Femoral Neck Stress Fractures: An Updated Review

Abstract and Introduction

Abstract

Femoral neck stress fractures represent a relatively rare spectrum of injuries that most commonly affect military recruits and endurance athletes. If unrecognized and if proper treatment is not initiated, this condition carries potentially devastating consequences. Patients will typically present with an insidious onset, atraumatic hip, and groin pain that is relieved with rest. The condition may be initially misdiagnosed because radiographs are often normal. Magnetic resonance imaging has demonstrated superior specificity, sensitivity, and accuracy compared with other diagnostic modalities in identifying and classifying stress fractures of the femoral neck. Treatment algorithms are based on the MRI fracture morphology and presence of an intra-articular effusion. Nonsurgical management consists of a period of non–weight-bearing followed by gradual return to activity. Surgical management consists of prophylactic fracture fixation with cannulated screws to prevent fracture progression. If left untreated, patients may progress to a complete displaced femoral neck fracture, which can be associated with complications that include nonunion, osteonecrosis of the femoral head, and long-term disability. These poor outcomes emphasize the importance of early diagnosis and treatment of incomplete femoral neck stress fractures.

Introduction

Femoral neck stress fractures (FNSF) are most commonly seen in military recruits and were first described in 1905 by Belcher, a German military surgeon. Since the 1990s, these injuries have been increasingly identified in the civilian population, specifically in long-distance running athletes, which has required the nonmilitary physicians to be aware of these injuries.^[1]

FNSFs account for approximately 3% to 5% of all sports-related stress fractures.^[2,3] The repetitive loading across the femoral neck, which sees 8.4 times body weight while running, results in recurring submaximal mechanical loads that induce bony absorption that exceeds metabolic repair.^[4] Continued loading without adequate osteoblastic repair leads to microfractures, which may progress to a completed and displaced fracture.^[5]

Over the past 20 years, our understanding of prevention, treatment, and complication management of FNSFs has improved. Early identification and management can prevent the potential complications of a complete, displaced FNSF.^[6] This review presents a discussion of the most recent literature on the diagnosis and management of stress reaction, incomplete fractures, and completed/displaced FNSF. A diagnostic and treatment protocol is proposed.

Table 1. Femoral Neck Stress Fracture Classifications
	Blickenstaff²⁵ (1966)	Fullerton-Snowdy¹⁷ (1988)	Shin²² (1996)	Rohena-Quinquilla²⁷ (2018)	Steele⁶ (2018)
Modality	Radiographs	Radiographsand bone scan	Radiographs and MRI	MRI	Radiographs and MRI
Categories	Type 1	Compression-sided	Compression-sided No fracture line Fracture line <50% Fracture line >50%	Low grade I: Endosteal edema ≤6 mm II: Endosteal edema >6 mm and no macroscopic fracture	Compression-sided No fracture line Fracture line <50% without effusion Fracture line <50% with effusion Fracture line >50% ± effusion
	Type II	Tension-sided	Tension-sided	High grade III*: Macroscopic fracture <50% neck width Macroscopic fracture ≥50% neck width	Tension-sided*
	Type III	Displaced	Displaced	—	Displaced