Deformity correction in children with hereditary hypophosphatemic rickets

Multi-segment osteotomy with interlocking intramedullary nail fixation in the treatment of lower limb deformity in older children with hypophosphatemic rickets

Objective

Malformations of the lower limbs caused by hypophosphatemic rickets in older children are mostly complex, occurring on multiple planes without a single apex and showing arcuate bending of the diaphysis combined with torsion deformity, and are difficult to correct. This study retrospectively investigated the effect of and indicators for multi-segment osteotomy with interlocking intramedullary nail fixation in the treatment of bony deformity caused by hypophosphatemic rickets.

Methods

The clinical data of 21 hypophosphatemic rickets patients seen between August 2007 and March 2022 were collected. The age range of the patients at the first surgery was 11 years and 1 month old to 15 years and 3 months old, with an average age of 12 years and 8 months. There were 6 males and 15 females. All patients had abnormal alignment of their lower limbs, with 32 limbs having varus deformity and 10 limbs having valgus deformity.

Results

A total of 67 surgeries were performed across the 21 patients, including 24 cases of femoral osteotomy with antegrade intramedullary nail fixation, 6 cases of femoral osteotomy with retrograde intramedullary nail fixation, and 20 cases of tibial osteotomy with interlocking intramedullary nail fixation. A total of 34 limbs eventually underwent interlocking intramedullary nail fixation, 9 with genu valgum and 25 with genu varus. All 21 patients were followed up for a period of 14∼96 months, with an average of 42.6 months. The ends of the osteotomies achieved bony union in 4-9 months (average 6.8 months), after which normal weight-bearing walking could be resumed. No infection, vascular or neurological complications, or nonunion occurred. During postoperative follow-up, the alignment the lower limbs passed through zone 1 in 13 limbs, zone 2 in 12 limbs, and zone 3 in 5 limbs. The overall rate of an excellent effect was 83.3%.

Conclusion

For lower limb deformity caused by hypophosphatemic rickets in older children, multi-segment osteotomy and strong fixation with interlocking intramedullary nails can achieve good correction outcomes.

Changes of the lower limb deformity in children with FGF23-related hypophosphatemic rickets treated with Burosumab: a single-center prospective study

Fibroblast growth factor 23 (FGF23)-related hypophosphatemic rickets (HPR) are characterized by excess circulating FGF23 and low concentrations of serum phosphorus, leading to skeletal manifestations of rickets, including lower limb deformities in children. The objective of this study was to prospectively evaluate whether treatment with burosumab, a monoclonal antibody neutralizing FGF23, changes lower limb deformities in HPR. Patients who were 15 years of age or younger with a documented clinical diagnosis of HPR, receiving burosumab treatment, and had a minimum follow-up period of one year were included in the study. Various radiological parameters were measured from anteroposterior and lateral radiographs of the bilateral lower limbs taken before administration of burosumab and at 3, 6, 9, and 12 months after treatment for evaluation of lower limb alignment. Outcome was classified as 'improvement', 'no change', or 'deterioration' after 12 months treatment. Five patients (10 limbs), with a mean age of 7.2 years were included in this study. The outcome was 'improvement' in six limbs and 'no change' in four limbs. There were no limbs of 'deterioration'. The improvement in deformities after treatment was more significant in younger patients who originally showed severe lower limb deformities. Older patients with milder deformities, on the other hand, showed less improvement. Burosumab therapy favorably changed lower-limb malalignment in children with FGF23-related HPR.

Predictive factors for recurrence after lower limb deformity correction in hypophosphatemic rickets

BACKGROUND

Surgical treatment for severe lower limb deformities in patients with hypophosphatemic rickets has shown satisfactory outcomes. However, the rates of recurrence of deformities after surgical correction were high, and studies on predictive factors of recurrence were limited. This study aimed to determine the predictive factors for the recurrence of lower limb deformities after surgical correction in patients with hypophosphatemic rickets, and the effects of each predictor on the recurrence of deformities.

METHODS

We retrospectively reviewed the medical records of 16 patients with hypophosphatemic rickets aged 5-20 years and who had undergone corrective osteotomies between January 2005 and March 2019. Demographic data from the patients, biochemical profiles, and radiographic parameters were collected. Univariable Cox proportional hazard analyses of recurrence were performed. Kaplan-Meier failure estimation curves for deformity recurrences of potential predictors were created.

RESULTS

A total of 38 bone segments were divided into 2 groups: 8 segments with recurrent deformities and 30 segments without recurrent. The average follow-up time was 5.5 ± 4.6 years. Univariable Cox proportional hazard analyses of recurrence found that an age < 10 years (hazard ratio [HR], 5.5; 95% CI, 1.1-27.1; p = 0.04), and gradual correction by hemiepiphysiodesis (HR, 7.0; 95% CI, 1.2-42.7; p = 0.03) were associated with recurrence after surgery. The Kaplan-Meier failure estimation for deformity recurrences by age at the time of surgery also achieved a statistically significant difference between ages < 10 years and those > 10 years (p = 0.02).

CONCLUSIONS

Identifying predictive factors for the recurrence of lower limb deformities after surgical correction in hypophosphatemic rickets can assist in early recognition, proper intervention, and prevention. We found that an age < 10 years at the time of surgery was associated with recurrence after deformity correction and gradual correction with hemiepiphysiodesis may also be a potential factor affecting the recurrence.

Single-Stage Tibial Osteotomy for Correction of Genu Varum Deformity in Children

Conservative and operative treatments with gradual or acute correction of severe varus deformities of the leg have been described. We evaluated whether the corrective osteotomy used within the NGO Mercy Ships is an effective treatment for genu varum deformity of different etiologies in children and which patient specific factors have an influence on the radiographic outcome. In total, 208 tibial valgisation osteotomies were performed in 124 patients between 2013 and 2017. The patients' mean age at the time of surgery was 8.4 (2.9 to 16.9 (min/max)) years. Seven radiographically measured angles were used to assess the deformity. Clinical photographs taken pre- and postoperatively were assessed. The mean time between the surgery and the end of physiotherapeutic treatment was 13.5 (7.3 to 28) weeks. Complications were monitored and classified according to the modified Clavien-Dindo-classification system. The mean preoperative mechanical tibiofemoral angle was 42.1° varus (range: 85°-12° varus). The mean postoperative mechanical tibiofemoral angle was 4.3° varus (range: 30° varus-13° valgus). The factors predicting a residual varus deformity were higher age, greater preoperative varus deformity and the diagnosis of Blount disease. The tibiofemoral angle measured on routine clinical photographs correlated well with the radiographic measurements. The single-stage tibial osteotomy described is a simple, safe and cost-effective technique to correct three-dimensional deformities of the tibia. Our study shows very good mean postoperative results, but with a higher variability than in other studies published. Nevertheless, considering the severity of preoperative deformities and the limited opportunities for aftercare, this method is excellent for the correction of varus deformities.

