
==== Front
BMC Musculoskelet Disord
BMC Musculoskelet Disord
BMC Musculoskeletal Disorders
1471-2474
BioMed Central London

39223554
7799
10.1186/s12891-024-07799-y
Systematic Review
A systematic review and meta-analysis:comparing the efficacy of the Ilizarov technique alone with lengthening over a nail for lower extremity bone defects
Tan Fei 12
Yang Cuixian 3
Zeng Jiankang 12
Li Jiahuan 12
Li Peijie 12
Qiao Yongjie 1
Wang Jing 12
Zhang Jiangming 12
Xie Dong 12
Ye Shuo 1
Zhou Shenghu zhoushenghu120@163.com

1
1 https://ror.org/05tf9r976 grid.488137.1 0000 0001 2267 2324 Department of Joint Surgery, The 940th Hospital of Joint Logistic Support Force of Chinese People’s Liberation Army, Lanzhou, Gansu China
2 grid.418117.a 0000 0004 1797 6990 Gansu University of Chinese Medicine, Lanzhou, Gansu China
3 https://ror.org/04ypx8c21 grid.207374.5 0000 0001 2189 3846 Zhengzhou University, Zhengzhou, Henan China
2 9 2024
2 9 2024
2024
25 69931 3 2024
20 8 2024
© The Author(s) 2024
2024
https://creativecommons.org/licenses/by-nc-nd/4.0/ Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.
Purpose

The task faced by surgeons becomes significantly more challenging when they encounter lower extremity bone defects due to a variety of causes requiring lengthening. The most discussed and successful approach is the Illizarov technique, or lengthening over a nail (LON):distraction osteogenesis is also widely performed with monoliteral external fixators and intramedullarylengthening nails have increasingly been used in the last decade.

Methods

The data were collected from PubMed, Cochrane Library, Embase, and the Web of Science for all available studies comparing the outcomes of Ilizarov technique alone and LON technique (from January 1, 1997, to November 30, 2023). The outcomes of interest encompassed the external fixation index (EFI) (month/cm), mean duration of follow-up (MFT) (month), length gained (LG) (cm), consolidation index (CIx) (month/cm), and bone healing index (BHI) (month/cm).Complications include pin tract infection rate (PTI), axial deviation rate (AD), occurrence of intramedullary infection (II), delayed consolidation rate (DC), as well as data categorized into three levels of problems, obstacles, and sequelae based on the severity of complications.Two reviewers independently assessed each study for quality and extracted data. The case–control or respective cohort studies were evaluated using the Newcastle–Ottawa scale (NOS) to determine their techniqueological rigor.The Cochrane Collaboration’s risk assessment tool was employed to perform quality evaluations for randomized controlled trials.

Results

This review included thirteen studies comprising a total of 629 patients.The external fixation index (month/cm) was significantly smaller in the LON technique compared to the Ilizarov technique alone [Mean Difference(MD) = -29.59, 95% CI -39.68–-19.49, P < 0.00001].In terms of the mean follow-up time(month) (MD = -0.92, 95% CI -3.49–1.65, P = 0.57), length gained (cm) (MD = -0.87, 95%CI -2.80–1.07, P = 0.38), consolidation index (month/cm) (MD = 0.66, 95% CI -3.44–4.77, P = 0.75), and bone healing index (month/cm) (MD = -3.33, 95% CI -13.07–6.41, P = 0.5), there were no significant differences observed. The LON technique exhibited a lower incidence of axial deviation [Odds Ratio(OR) = 0.06, 95%CI 0.03–0.16, P < 0.00001] and pin tract infection (OR = 0.30, 95%CI 0.18–0.50, P < 0.00001) compared to the Ilizarov technique alone.The remaining complications, such as intramedullary infection rate (OR = 0.93, 95%CI 0.42–2.06, P = 0.85) and delayed consolidation rate(OR = 0.61, 95%CI 0.20–1.86, P = 0.38), did not exhibit statistically significant differences.Our findings demonstrated that the LON technique results in lower incidences of problems (38.5%vs.58.6%) and sequelae (16.6% vs.30.9%) when compared to the Ilizarov technique alone. However, the rates of obstacles (32.4% vs.32.3%) were comparable between the two methods.

Conclusions

Our findings indicate that patients treated with the LON technique experienced significantly shorter external fixation durations and a lower incidence of complications (e.g., pin tract infections and axial deviation) compared to those treated with the Ilizarov technique alone. Other outcome metrics showed no significant differences between the two techniques. However, the LON technique offers substantial benefits, including reduced external fixation times and increased comfort, which enhance patient compliance. In conclusion, the LON technique is a safe, reliable, and effective method for treating tibial and femoral defects.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-024-07799-y.

Keywords

Ilizarov
Lengthening over a nail
Lower extremity lengthening
Meta analysis
issue-copyright-statement© BioMed Central Ltd., part of Springer Nature 2024
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pmcIntroduction

Segmental long bone defects present significant challenges for limb reconstruction surgeons, necessitating bone transport procedures to address bone loss. Such defects may arise from open fractures [1], the excision of necrotic bone in chronic osteomyelitis [2], the need for truncation lengthening in cases of poliomyelitis deformities [3], and idiopathic short stature. A predominant cause is large segmental bone defects resulting from open trauma. Without further intervention, these defects are unlikely to heal. Unhealed defects severely impair the patient’s quality of life, lead to psychological issues, and hinder their integration into normal society.

