Masakazu Kuriwaka

Reconstruction of the anterior cruciate ligament: SINGLE- VERSUS DOUBLE-BUNDLE MULTISTRANDED HAMSTRING TENDONS

A total of 108 patients with unilateral instability of the knee, associated with rupture of the anterior cruciate ligament, was prospectively randomised for arthroscopic single- or double-bundle reconstruction of the ligament using hamstring tendons. The same post-operative rehabilitation protocol was used for all. The patients were followed up for a mean of 32 months (24 to 36). We measured the anterior laxity and joint position sense at different angles of flexion of the knee to determine whether both bundles in the double-bundle reconstruction contributed to the stability of the joint and proprioception. No significant difference was found between the two groups with regard to anterior laxity measured by the KT-2000 arthrometer with the knee at 20 degrees or 70 degrees flexion nor with regard to proprioception. A notchplasty was required less often in the double- compared with the single-bundle reconstruction. We did not find any advantage in a double-bundle as opposed to a single-bundle reconstruction in terms of stability or proprioception.

Mechanoreceptors in the anterior cruciate ligament contribute to the joint position sense.

We have investigated the correlation between the number of mechanoreceptors in anterior cruciate ligament (ACL) remnants and the joint position sense just before an ACL reconstruction in 29 patients. The number of mechanoreceptors was evaluated histologically, using the Gairns gold chloride method. Mechanoreceptors were also found in patients who had a long interval between injury and the operation. A joint position sense test was done within 3 days before surgery. We found a positive correlation between the number of mechanoreceptors and accuracy of the joint position sense, suggesting that proprioceptive function of the ACL is related to the number of mechanoreceptors. Therefore, we should consider preserving ACL remnants during ACL reconstruction.

Harvesting hamstring tendons for ACL reconstruction influences postoperative hamstring muscle performance

IntroductionAnterior cruciate ligament (ACL) reconstruction using hamstring tendons has recently received attention because of less donor site morbidity. It has been reported that harvesting hamstring tendons has little effect on postoperative hamstring muscle performance based on the peak torque value of the hamstring strength. However, recent studies have clarified some adverse effects of harvesting hamstring tendons. There is still argument about the influences of harvesting hamstring tendons on postoperative hamstring muscle performance. The purpose of this study was to evaluate the postoperative hamstring muscle performance measured by various parameters after harvesting hamstring tendons for ACL reconstruction.Patients and methodsWe evaluated the postoperative hamstring muscle performance after harvesting hamstring tendons in 58 patients who underwent ACL reconstruction. We assessed peak torque value, total work, and peak torque angle in the isokinetic hamstring strength test and active knee flexion angle. We classified the patients into three groups according to the type of hamstring used for ACL reconstruction: 1) the autologous semitendinosus tendon (ST); 2) the autologous ST and the gracilis tendon, which were harvested from the ipsilateral knees; and 3) allogeneic fascia lata.ResultsThis study clearly demonstrated that the peak torque value and total work in the patients in each group compared to preoperative normal knees were not statistically different; however, the more hamstring tendons were harvested, the more loss of active knee flexion angle was observed and the more the peak torque angle was shifted to a shallow angle, suggesting that the hamstring strength might be weaker at the deep flexion angle.ConclusionPhysicians should recognize that the ACL reconstruction using autologous hamstring tendons is not appropriate for sportsmen or women who are required to flex their knees deeply or powerfully in their performance.

Optimum combination of monolayer and three-dimensional cultures for cartilage-like tissue engineering.

The autologous chondrocyte transplantation technique has been introduced for the repair of articular cartilage defects. The advantage of transplanting chondrocytes cultured in suspension includes the in vitro expansion of cell numbers. However, the disadvantages include the potential leakage of cells from defects, dedifferentiation of cellular phenotype, and uneven distribution of cells. Transplantation of chondrocytes cultured in collagen gel resolves those problems. However, the expansion of cells in three-dimensional culture is more difficult than in monolayer culture, and for practical reasons only limited numbers of chondrocytes can be obtained from an unloaded area of the knee. To develop a method for the production of high-quality cultured grafts, we investigated the combination of monolayer culture for cell expansion and three-dimensional culture for maintenance of cell phenotype. Articular chondrocytes from rabbits were divided into four groups, exposed to various combinations of culture conditions, and cultured for a total of 3 weeks. Each group was evaluated histologically, biochemically, and biomechanically. Our findings showed that the combination of 2 weeks of monolayer culture followed by 1 week of three-dimensional culture resulted in the highest chondroitin sulfate levels, sufficient cell numbers, and adequate stiffness of the chondrocyte-collagen composites, giving optimal graft preparation.

Determination of time of biologic fixation after anterior cruciate ligament reconstruction with hamstring tendons.

Background It has been unclear when a hamstring tendon graft becomes biologically fixed in the bone tunnel after anterior cruciate ligament reconstruction. Hypothesis Postoperative biomechanical testing and magnetic resonance images can indicate biologic fixation of the graft in the femoral bone tunnel. Study Design Prospective cohort study. Methods Sixty-four patients were evaluated by serial biomechanical testing, magnetic resonance imaging, and second-look arthroscopy 2 years after surgery. Biologic fixation of the graft was confirmed radiographically by injecting a contrast medium into the femoral bone tunnel. Results Forty-two stable knees with graft fixation maintained a high stiffness (120% of normal) and showed low signal intensity in an early postoperative magnetic resonance image (12 ± 8 months). Fourteen stable knees without graft fixation had gradually increased anterior displacement with nearly normal stiffness and high signal intensity. Five unstable knees with graft fixation retained low stiffness (70%) and showed late low signal intensity at 20 ± 9 months. Three unstable knees without biologic fixation had rapidly increased anterior displacement, with half the stiffness of a normal knee. Conclusion Postoperative low stiffness and high signal intensity might indicate late biologic graft fixation, predicting a possibility of postoperative anterior knee instability.