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Coronoid Fracture Height in Terrible-Triad Injuries
Coronoid Fracture Height in Terrible-Triad Injuries Job N. Doornberg, MS, Joppe van Duijn, MS, David Ring, MD From the Orthopaedic Hand and Upper Extremity Service, Harvard Medical School, Boston, MA; Orthotrauma Research Center, University of Amsterdam, Amsterdam, the Netherlands; and Orthopaedic Hand and Upper Extremity Service, Massachusetts General Hospital, Boston, MA.
Purpose: The coronoid fractures that occur in the terrible-triad pattern of traumatic elbow instability (posterior dislocation with fractures of the radial head and coronoid) usually are small transverse fragments. Attempts to classify these fragments according to height as suggested by Regan and Morrey have been inconsistent and contentious. The purpose of this study was to quantify coronoid fracture height in terrible-triad injuries. Methods: The height of the coronoid process of the ulna and the coronoid fracture fragment were measured on computed tomography scans of 13 patients with terrible-triad–pattern elbow injuries. Two observers performed the measurements with excellent intraobserver and interobserver reliability. Results: The total height of the coronoid process of the ulna averaged 19 mm. The average height of the coronoid fracture fragment was 7 mm. This corresponds to an average of 35% of the total height of the coronoid process. Conclusions: The transverse coronoid fractures associated with terrible-triad elbow injuries have a variable height that may not be easy to classify according to the system of Regan and Morrey. Classification of coronoid fractures according to fracture morphology and injury pattern may be preferable. (J Hand Surg 2006;31A:794 –797. Copyright © 2006 by the American Society for Surgery of the Hand.) Key words: Elbow, fracture, instability, coronoid process.
he combination of posterior dislocation of the elbow and fractures of the radial head and coronoid process often is referred to as the terrible triad of the elbow because of the propensity for complications related to instability, arthrosis, and stiffness.1– 4 It has been noted that the fractures of the coronoid that occur in association with the terrible-triad pattern of injury nearly always are transverse fractures of the tip that include the insertion of the anterior elbow capsule, but the height of these fragments is debated.5 The Regan and Morrey classification6 in particular, which is based on fragment height, has been applied inconsistently to these fragments. To help resolve this debate we used quantitative 3-dimensional computed tomography to measure the height of the coronoid fracture fragment associated with terrible-triad injuries.
T
794
The Journal of Hand Surgery
Materials and Methods Computed tomography scans of the elbow adequate for 3-dimensional reconstructions were available for 13 patients with terrible-triad–pattern elbow injuries over a 4-year period. The Human Research Committee at our institution approved a protocol for the use of these scans. A computed tomography scan was deemed suitable for measurements if the slice thickness was 1.25 mm or less. Three scans obtained over this time period were excluded. Thirteen 3-dimensional computed tomography scans were created. There were 10 men and 3 women with an average age of 50 years (range, 25–73 y). Measurements of Coronoid Fracture Fragment Height The height of the coronoid process of the ulna and the fracture fragment was measured according to a
Doornberg, van Duijn, and Ring / Coronoid Fracture Height
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Figure 1. A reproducible reference plane corresponding to the ridge in the center of the trochlear notch of the ulna was determined by using the apex of the ridge at 3 points: the olecranon process near its tip (O), near the transverse groove of the olecranon at the base of the trochlear notch (T), and the coronoid process near the fracture (C). This plane is marked with black and white lines on the left. The red and green lines represent reference planes related to the 3-dimensional image of the elbow and not to any measurements we made.
standardized protocol. Three-dimensional image manipulation was performed using software (Vitrea 2; Vital Images, Inc., Plymouth, MN). A reproducible reference plane corresponding to the ridge in the center of the trochlear notch of the ulna was determined by using the apex of the ridge at 3 points: (1) the olecranon process near its tip, (2) near the transverse groove of the olecranon at the base of the trochlear notch, and (3) the coronoid process near the fracture (Fig. 1). The base of the coronoid was selected on a 2-dimensional image created in this plane as a line connecting a point at the base of the trochlear notch with a point at the anterior ulnar cortical margin distal to the coronoid process.