Professor Ilizarov, a Soviet physician, pioneered the Ilizarov Technique in 1950 [4–6]. This method, founded on the principles of distraction osteogenesis, aims to lengthen limbs and correct discrepancies. It employs external fixators to enhance local vascular distribution while maintaining the limb’s weight-bearing capacity during bone transportation. The technique boasts a bone healing rate exceeding 90% and is extensively documented and utilized for bone transport and limb lengthening [7, 8]. Nevertheless, the prolonged use of external fixators can cause significant discomfort, restricting patients’ ability to engage in early functional exercises and potentially leading to joint contractures [9, 10]. This discomfort can psychologically affect patients, increasing frustration and reducing compliance. Moreover, the extended use of fine Kirschner wires that penetrate the limb and bone tissue is linked to a higher risk of pin tract infections [11].

Building upon the Ilizarov technique, various bone transfer methods have been developed to address bone defects in the lower extremities. These include the Lengthening Over Nailing (LON) technique [12], Lengthening and Then Nail (LATN) [13], and Lengthening and Then Plate (LATP) [14]. A study by Paley et al. [15] demonstrated the efficacy of the LON technique in treating lower extremity bone defects. This method reduces the duration of external fixator usage, offering a more convenient approach. Subsequent clinical applications have shown that employing the LON technique for bone defects caused by fractures or infections yields satisfactory results, notably decreasing the overall time required for external fixation, effectively repairing substantial bone defects, and minimizing related complications [16–18]. However, challenges persist with the LON technique, such as potential risks of intramedullary infection, intramedullary nail breakage, and locking screw failures [19, 20].

Choosing the optimal treatment for lower-extremity bone defects continues to be a significant challenge for clinicians. While previous studies have compared the Ilizarov technique alone to the LATN technique, to date, no comprehensive meta-analysis or systematic review has specifically evaluated the efficacy and outcomes of the LON technique against the Ilizarov technique alone. The aim of this study is to conduct a comparative analysis of the efficacy and outcomes of the LON technique relative to the Ilizarov technique alone in treating lower extremity bone defects.

Methods

The prospero registration number is CRD42023482000.

Search strategy

The present article was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A comprehensive search was conducted across English language databases, including PubMed, Web of Science, Cochrane Library, and Embase, using Medical Subject Headings (MESH) terms “Ilizarov Technique” and “Fracture Fixation, Intramedullary,” to identify relevant literature. The search included data up to November 30, 2023, with no restriction on the language of publication. In addition, a comprehensive manual search was conducted to retrieve additional eligible studies from paper-based sources, and all gray literature, as well as references cited in included articles, were carefully screened.

Selection criteria

The criteria for inclusion were established as follows:

(1) The LON technique was used in the intervention technique and only the Ilizarov technique was used in the control technique; (2) the type of study consisted of a randomized controlled trial (RCT), a case–control study (CCS), a retrospective clinical study (RCS), or a prospective clinical study; (3) at least one of the following outcome measures was reported: external fixation index (EFI), mean follow-up time (MFT), length gained (LG), consolidation index (CIx), bone healing index (BHI), and complications such as axial deviation (AD), pin tract infection (PTI), intramedullary infection (II), delayed consolidation (DC), problems, obstacles, and sequelae data. These data are either fully or partially available.and (4)The etiology of bone defects in the literature included could be open fractures, defects due to chronic osteomyelitis, limb length discrepancies, or idiopathic short stature osteotomy defects, but complete control of chronic osteomyelitis was required. All bone defects gained a lengthening length of ≤ 8 cm.

The exclusion criteria were as follows:

(1) Non-peer-reviewed publications are excluded from consideration.(2) certain study designs, such as non-human trials, observational studies, case reports, case series, review articles, and letters to the editor, are not included in this analysis.(3) reviews, letters, and recommendations are also excluded from the scope of this study. (4) in cases where the full text cannot be obtained or the original data is incomplete, those sources will not be considered.

Data extraction

Two academics conducted independent literature reviews, with any disputes resolved by a third reviewer. The following data was extracted from the included studies: (1) first author names, study period, author country, study type, number of cases, and patients’ age; (2) external fixation index (EFI), mean follow-up time (MFT), length gained (LG), consolidation index (CIx), bone healing index (BHI), as well as complications such as axial deviation (AD), pin tract infection (PTI), intramedullary infection (II), delayed consolidation (DC), and problems, obstacles, or sequelae. Secondly, we gathered a range of secondary outcome measures, including the etiology of long bone defects, sex, age, duration of surgery, amount of blood loss, average time to achieve full weight-bearing status, mean size of bone defects, excellent and good functional outcomes assessment results, as well as evaluations for knee and ankle dorsiflexion contractures (Supplementary Material 1). The EFI, which calculates the ratio between the duration of external fixation (in months) and the total bone delivery size (in centimeters).Furthermore, in cases where the data were incomplete or ambiguous in the studies reviewed, efforts were made to establish communication with the respective investigators for clarification purposes.

Study quality assessment

The methodological quality of each included study was assessed by two independent reviewers using the Newcastle–Ottawa Scale (NOS) [21], a tool commonly employed for evaluating the quality of cohort and case–control studies. Within this assessment, one of the domains considered was case definition, which encompassed selecting study cohorts, comparing cohorts, and determining outcomes. A NOS score of ≥ 6 indicates high quality, with a maximum total score of 9. For randomized controlled trials, the Cochrane Collaboration’s risk assessment tool was utilized to conduct quality assessments.

