In Vivo strain measurements in rat femur

The purpose of the present study was to evaluate strain in the femora of rats during walking. Uni-directional strain gauge units were implanted. Peak strain at the anterior and medial aspects of the rat femur was compressive, while peak strain at the posterior aspect was tensile during walking. Median strain values at the anterior mid-diaphyseal aspect varied between 297x10-6 and 434x10-6. There were no statistical differences between recordings at different times after implantation as evaluated by daily measurements for one week. Neither was there any statistically significant difference in strain values between the walking speeds of 6.0, 10.2, and 14.7 m/min, or between values for right and left femur. In vitro measurements on replaced gauges corresponded within 5 per cent with results from bones where gauges had been implanted for one week. Waterproofing the strain gauge unit with a resin did not significantly affect the measurements. The method, therefore, enables studies of strain behavior of bone from small species in vivo under physiological and pathophysiological conditions

Spinous Process Osteotomy to Facilitate the Access to the Spinal Canal When Decompressing the Spinal Canal in Patients with Lumbar Spinal Stenosis

Study DesignRetrospective study.PurposeThe main purpose of this study was to investigate the union-rate of the spinous process after performing a spinous process osteotomy and whether union affects the clinical results after surgery.Overview of LiteratureIn the present study, spinous process osteotomy was used to facilitate access to the spinal canal when performing a decompressive procedure for lumbar spinal stenosis. The aim of this study was to evaluate the union rate of the spinous process and its effect on the clinical results of the procedure.MethodsAll patients were included in the study that underwent a decompressive procedure through spinous process osteotomy be between January 1, 2007 and December 31, 2007. Operation protocols were reviewed. A computed tomography (CT) scan was performed to evaluate the union of the osteotomies of the spinous process. According to the CT-scans, patients were divided into three groups: "complete-union," "partial-union," and "non-union." Patients reported their clinical results through a self-administered questionnaire.ResultsThe mean period of follow up was 21.6 months (range, 16-28 months). A total of 44% of the performed osteotomies were considered as united. Ten patients (18%) were classified as "complete-union," 30 patients (55%) as "partial-union," and 15 patients (27%) as "non-union." The "complete-union" group showed better clinical results and scored significantly better in the Oswestry Disability Index and EQ-5D. However, no statistical difference was found in the pain-scores. There were no differences between the "partial-union" group and the "no-union" group.ConclusionsWe found a radiologic union for 60 out of 135 (44%) spinous process osteotomies

The Norwegian degenerative spondylolisthesis and spinal stenosis (NORDSTEN) study: study overview, organization structure and study population

Purpose To provide an overview of the The Norwegian Degenerative spondylolisthesis and spinal stenosis (NORDSTEN)-study and the organizational structure, and to evaluate the study population. Methods The NORDSTEN is a multicentre study with 10 year follow-up, conducted at 18 public hospitals. NORDSTEN includes three studies: (1) The randomized spinal stenosis trial comparing the impact of three different decompression techniques; (2) the randomized degenerative spondylolisthesis trial investigating whether decompression surgery alone is as good as decompression with instrumented fusion; (3) the observational cohort tracking the natural course of LSS in patients without planned surgical treatment. A range of clinical and radiological data are collected at defined time points. To administer, guide, monitor and assist the surgical units and the researchers involved, the NORDSTEN national project organization was established. Corresponding clinical data from the Norwegian Registry for Spine Surgery (NORspine) were used to assess if the randomized NORDSTEN-population at baseline was representative for LSS patients treated in routine surgical practice. Results A total of 988 LSS patients with or without spondylolistheses were included from 2014 to 2018. The clinical trials did not find any difference in the efficacy of the surgical methods evaluated. The NORDSTEN patients were similar to those being consecutively operated at the same hospitals and reported to the NORspine during the same time period. Conclusion The NORDSTEN study provides opportunity to investigate clinical course of LSS with or without surgical interventions. The NORDSTEN-study population were similar to LSS patients treated in routine surgical practice, supporting the external validity of previously published results.publishedVersio

Is the presence of foraminal stenosis associated with outcome in lumbar spinal stenosis patients treated with posterior microsurgical decompression

