Kapandji´s intra-focal pinning in treating unstable or irreducible displaced distal radius metaphyseal fractures in children: a prospective study

¹Department of Orthopaedics and Traumatology, Military Hospital Moulay Ismail, BP 50000 Meknes, Morocco

^&Corresponding author
Mouad Guenbdar, Department of Orthopaedics and Traumatology, Military Hospital Moulay Ismail, BP 50000 Meknes, Morocco

Introduction    

The distal radius accounts for 20-35% of pediatric fractures [1]. The primary way of treating these fractures is a manual reduction and cast immobilization [2]. Several authors have reported a secondary displacement rate that varies between 21% and 50% of patients treated with closed reduction and cast immobilization, compared to a 0-10% displacement rate among patients operated by percutaneous pinning. Pinning could significantly reduce the secondary displacement rate and is indicated for fractures initially or secondarily unstable [3-7].

Surgical techniques have been described in the literature. In fact, the majority of authors have used conventional pinning [4,8-10], others have carried out an intrafocal retrograde pinning associated with an extra-focal antegrade pinning [11] a double elastic pinning of Py [12] and stable elastic centromedullary nailing were also suggested [13].

The Kapandji intrafocal pinning, being described in 1976, was implemented in the treatment of distal fractures of the adult's radius, and resulted in these advantageous characteristics : simplicity, stability and recovery of a mobile and painless wrist [14].

Intrafocal Kapandji pinning is found to be an alternative technique to conventional pinning for the treatment of unstable distal radius pediatric fractures. Moreover, it allows the reduction of irreducible fractures by external maneuver. Although it is widely used by many surgeons, this technique is rarely reported in the literature [15]. The purpose of this study is to depict the outcome of Kapandji intrafocal pinning in treating unstable and irreducible displaced distal radius metaphyseal fracture in children.

Methods     

Study design

This is a study on children hospitalized in our department for a metaphyseal fracture of the distal radius with a dorsal displacement and treated with kapandji intrafocal pinning from January 2015 to January 2017. This surgical technique was indicated for fractures irreducible by external maneuvers or for fractures reduced by external maneuvers but judged to be unstable after the stability test (maximum flexion and extension). The origin of the trauma in all our patients was due to a fall from a height with reception on the palm of the wrist hand in extension during a sports accident or a domestic accident. Pre-operative lateral and anteroposterior radiographs of the wrist were performed for all patients. Radial shortening, dorsal angulation and percentage displacement were measured (Figure 1). No open fracture has been observed in our patients. Fourteen (14) patients had an associated ulnar fracture. Patients were operated after free and informed consent of parents or guardians. All patients were operated by the same surgical team and benefited from the same protocol of postoperative follow-up.

Surgical technique

The patient is placed supine and the affected upper limb is positioned on a table with radiolucent arm. We used 1.5mm or 2mm k-wires depending on the child's posture. After the detection by fluoroscopy, a dorsal incision of 10 mm was made and a dissection in front of the fracture site. The first intrafocal K-wire was manually inserted using an American wrist while tilting the distal cortical anterior and the proximal cortical posterior to obtain an alignment of the two cortices. Then, the spindle is pushed obliquely to the anterior cortex, or it is stuck with a pneumatic motor to stabilize the reduction.

The lateral and anteroposterior scopic control of the forearm were performed. In case of fracture reduction, an extra-focal k-wire introduced into the external cortex of the distal fragment is added (radial styloid or near conjugation cartilage) using a pneumatic motor up to the medial cortex of the proximal fragment where it is stuck. And in case of a lateral residual translation of the distal fragment, we introduced external intrafocal k-wire with the same procedure as the first pin to the medial cortical of the proximal fragment, and then we stabilized our reduction by an extrafocal external k-wire. The pins are bent and cut while leaving their ends exposed (Figure 2).

After pinning, the immobilization with below elbow splint was performed for 4 weeks. The removal of the pins was done after consolidation of the fracture. In immediate postoperative, the active mobility of the fingers was preconized and the rehabilitation of the wrist was prescribed after removal of the pins if there was limitation of the range of motion of the wrist.

Quantitative variables: the patients underwent a clinical and radiological review at the 1^st and 4^th week of the intervention, after the k-wire removal and last follow-up (4 weeks after the removal of the k-wire).

Functional outcomes: after the k-wire removal, the range of motion (flexion/extension, pronation/supination) was measured. We used the “Mayo modified wrist score” [16] system for evaluation of the function of the wrist (Table 1).

Radiological outcomes: anteroposterior and lateral radiographs of the wrist were performed to evaluate the consolidation, and anteroposterior radiographs were assessed for radial shortening in millimetres. Lateral radiographs were assessed for dorsal angulation and percentage displacement. An acceptable post-operative reduction was defined as < 20° dorsal angulation, < 50% displacement, and < 5 mm shortening [17].

Statistical methods: statistical analysis was performed using Epi info™ 7. Descriptive statistics were reported as the median and interquartile range for the quantitative variables, and as percentage for the qualitative variables. Student test was used to compare radiological measures between the groups (immediate postoperative and after k-wire removal). Statistical significance was defined as a p value < 0.05.