Statistical analysis

The statistical data were calculated using the Review Manager software (Cochrane Collaboration, Copenhagen, Denmark) and Stata17 software (Stata Corp., College Station, TX, USA). Weighted mean difference (WMD) and 95% confidence interval (CI) were utilized for continuous variables (EFI, MFT, LG, CIx, and BHI), while odds ratios (OR) and 95% confidence intervals (CI) were employed for categorical variables (pin tract infection, axial deviation, intramedullary infection, and delayed consolidation). Weighted averages were employed to calculate aggregated data, which were subsequently presented as either numerical values or proportions based on the sample size of each individual study. We conducted meta-analyses for relevant outcomes in each study using inverse variance statistics to combine effect sizes and apply logarithmic transformations when necessary. The combined effect sizes were expressed as percentages of their respective 95% confidence intervals (CIs). Heterogeneity and the proportion of variation between studies were quantified using the I2 statistic. I2 values below 50%, between 50 and 75%, and above 75% were categorized as low, moderate, and high heterogeneity, respectively. A P-value ≥ 0.05 and an I2 value < 50% indicated no statistical heterogeneity among the studies. A random-effects model was employed in cases of moderate or high heterogeneity; otherwise, a fixed-effects model was utilized. Sensitivity analysis was conducted to assess the robustness of the findings, if deemed necessary. Additionally, forest plots were employed to illustrate the results of each study and evaluate pooled estimates, respectively, while funnel plots were used to assess publication bias. The funnel plots were evaluated to identify potential publication bias. Funnel plots can only intuitively determine the presence of publication bias, and the results may be biased. This prompted us to perform the Begg test as a supplementary assessment.

Results

Search results

The initial search yielded a total of 784 articles, with 248 retrieved from PubMed, 258 from Web of Science, 9 from Cochrane Library, and 266 from Embase. Furthermore, the manual search identified three studies that met the inclusion criteria. After removing duplicates, a total of 563 studies remained. Among these, 500 were excluded based on abstract and title screening. Subsequently, we retrieved the remaining 63 full-text papers for a more comprehensive analysis. Out of these, 50 papers were excluded due to various reasons, including outcome does not meet the request (n = 33), inability to calculate results from available data (n = 4), and missing data on key outcome indicators (n = 13). The meta-analysis finally included thirteen articles (Fig. 1).Fig. 1 Literature searching procedure delineated in the form of a flow chart

Figure 1 shows the flowchart of the study selection process.

Demographic characteristics

Thirteen studies were conducted across eight countries, including the United States (one study), Japan (one study), Turkey (two studies), the United Kingdom (one study), Russia (one study), China (three studies), South Korea (three studies), and Egypt (one study). In limb lengthening surgery, a total of 308 cases using the Ilizarov technique alone and 321 cases using the combined technique were identified.In the 13 included studies, the follow-up ranged from 15.3 to 70 months, and the mean age of the patients was 30 years. The indications for limb lengthening were categorized into four main types: open fractures, defects due to chronic osteomyelitis, limb length discrepancies, or idiopathic short-stature osteotomy defects.Five studies conducted by Paley [15], Burghardt, et al. [22] specialized in limb lengthening for post-traumatic bone defects. Two studies conducted by Eralp [23], Sen et al. [24], specialized in limb lengthening for bone defects causing chronic osteomyelitis. Three studies conducted by Song [25], Watanabe, et al. [20] specialized in limb lengthening for lower limb inequality. Three studies conducted by Park and Sun specialized in limb lengthening for idiopathic short stature.For more information on the characteristics of the included studies, see Supplementary Table 1.

Quality assessment results

All studies [15, 20, 22–32], including 11 RCSs and 2 RCTs, were of high quality with NOS scores ≥ 6, involving 321 patients in the LON technique and 308 patients in the Ilizarov technique. The quality assessment and basic characteristics of the selected trials are shown in Tables 1 and 2. The results of LON technique pooled and combined with Ilizarov technique are shown in Table 3. According to the funnel plot (Fig. 4A, B, C, D, E), the publication bias of some outcome indicators could not be directly judged. Therefore, we performed the Begg test, and the results showed that all outcome indicators had no publication bias. Table 1 Characteristics of the included studies

