A simple CT scan protocol for planning of total hip arthroplasty in patients with femoral neck fractures.

We describe a method for planning total hip arthroplasty (THA) in patients with a displaced femoral neck fracture based on a simple CT scan protocol of the contralateral hip. This protocol was used on 22 consecutive patients during the inclusion period, followed by reconstruction and 2D templating to predict the implant size and positioning. The exact planned size was achieved in 21/22 (95%) cups, 14/22 (64%) femoral stems and 14/22 (64%) femoral heads. There were no intra- or postoperative fractures. After surgery in which this planning method had been applied, the differences in length and lateral offset were less than 5 mm on average relative to the opposite side (mean postoperative leg length difference of -2 mm (-8 to +3 mm) and lateralization of -4 mm (-14 to +3 mm)). While this technique exposes the patient to additional radiation, it does not require any specific devices or surgical approach and could be used in most hospitals. LEVEL OF EVIDENCE: IV.

Better operating room efficiency and reduced staff demand: Individualised versus off-the-shelf total knee arthroplasty.

PURPOSE: The purpose of this pilot cross-sectional study was to compare the operating room (OR) efficiency and intraoperative staff task load when performing individualised versus off-the-shelf (OTS) total knee arthroplasty (TKA). METHODS: A consecutive series of 28 patients randomised (1:1) to receive either OTS TKA or individualised TKA were included. The OR staff workload was assessed with the NASA Task Load Index (TLX), a subjective grading system assessing mental demand, physical demand, temporal demand, performance, effort and frustration on a scale from 0 (very low) to 20 (very high). The time for patient preparation, surgical time, closure and total OR time was recorded to assess OR efficiency. Effect sizes of differences between OTS and individualised TKA were expressed as mean differences (MDs) with 95% confidence intervals (CIs). RESULTS: Patients in both cohorts were similar in age (OTS vs. individualised TKA (median [IQR]), 67 [63-76] vs. 71 [68-79]; p = 0.207) and body mass index (BMI) (29 [24-33] vs. 29 [26-31]; p = 0.807), and there were no significant differences in other preoperative characteristics. The OR staff perceived individualised TKA as less demanding than OTS TKA: Individualised TKA was rated significantly better across the six domains of the NASA TLX: mental demand by 5.6 points, physical demand by 6.3 points, temporal demand by 5.3 points, performance by 3.6 points, effort by 5.9 points and frustration by 5.8 points. Individualised TKA resulted in statistically significantly shorter mean total OR time (MD, 10 min; p = 0.018). CONCLUSION: The staff in the OR found that individualised TKA is less mentally, physically and temporally demanding than OTS TKA. The average total time spent in the OR during individualised TKA is 10 min less than during OTS TKA. CLINICAL TRIAL REGISTRATION: This study constitutes a part of a larger registered randomised controlled trial comparing patient satisfaction following OTS versus individualised TKA (NCT04460989). LEVEL OF EVIDENCE: Level III.

Individualised compared to off-the-shelf total knee arthroplasty results in lower and less variable patellar tilt.

PURPOSE: The purpose of this study was to compare postoperative patellar tilt at 4 months follow-up in a consecutive series of randomised patients that received individualised or off-the-shelf (OTS) primary total knee arthroplasty (TKA). The hypothesis was that patellar tilt would be lower and less variable in patients who received individualised TKA compared to patients who received OTS TKA. METHODS: A consecutive series of 385 patients randomised (1:1) to receive either OTS TKA or individualised TKA were analysed. Pre- and postoperative radiographs at 4 months were obtained of weight-bearing long leg, anterior-posterior and lateral knee views and a skyline view at 30° of flexion. Postoperative patellar tilt was measured between the anterior femoral line and patellar resection surface (ß) and the anterior femoral line and mediolateral patellar axis (σ). Postoperative patellar tilt (absolute value) was compared between the individualised and OTS TKA groups based on preoperative phenotypes of their femoral mechanical angle, tibial mechanical angle and hip-knee-ankle angle. Variability in postoperative patellar tilt was compared using the 95% confidence intervals (CIs). RESULTS: Comparisons of baseline patient characteristics revealed no difference between the individualised and OTS TKA groups. Comparison of absolute postoperative patellar tilt revealed significant differences between individualised and OTS TKA (|ß|, 1.0° ± 1.0° and 2.5° ± 2.2°, respectively, p < 0.001; |σ|, 1.7° ± 1.6° and 2.8° ± 2.3°, respectively, p < 0.001). The 95% CI of postoperative patellar tilt (|ß|) was narrower in patients that received individualised compared to OTS TKA (0.0° to 3.8° and 0.1° to 8.3°, respectively), irrespective of their preoperative phenotype. CONCLUSION: Patients who underwent individualised TKA had lower and less variable postoperative patellar tilt than those with OTS TKA, irrespective of preoperative phenotype. Individualised TKA allows the decoupling of the tibiofemoral and patellofemoral joints, replicating anatomical trochlear orientation and improving patellar tilt, which could facilitate better clinical outcomes. CLINICAL TRIAL REGISTRATION: This study constitutes a part of a larger registered randomised controlled trial comparing patient satisfaction following OTS versus individualised TKA (NCT04460989). LEVEL OF EVIDENCE: Level II.

