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Purpose: To investigate the value of antero-posterior and lateral radiographs in predicting clubfoot relapse after treatment with the Ponseti method. Methods: This was a retrospective review of 104 children (157 feet) younger than 3 months of age with idiopathic clubfoot treated using the Ponseti method at our institution between January 2007 and December 2014. All patients underwent Achilles tenotomy and were divided into two groups according to the need for further surgery to correct the deformity: relapsed group (24 patients; 36 feet) and non-relapsed group (80 patients; 121 feet). All antero-posterior and lateral foot radiographs were performed less than 3 months after Achilles tenotomy. The talo-calcaneal (TC-AP) and talus-first metatarsal (TM-AP) angles were measured in the antero-posterior view, while the tibio-calcaneal (TIC-L), talus-first metatarsal (TM-L), and talo-calcaneal (TC-L) angles were measured in the lateral view. The multi-factor logistic regression model of the stepwise selection method was used to predict the relapse of clubfoot deformity from the potential predictive values. Results: The mean age at initial plain radiography examination was 99.45 ± 21.54 days. Differences in TC-AP, TM-AP, TC-L, and TIC-L between the two groups were statistically significant. However, only TM-AP and TIC-L were included in the “ risk of relapse” formula using the multi-factor logistic stepwise selection method. Conclusion: Early antero-posterior and lateral radiographs in children younger than 3 months of age at initial Ponseti treatment have positive predictive value for relapse. Reduced TM-AP angle and increased TIC-L were associated with an increased risk of relapse. Level of evidence: level III.

Purpose To investigate the success rate of the Tübingen hip flexion splint (THFS) for the treatment of developmental dysplasia of the hip (DDH), of different severity as per the Graf classification, among infants younger than six months of age. The type and incidence rate of complications associated with THFS treatment were also evaluated. Methods The following databases were searched using keywords and limited for age less than six months: PubMed, Embase, Web of Science, Cochrane Library, and SinoMed, between inception and July 2020. Articles were screened and extracted by two researchers, and the quality of the included literature was evaluated (methodological index for non-randomized studies criteria). R studio 1.3 was used for statistical analysis. The review process was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Results After screening, eight articles were included in the analysis, contributing 1211 hips (875 patients). The overall success rate of THFS treatment is 91% (95% confidence interval (CI) 0.82 to 0.95). The success rate by Graf type is as follows: type-II, 98% (95% CI 0.94 to 1.00); type-III, 96% (95% CI 0.88 to 1.00); and type-IV, 32% (95% CI 0.18 to 0.47). Complications (24/1211, 2%) included transient femoral nerve palsy (n = 1); avascular necrosis of the femoral head (n = 9) and residual acetabular dysplasia (n = 14). Conclusion THFS treatment is successful for Graf type-II and –III, but low for type-IV, with a low rate of complication. THFS may be an effective treatment option for DDH among infants less than six months of age. However, those with Graf type-IV require close monitoring. Level of Evidence III

Purpose The objective of this study was to explore the predictors for failed reduction in children with developmental dysplasia of the hip (DDH) managed by arthrogram, closed reduction (CR) and spica cast immobilization. Methods We retrospectively reviewed the clinical data of patients with DDH treated by CR and cast immobilization (2015-2020), including age, sex, affected side, presence/absence of an ossific nucleus, International Hip Dysplasia Institute classification, the delineation of labrum and acetabular surface on arthrogram, inverted labrum, acetabular index (AI), hip abduction angle and medial dye pool (MDP) distance. Predictors that potentially predicted failure of CR were evaluated by logistic regression analysis, simple t-test, Fisher's Exact Test and chi-square test. Results In total, 16 out of 187 hips failed to achieve initial CR (8.6%). Gender, age, preoperative AI and poor delineation of arthrogram were candidate predictors for failed CR in children aged six to 24 months with DDH; on the other hand, logistic regression analysis confirmed age and poor delineation of arthrogram significantly predicted failure of CR. Receive operating characteristic curve (ROC) showed MDP less than 6 mm and age higher than 14.5 months significantly increased the failure rate of CR in children aged six to 24 months with DDH. Conclusion Age and poor delineation of labrum and acetabular surface during arthrogram predicted failure of CR in children with DDH. In particular, age > 14.5 months and MDP distance ≥ 6 mm significantly increased the risk of CR failure. Level of evidence III

