Fixator-Assisted Plating and Nailing for Multiplanar Lower Limb Deformities in Adolescents: Indications, Technical Considerations, and Radiographic Outcomes

Abstract

Background

Uncorrected lower limb deformities in adolescents, particularly those with severe multiplanar deviations, can lead to early joint degeneration and functional impairment. When growth modulation is no longer feasible, corrective osteotomy becomes necessary. This study aims to demonstrate the efficacy of fixator-assisted techniques—fixator-assisted locked plating (FALP) and fixator-assisted nailing (FAN)—in achieving accurate correction of complex femoral and tibial deformities across the frontal, sagittal, and torsional planes.

Methods

A prospective study was conducted involving 27 adolescent patients (31 surgeries) treated with FALP or FAN techniques between 2021 and 2024. Patients were divided into 3 groups: group A (FALP-distal femur), group B (FALP-tibia), and group C (FAN). Data collected included demographics, surgical parameters, preoperative and postoperative deformity measurements, time to weight-bearing, bone consolidation, return to daily activities, and complications. Statistical analysis was performed using IBM SPSS Statistics 29.0. The mean follow-up was 20.9 months.

Results

Radiographic union was achieved in all cases, with a mean time to consolidation of 4 months. Mean mechanical axis deviation corrections reached 36.7 mm in valgus and 36.4 mm in varus deformities, achieving near-neutral postoperative alignment. Torsional corrections averaged 53.3° for internal femoral torsion and 36.3° for external tibial torsion. Sagittal corrections included 22° for femoral extension and 10° for tibial proximal flexion deformities. Patients treated with FAN achieved significantly earlier weight-bearing (mean 5.8 days). No clinically relevant secondary deformities, joint stiffness, or significant leg length discrepancies were identified during follow-up. Complications were rare and unrelated to the external fixator-assisted techniques. Implant removal was performed in 38.7% of cases.

Conclusions

FALP and FAN techniques are safe and effective methods for the acute correction of severe multiplanar lower limb deformities in adolescents. They enable precise 3-dimensional correction with reliable bone healing and early return to activities and may represent a useful alternative to gradual correction methods in appropriately selected cases.

Lower limb deformities in adolescents, particularly those involving multiple planes, can lead to premature degenerative changes in the hip, knee, and ankle joints. When growth modulation is no longer feasible, corrective osteotomy becomes the standard of care.¹,²,³⁾ While deformities in the frontal plane are the most frequently addressed,⁴,⁵⁾ sagittal plane malalignment can significantly alter knee biomechanics.⁶⁾ Although historically considered to be better tolerated, sagittal deviations have been associated with an increased risk of early osteoarthritis in long-term follow-up studies.⁷,⁸⁾

Rotational malalignment, especially excessive femoral anteversion, has been linked to patellofemoral instability and anterior knee pain.⁹,¹⁰⁾ Surgical correction is generally indicated for anteversion exceeding 50°, or when hip internal rotation surpasses 85° with limited external rotation.¹⁰⁾ Similarly, tibial derotation osteotomies are indicated for external torsion ≥ 30° or internal torsion > 15°.

Adolescent lower limb deformities may result from a variety of etiologies, including posttraumatic malunion,¹¹⁾ metabolic bone disorders,¹²⁾ congenital conditions such as Blount disease,¹³,¹⁴⁾ postaxial deficiencies, infectious sequelae, skeletal dysplasias, and other syndromic disorders. Treatment options include gradual correction using external fixation,¹⁵⁾ acute correction with internal fixation using plates or staples,¹⁶,¹⁷⁾ or intramedullary nailing.¹⁸⁾ Each approach presents limitations in precision, multiplanar control, or recovery time.

Fixator-assisted techniques, such as fixator-assisted locked plating (FALP) and fixator-assisted nailing (FAN), combine the accuracy of temporary external fixation with the stability and comfort of definitive internal fixation. While previous studies have primarily focused on valgus deformities,¹⁹,²⁰,²¹,²²⁾ there is limited evidence on their application for large varus corrections and severe rotational deformities, particularly in adolescent populations.

The purpose of this study was to describe the indications, technical aspects, and radiographic outcomes of FALP and FAN for acute multiplanar correction of femoral and tibial deformities in adolescents, and to outline the correction limits and practical applications of these techniques.

