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.

Quality of life, infection control, and complication rates using a novel custom-made articulating hip spacer during two-stage revision for periprosthetic joint infection.

INTRODUCTION: Two-stage revision remains the gold standard treatment for most chronically infected and complex total hip arthroplasty infections. To improve patient outcome and reduce complication rates, we have developed a novel custom-made articulating hip spacer technique and present our short-term results. MATERIALS AND METHODS: Between November 2017 and November 2019, 27 patients (mean age 70 years) underwent two-stage revision for periprosthetic joint infection of the hip using the articulating spacer design described here. We retrospectively analyzed spacer-related complications as well as rates for complication, infection control, and implant survivorship after final reimplantation. Furthermore, we prospectively collected patient-reported health-related quality of life (HRQoL) scores prior to spacer implantation, with the spacer and after reimplantation of the new prosthesis. RESULTS: An additional round of spacer exchange was performed in two patients (8.3%), persistent wound discharge was the reason in both cases. We had one (4.2%) spacer-related mechanical complication, a dislocation that was treated with closed reduction. After reimplantation, infection control was achieved in 96% with an implant survivorship of 92% after a mean follow-up time of 19 (range 7-32, SD 7.2) months. While the scores for VR-12 MCS, VAS hip pain and patient-reported overall satisfaction significantly improved after first stage surgery, the scores for WOMAC, UCLA and VR-12 PCS significantly improved after second stage surgery. CONCLUSIONS: Our two-stage approach for periprosthetic joint infection shows high infection eradication and implant survivorship rates at short-term follow-up. Spacer-related complication rates were low, and we achieved high patient satisfaction rates and low pain levels already during the spacer period. To further simplify comparison between different spacer designs, we propose a new hip spacer classification system.

Hip Spacers with a Metal-on-Cement Articulation Did Not Show Significant Surface Alterations of the Metal Femoral Head in Two-Stage Revision for Periprosthetic Joint Infection.

Two-stage revision is considered the gold standard treatment for chronic periprosthetic joint infection (PJI). During the interim period, between explantation of the infected hip endoprosthesis and revision arthroplasty, individually formed articulating hip spacers made of polymethylmethacrylate (PMMA) bone cement can be used to provide better soft tissue preservation, local antibiotic release, and improved postoperative mobilization. If effective prevention from luxation is achieved, hip function and hence overall patient satisfaction is improved. Zirconium oxide particles inside conventional PMMA bone cement, however, are known to enhance third-body wear, which may cause alterations of the metal head in the articulating spacer and hence become a serious risk for the patient. Therefore, the aim of our study was to analyze whether the articular surface of cobalt-chrome (CoCr) femoral heads is significantly altered in the setting of a metal-on-cement articulation during the interim period of two-stage revision for PJI. We analyzed a consecutive series of 23 spacer cases and compared them with femoral heads from two series of conventional hip arthroplasty revisions with metal-on-polyethylene articulations and different time intervals in situ. To investigate metallic wear, the femoral heads were thoroughly examined, and their surface roughness was measured and analyzed. We found no significant differences between the two conventional hip arthroplasty groups, despite their very different times in situ. Furthermore, the individually different times in situ within the spacer group had no significant impact on surface roughness, either. Compared with the spacer group, the surface roughness of the metal femoral heads from both conventional hip arthroplasty groups were even higher. Within the spacer group, roughness parameters did not show significant differences regarding the five predefined locations on the metal head. We conclude that metal-on-cement articulations do not cause enhanced surface alterations of the metal femoral head and hence do not limit the application in articulating hip spacers in the setting of two-stage revision for PJI.

What Is the Long-term (27- to 32-year) Survivorship of an Uncemented Tapered Titanium Femoral Component and Survival in Patients Younger Than 50 Years?

