RECONSTRUCTION 2023, Jan, 16 | 12:00 am

Computer Navigation in Hip Resurfacing Arthroplasty

Introduction                       

RESULTS OF HIP RESURFACING ARTHROPLASTY

Mid-term survivorship studies of hip resurfacing arthroplasty (HRA) (Fig. 15.1) have not equalled those of conventional total hip arthroplasty (THA).1-5 Despite higher revision rates, proponents of hip resurfacing generally indicate it for younger and more active individuals which may skew the data in the current literature. It is generally accepted that preservation of the proximal femoral bone stock, improved approximation of normal hip kinematics and joint proprioception, minimization of potential for iatrogenic leg length inequality, and increased joint stability are all desirable advantages of resurfacing over conventional replacement.6 Advocates believe that many of the causes of early failure are due to correctable surgical pitfalls.

 

COMPLICATIONS ASSOCIATED WITH HIP RESURFACING ARTHROPLASTY

Femoral neck fractures (Fig. 15.2) in particular present a potential for a “new” complication not associated with THA. These fractures are associated with intraoperative femoral neck

 

 

 

Figure 15.1: Hip resurfacing arthroplasty (Reproduced with permission and copyright © Smith and Nephew Orthopaedics Ltd)

Figure 15.2: Neck fracture after hip resurfacing due to notching

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notching and varus femoral component malposition.7,8 Besides component malposition, notching risk is also increased by incorrect sizing of components. Overzealous manipulation and increased stresses on the femoral neck due to intraoperative difficulties also complicate the relatively more technically demanding procedure.

Total Hip Arthroplasty

 

Increasing reports of a spectrum of local reactive inflammation to metal ions have also been witnessed.9-16 It is generally believed that these conditions may range from a true “allergy” to the metal to sensitivity due to particularly high wear particle volumes due to component malposition.17-18 A variety of clinical presentations including groin pain, pelvic fullness, weight loss, night sweats, superimposed infection, and other constitutional symptoms have been reported.14,16,19,20 These cases have flooded the recent literature and have constituted a significant number of revision cases involving metal-on-metal (MoM) technology.

It is therefore apparent that many cases of early failure of HRA may have been prevented by improved surgical technique. Recent advances in hip resurfacing surgery have assisted in decreasing these technical errors.

COMPUTER-ASSISTED NAVIGATION FOR JOINT REPLACEMENT SURGERY

Computer-aided navigation (CAS) in joint replacement surgery has been in use for over a decade. While CAS improves accuracy of component position, controversy lies in its cost effectiveness, practicality, potential complications, and lack of proven advantages in clinical outcome. With improved instrumentation used in “routine” joint replacement surgery, the enthusiasm for navigation has waned in the last few years.

COMPUTER-ASSISTED NAVIGATION FOR HIP RESURFACING ARTHROPLASTY

Compared to standard total joint replacement, HRA is more technically demanding and complications are more related to surgical error. Alternative bearing surfaces such as MoM have also been known to be “less forgiving” to implant malposition than traditional prostheses. Theoretical advantages of navigated HRA include: (1) improved component position,

(2) improved component sizing, (3) potentially easier and more reproducible procedure, and (4) a less steep learning curve.21,22 These advantages relate to lessening the chance for femoral neck fracture due to notching and incorrect component sizing as well as metallosis due to component malposition.

Navigation can therefore be potentially more appealing when applied to resurfacing surgery compared to standard THA.

 

Types      of      Navigation      Systems                

All navigation systems rely on methods of locating a patient’s anatomy on the operating table and relating this to the position of the surgical instruments used to position the final implants. Therefore, navigation involves the following steps: (1) acquisition of information on the patient’s bony anatomy, (2) relating this to the real-time position on the operating table, (3) determining the desired final implant position, (4) determining the position of instruments used for implantation of the prosthesis, and (5) relating the instruments for implantation to the desired position of the final prosthesis. A typical surgical suite for navigation would include a position sensor, a computer and monitor, and tracking devices on the patient and surgical tools.

