A case report and review of the literature of 7-millimeter lateral port-site herniation following total laparoscopic hysterectomy.

Port-site herniation (PSH) is a rare complication observed postlaparoscopic surgery, typically associated with port sizes of 10 mm or larger, commonly occurred at umbilicus. While occurrences of extra-umbilicus with port size smaller than 10 mm are rare, we present a case detailing a lateral 7 mm PSH diagnosed on the 8th day following a total laparoscopic hysterectomy. The patient exhibited clinical symptoms indicative of partial small bowel obstruction, which became apparent on the third postoperative day. Computed tomography revealed significant small bowel dilatation and herniation through the previously employed 7 mm trocar site. Notably, this trocar site had been utilized with uterine screw. Prompt laparoscopic repair successfully addressed the herniation. The patient demonstrated satisfactory recovery and was subsequently discharged. While current practice recommends fascial incision closure for port size ≥10 mm. In light of our case, we propose considering fascial closure for small-size trocar subjected to any use of a manipulator.

Trocar-assisted extraocular technique for intrascleral intraocular lens fixation using a 90°-curved forceps: a modified extraocular forceps-guided technique.

PURPOSE: To investigate the surgical outcomes of intrascleral intraocular lens (IOL) fixation using a modified extraocular forceps-guided technique. STUDY DESIGN: Retrospective case series. METHODS: Overall, 81 eyes of 78 patients who underwent intrascleral IOL fixation using the modified extraocular forceps-guided technique were included. The procedure entailed creating 2 scleral half-layer T-shaped incisions perpendicular to the main incision and forming a scleral tunnel. A 25-gauge trocar was inserted at the lower end of the T-shaped incision to perform vitrectomy. A 27-gauge needle was inserted from the left-hand port, and the leading haptic was inserted into the needle lumen. After removal of the right-hand trocar, a 90°-curved intrascleral fixation forceps was inserted into the eye, exposing the tip at the main incision, thus allowing the tip of the extraocular trailing haptic to be gripped and both haptics to be pulled out. The left-hand trocar was removed, and the haptics were buried in the scleral tunnel. The surgical outcomes of this technique were retrospectively evaluated on the basis of the medical records. RESULTS: The induction of haptics was successful in all cases. The preoperative best-corrected visual acuity improved from 0.35±0.68 to 0.12±0.36 logMAR postoperatively (P<0.01). The refractive error was -0.27±0.87 D; IOL decentration, 0.39±0.18 mm; IOL tilt, 5.97±2.65°; IOL astigmatism, 0.35±0.36 D; and corneal endothelial cell loss, 10.3±12.7%. There were no serious complications related to the surgical technique. CONCLUSION: The modified extraocular forceps-guided technique allows for safe and straightforward induction of the trailing haptics and enables the performance of intrascleral IOL fixation with minimal scleral incisions.

Extra-abdominal trocar and instrument detection for enhanced surgical workflow understanding.

PURPOSE: Video-based intra-abdominal instrument tracking for laparoscopic surgeries is a common research area. However, the tracking can only be done with instruments that are actually visible in the laparoscopic image. By using extra-abdominal cameras to detect trocars and classify their occupancy state, additional information about the instrument location, whether an instrument is still in the abdomen or not, can be obtained. This can enhance laparoscopic workflow understanding and enrich already existing intra-abdominal solutions. METHODS: A data set of four laparoscopic surgeries recorded with two time-synchronized extra-abdominal 2D cameras was generated. The preprocessed and annotated data were used to train a deep learning-based network architecture consisting of a trocar detection, a centroid tracker and a temporal model to provide the occupancy state of all trocars during the surgery. RESULTS: The trocar detection model achieves an F1 score of 95.06 ± 0.88 % . The prediction of the occupancy state yields an F1 score of 89.29 ± 5.29 % , providing a first step towards enhanced surgical workflow understanding. CONCLUSION: The current method shows promising results for the extra-abdominal tracking of trocars and their occupancy state. Future advancements include the enlargement of the data set and incorporation of intra-abdominal imaging to facilitate accurate assignment of instruments to trocars.

