Identification of novel homozygous nonsense SLC10A7 variant causing short stature, amelogenesis imperfecta, and skeletal dysplasia with scoliosis and surgical management of spine.

BACKGROUND: Short stature, amelogenesis imperfecta, and skeletal dysplasia with scoliosis is a rare, autosomal recessive, skeletal disorder first described in 2018. This syndrome starts with pre- and postnatal developmental delay, and gradually presents with variable facial dysmorphisms, a short stature, amelogenesis imperfecta, and progressive skeletal dysplasia affecting the limbs, joints, hands, feet, and spine. CASE PRESENTATION: We identified a homozygous novel nonsense mutation in exon 1 of SLC10A7 (NM_001300842.2: c.100G > T / p.Gly34*) segregating with the typical disease phenotype in a Han Chinese family. We reviewed the 12-year surgical treatment history with seven interventions on spine. CONCLUSION: To date, only 12 cases of the SLC10A7 mutation have been reported, mainly from consanguineous families. Our patient showed a relatively severe and broad clinical phenotype compared with previously reported cases. In this patient, annual check-ups and timely surgeries led to a good outcome.

[Total Hip Arthroplasty in the Treatment of Dwarfism Complicated with Bilateral Hip Dysplasia:Report of One Case].

The clinical data of a female patient with dwarfism complicated with developmental dysplasia of the hip(DDH) treated in the Department of Joint Surgery of the First Affiliated Hospital of Hainan Medical College in September 2019 was analyzed.We summarized the experience in the treatment and reviewed the latest literature to determine the reasonable method for clinical diagnosis and treatment of dwarfism complicated with DDH.The improved lower limb function and satisfactory recovery of this patient after operation indicated that the treatment scheme was effective.Total hip arthroplasty is an effective method for the treatment of dwarfism complicated with DDH.Wagner prosthesis(SL-Cone)can achieve satisfactory short-term clinical results.

3D printed models can guide safe halo pin placement in patients with diastrophic dysplasia.

PURPOSE: To trial the use of three-dimensional (3D) printed skull models to guide safe pin placement in two patients with diastrophic dysplasia (DTD) requiring prolonged pre-fusion halo-gravity traction (HGT). METHODS: Two sisters aged 8 (ML) and 4 (BL) with DTD were planned for staged fusion for progressive kyphoscoliosis. Both sisters were admitted for pre-fusion HGT. Models of their skulls were generated from computer tomography (CT) scans using Mimics Innovation Suite and printed on a Guider II in polylactic acid. The 3D models were cut axially proximal to the skull equator, in-line where pins are usually inserted, allowing identification of the thickest skull portion to guide pin placement. RESULTS: Eight pins were inserted into each patient's skull. Postoperative CT scans demonstrated adequate pin position. Pre-traction Cobb angles were 122° and 128° for ML and BL, improving to 83° and 86° following traction. Duration of HGT was 182 and 238 days for ML and BL. Prior to fusion, both patients returned to theatre twice for exchange of loose pins and there was one incidence of pin site infection. Surgery was performed via a posterior instrumented fusion. Postoperatively, both patients remained in their halos for 3 months. One pin in BL was removed for loosening. Both patients achieved fusion union by 9 months. CONCLUSION: 3D models of the skull can be a useful tool to guide safe pin placement in patients with skeletal dysplasias, who require prolonged pre-fusion HGT for severe deformity correction.

Revision Arthroplasty with Total Femur Replacement for the Management of Complex Post-traumatic Bone Defect in a Patient with Dwarfism. / Revisionsendoprothetik mit Totalfemurendoprothese zur Behandlung komplexer posttraumatischer Knochendefekte bei einem Patienten mit Zwergwuchs.

Dwarfism leads to an early onset of osteoarthritis of the joints of the lower limb. Due to bone deformities, arthroplasty is challenging. The incidence of implant-associated complications is higher compared to the normal population and often ends up with multiple revision arthroplasties. We report the first case in the literature of a 48-year-old patient with dwarfism who required implantation of a custom-made total femoral replacement due to aseptic stem loosening and a concomitant valgus gonarthrosis.

Intracranial aneurysms in microcephalic primordial dwarfism: a systematic review.