Hereditary Metabolic Bone Diseases: A Review of Pathogenesis, Diagnosis and Management

Hereditary metabolic bone diseases are characterized by genetic abnormalities in skeletal homeostasis and encompass one of the most diverse groups among rare diseases. In this review, we examine 25 selected hereditary metabolic bone diseases and recognized genetic variations of 78 genes that represent each of the three groups, including sclerosing bone disorders, disorders of defective bone mineralization and disorder of bone matrix and cartilage formation. We also review pathophysiology, manifestation and treatment for each disease. Advances in molecular genetics and basic sciences has led to accurate genetic diagnosis and novel effective therapeutic strategies for some diseases. For other diseases, the genetic basis and pathophysiology remain unclear. Further researches are therefore crucial to innovate ways to overcome diagnostic challenges and develop effective treatment options for these orphan diseases.

Complications and Treatments in Adult X-Linked Hypophosphatemia

X-linked hypophosphatemia (XLH) is a rare inherited disorder involving elevated levels of fibroblast growth factor (FGF) 23, and is caused by loss-of-function mutations in the PHEX gene. FGF23 induces renal phosphate wasting and suppresses the activation of vitamin D, resulting in defective bone mineralization and rachitic changes in the growth plate and osteomalacia. Conventional treatment with combinations of oral inorganic phosphate and active vitamin D analogs enhances bone calcification, but the efficacy of conventional treatment is insufficient for adult XLH patients to achieve an acceptable quality of life. Burosumab, a fully human monoclonal anti-FGF23 antibody, binds and inhibits FGF23, correcting hypophosphatemia and hypovitaminosis D. This review describes a typical adult with XLH and summarizes the results of clinical trials of burosumab in adults with XLH.

Orthopedic Complications and Management in Children with X-Linked Hypophosphatemia

X-linked hypophosphatemia is an inheritable disease of renal phosphate wasting that results in clinically manifestations associated with rickets or osteomalacia. The various symptoms in the skeletal system are well recognized, such as short stature; lower limb deformities; and bone, joint, or muscle pain, and it is often difficult to control these symptoms, despite the use of medication therapy in growing children. In addition, lower limb deformities can lead to degenerative osteoarthritis and dysfunction of lower limbs at the skeletal maturity. To prevent from future manifestation of those symptoms, orthopedic surgeries are applicable to growing patients with severe skeletal deformities or without response to conventional medication. Bone deformities are treated by acute or gradual corrective osteotomies and temporally hemiepiphysiodesis using guided growth method. The clinicians should choose the right procedure based on age, symptoms and state of deformities of the patient.

ONCOCYTIC ADRENOCORTICAL CARCINOMA IN A YOUNG PATIENT

Context

Adrenocortical carcinoma (ACC) is a rare neoplasm with an aggressive course and poor prognosis. The worldwide incidence is about 0.5 to 2 cases per million population per year. Oncocytic adrenocortical carcinoma is a rare histopathological variant of ACC with only a few reported cases in the literature.

Case report

We report a case of an oncocytic variant of adrenocortical carcinoma in a 21-year-old male patient who presented with a left adrenal mass. Imaging studies confirmed a large left adrenal mass with involvement of the left renal vein and inferior vena cava. Endocrine workup showed mildly elevated serum cortisol levels.

Discussion

Oncocytic AAC is a rare histopathological variant of ACC, as well as a rare subgroup of oncocytic adrenal neoplasms Hormonally active or functioning adrenocortical carcinomas most commonly secrete cortisol whereas co-secretion of multiple steroid hormones is a rare phenomenon.

Conclusions

Surgery remains the mainstay of treatment, but most of the patients present late with large masses and eventually become unsuitable for curative resection.

SLC34A3 GENE MUTATION AS A RARE CAUSE OF HYPOPHOSPHATEMIA IN TWO SIBLINGS

Context

Hereditary hypophosphatemic rickets with hypercalciuria (HHRH) is a rare autosomal recessive disorder, which is characterized by renal phosphate wasting, hypercalciuria, increased 1,25-dihydroxyvitamin D, and decreased parathormone (PTH) levels.

Objective

Here we report different clinical features of two siblings with HHRH, confirmed with molecular diagnosis.

Subjects and methods

16.4 years old boy (P1), and 8.7 years old girl (P2) were referred to our outpatient clinic due to clinical suspicion of metabolic bone diseases.

Results

P1 had severe hypophosphatemia. Additionally, PTH concentration was near to the lower limit, 1,25-dihydroxyvitamin-D concentration was near to the upper limit. P2 had relatively milder clinical and laboratory findings. Bilateral renal calculi were detected on ultrasound in both of them. HHRH was suspected due to their described biochemistry and the presence of bilateral renal calculi. Molecular analysis of SLC34A3 gene revealed a homozygous variant c.756G>A (p.Gln252=) and a splice donor variant c.1335+2T>A. After oral phosphate treatment, clinical and biochemical improvements were observed. However treatment nonadherence of patients was a barrier to reach treatment goal.

Conclusion

The clinical phenotype due to the same mutation in the SLC34A3 gene may vary even among the members of the same family. An accurate diagnosis is important for the appropriate treatment.

Burden of disease of X-linked hypophosphatemia in Japanese and Korean patients: a cross-sectional survey

The burden of disease of X-linked hypophosphatemia (XLH) in East Asia is poorly understood. This was a cross-sectional study using an online questionnaire to evaluate health-related quality of life (HRQOL) and disease complications in Japanese and Korean patients with XLH. Adults with XLH and the caregivers of children <18 years of age with XLH in Japan and Korea were surveyed. Respondents disclosed demographic data, family history, diagnostic history, medical history, surgical history, disease-specific clinical symptoms, treatment, medications, and use of ancillary equipment. Patient-reported outcomes (PROs; the Western Ontario and McMaster Universities Osteoarthritis Index, the brief pain inventory, and the 36-item short form health survey version 2) were used to assess pain, disability, and HRQOL in adults. Of those surveyed, all 14 children (100%) and 30/32 adults (93.8%) were receiving treatment for XLH. However, despite oral phosphate and active vitamin D use, short stature, gait abnormalities, dental conditions, and decreased physical function were reported. Stapling of the growth plates was reported in 14.3% of children but no adults. Adult patients reported high rates of bone pain (59.4%) and joint pain (65.6%). Caregivers of children with XLH also reported the occurrence of bone pain (35.7%) and joint pain (35.7%). Many adult patients had a history of impaired renal function (9.5%), nephrocalcinosis (15.6%), hyperparathyroidism (15.6%), and parathyroidectomy (6.3%), all of which are associated with conventional XLH treatments. These data show that patients (both pediatric and adult) continue to have symptoms such as pain, disability, and various complications despite receiving conventional therapies.

