JBJS | Displaced Scaphoid Fractures Treated with Open Reductio and Internal Fixation with a Cannulated Screw*

The Journal of Bone & Joint Surgery, Volume 82, Issue 5

Articles | May 01, 2000

Displaced Scaphoid Fractures Treated with Open Reductio and Internal Fixation with a Cannulated Screw*

Thomas E. Trumble, M.D.†; Mary Gilbert, M.A.†; Lorne W. Murray, B.S.†; Jeffery Smith, M.D.†; Wren V. McCallister, M.D.†

Investigation performed at the University of Washington Medical Center, Seattle, Washington
*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. No funds were received in support of this study.
†Department of Orthopaedics, University of Washington Medical Center, Box 356500, 1959 Pacific Street, Seattle, Washington 98195.

The Journal of Bone & Joint Surgery. 2000; 82:633-633

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Abstract

Background: This study was performed to determine if the accuracy of screw placement was improved with use of the Herbert-Whipple cannulated screw compared with use of the AO/ASIF cannulated screw and also to evaluate the functional results in patients with an acute displaced fracture of the waist of the scaphoid treated with open reduction and internal fixation with a cannulated screw.

Methods: We retrospectively reviewed the results for thirty-five patients in whom an acute displaced fracture of the waist of the scaphoid had been treated with internal fixation with use of a cannulated screw. The patients were divided into two groups; Group 1 consisted of nineteen patients managed with a 3.5-millimeter cannulated AO/ASIF screw from 1990 through 1997, and Group 2 consisted of sixteen patients managed with a Herbert-Whipple screw from 1993 through 1997.

Results: There were no clinical or radiographic differences between the two groups. The average time to union (and standard deviation), confirmed with tomography, was 4.2 ± 1.2 months for Group 1 and 4.0 ± 1.2 months for Group 2. Both screws significantly improved the alignment of the scaphoid and decreased carpal collapse (p < 0.01). Importantly, the use of either cannulated screw improved the height-to-length ratio and the lateral intrascaphoid angle, which were correlated with an increase in the range of motion of the wrist (r = 0.584 and 0.625). In addition, both screws allowed for accurate placement in the central portion of the proximal pole. Regardless of the type of screw used, the time to union increased with increasing age of the patient (r = 0.665) and with increasing initial displacement of the fracture (r = 0.541). Within both groups, the time to union was longer for the patients who smoked (p < 0.01).

Conclusions: Within both groups, cannulated screw fixation maintained the corrected fracture alignment and promoted healing and return of function. Our study shows cannulated screws to be a safe and effective method of treatment.

Figures in this Article

Introduction

Introduction | Materials and Methods | Results | Discussion | References

Treatment of acute displaced scaphoid fractures is difficult. Displacement can be defined as a gap of one millimeter between the fracture fragments, a 10-degree change in the lateral and anteroposterior intrascaphoid angles, or a height-to-length ratio of the scaphoid of 0.65 or more^2,3. Compared with nondisplaced fractures, displaced fractures are slower to heal, require a longer duration of immobilization, and are associated with a higher risk of post-traumatic osteoarthritis. Open reduction and internal fixation with Kirschner wires has become the preferred method of treatment for displaced fractures.

Several different screws have been developed to stabilize nonunions of the scaphoid and to decrease the duration of postoperative immobilization^16,20,22. These same screws have also been used to treat acute displaced scaphoid fractures. Although many different screws have been used to stabilize scaphoid fractures, the first screw specifically designed for scaphoid fractures was the double-threaded Herbert screw¹⁶ (Zimmer, Warsaw, Indiana). This screw provides fixation of the scaphoid with both ends of the screw buried completely within the bone. However, accurate placement of the screw is difficult despite the use of a Huene device, and compression of the screw often produces malrotation of the fragments^1,25. Screws inserted from an unfavorable position are often difficult to reorient, even with the aid of fluoroscopy and the placement of a second Kirschner wire parallel to the planned location of the screw before insertion to prevent rotation of the scaphoid fragments^1,12. Other modifications, such as removing a portion of the volar trapezial surface and predrilling the path for the screw with a cannulated sleeve in the Huene guide barrel, can improve the accuracy of placement of the noncannulated Herbert screw. However, the final path of the screw can still vary if the scaphoid fragments shift, and the use of the Huene device still requires the division of the entire volar capsule to place the device onto the proximal pole of the scaphoid.

