The Relationship of Cup Inclination and Anteversion in the Coronal Plane with Ante-Inclination in the Sagittal Plane: Exposing the Fallacy of Cup Safe Zones.

Background: This study aimed to establish an equation for calculating cup ante-inclination (AI) from radiographic cup inclination and anteversion, to validate this equation in a total hip arthroplasty (THA) cohort, and to test whether achieving previously described radiographic cup inclination and anteversion targets would also satisfy sagittal cup AI targets. Methods: A mathematical equation linking cup AI, radiographic inclination (RI), and anteversion (RA) was determined: tan(AI) = tan(RA)/cos(RI). Supine and standing anteroposterior and lateral radiographs of 440 consecutive THAs were assessed to measure cup RI and RA and spinopelvic parameters, including cup AI, using a validated software tool. Whether orientation within previously defined RI and RA targets was associated with achieving the AI target and satisfying the sagittal component orientation (combined sagittal index, 205° to 245°) was tested. Results: The cups in the THA cohort had a measured mean inclination (and standard deviation) of 43° ± 7°, anteversion of 26° ± 9°, and AI of 34° ± 10°. The calculated cup AI was 34° ± 12°. A strong correlation existed between measured and calculated AI (r = 0.75; p < 0.001), with a mean error of 0° ± 8°. The inclination and anteversion targets were both satisfied in 194 (44.1%) to 330 (75.0%) of the cases, depending on the safe zone targets that were used, and 311 cases (70.7%) satisfied the AI target. Only 125 (28.4%) to 233 (53.0%) of the cases satisfied the AI target as well as the inclination and anteversion targets. Satisfying inclination and anteversion targets was not associated with increased chances of satisfying the AI target. Conclusions: Achieving optimal cup inclination and anteversion does not ensure optimal orientation in the sagittal plane. The equation and nomograms provided can be used to determine and visualize how the 2 planes used for evaluating the cup orientation and the pertinent angles relate, potentially aiding in preoperative planning.

Elevated Blood Tantalum Concentrations in Patients Following Reconstruction of Severe Acetabular Defects in Total Hip Arthroplasty Using Modular Tantalum Augments in Combination With Uncemented Tantalum Cups.

INTRODUCTION: The reconstruction of acetabular defects in total hip arthroplasty (THA) can be challenging. An option to treat uncontained acetabular defects is to use modular tantalum augments in combination with cementless press-fit cups. However, modularity is associated with an increased risk of debonding and mechanical failure. In addition, metal wear particles can be released due to micromotions at the implant interface. Clinical data on the long-term results of this treatment strategy is limited. The purposes of this study were: (1) to evaluate the clinical and radiological outcome of complex THA using modular trabecular metal augments and uncemented revision cups; (2) to investigate the blood tantalum concentrations in these patients at mid-term (mean 4.5 year) follow-up; and (3) to report complications and mechanisms of failure related to this procedure. MATERIALS AND METHODS: In this single-center study, we retrospectively reviewed data from a consecutive cohort of 27 patients who underwent complex acetabular defect reconstruction using a modular tantalum acetabular augment in combination with an uncemented tantalum cup. We evaluated the implant survival, and the radiological and clinical outcomes after a mean follow-up of 4.5 years (SD 2.1; range 2.5 to 10.6 years) using patient-reported outcome scores (PROMs). Blood samples were analyzed regarding tantalum concentration and compared with a control group. RESULTS: The cumulative survival rate at 4.5 years with the endpoint "revision of the acetabular component for aseptic loosening" was 94.4% (95% confidence interval (CI) 71.6 to 99.2) and 82.9% (95 % CI 60.5 to 93.3) for the endpoint "revision for any reason." The PROMs improved significantly up to the latest follow-up, and radiographic data showed no signs of loosening or implant migration. Median blood tantalum concentrations were significantly higher in the study group (0.15 µg/L) compared to the control group (0.002 µg/L) (P < 0.001). CONCLUSIONS: This study demonstrated acceptable clinical and radiological results of cementless revision THA using modular trabecular metal implants for the reconstruction of large acetabular defects. Tantalum concentrations were significantly higher in patients who had tantalum implants compared to the control group, however, the systemic and local effects of an increased tantalum exposure are not yet fully understood and have to be further investigated.

Impact of Offset and Leg Length on Functional Outcomes Post-Total Hip Arthroplasty: How Accurate Should Coronal Reconstruction Be?

