Technology and Health Care 23 (2015) 215–221 DOI 10.3233/THC-140885 IOS Press
215
Establishing an optimal trajectory for calcaneotibial K-wire fixation in emergent treatment of unstable ankle fractures M. Schrödera , V. Stübera , E. Walendzika , P.F. O’Loughlinb, A. Zapfc , C. Kretteka and R. Gaulkea,∗ a Unfallchirurgische Klinik,
Medizinische Hochschule Hannover, Germany National Orthopaedic Hospital, Finglas, Dublin, Ireland c Institut für Biostatistik, Medizinische Hochschule Hannover, Germany b Cappagh
Received 16 August 2014 Accepted 23 November 2014 Abstract. OBJECTIVE: In unstable ankle fractures the associated soft tissue damage can be a therapeutic challenge. The aim of this study was to optimize planning of minimally invasive stabilization of ankle fractures by calcaneotibial transfixation, which is a demanding technique due to the complex hind foot anatomy. METHODS: In a retrospective radiographic analysis the angles and dimensions of a safe drill tunnel for calcaneotibial K-wire insertion were defined on standard radiographs of the ankle joint. 165 lateral weight-bearing radiographs (77 right; 88 left) and 147 (80 right; 67 left) mortise views of 186 (90 right; 96 left) uninjured feet from 123 patients (74 women (114 feet); 49 men (72 feet)) were included in this study. The average patient age was 49 (range, 13–85) years. Inter- and intra-observer reliability was evaluated on 20 randomized radiographs that were analyzed in a default set, three times, by two different examiners on three different days. RESULTS: In the lateral view the drilling tunnel was orientated at 59.4◦ to the plantar plane with a maximum proximal variance of 7.1 image-mm. Distal variance cannot be tolerated since an ankle joint injury would ensue. In the mortise view the drill tunnel was directed with a mean angle of 18.4◦ to the distal tibial articular surface. At most a mean of 11◦ fibular- and 13.4◦ tibial- expansion can be tolerated. Intra- and inter-observer reliability was higher for the angles than for the drill corridors. CONCLUSION: The three-dimensional (3D) orientation for safe K-wire placement for calcaneotibial transfixation should adhere to the drill tunnels established in this study. Keywords: Hind foot anatomy, ankle fracture, calcaneotibial transfixation, hind foot radiographs
1. Background Fractures of the ankle joint occur with an incidence of 100 to 114 per 100,000 citizens per year [1–3]. In most cases the fracture results from a joint subluxation mechanism following a slip or misstep [4]. High impact trauma caused by traffic accidents, a fall from greater height or direct forces is rarer, but may result in extensive soft-tissue damage and open fractures [5]. ∗ Corresponding author: Ralph Gaulke, Unfallchirurgische Klinik, Medizinische Hochschule Hannover, Carl-Neuberg-Straße 1, D-30525 Hannover, Germany. Tel.: +49 511 532 2026; Fax: +49 511 532 5877; E-mail: [email protected].
c 2015 – IOS Press and the authors. All rights reserved 0928-7329/15/$35.00
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M. Schröder et al. / Establishing an optimal trajectory for calcaneotibial K-wire fixation
(a)
(b)
(c)
(d)
Fig. 1. Unstable ankle fracture before (a,b) and after (c,d) temporary stabilization with an extra-articular calcaneotibial transfixation by a K-wire.
