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Stress fracture of the acromion
Stress fracture of the acromion Jon J. P. Warner, MD, and Joshua Port, MD, Pittsburgh, Pa.
Scapular fractures are most commonly associated with significant trauma and are relatively rare, accounting for 3% to 5% of fractures about the shoulder girdle and less than 1 % of all fractures. 1.7.12.18.21 Fractures of the acromion represent approximately 8% of all scapular fractures.': 5.12.18.21 The literature contains few reports of stress fractures of the scapula; these have been located in the corocoid," the lateral margin of the scapula" and the inferior glenoid neck.' Stress fractures of the acromion have been reported only in association with painful shoulder irnpinqernent." We report a case of a 16-year-old female gymnast, without any known history of shoulder trauma, who experienced a stress fracture at the base of the acromion.
CASE REPORT A 16-year-old right-hand-dominant female gymnast presented to the Shoulder Service complaining of "aching" discomfort over the top of her shoulder. This had been present for 8 months. Initially, her pain was associated only with gymnastics, but on presentation she had pain with all overhead motions. She was initially treated elsewhere with cessation of gymnastics followed by 2 months of immobilization in a sling. Physical examination demonstrated a full, symmetric range of motion in her shoulders but pain with abduction above 90° on the left. She was tender to palpation over the base of the
From The Shoulder Service, Deportment of Orthopaedic Surgery, The Center for Sports Medicine, University of Pittsburgh. Reprint requests: Jon J. P. Worner, MD, Director, Shoulder Service, Deportment of Orthopaedic Surgery, University of Pittsburgh, The Center for Sports Medicine, Baum Blvd. at Craig, Pittsburgh, PA 15213. J SHOULDER ELBOW SURG 1994;3:262-5. Copyright © 1994 by Journal of Shoulder and Elbow Surgery Boord of Trustees. 1058-2746/94/$3.00 + 0
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acromion. Plain radiographs demonstrated an irregular lucent line with sclerotic margins through the base of the acromion; comparison with the other side showed that it was a unilaterallesion (Figure 1). A computed tomography scan also demonstrated this finding (Figure 2), and a technetium bone scan showed regional uptake in this area as well (Figure 3). Because the patient had pain for more than 8 months, it was believed that this represented a nonunion of a stress fracture. She underwent an open reduction and internal fixation with a tension band wire and corticocancellous iliac crest bone grafting. At the time of surgery the entire acromion was found to be freely mobile through the nonunited stress fracture. At 2 years after surgery she has no pain and full shoulder function, and there is radiographic union of the stress fracture (Figure 4).
DISCUSSION Acromial fractures are rare and are usually the result of direct trauma or iatrogenic injury at the time of surqery."' 14. 18 Stress fractures of the sccpulc/" 11.20.21 are also rare, and acromial stress fractures have been reported only in association with rotator cuff orthropothy' or in a young jogger. 20 Recently Mugikura et ol." reported a traumatic scapular spine fracture in an anatomic location similar to that of our patient; however, to our knowledge no other reports of a stress fracture at the base of the acromion exist. Our patient was a gymnast who had no known trauma to her shoulder but had pain in association with gymnastics. Presumably, repetitive forceful contraction of the deltoid during gymnastic activities such as using parallel bars or tumbling may have caused her stress fracture by creating a bending moment across the base of the acromion. Mugikura et ol." believed this was the mechanism in a badminton player who experienced a traumatic fracture in this anatomic region. Because deltoid contraction would depress the acromion,
J. Shoulder Elbow Surg.
Volume 3, Number 4
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263
Figure 1 Axillary rad iograph shows rad iolucent line with marginal sclerosis at base of acromion .
Figure 2 Cross -section computed tomography sca n shows ac romial fracture. this might have caused continuing motion through the stress fracture and led to failure of healing. Though most stress fractures respond well to rest and immobilization, our patient had cantinued pain despite stopping gymnastics and wearing a sling.
Finally, it is important to cons ider the possibility that the lesion in our patient represented a symptomatic os ccrom iole." 9 , lS·18 These ossification centers usually develop during puberty and fuse by age 22. The incidence of os acromiale is 2.7% in the general population,
264 Warner and Port
J. Shoulder Elbow Surg. July/August 7994
Figure 3 Regional uptake in area of acromial stress fracture is demonstrated on bone scan.
