Stress Fracture of the Hip

DISEASE/DISORDER:

Definition

Stress fractures are common injuries that tend to occur in athletes or other people who participate in activities that place repetitive and excessive stress on bone. They are part of a continuum of injuries which is broadly classified as bone stress injury (BSI). BSI represents the inability of bone to withstand repetitive loading leading to structural fatigue and microarchitectural discontinuities.   BSI initially starts as a stress reaction which can progress to stress fracture and finally a complete bone fracture.  Stress fractures can be further broken down based upon whether they occur as the result of excessive and repetitive strain placed on structurally normal bone (fatigue reaction) or normal stress applied to structurally abnormal bone (insufficiency reaction).^1-5 Locations where femoral and/or “hip” stress fractures occur include: femoral shaft, femoral diaphysis, femoral neck, pubic rami, and sacral ala.

Femoral neck stress fractures can be divided into those that occur on the tension side (superior aspect when standing) and those that occur on the compression side (inferior aspect when standing). Tension-sided fractures are considered high-risk due to their tendency to displace if they progress to complete fracture, which results in increased incidence of healing problems and increases risk of avascular necrosis.^1-4 Stress fractures of the femoral shaft, pubic rami, sacral ala, and compression side of the femoral neck are considered low-risk fractures, examples of which include vitamin D deficiency, osteomyelitis and hypophosphatasia^1,3,10

Etiology

Fatigue fractures occur when continued repetitive loading exceeds the process of remodeling.^1,5 Insufficiency fractures occur when normal loading is applied to bone in which new bone formation is impaired, producing reduced mechanical strength.^1-5 Insufficiency or pathological fractures include those that occur in bone weakened by infection, tumor, or various processes producing low bone mineral density.^1,3,4-5

Epidemiology including risk factors and primary prevention

Stress fractures comprise up to 20% of athletic injuries; and 80% of stress fractures occur in the lower limb.^6,10 More specifically, femoral stress fractures account for 6.6% of all stress fractures, and pelvic stress fractures account for 1.6%.⁴ The incidence of sacral stress fracture is unknown.¹

Risk factors for stress fracture are divided into intrinsic and extrinsic factors.^1-2 Intrinsic factors are those related to the individual athlete, including anatomic alignment, other structural abnormalities, conditioning, insufficient blood supply, and endocrine and/or nutritional abnormalities such as small tibial width, hypoestrogenism and low energy intake^1-2,7,10 Extrinsic factors are related to training variables and other elements that affect how stresses are applied to bone including type of sport, training intensity/duration and technique, equipment utilized training surface and environmental factors.^1-2  Those most at risk for BSI include runners who rapidly increase mileage and duration and those who average over 30-40 miles per week, ballet dancers, military recruits and athletes who participate in track and field and gymnastics or those who exercise for over five hours per day. ¹⁰ 

The role of gender, age, and race in determining risk of developing stress fractures has also been discussed.^1-5 Women tend to be affected more often with pelvic stress fractures (pubic rami and sacral) often occur in female long distance runners.⁵ Tension-sided femoral neck stress fractures occur more commonly in older patients, whereas are compression-sided stress fractures occur more often in younger patients.⁵

Biomechanical risk factors are related to the specific locations where stress fractures occur. For femoral neck stress fractures, these include pes cavus, limb length inequality, and coxa vara.¹ Studies in military personnel and, more recently, in the general population have suggested pincer-type femoroacetabular impingement (FAI) as a risk factor for femoral neck stress fracture (FNSF).⁷ Femoral shaft stress fractures tend occur where the greatest compressive strain is applied – the proximal posteromedial shaft.¹The sacrum acts as the keystone in the arch of the pelvis; it is subjected to multiple forces which can lead to stress fracture.¹ Stress fractures of the pubic ramus occur at the site of attachment of the adductor magnus on the inferior pubic ramus, where repetitive tensile forces are applied.¹

Patho-anatomy/physiology

Wolff’s law states that normal stress placed on normal bone produces normal remodeling of the bone.^1-2,5 If sufficient time is allowed for remodeling and the load applied does not exceed the strength of the bone structure, the bone becomes stronger.^1,5

Remodeling begins with osteoclastic resorption of bone and is followed by osteoblastic new bone formation.^1,5 Osteoclastic resorption weakens the bone; if insufficient time is allowed for new bone formation, microfractures occur which can progress to stress reaction and eventual fracture.^1,3,4-5  The resorption phase peaks at about 3 weeks; but the normal duration for the complete remodeling process is 3 months.⁵

