PERSONALISED KNEE REPLACEMENT USING PATIENT SPECIFIC 3D MOULD
Like many features of an individual person, each person’s knees are also to some extent different. Studies have shown that good alignment of a knee replacement is important for optimal outcome. In addition, the component sizing is also important. During conventional knee replacements, manual guides are used and a certain amount of “eye balling” is involved. Many studies have shown that this can result in a proportion of “outliers” who can have less than optimal function. Computer guided surgery has been shown to reduce the “outliers” but the surgery takes longer and special equipments are needed.
A very recent technological development is “patient specific instrumentation” or a “custom fit knee”. In this technique, MRI scan of the person’s hip, knee and ankle is done few weeks before the operation. A special computer software creates the three dimensional model of the patient’s knee and allows the surgeon to plan the bone cuts and component placement on a personal computer. The model also allows the best sizing option and shape). These images are then used to create precise 3 dimensional plastic moulds which when placed on that particular patient’s knee during surgery allows customised bone preparation as planned previously in the computer. Essentially a the surgeon does a “virtual knee replacement” in the computer and then “executes” this plan during the actual surgery. Different companies call this technique by different names (PSI knee –
Potential advantages compared to conventional knee replacements
1. Accuracy in alignment –
2. Reduced instrumentation – instead of the usual 7 or 8 trays of instruments required for conventional knee replacements, by making the trays size specific Mr.Ganapathi has been able to reduce the number of instrument trays to 2 or 3 which reduces the sterilization cost and also helps faster turnover of patients.
3. Faster Surgery – While intuitively it would be expected that the surgical time would be less with the pre-planning in a 3-D model in a computer, many studies have reported no difference or very little difference in the surgical time! In Mr.Ganapathi’s own practice, the surgical time during the initial few cases was not reduced. However, careful pre-operative planning, reduced instruments, faster turnover, streamlining the surgical steps and optimising intra-operative processes using the analogy of a Formula 1 pit stop has allowed Mr.Ganapathi to take full advantage of the PSI technology and reduced the surgical time significantly without compromising on outcome (see below for functional outcome).
4. Minimal blood loss and transfusion requirement –
5. Functional outcome: While complications can still occur like in any other knee replacement and not every patient will have an entirely satisfactory outcome, in Mr.Ganapathi’s own series, the one year average patient reported functional outcome (PROMS score –
NJR Data
6. Even in some difficult cases, the results have been good.
Example1: Bilateral severe arthritis with valgus deformities (pre- op and post- op x- rays)
Example 2: Bilateral severe arthritis with stiffness, valgus deformity and high BMI (pre- op and post- op x- rays)
Example 3: Bilateral severe arthritis with varus deformity and stiffness with preoperative flexion deformity > 20 degrees (pre- op and post- op x- rays, post- op clinical picture and post- op range of movement at one year)
Example 4: Previous femoral malunion with arthritis (pre- op and post- op x- rays)
Not all patients would be suitable for this technique. If there is a contra-
If you are interested in having this surgery done privately, Mr.Ganapathi would be able to offer this type of knee replacement at Spire Yale Hospital, Wrexham. For further enquiries please click here.
Preoperative deformity
Preoperative x- rays
3- D model of the knee
Planned bone resection
Planned knee replacement
How the 3- D moulds will look on the patient’s knee
Before & After Knee Replacements
Preop and post operative x- rays (cruciate retaining knee replacements)
Excellent function at 3 months after both knee replacements
Case Study 1 – Complex Varus with Valgus on the Other Side – Windswiped Knees
Case Study 2 – Complex Valgus
Case Study 3 – Severe Patello-femoral Arthritus
Case Study 4 – Severe Stiffness
Case Study 5 – Previous High Tibial Osteotomy
AWARDS
1. The improvement which Mr.Ganapathi (in conjunction with theatre staff) has brought to theatre efficiency and faster rehabilitation by using this novel technique has been acknowledged by Betsi Cadwaladr University Health Board by awarding runner up prize at the “Improvement Award 2012” function.
2. ‘Best Podium presentation award’ in the CAOS UK Annual Meeting Nov 2013 (Computer Assisted Orthopaedic Surgery) for ‘Importance of Surgeon’s planning during PSI knee replacement’.
