Patient-specific instrumentation (PSI) has been greatly marketed in knee endoprosthetics for the past few years. By utilising PSI, the prosthesis´ accuracy of fit should be improved. Besides, both surgical time and hospital costs should be reduced. Whether these proposed advantages are achieved in medial UKA remains unclear yet. The aim of this study was to evaluate the preoperative planning accuracy, time saving, and cost effectiveness utilising PSI in UKA. Data from 22 patients (24 knees) with isolated medial unicompartmental knee osteoarthritis were analysed retrospectively. The sample comprised sixteen men and six women (mean age 61 ± 8 years) who were electively provided with a UKA utilising PSI between June 2012 and October 2014. For evaluation of preoperative planning accuracy (1) planned vs. implanted femoral component size, (2) planned vs. implanted tibial component size, and (3) planned vs. implanted polyethylene insert size were analysed. Since UKA is a less common, technically demanding surgery, depending in large part on the surgeon´s experience, preoperative planning reliability was also evaluated with regard to surgeon experience. Moreover, actual surgical time and cost effectiveness utilising PSI was evaluated. Preoperative planning had to be modified intraoperatively to a wide extend for gaining an optimal outcome. The femoral component had to be adjusted in 41.7% of all cases, the tibial component in 58.3%, and the insert in 87.5%. Less experienced surgeons had to change preoperative planning more often than experienced surgeons. Utilising PSI increased surgical time regardless of experience. Linear regression revealed PSI-planning and surgeon inexperience as main predictors for increased surgical time. Additionally, PSI increased surgical costs due to e.g. enlarged surgical time, license fees and extraordinary expenditure for MRI scans. The preoperative planning accuracy depends on many different factors. The advertised advantages of PSI could not be fully supported in case of UKA on the basis of the here presented data – especially not for the inexperienced surgeon.
An increasing demand for less traumatic THA combined with a faster recovery time has led to minimal invasive surgical approaches and to bone and soft tissue preserving short stem prostheses. Short stem prosthesis should have metaphyseal fixation, primary stability and lesser changes in femoral elasticity which would lead to less stress shielding. The need for a good joint stability and a higher mobility after THA has led to navigated hip surgery together with the use of modular necks to restore the biomechanics. From November 2004 to July 2008 we implanted 154 Metha prostheses by a modified less invasive Watson-Jones approach. 104 THA were navigated. The indication was primary (32%) or dysplastic coxarthritis (50%) or femoral head necrosis (18%) without affection of the femoral neck, patients age under 50 years and above with good bone density. Evaluation was done with regard to primary stability, ease of minimal invasive implantation and restoration of the biomechanics. The cup position was aimed at 45° of inclination and 15° of anteversion. The most used modular neck adapter in the non navigated group was standard (135°CCD, 0° antetorsion). In the navigated group more often different variations of neck adapters were used (mainly 135°CCD, 7.5° retrotorsion). Reliable length (+7mm overall) and offset (−3.5mm) measurements could be achieved in the navigated group. The average antetorsion of the stem was 20°. Bone loss is low with short stem and it is suitable for minimal invasive procedures. A good primary stability seems to be achievable. Modularity leads to a better restoration of the hip biomechanics. In the navigation of the short stem prosthesis the placement of the stem is separated from the restoration of the biomechanics of the hip. The criteria offset, leg length antetorsion, and center of rotation of the head and implant range of motion can be controlled for restoration by navigation. No dislocation was seen in the intraoperative test and in the postoperative follow up. The short term results show good functional result and a low complication rate without any dislocation. The use of a lesser invasive approach without detaching muscle led to a subjectively faster recovery. The navigation system helps to be precise in cup positioning and to restore biomechanics in term of center of rotation, leg length and offset by advising the best fitting modular neck and reliably predicting the safe range of motion. In our experience the navigated short stem prosthesis offered a good intraoperative handling and good preliminary results.
Malposition of cups and stems in THA leads to a higher rate of dislocation and wear, to leg length discrepancies and to a higher revision rate. Surgical navigation of the implant components should lead to a more accurate position of THA. 1481 consecutive THA were evaluated from November 2001 to June 2006. In a first series until December 2002 127 THA with navigated cups were compared with 110 manually implanted THA. In a second series all following 766 THA with navigated cups were compared to 384 THA with both navigated cup and stem. Navigated surgery was done as a routine procedure by all surgeons, from residents to consultants. Evaluation was done for radiographs, clinical results, the navigation system data for cup anteversion and inclination, centre of rotation, leg lengthening, offset and antetorsion of the stem, technical exclusions and intra- and postoperative complications as dislocation, seroma, thrombosis and duration of surgery. The results showed a better alignment in inclination and anteversion of navigated cups compared to non navigated cups and additional improvement when cup and stem were navigated. In stem navigation a good control of the leg lengthening and a reliable prediction of the safe range of motion could be seen. The overall dislocation rate was 0.3% in the navigated groups after December 2002. Thrombosis, seroma and infection were seen in a very low rate in all groups.
Introduction. In Mid-Europe developmental dysplasia of the hip (DDH) is diagnosed using the sonographic hip screening described by Graf. To learn the necessary standards three courses are mandatory. However, little is known about learning curves and measurement errors of doctors at different levels of training and experience. Material and Methods. Between 1997 and 2002 participants of the basic, advanced and final hip ultrasonogra-phy course were evaluated by a questionnaire and 34 normal and pathological sonograms. They were asked to measure the alpha and beta angle. “Normal” angles of each hip were created through the mean values of two experienced course organizers. Results. 186 doctors (40% orthopedic surgeons, 60% pediatricians) were evaluated. The group included 20% interns, 60% residents and 20% consultants. An average time of 6.3 months lay between the basic and the advanced, and of 16.7 months between the advanced and the final course. The evaluation of the sonograms according to Graf showed major inter-observer differences of up to 30°. Participants had more difficulties in evaluating a correct beta angle than an alpha angle. Sonographic pictures of minor quality and pathological hips produced more difficulties than pictures of Graf type I and II hips. In the basic course all measurements showed an average difference of 3,6°, in the advanced course of 3,1° and in the final course of 4,2°. The number of examinations between courses did not correlate with good measurements. Conclusion. Even participants of all three courses seem to develop major systemic errors if ultrasonography is regularly applied without supervision. Therefore, regular training and supervision should be mandatory in order to guarantee good quality.
