Technology and Health Care 21 (2013) 631–639 DOI 10.3233/THC-130763 IOS Press
631
Computer-assisted navigation of a complex femoral shaft fracture: Instruction in three steps – A technical note L. Claassena,∗ , N. Hawib , M. Ettingera , Ch. Stukenborg-Colsmana , E. Liodakisb and M. Citakb a Orthopaedic
b Trauma
Department of the Hannover Medical School, Hannover, Germany Department of the Hannover Medical School, Hannover, Germany
Received 17 August 2013 Accepted 9 October 2013 Abstract. The procedure of computer-assisted navigation of femoral shaft fractures is well described. Nevertheless, its use is less common. An unclear disposal and longer operation times might be two reasons. The aim of this technical note is to render assistance concerning the ideal disposal of the setup. Keywords: Femur shaft fracture, antetorsion, fracture reduction, internal fixation, computer-assisted navigation
1. Introduction In modern trauma surgery femoral nailing is the common treatment in cases of femoral shaft fractures [1,2]. In retrospect, up to 40% of patients have a torsion difference of 10◦ or more after femoral nailing [3]. Important perioperative complications are malrotation and malalignment with varus or valgus deformities. A helpful tool to avoid such complications is the computer-assisted navigation as recently described [4]. But its less common use does not embrace its possibilities. The first generation systems for computer-assisted navigation by Medivision did not lead to a proper torsion control. This drawback was eliminated by Brainlab when the second generation of computer assisted navigation was presented. The measurement of the contralateral side was possible with this system. After all, the handling was still uncomfortable and the procedure was vulnerable for mistakes. Due to further developments the workflow could be optimized, so that several error-prone steps can be skipped and the surgeon is able to select only the important sequences [4]. Today two navigation technologies are common: The Infrared and the electromagnetic systems, in which infrared systems have an advantage [5]. In this paper we describe the technique of computer-assisted navigation of a complex femoral shaft fracture in three steps. The ethical committee of the Hannover medical school approved the study. ∗ Correspending author: Leif Claassen, Orthopaedic Department of the Hannover Medical School, Anna-von-Borries-Str. 1-7, 30625 Hannover, Germany. E-mail: [email protected].
c 2013 – IOS Press and the authors. All rights reserved 0928-7329/13/$27.50
632
L. Claassen et al. / Computer-assisted navigation of a complex femoral shaft fracture
Fig. 1. xSpot.
Fig. 2. Placement of equipment. On the left there is the monitor of the navigation system, on the right there is the monitor of the c-arm.
Fig. 3. Headband.
2. Protocol 2.1. Recourses and personal Among self-evident equipment, like the operation table or the implant, a c-arm and the navigation system are needed. One important component of the navigation system is the xSpot (Fig. 1). It makes the correlation between radiographic image and navigation possible. At the apex it has three x-ray-dens components at every corner. It has to surround the designated structure in the radiograph. Simultaneously the xSpot has three markers that have to be visible for the sensor of the navigation. We used the system of Brainlab (Kolibri, Brainlab corporation, Feldkirchen, Germany). Besides the surgeon and his assistant three theatre nurses are necessary. One nurse is needed to arrange the instruments, one nurse to help with positioning and one nurse to serve the c-arm and the navigation system.
L. Claassen et al. / Computer-assisted navigation of a complex femoral shaft fracture
(a)
633
(b)
Fig. 4. Contralateral hip anteriorposterior, a) placement, b) radiograph.
(a)
(b)
Fig. 5. Contralateral knee anteriorposterior, a) placement, b) radiograph.
2.2. Positioning Initially the patient is positioned in supine position. The c-arm with its monitor and the monitor of the navigation monitor are placed on the contralateral side of the patient. The disposal of the setup is as follows: From proximal to distal the c-arm, the monitor of the c-arm and the monitor of the navigation system (Fig. 2). The sensor of the navigation system is placed on the ipsilateral side. The “headband” of the navigation system is positioned at the contralateral thigh proximal of the patella (Fig. 3). This is obligate to navigate the contralateral side noninvasive [6].
634
L. Claassen et al. / Computer-assisted navigation of a complex femoral shaft fracture
(a)
(b) Fig. 6. Contralateral knee lateral, a) placement, b) radiograph.
(a)
(b)
Fig. 7. Contralateral hip axial, a) placement, b) radiograph.