BACKGROUND: Uncemented femoral components in primary THA are in widespread use, especially in patients younger than 50 years, but few studies have evaluated their survival into the late third and early fourth decade. QUESTIONS/PURPOSES: We evaluated (1) survivorship using femoral revision for any reason as the endpoint, (2) survivorship using femoral revision for aseptic loosening as the endpoint, (3) survival in patients younger than 50 years, (4) cumulative incidence of stem revision for periprosthetic femoral fracture and (5) the overall risk of revision (change of any part of the implanted components) at a minimum of 27 years of follow-up with an uncemented tapered titanium stem still in clinical use today. METHODS: We reviewed the clinical and radiographic results of 326 THAs performed in 326 patients (for 28 patients with bilateral THA, only the first hip was included in the analysis to ensure independent observations) using an uncemented grit-blasted, tapered collarless titanium alloy (TiAl6Nb7) stem between January 1985 and December 1989. In that same timeframe, we performed 1038 primary THAs. During that time, we used cementless stems in patients without severe femoral canal deformity and adequate bone stock for uncemented femoral fixation as determined by using the indication criteria described by the developer. In all, 34% (354 of 1038) were cementless; all cementless stems implanted during that time were the stem being studied here. No others were used. The mean (range) age at the time of surgery was 56 years (13-81 years). Sixty-seven patients were younger than 50 years at the time of primary THA. A competing risk survivorship analysis was used to estimate long-term survival. The minimum follow-up was 27 years (mean 28 years; range 27-32 years); at that time, 169 patients had died, and four patients were lost to follow-up. RESULTS: Survivorship at 28 years with revision of the femoral component for any reason as the endpoint was 87% (95% CI 83 to 90). Survivorship for femoral revision for aseptic loosening as the endpoint was 94% at 28 years (95% CI 90 to 96). Survival in patients younger than 50 years at the time of primary THA was 89% (95% CI 78 to 95) and 95% (95% CI 86 to 98) at 28 years for the endpoints of all stem revisions and aseptic stem loosening, respectively. The overall cumulative incidence of stem revision for periprosthetic femoral fracture was 4% (95% CI 2 to 7) at 28 years. The overall THA survival rate at 28 years with revision for any reason as the endpoint was 57% (95% CI 51 to 62). CONCLUSIONS: Uncemented femoral fixation of a tapered collarless titanium alloy stem was reliable into the early fourth decade, especially in patients younger than 50 years. Late stem failures in the third and early fourth decade were mainly because of periprosthetic femoral fracture, while aseptic loosening occurred in undersized stems during the early second decade. LEVEL OF EVIDENCE: Level IV, therapeutic study.

Long-Term Results of a Second-Generation, Small-Diameter, Metal-On-Metal Bearing in Primary Total Hip Arthroplasty at 14-year Follow-Up.

(1) Background: The objective of the present study was to review the clinical and radiological results of a small-head, MoM bearing in primary THA and to determine blood metal ion levels at long-term follow-up. (2) Methods: We retrospectively evaluated the clinical and radiological results of 284 small-diameter, MoM 28-mm Metasul THA at a mean follow-up of 14.5 years, and measured blood metal ion concentrations in 174 of these patients. (3) Results: After 14 years, survival free for revision due to any reason was 94%. Proximal femoral osteolysis was seen in 23% of hips, and MRI demonstrated ARMD in 27 of the 66 investigated hips (41%). Mean cobalt, chromium, and titanium ion concentrations were 0.82 µg/L (range 0.22-4.45), 1.51 µg/L (0.04-22.69), and 2.68 µg/L (0.26-19.56) in patients with unilateral THA, and 2.59 µg/L (0.43-24.75), 2.50 µg/L (0.26-16.75), and 3.76 µg/L (0.67-19.77), respectively in patients with bilateral THA. Twenty-nine percent of patients showed cobalt or chromium ion levels > 2 µg/L. (4) Conclusions: Despite good clinical long-term results, increased blood metal ion levels (cobalt or chromium > 2 µg/L) were found in approximately one-third of asymptomatic patients, and proximal femoral osteolysis and ARMD were frequently seen in this cohort. Blood metal ion analysis appears helpful in the long-term follow-up of these patients in order to identify individuals at risk. In accordance with contemporary consensus statements, symptomatic patients with elevated metal ion levels and/or progressive osteolysis should be considered for additional CT or MARS MRI to determine the extent of soft tissue affection prior to revision surgery. Further studies are necessary to investigate the clinical relevance of ARMD in asymptomatic patients with small-head, MoM THA.

Fifty-six percent of proximal femoral cortical hypertrophies 6 to 10 years after Total hip arthroplasty with a short Cementless curved hip stem - a cause for concern?

