构建皮肤与手术巾摩擦力学模型，验证头低脚高位无会阴柱牵引技术的力学可行性，明确不同患者体重适应性与安全角度分析，为临床应用提供力学依据。

（1）离体实验：以新鲜猪皮模拟人体皮肤，采用摩擦系数仪测定40、80 mmHg压力下猪皮与手术巾的摩擦系数，每组5块猪皮，每块重复测量3次。（2）在体实验：纳入30例拟采用无会阴柱牵引技术行髋关节镜手术、自愿签署知情同意书等符合纳入标准的患者，排除既往髋部手术病史的患者，测量髋关节牵开10 mm时的实际牵引力和头低脚高角度，推导皮肤与手术巾的摩擦系数，对比离体与在体数据的一致性。（3）分组分析：将患者按体重分为轻体重组（体重<60 kg）、中体重组（60~79 kg）、高体重组（体重≥80 kg），分析各组摩擦系数和角度的趋势。数据的组间比较采用单因素方差分析或独立样本t检验。

（1）离体实验：40、80 mmHg压力下猪皮与手术巾平均摩擦系数分别为0.371、0.433，猪皮与手术巾间的摩擦系数随压力升高呈正相关（t=-4.35，P<0.001）。（2）在体实验：纳入30例患者，男性23例、女性7例，年龄16~66岁，平均（35±13）岁；体重48~100 kg，平均（72±13）kg；牵引力范围44.30~87.70 kg，平均（59.4±11.3）kg；头低脚高角度范围5.3°~14.3°，平均（9.9±2.8）°；摩擦系数范围0.43~1.18，平均0.70±0.22。（3）轻、中、高体重患者使用无会阴柱牵引技术适用的头低脚高度数分别为10°、13°和15°。

头低脚高10°~15°体位下，皮肤与手术巾的摩擦力可对抗下肢牵引力，确保髋关节间隙安全牵开；不同体重患者采用该技术时，需以最小角度减少并发症，且体重越小所需角度越大；本结果可为相关骨科手术体位提供参考。

To establish a mechanical friction model between human skin and surgical drapes, verify the mechanical feasibility of the perineal-post-free traction technique in the Trendelenburg position, clarify its adaptability to patients with different body weights and analyze the safe angles, so as to provide a mechanical basis for clinical application.

(1) In vitro experiment: fresh porcine skin was used to simulate human skin. A friction coefficient tester was employed to measure the friction coefficient between porcine skin and surgical drapes under pressures of 40 mmHg and 80 mmHg, with five porcine skin specimens per group and three repeated measurements for each specimen. (2) In vivo experiment: 30 patients scheduled for hip arthroscopy using the perineal-post-free traction technique who voluntarily signed informed consent forms and met the inclusion were enrolled. The patients with history of previous hip surgery were excluded. The actual traction force and Trendelenburg angle at 10 mm of hip joint distraction were measured, the friction coefficient between skin and surgical drapes was calculated, and the consistency between in vitro and in vivo data was compared. (3) Group analysis: Patients were divided into a low-weight group (<60 kg), a medium-weight group (60–79 kg), and a high-weight group (≥80 kg). The trends of friction coefficient and angle in each group were analyzed. Statistical analysis was performed using SPSS 26.0 software. One-way analysis of variance or independent-samples t test was used for intergroup comparisons, and P<0.05 was considered statistically significant.

(1) In vitro experiment: The mean friction coefficients between porcine skin and surgical drapes under 40 mmHg and 80 mmHg were 0.371 and 0.433, respectively. The friction coefficient was positively correlated with increasing pressure (t=-3.1165, P=0.0143). (2) In vivo experiment: Thirty patients were included, consisting of 23 males and seven females. Age were from 16 to 66 years, (35±13) years on average; body weight were from 48 to 100 kg, (72±13) kg on average . The traction force ranged from 44.30 to 87.70 kg, (59.4±11.3) kg on average, the Trendelenburg angle ranged from 5.3° to 14.3°, ( 9.9±2.8)°on average, and the friction coefficient ranged from 0.43 to 1.18, 0.70±0.22 on average. (3) The applicable Trendelenburg angles for patients with low, medium, and high body weights using the perineal-post-free traction technique are 10°, 13°, and 15°, respectively.

At a Trendelenburg angle of 10° to 15°, the frictional force between skin and surgical drapes can counteract the lower-extremity traction force and ensure safe distraction of the hip joint space. For patients of different body weights, the minimum safe angle should be used to reduce complications, and a smaller body weight requires a larger angle. The findings provide important references for positioning in related orthopedic surgeries.