Figure 4 Follow-up x-ray film 2 years after bone grafting and stabilization shows union of acromial stress fracture.
J. Shoulder Elbow Surg. Volume 3, Number 4
with 60% being biloterol .v"" The most common site is anterior or mid acromion (mesa and meta ocrorniola"]. A basi acromiale is located at the base of the acromion in the region of our patient's lesion, so it is possible that her lesion could have been an injury to a preexisting nonunited ossification center; however, the finding of a unilateral lucent line at the base of the acromion makes this less likely. Nevertheless our patient did not respond to conservative treatment, and we believed open reduction and internal fixation with bone grafting was appropriate treatment. Because the displacement of the stress fracture was through a bending moment or cantilever-effect produced by the deltoid depressing the acromion, we used a tension-band construct for fixation. Such a technique might also be useful in cases of acromial fractures from trauma.
REFERENCES 1. Armstrong CP, VanDerSpuy J. The fractured scapula: Importance in management based an a series of 62 patients. lnjurv 1984; 15:324-9.
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ogy , and clinical significance: twenty-eight cases including two fractures and separa tions. Rev Chir Orthop 1988;74:160-72. 7. Hardegger FH, Simpson LA, Weber BG. The operative treatment of scapu lar fractures. J Bone Joint Surg [Br] 1984;66B: 725-31. 8. Hulkko A, Orava S. Stress fractures in athletes. Int J Sports Med 1987;8:221-6 . 9. lieberson F.as Acromiale : a contested anomaly. J Bone Joint Surg 1937; 19:683-9. 10. Mar DC, Mesamore GW. Acrom ion nonunion after anterior acromioplasty: a case report . J SHOULDER ELBOW SURG 1992;2:317-20. 11. Matheson GO, Clement DB, McKenzie DC, Taunton JE, Lloyd-Smith DR, Macintyre JG. Stress fractures in athletes: a study of 320 cases. Am J Sports Med 1987;15:46-57. 12. McGahan JP, Rab GT, Dublin A. Fractures of the scapula. J Trauma 1980;20:880-3 . 13. Mugikura S, Hirayama T, Tuda H, Takemitsu Y. Avulsion fracture of the scapular spine: a case report . J SHOULDER ELBOW SURG 1993;2:39-42. 14. Nick CA, Wieland AJ. Pseudoarthrosis of a fracture of the acromion. J Trauma 1983;23:248-9. 15. Neer CS II. Anterior acromioplasty for chronic impinge ment syndrome in the shoulder: a preliminary report. J Bone Joint Surg [AmI 1972;54A:41-50. 16. Ogden JA, Phillips SB. The rad iology of post-natal skeletal deve lopment. Skel Radia l 1983;9 : 157-69. 17. Prather JL, Nysynowitz ML, Snowdy HA, Hughes AD , McCartney WH, Bagg RJ . Scintigraph ic find ings in stress fractures. J Bone Joint Surg [AmI 1977;59A :869-74.
2. Bennett GE. Shoulder and elbow lesions of the professional baseball pitcher. J Am Med Assoc 1941; 117: 510-4 .
18. Rockwood CA Jr, Matsen FA III. The shoulder. Philadelph ia : WB Saunders, 1990:335-66 .
3. Boyer DW Jr. Trap shooter's shoulder : stress fracture of the coracoid process: Case report . J Bone Joint Surg [Am] 1975;57A:862.
19. Schils JP, Freed HA, Richmond BJ, Pirano DW, Bergfeld JA, Belhobek GH. Stressfractures of the acromion . Am J Radial 1990;155: 1140-1.
4. Brower AC, Neff JR, Tillema DA. An unusual scapular stress fracture. Am J Roentgen 1977;129:519-20.
20. Veluvolu P, Kahn HS, Guten GN, Donahue PM, Isitman AT, Whalen JP, Collier BD. Unusual stressfracture of the scapula in a jogger. Clin Nuclear Med 1988;13:531-2.
5. Dennis DA, Ferlick DC, Claten ML. Acromial stress fractures associated with cuff tear arthropathy. J Bone Joint Surg [Am] 1986;68A:937-40. 6. Ferry A, Sommelet J. as acrom iole : diagnosis, pothol-
21. Wilbur MC, Evans EB. Fractures of the scapula: an analysis of forty cases and a review of the literature. J Bone Jaint Surg [Am] 1977;59A:358-62.