METHODS

All procedures were performed in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration, and its later amendments. The Institutional Review Board of the CEIm Fundació Sant Joan de Déu approved the study (IRB No. PIC-175-20), and written informed consent was obtained from all participants and/or their legal guardians.

Study Design and Patients

We conducted a prospective case series at a single center including all consecutive patients treated with fixator-assisted techniques for lower limb deformities between April 2021 and July 2024. All consecutive patients who met the inclusion criteria and had complete clinical and radiographic follow-up were included in the analysis. All surgeries were performed by the same surgical team. Treatment allocation (FALP or FAN) was not randomized but was based on anatomical considerations, deformity characteristics, and surgeon preference. Inclusion criteria were any etiology of deformity treated with FALP or FAN technique, with complete clinical and radiographic follow-up ≥ 12 months. Exclusion criteria were incomplete records or loss to follow-up. All patients were treated at a pediatric hospital. A total of 27 patients (31 procedures; 11 females, 20 males; mean age 15.6 years, range, 12.3–19.7 years) were included. Laterality was 20 right and 11 left. Etiologies comprised bone dysplasias (n = 8; 4 X-linked hypophosphatemic rickets [XLHR], 2 undiagnosed, 1 Ollier disease, 1 polyostotic fibrous dysplasia), idiopathic deformities (n = 7), posttraumatic (n = 7), postaxial deficiencies (n = 3), sequelae after guided growth (n = 2), infectious sequelae (n = 2), popliteal pterygium syndrome (n = 1), and Blount disease (n = 1). One patient presented a double-apex femoral deformity requiring double-level fixator-assisted nailing (DL-FAN) with 2 diaphyseal osteotomies in the right femur. In the same limb, an additional metaphyseal deformity was corrected with FALP, while the contralateral femur was treated with FAN. Patients were grouped as group A (distal femur FALP), group B (tibia FALP), and group C (FAN) (Table 1).

Table 1. Patient Distribution According to Surgical Technique and Type of Deformity Treated.

Group	Patients (n)	Bones treated	Technique	Deformities treated
A	20	21 Femora	FALP	12 Valgus, 5 varus, 3 rotational, 1 hyperextension
B	4	4 Tibiae	FALP	1 Flexion, 3 rotational
C	6	5 Femora, 1 tibia	FAN	2 Rotational (femur), 2 varus (femur), 1 valgus (femur), 1 valgus (tibia)

FALP: fixator-assisted locked plating, FAN: fixator-assisted nailing.

The choice between FALP and FAN was based on anatomical and clinical considerations. Intramedullary nailing was avoided in patients with open physes to prevent potential physeal injury. Metaphyseal deformities, particularly around the distal femur or proximal tibia, were generally treated with FALP, which allows stable fixation close to the joint. Diaphyseal femoral deformities were preferentially treated with FAN, as intramedullary fixation provides stable alignment along the mechanical axis. In tibial deformities, the choice between plating and nailing was made according to surgeon preference, considering bone morphology, canal diameter, and the characteristics of the deformity.

Data Collection

Recorded variables included demographics, laterality, deformity type, surgical technique, pre- and postoperative mechanical axis deviation (MAD), mechanical lateral distal femoral angle (mLDFA), medial proximal tibial angle (MPTA), sagittal parameters (sagittal mechanical axis angle, posterior distal femoral angle [PDFA], posterior proximal tibial angle [PPTA]), and torsional deformity assessed by computed tomography (CT), leg length discrepancy, surgical duration, hospital stay, time to partial weight-bearing, bone consolidation, return to daily activities, complications, and implant removal. Radiographic consolidation was defined as cortical bridging in at least 3 of 4 cortices visible on anteroposterior and lateral radiographs. Follow-up continued until radiographic union and clinical recovery were achieved, or until transition to adult care (≥ 18 years).

The goal of correction was to restore physiological limb alignment, aiming for a mechanical axis passing near the center of the knee joint and normalization of the relevant joint orientation angles (mLDFA for femoral deformities and MPTA for tibial deformities). Successful correction was defined as achieving radiographic alignment within clinically acceptable limits together with restoration of the mechanical axis.

