Hoffa's fracture of the medial femoral condyle in a child treated with open reduction and internal fixation: A case report.

BACKGROUND: Hoffa's fracture is a coronal oriented fracture of the femoral condyles. Isolated coronal fracture of medial femoral condyle with intact lateral femoral condyle is extremely rare in the pediatric patients. There are only few cases of a medial femoral condyle Hoffa's fracture in a skeletally immature patient that have been reported in the literature. THE CASE: In this case report; we present a case of a 12-year-old boy with Hoffa's fracture of the medial femoral condyle, successfully managed by open reduction and internal fixation.
CONCLUSION: Pediatric Hoffa's fractures are very rare and can be missed. Treatment should be with open reduction and internal fixation to prevent further complications in the long term.

Introduction

Hoffa's fracture, first described in 1904 [1], is an uncommon fracture pattern of the femoral condyle with its unique coronal slice. Lateral Hoffa's fractures are more common, but medial Hoffa's fractures have been described and are extremely rare especially in skeletally immature individuals. This type of fracture is intra-articular by definition and the principles of treatment are usually similar to those of typical intra-articular fractures. In addition, this type of injury is frequently missed due to lack of clinical suspicion and inadequate radiographic imaging [2]. The mechanism of injury is usually high-velocity energy [[3], [4], [5], [6]]. Here we present a case of 12-year-old boy with a rare type of injury which involved medial femoral condyle; later successfully treated by open reduction and internal fixation.

Case report

A 12-year-old boy presented to our emergency department with right knee pain and inability to bear weight. History revealed that the patient sustained an injury from a heavy object that fell on his knee. Clinical examination revealed that his knee was swollen and tender, but had no open wounds and the range of motion was restricted due to pain. Neurovascular examination was normal with no signs of compartment syndrome. Radiographs of the knee revealed a medial Hoffa's fracture (Fig. 1). Computed tomography and three-dimensional reconstruction showed a displaced medial condyle coronal fracture with comminution (Fig. 2). Surgical treatment with means of open reduction and internal fixation was planned. The fracture was exposed through a medial parapatellar approach (Fig. 3). Under the guidance of an image intensifier, the fracture was reduced with the aid of a bone clamp and two 4.0 mm partially threaded cancellous screws, which were placed perpendicular to the fracture line. To achieve a more posterior purchase of the fragment, passing the superior screw through the physis couldn't be avoided. The screw heads placed through the articular cartilage were countersunk. Following open reduction and internal fixation, the patient was kept on an above-knee back slab with 30° of knee flexion for approximately 2 weeks. After 2 weeks, he was placed into a removable posterior splint for 4 weeks and gradual range-of-motion exercises of knee were initiated. Strict instructions were given to avoid any weight-bearing flexion during this six-week period to minimize shear force on his coronal fracture pattern. Partial weight-bearing was allowed after 6 weeks postoperatively. At 10 weeks postoperatively, he gradually progressed to full weight-bearing. At six-month follow-up, he was walking without support and without pain and the knee range of motion was 15 to 130° (Fig. 4). Additionally, there was neither an angular deformity nor a limb-length discrepancy. Plain radiographs and CT showed a well-healed fracture with no evidence of collapse of the femoral condyle (Fig. 5, Fig. 6). Screws were planned to be removed in 9 months' time.

Fig. 1

Initial posttraumatic AP (A) and Lateral (B) radiographs of the right knee.

Fig. 2

3-D reconstruction (A), axial (B), coronal (C), and sagittal (D) CT images showing a displaced medial condyle Hoffa's fracture.

Fig. 3

Medial parapatellar arthrotomy with an assessment of the fracture line and cartilage (A). Fracture reduction achieved (B).

Fig. 4

Postoperative knee range of motion in flexion (A) and extension (B).

Fig. 5

AP (A) and lateral (B) radiographs 6 months postoperatively demonstrating complete fracture healing.

Fig. 6

Sagittal CT image 6 months postoperatively showed the superior screw passing through the physis and a consolidated fracture.

Discussion

The coronal plane fracture of the femoral condyle was first described by Hoffa in 1904 [1]. This type of injury can be classified into either medial Hoffa's fracture or lateral. Bali et al. [5] first described an isolated medial condyle Hoffa's fracture in a skeletally immature patient. In addition, Abhijeet et al. [2], described a medial Hoffa's fracture in a young girl with an associated ipsilateral fibular fracture. The usual cause of adult Hoffa's fracture is motor vehicle accidents [5] while pediatric Hoffa's fracture can be due to sports injury, trivial injury in addition to motor vehicle accidents [6]. In our case, the mechanism of injury was due to a heavy object fall on the affected knee. Little is known about pediatric Hoffa's fracture as only few case reports have been published about this fracture. McDonough et al. reported the first case of a nonunion of a Hoffa's fracture in a child [7]. Letenneur et al. [8] provided a classification illustrating three types of fracture. Type I is a vertical fracture involving the entire condyle parallel with the posterior cortex of the femur. Type II is a fracture of variable size horizontal to the base of the condyle. Type III is a fracture oblique to the femur and has the worst results. According to this classification, our patient had a Type III fracture. This rare injury corresponds to Salter and Harris type 4 and Orthopedic Trauma Association (OTA) type 33-B3.2 [9]. Surgical stabilization is the gold standard treatment in Hoffa's fracture and is necessary to achieve satisfactory functional outcome, as reduction of the fracture fragment is difficult to achieve and to maintain by closed means due to the absence of soft tissue attachment. Avascular necrosis, non-union and malunion have been reported when Hoffa's fracture was managed non-operatively [3,4,10]. Arthroscopically assisted reduction and internal fixation of Hoffa's fracture are also described [10]. Thorough clinical examination and proper imaging are important for the diagnosis of pediatric Hoffa's fracture because of high chances of these injuries to be missed. CT and 3-D reconstruction help to delineate proper orientation of the fracture line.

Conclusion

To conclude, we believe that the diagnosis of this fracture can be easily missed, so one should keep this in mind when dealing with traumatized knees in children. It is better to treat this fracture with open reduction and internal fixation to prevent further complications in the long term.