Hip Blog (Part II): Avulsion Injuries, Hip Pointers and Hip Subluxation

Hip Blog (Part II): Avulsion Injuries, Hip Pointers and Hip Subluxation

Created on: Thursday, July 05, 2018
Author: Ryan Fader, MD; Jessica Johnson

Since hockey never really stops in Minnesota, many players are in the midst of summer camps or leagues. With that in mind, we embarked on our second edition of the hip injury blog with Dr. Ryan Fader and the assistance of summer intern Jessica Johnson (University of Minnesota). 

In Part 1 of our hip injury blog, we focused on some of the most common reasons for hip pain in the athlete, including hip impingement with labral tears, groin strains, and other common muscle strains such as sports hernia. In this section, we will focus on other soft tissue/muscular origins of pain.

Avulsion injuries
As previously noted, hockey is an incredibly dynamic sport, with significant and sudden demands constantly being placed on the muscles and tendons around the hip joint. This makes the hip prone to injury in other dynamic sports as well (e.g. soccer, lacrosse, gymnastics, dance, football). In younger athletes, these demands can sometimes overcome the strength of the bone to which they attach, and will “avulse” or pull off a small piece of bone, creating a small fracture. Almost all avulsion fractures present between age of puberty and time of growth plate fusion (around 25 years of age).  The most common of these “avulsion injuries” are:
Hip flexor muscle (rectus femoris)
Tensor fasciae latae muscle (muscle that helps lift leg to the side)
Hamstring muscle 
Rectus abdominis (the “6-pack” abs)
Sartorius (a muscle that helps you with the movement of crossing your legs)
Of these, avulsion injury of the hamstring origin is most common, pulling away a small fragment of the ischial tuberosity or “butt bone” creating a pelvic fracture. This is often caused by sudden and extreme lengthening of the hamstring muscles during any explosive motion. Hockey and soccer players are especially prone to this type of avulsion as they frequently transition from a “ready position” in a low, semi-squatted position where the hamstring muscle is in a contracted position to a quick, explosive motion to the puck or a player which excessively lengthens the hamstring.1,2 
The second most common avulsion injuries is to the hip flexor muscle (rectus femoris), also creating a small “pelvic fracture”, or piece of bone adjacent to the cup portion of the hip joint.  This often follows a sudden aggressive kicking motion or hip flexion motion. Other possible mechanisms of avulsion injuries from the remaining of the previously mentioned muscles include pushing off, planting, cutting, jumping, or any motion where there is an excessive upwards movement of the leg, maximum flexion of the hip and extension of the knee, or abrupt changes in direction and speed.1
How do I know if I have sustained an avulsion injury?
The first sign is sudden onset pain and difficulties with walking/running during sport participation. Often times, you will first be evaluated by your team athletic trainers at the event, who do a wonderful job of identifying injury and identifying the need for further evaluation. If you are a weekend warrior, determining this may be up to you! Most importantly, it’s key to be evaluated by a hip specialist early so you are appropriately treated. A visit with a hip specialist will include a detailed history of how you hurt yourself, a physical exam to localize your pain and perform provocative maneuvers to isolate possible causes. Next, imaging is performed, which typically starts with X-rays. If there is strong clinical suspicious in the setting of negative X-rays, MRI will often be ordered to assess for the soft tissue equivalent/tendon injury.
Treatment of these injuries consists largely of non-operative management. This typically includes a period of limited weight-bearing, protection motions or motions, early physical therapy to maintain motion and increase strength, while improving biomechanics of the hip.  With higher level athletes (elite high school, college, pro), injections are sometimes considered, and these could be either steroid or biological (e.g. PRP) to assist with healing. Rarely are these injuries treated surgically, unless there is a very large piece of bone that is pulled far away from its original location, joint surface is involved, or there is compression of local nerves.
Long term sequelae are extremely rare, but include decreased strength, ongoing pain, or hip impingement in the setting of hip flexor avulsion.
Hip Pointers
The term “hip pointer” is familiar among the contact athletes such as hockey and football. What this term refers to are direct contact injuries to a part of the pelvis (the iliac crest), which is quite vulnerable with no overlying musculature, just above the hip joint itself.  This commonly occurs in hockey with a body to body check or contact with the boards, and in football when the “hip point” or iliac crest comes into contact with the ground or a helmet during tackle. This presents as pain and tenderness to touch overlying the “hip bone”. Occasionally there is associated numbness over this area, which is transient. Treatment consists of ice, rest, and anti-inflammatory medications. In very rare, painful hip pointers, X-rays are obtained to rule out fracture. Sport participation may be limited until the pain is tolerable, but limitations in weight bearing is rarely necessary.
Hip Subluxation
Hip dislocations are an uncommon but serious injury which occurs when the hip ball dislocates from the socket. This is often the result of a high impact traumatic injury, such as a car accident.  Hip subluxations are a less traumatic and more common injury, often described as a partial dislocation where the ball portion of the hip begins to come out of the socket but never fully dislocates. It has been demonstrated that femoroacetabular impingement (hip impingement) anatomy can predispose athletes to this type of injury.3 Hip subluxations most commonly occur during sporting activities including cutting and pivoting, or routine physical contact such as a body check or tackle. Because of the normalcy of the mechanism of injury, this can be misdiagnosed as a sprain/strain. There typically is an immediate onset of pain worsened with movement and ambulation. Rarely are there physical signs other than painful ambulation.4  
The potential harm of a subluxation includes damage to hip cartilage, fracture of the hip joint, or injury to surrounding nerves and blood vessels. These can all have significant long-term impact on hip function if not identified and addressed early. Evaluation consists of physical exam including evaluation of the nerve and vascular function. X-ray imaging is typically obtained to look for structural damage, and in many cases and MRI will be obtained to evaluate the cartilage. Treatment for hip subluxations varies widely but almost uniformly includes initial limitation from sport participation and protected weight bearing with crutches. Some cases respond well to conservative treatment and the patients are able to return to full activity, while others require surgery when there is structural injury such as cartilage injury, fracture, or labral tear. This is commonly addressed in a minimally invasive manner with hip arthroscopy.
The physical demands of ice hockey, and other dynamic sports, can result in a variety of sports related injuries to the hip. Although less frequently occurring than the diagnoses discussed in part 1 of this blog, hip avulsion, pointers, and subluxations can cause athletes to have pain and a need for treatment. It is most important for players, parents, and coaches to understand a variety of conditions exist, and rely on the experience of their team athletic trainer or a hip specialist when there is concern for a hip injury.  A multitude of treatment options exists for each diagnosis in attempt to aid the athlete back to full performance. 
1. Vandervliet EJM, Vanhoenacker FM, Snoeckx A, Gielen JL, Van Dyck P, Parizel PM. Sports‐related acute and chronic avulsion injuries in children and adolescents with special emphasis on tennis. British Journal of Sports Medicine. 2007;41(11):827-831. doi:10.1136/bjsm.2007.036921.
2. Gidwani S, Bircher MD. Avulsion Injuries of the Hamstring Origin – A Series of 12 Patients and Management Algorithm. Annals of The Royal College of Surgeons of England. 2007; 89(4):394-399. doi:10.1308/003588407X183427.
3. Steppacher SD, Albers CE, Siebenrock KA, Tannast M, Ganz R. Femoroacetabular impingement predisposes to traumatic posterior hip dislocation,. Clinical Orthopedics and Related Research. June 2013; 471 (6): 1937-43.
4. Moorman III C, Warren R, Guettler J, et al. Traumatic Posterior Hip Subluxation in American Football. Journal of Bone & Joint Surgery. July 2003;85(7):1190.





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