A systematic review of MIS and open decompression surgery for spinal metastases in the last two decades.

Objective: The primary intention of this review being to produce an updated systematic review of the literature on published outcomes of decompressive surgery for metastatic spinal disease including metastatic spinal cord compression, using techniques of MIS and open decompressive surgery.

Methods: The authors conducted database searches of OVID MEDLINE and EMBASE identifying those studies that reported clinical outcomes, surgical techniques used along with associated complications when decompressive surgery was employed for metastatic spinal tumors. Both retrospective and prospective studies were analysed. Articles were assessed to ensure the required inclusion criteria was met. Articles were then categorised and tabulated based on the following reported outcomes: predictors of survival, predictors of ambulation or motor function, surgical technique, neurological function, and miscellaneous outcomes.

Results: 2654 citations were retrieved from databases, of these 31 met the inclusion criteria. 5 studies were prospective, the remaining 26 were retrospective. Publication years ranged from 2000 to 2020. Study size ranged from 30 to 914 patients. The most common primary tumors identified were lungs, breast, prostate and renal cancers. One study ( Lo and Yang, 2017) reported that in those patients with motor deficit, survival was significantly improved when surgery was performed within 7 days of the development of motor deficit compared to situations when surgery was carried out 7 days after onset. This was the only study that showed that the timing of surgery plays a significant role w.r.t. survival following the onset of spinal cord compression symptoms. Four articles identified that a pre-operative intact motor function and or ambulatory status conferred a higher likelihood of a better post-operative outcome, not just in relation to survival but also in relation to post-operative ambulation as well as a greater tendency towards suitability for adjuvant treatment. Even for the same scoring system e.g. tokuhashi and its effectiveness in predicting survival, results from different studies varied in their outcome. The Karnofsky Performance Status (KPS) being the most commonly used tool to assess functional impairment, the Eastern Cooperative Oncology Group (ECOG) performance status being used in two studies. 23 studies identified an improvement in neurological function following surgery. The most common functional scale used to assess neurological outcome was the Frankel scale, 3 studies used the American Spinal Injury Association (ASIA) impairment scale for this purpose. Wound problems including infection and dehiscence appeared to be the most commonly reported surgical complication. (25 studies). The most commonly used surgical technique involved a posterior approach with decompression, with or without stabilisation. Less commonly employed techniques included percutaneous pedicle screw fixation associated with or without mini-decompression as well as anterior approaches involving corpectomy and instrumentation. 9 studies included in their data, the effect of radiation therapy in combination with surgery or as a comparison used as an alternative to surgery in spinal metastases.

Conclusions: We provide a systematic literature review on the outcomes of decompressive surgery for spinal metastases. We analyse survival data, motor function, neurological function, as well as the techniques of surgery used. Where appropriate complications of surgery are also highlighted. It is the authors' intention to provide the reader with a reference text where this information is ready to hand, allowing for the consideration of means and methods to improve and optimise the standard of care in patients undergoing surgical intervention for metastatic spinal disease.