Two other screws, the 3.5-millimeter cannulated AO/ASIF screw (Synthes, Paoli, Pennsylvania) and the cannulated Herbert-Whipple screw (Zimmer, Warsaw, Indiana), can be inserted in the optimal position with the placement of a guide-wire before insertion, thereby avoiding the need for the Huene device. The screws also facilitate the placement of a second Kirschner wire to control rotation^11,19,25.

Cannulated screws have been shown to provide more accurate internal fixation of scaphoid nonunions, and thus shorter times to union, when the proximal screw threads are located in the center of the proximal pole²⁵. We performed the present retrospective study (1) to determine whether the screw placement, which has been shown to affect times to union, was more accurate with use of either screw and (2) to evaluate the functional results for patients with an acute displaced fracture of the waist of the scaphoid treated with internal fixation with a cannulated screw.

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Fig. 1:: Displacement of the scaphoid fracture by 1.0 millimeter or more was measured on anteroposterior and scaphoid-view radiographs. The arrows point to the proximal and distal fragments adjacent to the step-off.

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Fig. 2:: Illustration showing the technique for measuring scaphoid angulation in the lateral plane. Normal values average 24 degrees. (Reprinted with permission of the Mayo Foundation.)

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Fig. 3:: Illustration showing the technique for measuring scaphoid angulation in the anteroposterior plane. Normal values average 45 degrees. (Reprinted with permission of the Mayo Foundation.)

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Fig. 4:: Computerized tomography scan showing the technique for measuring the height-to-length ratio. A baseline is drawn along the volar aspect of the scaphoid. The length of the scaphoid along the baseline is measured, as is the height of the scaphoid perpendicular to the baseline. Normal values average 0.60.

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Fig. 5:: Anteroposterior radiograph showing a Herbert-Whipple screw positioned in the central third of the proximal pole of the scaphoid.

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Fig. 6:: Lateral radiograph showing a Herbert-Whipple screw positioned in the central third of the proximal pole of the scaphoid.

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Fig. 7:: Radiograph made during the drilling process, showing the advancement of a guide-wire for the cannulated screw into the radius, to prevent the wire from dislodging.

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Fig. 8:: Sagittal computerized tomography scan showing scaphoid collapse with an increase in the lateral intrascaphoid angle following a fracture.

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Fig. 9:: Computerized tomography scan made postoperatively, showing that the lateral intrascaphoid angle decreased after open reduction and internal fixation with a cannulated screw.

Materials and Methods

Introduction | Materials and Methods | Results | Discussion | References

We reviewed the records of forty-three consecutive patients, identified through the University of Washington Medical Center and affiliated Harborview Medical Center surgery databases, who had been managed with internal fixation for an acute displaced fracture of the waist of the scaphoid. In order for patients to be included in our study, they had to (1) have been at least eighteen years of age with closed physes at the time of the fracture, (2) have been treated within one month from the time of the fracture, (3) have had no preexisting wrist problems, and (4) have had a classified displaced fracture of the waist of the scaphoid. Eight patients were excluded because of (1) injury to the contralateral hand that prevented reporting of the functional measurements on the injured side as a percentage of the values for the contralateral side, (2) fracture of the proximal pole of the scaphoid, (3) concomitant ipsilateral carpal dislocation such as perilunate dislocation, or (4) previous operative treatment of the acute displaced fracture. Thirty-five patients were included in the study.

The patients were divided into two groups depending on the method of fixation. Group 1 consisted of nineteen patients who had been managed from 1990 through 1997 with a 3.5-millimeter cannulated AO/ASIF screw, and Group 2 consisted of sixteen patients who had been managed from 1993 through 1997 with a cannulated Herbert-Whipple screw. We switched from the AO/ASIF screw to the Herbert-Whipple screw in 1993 in order to avoid symptoms related to the impingement of the head of the AO/ASIF screw on the trapezium²⁵. We did, however, use the AO/ASIF screw after 1993 in three patients when the Herbert-Whipple screw was unavailable.

The average age of the fourteen male and five female patients in Group 1 was twenty-eight years (range, eighteen to forty-six years). Eleven patients had involvement of the right wrist, and ten patients had involvement on the dominant side. The average delay from the time of the injury to the operation was eleven days (range, zero to twenty-six days). The average age of the eleven male and five female patients in Group 2 was thirty years (range, eighteen to forty-eight years). Eleven patients in Group 2 had involvement of the right wrist, and eleven patients had involvement on the dominant side. The average delay from the time of the injury to the operation was fourteen days (range, zero to thirty-two days).