Outcomes of total hip arthroplasty using collared versus collarless uncemented HA-coated stems: a meta-analysis.

Purpose: to systematically review comparative studies reporting revision rates, clinical outcomes, or radiographic outcomes of total hip arthroplasty (THA) using collared versus collarless conventional-length uncemented hydroxyapatite (HA)-coated stems. Methods: In adherence with PRISMA guidelines, a literature search was performed on Medline, Embase, and Scopus. Comparative clinical studies were eligible if they reported outcomes of collared versus collarless uncemented HA-coated stems for primary THA. Two reviewers screened titles, abstracts, and full-texts to determine eligibility; then performed data extraction; and assessed the quality of studies according to Joanna Briggs Institute (JBI) checklist. Results: The search returned 972 records, 486 were duplicates, and 479 were excluded after title/abstract/full-text screening. Three further studies were included from the references of eligible studies and from discussions with subject matter experts, resulting in 11 included studies. The JBI checklist indicated six studies scored ≥7 points and four studies ≥4 points. Pooled data revealed collared stems had significantly lower revision rates (OR = 0.45; 95% CI = 0.31-0.64) and subsidence (MD = -1 mm; 95% CI = -1.6--0.3), but no significant difference in intraoperative complication rates (OR = 0.94; 95% CI = 0.67-1.32) in the short term to mid-term. Unpooled data indicated that collared stems provide equivalent survival, equivalent or better outcomes, and equivalent or lower complication rates. Conclusion: In comparative studies, collared stems have lower revision rates than collarless stems, as well as equivalent or better clinical and radiographic outcomes. Differences could be due to a protective effect that the collar offers against subsidence, particularly in undersized or misaligned stems. Further studies are warranted to confirm long-term results and better understand differences between registry data and clinical studies.

Definition of normal, neutral, deviant and aberrant coronal knee alignment for total knee arthroplasty.

