Identification Of Plane Research Articles

Left basilar VATS segmentectomy for intra lobar pulmonary sequestration using indocyanine green for identification of the intersegmental plane

Left basilar VATS segmentectomy for intra lobar pulmonary sequestration using indocyanine green for identification of the intersegmental plane

Bicuspid aortic valve annulus: assessment of geometry and size changes during the cardiac cycle as measured with a standardized method to define the annular plane

PurposeBicuspid aortic valve (BAV) is a complex malformation affecting not merely the aortic valve. However, little is known regarding the dynamic physiology of the aortic annulus in these patients and whether it is similar to tricuspid aortic valves (TAV). Determining the BAV annular plane is more challenging than for TAV. Our aim was to present a standardized methodology to determine BAV annulus and investigate its changes in shape and dimensions during the cardiac cycle.MethodsBAV patients were prospectively included and underwent an ECG-gated cardiac CTA. The annulus plane was manually identified on reconstructions at 5% intervals of the cardiac cycle with a new standardized method for different BAV types. Based on semi-automatically defined contours, maximum and minimum diameter, area, area-derived diameter, perimeter, asymmetry ratio (AR), and relative area were calculated. Differences of dynamic annular parameters were assessed also per BAV type.ResultsOf the 55 patients included (38.4 ± 13.3 years; 58% males), 38 had BAV Sievers type 1, 10 type 0, and 7 type 2. The minimum diameter, perimeter, area, and area-derived diameter were significantly higher in systole than in diastole with a relative change of 13.7%, 4.8%, 13.7%, and 7.2% respectively (all p < 0.001). The AR was ≥ 1.1 in all phases, indicating an elliptic shape, with more pronounced flattening in diastole (p < 0.001). Different BAV types showed comparable dynamic changes.ConclusionsBAV annulus undergo significant changes in shape during the cardiac cycle with a wider area in systole and a more elliptic conformation in diastole regardless of valve type.Key Points• A refined method for the identification of the annulus plane on CT scans of patients with bicuspid aortic valves, tailored for the specific anatomy of each valve type, is proposed.• The annulus of patients with bicuspid aortic valves undergoes significant changes during the cardiac cycle with a wider area and more circular shape in systole regardless of valve type.• As compared to previously published data, the bicuspid aortic valve annulus has physiological dynamics similar to that encountered in tricuspid valves but with overall larger dimensions.

Review of Approaches to Developing Intersegmental Plane during Segmentectomy.

In recent years, with the popularity of computed tomography (CT) scanning, early lung cancer has been found in a large number of patients, and segmentectomy has been widely used in clinical practice. The development of intersegmental plane is the most critical step in segmentectomy. At present, there are many methods to identify the intersegmental plane. Also, dissection of the intersegmental plane has been a challenge for thoracic surgeons for decades because of the complicated anatomic variations. This study focuses on the safety and efficacy of relevant methods in both identification and dissection of the intersegmental plane in segmentectomy.

Lung segmentectomy assisted by highly selective independent segmental ventilation: a series of three cases

BackgroundThe identification of targeted intersegmental planes and resection with adequate surgical margins are among the crucial steps in anatomical pulmonary segmentectomy, and technical improvements are still needed.Case presentationWe reported three cases of intersegmental plane identification using highly selective independent segmental ventilation during segmentectomy. All cases required cooperation with an anesthesiologist who was able to perform segmental ventilation and double confirmation of segmental bronchus branches by the surgeon. The surgical procedure provides a direct visualization of spare segment inflation and saves time in deflation over the conventional residual segment inflation method.ConclusionsHighly selective independent segmental ventilation could be considered a suitable option for pulmonary intersegmental plane identification and could be universally used for lung segmentectomy.

Pretemporal Transcavernous Approach for Resection of an Orbito-Cavernous Oculomotor Schwannoma.

The following operative video demonstrates surgical tenets and nuances of the pretemporal transcavernous approach in an unusual case of a 33-year-old patient suffering new onset diplopia and a third nerve palsy due to an orbito-cavernous oculomotor schwannoma. Near total resection was accomplished through an extended pterional craniotomy with pretemporal transcavernous exposure of her lesion, resulting in resolution of her preoperative oculomotor palsy and visual dysfunction. When combined with extended pterional and modified frontotemporal orbitozygomatic approaches, the pretemporal transcavernous approach provides excellent surgical access to the parasellar region including the superior orbital fissure and cavernous sinus. Meticulous dissection and early identification of tissue planes, including cranial nerve and vascular anatomy, allows for safe removal of tumors arising in this region. The link to the video can be found at: https://youtu.be/EuIRTP7wWBQ .

