The term "computer-assisted musculoskeletal surgical navigational orthopedic procedure" describes navigation systems that provide additional information during a procedure in order to further integrate preoperative planning with intraoperative execution.  This document addresses procedures of the appendicular skeleton and does not address navigation when used for spinal or cranial procedures.

Investigational and Not Medically Necessary:

Computer-assisted musculoskeletal surgical navigation is considered investigational and not medically necessary as an adjunct to orthopedic procedures of the appendicular system.

General Information
Computer-assisted surgery has been investigated in three general settings: 1) as an adjunct to surgery for trauma or fracture; 2) as an adjunct to knee or hip arthroplasty procedures; or 3) as an adjunct to anterior cruciate ligament reconstruction.  Each of these categories will be discussed separately, but in general, computer-assisted surgery attempts to either provide increased efficiency in the surgical procedure or improve the biomechanical alignment of joints.  Improvements in surgical efficiency can be measured in terms of operating time or radiation exposure.  Changes in alignment are considered an intermediate outcome.  The final health outcome involves consideration of how these changes will impact final functional outcomes, which can be assessed with knee or hip scores, or surgical revision rates.  The following review focuses on the results of randomized controlled trials.

Trauma or Fracture  
Computer-assisted surgery has been most frequently mentioned as an adjunct to pelvic, acetabular or femoral fractures.  For example, fixation of these fractures typically requires percutaneous placement of screws or guidewires.  Conventional fluoroscopic guidance (i.e., C-arm fluoroscopy) provides imaging in only one plane.  Therefore, the surgeon must position the implant in one plane and then get additional images in other planes in a trial and error fashion to ensure that the device has been properly placed.  This process adds significant operating room (OR) time and radiation exposure.  It is hoped the computer-assisted surgery would allow for minimally invasive fixation and provide more versatile screw trajectories with less radiation exposure.  Therefore, computer-assisted surgery is considered an alternative to the existing image guidance using C-arm fluoroscopy.

Ideally, one would like controlled trials comparing the OR time, the radiation exposure and long-term outcomes of individuals whose surgery was conventionally guided using C-arm versus image-guided using computer-assisted surgery.  While several in vitro and review studies have been published (Schep, 2003; Hufner, 2002; Leenders, 2002; Digioia, 2002), a literature search identified only one clinical trial of computer-assisted surgery in trauma or fracture cases.  Suhm and colleagues reported on a case series of 27 individuals with femoral fractures who underwent implantation of a femoral nail (Slomczykowski, 2001).  Outcomes included precision of interlocking, exposure time and OR time.  Without a control or comparison group, it is not possible to determine the efficacy of the computer assistance.

Total Knee Arthroplasty (TKA) 
A total of nine randomized controlled trials enrolling more than 25 individuals and comparing computer-assisted with conventional TKA were identified in a literature search; two of these publications reported on long term follow-up of the same group of individuals (Chauhan 2004, Chin 2005, Decking 2005, Victor 2004, Matziolis 2007, Decking 2007, Ensini 2006, Kim 2007, Spencer 2007 Lutzner 2008).  These studies compared various measures of alignment in the two groups.  While all studies reported improvements in target alignments, only 4 of the 7 studies reported that the improvements in overall tibial/femoral alignment were statistically significant (Chauhan, Decking, Victor, Matziolis).  A key consideration is how changes in alignment relate to improvements in individual outcomes.  The largest study that reported outcomes was that of Ensini (2007), which reported no difference in knee scores or participant satisfaction at 2-3 year follow-up.  Other studies similarly did not report a significant improvement in functional outcome.  There were no studies that evaluated a reduction in the surgical revision rate associated with computer-assisted navigation. 

