Effects of distal radius fracture malunion on wrist joint mechanics An experimental
model using a static positioning frame, pressure-sensitive
microcomputer-based
videodigitizing
film (Fuji), and a system was used to measure contact areas and pressures
in the wrist. Contact areas and pressures were compared in a group of wrists between the normal state and with simulated distal radius fracture mahmions of varying degrees. In simulated malunions, radial shortening to any degree slightly increased the total contact area in the lunate fossa, and was significant at 2 mm of shortening. By angulating the distal radius more than 20 degrees either palmar or dorsal, there was a dorsal shift in the scaphoid and lunate high pressure areas, and the loads were more concentrated, but there was no change in the load distribution between the scaphoid and lunate. Decreasing the radial inclination shifted the load distribution so that there was more load in the lunate fossa and less load in the scaphoid fossa. (J HAND SURG 1990;15A:721-7.)
David J. Pogue, BS, Steven F. Viegas, MD, Rita M. Patterson, MEng, Pamela D. Peterson, David K. Jenkins, BS, Timothy D. Sweo, BS, and James A, Hokanson, PhD, Galveston, Texas
F ractures of the distal radius make up 8% to 15% of all bone injuries.’ The mechanism of injury in a distal radius fracture is almost always a fall on an outstretched hand, typically causing dorsal and radial displacement of the distal end of the radius.** 3 The fractures are usually treated with closed reduction and plaster splint or cast immobilization, or internal or external fixation.3-9 Distal radius fractures can include comminution of the distal fragment, articular surface involvement, and can be accompanied by ulna styloid avulsion fractures.*, 3. ‘-I* Complication rates in distal radius fractures are high, ‘2 *, 13-16with malunion among the most com-
From the Division of Orthopedic Surgery, and the Division of Biostatistics, University of Texas Medical Branch, Galveston, Texas. Study supported in part by a grant from the Orthopaedic Research and Education Foundation No. 87-459, and by a grant from the National Institute of Arthritis and Musculoskeletal and Skin Diseases No. 5 R29 AR 38640-02. Received for publication Oct. 14. 1989.
May 25, 1989; accepted
in revised form
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. Reprint requests: Steven F. Viegas, MD, Division of Orthopaedic Surgery, McCullough Bldg., Rm 6.136 (G-92), University of Texas Medical Branch, Galveston, TX 77551. 3/l/17719
mon. ‘. ‘I. 14.” Even though Colles’8 believed that most malunions would eventually return to a painless state with full range of motion, most authors agree that malunion leads to pain and/or disability.* Overgaard and Solgaard*’ studied 56 patients with displaced Colles’ fractures 7 years after injury and found radiographic changes of osteoarthritis in 25 of the 56 cases. Femandez”. ” and Jupiter and Masem’ found that radial shortening beyond 6 mm leads to ulnocarpal impingement, pain in the distal radioulnar joint, and decreased pronation and supination. Ambrose and Posner,13 and Taleisnik and WatsonI concluded that alteration of normal palmar inclination is the most serious problem in distal radius fractures because of its adverse effects on wrist mechanics. Jenkins and Mintowt-Czyz” and Palmer and Weme?’ showed that alterations in the normal radial inclination can influence grip strength and scaphoid-lunate load distribution, respectively. Methods used to correct malunions include closing wedge osteotomy with distal ulna resection, and open wedge osteotomy and bone grafting with or without distal ulna resection, 1. 10, 13, L4, 16. 17 Pain and degenerative changes are hypothesized to be caused by abnormal pressures in the joint resulting from fracture malunions. We investigated the effects various components of distal radius fracture malunion *l, 2, 5, 8, 9, 12-16, 19
THE JOURNAL
OF HAND SURGERY
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722
The Journal of HAND SURGERY
Pogue et al.
RADIAL INCLINATION
m ULNAR VARIANCE
o-2mm
PALYAR
19 - 30”
%
INCLINATION
Palmrr
Fig. 1. Methods of measurement of ulnar variance, radial inclination, and palmar inclination, and the range of values for the five arms tested. have on pressure distributions
and contact areas in the
wrist joint. Materials and methods Five unembalmed
cadaver
arms were studied.
The
ages ranged from 21 to 73 years, and radiographs revealed that the ulnar variance ranged from 0 to + 2.0 mm, palmar inclination ranged from 4 degrees to 8 degrees, and radial inclination ranged from 19 degrees to 30 degrees (Fig. 1). Every specimen was free of radiographic deformities and degenerative changes. Each was dissected to remove the soft tissue, leaving the joint capsule, palmar and dorsal radiocarpal, ulnocarpal and interosseous ligaments, the triangular fibrocartilage complex, and the radioulnar interosseous membrane intact. Each specimen was fixed to a loading jig by two transverse rods through the humerus. The humerus was held horizontal and the elbow was flexed 90 degrees. The jig allowed the wrist to be postured in any position within its range of motion. Twelve positions were studied. The forearm was held in neutral pronation and supination, and the wrist was positioned in combinations of 20 degrees of radial deviation, neutral or 10 degrees of ulnar deviation, and in 20 degrees of flexion, neutral, 20 degrees or 40 degrees of extension. A load of 143 Newtons (32 pounds) was applied through threaded pins in the second and third metacarpals.22 Malunited distal radius fractures were simulated by the following processes: resecting 1.47 cm of the radius
starting approximately 3 cm proximal to the distal radial articular surface; using an external fixation device to join the distal fragment to the proximal portion of the radius; and placing customized aluminum blocks in the osteotomy to obtain and maintain the desired grade of angulation or shortening at the distal joint level. The blocks also increased the stability of the system for loading, while the fixation device firmly held the deformity position (Fig. 2, A and B). To measure the pressures in the wrist joint, a transducer made of Fuji Superlow Prescale pressuresensitive film (C. Itoh, New York, N.Y.) was inserted into the joint through a small incision in the dorsal capsule. Spatial orientation of each contact area was determined by a “U” marker fixed to the dorsal aspect of the distal radius and included on each print. The contact pressure prints were videodigitized with use of a Hitachi VK-C2000 video camera (Hitachi Corp., Tokyo, Japan), and a Digisector DS-88 video digitizing board (Microwave, Del Mar, Calif.) in an IBM AT clone. The digitized images were analyzed with a Better Basic program, which calculated the areas of low, medium, and high pressure, the total contact areas, and the centroid of the high pressure area. These calculations were done on both the scaphoid and lunate fossa regions. Each arm was loaded in 12 positions for the normal wrist and each stage of the different malunion components. Radial shortening was studied in five increments: 0 mm (normal), 2 mm, 4 mm, 6 mm, and
Vol. 15A, No. 5 September 1990
Effects of distal radius fracture malunion on wrist joint mechanics
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A Fig. 2. A, 1Posteroanterior PA and B, late1al Iriews of the fixation device attached to a speciw :n. Note the interpositional wedged block (arrow).