PURPOSE: One of the most pertinent questions in total knee arthroplasty (TKA) is: what could be considered normal coronal alignment? This study aims to define normal, neutral, deviant and aberrant coronal alignment using large data from a computed tomography (CT)-scan database and previously published phenotypes. METHODS: Coronal alignment parameters from 11,191 knee osteoarthritis (OA) patients were measured based on three dimensional reconstructed CT data using a validated planning software. Based on these measurements, patients' coronal alignment was phenotyped according to the functional knee phenotype concept. These phenotypes represent an alignment variation of the overall hip knee ankle angle (HKA), femoral mechanical angle (FMA) and tibial mechanical angle (TMA). Each phenotype is defined by a specific mean and covers a range of ±1.5° from this mean. Coronal alignment is classified as normal, neutral, deviant and aberrant based on distribution frequency. Mean values and distribution among the phenotypes are presented and compared between two populations (OA patients in this study and non-OA patients from a previously published study). RESULTS: The arithmetic HKA (aHKA), combined normalised data of FMA and TMA, showed that 36.0% of knees were neutral within ±1 SD from the mean in both angles, 44.3% had either a TMA or a FMA within ±1-2 SD (normally aligned), 15.3% of the patients were deviant within ±2-3 SD and only 4.4% of them had an aberrant alignment (±3-4 SD in 3.4% and >4 SD in 1.0% of the patients respectively). However, combining the normalised data of HKA, FMA and TMA, 15.4% of patients were neutral in all three angles, 39.7% were at least normal, 27.7% had at least one deviant angle and 17.2% had at least one aberrant angle. For HKA, the males exhibited 1° varus and females were neutral. For FMA, the females exhibited 0.7° more valgus in mean than males and grew 1.8° per category (males grew 2.1° per category). For TMA, the males exhibited 1.3° more varus than females and both grew 2.3° and 2.4° (females) per category. Normal coronal alignment was 179.2° ± 2.8-5.6° (males) and 180.5 > ± 2.8-5.6° (females) for HKA, 93.1 > ± 2.1-4.2° (males) and 93.8 > ± 1.8-3.6° (females) for FMA and 86.7 > ± 2.3-4.6° (males) and 88 > ± 2.4-4.8° (females) for TMA. This means HKA 6.4 varus or 4.8° valgus (males) or 5.1° varus to 6.1° valgus was considered normal. For FMA HKA 1.1 varus or 7.3° valgus (males) or 0.2° valgus to 7.4° valgus was considered normal. For TMA HKA 7.9 varus or 1.3° valgus (males) or 6.8° varus to 2.8° valgus was considered normal. Aberrant coronal alignment started from 179.2° ± 8.4° (males) and 180.5 > ± 8.4° (females) for HKA, 93.1 > ± 6.3° (males) 93.8 > ± 5.4° (females) for FMA and 86.7 > ± 6.9° (males) and 88 > ± 7.2° (females) for TMA. This means HKA > 9.2° varus or 7.6° valgus (males) or 7.9° varus to 8.9° valgus was considered aberrant. CONCLUSION: Definitions of neutrality, normality, deviance as well as aberrance for coronal alignment in TKA were proposed in this study according to their distribution frequencies. This can be seen as an important first step towards a safe transition from the conventional one-size-fits-all to a more personalised coronal alignment target. There should be further definitions combining bony alignment, joint surfaces' morphology, soft tissue laxities and joint kinematics. LEVEL OF EVIDENCE: III.

Alignment and mechanics evaluation for a compaction broach stem versus a blade style proximal press fit stem using 3-Dimensional planning.

Three-dimensional (3D) preoperative planning tools can be used to help plan and compare component alignment scenarios for different total hip arthroplasty systems to ultimately improve postoperative outcomes and patient satisfaction. The objective of this study is to use 3D preoperative planning tools based on patient-specific bone models to compare two different stem designs, specifically a compaction broach stem and a proximal press fit stem. The planner uses patient-specific proximal femoral bone morphology to suggest a specific implant size and placement. The planner then allows for preoperative predictions of component head positioning, stem fit within the canal, and potential cortical bone reaming that must be done, as well as postoperative predictions of stability and mechanics. The stems were evaluated to determine the accuracy of stem placement, the theoretical volumetric bone removal/reaming required to achieve a desired fit, and the associated postoperative mechanics. This study demonstrated that there was a difference in component alignment and predicted postoperative mechanics between a compaction broach stem and a press fit stem, with the compaction broach stem allowing for more accurate alignment with less required bone removal, resulting in improved postoperative stability and mechanics. This study also demonstrated that much of the stem misalignment for both systems occurred in the anterior/posterior direction. Overall, 3D preoperative planning offers significant benefits and novel intraoperative insight, and the industry should continue to enhance their THA preoperative planning tools.

Artificial Intelligence Radiographic Analysis Tool for Total Knee Arthroplasty.

BACKGROUND: The postoperative follow-up of a patient after total knee arthroplasty (TKA) requires regular evaluation of the condition of the knee through interpretation of X-rays. This rigorous analysis requires expertize, time, and methodical standardization. Our work evaluated the use of an artificial intelligence tool, X-TKA, to assist surgeons in their interpretation. METHODS: A series of 12 convolutional neural networks were trained on a large database containing 39,751 X-ray images. These algorithms are able to determine examination quality, identify image characteristics, assess prosthesis sizing and positioning, measure knee-prosthesis alignment angles, and detect anomalies in the bone-cement-implant complex. The individual interpretations of a pool of senior surgeons with and without the assistance of X-TKA were evaluated on a reference dataset built in consensus by senior surgeons. RESULTS: The algorithms obtained a mean area under the curve value of 0.98 on the quality assurance and the image characteristics tasks. They reached a mean difference for the predicted angles of 1.71° (standard deviation, 1.53°), similar to the surgeon average difference of 1.69° (standard deviation, 1.52°). The comparative analysis showed that the assistance of X-TKA allowed surgeons to gain 5% in accuracy and 12% in sensitivity in the detection of interface anomalies. Moreover, this study demonstrated a gain in repeatability for each single surgeon (Light's kappa +0.17), as well as a gain in the reproducibility between surgeons (Light's kappa +0.1). CONCLUSION: This study highlights the benefit of using an intelligent artificial tool for a standardized interpretation of postoperative knee X-rays and indicates the potential for its use in clinical practice.