BACKGROUND: Accurate hip reconstruction is associated with improved biomechanical behavior following total hip arthroplasty (THA). However, whether this is associated with improved patient-reported outcome measures (PROs) is unknown. HYPOTHESIS/PURPOSE: This study aimed to: 1) Describe the ability to reconstruct coronal geometry during THA without advanced technology; 2) Assess whether restoration of global offset (GO) and leg length (LL) is associated with improved PROs; and 3) Investigate whether increased femoral offset (FO) to compensate for reduced acetabular offset (AO) influences PROs. METHOD: This was a prospective, multi-center, consecutive cohort study of 500 patients treated with primary THA without robotics or navigation. The Oxford Hip Score (OHS) was obtained pre-operatively and at 1-year follow-up. Supine anteroposterior (AP) pelvic radiographs were analyzed to determine AO, FO, GO, and LL relative to the native contralateral side. Contour plots for ΔOHS based on ΔLL and ΔGO were created, and ΔOHS was calculated within and outside various ranges (± 2.5, ± 5, or ± 10 mm). RESULTS: The mean GO and LL differences between sides were 0 ± 7 mm and 0 ± 8 mm, respectively. In the operated hip, mean FO increased to 3 ± 6 mm (range, -16 to 27), while AO decreased to 2 ± 4 mm (range, -17 to 10). The contour graph for ± 2.5 mm zones showed the best outcomes (ΔOHS > 25) with GO and LL centered on 0 ± 2.5 mm (P < 0.01). However, only 10% achieved such reconstruction. When GO and LL differences were within ± 10 mm, ΔOHS was superior when both AO and FO were within ± 5 mm (mean: 24 ± 10; range, -5 to 40) compared to when FO was above 5 mm to compensate for a reduction in AO (mean: 22 ± 11; range, -10 to 46; P = 0.040). DISCUSSION: Mean GO and LL reconstruction were both 0 mm, with a precision of 7 and 8 mm, respectively, using manual techniques. The PROs were associated with biomechanical reconstruction, and the best clinical improvement can be expected when GO and LL differences are both within 2.5 mm. Maintenance of AO is important, as compensation by increasing FO is associated with inferior OHS.

How Do Spinopelvic Characteristics Change Post-Total Hip Arthroplasty? A Longitudinal Assessment Raising Awareness of the Postoperative Period.

BACKGROUND: Spinopelvic characteristics, including sacral slope (SS), are commonly evaluated in different positions pre-total hip arthroplasty (THA). This study aimed to: 1) investigate the change in spinopelvic parameters at 7 days (early) and 1-year post-THA; and 2) identify patient characteristics associated with a change in SS of more than 7° post-THA. METHODS: We prospectively studied 250 patients who underwent unilateral THA [132 women, age 66 years (range, 32 to 88)] and underwent biplanar images preoperatively and at 7 days and 1-year post-THA. Parameters measured included pelvic incidence, standing lumbar lordosis, SS, and proximal femoral angle (PFA). A SS change ≥ 7° was considered the threshold as it would result in more than a 5° change in cup orientation. RESULTS: Early post-THA SSstanding remained within ± 6º from preoperative measurements in 75% of patients, reduced by ≥ 7° in 9%, and increased by ≥ 7° in 16%. Those that showed a reduction in SS had the lowest PFA and the highest SS pre-THA (P = .028, .107, and < 0.001, respectively). From 7 days until the 1-year mark, pelvic tilt increased, SS reduced (mean: -4º, range: -29 to 17º, P < .001), and patients stood with greater hip extension ΔPFAstanding (mean 7°, range: -34 to 37°, P < .001). At 1 year, SSseated had remained within ± 6º, relative to the pre-THA value, in 49% of patients. CONCLUSIONS: Standing spinopelvic characteristics, especially SSstanding, remain within ±6° in three-quarters of patients both early- and at 1-year post-THA. In the remaining cases, pelvic tilt changes significantly. In 9% of cases, SS reduces ≥ 7° early THA, probably due to the alleviation of fixed-flexion contractures. The SSseated changes by ≥ ± 7° in almost 50% of cases in this study, and its clinical value as a preoperative planning tool should be questioned. LEVEL OF EVIDENCE: Level II, diagnostic study.

How to Screen for Lumbar Spine Stiffness in Patients Awaiting Total Hip Arthroplasty.

