MRI Can Detect “Invisible” Femoral Neck Fractures in Patients with Shaft Fractures
For more than 40 years, orthopaedic trauma surgeons have been interested in this fairly common fracture combination, which is often seen in polytrauma patients. We have long hypothesized that much of the energy that fractures the femoral shaft is dissipated, leaving many ipsilateral neck fractures nondisplaced and difficult to recognize on plain radiographs.
But the consequences of missing a femoral neck fracture can be devastating. For example, because the neck fracture pattern is often vertical (Pauwels type III), the risk of displacing the neck fracture during intramedullary nailing is very high. Achieving reduction and fixation of a displaced neck fracture near an intramedullary nail—either intraoperatively or postoperatively—is extremely challenging.
Because of these issues, some authors recommend a thin-cut CT series to identify nondisplaced ipsilateral neck fractures preoperatively, and this protocol has been shown to significantly reduce the delay in identifying such fractures. In the February 19, 2020 issue of The Journal, Rogers et al. from UTHealth in Houston show that even with thin-cut CT, the crack can be missed. These authors added to the protocol limited-sequence MRI that identifies these fractures with very high sensitivity and takes <10 minutes to perform.
In this study, among 39 acute, high-energy femoral shaft fractures, the authors identified 4 ipsilateral neck fractures with MRI that were not seen on CT. Despite exhibiting polytrauma, 89% of all indicated patients in this study were evaluated preoperatively with the limited-sequence MRI protocol, including those in traction and those treated initially with external fixation.
The findings from this study should prompt trauma surgeons practicing in high-volume centers to develop similar MRI protocols. It may also be possible to develop such protocols in lower-volume centers, but in those settings it is especially incumbent on the surgical team to recognize that this fracture combination occurs in a fairly high percentage of cases and to carefully scrutinize plain radiographs and consider thin-cut CT scanning of the ipsilateral hip. In addition, the potential for an ipsilateral nondisplaced femoral neck fracture should trigger increased use of fluoroscopy during intramedullary nailing of shaft fractures, so that concomitant neck fractures can be recognized and stabilized with screws before they become displaced.
Marc Swiontkowski, MD
JBJS Editor-in-Chief
MRI for Detecting Rapidly Progressive Knee OA: No Crystal Ball
This post comes from Fred Nelson, MD, an orthopaedic surgeon in the Department of Orthopedics at Henry Ford Hospital and a clinical associate professor at Wayne State Medical School. Some of Dr. Nelson’s tips go out weekly to more than 3,000 members of the Orthopaedic Research Society (ORS), and all are distributed to more than 30 orthopaedic residency programs. Those not sent to the ORS are periodically reposted in OrthoBuzz with the permission of Dr. Nelson.
Knee osteoarthritis (KOA) typically develops over a decade or more. However, 1 in 5 people with KOA have more pain and disability at onset, have accelerated radiographic knee osteoarthritis (AKOA), and experience end-stage disease within 4 years. The use of demographics and clinical findings has resulted in only a 40% rate of correctly classifying patients who will develop AKOA instead of longer-term KOA.
Investigators recently conducted a case–control study using data from the OsteoArthritis Initiative (OAI), including demographic, clinical, and biochemical data, along with radiographic and magnetic resonance (MR) imaging data.1 The researchers hypothesized that the addition of an MR imaging-based scoring system would more accurately identify patients at risk for AKOA. They used classification and regression tree (CART) models to assess the ability of baseline MR features to classify participants who will develop AKOA and whether adding baseline MR features to an existing model improved classification of adults who will develop AKOA.
The existing model consisted of clinical data that included pain, function, physical exam findings, and quality-of-life measures. Demographic data included age, sex, and BMI collected at baseline. Biochemical data included high-sensitivity C-reactive protein and serum blood sugar. Data obtained from MR imaging scores included bone marrow lesion volume, effusion-synovitis volume, cartilage damage index, meniscal extrusion and degeneration, cruciate ligament degeneration, and patellar fat pad changes.
Contrary to the hypothesis, the CART models with and without MR features each explained approximately 40% of the variability. Adding MR-based features to the model improved specificity (0.90 vs. 0.82), but lowered sensitivity (0.62 vs. 0.70). Interestingly, the authors found that serum glucose, effusion-synovitis volume, and cruciate ligament degeneration were statistically important variables in classifying individuals who are likely to develop AKOA.
The clinical take home is that early MR data may be useful in sorting out mechanical complaints, but not in determining who will develop AKOA. In contrast, in later stages of KOA, MR images may reveal far greater damage than can be detected on radiographs.
