The study of spinopelvic anatomy and movement has received great interest as these characteristics influence the biomechanical behavior (and outcome) following hip arthroplasty. However, to-date there is little knowledge of what “normal” is and how this varies with age. This study aims to determine how dynamic spino-pelvic characteristics change with age, with well-functioning hips and assess how these changes are influenced by the presence of hip arthritis.

This is an IRB-approved, cross-sectional, cohort study; 100 volunteers (asymptomatic hips, Oxford-Hip-sore>45) [age:53 ± 17 (24-87) years-old; 51% female; BMI: 28 ± 5] and 200 patients with end-stage hip arthritis [age:56 ± 19 (16-89) years-old; 55% female; BMI:28 ± 5] were studied. All participants underwent lateral spino-pelvic radiographs in the standing and deep-seated positions to determine maximum hip and spine flexion. Parameters measured included lumbar-lordosis (LL), pelvic incidence, pelvic-tilt (PT), pelvic-femoral angles (PFA). Lumbar flexion (ΔLL), hip flexion (ΔPFA) and pelvic movement (ΔPT) were calculated. The prevalence of spinopelvic imbalance (PI–LL>10?) was determined.

There were no differences in any of the spino-pelvic characteristics or movements between sexes. With advancing age, standing LL reduced and standing PT increased (no differences between groups). With advancing age, both hip (4%/decade) and lumbar (8%/decade) flexion reduced (p<0.001) (no difference between groups). ΔLL did not correlate with ΔPFA (rho=0.1). Hip arthritis was associated with a significantly reduced hip flexion (82 ±;22? vs. 90 ± 17?; p=0.003) and pelvic movements (1 ± 16? vs. 8 ± 16?; p=0.002) at all ages and increased prevalence of spinopelvic imbalance (OR:2.6; 95%CI: 1.2-5.7).

With aging, the lumbar spine loses its lumbar lordosis and flexion to a greater extent that then the hip and resultantly, the hip's relative contribution to the overall sagittal movement increases. With hip arthritis, the reduced hip flexion and the necessary compensatory increased pelvic movement is a likely contributor to the development of hip-spine syndrome and of spino-pelvic imbalance.

Adverse spinopelvic characteristics (ASC) have been associated with increased dislocation risk following primary total hip arthroplasty (THA). A stiff lumbar spine, a large posterior standing tilt when standing and severe sagittal spinal deformity have been identified as key risk factors for instability. It has been reported that the rate of dislocation in patients with such ASC may be increased and some authors have recommended the use of dual mobility bearings or robotics to reduce instability to within acceptable rates (<2%).

The aims of the prospective study were to 1: Describe the true incidence of ASC in patients presenting for a THA 2. Assess whether such characteristics are associated with greater symptoms pre-THA due to the concomitant dual pathology of hip and spine and 3. Describe the early term dislocation rate with the use of ≤36mm bearings.

This is an IRB-approved, two-center, multi-surgeon, prospective, consecutive, cohort study of 220 patients undergoing THA through anterolateral- (n=103; 46.8%), direct anterior- (n=104; 27.3%) or posterior- approaches (n=13; 5.9%). The mean age was 63.8±12.0 years (range: 27.7-89.0 years) and the mean BMI 28.0±5.0 kg/m² (range: 19.4-44.4 kg/m²). There were 44 males (47.8%) and 48 females (52.2%). The mean follow-up was 1.6±0.5 years. Overall, 54% of femoral heads was 32 mm, and 46% was 36mm.

All participants underwent lateral spinopelvic radiographs in the standing and deep-flexed seated positions were taken to determine lumbar lordosis (LL), sacral slope (SS), pelvic tilt (PT), pelvic-femoral angle (PFA) and pelvic incidence (PI) in both positions. Spinal stiffness was defined as lumbar flexion <20° when transitioning between the standing and deep-seated position; adverse standing PT was defined as >19° and adverse sagittal lumbar balance was defined as mismatch between standing PI and LL >10°.

