Development and validation of machine learning models and nomograms for predicting the surgical difficulty of laparoscopic resection in rectal cancer

BACKGROUND

The objective of this study is to develop and validate a machine learning (ML) prediction model for the assessment of laparoscopic total mesorectal excision (LaTME) surgery difficulty, as well as to identify independent risk factors that influence surgical difficulty. Establishing a nomogram aims to assist clinical practitioners in formulating more effective surgical plans before the procedure.

METHODS

This study included 186 patients with rectal cancer who underwent LaTME from January 2018 to December 2020. They were divided into a training cohort (n = 131) versus a validation cohort (n = 55). The difficulty of LaTME was defined based on Escal's et al. scoring criteria with modifications. We utilized Lasso regression to screen the preoperative clinical characteristic variables and intraoperative information most relevant to surgical difficulty for the development and validation of four ML models: logistic regression (LR), support vector machine (SVM), random forest (RF), and decision tree (DT). The performance of the model was assessed based on the area under the receiver operating characteristic curve(AUC), sensitivity, specificity, and accuracy. Logistic regression-based column-line plots were created to visualize the predictive model. Consistency statistics (C-statistic) and calibration curves were used to discriminate and calibrate the nomogram, respectively.

RESULTS

In the validation cohort, all four ML models demonstrate good performance: SVM AUC = 0.987, RF AUC = 0.953, LR AUC = 0.950, and DT AUC = 0.904. To enhance visual evaluation, a logistic regression-based nomogram has been established. Predictive factors included in the nomogram are body mass index (BMI), distance between the tumor to the dentate line ≤ 10 cm, radiodensity of visceral adipose tissue (VAT), area of subcutaneous adipose tissue (SAT), tumor diameter >3 cm, and comorbid hypertension.

CONCLUSION

In this study, four ML models based on intraoperative and preoperative risk factors and a nomogram based on logistic regression may be of help to surgeons in evaluating the surgical difficulty before operation and adopting appropriate responses and surgical protocols.

Prediction of extraction difficulty for impacted maxillary third molars with deep learning approach

OBJECTIVE

The aim of this study is to determine if a deep learning (DL) model can predict the surgical difficulty for impacted maxillary third molar tooth using panoramic images before surgery.

MATERIALS AND METHODS

The dataset consists of 708 panoramic radiographs of the patients who applied to the Oral and Maxillofacial Surgery Clinic for various reasons. Each maxillary third molar difficulty was scored based on dept (V), angulation (H), relation with maxillary sinus (S), and relation with ramus (R) on panoramic images. The YoloV5x architecture was used to perform automatic segmentation and classification. To prevent re-testing of images, participate in the training, the data set was subdivided as: 80 % training, 10 % validation, and 10 % test group.

RESULTS

Impacted Upper Third Molar Segmentation model showed best success on sensitivity, precision and F1 score with 0,9705, 0,9428 and 0,9565, respectively. S-model had a lesser sensitivity, precision and F1 score than the other models with 0,8974, 0,6194, 0,7329, respectively.

CONCLUSION

The results showed that the proposed DL model could be effective for predicting the surgical difficulty of an impacted maxillary third molar tooth using panoramic radiographs and this approach might help as a decision support mechanism for the clinicians in peri‑surgical period.

Effect of thoracic cage width on surgery time and postoperative outcome in minimally invasive esophagectomy

INTRODUCTION

Minimally invasive esophagectomy (MIE) for esophageal cancer is a complex procedure that reduces postoperative morbidity in comparison to open approach. In this study, thoracic cage width as a factor to predict surgical difficulty in MIE was evaluated.

METHODS

All patients of our institution receiving either total MIE or robotic-assisted MIE (RAMIE) with intrathoracic anastomosis between February 2016 and April 2021 for esophageal cancer were included in this study. Right unilateral thoracic cage width on the level of vena azygos crossing the esophagus was measured by the horizontal distance between the esophagus and parietal pleura on preoperative computer tomography. Patients' data as well as operative and postoperative details were collected in a prospective database. Correlation between thoracic cage width with duration of the thoracic procedure and postoperative complication rates was analyzed.

