RECONSTRUCTION 2023, Jan, 16 | 12:00 am

Navigation in Total Hip Arthroplasty

Introduction                       

Computer assisted orthopedic surgery is an area in which machine capability is coupled with human judgment and skills to perform a task better than either could do alone.1-3 The navigation systems that use information from imaging (CT, MRI, fluoroscopy) are called as “image based systems”.4-7 The image free systems or imageless systems use combination of joint kinematics data and direct anatomic data instead of acquired medical images.8,9 The first hip navigation system was developed in 1992 and used preoperative CT scan.10 Imageless navigation system has proved to be as reliable as CT-based system.9

 

Navigation in Total Hip Arthroplasty

 

Rationale         for         Navigation                  

ACCURATE CUP POSITION

The placement of components in total hip arthroplasty is the most important step for both short-term and long-term outcomes. Acetabular component malposition can not only lead to impingement and dislocations but also can cause pelvic osteolysis, acetabular migration, and intercomponent polyethylene wear.11-15 The version of both femoral16-18 and acetabular component19-22 is misjudged even by experienced surgeons. The judgment errors are most common with the acetabulum because it is attached to the pelvis which is further influenced by the spine and longitudinal axis of the body. The surgeon’s judgment of cup position is confounded by the pelvis being buried under skin, fat, and muscles. Estimation of pelvic position is worse when the operation is performed in the lateral position because pelvic landmarks are more hidden than if the supine position is used. The only methodology to overcome human errors of judgment is use of computer navigation in the operating room. McCollum and Gray23 found that, in the lateral position, the lumbar lordotic curve flattens, the pelvis may be flexed as much as 35 degrees and the superior aspect of the acetabulum may be adducted toward the foot of the table by 10 to 15 degrees. In this situation, if the surgeon is using a mechanical alignment guide to place the cup in relation to the body or table, when the patient stands up, the cup may actually be retroverted or too vertical. Digioia et al compared mechanical alignment guides to computer navigation for cup placement and found that 78% of acetabular components are in an unacceptable position if mechanical guides are used.20 Hassan et al. found that acetabular components placed with mechanical guides were out of safe zone24 in twenty-one of 50 hips.25

36

 

 

 

COMBINED ANTEVERSION

Total Hip Arthroplasty

 

Accuracy of femoral stem anteversion and acetabular cup anteversion would nearly ensure mating of the femoral head in the cup without impingement of the two throughout all body positions. This requires a technique to repeatedly create this combined anteversion. McKibbin first introduced the term of combined anteversion in a study of infant cadavers and defined 30 to 40 degrees combined anteversion as being normal, with 15 degree anteversion of the femur.26 Men had lower combined anteversion than women. In a study of 200 adult cadavers, the combined anteversion for men was a mean 29.6 degrees and women 33.5 degrees, with femoral anteversion a mean 11.6 degrees (men were 11.1 degrees and women 12.2 degrees).27 In THA, the combined anteversion means the sum of cup anteversion and stem anteversion. In a study in THA, which investigated combined anteversion to find an optimal combination to avoid impingement, the conclusion was 37.3 degrees.28 Mathematical models also confirmed combined anteversion to be the measurement that must be considered to avoid impingement.29 Clinical use of combined anteversion has determined men to be between 25 and 35 degrees and up to 45 degrees in women.30 Combined anteversion has become more relevant with the use of noncemented implants. With cemented stems, because the stem is smaller than the canal and can be manipulated inside the canal, the anteversion can be more precisely controlled by the surgeon to provide the desired degree of anteversion to achieve the safe range of combined anteversion. Surgeons have much less control with noncemented stems which are rigidly press-fit in a fixed bony structure. Insertion of cementless stems are limited by anteversion of the bone, the anteroposterior isthmus at the level of the lesser trochanter, and the posterior fin of bone in Dorr type A and B bone.27,31-33 Fractures can occur when the surgeon, by rotating the implant inside the femur, attempts to introduce anteversion into the stem that is not present in the femoral bone. If the stem has only 5 degrees of anteversion, especially in a woman, the classical acetabular safe zone of 15 to 20 degrees does not give an acceptable combined anteversion28,30 and this means the cup anteversion needed must be up to 30 degrees to provide safe combined anteversion. Computer navigation helps in achieving the correct combined anteversion by giving absolute numbers and knowledge of stem and cup anteversion.

