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External fixators for wrist fractures: A biomechanical and clinical study
External fixators for wrist fractures: A biomechanical and clinical study The rigidity of four external fixators for the wrist was determined by using the Instron universal testing instrument. Using the equivalent stiffness index, the small A.O. was 7.6, the mini Hoffman was 3.7, Roger Anderson was 3.5, and Ace Colles' was 4.3. Thus, the small A.O. was about twice as rigid overall as the other three external fixators. Twenty-two patients with unstable distal radius fractures were treated with the mini Hoffman external fixator over a 3-year period; and follow-up data were obtained. The average final angle of the distal radial articular surface on the anteroposterior x-ray film was 17.5°. The final angle of the distal radial articular surface on the lateral x-ray film was 2° dorsal. The final height of the distal radial styloid averaged 8 mm. The final range of motion of the wrist compared with the opposite normal hand was extension 77%, flexion 77%, ulnar deviation 82%, radial deviation 73%, pronation 84%, supination 78%, and grip strength 72 %. Complications included three cases of broken pins, one of a pin loosening with migration, one case of tendon rupture, and one of intrinsic contracture. From our experience, the Hoffman external fixator gave adequate clinical and functional results and can be used safely in the small to average size patient. A more rigid external fixator should be used for larger and more active patients. External fixation is an excellent way to treat unstable distal radial fractures. (J HAND SURG 10A:845-51, 1985.)
Roland Y. Nakata, M.D., Yogesh Chand, M.D., James D. Matiko, M.D., Gary K. Frykman, M.D., and Virchel E. Wood, M.D., Lorna Linda, Calif.
Recently there has been renewed interest in using external fixators for the treatment of comminuted distal radius fractures. 1-5 However, very little data are published to guide the treating surgeon in his choice of one type of external fixator over another. This article compares in vitro the rigidity of four available designs of external fixators and presents our clinical results with one of the external fixators.
Methods and material In the first part of the study, we evaluated the rigidity of four external fixators of the wrist. They were each assembled according to the developers' recommendations. The external fixators studied were: (1) the small A.O. external fixator* (Fig. 1); (2) a combination of From the Hand Surgery Service, Department of Orthopedic Surgery, Lorna Linda University, Lorna Linda, Calif. Received for publication March 5, 1984; accepted in revised form Feb. 14, 1985. Reprint requests: Gary K. Frykman, M.D., Department of Orthopedic Surgery, Lorna Linda University, Lorna Linda, CA 92350. *Synthes Ltd., 983 Old Eagle School Rd., Wayne, PA 19087.
the mini and small Hoffman external fixator* (Fig. 2), hereafter called the Hoffman fixator; (3) the Roger Andersont device (Fig. 3); and (4) the Ace Colles':j: fixator (Fig. 4). All external fixation devices tested were provided by the distributors of the devices. For testing, the half pins were inserted into a 2 cm diameter wooden dowel to mount the various fixators. The distance between the two proximal and two distal pins (10 cm), the angle between the pins in each group (60°), and the distance between the wooden dowel and fixator (2 cm) were kept constant in all the fixators. The distances were chosen to closely approximate placement of the pins for applying fixators to distal radius fractures. After the fixator was mounted, a 1 cm gap was cut out of the center of the dowel between the two pin groups. The frames were then stressed with various jigs in an Instron universal testing instrument in compression, anteroposterior (AP) bending, and lat-
*Howmedica, Inc., 359 Veterans Blvd., Rutherford, NJ 07070. tKirschner Medical, 10 W. Aylesbury Rd., Timonium, MD 21093. tAce Orthopedic Mfg., 14105 S. Avalon Blvd., Los Angeles, CA 90061.
