The relationship between spino-pelvic-hip mobility and quality of life before and after total hip arthroplasty.

INTRODUCTION: Total hip arthroplasty (THA) can significantly improve quality of life (QOL) in patients with hip osteoarthritis. A relationship exists between activity levels and postoperative QOL, but its determinants are not well known. The aim of this work was to investigate the relationship between hip, pelvis and lumbar spine mobility and alignment before and after THA with QOL. MATERIAL AND METHODS: Consecutive patients with hip arthrosis and an indication for THA were included prospectively between July 2019 and December 2020, and they underwent lateral radiographs in free-standing, extension, relaxed- and flexed-seated position. Spinopelvic and hip parameters were measured, as well as their changes between positions to assess hip, pelvis and lumbar spine mobility. Patients were also administered QOL questionnaires. Data were collected preoperatively and 6 and 12 months postoperatively. RESULTS: Seventy patients were included; QOL significantly increased 6 months after THA (from 18 [10; 27] to 61 [48; 72], p < 0.001). QOL further increased by 10 points or more after 6 months in 18% of patients, while it decreased in 16%. The latter showed higher pelvic range of motion (between flexion and extension) than the former. CONCLUSIONS: This study confirmed that QOL is significantly improved by THA, and that spinopelvic alignment and function can play a role. Future work should elucidate how to better predict postoperative QOL from preoperative patient characteristics to improve patient treatment and establish early postoperative physical therapy for patients who could benefit from postoperative improvement of activity-related QOL.

CT-based analysis of sagittal and coronal lumbar endplate morphology: multivariate analysis of factors associated with endplate depth.

PURPOSE: Lumbar endplate morphology varies in individuals; thus, custom-made implants are sometimes more useful than standardized implants. This study aimed to analyze endplate morphology and factors associated with endplate depth using computed tomography (CT) in a non-symptomatic population. METHODS: In total, 118 lumbar CT images of non-symptomatic individuals without severe degenerative change (aged 20-79 years) were retrospectively reviewed. The following radiographic parameters were measured in each lumbar vertebral segment (T12-S1) to determine endplate depth: superior/inferior endplate depth in the midsagittal and midcoronal planes, disk angle, and height. The relationship between baseline demographics (age, sex, body mass index [BMI], Hounsfield unit of the L1 vertebral body, and pelvic incidence [PI]) and endplate depth was analyzed. RESULTS: Toward the caudal level, the superior endplate depth increased, sagittal inferior depth decreased, and coronal inferior depth increased. Multivariate analysis revealed that endplate depth was significantly associated with age (p < 0.001), while inferior endplate depth was associated with PI (p = 0.01). Superior endplate depth was associated with female sex (sagittal: p = 0.005, coronal: p = 0.002). Endplate depth, except for the inferior coronal region, was associated with low BMI (sagittal superior: p = 0.005; coronal superior and sagittal inferior: p = 0.02). CONCLUSION: Endplate depths tend to be larger toward the caudal level, particularly in the superior endplate. Surgeons should thoroughly evaluate the preoperative CT image because various endplate morphologies require attention to cage shape when performing lumbar interbody fusion, especially in patients who are older, are female, have low BMI, and have large PI. LEVEL OF EVIDENCE I: Diagnostic: individual cross-sectional studies with consistently applied reference standard and blinding.

Recurrence rate after posterior percutaneous screw fixation without anterior debridement for pyogenic spondylitis compared with conservative treatment: a propensity score-matched analysis.