Clinical outcomes of iris fixation and sutureless scleral fixation of dislocated foldable posterior chamber intraocular lenses.

PURPOSE: Explore the visual outcome and complications of iris fixation intraocular lenses (IFIOL) and sutureless scleral-fixated intraocular lenses (SSFIOL) in the surgical management of patients without exchanging dislocated posterior chamber intraocular lenses (PCIOLs) in the vitreous. METHODS: Retrospectively, 14 IFIOL and 15 SSFIOL reimplantations for dislocated PCIOLs were analyzed. Mean follow-up of reIFIOL group and reSSFIOL group: 11.3±2.0 (range: 9-15) months and 11.8±2.2 (range: 9-16) months, respectively. Preoperative and postoperative outcomes, operative indications, and complications were evaluated. RESULTS: Primary surgical indications were pseudoexfoliation (PXE) (21.4%), post-cataract surgery (PCS) (35.7%), trauma (42.8%) in the reIFIOL group, and PXE (26.6%), PCS (40%) trauma (33.3%) in reSSFIOL group, respectively. At the latest follow-up, there was an improvement in best-corrected visual acuity (BCVA) (0.053±0.051 to 0.53±0.13, P<0.0001) in reIFIOL group and (0.05±0.02 to 0.64±0.16, P<0.0001) in reSSFIOL group. Postoperative complications of reIFIOL group and reSSFIOL group included corneal edema (14.2%; nil), IOP elevation (21.4%; 7.1%), bullous keratopathy (14.2%; nil), anterior uveitis (35.7%; 13.3%), cystoid macular edema (CME) (21.4%; 7.1%), pupil ovalization (21.4%; nil), broken haptic (none; 13.3%), IOL exchange (nil; 13.3%), and vitreous hemorrhage (nil; 14.2%). CONCLUSIONS: Self-dislocated IOL reimplantation may enable much earlier visual rehabilitation in the reSSFIOL group than in the reIFIOL group. Moreover, the 27G trocar-assisted reSSFIOL technique takes a shorter operation time and relatively lower complication rates. However, further prospective studies with larger series and longer follow-up periods are required.

Long-term outcome of retroperitoneoscopic one-trocar-assisted pyeloplasty: a single-center and single-surgeon experience.

PURPOSE: The aim of this study was to assess the long-term outcomes of retroperitoneoscopic one-trocar-assisted pyeloplasty (OTAP) for ureteropelvic junction obstruction (UPJO) in children. METHODS: This retrospective analysis included 70 pediatric cases, all under the age of 5, diagnosed with UPJO and treated with the OTAP technique between May 2011 and June 2013 by a single surgeon. A single 10 mm operative scope with a 5 mm working channel was utilized to mobilize the ureteropelvic junction (UPJ) and exteriorize it through the trocar insertion site. Subsequently, conventional Anderson-Hynes dismembered pyeloplasty was conducted extracorporeally. Patient's demographics, operative time, hospital stay, complications, and success rate were evaluated. RESULTS: Seventy pediatric patients (65 males and 5 females) underwent OTAP, with ages at the time of operation ranging from 1 month to 5 years (mean = 22.6 ± 18.6 months). The mean operative time was 74.8 ± 15.2 min. There was a significant reduction in the mean renal pelvis size from 34.3 ± 8.1 mm preoperatively to 13.8 ± 4.7 mm postoperatively (p < 0.05). Moreover, the mean differential renal function (DRF) increased from 47.9 ± 9.8% preoperatively to 51.2 ± 5.9% postoperatively (p < 0.05). All patients experienced an uneventful postoperative recovery, with a median hospital stay of 3.4 days. The success rate was 95.7%, with a median follow-up time of 75 months (range: 6-125 months). CONCLUSION: OTAP is a safe and feasible minimally invasive technique to correct ureteropelvic junction obstruction in children. It could be considered as a treatment of choice for children under the age of 5 as it combines the advantages of open and retroperitoneoscopic pyeloplasty and presents excellent long-term outcomes. TRIAL REGISTRATION NUMBER: NCT06349161 April 4th, 2024, retrospectively registered.

Trocar-site incisional hernia after 8-mm robotic trocar placement: A prospective study.

