Among the general population of athletes, stress fractures can be a rare
cause of pain, accounting for only 2 percent of all reported sports injuries. However,
a considerably higher number of stress fractures are diagnosed in long distance
runners and triathletes.
Stress fractures occurring around the pelvis are significantly uncommon
although, a majority of them are often considered a differential diagnosis when
athletes, specifically long distance runners and triathletes, report hip, groin
or buttock pain during and after running. Because stress fractures around the
pelvic/hip region, including the sacral, pubic rami and femoral neck region,
are rarely diagnosed, understanding and discussing the anatomy of the injury,
their clinical presentation, diagnosis and treatment for each of these types of
stress fractures is important for an athlete in order to find a solution for
those who do encounter it.
How Stress Fractures Occur
Stress fractures occur over a determined period of time when the bone is
no longer capable of withstanding submaximal, repetitive forces. They
frequently result when normal stresses cause bone fracture with decreased bone
density, such as in an elderly osteoporotic individual, or as a result of an
abnormal stress being placed against a normal bone and causing a fracture, such
as in a long distance runner.
When the bones are exposed to loading, the introductory physiological
response is a respective increase in osteoclastic activity, or bone resorption,
leading to temporary structural weakening before new bone formation. If these
stresses continue to occur without having the bone properly adjust to this
additional, ongoing osteoclastic activity, the pressure may exceed bone regeneration,
causing microfractures to occur.
The first characteristic of a stress reaction observed through the use
of MRI is bone oedema as well as increased activity on bone scan. Bone scan in
the acute phase has high sensitivity but an increased uptake may also be due to
infection, bone infarction or neoplastic activity. Researchers from previous
studies stated that 60 to 70 percent of X-rays in the acute phase of stress
fractures, approximately less than 2 weeks after the injury, have a negative
result. Due to its high sensitivity as well as a lack of radiation and high
specificity, even despite its elevated cost, MRI is often the preferred procedure
to identify stress fractures in their early phases.
Various
distinct intrinsic and extrinsic elements have been determined as risk factors
for stress fractures. These include but are not limited to: biomechanics,
strength and flexibility, nutrition, hormonal and menstrual disturbances, and
footwear. These must all be considered prior to assessing an individual with a
suspected stress fracture. During an analysis of 8 female athletes with sacral
stress fractures, the most significant risk factor for these types of fractures
was the rapid increase in impact activity during more intense exercise
programs. An increase in workload should thus be considered a significant risk
factor for stress fractures.
Anatomy of Sacral Stress Fractures
The sacrum
consists of 5 fused vertebrae, S1 to S5, and is triangular in shape. It connects
with the ilium at the sacroiliac joint and, due to its shape and function to
distribute forces, it’s often described as the foundation to the arch of the
pelvis. The sacrum, much like an inverted arch, supports the entire weight of
the upper body and transfers force to the pelvis.
Sacral
stress fractures most commonly occur in the lateral portion of the sacrum and
are more frequently diagnosed in women. It’s been hypothesized that the shape
of the female pelvis can lead create difficulty when distributing weight
through the sacrum than the average male pelvis. However, it’s also been
reported that several male elite Australian triathletes have experienced sacral
stress fractures in recent years.
Symptoms
An athlete with a sacral stress fracture will often manifest acute onset
back, buttock or hip pain which is generally described to occur suddenly during
a run, making them incapable of continuing at the time. The individual may also
experience limited mobility and they could or could not suffer pain on the palpation
of the sacrum. Additionally, they may not experience any neurological symptoms
but symptoms of sciatica may be common during this type of stress fracture.
Sciatica can include pain, weakness or numbness and burning or tingling
sensations along the lower back, buttock or hip, often radiating down the
thigh. The individual may suffer pain or tightness when walking and they will
experience symptoms when hopping on the affected side. Athletes with sacral
stress fractures also frequently report pain during single leg loading tasks,
for example, when putting pants on.
Diagnosis
Due to the extreme overlying soft tissue and complex bone anatomy, simple
radiographs can rarely conclude the presence of a sacral stress fracture. Bone
scan, MRI or CT can be utilized to effectively diagnose a sacral stress
fracture. CT and MRI findings suggest that sacral stress fractures occur as a
result of constant compressive forces which lead to microfractures of the
trabecular bone. These fractures infrequently develop a visible callus on plain
radiograph, therefore, MRI or CT scans should be utilized as a follow up
imaging if poor healing is detected.
Treatment
The progression of treatment for an athlete with a sacral stress fracture
broadly depends on the athlete’s symptoms as these are generally stable
fractures. Rehabilitation procedures will progress from non-weight bearing to
weight bearing to progressive return to running activities as the symptoms
decrease. In most cases, a period of 6 weeks with no running followed by a 6 to
8-week period of a return to running progression may be required. A majority of
published works indicate athletes may have a full return to activity by 4
months with rare cases taking up to 14 months.
Repeated CT scans approximately 4 and 8 months after the individual’s
original diagnosis can often display no signs of previous fractures which
demonstrate a quicker and fuller healing of the well-vascularized trabeculae
microfractures when compared to fractures involving the less well-vascularized
cancellous bone. Researchers concluded that women with sacral stress fractures
who had the best diets and fewer prior stress injuries or menstrual
irregularities, healed the fastest.