Navigation systems can be classified according to: (1) the means by which information is sourced to model the patient’s anatomy and relating that information to the real-time position on the operating table (Data Collection), or (2) the means by which information is transmitted from the patient to the computer (Hardware Registration).

DATA COLLECTION

Data on the patient’s anatomy can be collected either by imaging preoperatively, imaging intraoperatively, or using image-free systems.

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CT-based Systems

Computer Navigation in Hip Resurfacing Arthroplasty

 

These systems were the first to be developed. They involve acquisition of information on the patient’s bony anatomy through preoperative 3-D imaging of the pelvis and femur. This method has the potential for great accuracy as it relies on specific information from the patient and takes into account the patient’s variation in anatomy. It does not rely on any default orientation of anatomy that is set by implant and software manufacturers. This method continues to improve as current helical CT scanners are becoming even more accurate and faster. Once the information is collected, bony landmarks are marked intraoperatively and are related to the known information to determine the patient’s real-time position. The landmarks may be verified by movement of the patient’s limb intraoperatively. The final implant position and sizing is also preoperatively planned using 3-D models. The desired position is achieved by relating the desired position to the direction and position of the surgical instruments intraoperatively.

Fluoroscopy-based Systems

These navigation systems eliminate the need for preoperative imaging. Information on the bony anatomy is acquired by taking two or more images with real-time radiographic image intensifier intraoperatively. The images include the position of the tracking device that had been placed on the patient’s bony landmark. Whilst the actual position of the trackers is taken into consideration, the information acquired is not as accurate or complete as when the position is based on pairs of 2-dimensional images. Nonetheless, the information derived relates to the virtual and actual position of the patient at that given time. The rest of the procedure is carried out in a similar fashion to the CT-based systems.

Image-free Systems

 

 

These navigation systems are similar to fluoroscopy-based systems, in that no preoperative anatomic information is collected and no preoperative surgical planning is conducted. All information and planning are gathered and performed intraoperatively. Unlike fluoroscopy however, no imaging is performed. While this makes image-free systems quicker to set-up and run, there is a disadvantage in that the information is acquired through palpation and direct visualization of landmarks. This may be difficult and even inaccurate in obese patients. Much of the “remaining” information is also derived from default settings on “normal anatomy” as set by the implant and software manufacturer. This type of system has become relatively popular as it is logistically easier to use and avoids high levels of radiation (Fig. 15.3).

 

Figure 15.3: Image-free navigation*

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HARDWARE REGISTRATION

Data from the surgical field may be transmitted to the computer using either infrared or electromagnetic emissions.

 

Infrared Data Transmission

Total Hip Arthroplasty

 

These systems have the advantage of having no “wires” in the field. Disposables are also reduced and sterility is maintained with more ease. The disadvantage is that a “line of sight” must be maintained between the tracking device and the sensor. Lower profile hardware has made this much easier to accomplish.

 

Electromagnetic Transmission

These systems require the use of wires that connect the trackers to the sensor. The wires may obstruct the procedure although this may not inconvenience a surgical team familiar with its use. There is an inherent need for sterile disposables. A “line of sight” is not required.

 

Current State of Navigated Hip Resurfacing Arthroplasty    

Popularity of HRA has been increasing due to the increasing number of young and active patients who access surgical management of hip arthritis. The option is attractive in the young patient population because the procedure is bone conserving on the femoral side and can potentially make later revision surgery less technically demanding with little femoral bone loss.

 

RATIONALE BEHIND USE OF NAVIGATION IN HIP RESURFACING ARTHROPLASTY

There are specific reasons why navigation is particularly attractive for use in HRA. Potentially, computer-assistance can: (1) reduce femoral notching and decrease the incidence of femoral neck fractures, (2) improve accuracy of component positioning and decrease the incidence of inflammatory reactions to metal wear particles, (3) play a major role in trainee and surgeon training, and (4) be helpful in femoral component position in cases where there is abnormal proximal femur anatomy.

