Surgeon-Stratified Periprosthetic Fracture Risk in a Single-Hospital Cohort of 1531 Uncemented ABG-II Femoral Stems at Primary Total Hip Arthroplasty

Purpose

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.

Methods

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.

Results

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% at one, 2.3% at 2, 3.2% at 5, and 6.5% at 10 years after the implantation. Higher patient's age at operation was an independent risk factor of subsequent periprosthetic fracture (hazard ratio 1.07, 95% confidence interval 1.03-1.10; p < 0.01), regardless of the operating surgeon. Most of the fractured femora were Dorr type C (stovepipe).

Conclusion

The study presents the largest published ABG-II femoral stem cohort from a single hospital so far with 9291 component-years of observation. Periprosthetic fracture risk of ABG-II increased with patients' age, had no variability between different surgeons, and was considerably higher from other uncemented femoral stems used at the same hospital.

Level of Evidence

III.

Clinical and laboratory predictors for prosthetic joint infection within the first postoperative days following primary total hip and knee arthroplasty

PURPOSE

To identify clinical and laboratory predictors for low- and high-grade prosthetic joint infection (PJI) within the first postoperative days following primary total hip/knee arthroplasty (THA/TKA).

METHODS

Institutional bone and joint infection registry of a single osteoarticular infection referral centre was reviewed to identify all osteoarticular infections treated between 2011 and 2021. Among them were 152 consecutive PJI (63 acute high-grade PJI, 57 chronic high-grade PJI, and 32 low-grade PJI) who also had primary THA/TKA performed at the same institution, which were retrospectively analyzed with multivariate logistic regression and covariables.

RESULTS

For each additional day of wound discharge, persistent wound drainage (PWD) predicted PJI in the acute high-grade PJI group with odds ratio (OR) 39.4 (p = 0.000, 95%CI 1.171-1.661), in the low-grade PJI group with OR 26.0 (p = 0.045, 95%CI 1.005-1.579), but not in the chronic high-grade PJI group (OR 16.6, p = 0.142, 95%CI 0.950-1.432). The leukocyte count product of pre-surgery and POD2 >100 predicted PJI in the acute high-grade PJI group (OR 2.1, p = 0.025, 95%CI 1.003-1.039) and in the chronic high-grade PJI group (OR 2.0, p = 0.018, 95%CI 1.003-1.036). Similar trend was also seen in the low-grade PJI group, but was not statistically significant (OR 2.3, p = 0.061, 95%CI 0.999-1.048).

CONCLUSIONS

The most optimal threshold value for predicting PJI was observed only in the acute high-grade PJI group, where PWD >three days after index surgery yielded 62.9% sensitivity and 90.6% specificity, whereby the leukocyte count product of pre-surgery and POD2 >100 showed 96.9% specificity. Glucose, erythrocytes, hemoglobin, thrombocytes, and CRP showed no significant value in this regard.

Case Report: Non-ossifying fibromas with pathologic fractures in a patient with NONO-associated X-linked syndromic intellectual developmental disorder

The NONO gene encodes a nuclear protein involved in transcriptional regulation, RNA synthesis and DNA repair. Hemizygous loss-of function, de novo or maternally inherited variants in NONO have been associated with an X-linked syndromic intellectual developmental disorder-34 (OMIM # 300967), characterized by developmental delay, intellectual disability, hypotonia, macrocephaly, elongated face, structural abnormalities of corpus callosum and/or cerebellum, congenital heart defect and left ventricular non-compaction cardiomyopathy. Few patients have been described in the literature and the phenotype data are limited. We report a 17-year-old boy with dolihocephaly, elongated face, strabismus, speech and motor delay, intellectual disability, congenital heart defect (ASD, VSD and Ebstein's anomaly), left ventricular non-compaction cardiomyopathy, bilateral inguinal hernia and cryptorchidism. Additional features included recurrent fractures due to multiple non-ossifying fibromas, thrombocytopenia, and renal anomalies. Exome sequencing revealed a de novo pathogenic variant (NM_001145408.2: c.348+2_ 348+15del) in intron 5 of the NONO gene. Renal anomalies and thrombocytopenia have been rarely reported in patients with NONO-X-linked intellectual disability syndrome, while recurrent fractures due to multiple non-ossifying fibromas have not previously been associated with this syndrome. The phenotypic spectrum of NONO-X-linked intellectual disability syndrome may be broader than currently known.

