Procedia Technology 11 ( 2013 ) 755 – 763

2212-0173 © 2013 The Authors. Published by Elsevier Ltd.Selection and peer-review under responsibility of the Faculty of Information Science & Technology, Universiti Kebangsaan Malaysia.doi: 10.1016/j.protcy.2013.12.255

ScienceDirect

The 4th International Conference on Electrical Engineering and Informatics (ICEEI 2013)

Implant Size Detection Algorithm for Digital CPT Stem in Total Hip Arthroplasty

Azrulhizam Shapiia,*, Zainal Rasyid Mahayuddina, Anton Satria Prabuwonoa, Riza Sulaimanb

aIndustrial Computing Research Group, Universiti Kebangsaan Malaysia, 43600 MalaysiabInstitute of Visual Informatics, Universiti Kebangsaan Malaysia, 43600 Malaysia

Abstract

Pre-operative planning is very important in the process of a Total Hip Arthroplasty (THA) because it is a method for determining the size and optimal implant position. Currently, a manual implant size identification technique of trial and error is used todetermine the appropriate implant size for patients. This step is used repeatedly until the appropriate implant for the patient is found and the survey found that this procedure requires a long time, and is said to be less efficient. Automated implant sizedetection techniques should be developed in order for pre-operative planning to be implemented effectively. In this research, a new algorithm for CPT implant size detection has been developed for the THA pre-operative planning procedure.

© 2013 The Authors. Published by Elsevier B.V.Selection and peer-review under responsibility of the Faculty of Information Science & Technology, Universiti Kebangsaan Malaysia.

Keywords: Implant; CPT stem; pre-operative; templating; detection; size.

* Corresponding author. Tel.: +60389216674E-mail address: azrul@ftsm.ukm.my

Available online at www.sciencedirect.com

© 2013 The Authors. Published by Elsevier Ltd.Selection and peer-review under responsibility of the Faculty of Information Science & Technology, Universiti Kebangsaan Malaysia.

756 Azrulhizam Shapii et al. / Procedia Technology 11 ( 2013 ) 755 – 763

1. Introduction

Preoperative planning is essential in total hip arthroplasty (THA) as it determines the size and position of the optimal implant before surgery. The accuracy of the results of the preoperative planning enables surgical procedures to improve, saves time, and minimizes damage to the implant after surgery. Conventional identification methods are still used to find a suitable implant size for the patient [1-4].Those researchers found doctors are using a trial and error method in their studies to find the suitable implant for patient. This method involves using the implant templates supplied by the supplier and then measuring the templates of the implant by doing image mapping on the patient’s general X-ray (film). This step is done repeatedly until the appropriate implant for the patient is found. However, this procedure takes a long time and is said to be less efficient. The manual procedure requires a long time to determine the size of the patient’s implant because the method used is repeated several times. This conventional approach also demands the time and labor of highly trained orthopaedic surgeons and can lead to high levels of intra and interobserver variability. Therefore, a digital method should be developed so that the implant size identification process can be effectively implemented. Although the digital trial and error method is much faster than manual methods or conventional methods, it would be better and faster if the implant size could be determined automatically. With classical tracing paper now obsolete, a new technique should be developed to undertake the templating procedure with digital implants and X-ray [5].

2. Introduction

Every joint disease, whether inflammatory or trauma, will cause erosion of cartilage and joint damage if the disease process is allowed to continue. When this happens, a patient may complain of pain, swelling, deformity, and instability of the joints involved. There are several methods of treatment for damaged joints. The first step is to attempt conservative treatment. If this fails then the next method of treatment is surgery. The most effective surgical method is total hip arthroplasty (THA). This surgery involves an artificial joint that replaces the original which has been damaged.

The main focus in the research is to produce an algorithm that can automatically recognize a CPT stem implantsize in THA. Among the main activities in this research is to undertake a study for the development of techniques through the analysis of algorithms developed by other researchers. As there are various types of medical images such as bones, organs, brain, tissues, and others, the scope of this research has been limited only to the images of bones, also known as orthopaedic images. An example of an orthopaedic image can be seen in Fig 1.

757 Azrulhizam Shapii et al. / Procedia Technology 11 ( 2013 ) 755 – 763

Fig. 1. Orthopaedic X-ray image

In general, the field of orthopaedics is divided into several specific areas, such as shoulder and elbow surgery, paediatric orthopaedics, total knee arthroplasty (TKA) and total hip arthroplasty (THA) [6]. THA procedures has been selected for this research. The study involved only patients with normal hips. THA was discovered by Sir John Charnley in 1961. He was a prominent orthopaedic surgeon who served at the Joint Diseases Hospital Wrighton in Wigan, England. He had been experimenting with various types of joint surfaces when he eventually created Charnley hip or low friction arthroplasty. Artificial joints are used to replace a damaged hip joint. It consists of a femoral stem made of stainless steel and the joint is made of high density polyethylene. After nearly 40 years, the same material is still used for latest artificial joints with reforms in terms of design [6]. Fig 2 shows the CPT stem implant used in total hip arthroplasty surgery.

