To evaluate the operating range and morphology of the surgical safe zone for oblique lumbar interbody fusion (OLIF). Twenty embalmed full-torso cadaveric specimens were dissected. The oblique corridor and the distance between adjacent lumbar arteries were measured in a static state and with psoas major retraction. The morphology and size of the safe zone for OLIF and the location of the lumbar sympathetic trunk were also recorded. The oblique corridor of the L1-L5 segments was significantly greater in the retracted state than in the static state (p < 0.05). With psoas major retraction, the distances between adjacent lumbar arteries at L1-4 were significantly greater (p < 0.05) than those in the static state. The lumbar sympathetic trunk is just located in the safe zone and travels downward adjacent to the psoas major. The shape of the safe zone for OLIF was approximately an oblique upward parallelogram at L1/2 and L2/3, an isosceles trapezoid at L3/4, and an irregular quadrangle or triangle at L4/5. The safe zone for OLIF at L1/2, L2/3, and L3/4 was significantly larger during retraction than in the static state (p < 0.05). On the lateral side of the lumbar spine there is a natural surgical safe zone for OLIF, which can provide a sufficient operating space. The safe zone has a certain morphological pattern in L1-5 segments and psoas major retraction can significantly enlarge it.

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Adding gentamicin to silk fibroin enhances both the antibacterial performance and degradation rate of silk-based materials. The increased material degradation rate can affect the strength of early internal fixation, resulting in internal fixation failure. This study sought to adjust the gentamicin concentration to control the material degradation rate, thereby better meeting clinical application requirements. The in vitro degradation, water absorption rate, and expansion rate of silk-based materials containing different gentamicin concentrations were studied. A gentamicin-loaded silk-based screw was implanted into the femurs of New Zealand rabbits. Micro-computed tomography was used to measure the screw diameter, which was then used to calculate the degradation rate. The specimens were stained with hematoxylin and eosin and Masson’s trichrome. The in vitro results revealed increasing material degradation rates with increasing gentamicin concentration but no significant differences in water absorption rates with different gentamicin concentrations. The degradation rates of gentamicin-loaded (4 mg/g) silk-based rod-like materials were approximately 11.08% at three months in vitro and 9.4% in the animal experiment. The time for complete degradation was predicted from the fitting curve to be approximately 16 months. No inflammatory hyperplasia was observed in bone or soft tissue. The degradation and biocompatibility of the material containing 4 mg/g gentamicin meet clinical application requirements, and previous experimental results demonstrate good antibacterial performance of materials containing this gentamicin concentration.

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