact articular surfaces at follow-up (Fig. 3). 3.2.4. Degenerative changes at follow-up Five patients (29.4%) had developed cartilage loss and had other associated degenerative changes (osteophytes and/or adjacent subchondral bone marrow lesions) at follow-up. The remaining 12 patients showed no cartilage loss at follow-up. Five (29.4%) of these patients did not present with any degenerative change and seven (41.2%) presented with isolated osteophytes or discrete bone marrow lesions. Among the 11 patients who had suffered a complete rupture of the ACL at baseline, only 3 (27.3%) presented with cartilage loss at follow-up. The two patients who had an initial complete rupture of the PCL and the four patients who had suffered a complete rupture (grade III) of the MCL presented at follow-up with a normal aspect of the ligament or graft and did not show signs of cartilage damage. Among the eight patients who had suffered a traumatic
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Fig. 1. Baseline and follow-up imaging after 8 years 8 months. (A) Baseline coronal T2-weighted gradient echo image demonstrates a post-traumatic complex tear of the body of the lateral meniscus (arrow). (B) Baseline sagittal T2-weighted gradient echo image. Note intact cartilage of the lateral compartment. (C) Follow-up coronal proton density-weighted fat-suppressed (PDFS) images show superficial cartilage loss in the central part of the lateral femur (arrowheads) Note the small size of the body of the lateral meniscus due to a partial meniscectomy (long white arrow). An incident osteophyte is observed in the central part of the lateral femur at follow-up imaging (short white arrow). (D) In addition to femoral cartilage loss sagittal image shows tibial cartilage damage posteriorly. Subchondral degenerative bone marrow lesions are observed adjacent to areas of cartilage loss (arrows).
meniscal tear at baseline, four (50%) presented with cartilage loss at follow-up. Among the five patients who had presented with an osteochondral fracture at baseline, two (40%) had developed cartilage loss at follow-up imaging (one osteochondral depression fracture, one osteochondral indentation). 4. Discussion In this long-term follow-up observation of patients with relevant acute knee trauma, we found degenerative changes only in a minority after a 7–10-year follow-up interval. Baseline meniscal injury and osteochondral fractures appeared to be associated with cartilage loss in the same compartment. Surprisingly, only few patients with complete ACL tears showed cartilage loss at follow-up. Two of the three patients with baseline ligament injury who developed cartilage loss presented with an abnormal aspect of the ACL graft and one presented with a persistent complete rupture of the ligament at follow-up imag-
ing. The remaining patients presented with a normal aspect of the ligament or graft and did not exhibit cartilage loss at the follow-up exam. A recent study by Neuman et al. also reported a favorable outcome after complete ACL disruption. Patients were re-examined after 15 years and found that only the meniscectomized knees had developed radiographic tibiofemoral OA [20]. However, patients with OA and incidental ACL tears not related to apparent trauma appear to be at greater risk for subsequent cartilage loss, which seems to be mediated by concurrent meniscal pathology [21]. We did not observe cartilage loss in those patients who had suffered a complete rupture of the PCL or the MCL. The effect of isolated cruciate ligament ruptures and the effectiveness of surgical repair on preventing long-term degenerative changes after isolated injury remain controversial. A complete ligament disruption seems to increase the risk of subsequent degenerative changes while the data on incomplete rupture is not conclusive [12,15]. A higher incidence of long-term degenerative changes and pain after injury of the cruciate ligaments seems to be attributed
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Fig. 2. Baseline and follow-up imaging after 10 years 5 months. (A) Baseline sagittal PDFS image demonstrates a post-traumatic osteochondral indentation in the anterior region of the lateral tibial plateau (white arrow), associated with adjacent tibial bone contusion. Note the missing anterior horn due to a displaced tear (black arrow). Anterior horn is dislocated dorsally to the posterior horn of the lateral meniscus (white arrowheads). Note intact cartilage at baseline. (B) Follow-up sagittal PDFS image shows persistence of anterior tibial indentation (long white arrow) with adjacent cartilage loss. After meniscal surgery the anterior horn is repositioned in its original location (short white arrow). Note the cartilage loss at the central region of the lateral femur (arrowheads). (C) Follow-up coronal PDFS image demonstrates diffuse cartilage loss in the central region of the lateral femur and tibia (arrowheads). In comparison to the medial meniscal body, the lateral body appears to be smaller and with irregular contour (arrow).
