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Radial head dislocation with acute plastic bowing of the ulna
J Orthop Sci (2005) 10:103–107 DOI 10.1007/s00776-004-0860-x
Case report Radial head dislocation with acute plastic bowing of the ulna Shigaku Sai, Katsuyuki Fujii, Hiroyuki Chino, and Junichi Inoue Department of Orthopaedic Surgery, The Jikei University School of Medicine, 3-25-8 Nishi-shinbashi, Minato-ku, Tokyo 105-8461, Japan
Abstract Five radial head dislocations with acute plastic bowing of the ulna in patients aged 6–12 years were reviewed. Closed reduction was successful in two, and open reduction was required in three patients in whom treatment was started more than 2 weeks after injury. In one child who presented 2 months after injury, realignment by osteotomy of the ulna as well as open reduction of the radial head was necessary. Follow-up evaluations at 6–24 months revealed good clinical outcomes in all patients. Awareness of this type of radial head dislocation is important to avoid delays in diagnosis and treatment. Key words Acute plastic bowing · Ulnar bow · Radial head dislocation · Monteggia fracture-dislocation
Introduction Dislocation of the radial head in the absence of concurrent ulnar fracture is uncommon and easily misdiagnosed, resulting in undue morbidity. In 1994, Lincoln and Mubarak10 reported that an “isolated” radial head dislocation does not, in fact, exist, although the literature is replete with reports describing traumatic isolated radial head dislocations. Probably most cases of “isolated” radial head dislocation in children are associated with plastic bowing of the ulna, which can be radiographically recognized as the ulnar bow sign. In the present study, we present five cases of this rare condition and analyze the outcomes.
Patients and methods Five children treated at our hospital were diagnosed as having anterior radial head dislocations with acute plasOffprint requests to: S. Sai Received: June 30, 2004 / Accepted: October 12, 2004
tic bowing of the ulna (Table 1). There were three girls and two boys, aged 6–12 years, with an average age of 8.4 years at the time of treatment. In all patients the injury was closed and was caused by a fall. No neurological or vascular complications or associated injuries were encountered. Closed reduction, open reduction, or osteotomy of the ulna with open reduction of the dislocated radial head was carried out. After reduction of the radial head, immobilization using a long-arm plaster cast with the elbow joint in 90° flexion and supination of the forearm was performed. The cast was removed after 3 weeks, and the patient was allowed to move the elbow freely. All patients were evaluated clinically and radiologically at follow-up. The true lateral projection plain radiographs obtained at the initial presentation and after reduction of the radial head were examined for each of the five patients. A straight line was drawn along the dorsal border of the ulna from the level of the olecranon to the distal ulnar metaphysis for accurate assessment of the plastic bowing. The maximum perpendicular distance (ulnar bow sign)10 of this line from the ulnar shaft was measured. The position of this maximum bow along the ulnar shaft from the proximal end was also obtained. The clinical assessment according to a modified version9 of a rating system4 was used, where 60 points were assigned to movement, 30 to pain, and 10 to deformity. A score of 100 was rated as an excellent outcome, 95–99 as good, and 80–94 as fair; anything below 80 was considered poor. The follow-up period ranged from 6 to 24 months, with an average of 11 months.
