A five to seven year follow-up comparing computer-assisted vs freehand TKR with regard to clinical parameters.

PURPOSE: Computer-assisted knee surgery has become established in routine clinical practice. Still, there is no study investigating midterm clinical outcome after five to seven years postoperatively. We aimed to test the hypothesis that there is no difference either for subjective [Western Ontario and McMaster Universities (WOMAC) scores] or for objective (Knee Society Score, degree of flexion) criteria between computer-assisted total knee replacement (TKR) and freehand TKR after 5.6-7.3 years. METHODS: We performed a matched-pair analysis; 100 patients who received a primary TKR were investigated after a median follow-up of 6.25 years. Group A was operated on with the support of a computer system, while surgery on patients in group B was performed with the freehand technique. We determined WOMAC Score, Knee Society Score and degree of flexion. RESULTS: Overall we found similar results for WOMAC Score [group A: 42.98 (SD 13.80); group B: 41.54 (SD 15.01; p = 0.62)], Knee Society Score [group A: 168.20 (SD 21.94); group B: 166.60 (SD 21.44; p = 0.71)] and range of motion [group A: 106° (SD 9.19); group B 107° (SD 7.44; p = 0.62)]. CONCLUSIONS: No significant differences in midterm clinical outcome were found after TKR performed in the freehand vs computer-assisted technique.

Two year follow-up comparing computer assisted versus freehand TKR on joint stability, muscular function and patients satisfaction.

Computer assisted (CAS) knee surgery has been established in clinical routine. There is still no study that investigates clinical outcome. Fifty patients who received a primary total knee replacement 2 years before were investigated. These patients were divided into two groups of matched-pairs; group A was operated in the freehand technique and group B with support of a computer system. We compared Womac score, Knee Society score, range of motion, leg alignment, knee stability and isokinetic muscle strength. We found similar results for WOMAC, Knee Society score and isokinetic muscle force. Stability and range of motion revealed slightly better values for the CAS group. A statistically significant difference could only be demonstrated for postoperative leg alignment. Two years after freehand versus computer assisted TKR we found slightly better values for range of motion and ligamentous stability. Only postoperative leg alignment was statistically better in the CAS group.

Minimal invasive and computer assisted total knee replacement compared with the conventional technique: a prospective, randomised trial.

Minimal invasive surgery (MIS) in total knee replacement (TKR) has been favoured by several authors and the industry and is asked for by the patients. Computer assisted surgery (CAS) is proposed to support the surgeon in terms of postoperative leg alignment and implant orientation. To prove the hypothesis that MIS in TKR fastens early rehabilitation compared to the standard approach and that CAS-MIS in TKR improves accuracy in implant position compared to the freehand MIS and freehand standard technique, we performed a prospective, randomised short-term trial which was approved by the local ethic committee. In total, 90 patients underwent TKR. The conventional group (n = 30) underwent conventional TKR, the MIS group (n = 30) underwent MIS-TKR without navigation, the CAS-MIS group (n = 30) underwent TKR using navigation and the MIS approach. Groups were comparable regarding patients' specific parameters. The length of incision in extension was significantly lower in the MIS (13.2 cm) and CAS-MIS technique (12.9 cm) compared to the conventional technique (17.3 cm) (P < 0.01). Knee Society and WOMAC Score were similar in all three groups after 1, 6 and 12 weeks, no significant differences were seen between groups at any point of time. Postoperative deviation of the mechanical leg axis was significantly better in the CAS-MIS group compared to the conventional group and the MIS one (P < 0.05). The clinical relevance of our results is that the benefit of the minimal invasive approach in TKR is still not proven and navigation improves postoperative accuracy of leg alignment and component orientation. Our study shows that for the group of patients included there is no statistically significant difference in early rehabilitation between MIS and the conventional approach based on the Knee Society and WOMAC Score. Using the CAS technique restoration of leg axis was more accurate.

The computer-assisted sequential lateral soft-tissue release in total knee arthroplasty for valgus knees.

