BACKGROUND: Constrained inserts in total knee arthroplasty (TKA) may offer additional stability, but can this insert type allow unrestricted movements or will the extra conformity cause kinematic conflict with the cam-post mechanism in deeper flexion? The objective of this study was to evaluate the weight-bearing kinematics of both traditional and constrained bicruciate stabilized (BCS) TKA inserts to determine if the rollback induced by the cam-post mechanism will work in unison with the constrained polyethylene insert.
METHODS: This study used previously published 3-dimensional model fitting techniques to compare weight-bearing flexion and femoro-tibial condylar motion patterns for 20 patients who had a traditional insert, 20 patients who had a constrained insert, and 10 previously published nonimplanted knees, all performing a deep knee bend activity while under fluoroscopic surveillance.
RESULTS: The results from this study indicate that subjects having a bicruciate stabilized TKA experienced similar postoperative kinematics for both constrained and unconstrained insert options, comparable to normal knees.
CONCLUSIONS: Subjects in this study having either a constrained or traditional insert experienced progressive rollback of both condyles, with the lateral condyle rolling more posterior than the medial condyle, leading to axial rotation. Although less in magnitude, these results were comparable to the normal knee in pattern, indicating that kinematic conflict did not occur for subjects having a constrained insert.

OBJECTIVE: This study reports the ten-year wear rates, incidence of osteolysis, clinical outcomes, and complications of a multicentre randomized controlled trial comparing oxidized zirconium (OxZr) versus cobalt-chrome (CoCr) femoral heads with ultra-high molecular weight polyethylene (UHMWPE) and highly cross-linked polyethylene (XLPE) liners in total hip arthroplasty (THA).
METHODS: Patients undergoing primary THA were recruited from four institutions and prospectively allocated to the following treatment groups: Group A, CoCr femoral head with XLPE liner; Group B, OxZr femoral head with XLPE liner; and Group C, OxZr femoral head with UHMWPE liner. All study patients and assessors recording outcomes were blinded to the treatment groups. The outcomes of 262 study patients were analyzed at ten years\' follow-up.
RESULTS: Patients in Group C were associated with increased mean liner wear rates compared to patients in Group A (0.133 mm/yr (SD 0.21) vs 0.031 mm/yr (SD 0.07), respectively; p < 0.001) and Group B (0.133 mm/yr (SD 0.21) vs 0.022 mm/yr (SD 0.05), respectively; p < 0.001) at ten years\' follow-up. Patients in Group C were also associated with increased risk of osteolysis and aseptic loosening requiring revision surgery, compared with patients in Group A (7/133 vs 0/133, respectively; p = 0.007) and Group B (7/133 vs 0/135, respectively; p = 0.007). There was a non-statistically significant trend towards increased mean liner wear rates in Group A compared with Group B (0.031 mm/yr (SD 0.07) vs 0.022 mm/yr (SD 0.05), respectively; p = 0.128). All three groups were statistically comparable preoperatively and at ten years\' follow-up when measuring normalized Western Ontario and McMaster Universities Osteoarthritis Index (p = 0.410), 36-Item Short Form Health Survey (p = 0.465 mental, p = 0.713 physical), and pain scale scores (p = 0.451).
CONCLUSIONS: The use of UHMWPE was associated with progressively increased annual liner wear rates after THA compared to XLPE. At ten years\' follow-up, the group receiving UHMWPE demonstrated an increased incidence of osteolysis and aseptic loosening requiring revision surgery compared to XLPE. Femoral heads composed of OxZr were associated with trend towards reduced wear rates compared to CoCr, but this did not reach statistical significance and did not translate to any differences in osteolysis, functional outcomes, or revision surgery between the two femoral head components. Cite this article: Bone Joint J 2022;104-B(7):833-843.

BACKGROUND: The effectiveness of modern ceramic bearings has been well established in reducing the osteolysis associated with wear of the bearing surfaces in total hip arthroplasty (THA). However, there are limited mid- to long-term follow-up data for complications associated with ceramic bearings.
METHODS: This case series analyzed 124 consecutive primary uncemented THAs in 108 patients with a mean age of 61 years using alumina ceramic-on-alumina ceramic bearing couples. Seventy THAs (56%) were evaluated at a minimum 14 years of follow-up; the mean follow-up period was 16 ± 1 years (14-20 years). Kaplan-Meier survivorship was determined with revision surgery for any reason as the end point. Complications were recorded focusing on osteolysis, ceramic fracture, and abnormal sounds until the final follow-up. Clinical data were scored according to the Merle d\'Aubigne and Postel hip score at 14 years after THA.
RESULTS: The survivorship was 93.5% (95% CI 86.7-97.0%) at 14-years postoperatively. Five patients (4.0%) underwent revision surgery due to instability or infection before 1-year postoperatively. Two patients (1.6%) underwent revision surgery due to ceramic liner fracture at 9- and 12-years postoperatively, respectively. There was no radiographic evidence of osteolysis. A total of 27 complications occurred: dislocations (n = 7/124), squeaking sounds (n = 3/124), clicking sounds (n = 6/124), ceramic liner fractures (n = 2/124), periprosthetic fractures (n = 4/124), deep infections (n = 2/124), transient sciatic nerve palsy (n = 2/124), and femoral stem breakage (n = 1/124). The Merle d\'Aubigne and Postel hip score was 16.8 ± 1.4 points.
CONCLUSIONS: The survivorship analysis demonstrates the uncemented THA using alumina ceramic bearings may provide favorable clinical outcome and can offer minimal wear at a minimum 14-year follow-up. Revision surgery was mostly required due to instability and infection in the short-term, and implant breakage in the mid- to long-term.

