This Article Abstract Full Text (PDF) Free Letters to the Editor: Submit a response Alert me when this article is cited Alert me when Letters to the Editor are posted Alert me if a correction is posted Services E-mail this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to My File Cabinet Download to citation manager Rights and Permissions Citing Articles Citing Articles via Google Scholar Google Scholar Articles by GOURINENI, P. V. R. K. V. Articles by NUBER, G. F. Search for Related Content PubMed PubMed Citation Articles by GOURINENI, P. V. R. K. V. Articles by NUBER, G. F. Social Bookmarking                   What's this?

Radiographic Evaluation of the Position of Implants in the Medial Malleolus in Relation to the Ankle Joint Space: Anteroposterior Compared with Mortise Radiographs*

PRASAD V. R. K. V. GOURINENI, M.D., ALBERT E. KNUTH, M.D. and GORDON F. NUBER, M.D.§, CHICAGO, ILLINOIS

Investigation performed at the Department of Orthopaedic Surgery, Northwestern University Medical School, Chicago

	Abstract

Top Abstract Introduction Materials and Methods Results Discussion References

 
Background: Displaced transverse fractures of the medial malleolus are commonly treated with open reduction and internal fixation with two screws or wires. A mortise radiograph is often used to verify the position of the implants relative to the joint space. However, because the medial and lateral talomalleolar spaces are normally not parallel, the mortise projection (which is colinear with the lateral space) does not provide an accurate radiograph of the medial joint space. Methods: In ten cadaveric ankles, two wires were inserted into the medial malleolus, as is done for fixation of a fracture, and the distance of the wires from the joint space was measured on an anteroposterior radiograph, on mortise radiographs made with the foot in 15 and 30 degrees of internal rotation, and on anatomical cross section. Results: The measurement on the anteroposterior radiograph exceeded the anatomical measurement in only two specimens, and the discrepancy was 0.5 millimeter in both instances. Measurement of the osseous thickness between the joint surface and the posterior wire on the mortise radiographs always revealed a lower value than the measurements on the anteroposterior radiograph and the anatomical cross section of the same specimen. There was a false appearance of intra-articular placement of the posterior wire on the 15-degree mortise radiographs of four specimens and on the 30-degree mortise radiographs of eight specimens. Conclusions: These findings demonstrate that the mortise projection provides an oblique radiograph of the medial joint space that can inaccurately reflect the true position of fixation implants in the medial malleolus. Because an anteroposterior radiograph is made with the articular surface of the medial malleolus tangential to the beam, it provides a more accurate representation of implants in the medial malleolus. Clinical Relevance: We recommend the use of an anteroposterior radiograph to properly evaluate the position of implants used in the treatment of transverse fractures of the medial malleolus. This type of radiograph allows a more lateral starting point for insertion of the fixation device, more accurate intraoperative evaluation of the position of the implants, and better fixation of fractures of the medial malleolus.

	Introduction

Top Abstract Introduction Materials and Methods Results Discussion References

 
A common treatment for transverse fractures of the medial malleolus is open reduction and internal fixation with two screws or wires. The reduction of the fracture and the position of the screws or wires after placement can be evaluated by means of direct inspection of the joint and intraoperative radiography⁷.

Anteroposterior, lateral, and mortise radiographs are recommended for intraoperative evaluation of the position of the implants in relation to the joint space. Some authors have emphasized reliance on the mortise radiograph^1-3,6. At the AO Basic Course held in Charlotte, North Carolina, in June 1997, twenty-three of the twenty-six faculty members were asked by one of us (P. V. G.) whether they found the anteroposterior or the mortise radiograph to be more reliable for evaluating the position of a medial malleolar screw in relation to the ankle joint space. Nineteen preferred the mortise radiograph, and four thought that the mortise radiograph might be misleading.

Normally, the talar dome is wider anteriorly than posteriorly, and the medial and lateral talomalleolar spaces are not parallel. Thus, in most patients, no single radiograph can show the two spaces colinear to the beam⁹. (Occasionally, the talar dome is not wider anteriorly, and the two spaces can be visualized on one radiograph.)

