Tae-Joon Cho

Background: Children with neurological complex chronic conditions (NCCCs) frequently undergo hip reconstruction for hip displacement. Impaired airway clearance and respiratory muscle weakness may increase the risk of postoperative respiratory events. This study evaluated the incidence and predictors of postoperative respiratory events in this population. Methods: We retrospectively reviewed children with NCCCs who underwent hip reconstruction between 2015 and 2024. Baseline characteristics included age, sex, diagnosis, comorbidities, feeding method, ambulatory status, and respiratory support. Operative and anesthesia‐related variables included the number of osteotomies, operative duration and scheduling, estimated blood loss, airway device, and arterial blood gas measurements. The primary outcome was postoperative desaturation (SpO ₂ < 95%) requiring supplemental oxygen. Secondary outcomes included pulmonary complications and intensive care unit (ICU) utilization. Predictors were initially evaluated using an expanded multivariable logistic regression model, followed by a reduced model using Firth's penalized logistic regression. Results: Among 126 children (mean age, 7.7 ± 4.1 years), postoperative desaturation occurred in 30 (23.8%). Pulmonary complications included respiratory failure ( n = 6), atelectasis ( n = 5), pulmonary edema ( n = 3), and pneumonia ( n = 1). ICU care was required for 22 children (17.5%). Predictors of postoperative desaturation included congenital brain malformation (adjusted odds ratio [aOR], 21.76; 95% confidence interval [CI], 3.33–249.48), surgery performed on Friday (aOR, 3.35; 95% CI, 1.11–10.24), ≥ 3 osteotomies (aOR, 7.82; 95% CI, 1.83–36.36), and elevated intraoperative bicarbonate (HCO ₃ ⁻ > 26 mEq/L; aOR, 6.49; 95% CI, 2.36–19.14). Conclusion: Postoperative desaturation was common after hip reconstruction in children with NCCCs, with a subset developing pulmonary complications or requiring ICU care. Identification of perioperative risk factors may improve risk stratification and support targeted respiratory monitoring and preventive strategies in this high‐risk population. Level of Evidence: Level III, retrospective cohort study.

Enzyme replacement therapy (ERT) with elosulfase alfa is the only approved treatment for mucopolysaccharidosis type IVA. This case report delineates the 5‐year outcomes of ERT in two Korean siblings with mucopolysaccharidosis type IVA, with the younger sibling initiating treatment at 0.8 years of age and the older one at 5.4 years. Both patients exhibited a progressive decline in their height standard deviation scores, with trajectories paralleling the natural history curves of the disease. At 5.2 years of age, persistent skeletal dysplasia was evident in both siblings. However, the younger sibling demonstrated attenuated disease severity, lacking cervical myelopathy or spinal stenosis requiring C1 laminoplasty. Cardiorespiratory assessment revealed normalized left ventricular mass index z‐scores, stable ejection fractions, and the absence of valvular pathology. Overall, these findings suggest that early ERT attenuates severe spinal and upper body manifestations but does not prevent lower limb skeletal progression, highlighting the need for early therapeutic initiation along with orthopedic intervention to preserve cardiorespiratory parameters and functional independence.

Osteogenesis imperfecta (OI) is a heterogeneous group of genetic skeletal disorders characterized by bone fragility and low bone mass, manifesting as multiple fractures and deformities of the spine and extremities. Although genotype‐phenotype correlations have been studied in various populations, large‐scale data in Koreans have been lacking. This study is aimed at characterizing the clinical and genetic spectrum of nonlethal OI in the Korean population and explore genotype–phenotype associations. This retrospective cohort study analyzed 198 genetically confirmed Korean OI probands evaluated at a single center between 2004 and 2024, with clinical features reviewed and genetic testing performed using Sanger sequencing and targeted next‐generation sequencing. A total of 160 distinct pathogenic variants were identified, including 44 novel variants. Variant pathogenicity was assessed according to the ACMG/AMP variant classification guidelines. Pathogenic variants of COL1A1 and COL1A2 accounted for 87.4% of cases, with COL1A1 variants being the most prevalent (66.7%). Only 4.0% of cases had autosomal recessive OI. Glycine substitution (GS) variants were associated with significantly more severe phenotypes than other variants, including shorter height (median z‐score−3.67 [IQR −8.37 to −1.78] vs. −1.17 [−1.96 to −0.16], p < 0.001) and earlier fracture onset (1.00 [0.00–8.25] vs. 15.00 [7.00–24.75] months, p < 0.001). In COL1A1 , GS variants closer to the C‐terminus correlated with significantly more severe height reduction (Spearman ρ = −0.478, p = 0.005). The genotype–phenotype analysis confirmed the phenotypic severity of GS, particularly for variants closer to the C‐terminus of COL1A1 , consistent with previous studies. Additionally, the identification of 44 novel variants expands the variant spectrum of OI. These findings provide valuable insights into genetic diagnosis, prognostic assessment, and clinical management of OI.