BACKGROUND: Microcephalic primordial dwarfism (MPD) is a heterogeneous group of rare disorders. Recent studies have reported a significant percentage of patients with MPD suffering from a spectrum of cerebrovascular abnormalities, including intracranial aneurysms (IAs) and moyamoya syndrome. The neurological literature has not as yet specifically assessed IAs in this population. This systematic review aimed to assess the clinical behavior, characteristics, treatment modalities and outcomes of IAs in patients with MPD. METHODS: We performed a systematic search in PubMed, Ovid MEDLINE and Ovid EMBASE for cases of MPD with IAs. We included three illustrative cases from our institution. RESULTS: Twenty-four patients with 71 aneurysms were included in this study. Twelve patients (50%) presented with subarachnoid hemorrhage. The majority of patients were aged ≤18 years (70.8%), with a mean age of 16.2 years at presentation. Median aneurysm size was 3 (IQR 1.8-6) mm, and the most frequent locations were the internal carotid (37.3%) and middle cerebral arteries (23.8%). Concomitant moyamoya disease was reported in nine (37.5%) patients. Median age of aneurysm detection in screened patients was significantly lower than in non-screened patients (P=0.02). Microsurgical clipping (55.3%) and endovascular coiling (26.3%) were the most used modalities. Twenty-two cases were managed conservatively. Overall, mortality occurred in 45.8% of cases. CONCLUSIONS: Screening for cerebrovascular disease seems reasonable and effective to detect aneurysms at an earlier age in this population. Efforts in the literature to emphasize early and regular screening for these patients can positively impact outcomes in this population, however more evidence is needed.

Conventional cementless total hip arthroplasty in patients with dwarfism with height less than 140 cm and minimum 10-year follow up: A clinical study.

BACKGROUND: Orthopedic complications can cause issues and severe disability in patients with dwarfism. Thus, these individuals frequently undergo total hip arthroplasty to mitigate decline in daily functioning. Although studies have reported on the difficulties of orthopedic surgery in patients with dwarfism, many do not clearly define dwarfism and have a short follow-up period. We aimed to retrospectively investigate the clinical and radiographic results of total hip arthroplasty for patients with dwarfism. METHODS: A total of 68 hips of 49 patients with height <140 cm and at least 10-year follow-up periods were enrolled. All patients had conventional cementless implants. All hips were evaluated using the Japanese Orthopaedic Association hip score. RESULTS: The main hip disease etiologies were primary hip osteoarthritis (58%) and secondary osteoarthritis due to developmental dysplasia (31%). Rheumatoid arthritis, rapidly destructive coxarthrosis, spondyloepiphyseal dysplasia, childhood infection, and femoral head aseptic necrosis were also causative pathologies. Hip scores significantly improved from 44 to 82 out of 100. Overall implant-associated survival rate after 10 years was 94.1%. Cup loosening was observed in 2 hips, and subsidence >5 mm was observed in 9 hips. Presence of Crowe IV in hips was a significant risk factor for total hip arthroplasty in patients with dwarfism (p < 0.05); leg lengthening had a weak but significant correlation (r = 0.253, p < 0.05). CONCLUSIONS: Total hip arthroplasty using conventional cementless implants for patients with dwarfism shows good clinical and radiological outcomes and has a relatively low perioperative risk.

Posterior vertebral column resection for rigid proximal thoracic kyphoscoliosis with broken growing rods in a patient with Desbuquois dysplasia.

STUDY DESIGN: Case report. OBJECTIVE: To describe the importance of preoperative halo-gravity traction and posterior vertebral column resection (PVCR) for severe proximal thoracic kyphoscoliosis associated with Desbuquois dysplasia, after breakage of a growing rod construct. Desbuquois dysplasia is a rare, autosomal recessive chondrodysplasia characterized by short stature, joint laxity, kyphoscoliosis, and characteristic facial dysmorphism. Our 8-year-old patient developed severe, progressive, infantile-onset kyphoscoliosis and had been initially treated with Vertical Expandable Prosthetic Titanium Rib (VEPTR) rods. She subsequently underwent growing rod placement, but the eventual rod fracture resulted in a severe angular kyphosis. METHODS: Clinical and radiographic case review. RESULTS: The broken implants were removed, and she was treated with 2.5 months of preoperative halo-gravity traction. She then underwent a T4 PVCR and C7-L4 instrumented posterior spinal fusion. The patient had an uneventful postoperative course without any neurologic problems. Two years postoperatively, correction was well maintained with appropriate alignment and balance without implant breakage. CONCLUSION: To our knowledge, this is the first report of treatment of spinal deformity associated with Desbuquois dysplasia. Our results suggest that preoperative halo-gravity traction and PVCR are safe and efficacious techniques for severe rigid kyphoscoliosis in the cervicothoracic region associated with broken growing rods in a patient with Desbuquois dysplasia. LEVEL OF EVIDENCE: Level IV.