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Fig. 1. The small A.O. external fixator. This device was applied to the bone as recommended by Jakob and Fernandez.' A, Placing two 2.5 mm diameter half pins into the second metacarpal at a 60° angle to each other and two pins in the same manner to the distal radius and connected to each other by 4 mm rods . B, Although the pins are angled to each other in one plane , at 90° to this plane. the pins and connecting rods are parallel to each other.
eral bending. The recorder plotted the stress/strain curves. We were careful to keep the testing in the elastic region of the curve. Clinical study From October 1980 through November 1983 , we used an external fixator on 26 patients with unstable distal radius fractures. An unstable fracture was defined as a fracture with marked comminution including intraarticular fragments and shortening of more than 10 mm, dorsal angulation greater than 20°, or significant loss of reduction after closed reduction and immobilization. In 25 of the patients, we used the Hoffman device configured as tested in the biomechanical study. A typical case in which we used the Hoffman device is shown in Fig. 5. In one case a regular-sized Hoffman device was used in a large-boned man with an unstable distal radius fracture secondary to a gunshot wound. Method of application. With the patient under gen-
eral or regional anesthesia in the operating room, the injured extremity is suspended by finger traps, and a 5- to 10-pound counter weight is attached to the upper arm . After a few minutes of distraction, closed reduction is performed, and x-ray films are taken to confirm the reduction. Under image intensifier control, the two distal pins were placed in the bases of the second and third metacarpals at a 60° angle to each other, and the proximal two pins were placed in the radius just proximal to the first extensor compartment tendons. All patients were called back for final follow-up examination at least 6 months after injury. Results The mean rigidity values for each type of external fixator and each mode tested are given in Table I. In the compression mode, the small A.O . external fixator was significantly more rigid statistically (p < 0.05) than the other three frames. With AP bending, the A.O.
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November 1985
Fig. 2. The Hoffman external fixator. We used 3 mm diameter haIf pins from the Hoffman "C" series set and connected them to four 3 mm diameter titanium rods from the mini Hoffman external fixator set to form a rectangular frame .
External jixators for wrist fractures
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Fig. 3. The Roger Anderson external fixator. The device used 2.5 mm half pins attached to the standard connecting rods forming a rectangular frame.
fixator was significantly more rigid statistically than the other three fixators (p < 0 .05). With lateral bending, the Hoffman device and the Ace Colles' fixator were significantly more rigid than the A.D. fixator and the Roger Anderson device (p < 0.05). The equivalent stiffness index is a calculated value defined by Chao et al. 6 as the mean sum of the individual rigidity values of each loading mode. This enables us to compare the overall rigidity of different fixators . Overall the A.D. fixator was about twice as rigid as the other three fixators.
Clinical study We had sufficient x-ray films and records on 22 patients for measuring end results and anatomic data. The mean age was 55 years (range of 25 to 82 years). Ten men and 12 women participated. There were 14 dominant wrists and eight nondominant wrists fractured. Nine patients were injured in a fall, six in motor vehicle accidents, five in motorcycle accidents , two from gunshot wounds, and one due to another cause. Three open fractures were present. Fourteen external fixators were applied primarily, and eight after failed closed reduction. The average duration of immobilization was 8 weeks (range of 4 to iO weeks). The Frykman method was used to classify the fractures/ as shown in Table II. On the final x-ray film, the angle of the distal radial articular surface on the AP x-ray film averaged 17.5° (normal is 23°). The plane of the distal radial articular surface on the lateral x-ray film averaged 2° dorsal tilt (normal is 11 0 palmar tilt) . The final length of the radial styloid beyond the ulnar styloid averaged 8 mm on the AP film. The loss in length of the radius from initial
Fig. 4. Ace Colles' external fixator using 3 mm half pins with a semicircular frame.
postreduction averaged 5 mm overall (range of 0 to 22 mm). However, if we eliminate the four cases with loss of fixation due to either broken pins or loss of fixation through osteoporotic bone, the average loss in length measured 2 mm (range of 0 to 4 mm) . If we again eliminate cases with loss of fixation, the frontal radial angle is an average of 19° with final dorsal tilt of 1.60 , and the final length of the radial styloid was iO mm. Four patients developed severe nerve injuries. One had compression of the median nerve and three of the ulnar nerve. All nerve compressions resolved spontaneously without requiring surgery. Other complications, which may be related to the device, occurred in six patients (27%) . One patient had a tendon rupture of the extensors to the ring and small fingers due to dorsal subluxation of the distal ulna 1 year after surgery. Another patient had a contracture of the third dorsal interosseous requiring intrinsic release. Three patients had broken
848
The Journal of HAND SURGERY
Nakata et ai.