Fig. 2. CPT stem implant for THA

Prior to surgery, the template preparation process is very important because it is a screening process in which an orthopaedic specialist can determine the optimal implant size before surgery. The orthopaedic specialist will do the

758 Azrulhizam Shapii et al. / Procedia Technology 11 ( 2013 ) 755 – 763

adjustment process of the implant templates first before bringing the results into the operating room. In the operating room, the orthopaedic specialist will make the final selection of the appropriate implant size. The use of implants in the templating process on the X-ray image of a patient before surgery can provide important information to the orthopaedic specialist in determining the size of the implant to be used [7]. By using the manual method, any error in template transformation such as rotating and scaling while recording the patient's hip bone radiographs prior tothe surgery will lead to errors in determining the size of implant templates. As a result the templating process should be done cautiously. Fig 3 shows the process of manual implant templating for CPT stem [8].

Fig. 3. Manual CPT stem templating

3. Material and Methods

The main goal of this research is to develop an algorithm for implant size detection of the THA. The first objective is to design a technique and algorithm for the detection of the size of the implant. The second objective is to implement the algorithm produced by developing a system to meet the first objective requirement. Finally, the third objective is to carry out testing and a comparison of the effectiveness of the algorithm produced. Fig 4 shows the approach to be used in this research.

Fig. 4. Research approach

759 Azrulhizam Shapii et al. / Procedia Technology 11 ( 2013 ) 755 – 763

3.1. Implant template

To obtain detailed information about total hip arthroplasty (THA) and how experts carry out the orthopaedic implant recognition or detection process, interviews with a few orthopaedic specialists were carried out. Those interviewed were experts from the Department of Orthopaedics and Traumalogy, Medical Center of Universiti Kebangsaan, Malaysia (PPUKM). As a result of the interviews with PPUKM, two important data used in the development of CPT implant detection algorithms have been successfully collected. The two important data are the implant template that is used manually during pre-operative planning and the patient’s digital X-ray radiograph images. Fig 5 shows the manual CPT stem implant template used by surgeons in THR procedure. Table 1 shows the information of the CPT stem implants produced by Zimmer.

Table 1. Details of CPT stem implant (Zimmer)

No Product No. Size Stem Width (mm) Stem Length (mm)

1 97-8114-000-00 0-STD 9.0 105

2 97-8114-001-00 1-STD 10.5 130

3 97-8114-002-00 2-STD 13.0 130

4 97-8114-003-00 3-STD 15.5 130

5 97-8114-004-00 4-STD 17.5 130

6 97-8114-005-00 5-STD 20.0 130

Fig. 5. CPT stem template

3.2. CPT Stem Implant Detection Algorithm

The process of designing and producing new algorithm for CPT implant detection is taking into consideration the methods of improvement which will be implemented on the latest techniques or algorithms. Through literature studies, most of the implant detection techniques used the trial and error method. This means that surgeons need to try several sizes to get the optimum implant. One of the potential new methods to be produced is the automated detection method.

760 Azrulhizam Shapii et al. / Procedia Technology 11 ( 2013 ) 755 – 763

The new CPT implant detection algorithm developed is based on conventional and computerized techniques in which the implant template will be matched with X-ray images [9-15]. A trial and error method will be repeated several times until the appropriate size is found. The proposed new algorithm has the ability to detect the size of the implant automatically. By using the concept of distance between two points, hip implants will be selected based on the femur size. Fig 6 shows the proposed algorithm for the CPT stem implant detection algorithm.

Fig. 6. CPT stem implant size detection algorithm

In the algorithm shown in Fig 6, the user must choose the first and the second points on the femur bone. The distance between the two points will be calculated and the size of the CPT implant will be determined by the femur size. The sizing method involves six conditions (Fig 6). For example, in Fig 7, the distance between the two points chosen (point A and point B) on the femur bone is 13.55 mm, and therefore the size that will be taken is size 2.

Fig. 7. Position of point A and point B

4. Results and discussion

Based on the algorithm in Fig 6, the first thing the user needs to do is choose two points on the patient’s femur bone. Fig 8 shows how to choose the points.

Point A

Point B

761 Azrulhizam Shapii et al. / Procedia Technology 11 ( 2013 ) 755 – 763

Fig. 8. Distance between two points

The distance between the two points on the line will be calculated to determine the size of the stem implant. In Fig 8, the distance drawn on the femur was 13.55 mm, so the value to be taken is 13 mm. A CPT stem implant with size 2 will be displayed automatically on the X-ray image (see Fig 9 and Fig 10).