Soft-tissue management is a critical factor in total knee arthroplasty, especially in valgus knees. The stepwise release has been based upon surgeon's experience. Computer-assisted surgery has gained increasing scientific interest in recent times and allows the intraoperative measurement of leg axis and gap size in extension and flexion. We therefore aimed to analyse the effect of sequential lateral soft-tissue release and the resulting change in the a.p. limb axis on the one hand and the tibiofemoral gaps on the other hand in extension as well as in flexion in eight cadaveric knees. Measurements were obtained using a CT-free navigation system. In extension the highest increase compared to the previous release step was found for the first (iliotibial band, P = 0.002), second (popliteus muscle, P = 0.0003), third (LCL, 0.007) and the sixth (entire PCL, P = 0.001) release step. In 90 degrees flexion all differences of the lateral release steps were statistically significant (P < 0.004). Massive progression of the lateral gap in flexion was found after the second (popliteus muscle, P = 0.004) and third (LCL, 0.007) release step. Computer-assisted surgery allows measurement of the effect of each release step of the sequential lateral release sequence and helps the surgeon to better assess the result.

[Loosening of a total hip arthroplasty due to metastasis]. / Metastatisch bedingte Lockerung einer Hüfttotalendoprothese.

A case report of a metastatic caused loosening of a total hip arthroplasty one year after primary implantation is presented. A primary cancer was unknown at surgery. Due to suspected low-grade infection, a revision surgery was performed and the diagnosis of a metastatically caused loosening could be made. A bronchial carcinoma was identified as primary cancer. In spite of the rare incidence of the described metastatic loosening, the significance of a differential diagnostic strategy and the importance of a histological examination in revision surgery is depicted.

[Minimally invasive total knee arthroplasty and navigation - a logical combination?]. / Minimal-invasive Knieendoprothetik und Navigation - eine sinnvolle Kombination?

The minimally invasive approach has been recommended for total knee arthroplasty by many surgeons and by industry in recent years, and patients now also expect it. The definition of a minimally invasive procedure is still the subject of some controversy. Some authors limit the length of the skin incision to 14 cm, while others propose the"least possible and barely adequate" approach. The main problem of the minimally invasive technique is still the increased risk of component malalignment owing to reduced visibility. As computer-assisted surgery has been shown in many studies to yield better component alignment than is obtained with the conventional technique, it seemed logical to use navigation systems in combination with the minimal invasive approach. The aim of this paper is to highlight and discuss the use of computer assistance with a minimally invasive approach.

[Navigated drilling for femoral head necrosis. Experimental and clinical results]. / Navigierte Anbohrung der Femurkopfnekrose. Experimentelle und klinische Ergebnisse.

INTRODUCTION: In the early stages of osteonecrosis of the femoral head, core decompression by exact drilling into the ischemic areas can reduce pain and achieve reperfusion. Using computer aided surgery, the precision of the drilling can be improved while simultaneously lowering radiation exposure time for both staff and patients. We describe the experimental and clinical results of drilling under the guidance of the fluoroscopically-based VectorVision navigation system (BrainLAB, Munich, Germany). MATERIALS AND METHODS: A total of 70 sawbones were prepared mimicking an osteonecrosis of the femoral head. In two experimental models, bone only and obesity, as well as in a clinical setting involving ten patients with osteonecrosis of the femoral head, the precision and the duration of radiation exposure were compared between the VectorVision system and conventional drilling. RESULTS: No target was missed. For both models, there was a statistically significant difference in terms of the precision, the number of drilling corrections as well as the radiation exposure time. The average distance to the desired midpoint of the lesion of both models was 0.48 mm for navigated drilling and 1.06 mm for conventional drilling, the average drilling corrections were 0.175 and 2.1, and the radiation exposure time less than 1 s and 3.6 s, respectively. In the clinical setting, the reduction of radiation exposure (below 1 s for navigation compared to 56 s for the conventional technique) as well as of drilling corrections (0.2 compared to 3.4) was also significant. CONCLUSIONS: Computer guided drilling using the fluoroscopically based VectorVision navigation system shows a clearly improved precision with a enormous simultaneous reduction in radiation exposure. It is therefore recommended for clinical routine.

A rare cause for knee pain: fracture of the femoral component after TKR. A case report.

We report the rare case of sudden knee pain due to fracture of the total knee replacement nine years after implantation. Fracture occurred because of subsequent osteolysis due to polyethylene wear.

[Pullout resistance of conventional pedicle screw implantation in comparison to fluoroscopic computer-assisted technique]. / Ausrissfestigkeit implantierter Pedikelschrauben in konventioneller und fluoroskopisch-navigierter Technik.