Rickets guidance: part II-management

Here, we discuss the management of different forms of rickets, including new therapeutic approaches based on recent guidelines. Management includes close monitoring of growth, the degree of leg bowing, bone pain, serum phosphate, calcium, alkaline phosphatase as a surrogate marker of osteoblast activity and thus degree of rickets, parathyroid hormone, 25-hydroxyvitamin D₃, and calciuria. An adequate calcium intake and normal 25-hydroxyvitamin D₃ levels should be assured in all patients. Children with calcipenic rickets require the supplementation or pharmacological treatment with native or active vitamin D depending on the underlying pathophysiology. Treatment of phosphopenic rickets depends on the underlying pathophysiology. Fibroblast-growth factor 23 (FGF23)-associated hypophosphatemic rickets was historically treated with frequent doses of oral phosphate salts in combination with active vitamin D, whereas tumor-induced osteomalacia (TIO) should primarily undergo tumor resection, if possible. Burosumab, a fully humanized FGF23-antibody, was recently approved for treatment of X-linked hypophosphatemia (XLH) and TIO and shown to be superior for treatment of XLH compared to conventional treatment. Forms of hypophosphatemic rickets independent of FGF23 due to genetic defects of renal tubular phosphate reabsorption are treated with oral phosphate only, since they are associated with excessive 1,25-dihydroxyvitamin D production. Finally, forms of hypophosphatemic rickets caused by Fanconi syndrome, such as nephropathic cystinosis and Dent disease require disease-specific treatment in addition to phosphate supplements and active vitamin D. Adjustment of medication should be done with consideration of treatment-associated side effects, including diarrhea, gastrointestinal discomfort, hypercalciuria, secondary hyperparathyroidism, and development of nephrocalcinosis or nephrolithiasis.

Clinical and genetic characteristics of 29 Chinese patients with X-linked hypophosphatemia

OBJECTIVE

The aim of this study was to fully describe the clinical and genetic characteristics, including clinical manifestations, intact fibroblast growth factor 23 (iFGF23) levels, and presence of PHEX gene mutations, of 22 and 7 patients with familial and sporadic X-linked dominant hypophosphatemia (XLH), respectively.

METHODS

Demographic data, clinical features, biochemical indicators, and imaging data of 29 patients were collected. All 22 exons and exon-intron boundaries of the PHEX gene were amplified by polymerase chain reaction (PCR) and directly sequenced. The serum level of iFGF23 was measured in 15 of the patients.

RESULTS

Twenty-nine patients (male/female: 13:16, juvenile/adult: 15:14) with XLH were included. The main symptoms were bowed lower extremities (89.7%), abnormal gait (89.7%), and short stature/growth retardation (78.6%). Hypophosphatemia with a high alkaline phosphatase level was the main biochemical feature and the median value of serum iFGF23 was 55.7 pg/ml (reference range: 16.1-42.2 pg/ml). Eight novel mutations in the PHEX gene were identified by Sanger sequencing, including two missense mutations (p. Gln682Leu and p. Phe312Ser), two deletions (c.350_356del and c.755_761del), one insertion (c.1985_1986insTGAC), and three splice mutations (c.1700+5G>C, c.1966-1G>T, and c.350-14_350-1del). Additionally, the recurrence rate after the first orthopedic surgery was 77.8% (7/9), and five of them had their first surgery before puberty.

CONCLUSION

Our study expanded the clinical phenotypes and gene mutation spectrum of XLH and provided a reference for the optimal timing of orthopedic surgeries.

Persistent Lower Limb Deformities Despite Amelioration of Rickets in X-Linked Hypophosphatemia (XLH) - A Prospective Observational Study

BACKGROUND

Gait deviations, lower limb pain and joint stiffness represent key symptoms in patients with X-linked hypophosphatemia (XLH, OMIM 307800), a rare disorder of mineral homeostasis. While the pathomechanism for rickets is well understood, the direct role of PHEX (Phosphate-regulating neutral endopeptidase) deficiency in non-rachitic features including complex deformities, skull and dental affections remains unclear. FGF23-inhibiting antibody treatment can normalize serum phosphate levels and to improve rickets in XLH patients. However, linear growth remains impaired and effects on lower limb deformity and gait are insufficiently studied.

AIMS

To characterize and evaluate the course of lower limb deformity in a case series of pediatric XLH patients receiving Burosumab therapy.

METHODS

Comparative assessment of planar radiographs, gait analysis, biochemical and clinical features of pediatric patients before and ≥12 months after initiation of FGF23-inhibiting was performed prospectively. Lower limb maltorsion was quantified by torsional MRI and gait analysis. Standardized deformity analysis of lower limb anteroposterior radiographs was conducted.

RESULTS

Seven patients (age 9.0 +/-3.6 years) were eligible for this study. All patients received conventional treatment before onset of antibody treatment. Maltorsion of the femur was observed in 8/14 legs using torsional MRI (mean antetorsion 8.79°). Maltorsion of the tibia was observed in 9/14 legs (mean external torsion 2.8°). Gait analysis confirmed MRI findings with femoral external malrotation prior to and one year after onset of Burosumab therapy. Internal foot progression (intoeing gait) remained pathological in all cases (mean 2.2°). Knee rotation was pathologically internal 10/14 legs. Mean mechanical axis deviation (MAD) of 16.1mm prior to Burosumab changed in average by 3.9mm. Three children underwent guided growth procedures within the observation period. Mild postprocedural rebound of frontal axis deviation was observed under Burosumab treatment in one patient.

CONCLUSIONS

This is the first study to investigate lower limb deformity parameters quantitatively in children with XLH receiving Burosumab. One year of Burosumab therapy was associated with persistent maltorsion and frontal axis deviation (varus/valgus) despite improved rickets in this small, prospective uncontrolled study.