BACKGROUND: Thigh pain and cortical hypertrophies (CH) have been reported in the short term for specific short hip stem designs. The purpose of the study was to investigate 1) the differences in clinical outcome, thigh pain and stem survival for patients with and without CHs and 2) to identify patient and surgery-related factors being associated with the development of CHs. METHODS: A consecutive series of 233 patients with 246 hips was included in the present retrospective diagnostic cohort study, who had received a total hip arthroplasty (THA) between December 2007 and 2009 with a cementless, curved, short hip stem (Fitmore, Zimmer, Warsaw, IN, USA). Clinical and radiographic follow-up, including the radiographic parameters for hip geometry reconstruction, were prospectively assessed 1, 3, and 6 to 10 years after surgery. RESULTS: Cortical hypertrophies were observed in 56% of the hips after a mean of 7.7 years, compared to 53% after 3.3 years being mostly located in Gruen zone 3 and 5. There was no significant difference for the Harris Hip Score and UCLA score for patients with and without CHs. Only one patient with a mild CH in Gruen zone 5 and extensive heterotopic ossifications around the neck of the stem reported thigh pain. The Kaplan Meier survival rate after 8.6 years was 99.6% (95%-CI; 97.1-99.9%) for stem revision due to aseptic loosening and no association with CHs could be detected. Postoperative increase in hip offset was the only risk factor being associated with the development of CHs in the regression model (ΔHO; OR 1.1 (1.0-1.2); p = 0.001). CONCLUSIONS: The percentage of cortical hypertrophies remained almost constant in the mid-term compared to the short-term with the present cementless short hip stem design. The high percentage of cortical hypertrophies seems not be a cause for concern with this specific implant in the mid-term. LEVEL OF EVIDENCE: Diagnostic Level IV.

Long-Term Survival of Retained Cementless Hip Stems at an Average of 13 Years After Isolated Cup Revision.

BACKGROUND: Cementless stems demonstrate excellent long-term survival, but little is known about the long-term survival rate of the stem after isolated cup revision. The aim of the present retrospective cohort study was to determine the long-term survival rate of cementless stems retained after prior cup revision. METHODS: We reviewed the clinical and radiographic results of 119 total hip arthroplasties (THAs) utilizing a cementless, grit-blasted, tapered titanium femoral stem that were performed in 113 patients between January 1985 and December 1989. The mean age at the time of the primary THA was 52 years (range, 16 to 74 years) and the mean time between primary THA and cup revision was 13 years (standard deviation [SD], 6 years; range, 0 to 30 years). At the time of the latest follow-up, no patient was lost to follow-up, 36 patients representing 37 hips had died, and 11 hips in 11 patients had required stem revision. The mean follow-up was 13 years following cup revision (SD, 6 years; range, 0 to 28 years). A competing risk analysis was performed to estimate the survival of the stem after isolated cup revision, with death being the competing risk factor. RESULTS: At 20 years after cup revision, the survival rate of retained stems was 89% (95% confidence interval [CI], 79% to 94%) for the end point of stem revision for any reason and 97% (95% CI, 91% to 99%) for the end point of stem revision for aseptic loosening. CONCLUSIONS: The long-term survival of cementless stems retained after cup revision was excellent. Well-fixed cementless stems should be retained during cup revision for aseptic loosening. LEVEL OF EVIDENCE: Level IV. See Instructions for Authors for a complete description of levels of evidence.

Cumulative Long-Term Incidence of Postoperative Periprosthetic Femoral Fractures Using an Uncemented Tapered Titanium Hip Stem: 26- to 32-Year Results.

BACKGROUND: Although falling is becoming a major problem in the elderly, little is known about the long-term incidence of postoperative periprosthetic femoral fractures (PFF) after total hip arthroplasty (THA) using uncemented stems with a minimum follow-up of 26 years postoperatively. METHODS: In a consecutive series, the cumulative incidence of PFF after uncemented THA using a straight, collarless, tapered titanium stem was retrospectively reviewed in 354 hips (326 patients). After a mean follow-up of 28 (26-32) years postoperatively, 179 hips had died and 5 hips had been lost to follow-up. Kaplan-Meier survival analysis was used to estimate cumulative percentage probability of PFF. RESULTS: At final follow-up, a total of 27 fractures in 27 patients had occurred. In 15 hips, the stem had to be revised, and in 10 the fracture was treated by open reduction and internal fixation. Two patients declined further surgery. The cumulative percentage probability of PFF was 1.6% (95% confidence interval, 0.7 to 3.8) at 10 years and 13.2% (95% confidence interval, 8.5 to 20.2) at 29 years after primary THA. There was no association between the occurrence of fracture and gender, age at primary THA, cup revision, or canal fill index. CONCLUSION: Our findings indicate that PFF is the major mode of failure in the long term after uncemented THA using a tapered titanium stem. More research is needed to evaluate the reasons and risk factors for PFF after THA, thus providing better prophylaxis for those at risk and to compare the long-term incidence using different fixation methods and implants. LEVEL OF EVIDENCE: IV.