 

PREVENTION OF IMPINGEMENT

In avoiding impingement, control of the center of rotation (COR) is more important than the absolute values for inclination and anteversion. The computer provides three dimensional information of the acetabulum and shows the center of rotation for the cup and center of the head of the femoral stem. If the COR, is lateralized, the metal neck can impact the edge of the metal shell (risk increases with poor combined anteversion); if COR is superior or medialized, the risk of bone-on-bone impingement increases unless the femoral offset is increased (by use of an offset stem or lengthening the hip/leg). For the greatest durability of arthroplasty, the COR should be achieved within 2 mm of anatomic normal.34 In our recent study we found that with the help of navigation the offset can be achieved within 6 mm of normal in 78 hips out of 82 hips.35 We found that, the key to optimal length and offset is restoration of the center of rotation of the hip within 3 mm.

 

KNOWLEDGE OF PELVIC TILT

While performing THA, the true spatial orientation of the acetabulum requires an assessment of the pelvic tilt angle.26,36 However, the surgeon cannot determine the true position of the pelvis with accuracy.5,23 During performance of THA, the pelvis can be tilted different from the coronal plane of the body.21,37-39 The surgeon tries to implant the cup in 40+/– 10 degrees of inclination and 15 +/– 10 degrees of anteversion [Lewinnek’s classical safe zone24] with mechanical guides in relation to bony landmarks and the plane of the operating table without knowledge of pelvic tilt. The pelvic tilt causes change of cup anteversion when measured on

36

 

 

 

Navigation in Total Hip Arthroplasty

 

the coronal plane, which has been quantified as 0.7 degrees for each degree of tilt in normal volunteers.37 A nomogram developed by CT scans and radiographs in patients undergoing THA also has a conversion factor of 0.7 degrees.21 The difference between the anterior pelvic plane (defined by two ASIS and pubic symphysis points) and the coronal plane of body (longitudinal plane of body) is defined as pelvic anterior or posterior tilt.21,37 The anterior pelvic plane has been used commonly with computer navigation for THA, and registered by touching each anterior superior iliac spine (ASIS) and the pubis with the patient in the supine position. If the operation is performed in the lateral position, the coronal plane of the body (long axis of the body) is registered by touching the pointer to the posterior pelvic and chest supports. The computer software mathematically computes the tilt of the pelvis to the longitudinal axis and adjusts the anteversion and inclination of the cup according to the tilt of pelvis.

 

ACCURATE PREPARATION OF ACETABULUM

The reaming is more accurate with the computer because the surgeon knows the reamer’s exact position in relation to medial, anterior and posterior walls. This information allows for the accurate reconstruction of the acetabular COR such that there is correct elevation and medialization of bone preparation for coverage of the cup by the osseous walls.

 

LOCATION OF FEMORAL NECK CUT

The level of neck cut can be located with computer navigation. This is especially important when mini-incision is used in which the lesser trochanter is obscured by the retained quadratus femoris muscle. If the computer is not used, manual measurement for level of cut is measured from the inferior rim of the femoral head.

 

MINI-INCISION APPROACH

The computer navigation is a great asset while using the mini-incision approach. The mini-incision surgery, by its nature, limits visualization and reduced visualization may lead to malpositioning of component.40 Studies have proved that if a minimally invasive approach is combined with navigation, component position is not compromised and reproducible results can be achieved.41,42

 

Technique                        

We use epidural anesthesia and sedation with continuous infusion of propofol. The airway is secured with laryngeal mask or oral airway. The operative technique we discuss here is with the use of an imageless navigation system (Orthosoft, Montreal, Canada). The calibration of tools is done by the scrub nurse while the patient is prepared for anesthesia.

 

PELVIC REGISTRATION

The registration of the pelvis is done with the patient in the supine position on the operating table. The pelvic skin is prepped with betadine and draped. Three threaded pins are used to attach the registration device to the pelvis at the thickest portion of the iliac crest (where bone graft is taken). Methylene blue is used to mark the holes of registration pins on the skin. Three puncture wound are made with a #15 blade to minimize skin damage (Fig. 36.1). The registration of anterior pelvic plane (APP) is done by touching the two ASIS and the pubis. The pointer should always puncture through the skin to the pubic bone because of the thickness of fat over the pubis. The pointer touching the ASIS does not need to puncture through the skin to the bone, but this should be done if there is fat over the ASIS obscuring the prominent bone. If the operation is to be performed in the lateral position, the array is removed but the attached device to the pelvis is covered with a sterile towel or iodine drape.

