Which method for femoral component sizing when performing kinematic alignment TKA? An in silico study

INTRODUCTION

The kinematically alignment (KA) technique for TKA aims to reproduce the pre-arthritic knee anatomy, including both the femoro-tibial and femoro-patellar joints. An in silico study was conducted to compare 3 different femoral component sizing techniques to identify the anatomical landmark which allows closest restoration of the native trochlear anatomy. Our study's question was: what was the best method for sizing the femoral component when performing KA-TKA? It was hypothesized that sizing the femoral component by aiming to restore the groove height would be the best method to restore the native trochlear anatomy.

METHODS

GMK sphere® (Medacta) femoral component 3D models were virtually kinematically aligned on 30 tri-dimensional (3D) bony osteoarthritis knee models. The femoral component was mediolaterally positioned to match distal native and prosthetic grooves. Three methods were used to size the femoral component: a conventional method with the anterior femoral cut flush to the femoral cortex (C-KATKA) and two alternative personalized methods aiming to recreate either the medial facet's height (ATM-KATKA) or the groove's height (ATG-KATKA). In-house analysis software was used to compare native and prosthetic trochlear articular surfaces and mediolateral implant overhangs.

RESULTS

Compared with the C-KATKA, ATG-KATKA and ATM-KATKA techniques increased the component size by a mean of 0.90 (SD 0.31, min 0.5 to max 1.5) (p<0.001) and 1.02 (SD 0.31, min 0.5 to max 1.5) (p<0.001), respectively. C-KATKA technique substantially proximally understuffed the trochleae with maximum values of 7.11mm (SD 1.39, min 3.93mm to max 10.57mm) in the medial facet, 4.72mm (SD 1.27, min 1.46mm to max 6.86mm) in the lateral facet and 4.51mm (SD 1.40, min 1.92mm to max 7.30mm) in the groove, respectively. Alternative techniques understuffed medial facet with maximum values of 5.07mm (SD 1.29, min 2.83mm to max 8.34mm) and 4.70mm (SD 1.52, min 0.83mm to max 8.04mm) for ATG-KATKA and ATM-KATKA techniques, respectively. There was no significant understuffing of the groove or lateral facet for alternative techniques (ATM and ATG). The ATM-KATKA and ATG-KATKA techniques generated mediolateral implant overhang, mainly postero-lateral, with a rate of 90.0% and 86.7%, respectively. In this study, no mediolateral implant overhang was found for C-KATKA.

DISCUSSION/CONCLUSION

The C-KATKA technique substantially understuffs the native trochlear articular surfaces in medial, lateral and groove parts. Alternative techniques (ATM-KATKA and ATG-KATKA) for sizing the femoral component better restore the native trochlear anatomy but also generate a high rate of postero-lateral implant overhangs. Would this postero-lateral implant overhang be clinically deleterious remains unknown? The aspect ratio of contemporary femoral TKA implants can probably be optimized to allow a better anatomical restoration of the anterior femoral compartment.

LEVEL OF EVIDENCE

II, in silico study.

Effectiveness of electronic patient reporting outcomes, by a digital telemonitoring platform, for prostate cancer care: the Protecty study

Research aim and purpose

The benefits of Electronic Patient -Reported Outcomes (e-PRO) for telemonitoring are well established, allowing early detection of illnesses and continuous monitoring of patients. The primary objective of the PROTECTY study was to assess the compliance with patient use of the telemonitoring platform Cureety. An exploratory objective was to assess if the first-month health status is a prognostic factor of progression free-survival (PFS) and overall survival (OS) for prostate cancer patient.

Methods

This prospective study was conducted at the Military Hospital Bégin on prostate cancer patients. Patients were allowed to respond to a symptomatology questionnaire based on CTCAE v.5.0, personalized to their pathology and treatment. An algorithm evaluates the health status of the patient based on the reported adverse events, with a classification into 2 different states: Good Health Status (GHS) and Poor Health status (PHS).

Results

Sixty-one patients were enrolled between July 1st, 2020 and September 30th, 2021. The median age was 74.0 (range 58.0-94.0). 78% presented a metastatic stage, and the most represented cancer was mHSPC. Overall, 2,457 questionnaires were completed by the patients, 4.0% resulted in a health classification in to monitor or critical state. 87% of patients were classified in the GHS group. The compliance was 72% in the overall population during the first month, 71% in GHS group and 75% in PHS group. The median follow-up was 8 months. PFS at 6 months was 84% in GHS group vs. 57% in PHS group, p = 0.19. OS at 6 months was 98% in GHS group vs. 83% in PHS group, p = 0.31.

Conclusions

Our study showed that compliance was satisfactory. The feasibility of remote monitoring for prostate cancer patients means that they should benefit from its implementation. Our study is also the first to assess the correlation between treatment tolerance and survival. The initial results suggest that e-PRO assessment could help identify in the early stages the patients that require further health assessment and potential therapeutic changes. While further follow-up of more patients will be required, our study highlights the importance of e-PRO in cancer patient care.

Evolution of Concepts: Can Personalized Hip Arthroplasty Improve Joint Stability?

Hip arthroplasty procedures are successful and reproducible. However, within the first two post-operative years, hip dislocations are the most common cause for revisions. This is despite the majority of the dislocations having the acetabular component within what is described as the 'safe zone'. The limitations of such boundaries do not take into account the variability of individual hip anatomy and functional pelvic orientation that exist. An alternative concept to address hip instability and improve overall outcomes is functional acetabular orientation. In this review article, we discuss the evolution of concepts, particularly the kinematic alignment technique for hip arthroplasty and the use of large-diameter heads to understand why total hip arthroplasty dislocations occur and how to prevent them.

Microphase separation of living cells

Self-organization of cells is central to a variety of biological systems and physical concepts of condensed matter have proven instrumental in deciphering some of their properties. Here we show that microphase separation, long studied in polymeric materials and other inert systems, has a natural counterpart in living cells. When placed below a millimetric film of liquid nutritive medium, a quasi two-dimensional, high-density population of Dictyostelium discoideum cells spontaneously assembles into compact domains. Their typical size of 100 μm is governed by a balance between competing interactions: an adhesion acting as a short-range attraction and promoting aggregation, and an effective long-range repulsion stemming from aerotaxis in near anoxic condition. Experimental data, a simple model and cell-based simulations all support this scenario. Our findings establish a generic mechanism for self-organization of living cells and highlight oxygen regulation as an emergent organizing principle for biological matter.

Limb alignment changes with knee flexion: A study based on CAS data

BACKGROUND

Recent evidence has questioned the value of standing limb alignment for predicting the adduction moment and forces exerted on healthy and prosthetic knees. The purpose of this study was to assess the lower limb alignment of OA knee patients at various knee flexion angles. The main hypothesis was that lower limb alignment measured throughout knee flexion does not significantly differ between patients displaying different extension alignment (neutral, varus or valgus).

METHODS

206 arthritic knee patients undergoing computer-assisted total (CAS) knee prosthesis were included. Frontal limb alignment was assessed in a systematic manner by CAS at three knee positions: extension, 90 degrees of flexion and maximal flexion. The HKA angle at each knee position and the change in HKA angle between two knee positions (delta value) were reported and compared.

RESULTS

A large proportion of OA patients had significant variation in their lower limb alignment (32% with Δ HKA > 5°). The extended limb deformity tended to reduce with knee flexion: mean of 5° and 6° deformity reduction for varus and valgus patients, 40% and 66% of varus and valgus patients progressed to neutral alignment with 90° knee flexion. Forty percent of neutral extended lower limb did not maintain their neutral alignment but rather progressed to either varus or valgus at 90° knee flexion.

