Radiographic Change in Articular Reduction After Volar Locking Plating for Intra-Articular Distal Radius Fractures

SCIENTIFIC ARTICLE

Radiographic Change in Articular Reduction After Volar Locking Plating for Intra-Articular Distal Radius Fractures Shun Hashimoto, MD,* Hiroshi Yamazaki, MD, PhD,* Masanori Hayashi, MD, PhD,† Fumihiro Isobe, MD,* Shunsuke Miyaoka, MD,* Yo Kitamura, MD,* Hiroyuki Kato, MD, PhD†

Purpose To examine the stability of the articular reduction 12 weeks after intra-articular distal radius fracture (DRF) fixation with a volar locking plate (VLP). Methods We prospectively assessed for losses in articular reduction, including gap and step, during the 12 weeks following surgery for intra-articular DRF treated with a VLP in 68 wrists. The mean patient age was 62 years (range, 16e88 years). Frontal and lateral digital tomosynthesis, a recently developed form of digital tomography, was employed to measure articular gap and step in the lunate and scaphoid fossa of the radius. The average time between surgery and imaging was 1.2 days (range, 0e2 days) for the first evaluation and 87.0 days (range, 74e105 days) for the second examination. Results The mean gap and step were similar at the first and second examinations: 0.4 mm (SD, 0.8) and 0.3 mm (SD, 0.6) and 0.3 mm (SD, 0.7) and 0.3 mm (SD, 0.5), respectively. Conclusions There was no change in the alignment of the fragments in cases treated with VLP. (J Hand Surg Am. 2019;-(-):1.e1-e6. Copyright Ó 2019 by the American Society for Surgery of the Hand. All rights reserved.) Type of study/level of evidence Therapeutic II. Key words Distal radius fracture, volar locking plate, digital tomosynthesis.

O

IN INTRA-ARTICULAR distal radius fractures (DRFs) with a volar locking plate (VLP) provides adequate fixation.1e3 Modern plating systems offer some potential benefits including locking fixation and an anatomical, lowSTEOSYNTHESIS

From the *Department of Orthopaedic Surgery, Aizawa Hospital; the †Department of Orthopaedic Surgery, Shinshu University School of Medicine, Matsumoto, Japan. Received for publication June 23, 2018; accepted in revised form August 20, 2019. No benefits in any form have been received or will be received related directly or indirectly to the subject of this article. Corresponding author: Hiroshi Yamazaki, MD, PhD, Department of Orthopaedic Surgery, Aizawa Hospital, Honjo 1-5-2, Matsumoto 390-8510, Japan; e-mail: [email protected]. 0363-5023/19/---0001$36.00/0 https://doi.org/10.1016/j.jhsa.2019.08.012

profile design. The literature suggests that intra- and extra-articular DRFs do not show differences in fracture reductions including volar tilt, radial inclination, or ulnar variance 6 months following osteosynthesis using a VLP.1,2 Articular incongruity (gap and step) can be determined using computed tomography (CT).4e6 A CT scan can improve the assessment of articular alignment, but is expensive and associated with radiation exposure. Digital tomosynthesis7e9 is an alternative technique that acquires a series of projection images over a limited angular range and allows the reconstruction of an arbitrary number of 2-dimensional image slices (Fig. 1) through a 3dimensional volume.10 It produces high-resolution sectional images at lower irradiation doses and potentially lower costs than CT.11 Moreover, the reliability

Ó 2019 ASSH

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FIGURE 1: Lateral digital tomosynthesis image showing articular step of 0.5 mm (A, arrow) and frontal image depicting articular gap of 1 mm (B, arrow).

METHODS Study design This is a single-center, 12-week, cohort study done at a private hospital in Japan. We prospectively identified patients with an intra-articular DRF treated with a VLP. Open fractures that required an external fixator were excluded. Other exclusion criteria were a history of prior wrist surgery or trauma and patients with open physes. Eighty-eight fractures in 87 patients entered this study between November 2014 and September 2017. We excluded 19 fractures owing to incomplete data, including loss to follow-up (n ¼ 4) and incomplete radiographic evaluations (n ¼ 15). No additional fixation of small fragments with K-wires, screws, or a plate was performed. No bone grafting was used. Ultimately, 68 fractures in 67 patients were enrolled in the study sample. The demographic characteristics, except distribution of the type of plate, were similar between the included and the excluded groups (Table 1). The study was completed in December 2017. There was no change to the methods after commencement of the study.

