Journal of Limb Lengthening & Reconstruction

CASE REPORT
Year
: 2021  |  Volume : 7  |  Issue : 1  |  Page : 57--61

Deformity correction with the ifixation system: A new era of six-axis correction frames


Yasser Elbatrawy1, Mohamed Khaled2, Mohamed Yahya Hassanein2, Ehlimana Agovic3, Elvir Bazdar3,  
1 Department of Orthopedics and Traumatology, Al-Azhar University, Faculty of Medicine for Girls, Cairo, Egypt
2 Department of Orthopaedic and Trauma Surgery, Assiut University Hospitals, Assiut, Egypt
3 Department of Orthopedics and Traumatology, Clinical Center University of Sarajevo, Sarajevo, Bosnia and Herzegovina

Correspondence Address:
Prof. Yasser Elbatrawy
Professor of Orthopedic Surgery: Al-Azhar University Villa 26E, Mayfair, Elsherouk, Cairo, 11837
Egypt

Abstract

The technology of computer-assisted six-axis frames is rapidly evolving. In this case report, we describe two cases of pediatric lower limb deformities treated by a novel hexapod device, the iFIXation system. For our knowledge, this is the first report in literature for its usage. The first case was a 14-years-old girl with posttraumatic shortening, varus and external rotation deformities of her lower limb around the ankle. All the deformities and shortening were corrected simultaneously with the iFIXation system. The second case was an 8-years-old girl with postinfection valgus and external rotation of the knee as well as shortening of the femur. Distal femoral deformities and shortening were simultaneously corrected by the iFIXation system and growth modulation to prevent recurrence of the deformity was done. The reported cases represent our earliest experience with the iFIXation system.



How to cite this article:
Elbatrawy Y, Khaled M, Hassanein MY, Agovic E, Bazdar E. Deformity correction with the ifixation system: A new era of six-axis correction frames.J Limb Lengthen Reconstr 2021;7:57-61


How to cite this URL:
Elbatrawy Y, Khaled M, Hassanein MY, Agovic E, Bazdar E. Deformity correction with the ifixation system: A new era of six-axis correction frames. J Limb Lengthen Reconstr [serial online] 2021 [cited 2021 Sep 28 ];7:57-61
Available from: https://www.jlimblengthrecon.org/text.asp?2021/7/1/57/320059


Full Text



 Introduction



The introduction of computer-assisted six-axis frames is a revolutionary breakthrough in the art of deformity correction.[1] These fixator systems apply the Stewart platform theory where six adjustable or telescopic struts are used to control motion in space. Taylor spatial frame (Smith and Nephew, Memphis, TN, USA) developed by the Taylor brothers in 1994 was probably the first documented application of this six-strut system for deformity correction.[1],[2] It has been followed by development of many other frames that replicate the original idea with technical differences.[3],[4] The extreme versatility of the frame, the ability to perform simultaneous correction in different planes and the precise software-assisted control of motion are among the countless advantages of six-axis frames.[1]

In order to apply six-axis frames in deformity correction, the surgeon needs to fully understand and master the software before embarking on operating cases. The current technological advent in the computer-assisted external fixators focuses on improving the accuracy and interface of the software, enhancing the mechanical properties of the construct, increasing the versatility of the frame as well as simplifying the required X-ray views.[1],[2],[3],[4]

The First author has used the Taylor spatial frame (TSF) since 1998 and reported his experience in previous published articles.[5],[6],[7] and here documents his new experience with iFIXation system (Dial Medicali, Milano, Italy). In this study, we report two cases of pediatric lower limb deformities which were corrected using the new iFIXation system to know the pros and cons of this new Hexapod over others we previously used as TSF and Orthosuv systems.

