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A study on outcome of various K-wire fixations in paediatric supracondylar humerus fractures

we advanced from the conservative approach to an operative approach with closed reduction percutaneous pinning as the acceptable treatment for displaced supracondylar humerus fracture is closed reduction and percutaneous pinning. This has given excellent results reported by various However, controversy still exists regarding which pin fixation is the best in terms of stability and iatrogenic ulnar Medial and lateral pin fixation has been presumed to be more stable, however it has the risk of iatrogenic ulnar nerve injury. Lateral only pinning is riddled with issue of lesser torsional stability but avoiding neurological complications. ABSTRACT Background: The ideal pin geometry for treatment of paediatric supracondylar humerus fracture is still debated. Various studies have been carried out comparing medial-lateral pinning (MLP) and lateral only pinning (LOP), but none have compared all three individually i.e. MLP, lateral divergent pinning and Lateral Trans olecranon fossa four cortex purchase pinning (TOF-FCP). This study aims to compare the cosmetic and functional outcome of these three pinning methods. Methods: children with supracondylar humerus (Gartland type 2 or 3) meeting inclusion criteria were treated operatively and followed up till 6 months postoperatively. At 6 months the cosmetic and functional outcomes were assessed using the modified Flynn criteria. Results: All fractures united within 3 to 6 weeks duration. The mean duration of fracture union was 4.05 weeks. Functional outcome was satisfactory (i.e. excellent or good) at 6 months according to Flynn criteria in 95% of cases in cross pinning, 100% cases in TOF-FCP construct and 89% cases in lateral entry divergent pinning. cosmetic outcome was satisfactory (i.e. excellent or good) at 6 months according to Flynn criteria in 95% of cases in cross pinning, 100% cases in TOF-FCP construct and 89% cases in lateral entry divergent. Conclusions: Functional and cosmetic outcome of all three pinning geometries after operative intervention of paediatric supracondylar humerus fracture is similar in expert hands. The incidence of complications with TOF-FCP construct is less amongst the lateral only pinning.


INTRODUCTION
Supracondylar humerus fracture is the most common elbow fracture in children. They account for 55% to 70% of all elbow fractures and are seen most frequently in children between the ages of 3 and 10 years. 1 The chances of residual deformity and that for rare but devastating neurovascular complications make supracondylar humerus fractures a dreaded injury. Over time, we have advanced from the conservative approach to an operative approach with closed reduction percutaneous pinning as the acceptable mode of treatment.
The current standard treatment for displaced supracondylar humerus fracture is closed reduction and percutaneous pinning. This method has consistently given excellent results reported by various authors. However, controversy still exists regarding which pin fixation is the best in terms of stability and iatrogenic ulnar nerve injury.
Medial and lateral pin fixation has been presumed to be more stable, however it has the risk of iatrogenic ulnar nerve injury. Lateral only pinning is riddled with issue of lesser torsional stability but avoiding neurological complications. Recently 'trans-olecranon fossa-four cortex purchase (TOF-FCP)' pin fixation technique has reports of having better torsional stability than conventional LOP and retaining its fewer complications. 2 But it affects mobility at elbow with early stiffness. Therefore, we conducted this prospective study to compare the outcome of all the three constructs for cosmetic and functional outcomes and complications comparison.