 

Femoral Notching and Femoral Neck Fractures

Traditional methods of preparation of the femoral head involve the use of surgical jigs that estimate the optimal implant position intraoperatively based on preoperative imaging. These methods have been shown to be inconsistent and may lead to improper insertion of the guide wire and ultimately poor preparation of the femoral head.23 This may lead to femoral notching and fracturing of the femoral neck which represent a major cause for early revision of HRA.8 Numerous papers have shown that the use of navigation can reduce the incidence of notching and potentially decrease fracture risk.24

 

Component Position and Metallosis

In the recent past, there have been increasing reports of a spectrum of local inflammatory reactions to metal ions. The reactions lead to an array of conditions and terms such as ALVAL, pseudotumors, and tumor-like reactions have been used to characterize this.9-16 These reactions have also been recently related to the “neck thinning” phenomenon, which in itself is poorly understood25 (Fig. 15.4). There is evidence that the likelihood for these reactions increase with increasing metal wear particle load. Component malposition appears to be a primary cause of unacceptable metal wear.26 Alternative bearings such as MoM and ceramic-on-ceramic are particularly unforgiving to small errors in component positioning.17,18 It is intuitive therefore that methods of improving accuracy of component positioning such as

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Computer Navigation in Hip Resurfacing Arthroplasty

 

Figure 15.4: Neck thinning

 

computer-assisted navigation can potentially decrease the incidence of inflammatory reactions to metal particles.

 

Surgeon Training

Navigation has also been shown to reduce the learning curve in HRA.27 In particular, navigation appears to have a positive effect on trainee learning in HRA.28 The live feedback provided by navigation not only improves component positioning but also facilitates teaching trainees in performing the operations without navigation in the future. Navigation also has been shown to decrease the incidence of component malposition in the clinical setting during a surgeon’s learning phase.29

 

Abnormal Anatomy

Results of use of navigation for hips with abnormal proximal femoral anatomy have been conflicting.30,31 Whilst some authors claim a greater rationale for use of navigation in these instances, others report inaccuracy of navigation. It appears that CT-based systems are more appropriate for use in these scenarios.32

 

ACCURACY OF COMPUTER-ASSISTED NAVIGATION FOR HIP RESURFACING ARTHROPLASTY

Numerous papers have reported the accuracy of CT-based, fluoroscopy-based, and image-free systems for use in HRA. Literature with methodologies using synthetic femoral models, human cadavers, and those involving use in a clinical setting are available.

 

CT-based Systems

Various CT-based software protocols have been introduced commercially for both femoral and acetabular navigation.32-37 While CT-based navigation should potentially be more accurate due to the massive amounts of patient-specific anatomic information gathered preoperatively, errors may occur when matching the anatomic information to the real-time position while the patient is on the operating table.35,38 While much information is written about these very impressive protocols, very little literature exists on their results in clinical use. This is because CT-based systems are less favored compared to image-free systems due to the

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Total Hip Arthroplasty

 

additional logistics and preparation required preoperatively. Some authors have pointed out that its main advantage over image-free systems is its use in patients with abnormal femoral head anatomy.32 In these instances, the image-free software settings are prone to error as the 3D modelling is based on normal anatomy.31 In the clinical setting, the available information indicates no great advantage with use of CT-based systems in decreasing femoral notching and may only have a trend for improved acetabular cup position. Its merit for use in minimally invasive approaches has also been described.38

 

Fluoroscopy-based Systems

Among the navigation systems, fluoroscopy-based ones may have the least information in clinical use. While it theoretically has the advantage of using real-time information on patient-specific anatomy, it actually falls short in providing the advantages of the other two systems at both ends of the spectrum. Compared to CT-based systems, the anatomic information is less accurate as it is based only on pairs of 2D images. Compared to image-free systems, the surgical set-up and procedure is more tedious in that the image intensifier disrupts the theater “traffic” and may potentially contaminate a procedure where strict sterility standards are required. Thus, while many protocols have been described using both synthetic phantoms and cadaver models with results on accuracy in these settings presented; hardly any literature on its accuracy in clinical use is available.35,39

 

Image-free Systems

Most of the current literature available on the use of navigation in HRA involves the use of image-free systems. Although these systems inherently rely on software manufacturer settings that may be inaccurate, especially on patients with abnormal anatomy, its ease of use in the clinical setting has made these systems the most widely described and used.

