Magnetic resonance-guided focused ultrasound (MRgFUS) is a noninvasive, incisionless, radiation-free technology used to ablate tissue deep within the body. This technique has gained increased popularity following FDA approval for treatment of pain related to bone metastases and limited approval for treatment of osteoid osteoma. MRgFUS delivers superior visualization of soft tissue targets in unlimited imaging planes and precision in targeting and delivery of thermal dose which is all provided during real-time monitoring using MR thermometry. This paper provides an overview of the common musculoskeletal applications of MRgFUS along with updates on clinical outcomes and discussion of future applications.

Spondylolisthesis is a common finding in middle-aged and older adults with back pain. The pathophysiology of degenerative spondylolisthesis is a subject of controversy regarding not only its etiology but also the mechanisms of its progression. It is theorized that degeneration of the facets and discs can lead to segmental instability, leading to displacement over time. Kirkaldy-Willis divided degenerative spondylolisthesis into three phases: dysfunction, instability, and finally, restabilization. There is a paucity of literature on the unification of the radiological hallmarks seen in spondylolisthesis within these phases. The radiographic features include (1) facet morphology/arthropathy, (2) facet effusion, (3) facet vacuum, (4) synovial cyst, (5) interspinous ligament bursitis, and (6) vacuum disc as markers of dysfunction, instability, and/or restabilization. We discuss these features, which can be seen on X-ray, CT, and MRI, with the intention of establishing a timeline upon which they present clinically. Spondylolisthesis is initiated as either degeneration of the intervertebral disc or facet joints. Early degeneration can be seen as facet vacuum without considerable arthropathy. As the vertebral segment becomes increasingly dynamic, fluid accumulates within the facet joint space. Further degeneration will lead to the advancement of facet arthropathy, degenerative disc disease, and posterior ligamentous complex pathology. Facet effusion can eventually be replaced with a vacuum in severe facet osteoarthritis. Intervertebral disc vacuum continues to accumulate with further cleft formation and degeneration. Ultimately, autofusion of the vertebra at the facets and endplates can be observed. With this review, we hope to increase awareness of these radiographical markers and their timeline, thus placing them within the framework of the currently accepted model of degenerative spondylolisthesis, to help guide future research and to help refine management guidelines.

The relationship between degenerative zygapophysial joint (facet) arthropathy and multifidus muscle atrophy has not been rigorously evaluated. The purpose of this study was to determine if specific morphological features of degenerative facet arthropathy are correlated with multifidus muscle atrophy. We retrospectively reviewed medical records and imaging studies of patients with lumbar spinal stenosis. Facet overhang, bridging osteophyte formation, facet effusion, and facet angles were evaluated by univariable and multivariable regression to identify independent associations with deep and superficial parts of the multifidus total cross-sectional area (tCSA), functional cross-sectional area (fnCSA), and fatty infiltration (FI). Facet overhang was classified as severe in 50 females (53.2%) versus 56 males (36.9%) (p = 0.030). Severity of facet overhang and female sex were independently associated with smaller deep part of the multifidus tCSA and fnCSA as well as higher FI, reflecting greater atrophy of the deep region compared to total muscle mass. In comparison, severe facet overhang (p < 0.001; OR = 3.47, 95% CI = 2.13-5.66) and female sex (p < 0.001; OR = 4.19, 95% CI = 2.58-6.79) were independently associated only with higher superficial part of the multifidus FI, reflecting muscle steatosis without significant lean muscle atrophy. In patients with degenerative lumbar spinal stenosis, facet overhang is an independent risk factor for deep part of the multifidus atrophy. Bridging osteophyte formation, facet effusion, and facet angles were not independently associated with deep part of the multifidus atrophy.