Results Closed reduction was attempted in four children and was successful in two; the two failures included patients not treated until 15 and 19 days following injury, respec-
104
S. Sai et al.: Radial head dislocation
Table 1. Summary of cases
Case 1 2 3 4 5
Sex
Age
Side
Injury
Time from injury to reduction (days)
M F F F M
12 6 8 9 7
R L L R L
Fall Fall Fall Fall Fall
0 4 15 19 62
Maximum ulnar bow (mm) Treatment
Pre
Post
CR CR OR OR OR ⫹ OU
6 7 5 7.5 4
6 7 4 7 ⫺11
6M
Location of bowa (%)
Follow-up (months)
5 6 4 6 ⫺10
41 59 71 52 53
6 24 12 6 8
R, right; L, left; CR, crossed reduction; OR, open reduction; OU, osteotomy of the ulna; Pre, before reduction; Post, after reduction; 6 M, 6 months after reduction a Percent distance along the length of the ulnar shaft from the proximal end
Table 2. Clinical results Case 1 2 3 4 5
Range of movement (60 points)
Pain (30 points)
Deformity (10 points)
End result
57 60 55 60 55
30 30 30 30 30
10 10 10 10 10
Good Excellent Good Excellent Good
tively. These two children were treated with open reduction and repair of the annular ligament. Correction of the ulnar bow was not required for successful reduction of the radial head. In the remaining patient whose treatment was delayed for 62 days after injury, opening wedge osteotomy of the proximal ulna and open reduction of the radial head without reconstruction of the annular ligament were performed (Table 1). In three patients, the radial head dislocation was missed on initial evaluation, resulting in delays in treatment. The ulnar bow sign was positive in all five patients. The maximum ulnar bow measured 5.9 mm on average at the initial presentation, 6.0 mm immediately after radial head reduction, and 5.3 mm at 6 months postoperatively (Table 1). For the latter two measurements, case 5 was excluded because osteotomy of the ulna had been performed. The maximum plastic deformation occurred near the mid-ulna, at a mean distance of 55% from the proximal end. No callus formation was observed. At the final follow-up, the position and appearance of the radial head was normal in all children, and an almost normal range of active motion in both elbow joint and forearm was obtained. The average forearm pronation was 84°, and supination was 91°. Objective overall results were excellent in two patients and good in three patients (Table 2).
Case presentation Case 2 A 6-year-girl fell and injured her left arm. Four days after the trauma she was seen at our hospital with swelling in the radial head area. The left forearm was pronated, and on palpation the radial head appeared to be anteriorly dislocated. Radiography revealed traumatic dislocation of the radial head with plastic bowing of the ulna (Fig. 1A). The dislocation was reduced the same day under general anesthesia using fluoroscopy, with the forearm in flexion and supination, by direct pressure over the radial head (Fig. 1B, top). After reduction, the radial head was stable in the proper position during elbow joint movement and forearm rotation. Range-ofmotion exercises were started after 3 weeks of immobilization. The maximum plastic ulnar bow occured at 59% distance from the proximal end of the ulna, and it was 7 mm at the initial presentation. This value remained unchanged after reduction of the radial head. On examination 24 months after injury, the position and appearance of the radial head were normal (Fig. 1B, bottom), the range of active motion was within normal limits, and the outcome was excellent. Case 4 A 9-year-old girl fell onto her outstretched hand while playing and injured her right arm. She presented to a
S. Sai et al.: Radial head dislocation
105
A
B Fig. 1. Case 2, a 6-year-old girl. A Initial radiographs: anteroposterior (AP) and lateral views of the left forearm. Note the dislocation of the radial head and plastic bowing of the ulna.