Otospondylomegaepiphyseal Dysplasia: A Case Report of Clinical and Radiographic Findings.

CASE: We present a long-term follow-up on a woman with otospondylomegaepiphyseal dysplasia (OSMED). At the age of 46 years, she is one of the oldest patients with the syndrome in the literature to date. We focus on the musculoskeletal anatomy and orthopaedic interventions over her lifetime. CONCLUSION: OSMED is a very rare syndrome. Arthritis and joint pains presented in her early adolescence and progressed to the point of requiring joint replacements by her 20s. Early intervention and monitoring improved the quality of life for this patient.

The Management of Kyphosis in Metatropic Dysplasia.

DESIGN: Retrospective review. OBJECTIVE: To describe the presentation and progression, and compare treatments of severe thoracic kyphosis in a cohort of patients with metatropic dysplasia. SUMMARY OF BACKGROUND DATA: Metatropic dysplasia is a rare skeletal dysplasia characterized by several abnormalities, including severe platyspondyly and vertebral wedging. These lead to marked kyphoscoliosis that begins in the first year of life and progresses to a stiff, short thorax and restrictive lung disease. There is no study that specifically addresses treatment of kyphosis in this cohort. METHODS: A 12-year retrospective chart review at a single institution was performed to identify metatropic dysplasia patients. Comparison between four main treatment groups-observation, bracing, anterior release and growing construct, and anterior release and final fusion-were made radiographically with regard to thoracolumbar, T2-T12, and major Cobb kyphosis; sagittal vertical alignment; and C7-kyphosis apex distance, taken at presentation, pre- and posttreatment, and final follow-up. RESULTS: Twenty patients with metatropic dysplasia presented at an average age of 3.1 years with a kyphosis of 75°, and were followed an average of 8.5 years. Those treated surgically presented with an average of 86.7° kyphosis, 88 mm C7-kyphosis apex distance, and 50 mm positive sagittal vertical alignment (SVA). Postsurgical reduction of kyphosis averaged 43° with less than 4° loss of correction in all groups except the constructs involving rib fixation. Recent use of staged thoracoscopic anterior soft tissue release, halo traction, and growing rod construct has produced the most dramatic results with average kyphosis correction of 71° and evidence of anterior bony remodeling. In those treated with observation, kyphosis progressed less than a quarter degree per year. CONCLUSIONS: Thoracic kyphosis in metatropic dysplasia does not uniformly progress in all patients and therefore can be initially observed. In those who progress, several surgical options exist including growth-friendly constructs that have demonstrated success without a higher rate of complications. LEVEL OF EVIDENCE: Level IV.

Midterm Survivorship and Complications of Total Knee Arthroplasty in Patients With Dwarfism.

BACKGROUND: Dwarfism is associated with skeletal dysplasias and joint deformities that frequently result in osteoarthritis requiring treatment with total knee arthroplasty (TKA). These surgeries can be challenging because of alignment deformities, poor bone stock, and smaller components. This study aims to compare TKA implant survivorship and complications between dwarf and nondwarf patients. METHODS: A retrospective case-control study was performed from 1997-2014 evaluating 115 TKAs in patients under the height threshold of 147.32 cm. This cohort was compared with 164 patients of normal height. Medical records were reviewed for demographics, surgical characteristics, and outcomes. All cases had 2-year minimum follow-up. RESULTS: The revision rate was 8.7% in dwarfs compared with 3.7% in controls (P = .08). The 2-, 5-, and 10-year implant survivorship in dwarfs was 96.4%, 92.5%, and 90.2%, respectively; and 96.6%, 95.6%, and 94.8% for controls, respectively (P = .24). Dwarfs underwent significantly more manipulations for arthrofibrosis (P = .002). There was greater femoral (17.4% vs 2.1%, P < .01) and tibial (6.5% vs 2.7%, P < .01) component overhang in dwarfs compared with controls. CONCLUSION: Despite a 2-fold increase in the revision rate of the dwarf cohort, the midterm survivorship is comparable between the dwarf and nondwarf patients. However, dwarfs were more likely to become stiff and undergo manipulation; the increased propensity for stiffness may be associated with oversized components, as evidenced by greater component overhang. Surgeons should be aware of this increased risk and may consider using smaller or customized implants to account for the morphological differences in this patient population.

Surgery of the head and neck in patient with Kniest dysplasia: Is wound healing an issue?