Arthroscopic popliteal tenotomy grants satisfactory outcomes in total knee arthroplasty with persistent localised posterolateral pain and popliteus tendon impingement.

PURPOSE: The purpose was to estimate the prevalence of popliteus tendon impingement following TKA, and to describe the characteristics and the differential diagnosis protocol for this rare condition. The hypothesis was that arthroscopic popliteal tenotomy in TKA patients with suspected popliteus tendon impingement would relieve pain and improve satisfaction. METHODS: Of 741 TKAs performed over three years, eight (1.1%, all women) had suspected popliteus tendon impingement, of which seven had severe localised posterolateral knee pain and one global knee pain. Upon confirmation of popliteus tendon impingement, arthroscopic popliteal tenotomy was performed, and outcomes (Pain on visual analogue scale (pVAS; best, 0; worst, 10), Oxford Knee Score (OKS; best, 48; worst, 0) and satisfaction (best, 100%; worst, 0%) assessed at mean 18-month follow-up. RESULTS: At four to 30 months after TKA, arthroscopic exploration revealed popliteus tendon impingement in all eight knees. Six reported complete pain relief (pVAS, 0) the day following arthroscopic popliteal tenotomy, whilst one reported some residual pain (pVAS, 2). The remaining patient with global pain reported no pain relief, and required revision TKA at 12 months. Excluding the revised TKA, OKS was between 19 and 43, and satisfaction was rated ≥ 80% in five of the remaining seven patients. CONCLUSIONS: Arthroscopic popliteal tenotomy relieved symptoms in TKA patients with persistent localised posterolateral pain and a positive popliteus test. These findings suggest that the popliteus test is reliable to diagnose popliteus tendon impingement following TKA, which could be treated by arthroscopic popliteal tenotomy. LEVEL OF EVIDENCE: Level IV, Small case series.

Custom total knee arthroplasty combined with personalised alignment grants 94% patient satisfaction at minimum follow-up of 2 years.

PURPOSE: The purpose was to report detailed patient-reported outcome measures (PROMs) and satisfaction rates for computed tomography (CT)-based custom TKA at minimum follow-up of 2 years. The hypothesis was that custom TKA combined with 'personalised alignment' would yield equivalent or better PROMs compared to values reported in systematic reviews and meta-analyses on off-the-shelf (OTS) TKA. METHODS: Of an initial cohort of 150 custom TKAs, four died (unrelated to surgery), one required a revision, and five refused participation, leaving 140 patients for analysis. Patients completed pre- and post-operative PROMs (Oxford Knee Score (OKS), Forgotten Joint Score (FJS), Knee injury and Osteoarthritis Outcome Score (KOOS), Western Ontario and McMaster osteoarthritis index (WOMAC)) as well as overall level of satisfaction. Proportions that attained a patient acceptable symptom state (PASS) were calculated for OKS and FJS. Clinical findings were compared to the average scores reported for PROMs in recent systematic reviews and/or meta-analyses on OTS TKA. Descriptive statistics were used to summarise the clinical findings as means, standard deviations (SD) and ranges, or numbers and percentages. RESULTS: At mean follow-up 33.5 ± 4.5 months, 94% (135/143) were either satisfied or very satisfied. Proportions that achieved PASS were 89% for OKS (120/135), and 85% for FJS (118/139). Median OKS, WOMAC and KOOS Symptoms and Pain scores were all within the 4th quartile of medians reported in systematic reviews and/or meta-analyses. CONCLUSIONS: At a minimum follow-up of two years following custom TKA combined with 'personalised alignment', 94% of patients were either satisfied or very satisfied, and the PASS criteria were achieved in 89% for OKS and 85% for FJS, all of which compare favourably to published outcomes of OTS TKA. Direct comparisons to the literature may not be appropriate, however, considering the heterogeneity of patient demographics and alignment techniques. Randomised controlled trials with sufficient statistical power are needed to corroborate these findings and generalise them to unselected TKA patients. LEVEL OF EVIDENCE: IV, retrospective cohort study.