BACKGROUND: The current literature supports the closure of trocar sites ≥10-mm for the risk of developing incisional hernias, while there is no need to suture the abdominal fascia when using 5-mm trocars. To date, evidence regarding the closure of 8-mm trocars that are use by new robotic systems is weak. The aim of our study was to investigate the incidence of incisional hernia for 8-mm trocars. METHODS: We prospectively collected data on all patients undergoing robotic-assisted abdominal wall surgery from 2020 to 2023, in whom the abdominal fascia of all 8-mm trocars was not closed. The enrolled patients underwent a follow-up visit during which we conducted clinical and sonographic evaluations of all 8-mm trocars, in addition to assessing the satisfaction levels of the patients. The primary outcome was the incidence of port-site hernia. RESULTS: We enrolled 166 patients, 155 men and 11 women, for a total of 513 trocars accessed. Mean age was 61.1 ± 14.0 years, and mean BMI was 27.0 ± 3.9 kg/m2. The follow-up visits were carried out after a median follow-up of 14.5 (9.0-23.2) months. Only one case developed an asymptomatic 1 × 1 cm supra-umbilical hernia that was not treated. Patient reported a satisfaction regarding the 8-mm trocars and skin sutures of 9.8 ± 0.5 out of 10 points. CONCLUSIONS: The occurrence of a trocar-site hernia after 8-mm robotic access is extremely low. Hence, the fascia closure may not be necessary.

Laparoscopic Sleeve Gastrectomy Smart Trocar Site Modification in Patients with Extreme Obesity.

PURPOSE: Laparoscopic sleeve gastrectomy (LSG) is one of the most common bariatric surgeries performed worldwide. Although it has established itself as a satisfactory procedure on its own, it can also function as the first part of a two-stage treatment strategy. This is especially true in situations of extreme obesity (obesity grade IV or higher). One rationale for choosing a two-stage treatment is the technical difficulty of doing other types of bariatric procedures involving anastomoses due to body physique and level of visceral adiposity. LSG in patients with such a high body mass index (BMI) is comparatively simpler technically, but it does also have a degree of complexity for similar reasons. Here, we present an innovative port configuration for LSG that can significantly reduce ergonomic challenges and enhance the safety of the procedure in patients with extreme obesity. MATERIALS AND METHODS: This new trocar site arrangement is generally suitable for individuals with grade IV obesity or above. It is especially effective for people with obesity at or above grade V. Only standard laparoscopic instruments are used. RESULTS: This design preserves the ideal manipulation and elevation angles at 60° and allows surgeons to use standard laparoscopic instruments with lowered shoulders, reducing muscular strain and fatigue. Additionally, it improves patient safety. CONCLUSION: In patients with extreme obesity, this proposed port configuration for LSG can significantly reduce ergonomic difficulties and increase surgical safety.

Early Drainage of Suprachoroidal Hemorrhage Combined with Surgical Correction of Hypotony after Trabeculectomy.

Aims and background: Delayed suprachoroidal hemorrhage (DSCH) is a vision-threatening complication of intraocular surgeries with a higher prevalence in postglaucoma filtering surgeries. Through these case series of trabeculectomy complicated with DSCH, we aim to emphasize that correction of hypotony (inciting factor) is fundamental for complete resolution and prevention of recurrence. Case description: All three glaucoma patients underwent trabeculectomy surgery followed by DSCH on postoperative day 1. Drainage of DSCH using a 23 gauge trocar cannula within 48 hours of onset was performed along with exploration for the cause of hypotony. All three patients had satisfactory visual and anatomical outcomes. Conclusion: Early drainage using 23 gauge trocar cannulas gives good results in DSCH. The cause of hypotony must simultaneously be corrected during the drainage of DSCH. Preventive measures against hypotony should be taken while doing glaucoma filtering surgery. Clinical significance: Surgical exploration for the cause of hypotony must simultaneously be performed during drainage of DSCH. Primary preventive measures against hypotony and bleeding during glaucoma filtering surgeries, like the use of releasable sutures, viscoelastic in the anterior chamber, and discontinuation of anticoagulants, can be done. Early drainage using trocar cannulas gives satisfactory results in DSCH postglaucoma surgeries. How to cite this article: Beri N, Verma S, Bukke AN, et al. Early Drainage of Suprachoroidal Hemorrhage Combined with Surgical Correction of Hypotony after Trabeculectomy. J Curr Glaucoma Pract 2024;18(1):23-27.