The posterior-to-anterior height of the remaining unfractured coronoid was measured in millimeters along a line perpendicular to the line defining the base of the coronoid process (Fig. 2). To measure the height of the coronoid fracture fragment the reference plane was translated sagittally to the apex of the trochlear ridge on the coronoid fracture fragment (Fig. 3). The total height of the coronoid process was calculated as the sum of the distance between the line defining the base of the coronoid to the fracture and the height of the coronoid fracture fragment. None of the patients had fragmentation that might distort the images. Distances were measured using imaging software (OSIRIS Imaging Software; Digital Imag-
Figure 2. Measurement of coronoid height (CH). The base of the coronoid was selected on a 2-dimensional image created in the reference plane as a line connecting a point at the base of the trochlear notch (TB) with a point at the anterior ulnar cortical margin (CM) distal to the coronoid process. The posterior to anterior height of the unfractured coronoid was measured in millimeters along a line perpendicular to the line defining the base of the coronoid process (CH).
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The Journal of Hand Surgery / Vol. 31A No. 5 May–June 2006
Figure 3. Coronoid fracture height (FX). The reproducible reference plane (RP) was translated sagittally to the apex of the trochlear ridge on the coronoid fracture fragment (AC). The height of the coronoid fracture fragment also was measured along the apex of the trochlear notch (FX). The red and green lines represent the reference planes of the 3-dimensional image and were not related directly to the measurements.
ing Unit, University Hospital of Geneva, Geneva, Switzerland).7 To evaluate the reliability of the measurement techniques, 2 observers performed all measurements of coronoid fragment height and the interobserver reliability was calculated. To evaluate intraobserver reliability each measurer repeated the measurements after a 2-week interval. Statistical Analysis A power analysis with statistical software (nQuery Advisor, version 5.0; Statistical Solutions, Boston, MA) indicated that a total sample size of 13 elbows would provide 80% power to detect differences of 1.0 mm with respect to intraobserver and interobserver reliability. The Pearson product-moment correlation coefficient (r) was used to measure the level of intraobserver and interobserver reliability for measurements of coronoid fracture fragment height. Correlations between 0.70 and 0.89 were regarded as good and r values of 0.90 or greater were considered excellent.8 Two-tailed p values of less than .05 were considered statistically significant. Statistical analysis was conducted using statistical software (SPSS statistical package, version 12.0; SPSS Inc., Chicago, IL).
Results Reliability of Measurements The measurement techniques had excellent intraobserver and interobserver reliability. Pearson correlations for intraobserver agreement were r ⫽ 0.95 and r ⫽ 0.97 for coronoid height and r ⫽ 0.94 and r ⫽ 0.99 for fracture fragment height. For interobserver reliability the correlation was r ⫽ 0.94 for coronoid
height and r ⫽ 0.94 for coronoid fragment height (all p ⬍ .001). Measurements of Coronoid Fracture Fragment Height The total height of the coronoid process of the ulna averaged 19 mm (range, 12–25 mm). The average height of the coronoid fracture fragment was 7 mm (range, 3–12 mm). This corresponds to an average of 35% of the total height of the coronoid process (range, 19%–59%).
