Not to be missed Part 1: High Risk Stress Fractures

Stress fractures are often misdiagnosed, within clinical settings, particularly the high risk Navicular and Femoral neck stress fractures. Early and accurate diagnosis of a bone stress injury increases the likelihood of a positive outcome for your athlete.

Physiotherapists’ are often the first clinical form of contact for sporting injuries. This highlights the importance for physiotherapists’ to have an in-depth understanding of bone stress injuries in order to identify and prevent progression to a true stress fracture.

First of all what is a stress fracture? Romani et al., (2002) defines a stress fracture as a partial or incomplete fracture caused by the accumulation of stress to a localised area. Warden (2007) builds upon this definition by specifying that stress fractures are a result of repeated submaximal loads causing fatigue of the bone structure. This repeated stress or load stimulates a process of remodeling to strengthen the integrity of the bone structure. Remodeling occurs at a cellular level by the re absorption of existing bone by osteoclasts in addition to the formation of new bone cells by osteoblasts (Romani et al., 2002). Problems arise when this oseteoclatic activity exceeds that of the osteoblastic formation as this leads to weakening of the bones integrity. If physical activity or the level of training load is continued with out sufficient rest, this may lead to early bone marrow edema and eventually a full cortical break. This progression from bone remodeling to a stress fracture is known as the bone stress continuum which is a reversible process.

Table 1: The bone stress continuum

Vascular Congestion and thrombosis

Osteoclastic and Osteoblastic activity leading to rarefaction

Weakened trabeculae and microfracture

Continual bone stress leads to a full fracture

Many risk factors have been identified as contributing to the formation of stress fractures. Thorough subjective and physical examination of your athlete should explore these risk factors in detail if a stress fracture is considered a possible diagnosis. These risk factors include:

– A rapid increase or change in load (volume and intensity)
– A change in training surfaces, footwear or equipment
– An energy imbalance  (Caloric deficiency)
– Leg length discrepancy
– Reduced muscle mass
– Increased hip external rotation
– Reduced ankle dorsiflexion
– Altered mechanics secondary to pain or injury
– Females are 1.2-10 times more likely to suffer stress fractures than males largely due to the female athlete triad

Certain stress fracture sites are deemed as high risk, due to the sites lack of blood supply leading to the potential for non-union and high risk of re occurrence. These localised sites require specific treatment and management in order to ensure an optimal outcome.  High-risk stress fracture sites include areas such as the following:

– Femoral neck*
– The Navicular*
– Anterior tibial cortex
– Medial malleolus
– Talus
– Proximal fifth metatarsal
– Sesamoid bone of the foot
– Second Metatarsal
– Hook of Hamate

Femoral neck and Navicular stress fractures are often overlooked and misdiagnosed due to a vague distribution of symptoms and high number of differential diagnosis in their respective regions.

Femoral neck stress fractures are often experienced as a gradual onset groin pain yet can also extend into hip, back & buttocks. The athlete’s pain is often poorly localised and aggravated by loaded physical activity such as running. The pain will get worse with activity, which differentiates itself from other pathologies such as tendon pain, that is generally sore with warming up and improves through out the exercise session.

Physical examination of femoral neck fractures may often reveal little. Clinical testing may reveal have some localised tenderness and pain at the extremes of hip range of movement, especially into internal rotation. It is importance to note that a negative X-ray should not be relied upon to rule out a femoral neck stress fracture. (Brukner and Khan 2012). This is why MRI is the investigation of choice to confirm the presence and exact location of a femoral neck stress fracture. If the stress fracture is on the superior aspect of the femoral neck (a result of tensile stress), it must be treated as a medial emergency. This involves either surgery via internal fixation or strict bed rest. The medical emergency is due to the potential of a full fracture that can then comprise the blood supply to the femoral head and cause avascular necrosis.

A fracture on the inferior aspect of the femoral neck (a result of compressive force) is less serious in comparison to the superior aspect fracture. These must be managed with initial non-weight bearing rest until the symptoms resolve. The athlete can then commence weight-bearing rest for six weeks before a gradual return to activity.

Image 1:  Compressive vs. tensile forces on the femoral neck

Navicular stress fractures typically present as insidious onset, poorly localised midfoot ache often associated with weight bearing physical activity. Stress fractures commonly occur in the middle third of the navicular bone, a relatively avascular region. Pain can radiate along the medial longitudinal arch or into the dorsal aspect of the foot. Physical examination reveals tenderness over the ‘N” spot, as depicted in image 2, which is located at the proximal dorsal aspect of the navicular. If tenderness  is present over this location, the athlete should be assumed to have a navicular stress fracture until proven otherwise. Seldom are there any signs of swelling or discolouration over the region.

