Ryuji Mori

Clinical significance of magnetic resonance imaging (MRI) for focal chondral lesions

To evaluate the diagnostic potential of magnetic resonance imaging (MRI) and define its role, focal chondral lesions of the femoral surface of the tibiofemoral joint were examined. Full-thickness defects were well detected prospectively (93%) with conventional MRIs initially administered for observation reference of ligaments and menisci. Optimized MRIs, which included right-angled planes to the lesion surface and magnetization transfer contrast (MTC) sequences, delineated the size of lesions (R2 = 0.648,p < 0.0001) and the difference between full-and partial-thickness defects (88% in accuracy). A forward-tilt of 30 degrees to the femoral shaft was the average plane angle that afforded optimal visualization of the chondral lesions. Our findings advocate that routine MRIs are sufficient in detecting severe chondral lesions that require further examination, and the optimized images are highly useful in facilitating the recently developed therapeutic approaches and follow-up studies for articular cartilage defects.

Treatment of growth plate injury with autogenous chondrocytes: a study in rabbits.

We designed this study to investigate transplantation of autogenous chondrocytes cultured in atelocollagen gel to treat the injured growth plate. An experimental model of growth arrest was made by resecting the medial two thirds of the left proximal tibial physis in 8-10-week-old Japanese white rabbits. Autogenous chondrocytes, which had been harvested from cartilage of the knee joints, embedded in atelocollagen gel, and cultured for a week, were transplanted into the defect in the growth plate. In two other experimental groups, we transplanted autogenous fat tissue into the same defects, or left them empty. Histological and radiographic examinations were done before and after transplantation at various times up to 52 weeks postoperatively. The histological study showed that grafted chondrocytes synthesized extracellular matrix and prevented early ossification and closure of the growth plate, which occurred in the Fat and Defect groups. Angular deformity and length discrepancy in the transplanted group were less than in the control group. Our findings suggest that transplantation of autogenous chondrocytes, cultured in atelocollagen gel, may improve treatment of the injured growth plate.

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.

Unilateral sciatic nerve injury stimulates contralateral nerve regeneration.

Axonal outgrowth in tissue cultures was measured to determine whether unilateral peripheral nerve injuries affect contralateral nerve regeneration. The right sciatic nerves of young male Wistar rats were cut at mid-thigh level. Sham operation as a control was limited to the exposure of the nerve without cutting. At day 6 post-surgery, bilateral L5 dorsal root ganglia (DRG) with attached nerve stumps were resected and cultured. Axonal outgrowth from the nerve stump was measured in situ. The contralateral preparations showed longer outgrowths than controls. Therefore the conditioning effect was not merely restricted to the ipsilateral neurons but also affected undamaged sensory neurons of the contralaretal DRG.

Effect of implant surface roughness on bone fixation: the differences between bone and metal pegs

BackgroundPegs made from cortical bone are used to fix osteochondral fractures and osteochondral dissecans. This technique has many advantages, but it requires long-term immobilization. This study examined the effect of surface roughness on fixation with bone and metal pegs.MethodsPegs with either rough or smooth surfaces were made of cortical bone from Japanese black cattle or from stainless steel (SUS316L). The mean roughness of the rough surface was 15.0 µm, whereas that of the smooth surface was less than 0.6 µm. Pegs were inserted into holes made in the distal femurs of 34 rabbits. At the time of surgery and 14 days later, mechanical tests and micro-computed tomography were performed.ResultsAt the time of surgery, although the push-out forces were less than 0.3 N, the rough surface had a higher value than the smooth surface (P = 0.0002). No difference was observed according to the material (P = 0.54). Fourteen days after surgery, no significant difference was detected in the push-out forces between bone pegs with rough and smooth surfaces (489.0 ± 149.6 vs 478.3 ± 134.4 N (mean ± SD), respectively), but a marked difference was seen with the metal pegs (235.7 ± 115.7 vs 2.2 ± 1.6 N). The bone pegs with rough surfaces made contact with the recipient bone at the high points on the abraded surfaces. After the mechanical tests, the fusion was broken within the new bone for bone pegs with rough or smooth surfaces, but no breakage occurred at the junction of bone peg and new bone.ConclusionThe surface roughness of bone pegs has little effect on bone-to-bone fusion 2 weeks postoperatively, unlike the effect with metal pegs.

Proximal half angle of the screw thread is a critical design variable affecting the pull-out strength of cancellous bone screws

BACKGROUND Screws with strong pull-out strength have been sought for the treatment of cancellous bone. We hypothesized that an obliquely angled screw thread has advantages over conventional vertical thread with a minimal proximal half angle. METHODS Metal and bone screws were made of stainless steel and porcine cortical bone. Their proximal half angle was set at 0 degrees , 30 degrees , or 60 degrees . The screws were inserted into porcine cancellous bone. At 0 degrees , the thread faced the recipient bone vertically. Pullout tests at a rate of 30 mm/min (n=40, each screw type) and microcomputed tomography (n=6) were conducted. FINDINGS The pull-out strength of the screws was maximal at 30 degrees ; 348.8 (SD, 44.1)N with metal and 326.6 (39.4)N with bone. It was intermediate at 0 degrees ; 301.9 (35.9)N with metal and 278.2 (30.6)N with bone. It was minimal at 60 degrees; 126.5 (39.0)N with metal and 174.8 (29.7)N with bone. Cancellous bone was damaged between the threads at 30 degrees , while intact cancellous bone was preserved between the threads at 0 degrees. INTERPRETATION A proximal half angle of around 30 degrees is appropriate because the pullout force is applied to the recipient bone evenly. Commercial cancellous screws can be improved by changing the thread shape to minimize the damage to recipient bone.