to a higher degree of additional baseline injuries within the knee [15,22]. Concerning traumatic meniscal lesions at follow-up, three patients who presented with a partial meniscectomy of the traumatized meniscus and one who presented with a persistent complex tear demonstrated cartilage loss. It is important to note that the cartilage loss was always observed within the area covered by the affected meniscus. It has been reported that meniscal tears and partial meniscectomy are associated with a high risk of radiographic and symptomatic tibiofemoral osteoarthritis at long-term follow-up [17,23]. Curiously, few patients presented at follow-up with a persistent and/or incident single tear and one presented with a partial meniscectomy did not exhibit adjacent cartilage loss. One explanation for these discrepant findings could be post-traumatic or postsurgical preservation of large parts of the circumferentially oriented fibers of the meniscus. Thus, the substantial meniscal function of shock absorption could remain
and the cartilage protective effect of the meniscus prevailed [24,25]. Concerning traumatic osteochondral lesions, all patients who presented with a persistent incongruent articular surface at followup showed cartilage loss within the same subregion. The remaining patients who showed an intact articular surface in the region of the initial fracture (osteochondral depression fracture) did not demonstrate cartilage loss at follow-up. Thus, the follow-up MR aspect of the articular surface after a traumatic osteochondral lesion seemed to be associated with the cartilage status in our study population. However, only few patients in our population had traumatic osteochondral lesions. It has been reported that the development of degenerative alterations following chondral and osteochondral injuries seems to be associated with the severity, the location and type of the initial traumatic lesion [26,27]. Two additional degenerative features, osteophytes and subchondral bone marrow lesions, were evaluated in our study. The
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Fig. 3. Baseline and follow-up imaging after 7 years 3 months. (A) Patient with complete ACL disruption (not shown). Baseline sagittal PDFS image shows an osteochondral depression in the lateral femur (arrow), associated with adjacent bone contusion. Note also the characteristic bone contusion in the postero-lateral tibia. (B) Follow-up sagittal PDFS image demonstrates an intact articular surface in the lateral femur with a normal appearance of the articular cartilage. Note complete resolution of baseline bone contusions.
significance of isolated small osteophytes, which we observed in six patients at follow-up, remains unclear. Degenerative subchondral bone marrow lesions observed at follow-up developed in areas of adjacent cartilage loss in most cases (75%). These lesions must be distinguished from post-traumatic bone contusions and are often associated with adjacent cartilage loss [28,29]. Several limitations of our study need mentioning. Probably most important is that a significant proportion of our baseline patient population (78%) was not available for follow-up. Possible selection bias may have occurred as patients with continued knee symptoms presumably had more interest in participating. It must further be noted that we presented a very small cohort where estimations of incidence, prevalence, and statistical correlations cannot be performed. We did not analyze other potential risk factors for incidence of degenerative features in our population, such as body mass index, occupational risks, specific injurious activities, nutritional factors, malalignment, and others [30]. We did not analyze clinical features in our population and do not know if the patients with degenerative changes at follow-up were more symptomatic than the patients without signs of early degeneration. Finally, nine patients (52.9%) had two relevant traumatic findings and two (11.8%) had three relevant traumatic findings at baseline. In cases with more than one relevant traumatic lesion in the knee joint it is difficult to decide which one is responsible for the incident degenerative changes. In summary, we presented a long-term follow-up observation of a small patient sample who had suffered acute knee trauma with consequent relevant structural injury in the past. We hypothesize that post-traumatic meniscal damage and the persistence of an irregular articular surface played a role in the development of subsequent adjacent cartilage loss. Although the majority of patients with cartilage loss exhibited an abnormal ACL graft/ligament at follow-up, all these patients also showed concomitant persistent meniscal damage or an incongruent articular surface at follow-up. A longitudinal prospective MRI study in a larger population adjusting for known risk factors of incident osteoarthritis would be of value to assess each structural injury separately as a predictor for the risk of subsequent degenerative changes in the traumatized knee joint.