PURPOSE: Previous studies have shown that percutaneous pedicle screw (PPS) posterior fixation without anterior debridement for pyogenic spondylitis can improve patient quality of life compared with conservative treatment. However, data on the risk of recurrence after PPS posterior fixation compared with conservative treatment is lacking. The aim of this study was to compare the recurrence rate of pyogenic spondylitis after PPS posterior fixation without anterior debridement and conservative treatment. METHODS: The study was conducted under a retrospective cohort design in patients hospitalized for pyogenic spondylitis between January 2016 and December 2020 at 10 affiliated institutions. We used propensity score matching to adjust for confounding factors, including patient demographics, radiographic findings, and isolated microorganisms. We estimated hazard ratios (HRs) and 95% confidence intervals (CIs) for recurrence of pyogenic spondylitis during the follow-up period in the matched cohort. RESULTS: 148 patients (41 in the PPS group and 107 in the conservative group) were included. After propensity score matching, 37 patients were retained in each group. PPS posterior fixation without anterior debridement was not associated with an increased risk of recurrence compared with conservative treatment with orthosis (HR, 0.80; 95% CI, 0.18-3.59; P = 0.77). CONCLUSIONS: In this multi-center retrospective cohort study of adults hospitalized for pyogenic spondylitis, we found no association in the incidence of recurrence between PPS posterior fixation without anterior debridement and conservative treatment.

Association of two-staged surgery with systemic perioperative complications in lateral lumbar interbody fusion for adult spinal deformity: a propensity score-weighted study.

PURPOSE: Adult spinal deformity (ASD) surgery carries a higher risk of perioperative systemic complications. However, evidence for the effect of planned two-staged surgery on the incidence of perioperative systemic complications is scarce. Here, we evaluated the effect of two-staged surgery on perioperative complications following ASD surgery using lateral lumbar interbody fusion (LLIF). METHODS: The study was conducted under a retrospective multi-center cohort design. Data on 293 consecutive ASD patients (107 in the two-staged group and 186 in the one-day group) receiving corrective surgery using LLIF between 2012 and 2021 were collected. Clinical outcomes included occurrence of perioperative systemic complications, reoperation, and intraoperative complications, operation time, intraoperative blood loss, transfusion, and length of hospital stay. The analysis was conducted using propensity score (PS)-stabilized inverse probability treatment weighting to adjust for confounding factors. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated in a PS-weighted cohort. RESULTS: In this cohort, 19 (18.4%) patients in the two-staged group and 43 (23.1%) patients in the one-day group experienced any systemic perioperative complication within 30 days following ASD surgery. In the PS-weighted cohort, compared with the patients undergoing one-day surgery, no association with the risk of systemic perioperative complications was seen in patients undergoing two-staged surgery (PS-weighted OR 0.78, 95% CI 0.37-1.63; p = 0.51). CONCLUSION: Our study suggested that two-staged surgery was not associated with risk for perioperative systemic complications following ASD surgery using LLIF.

Sagittal alignment in patients with flexion contracture of the hip before and after total hip arthroplasty.

INTRODUCTION: In hip osteoarthritis, hip flexion contracture can severely alter the patient's alignment, and, therefore, affect the patient's quality of life (QOL). Hip contracture is not well-studied, partly because of the difficulties of its diagnosis. The aim of this study was to propose a quantitative definition of hip flexion contracture, and to analyse sagittal alignment in these patients compared to non-contracture ones, before and 12 months after total hip arthroplasty (THA). MATERIALS AND METHODS: Consecutive patients with hip arthrosis and an indication for THA were included (N = 123). Sagittal full-body radiographs were acquired in free standing position and in extension. QOL questionnaires were administered before and after surgery. Spinopelvic parameters were measured, including the pelvic-femur angle (PFA). Patients with low pelvic incidence (< 45°) were included in the hip contracture group if PFA > 5°, or PFA > -5° when pelvic incidence ≥ 45°. RESULTS: 29% of patients were in the hip flexion contracture group, and they showed lower pelvic tilt than the no-contracture group (p < 0.001), larger lumbar lordosis (LL) and smaller PI-LL (p < 0.001), as well as a forward position of the head. 16% of patients still had hip contracture 12-months postop. Contracture patients showed higher QOL scores after surgery. CONCLUSIONS: The proposed method to diagnose hip contracture group allowed to define a group of patients who showed a specific pattern of sagittal spinopelvic alignment. These patients improved their alignment and quality of life postoperatively, but their hip mobility was not always restored. Diagnosing these patients is a first step toward the development of more specific surgical approaches, aiming to improve their surgical outcome.

