Accuracy considerations in navigated cup placement for total hip arthroplasty.

Computer assisted orthopaedic surgery (CAOS) technology has recently been introduced to overcome problems resulting from acetabular component malpositioning in total hip arthroplasty. Available navigation modules can conceptually be categorized as computer tomography (CT) based, fluoroscopy based, or image-free. The current study presents a comprehensive accuracy analysis on the computer assisted placement accuracy of acetabular cups. It combines analyses using mathematical approaches, in vitro testing environments, and an in vivo clinical trial. A hybrid navigation approach combining image-free with fluoroscopic technology was chosen as the best compromise to CT-based systems. It introduces pointer-based digitization for easily assessable points and bi-planar fluoroscopy for deep-seated landmarks. From the in vitro data maximum deviations were found to be 3.6 degrees for inclination and 3.8 degrees for anteversion relative to a pre-defined test position. The maximum difference between intraoperatively calculated cup inclination and anteversion with the postoperatively measured position was 4 degrees and 5 degrees, respectively. These data coincide with worst cases scenario predictions applying a statistical simulation model. The proper use of navigation technology can reduce variability of cup placement well within the surgical safe zone. Surgeons have to concentrate on a variety of error sources during the procedure, which may explain the reported strong learning curves for CAOS technologies.

The accuracy of free-hand cup positioning--a CT based measurement of cup placement in 105 total hip arthroplasties.

We studied 105 patients who received a total hip arthroplasty between June 1985 and August 2001 using freehand positioning of the acetabular cup. Using pelvic CT scan and the hip-plan module of SurgiGATE-System (Medivision, Oberdorf, Switzerland), we measured the angles of inclination and anteversion of the cup. Mean inclination angle was 45.8 degrees +/-10.1 degrees (range: 23.0-71.5 degrees ) and mean anteversion angle was 27.3 degrees +/-15.0 degrees (range: -23.5 degrees to 59.0 degrees ). We compared the results to the "safe" position as defined by Lewinnek et al. and found that only 27/105 cups were implanted within the limits of the safe position. We conclude that a safe position as defined by Lewinnek et al. [13] was only achieved in a minority of the cups that were implanted freehand.

[Cup placement in hip replacement surgery -- A comparison of free-hand and computer assisted cup placement in total hip arthroplasty -- a multi-center study]. / Pfannenplatzierung in der Hüftendoprothetik -- vergleichende Untersuchung freihand implantierter und computerassistiert platzierter Hüftpfannen -- eine Multizenterstudie.

AIM: The purpose of the current study was to determine the accuracy of free hand and computer-assisted (CAS) cup placement. MATERIAL AND METHODS: Between June 1985 and August 2001, 105 free-hand and from March to November 1999 80 total hip arthroplasties under computer assistance were implanted in the above mentioned centers. To determine the accuracy of the cups, the inclination and anteversion angles were measured. In all cases the cup position was measured with a CT-investigation of the pelvis. Statistical analysis was performed with the F-test. RESULTS: With regard to the inclination and anteversion angles the variability of the cup position was significantly higher in the group of free hand implanted cups. In the CAS group we could not find any "extreme" positions. CONCLUSION: Using computer-assisted surgery a significantly higher reproducible cup position can be obtained. Long time survey may present a lowering of the rate of early and late complications caused by better prostheses alignment in the follow up.

[Computer-assisted navigated cup placement of different cup types in hip arthroplasty--a randomised controlled trial]. / Computerassistierte navigierte Platzierung von verschiedenen Pfannentypen in der Hüftendoprothetik - eine randomisierte kontrollierte Studie.