Author	Year	Country	Study period	Study
type	Sample size	Numbers of femora or tibia	Mean age (years)	Mean follow-up time(month)	NOS
Score	Outcome	
Ilizarov	LON	Ilizarov	LON	Ilizarov	LON	Ilizarov	LON	measures	
Paley	1997	England	2003–2008	RCS	31	29	femora(32)	femora(32)	25	26	44.4	33.6	8	EFI,MFT,LG,CIx,PTI,AD,II,DC	
Song	2005	Korea	NA	RCS	11	3	tibia(11)	tibia(3)	33	33	66	66	7	EFI,MFT,LG,BHI,PTI,AD,DC	
Watanabe	2005	Japan	NA	RCS	16	8	tibia(17)	NA	14.6	22.2	48	42	6	EFI,MFT,LG,CIx,PTI,AD,DC	
Park	2008	Korea	1996–2006	RCS	16	28	tibia(32)	tibia(56)	23.4	22.3	40	48	8	EFI,MFT,LG,BHI,PTI,AD,DC	
Sun	2011	Korea	1995–2003	RCS	26	26	tibia(49)	tibia(49)	21.2	23	25.1	23.6	8	EFI,MFT,LG,BHI,PTI,AD,DC	
Guo	2012	China	2009–2011	RCT	13	26	tibia(23)	tibia(51)	22.7	25.4	38.4	40.8	8	EFI,MFT,LG,CIx,PTI,AD,DC	
ErALP	2012	Turkey	1998–2009	RCS	32	17	tibia(32)	tibia(17)	41	39	35.7	28.6	7	EFI,MFT,LG,CIx,II,DC	
EL-Husseini	2013	Egypt	2009–2011	RCS	13	15	femora:tibia(9:7)	femora:tibia(9:6)	28.4	31.3	18	18	-	EFI,MFT,LG,CIx,PTI,AD,II,DC	
Burghardt	2015	USA	NA	RCS	17	16	tibia(19)	tibia(19)	27	27	23	23	7	EFI,MFT,LG,CIx,AD,II,DC	
Yang	2018	China	2013–2016	RCT	35	36	femora(35)	femora(36)	34.9	33.1	31	31	-	MFT,PTI	
Sen	2019	Turkey	2003–2014	RCS	15	17	femora(15)	femora(17)	42	39	70	66	8	EFI,MFT,PTI,AD,II,DC	
Borzunov	2022	Russia	2012–2016	RCS	6	14	femora(6)	femora(14)	30.7	33	NA	NA	8	EFI,LG,PTI,II,DC	
Xu	2023	China	2018–2021	RCS	21	12	tibia(21)	tibia(12)	48.8	47.2	17.1	15.3	6	EFI,MFT,PTI,DC	
NA Not acquire, RCT Randomized controlled trials, RCS Retrospective clinical studies, LON lengthening over a nail, NOS Newcastle–Ottawa Scale, EFI External fixation index, MFT Mean follow-up time, LG Length gained, CIx Consolidation index, BHI Bone healing index, AD Axial deviation, PTI Pin tract infection, II Intramedullary infection, DC Delayed consolidation

Table 2 Risk of bias of the randomized controlled trials with the cochrane risk of bias tool

Lead Author
(Year)	Sequence
Generation	Allocation
Cincealment	Blinding of Participants	Incomplete
Outcome Data	Selective Outcome Reporting	Other Source of Bias	Total Risk
of Bias	
EL-Husseini (2013)	Adequate	Adequate	Yes	Adequate	Free	No	Low	
Yang (2018)	Adequate	Adequate	Yes	Inadequate	Free	No	Low	

Table 3 Comparison of postoperative outcomes between LON and Ilizarov procedures

Outcome or Surbgroup	Studies	Participants	Statistical methods	I2	Effect Estimate	P value	
Ilizarov	LON	
External fixator index(EFI)	12	217	211	WMD (IV, Random, 95% CI)	96%	-29.59 [-39.68, -19.49]	P＜ 00001	
Mean follow-up time(MFT)	12	246	233	WMD (IV, Random, 95% CI)	61%	-0.92 [-3.49, 1.65]	P＝0.48	
Length gained(LG)	10	181	182	WMD (IV, Random, 95% CI)	97%	-0.87 [-2.80, 1.07]	P＝0.38	
Consolidation index(CIx)	6	107	126	WMD (IV, Random, 95% CI)	66%	0.66 [-3.44, 4.77]	P＝0.75	
Bone healing index(BHI)	3	53	57	WMD (IV, Fixed, 95% CI)	12%	-3.33 [-13.07, 6.41]	P＝0.50	
Pin tract infection(PTI)	11	203	214	OR(M-H, Fixed, 95% CI)	47%	0.30 [0.18, 0.50]	P＜ 00001	
Axial deviation(AD)	9	158	168	OR(M-H, Fixed, 95% CI)	0%	0.06 [0.03, 0.16]	P＜00001	
Intramedullary infection(II)	6	114	108	OR(M-H, Fixed, 95% CI)	43%	0.93 [0.42, 2.06]	P＝0.85	
Delayed consolidation(DC)	12	217	211	OR(M-H, Random, 95% CI)	56%	0.61 [0.20, 1.86]	P＝0.38	

Outcomes analysis

External Fixation Index (EFI)

The EFI was recorded in twelve studies[15, 20, 22–31]. Data were analyzed using a random-effects model, and forest plots showed high heterogeneity (I2 = 96%, P < 0.00001), revealing a significant difference between the two techniques (MD = -29.59, [95% CI -39.68 to -19.49]; I2 = 96%, P < 0.00001). A meta-analysis of these twelve studies demonstrated that the LON technique exhibited a lower EFI compared to the Ilizarov technique alone (Fig. 2A). This finding holds clinical significance as it indicates that the duration of external fixation was shorter in the LON technique than in the Ilizarov technique. A visual assessment of the funnel plot indicated the presence of a slight publication bias (Fig. 4A). However,the Begger’s test was not statistically significant (P = 0.732).Fig. 2 Comparison of external fixation index results (A), mean follow-up time results (B), length gained results (C), consolidation index results (D), and bone healing index results (E) between the LON and Ilizarov techniques

Mean Follow-up Time(MFT)

Twelve studies[15, 20, 22–25, 27–32] involving 479 patients (233 in the LON technique and 246 in the Ilizarov technique) reported the MFT. The pooled results demonstrated that there was no significant difference in MFT between the two treatment techniques (MD = -0.92, [95% CI -3.49–1.65]; I2 = 61%; P = 0.48) with low heterogeneity (Fig. 2B). The results of the data showed no statistical differences in MFT between the two techniques. A visual assessment of the funnel plot indicated the presence of a slight publication bias (Fig. 4B). However, Begger’s test was not statistically significant (P = 0.945).

