[Long-Term Results of Computer-Navigated Total Knee Arthroplasties Performed by Low-Volume and Less Experienced Surgeon]. / Vplyv pocítacovej navigácie na dlhodobé výsledky po implantáciách totálnych endoprotéz kolenného klbu vykonaných menej skúseným operatérom.

PURPOSE OF THE STUDY The study aims to evaluate the long-term results of computer-navigated total knee arthroplasties performed by less experienced surgeon performing a small number of procedures per year. MATERIAL AND METHODS In the prospective randomised study functional and radiological results, rate of revision and probability of clinical and radiological survival were compared in 30 computer-navigated (in 28 patients: 19 women, 9 men, with the mean age of 66.9 years) and 31 conventionally implanted (in 30 patients: 27 women, 3 men, with the mean age of 66.5 years) cemented total knee replacements without patellar resurfacing. The group was composed of patients who underwent surgery performed by the same surgeon who at the time of enrolment of patient in the study had no previous experience with the total knee replacement surgery and performed up to 30 such procedures annually. The mean follow-up of patients was 11 years. RESULTS No statistically significant differences were detected regarding the mean age, sex, body mass index and etiology of osteoarthritis of the operated knee. The mean duration of computer-navigated surgeries (101±14.1; 80-140 min) was considerably longer than the duration of conventional joint replacements (94±8.2; 80-100 min; p = 0.01). When evaluating the radiological results, a statistically significant difference was found between the groups only with respect to the mean value of dorsal inclination of the tibial component (88.2˚±2.1 vs 86.2˚±3, p = 0.02). The mean values of other monitored angles did not show any significant differences. The number of correct implants (with a deviation of 3 degrees from the target values) was statistically significantly higher in the group of computer-navigated joint replacement surgeries in all the monitored parameters (aFT: 87% vs. 67%, p = 0.04; α: 87% vs. 71%, p = 0.04; ß: 87% vs. 65%, p = 0.03; γ: 93% vs. 74%, p = 0.02; δ: 90% vs. 77%, p = 0.04). Radiologic signs of unstable fixation were detected in 2 cases of computer-navigated joint replacement surgeries and in 7 cases of conventional replacements. Cumulative probability of radiologic survival at 10 years reached 93% in the compute-navigated surgery and 77.4% (p = 0.047) in the group with conventional procedure. In total, 4 revision surgeries with a reimplantation of at least one prosthetic component were reported. All the cases came from the conventional implantation group due to aseptic loosening of the endoprosthesis. In the computer-navigated group, one revision was performed for patellar pain, without replacing or adding any endoprosthetic component. The probability of clinical survival in computer-navigated replacements after 10 years was 100%, in conventional total knee replacements it was 87% (p = 0.04). The cumulative total endoprosthesis revision rate in the computer-navigated group was 3.3%, whereas in the group with conventional total knee replacements it was 12.9% (p = 0.04). The clinical assessment based on the WOMAC and Knee Society Scores showed no statistically significant differences. DISCUSSION The most common cause of the failure of total knee arthroplasties is the malposition of implants which results in early aseptic loosening. The radiologically correct position of knee endoprosthesis is seen in 80% of standard replacement surgeries performed by experienced surgeons. The potential error rate can even increase if the arthroplasties are performed by less experienced orthopaedic surgeons. The computer-navigated total knee replacement was introduced to make the position of implants more accurate. However, the question remains unanswered if more accurate positioning of the implants achieved with computer navigation decrease the revision rate and extend the long-term survival of knee endoprostheses. CONCLUSIONS Kinematic computer navigation allowed a less experienced and low-volume orthopaedic surgeon to make the implantation of endoprostheses more accurate, to decrease the total revision rate, and thus to ensure a higher probability of long-term survival of total knee arthroplasties. Key words:computer navigation, total replacement, knee joint, long-term outcomes, low-volume surgeon, less experienced surgeon.

[The incidence of osteopenia and osteoporosis in patients with cementless total hip arthroplasty]. / Incidencia osteopénie a osteoporózy u pacientov plánovaných na implantáciu necementovanej endoprotézy bedrového klbu.

