Impact of change in coronal plane alignment of knee (CPAK) classification on outcomes of robotic-assisted TKA.

BACKGROUND: Mechanical alignment with total knee arthroplasty (TKA) has been widely used since the implantation of the first prosthetic knee. Multiple studies have reported 80% patient satisfaction with TKA. However, the reported patients' dissatisfaction is believed to be caused by having to convert different knee alignments to neutral alignments. It is postulated that a change in the CPAK classification of knees leads to patient dissatisfaction. Thus, we hypothesized that a change in CPAK classification with robot-assisted TKA with mechanical alignment does not significantly lead to patient dissatisfaction. METHODS: We retrospectively analyzed 134 patients who underwent robot-assisted mechanical alignment total knee arthroplasty (MA-TKA) using cementless implants and classified them into CPAK system pre- and post-operatively. One year after TKA surgery, we recorded binary responses to patients' satisfaction with the outcome of surgery and analyzed if a change in CPAK classification is associated with the outcome of surgery. RESULTS: We found that 125 out of 134 patients (93.28%) were happy with the outcome of surgery. CPAK classification was changed in 116 patients (86.57%) and maintained in 18 patients (13.43%). Our results also showed that 111 (95.7%) out of 116 patients who had a change in CPAK and 14 (77.8%) out of 18 patients who maintained their CPAK post-surgery were happy with the outcome of surgery (OR = 6.3, CI 1.741-25.17, P value = 0.019). CONCLUSION: We concluded that changing the patient's native joint line and CPAK classification does not significantly change the outcome of surgery in terms of satisfaction. The dissatisfaction rate of 20% as published by previous researchers may be confounded by other reasons and not just due to changes in alignment and joint line.

Is 80% satisfaction still the expectation in modern TKA mechanically aligned with robot assist? We think not.

Several studies reported that20% of patients were unhappy with the outcome of their total knee arthroplasty (TKA). Having commenced robot assist TKA whilst maintaining the goal of implanting the prosthesis to a neutral mechanical axis, we reviewed our patients to find out if we also have a 20% rate of patients being unhappy with the outcome of their knee replacement surgery. We hypothesized that rate of patient satisfaction would be higher than 90% with robot-surgical assistant (ROSA) technique. The first 175 patients who underwent ROSA TKA were reviewed at a minimum of 1 year postoperatively. All TKAs were performed using ROSA technique with Persona cementless prosthesis aiming to restore neutral mechanical coronal alignment with flexion gap balancing. We investigated whether or not the patients were happy they had their knee replacement surgery and whether they were happy with the outcome. 165 (94%) of 175 patients, were contactable with 1 deceased and 9 uncontactable. From the 165 patients who participated in the study, 95% of patients were happy they had the surgery done and 93% were happy with the outcome of their knee replacement. A sub analysis showed that patients who had simultaneous bilateral TKA were significantly less likely to be happy than staged procedures (p < 0.05). Total knee replacement utilising robot technique with modern implants and aiming for mechanical coronal alignment of the implants to restore the mechanical axis with flexion gap balancing may result in > 90% of patients being happy with the outcome of their surgery.

Incidence of soft tissue releases in robotic assisted cementless TKA with mechanical alignment and flexion gap balancing.

BACKGROUND: To ensure the success of total knee arthroplasty (TKA), precise bone cuts and a well-balanced soft tissue envelope are crucial. Soft tissue release may be necessary, subject to various factors. Therefore, documenting the type, frequency, and necessity of soft tissue releases can establish a benchmark for comparing different alignment techniques and philosophies and evaluating their outcomes. The purpose of this study was to demonstrate that robotic-assisted knee surgery requires minimal soft tissue release. METHODS: We prospectively documented and retrospectively reviewed the soft tissue releases employed in securing ligament balance in the first 175 patients who received robotic-assisted TKAs at Nepean Hospital. ROSA was utilized in all surgeries with the aim of restoring mechanical coronal alignment, with a flexion gap balancing technique. Surgeries were performed between December 2019 to August 2021 by a single surgeon who used a standard medial parapatellar approach without a tourniquet, and the cementless persona prosthesis. All patients were followed up for a minimum of 6 months post-surgery. Soft tissue releases included any form of medial release for varus knee, posterolateral release for valgus knee and PCL fenestration or sacrifice. RESULTS: There were 131 female and 44 male patients, aged between 48 to 89 years (average 60 years). The preoperative HKA ranged from 22 degrees varus to 28 degrees valgus, with 71% of patients presenting with a varus deformity. For the whole group, the no need for soft tissue release was documented in 123 patients (70.3%), small fenestrated releases of PCL in 27 (15.4%), sacrifice of PCL in 8 (4.5%), medial releases in 4 (2.3%) and posterolateral releases in 13 (7.4%). In 29.7% of patients in whom a soft tissue release was necessary for balance, over half were/received minor fenestrations of the PCL. Outcomes to date included no revisions or impending revisions, 2 MUAs (1%), and Oxford knee scores averaged 40 at 6 months. CONCLUSION: We concluded that Robot technology enhanced the precision of bone cuts and allowed for titration of required soft tissue releases to achieve optimal balance.

