Comprehensive assessment of patients with sacral metastases: The surgical approach for sacral metastases is more complicated, and the rich surrounding blood supply and the abnormal proliferation of blood vessels of the tumor make the risk of surgery much higher than that of surgery for tumors in other locations, and close postoperative observation and care of patients require extensive experience. Before surgery, the patient’s general condition should be fully evaluated, while the nature of the primary tumor, the number of bone metastases, the extent of sacral lesions, and visceral metastases should be comprehensively evaluated, and the indications should be mastered. The types of sacral metastases include: bone metastases only, bone metastases with visceral metastases, isolated bone metastases with visceral metastases, multiple bone metastases with visceral metastases, etc. Patients with lung cancer mostly do not have visceral metastasis, but mostly have multiple bone metastases.
Patients with liver cancer mostly have both visceral and bone metastases, and the prognosis is the worst; patients with breast cancer, kidney cancer and thyroid cancer are less likely to have visceral metastases. For patients with isolated sacral metastases of breast cancer, kidney cancer and thyroid cancer, they should be treated with aggressive surgical procedures and postoperative supplemented with radiotherapy, and the prognosis is better. For more specific rectal cancer recurrence involving the sacrum, a large resection can be performed to try to cure the patient. Surgical indications: There is no clear literature on the indications for the surgical treatment of sacral metastases for reference. The selection of indications and surgical modality should be individualized under the condition that the purpose of surgical treatment is clear. Indications for surgical treatment of sacral metastatic cancer include: 1.release of severe pain caused by nerve compression by tumor, improving survival quality and reducing the use of analgesic drugs; 2.release of nerve compression by tumor and restoration of nerve function; 3.unsatisfactory relief of pain symptoms after radiotherapy; 4.unstable lumbosacral or sacroiliac joint caused by tumor involvement in lumbosacral spine; 5.single bone metastasis involving below sacrum. There is no clear evidence that surgical treatment of metastatic cancer can prolong the survival time of patients, so there is an important principle for the treatment of sacral metastatic cancer, that is, surgery should not increase the pain of patients. At present, the surgical treatment of sacral metastases still faces many problems, the most important of which is how to comprehensively judge patients’ indications for surgery and the timing of surgery. Pre-operative preparation of sacral metastatic cancer patients: the general condition of most metastatic cancer patients is relatively poor, and pre-operative examination of patients’ cardiopulmonary function, liver and kidney function, electrolyte condition and other aspects should be conducted to correct the negative nitrogen balance and factors unfavorable to surgical recovery such as anemia. The local anatomical relationship around the sacrum is complex, and there are more important tissues and structures adjacent to it, and the blood supply of the tumor is rich, so the risks of the operation must be fully understood before the operation. Thorough preoperative preparation is crucial to the success of surgery. In addition to the conventional preoperative preparation, bowel preparation and preparation for bleeding control should be performed preoperatively. Control of bleeding: the bleeding volume of surgical treatment for sacral metastatic cancer is usually around 1000-5000ml, and for tumors with rich blood supply and those of relatively large size, the bleeding volume can even reach more than 10000ml. According to clinical experience, when the bleeding volume is more than 4000-5000ml, the abnormalities of coagulation function can be obvious during the operation, mainly manifested as large amount of blood oozing from the trauma surface, obvious blood dilution and slowing down of coagulation speed. Because there are more blood vessels around the sacrum and the anterior part of the sacrum is relatively loose tissue, it does not have the ability to confine the hematoma around the incision, and the exuded blood may extend around along the retroperitoneal gap, and if the plasma as well as coagulation factors are not replenished in time, fatal bleeding may occur after surgery. Therefore, it is important to prepare an adequate blood supply including plasma, platelets, and the appropriate clotting factors before surgery. In addition to the preparation of adequate blood supply, preoperative tumor vascular embolization is an effective means to control bleeding. For metastatic cancers with rich blood supply, such as kidney cancer, liver cancer and lung cancer, preoperative embolization should be routinely performed if the tumor is large in size. Embolization should be performed on the day of surgery or the day before. Premature embolization leads to failure of embolization due to vascular proliferation around the tumor. The most common complications after embolization are postoperative fever and pain in the blood supply area, which do not require special management. The most effective means of controlling bleeding is temporary vascular blockade, including preoperative placement of an abdominal aortic balloon block and intraoperative temporary blockade of the abdominal aorta with ligation of the internal iliac artery, which can significantly control bleeding during surgery and reduce the risk of intraoperative hemorrhage. Temporary block of the abdominal aorta and ligation of the internal iliac artery in the anterolateral approach are also effective means of controlling bleeding. The surgical approach for sacral metastatic cancer is to relieve the symptoms, remove the tumor as much as possible and reduce local recurrence. The surgical approach for sacral tumor includes simple anterior approach, simple posterior approach and combined anterior and posterior approach. Because the treatment of metastatic cancer is mainly scraping, the most common surgical approach for metastatic cancer is the posterior approach. Sometimes a posterior approach is performed in conjunction with an anterior approach to control bleeding. The combined anterior-posterior approach can improve the safety of sacral osteotomy. Nowadays, embolization techniques and abdominal aortic block techniques are more mature and have replaced the anterolateral approach for vascular block. Posterior and combined anterior-posterior