RESULTS

Overall, 313 patients were eligible for this study. Thoracic width on vena azygos level ranged from 85 to 149 mm with a mean of 116.5 mm. In univariate analysis, a small thoracic width significantly correlated with longer duration of the thoracic procedure (p = 0.014). In multivariate analysis, small thoracic width and neoadjuvant therapy were identified as independent factors for long duration of the thoracic procedure (p = 0.006). Regarding postoperative complications, thoracic cage width was a significant risk factor for occurrence of postoperative pneumonia in the multivariate analysis (p = 0.045). Dividing the cohort into two groups of patients with narrow (≤ 107 mm, 19.5%) and wide thoraces (≥ 108 mm, 80.5%), the thoracic procedure was significantly prolonged by 17 min (204 min vs. 221 min, p = 0.014).

CONCLUSION

A small thoracic cage width is significantly correlated with longer operation time during thoracic phase of a MIE in Europe, which suggests increased surgical difficulty. Patients with small thoracic cage width may preferably be operated by MIE-experienced surgeons.

The preoperative M2BPGi score predicts operative difficulty and the incidence of postoperative complications in laparoscopic liver resection

BACKGROUND

Liver fibrosis or cirrhosis frequently makes parenchymal transection more difficult, but the difficulty score of laparoscopic liver resection (LLR), including the IWATE criteria, does not include a factor related to liver fibrosis. Therefore, this study aimed to evaluate M2BPGi as a predictor of the difficulty of parenchymal transection and the incidence of postoperative complications in LLR.

METHODS

Data from 54 patients who underwent laparoscopic partial liver resection (LLR-P) and 24 patients who underwent laparoscopic anatomical liver resection between 2017 and 2019 in our institution were retrospectively analyzed. All cases were classified according to M2BPGi scores, and reserve liver function, intraoperative blood loss, and postoperative complications were compared among these groups.

RESULTS

Sixteen cases (29.6%) were M2BPGi negative (cut-off index < 1.0), 25 cases (46.3%) were 1+ (1.0 ≤ cut-off index < 3.0), and 13 cases (24.1%) were 2+ (cut-off index ≥ 3.0). M2BPGi-positive cases had significantly worse hepatic reserve function (K-ICG: 0.16 vs 0.14 vs 0.08, p < 0.0001). Intraoperative bleeding was significantly greater in M2BPGi-positive cases [50 ml vs 150 ml vs 200 ml, M2BPGi (-) or (1+) vs M2BPGi (2+), p = 0.045]. Postoperative complications (Clavien-Dindo ≥ II) were significantly more frequent in M2BPGi-positive cases [0% vs 4% vs 33%, M2BPGi (-) or (1+) vs M2BPGi (2+), p = 0.001].

CONCLUSION

M2BPGi could predict surgical difficulty and complications in LLR-P. In particular, it might be better not to select M2BPGi (2+) cases as teaching cases because of the massive bleeding during parenchymal transection.

Identifying the preoperative factors predicting the surgical difficulty of robotic distal pancreatectomy

BACKGROUND

Few studies have evaluated the preoperative factors predicting the surgical difficulty of robotic distal pancreatectomy (RDP). This study aims to explore such factors and provide guidance on the selection of suitable patients to aid surgeons lacking extensive experience in RDP.

METHODS

A retrospective study was conducted on consecutive patients who underwent RDP to identify preoperative factors predicting surgical difficulty. High surgical difficulty was defined by both operation time and intraoperative estimated blood loss exceeding their median, or by conversion to laparotomy.

RESULTS

A total of 161 patients were ultimately enrolled, including 51 patients with high levels of surgical difficulty. Multivariate analysis revealed that male sex [OR (95% CI): 4.07 (1.77,9.40), p = 0.001], body mass index (BMI) ≥ 25 kg/m² OR (95% CI): 2.27 (1.03,5.00), p = 0.042], tumors located at the neck of the pancreas [OR (95% CI): 4.15 (1.49,11.56), p = 0.006] and splenic artery type B [OR (95% CI): 3.28 (1.09,9.91), p = 0.035] were independent risk factors for surgical difficulty. Regarding postoperative complications, high surgical difficulty was associated with the risk of overall complications and pancreatic fistula (grade B/C) (49.0% vs. 22.7%, p < 0.001; 39.2% vs. 19.1%, p = 0.006).