Extended Robotic Pulmonary Resections.

While lung cancer remains the most common cause of cancer-related mortality in the United States, surgery for curative intent continues to be a mainstay of therapy. The robotic platform for pulmonary resection for non-small cell lung cancer (NSCLC) has been utilized for more than a decade now. With respect to more localized resections, such as wedge resection or lobectomy, considerable data exist demonstrating shorter length of stay, decreased postoperative pain, improved lymph node dissection, and overall lower complication rate. There are a multitude of technical advantages the robotic approach offers, such as improved optics, natural movement of the operator's hands to control the instruments, and precise identification of tissue planes leading to a more ergonomic and safe dissection. Due to the advantages, the scope of robotic resections is expanding. In this review, we will look at the existing data on extended robotic pulmonary resections, specifically post-induction therapy resection, sleeve lobectomy, and pneumonectomy. Additionally, this review will examine the indications for these more complex resections, as well as review the data and outcomes from other institutions' experience with performing them. Lastly, we will share the strategy and outlook of our own institution with respect to these three types of extended pulmonary resections. Though some controversy remains regarding the use and safety of robotic surgery in these complex pulmonary resections, we hope to shed some light on the existing evidence and evaluate the efficacy and safety for patients with NSCLC.

Indications and technical details of sublobar resections for small-sized lung cancers based on tumor characteristics

With the recent increase in small-sized lung cancers, sublobar resection and minimally invasive surgeries are becoming preferred. In particular, the detection of ground-glass nodules (GGNs) on high-resolution computed tomography has increased. Although lobectomy has been considered a standard procedure for treating lung cancer, sublobar resections have been indicated for treating GGN-dominant small-sized lung cancers. Wedge resection and segmentectomy have generally been performed as sublobar resection; however, each procedure has some technical advantages and disadvantages. Although anatomical resection as a segmentectomy is a complicated procedure, it has recently been increasingly performed with the accurate anatomical grasp using three-dimensional computed tomography and the identification of the intersegmental plane. Other procedures involving the use of newer technologies can also be performed. Individualized sublobar resection might be a suitable procedure for small-sized lung cancer with the appropriate selection of procedures based on each tumor’s characteristics and improving the methods to overcome some technical difficulties.

Human Spinal Column Diagnostic Parameter Identification Using Geometrical Model of the Vertebral Body

Abstract A geometric model and related methods to easily define patient specific vertebral body models have been introduced in our previous studies. This paper proposes an angle measurement method that can be fully automated after the definition of the patient specific vertebral body model. A Principal Component Analysis based algorithm allowing the quick identification of the symmetry plane of the human spline is also developed and described. The clinical dataset used to analyse and validate the models and methods introduced consists of 39 patients’ lumbar section of the spinal column with 195 vertebrae. In terms of angle measurement the proposed geometric model and the measurement method is proven to be accurate enough for clinical diagnostics, the average mean value of the measurement error 0.15° and 0.75° comparing the measurements to the two reference datasets. The average standard deviation of the error was around 2.50° that is almost the same as the average standard deviation of the two reference datasets (2.34°).

The Use of Optical Coherence Tomography as an Intraoperative Adjunct of Oculoplastic Surgery.

The advent of integrated intraoperative optical coherence tomography (i2OCT) has opened the door for safer and more complex surgeries in the retina and cornea. However, to limit its use to just two subspecialties within ophthalmology is an opportunity lost for many other subspecialties. Here, we describe the use of i2OCT in oculoplastic surgery. It can be used in cases of severe symblepharon where the cornea is heavily involved, so that the surgeon is aware of the depth of the pannus when trying to remove it. It can also be used when the corneal planes are difficult to identify. In oculoplastic surgery the technology allows for identification of tissue planes when en face visualization is difficult due to developmental abnormalities and repeated surgeries. Our experience reflects some of the many uses of iOCT in ophthalmic surgery, highlighting its added value in surgical precision.

