The Hip in Ice Hockey: A Current Concepts Review

Level V Evidence

The Hip in Ice Hockey: A Current Concepts Review Andrew W. Kuhn, B.A., Benjamin C. Noonan, M.D., Bryan T. Kelly, M.D., Christopher M. Larson, M.D., and Asheesh Bedi, M.D.

Abstract: Ice hockey is a fast, physical sport with unique associated biomechanical demands often placing the hip in forced and repetitive supraphysiological ranges of motion. Ice hockey players commonly endure and are sidelined by nebulous groin injury or hip pain. Underlying causes can be chronic or acute and extra-articular, intra-articular, or “hipmimicking.” This article serves to review common hip-related injuries in ice hockey. For each, we define the particular condition; comment on risk factors and preventive strategies; discuss key historical, physical examination, and imaging findings; and finally, suggest nonoperative and/or operative treatment plans.

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ce hockey is a popular sport in North America, with participation rates generally rising across all ages, genders, and levels of play.1,2 Given the unique and demanding physical nature of the sport, musculoskeletal injuries are common and of concern. In particular, hip-related injuries not only comprise a large proportion of reported musculoskeletal injuries but also have increased in occurrence and contribute significantly to game-time loss in ice hockey.3-6 These injuries can be chronic or acute and extra-articular, intra-articular, or “hip mimicking,” which can complicate the diagnosis and management of ice hockey players presenting with groin pain.7 Understanding the incidence, causes, and outcomes of these injuries is crucial to improving established preventive strategies and treatment plans. The purpose of this review article was to summarize the

From MedSport and Department of Orthopaedic Surgery, University of Michigan (A.W.K., A.B.), Ann Arbor, Michigan; Sanford Orthopedics and Sports Medicine (B.C.N.), Fargo, North Dakota; Sports Medicine and Shoulder Service, Hospital for Special Surgery (B.T.K.), New York, New York; and Minnesota Orthopedic Sports Medicine Institute (C.M.L.), Edina, Minnesota, U.S.A. The authors report the following potential conflict of interest or source of funding: B.T.K. receives support from Arthrex and A3 Surgical. C.M.L. receives support from A3 Surgical (stock options) and Smith & Nephew (educational support). A.B. receives support from Arthrex. A.B. serves as a National Hockey League Players’ Association and Detroit Red Wings consulting physician. B.T.K. serves as the head team physician for the New York Rangers hockey club. Received March 10, 2016; accepted April 25, 2016. Address correspondence to Asheesh Bedi, M.D., Department of Orthopaedic Surgery, University of Michigan, MedSport, 24 Frank Lloyd Wright Dr, Lobby A, Ann Arbor, MI 48106, U.S.A. E-mail: [email protected] Ó 2016 by the Arthroscopy Association of North America 0749-8063/16219/$36.00 http://dx.doi.org/10.1016/j.arthro.2016.04.029

literature documenting hip-related injuries in ice hockey.

Extra-articular Hip Injuries Adductor Muscle Strain The hip adductor is a group of 6 muscles along the inner thigh, which originate from the pubis and insert along the medial side of the femur (Fig 1).8 In general, muscle strain occurs when a muscle is stretched passively or when contracting while lengthening, also known as eccentric contraction.9 In ice hockey, the adductor is critical to hip abduction-adduction while skating and is highly activated at the end of the “pushoff” phase, shifting from a decelerating eccentric contraction to a powerful concentric contraction during the “recovery portion” of the skating stride.10 Given the unique biomechanical demands of skating, the occurrence of adductor muscle strain in ice hockey is disproportionately common. Whereas adductor muscle strain accounts for nearly 10% of all injuries in professional hockey,8 Emery et al.11 found that across 2 National Hockey League (NHL) seasons of play, adductor muscle strain accounted for the majority (68.3%) of groin/abdominal injuries sustained. Risk factors for adductor strain in ice hockey players have been empirically investigated. First, if bilateral asymmetry in adductor strength exists, players may be at a greater risk of strain. In 1973 Merrifield and Cowan12 prospectively observed 54 high school and collegiate hockey players after using an isokinetic dynamometer to compute each player’s adductor maximal force and power outputs based on measured torques during the preseason. They found that players who reported groin strains during the regular season