Anatomy of Pubic Rami Stress Fractures
The inferior pubic ramus slopes downward and medial from the superior
ramus, narrowing as it goes down and it is the region where the adductor
magnus, brevis and gracilis connect, including the obturator internus and
externus. Pubic Rami stress fractures have been diagnosed among runners,
triathletes and military service members. These generally occur in the inferior
pubic rami next to the pubic symphysis. Researchers proposed that these
fractures are a result of repetitive forces being applied to and transmitted to
the bone through muscle contraction or fatigue. In a study on female military
service members, it was suggested that over-striding during marching procedures
was a potential factor contributing to pubic rami stress fractures.
Symptoms
Pubic rami stress fractures are generally detected either in competitive
races or during intensive training sessions. These frequently occur at the
insertion of the adductors and/or external rotators of the hip. Athletes with
pubic rami stress fractures commonly suffer from pain in the hip, buttock,
inguinal or adductor region which increases with activity and decreases with
rest. It’s important to remember that pain caused by irritation and swelling
along these regions may also cause symptoms similar to sciatica. It’s important
to receive a proper diagnosis to rule out a compression of the sciatic nerve
which could be causing neurological symptoms. Athletes with this type of injury
often limp and on clinical testing, they may experience symptoms with passive
hip abduction, resisted hip adduction and resisted hip external rotation. Stress
fractures of the pelvis can be determined even without radiographic evidence if
the following criteria are met by an individual. First, running will be
impossible for the athlete as a result of severe discomfort in the groin area.
Then, the individual will experience discomfort in the groin with an
unsupported stance on the affected leg. And last, an athlete may suffer
symptoms of pain and tenderness after deep palpation procedures.
Diagnosis
Simple radiographs may demonstrate displaced fracture lines but a lack of
radiographic evidence in the early phases of injury is not uncommon. Bone scan,
CT or MRI may be used to determine the presence of fracture and bone oedema may
be evident on MRI.
Treatment
These fractures tend to have a high rate for healing following 6 to 10
weeks of rest, however, they have a small risk of non-union and re-fracture if
the appropriate amount of rest is not followed. Fractures that display delayed
union will likely demonstrate full recovery when further conservative
procedures are followed. Progression of treatment should be guided by pain and
at first, the individual may require the utilization of crutches as walking may
be painful.
Anatomy of Femoral Neck Stress Fractures
The femoral neck is the flattened, pyramid shaped piece of bone which
connects the femoral head to the femoral shaft.
Athletes with femoral neck stress fractures generally report hip or groin
pain when running. This pain usually has an insidious onset and the symptoms
may become significantly worse depending on the intensity or duration of a run.
At first, symptoms may occur at the end of a run but as the stress reaction
worsens, the pain may begin showing earlier in the run where gradually more
time may be required to relieve the pain and discomfort. Athletes with femoral
neck stress fractures may experience hip and/or groin pain while resting and
may suffer restless nights of sleep due to the symptoms. Often, individuals
will also report pain while rolling in bed, single leg stance and during active
straight leg raise.
Femoral neck stress fractures are described as either tension or
compression stress fractures. Fracture displacement determines the outcome of
an injury and tension stress fractures generally have a higher rate of
displacement as a result of non-union, malunion or osteonecrosis. Due to this
fact, tension stress fractures are considered more serious than compression
fractures and may require surgical fixation.
Diagnosis
Conventional radiographs are often negative in
the acute setting but may shown signs during instances where symptoms have been
present for 2 weeks or more. MRI is the favored standard for diagnosis and
should be ordered when a stress fracture of the femoral neck is suspected.
Treatment
Tension side stress fractures require
diagnosis from a healthcare professional immediately after its occurred due to
their risk of displacement. Compression side fractures are often managed
conservatively with protected weight bearing and ongoing monitoring to keep
track of the individual’s healing process. Initial phases of management should
include non-weight bearing on crutches until there are no symptoms at rest,
then progress to partial weight bearing to full weight bearing over a period of
4-6 weeks. A gradual return to run program can be started at 8 to 12-weeks of
treatment, once the individual is able to properly walk without experiencing
pain and other symptoms.
Return to Activity Plan
With all stress fractures located around the pelvis, a careful, gradual
return to activity plan can be an essential element of the rehabilitation process.
To make sure the athlete receives progressive loading without sudden increases
in workload, the return to activity plan should be at least as long as the time
off the individual’s specific activity. For instance, if the athlete had a
sacral stress fracture which required 6 weeks of no running, then that athlete
needs at least a 6-week gradual return to running plan before they can return
to their previous running load.
Hip Strengthening Exercises
A strengthening program of the lower extremities can additionally be
implemented early in the rehabilitation process, first beginning with
non-weight bearing exercises, which can gradually change as the individual
becomes able to weight bear without pain. Early strengthening can also help
decrease muscle loss and address any biomechanical complications the athlete
might be facing. As the stress fractures heal and the tolerance for load
improves, these exercises can be progressed to other higher-load exercises to provide
the athlete’s body for the return of their specific sports activity.
By Dr. Alex Jimenez