How Are Bicycle Helmets Designed to Prevent Head Injuries?

Patient Presentation
A pediatrician was bike riding with her teenage son when she hit a rock, lost balance, and fell off her bike onto concrete pavement landing on her back. Her head hit quite hard and there was a loud “cracking” sound heard. Surprising she was only hurt on her hip slightly but had no other pain and was conscious throughout the event. Her son helped her to take off her helmet as she was sitting to catch her breath and exclaimed, “Wow you really hit hard. Look at the crack in your helmet! That must have been that loud sound. Wow!” When they returned home, she noticed that the plastic shell covering on his helmet was also damaged and asked him about it. “Oh, I noticed that before but its just decoration so I didn’t think it was important,” he answered. She informed him that the plastic shell wasn’t just decoration and needed to be replaced if it was cracked too. Two new helmets were purchased and the damaged ones were placed in the garbage.

Yellow arrows indicates damage.
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Figure 123a – Exterior view of crack in bike helmet foam.

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Figure 123b – Close of view of crack in bike helmet foam.

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Figure 123c – Exterior view of crack in bike helmet foam.

Discussion
Protective helmets are used for multiple occupational and recreational activities. They are designed to protect the head from the common problems associated with the activity. For example, hard hats for construction workers are meant to protect against superior and lateral objects contacting the head as something can fall from above or a worker may contact an object as they are moving. The helmet had a plastic suspension ring that sits on the head providing space between the plastic helmet and the head allowing for the striking force to be dissipated over that distance before the helmet contacts the head. Helmets are designed for a specific purpose therefore are not appropriate for other activities. Information about various protective helmets can be found here.

Bicycle riding is a great physical activity for individuals, families and groups. It is also a great activity for people of any age and modified bicycles are available for many people with disabilities. However any activity involves some risks including bike riding. In 2015 in the US, 818 bicyclists died, an increase of 12.2%. An additional 45,000 were reported injured. For children < 14 years of age, 44 died and 5000 were injured. Many cyclists (27%) who died had been drinking and 37% of motor vehicle/cycle crashes involved either the driver or cyclist drinking. Fatalities and injuries occurred more often during darkness hours too.

The National Highway Transportation Safety Administration notes:

  • “Bicyclists are considered vehicle operators; they are required to obey the same rules of the road as other vehicle operators, including obeying traffic signs, signals, and lane markings. When cycling in the street, cyclists must ride in the same direction as traffic.” Bike riding can be a very good introduction for children to learn motor vehicle driving rules even at a young age.
  • “Bicyclists should increase their visibility to drivers by wearing fluorescent or brightly colored clothing during the day, and at dawn and dusk. To be noticed when riding at night, use a front light and a red reflector or flashing rear light, and use retro- reflective tape or markings on equipment or clothing.”
  • “All bicyclists should wear properly fitted bicycle helmets every time they ride. A helmet is the single most effective way to prevent head injury resulting from a bicycle crash.”

Bike helmets are important to protect the head from injury. They must be properly fitted to maintain their protective effect. Fitting should be checked before each ride and readjusted as necessary. The helmet should also be checked that there are no parts broken or missing before each ride. For more information about properly fitting bike helmets, see here and here. The “best” bicycle helmet depends on many factors which can be reviewed here.

Learning Point
Bike helmets are designed with 3 major components:

  • Foam interior – this is the most important part of the helmet. It is usually made of extruded polystyrene foam and designed to compress under the force and distribute the force over more of the head.
  • Plastic shell – this is designed to allow the head to slide or skid on the ground. Remember there are items on the ground which can catch on the helmet and cause rotational or torque to the head and neck. The shell also helps to keep the foam intact.
  • Straps and buckles – the helmet must be secured to the head and remain in place during a crash for full effect.