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Fig 1. The pectineus, adductor longus, gracilis, and adductor magnus are 4 of 6 muscles that make up the hip adductor group.

exhibited injuries to the adductor muscle group on the side that was less powerful during preseason testing. All players with an adductor strain showed a bilateral force and power imbalance of at least 25%. A second risk factor for adductor strain in ice hockey players may be related to asymmetrical ipsilateral adductionabduction strength ratios. Tyler et al.13 measured preseason hip flexion, abduction, and adduction strength in 47 NHL players and prospectively observed them for 2 seasons. Of the 47 players, 8 had experienced 11 adductor muscle strains. Preseason hip adduction strength was 18% lower in the players who sustained an adductor strain, and a player was 17 times more likely to sustain an adductor muscle strain if ipsilateral adductor strength was less than 80% of abductor strength. Preventive preseason strengthening programs have aimed to identify and nullify these adductor strength or power imbalances, thus reducing the risk of adductor

strain during competition or regular season play. Tyler et al.14 examined the preseason adductor strengths of 83 professional ice hockey players across 2 consecutive NHL seasons. Data for 33 of the 58 players available for analysis (56.9%) identified them as being “at risk” of an adductor strain (operationally defined as an adductorto-abductor muscle strength ratio <80%). These players then underwent a preseason preventive intervention program, including a warm-up phase, strengthening phase, and sport-specific training, to reach an adductor-to-abductor ratio of at least 80%. Only 3 players had sustained an adductor strain the following season, and the authors concluded that their preseason prevention program reduced the incidence of adductor strain from 3.2 strains per 1,000 player-game exposures13 to 0.71 strains per 1,000 player-game exposures. Athletes who sustain acute adductor muscle strains may be able to recall a specific onset of injury, but others may not remember a specific instance of acute injury and may have long-standing or chronic adductor pain and present with localized groin pain, inhibited skating abilities, and decreased game play performance.15 Pertinent clinical findings for an adductor muscle strain on physical examination include pain with palpation of the adductor longus insertion on the pubic bone and/or pain with resisted adduction.16 Magnetic resonance imaging (MRI) and ultrasound (US) may play a role in objectively identifying and confirming the presence, location, and severity of soft-tissue injury.17,18 Although there are typically challenges in correlating clinical and radiologic findings with other groin-related injuries, Serner et al.17 found that clinically diagnosed acute adductor injuries in 110 athletes were frequently confirmed by MRI and US imaging, with only 3% to 6% of these injuries found in a different location (Fig 2).

Fig 2. Noncontrast magnetic resonance imaging in the axial (A) and coronal (B) planes of an acute adductor strain in a male collegiate ice hockey goaltender. As shown by the arrows, the pictured right adductor strain primarily involves the right adductor longus tendon with partial tendon avulsion from the superior pubic ramus. Lesserdegree muscle strain is involved in the pectineus and gracilis muscles.

HIP IN ICE HOCKEY Table 1. Key Points Regarding Adductor Muscle Strain Adductor strain is common in ice hockey. Asymmetries in bilateral adductor and/or ipsilateral adductorabductor strength ratios may be risk factors for adductor strain in ice hockey players. These injuries are typically managed nonoperatively.