8 mm of shortening. Loss of radial inclination was studied in three positions: normal, radial inclination set at 10 degrees, and radial inclination set at 0 degrees. Changes in palmar inclination were studied in five positions: 30 degrees palmar inclination, normal, 0 degrees, 15 degrees dorsal, and 30 degrees dorsal inclination. Some of the simulated malunion increments (radial shortening beyond 4 mm, 0 degrees radial inclination, 30 degrees palmar, and 15 degrees and 30 degrees dorsal inclination) could not be obtained in any of the specimens while the ulna styloid and ligamentous structures remained intact. The ulna styloid was fractured at its base so these increments could be obtained and tested. The normal state was tested before and after the ulna styloid fracture to determine the effects of ulna styloid fractures on wrist joint pressure patterns. Radial shortening 2 and 4 mm, 10 degrees radial inclination, and 0 degrees palmar inclination were tested with and without the ulna styloid fracture to explore the effects of the ulna styloid fracture on these malunion conditions. Radial shortening beyond 4 mm, 0 degrees radial inclination, 30 degrees palmar, and 15 degrees and 30 degrees dorsal inclination were not obtainable before the ulna styloid fracture was formed; therefore, no com-
parisons could be made between the presence and absence of an ulna styloid fracture for these conditions. Statistical analyses were done on the data by use of PC-SAS (SAS Institute, Cary, N.C.). Initially, univariant statistics were done on each condition and positioned to determine the frequency distributions and the suitability of using analysis of variance (ANOVA). A two-way ANOVA using the GLM (General Linear Model) in PC-SAS was used to test for differences in total contact areas, high pressure areas, scaphoid/lunate area ratios, and centroid coordinates. Contrast analyses were done to test specific hypotheses concerning conditions and positions. Unless explicitly stated otherwise, ap value of less than 0.01 was considered to be statistically significant. Results Radial shortening Scaphoid and lunate contact areas. Joint size variability was accommodated by dividing the contact areas within each joint by the total available area of that joint. Individual scaphoid and lunate contact areas are reported as a percentage of the total available joint surface. None of the increments of shortening showed a significant change from the normal in the scaphoid con-
724
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The Journal of HAND SURGERY
Fig. 3. Pressure print transducers from a right arm. The prints are seen as if looking at the articular surface of the radius from above, with the palmar direction being up and dorsal being down. radial direction to the left and ulnar to the right. The angled U-shaped curve is from the metal external reference marker. The transducers show an example in one wrist of (a) normal radial inclination (19 degrees), (b) radial inclination reduced to 10 degrees, and (c) radial inclination reduced to 0 degrees. Scaphoid contact area is on the left side and lunate is on the right. Note the increased lunate contact area in the RI 10 and RI 0 prints
tact area. While all increments of radial shortening had slightly higher lunate contact areas, 2 mm of radial shortening was the only one that displayed a significant change from the normal (radial shortening [RS] 2 mm = 15.6%, normal = 12.9%). Shortening of 6 to 8 mm was noted to cause the ulna to impinge on the triquetrum and/or the extreme ulnar aspect of the lunate outside the joint area. Scaphoid / lunate area ratio. The scaphoid/ lunate area ratio is the ratio of the scaphoid contact area divided by the lunate contact area. It is a reflection of the load distribution between the scaphoid and lunate fossae. In the five wrists studied, the normal scaphaid/ lunate ratio was 1.13. That is, the scaphoid contact area was 1.13 times larger than the lunate contact area. None of the increments of radial shortening tested had a scaphoid / lunate area ratio statistically different from the normal state. High pressure area centroids. The centroid is a point that represents the mathematical center of the contact area of the high pressure zone but does not define or reflect the shape of the contact area. For all radial shortening increments tested, the centroids of the scaphoid and lunate high pressure areas were not significantly different from the normal state.
Radial inclination Scaphoid and lunate contact areas. Loss of radial inclination to 0 degrees showed significantly less (p < 0.02) contact area in the scaphoid fossa than that seen in the normal wrist (RI 0 = 11.7%) normal = 14.3%). Both radial inclination of 10 degrees and 0 degrees showed more contact area in the lunate
fossa when compared with the normal state (RI 10 = 17.7%, RI 0 = 16.7%. normal = 12.9%). Scaphoid/lunate area ratio. Loss of normal radial inclination to 10 degrees and 0 degrees resulted in lower scaphoid/lunate area ratios than the normal (normal = 1.13, RI 10 = 0.84, RI 0 = 0.73). Therefore, the load distribution between the scaphoid and the lunate fossae changed so that the load transmitted through the scaphoid fossa decreased and/or the load transmitted through the lunate fossa increased as radial inclination decreased (Fig. 3). High pressure area centroids. The scaphoid high pressure area centroids did not move significantly in either of the radial inclination increments when compared to the normal state. Radial inclination of 10 degrees showed a slight dorsal shift in the lunate high pressure area centroid when compared with the normal state.
Palmar inclination Scaphoid and lunate contact areas. None of the increments of palmar inclination studied had significantly different scaphoid or lunate total contact areas. Palmar inclination 30 degrees had a significantly higher scaphoid high pressure area than the normal state, (palmar 30 = 7.9%, normal = 6.0%) and 30 degrees palmar and 30 degrees dorsal inclination both had more lunate high pressure area than the normal state (30 palmar = 6.6%, 30 dorsal = 5.7%, normal = 4.2%). Since the total contact area did not change, but more area was under high pressure, these positions displayed a more concentrated load in the scaphoid and/or lunate fossa.