Pre-operative patient reported outcomes was measured using the Oxford Hip Score (OHS) and EuroQol Five-Dimension questionnaire (EQ-5D). Dislocation rates were prospectively recorded. Non-parametric tests were used, significance was set at p<0.05.

The prevalence of PI-LL mismatch was 22.1% (43/195) and 30.4% had increased standing PT (59/194). The prevalence of lumbar stiffness was 3.5% (5/142) and these patients had all three adverse spinopelvic characteristics (5/142; 3.5%).

There was no significant difference in the pre-operative OHS between patients with (20.7±7.6) and patients without adverse spinopelvic characteristics (21.6±8.7; p=0.721), nor was there for pre-operative EQ5D (0.651±0.081 vs. 0.563±0.190; p=0.295).

Two patients sustained a dislocation (0.9%): One in the lateral (no ASC) and one in the posterior approaches, who also exhibited ASC pre-operatively.

Sagittal lumbar imbalance, increased standing spinal tilt and spinal stiffness are not uncommon among patients undergoing THA. The presence of such characteristics is not associated with inferior pre-operative PROMs. However, when all characteristics are present, the risk of instability is increased. Patients with ASC treated with posterior approach THA may benefit from the use of advanced technology due to a high risk of dislocation. The use of such technology with the anterior or lateral approach to improve instability is to date unjustified as the rate of instability is low even amongst patients with ASCs.

The presence of hip osteoarthritis is associated with abnormal spinopelvic characteristics. This study aims to determine whether the pre-operative, pathological spinopelvic characteristics “normalize” at 1-year post-THA.

This is a prospective, longitudinal, case-control matched cohort study. Forty-seven patients underwent pre- and post- (at one-year) THA assessments. This group was matched (age, sex, BMI) with 47 controls/volunteers with well-functioning hips. All participants underwent clinical and radiographic assessments including lateral radiographs in standing, upright-seated and deep-flexed-seated positions. Spinopelvic characteristics included change in lumbar lordosis (ΔLL), pelvic tilt (ΔPT) and hip flexion (pelvic-femoral angle, ΔPFA) when moving from the standing to each of the seated positions. Spinopelvic hypermobility was defined as ΔPT>30° between standing and upright-seated positions.

Pre-THA, patients illustrated less hip flexion (ΔPFA −54.8°±17.1° vs. −68.5°± 9.5°, p<0.001), greater pelvic tilt (ΔPT 22.0°±13.5° vs. 12.7°±8.1°, p<0.001) and greater lumbar movements (ΔLL −22.7°±15.5° vs. −15.4°±10.9°, p=0.015) transitioning from standing to upright-seated. Post-THA, these differences were no longer present (ΔPFApost −65.8°±12.5°, p=0.256; ΔPTpost 14.3°±9.5°, p=0.429; ΔLLpost −15.3°±10.6°, p=0.966). The higher prevalence of pre-operative spinopelvic hypermobility in patients compared to controls (21.3% vs. 0.0%; p=0.009), was not longer present post-THA (6.4% vs. 0.0%; p=0.194). Similar results were found moving from standing to deep-seated position post-THA.

Pre-operative, spinopelvic characteristics that contribute to abnormal mechanics can normalize post-THA following improvement in hip flexion. This leads to patients having the expected hip-, pelvic- and spinal flexion as per demographically-matched controls, thus potentially eliminating abnormal mechanics that contribute to the development/exacerbation of hip-spine syndrome.

Spinopelvic mobility describes the change in lumbar lordosis and pelvic tilt from standing to sitting position. For 1° of posterior pelvic tilt, functional cup anteversion increases by 0.75° after total hip arthroplasty (THA). Thus, spinopelvic mobility is of high clinical relevance regarding the risk of implant impingement and dislocation.

Our study aimed to 1) determine the proportion of OA-patients with stiff, normal or hypermobile spino-pelvic mobility and 2) to identify clinical or static standing radiographic parameters predicting spinopelvic mobility.

