Large Lytic Defects Produce Spinal Kinematic Instability
With the increasing effectiveness of immunotherapy and chemotherapy, patients with metastatic disease are surviving longer in much higher numbers. For many primary tumors (lung, breast, thyroid), a common site of metastases is the spine, giving rise to concomitant concerns regarding spine stability and the risk of neurologic compromise.
In the May 19, 2021 issue of JBJS, Alkalay et al. report the results of an in vitro study in which they simulated osteolytic defects in 3-level thoracic and lumbar segments of cadaveric spines. The simulations involved 2 patterns of lytic defects previously reported to be associated with increased risk of pathologic vertebral fracture: anterior-column compromise (40% of the vertebral body) and anterior plus middle-column compromise (extension of the model to include the ipsilateral pedicle and facet joint). The spinal segments were kinematically assessed in axial compression and axial compression with a flexion or extension moment, with testing before and after lesion simulation.
The authors concluded that “critical spinal lytic defects result in kinematic abnormalities and lower the compressive strength of the spine.” With greater lytic involvement, significantly higher translational motion along all 3 anatomic axes, and higher torsional and lateral-bending range of motion under axial compression with both flexion and extension moments were demonstrated.
The precision of the model in this cadaveric study was excellent. And the clinical implications of the findings are real: increasing lytic involvement of the vertebral body along with the pedicles could indicate impending instability, with the potential for neurologic injury. These data will be useful for surgeons and patients when formulating decisions regarding the need for intervention with fixation to limit flexion/extension forces in order to reduce pain and neurologic involvement. Future clinical data on the impact of these decisions in terms of pain and functional outcomes will be very valuable as we seek to optimize treatment of our patients with spinal metastatic disease.
Marc Swiontkowski, MD
JBJS Editor-in-Chief
Polytrauma Patients Face Cancer Risk from Imaging Radiation
Orthopaedic surgeons work with radiation in some capacity almost every day. We would struggle to provide quality patient care if it were not for the many benefits that radiographic images provide us. But the more we are exposed to something, the less we tend to think about it. For example, how often do we discuss the risks of radiation exposure with our patients—especially those who are exposed to a large amount of it after an acute traumatic injury?
The article by Howard et al. in the August 7, 2019 issue of JBJS strongly suggests that polytrauma patients need to better understand the risks associated with radiation exposure as they progress through treatment of their injuries. The authors evaluated the cumulative 12-month postinjury radiation exposure received by almost 2,400 trauma patients who had an Injury Severity Score of 16+ upon admission. Those patients received a median radiation dose (not counting fluoroscopy) of 18.46 mSv, and their mean radiation exposure was 30.45 mSv. These median-versus-mean data indicate that a small subset of patients received substantially more radiation than others, and in fact, 4.8% of the cohort was exposed to ≥100 mSv of radiation. To put these amounts in context, the average human in the UK (where this study was performed) is exposed to about 2 mSv of background radiation per year, and there is good evidence suggesting that carcinogenesis risk increases with acute radiation doses exceeding 50 mSv.
Based on mathematical models (actual occurrences of cancer were not tracked), the authors conclude that for these patients, the median risk of fatal carcinogenesis as a result of medical radiation following injury was 3.4%. In other terms, 85 of these patients would be expected to develop cancer as a result of medical imaging—which struck me as a startling estimate.
So what are we to do? In a Commentary accompanying this study, David A. Rubin, MD, FACR offers some practical suggestions for reducing unnecessary radiation exposure. I personally feel that because the radiation associated with CT scans and radiographs can be, quite literally, life-saving for patients who have sustained traumatic injuries, increasing the chance that patients develop cancer later in life in order to save their life now is a good risk-benefit proposition. But the findings from this study should make us think twice about which imaging tests we order, and they should encourage us to help patients better understand the risks involved.
Chad A. Krueger, MD
JBJS Deputy Editor for Social Media
Aggressive Treatment Improves QOL in Many Cases of Spinal Metastases
A significant portion of metastatic disease comes with no clear identification of a primary tumor; this is unfortunately the case with many spinal metastases. In the October 4, 2017 issue of The Journal, Ma et al. evaluate the survival and patient-reported quality-of-life (QOL) outcomes for patients with spinal metastases from cancer of unknown primary origin.
Their prospective longitudinal study confirms that a more aggressive strategy that combines surgery and radiation therapy results in better QOL (as measured with the four-domain FACT-G instrument) than radiation alone. There was no significant difference in survival time between the two groups. In a subgroup analysis of patients receiving surgery, those who underwent circumferential decompression had significantly better functional and physical well-being and higher total QOL scores than those who underwent decompressive laminectomy.
These findings emphasize the critical role of shared decision making in such difficult situations. A dire diagnosis with poor statistical chances of long-term survival does not mean that patients should not be informed of treatment options and have the opportunity to opt for an aggressive surgical approach, especially if that decision is likely to result in improved QOL. Let us endeavor to compassionately provide patients with the facts, as we understand them, and let them select from among the medical and surgical options that are at their disposal. More often than not, in this sad scenario, it seems aggressive is better in terms of quality of life.
Faster Relief for Patients with Painful Bone Metastases
A technique that combines magnetic resonance (MR) imaging with high-intensity focused ultrasound hyperthermia provides faster pain relief than conventional radiation therapy (RT) for patients with a painful bone metastasis.
In the September 20, 2017 issue of JBJS, Lee et al. report on a matched-pair study of 63 patients with a painful bone metastasis who received either magnetic resonance-guided focused ultrasound (MRgFUS) or RT as first-line treatment. Both modalities were effective overall, yielding response rates of >70% at the three-month follow-up evaluation. However, MRgFUS was more efficient, providing a 71% response rate at 1 week after treatment, compared with 26% for RT at that same time point.
