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Who Doesn’t Have a Screw Loose?

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.

Fracture fixation with a plate and screws has been around for a century—and so has the problem of screw loosening. Part of the cause of screw loosening seems to be toggling caused by radial forces arising from plate micromotion. Several decades ago, locked screws were designed to prevent loosening and provide better fixation, but screws still loosen.

Two tests can predict screw loosening associated with bone microfracture and absorption: axial pullout stress and toggling radial stress. Recent studies have investigated two hypotheses: radial stress is a predominant cause of screw loosening, and bone resorption is triggered by high radial stress.

Finite Element Analyses

A finite elemental model was used to replicate fixation of a tibial fracture with a 3-mm gap using either a dynamic compression plate (DCP) or locking compression plate (LCP).1 The model included contact with bone, tension on screw insertion, and the placement of two inner screws and one outer screw on either side of the fracture for an 8-hole plate. Axial loading, torsional loading, and bending were applied. Forces exceeding 55 megapascal (MPa) were considered adequate to cause microfracture, whether by radial or axial force. (For reference, 55 MPa is just about 8,000 pounds per square inch.)

The principal finding was that more bone was damaged by radial than by axial stress in both types of plates. Both plate types had more bone damaged by radial stress at the central two screws than at the two end screws for all bending models.

Radiographic Analyses

A separate study evaluated clinical radiographs of fixation for humeral, radial, ulnar, femoral, and tibial shaft fractures. Researchers looked for screw migration or bone absorption of  ≥1 mm around the screw. Both DCPs and LCPs were reviewed.

Researchers found that the outer screws loosened only after the inner screws loosened. There were 3 cases of bone loss with no loosening, 17 cases of bone loss with screw displacement, and no cases of screw loosening without bone loss. This strongly suggests that bone loss must occur for loosening to take place and that the earliest screw loosening occurs closer to the facture site.

Taken together, these results imply that the use of larger inner screws and/or the use of a different angle of fixation might reduce bone absorption that leads to loosening. In addition, radial stress testing might be more important than axial testing. Still, LCPs remain superior at resisting axial loading and bending moments, while DCPs remain superior at resisting torsional loading of unstable fractures.

Reference

  1. Feng X, Lin G, Fang CX, Lu WW, Chen B, Leung FKL. Bone resorption triggered by high radial stress: The mechanism of screw loosening in plate fixation of long bone fractures. J Orthop Res. 2019 Jul;37(7):1498-1507. doi: 10.1002/jor.24286. Epub 2019 Apr 8 PMID: 30908687

“It’s So Broken!”

Understanding the mechanism behind a bone fracture helps orthopaedic surgeons select the best approach to reduction and fixation. But patients who present emergently and in great pain are often not able to articulate exactly what happened. Furthermore, when the orthopaedic literature describes mechanisms of injury in words, such as “a high-energy abduction and external rotation of the ankle…,” it leaves a lot to the imagination.

The cell-phone video below had the unintended positive consequence of helping the orthopaedic surgeon understand how this ankle injury—a Weber Type C high fibula fracture, with a spiral pattern, a posterior butterfly, and a large posterior malleolus fracture involving 40% of the articular surface—came about.

The injury was treated using a posterolateral approach to the posterior malleolus. Lag screw fixation was followed by posterior plating of the Weber C level fibula fracture. The syndesmosis was found to be intact during intraoperative testing, and the patient is recovering well.

How Many X-Rays Does It Take to Treat a Distal Radial Fracture?

We orthopaedists obtain radiographs for many reasons—to diagnose an unknown problem, to determine the progress of healing, and occasionally because we follow X-ray “dogma” acquired over time. That last reason prompted van Gerven et al. to undertake a multicenter, prospective, randomized controlled trial, the findings of which appear in the August 7, 2019 issue of The Journal.

The authors set out to evaluate the clinical utility of radiographs taken after a distal radial fracture in >300 patients. Some of those fractures were treated nonoperatively, while others underwent operative fixation. Surgeons of the patients randomized to the “usual-care” pathway were instructed to obtain radiographs at 1, 2, 6, and 12 weeks following the injury/surgery. Surgeons of patients in the “reduced-imaging” arm did not obtain radiographs beyond 2 weeks after the injury/surgery unless there was a specific clinical reason for doing so.

The authors found no significant differences between groups in any of the 6 patient-reported outcomes measured in the study, including the DASH score. Furthermore, the complication rates were almost identical between the usual-care (11.4%) and reduced-imaging (11.3%) groups. Not surprisingly, patients in the reduced-imaging group had fewer radiographs obtained (median 3 vs 4) and were exposed to a lower overall dose of ionizing radiation than those in the usual-care group.