Reference
- Price LL, Harkey MS, Ward RJ, MacKay JW, Zhang M, Pang J, Davis JE, McAlindon TE, Lo GH, Amin M, Eaton CB, Lu B, Duryea J, Barbe MF, Driban JB. Role of Magnetic Resonance Imaging in Classifying Individuals Who Will Develop Accelerated Radiographic Knee Osteoarthritis. J Orthop Res. 2019 Nov;37(11):2420-2428. doi: 10.1002/jor.24413. Epub 2019 Jul 29. PMID: 31297900
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
Assessing Fatty Infiltration in Rotator Cuff Tears: MRI vs Ultrasound
In the setting of rotator cuff injuries, higher degrees of fatty infiltration into cuff muscles are positively correlated with higher repair failure rates and worse clinical outcomes. MRI continues to be the gold standard imaging modality for evaluating fatty infiltration of the rotator cuff, but ultrasound represents another viable modality for that assessment—at considerably lower cost. Such is the conclusion of Tenbrunsel et al. in a recent issue of JBJS Reviews.
The authors reviewed 32 studies that investigated imaging modalities used to assess fatty infiltration and fatty atrophy. They found that grading fatty infiltration using ultrasound correlated well with grading using MRI. However, the authors identified difficulties distinguishing severe from moderate fatty infiltration on ultrasound, but they added that discerning mild from moderate fatty infiltration is more important clinically. Tenbrunsel et al. also mention sonoelastography, which measures tissue elasticity and can also be used to help determine the severity of fatty atrophy of the rotator cuff.
Overall, the trade-off between MRI and ultrasound comes down to higher precision with the former and lower cost with the latter.
For more information about JBJS Reviews, watch this video featuring JBJS Editor-in-Chief Dr. Marc Swiontkowski.
Don’t Overlook Possible Osteoid Osteoma in Kids with Hip Pain
Orthopaedists are seeing an increasing number of active, young patients with hip pain. A study by May et al. in the March 20, 2019 issue of The Journal of Bone & Joint Surgery strongly suggests that osteoid osteoma (OO)—a small, benign tumor characterized by dense sclerotic bone tissue—should not be overlooked in the differential diagnosis when working up these patients.
The authors identified and reviewed the records of 50 children and adolescents (mean age of 12.4 years) at their tertiary-care pediatric center who had received a diagnosis of OO within or around the hip between 2003 and 2015. Nighttime hip and/or thigh pain (90%) and symptom relief with NSAIDs (88%) were common clinical findings.
Sclerosis/cortical thickening was visible in 58% of the radiographs. Perilesional edema and a radiolucent nidus was found on all 43 of the available CT scans, leading the authors to conclude that “CT scans provide definitive diagnosis” of OO.
Unfortunately, 46% of these patients initially received an alternative diagnosis, the most common of which was femoroacetabular impingement (FAI), and a delay in diagnosis of >6 months occurred in 43% of patients. The authors note that concerns regarding radiation exposure have led some clinicians to order MRI rather than CT when evaluating pediatric hip disorders, but this study found that identifying an OO nidus with MRI was not as accurate as doing so with CT.
Regarding treatment, among the 41 patients who ultimately underwent percutaneous radiofrequency ablation (RFA) to treat OO, 93% achieved complete post-RFA symptom resolution. Complications from RFA occurred in 7% of patients who underwent the procedure.
Full-Thickness Cartilage Defects More Predictive of Future TKA than Joint-Space Narrowing
Many older patients present to orthopaedic surgeons with clinical knee pain suggestive of osteoarthritis (OA) but with little or no radiographic evidence of disease. And a substantial proportion of those patients do not respond adequately to the recommended, first-line nonsurgical treatment approaches to knee OA. A prognostic study by Everhart et al. in the January 2, 2019 issue of The Journal of Bone & Joint Surgery helps explain why that might be.
The authors evaluated baseline knee radiographs and MRIs from >1,300 older adults (mean age of 61 years) who were enrolled in the Osteoarthritis Initiative, a multicenter observational cohort study with a median of 9 years of follow-up data. They sought to determine independent risk factors for progression to total knee arthroplasty (TKA) among this cohort, all of whom showed Kellgren-Lawrence grade 0 to 3 OA on knee radiographs. MRIs taken at baseline revealed that 38% of those patients had a full-thickness knee-cartilage defect. After the authors adjusted for various confounders (including age, weight, and symptom severity), they found that regardless of radiographic grade, the presence of a full-thickness cartilage defect was a strong independent risk factor for subsequent TKA. Moreover, patients with a defect ≥2 cm2 had twice the risk of arthroplasty compared with patients with defects <2 cm2.
