Aims

Concurrent hip and spine pathologies can alter the biomechanics of spinopelvic mobility in primary total hip arthroplasty (THA). This study examines how differences in pelvic orientation of patients with spine fusions can increase the risk of dislocation risk after THA.

Aims

Posterior tilt of the pelvis with sitting provides biological acetabular opening. Our goal was to study the post-operative interaction of skeletal mobility and sagittal acetabular component position.

Dislocation and accelerated wear have been the nemesis of hip surgeons. No study has been able to correlate cup position to instability. In recent years the influence of the spine-pelvis-hip construct has emerged as important to understand the shift in component position with postural change. Using measurements familiar to spine surgeons, we have correlated the pelvic incidence (PI), a static measurement of pelvic width and hip position; the static tilt, a dynamic measure of pelvic-spine mobility. For THR we have measured the sagittal cup position as the fixed angular change of the cup shifts with pelvic tilt, and this is named anteinclination; and the sacral acetabular angle (SAA) which is the relationship of the acetabulum to the absolute value of sacral tilt (ST) in both standing and sitting. The pelvic femoral angle (PFA) is a measure of femur/hip flexion/internal rotation correlated to pelvic mobility. Dislocation is most common in patients with low PI combined with an ST change <15 degrees. With normal PI and high PI, it occurs much less commonly and only in patients with ST change <5 degrees (very stiff). In patients with stiff pelvis (ST<13) the cup needs increased inclination and anteversion (45/20–25) to compensate for absence of cup opening by posterior tilt of pelvis. For patients with low PI and stiff pelvis we recommend constraint (such as dual mobility articulation)

Aims. This study compared the long-term results following Salter osteotomy and Pemberton acetabuloplasty in children with developmental dysplasia of the hip (DDH). We assessed if there was a greater increase in pelvic height following the Salter osteotomy, and if this had a continued effect on pelvic tilt, lumbar curvature or functional outcomes. Patients and Methods. We reviewed 42 children at more than ten years post-operatively following a unilateral Salter osteotomy or Pemberton acetabuloplasty. We measured the increase in pelvic height and the iliac crest tilt and sacral tilt at the most recent review and at an earlier review point in the first decade of follow-up. We measured the lumbar Cobb angle and the Short Form-36 (SF-36) and Harris hip scores were collected at the most recent review. Results. During the first decade of follow-up, there was a greater increase in pelvic height in the children who had a Salter osteotomy (Salter, 10.1%; Pemberton, 4.3%, p < 0.001). The difference in the increase in pelvic height was insignificant at the most recent review (Salter, 4.4%; Pemberton, 3.1%, p = 0.249). There was no significant difference between the two groups for the lumbar Cobb angle, (Salter, 3.1°; Pemberton, 3.3°, p = 0.906). A coronal lumbar curve was seen in 41 children (97%), 30 of these had a compensatory curve. Sacral tilt was the radiographic parameter for pelvic imbalance that correlated most with the lumbar Cobb angle (Pearson correlation co-efficient 0.59). The Harris hip score and SF-36 were good and showed no differences between the two groups. Conclusion. In the long-term, we found no difference in the functional results or pelvic imbalance between Salter osteotomy and Pemberton acetabuloplasty in the management of children with DDH. Cite this article: Bone Joint J 2016;98-B:1145–50