Kniest dysplasia is a type II collagen disorder that arises from a genetic mutation of the COL2A1 gene that results in short stature, midface anomalies, tracheomalacia, and hearing loss. Disruption of the normal collagen pathway can lead to many changes given its critical role in the body, and can cause complications with respect to wound healing. We present a case in which a patient with Kniest dysplasia successfully underwent multiple procedures in the head and neck region including cochlear implantation, mandibular distraction, palatoplasty, and laryngotracheal reconstruction. All procedures did not have any associated complications with respect to wound healing, indicating that surgery in this population can take place as indicated and surgery should not be contraindicated or delayed.

Surgical outcomes of Majewski osteodysplastic primordial dwarfism Type II with intracranial vascular anomalies.

OBJECTIVE Majewski osteodysplastic primordial dwarfism Type II (MOPD II) is a rare genetic disorder. Features of it include extremely small stature, severe microcephaly, and normal or near-normal intelligence. Previous studies have found that more than 50% of patients with MOPD II have intracranial vascular anomalies, but few successful surgical revascularization or aneurysm-clipping cases have been reported because of the diminutive arteries and narrow surgical corridors in these patients. Here, the authors report on a large series of patients with MOPD II who underwent surgery for an intracranial vascular anomaly. METHODS In conjunction with an approved prospective registry of patients with MOPD II, a prospectively collected institutional surgical database of children with MOPD II and intracranial vascular anomalies who underwent surgery was analyzed retrospectively to establish long-term outcomes. RESULTS Ten patients with MOPD II underwent surgery between 2005 and 2012; 5 patients had moyamoya disease (MMD), 2 had intracranial aneurysms, and 3 had both MMD and aneurysms. Patients presented with transient ischemic attack (TIA) (n = 2), ischemic stroke (n = 2), intraparenchymal hemorrhage from MMD (n = 1), and aneurysmal subarachnoid hemorrhage (n = 1), and 4 were diagnosed on screening. The mean age of the 8 patients with MMD, all of whom underwent extracranial-intracranial revascularization (14 indirect, 1 direct) was 9 years (range 1-17 years). The mean age of the 5 patients with aneurysms was 15.5 years (range 9-18 years). Two patients experienced postoperative complications (1 transient weakness after clipping, 1 femoral thrombosis that required surgical repair). During a mean follow-up of 5.9 years (range 3-10 years), 3 patients died (1 of subarachnoid hemorrhage, 1 of myocardial infarct, and 1 of respiratory failure), and 1 patient had continued TIAs. All of the surviving patients recovered to their neurological baseline. CONCLUSIONS Patients with MMD presented at a younger age than those in whom aneurysms were more prevalent. Microneurosurgery with either intracranial bypass or aneurysm clipping is extremely challenging but feasible at expert centers in patients with MOPD II, and good long-term outcomes are possible.

Anesthetic management for Cesarean delivery in parturients with a diagnosis of dwarfism.

PURPOSE: The literature on the anesthetic management of parturients with dwarfism is sparse and limited to isolated case reports. Pregnancy complications associated with dwarfism include an increased risk of respiratory compromise, an increased risk of Cesarean delivery, and an unpredictable degree of anesthesia with neuraxial techniques. Therefore, we conducted this retrospective review to evaluate the anesthetic management of parturients with a diagnosis of dwarfism. METHODS: We used a query of billing data to identify short statured women who underwent a Cesarean delivery during May 1, 2008 to May 1, 2013. We then hand searched the electronic medical record for qualifying patients with heights < 148 cm and a diagnosis of dwarfism. The extracted data included patient demographics and obstetric and anesthetic information. RESULTS: We identified 13 women with dwarfism who had 15 Cesarean deliveries in total. Twelve of the women had disproportionate dwarfism, and ten of the 15 Cesarean deliveries were due to cephalopelvic disproportion. Neuraxial anesthesia was attempted in 93% of deliveries. The dose chosen for initiation of neuraxial anesthesia was lower than the typical doses used in parturients of normal stature. Neuraxial anesthetic complications included difficult neuraxial placement (64%), high spinal (7%), inadequate surgical level (13%), and unrecognized intrathecal catheter (7%). CONCLUSIONS: The data collected suggest that females with a diagnosis of dwarfism may have difficult neuraxial placement and potentially require lower dosages of local anesthetic for both spinal and epidural anesthesia to achieve adequate surgical blockade.

Bone lengthening using the Fitbone(®) motorized intramedullary nail: The first experience in France.