Two additional randomized studies examined the role of computer-assisted navigation in individuals undergoing minimally invasive total knee arthroplasty.  Luring and colleagues (2008) randomized 60 subjects to undergo minimally invasive TKA with and without computer-assisted navigation.  While the postoperative deviation in leg axis was decreased in the navigation group, there were no differences in functional outcomes at 12 months.  Similarly in a randomized study of 108 individuals, Dutton and colleagues (2008) reported that while navigated minimally invasive TKA was associated with an improvement in postoperative alignment, there was no difference in functional outcomes.

In 2007, Bauwens and colleagues performed a systematic review and meta-analysis comparing navigated with conventional knee arthroplasty.  A total of 33 studies (of which 11 were randomized trials) of various methodological quality were reviewed to include a total of 3423 individuals with a mean age of 67.3 ± 4.1 years.  There was no significant difference in the mechanical axes alignment between the navigated and conventional TKA procedures.  Individuals who underwent the navigated procedure had a lower risk of malalignment at critical thresholds of greater than 3° (risk ratio, 0.79; 95% confidence interval, 0.71 to 0.87) and greater than 2° (risk ratio, 0.76; 95% confidence interval, 0.71 to 0.82).  However, as the authors point out, it is unclear if this marginal benefit will result in better long-term outcomes.  Computer-assisted navigation increased the length of the mean duration of surgery by 23%.  No solid conclusions could be drawn with regards to functional outcomes or complication rates.  The authors concluded that the clinical benefits of navigated TKA are still ambiguous and that additional research involving larger studies is needed.    

Seon and colleagues (2009) conducted a study comparing the clinical and radiological outcomes of TKA with and without navigation.  The study included 43 participants who underwent TKAs using a navigation system and 42 participants who underwent TKAs without a navigation system.  During the preoperative assessments, sealed envelopes were used to randomly assign the subjects into the TKA with navigation (NA-TKA) group or the TKA without navigation (CON-TKA) group.   The minimum follow-up period was two-years.  The exclusion criteria included individuals that had undergone prior open knee surgery and those with a severe deformity (>20° varus or >30° flexion contracture).  All study participants had primary osteoarthritis.  All of the TKAs carried out in the CON-TKA group were performed by a single physician who was also the primary author of this study.  Both the NA-TKAs and the CON-TKAs were performed using a standard medial parapatellar approach.  The NA-TKAs were carried out using the OrthoPilot® (version 4.08, Aesculap, Tuttlingen, Germany) navigation system.  Participants in both groups underwent the same postoperative rehabilitation protocol and active range of motion exercises.  Clinical evaluations were performed preoperatively and at final follow-up.  Clinical outcomes were measured using ROM, Hospital for Special Surgery (HSS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores.  Radiological comparisons were made using standing radiographs of the knees.  The HSS and WOMAC scores showed significant improvement at final follow-ups in both groups, but showed no significant inter-group differences (p>0.05).  There was no significant difference in ROM. (p=0.962).  TKAs performed with navigation resulted in significantly better outcomes in terms of mechanical angle and prosthetic alignment outliers than TKAs performed without navigation.  However, there was no significant difference in functional outcomes between TKAs performed with or without a navigation system at two-year follow-up.  The researchers suggested that another study be undertaken on a larger group with a longer follow-up period to determine the influence that the observed radiographic alignment improvements have on clinical results and survival rate.

Total Hip Arthroplasty (THA)
There are fewer controlled studies examining the role of THA with computer-assisted navigation.  Two randomized studies specifically focused on placement of the acetabular component.  Parratte and Argenson (2007) reported on the results of 60 individuals undergoing THA with and without computer navigation.  The primary outcome was cup anteversion and abduction angles; there were no significant differences between the two groups.  Similarly, in a randomized trial of 25 participants, Kalteis and colleagues reported improved anteversion angles in the navigated group, and that a higher percentage of individuals were within the target region of acetabular placement.  No functional outcomes were reported in either of these trials.  In another small randomized trial of 36 subjects undergoing femoral osteotomy for dysplastic hip, Hsieh and colleagues (2006) did not report any differences in functional outcomes at 24 months between the navigated and conventional surgical group.

