Background:Despite the longstanding awareness of the increasing incidence and consequences of periprosthetic proximal femoral fractures (PPFFs), and the rationale protective role of the preserved bone stock, no method for its evaluation, with the potential for routine clinical application, has been available. A novel method for the evaluation of preserved proximal femoral bone stock volume (V PF) in conventional primary total hip arthroplasty (THA) on routinely available hip radiographs was introduced and compared with clinical data. Methods:Study was designed according to the standard protocol for retrospective matched case-control research. 30 cases of late PPFFs (minimum 1 year postoperatively) were identified in the hospital database of all implanted Anatomic Benoist Girard (ABG) II femoral stems. For every case, 2 age-/sex-/implant size-/surgeon-matched controls were found. The V PF was evaluated for each hip, and the mean values in both groups were compared. The accuracy and intra-/inter-rater reliability of the novel method were tested. Regression subanalyses were performed to identify factors influencing the risk of PPFFs, and to assess correlations between VPF and other covariables. Results:The mean VPF in the group of cases was 113.8 ± 21.0 cm3 and significantly lower compared to 164.0 ± 38.4 cm3 in the control group (P < 0.01). The method's reliability and accuracy were within good to excellent range. The V PF was the sole significant factor influencing the risk of PPFFs (aOR = 0.92). The cut-off value was determined at 128.5 cm3. The regression analysis indicated an interplay of intuitively connected factors in the long-term PPFFs prognosis (V PF, stress shielding, subsidence). Conclusions:The presented results indicate that bone stock preservation (with VPF as a quantitative measure) is crucial for the prevention of late PPFFs.

Abstract: Periprosthetic proximal femoral fractures (PPFFs) are one of the main causes for revi-sion after total hip arthroplasty (THA), and are associated with some already known patient-/surgical-/implant-related risk factors. Despite the established increased risk of single and double-wedge femoral implants, the highest incidence in our institution has been observed with the anatomical cementless femoral component Anatomic Benoist Girard (ABG) II. The cumulative probability of PPFFs rose from 2.1% at 1 year to 6.5% at 10 years post-implantation, prompting comprehensive and multidisciplinary analy-sis. A novel parameter of preserved proximal femoral bone stock volume around im-planted ABG II femoral stems (VPF) and the modelling technique for its evaluation on the standing anteroposterior (AP) hip radiographs were introduced and estimated for each hip. Study was designed according to the standard protocol for matched case-control research. In the preliminary analysis, 5 age-/sex-/implant size-/surgeon-matched stratums, each comprising a case and 2 matched controls, were included. To calculate VPF, a mathematical model was constructed by composing parts of rotational bodies and a prism, subject to geometrical parameters of the proximal fe-mur that were assessed from radiographs. The mean value of VPF in the group of cases was 141.6 ± 36.2 cm3 and significantly lower compared to the mean volume of 254.2 ± 33.8 cm3 in the control group (P < 0.01). Based on the preliminary results, the VPF seems crucial for the PPFFs prevention. However, the mechanism of its effect works as a ‘black box’. At this point, it can be hypothesized that insufficient bone stock from the implantation onwards interferes with adequate osseointegration by itself acutely and with increased stress shielding in the long term. The bone stock preservation should be emphasized and considered at all steps, starting from the preoperative planning. The novel parameter in THA, and the method for its evaluation were introduced and are further extensively analysed. Keywords: Total Hip Arthroplasty, Periprosthetic Fracture, Bone Stock, Osseointegra-tion, Stress Shielding

Late periprosthetic fracture risk with uncemented ABG-II femoral stems at primary total hip arthroplasty (THA) has been reported before, but single-hospital surgeon-stratified reports of this implant have never been published. We asked whether periprosthetic fracture rates of ABG-II femoral stems implanted at a single tertiary hospital depended on patients’ age, gender and the operating surgeon. The study included 1531 consecutive primary ABG-II femoral stems implanted at a single tertiary hospital between January 1, 2012 and December 31, 2018. The Kaplan–Meier and Cox regression analyses were performed after 3.6–10.6 years of follow-up. In the cohort, we recorded 8 intraoperative, 22 early postoperative (within 90 days of implantation) and 26 late periprosthetic fractures (over 90 days postoperatively). The revision rate of ABG-II femoral stems was 5.1/100 component-years for early and 0.3/100 component-years for late periprosthetic fractures. The Kaplan–Meier cumulative probability of periprosthetic fracture was 2.1