BACKGROUND: This study aimed to (1) define the prevalence of spinopelvic abnormalities among patients who have hip osteoarthritis (OA) and controls (asymptomatic volunteers) and (2) identify factors that reliably predict the presence of lumbar spine stiffness. METHODS: This is a prospective, cross-sectional, case-cohort study of patients who have end-stage primary hip OA, who underwent primary total hip arthroplasty (THA). Patients were compared with a cohort of asymptomatic volunteers, matched for age, sex, and body mass index (BMI), serving as a control group. Spinopelvic pathologies were defined as: lumbar spine flatback deformity (difference of 10 or more degrees for pelvic incidence minus lumbar lordosis angle), a standing sagittal pelvic tilt of 19° or more and lumbar spine stiffness (lumbar flexion of less than 20° between both postures). RESULTS: The prevalence of spinopelvic pathologies was similar between patients and controls (flatback deformity: 16% versus 10%, P = .209; standing pelvic tilt >19°: 17% versus 24%, P = .218; lumbar spine stiffness: 6% versus 5%, P = .827). Age over 65 years-old and standing lumbar lordosis angle less than 45° were associated with high sensitivity and specificity for identifying lumbar spine stiffness (age >65 years: 82% and 66%; standing lumbar lordosis angle <45°: 85% and 73%). CONCLUSION: The presence of end-stage hip osteoarthritis was not associated with increased prevalence of adverse spinopelvic characteristics compared to matched, asymptomatic volunteers. Age and LLstanding are the strongest predictors of lumbar spine flexion and can guide clinical practice on when to obtain additional radiographs for patients who have hip OA before arthroplasty to identify at-risk patients. LEVEL OF EVIDENCE: II (prospective, cohort study).

Reply to Alt et al. Comment on "Lunz et al. Impact and Modification of the New PJI-TNM Classification for Periprosthetic Joint Infections. J. Clin. Med. 2023, 12, 1262".

We greatly appreciate the comments made by Alt et al. [...].

What Is the Correlation between Clinical and Radiographic Findings in Patients with Advanced Osteoarthritis of the Knee?

Knee range of motion and patient-reported outcome measures (PROMs) are often used as screening tools to assess the severity of knee osteoarthritis and guide the decision to refer patients to an arthroplasty clinic. However, there is little understanding regarding the correlation between these factors. Thus, the purpose of this study was to determine the correlation between patient-reported clinical function measured with the Oxford Knee Score (OKS), pain assessed using the visual analog scale (VAS), knee range of motion (ROM), and characteristic radiographic features in patients with advanced osteoarthritis of the knee. A prospective analysis of a consecutive series of 138 patients with advanced unilateral osteoarthritis (OA) of the knee was performed. The severity of radiographic OA was classified according to the most commonly used Kellgren and Lawrence classification (K&L). Spearman's rank correlation analysis and multiple linear regression analysis were performed. The OKS was used as a dependent variable and was adjusted for pain, ROM, and nine standardized radiographic parameters on multiple views of the tibiofemoral and patellofemoral joint. OKS and pain correlated weakly with the K&L grade (r = -0.289; p = 0.001; r = 0.258; p = 0.002). K&L grade and the degree of patellofemoral joint space narrowing were identified as independent factors being associated with a poorer OKS (coefficient -4.528, p = 0.021; coefficient -2.211, p = 0.038). Slightly worse results were identified for OKS and pain in patients with K&L grade 4 osteoarthritis compared to patients with K&L grade 3 osteoarthritis (∆OKS 5.5 points, p < 0.001; ∆VAS 1.7 points, p = 0.003). There was no significant difference for passive range of motion between patients with K&L grade 3 or 4. When counseling patients with advanced knee osteoarthritis who may be eligible for knee arthroplasty, it is essential to give primary consideration to pain levels and self-reported limitations experienced during daily activities. Relying solely on knee ROM and PROMs is not an effective screening method for guiding the decision to refer patients to an arthroplasty clinic.

Minimum 20-year follow-up of a press-fit acetabular cup in cementless total hip replacement in young patients.

