Magnetic resonance imaging aspects after surgical repair of knee cartilage: pictorial essay

Radiologists should be familiar with the main techniques of knee cartilage repair and the imaging methods available for its evaluation, in order to optimize the postoperative follow-up of patients. The objective of this study was to present a series of clinical cases seen at our facility, illustrating the main techniques necessary for the repair of knee cartilage, as well as the magnetic resonance imaging techniques used in the postoperative evaluation and the relevant radiological findings.

Keywords:
Knee; Cartilage; Magnetic resonance imaging

Authorship

Anthony Reis Mello Souza

Departamento de Imagem - Hospital Israelita Albert Einstein, São Paulo, SP, Brazil.Hospital Israelita Albert EinsteinBrazilSão Paulo, SP, BrazilDepartamento de Imagem - Hospital Israelita Albert Einstein, São Paulo, SP, Brazil.

a https://orcid.org/0000-0002-7113-6189;

http://orcid.org/0000-0002-7113-6189

Adham do Amaral e Castro Correspondence: Dr. Adham do Amaral e Castro. Departamento de Imagem - Hospital Israelita Albert Einstein. Avenida Albert Einstein, 627, Vila Leonor. São Paulo, SP, Brazil, 05652-901. Email: adham.castro@gmail.com.

b https://orcid.org/0000-0003-0649-3662;

http://orcid.org/0000-0003-0649-3662

Eduardo Kaiser Ururahy Nunes Fonseca

c https://orcid.org/0000-0002-0233-0041;

http://orcid.org/0000-0002-0233-0041

Letícia Maria Araújo Oliveira Nunes

d https://orcid.org/0000-0002-4079-3813;

http://orcid.org/0000-0002-4079-3813

Eduardo Baptista

e https://orcid.org/0000-0002-7167-194X;

http://orcid.org/0000-0002-7167-194X

Luiz Guilherme de Carvalho Hartmann

f https://orcid.org/0000-0003-4854-9193.

http://orcid.org/0000-0003-4854-9193

Correspondence: Dr. Adham do Amaral e Castro. Departamento de Imagem - Hospital Israelita Albert Einstein. Avenida Albert Einstein, 627, Vila Leonor. São Paulo, SP, Brazil, 05652-901. Email: adham.castro@gmail.com.

a
https://orcid.org/0000-0002-7113-6189;

b
https://orcid.org/0000-0003-0649-3662;

c
https://orcid.org/0000-0002-0233-0041;

d
https://orcid.org/0000-0002-4079-3813;

e
https://orcid.org/0000-0002-7167-194X;

f
https://orcid.org/0000-0003-4854-9193.

SCIMAGO INSTITUTIONS RANKINGS

Figures

Figures (13)

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Figure 1
Modified Outerbridge classification.

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Figure 2
Illustration of the microfracture steps. Debridement to create a stable margin in the cartilage; curettage of the calcified cartilage layer; penetration of the subchondral bone with a hole punch to produce communications with the bone marrow; the resulting clot contains mesenchymal stem cells, which treat the defect by forming fibrocartilage.

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Figure 3
A 26-year-old man submitted to microfracture. T2-weighted fat-saturated MRI sequences. Preoperative axial image (A) showing a deep chondral lesion in the center of the femoral trochlea (arrow). Follow-up imaging at seven months of the procedure: sagittal and axial images (B and C, respectively), showing the microfracture trajectories, together with subchondral edema (arrows) and fibrocartilaginous tissue filling the chondral lesion site.

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Figure 4
The mosaicplasty technique. The first step is debridement of the damaged cartilage, in order to stabilize the margins. Osteochondral cylinders are collected from the non–weight-bearing regions of the knee. At the site of the cartilage defect, cylindrical containers are created to receive the osteochondral grafts.

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Figure 5
A 39-year-old man who underwent arthroscopic mosaicplasty on the lateral aspect of the patella, with a favorable evolution. Axial T2-weighted fat-saturated MRI sequences, obtained one year after the procedure, demonstrate a nearly completely filled defect, with only a small central incongruity on the articular surface (arrow in A) and minimal osteochondral irregularity at the graft collection site on the lateral aspect of the femoral trochlea (arrow in B).

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Figure 6
Repair by stem-cell regeneration. The first surgical procedure is arthroscopic. Cartilage is harvested from the non–weightbearing area. The tissue is prepared, and the released chondrocytes are expanded. This process can occur in two ways: in a 3D alginate culture or on a synthetic plate, for matrix-assisted autologous chondrocyte transplantation (MACT). The second procedure is open surgery. Initially, the damaged cartilage is debrided. Cultured chondrocytes can be implanted as a high-density suspension of expanded chondrocytes under a periosteal or collagen flap. There is another technique in which chondrocytes are released into the defect from the cultured plate. There is no need for sutures. c-ACI, collagen-autologous chondrocyte implantation; p-ACI, periosteal-autologous chondrocyte implantation.