DP tf 7.( L.~205
• ~~Z8-8 ;. Fig. 5, A-C. A n-year-old woman who fell on her outstretched hand on June 27. 1981. A-B, She had a closed reduction of her comminuted unstable intra-articular fracture with a hematoma block followed by a long-arm cast. C, Follow-up x-ray film shows loss of reduction.
fixation pins, and one had loss of fixation due to migration of the pins through extremely osteoporotic bone. There were no cases of upper limb dystrophy or shoulder/hand syndrome. Sixteen patients returned for final standard followup examination with a mean follow-up of 25 months (range of 6 to 40 months). Of these 16 patients, seven had no aching or pain in the wrist, six had mild aching, and three had moderate aching requiring occasional medication. Ten had no stiffness, and six complained of mild stiffness in the wrist. Eight of 16 noted some weakness in the wrist. All but two of the nine patients
who were working before the injury returned to their previous job, one had to change jobs, and one was not working due to lower extremity trauma. Seven were not employed before the injury. Thirteen had tenderness at the distal radiocarpal joint, and six had slight tenderness at the distal radioulnar joint. Prominence of the distal ulna was noted in three cases. The mean active range of motion (ROM) of the wrist and forearm was measured in relation to the uninjured side and is as follows: extension 51 °/66° (77%), flexion 52°/68° (77%), radial deviation 18°/25° (73%), ulnar deviation 29°/35° (82%), pronation 49°/59° (84%), and supina-
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Fig. 5, D-F. D-E, She was taken to surgery week after injury, and a closed reduction was performed and a Hoffman external fixator applied. F, The fixator was removed upon healing 8 weeks later. The final radial angle of the distal radius was 20°, and palmar angle was 10.
Fig. 5, G-H. Appearance 2 years after fracture. The distal radial articular surface is well maintained. She denied wrist pain. Her wrist ROM was extension 65°170°, flexion 60°170°, ulnar deviation 40°/ 45°, radial deviation 15°/15°, pronation 50°/65°, and supination 70°/85°. Grip strength was 30/30 pounds.
tion 64°/82° (78%). Grip strength with the Jamar dynamometer averaged 48 pounds on the injured side versus 67 pounds on the uninjured side, or 72% of the uninjured side.
Discussion For the biomechanical study, we chose to insert the pins into a wooden dowel rather than into cadaver bone because of easy availability and consistency of size and
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Table I. Mean rigidity value of external fixators
Pin diameter Mode tested Compression: Kg/M XIO- 2 AP bending: KG/M XIO- 2 Lateral bending: Kg/M XIO- 2 Equivalent stiffness index
Small A.O.
Mini Hoffman
Roger Anderson
Ace Calles'
2.5 mm
3 mm
2.5 mm
3mm
20.3 16.7 5.0
5.5 4.6 10.2
7.7 4.1 6.7
7.8 5.3 9.5
6.7
3.7
3.5
4.3
Table II. Classification of fractures with the Frykman method7 Frykman class
II IV VI VII VIII
Cases I
3 2 15
shape. Since this is a comparison study, as long as the same rigid material is used for the pins, it does not matter what actual material is used. When material, pin number, pin separation, and height from the bone to the fixator are kept constant, rigidity is dependent primarily on the design and materials of the fixator. Although the equivalent stiffness index for the A.a. external fixator was two times more rigid than the other three fixators, it was the least rigid in the plane perpendicular to the plane of the pins and rods as might be predicted from observation of the design (Fig. 1). In choosing between these four external fixators to immobilize distal radius fractures, the A.a. was the most rigid, and the other three had little to choose between them on this basis. Other considerations for clinical use should be cost, ease of application, familiarity with the instrumentation, and availability. According to the distributors, the price for each of these external fixators is as follows: A.a., $2610; Hoffman, $1340; Ace Colles', $517; and Roger Anderson, $324. We have used the Hoffman fixator most frequently in our clinical series because it was most readily available to us at the inception of this series and because of its versatility in configuration and use throughout the wrist and hand. On the basis of price alone, the Roger Anderson should be chosen. However, according to the distributor, * it has recently been redesigned and simplified. *Kirschner Medical, 10 W. Aylesbury Rd., Timonium, MD 21093.