Long-Term Results of Acetabular Reconstruction Using Ganz Acetabular Rings.

BACKGROUND: Our study examines the long-term results of acetabular reconstruction using the Ganz acetabular reinforcement ring (GRR) in total hip arthroplasty. METHODS: Between 1998 and 2001, 135 hips (119 revision and 16 primary arthroplasties) were consecutively implanted with a GRR at our hospital. The average age was 65 years (range, 26-90). Clinical and radiographic evaluations were carried out. Long-term survivorship was estimated using a competing risks analysis, and multivariate survivorship using Cox regression model was used to identify risk factors for implant failure. RESULTS: At a mean follow-up of 16 years (range, 15-18), 3 patients were lost to follow-up and 19 had implant failure: 4 aseptic loosenings without re-revision, 4 septic, and 11 aseptic re-revisions. Survival was estimated at 86% after 16 years (95% confidence interval [CI], 78.5%-90.9%) using radiographic loosening or revision for any reason as the end point. Using aseptic loosening as the end point, the survival was estimated at 91.2% after 16 years (95% CI, 84.5%-95.0%). Multivariate analysis revealed that age at surgery was a significant risk factor for failure of the GRR. With acetabular revision or loosening as the end point, patients ≤60 years had 71.6% (95% CI, 53%-82.8%) and older patients had 92.2% (95% CI, 84%-96.2%) probability of implant survival after a mean 16-year follow-up. The median Harris Hip Scores and Western Ontario and McMaster Universities Osteoarthritis Index scores were 77 and 64.5, respectively, and mean Numerical Pain Rating Scale score was 1.6 at final follow-up. CONCLUSION: Our long-term study showed acceptable survival and functional results using the GRR in older patients, while young patients had less favorable survival.

Periprosthetic Bone Mineral Density Around Uncemented Titanium Stems in the Second and Third Decade After Total Hip Arthroplasty: A DXA Study After 12, 17 and 21 Years.

Implant failure and periprosthetic fractures because of periprosthetic bone loss are a major concern in total hip arthroplasty (THA). Hardly any clinical data exist on the long-term evolution of bone mineral density (BMD) around uncemented femoral implants. The question to address is whether relevant bone loss continues into third decade around well-fixed uncemented femoral implants. BMD around stable uncemented straight titanium femoral implants was assessed in a longitudinal cohort study. We included 142 hips of 128 patients and measured the development of the periprosthetic BMD using dual-energy X-ray absorptiometry. The baseline measurement was 12 years (t1) after the implantation of an uncemented femoral stem. Follow-up-measurements were performed at 17 (t2) and at 21 years (t3) after primary THA. The regions of interest (ROI) were selected conforming to Gruen et al. We acquired complete data including three consecutive measurements (t1, t2, t3) for 42 patients (49 hips). Performing radiographic evaluation at t1, t2 and t3, we found a regular bone-implant interface present in all cases. Significant decrease in BMD could be shown in ROI 1 (p = 0.0001; - 7.8%), 4 (p = 0.024; - 2.4%), 6 (p = 0.001; - 5.5%) and 7 (p < 0.0001; - 11.7%) between t1 and t3 and in ROI 1 (p = 0.002; - 3.7%), 2 (p = 0.046; - 3.6%), 4 (p = 0.002; - 2.7%) and 7 (p < 0.0001; - 8.0%) between t2 and t3. There were significant differences in overall bone density (netavg) between t1 and t3 (p = 0.001; - 3.6%) and between t2 and t3 (p = 0.020; - 2.1%). The data indicate clinically relevant changes of BMD especially in the proximal Gruen zones in the long-term after uncemented THA. Loss of periprosthetic BMD might be a risk factor for periprosthetic fractures.

Ion release in ceramic bearings for total hip replacement: Results from an in vitro and an in vivo study.