Scapular fractures are most commonly associated with significant trauma and are relatively rare, accounting for 3% to 5% of fractures about the shoulder girdle and less than 1 % of all fractures. 1.7.12.18.21 Fractures of the acromion represent approximately 8% of all scapular fractures.': 5.12.18.21 The literature contains few reports of stress fractures of the scapula; these have been located in the corocoid," the lateral margin of the scapula" and the inferior glenoid neck.' Stress fractures of the acromion have been reported only in association with painful shoulder irnpinqernent." We report a case of a 16-year-old female gymnast, without any known history of shoulder trauma, who experienced a stress fracture at the base of the acromion.
CASE REPORT A 16-year-old right-hand-dominant female gymnast presented to the Shoulder Service complaining of "aching" discomfort over the top of her shoulder. This had been present for 8 months. Initially, her pain was associated only with gymnastics, but on presentation she had pain with all overhead motions. She was initially treated elsewhere with cessation of gymnastics followed by 2 months of immobilization in a sling. Physical examination demonstrated a full, symmetric range of motion in her shoulders but pain with abduction above 90° on the left. She was tender to palpation over the base of the
From The Shoulder Service, Deportment of Orthopaedic Surgery, The Center for Sports Medicine, University of Pittsburgh. Reprint requests: Jon J. P. Worner, MD, Director, Shoulder Service, Deportment of Orthopaedic Surgery, University of Pittsburgh, The Center for Sports Medicine, Baum Blvd. at Craig, Pittsburgh, PA 15213. J SHOULDER ELBOW SURG 1994;3:262-5. Copyright © 1994 by Journal of Shoulder and Elbow Surgery Boord of Trustees. 1058-2746/94/$3.00 + 0
262
32/4/53860
acromion. Plain radiographs demonstrated an irregular lucent line with sclerotic margins through the base of the acromion; comparison with the other side showed that it was a unilaterallesion (Figure 1). A computed tomography scan also demonstrated this finding (Figure 2), and a technetium bone scan showed regional uptake in this area as well (Figure 3). Because the patient had pain for more than 8 months, it was believed that this represented a nonunion of a stress fracture. She underwent an open reduction and internal fixation with a tension band wire and corticocancellous iliac crest bone grafting. At the time of surgery the entire acromion was found to be freely mobile through the nonunited stress fracture. At 2 years after surgery she has no pain and full shoulder function, and there is radiographic union of the stress fracture (Figure 4).
DISCUSSION Acromial fractures are rare and are usually the result of direct trauma or iatrogenic injury at the time of surqery."' 14. 18 Stress fractures of the sccpulc/" 11.20.21 are also rare, and acromial stress fractures have been reported only in association with rotator cuff orthropothy' or in a young jogger. 20 Recently Mugikura et ol." reported a traumatic scapular spine fracture in an anatomic location similar to that of our patient; however, to our knowledge no other reports of a stress fracture at the base of the acromion exist. Our patient was a gymnast who had no known trauma to her shoulder but had pain in association with gymnastics. Presumably, repetitive forceful contraction of the deltoid during gymnastic activities such as using parallel bars or tumbling may have caused her stress fracture by creating a bending moment across the base of the acromion. Mugikura et ol." believed this was the mechanism in a badminton player who experienced a traumatic fracture in this anatomic region. Because deltoid contraction would depress the acromion,
J. Shoulder Elbow Surg.
Volume 3, Number 4
Warner and Port
263
Figure 1 Axillary rad iograph shows rad iolucent line with marginal sclerosis at base of acromion .
Figure 2 Cross -section computed tomography sca n shows ac romial fracture. this might have caused continuing motion through the stress fracture and led to failure of healing. Though most stress fractures respond well to rest and immobilization, our patient had cantinued pain despite stopping gymnastics and wearing a sling.
Finally, it is important to cons ider the possibility that the lesion in our patient represented a symptomatic os ccrom iole." 9 , lS·18 These ossification centers usually develop during puberty and fuse by age 22. The incidence of os acromiale is 2.7% in the general population,
264 Warner and Port
J. Shoulder Elbow Surg. July/August 7994
Figure 3 Regional uptake in area of acromial stress fracture is demonstrated on bone scan.
Figure 4 Follow-up x-ray film 2 years after bone grafting and stabilization shows union of acromial stress fracture.