A robust method for automatic identification of femoral landmarks, axes, planes and bone coordinate systems using surface models

The identification of femoral landmarks is a common procedure in multiple academic fields. Femoral bone coordinate systems are used particularly in orthopedics and biomechanics, and are defined by landmarks, axes and planes. A fully automatic detection overcomes the drawbacks of a labor-intensive manual identification. In this paper, a new automatic atlas- and a priori knowledge-based approach that processes femoral surface models, called the A&A method, was evaluated. The A&A method is divided in two stages. Firstly, a single atlas-based registration maps landmarks and areas from a template surface to the subject. In the second stage, landmarks, axes and planes that are used to construct several femoral bone coordinate systems are refined using a priori knowledge. Three common femoral coordinate systems are defined by the landmarks detected. The A&A method proved to be very robust against a variation of the spatial alignment of the surface models. The results of the A&A method and a manual identification were compared. No significant rotational differences existed for the bone coordinate system recommended by the International Society of Biomechanics. Minor significant differences of maximally 0.5° were observed for the two other coordinate systems. This might be clinically irrelevant, depending on the context of use and should, therefore, be evaluated by the potential user regarding the specific application. The entire source code of the A&A method and the data used in the study is open source and can be accessed via https://github.com/RWTHmediTEC/FemoralCoordinateSystem.

Mayer-Rokitansky-Küster-Hauser syndrome with rare findings of inferior crossed-fused renal ectopia and Gartner's duct cyst: a video case report

To describe the treatments of a patient using the laparoscopic Davydov's method for Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome and ureteral reimplantation for hydronephrosis and hydroureter. Surgical video article. A consent form from the patient was obtained as appropriate; the nature of the study did not necessitate ethics committee approval. There were no conflicts of interest. University hospital. A 28-year-old woman who presented at our gynecology department with the symptoms of primary amenorrhea and difficult intercourse. She had repaired congenital rectovestibular fistula and imperforate anus at the age of 8. At physical examination, she had a phenotypically normal vulva with a vaginal small pouch (0.5 cm). Magnetic resonance imaging of the pelvis revealed normal ovaries, a primordial uterus, absence of vaginal canal, and a 4.0 × 4.2 × 4.0 cm cystic structure posterior to the bladder. Magnetic resonance urography showed right to left renal crossed-ectopia with inferior fusion, and hydronephrosis and hydroureter from the superior kidney with Grade Ⅳ vesicoureteral reflux. Karyotype was 46, XX. Saline solution 300 mL was injected into the rectovesical space with an infusion of diluted adrenaline (1:200,000). The goal of this injection was to aid in the identification of tissue planes and reduce blood loss. The space between urethra/bladder and rectum progressively was dissected. Blunt dissection was performed initially with digital separation of tissues. Then, an 8-cm-long neovaginal vault of about 3 cm in diameter was created. The mobilized peritoneum was pulled downward with eight Vicryl sutures and connected to the vaginal epithelium. By cystoscope, we found the left orifice but could not find the right orifice of the hydroureter. Then we ligated the hydroureter by 2-0 absorbable suture near the cyst and cut off the hydroureter, and then incised of all the layers at the top of the bladder to make a bladder flap. We placed the 5 Fr double J stent in the hydroureter and the bladder and anastomozed with the ureteral stump (3-0 Vicryl). Then we removed the cyst laparoscopically. We performed a purse-string stitch to create the apex of the neovagina by taking posterior serosa of the bladder, the pelvic peritoneum between the ovary and rectum, primordial uterus, and anterior rectal serosa. Measurement of the final canal length, sexual function (Female Sexual Function Index), and degree of hydronephrosis. Three days later, we started to change the vaginal mold and the patient was advised to wear it day and night for the first postoperative month. The vaginal mold had to be worn each night until normal sexual intercourse was possible. Findings confirmed the cyst was Gartner's duct cyst. One year after the surgery, the final canal length was 9 cm and Female Sexual Function Index score was 28. The ultrasound showed that the degree of hydronephrosis of upper moiety was mild. The distal Wolffian ducts in the female are absorbed but may persist as vestigial remnants (Gartner's duct cysts). A few cases of the combined urogenital-Wolffian anomalies are reported; most of them are associated with the anomalies of müllerian duct fusion, such as Herlyn-Werner-Wunderlich syndrome (uterus didelphys, obstructed hemivagina, and mesonephric duct anomalies). The embryogenesis of the combined anomalies is not completely understood. With comprehensive preoperative assessments, laparoscopic surgery could be a safe and effective treatment to these cases.