Soft-tissue management is crucial in the treatment of these fractures. The compromised soft-tissue may deteriorate further circulatory or iatrogenic insults intra-operatively. Therefore, a two-step surgical approach is recommended, i.e., emergent and definitive treatment [6,7]: For emergent care, minimalinvasive procedures, such as external fixator application or calcaneotibial transfixation (Fig. 1), are recommended. This kind of stabilization minimizes further trauma to the soft tissues. The leg is elevated maximally until swelling subsides and definitive fixation may be undertaken [6]. The aim of the current study was to establish the optimal entry point and angle at the calcaneus for a safe extra-articular calcaneotibial K-wire fixation on standard radiographs. Furthermore, the dimensions of the osseous drill corridor in both planes were evaluated. 2. Methods In a retrospective study standard radiographs of 186 uninjured feet (90 right and 96 left) from 123 patients (74 women (114 feet) and 49 men (72 feet)) were analyzed. These radiographs were performed at the current investigators’ institution between 2005 and 2009. The current study was approved by the current investigators’ institutional ethics board. In all 165 (77 right; 88 left) lateral views of weight-bearing feet and 143 (78 right; 65 left) mortise views (ankle joint in 30◦ internal rotation) were evaluated. All measurements were performed with the software Centricity Radiology RA 1000 (Version 2006 GE Med Systems, GE Healthcare Integrated IT Solutions, Barrington, USA) on a 19 inch monitor with 2:1 magnification. The mean age of the patients was 49 (range, 13 to 85) years. The sagittal direction and dimension of the drilling corridors were measured in the lateral radiographs of the weight-bearing foot. The following anatomical landmarks were used: – The longitudinal axis of the calcaneus is defined by a straight line bisecting two diameters of the calcaneus AC and BD. AC runs from the highest point of the dorsal calcaneal processus (A) to the origin of the plantar aponeurosis (C). The ventral diameter BD runs parallel to AC through the highest point of the subtalar joint surface (B) and crosses the plantar corticalis in D (Fig. 2). – The entry point for the K-wire lies at the crossing of the longitudinal calcaneus axis and the dorsal cortex of the calcaneus (R) (Fig. 2).
M. Schröder et al. / Establishing an optimal trajectory for calcaneotibial K-wire fixation
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Fig. 2. Proximodistal dimension of the corridor.
– The corridor line connects “R” with the nearest point of the dorsal tibia. It shows the optimal position of the K-wire for a stable extraarticular calcaneotibial transfixation (Fig. 2). – Angle β is defined by the axis of the calcaneus and the corridor line and defines the optimal entry angle of the K-wire in relation to the calcaneal axis (Fig. 2). – The plantar level is defined by the soft tissues of the sole in the lateral weight-bearing view (Fig. 2). – The angle between the calcaneal axis and the parallel of the plantar level running through “R” is called γ (Fig. 2). – Angle α is calculated by adding the angles β and γ . It is the angle between the K-wire and the sole (Fig. 2). – The dimension of the proximodistal corridor illustrates the tolerance range, in which the K-wire must be placed to achieve a stabile transfixation. It is defined by the dorsal parallel to the corridor line running through the top of the dorsal calcaneal processus (A) and a distal parallel to the corridor line running through the dorsal edge of the distal tibia surface (Fig. 2). For the estimation of the lateromedial direction of the drilling corridor in relation to the distal articular surface of the tibia and the center of the calcaneus the angle δ in the standard mortise view in 30◦ internal rotation was defined. For calculation of this angle following x-ray landmarks were set: – The center of the calcaneus is defined as the crossing of the two diagonals running through the dorsal contour of the calcaneus. Diagonal EH runs from the medial basis of the dorsal calcaneal process (E) to the lateroplantar edge (H) of the calcaneus. Diagonal FG runs from the lateral basis of the dorsal calcaneal process (F) to the medioplantar edge (G) of the calcaneus (Fig. 3). – Line “g” shows the optimal localization of the K-wire in the mortise view. It runs through the center of the calcaneus and the most distal point of the anterior tibial edge. This point is defined by the maximal distance of the osseous contour of the anterior tibial edge to the distance IJ, which connects the highest medial (I) and lateral (J) point of the distal articular surface of the tibia (Fig. 3). – The angle between the line “g” and a line perpendicular to the distal articular surface of the tibia is called “δ”. It describes the frontal angle of the drilling tunnel in relation to the tibial articular
218
M. Schröder et al. / Establishing an optimal trajectory for calcaneotibial K-wire fixation Table 1 Values of lateral views in 165 weight bearing feet Angle α [◦ ] Angle β [◦ ] Angle γ [◦ ] Proximodistal corridor [image-mm]
Mean 59.4 37.9 21.5 7.1
Minimum 38.3 29.0 7.7 2.9
Maximum 71.9 47.5 36.6 12.2
Standard deviation 5.32 3.1 5.8 2.0
Fig. 3. The mediolateral dimension of the corridor for the K-wire lies between the parallels to “g”.
surface (Fig. 3). – The mediolateral dimension of the drilling corridor indicates the tolerance range of a stabile calcaneotibial transfixation. It is set by parallels to the line “g” which run through the middle of the distances EG and FH (Fig. 3). – For better comparison of the measurements, performed on the internal rotated mortise views of the ankle joints, we defined an angle ε between the longitudinal axes of the tibia and the third metatarsus. The longitudinal axis of the third metatarsal bone runs through the middle of two diameters of the shaft of the bone (Fig. 4).