Surgical Techniques

Distal femoral FALP technique

Patients were positioned supine on a radiolucent table with an x-ray grid. Two 6-mm half-pins were inserted under fluoroscopic guidance, 1 proximal and 1 distal to the planned osteotomy site. The proximal pin was placed anteromedially to avoid injury to the descending genicular artery, using soft-tissue protectors to prevent vascular damage. The distal pin was positioned parallel to the joint line near the distal femur, and the proximal pin perpendicular to the femoral midshaft axis, both kept flush with the lateral cortex to facilitate plate insertion. The angle between pins reflected limb deviation, acknowledging the 7° (range, 5°–9°) difference between the anatomical and mechanical axes not accounted for during placement. The pins were connected with a loosely attached external fixator. A lateral subvastus approach was used for the supracondylar femoral osteotomy, performed under direct visualization between the 2 pins. Correction proceeded sequentially: rotation first, then translation, and finally angular adjustment, until the pins were parallel. Rotational correction was performed first because it represents the most complex plane to control and establishes the correct orientation of the limb segments. Translation was then adjusted to restore mechanical alignment. Angular correction was performed last, as angular correction increases soft-tissue tension and performing it earlier may hinder subsequent adjustments. This sequence facilitates a simpler and more controlled reduction.

Rotational deformity was assessed preoperatively through clinical examination, including foot progression angle, hip internal and external rotation, and the thigh–foot angle. When rotational malalignment was suspected, torsional CT was obtained to quantify femoral anteversion or tibial torsion. The planned amount of rotational correction was determined preoperatively based on clinical and CT findings. Intraoperatively, rotational alignment was guided using anatomical landmarks. The external fixator pins were inserted with a predefined angular divergence corresponding to the desired rotational correction, using sterile triangular wedges as guides. After completing the osteotomy, the fragments were rotated until the pins became parallel, thereby achieving the planned derotation. The target rotational correction was defined preoperatively based on clinical examination and CT torsional measurements, aiming to restore physiological femoral anteversion or tibial torsion according to the patient’s clinical and anatomical characteristics. Intraoperatively, rotational correction was considered adequate when the planned correction was achieved through parallelization of the fixator pins after osteotomy. A small residual rotational error within approximately 5°–10° of the planned correction was considered clinically acceptable.

For torsional deformities, the choice between FALP and FAN was mainly determined by the planned osteotomy level and anatomical considerations. In cases where the osteotomy was located in the metaphyseal region, plating was generally preferred, whereas diaphyseal osteotomies could be treated with either technique depending on bone morphology and canal diameter. As currently no clear consensus exists in the literature regarding implant selection for rotational deformity correction, the final choice was made according to surgeon judgment.

The desired position was secured by tightening the fixator. Translation was essential to avoid “golf club” deformities. Alignment was verified intraoperatively with an x-ray grid or Bovie cord, ensuring the mechanical axis passed through the femoral head, knee, and ankle. Sagittal correction was checked on a true lateral view. Additional pins were placed for stability when needed, particularly in large rotational corrections, where lateral pins were inserted at the lesser trochanter and femoral intercondylar notch. Locking plates were placed submuscularly and extraperiosteally. Slight proximal plate separation from the bone was frequent when translation was required and did not compromise stability. Distal fixation used 4 to 5 locking screws; proximal fixation at least 3, placed percutaneously if necessary. Bone graft was added when indicated. After definitive fixation, external fixator pins were removed under soft-tissue protection (Fig. 1).

Fig. 1. (A) Preoperative standing telemetric radiograph showing valgus deformity. (B) Intraoperative images with the external fixator before and after osteotomy. (C) Postoperative standing telemetric radiograph.

Tibial FALP technique

Patients were positioned supine on a radiolucent table with a thigh tourniquet. Two medial half-pins, 1 proximal and 1 distal to the planned osteotomy, were connected with a monolateral external fixator. For rotational deformities, the proximal pin was aligned with the tibial plateau (patella forward) and the distal pin with the ankle mortise in neutral rotation. The desired degree of rotational correction was planned preoperatively and reproduced intraoperatively by placing the pins with the corresponding angular divergence before completing the osteotomy. Correction proceeded sequentially (rotation, translation, angular adjustment), and alignment was confirmed with an x-ray grid or Bovie cord. Definitive fixation was achieved with a locking plate.