The lateral space is externally rotated 15 to 20 degrees compared with the long axis of the foot; thus, an ankle mortise radiograph, which is made with the beam parallel to this joint (the radiograph is made with the foot in 15 to 20 degrees of internal rotation), shows this space well. The mortise radiograph also allows accurate measurement of the medial space with use of the anterior osseous landmarks of the talus and the medial malleolus. However, because the mortise projection is oblique (rather than parallel) to the joint surface of the medial malleolus, it does not provide an accurate radiograph of the medial joint space. In contrast, an anteroposterior radiograph is made with the articular surface of the medial malleolus tangential to the beam; consequently, an anteroposterior radiograph provides a more accurate view of the medial joint space.

We conducted a study to compare the accuracy of anteroposterior radiographs with that of mortise radiographs for verifying the position of fixation implants in the medial malleolus in relation to the ankle joint space.

	Materials and Methods

Top Abstract Introduction Materials and Methods Results Discussion References

 
Ten preserved cadaveric leg specimens with an intact foot and ankle were examined physically and radiographically to rule out gross anatomical abnormalities. Two Kirschner wires were inserted into the medial malleolus of each ankle and passed proximally into the distal part of the tibia with a technique similar to that used for fixation of transverse fractures of the medial malleolus. The wires were placed parallel and one centimeter apart, one anterior to and one posterior to the tip of the medial malleolus. In one cadaveric ankle (Specimen 10), the posterior margin of the medial malleolus was marked by placing a wire subperiosteally along the surface of the bone (Figs. 2-A, 2-B, and 2-C).

View larger version (110K): [in this window] [in a new window]   FIG2-A: Fig. 2-A Anteroposterior radiograph (Fig. 2-A), 15-degree mortise radiograph (Fig. 2-B), and 30-degree mortise radiograph (Fig. 2-C) of the same ankle-joint specimen. There is more obliquity with the internal rotations of the foot for the two mortise radiographs. The posterior margin of the articular surface of the medial malleolus is shown with a wire marker.

View larger version (104K): [in this window] [in a new window]   FIG2-B: Fig. 2-B Anteroposterior radiograph (Fig. 2-A), 15-degree mortise radiograph (Fig. 2-B), and 30-degree mortise radiograph (Fig. 2-C) of the same ankle-joint specimen. There is more obliquity with the internal rotations of the foot for the two mortise radiographs. The posterior margin of the articular surface of the medial malleolus is shown with a wire marker.

View larger version (117K): [in this window] [in a new window]   FIG2-C: Fig. 2-C Anteroposterior radiograph (Fig. 2-A), 15-degree mortise radiograph (Fig. 2-B), and 30-degree mortise radiograph (Fig. 2-C) of the same ankle-joint specimen. There is more obliquity with the internal rotations of the foot for the two mortise radiographs. The posterior margin of the articular surface of the medial malleolus is shown with a wire marker.

The medial malleolus was then cut with a saw at the level of the plafond with the wires in situ. The tibial plafond was visualized by removing the soft tissues. The anatomical thickness of the bone between the most lateral part of each wire and the nearest point of the medial articular surface was measured with a ruler on each cross section by an independent examiner.

	Results

Top Abstract Introduction Materials and Methods Results Discussion References

 
The measurement of osseous thickness on the anteroposterior radiograph exceeded the anatomical measurement in only two instances (Specimens 1 and 7 [posterior wires]), and the discrepancy was 0.5 millimeter in both (Table I). Measurement of the osseous thickness between the joint surface and the posterior wire on the two mortise radiographs consistently revealed lower values than did the measurements on the anteroposterior radiograph and the anatomical cross section (Table I). There was a false appearance of intra-articular placement of the implant on the 15-degree mortise radiographs of Specimens 2, 3, 4, and 9 (Figs. 1-A and 1-B) and on the 30-degree mortise radiographs of Specimens 2 through 6, 8, 9, and 10.

View larger version (113K): [in this window] [in a new window]   FIG1-A: Fig. 1-A Anteroposterior radiograph (Fig. 1-A) and 15-degree mortise radiograph (Fig. 1-B) of the same ankle-joint specimen. There is a false appearance of intra-articular placement of the posterior wire on the mortise radiograph.

View larger version (113K): [in this window] [in a new window]   FIG1-B: Fig. 1-B Anteroposterior radiograph (Fig. 1-A) and 15-degree mortise radiograph (Fig. 1-B) of the same ankle-joint specimen. There is a false appearance of intra-articular placement of the posterior wire on the mortise radiograph.

