Correction of the pelvic incidence using a bilateral extending pelvic osteotomy: a proof of concept study.

INTRODUCTION: The aim of this proof of concept human cadaver study was to quantify the effect of a bilateral extending pelvic osteotomy (BEPO) on pelvic incidence (PI) as a potential alternative for a pedicle subtraction osteotomy (PSO) in patients with severe spinal sagittal malalignment. MATERIALS AND METHODS: 10 fresh frozen human cadavers were treated with the BEPO technique. CT images were made before and after the osteotomy and pure sagittal images were created on which PI was measured. RESULTS: The mean pre-osteotomy PI was 47.9° (range 36.4-63.9) and the mean post-osteotomy PI was 36.5° (range 22.1-54.4). The mean correction was - 10.4° with a range of - 8.4° to - 17.3° (p = 0.03), which resulted in a mean decrease of 23% in the PI (range 16-42). CONCLUSIONS: There was a feasible and effective correction of PI using the BEPO technique on the os ilium. This was a preliminary cadaveric study. No conclusions could be made on global sagittal alignment. We postulate that an extending osteotomy of the ilium could be a potential alternative for a PSO reducing the complexity of spine surgery in patients with severe spinal sagittal malalignment.

Surgical techniques in restoration lumbar lordosis: a biomechanical human cadaveric study.

PURPOSE: Degenerative changes of the lumbar spine lead in general to decrease of lumbar lordosis (LL). This change affects the overall balance of the spine, and when surgery is deemed, necessary restoration of the LL is considered. How this restoration can be achieved is a matter of controversy. The main purpose of this cadaveric study was to investigate the different steps of common posterior surgical techniques to understand the contribution of each successive step in restoring LL. METHODS: Ten fresh-frozen human lumbar spine specimens were used to perform a sequential correction and instrumentation with a pedicle screw construct. RESULTS: The mean LL angle measured at L3-L4 in intact condition was 12.9°; after screw insertion and compression, this increased to 13.8° (+ 7%, p = 0.04), after bilateral facetectomy to 16.3° (+ 20%, p = 0.005), after discectomy and insertion of interbody cage to 18.0º (+ 9%, p = 0.012), after resection of the lamina and the processes spinosus to 19.8° (+ 10%, p = 0.017), and after resection of the anterior longitudinal ligament to 25.4° (+ 22%, p = 0.005). CONCLUSIONS: Each step contributed statistically significant to restoration of segmental lordosis with bilateral facetectomy contributing the most in terms of percentage. LEVEL OF EVIDENCE: IV.

The SNAP Trial: 2-Year Results of a Double-Blind Multicenter Randomized Controlled Trial of a Silicon Nitride Versus a PEEK Cage in Patients After Lumbar Fusion Surgery.

STUDY DESIGN: Randomized controlled trial. OBJECTIVES: Lumbar interbody fusion with cages is performed to provide vertebral stability, restore alignment, and maintain disc and foraminal height. Polyetheretherketone (PEEK) is commonly used. Silicon nitride (Si3N4) is an alternative material with good osteointegrative properties. This study was designed to assess if Si3N4 cages perform similar to PEEK. METHODS: A non-inferiority double-blind multicenter RCT was designed. Patients presenting with chronic low-back pain with or without leg pain were included. Single- or double-level instrumented transforaminal lumbar interbody fusion (TLIF) using an oblique PEEK or Si3N4 cage was performed. The primary outcome was the Roland-Morris Disability Questionnaire (RMDQ). The non-inferiority margin for the RMDQ was 2.6 points on a scale of 24. Secondary outcomes included the Oswestry Disability Questionnaire (ODI), Visual Analogue Scales (VAS), SF-36 Physical Function, patient and surgeon Likert scores, radiographic evaluations for subsidence, segmental motion, and fusion. Follow-up was planned at 3, 6, 12, and 24-months. RESULTS: Ninety-two patients were randomized (i.e. 48 to PEEK and 44 to Si3N4). Both groups showed good clinical improvements on the RMDQ scores of up to 5-8 points during follow-up. No statistically significant differences were observed in clinical and radiographic outcomes. Mean operative time and blood loss were statistically significantly higher for the Si3N4 cohort. Although not statistically significant, there was a higher incidence of complications and revisions associated with the Si3N4 cage. CONCLUSIONS: There was insufficient evidence to conclude that Si3N4 was non-inferior to PEEK.