The mechanism of injury in Group 1 was a fall for four patients, a sports-related accident for ten, and a motor-vehicle accident for five. The mechanism of injury in Group 2 was a fall for three patients, a sports-related accident for ten, and a motor-vehicle accident for three. There were no work-related injuries.

All patients had a fracture of the waist of the scaphoid extending from the volar surface distally to the dorsal surface proximally. Seven patients (four in Group 1 and three in Group 2) had comminution of the fracture as seen on the initial plain radiographs. All fractures were classified as being displaced on the basis of one of the following criteria: (1) a gap of one millimeter or more between the fracture fragments (Fig. 1), (2) a lateral intrascaphoid angle of more than 45 degrees as described by Amadio et al.² (Fig. 2), (3) an anteroposterior intrascaphoid angle of less than 35 degrees as described by Amadio et al.² (Fig. 3), or (4) a height-to-length ratio of the scaphoid of 0.65 or more measured on lateral radiographs as described by Bain et al.³ (Fig. 4). The average magnification of the radiographs (and standard deviation) was 20 ± 8 percent, as determined from twenty randomly selected radiographs from which the ratio of the length of the screw on the radiograph to the actual length of the screw was calculated. Selected radiographs on which the screws were orthogonal to the plane of view, confirmed by the appearance of parallel screw threads, were used as reference markers. The measurements from the radiographs were consistent and were in agreement with the measurements in other reports^18,25.

Sixteen of the nineteen patients in Group 1 and thirteen of the sixteen patients in Group 2 had sagittal and coronal computerized tomography scans to evaluate the displacement of the fracture preoperatively. Postoperative radiographs were made at monthly follow-up examinations. Once trabecular bridging was suspected on the basis of radiographs, computerized tomography scans were made with 0.5-millimeter nonreconstructed cuts in the sagittal and coronal planes.

The placement of the screw was assessed on the final follow-up anteroposterior radiographs made with the wrist in the neutral position and ulnar deviation and on lateral and oblique radiographs made with the forearm in pronation and supination². The proximal pole of the scaphoid was divided into three equal sections, with the middle section representing the central one-third. The screw was considered to be centrally placed if it was located in the central one-third of the proximal pole of the scaphoid²⁵ (Fig. 5 and Fig. 6). If the screw extended out of the central one-third of the scaphoid on a single radiograph, it was considered to be peripherally placed. Radiographic measurements were made in a blinded fashion by four orthopaedic surgeons and one plastic-surgery resident, and the final determination was arrived at by consensus.

The range of motion, grip strength, and pain were also measured at the final follow-up evaluation. Twenty-six patients were interviewed by an examiner who was blinded to the type of internal fixation that had been used. Nine patients were examined by local therapists and interviewed by one of us by telephone. The range of motion was reported as both an absolute measurement and as a percentage of that on the contralateral side. Flexion and extension of the wrist as well as radial and ulnar deviation were measured on both the injured and the contralateral side¹⁰. Maximum grip strength on the injured side was measured with a Jamar dynamometer (J. P. Marsh, Skokie, Illinois) and was reported as a percentage of the maximum strength on the contralateral side. With the use of a questionnaire, pain was assessed preoperatively and postoperatively as stage 0 (no pain), stage 1 (mild discomfort or pain that does not restrict work or sports activities), or stage 2 (pain that restricts work or sports activities). The patients were followed monthly until the fracture had united and they had resumed full activity. They were then followed on an annual basis. All physical and radiographic measurements were performed at the final follow-up evaluation for the purposes of this study only.

The final follow-up radiographs were examined to grade postoperative osteoarthritis as stage 0 (none), stage 1 (mild beaking of the radius without involvement of the radioscaphoid joint), stage 2 (narrowing of the radioscaphoid joint space), or stage 3 (loss of the radioscaphoid joint space). The numbers of patients with each stage were too small for us to make meaningful comparisons among stages; therefore, we combined the patients who had stage-1, 2, or 3 osteoarthritis into one group.

