This article is more than 5 years old. Information may no longer be current.

Status of Navigated Total Hip Arthroplasty in Dysplastic Osteoarthritis

Add topic to email alerts

Receive an email when new articles are posted on

Please provide your email address to receive an email when new articles are posted on .

Subscribe

Added to email alerts

You've successfully added to your alerts. You will receive an email when new content is published.

Click Here to Manage Email Alerts

You've successfully added to your alerts. You will receive an email when new content is published.

Click Here to Manage Email Alerts

Back to Healio

We were unable to process your request. Please try again later. If you continue to have this issue please contact customerservice@slackinc.com.

Back to Healio

Abstract

This article describes the results of 41 total hip arthroplasties (THAs) carried out using a new image-free hip navigation system. For the study, registration landmarks (tear drop, posterior rim, and inner wall of the acetabulum) were added to the hip navigation system OrthoPilot (B. Braun Aesculap, Tuttlingen, Germany). The reamer center was indicated in reference to these landmarks, and final cup angle was indicated as the radiologic angle. Forty-one total THAs to treat dysplastic osteoarthritis of the hip were performed. The difference between reamer center and cup center was 4.1±3.0 mm. The difference in cup abduction angle between navigation and radiography was 6.4º±5.1º and of anteversion was 5.9º±5.0º. Our preliminary clinical results showed adequate accuracy.

In total hip arthroplasty (THA), malposition of the cup restricts the range of motion and is the most common cause of dislocation.^1-5 Cup setting angle is reported to affect cup wear rates.^6,7 Lewinnek et al⁸ defined the safe zone of cup setting angle as 40°±10° in abduction and 15°±10° in anteversion. However, the cup setting angle within this safe zone is not assured even if mechanical alignment guides are used.^9,10 It is sometimes difficult to determine the position of the pelvis precisely because proper fixation of the pelvis is not always obtainable on the operating table and because the position of the pelvis can change during surgery. Hip navigation systems have been developed to aid surgeons in determining the position and angle of the cup in pelvic coordinates. In navigation systems based on computed tomography, 3-dimensional (3-D) images are obtainable, and the position and angle of the cup can be planned and navigated.

In image-free navigation systems, alignment of the cup is made based on the position of bony landmarks (anterior superior iliac spines and pubic symphysis) determined intraoperatively by the surgeon using a reference pointer. Pelvic coordinates are based on the frontal pelvic plane and only the angle of cup, without information about cup position, is indicated. On the other hand, exposure to radiation is lower with image-free navigation and use of the system is cost-effective.

In dysplastic osteoarthritis (OA) of the hip, the femoral head is usually migrated superiorly and laterally to the original acetabulum. To correct these deformities, surgeons plan the size, position, and angle of the cup for each patient before surgery. In preoperative templating on standard radiography, the tear drop, superolateral edge of the acetabulum, and inner wall of the acetabulum are used as landmarks.

We developed an image-free hip navigation system for dysplastic OA. In this study, we explain the strategy of our image-free hip navigation system for dysplastic OA and investigate preliminary clinical results to evaluate the usefulness and accuracy of our system.

Materials and Methods

Strategy of image-free hip navigation for dysplastic OA

The hip navigation system was modified from a hip navigation system (OrthoPilot; B. Braun Aesculap; Tuttlingen, Germany). In preoperative templating on standard anteroposterior (AP) radiography, the cup center was determined, and the craniocaudal distance from the tear-drop line and the mediolateral distance from the superolateral edge of the acetabulum to the planned cup center were measured (Figure 1). Intraoperatively, the pelvic coordinates were determined by registering both the anterosuperior iliac spines and the pubic symphysis. After exposure of the acetabulum, the tear-drop, superolateral edge of the acetabulum, and posterior rim of the acetabulum were registered. The position of cup center was navigated in reference to the distance from the tear-drop and the posterior rim of acetabulum (Figure 2). The acetabulum was registered by use of a small pilot hole drilled at the navigated cup center that perforated the inner wall of the acetabulum. The reamer center was indicated on the screen by the distance from the tear drop in the craniocaudal axis, from the superolateral edge and inner wall of acetabulum in mediolateral axis, and from the posterior rim of the acetabulum in the AP axis. The abduction angle and anteversion of the reamer were also indicated on the screen (Figure 3). These data enabled the surgeons to ream the deformed acetabulum for cup placement at the planned position. For final cup implantation, the abduction angle and anteversion of cup were indicated on the screen as radiologic angle.¹¹

Patients

Since 2006, 41 consecutive THAs in 38 patients were performed in the lateral decubitus position. The average age at surgery was 54.7 years (range, 29-65). The average body mass index (BMI) was 23.2 (range, 16.2-33.8). The diagnoses were 24 dysplastic OAs, 13 avascular necroses, and four femoral neck fractures. Cup center was planned by the surgeons, and THA with navigation was performed as described. BiContact stem and Plasmacup (B. Braun Aesculap) with alumina against alumina articulation were implanted using our image-free hip navigation system.

To evaluate the efficacy of our system, the abduction angle and anteversion of the cup were measured on standard AP radiography with the patient in the supine position. The percentage of cups that were fixed within the Lewinnek safe zone was calculated. To evaluate the accuracy of our system, the abduction angle and anteversion of the cup indicated by the navigation system were compared with those measured using standard radiography. The comparison was done to investigate the effects of three factors: diagnosis, BMI, and experience in using the navigation system. The difference between tear drop reamer center distance indicated by the navigation and tear drop-cup center distance measured using standard AP radiography was evaluated for craniocaudal accuracy. The comparison was done to investigate the effects of two factors: diagnosis and BMI.