In a series using the Roger Anderson external fixators, Cooney et al. 1 stated that the final AP angle of the distal radius averaged 21°, dorsal angle was 3°, and radial shortening was 2 mm. When these figures are compared with our results with the Hoffman external fixator, they are very similar. Cooney3 found that ROM of the wrist using the external fixator for unstable wrist fractures was as follows: average wrist extension of 50°, flexion of 48°, radial deviation of 10°, ulnar deviation of 25°, pronation of 75°, and supination of 70°. These results are very similar to ours. Grip strength in our cases, however, was greater, averaging 72% versus 54% in his series. Whether the external fixator should be applied by distraction across the distal radiocarpal joint as was done in our series, or whether the distal pins should be put in the distal radius, which theoretically would allow better wrist motion, remains to be determined. In his series, ROM of the wrist was not significantly improved when the radiocarpal joint was spared. 3 We feel that the bone stock of the comminuted distal radial fragments is frequently not inadequate to hold the pins, and therefore we believe that better fixation is assured by placing the distal pins in the base of the metacarpals. Using the external fixator for unstable Colles' fractures seems justified in achieving better anatomic results since studies have shown that poor anatomic results frequently lead to poor functional results. I. 7. 8 Comparing the use of pins and plaster9 as an alternative to the external fixator, the anatomic end results seem to be similar since the final distal radial angle was 16° with a dorsal tilt of 4°. However, the complication rate was higher with pins in plaster,9 i.e., pin loosening rate of 21 %, an iatrogenic fracture rate of 9%, and 20% pin tract infection. We had a pin fracture and loosening rate of 18%, 0% iatrogenic fractures, and 0% pin tract infections. We believe that the additional advantage of having no constricting plaster about the traumatized wrist is significant. In addition, with the external fixator no pins are inserted into the ulna; thus the patient is allowed to rotate the forearm as he or she is able during
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fracture healing. The external fixation frame is much lighter than pins in plaster and is thus very well accepted by patients. Finally, in open fractures, the external fixator has a decided advantage because it allows easy wound access. One of our open fractures required a groin flap and another a split-thickness skin graft, both of which were easily managed with the external fixator. From our clinical studies with the Hoffman external fixator, which is one of the less rigid frames for fractures, we believe that all of these external fixators will give adequate rigidity for fixation of unstable distal radius fractures if used properly. Because distraction of the comminuted distal radius fragments probably slows healing, we recommend that the external fixator be left in place for 8 weeks before removal. However, the way in which we used the Hoffman external fixator is not recommended for large-boned individuals and very active people. A few patients overstressed the system and sustained pin fractures, which were the most common complication in our series. Perhaps using a more rigid fixator such as the larger Hoffman device or the A.a. fixator would be advantageous in these patients. In summary, we have compared four external fixators, all of which appear to provide adequate rigidity for the treatment of common unstable distal radius fractures, particularly in the older population. Our clinical results show that the Hoffman external fixator for these severe wrist fractures gives acceptable anatomic and clinical results. The authors thank Vincent Leung, M.D., for his helpful review and advice in the preparation of this manuscript.
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REFERENCES 1. Cooney WP III, Linsheid RL, Dobyns JH: External pin fixation for unstable Colles' fractures. J Bone Joint Surg [Am] 61:840-5, 1979 2. Cooney WP III, Dobyns JH, Linsheid RL: Complications of Colles' fractures. J Bone Joint Surg [Am] 62:613-9, 1980 3. Cooney WP III: External fixation of distal radial fractures. Clin Orthop 180:44-9, 1983 4. Jakob RP, Fernandez DL: In Uhthoff HK, editor: Current concepts of external fixation in fractures. Berlin, Heidelberg, 1982, The Springer-Verlag Co., pp 307-14 5. Grana WA, Kopta JA: The Roger Anderson device in the treatment of fractures of the distal end of the radius. J Bone Joint Surg [Am] 61:1234-8, 1979 6. Chao EYS, Briggs BT, McCoy MT: In Brooker AF Jr, Edwards CC, editors: External fixation the current state of the art. Baltimore, 1979, The Williams & Wilkins Co., p 348 7. Frykrnan G: Fracture of the distal radius including sequelae-shoulder-hand-finger syndrome, disturbance in the distal radio-ulnar joint and impairment of nerve function. A clinical experimental study. Acta Orthop Scand Suppl 108;30-1, 1967 8. Green DP: Pins and plaster treatment of comminuted fractures of the distal end of the radius. J Bone Joint Surg [Am] 57:304-10, 1975 9. Chapman DR, BennettJB, Bryan WJ, et al: Complications of distal radial fractures: pins and plaster treatment. J HAND SURG 7:509-12, 1982
Roland Y. Nakata, M.D., Yogesh Chand, M.D., James D. Matiko, M.D., Gary K. Frykman, M.D., and Virchel E. Wood, M.D., Lorna Linda, Calif.