36

 

 

 

 

 

Total Hip Arthroplasty

 

Figure 36.1: The threaded pin is inserted through stab wound. Marks are made with methylene blue through the holes of pelvic attachment device for insertion of threaded pins

 

 

 

 

Figure 36.2: Patient supported with chest and pelvic supports in lateral position. The pointer guide is touched at 3 points (asterisks) on posterior supports, two on posterior pelvic support and one on chest support in manner that the three points forms a triangle

 

 

The patient is secured in the lateral position with two anterior and two posterior supports (Fig. 36.2). The longitudinal axis (coronal plane) of body is registered by touching the posterior pelvis and chest supports in a fashion to create a triangle (two points on posterior pelvic support and one point on posterior chest support) (Fig. 36.2). The computer software measures the tilt of the pelvis which is the difference between the anterior pelvic plane (APP) and coronal plane (longitudinal axis). Knowledge of pelvic tilt allows the acetabular component inclination and anteversion to be positioned on the coronal plane.

We use the posterior mini-incision approach for all our THAs. Our focus in this chapter is computer navigation and so we are not going to discuss the approach. After the greater trochanter (GT) has been exposed, a small unicortical screw is placed in the GT for leg length and offset measurements. The pointer guide is touched to this screw before dislocating the hip with the assistant aligning the operative leg on the lower leg (Fig. 36.3A). It is important that the same assistant aligns the leg before and after the reconstruction of hip so the computer can show us the change in offset and leg length (Fig. 36.3B).

36

 

 

 

 

 

Figures 36.3A and B: (A) Pointer guide is touched to the screw on GT before dislocating the hip and as well after reconstruction of hip. At both the time the legs are overlaid one over another by the same assistant (B) Computer screen in left column is showing change in leg length and offset

 

Navigation in Total Hip Arthroplasty

 

FEMORAL PREPARATION

After dislocating the hip, the neck cut is made at the desired level as planned on preoperative templating. The femur is prepared first so the anteversion of femoral stem can be judged.43 The cup can be anteverted accordingly to give the correct combined anteversion (mean 37

+/– 12 degrees). In our studies we found that femoral anteversion can be calculated more accurately with computer navigation, but it requires pins in femoral diaphysis.17,43 We learned with our experience that these pins cause residual pain for 6-8 weeks for many patients so we stopped doing that. We found that femoral anteversion can be judged by the surgeon within 5 degrees with experience.

 

ACETABULAR PREPARATION

The acetabulum is exposed by retracting the femur anteriorly. If there is any difficulty in retracting the femur, the surgeon may be required to release the anterior superior capsule and the reflected head of the rectus muscle. The labrum is excised. The cotyloid notch is exposed by removing the pulvinar. For registration of the acetabulum, sixteen points are taken on its walls (Fig. 36.4A), avoiding the osteophytes and four points are taken on the cotyloid notch (Fig. 36.4B). The points on the cotyloid notch allow the computer to estimate the medial wall of the acetabulum. With these 20 points, the computer calculates the center of rotation of the anatomic acetabulum and the position of acetabulum in relation to the pelvis (Fig. 36.5). The computer also shows the anteversion and inclination of the native acetabulum. The anatomic inclination of the bony acetabulum has a mean of 55 degrees44 and 40% of acetabulae have inclination more than 55 degrees. The vertical inclination of native bony acetabulum is the reason the posterior superior edge of the cup is commonly uncovered by bone, with up to 3 mm of metal exposed. In the arthritic acetabulae, the mean anteversion is 11 degrees to 13 degrees that means the cup anteversion needed most often exceeds, which would be obtained by an “anatomic cup position” using either the bony walls or the transverse acetabular ligament. If the metal cup is covered entirely by native acetabulum bone, either the inclination is too great or the cup has been reamed excessively superior and medially (COR elevated 5 mm or more).