CONCLUSION

Male sex, body mass index ≥ 25 kg/m2, tumor located at the neck of the pancreas and splenic artery type B are associated with a high RDP difficulty level. These factors can be used preoperatively to assess the difficulty level of surgery, to help surgeons choose patients suitable for them and ensure surgical safety.

A Scoring System That Predicts Difficult Lipoma Resection: Logistic Regression and Tenfold Cross-Validation Analysis

Introduction

Most lipomas are readily dissected and removed. However, some cases can pose surgical difficulties. This retrospective study sought to identify clinical and radiological risk factors that predict difficult lipoma resection and can be used in a clinically useful scoring system that predicts difficulty preoperatively.

Methods

The study cohort consisted of all consecutive patients who underwent resection of pathology-confirmed lipoma during 2016–2018 at a tertiary care referral center in Tokyo, Japan. Surgical difficulty was defined as difficulty separating some/all of the tumor from the surrounding tissue by hand and inability to extract the tumor in one piece. Descriptive, univariate, and multivariate logistic regression analyses were conducted to identify predictive factors. The predictive accuracy of the scoring system that included these factors was assessed by tenfold cross-validation analysis. Receiver-operating curve (ROC) analysis was conducted to identify the optimal cutoff score for predicting surgical difficulty.

Results

Of the 86 cases, 36% involved surgical difficulty. Multivariate analysis showed that subfascial intramuscular location (odds ratio 42.7, 95% confidence interval 3.0–608.0), broad touching of underlying structures (46.5, 3.7–586.0), in-flowing blood vessels (9.3, 1.1–78.5), and unclear boundaries (109.0, 1.1–1110.0) significantly predicted surgical difficulty. These factors were used to construct a 0–4 point scoring system (with one point per variable). On cross-validation, the accuracy of the scoring system was 82.4% (Cohen’s kappa of 0.57). ROC analysis showed that scores ≥ 2 predicted surgical difficulty with sensitivity and specificity of 55% and 98%, respectively.

Conclusions

Our scoring system accurately predicted lipoma resection difficulty and may help operators prepare, thereby facilitating surgery.

A retrospective and prospective study to establish a preoperative difficulty predicting model for video-assisted thoracoscopic lobectomy and mediastinal lymph node dissection

Background

In previous studies, the difficulty of surgery has rarely been used as a research object. Our study aimed to develop a predictive model to enable preoperative prediction of the technical difficulty of video-assisted thoracoscopic lobectomy and mediastinal lymph node dissection using retrospective data and to validate our findings prospectively.

Methods

Collected data according to the designed data table and took the operation time as the outcome variable. A nomogram to predict the difficulty of surgery was established through Lasso logistic regression. The prospective datasets were analyzed and the outcome was the operation time.

Results

This retrospective study enrolled 351 patients and 85 patients were included in the prospective datasets. The variables in the retrospective research were selected by Lasso logistic regression (only used for modeling and not screening), and four significantly related influencing factors were obtained: FEV1/FVC (forced expiratory volume in the first second/forced vital capacity) (p < 0.001, OR, odds ratio = 0.89, 95% CI, confidence interval = 0.84–0.94), FEV1/pred FEV1 (forced expiratory volume in the first second/forced expiratory volume in the first second in predicted) (p = 0.076, OR = 0.98, 95% CI = 0.95–1.00), history of lung disease (p = 0.027, OR = 4.00, 95% CI = 1.27–15.64), and mediastinal lymph node enlargement or calcification (p < 0.001, OR = 9.78, 95% CI = 5.10–19.69). We used ROC (receiver operating characteristic) curves to evaluate the model. The training set AUC (area under curve) value was 0.877, the test set’s AUC was 0.789, and the model had a good calibration curve. In a prospective study, the data obtained in the research cohort were brought into the model again for verification, and the AUC value was 0.772.

Conclusion

Our retrospective study identified four preoperative variables that are correlated with a longer surgical time and can be presumed to reflect more difficult surgical procedures. Our prospective study verified that the variables in the prediction model (including prior lung disease, FEV1/pred FEV1, FEV1/FVC, mediastinal lymph node enlargement or calcification) were related to the difficulty.