 Case Reports



Case 1

A 13-years-old girl had right leg shortening and ankle deformity which developed over the past 10 years after sustaining trauma to her right ankle that was managed conservatively. On examination and radiological assessment, the patient had 4 cm of shortening, 20°varus and 10° external rotation deformities of her right lower limb around the ankle. Radiographs showed partial physeal arrest of the distal tibia on the medial side as well as differential growth between the tibia and fibula [Figure 1]. Ankle showed full range of motion and there were no other abnormalities. Neurovascular status was intact. The Multiplier application (Rubin Institute for Advanced Orthopedics, Baltimore, Maryland, USA) showed an expected final LLD of 4.3 cm at skeletal maturity.{Figure 1}

Gradual correction and lengthening using the iFIXation frame was decided. A bifocal approach was applied with the proximal osteotomy utilized for simple lengthening and the distal for gradual correction of varus and external rotation deformities with simultaneous lengthening just enough to correct the relation between the tibia and the fibula distally while the proximal lengthening aimed at compensation of the limb discrepancy. The iFIXation frame consisted of two full rings-one on either side of the distal osteotomy-connected by six struts. Another ring was added proximally above the lengthening osteotomy [Figure 2]. HA-coated pins (Dial Medicali, Milano, Italy) were used to increase the frame stability and decrease the rate of the infection and loosening to the minimal possible. No postoperative neurovascular deficits were detected. Postoperative X-rays were fed into the software in which it is easy for the specialist to measure all parameters needed automatically by the software saving many troubles and hassles doing that on the X-rays itself.{Figure 2}

Distraction started after 7 days at both the distal and the proximal osteotomies according to the schedule generated by the software at a rate of — mm per day for both levels. Immediate postoperative partial (25%) weight-bearing was allowed as we used the hybrid fixation technique of Catagni which permits early gradual ambulation and better rehabilitation of the patient.[8] Full knee and ankle range-of-motion exercises were instructed. No pin tract infections were encountered during the treatment period. Distraction continued till full clinical and radiological correction of deformity and limb length equalization (34 days). The fixator was left in place until radiologic evidence of complete union was achieved. The frame was removed after 135 days at the operating theatre after radiological and clinical signs of full consolidation were detected and the patient was able to weight bear without support. Frame dynamization was performed during the last 2 weeks before removal. Follow-up of the patient was continued for 38 months after surgery and showed satisfactory results with no evidence of recurrence of the deformity or any other postoperative complications.

The ifixator has a wide range of components. The spheres help the software in understanding what is the orientation of the reference ring and the magnification of the X-ray. No need to calculate or calibrate the image as we used to do in TSF, it is already done automatically by the software through the spheres. We don't have to be “obsessively” orthogonal to the shaft or parallel to the joint as we do for TSF from ifixator software point of view because the location of the spheres tells the software the correct orientation of the ring.

Flexible Strut mounting: We can put the struts wherever we want even not close to each others. We just need to be aware of the rules on stability of the mounting as in Ilizarov frame in general.

Easy and smart software: We take 3–4 min to do the software.

The software follows rules on Cora [Figure 3].{Figure 3}

Case 2

An 8-years-old girl presented with left lower limb shortening and knee deformity after acute osteomyelitis of the left distal femur 2 years earlier which was managed conservatively with antibiotics, anti-inflammatory medications and splintage. On examination, she had 15° valgus (measured on the X-rays) and 20° external rotation deformities of the left lower limb (measured clinically) as well as 1.2 cm of length discrepancy [Figure 4]. The problem was due to partial physeal growth arrest of the distal femoral physis. The Multiplier method showed an expected limb length inequality of 5.2 cm at puberty.{Figure 4}

The plan of management was to apply guided growth using an eight plate for hemiepiphysiodesis to prevent recurrence of the deformity after correction and to perform gradual lengthening of the left femur with the iFIXation system simultaneously with correction of the valgus and the external rotation deformities to compensate for 4.2 cm discrepancy to be followed by a subsequent contralateral planned physiodesis at the age of 12 years and 8 months to correct the remaining 1 cm of limb discrepancy according to the calculations performed using the Multiplier application. She was advised to wear temporary shoe lift 2.5 cm on the contra lateral side with decreasing its height annually 1 cm.