Numerous papers on the accuracy of image-free systems when tested in vitro using phantom models are available.40 Most authors confirm that accuracy is better on the frontal (coronal) than the lateral (sagittal) plane. Olsen et al recently compared the accuracy of five commercially available jigs to an image-free system using both synthetic femurs and cadavers.23 They demonstrated that while navigation is superior in accuracy to all the manual jigs in the coronal plane, no advantage was demonstrated with femoral version. They also reported the superiority of some commercially available manual jigs compared to others.

Most of the research on accuracy of image-free navigation is based on comparison of the intraoperative plan to the postoperative alignment based on plane radiographs.29,41-43 Unfortunately, despite attempts to standardize postoperative radiographic protocols, the methodology has an inherent limitation of being dependent on obtaining true AP films to measure the CCD angle accurately and is unable to assess version of the femoral component accurately. Methodologies based on cadaveric models minimize this limitation as radiographs can be taken in the proper plane with ease and accuracy.44 Furthermore, radiation exposure is not an issue and postoperative measurements may be taken from CT scans instead of plane radiographs.45 Using CT scans not only allows more accurate CCD angle measurements but is also allows component version to be assessed.46-48 Schnurr et al were the first to assess the accuracy of image-free navigation using 3D reformatted CT images and concluded that these navigation systems are highly accurate.49 They recommended however that caution must be exercised in accepting the automated proposed implant position as this may need to be modified by the surgeon in some instances. Olsen et al also recommend preoperative templating as misleading information may be registered intraoperatively when using image-free navigation.50 This will lead to inappropriate sizing and positioning of the femoral component.

The clinical use of image-free navigation in HRA is more widespread than the other systems and accuracy for use in live surgery has been reported by many authors.29,41-43,49,51

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Computer Navigation in Hip Resurfacing Arthroplasty

 

Most available literature report navigating only the femoral side of the operation as most early postoperative complications are related to surgical errors in positioning the femoral component.52 Furthermore, aside from CT-based systems, previous literature on navigation of the acetabular component in THA have been unconvincing. Although most authors validate the accuracy of CAS for HRA compared to standard jigs in the coronal plane, there is some controversy about its advantage over traditional methods for femoral component version. Although the improvement in accuracy varies among the different authors, almost all agree that there is almost complete elimination of outliers and intraoperative femoral notching.

 

EFFECT OF NAVIGATION FOR HIP RESURFACING ARTHROPLASTY ON OPERATIVE TIME

Most current literature would quote an increase of operative time within the range of 5-20 minutes, depending on whether both the femoral and acetabular sides are navigated or if only the femoral side is computer-assisted.29,42,43,49 Authors do point out that the increase in operative time markedly diminishes with evolving surgeon experience.29,42 Although there is a learning curve observed in the time taken for navigation, none was observed in the accurate placement of the implant.29,42 Less commonly, no significant increase in operating time is observed, especially in the hands of surgeons experienced in the procedure.38 Rarely, some authors claim a decrease in operative time with navigation.53 This again may be related to the familiarity of the surgeon with the navigation system at the time the study was initiated.

 

EFFECT OF NAVIGATION FOR HIP RESURFACING ON CLINICAL OUTCOMES

Accuracy of component positioning as an outcome is inherent in studies involving computer-assisted surgery. It must not be forgotten however that the aim of accuracy is improvement in clinical outcome which would involve an attempt to measure functional outcome, patient satisfaction, quality of life, and implant longevity. As CAS in HRA is a relatively new procedure, there is a paucity of current literature that addresses these outcome measures.