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Scaphoid/lunate area ratio. None of the increments studied varied significantly from the normal scaphoid/lunate area ratio. Thus the load distribution between the scaphoid and lunate fossae did not change from the normal state. High pressure area centroids. When compared with the normal state, 30 degrees palmar and 30 degrees dorsal inclination both displayed a significant dorsal shift of the lunate high pressure area centroid. As dorsal inclination increased, the scaphoid high pressure area centroids moved more dorsal than in the normal state, but the differences were not statistically significant (Fig. 4). Ulna styloid fracture When the normal wrist without an ulna styloid fracture (fx) was compared with the normal wrist with an ulna styloid fracture, the normal wrist with the ulna styloid fracture displayed an increased scaphoid/ lunate area ratio (w/o fx = 1.13, w/ fx = 1.46), but no other significant differences. Radial shortening 2 and 4 mm, radial inclination 10 degrees, and palmar inclination 0 degrees are the deformities that were obtainable with the ulna styloid intact. To determine the effe,cts of the ulna styloid fracture on these deformity positions, they were tested again after the ulna styloid fracture was formed. Both of the radial shortening increments and radial inclination 10 degrees showed no significant differences between the conditions before and after the ulna styloid fracture. Palmar inclination 0 degrees tested with the ulna styloid fracture had a lower lunate total contact area and a higher scaphoid/lunate area ratio than without the ulna styloid fracture (lunate area: w/ fx = 11.3%, w/o fx = 14.0%; S/L ratio: w/ fx = 1.57, w/o fx = 1.17). The presence of the ulna styloid fracture also caused a dorsal shift in the lunate high pressure area centroid in this simulated malunion position. Radial shortening beyond 4 mm, radial inclination 0 degrees, palmar inclination 30 degrees, and dorsal inclination 15 degrees and 30 degrees were not obtainable unless an ulna styloid fracture was present. Since these positions could only be tested with an ulna styloid fracture, the deformity positions with an ulna styloid fracture could not be compared with the same positions without an ulna styloid fracture.
Discussion Distal radius fractures are the subject of much discussion. ‘-*O,22 They are relatively common fractures and have been reported to have a high complication rate. ‘3‘. 13-16In a study of 2122 cases, Bacom and Kurtzke2 discovered that more than 97% of Colles’ frac-
Fig. 4. Pressure print transducers from a right arm, (I) normal (6 degrees palmar), and (II) dorsal inclination 30 degrees. Scaphoid is on the left side (arrow) and lunate is on the right (double arrow). (III) diagram showing scaphoid and lunate high pressure areas of normal (-_) superimposed with dorsal inclination 30 degrees (. . . . ). (IV) diagram showing dorsal shift in scaphoid and lunate high pressure area centroids as dorsal inclination increases; (a) normal (6 degrees palmar), (b) palmar inclination reduced to 0 degrees, (c) 15 degrees dorsal inclination, and (d) 30 degrees dorsal inclination.
tures resulted in some permanent disability. The most common disability was a loss of flexion, which was found in 95% of the cases. Eighty percent of the cases showed a loss of extension, and one third had a diminution of grip strength. They found a positive correlation between disability and deformity but did not mention what type or degree of deformities lead to serious disabilities. Other authors have addressed the effects of specific malunion parameters. Solgaard’ stated that functional results decrease as the amount of dorsal angulation and radial shortening increase. Femandez17 wrote that deformities with dorsal angulation greater than 25 degrees or more than 6 mm of radial shortening usually become symptomatic. This study found that dorsal angulation of 30 degrees causes more concentrated loads in the scaphoid and lunate fossae, and these contact areas are located more dorsally than those in the normal wrist. Although it can not be stated with certitude, changes in the wrist joint pressure distributions such as these may be factors that cause or add to symptoms in a clinical setting such as Femandez described. He also found that 6 mm or more of radial shortening causes a
726
Pogue
et al.
decrease in pronation and supination range of motion. Jenkins and Mintowt-Czyz” concluded that radial shortening does not affect function, but it only affects levels of pain. Conversely, Villar et a1.9found that grip strength is affected only by residual radial shortening, and residual dorsal angulation reduces the range of motion. Some authors believe that radial shortening is the primary cause of poor end results. Pemandez” reported that ulnocarpal impingement was present in patients with radial shortening beyond 6 mm. In this work, with 6 to 8 mm of radial shortening, the ulna contacted the triquetrum and the extreme ulnar aspect of the lunate outside the joint. Palmer and Weme? found that changes in ulnar variance (either ulnar lengthening or shortening) up to 2.5 mm lead to changes in the loads within the wrist. This study also found that 2 mm of radial shortening causes a significant increase in the lunate contact area. Older and associates’ and Lindstrom” stated that the restoration of radial length is the most important factor influencing favorable end results, but they did not specify if radial shortening affects the radiocarpal joint or the radioulnar joint. This study was unable to show any significant changes in radiocarpal joint pressure patterns with shortening beyond 2 mm. Radioulnar joint forces, however, were not measured. Jupiter and Masem’ found residual shortening beyond 6 mm leads to pain in the distal radioulnar joint, and called radial shortening the most common and disabling source of problems in the malunited distal radius fracture. Shortening of 6 to 8 mm in this study was noted to cause the ulna to impinge on the triquetrum and/or the extreme ulnar aspect of the lunate outside the joint area. Although these reports suggest that radial shortening is an important factor influencing end results, other authors believe that dorsal angulation is the primary cause of disabilities related to wrist mechanics.” Taleisnik and WatsonI reported that changes in palmar inclination disturb the radiocarpal function and cause midcarpal instabilities. They found that even small changes in palmar inclination can lead to midcarpal instabilities. Older and colleagues3 stated that dorsal angulation is a problem only when it is excessive, but did not define excessive. This study showed that changes in palmar or dorsal inclination greater than 20 degrees cause significant changes in the load distributions in the wrist joint. Short et al.6 explained that as dorsal angulation increases, pressures on the radial and ulnar articular surfaces become more concentrated, and