36

 

 

 

 

 

 

 

Total Hip Arthroplasty

 

Figures 36.4A and B: (A) Intraoperative view of the pointer guide touching the walls of acetabulum. Total 16 points are taken on the periphery of acetabulum for registration (B) Intraoperative view of the pointer guide touching the cotyloid notch of acetabulum. Total 4 points are taken on the cotyloid notch

 

 

 

Figure 36.5: Computer screen showing mosaic of acetabulum in which medial wall which is represented by yellow dots and blue dot is center of rotation and red dots are periphery

 

 

The computer provides the size of acetabulum and so surgeon can use this information to select the starting reamer size. The reaming of the acetabulum can be monitored on the computer as reamer position is fully outlined on the computer screen which displays the change of COR medially, anteriorly, posteriorly or superiorly (Figs 36.6A and B). The initial reaming is done transversely to ream away the acetabular ridge. Reaming is done to the level of cortical bone of the cotyloid notch, which means advancing the reamer until it touches the yellow dots on the computer screen (yellow dots represent the medial wall). The surgeon needs to know the depth of reaming required by their cup system. There should be 4 to 5 mm medialization to allow correct coverage of the cup. We need to ream 3-5 mm superior for the cup COR to be 2 mm superior because of cup and polyethylene thickness. The control of COR is the most important technical accomplishment for the surgeon with computer navigation and is very important in preventing the impingement.

36

 

 

 

 

 

 

 

Navigation in Total Hip Arthroplasty

 

Figure 36.6A: Computer screen showing the information available during reaming. In left column, the angles of the reamer are given. Because this reaming is done transversely, the inclination is steep. The reamer can be adjusted into anteversion as desired. There is relatively little anteversion in reamer during the transverse removal of ridge. The upper two quadrants show the reamer and its position in the acetabulum. The CC number (2) means that the reamer is 2 mm superior to the center of rotation of osseous acetabulum. The ML number (-2) means reamer is 2 mm medial to the osseous center (COR). In the upper right quadrant, the CC number (2) means that the reamer is 2 mm superior, and the AP number (-1) means that the reamer is 1 mm posterior from center. This gives the surgeon complete information with regard to the change in acetabular COR induced by reaming

 

Figure 36.6B: The reamer has been advanced to the level of the medial wall, as indicated by reamer touching the yellow dots. In upper right quadrant, the AP number indicates that the center has been moved 2 mm posteriorly. The upper left quadrant shows that the center of rotation has been elevated 4 mm and medialized 5 mm. The lower right quadrant provides a graphic illustration of coverage of the cup with the reamer in its current position compared with values of the native acetabulum

 

CUP PLACEMENT

The trial cup is placed and the position of the trial cup is recorded with the array attached to the cup holder. The computer gives the surgeon real time information of medialization, center of rotation and anterior-posterior position of the cup (Fig. 36.7). The computer also displays inclination and anteversion of the cup and their adjusted values as well. The adjusted values should be selected because they are adjusted for the patient’s pelvic tilt and are therefore in the functional position of the coronal plane. The inclination must be below 45 degrees to optimize wear. We place our cups at 38-40 degrees +/– 2 degrees, because the computer has precision of 4-5 degrees.19 This means the superior-posterior edge of the cup may be uncovered by bone by 3 +/– 2 mm. The anteversion of the cup is determined by the anteversion of the femoral stem to provide a safe combined anteversion (for men 25 to 35 degrees, up to 45 degrees for women). It is important for cementless stems, which have anteversion less than 10 degrees, and sometimes less than 5 degrees, to adjust cup anteversion up to 30 degrees. It is difficult to provide anteversion of the cup more than 30 degrees

36

 

 

 

 

 

 

 

Total Hip Arthroplasty

 

Figure 36.7: Computer screen showing the position of trial component which has been seated into the osseous acetabulum. The COR is 2 mm superior (CC: 2), 3 mm medial (ML: 3) and 2 mm posterior (AP: 2). Lower left column shows adjusted inclination and anteversion of trial cup. The adjusted values are taken into consideration. The graphic illustration of fit plane is shown in lower right of computer screen and it shows why the posterior superior edge of the cup needs to be proud

 

Figure 36.8: Computer screen showing the seating of the acetabular cup with position of center of rotation (COR) 2 mm superior, 4 mm medial and 2 mm posterior. (Cup COR differs from reaming COR.) The adjusted inclination is 42 degrees and the adjusted anteversion, 28 degrees. The numbers in the lower right are those of the osseous acetabulum

 

because the metal shell will protrude above the posterior bony wall and cause impingement in extension. If the trial cup has COR which is lateralized, then the acetabulum is reamed deeper. If the COR is 5 mm or more superior, then assess visually and if the anterior-superior edge of the cup is below the anterior-superior edge of bone that means bone-on-bone impingement can occur. In this situation, the periphery of the acetabulum is reamed with the next size reamer (without reaming the depth) so as to bring the COR laterally.

