Management of Pediatric Displaced Distal Metaphyseal Forearm Fracture: Comparison between Cast Immobilization and Percutaneous kirschner Wire Fixation

METHODS: Thirty five children (group I) of age between 6 to 13 yrs with displaced ( more than 50% of cortical diameter) or angulated (more than 20°) distal metaphyseal forearm fracture managed with closed reduction and above elbow cast were compared with 21 children (group II) managed with closed reduction and percutaneous crossed Kirschner fixation. Clinical outcomes and complications were compared in both groups after 12 weeks of follow up.


INTRODUCTION
Distal forearm bone fractures comprise 75% of all forearm fracture in children and are mostly treated with closed reduction and cast application but recently the trends are changing towards primarily closed reduction and percutaneous Kirschner wire (K wire) fixation to prevent redisplacement of the fracture in the cast. [1][2][3][4][5] The reported incidence of displacement of metaphyseal fracture of distal radius in cast varies from 7% to 25% with various studies. 3,6 Poor casting technique, presence of associated fracture or plastic deformity of ulna, initially grossly displaced and angulated fracture of radius and increased residual angulations and displacement after reduction are considered to be the factors responsible for displacement after closed reduction and cast application. 1,[7][8][9] Some degree of residual angulations and displacement are accepted because of extremely well remodeling capacity of fracture in children but displacement requiring remanipulation not only have poor results but also creates significant parental distress. 10 Many authors recommend use of percutaneous K wires for fracture fixation in initially grossly displaced and angulated fracture with associated ulna fracture but these studies have either included all types of distal radius fracture including epiphyseal injury and isolated radius fracture or used single K wire or are retrospective studies. 2,11,12 The present prospective cohort study compares clinical outcomes in children with grossly displaced and angulated distal both bone metaphyseal fractures treated with either Original Article closed reduction and long arm cast or closed reduction with percutaneous crossed K wire fixation.

MATERIALS AND METHODS
One hundred and thirty one children of aged 6 to 13 years with distal radius fracture were managed in Dhulikhel Hospital in between July 2007 to June 2009. Among them 63 were distal radius metaphyseal fracture with displacement more than half the diameter of the bone (grade III or IV) or angulations more than 20° and associated with ulna fracture. Isolated fracture of radius, minimally displaced (grade I: no translation and grade II: translation less than half the diameter of bone) or angulated (<20°), compound fractures, radiological suspicion of epiphyseal involvement, bilateral forearm fracture or ipsilateral upper extremity fracture were excluded from the study.
Among 63 children, 41 children (group I) were managed with closed reduction and above elbow cast with standard technique with fluoroscopy guidance under general anesthesia by attending orthopedic surgeon. (Fig.  1a,1b) The acceptable criteria for reduction was fracture apposition more than 80% in both plane and angulations in sagittal plane less than 15°for children below 10 years of age and less than 10° for children more than 10 years of age.

Fig Pre (1a) and post (1b) reduction with closed reduction and above elbow cast application
Twenty two children (group II) underwent closed reduction and percutaneous crossed K wire fixation with fluoroscopy guidance under general anesthesia. First K wire was passed through radial styloid process or just above the physis across the fracture dorso-medially and second K wire through Lister's tubercle towards volar and radial side. (Fig. 2a,2b) Both K wires purchased opposite cortex. Optimal care was taken not to entrap extensor tendons and radial cutaneous nerve. The tip of the K wires bent outside the skin. When closed reduction was not possible, pin leverage technique was used for reduction. 13 Light weight forearm brace was applied post operatively for four weeks. Children were discharged on second day of the procedure and followed up on 1 st and 2 nd week for radiological evaluation of fracture displacement and pin tract infection and on 4 th week for removal of K wires on out patient basis for group II and on 5 th week for removal of cast in group I. Choice of further immobilization with forearm slab or brace was dependent upon radiological sign of fracture healing. Active mobilization of fingers, wrist, forearm and elbow was started immediately after removal of K wires or cast. Fracture displaced with apposition less than half the diameter of bone and angulations in sagittal plane more than 15° in children below 10 years of age and more than 10° in children more than 10 years of age detected in first two weeks of follow up were considered as redisplacement and subjected for remanipulation. Functional outcome in terms of loss of extension and flexion of elbow and wrist and supination and pronation of forearm were recorded and compared with contralateral side on 12 week. Six patients in group I and 1 patient in group II who could not be followed up for at least for 12 weeks were excluded from final analysis. MANAGEMENT  Statistical analysis was performed by using SPSS (Chicago, Illinois) version 11 software for Window. Non parametric test, as appropriate for data, were used for comparison of pre operative and outcome variables. A p value <0.05 was regarded as significant.