Implant Survival of 680 Consecutive EcoFit® Flat Single-Wedge Cementless Femoral Stems is Equivalent to the Taperloc® Total Hip Arthroplasty Series

Introduction

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.

Materials and Methods

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.

Results

The cumulative proportion of revision-free surviving EcoFit® femoral stems 5/10 years after the primary implantation was 96/94%, respectively, and the cumulative proportion of unremoved stems was 99/98%, respectively. The EcoFit® stem revision rate of 0.46 per 100 components-years was not significantly different from most Taperloc® cohorts. Higher age increased the risk of subsequent EcoFit® femoral stem revision (hazard ratio 1.039, p = 0.048) while the impact of gender and the operating surgeon was not statistically significant.

Conclusions

The study presents the first surgeon-stratified cohort analysis of the EcoFit®-Implantcast femoral stem from a single hospital with 5851 component years of observation. Long-term EcoFit® survival rates are comparable to the Taperloc® hip system. Caution is warranted when using such flat cementless single-wedge stems in the elderly population.

Giant Cell Tumor of Bone Versus Tenosynovial Giant Cell Tumor - Similarities and Differences

Giant cell tumor of bone (GCTB) and tenosynovial giant cell tumor (TGCT) share misleadingly similar names, soft texture and brown color macroscopically, osteoclast-like multinucleated giant cells microscopically and localisation in the musculoskeletal system. However, these two tumor types are biologically and clinically two distinct entities with different natural courses of progression and considerably different modes of surgical and medical treatment. In this article, we provide a detailed update on the similarities and the differences between both tumor types.GCTB is a locally aggressive osteolytic bone tumor, commonly seen in patients in their third decade of life. It usually occurs as a solitary lesion in the meta-epiphyseal region of long bones. It can be diagnosed using plain radiographic imaging, CT radiography or MRI to estimate the tumor extent, soft tissue and joint involvement. GCTB is usually treated with intralesional excision by curettage. Systemically, it can be treated with bisphosphonates and denosumab or radiotherapy.TGCT is a rare, slowly progressing tumor of synovial tissue, affecting the joint, tendon sheath or bursa, mostly seen in middle-aged patients. TGCT is usually not visible on radiographs and MRI is mostly used to enable assessment of potential bone involvement and distinguishing between two TGCT types. Localised TGCT is mostly treated with marginal surgical resection, while diffuse TGCT is optimally treated with total synovectomy and is more difficult to remove. Additionally, radiotherapy, intraarticular injection of radioactive isotopes, anti-TNF-α antibodies and targeted medications may be used.

Surgeon-stratified cohort analysis of 1976 cementless Zweymüller total hip arthroplasties from a single hospital with 23,255 component years of follow-up

INTRODUCTION

The third-generation Zweymüller hip endoprosthesis has been used for decades with excellent results in arthroplasty registries, but surgeon-stratified reports on this implant are still scarce. The aim of the presented single-hospital cohort analysis of the third-generation Endoplus-Zweymüller primary total hip arthroplasty was to determine implant survival rates until the first revision/removal at 10/15/20/25 years after implantation and to find out whether implant survival depended on the operating surgeon, patient's age and gender, operated side (right/left), season of the year and the set of implanted components (SL-PLUS femur, BICON-PLUS acetabulum or both components).

MATERIALS AND METHODS

The retrospective observational cohort study included 1976 consecutive patients with primary BICON/SL-PLUS Zweymüller hip endoprosthesis implanted at the same operating theater block of the University Medical Centre Ljubljana, Department of Orthopaedic Surgery (Ljubljana, Slovenia) between January 1, 1993 and May 1, 2014. Survival analyses were performed with the Kaplan-Meier method and the Cox regression analysis after minimum 5 and maximum 26 years of follow-up.

RESULTS

At 10/15/20/25 years after implantation, the cumulative proportion of revision-free surviving Zweymüller total hip endoprostheses was 92/90/85/81% and the cumulative proportion with unremoved immobile components was 93/91/87/84%, respectively. After adjustment for age, gender and operated side, less experienced surgeons (odds ratios 2.34-5.00), season of the year at primary implantation (spring vs. winter odds ratio 1.74) and the use of BICON-PLUS acetabulum with femoral stem from another manufacturer (odds ratio 2.23) were significant risk factors of worse implant survival.

CONCLUSIONS

The study presents the largest published third-generation Zweymüller BICON/SL-PLUS total hip arthroplasty cohort from a single non-developmental hospital with 23,255 component years of observation. Study findings indicate the impact of environmental factors at primary implantation and variability between different surgeons on the long-term implant survival.

