Introduction

The functional ante-inclination (AI) of the cup after total hip arthroplasty (THA) is a key component in the combined sagittal index (CSI) to predict joint stability after THA. To accurately predict AI, we deducted a mathematic algorithm between the radiographic anteversion (RA), radiographic inclincation (RI), pelvic tilting (PT), and AI. The current study aims (1) to validate the mathematic algorithm; (2) to convert the AI limits in the CSI index (standing AI ≤ 45°, sitting AI ≥ 41°) into coronal functional safe zone (CFSZ) and explore the influences of the stand-to-sit pelvic motion (PM) and pelvic incidence (PI) on CFSZ; (3) to locate a universal cup orientation that always fulfill the AI criteria of CSI safe zone for all patients or subgroups of PM(PM ≤ 10°, 10° < PM ≤ 30°, and PM > 30°) and PI (PI≤ 41°, 41°< PI ≤ 62°, and PI >62°), respectively.

Chronic postsurgical pain (CPSP) can occur after elective mid/hindfoot and ankle surgery. Effective treatment approaches for CPSP in this population have not been extensively investigated. The impact of multimodal strategies on CPSP following elective mid/hindfoot surgery is unknown due to both the heterogeneity of acute pain management and the lack of a recognized definition specific to this type of surgery. This study aimed to identify and evaluate current pain management strategies after elective mid/hindfoot and ankle surgery.

We conducted a systematic review under Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Three databases (MEDLINE, Embase and Cochrane Library) were electronically searched for English studies published between 1990 and July 2017. Reference lists of relevant systematic reviews were also manually searched. Comparative studies of adults undergoing elective mid/hindfoot and ankle surgery were included. Two reviewers independently reviewed studies and assessed their methodological quality.

Of 1,159 studies, seven high-quality randomized controlled trials met our inclusion criteria. Though all studies examined regional anesthesia techniques, intervention heterogeneity precluded meta-analysis. Participants were typically followed up to 48 hours post-operatively. Interventions effective at reducing postoperative pain and/or opioid consumption included inserting popliteal catheters under ultrasound instead of nerve stimulation guidance, infusing perineural dexamethasone, bupivacaine, or ropivacaine perioperatively, and adding a femoral catheter infusion to a popliteal catheter infusion. Only one study assessed pain six months following elective mid/hindfoot and ankle surgery, demonstrating significant pain reduction with activity with the addition of a femoral to popliteal catheter infusion.

There is an overwhelming lack of evidence regarding CPSP and its management for patients undergoing elective mid/hindfoot and ankle surgery. Although specific regional anesthesia techniques and adjuncts may be effective at reducing in-hospital pain and opioid consumption after elective mid/hindfoot and ankle surgery, our systematic review identified only seven studies addressing multimodal pain management in this population. Further comparative studies with longer-term follow-up are required.

Chronic postoperative pain (CPP) can occur in elective mid/hindfoot and ankle surgery patients. Multimodal pain management has been reported to reduce postoperative pain and opioid use, which may prevent the development of CPP. However, few studies have examined the impact of multimodal pain management strategies on CPP following complex elective mid/hindfoot and ankle surgery. The purpose of this study was to 1) evaluate current pain management strategies and 2) determine current definitions, incidence, and prevalence of CPP after elective mid/hindfoot and ankle surgery.

Three databases (MEDLINE, Embase and Cochrane Library) were manually and electronically searched for English language studies published between 1990 and July 2017. For the first aim, we included comparative studies of adults undergoing elective mid/hindfoot and ankle surgery that investigated pre-, peri- or postoperative pain management. For the second aim, we included observational studies examining CPP definition, incidence, and prevalence. Two reviewers independently screened titles and abstracts, followed by full texts. Conflicts were resolved through discussion with a third reviewer. Reviewers also independently assessed the quality of studies meeting inclusion criteria using the Joanna Briggs Institute Critical Appraisal Checklist.