Optical Trocar Access for Retroperitoneal Robotic-Assisted Pyeloplasty in Children with Ureteropelvic Junction Obstruction.

Purpose: Retroperitoneal robotic-assisted pyeloplasty (ret-RAP) for ureteropelvic junction obstruction (UPJO) requires a larger retroperitoneal space (RS) to maintain specified distances between robotic (da Vinci) trocars and between trocars and the region of interest. A modified closed technique (MOT) and conventional closed technique (COT) were compared for creating an adequate RS with optical trocars. Methods: RS access in children with UPJO who underwent ret-RAP (n = 30) was MOT (n = 15) and COT (n = 15). All patients were positioned laterally. For MOT, a 5 mm optical trocar was inserted at the angle formed between the 12th rib and the erector spinae muscles. As the trocar was advanced under direct vision, it pierced the superficial subcutaneous layer, Scarpa's fascia, lumbar fascia, internal/external oblique and transversus abdominalis muscles, and the posterior renal fascia. Once in the RS, the tip of the scope was used for blunt dissection of perirenal fat, the tip was withdrawn until it was outside the perirenal fascia, and used to dissect toward the anterior abdomen in the pararenal fat layer. Results: Ages and weights at ret-RAP were similar (MOT: 5.6 ± 1.8 years versus COT: 7.8 ± 4.6 years; MOT: 20.6 ± 10.1 kg versus COT: 27.6 ± 13.9 kg). Times for RS access were similar (MOT: 1.6 ± 0.5 minutes versus COT: 1.9 ± 0.7 minutes), but RS expansion was significantly quicker in MOT (32.3 ± 8.7 minutes versus 52.0 ± 15.1 minutes; P < .001). Peritoneal injury caused carbon dioxide leakage in 4 of 15 COT cases and 0 of 15 MOT cases. Conclusion: RS expansion with MOT was safer because there were no peritoneal injuries and MOT was quicker than COT.

Trocar blade-assisted skewer technique for phacoemulsification of a dislocated lens.

A posteriorly dislocated lens is often managed with a fragmatome through a pars plana approach because it is difficult to manage anteriorly. The lens often sinks to the surface of the retina or floats around in the vitreous cavity during pars plana lensectomy. Mechanical trauma can occur while removing the dislocated lens fragments. However, sometimes the lens can be confined to the anterior vitreous cavity even though the zonules are completely disrupted. It would be ideal if there was a simple way to stabilize and support the lens so that the lens could remain in the posterior chamber while phacoemulsification is performed through a corneal incision as usual. We describe a technique using a trocar blade to stabilize the lens while performing phacoemulsification through a corneal incision. We found it to be a useful and safe instrument to support the subluxated lens during phacoemulsification.

The influence of microwave ablation parameters on the positioning of trocar in different cancerous tissues: a numerical study.

The present study analyzed the microwave ablation of cancerous tumors located in six major cancer-prone organs and estimated the significance of input power and treatment time parameters in the apt positioning of the trocar into the tissue during microwave ablation. The present study has considered a three-dimensional two-compartment tumour-embedded tissue model. FEA based COMSOL Multiphysics software with inbuilt bioheat transfer, electromagnetic waves, heat transfer in solids and fluids, and laminar flow physics has been used to obtain the numerical results. Based on the mortality rates caused by cancer, the present study has considered six major organs affected by cancer, viz. lung, breast, stomach/gastric, liver, liver (with colon metastasis), and kidney for MWA analysis. The input power (100 W) and ablation times (4 minutes) with apt and inapt positioning of the trocar have been considered to compare the ablation volume of various cancerous tissues. The present study addresses one of the major problems clinicians face, i.e. the proper placement of the trocar due to poor imaging techniques and human error, resulting in incomplete tumor ablation and increased surgical procedures. The highest values of the ablation region have been observed for the liver, colon metastatic liver and breast cancerous tissues compared with other organs at the same operating conditions.