Disease progression including natural history, disease phases or stages, disease trajectory (clinical features and presentation over time)

1. New onset/acute:
   Repetitive loading of bone in the context of insufficient time for new bone formation produces an environment in which resorption predominates, leading to weakening of the bone.⁵ The process of fatigue fracture begins with crack initiation which progresses to crack propagation and eventual complete fracture unless the conditions which precipitated the problem are altered to allow resumption of normal remodeling of bone.² In athletes manifestation of stress fracture symptoms is usually seen around two months after an abrupt and large increase in exercising. Pain related to stress fracture occurs in the groin region for pubic rami and femoral neck fractures, the anterior thigh for femoral shaft fractures, and the lower back and/or buttock for sacral fractures.^4-5 The initial onset of pain is insidious. At first, mild pain occurs only after a certain amount of activity and improves or even resolves fairly quickly after the activity is discontinued.^1-3,5
2. Subacute:
   As the process of fatigue fracture continues, less activity is required to bring on symptoms until eventually pain occurs at rest.^1-3,5 Often (especially in competitive athletes) patients will not seek medical care until symptoms begin to interfere with training and/or function.³

ESSENTIALS OF ASSESSMENT

History

Common history factors in suspected stress fractures include pain characteristics, training regimen, footwear, medical history, medications, nutrition, lifestyle habits, and any previous history of injuries related to over-training of the area currently injured.^1,3-4

Pain	Location; onset; quality (aching); modifying factors; progression
Training	Type of activity or sport; recent changes in regimen (especially increased intensity and/or duration), sport surface, equipment/shoes; timing of injury relative to athlete’s sport season
Footwear	Sport-specific; how old?; fit; history of use of orthoses/inserts
Medical history	Diseases that affect bone; menstrual history11
Previous injury	Previous stress fracture (same or different location); other injuries and/or treatment that may have changed biomechanics (laxity after joint sprain or poor flexibility after immobilization)
Medications	Particularly medications that can alter bone density (corticosteroids or hormones), Oral contraceptive use
Nutrition	Intake of vitamin D, calcium, calories, recent weight changes11
Lifestyle habits	Smoking, ethanol intake, disordered eating

Physical examination

Key or classic physical examination findings include: focal bony tenderness, limp due to pain with ambulation, and swelling over the location of the stress fracture.⁴ In femoral neck stress fractures, pain is elicited at end ranges of hip rotation and with active straight leg raise, rather than tenderness to palpation.^1,5

Pain elicited during a one-legged hop (particularly during landing) can aid in the diagnosis.

Pubic rami fractures tend to produce marked tenderness to palpation and pain can be reproduced with single leg stance.⁵ Sacral stress fractures are painful both to palpation and to stressing of the sacroiliac joint.⁵

In addition to a thorough musculoskeletal exam it is important to document accurate height and weights on all patients with suspicion or confirmed stress fractures.  Calculating body mass index (BMI) and tracking weight changes are important predictors of recovery and preventing future stress injuries. ^10,11,13

Functional assessment

Treatment of stress fracture could include a period of protected weight bearing, thus compromising the functional state of the patient who may require full or partial assistance with some self-care activities for a limited time period.

Laboratory studies

Can consider Vitamin D levels, thyroid function tests and basic chemistry panel in high risk individuals or those with recurrent stress fractures.¹⁰

For osteoporosis in males, testosterone levels.

For suspected cancers, PSA or SPEP.

Imaging

Plain radiographs may aid in diagnosis by revealing subtle periosteal/cortical changes.¹ In light of studies indicating an association between pincer-type FAI and increased risk for FNSF, findings of coxa profunda and/or acetabular retroversion should increase index of suspicion for occult FNSF; especially if other risk factors for stress fracture are present.⁷ False negative radiographs are common (especially in the first 2-3 weeks after onset of symptoms).^1-5 Bone scan has high sensitivity but lower specificity so has fallen out of favor.^1-5 MRI is considered the gold standard for imaging suspected stress fractures.^1-5 It can identify early signs of stress fracture (bony and/ or soft tissue edema) as early as one to two days after symptoms onset. ¹⁰  CT (computed tomography) and/or SPECT (single positron emission CT) are helpful when imaging of bony detail is needed (e.g., determining whether fracture is complete or incomplete; or imaging of sacrum or pars interarticularis) or when MRI is contraindicated.^1-5,10

