Summary
Postural fatigue syndrome (PFS) is one of the most common causes of postvertebral augmentation pain and is typically located in the thoracic spine and is seen more often in women. This pain is typically less severe than pain seen in patients with vertebral compression fractures (VCFs) and is worse when the patient is upright and better when they are recumbent or lying down. It is important to recognize PFS as a cause of pain to avoid misdiagnosing this persistent pain as some other type of pathology. It probably results from biomechanical alterations in spine after a VCF that places additional stress and strain on the posterior elements. The treatment for PFS is medial branch blocks or facet joint injections followed by radiofrequency rhizotomy if the pain relief from the initial injections meets or exceeds 80% but does not last beyond 12 weeks. A less invasive approach can also be taken as the pain from PFS usually goes away or decreases substantially in six to ten months after the vertebral augmentation. Physical therapy and bracing can be used as an alternative treatments to aid in the patient’s recovery.
Keywords: postural fatigue syndrome, thoracic spine, posterior elements, pain, medial branch blocks, trauma, multiple myeloma, malignancy, kyphoplasty
PFS is defined as persistent back pain after vertebral augmentation or other posture altering spine injury that worsens with upright posture and increased time standing and is relieved when sitting or lying recumbent. This syndrome most commonly affects the mid-thoracic and thoracolumbar junction regions. Being able to recognize this syndrome is extremely important for postprocedural patient care. Patients will present on follow-up with residual back pain that is not as severe as before the vertebral augmentation procedure but still bothersome to the patient. The characteristics of the pain are also different from VCF pain that worsens with patient movement and transition from one position to another. A lack of awareness of PFS can lead to misdiagnosing this syndrome and physicians labeling an otherwise well-performed vertebral augmentation as a “failed” intervention. More importantly, PFS was not diagnosed nor mentioned in three controversial randomized controlled trials.1–3 The lack of assessment of this syndrome was a likely contributor to the absence of statistical superiority of the vertebroplasty arm in comparison to the sham group. Given the precarious statistical balance of the sham and vertebroplasty arms, it is possible that if this syndrome had been taken into consideration in those studies, different outcomes would have been published. This pathology can be easily and affectively treated by medial branch blocks, and most patients will do very well after a single medial branch block treatment. Even without treatment the pain typically decreases substantially within 6 to 10 months following vertebral augmentation.
Patients with PFS most often present at approximately 2 to 6 weeks after vertebral augmentation with nonradicular back pain in the mid-thoracic and/or thoracolumbar junction region. This pain increases when standing upright and decreases when sitting down and typically increases the longer the patient stands or works with their arms extended out from the body. Most patients will have pain with a VAS intensity score of 3–5/10. Also, this pain is categorically different from a fracture pain and usually presents with a severity that is approximately half of what the original fracture pain was. The pain tends to fluctuate according to what position this patient is in but is not transitional pain that worsens during the change to different positions. Although postural fatigue pain is less intense than the initial VCF-related pain, the patient often considers it annoying enough to seek medical evaluation. This syndrome seems to occur less frequently with balloon kyphoplasty (or vertebral body implants) and more frequently with vertebroplasty, probably related to better correction of the vertebral body height, kyphotic angle, and realignment of the end plates seen with balloon kyphoplasty and implants. PFS can last up to 6 months before fading gradually with time. Since this is the first known description of this syndrome, the incidence of this pain disorder is not yet known but, according to our estimation, it is seen in approximately 5 to 10% of our vertebral augmentation patients at the time of follow-up.
After a VCF, nucleus pulposus pressure decreases,4 with higher loads being redistributed toward the neural arch and facets when the patient stands upright. The fracture mechanical instability is corrected after adequate polymethyl methacrylate (PMMA) cement is injected. A subanatomic fracture restoration (i.e., incomplete correction of the kyphotic angle and/or vertebral body height restoration and/or end-plate realignment), however, leads to residual functional spinal unit (FSU) instability and persistent increase in stress on the posterior arch and facet joints when the patient stands upright (Chapter 18). This phenomenon is supported by previous studies that suggest that the ability to restore vertebral body height and the kyphotic deformity of the fractured end plate should be the ideal end point to normalized load transmission across the FSU and fractured level.4,5 In brief, in a patient with a subanatomic VCF restoration, when a patient stands upright the facet loading increases, and when the patient sits or is in flexed position, the load is transferred toward the anterior column resulting in relief for the patient.6,7 It can take a few months before the patient accommodates to their altered biomechanics and experiences a subsequent decrease in pain.
Treating patients with PFS consist of bracing, physical therapy, or performing medial branch blocks at the VCF-PMMA-treated level in addition to one or two levels above the fracture and one or two levels below the fracture. Typically, the postural fatigue pain fades within 6 to 10 months following the vertebral augmentation. Most patients do very well after a single medial branch block; however, in some cases a second medial branch block or even thoracic radiofrequency rhizotomy might be required.
• PFS is defined as persistent pain after vertebral augmentation that worsens with upright posture, working with the arms and hands extended, and is relieved when the patient sits down or lies down.
• This syndrome affects most frequently the mid-thoracic and thoracolumbar junction region.
• The PFS pain is categorically different from a fracture pain by being significantly less intense and fluctuates according to what position the patient is in (standing vs. sitting).
• This syndrome is more frequently seen in patients treated with vertebroplasty and less frequently in patients treated with balloon kyphoplasty, vertebral body implants, or other modalities that can optimally restore the vertebral body height and improve the kyphotic angle.
• Typically, the pain fades within 6 to 10 months following vertebral augmentation.
• Treatment of PFS consists of bracing, physical therapy, and performing medial branch blocks or thoracic radiofrequency rhizotomy at the painful levels.
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