Length Gained (LG)

We performed a meta-analysis comparing the LG in patients with the LON technique versus the Ilizarov technique, including ten studies[15, 20, 22, 23, 25–30]. The random-effects model analysis showed no significant difference between the LON and Ilizarov techniques (MD = -0.87, [95%CI -2.80–1.07]; I2 = 97%; P = 0.38). The results of the data showed no significant difference in LG between the two techniques (Fig. 2C). A visual assessment of the funnel plot indicated the presence of a slight publication bias (Fig. 4C). However, Begger’s test was not statistically significant (P = 1.00).

Consolidation Index (CIx)

Six studies[15, 20, 22, 23, 27, 28] reported CIx, including 233 patients. There were 126 patients in the LON technique and 107 patients in the Ilizarov technique. Heterogeneity analysis showed that there was no significant statistical heterogeneity between these studies (MD = 0.66, 95%CI -3.44–4.77; I2 = 66%, P = 0.75). The results of the data showed no significant difference in CIx between the two techniques (Fig. 2D).

Bone Healing Index (BHI)

Three studies [25, 29, 30] involving 110 patients (57 in the LON technique and 53 in the Ilizarov technique) reported the BHI. The pooled results demonstrated that there was no significant difference in BHI between the two treatment techniques (MD = -3.33, [95%CI -13.07–6.41]; I2 = 12%; P = 0.50) with low heterogeneity (Fig. 2E). Therefore, there were no statistical differences in BHI between the two techniques.

Adverse events

Thirteen studies [15, 20, 22–32] reported adverse events. Table 4 summarizes the incidence of axial deviation (AD), needle tract infection (PTI), intramedullary infection (II), and delayed consolidation (DC). Table 4 The statistical data for complications

Complication	Pin tract infection(%)	Intramedullary infection(%)	Axial deviation(%)	Delayed consolidation(%)	
Authors	Ilizarov	LON	Ilizarov	LON	Ilizarov	LON	Ilizarov	LON	
Paley 1997	0	3.4	6.4	3.4	9.6	0	9.6	6.8	
Song 2005	9	66	0	0	45	0	45	100	
Watanabe 2005	62.5	12.5	0	0	12.5	0	12.5	0	
Park 2008	56.3	46.4	0	0	31.3	0	31.3	0	
Sun 2011	80.8	50	0	0	96.2	11.5	15.4	53.8	
Guo 2012	84.6	30.8	0	0	7.7	0	15.4	3.8	
ErALP 2012	0	0	12.5	0	0	0	15.6	0	
EL-Husseini 2013	69.2	33.3	0	23.1	33.3	0	23.1	0	
Burghardt 2015	100	100	0	23.5	43.8	0	0	6.3	
Yang 2018	25.7	2.8	0	0	0	0	0	0	
Sen 2019	93.3	52.9	46.7	17.6	20	5.9	40	5.9	
Borzunov 2020	16.7	14.3	0	16.7	0	0	0	16.7	
Xu 2022	4.8	8.3	0	0	0	0	8.3	8.3	
Total	42.4	26.2	11.4	11.1	35.4	2.3	16.6	11.4	

Axial Deviation (AD)

Nine[15, 20, 22, 24, 25, 27–30] studies compared the rate of AD in patients with the LON technique versus the Ilizarov technique. Meta-analysis of these 9 studies showed that the rate of AD was significantly higher in the Ilizarov technique than that in the LON technique (56/158 vs. 4/168; OR 0.06, [95% CI 0.03–0.16]; I2 = 0%; P < 0.00001) (Fig. 3A).Fig. 3 Comparison of axial deviation results (A), pin tract infection results (B), intramedullary infection results (C), and delayed consolidation results (D) between the LON and Ilizarov techniques

Pin Tract Infection (PTI)

A total of eleven studies [15, 20, 24–32] provided data comparing the PTI rate in patients with LON versus the Ilizarov technique. The meta-analysis revealed that patients with the Ilizarov technique dramatically increased the risk of PTI compared to patients with the LON technique (86/203vs.56/214;OR 0.30, [95%CI 0.18–0.50];I2 = 47%;P < 0.00001) (Fig. 3B). A visual assessment of the funnel plot indicated the presence of a slight publication bias (Fig. 4D). However,the Begger’s test was not statistically significant (P = 0.119).

Intramedullary Infection (II)

Five studies [15, 22–24, 26, 27] provided data comparing the intramedullary infection rate in patients in the LON technique versus the Ilizarov technique. The meta-analysis demonstrated that patients in the LON technique showed no statistically significant difference compared to the Ilizarov technique (12/108 vs.13/114; OR 0.93, [95% CI 0.42–2.06]; I2 = 43%; P = 0.85) (Fig. 3C).