B Lateral views of the left forearm. Top, Immediately after closed reduction of the dislocated radial head. Bottom, Twenty-four months after reduction
A
B Fig. 2. Case 4, a 9-year-old girl. A Initial radiographs: AP and lateral views of the right forearm 18 days after the injury. Note the dislocation of the radial head with ulna bowing. B Lateral
views of the right forearm. Top, Immediately after open reduction of the radial head with repair of the annular ligament. Bottom, Six months after the surgery
local emergency room, where the radial head dislocation was unrecognized. She was referred to our hospital 18 days after the injury complaining of pain and limitation of movement of her right elbow joint and forearm. Physical examination revealed tenderness in the radial head area and a dislocated head of the radius. Extension at the elbow joint was ⫺30°, flexion 70°, pronation of the forearm was 70°, and supination 0°. Radiography revealed traumatic anterior dislocation of the radial head with plastic bowing of the ulna (Fig. 2A). The patient was brought to surgery the following day, at which time closed reduction was initially attempted under general anesthesia. Closed reduction was unsuccessful, so open reduction through a lateral approach was performed. It was noted that the radial head had buttonholed through a transverse tear of the annular ligament, as pointed out by Neviaser and Lefevre.12 After reduction of the radial head and repair of the annular ligament, the radial head was stabilized in proper posi-
tion (Fig. 2B, top). Active range-of-motion exercises were initiated after 3 weeks of immobilization. The maximum plastic ulnar bow occurred at 52% distance from the proximal end of the ulna, and it was 7.5 mm at the initial presentation; this value decreased to 6 mm by 6 months after surgery. A follow-up examination 6 months later showed full range of motion in all planes equal to that of the uninjured elbow; the treatment results were excellent (Fig. 2B, bottom). Case 5 A 7-year-old boy fell on his outstretched hand while playing and sustained an injury to his left elbow. He presented to a local hospital, where his condition was mistakenly diagnosed as a sprain. His elbow joint was immobilized for 3 weeks in a long arm splint. He was referred to our hospital 50 days after the injury. Physical examination revealed tenderness over the
106
S. Sai et al.: Radial head dislocation
A
B Fig. 3. Case 5, a 7-year-old boy. A Initial radiographs: AP and lateral views of the left forearm 50 days after the injury. Note the dislocation of the radial head with plastic bowing of the ulna. B Lateral views of the left forearm. Top, Immediately
after open reduction of the radial head with ulnar osteotomy. Bottom, Eight months after open reduction. The plate and screws have been removed
radial head area and painful motion in both flexionextension and pronation-supination planes. Extension at the elbow joint was 6°, and flexion was 120°; pronation of the forearm was 70°, and supination was 80°. Radiography revealed a traumatic anterior dislocation of the radial head with plastic bowing of the ulna. There was also anterior bow deformity of the proximal part of the radius (Fig. 3A). The maximum plastic ulnar bow occured at 53% distance from the proximal end of the ulna and was 4 mm before the surgery. Open reduction through a lateral approach was performed 62 days after the injury. During the operation the annular ligament was avulsed, and there was fibrotic tissue in the joint space. The radial head was reduced following débridement of the joint, but it was unstable: The radial head could easily redislocate during rotation of the forearm from neutral to pronation position. Opening-wedge osteotomy of the proximal ulna was then considered necessary, and it was stabilized with angulated plate and screw fixation. After the procedure, the radial head became stable enough (Fig. 3B, top) to allow active range-of-motion exercises following 3 weeks of immobilization. The plate and screws were removed after healing of the ulnar osteotomy 6 months after the operation. A follow-up examination at 8 months after surgery showed a decrease in pronation (10°) compared to the opposite side. The treatment outcome was good (Fig. 3B, bottom).