Remember if ANY part of the helmet is broken (this includes buckle parts) then the helmet needs to be replaced. Parents and children should inspect the helmet and adjust fittings before each ride. Also remember bike helmets are designed for biking – they are not designed for other activities and appropriate protective helmets and other protective gear designed for the activity should be used. Children should be taught that bike helmets are to be used when biking only and to be taken off when done. They should not continue to be worn when playing on playgrounds, climbing trees, etc. Children should be taught that a bike helmet goes on before the wheels move and taken off when the wheels stop.

Questions for Further Discussion
1. What other recreational activities require helmets for protection and how are they different from bike helmets?
2. How are car seats and bike helmets similar in design and use?

Related Cases

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Evidence-based medicine information on this topic can be found at SearchingPediatrics.com, the National Guideline Clearinghouse and the Cochrane Database of Systematic Reviews.

Information prescriptions for patients can be found at MedlinePlus for these topics: Sports Safety and Exercise and Physical Fitness.

To view current news articles on this topic check Google News.

To view images related to this topic check Google Images.

To view videos related to this topic check YouTube Videos.

National Highway Transportation Safety Administration. Traffic Safety Facts Bicyclists and Other Cyclists.
Available from the Internet at https://crashstats.nhtsa.dot.gov/Api/Public/ViewPublication/812382 (rev. March 2017, cited 7/24/18).

Bicycle Helmet Safety Institute. Helmets: How they Work, and What Standards Do.
Available from the Internet at https://helmets.org/general.htm (rev. 10/18/2017, cited 7/24/18).

Consumer Product Safety Commission. Bicycle Helmets Business Guidance
Available from the Internet at https://www.cpsc.gov/Business–Manufacturing/Business-Education/Business-Guidance/Bicycle-Helmets (cited 7/24/18).

Author
Donna M. D’Alessandro, MD
Professor of Pediatrics, University of Iowa

What is the Odds Ratio for Testicular Cancer after Cryptorchidism?

Patient Presentation
A 12-year-old male came to clinic for his health supervision visit. He was doing well in school, had recently started to play the trumpet and was active in baseball and basketball. He was looking forward to starting junior high school. He had not seen a physician for several years and in the past had seen other health care providers in the area, so no medical records were available other than immunization records that showed he was current. The past medical history was non-contributory.

The pertinent physical exam showed a happy male with normal vital signs and growth parameters in the 50-75%. His examination was normal except that no testis was palpable on the left side. The scrotum also looked very underdeveloped. He was Tanner I for public hair, testis and penis. The diagnosis of a healthy male with an undescended left testis was made. The mother was surprised and did not remember any health care provider mentioning any problems in the past. The boy just said that he thought everything was normal. The physician told the family that it was very important that he be evaluated and followed by an urologist. “It’s possible that everything was normal for several years and then the testis moved upward, or it is possible that it never moved into the scrotum as it should have. Either way there are risks for fertility and possibly cancer that need to be watched out for as he grows,” the pediatrician explained. “If it is okay with you, I want to get his medical records from when he was born and for the next few years afterward to see what was documented about his genitals. That is important for the urologist and how you might be treated,” she further explained.

Discussion
Cryptorchidism is the failure of one or both testes to descend from the abdomen into the scrotum.

Congenital undescended testis (UDT)is common in young infants (1-4% in term infants and 45% in preterm infants) in that the testes will be palpable but remain high, but most testes will descend by 3-6 months and by 9 months of age only 1% remain undescended. The scrotum often appears underdeveloped. Sometimes the testes cannot be identified and is intra-abdominal at birth. Intra-abdominal testes are less likely to migrate to the scrotum and therefore are more likely to remain undescended. Acquired undescended testis is thought to be caused by the spermatic cord not elongating at the same rate as the body (especially the pelvis). A common cause is a fibrous remnant of the processus vaginalis that does not elongate. The scrotum may be normal or underdeveloped. Retractile testes are testis that remain high in the scrotum and/or groin but can be brought down into the scrotum without difficulty.

Orchiopexy, where the testes is surgically placed into position within the scrotum, is recommended to be accomplished by around 1 year of age because of the increased risks of cosmetic problems, infertility and testicular malignancy.