Cemented total hip endoprosthesis Link Lubinus SP II has been used for decades with very good results in arthroplasty registries, but surgeon-stratified reports of endoprosthetic survival are very rare. The aim of the presented single hospital cohort analysis of this implant was to determine Link Lubinus SP II survival rates 10/15/20/25/30 years after the primary implantation and to find out whether endoprosthesis survival depended on patients’ age, gender, operated side, implanted femoral head diameter, and the operating surgeon. The study included 2943 consecutive primary Link Lubinus SP II hip endoprostheses implanted at the University Medical Centre Ljubljana, Department of Orthopaedic Surgery (Ljubljana, Slovenia) between January 1, 1985, and December 31, 2018. Kaplan–Meier analysis and Cox regression were performed after minimum two and maximum 30 years of follow-up. At 10/15/20/25/30 years after implantation, the estimated cumulative proportion of revision-free surviving Link Lubinus SP II total hip endoprostheses was 94/90/88/87/87% and the cumulative proportion with unremoved endoprosthetic components was 96/93/90/89/89%, respectively. Higher patient’s age at operation was associated with lower risk of subsequent implant removal (hazard ratio 0.97 for each additional year of age; 95% confidence interval 0.95–0.99; p = 0.00), while the patient’s gender, the implanted femoral head diameter, and the operating surgeon had no significant impact on implant survival. The study presents the largest published Link Lubinus SP II total hip arthroplasty cohort from a single non-developmental hospital with 26,981 component-years of observation. The findings highlight excellent outcomes of this implant in the elderly population, regardless of performance variability between surgeons.

The EcoFit® total hip endoprosthesis has recently been approved for clinical use in the USA as a substantially equivalent implant to the Taperloc® Hip System, but no report has directly compared their long-term results so far. The primary aim of the presented single-hospital EcoFit® cohort analysis was to determine femoral stem survival rates at 5/10 years of follow-up in comparison to eight Taperloc® studies published within the last decade (2011–2021). The secondary aim was to find out whether femoral stem survival depended on the patients’ age, gender and the operating surgeon. The retrospective surgeon-stratified observational cohort study included 680 consecutive patients with primary EcoFit® femoral stem implanted at the same operating theatre block of a single tertiary hospital between April 2009 and December 2015. Survival analyses after 6–12 years of follow-up were performed with the Kaplan–Meier method and the Cox regression. The cumulative proportion of revision-free surviving EcoFit® femoral stems 5/10 years after the primary implantation was 96/94

Our aim was to investigate the association of inflammasome polymorphisms NLRP3 rs35829419 (p. Q705K) and CARD8 rs2043211 (p. C10X) with aseptic loosening of total hip endoprostheses. We asked whether patients with the loosening of total hip arthroplasty earlier than 15 years after primary implantation had a higher proportion of the polymorphisms Q705K and C10X in comparison to subjects without loosening. A retrospective case-control study compared 36 patients with total hip endoprosthesis loosening earlier than 15 years after primary implantation and 51 control subjects with unloosened total hip endoprostheses, matched for gender, age, and follow-up period. Buccal mucosa samples were used for genomic DNA analysis and genotyped for NLRP3 rs35829419 and CARD8 rs2043211 using a fluorescence-based competitive allele-specific real-time polymerase chain reaction. The proportion of subjects with both wild-type NLRP3 and CARD8 (i.e., without Q705K or C10X) was considerably higher in the control group when compared with patients with early total hip arthroplasty loosening (49% vs. 28%; p = 0.05). After adjustment for gender, age, and follow-up, patients with combined wild type of both NLRP3 and CARD8 had significantly smaller odds for early implant loosening (odds ratio 0.33, p = 0.02). Investigated polymorphisms may influence several inflammatory pathways and contribute to the loosening of artificial implants with potential clinical significance for the appropriate selection of patients and endoprostheses when planning elective total hip arthroplasty. (c) 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:417-421, 2020