RESULTS
Pre operative variables were comparable as shown in table 1. All fractures were managed with closed reduction followed by cast (group I) or percutaneous K wire fixation (group II) within 24 hours of hospital admission but injury-treatment interval varied between six hours to five days. All fractures united in three months follow up. The mean follow up period in group I was 13.4 weeks and 15 weeks in group II. At final follow up, there was increased loss of flexion and extension of elbow and wrist as well as pronation and supination of forearm in group I as compare to group II but non of them were statistically significant. (Table 2) In group I, six children (17.14%) had fracture displacement in cast and among them, three were noticed on 1st week of follow up and underwent remanipulation and above elbow cast application; two children presented late (6weeks) with radiological signs of union and hence planned for further management later on and another patient asked for referral for second opinion. Others complications were swelling requiring splitting of cast in four children. Among these 10 children in group I, seven patients had injury hospital interval more than 24 hours and six had completely displaced fracture.
In group II, there were four pin tract related complications. Two presented with serous discharge and two with purulent discharge. They came late for follow up and had poor compliance for pin tract dressing. Both of them had also sprouting infected granuloma at pin insertion site which was excised after removal of K wires under general anesthesia. All children improved with oral antibiotics and routine care of wound or pin tract.

DISCUSSION
Despite being one of the common injury, the management options for distal metaphyseal radius and ulna fracture MANAGEMENT 1,3,16 Another randomized controlled trail by Milller BS et al , concludes that potentially unstable radius fracture may be effectively treated with either closed reduction and cast immobilization alone or closed reduction with percutaneous pin fixation because they found no significant difference in fracture angulations between two groups in subsequent follow up. 17 The present study compared the loss of movement of elbow, forearm and wrist instead of fracture angulations because clinical outcomes in terms of movement loss are more important than radiological evaluation of fracture angulations. Though there are slightly increased loss of flexion and extension of elbow and wrist and supination and pronation of forearm in children treated with closed reduction and cast application than in K wire fixation group, statistically they are insignificant. Mean loss of elbow flexion and extension (12° vs. 4°, p =0.08), wrist dorsflexion and palmerflexion (27° vs. 14°, p=0.12) and forearm supination and pronation (27° vs. 15°, p= 0.143) were statistically not significant between group I and II.
Another major issue in distal metaphyseal pediatric forearm fracture treated with closed reduction and cast application is redisplcaemnet and various risk factors are attributed for this complication. Gibbon CL et al consider isolated radius fracture is more prone to redipsplacement where as Schnieder J et al and Bohm ER et al consider associated ulna fracture is a risk factor for redisplacement. 8,9,18 The cast indexes, type of anesthesia, surgeon's experience are few among the risk factors considered responsible for redisplacement but consensus are lacking. 14,17 The initial displacement and post reduction residual translation were found to be a statistically significant risk factor for redisplacement by various authors. 1,3,7 The present study excluded all isolated radius fractures; all reduction was performed by attending orthopedic surgeons under general anesthesia so that clinical outcomes can be compared with least confounding factors possible. Since age of the children does not significantly influence the risk of redisplacemnt and criteria of adequate reduction or loss of reduction which has been adjusted for remaining growth potential according to age( below and above 10 yrs) is similar for both group I and II, outcome measurement was not analyzed in different age group in the present study. 9,16 Redisplacement requiring remanipulation are associated with poor outcome. 19,20 But due to lack of uniform criteria for defining redisplacement in literature, reported incidence varies from 7% to 25%. In the present study, redisplacement was defined when fracture loss more than 50% cortical contact or sagittaly angulated (more than 15° for children less than 10 years and more than 10° children more than 10 years). With these criteria, six children (17.14%) had redisplacement in the cast which is comparable to 14.04% as reported by Monga P et al. 1 Among these six children, five children presented after 24 hours of injury ( 2-5 days after injury) and had dorsally displaced fracture which is similar to finding reported by Schneider J et al. 9 In the present study, complication rate (28.5%) is higher in the cast group (including both fracture displacement and swelling requiring splitting the cast) as compare to 19.04% in K wire fixation group (pin tract infection) which is statistically significant (p=0.04). similar results have been reported by Miller BS et al. 17 But we did not encounter radial cutaneous nerve injury or entrapment of extensor tendons. Making a small stab incision and blunt dissection with hemostat up to bone is recommended before inserting the K wires. Pin tract related complications like loosening, migration or infection are usual complications of percutaneous technique of fracture fixation. We ensured double cortical purchase of both K wires in all cases except in two cases where one of the wires was passed intramedullary. Bending the K wire and leaving outside skin not only prevents migration but also allow removal on out patient basis under mild sedation if required. superficial infection usually resolves with repeated pin tract dressing and oral antibiotics but deep infection need MANAGEMENT  incision and drainage and wound care. Non compliance for follow up because of various reasons is not uncommon in our practice. Two patients in the preset study who presented late because of difficulty in transportation had infected sprouting granuloma at K wire insertion site which resolved after excision without long term effect.
Another important concern is risk of growth plate injury by K wire insertion. Though various techniques have been reported to avoid growth plate while inserting K wire, it has been found that there is no long term squeal as a result of trans-epiphyseal smooth K wire insertion. 17,21,22 CONCLUSION Grossly displaced or angulated distal metaphyseal forearm both bone fracture in children treated with either closed reduction and above elbow cast or closed reduction with crossed K wire fixation have no statistically significant clinical outcomes in terms of loss of movement of elbow, wrist and forearm. However, loss of movement and complication rate is higher in cast group and per cutaneous K wire fixation can prevent redisplacement. Randomized controlled trial with larger sample size is required to confirm our findings.