PRESENTATIONS
1.’ My PSI Journey ‘
Invited speaker at the PSI user group meeting, Warrington –
2. Comparison of peri- opertative outcomes of TKRs done using Computer Navigation and PSI
Invited speaker at the 6th International Arthroplasty Conference, Sharm El Sheik, Egypt –
3. Single surgeon experience of 100 consecutive TKA using Zimmer PSI technique
Invited speaker at the 6th International Arthroplasty Conference, Sharm El Sheik, Egypt –
4. Importance of planning and how PSI works in a public hospital setting
Invited speaker at the PSI user group meeting, Florence, Italy –
5. Comparison of peri- operative outcomes of TKRs done using Computer Navigation and Patient Specific Instrumentation
S.Aranganathan, S.Thati, M Ganapathi –
6. Comparison of peri- operative outcomes of TKRs done using Computer Navigation and Patient Specific Instrumentation
S.Aranganathan, S.Thati, M Ganapathi –
7. Preoperative planning in Patient Specific Instrumentation Total Knee Replacement
S.Aranganathan, S.Thati, M Ganapathi –
8. Patient Specific Instrumentation Total Knee Arthroplasty improves theatre efficiency
S.Aranganathan, S.Thati, M Ganapathi Poster presentation at the IOS UK Annual Meeting, Huddersfield –
9. Comparison of peri- operative outcomes of TKRs done using Computer Navigation and Patient Specific Instrumentation
S.Aranganathan, S.Thati, M Ganapathi –
10. A single surgeon experience in using Patient Specific Instrumentation technique for knee replacement
S.Aranganathan, S.Thati, M Ganapathi –
11. Patient Specific Instrumentation – preoperative planning
S.Aranganathan, S.Thati, M Ganapathi –
12. Patient Specific Instrumentation Total Knee Arthroplasty improves theatre efficiency
S.Aranganathan, S.Thati, M Ganapathi –
13. Comparison of perioperative outcomes of TKRs done using Computer Navigation and Patient Specific Instrumentation
S.Aranganathan, S.Thati, M Ganapathi –
14. ‘PSI Effect’
Invited speaker at the 34th SICOT Orthopaedic World Congress, Hyderabad, India –
15. Comparison of peri- operative outcomes of TKRs done using Computer Navigation and Patient Specific Instrumentation
S.Aranganathan, S.Thati, M Ganapathi –
16. Careful planning during virtual knee replacement improves component prediction and reduced intraoperative changes
S.Aranganathan, S.Thati, M Ganapathi –
17. MRI study of distal femoral rotational axes and their effect on flexion gap
A.Kaminskas, S.Thati, M Ganapathi –
18. PSI knee replacement – a single surgeon experience in a DGH
S.Thati, M Ganapathi –
19. The Importance Of Surgeon’S Input In Preoperative Planning Of Patient Specific Knee Replacement
S.Thati, S. Aranganathan, M Ganapathi –
20. Anatomical Variation In Distal Femoral Rotational Axes And Its Effect On Flexion Gap: MRI Analysis
A.Kaminskas, S.Thati, M Ganapathi –
The following are some relevant selected scientific references:
1. Frontal plane alignment after total knee arthroplasty using patient- specific instruments.
Int Orthop. 2013 Jan;37(1):45-
Daniilidis K, Tibesku CO.
Department of Orthopaedic Surgery, Annastift Hannover Medical School, Hannover, Germany.
PURPOSE: Although total knee arthroplasty (TKA) is regularly associated with favorable outcomes, considerable research efforts are still underway to improve its ability to achieve a neutral postoperative mechanical axis. Patient-
METHODS: A long-
RESULTS: There were 100 knees (average age, 66.8 years) with follow-
CONCLUSIONS: The use of PSI technology was able to achieve a neutral mechanical axis on average in patients undergoing TKA. Further follow-
2. Improved femoral component rotation in TKA using patient- specific instrumentation.
Knee. 2012 Nov 7. pii: S0968-
Heyse TJ, Tibesku CO.
Department of Orthopedics and Rheumatology, University Hospital Marburg, Germany.
BACKGROUND: Patient-
METHODS: A magnetic resonance imaging (MRI) analysis of 94 patients following TKA was conducted. Of these, 46 operations were performed using PSI and 48 using conventional instrumentation. The rotation of the femoral components was determined in the MRI and deviations >3° were considered outliers. Data were analyzed for positional outliers, observer reliability, and a variance comparison between implant groups.
RESULTS: There was excellent inter-
CONCLUSION: In this setup, PSI was effective in significantly reducing outliers of optimal rotational femoral component alignment during TKA.
3. Improved accuracy of alignment with patient- specific positioning guides compared with manual instrumentation in TKA.
Clin Orthop Relat Res. 2012 Jan;470(1):99-
Ng VY, DeClaire JH, Berend KR, Gulick BC, Lombardi AV Jr.
Department of Orthopaedics, The Ohio State University Medical Center, Columbus, OH, USA.
BACKGROUND: Coronal malalignment occurs frequently in TKA and may affect implant durability and knee function. Designed to improve alignment accuracy and precision, the patient-
QUESTIONS/PURPOSES: We compared the effectiveness of patient-
METHODS: We retrospectively reviewed 569 TKAs performed with patient-
RESULTS: The overall mechanical axis passed through the central third of the knee more often with patient-
CONCLUSIONS: Patient-
4. Comparison of custom to standard TKA instrumentation with computed tomography.
Knee Surg Sports Traumatol Arthrosc. 2013 Aug 25.
Ng VY, Arnott L, Li J, Hopkins R, Lewis J, Sutphen S, Nicholson L, Reader D, McShane MA.
Author information Department of Orthopaedics, The Wexner Medical Center, The Ohio State University
Abstract
PURPOSE: There is conflicting evidence whether custom instrumentation for total knee arthroplasty (TKA) improves component position compared to standard instrumentation. Studies have relied on long-
METHODS: We prospectively evaluated a single-
RESULTS: Preoperative templating for custom instrumentation was 87 and 79 % accurate for femoral and tibial component size. All custom components were within 1 size except for the tibial component in one patient (2 sizes). Tourniquet time was 5 min longer for custom (30 min) than standard (25 min). In no case was custom instrumentation aborted in favour of standard instrumentation nor was original alignment of custom instrumentation required to be adjusted intraoperatively. There were more outliers greater than 2° from intended alignment with standard instrumentation than custom for both components in all three planes. Custom instrumentation was more accurate in component position for tibial coronal alignment (custom: 1.5° ± 1.2°; standard: 3° ± 1.9°; p = 0.0001) and both tibial (custom: 1.4° ± 1.1°; standard: 16.9° ± 6.8°; p < 0.0001) and femoral (custom: 1.2° ± 0.9°; standard: 3.1° ± 2.1°; p < 0.0001) rotational alignment, and was similar to standard instrumentation in other measurements.
CONCLUSIONS: When evaluated with CT, custom instrumentation performs similar or better to standard instrumentation in component alignment and accurately templates component size. Tourniquet time was mildly increased for custom compared to standard.