Orthopedic and neurosurgical care of X-linked hypophosphatemia

X-linked hypophosphatemia (XLH) is due to mutations in the PHEX gene leading to unregulated production of FGF23 and uncontrollable hypophosphatemia. XLH is characterized in children by rickets, short stature, waddling gait, and leg bowing of variable morphology and severity. Phosphate supplements and oral vitamin D analogs partially or, in some cases, fully restore the limb straightness. XLH patients may also be affected by premature, complete, or partial ossification of sutures between cranial bone, which could eventually result in cranial dysmorphia, decreased intracranial volume, and secondary abnormally high intracranial pressure with a cerebral compression. Our goal is to address the criteria and the management of the skeletal complications associated with XLH, mainly orthopedic and neurosurgical care, and reflect on decision-making and follow-up complexities.

Lower Limb Deformity and Gait Deviations Among Adolescents and Adults With X-Linked Hypophosphatemia

BACKGROUND

X-linked hypophosphatemia (XLH) is a rare genetic disorder characterized by lower limb deformity, gait and joint problems, and pain. Hence, quality of life is substantially impaired. This study aimed to assess lower limb deformity, specific radiographic changes, and gait deviations among adolescents and adults with XLH.

DESIGN

Data on laboratory examination and gait analysis results were analyzed retrospectively. Deformities, osteoarthritis, pseudofractures, and enthesopathies on lower limb radiographs were investigated. Gait analysis findings were compared between the XLH group and the control group comprising healthy adults.

PATIENTS AND CONTROLS

Radiographic outcomes were assessed retrospectively in 43 patients with XLH (28 female, 15 male). Gait analysis data was available in 29 patients with confirmed XLH and compared to a healthy reference cohort (n=76).

RESULTS

Patients with XLH had a lower gait quality compared to healthy controls (Gait deviation index GDI 65.9% +/- 16.2). About 48.3% of the study population presented with a greater lateral trunk lean, commonly referred to as waddling gait. A higher BMI and mechanical axis deviation of the lower limbs were associated with lower gait scores and greater lateral trunk lean. Patients with radiologic signs of enthesopathies had a lower GDI.

CONCLUSIONS

This study showed for the first time that lower limb deformity, BMI, and typical features of XLH such as enthesopathies negatively affected gait quality among adolescents and adults with XLH.

Disease-specific gait deviations in pediatric patients with X-linked hypophosphatemia

BACKGROUND

X-linked hypophosphatemia (XLH) represents the most common genetic form of rickets featuring profound hypophosphatemia with associated skeletal and non-skeletal manifestations. Early onset gait disturbances contribute strongly to the burden of disease. However, no study has comprehensively characterized naturally occurring gait deviations in pediatric patients with XLH.

RESEARCH QUESTIONS

Can disease-specific gait deviations and potentially influencing factors be identified by gait analysis in non-surgically treated children with XLH?

METHODS

Gait laboratory assessments of 12 pediatric patients with XLH without previous long bone surgery was retrospectively analyzed and compared to age-matched healthy controls. Radiologic and clinical parameters of XLH patients were correlated with kinematic gait variables and gait scores.

RESULTS

Reduced external knee rotation and increased external hip orientation was ubiquitous in children with XLH. Increased lateral trunk lean, or "waddling gait", occurred in five children and was associated with varus knee deformities. Overall, children with XLH showed a reduced Gait Deviation Index (GDI) compared to controls. Radiologic and gait analysis revealed complex combined frontal and torsional deformity of the lower limbs as a common feature in XLH. Higher Body Mass Index (BMI) was associated with both lateral trunk lean and impaired GDI.

SIGNIFICANCE

Gait analysis is feasible to quantify gait deviations and lower limb deformities in pediatric patients with XLH. Specific gait characteristics including internal knee rotation and external hip rotation are common among patients with XLH and contribute to impaired gait scores. Our data suggest the use of gait and deformity data assessment as outcome parameters in future observational and interventional studies. Standardized assessment might contribute to targeted treatments to improve life quality in XLH patients.

Diagnosis and management of pediatric metabolic bone diseases associated with skeletal fragility

PURPOSE OF REVIEW

The goal of this review is to give an overview of diagnosis and up-to-date management of major pediatric metabolic bone diseases that are associated with bone fragility, including nutritional rickets, hypophosphatemic rickets, osteogenesis imperfecta, Ehlers--Danlos syndrome, Marfan's syndrome, hypophosphatasia, osteopetrosis and skeletal fluorosis.

RECENT FINDINGS

During the past decade, a number of advanced treatment options have been introduced and shown to be an effective treatment in many metabolic bone disorders, such as burosumab for hypophosphatemic rickets and asfotase alfa for hypophosphatasia. On the other hand, other disorders, such as nutritional rickets and skeletal fluorosis continue to be underrecognized in many regions of the world. Genetic disorders of collagen-elastin, such as osteogenesis imperfecta, Ehlers--Danlos syndrome and Marfan's syndrome are also associated with skeletal fragility, which can be misdiagnosed as caused by non-accidental trauma/child abuse.

SUMMARY

It is essential to provide early and accurate diagnosis and treatment for pediatric patients with metabolic bone disorders in order to maintain growth and development as well as prevent fractures and metabolic complications.

Rotational and translational osteotomy for treatment of severe deformity in hypophosphatemic rickets: A case report

RATIONALE

Hypophosphatemic rickets (HR) is a rare hereditary disease characterized by hypophosphatemia, defects in bone mineralization, and rickets, and surgical intervention is warranted for the patient of severe skeletal deformity.

PATIENT CONCERNS

Here we report a case of an 11-year-old boy who presented with severe varus deformities of the bilateral lower extremities and was associated with uncoordinated gait with multiple unintentional falls onto ground resulting in fractures of lower extremities.

DIAGNOSES

He was diagnosed as HR caused by genetic mutations in the phosphate-regulating endopeptidase homologue. Based on his family history and laboratory tests, including high serum alkaline phosphatase, high urinary phosphorus, hypophosphatemia, and normal serum calcium level, the patient was diagnosed with this disorder.

INTERVENTIONS

Rotational and translational osteotomy was performed to redress the severe varus deformity and readjust the malalignment of the lower extremity.

OUTCOMES

Right after the surgery, the alignment in the left lower extremity was readjusted, and his appearance seemed normal. Combined with rehabilitation and pharmacological intervention, including oral intake of phosphate and alphacalcidol, the bone healed uneventfully. After the second surgery of a similar procedure on the right femur, the patient was able to walk almost like a normal teenager.

LESSONS

This case proposed a novel technique to treat severe varus or valgus deformity of the lower extremity. HR is a rare disease, and it is important to stress its recognition to avoid delay of diagnosis and surgical intervention if necessary.