Results     

Descriptive data

The average age of our patients at the time of the trauma was 10 years (range 6 - 14 years). Our study included (40 children) 25 males and 15 females. All our patients had metaphyseal fractures with posterolateral displacement that are visible on preoperative radiographs. Median pre-operative radial shortening was 5 mm (IQR=3mm), displacement was 82.5% (IQR=25%) and dorsal angulation was 20° (IQR=11.5°). An extrafocal pinning was associated to intrafocal pinning for all our patients. We used 2 k-wires for 30 patients (75%) and 3 k-wires for the rest (25%). The cubital fractures were treated by pinning only in 06 patients. The average duration of Kapandji pinning was 9 min (7-10min).

Radiological outcome

Median immediate post-operative of radial shortening was 1.5 mm (IQR=2.75 mm), displacement was 3.5% (IQR=3.5%) and dorsal angulation was 3° (IQR=2.5°). All patients had an acceptable post-operative reduction (Figure 3). The removal of the k-wires was performed between the 4^th and the 8^th week, with an average of 6.2 weeks. After the k-wires removal, there was no significant change in displacement, radial shortening or dorsal angulation when comparing immediate post-operative and these follow-up radiograph (Table 2). The fractures were healed in all our patients (Figure 4).

Functional outcome

After the k-wires removal: six patients (15%) had limits of rotation from 3° to 10° resolved with physiotherapy. According to the Mayo modified wrist score: 33 patients (82%) had an excellent result and 7 patients (18%) had a good result. Median follow-up was 5.6 months (IQR= 4.5 months). All patients had a painless and mobile wrist with no limitation to flexion/extension or prono-supination movements.

Complications

Neither pin site infection and migration nor plaster complications (compartment syndrome, allergic dermatitis) were diagnosed.

Discussion     

The distal radius is the most common site of pediatric fracture, accounting for 20-35% of all fractures. Metaphyseal fracture is the frequent type of distal radius fracture in children [18]. Surgical indications are: open fractures, non-reducible fractures, unstable fractures and the presence of associated nerve injury [19]. Intrafocal pinning is one of the surgical techniques for treating unstable displaced metaphyseal fractures. It is rarely reported in the literature, as only 6 series have published the clinical and radiological outcomes of this technique [20-25]. They are based on the same principle, but the technique and the indications are different. In the current study, one or two intrafocal k-wires have been used to lever out and reduce the distal fragment, and one extrafocal k-wire has been implemented to maintain this reduction. We indicated this surgical technique for unstable displaced metaphyseal distal radius fractures.

Rubin et al. [21] et Guichet et al. [25] indicated this technique for the fractures with volar displacement. In a single study, an additional extra-focal k-wire was not used [24]. In two studies, intra-focal pinning was indicated only for completely displaced pediatric distal radial fractures [22,23]. Postoperatively, in the current study, the forearm was immobilized by below-elbow splint for 4 weeks and four series used the same plaster for 4-6 weeks [20-23,25]. In one series, the immobilization was used by the above-elbow cast [24]. There is no difference between the two types of immobilization concerning the secondary displacement rate [26-28]. Below-elbow cast allows a reduction during the school absence and the limitation of daily activities [28].

In one prospective randomized trial of over 100 fractures of the distal radius in adults, Sthorm et al. [29], observed that results of the Kapandji method were better than those of conventional k-wires pinning. In our study, rates of complications were comparable to those reported in the literature [20-25]. In one study on the Kapandji technique in children, one case of pin site infections was observed [20]. Zeng et al. [2] observed, in their systematic review that average rate of complications was 28% in children treated by conventional pinning. Ramoutar et al. observed that conventional pinning does not prevent loss of reduction, especially in dorsal angulation [9]. All series [20-25], as well as the present series, concluded that Kapandji pinning prevented loss of reduction.

Traction and external maneuvering did not always reduce the completely displaced fracture [22]. We observed that leverage technique could quickly reduce the displacements associated with low radiation exposure. Choi et al. reported that open reduction was necessary in 8% of the patients treated by conventional pinning [8]. In the current study, with the Kapandji leverage technique, the anatomical closed fracture reduction was achieved in all cases. In any case, open reduction was necessary. Likewise, in all studies on Kapandji technique in children, intrafocal pinning aided to achieve a closed reduction of distal radius fracture regardless of degree of displacement [20-24].

Our study had limitations as the number of participants was too small and there was no control group for being compared with intra-focal pinning.

Conclusion     

Distal radius fracture in children presents two major difficulties: instability and irreducibility. The immobilization in a plaster cast is related to issues of instability. Thus, the conventional k-wire pinning does not allow to reduce high displacement whereas the intra-focal pinning provides excellent and promising functional and radiological outcomes in children with unstable or irreducible displaced metaphyseal distal radius.

Competing interests     

The authors declare no competing interests.

Authors' contributions     

MG and MO: analysis and interpretation of data. TC and HZ: drafting the article or revising it critically for important intellectual content. All authors have read and agreed to the final manuscript.

Tables and figures     

Table 1: Mayo modified wrist score

Table 2: radiological measurements

Figure 1: pre-operative anteroposterior (A) and lateral (B) X-ray of right wrist: distal radius fracture metaphyseal completely displaced associated with a greenstick ulnar fracture

Figure 2: intraoperative anteroposterior (A) and lateral (B) of the right wrist

Figure 3: immediate postoperative (anteroposterior and lateral) x-rays: the absence of loss of reduction

Figure 4: anteroposterior and lateral X-rays after ablation of the k-wires: showed the healed distal radius fracture after removal pin

References