AIM: The position of the acetabular implant has a great influence on the outcome of total hip arthroplasty. The acetabular implants differ in their characteristics during insertion. In order to control the influence of the implant in different axes, 80 implantations of acetabular component were performed under computer-assisted control by a surogate navigation system. METHOD: Within a prospective randomised study, 70 total hip replacements were performed by one surgeon using two different uncemented implants (PPF screw cup/Hedrocel pressfit cup). The position of the cup was measured at different times during surgery and was compared to 10 cemented PE cup placements. RESULTS: During the milling procedure the anteversion of the two uncemented cups differed significantly (p = 0.026). The standard deviation of anteversion during implantation different significantly relating to the cup type: press-fit cup 3.86 degrees, screw cup 2.1 degrees and cemented PE cups 0,84 degrees. The inclination was less susceptible. CONCLUSION: The cup design of uncemented acetabular implants influences the outcome of surgery. In our trial a spherical press-fit cup showed a greater variability than the screw-cup. The CAS system can be used as a tool to minimise these effects.

Lumbar micro disc surgery with and without autologous fat graft. A prospective randomized trial evaluated with reference to clinical and social factors.

Epidural scarring is one of the possible complications after lumbar disc surgery. Perineural scar tissue has been considered responsible for recurrent neurological symptoms in patients operated on for disc herniation and leads to a high rate of unsatisfactory results. In addition, postoperative scars may increase the technical difficulty and risk of subsequent procedures. Various materials have been used in animal studies to try to affect the degree of epidural scar tissue with controversial results. In particular, free fat transplantation has been described to reduce the degree of intraspinal scar tissue. We therefore performed a prospective, double-blind, randomized study comparing clinical and social factors of patients being operated on for the first time for lumbar disc herniation. A total of 92 patients received an implantation of autologous fat graft, 94 did not. After a median of 24.2 months after their surgery, an objective examinator compared various clinical parameters and the social situation of patients in both groups without knowing the operation method used. We found no significant differences between the fat-graft group and the control group regarding either the clinical outcome or the social aspects.

[Using the CAS (computer-assisted surgery) system in arthroscopic cruciate ligament surgery--adaptation and application in clinical practice]. / Anwendung eines CAS-Systems in der Arthroskopischen Kreuzbandchirurgie--Adaptation und Applikation in der klinischen Praxis.

AIM AND METHOD: The anterior cruciate ligament (ACL) is of great importance for the knee joint function. In the case of a complete ligament injury there is hardly any chance for complete recovery. The clear advantages of an operative reconstruction by replacing the ACL has been shown in many trails. The accurate placement of the graft's insertions has a significant effect on the mid- and probably long-term outcome of this procedure. Reviewing the literature, there are poor long-term results of ACL replacement in 5 to 52% of all cases, depending on the score system. One of the main reasons for unacceptable results is graft misplacement. This led to the construction of a CAS system for ACL replacement. The system assists this surgical procedure by navigating the exact position of the drilling holes. The Potential deformation quantity of the transplant can be controlled by this system in real time. RESULTS: 40 computer-assisted ACL replacements have been performed under active use of the CAS system. The short-term results are encouraging, no special complications have been seen so far. Prospective long-term follow-up studies are ongoing. CONCLUSION: ACL reconstruction by manual devices has many sources of error. The CAS system is able to give the surgeon reasonable views that are unachieveable by conventional surgery. He is therefore able to control a source of error and to optimise the results. The feasibility of this device in clinical routine use has been proven.

[Intervertebral disk displacement and trauma]. / Bandscheibenvorfall und Trauma.

It is difficult to find medical evidence of a correlation between a lumbar disk disease and trauma. One should consider whether the individual degeneration of lumbar disks or the trauma lead to the typical complaints. Disk disease in the population are very common. Therefore the relevance of the individual affection before trauma has to be considered. Spinal trauma with its sudden, incidental onset needs to be differentiated from purposeful and conscious movements. An intervertebral disk disease can be classified as accident related only in cases involving adequate trauma, with no previous complains, and a sudden onset of pain.

[Computer-assisted navigated acetabulum placement in hip prosthesis implantation--application study in routine clinical care]. / Computerassistiert navigierte Pfannenplatzierung in der Hüftendoprothetik--Anwendungsstudie im klinischen Routinealltag.