The Journal of HAND SURGERY
the contact areas move dorsally. This study also found this to be the case and corroborates their view. Rubinovich and Rennie” have said that remaining dorsal angulation is the only factor affecting the final results of a distal radius fracture. Our work found that large changes in palmar inclination do cause noteworthy alterations in wrist joint mechanics, but changes in radial inclination also cause significant variations in the load distributions in the wrist joint. Few reports have discussed load distributions in the radiocarpal joint in relation to radial inclination. In a study that recognizes a relationship between final radiographic parameters and poor end results, Jenkins and Mintowt-Czyz’g showed that flattening of the radial angle had a significant (p < 0.01) correlation with decreased grip strength. We found that even small changes in radial inclination caused dramatic changes in load distribution between the scaphoid and lunate, but the relationship between grip strength and load distributions in the radiocarpal joint has not been addressed. By studying simulated surgical procedures used for the treatment of Kienbijck’s disease, Palmar and WemeI2” showed that by increasing the radial inclination through either a lateral opening wedge or medial closing wedge osteotomy, the load in the lunate fossa is decreased. From this, one might extrapolate that decreased radial inclination would lead to increased load in the lunate fossa: this is what the results of this work have shown. Few articles have addressed the relationship between ulna styloid fractures and wrist joint mechanics. Distal radius fractures are accompanied by ulna styloid fractures more than 50% of the time.‘. ” Steward and associates” and Lindstrom” claimed that the presence of an ulna styloid fracture does not affect the functional end results. This study found that the presence of an ulna styloid fracture increases the scaphoid/ lunate area ratio only, and does not change the positions of the scaphoid and lunate high pressure areas or the scaphoid and lunate total contact areas. This may support the fact that ulna styloid fractures by themselves, frequently are clinically asymptomatic. Jupiter and Masem’ pointed out that an ulna styloid fracture may reflect a disruption of the triangular fibrocartilage complex (TFCC) and an instability in the distal radioulnar joint. Our inability to obtain displacements of the distal radius involving shortening greater than 4 mm, or angulations greater than approximately 20 degrees with the ulna styloid and TFCC intact may suggest that severely displaced fractures not displaying an ulna styloid fracture might have a TFCC disruption.
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Effects of distal radius fracture
REFERENCES 1. Jupiter JB , Masem M. Reconstruction of post-traumatic deformity of the distal radius and ulna. Hand Clinics 1988;4:377-90. 2. Bacom RW, Kurtzke JF. Colles’ fracture. A study of two thousand cases from the New York State Workman’s Compensation Board. J Bone Joint Surg 1953;35:64358. 3. Older TM, Stabler EV, Cassebaum WI-I. Colles’ fracture: evaluation and selection of therapy. J Trauma 1965; 51469-76. 4. Gartland JJ Jr, Werley CW. Evaluation of healed Colles’ fractures. J Bone Joint Surg 1951;33:895-907. 5. McQueen M, Caspers J. Colles’ fracture: does the anatomical result affect the final function? J Bone Joint Surg 1988;70:649-5 1. 6. Short WH, Palmer AK, Werner FW, Murphy DJ. A biomechanical study of distal radius fractures. J HANDSURG 1987;12:529-34. 7. Solgaard S. Classification of distal radius fractures. Acta Grthop Scat-id 1984;56:249-52. 8. Solgaard S. Function after distal radius fracture. Acta Grthop Scand 1988;59:39-42. 9. Villar RN, Marsh D, Rushton N, Greatorex RA. Three years after Colles’ fracture. J Bone Joint Surg 1987; 69635-8. 10. Femandez DL. Radial osteotomy and Bowers arthroplasty for malunited fractures of the distal end of the radius. J Bone Joint Surg 1988;70: 1538-5 1. 11. Lindstrom A. Fractures of the distal end of the radius. Acta Orthop Stand 1959;41(suppl):l-118 12. Stewart HD, Innes AR, Burke FD. Factors affecting the outcome of Colles’ fracture: an anatomical and functional study. Injury 1985;16:289-95.
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13. Ambrose L, Posner MA. Biplanar osteotomy for the treatment of malunited Colles’ fractures. Presented at The 43rd Annual Meeting of the American Society for Surgery of the Hand. Baltimore, Maryland: Sept. 14-17, 1988. 14. Cooney WP, Dobyns JH, Linscheid RL. Complications of Colles’ fracture. J Bone Joint Surg 1980;62:613-19. 15. Rubinovich RM, Rennie WR. Colles’ fracture: end results in relation to radiologic parameters. Can J Surg 1983;26:361-3. 16. Taleisnik J, Watson HK. Midcarpal instability caused by malunited fractures of the distal radius. J HAND SURG 1984;9A:350-7. 17. Femandez DL. Correction of post-traumatic wrist deformity in adults by osteotomy, bone-grafting, and internal fixation. J Bone Joint Surg 1982;64:1164-78. 18. Colles A. On the fractures of the carpal extremity of the radius. Edinb. Med Surg J 1814;10:182-6. 19. Jenkins NH, Mintowt-Czyz WJ. Mal-union and dysfunction in Colles’ fracture. J HAND SURG 1988;13B: 291-3. 20. Overgaard S, Solgaard S. Osteoarthritis after Colles’ fracture. Orthopedics 1989;12:413-16. 21. Palmer AK, Werner FW. Biomechanics of the distal radioulnar joint. Clin Orthop 1984;187:26-35. 22. Viegas SF, Tencer AF, Cantrell J, et al. Load transfer characteristics of the wrist. Part I: the normal joint. J HANDSURG 1987;12A:971-8. 23. Palmer AK, Werner FW. A biomechanical evaluation of operative procedures performed for the treatment of Kienbiick’s disease. Presented at The 43rd Annual Meeting of the American Society for Surgery of the Hand. Baltimore, Maryland: Sept. 14-17, 1988.