Recently there has been renewed interest in using external fixators for the treatment of comminuted distal radius fractures. 1-5 However, very little data are published to guide the treating surgeon in his choice of one type of external fixator over another. This article compares in vitro the rigidity of four available designs of external fixators and presents our clinical results with one of the external fixators.
Methods and material In the first part of the study, we evaluated the rigidity of four external fixators of the wrist. They were each assembled according to the developers' recommendations. The external fixators studied were: (1) the small A.O. external fixator* (Fig. 1); (2) a combination of From the Hand Surgery Service, Department of Orthopedic Surgery, Lorna Linda University, Lorna Linda, Calif. Received for publication March 5, 1984; accepted in revised form Feb. 14, 1985. Reprint requests: Gary K. Frykman, M.D., Department of Orthopedic Surgery, Lorna Linda University, Lorna Linda, CA 92350. *Synthes Ltd., 983 Old Eagle School Rd., Wayne, PA 19087.
the mini and small Hoffman external fixator* (Fig. 2), hereafter called the Hoffman fixator; (3) the Roger Andersont device (Fig. 3); and (4) the Ace Colles':j: fixator (Fig. 4). All external fixation devices tested were provided by the distributors of the devices. For testing, the half pins were inserted into a 2 cm diameter wooden dowel to mount the various fixators. The distance between the two proximal and two distal pins (10 cm), the angle between the pins in each group (60°), and the distance between the wooden dowel and fixator (2 cm) were kept constant in all the fixators. The distances were chosen to closely approximate placement of the pins for applying fixators to distal radius fractures. After the fixator was mounted, a 1 cm gap was cut out of the center of the dowel between the two pin groups. The frames were then stressed with various jigs in an Instron universal testing instrument in compression, anteroposterior (AP) bending, and lat-
*Howmedica, Inc., 359 Veterans Blvd., Rutherford, NJ 07070. tKirschner Medical, 10 W. Aylesbury Rd., Timonium, MD 21093. tAce Orthopedic Mfg., 14105 S. Avalon Blvd., Los Angeles, CA 90061.
THE JOURNAL OF HAND SURGERY
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Fig. 1. The small A.O. external fixator. This device was applied to the bone as recommended by Jakob and Fernandez.' A, Placing two 2.5 mm diameter half pins into the second metacarpal at a 60° angle to each other and two pins in the same manner to the distal radius and connected to each other by 4 mm rods . B, Although the pins are angled to each other in one plane , at 90° to this plane. the pins and connecting rods are parallel to each other.
eral bending. The recorder plotted the stress/strain curves. We were careful to keep the testing in the elastic region of the curve. Clinical study From October 1980 through November 1983 , we used an external fixator on 26 patients with unstable distal radius fractures. An unstable fracture was defined as a fracture with marked comminution including intraarticular fragments and shortening of more than 10 mm, dorsal angulation greater than 20°, or significant loss of reduction after closed reduction and immobilization. In 25 of the patients, we used the Hoffman device configured as tested in the biomechanical study. A typical case in which we used the Hoffman device is shown in Fig. 5. In one case a regular-sized Hoffman device was used in a large-boned man with an unstable distal radius fracture secondary to a gunshot wound. Method of application. With the patient under gen-
eral or regional anesthesia in the operating room, the injured extremity is suspended by finger traps, and a 5- to 10-pound counter weight is attached to the upper arm . After a few minutes of distraction, closed reduction is performed, and x-ray films are taken to confirm the reduction. Under image intensifier control, the two distal pins were placed in the bases of the second and third metacarpals at a 60° angle to each other, and the proximal two pins were placed in the radius just proximal to the first extensor compartment tendons. All patients were called back for final follow-up examination at least 6 months after injury. Results The mean rigidity values for each type of external fixator and each mode tested are given in Table I. In the compression mode, the small A.O . external fixator was significantly more rigid statistically (p < 0.05) than the other three frames. With AP bending, the A.O.
