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The PDF document may be downloaded below.

The PDF document may be downloaded below.

Summary Precise pre-operative planning with determination of the implant size and position and reconstruction of the joint geometry is an important initial prerequisite for the success of a hip endoprosthesis implantation or of an osteotomy at the hip joint. In addition to the possibilities of a three-dimensional simulation, there are benefits to two-dimensional planning as well, particularly when changes to joint biomechanics are also taken into consideration. A computer-aided planning system has been developmed that contains data from 60 different hip endoprosthesis models. In a biomechanical analysis, the surgeon is given a proposal for an optimal prosthesis position through determination of the center of rotation. The joint reconstruction can be evaluated pre- and post-operatively with the aid  of a 12-point score.

The computer-aided system was utilized for planning of 542 hip endoprosthesis-plasties. Despite the high proportion  of 469 dysplastic coxarthroses, we post-operatively determined an anatomically correct prosthesis position on 343 prostheses. On 63% of the cups and 91% of the prosthetic shafts, the planned implant size was actually used. Initial clinical results are presented. This method is also suitable for planning osteotomies at the hip joint.

Abstract:
Corrective osteotomies of the lower extremity are elective orthopaedic procedures. The main interest in corrective osteotomies of the lower extremity is to realign the mechanical axis and joint orientation lines. Biomechanical loading forces on the joints are brought into physiological range to prevent early joint degeneration. Operative procedures with a high preventive character needs a careful and valid preoperative planning and simulation as well as an exact operative technique. For this planning we use a PC based program, the Osteotomiemodul II. The Osteotomiemodul II is a CAD Software optimised to orthopaedic questions in the field of
mechanical axis reconstruction. The planning is based on a standardised long standing x-ray of the lower extremity. A computertomography to create a three dimensional database is not needed. The long standing x-ray becomes digitised by a film digitizer. Film formats of 35,6 cm x 129,5 cm are scanned in a one step procedure. The analysis of the deformity and mechanical axis deviation including the simulation of corrective osteotomies can be seen on the PC screen. A 1 : 1 printout of the deformity analysis as well as the postoperative simulation increase intraoperative precision during deformity correction. The time consuming procedures of planning corrective osteotomies especially multi level osteotomies are shortened significant. Integrated automatism visualise secondary corrective effects resulting from different positions of the axis of correction of angulation (ACA). Different options can be simulated and compared in shortest of time. Secondary translation and secondary change in length of the mechanical axis is quantified and visible for each osteotomy. With regard to the great variety of simulations, planning time and the comfortable storage and documentation possibilities based on electronic data, the Osteotomiemodul II is thought to be superior to the conventional way of planning with paper drawings. This planning software is recommended for orthopaedic surgeons in the field of reconstructive surgery of the lower extremity.

Objective The benefits of detailed pre-operative planning are undisputed for both joint-preserving operations as well as in joint endoprostheses. Planning with the pre-operative radiograph through the use of special radiograph templates and drawings is the first integrative component of the actual prosthesis implantation [1-4]. Among the objectives are precise prediction of the size and position of the prosthesis, compensation for existing differences in leg lengths, and recognition of any intra-operative peculiarites of the procedure. This shortens the operation time and reduces the potential for unanticipated complications. Whenever possible, planning should proceed on standardized radiographs in two levels in order to avoid projection errors.

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With 1,100 beds, the Ludwigsburg hospital center is the largest in the group. Composed of 12 clinics, five departments and four institutes, this center for full-level care covers about 500,000 people in the Ludwigsburg administrative district. The Clinic for Accident, Hand and Restorative Surgery at the Ludwigsburg hospital center carries out approximately 2,700 operations each year. Much of the Clinic’s treatment involves endoprosthetics and the provision of medical care to patients with post-traumatic conditions.

Abstract
Exact radiographic evaluation of lower limb alignment, joint orientation and leg length is crucial for preoperative planning and successful treatment of deformities, fractures and osteoarthritis. Improvement of the accuracy of radiographic measurements is highly desirable. To determine the intraobserver reliability of conventional analysis of lower extremity geometry, 59 long leg radiographs were randomly analyzed 5 times by a single surgeon. The measurements revealed a standard deviation between 0.368 and 1.178 for the angles mLPFA, mLDFA, MPTA, LDTA, JLCA and AMA (nomenclature according to Paley), and 0.94 mm and 0.90 mm for the MAD and leg length, respectively.

Computer-assisted analysis with a special software significantly reduced the standard deviation of the mLDFA, MPTA, LDTA, JLCA (each p , 0.001), AMA (p ¼ 0.032) and MAD (p ¼ 0.023) by 0.05–0.368 and 0.14 mm, respectively. Measuring time was reduced by 44% to 6:34+0:45 min (p , 0.001). Digital calibration by the software revealed an average magnification of conventional long leg radiographs of 4.6+1.8% (range: 2.7–11.9%).

Computer-assisted analysis increases the intraobserver reliability and reduces the time needed for the analysis. Another major benefit is the ease of storage and transfer of digitized images. Due to the varying magnification factors on long leg radiographs, the use of magnification markers for calibration is recommended.