Computer Assisted Surgery - abstracts

Minimally invasive computer-assisted total knee arthroplasty through a subvastus approach.

Zanasi S.
Villa Erbosa Hospital, Bologna, Italy.
Orthopedics. 2006 Oct;29(10 Suppl):S142-4.

Computer-assisted total knee arthroplasty (TKA) has traditionally been performed through an anterior midline incision approximately 16 cm long, using a capsular incision that separates the interval between the rectus femoris and vastus medialis muscles. The incision disrupts the suprapatellar pouch and frequently leads to adhesions and difficulty in fast and complete flexion recovery despite the wide exposure. The minimally invasive surgery subvastus approach with computer-assisted soft tissue balancing using OrthoPilot TKA (B. Braun Aesculap, Tuttlingen, Germany) not only provides optimal alignment and balancing of the components but also results in maximal and faster flexion recovery and reduces the need for postoperative narcotic medication.

Reproducibility of intra-operative measurement of the mechanical axes of the lower limb during total knee replacement with a non-image-based navigation system.

Jenny JY, Boeri C, Picard F, Leitner F.
Centre de Traumatologie et d'Orthopedie, Illkirch, France.
jean-yves.jenny@evc.net
Comput Aided Surg. 2004;9(4):161-5.

OBJECTIVE: The restoration of a normal mechanical axis of the lower limb following total knee prosthesis (TKP) depends on the accuracy of the intra-operative measurement of the femoro-tibial angle. We have studied the reproducibility of intra-operative measurement of the coronal mechanical femoro-tibial axis with the OrthoPilot (Aesculap, Tuttlingen, Germany) non-image-based navigation system.

MATERIAL AND METHODS: A consecutive series of 20 TKP (Aesculap SEARCH Evolution prosthesis) implanted by the same surgical team of two senior orthopedic surgeons was analyzed. They used a non-image-based navigation system that allows the mechanical axes of the femur and tibia to be defined with a kinematic analysis. The operating surgeon and assistant surgeon performed the kinematic analysis twice and once, respectively, and measured coronal mechanical femoro-tibial angles in maximal extension and at 90 degrees flexion without varus or valgus stress. RESULTS: The mean intra-observer variation in the measurement of the coronal mechanical femoro-tibial angle in maximal extension was 0.1 degrees (SD = 0.7 degrees). The mean intra-observer variation in the measurement of the coronal mechanical femoro-tibial angle at 90 degrees of knee flexion was 0.2 degrees (SD = 0.6 degrees). The mean inter-observer variation in the measurement of the coronal mechanical femoro-tibial angle in maximal extension was 0.1 degrees (SD = 0.7 degrees). The mean inter-observer variation in the measurement of the coronal mechanical femoro-tibial angle in maximal extension was 0.0 degrees (SD = 0.6 degrees). There were no significant differences and a high correlation between all paired intra- and inter-observer measurements.

CONCLUSION: This system allows high reproducibility of the intra-operative measurement of the mechanical axes of the lower limb by a non-image-based kinematic registration of the hip, knee and ankle centers.

Computer-assisted navigation increases precision of component placement in total knee arthroplasty.
Haaker RG, Stockheim M, Kamp M, Proff G, Breitenfelder J, Ottersbach A.
Department of Orthopaedic Surgery, St. Vincenz-Hospital, Danziger Strasse 17, D-33034 Brakel, Germany. rolf.haaker@gmx.de
Clin Orthop Relat Res. 2005 Apr;(433):152-9.