AIM: Aim of the study was to compare pullout resistance of pedicle screws after conventional and fluoroscopic computer-assisted implantation in the cadaveric thoracic and lumbar spine. METHODS: Pedicle screws were inserted in a total of 10 vertebrae of different human specimens: 10 screws were placed using conventional technique (group 1) and 10 screws were inserted with fluoroscopic computer-assisted system contralaterally (group 2). Then pedicle screws were evaluated for biomechanical axial pullout resistance. RESULTS: Mean pullout force was 232 N (range 60-600 N) in group 1 and 353 N (range 112-625 N) in group 2. The difference was significant (p=0,0425). CONCLUSION: Fluoroscopic navigated implantation of pedicle screws increases the pullout strength in thoracic and lumbar cadaveric spines as compared with conventional methods.

[Revision prosthetic of the knee joint. The influence of a navigation system on the alignment and reconstruction of the joint line]. / Revisionsendoprothetik des Kniegelenks. Einfluss eines Navigationssystems auf das Alignment und die Rekonstruktion der Gelenklinie.

Recognizing the rising number of primary total knee arthroplasties (TKA) over the last decade, one may assume an increasing number for revisions after a certain time delay. Studies showing a rate of only 78% satisfied patients provide a hint that there is still room for improvement. Therefore, it seemed worthwhile to evaluate the benefits of the computer assisted technique in revision TKA and compare the alignment results with the conventional technique. In a prospective study, 120 patients were operated for revision TKA using either the Vector-Vision navigation system (n=60) or the conventional technique (n=60). The axial limb alignment was evaluated on standardized pre- and postoperative full length weight-bearing radiographs and the variation of the joint line was determined by the method of Figgie from 1986.A precise reconstruction of the mechanical limb axis was achieved in 57/60 Patients (95%) in the computer assisted group and in 48/60 (80%) in the conventional group. A reconstruction of the joint line with a variation of less then 4 mm was achieved in 47/60 (78%) in the computer assisted and in 33/60 (55%) in the conventional group. Revision TKA remains a challenging procedure for the surgeon. Modern navigation systems offer additional information intraoperatively and might therefore simplify the procedure. In particular, the adjustment of the extension and flexion gap and the reconstruction of the joint line the results were superior. Furthermore, the use of a CT-free navigation system provides a significant improvement of prosthesis and leg alignment in revision TKA.

[Advances in soft tissue management in total knee arthroplasty. The use of imageless navigation systems]. / Fortschritte im Weichteilmanagement in der Knieendoprothetik. Einsatz von bildfreien Navigationssystemen.

Computer aided surgery has become established in the clinical routine over the past years. There are some very good studies which show that navigation optimizes reconstruction of the leg axis in total knee replacement. The question of why outliers occur in spite of navigation has to be asked. It is clear that total knee replacement is not only a bony procedure, but the soft tissues have an immense influence on postoperative stability of the prosthesis over the full range of movement. Current navigation systems allow visualization of the leg axis and size of the extension and flexion gap, and support the surgeon during soft tissue management. The current paper shows how the anatomic approach and the position of the patella influence soft tissue tension and support the surgeon during release of soft tissues in severe leg axis deformities.

Computer assistance in total knee replacement - a critical assessment of current health care technology.

The last five years have seen the rapid development of computer assisted surgery (CAS) in total knee replacement (TKR). Many surgeons perform TKR using navigation systems, which offer user-friendly workflows and reproducible results. A number of level 1 and 2 studies, according to evidence-based medicine criteria, have demonstrated that navigation in TKR allows a more precise implantation of the prosthesis, though CAS still requires an experienced surgeon and is time consuming. Nevertheless, 30% of surgeons in Germany who perform TKR have used navigation. It is still not known whether this new technique improves the longevity of TKR, however, and we therefore performed a meta-analysis to assess the results of this new health care technology.

Precision of computer-assisted core decompression drilling of the femoral head.

INTRODUCTION: Osteonecrosis of the femoral head is a local destructive disease with progression into devastating stages. Left untreated it mostly leads to severe secondary osteoarthrosis and early endoprosthetic joint replacement. Core decompression by exact drilling into the ischemic areas can be performed in early stages according to Ficat or ARCO. Computer-aided surgery might enhance the precision of the drilling and lower the radiation exposure time of both staff and patients. The aim of this study was to evaluate the precision of the fluoroscopically based VectorVision navigation system in an in vitro model. MATERIALS AND METHODS: Thirty sawbones were prepared with a defect filled up with a radiopaque gypsum sphere mimicking the osteonecrosis. Twenty sawbones were drilled by guidance of an intraoperative navigation system VectorVision (BrainLAB, Munich, Germany) and 10 sawbones by fluoroscopic control only. RESULTS: No gypsum sphere was missed. There was a statistically significant difference regarding the three-dimensional deviation (Euclidian norm) as well as maximum deviation in x-, y- or z-direction (maximum norm) to the desired mid-point of the lesion, with a mean of 0.51 and 0.4 mm in the navigated group and 1.1 and 0.88 mm in the control group, respectively. Furthermore, significant difference was found in the number of drilling corrections as well as the radiation time needed: no second drilling or correction of drilling direction was necessary in the navigated group compared to 1.4 in the control group. The radiation time needed was less than 1 s compared to 3.1 s, respectively. CONCLUSION: The fluoroscopy-based VectorVision navigation system shows a high feasibility of computer-guided drilling with a clear reduction of radiation exposure time and can therefore be integrated into clinical routine. The additional time needed is acceptable regarding the simultaneous reduction of radiation time.