Short-term results reported by Olsen and Shemitsch demonstrated no femoral notching and fracturing on 86 patients with a minimum 2 year follow-up.24 Resubal and Morgan reported similar results and reported superior early results compared to the mechanical jig technique in these parameters on a retrospective cohort study.43 Literature on improvements in functional outcome, patient satisfaction, and improved quality of life with use of computer navigation are unavailable.

As neck fractures usually occur early, the decrease in fracture incidence may presumably translate to improved longevity in the long-term.52 This is however, not supported by more recent literature demonstrating that neck thinning, stem radiolucencies, and stem migration remain sequelae of hip resurfacing despite the use of navigation.24 There has been a recent influx of current literature on problems with resurfacing technology. Most of the available literature describes outcomes of hip resurfacing using traditional methods; and only few involve cohorts pertaining to navigated procedures. Nonetheless, as the future of hip resurfacing arthroplasty is still in question, the fate of computer-assisted navigation for this procedure is also unknown.

 

Technique of Image-free Navigated Hip Resurfacing Arthroplasty

The patient is initially positioned supine. The pelvic landmarks are first registered. The patient is then positioned in a lateral decubitus position (Fig. 15.5). The hip is approached through a posterior approach. Key to acetabular exposure is the anterosuperior capsulotomy which serves as a “pocket” to contain the femoral head. The limb is externally rotated to “tuck” the head into the pocket. The acetabular landmarks are registered. After acetabular preparation and component implantation, the femoral landmarks are registered. The femoral head is then prepared and its component positioned.

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Total Hip Arthroplasty

 

Figure 15.5: The theater set-up*

 

 

Navigation is performed using the BrainLab Computer Navigation System (BrainLab Inc., Munich, Germany). This is an image-free infrared system. Tracking spheres (arrays) are placed on the patient’s pelvis and proximal femur by drilling Shantz pins into the ASIS and lesser trochanter respectively. The implantation tools used for positioning of the acetabular component and the guide pin for the femoral component also have similar arrays. These arrays are recognized by the sensor to provide real-time information on the component positioning relative to the patient’s anatomy.

 

NAVIGATING THE ACETABULUM

With the patient supine on the operating table, the area of the anterior superior iliac spine (ASIS) of the operative side is prepared with skin bactericidal solution. A Shantz pin is drilled into the ASIS to serve as a post to attach the navigating tower fitted with arrays (Fig. 15.6).

Point registration of both the ASIS and the most medial prominences of the superior pubic rami is performed (Fig. 15.7). These landmarks are used to calculate the anterior

 

 

 

Figure 15.6: Pelvic arrays fixed onto ASIS* Figure 15.7: Pelvic plane registration*

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Computer Navigation in Hip Resurfacing Arthroplasty

 

Figure 15.8: Registration of acetabular anatomy*

 

Figure 15.9: Navigating the cup position*

 

pelvic and midsagittal planes. Points should be registered close to bone to increase accuracy. The patient is then repositioned in a lateral decubitus position. The hip is then approached posteriorly. The femoral neck is measured to determine the femoral component size from which the acetabular cup diameter will be calculated. The acetabulum is exposed. Point registration of the acetabular fossa and surface registration of the acetabular cavity are then performed (Fig. 15.8). A 3D model of the acetabulum is developed. The diameter and depth of the acetabulum and the center of rotation of the hip are estimated. Accuracy of the bone model is verified. The cup position is then planned based on the cup diameter previously determined by measurement of neck diameter intraoperatively. The targeted cup position is 40-45 degrees of inclination and 15-20 degrees of anteversion. The acetabulum is reamed to the desired depth, direction, and diameter. The cup is then applied with an introducer to

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Total Hip Arthroplasty

 

Figure 15.10: Femoral arrays on the lesser trochanter*

 

which navigating arrays are attached, aiming to achieve the desired direction and depth (Fig. 15.9). Final cup position is then verified and the introducer is removed. The cup is protected with a moistened sponge.