Vol. lOA. No.6, Part 1
November 1985
Fig. 2. The Hoffman external fixator. We used 3 mm diameter haIf pins from the Hoffman "C" series set and connected them to four 3 mm diameter titanium rods from the mini Hoffman external fixator set to form a rectangular frame .
External jixators for wrist fractures
847
Fig. 3. The Roger Anderson external fixator. The device used 2.5 mm half pins attached to the standard connecting rods forming a rectangular frame.
fixator was significantly more rigid statistically than the other three fixators (p < 0 .05). With lateral bending, the Hoffman device and the Ace Colles' fixator were significantly more rigid than the A.D. fixator and the Roger Anderson device (p < 0.05). The equivalent stiffness index is a calculated value defined by Chao et al. 6 as the mean sum of the individual rigidity values of each loading mode. This enables us to compare the overall rigidity of different fixators . Overall the A.D. fixator was about twice as rigid as the other three fixators.
Clinical study We had sufficient x-ray films and records on 22 patients for measuring end results and anatomic data. The mean age was 55 years (range of 25 to 82 years). Ten men and 12 women participated. There were 14 dominant wrists and eight nondominant wrists fractured. Nine patients were injured in a fall, six in motor vehicle accidents, five in motorcycle accidents , two from gunshot wounds, and one due to another cause. Three open fractures were present. Fourteen external fixators were applied primarily, and eight after failed closed reduction. The average duration of immobilization was 8 weeks (range of 4 to iO weeks). The Frykman method was used to classify the fractures/ as shown in Table II. On the final x-ray film, the angle of the distal radial articular surface on the AP x-ray film averaged 17.5° (normal is 23°). The plane of the distal radial articular surface on the lateral x-ray film averaged 2° dorsal tilt (normal is 11 0 palmar tilt) . The final length of the radial styloid beyond the ulnar styloid averaged 8 mm on the AP film. The loss in length of the radius from initial
Fig. 4. Ace Colles' external fixator using 3 mm half pins with a semicircular frame.
postreduction averaged 5 mm overall (range of 0 to 22 mm). However, if we eliminate the four cases with loss of fixation due to either broken pins or loss of fixation through osteoporotic bone, the average loss in length measured 2 mm (range of 0 to 4 mm) . If we again eliminate cases with loss of fixation, the frontal radial angle is an average of 19° with final dorsal tilt of 1.60 , and the final length of the radial styloid was iO mm. Four patients developed severe nerve injuries. One had compression of the median nerve and three of the ulnar nerve. All nerve compressions resolved spontaneously without requiring surgery. Other complications, which may be related to the device, occurred in six patients (27%) . One patient had a tendon rupture of the extensors to the ring and small fingers due to dorsal subluxation of the distal ulna 1 year after surgery. Another patient had a contracture of the third dorsal interosseous requiring intrinsic release. Three patients had broken
848
The Journal of HAND SURGERY
Nakata et ai.
DP tf 7.( L.~205
• ~~Z8-8 ;. Fig. 5, A-C. A n-year-old woman who fell on her outstretched hand on June 27. 1981. A-B, She had a closed reduction of her comminuted unstable intra-articular fracture with a hematoma block followed by a long-arm cast. C, Follow-up x-ray film shows loss of reduction.