Delayed Consolidation (DC)

Twelve studies [15, 20, 22–31] reported delayed consolidation between LON technique patients and Ilizarov technique patients. The rate of delayed consolidation after surgery showed no statistical difference between LON technique patients and Ilizarov technique patients (24/211 vs. 36/217; OR 0.61, [95% CI 0.20–1.86]; I2 = 56%; P = 0.38) (Fig. 3D). A visual assessment of the funnel plot indicated the presence of a slight publication bias (Fig. 4E). However, the Begger’s test was not statistically significant ( P = 0.837).Fig. 4 Funnel plots show the results of the external fixation index (A); mean follow-up time (B); length gained (C); pin tract infection (D); and delayed consolidation (E)

Subgroup analysis

When total heterogeneity is high and within-group heterogeneity is low, this indicates that the grouping factor is significant for heterogeneity.First, the article categorized the etiology of bone defects into defects due to open fractures, defects due to chronic osteomyelitis, and defects due to limb length discrepancy and idiopathic short stature osteotomies. In order to exclude the confounding factors mentioned above, the authors performed subgroup analyses of EFI, LG, MFT, and DC. The results showed that the four different etiologies were not significant factors in their heterogeneity (Table 5). Second, we conducted subgroup analyses of EFI, LG, MFT, and DC according to different regions, and the results showed that articles published in different regions were also not a significant factor in the heterogeneity of this study (Table 5). Finally, there may be other reasons for the source of heterogeneity, such as the fact that the literature is all retrospective studies and the included literature itself. Table 5 Subgroup analysis

Subgroup	External fixator index (EFI)	Length gained (LG)	
literatures	MD[95%CI]	P values	I2	literatures	MD[95%CI]	P values	I2	
Bone defect causes	
 Total	12	-29.59 [-39.68, -19.49]	0.00001	96%	10	-0.87 [-2.80, 1.07]	0.38	97%	
 Traumatic	5	-25.91 [-42.91, -8.92]	0.003	98%	4	0.05 [-0.35, 0.46]	0.80	3%	
 Chronic osteomyelitis	2	-28.47 [-51.10, -5.83]	0.01	92%	1	1.70 [-0.42, 3.82]	0.12	-	
 Limb-length discrepancy	2	-28.47 [-51.10, -5.83]	0.16	97%	2	0.81 [-0.94, 2.57]	0.36	72%	
 Idiopathic Short Stature	3	-21.28 [-36.12, -6.45]	0.005	81%	3	-4.06 [-12.58, 4.46]	0.35	99%	
Regions	
 Total	12	-29.59 [-39.68, -19.49]	0.00001	96%	10	-0.87 [-2.80, 1.07]	0.38	97%	
 Asia	6	-29.16 [-46.68, -11.63]	0.001	96%	5	-2.07 [-6.58, 2.44]	0.37	98%	
 Europe	4	-31.89 [-42.47, -21.30]	0.00001	84%	3	0.32 [-0.31, 0.94]	0.32	19%	
 Other regions	2	-31.77 [-53.92, -9.62]	0.005	65%	2	-0.51 [-1.75, 0.72]	0.41	19%	
Subgroup	Mean follow-up time (MFT)	Delayed consolidation (DC)	
literatures	MD[95%CI]	P values	I2	literatures	OR[95%CI]	P values	I2	
Bone defect causes	
 Total	9	-0.92 [-3.49, 1.65]	0.48	61%	11	0.61 [0.20, 1.86]	0.38	56%	
 Traumatic	3	-3.08 [-7.59, 1.43]	0.18	77%	4	0.82 [0.25, 2.73]	0.75	0%	
 Chronic osteomyelitis	1	-6.78 [-18.93, 5.37]	0.27	0%	1	0.11 [0.02, 0.66]	0.02	0%	
 Limb-length discrepancy	2	-0.36 [-5.48, 4.76]	0.89	0%	3	1.67 [0.07, 38.04]	0.75	49%	
 Idiopathic Short Stature	3	2.39 [-3.15, 7.94]	0.40	82%	3	0.45 [0.02, 12.53]	0.64	85%	
Regions	
 Total	11	-0.92 [-3.49, 1.65]	0.48	61%	9	0.61 [0.20, 1.86]	0.38	56%	
 Asia	7	0.64 [-2.17, 3.45]	0.66	51%	5	0.91 [0.15, 5.49]	0.91	67%	
 Europe	3	-10.17 [-14.98, -5.36]	0.0001	0%	2	0.33 [0.10, 1.11]	0.07	0%	
 Other regions	1	0.00 [-2.48, 2.48]	0.0001	0%	2	0.55 [0.02, 17.89]	0.73	59%	

Sensitivity analysis

Sensitivity analyses were used to test the stability of the combined results. As shown, sensitivity results were stable for the external fixation index (Fig. 5A), mean follow-up time (Fig. 5B), length gained (Fig. 5C), and consolidation index (Fig. 5D), axial deviation (Fig. 6A), pin tract infection (Fig. 6B), intramedullary infection (Fig. 6C), and delayed consolidation (Fig. 6D).Fig. 5 Sensitivity analysis diagram of the external fixation index (A), mean follow-up time (B), length gained (C), and consolidation index (D) in high heterogeneity outcomes

Fig. 6 Sensitivity analysis diagram of the axial deviation (A), pin tract infection (B), intramedullary infection (C), and delayed consolidation (D) in high heterogeneity outcomes

However, by manually eliminating the literature one by one by Revman, the heterogeneity decreased to 25% after removing the Park (2008) [29] literature in LG and 21% after removing the Sun (2011) [30] literature in DC. These two pieces of literature were the source of heterogeneity for their respective outcome indicators.The remaining outcome indicators, such as EFI, MFT, and CI, had high heterogeneity but stable results by subgroup analysis and sensitivity analysis.

Discussion

Previous meta-analyses have highlighted the advantages of the LATN technique over the Ilizarov method alone. Sheridan et al. [33] utilized Kaplan–Meier survival curves to demonstrate that the mean time to external fixation removal in the Ilizarov-only group was 32.6 weeks (σ = 8.43, 95% CI 24.7–40.3), which is double that of the LATN group at 16.3 weeks (σ = 8.02, 95% CI 8.9–23.7), with a statistically significant difference (P = 0.0015). Additionally, Xu (2017) et al. [34] reviewed four retrospective cohort studies, revealing that external fixation duration was significantly reduced in the LATN group compared to the Ilizarov group, along with enhanced postoperative bone healing and restoration of lower limb function. Thus, our study aims to further this comparison by analyzing the Modified LON technique against the Ilizarov method to provide objective evidence for treating lower extremity bone defects.