PURPOSE OF THE STUDY: The aim of the study was to evaluate the incidence of osteopenia and osteoporosis in the patients elected to cementless total hip replacement. MATERIAL AND METHODS: The group evaluated comprised 100 patients with primary or secondary forms of coxarthrosis who underwent cementless total hip arthroplasty (THA). The results of densitometric examination of the lumbar spine and proximal femur were analysed. Based on the lowest T-score value, the patients were divided into three groups, i.e., fist, normal bone density; second, osteopenia; third, osteoporosis. Clinical examination included patient medical history, Harris hip scores and visual analogue scale assessment for pain intensity; the Kellgren-Lawrence classification was used to measure the grade of hip osteoarthritis; blood tests were made to assess the levels of total calcium, ionised calcium, phosphorus, vitamin D and the markers of bone resorption and formation. RESULTS: Osteoporosis was found in 32 and osteopenia in 21 patients; 47 patients had normal bone density. Osteoporosis was detected in the lumbar spine of 21 patients, in the proximal femur of nine patients and at both sites in two patients. In 13 patients this diagnosis was made for the fist time. The patients with osteoporosis had a significantly lower body mass index. There were no differences in the other characteristics, i.e., age, functional, radiological and laboratory findings, among the groups; all three showed the mean vitamin D concentration below the lowest level of its physiological range. Insufficient vitamin D levels were found in 54 women and 18 men. Of all patients, only 13 women and four men took vitamin D supplements. DISCUSSION Osteoarthritis and osteoporosis are the most frequent complex musculoskeletal diseases. Several studies have suggested that these disorders are mutually exclusive. This assumption has been based on the absence of radiographic evidence of osteoarthritis seen in many elderly patients with femoral neck fractures. Our relatively frequent findings of osteopenia and osteoporosis in this study show that patients with osteoarthritis may not be protected from the development of generalised osteoporosis. Our results are compared with the relevant literature data and potential effects of osteoporosis and vitamin D deficiency on total hip arthroplasty are discussed. CONCLUSIONS: Hip osteoarthritis does not reduce the risk of generalised osteoporosis. We found a relative high incidence of osteopenia and osteoporosis as well as vitamin D deficiency in patient with advanced form of hip osteoarthritis.

[Bone Remodelling in the Proximal Femur after Uncemented Total Hip Arthroplasty in Patients with Osteoporosis]. / Kostná remodelácia proximálneho femuru po implantácii necementovanej endoprotézy bedra u pacientov s osteoporózou.

PURPOSE OF THE STUDY: The aim of the study was to investigate the involvement of osteoporosis during remodelling of the proximal femur after uncemented total hip arthroplasty (THA) and the effect of bisphospohonate treatment on these changes. MATERIAL AND METHODS: Sixty evaluated patients with non-cemented THA were divided into three groups on the basis of pre-operative densitometric examinations. Group 1 (15 patients with osteoporosis) received a single dose of 5 mg zoledronic acid in infusion during the second post-operative week. Group 2 (15 patients with osteoporosis) were not treated by bisphospohonate. The patients of both groups took oral calcium and vitamin D medication. Group 3 (control) comprised 30 patients with normal bone density who did not take any osteoactive drugs. By measurement of bone mineral density (BMD) at 12 months after surgery, changes in periprosthetic bone of the proximal femur in 7 Gruen zones were recorded by densitometry. In addition, radiological findings on native X-ray images were assessed and the patients' clinical health status was rated by the Harris hip score. RESULTS: No significant differences in either the average age or the body mass index were found between the groups at the time of THA surgery. The mean BMD value in all assessed Gruen zones measured at the first post-operative week was higher in patients with normal bone density than in those with osteoporosis. The mean BMD value measured at 12 months decreased in all Gruen zones in comparison with the initial value, and this was found in all three groups. The lowest values were recorded in the untreated patients (group 2); in comparison with the patients who had normal bone density, the difference was statistically significant in Gruen zones 1, 2, 6 and 7. Although the patients with treated osteoporosis also showed lower BMD values, these were not statistically significant compared to group 3. The worst post-operative outcome in clinical health status was recorded in the patients with untreated osteoporosis. X-ray examination revealed stable fibrous ingrowth in one patient with untreated osteoporosis and in one with normal bone density. All remaining patients had stable bone ingrowth fixation. DISCUSSION: In THA the majority of compressive loads are transferred through the stem to the femoral bone below the apex of the stem. This results in reduction of bone density in the calcar and greater trochanter regions. Osteoporosis is the most important factor related to changes in periprosthetic bone mass. Therefore, it can be anticipated that an excess loss of bone mass in the proximal femur may, in a long term, interfere with THA stability and may increase the risk of periprosthetic fractures and aseptic loosening. CONCLUSIONS: The results of our study showed that the patients with untreated osteoporosis, who underwent uncemented THA, experienced a considerable decrease in the periprosthetic bone density of the proximal femur and were in worse clinical health. A bisphospohonate therapy was effective in eliminating this negative outcome. Both the clinical and densitometric findings in patients with treated osteoporosis were similar to those in patients with no osteoporosis.