Introduction. The potential structural effect of the sacral tilt on the development of disc wedging adjacent to lowest instrumented vertebra (LEV), and consequent postoperative coronal trunk decompensation in the surgical treatment of idiopathic scoliosis are well known. The aim of this study is firstly to establish the possible role of sacral tilt, limb length inequality, and associated pelvic girdle anomalies in the cause of idiopathic scolisosis, and secondly to determine the effect of sacral tilt on adjacent disc wedging below LEV in some idiopathic curves such as thoracolumbar/lumbar curves, and double major curves postoperatively. Methods. Between 2006 and 2008, 159 patients with idiopathic scoliosis from outpatient clinics were included in analyses. In all patients, standing posteroanterior and lateral spinal column and Ferguson radiographs were routinely taken. If direct radiographs suggested iliac bone asymmetry, hemi-pelvis volume measurements were done with CT scan. Curve type, sacral tilt, L5 tilt, iliac asymmetry, and limb-length differences were measured. As a second part of study, 87 surgically treated patients with double major curves were examined retrospectively in terms of adjacent subjacent disc wedging below LEV and sacral tilt. Results. In the first part of the study, the mean age of patients was 14·21 years (range 2–25) and all but 14 were female. The curve types were lumbar in 31 patients, thoracolumbar in 42, double major in 55, thoracic in 27, and triple in four. Sacral tilt towards the convex side of TL/L curve was present in 117 (74%) patients with an average of 8° measured from Ferguson graphs. L5 tilt towards the convex side of TL/L curve, and limb length inequality of less than 5 mm on the convex side of TL/L curve were more prevalent in patients with sacral tilt (57%) than in those without sacral tilt (p=0·021). On hemi-pelvis volume measurement, patients with no sacral tilt (n=42) had no difference in both sides whereas patients with sacral tilt (n=117) showed significant difference, with the convex side being smaller. We noted a correlation between L5 tilt and sacral tilt (p=0·048) and between sacral tilt and hemi-pelvis volume (p=0·024). There was no correlation between sacral tilt and pelvic asymmetry, age, sex, curve type, or amount of limb length inequality. In the second part of the study, disc wedging adjacent to LEV was present in 75 of 87 patients and sacral tilt was present in 72 of 75 (96%) (p=0·008). Six patients had limb length inequality of more than 1 cm, showing the postoperative trunk decompensation, which was corrected by elevating the shorter leg by shoe-lift. Conclusions. This study revealed significant association between sacral tilt and hemi-pelvis hypoplasia independent from age. This association may have a primary role in the cause of this disease. Although LEV is paralel to pelvis, intervertebral disc adjacent to LEV is often wedged and there is lumbosacral hemicurve distally below the instrumentation in patients treated by either anterior or posterior surgery. We believe that lumbosacral hemicurve due to sacral tilt behaves like hemivertebra, which is impossible to detect with preoperative standing anteroposterior radiographs. Ferguson view is necessary to detect the sacral tilt. The postoperative trunk decompensation is greater with presence of sacral tilt and limb length inequality

Introduction: The goal of the study was to analyse the modification of the sagittal lombo-pelvic equilibrium after total hip replacement for osteoarthritis. Materials and Methods: The sagittal lombo-pelvic equilibrium was analysed among 89 patients who underwent total hip replacement for osteoarthritis, using lateral X-rays of the whole spine including the hips performed pre-operatively and at one year post-operatively. Reference values were calculated by carrying out the same analysis among 100 asymptomatic healthy volunteers. The studied parameters were: the sacral tilt (ST), the pelvic version (PV) and the sacral incidence (SI). Results: The mean pre-operative value of STangle was significantly lower in the osteoarthritis group (20.6° +/−6) compared to the reference group (39.4 +/6, p< 0,00001). The mean pre-operative value of VP angle was significanlty higher in the osteoarthritis group (31°+/−8) compared to the reference group (13.5 +/−6 p < 0,00001). There was no significant difference between the two groups for the sacral incidence (p=0,3). At one year post-operatively, the sacral tilt has significantly increased by 5.5° (p< 0.00001). Discussion: Compared to asymptomatic healthy volunteers, patients affected by osteoarthritis had a pelvic retroversion that has decreased post-operatively but still remained lower than the norm. Conclusion: The lombo-pelvic equilibrium is different in case of osteoarthritis. After total hip replacement the pelvis remained retroverted. This phenomenon should be taken into account for the planning of total hip arthroplasty