Precision of computer-assisted core decompression drilling of the knee.

INTRODUCTION: Core decompression by exact drilling into the ischemic areas is the treatment of choice in early stages of osteonecrosis of the femoral condyle. Computer-aided surgery might enhance the precision of the drilling and lower the radiation exposure time of both staff and patients. The aim of this study was to evaluate the precision of the fluoroscopically based VectorVision-navigation system in an in vitro model. MATERIALS AND METHODS: Thirty sawbones were prepared with a defect filled up with a radiopaque gypsum sphere mimicking the osteonecrosis. 20 sawbones were drilled by guidance of an intraoperative navigation system VectorVision (BrainLAB, Munich, Germany). Ten sawbones were drilled by fluoroscopic control only. RESULTS: A statistically significant difference with a mean distance of 0.58 mm in the navigated group and 0.98 mm in the control group regarding the distance to the desired mid-point of the lesion could be stated. Significant difference was further found in the number of drilling corrections as well as radiation time needed. CONCLUSION: The fluoroscopic-based VectorVision-navigation system shows a high feasibility and precision of computer-guided drilling with simultaneously reduction of radiation time and therefore could be integrated into clinical routine.

Imageless navigation for insertion of the acetabular component in total hip arthroplasty: is it as accurate as CT-based navigation?

In a prospective randomised clinical study acetabular components were implanted either freehand (n = 30) or using CT-based (n = 30) or imageless navigation (n = 30). The position of the component was determined post-operatively on CT scans of the pelvis. Following conventional freehand placement of the acetabular component, only 14 of the 30 were within the safe zone as defined by Lewinnek et al (40 degrees inclination sd 10 degrees ; 15 degrees anteversion sd 10 degrees ). After computer-assisted navigation 25 of 30 acetabular components (CT-based) and 28 of 30 components (imageless) were positioned within this limit (overall p < 0.001). No significant differences were observed between CT-based and imageless navigation (p = 0.23); both showed a significant reduction in variation of the position of the acetabular component compared with conventional freehand arthroplasty (p < 0.001). The duration of the operation was increased by eight minutes with imageless and by 17 minutes with CT-based navigation. Imageless navigation proved as reliable as that using CT in positioning the acetabular component.

Eversion or subluxation of patella in soft tissue balancing of total knee arthroplasty? Results of a cadaver experiment.

Correct postoperative leg alignment and stability of total knee prosthesis over the full range of movement are critical factors for successful TKA. This is achieved by correct implantation of prosthesis and soft tissue handling. However, the surgical approach and how to displace the patella are still controversial. We have carried out a cadaver study looking at the effect of patella eversion or subluxation on limb axis alignment during balancing of the knee in three different standard surgical approaches; subvastus, midvastus, or medial parapatellar. For each approach, five knees were studied. Leg alignment was visualised by the Ci CT-free DePuy/BrainLAB navigation system. Using a navigation system alignment was determined in the AP axis in both extension and 90 flexion, with the patella everted as well as subluxated. Eversion of the patella gave a more valgus axis reading than subluxation in both extension 0.58 (SD: 0.03, range 0.54 -0.60 ) and 90 flexion 0.48 (SD: 0.11, range 0.38 -0.60 ). The effect was greatest using the medial paraptellar approach. Surgeons should be aware that everting the patella influences the AP alignment when soft tissue balancing in total knee replacement.

Two-year follow-up on joint stability and muscular function comparing rotating versus fixed bearing TKR.