For the first aim, 1159 studies were identified by the primary search, and seven high quality randomized controlled trials were included. Ankle arthroplasty or fusion and calcaneal osteotomy were the most common procedures performed. The heterogeneity of study interventions, though all regional anesthesia techniques, precluded meta-analysis. Most investigated continuous popliteal, sciatic and/or femoral nerve blockade. Participants were typically followed up to 48 hours postoperatively to examine postoperative pain levels and morphine consumption in hospital. Interventions effective at reducing postoperative pain and/or morphine consumption included inserting popliteal catheters using ultrasound instead of nerve stimulation guidance, perineural dexamethasone, and adding continuous femoral blockade to continuous popliteal blockade. Using more than one analgesic was generally more effective than using a single agent. Only two studies examined longer term pain management. One found no difference in pain levels and opioid consumption at two weeks with perineural or systemic dexamethasone use. The other found that pain with activity was significantly reduced at six months postoperatively with the addition of a femoral catheter infusion to a popliteal catheter infusion. For the second aim, only two studies of the 747 identified were selected. One prospective observational study defined CPP as moderate-to-severe pain at one year after foot and ankle surgery, and reported 21% and 43% of patients as meeting their definition at rest and with activity, respectively. The other study was a systematic review that reported 23–60% of patients experienced residual pain after total ankle arthroplasty.

There is no standardized definition of CPP in this population, and incidence and prevalence are rarely reported and vary largely based on definition. Although regional anesthesia may be effective at reducing in-hospital pain and opioid consumption, evidence is very limited regarding longer-term pain management and associated outcomes following elective mid/hindfoot and ankle surgery.

Biodegradable metals as orthopaedic implant materials receive substantial scientific and clinical interest. Marketed cardiovascular products confirm good biocompatibility of iron. Solid iron biodegrades slowly in vivo and has got supra-physiological mechanical properties as compared to bone and porous implants can be optimized for specific orthopaedic applications. We used Direct Metal Printing (DMP)3 to additively manufacture (AM) scaffolds of pure iron with fine-tuned bone-mimetic mechanical properties and improved degradation behavior to characterize their biocompatibility under static and dynamic 3D culture conditions using a spectrum of different cell types.

Atomized iron powder was used to manufacture scaffolds with a repetitive diamond unit cell design on a ProX DMP 320 (Layerwise/3D Systems, Belgium). Mechanical characterization (Instron machine with a 10kN load cell, ISO 13314: 2011), degradation behavior under static and dynamic conditions (37ºC, 5% CO2 and 20% O2) for up of 28 days, with μCT as well as SEM/energy-dispersive X-ray spectroscopy (EDS) (SEM, JSM-IT100, JEOL) monitoring under in vivo-like conditions. Biocompatibility was comprehensively evaluated using a broader spectrum of human cells according to ISO 10993 guidelines, with topographically identical titanium (Ti-6Al-4V, Ti64) specimen as reference. Cytotoxicity was analyzed by two-way ANOVA and post-hoc Tukey's multiple comparisons test (α = 0.05).

By μCT, as-built strut size (420 ± 4 μm) and porosity of 64% ± 0.2% were compared to design values (400 μm and 67%, respectively). After 28 days of biodegradation scaffolds showed a 3.1% weight reduction after cleaning, while pH-values of simulated body fluids (r-SBF) increased from 7.4 to 7.8. Mechanical properties of scaffolds (E = 1600–1800 MPa) were still within the range for trabecular bone, then. At all tested time points, close to 100% biocompatibility was shown with identically designed titanium (Ti64) controls (level 0 cytotoxicity). Iron scaffolds revealed a similar cytotoxicity with L929 cells throughout the study, but MG-63 or HUVEC cells revealed a reduced viability of 75% and 60%, respectively, already after 24h and a further decreased survival rate of 50% and 35% after 72h. Static and dynamic cultures revealed different and cell type-specific cytotoxicity profiles. Quantitative assays were confirmed by semi-quantitative cell staining in direct contact to iron and morphological differences were evident in comparison to Ti64 controls.

This first report confirms that DMP allows accurate control of interconnectivity and topology of iron scaffold structures. While microstructure and chemical composition influence degradation behavior - so does topology and environmental in vitro conditions during degradation. While porous magnesium corrodes too fast to keep pace with bone remodeling rates, our porous and micro-structured design just holds tremendous potential to optimize the degradation speed of iron for application-specific orthopaedic implants. Surprisingly, the biological evaluation of pure iron scaffolds appears to largely depend on the culture model and cell type. Pure iron may not yet be an ideal surface for osteoblast- or endothelial-like cells in static cultures. We are currently studying appropriate coatings and in vivo-like dynamic culture systems to better predict in vivo biocompatibility.