PURPOSE: We aimed to determine the minimum 20-year survival rates of a cementless press-fit cup in young patients. PATIENTS AND METHODS: This is a retrospective, single-center, multi-surgeon cohort study investigating the minimum 20-year clinical and radiological outcome of the first 121 consecutive total hip replacements (THRs) using a cementless, press-fit cup (Allofit, Zimmer, Warsaw, IN, USA) performed between 1999 and 2001. 28-mm metal-on-metal (MoM) and ceramic-on-conventionally not highly crosslinked polyethylene (CoP) bearings were used in 71% and 28%, respectively. Median patient age at surgery was 52 (range 21-60) years. Kaplan-Meier survival analysis was conducted for different endpoints. RESULTS: The 22-year survival rate for the endpoint aseptic cup or inlay revision was 94% (95% confidence interval [CI] 87-96) and 99% (CI 94-100) for aseptic cup loosening. 20 patients (21 THRs; 17%) had died and 5 (5 THRs; 4%) were lost to follow-up. No THR showed evidence of radiographic cup loosening. Osteolysis was observed in 40% of THRs with MoM and 77% with CoP bearings. 88% of THRs with CoP bearings showed significant polyethylene wear. CONCLUSION: The investigated cementless press-fit cup, which is still in clinical use today, showed excellent long-term survival rates in patients under the age of 60 years at surgery. However, osteolysis due to polyethylene and metal wear was frequently observed and is a matter of concern in the third decade after surgery.

How is hip anatomy reconstruction and inlay wear associated up to 10 years after primary THA using ceramic on highly crosslinked polyethylene bearings?

INTRODUCTION: Conventional polyethylene (PE) wear has been reported to be associated with femoral offset reconstruction and cup orientation after THA. Thus, the present study aimed (1) to determine the polyethylene wear rate of 32 mm ceramic heads with highly cross-linked polyethylene (HXLPE) inlays up to 10 years postoperatively and (2) to identify patient and surgery-related factors affecting the wear rate. METHODS: A prospective cohort study was performed, investigating 101 patients with 101 cementless THAs and ceramic (32 mm) on HXLPE bearings after 6-24 months, 2-5 years and 5-10 years postoperatively. The linear wear rate was determined using a validated software (PolyWare®, Rev 8, Draftware Inc, North Webster, IN, USA) by two reviewers, blinded to each other. A linear regression model was used to identify patient and surgery-related factors on HXLPE -wear. RESULTS: After an initial bedding-in phase of 1 year after surgery, the mean linear wear rate was 0.059 ± 0.031 mm/y at ten years (mean 7.7 years; SD 0.6 years, range 6-10), being below the osteolysis relevant threshold of 0.1 mm/year. The regression analysis demonstrated that age at surgery, BMI, cup inclination or anteversion and the UCLA score were not associated with the linear HXLPE-wear rate. Only increased femoral offset showed a significant correlation with an increased HXLPE-wear rate (correlation coefficient of 0.303; p = 0.003) with a moderate clinical effect size (Cohen's f²=0.11). CONCLUSION: In contrast to conventional PE inlays, hip arthroplasty surgeons may be less concerned about osteolysis-related wear of the HXLPE if the femoral offset is slightly increased. This allows focusing on joint anatomy reconstruction, hip stability and leg length.

Spinopelvic challenges in primary total hip arthroplasty.

There is no universal safe zone for cup orientation. Patients with spinal arthrodesis or a degenerative lumbar spine are at increased risk of dislocation. The relative contributions of the hip (femur and acetabulum) and of the spine (lumbar spine) in body motion must be considered together. The pelvis links the two and influences both acetabular orientation (i.e. hip flexion/extension) and sagittal balance/lumbar lordosis (i.e. spine flexion/extension). Examination of the spino-pelvic motion can be done through clinical examination and standard radiographs or stereographic imaging. A single, lateral, standing spinopelvic radiograph would be able to providemost relevant information required for screening and pre-operative planning. A significant variability in static and dynamic spinopelvic characteristics exists amongst healthy volunteers without known spinal or hip pathology. The stiff, arthritic, hip leads to greater changes in pelvic tilt (changes are almost doubled), with associated obligatory change in lumbar lordosis to maintain upright posture (lumbar lordosis is reduced to counterbalance for the reduction in sacral slope). Following total hip arthroplasty and restoration of hip flexion, spinopelvic characteristics tend to change/normalize (to age-matched healthy volunteers). The static spinopelvic parameters that are directly associated with increased risk of dislocation are lumbo-pelvic mismatch (pelvic incidence - lumbar lordosis angle >10°), high pelvic tilt (>19°), and low sacral slope when standing. A high combined sagittal index (CSI) when standing (>245°) is associated with increased risk of anterior instability, whilst low CSI when standing (<205°) is associated with increased risk of posterior instability. Aiming to achieve an optimum CSI when standing within 205-245° (with narrower target for those with spinal disease) whilst ensuring the coronal targets of cup orientation targets are achieved (inclination/version of 40/20 ±10°) is our preferred method.