'Seven-step two-lobe' HoLEP: a modification to gain efficiency of the enucleation applying relatively low-power holmium laser devices.

In order to increase the efficiency of the low-power holmium laser enucleation of the prostate (LP-HoLEP), and introduce it as a standard surgery for BPH, we described a modified 'seven-step two-lobe' HoLEP (ST HoLEP) technique applying 60-W device in a stepwise manner. From July 2016 to August 2019, 120 patients who received LP-HoLEP at our hospital because of urinary tract symptoms caused by BPH were included in the study. The patients were assigned into two groups, 60 consecutive patients received modified ST HoLEP compared with another preexisting 60 consecutive patients who received the conventional three-lobe HoLEP (T HoLEP) before the technical modification. The clinical parameters, including patient characteristics, perioperative data, as well as voiding outcomes, and complications were evaluated after at least 3-month follow-up. The median enucleation efficiency of the ST HoLEP was 0.72gm/min, which was significantly higher than 0.62gm/min of the T HoLEP. Despite the preoperative IPSS was slightly higher in T HoLEP group, the other preoperative and perioperative data showed no statistical difference between the two groups. After ST HoLEP procedure, the urinary incontinence rate was continually improved at 1-week, 1-month, and 3-month follow-up which were 13.3%, 6.7%, and 1.7%, respectively. There was no significant difference in postoperative voiding outcomes and urinary continence results in 3-month follow-up. The ST HoLEP technique was proved to increase the efficiency which was benefit from minimizing the surgical incision, facilitating the single surgical plane identification and maintenance during the whole enucleation procedure.

Fluorescence navigation with indocyanine green for identification of intersegmental planes using a photodynamic eye camera.

BackgroundPulmonary segmentectomy is an important surgical option for complete resection in patients with poor lung function. However, correctly recognizing the intersegmental plane for accurate segmentectomy is sometimes difficult. We therefore developed a novel method that allows the detection of intersegmental planes using an indocyanine green (ICG) fluorescence imaging device, photodynamic eye (PDE) camera, PDE-neo.MethodsAs a prospective study, we performed bronchial ICG-guided segmentectomy using PDE-neo. The patients were placed in a lateral position under general anesthesia, and we performed a combined muscle-sparing minithoracotomy with video assistance. The pulmonary artery, pulmonary vein, and segmental bronchi were separated, and ICG mixed with autologous blood was introduced by spraying through the resected segment bronchi to enable visualization of the intersegmental surface with PDE-neo. This study protocol was approved by the Research Ethics Board of Hamamatsu University School of Medicine, Japan. Written informed consent was obtained from all patients.ResultsOverall, 10 lung malignancy patients, including 8 males and 2 females, participated in this study from March 2011 to October 2013. The median age was 69 years (range, 29–76 years). Pathologic diagnoses were 7 adenocarcinomas, 1 adenosquamous carcinoma, 1 carcinoid tumor, and 1 lung metastasis from the parotid gland cancer. The intersegmental planes of 8 cases could be identified by this method using a PDE-neo, whereas those of 2 cases did not show clear demarcations. The reason was that because of severe emphysema, air flowed from the resected segment to the surrounding segments, obliterating the demarcation between the two segmental planes. There were no recurrent cases and only two deaths due to other diseases were observed; and the 5-year cause-specific survival rate was 100%.ConclusionsIntersegmental planes could be more easily identified using ICG fluorescence imaging during segmentectomy. This method is feasible and effective and has a good long-term prognosis.

Ultrasound-guided Hydro-dissection Facilitates Tissue Expander Placement and Components Separation in Complex Ventral Hernia Repair

Summary:Tissue expanders are known adjuncts in ventral hernia repair, used in a staged approach where tissue closure or coverage of the defect is preferred but inadequate. Placement of tissue expanders in the correct tissue plane can be difficult, especially in thin patients or with loss of domain. This case series describes a technique in which tissue expander placement is facilitated by ultrasound-guided hydro-dissection, following the placement of a transversus abdominis plane (TAP) block. In short, after induction of anesthesia, the same needle used for the ultrasound-guided TAP block can be repositioned by the anesthesiologist to instill tumescent solution into the fascial plane between the internal and external oblique muscles. This allows for identification of the fascial planes in the ensuing operation. Our technique may prove to be an alternative tool in the placement of tissue expanders for ventral hernia repair, or in other procedures requiring device placement.