FAN technique

Patients were positioned supine on a radiolucent table with an x-ray grid. Osteotomy level and nail dimensions were planned preoperatively. Half-pins were placed to avoid nail interference: proximally near the lesser trochanter for antegrade femoral nails, at the posterior condyles for retrograde nails, or posterior to the tibial plateau for tibial nails. A diaphyseal pin was added distal to the nail endpoint. To reduce fat embolism risk, multiple drill holes were made before reaming; osteotomy completion followed with an osteotome. Correction of all planes was achieved with the fixator locked in position. The intramedullary nail was then inserted and statically locked proximally and distally. Poller screws were used as needed. The fixator was removed under soft-tissue protection at the end of the procedure. Alignment was verified intraoperatively, ensuring the femoral head, knee, and ankle were colinear. For double-apex deformities, the DL-FAN technique involved a second osteotomy at the additional apex, with Poller screws preplanned accordingly (Fig. 2).

Fig. 2. (A) Preoperative standing telemetric radiograph of a patient with X-linked hypophosphatemic rickets showing bilateral deformities. (B) Correction of a double-apex diaphyseal deformity of the right femur using double-level fixator-assisted nailing, contralateral femur with fixator-assisted nailing technique, and guided growth at the proximal tibiae. (C) Fixator-assisted locked plating for the correction of a right metaphyseal deformity. The apparent rotational asymmetry visible in the image reflects preexisting tibial torsion that was not addressed surgically in this procedure.

Statistical Analysis

Data were analyzed using IBM SPSS Statistics version 29 (IBM Corp.). Quantitative variables were expressed as means with 95% CIs or medians with interquartile ranges, depending on distribution. Group comparisons were performed with 1-way analysis of variance or Mann-Whitney U-tests; paired comparisons with the Wilcoxon signed-rank test; and categorical variables with chi-square or Fisher’s exact tests. A p-value < 0.05 was considered statistically significant.

RESULTS

There were no statistically significant differences in age or sex between groups. All treatment goals—correction of MAD, mLDFA, MPTA, sagittal plane alignment, and torsional deformity—were successfully achieved in all patients, with radiological union confirmed in every case. No clinically relevant secondary deformities at the level of the treated segment were identified on follow-up radiographs.

Surgical Times and Hospitalization

Mean surgical duration was 3 hours (standard deviation [SD], 55 minutes) for group A (FALP-distal femur), 2 hours and 14 minutes (SD, 26 minutes) for group B (FALP-tibia), and 4 hours and 28 minutes (SD, 85 minutes) for group C (FAN), with a statistically significant difference between groups (p = 0.006).

The mean hospital stay was 4.0 days (SD, 2.8), with no statistically significant differences between groups (p > 0.05). Group A (FALP-distal femur) had a mean hospitalization of 3.4 days (SD, 1.0), group B (FALP-tibia) 7 days (SD, 7.3), and group C (FAN) 4.2 days (SD, 0.8). The prolonged hospitalization in group B (FALP-tibia) was attributed to a case of compartment syndrome requiring extended care.

Weight-Bearing, Consolidation, and Return to Activities

The mean time to initiate partial weight-bearing was 33.5 days, varying across groups: 40.0 days (SD, 10.5) in group A (FALP-distal femur), 34.5 days (SD, 14.4) in group B (FALP-tibia), and 5.8 days (SD, 6.8) in group C (FAN). The FAN group demonstrated a markedly shorter time to weight-bearing initiation (p < 0.001), although 1 patient treated with DL-FAN delayed weight-bearing, increasing the group’s mean. Given the presence of these outliers, the results should be interpreted with caution. All procedures included in this study were unilateral, and no patients underwent simultaneous bilateral surgery; therefore, weight-bearing timing was not influenced by bilateral procedures.

The mean time to bone consolidation was 4 months (SD, 1.7), without significant differences between groups. Specifically, bone union was achieved in 3.6 months (SD, 1.0) in group A (FALP-distal femur), 5.3 months (SD, 3.6) in group B (FALP-tibia), and 4.6 months (SD, 1.5) in group C (FAN). Although intramedullary fixation is generally considered a load-sharing construct that may favor early bone healing, consolidation time in the FAN group was not shorter than in the FALP group in our series. Most cases achieved radiographic union within 3–4 months, which is consistent with expected healing after corrective osteotomy. Importantly, no statistically significant differences in consolidation time were observed between groups, suggesting comparable healing dynamics. Given the small and heterogeneous subgroup sizes, comparisons between groups should be interpreted with caution and considered exploratory rather than confirmatory.