Novel ASAP1-USP6, FAT1-USP6, SAR1A-USP6, and TNC-USP6 fusions in primary aneurysmal bone cyst

Aneurysmal bone cyst (ABC) is a benign but locally aggressive neoplasm, with a tendency for local recurrence. In contrast to other bone tumors with secondary cystic change, ABC is characterized by USP6 gene rearrangement. There is a growing list of known USP6 fusion partners, characterization of which has been enabled with the advent of next-generation sequencing (NGS). The list of known fusion partners includes CDH11, CNBP, COL1A1, CTNNB1, EIF1, FOSL2, OMD, PAFAH1B1, RUNX2, SEC31A, SPARC, STAT3, THRAP3, and USP9X. Using NGS, we analyzed a series of 11 consecutive ABCs and identified USP6 fusions in all cases, providing further evidence that USP6 fusions are universally present in primary ABCs. We identified four novel fusion partners in five ABCs and confirmed them by RT-PCR and Sanger sequencing, ASAP1, FAT1, SAR1A, and TNC (in two cases). Because of high sensitivity and specificity, detection of a USP6 fusion by NGS may assist in differentiating between ABC and its mimics, especially in small biopsy samples when a definite diagnosis cannot be achieved on morphological grounds alone. Further studies with a large number of cases and follow-up are needed to determine whether different fusion partners are associated with specific clinical and pathologic features of ABCs.

Association of NLRP3 and CARD8 Inflammasome Polymorphisms With Aseptic Loosening After Primary Total Hip Arthroplasty

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. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:417-421, 2020.

What Factors Are Associated With Neck Fracture in One Commonly Used Bimodular THA Design? A Multicenter, Nationwide Study in Slovenia

BACKGROUND

Femoral stems with bimodular (head-neck as well as neck-body) junctions were designed to help surgeons address patients' hip anatomy individually. However, arthroplasty registers have reported higher revision rates in stems with bimodular junctions than in stems with modularity limited to the head-neck trunnion. However, to our knowledge, no epidemiologic study has identified patient-specific risk factors for modular femoral neck fractures, and some stems using these designs still are produced and marketed.

QUESTIONS/PURPOSES

The purposes of this study were (1) to establish the survival rate free from aseptic loosening of one widely used bimodular THA design; (2) to define the proportion of patients who experienced a fracture of the stem's modular femoral neck; and (3) to determine factors associated with neck fracture.

METHODS

In this retrospective, nationwide, multicenter study, we reviewed 2767 bimodular Profemur® Z stems from four hospitals in Slovenia with a mean followup of 8 years (range, 3 days to 15 years). Between 2002 and 2015, the four participating hospitals performed 26,132 primary THAs; this implant was used in 2767 of them (11%). The general indications for using this implant were primary osteoarthritis (OA) in 2198 (79%) hips and other indications in 569 (21%) hips. We followed patients from the date of the index operation to the date of death, date of revision, or the end of followup on March 1, 2018. We believe that all revisions would be captured in our sample, except for patients who may have emigrated outside the country, but the proportion of people immigrating to Slovenia is higher than the proportion of those emigrating from it; however, no formal accounting for loss to followup is possible in a study of this design. There were 1438 (52%) stems implanted in female and 1329 (48%) in male patients, respectively. A titanium alloy neck was used in 2489 hips (90%) and a cobalt-chromium neck in 278 (10%) hips. The mean body mass index (BMI) at the time of operation was 29 kg/m (SD ± 5 kg/m). We used Kaplan-Meier analysis to establish survival rates, and we performed a chart review to determine the proportion of patients who experienced femoral neck fractures. A binary logistic regression model that controlled for the potential confounding variables of age, sex, BMI, time since implantation, type of bearing, diagnosis, hospital, neck length, and neck material was used to analyze neck fractures.

RESULTS

There were 55 (2%) aseptic stem revisions. Survival rate free from aseptic loosening at 12 years was 97% (95% confidence interval [CI] ± 1%). Fracture of the modular neck occurred in 23 patients (0.83%) with a mean BMI of 29 kg/m (SD ± 4 kg/m.) Twenty patients with neck fractures were males and 19 of 23 fractured necks were long. Time since implantation (odds ratio [OR], 0.55; 95% CI 0.46-0.66; p < 0.001), a long neck (OR, 6.77; 95% CI, 2.1-22.2; p = 0.002), a cobalt-chromium alloy neck (OR, 5.7; 95% CI, 1.6-21.1; p = 0.008), younger age (OR, 0.91; 95% CI, 0.86-0.96; p < 0.001), and male sex (OR, 3.98; 95% CI, 1.04-14.55; p = 0.043) were factors associated with neck fracture.

