Introduction Stem malalignment can affect offset reconstruction and may result in gluteal muscle insufficiency. In this retrospective study, a novel geometric angle named ‘critical trochanter angle’ (CTA) is described and investigated towards the risk of malposition of a collarless straight tapered hydroxyapatite-coated stem in primary total hip arthroplasty (THA). Material and methods A total of 100 cementless THA were implanted in patients with unilateral coxarthrosis via the direct anterior ( n = 50) or direct lateral Hardinge approach ( n = 50) in a two surgeon setting using the Corail® or Trendhip® stem (DePuy Synthes or Aesculap). Stem alignment was analysed in postoperative AP pelvic radiographs and correlated to the CTA: the angle crest was defined by the intersection of the femoral shaft and neck axis and the angle was measured between the shaft axis and a leg intersecting the vertex between the lateral and superoposterior facet of the trochanter. Results Forty-seven stems were implanted in varus (≥ + 1°), 42 in neutral (< + 1°/> − 1°) and 11 in valgus position (≤ − 1°). The mean critical trochanter angle was 25.0° (SD ± 7.5°), and there was a negative and statistically significant correlation to stem alignment ( r = − 0.52; p ≤ 0.001) independent from the surgical approach. For stem malposition of 2° and above ( n = 23), mean CTA was 17.2° for varus ( n = 20) and 31.6° for valgus ( n = 3). A CTA lesser or equal to 22.75° had a sensitivity of 90% and specificity of 80% for varus stem position of 2° or greater. Specificity raised to 100% with a cutoff CTA of 12.5° or lesser. Conclusion Varus stem alignment in THA is associated with coxa vara deformity and a radiological low CTA. In preoperative planning, the critical trochanter angle can help to evaluate the risk for intraoperative stem malpositioning. If navigation or robotic assistance is not available when using this stem design, we recommend an intraoperative x-ray to verify correct implant positioning in patients with a CTA under 20° or above 30°.

Osteoarthritis and lesions to cartilage tissue are diseases that frequently result in impaired joint function and patient disability. The treatment of osteoarthritis, along with local bone defects and systemic skeletal diseases, remains a significant clinical challenge for orthopaedic surgeons. Several bone morphogenetic proteins (BMPs) are known to have osteoinductive effects, whereof BMP-2 and BMP-7 are already approved for clinical applications. There is growing evidence that the metabolism of bone as well as the cartilage damage associated with the above disease processes are strongly inter-related with the interactions of the inflammation-related pathways (in particular prostaglandin E₂ (PGE₂)) and osteogenesis (in particular bone morphogenetic protein-2 (BMP-2)). There is strong evidence that the pathways of prostaglandins and bone morphogenetic proteins are intertwined, and they have recently come into focus in several experimental and clinical studies. This paper focuses on PGE₂ and BMP-2 intertwining pathways in bone and cartilage metabolism, and summarizes the recent experimental and clinical data.

Background: Core decompression is a common surgical technique to treat osteonecrosis of the femoral head. The aim of this study is to evaluate the effect of the parameters "age" and "sex" on the outcome of this type of treatment. Methods: A prospective cohort study was performed. Eighty-six osteonecrotic hips with a mean follow-up of 32.5 months (± 24.8) after advanced core decompression were analysed regarding age-and sex-dependent treatment failure. Additionally, the modified Harris Hip Score and Numeric Rating Scale were compared regarding the parameters age and sex. Results: The mean hip survival of the male participants was 51.3 months (39.4% treatment failure), whereas females presented a longer, thus not significant, mean survival of 61.4 months (30% therapy failure; p = 0.48). The further evaluation revealed significantly better survival in the patients aged < 40 years (mean survival 66.09 months, 16% treatment failure) in comparison to those aged ≥ 40 years (mean survival 50.14 months, 46% therapy failure; p = 0.03). The modified Harris Hip Score and Numeric Rating Scale results of patients whose treatment did not fail during the study period were similar, irrespective of the patient's sex or age. Conclusions: The study shows that the number of therapy failures is significantly higher in older patients, with 40 years of age marking the borderline. Patients' sex does not seem to affect the outcome of treatment, and postoperative clinical scores appear to be identical with individuals not affected by therapy failure. Since age and sex are unalterable parameters, the study helps to provide valuable predictions regarding the chances of long-term hip survival after treatment of osteonecrosis.

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Purpose:Expandable titanium transforaminal lumbar interbody fusion (TLIF) devices are a relatively new group of implants allowing restoration of lumbar lordosis (LL) and thus improvement of sagittal alignment. The purpose of our study is to compare clinical and radiological results of two different expandable TLIF devices.Materials and Methods:In a retrospective study, patients who underwent TLIF surgery with a banana-shaped or straight TLIF cage in our spine center were analyzed. Primary outcome was change of disc height (DH), segmental lordosis angle (SLA), and lumbar lordotic angle (LLA). Moreover, basic patients parameters and cage subsidence were evaluated.Results:Sixty-one patients were studied (33 banana-shaped and 28 straight cages). DH changed in the banana group from 4.8 mm (standard deviation SD 2.5) to 10.4 (SD 2.4) and in the straight cage group from 6.2 mm (SD 2.5) to 9.6 mm (SD 1.7). The difference was statistically significant (P = 0.03). In addition, SLA correction was higher in the banana group with 5.8° (SD 5.0)–3.7° (SD 3.6), but not significant. LLA improved in the straight group with 5.2 (SD 6.4) compared to 3.7° (SD 5.8) in the banana group. We found subsidence in four patients (6.6%) in the banana-shaped group and nine cases (14.8%) in the other group.Conclusions:Expandable titanium implants show similar improvements in restoring segmental and global lordosis. Banana-shaped expandable cages offer higher potency restoring the intervertebral DH and show less rates of subsidence compared to straight expandable cages.