Mild internal rotation of the medial joint space was noted even on the anteroposterior radiograph, and the obliquity increased with the internal rotations of the ankle for the two mortise radiographs (Figs. 2-A, 2-B, and 2-C). In the seven ankles (Specimens 1, 2, 4, 5, 7, 8, and 10) in which the joint lines were clearly visualized on all three radiographs, the measurement of the medial space was the same on the anteroposterior radiograph and the two mortise radiographs.

The mean difference between the position of the posterior wire that was determined by anatomical measurement and that measured on the anteroposterior radiographs was 1.70 millimeters (range, -0.5 to 5.5 millimeters) (p < 0.02, one-sample t test). The mean difference between the anatomical measurements and the measurements on the 15-degree mortise radiographs was 5.25 millimeters (range, 1.5 to nine millimeters) (p < 0.0002, one-sample t test). The measurements on the 30-degree mortise radiographs of Specimens 3, 6, and 9 were unclear; the mean difference between the anatomical measurements and the measurements on the 30-degree mortise radiographs of the remaining specimens was 7.57 millimeters (range, 3.5 to 13.5 millimeters). As the values on the 30-degree mortise radiographs were so different from the anatomical measurements, no statistical analysis was performed. When the three ankles (Specimens 4, 9, and 10) with the false increases in the anatomical measurements were excluded from the statistical analysis, the mean difference between the anatomical measurements and the measurements on the anteroposterior radiographs was 0.64 millimeter (p < 0.07) and the mean difference between the anatomical measurements and the measurements on the 15-degree mortise radiographs was 4.29 millimeters (p < 0.004). The lateral radiographs showed all of the wires to be within the outline of the tibia.

A repeated-measures analysis of four measures (the anatomical measurement and the measurements on the anteroposterior, 15-degree mortise, and 30-degree mortise radiographs) showed an overall p value of <0.001. (The three specimens for which the measurements on the 30-degree mortise radiographs were unclear were excluded from this analysis.) With the numbers available, no significant difference could be detected between the measurements on the anteroposterior radiographs and the anatomical measurements, but the measurements on the 15-degree and 30-degree mortise radiographs differed from each other and from the measurements on the anteroposterior radiographs and the anatomical measurements according to the Student-Newman-Keuls test for multiple comparisons (p < 0.05). The measurements on the anteroposterior and 15-degree mortise radiographs correlated with the anatomical measurements (Pearson's correlation coefficient, r = 0.6). No correlation was found between the measurements on the 30-degree mortise radiographs and the anatomical measurements (Pearson's correlation coefficient, r = -0.04).

An additional analysis to assess the agreement between the anatomical measurements of the osseous thickness between the joint surface and the posterior wire and the measurements of that parameter on the anteroposterior radiographs revealed no correlation of the difference between the two with the estimated size.

	Discussion

Top Abstract Introduction Materials and Methods Results Discussion References

 
Transverse fractures are common in the medial malleolus and are usually treated with open reduction and fixation with anterior and posterior wires or cancellous-bone screws. However, fixation of these fractures is technically challenging. The starting point of the drill at the tip of the medial malleolus is important.

A medial starting hole can keep the fixation implant clear of the joint, but the medial cortical bridge between the fracture and the starting hole becomes smaller, risking comminution and poor fixation of the fracture fragment. If the starting point is too medial, the implant may not be perpendicular to the fracture, and the fixation is usually suboptimum (especially in smaller fragments) (Fig. 3).

View larger version (24K): [in this window] [in a new window]   FIG3: Fig. 3 Illustration of the two starting points on the tip of the medial malleolus for the placement of an implant. A medial starting point (A) may not provide adequate fixation. If the starting point is too lateral (B), the implant may penetrate the joint.

Direct inspection of the joint and intraoperative radiography are important means with which to evaluate the placement of the implant⁷. Direct inspection of the superomedial corner of the ankle joint appears to be a logical method, but it has limitations. Once the fracture is reduced and fixed, the deltoid ligament may not allow much displacement of the talus, making adequate visualization of the joint surface difficult. Also, the threads of the cancellous-bone screw can cut into the cartilage in their path to the metaphyseal bone, even though the narrower shank of the screw is outside of the joint.

