The key aspects of the study: 1) what has changed in the structure of revisions in recent years? 2) what is the spectrum of reasons for revision after primary hip arthroplasty and re-revision? 3) what are the demographic features of patients’ population undergoing the revision? Materials and methods. The authors conducted a retrospective evaluation of 2415 hip revision cases during the period of time from 2014 until 2018. Separately the authors assessed revisions after primary surgeries and re-revisions as well as the group of early revisions. Results. In the period from 2014 until 2018 the overall share of revisions was 16,6% from all total hip arthroplasties, at the same time the authors reported the absolute 1.7 times increase in number of revisions as well as increased share of revisions in the total structure of hip arthroplasty from 12,5% to 18,9% without significant variances in the number of primary procedures. The share of early revisions increased from 32.9% in 2013 to 56.7% while the number of early revisions amounted to 37.4% of all primary revisions. Gender composition in primary and revision hip arthroplasty varied insignificantly. Mean age at the moment of hip revision was 59.2% (95% CI from 58.7 to 59.7; Me 60 years) which is slightly less than in primary replacement — 60.2 years (95% CI from 58.9 to 61.1; Me 62 years), but such variances had a high statistical significance, р0.001. The main reasons for primary revisions were aseptic loosening of prosthesis components (50.3%), infection (27.6%), polyethylene wear and osteolysis (9.0%) as well as dislocations (6,2%). Re-revisions structure featured prevalence of infection (69.0%), aseptic loosening (20.8%) and dislocations (7,8%). Mean period of time after primary hip arthroplasty to revision was 7.9 years (95% CI from 7.7 to 8.2; Me 7.3), to first re-revision — 2.9 (95% CI from 2.6 to 3.2; Me 1.2), to second re-revision — 2.2 (95% CI from 1.8 to 2.7; Me 1.1), to third — 2,2 (95% CI from 1.7 to 2.8; Me 1.1), to fourth — 1.0 (95% CI from 0.6 to 1.3; Me 0.6), remaining cases demonstrated rather high heterogeneity. Conclusion. In the result of the present study the authors observed increased number of all revision hip arthroplasties, especially the share of early revisions within first five years from the moment of previous surgery. The most often reason for revision after primary hip arthroplasty was aseptic loosening of one or both components of prosthesis. Infection was the absolute leader in the group of re-revisions constituting over half of all reasons for secondary intervention.

The authors retrospectively reviewed RNIITO Arthroplasty Registry data of revision total hip arthroplasties performed in RNIITO in 3 year period (2011-2013). Part of early revisions within 5 years after the index procedure in general revision structure was 33% . Two hundred seventy three (64%) procedures had infection reason, 79 (19%) - aseptic loosening, 35 (8%) - dislocation and 27 (6%) - periprosthetic fractures in reasons of revision, respectively. More than half of revisions were performed within the first year after the index procedure. Early primary revisions after index total hip arthroplasty were performed in 254 (59,8%)cases, and repeated revisions were performed in 171cases one or more times. Of early primary revisions 125(49,2%) patients had index total hip athroplasty in our hospital, and 129 (50,8%) patients had index total hip athroplasty in other hospitals of Russian Federation. Our THA early revision structure is differs significantly from published in literature, moreover there is difference between revision reasons after primary total hip arthroplasty of our hospital and other hospitals. Revision reasons structure doesn’t show rate of primary THA complications, but defines main problems that should be solved.

The   paper   presents   data   analysis   of  the   Hip   Arthroplasty  Register   of  Vreden   Russian   Research   Institute of Traumatology and Orthopedics, namely information on 37373 primary THA performed at the Vreden Institute and at several other orthopedic centers and 1200 hip replacements at other hospitals of St. Petersburg.There were 1.5 times more women in the studied cohort than men. A significant predominance of women with dysplastic osteoarthritis (72.4%) and rheumatoid arthritis (82.1%) was reported. A male predominance was noted in patients with secondary osteoarthritis (53.1%), post-traumatic changes of hip (61.0%) and osteonecrosis of the femoral head (68.6 %). The mean age of patients was 58.0±12.9 years (95% CI from 57.9 to 58.1, median 59 years). Age data of the study revealed that  patients were 10-12 years younger than reported in the national  arthroplasty registers of other countries.Total  hip arthroplasty was performed  in the  absolute  majority  of patients – 37295  cases (99,8%).  Uncemented implants  were used in 59.3% of cases, hybrid – in 29.6%, cemented – in 10.2%, reverse-hybrid – in 0.9% of all patients. The  most  common  bearing  used  was metal  on  crosslink  polyethylene, which  was applied  in 50.1% of all cases of arthroplasty. The  type  of fixation  of the  implant,  and  the  use of different  bearings  varied  in different  age groups. The paper presents  not only the absolute  numbers  of the data, but also demonstrated the dynamics  of the changes in time starting from 2007.The  present  epidemiological  study  does not  claim the  absolute  completeness of the  presented data,  but  contains the  analysis of the  large number  of cases, comparable  with  follow-ups  of patients in some national  registers  of certain European countries. The authors  analyzed about  10% of all cases of hip replacements performed  on the territory of the Russian Federation in ten-year  period.