Effect of Aspirin vs Enoxaparin on 90-Day Mortality in Patients Undergoing Hip or Knee Arthroplasty: A Secondary Analysis of the CRISTAL Cluster Randomized Trial.

Importance: Ischemic heart disease remains the leading cause of mortality following hip and knee arthroplasty. Due to its antiplatelet and cardioprotective properties, aspirin has been proposed as an agent that could reduce mortality when used as venous thromboembolism (VTE) prophylaxis following these procedures. Objective: To compare aspirin with enoxaparin in reducing 90-day mortality for patients undergoing hip or knee arthroplasty procedures. Design, Setting, and Participants: This study was a planned secondary analysis of the CRISTAL cluster randomized, crossover, registry-nested trial performed across 31 participating hospitals in Australia between April 20, 2019, and December 18, 2020. The aim of the CRISTAL trial was to determine whether aspirin was noninferior to enoxaparin in preventing symptomatic VTE following hip or knee arthroplasty. The primary study restricted the analysis to patients undergoing total hip or knee arthroplasty for a diagnosis of osteoarthritis only. This study includes all adult patients (aged ≥18 years) undergoing any hip or knee arthroplasty procedure at participating sites during the course of the trial. Data were analyzed from June 1 to September 6, 2021. Interventions: Hospitals were randomized to administer all patients oral aspirin (100 mg daily) or subcutaneous enoxaparin (40 mg daily) for 35 days after hip arthroplasty and 14 days after knee arthroplasty procedures. Main Outcomes and Measures: The primary outcome was mortality within 90 days. The between-group difference in mortality was estimated using cluster summary methods. Results: A total of 23 458 patients from 31 hospitals were included, with 14 156 patients allocated to aspirin (median [IQR] age, 69 [62-77] years; 7984 [56.4%] female) and 9302 patients allocated to enoxaparin (median [IQR] age, 70 [62-77] years; 5277 [56.7%] female). The mortality rate within 90 days of surgery was 1.67% in the aspirin group and 1.53% in the enoxaparin group (estimated difference, 0.04%; 95% CI, -0.05%-0.42%). For the subgroup of 21 148 patients with a nonfracture diagnosis, the mortality rate was 0.49% in the aspirin group and 0.41% in the enoxaparin group (estimated difference, 0.05%; 95% CI, -0.67% to 0.76%). Conclusions and Relevance: In this secondary analysis of a cluster randomized trial comparing aspirin with enoxaparin following hip or knee arthroplasty, there was no significant between-group difference in mortality within 90 days when either drug was used for VTE prophylaxis. Trial Registration: http://anzctr.org.au Identifier: ACTRN12618001879257.

Effect of Aspirin vs Enoxaparin on Symptomatic Venous Thromboembolism in Patients Undergoing Hip or Knee Arthroplasty: The CRISTAL Randomized Trial.

Importance: There remains a lack of randomized trials investigating aspirin monotherapy for symptomatic venous thromboembolism (VTE) prophylaxis following total hip arthroplasty (THA) or total knee arthroplasty (TKA). Objective: To determine whether aspirin was noninferior to enoxaparin in preventing symptomatic VTE after THA or TKA. Design, Setting, and Participants: Cluster-randomized, crossover, registry-nested trial across 31 hospitals in Australia. Clusters were hospitals performing greater than 250 THA or TKA procedures annually. Patients (aged ≥18 years) undergoing hip or knee arthroplasty procedures were enrolled at each hospital. Patients receiving preoperative anticoagulation or who had a medical contraindication to either study drug were excluded. A total of 9711 eligible patients were enrolled (5675 in the aspirin group and 4036 in the enoxaparin group) between April 20, 2019, and December 18, 2020. Final follow-up occurred on August 14, 2021. Interventions: Hospitals were randomized to administer aspirin (100 mg/d) or enoxaparin (40 mg/d) for 35 days after THA and for 14 days after TKA. Crossover occurred after the patient enrollment target had been met for the first group. All 31 hospitals were initially randomized and 16 crossed over prior to trial cessation. Main Outcomes and Measures: The primary outcome was symptomatic VTE within 90 days, including pulmonary embolism and deep venous thrombosis (DVT) (above or below the knee). The noninferiority margin was 1%. Six secondary outcomes are reported, including death and major bleeding within 90 days. Analyses were performed by randomization group. Results: Enrollment was stopped after an interim analysis determined the stopping rule was met, with 9711 patients (median age, 68 years; 56.8% female) of the prespecified 15 562 enrolled (62%). Of these, 9203 (95%) completed the trial. Within 90 days of surgery, symptomatic VTE occurred in 256 patients, including pulmonary embolism (79 cases), above-knee DVT (18 cases), and below-knee DVT (174 cases). The symptomatic VTE rate in the aspirin group was 3.45% and in the enoxaparin group was 1.82% (estimated difference, 1.97%; 95% CI, 0.54%-3.41%). This failed to meet the criterion for noninferiority for aspirin and was significantly superior for enoxaparin (P = .007). Of 6 secondary outcomes, none were significantly better in the enoxaparin group compared with the aspirin group. Conclusions and Relevance: Among patients undergoing hip or knee arthroplasty for osteoarthritis, aspirin compared with enoxaparin resulted in a significantly higher rate of symptomatic VTE within 90 days, defined as below- or above-knee DVT or pulmonary embolism. These findings may be informed by a cost-effectiveness analysis. Trial Registration: ANZCTR Identifier: ACTRN12618001879257.