CONCLUSIONS

The loosening and neck fracture rates of the Profemur® Z stem were lower than in some of previously published series. However, the use of modular femoral necks in primary THA increases the risk for neck fracture, particularly in young male patients with cobalt-chromium long femoral necks. The bimodular stem we analyzed fractured unacceptably often, especially in younger male patients. For most patients, the risks of using this device outweigh the benefits, and several dozen patients had revisions and complications they would not have had if a different stem had been used.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Patient-dependent risk factors for self-perceived leg length discrepancy after total hip arthroplasty

PURPOSE

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).

MATERIALS AND METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

The impact of canal flare index on leg length discrepancy after total hip arthroplasty

INTRODUCTION

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.

MATERIALS AND METHODS

The study cohort included 126 patients with unilateral primary total hip arthroplasty due to idiopathic osteoarthritis and three different types of implanted femoral stems. The impact of CFI on postoperative LLD was assessed with separate logistic regression model for each implant and covariables of age, gender, body mass index and femoral neck resection level.

RESULTS

Higher CFI was an independent risk factor for postoperative LLD ≥ 5 mm with odds ratio 4.5 (p = 0.03) in 49 stems with cementless metaphyseal fixation Implantcast-EcoFit®, regardless of the femoral neck resection level. CFI had no significant impact on LLD in 30 stems with cementless diaphyseal fixation EndoPlus-Zweymüller® or 47 cemented collared stems Link-SPII®. No significant difference was observed between groups in pre/postoperative WOMAC scores, postoperative radiographic LLD, subjectively reported LLD, insole use or complications after mean 6.8 years of follow-up.

CONCLUSIONS

Higher CFI increases the risk of clinically detectable postoperative LLD in single-wedge femoral stems with cementless metaphyseal fixation. CFI has no significant impact on LLD in femoral stems with cementless diaphyseal fixation or cemented fixation.

Risk factors for unsuccessful acetabular press-fit fixation at primary total hip arthroplasty

BACKGROUND

Surgeon at primary total hip arthroplasty sometimes cannot achieve sufficient cementless acetabular press-fit fixation and must resort to other fixation methods. Despite a predominant use of cementless cups, this issue is not fully clarified, therefore we performed a large retrospective study to: (1) identify risk factors related to patient or implant or surgeon for unsuccessful intraoperative press-fit; (2) check for correlation between surgeons' volume of operated cases and the press-fit success rate.

HYPOTHESIS

Unsuccessful intra-operative press-fit more often occurs in older female patients, particular implants, due to learning curve and low-volume surgeons.

MATERIALS AND METHODS

Retrospective observational cohort of prospectively collected intraoperative data (2009-2016) included all primary total hip arthroplasty patients with implant brands that offered acetabular press-fit fixation only. Press-fit was considered successful if acetabulum was of the same implant brand as the femoral component without additional screws or cement. Logistic regression models for unsuccessful acetabular press-fit included patients' gender/age/operated side, implant, surgeon, approach (posterior n=1206, direct-lateral n=871) and surgery date (i.e. learning curve).

RESULTS

In 2077 patients (mean 65.5 years, 1093 females, 1163 right hips), three different implant brands (973 ABG-II™-Stryker, 646 EcoFit™ Implantcast, 458 Procotyl™ L-Wright) were implanted by eight surgeons. Their unsuccessful press-fit fixation rates ranged from 3.5% to 23.7%. Older age (odds ratio 1.01 [95% CI: 0.99-1.02]), female gender (2.87 [95% CI: 2.11-3.91]), right side (1.44 [95% CI: 1.08-1.92]), surgery date (0.90 [95% CI: 1.08-1.92]) and particular implants were significant risk factors only in three surgeons with less successful surgical technique (higher rates of unsuccessful press-fit with Procotyl™-L and EcoFit™ [P=0.01]). Direct-lateral hip approach had a lower rate of unsuccessful press-fit than posterior hip approach (P<0.01), but there was no correlation between surgeons' volume and rate of successful press-fit (Spearman's rho=0.10, P=0.82). Subcohort of 961 patients with 5-7-years follow-up indicated higher early/late cup revision rates with unsuccessful press-fit.