Anteroposterior, lateral, and mortise radiographs are commonly used to evaluate ankle fractures and their treatment. Two parallel wires or screws, one placed anterior and one positioned posterior to the tip of the malleolus, are used for internal fixation of transverse fractures of the medial malleolus. The posterior wire must be positioned more medially to appear to be outside of the joint on the mortise radiograph. This is not the case with anteroposterior radiographs. Most posterior implants that are inserted through the tip of the medial malleolus appear to be well placed on anteroposterior radiographs but seem to be in an unacceptable position on mortise radiographs.

On cross section, the medial malleolus is D-shaped with a straight joint surface. On anteroposterior radiographs, the anterior and posterior margins of the joint surface overlap, and the medial and superior joint spaces are seen clearly from front to back (Fig. 4-A). On mortise radiographs, the superior and lateral spaces are seen clearly, but the medial space is oblique, with overlap of the posterior margin of the malleolus on the talus (Fig. 4-B). This leads to the false appearance of intra-articular placement of the posterior implant on the mortise radiograph, while the anteroposterior radiograph shows the true position (Figs. 5-A, 5-B, 5-C and 5-D).

View larger version (20K): [in this window] [in a new window]   FIG4-A: Fig. 4-A Illustrations of the radiographic appearance of the medial malleolus. The anteroposterior radiograph (Fig. 4-A) shows the medial and superior joint spaces well, but the lateral space is not visualized. The mortise radiograph (Fig. 4-B) shows the superior and lateral spaces well, but the medial space is oblique with overlap of the posterior margin of the malleolus on the talus.

View larger version (21K): [in this window] [in a new window]   FIG4-B: Fig. 4-B Illustrations of the radiographic appearance of the medial malleolus. The anteroposterior radiograph (Fig. 4-A) shows the medial and superior joint spaces well, but the lateral space is not visualized. The mortise radiograph (Fig. 4-B) shows the superior and lateral spaces well, but the medial space is oblique with overlap of the posterior margin of the malleolus on the talus.

View larger version (19K): [in this window] [in a new window]   FIG5-A: Fig. 5-A Illustrations of the radiographic appearance of the medial malleolus after placement of fixation screws. The anteroposterior radiograph (Fig. 5-A) shows the actual position of the screws. The mortise radiograph (Fig. 5-B) erroneously shows intra-articular positioning of the posterior screw.

View larger version (19K): [in this window] [in a new window]   FIG5-B: Fig. 5-B Illustrations of the radiographic appearance of the medial malleolus after placement of fixation screws. The anteroposterior radiograph (Fig. 5-A) shows the actual position of the screws. The mortise radiograph (Fig. 5-B) erroneously shows intra-articular positioning of the posterior screw.

View larger version (21K): [in this window] [in a new window]   FIG5-C: Fig. 5-C Illustrations showing that when the radiographic beam (arrows) is tangential to the medial joint space, as it is for an anteroposterior radiograph (Fig. 5-C), the position of the screws is accurately depicted. When the radiographic beam is at an angle to the medial joint space, as it is for a mortise radiograph (Fig. 5-D), the position of the posterior screw erroneously appears to be intra-articular.

View larger version (22K): [in this window] [in a new window]   FIG5-D: Fig. 5-D Illustrations showing that when the radiographic beam (arrows) is tangential to the medial joint space, as it is for an anteroposterior radiograph (Fig. 5-C), the position of the screws is accurately depicted. When the radiographic beam is at an angle to the medial joint space, as it is for a mortise radiograph (Fig. 5-D), the position of the posterior screw erroneously appears to be intra-articular.

The measurements of the medial joint space were the same on the anteroposterior and mortise radiographs when the anterior landmarks were used. However, on the mortise radiographs, the posterior part of the malleolus overlapped on the talus because of internal rotation of the tibia and the posterior margin of the joint was not clearly visualized.

In our study, the anatomical measurements of osseous thickness were almost all equal to or greater than the measurements on the anteroposterior radiographs; this finding indicates that osseous thickness will not be overestimated on such radiographs. The anatomical measurements were much greater than all of the measurements on the mortise radiographs of all of the specimens. This discrepancy on the mortise radiographs increased as the degree of internal rotation of the foot increased (Figs. 2-A, 2-B, and 2-C). In addition, the posterior wire appeared to be intra-articular on the 15-degree mortise radiographs of four specimens and on the 30-degree mortise radiographs of eight specimens when, in fact, none of the wires were intra-articular.