Discussion The concept of a terrible-triad injury of the elbow has become well accepted because when a coronoid fracture is associated with a posterior elbow dislocation and a fracture of the radial head, substantial problems with stability and arthrosis are encountered.1,9 It also is recognized that although these fragments are small, repairing them contributes substantially to elbow stability and improves the clinical results.8 Furthermore although most observers agree that these fractures are relatively small and nearly always transverse in morphology,10 disagreement has arisen regarding whether they represent a fleck of bone or a type 1 fracture according to the classification of Regan and Morrey. According to the interpretation by Schneeberger et al4 of the Regan and Morrey classification6 (based on biomechanic studies that suggested that ⬎30% loss of coronoid height was associated with increased elbow instability in the setting of a terrible-triad injury pattern), 2 of the coronoid fractures is this study were type 1 (tip fracture ⬍30% of total height of coronoid process), 10 were type 2 (⬎30% and
Doornberg, van Duijn, and Ring / Coronoid Fracture Height
⬍50% of total coronoid height), and 1 was type 3 (⬎50% of total coronoid height). In a series of surgically treated patients 31 of 32 patients with terribletriad–pattern injuries had a small transverse fracture that included the capsular insertion; the remaining patient had an anteromedial facet fracture (Doornberg and Ring, presented at the Annual Meeting of the American Society for Surgery of the Hand, 2003). The classification scheme by O’Driscoll et al11 may be more suitable: a transverse fracture large enough to have the anterior capsular insertion on— but not involving—the entire coronoid to its base is type 1, subtype 2; a smaller transverse fracture that likely would be an intra-articular loose fragment is type 1, subtype 1. We contend that the fracture morphology and injury pattern are more important than the classification of the coronoid fracture according to height. The vast majority of terrible-triad injuries have a transverse fracture of the coronoid process that is less than 50% of the coronoid height. These fragments may seem small on radiographs but are very important to elbow stability by virtue of both the contribution to an anterior bony buttress against posterior elbow dislocation and stability of the anterior capsular insertion.6 Received for publication November 28, 2005; accepted in revised form January 12, 2006. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Supported by an unrestricted AO-research grant, an Orthopaedic Research Alumni Council Summer Research Grant 2005, and an unrestricted research grant from the Stichting Anna-Fonds, Leiden, the Netherlands.
797
Corresponding author: David Ring, MD, Orthopaedic Hand and Upper Extremity Service, Massachusetts General Hospital, Yawkey Center, Ste 2100, 55 Fruit St, Boston, MA 02114; e-mail: [email protected]. Copyright © 2006 by the American Society for Surgery of the Hand 0363-5023/06/31A05-0017$32.00/0 doi:10.1016/j.jhsa.2006.01.004
References 1. Ring D, Jupiter JB, Zilberfarb J. Posterior dislocation of the elbow with fractures of the radial head and coronoid. J Bone Joint Surg 2002;84A:547–551. 2. McKee MD, Pugh DM, Wild LM, Schemitsch EH, King GJ. Standard surgical protocol to treat elbow dislocations with radial head and coronoid fractures. Surgical technique. J Bone Joint Surg 2005;87A(suppl 1):22–32. 3. Deutch SR, Jensen SL, Tyrdal S, Olsen BS, Sneppen O. Elbow joint stability following experimental osteoligamentous injury and reconstruction. J Shoulder Elbow Surg 2003; 12:466 – 471. 4. Schneeberger AG, Sadowski MM, Jacob HA. Coronoid process and radial head as posterolateral rotatory stabilizers of the elbow. J Bone Joint Surg 2004;86A:975–982. 5. Morrey BF, An KN. Stability of the elbow: osseous constraints. J Shoulder Elbow Surg 2005;14(suppl S):174S– 178S. 6. Regan W, Morrey B. Fractures of the coronoid process of the ulna. J Bone Joint Surg 1989;71A:1348 –1354. 7. Ligier Y, Ratib O, Logean M, Girard C, Perrier R, Scherrer JR. Object-oriented design of medical imaging software. Comput Med Imaging Graph 1994;18:125–135. 8. Pugh DM, Wild LM, Schemitsch EH, King GJ, McKee MD. Standard surgical protocol to treat elbow dislocations with radial head and coronoid fractures. J Bone Joint Surg 2004; 86A:1122–1130. 9. Josefsson PO, Gentz CF, Johnell O, Wendeberg B. Dislocations of the elbow and intraarticular fractures. Clin Orthop 1989;246:126 –130. 10. Doornberg JN, Ring D. Coronoid fracture patterns. J Hand Surg 2006;31A:45–52. 11. O’Driscoll SW, Jupiter JB, Cohen MS, Ring D, McKee MD. Difficult elbow fractures: pearls and pitfalls. Instr Course Lect 2003;52:113–134.