The present study has investigated the application of microwave ablation for cancer treatment in six major organs, specifically emphasizing the evaluation of ablation volume during the procedure. Using COMSOL-Multiphysics software, the study has investigated MWA of tumor embedded organs in the lung, breast, stomach, liver, and kidney. The positioning of the trocar, a crucial element in the treatment process, has been examined to address challenges in effectively ablating tumors.From the results, it has been revealed that liver, colon metastatic liver, and breast cancer tissues exhibited the largest areas of ablation volume compared with other organs.Organs like the breast and hepatic glands, characterized by lower heat capacity and density, have shown larger ablation zones. Trocar positioning significantly influenced the stomach, liver, and kidney, where improper placement led to notable increases in ablation volume, posing a risk of unintended damage to healthy tissue.Further, the study has concluded that precise trocar positioning plays a crucial role in optimizing microwave ablation. This precision has the potential to enhance the effectiveness of cancer treatments while minimizing harm to healthy tissue. The insights gained from this research offer valuable information for clinicians looking to enhance the precision of cancer therapies, ultimately aiming for improved outcomes for patients.

Robotic 8-mm trocar fascial wounds: To close or not to close?

BACKGROUND: The aim of this study was to investigate 8-mm robotic trocar site hernia (TSH) rate over the short and long term, providing aids to manage the related fascial wounds. METHODS: A retrospective analysis of 320 patients undergoing robotic surgery was conducted. The primary outcome was 8-mm TSH rate with a minimum follow-up of 12 months. The secondary outcome was the rate of haematomas and infections related to 8-mm wounds and their association with patient comorbidities and trocar position. RESULTS: One case of TSH was observed (0.31%). There were 15 cases of wound infection (4.68%) and 22 cases of wound haematoma (6.87%). Trocar related complications were significantly associated with patient comorbidities, not with trocar position. CONCLUSIONS: Our results do not justify the 8-mm fascial wound closure. Data concerning the association between trocar-related complications and patient comorbidities strengthen the need to implement the control of metabolic state and correct administration of perioperative therapy in high-risk patients.

A Safe Laparoscopic Approach for Ovarian Tumors during Pregnancy.

Objectives: Surgery for pregnant women with ovarian tumors poses the risk of uterine irritation. We aimed to demonstrate the superiority of our laparoscopic technique over conventional methods and to compare the outcomes of laparoscopy with those of laparotomy for ovarian tumors during pregnancy. Materials and Methods: This retrospective study included 50 patients undergoing procedures for ovarian tumors during pregnancy at the Tokushima University Hospital between January 2005 and December 2021. We compared surgical outcomes between laparoscopic procedures and laparotomy, along with complications. In addition, we compared the frequency of uterine stimulation with the conventional trocar position to that with the currently used trocar position in laparoscopic surgery. Results: Forty patients in the laparoscopy group and 10 in the laparotomy group underwent procedures. The laparoscopy group had less bleeding (16.4 ± 28.8 vs. 58 ± 72.2 mL, P < 0.05) and shorter hospital stays (7.6 ± 1.7 vs. 12.8 ± 13.1 days, P < 0.05) compared with those of the laparotomy group. The outcomes showed no significant differences between groups. All laparoscopies and laparotomies were successful and without complications. Furthermore, the current trocar position tended to stimulate the uterus less frequently. Conclusion: The results suggested that, compared to laparotomy, laparoscopy for ovarian tumors during pregnancy had better outcomes. The trocar position in our technique allows for easy operation of ovarian tumors without interference by forceps or cameras, resulting in minimal irritation of the uterus. Our original laparoscopic method may be safer with superior outcomes over the conventional method.

Does the angle of trocar insertion affect the fascial defect caused? A porcine model.