DISCUSSION

Success of press-fit fixation depends entirely on the surgeon and surgical approach. With proper operative technique, the unsuccessful press-fit fixation rate should be below 5% and the impact of patients' characteristics or implants on press-fit fixation is then insignificant. Findings of huge variability in operative technique between surgeons of the presented study emphasize the need for surgeon-specific data stratification in arthroplasty studies and indicate the possibility of false attribution of clinically observed phenomena to patient-related factors in pooled data of large centers or hip arthroplasty registers.

LEVEL OF EVIDENCE

Level III, retrospective observational case control study.

Does Preoperative Antimicrobial Prophylaxis Influence the Diagnostic Potential of Periprosthetic Tissues in Hip or Knee Infections?

BACKGROUND

Undiagnosed low-grade prosthetic joint infections (PJI) are recognized as an important reason for early failure of presumably aseptic revisions. Preoperatively administered antimicrobial prophylaxis reduces the incidence of PJI but it may reduce the sensitivity of microbiologic periprosthetic tissue cultures and consequently increase the incidence of undiagnosed septic prosthetic joint failures, which can lead to catastrophic serial revisions.

QUESTIONS/PURPOSES

We wished to determine whether administration of preoperative antibiotics decreases the likelihood of diagnosing PJI in patients undergoing revision hip or knee arthroplasty in whom infection is suspected.

METHODS

We prospectively enrolled and evaluated 40 patients (29 with THAs and 11 with TKAs) who met the following inclusion criteria: older than 18 years, with suspected PJI of unknown cause, undergoing surgical revision. After arthrotomy, three tissue samples were obtained for microbiologic analysis and diagnosis, and antimicrobial prophylaxis (cefazolin 2 g intravenously) then was administered. Later during the procedure, but before débridement and irrigation, the second set of three tissue samples was obtained from the same surgical area and was cultured. Tissue concentration of prophylactic antibiotic was verified with the second set of samples. A positive culture result was defined as one or more positive cultures (growth on agar at or before 14 days). We then compared the yield on the microbiologic cultures obtained before administration of antibiotics with the yield on the cultures obtained after antibiotics were administered. An a priori analysis was performed; with the numbers available, we had 98% power to detect a difference in diagnostic sensitivity of 33%.

RESULTS

With the numbers available, we found no difference in the likelihood that an infection would be diagnosed between the samples obtained before and after administration of antimicrobial prophylaxis (odds ratio [OR] for positive microbial culture = 0.99; 95% CI, 0.40-2.48; p = 0.99). All measured tissue concentrations of cefazolin were greater than the minimum inhibitory concentration, therefore we found that antibiotic prophylaxis was adequate at the time of second-set tissue specimen recovery.

CONCLUSIONS

Results from this small, prospective series suggest that preoperative antimicrobial prophylaxis may be administered safely even in patients undergoing revision hip or knee arthroplasty in which microbiologic sampling is planned without compromising the diagnostic sensitivity of tissue sample cultures. However, before applying our results more generally, our findings need to be confirmed in larger, multicenter studies that would allow evaluation by sex, procedure, bacteriology, and other potentially important factors.

LEVEL OF EVIDENCE

Level I, diagnostic study.

Geometric analysis of indications for minimally invasive distal metatarsal osteotomy in treatment of hallux valgus

Background

Minimally invasive distal metatarsal osteotomy (MIDMO) is to be indicated for all patients with angles of IMA <20° and HV <40°, but many authors doubt whether this procedure is capable of correcting all types of hallux valgus deformities. The aims of this study were to perform a geometric analysis of MIDMO indications and to show which preoperative radiological parameters are necessary to achieve sufficient contact between bone fragments and sufficient correction with this operative technique.

Methods

A geometric mathematical model in AP and lateral radiographic plane was created based on preoperative measurements of the intermetatarsal angle (IMA), subcapital metatarsal width, medial bunion eminence, and metatarsal length. MIDMO was simulated with possible dorsal/plantar fragment displacement in order to assess postoperative contact between fragments (either 4–5 mm or half of the metatarsal width) and sufficient correction (postoperative IMA 8°).

Results

The metatarsal neck should be at least 8 mm wider from the bunion eminence to achieve the minimally required contact between fragments. For sufficient correction, the metatarsal head translation should be at least 0.018 of the metatarsal length for every degree of IMA reduction. The medial bunion eminence, in comparison with metatarsal width/length size, determines whether MIDMO is a suitable procedure for a given patient.