Custom TKA enables adequate realignment with minimal ligament release and grants satisfactory outcomes in knees that had prior osteotomies or extra-articular fracture sequelae.

PURPOSE: To report the early clinical and radiographic outcomes of custom total knee arthroplasty (TKA) in knees that had prior osteotomies and/or extra-articular fracture sequelae. METHODS: The authors retrospectively analysed a consecutive series of 444 knees that received custom TKA between 2016 and 2019 and identified 41 knees that had prior extra-articular events (osteotomies or fracture sequelae). Patients responded to pre- and post-operative (> 12 months) questionnaires, including Knee Society Score (KSS), Oxford Knee Score (OKS), Forgotten Joint Score (FJS) and Knee injury and Osteoarthritis Outcome Score (KOOS). Net improvements were calculated by subtracting pre- from post-operative scores. In addition to a preoperative CT scan, pre- and post-operative long-leg weight-bearing radiographs were obtained, on which the hip-knee-ankle (HKA) angle, femoral mechanical angle (FMA, between femoral mechanical axis and joint line) and tibial mechanical angle (TMA, between tibial mechanical axis and joint line) angles were measured, and alignment was planned within a 'target zone' of FMA and TMA within 85°-95° and HKA angle within 175°-183°. Agreements between preoperative, planned and post-operative angles were calculated using intra-class correlation coefficients (ICC). RESULTS: From the initial 41 knees, 3 had incomplete post-operative data and 1 was revised for painful stiffness due to uncorrected rotational malunion, leaving 37 knees for analysis. Twenty had prior osteotomies (tibia, n = 18, femur, n = 2), 8 had isolated fractures (tibial, n = 3; femoral, n = 5), and 9 had both osteotomies and fractures. Postoperative coronal alignments were 90.4° ± 2.4° for FMA, 89.3° ± 2.6° for TMA and 179.9° ± 3.0° for HKA angle. Agreements between planned and achieved alignments were fair to excellent, and 29 (78%) knees were within the 'target zone'. At a mean follow-up of 15 ± 5 months, all clinical scores had improved significantly (p < 0.001). CONCLUSIONS: Custom TKA granted satisfactory clinical outcomes and a low complication rate in knees that had prior osteotomies and/or extra-articular fracture sequelae. Using custom implants and strategies for coronal alignment, 29 (78%) of the 37 knees were successfully aligned within the 'target zone', and 35 (95%) of the 41 knees did not require ligament release. LEVEL OF EVIDENCE: IV.

Considerable inter-individual variability of tibial geometric ratios renders bone-implant mismatch unavoidable using off-the-shelf total knee arthroplasty: a systematic review and meta-analysis.

PURPOSE: The purpose of this systematic review and meta-analysis was to investigate the variability in tibial geometric ratios among knees of different sexes and races to determine whether commercially-available tibial baseplates accommodate the morphologic diversity. The hypothesis was that anthropometric studies report considerable variability of tibial geometric ratios among sexes and races. METHODS: This systematic review and meta-analysis was performed according to the preferred reporting items for systematic reviews and meta-analyses (PRISMA) criteria. Two authors independently conducted an electronic search using MEDLINE® and Embase® on 28 January 2021 for clinical studies reporting on tibial geometric ratios. Tibial geometric ratios, as reported by the clinical studies, were represented by plotting their means and two standard deviations for comparison to two symmetric and two asymmetric commercially-available tibial baseplates. RESULTS: A total of 27 articles that reported on a combined total of 20,944 knees were eligible for data extraction. Variation in tibial aspect ratios was equal among sexes. The greatest variation in aspect ratio was observed among East Asians, followed by Caucasians, African-Americans, Indian and Middle Easterns. The variation in tibial asymmetry ratio was larger among men compared to women. The greatest variation in asymmetry ratio was observed among African-Americans, followed by Caucasians, East Asians, Indian and Middle Easterns. Bone-implant mismatch of > 3 mm overhang or > 4 mm under-coverage with four commercially-available tibial baseplates occurred in large proportions of knees due to variations in aspect ratio (in 17-100% of knees) and asymmetry ratio (in 7-100% of knees). CONCLUSION: Anthropometric studies reported considerable inter-individual variability of tibial geometric ratios, which exceeded effects of sexual dimorphism and racial diversity. Bone-implant mismatch may be unavoidable in a large proportion of knees, when considering that a surgeon generally only uses one or a few TKA brands. These findings support the drive towards patient-specific implants to potentially achieve accurate bone-implant fit by implant customisation. LEVEL OF EVIDENCE: IV.