CONCLUSIONS

Limb alignment in extension is a poor predictor of limb alignment in flexion in OA patients. Only considering the traditional frontal alignment of an extended lower limb for planning knee arthroplasty or osteotomy is likely insufficient.

Caliper-Verified Kinematically Aligned Total Knee Arthroplasty: Rationale, Targets, Accuracy, Balancing, Implant Survival, and Outcomes

Peer-reviewed studies published up to May 2022 are used to provide a comprehensive understanding of unrestricted kinematically aligned total knee arthroplasty. The intent is to cultivate the curiosity of those interested in this method of personalized alignment. The rationale of unrestricted kinematic alignment is to set the femoral and tibial components coincident with the patient's prearthritic joint lines, restore the femoral and tibial phenotypes, and coalign the three kinematic axes of the components with those of the knee. The surgical technique, learning curve, and accuracy of performing kinematically aligned total knee arthroplasty with a caliper and company manufactured manual instrumentation should be explored and compared with robotic instrumentation. Kinematic alignment restores the native knee's medial and lateral tibial compartment forces, which mechanically aligned total knee arthroplasty cannot do even after ligament release. In addition, insert conformity plays a role in restoring native tibiofemoral kinematics. A literature review of clinical outcomes, long-term durability, and the risk of varus tibial component failure and patellofemoral instability shows unrestricted kinematic alignment has comparable if not superior results when compared with mechanical alignment.

The significant relationship among the factors of pelvic incidence, standing lumbar lordosis, and lumbar flexibility in Japanese patients with hip osteoarthritis: A descriptive radiographic study

INTRODUCTION

Spine stiffness is known to increase the risk of total hip replacement (THR) instability. The sagittal posture and lumbo-pelvic kinematics have therefore become parameters of interest when planning THR. We conducted this study to investigate (1) the distribution and characteristics of the spino-pelvic standing alignment, (2) the relationship between pelvic incidence (PI) and standing lumbar lordosis (LL) and lumbar flexibility, in Japanese hip osteoarthritis patients.

HYPOTHESIS

(1) Japanese hip osteoarthritis patients with different sagittal spino-pelvic alignments do not differ markedly in their demographics, PI, or lumbar flexibility; and (2) there is no significant relationship between PI, standing LL, and lumbar flexibility in a population of Japanese hip osteoarthritis patients.

MATERIAL AND METHODS

A retrospective study of radiographs from 945 Japanese patients who consecutively received THR for the treatment of hip osteoarthritis. All patients pre-operatively underwent lateral standing and deep-seated lumbo-pelvic radiography on which the spino-pelvic parameters were measured. The difference between the standing and deep-seated LL angles defined the lumbar flexibility and was calculated as the delta (Δ) LL. Individual spino-pelvic standing alignment was stratified based on the difference between the PI and standing LL ('PI-LL mismatch'). 'PI-LL mismatch' of<-10°, between -10° and 10°, and>10° was defined as hyperlordosis, normolordosis, and flatback, respectively.

RESULTS

In the present study, the spinal alignment of 115/945 (12.2%), 559/945 (59.2%), and 271/945 (28.6%) patients were classified as hyperlordosis, normolordosis, and flatback, respectively. Hyperlordotic patients had significantly lower PI (47.6°±7.8° vs. 52.7°±10.5°, p<0.001) and higher ΔLL (60.6°±12.6° vs. 51.6°±12.8°, p<0.001) than normolordotic patients. Patients with flatback were significantly older (age, 69.1±9.1 years vs. 62.7±9.8 years, p<0.001) with higher PI (56.9°±11.7° vs. 52.7°±10.5°, p<0.001) and lower ΔLL (35.2°±17.4° vs. 51.6°±12.8°, p<0.001) than normolordotic patients. A significant relationship between PI and the standing LL was found in the whole cohort (r=0.409, p=0.009), hyperlordotic (r=0.785, p<0.001), normolordotic (r=0.857, p<0.001), and flatback (r=0.664, p<0.001) patients. Significant relationships between the PI and ΔLL were also found in normolordotic (r=0.442, p=0.004) and flatback (r=0.449, p=0.003) patients but not hyperlordotic patients (r=0.154, p=0.367).

DISCUSSION

A large proportion of Japanese hip osteoarthritis patients have abnormal PI-LL mismatch (12% and 29% have hyperlordosis and flatback, respectively). The PI was a determinant of the standing LL and the lumbar flexibility, especially in the normolordotic and flatback individuals.

LEVEL OF EVIDENCE

III; retrospective diagnostic radiographic study.

Kinematic alignment of medial UKA is safe: a systematic review

PURPOSE

Owing to the improved understanding of knee kinematics and the successful introduction of the kinematic alignment (KA) technique for implanting total knee arthroplasty (TKA), it was recently understood that the "Cartier angle technique" corresponds to a kinematic implantation of the uni-compartmental knee arthroplasty (UKA) components. When compared to the universally spread mechanical alignment (MA) technique for implanting UKA, the KA method generates a more anatomic prosthetic knee that may be clinically advantageous. The aims of this study are to determine if KA UKAs are associated with acceptable functional performance and patient satisfaction (question 1), rates of residual pain and tibia plateau fracture (question 2), and rates of reoperation and revision (question 3), and to define the component orientation and limb alignment as measured on radiograph (question 4), and the stress shielding related bone loss in the proximal tibia (question 5) with KA UKA, and where possible to compare with MA UKA.

STUDY HYPOTHESIS

KA UKA generates good clinical outcomes, similar or superior to the ones of MA UKA.

METHOD

Systematic review of literature databases were primarily searched using Healthcare Databases Advanced Search (HDAS). Two primary searches were conducted using the electronic databases MEDLINE, EMBASE, and PubMed, and a secondary search was conducted using review articles and bibliography of obtained papers in order to ascertain more material.

RESULTS

Nine eligible non-comparative prospective (3) or retrospective (6) cohort studies, which cumulated 593 KA UKAs with follow-up between 3.2 and 12 years, fulfilled the inclusion criteria for this systematic review. The findings demonstrated high Knee Society Score (KSS) (from 87 to 95) and function scores (from 81 to above 91) in addition to patient satisfaction scores of 88%. There was no revision for tibia plateau fracture, 0.8% (5 cases) for unexplained pain tibia, 2.0% (12 cases) for component loosening, and 5.6% (33 cases) for any causes of aseptic failures reported for KA UKA. The prosthetic lower limb and tibia implant alignments were both found to be in slight varus (means between 3 and 5°), and the postoperative joint line and tibia component was shown to be parallel to the floor when standing. The KA UKA components migration, as measured on radiostereometry, was acceptable.

DISCUSSION/CONCLUSION

The KA technique is an alternative, personalised, more physiological method for implanting UKA, which could be clinically advantageous when compared to the MA technique. The literature supports the good mid- to long-term clinical safety and good efficacy of KA UKA; however, comparison between KA and MA techniques for UKA was not performed due to limited literature. Further investigations are needed to better define the clinical impact of KA UKA, and the acceptable limits for KA of the UKA tibial component.

LEVEL OF EVIDENCE

Level 4; systematic review of level 4 studies.

Moderate relationship between function and satisfaction of total hip arthroplasty patients: a cross sectional study

PURPOSE

Patient satisfaction regarding their hip replacement is often assumed to be directly linked to functional outcomes. We led this study to answer 2 questions: (1) what is the level of patient satisfaction, function, and quality of life after primary total hip replacement (THR); and (2) what is the relationship between patient satisfaction and functional and quality of life PROMs after THR?