Case-reports of broken modular femoral necks have implied increased shear loading as the main culprit. The study aim was to determine whether total hip endoprostheses with modular femoral necks produced larger magnitudes of shear force, smaller leg length discrepancy and better WOMAC score in comparison to nonmodular implants. A single-surgeon series of unilateral uncemented primary total hip arthroplasties (50 modular ProfemurZ and 52 nonmodular Zweymuller) was compared retrospectively in hip force magnitudes computed with a previously validated static biomechanical model, radiographic changes before/after total hip arthroplasty, leg lengths and WOMAC. Modular implants ProfemurZ on average had larger shear force magnitudes in the femoral neck than nonmodular Zweymuller, but there was no significant difference in leg-length discrepancy or WOMAC score. In multivariate regression (adjusted for implant type, gender, age, BMI, leg length discrepancy) increase in shear force magnitude was an independent predictor of better WOMAC score, regardless of the implant type.

Our aim was to analyse the implant survival and infection rates of 101 consecutive silver-coated MUTARS (R) (= Modular Universal Tumour And Revision System) endoprostheses implanted at an independent orthopaedic tertiary hospital between April 1, 2011 and December 31. 2018 and to compare them with previous outcomes of the MUTARS (R) developmental hospitals. In addition, we tested the hypothesis that the infection-free survival rates of silver-coated implants depend on the patient's age, gender, pre-operative diagnoses and anatomical localization of the reconstruction. The cohort included 47 sarcoma resections, 29 revision arthroplasties, 20 metastatic resections. 3 benign bone tumours and 2 primary arthroplasties. Endoprosthesis was located in the distal femur (38 patients), proximal femur (29 patients), proximal humerus (12 patients), proximal tibia (10 patients), pelvis (6 patients), total femur (5 patients) and distal humerus (1 patient). The mean age at implantation was 49 (range 11-86) years and the mean follow-up 3.2 (range 0.1-7.7) years. Twenty-four patients required at least one subsequent revision operation and 15 endoprostheses had to be partially/totally removed. Patients' age was an independent risk factor for postoperative infection regardless of other confounding factors (hazard ratio 1.05 for each year; p = 0.02). With the overall postoperative infection rate 12 % (4 % reinfection + 8 % newly acquired) and cumulative partial/total implant removal rate 25 % after 5 years, complications were comparable to the previous series of the MUTARS (R) developmental hospitals with high variability between preoperative diagnoses and anatomical localizations. Silver-coated implants show a consistent trend of preventing infections in high-risk body regions and enabling more successful treatment should infection occur, but 10-15 years of clinical follow-up is required for further assessment.

Patients with equal objective leg length discrepancy (LLD) may have different subjective perceptions of this condition. Our aim was to analyze the effects of gender, age, operated side, surgical approach, body height, body mass index (BMI) and LLD measurements on self-perceived LLD after total hip arthroplasty (THA). Observational cohort study with minimum 5-year follow-up included 159 patients with unilateral primary THA at a single institution, who reported subjective feeling of equal or unequal leg lengths after THA. Gender, age, body height, BMI, surgical approach, preoperative and postoperative absolute/relative/pelvic radiographic LLD measurements were included in direct comparison between groups and multivariate analyses with self-perceived LLD as the outcome variable. Out of 159 participants, 39% subjectively perceived postoperative LLD, while others reported equal leg lengths. The two groups postoperatively differed in the median relative LLD (10 mm vs. 5 mm; p = 0.01) and WOMAC (230 mm vs. 110 mm; p < 0.01), but not in the pelvic radiographic LLD. After adjustment for gender, age, operated side and surgical approach, postoperative relative LLD (odds ratio 1.38 for each 5 mm increment; 95% CI 1.01–1.74) and combination of BMI < 26 kg/m2 and body height < 1.75 m (odds ratio 2.49; 95% CI 1.14–5.41) were independent risk factors for self-perceived LLD. Clinical relative LLD measurements are better predictors of self-perceived postoperative LLD than pelvic radiographic measurements. Patients with smaller body dimensions will more likely report subjective leg length inequality at a given objective LLD, regardless of gender or age.