Cosmetic problems are not uncommon. Boys and men who underwent orchiopexy as infants often will have a smaller testicle or for it to be aligned higher in the scrotum after puberty. Rates of testicular atrophy are about 3-4% and increase to ~14% with an intra-abdominal testis. If the atrophy is significant, a prosthesis may be an option.

Congenital cryptorchidism has a higher risk of infertility. Normal sperm count and motility remain relatively normal if orchiopexy is preformed in the first year of life. These decrease if treatment is after the first year. Patients with unilateral, acquired UDT may still have spontaneous descent by puberty (up to 50%) and therefore some people choose close monitoring. Bilateral acquired cryptorchidism seems to have a better fertility outcome if treated with orchiopexy at diagnosis.

Learning Point
Testicular cancer is one of the most common malignancies in young men peaking around age 30 years. Germ cell tumors are the most common type (95%). Cryptorchidism is associated with 5-10% of testicular cancers. Overall, “[f]or a boy with cryptorchidism, the relative risk of developing a subsequent testicular malignancy was 2.2 to 3.8 times higher than the background population….” However the younger the boy was at orchiopexy, the lower the risk. Odds ratios for boys at the time of surgery were: 0-9 years was 1.1, 10-14 years was 2.9, > 15 years was 3.5 and for adults with persistent cryptorchidism it was 14.4. Rates are lower for unilateral cryptorchidism (odds radio 2.9) than for bilateral disease (4.9).

Questions for Further Discussion
1. Name other risk factors for testicular cancer?
2. How is male infertility evaluated?
3. How is female infertility evaluated?

Related Cases

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Evidence-based medicine information on this topic can be found at SearchingPediatrics.com, the National Guideline Clearinghouse and the Cochrane Database of Systematic Reviews.
Information prescriptions for patients can be found at MedlinePlus for these topics: Testicular Disorders and Testicular Cancer

To view current news articles on this topic check Google News.

To view images related to this topic check Google Images.

To view videos related to this topic check YouTube Videos.

Thorup J, Cortes D. Long-Term Follow-Up after Treatment of Cryptorchidism. Eur J Pediatr Surg. 2016 Oct;26(5):427-431.

Moirano G, Zugna D, Grasso C, Mirabelli D, Lista P, Ciuffreda L, et.al. Postnatal risk factors for testicular cancer: The EPSAM case-control study.Int J Cancer. 2017 Nov 1;141(9):1803-1810.

Rohayem J, Luberto A, Nieschlag E, Zitzmann M, Kliesch S. Delayed treatment of undescended testes may promote hypogonadism and infertility. Endocrine. 2017 Mar;55(3):914-924.

Author
Donna M. D’Alessandro, MD
Professor of Pediatrics, University of Iowa

What is Hemiephysiodesis?

Patient Presentation
A new 14-year-old male came to clinic after moving to the area for concerns for increasingly being knock-kneeded. He and his parents had noticed it more over the past couple of years as he had become more active in school activities. He looked more awkward running and he had increased shoe wear. He occasionally would fall but parents didn’t think it was more often than others and always occurred with a physical activity. The past medical history showed mild intellectual disability without cerebral palsy or other co-morbidities. The family history was negative for musculoskeletal problems but there was a family history of mild intellectual disability on both sides of the family. The review of systems was negative.

The pertinent physical exam showed a healthy male with normal vital signs. His height was 161 cm (75%) and weight was 60.2 kg (95%). With standing and forward-bend test there was no scoliosis. With standing, the hips appeared to be symmetric in height. The distances between the ipsilateral iliac crest to lateral malleolus was the same bilaterally. The distances between the contralateral iliac crest and medial malleolus were also the same. With both patellas facing forward he stood with knees together and there was obvious genu valgum with the intramalleolar distance being 31.5 cm. There was no pain and full range of motion in his lower extremities. He had flexible pes planus bilaterally. Inspection of his shoe soles showed more wear on the medial surfaces bilaterally.

