Biomechanical evaluation of lumbosacral reconstruction after subtotal sacrectomy: A three-dimensional finite element analysis

Objective： The aim of this study was to investigate the biomechanical property of lumbosacral reconstruction after subtotal sacrectomy. Methods： Three three-dimensional finite element models of lumbosacral region were established： （1） An intact model （INT）; （2） A defective model （DEF） on which subtotal sacrectomy was performed cephalad to the $1 foramina; （3） A reconstructed model （REC）. These models were validated by compared with literature. Upright posture was stimulated under a compression load of 925N. A finite element analysis was performed to account for the displacement and stress on the models. The REC model was calculated twice, with the material property of reconstruction instrument set as titanium and stainless steel, respectively. Results： The displacements of anchor point on the L3 vertebrae in INT, DEF and REC model were 6.63 mm, 10.62 mm, 4.29 mm （titanium） and 3.86 mm （stainless steel）, respectively. The stress distribution of the instrument in REC model showed excessively concentration on caudal spinal rod, which may cause rod failure between spine and ilia. The maximum von Mise stress of stainless steel instrument was higher than that of titanium instruments （992 MPa vs 655 MPa）, and the value of stress of anchor point around sacroiliac joint in REC model were 26.4 MPa with titanium instruments and 23.9 MPa with stainless steel instruments. Conclusion： Lumbosacral reconstruction can significantly increase the stiffness of spino-pelvis of the patient who underwent subtotal sacrectomy. However, the rod between L5 and ilia is the weakest region of all the instruments. It is suggested that the bending of rod should be conducted carefully and smoothly to avoid significant stress concentration so as to reduce the risk of rod failure. And stainless steel instrument has higher maximum stress and significantly greater stress shielding effect than titanium instrument, which means stainless steel instruments are of higher risk of rod failure and less favorable for lumboiliac arthrodesis than titanium instruments.

Advances in surgical management for locally recurrent rectal cancer: How far have we come?

Locally recurrent rectal cancer(LRRC) is a complex disease with far-reaching implications for the patient. Until recently, research was limited regarding surgical techniques that can increase the ability to perform an en bloc resection with negative margins. This has changed in recent years and therefore outcomes for these patients have improved. Novel radical techniques and adjuncts allow for more radical resections thereby improving the chance of negative resection margins and outcomes. In the past contraindications to surgery included anterior involvement of the pubic bone, sacral invasions above the level of S2/S3 and lateral pelvic wall involvement. However, current data suggests that previously unresectable cases may now be feasible with novel techniques, surgical approaches and reconstructive surgery. The publications to date have only reported small patient pools with the research conducted by highly specialised units. Moreover, the short and long-term oncological outcomes are currently under review. Therefore although surgical options for LRRC have expanded significantly, one should balance the treatment choices available against the morbidity associated with the procedure and select the right patient for it.

Critical evaluation of contemporary management in a new Pelvic Exenteration Unit: The first 25 consecutive cases

To critically appraise short-term outcomes in patients treated in a new Pelvic Exenteration (PE) Unit. METHODSThis retrospective observational study was conducted by analysing prospectively collected data for the first 25 patients (16 males, 9 females) who underwent PE for advanced pelvic tumours in our PE Unit between January 2012 and October 2016. Data evaluated included age, co-morbidities, American Society of Anesthesiologists (ASA) score, Eastern Cooperative Oncology Group (ECOG) status, preoperative adjuvant treatment, intra-operative blood loss, procedural duration, perioperative adverse event, lengths of intensive care unit (ICU) stay and hospital stay, and oncological outcome. Quantitative data were summarized as percentage or median and range, and statistically assessed by the χ2 test or Fisher’s exact test, as applicable. RESULTSAll 25 patients received comprehensive preoperative assessment via our dedicated multidisciplinary team approach. Long-course neoadjuvant chemoradiotherapy was provided, if indicated. The median age of the patients was 61.9-year-old. The median ASA and ECOG scores were 2 and 0, respectively. The indications for PE were locally invasive rectal adenocarcinoma (n = 13), advanced colonic adenocarcinoma (n = 5), recurrent cervical carcinoma (n = 3) and malignant sacral chordoma (n = 3). The procedures comprised 10 total PEs, 4 anterior PEs, 7 posterior PEs and 4 isolated lateral PEs. The median follow-up period was 17.6 mo. The median operative time was 11.5 h. The median volume of blood loss was 3306 mL, and the median volume of red cell transfusion was 1475 mL. The median lengths of ICU stay and of hospital stay were 1 d and 21 d, respectively. There was no case of mortality related to surgery. There were a total of 20 surgical morbidities, which occurred in 12 patients. The majority of the complications were grade 2 Clavien-Dindo. Only 2 patients experienced grade 3 Clavien-Dindo complications, and both required procedural interventions. One patient experienced grade 4a Clavien-Dindo complication, requiring temporary renal dialysis without long-term disability. The R0 resection rate was 64%. There were 7 post-exenteration recurrences during the follow-up period. No statistically significant relationship was found among histological origin of tumour, microscopic resection margin status and postoperative recurrence (P = 0.67). Four patients died from sequelae of recurrent disease during follow-up. CONCLUSIONBy utilizing modern assessment and surgical techniques, our PE Unit can manage complex pelvic cancers with acceptable morbidities, zero-rate mortality and equivalent oncologic outcomes.