2.1. Inter- and intraobserver reliability Reliability of the measurements was evaluated on lateral views of weight bearing feet and mortise views of 20 feet picked randomly from the 123 patients. Those images were analyzed three times by two examiners (EW and MS) on three different days. The maximal accepted deviation was 5%.
M. Schröder et al. / Establishing an optimal trajectory for calcaneotibial K-wire fixation
Angle δ [◦ ] Angle ε [◦ ] Tibial deviation [image-mm] Fibular deviation [image-mm] Mediolateral corridor[image-mm]
Table 2 Values of 143 feet in the mortise view Mean Minimum Maximum 18.4 2.4 35.2 145.7 119.4 172.9 11.0 6.2 16.1 13.4 8.6 18.4 24.4 15.5 32.0
219
Standard deviation 6.5 10.6 1.8 1.8 3.2
Fig. 4. Angle ε shows the internal rotation of the foot in the mortise view.
2.2. Statistics For each parameter (Tables 1 and 2) the mean value (x) and the standard deviation (s) were estimated. For the intraobserver reliability the percentage difference per patient was calculated. For the interobserver reliability the percentage difference of the two examiners (using the mean of the three repetitions) was calculated. Afterwards, for inter- and intraobserver reliability the mean percentage difference with the corresponding two-sided 95% confidence interval was estimated. A good reliability is defined by maximal 5% deviation. This means that the upper limit of the confidence interval is below 5%. All calculations were performed using the statistical software R (version 2.12) and Microsoft Excel 2004 for Mac Version 11.6.6. Figure 5 was created with R 2.12.
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M. Schröder et al. / Establishing an optimal trajectory for calcaneotibial K-wire fixation
Fig. 5. Intra- and interobserver reliability.
3. Results The optimal K-wire insertion point in the sagittal direction lies between the crossing of the calcaneal axis, the dorsal calcaneal cortex and the highest point of the dorsal calcaneal process. The angle of the corridor line to the sole lies between 38.3◦–71.9◦ (mean, 59.4◦ ) (Table 1). The K-wire enters the calcaneus proximal to the insertion of the achilles tendon and reaches the posterior cortex of the tibia without damaging the ankle and subtalar joints. The proximodistal dimension of the corridor for the correct position of the K-wire varies from 2.9 to 12.2 (mean, 7.1) image-mm (Table 1). A distal deviation of the wire would lead to a penetration of the ankle and subtalar joints. The optimal angle of entry (angle δ) in the mortise view varies from 2.4◦ to 35.2◦ (mean, 18.4◦ ) (Table 2). The dimension of the drilling corridor in the mortise view ranges from 8.6 to 18.4 (mean, 13.4) image-mm fibularly and from 6.2 to 16.1 image-mm (mean, 11.0) tibially. Fibular drilling outside the corridor leads to damage in the distal fibulotibial joint. The total wide of the corridor in the mortise view ranges from 15.5 to 32.0 (mean, 24.4) image-mm (Table 2). 3.1. Intra-observer reliability Good reliability of the measurements (maximal 5% deviation) was found for examiner 1 (EW) for the angles α, β , and ε, and for examiner 2 (MS) for the angles α and ε (Fig. 5).