The diagnosis of genu valgum without an obvious cause including leg length discrepancy was made. The patient was referred to orthopaedics who offered the family the options of continued monitoring, hemiephysiodesis (i.e. guided growth) with tension plates or other hardware. They did not recommend osteotomy. The patient and family chose hemiephysiodesis with tension banding. At followup for his well child health supervision visit, he reported some minor pain initially after surgery which improved with physical therapy and was doing well currently. He had a followup surgery appointment in another 2 months.

Discussion
Angular deformities of the lower extremities are common problems and can be idiopathic, congenital or acquired. Idiopathic knee deformities are usually managed by monitoring and family reassurance as these often improve with time or are minimal and do not cause problems. Those ≤ 10 degrees are considered non-problematic. Genu varus usually peaks between 1-3 years and if problematic can cause waddling gait, lateral thrust and ligamentous laxity. Genus valgus usually peaks around 3-6 years and if problematic can cause circumduction gait, anterior knee pain and patellofemoral instability.

Treatment options are meant to improve alignment.

  • Osteotomy is usually considered the gold standard but has many potential complications including potential need for revision, immobilization, potential hospitalization, pain, increased recovery time, compartment syndrome and other risks of neurovascular complications.
    Many view it as a secondary or tertiary option for patients needing angular correction whose physis is still open.

  • Partial physeal ablation – this is a permanent technique and problems can include difficulty in performing the procedure, delay in bone bridge formation and it may not work adequately.
  • Blount’s stapling was introduced in 1949 using heavy staples/wires to fix the physis unilaterally but to guide the growth of the physis. The hardware can break or migrate and therefore may not be as helpful.

Learning Point
Hemiepiphysiodesis is also known as guided growth. This surgical technique temporarily fixes one side of the physis, thus allowing normal growth to be guided and the limb’s angular deformity corrected over time in skeletally immature patients. Partial physeal ablation and Blount’s stapling are types of hemiepiphysiodesis.

In 2007 Dr. Peter Stevens published a paper on the use of a new hemiepiphysiodesis system using a tension band plate (now known as eight-Plate®). The plate looks like a the number 8, and is attached extraperiostally across a physis by two screws. In varus deformities the plate is attached on the lateral side, and in valgus deformities it is attached on the medial side. Patients are then monitored and once correction is achieved, the plate is removed. Outcomes for a variety of conditions including idiopathic, Blount’s disease (i.e. genu vara), dysplasias, exostoses, etc. have been very good with fewer problems. Those with an incomplete treatment usually have some significant improvement of the problem. The system is being used in patients of different age ranges also. Correction is reportedly faster in idiopathic cases than in those that are congenital or acquired. Patients often after surgery are easily controlled with minimal pain medication, no crutch or minimal crutch use and a quick return to activities. A followup study did find that for patients who are older (adolescents), have more plates implanted, had femoral plates or had bilateral fixation, do have higher chances of needing more types of physical therapy and delayed return to activities. However, these delays are usually much less than required for other types of surgery particularly osteotomy.

A picture of the system from the company can be found here.

Questions for Further Discussion
1. How do you perform the physical examination for genu varus and valgus?
2. How common is Blount’s disease?
3. What are indications for referral to physical therapy?

Related Cases

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Evidence-based medicine information on this topic can be found at SearchingPediatrics.com, the National Guideline Clearinghouse and the Cochrane Database of Systematic Reviews.
Information prescriptions for patients can be found at MedlinePlus for this topic: Leg Injuries and Disorders

To view current news articles on this topic check Google News.

To view images related to this topic check Google Images.

To view videos related to this topic check YouTube Videos.

Stevens PM. Guided growth for angular correction: a preliminary series using a tension band plate. J Pediatr Orthop 2007; 27:253-259.