children.6 Predisposing factors are the pliability of children’s bones, the thick active periosteum, and the natural curve of the long bones.3,13 The ulna is more likely to sustain this type of injury than the radius.2 Plastic deformation of both bones of the forearm is less common than single forearm bone deformation.6 The biomechanics of plastic deformation was elucidated by the work of Chamay.5 It has been proposed that plastic deformation results when axial compression force applied to a curved bone exceeds the bone’s elasticity but below the fracture threshold. In other words, the newly produced curve persists even after removal of the compression force.5 Histopathologically, plastic deformation consists of multiple microfractures without evidence of subperiosteal hematoma or subsequent callus formation. This injury could be better described as a precursor of a greenstick-type fracture. Letts et al.9 reported that radial head dislocation with concurrent ulnar bowing should be classified as a variant of the Monteggia fracture-dislocation. Flexibility of the ulna in children allows for some anterior bowing without fracture and permits radial head dislocation. The mechanism of injury is thought to be similar to that of a Monteggia fracture. Eváns7 suggested that the injury occurs as the trunk pivots around the affected upper extremity, which remains fixed when the subject falls to the ground with the hand in pronation. This hyperpronation force brings about rupture of the annular ligament and dislocation of the radial head. Although other mechanisms of the injury have been also reported,16,19 the “hyperpronation theory” remains most widely accepted. The clinical diagnosis of radial head dislocation without concurrent fracture of the ulna is often difficult, and delays in correct diagnosis are quite common.1,8,9,11,18
Discussion Plastic bowing or deformation of long bones was first described by Borden in 1974.3 This rare type of incomplete fracture is seen almost exclusively in forearms of
S. Sai et al.: Radial head dislocation
These delays lead to increased morbidity and increase the risk of inevitable open surgery, necessary to achieve reduction of the dislocated radial head.9,14,15,17,18,20 Our results indicate that radial head dislocation with acute plastic bowing of the ulna in children can be treated by closed reduction; but when diagnosis and treatment are delayed, open reduction of the radial head is necessary. When the injury has been missed for more than 3 weeks, realignment by osteotomy of the ulna may be required. Therefore, missed dislocations of the radial head and delays in initiating the proper treatment are of serious concern. Thus, it is important to draw a straight line (radiocapitellar line) through the long axis of the radial shaft on the radiographs and examine its intersections with the capitellum in all views. In addition, ulnar bow evaluation helps recognize plastic bowing of the ulna. Remodeling of the plastic bowing cannot be demonstrated in this study because of the short follow-up and the small number of patients. Further studies are necessary. References 1. Armstrong RD, McLaren AC. Biceps tendon blocks reduction of isolated radial head dislocation. Orthop Rev 1987;16:104– 8. 2. Attia MW, Glasstetter DS. Plastic bowing type fracture of the forearm in two children. Pediatr Emerg Care 1997;13:392– 3. 3. Borden SIV. Traumatic bowing of the forearm in children. J Bone Joint Surg Am 1974;56:611–6.
107 4. Bruce HE, Harvey JP Jr, Wilson JC Jr. Monteggia fractures. J Bone Joint Surg Am 1974;56:1563–76. 5. Chamay A. Mechanical and morphological aspects of experimental overload and fatigue in bone. J Biomech 1970;3:263–70. 6. Demos T. Radiologic case study. Orthopedics 1980;3:1108–21. 7. Evans EM. Pronation injuries of the forearm: with special reference to the anterior Moteggia fracture. J Bone Joint Surg Br 1949;31:578–88. 8. Hamilton W, Parkes JC II. Isolated dislocation of the radial head without fracture of the ulna. Clin Orthop 1973;97:94–6. 9. Letts M, Locht R, Wiens J. Monteggia fracture-dislocations in children. J Bone Joint Surg Br 1985;67:724–7. 10. Lincoln TL, Mubarak SJ. “Isolated” traumatic radial-head dislocation. J Pediatr Orthop 1994;14:454–7. 11. Lloyd-Roberts GC, Bucknill TM. Anterior dislocation of the radial head in children: aetiology, natural history and management. J Bone Joint Surg Br 1977;59:402–7. 12. Neviaser RJ, Lefevre GW. Irreducible isolated dislocation of the radial head: a case report. Clin Orthop 1971;80:72–4. 13. Rydholm U, Nilsson JE. Traumatic bowing of the forearm: a case report. Clin Orthop 1979;139:121–4. 14. Sano S, Rokkaku T, Imai K, et al. Radial head dislocations with ulnar plastic bowing. Seikeigeka (Orthopaedic Surgery) 2003;54:1619–23 (in Japanese). 15. Sturm PF, Levine J, Sedlin ED, et al. Isolated dislocation of the radial head. Mt Sinai J Med 1989;56:304–8. 16. Tompkins DG. The anterior Monteggia fracture: observations on etiology and treatment. J Bone Joint Surg Am 1971;53:1109– 14. 17. Vesely DG. Isolated traumatic dislocations of the radial head in children. Clin Orthop 1967;50:31–6. 18. Vinz VH. Isolated dislocation of the radial head in childhood. Beitr Orthop Traumatol 1989;36:169–76 (in German). 19. Wiley JJ, Pegington J, Horwich JP. Traumatic dislocation of the radius at the elbow. J Bone Joint Surg Br 1974;56:501–7. 20. Yamamoto M, Kino Y, Hattori Y, et al. Radial head dislocation with acute plastic bowing of the ulna: report of three cases. Seikeigeka (Orthopaedic Surgery) 2003;54:663–7 (in Japanese).