Adductor muscle strain is typically managed nonoperativelydprogressing athletes through phases of physical therapy and rehabilitationdincluding a combination of modalities and passive treatment, followed by an active training program focused on eccentric resistive exercise based on clinical milestones.19 Should nonoperative treatment be ineffective to relieve symptoms, surgical intervention, including adductor tenotomy, may become a viable, last-resort option, which is typically more used in the chronic adductor/athletic pubalgia setting. Whereas only 6% of the studies on treatment of athletes with groin pain are deemed “high quality,” a systematic review published in 2015 found moderate evidence supporting the following for athletes with adductor-related groin pain: (1) active exercises improve treatment success compared with passive treatment, (2) multimodal treatment with manual therapy technique shortens time to return to play, and (3) adductor tenotomy may improve treatment success over time20 (Table 1). Hip Flexor Muscle Injury and Iliopsoas Tendinitis The hip flexors are collectively a group of muscles around the front of the hip, which include the iliopsoas, rectus femoris, and sartorius. Traditionally, the iliopsoas tendon is described as a conjoined tendon of the psoas major (originating from the transverse process of the lumbar vertebrae) and iliacus muscles (originating from the upper two-thirds of the iliac fossa and inner lip of the iliac crest) with insertion on the lesser trochanter.21,22 This particular muscle group is often implicated in hip flexion,23 including movements such as kicking and running, and thus the prevalence of iliopsoas injury is observed to be highest among soccer players and running athletes.16 However, it can also be a cause of groin pain in the ice hockey player because the iliopsoas is also implicated in lumbar posture and pelvic control.11,24 A biomechanical analysis of hockey treadmill skating found that increased treadmill velocity corresponded to increased activation of the hip flexor muscles.25 In addition, during “steady-state skating strides,” high-caliber hockey players showed greater hip range of motion, initiated ice contact with greater hip flexion, and ended with greater hip extension than low-caliber players.26 These findings support the hypothesis that the biomechanical demands of the hip flexor group are increased commensurate with higher level of play and increased speed required on the ice.

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Whereas the hip flexor muscle is at risk of strain or injury, internal snapping of the iliopsoas tendon over the iliopectineal eminence, femoral head, or lesser trochanter, termed “internal snapping syndrome,” can lead to iliopsoas tendinitis, inciting groin pain or discomfort in athletes as well.7 The incidence of internal snapping syndrome is relatively unknown, but it has been identified in different athletic populations, including ballet dancers, and is thought to be caused by repetitive supraphysiological movements and ranges of hip motion.16,19,27 Although the syndrome is not common, hockey players may be at some risk of this condition because of the unique biomechanical demands of ice skating. On clinical examination, athletes with iliopsoas syndrome have difficulty with passive hip extension and resisted hip flexion (Thomas test) and pain or tenderness on palpation through the lower lateral part of the abdomen and/or just distal of the inguinal ligament.16,28,29 In addition, when the hip is brought from flexion to extension and/or with circumduction, the iliopsoas tendon is dragged across the anterior pelvic brim, which may reproduce snapping. Although MRI and US have clinical utility in confirming other soft-tissue injury diagnoses, their utility in diagnosing iliopsoas or proximal rectus femoris injury is limited, given that 35% to 46% and 39% to 41% of the time, MRI and US, respectively, pinpoint the injury in a location different from clinical findings or identify concomitant, potentially asymptomatic pathology.17 Iliopsoas tendinitis can also be managed conservatively. Acute pain can be ameliorated with nonsteroidal anti-inflammatory drugs (NSAIDs), ice, and compression; flexibility deficits with stretching; and core stability, hip strength, and other lower extremity musculature can be targeted with a gradual progression of exercises.19 Should symptoms prove refractory to nonoperative treatment, US-guided injection with lidocaine and corticosteroids and arthroscopic lengthening at the musculotendinous junction or release near the tendon insertion on the lesser trochanter are other options discussed in the literature bearing some success in athletic populations30-33 (Table 2).

Table 2. Key Points Regarding Hip Flexor Muscle Injury and Iliopsoas Tendinitis The biomechanical demands placed on the hip flexor group may be directly proportional to level of play and speed of the game in ice hockey. Although rare, ice hockey players may be at risk of internal snapping syndrome and iliopsoas tendinitis. These conditions can be managed conservatively, and if symptoms persist, surgical options exist.

