A finite element model of the shoulder: application to the changes of biomechanical environment induced by postoperative malrotation of humeral shaft fracture.

OBJECTIVES: The humerus fracture is one of the most commonly occurring fractures. In this research, we attempted to evaluate and compare the extent of malrotation and biomechanical environment after surgical treatment of humeral shaft fractures. METHODS: A finite element (FE) model of the shoulder was built based on Computed Tomography (CT) data of a patient with a humeral shaft fracture. The muscle group around the shoulder joint was simulated by spring elements. The changes of shoulder stresses under rotation were analyzed. The biomechanics of the normal shoulder and postoperative malrotation of the humeral shaft was analyzed and compared. RESULTS: During rotations, the maximum stress was centered in the posterosuperior part of the glenoid for the normal shoulder. The von Mises shear stresses were 4.40 MPa and 4.89 MPa at 40° of internal and external rotations, respectively. For internal rotation deformity, the shear contact forces were 7-9 times higher for the shoulder internally rotated 40° than for the normal one. For external rotation deformity, the shear contact forces were about 3-5 times higher for the shoulder with 40° external rotation than the normal one. CONCLUSION: Postoperative malrotation of humeral shaft fracture induced the changes of the biomechanical environment of the shoulders. The peak degree of malrotation was correlated with increased stresses of shoulders, which could be paid attention to in humeral shaft fracture treatment. We hoped to provide information about the biomechanical environment of humeral malrotation.

Loss of p120 catenin aggravates alveolar edema of ventilation induced lung injury.

BACKGROUND: p120 catenin (p120ctn) is an adheren junction protein that regulates barrier function, but its role has not been explored in alveolar edema induced by ventilation. We measured stretch-induced cell gap formation in MLE 12 cells due to the loss of p120. We hypothesized that alveolar permeability was increased by high lung inflation associated with alveolar epithelia cell tight junctions being destroyed, which resulted from the loss of p120. METHODS: Cultured MLE12 cells were subjected to being stretched or un-stretched (control) and some cells were pretreated with pp2 (c-src inhibitor). After the end of stretching for 0, 1, 2, and 4 hours, the cells were lysed, and p120 expression and c-src activation was determined by Western blotting analysis. In vivo, SD rats were taken to different tidal volumes (Vt 7 ml/kg or 40 ml/kg, PEEP = 0, respiratory rate 30-40 betas/min) for 0, 1, 2, and 4 hour and some were pretreated with pp2, and alveolar edema was calculated. RESULTS: It was found that p120 expression was reduced and c-src activation increased in a time-dependent and strain-dependent manner due to cyclic-stretch of the alveolar epithelial cells. These changes could be reversed by inhibition of c-src. We obtained similar changes in rats when they were subjected to large tidal volumes and the alveolar edema increased more than in rats in the low Vt group. Pretreated the rats with inhibition of c-src had less pulmonary edema induced by the high tidal volume ventilation. CONCLUSIONS: Cyclic stretch MLE 12 cells induced the loss of p120 and may be the same reason by high tidal volume ventilation in rats can aggravate alveolar edema. Maintenance of p120 expression may be a novel therapeutic strategy for the prevention and treatment of ventilation induced lung injury (VILI).

[Efficacy of intra-articular injection of sodium hyaluronate in post-operation treatment of the knee].

OBJECTIVE: To investigate the effects of intra-articular injection of sodium hyaluronate in post-operation treatment of the knee. METHODS: From January 1998 to February 2001, 4 ml of sodium hyaluronate injection was injected into the knee joint of the 134 cases at the end of arthroscope operation, or the 91 cases undergoing open operation of the knee at the time when the drain tube was removed (treatment group). Five days after operation, the hydrarthrosis was removed and 2 ml of sodium hyaluronate was injected into the knee joint. According to the patient's condition, injection of sodium hyaluronate was performed once a week for several weeks. Clinical evaluation was made by evaluating pain visual analog scale (VAS) and painless range of movement (ROM) of the joint at every definite point of time. The 85 patients in control group used nothing at the same time. RESULTS: The VAS score of patients in the treatment group was significant lower than that of the control group. The period to the maximal painless ROM of the joint was 6 days in the treatment group after open operation, while 9 days in the control group. CONCLUSION: Sodium hyaluronate appears effective in relieving post-operation pain of the knee joint.

[The clinical study of adhesion prevention of sodium hyaluronate in flexor tendon surgery].

OBJECTIVE: To evaluate the effects of sodium hyaluronate on adhesion prevention after flexor tendon surgery. METHODS: In 47 cases with the flexor tendon surgery, two kinds of sodium hyaluronate jelly preparations were injected into the tendon sheath before suture. Preparation I (20 mg/2 ml) was for group A (17 patients) and preparation II (20 mg/2 ml) was for group B (16 patients). The control group (group C, 14 patients) were treated in the same way except injection of sodium hyaluronate. The functions of afflicted fingers including flexibility, pain and swelling were measured immediately, at the first, second and the third month after operation. RESULTS: All 47 patients were followed up 1 to 3 months. 64.71% patients in group A and 68.75% in group B showed significant improvement. There were significant difference compared with group C (P < 0.05). There were no significant adverse reactions were observed in all groups. CONCLUSION: Two sodium hyaluronate preparations have effects in adhesion prevention after flexor tendon surgery with safety and expedience.