The total treatment time and cost of the two modalities were similar, and neither was associated with adverse events above grade 2. Among MRgFUS patients, there was a 14% rate of positioning-related pain and a 33% rate of sonication-related pain, which typically resolved within 1 day after treatment.
Lee et al. report that the median overall survival of patients in the study was 12.7 months in the MRgFUS group and 9.8 months in the RT group, a statistically nonsignificant difference. But the authors emphasize that the study was more about pain relief than extending life. “Reduc[ing] pain, restor[ing] function, and maintain[ing] quality of life is imperative” for those with bone metastasis, the authors conclude. They also caution that MRgFUS is not appropriate for bone metastases of the skull or most of the spine, or for any lesion that is not at least 1 cm away from “tissues at risk.”
JBJS Editor’s Choice: Research into Female Surgeon Safety
The evolution of more rational educational programs and other societal changes point to a future where an increasing number of orthopaedic surgeons will be female. Thankfully, we have made gains in adjusting the medical community’s perspective on careers in orthopaedic surgery. No longer are we perceived to be “stronger than a mule and twice as smart” or merely “buckles and braces men.” Evolving interventional techniques that rarely require brute force have also helped change this view.
At the same time, with the rapidly increasing need for musculoskeletal care as the population ages, we need every orthopaedic practitioner—male and female—to remain as healthy and active as possible. Epidemiologic studies of surgeon health have revealed real concerns for neck and back degenerative changes and cancer risk.
In the November 2, 2016 edition of The Journal, Valone et al. tackle the issue of exposure of the female breast to intraoperative radiation. In a nifty study incorporating C-arm fluoroscopy and an anthropomorphic torso phantom equipped with breast attachments and dosimeters, the authors found that:
- The median dose-equivalent rate of scatter radiation to the breast’s upper outer quadrant (UOQ) was higher than that to the lower inner quadrant.
- C-arm cross-table lateral projection was associated with higher breast radiation exposure than anteroposterior projection.
- Size, fit, and breast coverage of lead protection matter.
The findings should prompt redesign of protective aprons and vests to more effectively cover the breast and axilla. We could also use more well-designed longitudinal studies to identify the risk factors for neck, back, and shoulder injury as well as gain a better understanding of the real risk of surgeon exposure to intraoperative radiation.
Annual occupational radiation dose limits to the breast have not yet been established. But in the meantime, Valone et al. recommend distancing the axilla from the C-arm and placing the X-ray source beneath the operating table or on the contralateral side to reduce radiation exposure to the UOQ of the breast.
Marc Swiontkowski, MD
JBJS Editor-in-Chief
No BMP–Cancer Link Found in Older Patients After Lumbar Arthrodesis
The July 6, 2016, edition of The Journal of Bone & Joint Surgery features a large case-cohort study that may help older patients and clinicians decide whether to use bone morphogenetic protein (BMP) as an adjunct to lumbar arthrodesis. Among Medicare patients aged 65 years and older, Beachler et al. found that BMP use was not associated with the following:
- Overall cancer risk
- Increased risk of individual cancer types
- Increased risk of cancer in people who had cancer prior to undergoing lumbar arthrodesis
- Increased mortality after a cancer diagnosis
BMP was used in 30.7% of >3,600 lumbar-arthrodesis patients analyzed, and the lack of association between BMP use and cancer held whether patients received the growth factor as part of an FDA-approved anterior lumbar interbody fusion or as an off-label application.
In an accompanying commentary, Singh et al. laud the authors for designing a study that was not only well-powered but also analyzed risk among those with a medical history of cancer. The commentators emphasize, however, that the median follow-up in this study was 2.4 years, leading them to wonder “whether this time frame is sufficient to evaluate the impact of BMPs on carcinogenesis.”
Until a large, prospective, randomized trial on this subject is conducted, Singh et al. say, “the decision to use BMPs should be made on the basis of sound clinical judgment by the treating physician after a full disclosure of the potential risks to the patient.”
Thank You, Dr. Page
The July 7, 2015 edition of JAMA includes a moving and powerful essay from orthopaedic surgeon Alexandra Page, MD, titled “Stopping Time.”
We in orthopaedic surgery rarely stop to think about the important foundations of our personal and professional lives. Dr. Page’s very intimate story begs us all to pause, take stock, and be grateful. I thank her for sharing her story with our community, and I encourage everyone to read it.
Marc Swiontkowski, MD
JBJS Editor-in-Chief
3D Printing Moves from Metal to “Real” Bone
OrthoBuzz has reported previously on the 3D printing of implantable skeletal structures (click here for an example), but the materials used were metallic. Now, two new accomplishments with 3D printing have produced material that mimics the physiochemical properties and porous structure of real bone.
First, students from California State University in Long Beach created the LuxNova OsBot 3D printer. The students say that the OsBot can replicate the unique and complex structure of human bone tissue down to the micro and nano levels.
Meanwhi
le, in China, the Xi’an Particle Cloud Advanced Materials Technology Co. has wrapped up animal testing on a similar bioprinting device and is poised to enter human trials. The device uses both UV light and heat to “laminate” binder material until a bonelike structure is fabricated. In rabbits, the 3D-printed bone exhibited new bone-cell activity on its surface almost immediately after implantation.
Theoretically, surgeons could use 3D-printed bone grafts to replace cancerous or severely traumatized bone tissue, obviating the need for amputation or cadaver grafts.
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