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Table 3. Key Points Regarding Hip Pointer In ice hockey, hip pointers can result from being checked into the boards or by contact with another player or player’s equipment. Padding worn around the hip may not be enough to dissipate the force or insult. Controlling bleeding and/or swelling is a top priority and can be performed with ice and compression.

Hip Pointer Hip pointers were originally described in 1967 as contusions to the iliac crest after a direct insult to the area.34 Pain typically follows and can be the result of subperiosteal edema, bleeding from nutrient vessels of underlying bone, or hematoma formation in muscle; it often results in training and game loss time.35 Hip pointers are frequent in contact sports.36 In a descriptive epidemiologic study analyzing 16 seasons of men’s National Collegiate Athletic Association hockey play, hip contusions were found to represent nearly 2.4% of all injuries, ranking eighth among the most common injuries. In ice hockey, hip pointers can result after contact with a hard object (e.g., being checked into the boards or by contact with another player and his or her equipment). The layers of padding often worn around the hip by ice hockey players may not be enough to dissipate or redistribute the force of insult. In 2009 LaPrade et al.37 described a regimen for treating hip pointers in National Collegiate Athletic Association Division I hockey athletes. Controlling the bleeding or swelling is a top priority and can be performed using ice and compression; crutches are used for more severe hip pointers and until players can walk without a limp; and painrelieving drugs, including acetaminophen or acetaminophen with codeine, can also be administered. Acute NSAIDs should be avoided to minimize bleeding. A rehabilitation program focusing on hip abduction is then initiated until players have enough strength and are cleared to return to on-ice action (Table 3). Other and Rare Extra-articular Hip Injuries Adductor, hip flexor, and hip pointer injuries are the more common extra-articular injuries inciting hip pain in hockey players; however, there are some other less common extra-articular injuries documented by case reports in the literature. Adhau et al.38 presented a 21-year-old junior national-level hockey player who fell on his buttock during a game. Although the fall was seemingly harmless, the player was diagnosed with multiple hip muscle tears, including grade II iliopsoas and piriformis muscle tears and grade III gluteus medius and minimus tears. Southam et al.39 reported on a 27-year-old professional hockey player with a history of treated bilateral sports hernias and right-sided hip adductor release who presented with right-sided lower back, posterior gluteal, and lateral upper thigh pain.

The onset of pain did not follow a fall or collision, but it was exacerbated during game play and skating became difficult. The player was diagnosed with a sacral stress fracture. Lastly, Nodzo et al.40 reported on the evaluation of a 15-year-old boy 2 days after a lateral compression injury sustained during a hockey game. The patient was checked into the boards by a larger opposing player and immediately felt bilateral hip pain in and around the groin. After radiographic and computed tomography imaging, the patient was found to have callus formation at the medial acetabular walls, as well as bilateral anterior wall acetabular fractures (Table 4). Hip-Mimicking Injuries: Sports Hernia, Athletic Pubalgia, and Core Muscle Injury Whereas groin pain can be the result of hip flexor or primary adductor injury, some patients present with pain in the lower abdominal wall and inguinal region (similar to but distinguishable from hernia), termed “sportsman’s hernia” (sports hernia), or athletic pubalgia.41,42 Other names given to or associated with this particular condition include Gilmore’s groin, hockey groin syndrome, and osteitis pubis.43-45 Most recently, this condition has been labeled as “core muscle injury” because many clinicians believe it highlights the true pathophysiology of the injury.46 The pubic symphysis acts as a fulcrum for the anterior pelvis and structures implicated in core muscle injury, including the external oblique fascia and muscle, internal oblique fascia and muscle, transverse abdominis muscle and fascia, and fascia transversalis.47 The rectus abdominis, conjoined tendon, and external oblique merge and form the pubic aponeurosis, connecting with the adductor and gracilis origin. Injury to the abdominal wall at the fascial attachments of the rectus and adductors onto the pubis is the primary cause of core muscle injury (Fig 3).48 In ice hockey, this condition comprises a large proportion of groin-related injuries. Over 2 seasons of play in the NHL, abdominal muscle strains were found to account for 23.2% of all groinrelated strains.11 Core muscle injury may be due to forceful abduction movements in specific athletic situations.49 In ice hockey, the core muscles play an important role in skating but also in shooting and passing. In a case series of 10 professional ice hockey players, Simonet et al.42 discovered consistent distinct thinning or tearing in the internal oblique muscle at the inguinal ring and