carried out through a flexor carpi radialis sheath approach. After release of the pronator quadratus muscle from the radius, fracture reduction was done using the Kapandji technique12 with K-wires placed into the fracture under fluoroscopy (Premier Encore; Hologic, Bedford, MA). Fluoroscopic images were obtained to evaluate articular reduction and included standard posteroanterior and lateral views as well as anatomical posteroanterior (11 tilt) and lateral (23 tilt) views.13 Two comminuted fractures with central depression required supplementary arthroscopic reduction. No arthrotomy was performed. Fractures were fixed with an anatomically designed VLP selected according to the surgeon’s preference (Table 1). All cases followed the same postoperative rehabilitation protocol. The wrist was immobilized in a short-arm volar plaster orthosis immediately after surgery, and the patient was encouraged to perform active shoulder, elbow, and finger movements in addition to rotational exercises of the forearm. At the first postoperative visit approximately 3 days after surgery, a removable orthosis was applied and active wrist range of movement exercises were initiated. The patient was instructed to wear the orthosis at all times except during exercises. At 3 weeks after surgery, patients were weaned from the orthosis. At 6 weeks after surgery, gentle passive wrist range of motion exercises were started as guided by a physiotherapist. At 9 weeks, gentle strengthening exercises were encouraged. Lifting heavy objects and load-bearing were discouraged until the completion of rehabilitation at 12 weeks after surgery.

Intervention Surgeries were performed by an author (H.Y.), or 1 of 7 surgeons under his supervision. Volar plating was

Outcomes The primary outcome of interest was defined as the loss of articular reduction during the 12 weeks

of this method for assessing articular incongruities in intra-articular DRFs is reportedly equal to that of CT.7 The purpose of this study was to examine the stability of the articular reduction 12 weeks after intra-articular DRF fixation with a VLP.

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iSite Picture Archiving and Communication System (PACS) workstation (V5 Impax; Agfa Health Care Japan, Ltd., Tokyo, Japan).

TABLE 1. Demographic Characteristics of Wrists Related to the Present Study

Age (y)* †

Female

Included Group (n ¼ 68)

Excluded Group (n ¼ 19)

62  15

65  17

46 (67)

13 (68)

Raters: Two orthopedic surgeons not involved in the care of the patients assessed all wrist images. The raters measured the articular gap and step at the lunate and scaphoid fossa using digital tomosynthesis. Representative digital tomosynthesis images, which had the largest articular displacement, were selected for measurement by consensus between the raters. The same sites of articular displacement were measured at the first and second evaluations. The selected images were randomly mixed for each patient. However, we did not combine the studies from the 2 sessions nor sort them randomly. The raters also assessed for screw penetration into the radiocarpal joint. Radiographic alignment, including radial inclination, ulnar variance, and volar tilt, were measured according to the methods described by Kreder et al14 by a single measurement under suitable magnification from a PACS monitor. Measurements were recorded at minimum units of 0.5 mm and 1 . The measurements were taken using the digital measuring tool on the PACS. The raters classified the fractures according to the AO group. Discrepancies between raters regarding the fracture classification were resolved by consensus.

Fracture type (AO type)† B

13 (19)

3 (16)

C1

27 (40)

12 (63)

C2

18 (26)

2 (11)

C3

10 (15)

2 (11)

Acu-Loc 2 distal

35 (51)

6 (32)

Acu-Loc 2 proximal

18 (26)

3 (16)

VariAx

14 (21)

8 (42)

1 (1)

2 (11)

Plate system

DVR

†

Acu-Loc 2, Acu-Loc 2 VDR Plate (Acumed, Hillsboro, OR); DVR, DVR Anatomic Volar Plating System (Zimmer Biomet, Warsaw, IN); VariAx, VariAx Distal Radius Locking Plate System (Stryker Corporation, Kalamazoo, MI). *Values are expressed as the mean and SD. †Values are expressed as the number of patients, with percentages in parentheses.

following surgery. Articular incongruity, including gap and step, was determined by digital tomosynthesis.

Sample size Intra-articular displacement of with 0.5 mm or greater was considered as a minimal clinically important difference.3 A minimum sample size of 88 patients was estimated to detect a medium effect size (0.3) in the proportion of cases with intra-articular displacement that exceeded 0.5 mm, with 80% power at a of 0.05, using a 2-sided Fisher exact test.

Assessment: All patients were investigated by means of both digital tomosynthesis and standard radiographs of the wrist obtained the next day and at 12 weeks after surgery. We used frontal and lateral views of digital tomosynthesis to measure articular gap and step in the lunate and scaphoid fossa of the radius (Fig. 1). Standard anteroposterior and lateral radiographs were employed to assess fracture reduction, including volar tilt, radial inclination, and ulnar variance.

Statistical analysis The sample and measurement data are summarized by proportions for categorical variables (sex, fracture type, plate system, and screw penetration into the radiocarpal joint) and mean and SD for continuous variables (age, gap, step, radial inclination, volar tilt, and ulnar variance). The proportion of patients in whom there was a difference that exceeded the definition of clinical relevance is expressed as lost reduction group (gap or step  0.5 mm) and maintained reduction group (< 0.5 mm). Fisher exact test was used to compare the proportions of the groups. A P value of less than .05 was considered statistically significant.