In an uncontrolled case series, Leenders and colleagues studied the variability in placement of the acetabular component among three groups of participants: 1) those undergoing THA using free hand placement before computer-assisted surgery was available; 2) those undergoing THA with computer assistance, and 3) those undergoing free hand placement after computer assistance was available (Leenders, 2002).  While there was a reduction in variability between groups one and two, there was not a significant difference between groups two and three.  No data regarding long-term outcome was reported.  Digioia and colleagues reported on a case series of 78 individuals (82 hips) who underwent THA and compared the alignment directed by a mechanical guide and computer assistance.  The authors hypothesized that the use of the mechanical guide rather than computer assistance would have resulted in an unacceptable acetabular alignment in 78% of hips (Digioia, 2002).  More recently there appears to be growing interest in imageless navigation systems, for both arthroplasties and hip resurfacing procedures.  Numerous case series and retrospective reviews have been published that report improved alignment (Olsen 2009, Bailey 2009, Romanowski 2008, Najarian 2009, Dorr 2007).  However, as noted above, controlled studies with functional outcomes are needed to validate that computer-assisted navigation results in improved health outcomes.

Anterior Cruciate Ligament Reconstruction
The positioning of the tibial and femoral tunnels is considered an important variable in anterior cruciate ligament (ACL) reconstructions.  Plaweski and colleagues (2006) reported the results of 60 subjects randomized to undergo ACL reconstruction with and without computer-assisted navigation.  The navigated group had improved measures of laxity and other alignment variables, but there was no report in improvement in functional outcomes.  Two other smaller randomized trials also reported some improvements of tunnel placement associated with computer navigation compared to conventional treatment, but with no reported improvements in functional outcomes (Hart 2008, Mauch 2007).

Summary
While results of controlled trials suggest improvements in the intermediate biomechanical outcomes, there is inadequate data on final health outcomes, as assessed by improvements in functional outcomes or surgical revision rates.  Computer-assisted musculoskeletal navigation has been primarily investigated as an adjunct to surgery of the appendicular skeletal system.  Most of the research has focused on its use in the knee and hip.  There is only very preliminary literature regarding its use in the upper extremity (i.e. shoulder and elbow) and axial skeleton (i.e. spine).   

Computer-assisted musculoskeletal surgical navigational systems allow surgeons to perform complex, traditionally invasive trauma surgeries, such as femoral and pelvic fracture fixation, through small incisions. Using this navigational technology, surgeons may be able to reduce the amount of time an individual is in surgery, limit radiation exposure, blood loss and rehabilitation time while increasing surgical accuracy. Computer-assisted musculoskeletal surgical navigation involves three steps; data acquisition, registration and tracking.

Data Acquisition 
Data can be acquired in three different ways, i.e., fluoroscopic, CT/MRI guided or imageless systems. This data is then used for registration and tracking, described below. Image guided systems are somewhat self explanatory. The image-less systems rely on other information such as centers of rotation of the hip, knee or ankle, or visual information like anatomical landmarks.

Registration 
Registration refers to the ability of relating images (i.e., x-rays, CT, MRI or the subjects' 3-D anatomy) to the anatomical position in the surgical field.  Early registration techniques required the placement of pins or "fiduciary markers" in the target bone.  This required an additional surgical procedure.  More recently, a surface matching technique can be used in which the shapes of the bone surface model generated from preoperative images are matched to surface data points collected during surgery.

Tracking
Tracking refers to the sensors and measurement devices that can provide feedback during surgery regarding the orientation and relative position of tools to bone anatomy. For example, optical or electromagnetic trackers can be attached to regular surgical tools which can then provide real time information of the position and orientation of the tools' alignment with respect to the bony anatomy of interest.

The most commonly performed orthopedic computer-assisted surgeries appear to be as an adjunct to fixation of pelvic, acetabular or femoral fractures, and as an adjunct to hip and knee arthroplasty procedures.