Case report Radial head dislocation with acute plastic bowing of the ulna Shigaku Sai, Katsuyuki Fujii, Hiroyuki Chino, and Junichi Inoue Department of Orthopaedic Surgery, The Jikei University School of Medicine, 3-25-8 Nishi-shinbashi, Minato-ku, Tokyo 105-8461, Japan
Abstract Five radial head dislocations with acute plastic bowing of the ulna in patients aged 6–12 years were reviewed. Closed reduction was successful in two, and open reduction was required in three patients in whom treatment was started more than 2 weeks after injury. In one child who presented 2 months after injury, realignment by osteotomy of the ulna as well as open reduction of the radial head was necessary. Follow-up evaluations at 6–24 months revealed good clinical outcomes in all patients. Awareness of this type of radial head dislocation is important to avoid delays in diagnosis and treatment. Key words Acute plastic bowing · Ulnar bow · Radial head dislocation · Monteggia fracture-dislocation
Introduction Dislocation of the radial head in the absence of concurrent ulnar fracture is uncommon and easily misdiagnosed, resulting in undue morbidity. In 1994, Lincoln and Mubarak10 reported that an “isolated” radial head dislocation does not, in fact, exist, although the literature is replete with reports describing traumatic isolated radial head dislocations. Probably most cases of “isolated” radial head dislocation in children are associated with plastic bowing of the ulna, which can be radiographically recognized as the ulnar bow sign. In the present study, we present five cases of this rare condition and analyze the outcomes.
Patients and methods Five children treated at our hospital were diagnosed as having anterior radial head dislocations with acute plasOffprint requests to: S. Sai Received: June 30, 2004 / Accepted: October 12, 2004
tic bowing of the ulna (Table 1). There were three girls and two boys, aged 6–12 years, with an average age of 8.4 years at the time of treatment. In all patients the injury was closed and was caused by a fall. No neurological or vascular complications or associated injuries were encountered. Closed reduction, open reduction, or osteotomy of the ulna with open reduction of the dislocated radial head was carried out. After reduction of the radial head, immobilization using a long-arm plaster cast with the elbow joint in 90° flexion and supination of the forearm was performed. The cast was removed after 3 weeks, and the patient was allowed to move the elbow freely. All patients were evaluated clinically and radiologically at follow-up. The true lateral projection plain radiographs obtained at the initial presentation and after reduction of the radial head were examined for each of the five patients. A straight line was drawn along the dorsal border of the ulna from the level of the olecranon to the distal ulnar metaphysis for accurate assessment of the plastic bowing. The maximum perpendicular distance (ulnar bow sign)10 of this line from the ulnar shaft was measured. The position of this maximum bow along the ulnar shaft from the proximal end was also obtained. The clinical assessment according to a modified version9 of a rating system4 was used, where 60 points were assigned to movement, 30 to pain, and 10 to deformity. A score of 100 was rated as an excellent outcome, 95–99 as good, and 80–94 as fair; anything below 80 was considered poor. The follow-up period ranged from 6 to 24 months, with an average of 11 months.
