Closed Reduction of Severely Angulated Rockwood and Wilkins’ Type C Thumb Metacarpal Base Fractures in Children

Background (cid:0) Management of severely angulated Rockwood and Wilkins’ type C(RW-C) thumb metacarpal base fractures in children is challenging. We report experiences of percutaneous leverage reduction and dual antegrade crossing Kirschner (DACK) wire xation in these fractures, aiming to assess the results using our reduction technique. Methods (cid:0) From October 2011 to September 2015, A total of 17 patients with severely angulated RW-C thumb metacarpal base fractures were treated at our hospital. The injured arm, including the entire rst ray, was immobilized with a thumb-spica cast for 4-6 weeks and evaluated radiologically and clinically. Percutaneous leverage reduction and DACK wire xation were successfully performed for 17 patients. No patients were treated with open reduction. 16 patients were followed up for a mean of 32 months (range 24-41 months). The results were assessed using the modied Mayo score. The level of signicance was set to be p<0.05.

patients with an excellent outcome and one patient with a good outcome. Cosmetic results were described as good and satisfactory by all patients. There were no refractures and no incidences of nonunion, growth arrest in the proximal epiphysis. Only one patient suffered from a super cial infection, which was resolved after the removal of the k-wires and the administration of oral antibiotics.
Conclusion Our percutaneous leverage technique with DACK wire xation can be successfully used to treat these fractures. This technique is simple to learn and minimally invasive, and the results are satisfactory. It may be an appropriate choice for the treatment of irreducible RW-C fractures.

Background
Thumb metacarpal fractures account for 1% to 5% of hand fractures in children, with most occurring at the base [1,2,3]. There are four types of thumb metacarpal base fractures in children: type A, metaphyseal fractures; type B, Salter-Harris (S-H) type II physeal fractures with lateral angulation; type C, S-H type II physeal fractures with medial angulation; and type D, S-H type III fractures (paediatric Bennett fractures) [4,5,6]. Closed reduction is more di cult to perform for type C (RW-C) thumb metacarpal base fractures due to the mobility of the metacarpal base and swelling [4]. Some authors have advocated that if closed reduction is performed successfully and the result is stable, short-arm spica splint or cast immobilization is possible [4,7,8,9]. Otherwise, percutaneous pinning and open reduction and internal xation are recommended for unstable and irreducible RW-C thumb metacarpal base fractures [4,10,11,12]. Several techniques have been reported, including the Iselin technique and percutaneous K-wire xation [4,5,6].
Percutaneous leverage reduction and xation techniques for irreducible RW-C thumb metacarpal base fractures have not been mentioned before. This article is a retrospective study of our experience treating severely angulated RW-C thumb metacarpal base fractures using the percutaneous leverage technique and dual antegrade crossing Kirschner wire (DACK wire) xation.

Patients
This study was approved by the Institutional Ethical Review Board of Dalian Children's Hospital (approval number 20003). Written informed consent was obtained from all guardians for anonymized data analysis and publication. A total of 17 patients with severely angulated RW-C thumb metacarpal base fractures were treated at our hospital from October 2011 to September 2015. A total of 16 patients were followed up for a mean of 32 months (range 24-41 months). All cases were classi ed as severely angulated RW-C fractures. There were 9 girls and 7 boys, with an average age of 10.8 years (range 7.5 to 14.0 years). A total of 10 patients had fractures on the right side, and 6 patients had fractures on the left side. All surgeries were performed by the senior surgeon, and the average surgery time was 20 minutes (range 12-32 minutes). The injured arm, including the entire rst ray, was immobilized with a thumb-spica cast for 4-6 weeks and evaluated radiologically and clinically.

Surgical Procedures
General anaesthesia was induced in all patients. First, with the guidance of the C-arm image intensi er, a leverage K-wire with a 1.5 mm diameter was percutaneously inserted into the bone fragment from the displacement direction of the fractured thumb metacarpal base fragment (Figs. 1, 2). The procedure was performed carefully so that the wire did not penetrate too deeply past the dorsal cortex of the distal fragment. Once the K-wire crossed the fracture site, it was moved into position, and supplementary pressure was placed on the volar rim of the distal fragment for reduction. Then, reduction was con rmed with an image intensi er (Fig. 3a, 3b). Anatomic reduction was maintained with DACK wires measuring 1.0 mm in diameter (Fig. 3c). After successful reduction and xation, the external part of the nail was bent to an angle of 90°. The injured arm, including the entire rst ray, was immobilized with a thumbspica cast for 4-6 weeks; when the wires and cast were removed at the outpatient department, continuous passive motion (CPM) was encouraged.