Perioperative factors influencing the difficulty of retroperitoneal laparoscopic adrenalectomy: a single-center retrospective study

Purpose

Identifying patients in whom adrenalectomy may be more difficult can help with surgical decision-making. This study investigated the perioperative factors affecting the difficulty of retroperitoneal laparoscopic adrenalectomy (RLA).

Methods

Sixty-eight patients who underwent RLA at our hospital between December 1, 2020 and May 1, 2021 were included. The difficulty of RLA was assessed by operating time and intraoperative blood loss. We analyzed the relationship between surgical difficulty and patient sex, age, and body mass index, pathological type, tumor side, tumor size, distance from the lower pole of the adrenal tumor to the upper pole of the kidney (DAK), and distance from the lower pole of the adrenal tumor to the renal pedicle (DARP).

Results

Mean operating time was 105.38 ± 33.31 min and mean intraoperative blood loss was 32.28 ± 22.88 ml. Univariate linear regression analysis showed that age (P = 0.047), tumor size (P = 0.002), DAK (P = 0.002), and DARP (P < 0.001) were significantly correlated with a longer operating time. Univariate logistic regression analysis showed that DARP (P = 0.001), DAK (P = 0.001), tumor size (P = 0.002), and age (P = 0.033) were significantly correlated with a longer operating time. Multivariate logistic regression indicated that DARP (OR 5.341; 95% CI 1.704–16.739; P = 0.004), and tumor size (OR 4.433; 95% CI 1.434–13.709; P = 0.010) were independent predictors of operating time.

Conclusion

Age, tumor size, DAK, and DARP were predictors of the difficulty of RLA. Older age, lower DARP and DAK, and a larger tumor size were associated with a longer operating time. DARP and tumor size were independent predictors of surgical difficulty.

Establishment of a nomogram for predicting the surgical difficulty of anterior cervical spine surgery

Background

For a long time, surgical difficulty is mainly evaluated based on subjective perception rather than objective indexes. Moreover, the lack of systematic research regarding the evaluation of surgical difficulty potentially has a negative effect in this field. This study was aimed to evaluate the risk factors for the surgical difficulty of anterior cervical spine surgery (ACSS).

Methods

This was a retrospective cohort study totaling 291 consecutive patients underwent ACSS from 2012.3 to 2017.8. The surgical difficulty of ACSS was defined by operation time longer than 120 min or intraoperative blood loss equal to or greater than 200 ml. Evaluation of risk factors was performed by analyzing the patient’s medical records and radiological parameters such as age, sex, BMI, number of operation levels, high signal intensity of spinal cord on T2-weighted images, ossified posterior longitudinal ligament (OPLL), sagittal and coronal cervical circumference, cervical length, spinal canal occupational ratio, coagulation function index and platelet count.

Results

Significant differences were reported between low-difficulty and high-difficulty ACSS groups in terms of age (p = 0.017), sex (p = 0.006), number of operation levels (p < 0.001), high signal intensity (p < 0.001), OPLL (p < 0.001) and spinal canal occupational ratio (p < 0.001). Multivariate logistic regression analysis revealed that number of operation levels (OR = 5.224, 95%CI = 2.125–12.843, p < 0.001), high signal intensity of spinal cord (OR = 4.994, 95%CI = 1.636–15.245, p = 0.005), OPLL (OR = 6.358, 95%CI = 1.932–20.931, p = 0.002) and the spinal canal occupational ratio > 0.45 (OR = 3.988, 95%CI = 1.343–11.840, p = 0.013) were independently associated with surgical difficulty in ACSS. A nomogram was established and ROC curve gave a 0.906 C-index. There was a good calibration curve for difficulty estimation.

Conclusion

This study indicated that the operational level, OPLL, high signal intensity of spinal cord, and spinal canal occupational ratio were independently associated with surgical difficulty and a predictive nomogram can be established using the identified risk factors. Optimal performance was achieved for predicting surgical difficulty of ACSS based on preoperative factors.

Analysis of economic impact of laparoscopic liver resection according to surgical difficulty

INTRODUCTION

The advantages of laparoscopic liver resection (LLR) are well known, but their financial costs are poorly evaluated. The aim of this study was to analyze the economic impact of surgical difficulty on LLR costs, and to identify clinical factors that most affect global charges.