INTRODUCTION: Intramedullary limb lengthening systems include mechanical systems (the Albizzia nail and the ISKD nail) as well as motorized systems with the Fitbone(®) (Wittenstein, Igersheim, Germany) and the Precice(®) (Ellipse Technologies, Irvine, CA, USA) nails. We hypothesized that limb lengthening using the Fitbone(®) nail was reliable, reproducible, and comfortable for the patient. PATIENTS AND METHODS: Between 2010 and 2013, a prospective single-center, single-operator (FA) study was conducted on patients who had undergone limb lengthening using the Fitbone(®) nail. The inclusion criteria were length discrepancy of the limbs equal to or greater than 25 mm or a short stature. The exclusion criteria were indications for cosmetic reasons and/or growth plates that were still open. The lengthening parameters were assessed postoperatively and at the last follow-up. Lengthening was considered achieved when the lengthening objective did not differ by more than 5 mm. All complications were noted. A statistical analysis was performed. RESULTS: Twenty-six Fitbone(®) nails were implanted in 23 patients, in the femur in 15 cases and the tibia in 11 cases. The patients' mean age was 22.5 years (range: 15-53 years) and the mean follow-up was 3.4 years (range: 2-5.3 years). The limb lengthening targeted was obtained in 23 cases (88%) and the mean lengthening was 45.3±18 mm (range: 20-80 mm). The mean time to healing was 277±167 days (range: 86-638 days). The mean healing index was 73±57 days/cm for the femurs and 83.5±65 days/cm for the tibias. The mean complication rate was 15.4%. DISCUSSION: This study emphasizes the good short-term results of this motorized intramedullary lengthening system. An evaluation over the longer term and with a higher number of patients remains necessary. LEVEL OF EVIDENCE: IV: uncontrolled, prospective, continuous study.

Visual Recovery and Endothelial Cell Survival After Descemet Stripping Automated Endothelial Keratoplasty for Failed Penetrating Keratoplasty Grafts­A Cohort Study.

PURPOSE: To assess visual recovery and donor cell survival after Descemet stripping automated endothelial keratoplasty (DSAEK) for the repair of failed penetrating keratoplasty (PK) grafts. METHODS: Best spectacle-corrected Snellen visual acuity results after DSAEK were compared with best-ever documented visual acuity (BDVA) results obtained with the previous PK graft in a prospective cohort study. Donor cell survival after DSAEK for PK repair was compared with cell survival after DSAEK for Fuchs endothelial dystrophy and pseudophakic bullous keratopathy. Differences in the logMAR best spectacle-corrected Snellen visual acuity and endothelial cell loss rates were calculated. RESULTS: Twenty-eight eyes with DSAEK for PK repair were identified, 21 of which lacked vision-limiting comorbidities. The mean follow-up was 18.4 ± 10.6 months. At 3 months postoperatively, 10/21 eyes (48%) regained their BDVA. By 24 months, only 14% remained with 0.2 logMAR below their BDVA. Endothelial cell counts decreased significantly faster in patients with DSAEK for failed PK (P = 0.024) or pseudophakic bullous keratopathy (P = 0.018) than in patients with DSAEK for Fuchs endothelial dystrophy. CONCLUSIONS: DSAEK for the restoration of failed PK grafts promotes rapid visual recovery within the visual limits of the previous PK graft. Increased endothelial cell loss is noted relative to other DSAEK indications, which may result in earlier endothelial graft failure in renovated PK.

Total knee arthroplasty in patients with skeletal dysplasia.

INTRODUCTION: Dwarfism is a challenge in arthroplasty. The anatomical features provide a lot of pitfalls. The aim of this study was to follow-up growth-restricted patients after endoprosthetic treatment. MATERIALS AND METHODS: 138 knee arthroplasties in patients with a height ≤150 cm between January 1, 2000 and May 5, 2013 at our institution were enrolled in this study. 124 cases were available for 1-year follow-up. Out of these, 43 cases were available for 5-year follow-up so far. 14 patients were lost to follow-up. RESULTS: IKS score increased from 35 ± 16 on admission to 67 ± 22 (p < 0.001) at 1-year follow-up and 65 ± 23 (p < 0.001) at 5-year follow-up. Function Score increased from 40 ± 29 on admission to 64 ± 21 (p < 0.001) at 1-year follow-up and 63 ± 23 (p < 0.001) at 5-year follow-up. Revision surgery was required in one case (0.8 %) after 1-year follow-up, and in an additional three cases (7 %) after 5-year follow-up. CONCLUSIONS: Knee arthroplasty can be performed in patients suffering from dwarfism with good clinical benefits. However, survival rates are worse compared to the general population.