Conclusions

MIDMO cannot sufficiently correct all deformations within the boundaries of IMA angle <20° and HV angle <40°. In patients with large eminences and narrow metatarsals, complications related to insufficient postoperative fragment contact can be expected, while sufficient hallux valgus correction in patients with small eminences and long metatarsals is questionable.

Electronic supplementary material

The online version of this article (doi:10.1186/s13018-015-0304-7) contains supplementary material, which is available to authorized users.

Unfavorable hip stress distribution after Legg-Calvé-Perthes syndrome: a 25-year follow-up of 135 hips

To study the effect of hip and pelvis geometry on development of the hip after Perthes disease, we determined the resultant hip force and contact hip stress distribution in a population of 135 adult hips of patients who had been treated for Perthes disease in childhood. Contra-lateral hips with no record of disease were taken as the control population. Biomechanical parameters were determined by mathematical models for resultant hip force in one-legged stance and for contact hip stress, which use as an input the geometrical parameters assessed from anteroposterior radiographs. The mathematical model for stress was upgraded to account for the deviation of the femoral head shape from spherical. No differences were found in resultant hip force and in peak contact hip stress between the hips that were in childhood subject to Perthes disease and the control population, but a considerable (148%) and significant (p < 0.001) difference was found in the contact hip stress gradient index, expressing an unfavorable, steep decrease of contact stress at the lateral acetabular rim. This finding indicates an increased risk of early coxarthritis in hips subject to Perthes disease.

The impact of leg length discrepancy on clinical outcome of total hip arthroplasty: comparison of four measurement methods

In a single-surgeon series of 119 patients with unilateral primary uncemented total hip arthroplasty, four leg-length discrepancy measurement methods (absolute, relative, trochanteric, standardized-trochanteric) were analyzed for their impact on WOMAC score, Oxford Hip Score and self-perceived leg-length discrepancy. After adjustment for age, gender and BMI, postoperative WOMAC scores correlated only with clinical absolute measurements of leg elongation (P=0.05). Self-perceived leg-length discrepancy corresponded best to the clinically measured relative leg-length discrepancy (11 mm perceived vs. 7 mm unperceived; P=0.04) while there was no significant correspondence with radiographic measurements or leg elongation magnitudes. Within the <10 mm range of mean postoperative leg length discrepancy in the studied series, its impact on the overall clinical satisfaction was detectable but not considerable.

Optimal mechanical environment of the healing bone fracture/osteotomy

The aim of this paper is to review recent experimental and clinical publications on bone biology with respect to the optimal mechanical environment in the healing process of fractures and osteotomies. The basic postulates of bone fracture healing include static bone compression and immobilisation/ fixation for three weeks and intermittent dynamic loading treatment afterwards. The optimal mechanical strain should be in the range of 100-2,000 microstrain, depending on the frequency of the strain application, type of bone and location in the bone, age and hormonal status. Higher frequency of mechanical strain application or larger number of repetition cycles result in increased bone mass at the healing fracture site, but only up to a certain limit, values beyond which no additional benefit is observed. Strain application and transition period from non-load-bearing to full load-bearing can be modified by implants allowing dynamisation of compression and generating strains at the fracture healing site in a controlled manner.

Cumulative hip contact stress predicts osteoarthritis in DDH

Hip stresses are generally believed to influence whether a hip develops osteoarthritis (OA); similarly, various osteotomies have been proposed to reduce contact stresses and the risk of OA. We asked whether elevated hip contact stress predicted osteoarthritis in initially asymptomatic human hips. We identified 58 nonoperatively treated nonsubluxated hips with developmental dysplasia (DDH) without symptoms at skeletal maturity; the control group included 48 adult hips without hip disease. The minimum followup was 20 years (mean, 29 years; range, 20-41 years). Peak contact stress was computed with the HIPSTRESS method using anteroposterior pelvic radiographs at skeletal maturity. The cumulative contact stress was determined by multiplying the peak contact stress by age at followup. We compared WOMAC scores and radiographic indices of OA. Dysplastic hips had higher mean peak contact and higher mean cumulative contact stress than normal hips. Mean WOMAC scores and percentage of asymptomatic hips in the study group (mean age 51 years) were similar to those in the control group (mean age 68 years). After adjusting for gender and age, the cumulative contact stress, Wiberg center-edge angle, body mass index, but not the peak contact stress, independently predicted the final WOMAC score in dysplastic hips but not in normal hips. Cumulative contact stress predicted early hip OA better than the Wiberg center-edge angle.

LEVEL OF EVIDENCE

Level II, prognostic study. See the Guidelines for Authors for a complete description of levels of evidence.