Are sagittal spinopelvic radiographic parameters significantly associated with quality of life of adult spinal deformity patients? Multivariate linear regression analyses for pre-operative and short-term post-operative health-related quality of life.

PURPOSE: To evaluate the association in ASD patients between spinopelvic sagittal parameters and health-related quality of life (HRQL), adjusted for demographic and surgical variables. METHODS: We constructed multiple linear regression models to investigate pre-operative (PreOp) and 6-month post-operative (PostOp) HRQL as assessed by the Oswestry Disability Index (ODI), with sagittal parameters as independent variables adjusted for potential confounders, such as age, sex, body mass index, past spine surgery, types of surgical treatment, and complications. RESULTS: A total of 204 patients (164 women, 40 men, mean age 53.1 years) were included in this study. In multivariate models for PreOp ODI, no significant association was observed between PreOp HRQL and sagittal parameters when adjusted for covariates. Interestingly, age, sex, American Society of Anesthesiologists score, and body mass index were still significantly associated with PreOp HRQL. In contrast to PreOp analysis, there was a significant association between PostOp worse HRQL (higher ODI) and positive T1 sagittal tilt (T1ST: the angle between a line drawn from the center of the femoral head axis to the midpoint of the T1 vertebral body and a vertical line). Sagittal vertical axis had a weaker association with HRQL than T1ST. PostOp ASD patients lose flexibility in the fused spinal segment, and might be predisposed to symptoms related to spinal sagittal malalignment due to limited compensatory ability to maintain a balanced standing posture. Interestingly, in patients with sagittal imbalance, low pelvic tilt (PT) of <20 was significantly associated with PostOp worse HRQL; this suggests that lack of pelvic compensatory ability can cause significant disability after ASD surgery. CONCLUSIONS: Pre-operatively, the impact of sagittal parameters on HRQL was not as strong as reported in the previous studies that used univariate analysis. Not only sagittal parameters, but also the pre-operative patient's general condition should be carefully reviewed when considering indication for ASD surgery. In contrast, although this is a short-term follow-up study, PostOp HRQL was significantly associated with sagittal parameters. When ASD surgery has been indicated, restoration of spinal sagittal alignment is certainly important for PostOp HRQL.

Sagittal malalignment has a significant association with postoperative leg pain in adult spinal deformity patients.

PURPOSE: To evaluate the association between spinopelvic sagittal parameters and leg pain in patients with adult spinal deformity (ASD) after adjusting for demographic and surgical variables. METHODS: A multicenter prospective ASD database (European Spine Study Group) was retrospectively reviewed. The characteristics (age, sex, body mass index, comorbidity, history of spine surgery, and radiographical coronal and sagittal parameters) of patients with preoperative and 6-month postoperative leg pain (PostLP; numerical rating scale score ≥5) were analyzed using univariate and multivariate analyses. RESULTS: In this study, 204 patients (164 women and 40 men; mean age 53.1 years) were included. Fifty-three percent of the patients had preoperative leg pain (PreLP). The patients with PreLP had significantly worse sagittal parameters and less coronal Cobb angle than those with less leg pain; however, this association disappeared after adjustment for covariates. The PreLP of the ASD patients was successfully treated surgically in most cases; however, 24 % of the patients still had unexpected residual leg pain. Postoperative sagittal malalignment (sagittal vertical axis ≥40 mm, T1 sagittal tilt ≥0°, pelvic tilt ≥30°) was a significant risk factor of PostLP even after adjusting for covariates. CONCLUSIONS: Leg pain in patients with ASD was significantly associated with sagittal malalignment especially after surgical treatments. As these patients lose flexibility in the fused spinal segment, they can only depend on the remaining compensatory mechanisms below the pelvis (e.g., the hips and knees) to maintain a balanced posture. This may lead to a predisposition of these patients to postoperative leg symptoms related to spinal sagittal malalignment.