M. Schröder et al. / Establishing an optimal trajectory for calcaneotibial K-wire fixation
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3.2. Inter-observer reliability A difference of 5% or less in the comparison of the two examiners was found for angle α and β (Fig. 5). 4. Discussion In the current study the optimal entry angle (α), the optimal placement of the K-wire and the dimension of the drilling corridor for a strict extraarticular calcaneotibial transfixation of the ankle and subtalar joint were determined on standard radiographs in two planes. To the authors’ knowledge, as per April 2014, no similar study had been conducted. The mean entry angle for the K-wire at the calcaneus is 59.4◦ with respect to the sole in the distoproximal direction. The mean drilling corridor for the extraarticular calcaneotibial transfixation is 7.1 image-mm high and 24.4 image-mm wide. This is a narrow range for placing a 3 mm K-wire freehanded. Therefore, definition of the orientation in three planes is useful and the utility of a targeting device can be argued to prevent inaccurate drilling with consequent intra-articular injury. Some limitations of this study are that in the weight-bearing plain radiographic image, the axis of calcaneus in a flexible hind foot valgus is flatter than it would be during an actual fracture reduction scenario, which is performed with a varus force upon the hind foot. This means that the real angle α is greater than the one seen in the radiograph. In a rigid hind foot varus the difference between weightbearing and repositioning position is lower. In the mortise view the hind foot is 30◦ internal rotated to get access to the surface of the ankle joint, because the ankle mortise is 30◦ externally rotated. This may lead to bias in the measurement of the entry path angle. On the other hand, in order to control the reposition of the ankles, analogous to the images used in the current study, repositioning is performed in the mortise view, too. Despite these limitations, the data assessed in this study are helpful as a guide for the free-handed placement of a K-wire in extraarticular calcaneotibial transfixation and may prevent injury of the ankle, subtalar or distal tibiofibular joints during this procedure. On the basis of these data an aiming device will be developed to assist correct placement of the fixation wire. Acknowledgements We thank the Radiologische Klinik of the Medizinische Hochschule Hannover, that performed the radiographs that were analized in this study. References [1] [2] [3] [4] [5] [6] [7]
Ochs U, Winter E, Weise K. Malleolenfrakturen. Trauma Berufskrankh 2001; 4: 338-343. Steen L Jensen, Bjarke K Andresen, Steen Mencke, Poul T Nielsen. Epidemiology of ankle fractures. Acta Orthop Scand 1998; 69(1): 48-50. Lindsjö U. Operative Treatment of Ankle Fracture-Dislocations. Clin Orthop Relat Res. 1985; 199: 28-38. Rammelt S, Grass R, Biewener A, Zwipp H. Anatomie, Biomechanik und Klassifikation der Sprunggelenkfrakturen. Trauma Berufskranh 2004; 6 [Suppl 4]: 384-392. Zwipp H. Chirurgie des Fußes. Wien New York: Springer Verlag, 1994: 36-39. Hahn MP, Thies JW. Pilon-tibiale-Frakturen. Unfallchirurg 2002; 73: 1115-1132. Sirkin M, Sanders R, DiPasquale T, Herscovici D. A Staged Protocol for Soft Tissue Management in the Treatment of Complex Pilon Fractures. J Orthop Trauma 1999; 13(2): 32-38.
Copyright of Technology & Health Care is the property of IOS Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.
215
Establishing an optimal trajectory for calcaneotibial K-wire fixation in emergent treatment of unstable ankle fractures M. Schrödera , V. Stübera , E. Walendzika , P.F. O’Loughlinb, A. Zapfc , C. Kretteka and R. Gaulkea,∗ a Unfallchirurgische Klinik,
Medizinische Hochschule Hannover, Germany National Orthopaedic Hospital, Finglas, Dublin, Ireland c Institut für Biostatistik, Medizinische Hochschule Hannover, Germany b Cappagh
Received 16 August 2014 Accepted 23 November 2014 Abstract. OBJECTIVE: In unstable ankle fractures the associated soft tissue damage can be a therapeutic challenge. The aim of this study was to optimize planning of minimally invasive stabilization of ankle fractures by calcaneotibial transfixation, which is a demanding technique due to the complex hind foot anatomy. METHODS: In a retrospective radiographic analysis the angles and dimensions of a safe drill tunnel for calcaneotibial K-wire insertion were defined on standard radiographs of the ankle joint. 165 lateral weight-bearing radiographs (77 right; 88 left) and 147 (80 right; 67 left) mortise views of 186 (90 right; 96 left) uninjured feet from 123 patients (74 women (114 feet); 49 men (72 feet)) were included in this study. The average patient age was 49 (range, 13–85) years. Inter- and intra-observer reliability was evaluated on 20 randomized radiographs that were analyzed in a default set, three times, by two different examiners on three different days. RESULTS: In the lateral view the drilling tunnel was orientated at 59.4◦ to the plantar plane with a maximum proximal variance of 7.1 image-mm. Distal variance cannot be tolerated since an ankle joint injury would ensue. In the mortise view the drill tunnel was directed with a mean angle of 18.4◦ to the distal tibial articular surface. At most a mean of 11◦ fibular- and 13.4◦ tibial- expansion can be tolerated. Intra- and inter-observer reliability was higher for the angles than for the drill corridors. CONCLUSION: The three-dimensional (3D) orientation for safe K-wire placement for calcaneotibial transfixation should adhere to the drill tunnels established in this study. Keywords: Hind foot anatomy, ankle fracture, calcaneotibial transfixation, hind foot radiographs
1. Background Fractures of the ankle joint occur with an incidence of 100 to 114 per 100,000 citizens per year [1–3]. In most cases the fracture results from a joint subluxation mechanism following a slip or misstep [4]. High impact trauma caused by traffic accidents, a fall from greater height or direct forces is rarer, but may result in extensive soft-tissue damage and open fractures [5]. ∗ Corresponding author: Ralph Gaulke, Unfallchirurgische Klinik, Medizinische Hochschule Hannover, Carl-Neuberg-Straße 1, D-30525 Hannover, Germany. Tel.: +49 511 532 2026; Fax: +49 511 532 5877; E-mail: [email protected].
