Yutaka Otsuka

Stabilometric assessment in the anterior cruciate ligament-reconstructed knee.

OBJECTIVE To examine the hypotheses that anterior cruciate ligament (ACL) reconstruction improves the proprioception of the knee beyond the level of ACL-deficient knees, and that proprioception of the knee correlates well with knee function after ACL reconstruction. PATIENTS Fifty-three patients with ACL-reconstructed knees (22 men and 31 women), 30 physically active healthy volunteers with normal knees (15 men and 15 women), and 30 patients with chronic ACL-deficient knees (15 men and 15 women). MAIN OUTCOME MEASURES A stabilometric assessment, which is considered to be a useful method for evaluating proprioception objectively, was used to compare the one-leg standing balance among three groups; and the relationship between subjective knee function, satisfaction, hop index, knee laxity, isokinetic thigh muscle strength, and one-leg standing balance in the ACL-reconstructed patients was also analyzed. RESULTS The one-leg standing balance of the patients with ACL-reconstructed knees was still impaired compared with that of healthy volunteers (men, p < 0.05; women, p < 0.01), but significantly better than that of the patients with ACL-deficient knees (men, p < 0.001; women, p < 0.001). The one-leg standing balance of the patients with ACL-reconstructed knees correlated well with their functional outcomes such as subjective knee function (men, p < 0.001; women, p < 0.01), satisfaction (men, p < 0.01; women, p < 0.001), and hop index (men, p < 0.001; women, p < 0.001), whereas poor correlation was seen between functional outcomes and mechanical stability. CONCLUSIONS The results suggest that knee function after ACL-reconstruction should be closely related with knee proprioception, and indicate that the usefulness of stabilometric assessment in the evaluation of the function of ACL-reconstructed knees.

Tenosynovial giant-cell tumor arising from the anterior cruciate ligament of the knee

The localized form of tenosynovial giant-cell tumor is rarely located intraarticularly, especially in the large weight-bearing joints. We report the first case of localized, intraarticular tenosynovial giant-cell tumor arising from the anterior cruciate ligament of a knee in which locking and effusion had occurred. After arthroscopic removal of this tumor, the patient became asymptomatic.

Inhibition of Chondrogenesis by Parathyroid Hormone In Vivo During Repair of Full‐Thickness Defects of Articular Cartilage

We studied the effects of parathyroid hormone (PTH) on differentiation of chondroprogenitor cells during the repair of full‐thickness articular cartilage defects. Three‐millimeter cylindrical full‐thickness articular cartilage defects, which are small enough to be resurfaced spontaneously by hyaline cartilage, were created in the femoral trochlea of the rabbit knee. Recombinant human PTH(1–84) (hPTH[1–84]) (25 ng/h) then was administered into the joint cavity with an osmotic pump, or in control animals, saline alone was administered. The animals were killed at 1, 2, 4, and 8 weeks. At 1 week, the defects were filled with undifferentiated cells, regardless of the PTH treatments. By 8 weeks, well‐developed cartilage covered the defects with reconstitution of subchondral bone up to the original bone–articular cartilage junction. In contrast, no evidence of chondrogenic differentiation was seen at any time during the experimental period in the defects treated with PTH. The reparative tissues also were examined immunohistochemically using anti‐proliferating cell nuclear antigen (PCNA) and anti‐PTH/PTH–related peptide (PTHrP) receptor antibodies. Interestingly, the chondro‐progenitor cells that filled the defects expressed PTH/PTHrP receptor, suggesting that these cells are capable of responding to PTH/PTHrP signaling before overt chondrogenesis. Application of PTH did not interfere with proliferation but inhibited chondrogenic differentiation of the cells resulting in the formation of fibrous tissue that lost the expression of PTH/PTHrP receptor within 4 weeks. (J Bone Miner Res 2000;15:253–260)

Leg lengthening and glycosaminoglycans in the rabbit knee

We investigated the effects of tibial lengthening by callotasis on glycosaminoglycan (GAG) metabolism of the knee articular cartilage in 30 rabbits. The distraction rate was 1 mm per day. On the right side, the daily distraction was in 2 steps, while on the left it was in 120 steps. The animals were divided into 3 subgroups based on length gain; 10, 20, and 30 percent, respectively. The knee joint fluid and medial tibial cartilage were examined by quantitative analysis of the GAG content and/or synthesis. The immunoreactivity for chondroitin sulfate in the cartilage was also examined by immunohistochemistry. For all length gains, the GAG concentration in the synovial fluid was higher on both sides than in controls, with no difference between sides. The GAG content and synthesis in the cartilage on the 2-step side decreased gradually with increasing length. On the 120-step side, the content did not differ from control values in any length gain, and the level of synthesis at 20 and 30 percent lengthening was higher than the control level. Our findings indicate that the alterations in GAG metabolism are attributable to increased mechanical stress on the articular cartilage, suggesting a moderate increase on the 120-step side compared to an excessive one on the 2-step side.