Bound volumes available to subscribers Bound volumes of the JOURNALOF HANDSURGERYare available to subscribers (only) for the 1990 issues from the Publisher, at a cost of $35.00 ($43.00 international) for Vol. 15A (January-December). Shipping charges are included. Each bound volume contains a subject and author index and all advertising is removed. Copies are shipped within 60 days after publication of the last issue of the volume. The binding is durable buckram with the journal name, volume number, and year stamped in gold on the spine. Payment must accompany all orders. Contact Mosby-Year Book, Inc., Circulation Department, 11830 Westline Industrial Drive, St. Louis, Missouri 63146-3318, USA; phone (800)325-4177, ext. 7351. Subscriptions must be in force to qualify. Bound volumes are not available in place of a regular journal subscription.
model using a static positioning frame, pressure-sensitive
microcomputer-based
videodigitizing
film (Fuji), and a system was used to measure contact areas and pressures
in the wrist. Contact areas and pressures were compared in a group of wrists between the normal state and with simulated distal radius fracture mahmions of varying degrees. In simulated malunions, radial shortening to any degree slightly increased the total contact area in the lunate fossa, and was significant at 2 mm of shortening. By angulating the distal radius more than 20 degrees either palmar or dorsal, there was a dorsal shift in the scaphoid and lunate high pressure areas, and the loads were more concentrated, but there was no change in the load distribution between the scaphoid and lunate. Decreasing the radial inclination shifted the load distribution so that there was more load in the lunate fossa and less load in the scaphoid fossa. (J HAND SURG 1990;15A:721-7.)
David J. Pogue, BS, Steven F. Viegas, MD, Rita M. Patterson, MEng, Pamela D. Peterson, David K. Jenkins, BS, Timothy D. Sweo, BS, and James A, Hokanson, PhD, Galveston, Texas
F ractures of the distal radius make up 8% to 15% of all bone injuries.’ The mechanism of injury in a distal radius fracture is almost always a fall on an outstretched hand, typically causing dorsal and radial displacement of the distal end of the radius.** 3 The fractures are usually treated with closed reduction and plaster splint or cast immobilization, or internal or external fixation.3-9 Distal radius fractures can include comminution of the distal fragment, articular surface involvement, and can be accompanied by ulna styloid avulsion fractures.*, 3. ‘-I* Complication rates in distal radius fractures are high, ‘2 *, 13-16with malunion among the most com-
From the Division of Orthopedic Surgery, and the Division of Biostatistics, University of Texas Medical Branch, Galveston, Texas. Study supported in part by a grant from the Orthopaedic Research and Education Foundation No. 87-459, and by a grant from the National Institute of Arthritis and Musculoskeletal and Skin Diseases No. 5 R29 AR 38640-02. Received for publication Oct. 14. 1989.
May 25, 1989; accepted
in revised form
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. Reprint requests: Steven F. Viegas, MD, Division of Orthopaedic Surgery, McCullough Bldg., Rm 6.136 (G-92), University of Texas Medical Branch, Galveston, TX 77551. 3/l/17719
mon. ‘. ‘I. 14.” Even though Colles’8 believed that most malunions would eventually return to a painless state with full range of motion, most authors agree that malunion leads to pain and/or disability.* Overgaard and Solgaard*’ studied 56 patients with displaced Colles’ fractures 7 years after injury and found radiographic changes of osteoarthritis in 25 of the 56 cases. Femandez”. ” and Jupiter and Masem’ found that radial shortening beyond 6 mm leads to ulnocarpal impingement, pain in the distal radioulnar joint, and decreased pronation and supination. Ambrose and Posner,13 and Taleisnik and WatsonI concluded that alteration of normal palmar inclination is the most serious problem in distal radius fractures because of its adverse effects on wrist mechanics. Jenkins and Mintowt-Czyz” and Palmer and Weme?’ showed that alterations in the normal radial inclination can influence grip strength and scaphoid-lunate load distribution, respectively. Methods used to correct malunions include closing wedge osteotomy with distal ulna resection, and open wedge osteotomy and bone grafting with or without distal ulna resection, 1. 10, 13, L4, 16. 17 Pain and degenerative changes are hypothesized to be caused by abnormal pressures in the joint resulting from fracture malunions. We investigated the effects various components of distal radius fracture malunion *l, 2, 5, 8, 9, 12-16, 19
THE JOURNAL
OF HAND SURGERY
721
722
The Journal of HAND SURGERY
Pogue et al.
RADIAL INCLINATION
m ULNAR VARIANCE
o-2mm
PALYAR
19 - 30”
%
INCLINATION
Palmrr
Fig. 1. Methods of measurement of ulnar variance, radial inclination, and palmar inclination, and the range of values for the five arms tested. have on pressure distributions
and contact areas in the
wrist joint. Materials and methods Five unembalmed
cadaver
arms were studied.
The
ages ranged from 21 to 73 years, and radiographs revealed that the ulnar variance ranged from 0 to + 2.0 mm, palmar inclination ranged from 4 degrees to 8 degrees, and radial inclination ranged from 19 degrees to 30 degrees (Fig. 1). Every specimen was free of radiographic deformities and degenerative changes. Each was dissected to remove the soft tissue, leaving the joint capsule, palmar and dorsal radiocarpal, ulnocarpal and interosseous ligaments, the triangular fibrocartilage complex, and the radioulnar interosseous membrane intact. Each specimen was fixed to a loading jig by two transverse rods through the humerus. The humerus was held horizontal and the elbow was flexed 90 degrees. The jig allowed the wrist to be postured in any position within its range of motion. Twelve positions were studied. The forearm was held in neutral pronation and supination, and the wrist was positioned in combinations of 20 degrees of radial deviation, neutral or 10 degrees of ulnar deviation, and in 20 degrees of flexion, neutral, 20 degrees or 40 degrees of extension. A load of 143 Newtons (32 pounds) was applied through threaded pins in the second and third metacarpals.22 Malunited distal radius fractures were simulated by the following processes: resecting 1.47 cm of the radius
starting approximately 3 cm proximal to the distal radial articular surface; using an external fixation device to join the distal fragment to the proximal portion of the radius; and placing customized aluminum blocks in the osteotomy to obtain and maintain the desired grade of angulation or shortening at the distal joint level. The blocks also increased the stability of the system for loading, while the fixation device firmly held the deformity position (Fig. 2, A and B). To measure the pressures in the wrist joint, a transducer made of Fuji Superlow Prescale pressuresensitive film (C. Itoh, New York, N.Y.) was inserted into the joint through a small incision in the dorsal capsule. Spatial orientation of each contact area was determined by a “U” marker fixed to the dorsal aspect of the distal radius and included on each print. The contact pressure prints were videodigitized with use of a Hitachi VK-C2000 video camera (Hitachi Corp., Tokyo, Japan), and a Digisector DS-88 video digitizing board (Microwave, Del Mar, Calif.) in an IBM AT clone. The digitized images were analyzed with a Better Basic program, which calculated the areas of low, medium, and high pressure, the total contact areas, and the centroid of the high pressure area. These calculations were done on both the scaphoid and lunate fossa regions. Each arm was loaded in 12 positions for the normal wrist and each stage of the different malunion components. Radial shortening was studied in five increments: 0 mm (normal), 2 mm, 4 mm, 6 mm, and
Vol. 15A, No. 5 September 1990
Effects of distal radius fracture malunion on wrist joint mechanics
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A Fig. 2. A, 1Posteroanterior PA and B, late1al Iriews of the fixation device attached to a speciw :n. Note the interpositional wedged block (arrow).