c 2015 – IOS Press and the authors. All rights reserved 0928-7329/15/$35.00
216
M. Schröder et al. / Establishing an optimal trajectory for calcaneotibial K-wire fixation
(a)
(b)
(c)
(d)
Fig. 1. Unstable ankle fracture before (a,b) and after (c,d) temporary stabilization with an extra-articular calcaneotibial transfixation by a K-wire.
Soft-tissue management is crucial in the treatment of these fractures. The compromised soft-tissue may deteriorate further circulatory or iatrogenic insults intra-operatively. Therefore, a two-step surgical approach is recommended, i.e., emergent and definitive treatment [6,7]: For emergent care, minimalinvasive procedures, such as external fixator application or calcaneotibial transfixation (Fig. 1), are recommended. This kind of stabilization minimizes further trauma to the soft tissues. The leg is elevated maximally until swelling subsides and definitive fixation may be undertaken [6]. The aim of the current study was to establish the optimal entry point and angle at the calcaneus for a safe extra-articular calcaneotibial K-wire fixation on standard radiographs. Furthermore, the dimensions of the osseous drill corridor in both planes were evaluated. 2. Methods In a retrospective study standard radiographs of 186 uninjured feet (90 right and 96 left) from 123 patients (74 women (114 feet) and 49 men (72 feet)) were analyzed. These radiographs were performed at the current investigators’ institution between 2005 and 2009. The current study was approved by the current investigators’ institutional ethics board. In all 165 (77 right; 88 left) lateral views of weight-bearing feet and 143 (78 right; 65 left) mortise views (ankle joint in 30◦ internal rotation) were evaluated. All measurements were performed with the software Centricity Radiology RA 1000 (Version 2006 GE Med Systems, GE Healthcare Integrated IT Solutions, Barrington, USA) on a 19 inch monitor with 2:1 magnification. The mean age of the patients was 49 (range, 13 to 85) years. The sagittal direction and dimension of the drilling corridors were measured in the lateral radiographs of the weight-bearing foot. The following anatomical landmarks were used: – The longitudinal axis of the calcaneus is defined by a straight line bisecting two diameters of the calcaneus AC and BD. AC runs from the highest point of the dorsal calcaneal processus (A) to the origin of the plantar aponeurosis (C). The ventral diameter BD runs parallel to AC through the highest point of the subtalar joint surface (B) and crosses the plantar corticalis in D (Fig. 2). – The entry point for the K-wire lies at the crossing of the longitudinal calcaneus axis and the dorsal cortex of the calcaneus (R) (Fig. 2).
M. Schröder et al. / Establishing an optimal trajectory for calcaneotibial K-wire fixation
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Fig. 2. Proximodistal dimension of the corridor.