Background We aim to investigate associations between preoperative radiological findings of lumbar foraminal stenosis with clinical outcomes after posterior microsurgical decompression in patients with predominantly central lumbar spinal stenosis (LSS). Methods The study was an additional analysis in the NORDSTEN Spinal Stenosis Trial. In total, 230 men and 207 women (mean age 66.8 (SD 8.3)) were included. All patients underwent an MRI including T1- and T2-weighted sequences. Grade of foraminal stenosis was dichotomized into none to moderate (0–1) and severe (2–3) category using Lee’s classification system. The Oswestry Disability Index (ODI), Zurich Claudication Questionnaire (ZCQ), and numeric rating scale (NRS) for back and leg pain were collected at baseline and at 2-year follow-up. Primary outcome was a reduction of 30% or more on the ODI score. Secondary outcomes included the mean improvement on the ODI, ZCQ, and NRS scores. We performed multivariable regression analyses with the radiological variates foraminal stenosis, Pfirrmann grade, Schizas score, dural sac cross-sectional area, and the possible plausible confounders: patients’ gender, age, smoking status, and BMI. Results The cohort of 437 patients presented a high degree of degenerative changes at baseline. Of 414 patients with adequate imaging of potential foraminal stenosis, 402 were labeled in the none to moderate category and 12 in the severe category. Of the patients with none to moderate foraminal stenosis, 71% achieved at least 30% improvement in ODI. Among the patients with severe foraminal stenosis, 36% achieved at least 30% improvement in ODI. A significant association between severe foraminal stenosis and less chance of reaching the target of 30% improvement in the ODI score after surgery was detected: OR 0.22 (95% CI 0.06, 0.83), p=0.03. When investigating outcome as continuous variables, a similar association between severe foraminal stenosis and less improved ODI with a mean difference of 9.28 points (95%CI 0.47, 18.09; p=0.04) was found. Significant association between severe foraminal stenosis and less improved NRS pain in the lumbar region was also detected with a mean difference of 1.89 (95% CI 0.30, 3.49; p=0.02). No significant association was suggested between severe foraminal stenosis and ZCQ or NRS leg pain. Conclusion In patients operated with posterior microsurgical decompression for LSS, a preoperative severe lumbar foraminal stenosis was associated with higher proportion of patients with less than 30% improvement in ODI.publishedVersio

Postoperative Dural Sac Cross-Sectional Area as an Association for Outcome After Surgery for Lumbar Spinal Stenosis: Clinical and Radiological Results From the NORDSTEN-Spinal Stenosis Trial

Objective - The aim was to investigate the association between postoperative dural sac cross-sectional area (DSCA) after decompressive surgery for lumbar spinal stenosis and clinical outcome. Furthermore, to investigate if there is a minimum threshold for how extensive a posterior decompression needs to be to achieve a satisfactory clinical result. Summary of Background Data - There is limited scientific evidence for how extensive lumbar decompression needs to be to obtain a good clinical outcome in patients with symptomatic lumbar spinal stenosis. Materials and Methods - All patients were included in the Spinal Stenosis Trial of the NORwegian Degenerative spondylolisthesis and spinal STENosis (NORDSTEN)-study. The patients underwent decompression according to three different methods. DSCA measured on lumbar magnetic resonance imaging at baseline and at three months follow-up, and patient-reported outcome at baseline and at two-year follow-up were registered in a total of 393 patients. Mean age was 68 (SD: 8.3), proportion of males were 204/393 (52%), proportion of smokers were 80/393 (20%), and mean body mass index was 27.8 (SD: 4.2). The cohort was divided into quintiles based on the achieved DSCA postoperatively, the numeric, and relative increase of DSCA, and the association between the increase in DSCA and clinical outcome were evaluated. Results - At baseline, the mean DSCA in the whole cohort was 51.1 mm2 (SD: 21.1). Postoperatively the area increased to a mean area of 120.6 mm2 (SD: 46.9). The change in Oswestry disability index in the quintile with the largest DSCA was −22.0 (95% CI: −25.6 to −18), and in the quintile with the lowest DSCA the Oswestry disability index change was −18.9 (95% CI: −22.4 to −15.3). There were only minor differences in clinical improvement for patients in the different DSCA quintiles. <p<Conclusion - Less aggressive decompression performed similarly to wider decompression across multiple different patient-reported outcome measures at two years following surgery

Surgery in Degenerative Spondylolisthesis: Does fusion improve outcome in subgroups? A secondary analysis from a randomized trial (NORDSTEN trial)