Of the 13 studies [15, 20, 22–32] reviewed, all focused on tibial or femoral defects. Our systematic evaluation found that the LON technique generally results in shorter external fixation times, a lower incidence of axial deviation, and fewer pin tract infections compared to the Ilizarov method alone. There were no significant differences between the two groups concerning lengthening length, mean follow-up time, consolidation time, and bone healing, aligning with the findings of 12 included studies [15, 20, 22–26, 28–32]. Exceptionally, EL-Husseini et al. [27] reported a significantly longer mean consolidation time in the LON group.

The LON technique, specifically modified for tibial and femoral lengthening, is designed to shorten the duration of external fixation, promote early weight-bearing, prevent scab and newly formed bone breakage [10, 35], thus enabling quicker resumption of daily activities. The primary difference between the two methods is that while the Ilizarov technique requires external fixation until consolidation is complete, the LON method only during the distraction phase, thereby reducing the overall duration of fixation [36]. In all literature concerning bone lengthening, the external fixation index has been a reliable measure of healing time. In a 2023 study by Xu [31], the mean EFI for the LON technique was 0.58 ± 0.07 (months/cm), significantly lower than the 0.73 ± 0.15 (months/cm) for the Ilizarov technique. Oh CW et al. [8] also reported shorter average external fixation times with the LON technique for bone transfer in tibial or femoral defects, noting that a low EFI was associated with immediate frame removal after a prolonged distraction phase, concluding that this technique facilitates a swift return to daily activities with minimal complications. Similarly, our study demonstrated a much longer mean external fixation time using the Ilizarov technique.

Across the reviewed literature, external fixation durations were consistently shorter with the LON technique compared to the Ilizarov method alone. To identify factors influencing this disparity, we investigated potential reasons for the reduced external fixation time associated with the LON technique. A plausible explanation is that bone reaming induces significant osteoinductive debris and restores, or even enhances, periosteal blood flow within days. This increased blood flow likely promotes periosteum formation, thereby facilitating and accelerating the bone healing process [37, 38]. Moreover, the insertion of intramedullary nails appears to stimulate the production of small bone marrow proteins, such as VEGFA-10 [39], which aid in developing microvascular structures. Presently, mRNA corresponding to this protein has been detected in the marrow cavity. The combination of the Ilizarov method with intramedullary nailing has been shown to effectively promote bone healing. Rozbruch et al. [40] have demonstrated that reaming of the medullary cavity positively impacts distraction osteogenesis, though there is also evidence suggesting that medullary reaming can impair distraction osteogenesis.

In Guo’s (2012) study[28], excessive lengthening was found to cause malformation in regenerating bone. The literature indicates that higher percentages of bone lengthening correlate with increased risk of complications [41]. Kocaoglu et al. [42] established a threshold of 6 cm for total limb lengthening, beyond which the likelihood of complications increased. For defects exceeding 10 cm, trifocal segment transmission significantly reduced external fixator time and related complications [43]. In this study, the extent of lengthening reported in the literature was maintained within 8 cm, and a forest plot comparison revealed no significant differences in lengthening between the two groups, thereby discounting length as a confounding factor and strengthening the validity of the results. The LON technique maintains axial alignment and preserves normal force lines in the lower extremity bones. It has been documented that premature removal of the frame can result in secondary axial deviation. In this study, the incidence of axial deviation was markedly lower in the LON technique group than in the Ilizarov group, suggesting that early intramedullary nail fixation may prevent axial deviations.

Guo’s study (2012) [28] revealed a significant difference in the rate of pin tract infections between the Ilizarov and LON techniques (47.8% and 15.7%, respectively), with the Ilizarov group exhibiting a higher risk due to prolonged use of external fixation braces—a finding consistent with our results (OR = 0.32, 95% CI 0.12–0.85, P = 0.02).The LON technique has been associated with a significant risk of intramedullary infection, with reported incidence rates between 3 and 15%. To minimize this complication, it is advisable to prevent contact between the wire and intramedullary nails [15, 44]. Despite these precautions, deep infections can still occur [45]. In our study, the rate of intramedullary infections was comparable between the LON and the Ilizarov techniques, with isolated infections observed in both. We hypothesized that these were not due to wire and nail contact but rather local infection spread at the osteotomy site. Other studies have suggested that patients undergoing the LATN technique are more prone to infection at the time of intramedullary nail implantation [40], as prolonged external fixator wear may lead to pin tract infections, thereby increasing the risk of deep infections upon intramedullary nail insertion [46, 47]. Therefore, perioperative adverse events may be reduced with proper preoperative management of LATN techniques. During the perioperative period, pin tract infections should be aggressively managed to prevent deep infections in patients post-LATN [48, 49]. However, Sheridan et al. [33] reported that neither LATN nor LATP techniques resulted in higher rates of deep infections.