Digital tomosynthesis: A volumetric x-ray digital linear tomosynthesis system (Sonialvision Safire; Shimadzu Co., Kyoto, Japan) was used to obtain tomosynthesis images of 0.5 mm slice thickness. Frontal and lateral image slices numbered approximately 90 to 120 and 120 to 150, respectively. The images were reconstructed using filtered back-projection algorithms. Image filtering to minimize the effects of metal artifacts included Thicknessþþ reconstruction. Images were transferred from the scanner to a Ziosoft M900 Quadra version 3.10f workstation (Ziosoft Inc., Tokyo, Japan) and visualized on a Phillips-Stentor J Hand Surg Am.

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TABLE 2.

LOSS OF ARTICULAR REDUCTION AFTER VOLAR PLATING

Radiographic Outcomes First Examination

Second Examination

31 (46)

27 (40)

Gap (mm)

0.4  0.8

Step (mm)

0.3  0.7 21  3 74 0.2  1.2

0.6  1.3

1 (1)

1 (1)

0.5 mm or greater in gap or step*

Difference

95% CI

0.3  0.6

e0.1

e0.3 to 0.0

0.2  0.5

e0.1

e0.2 to 0.0

22  3

0.4

e0.1 to 0.8

64

e0.5

e1.1 to 0.3

Radiographic parameters†



Radial inclination ( ) Volar tilt ( ) Ulnar variance (mm) Screw penetration into radiocarpal joint*

0.4

0.2 to 0.6

95% CI, 95% confidence interval. *Values are expressed as the number of patients, with percentages in parentheses. †Values are expressed as the mean and SD.

RESULTS The average time between surgery and imaging was 1.2 days (SD, 1.3; range, 0e2 days) for the first evaluation and 87.0 days (SD, 11.6; range, 74e105 days) for the second examination. The radiographic measurements are summarized in Table 2. The proportion of the lost reduction group was similar between the 2 radiographic assessments obtained the next day and at 12 weeks after surgery (Table 2). In addition, the mean gap and step were similar between the first and the second examinations. Other measurements, including volar tilt and radial inclination, were also similar between each evaluation point. Only ulnar variance at the second evaluation was larger than at the first evaluation. We detected 1 case (1%) of screw penetration in the radiocarpal joint and none over the dorsal cortex of the radius. Bone healing had occurred in all patients at 12 weeks of follow-up. Demographic characteristics of the lost reduction group and the maintained reduction group are shown in Table 3. Women were more likely to develop loss of articular reduction than men. Patient age, fracture type, and plate systems were similar between the groups. The proportion of the patients in whom loss of articular step or gap was 0.5 mm or greater was similar between the younger group (< 65 years old, n ¼ 34) and the older group ( 65 years old, n ¼ 34): 7 patients (21%) in the younger group and 10 patients (29%) in the older group. In addition, the mean changes in the gap and step were similar between the groups: 0.2 mm (SD, 0.6) and 0.0 mm (SD, 0.5) in the younger group and 0.1 mm (SD, 0.7) and 0.0 mm (SD, 0.3) in the older group. J Hand Surg Am.

TABLE 3. Demographic Characteristics of Lost Reduction Group (Gap or Step ‡ 0.5 mm) and Maintained Reduction Group (< 0.5 mm) Lost Reduction Group (n ¼ 17)

Maintained Reduction Group (n ¼ 51)

67  8

60  17

15 (88)

31 (61)

B

2 (12)

11 (22)

C1

4 (24)

23 (45)

C2

6 (35)

12 (24)

C3

5 (29)

5 (10)

Acu-Loc 2 distal

9 (53)

26 (51)

Acu-Loc 2 proximal

6 (35)

12 (24)

VariAx

2 (12)

12 (24)

0

1 (2)

Age (y)* Female

†

Fracture type (AO type)†

Plate system†

DVR

Acu-Loc, Acu-Loc 2 VDR Plate (Acumed, Hillsboro, OR); DVR, DVR Anatomic Volar Plating System (Zimmer Biomet, Warsaw, IN); VariAx, VariAx Distal Radius Locking Plate System (Stryker Corporation, Kalamazoo, MI). *Values are expressed as the mean and standard deviation. †Values are expressed as the number of patients, with percentages in parentheses.