Once all numbers are satisfactory then the trial is removed and the final cup is implanted with the cup holder with attached array (Fig. 36.8). To check for the stability of the cup, pull on the handle of the cup holder. If vigorous pulling does not move the cup, it means the cup is press fit and does not need any augmentation with screws. If the surgeon feels the cup is not tight enough, the screws can be added. The anteversion and inclination may change after screws are added. So these numbers are confirmed one more time by touching the rim of the shell with the pointer guide at six different points. The fit plane measurement can be repeated

36

 

 

 

once the plastic liner has been inserted into metal shell by touching the periphery of liner at six points.

 

LEG LENGTH AND OFFSET

After the cup is implanted, the femur is exposed and trial stem and head are inserted. Hip reduction is done and the legs are overlaid on each other by the same assistant who did it before dislocating the hip. The pointer guide touches the screw in the greater trochanter and the computer will display the change in leg length and offset. If these changes are the same as desired by preoperative planning, the real stem and head are inserted. If the changes in offset and leg length are not what are desired then adjustments have to be made in neck length of the femur or position of the stem relative to the neck cut. For example, if the trial neutral head gives 3 mm of increase in offset and 6 mm increase in leg length then a short head should be used. With a short head, if the leg length is corrected but the offset is decreased and causing impingement, then either an offset stem is used or the bony neck is recut to decrease the length and standard stem with neutral head can be used. When COR is not restored to normal, these types of decision problems can occur. Providing the quantitative knowledge of leg length and offset is great advantage of the computer navigation.

 

Navigation in Total Hip Arthroplasty

 

Results                         

Accuracy and precision of computer navigation in THA, results in very few outliers as proved in multiple studies.19,20,22,25,45,46 In our study of 101 hips, comparing precision of computer navigation to an experienced surgeon’s estimate, we found that even the experienced surgeon has precision of 11.5 degrees for inclination and 12.3 degrees for anteversion. The less experienced surgeon has precision of 13.1 degrees for inclination and 13.9 degrees for anteversion. The computer had precision of 4.4 degrees for inclination (bias of 0.03 degrees) and 4.1 degrees for anteversion (bias of 0.73 degrees). The precision of the computer was statistically better than that of the experienced surgeon.19 In estimation of femoral anteversion for cementless stems, in 109 hips, the surgeon’s precision was also poor.17,43

In our study of combined anteversion, we could achieve safe combined anteversion (25 to 50 degrees) in 96% of hips.43,47

 

 

In our study of 477 hips, we found that pelvic tilt can vary from 25 degrees posterior to 20 degrees anterior.48 We found that 10 degrees of pelvic tilt can cause an error of 8 degrees in cup position judgment on coronal plane and surgeon’s estimation errors are in addition to it.48

 

Figure 36.9: Preoperative X-ray with migration of femoral head superior and lateral. To restore the COR the offset need to be reduced

36

 

 

 

 

 

Total Hip Arthroplasty

 

Figure 36.10: Postoperative X-ray shows restoration of COR as well as offset, and leg length

 

We would like to show an example of restoration of COR near to normal with the use of computer navigation. The preoperative x-ray (Fig. 36.9) of a patient undergoing THA, shows arthritis of the right hip with superior and lateral migration. In the postoperative X-ray (Fig. 36.10) the restoration of COR is achieved with the help of computer.

 

References

 

  1. DiGioia AM 3rd. What is computer assisted orthopaedic surgery? Clin Orthop Relat Res 1998; 354:2-4.

  2. DiGioia A. Operative Tech Orthop 2000;10(1):1-2.

  3. Taylor RH, Lavallee S, Burdea GC, et al. Computer integrated surgery: Technology and clinical Applications. Cambridge, MA: MIT Press 1995.pp. xiii-xviii.

  4. DiGioia AM, Jaramaz B, Blackwell M, Simon DA, Morgan F, Moody JE, et al. The Otto Aufranc Award. Image guided navigation system to measure intraoperatively acetabular implant alignment. Clin Orthop Relat Res 1998;355:8-22.

  5. Jaramaz B, DiGioia AM 3rd, Blackwell M, Nikou C. Computer assisted measurement of cup placement in total hip replacement. Clin Orthop Relat Res 1998;354:70-81.