METHODS

We led a retrospective study using our institutional registry of prospectively and consecutively collected data on patients after primary THR undertaken between 2004 and 2017. We included 6710 patients with a complete 2-year set of follow-up data for Oxford Hip Score (OHS) (for assessing patient's function), EQ-5D (for assessing patient's quality of life) and satisfaction PROM scores.

RESULTS

There was a significant improvement in all OHS and EQ-5D scores from preoperative level, and the mean postoperative satisfaction score was 89/100. We found moderate positive correlations between the patients' outcome satisfaction VAS score and OHS (r = 0.665) and EQ-5D (r = 0.554).

CONCLUSIONS

THR is a successful procedure generating high levels of patient function and satisfaction. Because patients' OHS and EQ-5D scores may be influenced by comorbidities, those scores are of poor predictive value in estimating patient satisfaction, and therefore should not be used as a surrogate to determine the success of the THR procedure.

Specific case consideration for implanting TKA with the Kinematic Alignment technique

The Kinematic Alignment (KA) technique for total knee arthroplasty (TKA) is an alternative surgical technique aiming to resurface knee articular surfaces.The restricted KA (rKA) technique for TKA applies boundaries to the KA technique in order to avoid reproducing extreme constitutional limb/knee anatomies.The vast majority of TKA cases are straightforward and can be performed with KA in a standard (unrestricted) fashion.There are some specific situations where performing KA TKA may be more challenging (complex KA TKA cases) and surgical technique adaptations should be included.To secure good clinical outcomes, complex KA TKA cases must be preoperatively recognized, and planned accordingly.The proposed classification system describes six specific issues that must be considered when aiming for a KA TKA implantation.Specific recommendations for each situation type should improve the reliability of the prosthetic implantation to the benefit of the patient.The proposed classification system could contribute to the adoption of a common language within our orthopaedic community that would ease inter-surgeon communication and could benefit the teaching of the KA technique. This proposed classification system is not exhaustive and will certainly be improved over time. Cite this article: EFORT Open Rev 2021;6:881-891. DOI: 10.1302/2058-5241.6.210042.

Kinematic Alignment Technique for TKA on Degenerative Knees with Severe Bone Loss: A Report of 3 Cases

A severely degenerative knee joint with substantial bone attrition poses a significant challenge when performing Total Knee Arthroplasty (TKA) using the Kinematic Alignment (KA) technique. In order to restore the pre-arthritic knee anatomy, the surgeon has the task of estimating quantity and location of bone loss. We present three such cases and describe the key steps to safely perform KATKA in these complex situations.

Disappointing Relationship between Functional Performance and Patient Satisfaction of UKA Patients: A Cross Sectional Study

BACKGROUND

Following a Unicompartmental knee arthroplasty (UKA) satisfaction is often conflated with functional outcome. Recent studies have shown that satisfaction is not linked to functional outcome. The research questions were: (1) what is the relationship between satisfaction and functional performance and quality of life (absolute and gain values) after UKA? And (2) what is the level of satisfaction, function, and quality of life after UKA?

HYPOTHESIS

There is a poor relationship between functional performance and patient satisfaction following UKA.

METHODS

This was a retrospective study using a locally held arthroplasty register to identify patients who had undergone UKA between 2004 and 2017. Patient reported outcome measures (PROMs) were collected prospectively and included EQ-5D, Oxford Knee Score (OKS) and satisfaction score (based on a visual analogue score with 0 being worst and 100 being best). Patients with a complete set of pre-operative and 2-year post-operative outcome scores were included. Patients who subsequently underwent revision surgery were excluded. 1638 patients were identified, of which 896 were eligible for inclusion. The average age was 66.7 years old, with 46.3% of patients being female.

RESULTS

There was a moderate to strong correlation between the absolute or relative values for OKS and the patient satisfaction following UKA (r=0.705 and r=0.522, respectively). The average pre-operative scores improved from a median of 23 (IQR 18-28) to 43 (IQR 35-46) (p<0.001) and from a median of 0.62 (IQR 0.186-0.691) to 0.85 (IQR 0.691 - 1) (p<0.001) for OKS and EQ-5D, respectively. In terms of satisfaction with outcome, 82.6% of patients were very satisfied and 4.4% were dissatisfied (scoring ≥80% and <50%, respectively). At 2 years, the PASS was met or surpassed by 73.1% and 54.9% (OKS and EQ-5D, respectively). The MCID was met or surpassed by 93% and 78% (OKS and EQ-5D, respectively).

DISCUSSION/CONCLUSION

UKA is a successful procedure generating high levels of patient function and satisfaction. Because patients' OKS and EQ-5D scores may be influenced by comorbidities, those scores are of disappointing predictive value in estimating patient satisfaction, and therefore should not be used as a surrogate to determine the success of the UKA procedure.

LEVEL OF EVIDENCE

III; Restrospective cohort study.

Calipered kinematic alignment technique for implanting a Medial Oxford®: A technical note

This note describes a surgical technique to kinematically align a medial Oxford® UKA. Applying kinematic alignment principles is an alternative, personalised, physiological, and potentially clinically advantageous method for implanting the medial Oxford® UKA. Further investigations are needed to better define the reproducibility and clinical impact of this new surgical technique.

Oxford Knee Score and EQ-5d poorly predict patient's satisfaction following mechanically aligned total knee replacement: A cross-sectional study

BACKGROUND

Patient satisfaction is increasingly used to measure the success of arthroplasty. Satisfaction with the outcome of a total knee replacement (TKR) is traditionally thought to be associated with improvements in functional status and quality of life measures. This study aims to answer the following questions: 1. What is the level of patient satisfaction, improvement in knee function and patient quality of life associated with mechanically aligned TKR? 2. What is the relationship between OKS, EQ-5d scores and 'outcome satisfaction'?

HYPOTHESIS

TKR is associated with a significant improvement in function, satisfaction and quality of life and that there is a strong correlation between OKS, EQ-5d and 'outcome satisfaction'.

METHOD

Five thousand eight hundred and ninety six patients underwent primary TKR between January 2010 and December 2017 and had complete preoperative and 2-year follow-up data for OKS, EQ-5d and satisfaction scores. Outcomes data were collected prospectively and recorded on our institutional database. Minimal clinically important difference (MCID) and the Patient acceptable symptomatic state (PASS) were calculated for OKS and EQ-5d, the association between OKS, EQ-5d and 'outcome satisfaction' was measured using regression analysis.

RESULTS

The median 2-year 'outcome satisfaction' score was 90/100 with 79% of patients reporting excellent satisfaction (≥80/100) and 93.4% of patients satisfied (≥50/100). Postoperatively, median scores were 39 for OKS and 0.8 for EQ-5d. The mean increase in scores was 15.85 for OKS and 0.32 for EQ-5d. Satisfaction showed moderate positive correlation with postoperative OKS (r=0.69) and EQ-5D (0.58) scores, but weaker correlation with the change in OKS (r=0.57) and EQ-5d (r=0.32) scores from preoperative levels.

DISCUSSION/CONCLUSION

Mechanically aligned TKR is overall a successful operation responsible of fair rate of patient satisfaction. OKS and EQ-5d are imperfect predictors for satisfaction as they are significantly influenced by patients' comorbidities. This should be taken into account when evaluating the success of an operation.

LEVEL OF EVIDENCE

IIc; observational study (based on prospectively collected data from an institutional registry).

