Ryosuke Kuroda

Evaluation of Hamstring Strength and Tendon Regrowth After Harvesting for Anterior Cruciate Ligament Reconstruction

Background It is generally thought that tissue regeneration and good functional recovery can be expected after anterior cruciate ligament reconstruction using the hamstring tendons. However, persistent strength deficit in deep knee flexion has also been reported. Hypothesis Morphologic regeneration of the harvested hamstring tendon is not necessarily associated with its functional recovery. Study Design Retrospective follow-up study. Method Twenty-eight patients who underwent anterior cruciate ligament reconstruction with hamstring graft were evaluated after a minimum period of 2 years. Status of tendon regrowth was assessed by magnetic resonance imaging. To specifically analyze the functional deficit after graft harvest, the isometric hamstring strength was examined in a sitting position at 90° of flexion and a prone position at 90° and 110° of flexion. Then, the strength data were correlated with the extent of tendon regeneration. Results In 22 of the 28 patients, a regrowth of the semitendinosus tendon was found, whereas regeneration of the gracilis tendon was observed in 13 patients. In the evaluation of hamstring strength, the isometric peak torque was reduced to 86.2%, 54.6%, and 49.1%, respectively, in the aforementioned 3 postures as compared with the contralateral side. Conclusions Significant functional deficit of hamstring strength remains regardless of morphologic regeneration.

Prosthetic alignment and sizing in computer-assisted total knee arthroplasty

We implanted 60 posterior stabilized total knee prostheses (P.F.C. Sigma, DePuy, Warsaw, USA). In 30 cases, we used a CT-free navigation system (Vector Vision, Brain LAB, Heimstetten, Germany), and in 30 matched-paired controls, we used a conventional manual implantation. We compared postoperative long-leg radiographs in the two groups. The results revealed a significant difference in favor of navigation. In addition, we compared the preoperative anteroposterior dimension of the femoral condyle with the postoperative value. While there were no significant differences in the preoperative anteroposterior dimension of the femoral condyle between the two groups, the postoperative value in the navigation group was significantly larger than that of the preoperative value. Therefore, surgeons using navigation systems should guard against the possibility of oversizing when determining the size of the femoral component.RésuméNous avons implanté 60 prothèses totales postéro-stabilisées du genou (P.F.C. Sigma, DePuy). Dans 30 cas nous avons utilisé un système de navigation sans scanner (Vector vision R, Laboratoire du Cerveau, Heimstetten, Allemagne) et dans 30 contrôles appairés nous avons utilisé une implantation manuelle habituelle. Nous avons comparé les grandes radiographies postopératoires des membres inférieurs dans les deux groupes. Les résultats ont révélé une différence notable en faveur de la navigation. De plus nous avons comparé la dimension antéro-postérieure du condyle fémoral avant l’intervention avec la valeur postopératoire. Tandis qu’il n’y avait pas de différence notable dans la dimension antéro-postérieure préopératoire du condyle fémoral entre les deux groupes, la valeur postopératoire dans le groupe de la navigation était nettement plus grande que la valeur préopératoire. Par conséquent les chirurgiens qui utilisent des systèmes de navigation doivent prendre garde à ne pas implanter un composant fémoral sur-dimensionné.

The role of cell type in bone healing mediated by ex vivo gene therapy

BackgroundThe ideal cellular vehicle for use in cell-mediated gene therapy to enhance bone healing has not yet been identified. The purpose of this study was to compare the capacity of two types of cells transduced with retro-bone morphogenetic protein 4 (BMP4)—muscle-derived cells (MDCs) and unfractioned bone marrow stromal cells (BMSCs).MethodPrimary rat MDCs and unfractioned rat BMSCs were transduced with a retrovirus to express BMP4. A 7-mm, critical-sized femur defect was created in adult rats, and 5×106 transduced cells were implanted into the femoral defect. Bone healing was monitored radiographically and histologically at 4, 8, and 12 weeks post-implantation.ResultsAll specimens in the MDC-BMP4 group and BMSC-BMP4 group showed a bridging callus at 8 and 12 weeks. At 12 weeks post-implantation the calluses of the MDC-BMP4 femora displayed significantly higher bone photodensity than the BMSC-BMP4 femora (P<0.05). Histomorphometry revealed no difference between the two treatment groups. However, non-union between newly formed and original bone was observed in none of the MDC femora but in six femora from the BMSC-BMP4 group.ConclusionBoth MDCs and unfractioned BMSCs can improve healing of a critical-sized bone defect following transduction of the cells with retroBMP4. However, MDCs appear to yield superior results when compared with BMSCs in terms of improved healing of segmental defects.