INTRODUCTION: With an incidence of 0-5.2%, trocar site hernias frequently occur following laparoscopy. It is unclear to what extent the angle of trocar insertion affects the size of the fascial defect caused. Hence, we performed a porcine model. METHODS: In October 2022, a total of five female pigs were euthanized. In alternating order, three bladeless and two bladed conical 12-mm trocars were inserted at an angle of 45° on each side for 60 min twice each pig. For this purpose, an epoxy resin handmade cuboid with a central channel that runs at an angle of 45° was used. Subsequently, photo imaging and defect size measurement took place. The results were compared with those of our previously conducted and published porcine model, in which the trocars were inserted at an angle of 90°. Effects of trocar type (bladed vs. bladeless) and angle on defect size were analyzed using a mixed model regression analysis. RESULTS: The bladeless trocars caused statistically significant smaller defects at the fascia than the bladed (23.4 (SD = 16.9) mm2 vs. 41.3 (SD = 14.8) mm2, p < 0.001). The bladeless VersaOne trocar caused the smallest defect of 16.0 (SD = 6.1) mm2. The bladed VersaOne trocar caused the largest defect of 47.7 (SD = 10.5) mm2. The defect size of the trocars used at a 45° angle averaged 30.5 (SD = 18.3) mm2. The defect size of trocars used at a 90° angle was significantly larger, averaging 58.3 (SD = 20.2) mm2 (p = 0.007). CONCLUSION: When conical 12-mm trocars are inserted at a 45° angle, especially bladeless ones, they appear to cause small fascial defects compared with insertion at a 90° angle. This might lead also to a lower rate of trocar hernias. Bladeless trocars might cause smaller fascial defects than bladed trocars.

Intracorporeal antimesenteric ancillary trocar: an anastomotic technique facilitating natural orifice specimen extraction in left-sided colorectal surgery.

AIM: Natural orifice specimen extraction (NOSE) in left-sided colorectal surgery requires application of the circular stapler anvil to the proximal bowel without exteriorization through an additional abdominal incision. We describe an intracorporeal method to secure the stapler anvil, termed the intracorporeal antimesenteric ancillary trocar (IAAT) technique. METHOD: The ancillary trocar is attached to the stapler anvil before introduction into the abdominal cavity through the anal or vaginal orifice. The colon is incised before the trocar spike is brought out through the antimesenteric surface 3-4 cm within the cut edge. A linear stapler is used to seal the bowel end. The ancillary trocar is detached and retrieved via the NOSE conduit. Following the NOSE procedure, a side-to-end colorectal anastomosis is performed with the transanal circular stapler. RESULTS: Ten consecutive patients underwent elective left-sided colorectal resection with IAAT for NOSE (seven transanal, three transvaginal) from January to June 2023. Median age and body mass index were 66 (range 47-74) years and 24.3 (range 17.9-30.8) kg/m2 respectively. Two (20%) patients underwent sigmoid colectomy for sigmoid volvulus while eight (80%) underwent anterior resection for colorectal cancer. Median operating time, operative blood loss and postoperative length of hospital stay were 170 (range 140-240) min, 20 (range 10-40) mL and 1 (range 1-3) day respectively. There were no postoperative complications, readmissions or reoperations. Median follow-up duration was 3 (range 1-6) months. CONCLUSION: The IAAT double-stapling side-to-end anastomotic technique is safe and feasible for patients undergoing left-sided colorectal resection with NOSE, resulting in good outcomes.

Neonatal Subcutaneous Emphysema Secondary to Chest Tube Placement Using the Trocar Technique: A Case Report.

Subcutaneous emphysema is a type of air leak in which air accumulates within the subcutaneous layer of the skin underneath the dermal layers. The accumulation of air can be seen on imaging in relevant body areas such as the abdomen, chest, face, or neck. During physical examination, crepitus, the sensation or sound of crackling upon palpation, is the most common associated finding. Various causes for subcutaneous emphysema exist, with one such cause being thoracostomy or chest tube placement. The trocar technique, in particular, has been associated with greater complications when compared to other techniques. Here, we present a case of subcutaneous emphysema in a neonate occurring after placement of a chest tube using the trocar technique. At this time, much of the knowledge regarding subcutaneous emphysema related to chest tube placement is in the adult population. Clinicians should be aware of this complication in neonates as the body of knowledge regarding this topic continues to grow.