The proportion of patients in whom loss of articular step or gap was 0.5 mm or greater was similar between the AO type B fracture (n ¼ 13) and the AO type C fracture (n ¼ 55): 2 patients (15%) in the type B and 15 patients (27%) in the type C. In addition, the mean changes in the gap and step were similar r

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between the AO type B and the AO type C: 0.1 mm (SD, 0.6) and 0.1 mm (SD, 0.3) in the type B and 0.1 mm (SD, 0.7) and 0.1 mm (SD, 0.5) in the type C. The proportion of the patients in whom loss of articular step or gap was 0.5 mm or greater was similar in the AO fracture subtype C: 4 patients (15%) in the subtype C1 (n ¼ 27), 6 patients (33%) in the subtype C2 (n ¼ 18), and 5 patients (50%) in the subtype C3 (n ¼ 10). In addition, the mean changes in the gap and step were similar in the AO fracture subtype C: 0.2 mm (SD, 0.4) and 0.1 mm (SD, 0.4) in the subtype C1 (n ¼ 27) and 0.1 mm (SD, 0.7) and 0.0 mm (SD, 0.4) in the subtype C2 (n ¼ 18), and 0.3 mm (SD, 1.1) and 0.3 mm (SD, 0.7) in the subtype C3 (n ¼ 10). The losses in articular reduction were similar between the plate systems. The proportion of the patients in whom losses of articular step or gap were 0.5 mm or greater is summarized in Table 3. In addition, the mean changes in the gap and step were similar between the plate systems: 0.1 mm (SD,: 0.5) and 0.0 mm (SD, 0.3) in AcuLoc 2 distal plate, 0.3 mm (SD, 0.9) and 0.1 mm (SD, 0.7) in AcuLoc 2 proximal plate, 0.1 mm (SD, 0.6) and 0.1 mm (SD, 0.3) in VariAx, and 0.0 mm and 0.0 mm in the DVR Anatomic Volar Plating System (Zimmer Biomet, Warsaw, IN).

configuration and technique. One of the most important factors in providing stability to volar plating is the positioning of distal screws close to the subchondral cortex,17,18 although overly distal placement of the plate can cause flexor tendon problems19e21 and intra-articular screw penetration.16 In our cohort, plate systems including a proximally or distally placed device seemed to be unrelated to loss of articular reduction. Anatomical reduction is the main surgical goal for intra-articular DRFs, but this outcome might be disrupted during postoperative exercise or due to osteoporosis in the elderly. We found that female patients were more likely to develop loss of articular reduction than male patients. We evaluated articular reduction at 12 weeks of follow-up because DRFs are usually healed after 7 to 11 weeks22 and confirmed bone healing in all patients. Our study had several limitations. First, a large number of patients (20 patients; 23%) were removed. The exclusion of those patients could have distorted our data. Second, the type of implants varied between those patients included and those excluded. This suggests some risk of selection bias. Third, most of the fractures might be of a relatively minor degree of severity. There were only 2 cases that required supplementary arthroscopic reduction. The findings might be different in more unstable fractures. Fourth, this study contained relatively young patients; our findings might have been different for more elderly patients with osteopenia. Fifth, the studies from the 2 sessions were not combined and sorted randomly. Our strategy might have injected some bias into the data because raters would have knowledge of where and by how much there was articular displacement. Lastly, it is uncertain if the accuracy of the digital tomosynthesis can detect changes as small as 0.5 mm. This measurement tool might be inadequate for investigating the subtle changes.

DISCUSSION This study assessed for losses in articular reduction after volar locking plating for intra-articular DRFs using digital tomosynthesis. Compared with the first postoperative evaluation, digital tomosynthesis taken at the second evaluation 12 weeks later revealed similar findings in relation to articular gap or step. The proportion of patients with articular reduction loss was also similar between each evaluation points. Our data suggest that articular reduction can be preserved by the VLP system in patients treated for intraarticular DRF. We detected similarly minor, likely clinically irrelevant, changes in ulnar variance of 0.4 mm. Neuhaus et al15 reported that secondary displacement of ulnar variance at 3 months or more after volar locking plating was small (0.7 mm) and unremarkable. Loss of radial height and radiographs in different positions of rotation of the forearm could produce the change in ulnar variance. In examination of intra-articular screw penetration, we observed rates (1 of 68, 1%) that were comparable with those of published data (3 of 315, 1%; and 1 of 114, 1%).16 Positioning of the distal radial screws depends on many factors, such as fracture J Hand Surg Am.

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ACKNOWLEDGMENTS The institutional review board reviewed and approved the protocol prior to study initiation. All patients provided written informed consent for participation in the study. REFERENCES 1. Souer JS, Ring D, Jupiter J, et al. Comparison of intra-articular simple compression and extra-articular distal radial fractures. J Bone Joint Surg Am. 2011;93(22):2093e2099. 2. Souer JS, Ring D, Matschke S, et al. Effect of an unrepaired fracture of the ulnar styloid base on outcome after plate-and-screw fixation of a distal radial fracture. J Bone Joint Surg Am. 2009;91(4):830e838.

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