Avulsion of bone fragments are not uncommon in children with open cartilage at sites of tendon attachment. There are multiple sites around the hip that sustain these injuries and they are more commonly associated with stiff hips and hip impingement. Muscles are tighter on the side of hip impingement. The need for surgical treatment for fractures displaced more than 10 mm is controversial.
Anterior Inferior Iliac Spine Avulsion fractures
Anterior Inferior Iliac Spine (AIIS) avulsion fracture is caused by sudden pull of the straight head of rectus femoris during sports activities like soccer and football. The fracture heals quickly with weight bearing as tolerated even when displaced and leaves a bony prominence that squeezes the soft tissues against the femoral neck with straight hip flexion called AIIS or Subspine impingement. Initial displacement does not correlate with the risk of impingement and and there is no indication for acute repair. Subspine impingement can be treated with open or arthroscopic excision of the bony prominence.
Anterior Superior Iliac Spine Avulsion fractures
Anterior Superior Iliac Spine (ASIS) Avulsion fractures are caused by sudden pull of the Sartorius muscle during forced flexion activities. The inguinal ligament also attaches to it, but displaced fractures are not known to cause any problems. Pain resolves quickly and weight bearing and activities can be resumed as tolerated.
Iliac Crest Avulsion fractures
Abdominal muscles can cause avulsion of iliac crest apophysis. This injury heals well with early mobilization.
Pubic Tubercle and Crest Avulsion fractures
Pubic Tubercle Avulsion fractures are caused by the pull of Adductor Longus and pectineus muscles and heal well with activity modification till the pain resolves.
Pubic Symphysis Avulsion fractures
Pubic Symphysis Avulsion fractures are caused by forceful pull of rectus abdominus insertion. Often treated nonoperatively with early mobilization.
Ischial Tuberosity Avulsion fractures
Ischial Tuberosity Avulsion fractures are caused by pull of the proximal hamstring tendons. Complete ruptures cause chronic pain and weakness. Surgical repair is commonly performed with better outcomes and more complications. Delayed repair can also give good results if nonoperative treatment fails, especially for partial avulsion injuries.
Greater Trochanter Avulsion fractures
Greater Trochanter Avulsion fractures are rare injuries caused by direct trauma and pull of hip abductor muscles. Displaced fractures in children seem to have a high risk of avascular necrosis regardless of the method of treatment. Displacement of more than 5 mm is better treated with surgical repair to restore abductor function and decreased greater trochanter prominence.
Lesser Trochanter Avulsion fractures
Lesser Trochanter Avulsion fractures are caused by sudden pull of Iliopsoas tendon. These may heal with a bony prominence that can cause Lesser trochanter impingement / Ischiofemoral impingement. Late treatment with lesser trochanter excision or distal transfer are options for persistent pain.