Objective:To investigate the effect of vector sum concept in fine-tuning posterior column screw channel via ilioinguinal approach for the treatment of bi-column acetabular fracture.Methods:A retrospective cohort study was conducted to analyze the clinical data of 42 patients with acetabular double column fracture admitted to Weifang People′s Hospital from July 2015 to May 2021, including 22 males and 20 females, aged 23-77 years [(49.3±16.3)years]. The ilioinguinal approach was used in all patients with the anterior column fixed with a plate and posterior column fixed with a lag screw. The vector sum concept was used intraoperatively to fine-tune the posterior column screw channel in 19 patients (channel fine-tuning group): namely, a 2.5 mm Kirschner wire was inserted into the bony channel of the posterior column screw under fluoroscopy of iliac oblique and obturator oblique positions; when the Kirschner wire was not located in the middle of the ischial ramus under single fluoroscopy, the vector only needed to be adjusted in one direction, with zero in the other direction; when the Kirschner wire was not located in the middle of the ischial ramus under fluoroscopy of both the iliac oblique and obturator obturator oblique positions, the sum of the deviation vectors in the two directions was calculated before fine-tuning. The vector sum concept was not used to fine-tune the posterior column channel screw in 23 patients (channel non-fine-tuning group). The time of posterior column screw placement, intraoperative blood loss, frequency of guide wire adjustment and fracture healing time were recorded and compared between the two groups. At 6 months after operation, the quality of fracture reduction and hip function were assessed by Matta score and Merle D′Aubigne-Postel score, respectively. The complications were observed.Results:All patients were followed up for 7-71 months [(35.7±8.5)months]. In channel fine-tuning group, the time of posterior column screw placement was (5.1±1.5)minutes, with intraoperative blood loss of (798.8±83.9)ml, frequency of guide wire adjustment of (1.8±0.5)times and fracture healing time of (12.4±3.2)weeks; while these parameters [(39.8±12.0)minutes, (1 119.3±172.0)ml, (5.6±1.6)times and (15.6±4.2)weeks] were significantly shorter or less in channel non-fine-tuning group ( P<0.05 or 0.01). There were no significant difference in the quality of fracture reduction and hip function between the two groups at 6 months postoperatively (all P>0.05). After operation, symptoms of lateral femoral cutaneous nerve was found in seven patients, superficial incision infection in two who was healed after debridement and dressing change, deep venous thrombosis of lower limbs in three. There was no significant difference in the incidence of postoperative complications between the two groups [channel fine-tuning group: 26%(5/19), channel non-fine-tuning group: 30%(7/23)] ( P>0.05). Conclusion:For bi-column acetabular fractures via ilioinguinal approach, application of vector and concept to fine-tune the posterior column screw channel is beneficial for rapid screw placement into the osseous channel, significant reduction of intraoperative blood loss and early fracture healing.

Objective:To perform a prospective cohort study to identify individual susceptibility of glucocorticoid (GC) -associated osteonecrosis of the femoral head (GA-ONFH) and their clinical and genetic risk factors. Methods:The present prospective cohort study enrolled patients who received their first GC therapy between July 2015 and January 2018 at Zhongshan Hospital. All patients did not receive any GC treatment before enrollment. Further, they planned to start GC treatment with the dose (equivalent prednisone) of ≥30 mg/d, lasted ≥3 weeks, or pulse dose ≥200 mg/d, lasted ≥3 d. Blood samples were collected before GC treatment to evaluate bone metabolism and its released factors. Hip MRI was performed at the 1st, 3rd, 6th, 12th and 24th month to diagnose GA-ONFH. All patients were followed-up for ≥2 years. The endpoint was regarded as diagnosis of GA-ONFH or completion of 2 years follow-up. Lasso regression was performed to determine which clinical features were associated with GA-ONFH. A nested case-control sub-cohort (A, n=12) was established prospectively based on the main cohort by 1∶1 matching. Whole exome sequencing was performed to screen differential and functional candidate single nucleotide polymorphisms and insertion-deletions (SNP/InDels). Another sub-cohort (B, n=50) was constructed retrospectively in patients with GA-ONFH and non-ONFH patients received standard high dose GC treatment for more than two years. The candidate SNP/InDels were verified by Sanger sequencing based on the patients from sub-cohort B. Results:A total of 96 patients were enrolled of which 88 of them (32 males and 56 females, mean age 42.30 years) completed follow-up. Eight cases (9.1%) were diagnosed with GA-ONFH. The median time from the start of GC therapy to the diagnosis of ONFH was 53.00(34.00,13.50) days. The baseline characteristics, such as age, sex and body mass index, indicated no significant difference between the ONFH group and the non-ONFH group. The cumulative GC dose of the ONFH patients in the first month was higher than that of non-ONFH [32.74(29.55, 47.05) mg/kg vs. 24.00(21.10, 29.45) mg/kg, Z=-2.410, P=0.016]. However, there was no significant difference of patients who underwent pulse therapy (37.5% vs. 10.0%, adjusted χ 2=2.829, P=0.093). The ratio of serum apolipoprotein B/apolipoprotein A1 (ApoB/ApoA1) in patients with ONFH was higher than that in non-ONFH group before GC use [0.95(0.80, 1.50) vs. 0.70(0.60, 0.80), Z=-2.875, P=0.000]. Due to the multicollinearity, Lasso regression model was performed to reduce overfitting. All variables were included in the model. The results suggested that higher ApoB/ApoA1 ratio, lower serum β-c-terminal telopeptide (β-CTX) and higher cumulative GC dose in the first month were the top three risk factors of GA-ONFH. This model had an accuracy of 0.982 in internal validation. Seven differential candidate SNP/InDels were found by whole exome sequencing of sub-cohort A. We further verified these SNP/InDels in sub-cohort B. The patients with COLEC12 mutation (rs2305027, G1816A) were at risk of GA-ONFH ( OR=6.00, 95% CI: 1.17, 30.73). Conclusion:Higher first-month GC dose, lower serum β-CTX level before treatment, higher ApoB/ApoA1 ratio and COLEC12 mutation (rs2305027, G1816A) could increase the risk of GA-ONFH.