Fractures in children with myelomeningocele

Update on bone fragility in spina bifida

BACKGROUND CONTEXT

Patients with spina bifida (SB) are at risk for pathological fractures and low bone mineral density (BMD).

PURPOSE AND METHODS

This article reviews the literature and provides a comprehensive overview of how the characteristics of SB and its associated comorbidities intersect with bone fragility to identify possible pathophysiological mechanisms of fractures and low BMD.

RESULTS

Bone fragility occurs early in the life of patients with SB as a result of a disturbance that determines changes in bone shape, quantity, and quality, as poor mineralization reduces bone stiffness. Bone fragility in SB occurs due to local and systemic factors and may be considered a state of impaired bone quality of multifactorial aetiology, with complex interacting influences of neurological, metabolic, and endocrinological origins and the presence of smaller bones. Bone fragility should be evaluated globally according to skeletal age and Tanner staging. The phases of the evolution of Charcot joints seem to intercept the evolution of epiphyseal fractures. Charcot arthropathy in SB may be initiated by the occurrence of repetitive trauma and fractures in epiphyseal and subepiphyseal regions, where there is a deficit of bone mineralization and greater bone mass deficits.

CONCLUSION

Bone fragility in MMC potentially has a multifactorial neuro-endocrinological-metabolic-renal dimension, with smaller bones, lower bone mass, and mineralization deficits affecting bone strength.

Metabolic consequences after urinary diversion

Metabolic disturbances are well-known, but sometimes neglected immediate consequences or late sequelae following urinary diversion (UD) using bowel segments. Whereas subclinical disturbances appear to be quite common, clinically relevant metabolic complications, however, are rare. Exclusion of bowel segments for UD results in loss of absorptive surface for its physiological function. Previous studies demonstrated that at least some of the absorptive and secreting properties of the bowel are preserved when exposed to urine. For each bowel segment typical consequences and complications have been reported. The use of ileal and/or colonic segments may result in hyperchloremic metabolic acidosis, which can be prevented if prophylactic treatment with alkali supplementation is started early. The resection of ileal segments may be responsible for malabsorption of vitamin B12 and bile acids with subsequent neurological and hematological late sequelae as well as potential worsening of the patient's bowel habits. Hence, careful patient and procedure selection, meticulous long-term follow-up, and prophylactic treatment of subclinical acidosis is of paramount importance in the prevention of true metabolic complications.

Bladder augmentation and urinary diversion in patients with neurogenic bladder: non-surgical considerations

Segments from almost all parts of the bowel have been used for urinary diversion. As a result, the available absorptive surface area of the bowel is reduced, and the incorporation of bowel segments into the urinary tract may have metabolic consequences. This is an area somewhat neglected in the literature. Metabolic complications are rare, but sub-clinical metabolic disturbances are quite common. Several studies have demonstrated that some of the absorbent and secreting properties of the bowel tissue are preserved after incorporation into the urinary tract. Hyperchloraemic metabolic acidosis can occur if ileal and/or colon segments are used, as well as malabsorption of vitamin B(12) and bile acid after the use of ileal segments. These metabolic effects are not as severe as may be suspected and can be prevented by prophylactic substitution. Secondary malignancies can develop as a long-term consequence of bladder augmentation. Using colonic segments, tumours are most likely to occur at the ureteral implantation site. To prevent metabolic complications, careful patient selection and meticulous and lifelong follow up, as well as prophylactic treatment, are mandatory. Endoscopy for early detection has been recommended, starting 10 years postoperatively for patients who underwent surgery for a benign condition.

Osteoporosis in paediatric patients with spina bifida

The prevalence and morbidity associated with osteoporosis and fractures in patients with spina bifida (SB) highlight the importance of osteoporosis prevention and treatment in early childhood; however, the issue has received little attention. The method for the selection of appropriate patients for drug treatment has not been clarified.

OBJECTIVE

To review the literature concerning fracture risks and low bone density in paediatric patients with SB. We looked for studies describing state-of-the-art treatments and for prevention of secondary osteoporosis.

METHODS

Articles were identified through a search in the electronic database (PUBMED) supplemented with reviews of the reference lists of selected papers. The main outcome measures were incidence of fractures and risk factors for fracture, an association between bone mineral density (BMD) and occurrence of fracture, risk factors of low BMD, and effects of pharmacological and non-pharmacological treatments on BMD and on the incidence of fractures. We considered as a secondary outcome the occurrence of fractures in relation to the mechanism of injury.

RESULTS

Results indicated that patients with SB are at increased risk for fractures and low BMD. Risk factors that may predispose patients to fractures include higher levels of neurological involvement, non-ambulatory status, physical inactivity, hypercalciuria, higher body fat levels, contractures, and a previous spontaneous fracture. Limitations were observed in the number and quality of studies concerning osteoporosis prevention and treatment in paediatric patients with SB. The safety and efficiency of drugs to treat osteoporosis in adults have not been evaluated satisfactorily in children with SB.

Incidence, prevalence, and characteristics of fractures in children, adolescents, and adults with spina bifida

OBJECTIVE

To determine the age-specific incidence, prevalence, and characteristics of fractures in persons with spina bifida.

DESIGN

Year-long historical cross-sectional study.