Total Hip Arthroplasty in Patients with Skeletal Dysplasia.

127 patients with a height ≤ 150 cm (non metric ≤ 4 feet and 11 inches) who received hip arthroplasty surgery between July 1, 2006 and May 30, 2013 at our institution were enrolled. Retrospective data evaluation was performed for two different times of follow-up (1 year and 5 years respectively). 115 patients were evaluated for 1-year follow up. Out of these, 27 patients were available for 5-year follow up. The mean Harris Hip Score increased from 40 ± 13 on admission to 82 ± 20 (P<0.001) at 1-year follow-up and 79 ± 17 (P<0.001) at 5-year follow-up. Hip arthroplasty can be performed in patients with dwarfism with good clinical benefits. However, survival rates are worse compared to the general population.

Autologous fat graft as treatment of post short stature surgical correction scars.

INTRODUCTION: Surgical limb lengthening is undertaken to correct pathological short stature. Among the possible complications related to this procedure, painful and retractile scars are a cause for both functional and cosmetic concern. Our team has already shown the efficacy of autologous fat grafting in the treatment of scars with varying aetiology, so we decided to apply this technique to scars related to surgical correction of dwarfism. A prospective study was conducted to evaluate the efficacy of autologous fat grafting in the treatment of post-surgical scars in patients with short-limb dwarfism using durometer measurements and a modified patient and observer scar assessment scale (POSAS), to which was added a parameter to evaluate movement impairment. PATIENTS AND METHODS: Between January 2009 and September 2012, 36 children (28 female and 8 male) who presented retractile and painful post-surgical scars came to our unit and were treated with autologous fat grafting. Preoperative and postoperative mean durometer measurements were analysed using the analysis of variance (ANOVA) test and POSAS parameters were studied using the Wilcoxon rank sum test. RESULTS: There was a statistically significant reduction in all durometer measurements (p-value <0.05) and in all but one of the POSAS parameters (p-value <0.05) following treatment with autologous fat grafting. DISCUSSION: Surgical procedures to camouflage scars on lower limbs are not often used as a first approach and non-surgical treatments often lead to unsatisfactory results. In contrast, our autologous fat grafting technique in the treatment of post-surgical scars has been shown to be a valuable option in patients with short-limb dwarfism. CONCLUSION: There was a reduction of skin hardness and a clinical improvement of all POSAS parameters in all patients treated. Moreover, the newly introduced POSAS parameter appears to be reliable and we recommend that it is included to give a more complete evaluation of patient perception.

Early and late fracture following extensive limb lengthening in patients with achondroplasia and hypochondroplasia.

Two types of fracture, early and late, have been reported following limb lengthening in patients with achondroplasia (ACH) and hypochondroplasia (HCH). We reviewed 25 patients with these conditions who underwent 72 segmental limb lengthening procedures involving the femur and/or tibia, between 2003 and 2011. Gender, age at surgery, lengthened segment, body mass index, the shape of the callus, the amount and percentage of lengthening and the healing index were evaluated to determine predictive factors for the occurrence of early (within three weeks after removal of the fixation pins) and late fracture (> three weeks after removal of the pins). The Mann­Whitney U test and Pearson's chi-squared test for univariate analysis and stepwise regression model for multivariate analysis were used to identify the predictive factor for each fracture. Only one patient (two tibiae) was excluded from the analysis due to excessively slow formation of the regenerate, which required supplementary measures. A total of 24 patients with 70 limbs were included in the study. There were 11 early fractures in eight patients. The shape of the callus (lateral or central callus) was the only statistical variable related to the occurrence of early fracture in univariate and multivariate analyses. Late fracture was observed in six limbs and the mean time between removal of the fixation pins and fracture was 18.3 weeks (3.3 to 38.4). Lengthening of the tibia, larger healing index, and lateral or central callus were related to the occurrence of a late fracture in univariate analysis. A multivariate analysis demonstrated that the shape of the callus was the strongest predictor for late fracture (odds ratio: 19.3, 95% confidence interval: 2.91 to 128). Lateral or central callus had a significantly larger risk of fracture than fusiform, cylindrical, or concave callus. Radiological monitoring of the shape of the callus during distraction is important to prevent early and late fracture of lengthened limbs in patients with ACH or HCH. In patients with thin callus formation, some measures to stimulate bone formation should be considered as early as possible.