This prospective diagnostic cohort study followed 122 consecutive patients with end-stage osteoarthritis awaiting THA. Preoperatively, the Oxford Hip Score, Oswestry Disability Index and Schober's test were assessed in a standardized clinical examination. Lateral view radiographs were taken of the lumbar spine, pelvis and proximal femur using EOS© in standing position and with femurs parallel to the floor in order to achieve a 90°-seated position. Radiographic measurements were performed for the lumbar lordosis angle (LL), sacral slope (SS), pelvic tilt (PT), pelvic incidence (PI) and pelvic-femoral-angle (PFA). The difference in PT between standing and seated allowed for patient classification based on spino-pelvic mobility into stiff (±30°).

From the standing to the sitting position, the pelvis tilted backwards by a mean of 19.6° (SD 11.6) and the hip was flexed by a mean of 57° (SD 17). Change in pelvic tilt correlated inversely with change in hip flexion.

Spinopelvic mobility is highly variable in patients awaiting THA and we could not identify any clinical or static standing radiographic parameter predicting the change in pelvic tilt from standing to sitting position. In order to identify patients with stiff or hypermobile spinopelvic mobility, we recommend performing lateral view radiographs of the lumbar spine, pelvis and proximal femur in all patients awaiting THA. Thereafter, implants and combined cup inclination/anteversion can be individually chosen to minimize the risk of dislocation.

No predictors could be identified. We recommend performing sitting and standing lateral view radiographs of the lumbar spine and pelvis to determine spinopelvic mobility in patients awaiting THA.

Introduction

The optimal bearing for hip arthroplasty is still a matter of debate. in younger and more active patients ceramic-on-polyethylene (CoP) bearings are frequently chosen over metal-on-polyethylene (MoP) bearings to reduce wear and increase biocompatibility. However, the fracture risk of ceramic heads is higher than that of metal heads. This can cause serious issue, as ceramic fractures pose a serious complication often necessitating major revision surgery – a complication more frequently seen in ceramic-on-ceramic bearings. To date, there are no long-term data (> 20 years of follow-up) reporting fracture rates of the ceramic femoral heads in CoP bearings.

Corrosion in modular taper connections of total joint replacement has become a hot topic in the orthopaedic community and failures of modular systems have been reported. The objective of the present study was to determine in vivo titanium ion levels following cementless total hip arthroplasty (THA) using a modular neck system.

A consecutive series of 173 patients who underwent cementless modular neck THA and a ceramic on polyethylene bearing was evaluated retrospectively. According to a standardized protocol, titanium ion measurements were performed on 67 patients using high-resolution inductively coupled plasma-mass spectrometry. Ion levels were compared to a control group comprising patients with non-modular titanium implants and to individuals without implants.

Although there was a higher range, modular-neck THA (unilateral THA: 3.0 μg/L (0.8–21.0); bilateral THA: 6.0 μg/L (2.0–20.0)) did not result in significant elevated titanium ion levels compared to non-modular THA (unilateral THA: 2.7 μg/L (1.1–7.0), p = 0.821; bilateral THA: 6.2 μg/L, (2.3–8.0), p = 0.638). In the modular-neck THA group, patients with bilateral implants had significantly higher titanium ion levels than patients with an unilateral implant (p < 0.001). Compared to healthy controls (0.9 μg/L (0.1–4.5)), both modular THA (unilateral: p = 0.029; bilateral p = 0.003) and non-modular THA (unilateral: p < 0.001; bilateral: p < 0.001) showed elevated titanium ion levels.

The data suggest that the present modular stem system does not result in elevated systemic titanium ion levels in the medium term when compared to non-modular stems. However, more outliner were seen in modular-neck THA. Further longitudinal studies are needed to evaluate the use of systemic titanium ion levels as an objective diagnostic tool to identify THA failure and to monitor patients following revision surgery.