Clinical application of computer guidance and navigation in orthopaedic trauma surgery at the extremities and the pelvis : a systematic review

examined the feasibility of naviga­ tion for interlocking procedures of intramedullary nails in fractures of the lower extremity. However, the majo­ rity of works included patients with injuries of the pelvic ring; computer­ assisted systems were mainly used to insert cannulated screws, stabilising acetabular fractures or the sacro–iliac joint. Only one publication included computerised treatment methods of the upper extremity. Conclusion Computer­assisted techniques in orthopaedic trauma surgery are a real­ ity and are being applied in clinical set­ tings. At the moment, these techniques are most frequently used in surgical procedures at the pelvis. At the lower extremity, the best examined modal­ ity is the placement of locking screws for intramedullary nailing. Navigated treatment of fractures including reduction and fixation is definitely not being performed in larger, clinical series and remain single­centre expe­ riences. Neither reference­based nor trajectory­based techniques are being used at the upper extremity frequently so far. Most limiting for the employ­ ment of classical navigation techniques is its dependence on fixed reference arrays. This problem has to be over­ come, before navigation can be used in trauma surgery on a larger scale. However, so far, published results are promising and further developments in this exciting field may contribute to decrease surgical risks and improve finally clinical outcome parameters.


Introduction
Computerassisted surgery was introduced in orthopaedic surgery in 1995.First applications were spine and pelvis surgery for different indi cations, among these degenerative diseases, traumatic injuries and, later, also tumour cases.Several navigation techniques are available.The first systems were based on computed tomography (CT) images, which were transferred manually to the work station of the navigation system.Major limitations regarding naviga tion in trauma surgery are potentially moving parts of a fracture which may have changed between the time of imaging and the surgical procedure.In the late 90s of the last century, better suitable techniques based on fluoroscopic images, acquired in the operation room (OR), were intro duced.Initially, images in different planes were used for navigation, allowing guiding instruments and implants in twodimensional (2D) images of the fluoroscope.Advantage over CTbased navigation is that fluoroscopic images are acquired after positioning of the patient in the OR, therefore ensuring to display the current situation.Of course, CT images allow navigation in different planes, giving better orientation in anatomically challenging regions in comparison to plain 2D images.A rel atively new Carm technology allows

Introduction
Computerassisted surgery was intro duced in orthopaedic surgery in 1995.It is frequently used in spine surgery, but not in orthopaedic trauma sur gery at the pelvis and the upper and lower extremity.This study aims to give a systematic review on current techniques and future developments in the field of navigation and image guidance in orthopaedic trauma sur gery focusing on the clinical applica tion at the pelvis, the upper and the lower extremity.

Material and methods
A systematic review of Medlars Online International Literature via PubMed was performed.
Search terms were [Navigation] and [Trauma], [Computer Aided Surgery] and [Orthopaedic Trauma Surgery] and [Navigation] and [Fracture], connected by the Boolean operator [and].We included all arti cles that employed navigated meth ods at least in 10 clinical cases in orthopaedic trauma surgery.Spine surgery, tumour surgery and degen erative indications were excluded.

Results
Finally, 28 articles were identified.The first published studies in this field were published in the year 2000 and attached to instruments and the object of interest (Figure 3).Another prerequisite for this navigation type is a camera system, tracking con stantly movements of instruments and the marked object of interest.
The general usage of navigated procedures in trauma surgery is limited by the dependence on these fixed reference arrays that must be firmly attached to all movable parts.
In fractures, theoretically all rel evant fragments have to be marked with such references.Of course, this is neither practically achievable nor feasible.Therefore, in trauma, only few indications are eligible to be treated with navigated methods in the daily clinical routine.Recently, other techniques as trackerbased navigation were described in the lit erature.Still, these works are more or less experimental and no novel technology brought a breakthrough, replacing standard, often fluoros copybased techniques.
Computer navigation is well exam ined and most frequently used in spine surgery for different indications (i.e.degenerative, trauma and, to a lesser degree, in tumour surgery).In oppo site to spinal procedure, navigation and guidance is much less extensively examined for trauma procedures at the extremities and the pelvis.
This study aims to give a system atic review on current techniques and future developments in the field of navigation and image guidance in orthopaedic trauma surgery focus ing on the clinical application of these techniques at the pelvis and the upper and lower extremity.

Material and methods
A systematic review of Medlars Online International Literature via PubMed was performed.All arti cles found in the database up to 13 th April 2013 are displayed in Figure 1: To begin a navigated procedure, a verification procedure has to ensure that virtual and real anatomy is congruent (A).Only after a successful verification, the navigated procedure can be started.In this case, a 3D scan of the SI joint was performed and the images were uploaded to the workstation of the navigation system (B).Whenever a tracked tool is brought into position, trajectories are displayed in realtime, pointing in the direction of the tool.The surgeon can control the direction in different planes, ensuring to insert the screw or wire correctly.3, the surgeon holds a tracked drill guide, while a second surgeon inserts a guide wire (A).Over the wire, a can nulated screw is inserted stabilising the posterior pelvic ring.In the postopera tive control image in anterio-posterior direction, a correctly placed SI screw is displayed (B).