2.3. Step 1 Navigation of the contralateral femur Patient in supine position, c-arm in anteriorposterior position. First the contralateral hip is analyzed. The navigation marker is placed above the hip, visible for the navigation sensor (Fig. 4). The leg has to be hold in neutral position all the time. Afterwards an image of the knee has to be taken in the similar manner (Fig. 5). Now the c-arms position is changed to the lateral view to analyze the knee (Fig. 6). For the axial view of the contralateral hip the ipsilateral leg has to be flexed in the hip to a high extend (Fig. 7). When these images are taken properly it becomes visible on the navigation monitor (Fig. 8).
L. Claassen et al. / Computer-assisted navigation of a complex femoral shaft fracture
635
Fig. 8. Navigation monitor after navigation the contralateral leg.
Fig. 9. Positioning of the contralateral leg with hip flexion.
Fig. 10. Left leg ready to precede the operation.
Fig. 11. Placed navigation pins. The other wounds were due to removal of the previously implanted nail in this case.
Then the crucial landmarks have to be marked (Fig. 13, shown for the left leg). These are the apex of the trochanter major, the center of the femoral head, medial femur condyle and the lateral posterior femur condyle. The contralateral hip has to be held in flexion in order to proceed to the next step of the surgery. The flexion of contralateral hip is necessary for axial radiographs of the ipsilateral hip (Fig. 9). 2.4. Step 2 Navigation of the ipsilateral femur The disposal of the setup is not changed for this step. The left leg was covered sterile before (Fig. 10). Two navigation pins are placed, one in the proximal and one in the distal fragment (Fig. 11). One potential drawback of placement is that the navigation pins have contact with the implant. This may lead to a changed position of the pins and might cause measurement errors. After implantation of the nail the navigation of the landmarks has to be done as described for contralateral side (Fig. 12 a-h; Fig. 13).
636
L. Claassen et al. / Computer-assisted navigation of a complex femoral shaft fracture
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
Fig. 12. Navigation of the left femur, a + b) hip anteriorposterior, c + d) hip axial, e + f) knee anteriorposterior, g + h) knee lateral.
L. Claassen et al. / Computer-assisted navigation of a complex femoral shaft fracture
(a)
637
(b)
Fig. 13. Marking the landmarks for knee and trochanter major.
(a)
(b)
(c)
(d)
Fig. 14. Navigation of the fracture, a + b) fracture anteriorposterior placement and radiograph, c + d) fracture lateral placement and radiograph.
638
L. Claassen et al. / Computer-assisted navigation of a complex femoral shaft fracture
Fig. 15. Presented fragments of the fracture with their axes, length and rotation.
2.5. Step 3 Navigation of the fracture Anterior-posterior and lateral images are needed to determine the fracture (Fig. 14). In addition the axis of the proximal and the distal main fragment have to be marked. Afterwards the navigation system is able to present the axis, rotation and length compared to the contralateral side (Fig. 15). The rotation, axis and length can be checked and adjusted. The nail can be locked in the planned position under direct and continuous control. 3. Discussion Complex femoral shaft fractures or postoperative deformities after treating a femoral shaft fracture are difficult to treat. The computer-assisted navigation might be a helpful tool. The procedure described above is still prone to errors: Especially the navigation pins are vulnerable for manipulation. They have to be adjusted stable but may not interfere with the intramedullary nail. A changed position of the pins leads to mistakes in measured values [7]. The advantage of a computer-assisted operation is the direct intraoperative control concerning axes and angles. Crucial is the angle of antetorsion. It has to be adjusted to 10–15◦. That value is assumed to be the anatomical standard [8–10]. Alternatives like the clinical determination is imprecise, as Cordier and Jaarsma showed [11,12]. A postoperative CT scan has two disadvantages. First the postoperative realization would make a further operation necessary to correct detected errors. In addition the intraobserver differences between two measurements are up to 10.8◦ and the interobserver difference up to 15.6◦ [13]. Considering that a difference of 15◦ is in