Healing of the Torn Anterior Horn of Rabbit Medial Meniscus to Bone after Transtibial Pull-Out Repair and Autologous Platelet-Rich Plasma Gel Injection.

OBJECTIVES: The transtibial pull-out repair (TP) is a relatively new method for treating meniscal root tear; however, the clinical evaluation of its healing effect remains controversial. Due to ethical constraints and limitations of imaging techniques in humans, here we dynamically observe the healing effects of TP and TP with platelet-rich plasma gel (PRG) at the histological level using an animal model. METHODS: Platelet-rich plasma (PRP) and PRG of rabbits were prepared. Platelet-derived growth factor (PDGF) and transforming growth factor-ß1 (TGF-ß1) levels in PRP and PRG were determined using an enzyme-linked immunosorbent assay. A rabbit model of anterior horn tear of the medial meniscus and TP surgery were created. PRG was injected between the anterior horn of the medial meniscus and the tibial tunnel. Rabbits were divided into three groups: the anterior horn tear group (Tear group), the anterior horn tear + TP group (TP group), and the anterior horn tear + TP + PRG group (TP + PRG group). The healing effect was observed dynamically using histopathological studies and biomechanical experiments. RESULTS: The platelet content in PRP significantly increased to approximately 4.57 times that of whole blood. PDGF and TGF-ß1 concentrations in PRG increased to 2.46 and 4.15 times those in PRP, respectively. Hematoxylin and eosin (H&E) and Masson staining showed that the number of inflammatory cells in healing tissue decreased and the collagen fibers significantly increased in TP and TP + PRG groups at 4, 8, and 12 weeks postoperatively compared to those in Tear group. Neatly arranged, interlaced, and dense collagen fibers were found between the anterior horn and bone at 12 weeks. H&E and toluidine blue staining showed that the injury to the femoral condyle cartilage was alleviated. The healing performance in TP + PRG group was better and faster than that in TP group. The maximum tensile fracture strength of the meniscus progressively increased at 8 and 12 weeks postoperatively. CONCLUSIONS: Anterior horn injury of the medial meniscus in rabbits can be repaired using the TP technique, and the addition of autologous PRG to the bone tunnel promotes early healing of the meniscus and bone postoperatively. Meanwhile, both treatments can reduce the secondary damage to the cartilage due to osteoarthritis.

[Effect of increased posterior tibial slope or partial posterior cruciate ligament release on knee kinematics of total knee arthroplasty].

OBJECTIVE: To compare the effects of increased posterior tibial slope or partial posterior cruciate ligament (PCL) release on knee kinematics of total knee arthroplasty (TKA). METHODS: Anteroposterior laxity, rotational laxity, varus and valgus laxity and maximum flexion angle were evaluated in 6 normal cadaver knees and the knees after TKA at flexion 0 degrees , 30 degrees , 60 degrees , 90 degrees and 120 degrees . Then the femoral prosthesis was shifted 5 mm posteriorly to simulate the tightly implanted knee. The same tests were performed on the tightly implanted knees. After that, the posterior tibial slope was increased 4 degrees or the PCL was partially released, and the same tests were made as in the normal knees respectively. Statistical analysis of the results was made using student's t test. RESULTS: Anteroposterior laxity, rotational laxity and varus and valgus laxity of the tightly implanted knees at flexion 30 degrees , 60 degrees , 90 degrees and 120 degrees were significantly less than those of the normal TKA knees (P < 0.05). Compared with the tightly implanted knees, anteroposterior laxity, rotational laxity and varus and valgus laxity at flexion 30 degrees , 60 degrees , 90 degrees and 120 degrees significantly improved after increased 4 degrees posterior tibial slope (P < 0.05); in the partial PCL released group, anteroposterior laxity at flexion 30 degrees , 60 degrees , 90 degrees and 120 degrees was significantly improved (P < 0.05), varus and valgus laxity was significantly improved only at flexion 90 degrees (P < 0.05), and rotational laxity was significantly improved at flexion 30 degrees , 60 degrees and 90 degrees (P < 0.05). Compared with PCL released group, varus and valgus laxity at flexion 30 degrees , 60 degrees and 90 degrees and rotational laxity at flexion 0 degrees , 30 degrees , 60 degrees and 90 degrees were significantly improved in the group of increased 4 degrees posterior tibial slope (P < 0.05). Maximum flexion angle of the tightly implanted knee (120.4 degrees ) was less than that of the normal TKA knees (130.3 degrees , P < 0.05) and that of increased 4 degrees posterior tibial slope group (131.1 degrees , P < 0.05). There was no significant difference at the maximum flexion angle between the increased 4 degrees posterior tibial slope group and the PCL released group (131.1 degrees vs 124.0 degrees , P = 0.0816). CONCLUSIONS: Anteroposterior laxity, varus and valgus laxity, rotational laxity and maximum flexion angle of the tightly implanted knees are less than those of the normal TKA knees. After increased 4 degrees posterior tibial slope, these indexes are improved significantly. Partial PCL released can significantly improve the anteroposterior laxity and had less effect on the varus and valgus laxity, rotational laxity and maximum flexion angle. So, a knee that is tight in flexion can be more likely to be corrected by increasing posterior tibial slope than by partially releasing PCL.

Electrophysiologic effects of adenosine triphosphate on rabbit sinoatrial node pacemaker cells via P1 receptors.

AIM: To study the electrophysiologic effects of adenosine triphosphate (ATP) on rabbit sinoatrial node pacemaker cells and the receptors related with the action of ATP. METHODS: Intracellular microelectrode method was used to record the parameters of action potential (AP) in the rabbit sinoatrial nodes. RESULTS: ATP (0.1-3 mmol/L) decreased the rate of pacemaker firing (RPF) by 16 %-43 % and velocity of diastolic depolarization (VDD) by 33 %-67 %, increased the amplitude of AP (APA) by 6 %-9 % and maximal rate of depolarization (V(max)) by 30 %-76 %, shortened APD50 by 7 %-12 % and APD(90) by 6.3 %-9 %, concentration-dependently. The effects of ATP, adenosine (Ado), and adenosine diphosphate at the same concentration on AP were not different from each other significantly. Neither uridine triphosphate nor alpha,beta-methylene ATP had significant electrophysiologic effects on the sinoatrial node of rabbits. Both the electrophysiologic effects of ATP and Ado on pacemaker cells were inhibited by P1 receptor antagonist aminophylline 0.1 mmol/L (P<0.05) in a closely similar manner, and the effects of ATP were not affected by P2 receptor antagonist reactive blue 2 at 0.05 mmol/L (P>0.05). CONCLUSION: There are no functional P2X(1) and P2Y(2) receptors on pacemaker cells of the rabbit sinoatrial nodes, and the electrophysiologic effects of ATP in the rabbit sinoatrial node pacemaker cells are mediated via P1 receptors by Ado degraded from ATP.