According to the authors, the findings highlight the “greater importance of full-thickness cartilage loss over radiographic OA grade as a determinant of OA severity, specifically regarding the risk of future knee arthroplasty in older adults.” In his commentary on this study, Drew A. Lansdown, MD emphasizes that Everhart et al. “do not advocate for the routine use of MRI in the diagnosis of knee osteoarthritis,” but he says the findings “do suggest that early MRI may have a diagnostic role for patients who are not responding as expected to nonoperative measures.” Noting that the patients in this cohort would probably not be ideal candidates for current cartilage-restoration procedures, Dr. Lansdown encourages further research focused on identifying “patient-specific factors that can match patients with the treatment…that will provide the greatest likelihood of symptom relief and functional improvement.”
Helpful Hint for Managing Femoral Neck Stress Fractures
The incidence of patients presenting with proximal thigh and groin pain is increasing along with increased interest in recreational athletic activity. When it is associated with a history of increased physical activity, this pain profile often prompts the ordering of a hip MRI if presenting radiographs are unremarkable. However, surgeons often find it difficult to make accurate prognoses and treatment recommendations when the MRI findings suggest a femoral neck stress fracture.
In the September 5, 2018 issue of The Journal, Steele et al. provide us with helpful hints for determining when to proceed with surgical stabilization of the femoral neck in this clinical scenario. Of the femoral neck stress fracture patients in this study who progressed to a surgical procedure, >85% had an effusion on the initial MRI, compared with only 26% of those whose condition resolved with nonoperative treatment. In statistical terms, those who had a hip effusion had an 8-fold increased risk of progression to surgery compared to those without a hip effusion. Meanwhile, the overall fracture-line percentage on the initial MRI turned out to be a poor metric for predicting progression.
Stabilization of a femoral neck stress fracture with percutaneous implants usually improves pain and predictably prevents displacement of the fracture and the attendant risk of nonunion and osteonecrosis of the femoral head. Further clinical research should help validate the seemingly reliable MRI-based predictor identified by these authors.
Marc Swiontkowski, MD
JBJS Editor-in-Chief
Getting to the Core of Bone Marrow Lesions
This post comes from Fred Nelson, MD, an orthopaedic surgeon in the Department of Orthopedics at Henry Ford Hospital and a clinical associate professor at Wayne State Medical School. Some of Dr. Nelson’s tips go out weekly to more than 3,000 members of the Orthopaedic Research Society (ORS), and all are distributed to more than 30 orthopaedic residency programs. Those not sent to the ORS are periodically reposted in OrthoBuzz with the permission of Dr. Nelson.
The terms “bone marrow edema,” “bone marrow lesion” (BML), and “bone bruise” are often used interchangeably to refer to areas in cancellous bone that have hyperintense marrow signal in fluid-sensitive, fat-suppressed MRI sequences. Although most commonly observed in knee MRIs, BMLs can be seen in a variety of joints. In the hip, they are seen in transient osteoporosis and rapid-onset osteoarthritis. The term “bone bruise” is often specifically applied in the setting of an injury, such as lateral tibial plateau hyperintense changes that are seen after an anterior cruciate ligament rupture.
In the setting of knee osteoarthritis, BMLs are a response to degeneration of menisci, articular cartilage, synovium, or bone itself. One of the mechanisms associated with BMLs seems to be secondary to circulatory response and bone turnover. In one study covered in a 2017 review article1, patients with OA and associated BMLs were randomized to receive the bone antiresorptive agent zoledronic acid (ZA) or placebo. At 6 months, VAS pain scores in the ZA group were reduced by ZA, the reduction in BML area was greater in the ZA group than in the placebo group, and a greater proportion in the ZA group achieved a clinically significant reduction in BML size (39% vs. 18%, p <0.044). A larger study is planned to further define the relationship between reduction in BML size and pain scores.
Regarding “crosstalk” between subchondral bone and articular cartilage in joint disease, recent data suggest that numerous canals and porosities connect the bone to cartilage at the interface. Treatment of the bone compartment with antiresorptives and anti-TGF-β at specific early time points has been shown to have chondroprotective effects in animal models. Additionally, one study identified s14-3-3ε, a short extracellular protein, as a mediator critical in the communication between subchondral bone and cartilage in OA. This may prove to be a potential target for therapeutic or prognostic use.