Purpose The purpose of this study was to identify if any correlation between size of the proximal femoral epiphysis and avascular necrosis (AVN) exists. Methods We retrospectively reviewed 111 patients with developmental dysplasia of the hip treated by closed reduction (124 hips). The diameter and height of both femoral head and ossific nucleus were assessed on preoperative MRI. Results The diameter and the height of the femoral head as well as of the ossific nucleus of the contralateral side were significantly greater than the dislocated side. AVN occurred in 21 (16.9%) out of 124 hips. The rate of AVN gradually decreased with age: 30.0% at six to 12 months, 18.2% at 12 to 18 months and 3.7% at 18 to 24 months. Spearman correlation analysis showed that age is negatively correlated with the incidence of AVN (r = -0.274; p = 0.002) and the diameter of the femoral head has a significantly negative association with the incidence of AVN (r = -0.287; p = 0.001). No significant association was observed between the incidence of AVN and height of the femoral head or size of the ossific nucleus. Hips with AVN were significantly smaller than hips without AVN. Conclusions The size of both the femoral head and the ossific nucleus increase with age although the dislocated femoral head is smaller compared with the contralateral side. The diameter of the femoral head and not the size of the ossific nucleus negatively correlate with the risk of AVN, with a bigger femoral head showing lower risk of AVN. Level of evidence III

Purpose The purpose of this study was to explore whether increasing the hip abduction angle would increase the incidence of avascular necrosis (AVN) in patients with late- detected developmental dysplasia of the hip (DDH) treated by closed reduction (CR) and spica cast immobilization. Methods A total of 55 patients (59 hips) with late-detected DDH underwent MRI after CR. Hip abduction angle and hip joint distance were measured on postoperative MRI transverse sections. The acetabular index and centre-edge angle were measured on plain radiographs at the last follow-up. The presence of AVN according to Kalamchi and McEwen's classification was assessed. We retrospectively analyzed the associations among abduction angles, hip joint distances, radiographic parameters, AVN and final outcomes, exploring the relationship between hip joint abduction angle and AVN rate. Results The mean age at the time of CR was 14.4 months SD 5.5 (6 to 28), and the mean follow-up was 26.2 months SD 8.1 (12.4 to 41.7). The mean hip abduction angle was 70.2° SD 7.2° (53° to 85°) on the dislocated side and 63.7° SD 8.8° (40° to 82°) on the normal side; the mean hip joint distance was 5.1 mm SD 1.9 (1.3 to 9.1) on the dislocated side and 2.2 mm SD 0.6 on the normal side (1.3 to 3.3). Eight of 59 hips (13.6%) developed AVN. Neither the amount of abduction nor hip joint distance increased the AVN rate (p = 0.97 and p = 0.65, respectively) or the dislocation rate (p = 0.38 and p = 0.14, respectively). Conclusion Abduction angle up to 70.2° following CR did not increase the AVN rate in children aged six to 28 months with late-detected DDH treated by CR. Level of evidence III.

Purpose The purpose of this study was to identify the correlation between the vascular development of the femoral head and avascular necrosis (AVN) in patients with developmental dysplasia of the hip (DDH) treated by closed reduction (CR). Methods We retrospectively reviewed 78 patients with DDH treated by CR (83 hips). The vascular maturity, number of vessels and perfusion changes of the femoral head were assessed on perfusion MRI (pMRI) before and after CR. Results The number of vessels (mean 4.2 sd 1.4) of the femoral head and the ratio (36.1%) of mature vessels (type III) on the dislocated side were significantly less than those at contralateral side (mean 6.0 sd 1.2; 82.2%) (p < 0.001). Of the included 83 hips, 39 hips (61.5%) showed decreased perfusion of the femoral head, including partial decreased (Class B, 47.0%) and global decreased (Class C, 14.5%), at the dislocated side, which was significantly more than those at contralateral side (0.0%) (p < 0.001). In total, 32 out of 83 hips (38.5%) developed AVN. The rate of AVN with Class A (18.8%) which perfusion of the femoral head was normal (unchanged or enhanced) was significantly less than those with Class C (66.7%) (p = 0.006). Conclusion The vascular development and perfusion changes of the femoral head on the dislocated side are significantly worse than those at contralateral side. Immature vascularity of the femoral head before CR and poor perfusion of the femoral head after CR may be risk factors for AVN in patients with DDH. Level of evidence III