Orientation of acetabular component, influenced by pelvic tilt, body position and individual variations affects the outcome following total hip arthroplasty (THA). Currently available methods of evaluation are either imprecise or require advanced image processing. We analyzed inter-subject and intra-subject variability of pelvic tilt, measured by sagittal sacral tilt (ST) and its relationship with acetabular component tilt (AT) by using a simple method based on standard radiographs. ST was measured on lateral radiographs of pelvis including lumbosacral spine obtained in supine, sitting, standing and lateral decubitus position for 40 asymptomatic THA patients and compared to CT data obtained in supine position. AT was measured on lateral radiographs (measured acetabular tilt: MAT) in each position and compared to measurement of AT on CT and an indirectly calculated acetabular component tilt(CAT). Mean ST changed from supine to sitting, standing and lateral decubitus positions as follows: 26.5°±15.5 (range, 4.6°–73.4°), 8.4°±6.2° (range, 0.6°– 24.5°) and 13.4°±8.4° (range, 0.1°–24.2°) (p< 0.0001, p=0.002, p=0.0055). The MAT on radiographs was not significantly different from the MAT measured on CT (p= 0.002) and the CAT (p=0.058). There is a good correlation between change in ST and MAT in sagittal plane (r =0.93). Measurement of ST on radiographs is a simple and reliable method to track changes in pelvic tilt in different body positions. There is significant inter-subject and intra-subject variation of ST and MAT with postural changes and it may explain causes of impingement or instability following THA, which could not be previously explained

Introduction The concept of accelerated degeneration of adjacent disc levels as a consequence of increased stress caused by interbody fusion of the lumbar spine has been widely postulated. Total disc arthroplasty may offer the same clinical benefits as fusion while providing motion that may protect the adjacent level discs from the abnormal and undue stresses associated with fusion. The goal of this study was to prospectively analyse the results of the Maverick Lumbar Disc Prosthesis (Medtronic, USA) at 4 years follow-up. Methods We conducted a prospective analysis of the Maverick Lumbar Disc Prosthesis implanted in the first 50 consecutive patients for the treatment of degenerative disc disease of the lumbar spine resistant to conservative treatment for more than 1 year. 253 Maverick have been implanted in our spine unit and these 50 have the longest follow-up. The outcome data collected included the Oswestry Questionnaire and Visual Analog Scale (VAS) preoperatively and at routine scheduled follow-ups. Radiographic analysis included sagittal balance parameters on standing full length lateral radiographs of the spine and range of motion on flexion/extension dynamic radiographs. 3 European centres were included in the study. The offset on AP x-rays was calculated for all patients and correlated with clinical outcomes. Results There were 32 females and 28 males with an average age of 43, 4 years and average follow-up of 3.1 years (22 to 48 months). The Maverick was implanted at L5S1: 20 cases; L4L5: 17 cases; 3 patients had 2 levels arthroplasty and 10 had a fusion at L5S1 and a prosthesis at L4L5. Clinical success, defined by the FDA as improvement of at least 25% on the Oswestry, was 76% and 81%, at 6 months and 1 year follow-up respectively. The VAS showed an improvement in back pain from 7.1 (+/− 2, 1) pre-operatively to 3.0 (+/− 1.8) post-operatively. Leg pain was significantly higher according to VAS when patients have been previously operated for disc herniation (HD). At the latest follow-up, there was no measurable subsidence of the devices except in one case at L5S1 due to a technical error and no evidence of device migration. The measured range of motion in flexion-extension ranged from 3 to 16 degrees (mean range of motion, 6 +/− 4 degrees). L4–L5 level is more mobile: average 8.4 degrees. With regards to sagittal balance, there was no significant change in any of the variables studied including sacral tilt, pelvic tilt, or overall lordosis after placement of total disc arthroplasty. Only the lordosis at the level above the prosthesis was significantly decreased. The position of the implant on AP and lateral x ray was analyzed and correlated with the clinical results. Less than 19% of offset on AP view had no influence on clinical results. One complication, a ureter injury occurred during the approach in one procedure. One left iliac vein injury occurred per-operatively and treated with vascular clip. One patient with two discs with persistent low back was re-operated for posterior fusion with a significant improvement of pain at two years. This patient had been operated 3 times before for disc herniation and recurrence of HD. Discussion These results of total disc arthroplasty compare favorably with the mid-term clinical outcomes associated with anterior lumbar discectomy and fusion reported in the literature. Unlike fusion however, it appears that the prosthesis has enough freedom of motion to allow the patient to maintain the natural sagittal and spinopelvic balance with radiographic evidence of normal range of motion. However, these early favorable clinical results in addition to the influence on adjacent motion segments can be assessed only after long term follow-up. Previous surgery for HD isn’t the better indication to restore the motion