The mean time to resume activities of daily living was 5.9 months (SD, 2.1), with no statistically significant differences. Group A (FALP-distal femur) had a mean recovery time of 5.7 months (range, 4–6 months; SD, 1.9), group B (FALP-tibia) 6.3 months (range, 4–10 months; SD, 3.2), and group C (FAN) 6.6 months (range, 3–7 months; SD, 2.5). No cases of joint stiffness were reported, and all patients achieved full range of motion (Table 2).

Table 2. Results.

Variable	Group A (n =21): FALP (femora)	Group B (n=4): FALP (tibiae)	Group C (n=6): FAN (5 femora, 1 tibiae)	p-value
Surgical time	3 hr (SD, 55 mo)	2 hr 14 mo (SD, 26 mo)	4 hr 28 mo (SD, 1 hr 25 mo)	0.006
Hospital stay	3.4 day (SD, 1.0)	7 day (SD, 7.3)	4.2 day (SD, 0.8)	> 0.05
Time to weight-bearing	40.0 day (SD, 10.5)	34.5 day (SD, 14.4)	5.8 day (SD, 6.8)	0.001
Time to bone consolidation	3.6 mo (SD, 1.0)	5.3 mo (SD, 3.6)	4.6 mo (SD, 1.5)	> 0.05
Time to resume activities	5.7 mo (SD, 1.9)	6.3 mo (SD, 3.2)	6.6 mo (SD, 2.5)	> 0.05
Complication	Plate loosening	Wound dehiscence, compartment syndrome	CPN injury	NA

FALP: fixator-assisted locked plating, FAN: fixator-assisted nailing, SD: standard deviation, CPN: common peroneal nerve, NA: not applicable.

Complications

Complications occurred in 5 patients (16%), none directly related to the external fixator-assisted technique. In group A (FALP-distal femur), 1 case of plate loosening occurred after a fall, successfully revised with new fixation. In group B (FALP-tibia), 1 case of wound dehiscence was treated with a negative-pressure therapy, and 1 case of compartment syndrome requiring fasciotomies, complicated by a checkrein deformity, which was corrected with a flexor hallucis longus lengthening. In group C (FAN), 1 case of common peroneal nerve (CPN) injury was observed, which improved after a surgical neurolysis.

No cases of joint stiffness or significant postoperative leg length discrepancies were observed. Implant removal was performed in 38.7% of cases, leading to symptom relief in patients who reported discomfort. The mean follow-up time was 20.9 months (SD, 11.1), with a maximum of 45.5 months.

Radiographic Outcomes (Tables 3 and 4)

Table 3. Radiographic Femoral Correction.

Parameter	Group A – FALP femur	Group C – FAN femur
MAD correction – valgus (mm)	36.7 ± 13.4 (n = 12)	18.5 (14–23) (n = 2)
MAD correction – varus (mm)	36.4 ± 15.5 (n = 5)	22.5 (8–37) (n = 2)
Angular correction mLDFA (°) – valgus	12.1 ± 5.8 (n = 12)	6.1 (4.2–8.1) (n = 2)
Angular correction mLDFA (°) – varus	14.9 ± 8.5 (n = 5)	6.6 (6.3–6.9) (n = 2)
Femoral anteversion correction (°)	53.3 ± 23.6 (n = 3)	42.5 ± 3.5 (n = 2)
PDFA correction (°)	22 (n = 1)	NA

Values are presented as mean ± standard deviation when sample size was ≥ 3. For very small sample sizes (n ≤ 2), ranges are reported.

FALP: fixator-assisted locked plating, FAN: fixator-assisted nailing, MAD: mechanical axis deviation, mLDFA: mechanical lateral distal femoral angle, PDFA: posterior distal femoral angle, NA: not applicable.

Table 4. Radiographic Tibial Correction.

Parameter	Group B – FALP tibia	Group C – FAN tibia
External tibial torsion correction (°)	36.3 ± 11.8 (n = 3)	NA
PPTA correction (°)	10 (n = 1)	NA

Values are presented as mean ± standard deviation when sample size was ≥ 3. For very small sample sizes (n ≤ 2), ranges are reported.

FALP: fixator-assisted locked plating, FAN: fixator-assisted nailing, PPTA: posterior proximal tibial angle, NA: not applicable.