fixation pins, and one had loss of fixation due to migration of the pins through extremely osteoporotic bone. There were no cases of upper limb dystrophy or shoulder/hand syndrome. Sixteen patients returned for final standard followup examination with a mean follow-up of 25 months (range of 6 to 40 months). Of these 16 patients, seven had no aching or pain in the wrist, six had mild aching, and three had moderate aching requiring occasional medication. Ten had no stiffness, and six complained of mild stiffness in the wrist. Eight of 16 noted some weakness in the wrist. All but two of the nine patients
who were working before the injury returned to their previous job, one had to change jobs, and one was not working due to lower extremity trauma. Seven were not employed before the injury. Thirteen had tenderness at the distal radiocarpal joint, and six had slight tenderness at the distal radioulnar joint. Prominence of the distal ulna was noted in three cases. The mean active range of motion (ROM) of the wrist and forearm was measured in relation to the uninjured side and is as follows: extension 51 °/66° (77%), flexion 52°/68° (77%), radial deviation 18°/25° (73%), ulnar deviation 29°/35° (82%), pronation 49°/59° (84%), and supina-
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External flXators for wrist fractures
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Fig. 5, D-F. D-E, She was taken to surgery week after injury, and a closed reduction was performed and a Hoffman external fixator applied. F, The fixator was removed upon healing 8 weeks later. The final radial angle of the distal radius was 20°, and palmar angle was 10.
Fig. 5, G-H. Appearance 2 years after fracture. The distal radial articular surface is well maintained. She denied wrist pain. Her wrist ROM was extension 65°170°, flexion 60°170°, ulnar deviation 40°/ 45°, radial deviation 15°/15°, pronation 50°/65°, and supination 70°/85°. Grip strength was 30/30 pounds.
tion 64°/82° (78%). Grip strength with the Jamar dynamometer averaged 48 pounds on the injured side versus 67 pounds on the uninjured side, or 72% of the uninjured side.
Discussion For the biomechanical study, we chose to insert the pins into a wooden dowel rather than into cadaver bone because of easy availability and consistency of size and
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The Journal of
Nakata et al.
HAND SURGERY
Table I. Mean rigidity value of external fixators
Pin diameter Mode tested Compression: Kg/M XIO- 2 AP bending: KG/M XIO- 2 Lateral bending: Kg/M XIO- 2 Equivalent stiffness index
Small A.O.
Mini Hoffman
Roger Anderson
Ace Calles'
2.5 mm
3 mm
2.5 mm
3mm
20.3 16.7 5.0
5.5 4.6 10.2
7.7 4.1 6.7
7.8 5.3 9.5
6.7
3.7
3.5
4.3
Table II. Classification of fractures with the Frykman method7 Frykman class
II IV VI VII VIII
Cases I
3 2 15
shape. Since this is a comparison study, as long as the same rigid material is used for the pins, it does not matter what actual material is used. When material, pin number, pin separation, and height from the bone to the fixator are kept constant, rigidity is dependent primarily on the design and materials of the fixator. Although the equivalent stiffness index for the A.a. external fixator was two times more rigid than the other three fixators, it was the least rigid in the plane perpendicular to the plane of the pins and rods as might be predicted from observation of the design (Fig. 1). In choosing between these four external fixators to immobilize distal radius fractures, the A.a. was the most rigid, and the other three had little to choose between them on this basis. Other considerations for clinical use should be cost, ease of application, familiarity with the instrumentation, and availability. According to the distributors, the price for each of these external fixators is as follows: A.a., $2610; Hoffman, $1340; Ace Colles', $517; and Roger Anderson, $324. We have used the Hoffman fixator most frequently in our clinical series because it was most readily available to us at the inception of this series and because of its versatility in configuration and use throughout the wrist and hand. On the basis of price alone, the Roger Anderson should be chosen. However, according to the distributor, * it has recently been redesigned and simplified. *Kirschner Medical, 10 W. Aylesbury Rd., Timonium, MD 21093.