Mobile and fixed bearing in total knee replacement are still discussed controversially. In a retrospective, matched-pair study, we investigated 40 patients with computer-assisted (BrainLAB) primary total knee replacement (PFC Sigma, DePuy) performed two years before. Twenty patients each received a mobile bearing and a fixed bearing. We compared Womac Score, Knee Society Score, postoperative ROM, fluoroscopic measurement of knee stability in flexion and extension and isokinetic muscle strength using a Biodex-3 dynamometer. Both groups showed similar results concerning WOMAC Score (total rotating bearing: 23.05; fixed bearing: 22.57), KSS (rotating bearing: 174.89; fixed bearing: 176.1). Isokinetic muscle force demonstrated statistically significant superior results for knee flexion in the rotating bearing group. Medio-lateral stability revealed statistically significant superior results for the rotating bearing compared to fixed bearing in extension (P>0.05). In flexion only lateral stability was superior (P>0.05). Two-year clinical follow-up after computer-assisted total knee replacement resulted in good clinical outcome with high patient satisfaction. Statistically significant better values for the rotating platform group were found for the medio-lateral stability in extension and the peak flexion torque.

Micromotion in cemented rotating platform total knee arthroplasty: cemented tibial stem versus hybrid fixation.

INTRODUCTION: Improving the longevity and reliability of cemented total knee arthroplasty (TKA) remains a major step to achieve. It is still unclear, whether a cemented tibial stem reduces micromotion of the tibial tray and produces therefore a better initial stability or not. The higher conformity of rotating platform design and the possible rotary forces to the tibial platform may produce higher micromotion when the tibial stem remains cementless (hybrid fixation). MATERIALS AND METHODS: An in vitro study was performed using the PFC mobile bearing tibial tray (DePuy, Warswa, IN, USA) to test the hypothesis that the addition of cement surrounding the tibial stem reduces micromotion of the tibial tray in cemented TKA with mobile bearing design. Ten tibial trays with mobile design were implanted in sawbones with a 3-mm cement mantle beneath the baseplate of the tibial tray and with or without the cemented stem. Tibial trays were loaded additionally in the ventral, lateral, medial and posterior positions with 2,500 N using the Zwick Z010 instrumentation and HBM pick up Hottinger Baldwin. RESULTS: In this study, a significant increased mean maximum liftoff was found when only cementing the tibial baseplate (hybrid fixation), compared to the fully cemented tibial tray (P<0.02). CONCLUSION: In conclusion, the stem of mobile bearing tibial components should be cemented to provide increased micromotion and earlier loosening.

[Changes in muscle torque in patients after total knee arthroplasty]. / Veränderungen der muskulären Leistungsfähigkeit bei Trägern von Kniegelenkstotalendoprothesen.

AIM: The purpose of this study was to compare muscle torque during isokinetic knee movements of patients after total knee arthroplasty (TKA) with a similar healthy group. METHOD: 43 patients were examined 3 years after primary total knee arthroplasty with an isokinetic dynamometer (Cybex 340). Torque measurements were evaluated for extension and flexion with 4 different velocities. The results were compared with a group of 43 people without knee disease. Bouth groups consist of 29 women and 14 men. The mean age was also comparable (66.4 vs. 65.8 years). RESULTS: A mean peak torque of 65.9 Nm was measured during extension with low velocity (60 degrees /s) in the group of patients with TKA -- 84.3 % of the control group (p = 0.079). At the highest velocity the patients produced 30.2 Nm. This was 72.8 % of the control group (difference statistically significant, p = 0.006). No differences were found in the Extension/Flexion ratio between the two groups. CONCLUSION: The deficites of knee strength in patients after TKA are more distinct in high velocities of motion.

[Soft tissue management in knees with varus deformity. Computer-assisted sequential medial ligament release]. / Weichteilmanagement bei der Varusgonarthrose. Der navigationsgestützte schrittweise mediale Bandrelease.

BACKGROUND: Knees with severe varus deformities and contractures of the medial and lateral collateral ligaments and the posterior capsule require special soft tissue management to gain a stable knee over the full range of movement. The introduction of navigation systems into knee surgery has now made precise measurement of the leg axis and gap size possible. METHODS: Ten knee joints received a computer-assisted total knee replacement (Ci navigation system DePuy) I-Orthopaedics, Munich). The change of the leg axis and the size of the mediolateral gaps were measured and documented when performing a standardized medial ligament release sequence. RESULTS: We found a significant effect after each release step regarding the change of the leg axis as well as the gap width (p<0.001). The highest effect was seen for the 6-cm capsule release in extension and the release of the medial collateral ligament in 90 degrees flexion. CONCLUSION: Implementation of computer-assisted navigation facilitates visualization and quantification of the effect of the sequential medial soft tissue release in total knee arthroplasty.