Wachsmuth first described stress fractures of the pubic ramus in three male military recruits in 1937 [27]. Although these are rare injuries with few described in the literature, they have been found to be common in female military personnel and athletes [28–31]. In the female military population, it has been hypothesized that an increased force is placed on the pubic rami in order for these recruits to maintain the same stride length as their male colleagues [32]. Another explanation is a greater concentration of cancellous bone in this pelvic region in the female gender [33].

Pubic ramus stress fractures usually occur at the medial portion of the inferior pubic ramus adjacent to the pubic symphysis. This injury is caused by excessive contraction of the adductor magnus muscle at its origin between the ischial tuberosity and the inferior pubic ramus [29]. The adductor magnus pulls the lateral aspect of the pubic ramus when the hip is extended thus initiating the development of these fractures [30]. These injuries have been postulated to occur more frequently in females because females have a greater reliance on hip external rotation in their gait cycle [34, 35] (Fig. 7.2).

Iliac wing stress fractures are extremely rare, consisting of 4 % of all pelvic stress fractures [37, 38]. There are only a total of four case reports in the literature of these injuries: two case reports of iliac wing injuries that extend into the SI joint, and two other reports that do not involve the SI joint. Patients with this condition are usually long distance runners complaining of lateral-based hip pain without a history of trauma. The mechanism of injury is believed to be the result of osseous failure secondary to two opposing repetitive loads: cephalad traction from the musculature of the abdominal wall and a caudal force from the abductors inserting onto the iliac crest (Fig. 7.3a–f).

Apophyseal avulsion fractures are stress injures about the pelvis that are present in adolescent athletes and, occasionally, patients in their mid-20s [39]. These stress injuries are the result of indirect trauma caused by a forceful concentric or eccentric contraction of the muscle that is attached to the apophysis. This causes failure through the growth plate and is the result of the inherent weakness across the unfused apophysis of a skeletally immature athlete. In a more skeletally mature athlete with the same mechanism of injury, these injuries would result in a musculotendinous tear of the affected muscle (Fig. 7.4).

In this adolescent population, there are two types of epiphyses: pressure epiphyses and traction epiphyses. A pressure epiphysis is at the end of long bones and is subjected to the pressures across the joint. Meanwhile, a traction epiphysis is an apophyseal growth plate on which a major muscle or muscle group originates or inserts and is most commonly involved in these avulsion injuries (Table 7.1). Within the traction epiphysis, the epiphyseal plate is the weakest point because the tendon’s Sharpey’s fibers that attach to the growth plate are stronger than the junction of cells between the calcified and uncalcified epiphysis. As a result, osseous failure occurs within the zone of hypertrophy of the growth plate [40].

In a radiologic epidemiologic study, Rossi et al. studied more than 1,000 radiographs and found 203 pelvic apophyseal avulsion injuries [41]. In this series, the most common injuries were at the ischial tuberosity (54 %) followed by the anterior inferior iliac spine (22 %), the anterior superior iliac spine (19 %), the pubic symphysis (3 %), and the iliac crest (1 %). Soccer players were at greatest risk (74 injuries) followed by gymnasts (55 injuries) [37].

The majority of the aforementioned pelvic stress fractures can be treated through nonsurgical means consisting of rest, activity modification, and then a gradual return to athletics. Additionally, any patient with a suspected pelvic stress fracture should undergo a metabolic evaluation consisting of blood and urine work as well as the intake of calcium and vitamin D. A three-phase program has been developed to get athletes back to sport with the presence of pain as the guiding factor in progression through the program [25, 43].

Stage 1 consists of avoiding painful activities. Some sacral fractures may require the athlete to be non-weightbearing with the assistance of crutches. Once pain with ambulation has been eliminated, these crutches can be discontinued. Stage 2 is then initiated once the patient has been pain-free with activities of daily living for 3–5 days. This second phase focuses on strength training and correcting any pelvic muscular imbalance through light-weight and nonimpact exercises. Additionally, sports-specific muscular rehabilitation is initiated at this time. Stage 3 allows the athlete to gradually return to play with progression to normal athletic load for the athlete’s specific sport. Overall, this process can range from 3 to 18 weeks [25]. It is important to note that premature return to sport prior to complete union can increase the risk of complications such as delayed union or nonunion.

Apophyseal avulsion fractures are also treated conservatively similar to the previously described program. These athletes generally return to athletics no earlier than 2 months after the initial injury [44]. Unlike the other pelvic stress fractures, apophyseal injuries can be amenable to surgical intervention with open reduction internal fixation in order to prevent disability in competitive athletes. Some advocate operative intervention if the avulsed fracture fragment is more than 2 cm in size; however, these indications and the optimal timing of surgery still remain debated [45].

In athletes with stress fractures, nutritional and hormonal imbalances are frequently prevalent. Any patient with a suspected pelvic stress fracture should undergo a metabolic evaluation consisting of blood and urine work as well as the dietary intake of calcium and vitamin D. These two minerals have been found to be integral components of nutrition required to achieve and maintain bone homeostasis. Calcium provides strength to the bone through a mineralized matrix and serves as the primary storage of calcium in the body. Vitamin D assists with the absorption of calcium from the digestive tract and renal systems and promotes bone growth and remodeling. Additionally, these minerals have been shown to improve bone density and prevent fractures at all ages. These injuries are most commonly seen in the female gender as this group of athletes experiences the loss of the bone-maintaining effects of estrogen. Additionally, these athletes have a reduction in calcium and vitamin D all of which place them at an increased risk of stress fractures.