Interventional pain management includes a range of specialised invasive techniques for treating pain that are usually offered by either anaesthetists or interventional radiologists. The most common techniques used for palliative care pain management include vertebral augmentation, neuraxial analgesia and neurolytic techniques. The availability of interventional pain management varies according to the setting of care and the local availability of skilled and experienced providers. The place of these techniques within a hierarchy of pain management options is still evolving.
External beam radiotherapy is the mainstay of treatment of painful bone metastases.  A recent review found the intervention is underutilised due to poor referral processes and a lack of knowledge about its therapeutic benefits.  Single fraction radiotherapy to palliate painful bone metastases is as effective as multiple fractions for controlling pain. [3-5] Systematic reviews show that more patients who have had single fraction radiotherapy may require retreatment for pain, and there is a non-significant trend to more fractures. [4,6] When there are multifocal painful bone metastases, treatment with radioisotopes such as strontium-89 or samarium-153 can produce sustained analgesia, although they are associated with bone marrow toxicities. [7-8]
Vertebroplasty and kyphoplasty both involve the injection of cement into vertebrae affected by compression fractures with the aim of improving pain and restoring function. A recent review found both vertebroplasty and kyphoplasty provided clinically relevant decreases in pain for patients with cancer-related vertebral compression fractures.  Both techniques reported cement leakage as a common complication, although low incidence, and the review noted that leakage was less common in kyphoplasty.  There is still limited evidence to guide recommendations for the indications and timing of this intervention. 
Neuraxial analgesic techniques, such as spinal and intrathecal routes, are sometimes used for the management of retractable pain. Retractable or refractory pain is defined as pain that has not responded to conventional analgesic approaches. A systematic review examining the analgesic efficacy of opioids with or without adjuvants administered via the neuraxial route in adult patients with cancer found all interventions reviewed provided improved pain control.  Single neuraxial medication bolus compared with placebo, single neuraxial medication bolus compared with continuous infusion and neuraxial combinations of opioid and adjuvant analgesics compared with opioid alone were all examined in this review.  Systematic reviews of evidence in this area are limited by small sample sizes and variable medication combinations which make meta-analysis difficult.  Referral issues are also significant with these modalities as the availability of anaesthetic expertise and sufficient logistics to support ongoing care needs is limited.  The indication for using these techniques relies on expert opinion due to the limited number of studies, however the lack of research is not indicative of poor efficacy. [11,12]
There is moderate quality evidence for the use of intrathecal baclofen, a centrally acting skeletal muscle relaxant, for pain secondary to hypertonia in spasticity. [12,13]
Catheter associated problems may occur with longer-term use of implanted devices, such as pumps and administration ports  however a systematic review looking specifically at this issue has concluded that these events are rare in both hospital and community settings. 
Neurolytic techniques are available to target various specific pain syndromes. Sympathectomy is a procedure that damages part of the nervous system (the sympathetic chain) in order to provide analgesia. A recent systematic review has found low quality evidence to support the procedure for the treatment of neuropathic pain.  There is also low quality evidence for the procedure in the management of pain associated with limb ischemia, although the procedure is considered promising in both conditions. [15,16]
One of the best studied neurolytic techniques is the coeliac plexus block which has been developed to treat severe abdominal pain, most commonly from pancreatic cancer. There is good quality evidence to support the use of this block in pancreatic cancer patients. [17,18] There is low quality evidence to support the use of superior hypogastric plexus block. 
Another neurolytic technique is radiofrequency ablation, used for the treatment of pain associated with vertebral metastases. While the evidence base for this procedure is limited and sample sizes in studies are small, this techniques has been shown to reduce pain with limited complications.  Cryoablation uses extreme cold to induce tissue necrosis to reduce tumour size and inhibit neural activity.  Like other studies in this area there are limited sample sizes but there are some positive outcomes suggesting this may be a viable treatment, particularly when combined with other therapies like vertebral augmentation. 
- For bone pain due to metastases, external beam radiotherapy is an effective treatment and may, if possible, be offered first line along with opioid analgesia. Radioisotope treatment may be highly effective for multiple sites of bone pain but is associated with the potential for significant marrow toxicity.
- In considering a radiotherapy fractionation schedule the palliative goals, prognosis, and whether the problem is uncomplicated, should be taken into account. Whilst patients who have had single fraction (hypofractionated) radiotherapy may require re-treatment more often than those treated with other schedules, overall, shifting to hypofractionated schedules reduces the burden on patients and the workload of radiotherapy units  and the practice is supported by evidence. 
- Where interventional pain management approaches are available, they need to be incorporated into a holistic plan of care for each patient.
- The literature suggests that for carefully selected patients there are benefits to be achieved from neuraxial analgesia, and from neurolytic procedures such as coeliac plexus blocks.
- Neuraxial analgesia requires close ongoing follow-up from a specialist service to manage implanted devices and medications, and is associated with significant costs and burdens. However when available it may provide an alternative for patients with complex pain that is not well controlled by medical management.
- There is good quality evidence to support the use of vertebral augmentation techniques for compression fractures.