 

NAVIGATING THE FEMUR

The femoral head and neck are fully exposed and delivered to the center of the wound. Proper positioning of the lower extremity is essential. Varying the position of the knee and degree of limb rotation are dictated by which part of the proximal femur anatomy requires access.

The inferior part of the neck and the lesser trochanter are exposed first. A Homan retractor is useful to fully visualize the lesser trochanter. A Shantz pin is drilled into the lesser trochanter and serves as a post to attach the navigating tower with the tracking arrays (Fig. 15.10). Communication between the arrays and the sensor is established and a 3-dimensional realtime model of the proximal femur is developed.

Landmark acquisition starts with point registration of bony landmarks including the medial and lateral femoral condyles, piriformis fossa, and head-neck junction (Fig. 15.11). Surface registration is then performed on the femoral head, anterior, superior, posterior, and inferior femoral neck, and the superior notching zone (Fig. 15.12).

After acquisition of the anatomic information, surgical planning is conducted by plotting in the desired CCD angle. The authors prefer to put the implant in 15 degrees valgus to the anatomic CCD angle (usually 150 degrees). The implant axes on the coronal and axial planes are determined (Fig. 15.13).

The final position of the femoral implant is then planned in the coronal, axial, and sagittal planes. Notching risk is indicated by red dots on the 3 axes. The position is adjusted to minimize notching risk (Fig. 15.14).

The guide pin is then navigated (Fig. 15.15). The pin is guided by a cannulated tool with arrays attached to it. The ideal entry point on the femoral head is first determined. The correct direction is then established. An assistant inserts the guide pin into the navigated tool, ready to drill the pin once the proper entry point and direction are achieved by the surgeon (Fig. 15.16). The accuracy of insertion is then confirmed. The navigation process of the femoral head takes on average 8 minutes. The femoral head is then prepared in the usual manner followed by implantation of the femoral component.

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Computer Navigation in Hip Resurfacing Arthroplasty

 

Figure 15.11: Point registration of femur*

 

 

 

Figure 15.12: Surface registration of femur*

 

Figure 15.13: Establishing the CCD angle and implant size*

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Total Hip Arthroplasty

 

Figure 15.14: Planning the final implant position in three planes*

 

Figure 15.15: Navigating the guide pin*

 

Summary                        

Hip resurfacing arthroplasty is a more technically demanding procedure compared to standard THA. Early failures are related to poor surgical technique that may lead to component malposition and incorrect component sizing. This may lead to femoral neck fractures and metallosis which represent a significant percentage of the cause for early revision. Computer-aided navigation can potentially improve the quality of surgery and improve implant survivorship. Use of these novel techniques may be more appealing in hip resurfacing

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Computer Navigation in Hip Resurfacing Arthroplasty

 

Figure 15.16: Drilling the guide pin*

 

arthroplasty compared to standard total hip replacement. The recent increasing reports of early failures of resurfacing technology however make the future of this procedure uncertain.

*Pictures on navigation reprinted with permission from BrainLab and Smith and Nephew.54

 

References                       

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  2. Amstutz HC, Le Duff MJ, Campbell PA, Gruen TA, Wisk LE. Clinical and radiographic results of metal-on-metal hip resurfacing with a minimum ten-year follow-up. J Bone Joint Surg Am 2010;92(16):2663-71.

  3. Neumann DR, Thaler C, Hitzl W, Huber M, Hofstädter T, Dorn U. Long-term results of a contemporary metal-on-metal total hip arthroplasty: a 10-year follow-up study. J Arthroplasty 2010;25(5):700-8.

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  9. Mahendra G, Pandit H, Kliskey K, Murray D, Gill HS, Athanasou N. Necrotic and inflammatory changes in metal-on-metal resurfacing hip arthroplasties. Acta Orthop 2009;80(6):653-9.

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  12. Kwon YM, Thomas P, Summer B, Pandit H, Taylor A, Beard D, Murray DW, Gill HS. Lymphocyte proliferation responses in patients with pseudotumors following metal-on-metal hip resurfacing arthroplasty. J Orthop Res 2010;28(4):444-50.

