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The osteonecrosis of the femoral head implies significant disability partly due to pain. After conventional core decompression using a 10-mm drill, patients normally are requested to be non-weight bearing for several weeks due to the risk of fracture. After core decompression using multiple small drillings, patients were allowed 50% weight bearing. The alternative of simultaneous implantation of a tantalum implant has the supposed advantage of unrestricted load bearing postoperatively. However, these recommendations are mainly based on clinical experience. The aim of this study was to perform a finite element analysis and confirm the results by clinical data after core decompression and after treatment using a tantalum implant. Postoperatively, the risk of fracture is lower after core decompression using multiple small drillings and after the implantation of a tantalum rod according to finite element analysis compared to core decompression of one 10-mm drill hole. According to the results of this study, a risk of fracture exists only during extreme loading. The long-term results reveal a superior performance for core decompression presumably due to the lack of complete bone ingrowth of the tantalum implant. In conclusion, core decompression using small drill holes seems to be superior compared to the tantalum implant and to conventional core decompression. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to analyze predicting factors for a conversion to a total hip replacement (THR) after mini-open arthrotomy for treatment of femoroacetabular impingement (FAI)., Methods: Between 2011 and 2016, we identified 32 patients, who were treated for FAI with a mini-open arthrotomy and received after mean time of 2.1 ± 1.4 years a THR. These patients were compared to 47 cases who did not receive a THR (mean follow-up: 4.3 ± 0.7 years) to explore pre- and intra-operative factors associated with a conversion to THR. The results were presented in separated Kaplan-Meier curves with log rank test for significance and hazard ratios., Results: A lateral joint space width of > 4 mm showed a higher THR-free survival rate compared to < 4 mm (p = 0.001); analogously one-sided (acetabular/femoral) 3-4° cartilage damage had a comparable THR-free survival rate than 1-2° kissing lesions (p = 0.001). Furthermore, an intact labrum without treatment and good cartilage status, a refixed labrum after rim resection in case of a pincer type FAI, or a refixed teared labrum were associated with a longer THR-free time than an untreated labrum accompanied by a poor cartilage status or an ossified labrum (p = 0.002). The strongest independent factor for a conversion to THR was femoral cartilage damage grade 1 and higher (p = 0.046). However, the rate of available patients was 53.0%., Conclusion: The success of a joint-preserving mini-open arthrotomy seems to be dependent on the status of the radiological joint space width and the intra-operative cartilage status of the lateral edge., (© 2021. SICOT aisbl.)

Background: The diagnosis of low-grade periprosthetic joint infections (PJIs) is challenging, because patients may present with unspecific symptoms, false-negative cultures, or marginally elevated values of serum biomarkers like C-reactive protein (CRP). This may lead to the unintended implantation of a revision prosthesis into an infected surgical site with a repeat risk of short-term failure. Conversely, false diagnosis of joint infection may result in multistage revision procedures, which expose the patient to unnecessary surgical procedures and inappropriate antibiotic treatment. Here, we investigated whether synovial biomarkers can preoperatively distinguish between aseptic prosthesis loosening and low-grade joint infection and the most accurate biomarker combinations., Methods: Inclusion criteria for the study were indication for revision arthroplasty due to aseptic implant failure, acute high-grade infection, or (suspected) low-grade infection. We prospectively collected synovial fluid of patients undergoing revision arthroplasty for quantitative measurement of alpha defensin, CRP, interleukin (IL-6), IL-10, and lipopolysaccharide binding protein (LBP)., Results: The classification tree method revealed alpha defensin and CRP as the most suitable biomarker combination to distinguish between aseptic loosening and low-grade joint infection. The combination of CRP > 2.0 mg/L and alpha defensin > 90.000 pg/mL correctly identified nine  of 11 patients with low-grade infection., Conclusions: Alpha defensin plus CRP seems to be the most helpful combination for pre-operative discrimination of aseptic loosening vs. low-grade joint infection.

Purpose: Local cartilage and bony defects, which are too large for joint preserving cartilage treatment are difficult to treat. The implantation of a mini-resurfacing implant (Hemicap®, 2med, Hamburg, Germany) may be a possible alternative treatment for these patients. This partial replacement fills the defect and restores a smooth and continuous articular surface. The aim of this study was to determine short- to midterm results of the treatment of local cartilage defects of the femoral head using the Hemicap®., Methods: Since 04/2011 16 patients with osteonecrosis of the femoral head greater ARCO stage II or local femoral cartilage lesions (< 35 mm) were treated with the implantation of the Hemicap® implant. A clinical and radiological follow-up was conducted., Results: The clinical results showed a significant improvement of the function and pain of the hip according to the Harris Hip Score from 56 (±14) preoperative to 77 (±15) post-operative 25 months after implantation of the Hemicap®. In the meantime, in four patients the Hemicap® had to be converted to a total hip arthroplasty due to loosening, progredience of the osteonecrosis or degeneration of the acetabulum., Conclusions: The implantation of the mini-resurfacing implant Hemicap® seemed to be an alternative treatment for local cartilage defects of the femoral head to postpone the implantation of a total hip arthroplasty. However, the clinical outcome seems to be inferior to total hip arthroplasty. Furthermore, due to a high rate of conversion to total hip arthroplasty (25%) the application of this implant is questionable. If the implant is considered as a treatment option at least patient selection and enlightenment for this treatment with the high risk of failure and progression of osteoarthritis is very important.

