Fractures of the lateral condyle of humerus (lateralcondylarfracturesofthehumerus,LCF) in children are the most common elbow fractures involving the growth plate, accounting for 12–20% of all upper limb fractures in children. These fractures most commonly occur in children between 4 and 10 years old, with the highest incidence in children around 6 years old.4 The common injury mechanism leading to fracture is supination of the forearm in the straight position when falling, and varus violence leads to traction of the extensor tendon and brachioradialis muscle of the forearm (traction mechanism, pull-off). Other injury mechanisms include fracture of the lateral condyle caused by elbow valgus impact (push-out mechanism, push-off) and direct injury of the elbow.5 As we all know, missed diagnosis or delayed diagnosis and treatment of LCF may lead to joint stiffness, fracture nonunion, followed by serious cubitus valgus, delayed ulnar nerve paralysis and other complications. At present, we have basically reached a consensus on the diagnosis and treatment of LCF, but there are still some disputes.
I. selection of surgical indications and surgical methods
At present, the treatment of LCF is mainly based on the specific classification of fracture, the commonly used types are: 1Milch type, according to whether the pulley joint surface is involved into type 2, 2Jakob type, according to whether the cartilage hinge is broken and the degree of displacement is divided into 3 types. Milch type I can be considered as a variant of Salter- Harris type IV epiphyseal injury, while Milch type II is equivalent to Salter- Harris type II epiphyseal injury.6
At present, the research of evidence-based medicine thinks that the degree of X-ray fracture displacement can be used as the best basis for guiding operation and clinical decision. According to fracture displacement, type Ⅰ: < 2mm, long arm plaster fixation, type Ⅱ: 2mm 4mm, closed reduction percutaneous needle (closedreductionandpercutaneouspinning,CRPP), type Ⅲ: > 4mm, open reduction percutaneous needle (openreductionandpercutaneouspinning,ORPP).7 However, there are still controversial areas, such as Song et al.8 think that closed reduction and internal fixation is an effective method for the treatment of unstable displacement of LCF in children. If the fracture displacement is more than 2mm after closed reduction, open reduction and internal fixation is recommended. For the fracture with small displacement, conservative or surgical treatment is chosen, mainly based on the stability of the fracture, the existence of articular cartilage hinges determines the stability of LCF.9
Therefore, for micro-displaced fractures whose stability can not be completely judged by X-ray films, it is suggested that the integrity of articular cartilage hinges can be judged by elbow arthrography,10 or the articular surface can be detected by arthroscopy, so as to determine whether cartilage hinges are broken or not, so as to avoid missed diagnosis and mistreatment of micro-displaced LCF in children.9 There are also multicenter studies in China that LCF with displacement ≤ 2mm is prone to re-displacement. Early percutaneous fixation is recommended to avoid complications such as open reduction, poor function and premature closure of epiphysis caused by fracture redisplacement.11
II. Comparison of the selection of different internal fixation materials
At present, for the LCF, internal fixation materials that need surgical treatment, the main choice is Kirschner wire, hollow or lag screw, absorbable screw and so on. The selection advantage of Kirschner needle is that it is easy to operate and easy to take out, and even the Kirschner needle outside the skin can be taken out in the outpatient clinic, and there is no need for special tools. And the advantages of Kirschner wire fixation include the ability to fix smaller epiphysis or reduce the risk of epiphyseal injury.12 However, the debate on Kirschner wire fixation is mainly focused on whether the Kirschner wire should be kept outside the skin. Some studies have found that there is no significant difference in the subcutaneous infection rate of whether the Kirschner wire is embedded or not, but the skin erosion rate of the buried subcutaneous group is higher, so it is suggested that it should not be routinely buried subcutaneously in order to save more economic costs.13
As for the scholars who choose screw fixation, they think that screw fixation is more stable in biomechanics than Kirschner wire fixation.14 Li et al.15 comparison of Kirschner wire and cannulated screw internal fixation can effectively treat displaced LCF, there is no statistical difference between the two clinical outcomes, but Kirschner needle will occur surrounding skin infection. Das et al.16 reported that the infection rate of percutaneous fixation of Kirschner needle ranged from 2–9.8%, and the subcutaneous infection rate of buried skin ranged from 0.5–2%. Due to the deep placement of screws, it rarely irritates the skin, so the infection rate is very low. However, compared with the Kirschner wire that can penetrate the head epiphysis, Gilbert et al17 suggested that screws are usually placed through the metaphysis of the lateral condyle, rather than through the ossification nucleus of the capitulum humeri, to reduce the risk of re-injury of the epiphysis.
