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Background and purpose: Magnetically controlled motorized intramedullary lengthening nails (ILNs) can be employed for simultaneous correction of angular deformities of the distal femur and leg length discrepancy. This spares typical complications of external fixators but requires precise preoperative planning and exact intraoperative execution. To date, its results are insufficiently reported. We aimed to elucidate the following questions: (i) Is acute angular deformity correction and gradual femoral lengthening via a retrograde ILN a reliable and precise treatment option? (ii) What are the most common complications of treatment? Methods: Acute angular deformity correction and subsequent gradual lengthening of the distal femur with retrograde ILN was retrospectively analyzed in 45 patients (median patient age: 15 years, interquartile range [IQR] 13–19 and median follow-up: 40 months, IQR 31–50). Outcome parameters were accuracy, precision, reliability, bone healing, and complications of treatment. Results: The median distraction was 46 mm (IQR 29–49), median distraction and consolidation index 0.9 mm/day (IQR 0.7–1.0) and 29 days/cm (IQR 24–43), respectively. The median preoperative mechanical axis deviation (MAD) was 30 mm (IQR 23–39) in the varus cohort and –25 mm (IQR –29 to –15) in the valgus cohort and reduced to a mean of 8 mm (standard deviation [SD] 8) and –3 (SD 10), respectively. Accuracy, precision, and reliability of lengthening were 94%, 95% and 96%, respectively. Accuracy and precision of deformity correction were 92% and 89%, respectively. In total, 40/45 of patients achieved distraction with a difference of less than 1 cm from the initial plan and a postoperative MAD ranging from –10 mm to +15 mm. In 13/45 patients unplanned additional surgeries were conducted to achieve treatment goal with nonunion being the most frequent (4/45) and knee subluxation (3/45) the most severe complication. Conclusion: Acute deformity correction and subsequent lengthening of the distal femur with retrograde ILN is a reliable and accurate treatment achieving treatment goal in 89% but unplanned additional surgeries in 29% of patients should be anticipated.

Background and purpose: Bilateral femoral distraction osteogenesis in patients with achondroplasia is insufficiently reported. We aimed to perform the first study that exclusively analyzed simultaneous bilateral femoral distraction osteogenesis with motorized intramedullary lengthening nails via an antegrade approach in patients with achondroplasia focused on reliability, accuracy, precision, and the evolving complications. Patients and methods: In this retrospective singlecenter study we analyzed patients with achondroplasia who underwent simultaneous bilateral femoral lengthening with antegrade intramedullary lengthening nails between October 2014 and April 2019. 15 patients (30 femoral segments) of median age 14 years (interquartile range [IQR] 12–15) were available for analysis. The median follow-up was 29 months (IQR 27–37) after nail implantation. Results: The median distraction length per segment was 49 mm (IQR 47–51) with a median distraction index of 1.0 mm/day (IQR 0.9–1.0), and a median consolidation index of 20 days/cm (IQR 17–23). Reliability of the lengthening nails was 97% and their calculated accuracy and precision were 96% and 95%, respectively. The most common complication was temporary restriction of knee range of motion during distraction in 10 of 30 of the lengthened segments. 1 patient was treated with 2 unplanned additional surgeries due to premature consolidation. Conclusion: The method is reliable and accurate with few complications.

Background and purpose: For correction of leg-length discrepancy or angular deformity of the lower limb in skeletally immature patients temporary or permanent (hemi-)epiphysiodesis can be employed. These are reliable treatments with few complications. Recently, radiographic analysis of treatment-related alterations of the central knee anatomy gained interest among pediatric orthopedic surgeons. To date the comparison and adequate interpretation of potential changes of the central knee anatomy is limited due to the lack of defined standardized radiographic references. We aimed to establish new reference values of the central knee anatomy. Patients and methods: A retrospective analysis of calibrated longstanding anteroposterior radiographs of 254 skeletally immature patients with a chronological age ranging from 8 to 16 years was conducted. The following radiographic parameters were assessed: (1) femoral floor angle, (2) tibial roof angle, (3) width at femoral physis, and (4) femoral notch–intercondylar distance. Results: All observed radiographic parameters were normally distributed with a mean age of 12.4 years (standard deviation [SD] 2, 95% confidence interval [CI] 12.2–12.6). Mean femoral floor angle was 142° (SD 6, CI 141.8–142.9), mean tibial roof angle was 144° (SD 5, CI 143.7–144.1), mean width at femoral physis was 73 mm (SD 6, CI 72.8–73.9), and mean femoral notch–intercondylar distance was 8 mm (SD 1, CI 7.5–7.7). The estimated intraclass correlation coefficient values were excellent for all measurements. Conclusion: This study provides new radiographic reference values of the central knee anatomy for children between 8 and 16 years and we suggest considering values within the range of 2 SD as the physiological range.

Background and purpose — Motorized intramedullary lengthening nails (ILNs) have been developed as an alternative to external fixators for long bone lengthening. The antegrade approach represents the standard method for tibial ILN insertion. In patients with preexisting ankle and hindfoot fusion a retrograde approach provides an alternative technique that has not been evaluated so far. We report the outcome of this method in 10 patients. Patients and methods — This retrospective study included 10 patients (mean age 18 years [13–25]) with preexisting ankle and hindfoot fusion who underwent tibial lengthening with a retrograde ILN (PRECICE). The mean leg length discrepancy (LLD) was 58 mm (36–80). The underlying conditions were congenital (n = 9) and post tumor resection (n = 1). The main outcome measures were: ILN reliability, distraction achieved, distraction index (DIX), time to bone healing, consolidation index (CIX), complications, and functional results. Results — All patients achieved the goal of lengthening (mean 48 mm [26–80]). Average DIX was 0.6 mm/day (0.5–0.7) and mean CIX was 44 days/cm (26–60). Delayed consolidation occurred in 2 patients and healed after ILN dynamization or nail exchange with grafting. Toe contractures in 2 other patients were resolved with physiotherapy or tenotomy. Until last follow-up (mean 18 months [12–30]) no true complications were encountered, knee motion remained unaffected, and full osseous consolidation occurred in all patients. Interpretation — In patients with LLD and preexisting ankle and hindfoot fusion distal tibial lengthening using a retrograde ILN is a reliable alternative to the standard approach with equivalent bone healing potential and low complication rates leaving the knee unaffected.

Background and purpose — To date there is a lack of studies defining the anatomical position of the proximal fibula. This is especially relevant when planning surgical interventions affecting the knee joint such as permanent or temporary epiphysiodesis to correct leg length discrepancies or angular deformities in growing patients. The goal of this study is to establish a standardized measurement technique and radiological reference values for the position of the proximal fibula in children. Patients and methods — 500 measurements were performed in calibrated long standing anteroposterior radiographs of 256 skeletally immature patients (8–16 years; 233 female, 267 male legs). As a radiographic reference in the frontal plane, the distance between the center of the proximal tibial growth plate and a line tangential to the tip of the fibular head and horizontal to the imaging plane was measured (dPTFH). Results — The average value of dPTFH in the studied population (median age 12 years) was –2.7 mm (SD 3, CI –3.0 to –2.5) and normally distributed (p = 0.1). There were no clinically significant sex or age-dependent differences. The inter-rater reliability analysis showed excellent ICC values (ICC = 0.88; CI 0.77–0.93). Interpretation — This study provides a new radiographic reference value to assess the position of the proximal fibula in relation to the proximal tibia in children and adolescents. This reference can aid preoperative decision-making as to whether additional fibular epiphysiodesis is necessary when performing tibial epiphysiodesis to correct moderate leg-length discrepancies.