The relationship between pelvic incidence and anatomical acetabular anteversion in female Japanese patients with hip osteoarthritis: a retrospective iconographic study

PURPOSE

This study aimed (1) to investigate the relationship between pelvic incidence (PI) and the anatomical acetabular anteversion (AA) relative to the spino-pelvic tilt (SPT) plane (anatomical AA_SPT), relative to the anterior pelvic plane (anatomical AA_APP), and functional standing AA; and (2) to compare AA and the sagittal spino-pelvic parameters of lumbo-pelvic complex types 1 (PI ≤ 30°) and 2 (PI > 30°), in Japanese females with hip osteoarthritis.

METHODS

We conducted a retrospective study on 110 Japanese females with unilateral hip osteoarthritis. PI, standing lumbar lordosis (LL), standing SPT, anatomical AA_SPT, anatomical AA_APP, and functional standing AA were measured and calculated using radiographs and computed tomography. The PI-LL difference was defined as the mathematical difference between the PI and standing LL angles. Pearson's correlation test was used to measure the relationship between the PI and AA. Student's t test was used to compare spino-pelvic parameters between lumbo-pelvic complex type 1 (n = 24) and type 2 (n = 86).

RESULTS

There was a significant relationship between the PI and anatomical AA_SPT (r =  -0.532, p < 0.001), but no significant relationship between the PI and anatomical AA_APP (r =  -0.021, p = 0.824) or functional standing AA (r = 0.104, p = 0.299). Lumbo-pelvic complex type 1 had a higher anatomical AA_SPT (22.4° ± 9.1° vs. 5.4° ± 15.1°, p < 0.001), similar anatomical AA_APP (15.0° ± 10.6° vs. 15.1° ± 15.3°, p = 0.981) and functional standing AA (12.4° ± 8.0° vs. 15.0° ± 14.1°, p = 0.254), a lower standing SPT (- 14.3° ± 11.0° vs. 13.7° ± 12.6°, p < 0.001), and a lower PI-LL difference (- 14.4° ± 18.5° vs. 6.4° ± 17.1°, p < 0.001) in comparison to lumbo-pelvic complex type 2.

CONCLUSION

Our findings will help to improve the understanding of hip anatomy and its relationship with the standing spino-pelvic alignment in Japanese females with hip osteoarthritis.

What you need to know about kinematic alignment for total knee arthroplasty

This lecture outlines the various alignment philosophies for total knee arthroplasty (TKA). It is logical that our desire to improve clinical outcomes for TKA involves a more personalized and physiological implantation process that preserves each patient's anatomical features. We will take a deep dive into the kinematic alignment concept by describing its rationale, surgical steps and results. Kinematic implantation of TKA can be done reliably at a low cost and appears to achieve acceptable implant biomechanics. While its short-term clinical results are encouraging, it must be evaluated further. The thresholds for acceptable alignment (indications for restricted kinematic alignment) still need to be specified. LEVEL OF EVIDENCE: V; Expert opinion.

Ceramic-on-ceramic total hip arthroplasty is superior to metal-on-conventional polyethylene at 20-year follow-up: A randomised clinical trial

BACKGROUND

Metal-on-conventional polyethylene (MoPc) bearing wear-related biological reactions in total hip arthroplasty (THA) continue to raise concerns among young, active patients. Ceramic-on-ceramic (CoC) bearings may offer improved outcomes in this patient population.

QUESTIONS/PURPOSES

The aim of this study was to determine if, more than 20years postoperatively, there is a difference between MoPc and CoC THA in terms of (1) survivorship, (2) related complications, (3) radiographic signs of wear, and (4) functional scores.

HYPOTHESIS

CoC bearing THAs have superior clinical results compared to MoPc THAs.

PATIENTS AND METHODS

A total of 140 hips in 116 patients with a mean age of 42years were randomised to receive CoC or MoPc THA between 1996 and 2001. Sixty-nine hips in 58 patients received MoP and 71 hips in 68 patients received CoC. Revision rate, WOMAC score, and radiological signs of osteolysis and loosening were compared at last follow-up.

RESULTS

After a mean follow-up of 21years (19-23), 40 patients (48 THAs; 34%) had died and 6 patients (6 THAs; 4%) were lost to follow-up. Aseptic revision rate was significantly higher in the MoPc group (17/69; 24.6%) versus CoC (2/71; 2.8%; p<0.001). Kaplan-Meier survivorship estimator with revision for aseptic reasons was 73.6% (95% CI: 63.3-84.9%) for MoPc and 96.9% (95% CI: 92.8-100%) for CoC (p<0.001). On radiographic evaluation, 13% (3/23) MoPc were considered loose versus no CoC, and 61% (14/23) MoPc versus 6% (2/33) CoC showed osteolytic signs (p<0.001). CoC had better mean WOMAC scores than MoPc (11.0 vs. 19.4; p=0.048). No ceramic fracture was observed.

CONCLUSION

In this RCT, CoC bearings provided excellent results and were safer than MoPc bearings at more than 20-year follow-up. The long-term in vivo behaviour of CoC bearing makes it a great THA option for middle-aged patients and should be compared to newer polyethylene bearings.

LEVEL OF EVIDENCE

I.

A new agarose-based microsystem to investigate cell response to prolonged confinement

Emerging evidence suggests the importance of mechanical stimuli in normal and pathological situations for the control of many critical cellular functions. While the effect of matrix stiffness has been and is still extensively studied, few studies have focused on the role of mechanical stresses. The main limitation of such analyses is the lack of standard in vitro assays enabling extended mechanical stimulation compatible with dynamic biological and biophysical cell characterization. We have developed an agarose-based microsystem, the soft cell confiner, which enables the precise control of confinement for single or mixed cell populations. The rigidity of the confiner matches physiological conditions and its porosity enables passive medium renewal. It is compatible with time-lapse microscopy, in situ immunostaining, and standard molecular analyses, and can be used with both adherent and non-adherent cell lines. Cell proliferation of various cell lines (hematopoietic cells, MCF10A epithelial breast cells and HS27A stromal cells) was followed for several days up to confluence using video-microscopy and further documented by Western blot and immunostaining. Interestingly, even though the nuclear projected area was much larger upon confinement, with many highly deformed nuclei (non-circular shape), cell viability, assessed by live and dead cell staining, was unaffected for up to 8 days in the confiner. However, there was a decrease in cell proliferation upon confinement for all cell lines tested. The soft cell confiner is thus a valuable tool to decipher the effects of long-term confinement and deformation on the biology of cell populations. This tool will be instrumental in deciphering the impact of nuclear and cytoskeletal mechanosensitivity in normal and pathological conditions involving highly confined situations, such as those reported upon aging with fibrosis or during cancer.

Hip Resurfacing Compared with 28-mm Metal-on-Metal Total Hip Replacement: A Randomized Study with 15 Years of Follow-up

BACKGROUND

Bone stock conservation, hip anatomy preservation, and greater stability are among the promoted advantages of hip resurfacing (HR). However, the disappointing failure of some implants nearly led to its abandonment. The aim of this study was to compare clinical scores and revision and complication rates after HR with those after total hip arthroplasty (THA).

METHODS

Two hundred and three hips were randomized to 28-mm metal-on-metal (MoM) THA (99 hips) or to HR (104 hips). Main outcome measures compared between groups were the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score, the revision rate, and the complication rates. The radiographic findings were also assessed.