general an indication for a revision this is a high value [4]. Other intraoperative tools to estimate and control antetorsion angle are also inadequate [2,14]. A significant malrotation or fracture malunion are risk factors for osteoarthritis [15,16]. The computerassisted navigation as described here compares the affected leg directly with the contralateral side. This leads to an individual treatment with a lower radiation load compared to conventional treatment [17]. It is notable that a CT scanner and computer assisted navigation uses different ways to estimate the antetorsion angle. While via the CT scanner the femoral neck and the intercondyle axis are compared to
L. Claassen et al. / Computer-assisted navigation of a complex femoral shaft fracture
639
the baseline the antetorsion in computer-assisted navigation is measured direct via apex of the trochanter major, center of the femoral head and intercondyle axis [4,13]. The aim is a maximum length difference not exceeding 1 mm and a rotation difference of 1◦ compared to the contralateral side [4]. In conclusion, the computer assisted navigation leads to a high level of security. More efforts are necessary to distribute the experience with this method. Conflict of interest The authors have no financial conflict of interest. References [1]
Braten M, Terjesen T, Rossvoll I. Femoral shaft fractures treated by intramedullary nailing. A follow-up study focusing on problems related to the method. Injury 1995 Jul; 26(6): 379-383. [2] Krettek C, Rudolf J, Schandelmaier P, Guy P, Konemann B, Tscherne H. Unreamed intramedullary nailing of femoral shaft fractures: operative technique and early clinical experience with the standard locking option. Injury 1996 May; 27(4): 233-254. [3] Liodakis E, Kenawey M, Petri M, Zumrut A, Hawi N, Krettek C, et al. Factors influencing neck anteversion during femoral nailing: A retrospective analysis of 220 torsion-difference CTs. Injury 2011 Nov; 42(11): 1342-1345. [4] Hawi N, Haentjes J, Suero EM, Liodakis E, Krettek C, Stubig T, et al. Navigated femoral shaft fracture treatment: current status. Technol Health Care 2012; 20(1): 65-71. [5] Liodakis E, Macke C, Kenawey M, Krettek C. Mini-navigator: A new system for navigated deformity corrections. Int J Med Robot 2012 Sep; 8(3): 319-326. [6] Kendoff D, Citak M, Gardner MJ, Gosling T, Krettek C, Hufner T. Navigated femoral nailing using noninvasive registration of the contralateral intact femur to restore anteversion. Technique and clinical use. J Orthop Trauma 2007 Nov-Dec; 21(10): 725-730. [7] Citak M, Gardner MJ, Citak M, Krettek C, Hufner T, Kendoff D. Navigated femoral anteversion measurements: A new intraoperative technique. Injury 2008 Apr; 39(4): 467-471. [8] Grutzner P, Hochstein P, Simon R, Wentzensen A. Determination of torsion angle after shaft fractures of the lower extremity–clinical relevance and measurement techniques. Chirurg 1999 Mar; 70(3): 276-284. [9] Strecker W, Hoellen I, Keppler P, Suger G, Kinzl L. Correcting torsion after intramedullary nailing osteosynthesis of the lower extremity. Unfallchirurg 1997 Jan; 100(1): 29-38. [10] Ettinger M, Maslaris A, Kenawey M, Petri M, Krettek C, Jagodzinski M, et al. A preliminary clinical evaluation of the “greater trochanter-head contact point” method for the intraoperative torsional control of femoral fractures. J Orthop Sci 2012 Nov; 17(6): 717-721. [11] Cordier W, Katthagen BD. Femoral torsional deformities. Orthopade 2000 Sep; 29(9): 795-801. [12] Jaarsma RL, Pakvis DF, Verdonschot N, Biert J, van Kampen A. Rotational malalignment after intramedullary nailing of femoral fractures. J Orthop Trauma 2004 Aug; 18(7): 403-409. [13] Jaarsma RL, Bruggeman AW, Pakvis DF, Verdonschot N, Lemmens JA, van Kampen A. Computed tomography determined femoral torsion is not accurate. Arch Orthop Trauma Surg 2004 Oct; 124(8): 552-554. [14] Herzberg W, Meitz R, Halata Z. Antetorsion of the femur neck. A variable of the trochanter minor? Unfallchirurg 1991 Apr; 94(4): 168-171. [15] Eckhoff DG. Effect of limb malrotation on malalignment and osteoarthritis. Orthop Clin North Am 1994 Jul; 25(3): 405-414. [16] Kettelkamp DB, Hillberry BM, Murrish DE, Heck DA. Degenerative arthritis of the knee secondary to fracture malunion. Clin Orthop Relat Res 1988 Sep; (234): 159-169. [17] Hufner T, Kendoff D, Citak M, Geerling J, Krettek C. Precision in orthopaedic computer navigation. Orthopade 2006 Oct; 35(10): 1043-1055.