  6. Merloz P, Tonetti J, Eid A, Faure C, Lavallee S, Troccaz J, et al. Computer assisted spine surgery. Clin Orthop Relat Res 1997;337:86-96.

  7. Foley KT, Simon DA, Rampersaud YR. Virtual fluoroscopy: Computer assisted fluoroscopic navigation. Spine (Phila Pa 1976) 2001;26(4):347-51.

  8. Dorr LD, Hishiki Y, Wan Z, Newton D, Yun A. Development of imageless computer navigation for acetabular component position in total hip replacement. Iowa Orthop J 2005;25:1-9.

  9. Kalteis T, Handel M, Bathis H, Perlick L, Tingart M, Grifka J. Imageless navigation for insertion of the acetabular component in total hip arthroplasty: is it as accurate as CT-based navigation? J Bone Joint Surg Br 2006;88(2):163-7.

  10. Bargar WL. Robots in orthopaedic surgery: past, present, and future. Clin Orthop Relat Res 2007;463:31-6.

  11. Kennedy JG, Rogers WB, Soffe KE, Sullivan RJ, Griffen DG, Sheehan LJ. Effect of acetabular component orientation on recurrent dislocation, pelvic osteolysis, polyethylene wear, and component migration. J Arthroplasty 1998;13(5):530-4.

  12. Ries MD. Complications in primary total hip arthroplasty: Avoidance and management: wear. Instr Course Lect 2003;52:257-65.

  13. Patil S, Bergula A, Chen PC, Colwell CW Jr, D’Lima DD. Polyethylene wear and acetabular component orientation. J Bone Joint Surg Am 2003;85-A(Suppl 4):56-63.

    36

     

     

     

  14. Nizard RS, Sedel L, Christel P, Meunier A, Soudry M, Witvoet J. Ten-year survivorship of cemented ceramic-ceramic total hip prosthesis. Clin Orthop Relat Res 1992;282:53-63.

  15. Hart AJ, Buddhdev P, Winship P, Faria N, Powell JJ, Skinner JA. Cup inclination angle of greater than 50 degrees increases whole blood concentrations of cobalt and chromium ions after metal-on-metal hip resurfacing. Hip Int 2008;18(3):212-9.

    Navigation in Total Hip Arthroplasty

     

  16. Wines AP, McNicol D. Computed tomography measurement of the accuracy of component version in total hip arthroplasty. J Arthroplasty 2006;21(5):696-701.

  17. Dorr LD, Wan Z, Malik A, Zhu J, Dastane M, Deshmane P. A comparison of surgeon estimation and computed tomographic measurement of femoral component anteversion in cementless total hip arthroplasty. J Bone Joint Surg Am 2009;91(11):2598-604.

  18. Pierchon F, Pasquier G, Cotten A, Fontaine C, Clarisse J, Duquennoy A. Causes of dislocation of total hip arthroplasty. CT study of component alignment. J Bone Joint Surg Br 1994;76(1):45-8.

  19. Dorr LD, Malik A, Wan Z, Long WT, Harris M. Precision and bias of imageless computer navigation and surgeon estimates for acetabular component position. Clin Orthop Relat Res 2007;465:92-9.

  20. Digioia AM 3rd, Jaramaz B, Plakseychuk AY, Moody JE Jr., Nikou C, Labarca RS, et al. Comparison of a mechanical acetabular alignment guide with computer placement of the socket. J Arthroplasty 2002;17(3):359-64.

  21. Babisch JW, Layher F, Amiot LP. The rationale for tilt-adjusted acetabular cup navigation. J Bone Joint Surg Am 2008;90(2):357-65.

  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):494-9.

  23. McCollum DE, Gray WJ. Dislocation after total hip arthroplasty. Causes and prevention. Clin Orthop Relat Res 1990;261:159-70.

  24. Lewinnek GE, Lewis JL, Tarr R, Compere CL, Zimmerman JR. Dislocations after total hip-replacement arthroplasties. J Bone Joint Surg Am 1978;60(2):217-20.

  25. Hassan DM, Johnston GH, Dust WN, Watson G, Dolovich AT. Accuracy of intraoperative assessment of acetabular prosthesis placement. J Arthroplasty 1998;13(1):80-4.

  26. McKibbin B. Anatomical factors in the stability of the hip joint in the newborn. J Bone Joint Surg Br 1970;52(1):148-59.

  27. Maruyama M, Feinberg JR, Capello WN, D’Antonio JA. The Frank Stinchfield Award: Morphologic features of the acetabulum and femur: anteversion angle and implant positioning. Clin Orthop Relat Res 2001;393:52-65.

