Table 2.

Predictors of ambulatory status or motor function.

Authors & Year	Classification	Evidence Level	No. of Patients	Age (yrs) ∗	Surgery Type	Primary Tumor Site		Complications	Outcome Scale	Outcomes
Zhu et al. 2020	Retrospective review	3	154	TOS group 54.10 MISS group 53.84	Separation surgery performed in a postero- lateral approach MISS under C-arm guidance	Breast (19%), Lung (18%) Kidney (10%), Liver (9%) Throid (4.5%) Colrectal (3%), Unknown (8%) Prostate (4%), Nasopharynx (5%), Other (15%)	Myeloma (4.5%)	Dural tear in one of 49 patients in the MISS group (2.04%) and two of 105 patients (1.90%) in the TOS group. Only one patient (2.04%) in the MISS group had a surgical wound infection, whereas six patients (5.71%) in the TOS group got infected.	FRANKEL	Pre-operative Frankel grades of patients in the two groups exhibited no significant difference (P = 0,59). Twenty three of 49 (47%) patients in MISS group and 43 of 105 (41%) patients in TOS group obtained improvement in neurological function (P = 0.48). 49% (24/49) and 55.3% (58/105) of patients had stable functional status after surgery in the MISS and TOS group, respectively (P = 0.47). Only two (4%) patients in MISS group and four (3.7%) in TOS group experienced worse postoperative neurological status.
Colangeli et al. 2020	Retrospective review	3	52	59.3	percutaneous pedicle screw fixations (PPSF)coup- led with mini-decompressi ions if required by spinal cord compressions.	Breast (27%), Renal (17%), Lung (8%), Prostate (2%), Other (44%)		3 minor and 3 major complications were reported. In one case an aseptic screw mobilization was detected without clinical consequences, while two patients had wound dehiscence healed without additional surgeries. As to the major complications, in two cases an intra- operative lesion of the dural sac during mini-decompression procedure was reported without consequences, in another patient a hematoma was reported with neurological compression symptoms, which required further surgical decompression resulting in symptom regression.	FRANKEL and VAS	Frankel were E in 37 patients, D3 in in 6 patients, D2 in 3 cases, D1 in 3 cases, B in one patient, and C in two of them. The Frankel score improved in 10 patients, remained stable in 40 patients and worse- ned only in two patients. Preoperatively, the VAS score in 29 patients treated with PPSF procedure along with spinal decompression was 7 on average, while postoperatively, the VAS score became 5 on average. In 23 patients who underwent only PPSF procedure without spinal decompression VAS score was 5 on average, post- operatively the VAS score became 3 on average.
Xiaozhou et al 2020	Retrospective review	3	52	56.7 ± 7.4 yrs	All patients undergoing separation surgery -similar to the classic posterior pedicle approach. Following this patients had stereotac- tic body radiotherapy (SBRT). This being performed 10 - 20 days after surgery, and the target area design is generally 2–3 mm outside the tumor involvement range.	Lung 19, Breast 8, Renal 5, Thyroid 4, Liver 3, Prostate 2, Rectal 1, Gastric 1, Nasopharyngeal 1, foot rhabdomyosarcoma 1 Unknown origin 7		Three cases of postoperative complicat- ions, including two cases of wound infec- tion which improved after anti-infection and local debridement, and one case of CSF leakage which imp- roved after intraoperatively repairing the injured dura and postoperative conserv- ative treatment for 2 weeks.	FRANKEL, Karnofsky, VAS, ESCC grading and muscle grading	Postoperative Frankel neurological function grading: one case of grade A, three cases of grade B, 22 cases of grade C, 21 cases of grade D, and five cases of grade E. This compares with preoperative Frankel grades 4 cases grade A, 18 cases grade B, 24 cases grade C, six cases grade D, zero cases of grade E. Postoperative ESCC grading: 38 cases of grade 0, eight cases of grade 1a, two cases of grade 1b, three cases of grade 1c, and one case of grade 2. Preoperative ESCC grading showed one case of grade 1a, three cases of grade 1b, six cases of grade 1c, 24 cases of grade 2, and 18 cases of grade 3. The average VAS score decreased to 2.17 ± 0.52 points, which was significantly improved compared with preoperative (P < 0.01). Karnofsky performance scores: six cases of 80–100 points, 38 cases of 50 - 70 points, and eight cases of less than 50 points, which was also significantly improved compared with preoperative scores (P < 0.01).