Image 2: The “N” spot will be tender in when a stress fracture is present

The investigative procedures of choice are the MRI (image 3 and 4) or CT scan. CT allows differentiation between a stress fracture and a stress reaction and also enables accurate fracture definition (Kiss et al 1993). X-rays are not recommended to confirm or deny the presence of a navicular stress fracture due to their poor sensitivity (Bukner & Kahn, 2012).

The navicular stress fracture is initially managed with non weight bearing cast immobilisation for six to eight weeks. Screw fixation (ORIF) may be required in cases of delayed or non-union.  A study by Potter et al (2005) found there was no statistical difference in pain or function between conservative and surgical management for a navicular stress fracture. However, there was a slightly higher proportion of navicular point tenderness for the surgical managed patient even following a full return to sport. Tenderness on navicular palpation is an important method of assessing healing in the short term and used as a guide for loading progressions during rehabilitation.  With the modern day advancement in the quality of imaging, follow up CT scans may be used to further assess the degree of healing. However, it must be noted, in some cases complete clinical recovery is not matched radiologically (Potter et al 2005).

Images 3 and 4: MRI detailing a type II undisplaced stress fracture of the Navicular bone.

The athlete with a diagnosed navicular stress fracture is often out of sports for four to six months. In many cases, the athlete, may continue to have a small yet measurable amount of discomfort and loss of function in the long term.

All high-risk stress fractures should be referred to a sports physician or an orthopaedic specialist whom will the guide initial management protocols.  The return to physical activity and sport should be managed in a multi-disciplinary team involving the specialist, a nutritionist, physiotherapists, coach, and the strength & conditioning staff.

Through out the rehabilitation process active REST in recommended to maintain fitness and prevent atrophy of muscles. Elkstrad & Torstviet  (2012) postulate the following procedures as a management guideline:

R: Removal of abnormal stress

E– Exercise to maintain cardiovascular fitness and prevent atrophy

S- Safe, pain free return to previous level of activity

T: Time for bone maturity to catch up with increased remodeling.

When physical activity resumes it becomes very important to focus upon and carefully manage the athletes training loads. Bone is at it weakest in the third week following the initial stressful activity (Elkstrad & Torstviet 2012). Reducing or altering the intensity of the athletes’ training within the third week will allow for the remodeling and maturing process of bone to occur.

Further comprehensive management throughout the athlete’s rehabilitation process should also include monitoring and assessment of the individual’s biomechanics, nutrition and endocrine levels.

In summary the initial diagnosis of high-risk stress fractures, practically to the femoral neck and navicular bones, can be quite challenging for a clinician. It should be noted the importance of MRI or CT imaging in detecting a bone stress injury and for determining the exact location in order to guide initial medical management. A thorough subjective & physical examination is imperative to discern the causative factors of the stress response, which must be addressed through out the rehabilitation process to prevent reoccurrence. A sports physician or orthopaedic specialist in conjunction with a multi disciplinary team should be utilised to guide the management and rehabilitation of an athlete recovering from a high-risk stress fracture.

Nick Kane

Acknowledgements: Perth based Sports Physician Simon Jenkins for initially presenting to the Physiotherapy community on High Risk Stress Fractures 2014

Editing by Kelly Taylor Lewis

References

Brukner & Khan (2012). Clinical Sports Medicine 4th Ed 2012 617,1027

Ekstrand, J, Torstveit, M.K Stress fractures in elite male football players. Scand J m Med Sci Sports 2012: 22: 341-346

Kiss ZA, Khan KM, Fuller PJ. Stress fractures of the tarsal navicular bone: CT findings in 55 cases. AmJ Reentgenol 1993; 160:111-115

Potter NJ, Brukner PD, Makdissi M, Crossley K, Kiss ZS. Navicular Stress Fractures: outcomes of surgical and conservative management. Br J Sports Med 2006; 40-692-695.

Romani, W.A, Geick, J.H, Perrin, D.H, Saliba, E.N, Kahler, D.M Mechanisms and management of stress fractures in Physically Active Persons. Journal of Athletic Training 2002: 37 (3): 306-314

Warden  SJ, Creaby MW, Bryant AL, Crossley KM. Stress fracture risk factors in female football players and their clinical implications Br J Sports Med 2007: 41 Suppl. 1:138-143

 

Share: Pinterest