OBJECTIVE: To find out if there is an inverse association between estimated glomerular filtration rate (eGFR) and whole blood cobalt (Co) and chromium (Cr) levels in patients with metal-on-metal (MoM) hip arthroplasties and renal insufficiency, suggesting that renal insufficiency could cause accumulation of Co and Cr in blood.
METHODS: Out of 2,520 patients with 3,013 MoM hip arthroplasties, we identified 1,244 patients with whole blood Co, Cr, and creatinine measured within no more than a one-year interval. We analyzed the correlation of blood metal ion levels and eGFR to identify a potential trend of accumulating Co or Cr with decreasing eGFR.
RESULTS: Of the 1,244 patients, 112 had normal renal function (eGFR > 90 ml/min/1.73 m2), 715 had mild renal insufficiency (eGFR 60 to 89), 384 had moderate renal insufficiency (eGFR 30 to 59), 27 had severe renal insufficiency (eGFR 15 to 29), and six had end-stage renal insufficiency (eGFR < 15). Median eGFR was 68 ml/min/1.73 m2 (interquartile range (IQR) 56 to 82), median whole blood Co was 3.3 µg/l (IQR 1.1 to 9.9), and median Cr was 2.0 µg/l (IQR 1.2 to 3.6). We did not observe an association between decreased eGFR and increased whole blood Co and Cr concentrations, but instead both increased Co and Cr were associated with higher eGFR, indicating better kidney function.
CONCLUSIONS: As patients with MoM hip arthroplasties get older, the prevalence of renal insufficiency among them will increase, and orthopaedic surgeons will increasingly have to evaluate whether or not this affects patient follow-up. The USA Food and Drug Administration suggests that closer follow-up may be needed for MoM patients with renal insufficiency. We did not observe accumulation of blood Co or Cr in MoM hip arthroplasty patients with mild to severe renal insufficiency. Cite this article: Bone Joint J 2021;103-B(7):1231-1237.

BACKGROUND: To evaluate the clinical features and results of the revision total hip arthroplasties (THA) in patients with catastrophic failures and metallosis.
METHODS: Fifteen hips of 14 patients with catastrophic failure and metallosis in hip arthroplasties were evaluated. They were followed for at least 4.2 years after the revision THA. Clinical evaluation was performed using Harris hip score. Osteolysis, loosening or presence of metallosis was evaluated with standard radiographs. Metallosis was evaluated intraoperatively according to the metallosis severity classification.
RESULTS: The mean time from failure until revision surgery was 9.4 years. It was observed that in the primary THA, metal-on-ceramic (MoC), ceramic-on-ceramic (CoC) and metal-on-conventional polyethylene (MoCPE) bearings were used in 1, 3 and 11 hips, respectively. Grade III metallosis was observed in all patients during revision surgeries. The mean Harris hip score increased from 55 points before revision THA to 75 points at the final follow-up. In revision arthroplasty, MoCPE and CoC bearings were used in 13 and 2 hips, respectively. The femoral stem was replaced in 5 hips. All acetabular cups, except that of one hip, were revised.
CONCLUSIONS: Revisions of THAs with catastrophic failures and metallosis are quite challenging. Routine follow-up of arthroplasty patients is beneficial to examine for osteolysis, loosening, and asymmetric wear.

Introduction An optimal hip implant is biocompatible, durable, and resistant to chemical and mechanical wear. This analysis aimed to compare failure (revision) and complication rates between ceramic-on-ceramic (CoC) and ceramic-on-highly-crosslinked-polyethylene (CoHXLPE) implants. Methods This review comprised of scientific literature published between 1995 and 2019. We included randomized controlled trials in adults (>18 years) that presented results of CoC and CoHXLPE total hip arthroplasty (THA) with more than two years of mean follow-up and drafted in English. The primary outcomes for this analysis were complications, revision rates, and loosening rates. Results Eight studies (1,689 hips) were included in this systematic review. There was no significant differences between COC and CoHXLPE for the risk of post-surgical complications (relative risk [RR]: 1.98, 95% confidence interval [CI]: 0.83-4.69, P = 0.12). Revision rates (RR: 1.25, 95% CI: 0.71-2.20, P = 0.43] and loosening rates between the two implants were not significantly different (RR: 1.17, 95% CI: 0.30-4.52, P = 0.82). Conclusion We report no significant differences between CoHXLPE and CoC in adults undergoing primary THA. Although introduced relatively recently, CoHXLPE is a cost-effective bearing that can be used for younger patients with no risk of increased complications in comparison to CoC. Further studies with longer follow-up periods are recommended to confirm the findings of this meta-analysis.