In a series using the Roger Anderson external fixators, Cooney et al. 1 stated that the final AP angle of the distal radius averaged 21°, dorsal angle was 3°, and radial shortening was 2 mm. When these figures are compared with our results with the Hoffman external fixator, they are very similar. Cooney3 found that ROM of the wrist using the external fixator for unstable wrist fractures was as follows: average wrist extension of 50°, flexion of 48°, radial deviation of 10°, ulnar deviation of 25°, pronation of 75°, and supination of 70°. These results are very similar to ours. Grip strength in our cases, however, was greater, averaging 72% versus 54% in his series. Whether the external fixator should be applied by distraction across the distal radiocarpal joint as was done in our series, or whether the distal pins should be put in the distal radius, which theoretically would allow better wrist motion, remains to be determined. In his series, ROM of the wrist was not significantly improved when the radiocarpal joint was spared. 3 We feel that the bone stock of the comminuted distal radial fragments is frequently not inadequate to hold the pins, and therefore we believe that better fixation is assured by placing the distal pins in the base of the metacarpals. Using the external fixator for unstable Colles' fractures seems justified in achieving better anatomic results since studies have shown that poor anatomic results frequently lead to poor functional results. I. 7. 8 Comparing the use of pins and plaster9 as an alternative to the external fixator, the anatomic end results seem to be similar since the final distal radial angle was 16° with a dorsal tilt of 4°. However, the complication rate was higher with pins in plaster,9 i.e., pin loosening rate of 21 %, an iatrogenic fracture rate of 9%, and 20% pin tract infection. We had a pin fracture and loosening rate of 18%, 0% iatrogenic fractures, and 0% pin tract infections. We believe that the additional advantage of having no constricting plaster about the traumatized wrist is significant. In addition, with the external fixator no pins are inserted into the ulna; thus the patient is allowed to rotate the forearm as he or she is able during
Vol. lOA, No.6, Part 1 November 1985
fracture healing. The external fixation frame is much lighter than pins in plaster and is thus very well accepted by patients. Finally, in open fractures, the external fixator has a decided advantage because it allows easy wound access. One of our open fractures required a groin flap and another a split-thickness skin graft, both of which were easily managed with the external fixator. From our clinical studies with the Hoffman external fixator, which is one of the less rigid frames for fractures, we believe that all of these external fixators will give adequate rigidity for fixation of unstable distal radius fractures if used properly. Because distraction of the comminuted distal radius fragments probably slows healing, we recommend that the external fixator be left in place for 8 weeks before removal. However, the way in which we used the Hoffman external fixator is not recommended for large-boned individuals and very active people. A few patients overstressed the system and sustained pin fractures, which were the most common complication in our series. Perhaps using a more rigid fixator such as the larger Hoffman device or the A.a. fixator would be advantageous in these patients. In summary, we have compared four external fixators, all of which appear to provide adequate rigidity for the treatment of common unstable distal radius fractures, particularly in the older population. Our clinical results show that the Hoffman external fixator for these severe wrist fractures gives acceptable anatomic and clinical results. The authors thank Vincent Leung, M.D., for his helpful review and advice in the preparation of this manuscript.
External jixators for wrist fractures
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REFERENCES 1. Cooney WP III, Linsheid RL, Dobyns JH: External pin fixation for unstable Colles' fractures. J Bone Joint Surg [Am] 61:840-5, 1979 2. Cooney WP III, Dobyns JH, Linsheid RL: Complications of Colles' fractures. J Bone Joint Surg [Am] 62:613-9, 1980 3. Cooney WP III: External fixation of distal radial fractures. Clin Orthop 180:44-9, 1983 4. Jakob RP, Fernandez DL: In Uhthoff HK, editor: Current concepts of external fixation in fractures. Berlin, Heidelberg, 1982, The Springer-Verlag Co., pp 307-14 5. Grana WA, Kopta JA: The Roger Anderson device in the treatment of fractures of the distal end of the radius. J Bone Joint Surg [Am] 61:1234-8, 1979 6. Chao EYS, Briggs BT, McCoy MT: In Brooker AF Jr, Edwards CC, editors: External fixation the current state of the art. Baltimore, 1979, The Williams & Wilkins Co., p 348 7. Frykrnan G: Fracture of the distal radius including sequelae-shoulder-hand-finger syndrome, disturbance in the distal radio-ulnar joint and impairment of nerve function. A clinical experimental study. Acta Orthop Scand Suppl 108;30-1, 1967 8. Green DP: Pins and plaster treatment of comminuted fractures of the distal end of the radius. J Bone Joint Surg [Am] 57:304-10, 1975 9. Chapman DR, BennettJB, Bryan WJ, et al: Complications of distal radial fractures: pins and plaster treatment. J HAND SURG 7:509-12, 1982