BACKGROUND: Previous studies have reported that magnetic resonance imaging (MRI) and computed tomography (CT) do not predict response to facet blocks. However, single photon emission computed tomography (SPECT) uptake within facet joints has been shown to correlate with pain relief after intervention in the lumbar spine. There is minimal data regarding the predictive value of single photon emission computed tomography/computed tomography (SPECT/CT) for neck pain.
OBJECTIVE: The aim of this study was to evaluate the utility of SPECT/CT in patients with axial neck pain for the identification of specific facet joints that would benefit from diagnostic and therapeutic facet joint steroid injections and/or medial branch block/RFA treatments.
METHODS: A retrospective cohort study.
METHODS: One hundred seventy-nine patients at a single institution pain center with neck pain and a SPECT/CT scan between 2009 and 2015. One hundred twelve patients had no prior intervention at the level of interest and met inclusion criteria.
METHODS: Pain reduction at 50% and 80% thresholds within 24 hours of facet intervention. Concordance of facet intervention with the focus of maximal uptake on SPECT/CT scan.
METHODS: All patients were referred to our institution\'s Center for Pain Medicine and were treated with facet interventions. The site of facet intervention was determined by pain center providers based on their clinical examination and interpretation of images. Groups were formed based on whether the facet intervention included the level of maximal uptake on SPECT/CT scan. A positive response to intervention was defined at both 50% and 80% thresholds for reduction in pain within 24 hours of facet injection with steroid and local anesthetic or medial branch block with local anesthetic only. These were the facet interventions used for our data collection. A Chi-square statistic was used to analyze categorical data and a Student\'s t-test was used to analyze non-categorical data. SPSS (IBM Corp. IBM SPSS Version 24.0) was used for all analyses.
RESULTS: Of our 112 patients, Group 1 consisted of 89 with an intervention occurring at the level with increased uptake on SPECT/CT. Group 2 consisted of 23 patients with an intervention at a level without uptake on SPECT/CT. Demographic data did not significantly differ between cohorts. A Chi-square test of independence demonstrated that intervention at a level concordant with SPECT/CT was significantly correlated with self-reported pain relief thresholds of both 50% and 80% (p=.0002).
CONCLUSIONS: Facet interventions based on SPECT/CT scan uptake were more successful in pain reduction than those which were not. This suggests a role for SPECT/CT in diagnosing therapeutic targets for neck pain.
METHODS:

Neck and back pain is increasingly prevalent, and has increased exponentially in recent years. As more resources are dedicated to the diagnosis of pain conditions, it is increasingly important that the diagnostic techniques used are as precise and accurate as possible. Traditional diagnostic methods rely heavily upon patient history and physical examination to determine the most appropriate treatments and/or imaging studies. Though traditional means of diagnosis remain a necessity, in many cases, correlation with positive or negative responses to injections may further enhance diagnostic specificity, and improve outcomes by preventing unnecessary treatments or surgeries. This narrative review aims to present the most recent literature describing the diagnostic validity of precision injections, as well as their impact on surgical planning and outcomes. Diagnostic injections are discussed in terms of facet arthropathy, lumbar radiculopathy, discogenic pain and discography, and sacroiliac joint dysfunction. There is a growing body of evidence supporting the use of diagnostic local anesthetic injections or nerve blocks to aid in diagnosis. Spinal injections add valuable objective information that can potentially improve diagnostic precision, guide treatment strategies, and aid in patient selection for invasive surgical interventions.

OBJECTIVE: Axial neck pain is common and often debilitating. Diagnosis of the specific pain source can be a challenge, and this confounds effective treatment. Cervical facet arthropathy is implicated in many of these cases. The diagnosis is readily made on conventional cross-sectional imaging modalities, particularly CT imaging. However, this modality falls short in determining if an osteoarthritic facet joint is truly the source of symptoms. Radionucleotide imaging presents a noninvasive radiological adjunct to conventional cross-sectional imaging in the workup of patients with suspected facetogenic pain. Herein, the authors present the patient-reported outcomes (PROs) following posterior instrumented arthrodesis of the subaxial cervical spine from a consecutive case series of patients with a diagnosis of cervical facet joint arthropathy and a concordant positive radionucleotide tracer uptake.
METHODS: The clinical case series of patients treated by the senior author at a single tertiary care institution between September 2014 and April 2018 was reviewed. Patients were selected for inclusion if their primary symptom at presentation was axial neck pain without neurological deficits and if CT imaging revealed facet arthropathy of the cervical spine. These patients underwent radionucleotide imaging in the form of a planar 99mTc methylene diphosphonate (99mTc MDP) bone scintigraphy study. Those with a finding of radionucleotide tracer uptake at a location concordant with the facet arthropathy were selected to undergo posterior cervical instrumented arthrodesis of the affected levels. PROs were recorded at the time of surgical consultation (i.e., after nonoperative treatment) and at 6 weeks, 3 months, 6 months, and 1 year following surgery. These included neck and arm pain, the Neck Disability Index (NDI) and the 12-Item Short Form Health Survey responses.
RESULTS: A total of 11 patients were included in this retrospective case series. The average reported neck pain and NDI scores were high at baseline; 7.6 ± 2.3 and 37.1 ± 13.9 respectively. Twelve months after surgical intervention, a significant decrease in reported neck pain of -4.5 (95% CI -6.9, -2.1; p = 0.015) and a significant decrease in NDI of -20.0 (95% CI -29.4, -10.6; p = 0.014) was observed.
CONCLUSIONS: This case series represents the largest to date of patients undergoing surgical arthrodesis following a finding of facet arthropathy with a concordant positive radioisotope image study. These observations add support to a growing body of evidence that suggests the utility of radioisotope imaging for identification of a facetogenic pain generator in patients with primary axial neck pain and a finding of cervical facet arthropathy. These preliminary data should serve to promote future prospective, controlled studies on the incorporation of radionucleotide imaging into the workup of patients with suspected facetogenic pain of the cervical spine.