Probably because the study was conducted in the Netherlands, it did not address the widespread practice of “defensive medicine” in the US—the unnecessary overuse of medical tests and procedures to reduce the risk of a malpractice claim. While that may limit the external validity of these findings among orthopaedists in the United States, this relatively simple yet well-designed study should remind us that it is important to have a definite clinical purpose when ordering a test of any type. A picture may be worth a thousand words, but sometimes it takes only 2 pictures to tell the full story of a healing distal radial fracture.

Chad A. Krueger, MD
JBJS Deputy Editor for Social Media

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

What’s New in Orthopaedic Trauma 2019

Every month, JBJS publishes a review of the most pertinent and impactful studies published in the orthopaedic literature during the previous year in 13 subspecialties. Click here for a collection of all OrthoBuzz Specialty Update summaries.

This month, Chad A. Krueger, MD, JBJS Deputy Editor for Social Media, selected the five most clinically compelling findings from among the 25 noteworthy studies summarized in the July 3, 2019 What’s New in Orthopaedic Trauma” article.

Proximal Humeral Fractures in the Elderly
–A recent meta-analysis1 analyzing data from >1,700 patients older than 65 who experienced a proximal humeral fracture found no difference in Constant-Murley scores at 1 year between those treated operatively (most with ORIF using a locking plate) and those treated nonoperatively. There was also no between-group difference with respect to reoperation rates among a subgroup of patients from the 7 randomized trials examined in the meta-analysis.

Elbow Dislocation
–A study using MRI to evaluate soft-tissue injuries in 17 cases of “simple elbow dislocation”2 found that the most common soft-tissue injury was a complete tear of the anterior capsule (71% of cases), followed by complete medial collateral ligament (MCL) tears (59%) and lateral collateral ligament tears (53%). These findings challenge previous theories positing that elbow instability starts laterally, with the MCL being the last structure to be injured.

Pertrochanteric Hip Fractures
–A trial randomized 220 patients with a pertrochanteric fracture to receive either a short or long cephalomedullary nail.3 There were no significant differences between the 2 groups at 3 months postsurgery in terms of Harris hip and SF-36 scores, but patients treated with the short nail had significantly shorter operative times, less blood loss, and shorter hospital stays. The incidence of peri-implant fractures between the 2 devices was similar.

 Ankle Syndesmosis Injuries
–A randomized trial involving 97 patients with syndesmosis injuries compared functional and radiographic outcomes between those treated with a single syndesmotic screw and those treated with suture-button fixation. At 6 months, 1 year, and 2 years after surgery, patients in the suture-button group had better AOFAS scores than those in the screw group. CT scans at 2 years revealed a significantly higher tibiofibular distance among the screw group, an increase in malreduction that was noted only after screw removal. That finding could argue against early routine syndesmotic screw removal.

Infection Prevention
–A randomized trial among 470 patients4 facing elective removal of hardware used to treat a below-the-knee fracture compared the effect of intravenous cefazolin versus saline solution in preventing surgical site infections (SSIs). The SSI rate was surprisingly high in both groups (13.2% in the cefazolin group and 14.9% in the saline-solution group), with no statistically significant between-group differences. The authors recommend caution in interpreting these results, noting that there may have been SSI-diagnosis errors and that local factors not applicable to other settings or regions may have contributed to the high SSI rates.

References

  1. Beks RB, Ochen Y, Frima H, Smeeing DPJ, van der Meijden O, Timmers TK, van der Velde D, van Heijl M, Leenen LPH,Groenwold RHH, Houwert RM. Operative versus nonoperative treatment of proximal humeral fractures: a systematic review, meta-analysis, and comparison of observational studies and randomized controlled trials. J Shoulder Elbow Surg.2018 Aug;27(8):1526-34. Epub 2018 May 4.
  2. Luokkala T, Temperley D, Basu S, Karjalainen TV, Watts AC. Analysis of magnetic resonance imaging-confirmed soft tissue injury pattern in simple elbow dislocations. J Shoulder Elbow Surg.2019 Feb;28(2):341-8. Epub 2018 Nov 8.
  3. Shannon S, Yuan B, Cross W, Barlow J, Torchia M, Sems A. Short versus long cephalomedullary nailing of pertrochanteric hip fractures: a randomized prospective study. Read at the Annual Meeting of the Orthopaedic Trauma Association; 2018 Oct 17-20; Orlando, FL. Paper no. 68.
  4. Backes M, Dingemans SA, Dijkgraaf MGW, van den Berg HR, van Dijkman B, Hoogendoorn JM, Joosse P, Ritchie ED,Roerdink WH, Schots JPM, Sosef NL, Spijkerman IJB, Twigt BA, van der Veen AH, van Veen RN, Vermeulen J, Vos DI,Winkelhagen J, Goslings JC, Schepers T; WIFI Collaboration Group. Effect of antibiotic prophylaxis on surgical site infections following removal of orthopedic implants used for treatment of foot, ankle, and lower leg fractures: a randomized clinical trial. 2017 Dec 26;318(24):2438-45.