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Figure 7
A 25-year-old woman submitted to arthroscopic injection of autologous mesenchymal stem cells into the medial aspect of the patella. Sagittal T2- weighted fat-saturated MRI sequences. Preoperative sequence (A) showing the lesion, with deep chondral fissures (arrows). Sequence obtained one week after the procedure (B), showing bone and soft-tissue edema adjacent to the repair zone (arrows), with mild joint effusion. Sequence obtained four months later (C), showing slightly irregular fibrocartilaginous tissue, with deep fissures, in the repair zone (arrows), without subchondral edema.

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Figure 8
A 10-year-old boy submitted to surgical fixation of the chondral fragment. Coronal T2-weighted fat-saturated MRI sequences. Preoperative sequence (A) showing osteochondral involvement accompanied by bone marrow edema, without detachments in the central part of the weight-bearing area of the medial femoral condyle. Sequence obtained eight months after the procedure (B), showing a linear area of high signal intensity (arrow) at the subchondral cartilage/ bone interface in the inner portion of the lesion focus, representing granulation tissue. A linear area of low signal intensity at the most anterior margin of the cartilage in the focus of osteochondral injury, the site of a previous fissure, inferring coaptation, possibly with fibrocartilage tissue.

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Figure 9
The biomembrane procedure. In the first stage of the arthroscopic procedure, the unstable and damaged cartilage is removed until regular margins are achieved. An exact impression of the defect is made using sterile aluminum foil. The model is removed and placed into the biomembrane, which is then cut out to match. In the second stage of the arthroscopic procedure, the subchondral bone at the base of the lesion is perforated from the periphery of the lesion toward the center. Fibrin glue is applied directly to the subchondral bone surrounding the perforations. The membrane, already cut to the size and shape of the lesion, is then placed in the defect, its porous face in contact with the bone surface.

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Figure 10
A 31-year-old man submitted to the biomembrane procedure. Postoperative axial T2-weighted fat-saturated MRI sequence (A) showing patellar chondropathy characterized by sparse foci of altered signal intensity, slight narrowing with superficial irregularities in the medial aspect of the vertex and deep fissure in its middle third, accompanied by mild subchondral bone edema. Signs of chondroplasty in the sulcus (arrow) and beginning of the aspects of the femoral trochlea, with a thin collagen membrane and narrow, irregular fibrocartilaginous tissue covering the subchondral bone, which is also irregular, with foci of edema. A T1-weighted sequence acquired at two months after the procedure (B), showing the area where the membrane joins the adjacent cartilage, where there is a slight change in signal intensity (arrow).

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Figure 11
Axial MRI T2 mapping showing normal stratification of the patellofemoral cartilage surface.

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Figure 12
Axial T2 mapping showing stratification of the cartilage in the region where chondral manipulation was performed, similar to the hyaline cartilage of the adjacent healthy femoral trochlea.

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Figure 13
A 39-year-old patient who underwent mosaicplasty with favorable evolution (the same described in Figure 5). T2 mapping shows the stratification of the cartilage surface in the repair zone (arrow), similar to the normal hyaline cartilage in the adjacent aspect of the patella.

Figure 1 Modified Outerbridge classification.

Figure 2 Illustration of the microfracture steps. Debridement to create a stable margin in the cartilage; curettage of the calcified cartilage layer; penetration of the subchondral bone with a hole punch to produce communications with the bone marrow; the resulting clot contains mesenchymal stem cells, which treat the defect by forming fibrocartilage.

Figure 3 A 26-year-old man submitted to microfracture. T2-weighted fat-saturated MRI sequences. Preoperative axial image (A) showing a deep chondral lesion in the center of the femoral trochlea (arrow). Follow-up imaging at seven months of the procedure: sagittal and axial images (B and C, respectively), showing the microfracture trajectories, together with subchondral edema (arrows) and fibrocartilaginous tissue filling the chondral lesion site.

Figure 4 The mosaicplasty technique. The first step is debridement of the damaged cartilage, in order to stabilize the margins. Osteochondral cylinders are collected from the non–weight-bearing regions of the knee. At the site of the cartilage defect, cylindrical containers are created to receive the osteochondral grafts.