This study also categorized complications encountered in both techniques using the Paley scoring system. Among the 13 studies reviewed [15, 20, 22–32], Yang (2018) [32] and Xu (2023) [31] reported no problems, obstacles, or sequelae(Table 6). Our findings demonstrated that the LON technique results in lower incidences of problems (38.5%vs.58.6%) and sequelae (16.6% vs.30.9%) when compared to the Ilizarov technique alone. However, the rates of obstacles (32.4% vs.32.3%) were comparable between the two methods (Table 6). A random-effects meta-analysis of “problems” by Sheridan et al. [33] confirmed a significantly higher relative risk of problems with the Ilizarov technique (RR = 1.66, 95%CI 1.40–1.97, P < 0.001). Similarly, the relative risk of “sequelae” was also significantly higher with the Ilizarov technique (RR = 1.79, 95%CI 1.28–2.49, P = 0.001). However, for “obstacles,” there was no significant difference between the techniques (RR = 0.97, 95%CI 0.85–1.10, P = 0.621), aligning with our findings. Table 6 The number of problems, obstacles or sequelae

Complications	Problem	Obstacles	Sequelae	
Authors	Ilizarov	LON	Ilizarov	LON	Ilizarov	LON	
Paley 1997	54.8	29.3	29	32.2	14.5	12	
Song 2005	45.5	66.7	0	0	4.5	66.7	
Watanabe 2005	62.5	50	56.3	17.9	31.3	0	
Park 2008	59.4	62.5	53.3	58.9	9.3	1.8	
Sun 2011	75	36.5	55.9	50.5	89.7	44.2	
Guo 2012	76.9	36.5	11.5	3.8	0	0	
ErALP 2012	25	11.8	15.6	17.6	15.6	11.7	
EL-Husseini 2013	65.4	26.7	23.1	3.3	0	10	
Burghardt 2015	52.9	50	41.2	31.3	17.6	12.5	
Yang 2018	-	-	-	-	-	-	
Sen 2019	70	35.3	23.3	11.8	16.7	5.9	
Borzunov 2020	33.3	28.6	33.3	14.3	33.3	21.4	
Xu 2022	-	-	-	-	-	-	
Total	58.9	38.5	32.3	32.4	30.9	16.6	

Optimal bone healing and the restoration of lower limb function are paramount in treating bone defects. Deniz G. et al. [50] achieved complete bone restoration (100%) and high functional recovery (90%) in limb lengthening using the LON technique. The timeframe for resuming previous activities was comparable between techniques, with no significant differences in physical activity limitations at the final follow-up, corroborating the bone healing outcomes observed in our study.

Several limitations must be considered when interpreting the results of this study. Firstly, we were unable to obtain detailed information on potential confounders, such as the number of previous surgeries, type of antibiotics, or other nonmeasurable factors (e.g., types of intramedullary nails). Secondly, some studies from over a decade ago may have employed different surgical concepts than those currently in use. Consequently, our study could not analyze these risk factors or outcomes with uniform criteria. Consequently, we could not uniformly analyze these risk factors or outcomes. Moreover, most of the included studies were retrospective cohort studies, with only two being randomized controlled trials. The small number of comparable studies resulted in insufficient data and variability in patient demographics, techniques, and reported outcomes. Therefore, additional prospective studies and tighter controls for confounding factors are essential to more accurately assess the clinical efficacy of the LON technique. These recognized limitations are inherent to all studies utilizing this database design and could be mitigated through prospective data collection.

Our findings indicate that patients treated with the LON technique experienced significantly shorter external fixation durations and a lower incidence of complications (e.g., pin tract infections and axial deviation) compared to those treated with the Ilizarov technique alone. Other outcome metrics showed no significant differences between the two techniques. However, the LON technique offers substantial benefits, including reduced external fixation times and increased comfort, which enhance patient compliance. In conclusion, the LON technique is a safe, reliable, and effective method for treating tibial and femoral defects.

Supplementary Information

Supplementary Material 1.

Supplementary Material 2.

Abbreviations

LON Lengthening over a nail

LATN Lengthening and then nail

LATP Lengthening and the plate

EFI External fixtor index

MFT Mean follow-up time

LG Length gained

CIx Consolidation index

BHI Bone healing index

PTI Pin tract infection

II Intramedullart infection

AD Axial deviation

WMD Weighted mean difference

CI Confidence interval

NOS Newcastle–Ottawa Scale

CCS Case–control studies

RCS Retrospective cohort studies

PCS Prospective cohort studies

MD Mean difference

OR Odds ratio

RR Relative risk

Acknowledgements

The authors are grateful to all authors who provided information of their studies.

Informed consent

Not applicable.

Authors’ contributions

Fei Tan, Cuixian Yang, and Shenghu Zhou conceived the study, participated in the study design, performed the statistical analysis, and drafted the manuscript. Fei Tan, Jiankang Zeng, Peijie Li Jiangming Zhang, and Jiahuan Li contributed to data collection and the statistical interpretation. Yongjie Qiao, Dong Xie, and Shenghu Zhou participated in the study design, and oversaw the manuscript drafting process. Jing Wang as well as Shuo Ye helped with the language. All authors reviewed the manuscript.

Funding

This study was funded by Tutor Project of Gansu University of Traditional Chinese Medicine (2023YXKY015), Lanzhou Science and Technology Plan (2023–2-11), Gansu province Science and Technology Plan (22JR5RA009), and Lanzhou Science and Technology Plan (2023-ZD-170).

Availability of data and materials

All data generated or analyzed during this study is included in the Additional File.

Declarations

Ethics approval and consent to participate

Not applicable.

Consent for publication

Not applicable in the section.

Competing interests

The authors declare no competing interests.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Fei Tan and Cuixian Yang contributed equally to this work.
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