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.
631
Computer-assisted navigation of a complex femoral shaft fracture: Instruction in three steps – A technical note L. Claassena,∗ , N. Hawib , M. Ettingera , Ch. Stukenborg-Colsmana , E. Liodakisb and M. Citakb a Orthopaedic
b Trauma
Department of the Hannover Medical School, Hannover, Germany Department of the Hannover Medical School, Hannover, Germany
Received 17 August 2013 Accepted 9 October 2013 Abstract. The procedure of computer-assisted navigation of femoral shaft fractures is well described. Nevertheless, its use is less common. An unclear disposal and longer operation times might be two reasons. The aim of this technical note is to render assistance concerning the ideal disposal of the setup. Keywords: Femur shaft fracture, antetorsion, fracture reduction, internal fixation, computer-assisted navigation
1. Introduction In modern trauma surgery femoral nailing is the common treatment in cases of femoral shaft fractures [1,2]. In retrospect, up to 40% of patients have a torsion difference of 10◦ or more after femoral nailing [3]. Important perioperative complications are malrotation and malalignment with varus or valgus deformities. A helpful tool to avoid such complications is the computer-assisted navigation as recently described [4]. But its less common use does not embrace its possibilities. The first generation systems for computer-assisted navigation by Medivision did not lead to a proper torsion control. This drawback was eliminated by Brainlab when the second generation of computer assisted navigation was presented. The measurement of the contralateral side was possible with this system. After all, the handling was still uncomfortable and the procedure was vulnerable for mistakes. Due to further developments the workflow could be optimized, so that several error-prone steps can be skipped and the surgeon is able to select only the important sequences [4]. Today two navigation technologies are common: The Infrared and the electromagnetic systems, in which infrared systems have an advantage [5]. In this paper we describe the technique of computer-assisted navigation of a complex femoral shaft fracture in three steps. The ethical committee of the Hannover medical school approved the study. ∗ Correspending author: Leif Claassen, Orthopaedic Department of the Hannover Medical School, Anna-von-Borries-Str. 1-7, 30625 Hannover, Germany. E-mail: [email protected].
c 2013 – IOS Press and the authors. All rights reserved 0928-7329/13/$27.50
632
L. Claassen et al. / Computer-assisted navigation of a complex femoral shaft fracture
Fig. 1. xSpot.
Fig. 2. Placement of equipment. On the left there is the monitor of the navigation system, on the right there is the monitor of the c-arm.
Fig. 3. Headband.
2. Protocol 2.1. Recourses and personal Among self-evident equipment, like the operation table or the implant, a c-arm and the navigation system are needed. One important component of the navigation system is the xSpot (Fig. 1). It makes the correlation between radiographic image and navigation possible. At the apex it has three x-ray-dens components at every corner. It has to surround the designated structure in the radiograph. Simultaneously the xSpot has three markers that have to be visible for the sensor of the navigation. We used the system of Brainlab (Kolibri, Brainlab corporation, Feldkirchen, Germany). Besides the surgeon and his assistant three theatre nurses are necessary. One nurse is needed to arrange the instruments, one nurse to help with positioning and one nurse to serve the c-arm and the navigation system.
L. Claassen et al. / Computer-assisted navigation of a complex femoral shaft fracture
(a)
633
(b)
Fig. 4. Contralateral hip anteriorposterior, a) placement, b) radiograph.
(a)
(b)
Fig. 5. Contralateral knee anteriorposterior, a) placement, b) radiograph.
2.2. Positioning Initially the patient is positioned in supine position. The c-arm with its monitor and the monitor of the navigation monitor are placed on the contralateral side of the patient. The disposal of the setup is as follows: From proximal to distal the c-arm, the monitor of the c-arm and the monitor of the navigation system (Fig. 2). The sensor of the navigation system is placed on the ipsilateral side. The “headband” of the navigation system is positioned at the contralateral thigh proximal of the patella (Fig. 3). This is obligate to navigate the contralateral side noninvasive [6].
634
L. Claassen et al. / Computer-assisted navigation of a complex femoral shaft fracture
(a)
(b) Fig. 6. Contralateral knee lateral, a) placement, b) radiograph.
(a)
(b)
Fig. 7. Contralateral hip axial, a) placement, b) radiograph.
