Surgery Section - Computer Assisted Navigation for Orthopedic Procedures of the Pelvis and Appendicular Skeleton

IMPORTANT REMINDER

This Medical Policy has been developed through consideration of medical necessity, generally accepted standards of medical practice, and review of medical literature and government approval status.

Benefit determinations should be based in all cases on the applicable contract language. To the extent there are any conflicts between these guidelines and the contract language, the contract language will control.

The purpose of medical policy is to provide a guide to coverage. Medical Policy is not intended to dictate to providers how to practice medicine. Providers are expected to exercise their medical judgment in providing the most appropriate care.

Description

The term “computer assisted musculoskeletal surgical navigational orthopedic procedure” describes navigation systems that provide additional information during a procedure that attempt to further integrate preoperative planning with intraoperative execution. Computer assisted navigation involves the three steps described below:

1. Data Acquisition

   As described by three 2004 CPT category III codes, data can be acquired in three different ways: fluoroscopic, CT/MRI guided, or via 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.

2. Registration

   Registration refers to relating images (e.g., x-rays, CT, MRI or patients’ 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 is used in which the shapes of the bone surface model generated from preoperative images are matched to surface data points collected during surgery.

3. 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 related to the position and orientation of the tools’ alignment with respect to the bony anatomy of interest.

With respect to orthopedic procedures, computer assisted navigation is most commonly performed as an adjunct to fixation of pelvic, acetabular or femoral fractures, and as an adjunct to hip and knee arthroplasty procedures.

Surgical navigation systems require FDA clearance, but generally are subject only to 510(k) clearance since computer assisted surgery is considered analogous to a surgical information system in which the surgeon is only acting on the information that is provided by the navigation system. As such, the FDA does not require data documenting the intermediate or final health outcomes associated with computer assisted surgery. (In contrast, robotic procedures, in which the actual surgery is robotically performed, are subject to the more rigorous requirement of the PMA process.) A variety of surgical navigation procedures have received FDA clearance through the 510(k) process, and in general, the labeled indications are very broad. Below is one example.

“The OEC FlurorTrak™ 9800 Plus provides the physician with fluoroscopic imaging during diagnostic, surgical and interventional procedures. The surgical navigation feature is intended as an aid to the surgeon for locating anatomical structures anywhere on the human body during either open or percutaneous procedures. It is indicated for any medical condition that may benefit from the use of stereotactic surgery and which provides a reference to rigid anatomical structures such as sinus, skull, long bone or vertebra visibile on fluoroscopic images.”

Policy/Criteria

Computer assisted navigation for orthopedic procedures involving the pelvis and appendicular skeleton is considered investigational.

Scientific Background

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 guide wires. 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 time and radiation exposure. It is hoped the computer assisted navigation would allow for minimally invasive fixation and provide more versatile screw trajectories with less radiation exposure. Therefore, computed assisted navigation is considered an alternative to the existing image guidance using C-arm fluoroscopy.

In order to determine whether or not computer assisted surgery results in improved health outcomes, controlled trials are needed, comparing the operating time, the radiation exposure and long term outcomes of those 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 (2-5), a literature search through June 27, 2006 identified only one clinical trial of computer assisted surgery in trauma or fracture cases. Suhm and colleagues reported on a case series of 27 patients with femoral fractures who underwent implantation of a femoral nail. (6) Outcomes included precision of interlocking, exposure time and OR time. However, without a control or comparison group, it is not possible to determine the impact of the computer assistance on final health outcomes.

Arthroplasty (Total hip [THA] and total knee [TKA])

Unlike fractures, for which the surgery is typically image-guided using C-arm fluoroscopy, routine arthroplasties are conventionally done without image guidance. Therefore, in this setting computer assisted surgery is not considered an alternative to C-arm fluoroscopy, but a novel approach.