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European Journal of Radiology journal homepage: www.elsevier.com/locate/ejrad
Relevant traumatic injury of the knee joint—MRI follow-up after 7–10 years Michel D. Crema a,∗ , Monica D. Marra a,1 , A. Guermazi a,2 , Klaus Bohndorf b,3 , Frank W. Roemer a,b,4 a b
Department of Radiology, Boston Medical Center, Boston University Medical School, FGH Building, 3rd floor, 820 Harrison Avenue, Boston, MA 02118, United States Department of Radiology, Klinikum Augsburg, Stenglinstr. 2, 86156 Augsburg, Germany
a r t i c l e
i n f o
Article history: Received 15 April 2008 Received in revised form 29 July 2008 Accepted 6 August 2008 Keywords: MRI Knee Trauma Meniscal tear
a b s t r a c t Objective: To evaluate prospectively the history of relevant traumatic knee injuries at least 7 years after trauma by MRI focusing on the development of degenerative changes. Materials and methods: Seventeen patients without baseline degenerative changes had a follow-up knee MRI several years after relevant knee injury (interval baseline—follow-up was 9.1 years, S.D. ±1.3 years). Relevant knee injury was defined as complete cruciate or collateral ligament rupture, traumatic meniscal tear or osteochondral injury. Baseline MRI examinations were evaluated for traumatic ligamentous, chondral, meniscal and osseous lesions. Follow-up MRIs were evaluated for ligamentous and meniscal status, articular surface and incidence of degenerative changes such as cartilage loss, osteophytes and bone marrow lesions. Results: Among the 11 patients who had a complete rupture of the ACL at baseline, 3 (27.3%) presented with cartilage loss. Among the eight patients who had suffered a post-traumatic meniscal tear at baseline, four (50%) presented with cartilage loss at follow-up. Among the five patients who had an osteochondral fracture at baseline, two (40%) presented with cartilage loss at follow-up imaging. Cartilage loss in all cases was observed adjacent to the subregions where meniscal damage and/or osteochondral incongruence was/were present at follow-up imaging. Conclusion: We hypothesize that the post-traumatic or postsurgical meniscal damage and the persistence of an irregular articular surface may have played a role in the subsequent loss of cartilage in our patient population. Published by Elsevier Ireland Ltd.
1. Introduction Knee trauma is very common, especially among the young population, with a yearly incidence of 1.1% [1]. Knee injury is associated with an increased risk for post-traumatic degenerative changes [2–6]. The majority of prospective longitudinal studies have assessed the development of degenerative changes after acute knee trauma using plain film radiographs of the knee [6–8]. Although osteoarthritis is defined by radiographic features such as presence of osteophytosis and joint space narrowing, magnetic resonance imaging (MRI) has a higher sensitivity and specificity for
∗ Corresponding author. Tel.: +1 617 414 4957; fax: +1 617 638 6616. E-mail addresses: [email protected] (M.D. Crema), monica [email protected] (M.D. Marra), [email protected] (A. Guermazi), [email protected] (K. Bohndorf), [email protected] (F.W. Roemer). 1 Tel.: +1 617 414 4959; fax: +1 617 638 6616. 2 Tel.: +1 617 414 3893; fax: +1 617 638 6616. 3 Tel.: +49 821 400 2441; fax: +49 821 400 3312. 4 Tel.: +1 617 414 4954; fax: +1 617 638 6616. 0720-048X/$ – see front matter. Published by Elsevier Ireland Ltd. doi:10.1016/j.ejrad.2008.08.001
demonstrating acute traumatic lesions within the knee and early post-traumatic degenerative changes [9–11]. The aim of this study is to describe the history of relevant traumatic knee injuries 7–10 years after acute knee trauma using MRI and to focus on the development of degenerative changes. To our knowledge there are only few reports in the literature on this particular subject [12–14]. 2. Materials and methods We performed a retrospective review of all written MRI reports of patients who had been referred for an examination of the knee in our institution between January 1995 and March 1999. Of 904 patients who underwent a knee MRI during this period, 253 were referred for assessment of acute knee trauma. All of these patients were examined within 14 days after the trauma. According to several previous reports in the literature, we defined a “relevant” traumatic injury as a traumatic lesion within the knee that may increase the risk of developing premature degenerative changes [12,15–18]: a complete anterior cruciate ligament (ACL) or posterior cruciate ligament (PCL) rupture, complete (grade III) collateral ligament rupture, disruptions of the articular surface including