RESULTS

After a mean follow-up of 15 years (range, 14 to 16 years), 9 (4.4%) of the 203 patients were lost to follow-up and 15 (7.4%) had died. The Kaplan-Meier survivorship, with revision for any reason as the end point, was 89.2% (95% confidence interval [CI], 82.3% to 96.1%) for HR and 94.2% (95% CI, 89.3% to 99.1%) for THA (p = 0.292). The reasons for revision included infection (3 patients), recurrent dislocation (1 patient), and adverse reaction to metal debris (ARMD) (1 patient) in the THA group and ARMD (2 patients) and femoral head loosening (7 patients) in the HR group. With aseptic revision as the end point, the Kaplan-Meier survivorship was significantly higher in the THA group (97.4% versus 89.2%; p = 0.033). No dislocation occurred in the HR group compared with 4 in the THA group (p = 0.058). Both groups achieved a similar mean WOMAC score (10.7 in the HR group and 8.8 in the THA group; p = 0.749), Forgotten Joint Score (87.1 and 85.3, respectively; p = 0.410), University of California Los Angeles (UCLA) activity score (6.3 and 6.4, respectively; p = 0.189), and overall joint perception (p = 0.251).

CONCLUSIONS

The specific HR and MoM 28-mm THA implants used in this study showed good long-term survival and function. The overall rates of complications and revisions were similar in both groups but were of different types. As it provides better femoral bone preservation and biomechanical reconstruction, HR may continue to have a role in selected patients when performed by experienced surgeons and using validated implants.

LEVEL OF EVIDENCE

Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

Short-term follow-up of kinematically vs. mechanically aligned total knee arthroplasty with medial pivot components: A case-control study

INTRODUCTION

The kinematic alignment (KA) technique for total knee arthroplasty (TKA) and the medial pivot (MP) component design are two options promoting a physiologic prosthetic knee kinematics when used in combination that could improve TKA outcomes. Case-control study is initiated to compare the 1-year radio-clinical outcomes between kinematic alignment medial pivot total knee arthroplasty (KA MP-TKAs) and mechanical alignment medial pivot total knee arthroplasty (MA MP-TKA). Goal of a study was to answer the following questions: Do KA MP-TKAs patients have improved functional outcomes compared to MA MP-TKAs patients? (Q1); Do prosthetic knee and lower limb alignments differ between KA and MA patients (Q2)? And does kinematic implantation of MP TKA has higher risk of reoperations and revisions (Q3)?

MATERIAL AND METHODS

A case-control study was carried out to compare the 1-year clinical and radiographic outcomes between 24 consecutive KA-TKA patients and 24 matched MA-TKA patients. All patients had implantation with manual instruments and a cemented medial pivot TKA with excision of the PCL. All data were collected prospectively, and outcome scores were patient reported.

RESULTS

KA patients had superior values in Forgotten Joint Score (FJS) at 1-year (KA 77 vs. MA 51) (p=0.05) follow-up. After one year KA patients scored better in objective section of the new Knee Society Score (KSS) (p=0.02), and in sport section of the Knee Osteoarthritis Outcome Score (KOOS) (p=0.01). Eleven out of 24 patients (46%) in KA group and 7/24 patients (29%) in MA group had limb alignment out of 180°±3°, whereas 17/24 (70%) of KA patients, and 14/24 (58%) of MA patients had orientation of tibial component with more than 3° of varus. No reoperation or revision occurred in either group.

DISCUSSION/CONCLUSION

The KA of MP TKA design seems to have a good efficacy at early-term, with some 1-year functional performance higher to the ones from MA MP TKAs. Further research is needed to define if those early results will last over time.

LEVEL OF EVIDENCE

III, case-controlled study.

Kinematic alignment in total knee arthroplasty

Kinematic alignment (KA) is an alternative philosophy for aligning a total knee replacement (TKR) which aims to restore all three kinematic axes of the native knee.

Many of the studies on KA have actually described non-KA techniques, which has led to much confusion about what actually fits the definition of KA.

Alignment should only be measured using three-dimensional cross-sectional imaging. Many of the studies looking at the influence of implants/limb alignment on total knee arthroplasty outcomes are of limited value because of the use of two-dimensional imaging to measure alignment, potentially leading to inaccuracy.

No studies have shown KA to be associated with higher complication rates or with worse implant survival; and the clinical outcomes following KA tend to be at least as good as mechanical alignment.

Further high-quality multi-centre randomized controlled trials are needed to establish whether KA provides better function and without adversely impacting implant survival.

Cite this article: EFORT Open Rev 2020;5:380-390. DOI: 10.1302/2058-5241.5.200010

[Alignment techniques for implantation of a total knee endoprosthesis with particular focus on kinematic alignment]

BACKGROUND

This review introduces various techniques for implantation of a total knee endoprosthesis and scrutinizes the "mechanical alignment" of a total knee endoprosthesis, whereby the various alignment concepts are examined. In particular, kinematic alignment, in terms of its significance, the individual steps of the implantation technique and the data collected, will be examined in more detail.

METHODS

Improvement in the clinical results after implantation of a total knee endoprosthesis can be achieved by a personalized, individualized, physiological implantation that respects the unique anatomical characteristics of each patient. In recent years, many alternative alignment techniques have been developed, some of them showing promising approaches.

RESULTS

The kinematic implantation technique can be performed reliably and inexpensively, and shows good biomechanical results. Although the first clinical results are encouraging, further studies should be carried out to determine the limits of optimal alignment.

Hip resurfacing generates a more physiological gait than total hip replacement: A case-control study

BACKGROUND

Restoration of the constitutional joint anatomy after hip replacement favours physiological peri-articular soft-tissue tension and kinematics, and is likely to be functionally beneficial. Hip resurfacing (HR) and conventional total hip replacement (THR) are two different options for replacing degenerated hips, and are likely to result in different anatomical reconstruction. We initiated this study to investigate the differences in gait performance between these two prosthetic options, and aimed to answer the following questions: (1) does HR result in better restoration of the frontal hip anatomical parameters, (2) and generate a more physiological gait compared to THR? (3) Does the quality of the anatomical restoration after THR influence gait performance?

HYPOTHESES

Our hypothesis was that a better anatomical restoration using HR versus THR would produce more physiological (symmetric) gait.

METHODS

We retrospectively reviewed 52 patients who had unilateral primary osteoarthritis successfully treated by replacement (40 THRs and 12 HRs). Hip anatomical parameters were measured on standing pelvic radiographs on both the prosthetic and the contralateral healthy hips. Patients undertook gait assessment under both normal and stress conditions at a mean follow-up of 14 months (7 to 16 months). Gait performances were compared between HR and THR, and the relationship between gait performances and quality of frontal anatomical restoration (estimated on radiograph) were assessed.

RESULTS

Compared to the native contralateral side, the HR procedure tended to decrease all independent anatomical radiographic parameters with the exception of the vertical centre of rotation offset, whilst the THR procedure tended to increase them; the difference between HR and THR was only statistically significant for femoral offset and global horizontal offset (increased after THR while reduced after HR). Only 50% of THR and 25% of HR procedures closely anatomically (±15%) recreated both global horizontal offset and global vertical offset. Under normal conditions (normal walking speed and flat ramp), the gait was fairly symmetric for both the HR and the THR patients with a symmetry index of 0.62% and 3.14% respectively. At high walking speed (stress conditions), the symmetry index degraded for both groups, but the gait remained more symmetric in the HR group (2.09%), compared to the THR group (5.74%); nevertheless, the difference remained not statistically significant (p=0.159). We were unable to detect any significant relationship between gait performances and radiographically measured hip frontal anatomical parameters.

DISCUSSION/CONCLUSIONS

HR procedure is more consistent than conventional THR in generating a more physiological gait under stress conditions. Radiographic estimation of the quality of the frontal anatomical hip restoration is of poor value to predict gait performances of THR patients.