– The corridor line connects “R” with the nearest point of the dorsal tibia. It shows the optimal position of the K-wire for a stable extraarticular calcaneotibial transfixation (Fig. 2). – Angle β is defined by the axis of the calcaneus and the corridor line and defines the optimal entry angle of the K-wire in relation to the calcaneal axis (Fig. 2). – The plantar level is defined by the soft tissues of the sole in the lateral weight-bearing view (Fig. 2). – The angle between the calcaneal axis and the parallel of the plantar level running through “R” is called γ (Fig. 2). – Angle α is calculated by adding the angles β and γ . It is the angle between the K-wire and the sole (Fig. 2). – The dimension of the proximodistal corridor illustrates the tolerance range, in which the K-wire must be placed to achieve a stabile transfixation. It is defined by the dorsal parallel to the corridor line running through the top of the dorsal calcaneal processus (A) and a distal parallel to the corridor line running through the dorsal edge of the distal tibia surface (Fig. 2). For the estimation of the lateromedial direction of the drilling corridor in relation to the distal articular surface of the tibia and the center of the calcaneus the angle δ in the standard mortise view in 30◦ internal rotation was defined. For calculation of this angle following x-ray landmarks were set: – The center of the calcaneus is defined as the crossing of the two diagonals running through the dorsal contour of the calcaneus. Diagonal EH runs from the medial basis of the dorsal calcaneal process (E) to the lateroplantar edge (H) of the calcaneus. Diagonal FG runs from the lateral basis of the dorsal calcaneal process (F) to the medioplantar edge (G) of the calcaneus (Fig. 3). – Line “g” shows the optimal localization of the K-wire in the mortise view. It runs through the center of the calcaneus and the most distal point of the anterior tibial edge. This point is defined by the maximal distance of the osseous contour of the anterior tibial edge to the distance IJ, which connects the highest medial (I) and lateral (J) point of the distal articular surface of the tibia (Fig. 3). – The angle between the line “g” and a line perpendicular to the distal articular surface of the tibia is called “δ”. It describes the frontal angle of the drilling tunnel in relation to the tibial articular
218
M. Schröder et al. / Establishing an optimal trajectory for calcaneotibial K-wire fixation Table 1 Values of lateral views in 165 weight bearing feet Angle α [◦ ] Angle β [◦ ] Angle γ [◦ ] Proximodistal corridor [image-mm]
Mean 59.4 37.9 21.5 7.1
Minimum 38.3 29.0 7.7 2.9
Maximum 71.9 47.5 36.6 12.2
Standard deviation 5.32 3.1 5.8 2.0
Fig. 3. The mediolateral dimension of the corridor for the K-wire lies between the parallels to “g”.
surface (Fig. 3). – The mediolateral dimension of the drilling corridor indicates the tolerance range of a stabile calcaneotibial transfixation. It is set by parallels to the line “g” which run through the middle of the distances EG and FH (Fig. 3). – For better comparison of the measurements, performed on the internal rotated mortise views of the ankle joints, we defined an angle ε between the longitudinal axes of the tibia and the third metatarsus. The longitudinal axis of the third metatarsal bone runs through the middle of two diameters of the shaft of the bone (Fig. 4).
2.1. Inter- and intraobserver reliability Reliability of the measurements was evaluated on lateral views of weight bearing feet and mortise views of 20 feet picked randomly from the 123 patients. Those images were analyzed three times by two examiners (EW and MS) on three different days. The maximal accepted deviation was 5%.
M. Schröder et al. / Establishing an optimal trajectory for calcaneotibial K-wire fixation
Angle δ [◦ ] Angle ε [◦ ] Tibial deviation [image-mm] Fibular deviation [image-mm] Mediolateral corridor[image-mm]
Table 2 Values of 143 feet in the mortise view Mean Minimum Maximum 18.4 2.4 35.2 145.7 119.4 172.9 11.0 6.2 16.1 13.4 8.6 18.4 24.4 15.5 32.0
219
Standard deviation 6.5 10.6 1.8 1.8 3.2
Fig. 4. Angle ε shows the internal rotation of the foot in the mortise view.
2.2. Statistics For each parameter (Tables 1 and 2) the mean value (x) and the standard deviation (s) were estimated. For the intraobserver reliability the percentage difference per patient was calculated. For the interobserver reliability the percentage difference of the two examiners (using the mean of the three repetitions) was calculated. Afterwards, for inter- and intraobserver reliability the mean percentage difference with the corresponding two-sided 95% confidence interval was estimated. A good reliability is defined by maximal 5% deviation. This means that the upper limit of the confidence interval is below 5%. All calculations were performed using the statistical software R (version 2.12) and Microsoft Excel 2004 for Mac Version 11.6.6. Figure 5 was created with R 2.12.
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M. Schröder et al. / Establishing an optimal trajectory for calcaneotibial K-wire fixation
Fig. 5. Intra- and interobserver reliability.
