Valgus-impacted fracture of neck of femur in a 12-year-old child

Abstract

Though uncommon, fracture of neck of femur in children is a devastating injury due to the complications it may cause. Treatment depends on the age of the child, the displacement of the fracture and the type of fracture based on Delbet classification. Surgical treatment is indicated in displaced fractures. We report a case of an impacted fracture of neck of femur in a 12-year-old girl. The girl was managed non-operatively. The fracture united uneventfully. An impacted fracture of neck of femur is common in the adult population. To the best of our knowledge, this fracture pattern has not been reported in the paediatric age group.

Background

Fracture of neck of femur is rare in children. Significant force is required to disrupt the thick, resilient periosteum and cause fracture. They usually occur as a result of high-velocity injury such as motor vehicle accident and fall from height. However, sometimes, a trivial injury may cause a pathological fracture and repetitive injury may cause a stress fracture. Due to the tenuous blood supply and proximity to the proximal femoral epiphysis, fractures of the femoral neck have the potential to cause significant long-term complications such as avascular necrosis (AVN), non-union and coxa vara. These fractures are classified according to the system described by Delbet and adapted by Colonna,¹ and literature reports that the transcervical type of femur neck fractures (Delbet type 2) is the most common, followed by the cervicotrochanteric type (Delbet type 3).²

The case presented here features a valgus-impacted fracture of the neck of femur in a 12-year-old girl. This fracture pattern is commonly seen in the adult population and classified according to the Garden classification as type 1. However, such a fracture pattern is unusual in the paediatric population. This case report highlights a rare, unreported variant of femoral neck fracture in the paediatric age group and its management.

Case presentation

A 12-year-old girl sustained a fall while playing at her residential school, following which she reported pain around her left hip. She was able to bear weight and walk, although, with a limp. The child continued to attend school and carry out her activities of daily living, however, she could not play among her peers due to pain and limp. Over the course of the following 10 days, the complaints were reduced to pain on weight-bearing and walking. With pain persisting, the child was brought to our outpatient clinic for evaluation. There were no history of fever, swelling, pain prior to the fall, and loss of weight or appetite.

On physical examination, the child walked with an antalgic gait. Palpation of the anterior hip joint line revealed tenderness. Movements at the hip joint, especially the rotations, were painfully restricted. There were no deformities or limb-length discrepancy.

There were no signs of injury to any other region of the body.

Investigations

Anteroposterior and frog-lateral radiographs of pelvis with both hips showed a faint line in the neck (Delbet type 2) with a slight coxa valga (figure 1). A non-contrast CT confirmed the presence of a cortical break (medial and lateral sides), which showed a valgus-impacted fracture of the neck of left femur. There were no features of a pathological fracture (figures 2 and 3).

Figure 1.

Standard anteroposterior and frog-lateral plain radiographs showing a valgus-impacted fracture of the neck of left femur.

Figure 2.

CT scan confirming the presence of a cortical break involving both medial and lateral cortex.

Figure 3.

CT scan confirming the presence of a cortical break involving both anterior and posterior cortex.

Routine blood investigations including complete blood picture and inflammatory markers (erythrocyte sedimentation rate and C reactive protein) were normal. The child was examined by a paediatrician to rule out rickets, osteopenia and other pathological fractures. Serum calcium, phosphorus and alkaline phosphate were normal.

Dual-energy X-ray absorptiometry (DEXA) scan is useful in identifying stress fractures and pathological fractures.³ However, since the child was active and had no history of fractures, and radiographs showed an impacted fracture with no features of osteoporosis, DEXA scan was not performed.

Differential diagnosis

Stress fracture

If an adolescent child presenting with pain, limp and restriction of movements at the hip joint after a trivial injury, one must exclude stress fractures of the femoral neck. However, there was no history suggestive of the patient being subjected to repetitive stressful activities like long-distance running or athletic training. While plain radiographs are sufficient to arrive at a final diagnosis, they may not reveal the cortical breaks in undisplaced fractures. Advanced imaging such as a CT or an MRI scan is required to make a diagnosis.