More Mortality Data on Hip Fractures in the Elderly

OrthoBuzz occasionally receives posts from guest bloggers. This guest post comes from Matthew Herring, MD, in response to a recent study in the Journal of Orthopaedic Trauma.

Among the elderly, low-energy hip fractures are common injuries that almost all orthopaedic surgeons encounter. While operative management is typically the standard of care, there are some patients for whom nonoperative treatment is most aligned with their goals of care, usually because of chronic disease, fragility, and/or high risk of perioperative mortality.

When counseling elderly patients and family members about the risks and benefits of surgical management for a hip fracture, we have abundant data. We can estimate the length of rehabilitation, discuss the likelihood of regaining independence with ambulation, and quote the 30-day, 1-year, and 5-year mortality statistics. But what about the risks and benefits of nonoperative care? How long do these patients live? How many are alive 1 year after the fracture?

Chlebeck and colleagues attempt to answer those questions with a retrospective cohort study of 77 hip fracture patients who were treated nonoperatively and a matched cohort of 154 operatively treated hip fracture patients. Nonoperative management was chosen only after a palliative-care consult was obtained and after a thorough multidisciplinary discussion of treatment goals with the patient and family. Patients who elected nonoperative care were treated with early limited weight bearing and a focus on maximizing comfort. Researchers established a comparative operative cohort through 2:1 matched pairing, controlling for age, sex, fracture type, Charlson Comorbidity Index, preinjury living situation, preinjury ambulatory status, and presence of dementia and cardiac arrhythmia.

As one might expect, there was significantly lower mortality in the operative group. The in-hospital, 30-day, and 1-year mortality for nonoperatively treated patients was 28.6%, 63.6%, and 84.4% respectively. The mortality rates seen in the operative cohort were 3.9%, 11.0%, and 36.4% respectively. A Kaplan-Meier survival analysis revealed the median life expectancy in the nonoperative cohort to be 14 days, versus 839 days in the operative group (p <0.0001). Interestingly, the researchers found no difference in hospital length of stay between the two groups (5.4 vs. 7.7 days; p=0.10).

These results provide useful references for orthopedic surgeons to use when counseling hip fracture patients and their families. Surgical intervention remains the standard of care in most instances, and this study suggests that operative care offers a significant mortality benefit over nonoperative care even in relatively unhealthy patients, like those selected for the matched operative cohort.

This study also gives us data to help guide the expectations of patients who decide surgery is not in line with their wishes. Half of the patients who elected nonoperative care in this study died within 14 days of admission, and only 15.6% were still alive at 1 year. Additionally, choosing nonoperative care does not lengthen hospitalization, suggesting that these patients can be quickly transferred to a more comfortable setting.

Matthew Herring, MD is a fellow in orthopaedic trauma at the University of California, San Francisco and a member of the JBJS Social Media Advisory Board.

New Minute-Commentary Video

See what JBJS Deputy Editor for Social Media Chad Krueger, MD thinks about the just-published Level-I trial comparing nonoperative treatment to volar locking plate fixation among 140 elderly patients with dorsally displaced distal radial fractures.

Pelvic Fracture Classification Will Benefit Elderly Patients

The orthopaedic community began to move away from individual fracture classifications in the mid-1980s. The basis for that shift was the need for wider recognition that fractures represent a “continuous variable,” with infinite varieties of orientations and combinations of fracture lines. Trying to fit fractures into a narrow classification system can lead to confusion and misinformation. Furthermore, surgeons often disagree when determining a fracture’s classification and, therefore, which treatment is best.

To move away from individual classification systems, orthopaedic journals have generally moved toward the compendium of fracture classifications approved by the OTA and AO. Still, there are times when a new fracture classification seems appropriate, and in the June 5, 2019 issue of The Journal, Pieroh et al. have provided us with an example that classifies fragility fractures of the pelvis (FFP). The 4-group FFP classification is based on fracture morphology with different degrees of instability and includes treatment recommendations.

The authors collected the CT scans of 60 patients from 6 different hospitals who were ≥60 years old and had sustained a pelvic fracture from low-energy trauma. These CT scans were shown to 6 experienced surgeons, 6 inexperienced surgeons, and 1 surgeon who had direct experience/training with the FFP system. Each surgeon was asked to classify the pelvic fractures according to the FFP classification. Inter- and intra-rater reliabilities for the fracture classifications were calculated from these readings, and the overall inter-rater Kappa coefficient was found to be 0.53, while the overall intra-rater Kappa coefficient was 0.46 (Kappa coefficients of 0.61 to 0.41 constitute “moderate” reliability). In terms of percent agreement, there was greater agreement between surgeons when it came to classifying FFP Group 1 fractures than for FFP Group 2 and 3 fractures. This is noteworthy because Group 3 fractures are thought to require surgical treatment, while primary treatment for Group 2 fractures is usually nonoperative.