In our clinical study, 200 total knee arthroplasties were evaluated to compare the use of the OrthoPilot system with conventional mechanical instrumentation. Long-term outcome of total knee replacement depends mainly on the accuracy of implant positioning and restoration of the mechanical leg axis. Our experience was that navigation could achieve a greater degree of accuracy concerning the aforementioned aspects. Among 513 primary-inserted total knee replacements, 100 navigated knees were compared with 100 conventionally implanted knees after matching the two groups of patients by gender, body mass index, age, preoperative deformities, radiographic findings, and operating time. Three weeks after surgery, the radiographic results were significantly better in the computer-assisted group compared with the results in the conventional group when we assessed component positioning in four axes. Only the sagittal tibial component angle was not significantly different. Total knee arthroplasty using the OrthoPilot system led to increased precision of tibial and femoral component positioning in comparison with hand-guided replacement surgery. An additional 10 minutes of operating time was acceptable. Navigation-specific complications were not seen, and the number of outliers decreased. Because computer navigation in orthopaedics is a new technology, data regarding long-term outcomes are not available. LEVEL OF EVIDENCE: Diagnostic study, Level II-1 (retrospective study). See the Guidelines for Authors for a complete description of levels of evidence.

Computer-navigated ACL reconstruction with the OrthoPilot.
Degenhart M.
Orthopedics Clinic, Schelztorklinik, Esslingen, Germany.
Surg Technol Int. 2004;12:245-51

Within the minimally invasive-operation techniques, small approaches are desirable in many fields of the surgery to reduce soft-tissue trauma; however, the risk exists that the surgeon will lose the general view of the topographic structures. The remedy lies in computer navigation with the OrthoPilot. This navigation system has already been used successfully for knee endoprosthesis. A special software was developed for use of the navigation-system, OrthoPilot, for ACL reconstruction. This system is capable of determining the exact optimum position of tunnel replacement by computer navigation. This determination is made by a high-precisive infra-red camera and rigid bodies fixed onto the patient. The experience gained in performing 150 ACL reconstructions to date demonstrates the ease of handling, reduction in extra operation time to a minimum of 10-15 minutes, and only minimal trauma by fixing the rigid bodies. In all cases, an optimum position was documented for the tunnel replacement. Furthermore, no expensive pre-operation x-rays (CT scan, nuclear spin) are needed. Use of the computer-assisted navigation system demonstrated that femoral and tibial tunnel replacement can be positioned precisely. Thus, a false position of the tunnel replacement, the main cause of' transplant-failure, can be avoided. The OrthoPilot is an important support system for both less-experienced and experienced surgeons when performing surgical ACL revisions.

The radiological outcomes of total knee arthroplasty using computer assisted navigation ORTHOPILOT.
Skowronski J, Bielecki M, Hermanowicz K, Skowronski R.
Department of Orthopaedics and Traumatology, Medical University of Bialystok.
Chir Narzadow Ruchu Ortop Pol. 2005; 70(1) : 5- 8

The Comprehensive radiographic analysis of total knee arthroplasty performed traditionally and with the use of Computer Assisted Navigation (CAN) is presented. The aim of this study was to compare the precision of implant alignment considering two operating techniques. The analyzed material consisted of 100 radiograms of patients operated on traditional way and 100 knee joint radiograms of patients operated on with a use of CAN. Assessment of postoperative radiograms was carried out in order to analyze coronal mechanical axis and sagital orientation of both femoral and tibial components. Measurements were taken precisely up to 1 degrees and therefore results were classified as good (0-2 degrees deviation due to mechanical axis), satisfactory (2-4 degrees) and poor (over 4 degrees). The radiological outcome allows to present the following conclusions: CAN allows to minimize the risk of incorrect prosthesis alignment and therefore significantly improves the radiological outcome of total knee arthroplasty. This improvement can lead to better long time "survival" of implant components. The only price one pays for this improvement is 15-20 minute surgery delay, however it needs further studies to determine other possible disadvantages.

OrthoPilot cup navigation--how to optimise cup positioning?
Kiefer H.
Department of Orthopaedic and Trauma Surgery,LukasHospital,Hindenburgstrasse 56, 32257 Buende, Germany. h.kiefer@lukas-krankenhaus.de
Int Orthop. 2003;27 Suppl 1:S37-42

The kinematic cup navigation procedure is a surgically simple technique for improving the precision of cup placement. Without CT scans, a reduction of cup malpositions is possible. The rate of desired cup inclination and anteversion angles is markedly increased as shown by the first results of 147 navigated cups. While the inclination is reached precisely with a tendency to a slightly larger angle than desired, the postoperative anteversion angle shows a somewhat bigger variation than the intraoperatively navigated angle with a tendency to less anteversion. This might be due to a lack of information about the real pelvis position during X-ray control. Clinical relevance: dislocations of the prostheses might be reduced significantly. The kinematic cup navigation with the use of the OrthoPilot is an additional and useful tool for the surgeon. The procedure is simple, quick, and cost effective, does not cause specific complications, and does not require additional CT or MRI scans. Further improvement can be expected by additional hip stem navigation techniques in the near future.