Advances in Identification of Intersegmental Plane during Pulmonary Segmentectomy

近年来随着计算机断层扫描（computed tomography, CT）的普及，早期肺癌被大量发现，肺段切除术得到广泛临床应用。段间平面的显示是肺段切除术的关键步骤之一，当前显示段间平面的方法众多且各有优劣，我们将对相关方法进行回顾，以期对临床实践有所帮助。

Better understanding of interfacial planes in colorectal cancer surgery and the value of small vessels on fascia in the identification of interfacial planes

The introduction of total mesorectal excision and wider use of laparoscopic surgery pushed the field of colorectal surgery into an era of interfasical dissection. The Japanese suggestion of fascial arrangement of the trunk in a multilaminar, symmetrical and parallel way helps in better understanding of fascial relationship and interfascial planes surrounding the colon and the rectum. However, different interpretations of the multilayer retroperitoneal fascial relationship, complexity of fascial structures within the pelvis and dense adhesion between two apposed fasciae at special points make it still challenging for the surgeon to decide on the precise interfascial plane for colorectal mobilization. Small vessels on fasica propria of the rectum and various retroperitoneal fascia, especially ureterohypogastric fascia show distinctive features. The root of small vessels on fascia propria of the rectum helps to identify the anterolateral and posterolateral interfascial plane in the middle and low rectum. The longitudinal trajectory of small vessel on ureterohypogastric fascia and scarcity interfascial vascular communication between mesocolic and retroperitoneal fascia help the surgeon to find and stay in the interfacial plane during colorectal mobilization. More knowledge of fascial and interfascial plane will certainly help achieve better mesocolic mesorectal integrity and reduce the risk of injuries to autonomic nerves. More anatomical, histological and embryological studies are warranted with respect to relationship between small vessels and fasciae.

A cystectomic technique with low risk of rupture for women with benign ovarian cyst

The majority of patients with benign ovarian cysts undergo laparoscopic surgery using both cystectomy and stripping techniques. However, these techniques have difficulty correctly identifying cleavage planes and are prone to cyst rupture. We present a surgical cystectomy technique that correctly identifies the cleavage plane with a low risk of ovarian cyst rupture, even in patients with multicystic ovarian cysts. Cystectomy was performed using Maryland forceps with gentle open and close dissecting motions only. Both the surgeon and assistant handled the ovarian cortex and cyst wall, and soft traction between the cortex and cyst wall as far as the nearby dissection plane without grasping the cyst wall was essential. In patients with multicystic ovarian cysts, making a plane at the notch between cysts decreases the risk of cyst rupture. This technique allows the correct identification of the cleavage plane for dissection and avoids the risk of cyst rupture. Impact Statement What is already known on this subject? The majority of patients with benign ovarian cysts undergo laparoscopic surgery using both cystectomy and stripping techniques. These techniques have difficulty correctly identifying cleavage planes and are prone to cyst rupture. What do the results of this study add? This technique allows the correct identification of the cleavage plane for dissection and avoids the risk of cyst rupture. What are the implications of these findings for clinical practice and/or further research? Our technique might be useful for the preservation of the ovarian reserve because patients in this study had a low proportion of ovarian follicles in the surgical specimen.

How to identify intersegmental planes in performing sublobar anatomical resections.