INTRODUCTION: Literature on the potential release of trace elements following implantation of Zirconia-platelet toughened alumina (ZPTA) ceramic components is scant. The present study therefore analysed the in vitro and in vivo potential release of ions from ZPTA bearings. MATERIAL AND METHODS: An in vitro and in vivo study was conducted. The in vitro study compared leaching in bovine serum from two groups: ZPTA ceramic heads and Co-28Cr-6Mo alloy heads, both 28-mm diameter. A third group without implant served as reference group. An in vivo clinical study compared trace elements in the whole blood of patients with 36-mm diameter ZPTA ceramic-on-ceramic articulation after three and 12 months. A cohort of subjects without any prosthesis was used as control group. The release of ions was determined by high resolution-inductively coupled plasma-mass spectrometry. RESULTS: In the in vitro experiment, significant differences (p ≤ 0.01) in trace element release for chromium, cobalt and molybdenum were found, with increased levels of ion release in the Co-28Cr-6Mo metal group. The very low detection limit for yttrium allowed detection of a small yttrium release from the ZPTA heads, which was not confirmed by the in vivo study. No significant difference between the groups was found for strontium, aluminium, and zirconium. In the in vivo study, no relevant differences in ion levels between the reference group without any implant and the study group were found at the three and 12-month follow-up. CONCLUSION: This study supports that ZPTA ceramic articulation components are safe in terms of ion release, and may be an excellent alternative to bearings based on Co-28Cr-6Mo alloys.

Additive Influence of Hip Offset and Leg Length Reconstruction on Postoperative Improvement in Clinical Outcome After Total Hip Arthroplasty.

BACKGROUND: There is a lack of prospective studies investigating the additive effect of both acetabular and femoral reconstruction parameters on the functional outcome following total hip arthroplasty (THA). METHODS: The aim of this prospective cohort study was to determine the combined influence of hip geometry reconstruction and component positioning on the clinical outcome following primary THA for unilateral osteoarthritis. We prospectively assessed the clinical outcome and radiographic parameters for hip geometry reconstruction, component position, and orientation using validated measurements for the operated hip compared to the contralateral native hip in a consecutive series of 113 patients with primary unilateral cementless THA. The correlation of reconstruction parameters was investigated using a multivariate polynomial regression model for the dependent variable ΔHHS (difference between the Harris hip scores preoperatively and 2.0-4.8 years postoperatively). Target zones for hip reconstruction and component positioning were investigated for an association with superior clinical outcome. RESULTS: The regression model demonstrated a significant correlation for the ΔHHS and both hip offset (HO) reconstruction and leg length difference. Patients with accurate to slightly increased HO reconstruction combined with balanced leg length demonstrated a significantly higher ΔHHS than patients outside this zone (HO: 5 ± 5 and LLD: 0 ±5 mm, P = .029). This finding could be confirmed for 2 enlarged zones (zone 1: HO, 7.5 ± 7.5 and LLD, 2.5 ± 7.5 mm, P = .028; zone 2: HO, 7.5 ± 7.5 and LLD, 7.5 ± 7.5 mm, P = .007). CONCLUSION: HO and leg length reconstruction demonstrated an additive effect on clinical outcome and surgeons should aim for high accuracy in the reconstruction of both factors.

Comparable Cumulative Incidence of Late Periprosthetic Femoral Fracture and Aseptic Stem Loosening in Uncemented Total Hip Arthroplasty-A Concise Follow-Up Report at a Minimum of 20 Years.

BACKGROUND: There is a lack of long-term studies into the third decade reporting on the incidence of periprosthetic femoral fracture (PPFF) and aseptic stem loosening (ASL) after cementless total hip arthroplasty (THA). The aim of the present retrospective, longitudinal cohort study was to compare the cumulative incidence of PPFF and ASL in a consecutive cohort of 326 patients with 354 primary uncemented THAs after 20-25 years and to identify risk factors being associated with PPFFs. METHODS: Postoperative femoral fractures were investigated for timing, mechanism of injury, Vancouver classification, and subsequent treatment. The cumulative incidence of PPFF and ASL was estimated using Kaplan-Meier survival analysis. Risk factors for PPFFs were analyzed using a Cox proportional hazards regression model. RESULTS: One hundred sixty-three patients (180 hips) were available for follow-up at a mean of 22 years. Twenty-one fractures occurred during the follow-up period. The cumulative incidence of PPFF was 1.6% at 10 years, 4.5% at 17 years, and 9.4% at 22 years after surgery. The cumulative incidence of PPFF and ASL after 22 years was comparable (9.4% [95% confidence interval, 5.9%-14.7%] and 6.9% [95% confidence interval, 4.5%-10.5%]). Gender, age at surgery, diagnosis, cup revision, and canal fill index of the stem in the proximal femur were no risk factors for the occurrence of a PPFF. CONCLUSION: The cumulative incidence of PPFF after primary uncemented THA further increased in the second decade and reached the incidence of ASL in the third decade, while no risk factors for the occurrence of a PPFF could be identified.