For both total hip and knee arthroplasties, optimal alignment is considered an important aspect of long term success.  Malalignment of arthroplasty components is one of the leading causes of instability and reoperation.  In THA, orientation of the acetabular component of the THA is considered critical.  For TKA, alignment of the femoral and tibial components as well as ligament balancing are considered important factors in determining success.  The alignment of the knee prosthesis can be measured along several different axes, including the mechanical axis and the frontal and sagittal axes of both the femur and tibia.  Incorrect positioning or orientation of the implant and improper alignment of the limb can lead to accelerated implant wear and loosening, as well as suboptimal functioning. It is proposed that computer assisted surgery improves the alignment of the various components of THA and TKA.

A search of the MEDLINE database concentrated on identifying controlled trials comparing stability and reoperation rates between conventional THA and computer assisted surgery. Intermediate outcomes include the percentage of implants which achieve a predetermined level of acceptable alignment. No controlled trials regarding total hip arthroplasty were identified. In an uncontrolled case series, Leenders and colleagues studied the variability in placement of the acetabular component among three groups of patients: 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. (7) While there was a reduction in variability between groups 1 and 2, there was no significant difference between groups 2 and 3. No data regarding long term outcomes were reported. Digioia and colleagues reported on a case series of 78 patients (82 hips) who underwent THA and compared the alignment directed by a mechanical guide and computer assistance. (8)  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.

Regarding TKA, five randomized trials were identified in an updated MEDLINE search (9-13):

• Saragaglia and colleagues randomized 25 patients to receive computer-assisted TKA and 25 to conventional TKA. (9)  The principal outcome of the procedure was the achievement of target alignment of the prosthesis.  There was no significant difference in outcomes between the two groups — both met the target orientation of mechanical alignment of 0-3 degrees.
• Decking and colleagues reported on a similarly designed study of 52 patients randomized to computer assisted or conventional TKA. (10)  The primary outcomes was alignment measured 3 months postoperatively.  While both groups showed a tendency for varus or valgus deviation of the mechanical axis of the leg, 8 of the manually implanted knees vs only 1 computed-assisted implanted knee showed a deviation of 5 degrees or more, a statistically significant difference.  Other radiologic measures of alignment were not significantly different between the two groups.
• Stockl and colleagues conducted a trial randomizing 64 patients to undergo computer assisted navigation or conventional TKA. (11)  A variety of measures of alignment were improved in the navigated group.
• Sparmann and colleagues reported on the largest study of 240 patients randomized to replacement with or without computer assisted navigation. (12)  A total of 97.5% in the navigated group had a mechanical alignment between 0-2 degrees, compared to 77.5% in the conventional group.
• Finally, Victor and Hoste studied 100 patients who were randomized to conventional or image-guided computer navigated TKA. (13)  In the navigated group, all patients showed alignment of the mechanical axis between 0 and 2 degrees.  In contrast, only 73.2% achieved mechanical alignment between 0 and 2 degrees in the conventional group.

Several case series have also been published.  Haaker and colleagues published the largest case series of 100 TKA inserted with an image-less computer navigation system, compared with a matched control group of conventionally implanted knees. (14)  An excellent outcome was defined as 0-3 degrees of deviation on the mechanical axis and 0-2 degrees of deviation on other axes of alignment.  The percentage of excellent results was significantly higher in the navigated groups for all alignment measures except for the sagittal tibial axis angle.  Zorman and Etuin reported on the axis alignment of 72 TKAs performed with the navigational assistance compared to a historical cohort of 62 TKAs performed with conventional instrumentation. (15)  There was a highly significant improvement in the alignment along the mechanical axis in the navigated group; all of those in the navigated group showed neutral alignment, while 47% of those in the conventional group showed a deviation of the mechanical axis of more than two degrees from neutral alignment.  Jenny and Boeri compared the outcome of 30 patients undergoing computer-assisted TKA with 30 matched and paired patients. (16)  The outcome studied was the femorotibial angle.  The authors concluded that those in the computer-assisted group showed an improved quality of implantation.  Other case series have also reported improved alignment using computer-assisted navigation systems. (17-19)

