Case report of LCP pediatric hip osteosynthesis of a proximal femoral fracture in a child with marble bone disease

We present a case report demonstrating the experience of the department of pediatric orthopaedics of the University Orthopedic Hospital at Sofia Medical University in the treatment of an intertrochanteric proximal femoral fracture in a child with osteopetrosis. We performed open fracture reduction with stable 120° LCP (Locking Compression Plate) Pediatric hip osteosynthesis. Fracture consolidation and ability to walk without crutches was achieved in a half a year. The presented case is the first for Bulgaria. There are still no publications in the world literature on application of such osteosynthesis in marble bone disease.


Introduction
Osteopetrosis (marble bone disease) [1] is a group of extremely rare bone dysplasias. The pathology is chracterized by increased bone density due to osteoclastic dysfunction. The osteoclasts do not resorb bone tissue and enchondral cartilage thus leading to impaired bone remodelling and accumulation of large quantities of immature bone. The most common fractures in marble bone disease are in the proximal femur. In the severe (early onset) with autosomalrecessive inheritance form, the pathologic fractures occur in early infancy. The presentation of the milder (late onset, osteopetrosis tarda) form with autosomal-dominant inheritance, varies from asymptomatic course, detected incidentally on X-ray, to occurrence of frequent fractures of the long and short bones -up to 78% of the patients [2]. Usually their conservative treatment is unsuccessful, while the operative treatment is technically difficult and followed by complications due to defective bone marrow function, delayed consolidation and higher risk of additional fractures during surgical application of orthopedic ostheosynthesis.

Patient and observation
Our clinical case is a 13 year old girl, born from a second delivery with pathologic contractions in 5 l.m. and maternal edema with albuminuria at the end of the pregnancy. Delivery was normal; with birth weight 3 500 grams and 50 cm in length fetus. In the neonatal period were detected dolichocephalism, hepatosplenomegaly, amaurosis, osteosclerotic bone changes on X-ray, hematologic aberrations; the iagnosis of osteopetrosis was made. Corticosteroid therapy was instituted. In November 2008 the patient suffered from edema in the right mandible and she was surgically treated for osteomyelitis. After 2009 there is a lack of genetic and hematologic control. The child attends a special school for blind with very high success. She is independent in everyday living, intellectually she is absolutely intact.
In After the sixth month the child walks independently outside home only with a cane.
On the X-rays in March 2013 (1 year postoperatively) we see consolidated fracture with a normal femoral neck-shaft angle. Lower leg length discrepancy is below 0.5 cm (Figure 3). Range of motion in the operated hip joint is: active flexion -90°, extension -5°, abduction -30° (Figure 4). The patient is painless and her gait substantially improved. The child returned to her specialized for blind school for the new school year.

Discussion
With a typical X-ray, the diagnosis of osteopetrosis is not difficult.
Phenotype clarification of the disease type requires genetic counseling. In our case this wasn't done because of the lack of such possibility in Bulgaria. Clinical data alone in our case is not enough for type differentiation. On one side there were symptoms of osteopetrosis maligna -dolichocephalic configuration of the head, amaurosis, early hepatosplenomegaly and hematologic impairments, but on the other side, symptoms of osteopetrosis tarda were present -lack of early fractures, with the first fracture occurrence on 13 years of age, anamnesis of mandible osteomyelitis.
In the absence of genetic investigations, we assume that our case is most probably autosomal-dominant type II marble bone disease.
The present fracture of the proximal femur in the described case is typical for the disease. This site is the most common localization of pathologic fractures in osteopetrosis [3]. Relatively rarer are the fractures of tibia, upper limb, cervical spine and spondylolyses.
Usually the fracture line is transverse. Normal fracture callus develops, but healing is delayed due to faulty remodeling and maturation of the abundant newly formed bone. The newly formed callus envelopes like a bulb the old bone [4].
In children and adolescents, closed reduction and immobilization lead to successfull healing of mainly fractures of the upper extremity and tibia. The conservative treatment in the proximal femur is unreliable [5]. Pseudoarthrosis risk is high. Surgical treatment of these fractures is preferable. It requires thorough preoperative preparations because of high anaesthesiologic risk due to accompanying anemia and quite often lack of adequate control over the disease course.
The surgical intervention alone is difficult to perform due to the britle osteosclerotic bone during its technical preparation [6][7][8].
While drilling, the flutes of the drill bit are frequently filled with dense accumulated bone swarf, which reduces its effectiveness [8]. Early postoperative physiotherapy in children with osteopetrosis is also a problem. It is due to the high incidence of visual impairments.
In our case this problem was easily overcome due to the stability of the used of osteosynthesis. Physiotherapy was started immediately after the operation and was performed according to a program for blind children.
A possible complication in the early postoperative period is the development of osteomyelitis due to lack of intramedullary blood supply [4]. Another threat is the progression of the already present aplastic anaemia due to higher blood loss related to a longer intraoperative time. This necessitates regular check-up of haematologic indices and substitution therapy when indicated. All these complications were avoided in our case due to perfect interdisciplinary collaboration in therapy.
Page number not for citation purposes 4

Conclusion
Operative treatment of proximal femoral fractures in children with osteopetrosis is difficult, but not impossible. We assume that stable osteosynthesis after careful open reduction is obligatory. LCP pediatric hip is exactly such synthesis that guarantees successful treatment.

Competing interests
The authors declare no competing interest. Both authors did not receive any funds from anywhere personally. Application of the LCP Pediatric hip osteosynthesis was possible due to financing by the Bulgarian Fund for Treating Children; a state organization that covers everything in the management of Bulgarian citizens below 18 years of age, that is not covered by the national health insurance system, especially expensive orthopaedic implants.