Results Closed reduction was attempted in four children and was successful in two; the two failures included patients not treated until 15 and 19 days following injury, respec-
104
S. Sai et al.: Radial head dislocation
Table 1. Summary of cases
Case 1 2 3 4 5
Sex
Age
Side
Injury
Time from injury to reduction (days)
M F F F M
12 6 8 9 7
R L L R L
Fall Fall Fall Fall Fall
0 4 15 19 62
Maximum ulnar bow (mm) Treatment
Pre
Post
CR CR OR OR OR ⫹ OU
6 7 5 7.5 4
6 7 4 7 ⫺11
6M
Location of bowa (%)
Follow-up (months)
5 6 4 6 ⫺10
41 59 71 52 53
6 24 12 6 8
R, right; L, left; CR, crossed reduction; OR, open reduction; OU, osteotomy of the ulna; Pre, before reduction; Post, after reduction; 6 M, 6 months after reduction a Percent distance along the length of the ulnar shaft from the proximal end
Table 2. Clinical results Case 1 2 3 4 5
Range of movement (60 points)
Pain (30 points)
Deformity (10 points)
End result
57 60 55 60 55
30 30 30 30 30
10 10 10 10 10
Good Excellent Good Excellent Good
tively. These two children were treated with open reduction and repair of the annular ligament. Correction of the ulnar bow was not required for successful reduction of the radial head. In the remaining patient whose treatment was delayed for 62 days after injury, opening wedge osteotomy of the proximal ulna and open reduction of the radial head without reconstruction of the annular ligament were performed (Table 1). In three patients, the radial head dislocation was missed on initial evaluation, resulting in delays in treatment. The ulnar bow sign was positive in all five patients. The maximum ulnar bow measured 5.9 mm on average at the initial presentation, 6.0 mm immediately after radial head reduction, and 5.3 mm at 6 months postoperatively (Table 1). For the latter two measurements, case 5 was excluded because osteotomy of the ulna had been performed. The maximum plastic deformation occurred near the mid-ulna, at a mean distance of 55% from the proximal end. No callus formation was observed. At the final follow-up, the position and appearance of the radial head was normal in all children, and an almost normal range of active motion in both elbow joint and forearm was obtained. The average forearm pronation was 84°, and supination was 91°. Objective overall results were excellent in two patients and good in three patients (Table 2).
Case presentation Case 2 A 6-year-girl fell and injured her left arm. Four days after the trauma she was seen at our hospital with swelling in the radial head area. The left forearm was pronated, and on palpation the radial head appeared to be anteriorly dislocated. Radiography revealed traumatic dislocation of the radial head with plastic bowing of the ulna (Fig. 1A). The dislocation was reduced the same day under general anesthesia using fluoroscopy, with the forearm in flexion and supination, by direct pressure over the radial head (Fig. 1B, top). After reduction, the radial head was stable in the proper position during elbow joint movement and forearm rotation. Range-ofmotion exercises were started after 3 weeks of immobilization. The maximum plastic ulnar bow occured at 59% distance from the proximal end of the ulna, and it was 7 mm at the initial presentation. This value remained unchanged after reduction of the radial head. On examination 24 months after injury, the position and appearance of the radial head were normal (Fig. 1B, bottom), the range of active motion was within normal limits, and the outcome was excellent. Case 4 A 9-year-old girl fell onto her outstretched hand while playing and injured her right arm. She presented to a
S. Sai et al.: Radial head dislocation
105
A
B Fig. 1. Case 2, a 6-year-old girl. A Initial radiographs: anteroposterior (AP) and lateral views of the left forearm. Note the dislocation of the radial head and plastic bowing of the ulna.
B Lateral views of the left forearm. Top, Immediately after closed reduction of the dislocated radial head. Bottom, Twenty-four months after reduction
A
B Fig. 2. Case 4, a 9-year-old girl. A Initial radiographs: AP and lateral views of the right forearm 18 days after the injury. Note the dislocation of the radial head with ulna bowing. B Lateral
views of the right forearm. Top, Immediately after open reduction of the radial head with repair of the annular ligament. Bottom, Six months after the surgery