Purpose: The coronoid fractures that occur in the terrible-triad pattern of traumatic elbow instability (posterior dislocation with fractures of the radial head and coronoid) usually are small transverse fragments. Attempts to classify these fragments according to height as suggested by Regan and Morrey have been inconsistent and contentious. The purpose of this study was to quantify coronoid fracture height in terrible-triad injuries. Methods: The height of the coronoid process of the ulna and the coronoid fracture fragment were measured on computed tomography scans of 13 patients with terrible-triad–pattern elbow injuries. Two observers performed the measurements with excellent intraobserver and interobserver reliability. Results: The total height of the coronoid process of the ulna averaged 19 mm. The average height of the coronoid fracture fragment was 7 mm. This corresponds to an average of 35% of the total height of the coronoid process. Conclusions: The transverse coronoid fractures associated with terrible-triad elbow injuries have a variable height that may not be easy to classify according to the system of Regan and Morrey. Classification of coronoid fractures according to fracture morphology and injury pattern may be preferable. (J Hand Surg 2006;31A:794 –797. Copyright © 2006 by the American Society for Surgery of the Hand.) Key words: Elbow, fracture, instability, coronoid process.
he combination of posterior dislocation of the elbow and fractures of the radial head and coronoid process often is referred to as the terrible triad of the elbow because of the propensity for complications related to instability, arthrosis, and stiffness.1– 4 It has been noted that the fractures of the coronoid that occur in association with the terrible-triad pattern of injury nearly always are transverse fractures of the tip that include the insertion of the anterior elbow capsule, but the height of these fragments is debated.5 The Regan and Morrey classification6 in particular, which is based on fragment height, has been applied inconsistently to these fragments. To help resolve this debate we used quantitative 3-dimensional computed tomography to measure the height of the coronoid fracture fragment associated with terrible-triad injuries.
T
794
The Journal of Hand Surgery
Materials and Methods Computed tomography scans of the elbow adequate for 3-dimensional reconstructions were available for 13 patients with terrible-triad–pattern elbow injuries over a 4-year period. The Human Research Committee at our institution approved a protocol for the use of these scans. A computed tomography scan was deemed suitable for measurements if the slice thickness was 1.25 mm or less. Three scans obtained over this time period were excluded. Thirteen 3-dimensional computed tomography scans were created. There were 10 men and 3 women with an average age of 50 years (range, 25–73 y). Measurements of Coronoid Fracture Fragment Height The height of the coronoid process of the ulna and the fracture fragment was measured according to a
Doornberg, van Duijn, and Ring / Coronoid Fracture Height
795
Figure 1. A reproducible reference plane corresponding to the ridge in the center of the trochlear notch of the ulna was determined by using the apex of the ridge at 3 points: the olecranon process near its tip (O), near the transverse groove of the olecranon at the base of the trochlear notch (T), and the coronoid process near the fracture (C). This plane is marked with black and white lines on the left. The red and green lines represent reference planes related to the 3-dimensional image of the elbow and not to any measurements we made.
standardized protocol. Three-dimensional image manipulation was performed using software (Vitrea 2; Vital Images, Inc., Plymouth, MN). A reproducible reference plane corresponding to the ridge in the center of the trochlear notch of the ulna was determined by using the apex of the ridge at 3 points: (1) the olecranon process near its tip, (2) near the transverse groove of the olecranon at the base of the trochlear notch, and (3) the coronoid process near the fracture (Fig. 1). The base of the coronoid was selected on a 2-dimensional image created in this plane as a line connecting a point at the base of the trochlear notch with a point at the anterior ulnar cortical margin distal to the coronoid process.