BACKGROUND CONTEXT Patients with spinal stenosis and degenerative spondylolisthesis are treated surgically with decompression alone or decompression with fusion. However, there is debate regarding which subgroups of patients may benefit from additional fusion. PURPOSE To investigate possible treatment effect modifiers and prognostic variables among patients operated for spinal stenosis and degenerative spondylolisthesis. DESIGN A secondary exploratory study using data from the Norwegian Degenerative Spondylolisthesis and Spinal Stenosis (NORDSTEN-DS) trial. Patients were randomized to decompression alone or decompression with instrumented fusion. PATIENT SAMPLE The sample in this study consists of 267 patients from a randomized multicenter trial involving 16 hospitals in Norway. Patients were enrolled from February 12, 2014, to December 18, 2017. The study did not include patients with degenerative scoliosis, severe foraminal stenosis, multilevel spondylolisthesis, or previous surgery. OUTCOME MEASURES The primary outcome was an improvement of ≥ 30% on the Oswestry Disability Index score (ODI) from baseline to 2-year follow-up. METHODS When investigating possible variables that could modify the treatment effect, we analyzed the treatment arms separately. When testing for prognostic factors we analyzed the whole cohort (both treatment groups). We used univariate and multiple regression analyses. The selection of variables was done a priori, according to the published trial protocol. RESULTS Of the 267 patients included in the trial (183 female [67%]; mean [SD] age, 66 [7.6] years), complete baseline data for the variables required for the present analysis were available for 205 of the 267 individuals. We did not find any clinical or radiological variables at baseline that modified the treatment effect. Thus, none of the commonly used criteria for selecting patients for fusion surgery influenced the chosen primary outcome in the two treatment arms. For the whole cohort, less comorbidity (American Society of Anesthesiologists Classification [ASA], OR = 4.35; 95% confidence interval (CI [1.16–16.67]) and more preoperative leg pain (OR = 1.23; CI [1.02–1.50]) were significantly associated with an improved primary outcome. CONCLUSIONS In this study on patients with degenerative spondylolisthesis, neither previously defined instability criteria nor other pre-specified baseline variables were associated with better clinical outcome if fusion surgery was performed. None of the analyzed variables can be applied to guide the decision for fusion surgery in patients with degenerative spondylolisthesis. For both treatment groups, less comorbidity and more leg pain were associated with improved outcome 2 years after surgery.publishedVersio

Wear and Migration of Highly Cross-Linked and Conventional Cemented Polyethylene Cups with Cobalt Chrome or Oxinium Femoral Heads: A Randomized Radiostereometric Study of 150 Patients

ABSTRACT: This randomized study was performed to compare wear and migration of five different cemented total hip joint articulations in 150 patients. The patients received either a Charnley femoral stem with a 22.2 mm head or a Spectron EF femoral stem with a 28 mm head. The Charnley articulated with a g-sterilized Charnley Ogee acetabular cup. The Spectron EF was used with either EtOsterilized non-cross-linked polyethylene (Reflection All-Poly) or highly cross-linked (Reflection All-Poly XLPE) cups, combined with either cobalt chrome (CoCr) or Oxinium femoral heads. The patients were followed with repeated RSA measurements for 2 years. After 2 years, the EtO-sterilized non-cross-linked Reflection All-Poly cups had more than four times higher proximal penetration than its highly cross-linked counterpart. Use of Oxinium femoral heads did not affect penetration at 2 years compared to heads made of CoCr. Further follow-up is needed to evaluate the benefits, if any, of Oxinium femoral heads in the clinical setting. The Charnley Ogee was not outperformed by the more recently introduced implants in our study. We conclude that this prostheses still represents a standard against which new implants can be measured. Osteolysis induced by wear debris of ultra-high molecular weight polyethylene (UHMWPE) is considered the most common cause for failure of total hip arthroplasties (THA). 1 Sterilization technique and UHMWPE quality are related to wear. 2 Sterilization with gamma irradiation in air breaks the polymer chains and generates free radicals. Free radicals may combine with each other creating cross-links between adjacent molecules, which reduces abrasive wear. However, they entail the disadvantage of oxidative degradation of polyethylene (PE) when exposed to the body&apos;s oxidative environment, which may lead to deterioration of mechanical properties. 3 To address the problem, sterilization methods in inert environments with ethylene oxide (EtO) or gas plasma were introduced. However, these methods do not have the benefits of cross-linking, and an earlier report showed increase in early in vivo wear after EtO sterilization. 4 Highly cross-linked polyethylenes (HXLPE) provides a considerable reduction of wear compared to conventional polyethylene (PE). Concerns of PE wear have also been addressed by introducing alternative femoral head materials. Oxidized zirconium (Oxinium, Smith &amp; Nephew) was introduced in the last decade for use in THA. Radiostereometric analysis (RSA) enables in vivo measurement of relative 3D motion in the range of 0.1 mm and 0.058. Due to its accuracy, few patients are needed to obtain satisfactory statistical power. With RSA the degree of migration during the first years after surgery correlates with the implant&apos;s longterm performance. We wanted to evaluate wear and migration patterns of the cemented highly cross-linked Reflection All-Poly XLPE cup and its non-irradiated counterpart, the cemented Reflection All-Poly cup, when articulating with either Oxinium or traditional cobalt chrome (CoCr) femoral heads (Smith &amp; Nephew). Our null hypothesis was that wear and migration were equal to the Charnley Ogee prostheses (DePuy Intl