Slipped capital femoral epiphysis

Another cause for hip pain in children and adolescents is slipped capital femoral epiphysis (SCFE). In chronic stable SCFE, the child will be able to walk. Here the CT scan was crucial to rule out SCFE and aid in our diagnosis.

Pathological fracture

Since femoral neck fractures are uncommon in children and usually happen with high-energy trauma, it was imperative to investigate for a pathological fracture when the history was suggestive of a seemingly trivial injury. The pathology may have been osteomyelitis, bone tumours, metabolic conditions such as rickets, or congenital conditions such as osteopetrosis or type 1 osteogenesis imperfecta. A thorough history, physical examination and routine blood investigations ruled out these possible causes of a pathological fracture. The child was perfectly normal without any history of fracture, hence osteogenesis imperfecta was ruled out. The child was also evaluated by a senior paediatrician for other metabolic bone diseases. Blood parameters including electrolytes were normal in the child.

Soft tissue injury

The soft tissue injury including traumatic synovitis can lead to painful limp. The radiographs of hip joint would be normal. In presence of normal radiographs, MRI is indicated to demonstrate soft tissue injury around the hip joint.

A flow chart showing diagnostic algorithm and probable treatment may be useful for suspected neck femur fracture in a child (figure 4).

Figure 4.

Diagnostic workflow for evaluating a child with hip pain and limp following trivial trauma. AP, anteroposterior.

Treatment

The nature of the injury and the prognosis were explained to the parents and they were counselled for surgical treatment. However, they opted for non-operative management. The child was managed conservatively with non-weight-bearing mobilisation and analgesics. The parents were explained the chances of secondary fracture displacement despite being completely compliant with non-weight-bearing mobilisation and in such an event, surgery would be inevitable. At 6-week and 3-month follow-up, plain radiographs were repeated which showed no displacement (figure 5). The child was allowed to gradually walk with weight-bearing by 3 months.

Figure 5.

Anteroposterior and frog-lateral view of the pelvis at 3 months showing fracture union with no secondary displacement.

Outcome and follow-up

At 3-month follow-up, the child was allowed to walk full weight-bearing without the help of walking aid. Follow-up radiographs at 1 year showed complete union of fracture with no residual deformity and no features of AVN of the femoral head (figure 6). Clinically, the child was asymptomatic, had no limb-length discrepancy and full range of movements at the hip joint at 2-year follow-up (figure 7).

Figure 6.

Anteroposterior and frog-lateral view at 1 year showing fracture union with no residual deformity and a comparable neck-shaft angle.

Figure 7.

Anteroposterior and frog-lateral view at 2 years showing normal hip joint with no signs of avascular necrosis of the femoral head.

Discussion

It is not uncommon to encounter a child with a history of road traffic accident or fall from height in a populated country such as India. One of the injuries a child may sustain following such a high-velocity trauma is the fracture neck of femur. Though estimated to account for less than 1% of all paediatric fractures, the long-term complications are feared by orthopaedic surgeons across the world.^{2 4} Hence, there is an abundance of literature on paediatric femoral neck fracture and its complications. However, there seems to be no reported cases of impacted femoral neck fracture in this age group.

In this case, the child sustained a femoral neck fracture following a fall. Thereafter, the child was able to walk, although with a limp and pain. The valgus-impacted nature of the fracture perhaps explains why the child was able to bear weight and walk. This is different from the vast majority of cases reported in the literature (table 1).

Table 1.

Review of literature of neck femur fracture in children.