In conclusion, we found that a mortise radiograph provides an oblique view of the medial joint space; consequently, the positions of wires or screws in the medial malleolus can be misrepresented. In contrast, with an anteroposterior radiograph, the articular surface of the medial malleolus is tangential to the beam; thus, the positions of implants in the medial malleolus are seen more accurately.

We recommend the use of an anteroposterior radiograph to properly evaluate the positions of screws or wires used in the treatment of transverse fractures of the medial malleolus. This will allow for a lateral starting point of insertion on the tip of the medial malleolus, more accurate evaluation of the position of the implants, and better fixation of these fractures.

	Footnotes

 
*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.

628 South Adams, Hinsdale, Illinois 60521. E-mail address for Dr. Gourineni: gourineni@hotmail.com.

450 West Highway 22, Suite 100, Barrington, Illinois 60010.

§680 North Lake Shore Drive, Suite 1206A, Chicago, Illinois 60611.

	References

Top Abstract Introduction Materials and Methods Results Discussion References

 

1. Geissler, W. B.; Tsao, A. K.; and Hughes, J. L.: Fractures and injuries of the ankle. In Rockwood and Green's Fractures in Adults. Ed. 4, pp. 2219-2227. Philadelphia, Lippincott-Raven, 1996.
2. Goergen, T. G.; Danzig, L. A.; Resnick, D.; and Owen, C. A.: Roentgenographic evaluation of the tibiotalar joint. J. Bone and Joint Surg., 59-A: 874-877, Oct. 1977.[Free Full Text]
3. Pankovich, A. M.: Trauma to the ankle. In Disorders of the Foot and Ankle. Medical and Surgical Management, edited by M. H. Jahss. Ed. 2, p. 2389. Philadelphia, W. B. Saunders, 1991.
4. Resnick, D., and Niwayama, G.: Anatomy and individual joints. In Diagnosis of Bone and Joint Disorders, edited by D. Resnick. Ed. 3, p. 751. Philadelphia, W. B. Saunders, 1995.
5. Sartoris, D. J., and Resnick, D.: Plain film radiography: routine and specialized technique and projections. In Diagnosis of Bone and Joint Disorders, edited by D. Resnick. Ed. 3, p. 34. Philadelphia, W. B. Saunders, 1995.
6. Shelton, M. L.: Complications of fractures and dislocations of the ankle. In Complications in Orthopaedic Surgery, edited by C. H. Epps, Jr. Ed. 3, vol. 2, p. 621. Philadelphia, J. B. Lippincott, 1994.
7. Taylor, J. C.: Fractures of lower extremity. In Campbell's Operative Orthopaedics, edited by A. H. Crenshaw. Ed. 8, p. 785. St. Louis, Mosby-Year Book, 1992.
8. Weber, M. J.: Ankle fractures and dislocations. In Operative Orthopaedics, edited by M. W. Chapman. Ed. 2, vol. 1, p. 732. Philadelphia, J. B. Lippincott, 1993.
9. Yablon, I. G., and Segal, D.: Ankle fractures. In Surgery of the Musculoskeletal System, edited by C. McC. Evarts. Ed. 2, p. 3831. New York, Churchill Livingstone, 1990.

CiteULike

Connotea

Del.icio.us

Facebook

Technorati

Twitter

This Article Abstract Full Text (PDF) Free Letters to the Editor: Submit a response Alert me when this article is cited Alert me when Letters to the Editor are posted Alert me if a correction is posted Services E-mail this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to My File Cabinet Download to citation manager Rights and Permissions Citing Articles Citing Articles via Google Scholar Google Scholar Articles by GOURINENI, P. V. R. K. V. Articles by NUBER, G. F. Search for Related Content PubMed PubMed Citation Articles by GOURINENI, P. V. R. K. V. Articles by NUBER, G. F. Social Bookmarking                   What's this?

Stanford University Libraries' HighWire Press (TM) assists in the publication of JBJS Online.
Copyright © 1999 by The Journal of Bone and Joint Surgery, Inc. Online ISSN: 1535-1386.
The Journal of Bone and Joint Surgery®, JBJS®, JB&JS®, and eJBJS® are registered in the U.S. Patent and Trademark Office.