AIM: This study serves to examine the feasibility of a CAS system in clinical routine use in the field of total hip replacement. METHOD: Within a prospective study 70 total hip replacements were performed by one surgeon (KB) between March and November, 1999 using a CAS system for preoperative planning and intraoperative cup placement. RESULTS: The average operating time was 70 min. This means an average increase in total time of operation about 15-20 min. The average blood loss was 630 ml. No additional specific complications due to the use of the system were seen. There was no additional trauma created by percutaneous pointing at the spina or flxing a dynamic reference base (DRB) at the pelvis. CONCLUSION: The active application of this CAS system in clinical routine use showed very good results in feasibility and can be considered as reliable. The navigated cup placement shows the potential of improving the results in cup placement, thus improving the outcome of hip arthroplasty.

[Quality management. Concepts and application in orthopedics]. / Qualitätsmanagement. Konzepte und Umsetzungsmöglichkeiten im orthopädischen Kontext.

A growing number of Health Care Systems have introduced Quality Management Systems to manage both quality in medicine and financial resources of the society. These Systems have been developed successfully for manufacturing and service business. Service Quality Management Systems can be modified for the purpose of non-profit-systems, such as Health Care. The view of quality differs among institutions and persons acting within this system. The focus of the customer is most important for any service offer to the patient. The variety of external, internal and total Quality Management Systems is discussed with regard to the adoption in elective orthopaedic surgery. Strong process orientation may favour the DIN ISO System, as the definition of processes in medicine should be enforced. Once the processes are clearly defined, elaborated (total) systems may be introduced easily. The process of the implantation of a total hip prothesis has been designed to DIN ISO conformity by a project team of experienced surgeons and is given here as an example for process orientation in elective surgery.

[Evaluation of standardized routine documentation with implementation of the requirements of multicenter studies. Presentation on the example of a knee endoprosthesis]. / Evaluation einer standardisierten Routinedokumentation mit Implementierung der Anforderung multizentrischer Studien. Darstellung am Beispiel der Knieendoprothetik.

In 1988 we did develop an EDP-System for data collection of daily routine documentation, which allows on the one hand a complete registration and on the other hand only offers entire and plausible data because of the logical program structure. The registered data are saved in a data bank structure as well as in report form for routine documentation. The substitution of routine documentation by such a system essentially depends on the content of interrogation which has to reflect the user's individual indication and operative technique. First doubts about reflection of the high variation of the individual operative technique could be disproved with help of the evaluation of this system of documentation. None of the 200 registered cases had to be documented without the help of the standardized system. The use in a prospective multicenter study for endoprosthesis of the knee was the starting point of the evaluation for the system's efficiency and acceptance. It had been analyzed the expressiveness of the study's documentation. As there was no standard in free dictated operation records the information content seemed to be reduced and with regard to scientific aspects unqualified. The analysis of the EDP-system especially checked three aspects: the general suitability to represent medical facts by standardized evaluation as well as the user's and patient's acceptance. All in all this system is an instrument for standardized daily routine documentation in a clinic which seems able to establish a quality management because of the high data quality, the differentiated registrations of multiple parameters and timeneutral application.

Quality management. Concepts and applications in orthopaedics.

A growing number of Health Care Systems have introduced Quality Management Systems to manage both quality in medicine and financial ressources of the society. These Systems have been developed successfully for manufactoring and service business. Service Quality Management Systems can be modified for the purpose of non-profit-systems, such as Health Care. The view of quality differs among institutions and persons acting within this system. The focus of the customer is most important for any service offer to the patient. The variety of external, internal and total Quality Management Systems is discussed with regard to the adoption in elective orthopaedic surgery. Strong process orientation may favour the DIN ISO System, as the definition of processes in medicine should be enforced. Once the processes are clearly defined, elaborated (total) systems may be introduced easily. The process of the implantation of a total hip prothesis has been designed to DIN ISO conformity by a project team of experienced surgeons and is given here as an example for process orientation in elective surgery.

Evaluation of standardized routine documentation with implementation of the requirement of multicenter studies. : Presentation with knee endoprosthetics as an example.