Comparative Analysis of the Reconstruction of Individual Hip Anatomy Using 3 Different Cementless Stem Designs in Patients With Primary Hip Osteoarthritis.

BACKGROUND: We questioned whether there was a radiographic difference in hip geometry reconstruction and implant fixation between 3 different cementless stem design concepts in patients with primary end-stage hip osteoarthritis. METHODS: We retrospectively evaluated the preoperative and postoperative radiographs by 2 independent and blinded reviewers in a series of 264 consecutive patients who had received either a straight double-tapered stem with 3 offset options (group A), a straight double-tapered stem with 2 shape options and modular necks (group B), and a bone-preserving curved tapered stem with 4 offset options (group C). The following parameters were assessed: acetabular, femoral and hip offset (HO), center of rotation height, leg length difference (LLD), and the endosteal fit of stem in the proximal femur (canal fill index). Group comparisons were performed using a one-way analysis of variance and subsequent pairwise comparisons (t-test). RESULTS: Postoperatively, HO could be equally restored with all 3 stem designs (P = .079). The postoperative LLD was smaller in group C compared to group A (0.8 mm [standard deviation, 3.2] vs 2.6 mm [standard deviation, 4.5], P = .002). Best combined reconstruction of HO and LLD could be achieved with the short curved stem by junior and senior surgeons (HO: -2.0 and -2.1 mm; LLD: 1.9 and 0.7 mm, respectively). The proximal and mid-height canal fill indexes were higher in groups B and C compared to group A, indicating a better metaphyseal and diaphyseal fit in the proximal femur (both P < .001). CONCLUSION: All 3 cementless stem designs allowed for good hip geometry reconstruction. Multiple shape and offset options allowed for a better metaphyseal stem fit and offered minor clinical advantages for leg length reconstruction. Modular necks did not provide reconstructive advantages in patients with primary hip osteoarthritis.

The influence of different sets of surgical instrumentation in Oxford UKA on bearing size and component position.

INTRODUCTION: The Oxford unicompartmental knee arthroplasty (OUKA) has been proven to be an effective treatment for anteromedial osteoarthritis of the knee joint. New instrumentation has been introduced to improve the reproducibility of implant positioning and to minimize bone loss during tibial resection (Oxford Microplasty; Zimmer Biomet, Warsaw, Indiana, USA). METHODS: To assess the effect of the new instrumentation, we retrospectively evaluated the postoperative radiographs and surgical records of 300 OUKAs in three consecutive cohorts of patients. The first cohort consists of the first 100 minimal invasive implantations of the OUKA using the conventional phase III instrumentation, the second cohort consists of the 100 most recent minimal invasive OUKA with the conventional phase III instrumentation and the third cohort consists of the first 100 minimal invasive OUKA using the new Oxford Microplasty instrumentation. RESULTS: Mean bearing thickness was statistically significant and lower in OUKA with use of the updated instrumentation than with the conventional instrumentation (p = 0.01 and p = 0.04). Additionally, statistically significant and more femoral components were aligned within the accepted range of tolerance in both the coronal and the sagittal plane with use of the updated instrumentation compared to the conventional phase III instrumentation in group A (p = 0.029 and p = 0.038) and in the sagittal plane with use of the updated instrumentation compared to the conventional phase III instrumentation in group B (p = 0.002). CONCLUSION: The new modified instrumentation seems to be an effective tool to reduce the risk of malalignment of the femoral component in the coronal and in the sagittal plane compared to the conventional phase III instrumentation. Furthermore, the instrumentation is also effective in determining an adequate level of tibial resection and thus avoiding unnecessary bone loss.

Minimally invasive Oxford medial unicompartmental knee arthroplasty in young patients.