LEVEL OF EVIDENCE

III - retrospective case-control study with prospective data collection.

Constraints on Lorentz Invariance Violation from HAWC Observations of Gamma Rays above 100 TeV

Because of the high energies and long distances to the sources, astrophysical observations provide a unique opportunity to test possible signatures of Lorentz invariance violation (LIV). Superluminal LIV enables the decay of photons at high energy. The high altitude water Cherenkov (HAWC) observatory is among the most sensitive gamma-ray instruments currently operating above 10 TeV. HAWC finds evidence of 100 TeV photon emission from at least four astrophysical sources. These observations exclude, for the strongest of the limits set, the LIV energy scale to 2.2×10^{31}  eV, over 1800 times the Planck energy and an improvement of 1 to 2 orders of magnitude over previous limits.

Multiple Galactic Sources with Emission Above 56 TeV Detected by HAWC

We present the first catalog of gamma-ray sources emitting above 56 and 100 TeV with data from the High Altitude Water Cherenkov Observatory, a wide field-of-view observatory capable of detecting gamma rays up to a few hundred TeV. Nine sources are observed above 56 TeV, all of which are likely galactic in origin. Three sources continue emitting past 100 TeV, making this the highest-energy gamma-ray source catalog to date. We report the integral flux of each of these objects. We also report spectra for three highest-energy sources and discuss the possibility that they are PeVatrons.

Less gap imbalance with restricted kinematic alignment than with mechanically aligned total knee arthroplasty: simulations on 3-D bone models created from CT-scans

Background and purpose - Mechanical alignment techniques for total knee arthroplasty (TKA) introduce significant anatomic alteration and secondary ligament imbalances. We propose a restricted kinematic alignment (rKA) protocol to minimize these issues and improve TKA clinical outcomes.Patients and methods - rKA tibial and femoral bone resections were simulated on 1,000 knee CT scans from a database of patients undergoing TKA. rKA was defined by the following criteria: independent tibial and femoral cuts within 5° of the bone neutral mechanical axis, with a resulting HKA within 3° of neutral. Imbalances in the extension space, flexion space at 90°, medial compartment and lateral compartment were calculated and compared with measured resection mechanical alignment (MA) results. 2 MA techniques were simulated for rotation using the surgical transepicondylar axis (TEA) and 3° to the posterior condyles (PC).Results - Extension space imbalances ≥ 3 mm occurred in 33% of TKAs with MA technique versus 8.3% with rKA (p < 0.001). Similarly, more frequent flexion space imbalance ≥ 3mm was created by MA technique (TEA 34% or 3° PC 15%) versus rKA (6.4%, p < 0.001). Using MA with TEA or PC, there were only 49% and 63% of the knees respectively with < 3 mm of imbalance throughout the extension and flexion spaces and medial and lateral compartments versus 92% using rKA (p < 0.001).Interpretation - significantly fewer imbalances are created using rKA versus MA for TKA. rKA may be the best compromise, by helping the surgeon to preserve native knee ligament balance during TKA and avoid residual instability, whilst keeping the lower limb alignment within a safe range.

Kinematic alignment versus conventional techniques for total hip arthroplasty: A retrospective case control study

BACKGROUND

Residual complications of conventionally implanted hip components have only been partially reduced by improved implant design and higher surgical precision, and their occurrence is poorly predicted by the radiographic standing/supine cup orientation. This has raised awareness that conventional techniques may not aim for the correct component orientation target, and the lumbo-pelvic kinematics, which influences the functional acetabular orientation, may be of interest to further improve THA clinical outcomes. This has led to the development of the Lumbo-Pelvic kinematic alignment (KA) technique for THA that aims to anatomically position and kinematically align hip implants (acetabular and femoral, total and resurfacing components), in order to optimise prosthetic hip biomechanics and hopefully improve prosthetic function, patient satisfaction, and components' lifespan. Therefore, we conducted a case control investigation to assess the early-term safety and efficacy of this new technique by answering the following questions: does the KA technique for THA: (1) better restore the native hip anatomy, (2) generate a different radiographic supine cup position, and (3) improve clinical outcomes in comparison to the conventional mechanical alignment technique?

HYPOTHESES

Using KA technique allows there is no statistically significant difference between the pre to postoperative differential for acetabular medial and vertical offsets, femoral offset, and leg length.

METHODS

We led a case control retrospective study with prospectively collected clinical data. Forty-one consecutive unselected KA-THAs performed with manual instrumentation were paired with 41 mechanically aligned THAs. The 1-year clinical outcomes and radiographical measurements were compared.

RESULTS

Compared to the mechanical alignment technique, the KA technique resulted in a more anatomical restoration of the prosthetic hip centre of rotation with a lower delta pre- to post-operative horizontal acetabular offset (1.47mm for KA versus -5.1mm for MA, p=0.001), and with 74% of KA versus 50% of MA cups (p=0.044) being within 15% of native anatomy for the horizontal acetabular offset. In addition, the KA technique resulted in a higher cup anteversion (22°±7° vs 15°±8°, p<0.001) but similar cup inclination (41°±6° vs. 42°±7°, p=0.25), a similar proportion of cups within the Lewinnek zone (65% vs. 70%, p=0.8), similar excellent functional outcomes (delta Oxford score pre- to follow-up of 24.3 and 23.5 points for KA and MA groups, respectively, p=0.88), similar patient satisfaction scores of 95.4/100 and 89.5/100 for KA and MA groups, respectively, and the same absence of aseptic complications.

CONCLUSION

The KA technique for THA has been demonstrated to be safe, efficacious, and not inferior to the conventional MA technique at early-term. As the concept of the KA technique for THA is only at an early stage, its influence on mid to long-term clinical outcomes remains to be determined and further refinements of the concept are yet to be made.

LEVEL OF EVIDENCE

III; case-control retrospective study.

Dual mobility device reduces the risk of prosthetic hip instability for patients with degenerated spine: A case-control study

INTRODUCTION

The pelvic incidence is an anatomical and biomechanical pelvic parameter determining spine sagittal morphology and kinematics. Stiffening of the lumbo-pelvic complex, a result of degeneration, affects the functional cup positioning, putting prosthetic hip patients at risk of instability. The anti-dislocation dual mobility (DM) device may be clinically advantageous by reducing the risk of prosthetic instability for older patients with spine ageing. Our study aims to answer the following questions: (1) is there a relationship between prosthetic hip instability and the standing cup position, (2) is there a relationships between prosthetic hip instability and the pelvic incidence, (3) is there a relationships between prosthetic hip instability and the severity of the spine degeneration?, (4) is the DM cup device an effective option for reducing the risk of prosthetic instability related to spine degeneration?

HYPOTHESIS

There is a relationship between prosthetic hip instability and the standing cup position and pelvic parameters.

METHODS

Case-control study on prospectively collected data since 2009. From 1672 conventional total hip replacements (THR-5.4% dislocation rate) and 1056 DM-THRs (1.1% dislocation rate) performed at our institute since 2009, we created three groups: 33 patients with unstable THR (group 1-case), 41 patients with stable THR (group 2-control), and 42 patients with stable DM-THR (group 3-control). The cup orientation was measured on standing pelvic radiographs and the spino-pelvic parameters were measured on standing EOS™ biplanar images or lateral full spine radiographs.

