Limb lengthening with PRECICE magnetic nail in pediatric patients: A systematic review

Abstract

BACKGROUND

Limb lengthening techniques play an increasingly important role in the pediatric orthopedic field. The principles of the osteogenesis distraction bonded traditionally with external fixators; however, the recent deployment of fully implantable systems has been able to overcome severities related to external fixators. The PRECICE^® is an implantable limb lengthening intramedullary nail system that is remotely controlled and magnetically driven.

AIM

To review the current literature available on this matter in order to assess the PRECICE clinical and radiological outcomes and its possible complications in a population of pediatric patients undergoing limb lengthening.

METHODS

Only five studies met the inclusion criteria and were consequently included in the review for a total of 131 patients and 135 femurs. The clinical and radiological outcomes of interest were: the main lengthening obtained, the distraction rate, the period of time to full weight bearing, the consolidation index, and the Association for the Study and Application of Methods of Ilizarov score.

RESULTS

In conclusion, data collected from the articles under investigation were comparable with the exception of the consolidation index. Unfortunately, the study population was too small and the patients’ follow-up was too short to make definitive conclusions.

CONCLUSION

This review shows that the PRECICE Nail System is still a therapeutic challenge in limb lengthening for pediatric orthopedic surgeons; however, careful pre-operative planning and an accurate surgical technique could allow the correction of more complex deformities with a low rate of complications.

Core Tip: Limb lengthening techniques play an increasingly important role in the pediatric orthopedic field. The PRECICE^® is an implantable limb lengthening intramedullary nail system that is remotely controlled and magnetically driven. The aim of our study was to review the current literature in order to assess the clinical and radiological outcomes and possible complications in a population of pediatric patients undergoing limb lengthening. This review shows that the PRECICE allows correction of the more complex deformities with a low rate of complications.

INTRODUCTION

Limb lengthening techniques play an increasingly important role in the field of pediatrics orthopedics with regard to length discrepancy, angular deformities (referable either to fractures sequelae or congenital malformations), and short stature correction[1-4]. The osteogenesis distraction is a reparative process involving not only the bone but also the soft tissues including the muscles, nerves, and skin. Therefore, accurate distraction control is required since too rapid correction could lead to nonunion, nerve damage, and joint contractures, while on the other hand a process that is too slow could result in premature consolidation[5].

The principles of the osteogenesis distraction bonded traditionally with the external fixators, considering both monolateral and circular fixators[6,7]. More recently, the deployment of fully implantable systems for limb lengthening has allowed overcoming external fixator-related severities such as pin-site infections, soft tissue tethering, and patient device intolerance during treatment, to name a few[8-10]. Intramedullary nails were initially used in conjunction with external fixation in hybrid techniques such as lengthening over nail or lengthening and then nailing[11,12], in order to reduce fixator time and prevent secondary deformities. However, these techniques are not free from external fixator-related complications. Over the past couple of decades, internal bone lengthening devices have been developed to obviate the need for external fixators. They seem to decrease patients’ pain and discomfort and facilitate a more rapid and effective rehabilitation compared with external fixation[13].

At present, three types of telescopic nails are mainly used: mechanically activated nails, motorized nails, and magnetically driven nails[14-16]. The PRECICE^® Intramedullary Limb Lengthening System (NuVasive Specialized Orthopedics, San Diego, CA, United States) is a remotely controlled, magnetically driven, implantable limb lengthening intramedullary nail system first used in Europe in 2012[17-19]. The PRECICE nail is a magnet-operated telescopic internal lengthening device with an ERC that contains two rotating magnets[20]. When placed by the patient on the skin, above the magnet which is within the nail, it causes this internal magnet to rotate, which translates to the thinner nail element telescoping out of the thicker surrounding nail; the nail can be both extended and retracted by altering the settings on the ERC as well as accurately setting the rate of distraction. A distance of 1 mm requires the ERC to be placed over the magnet within the nail for 7 min[21].

The PRECICE represents a safe and accurate technique able to correct both deformity and limb-length discrepancy, lengthening but also shortening (unlike other lengthening nails[22]) with reduced side effects . Among the advantages of opting for this implant, there is the ability to maintain the knee range of motion during the lengthening process and also the rapid bone healing allows a relatively early return to weight bearing[23,24].

The aim of our study was to review the current literature available on this matter in order to assess the PRECICE clinical and radiological outcomes and its possible complications in a population of pediatric patients undergoing limb lengthening.