PURPOSE: Advanced knee arthritis in young patients is a challenging problem that may necessitate surgical treatment. There are few published studies of mobile-bearing unicompartmental knee arthroplasty (UKA) in young patients, while indications have expanded to its use in this demanding patient group. METHODS: The clinical and radiographic results of the first 118 consecutive Oxford medial UKAs (OUKA) using a minimally invasive technique (phase 3) in 101 patients 60 years of age or younger at the time of surgery were evaluated. Median age at surgery was 57 (25-60) years. Kaplan-Meier survivorship analysis was used to estimate implant survival. RESULTS: Mean time of follow-up evaluation was five (SD 1.6) years. At final follow-up, three patients (three knees) had died, and two patients (three knees) were lost to follow-up. Five knees were revised: three for unexplained pain, one for early infection and one for bearing fracture. There was one impending revision for progression of osteoarthritis in the lateral compartment. The radiographic review demonstrated that 5 % of the knees had progressive arthritis in the lateral knee compartment, of those 2 % with full joint space loss and pain. The Kaplan-Meier survival analysis, using revision for any reason as the endpoint, estimated the five-year survival rate at 97 % (95 % CI 91-99). Ninety-six per cent of the non-revised patients were satisfied with the outcome, and 4 % were dissatisfied. The mean Oxford knee score was 41 (SD 7), with 6 % of the knees having a poor result. The mean AKSS was 89 (SD 14), mean flexion was 129° (SD 13) and the mean UCLA score was 6.8 (SD 1.5). CONCLUSION: Minimally invasive Oxford medial UKA was reliable and effective in this young and active patient cohort providing high patient satisfaction at mid-term follow-up. Progressive arthritis in the lateral knee compartment was a relevant failure mode in this age group. Most revisions were performed for unexplained pain, while we did not find loosening or wear in any patient. LEVEL OF EVIDENCE: IV.

Early Migration Predicts Aseptic Loosening of Cementless Femoral Stems: A Long-term Study.

BACKGROUND: Excessive early migration of cemented stems and cups after THA has been associated with poor long-term survival and allows predictable evaluation of implant performance. However, there are few data regarding the relationship between early migration and aseptic loosening of cementless femoral components, and whether early migration might predict late failure has not been evaluated, to our knowledge. Einzel-Bild-Röntgen-Analyse-femoral component analysis (EBRA-FCA) is a validated technique to accurately measure axial femoral stem migration without the need for tantalum markers, can be performed retrospectively, and may be a suitable tool to identify poor performing implants before their widespread use. QUESTIONS/PURPOSES: We asked: (1) Is axial migration within the first 24 months as assessed by EBRA-FCA greater among cementless stems that develop aseptic loosening than those that remain well fixed through the second decade; (2) what is the diagnostic performance of implant migration at 24 months postoperatively to predict later aseptic loosening of these components; and (3) how does long-term stem survivorship compare between groups with high and low early migration? METHODS: We evaluated early axial stem migration in 158 cementless THAs using EBRA-FCA. The EBRA-FCA measurements were performed during the first week postoperatively (baseline measurement) and at regular followups of 3, 6, and 12 months postoperatively and annually thereafter. The mean duration of followup was 21 years (range, 18-24 years). The stems studied represented 45% (158 of 354) of the cementless THAs performed during that time, and cementless THAs represented 34% (354 of 1038) of the THA practice during that period. No patient enrolled in this study was lost to followup. Multivariate survivorship analysis using Cox's regression model was performed with an endpoint of aseptic loosening of the femoral component. Loosening was defined according to the criteria described by Engh et al. and assessed by two independent observers. Patients with a diagnosis of prosthetic joint infection were excluded. Receiver operating characteristic (ROC) curve analysis was used to evaluate diagnostic performance of axial stem migration 1, 2, 3, and 4 years postoperatively as a predictor of aseptic loosening. Survivorship of hips with high (≥ 2.7 mm) and low (< 2.7 mm) migration was compared using a competing-events analysis. RESULTS: Femoral components that had aseptic loosening develop showed greater mean distal migration at 24 months postoperatively than did components that remained well fixed throughout the surveillance period (4.2 mm ± 3.1 mm vs 0.8 mm ± 0.9 mm; mean difference, 3.4 mm, 95% CI, 2.5-4.4; p ≤ 0.001). Distal migration at 24 months postoperatively was a strong risk factor for aseptic loosening (hazard ratio, 1.98; 95% CI, 1.51-2.57; p < 0.001). The associated overall diagnostic performance of 2-year distal migration for predicting aseptic loosening was good (area under the ROC curve, 0.86; 95% CI, 0.72-1.00; p < 0.001). Sensitivity of early migration measurement was high for the prediction of aseptic loosening during the first decade after surgery but decreased markedly thereafter. Stems with large amounts of early migration (≥ 2.7 mm) had lower 18-year survivorship than did stems with little early migration (29% [95% CI, 0%-62%] versus 95% [95% CI, 90%-100%] p < 0.001). CONCLUSIONS: Early migration, as measured by EBRA-FCA at 2 years postoperatively, has good diagnostic capabilities for detection of uncemented femoral components at risk for aseptic loosening during the first and early second decades after surgery. However, there was no relationship between early migration patterns and aseptic loosening during the late second and third decades. EBRA-FCA can be used as a research tool to evaluate new cementless stems or in clinical practice to evaluate migration patterns in patients with painful femoral components. LEVEL OF EVIDENCE: Level III, diagnostic study.