J. Shoulder Elbow Surg. Volume 3, Number 4
with 60% being biloterol .v"" The most common site is anterior or mid acromion (mesa and meta ocrorniola"]. A basi acromiale is located at the base of the acromion in the region of our patient's lesion, so it is possible that her lesion could have been an injury to a preexisting nonunited ossification center; however, the finding of a unilateral lucent line at the base of the acromion makes this less likely. Nevertheless our patient did not respond to conservative treatment, and we believed open reduction and internal fixation with bone grafting was appropriate treatment. Because the displacement of the stress fracture was through a bending moment or cantilever-effect produced by the deltoid depressing the acromion, we used a tension-band construct for fixation. Such a technique might also be useful in cases of acromial fractures from trauma.
REFERENCES 1. Armstrong CP, VanDerSpuy J. The fractured scapula: Importance in management based an a series of 62 patients. lnjurv 1984; 15:324-9.
Warner and Port
265
ogy , and clinical significance: twenty-eight cases including two fractures and separa tions. Rev Chir Orthop 1988;74:160-72. 7. Hardegger FH, Simpson LA, Weber BG. The operative treatment of scapu lar fractures. J Bone Joint Surg [Br] 1984;66B: 725-31. 8. Hulkko A, Orava S. Stress fractures in athletes. Int J Sports Med 1987;8:221-6 . 9. lieberson F.as Acromiale : a contested anomaly. J Bone Joint Surg 1937; 19:683-9. 10. Mar DC, Mesamore GW. Acrom ion nonunion after anterior acromioplasty: a case report . J SHOULDER ELBOW SURG 1992;2:317-20. 11. Matheson GO, Clement DB, McKenzie DC, Taunton JE, Lloyd-Smith DR, Macintyre JG. Stress fractures in athletes: a study of 320 cases. Am J Sports Med 1987;15:46-57. 12. McGahan JP, Rab GT, Dublin A. Fractures of the scapula. J Trauma 1980;20:880-3 . 13. Mugikura S, Hirayama T, Tuda H, Takemitsu Y. Avulsion fracture of the scapular spine: a case report . J SHOULDER ELBOW SURG 1993;2:39-42. 14. Nick CA, Wieland AJ. Pseudoarthrosis of a fracture of the acromion. J Trauma 1983;23:248-9. 15. Neer CS II. Anterior acromioplasty for chronic impinge ment syndrome in the shoulder: a preliminary report. J Bone Joint Surg [AmI 1972;54A:41-50. 16. Ogden JA, Phillips SB. The rad iology of post-natal skeletal deve lopment. Skel Radia l 1983;9 : 157-69. 17. Prather JL, Nysynowitz ML, Snowdy HA, Hughes AD , McCartney WH, Bagg RJ . Scintigraph ic find ings in stress fractures. J Bone Joint Surg [AmI 1977;59A :869-74.
2. Bennett GE. Shoulder and elbow lesions of the professional baseball pitcher. J Am Med Assoc 1941; 117: 510-4 .
18. Rockwood CA Jr, Matsen FA III. The shoulder. Philadelph ia : WB Saunders, 1990:335-66 .
3. Boyer DW Jr. Trap shooter's shoulder : stress fracture of the coracoid process: Case report . J Bone Joint Surg [Am] 1975;57A:862.
19. Schils JP, Freed HA, Richmond BJ, Pirano DW, Bergfeld JA, Belhobek GH. Stressfractures of the acromion . Am J Radial 1990;155: 1140-1.
4. Brower AC, Neff JR, Tillema DA. An unusual scapular stress fracture. Am J Roentgen 1977;129:519-20.
20. Veluvolu P, Kahn HS, Guten GN, Donahue PM, Isitman AT, Whalen JP, Collier BD. Unusual stressfracture of the scapula in a jogger. Clin Nuclear Med 1988;13:531-2.
5. Dennis DA, Ferlick DC, Claten ML. Acromial stress fractures associated with cuff tear arthropathy. J Bone Joint Surg [Am] 1986;68A:937-40. 6. Ferry A, Sommelet J. as acrom iole : diagnosis, pothol-
21. Wilbur MC, Evans EB. Fractures of the scapula: an analysis of forty cases and a review of the literature. J Bone Jaint Surg [Am] 1977;59A:358-62.