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chondral or osteochondral fractures and acute traumatic meniscal tears. Patients who reported prevalent degenerative changes such as non-traumatic cartilage loss, osteophytosis and prior meniscectomy were excluded. Eighty patients fulfilled the criteria of having suffered a relevant traumatic knee injury as defined above according to the written radiology report. None of the MRI reports mentioned additional degenerative changes. The study design was approved by the local institutional review board. 2.1. Subjects We were able to contact 42 patients. Nineteen (23.8%) patients agreed to participate in the follow-up examination. The follow-up MRI was offered free of charge, but we could not reimburse the costs of travel or time spent for the examination. Patients gave several reasons for not participating: a convenient examination appointment could not be found, no reimbursement for travel or time could be offered, unwillingness to participate in any clinical studies, patients were symptom-free and not interested, or they had had a pacemaker implantation since the baseline exam. All patients were informed about the possible risks of MRI and signed a consent form prior to the examination. Two patients were excluded from this study after we analyzed baseline and follow-up examinations. One was excluded due to the presence of pre-existing degenerative changes at the baseline examination that were not noted in the original report. The other was excluded due to a partial rupture of the ACL at baseline instead of a complete rupture as described in the initial report. A baseline partial ACL disruption was not considered a relevant traumatic lesion for inclusion in this study. Thus, altogether baseline and follow-up MRI examinations of 17 patients were available for analysis. 2.2. MR imaging Baseline imaging was performed with a 1.5 T MRI (Philips ACSNT, Eindhoven, NL), using a standard knee coil. The sequence protocol at baseline imaging included short tau inversion recovery (STIR) sequences in the sagittal, coronal and axial planes (TR 2580 ms, TE 12 ms, TI 160 ms, 4 mm slice thickness, 0.8 interslice gap, 20 slices, 256 × 203 matrix, 4 numbers of excitations (NEX), 160 mm2 field of view (FOV), echo train length 8); a sagittal T1w sequence (TR 450 ms, TE 15 ms, 4 mm slice thickness, 0.4 interslice gap, 20 slices, 256 × 204 matrix, 2 NEX, 160 mm2 FOV, echo train length 5); and a sagittal T2w sequence (TR 2250 ms, TE 108 ms, 4 mm slice thickness, 0.4 interslice gap, 20 slices, 512 × 256 matrix, 3 NEX, 160 mm2 FOV, echo train length 13). Additional coronal and sagittal T2w 3D gradient echo sequences were acquired for some patients for better visualization of the cartilage (TR 700 ms/TE 18 ms, flip angle 30◦ , 3 mm slice thickness, 0 interslice gap, 28 slices, 512 × 256 matrix, 4 NEX, 160 mm2 FOV). Follow-up examinations were performed with a dedicated 1.0 T open MRI system (OrthOneTM , ONI Medical Systems, Wilmington, MA) with a 160 mm diameter circumferential extremity coil. The sequence protocol at the follow-up examination included triplanar proton density-weighted fat-suppressed (PDFS) sequences (TR 4800 ms, TE 35 ms, 3 mm slice thickness, 0 mm interslice gap, 32 slices, 288 × 192 matrix, 2 NEX, 140 mm2 FOV, echo train length 8) and a sagittal T1w spin echo sequence (TR 660 ms, TE 15 ms, 4 mm slice thickness, 0 mm). In case of marked postsurgical susceptibility artifacts, the PDFS sequences were replaced by STIR sequences (TR 6650 ms, TE 15 ms, TI 100 ms, 3 mm slice thickness, 0 mm interslice gap, 28 slices, 256 × 192 matrix, 2 NEX, 140 mm2 FOV, echo train length 8).