Image-guided percutaneous cholecystostomy: challenging the norms.

Image-guided percutaneous cholecystostomy (IGPC) is a widely recognized and regularly employed procedure in numerous institutions, serving as an indispensable cornerstone in the management of patients with acute cholecystitis. The most up-to-date literature has found that the transperitoneal route is at least as safe as the transhepatic route and that both the trocar and Seldinger techniques are equally safe and effective. The above novel insights may offer reassurance and alleviate concerns among operators performing IGPC by dispelling the fixation on previously established beliefs and thus providing flexibility, which lightens the load on the operator. Future studies could further investigate these findings and shed light on potential disparities in the safety and efficacy profiles associated with the subcostal and intercostal approaches, different drainage catheter sizes, and/or the impact of operator experience on complication rates.

Laparoscopic Trocars: Marketed Versus True Dimensions-A Descriptive Study.

STUDY OBJECTIVE: To establish true dimensions of single-use laparoscopic trocars compared with marketed dimensions, calculate corresponding incision sizes, examine what trocar size categories are based on, and outline accessibility of information regarding true dimensions. DESIGN: Descriptive study. SETTING: Laparoscopic disposable trocars available in North America and Europe are marketed in several distinct categories. In practice, trocars in the same-size category exhibit different functionality (ability to introduce instruments/needles and retrieve specimens) and warrant different incision lengths. PATIENTS: Not applicable. INTERVENTIONS: Not applicable. MEASUREMENTS AND MAIN RESULTS: True dimensions for 125 trocars (bladeless, optical, and balloon) were obtained from 9 vendors covering 8 marketed size categories (3-, 3.5-, 5-, 8-, 10-, 11-, 12-, and 15-mm trocars). On average, true inner cannula diameter was 0.92 mm wider (SD, 0.41 mm; range, 0-2.4 mm) than the marketed size category, with the widest range in the 5 mm category. For 5-mm trocars, mean true inner diameter was 6.1 mm (SD, 0.45; range, 5.5-7.4) and true outer diameter 8.3 mm (SD, 0.71; range, 8.0-10.7). For 12-mm trocars, mean true inner diameter was 13.0 mm (SD, 0.21; range, 12-13.3) and outer diameter 15.3 mm (SD, 0.48; range, 14.4-16.8). Five-mm trocars necessitate a mean incision size of 13.0 mm (SD, 1.1; range, 12.1-16.8) and 12-mm trocars a mean incision of 24.0 mm (SD, 0.75; range, 22.6-26.4). No vendors stated actual diameters on company website or catalog. In one instance the Instructions For Use document contained the true inner diameter. CONCLUSION: Trocar size categories give a false sense of standardization when in actuality there are considerable within-category differences in both inner and outer diameters, corresponding to differences in functionality and required incision sizes. There is no universally applied definition for trocar size categories. Accessibility of information on true dimensions is limited.

Trocar localisation for robot-assisted vitreoretinal surgery.

PURPOSE: Robot-assisted vitreoretinal surgery provides precise and consistent operations on the back of the eye. To perform this safely, knowledge of the surgical instrument's remote centre of motion (RCM) and the location of the insertion point into the eye (trocar) is required. This enables the robot to align both positions to pivot the instrument about the trocar, thus preventing any damaging lateral forces from being exerted. METHODS: Building on a system developed in previous work, this study presents a trocar localisation method that uses a micro-camera mounted on a vitreoretinal surgical forceps, to track two ArUco markers attached on either side of a trocar. The trocar position is the estimated midpoint between the markers. RESULTS: Experimental evaluation of the trocar localisation was conducted. Results showed an RMSE of 1.82 mm for the localisation of the markers and an RMSE of 1.24 mm for the trocar localisation. CONCLUSIONS: The proposed camera-based trocar localisation presents reasonable consistency and accuracy and shows improved results compared to other current methods. Optimum accuracy for this application would necessitate a 1.4 mm absolute error margin, which corresponds to the trocar's radius. The trocar localisation results are successfully found within this margin, yet the marker localisation would require further refinement to ensure consistency of localisation within the error margin. Further work will refine these position estimates and ensure the error stays consistently within this boundary.