Detecting reasons for recurrent deformity in treatment of patients with vitamin D-resistant rickets using diagnostic imaging

PURPOSE

To assess age related manifestations of the femur and tibia in patients with vitamin D-resistant rickets (VDR) and explore causes for recurrent deformity using imaging modalities.

METHODS

Computed tomography (CT), magnetic resonance imaging (MRI) and dual energy X-ray densitometry (DEXA) were used to assess conditions of long bones of lower limbs in patients with vitamin D-resistant rickets aged from 4 years to 30 years preoperatively and after limb lengthening.

RESULTS

Age related MRI findings showed specific structure of the femur and tibia in patients with VDR preoperatively and after operative treatment. Abundant irregular osteoid formed in femoral and tibial physes was shown to reveal complicated nature of bone deformity causing recurrence in patients with VDR at childhood. CT findings allowed us to detect early cortical injury, measure its length with forming Looser's zones, examine significant differences in density measurements of Looser's zones preoperatively and after deformity correction using transosseous osteosynthesis.

CONCLUSION

Recurrent deformity can develop in patients with VDR due to progression of the disease, irregular osteoid deposited in the medial and lateral metaepiphysis, osteoid area measuring over 50% of epiphyseal cross section, insufficient regenerate mineralization, and formation of Looser's zones.

The Lifelong Impact of X-Linked Hypophosphatemia: Results From a Burden of Disease Survey

CONTEXT

X-linked hypophosphatemia (XLH) is characterized by excess fibroblast growth factor 23 (FGF23), hypophosphatemia, skeletal abnormalities, and growth impairment. We aimed to understand the burden of disease of XLH across the lifespan.

METHODS

Responses were collected from adults with XLH and parents/caregivers of a child with XLH in an online survey, including multiple-choice and open-ended questions on demographics, disease manifestations, treatment history, assistive device use, and age-specific patient-reported outcomes (PROs).

RESULTS

Data were collected from 232 adults with XLH (mean age, 45.6 years; 76% female) and 90 parents/caregivers of a child with XLH (mean age, 9.1 years; 56% female). Mean age recalled for symptom onset was 3.2 years for adults and 1.3 years for children. When surveyed, nearly all children (99%) and 64% of adults were receiving oral phosphate, active vitamin D, or both. Prior participation in a trial investigating burosumab, a fully human monoclonal antibody against FGF23, was reported in 3% of children and 10% of adults; of these respondents, only one child reported current treatment with burosumab at the time of the survey. Both children and adults reported typical features of XLH, including abnormal gait (84% and 86%, respectively), bowing of the tibia/fibula (72% and 77%), and short stature (80% and 86%). Nearly all adults (97%) and children (80%) reported bone or joint pain/stiffness. Adults reported a history of fractures (n/N = 102/232; 44%), with a mean (SD) age at first fracture of 26 (16) years. Adults reported osteophytes (46%), enthesopathy (27%), and spinal stenosis (19%). Mean scores for PROs evaluating pain, stiffness, and physical function were worse than population norms. Analgesics were taken at least once a week by 67% of adults.

CONCLUSIONS

Despite the common use of oral phosphate and active vitamin D established in the 1980s, children with XLH demonstrate a substantial disease burden, including pain and impaired physical functioning that persists, as demonstrated by similar responses reported in adults with XLH.

Clinical practice recommendations for the diagnosis and management of X-linked hypophosphataemia

X-linked hypophosphataemia (XLH) is the most common cause of inherited phosphate wasting and is associated with severe complications such as rickets, lower limb deformities, pain, poor mineralization of the teeth and disproportionate short stature in children as well as hyperparathyroidism, osteomalacia, enthesopathies, osteoarthritis and pseudofractures in adults. The characteristics and severity of XLH vary between patients. Because of its rarity, the diagnosis and specific treatment of XLH are frequently delayed, which has a detrimental effect on patient outcomes. In this Evidence-Based Guideline, we recommend that the diagnosis of XLH is based on signs of rickets and/or osteomalacia in association with hypophosphataemia and renal phosphate wasting in the absence of vitamin D or calcium deficiency. Whenever possible, the diagnosis should be confirmed by molecular genetic analysis or measurement of levels of fibroblast growth factor 23 (FGF23) before treatment. Owing to the multisystemic nature of the disease, patients should be seen regularly by multidisciplinary teams organized by a metabolic bone disease expert. In this article, we summarize the current evidence and provide recommendations on features of the disease, including new treatment modalities, to improve knowledge and provide guidance for diagnosis and multidisciplinary care.

Magnetic Resonance Imaging Features as Surrogate Markers of X-Linked Hypophosphatemic Rickets Activity

OBJECTIVE

X-linked hypophosphatemic rickets (XLH) is the most common form of inheritable rickets. Rickets treatment is monitored by assessing alkaline phosphatase (ALP) levels, clinical features, and radiographs. Our objectives were to describe the magnetic resonance imaging (MRI) features of XLH and to assess correlations with disease activity.

STUDY DESIGN

Twenty-seven XLH patients (median age 9.2 years) were included in this prospective single-center observational study. XLH activity was assessed using height, leg bowing, dental abscess history, and serum ALP levels. We looked for correlations between MRI features and markers of disease activity.

RESULTS

On MRI, the median maximum width of the physis was 5.6 mm (range 4.8-7.8; normal <1.5), being >1.5 mm in all of the patients. The appearance of the zone of provisional calcification was abnormal on 21 MRI images (78%), Harris lines were present on 24 (89%), and bone marrow signal abnormalities were present on 16 (59%). ALP levels correlated with the maximum physeal widening and with the transverse extent of the widening.

CONCLUSIONS

MRI of the knee provides precise rickets patterns that are correlated with ALP, an established biochemical marker of the disease, avoiding X-ray exposure and providing surrogate quantitative markers of disease activity.

Simultaneous bilateral correction of genu varum with Smart frame

PURPOSE

The aim of this study is to evaluate clinical and radiological results of simultaneous bilateral correction of genu varum with Smart frame.

METHODS

Between 2011 and 2015, a total of 25 patients (10 females, 15 males) who had bilateral genu varum deformity were operated bilaterally with tibial and fibular osteotomy in the same session, using Smart frame. The mean follow-up period was 28.7 (range, 13-45) months. All patients had bilateral tibial varus deformity. Femoral deformity was corrected in an earlier session in nine patients. Mechanical axis deviation (MAD), mechanical lateral distal femoral angle, mechanical medial proximal tibial angle (mMPTA) and posterior proximal tibial angle (PPTA) were measured preoperatively and postoperatively. Short Form-36 questionnaire was filled by the patients preoperatively and during the last follow-up.