2.3. Step 1 Navigation of the contralateral femur Patient in supine position, c-arm in anteriorposterior position. First the contralateral hip is analyzed. The navigation marker is placed above the hip, visible for the navigation sensor (Fig. 4). The leg has to be hold in neutral position all the time. Afterwards an image of the knee has to be taken in the similar manner (Fig. 5). Now the c-arms position is changed to the lateral view to analyze the knee (Fig. 6). For the axial view of the contralateral hip the ipsilateral leg has to be flexed in the hip to a high extend (Fig. 7). When these images are taken properly it becomes visible on the navigation monitor (Fig. 8).
L. Claassen et al. / Computer-assisted navigation of a complex femoral shaft fracture
635
Fig. 8. Navigation monitor after navigation the contralateral leg.
Fig. 9. Positioning of the contralateral leg with hip flexion.
Fig. 10. Left leg ready to precede the operation.
Fig. 11. Placed navigation pins. The other wounds were due to removal of the previously implanted nail in this case.
Then the crucial landmarks have to be marked (Fig. 13, shown for the left leg). These are the apex of the trochanter major, the center of the femoral head, medial femur condyle and the lateral posterior femur condyle. The contralateral hip has to be held in flexion in order to proceed to the next step of the surgery. The flexion of contralateral hip is necessary for axial radiographs of the ipsilateral hip (Fig. 9). 2.4. Step 2 Navigation of the ipsilateral femur The disposal of the setup is not changed for this step. The left leg was covered sterile before (Fig. 10). Two navigation pins are placed, one in the proximal and one in the distal fragment (Fig. 11). One potential drawback of placement is that the navigation pins have contact with the implant. This may lead to a changed position of the pins and might cause measurement errors. After implantation of the nail the navigation of the landmarks has to be done as described for contralateral side (Fig. 12 a-h; Fig. 13).
636
L. Claassen et al. / Computer-assisted navigation of a complex femoral shaft fracture
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
Fig. 12. Navigation of the left femur, a + b) hip anteriorposterior, c + d) hip axial, e + f) knee anteriorposterior, g + h) knee lateral.
L. Claassen et al. / Computer-assisted navigation of a complex femoral shaft fracture
(a)
637
(b)
Fig. 13. Marking the landmarks for knee and trochanter major.
(a)
(b)
(c)
(d)
Fig. 14. Navigation of the fracture, a + b) fracture anteriorposterior placement and radiograph, c + d) fracture lateral placement and radiograph.
638
L. Claassen et al. / Computer-assisted navigation of a complex femoral shaft fracture
Fig. 15. Presented fragments of the fracture with their axes, length and rotation.
2.5. Step 3 Navigation of the fracture Anterior-posterior and lateral images are needed to determine the fracture (Fig. 14). In addition the axis of the proximal and the distal main fragment have to be marked. Afterwards the navigation system is able to present the axis, rotation and length compared to the contralateral side (Fig. 15). The rotation, axis and length can be checked and adjusted. The nail can be locked in the planned position under direct and continuous control. 3. Discussion Complex femoral shaft fractures or postoperative deformities after treating a femoral shaft fracture are difficult to treat. The computer-assisted navigation might be a helpful tool. The procedure described above is still prone to errors: Especially the navigation pins are vulnerable for manipulation. They have to be adjusted stable but may not interfere with the intramedullary nail. A changed position of the pins leads to mistakes in measured values [7]. The advantage of a computer-assisted operation is the direct intraoperative control concerning axes and angles. Crucial is the angle of antetorsion. It has to be adjusted to 10–15◦. That value is assumed to be the anatomical standard [8–10]. Alternatives like the clinical determination is imprecise, as Cordier and Jaarsma showed [11,12]. A postoperative CT scan has two disadvantages. First the postoperative realization would make a further operation necessary to correct detected errors. In addition the intraobserver differences between two measurements are up to 10.8◦ and the interobserver difference up to 15.6◦ [13]. Considering that a difference of 15◦ is in general an indication for a revision this is a high value [4]. Other intraoperative tools to estimate and control antetorsion angle are also inadequate [2,14]. A significant malrotation or fracture malunion are risk factors for osteoarthritis [15,16]. The computerassisted navigation as described here compares the affected leg directly with the contralateral side. This leads to an individual treatment with a lower radiation load compared to conventional treatment [17]. It is notable that a CT scanner and computer assisted navigation uses different ways to estimate the antetorsion angle. While via the CT scanner the femoral neck and the intercondyle axis are compared to