Background: Spinal muscular atrophy (SMA) destroys spinal cord anterior horn cells, causing progressive muscle weakness and atrophy. Despite the introduction of disease-modifying therapies (DMTs), their effects on hip displacement remain unclear. This study investigated the development and progression of hip displacement in SMA, with emphasis on the impact of DMTs. Methods: Patients diagnosed with SMA between 2000 and 2022 who underwent hip surveillance ≥3 times at different ages were included. SMA classification, bilaterality, radiographic parameters, age at DMT initiation, and hip pain were analyzed. Hip displacement was classified by migration percentage. Study-defined early (SDE) DMT use was defined as treatment before 6 months in type 1 SMA or before 2 years in type 2 SMA. Results: Twenty-one patients (10 with type 1 and 11 with type 2 SMA) were included, with a mean follow-up of 31±6 months. In type 1 SMA, 90% of patients developed hip displacement (2 with subluxation and 7 with dislocation), occurring at mean ages of 22.0±7.0 months and 33.0±7.8 months, respectively. In type 2 SMA, 72% of patients developed hip displacement (7 with subluxation and 1 with dislocation), occurring at mean ages of 37.8±16.2 months and 32 months, respectively. SMA classification ( P =0.016), bilaterality ( P P =0.006), and final acetabular index ( P =0.002) were associated with final hip displacement. SDE DMT use was not statistically significant ( P =0.163); however, one type 1 SMA patient who initiated DMT at 1 month maintained a contained hip throughout follow-up. Hip pain was absent in contained or subluxated hips but occurred in 75% of dislocated hips. Conclusions: Hip displacement in SMA begins early, with progression patterns differing by disease severity. Hip displacement is also associated with pain, which was observed primarily in dislocated hips. These findings highlight the need for routine hip surveillance from early infancy and pain assessment. DMT initiation may confer only minimal benefit when instituted at a later age, but may yield more substantial benefit when administered presymptomatically soon after birth. Level of Evidence: Level III.

Background: Physeal-sparing procedures are preferred for treating early-onset slipped capital femoral epiphysis (SCFE), reducing limb-length discrepancy (LLD), and femoroacetabular impingement (FAI). This study aimed to investigate the treatment outcomes after physeal-sparing procedures for early-onset SCFE. Methods: We reviewed medical and radiographic records of SCFE patients from 1992 to 2022. Patients under 11 years old and followed up to skeletal maturity were included. Physeal-sparing procedures using a long screw with a short-threaded tip were performed in patients with mild to moderate slips since 2008. Patients were dichotomized into physeal-sparing and traditional in situ fixation (ISF) groups. Radiographic and clinical outcomes were comparatively analyzed between the groups. Results: Fifteen patients underwent physeal-sparing procedures, whereas 12 patients underwent traditional ISF. There was no further slippage in either group. During follow-up, slip angle was significantly decreased in the physeal-sparing group compared with the traditional ISF group (22.0 vs. 8.8 deg, respectively, P20 mm did not occur in the physeal-sparing group, but was observed in the traditional ISF group (PP=0.08, P=0.25, P=0.14, P=0.13), but differences were seen in healthy versus traditional ISF sides (PPPP<0.01, respectively). In addition, consistent growth was observed in the physeal-sparing side, but premature physeal arrest developed in the traditional ISF side. Six physeal-sparing patients required screw change procedures as the proximal femur outgrew the screw. The physeal-sparing group scored higher modified Harris Hip Score points than the traditional ISF group (89.5 vs. 85.3, respectively). Conclusions: Using a long screw with a short-threaded tip can stabilize the proximal femoral physis. It may also allow the continual growth and remodeling of the proximal femur in the treatment of early-onset SCFE. Level of Evidence: Level III.