Cardiac Effects of Attenuating Gsα - Dependent Signaling.

AIMS: Inhibition of ß-adrenergic signalling plays a key role in treatment of heart failure. Gsα is essential for ß-adrenergic signal transduction. In order to reduce side-effects of beta-adrenergic inhibition diminishing ß-adrenergic signalling in the heart at the level of Gsα is a promising option. METHODS AND RESULTS: We analyzed the influence of Gsα on regulation of myocardial function and development of cardiac hypertrophy, using a transgenic mouse model (C57BL6/J mice) overexpressing a dominant negative Gsα-mutant under control of the α-MHC-promotor. Cardiac phenotype was characterized in vivo and in vitro and under acute and chronic ß-adrenergic stimulation. At rest, Gsα-DN-mice showed bradycardia (602 ± 13 vs. 660 ± 17 bpm, p<0.05) and decreased dp/dtmax (5037 ± 546- vs. 6835 ± 505 mmHg/s, p = 0.02). No significant differences were found regarding ejection fraction, heart weight and cardiomyocyte size. ß-blockade by propranolol revealed no baseline differences of hemodynamic parameters between wildtype and Gsα-DN-mice. Acute adrenergic stimulation resulted in decreased ß-adrenergic responsiveness in Gsα-DN-mice. Under chronic adrenergic stimulation, wildtype mice developed myocardial hypertrophy associated with increase of LV/BW-ratio by 23% (4.4 ± 0.2 vs. 3.5 ± 0.1 mg/g, p<0.01) and cardiac myocyte size by 24% (14927 ± 442 px vs. 12013 ± 583 px, p<0.001). In contrast, both parameters were unchanged in Gsα-DN-mice after chronic isoproterenol stimulation. CONCLUSION: Overexpression of a dominant negative mutant of Gsα leads to decreased ß-adrenergic responsiveness and is protective against isoproterenol-induced hypertrophy. Thus, Gsα-DN-mice provide novel insights into ß-adrenergic signal transduction and its modulation in myocardial overload and failure.

Cortical hypertrophy with a short, curved uncemented hip stem does not have any clinical impact during early follow-up.

BACKGROUND: Short stems have become more and more popular for cementless total hip arthroplasty in the past few years. While conventional, uncemented straight stems for primary total hip arthroplasty (THA) have shown high survival rates in the long term, it is not known whether uncemented short stems represent a reasonable alternative. As cortical hypertrophy has been reported for short stems, the aim of this study was to determine the radiographic prevalence of cortical hypertrophy and to assess the clinical outcome of a frequently used short, curved hip stem. METHODS: We retrospectively studied the clinical and radiographic results of our first 100 consecutive THAs (97 patients) using the Fitmore® hip stem. Mean age at the time of index arthroplasty was 59 years (range, 19 - 79 years). Clinical outcome and radiographic results were assessed with a minimum follow-up of 2 years, and Kaplan-Meier survivorship analysis was used to estimate survival for different endpoints. RESULTS: After a mean follow-up of 3.3 years (range, 2.0 - 4.4 years), two patients (two hips) had died, and three patients (four hips) were lost to follow-up. Kaplan-Meier analysis estimated a survival rate of 100 % at 3.8 years, with revision for any reason as the endpoint. No femoral component showed radiographic signs of loosening. No osteolysis was detected. Cortical hypertrophy was found in 50 hips (63 %), predominantly in Gruen zone 3 and 5. In the cortical hypertrophy group, two patients (two hips; 4 %) reported some thigh pain in combination with pain over the greater trochanter region during physical exercise (UCLA Score 6 and 7). There was no significant difference concerning the clinical outcome between the cortical hypertrophy and no cortical hypertrophy group. CONCLUSIONS: The survival rate and both clinical and the radiographic outcome confirm the encouraging results for short, curved uncemented stems. Postoperative radiographs frequently displayed cortical hypertrophy but it had no significant effect on the clinical outcome in the early follow-up. Further clinical and radiographic follow-up is necessary to detect possible adverse, long-term, clinical effects of cortical hypertrophy.