The iFIXation construct consisted of two full rings connected by six struts. The postoperative period was uneventful and gradual distraction at a rate of 1 mm per day was started 1 week after the surgery. Distraction was continued till achievement of 4.2 cm lengthening as planned. Rotational malalignment was corrected simultaneously [Figure 5]. Weight bearing was allowed postoperatively as tolerated and knee motion was encouraged. The frame was removed after union was verified radiologically. Our eyes were kept on the knee range of motion to avoid knee stiffness during the lengthening process. The patient was followed up for 38 months. The results of this patient were excellent, and all our planned goals were accurately achieved [Figure 6].{Figure 5}{Figure 6}

 Discussion



The application of Ilizarov frames in correction of multiplanar deformities is quite laborious. It requires either complex frame constructs or re-assembly and modification of the frame many times after correction of every single element of the deformity.[7],[9] The six-axes frames were introduced to provide meticulous software-guided correction of multi-component deformities at the same time.[7]

The TSF is the prototype of six-axis correction frames.[1] It consists of two full/partial rings connected by six telescopic struts at special universal joints. Regardless of the complexity of the deformity, essentially the same construct is applied.[6],[10] Accurate orthogonal radiographs and clinical examination data, as well as other relevant information as the structures at risk and the safe velocity of correction, are fed into the software. Accurate entry of the input parameters is mandatory to achieve successful results. The adjustment schedule is generated and can be modified later on at any time as needed.[10]

The six-axis frame technology has been one of the fastest changing technologies in orthopedic surgery over the past 25 years.[1] Different types of hexapod frames have evolved from Russia, Germany, The United States, Turkey, Korea and Italy with each having its pros and cons.[1],[4],[11] The main differences include improvement of biomechanical properties, better software interface and refinement of the adjustment system. Some devices-as the Ortho-SUV (Saint Petersburg, Russia) and the Hexapod (Hamburg, Germany)-have the advantage of allowing telescopic rods to be connected to the standard Ilizarov rings.[4],[11]

The new iFIXation device we used in these two reported cases represents a new generation of orthopedic hexapods. The frame consists of two rings connected by six telescopic struts. The reference ring has two full spheres and one incomplete sphere (metal balls) [Figure 7]. The spheres help the software to understand the orientation of the reference ring and the magnification of the X-rays. There is no need to calculate or calibrate the images, as it is already done by the software through the spheres. The treating physician does not have to be “obsessively” orthogonal to the shaft of the bone or parallel to the joint from the software point of view because the location of the spheres tells the software the correct orientation of the rings. This adds more flexibility when doing the X-rays to gather the data needed for the input parameters of the software.{Figure 7}

Another advantage of the iFIXation frame is the flexible Strut mounting. The connecting struts can be placed at any position even not close to each other taking in consideration the general rules of stability of circular frames unlike the TSF and many other hexapods in the market where there are fixed holes for strut connection. This gives the surgeon more versatility during application of the frame intra-operatively. The software is quite user-friendly, and the calculation of the adjustment schedule takes no more than 5 min to do it. The presence of two full rows of holes in the rings allows addition of wires and pins according to the surgeon's preference with minimal limitation.

The reported cases represent our earliest experience with the iFIXation system. The device proved to be effective in correction of two cases of pediatric complex multiplanar lower limb deformities associated with limb length discrepancy. The correction process went smoothly and uneventfully till the desired goals were achieved. We did not need to do further software as we achieved our goals in both patients by the end of the first software program. Further large-scale and possibly comparative studies should follow. Moreover, the efficiency of the iFIXation frame in treatment of other conditions as acute trauma and nonunions needs to be tested. As any computer-assisted device, the surgeon has to learn well the software and understand its scopes before applying the device clinically. We did not find any difficulty to learn the software of the iFIXator device as it was friendly and easier to use than other previous systems we used as TSF and Orthosuv. It is possible to re-use all the components except for sure the pins and wires that connect the frame to the bone. We reported its success in treating two cases with complex multiplane deformities in our report.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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