36: Pediatric Orthopaedics: Use of the Direct Anterior Approach in Children and Adolescents

Adam Y. Nasreddine

David B. Frumberg

Michael B. Millis

Introduction

One of the unique aspects of pediatric orthopaedics is the dynamic nature of growth and the development of the musculoskeletal anatomy. Malformations, deformations, and dysplasia are the result of anomalies in the developmental process at different stages and can lead to disorders that adversely affect the normal growth and mechanical function in the hips of growing children. The role of the pediatric orthopaedic surgeon has historically been to optimize stability and function in the growing child. However, children are not small adults and surgical techniques applied in adults should not simply be transposed to the pediatric population.

As such, the pediatric orthopaedic surgeon should be familiar with the developmental stages of the hip as well the dynamic nature of the pediatric anatomy including age-related variability in the neck-shaft angle and also consider the transitioning vasculature of the femoral head to help guide treatment and the surgical technique. ¹ Pediatric hip vascular supply development can be divided into three phases as described by Dial et al. ² In the first stage, there is a three-vessel supply to the femoral head including the medial femoral circumflex artery (MFCA), the lateral femoral circumflex artery (LFCA), and the artery of the ligamentum teres. In the second stage, the blood supply to the femoral head becomes dependent solely on the MFCA with the superior retinacular artery being the main supply to the femoral head. The subcapital physis blocks retinacular vessels from the LFCA. In the third stage of development, in addition to the MFCA, there is some blood supply from the LFCA and the artery of the ligamentum teres. The onus is on the orthopaedic surgeon to pay careful attention to the MFCA because it is the only source of blood supply to the femoral head during most of childhood.

The DAA to the hip in pediatric patients has been well described with modifications that are unique to the pediatric population. ³ ^, ⁴ This chapter discusses the usefulness of the DAA to treat a selected group of pediatric hip pathologies and injuries.

Use in a Septic Hip

Indications

A septic hip is a true emergency at any age but especially in the pediatric population due to the risks of secondary cartilage damage, osteonecrosis, growth disturbance, and early-onset osteoarthritis. The use of ultrasound is important initially in the workup. Synovial drainage must be done quickly to relieve pressure, even if it is not clear that the joint is infected with bacteria. The ability to differentiate between septic arthritis and transient synovitis has been illustrated by Kocher et al ^5-7 in their widely accepted algorithm. According to their algorithm, fever, an elevated white cell count (>12,000 mm³), the inability to walk, and the erythrocyte sedimentation rate are the four main data points needed to make the distinction. Caird et al ⁸ further added C-reactive protein to the algorithm to achieve higher sensitivity. There have been various reports on the use of magnetic resonance imaging (MRI) to further differentiate between transient synovitis and septic arthritis in the pediatric population. ⁹ ^, ¹⁰ Once diagnosed, septic arthritis in children and adolescents should be treated emergently through irrigation and debridement followed by culture-specific antibiotics. ¹¹

Surgical Approach

The DAA is the preferred method for draining a septic hip in children and adolescents. Medial and posterior approaches are contraindicated due to the risk of damage to important neurovascular structures. An oblique, bikini-type skin incision is made, crossing the tensor-sartorius interval distal to the anterior superior iliac spine (ASIS) at the level of the inguinal skin fold (Figures 36.1 and 36.2). A longitudinal incision was historically used, but this heals with an unattractive scar and has no advantages for this procedure. As with all Smith-Petersen-based anterior hip approaches, the internervous and intervascular plane between the tensor muscle laterally and the sartorius medially is the key to gaining access to the anterior hip capsule.

Figure 36.1

Patient is placed supine on the OR table with bump under the ipsilateral right hip.

Figure 36.2

A, The anterior superior iliac spine (ASIS) is marked on the right hip. B, Then, an oblique, bikini-type skin incision is made, crossing the tensor-sartorius interval distal to the ASIS at the level of the inguinal skin fold.

The lateral femoral cutaneous nerve (LFCN), which routinely crosses the interval from proximal to medial to distal to lateral, is the structure at greatest risk during exposure. The LFCN may be directly exposed for identification, but the authors believe it is better left protected by retracting it medially with the medial fascia of the tensor muscle as the interval between the tensor and sartorius is entered. The rectus femoris muscle is then identified (Figure 36.3). The direct and reflected heads are dissected off the anterior inferior iliac spine (AIIS) and the anterior aspect of the acetabulum, respectively, and together these are retracted distally; 0 Vicryl (Ethicon, Bridgewater, NJ, USA) suture is used to tag the dissected heads of the rectus for later repair. The anterior capsule is identified (Figure 36.4), and a 1 × 1 cm window is made to access the joint (Figures 36.5 and 36.6). Once intra-articular cultures are obtained, the joint is irrigated copiously with saline and broad-spectrum antibiotics are started. A flexible catheter tip can be inserted into the joint to assist with intra-articular lavage.