Valgus correction

In group A (FALP-distal femur), 12 patients underwent valgus correction. The mean preoperative MAD was 40.5 mm (range, 27 to 80 mm; SD, 16) improving to a mean postoperative MAD of 3.8 mm (range, –8 to 26 mm; SD, 8.7). The mean MAD correction was 36.7 mm (range, 27 to 73 mm; SD, 13.4). The preoperative mLDFA was 75.1° (range, 62.5° to 85.4°; SD, 7.3), improving to 87.2° (range, 83.4° to 92.5°; SD, 3.1°), corresponding to a mean angular correction of 12.1° (range, 6.2° to 23°; SD, 5.8).

One patient with a postoperative MAD of 26 mm had a concurrent tibial valgus deformity. The femoral alignment (mLDFA) was appropriately corrected, and the residual MAD was related to the tibial deformity, which was subsequently treated. In group C (FAN), 2 valgus corrections were performed: 1 tibial and 1 femoral. The tibial valgus case achieved a correction of 4.2°, although complicated by a CPN injury, while the femoral case achieved a MAD correction of 23 mm without complications.

Varus correction

In group A (FALP-distal femur), 5 patients were treated for distal femoral varus deformities. The mean preoperative MAD was –29.8 mm (range, –17 to –45 mm; SD, 12.1), improving to a mean postoperative MAD of 6.6 mm (range, –5 to 38 mm; SD, 17.6). The mean correction achieved was 36.4 mm (range, 16 to 55 mm; SD, 15.5). The preoperative mLDFA was 102.4° (range, 93.8° to 116.5°; SD, 8.5), corrected to 87.5° (range, 84.3° to 89.4°; SD, 2.1) corresponding to a mean angular correction of 14.9° (range, 5.3° to 27.6°; SD, 8.5). One patient with a postoperative MAD of 38 mm had a concurrent tibial valgus deformity, which was corrected, restoring the mLDFA.

In group C (FAN), 2 varus deformities were corrected using the FAN technique in the femur, achieving a mean MAD correction of 22.5 mm (range, 8–37 mm) and a mean angular correction of 6.6° (range, 6.3°–6.9°) in the coronal femoral alignment (mLDFA). Overall, correction in the coronal plane was successfully achieved across all treatment groups, with significant improvements in MAD and angular parameters (mLDFA and MPTA).

Torsional corrections

Torsional corrections were assessed using torsional CT scans in all 3 groups. In group A (FALP-distal femur), 3 patients with excessive femoral anteversion were corrected from a mean preoperative anteversion of 82.7° (range, 68°–97°; SD, 14.5°) to a mean postoperative anteversion of 29.3° (range, 17°–38°; SD, 11.0°), achieving a mean correction of 53.3° (range, 35°–80°; SD, 23.6°). In group B (FALP-tibia), 3 patients with external tibial torsion were corrected from a mean preoperative torsion of 59.7° (range, 49°–78°; SD, 15.9°) to a postoperative mean of 23.3o (range, 20°–28°; SD, 4.2°), with a mean correction of 36.3° (range, 29°–50°; SD, 11.8°). In group C (FAN), 2 patients with femoral anteversion were corrected from a mean preoperative anteversion of 67.0° (range, 65°–69°; SD, 2.8°) to a postoperative mean of 24.5° (range, 24°–25°; SD, 0.7°) achieving a mean correction of 42.5° (range, 40°–45°; SD, 3.5°).

Sagittal plane corrections

Sagittal corrections were achieved exclusively using the FALP technique. In group A (FALP-distal femur), 1 patient with a distal femoral hyperextension deformity presented with a preoperative PDFA of 109°, corrected by 22°, resulting in a final angle of 87°. In group B (FALP-tibia), 1 patient with a proximal tibial flexion deformity had a preoperative PPTA of 67°, corrected by 10°, reaching a final angle of 77°.

DISCUSSION

This study demonstrates that fixator-assisted techniques—both FALP and FAN—are reliable and reproducible methods for the acute correction of severe multiplanar lower limb deformities in adolescents. Beyond achieving consistent restoration of the mechanical axis, these techniques allowed accurate correction in the sagittal and torsional planes, which are traditionally more difficult to address. Importantly, they proved useful not only in idiopathic or posttraumatic deformities but also in patients with skeletal dysplasias and metabolic disorders, a population in which external fixation is often the only feasible option. By providing the precision of external fixation intraoperatively while avoiding its postoperative morbidity, FALP and FAN represent a valuable alternative to gradual correction with external fixators.