METHODS
A prospective study which was carried out over a period of 18 months from January 2018 to July 2019 at Surat Municipal Institute of Medical Education and Research, Surat, Gujarat, India. The study protocol was approved by the ethics committee of our institution. Gartland classification was used to classify fractures. 3 All displaced supracondylar humerus fracture (Gartland type II or III fracture) of children aged less than 16 years were included. Only fresh (<7 days) fractures were included. Children with other ipsilateral limb fractures, Gartland type 1 fracture and with preoperative distal neuro-vascular deficits were excluded.
On operation table closed reduction was done under anaesthesia. After achieving an acceptable reduction confirmation under IITV, the corresponding pinning was carried out. Three consultants with adequate experience, each operating with one fixation technique carried out the surgery, sampling technique being purposive sampling.
Crossed pin configuration was carried out according to the mini-open technique described by Green et al. 4 In lateral only pinning, divergent pinning was carried out according to the technique explained by Aroson and Prager in their study, TOF-FCP pinning was done according to the technique described by Kasirajan et al in their study. 5 In TOF-FCP construct the entry of the K-wire is at the capitellum, being the first cortex the next two being those of the olecranon fossa and fourth, the medial column. The pin size used was 1.5 mm in younger children (<20 kg weight) and 2 mm in older children (>20 kg weight).
Betadine soaked gauze piece were put around each pin and an above elbow slab was applied. A single shot of injectable antibiotic was given intra-operatively with oral antibiotics continued post-operatively only in cases with post-operative pin tract infection.
All cases were followed up at 3 weeks and thereafter weekly till clinical evidence of absent fracture site tenderness and radiological reporting of evidence of union. On confirmation of both, the pins were removed, and gradual mobilization was started as tolerated. After that they were followed up at 3 months and 6 months. The 6 months assessment were used to assess and compare the cosmetic and functional outcomes. The functional and cosmetic outcome were graded according to the modified Flynn criteria. 6 Analysis was done of the qualitative data using cross tab analysis.

RESULTS
Our study was carried out amongst paediatric patients with supracondylar humerus fracture, wherein a total of 54 displaced supracondylar humerus (Gartland type 2 and 3) fractures in children were studied. Age distribution wise, 22 (40.7%) children were under 6 years, 26 (48.1%) children were between 6 to 10 years and 6 (11.1%) children were above 10 years. Mean age was 6 years. (range from 2 to 12 years). Sex distribution wise, 31 were males (57.4%) and 23 children were females (42.6%), showing near equal distribution. Out of 54, in 19 cases cross pinning was done and in 35 cases lateral pinning was done. Out of 35 lateral pinned cases 17 were 'trans olecranon fossa four cortex purchase' (TOF-FCP) and 18 were divergent lateral entry. All patients having extension type injuries were included in our study.
Of the total of 54, 15 (27.8%) were Gartland type 2 and 33 were Gartland type 3 fractures. Twenty-five (53.7%) were type 3a and 8 (18.5%) were type 3b. Distribution amongst the pinning method of various fracture types was random and found to be equivocal. Out of 54 cases, 43 (79.6%) cases were operated within 1 day and the rest 11 (20.4%) cases were operated after 24 hours and within 1 week due to delayed presentation (3 cases by cross pinning and 8 cases by lateral pinning: 5 TOF-FCP; 3 divergent). Mean duration between injury and surgery was 1.5 days.
Out of 19 cross pinned cases, according to Flynn criteria showed excellent functional outcome in 15 cases, good in 3 case and fair in 1 case. The cosmetic outcome according to Flynn criteria showed excellent outcome in 15 cases, good in 3 case and fair in 1 case (Table 1). However, the cosmetic outcome and functional outcome is not correlated.
The average time to clinico-radiological union in this fixation was 3.8 weeks. Pin tract infection of very mild nature was detected in 4 patients. In one patient one of the wires backed out due to loss of cortical purchase leading to secondary displacement. It was revised with close reduction and percutaneous pinning. The functional outcome was fair in that case. 4 (21.1%) cases showed mild displacement as per Skaggs criteria on assessment of follow up Baumann's angle ( Figure 1) shows radiographs and clinical photograph of a 7 years old male child operated with medial lateral pinning and excellent radiological and functional outcome. Out of 17 TOF-FCP cases, the functional outcome according to Flynn criteria showed excellent outcome in 12 cases and good in 5 cases. The cosmetic outcome according to Flynn criteria showed excellent outcome in 14 cases, good in 3 cases (Table 2).  The average time to clinico-radiological union in this fixation was four weeks. Pin tract infection of very mild nature was detected in 4 patients. Four cases showed mild displacement as per Skaggs criteria on assessment of follow up Baumann's angle without secondary displacement ( Figure 2) shows radiographs and clinical photograph of an 8 years old child operated with TOF-FCP pinning with excellent radiological and functional outcome.
Out of 18 laterals only pinned cases the functional outcome according to Flynn criteria showed excellent outcome in 12 cases and good in 2 cases and fair in 2 cases. The cosmetic outcome according to Flynn criteria showed excellent outcome in 14 cases, good in 3 cases and fair in 1 case (Table 3).  The average time to clinico-radiological union in this fixation was 4.2 weeks. Pin tract infection of very mild nature was detected in 6 patients, in one of those case it was the cause of elbow stiffness in the early follow up. In one patient, both the wires were crossing too close to fracture site leading to secondary displacement and in one patient one of the wires became unicortical postoperatively leading to secondary displacement due to inadequate fixation.  They were revised with close reduction and percutaneous pinning. Both had fair functional outcome and cosmetic outcome was fair in one and good in the second. 5 (27.8%) cases showed mild displacement, one (5.6%) showed major displacement as per Skaggs criteria. Figure 3 shows radiographs and clinical photograph of a 4 years old child operated with lateral only pinning with excellent radiological and functional outcome.  The average time to union in cross K-wire fixation was minimal i.e. 3.8 weeks, in TOF-FCP construct was 4 weeks and divergent lateral only pinning is 4.2. weeks. ANOVA analysis has been carried out on this data which showed that the difference in the union time amongst them was not significant (Table 4). Table 5 is the cross-tab analysis of all pinning methods' cosmetic and functional outcome. It shows that the cosmetic outcome is not necessarily related to the functional outcome. A fair (unsatisfactory) cosmetic outcome is associated with good (satisfactory) functional outcome.
Out of 19 cross pinned cases, no patient developed postoperative partial ulnar nerve injury following cross pinning. In the 35 lateral pinned cases no post-operative neurological loss was seen.  For cosmetic outcome the mean carrying angle in our study with its standard deviations was well within the range of the same obtained in other similar studies (Table 6). Also, there was minimal difference amongst them in the three different constructs which was not significant.