Boero S, Michelis MB, Riganti S. Use of the eight-Plate for angular correction of knee deformities due to idiopathic and pathologic physis: initiating treatment according to etiology. J Child Orthop. 2011 Jun;5(3):209-16.

Fillingham YA, Kroin E, Frank RM, Erickson B, Hellman M, Kogan M. Post-operative delay in return of function following guided growth tension plating and use of corrective physical therapy. J Child Orthop. 2014 May;8(3):265-71.

Heflin JA, Ford S, Stevens P. Guided growth for tibia vara (Blount’s disease). Medicine (Baltimore). 2016 Oct;95(41):e4951.

Welborn MC, Stevens P. Correction of Angular Deformities Due to Focal Fibrocartilaginous Dysplasia Using Guided Growth: A Preliminary Report. J Pediatr Orthop. 2017 Apr/May;37(3):e183-e187.

Author
Donna M. D’Alessandro, MD
Professor of Pediatrics, University of Iowa

What is the Blood Culture Recovery Rate After Antibiotic Pretreatment?

Patient Presentation
A pediatrician was listening to a news report on the radio discussing a government representative introducing legislation allowing emergency medical technicians to administer antibiotics to patients with suspected sepsis. The representative stated that this would allow sepsis patients to receive treatment earlier. While early antibiotic treatment is a great idea, the pediatrician began to think about several other potentially negative aspects of this policy such as decreased ability to identify the organisms due to antibiotic pretreatment, difficulty in making the diagnosis of sepsis initially and therefore patients would receive antibiotics that should not, increased antibiotic resistance, potential delay of transport to the hospital as the antibiotic is being given, decreased uptake of the antibiotic as it may need to be delivered by intramuscular than intravenous pathway, risk of allergic reactions, etc. He thought, “I wonder how much of a decrease there is in identifying the organism because of antibiotic pre-treatment?”

Discussion
Sepsis is an inflammatory response syndrome in the presence of an infection, it can be caused by bacteria, viruses or fungi. Bacteremia is the presence of bacteria in the blood. Studies from the US show an increased incidence of sepsis (0.56 to 0.89 cases/1000 children in all age groups) but a decreased fatality rate from 10.3% to 8.9%. The prevalence of severe sepsis in pediatric intensive care settings is reported in as many as 7.7% of admissions. Severe sepsis is more common when patients have co-morbities. Primary prevention includes immunization and appropriate precautions and procedures (i.e. catheter access) in hospitalized children or those with chronic medical needs. Prophylactic antibiotics for patients with neutropenia are also a secondary intervention.

Sepsis can be difficult to diagnose in any patient and particularly in children; symptoms can be non-specific or vague. One of the biggest problems with sepsis treatment is its recognition. Body temperature may be inappropriately low or high, inappropriate tachycardia or mental status changes and reduced peripheral perfusion are clinical features of sepsis. Hypotension may not occur initially but it can also be difficult to obtain a blood pressure on a child. Mainstays of treatment are early antibiotic administration and supportive measures especially fluid resuscitation. Vasopressor medications also can help support patients. Obtaining peripheral and central access can be difficult in pediatric patients and can hinder resuscitation and treatment of sepsis.

Learning Point
Recovery of bacterial organisms from the human body depends on many factors including the specific organism, antibiotic pretreatment, specimen adequacy especially blood volume, specimen site and detection methods.
If patients are given antibiotics, there are blood culture systems designed to bind the antibiotics and allow the bacteria to grow for identification. A 2007 study found a decrease in recovery of various bacteria with antibiotics relative to control bottles with no antibiotics, showing that the binder systems are not complete. The percentage of bacteria recovered depended on the specific organisms, the specific antibiotic and the blood culture system. Of note for pediatric patients, no system recovered Streptococcus pneumoniae in the presence of ceftriaxone which is one of the most common bacteria causing bacteremia, sepsis or invasive disease in this age group and very often ceftriaxone is the first choice of antibiotics.