The magnitude of deformity corrected in our series was substantial. In the frontal plane, mean MAD corrections reached 36.7 mm for valgus and 36.4 mm for varus deformities, with angular corrections of 12.1° and 14.9°, respectively. These results are comparable to those reported by Eidelman et al.¹⁹⁾ and Yılmaz and Bakırcıoğlu²⁰⁾ who described similarly high correction magnitudes. However, it is important to highlight that previous series by Eidelman et al.,¹⁹⁾ Yılmaz and Bakırcıoğlu,²⁰⁾ Malik et al.,²¹⁾ and Rozbruch²²⁾ focused exclusively on valgus deformities, without addressing varus corrections.

In contrast, our study includes a significant number of varus deformities, achieving large corrections both in MAD and angular parameters. The only previous report including varus deformities is that of Bar-On et al.,²³⁾ but the magnitude of varus correction in their series was modest compared to ours. Our findings thus contribute new and valuable evidence supporting the efficacy of fixator-assisted techniques for the correction of substantial varus deformities, an area with limited prior documentation.

Rotational corrections achieved in our femoral osteotomies (mean, 53.3°; range, 35°–80°) and tibial derotations (mean, 36.3°; range, 29°–50°) were notable, exceeding the typical corrections reported by Bar-On et al.,²³⁾ who described derotations between 30° and 45°. These substantial corrections were achieved acutely without residual deformities, highlighting the robustness and precision of our approach in addressing complex multiplanar deformities. These correction magnitudes illustrate the practical correction limits that can be safely achieved with fixator-assisted techniques in adolescent patients.

The operative time observed in the FAN group was longer than typically reported for standard intramedullary nailing procedures. This difference is likely explained by the complexity of several cases included in this cohort, particularly patients with skeletal dysplasias such as XLHR and fibrous dysplasia. In these patients, altered bone morphology and reduced bone quality made canal preparation and nail insertion more technically demanding than in normal bone. In addition, the FAN technique requires several additional steps compared with plating procedures, including canal preparation, reaming, and proximal and distal locking of the nail. When considering only the idiopathic deformity cases, the mean operative time was approximately 3 hours and 31 minutes, suggesting that the longer overall mean operative time of the FAN group was influenced by the inclusion of these more complex pathological conditions.

Regarding FAN techniques, our findings are consistent with the results reported by Wahab et al.,²⁴⁾ showing that FAN effectively corrects complex deformities and facilitates early weight-bearing. Although Wahab et al.²⁴⁾ reported mean MAD improvements from 38.9 mm to 17.5 mm, our series achieved comparable or greater corrections with early mobilization and satisfactory clinical recovery. Additionally, our successful use of DL-FAN in 1 patient aligns with observations by Chaudhary and Lakhani²⁵⁾ who supported this method for treating double-apex deformities with minimal external fixation time. Moreover, our approach is technically supported by the principles outlined by Kocaoglu and Bilen,²⁶⁾ who emphasized that FAN combines the precision of external fixation with the stability and comfort of internal fixation.

Our cohort notably included a significant proportion of patients with skeletal dysplasias and metabolic bone disorders, populations that often present increased challenges for bone healing and deformity correction. Despite these complexities, our results demonstrated consistent bone union and mechanical axis restoration, supporting the versatility and stability provided by FALP and FAN techniques in these high-risk groups, as previously highlighted by Eralp et al.¹⁸⁾ These conditions are frequently associated with altered bone quality and impaired remodeling, which can complicate deformity correction.

Beyond coronal plane corrections, our study reinforces the importance of addressing sagittal and rotational deformities, often underrecognized but biomechanically significant. Sagittal corrections of up to 22° in femoral hyperextension and systematic derotation for severe femoral anteversion and tibial torsion were successfully performed, expanding the traditional scope of fixator-assisted techniques. Sagittal corrections were achieved exclusively using the FALP technique. In our series, only 2 sagittal deformities were treated. One occurred after a fracture of a previous distraction regenerate, in which intramedullary nailing was technically challenging due to the altered bone structure. The second case corresponded to a sequela of osteomyelitis previously treated with a vascularized fibular graft, which significantly modified the medullary canal and did not allow safe intramedullary nailing. For these reasons, plating was selected in both cases to achieve stable fixation and precise correction.