METHODS

All patients who underwent LLR from 2014 to 2018 in a single French center were included. The IMM classification was used to stratify surgical difficulty, from group I through group III. The costing method was done combining top-down and bottom-up approaches. A multivariate analysis was performed in order to identify clinical factors that most affect global charges.

RESULTS

Two hundred seventy patients were included (Group I: n = 136 (50%), Group II: n = 60 (22%), Group III: n = 74 (28%)). Total expenses significantly increased (p < 0.001) from Group I to Group III, but there was no difference regarding financial income (p = 0.133). Technical platform expenses significantly increased (p < 0.001) from Group I to Group III and represented the main expense among all costs with a total of 4 930 ± 2 601€. Among technical platform expenses, the anesthesia platform represented the main expense. In multivariate analysis, the four clinical factors that affected global charges in the whole study population were operating time (p < 0.001), length of stay (p < 0.001), admission in ICU (p < 0.001) and the occurrence of major complication (p < 0.05). An admission in ICU was the clinical factor that affected most global charges, as an ICU stay had a 39.1% increase effect on global charges in the whole study population.

CONCLUSION

LLR is a cost-effective procedure. The more complex is the LLR, the higher is the hospital cost. An admission in ICU was the clinical factor that most affected global charges.

Deep learning-based lumbosacral reconstruction for difficulty prediction of percutaneous endoscopic transforaminal discectomy at L5/S1 level: A retrospective cohort study

BACKGROUND

Deep learning has been validated as a promising technique for automatic segmentation and rapid three-dimensional (3D) reconstruction of lumbosacral structures on CT. Simulated foraminoplasty of percutaneous endoscopic transforaminal discectomy (PETD) through the Kambin triangle may benefit viability assessment of PETD at L5/S1 level.

MATERIAL AND METHODS

Medical records and radiographic data of patients with L5/S1 lumbar disc herniation (LDH) who received a single-level PETD from March 2013 to February 2018 were retrospectively collected and analyzed. Deep learning was adopted to achieve semantic segmentation of lumbosacral structures (nerve, bone, disc) on CT, and the segmented masks on reconstructed 3D models. Two observers measured the area of the Kambin triangle on 6 selected deep learning-derived 3D (DL-3D) models and ground truth-derived 3D (GT-3D) models, and intraclass correlation coefficient (ICC) was calculated to assess the test-retest and interobserver reliability. Foraminoplasty of PETD was simulated on L5/S1 lumbosacral 3D models. Patients with extended foraminoplasty or stuck canula occurs on simulations were predicted as PETD-difficult cases (Group A). The remaining patients were regarded as PETD-normal cases (Group B). Clinical information and outcomes were compared between the two groups.

RESULTS

Deep learning-derived 3D models of lumbosacral structures (nerves, bones, and disc) from thin-layer CT were reliable. The area of the Kambin triangle was 161.27 ± 40.10 mm² on DL-3D models and 153.57 ± 32.37 mm² on GT-3D models (p = 0.206). Reliability test revealed strong test-retest reliability (ICC between 0.947 and 0.971) and interobserver reliability of multiple measurements (ICC between 0.866 and 0.961). The average operation time was 99.62 ± 17.39 min in Group A and 88.93 ± 21.87 min in Group B (P = 0.025). No significant differences in patient-reported outcomes or complications were observed between the two groups (P > 0.05).

CONCLUSION

Deep learning achieved accurate and rapid segmentations of lumbosacral structures on CT, and deep learning-based 3D reconstructions were efficacious and reliable. Foraminoplasty simulation with deep learning-based lumbosacral reconstructions may benefit surgical difficulty prediction of PETD at L5/S1 level.

Utility of thoracic cage width in assessing surgical difficulty of minimally invasive esophagectomy in left lateral decubitus position

BACKGROUND

This study aimed to assess the surgical difficulty of minimally invasive esophagectomy in the left lateral decubitus position for patients with esophageal cancer from the perspective of short-term outcomes, including operation time, blood loss, and morbidity.

