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We investigated the surface fatigue crack behaviors including initial surface crack appearances depend on three artificial notch lengths applied with the axle load level of the maximum load, 1,103 MPa and minimum load 55.3 MPa at the stress ratio of 0.05. This load level is the F100 engine's maximum operation condition of Waspaloy. The initial cracking site in depth is started from multi-origin. The effectiveness of crack growth rate by ductile striation space measurement on the fractured surface is confirmed by the working load and the stress intensity factor range. The surface cracks of Waspaloy at room temperature in air follow the ΔK vs da/dN and db/dN relation, even though the crack length initiated early in notch size 1 mm and initiated very late in notch size 4 mm. And the ΔK vs da/dN and db/dN relation have similar slope at 3 kinds of notches.

Up to now there have been two contradictory opinions in regard to lumbar facet role in the development of disc degeneration and herniation. To reconfirm the clinical validity of facet arrangement in the development of early disc degeneration and herniation, this study was carried out. For this purpose, the relationship between lumbar unilateral disc protrusion and geometry of the facet joints in the transverse plane was investigated. Method: The facet geometry was measured at the L₄ disc level in the 35 protruded disc patients and L₅ disc level in the 19 protruded disc patients. The computed tomographic scan sections were made 2mm intervals. The discs of L₄ and L₅ levels in the patients without disc protrusion and patients with spine injury were used as control. Results: 1. The facet angle showed the different individual variance. Among the L${}_{4-5}$ disc herniation group, the mean facet angle in the protruded and opposite sides and control were $49\pm 8.8^{\circ }$ (29–70${}^{\circ }$), $48\pm 8^{\circ }$ (29–65${}^{\circ }$), and $48\pm 8^{\circ }$ (30–65${}^{\circ }$). Those values at L₅-S₁ level were $53\pm 11^{\circ }$ (35–79${}^{\circ }$), $51\pm 7^{\circ }$ (36–79${}^{\circ }$), and $52\pm 10^{\circ }$ (36–79${}^{\circ }$), respectively. 2. Transverse interfacet angle (TIFA) of the L${}_{\mathrm{\text{4-5}}}$ protruded disc level and that of control were 97–14${}^{\circ }$ (59–125${}^{\circ }$) and $96\pm 16^{\circ }$ (66–127${}^{\circ }$). Those of L₅-S₁ level were $104\pm 19^{\circ }$ (70–132${}^{\circ }$) and $104\pm 19^{\circ }$ (76–151${}^{\circ }$). 3. The angle difference between both sides in the case of the facet asymmetry at L${}_{4-5}$ disc level was $6.51\pm 5.91^{\circ }$ (0–30${}^{\circ }$), and that of the control was $4.95\pm 3.88^{\circ }$ (0–15${}^{\circ }$), and those of L₅-S₁ level were $8\pm 6.41^{\circ }$ (0–24${}^{\circ }$) and $6.18\pm 6.64^{\circ }$ (0–24${}^{\circ }$), respectively. Disc herniation developed toward the more obliquely aligned facet joint side in 19 (54.2%) out of the 35 patients at the L${}_{4-5}$ disc, while disc herniation at L₅-S₁ level developed toward the more obliquely aligned facet joint side in 11 (57.9%) out of the 19 patients. 4. Among the L${}_{4-5}$ disc level, the mean moment arm angles in the disc-protruded side, the opposite side and control were $22\pm 4^{\circ }$ (16–40${}^{\circ }$), $22\pm 4^{\circ }$ (15–35${}^{\circ }$), and $22.4\pm 4^{\circ }$ (16–35${}^{\circ }$). Those of L₅-S₁ level each were $26\pm 4^{\circ }$ (21–36${}^{\circ }$), $25\pm 5^{\circ }$ (17–35${}^{\circ }$), and $28\pm 4^{\circ }$ (16–35${}^{\circ }$), respectively. 5. At the L${}_{4-5}$ level, the mean non-dimensional facet depths in the disc-protruded side, the opposite side, and control were $0.14\pm 0.08^{\circ }$ (0–0.36${}^{\circ }$), $0.15\pm 0.08^{\circ }$ (0–0.41${}^{\circ }$), and $0.18\pm 0.06^{\circ }$ (0.02–0.28${}^{\circ }$). Those facet depths at L₅-S₁ level were $0.12\pm 0.07^{\circ }$ (0.02–0.28${}^{\circ }$), $0.09\pm 0.04^{\circ }$ (0.02–0.2${}^{\circ }$), and $0.11\pm 0.05^{\circ }$ (0.02–0.28${}^{\circ }$). Conclusion: The five parameters including facet angle showed clinically no significant correlation with the disc herniation.

Background: Common cause of chronic low back pain is lumbar facet joint arthropathy. Radiofrequency ablation (RFA) of medial branch currently preferred treatment in facet joint pain syndrome. Platelet-rich plasma (PRP) is known to initiate mesenchymal tissue healing by concentration of several fundamental protein growth factors. Our aim in this study is to evaluate the effect of co-administration of autologous PRP in lumbar facet and RFA of the medial branch of the dorsal ramus for lumbar facet arthropathy.

Methodology: This was a prospective randomised study with a blind assessor. Eighty-one consecutive patients who complained of low back pain secondary to lumbar facet joint arthropathy were randomly allocated into three-groups: Group RF: only RFA done. Group PR: received both PRP plus RFA. Group PL: received only PRP. Primary outcome of the study was assessment of pain intensity using visual analogue scale (VAS).

Result: The patients who had both RFA and PRP therapy had significant decrease in VAS score as compared to its baseline in the immediate and long term follow up period ($p$ < 0.001). However, for those who received only PRP, the decrease in VAS was more significant at 1 and 4 months. Similarly, there was a significant improvement in ODI score in patients who received both RFA and PRP ($p$ < 0.001). There was a gradual improvement in ODI in PRP group at 4-month interval. Rescue analgesics requirement was reduced and patients were better satisfied in those who received both RFA and PRP therapy. ($p$ < 0.05).

Conclusion: The combined administration of RFA and PRP proved to provide better analgesia in both short-term follow up and long-term follow up than treatment with either method in patients with lumbar facet syndrome.