Table 4. Key Point Regarding Other and Rare Extra-articular Hip Injuries Other rare extra-articular hip-related injuries in ice hockey have been documented in the literature, including multiple muscle tears, sacral stress fracture, and bilateral anterior wall acetabular fractures.

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Fig 3. Tension imbalances and instability of the surrounding muscles, as shown by the arrows, can cause injury to the fascial attachments at the pubic aponeurosis and core muscle injury.

concluded that this particular pathology is the most accurate depiction of core muscle injury in ice hockey players. Lacroix et al.50 also examined professional hockey players with chronic groin pain. On surgical exploration, the authors found extensive tearing of the external oblique aponeurosis in the direction of the fibers and lateral tearing of the superficial inguinal ring in all 11 cases. Interestingly, the injuries in these athletes were exclusively on the opposite side of their forehand shot. The authors postulated that specific biomechanical demands in hockey, such as skating and shooting, and certain conditions, including musculoskeletal fatigue, weak abdominal muscles, overtraining, and perhaps, the use of outdated or poor equipment, are unique and may favor the onset of these injuries in this particular population. Preventive strategies, though not yet scientifically investigated, should focus on mitigating these risk factors. Patients with severe core muscle injury will likely recall the onset of injury and complain of abdominal pain located in the inguinal canal near the insertion of

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the rectus abdominis muscle on the pubis during activity but not during rest.51 Athletes may also report pain with coughing or radiation of pain into the groin, thigh, and testicular regions due to the entrapment of surrounding nerves.47 On clinical examination, all related structures including the abdominal obliques, transversus abdominis, and conjoined tendon/rectus abdominis should be palpated.47 Tenderness may also be elicited at the insertion of the adductors, as well as at the pubic symphysis itself. A resisted sit-up while palpating the inferolateral edge of the distal rectus abdominis may re-create symptoms, as can resisted hip adduction.51 Noncontrast MRI could prove useful in pubic symphysis characterization (osteitis pubis due to core muscle injury), in addition to identification of rectus abdominis/adductor aponeurosis lesions or tearing or detachment of other structures from the pubic bone or symphysis itself (Fig 4A).46,52,53 The use of US for diagnosing core muscle injury in elite athletes usually renders negative findings.54 However, clinical use of US in identifying the associated pathology of core muscle injury is becoming more common (Fig 4B). Nonoperative treatment typically includes core stabilization exercises, postural training, and re-establishing the dynamic relation between the hip and pelvic muscles.47 However, there is a paucity of literature defining the success of nonoperative treatment for core muscle injury. Conversely, there is a preponderance of studies documenting the success of operative treatment for core muscle injury in athletes, particularly in ice hockey players. Irshad et al.43 reported on a case series of 22 NHL players with groin pain that limited ability to play and failed nonoperative treatment. The athletes were then managed operatively. Surgical treatment included an excision of all perforating neurovascular bundles, ablation of the main trunk of the ilioinguinal nerve, and repair of the external oblique aponeurosis. Every player underwent a 9-week rehabilitation

Fig 4. As demonstrated by the arrows, (A) noncontrast magnetic resonance imaging can aid in the identification of core muscle injury and associated pathology around the pubic symphysis and at the proximal adductor. Reprinted with permission.47 (B) Dynamic ultrasound imaging can also help to distinguish pathology commonly associated with core muscle injury, such as chronic adductor tendinopathy and cortical irregularities of the pubic symphysis (PS). (AB, adductor brevis; AL, adductor longus; AM, adductor magnus.)