Purpose: Short-stem implants provide a bone-preserving alternative in total hip arthroplasty. However, some evidence exists that the smaller implant-bone contact surface may compromise primary stability and impair osseo-integration. The purpose of this study was to analyse the migration characteristics of the Nanos® short stem over two years by means of model-based roentgen stereophotogrammetric analysis (MBRSA)., Methods: Eighteen patients aged 53.6 ± 7.2 years were included. After being treated with a Nanos implant, 14 patients were followed-up radiologically at three, six, 12 and 24 months by means of MBRSA. Early implant migration was calculated. Clinical data have been assessed in addition., Results: Highest translational migration was observed with a mean value of -0.22 ± 0.39 mm along the proximo-distal axis after three months and highest rotational migration with 0.8 ± 3.2° also around the y-axis after two years. The resulting total migration was 0.46 ± 0.31 mm, with the largest proportion occurring within three months after surgery (0.40 ± 0.34 mm)., Conclusion: The Nanos short-stem hip implant shows only a slight initial migration within three months after implantation, followed by secondary stabilisation. These results suggest both good primary stability and osseo-integration, suggesting a low risk of aseptic loosening.

Purpose: For further development of better bone-preserving implants in total hip arthroplasty (THA), we need to look back and analyse established and clinically approved implants to find out what made them successful. Finite element analysis can help do this by simulating periprosthetic bone remodelling under different conditions. Our aim was thus to establish a numerical model of the cementless straight stem for which good long-term results have been obtained., Methods: We performed a numeric simulation of a cementless straight stem, which has been successfully used in its unaltered form since 1986/1987. We have 20 years of experience with this THA system and implanted it 555 times in 2012. We performed qualitative and quantitative validation using bone density data derived from a prospective dual-energy X-ray absorptiometry (DEXA) investigation., Results: Bone mass loss converged to 9.25% for the entire femur. No change in bone density was calculated distal to the tip of the prosthesis. Bone mass decreased by 46.2% around the proximal half of the implant and by 7.6% in the diaphysis. The numeric model was in excellent agreement with DEXA data except for the calcar region, where deviation was 67.7%., Conclusions: The higher deviation in the calcar region is possibly a sign of the complex interactions between the titanium coating on the stem and the surrounding bone. We developed a validated numeric model to simulate bone remodelling for different stem-design modifications. We recommend that new THA implants undergo critical numeric simulation before clinical application.

Purpose: The number of candidates for a total hip arthroplasty (THA) is steadily increasing, while the average patient age is decreasing for primary THA. The rise in THA is mainly due to excellent clinical outcomes and the extended longevity of modern implants. Short stem arthroplasties with predominantly metaphyseal fixation such as the Metha® stem are suggested for young patients. It is hypothesised that the more physiological load transfer of these devices reduces stress shielding, which in turn may reduce the risk of aseptic loosening. However, patients with femoral deformities often require a deviation of the resection height. To this end, our aim was to evaluate how resection height influences strain patterns in order to characterise possible limits for short stem implantation., Methods: Biomechanical testing using ten strain gauges on synthetic bone illustrated the strain patterns of three different resection heights (0, +5 and +10 mm) for the Metha stem., Results: The greatest differences in strains were displayed at the "high" (most proximal) resection height (+10 mm) when compared to the non-implanted strain pattern. At the medial calcar, the strain was 143% for +10 mm, 96% for +5 mm and 94% for 0 mm. Overall, discrepancies were less for deeper resections., Conclusions: The deeper the resection, the more similar the strain patterns are when compared to a non-implanted synthetic bone. Changes in strain patterns are induced by variation in the varus/valgus positioning of the implant and by different offsets.