Basing on scientific publications and original research the authors specified the effect of incorporation and adsorption of different ions and water molecules on physical, chemical and mechanical properties of bioapatite and determined new directions for investigations of intercrystallite interactions in nanoscale. Inner structure of the apatite crystallites more adaptable to chemical substitutions in comparison with other minerals controls their important characteristics such as a size, solubility, hardness, fragility, formability and thermal stability. The water molecules incorporated in crystallites and adsorbed on their surfaces stabilize them. In case the distances between crystallites become shorter than 10 nm the water molecules adsorbed on their surface play dominant role in bonding between the crystallites. This bond determines the main mechanical properties of bones. We bring forward a suggestion that theoretical model developed on the basis of near edge X-ray spectroscopic studies of bones using the contemporary high brilliant sources of X-ray radiation (synchrotrons and X-ray free electrons lasers) will allow to receive new quantitative data on local electronic and atomic structure (coordination numbers, ionic charges, interatomic distances interatomic and intercrystallite forces) of nanoelements in osseous tissue. The investigation results must bring to construction of new morphologically correct model providing deeper understanding of processes occurring in mineral matrix and mechanical properties of bones.

The main questions of the study: 1) is there any difference in anatomical features between subtypes C1 and C2 of high hip dislocation by Hartofolakidis classification; 2) are the conditions for performing the THA different and what are the surgical decisions; 3) what are the THA results in different groups? Materials and Methods. In a single center study the authors retrospectively evaluated the outcomes of 561 THAs performed in 349 patients with a high hip dislocation including 32 men (9.2%) and 317 women (90.8%) with the follow up from 12 to 188 months (average 69,4 months). In 326 cases (58.1%) the dislocation was assessed as type C1, and in 235 cases (41.9%) — as type C2. The average age of the patients at the time of surgery was 47.6 (19 to 74) years, for men — 39.1 years and 48.1 years for women. Results. Paavilainen shortening osteotomy was performed in 100% of patients with type C2 and only in 50.6% of patients with type C1, p<0.001. The cup was implanted into the true acetabulum cavity in 99.1% of cases with type C2, and for type C1 only in 69.0% of cases, p<0.001. Lateral under-coverage of the cup in patients with type C2 required supplementing by femoral head autograft only in three cases, and for type C1 — in 18 patients, p = 0.009. In the group of C2, the mean length of the osteotomized fragment of the proximal femur was 78.6 mm compared to 62.5 mm in patients with type C1. This provided a better contact area between the greater trochanter and the femur and in 92.8% of cases fixation was done by cerclage wires and two screws. In the group of patients with type C1, this option was feasible only in 60.0% of cases. Odds ratio (OR) for fixation of the greater trochanter by a special plate for primary indications in patients with type C1 were 10 367, p = 0.008. Harris Hip score improved averaged from 39.5 points to 83.6, without statistically significant differences between groups of C1 and C2. Early complications included 9 dislocations (1.6%), 8 cases of femoral nerve neuropathy (1.4%) and 3 early infections (0.5%). No cases of sciatic nerve paresis were observed. Non-union of the greater trochanter was observed with almost equal frequency in patients with C1 and C2 types, and revision fixation was needed in 27 patients (6.8%). Revision arthroplasty was performed in 22 cases (3.9%) due to 4 infections, 2 aseptic loosening of the stem, 11 aseptic loosening of the acetabular component and 5 recurrent dislocations. Conclusion. The group of patients with high hip dislocation is very heterogenic in terms of severity of anatomical changes and demands different surgical tactics. Hartofolakidis classification helps the surgeon to select the best type of the surgical procedure, minimize the mistakes and predict treatment outcomes.