3. Results The optimal K-wire insertion point in the sagittal direction lies between the crossing of the calcaneal axis, the dorsal calcaneal cortex and the highest point of the dorsal calcaneal process. The angle of the corridor line to the sole lies between 38.3◦–71.9◦ (mean, 59.4◦ ) (Table 1). The K-wire enters the calcaneus proximal to the insertion of the achilles tendon and reaches the posterior cortex of the tibia without damaging the ankle and subtalar joints. The proximodistal dimension of the corridor for the correct position of the K-wire varies from 2.9 to 12.2 (mean, 7.1) image-mm (Table 1). A distal deviation of the wire would lead to a penetration of the ankle and subtalar joints. The optimal angle of entry (angle δ) in the mortise view varies from 2.4◦ to 35.2◦ (mean, 18.4◦ ) (Table 2). The dimension of the drilling corridor in the mortise view ranges from 8.6 to 18.4 (mean, 13.4) image-mm fibularly and from 6.2 to 16.1 image-mm (mean, 11.0) tibially. Fibular drilling outside the corridor leads to damage in the distal fibulotibial joint. The total wide of the corridor in the mortise view ranges from 15.5 to 32.0 (mean, 24.4) image-mm (Table 2). 3.1. Intra-observer reliability Good reliability of the measurements (maximal 5% deviation) was found for examiner 1 (EW) for the angles α, β , and ε, and for examiner 2 (MS) for the angles α and ε (Fig. 5).
M. Schröder et al. / Establishing an optimal trajectory for calcaneotibial K-wire fixation
221
3.2. Inter-observer reliability A difference of 5% or less in the comparison of the two examiners was found for angle α and β (Fig. 5). 4. Discussion In the current study the optimal entry angle (α), the optimal placement of the K-wire and the dimension of the drilling corridor for a strict extraarticular calcaneotibial transfixation of the ankle and subtalar joint were determined on standard radiographs in two planes. To the authors’ knowledge, as per April 2014, no similar study had been conducted. The mean entry angle for the K-wire at the calcaneus is 59.4◦ with respect to the sole in the distoproximal direction. The mean drilling corridor for the extraarticular calcaneotibial transfixation is 7.1 image-mm high and 24.4 image-mm wide. This is a narrow range for placing a 3 mm K-wire freehanded. Therefore, definition of the orientation in three planes is useful and the utility of a targeting device can be argued to prevent inaccurate drilling with consequent intra-articular injury. Some limitations of this study are that in the weight-bearing plain radiographic image, the axis of calcaneus in a flexible hind foot valgus is flatter than it would be during an actual fracture reduction scenario, which is performed with a varus force upon the hind foot. This means that the real angle α is greater than the one seen in the radiograph. In a rigid hind foot varus the difference between weightbearing and repositioning position is lower. In the mortise view the hind foot is 30◦ internal rotated to get access to the surface of the ankle joint, because the ankle mortise is 30◦ externally rotated. This may lead to bias in the measurement of the entry path angle. On the other hand, in order to control the reposition of the ankles, analogous to the images used in the current study, repositioning is performed in the mortise view, too. Despite these limitations, the data assessed in this study are helpful as a guide for the free-handed placement of a K-wire in extraarticular calcaneotibial transfixation and may prevent injury of the ankle, subtalar or distal tibiofibular joints during this procedure. On the basis of these data an aiming device will be developed to assist correct placement of the fixation wire. Acknowledgements We thank the Radiologische Klinik of the Medizinische Hochschule Hannover, that performed the radiographs that were analized in this study. References [1] [2] [3] [4] [5] [6] [7]
Ochs U, Winter E, Weise K. Malleolenfrakturen. Trauma Berufskrankh 2001; 4: 338-343. Steen L Jensen, Bjarke K Andresen, Steen Mencke, Poul T Nielsen. Epidemiology of ankle fractures. Acta Orthop Scand 1998; 69(1): 48-50. Lindsjö U. Operative Treatment of Ankle Fracture-Dislocations. Clin Orthop Relat Res. 1985; 199: 28-38. Rammelt S, Grass R, Biewener A, Zwipp H. Anatomie, Biomechanik und Klassifikation der Sprunggelenkfrakturen. Trauma Berufskranh 2004; 6 [Suppl 4]: 384-392. Zwipp H. Chirurgie des Fußes. Wien New York: Springer Verlag, 1994: 36-39. Hahn MP, Thies JW. Pilon-tibiale-Frakturen. Unfallchirurg 2002; 73: 1115-1132. Sirkin M, Sanders R, DiPasquale T, Herscovici D. A Staged Protocol for Soft Tissue Management in the Treatment of Complex Pilon Fractures. J Orthop Trauma 1999; 13(2): 32-38.
Copyright of Technology & Health Care is the property of IOS Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.
