Evaluation of the anatomical features, details of surgical technique and results of the THA in patients with CDH (type C1 and C2 by G. Hartofilakidis).

From 2001 to 2016 years one surgical team performed 683 THA in patients with CDH. We retrospectively studied 561 total hip arthroplasties in 349 patients, follow-up rate was 82.1%, from 12 to 188 months (mean 69.4). The results were evaluated by clinical examination, X-rays analysis, Harris Hip Score.

Unilateral high hip dislocation was observed in 175 patients (31.2%), in these cases often have underdeveloped half of the pelvis on the side of the dislocation. Type C1 was observed in 326 cases and type C2 – in 235 cases. Type C1 in comparison with C2 has less leg length discrepancy, developed shape of proximal femur, presence of supraacetabular osteophyte. The mean displacement of femoral head was 47.6 mm (from 29 to 55) for C1 and 63.4 mm (from 41 to 78) for C2. Average offset in C1 was 50.1 mm (37–63) and in C2 − 44.3 mm (34–52).

Shortening osteotomy by T. Paavilainen performed in 165 cases (50.6%) with C1 dysplasia and in 235 cases (100%) with C2. The features of surgical technique were small size of the cups with obligatory additional screw fixation of the cup and small offset of the stems. The cup was positioned into the true acetabulum in 99.1% cases of C2 type, for C1 – only 69.0%). The cups size 44 mm were used in 97.3% cases for type C2 and in 78.6% cases for type C1. For shortening osteotomy in 76.3% cases Wagner Cone stems were used.

Early complications included 9 dislocations (1.6%), 8 femoral nerve neuropathies (1.4%) and 3 infections (0.5%). There is no sciatic nerve palsy. Late complications included dislocation in two hips (1.1%), nonunion of the greater trochanter (8.4%), aseptic loosening of the femoral component − 2 (0.8 %), aseptic loosening of the cup − 11 (1.6%). Average Harris Hip score improved from 39.5 to 83.6 with unsignificant diffence between types C1 and C2 (from 37.3 to 81.4 and from 40.4 to 85.1 consequently). Revision rate was 2.1% for type C1 and 5.5% for type C2.

Hip replacement surgery in patients with high hip dislocation is very challenging. Type C2 dysplasia has only one surgical option with good long-term results – placement of the cup into the true acetabulum and shortening osteotomy. Its advantages include leg length alignment and decreased risk of sciatic nerve injury. Type C1 dysplasia presents more heterogenic group of patients and allows to use several surgical options – different placement of the cup and surgical approach without shortening osteotomy. Functional results in patients with type C1 are a little bit worse in comparison with type C2, but C1 had less risk of complications. The main problem of shortening osteotomy by Paavilainen is delayed union and non-union of great trochanter.

To evaluate the proportion of microbial associations causing PJI, diversity of their strains and impact on treatment failure after the removal of the hip implant and insertion of a spacer.

Spectrum of pathogens in 189 cases of PJI was studied retrospectively. Strains were isolated from the joint aspirates, tissue samples and removed orthopedic devices. The cohort comprised 144 cases of PJI after primary THA and 45 cases after the hip replacement revision surgery. All patients underwent first stage of two-stage revision procedure which involves the removal of a hip implant, debridement of infected periprosthetic tissues and subsequent insertion of a bone cement spacer. There were 92 males and 97 females (median age of 57 yrs). Statistical analysis of the results was performed with GraphPad Prism 6.0 (California, USA).

Microbial associations were detected in 28.6% (n=54) of PJI cases. Gram-positive bacteria prevailed in both groups with mono- and polymicrobial etiology. There were 52.5% of S. aureus isolates in monomicrobial group and 25% isolates in polymicrobial group (p=0.0002). This also included 8.4 and 20.6% isolates of MRSA, respectively (p<0.0001). CNS were detected in 20.1% of mono- and 27.9% of polymicrobial infection isolates, including about 40% of MRSE in both groups. Gram-negative pathogens accounted for 25.7% of isolates in polymicrobial group and 14.1% in monomicrobial group (p=0.022). Non-fermenting bacteria prevailed among Gram-negative strains presented in associations. Acinetobacter sp. and P. aeruginosa were identified in 7.4% (p=0.043) and 5.1% (p=0.56) of polymicrobial isolates. The percentage of treatment failure after the removal of the hip implant and insertion of a spacer was considerably higher (p<0.0001) in patients with polymicrobial than monomicrobial infection: 72.2 vs 25.2%, respectively. The proportion of isolates in microbial associations involving Gram-negative pathogens was 61.5% in patients with infection recurrence and 26.7% in patients with a successful outcome of the surgery (p=0.033).

Microbial associations were found in 28.6% of PJI cases after hip arthroplasty. They posed a significant risk for treatment failure after removal of the hip implant and insertion of a spacer. The multidrug-resistant strains (MRSA, Acinetobacter sp. and P. aeruginosa) were often isolated in microbial associations. Our results suggest that further study of the risk factors for polymicrobial infection is necessary in patients with PJI. Identification of a patient group at high risk for developing polymicrobial PJI will allow prescription of empiric antimicrobial therapy in time, taking into account possible multi-resistant pathogens.