Pitting damage on implants has been reported and attributed to the use of electrocautery. This study aimed to determine how different total knee arthroplasty bearing surfaces are susceptible to this type of damage and whether surgeons are aware that this damage can occur.
A survey was sent to Hip and Knee Society members to determine what percentage of adult reconstructive surgeons use electrocautery after implantation of components. Three bearing surfaces for total knee arthroplasty were selected: cobalt chromium, Oxinium, and zirconium nitride to be damaged by electrocautery with a monopolar (MP) and bipolar (BP) electrocautery with 3 different energy settings. A comparison of surface damage using scanning electron microscopy and elemental differences using energy dispersion spectroscopy was performed. Average roughness (Ra), maximal peak-to-valley height (Rz), kurtosis (Rk), and skewness (Rsk) were recorded for comparison using a profilometer was performed.
Median Rz and Ra measurements were larger for BP damaged areas compared to MP for all bearing surfaces. The Oxinium surface had the greatest increase in roughness parameters. Survey results indicate that a significant percentage of adult reconstructive surgeons use the electrocautery after implants are in place and are not aware of this type of damage. Backscatter scanning electron microscopy analysis found significant changes for BP damage compared to MP.
Surface damage caused by electrocautery can have significant effects on the bearing surfaces of implants but further study needs to be performed to determine if this is a clinical issue. Our survey determined that many arthroplasty experts are unaware that this damage can occur.

Prosthetic joint infection (PJI) is one of the most frequent and devastating causes of short-term revision total knee arthroplasty (TKA). In vitro evidence suggests ceramic surfaces demonstrate resistance to biofilm, but the clinical effect of bearing surface modifications on the risk of PJI remains unclear. This premier registry-based study examines the influence of ceramic bearing surface coatings on the outcome in cemented primary TKA.
In total, 117,660 cemented primary TKAs in patients with primary osteoarthritis recorded in the German arthroplasty registry since 2012 were followed up for a maximum of 3 years. The primary endpoint was risk of revision for PJI on ceramic coated and uncoated cobalt-chromium-molybdenum femoral components. Propensity score matching for age, gender, obesity, diabetes mellitus, depression and Elixhauser comorbidity index, and substratification on common design twins with and without coating was performed.
In total, 4637 TKAs (85.1% female) with a ceramic-coated femoral component were identified, 42 had been revised for PJI and 122 for other reasons at 3 years. No survival advantage due to the risk of revision for PJI could be determined for ceramic-coated components. Revision for all other reasons demonstrated a significant higher rate for TKAs with ceramic-coated components. However, the results of this were confounded by a strong prevalence (20.7% vs 0.3%) of metal sensitivity in the ceramic-coated group.
No evidence of reduced risk for PJI due to ceramic-coated implants in cemented primary TKA was found. Further analysis for revision reasons other than PJI is required.

Unicompartmental knee arthroplasty (UKA) is a bone- and ligament-sparing alternative to total knee arthroplasty in the patients with end-stage single-compartment degeneration of the knee. Despite being a successful procedure, the multiple advantages of UKA do not correlate with its usage, most likely due to the concerns regarding prosthesis survivability, patient selection, ideal bearing design, and judicious use of advanced technology among many others. Therefore, the purpose of this study is to review and summarize the debated literature and discuss the controversies as \"Ten Enigmas of UKA.\"

OBJECTIVE: The primary study aim was to compare early knee-specific function of patients undergoing cemented total knee arthroplasty (TKA) with either a cruciate-retaining (CR) polyethylene insert or a highly congruent condylar-stabilizing (CS) insert. Secondary aims were to compare general health and satisfaction between the groups.
METHODS: A total of 418 consecutive primary TKAs were identified retrospectively. Demographics and preoperative and 1-year postoperative patient-reported outcome measures (PROMs) were collected prospectively. PROMs consisted of Oxford Knee Scores, EuroQol-5 Dimensions scores, and Short Form-12 scores.
RESULTS: A total of 54 (12.9%) patients received a CS insert and 364 patients received a CR TKA. The CS group had a significantly (odds ratio (OR) 2.9; p = 0.002) greater proportion of females (77.8% versus 54.9%). The only significant difference in postoperative PROMs was a higher Short Form-12 physical component score in the CR group (difference 3.1; 95% confidence interval (CI) 0.1 to 6.1; p = 0.04). Linear regression analysis demonstrated no significant difference for all postoperative PROMs (p > 0.25). There was no significant difference in satisfaction rate (OR 0.94; 95% CI 0.42 to 2.12; p = 0.56) or pain visual analogue score (difference 6.1; 95% CI -1.9 to 14.0; p = 0.14) between the groups.
CONCLUSIONS: More congruent CS inserts have equivalent PROMs and patient satisfaction at 1 year compared with less congruent CR inserts. These represent an option for surgeons undertaking TKA where increased congruency is desired.