Measurement characteristics of a force-displacement curve for chronic patellar instability.

Objective:The clinical diagnosis of patellar instability is subjective, depending on the patients apprehension. We hypothesized that a subjective diagnosis could be supported by a numerical evaluation of the slope, or compliance, of the early phase of a force-displacement curve. Design:Cross-sectional control group comparison. Setting:A university-based sports clinic. Participants:Healthy volunteers (n = 21; 16-40 years old) and patients (n = 21; 15-34 years old) who had a clearly definable diagnosis of unilateral dislocation, followed by chronic anterior knee pain, and positive apprehension signs for more than 6 months, without patella alta or abnormal limb alignment. Intervention:Lateral displacement and reactive forces were measured with a Patella Stability Tester. Main Outcome Measures:Sensitivity in detecting injured knees was defined, with the 95% confidence interval of healthy subjects determined as the normal range. Results:Compliance at 5 mm in displacement showed the highest reproducibility (plot difference of 4.7%) and the highest sensitivity (95%). Among injured knees, compliance was significantly correlated with the activity-related symptoms of the Kujala score (correlation coefficient, −0.61; P = 0.004). Compliance at 5 mm of displacement showed the highest sensitivity (95%) and significant correlation with the activity-related symptoms of the Kujala score among injured knees (coefficient of determination, 0.37; P = 0.004). Conclusions:It is a novel finding that early compliance at 5 mm of displacement showed a correlation with the subjective diagnosis and symptoms.

Comparison of elastic versus rigid suture material for peripheral sutures in tendon repair

BACKGROUND For secure tendon repair, while core suture materials have been previously investigated, the optimum material for peripheral sutures remains unclear. METHODS Transected bovine gastrocnemius tendons were repaired by 2-strand side-locking loop technique using no.2 braided polyblend polyethylene thread for the core suture. Then, 8-strand peripheral cross-stitches were added using either 2-0 rigid sutures (braided polyblend polyethylene) or USP 2-0-sized elastic sutures (nylon). The holding area of each peripheral suture was set at either 3 × 1 mm (shallow holding) or 6 × 2 mm (deep holding). Therefore, 4 groups were compared (the shallow-rigid, deep-rigid, shallow-elastic, and deep-elastic groups). The gap formation, ultimate tensile strength, and suture migration state were measured after 500 cyclic loadings (from 10 to 200 N). METHODS The shallow-rigid group had inferior outcomes compared to the other groups. Although the deep-rigid group had the smallest gap and highest ultimate strength, all peripheral sutures had failure prior to core suture rupture. The two elastic groups showed no significant differences, irrespective of the size of the holding area. Suture migration did not occur in the two elastic groups until the ultimate strength was reached and the core suture ruptured. INTERPRETATION Depending on the suturing method, rigid suture material may not be appropriate for peripheral sutures, when accompanying rigid core suture material. If peripheral sutures can be made with accurate deep holding, rigid suture material will provide favorable outcome. However, in other cases, elastic suture material is considered best for supporting a rigid core suture, as elasticity is another important factor for peripheral sutures.

Modification of Side-locking Loop Suture Technique Using an Antislip Knot for Repair of Achilles Tendon Rupture

The 2-strand side-locking loop suture technique provides high tensile strength and stiffness immediately after surgery, and good clinical results have been reported in the treatment of Achilles tendon rupture. However, it is assumed that major differences exist among surgeons with regard to the optimal tension of the side-locking loop suture. We report a detailed technique to ensure application of a standard tension with the use of the side-locking loop suture in the clinical setting.

Optimum predrilled hole size for bone screws used in osteochondral fixation: in vitro biomechanical study and clinical case.

BackgroundBone screws have a mechanical advantage over bone pegs for fixation of osteochondral fractures. The purpose of this study was to investigate predrilling methods to facilitate bone screw insertion.MethodsThe 162 bone screws (major diameter 3.0 mm; minor diameter 2.5 mm; length 10 mm) used were made from porcine tibial cortical bone. Metal screws of the same design were used as a control. The screws were inserted, without tapping, into predrilled holes of six different sizes (2.4–2.9 mm diameter; 80%–97% of the screw) made in cancellous bone harvested from porcine femoral condyle, and pullout strength was determined. The volumetric bone mineral densities of porcine bones were compared to those of human bones. In a clinical case, an osteochondral fracture of the patella was repaired using three autologous bone screws.ResultsBone screws occasionally broke due to high insertion torque (108–158 N·mm); the incidences were 30% and 19% with the 80% and 83% sized holes, respectively. None of the screws inserted into holes of size ≥ 87% broke, and their insertion torques never exceeded 100 N·mm. Metal screws were inserted without breakage regardless of hole size. Bone screws inserted into 80%-93% holes had the greatest pullout strengths (range 154–165 N), whereas 97% holes had a mean strength of 84 N. Metal screws had large pullout strengths when inserted into 80% and 83% holes (164 and 169 N, respectively). The mineral density of porcine bone was lower than that of human bone (1167 and 1357 mg/cm3 for cortical bone and 193 and 269 mg/cm3 for cancellous bone, respectively). In the clinical case, bone screws were inserted smoothly into 90% holes.ConclusionsThe optimal size of predrilled holes for bone screws (87%–93%) differs from that for metal screws.