MATERIALS AND METHODS

A systematic review of the literature indexed in PubMed MEDLINE and Cochrane Library databases using the search key word “PRECICE” was carried out. To minimize the number of missed studies, no filters were applied to the search strategy. The bibliography of the selected studies was accurately searched by hand, in order to identify further studies not found during our electronic search. No restrictions on the date of publication or language were applied. The title of the journal, name of authors, or supporting institutions were not masked at any stage. No attempt to contact authors in order to obtain individual patient data was made. The Preferred Reporting Items for Systematically Reviews and Meta-Analyses (PRISMA) was followed as reported in Figure 1. In order to be considered for this review, the articles needed to comply with the following inclusion criteria: use of the PRECICE^® Intramedullary Limb Lengthening System (NuVasive Specialized Orthopedics) for femur lengthening and patient age under 18 years. No restrictions for surgical approach to nailing were applied. Abstracts and full texts were independently screened by two authors (Vitiello R and Maccauro G), and any discordance was solved by consensus with a third author (Palmacci O). The methodological quality of the studies was assessed using the modified Coleman Methodology Score (mCMS)[25]. Each article was evaluated by two independent investigators (Vitiello R and Bocchi MB); in cases with more than a five-point difference between their rating, the discrepancy was solved by consensus with a third author (Palmacci O). The mCMS ranges from 0 to 100 points, representing a well-designed study with no bias or confounding factors.

Figure 1.

PRISMA flowchart.

RESULTS

The electronic search resulted in 60 hits. Following the PRISMA flow chart[26], only five studies met the inclusion criteria and were taken into consideration in the review[27-31]. Eight papers partially followed the inclusion criteria; these studies included a non-specific pediatric population. An extra analysis was performed for these latter papers. All of the selected studies were retrospectively analyzed. The target population consisted of 131 patients for a total of 135 femurs. According to the mCMS evaluation, the mean score of the studies reached was 47 points (25-57 points) showing a poor-mediocre result. The papers we took into consideration had several methodological issues, particularly when considering the procedure in assessing the outcomes. Moreover, the study population was too small and the patient’s follow-up was too short. However, all of the papers accurately reported the indications for surgical intervention and the surgical technique (respectively 5 points each). Studies by Szymczuk et al[30] and Hammouda et al[32] compared the PRECICE intramedullary nailing with external fixation, but in our analysis, we only took into account the PRECICE nailing results. In studies by Nasto et al[27] and Iliadis et al[29], both retrograde and antegrade approaches were used, and some tibia nailing was included. Other studies preferred the antegrade approach to the femur.

DISCUSSION

Demographic data and etiology

We reached a population of 131 male and female patients for a total of 135 femurs. Males and females numbered 69 and 62, respectively. The mean age was 14.8 years old, ranged between 7 and 18 years old[31]. All of the studies reported pre-operative discrepancy except one[31], with a mean value of 5.2 cm (range, 4.9 to 6.3). The mean follow-up was 1.7 years when reported (Table 1). Concerning surgical indications, one study only focused on a single pathology; in particular, Szymczuk et al[30] focused on congenital femoral deficiency treatment for a total of 30 femurs (Table 2). Among other papers, the principal surgical indication was congenital femoral deficiency (19 femurs), and yet post-traumatic malformations (18 femurs), achondroplasia (8 femurs), hemihypertrophy (8 femurs) and Ollier disease (6 femurs). Nevertheless, the main indication remained “miscellaneous” (46 femurs).

Table 1.

Demographic data

Ref.	Number of patients	Gender	Tibia nailing	Age (yr)	Discrepancy (cm)	Follow-up (yr)	mCMS
Hammouda et al[32]	28 patients; 31 femurs	17 males; 11 females	-	12.9	-	1.9	49
Szymczuk et al[30]	30	14 males; 16 females	-	15.4	4.9	1.9	51
Iliadis et al[29]	42 patients; 43 femurs	20 males; 22 females	7	15	4.9	-	54
Nasto et al[27]	26	15 males; 11 females	5	14.7	4.9	1.4	57
Tomaszewski et al[28]	5	3 males; 2 females	-	16.3	6.3	-	27

In brackets measurement unit; Data are reported as absolute value. mCMS: Modified Coleman Methodology Score.

Table 2.

Etiology

Ref.	Congenital femoral deficiency	Achondroplasia	Post-traumatic	Hemihypertrophy	Ollier disease	Miscellaneous
Hammouda et al[32]	10	6	5	3	2	5
Szymczuk et al[30]	30	-	-	-	-	-
Iliadis et al[29]	5	2	7	5	1	23
Nasto et al[27]	4	-	4	-	3	15
Tomaszewski et al[28]	-	-	2	-	-	3

In brackets measurement unit; Data are reported as absolute values.