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Table 5. Key Points Regarding Hip-Mimicking Injuries: Sports Hernia, Athletic Pubalgia, and Core Muscle Injury In ice hockey, the biomechanics of skating, shooting, and passing, in addition to certain conditions such as muscle fatigue, may favor the development of core muscle injury. On clinical examination, all related structures should be palpated, and a resisted sit-up while palpating the inferolateral edge of the distal rectus abdominis may re-create symptoms, as can resisted hip adduction. Operative treatment has been described as relatively successful in elite ice hockey players, with a large proportion of these athletes returning to competition at levels comparable to preinjury play, although further long-term study is needed.

program postoperatively. All patients returned to playing hockey, and 86% were able to continue playing in the NHL. Brown et al.55 retrospectively reviewed the medical charts of 98 hockey players across 3 playing levels (NHL, American Hockey League, Major Junior A) who underwent surgical exploration and repair for lower abdominal and groin pain and found that the surgical procedure was successful. Only one player, an NHL goalie, was unable to resume his playing career. With regard to effects of surgical intervention on actual game play performance, Jakoi et al.56 compared NHL game play statistics for 43 players 2 seasons before surgical repair and after surgical repair for core muscle injury and found that, in general, all players returned to performance levels comparable to presurgical play. However, the authors did find that those with 7 or more years of experience were more likely to have decreases in overall performance levels and concluded that older players may have less durable outcomes after surgical repair (Table 5).

Intra-articular Hip Injuries Femoroacetabular Impingement Femoroacetabular impingement (FAI) is caused by abnormal contact between the proximal femur and acetabulum (Fig 5). It is thought to be a result of dynamic and static factors, including loss of femoral headneck offset (cam-type lesion), focal or global acetabular overcoverage (pincer-type lesion), or a combination of the two.57 Repetitive entry of a cam-type lesion into the hip joint, typically with flexion and internal rotation, may result in shearing of the transition zone and adjacent cartilage; pincer-type deformity may lead to an impaction mechanism of injury of repetitive microtrauma of the acetabular rim, leading to labral degeneration and tearing.58 In addition, in certain populations, FAI may be a cause of early-onset osteoarthritis.59 As mentioned earlier, the mechanics of skating in hockey are unique and place the hip in demanding positions of flexion, abduction, and external and internal rotation.60,61 Intra-articular hip injuries in

general and FAI in particular are thought to be relatively common in hockey.62,63 Epstein et al.62 retrospectively reviewed the NHL injury surveillance database for injury records between 2006 and 2010 and found that 10.6% of all hip and groin injuries were identified as intra-articular and that FAI accounted for 5.3% of these injuries. Although the unique dynamic stresses endured by skating in hockey may predispose mature athletes to the secondary symptoms of FAI, youth hockey players may be at risk of the development of symptomatic, primary FAI deformity. In a systematic review and meta-analysis published in 2015, Nepple et al.64 found an increased risk of development of cam-type deformity in certain sports with intensive impact such as hockey and basketball, as well as other jumping sports. Highlevel male athletes were 1.9 to 8.0 times more likely to have cam deformity development than controls, and hockey players in particular were at 10 times the likelihood. In one of the studies they reviewed, Philippon et al.65 compared 61 asymptomatic youth ice hockey players with 27 controls (both groups aged 10 to 18 years) and found that the ice hockey players had significantly higher alpha angle66 measurements (>55 ). The relation increased in strength with age. Similarly, in 2013 Siebenrock et al.67 enrolled 77 elite ice hockey players from the national league of Switzerland (mean age, 16.5 years) to undergo questionnaire completion, clinical examination, and MRI. Although there was no matched control group, the authors found that alpha angles were higher in athletes with closed physes versus open physes and concluded that playing ice hockey at an elite level during childhood may be associated with an increased risk of cam-type deformity. The etiology is believed to be multifactorial, with repetitive axial loading/hip flexion and genetic predisposition as contributory factors to anterolateral extension and overgrowth of the physes, resulting in cam deformity.64,65

Fig 5. Osseous deformity at the femoral head-neck junction (cam type) or acetabulum (pincer type) can cause intraarticular hip injury during movements such as flexion and internal rotation.