The posterior-to-anterior height of the remaining unfractured coronoid was measured in millimeters along a line perpendicular to the line defining the base of the coronoid process (Fig. 2). To measure the height of the coronoid fracture fragment the reference plane was translated sagittally to the apex of the trochlear ridge on the coronoid fracture fragment (Fig. 3). The total height of the coronoid process was calculated as the sum of the distance between the line defining the base of the coronoid to the fracture and the height of the coronoid fracture fragment. None of the patients had fragmentation that might distort the images. Distances were measured using imaging software (OSIRIS Imaging Software; Digital Imag-
Figure 2. Measurement of coronoid height (CH). The base of the coronoid was selected on a 2-dimensional image created in the reference plane as a line connecting a point at the base of the trochlear notch (TB) with a point at the anterior ulnar cortical margin (CM) distal to the coronoid process. The posterior to anterior height of the unfractured coronoid was measured in millimeters along a line perpendicular to the line defining the base of the coronoid process (CH).
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The Journal of Hand Surgery / Vol. 31A No. 5 May–June 2006
Figure 3. Coronoid fracture height (FX). The reproducible reference plane (RP) was translated sagittally to the apex of the trochlear ridge on the coronoid fracture fragment (AC). The height of the coronoid fracture fragment also was measured along the apex of the trochlear notch (FX). The red and green lines represent the reference planes of the 3-dimensional image and were not related directly to the measurements.
ing Unit, University Hospital of Geneva, Geneva, Switzerland).7 To evaluate the reliability of the measurement techniques, 2 observers performed all measurements of coronoid fragment height and the interobserver reliability was calculated. To evaluate intraobserver reliability each measurer repeated the measurements after a 2-week interval. Statistical Analysis A power analysis with statistical software (nQuery Advisor, version 5.0; Statistical Solutions, Boston, MA) indicated that a total sample size of 13 elbows would provide 80% power to detect differences of 1.0 mm with respect to intraobserver and interobserver reliability. The Pearson product-moment correlation coefficient (r) was used to measure the level of intraobserver and interobserver reliability for measurements of coronoid fracture fragment height. Correlations between 0.70 and 0.89 were regarded as good and r values of 0.90 or greater were considered excellent.8 Two-tailed p values of less than .05 were considered statistically significant. Statistical analysis was conducted using statistical software (SPSS statistical package, version 12.0; SPSS Inc., Chicago, IL).
Results Reliability of Measurements The measurement techniques had excellent intraobserver and interobserver reliability. Pearson correlations for intraobserver agreement were r ⫽ 0.95 and r ⫽ 0.97 for coronoid height and r ⫽ 0.94 and r ⫽ 0.99 for fracture fragment height. For interobserver reliability the correlation was r ⫽ 0.94 for coronoid
height and r ⫽ 0.94 for coronoid fragment height (all p ⬍ .001). Measurements of Coronoid Fracture Fragment Height The total height of the coronoid process of the ulna averaged 19 mm (range, 12–25 mm). The average height of the coronoid fracture fragment was 7 mm (range, 3–12 mm). This corresponds to an average of 35% of the total height of the coronoid process (range, 19%–59%).