Additive-manufactured patient-specific titanium templates for thoracic pedicle screw placement: novel design with reduced contact area.

PURPOSE: Image-based navigational patient-specific templates (PSTs) for pedicle screw (PS) placement have been described. With recent advances in three-dimensional computer-aided designs and additive manufacturing technology, various PST designs have been reported, although the template designs were not optimized. We have developed a novel PST design that reduces the contact area without sacrificing stability. It avoids susceptibility to intervening soft tissue, template geometric inaccuracy, and difficulty during template fitting. METHODS: Fourteen candidate locations on the posterior aspect of the vertebra were evaluated. Among them, locations that had high reproducibility on computed tomography (CT) images and facilitated accurate PS placement were selected for the final PST design. An additive manufacturing machine (EOSINT M270) fabricated the PSTs using commercially pure titanium powder. For the clinical study, 36 scoliosis patients and 4 patients with ossification of the posterior longitudinal ligament (OPLL) were treated with thoracic PSs using our newly developed PSTs. We intraoperatively and postoperatively evaluated the accuracy of the PS hole created by the PST. RESULTS: Based on the segmentation reproducibility and stability analyses, we selected seven small, round contact points for our PST: bilateral superior and inferior points on the transverse process base, bilateral inferior points on the laminar, and a superior point on the spinous process. Clinically, the success rates of PS placement using this PST design were 98.6 % (414/420) for scoliosis patients and 100 % (46/46) for OPLL patients. CONCLUSION: This study provides a useful design concept for the development and introduction of patient-specific navigational templates for placing PSs.

A multi-center study of reoperations within 30 days of spine surgery.

PURPOSE: To investigate the incidence and causes of reoperations within 30 days of spine surgery. METHODS: Patients who underwent spine surgery between 2002 and 2012, at one of 9 institutions, were enrolled. The causes of all reoperations, within 30 days of the index surgery, were reviewed. The incidence of reoperations within 30 days were calculated and compared according to the preoperative diagnosis, use of instrumentation, surgical level, and approach. Moreover, the distribution of the causes for reoperations within the 30-day period was also assessed. RESULTS: The overall incidence of reoperations, within 30 days of spine surgery, was 1.6% (175/10,680). Patients who underwent instrumentation procedures demonstrated a higher incidence of reoperations than patients who underwent procedures without instrumentation (P < 0.001). Moreover, patients diagnosed with preoperative trauma had a higher incidence of reoperation than those with other diagnoses (P < 0.001). Surgical site infection (SSI), postoperative epidural hematoma, pedicle screw malposition, and inadequate decompression were the four main causes of reoperation. Motor paralysis, due to epidural hematoma, was the predominant cause of reoperations during the hyper-acute phase (0-1 days, postoperatively), whereas SSI was the dominant cause during the sub-acute phase (11-30 days, postoperatively). CONCLUSIONS: This large, multi-center study indicated the causes and incidence of reoperations, within 30 days of the initial spinal surgery. Based on these data, spinal surgeons can provide patients with information that allows them to better understand the surgical risk and expected post-surgical management.

Spontaneous anterior arch fracture of the atlas following C1 laminectomy without fusion: A report of three cases and finite element analysis.

BACKGROUND: Only four cases of anterior arch fracture after C1 laminectomy without fusion have been previously reported. Although atlas fractures commonly occur in response to high-energy trauma, no obvious trauma that could cause the fracture was observed in these reported cases. The purpose of this study was to elucidate the biomechanical mechanism of anterior arch fracture of the atlas following C1 laminectomy and present three cases of this fracture. METHODS: Three cases of fracture of the anterior arch of the atlas following C1 laminectomy were retrospectively reviewed. Three atlas models (an intact model, a laminectomy model, and a transverse ligament-resected model) were created from computed tomography data of each case using a three-dimensional finite element method. Axial load was applied on the superior facet to mimic four conditions (neutral, flexion, extension, lateral bending). The distribution of von Mises stress in the anterior arch and the displacement of the posterior arch were compared among the three models. RESULTS: In all three cases, the anterior arch fracture clinically occurred after C1 laminectomy despite there being no obvious inciting trauma. During the finite element analysis, increased stress was observed in all postures of the laminectomy model as compared with the intact model. The stress-concentrated location observed in the finite element model was consistent with the fracture sites that were clinically observed. In terms of loading condition, much higher stress was observed in extension and lateral bending as compared with other postures. There were no significant differences in stress distribution between the laminectomy model and the transverse ligament-resected laminectomy model. CONCLUSIONS: Stress distribution concentrates in the anterior arch after C1 laminectomy, leading to fracture of the anterior arch despite no inciting trauma. There may be more frequent occult fractures observed after C1 laminectomy than has been reported. Therefore, surgeons should recognize anterior arch fracture as a possible complication of C1 laminectomy without fusion.