Summary

In summary, four randomized studies and several case series have consistently shown that computer-assisted navigation is associated with improved postoperative alignment along several different axes.  However, the published studies report only immediate postoperative outcomes, and there are no reports of patient-oriented outcomes, such as pain, range of motion, or reoperation rate.  Thus, there is inadequate scientific data to permit conclusions regarding whether the improvement in alignment associated with computer assisted navigation will result in significant clinical improvement in patients undergoing TKA.

References

1. BlueCross BlueShield Association Medical Policy Reference Manual, Policy No. 7.01.96
2. 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
3. Hufner T, Pohlemann T, Tarte S et al. Computer-assisted fracture reduction of pelvic ring fractures: an in vitro study. Clin Orthop 2002;399:231-9
4. 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):122-31
5. Hofstetter R, Slomczykowski M, Krettek C et al. Computer-assisted fluoroscopy-based reduction of femoral fractures and antetorsion correction. Comput Aided Surg 2000;5(5):311-25
6. Suhm N, Jacob AL, Nolte LP et al. Surgical navigation based on fluoroscopy-clinical application for computerassisted distal locking of intramedullary implants. Comput Aided Surg 2000;5(6):391-400
7. Leenders T, Vandevelde D, Mahieu G et al. Reduction in variability of acetabular cup abduction using computer assisted surgery: a prospective and randomized study. Comput Aided Surg 2002;7(2):99-106
8. 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):359-64
9. Saragaglia D, Picard F, Chaussard C et al. [Computer-assisted knee arthroplasty: comparison with a conventional procedure. Results of 50 cases in a prospective, randomized study.] (Article in French.) Rev Chir Orthop Reparatrice Appar Mot 2001;87(1):18-28
10. Decking R, Markmann Y, Fuchs J et al.  Leg axis after computer navigated total knee arthroplasty.  J Arthroplasty  2005;20(3):282-88
11. Stockl B, Nogler M, Rosiek R et al.  Navigation improved accuracy of rotational alignment in total knee arthroplasty.  Clin Orthop Relat Res  2004;426:180-6
12. Sparmann M, Wolke B, Czupalla H et al.  Positioning of total knee arthroplasty with and without navigation support.  A prospective, randomized study.  J Bone Joint Surg Br  2003;85(6):830-5
13. Victor J, Hoste D.  Image based computer assisted total knee arthroplasty leads to lower variability in coronal alignment.  Clin Orthop Rel Res  2004;428:131-39
14. Haaker RG, Stockheim M, Kamp M et al.  Computer-assisted navigation increases precision of component placement in total knee arthroplasty.  Clin Orthop Rel Res  2005;433:152-59
15. Zorman D, Etuin P, Jennart H et al.  Computer-assisted total knee arthroplasty: comparative results in a preliminary series of 72 cases.  Acta Orthop Belg  2005;71(6):696-702
16. Jenny JY, Boeri C. Computer-assisted implantation of total knee prostheses: a case-control comparative study with classical instrumentation. Comput Aided Surg 2001;6(4):217-20
17. Anderson KC, Buehler KC, Markel DC.  Computer assisted navigation in total knee arthroplasty: comparison with conventional methods.  J Arthroplasty  2005;20(7 suppl 3):132-8
18. Kim SJ, MacDonald M, Hernandex J, Wixson RL.  Computer assisted navigation in total knee arthroplasty: improved coronal alignment.  J Arthroplasty  2005;20(7 suppl 3);123-31
19. Bathis H, Perlick L, Tingart M et al.  Alignment in total knee arthroplasty.  A comparison of computer-assisted surgery with conventional technique.  J Bone Joint Surg Br   2004;86(5):682-7

Cross References

None

Surgery Section Table of Contents