local emergency room, where the radial head dislocation was unrecognized. She was referred to our hospital 18 days after the injury complaining of pain and limitation of movement of her right elbow joint and forearm. Physical examination revealed tenderness in the radial head area and a dislocated head of the radius. Extension at the elbow joint was ⫺30°, flexion 70°, pronation of the forearm was 70°, and supination 0°. Radiography revealed traumatic anterior dislocation of the radial head with plastic bowing of the ulna (Fig. 2A). The patient was brought to surgery the following day, at which time closed reduction was initially attempted under general anesthesia. Closed reduction was unsuccessful, so open reduction through a lateral approach was performed. It was noted that the radial head had buttonholed through a transverse tear of the annular ligament, as pointed out by Neviaser and Lefevre.12 After reduction of the radial head and repair of the annular ligament, the radial head was stabilized in proper posi-
tion (Fig. 2B, top). Active range-of-motion exercises were initiated after 3 weeks of immobilization. The maximum plastic ulnar bow occurred at 52% distance from the proximal end of the ulna, and it was 7.5 mm at the initial presentation; this value decreased to 6 mm by 6 months after surgery. A follow-up examination 6 months later showed full range of motion in all planes equal to that of the uninjured elbow; the treatment results were excellent (Fig. 2B, bottom). Case 5 A 7-year-old boy fell on his outstretched hand while playing and sustained an injury to his left elbow. He presented to a local hospital, where his condition was mistakenly diagnosed as a sprain. His elbow joint was immobilized for 3 weeks in a long arm splint. He was referred to our hospital 50 days after the injury. Physical examination revealed tenderness over the
106
S. Sai et al.: Radial head dislocation
A
B Fig. 3. Case 5, a 7-year-old boy. A Initial radiographs: AP and lateral views of the left forearm 50 days after the injury. Note the dislocation of the radial head with plastic bowing of the ulna. B Lateral views of the left forearm. Top, Immediately
after open reduction of the radial head with ulnar osteotomy. Bottom, Eight months after open reduction. The plate and screws have been removed
radial head area and painful motion in both flexionextension and pronation-supination planes. Extension at the elbow joint was 6°, and flexion was 120°; pronation of the forearm was 70°, and supination was 80°. Radiography revealed a traumatic anterior dislocation of the radial head with plastic bowing of the ulna. There was also anterior bow deformity of the proximal part of the radius (Fig. 3A). The maximum plastic ulnar bow occured at 53% distance from the proximal end of the ulna and was 4 mm before the surgery. Open reduction through a lateral approach was performed 62 days after the injury. During the operation the annular ligament was avulsed, and there was fibrotic tissue in the joint space. The radial head was reduced following débridement of the joint, but it was unstable: The radial head could easily redislocate during rotation of the forearm from neutral to pronation position. Opening-wedge osteotomy of the proximal ulna was then considered necessary, and it was stabilized with angulated plate and screw fixation. After the procedure, the radial head became stable enough (Fig. 3B, top) to allow active range-of-motion exercises following 3 weeks of immobilization. The plate and screws were removed after healing of the ulnar osteotomy 6 months after the operation. A follow-up examination at 8 months after surgery showed a decrease in pronation (10°) compared to the opposite side. The treatment outcome was good (Fig. 3B, bottom).
children.6 Predisposing factors are the pliability of children’s bones, the thick active periosteum, and the natural curve of the long bones.3,13 The ulna is more likely to sustain this type of injury than the radius.2 Plastic deformation of both bones of the forearm is less common than single forearm bone deformation.6 The biomechanics of plastic deformation was elucidated by the work of Chamay.5 It has been proposed that plastic deformation results when axial compression force applied to a curved bone exceeds the bone’s elasticity but below the fracture threshold. In other words, the newly produced curve persists even after removal of the compression force.5 Histopathologically, plastic deformation consists of multiple microfractures without evidence of subperiosteal hematoma or subsequent callus formation. This injury could be better described as a precursor of a greenstick-type fracture. Letts et al.9 reported that radial head dislocation with concurrent ulnar bowing should be classified as