Retrospective analysis of robot‐assisted laparoscopic transabdominal anterior approach for the treatment of lumbar paravertebral schwannoma

The main objective of this study was to investigate the impact of robot‐assisted laparoscopic resection on paravertebral tumours using the anterior peritoneal approach.


| Basic information for each group
In the SW group, there were a total of 45 patients, including 21 females and 24 males.The average age of the patients was 68.6 � 7.1 years, with a range of 53-79 years.The average body mass index (BMI) was 24.1 � 3.1 kg/m2, ranging from 18.0 kg/m2 to 33.7 kg/m2.The average hospitalisation cost for these patients was 38 935.2 � 7739.5 CNY.
In the RT group, there were a total of 21 patients, including 7 females and 14 males.The average age of the patients in this group was 68.6 � 7.1 years, ranging from 55 to 77 years.Their average BMI was 23.3 � 3.2 kg/m2, ranging from 19.0 kg/m2 to 32.3 kg/m2 (Table 1).

| Surgical procedure
Step 1. Patient's Position and Placement of Trocars After the induction of general endotracheal anaesthesia, the Foley catheter was inserted, and the patient was placed in a standard flank position at 90°.A pneumoperitoneum of 14 mmHg was achieved using a Verses needle in a standard fashion.The first 12-mm robotic port camera of da Vinci (The da Vinci robot is a surgical robotic system developed and manufactured by Intuitive Surgical.It consists of five main components: "Console, Robotic Arms, Trocar, Camera System, and Power and Control Unit."This robotic system is designed to assist surgeons in performing various surgical procedures.Surgeons sit at the console, where they control the robotic arms and instruments using joysticks and foot pedals, while simultaneously observing the surgical field through the camera system.This system enables surgeons to perform minimally invasive surgery, reducing the need for large incisions and minimising tissue damage compared to traditional surgery).Was placed lateral and superior to the umbilicus lateral to the rectus muscle.After placing the camera port, peritonectomy was performed and the rest of the assisted port and robotic ports were placed as dictated by the intra-abdominal anatomy after inflation and body habitus.The second robotic 8-mm port was placed under the costal margin of the 12th rib lateral to the rectus muscle.The third 8 mm robotic port was placed about 8 cm lateral to the anterior axillary line, and the fourth 8 mm robotic port was placed about 6-8 cm caudal to the camera port and lateral to the rectus muscle.Finally, the 12-cm assistant port was placed midline 2-3 cm caudal to the umbilicus.The robot was docked perpendicular to the patient from the back on the ipsilateral side (Figure 1).
Step 2. Exposure of the Schwannoma During the surgical procedure, it was usually observed that the colon had slight adhesion to the lateral abdominal wall.The operator needed to carefully separate the intestinal adhesion and then gently push the colon medially.
For tumours that involve the L2 level and above, the initial step was to perform the mobilisation and exposure of adjacent organs.For right-sided neoplasms, the liver was retracted anteriorly and cephalad; for left-sided neoplasms, the spleen and pancreas were reflected medially.The next step was to open the Gerota's fascia and carefully explore the posterior retroperitoneal space for tumours while ensuring the protection of the adjacent renal artery, renal vein, renal pelvis, and ureter.
For tumours located below the L2 level, the initial step was full exposure of the lateral peritoneum, which was subsequently opened at the point where the ureter crossed over the iliac vessels.The nearby ureter and iliac vessels were completely dissociated, taking care to protect the blood supply to the ureter and prevent excessive traction or damage.The schwannoma, measuring 3.5 cm, was identified lateral to the iliac vessels (Figure 2).

Step 3. Resection of the Schwannoma
The schwannomas were carefully separated along the periphery, and the integrity of the tumour sheath was maintained as much as possible.Above the psoas major muscle and lateral to the iliac vessels, the schwannoma was completely separated and resected.Moreover,

SW approach
RT approach P Age, y 67.