In a 2017 multi-institutional, international study of bacteria detection in children with pneumonia, “Antibiotics were associated with a 45% reduction in blood culture yield and approximately 20% reduction in yield from induced sputum culture.” There were also reductions in bacteria identification from other body sites and by different detection methods including polymerase chain reaction. They also found that “For every additional 1 mL of blood culture specimen collected, microbial yield increased 0.51% …. from 2% when volume was ≤ 1 mL to approximately 6% for ≥ 3 mL.

In a 2016 study of blood culture yield relative to fever timing in children, they found that antibiotics before blood culture decreased the rate of positive blood cultures by almost 50% from 26.3% for no antibiotics to 12.7% with antibiotics (P <0.001). Additionally, they did not find a relationship to fever timing and blood sampling, noting "…timing of pediatric blood cultures relative to fever is unimportant. Bacteremia precedes a fever, but this is of limited clinical applicability."

A 2014, multi-center, U.S.-based study of timing of fever to blood culture positivity in young infants < 90 days old, found that the mean time from fever to blood culture positivity was 15.4 hours, and by 24, 36 and 48 hours, the blood culture had turned positive in 91%, 96% and 99% of babies. Only 6 babies had been pre-treated with antibiotics in this study, so pretreatment effects on blood culture results could not be assessed.

Questions for Further Discussion
1. What do you think about the potential public health policy of allowing emergency medical technicians to give antibiotics earlier? If so under what circumstances?
2. What antibiotics would be your first line treatment for neonates, young children or older children?
3. what are indications for placement of an intraosseous intravenous catheter or central line catheter?

Related Cases

    Age: Not appropriate

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Evidence-based medicine information on this topic can be found at SearchingPediatrics.com, the National Guideline Clearinghouse and the Cochrane Database of Systematic Reviews.

Information prescriptions for patients can be found at MedlinePlus for these topics: Sepsis and Bacterial Infections.

To view current news articles on this topic check Google News.

To view images related to this topic check Google Images.

To view videos related to this topic check YouTube Videos.

Flayhart D, Borek AP, Wakefield T, Dick J, Carroll KC. Comparison of BACTEC PLUS blood culture media to BacT/Alert FA blood culture media for detection of bacterial pathogens in samples containing therapeutic levels of antibiotics. J Clin Microbiol. 2007 Mar;45(3):816-21.

Riedel S, Bourbeau P, Swartz B, Brecher S, Carroll KC, Stamper PD, Dunne WM, McCardle T, Walk N, Fiebelkorn K, Sewell D, Richter SS, Beekmann S, Doern GV. Timing of specimen collection for blood cultures from febrile patients with bacteremia. J Clin Microbiol. 2008 Apr;46(4):1381-5.

Kee PP, Chinnappan M, Nair A, Yeak D, Chen A, Starr M, Daley AJ, Cheng AC, Burgner D. Diagnostic Yield of Timing Blood Culture Collection Relative to Fever. Pediatr Infect Dis J. 2016 Aug;35(8):846-50.

Biondi EA, Mischler M, Jerardi KE, Statile AM, French J, Evans R, Lee V, Chen C, Asche C, Ren J, Shah SS; Pediatric Research in Inpatient Settings (PRIS) Network.
Blood culture time to positivity in febrile infants with bacteremia. JAMA Pediatr. 2014 Sep;168(9):844-9.

Plunkett A, Tong J. Sepsis in children. BMJ. 2015 Jun 9;350:h3017.

Melendez E, Bachur R. Quality improvement in pediatric sepsis. Curr Opin Pediatr. 2015 Jun;27(3):298-302.

Driscoll AJ, Deloria Knoll M, Hammitt LL, Baggett HC, Brooks WA, Feikin DR, et.al. The Effect of Antibiotic Exposure and Specimen Volume on the Detection of Bacterial Pathogens in Children With Pneumonia. Clin Infect Dis. 2017 Jun 15;64(suppl_3):S368-S377.

Author
Donna M. D’Alessandro, MD
Professor of Pediatrics, University of Iowa