Avascular necrosis was evaluated at the time of the final follow-up on plain radiographs. Postoperative magnetic resonance images were not made. Avascular necrosis was graded as stage 0 (none), stage 1 (patchy areas of radiodensity of the proximal pole), stage 2 (involvement of the entire proximal pole), or stage 3 (avascular necrosis with carpal collapse)²⁵. The tourniquet was not released intraoperatively for the purpose of assessing blood flow to the scaphoid fragments.

Operative Technique

A palmar approach²¹ was used in all patients. Care was taken not to divide the radioscaphoid capitate ligament. Preservation of the radioscaphoid ligament maintained the proximal pole of the scaphoid in a reduced position in the fossa of the distal part of the radius. When the ligament is divided, the proximal pole can translate in a palmar direction during efforts to reduce the fracture. In addition, instability of the scaphoid and lunate ligament complex increases with widening of the scapholunate interval, and rotation of the scaphoid has been demonstrated¹⁴. When the fracture was not seen to reduce under fluoroscopy with extension and ulnar deviation of the wrist, the fracture site was exposed by extending the capsular incision to the level of the radioscaphoid capitate ligament. One of the most important landmarks to guide the realignment of the fractured scaphoid was the articular border of the scaphoid with the capitate. Operative dental picks were used to manipulate and rotate the fragments. The operative dental picks caused less damage to the fracture site than did Kirschner wires inserted perpendicularly as so-called joysticks. Corticocancellous bone graft obtained from the distal aspect of the radius, the olecranon, or the iliac crest was morseled and packed into the fracture site when comminution resulted in the loss of bone continuity following reduction of the fracture. Ten patients in Group 1 and seven patients in Group 2 received a bone graft. When the fracture had minimal comminution and the scaphoid reduced anatomically with manipulation under fluoroscopy, the surgical approach was narrowed to a small longitudinal 1.5-centimeter incision that was centered over the scaphotrapezial joint. Radial and ulnar flaps were elevated to expose the scaphotrapezial joint. A rongeur was used to remove the foot process of the trapezium that lies over the distal pole of the scaphoid; this was done to allow for the placement of the guide-wires or screw into the center of the scaphoid. This portion of the trapezium has no articular cartilage, and its removal causes no degenerative changes in the scaphotrapezial joint²⁵. A 1.0-millimeter guide-wire for the cannulated screw was placed first so that it could be positioned into the center of the scaphoid. The guide-wire was driven up to the level of the subchondral bone of the proximal pole of the scaphoid in order to determine the screw length. We recommend that, when selecting the appropriate cannulated screw, the surgeon err on the side of choosing the shorter screw, as a longer one can either result in a prominent screw in the distal pole of the scaphoid or cause distraction of the scaphoid fracture. In one patient with a severely comminuted fracture, a second 0.035-inch (0.889-millimeter) Kirschner wire was placed across the radial border of the scaphoid perpendicular to the plane of the fracture, to control rotation. The wire was placed to avoid interference with the drill-guide for the cannulated screws. The temporary Kirschner wire controlling rotation was removed eight weeks postoperatively with the use of a local anesthetic.

Once the screw length had been determined with the use of the guide-wire, the guide-wire was driven into the distal part of the radius to prevent it from being dislodged during the drilling and tapping process (Fig. 7). The screw was inserted without the use of a Huene device, the position was confirmed with fluoroscopy, and the guide-wire was removed.

Postoperatively, the upper extremity was placed in a below-the-elbow thumb-spica cast, which was worn for six to eight weeks, and the patients were restricted from any lifting activities. Two patients in Group 1 and three patients in Group 2 who were noncompliant with instructions to avoid lifting wore an above-the-elbow thumb-spica cast for an additional four weeks. After removal of the cast, the patients wore a removable thumb-spica splint for four weeks and were advised to avoid lifting more than ten pounds (4.5 kilograms) until there was radiographic union.

Analysis of Data

The potential confounding variables included age, gender, delay until treatment, involvement of the dominant extremity, severity of the collapse, and severity of the displacement of the fracture as measured on the radiographs. For continuous variables, multiple linear-regression analyses were used, with adjustment for the potential confounding variables. The Cox regression model was used to evaluate the time to union and the placement of the screw along with age, gender, delay until treatment, involvement of the dominant extremity, severity of the initial radiographic displacement, and smoking⁹.