Postoperative evaluation
The rst clinical review was conducted two weeks after surgery. Then, the cases were assessed radiographically for xation and bone union at 4 weeks, 6 weeks, 8 weeks and 6 months postoperatively and every 6 months thereafter. When calluses formed, the cast and K-wires were removed without anaesthesia, and active exercise was encouraged to recover the full range of motion (ROM) of the thumb.
Statistical analysis SPSS v22(IBM Corp., Armonk, NY, USA) was used for statistical analysis. For the nonnormally distributed data, the Mann-Whitney U test for independent samples was conducted. For the normally distributed data, the paired-samples t test was used to assess the differences between the preoperative and postoperative results. The level of signi cance was set to be p<0.05.

Results
There were 9 girls and 7 boys, with ages ranging from 7.5 to 14.0 years and an average age of 10.8 years.
Percutaneous leverage reduction and DACK wire xation were successfully performed within an average total surgery time of 20 minutes (range 12-32 minutes). Bone union was achieved in all patients within a mean time of 4.2 weeks (range 4-6 weeks). The average angulation (preoperation: 50.5° (range 40.8°-67.0°) vs postoperation: 5° (range 0.0°-7.0°)) signi cantly changed from before to after surgery (P<0.05). Only one patient suffered from a super cial infection, which was resolved after the removal of the k-wires and the administration of oral antibiotics. The clinical outcomes were evaluated by the modi ed Mayo score, and there were 15 patients with an excellent outcome and one patient with a good outcome. There were no cases of deep infection, secondary displacement, malunion, or growth arrest in the proximal physis (at least 2 years follow-up). All 16 patients recovered full mobility of the rst ray with respect to that on the contralateral side.