Fig. 9. Stem implant displayed on the X-ray

Point B

Point A

Distance between two

points

762 Azrulhizam Shapii et al. / Procedia Technology 11 ( 2013 ) 755 – 763

Fig. 10. Patient and implant information

5. Conclusion

Pre-operative planning procedures play an important role in determining the size of the implant to be used in totalhip arthroplasty surgery (THA). In this research, a new implant detection algorithm has been developed to do an automated templating process using digital CPT implants and digital X-ray images. The new algorithm provides a simple solution to overcoming the problems faced by orthopaedic specialists when using conventional methods during the implant templating process for THA. This algorithm allows the orthopaedic specialist to choose the CPT digital implant automatically in pre-operative planning. One of the advantages of using the digital automated algorithm in pre-operative planning is that an X-ray image (film) is no longer required and this can reduce the risk of losing a patient’s X-ray images [5]. In addition, by using the new implant size detection algorithm, orthopedic specialists can make an accurate and quick decision during the selection of the CPT implant size for patients.

Acknowledgements

This research project was conducted in collaboration with Dr. Abdul Yazid Mohd Kassim and Dr. Nor Hazla Haflah from the Department of Orthopaedics and Traumatology and Dr. Hamzaini Abd Hamid from the Department of Radiology, Medical Centre of University Kebangsaan Malaysia. This research was also funded by the University Grants UKM-GGPM-2012-003 and UKM-GUP-2012-010.

References

[1] Yusoff SF. Knee Joint Replacement Automation Templates. M.sc Thesis, 2009, Universiti Kebangsaan Malaysia, Bangi, Malaysia.[2] Bono JV. Digital Templating in Total Hip Arthroplasty. Journal of Bone Joint Surg Am 2004:86 (2):118-122.[3] Davila JA, Kransdof MJ, Duffy GP. Surgical Planning of Total Hip Arthroplasty: Accuracy of computer assisted EndoMap software in

predicting component size. Journal of Skeletal Radiology 2006: 35: 390-393.[4] Berry DJ. Primary Total Hip Arthroplasty. In: Chapman M.W., ed. Chapman’s Orthopaedic Surgery.[5] Michalikova M, Bednarcikova L, Petrik M, Rasi R, Zivcak J. The Digital Pre-Operative Planning of Total Hip Replacement. Proceedings of

8th IEEE International Symposium on Applied Machine Intelligence and Informatics 2010.[6] Garino PJ, Beredjiklian PK, Elsevier M. Adult Reconstruction Arthroplasty Core Knowledge in Orthoapaedics. Elsevier, United States, 2007.[7] Murzic WJ, Glozman Z, Lowe P. The Accuracy of Digital (filmless) Templating in Total Hip Replacement. 72nd Annual Meeting of the

American Academic of Orthopaedic Surgeons 2005.[8] Versys Fiber Metal Taper Hip Prosthesis: Surgical Technique, Zimmer, 2007.

763 Azrulhizam Shapii et al. / Procedia Technology 11 ( 2013 ) 755 – 763

[9] Testi D, Quadrani P, Petrone M, Zannoni C, Fontana F, Viceconti M.. JIDE: A New Software for Computer-Aided Design of Hip Prosthesis.Computer Methods and Programs in Biomedicine 2004: 75: 213-220.

[10]Viceconti M, Lattanzi R, Antonietti B, Paderni S, Olmi R, Sudanese A, Toni A. CT-based Surgical Planning Software Improves the Accuracy of Total Hip Replacement Preoperative Planning. Medical Engineering & Physics 2003: 25: 371-377.

[11]Todsaporn F, Amnach K, Mitsuhashi W. Computer-Aided Pre-Operative planning for Total Hip Replacement by using 2D X-ray images. Proceedings of SICE Annual Conference 2008: Tokyo.

[12]Crooijmans HJ, Laumen AM, Pul C, Mourik V. A new digital preoperative planning method for total hip arthroplasties. Clin Orthop Relat Res 2009: 467: 909–916.

[13]Gamble PJ, Beer D, Petruccelli D, Winemaker M. The accuracy of digital templating in uncemented total hip arthroplasty. Journal of Arthroplasty 2010:25(4): 529-532.

[14]Iorio R, Siegel J, Specht LM, Tilzey JF, Hartman A, Healy WL. A comparison of acetate vs digital templating for preoperative planning of total hip arthroplasty: is digital templating accurate and safe. Journal of Arthroplasty 2009: 24(2): 175–179.

[15] Shapi’i A, Sulaiman R, Hasan MK, Kassim AYM. Digital stem implant detection technique for total hip replacement based on femur size.International Journal of Research and Reviews in Computer Science 2011: 2(2): 566-571.