  28. Widmer KH, Zurfluh B. Compliant positioning of total hip components for optimal range of motion. J Orthop Res 2004;22(4):815-21.

  29. Yoshimine F. The safe-zones for combined cup and neck anteversions that fulfill the essential range of motion and their optimum combination in total hip replacements. J Biomech 2006; 39(7):1315-23.

  30. Ranawat CS, Maynand MJ. Modern techniques of cemented total hip arthroplasty. Tech Orthopedics 1991;6:17-25.

  31. Dorr LD, Faugere MC, Mackel AM, Gruen TA, Bognar B, Malluche HH. Structural and cellular assessment of bone quality of proximal femur. Bone 1993;14(3):231-42.

  32. D’Lima DD, Urquhart AG, Buehler KO, Walker RH, Colwell CW Jr. The effect of the orientation of the acetabular and femoral components on the range of motion of the hip at different head neck ratios. J Bone Joint Surg Am 2000;82(3):315-21.

  33. Malik A, Maheshwari A, Dorr LD. Impingement with total hip replacement. J Bone Joint Surg Am 2007;89(8):1832-42.

  34. Karachalios T, Hartofilakidis G, Zacharakis N, Tsekoura M. A 12- to 18-year radiographic followup study of Charnley low-friction arthroplasty. The role of the center of rotation. Clin Orthop Relat Res 1993;296:140-7.

  35. Dastane M, Dorr LD, Tarwala R, Wan Z. Hip offset in total hip arthroplasty: quantitative measurement with navigation. Clin Orthop Relat Res 2011;469(2):429-36.

  36. Visser JD. Functional treatment of congenital dislocation of the hip. Acta Orthop Scand Suppl 1984;206:1-109.

  37. Lembeck B, Mueller O, Reize P, Wuelker N. Pelvic tilt makes acetabular cup navigation inaccurate. Acta Orthop 2005;76(4):517-23.

    36

     

     

     

  38. Nishihara S, Sugano N, Nishii T, Ohzono K, Yoshikawa H. Measurements of pelvic flexion angle using three-dimensional computed tomography. Clin Orthop Relat Res 2003;411:140-51.

  39. DiGioia AM, Hafez MA, Jaramaz B, Levison TJ, Moody JE. Functional pelvic orientation measured from lateral standing and sitting radiographs. Clin Orthop Relat Res 2006;453:272-6.

    Total Hip Arthroplasty

     

  40. Berry DJ, Berger RA, Callaghan JJ, Dorr LD, Duwelius PJ, Hartzband MA, et al. Minimally invasive total hip arthroplasty. Development, early results, and a critical analysis. Presented at the Annual Meeting of the American Orthopaedic Association, Charleston, South Carolina, USA, June 14, 2003. J Bone Joint Surg Am 2003;85-A(11):2235-46.

  41. Murphy SB, Ecker TM, Tannast M. THA performed using conventional and navigated tissue-preserving techniques. Clin Orthop Relat Res 2006;453:160-7.

  42. Wixson RL, MacDonald MA. Total hip arthroplasty through a minimal posterior approach using imageless computer-assisted hip navigation. J Arthroplasty 2005;20(7 Suppl 3):51-6.

  43. Dorr LD, Malik A, Dastane M, Wan Z. Combined anteversion technique for total hip arthroplasty. Clin Orthop Relat Res 2009;467(1):119-27.

  44. Dorr LD. Hip Arthroplasty: Minimally Invasive Techniques and Computer navigation. Philadeplphia: WB Saunders Elsevier 2005.

  45. Jolles BM, Genoud P, Hoffmeyer P. Computer-assisted cup placement techniques in total hip arthroplasty improve accuracy of placement. Clin Orthop Relat Res 2004;426:174-9.

  46. Kalteis T, Handel M, Herold T, Perlick L, Baethis H, Grifka J. Greater accuracy in positioning of the acetabular cup by using an image-free navigation system. Int Orthop 2005;29(5):272-6.

  47. Amuwa C, Dorr LD. The combined anteversion technique for acetabular component anteversion. J Arthroplasty 2008;23(7):1068-70.

  48. Zhu J, Wan Z, Dorr LD. Quantification of pelvic tilt in total hip arthroplasty. Clin Orthop Relat Res 2010;468(2):571-5.