BACKGROUND/OBJECTIVES Since a high prevalence of back anomalies has been reported among subjects with crossbite, the aim was to assess the degree of back symmetry among subjects with (crossbite) and without (control) unilateral functional crossbite during the pre-pubertal growth phase. METHODS A group of 70 subjects (36 boys, 34 girls; 6.8 ± 1.2 years) in the primary or mixed dentition phase were included. Clinical assessment of head posture, shoulder, scapula and hip height were performed with the subject standing, and differences between the left and right side greater than 5 mm recorded. Asymmetry of the scapula and trunk prominence greater than 8 mm was recorded along with the prominence of thoracic and lumbar paravertebral musculature during the forward-bending test. Back symmetry was assessed qualitatively and quantitatively on colour deviation maps of superimposed mirrored three-dimensional back scans at a tolerance level of 2 mm. RESULTS No significant differences were observed between the groups regarding the frequency of clinically assessed back anomalies. The percentage of back symmetry was slightly lower in the crossbite than that in the control group (71.4 ± 13.3% and 79.2 ± 12.1%, respectively). A significant association (P < 0.05) was seen between scapula plane inclination (OR = 3.41) and scapula prominence inequalities (OR = 3.29) and unilateral functional crossbite, while hip height inequalities (OR = 0.94) were more frequent in the control group. No associations were detected between the side of crossbite and side of prominence of back parameters. LIMITATIONS The use of different thresholds for clinical (5-8 mm) and three-dimensional (2 mm) symmetry assessment. CONCLUSIONS Although some degree of back asymmetry was detected in the crossbite group during the pre-pubertal growth phase, this asymmetry does not appear to be clinically relevant.

The femoral stem should protrude from femur by an appropriate vertical distance to allow leg length equalization at hip arthroplasty; this distance depends on the size/shape of medullary canal and implant. The relationship between femoral morphology and achievability of leg length restoration is currently unclear. Our aim was to examine the impact of the femoral canal flare index (CFI) on the risk of leg length discrepancy (LLD) after total hip arthroplasty with different femoral stems.

Stable insertion of large Schanz screws behind an intramedullary (IM) nail when lengthening over nails (LON) may be difficult due to the limited bone stock. Additionally, the highly probable contact between the screws and IM nail (which is difficult to avoid) increases the likelihood of infection spreading from the skin via Schanz screws directly to the IM nail. A new device for LON has been developed. Instead of inserting Schanz screws from the external fixator beside the IM nail (as in standard LON), a system of two overlaying plates was constructed. Schanz screws can be fixed to the plates without entering the bone. The plates are fixed to the bone using four angle stability screws. The holes in the plates offer stabile fixation for a chosen angle under which the screw is positioned through the cortical bone. Using the new system there is no need to place Schanz screws behind the IM nail. Instead, Schanz screws pass to the plate and not through the bone. The new system for elongation over IM nail is called “Over Nail Angle Stability-Double Plate System” (ONAS-DPS) [Antolič V (2013) Modular side device with an intramedullary nail for guiding a bone during its lengthening. World Intellectual Property Organization. International Publication number: WO 2013/176632 A1].

The evaluation of the biomechanical status of human hip joint was performed. Required parameters were assessed from standard antero-posterior rentgenographs and the value of contact stress on the weight bearing area is calculated. We analysed 45 dysplastic human hips and compared measured values to 81 healthy hips. The peak contact stress on the weight bearing area is considerably and statistically significantly higher in dysplastic hips compared to healthy hips. The Wiberg centre-edge angle is statistically significantly smaller in group of dysplastic hips compared to healthy hips.

The contact stress in a human hip is not uniform and it changes with different body positions. The changing location of the peak contact stress during gait may indicate the predilection sites for further development of osteoarthritis in the hip. On the basis of laboratory measurements and by using mathematical models of forces and stresses in human hip we determined the points of the peak contact stress in successive phases of gait. Results show that the peak stress points are mostly located in the posterior-medial portion of the weight bearing area, which corresponds well to the clinical observations. It is also shown that in the pathological conditions of hip dysplasia the peak contact stress trajectory is located more laterally and anteriorly.