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  14. Molvik H, Hanna SA, de Roeck NJ. Failed metal-on-metal total hip arthroplasty presenting as painful groin mass with associated weight loss and night sweats. Am J Orthop (Belle Mead NJ). 2010;39(5):E46-9.

  15. Watters TS, Cardona DM, Menon KS, Vinson EN, Bolognesi MP, Dodd LG. Aseptic lymphocyte-dominated vasculitis-associated lesion: a clinicopathologic review of an underrecognized cause of prosthetic failure. Am J Clin Pathol 2010;134(6):886-93.

  16. Watters TS, Eward WC, Hallows RK, Dodd LG, Wellman SS, Bolognesi MP. Pseudotumor with superimposed periprosthetic infection following metal-on-metal total hip arthroplasty: a case report. J Bone Joint Surg Am 2010;92(7):1666-9.

  17. Kwon YM, Glyn-Jones S, Simpson DJ, Kamali A, McLardy-Smith P, Gill HS, Murray DW. Analysis of wear of retrieved metal-on-metal hip resurfacing implants revised due to pseudotumours. J Bone Joint Surg Br 2010;92(3):356-61.

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  23. Olsen M, Chiu M, Gamble P, Boyle RA, Tumia N, Schemitsch EH. A comparison of conventional guide wire alignment jigs with imageless computer navigation in hip resurfacing arthroplasty. J Bone Joint Surg Am 2010;92(9):1834-41.

  24. Olsen M, Schemitsch EH. Avoiding short-term femoral neck fracture with imageless computer navigation for hip resurfacing. Clin Orthop Relat Res 2010. [Epub ahead of print].

  25. Grammatopoulos G, Pandit H. Oxford Hip and Knee Group, Murray DW, Gill HS. The relationship between head-neck ratio and pseudotumour formation in metal-on-metal resurfacing arthroplasty of the hip. J Bone Joint Surg Br 2010;92(11):1527-34.

  26. Beaulé PE, Lee JL, Le Duff MJ, Amstutz HC, Ebramzedah E. Orientation of the femoral component in surface arthroplasty of the hip: a biomechanical and clinical analysis. J Bone Joint Surg Am 2004;86:2016-21.

  27. Cobb JP, Kannan V, Brust K, Thevendran G. Navigation reduces the learning curve in resurfacing total hip arthroplasty. Clin Orthop Relat Res 2007;463:90-7.

  28. Saithna A, Dekker AP. The influence of computer navigation on trainee learning in hip resurfacing arthroplasty. Comput Aided Surg 2009;14(4-6):117-22.

  29. 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.

  30. Olsen M, Schemitsch EH. Computer navigated hip resurfacing for patients with abnormal femoral anatomy. Bull NYU Hosp Jt Dis 2009;67(2):159-63.

  31. Pitto RP, Malak S, Anderson IA. Accuracy of computer-assisted navigation for femoral head resurfacing decreases in hips with abnormal anatomy. Clin Orthop Relat Res 2009;467(9):2310-7. Epub May 7.

  32. Cobb JP, Kannan V, Dandachli W, Iranpour F, Brust KU, Hart AJ. Learning how to resurface cam-type femoral heads with acceptable accuracy and precision: The role of computed tomography-based navigation. J Bone Joint Surg Am 2008;90(Suppl 3):57-64.

  33. Barrett ARW, Davies BL, Gomes MPSF, Harris SJ, Henckel J, Jakopec M, Kannan V, et al. Computer-assisted hip resurfacing surgery using the Acrobat® Navigation System. Proc ImechE Part H 2007;221:773-85.

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  34. Dandachli W, Richards R, Harris SJ, Barrett ARW, Davies BL, Cobb JP. A practical reference coordinate system for planning hip resurfacing surgery. In Proceedings of the 5th CAOS, Finland, 2005.pp.78-80.

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    Computer Navigation in Hip Resurfacing Arthroplasty

     

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