Results

Introduction | Materials and Methods | Results | Discussion | References

In Group 1, the average duration of follow-up was thirty-five months (range, twenty-six to forty months) and the average time to union of the fracture (and standard deviation) was 4.2 ± 1.2 months (range, 2.5 to 7.0 months). In Group 2, the average duration of follow-up was twenty-seven months (range, twenty-four to thirty-three months) and the average time to union of the fracture was 4.0 ± 1.2 months (range, 2.5 to 8.0 months). Five patients in Group 1 and two patients in Group 2 had a delay to union of five months or more.

We were unable to detect any significant differences between the two groups with regard to age, gender, delay until the operation, displacement of the scaphoid fracture, or the presence of avascular necrosis. The scaphoid united in all patients. There was no difference between Group 1 and Group 2 with regard to the severity of deformity on the initial radiographs (Fig. 8). Preoperatively, the average lateral intrascaphoid angle was 51 ± 7 degrees in Group 1 and 50 ± 4 degrees in Group 2; the average anteroposterior intrascaphoid angles were 34 ± 6 and 31 ± 6 degrees, respectively; the average height-to-length ratios were 0.84 ± 0.43 and 0.82 ± 0.44, respectively; and the fractures were displaced an average of 1.2 ± 0.6 and 1.3 ± 0.4 millimeters, respectively.

Postoperatively, the average lateral intrascaphoid angle in both groups decreased significantly (to 33 6 and 35 6 degrees, respectively) (p < 0.01) (Fig. 9). In Group 1 the average anteroposterior angle increased postoperatively to 42 ± 3 degrees, whereas in Group 2 it increased to 40 ± 3 degrees. The height-to-length ratio improved postoperatively to 0.60 ± 0.04 and 0.62 ± 0.04 in Group 1 and Group 2, respectively. The average displacement of the fracture decreased significantly, both in Group 1 (from 1.2 ± 0.6 millimeters preoperatively to 0.3 ± 0.1 millimeter postoperatively; p < 0.05) and in Group 2 (from 1.3 ± 0.4 millimeters preoperatively to 0.1 ± 0.2 millimeter postoperatively; p < 0.05). Postoperatively, the lateral intrascaphoid angle was measured only on the lateral computerized tomography images made at the time of union; therefore, we could not determine if the measurements changed with time. There was no significant difference between the two groups in terms of the degree of correction of the lateral intrascaphoid angle, the scaphoid height-to-length ratio, or the displacement of the fracture (at the 80 percent confidence level).

The time to union in patients with central placement of the screw was compared with that in patients with peripheral placement of the screw, and the time to union in smokers was compared with that in nonsmokers. We defined smokers as patients who, at the time of surgery, smoked at least one cigarette a day. The screw was determined to be peripherally placed in two patients in Group 1 and in one patient in Group 2. Six patients in Group 1 and five patients in Group 2 were classified as smokers. With the use of a Cox proportional-hazards model with backwards stepwise adjustment of the baseline clinical and radiographic variables, central placement of the screw was not found to be associated with more rapid healing in either group because of the extremely small number of peripherally placed screws in each group⁹. However, smoking was found to be associated with slower healing at the 95 percent confidence level in both groups (p < 0.01). Fractures in patients who smoked healed at an average of 5.2 months compared with 3.5 months in patients who did not smoke.

Because the duration of follow-up was different in each of the groups, a Kaplan-Meier¹⁷ estimate was used to evaluate the difference in the time to union between the two screw types; there was no significant difference, with a power of 0.8. A shorter time to union was associated with greater grip strength and with a better range of motion of the wrist in both groups (p < 0.05). An increase in the time to union was correlated with increasing age of the patient (r = 0.665) and with increasing preoperative displacement of the fracture (r = 0.541). The use of bone graft correlated with increasing time to union (p < 0.05), which may represent preselection of patients with a more severe injury (with comminution), as all patients who received bone graft had comminution noted at the time of surgery. The time to union did not correlate with the lateral intrascaphoid angle, anteroposterior intrascaphoid angle, or height-to-length ratio on preoperative radiographs. There was also no correlation between the time to union and gender or hand dominance.