Pulmonary segmentectomy is a common surgical procedure in thoracic surgery nowadays. Though this technique helps preventing postoperative pulmonary function loss, potential challenges are the management of air leaks and the difficulty of palpating ground-glass components during surgery, as well as how to deal with the intersegmental planes. Several techniques have been proposed for the identification and treatment of the intersegmental planes during sublobar anatomical resections: this review focuses on preoperative planning and workup and intraoperative strategies. Three-dimensional computed tomography bronchography and angiography (3D-CTBA), virtual-assisted mapping (VAL-MAP) using bronchoscopy multi-spot dye marking and three-dimensional computed tomography (3D-CT) are preoperative tools that may facilitate the planning of operation. Inflation-deflation techniques, infrared-fluorescence-enhanced method combined with bronchial and intravenous injection of indocyanine green (ICG) and near-infrared fluorescence (NIF) mapping with ICG have been described as intraoperative strategies to identify the intersegmental plane. The treatment and section of the intersegmental planes is mainly accomplished by stapler and electrocautery or energy devices. The use of staplers reduces postoperative air leaks, bleeding risks and operative time but seems to reduce preserved lung volume, compromising adjacent lung expansion; in addition, higher costs and sometimes non-adequate oncological margins, being a non-anatomical technique have been described. The electrocautery and energy devices allow for a more anatomical and precise dissection maintaining safe oncological margins, with a better lung expansion and so an increased postoperative lung function. Time consuming procedure and frequent requirement of aero-haemostatic tools to treat air and blood leaks are the main drawbacks. In conclusion, there are several methods to identify and treat the intersegmental planes but there are no significant differences between the different tools, therefore the use of one technique rather than another depends overall on surgeon’s preference and the location of the segment.

Novel technique for identification of the pulmonary intersegmental plane using manual jet ventilation during pulmonary segmentectomy.

IntroductionFor successful pulmonary segmentectomy, the identification of boundaries between segments is important. Previous measures include tracing the intersegmental vessels by staining with a dye via the affected pulmonary artery or bronchus and inflating with oxygen via a high frequency ventilator. However, problems with these methods have been reported.AimWe developed a novel method using a manual jet ventilator (MJV) and investigated its efficacy in identification of the pulmonary intersegmental plane.Material and methodsPatients underwent MJV for pulmonary segmentectomy in the period from January 2013 to December 2017 at our institution. The patients’ characteristics, resected segments, availability of clear resection planes, and complications associated with MJV from medical records were investigated. A questionnaire survey was conducted with the surgeons on the effectiveness of lung segment identification using MJV.ResultsOf 199 cases of planned pulmonary segmentectomy, 171 cases with descriptions of identified intersegmental planes were analyzed. Of these, 152 (89%) cases showed a clear boundary. There were 19 cases where the exact boundaries were not clearly identified, but segmentectomy was still performed. Furthermore, we found that identification of the right upper lobes was difficult (p = 0.0028). A subjective questionnaire was answered by the 12 surgeons who performed the procedures. All 12 responded that MJV was very effective or effective regarding clarity, safety, shorter identification time, and shorter resection time.ConclusionsMJV enabled surgeons to more easily and safely identify the pulmonary intersegmental plane, thereby suggesting that MJV has clinical significance during pulmonary segmentectomy.

How to identify intersegmental planes in performing sublobar anatomical resections

Pulmonary segmentectomy is a common surgical procedure in thoracic surgery nowadays. Though this technique helps preventing postoperative pulmonary function loss, potential challenges are the management of air leaks and the difficulty of palpating ground-glass components during surgery, as well as how to deal with the intersegmental planes. Several techniques have been proposed for the identification and treatment of the intersegmental planes during sublobar anatomical resections: this review focuses on preoperative planning and workup and intraoperative strategies. Three-dimensional computed tomography bronchography and angiography (3D-CTBA), virtual-assisted mapping (VAL-MAP) using bronchoscopy multi-spot dye marking and three-dimensional computed tomography (3D-CT) are preoperative tools that may facilitate the planning of operation. Inflation-deflation techniques, infrared-fluorescence-enhanced method combined with bronchial and intravenous injection of indocyanine green (ICG) and near-infrared fluorescence (NIF) mapping with ICG have been described as intraoperative strategies to identify the intersegmental plane. The treatment and section of the intersegmental planes is mainly accomplished by stapler and electrocautery or energy devices. The use of staplers reduces postoperative air leaks, bleeding risks and operative time but seems to reduce preserved lung volume, compromising adjacent lung expansion; in addition, higher costs and sometimes non-adequate oncological margins, being a non-anatomical technique have been described. The electrocautery and energy devices allow for a more anatomical and precise dissection maintaining safe oncological margins, with a better lung expansion and so an increased postoperative lung function. Time consuming procedure and frequent requirement of aero-haemostatic tools to treat air and blood leaks are the main drawbacks. In conclusion, there are several methods to identify and treat the intersegmental planes but there are no significant differences between the different tools, therefore the use of one technique rather than another depends overall on surgeon's preference and the location of the segment.