Total knee arthroplasty implanted with and without kinematic navigation.
Hart R, Janecek M, Chaker A, Bucek P.
Alloplasty Center, Trauma Hospital, 6 Ponavka Street, 662 50, Brno, Czech Republic. r.hart@volny.cz
Int Orthop. 2003;27(6):366-9. Epub 2003 Aug 26

Between September 2000 and February 2002 we inserted 120 total knee arthroplasties. In 60 patients we used the standard technique, and in 60 patients we used the OrthoPilot navigation system. Postoperatively all patients had standing long radiographs of the lower extremity from the hip joint to the ankle. We considered the ideal value of the anatomic lateral tibiofemoral angle (LTFA) to be 174 degrees. In the standard group the mean value of LTFA was 174.9 degrees and in the navigation group 174.3 degrees. A deviation between 0 degrees and 2 degrees from the ideal value was seen in 42 cases in the standard group and in 53 cases in the navigation group. In the standard group 18 cases had a deviation of more than 2.1 degrees, whereas there were only seven cases in the navigation group with a deviation exceeding 2.1 degrees. There were no complications related to the use of the navigation system. The system affords a possibility to place femoral and tibial components precisely with less axis deviation than with the conventional technique

Experience using the latest OrthoPilot TKA software: a comparative study.
Clemens U, Miehlke RK.
Department for Arthritis Surgery, North-West-German-Centre for Rheumatology, St. Josef Stift Sendenhorst, Germany.
Surg Technol Int. 2003;11:265-73

The OrthoPilot (Aesculap, Tuttlingen, Germany) Knee Navigation System represents a computed tomography (CT)-free system. In older software versions, a rigid-body at the iliac crest was necessary to calculate the centre of the hip. The latest software versions, 3.0 and 4.0, use a new mathematical algorithm to reconstruct the mechanical axis. Using the OrthoPilot system, an intraoperative cinematic study can be done that results in calculation of the mechanical axis and navigation of resection cuts. According to flexion- and extension-gap balancing, the anterior/posterior (a.p.) position and rotation of the femoral component also are navigated. Thirty navigated SEARCH (Aesculap, Tuttlingen, Germany) total knee arthroplasties (TKA) using the software version 3.0 of an uninterrupted series were evaluated, versus 30 navigated knees using older software and a manual group. Results concerning alignment were determined to be superior to the older navigation and manual groups. The number of cases with a good mechanical axis, 0; low; or 2 of deviation from optimum, was reached in 17 of the manual, 19 of the older-version, and 27 of the newer-version navigation cases. More features were solved in a convincing manner. The numbers of ouliers were diminished. Navigation in TKA using the OrthoPilot has become more safe and effective.

Computer-assisted implantation of total knee prostheses: a case-control comparative study with classical instrumentation.
Jenny JY, Boeri C.
Centre de Traumatologie et d'Orthopedie, Strasbourg, France. jyjenny@aol.com
Comput Aided Surg. 2001;6(4):217-20

A navigation system should improve the quality of a total knee prosthesis implantation in comparison to that obtained with the classical, surgeon-controlled operative technique. The authors implanted 30 total knee prostheses with an infrared navigation system (Orthopilot, Aesculap, Tuttlingen, Germany). The quality of implantation was studied on postoperative long-leg coronal and lateral X-rays, and compared to a control group of 30 matched-paired total knee prostheses of the same type (Search prosthesis, Aesculap, Tuttlingen, Germany) implanted with a classical, surgeon-controlled technique. An optimal mechanical femorotibial angle (177 to 183 degrees) was obtained in 25 cases in the study group and 21 cases in the control group (p > 0.05). Similar differences were seen for the coronal and sagittal orientations of both tibial and femoral components. Globally, 23 cases in the study group and 8 cases in the control group were implanted in an optimal manner for all studied criteria (p < 0.001). The navigation system used allows a significant improvement in the quality of implantation of a total knee prosthesis in comparison to that obtained with a classical, surgeon-controlled instrumentation, and long-term outcome could consequently be improved.

