INTRODUCTION
Late sequelae of hip septic arthritis vary from just minor changes of the hip and acetabulum to marked destruction causing functional impairment. Delayed or missed diagnosis, especially in newborns is one of the major factors for poor outcome but the residual sequelae is quite diverse and unpredictable. Various procedures have been described to overcome residual deformities as a result of septic arthritis of the hip (Dobbs et al. 2003; Choi et al. 2005; Wang et al. 2007), with varied results. Generally, age at presentation and types or severity of the condition determine the choice of management. The more severe the sequelae, the worse prognosis is expected and the more likely salvage or reconstructive surgeries are needed.
Earlier radiographic classifications have been introduced to describe the residual deformities as a result from septic hip and those were useful guides for treatment (Hunka et al. 1982; Choi et al. 1990). However, they were criticized to be too complex and have poor intraobserver agreement (Forlin & Milani 2008). More recently, the sequelae of septic hip has been reclassified based on the presence of the femoral head (Forlin & Milani infection2008; Johari et al. 2011). Our report highlights the successful treatment of a child with septic hip dislocation and a preserved femoral head.
CASE REPORT
A 2-year-old girl was referred with a painless limp to our clinic. She had been treated during infancy with left knee septic arthritis in another hospital but the septic arthritis of the right hip was missed. She had a 2 cm limb length discrepancy. Radiographs revealed a right hip dislocation with a preserved femoral head. The left knee showed delayed ossification in the lateral femoral condyle (Figures 1a & b).
Open reduction and varus derotation osteotomy was performed for the septic hip dislocation. The femoral head was flattened medially with erosions of the overlying cartilage (Figure 2). The hip was immobilized in a spica for 2 months. Trochanteric epiphysiodesis was subsequently done at age 7 years to minimise trochanteric overgrowth.
At 11 years follow-up, the femoral head had healed with a coxa breva deformity (Figure 3a). The left lateral femoral condyle also healed with minimal deformity (Figure 3b). The child at age 13 years remained asymptomatic and had no limitation of daily activities (Figure 3c).
DISCUSSION
Septic arthritis in neonates is uncommon and can be difficult to diagnose compared to older children (Kabak et al. 2002; Forlin & Milani 2008). This can lead to a delay of treatment which subsequently affects the growth of the femoral head and proximal femur. A child is at risk of a poorer prognosis especially with sepsis during early infancy and with a delay in initial therapy. Kabak et al. (2002) followed up 14 neonates treated for septic arthritis of various joints for at least 2 years and found 12 of them had no severe sequelae. The other 2 patients (1 death and 1 unfavourable hip outcome) were related to late diagnosis and therapy.
Once the patient developed a severe sequelae, it is a challenge for the surgeon to improve the damaged hip. This would be a temporary measure to produce the optimum function and delay the definitive surgery which may be needed in adulthood. The first classification to describe these residual deformity of septic hips in children has 5 types and 4 subtypes, from minimal to increasing severity (Hunka et al. 1982). Type V being the most severe is when the hip is dislocated with completely destroyed femoral head. Hunka et al. (1982) performed trochanteric arthroplasty in 5 of his patients with type V hips which showed satisfactory outcome in 3 of them. They also advocated the criteria for satisfactory hip outcome which include a stable joint, arc of flexion >500 and pain-free hip that allows usual daily activities.
Choi et al. (1990) modified Hunka classification into 8 subtypes which gives a more comprehensive guideline. The author also retrospectively reviewed 43 patients which were operated with various reconstructive and salvage surgeries and devised a treatment algorithm for severe sequelae of infantile septic arthritis of the hip. Although the classification was very detailed, it is complex and can be difficult to apply. Both Hunka and Choi did not emphasize the significance of the femoral head.
Other studies regarding surgical treatment of septic hip sequelae were focused on the most severe type, where the femoral head was absent. Dobbs et al. (2003) evaluated their own patients with Hunka type V hips which were treated with trochanteric arthroplasty and proximal varus osteotomy (Dobbs et al. 2003). At a mean of 15-year follow-up, they reported satisfactory outcome in 5 patients and recommended staged procedure to reduce the risk of avascular necrosis. Another study reviewed 30 hips with Hunka type V treated with trochanteric arthroplasty (Wang et al. 2007). They recommended a single stage procedure as early as one year of age. This includes resecting any remnant of femoral head or neck, before the proximal femur is reshaped to replace the head.
Recently, the sequelae of septic hip have been reclassified based on presence of the femoral head. Septic hips with femoral head present are classified as a separate entity (Forlin & Milani 2008; Johari et al. 2011). Forlin and Milani (2008) treated 3 dislocated hips with femoral head present. They chose early reconstruction procedures and believed it produced better results. These included open reduction, proximal varus osteotomy and Dega acetabuloplasty.
Johari et al. (2011) further discussed this specific group in detail, and presented the outcome of 21 hips (Johari et al. 2011). They performed closed reduction in young patients and had a 35% success rate. For patients treated with open reduction, supplementary procedures were done when indicated. Femoral shortening for high dislocation, acetabular procedures for dysplasia, and femoral derotation osteotomy for ante version were performed on 14 hips. Nine out of 18 patients had good clinical results, with the longest follow up at 16 years of age. The importance of recognizing the absence of femoral head was highlighted in this case series. In cases that the femoral head had avascular necrosis or absent were associated with poor results. Other factors that also led to poor outcome include hip stiffness and premature fusion of the triradiate cartilage.
Our patient was operated on at the age of two years. Open reduction with varus derotation osteotomy of the femur was done to ensure concentric reduction. We retained the remnant of the femoral head even though it was deformed. We were able to avoid any salvage or complex reconstructive procedures as the right femoral head and the left distal femoral condyle both healed with minimal residual deformities. We concur with the previous authors (Johari et al. 2011; Forlin & Milani 2008) that when the femoral head is present after septic hip dislocations, the outcome is favourable after reduction.
CONCLUSION
Children have enormous capability of bone remodeling. We have shown that even with a deformed femoral head initially, our patient had a good hip outcome following open reduction and femoral varus osteotomy. When femoral head is present after septic hip dislocation, complex surgeries are unnecessary and parents can be informed of a better prognosis for their children.