Two-year migration characteristics of a novel cementless femoral stem: a radiostereometric analysis and clinical outcomes study.

BACKGROUND: Radiostereometric analysis (RSA) is an established high precision tool enabling us to detect early implant migration in total hip arthroplasty. The aim of this study is to present the RSA and clinical results of a new cementless hip stem and to compare those with established benchmarks. METHODS: A total of 45 patients (46 hips) undergoing total hip arthroplasty were available for full radiographic and clinical assessment at 2 years post-operatively. Mean patient age was 69 (range 43-85) years and mean body mass index was 29 (range 21-38) kg/m2 . RSA was undertaken at day 1, 6 weeks, 6 months and 1 and 2 years post-operatively. Oxford hip score and EQ-5D-5L scores were recorded preoperatively and at the same other time points. Results were compared to published data of established implants. RESULTS: At 2 years, mean subsidence and retroversion were 0.61 mm (standard deviation 0.7 mm, range -0.19 to 3.06 mm) and 0.44° (standard deviation 0.81°, range 0.98 to 3.29°), respectively. Stem migration occurred primarily in the first 6 weeks with no detectable subsidence or rotation at 6 months or 2 years. Mean Oxford hip score and EQ-5D-5L improved from 18.6 to 44.7, and 69 to 86, respectively. There was one cup-only revision and no revisions for stem loosening. CONCLUSION: RSA serves as an accurate measure of femoral stem stability early in the post-operative period. Our data confirm that stability occurs as early as 6 weeks and is sustained at 2 years. The Paragon stem demonstrates stability parameters at 2 years that exceed other established benchmark implants.

Different targets of mechanical alignment do not improve knee outcomes after TKA.

BACKGROUND: Accurate alignment is a basic principle of TKA surgery, but achieving alignment within this target may not translate into superior outcomes after surgery. PURPOSE: To assess if neutral TKA mechanical alignment was associated with superior knee outcomes and to examine the effect of various aspects of pre-operative and post-operative alignment on knee function. METHODS: Analysis of a database of 444 TKA patients between June 2009 and October 2016. Knee outcomes (WOMAC, AKSS and knee range of motion) were collected before surgery and during follow-up at a minimum of six months. RESULTS: Analysis included 444 TKA patients (62% female, mean age 66 years, mean follow-up 23 months). Deformity varied from 21° varus (mean = 7.9, SD = 2.8) to 17° valgus deformity (mean = 7.7, SD = 2.8). Pre-operatively, 101 (23%) knees were in native neutral mechanical alignment, while 278 (63%) were in varus and 65 (15%) were in valgus. Post-operatively, a group of 365 (82%) TKA were found to be in neutral mechanical alignment and a group of 79 (18%) TKA were noted to be 'Outliers' (17 [4%] TKA > 3° varus and 62 [14%] TKA > 3° valgus alignment). Restoration of the target of alignment of 0 ±â€¯3° or 0 ±â€¯1°, did not have better functional outcomes scores, range of motion or prosthesis longevity than those in the outlier range. CONCLUSION: Neutral TKA alignment did not appear to be a significant contributing factor to the improvement in knee function in short-medium term follow-up.

Total knee arthroplasty after patellectomy: A meta-analysis of case-control studies.