Background: In lumbar scoliosis curves of school screening referrals were evaluated (1) for the possible relation of pathomechanisms to standard and non-standard vertebral rotation (NSVR) [. 1. ], and (. 2. ) the relation between apical lumbar axial vertebral rotation and the frontal plane spinal offset angle (FPTA) [. 2. ]. Methods: Consecutive patients referred to hospital during routine school screening using the Scoliometer were examined in 1996–9. None had surgery for their scoliosis. There are 40 subjects with either pelvic tilt scoliosis (11), idiopathic lumbar scoliosis (19), or double curves (10)(girls 31, postmenarcheal 25, boys 9, mean age 15.3 years). One observer (RGB) measured: 1) in AP spinal radiographs Cobb angles (CAs), apical vertebral rotations (Perdriolle AVRs), and trigonometrically sacral alar tilt angle (SATA), and FPTA as the tilt of the T1–S1 line to the vertical; and 2) total leg lengths (tape). Results: Excluding the double curves there are 16 left and 14 right lumbar curves mean CA 11 degrees (range 4–24 degrees), mean AVR 9 degrees (concordant to CA in 18/30, discordant in 7/30), SATA 2.8 degrees (range 0.2–7.7 degrees associated with CA side and severity, p=0.0003), and leg-length inequality 0.7 cm (significantly shorter on left, p< 0.0001 and associated with SATA (p=0.02) but not CA). Neither CA nor AVR in each of the laterality concordant and discordant lumbar or thoracic curves is significantly different. Twenty-six subjects have thoracic curves (16 right) 22 with AVR (mean CA 11 degrees, range 4–17 degrees, AVR 9 degrees, n=22) the CA being associated with each of lumbar CA and SATA (respectively p< 0.0001, p=0.003, n=26). Thoracic curve laterality of CA and AVR is concordant in 12/26 curves and discordant in 10/26 and for concordance/discordance neither is significantly different; thoracic AVR sides with laterality of lumbar curve AVR shown by thoracic AVR (but not CA) being greater in lumbar discordant than in lumbar concordant curves (14 & 7 degrees respectively, p=0.03, n=18 & 7). Both for lumbar curves alone and for lumbar with double curves, AVR by side is significantly associated with FPTA by side (r= −0.568, p=0.001, n=30; r=−0.560, p=0.0002, n=40). Conclusion: (1) It is hypothesized that different pathomechanisms may separately affect the frontal (CA) and transverse (AVR) planes: in discordant curves these mechanisms may neutralize each other and limit curve progression; concordant curves require these biplanar mechanisms to summate and facilitate curve progression. (2) The association of frontal plane spinal tilt angle and lumbar AVR may result from balance mechanisms affecting trunk muscles – mechanisms that may underlie the complication of post-operative frontal plane spinal imbalance or decompensation [. 2. ]

Study Design: Prospective Cohort study. Objective: To prospectively evaluate the Maverick Lumbar Disc Prosthesis (Medtronic, USA) at one year follow-up. Methods: Prospective analysis of the Maverick Lumbar Disc Prosthesis implanted in the first 30 consecutive patients for the treatment of single-level degenerative disc disease of the lumbar spine resistant to conservative treatment for more than one year. Subjects: Sixteen females and 14 males with an average age of 44 years and minimum follow-up of 1 year. The prosthesis was implanted at L4-L5 in 18 patients and at L5-S1 in 12. Outcome Measures: Oswestry Disability Index (ODI) and Visual Analogue Scale (VAS) preoperatively and at routine scheduled follow-ups. Radiographic analysis included sagittal balance parameters on standing full length lateral radiographs of the spine and range of motion on flexion/extension dynamic radiographs. Results: Clinical success (ODI improvement > 15), was 82% and 86%, at 6 months and one year follow-up respectively. The VAS showed an improvement in back pain from 7.1 (+/− 2) pre-operatively to 3.0 (+/− 1.8) post-operatively. At one year there were no device related complications. The measured range of motion in flexion-extension ranged from 3 to 12 degrees (mean range of motion, 6 +/− 4 degrees). There was no significant change in sacral tilt, pelvic tilt, or overall lordosis after disc replacement. In one case the ureter was injured during the approach. Conclusions: The results of total disc arthroplasty presented here compare favourably with results reported in the literature following ALIF. It appears that the disc prosthesis has enough freedom of motion to allow the patient to maintain normal sagittal and spino-pelvic balance with radiographic evidence of normal range of motion. These early favourable clinical results and the influence on adjacent motion segments can be assessed only after long term follow-up

