Open vs closed reduction

Open reduction is used for the majority of pediatric femoral neck fractures.

Reasons for considering open reduction include:

To reduce the risk of avascular necrosis
To avoid/prevent the risk of delayed union/nonunion
To avoid/prevent the risk of malunion

Introduction

Avascular necrosis (AVN) is the most common serious complication of femoral neck fractures in children. Published literature estimates an overall risk of this complication of approximately 20%. Precise figures are, however, difficult to cite because of small numbers of patients in most series and considerable variation in treatment methods reported.

The risk of AVN may be influenced by:

Mechanism of injury (high-energy vs low-energy fracture)
Initial displacement of the fracture
Fracture pattern
Timing of reduction
Possibility of damage to the blood supply during reduction maneuvers
Quality of final reduction
Stability of the fixation
Decompression of the joint cavity at the time of surgery

Factors which are directly under the surgeon’s control include:

Force applied during reduction
Accuracy of reduction
Decompression of hemarthrosis
Stability of the fixation

Control of these factors may reduce the incidence of AVN, and, in many cases, will require open reduction and internal fixation.

In cases where in-situ fixation is performed, the joint cavity can safely be decompressed using a limited anterior approach.

Anatomy

Detailed knowledge of the anatomy of the proximal femoral blood supply is the key to successful management of femoral neck fractures.

The two main vessels for femoral head blood supply run along the femoral neck within the inferior and superior retinacula. The strong structure of each retinaculum protects the vessels even when the fracture occurs.

Note: Incarceration of the superior retinaculum and the medial femoral circumflex artery in the fracture during closed reduction is an important cause of AVN.

The medial femoral circumflex artery

The deep branch of the medial femoral circumflex artery (MFCA) provides the main blood supply to the femoral head.

The MFCA arises from the profunda femoris artery anteriorly, and passes posteriorly, between iliopsoas and pectineus, to curve around the lower edge of the obturator externus muscle. It supplies the femoral head from posterior via the artery of the superior retinaculum.

Additionally, the MFCA also gives branches to the cruciate anastomosis that lies on the posterior surface of the quadratus femoris muscle.

The branch within the inferior retinaculum (Weitbrecht's ligament) originates from MFCA.

The MFCA runs around the inferior border of the obturator externus muscle, as illustrated. This protects the MFCA from injury and it is essential to preserve this muscle and tendon.

Note: The inferior and superior retinacula are only loosely attached to the periosteum of the femoral neck. This is demonstrated in the MRI with contrast. The vessels are therefore, not always damaged when the neck fracture displaces.

The following guidelines are the recommendations of the of AO Pediatric Expert Group, and are based on analysis of the contemporary literature.