Case Study: Shiraniwa Hospital


THA Pre-Operative Planning

X-ray film templating

Advantage(s)
  • Easy to use
  • No extra cost
Disadvantage(s)
  • Inaccurate magnification ratio
  • Accuracy lower than 3D templating (Carter LW. J Arthro. 1995)

2D digital templating

Advantage(s)
  • Easy to use
Disadvantage(s)
  • Inaccurate magnification ratio, expensive, accuracy equivalent to the conventional method (Gamble P et al. J Arthro. 2010)

Navigation system

Advantage(s)
  • High accuracy
Disadvantage(s)
  • Extended operation time, cumbersome equipment, expensive (Stiehl JB. Comput Aided Surg. 2007)

3D templating

Advantage(s)
  • High accuracy (Viceconti M et al. Med Inform Internet. 2002, Manaka et al. Hip Joint. 2006, Sariali E et al. JBJS-B. 2009)

Purpose of this study

To examine effectiveness of ZedHip in THA pre-operative planning.

Subjects

Period and the number of samples

32 patients with 34 hips (4 male and 28 female) for THA from July 2011 to August 2012.

Average age

72 years old (50-89 years old).

Used implants

  • Cup:Trident PSL (Stryker)
  • Stem:Profemur Z (Wright Medical)

Primary diseases

  • Hip osteoarthritis: 30 hips
  • Idiopathic femoral head necrosis: 3 hips
  • Femoral neck fracture: 1 hip

Items to be examined

  • Match rate between planned and used implants
  • Angles of post-operative implant position
  • Post-operative complications

Results

Cup

Match rate of implants

  • Perfect matching: 31 hips (91%)
  • 1 size up: 2 hips
  • 1 size down: 1 hip

Angles of implant position (in degrees)

  • Inclination: 43.8±4.5
  • Anteversion: 18.2±6.7

Stem

Match rate of implants

  • Perfect matching: 20 hips (59%) (*1)
  • 1 size down: 14 hips (41%)

Angles of implant position (in degrees)

  • Varus: 2.1±1.2 (range: 0―4.9)
  • Flexion: 3.2±2.0 (range: -0.7―7.1)
  • Anteversion: 8.2±5.9 (range: -16.5―19.1)
*1: Reasons for the low match rate of the stem may include:

– Rotation (dispersion of anteversion)

– Bone resection distance error

– Insert position error

– Stem shape etc.

Case 1

Case 2

Summary

2D 3D
Conventional
frontal plain X-ray
Digital Templating Navigation System Digital Templating
(ZedHip)
Accuracy of implant positions ○ (*1)
Radiation exposure
User-friendliness ○ (*2)
Cost ×

*1: Accuracy higher than 2D and almost equivalent to the navigation system
*2: About 15 minutes for pre-operative planning and simulation

Advantages of ZedHip

  • ROM simulation (dislocation test)
  • Simulations of osteophyte resection and pelvic reference plane change
  • Easy for inexperienced surgeons to imagine the actual surgery

* What is most important here is how accurately ZedHip helps realize its pre-operative planning in the actual surgical field.

Conclusions

  • The match rates of implants were 91% for the cup and 59% for the stem.
  • ZedHip pre-operatively allows us to identify osteophytes and bone cysts in 3D, hence to understand their sizes and locations more accurately than other methods.
  • Pre-operative planning by ZedHip would be a useful tool for preparing for surgery with confidence.
  • There still remains the difficulty of placing implants as planned.
  • It would be a more practical method for general hospitals in planning surgery pre-operatively.

Joint Arthroplasty Center, Shiraniwa Hospital

6-10-1 Shiraniwadai, Ikoma, Nara, 630-0136 Japan

http://www.allpines.jp/index.html