2.3. MR assessment 2.3.1. Baseline Baseline images were interpreted in consensus by three musculoskeletal radiologists (FWR, MDC, and MDM). We did not evaluate the patellofemoral compartment as none of the subjects included in this study presented with patellofemoral injury at baseline. The cruciate ligaments, collateral ligaments, menisci, bone marrow and cartilage of the tibiofemoral compartments were assessed for traumatic injury at baseline using the following grading scheme. The cruciate ligaments were evaluated as either of normal signal and morphology, as a partial rupture or a complete rupture. The collateral ligaments were graded as normal, as a grade I lesion (fluid-equivalent signal surrounding a normal ligament), as a grade II lesion (abnormal signal within the ligament) or as a grade III lesion (complete rupture). The menisci were evaluated by region (anterior horn, body, and posterior horn) as presenting with a normal aspect, intrameniscal degenerative signal change, a single tear, a complex tear, or a displaced tear. Articular surface lesions were subdivided into categories: subchondral impaction, osteochondral depression, osteochondral indentation, detached chondral fracture, or detached osteochondral fracture [19]. Associated subchondral bone contusions were also noted, but not scored for volume. 2.3.2. Follow-up Follow-up images were interpreted in consensus by the same readers. For those patients who underwent knee surgery after baseline imaging, all surgical reports were available. For the cruciate ligaments and collateral ligaments, the presence of a surgical repair was evaluated. If surgical repair was obvious, we evaluated the graft (cruciate) or the ligament (collateral) as presenting with a normal aspect, as of abnormal signal intensity in a continuous graft/ligament or a complete rupture. If surgical repair was absent, we evaluated the ligament as being continuous or ruptured. For the menisci, we evaluated the persistence or absence of baseline tears and the presence of mucoid degeneration, partial meniscectomy and complete meniscectomy. In the cases of baseline disruption of the articular surface, at follow-up the surfaces were graded as being either intact or with persistent osteochondral disruption. Finally, we evaluated the presence of degenerative changes in the tibiofemoral compartments, which included cartilage loss, presence of osteophytes, and presence of degenerative bone marrow lesions (edema and subchondral cysts). These compartments were subdivided into four regions: medial weight-bearing femur, lateral weight-bearing femur, medial tibia, and lateral tibia. The weight-bearing femur was subdivided into central (region covering the menisci) and posterior, and the tibial plateau was divided into the anterior (below the anterior horn of menisci), central (between the horns of menisci), and posterior (below the posterior horn of menisci) subregions. We did not evaluate the femoral trochlear region (anterior) because it is part of the patellofemoral compartment. Cartilage thickness loss was evaluated with the following classification scheme: 0—none, 1—partial thickness loss or 2—full thickness loss. The area of cartilage thickness loss was obtained with measurements in sagittal and coronal planes. Osteophytes and degenerative bone marrow lesions were evaluated with the following classification: 0—none, 1—mild, 2—moderate or 3—large. 3. Results Among the 17 patients, there were 11 men and 6 women. The average patient age at baseline was 33.9 ± 11.9 standard deviation (S.D.) years (range 20–54), and the mean time interval between
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Table 1 Overview of patient demographics, inclusion criteria and follow-up findings Patient
Age (BL)
Gender
Interval BL–FU
Lesions (inclusion criteria)
Degenerative changes at the FU
1 2
33 23
M M
7Y1M 9Y2M
ACL (complete rupture)/MM (single tear) ACL (complete rupture)/MM (single tear)
3 4
29 25
F M
7Y1M 10Y5M
ACL (complete rupture)/MM (single tear) LM (displaced tear)/OCF (osteochondral indentation)
5
35
F
10Y6M
ACL (complete rupture)/MM (complex tear)
6 7 8
23 23 54
M M M
10Y9M 7Y8M 8Y8M
MCL (grade III)/OCF (osteochondral depression) MCL (grade III) ACL (complete rupture)/OCF (osteochondral depression)
9 10 11 12 13 14 15 16 17
32 20 54 45 27 26 28 51 49
F F F M M F M M F
9Y3M 10Y10M 10Y1M 10Y3M 9Y11M 10Y3M 7Y10M 7Y3M 8Y8M