Fixed-bearing is superior to mobile-bearing in lateral unicompartmental knee replacement: a retrospective matched-pairs analysis.

PURPOSE: Due to low incidence of isolated lateral osteoarthritis (OA), there are limited data on whether a fixed-bearing (FB) or a mobile-bearing (MB) design is superior for lateral unicompartmental knee replacement (UKR). The aim of this matched-pairs analysis was to compare both designs in terms of implant survival and clinical outcome. METHODS: Patients who received MB-UKR (Group A) and FB-UKR (Group B) at a single centre were matched according to gender, age at time of surgery and body mass index (BMI). Survivorship analysis was performed with the endpoint set as "revision for any reason". Clinical outcome was assessed using the Oxford knee score (OKS), visual analogue scale for pain (VAS), patients' satisfaction, University of California Los Angeles activity scale (UCLA) and the Tegner activity score (TAS). RESULTS: A total of 60 matched pairs were included with a mean follow-up (FU) of 3.4 ± 1.3 (range 1.2-5.0) years in Group A and 2.7 ± 1.2 (range 1.0-5.0) years in Group B. Survivorship between both groups differed significantly (Group A: 78.7%; Group B: 98.3%, p = 0.003) with bearing dislocation being the most common reason for revision in Group A (46.2%). The relative and absolute risk reduction were 92.2% and 20%, respectively, with 5 being the number needed to treat. There were no differences in OKS (Group A: 41.6 ± 6.5; Group B: 40.4 ± 7.7), VAS (Group A: 2.9 ± 3.2; Group B: 1.6 ± 2.2), UCLA (Group A: 5.7 ± 1.3; Group B: 5.9 ± 1.8) and TAS (Group A: 3.0 ± 1.0; Group B: 3.1 ± 1.2) between both groups on follow-up. CONCLUSION: Despite modern prosthesis design and surgical technique, implant survival of lateral MB-UKR is lower than that of FB-UKR on the short- to mid-term due to bearing dislocation as the most common cause of failure. Since clinical results are equivalent in both groups, FB-UKR should be preferred in treatment of isolated lateral OA. LEVEL OF EVIDENCE: Retrospective case-control study, Level III.

Impact and Modification of the New PJI-TNM Classification for Periprosthetic Joint Infections.

The comprehensive "PJI-TNM classification" for the description of periprosthetic joint infections (PJI) was introduced in 2020. Its structure is based on the well-known oncological TNM classification to appreciate the complexity, severity, and diversity of PJIs. The main goal of this study is to implement the new PJI-TNM classification into the clinical setting to determine its therapeutic and prognostic value and suggest modifications to further improve the classification for clinical routine use. A retrospective cohort study was conducted at our institution between 2017 and 2020. A total of 80 consecutive patients treated with a two-stage revision for periprosthetic knee joint infection were included. We retrospectively assessed correlations between patients' preoperative PJI-TNM classification and their therapy and outcome and identified several statistically significant correlations for both classifications, the original and our modified version. We have demonstrated that both classifications provide reliable predictions already at the time of diagnosis regarding the invasiveness of surgery (duration of surgery, blood and bone loss during surgery), likelihood of reimplantation, and patient mortality during the first 12 months after diagnosis. Orthopedic surgeons can use the classification system preoperatively as an objective and comprehensive tool for therapeutic decisions and patient information (informed consent). In the future, comparisons between different treatment options for truly similar preoperative baseline situations can be obtained for the first time. Clinicians and researchers should be familiar with the new PJI-TNM classification and start implementing it into their routine practice. Our adjusted and simplified version ("PJI-pTNM") might be a more convenient alternative for the clinical setting.

Physical Activity of Young Patients following Minimally Invasive Lateral Unicompartmental Knee Replacement.