[Navigated implantation of total knee endoprostheses--a comparative study with conventional instrumentation]
[Article in German] Jenny JY, Boeri C.
JYJENNY@AOL.COM
Z Orthop Ihre Grenzgeb. 2001 Mar-Apr;139(2):117-9

OBJECTIVE: A navigation system should improve the quality of a total knee prosthesis implantation in comparison to the classical, surgeon-controlled operative technique. METHODS: The authors have implanted 40 knee total prostheses with an optical infrared navigation system (Orthopilot AESCULAP, Tuttlingen--group A). The quality of implantation was studied on postoperative long leg AP and lateral X-rays, and compared to a control group of 40 computer-paired total knee prostheses o the same model (Search Prosthesis, AESCULAP, Tuttlingen) implanted with a classical, surgeon-controlled technique (group B). RESULTS: An optimal mechanical femorotibial angle (3 degrees valgus to 3 degrees varus) was obtained by 33 cases in group A and 31 cases in group B (p > 0.05). Better results were seen for the coronal and sagittal orientation of both tibial and femoral components in group A. Globally, 26 cases of the group A and 12 cases of the group B were implanted in an optimal manner for all studied criteria (p < 0.01). CONCLUSIONS: The used navigation system allows a significant improvement of the quality of implantation of a knee total prosthesis in comparison to a classical, surgeon-controlled instrumentation. Long-term outcome could be consequently improved.

[Navigation in knee endoprosthesis implantation--preliminary experiences and prospective comparative study with conventional implantation technique]
[Article in German]

Mielke RK, Clemens U, Jens JH, Kershally S.
Abt. fur Rheumaorthopadie, Nordwestdeutsches Rheumazentrum, St. Josef-
: Stift Sendenhorst. mielke@st-josef-stift.de
Z Orthop Ihre Grenzgeb. 2001 Mar-Apr;139(2):109-16

OBJECTIVES: The efficiency of a computer-integrated instrumentation system in knee arthroplasty was evaluated and compared with a conventional instrumentation system. BACKGROUND: The OrthoPilot System defines the individual axis of the leg by means of an intraoperative kinematic analysis. LED's mounted on rigid bodies and screwed to the pelvis, femur and tibia are localized by a 3D infrared camera which is linked to a UNIX work station. The integrated calculation program leads to definition of the centres of hip, knee and ankle. Thereafter, LED-equipped alignment instruments allow definition of the femoral and tibial main resection planes. METHOD: The first sixty cases were included in the study. In addition, thirty cases each were entered into an OrthoPilot group and in a similar conventional control group. The navigated cohort consists of cases one to thirty, thus enclosing the "learning curve". RESULTS: Leg axes and femoral and tibial angles were assessed radiographically at the three-months postoperative control. Radiological measurements of the OrthoPilot group were clearly superior to those of the manual group. The differences, however, were not statistically different in the parameters "mechanical axis", "femoral axis lat." and "tibial axis ap.". With regard to the parameter "tibial axis lat." a significant difference in favour of the navigation system was observed. The measurements of "femoral axis ap." were insignificantly better in the manual group. In general, a slight tendency towards valgus positioning of the femoral components when using the navigation system has to be discussed. Complications influencing the clinical outcome did not occur. Additional time for navigation is calculated in a range of ten to fifteen minutes. CONCLUSIONS: The OrthoPilot system clearly facilitates proper alignment of endoprosthetic components in femur and tibia. Generally, the obtained values representing endoprosthetic alignment are superior to conventional technique. Marked deviations from ideal alignment can almost be avoided by means of the navigation system. During the learning curve the OrthoPilot system gained in reliability and reproducability.