Figure 36.3

The direct head of the rectus femoris is identified, and then, the direct and reflected heads are dissected off the anterior inferior iliac spine and the anterior aspect of the acetabulum, respectively, and together these are retracted distally.

Figure 36.4

Figure demonstrating the thick hip joint capsule.

Figure 36.5

A 1 × 1 cm window is made into the joint to allow access into the joint.

Figure 36.6

The femoral head is then visualized to allow for adequate irrigation.

The joint is then inspected for evidence of osteomyelitis. After the irrigation and debridement, a drain is passed behind the greater trochanter to exit the skin laterally (Figure 36.7). The joint capsule is then repaired with 0 Vicryl sutures, but frequently a small window is left open to allow for continued articular drainage. The rectus femoris tendons (if released) are repaired back to their origins on the AIIS and anterior hip capsule with 0 Vicryl sutures. The subcutaneous tissues are repaired with 2-0 Vicryl (Ethicon) sutures, and the skin is then reapproximated with subcuticular Monocryl (Ethicon) suture. ⁹ ^, ^11-13

Figure 36.7

Penrose drain exiting laterally from the skin after being passed behind the greater trochanter to help with continued drainage.

Postoperative Course

Pediatric infectious disease consultation is typically recommended for guidance of antibiotic chemotherapy. Drain output is monitored every 8 hours and removed when output is less than 30 mL over 24 hours or 2 days postoperatively. The patient’s vital signs, pain levels, and ambulatory status are closely monitored for improvement. The child is usually allowed to weight bear as tolerated on the affected extremity. If the patient fails to improve their pain and/or remains febrile, a repeat irrigation and debridement may be necessary with the wound left open. Otherwise, the patient may be discharged home when clinically stable and pain is controlled appropriately.

Use in Developmental Dysplasia of the Hip

Indications

Developmental dysplasia of the hip (DDH) is a common disorder in the pediatric population. Dysplasia represents a spectrum of pathologies, each with its own treatment affecting the acetabulum as well as the proximal femur. Screening of all newborns is now supported by both the American Academy of Pediatrics and the American Academy of Orthopaedic Surgery clinical practice guidelines. The goal of screening is early detection, which improves the chance for successful nonoperative treatment. If nonoperative treatment fails, there are several surgical treatment options available to obtain a concentric and stable hip reduction while maintaining a low risk of osteonecrosis. ^14-17

The most suitable treatment option depends largely on the patient’s age, function, and degree and type of deformity. As the child gets older, reduction of a true dislocation through bracing or closed reduction becomes more difficult and is more likely to result in an imperfect hip than open treatment. Hoellwarth et al ¹⁸ illustrated their approach to DDH treatment based on age. The first line of treatment is closed reduction with a Pavlik harness. For children younger than 12 months who failed nonoperative treatment with a Pavlik harness, closed reduction and spica casting with or without adductor tenotomy are recommended. For children 12 to 18 months old, open reduction and casting are often the treatment of choice. In children aged 18 months to 3 years, femoral and/or pelvic osteotomies combined with open reduction are the treatment of choice given soft tissue contracture as well as residual bony deformity. In children who are older than 3 years, both femoral and pelvic osteotomies in addition to open reduction are required to achieve a stable hip.

Our preferred surgical technique for open reduction of DDH uses the DAA. Open reduction is used in patients younger than walking age who have failed well-executed nonoperative treatment. It is also needed in children at walking age who require realigning osteotomy even after an initial apparently stable closed reduction. The goal of open reduction is to achieve deep concentric reduction. This requires that all soft tissue obstacles to reduction are removed as well as releasing problematic extra-articular soft tissue contractures. Anteroposterior (AP), frog leg, and von Rosen (abduction internal rotation view) hip radiographs are routinely obtained during operative planning. A computed tomographic scan of the hips and pelvis with cuts through the femoral condyles may be useful for complex cases in which abnormalities of version are suspected.

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