RESULTS

The mean preoperative MAD was 37.6 mm (range, 9-98 mm), which improved to 8.4 mm (range, 3-44 mm) postoperatively ( p < 0.05). The mean preoperative mMPTA was 76°, which improved to 89° ( p < 0.05). The mean preoperative PPTA was 75.5°, which improved to 80.3 ( p < 0.05). Ten problems (20%), two obstacles (4%) and no sequelae occurred in 50 legs of 25 patients.

CONCLUSIONS

In conclusion, Smart frame is an accurate and reliable method for performing bilateral simultaneous deformity correction in patients with bilateral genu varum deformity. It can be applied for various childhood-induced severe tibial deformities such as achondroplasia, rickets, skeletal dysplasia and Blount's disease.

Outcomes of orthopedic surgery in a cohort of 49 patients with X-linked hypophosphatemic rickets (XLHR)

BACKGROUND

X-linked hypophosphatemic rickets (XLHR) is due to mutations in PHEX leading to unregulated production of FGF23 and hypophosphatemia. XLHR is characterized by leg bowing of variable severity. Phosphate supplements and oral vitamin analogs, partially or, in some cases, fully restore the limb straightness. Surgery is the alternative for severe or residual limb deformities.

OBJECTIVE

To retrospectively assess the results of surgical limb correction in XLHR (osteotomies and bone alignment except for 3 transient hemiepiphysiodesis).

METHODS

We analyzed the incidence of recurrence and post-surgical complications in 49 XLHR patients (29F, 20M) (mean age at diagnosis 6.0 years (± 7.1)).

RESULTS

At first surgery, the mean age was 13.4 years (± 5.0). Recurrence was observed in 14/49 (29%) patients. The number of additional operations significantly decreased with age (2.0 (± 0.9), 1.7 (± 1.0) and 1.2 (± 0.4) in children <11 years, between 11 and 15, and >15 years; P < 0.001). Incidence of recurrence seemed to be lower in patients with good metabolic control of the rickets (25% vs 33%). Complications were observed in 57% of patients.

CONCLUSION

We report a large series of surgical procedures in XLHR. Our results confirm that phosphate supplements and vitamin D analog therapy is the first line of treatment to correct leg bowing. Surgery before puberty is associated with a high risk of recurrence of the limb deformity. Such procedures should only be recommended, following multidisciplinary discussions, in patients with severe distortion leading to mechanical joint and ligament complications, or for residual deformities once growth plates have fused.

The orthopaedic management of lower limb deformity in hypophosphataemic rickets

BACKGROUND

Many patients with X-linked hypophosphataemic rickets (X-LHPR) demonstrate significant lower limb deformity despite optimal medical management. This study evaluates the use of guided growth by means of hemi-epiphysiodesis to address coronal plane deformity in the skeletally immature child.

METHODS

Since 2005, 24 patients with X-LHPR have been referred to our orthopaedic unit for evaluation. All patients had standardised long leg radiographs that were analysed sequentially before and after surgery if any was performed. The rate of correction of deformity was calculated based on peri-articular angles and diaphyseal deformity angles measured at regular intervals using Traumacad software. Clinical records were reviewed to obtain relevant clinical and demographic details. Statistical analysis was performed using SPSS 23 (SPSS Inc., Chicago, IL, USA).

RESULTS

The indication for surgical intervention was a mechanical axis progressing through Zone 2 or in Zone 3 despite one year of optimised medical treatment. The 15 patients underwent 16 episodes of guided growth (30 limbs, 38 segments) at a mean age of 10.3 years. In four limbs, surgery has only taken place recently; and in three limbs, correction is ongoing. Neutral mechanical axis was restored in 16/23 (70%) limbs: six improved and one limb (one segment) required osteotomy for residual deformity. The mean rate of angular correction per month was 0.3° for the proximal tibia and 0.7° for the distal femur. Patients with ≥ 3 years of growth remaining responded significantly better than older patients (p = 0.004). Guided growth was more successful in correcting valgus than varus deformity (p = 0.007). In younger patients, diaphyseal deformity corrected at a rate of 0.2° and 0.6° per month for the tibia and the femur, respectively. There has been one case of recurrent deformity. Patients with corrected coronal plane alignment did not complain of significant residual torsional malalignment. Serum phosphate and alkaline phosphatase levels did not affect response to surgery.

CONCLUSIONS

Guided growth is a successful, minimally invasive method of addressing coronal plane deformity in X-LHPR. If coronal plane deformity is corrected early in patients with good metabolic control, osteotomy can be avoided.

Computer Hexapod-Assisted Orthopaedic Surgery for the Correction of Tibial Deformities

We describe the intraoperative use of the Taylor Spatial Frame to correct complex multiplanar deformities of the tibia before definitive internal stabilization using minimally invasive techniques. Thirteen consecutive procedures were performed in 12 patients. All deformities of the tibia were assessed with standardized radiographs allowing estimation of the center of rotation of angulation (CORA) or multiple CORA for multiplanar deformities. The cause of the deformity included both posttraumatic and metabolic conditions. A wide range of deformities was deemed appropriate for correction with this technique. All underwent acute intraoperative correction through single or multiple osteotomies mediated by the Taylor Spatial Frame before definitive internal stabilization using a locked intramedullary nail. Deformity correction and restoration of the tibial mechanical axis was achieved in all cases. There were no cases of nonunion. There was only one superficial infection necessitating removal of implants following union of the osteotomies. Two patients developed a common peroneal nerve palsy, 1 had full recovery at 18 months and 1 had partial recovery. Another patient developed a tibial artery pseudoaneurysm treated successfully with a percutaneous stent. This series demonstrates the use of the Taylor Spatial Frame for acute intraoperative correction of complex tibial deformities and definitive internal stabilization.

Multiplanar Deformities Correction Using Taylor Spatial Frame in Skeletally Immature Patients

Background:

Taylor Spatial Frame (TSF) is a modern circular external fixator that, using a virtual hinge, is able to correct six axis deformities simultaneously. Despite the growing popularity of this method, few reports exist about its use in children and adolescents. To evaluate the effectiveness of TSF in correcting multiplanar deformities in patients with open physis, we reviewed the results of treatment in children who had at least two planes deformities of lower limbs.

