Malignant pigmented villonodular synovitis in the knee - report of a case with rapid clinical progression.

Malignant pigmented villonodular synovitis (PVNS) (or malignant giant cell tumor of tendon sheath (GCTTS) is an extremely rare condition defined as a malignant lesion occurring with concomitant or previously documented PVNS at the same site. To date, only less than 20 cases have been reported in English literatures. We report a case of malignant PVNS in the knee in a 56-year-old woman with unpredictable rapid progression. This case raised a caution that when atypical components in specimens of recurrent benign PVNS are detected, even if low-grade or tiny, both pathologists and surgeons should consider the risk of malignant PVNS, which could display aggressive clinical progression.

Double-bundle ACL reconstruction: influence of femoral tunnel orientation in knee laxity analysed with a navigation system - an in-vitro biomechanical study.

BACKGROUND: This paper reports an in-vitro study for evaluating the influence of the femoral tunnel orientation in anterior cruciate ligament (ACL) double-bundle reconstructions. METHODS: This work describes the experimental protocol and results obtained for six cadaver knees using the FlashPoint optical system (Image Guided, Boulder, Colorado, USA) and a computer-assisted technique for the elaboration of anatomical and kinematic data. Each specimen was examined by the same surgeon in the following steps: (1) intact knee stability was evaluated by performing antero-posterior displacement and internal-external rotation test at 90 degrees ; (2) the ACL was resected and the knee evaluated again; (3) the ACL was reconstructed using the gracilis semi-tendinous tendon (through horizontal tunnels in femur), and the new kinematics recorded; (4) the ACL was reconstructed again with the same tendon, but with a more vertical orientation of the femoral tunnel (vertical tunnel) and kinematics was once more recorded; (5) finally the knee was dissected to digitise the anatomical structures. RESULTS: Off-line computer analysis of the acquired anatomical and kinematic data showed that there was a significant statistical difference (Wilcoxon test with the Montecarlo method for small samples - p = 0.035) between horizontal tunnel (HT) and vertical tunnel (VT) reconstruction both in the antero-posterior test (median antero-posterior displacement in horizontal tunnel was 0.8 mm less than in vertical tunnel reconstruction) and in the internal-external (IE) rotation test (median internal-external rotation in horizontal tunnel reconstruction was 5 degrees less than in vertical tunnel reconstruction). CONCLUSION: The analysis of graft behavior in reconstructed knees compared with normal and ACL-deficient knees suggests that the most horizontal tunnel performed better than the vertical tunnel, thus constraining optimally both antero-posterior and internal-external rotations. This finding suggests that femoral tunnel direction may be an important issue in ACL surgery.

Perioperative d-dimer levels in patients with musculoskeletal tumors.

BACKGROUND: D-dimer (DD) levels have been reported as a sensitive but non-specific indicator for deep vein thrombosis (DVT) and pulmonary embolism (PE). Few reports have examined perioperative DD levels in musculoskeletal tumor. MATERIALS/METHODS: Subjects comprised 77 patients who had undergone oncological resection of musculoskeletal tumor. DD levels were assessed preoperatively and on postoperative days 1 and 7. Multidetector-row computed tomography (MD-CT) was performed to detect DVT/PE for cases with DD level >10.0 microg/ml. RESULTS: Mean preoperative DD level was 0.84 microg/ml. Significant elevation of postoperative DD levels was confirmed. DD levels were significantly changed by various clinical conditions, such as malignancy, age and prosthetic reconstruction. In 4 of 5 cases with postoperative DD levels >10.0 microg/ml, DVT/PE was detected. CONCLUSION: Activation of the coagulation system by surgery and heterogeneity of DD levels under various clinical conditions in musculoskeletal tumor patients were suggested.

Experimental study on thermal welding for the knee meniscal white zone.

It is difficult to repair tears of the meniscus at the white zone by suturing. We considered that there might be an optimal tissue welding temperature when thermally welding the meniscal white zone, so we conducted a thermal welding experiment using bovine and human menisci. The samples prepared after thermal welding were investigated by measuring the tensile strength, analyzing the histological findings of the welded portion and the meniscal parenchyma, and conducting biochemical analyses. In the experiment using human menisci, histological findings were investigated using transmission electron microscopy (TEM). As the findings on the welded tissue in the white zone of the bovine meniscus indicated positive results at 63 degrees C and 69 degrees C, the experiments using human meniscal white zone were conducted at these two temperatures. The highest tensile strength after thermal welding of the human meniscal white zone was 101.4 +/- 2.6 g/cm(2) at 63 degrees C. Although there were no significant differences in the amount of pyridinoline per unit collagen weight [Pyr/Hpr (%)] in the human meniscus after thermal welding between the control group and various temperature groups (55 degrees C, 63 degrees C, 69 degrees C, 75 degrees C), the amount of pyridinoline per unit of collagen weight tended to decline as the welding temperature increased. According to the TEM findings, the internal structure of the nuclei of the cells was preserved in the 63 degrees C group, whereas cells were denatured inside the nuclei in the 69 degrees C group. They exhibited necrosis, making cell regeneration difficult. Therefore, it seems feasible that thermal welding at 63 degrees C can repair tears in the human meniscal white zone.