DISCUSSION
The advantage of medial-lateral pin fixation geometry is higher biomechanical stability, with iatrogenic ulnar nerve injury as its disadvantage. [13][14][15] Conversely, the advantage of lateral entry pin fixation is avoidance of iatrogenic ulnar nerve injury, but the construct is less stable biomechanically. 16  found no significant difference between the two methods in terms of loss of reduction and found no significant difference between the two methods in terms of functional outcome. Only one showed a difference in favour of lateral pinning method in terms of iatrogenic nerve injury.
In our study results are consistent with the results of most of the previous studies with similar functional outcome in all three pinning methods without significant differences in outcome amongst them.
Furthermore, in our study in lateral only pinning, there are two configurations. One with a divergent configuration and one with a parallel configuration (TOF-FCP) with one of the entries with a capitellar entry point.
Gottschalk et al studies the two entry points in lateral only pinning in supracondylar humerus in their biomechanical study and found superiority in the capitellar entry pin. 19 This was used in our TOF-FCP construct.
No cases of iatrogenic ulnar nerve injury were seen in our study. 3 cases of post-operative loss of reduction were seen in our study. Incidence of pin-tract infection were similar in all geometries in 3-4 range. Balakumar et al studied and reported the cause of loss of reduction in paediatric SCFH treated with percutaneous pinning. 20 They reported loss of reduction in 14 out of 77 cases (18.2%). Reduction was lost in 10 out of 29 children (34.5%) who underwent lateral only pinning fixation and 4 out of 48 (8.3%) children who had cross pinning fixation. They attributed the inadequate hold of pins or reduced spread of the pins.
In our study this was seen in 2 cases (11.1%) in divergent LOP and 1 case (5.3%) in cross pinning. In TOF-FCP construct in our study no case of loss of reduction was seen. The TOF-FCP fixation was stable enough to hold the fracture throughout the period of healing.

CONCLUSION
If a uniform standardized operative technique is followed in each method, then the result of all three percutaneous fixation methods will be same in terms of safety and efficacy. The selection of fixation method thus rests on the surgeon's preference and his confidence and familiarity with the method. The newer TOF-FCP does have lower rate of complications according to our study.