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Fig 6. The alpha angle can be quantified on the anteroposterior (Dunn) radiograph for diagnosis and confirmation of cam-type femoroacetabular impingement deformity.

Position played may also be a factor in the development of FAI. Over 4 seasons of NHL play, proportionally, goaltenders were found to sustain significantly more intraarticular hip injuries than their offensive and defensive counterparts.62 They are required to make different types of “saves,” subjecting themselves to supraphysiological positions and ranges of motion. In the “butterfly” save, for example, goaltenders drop to their knees and internally rotate their hip so that their pad is parallel to the ice, resulting in repetitive internal rotation with axial loading.62 Whiteside et al.68 analyzed 14 collegiate and professional goaltenders in a descriptive laboratory study quantifying the biomechanics of skating, the butterfly save, and recovery movements on the ice. During skating (32.6 ) and the butterfly save (21.2 ), hip internal rotation was found to be close to end-range passive motion, and the authors concluded that this repetitive end-range hip internal rotation may be a precursor to symptomatic FAI seen commonly in goaltenders. Patients presenting with symptomatic FAI report an insidious onset of groin pain that becomes moderate to severe by the time of presentation and is exacerbated with activity.69 Patients may show deficits in terminal hip range of motion. Hip flexion and internal rotation at 90 of flexion may be restricted, and deficits in abduction and flexion strength may exist.70-73 Ice hockey players presenting with FAI may report difficulty or pain when skating or squatting. Radiographs and advanced imaging, including MRI and computed tomography, are confirmatory of the deformity and associated chondrolabral injury (Fig 6).66,74,75

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Early recognition of FAI in young athletes may allow clinicians to counsel these patients with regard to prevention and treatment plans, including activity-based modifications and physical therapy to prevent further progression of FAI symptoms.76 Nonoperative treatment, including physical therapy, is typically based on a staged approach, with a focus on core hip musculature and improvement in hip external rotation and abduction in extension and flexion; education or prevention may include counseling patients on avoiding aggravating factors; early use of NSAIDs may be useful as well.77-79 Whereas the use of cortisone injections for FAI is common practice for in-season athletes, the empirical evidence of its efficacy is unclear, mixed, and understudied.80 Open surgical dislocation for treating FAI in hockey players has been documented.81-83 However, an arthroscopic approach seems to be increasing in both occurrence and effectiveness. In a cross-sectional study of 622 high-level and recreational athletes, among those classified as high-level male athletes, hockey players underwent the greatest number of arthroscopic procedures to treat FAI.84 A case series of 28 NHL players was conducted by Philippon et al.61 to report on arthroscopic treatment of symptomatic FAI in this group.85,86 Two players (7.14%) had reinjuries. However, all players returned to skating/hockey drills at an average of 3.8 months, modified Harris Hip Scores improved from 70 preoperatively to an average of 95 of 100 postoperatively, and the median patient satisfaction rating was 10 on a scale of 1 to 10. The authors also found that players who underwent surgery within 1 year from the time of injury returned to sport 1.1 months earlier than those who waited more than 1 year. In addition, time from injury to surgery was associated with increased femoral and acetabular chondral defects. Postoperative rehabilitation and return to play typically include restoration and improvement in passive hip motion, followed by active motion and strengthening with a particular focus on restoring internal rotation and then external rotation.61 As previously mentioned, given the unique biomechanical demands of the goaltender position, a position-specific rehabilitation protocol for goalies after arthroscopic hip surgery for FAI has been proposed.87 Table 6. Key Points Regarding FAI Age of first exposure and position played may be risk factors for the development of FAI cam-type deformity in ice hockey players. Hip flexion and internal rotation at 90 of flexion may be restricted in patients presenting with FAI, and ice hockey players in particular may display difficulties ice skating or squatting. Open surgical dislocation and newer arthroscopic approaches in treating FAI in elite ice hockey players have shown relatively successful results with regard to return to play, although further long-term studies are needed. FAI, femoroacetabular impingement.