RESULTS

By comparing patients from group 1 with those of group 2 we found they had similar cup position (57% versus 51% fitting the safe zone, p=0.58), higher pelvic incidence (58° versus 51°, p=0.01), and more severe spine degeneration (smaller anterior pelvic plane Tilt (2° versus 7° [p=0.002]), a larger pelvic incidence-lumbar lordosis mismatch (17° versus 8° [p=0.005]), and a higher proportion of spino-sacral angle<127° (70% versus 43%, (p=0.02)). Patients from group 3 had similar cup position, pelvic incidence, and spine degeneration compared to patients from group 1.

DISCUSSION/CONCLUSION

Patients with spine-hip relation type 2C/D (high pelvic incidence and severe spine degeneration) have an increased risk of instability that is partly compensated for by the use of a DM device. Preoperative screening of patients with abnormal spine-hip relation would improve THR planning and reduce the risk of prosthetic hip instability. The use of a DM device on spine-degenerated elderly patients is probably sound.

LEVEL OF EVIDENCE

III, case-control study.

Kinematic alignment technique for medial OXFORD UKA: An in-silico study

BACKGROUND

Mobile bearing unicompartmental knee arthroplasty (UKA) Oxford™ components are recommended to be systematically and mechanically aligned (MA) for restoring the constitutional lower-limb alignment. Good long-term clinical outcomes have been generated with the medially implanted MA Oxford™, but some sub-optimal biomechanical-related complications still remain. Kinematic Alignment (KA) is a personalised technique for anatomically and kinematically implanting components (total knee, fixed bearing partial knee, total hip) aimed at creating more physiological prosthetic joint biomechanics. Interestingly, for decades the principles for implanting fixed bearing UKA components were consistent with those promoted by the KA technique, but differently formulated. We initiated this computational study to assess the feasibility of this technique with the Oxford™ components, as we thought this more anatomical implantation may be clinically advantageous.

HYPOTHESIS

We surmised that kinematically aligning the Oxford™ medial UKA would maximise the prosthesis-bone interface through maximising the implants' size used (question 1), and alter, within an acceptable limit, the components' orientation (question 2) compared to conventional mechanical alignment.

METHODS

A cohort of 40 consecutive medial osteoarthritic knee patients scheduled for UKA had a preoperative CT scan that was segmented to create 3D knee bone models. MA and KA of medial UKA Oxford^® components (Zimmer-Biomet, Warsaw, Indiana, USA) were simulated. Component sizing and positioning were compared between the two techniques.

RESULTS

We found no difference in component size, but significantly fewer occurrences of borderline fit with the KA simulation. KA technique oriented the femoral component 3.6° more valgus (from 1° varus to 7° valgus) and the tibial component 2.9° more varus (from 8° varus to 0°) compared to the MA technique. The tibial component slope in KA simulation was 6.4° posterior (from 0 to 12°) compared to a systematic 7° posterior for MA positioning.

DISCUSSION AND CONCLUSION

Kinematic alignment of the medial Oxford™ generated a different, albeit still acceptable (Oxford group recommendations), implant orientation, in addition to a likely better shape-fit between components and the supportive bone cut, compared to the MA technique. The potential to improve the implants' interaction and to restore a more physiological bone loading makes the KA of Oxford™ an attractive, potentially clinically beneficial option. Clinical investigations are needed to assess its true value.

LEVEL OF EVIDENCE

I, computational study.

Publisher Correction: Very-high-energy particle acceleration powered by the jets of the microquasar SS 433

In this Letter, owing to a production error, the penultimate version of the PDF was published. The HTML version was always correct. The PDF has been corrected online.

Kinematic alignment of current TKA implants does not restore the native trochlear anatomy

INTRODUCTION

Preserving constitutional patellofemoral anatomy, and thus producing physiological patellofemoral kinematics, could prevent patellofemoral complications and improve clinical outcomes after kinematically aligned TKA (KA TKA). Our study aims 1) to compare the native and prosthetic trochleae (planned or implanted), and 2) to estimate the safety of implanting a larger Persona^® femoral component size matching the proximal lateral trochlea facet height (flange area) in order to reduce the native articular surfaces understuffing generated by the prosthetic KA trochlea.

METHODS

Persona^® femoral component 3D model was virtually kinematically aligned on 3D bone-cartilage models of healthy knees by using a conventional KA technique (group 1, 36models, planned KA TKA) or an alternative KA technique (AT KA TKA) aiming to match the proximal (flange area) lateral facet height (10 models, planned AT KA TKA). Also, 13postoperative bone-implant (KA Persona^®) models were co-registered to the same coordinate geometry as their preoperative bone-cartilage models (group 2implanted KA TKA). In-house analysis software was used to compare native and prosthetic trochlea articular surfaces and medio-lateral implant overhangs for every group.

RESULTS

The planned and performed prosthetic trochleae were similar and valgus oriented (6.1 and 8.5, respectively), substantially proximally understuffed compared to the native trochlea. The AT KA TKAs shows a high rate of native trochlea surface overstuffing (70%, 90%, and 100% for lateral facet, groove, medial facet) and mediolateral implant overhang (60%). There was no overstuffing with conventional KA TKAs having their anterior femoral cut flush.

CONCLUSION

We found that with both the planned and implanted femoral components, the KA Persona^® trochlea was more valgus oriented and understuffed compared to the native trochlear anatomy. In addition, restoring the lateral trochlea facet height by increasing the femoral component size generated a high rate of trochlea overstuffing and mediolateral implant overhang. While restoring a native trochlea with KA TKA is not possible, the clinical impact of this is low, especially on PF complications. In current practice it is better to undersize the implants even if it does not restore the native anatomy. Longer follow-up is needed for KA TKAs performed with current implant, and the debate of developing new, more anatomic, implants specifically designed for KA technique is now opened.

LEVEL OF EVIDENCE

II, Laboratory controlled study.

Day-case surgery for total hip and knee replacement: How safe and effective is it?

Multimodal protocols for pain control, blood loss management and thromboprophylaxis have been shown to benefit patients by being more effective and as safe (fewer iatrogenic complications) as conventional protocols.Proper patient selection and education, multimodal protocols and a well-defined clinical pathway are all key for successful day-case arthroplasty.By potentially being more effective, cheaper than and as safe as inpatient arthroplasty, day-case arthroplasty might be beneficial for patients and healthcare systems. Cite this article: EFORT Open Rev 2018;3:130-135. DOI: 10.1302/2058-5241.3.170031.

Extended gamma-ray sources around pulsars constrain the origin of the positron flux at Earth

The unexpectedly high flux of cosmic-ray positrons detected at Earth may originate from nearby astrophysical sources, dark matter, or unknown processes of cosmic-ray secondary production. We report the detection, using the High-Altitude Water Cherenkov Observatory (HAWC), of extended tera-electron volt gamma-ray emission coincident with the locations of two nearby middle-aged pulsars (Geminga and PSR B0656+14). The HAWC observations demonstrate that these pulsars are indeed local sources of accelerated leptons, but the measured tera-electron volt emission profile constrains the diffusion of particles away from these sources to be much slower than previously assumed. We demonstrate that the leptons emitted by these objects are therefore unlikely to be the origin of the excess positrons, which may have a more exotic origin.

Differences in trochlear parameters between native and prosthetic kinematically or mechanically aligned knees

INTRODUCTION

Kinematic (KA) and mechanical (MA) alignment techniques are two different philosophies of implant positioning that use the same TKA implants. This might generate differences in the resulting prosthetic trochleae parameters between the two techniques of alignment. Our study aim was to test the following hypotheses : (1) mechanically or kinematically aligned femoral implant understuffs the native trochlear articular surface and poorly restores the native groove orientation, and (2) the orientation of the prosthetic trochlear groove and trochlear fill are different between MA and KA.