F I G U R E 1
The appearance of the da vinci Robot and the placement of trocars.
ZHAO ET AL.
-3 of 7 we were focus on protect the ventrolateral cutaneous nerve, genitofemoral nerve, and other nerves on the surface of the psoas major muscle.After sufficient haemostasis of the wound, the sheath above the psoas major muscle was closed with a 3-0 barbed suture (Figure 3).
Step 4. Specimen Extraction A negative pressure drain was set on the lateral side of the iliac vessel.The specimen was placed in an extraction bag and removed by extending the 12-mm assistant port in the midline of the lateral port.recurrence in either group.It is important to note that there was no statistically significant difference between the two groups in terms of tumour recurrence during this timeframe (Table 2).

| DISCUSSION
In previous reports, the Wiltse approach for paravertebral tumours has been shown to result in fewer postoperative complications and less overall injury compared with the traditional posterior median approach.However, it is important to acknowledge that the Wiltse approach also has some disadvantages.One major challenge is determining the appropriate surgical incision.The dissection position of the multifidi muscles can vary from person to person; therefore, it is crucial to adjust the incision based on the MRI results before making the final decision.If the incision is not chosen properly, the tumour may not be fully exposed during surgery, potentially leading to damage to the multifidi muscles and surrounding normal tissues.3][14][15][16][17] Another challenge associated with the Wiltse approach is the limited surgical field of vision.When accessing the paravertebral space through the muscle gap between the multifidus and longissimus muscles, there is a possibility of encountering difficulties due to the stenosis of the surgical space or the presence of a large tumour.In such cases, it may be necessary to excise the transverse process or dissect the muscle attachments to create sufficient space for tumour removal.However, these additional procedures can increase the risk of postoperative complications, including chronic low back pain and spinal instability.In some instances, if spinal instability is present, it may require the use of additional spinal instrumentation and fixation devices to ensure stability and prevent further complications. 4,23Moreover, Wiltse approach is the presence of numerous spinal nerve posterior sidelines and lumbar vascular dorsal branches between the multifidus and longissimus muscles.During the separation of the tumour, there is a higher risk of bleeding, which can impact the clarity of the surgical field.This can make it more challenging for the surgeon to visualise and navigate during the procedure.The presence of these structures adds complexity to the surgery and requires careful dissection and haemostasis to minimise the risk of complications. 24erefore, the advantages of Robotic-assisted transperitoneal approach are showed up. 1.Because of the Trans-abdominal anterior approach, the surgery can proceed in an extremely spacious space.
Coupled with the Surgical robot high-definition 3D camera, it can provide a perfect surgical vision for the surgeon.In addition, this surgical approach does not need to bite off vertebrae, so patients do not suffer from the Spinal instability post-surgery. 252. We can also use the robot's dexterous robotic arm to remove the tumour near the root of nerves.In Robotic-assisted transperitoneal approach, we did not need to separate muscle, nerves, and blood vessels next to the tumour.Therefore, there is less bleeding during the operation. 25,263.
The RT approach does not need to pull open the muscles (multifidi and longissimus) to expose the tumour.Hence, it will not damage the nerves between the muscle gap, and our outcomes also reveal that the indwelling duration of analgesic pump in the RT group was significantly shorter than that in the SW group.Hence, the patients would not suffer from chronic lower back pain and Segmental hypoesthesia after surgery.6][27][28] Our group has extensive experience with robotic surgery since adopting this innovative technology more than 4 years ago.Many features of robot-assisted laparoscopic surgery facilitate safe complete resection of lumbar paravertebral schwannoma, particularly those in extreme locations of the retroperitoneal ureter area such as those described in this report.
However, It is not always necessary to resect lumbar paravertebral schwannomas if the preoperative diagnosis can be reached, but given the possibility of lumbar paravertebral schwannomas to become recur, metastasise or malignant, doctors still need to resect the tumour as completely as possible in the surgical process.Robotassisted surgery is a promising surgical method that has been widely used in the clinic, and robot-assisted resection of lumbar paravertebral schwannomas should be highly considered by a neurosurgeon or spinal surgeon.
This study has also shown few limitations: 1.This technique was studied only in our single centre and has not been validated in multiple centres.2. This procedure was only appropriate for lumbar paravertebral schwannomas, and it is not suitable if the tumour was located next to the cervical vertebra or thoracic vertebra.3.Many prospective studies are still needed for validation.

| CONCLUSION
Robot-assisted laparoscopic resection of lumbar parapneumonic schwannoma through anterior peritoneal approach has the advantages which including less pain, mild effect, better surgical field of vision, and protect the muscle of back.Its supply vessels and innervation nerves, which could be beneficial to maintain the stability of lumbar spine and avoid the occurrence of chronic low back pain after surgery.It is a safe and feasible surgical approach and provides a relative-new choice for the treatment of paraspinal schwannoma.