Unicompartmental knee replacement (UKR) has increased in popularity in recent years, especially in young patients with high demands on their athletic ability. To date, there are no data available on the physical activity of young patients following lateral UKR. The aim of this study was to demonstrate return-to-activity rate and sporting activity of patients aged 60 years or younger following lateral UKR with a fixed-bearing (FB) prosthesis. Thirty-seven patients aged 60 years or younger after lateral FB-UKR were included. Sporting activities were assessed using the University of California Los Angeles activity scale (UCLA) and the Tegner activity score (TAS). Clinical outcome was measured using the Oxford Knee Score (OKS), range of motion (ROM) and visual analogue scale (VAS). The mean follow-up (FU) was 3.1 ± 1.5 years and the mean age at surgery was 52.8 ± 3.1 years. The return-to-activity rate was 87.5% and 49% of patients were highly active postoperatively as defined by an UCLA score of 7 or higher. All clinical parameters increased significantly postoperatively. We demonstrated a high return-to-activity rate with nearly half of the patients achieving high activity levels. Longer FU periods are necessary to evaluate the effect of activity on implant survival.

Sacral Slope Change From Standing to Relaxed-Seated Grossly Overpredicts the Presence of a Stiff Spine.

BACKGROUND: Several authors propose that a change in sacral slope of ≤10° between the standing and relaxed-seated positions (ΔSSstanding→relaxed-seated) identifies a patient with a stiff lumbar spine and has suggested the use of dual-mobility bearings for such patients undergoing a total hip arthroplasty (THA). The aim of this study was to assess how accurately ΔSSstanding→relaxed-seated can identify patients with a stiff spine. METHODS: A prospective, multicentre, consecutive cohort series of 312 patients had standing, relaxed-seated, and flexed-seated lateral radiographs prior to THA. ΔSSstanding→relaxed-seated was determined by the change in sacral slope between the standing and relaxed-seated positions. Lumbar flexion (LF) was defined as the difference in lumbar lordotic angle between standing and flexed-seated. LF ≤20° was considered a stiff spine. The predictive value of ΔSSstanding→relaxed-seated for characterizing a stiff spine was assessed. RESULTS: A weak correlation between ΔSSstanding→relaxed-seated and LF was identified (r2 = 0.13). Eighty six patients (28%) had ΔSSstanding→relaxed-seated ≤10° and 19 patients (6%) had a stiff spine. Of the 86 patients with ΔSSstanding→relaxed-seated ≤10°, 13 had a stiff spine. The positive predictive value of ΔSSstanding→relaxed-seated ≤10° for identifying a stiff spine was 15%. CONCLUSION: In this cohort, ΔSSstanding→relaxed-seated ≤10° was not correlated with a stiff spine. Using this simplified approach could lead to a 7-fold overprediction of patients with a stiff lumbar spine and abnormal spinopelvic mobility, unnecessary use of dual-mobility bearings, and incorrect component alignment targets. Referring to patients with ΔSSstanding→relaxed-seated ≤10° as being stiff is misleading. The flexed-seated position should be used to effectively assess a patient's spine mobility prior to THA.

Minimally invasive Oxford medial unicompartmental knee replacement in patients 50 years of age or younger.

INTRODUCTION: The aim of the present study was to assess clinical outcome and mid-term survivorship of mobile-bearing unicompartmental knee arthroplasty in patients 50 years of age or younger. METHODS: This study reports the results of 119 patients (130 knees) following mobile-bearing medial UKA. Primary indication was advanced osteoarthritis or avascular necrosis of the femoral condyle. The anterior cruciate ligament (ACL) as well as the collateral ligaments were functionally intact, the varus deformity was manually correctable and there was no evidence of osteoarthritis in the lateral compartment. Survivorship analysis was performed with different endpoints and clinical outcome was measured using the Oxford Knee Score (OKS), American Knee Society Score and Functional Score (AKSS-O, AKSS-F), range of motion (ROM), Tegner activity score, University of California Los Angeles score (UCLA) and visual analogue scale for pain (VAS). RESULTS: The survival rate was 96.6% at 6.5 years (95% CI 98.7-91.3%; number at risk: 56) and 91.7% (95% CI 96.7-80%; number at risk: 22) at 10 years for the endpoint device related revisions and 91.5% at 6.5 years (95% CI 95.4-84.5%; number at risk: 56) and 86.8% (95% CI 93-76.2%; number at risk: 22) at 10 years for the endpoint revision for any reason. Outcome scores, VAS and ROM showed significant improvements (p < 0.001). The mean OKS increased from 26.7 (standard deviation (sd): 7.2) preoperatively to 40.9 (sd: 7.6) at final follow-up, the mean AKSS-O from 48.3 (sd: 13.3) to 87.8 (sd: 14.4) and the mean ROM from 118° (sd: 16.7) to 125° (sd: 11.4). The radiological analysis revealed progression of degenerative changes in the lateral compartment in 39.6% of patients without affecting the functional outcome. CONCLUSIONS: Medial mobile-bearing UKA is a viable surgical treatment option in young patients with significant improvements in knee function and pain. Further follow-up is necessary to evaluate the long-term efficacy. LEVEL OF EVIDENCE: Retrospective cohort study, Level III.