ACL (complete rupture)/PCL (complete rupture)/MCL (grade III) ACL (complete rupture) ACL (complete rupture)/MCL (grade III) LM (single tear)/OCF (osteochondral depression) ACL (complete rupture) ACL (complete rupture) PCL (complete rupture) ACL (complete rupture)/MM (single tear)/OCF (osteochondral depression) LM (complex tear)
Osteophyte (MF—grade 1) Cartilage loss (MT—grade 1), osteophyte (MF—grade 1) – Cartilage loss (LT—grade 1, LF—grade 2), osteophyte (LF—grade 1), bone marrow lesion (LT, LF—grade 1) Cartilage loss (MT, MF—grade 1), osteophyte (MT, MF, LF—grade 1), bone marrow lesion (MT—grade 1) Bone marrow lesion (LT—grade 1) Osteophyte (MT—grade 1) Cartilage loss (LF—grade 1), osteophyte (MF—grade 1) Osteophyte (MF—grade 1) Osteophyte (LT, LF—grade 1) – Osteophyte (LF—grade 1) – – – Osteophyte (MF—grade 1) Cartilage loss (LT—grade 2, LF—grade 1), osteophyte (MF—grade 2, LT, LF—grade 1), bone marrow lesion (LT, LF—grade 1)
Interval between baseline (BL) and follow-up (FU) MRI studies, relevant lesions present at baseline, and degenerative changes detected at follow-up. M: male; F: female; Y: years; M: months; ACL: anterior cruciate ligament; PCL: posterior cruciate ligament; MCL: medial collateral ligament; MM: medial meniscus; LM: lateral meniscus; OCF: osteochondral fracture; MF: medial femur; MT: medial tibia; LF: lateral femur; LT: lateral tibia; (–): no degenerative changes detected.
baseline and follow-up studies was 9 years (Y) and 2 months (M) (range 7Y1M–10Y10M, S.D. ±1Y4M). We will present only findings concerning relevant traumatic lesions in our patient population. All associated partial ligamentary ruptures and bone contusions observed at baseline, which were considered as non-relevant lesions in this study, demonstrated complete resolution at followup. 3.1. Baseline findings Table 1 gives an overview of the patient population, the MRI findings of relevant lesions at baseline and the findings of degenerative changes at follow-up. Eleven patients (64.7%) had a complete rupture of the ACL, two (11.7%) had a complete rupture of the PCL, four (23.5%) had a grade III lesion of the medial collateral ligament (MCL), five (29.4%) had a traumatic tear of the medial meniscus, three (17.6%) had a traumatic tear of the lateral meniscus and five (29.4%) had suffered an osteochondral fracture (one with an osteochondral indentation and four with osteochondral depression fractures). Nine patients (52.9%) had two relevant traumatic findings and two (11.8%) had three relevant traumatic findings at baseline. 3.2. Follow-up findings 3.2.1. Ligaments At follow-up, among the 11 patients who had suffered a complete rupture of the ACL, 10 had undergone surgical repair (8 presented with a normal aspect of the graft, and 2 presented with a continuous graft with abnormal signal intensity). One patient still had a complete rupture of the ligament, with no surgical repair. Both patients who had a complete rupture of the PCL underwent surgical repair, with a normal aspect of the graft at the follow-up examination. All four patients who had a grade III lesion of the MCL
had surgical repair. A continuous ligament with normal signal was observed at follow-up imaging. 3.2.2. Menisci Two of five patients who had a traumatic tear of the medial meniscus and two of three patients who had a traumatic tear of the lateral meniscus had undergone partial meniscectomy (Fig. 1). The remaining four meniscal tears did not change from baseline to follow-up. 3.2.3. Articular surface Among the five patients who had suffered an osteochondral fracture at baseline, one patient showed persistence of an osteochondral indentation (Fig. 2), and another patient showed persistence of an osteochondral depression fracture at follow-up. All other patients who had baseline osteochondral fractures or subchondral impactions had intact articular surfaces at follow-up (Fig. 3). 3.2.4. Degenerative changes at follow-up Five patients (29.4%) had developed cartilage loss and had other associated degenerative changes (osteophytes and/or adjacent subchondral bone marrow lesions) at follow-up. The remaining 12 patients showed no cartilage loss at follow-up. Five (29.4%) of these patients did not present with any degenerative change and seven (41.2%) presented with isolated osteophytes or discrete bone marrow lesions. Among the 11 patients who had suffered a complete rupture of the ACL at baseline, only 3 (27.3%) presented with cartilage loss at follow-up. The two patients who had an initial complete rupture of the PCL and the four patients who had suffered a complete rupture (grade III) of the MCL presented at follow-up with a normal aspect of the ligament or graft and did not show signs of cartilage damage. Among the eight patients who had suffered a traumatic
