Evaluation of 2 cement techniques for augmentation of stripped 1.5 mm screw sites in the distal metaphysis of feline radii

OBJECTIVE: To evaluate the effect of 2 cement augmentation techniques on pullout strength of 1.5 mm screws placed in stripped 1.5 mm screw sites in the distal metaphysis of feline radii. STUDY DESIGN: Experimental study. SAMPLE POPULATION: Feline radii (21 pairs). METHODS: Treatment groups (n=4) were allocated according to a Latin square design to 4 sites in each pair of radii. Positive and negative controls were a 1.5 mm screw and a screw of the same diameter in a previously stripped screw hole, respectively. Treatment groups were a 1.5 mm screw implanted in a previously stripped screw hole after injection of polymethylmethacrylate (PMMA) or a bioresorbable calcium phosphate cement (CPC, Norian skeletal repair system (SRS)). The ultimate pullout strength was compared between groups. RESULTS: The mean (+/-SEM) pullout strength of screws augmented with either bone cement was less than that of the positive control group and greater than that of the negative control. Injection of CPC or PMMA before screw implantation increased the pullout strength of the negative control by 86.8+/-22.9% and 104.1+/-32.1%, respectively. Holding power of the positive control screws differed from these 2 groups, and was 274.8+/-39.17% higher than that of the negative control. CONCLUSION: Injection of CPC or PMMA increases but does not restore the holding power of stripped 1.5 mm diameter screws. CLINICAL RELEVANCE: The use of CPC (Norian SRS) augmentation of stripped 1.5 mm diameter screws warrants clinical investigation as it combines biomechanical results similar to PMMA with osteoconduction and resorbability.     

Mechanical performance of a screw-type veterinary suture anchor subjected to single load to failure and cyclic loads

OBJECTIVE: To characterize the mechanical performance of a veterinary bone anchor under static and cyclic loads. STUDY DESIGN: Mechanical testing study. ANIMALS: Cadaveric canine humeri. METHODS: Humeri (6 pairs) were collected from skeletally mature dogs (mean [+/-SD] age, 17.2+/-2.1 months; weight, 20.8+/-1.5 kg). Bone anchors were inserted in the proximal metaphysis using nylon, and were longitudinally extracted. For the opposite humerus, anchors were subjected to longitudinal cyclic load (50% of the load at failure of their pair) for 1200 cycles then longitudinally loaded to failure. Anchors were then installed in a similar and adjacent area of these 2(nd) humeri with nylon and cyclically tested perpendicular to the axis of anchor insertion (100% of the longitudinal holding power of their pair) for 1200 cycles, then perpendicularly loaded to failure. Paired t-tests were used to compare holding power before and after longitudinal cyclic testing. RESULTS: Longitudinal holding power of the screw-type anchor in the proximal humerus was 385+/-30 N. Anchor pullout was the only mode of failure. Anchors in the paired humeri did not fail after 1200 cycles of 50% longitudinal loading, and post-cycle holding strength was not different (335+/-87 N; P=.32). Perpendicularly loaded anchors did not fail after 1200 cycles of 100% of opposite longitudinal holding strength, and had post-cycle perpendicular holding strengths of 514+/-72 N. Suture breakage was the mode of failure. CLINICAL RELEVANCE: Bone anchor holding strength is dependent on orientation of suture load. Screw-type bone anchor holding strength was not affected by longitudinal cyclic loading, and holding strengths of approximately 385 N can be expected in metaphyseal bone of large-breed mature dogs. Perpendicularly loaded anchors have higher failure loads, and holding strength of approximately 514 N can be expected in metaphyseal bone of the proximal humerus.     

An unusual cyst‐like lesion in the metaphysis of the tibia in a horse

A 6‐year‐old Haflinger gelding was presented with a chronic right hindlimb lameness. Scintigraphy, radiography and computed tomography confirmed an active large cyst‐like lesion in the distal metaphysis of the right tibia. A transcortical surgical approach was used to curette the lesion and fill it with an autologous bone graft and a calcium phosphate bone substitute material. Histopathology revealed mild histiocytic inflammatory changes, mild fibrosis and bone necrosis. This case report describes an unusual cyst‐like lesion in the tibial metaphysis of a horse.     

A large cyst in the distal femur of a horse

A 10-year-old Warmblood gelding presented with a left hindlimb lameness. Diagnostic analgesia located the lameness to the stifle. Radiography showed an unusually large cyst in the distal femur. Diagnostic arthroscopy of the stifle did not reveal any significant abnormalities. An extra-articular transcortical approach to the cyst was performed for drainage, curettage, and provision of an autologous, cancellous bone graft, gentamicin-impregnated collagen fleeces and injectable steroid. The horse returned to a higher level of competitive dressage than prior to surgery. This report describes a large cyst in the distal femur of a horse.     

柞蚕变态期雌体生殖系统发育的组织结构观察

采用石蜡切片法对柞蚕雌体生殖系统的组织结构进行了研究，结果发现，在蛹发育的前期卵巢及卵巢管发育较快，卵巢管壁分泌卵泡细胞，将外语系平细胞及滋养细胞包围起来形成卵室和滋养室，中期滋养细胞发达，核分枝，后期卵母细胞进一步发育，滋养细胞萎缩退化，卵母细胞增大，同时卵泡细胞分泌卵壳物质形成卵壳。蛹发育前期附腺开始形成，中期开始分泌粘液，此时附腺的端部，中部和基部的组织结构无明显差别，后期端部的腺细胞发达并形成皱褶，而中部和基部的腺腔扩大，腺细胞逐渐失去分泌功能，受精囊腺在蛹发育前期逐渐形成，到中后期其端部，中部和基部的组织结构发生变化，端部的腺细胞发达，形成大量的皱褶，中部的腺细胞皱褶减少，腺腔扩大，外层肌肉增厚，基部腺细胞不发达，腺腔增大与受精囊相连。