The following codes for treatments and procedures applicable to this document are included below for informational purposes.  Inclusion or exclusion of a procedure, diagnosis or device code(s) does not constitute or imply member coverage or provider reimbursement policy. Please refer to the member's contract benefits in effect at the time of service to determine coverage or non-coverage of these services as it applies to an individual member.

When services are Investigational and Not Medically Necessary:

Peer Reviewed Publications:

1. Bailey C, Gul R, Falworth M, et al. Component alignment in hip resurfacing using computer navigation. Clin Orthop Relat Res. 2009; 467(4):917-922.
2. Bauwens K, Matthes G, Wich M, et al. Navigated total knee replacement. A meta-analysis. J Bone Joint Surg Am. 2007; 89(2):261-269.
3. Chauhan SK, Scott RG, Breidahl W, Beaver RJ. Computer assisted knee arthroplasty versus a conventional jig-based technique. A randomised, prospective trial.  J Bone Joint Surg Br. 2004; 86(3):372-377.
4. Chin PL, Foo LS, Yang KY, et al. Randomized controlled trial comparing the radiologic outcomes of conventional and minimally invasive techniques for total knee arthroplasty. J Arthroplasty. 2007; 22(6):800-806.
5. Decking R, Markmann Y, Fuchs J, et al. Leg axis after computer-navigated total knee arthroplasty: a prospective randomized trial comparing computer-navigated and manual implantation. J Arthroplasty. 2005; 20(3):282-288.
6. Decking R, Markmann Y, Mattes T, et al. On the outcome of computer-assisted total knee replacement.  Acta Chir Orthop Traumatol Cech. 2007; 74(3):171-174.
7. Digioia AM, Jaramaz B, Plakseychuk AY, et al. Comparison of a mechanical acetabular alignment guide with computer placement of the socket. J Arthroplasty. 2002; 17(3):359-364.
8. Dorr LD, Malik A, Wan Z, et al. Precision and bias of imageless computer navigation and surgeon estimates for acetabular component position. Clin Orthop Relat Res. 2007; 465:92-99.
9. Dutton AQ, Yeo SJ, Yang KY, et al. Computer-assisted minimally invasive total knee arthroplasty compared with standard total knee arthroplasty. A prospective, randomized study. J Bone Joint Surg Am. 2008; 90(1):2-9.
10. Ensini A, Catani F, Leardini A et al. Alignments and clinical results in conventional and navigated total knee arthroplasty.  Clin Orthop Relat Res. 2007; 457:156-162.
11. Hart R, Krejzla J, Sváb P, et al. Outcomes after conventional versus computer-navigated anterior cruciate ligament reconstruction.  Arthroscopy. 2008; 24(5):569-578.
12. Hsieh PH, Chang YH, Shih CH.  Image-guided periacetabullar osteotomy: computer assisted navigation compared with the conventional technique: a randomized study of 36 patients followed for 2 years.  Acta Orthop. 2006; 77(4):591-597.
13. Hufner T, Pohlemann T, Tarte S, et al. Computer-assisted fracture reduction of pelvic ring fractures: an in vitro study. Clin Orthop Relat Res. 2002; 399:231-239.
14. Kim YH, Kim JS, Yoon SH. Alignment and orientation of the components in total knee replacement with and without navigation support: a prospective, randomized study.  J Bone Joint Surg Br. 2007; 89(4):471-476.
15. Leenders T, Vandevelde D, Mahieu G, Nuyts R. Reduction in variability of acetabular cup abduction using computer-assisted surgery: a prospective and randomized study. Comput Aided Surg. 2002; 7(2):99-106.
16. Lüring C, Beckmann J, Haiböck P, et al. Minimal invasive and computer assisted total knee replacement compared with the conventional technique: a prospective, randomised trial.  Knee Surg Sports Traumatol Arthrosc. 2008; 16(10):928-934.