Discussion The concept of a terrible-triad injury of the elbow has become well accepted because when a coronoid fracture is associated with a posterior elbow dislocation and a fracture of the radial head, substantial problems with stability and arthrosis are encountered.1,9 It also is recognized that although these fragments are small, repairing them contributes substantially to elbow stability and improves the clinical results.8 Furthermore although most observers agree that these fractures are relatively small and nearly always transverse in morphology,10 disagreement has arisen regarding whether they represent a fleck of bone or a type 1 fracture according to the classification of Regan and Morrey. According to the interpretation by Schneeberger et al4 of the Regan and Morrey classification6 (based on biomechanic studies that suggested that ⬎30% loss of coronoid height was associated with increased elbow instability in the setting of a terrible-triad injury pattern), 2 of the coronoid fractures is this study were type 1 (tip fracture ⬍30% of total height of coronoid process), 10 were type 2 (⬎30% and
Doornberg, van Duijn, and Ring / Coronoid Fracture Height
⬍50% of total coronoid height), and 1 was type 3 (⬎50% of total coronoid height). In a series of surgically treated patients 31 of 32 patients with terribletriad–pattern injuries had a small transverse fracture that included the capsular insertion; the remaining patient had an anteromedial facet fracture (Doornberg and Ring, presented at the Annual Meeting of the American Society for Surgery of the Hand, 2003). The classification scheme by O’Driscoll et al11 may be more suitable: a transverse fracture large enough to have the anterior capsular insertion on— but not involving—the entire coronoid to its base is type 1, subtype 2; a smaller transverse fracture that likely would be an intra-articular loose fragment is type 1, subtype 1. We contend that the fracture morphology and injury pattern are more important than the classification of the coronoid fracture according to height. The vast majority of terrible-triad injuries have a transverse fracture of the coronoid process that is less than 50% of the coronoid height. These fragments may seem small on radiographs but are very important to elbow stability by virtue of both the contribution to an anterior bony buttress against posterior elbow dislocation and stability of the anterior capsular insertion.6 Received for publication November 28, 2005; accepted in revised form January 12, 2006. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Supported by an unrestricted AO-research grant, an Orthopaedic Research Alumni Council Summer Research Grant 2005, and an unrestricted research grant from the Stichting Anna-Fonds, Leiden, the Netherlands.
797
Corresponding author: David Ring, MD, Orthopaedic Hand and Upper Extremity Service, Massachusetts General Hospital, Yawkey Center, Ste 2100, 55 Fruit St, Boston, MA 02114; e-mail: [email protected]. Copyright © 2006 by the American Society for Surgery of the Hand 0363-5023/06/31A05-0017$32.00/0 doi:10.1016/j.jhsa.2006.01.004
References 1. Ring D, Jupiter JB, Zilberfarb J. Posterior dislocation of the elbow with fractures of the radial head and coronoid. J Bone Joint Surg 2002;84A:547–551. 2. McKee MD, Pugh DM, Wild LM, Schemitsch EH, King GJ. Standard surgical protocol to treat elbow dislocations with radial head and coronoid fractures. Surgical technique. J Bone Joint Surg 2005;87A(suppl 1):22–32. 3. Deutch SR, Jensen SL, Tyrdal S, Olsen BS, Sneppen O. Elbow joint stability following experimental osteoligamentous injury and reconstruction. J Shoulder Elbow Surg 2003; 12:466 – 471. 4. Schneeberger AG, Sadowski MM, Jacob HA. Coronoid process and radial head as posterolateral rotatory stabilizers of the elbow. J Bone Joint Surg 2004;86A:975–982. 5. Morrey BF, An KN. Stability of the elbow: osseous constraints. J Shoulder Elbow Surg 2005;14(suppl S):174S– 178S. 6. Regan W, Morrey B. Fractures of the coronoid process of the ulna. J Bone Joint Surg 1989;71A:1348 –1354. 7. Ligier Y, Ratib O, Logean M, Girard C, Perrier R, Scherrer JR. Object-oriented design of medical imaging software. Comput Med Imaging Graph 1994;18:125–135. 8. Pugh DM, Wild LM, Schemitsch EH, King GJ, McKee MD. Standard surgical protocol to treat elbow dislocations with radial head and coronoid fractures. J Bone Joint Surg 2004; 86A:1122–1130. 9. Josefsson PO, Gentz CF, Johnell O, Wendeberg B. Dislocations of the elbow and intraarticular fractures. Clin Orthop 1989;246:126 –130. 10. Doornberg JN, Ring D. Coronoid fracture patterns. J Hand Surg 2006;31A:45–52. 11. O’Driscoll SW, Jupiter JB, Cohen MS, Ring D, McKee MD. Difficult elbow fractures: pearls and pitfalls. Instr Course Lect 2003;52:113–134.