Healio
Healio
October 01, 2006
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Navigation-guided Transfer of Cartilage Defect Geometry for Arthroscopic Autologous Chondrocyte Transplantation

Abstract

Cartilage repair with autologous chondrocyte transplantation shows intriguing results. Chondrogenic transplants generally must be inserted into cartilage defects via arthrotomy. The following study showed that arthroscopically- guided navigation could detect and precisely measure the cartilage defect sizes of different geometries. The new cartilage defect-managing module allowed for the precise transfer of navigated cartilage defect geometries for exact size preparation of the tissue engineering scaffolds. Therefore, navigation can help accomplish chondrocyte transplantation arthroscopically.

Human articular cartilage is very limited in its self-repair capacity compared with that in other tissues. Joint cartilage damaged through wear or trauma can result in painful conditions, loss of joint movement, and limb weight-bearing ability. Generally, joint deterioration progresses slowly over many years and episodes of clinical improvement are common.1 Standard clinical therapy procedures for cartilage defect repair, such as tissue response methods and osteochondral transplantation, achieve defect replenishment with biomechanically inferior repair tissue, which in most cases cannot prevent arthrosis.2,3

New treatment options using tissue engineering strategies for cartilage repair such as autologous chondrocyte transplantation (ACT) showed intriguing results.4,5 Chondrocytes are isolated from healthy cartilage tissue in patients undergoing the new procedure. The cells are applied either in a cell suspension or in combination with three-dimensional, bioresorbable tissue engineering scaffolds such as poly (DL-lactide-co-glycolide [PLGA]), gelatine, hyaluronan acid, collagen, fibrin, agarose, and alginate.6,7 The chondrogenic transplants, however, generally need to be inserted in the cartilage defects via arthrotomy.

Navigation has helped to optimize and improve outcomes for certain surgical procedures such as total knee arthroplasty8-12 and anterior cruciate ligament (ACL) reconstruction.13-15 For chondrocyte transplantation, navigation is a useful tool, especially for the assessment of cartilage defect size.16

The overall goals of this study were to assess whether navigation in general could help to enable a minimally invasive approach for ACT arthroscopically and, particularly, whether the new cartilage defect-managing module is able to precisely transfer arthroscopically mapped cartilage defect geometry to the outside scaffold. This would help in preparing a customized graft for an arthroscopical approach for ACT.

Materials and Methods

The newly developed cartilage defect-managing module was tested by two experienced surgeons with expertise in navigated surgery and ACT, and by two technicians with knowledge of navigation.

The tests were conducted with the OrthoPilot navigation system (B. Braun Aesculap, Tuttlingen, Germany). Under arthroscopically comparable conditions, surgeons and technicians navigated exactly defined defect geometries from the cartilage defect-managingtest knee (Figure 1). The navigated dots were represented as small holes at the edges of the defect geometries of the cartilage defect-managing test knee and were palpated dot by dot with the tip of a straight navigated pointer. Three defect geometries were tested: square (length: 10 mm; diagonal: 14.2 mm), mushroom-shaped (width: 15 mm; height: 13.2 mm) and circular (diameter: 10 mm). The navigated defect geometry (height and width) was compared with the exactly defined defect geometries from the cartilage defect-managing test knee.

figure 1a

figure 1b

figure 1c

figure 1d

Figure 1: Transfer of defect geometry. The navigated dots (A), representing the exactly defined defect geometries of the cartilage defect-managing test knee, were transferred to a paper sheet with the OrthoPilot Camera-System (B). This system consisted of an arthroscopic camera, which combined the picture of the OrthoPilot screen to a transfer platform. Note the adjustment in size (red dots; C). While looking to the monitor, the test probands have to connect the navigated dots to achieve the transferred geometries on a paper sheet on the transfer platform (D).

The OrthoPilot camera system, consisting of a standard arthroscopic camera system (DAVID 1-chip camera PV280, B. Braun Aesculap) and a transfer platform, was connected to the OrthoPilot navigation screen. The arthroscopic camera, including the transfer platform, was used in a sterile manner to duplicate clinical conditions. The camera transferred the picture on a sheet of paper (simulating the graft of a matrix-assisted ACT) fixed on the transfer platform to the navigation screen. Equal magnification between the paper and the navigation screen could be obtained by overlapping the four red dots on the OrthoPilot navigation screen with four corresponding dots on the transfer platform by changing the distance of the camera to the transfer platform and by adjusting the magnification of the camera (Figure 1). The transfer of the defect geometries was marked on the paper with a pen, and the navigated dots were followed and adjusted on the navigation screen by four test administrators. The procedure was conducted for all defect geometries (n=3) and repeated three times by all four test administrators. Afterward, all drawn geometries were measured with a ruler, and the experiments were compared with the exactly defined defect geometries of the cartilage defect-managing test knee.

figure 2

figure 2

figure 2

Figure 2: Navigation of defect geometries. Navigated dots represent the transfer of small holes, marking the defect geometries in a cartilage defect-managing test knee. Note the calculated defect geometry.

Results

The defect geometry obtained with the navigation device varied from the exactly defined defect sizes of the cartilage defect-managing knee by ±1 mm, which is inside the OrthoPilot system accuracy of ±1.5 mm (Figure 2).

The transfer from exactly defined defect geometries was recorded with the OrthoPilot camera system (Figure 1). The transfer procedure lasted between 10 seconds and 20 seconds, depending on the complexity of the defect geometry. The measurements of the drawn geometries are summarized in Table 1. The exactly defined defect geometries of the cartilage defect-managing test knee were successfully transferred to the sheets of paper with clinically irrelevant differences in size, thus, the sheets of paper can be used as useful copies of the cartilage defect geometry for preparation of the tissue engineering repair scaffolds (Table 1). Reproducibility of the transfer of different defect geometries was observed (Figure 3).

figure 3

Figure 3: Reproducibility of the defect geometries transferred to the paper sheet.

Discussion

The study shows that navigation can detect and precisely measure cartilage defect sizes of different geometries. The accuracy is within ±1 mm of the clinically relevant level. This accuracy was also seen in earlier studies, particularly for navigation-guided ACL reconstruction.13-15

The new cartilage defect-managing module allowed for the precise transfer of the navigated cartilage defect geometries for exact size preparation of the tissue engineering scaffolds. The navigated cartilage defect geometries were transferred to paper sheets, which are used as a pattern of the cartilage defect geometry for preparation of the tissue engineering repair scaffolds. The entire procedure can be performed in the operating room under sterile conditions. The equipment necessary to perform the described transfer, such as a navigation system or arthroscopic set-up, is primarily available in an operating room of a full-service hospital. The procedure is not extensively time consuming, and the navigation of the defect sizes and transfer of the navigated defect sizes to the paper sheets were estimated with an additional surgery time of approximately 10 minutes. The transfer time for the navigated defect sizes to the paper sheets was short. Additional improvement in the set-up is considered for camera calibration, which must be adjusted manually. The study shows that navigation can help carry out ACT arthroscopically in the very near future. The transfer of the navigated defect geometries can be performed in a clinical, relevant setting.

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References

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Authors

Dr Angele is from the Department of Trauma Surgery, University Hospital Regensburg and Dr Fritz is from the Hospital for Workers Compensation, Department of Trauma Surgery, University of Tübingen, Germany.