An extremely rare case of a glomus tumor in the popliteal fossa.

Glomus tumors are the benign perivascular tumors that typically present with hypersensitivity to cold, paroxysmal severe pain, and pinpoint tenderness. This tumor is usually subungual lesions and accounts for 1.6% of all soft-tissue tumors. However, extradigital glomus tumors are extremely rare and can be difficult to diagnose, as they typically have a diameter of less than about 1 cm. We report a glomus tumor in the popliteal fossa of a 17-year-old male patient who experienced severe posterior knee pain while playing sports. A physical examination did not reveal a mass, although a glomus tumor was identified in the popliteal fossa using magnetic resonance imaging. We successfully performed open excision to remove the tumor, and the patient achieved a restored postoperative gait and could perform sports activities with no pain. These tumors are extremely rare in the knee area, and typically have a diameter of less than about 1 cm, which can complicate their diagnosis and treatment, despite the presence of severe pain. Therefore, we recommend that clinicians be aware of extradigital glomus tumors, as careful imaging can facilitate an early diagnosis and treatment.

Mobilization of bone marrow-derived mesenchymal stem cells into the injured tissues after intraarticular injection and their contribution to tissue regeneration.

The purpose of present study was to evaluate active mobilization effect of mesenchymal stem cells (MSCs) into injured tissues after intraarticular injection of MSCs, and to evaluate their contribution to tissue regeneration. MSCs, which were obtained from green fluorescent protein (GFP) transgenic Sprague-Dawley (SD) rat and cultivated, were injected into normal SD rats in which multiple tissues had been injured including anterior cruciate ligament (ACL), medial meniscus, and articular cartilage of the femoral condyles. At 4 weeks after injection of MSCs, fluorescent microscopic observation, immunohistochemical or histological examinations were performed to evaluate mobilization of MSCs into injured tissue and their contribution to tissue regeneration. In the group of 1 x 10(6) MSCs injection, GFP positive cells could mobilize into the injured ACL alone in all 8 knees. In the group of 1 x 10(7) MSCs injection, GFP positive cells were observed in the injured site of ACL in all 8 knees and in the injured site of medial meniscus and cartilage of femoral condyles in 6 of 8 knees. More interestingly, extracellular matrix stained by toluidine blue was present around GFP positive cells in the injured femoral condyles cartilage and medial meniscus, indicating tissue regeneration. Intraarticularly injected MSCs could mobilize into the injured tissues, and probably contributed to tissue regeneration. This study demonstrated the possibility of intraarticular injection of MSCs for the treatment of intraarticular tissue injuries including ACL, meniscus, or cartilage. If this treatment option is established, it can be minimally invasive compared to conventional surgeries for these tissues.

New hamstring fixation technique for medial collateral ligament or posterolateral corner reconstruction using the mosaicplasty system.

In this study, we describe a new hamstring fixation technique with a bone graft using the Mosaicplasty system for the reconstruction of the medial collateral ligament (MCL) or posterolateral corner (PLC) of the knee. In this technique, a cylindrical bone plug (6.5 mm in diameter, 15 mm in length) is harvested from the anatomical femoral attachment of the MCL or popliteal tendon using the Mosaicplasty system. After placing the autologous semitendinosus or gracilis tendon as a graft in the created bone socket, the bone plug is replaced over the graft. The graft is secured with a spike staple after appropriate tension is applied to the graft. This fixation technique can provide rigid and less invasive fixation, because the distance between the fixation sites can be shorter than that in the Endobutton technique. Compared to fixation with only a staple with no bone graft, the bone graft may enhance tendon to bone healing.

Lateral compartment osteoarthritis of the knee after meniscectomy treated by the transplantation of tissue-engineered cartilage and osteochondral plug.

Management of osteoarthritis of the knee after meniscectomy has been challenging, especially for young patients, because articular cartilage has very poor healing capacity because of its lack of vessels, nerve supply, and isolation from systemic regulation. Osteoarthritic lesions often involve both femoral and tibial cartilage, requiring treatments for both lesions. We report the case of a 14-year-old girl with lateral compartment osteoarthritis of the knee after a total meniscectomy of the discoid meniscus, who was successfully treated by the transplantation of both tissue-engineered cartilage made ex vivo for a femoral lesion and an autologous osteochondral plug for a tibial lesion. We treated both femoral and tibial cartilage defects simultaneously with this procedure. We confirmed cartilaginous regeneration in both femoral and tibial lesions at second-look arthroscopy. This procedure is one option to prevent further development of osteoarthritis in young patients.

Meniscal regeneration using tissue engineering with a scaffold derived from a rat meniscus and mesenchymal stromal cells derived from rat bone marrow.

The purpose of this study was to regenerate a meniscus using a scaffold from a normal meniscus and mesenchymal stromal cells derived from bone marrow (BM-MSCs). Thirty Sprague-Dawley rat menisci were excised and freeze-thawed three times with liquid nitrogen to kill the original meniscal cells. Bone marrow was aspirated from enhanced green fluorescent protein transgenic Sprague-Dawley rats. BM-MSCs were isolated, cultured for 2 weeks, and 2 x 10(5) cells were then seeded onto the meniscal scaffolds. Using a fluorescent microscope and immunohistochemical staining, repopulation of enhanced green fluorescent protein positive cells was observed in the superficial zone of the scaffold after 1 week of culture, and then in the deep zone after 2 weeks. At 4 weeks, expression of extracellular matrices was detected histologically and expression of mRNA for aggrecan and type X collagen was detected. Stiffness of the cultured tissue, assessed by the indentation stiffness test, had increased significantly after 2 weeks in culture, and approximated the stiffness of a normal meniscus. From this study, we conclude that a scaffold derived from a normal meniscus seeded with BM-MSCs can form a meniscus approximating a normal meniscus.

Meniscal repair using bone marrow-derived mesenchymal stem cells: experimental study using green fluorescent protein transgenic rats.

Meniscal tears in the avascular zone have very limited potential to heal because of a poor blood supply. Although there have been many attempts to promote the healing potential of the torn meniscus, no established treatments have achieved sufficient meniscal healing. In this study, we evaluated the efficacy of mesenchymal stem cell transplantation as a cell source to promote meniscal healing, using cells from the green fluorescent protein (GFP) transgenic rat and organ culture model. Mesenchymal stem cells from bone marrow were isolated and expanded in monolayer culture. They were embedded in fibrin glue and were transplanted into the meniscal defects of Sprague-Dawley rats. In the control groups, the defects remained untreated, or only fibrin glue without cells was transplanted. The GFP-positive cells enabled us to detect the transplanted cells from recipient cells easily. As a result, transplanted mesenchymal stem cells could survive and proliferate in the meniscal defects in the organ culture model. They also could produce an abundant extracellular matrix stained by toluidine blue around the cells which contributed to meniscal healing in the avascular status. We could detect transplanted GFP cells under a fluorescent microscope until 8 weeks after transplantation. In a clinical situation, mesenchymal stem cell transplantation is a promising new clinical strategy for the treatment of meniscal tears in the avascular zone.