A randomized study on migration of the Spectron EF and the Charnley flanged 40 cemented femoral components using radiostereometric analysis at 2 years

Background and purpose: We performed a randomized study to determine the migration patterns of the Spectron EF femoral stem and to compare them with those of the Charnley stem, which is regarded by many as the gold standard for comparison of implants due to its extensive documentation. Patients and methods: 150 patients with a mean age of 70 years were randomized, single-blinded, to receive either a cemented Charnley flanged 40 monoblock, stainless steel, vaquasheen surface femoral stem with a 22.2-mm head (n = 30) or a cemented Spectron EF modular, matte, straight, collared, cobalt-chrome femoral stem with a 28-mm femoral head and a roughened proximal third of the stem (n = 120). The patients were followed with repeated radiostereometric analysis for 2 years to assess migration. Results: At 2 years, stem retroversion was 2.3° and 0.7° (p < 0.001) and posterior translation was 0.44 mm and 0.17 mm (p = 0.002) for the Charnley group (n = 26) and the Spectron EF group (n = 74), respectively. Subsidence was 0.26 mm for the Charnley and 0.20 mm for the Spectron EF (p = 0.5). Interpretation: The Spectron EF femoral stem was more stable than the Charnley flanged 40 stem in our study when evaluated at 2 years. In a report from the Norwegian arthroplasty register, the Spectron EF stem had a higher revision rate due to aseptic loosening beyond 5 years than the Charnley. Initial stability is not invariably related to good long-term results. Our results emphasize the importance of prospective long-term follow-up of prosthetic implants in clinical trials and national registries and a stepwise introduction of implants

Higher revision risk for unicompartmental knee arthroplasty in low-volume hospitals

Background and purpose — Some studies have found high complication rates and others have found low complication rates after unicompartmental knee arthroplasty (UKA). We evaluated whether hospital procedure volume influences the risk of revision using data from the Norwegian Arthroplasty Register (NAR). Materials and methods — 5,791 UKAs have been registered in the Norwegian Arthroplasty Register. We analyzed the 4,460 cemented medial Oxford III implants that were used from 1999 to 2012; this is the most commonly used UKA implant in Norway. Cox regression (adjusted for age, sex, and diagnosis) was used to estimate risk ratios (RRs) for revision. 4 different volume groups were compared: 1–10, 11–20, 21–40, and > 40 UKA procedures annually per hospital. We also analyzed the reasons for revision. Results and interpretation — We found a lower risk of revision in hospitals performing more than 40 procedures a year than in those with less than 10 UKAs a year, with an unadjusted RR of 0.53 (95% CI: 0.35–0.81) and adjusted RR of 0.59 (95% CI: 0.39–0.90). Low-volume hospitals appeared to have a higher risk of revision due to dislocation, instability, malalignment, and fracture than high-volume hospitals

Metallionenivåer i blod fra pasienter med metall-mot-metall-hofteprotese

Bakgrunn: BHR-protese (Birmingham hip resurfacing) er satt inn i hoften til 445 personer i Norge. Bivirkninger av metallfrigjøring fra metall-mot-metall-leddflater av kobolt-krom-legering kan forekomme. Målet med studien var å analysere frigjøringen av metallioner i løpet av de første fem årene etter operasjon hos pasienter med BHR-protese og å undersøke om det hadde sammenheng med kliniske komplikasjoner. Materiale og metode: 44 mannlige pasienter (medianalder 53 år) med BHR-protese satt inn ved Kysthospitalet i Hagevik i perioden oktober 2009–mai 2013 ble fulgt med blodprøver før implantasjon og tre måneder, ett år, tre år og fem år etter. Analyser av kobolt og krom i helblod ble utført. Klinisk vurdering av proteseleddet ble gjort ved funksjonsskåring. Resultater: Metallionkonsentrasjonene økte fra operasjonstidspunktet til ett år etter operasjon (p < 0,001), deretter holdt konsentrasjonene seg stabile. Etter fem år var mediankonsentrasjon (min.–maks.) av kobolt og krom henholdsvis 1,1 µg/L (0,4–6,3 µg/L) og 1,4 µg/L (0,4–11,7 µg/L) ved unilateral protese (n = 36), og henholdsvis 2,3 µg/L (1,6–28,5 µg/L) og 2,6 µg/L (1,7–14,1 µg/L) ved bilaterale proteser (n = 8). Fem pasienter ble reoperert, mens øvrige pasienter hadde god funksjon. Fortolkning: Pasienter med BHR-protese fikk signifikant økning av kobolt og krom i blod ett til fem år etter kirurgi, men medianverdiene var likevel godt under grenseverdien på 7 μg/L som indikerer økt risiko for komplikasjoner