Are the Roland Morris Disability Questionnaire and Oswestry Disability Index interchangeable in patients after lumbar spinal fusion?

BACKGROUND: Low back pain is a common health problem for which there are several treatment options. For optimizing clinical decision making, evaluation of treatments and research purposes it is important that health care professionals are able to evaluate the functional status of patients. Patient reported outcome measures (PROMs) are widely accepted and recommended. The Roland Morris Disability Questionnaire (RMDQ) and the Oswestry Disability Index (ODI) are the two mainly used condition-specific patient reported outcomes. Concerns regarding the content and structural validity and also the different scoring systems of these outcome measures makes comparison of treatment results difficult. OBJECTIVE: Aim of this study was to determine if the RMDQ and ODI could be used exchangeable by assessing the correlation and comparing different measurement properties between the questionnaires. METHODS: Clinical data from patients who participated in a multicenter RCT with 2 year follow-up after lumbar spinal fusion were used. Outcome measures were the RMDQ, ODI, Short Form 36 - Health Survey (SF-36), leg pain and back pain measured on a 0-100 mm visual analogue scale (VAS). Cronbach's alpha coefficients, Spearman correlation coefficients, multiple regression analysis and Bland-Altman plots were calculated. RESULTS: three hundred and seventy-six completed questionnaires filled out by 87 patients were used. The ODI and RMDQ had both a good level of internal consistency. There was a very strong correlation between the RMDQ and the ODI (r= 0.87; p< 0.001), and between the VAS and both the ODI and RMDQ. However, the Bland-Altman plot indicated bad agreement between the ODI and RMDQ. CONCLUSIONS: The RMDQ and ODI cannot be used interchangeably, nor is there a possibility of converting the score from one questionnaire to the other. However, leg pain and back pain seemed to be predictors for both the ODI and the RMDQ.

Surgical Restoration of Sagittal Alignment of the Spine: Correlation with Improved Patient-Reported Outcomes: A Systematic Review and Meta-Analysis.

BACKGROUND: The sagittal-plane curvatures of the human spine are the consequence of evolution from quadrupedalism to bipedalism and are needed to maintain the center of mass of the body within the base of support in the bipedal position. Lumbar degenerative disorders can lead to a decrease in lumbar lordosis and thereby affect overall alignment of the spine. However, there is not yet enough direct evidence that surgical restoration of spinal malalignment would lead to a better clinical outcome. Therefore, the aim of this study was to assess the correlation between patient-reported outcomes and actual obtained spinal sagittal alignment in adult patients with lumbar degenerative disorders who underwent surgical treatment. METHODS: A comprehensive literature search was conducted through databases (PubMed, Cochrane, Web of Science, and Embase). The last search was in November 2018. Risk of bias was assessed with the Newcastle-Ottawa quality assessment scale. A meta-regression analysis was performed. RESULTS: Of 2,024 unique articles in the original search, 34 articles with 973 patients were included. All studies were either retrospective or prospective cohort studies; no randomized controlled trials were available. A total of 54 relations between preoperative-to-postoperative improvement in patient-reported outcome measures (PROMs) and radiographic spinopelvic parameters were found, of which 20 were eligible for meta-regression analysis. Of these, 2 correlations were significant: pelvic tilt (PT) versus Oswestry Disability Index (ODI) (p = 0.009) and PT versus visual analog scale (VAS) pain (p = 0.008). CONCLUSIONS: On the basis of the current literature, lower PT was significantly correlated with improved ODI and VAS pain in patients with sagittal malalignment caused by lumbar degenerative disorders that were treated with surgical correction of the sagittal balance. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

The Survivorship of the Uncemented Iso-Elastic Monoblock Acetabular Component at a Mean of 6-Year Follow-up.