METHODS

Three-dimensional models of the femur were made from segmentation of preoperative Magnetic Resonance Imaging scans (MRIs) of ten subjects with isolated medial tibiofemoral osteoarthritis. In-house planning and analysis software kinematically and mechanically aligned a modern cruciate retaining femoral component and determined differences in parameters of the trochlear fit between native and prosthetic trochleae, and between KA and MA prosthetic trochleae.

RESULTS

The MA prosthetic trochleae did not fill (understuffed) the entire length of the native medial facet and the proximal 70% of the native groove and lateral facet, and oriented the trochleae groove 8° more valgus than native. The KA prosthetic trochleae understuffed the proximal 70% of the native trochleae, and had a groove 6° more valgus than native. The KA trochleae understuffed the medial facet distally and oriented the groove 2° less valgus and 3° more internally rotated than the MA trochleae.

CONCLUSION

MA and KA prosthetic trochleae substantially understuff and create a prosthetic groove more valgus compared to native trochlear anatomy, and they also differed between each other regarding trochleae stuffing and groove alignment. Although randomized trials have not shown differences in patellofemoral complications between KA and MA, a femoral component designed specifically for KA that more closely restores the native trochlear anatomy might improve patient reported satisfaction and function.

LEVEL OF EVIDENCE

Level 2 controlled laboratory study.

Kinematic alignment technique for total hip and knee arthroplasty: The personalized implant positioning surgery

Conventional techniques for hip and knee arthroplasty have led to good long-term clinical outcomes, but complications remain despite better surgical precision and improvements in implant design and quality.

Technological improvements and a better understanding of joint kinematics have facilitated the progression to ‘personalized’ implant positioning (kinematic alignment) for total hip (THA) and knee (TKA) arthroplasty, the true value of which remains to be determined.

By achieving a true knee resurfacing, the kinematic alignment (KA) technique for TKA aims at aligning the components with the physiological kinematic axes of the knee and restoring the constitutional tibio-femoral joint line frontal and axial orientation and soft-tissue laxity.

The KA technique for THA aims at restoring the native ‘combined femoro-acetabular anteversion’ and the hip’s centre of rotation, and occasionally adjusting the cup position and design based on the assessment of the individual spine-hip relation.

The key element for optimal prosthetic joint kinematics (hip or knee) is to reproduce the femoral anatomy.

The transverse acetabular ligament (TAL) is the reference landmark to adjust the cup position.

Cite this article: EFORT Open Rev 2018;3:98-105. DOI: 10.1302/2058-5241.3.170022

Long-term bone remodelling around 'legendary' cementless femoral stems

Bone remodelling around a stem is an unavoidable long-term physiological process highly related to implant design. For some predisposed patients, it can lead to periprosthetic bone loss secondary to severe stress-shielding, which is thought to be detrimental by contributing to late loosening, late periprosthetic fracture, and thus rendering revision surgery more complicated.However, these concerns remain theoretical, since late loosening has yet to be documented among bone ingrowth cementless stems demonstrating periprosthetic bone loss associated with stress-shielding.Because none of the stems replicate the physiological load pattern on the proximal femur, each stem design is associated with a specific load pattern leading to specific adaptive periprosthetic bone remodelling. In their daily practice, orthopaedic surgeons need to differentiate physiological long-term bone remodelling patterns from pathological conditions such as loosening, sepsis or osteolysis.To aid in that process, we decided to clarify the behaviour of the five most used femoral stems. In order to provide translational knowledge, we decided to gather the designers' and experts' knowledge and experience related to the design rationale and the long-term bone remodelling of the following femoral stems we deemed 'legendary' and still commonly used: Corail (Depuy); Taperloc (Biomet); AML (Depuy); Alloclassic (Zimmer); and CLS-Spotorno (Zimmer). Cite this article: EFORT Open Rev 2018;3:45-57. DOI: 10.1302/2058-5241.3.170024.

Spine-hip relations in patients with hip osteoarthritis

Patients with hip osteoarthritis often have an abnormal spine-hip relation (SHR), meaning the presence of a clinically deleterious spine-hip and/or hip-spine syndrome.

Definition of the individual SHR is ideally done using the EOS® imaging system or, if not available, with conventional lumbopelvic lateral radiographs.

By pre-operatively screening patients with abnormal SHR, it is possible to refine total hip replacement (THR) surgical planning, which may improve outcomes.

An important component of the concept of kinematically aligned total hip arthroplasty (KA THA) consists of defining the optimal acetabular cup design and orientation based on the assessment of an individual’s SHR, and use of the transverse acetabular ligament to adjust the cup positioning.

The Bordeaux classification might advance the understanding of SHR and hopefully help improve THR outcomes.

Cite this article: EFORT Open Rev 2018;3:39-44. DOI: 10.1302/2058-5241.3.170020

Current concepts for aligning knee implants: patient-specific or systematic?

Mechanical or anatomical alignment techniques create a supposedly ‘biomechanically friendly’ but often functionally limited prosthetic knee.

Alternative techniques for alignment in total knee arthroplasty (TKA) aim at being more anatomical and patient-specific, aiming to improve functional outcomes after TKA.

The kinematic alignment (KA) technique for TKA has shown good early clinical outcomes. Its role in extreme anatomical variation remains to be defined.

The restricted KA technique for TKA might be a reasonable option for patients with extreme anatomical variation.

While unicompartmental knee arthroplasty (UKA) has many advantages over TKA, the revision rate remains higher compared with TKA. One major explanation is the relative ease with which a UKA can be converted to a TKA, compared with revising a TKA. This can be considered as an additional advantage of UKA. Another reason is that surgeons favour revising a UKA to a TKA in cases of degeneration of the other femorotibial compartment rather than performing a relatively simple re-operation of the knee by doing an additional UKA (staged bi-UKA).

Cite this article: EFORT Open Rev 2018;3:1–6. DOI: 10.1302/2058-5241.3.170021

Alignment options for total knee arthroplasty: A systematic review

In spite of improvements in implant designs and surgical precision, functional outcomes of mechanically aligned total knee arthroplasty (MA TKA) have plateaued. This suggests probable technical intrinsic limitations that few alternate more anatomical recently promoted surgical techniques are trying to solve. This review aims at (1) classifying the different options to frontally align TKA implants, (2) at comparing their safety and efficacy with the one from MA TKAs, therefore answering the following questions: does alternative techniques to position TKA improve functional outcomes of TKA (question 1)? Is there any pathoanatomy not suitable for kinematic implantation of a TKA (question 2)? A systematic review of the existing literature utilizing PubMed and Google Scholar search engines was performed in February 2017. Only studies published in peer-reviewed journals over the last ten years in either English or French were reviewed. We identified 569 reports, of which 13 met our eligibility criteria. Four alternative techniques to position a TKA are challenging the traditional MA technique: anatomic (AA), adjusted mechanical (aMA), kinematic (KA), and restricted kinematic (rKA) alignment techniques. Regarding osteoarthritic patients with slight to mid constitutional knee frontal deformity, the KA technique enables a faster recovery and generally generates higher functional TKA outcomes than the MA technique. Kinematic alignment for TKA is a new attractive technique for TKA at early to mid-term, but need longer follow-up in order to assess its true value. It is probable that some forms of pathoanatomy might affect longer-term clinical outcomes of KA TKA and make the rKA technique or additional surgical corrections (realignment osteotomy, retinacular ligament reconstruction etc.) relevant for this sub-group of patients. Longer follow-up is needed to define the best indication of each alternative surgical technique for TKA. Level I for question 1 (systematic review of Level I studies), level 4 for question 2.