Navigation-assisted surgical procedures in orthopedics and trauma surgery have become increasingly widespread over the last 20 years. In addition to applications in spinal surgery, they are primarily available for knee and hip endoprosthetics. On the one hand, computer-assisted procedures have been increasingly expanded with robotic assistance systems in recent years, and on the other hand, so-called handheld navigation systems have been developed, which enable specialized use directly in the operating field at lower acquisition costs. The aim of this overview is to describe current handheld systems and to present the respective technical principles and the available scientific results. Three handheld systems for TKA use, two for THA use and one system to support pedicle screw placement on the spine are presented.

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.

INTRODUCTION:The cementing technique is one of the various speculated factors that might contribute to the failures of resurfacing arthroplasty of the hip. The influence of bony preparation by jet lavage or lavage only in combination with different cementing techniques and cements of different viscosity in a study on fresh human femoral heads has not been evaluated so far.MATERIALS AND METHODS:Sixty fresh human femoral heads were prepared for resurfacing following manufacturers' instructions and divided into 12 groups. The different groups received either syringe lavage or jet lavage and either a low-, medium- or high-viscosity cement with either packing or quarter filling of the implant with recess of the femoral stem in each case. Application of the implant was standardized. After polymerization, the femoral heads were cut into quarters and polished. Cement penetration was assessed using a square millimeter grid under optical zoom.RESULTS:Manual packing with high viscosity cement is a reproducible method in resurfacing arthroplasty. Syringe lavage and jet lavage mainly showed comparable cement penetration patterns when applied same cementing techniques. The penetration depth ranged from a mean of 0.6 to 3.2 mm with 0.4 being the lowest and 4.0 being the deepest. The mantle thickness ranged from 0.8 to 2.4 mm with statistically significant thicker mantles with filling, compared to packing.CONCLUSION:Our results showed distinct less penetration depth than previously reported and that just medium viscosity cement reached reliable results in the supposed range of penetration depth and cement mantle thickness. Jet lavage should be recommended for the low-viscosity cement but avoided in combination with a cement filling technique of lower viscosity cements. Filling of the implant caused the greatest penetration depth and a higher number of incomplete seatings and should therefore be avoided.

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.

INTRODUCTION:During the last years the extracorporal shock wave therapy has shown its efficiency in the treatment of the conservative non curable epicondylitis humeri radialis. This study evaluates the outcome of the ESWT and the operative treatment.METHODS:Between 1996 and 1997 60 patients suffering from lateral epicondylitis were analyzed. 30 were treated operative by using the Mittelmeier-procedure (tangential partial bone resection of the epicondylus humeri radialis) and further 30 with extracorporal shock waves. These patients received 2000 impulses of 0.23 mJ/mm2 in two sessions.RESULTS:Follow-up of the group who underwent the Mittelmeier procedure showed good and excellent results in 73% after one year using the score of Roles and Maudsley (1972). The patients treated by the ESWT showed good and excellent results in 43%.DISCUSSION:Regarding to the duration of symptoms and large scale of the primary treatment and operative hazards the results are showing the benefit of the medium energetic extracorporal shock wave application in the treatment of patients with no response on regular therapy.

An analysis of the MR-images of 75 patients with calcifying tendinitis of the shoulder was performed. The aim of the study was to recognice characteristic findings of the calcific deposits and their relation to the involved tendons as well as the coincidence with additional degenerative alterations of the rotator cuff. The calcifications can be demonstrated with high accuracy (>95 %) in T1-weighted images as areas of decreased signal intensity. It is possible to characterice the calcifications similar to Gartner's radiologic classification differentiating form and density of the calcific deposits as well as their delimitation to the tendon structure. In T2-images there frequently is a perifocal band of increased signal intensity which can be identified as an oedema around the calcification. Analysing two perpendicular planes the calcifications can de assigned to the corresponding anatomical structure. 83 percent were located in the supraspinatus tendon above the humeral head or in the superior part of the subscapularis tendon. Degenerative areas of the rotator cuff are demonstrated as small zones of increased signal intensity, abnormal morphology or discontinuity of the tendon. Only in one patient a partial tear could be found; II percent showed variable signs of degenerative alteration of the involved tendon.

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° 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.

Degeneration of the meniscus and the articular cartilage in unicompartmental osteoarthritis of the knee results in progressive deformity of the leg axis. It is the aim of this study to evaluate if a leg axis correction can be achieved by implanting a customised metallic interpositional device for the knee (ConforMIS iForma™). Before and after implanting a ConforMIS iForma™ knee implant, a radiological analysis of the leg axis deviation in the frontal plane was performed prospectively in 27 patients by evaluating anteroposterior single-leg stance radiographs. We achieved a sufficient leg axis correction with an average correction of 3.8° and an averaged small under-adjustment of 0.9° by inserting the ConforMIS iForma™ interpositional knee implant. Apart from the primary treatment objective of articular surface restitution the ConforMIS iForma™ knee implant can be reliably used to correct axis deformity occurring with unicompartmental osteoarthritis of the knee.

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.