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Table 7. Key Points Regarding Labral Tears, Chondral Damage, and Loose Bodies Labral tears were discovered to be the most common intra-articular hip injury across 4 seasons of NHL play. The prevalence of these injuries may be underestimated because a large proportion of ice hockey players may have labral pathology but remain asymptomatic. Labral repair during FAI surgery has been deemed superior to labral debridement, and the role of labral reconstruction is unclear and requires further study. FAI, femoroacetabular impingement; NHL, National Hockey League.

In a game play performanceebased study, McDonald et al.88 compared 17 professional (NHL and American Hockey League) male hockey players who underwent arthroscopy and microfracture surgery for treatment of FAI with a matched control group. In the season after surgery, there were no statistical differences between groups across games played, time on ice, points, and for goalies, save percentage or shots on goal. There was a trend toward a decrease in games played and points for the treatment group postoperatively, and it is unclear whether these differences would have reached statistical significance in a larger sample. However, the authors concluded that professional hockey players are able to return to the same elite performance level after arthroscopic treatment of FAI, even in the setting of some full-thickness chondral injury (Table 6). Labral Tears, Chondral Damage, and Loose Bodies The acetabular labrum is fibrocartilaginous in nature; surrounds the acetabular socket89; and functions in shock absorption, joint lubrication, pressure distribution, and stabilization.90 Across 4 seasons of NHL play, labral tears were found to comprise the majority (69.1%) of all intra-articular hip injuries. This figure, however, is likely an underestimation of the total amount of labral pathology in professional hockey players because this particular injury may go undetected in those who are asymptomatic and do not miss games.91 For example, in a study of 39 asymptomatic professional and collegiate hockey players, 22 (56%) were found to have acetabular labral tears as determined by MRI.92 Labral tears can be due to traumatic injury93 but are more often the result of underlying FAI coupled with specific repetitive dynamic movements. In the aforementioned study, 12 of the 15 hockey players (80%) with abnormal alpha angles (cam deformity) were found to have an acetabular labral tear of the ipsilateral hip, indicating that labral pathology may be due to cam-type FAI.92 Hip osteoarthritis and loose bodies were found to represent 13.8% and 6.3%, respectively, of all intra-articular injuries across the same 4 seasons of NHL play.62 Isolated trauma to the hip joint during contact sports, such as hockey, may result in either subluxation or dislocation of the femoral

head causing traumatic labral tears and chondral injuries to the femoral head.94 Osteoarthritis and loose bodies, however, may also be due to underlying structural abnormalities and the dynamic biomechanical demands of ice hockey. Typically, these conditions are managed arthroscopically with relatively high rates of reported patient satisfaction.95,96 Recent data have shown that outcomes of labral repair during FAI surgery are superior to labral debridement procedures.97,98 The role of labral reconstruction is unclear and further study is needed. Suggested indications include young, active patients with minimal arthritis and a nonsalvageable or deficient labrum and/or a segmental labral defect99 (Table 7).

Conclusions and Future Implications Certain hip-related injuries, whether extraarticular, hip mimicking, or intra-articular, seem to be more prevalent in ice hockey than other sports because of the unique biomechanical demands of the sport. The preponderance of literature has reported on adductor strain, core muscle injury, and FAI. Future areas of study include (1) developing offseason training and strengthening programs for the preventive avoidance of groin- and hip-related injuries during the regular season and (2) improving outcomes after arthroscopic surgery for these injuries in this particular population.

Acknowledgment Figures 1, 3, and 5 were generated by the software program Essential Anatomy (version 5.0), programmed by 3D4 Medical. The authors thank Dr. Tariq Awan for his assistance in producing Figure 4B and Liz SibilskyEnselman and Tom Cichonski for their help in preparing the manuscript for publication.

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