Discussion
Obviously displaced RW-C thumb metacarpal base fractures are rare in children and still challenging for paediatric orthopaedic clinicians to manage. Closed reduction is di cult to perform for severely angulated and displaced RW-C fractures. According to some authors, RW-C fractures with fewer than 30 degrees of angulation disbalance can be treated by closed reduction and splinting. Ruptures of the medial periosteum make the fracture unstable, and immobilization with the rst ray yields unreliable results [6]. Some researchers have recommended that aggressive procedures are performed in children when the maximum angle of fracture is > 30 degrees, the magnitude of displacement of the fracture is > 2/3 of the diameter of growth plate, or a rotational deformity is present [6,8,9]. All 17 cases exhibited these operative indications. Thus, the indications of acceptability of imperfect reduction exist for two reasons. First, the rst ray is constituted by a series of joints that can compensate for small extra-articular displacements without causing severe disability. Second, such displacements can be corrected by remodelling the growth plate [14,15]. However, this spontaneous correction requires two years [5]. We must remember that the growth plate closes at an average age of 14.5 years in girls and 16.5 years in boys when considering the indications for the treatment of these fractures [6,15].
Some studies have reported that severely displaced RW-C fractures might require open reduction to remove any portions of interposed periosteum that prevent reduction. Open reduction is indicated for irreducible RW-C fractures [4,12]. However, Jehanno et al reported that open reduction is not di cult due to interposition of tendons or of the periosteum [6]. The mobility of the metacarpal base and swelling make closed reduction di cult. Comminution, soft tissue interposition, or transperiosteal "buttonholing" may further complicate reduction [4,10]. Manual closed reduction of RW-C fractures requires axial traction on the thumb, and pressure is placed on the base of the distal fragment [17]. Both the second metacarpal and thenar impact manual closed reduction. In theory, these are the true reasons that closed reduction fails. When closed reduction is performed unsuccessfully, open reduction is also required [4]. The leverage technique that we described in this study showed a minimally invasive and reliable choice to avoid open reduction.
In general, manual reduction and leverage treatment for paediatric fractures, including S-H type II fractures of the distal radius, radial neck fractures, supracondylar fractures, and Bennett fractures, are successful and yield good results, and satisfactory results have been reported [18][19][20][21]. We performed leverage reduction to anatomically reduce these fractures. The number of leverage manual reduction attempts can be reduced to fewer than 3, while injury to the physis caused by the tip of the leverage k-wire can be avoided. For at least 2 years follow-up, there were no cases of premature physis closure, bone bridge formation or epiphyseal ischemic necrosis in our study.
There are many pin con guration options, including pinning across the reduced carpometacarpal (CMC) joint, the Iselin technique, the modi ed Iselin technique, and direct xation across the fracture [6,12,22,23,24]. Some authors have shown that intraarticular k-wires may aggravate articular surface lesions and cause posttraumatic arthritis. Thus, the Iselin method was proposed [25]. Some researchers have determined the incidence of secondary displacement because of the faulty Iselin technical approach and a decrease in the quality of reduction [17]. Wiggins preferred the technique of trans xing a k-wire across the epiphyseal growth plate, which has never been reported to cause epiphysiodesis [26]. Hastings also demonstrated that thumb base fracture xation with longitudinal K-wire xation yields good results [22]. We prefer DACK wire xation, which has been proven to be a good technique in previous studies.
Bone union was achieved in all 16 patients within a mean time of 4.2 (range 4~6 weeks). A total of 15 patients had an excellent outcome, and one had a good outcome, without secondary displacement of the fracture or tendinous adhesion. In our experience, the advantages of DACK wire xation include the easy selection of the needle puncturing point and stable trans xion of K-wires across the epiphyseal growth plate, which is yields higher stability than does the Iselin technique.
In our research, most of the leverage procedures were performed within 0.30 min with 1-3 leverage attempts. A longer duration of the leverage procedure is associated with more radiation exposure (RE).
The risk of RE needs to be understood and minimized in paediatric trauma theatres, as RE is associated with malignant diseases [27]. Ultrasonography (US) has also been used for intraoperative monitoring for the treatment of radial neck fractures in children to reduce the dose of RE [28]. US could be a useful alternative to X-ray in the future for this kind of fracture during intraoperative intensi cation.
Our results show that the following key points should be understood when performing the procedures: (1) According to the preoperative imaging and C-arm image intensi er data, the plane with the largest displacement and angulation of fractures should be chosen as the leverage plane to achieve anatomical reduction and reduce the number of leverage attempts. (2) The abductor pollicis longus tendon and the rst metacarpal epiphysis should be considered the puncturing points for the wires to reduce tendinous adhesion.
(3) DACK wire xation is more reliable. (4) When leveraging, the tip of the K-wire should be moved towards the metaphysis to prevent injury to the physis. (5) In contrast to other metacarpals, the thumb metacarpal is visible on both AP and lateral X-rays, and the angulation and displacement can more reliably be assessed.
The main limitation of this study is that it is a retrospective cohort study with a small sample size and without a control group. We cannot con rm that our technique is superior to others. However, our technique yielded satisfactory outcomes with few complaints. Additional studies with large sample sizes are needed.

Conclusions
Our percutaneous leverage technique with DACK wire xation can be successfully used to treat these fractures. This technique is simple to learn and minimally invasive, and the results are satisfactory. It may be an appropriate choice for the treatment of irreducible RW-C fractures.
Abbreviations RW-C, Rockwood and Wilkins' type C

Consent for publication
Written informed consent was obtained from all guardians for anonymized data analysis and publication.

Availability of data and materials
All data generated and/or analyzed during the current study are available in this published article. Data required that are not in the article are available from the corresponding author on reasonable request.

Competing interests
The authors declare that they have no competing interests.

Funding
None.
Authors' contributions FQ and FJ collected patient material, designed and drafted the manuscript. FQ and FJ collected material, advised on the main subject and worked on the manuscript, FQ was the main statistician. FQ edited manuscript and presented the concept of the study. All authors read and approved the nal manuscript.  Examination Findings  Pain  25  No pain  20  Pain only with weather change  15  Moderate pain on exertion  15  Slight pain with activities of daily living  5  Moderate pain with activities of daily living  0  Pain at rest  Satisfaction  25  Very satisfied  20 Moderately ‡ Defined as the distance of the thumb pulp to the metacarpophalangeal furrow of the fifth digit in centimeter. § Sum of adduction and pinch grip. ‖ By Semmes-Weinstein monofilaments. A score of 97 points or better was considered to be a "satisfactory result".