L. Claassen et al. / Computer-assisted navigation of a complex femoral shaft fracture
639
the baseline the antetorsion in computer-assisted navigation is measured direct via apex of the trochanter major, center of the femoral head and intercondyle axis [4,13]. The aim is a maximum length difference not exceeding 1 mm and a rotation difference of 1◦ compared to the contralateral side [4]. In conclusion, the computer assisted navigation leads to a high level of security. More efforts are necessary to distribute the experience with this method. Conflict of interest The authors have no financial conflict of interest. References [1]
Braten M, Terjesen T, Rossvoll I. Femoral shaft fractures treated by intramedullary nailing. A follow-up study focusing on problems related to the method. Injury 1995 Jul; 26(6): 379-383. [2] Krettek C, Rudolf J, Schandelmaier P, Guy P, Konemann B, Tscherne H. Unreamed intramedullary nailing of femoral shaft fractures: operative technique and early clinical experience with the standard locking option. Injury 1996 May; 27(4): 233-254. [3] Liodakis E, Kenawey M, Petri M, Zumrut A, Hawi N, Krettek C, et al. Factors influencing neck anteversion during femoral nailing: A retrospective analysis of 220 torsion-difference CTs. Injury 2011 Nov; 42(11): 1342-1345. [4] Hawi N, Haentjes J, Suero EM, Liodakis E, Krettek C, Stubig T, et al. Navigated femoral shaft fracture treatment: current status. Technol Health Care 2012; 20(1): 65-71. [5] Liodakis E, Macke C, Kenawey M, Krettek C. Mini-navigator: A new system for navigated deformity corrections. Int J Med Robot 2012 Sep; 8(3): 319-326. [6] Kendoff D, Citak M, Gardner MJ, Gosling T, Krettek C, Hufner T. Navigated femoral nailing using noninvasive registration of the contralateral intact femur to restore anteversion. Technique and clinical use. J Orthop Trauma 2007 Nov-Dec; 21(10): 725-730. [7] Citak M, Gardner MJ, Citak M, Krettek C, Hufner T, Kendoff D. Navigated femoral anteversion measurements: A new intraoperative technique. Injury 2008 Apr; 39(4): 467-471. [8] Grutzner P, Hochstein P, Simon R, Wentzensen A. Determination of torsion angle after shaft fractures of the lower extremity–clinical relevance and measurement techniques. Chirurg 1999 Mar; 70(3): 276-284. [9] Strecker W, Hoellen I, Keppler P, Suger G, Kinzl L. Correcting torsion after intramedullary nailing osteosynthesis of the lower extremity. Unfallchirurg 1997 Jan; 100(1): 29-38. [10] Ettinger M, Maslaris A, Kenawey M, Petri M, Krettek C, Jagodzinski M, et al. A preliminary clinical evaluation of the “greater trochanter-head contact point” method for the intraoperative torsional control of femoral fractures. J Orthop Sci 2012 Nov; 17(6): 717-721. [11] Cordier W, Katthagen BD. Femoral torsional deformities. Orthopade 2000 Sep; 29(9): 795-801. [12] Jaarsma RL, Pakvis DF, Verdonschot N, Biert J, van Kampen A. Rotational malalignment after intramedullary nailing of femoral fractures. J Orthop Trauma 2004 Aug; 18(7): 403-409. [13] Jaarsma RL, Bruggeman AW, Pakvis DF, Verdonschot N, Lemmens JA, van Kampen A. Computed tomography determined femoral torsion is not accurate. Arch Orthop Trauma Surg 2004 Oct; 124(8): 552-554. [14] Herzberg W, Meitz R, Halata Z. Antetorsion of the femur neck. A variable of the trochanter minor? Unfallchirurg 1991 Apr; 94(4): 168-171. [15] Eckhoff DG. Effect of limb malrotation on malalignment and osteoarthritis. Orthop Clin North Am 1994 Jul; 25(3): 405-414. [16] Kettelkamp DB, Hillberry BM, Murrish DE, Heck DA. Degenerative arthritis of the knee secondary to fracture malunion. Clin Orthop Relat Res 1988 Sep; (234): 159-169. [17] Hufner T, Kendoff D, Citak M, Geerling J, Krettek C. Precision in orthopaedic computer navigation. Orthopade 2006 Oct; 35(10): 1043-1055.
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.