Clinical and radiological outcomes

Regarding the PRECICE system results, the studies examined focused on the following issues: The main lengthening obtained with particular reference to accuracy and reliability, the distraction rate, the period to reach full weight bearing, the consolidation index, and the Association for the Study and Application of Method of Ilizarov (ASAMI) score (Table 3 and Table 4). Nail accuracy is defined as the ratio between the lengthening obtained and the planned length, while nail reliability is the ratio between the number of implanted lengthening devices and the number of successfully ended lengthening treatments. Analyzing the main lengthening obtained, the results were similar across all studies. In particular, Hammouda et al[31] reported a mean lengthening of 5.6 (3-6.7), with no reference to accuracy and reliability. It is relevant to notice that the authors performed intramedullary nailing using the trochanteric entry. During the follow-up time no patients showed radiographic nor clinical signs of femoral head necrosis. The average lengthening achieved reported by Nasto et al[27] was 4.4 ± 1.2, with a nail accuracy and reliability of 91% and 88% respectively. Iliadis et al[29] reported a nail accuracy of 96% and a nail reliability of 98%, due to a single case where a nail was implanted without lengthening because of the patient’s mental health issues.

Table 3.

Result

Ref.	Mean lengthening (cm)	Accuracy	Reliability	Distraction rate (mm/d)	Day to full weight bearing	Consolidation index (d/cm)	ASAMI functional score	ASAMI bone score
Hammouda et al[32]	5.6 (3-6.7)	-	-	-	-	-	-	-
Szymczuk et al[30]	4.75 ± 1.43	95%	-	0.7 ± 0.18	-	34.7 ± 11.2	-	-
Iliadis et al[29]	-	96%	98%	0.92 (0.67-1)	45 (21-132)	28 (18-43)	35 excellent; 11 good; 3 fairs; 1 poor	41 excellent; 8 good; 1 fair
Nasto et al[27]	4.4 ± 1.2	91%	88%	0.9 ± 0.1	-	11.9 ± 2.1	22 excellent; 3 good; 1 fair	24 excellent; 1 fair; 1 poor
Tomaszewski et al[28]	4.9 (4-5.8)	-	-	0.8 (0.8-1)	-	29.3 (21-33)	-	-

In brackets measurement unit; Data are reported as absolute values.

Table 4.

Complication

Ref.	Number of patients	Problem	Obstacle	Complication
Hammouda et al[32]	28 patients; 31 femurs	-	-	2
Szymczuk et al[30]	30	8	19	4
Iliadis et al[29]	42 patients; 43 femurs	7	4	4
Nasto et al[27]	26	5	1	3
Tomaszewski et al[28]	5	1	-	-

In brackets measurement unit; Data are reported as absolute values. Problems are post-operative difficulties that resolved completely with non-operative intervention; obstacles were difficulties that needed an operative intervention, resolved completely after surgery; complications consisted of all intra- and post-operative complications that remained unresolved even after treatment was completed.

The distraction index (DI), defined as the ratio between the number of days of distraction and the achieved length (days/cm), was reported in all of the studies analyzed, except for Hammouda et al[31]. Among the articles, the results were almost comparable. Szymczuk et al[30] described a DI of 0.7 ± 0.18, while Iliadis et al[29] reported a DI of 0.92 (0.67-1). Furthermore, this latter retrospective review was the only one considering the days to full weight bearing from lengthening accomplishment with a mean of 45 days. All patients in fact gradually obtained full weight bearing over a 4-wk period after the planned length achievement. The consolidation index (CI) is defined as the ratio between the total duration required to achieve bone healing and the achieved length (day/cm). The data collected in the articles under investigation were different. Nasto et al[27] in particular obtained a CI of 11.9 ± 2.1, while Szymczuk et al[30] obtained a CI of 34.7 ± 11.2. Nasto et al[27] and Iliadis et al[29] reported the modified ASAMI score, which is a scoring system that classifies clinical results into excellent, good, fair, and poor based on four different parameters. The data we collected were similar and encouraging, supporting the efficacy of this device. In the paper by Iliadis et al[29], patients reported a low pain score throughout the lengthening and consolidation period. No significant impact on daily living activities was reported by 66% of patients, to the extent that 92% of patients were satisfied with the surgical treatment results and felt that they had achieved their goals.

Complications

Adverse events were divided into problems, obstacles, and complications in accordance with the data previously described by Paley[17]. Problems were defined as difficulties after the surgical procedure resolved with conservative treatment, obstacles were difficulties that required surgical treatment, and complications were true intra or post-operative complications that persisted after the treatment. Hammouda et al[31] reported no problems or obstacles in 28 patients and two complications. Among them, 1 patient developed hip subluxation and delayed union of the regenerate, which was treated surgically. In addition, the nail was exchanged 6 mo after surgery. Iliadis et al[29] reported instead seven problems, four obstacles, and four complications. In 7 cases, they reported joint stiffness during the lengthening period, which was resolved with physiotherapy and by slowing down the distraction. Two femoral nails required the locking bolts removal as they were causing discomfort after consolidation. One patient with fibrous dysplasia, who previously underwent proximal femoral osteotomy with locking plate fixation, had a periprosthetic fracture so the PRECICE was exchanged with a trauma nail, but with loss of about 30 mm of lengthening.