BACKGROUND: Aseptic loosening, caused by wear and osteolysis, is the most frequent reason for hip replacement revision in the UK. To prevent aseptic loosening, an acetabular component with vitamin E added to irradiated highly cross-linked polyethylene (HXLPE) was developed to reduce oxidative degradation. QUESTIONS/PURPOSES: A prior study of the vitamin E-blended HXLPE acetabular component after 2 years of follow-up reported no adverse reactions or abnormal mechanical behavior. To further examine this hypothesis of reducing wear and osteolysis, we sought to evaluate outcomes after 6-year follow-up. METHODS: A cohort of 95 of the 112 initial patients (84.2%) completed the 6 years of follow-up after receiving a vitamin E-blended HXLPE acetabular component. Evaluation was performed in terms of clinical (visual analog scale [VAS] score, VAS score with weight-bearing, VAS score for satisfaction, and Harris Hip Score) and radiological (inclination, polar gap, radiolucencies, migration, and 2-D linear femoral head penetration rate) assessment. RESULTS: The mean VAS score for patient satisfaction was 8.75 and the mean Harris Hip Score was 91.8. There were two revisions because of deep infections and one because of a peri-prosthetic femoral fracture. Two acetabular components migrated initially; however, delayed acetabular stabilization occurred. Both patients had good clinical scores at 72 months. The mean femoral head penetration rate was 0.036 mm/year. CONCLUSIONS: This prospective cohort study has shown no adverse reactions concerning the vitamin E additive, promising wear rates, no signs of osteolysis, a 100% survival rate for aseptic loosening, and an all-cause survivorship percentage of 97.4% at 6 years of follow-up.

Advocacy for use of the modified Iowa Level of Assistance Scale for clinical use in patients after hip replacement: an observational study.

OBJECTIVES: To test the internal consistency and item difficulty of the modified Iowa Level of Assistance Scale (mILAS). DESIGN: Retrospective observational study. SETTING: Two orthopaedic wards of two general hospitals. PARTICIPANTS: Following elective primary unilateral total hip replacement surgery, all participants performed mILAS activities that were scored daily to assess their recovery of activities during hospitalisation. MAIN OUTCOME MEASURES: The internal consistency and the level of assistance needed by the patient (item difficulty) of the mILAS were calculated using data from Deventer Hospital, Deventer, the Netherlands (n=255). A cross-validation was performed using data from Nij Smellinghe Hospital, Drachten, the Netherlands (n=224). RESULTS: The internal consistency of the mILAS was acceptable on all three postoperative days (α=0.84 to 0.97). Cronbach's α and Rasch analysis revealed a misfit of stair climbing with the other items of the mILAS. The item difficulty of the mILAS items changed over the first two postoperative days. During the first three postoperative days, the sit to supine transfer was generally the most difficult item to achieve, and the sit to stand transfer was the least difficult item to achieve as rated by physiotherapists. The cross-validation analysis revealed similar results. CONCLUSIONS: The mILAS is a clinically sound measurement tool to assess the ability of patients to perform five functional tasks safely during hospitalisation. Stair climbing appears to be the easiest item to complete, and the sit to supine transfer is generally the most difficult after surgery.

Trigonometric Algorithm Defining the True Three-Dimensional Acetabular Cup Orientation: Correlation Between Measured and Calculated Cup Orientation Angles.

BACKGROUND: Acetabular cup orientation plays a key role in implant stability and the success of total hip arthroplasty. To date, the orientation has been measured with different imaging modalities and definitions, leading to lack of consensus on optimal cup placement. A 3-dimensional (3D) concept involving a trigonometric description enables unambiguous definitions. Our objective was to test the validity and reliability of a 3D trigonometric description of cup orientation. METHODS: Computed tomographic scans of the pelvis, performed for vascular assessment of 20 patients with 22 primary total hip replacements in situ, were systematically collected. On multiplanar reconstructions, 3 observers independently measured cup orientation retrospectively in terms of coronal inclination, sagittal tilt, and transverse version. The angles measured in 2 planes were used to calculate the angle in the third plane via a trigonometric algorithm. For correlation and reliability analyses, intraobserver and interobserver differences between measured and calculated angles were evaluated with use of the intraclass correlation coefficient (ICC). RESULTS: Measured and calculated angles had ICCs of 0.953 for coronal inclination, 0.985 for sagittal tilt, and 0.982 for transverse version. Intraobserver and interobserver reliability had ICCs of 0.987 and 0.987, respectively, for coronal inclination; 0.979 and 0.981, respectively, for sagittal tilt; and 0.992 and 0.978, respectively, for transverse version. CONCLUSIONS: The 3D concept with its trigonometric algorithm is a valid and reliable tool for the measurement of cup orientation. CLINICAL RELEVANCE: By calculating the transverse version of cups from coronal inclination and sagittal tilt measurements, the trigonometric algorithm enables a 3D definition of cup orientation, regardless of the imaging modality used. In addition, it introduces sagittal tilt that, like pelvic tilt, rotates around the transverse axis.