Methods:

Over a period of 8 years, we treated 51 patients, 40 boys, 11 girls, with a mean age of 12.4 years (range, 2-16 years). All patients had open physis at the time of the TSF application. All patients had at least two deformities (angular and/or rotational). Fifty-five osteotomies (11 femoral, 44 tibial) were performed. Patients were divided into four groups: 13 with post-traumatic malunions, 18 with tibia vara, six with rickets, and 14 with miscellaneous deformities. Correction goal was determined as correction of deformities to population-average parameters of the lower limbs in frontal and sagittal views and normal mechanical axis deviation.

Results:

Correction goal was achieved in all except one patient; four patients had recurrence of deformities post-operatively and were re-operated. Most common complications were pin tract infection (20 patients), delayed union (2), regenerate translation (1), post-removal femoral fractures (2), knee subluxation (1), nonunion (1), and one patient developed chronic osteomyelitis secondary to deep pin tract infection.

Conclusion:

TSF allowed accurate correction of complex limb deformities in children and adolescents with relatively few serious complications.

Level of Evidence:

Level IV. Case series.

Description and evaluation of operative deformity correction in calcium-deficiency rickets in Kaduna, northern Nigeria

PURPOSE

Rickets is a recurrent disease worldwide, especially in countries with limited resources (Nield et al Am Fam Physician 74(4):619-626, 2006; Thacher et al Ann Trop Paediatr 26(1):1-16, 2006). Medical therapy including orally administered calcium substitution is shown to improve a patients clinical symptoms and positively impact bone deformities, especially in the lower extremity. Even though orthopaedic intervention is necessary in a significant percentage of patients, few reports exist about operative deformity correction in patients wtih rickets.

METHODS

We describe our concept of operative treatment by single-stage, three-dimensional closing-wedge osteotomies on 45 deformed legs in 27 patients from the rural area of Kaduna, North Nigeria, with calcium-deficiency rickets and evaluate the early results in a 1.5-year follow-up.

RESULTS

We found a significant improvement in parameters of quality of life, functionality, clinical and radiological angulation and angles following the definition of Paley et al., with a complication rate of 4 % under 88 osteotomies (Paley et al Orthop Clin North Am 25(3):425-65, 1994).

CONCLUSION

The described operative therapy shows to be sufficient and with satisfactory results in correcting rickets-related leg deformities under rural circumstances with low availability of medical resources.

Results of deformity correction in children with X-linked hereditary hypophosphatemic rickets by external fixation or combined technique

BACKGROUND

The operative procedures to correct multiplanar bone deformities may be indicated for prevention of secondary orthopaedic complications in children with X-linked hereditary hypophosphatemic rickets (XHPR). Different problems related to surgical correction were reported: increased rate of non-union, delayed union, recurrent deformity, deep intramedullary infection, refracture, nerve palsy, and pin tract infection. The aim of this retrospective study was comparison of results of correction in children with XHPR who underwent the treatment with either the Ilizarov device alone or a combined technique: the Ilizarov fixator with flexible intramedullary nailing (FIN) with hydroxyapatite bioactive coating and FIN.

MATERIAL AND METHODS

We retrospectively analysed 47 cases (children of age under 14 years) affected by XHPR. Simultaneous deformity correction in femur and tibia was performed with the Ilizarov device (group I) or the combined method (group II). This article is based on the results of a historical comparative retrospective study from the same institution.

RESULTS

The duration of external fixation is noted to be shorter applying the combined technique: 124.7 days (group I) vs 87.4 days (group II). In both groups deformity correction was achieved with a proper alignment. Nevertheless, while a child continues to grow during long-term follow-up, deviations of the mechanic axis from the centre of the knee joint have been developing again and values of mLDFA, mMPTA have become pathologic in the most of the cases. In group I location of a newly developed deformity resembled a pre-operative one, whereby both diaphyseal and metaphyseal parts were deformed. In group II in all the cases an apex of deformity was located in distal metadiaphyseal zone of the femur and proximal metadiaphyseal zone of the tibia. It is important to note that all of those in group II were out of the zone of the intramedullary nail.

CONCLUSION

Simultaneous correction of femoral and tibial deformities by means of circular external fixators is preferable. Application of a combined osteosynthesis allows to considerably reduce the duration of external fixation and decrease the number of complications. There were no recurrent deformities in parts of bone reinforced by intramedullary nails.

Contemporary Medical and Surgical Management of X-linked Hypophosphatemic Rickets

X-linked hypophosphatemia is an inheritable disorder of renal phosphate wasting that clinically manifests with rachitic bone pathology. X-linked hypophosphatemia is frequently misdiagnosed and mismanaged. Optimized medical therapy is the cornerstone of treatment. Even with ideal medical management, progressive bony deformity may develop in some children and adults. Medical treatment is paramount to the success of orthopaedic surgical procedures in both children and adults with X-linked hypophosphatemia. Successful correction of complex, multiapical bone deformities found in patients with X-linked hypophosphatemia is possible with careful surgical planning and exacting surgical technique. Multiple methods of deformity correction are used, including acute and gradual correction. Treatment of some pediatric bony deformity with guided growth techniques may be possible.

The significance of serum phosphate level on healing index and its relative effects in skeletally immature and mature patients with hypophosphatemic rickets

The aim of this study was to find out the ideal cut-off level of phosphate for safe healing when deformity correction and concomitant lengthening are indicated in the two different skeletal maturity groups of patients with rickets. Thirty-nine hypophosphatemic rickets patients were selected for the study and were divided into two groups: 27 skeletally immature (group IM) and 12 skeletally mature (group M). The outcomes were evaluated with respect to the healing index (HI), laboratory findings, and complications with the mean follow-up of 5.1 years (range, 3.1-7.9). The healing index (HI) of group IM was 1.44 month/cm and HI of group M was 1.68 month/cm. The negative correlation between the level of serum phosphate and HI in group M (coefficient=-0.94) was evaluated to be less than the correlation in group IM (coefficient=-0.50), indicating that the HI is more likely to be affected by serum phosphate in group M than in group IM. Preoperative serum phosphate levels of 2.3 mg/dL and 2.6 mg/dL were analyzed to be the cut-off values of group IM and group M, respectively, in which the cut-off points divided the series into two groups having the most significantly different HI.