8 mm of shortening. Loss of radial inclination was studied in three positions: normal, radial inclination set at 10 degrees, and radial inclination set at 0 degrees. Changes in palmar inclination were studied in five positions: 30 degrees palmar inclination, normal, 0 degrees, 15 degrees dorsal, and 30 degrees dorsal inclination. Some of the simulated malunion increments (radial shortening beyond 4 mm, 0 degrees radial inclination, 30 degrees palmar, and 15 degrees and 30 degrees dorsal inclination) could not be obtained in any of the specimens while the ulna styloid and ligamentous structures remained intact. The ulna styloid was fractured at its base so these increments could be obtained and tested. The normal state was tested before and after the ulna styloid fracture to determine the effects of ulna styloid fractures on wrist joint pressure patterns. Radial shortening 2 and 4 mm, 10 degrees radial inclination, and 0 degrees palmar inclination were tested with and without the ulna styloid fracture to explore the effects of the ulna styloid fracture on these malunion conditions. Radial shortening beyond 4 mm, 0 degrees radial inclination, 30 degrees palmar, and 15 degrees and 30 degrees dorsal inclination were not obtainable before the ulna styloid fracture was formed; therefore, no com-
parisons could be made between the presence and absence of an ulna styloid fracture for these conditions. Statistical analyses were done on the data by use of PC-SAS (SAS Institute, Cary, N.C.). Initially, univariant statistics were done on each condition and positioned to determine the frequency distributions and the suitability of using analysis of variance (ANOVA). A two-way ANOVA using the GLM (General Linear Model) in PC-SAS was used to test for differences in total contact areas, high pressure areas, scaphoid/lunate area ratios, and centroid coordinates. Contrast analyses were done to test specific hypotheses concerning conditions and positions. Unless explicitly stated otherwise, ap value of less than 0.01 was considered to be statistically significant. Results Radial shortening Scaphoid and lunate contact areas. Joint size variability was accommodated by dividing the contact areas within each joint by the total available area of that joint. Individual scaphoid and lunate contact areas are reported as a percentage of the total available joint surface. None of the increments of shortening showed a significant change from the normal in the scaphoid con-
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Fig. 3. Pressure print transducers from a right arm. The prints are seen as if looking at the articular surface of the radius from above, with the palmar direction being up and dorsal being down. radial direction to the left and ulnar to the right. The angled U-shaped curve is from the metal external reference marker. The transducers show an example in one wrist of (a) normal radial inclination (19 degrees), (b) radial inclination reduced to 10 degrees, and (c) radial inclination reduced to 0 degrees. Scaphoid contact area is on the left side and lunate is on the right. Note the increased lunate contact area in the RI 10 and RI 0 prints
tact area. While all increments of radial shortening had slightly higher lunate contact areas, 2 mm of radial shortening was the only one that displayed a significant change from the normal (radial shortening [RS] 2 mm = 15.6%, normal = 12.9%). Shortening of 6 to 8 mm was noted to cause the ulna to impinge on the triquetrum and/or the extreme ulnar aspect of the lunate outside the joint area. Scaphoid / lunate area ratio. The scaphoid/ lunate area ratio is the ratio of the scaphoid contact area divided by the lunate contact area. It is a reflection of the load distribution between the scaphoid and lunate fossae. In the five wrists studied, the normal scaphaid/ lunate ratio was 1.13. That is, the scaphoid contact area was 1.13 times larger than the lunate contact area. None of the increments of radial shortening tested had a scaphoid / lunate area ratio statistically different from the normal state. High pressure area centroids. The centroid is a point that represents the mathematical center of the contact area of the high pressure zone but does not define or reflect the shape of the contact area. For all radial shortening increments tested, the centroids of the scaphoid and lunate high pressure areas were not significantly different from the normal state.
Radial inclination Scaphoid and lunate contact areas. Loss of radial inclination to 0 degrees showed significantly less (p < 0.02) contact area in the scaphoid fossa than that seen in the normal wrist (RI 0 = 11.7%) normal = 14.3%). Both radial inclination of 10 degrees and 0 degrees showed more contact area in the lunate
fossa when compared with the normal state (RI 10 = 17.7%, RI 0 = 16.7%. normal = 12.9%). Scaphoid/lunate area ratio. Loss of normal radial inclination to 10 degrees and 0 degrees resulted in lower scaphoid/lunate area ratios than the normal (normal = 1.13, RI 10 = 0.84, RI 0 = 0.73). Therefore, the load distribution between the scaphoid and the lunate fossae changed so that the load transmitted through the scaphoid fossa decreased and/or the load transmitted through the lunate fossa increased as radial inclination decreased (Fig. 3). High pressure area centroids. The scaphoid high pressure area centroids did not move significantly in either of the radial inclination increments when compared to the normal state. Radial inclination of 10 degrees showed a slight dorsal shift in the lunate high pressure area centroid when compared with the normal state.