Introduction Lumbar fusion may alter the sagittal balance of the spine, including a decrease in the sacral tilt ST and lumbar lordosis. Postoperative pain following a spinal fusion has been shown to be related to changes in sagittal balance, independent of other factors including pseudarthrosis. The goal of this radiological study was to prospectively determine the effect of a single-level, total disc replacement on the sagittal balance of the spine, especially on sacral tilt (ST), pelvic tilt (PT), and lumbar lordosis (Le Huec J, et al; Spine J. 2004). Method 35 patients received a single level disc replacement using the Maverick Total Disc Arthroplasty system (Medtronic Sofamor Danek). The preoperative and postoperative radiographic evaluation included standing anteroposterior and lateral full spine films that included the femoral heads. The parameters studied were ST, PT, global and segmental lordosis, and global kyphosis. The average age of the 35 patients studied was 44.3 years (range 35–57). There were 18 females and 17 males. The disc arthroplasty was performed at the L4–L5 level in 19 patients and at the L5-S1 level in 16 patients. The average follow-up was 14 months (range 6–22 months). Results The preoperative values of global lordosis, ST, PT and global lordosis were not significantly different at last follow-up. When the groups were compared according to the level operated, there was no statistical difference with regard to the overall lordosis, ST, PT or kyphosis from pre- to postoperative period or when the two groups were compared with each other. The level above the prosthesis has significantly less lordosis. Discussion In the present study with use of a motion-preserving intervertebral disc prosthesis, it appears that the patient is able to maintain the preoperative sagittal balance. The prosthesis has enough freedom of motion to allow the patient to maintain the natural sagittal and spinopelvic balance needed to prevent potentially undue stress on the muscles and the sacroiliac joint. Although the number of patients is small, this is the first study that evaluates the sagittal balance after motion-preserving total disc arthroplasty

Purpose: Uncertain position of the acetabular implant has been the cause of dysfunction in certain cases of total hip arthroplasty (THA). Classical computed tomographic analysis of anteversion has certain limitations. Integrated reconstruction of positions at risk allows a better diagnostic approach. Material and methods: We studied 46 THA because of posterior malposition (n=17, anterior subluxation in the standing position in twelve, and true dislocation in five) and anterior malposition (n=29, posterior subluxation in sixteen and true dislocation in thirteen). Two groups of 70 naïve hips and a group of 56 THA with no functional problem served as controls. The position of the acetabulum was studied on optimised computed tomography slices reconstructing the planes of analysis for the standing, sitting and reclining positions. The reference planes for the slices was given by the sacral tilt angle measured on the lateral views of the patient in the corresponding positions. The optimised computed tomographic measurements of anteversion were compared with the classical measures. None of the patients had abnormal femoral anteversion and/or an oblique pelvis and/or leg length discrepancy greater than 10 mm. The frontal inclination of the acetabular implants was 40°–50°. Results: In the naïve hips, acetabular anteversion varied: 19.2 with the conventional method, 15.7 in the standing position and 31 in the sitting position. In the THA controls, anteversion measurements differed: 21.3 with the conventional method, 21.4 in the standing position and 35.8 in the sitting position. In the THA with a posterior malposition, 18/29 could not be explained by the conventional measurement, but the optimised measurement enabled an understanding in 17 hips (defective anteversion in the sitting position). Discussion: Changes in pelvis orientation between the sitting and standing positions modifies real anteversion of the cup. In particular, subjects with THA tend to have a spontaneous posterior tilt of the pelvis related to trunk ageing. This element should be taken into account for the analysis of both major and minor THA dysfunction