Therapeutic management of hypophosphatemic rickets from infancy to adulthood

In children, hypophosphatemic rickets (HR) is revealed by delayed walking, waddling gait, leg bowing, enlarged cartilages, bone pain, craniostenosis, spontaneous dental abscesses, and growth failure. If undiagnosed during childhood, patients with hypophosphatemia present with bone and/or joint pain, fractures, mineralization defects such as osteomalacia, entesopathy, severe dental anomalies, hearing loss, and fatigue. Healing rickets is the initial endpoint of treatment in children. Therapy aims at counteracting consequences of FGF23 excess, i.e. oral phosphorus supplementation with multiple daily intakes to compensate for renal phosphate wasting and active vitamin D analogs (alfacalcidol or calcitriol) to counter the 1,25-diOH-vitamin D deficiency. Corrective surgeries for residual leg bowing at the end of growth are occasionally performed. In absence of consensus regarding indications of the treatment in adults, it is generally accepted that medical treatment should be reinitiated (or maintained) in symptomatic patients to reduce pain, which may be due to bone microfractures and/or osteomalacia. In addition to the conventional treatment, optimal care of symptomatic patients requires pharmacological and non-pharmacological management of pain and joint stiffness, through appropriated rehabilitation. Much attention should be given to the dental and periodontal manifestations of HR. Besides vitamin D analogs and phosphate supplements that improve tooth mineralization, rigorous oral hygiene, active endodontic treatment of root abscesses and preventive protection of teeth surfaces are recommended. Current outcomes of this therapy are still not optimal, and therapies targeting the pathophysiology of the disease, i.e. FGF23 excess, are desirable. In this review, medical, dental, surgical, and contributions of various expertises to the treatment of HR are described, with an effort to highlight the importance of coordinated care.

Successful Medical Therapy for Hypophosphatemic Rickets due to Mitochondrial Complex I Deficiency Induced de Toni-Debré-Fanconi Syndrome

Primary de Toni-Debré-Fanconi syndrome is a non-FGF23-mediated hypophosphatemic disorder due to a primary defect in renal proximal tubule cell function resulting in hyperphosphaturia, renal tubular acidosis, glycosuria, and generalized aminoaciduria. The orthopaedic sequela and response to treatment of this rare disorder are limited in the literature. Herein we report a long term followup of a 10-year-old female presenting at 1 year of age with rickets initially misdiagnosed as vitamin D deficiency rickets. She was referred to the metabolic bone and genetics clinics at 5 years of age with severe genu valgum deformities of 24 degrees and worsening rickets. She had polyuria, polydipsia, enuresis, and bone pain. Diagnosis of hypophosphatemic rickets due to de Toni-Debré-Fanconi syndrome was subsequently made. Respiratory chain enzyme analysis identified a complex I mitochondrial deficiency as the underlying cause. She was treated with phosphate (50-70 mg/kg/day), calcitriol (30 ng/kg/day), and sodium citrate with resolution of bone pain and normal growth. By 10 years of age, her genu valgus deformities were 4 degrees with healing of rickets. Her excellent orthopaedic outcome despite late proper medical therapy is likely due to the intrinsic renal tubular defect that is more responsive to combined alkali, phosphate, and calcitriol therapy.

Rickets

Rickets is disorder of a growing child arising from disorders that result in impaired apoptosis of hypertrophic cells and mineralization of the growth plate. Rickets due to nutritional causes remains an important global problem. The factors responsible for resurgence of rickets among dark-skinned infants living in developed countries include the following: residence in northern or southern latitudes, voluntary avoidance of exposure to solar ultraviolet B radiation, maternal vitamin D deficiency during pregnancy, and prolonged breastfeeding without provision of vitamin D supplements. Fibroblast growth factor 23 (FGF23), secreted by osteocytes, is an important regulator of serum phosphate and 1,25(OH)(2)D(3) levels. Hypophosphatemic rickets resulting from increased synthesis or under-catabolism of FGF23 is reviewed.

Evaluation of hypophosphatemia: lessons from patients with genetic disorders

Phosphate is a key component of several physiologic pathways, such as skeletal development, bone mineralization, membrane composition, nucleotide structure, maintenance of plasma pH, and cellular signaling. The kidneys have a key role in phosphate homeostasis, with 3 hormones having important roles in renal phosphate handling: parathyroid hormone, fibroblast growth factor 23 (FGF-23), and 1,25-dihydroxyvitamin D. Independent of the genetic diseases affecting the FGF-23 pathway (such as hypophosphatemic rickets), hypophosphatemia is a frequent condition encountered in daily practice, and untreated critical hypophosphatemia can induce hemolysis, rhabdomyolysis, respiratory failure, cardiac dysfunction, and neurologic impairment. Rapid correction thus is necessary to avoid severe complications. The aims of this teaching case are to summarize the causes and biological evaluation of hypophosphatemia and provide an overview of our current understanding of phosphate metabolism.

Combined technique for the correction of lower-limb deformities resulting from metabolic bone disease

We present the results of the surgical correction of lower-limb deformities caused by metabolic bone disease. Our series consisted of 17 patients with a diagnosis of hypophosphataemic rickets and two with renal osteodystrophy; their mean age was 25.6 years (14 to 57). In all, 43 lower-limb segments (27 femora and 16 tibiae) were osteotomised and the deformity corrected using a monolateral external fixator. The segment was then stabilised with locked intramedullary nailing. In addition, six femora in three patients were subsequently lengthened by distraction osteogenesis. The mean follow-up was 60 months (18 to 120). The frontal alignment parameters (the mechanical axis deviation, the lateral distal femoral angle and the medial proximal tibial angle) and the sagittal alignment parameters (the posterior distal femoral angle and the posterior proximal tibial angle) improved post-operatively. The external fixator was removed either at the end of surgery or at the end of the lengthening period, allowing for early mobilisation and weight-bearing. We encountered five problems and four obstacles in the programme of treatment. The use of intramedullary nails prevented recurrence of deformity and refracture.

Hip and knee arthroplasty in hypophosphatemic rickets

There is very limited published information about the technical aspects and durability of lower extremity arthroplasty in hypophosphatemic rickets. Between 1972 and 2006, 8 total hip arthroplasties (THAs) and 6 total knee arthroplasties (TKAs) were performed in 8 patients with degenerative arthritis and bone deformity secondary to hypophosphatemic rickets. Two hips required osteotomies at the time of arthroplasty, and 1 TKA patient required postoperative osteotomies. Specialized implants were required in 3 hips and 1 knee. At average follow-up of 7 years, mean Harris hip scores improved to 21 points, and mean Knee Society pain and function scores improved to 48 points and 27 points, respectively. One cemented THA failed due to femoral aseptic loosening at 13 years postoperatively; all other implants remained well fixed. Lower extremity arthroplasty is effective and durable for patients with arthritis associated with hypophosphatemic rickets, but corrective osteotomies and use of special implants should be anticipated with more severe deformities.