In 1988 we did develop an EDP-System for data collection of daily routine documentation, which allows on the one hand a complete registration and on the other hand only offers entire and plausible data because of the logical program structure. The registered data are saved in a data bank structure as well as in report form for routine documentation. The substitution of routine documentation by such a system essentially depends on the content of interrogation which has to reflect the user's individual indication and operative technique. First doubts about reflection of the high variation of the individual operative technique could be disproved with help of the evaluation of this system of documentation. None of the 200 registered cases had to be documented without the help of the standardized system. The use in a prospective multicenter study for endoprosthesis of the knee was the starting point of the evaluation for the system's efficiency and acceptance. It had been analyzed the expressiveness of the study's documentation. As there was no standard in free dictated operation records the information content seemed to be reduced and with regard to scientific aspects unqualified. The analysis of the EDP-system especially checked three aspects: the general suitability to represent medical facts by standardized evaluation as well as the user's and patient's acceptance. All in all this system is an instrument for standardized daily routine documentation in a clinic which seems able to establish a quality management because of the high data quality, the differentiated registrations of multiple parameters and timeneutral application.

Diagnosis of knee instability using sonography.

OBJECTIVE: A sonographic method has been developed to diagnose knee joint instabilities and to gain exactly quantifiable and reproducible measurements. DESIGN: Based on biomechanical considerations, a new positioning device to analyse knee instabilities sonographically has been developed and tested in in vivo studies. BACKGROUND: Common instrumental testing techniques are difficult to reproduce and show a lack of reliability. METHOD: Using sonography the cortical line of the femur and tibia are observed. At the same time a translation of these two partners at the knee joint is provoked in a defined position using the special holding device and under a defined amount of stress. Using this method 142 healthy people, placed in different age groups, were tested to establish standard values for the physiological knee joint translation. A prearthroscopic stability analysis was performed on 101 patients. RESULTS: This study proves that the special device developed, together with the technique used, provides reliable and exact measurements for knee instability in different translation directions. In healthy subjects the lateral compartment always showed a larger translation than the medial compartment. A gradual increase in translation was determined in the age groups over 30 years. A significant difference of 0.0001 was shown between knee stability and instabilities. Moreover, a further differentiation between partial and total ACL ruptures and chronic instabilities was determined. This provides an important advantage not offered by usual instrumental testing techniques. CONCLUSIONS: The ability to diagnose even a very low extent of instability and to differentiate between different kinds of instabilities enables exact controls to be carried out for both conservative and operative treatment.

[Late hip dislocation--treatment results of 1193 hips in attenuated abduction (Hanausek position)]. / Späte Hüftluxation--Behandlungsergebnisse von 1193 Hüften in der abgeschwächten Beuge-Spreizstellung (Hanausekposition).

Results of 1193 dislocated and dysplastic hips in 695 children of a consistent treatment by skin traction and splinting in a mitigated abduction device (Hanausek position) are given with regard to the acetabular development and avascular head necroses. The acetabular development depends on the initial acetabular dysplasia and is overall satisfactory through final acetabular angles (Hilgenreiner) between 22 and 25 degrees even in highly dysplastic acetabula in late cases. The procedure is non-aggressive proven by low rate of femoral head necroses of 3.4%. Factors contributing to higher rates and degrees of iatrogenic damage to the femoral head are short time or no preceding longitudinal traction, low initial acetabular pathology and prolonged splinting.

[The psychiatric hospital between obligatory admission and legal responsibilities (author's transl)]. / Das psychiatrische Krankenhaus zwischen Aufnahmepflicht und Verantwortung aus strafrechtlicher Sicht.

This article focuses on the risks to which a physician is exposed under the provisions of the penal code if he is called upon to decide whether a patient should be admitted to the hospital or not. The conflict between the physician's obligation to protect the patient to be admitted, on the one hand, and to treat all inmates in accordance with the state of the art ("lege artis") and with humanitarian principles, on the other, necessarily leads to problems which are difficult to manage from the legal point of view. It is less likely that such problems can be solved by issuing strict regulations standardizing the procedure, than by improving the overall availability of medical care and treatment facilities.