17. Lützner J, Krummenauer F, Wolf C, et al. Computer-assisted and conventional total knee replacement: a comparative, prospective, randomised study with radiological and CT evaluation. J Bone Joint Surg Br. 2008; 90(8):1039-1044.
18. Matziolis G, Krocker D, Weiss U, et al.  A prospective, randomized study of computer-assisted and conventional total knee arthroplasty. Three-dimensional evaluation of implant alignment and rotation.  J Bone Joint Surg Am. 2007; 89(2):236-243. 
19. Mauch F, Apic G, Becker U, Bauer G.  Differences in the placement of the tibial tunnel during reconstruction of the anterior cruciate ligament with and without computer-assisted navigation.  Am J Sports Med. 2007; 35(11):1824-1832.
20. Najarian BC, Kilgore JE, Markel DC. Evaluation of component positioning in primary total hip arthroplasty using an imageless navigation device compared with traditional methods. J Arthroplasty. 2009; 24(1):15-21.
21. Olsen M, Davis ET, Waddell JP, Schemitsch EH. Imageless computer navigation for placement of the femoral component in resurfacing arthroplasty of the hip. J Bone Joint Surg Br. 2009; 91(3):310-315.
22. Parratte S, Argenson JN. Validation and usefulness of a computer-assisted cup-positioning system in total hip arthroplasty. A prospective, randomized, controlled study.  J Bone Joint Surg Am. 2007; 89(3):494-499.
23. Plaweski S, Cazal J, Rosell P, Merloz P. Anterior cruciate ligament reconstruction using navigation. a comparative study on 60 patients.  Am J Sports Med. 2006; 34(4):542-552.
24. Romanowski JR, Swank ML. Imageless navigation in hip resurfacing: avoiding component malposition during the surgeon learning curve. J Bone Joint Surg Am. 2008; 90(Suppl 3):65-70.
25. Schep NW, Broeders IA, van der Werken C. Computer-assisted orthopaedic and trauma surgery. State of the art and future perspectives. Injury. 2003; 34(4):299-306.
26. Seon JK, Park SJ, Lee KB, et al. Functional comparison of total knee arthroplasty performed with and without a navigation system. Int Orthop. 2009; 33(4):987-990.
27. Slomczykowski MA, Hofstetter R, Sati M, et al. Novel computer-assisted fluoroscopy system for intraoperative guidance: feasibility study for distal locking of femoral nails. J Orthop Trauma. 2001; 15(2):122-131.
28. Spencer JM, Chauhan SK, Sloan K, et al. Computer navigation versus conventional total knee replacement:  no difference in functional results at two years.  J Bone Joint Surg Br. 2007; 89(4):477-480.
29. Suhm N, Jacob AL, Nolte LP, et al. Surgical navigation based on fluoroscopy--clinical application for computer-assisted distal locking of intramedullary implants. Comput Aided Surg. 2000; 5(6):391-400.
30. Victor J, Hoste D. Image-based computer-assisted total knee arthroplasty leads to lower variability in coronal alignment.  Clin Orthop Relat Res. 2004; 428:131-139.

Government Agency, Medical Society, and Other Authoritative Publications: 

1. Blue Cross Blue Shield Association. Computer-assisted navigation for total knee arthroplasty. TEC Assessment, 2008; 22(10)

BrainLab AG Vector Vision fluoro3D
Computer-Assisted Musculoskeletal Surgical Navigational Orthopedic Procedures
DePuy CAS Knee Instrumentation
InstaTrak 3500 Plus SystemOrthoMap® 3D Module
Orthopilot® Next Generation
Rio^™ Robotic Arm Interactive Orthopedic System (MAKOplasty^®)
StealthStation® System
Surgetics Ortho Kneelogics Navigation System
VectorVisionA CT-free navigation system
Zimmer Ortho Guidance Systems

The use of specific product names is illustrative only.  It is not intended to be a recommendation of one product over another, and is not intended to represent a complete listing of all products available.