Hamad et al. 2017	Retrospective review	3	51	60	Percutaneous pedicle screw fixation (PPSF) with or without mini- decomopression	Breast 11 (23%), Renal 9 (19%), Prostate 8 (16%), Haematological 6 (12%), Lung 4 (8%), Upper GI 3 (6%), Thyroid 2 (4%), Other 6 (12%)		One patient had septic loosening at 3 months following surgery, this required removal of implant, debridement and washout. Two patients suffered aseptic loosening at 4 months and 9 months following surgery. Implant removal alone was needed in one case. revision with open fixation in the other. One patient had unexpected major haem- orrhage (2000 mls) during mini-open decompression for metastasis from a hepatocellular carcinoma. Attempted debulking of the involved paravertebral muscles resulted in severe bleeding, which could only be controlled by clos- ure related tamponade with packs, resuscitation and return to theatre after 36 h for pack removal and re-closure. He recovered well, with improvement in KPS and pain. In the 48 remaining pat- ients the mean intraoperative blood loss was 157 mls. In patients with only a percutaneous stabilisation the mean blood loss was 92 mls, and in those with an additional decompression it was 222 mls. Overall surgical complication rate of 10%.	FRANKEL, KPS	At the time of final censoring of data, 25 patients had died (median survival of these 25 patients was 3.6 months (95% CI: 2.1–5.0). Mean follow up of patients who were still alive was 11.5 months (2–60 months). 14 patients presented with neurological symptoms, 1 with radiculopathy and 13 with incomplete cord lesions (2 Frankel B, 8 Frankel C and 1 Frankel D). Foll- owing mini-decompression, six of these 13 patients improved by one Frankel grade and none worsened. One patient had a post-operative transient foot drop that resolved spontaneously within 4 weeks. 27 patients (55%) had improvements in KPS by at least 10 points (p < 0.0005) and another 20 patients (41%) maintained their KPS score. Only 2 patients (4%) had a worsening of functional outcome, both unrelat- ed to MISS surgery. There was no significant difference in functional outcome in patients who had a fixation with decompression compared to those who had a stand-alone fixation (p = 0.33). Significant pain improvement was reported by 42 of 44 patients that presented with back pain (95%). Of the 2 patients with no improvement in pain, one pat- ient needed a proximal femoral endoprosthesis for significant post-op pain due to trochanteric metast- asis. The other patient with no change in pain had a Frankel D incomplete cord lesion. There was no diff- erence in pain outcomes in patients who had a fixat- ion with decompression compared to those who had a stand-alone fixation (p = 0.94).
Chen et al. 2000	Retrospective review	3	60	54	All patients underwent palliative surgery by ant- erior corpectomy and Zielke instrumentation. Anterior vertebral corp- ectomy allowing debulking of the occupying tumour, and reconstruction with methylmethacrylate bone cement plus Zielke's VDS internal fixator.	Lung 12 (20%), colon 10 (16.7%), liver 9 (15%), thyroid 7 (11.7%), breast 3 (5%), 1 (1.7%) for each of the following stomach, renal, nasopharynx, long bone, skin and cervical, unknown origin 13 (21.7%)		3 patients developed wound infection with localised dehiscence. In each case this was managed by local wound care. No patients suffered neurologic deterioration postop- eratively		Of the 60 patients, 4 died within 1 month, 1 each due to hepatic failure and sepsis, and 2 to respiratory failure. Five patients died within 3 months. 51 patients (85%) survived longer than 3 months postoperatively. 39 patients (67%) survived longer than 6 months, of whom 14 patients were still alive at an average of 21 months (range 13–85 months) after surgery. The average postoperative survival time for the 12 patients with lung cancer, 10 with colorectal cancer, 9 with hepatoma, and 7 with thyroid cancer documented in this series were 7, 10, 11, and 18 months, respect- ively. Neurologic improvement of at least one Frankel grade was noted in 33 patients (72%). No improve- ment was noted in the patients with a Frankel A neurologic deficit. Of the 40 patients who were bed- ridden before surgery due to pain or paresis, 30 patients experienced an increase in activity tolerance. 20 patients were able to recover functional ambulation. Sphincter dysfunction was significantly improved in 10 cases.