Numerous articles have outlined the abundance of trabecular microfractures seen in areas where BMLs are present. A commonly held hypothesis is that resorption cavities caused by bone remodeling can act as stress concentrations, promoting further microdamage and leading to a cycle of damage-remodeling-damage. Some individuals may be more prone to rapid bone turnover and thus more prone to developing bone edema.
When your clinical attention is directed to BMLs, their shape and extent may influence nonsurgical treatment decisions. Conservative management may be directed by a better understanding of how BMLs contribute to pain and OA progression.
Reference
- Alliston T, Hernandez CJ, Findlay DM, Felson DT, Kennedy OD. Bone marrow lesions in osteoarthritis: What lies beneath. J Orthop Res. 2017 Dec 21. doi: 10.1002/jor.23844. [Epub ahead of print] PMID: 29266428
JBJS 100: Lumbar MRI and Bunions
Under one name or another, The Journal of Bone & Joint Surgery has published quality orthopaedic content spanning three centuries. In 1919, our publication was called the Journal of Orthopaedic Surgery, and the first volume of that journal was Volume 1 of what we know today as JBJS.
Thus, the 24 issues we turn out in 2018 will constitute our 100th volume. To help celebrate this milestone, throughout the year we will be spotlighting 100 of the most influential JBJS articles on OrthoBuzz, making the original content openly accessible for a limited time.
Unlike the scientific rigor of Journal content, the selection of this list was not entirely scientific. About half we picked from “JBJS Classics,” which were chosen previously by current and past JBJS Editors-in-Chief and Deputy Editors. We also selected JBJS articles that have been cited more than 1,000 times in other publications, according to Google Scholar search results. Finally, we considered “activity” on the Web of Science and The Journal’s websites.
We hope you enjoy and benefit from reading these groundbreaking articles from JBJS, as we mark our 100th volume. Here are two more:
Abnormal Magnetic-Resonance Scans of the Lumbar Spine in Asymptomatic Subjects
S D Boden, D O Davis, T S Dina, N J Patronas, S W Wiesel: JBJS, 1990 March; 72 (3): 403
Many important subsequent studies were inspired by the findings of this landmark JBJS study. Most of them emphasize that for lumbar-spine diagnoses, an MRI is only one (albeit important) piece of data; that interpretation of MRI is variable; and that all imaging information must be correlated to the patient’s clinical condition.
A Conservative Operation for Bunions
E D McBride: JBJS, 1928 October; 10 (4): 735
Many other bunion procedures have been described since 1928, but the principle of restoring congruency of the first metatarsophalangeal joint remains very important in bunion operations. The most substantial modification of McBride’s procedure is that the lateral sesamoid is no longer typically excised.
Cord Compression Reflects Neurological Outcomes after Thoracolumbar Injuries
The association between spinal cord compression and functional deficits following cervical spine trauma has been well studied using both CT and MRI. However, until now, there was little data evaluating whether that same association is true for thoracic spine injuries. In the February 21, 2018 edition of The Journal, Skeers et al. identified the same correlations between canal compromise, cord compression, and functional outcome in the T1 to L1 region.
Using retrospective data, the authors showed that the severity of neurologic deficits was associated with the amount of maximal cord compression, as measured with advanced imaging. More specifically, their univariate analysis showed that cord compression >40% was associated with a tenfold greater likelihood of complete spinal cord injury compared to cord compression <40%. This study also found that MRI measures osseous canal compromise more accurately than CT, probably because it more clearly visualizes soft tissue changes related to the posterior longitudinal ligament, ligamentum flavum, and facet capsule.
A major issue with this study (and with almost all studies that evaluate spine trauma) is that these advanced imaging techniques are temporally static; even when they’re obtained relatively soon after injury, they cannot capture the position of vertebral body fragments and posterior structure deformities that existed upon impact. This shortcoming is probably more relevant for younger patients, who are more likely to experience higher-velocity trauma.
The population in the Skeers et al. study is skewed a bit toward older patients (mean age 34.8) with relatively severe spinal injuries (mean TLICS of 7.8 and mean cord compression of 40%). These factors may highlight the roles that lower bone density and decreased soft tissue elasticity play in the setting of high-energy spine trauma.
Although the data reflect some variability, this study should help spine surgeons counsel patients and their families following these tragic injuries. The more severe the initial cord compression in the thoracic spine, the more likely there is to be severe neurologic injury without improvement.
Marc Swiontkowski, MD
JBJS Editor-in-Chief
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