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Fig. 1. Baseline and follow-up imaging after 8 years 8 months. (A) Baseline coronal T2-weighted gradient echo image demonstrates a post-traumatic complex tear of the body of the lateral meniscus (arrow). (B) Baseline sagittal T2-weighted gradient echo image. Note intact cartilage of the lateral compartment. (C) Follow-up coronal proton density-weighted fat-suppressed (PDFS) images show superficial cartilage loss in the central part of the lateral femur (arrowheads) Note the small size of the body of the lateral meniscus due to a partial meniscectomy (long white arrow). An incident osteophyte is observed in the central part of the lateral femur at follow-up imaging (short white arrow). (D) In addition to femoral cartilage loss sagittal image shows tibial cartilage damage posteriorly. Subchondral degenerative bone marrow lesions are observed adjacent to areas of cartilage loss (arrows).
meniscal tear at baseline, four (50%) presented with cartilage loss at follow-up. Among the five patients who had presented with an osteochondral fracture at baseline, two (40%) had developed cartilage loss at follow-up imaging (one osteochondral depression fracture, one osteochondral indentation). 4. Discussion In this long-term follow-up observation of patients with relevant acute knee trauma, we found degenerative changes only in a minority after a 7–10-year follow-up interval. Baseline meniscal injury and osteochondral fractures appeared to be associated with cartilage loss in the same compartment. Surprisingly, only few patients with complete ACL tears showed cartilage loss at follow-up. Two of the three patients with baseline ligament injury who developed cartilage loss presented with an abnormal aspect of the ACL graft and one presented with a persistent complete rupture of the ligament at follow-up imag-
ing. The remaining patients presented with a normal aspect of the ligament or graft and did not exhibit cartilage loss at the follow-up exam. A recent study by Neuman et al. also reported a favorable outcome after complete ACL disruption. Patients were re-examined after 15 years and found that only the meniscectomized knees had developed radiographic tibiofemoral OA [20]. However, patients with OA and incidental ACL tears not related to apparent trauma appear to be at greater risk for subsequent cartilage loss, which seems to be mediated by concurrent meniscal pathology [21]. We did not observe cartilage loss in those patients who had suffered a complete rupture of the PCL or the MCL. The effect of isolated cruciate ligament ruptures and the effectiveness of surgical repair on preventing long-term degenerative changes after isolated injury remain controversial. A complete ligament disruption seems to increase the risk of subsequent degenerative changes while the data on incomplete rupture is not conclusive [12,15]. A higher incidence of long-term degenerative changes and pain after injury of the cruciate ligaments seems to be attributed
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Fig. 2. Baseline and follow-up imaging after 10 years 5 months. (A) Baseline sagittal PDFS image demonstrates a post-traumatic osteochondral indentation in the anterior region of the lateral tibial plateau (white arrow), associated with adjacent tibial bone contusion. Note the missing anterior horn due to a displaced tear (black arrow). Anterior horn is dislocated dorsally to the posterior horn of the lateral meniscus (white arrowheads). Note intact cartilage at baseline. (B) Follow-up sagittal PDFS image shows persistence of anterior tibial indentation (long white arrow) with adjacent cartilage loss. After meniscal surgery the anterior horn is repositioned in its original location (short white arrow). Note the cartilage loss at the central region of the lateral femur (arrowheads). (C) Follow-up coronal PDFS image demonstrates diffuse cartilage loss in the central region of the lateral femur and tibia (arrowheads). In comparison to the medial meniscal body, the lateral body appears to be smaller and with irregular contour (arrow).