Cup orientation following posterior approach THA - the effect of different visual aids and pelvic supports.

INTRODUCTION: This study aims to compare cup inclination achieved (1) Using two orientation guides, whilst using the same 3-point pelvic positioner and (2) Using two types of pelvic positioners, whilst measuring intra-operative cup inclination with an inclinometer. MATERIALS AND METHODS: This is a prospective, diagnostic cohort study of a consecutive series of 150 THAs performed through a posterior approach. Two types of 3-point pelvic positioners were used (Stulberg and modified Capello Hip Positioners) and the cup was positioned freehand using one of two orientation guides (mechanical guide or digital inclinometer). Intra-operative inclination was recorded, radiographic cup inclination and anteversion were measured from radiographs. The differences in inclination due to pelvic position (ΔPelvicPosition) and orientation definitions (ΔDefinition) were calculated. Target radiographic inclination and anteversion was 40/20° ± 10°. RESULTS: There was no difference in radiographic cup inclination/ (p = 0.63) using a mechanical guide or digital inclinometer. However, differences were seen in ΔPelvicPosition between the positioners ((Stulberg: 0° ± 5 vs. Capello: 3° ± 6); p = 0.011). Intra-operative inclination at implantation was different between positioners and this led to equivalent cases within inclination/anteversion targets (Stulberg:84%, Capello:80%; p = 0.48). CONCLUSIONS: With the pelvis securely positioned with 3-point supports, optimum cup orientation can be achieved with both alignment guides and inclinometer. Non-optimal cup inclinations were seen when intra-operative inclinations were above 40° and below 32°, or the ΔPelvicPosition was excessive (> 15°; n = 2). We would thus recommend that the intra-operative cup inclination should be centered strictly between 30° and 35° relative to the floor. Small differences exist between different type of pelvic positioners that surgeons need to be aware off and account for.

Defining "Normal" Static and Dynamic Spinopelvic Characteristics: A Cross-Sectional Study.

Spinopelvic characteristics influence the hip's biomechanical behavior. However, there is currently little knowledge regarding what "normal" characteristics are. This study aimed to determine how static and dynamic spinopelvic characteristics change with age, sex, and body mass index (BMI) among well-functioning volunteers. Methods: This was a cross-sectional cohort study of 112 asymptomatic volunteers (age, 47.4 ± 17.7 years; 50.0% female; BMI, 27.3 ± 4.9 kg/m2). All participants underwent lateral spinopelvic radiography in the standing and deep-seated positions to determine maximum hip and lumbar flexion. Lumbar flexion (change in lumbar lordosis, ∆LL), hip flexion (change in pelvic-femoral angle, ∆PFA), and pelvic movement (change in pelvic tilt, ΔPT) were determined. The hip user index, which quantifies the relative contribution of the hip to overall sagittal movement, was calculated as (∆PFA/[∆PFA + ∆LL]) × 100%. Results: There were decreases of 4.5° (9%) per decade of age in lumbar flexion (rho, -0.576; p < 0.001) and 3.6° (4%) per decade in hip flexion (rho, -0.365; p < 0.001). ∆LL could be predicted by younger age, low standing PFA, and high standing LL. Standing spinopelvic characteristics were similar between sexes. There was a trend toward men having less hip flexion (90.3° ± 16.4° versus 96.4° ± 18.1°; p = 0.065) and a lower hip user index (62.9% ± 8.2% versus 66.7% ± 8.3%; p = 0.015). BMI weakly correlated with ∆LL (rho, -0.307; p = 0.011) and ∆PFA (rho, -0.253; p = 0.039). Conclusions: Spinopelvic characteristics were found to be age, sex, and BMI-dependent. The changes in the lumbar spine during aging (loss of lumbar lordosis and flexion) were greater than the changes in the hip, and as a result, the hip's relative contribution to overall sagittal movement increased. Men had a greater change in posterior pelvic tilt when moving from a standing to a deep-seated position in comparison with women, secondary to less hip flexion. The influence of BMI on spinopelvic parameters was low.

Which Safe Zone Is Safe in Total Hip Arthroplasty? The Effect of Bony Impingement.