Survival and Clinical Outcomes at 30 to 35 Years Following Primary Total Hip Arthroplasty With a Cementless Femoral Stem Fully Coated With Hydroxyapatite.

BACKGROUND: The purpose of the present study was to update and report clinical outcomes and survival of primary total hip arthroplasty using a cementless double-tapered titanium fully hydroxyapatite-coated stem at a follow-up > 30 years. METHODS: The outcomes of this series of 347 primary total hip arthroplasties were already published at a follow-up > 25 years, during which only 12 stems were revised. Since then, there were two additional stem revisions, bringing the total to 14 stem revisions (all of which also required cup revision). Patients still living with the original stem were assessed using the modified Harris Hip Score and patient satisfaction (very satisfied, satisfied, dissatisfied, and very dissatisfied). Revision incidence was calculated using the Kaplan-Meier (KM) method and Cumulative Incidence Function (CIF) at 35 years. RESULTS: At a mean follow-up of 33 years (range, 31 to 35 years), 32 patients (34 hips) were still living with the original stem. Their mean modified Harris Hip Score was 86 points (range, 46 to 100) and all patients (100%) were very satisfied or satisfied with surgery. The revision incidence at 35 years considering (a) stem revision for any reason was 9.5% using KM and 4.5% using CIF; (b) stem revision for aseptic loosening was 3.1% using KM and 2.1% using CIF; and (c) reoperation or revision of any component for any reason was 45.3% using KM and 26.3% using CIF. CONCLUSION: The present study has demonstrated excellent survival at 35 years for a cementless double-tapered titanium fully hydroxyapatite-coated stem. LEVEL OF EVIDENCE: Level IV, Retrospective cohort study.

What are the perceived benefits and barriers to the use of robot-assisted total knee arthroplasty? A survey of members of the European Knee Society.

PURPOSE: Members of the European Knee Society (EKS) recently took part in an online questionnaire on robot-assisted TKA. The purpose of this study was to report and analyse the questionnaire results on the demographics of users versus non-users, the drivers for users of the technology, and the barriers or limitations that hinder the uptake of robot-assisted TKA. METHODS: The questionnaire was composed of 16 questions covering surgeon demographics and drivers for or barriers to the use of robotics. Responses on four- or five-point Likert scales were trichotomised depending on the type of question ("not important" - "moderately important" - "important/very important" or "fully disagree/disagree" - "neutral" - "agree/fully agree"). Consensus on a statement was defined as at least 75% agreement. RESULTS: There was a 67% response rate. Forty-five surgeons performed conventional TKA, of which 78% aimed for systematic alignment, while 22 performed robot-assisted TKA, of which 82% aimed for individualised alignment, and 16 performed technology-assisted TKA, of which 56% aimed for systematic alignment. Respondents agreed that robotics significantly impact accuracy of bone cuts (51/62, 82%), intra-operative feedback on ligament balancing (56/62, 90%) as well as bone cut orientation and implant positioning (57/ 62, 92%), and assistance to customise alignment (56/62, 90%). Respondents agreed that associated costs (14/18, 78%) are an important aspect for not using or to stop using robotics. CONCLUSION: The majority of respondents still perform conventional TKA (54%), while only a small portion perform robot-assisted TKA (27%) or other technology-assisted TKA (19%). Most robot users aim for individualised lower limb alignment, whereas most other surgeons aimed for systematic lower limb alignment. There is consensus that robotic assistance has a positive impact on accuracy of bone cuts and alignment, but no consensus on its impact on other peri- or post-operative outcomes. Finally, the associated cost of robot-assisted TKA remains the main barrier to its uptake. LEVEL OF EVIDENCE: V.

Sagittal femoral condylar shape varies along a continuum from spherical to ovoid: a systematic review and meta-analysis.