to a higher degree of additional baseline injuries within the knee [15,22]. Concerning traumatic meniscal lesions at follow-up, three patients who presented with a partial meniscectomy of the traumatized meniscus and one who presented with a persistent complex tear demonstrated cartilage loss. It is important to note that the cartilage loss was always observed within the area covered by the affected meniscus. It has been reported that meniscal tears and partial meniscectomy are associated with a high risk of radiographic and symptomatic tibiofemoral osteoarthritis at long-term follow-up [17,23]. Curiously, few patients presented at follow-up with a persistent and/or incident single tear and one presented with a partial meniscectomy did not exhibit adjacent cartilage loss. One explanation for these discrepant findings could be post-traumatic or postsurgical preservation of large parts of the circumferentially oriented fibers of the meniscus. Thus, the substantial meniscal function of shock absorption could remain
and the cartilage protective effect of the meniscus prevailed [24,25]. Concerning traumatic osteochondral lesions, all patients who presented with a persistent incongruent articular surface at followup showed cartilage loss within the same subregion. The remaining patients who showed an intact articular surface in the region of the initial fracture (osteochondral depression fracture) did not demonstrate cartilage loss at follow-up. Thus, the follow-up MR aspect of the articular surface after a traumatic osteochondral lesion seemed to be associated with the cartilage status in our study population. However, only few patients in our population had traumatic osteochondral lesions. It has been reported that the development of degenerative alterations following chondral and osteochondral injuries seems to be associated with the severity, the location and type of the initial traumatic lesion [26,27]. Two additional degenerative features, osteophytes and subchondral bone marrow lesions, were evaluated in our study. The
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Fig. 3. Baseline and follow-up imaging after 7 years 3 months. (A) Patient with complete ACL disruption (not shown). Baseline sagittal PDFS image shows an osteochondral depression in the lateral femur (arrow), associated with adjacent bone contusion. Note also the characteristic bone contusion in the postero-lateral tibia. (B) Follow-up sagittal PDFS image demonstrates an intact articular surface in the lateral femur with a normal appearance of the articular cartilage. Note complete resolution of baseline bone contusions.
significance of isolated small osteophytes, which we observed in six patients at follow-up, remains unclear. Degenerative subchondral bone marrow lesions observed at follow-up developed in areas of adjacent cartilage loss in most cases (75%). These lesions must be distinguished from post-traumatic bone contusions and are often associated with adjacent cartilage loss [28,29]. Several limitations of our study need mentioning. Probably most important is that a significant proportion of our baseline patient population (78%) was not available for follow-up. Possible selection bias may have occurred as patients with continued knee symptoms presumably had more interest in participating. It must further be noted that we presented a very small cohort where estimations of incidence, prevalence, and statistical correlations cannot be performed. We did not analyze other potential risk factors for incidence of degenerative features in our population, such as body mass index, occupational risks, specific injurious activities, nutritional factors, malalignment, and others [30]. We did not analyze clinical features in our population and do not know if the patients with degenerative changes at follow-up were more symptomatic than the patients without signs of early degeneration. Finally, nine patients (52.9%) had two relevant traumatic findings and two (11.8%) had three relevant traumatic findings at baseline. In cases with more than one relevant traumatic lesion in the knee joint it is difficult to decide which one is responsible for the incident degenerative changes. In summary, we presented a long-term follow-up observation of a small patient sample who had suffered acute knee trauma with consequent relevant structural injury in the past. We hypothesize that post-traumatic meniscal damage and the persistence of an irregular articular surface played a role in the development of subsequent adjacent cartilage loss. Although the majority of patients with cartilage loss exhibited an abnormal ACL graft/ligament at follow-up, all these patients also showed concomitant persistent meniscal damage or an incongruent articular surface at follow-up. A longitudinal prospective MRI study in a larger population adjusting for known risk factors of incident osteoarthritis would be of value to assess each structural injury separately as a predictor for the risk of subsequent degenerative changes in the traumatized knee joint.
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