approaches are now commonly used. One of the important steps in surgery is bleeding control. Controlling bleeding allows for a clear surgical field and facilitates a more complete removal of the tumor and protection of the nerve root. The timing of the abdominal aortic block should be chosen after separating the soft tissues posterior to the sacrum and before entering the tumor. Care should be taken during the separation of the soft tissues on the posterior aspect of the sacrum along the anatomical gap of the tissue to avoid bleeding as much as possible. The process of removing the sacral tumor should be quick and efficient to avoid unnecessary repetitive steps. It is important to collaborate with the anesthesiologist during the procedure to avoid a rapid decrease in blood volume. After tumor removal, the residual cavity formed after tumor resection can be filled with appropriate fillers, which can fill the residual cavity formed after tumor resection on the one hand, and can effectively control bleeding on the other hand. The suturing process should be fast, and pressure should be applied to the site of tumor removal to stop bleeding at the same time. Protection of nerve function: The important nerves involved in sacral metastatic cancer include the function of part of the sciatic nerve and the function of the internal nerve of the pubic area. The sacral 1 nerve root innervates the posterior group of calf muscles, and the sacral 2 nerve mainly innervates the posterior group of thigh muscles. The sacral 2-sacral 4 nerves form the internal pubic nerve, which together with the joined sympathetic and parasympathetic nerve fibers innervate the bladder and rectal sphincter function and sexual function. Most sacral metastatic cancers involve sacral 1 and sacral 2 and the surgical option adopted is mostly tumor curettage, so it is important to preserve the nerve integrity of the patient as much as possible intraoperatively. Preservation of sacral 1 nerve can maintain normal gait; preserving bilateral sacral 1 and sacral 2 nerves, 40% of patients have normal bowel function and 25% have normal bladder function; preserving bilateral sacral 1 and sacral 2 nerves and unilateral sacral 3 nerves, 67% and 60% have these two functions, respectively;
With bilateral preservation of sacral 1 to sacral 3 nerves, 100% and 69% had normal bowel function and normal bladder function, respectively; with unilateral preservation of sacral 1 to sacral 5 nerves, 87% of patients had normal bowel function and 89% had normal bladder function;
The surgical treatment of sacral metastatic cancer is mostly symptomatic and palliative, and the nerve function is preserved as much as possible under the condition of surgery in order to improve the survival quality of patients. According to the specific situation, under the condition that the tumor is not affected by more complete resection
Bilateral sacral 1~2 and at least one sacral 3 nerve root, or one sacral 1~3 nerve root should be preserved as much as possible, together with appropriate functional exercise to maximize the preservation of walking, urinary and faecal and sexual functions. Stability reconstruction of the pelvis: The sacrum is involved in forming the sacroiliac joint, which is responsible for transmitting the weight of the trunk to the lower extremities, and an injury to the sacroiliac joint will have an important impact on the stability of the spine. There has been a debate on whether to perform sacral reconstruction after sacral tumor resection. Wuisman believes that the decision to perform reconstruction depends on the extent of iliac wing resection and the patient’s condition, and that serious complications should be avoided to allow for a faster recovery. Without sacral reconstruction after total or subtotal sacral resection, patients need to be bedridden for a long time after surgery, relying on the ligamentous tissue and residual joint between the sacrum and the pelvis, between the sacrum and the spine, and on the scar tissue formed after surgery to maintain stability. And there is a postoperative effect on the stability of the spine. In recent years, internal fixation devices for the spine have developed rapidly, and as a result, many surgeons have performed internal fixation surgery to rebuild the stability of the spinal sacrum in patients after total or subtotal sacral resection. Sacrum 2 is involved in forming most of the articular surface of the sacroiliac joint, so we routinely perform adjuvant fixation to enhance the stability of the pelvic ring in patients whose resection extends above sacrum 2. The situation of patients with metastatic cancer is different from that of patients with primary tumor, and the purpose of treatment is different. For patients with metastatic cancer, reducing symptoms and restoring patients’ certain ability to take care of themselves are the ultimate surgical goals, so strengthening the stability of the sacroiliac joint can enable patients to move down to the ground early, which may be more meaningful for patients with metastatic cancer. Management of postoperative complications of sacral metastatic cancer The main complications of sacral metastatic cancer surgery include hemorrhage, nerve injury, non-healing incision infection, rectal injury, etc. Sacral metastases with rich blood supply are prone to haemorrhage. We routinely perform preoperative embolization and temporary block of abdominal aorta for metastases with rich blood supply and patients with large tumor size, which can significantly reduce intraoperative bleeding and a series of complications caused by hemorrhage. After surgery, attention should be paid to check electrolytes, blood routine and coagulation function to correct anemia and abnormal coagulation function in a timely manner. The posterior flap blood flow of the posterior side of the operation is obviously reduced, while the surgical tumor removal causes the formation of a large local residual cavity, which is prone to postoperative ischemic necrosis of the flap. The thoroughness of tumor resection and tumor disclosure are closely related, but at the same time have a great impact on the blood flow of the flap, and a trade-off between the two should be made during surgery. Patients with metastatic cancer are usually in an immunosuppressed state, which requires stricter intraoperative aseptic operation, and the rational use of postoperative antibiotics is very important. Damage to the rectum often leads to severe infection of the wound and usually requires colostomy treatment and wound debridement surgery. Patients with cerebrospinal fluid leaks are cured by pressure dressing of the wound and elevation of the end of the bed.