Diffuse idiopathic skeletal hyperostosis (DISH) is a risk factor for further surgery in short-segment lumbar interbody fusion.

PURPOSE: To elucidate the effect of diffuse idiopathic skeletal hyperostosis (DISH) on the clinical results of short-segment lumbar interbody fusion (LIF) for the treatment of degenerative lumbar spinal diseases. METHODS: The 208 patients who underwent one- or two-level LIF were selected as the subjects of this study. Patients with prior lumbar fusion surgery or follow-up <1 year were excluded. Outcome measures were surgery-free survival or the need for further surgery for pseudoarthrosis and/or adjacent segment disease (ASD). The Cox proportional-hazards model was used to identify possible risk factors (DISH, age, sex, number of levels fused, level of the lowest instrumented vertebra, and laminectomy adjacent to the index fused levels) for further surgery. RESULTS: Among the 208 patients (39 with DISH), 21 patients required further surgery during follow-up. Cox analysis showed that DISH (hazard ratio = 5.46) and two-level fusion (hazard ratio = 2.83) were significant independent predictors of further surgery. Age, sex, level of the lowest instrumented vertebra, and laminectomy adjacent to the index fused levels were not significant predictors. CONCLUSIONS: DISH after short-segment LIF surgery is a significant risk factor for further surgery because of pseudoarthrosis or ASD.

Osteoinductive potential of highly purified porous ß-TCP in mice.

Material-induced osteoinduction of calcium phosphate ceramics has been reported in specific animals. We previously reported that recruitment of tartrate-resistant acid phosphatase (TRAP)-positive cells might be one of the main factors responsible for the difference in the occurrence of material-induced osteoinduction between dogs and rats. In this study, we evaluated the osteoinductive potential of highly purified porous beta-tricalcium phosphate materials (HPP-ß-TCP) with two different porosities, 75 and 60 % (Olympus Terumo Biomaterials, Tokyo, Japan), implanted into subcutaneous pockets of FVB and C57BL/6 mice. Twelve weeks after implantation, histological examination and gene expression analysis using reverse transcription-polymerase chain reaction were performed. We observed osteoinduction in half of the HPP-ß-TCP materials with 60 % porosity implanted into FVB mice. This group of mice also exhibited the most TRAP-positive cells. Significantly more vessels were found in FVB mice than in C57BL/6 mice, but the greatest number of vessels was counted in implants from materials with 75 % porosity implanted into FVB mice, which did not show osteoinduction. These results indicate that recruitment of TRAP-positive cells is one factor responsible for osteoinduction caused by HPP-ß-TCP materials in both FVB mice and dogs. Vessel formation seems to be necessary but appears to be less influential for osteoinduction than TRAP-positive cell recruitment.

The O-C2 angle established at occipito-cervical fusion dictates the patient's destiny in terms of postoperative dyspnea and/or dysphagia.