Licensee OA Publishing London 2013. Creative Commons Attribution License (CC-BY)
Competing interests: none declared.Conflict of interests: none declared.
All authors contributed to the conception, design, and preparation of the manuscript, as well as read and approved the final manuscript.
All authors abide by the Association for Medical Ethics (AME) ethical rules of disclosure.
For citation purposes: Kraus M, Krischak G, Dehner C, Gebhard F. Clinical application of computer guidance and navigation in orthopaedic trauma surgery at the extremities and the pelvis: a systematic review.OA Musculoskeletal Medicine 2013 Jul 01;1(2):14.
crosschecking the references of already identified publications.The first report dates back to the year 2000.Publication rates were grow ing constantly, reaching a plateau since 2009 with four to six articles each year (Figure 4).Table 2 gives an overview on all included articles.The majority of works included patients with injuries of the pelvic ring; there, computer assistedsystems were mainly used to insert cannulated screws stabilising acetabular frac tures or the sacro-iliac (SI) joint.Firstly, navigated applications were used for the treatment of conditions of the lower extremity.Only one publication included computerised treatment methods of the upper extremity.

Discussion
The authors have referenced some of their own studies in this syste matic review.These referenced studies have been conducted in accordance with the Declaration of Helsinki (1964) and the protocols of these studies have been approved by the relevant ethics committees related to the institution in which they were performed.All human subjects, in these referenced studies, gave informed consent to participate in these studies.
Computeraided systems are being used in orthopaedic trauma surgery at the extremities and the pelvis since the year 2000 in clinical studies with at least 10 patients involved.In the first years, most studies focused on its use in treatment of conditions of the lower extremities, whereas pelvic injuries are dominating the last cou ple of years.The upper extremity is still not being treated with navigated methods on a larger scale.

Lower extremity
Suhm and his team 20 were the first to report on 27 patients with pertro chanteric femur fractures to be treated with assistance of a computeraided

Results
A total of 28 articles fulfilled the above described inclusion crite ria.Most articles were delivered by the system using the search terms [Navigation] and [Trauma].However, seven additional articles were iden tified with the other two search terms; three articles were identified  20 patients with femoral neck frac tures navigated vs. 20 nonnavigated procedures and declared that navi gation increased the accuracy and allowed a reduction of the procedure time as well as surgical complications.
In a large case series, Zhang et al. 25 examined 130 navigated screw oste osynthesis of calcaneal fractures and were convinced of the new technique (Figure 5).However, a control group was not included.Rübberdt and his team 18 examined 11 patients with 15 calcaneal fractures and stated that navigation helped to reduce the inva sivity of the procedure.
Another technique without fixed reference markers was applied by Herman et al. 7 , who used marked instruments that were used to dis play a simple trajectory in standard, 2D fluoroscopic images for guide wire placement in proximal femur fractures to be stabilised with a dynamic hip screw.In a prospective, randomised trial, our working group was able to demonstrate with the same system as the latter mentioned authors that this system allowed reducing number of trials and pro cedure time in the treatment of metatarsal five fractures with guide wirebased cannulated screws 10 .In another, prospective cohort study, we used this system for different indica tions at the lower extremity.We see this new technique, which is inde pendent of fixed reference arrays, suitable for indications, using guide or Kwires 11 .

Pelvic ring and acetabular injuries
Stöckle and his team 19 were the first to report a clinical series of patients, in whom CTbased and 2Dbased navigation was used to insert SI In an article in Chinese language, Luo et al. 14 reported in their abstract on 22 patients receiv ing 2Dbased navigated pubic ramus screws, SI and acetabular screws.They expected the new technique to increase precision and reduce OR and radiation time.However, no control group was included.Gras 4 reported one year later on 14 patients, in whom acetabular screws were inserted via 3Dbased navigation.Again, no control group was examined.Also in 2008, Sun et al. 22 expected the same advantages as the two latter mentioned studies, but warned of high costs and a pro longed OR time due to high technical requirements.Another work, pub lished in Chinese language, included 22 prospective patients with pelvic fractures, receiving percutaneous screw fixation.The authors reported a 22month followup period and mentioned that all fractures were healed and that the clinical results were excellent 23 .Two prospective, not randomised trials with a non navigated control group regarding Figure 5: After a 3D scan of a fractured calcaneus was performed intraoperatively, the images were uploaded automati cally to the navigation system.Via a navigated pointer, a screw was planned in these images.Finally, the surgeon used a navigated screw driver to insert the screw following the planned trajectory.It is also possible to control the depth of the inserted screw, preventing the screw from breaching the corticalis or the joint line.the placement of SI screws were identified.Zwingmann et al. 27,28 reported on reduced radiation and increased precision in the navigated group in comparison to the fluoro scopic technique without navigation.Another working group came to a similar conclusion in a controlled, retrospective study 6 .In a controlled, prospective trial Oberst et al. 16 included patients with acetabular fractures.Although navigation pro longed the OR time, the complica tion rate was lower.For acetabular fractures and SI screw placement without a control group, navigation systems were employed successfully by other working groups as well, all coming to the conclusion that navigation may potentially contri bute increasing the precision of the placement procedure 2,3,5,8,9,24,26 .Our working group quantified the effec tive dose of patients receiving navi gated and nonnavigated SI screws 12 .Navigation was able to reduce the effective dose significantly.Recently, Peng et al. 17