2. 1 . 2 |
Inclusion criteria 1.All patients included in the study were diagnosed with lumbar paravertebral schwannoma based on postoperative pathological biopsy.Patients with vascular tumours or other malignancies were excluded from the study.2. The study specifically focused on schwannomas located adjacent to the lumbar spine (Located at or below the L1 level).Patients with cervical paravertebral schwannoma and thoracic paravertebral schwannoma were excluded from the study.3.All patients had no personal history of malignancy prior to their diagnosis of lumbar paravertebral schwannoma.4. None of the patients had received any medical treatment specifically related to schwannoma prior to undergoing surgery.

SPSS 26 .
0 software was used to perform statistical analyses.Our research and data analysis follow the STROBE guidelines.Student's t test was used for quantitative data.p < 0.05 was considered a statistically significant difference.Classification data are collected and analysed as numbers and percentages.3| RESULTIn both the SW and RT groups, there were no instances of intraoperative conversion to laparotomy.Pathologic examination confirmed that the tumours were schwannomas, and the resection margins were negative, indicating successful removal of the tumours with no remaining tumour tissue at the margins.During the 48-month follow-up period, no instances of tumour recurrence or residual tumour were detected in MRI examinations (Figure4).DR examinations also did not reveal any spinal deformities.Importantly, there were no alarms for somatosensory evoked potentials (SEP) or motor evoked potentials (MEP) in either group during the surgical procedures.In the SW group, 11 patients experienced an electromyogram (EMG) alarm during the operation.Fortunately, the EMG readings returned to normal after the operation was temporarily halted.No abnormal EMG signals were observed at the end of the surgery.The operation time in the RT group, with an average of 66.2 � 14.5 min (incision of the skin to the end of the surgery), was significantly shorter compared to the SW group, which had an average operation time of 89.4 � 21.0 min (p < 0.01).Additionally, the RT group experienced significantly less blood loss, with an average of 11.4 � 7.9 mL, compared to the SW group, which had an average blood loss of 59.2 � 54.2 mL (p < 0.01).It is noteworthy that no postoperative complications were reported in the RT group.However, in the SW group, nine patients developed postoperative chronic low back pain (long-term, persistent pain in the back, typically lasting for a period of 3 months or longer.This type of pain can affect any part of the back, including the upper back, middle back, or lower back), and there were 2 cases of postoperative segmental hypoesthesia (a local sensory disturbance, involving a decreased perception of touch, temperature, pain, or other sensory stimuli).One patient reported numbness and decreased sensation in both hands during the 1-month follow-up, while another patient reported occasional pain in both lower limbs during the 3-month follow-up.In the SW group, one patient was diagnosed with cerebrospinal fluid leakage immediately after the surgery.Furthermore, the tumour size in the RT group, with an average of 4.8 � 2.3 cm, was significantly larger compared to the SW group, which had an average tumour size of 2.5 � 0.7 cm (p < 0.01).Additionally, the length of postoperative hospitalisation in the RT group, with an average of 3.2 � 0.9 days, was significantly shorter compared to the SW group, which had an average hospital stay of 5.2 � 1.4 days (p < 0.01); The indwelling duration of the analgesic pump in the RT group, with an average of 1.4 � 0.6 days, was significantly shorter compared to the SW group, which had an average duration of 2.6 � 0.8 days (p < 0.01).Regarding the 48-month follow-up period, there were no instances of tumour F I G U R E 2 Exposure of the schwannoma.F I G U R E 3 Resection of the schwannoma.
Comparison of preoperative and postoperative radiological images for two patients.Perioperative outcomes.