PURPOSE: We have revealed that the cause of postoperative dyspnea and/or dysphagia after occipito-cervical (O-C) fusion is mechanical stenosis of the oropharyngeal space and the O-C2 alignment, rather than total or subaxial alignment, is the key to the development of dyspnea and/or dysphagia. The purpose of this study was to confirm the impact of occipito-C2 angle (O-C2A) on the oropharyngeal space and to investigate the chronological impact of a fixed O-C2A on the oropharyngeal space and dyspnea and/or dysphagia after O-C fusion. MATERIALS AND METHODS: We reviewed 13 patients who had undergone O-C2 fusion, while retaining subaxial segmental motion (OC2 group) and 20 who had subaxial fusion without O-C2 fusion (SA group). The O-C2A, C2-C6 angle and the narrowest oropharyngeal airway space were measured on lateral dynamic X-rays preoperatively, when dynamic X-rays were taken for the first time postoperatively, and at the final follow-up. We also recorded the current dyspnea and/or dysphagia status at the final follow-up of patients who presented with it immediately after the O-C2 fusion. RESULTS: There was no significant difference in the mean preoperative values of the O-C2A (13.0 ± 7.5 in group OC2 and 20.1 ± 10.5 in group SA, Unpaired t test, P = 0.051) and the narrowest oropharyngeal airway space (17.8 ± 6.0 in group OC2 and 14.9 ± 3.9 in group SA, Unpaired t test, P = 0.105). In the OC2 group, the narrowest oropharyngeal airway space changed according to the cervical position preoperatively, but became constant postoperatively. In contrast, in the SA group, the narrowest oropharyngeal airway space changed according to the cervical position at any time point. Three patients who presented with dyspnea and/or dysphagia immediately after O-C2 fusion had not resolved completely at the final follow-up. The narrowest oropharyngeal airway space and postoperative dyspnea and/or dysphagia did not change with time once the O-C2A had been established at O-C fusion. CONCLUSIONS: The O-C2A established at O-C fusion dictates the patient's destiny in terms of postoperative dyspnea and/or dysphagia. Surgeons should pay maximal attention when establishing the O-C2A during surgery, because their careless decision for the O-C2A may cause persistent dysphagia or a life-threatening consequence. We recommend that the O-C2A in O-C fusion should be kept at least at more than the preoperative O-C2A in the neutral position.

Development of a novel calcium phosphate cement composed mainly of calcium sodium phosphate with high osteoconductivity.

Two novel calcium phosphate cements (CPC) have been developed using calcium sodium phosphate (CSP) as the main ingredient. The first of these cements, labeled CAC, contained CSP, α-tricalcium phosphate (TCP), and anhydrous citric acid, whereas the second, labeled CABC, contained CSP, α-TCP, ß-TCP, and anhydrous citric acid. Biopex(®)-R (PENTAX, Tokyo, Japan), which is a commercially available CPC (Com-CPC), and OSferion(®) (Olympus Terumo Biomaterials Corp., Tokyo, Japan), which is a commercially available porous ß-TCP, were used as reference controls for analysis. In vitro analysis showed that CABC set in 5.7 ± 0.3 min at 22 °C and had a compressive strength of 86.0 ± 9.7 MPa after 5 days. Furthermore, this material had a compressive strength of 26.7 ± 3.7 MPa after 2 h in physiologic saline. CAC showed a statistically significantly lower compressive strength in the presence of physiologic saline and statistically significantly longer setting times than those of CABC. CABC and CAC exhibited apatite-forming abilities in simulated body fluid that were faster than that of Com-CPC. Samples of the materials were implanted into the femoral condyles of rabbits for in vivo analysis, and subsequent histological examinations revealed that CABC exhibited superior osteoconductivity and equivalent bioresorbability compared with Com-CPC, as well as superior osteoconductivity and bioresorbability compared with CAC. CABC could therefore be used as an alternative bone substitute material.

Bone bonding ability of a chemically and thermally treated low elastic modulus Ti alloy: gum metal.