Tomaszewski et al[28] reported no inflammatory complications, but in 1 case, after a lengthening of more than 45 mm, they noted a knee flexion contracture of about 10° despite the physiotherapy. Moreover, they had to stop the lengthening treatment in 1 case due to the pain and femoral nerve paresthesia. In the retrospective multi-center study conducted by Nasto et al[27], a total of five problems (joint contractures), one obstacle (femur fracture), and three complications (hip subluxation, 1 deep infection and 1 nail running back) were encountered. No bone healing complications were reported. Considering the patient who developed deep infection, the treatment was suspended and the nail removed. Regarding the case of hip subluxation, we would like to note that the patient had a developmental hip dysplasia history treated with proximal femur varus derotation osteotomy (VDRO) and Dega osteotomy. This complication was surgically treated with periacetabular osteotomy and VDRO; at the latest follow-up, the patient was asymptomatic and pain free during walking.

Non-specific pediatric population

Analyzing the entire population, a great heterogeneity has emerged in terms of age (7-72), male/female ratio, surgical access and surgical site[18,19,21,32-36]. The rise in the average population age has led to an increase of post-traumatic etiology[32], although the congenital and syndromic causes are still well represented[18,32,36]. All of the reviewed articles analyzed both femoral and tibial lengthening nails outcomes, except one[32]. In a retrospective review by Wagner et al[18], both PRECICE nail accuracy and precision reached 97.3% and 92.4%, respectively, with a total of nine complications (28%), all of which were successfully resolved without any long-term sequelae. In his 24-nail series, Kirane et al[21] revealed an accuracy of 96% and a precision of 86% with only one (4%) implant-related failure caused by a non-functional distractor mechanism and 6 (24%) non-implant-related obstacles; the minimum follow-up was 3 wk (mean 14 wk). In a different 9 case series by Wiebking et al[34], there were significant differences regarding the lengthening goal achievement and thus also the full weight bearing among patients. Consequently, the accuracy and the precision rate were 78% vs 61%, respectively. Despite the complications, patient satisfaction was generally positive.

A slight improvement in the quality of life was shown in preoperative and 12-mo postoperative Enneking scores; no differences were revealed in the physical and mental SF-12 score[18].

Concerning complications, a low complication rate was demonstrated in a series of 17 post-traumatic femoral lengthening nails with 2.2-year follow-up[32]. Hammouda et al[32] reported 3 patients (18%) with non-implant related complications that all resolved without permanent sequelae. Similar outcomes were reported by Horn et al[35] who described 8 of 50 complications, which were treated by surgery without sequelae and therefore were graded as obstacles. However, in this study, 16 nails were not PRECICE[35].

CONCLUSION

This review shows that the PRECICE Nail System is still a therapeutic challenge in limb lengthening for pediatric orthopedic surgeons. In the literature, only few studies have been published; nevertheless, the outcome demonstrates excellent clinical results and patient satisfaction. Careful pre-operative planning and an accurate surgical technique could allow correction of the more complex deformities with a low rate of complications.

ARTICLE HIGHLIGHTS

Research background

Limb lengthening devices have evolved in the last century to correct limb length discrepancies, congenital short statures, and limb deformities. The unilateral external fixator has been the standard method of fixation for a long time; however, the method of fixation has rapidly evolved from unilateral external fixator to the ring fixator, to the computer-assisted fixator, and finally to the lengthening of intramedullary nails.

Research motivation

The large number of complications related to the use of external fixation has led to the development of alternatives. The PRECICE represents an innovative and less invasive option to external fixation with regard to limb lengthening, allowing a controlled lengthening phase with the ability to shorten and regulate the device if necessary.

Research objectives

To review the current literature available on the specific matter in order to assess the PRECICE clinical and radiological outcomes and its possible complications in a population of pediatric patients undergoing femur lengthening.

Research methods

The current study is the result of a systematic review of the available literature using a single search term “PRECICE”. The articles were sorted according to both predetermined inclusion and exclusion criteria. PRISMA was followed.

Research results

Five studies met the inclusion criteria for a total of 131 patients. The studies examined focused on the following issues: the main lengthening obtained, the distraction rate, the number of days necessary to reach full weight bearing, the consolidation index and the ASAMI score. Among the articles all the results were almost comparable with the only exception of the consolidation index. Adverse events that emerged in a low percentage were divided into problems, obstacles, and complications.

Research conclusions

Although the PRECICE nail system is still a therapeutic challenge, the results have shown excellent clinical results and patient satisfaction with a low rate of complications. Therefore this approach could represent a valid alternative to the traditional limb lengthening systems.

Research perspectives

Future studies on larger and more homogeneous samples are needed to validate the use of PRECICE.