Palmar inclination Scaphoid and lunate contact areas. None of the increments of palmar inclination studied had significantly different scaphoid or lunate total contact areas. Palmar inclination 30 degrees had a significantly higher scaphoid high pressure area than the normal state, (palmar 30 = 7.9%, normal = 6.0%) and 30 degrees palmar and 30 degrees dorsal inclination both had more lunate high pressure area than the normal state (30 palmar = 6.6%, 30 dorsal = 5.7%, normal = 4.2%). Since the total contact area did not change, but more area was under high pressure, these positions displayed a more concentrated load in the scaphoid and/or lunate fossa.
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Scaphoid/lunate area ratio. None of the increments studied varied significantly from the normal scaphoid/lunate area ratio. Thus the load distribution between the scaphoid and lunate fossae did not change from the normal state. High pressure area centroids. When compared with the normal state, 30 degrees palmar and 30 degrees dorsal inclination both displayed a significant dorsal shift of the lunate high pressure area centroid. As dorsal inclination increased, the scaphoid high pressure area centroids moved more dorsal than in the normal state, but the differences were not statistically significant (Fig. 4). Ulna styloid fracture When the normal wrist without an ulna styloid fracture (fx) was compared with the normal wrist with an ulna styloid fracture, the normal wrist with the ulna styloid fracture displayed an increased scaphoid/ lunate area ratio (w/o fx = 1.13, w/ fx = 1.46), but no other significant differences. Radial shortening 2 and 4 mm, radial inclination 10 degrees, and palmar inclination 0 degrees are the deformities that were obtainable with the ulna styloid intact. To determine the effe,cts of the ulna styloid fracture on these deformity positions, they were tested again after the ulna styloid fracture was formed. Both of the radial shortening increments and radial inclination 10 degrees showed no significant differences between the conditions before and after the ulna styloid fracture. Palmar inclination 0 degrees tested with the ulna styloid fracture had a lower lunate total contact area and a higher scaphoid/lunate area ratio than without the ulna styloid fracture (lunate area: w/ fx = 11.3%, w/o fx = 14.0%; S/L ratio: w/ fx = 1.57, w/o fx = 1.17). The presence of the ulna styloid fracture also caused a dorsal shift in the lunate high pressure area centroid in this simulated malunion position. Radial shortening beyond 4 mm, radial inclination 0 degrees, palmar inclination 30 degrees, and dorsal inclination 15 degrees and 30 degrees were not obtainable unless an ulna styloid fracture was present. Since these positions could only be tested with an ulna styloid fracture, the deformity positions with an ulna styloid fracture could not be compared with the same positions without an ulna styloid fracture.
Discussion Distal radius fractures are the subject of much discussion. ‘-*O,22 They are relatively common fractures and have been reported to have a high complication rate. ‘3‘. 13-16In a study of 2122 cases, Bacom and Kurtzke2 discovered that more than 97% of Colles’ frac-
Fig. 4. Pressure print transducers from a right arm, (I) normal (6 degrees palmar), and (II) dorsal inclination 30 degrees. Scaphoid is on the left side (arrow) and lunate is on the right (double arrow). (III) diagram showing scaphoid and lunate high pressure areas of normal (-_) superimposed with dorsal inclination 30 degrees (. . . . ). (IV) diagram showing dorsal shift in scaphoid and lunate high pressure area centroids as dorsal inclination increases; (a) normal (6 degrees palmar), (b) palmar inclination reduced to 0 degrees, (c) 15 degrees dorsal inclination, and (d) 30 degrees dorsal inclination.
tures resulted in some permanent disability. The most common disability was a loss of flexion, which was found in 95% of the cases. Eighty percent of the cases showed a loss of extension, and one third had a diminution of grip strength. They found a positive correlation between disability and deformity but did not mention what type or degree of deformities lead to serious disabilities. Other authors have addressed the effects of specific malunion parameters. Solgaard’ stated that functional results decrease as the amount of dorsal angulation and radial shortening increase. Femandez17 wrote that deformities with dorsal angulation greater than 25 degrees or more than 6 mm of radial shortening usually become symptomatic. This study found that dorsal angulation of 30 degrees causes more concentrated loads in the scaphoid and lunate fossae, and these contact areas are located more dorsally than those in the normal wrist. Although it can not be stated with certitude, changes in the wrist joint pressure distributions such as these may be factors that cause or add to symptoms in a clinical setting such as Femandez described. He also found that 6 mm or more of radial shortening causes a
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decrease in pronation and supination range of motion. Jenkins and Mintowt-Czyz” concluded that radial shortening does not affect function, but it only affects levels of pain. Conversely, Villar et a1.9found that grip strength is affected only by residual radial shortening, and residual dorsal angulation reduces the range of motion. Some authors believe that radial shortening is the primary cause of poor end results. Pemandez” reported that ulnocarpal impingement was present in patients with radial shortening beyond 6 mm. In this work, with 6 to 8 mm of radial shortening, the ulna contacted the triquetrum and the extreme ulnar aspect of the lunate outside the joint. Palmer and Weme? found that changes in ulnar variance (either ulnar lengthening or shortening) up to 2.5 mm lead to changes in the loads within the wrist. This study also found that 2 mm of radial shortening causes a significant increase in the lunate contact area. Older and associates’ and Lindstrom” stated that the restoration of radial length is the most important factor influencing favorable end results, but they did not specify if radial shortening affects the radiocarpal joint or the radioulnar joint. This study was unable to show any significant changes in radiocarpal joint pressure patterns with shortening beyond 2 mm. Radioulnar joint forces, however, were not measured. Jupiter and Masem’ found residual shortening beyond 6 mm leads to pain in the distal radioulnar joint, and called radial shortening the most common and disabling source of problems in the malunited distal radius fracture. Shortening of 6 to 8 mm in this study was noted to cause the ulna to impinge on the triquetrum and/or the extreme ulnar aspect of the lunate outside the joint area. Although these reports suggest that radial shortening is an important factor influencing end results, other authors believe that dorsal angulation is the primary cause of disabilities related to wrist mechanics.” Taleisnik and WatsonI reported that changes in palmar inclination disturb the radiocarpal function and cause midcarpal instabilities. They found that even small changes in palmar inclination can lead to midcarpal instabilities. Older and colleagues3 stated that dorsal angulation is a problem only when it is excessive, but did not define excessive. This study showed that changes in palmar or dorsal inclination greater than 20 degrees cause significant changes in the load distributions in the wrist joint. Short et al.6 explained that as dorsal angulation increases, pressures on the radial and ulnar articular surfaces become more concentrated, and