"Safe zones" for cup position are currently being investigated in total hip arthroplasty (THA). This study aimed to evaluate the impact of bony impingement on the safe zone and provide recommendations for cup position in THA. CT scans were performed on 123 patients who underwent a cementless THA. Using the implant data and bone morphology from the CT scans, an impingement detection algorithm simulating range of motion (ROM) determined the presence of prosthetic and/or bony impingement. An impingement-free zone of motion was determined for each patient. These zones were then compared across all patients to establish an optimized impingement-free "safe zone". Bony impingement reduced the impingement-free zone of motion in 49.6% (61/123) of patients. A mean reduction of 23.4% in safe zone size was observed in relation to periprosthetic impingement. The superposition of the safe zones showed the highest probability of impingement-free ROM with cup position angles within 40-50° of inclination and 20-30° of anteversion in relation to the applied cup and stem design of this study. Virtual ROM simulations identified bony impingement at the anterosuperior acetabular rim for internal rotation at 90° of flexion and at the posteroinferior rim for adduction as the main reasons for bony impingement.

Cup placement in primary total hip arthroplasty: how to get it right without navigation or robotics.

Acetabular component orientation and position are important factors in the short- and long-term outcomes of total hip arthroplasty. Different definitions of inclination and anteversion are used in the orthopaedic literature and surgeons should be aware of these differences and understand their relationships. There is no universal safe zone. Preoperative planning should be used to determine the optimum position and orientation of the cup and assess spinopelvic characteristics to adjust cup orientation accordingly. A peripheral reaming technique leads to a more accurate restoration of the centre of rotation with less variability compared with a standard reaming technique. Several intraoperative landmarks can be used to control the version of the cup, the most commonly used and studied is the transverse acetabular ligament. The use of an inclinometer reduces the variability associated with the use of freehand or mechanical alignment guides.

Spinopelvic Characteristics Normalize 1 Year After Total Hip Arthroplasty: A Prospective, Longitudinal, Case-Controlled Study.

BACKGROUND: The presence of hip osteoarthritis is associated with abnormal spinopelvic characteristics. This study aimed to determine whether the preoperative, pathological spinopelvic characteristics normalize at 1 year after total hip arthroplasty (THA). METHODS: This was a prospective, longitudinal, case-control, matched cohort study. Forty-seven patients undergoing THA underwent preoperative and 1-year postoperative assessments. This group was matched with regard to age, sex, and body mass index with 47 controls (volunteers) with well-functioning hips. All participants underwent clinical and radiographic assessments including lateral radiographs in standing, relaxed-seated, and deep-flexed-seated positions. Spinopelvic characteristics included change in lumbar lordosis (ΔLL), change in pelvic tilt (ΔPT), and hip flexion (change in pelvic-femoral angle, ΔPFA) when moving from a standing position to either of the seated positions. Spinopelvic hypermobility was defined as ΔPT > 30° between the standing and upright-seated positions. RESULTS: Patients who underwent THA, compared with the control group, preoperatively demonstrated less mean change in hip flexion (ΔPFA, -54.8° ± 17.1° compared with -68.5° ± 9.5°; p < 0.001), greater mean change in pelvic tilt (ΔPT, 22.0° ± 13.5° compared with 12.7° ± 8.1°; p < 0.001), and greater mean lumbar movement (ΔLL, -22.7° ± 15.5° compared with -15.4° ± 10.9°; p = 0.015) transitioning from a standing position to an upright-seated position. After THA, these differences were no longer present between the THA group and the control group: the mean postoperative changes were -65.8° ± 12.5° (p = 0.256) for ΔPFA, 14.3° ± 9.5° (p = 0.429) for ΔPT, and -15.3° ± 10.6° (p = 0.966) for ΔLL. The higher prevalence of spinopelvic hypermobility in the THA group compared with the control group that was observed preoperatively (21% compared with 0%; p = 0.009) was no longer present after THA (6% compared with 0%; p = 0.194). Similar results were found moving from a standing position to a deep-seated position after THA. CONCLUSIONS: Preoperative spinopelvic characteristics that contribute to abnormal mechanics can normalize after THA following improvement in hip flexion. This leads to patients having the expected hip, pelvic, and spinal flexion as demographically matched controls, thus potentially eliminating abnormal mechanics that contribute to the development or exacerbation of hip-spine syndrome. LEVEL OF EVIDENCE: Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.