Authors	Year of publication	Type of study	Remarks
Yeranosian et al22	2013	Systematic review of 30 studies (3 with level III evidence and 27 with level IV evidence) with 935 patients	Of the 935 patients, the classification of 876 were recorded and in none of those 876 cases a valgus-impacted fracture was noted.
Moon and Mehlman21	2006	Meta-analysis of 360 cases from 20 studies	Objective was to identify risk factors for avascular necrosis (AVN) following femoral neck fractures. The type of fracture was an independent risk factor for AVN. However, there is no mention of valgus-impacted femoral neck fracture in any of the 360 cases.
Al Khatib et al23	2019	Meta-analysis of 6 studies with 231 paediatric femoral neck fractures	All fractures were classified according to the Delbet classification, and no mention of a valgus-impacted fracture.
Bali et al4	2011	Retrospective observational study over a 10-year period; 36 cases were observed for clinical outcomes and complications	All fractures were classified according to Delbet classification; 8 out of 36 fractures were classified as undisplaced, but there is no mention of valgus-impacted fracture.
Shrader et al16	2006	Retrospective observational study over a 30-year period; 20 cases were observed for clinical outcomes and complications	Delbet classification was used to classify the 20 fractures; 3 out of 20 were minimally displaced, however there is no mention of a valgus-impacted fracture.
Forster et al14	2006	Series of 3 cases of undisplaced femoral neck fractures	All 3 cases were classified as Delbet type 3, however there is no mention of a valgus-impacted fracture.
Wang et al17	2019	Retrospective observational study to clarify the risk factors predicting avascular necrosis following femoral neck fractures in children	Identified two independent risk factors—age of the child and severity of initial displacement. Categorised fractures into three groups based on severity of displacement.
Wang et al18	2020	Retrospective, multicentric observational study to evaluate the correlation between AVN and severity and direction of initial displacement	Initial translation better predicts AVN than angulation.

Paediatric femoral neck fractures are classified according to the popular Delbet classification.^{2 5} This is a four-part classification system based on the location of the fracture line, and each type may be displaced or undisplaced.

Our patient had a transcervical type (Delbet type 2) of femoral neck fracture which was impacted in a valgus position with a neck-shaft angle of 152° as compared with 144° on the contralateral side. The mode of injury—fall while playing, a relatively lower velocity injury—probably explains the minimally displaced nature of the fracture. The mechanism of valgus impaction of femoral neck fractures was described by Linton⁶ first, and then Bentley.^{7 8} Linton showed that there was little difference between the adduction-displaced fracture and the abduction-valgus impaction fracture, as for both of these the mechanism remains the same—an external rotation strain. The only difference between the two was the degree of displacement. Bentley explained that impaction happens when the injuring force is not strong enough to cause displacement. However, in children these fractures are usually displaced and are almost never impacted.⁹ Craig¹⁰ explained that in children, unlike in adults, the orientation of the trabeculae is not along the stress lines, thus making the fracture surfaces smooth with sparse interlocking and little impaction. This also explains why undisplaced femoral neck fractures have a high tendency of secondary displacement.

These fractures are different from stress fractures of the femoral neck, which have different mechanisms of injury. They are rare in the paediatric population and occur as undisplaced fractures mostly on the compressive side of the femoral neck.¹¹ Devas¹² followed up on 32 stress fractures of the femoral neck in adults and classified them into two categories—the compression type and the transverse type. The compression-type fractures were considered stable, whereas the transverse-type fractures were found to be unstable with high tendency for displacement. St Pierre et al¹³ reported on femoral neck stress fractures in five children. All the five fractures were undisplaced and occurred on the compressive side of the neck. They described two aetiological varieties—fatigue fractures which occur due to repetitive microtrauma due to abnormal muscular stress on a bone that has normal elastic resistance, and insufficiency fractures which occur in bones that are deficient in minerals or elastic resistance under the influence of physiological muscular stress.