III. Comparison of postoperative complications and functional recovery.
The postoperative complications of LCF included bone nonunion, ischemic necrosis, premature fusion of epiphysis, overgrowth of lateral condyle, stiffness, cubitus varus or cubitus valgus and fish tail deformity.18 Launay et al.19 calculated that the operative complications after Kirschner wire fixation included pin site infection, lateral overgrowth and loss of fixation, while fixation failure or loss of position led to fracture displacement and reoperation or nonunion, which was a serious complication of LCF. Pace et al.20 found that the overall incidence of bone nonunion after LCF was 1.4%, and the only important risk factor for bone nonunion was type III fracture. Compared with Kirschner wire fixation, screw fixation provides stronger biomechanical stability, and the incidence of lateral overgrowth, loss of fixation and infection is relatively low. However, Shirley et al.12 also pointed out that the results of screw fixation and the subsequent risk of iatrogenic epiphyseal injury have not been well determined, so early epiphyseal closure and growth arrest caused by screws are still noteworthy.
Foreign studies have found that 4% of the patients with LCF screw fixation have the phenomenon of overflexion or loss of activity, and there is no growth stagnation or change of lifting angle. Long-term follow-up showed that the average extension loss was 2 °(range 0 °25 °) and the average flexion loss was 8 °(range 0 °25 °).12 The growth disorder of the epiphysis of the distal humerus may affect the carrying angle and lead to cubitus valgus or varus deformity. In some cases, the hypertrophy of the posterolateral condyle of the fracture can increase the Baumann angle, leading to cubitus varus deformity, while growth stagnation reduces the Baumann angle, leading to cubitus valgus deformity.21
IV. about the postoperative nursing and the timing of internal fixation
Whether closed or open reduction, internal fixation with Kirschner wire or screw fixation, scholars at home and abroad seem to agree that postoperative fixation should be supplemented by plaster or brace. As for how long external fixation is appropriate, there is no unified standard. Li et al.15 think that Kirschner wire fixation requires longer external fixation and local skin care. Gilbert et al.17 believe that screw fixation can appropriately reduce the time of plaster external fixation, which is more conducive to postoperative exercise of elbow function and a wide range of joint motion. The external fixation time in the screw fixation group was also shorter than that in the Kirschner wire group. Early removal of external fixation and functional exercise were considered to avoid joint stiffness.
There is no uniform standard for how long to take internal fixation after LCF, and considering that intra-articular fracture healing may take longer, Cardona et al.22 suggested that the time of internal fixation ranges from 3 to 8 weeks. Raghavan et al.23 believe that buried Kirschner wires can allow indwelling longer, thus promoting better fracture healing, while exposure to the skin seems to need to be removed earlier, mainly to reduce the risk of pin tract infection. More studies are based on the time of fracture healing, and some studies have found that fractures heal within 6 weeks clinically and radiographically, so it is recommended that the average time of internal fixation is 6 weeks or more.22 Another study found that the average healing time in the Kirschner wire group was 9.6 weeks, and the average healing time of all fractures after screw fixation was 7.8 weeks.17
V. Some focus and prospects on LCF
At present, about the clinical prognosis of Kirschner wire or screw fixation, most of the literature data show that there is no statistical difference. Whether the Kirschner wire is buried under the skin and whether the screw can penetrate the epiphysis of capitulum humeri, the length of fixation time is not final. Due to the bleeding and swelling after soft tissue tear, the infiltration of synovial fluid, the stimulation of internal fixation and other factors, incision infection can not be completely controlled, especially the incision scar caused by open reduction and the need for secondary internal fixation. it has been reported that the use of absorbable screws for fracture fixation will overcome the shortcomings of metal screw fixation which need to be removed by second operation. At the same time, it still retains the advantage of biomechanical stability.24 It has also been reported that arthroscopy can be used to assist the displacement of humeral lateral condyle fractures larger than 2mm to achieve closed reduction and percutaneous needle puncture.25 In the case of ischemic necrosis of the lateral condyle (avascularnecrosis,AVN) after LCF, Conaway et al.  believed that the occurrence of AVN was mainly due to excessive peeling of the soft tissue of the lateral condylar fracture, rather than the approach used, and recommended that the posterior approach did not need to peel off the soft tissue, and still had a good visibility of fracture reduction.