MATERIALS AND METHODS

The initial 44 consecutive patients with esophageal cancer who underwent minimally invasive esophagectomy were statistically analyzed retrospectively. Thoracic cage area was measured from preoperative computed tomography as a factor affecting the surgical difficulty of minimally invasive esophagectomy, as well as other patient characteristics. Correlations with short-term outcomes including chest operation time, blood loss, and morbidity rate were then examined.

RESULTS

In univariate analyses, smaller area of the upper thoracic cage width correlated with prolonged thoracic procedure time (p = 0.0119) and greater blood loss during thoracic procedures (p = 0.0283), but area of the lower thoracic cage showed no correlations. History of respiratory disease was associated with thoracic procedure time (p < 0.0001), but not blood loss. In multivariate analysis, small area of the upper thoracic cage was independently associated with prolonged thoracic procedure time (p = 0.0253). Small upper thoracic cage area was not directly correlated with morbidity rate, but prolonged thoracic procedure time was associated with increased blood loss (p < 0.0001) and morbidity rate (p = 0.0204). Empirical time reduction (p = 0.0065), but not blood loss, was associated with thoracic procedure time. However, area of the upper thoracic cage did not correlate with empirical case number. In multivariate analysis, area of the upper thoracic cage (p = 0.0317) and empirical case number (p = 0.0193) correlated independently with thoracic procedure time.

CONCLUSION

A small area of the upper thoracic cage correlated significantly with prolonged thoracic procedure time and increased thoracic blood loss for minimally invasive esophagectomy in the left lateral decubitus position, suggesting the surgical difficulty of minimally invasive esophagectomy in the left lateral decubitus position.

Delphi consensus on bile duct injuries during laparoscopic cholecystectomy: an evolutionary cul-de-sac or the birth pangs of a new technical framework?

Bile duct injury (BDI) during laparoscopic cholecystectomy remains a serious iatrogenic surgical complication. BDI most often occurs as a result of misidentification of the anatomy; however, clinical evidence on its precise mechanism and surgeons' perceptions is scarce. Surgeons from Japan, Korea, Taiwan, and the USA, etc. (n = 614) participated in a questionnaire regarding their BDI experience and near-misses; and perceptions on landmarks, intraoperative findings, and surgical techniques. Respondents voted for a Delphi process and graded each item on a five-point scale. The consensus was built when ≥80% of overall responses were 4 or 5. Response rates for the first- and second-round Delphi were 60.6% and 74.9%, respectively. Misidentification of local anatomy accounted for 76.2% of BDI. Final consensus was reached on: (1) Effective retraction of the gallbladder, (2) Always obtaining critical view of safety, and (3) Avoiding excessive use of electrocautery/clipping as vital procedures; and (4) Calot's triangle area and (5) Critical view of safety as important landmarks. For (6) Impacted gallstone and (7) Severe fibrosis/scarring in Calot's triangle, bail-out procedures may be indicated. A consensus was reached among expert surgeons on relevant landmarks and intraoperative findings and appropriate surgical techniques to avoid BDI.

Anatomical factors affecting the time required for microsurgical subinguinal varicocelectomy

Background

Microsurgical subinguinal varicocelectomy (MSV) is considered an effective and less morbid procedure, but the difficulty in preserving testicular arteries is a limitation of this procedure. We identified the microanatomy encountered during MSV and clarify its significance to the difficulty of the procedure.

Methods

Three hundred and twenty-six patients who underwent left MSV were evaluated. Detailed intraoperative microanatomy was recorded for each case. A classification system was used to assess the anatomical relationship between the internal spermatic artery and the varicose veins as follows: type I (non-adherent to the veins), type II (adherent to the veins), and type III (surrounded by veins). Type III cases were further divided into types III-a (an arterial pulse) and III-b (a blurred arterial pulse). A linear regression analysis of the factors associated with the length of the operation was used to determine the difficulty of the surgery.

Results

A mean number of 8.2 internal spermatic veins were ligated. Internal spermatic arteries were classified as type I in 14 % of patients, type II in 57 %, and type III in 29 % (III-a in 20 % and III-b in 9 %). A large number of internal spermatic veins and higher internal spermatic artery type were observed significantly more often in grade 3 varicoceles (p < 0.05). The types of internal spermatic arteries (ρ = 0.458) and numbers of internal spermatic veins (ρ = 0.431), cremasteric veins (ρ = 0.197), and gubernacular veins (ρ = 0.119) were significantly associated with the length of the operation (p < 0.05).