Pelvic fractures that are associated with low bone density and low-energy trauma are becoming increasingly frequent as our population continues to skew older. Having a validated, relatively straightforward classification system like the FFP to assist us in managing these patients will be of great assistance. The sound methodology used to develop the FFP classification system and its decent reliability, face validity, and construct and criterion validity can assure all of us about the usefulness of the FFP classification as the basis for future clinical investigations and to advance the care of these patients.

Marc Swiontkowski, MD
JBJS Editor-in-Chief

Trauma in the Developing World: A Call to Action

Over the past decade and a half, the problem of musculoskeletal trauma has been identified as impacting more individuals in developing countries than HIV, drug-resistant tuberculosis, and other infectious diseases that are commonly recognized as public health crises. The need for access to surgical treatment for patients who sustain traumatic injuries has recently garnered more attention. Yet funding from nongovernmental organizations and other national/international foundations has not reached the levels necessary to appropriately address this important public health issue.

In the May 15, 2019 issue of The Journal, Agarwal-Harding et al. document the issue of patients experiencing delayed access to musculoskeletal trauma care in the sub-Saharan country of Malawi. Thanks to the development of a trauma-care registry serving both rural and urban health centers in Malawi, the authors were able to clarify the factors associated with delayed presentation for care.

Not surprisingly, those factors included distance from treatment centers and sustaining an injury during a weekend. These issues are likely widespread throughout Africa and in many other developing countries, where EMS services are sparse at best and treatment facilities are generally under-resourced. Although an increasing number of people in developing countries are being injured in road/vehicle-related accidents, many of the patients evaluated in this study did not experience high-energy trauma, but were instead injured from falls and during sporting activities. In short, they experienced the types of injuries that are likely to occur to everyday people doing everyday activities anywhere in the world.

The issue of delayed access to care is addressable if we continue to acknowledge the incredible public health burden that musculoskeletal trauma places on individuals and society within the developing world. These injuries not only affect patient quality of life, but they also have large impacts on families and communities due to a loss of income or disability-imposed restrictions on community engagement. Addressing this issue is of great interest to the readers of JBJS, who are volunteering to serve the orthopaedic needs of the developing world in ever-increasing numbers.

Marc Swiontkowski, MD
JBJS Editor-in-Chief

A Rash of Broken Femoral Nails—What’s Up?

I’ll be honest: I have never worried much about breakage of the cephalomedullary nails I implant for proximal femur fractures. Instead, I’m focused on the fracture reduction, soft-tissue handling, and proper implant positioning. These nails are very strong. Sure, failures of these implants may occur and have been reported. But I have never had a lengthy discussion with a patient about the potential risk of the implant breaking during normal activity—and I doubt many other surgeons have either.

That is why the article by Lambers et al. in the May 1, 2019 issue of The Journal grabbed my attention. The authors carefully analyzed 16 cases in which a specific cephalomedullary nail (the TFNA, made from a titanium-molybdenum alloy) broke in 13 patients after an average of 5 months. Of note, 3 patients who underwent a revision with the same type of nail had a repeat fracture of the implant. The majority of these patients had been treated for a reverse oblique intertrochanteric fracture —a type that we all commonly see and treat—and all the fractures had been well reduced at the time of nail insertion.

The implant fractures all occurred at the proximal aperture of the nail and were consistent with fatigue fracture of the alloy. But they all showed a unique “stepped propagation” pattern, whereby, according to the authors, “a planar crack arrested, changed planes by 90°, progressed, arrested, and then changed planes again by 90° until final failure.”

These types of implant failures are not common for this nail, but they apparently happen more often than I thought. I am certain that the manufacturer will be responding to this data, and I look forward to future design changes—especially because the authors hypothesize that prior changes to this nail’s design and/or alloy may have contributed to these breakages. Then again, there may have been errors in technique that made these types of failures more common, or maybe a different implant would have been a better choice for some of these patients. To me, matching fracture type and implant choice is very important.

I look forward to learning more about this issue and will keep these types of implant failures in the back of my mind during hip-fracture cases. In the meantime, Lambers et al. advise “vigilant clinical and radiographic surveillance of patients with unstable hip fracture patterns who undergo osteosynthesis with use of a TFNA implant.”

Chad A. Krueger, MD
JBJS Deputy Editor for Social Media