Our experience confirmed that temporary external fixation ensures optimal control of coronal, sagittal, and rotational deformities without the morbidity associated with prolonged external fixation, as also demonstrated by Vandenbulcke et al.²⁷⁾ in a preclinical model.

From a technical perspective, the use of fixator-assisted techniques allowed precise control of translation at the osteotomy site, which is crucial when the osteotomy is performed away from the deformity apex, as often occurs in distal femoral valgus deformities. This ability to achieve planned translation intraoperatively, which was confirmed radiographically, likely contributed to the high degree of correction accuracy observed in our series and reinforces the technical recommendations made by Rozbruch²²⁾ and Bar-On et al.²³⁾ The temporary external fixator provides precise intraoperative control of rotation, translation, and angulation, allowing accurate correction before definitive internal fixation is applied.

Implant removal is relatively common in adolescents due to local discomfort related to hardware prominence, particularly in metaphyseal regions. In the early part of our series, a plate designed for adult distal femoral fractures was used and occasionally caused distal irritation. Later, a lower-profile plate was adopted, after which implant-related discomfort appeared to decrease, although this was not formally analyzed in the present study.

One patient in the tibial group developed compartment syndrome after correction of a large torsional deformity. Although this complication was successfully treated with fasciotomies, it highlights the importance of careful postoperative monitoring in cases involving substantial tibial rotational correction.

Despite these encouraging results, certain limitations must be acknowledged. The relatively small sample size and the heterogeneity of underlying etiologies of deformities may affect the generalizability of the findings. Another limitation of this study is the small size of some subgroups, particularly the tibial FALP group and the FAN group. This limited sample size reduces the statistical power for comparative analysis between groups. Therefore, the results should be interpreted primarily as descriptive findings illustrating the feasibility and outcomes of fixator-assisted techniques, rather than as definitive comparative conclusions. The mean follow-up of 20.9 months was sufficient to assess the radiological and functional outcomes in this cohort. Some patients were administratively discharged from follow-up at 18 years of age, as our institution is a pediatric hospital, although all had achieved radiographic union and stable alignment at that time.

In our practice, fixator-assisted techniques are routinely used for distal femoral metaphyseal osteotomies to facilitate accurate intraoperative alignment control. FAN is preferentially used in complex deformities requiring diaphyseal osteotomy, particularly when multiplanar correction is needed. In tibial deformities, the use of fixator-assisted techniques is more selective and is generally reserved for more complex cases requiring precise control of alignment.

Another limitation of this study is the absence of formal functional or patient-reported outcome measures. As this work primarily focuses on surgical technique and radiographic correction, the analysis was centered on alignment parameters. Nevertheless, all patients achieved clinical recovery with return to their activities of daily living during follow-up. Future studies including standardized functional outcomes and patient-reported measures would provide a more comprehensive evaluation of these techniques. Therefore, functional outcomes in this study should be interpreted cautiously and are primarily based on clinical recovery and return to daily activities rather than standardized functional scores.

Another potential limitation is the possibility of selection bias, as fixator-assisted techniques are often used for deformities requiring precise correction. In our practice, FALP is routinely used for distal femoral metaphyseal osteotomies, as it facilitates accurate alignment correction and stable fixation close to the joint. In contrast, in tibial deformities, the use of fixator-assisted techniques was more selective, typically reserved for more complex cases where precise alignment control was required. These factors should be considered when interpreting the results. In addition, the exclusion of patients with incomplete follow-up may introduce selection (attrition) bias, as patients with less favorable outcomes may be more likely to be lost to follow-up. Unfortunately, detailed data on excluded cases were not available, which represents a limitation of the present study.

Finally, the absence of a control group limits direct comparison with gradual correction techniques, such as Taylor Spatial Frame or other hexapod systems. Nevertheless, this study was not designed for comparative analysis but rather to define indications, achievable correction limits, and reproducible surgical principles of fixator-assisted plating and nailing in adolescents.

FALP and FAN provide accurate, versatile, and safe options for the acute correction of complex multiplanar lower limb deformities in adolescents. These techniques allow precise 3-dimensional correction, reliable bone healing, and early return to daily activities. They may represent a useful alternative to gradual correction methods in appropriately selected patients, particularly when prolonged external fixation is undesirable.