Upper extremity
To the best of our knowledge, we were the only working group employ ing an imagebased guidance sys tem for traumatic conditions of the upper extremity in a clinical series including 16 patients with different indications for surgical therapy 11 .Among these were acromioclavicu lar joint dislocations, one fracture of the humeral head, one fracture of the coracoid process and fractures of the scaphoid (Figure 6).We employed the same system as Herman et al. 7 used to insert dynamic hip screw in proximal femur fracture.We were of the opinion that trajectory guidance without camera tracking and fixed reference arrays is suitable for indi cations, where guide wire fixation, eventually followed by a cannulated screw, can be used.
Figure 6: Image guidance is not using fixed reference markers.In this new technique, the instruments contain radioopaque markers (black arrow), which are detected by the system's workstation.These integrated markers serve to reference the image (A).Furthermore, this system is not using a camera; there fore, no live tracking of instruments and the object of interest is possible.The displayed trajectory is only valid for the moment it was obtained.Any move ment of patient or instrument requires a new Carm shot.Beside trajectories, templates of implants can be visualised (B).

Conclusion
Computerassisted techniques in orthopaedic trauma surgery are a reality and are being applied in clini cal settings.At the moment, these techniques are most frequently used in surgical procedures at the pel vis.At the lower extremity, the best examined modality is the placement of locking screws for intramedul lary nailing.Navigated treatment of fractures including reduction and fixation is definitely not being performed in larger, clinical series and remain singlecentre expe riences.Neither referencebased nor trajectorybased techniques are being used at the upper extremity frequently so far.A limitation for the employment of classical naviga tion techniques is its dependence on fixed reference arrays.This problem has to be overcome, before naviga tion can be used in trauma surgery on a larger scale.However, so far, published results are promising and further developments in this exciting field may contribute to decrease sur gical risks and improve, finally, clini cal outcome parameters.

Figure 2 :
Figure 2: Continuing the scenario of Figure3, the surgeon holds a tracked drill guide, while a second surgeon inserts a guide wire (A).Over the wire, a can nulated screw is inserted stabilising the posterior pelvic ring.In the postopera tive control image in anterio-posterior direction, a correctly placed SI screw is displayed (B).

Figure 3 :
Figure 3: For CTbased, 2Dbased and 3Dbased navigation, reference markers attached to patient (the bone to be navigated) (a) and instruments (b) are a necessary prerequisite.A camera registers any movement of the markers.With an additional tool (c), instruments can be registered and used for navigation.

Figure 4 :
Figure 4: In the beginning, first reports examined indications at the lower extremity.In recent years, more and more articles were published on navigated screw insertion in the pelvis.
used intraoperative CT to navigate SI screws.The accuracy was described as very high, but sur geons were exposed to an increased effective dose in comparison to the fluoroscopy-based method

Table 1
. No limits were used for article type, year of publication or language.All results were scanned manually for relevance to the topic.All eligible articles were entered again in the database and a crosscheck research was performed.Included were all articles, reviews and case series on the use of computerassisted tech niques, referencebased or not, in orthopaedic trauma surgery, if these techniques were applied in a clinical study including at least 10 patients.Excluded were technical notes, experimental articles on saw bones, cadaver studies and articles report ing on nontraumarelated condi tions, i.e., degenerative diseases, drilling of osteochondral lesions, total knee, hip and shoulder replace ments due to osteoarthritis and all tumourrelated surgeries as well as all spinerelated procedures and leg axis corrections.Furthermore, all articles including less than 10 clinical cases were excluded.Articles in other languages than English or German were excluded, if the English abstract did fail to provide all required essen tial information (i.e.number of patients, diagnosis, treatment and techniques).

Table 2 In this systematic review, 28 studies were identified including at least 10 patients treated with computer-assisted techniques in orthopaedic trauma surgery Author, year and journal name Study design Number Diagnosis Treatment Technique Results/conclusion
Licensee OA Publishing London 2013.Creative Commons Attribution License (CC-BY)Competing interests: none declared.Conflict of interests: none declared.All authors contributed to the conception, design, and preparation of the manuscript, as well as read and approved the final manuscript.All authors abide by the Association for Medical Ethics (AME) ethical rules of disclosure.For citation purposes: Kraus M, Krischak G, Dehner C, Gebhard F. Clinical application of computer guidance and navigation in orthopaedic trauma surgery at the extremities and the pelvis: a systematic review.OA Musculoskeletal Medicine 2013 Jul 01;1(2):14.CT, computed tomography; DHS, dynamic hip screw; nav, navigation; SI, sacro-iliacal.