INTRODUCTION: Considerable anatomic variations of sagittal femoral condylar shape have been reported, with a continuum between spherical (or single-radius) and ovoid (or multi-radius) condyles. The purpose of this systematic review and meta-analysis was to critically appraise and synthesise the available literature on the sagittal femoral profile. The hypothesis was that studies would reveal considerable variability among individuals, but also in their methodology to quantify sagittal profiles. METHODS: This systematic review was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. On 10 September 2021 two authors searched for Level I to IV studies that reported on the sagittal curvature of the medial and/or lateral femoral condyles using the MEDLINE®, EMBASE® and Cochrane Library. Results were summarised by tabulating means, standard deviations and/or ranges for the reported radii-of-curvature, or ellipsoidal semi-major and semi-minor lengths of the condyles. To quantify sagittal 'ovoidicity' and asymmetry, results were stratified according to coordinate reference frame (posterior condylar axis (PCA), clinical and surgical transepicondylar axis (cTEA and sTEA), unified sagittal plane (USP), or unclear) and summarised in forest plots as standardised mean differences (SMD). RESULTS: Thirty-eight articles were eligible for full text extraction, quantifying sagittal radii-of-curvature by best-fit circles (BFC), ellipsoids, polynomials, spherical or cylindrical fitting. Studies with clear definition of the measurement plane revealed that both condyles were generally ovoid, with considerably greater 'ovoidicity' at the medial condyle (SMD, 4.09) versus the lateral condyle (SMD, 3.33). In addition, distal condylar radii were greater medially when measured normal to the TEA (cTEA: SMD, 0.81; sTEA: SMD, 0.79), but greater laterally when measured in a USP (SMD, - 0.83). Posterior condylar radii were greater laterally when measured in a USP (SMD, - 0.60). CONCLUSION: Studies reported considerable variability of sagittal femoral condylar radii-of-curvature, which are not incremental, but rather a continuum that ranges from spherical to ovoid. Although this variation could be accommodated by single-, dual- and multi-radii femoral components, a surgeon typically uses only one or two TKA designs. Hence, there is a risk of mismatch between the native and prosthetic sagittal profile that could result in mid-flexion ligament imbalance unless other parameters are changed. These findings support the drive towards patient-specific implants to potentially achieve accurate sagittal bone-implant fit through implant customisation. LEVEL OF EVIDENCE: IV.

Comparative Cost Analysis of Four Different Computer-Assisted Technologies to Implant a Total Knee Arthroplasty over Conventional Instrumentation.

Several computer-assisted technologies, such as navigation and robotics, have been introduced to Total Knee Arthroplasty (TKA) in order to increase surgical precision and reduce complications. However, these technologies are often criticized due to the increased costs and effort associated with them; however, comparative data are missing. The aim of the present study was to evaluate differences in intraoperative workflows and the related perioperative cost-profiles of four current computer-assisted technologies, used to implant a TKA, in order to gain a comparison to conventional instrumentation. For the cost analysis, additional preoperative imaging and instruments, increased operating room (OR) and planning-time, and expenditures for technical support of the equipment and disposals were calculated, in comparison to conventional TKA, for (1) standard computer-navigation, (2) patient specific instruments (PSI), (3) image-based robotic assistance, and (4) imageless robotic assistance. Workflows at four expert centers which use these technologies were reviewed by an independent observer. The total cost calculation was based on a 125 TKA per year unit in Switzerland. Computer-navigation resulted in 14 min (+23%) increased surgery time and, overall, USD 650 in additional costs. PSI technology saved 5 min (8%) OR time but it created USD 1520 in expenditures for imaging and disposals. The image-based robotic system was the most expensive technology; it created overall additional costs of USD 2600, which predominately resulted from technical support, disposals, the CT-Scan, and 14 min of increased OR time. The imageless robotic assistance resulted in the largest increase in OR-time, as it resulted in an additional 25 min (+42%) on average. Overall, additional costs of USD 1530 were calculated. Every one of the assistive technologies in this study increased the total cost of TKA when compared to a conventional technique, and the most important variables, related to cost, were technical support and additional disposables. The longer surgical times and additional surgical trays required for the techniques had a marginal effect on overall costs. This comparative cost analysis gives valuable information for future efforts to calculate the real costs of these technologies and the subsequent return on investment of each technique.

Custom TKA combined with personalised coronal alignment yield improvements that exceed KSS substantial clinical benefits.