Figure 5 A 39-year-old man who underwent arthroscopic mosaicplasty on the lateral aspect of the patella, with a favorable evolution. Axial T2-weighted fat-saturated MRI sequences, obtained one year after the procedure, demonstrate a nearly completely filled defect, with only a small central incongruity on the articular surface (arrow in A) and minimal osteochondral irregularity at the graft collection site on the lateral aspect of the femoral trochlea (arrow in B).

Figure 6 Repair by stem-cell regeneration. The first surgical procedure is arthroscopic. Cartilage is harvested from the non–weightbearing area. The tissue is prepared, and the released chondrocytes are expanded. This process can occur in two ways: in a 3D alginate culture or on a synthetic plate, for matrix-assisted autologous chondrocyte transplantation (MACT). The second procedure is open surgery. Initially, the damaged cartilage is debrided. Cultured chondrocytes can be implanted as a high-density suspension of expanded chondrocytes under a periosteal or collagen flap. There is another technique in which chondrocytes are released into the defect from the cultured plate. There is no need for sutures. c-ACI, collagen-autologous chondrocyte implantation; p-ACI, periosteal-autologous chondrocyte implantation.

Figure 7 A 25-year-old woman submitted to arthroscopic injection of autologous mesenchymal stem cells into the medial aspect of the patella. Sagittal T2- weighted fat-saturated MRI sequences. Preoperative sequence (A) showing the lesion, with deep chondral fissures (arrows). Sequence obtained one week after the procedure (B), showing bone and soft-tissue edema adjacent to the repair zone (arrows), with mild joint effusion. Sequence obtained four months later (C), showing slightly irregular fibrocartilaginous tissue, with deep fissures, in the repair zone (arrows), without subchondral edema.

Figure 8 A 10-year-old boy submitted to surgical fixation of the chondral fragment. Coronal T2-weighted fat-saturated MRI sequences. Preoperative sequence (A) showing osteochondral involvement accompanied by bone marrow edema, without detachments in the central part of the weight-bearing area of the medial femoral condyle. Sequence obtained eight months after the procedure (B), showing a linear area of high signal intensity (arrow) at the subchondral cartilage/ bone interface in the inner portion of the lesion focus, representing granulation tissue. A linear area of low signal intensity at the most anterior margin of the cartilage in the focus of osteochondral injury, the site of a previous fissure, inferring coaptation, possibly with fibrocartilage tissue.

Figure 9 The biomembrane procedure. In the first stage of the arthroscopic procedure, the unstable and damaged cartilage is removed until regular margins are achieved. An exact impression of the defect is made using sterile aluminum foil. The model is removed and placed into the biomembrane, which is then cut out to match. In the second stage of the arthroscopic procedure, the subchondral bone at the base of the lesion is perforated from the periphery of the lesion toward the center. Fibrin glue is applied directly to the subchondral bone surrounding the perforations. The membrane, already cut to the size and shape of the lesion, is then placed in the defect, its porous face in contact with the bone surface.

Figure 10 A 31-year-old man submitted to the biomembrane procedure. Postoperative axial T2-weighted fat-saturated MRI sequence (A) showing patellar chondropathy characterized by sparse foci of altered signal intensity, slight narrowing with superficial irregularities in the medial aspect of the vertex and deep fissure in its middle third, accompanied by mild subchondral bone edema. Signs of chondroplasty in the sulcus (arrow) and beginning of the aspects of the femoral trochlea, with a thin collagen membrane and narrow, irregular fibrocartilaginous tissue covering the subchondral bone, which is also irregular, with foci of edema. A T1-weighted sequence acquired at two months after the procedure (B), showing the area where the membrane joins the adjacent cartilage, where there is a slight change in signal intensity (arrow).

Figure 11 Axial MRI T2 mapping showing normal stratification of the patellofemoral cartilage surface.

Figure 12 Axial T2 mapping showing stratification of the cartilage in the region where chondral manipulation was performed, similar to the hyaline cartilage of the adjacent healthy femoral trochlea.

Figure 13 A 39-year-old patient who underwent mosaicplasty with favorable evolution (the same described in Figure 5). T2 mapping shows the stratification of the cartilage surface in the repair zone (arrow), similar to the normal hyaline cartilage in the adjacent aspect of the patella.

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Magnetic resonance imaging aspects after surgical repair of knee cartilage: pictorial essay

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[1] Correspondence: Dr. Adham do Amaral e Castro. Departamento de Imagem - Hospital Israelita Albert Einstein. Avenida Albert Einstein, 627, Vila Leonor. São Paulo, SP, Brazil, 05652-901. Email: adham.castro@gmail.com.