Background: An intramedullary rodding is the preferred fixation method in limb stabilization of OI patients. However, the intramedullary rod may not provide adequate fixation and rotational stability, especially in adolescents and adults. The incorporation of adjunctive plate fixation alongside intramedullary rodding has been introduced to enhance this stability, although its complications remain insufficiently understood. The goal of this study was to explore the outcomes of adjunctive plating in conjunction with intramedullary rodding for limb stabilization in OI patients, emphasizing the complications related to the plates during the healing phase and following plate removal. Methods: This retrospective study examined 74 limb segments from 45 patients with OI who underwent intramedullary rodding and adjunctive plating from 2008 to 2022. Criteria for inclusion comprised surgical treatment followed by a minimum of 2 years of follow-up or complication before that time point. The need for adjunctive plating arose from inadequate fixation, rotational instability, and persistent cortical gaps with intramedullary rodding alone. Medical records and follow-up radiographs were reviewed to assess the healing of the target lesion and any complications. Results: The study encompassed 30 males and 15 females, ranging in age from 4 to 38 years, with 51 femoral and 23 tibial segments receiving treatment. Union was successfully achieved in 63 cases (85.3%), with an average union time of 14.4 months. Plates were subsequently removed in 62 cases after an average duration of 18.0 months. Before union, 11 revision surgeries were performed in 4 peri-implant fractures, 1 screw pull-out, and 6 failure of union. One sustained peri-implant fracture after the union. Following the removal of plates, complications included 10 refractures at screw sites, 3 progressive angulations at the previously targeted lesions, and 1 osteomyelitis. Kaplan-Meier analysis revealed that half of the refractures occurred within 1.8 years postplate removal. The overall complication showed borderline significance (P=0.056) among age groups. All the plate-related complications occurred at the diaphyseal, unicortical screws. Conclusions: Plate fixation, when used as an adjunct to intramedullary rodding, effectively stabilizes limbs in OI patients when intramedullary rods alone are inadequate. Nevertheless, given the significant risks associated with plate-related complications, adjunctive plating should be employed selectively only in instances where the union is unlikely to be achieved with intramedullary rodding alone. Level of Evidence: Level IV—case series.