The Journal of HAND SURGERY
the contact areas move dorsally. This study also found this to be the case and corroborates their view. Rubinovich and Rennie” have said that remaining dorsal angulation is the only factor affecting the final results of a distal radius fracture. Our work found that large changes in palmar inclination do cause noteworthy alterations in wrist joint mechanics, but changes in radial inclination also cause significant variations in the load distributions in the wrist joint. Few reports have discussed load distributions in the radiocarpal joint in relation to radial inclination. In a study that recognizes a relationship between final radiographic parameters and poor end results, Jenkins and Mintowt-Czyz’g showed that flattening of the radial angle had a significant (p < 0.01) correlation with decreased grip strength. We found that even small changes in radial inclination caused dramatic changes in load distribution between the scaphoid and lunate, but the relationship between grip strength and load distributions in the radiocarpal joint has not been addressed. By studying simulated surgical procedures used for the treatment of Kienbijck’s disease, Palmar and WemeI2” showed that by increasing the radial inclination through either a lateral opening wedge or medial closing wedge osteotomy, the load in the lunate fossa is decreased. From this, one might extrapolate that decreased radial inclination would lead to increased load in the lunate fossa: this is what the results of this work have shown. Few articles have addressed the relationship between ulna styloid fractures and wrist joint mechanics. Distal radius fractures are accompanied by ulna styloid fractures more than 50% of the time.‘. ” Steward and associates” and Lindstrom” claimed that the presence of an ulna styloid fracture does not affect the functional end results. This study found that the presence of an ulna styloid fracture increases the scaphoid/ lunate area ratio only, and does not change the positions of the scaphoid and lunate high pressure areas or the scaphoid and lunate total contact areas. This may support the fact that ulna styloid fractures by themselves, frequently are clinically asymptomatic. Jupiter and Masem’ pointed out that an ulna styloid fracture may reflect a disruption of the triangular fibrocartilage complex (TFCC) and an instability in the distal radioulnar joint. Our inability to obtain displacements of the distal radius involving shortening greater than 4 mm, or angulations greater than approximately 20 degrees with the ulna styloid and TFCC intact may suggest that severely displaced fractures not displaying an ulna styloid fracture might have a TFCC disruption.
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Effects of distal radius fracture
REFERENCES 1. Jupiter JB , Masem M. Reconstruction of post-traumatic deformity of the distal radius and ulna. Hand Clinics 1988;4:377-90. 2. Bacom RW, Kurtzke JF. Colles’ fracture. A study of two thousand cases from the New York State Workman’s Compensation Board. J Bone Joint Surg 1953;35:64358. 3. Older TM, Stabler EV, Cassebaum WI-I. Colles’ fracture: evaluation and selection of therapy. J Trauma 1965; 51469-76. 4. Gartland JJ Jr, Werley CW. Evaluation of healed Colles’ fractures. J Bone Joint Surg 1951;33:895-907. 5. McQueen M, Caspers J. Colles’ fracture: does the anatomical result affect the final function? J Bone Joint Surg 1988;70:649-5 1. 6. Short WH, Palmer AK, Werner FW, Murphy DJ. A biomechanical study of distal radius fractures. J HANDSURG 1987;12:529-34. 7. Solgaard S. Classification of distal radius fractures. Acta Grthop Scat-id 1984;56:249-52. 8. Solgaard S. Function after distal radius fracture. Acta Grthop Scand 1988;59:39-42. 9. Villar RN, Marsh D, Rushton N, Greatorex RA. Three years after Colles’ fracture. J Bone Joint Surg 1987; 69635-8. 10. Femandez DL. Radial osteotomy and Bowers arthroplasty for malunited fractures of the distal end of the radius. J Bone Joint Surg 1988;70: 1538-5 1. 11. Lindstrom A. Fractures of the distal end of the radius. Acta Orthop Stand 1959;41(suppl):l-118 12. Stewart HD, Innes AR, Burke FD. Factors affecting the outcome of Colles’ fracture: an anatomical and functional study. Injury 1985;16:289-95.
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13. Ambrose L, Posner MA. Biplanar osteotomy for the treatment of malunited Colles’ fractures. Presented at The 43rd Annual Meeting of the American Society for Surgery of the Hand. Baltimore, Maryland: Sept. 14-17, 1988. 14. Cooney WP, Dobyns JH, Linscheid RL. Complications of Colles’ fracture. J Bone Joint Surg 1980;62:613-19. 15. Rubinovich RM, Rennie WR. Colles’ fracture: end results in relation to radiologic parameters. Can J Surg 1983;26:361-3. 16. Taleisnik J, Watson HK. Midcarpal instability caused by malunited fractures of the distal radius. J HAND SURG 1984;9A:350-7. 17. Femandez DL. Correction of post-traumatic wrist deformity in adults by osteotomy, bone-grafting, and internal fixation. J Bone Joint Surg 1982;64:1164-78. 18. Colles A. On the fractures of the carpal extremity of the radius. Edinb. Med Surg J 1814;10:182-6. 19. Jenkins NH, Mintowt-Czyz WJ. Mal-union and dysfunction in Colles’ fracture. J HAND SURG 1988;13B: 291-3. 20. Overgaard S, Solgaard S. Osteoarthritis after Colles’ fracture. Orthopedics 1989;12:413-16. 21. Palmer AK, Werner FW. Biomechanics of the distal radioulnar joint. Clin Orthop 1984;187:26-35. 22. Viegas SF, Tencer AF, Cantrell J, et al. Load transfer characteristics of the wrist. Part I: the normal joint. J HANDSURG 1987;12A:971-8. 23. Palmer AK, Werner FW. A biomechanical evaluation of operative procedures performed for the treatment of Kienbiick’s disease. Presented at The 43rd Annual Meeting of the American Society for Surgery of the Hand. Baltimore, Maryland: Sept. 14-17, 1988.
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