Supplemental assessment tools

DEXA scan to assess for osteoporosis or low bone mineral density in individuals with recurrent stress fractures. ¹¹

Early predictions of outcomes

Outcome depends upon anatomic location and grade of the injury. The grade of the injury (usually based upon MRI findings) indicates severity of injury, ranging from stress reaction to complete fracture.^2,13 The grade of the injury has been found to be predictive of time to healing and return to play for athletes.² Higher grade injuries carry a greater risk of developing complications and require longer to progress to healing.^1,2

Environmental

Environmental factors include: the terrain/surface upon which an activity is performed and the equipment used for the activity. More specifically, with reference to surfaces, activities performed on hard (unyielding) surfaces are at higher risk of producing stress fractures. Running on irregular terrain and/or hills also increases risk.⁶  Femoral neck¹, sacral, and pubic rami¹stress fractures occur more commonly in long distance runners.^3,5 Femoral shaft fractures are more related to jumping.³

Social role and social support system

High-risk fractures like the tension-sided femoral neck fractures may require a lengthy period of non-weight-bearing, causing the patient to require assistance for certain activities (carrying things is difficult due to the need to use crutches). Athletes who are part of a team may have additional anxiety about inability to participate. Military recruits with stress fractures may have to delay training, or maybe medically discharged if complications like fracture completion and/or avascular necrosis occur.

Professional Issues

The evaluating and treating physiatrist should pay special attention to complaints of severe groin, leg or foot pain or findings of antalgic gait or pain with hopping as such findings could indicate the presence of a stress fracture. Failure to identify a stress fracture might result in a displaced fracture and less favorable outcome if left untreated.

REHABILITATION MANAGEMENT AND TREATMENTS

Available or current treatment guidelines

A method has been proposed for grading stress fracture severity based upon MRI findings^2,13 The authors of the article in which the method is presented used this grading system to make recommendations for “duration of rest needed for healing” in weeks.² Grade 1 injuries require only 3 weeks of rest, while Grade 4 injuries require 16 weeks or more.²

A review article published in 2013 looked at evidence-based protocols for functional rehabilitation and resumption of running after stress fractures involving the lower limbs.⁸ The authors’ stated intent was to provide a practical resource for clinicians.⁸

At different disease stages

1. New onset/acute
   If the fracture is high-risk and/or high-grade, the patient should be referred for consultation with the appropriate orthopaedic/sports medicine/musculoskeletal specialist. Acutely displaced femoral neck stress fractures should be treated ASAP with open reduction internal fixation (ORIF).⁵Modifying weight bearing status helps to protect the limb from progression of the fracture and  also decreases pain. Some advocate the use of acetaminophen or opioids (for severe pain) over NSAIDs for acute pain relief, due to the risk of delayed healing associated with the use of anti-inflammatory medication.^2-3 However, precaution should be taken when prescribing opioids and consideration given to multi-modality management of pain without use of opioids whenever possible.
2. Subacute
   The keys to maximizing healing include restriction of activity as soon as stress fracture is suspected; and repeat evaluation to ensure pain-free function.⁴ As the fracture is healing, any contributing factors to the development of the fracture should be addressed (training/technique errors, equipment modification, modify nutrition, etc.).⁵ Deconditioning can be minimized by allowing participation in activities with modified or minimal weight bearing.  Athletes can begin gradual return to sports activities after being asymptomatic with normal daily activities for 10 – 14 days.   Markers of recovery on imaging include bone callous formation and resolution of fracture line. ¹⁰
3. Chronic
   Fractures with nonunion or avascular necrosis (AVN) require surgical treatment. Nonunion requires debridement and bone grafting.⁵ AVN of the femoral head requires hemiarthroplasty or possibly total hip arthroplasty.

Prevention of recurrent stress fractures

It is important to address not only the treatment of stress fractures but the prevention of future injuries, especially for those at risk. While the data is not clear in relation to oral contraceptives and bone mineral density, multiple studies have shown that estrogen containing oral contraceptives may provide a protective effect in female athletes. ^5,11 Due to the association between low energy intake and stress fractures it is important to discuss good nutritional and training principles. ¹¹ Recommendations can include increasing intake of low-fat dairy products in addition to adding supplements such as oral calcium and vitamin D. ¹⁰

Coordination of care

Treatments for stress fractures span the full spectrum of management from rest to active medical/rehabilitative care under the direction of a multidisciplinary team including physicians, physical and occupational therapists, athletic trainers, exercise physiologists, nutritionists, and psychologists to orthopedic surgeons and other medical and surgical physician specialists. The physiatrist must coordinate the care of all these treatment professionals on the team.