Purpose: The cementless Bicontact total hip arthroplasty (THA) system (AESCULAP AG, Tuttlingen, Germany) was introduced in 1986/1987 and has been in successful clinical use in an unaltered form up to today. Although good long-term results with the Bicontact stem have been published, it is questionable whether the implant provides the criteria for a state-of-the-art stem regarding proximal bone stock preservation. The purpose of the study was to monitor the periprosthetic bone mineral density (BMD) in a prospective two-year follow-up dual-energy X-ray absorptiometry (DEXA) study., Methods: After power analysis, a consecutive series of 25 patients with unilateral Bicontact stem implantation was examined clinically and underwent DEXA examinations. Scans of seven regions of interest were taken preoperatively and at one week, six months, and one and two years., Results: One patient required stem revision due to a deep infection. The Harris Hip Score increased significantly by 44 points. The most significant bone loss was observed in the calcar region (R7) in the first six months (-19.2 %). It recovered in the following 18 months to -8.5 %. The BMD in the greater trochanter dropped significantly after six months and remained stable at this level. BMD exceeded baseline values in distal regions and even more in the lesser trochanter region after two years., Conclusions: We conclude that the Bicontact stem provides adequate proximal bone stock preservation. We observed some signs of stress shielding at the tip of the stem, which is inevitable to some degree in THA with cementless straight stems. However, in this prospective DEXA investigation, we showed that proximal off-loading does not occur after THA with the Bicontact system. Thus, we believe that this stem is still a state-of-the-art implant.

Purpose: On the basis of positive clinical results with mid- and long-term follow-up using the Mayo short stem, the Metha neck-preserving stem (BBraun, Aesculap, Tuttlingen, Germany) was introduced. The purpose of this study was to validate the implant design by direct acquisition of bone remodelling data from total hip arthroplasty (THA) recipients using dual-energy X-ray absorptiometry (DEXA)., Methods: After power analysis, 25 patients were included in this prospective study. Patients were examined clinically and underwent DEXA examinations preoperatively and postoperatively at one week, six months and one and two years after THA. Gruen zones were adapted to the short stem design (R1-R7)., Results: The Harris Hip Score (HHS) increased significantly by 31 points. No stem had to be revised. Bone mineral density (BMD) in the greater trochanter decreased significantly from 0.78 g/cm(2) postoperatively to 0.72 g/cm(2) two years after surgery. Marginal changes were seen in the lateral distal regions (R4-R5). In the minor trochanter region, BMD increased significantly after two years by 12.9%. In the calcar region, BMD exceeded the baseline value by 6.1% two years after implantation., Conclusions: Stress shielding seems to occur at the greater trochanter due to the vast cross-section of the implant. However, the aim of proximal load transfer of the Metha stem seems to be partially achieved. DEXA analysis revealed a concentrated load distribution on the medial portion of the femur, which is an important region to guarantee long-term implant survival.

Purpose: The treatment of severe foot deformities in children or adolescents is complex and demanding to the surgeon. This paper describes the technical strategy of using a Taylor spatial frame and reports on the functional outcome., Methods: The Taylor spatial frame was used by a single surgeon in patients with severe foot deformities. Seven patients with eight severe deformities were treated. Mean patient age at surgery was 15.1 (9-29) years. A double Taylor spatial frame reconstruction was mounted to the limb. All patients had a midtarsal osteotomy and an additional inverse dome-shaped calcaneus osteotomy. Assessed measures were pre- and postoperative deformity and associated complications and clinical results according to Ferreira et al., Results: Mean follow-up was 576.5 (359-987) days. The final functional outcome according to Ferreira was good in seven cases, fair in none, and poor in one. Early complications included pin-tract infection, temporary hypoesthesia, and temporary shortening of the tendon of the M. flexor digitorum. At follow-up there was no deformity recurrence., Conclusion: In children or adolescents, the innovative treatment using the Taylor spatial frame and a double osteotomy allows joint-preserving correction of severe foot deformities. However, the complication rate is relatively high due to the severely deformed feet. Furthermore, the Taylor spatial frame is expensive. Thus, this treatment is only recommended for severe foot deformities and should be handled by experienced orthopedic surgeons.

The aim of this study was to evaluate the clinical and radiological outcome of the treatment of osteonecrosis of the femoral head by implantation of an osteonecrosis intervention rod. In this retrospective study the follow-up of 19 patients with 23 osteonecrotic femoral heads treated with implantation of an osteonecrosis intervention implant was assessed. From 19 patients with 23 necrotic femoral heads, there were 13 cases in which a total hip replacement was necessary. This implies a survival rate of 44% after implantation of an osteonecrosis intervention rod after a mean follow-up of 1.45 years. The outcome after core decompression combined with the insertion of a tantalum osteonecrosis intervention implant did not show superior results compared to core decompression alone. This is in contrast to existing studies. In addition, this study showed that in cases of total hip replacement, no problems appeared during explantation of the tantalum rod.