Postoperatively, the average total range of motion on the involved side was 86 ± 8 percent of that on the contralateral side in Group 1; the patients had an average of 120 ± 16 degrees of flexion-extension of the wrist and 35 ± 10 degrees of radioulnar deviation. These results are similar to those in Group 2, in which the range of motion was 86 ± 7 percent of that on the contralateral side and the patients had an average of 113 ± 16 degrees of flexion-extension of the wrist and 35 ± 6 degrees of radioulnar deviation. There was no significant difference in the range of motion between the two groups. Logistic regression analysis with adjustment for clinical and radiographic variables showed that an increasing postoperative range of motion correlated with a decreasing lateral intrascaphoid angle (r = 0.625) and a decreasing scaphoid height-to-length ratio (r = 0.584). Postoperatively, the patients in Group 1 regained an average of thirty-eight kilograms of grip strength, or 80 ± 11 percent of the strength on the contralateral side. The patients in Group 2 regained an average of forty-two kilograms of grip strength, or 79 ± 16 percent of the strength on the contralateral side. Twenty-eight patients who were employed preoperatively returned to their previous occupation after the surgery.

Complications

Two of the patients treated with an AO/ASIF cannulated screw had symptoms related to a prominent screw-head after union of the scaphoid. One patient in each group had pain and irritation related to a prominent wire, requiring early removal of the wire. Only one patient, in Group 1, had evidence of partial avascular necrosis (stage 1) at the final follow-up examination. One patient in Group 1 and one in Group 2 had osteoarthritis (stage 1 in both) by the time of the final follow-up evaluation. None of the patients in either group had symptoms that limited their ability to work. Three patients in Group 1 noted slight pain with strenuous activities (grade 1), as did two patients in Group 2. There was no significant difference in terms of pain at work or during strenuous activity between the groups (p < 0.05).

Discussion

Introduction | Materials and Methods | Results | Discussion | References

Most reports regarding scaphoid fractures have focused on nonunions. Herbert and Fisher¹⁶ reported a 100 percent rate of union following the treatment of 158 acute displaced fractures of the waist of the scaphoid. We are not aware of any published reports that have included patients treated with cannulated screws. In the present retrospective study, we evaluated the results of treatment with two different cannulated screws. We had initially used the cannulated AO/ASIF screw because it was the first screw available on the market that met the design parameters needed to treat scaphoid fractures. Because of problems related to the prominent screw-head in some patients in a previous study²⁵ on the use of 3.5-millimeter cannulated AO/ASIF screws for treatment of scaphoid nonunion, we have subsequently preferred the double-threaded Herbert-Whipple screw, which is a cannulated screw specifically designed for the treatment of scaphoid fractures. Although Stark et al.²⁴ noted an improvement in the scapholunate angle after treatment of scaphoid nonunion with Kirschner wires and bone graft, we know of no reports of improvement in scaphoid alignment as assessed with measurement of the intrascaphoid angle or the scaphoid height-to-length ratio after treatment of scaphoid fractures or nonunions with internal fixation devices.

The rate of union in the present study was 100 percent for both groups of patients. This success rate is most likely attributable to our strict inclusion criteria, which enabled us to select an ideal group of patients. We excluded patients who had a fracture of the proximal pole, osteoarthritis, or carpal instability, all of which have been associated with a decreased rate of union^7,23. Manske et al.¹⁹ demonstrated that the use of a Kirschner wire in addition to a screw controlled the rotation of the fracture fragments and improved both the time to union and the rate of union after treatment of scaphoid nonunion. Therefore, we incorporated this technique into our treatment of acute displaced scaphoid fractures when comminution was present.

Because it is difficult to design a comparative study in which the number of patients is large enough for the rate of union to be used as the end point, we studied the time to union as confirmed by computerized tomography. The importance of using tomography for this purpose was demonstrated by Cooney et al.⁸, who found that patients managed with screw fixation who were thought to have a healed nonunion on the basis of plain radiographs often needed another bone-grafting procedure because of persistent instability. In another study⁷, they used a variety of techniques, including Kirschner wires, in forty-four patients in whom volar inlay grafts were placed, and the time to union averaged eighteen weeks. Stark et al.²⁴ reported an average time to union of seventeen weeks in 147 of 151 patients who had fixation with Kirschner wires in addition to bone-grafting for nonunion of the scaphoid. In the present study of patients with acute fractures, the average time to union was 4.1 ± 1.2 months (range, 2.8 to 8.0 months), although it usually took one month longer to identify a scaphoid union with use of computerized tomography scans than with use of plain radiographs.