Background: We investigated the normal development of the secondary ossification centers of the acetabulum, focusing on their location and the amount of acetabular coverage increased by them. Methods: We enrolled 132 patients who were 7 to 16 years of age and had no pelvic deformity but did have ≥1 os ischium, os ilium, and/or os pubis on abdominal or pelvic computed tomographic (CT) scans. The locations of the ossification centers were evaluated by adopting an orientation using 0° for the superior acetabulum, 90° for the anterior acetabulum, 180° for the inferior acetabulum, and 270° for the posterior acetabulum, on a reconstructed 3-dimensional (3D) CT image. The acetabular coverage increase by the os ischium, os ilium, or os pubis was defined as the difference in the posterior acetabular sector angle (ΔPASA), posterosuperior acetabular sector angle (ΔPSASA), superior acetabular sector angle (ΔSASA), anterosuperior acetabular sector angle (ΔASASA), or anterior acetabular sector angle (ΔAASA) measured with and without each secondary ossification center. Patients were grouped into 3 age ranges: late childhood, preadolescence, and early adolescence. The location of each ossification center and the increase in acetabular coverage were compared between these groups. Results: In the late-childhood group, the median start-to-end positions in right hips were 269° to 316° for the os ischium, 345° to 356° for the os ilium, and 81° to 99° for the os pubis. These positions tended to be wider in the early-adolescence group at 252° to 328° for the os ischium (p < 0.001), 338° to 39° for the os ilium (p = 0.005), and 73° to 107° for the os pubis (p = 0.049) in right hips. In right hips in the late-childhood group, the median values were 8.1° for ΔPASA, 14.0° for ΔPSASA, 9.9° for ΔSASA, 11.1° for ΔASASA, and 3.9° for ΔAASA; and in the early-adolescence group, the median values in right hips were 10.7° for ΔPASA, 12.9° for ΔPSASA, 8.4° for ΔSASA, 7.4° for ΔASASA, and 5.6° for ΔAASA. Only the median ΔPASA was larger in the early-adolescence group than in the late-childhood group (p = 0.026). Similar results were observed in left hips. Conclusions: In early adolescence, the secondary ossification centers appeared at more extended areas along the acetabular rim, and the increase in acetabular coverage by the secondary ossification centers tended to be larger in the posterior area but not in the anterior or superior area. Level of Evidence: Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Purpose: Fibular hemimelia has denoted a spectrum of postaxial longitudinal deficiency with fibular aplasia/hypoplasia; the term “terminal hemimelia” is reserved for patients with postaxial longitudinal deficiency having a normal fibula. We aimed to delineate the characteristics of terminal hemimelia. Methods: In total, 30 patients with postaxial longitudinal deficiency who had a normal or hypoplastic fibula and visited our institution between 1992 and 2022 were reviewed. Patients were divided into terminal hemimelia and classic fibular hemimelia groups, and their demographic characteristics and clinical and radiographic findings were compared. Results: Femoral shortening, knee valgus, and tibial spine hypoplasia were less common in terminal hemimelia (n = 13) than in classic fibular hemimelia (n = 17) (p = 0.03, p < 0.001, and p = 0.003, respectively). None of the patients in the terminal hemimelia group exhibited knee instability, whereas 12% of patients with classic fibular hemimelia did. Ball-and-socket ankle and absence of lateral rays were commonly observed in both groups. However, tarsal coalition was observed less frequently in terminal hemimelia (p = 0.004). All terminal hemimelia patients exhibited a painless plantigrade foot without ankle instability. Despite limb-length discrepancy at maturity averaging 40.4 mm for terminal hemimelia and 67.0 mm for classic fibular hemimelia (p < 0.001), patients with terminal hemimelia, except for one, exhibited > 20 mm of limb-length discrepancy. However, 46% of them underwent limb-length equalization procedures, mostly single-stage tibial lengthening, at a mean age of 11.2 years. Conclusion: Terminal hemimelia may present with a milder phenotype than classic fibular hemimelia. It mainly overlaps with the symptoms of fibular hemimelia below the ankle joint and manifests as limb-length discrepancy. However, a considerable number of patients with terminal hemimelia required limb-length equalization procedures, for example single-stage tibial lengthening. Level of evidence: level IV.

Background: Endocrinopathy is a risk factor for slipped capital femoral epiphysis (SCFE). We aimed to determine (1) the incidence of endocrinopathy-associated SCFE compared with that of non-endocrinopathy-associated SCFE, (2) whether the incidence of SCFE increases with the number of deficient hormones, and (3) the clinical characteristics of endocrinopathy-associated SCFE. Methods: We conducted a population-based cohort study using a nationwide database in South Korea. All new diagnoses of endocrinopathy or SCFE between 2002 and 2019 in children born between 2002 and 2005 were identified. The incidence of SCFE was calculated for each type of endocrinopathy. The trend of the incidence of SCFE relative to the number of deficient hormones was analyzed. The male:female ratio was compared between endocrinopathy-associated SCFE and non-endocrinopathy-associated SCFE. For endocrinopathy-associated SCFE, the time between the diagnoses of SCFE and endocrinopathy was evaluated. Results: The incidence of SCFE was higher in children with endocrinopathy than in those without endocrinopathy (37.1/100,000 versus 9.0/100,000 children) (relative risk, 4.1 [95% confidence interval, 2.8-6.1]). Among various endocrinopathies, growth hormone deficiency showed the highest incidence of SCFE (583.8/100,000 children). The Cochran-Armitage test showed a linear trend, with an increased number of deficient hormones being associated with a higher incidence of SCFE (p < 0.001). Male sex was dominant in the non-endocrinopathy-associated SCFE group (73%; 117 of 161), whereas female sex was dominant in the endocrinopathy-associated SCFE group (53%; 16 of 30) (p = 0.009). Twenty-two of the 30 cases of endocrinopathy-associated SCFE were diagnosed after the diagnosis of endocrinopathy, with a median time of 3.6 years between the diagnoses. Six (27%) of these 22 children developed SCFE >5 years after the diagnosis of endocrinopathy. Conclusions: The incidence of SCFE was approximately 4 times higher in children with endocrinopathy than in those without endocrinopathy. The risk of SCFE increased with an increased number of deficient hormones. Long-term monitoring of SCFE occurrence in children with endocrinopathies is strongly recommended. Level of Evidence: Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.