Gene therapy to improve osteogenesis in bone lesions with severe soft tissue damage

BackgroundEx vivo gene therapy can induce bone formation when delivery cells carrying the bone morphogenetic protein (BMP) gene are used. The hypothesis for this study was that the cell-mediated gene therapy could improve the healing of bony lesions with severe soft tissue damage.MethodAn animal model with a femoral osteotomy lesion associated with soft tissue damage was developed in rats. Muscle-derived cells, genetically engineered to express BMP4, were inserted within the osteotomy gap. Cells genetically engineered to express LacZ were used for the control group. The groups were subdivided with regard to the fixation method: stable and unstable fixation. The rats were killed for histological and radiographic evaluation 3 and 6 weeks post-surgery.ResultsNo callus formation was found in the control group at any time point, whereas sufficient callus formation appeared in the treatment group after 6 weeks. A bridging callus with woven bone and hypertrophic chondrocytes was achieved in the treatment group when a stable fixation was used, but failed to appear in unstable fixation.ConclusionThe combination of muscle-derived cells expressing BMP4 and a stable fixation were able to bridge the bone defect within 6 weeks, but with prolonged osteochondral ossification. Therefore, the ex vivo gene therapy could be an efficient biological approach to improve the treatment of bone lesions with severe soft tissue damage.

Expression of Transcription Factor Sox9 in Rat L6 Myoblastic Cells

Muscle-derived cells can differentiate into chondrogenic cells. In our present study, we investigated the pattern of expression of Sox9, a transcription factor known to play a key role in chondrogenesis, in a rat myoblastic cell line, L6. In addition, we evaluated expression of type II collagen and myogenic regulatory markers by reverse-transcript polymerase chain reaction. We also investigated the effect of transforming growth factor (TGF)-β 3, which is known to induce chondrogenesis, on Sox9 mRNA expression. On the first day of culture, we observed a high expression of Sox9. However, on the seventh day of culture, there was a decline in the level of Sox9 and type II collagen mRNAs and an increased expression of Myf5 and myogenin mRNAs. Sox9 mRNA expression was increased after stimulation of TGF-β 3 at 2, 6, and 24 hr. Cartilage nodules were observed in L6 cells treated with TGF-β 3 and dexamethasone. These results indicated that L6 myoblasts originally possess the capacity to differentiate into chondrogenic cells, but that capacity is lost as the cells differentiate toward the myogenic lineage. In addition, TGF-β 3 may modulate Sox9 mRNA expression in L6 cells and retain the capacity to differentiate into chondrogenic lineage.

Die Knochenheilung im osteoporotischen Rattenmodell und deren gentherapeutische Behandlungsmöglichkeit mittels retro-BMP4 (Bone morphogenic Protein 4)

Background: Recent studies have shown a delayed fracture healing in ovariectomized rats comparing to normal rats. We hypothesized, that the hard callus formation in a delayed fracture model in osteoporotic rats is reduced comparing to normal bone and can be improved using the cell mediated ex-vivo gene therapy to deliver BMP-4. Method: 60 ten-week-old rats were used. 40 were bilateral ovariectomized (OVX). The remaining 20 rats were used as a normal control group (NC). At the age of 5 month, a mid-diaphyseal femur-osteotomy was created. The ovariectomized rats were divided into two groups: [1] osteoporotic control group (OC), treated with muscle derived cells (MDC) expressing LacZ and [2] osteoporotic treatment group (OT), treated with MDC expressing BMP-4. No cell treatment was made in the NC. Histology and micro-CT was used for evaluation after 4 and 12 weeks. The bone volume (BV) represented the new formed hard callus. Results: The BV after 4 weeks was 2,7 mm3 (sd = 1,3) in the NC-group and significant (p < 0,05) more than in the OC-group with 1,1 mm3 (sd = 0,5). The BV in the OT-group revealed 3,0 mm3 (sd= 1,0) with a significant (p < 0,05) improvement comparing to the OC-group. The endochondral ossification was delayed in osteoporotic bone, whereas the ex-vivo gene therapy could improve near normal. The BV after 12 weeks revealed no differences (p = 0,817) between all groups. Conclusion: The osteoporotic bone has a lower capacity in the early fracture healing comparing to normal bone. The ex-vivo gene therapy using muscle derived cells to deliver BMP4 are able to improve the bone formation in OVX-rats similar to normal rats.