Intraoperative evaluation of the anatomical double-bundle anterior cruciate ligament reconstruction with the OrthoPilot navigation system.
Ishibashi Y, Tsuda E, Tazawa K, Sato H, Toh S.
Hirosaki University School of Medicine, Hirosaki Aomori, Japan.
Orthopedics. 2005 Oct;28(10 Suppl):s1277-82

The purpose of this study was to assess double-bundle anterior cruciate ligament (ACL) reconstruction, which reproduces the anteromedial bundle and posterolateral bundle, using a navigation system. In 32 patients, anteroposterior (AP) displacement and rotation of the tibia were measured before reconstruction and after posterolateral bundle fixation, anteromedial bundle fixation, and double-bundle ACL reconstruction (in posterolateral and anteromedial bundles fixation). The posterolateral bundle has an important role in the extension position, whereas the anteromedial bundle restricts AP displacement from extension to flexion. AP displacement after double-bundle ACL reconstruction was significantly improved compared to AP displacement after posterolateral bundle or anteromedial bundle fixation. Although traditional reconstruction for reproducing the anteromedial bundle is reasonable, double-bundle ACL reconstruction is recommended for improved knee stability.

Advanced navigation planning including soft tissue management.
Clemens U, Miehlke RK.
Northwest German Center for Rheumatology in Sendenhorst, Germany.
Orthopedics. 2005 Oct;28(10 Suppl):s1259-62

The OrthoPilot TKA Version 4.2 (B. Braun-Aesculap, Tuttlingen, Germany) offers software support for orthopedic surgeons. The system provides nearly normal manual workflow, creates perfect cuts, allows for sophisticated management of soft tissue, and respects individual anatomies. The OrthoPilot TKA Version 4.2 displays information to guide surgical decisions. However, surgeons decide if the information will be used during the resection. The most important advancements in the Version 4.2 software are the calculation of perfect rotation of the femoral component and optimal gap balancing.

OrthoPilot total hip arthroplasty workflow and surgery.
Kiefer H, Othman A.
Department of Orthopaedic and Trauma Surgery, Lukas Hospital, Bunde, Germany.
Orthopedics. 2005 Oct;28(10 Suppl):s1221-6.

To analyze the workflow and navigation principles of the OrthoPilot total hip arthroplasty (THA) Version 2.0 (B. Braun-Aesculap, Tuttlingen, Germany), a consecutive series of 60 patients was used to compare the navigated intraoperative data and postoperative measurements of stem and cup position. Within the safe zone, 96.3% of 54 acetabular cups were positioned. The rotational accuracy of femoral instruments was 65 degrees in 41 THAs. The femoral offset was medialized by 6.05 mm in 76% and lateralized by 2.1 mm in 14%. The data for leg length and range of motion from 60 THAs and the navigated data were similar. Thus, the first clinical validation of the workflow of the OrthoPilot THA Version 2.0 is encouraging.

Consistency of implantation of a total knee arthroplasty with a non-image-based navigation system a case-control study of 235 cases compared with 235 conventionally implanted prostheses.
Jenny JY, Clemens U, Kohler S, Kiefer H, Konermann W, Miehlke RK.
Centre de Traumatologie et d'Orthopedie, Strasbourg, France.
J Arthroplasty. 2005 Oct;20(7):832-9.

The aim of the study was to assess the consistency of the non-image-based navigation system OrthoPilot(R), Aesculap, Tuttlingen, Germany, in total knee arthroplasty (TKA) implantation in 5 European centers. Two hundred thirty-five TKAs implanted with this navigation system were matched (according to severity of the preoperative coronal deformation and body mass index) to a historical control group of 235 TKAs implanted with a conventional technique. Consistency of implantation was studied on a 3-month postoperative radiological control with coronal long-leg and sagittal standard x-rays. The use of the OrthoPilot(R) navigation system allowed a statistically significant improvement in the consistent placement of both tibial and femoral components. In accordance with current literature, survival of the navigated implanted prostheses is expected to be longer.

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