Conclusions

Anatomical factors were associated with the varicocele grade and surgical difficulty. These findings are helpful to perform MSV.

A novel difficulty scoring system for laparoscopic liver resection

Early on, laparoscopic liver resection (LLR) was limited to partial resection, but major LLR is no longer rare. A difficulty scoring system is required to guide surgeons in advancing from simple to highly technical laparoscopic resections. Subjects were 90 patients who had undergone pure LLR at three medical institutions (30 patients/institution) from January 2011 to April 2014. Surgical difficulty was assessed by the operator using an index of 1-10 with the following divisions: 1-3 low difficulty, 4-6 intermediate difficulty, and 7-10 high difficulty. Weighted kappa statistic was used to calculate the concordance between the operators' and reviewers' (expert surgeon) difficulty index. Inter-rater agreement (weighted kappa statistic) between the operators' and reviewers' assessments was 0.89 with the three-level difficulty index and 0.80 with the 10-level difficulty index. A 10-level difficulty index by linear modeling based on clinical information revealed a weighted kappa statistic of 0.72 and that scored by the extent of liver resection, tumor location, tumor size, liver function, and tumor proximity to major vessels revealed a weighted kappa statistic of 0.68. We proposed a new scoring system to predict difficulty of various LLRs preoperatively. The calculated score well reflected difficulty.

Effect of age, sex and level of surgical difficulty on inflammatory complications after third molar surgery

BACKGROUND

Patients' factors such as age and sex and surgical variables such as level of difficulty have been linked with surgical outcome in third molar surgery. The aim of this study was to determine the effect of these variables on inflammatory complications in patients undergoing third molar surgery.

METHODS

Patients referred to our institution for surgical extraction of their impacted lower third molar between January 2007 and December 2008 were the subjects of the study. Patients' demographics as well as types of impaction, indication and level of difficulty based on Pederson criteria were obtained. Post operative pain, swelling and mouth opening limitation were evaluated at day 1, day 2, day 3, day 5 and 1 week after the surgery and analyzed. A p value of less than 0.05 was considered significant.

RESULTS

A total of 150 patients aged 16-38 years (25.9 ± 4.47) met the inclusion criteria. Male accounted for 66 (44.0 %) while females were 84 (56.0 %), giving male to female ratio of 1:1.3. Age, sex and difficulty index had no effect on pain and trismus throughout the periods of postoperative evaluation (p > 0.05). Postoperative swelling was not affected by gender but patients above 25 years who had high scores of difficulty index had more facial swelling.

CONCLUSION

The results of this study shows that age, gender and the level of surgical difficulty have no effect on pain and mouth opening limitation after third molar surgery.

Role of patients' demographic characteristics and spatial orientation in predicting operative difficulty of impacted mandibular third molar

BACKGROUND

The influence of patient factors such as age, sex, weight, body mass index (BMI) and spatial orientation on operative difficulty of impacted mandibular third molar (M3) surgery is a subject of controversy in the literature.

AIM

To assess the risk indicators of operative difficulty of mandibular third molar surgery at our institution.

SUBJECTS AND METHODS

A descriptive cross-sectional study involving patients that presented for wisdom tooth extraction between January 2010 and December 2011. The correlation between patients' factors such as age, sex, weight, height, BMI, radiographic spatial relationship of the impacted tooth and operation time was determined with Spearman's rank correlation coefficient. Statistically significant variables were selected for multiple regression analysis to determine which factors contribute most to operative difficulty of M3. P value was set at 0.05. Statistical analysis used SPSS 17.0.

RESULTS

Only patients' age and radiographic spatial relationship showed a statistically significant correlation with operation time (P = 0.038 and 0.008, respectively). Linear regression analysis of patients' age and angulation of M3 showed that both contribute 44.8% risk of increased operation time (regression coefficient = 0.448), with M3 angulation contributing more significantly to increase in operation time (P = 0.001) than increasing age of the patient (P = 0.005).

CONCLUSIONS

Findings from this study have shown that increasing age of the patient and the angulation of M3 impaction increases the risk of operative difficulty of the impacted M3 significantly.