The gum metal with composition Ti-36Nb-2Ta-3Zr-0.3O, is free from cytotoxic elements and exhibits a low elastic modulus as well as high mechanical strength. We have previously demonstrated that this gum metal, once subjected to a series of surface treatments--immersion in 1 M NaOH (alkali treatment) and then 100 mM CaCl2, before heating at 700 °C (sample: ACaH-GM), with an optional final hot water immersion (sample: ACaHW-GM)--has apatite-forming ability in simulated body fluid. To confirm the in vivo bioactivity of these treated alloys, failure loads between implants and bone at 4, 8, 16, and 26 weeks after implantation in rabbits' tibiae were measured for untreated gum metal (UT-GM), ACaH-GM and ACaHW-GM, as well as pure titanium plates after alkali and heat treatment (AH-Ti). The ACaH-GM and UT-GM plates showed almost no bonding, whereas ACaHW-GM and AH-Ti plates showed successful bonding by 4 weeks, and their failure loads subsequently increased with time. The histological findings showed a large amount of new bone in contact with the surface of ACaHW-GM and AH-Ti plates, suggesting that the ACaHW treatment could impart bone-bonding bioactivity to a gum metal in vivo. Thus, with this improved bioactive treatment, these advantageous gum metals become useful candidates for orthopedic and dental devices.

Quantification of changes in gait characteristics associated with intermittent claudication in patients with lumbar spinal stenosis.

STUDY DESIGN: Cross-sectional observational study. OBJECTIVE: To quantify changes in gait characteristics associated with claudication after continuous walking, and to investigate the relationship between walking capacity and gait characteristics in patients with lumbar spinal stenosis (LSS). SUMMARY OF BACKGROUND DATA: Walking difficulty due to pain or neurological symptoms accompanied by continuous walking may have negative effects on gait characteristics in patients with LSS. However, there are few detailed reports on the association of these changes with intermittent claudication and their relationship with walking capacity. METHODS: For this study, 11 LSS patients with intermittent claudication were recruited. The subjects continued walking until they expressed a difficulty in continuing further. Postural sway, autocorrelation peak (AC), stride frequency (SF), and coefficient of variance (CV) were analyzed using accelerometers. To detect changes in gait parameters, we compared acceleration at the start and at the end of the walking task. RESULTS: Walking difficulty during the test increased from 4 (interquartile range, 1-5) to 9 (interquartile range, 7-10). The postural sway significantly increased after the onset of maximum walking difficulty. AC, SF, or CV did not show significant change. Maximum walking distance significantly correlated with postural sway at the cervical sensor (r=-0.64), and CV (ρ=-0.66), an index of gait variability, at the beginning of the walking task. CONCLUSIONS: The change in gait parameters associated with claudication during continuous walking is detectable using accelerometers. Postural sway increases after the provocation of walking difficulty due to pain or neurological symptoms. In addition, walking capacity correlated with postural sway of the upper trunk and gait variability during walking initiation. This methodology warrants further studies to confirm its usefulness as an assessment tool for patients with LSS.

The reinforcement of a C2 laminar screw by a C2 laminar hook as an anchor of occipito-C2 fusion.

Although a C1-C2 transarticular screw (TAS) or a C2 pedicle screw (PS) is the most rigid anchor for C2, each entails the risk of vertebral artery injury. Although a C2 laminar screw (LS) is often used as an alternative anchor in such cases, its anchoring strength may be inadequate. We introduce a technical tip, in which a C2 LS is reinforced by a C2 infralaminar hook without extending the fusion range. Six patients, for whom a unilateral TAS or C2 PS was risky or impossible, were treated with O-C2 fusion using this technique. The post-operative course of each patient was uneventful. Bone union was achieved in all patients, except one who died of indifferent disease before the confirmation of bone union by computed tomography. This method would be a safe and non-technical-demanding option when the placement of a TAS or PS is risky or impossible.

The Impact of Pelvic Incidence on Spinopelvic and Hip Alignment and Mobility in Asymptomatic Subjects.