Results

There were no surgical complications related to the use of navigation. No patient suffered a neurovascular complication, infection, or dislocation.

Thirty-six of 41 cups were within the Lewinnek safe zone (Figure 4). In cups outside the safe zone, the abduction angle of the cup was 51° in 3 cups, 52° in 1 cup, and 28° in 1 cup. In terms of anteversion, all cups were within the Lewinnek safe zone.

Overall, the difference between navigated angle and measured angle was 6.4°±5.1° in abduction and 5.9°±5.0° in anteversion. The difference in terms of diagnosis and BMI is shown in Table 1. The difference of anteversion was slightly lower in patients with avascular necrosis. The difference of anteversion was greater in patients with a BMI>5.0.

To analyze the learning curve involved in incorporating image-free navigation in THA, the difference between navigated and measured angle of the cup was compared every 10 cases. There was no change in the difference of both abduction angle and anteversion from the time navigation was introduced to the last procedure (Table 1).

For craniocaudal accuracy, the difference between reamer center and cup center was 4.1±3.0 mm. The difference in terms of diagnosis and BMI is shown in Table 2. In patients with a BMI>25.0, the difference was greater.

Discussion

Establishing the point of planned cup center in the acetabulum during surgery is key to treating dysplastic OA by THA. Theoretically, a point can be defined by three axes in 3D coordinates. In our system, planned cup center is indicated by the distances from the tear drop in the craniocaudal axis, from the superolateral edge of the acetabulum and the inner wall of the acetabulum in mediolateral axis, and from the posterior rim of the acetabulum in the AP axis. Registration of these bony landmarks is critical. To investigate the accuracy of registration, we mapped these bony landmarks during surgery and obtained radiographic images in all cases. As intended, all bony landmarks were well established. Because these bony landmarks can be registered in revision surgery, application of our system to revision cases may be an option.

From our results, the percentage of cups within the Lewinnek safe zone was 90.2%. This finding is slightly lower that reported with other image-free navigation systems (Table 3)^12-15; however, four failed cups were within 2° out of the Lewinnek safe zone, which is an established margin of error in radiographic measurement. Thus, our preliminary clinical results show adequate accuracy.

The difference between the navigated value and the measured value in the angle and position of the cup was attributable to several factors: (1) the registration landmarks were not correctly pointed; (2) the active infrared light-emitting tracker in the ilium was unstable; and (3) the cup was not always implanted at the bottom of reamed concavity. Considering these factors, the accuracy of our system was considered satisfactory. We did not detect a learning curve, presumably because of the simplicity of the procedures.

In patients with a BMI>25.0, the difference between the navigated value and the measured value in the angle and the position of the cup was greater. We presume that this discrepancy is attributable to inaccurate registration of bony landmarks. To improve accuracy, precise methods for registration should be developed.

References

1. McCollum DE, Gray WJ. Dislocation after total hip arthroplasty. Causes and prevention. Clin Orthop Relat Res. 1990 Dec; (261):159-170.
2. Pierchon F, Pasquier G, Cotten A, Fontaine C, Clarisse J, Duquenney A. Causes of dislocation of total hip arthroplasty. CT study of component alignment. J Bone Joint Surg Br. 1994; 76(1):45-48.
3. Paterno SA, Lachiewicz PF, Kelley SS. The influence of patient-related factors and the position of the acetabular component on the rate of dislocation after total hip replacement. J Bone Joint Surg Am. 1997; 79(8):1202-1210.
4. Kummer FJ, Shah S, Iyer S, DiCesare PE. The effect of acetabular cup orientations on limiting hip rotation. J Arthroplasty. 1999; 14(4):509-513.
5. Jolles BM, Zangger P, Leyvraz PF. Factors predisposing to dislocation after primary total hip arthroplasty: a multivariate analysis. J Arthroplasty. 2002;17(3):282-288.
6. Del Schutte H Jr, Lipman AJ, Bannar SM, Livermore JT, Ilstrup D, Morrey BF. Effects of acetabular abduction on cup wear rates in total hip arthroplasty. J Arthroplasty. 1998; 13(5):621-626.
7. 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):530-534.
8. Lewinnek GE, Lewis JL, Tarr R, Compere CL, Zimmermann JR. Dislocations after total hip-replacement arthroplasties. J Bone Joint Surg Am. 1978; 60(2):217-220.
9. 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.
10. Nogler M, Kessler O, Prassl A, et al. Reduced variability of acetabular cup positioning with use of an imageless navigation system. Clin Orthop Relat Res. 2004 Sep; (426):159-163.
11. Murray DW. The definition and measurement of acetabular orientation. J Bone Joint Surg Br. 1993; 75(2):228-232.
12. 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):272-276. Epub 2005 Aug 5.
13. Kiefer H, Othman A. OrthoPilot total hip arthroplasty workflow and surgery. Orthopedics. 2005; 28(10 suppl):S1221-S1226.
14. Lazovic D, Kaib N. Results with navigated bicontact total hip arthroplasty. Orthopedics. 2005; 28(10 suppl):S1227-S1233.
15. Kalteis T, Handel M, Bäthis 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):163-167.

Authors

Drs Ohashi, Matsuura, Okamoto, Ebara, Kakeda, and Takahashi are from the Department of Orthopaedic Surgery, Saiseikai Nakatsu Hospital, Osaka, Japan.

Correspondence should be addressed to: Hirotsugu Ohashi, MD, Department of Orthopaedic Surgery, Saiseikai Nakatsu Hospital, 2-10-39, Shibata, Kita-ku, Osaka 530-0012, Japan.

Drs Ohashi, Matsuura, Okamoto, Ebara, Kakeda, and Takahashi have no financial relationships to disclose.