Purpose Percutaneous vertebroplasty is a widely used vertebral augmentation technique. It is a minimally invasive and low-risk procedure, but has some disadvantages with a relatively high number of bone cement leaks and adjacent vertebral fractures. The aim of this cadaveric study was to determine the minimum percentage of cement fill volume in vertebroplasty needed to restore vertebral stiffness and adjacent intradiscal pressure.Methods Thirteen thoracolumbar spine mobile segments were loaded to induce a vertebral fracture. After fracture vertebroplasty was performed, four times in the same fractured vertebra. The injected cement volume was 5 % of the fractured vertebral volume to reach 5, 10, 15 and 20 % of cement fill. Biomechanical testing was performed before the fracture, after the fracture and after each cement injection.Results After vertebral fracture compressive stiffness was reduced to 47 % of the pre-fracture value and was partially restored to 61 % after 10 % cement fill. With vertebroplasty intradiscal pressure gradually increased, depending on specimen position, from 48 to a total of 71 % at 15 % of cement fill.Conclusions Compressive stiffness and intradiscal pressure increase with the percentage of cement fill. Fifteen per cent of cement fill was the limit beyond which no substantial increase in compressive stiffness or intradiscal pressure could be detected and is the minimum volume of cement we recommend for vertebroplasty. In the average thoracolumbar vertebra this means 4-6 ml of cement.

Abstract:Congenital idiopathic clubfoot is a deformity typically occurring in an otherwise healthy child which occurs in 11,4 in 10.000 live births. Approximately one-half of cases present with bilateral deformity and affects boys and girls equally. Clubfoot is characterized by adduction, supination and cavus deformity of the forefoot and midfoot, varus of the heel, and a fixed plantar flexion (equinus) of the ankle. Treatment od idiopathic type of clubfoot consists of corrective manipulation and casting by the Ponseti method, where usually four to six casts are needed. Equinus is corrected with tendo Achillis tenotomy followed by foot abduction brace application.Complex type of clubfoot, which has more severe rigid deformation, is present in 6,5% of all clubfeet and is refractory to the usual corrective manipulation and casting by the Ponsetti method. Clinically, complex clubfoot is characterized as short, stubby foot, having rigid equinus, severe adduction and plantar flexion of all metatarsals, a deep crease above the heel and a transverse crease in the sole of the foot. Modified Ponsetti method for treatment of complex clubfoot consists of simultaneus correction of adduction and heel varus and subsequent cavus and rigid equinus correction. After the Achillis tendon tenotomy, modified foot abduction brace is applied, where foot is in 40° outer rotation in contrast to 70° abduction used in less rigid congenital idiopathic clubfoot. Relapse occurs in 14% and is ussually related to problems with shoe fit and patient coplience.

STUDY DESIGN:Pilot single-centre, stratified, prospective, randomized, double-blinded, parallel-group, controlled study.OBJECTIVE:To determine whether vertebral end-plate perforation after lumbar discectomy causes annulus reparation and intervertebral disc volume restoration. To determine that after 6 months there would be no clinical differences between the control and study group.SUMMARY OF BACKGROUND DATA:Low back pain is the most common long-term complication after lumbar discectomy. It is mainly caused by intervertebral disc space loss, which promotes progressive degeneration. This is the first study to test the efficiency of a previously described method (vertebral end-plate perforation) that should advocate for annulus fibrosus reparation and disc space restoration.METHODS:We selected 30 eligible patients according to inclusion and exclusion criteria and randomly assigned them to the control (no end-plate perforation) or study (end-plate perforation) group. Each patient was evaluated in 5 different periods, where data were collected [preoperative and 6-mo follow-up magnetic resonance imaging and functional outcome data: visual analogue scale (VAS) back, VAS legs, Oswestry disability index (ODI)]. Intervertebral space volume (ISV) and height (ISH) were measured form the magnetic resonance images. Statistical analysis was performed using paired t test and linear regression. P<0.05 was considered statistically significant.RESULTS:We found no statistically significant difference between the control group and the study group concerning ISV (P=0.6808) and ISH (P=0.8981) 6 months after surgery. No statistically significant differences were found between ODI, VAS back, and VAS legs after 6 months between the 2 groups, however, there were statistically significant differences between these parameters in different time periods. Correlation between the volume of disc tissue removed and preoperative versus postoperative difference in ISV was statistically significant (P=0.0020).CONCLUSIONS:The present study showed positive correlation between the volume of removed disc tissue and decrease in postoperative ISV and ISH. There were no statistically significant differences in ISV and ISH between the group with end-plate perforation and the control group 6 months after lumbar discectomy. Clinical outcome and disability were significantly improved in both groups 3 and 6 months after surgery.