a variant of the Monteggia fracture-dislocation. Flexibility of the ulna in children allows for some anterior bowing without fracture and permits radial head dislocation. The mechanism of injury is thought to be similar to that of a Monteggia fracture. Eváns7 suggested that the injury occurs as the trunk pivots around the affected upper extremity, which remains fixed when the subject falls to the ground with the hand in pronation. This hyperpronation force brings about rupture of the annular ligament and dislocation of the radial head. Although other mechanisms of the injury have been also reported,16,19 the “hyperpronation theory” remains most widely accepted. The clinical diagnosis of radial head dislocation without concurrent fracture of the ulna is often difficult, and delays in correct diagnosis are quite common.1,8,9,11,18
Discussion Plastic bowing or deformation of long bones was first described by Borden in 1974.3 This rare type of incomplete fracture is seen almost exclusively in forearms of
S. Sai et al.: Radial head dislocation
These delays lead to increased morbidity and increase the risk of inevitable open surgery, necessary to achieve reduction of the dislocated radial head.9,14,15,17,18,20 Our results indicate that radial head dislocation with acute plastic bowing of the ulna in children can be treated by closed reduction; but when diagnosis and treatment are delayed, open reduction of the radial head is necessary. When the injury has been missed for more than 3 weeks, realignment by osteotomy of the ulna may be required. Therefore, missed dislocations of the radial head and delays in initiating the proper treatment are of serious concern. Thus, it is important to draw a straight line (radiocapitellar line) through the long axis of the radial shaft on the radiographs and examine its intersections with the capitellum in all views. In addition, ulnar bow evaluation helps recognize plastic bowing of the ulna. Remodeling of the plastic bowing cannot be demonstrated in this study because of the short follow-up and the small number of patients. Further studies are necessary. References 1. Armstrong RD, McLaren AC. Biceps tendon blocks reduction of isolated radial head dislocation. Orthop Rev 1987;16:104– 8. 2. Attia MW, Glasstetter DS. Plastic bowing type fracture of the forearm in two children. Pediatr Emerg Care 1997;13:392– 3. 3. Borden SIV. Traumatic bowing of the forearm in children. J Bone Joint Surg Am 1974;56:611–6.
107 4. Bruce HE, Harvey JP Jr, Wilson JC Jr. Monteggia fractures. J Bone Joint Surg Am 1974;56:1563–76. 5. Chamay A. Mechanical and morphological aspects of experimental overload and fatigue in bone. J Biomech 1970;3:263–70. 6. Demos T. Radiologic case study. Orthopedics 1980;3:1108–21. 7. Evans EM. Pronation injuries of the forearm: with special reference to the anterior Moteggia fracture. J Bone Joint Surg Br 1949;31:578–88. 8. Hamilton W, Parkes JC II. Isolated dislocation of the radial head without fracture of the ulna. Clin Orthop 1973;97:94–6. 9. Letts M, Locht R, Wiens J. Monteggia fracture-dislocations in children. J Bone Joint Surg Br 1985;67:724–7. 10. Lincoln TL, Mubarak SJ. “Isolated” traumatic radial-head dislocation. J Pediatr Orthop 1994;14:454–7. 11. Lloyd-Roberts GC, Bucknill TM. Anterior dislocation of the radial head in children: aetiology, natural history and management. J Bone Joint Surg Br 1977;59:402–7. 12. Neviaser RJ, Lefevre GW. Irreducible isolated dislocation of the radial head: a case report. Clin Orthop 1971;80:72–4. 13. Rydholm U, Nilsson JE. Traumatic bowing of the forearm: a case report. Clin Orthop 1979;139:121–4. 14. Sano S, Rokkaku T, Imai K, et al. Radial head dislocations with ulnar plastic bowing. Seikeigeka (Orthopaedic Surgery) 2003;54:1619–23 (in Japanese). 15. Sturm PF, Levine J, Sedlin ED, et al. Isolated dislocation of the radial head. Mt Sinai J Med 1989;56:304–8. 16. Tompkins DG. The anterior Monteggia fracture: observations on etiology and treatment. J Bone Joint Surg Am 1971;53:1109– 14. 17. Vesely DG. Isolated traumatic dislocations of the radial head in children. Clin Orthop 1967;50:31–6. 18. Vinz VH. Isolated dislocation of the radial head in childhood. Beitr Orthop Traumatol 1989;36:169–76 (in German). 19. Wiley JJ, Pegington J, Horwich JP. Traumatic dislocation of the radius at the elbow. J Bone Joint Surg Br 1974;56:501–7. 20. Yamamoto M, Kino Y, Hattori Y, et al. Radial head dislocation with acute plastic bowing of the ulna: report of three cases. Seikeigeka (Orthopaedic Surgery) 2003;54:663–7 (in Japanese).