BACKGROUND: The influence of pelvic incidence (PI) on spinopelvic and hip alignment and mobility has not been well investigated. The aim of this study was to evaluate the influence of PI on spinopelvic and hip alignment and mobility, including the pelvic-femoral angle (PFA) and motion (ΔPFA), in functional positions in a cohort of asymptomatic volunteers. METHODS: This was a single-center, prospective, cross-sectional study. We included 136 healthy volunteers (69% female; mean age, 38 ± 11 years; mean body mass index, 22 ± 3 kg/m2) divided into 3 subgroups on the basis of their PI: PI < 45° (low PI), 45° ≤ PI ≤ 60° (medium PI), and PI > 60° (high PI). We made full-body lateral radiographs in free-standing, standing with extension, relaxed-seated, and flexed-seated positions. We measured the sacral slope (SS), lumbar lordosis (LL), and PFA. We calculated lumbar (∆LL), pelvic (∆SS), and hip (∆PFA) mobilities as the change between the standing (i.e., standing with or without extension) and sitting (i.e., relaxed-seated or flexed-seated) positions. RESULTS: There were significant differences between some of the 3 subgroups with respect to the LL, SS, and PFA in each of the 4 positions. There were no significant differences in ΔLL, ΔSS, or ΔPFA between the 3 groups when moving from a standing to a sitting position. PI had an inverse linear correlation with PFAextension (R = -0.48; p < 0.0001), PFAstanding (R = -0.53; p < 0.0001), PFArelaxed-seated (R = -0.37; p < 0.0001), and PFAflexed-seated (R = -0.47; p < 0.0001). However, PI was not correlated with ΔPFAstanding/relaxed-seated (R = -0.062; p = 0.48) or ΔPFAextension/flexed-seated (R = -0.12; p = 0.18). Similarly, PI was not significantly correlated with ΔLL or ΔSS in either pair of positions. CONCLUSIONS: This study confirmed that spinopelvic and hip parameters in functional positions were affected by PI, whereas lumbar, pelvic, and hip mobilities did not depend on PI. These findings suggest that hip surgeons should consider the PI of the patient to determine the patient's specific functional safe zones before and after total hip arthroplasty. LEVEL OF EVIDENCE: Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Strontium-loaded 3D intramedullary nail titanium implant for critical-sized femoral defect in rabbits.

The treatment of critical-sized bone defects has long been a major problem for surgeons. In this study, an intramedullary nail shaped three-dimensional (3D)-printed porous titanium implant that is capable of releasing strontium ions was developed through a simple and cost-effective surface modification technique. The feasibility of this implant as a stand-alone solution was evaluated using a rabbit's segmental diaphyseal as a defect model. The strontium-loaded implant exhibited a favorable environment for cell adhesion, and mechanical properties that were commensurate with those of a rabbit's cortical bone. Radiographic, biomechanical, and histological analyses revealed a significantly higher amount of bone ingrowth and superior bone-bonding strength in the strontium-loaded implant when compared to an untreated porous titanium implant. Furthermore, one-year histological observations revealed that the strontium-loaded implant preserved the native-like diaphyseal bone structure without failure. These findings suggest that strontium-releasing 3D-printed titanium implants have the clinical potential to induce the early and efficient repair of critical-sized, load-bearing bone defects.

Osteoconduction of porous Ti metal enhanced by acid and heat treatments.

Bone ingrowth into porous Ti metal is important for stable fixation of Ti metal implants to surrounding bone. However, without surface treatment this is limited to only a thin region of the outer surface of the Ti metal. In the present study, a porous Ti metal with a porosity of ~60 % and interpore connections of 70-200 micrometers in diameter was investigated in terms of its chemical and heat treatments, by implanting it into rabbit femur for periods varying from 3 to 12 weeks. The porous Ti metal subjected to heat treatment at 600 °C after H2SO4/HCl mixed acid treatment showed the largest bone ingrowth in comparison with those subjected to no treatment, only acid treatment, and only heat treatment even at an early stage after implantation, and remained as such even 12 weeks after implantation. Their bone ingrowths were well interpreted in terms of apatite-forming abilities of the Ti metals in body environment. Their apatite-forming abilities did not depend upon their surface roughness nor type of crystalline phase, but upon the positive surface charge.