Patient & family education

In the context of stress fractures in athletes, patients, family, and coaches may all benefit from education on prevention of stress fractures. Once the fracture has occurred, education can be provided on maximizing healing, maintenance of function, and prevention of recurrence. The website eOrthopod.com is a nice resource for patient education materials on numerous topics, including stress fracture of the hip.⁶

Emerging/unique Interventions/Assessments

Function-based measures such as Oswestry or SF-36 can be used for research or clinical outcomes. VAS scales for pain may be useful.

Translation into practice: practice “pearls”/performance improvement in practice (PIPs)/changes in clinical practice behaviors and skills

Any lower extremity pain associated with increased activity that resolves with rest should result in stress fracture being considered in the differential diagnosis.

CUTTING EDGE/EMERGING AND UNIQUE CONCEPTS AND PRACTICE

Cutting edge concepts and practice

Acuity of fracture can be assessed using Doppler to provide a semiquantitative estimate of bone turnover.³

The use of parathyroid analog teriparatide (Forteo) may accelerate fracture healing in patients with stress fractures or with delayed fracture healing. ^10,12

GAPS IN THE EVIDENCE-BASED KNOWLEDGE

Gaps in the evidence-based knowledge

More study on injury prevention and optimum treatment guidelines including new medications and rehabilitation practices would be helpful.

REFERENCES

1. Harrast MA, Colonno D. Stress fractures in runners. Clin Sports Med. 2010;29:399-416.
2. Kaeding CC, Najarian RG. Stress fractures: classification and management. Phys Sportsmed. 2010;38(3):45-54.
3. Patel DR. Stress fractures: diagnosis and management in the primary care setting. Pediatr Clin N Am. 2010;57:819-827.
4. Patel DS, Roth M, Kapil N. Stress fractures: diagnosis, treatment, and prevention. Am Fam Physician. 2011;83(1):39-46.
5. Teague DC. Stress fractures. In: Bucholz RW, Court-Brown CM, Heckman JD, Tornetta P III, eds. Rockwood and Green’s Fractures in Adults. 7th ed. Philadephia, PA: Lippincott Williams & Wilkins; 2010: 518-530.
6. Kahanov L, Eberman LE, Games KE, Wasik M. Diagnosis, treatment, and rehabilitation of stress fractures in the lower extremity in runners. Open Access Journal of Sports Medicine. 2015; 6: 87-95.
7. Goldin M, Anderson CN, Fredericson M, et al. Femoral neck stress fractures and imaging features of femoroacetabular impingement. PM&R. 2015; 7(6): 584-592.
8. Liem BC, Truswell HJ, Harrast MA. Rehabilitation and return to running after lower limb stress fractures. Curr Sports Med Rep. 2013 May-Jun; 12(3): 200-7.
9. A Patient’s Guide to Stress Fractures of the Hip. eOrthopod.com; http://www.eOrthopod.com/public; Accessed August 12, 2011.
10. Moriera A, Bilezikian J. Stress Fractures: Concepts and Therapeutics. Journal of Clinical Endocrinology and Metabolism. 2017; 102(2): 525-534.
11. Joy EA. Address risk factors to prevent bone stress injuries in male and female athletes.  British Journal of Sports Medicine. 2019; 53(4): 205-206.
12. Almirol EA, et al. Short term effects of teriparatide versus placebo on bone biomarkers, structure, and fracture healing in women with lower extremity-stress fractures: A pilot study. Journal of Clinical and Translational Endocrinology. 2016; 6: 7-14.
13. Ramey LN, McInnis KC, Palmer WE. Femoral neck stress fracture. The American journal of sports medicine. 2016. 44 (8) 2122-2129.

Original Version of the Topic:

Laura Peter, MD. Stress Fracture of the Hip. Publication Date: 2011/11/15.

Previous Revision(s) of the Topic

Laura Peter, MD. Stress Fracture of the Hip. Publication Date: 05/05/2016.

Author Disclosure

Gregory Mulford, MD
Nothing to Disclose

Maria Janakos, MD
Nothing to Disclose