SUBJECTS

Two hundred twenty-one consecutive patients aged 2-58 years evaluated in 2003 at a regional referral center. Twenty percent (n=44) were children age 2-10 years; 30% (n=68) were adolescents age 11-18 years; and 50% (n=109) were adults age 19-58 years. Fifty-five percent (n=121) were female; 64% (n=141) had shunted hydrocephalus. Fifty-eight percent (n=129) were community ambulators. Defect levels included 14% (n=31) thoracic; 37% (n=81) mid-lumbar; 35% (n=79) low-lumbar; and 14% (n = 30) sacral.

METHODS

Chart review of 221 consecutive children, adolescents, and adults enrolled in a spina bifida program in Syracuse, New York, was used to determine incidence and prevalence rates. Chi-square was used for subgroup analyses, and linear regression was used to examine independent association of motor level, functional independence (Functional Independence Measures score), body mass index (BMI), shunted hydrocephalus, epilepsy, and/or other congenital anomalies with fractures, controlling for insurance status, race/ethnicity, age, and sex.

RESULTS

Annual incidence of fractures among children, adolescents, and adults was 23/1000; 29/1000; and 18/1000, respectively. Overall prevalence was 200/1000. One in 4 patients with fractures reported multiple fractures. Median age at first fracture was 11 years. Most fractures involved the femur or tibia. Comparisons between adult- and childhood-onset fractures were not significant for difference in sex, BMI, defect level, functional independence, shunted hydrocephalus, epilepsy, or other congenital anomalies. In regression models only defect level RR = 1.646 (P = 0.019; 95% CI 1.085-2.498) and age RR = 1.033 (P= 0.036; 95% CI 1.002-1.065) were independently associated with fractures.

CONCLUSIONS

Fractures in persons with spina bifida are most common during early adolescence. Environmental modifications may be more effective than pharmacological treatment in reducing the prevalence of fractures in this population.

Whole-body potassium and bone mineral density up to 30 years after urinary diversion

OBJECTIVES

To evaluate the long-term effects of different types of urinary diversion on skeletal bone density and whole-body potassium content in patients with an early correction of base excess (< -2.5).

PATIENTS AND METHODS

The early correction of base excess (< -2.5) is one of the principles of the treatment of patients undergoing urinary diversion at our institution. In 27 patients with urinary diversion, bone mineral density (assessed by dual-photon absorptiometry), whole-body potassium, electrolyte and creatinine levels were determined, and capillary blood gas analysed. The mean time since surgery was 16.8 years in 16 patients with a rectal reservoir, 20.5 years in six patients with a colonic conduit, 7.8 years in four patients with an ileocaecal pouch and 5 years in one adolescent with an ileal bladder augmentation.

RESULTS

Bone mineral density was normal in 25 of the 27 patients; no exact measurement was possible in the remaining two. The whole-body potassium content was reduced in eight of the 27 patients (three with a conduit, two with a rectal reservoir, two with an ileocaecal pouch and one with ileal augmentation). In four of these eight patients the base excess was < -2.5 (-2.7 to -5). Of the other four, two had no regular testing of their base balance and two were obese. The electrolytes were within the normal ranges. None of the patients had hyperchloraemic metabolic acidosis.

CONCLUSION

With early correction of the base excess (< -2.5), there was no decrease in bone mineral density and no hyperchloraemic acidosis. There was no significant difference between the different types of urinary diversion. There seems to be a relationship between low base excess and decreased whole-body potassium.

Long-term metabolic effects of urinary diversion: a comparison of myelomeningocele patients managed by clean intermittent catheterization and urinary diversion

We previously reported that chronic urinary diversion through intestinal segments may have adverse effects on bone and mineral metabolism. This study examined the long-term health of patients managed by urinary diversion (94% by ileal conduit) for neuropathic bladders secondary to myelomeningocele defects and compared them to a control population of myelomeningocele patients managed by intermittent catheterization. Of the patients 93 were studied by personal interview, chart review, morphometric analysis, serum studies and dual-photon bone density determination. Average followup was 23 +/- 6 years in the urinary diversion group and 17 +/- 5 years in the intermittent catheterization group. Fractures occurred in 40% of the patients in both groups. Patients with a urinary diversion had an increased need for surgery to correct spinal curvature (57% versus 40%) and a significantly increased incidence of complications resulting from orthopedic procedures (17% versus 3%, p less than or equal to 0.05). There was also an adverse effect on renal function. The urinary diversion group had an increased incidence of radiographic renal deterioration (57% versus 8%, p less than 0.001), nephrolithiasis (43% versus 2%, p less than 0.001), pyelonephritis (60% versus 21%, p less than 0.001) and intermittent metabolic acidosis (20% versus 5%, p = 0.05). Surgery was required in 37% for stomal complications and in 17% for ureterointestinal stricture. Linear growth was adversely affected by urinary diversion. Patients with urinary diversion had decreased lengths for all morphometric parameters and a greater percentage of them were at or below the 10th percentile standards. Serum electrolytes, liver function studies, vitamin D3 and parahormone showed no differences in the 2 groups. No patient had a significant metabolic acidosis at the time of study. Bone densities were significantly diminished in both groups and not significantly different. This study strongly suggests that urinary diversion through intestinal segments is associated with adverse effects on bone health.