The number of patients who were smoking during the treatment was small. Nevertheless, as noted in reports on lower-extremity injuries^4,5,15, smoking was found to have a significant effect on fracture-healing. Regardless of the type of screw used, the time to union was increased in patients who smoked. The mechanism by which smoking affects fracture-healing is unknown.

The functional results in terms of grip strength and range of motion in our study compare very well with those in reports involving nonunions of the scaphoid, although there is very little information on the functional results following internal fixation of acute fractures. It is difficult to compare some of the studies of fractures and nonunions of the scaphoid because the results were not normalized as a percentage of the contralateral side. Although exact numbers were not given, Herbert and Fisher¹⁶ and Filan and Herbert¹³ reported a recovery of grip strength of more than 90 percent compared with that on the contralateral side. With use of a Jamar dynamometer to measure grip strength, we noted an average recovery of 79 percent compared with that on the contralateral side.

The range of motion after internal fixation with or without bone-grafting was reported as a percentage of that on the contralateral side. In the present study, we observed an average total flexion-extension arc of 89 percent of that on the contralateral side and an average radioulnar deviation of 76 percent of that on the contralateral side. Filan and Herbert¹³ noted that their patients regained more than 90 percent of the normal range of motion of the wrist, although specific values were not given. We are not aware of any other studies in which the range of motion was measured and compared with the range on the uninjured side after internal fixation of acute scaphoid fractures. In studies of scaphoid nonunions treated with screw fixation, the range of motion has varied from a flexion-extension arc of 67 percent and a radioulnar deviation of 55 percent¹ to a flexion-extension arc of 84 percent and a radioulnar deviation of 76 percent²⁵.

Another finding in our study, similar to that in other reports, was the relief of pain. Of the thirty-five patients whom we treated, only five (14 percent) continued to have occasional mild pain. These results correspond well with those reported by Filan and Herbert¹³, who noted that 14 percent of 431 patients had an unspecified degree of pain at the time of the latest review. Cooney et al.^6,7 noted that fourteen (21 percent) of sixty-eight patients in whom a scaphoid nonunion had healed continued to have occasional mild pain.

None of the reports that we reviewed provided specific values for preoperative and postoperative intracarpal angles in patients treated for an acute displaced scaphoid fracture. One of the major factors associated with the results in our study was improvement in the alignment of the scaphoid. Amadio et al.² noted that patients who had a malunion of the scaphoid had a twofold increase in the prevalence of osteoarthritis; however, a multivariate regression analysis showed no association between a postoperatively corrected scapholunate angle and an increased prevalence of osteoarthritis, presumably because very few patients had an abnormal scapholunate angle either before or after the surgery. Preoperatively, all of our patients had collapse of the scaphoid with alteration of the anteroposterior intrascaphoid angle, the lateral intrascaphoid angle, or the height-to-length ratio of the scaphoid. We found that patients with more correction of the lateral intrascaphoid angle or the scaphoid height-to-length ratio had more postoperative wrist motion, possibly indicating that the mechanics of the wrist were improved as the scaphoid alignment and height were restored to normal.

There were several weaknesses in our small retrospective study on acute scaphoid fractures. The patient data were provided by a team of different physicians and medical staff, the surgical procedures were performed sequentially by different doctors, and the implants were not randomized for the purpose of this study.

Despite the inherent limitations of our study, we concluded that fixation with use of either the AO/ASIF or the Herbert-Whipple cannulated screw is an effective technique for the internal fixation of displaced fractures of the waist of the scaphoid.

References

Introduction | Materials and Methods | Results | Discussion | References

Adams, B. D., Blair, W. F., Reagan, D. S.,Grundberg, A. B.. Technical factors related to Herbert screw fixation. J. Hand Surg.,13A: 893-899. 1988;13A893 1988

Amadio, P. C., Berquist, T. H., Smith, D. K., Ilstrup, D. M., Cooney, W. P., III,Linscheid, R. L.. Scaphoid malunion. J. Hand Surg.,14A: 679-687. 1989;14A679 1989

Bain, G. I., Bennett, J. D., MacDermid, J. C., Slethaug, G. P., Richards, R. S.,Roth, J. H.. Measurement of the scaphoid humpback deformity using longitudinal computed tomography: intra- and interobserver variability using various measurement techniques.. J. Hand Surg.,23A: 76-81. 1998;23A76 1998

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