Hockey is known as the fastest game on earth. And it continues to get faster. The sheer speed and physicality of the sport puts players at high risk for some serious collisions. Most of the brunt force of these collisions is absorbed by the upper body, particularly the shoulders. Unfortunately, this makes the shoulder prone to a high prevalence of injuries in hockey players.
Two studies from Agel et al. (2007) looked at the injuries in men’s and women’s NCAA ice hockey over a number of years. Both papers found that AC joint injuries were the 3rd most common injury to occur during a game, behind concussions and knee injuries. Interestingly, the main cause of these injuries in both men’s and women’s hockey was contact with another player or with the glass/boards. So even without body checking, like in women’s hockey, AC joint injuries are still very common.
AC Joint Anatomy
The acromioclavicular (AC) joint articulates the clavicle and the acromion process of the scapula. The articulation is surrounded by a joint capsule and two ligaments – the coracoclavicular ligament and the acromioclavicular ligament providing static stability to the joint. The coracoclavicular ligament can be divided into two smaller ligaments, the conoid ligament and the trapezoid ligament. All three ligaments help maintain static stability of the AC joint, creating a stable joint with a small amount of motion. The AC joint is used as a pivot point for scapular motion, in particular protraction and retraction. With shoulder elevation, the clavicle goes through 5-8deg of rotation, 11-15deg of elevation and 15-29deg of retraction. As the shoulder is elevated, it is believed that the coracoclavicular ligaments becomes taught and guides the pseudo-passive motion of the clavicle throughout the motion.
Unlike a lot of other joints, the AC joint doesn’t have a great number of muscles crossing the joint to provide dynamic stability. Two muscles directly cross the AC joint – the deltoid and the trapezius, although neither are in a position to produce much force around the joint as both attach close the axis of rotation, both can assist in stabilizing. Other muscles, such as the serratus anterior, may provide indirect stability to the AC joint which will be further discussed later.
Classification of AC Joint Injuries
The most common classification system for the AC joint was developed by Rockwood et al. who classified the injury into 6 types. Types I-III are partial dislocations while Types IV-VI are complete dislocations. Since the latter types usually require surgical interventions, our focus will be Types I-III, which are at the very least often initial treated conservatively. These AC injuries are classified as follows:
Type I – sprain of the AC ligaments with intact coracoclavicular ligament
Type II – disruption of the AC ligaments and sprained coracoclavicular ligament
Type III – disruption of both AC and coracoclavicular ligaments
With a type II and III injury, the clavicle appears higher than the acromion process. This presents as a step deformity at the AC joint, which is a visible sign of AC joint disruption. Direct force to the outside of the shoulder pushes the acromion under the tip of the clavicle (Phadke et al., 2019). After the initial impact of injury, the gravitational forces acting on the arm displace the acromion inferiorly as the static stabilizers are unable to resist these forces. This is why wearing a sling to support the weight of the arm after an acute AC joint injury provides relief.
4 Keys to AC Joint Rehab for Hockey Players
Like most other joints, when static stability of the joint is disrupted, dynamic stability must be pristine. What makes the AC joint unique is that anatomically, there aren’t many dynamic stabilizers. This is where I often felt helpless and lost when treating AC joint injuries. What do you do with an unstable joint that doesn’t have effective dynamic stabilizers? There are ways to create dynamic stability of the AC joint through other muscles. For hockey players, this is very important to return to giving and receiving hits, boxing out and gaining position on opponents and bearing weight through the shoulder during a shot. These 4 keys to AC joint rehab will hopefully help guide your treatments for a more successful return to the ice.
1 – Restore Restricted Scapular Motion
After an AC joint injury, players will often present with compensatory elevation, protraction and anterior tilt of the shoulder. This “natural sling” position decreases the traction on AC joint from the weight of the arm. Positions of protraction and anterior tilt increase stress on the coracoclavicular ligaments which can slow healing. Reducing the amount of stress on the injured ligaments allow for better management of acute pain with a more gradual increase in tissue stress to promote healing and tissue alignment.
Kim et al. 2015Often times, the tissues creating guarding the AC joint include upper fibers of trapezius, pec minor and pec major which will almost lock down the scapula to prevent any movement. A combination of soft tissue work, SMR and stretching of these tissues can help reduce tone and allow for less restricted motion.
2 – Upward Scapular Rotation
After decreasing tone and gaining more motion, we want to retrain strength and control in the “new” ranges of motion. With a disrupted AC joint, it’s ability to act as a pivot point for scapular motion may be compromised due to the lack of static stability between the clavicle and acromion. Without a stable pivot point, the role of the force couples around the scapula becomes much more important in order to maintain good scapulohumeral rhythm. This can initially be AAROM shoulder elevation in a player who is more acute and has pain with shoulder elevation, and progressed to things like serratus jabs, prone Ts, wall slides, landmine presses, bottom up kettlebell press and downward dog push ups.
3 – Stability in Closed Chain and Traction
Possibly one of the most challenging parts of AC joint rehab is restoring joint stability since the main stabilizers of the joint, the ligaments and capsule, are disrupted. Regaining complete stability of the AC joint without surgery may not be achievable so we want to maximize dynamic joint stability after an injury. We can work on improving joint stability by challenging the dynamic stabilizers to different forces in different positions.
Building stability against traction of the arm will help provide vertical stability to the joint, which is lost with the disruption of the coracoclavicular ligament. This is important for hockey players to protect against further contact injuries which typically drive the acromion inferior to the clavicle. Building resilience to traction can be done in the form of deadlifts and heavy carrying variations.
Retraining closed chain stability can help to prepare players for the pushing and battling in the corners, along the boards and in front of the net. Different push up variations including those on unstable surfaces and side plank variations also with the arm on an unstable surface are great to challenge stability and compression of the AC joint in loaded positions.
4 – Upper Body Plyometrics
Finally, using upper body plyometrics to increase power output and reactive neuromuscular control through the stretch shortening cycle and enhanced neural firing are important for performance and for return to sport. The shoulder must be able to react fast to brace for a hit or for a fall. Drills like plyo pushups, wall dribbles and a variety of med ball throws can enhance shoulder stability and power before returning to the ice.
Keys To AC Joint Rehab
In summary, AC joint rehab can be tricky as it mainly relies on static stabilizers. But these are the 4 keys I follow to help guide my thought process in developing a treatment plan for each player.
References
Agel, J., Dompier, T. P., Dick, R., & Marshall, S. W. (2007). Descriptive epidemiology of collegiate men’s ice hockey injuries: National Collegiate Athletic Association Injury Surveillance System, 1988–1989 through 2003–2004. Journal of athletic training, 42(2), 241.
Agel, J., Dick, R., Nelson, B., Marshall, S. W., & Dompier, T. P. (2007). Descriptive epidemiology of collegiate women’s ice hockey injuries: National Collegiate Athletic Association Injury Surveillance System, 2000–2001 through 2003–2004. Journal of athletic training, 42(2), 249.
Kim, Y. S., Kim, I. S., Yoo, Y. S., Jang, S. W., & Yang, C. J. (2015). An Analysis of Stress Pattern in the Coracoclavicular Ligaments with Scapular Movements: A Cadaveric Study Using Finite Element Model. Clinics in Shoulder and Elbow, 18(3), 152-158.
Mazzocca, A. D., Arciero, R. A., & Bicos, J. (2007). Evaluation and treatment of acromioclavicular joint injuries. The American journal of sports medicine, 35(2), 316-329.