The reason why a valgus-impacted fracture in the paediatric population has not been brought to light, perhaps, is because most of these fractures occur as a result of high-velocity injury, sufficiently large enough to cause displacement. Further, even the undisplaced fractures have a tendency for displacement after initial evaluation. Bentley⁸ followed up 70 adult patients with impacted neck fracture, of which 43 were managed by various non-operative means. Thirty-six of 43 fractures went onto unite uneventfully, while the remaining 7 had secondary displacement. Forster et al¹⁴ reported a series of three cases of undisplaced cervicotrochanteric type (Delbet type 3) of femoral neck fractures which showed secondary displacement with primary non-operative treatment. They concluded that undisplaced femoral neck fractures are prone to secondary displacement if strict non-weight-bearing protocol is not ensured until there are signs of fracture consolidation. Bali et al⁴ reported on 36 children with femoral neck fractures, of which 8 had undisplaced fractures and all were initially managed non-operatively. Four of these eight displaced within the hip spica and had to be operated. They further reported that only two patients who were managed exclusively by non-operative measures had satisfactory outcome.

Impacted femoral neck fractures are common in the adult population. They usually form a valgus impaction and very rarely, a varus impaction. The valgus impaction is considered as a relatively stable fracture, and it is usually managed with osteosynthesis in the adult population.¹⁵ On the same lines, the parents of our patient were counselled for internal fixation. They, however, opted for conservative treatment. The possibility of secondary displacement despite following strict non-weight-bearing protocol was conveyed to them. The patient was managed non-operatively with strict non-weight-bearing mobilisation for 3 months. Radiographs were taken at 6 weeks and 3 months to look for fracture consolidation, displacement and deformity. The fracture had completely united uneventfully by 3 months. At 1-year follow-up, the child was completely asymptomatic, there was no residual valgus deformity or varus collapse, and there were no features of AVN.

Fractured neck of femur in this age group is fraught with complications. The tenuous blood supply and often, the high-velocity injury that precedes the fracture, make these injuries prone to devastating complications such as AVN, non-union of fracture and coxa vara. AVN of the femoral head is by far the most common complication of such fractures.2 5 16–20 Dendane et al²⁰ reported an overall complication rate of 33.3% in their series, of which 28.5% had AVN. Moon and Mehlman²¹ did a meta-analysis of 360 cases of these fractures from 20 studies with an objective to identify the risk factors for developing AVN following femoral neck fractures. They concluded that the rate of AVN decreases as one progresses from Delbet type 1 (38%) to Delbet type 4 (5%) with the type of fracture. The type of fracture and age of the child at presentation were the most significant risk factors for developing AVN. Wang et al recently updated on various factors that predicted the development of AVN following femoral neck fractures.¹⁷ They reviewed 239 children with femoral neck fractures and identified two independent risk factors—initial displacement and age of the child. They concluded that the rate of AVN increases with age, particularly in children above the age of 12 years and with severity of displacement. With respect to initial displacement, Wang et al¹⁸ categorised the fractures into three groups. The first group consisted of incomplete fractures with no translation and angulation <30°, the second consisted of complete fractures with any translation and angulation <50°, and the third had complete fractures with translation and angulation >50°. They reported no AVN in the first group and concluded that initial translation is a better predictor than angulation. Our child, having had a valgus-impacted fracture with no translation (group 2 according to Wang et al), was at a low risk for developing AVN. She was, however, closely monitored for the same with timely clinical examination and radiographic evaluation. The valgus-impacted nature of the fracture in this case provided a stable configuration, preventing secondary displacement despite the child walking weight-bearing for the first 10 days following the injury. Also, theoretically, the chances of non-union and coxa vara are lesser in a valgus-impacted fracture for the same reason.

Learning points.

• Valgus-impacted fracture of the neck of femur can happen in adolescents. It is relatively stable and can be managed conservatively.

• Though these fractures are stable, they should be monitored regularly for displacement.

• On encountering an undisplaced fracture, the possibility of stress fracture should be ruled out.

• Fracture union and remodelling is associated with correction of the valgus deformity.

• It is imperative to thoroughly investigate when one encounters such an unusual fracture pattern.