Objective: Various studies have shown the benefit of the extracorporal shock wave therapy in the treatment of the calcific tendinitis. It was the aim of this study to examine the energy needed to desintegrate a calcific deposit.Method: By using the in vitro model of the pig shoulder the mechanical effects of different energy levels and impulse rates on the calcifying deposits are investigated. Results: The results are showing the energy- and impulse-depending effect of the shockwaves. The desintegration of the implanted "bonn-stones" with development of an large amount of fragments smaller then 1000 um requires an energy of 0,42 mJ/mm(2) and between 2000 and 3000 impulses.Conclusions: According to the experimental results a instant mechanical effect on the calcifying deposits using the ordinary parameter is unlikely. The absorption of the calcifying deposits in Likely induced through cellular clearing function. Clinical trials confirmed the good therapeutical results after two sessions with at least 1500 pulses and an energy of 0,28-0,30 mJ/mm(2).

Objective: Exact drilling into the ischemic areas of necrotic lesions of the femoral head remains a challenging procedure, particularly in obese patients. This study was conducted to evaluate the precision of fluoroscopically based drilling and the associated radiation exposure in an in-vitro model of adiposis.Materials and Methods: In an in-vitro model of necrotic lesions in adiposis, 20 sawbones were drilled under the guidance of an intraoperative navigation system (VectorVision®, BrainLAB, Munich, Germany) and 20 more were drilled conventionally under fluoroscopic control only.Results: A statistically significant difference was found with respect to the distance from the drill tip to the desired mid-point of the lesion, with a mean distance of 0.56 mm for the navigated group and 1.15 mm for the control group. Furthermore, a significant difference was found in the number of drilling corrections required, as well as the radiation exposure time: The navigated group required a mean of 0.35 second drillings or corrections of the drilling direction, compared to 2.45 for the control group, and the duration of radiation exposure was less than 1 second for the navigated group and 3.85 seconds for the control group.Conclusions: Drilling guided by the VectorVision® navigation system shows high precision, even under difficult circumstances such as those encountered in adiposis, with a marked reduction in the duration of radiation exposure.

Restoration of the mechanical leg axis and component positioning are crucial factors affecting long-term results in total knee arthroplasty (TKA). In a prospective study, 1,000 patients were operated on either using a CT-free navigation system or the conventional jig-based technique. Leg alignment and component orientation were determined on postoperative X-rays. The mechanical leg axis was significantly better in the computer-assisted group (95%, within +/-3 degrees varus/valgus) compared to the conventional group (74%, within +/-3 degrees varus/valgus) (P < 0.001). On average, the operating time was increased by 8 min in the computer-assisted group. No significant differences were seen between senior and younger surgeons regarding postoperative leg alignment and operating time. Computer-assisted TKA leads to a more accurate restoration of leg alignment and component orientation compared to the conventional jig-based technique. Potential benefits in long-term outcome and functional improvement require further investigation.

Die Entwicklungen der letzten Jahre haben dazu beigetragen, dass sich die Knieendoprothetik als Behandlungsstandard der fortgeschrittenen Gonarthrose etablieren konnte. Aus großen Erhebungen wie z. B. dem schwedischen Knieprothesenregister kann bei etwa 80% der behandelten Patienten eine hohe subjektive Zufriedenheit erwartet werden [47]. Die Standzeit der Prothesen wird zum aktuellen Zeitpunkt mit 85% nach zehn Jahren angegeben. Dabei stellt das Hauptproblem die aseptische Prothesenlockerung mit unterschiedlichen Ursachen dar: Einerseits aufgrund des Polyethylenabriebs [7, 16, 20], andererseits aufgrund verbliebener Gelenkinstabilität [47]. Darüber hinaus ist ein postoperatives Malalignment von mehr als drei Grad Achsabweichung im Varus- oder Valgussinne in der Frontalebene ebenfalls ein entscheidender Faktor. Während in den vergangenen Jahrzehnten vor allem die Weiterentwicklungen des Prothesendesigns und der Materialien im Mittelpunkt standen, rückte in den letzten Jahren zunehmend die Optimierung der Operationstechnik in den Vordergrund des wissenschaftlichen Interesses.

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.

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

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.

Rotational adjustment of the femoral component in total knee arthroplasty influences patellar tracking. Sixty patients underwent TKA; the femoral component was placed parallel to the epicondylar axis in 30 patients and the femoral component was placed in 3 degrees external rotation to the posterior condylar axis in 30 patients. The epicondylar axis was identified using an image-guided navigation system. Mean patellar shift was 2.65 degrees for the computer assisted group and 3.50 degrees for the control group. Mean patellar tilt was 4.88 degrees for the computer assisted group and 6.68 degrees for the control group. Aligning the femoral component parallel to the epicondylar axis leads to significantly better patellar tracking.

In den frühen Stadien der Femurkopfnekrose kann eine lokale intraossäre Druckentlastung durch exakte Anbohrung der ischämischen Areale zu Schmerzreduktion und sogar Reperfusion führen. Mit Hilfe der Computer-Aided Surgery kann die Präzision dieser Anbohrung verbessert werden bei gleichzeitiger Reduktion der Strahlenbelastung von Patient und Operationsteam. Vorgestellt werden die experimentellen und klinischen Erfahrungen mit der fluoroskopischbasierten Anbohrung mit dem VectorVision®-Navigationssystem.