Precision and accuracy of imageless navigation versus freehand implantation of total hip arthroplasty: A systematic review and meta-analysis.

BACKGROUND: Total hip arthroplasty (THA) is named the most successful surgical procedure of the twentieth century. To remain a success in the twenty-first century THA should meet the higher demands of patients and society with regard to technical and functional outcome, costs and implant survival. To meet these demands optimal acetabular cup positioning is necessary. An imageless navigation system (NAV) might prevent malpositioning of the acetabular cup in THA. The aim of this study has been to compare the precision and accuracy of the anteversion and inclination of the acetabular cup position after NAV implantation and after freehand implantation of THA. METHODS: A systematic review and meta-analysis was conducted to assess the precision (variance) and accuracy (deviation from the target) from all available high-quality randomised control trials to date. RESULTS: Six out of seven studies concluded a statistically significant difference in precision in anteversion between the NAV group and the freehand group. Five out of seven studies concluded a statistically significant difference in precision in inclination. There is a significantly better accuracy for the NAV group than for the freehand group for anteversion (p = 0.002) and for inclination (p = 0.01). CONCLUSION: This study showed that NAV placement is more precise and has an improved accuracy for anteversion and inclination than freehand placement of the acetabular cup. However, there is a lack of evidence to support an improved functional outcome and a reduction of complications and revisions.

Bone tissue engineering for spine fusion: an experimental study on ectopic and orthotopic implants in rats.

Alternatives to the use of autologous bone as a bone graft in spine surgery are needed. The purpose of this study was to examine tissue-engineered bone constructs in comparison with control scaffolds without cells in a posterior spinal implantation model in rats. Syngeneic bone marrow cells were cultured in the presence of bone differentiation factors and seeded on porous hydroxyapatite particles. Seven rats underwent a posterior surgical approach, in which scaffolds with (five rats) or without cells (two rats) were placed on both sides of the lumbar spine. In addition, separate scaffolds were inserted intramuscularly and subcutaneously during the surgical procedure. After 4 weeks, all rats were killed and examined radiographically, by manual palpation of the excised spine and histologically for signs of bone formation or spine fusion. All rats that received cell-seeded scaffolds showed newly formed bone in all three locations, whereas none of the locations in the control rats showed bone formation. The results of this study support the concept of developing tissue-engineering techniques in posterior spine fusion as an alternative to autologous bone.

Bone tissue engineering and spinal fusion: the potential of hybrid constructs by combining osteoprogenitor cells and scaffolds.

In this paper, we discuss the current knowledge and achievements on bone tissue engineering with regard to spinal fusion and highlight the technique that employs hybrid constructs of porous scaffolds with bone marrow stromal cells. These hybrid constructs potentially function in a way comparable to the present golden standard, the autologous bone graft, which comprises besides many other factors, a construct of an optimal biological scaffold with osteoprogenitor cells. However, little is known about the role of the cells in autologous grafts, and especially survival of these cells is questionable. Therefore, more research will be needed to establish a level of functioning of hybrid constructs to equal the autologous bone graft. Spinal fusion models are relevant because of the increasing demand for graft material related to this procedure. Furthermore, they offer a very challenging environment to further investigate the technique. Anterior and posterolateral animal models of spinal fusion are discussed together with recommendations on design and assessment of outcome parameters.