Facet joint osteoarthritis/arthropathy of the spine is a common cause of back and neck pain that frequently overlaps clinically with other diseases of the spine. Because of the possible overlap, it is crucial to have an accurate diagnostic strategy, especially when determining the management approach. Various strategies have been suggested and adopted, with several these still being used in clinics. Over the years, because of the disadvantages of single-modality imaging methods (computed tomography, magnetic resonance imaging, single-photon emission computed tomography), the interest in radiologic examination started to move toward hybrid imaging techniques. Although the data are mixed, many initial studies have shown promise. However, there are relatively few data with comparative medial branch blocks, and further investigation is needed. Given the advantages and disadvantages of these new techniques, the imaging results have to be interpreted within clinical context and with consideration of the current state of knowledge in the decision-making process.

BACKGROUND: The pathogenesis of synovial cysts is largely unknown; however, they have been increasingly thought of as markers of spinal facet instability and typically associated with degenerative spondylosis. We specifically investigated the incidence of concomitant synovial cysts with underlying degenerative spondylolisthesis.
METHODS: A literature search was performed using 4 online databases to assess the association between lumbar synovial cysts and degenerative spinal pathological features. Meta-analyses were performed on the prevalence rates of coexisting degenerative spinal pathological entities and treatment modalities. A random effects model was used to calculate the mean and 95% confidence intervals.
RESULTS: A total of 17 studies encompassing 824 cases met the inclusion criteria. The pooled prevalence rates of concurrent spondylolisthesis, facet arthropathy, and degenerative disc disease at the same level of the synovial cysts were 42.5% (range, 39.0%-46.1%), 89.3% (range, 79.0%-94.8%), and 48.8% (range, 43.8%-53.9%), respectively. Among these, patients with coexisting spondylolisthesis were more likely to undergo spinal fusion surgery (vs. laminectomy alone) and reoperation than were patients without spondylolisthesis with a pooled odds ratio of 11.5 (95% confidence interval, 4.5-29.1; P < 0.0001) and 2.0 (95% confidence interval, 0.9-4.2; P = 0.088), respectively.
CONCLUSIONS: Patients with a combination of synovial cysts and degenerative spondylolisthesis are more likely to undergo spinal fusion surgery than laminectomy alone compared with patients with synovial cysts and no preoperative spondylolisthesis. Furthermore, patients with synovial cysts and spondylolisthesis are more likely to require additional fusion surgery. The results from the present review lend credence to the argument that synovial cyst herniation might be a manifestation of an unstable spinal level.

OBJECTIVE: Standard imaging techniques have low predictive value for identifying sources of neck pain. Single-photon emission computed tomography (SPECT) imaging in conjunction with computed tomography (CT) provides the sensitivity of bone scanning for areas of high metabolic activity with the sensitivity of CT for anatomic localization. We evaluated the usefulness of SPECT-CT imaging in identifying pain generators in upper cervical facet arthropathy.
METHODS: In a retrospective study, we reviewed 7 patients (mean age, 68.7 years) who underwent diagnostic SPECT-CT imaging for upper cervical neck pain at our institution from August 2011 to February 2015. We assessed SPECT-CT radiotracer uptake and postoperative neck disability index (NDI) and visual analog scale (VAS) scores.
RESULTS: Mean preoperative NDI and VAS scores were 42% (range, 34%-72%) and 7/10 (range, 5-8), respectively. SPECT-CT showed increased radiotracer uptake and inflammation at the level of pain generation indicated by history and physical examination. Intraoperatively, all patients had corresponding facet hypertrophy with degeneration at the site of increased radiotracer uptake. The mean postoperative NDI and VAS scores at 9 months were 23% (0%-54%) and 2/10 (0-5), respectively, representing improvements of 20% (P = 0.025) and 4 (P = 0.0028), respectively.
CONCLUSIONS: SPECT-CT imaging of the upper cervical spine is a potentially sensitive diagnostic test that can implicate pain generators with increased metabolic activity. We propose that SPECT-CT may be a useful adjunct in the workup for neck pain secondary to facet arthropathy that could obviate diagnostic injections.