PURPOSE: The purpose of this study was to report Knee Society Scores (KSS) at 12-month follow-up in a series of 266 knees that received custom TKA. The hypothesis was that custom TKA combined with personalised alignment would yield improvements greater than substantial clinical benefits (SCB) of KSS Knee and Function. METHODS: From a consecutive series of 905 patients (918 knees) that received primary TKAs, 261 (29%) patients (266 knees) received computed tomography (CT)-based posterior-stabilised cemented custom TKA. Knees were aligned aiming to preserve or restore constitutional alignment within predetermined limits of 85°-95° for femoral mechanical angle (FMA) and tibial mechanical angle (TMA), and 175°-183° for hip knee ankle (HKA) angle. The KSS Knee and Function were collected preoperatively and 12 months postoperatively, to determine if patients achieved SCB. Uni- and multivariable analyses were performed to determine associations between KSS scores (Knee and Function) and patient demographics as well as pre- and postoperative radiographic alignments. RESULTS: Of the initial cohort of 261 patients, 4 (1.8%) were reoperated for patellar resurfacing, 1 (0.4%) for lavage to treat infection, and 1 (0.4%) had arthroscopy to treat a stiff knee with < 90° range of motion. Complete clinical records were available for 227 patients (232 knees, 87%) that comprised 102 men (5 bilateral) and 125 women. At 12-month follow-up, mean improvements in KSS Knee and Function scores were, respectively, 61.0 ± 13.0 and 42.7 ± 16.7, which exceeded the SCB of KSS. Comparison of knees inside versus outside the target zone revealed no differences in KSS Knee (94.1 ± 9.1 versus 94.3 ± 9.0, n.s.) and Function (96.1 ± 9.2 versus 96.3 ± 8.9, n.s.). Multivariable analysis revealed worse KSS Knee in knees with preoperative FMA > 95° (ß = - 6.21; p = 0.023), but no association between KSS Function and patient demographics or pre- and postoperative radiographic alignments. CONCLUSIONS: Custom TKA combined with personalised alignment yielded improvements that exceeded substantial clinical benefits of KSS Knee and Function scores. These findings demonstrate the feasibility of custom TKA with 'personalised alignment' and encourage further investigations using comparative studies at longer follow-up. LEVEL OF EVIDENCE: IV, case series.

Stem-bone contact patterns of a long straight tapered uncemented stem for primary THA.

INTRODUCTION: Despite excellent long-term survival, total hip arthroplasty (THA) can fail due to aseptic loosening, dislocations, sepsis and periprosthetic fractures, all of which remain considerably burdensome. Aseptic loosening is one of the main causes of THA failure, often due to osteolysis, stress shielding and/or lack of primary stability. This study aimed to investigate stem-bone contact patterns of a long straight-tapered uncemented stem following primary THA, and to determine whether these contact patterns are related to preoperative femoral morphology and whether they influence postoperative outcomes. MATERIALS AND METHODS: The authors reviewed a continuous series of 60 hips (55 patients) that underwent primary THA using the Corail® stem (DePuy, Leeds, UK). Patients were evaluated pre- and post-operatively using the Japanese Orthopaedic Association (JOA) score. Computed-tomography (CT) scans were performed preoperatively to assess femoral bone morphology, and immediate postoperatively to assess stem-bone contact patterns. Postoperative radiographs were performed to calculate the Engh score. Regression analyses were performed to determine associations of postoperative JOA and Engh score with 27 independent variables. RESULTS: Forty-nine patients (54 hips) were assessed at 31 ± 8 months, with a JOA score of 92.9 ± 8.1 and an Engh score of 21.2 ± 1.9. Six patients (6 hips) were lost-to-follow-up. There were no revisions and only one complication (recurrent dislocation). Stem-bone contact patterns were associated with preoperative femoral morphology (sagittal CFI [p = 0.006], femoral offset [p = 0.028], and NSA [p = 0.022]), but were not associated with either postoperative JOA or postoperative Engh score. CONCLUSIONS: The stem-bone contact patterns of a long straight-tapered uncemented stem are related to preoperative femoral morphology, but do not influence short-term postoperative outcomes. Contact patterns were related to preoperative femoral offset, NSA, and sagittal CFI, but not coronal CFI. Surgeons should, therefore, consider sagittal morphology for surgical planning and templating, in addition to the conventional parameters of coronal morphology.