BACKGROUND: Post-patellectomy patients represent a specific subset of patients who can develop painful and disabling knee osteoarthritis that requires Total Knee Arthroplasty (TKA). The aim of this study was to conduct a meta-analysis comparing the outcome of TKA in patients with previous patellectomy to those with an intact patella. METHODS: A systematic search of electronic databases (PubMed, Medline, Embase, and Cochrane Library) was performed. Data on study setting, type of implant, outcome and associated complications were extracted. Quality assessment was performed using the Newcastle-Ottawa Scale. Random effects meta-analyses were used to combine the results of included studies. RESULTS: Seven case-control studies were found that met the search criteria. Compared to patients with an intact patella, patients with a previous patellectomy were less likely to have an 'excellent' or 'good' outcome (OR: 0.3, 95% CI: 0.14 to 0.65). The weighted mean post-operative knee flexion arc was 6.58° less in patients with a previous patellectomy (95% CI: -12.79, -0.37). The risk of complication occurring in a patella-deficient knee was higher, with a pooled OR of 1.97 (95% CI=1.10 to 3.51). CONCLUSIONS: The current evidence that compares the outcome of knee arthroplasty in patients with a previous patellectomy to patients with an intact patella is mostly based on TKAs performed in the 1980s and 1990s. Total knee replacement in patients with an intact patella results in superior outcomes compared to those with a previous patellectomy. In patients with a previous patellectomy, the arc of flexion is slightly less and the complication rate is significantly higher.

Thirteen-year outcomes in the Anatomique Benoist Girard II hip prosthesis.

BACKGROUND: The Stryker Anatomique Benoist Girard (ABG) hip implant system was a commonly used cementless prosthesis in the early 2000s, which fell from favour after several studies emerged implicating the prosthesis in high rates of revision. This retrospective, single-surgeon clinical study examines the fracture rate, revision rate and reasons for revision in 500 consecutive ABG II primary total conventional hip replacements. METHODS: Follow-up was conducted by audit of patient notes, patient mailout survey, patient phone contact and audit of the Australian National Joint Replacement Registry (NJRR) database to find instances of fracture and revision. End points were periprosthetic fracture and revision for any reason. RESULTS: Follow-up was 1.2-13.8 years with a mean of 6.58 years. Of the 500 hips, 17 (3.4%) had undergone a revision. Of these, 13 were due to periprosthetic fracture. Four further fractures occurred that were not revised. Eight of these periprosthetic fractures occurred within 1 year post-operatively. There were four revisions for recurrent dislocations. Kaplan-Meier survival curve demonstrates a 93.7% survivorship at 6.58 years for revision for any reason. Multivariate analysis showed the only statistically significant factor for increased risk of revision was smaller stem size. CONCLUSION: Our results were consistent with the literature in that the ABG II system has good medium-term results but is prone to periprosthetic fractures, especially in the early post-operative period. When used as a primary total hip arthroplasty, the ABG II system has an 8-year revision rate of 5.6% compared with the 4.9% of all primary total hip arthroplasties.

Component position alignment with patient-specific jigs in total knee arthroplasty.

BACKGROUND: The failure to restore mechanical alignment and appropriate rotational axis intraoperatively has been described as one of the most common causes of implant failure in total knee arthroplasty (TKA). Both conventional and computer-assisted TKA have their limitations. Patient-specific jigs (PSJ) offer a possible alternative method for TKA. The aim of this study was to investigate if the use of PSJ offers reproducible and accurate orientation of the components in TKA compared with conventional and computer-assisted surgery. METHODS: We conducted a prospective case series looking at 261 consecutive patients undergoing TKA for osteoarthritis using the Signature Patient Specific System (Biomet, North Ryde, NSW, Australia). Each patient underwent a preoperative magnetic resonance imaging for planning. Using a computer software program, specialized femoral and tibial pin placement jigs were generated. Post-operative femoral and tibial component alignment was measured using computed tomography. RESULTS: Of patients, 96.2% achieved femoral rotational alignment ±3 degrees of the transepicondylar axis. Tibial coronal alignment showed 92.7% of cases were 90 ± 3 degrees to the tibial medullary axis. Implant measurements of the posterior tibial slope demonstrated 76.6% of cases were within our accepted 0 to 7 degrees slope and 81.2% of patients had an overall mechanical axis within ±3 degrees of neutral. We also recorded femoral coronal alignment of the last 98 patients of our group and found that 99% were within 90 ± 3 degrees. CONCLUSION: PSJ for TKA shows good accuracy in alignment when compared with conventional TKA. However, improvements in the development of the tibial alignment cutting guides will aid in further increasing its overall accuracy and reproducibility.

Defining distal femoral anatomy for rotational alignment in total knee arthroplasty: a magnetic resonance imaging-based study.

BACKGROUND: The rotational alignment of the femoral component in total knee arthroplasty (TKA) is regarded as being one of the critical factors associated with its long-term success. Traditionally, the femoral component is aligned parallel to the transepicondylar axis (TEA), perpendicular to the Whiteside's line (WL) or at 3 degrees external rotation to the posterior condylar line (PCL). The aim of this study was to use magnetic resonance imaging (MRI) to evaluate the relationship between these anatomical axes used for femoral component rotation (TEA to WL and PCL to TEA) and identify if any of these relationships were influenced by age, sex or coronal axial deformity (mechanical axis). METHODS: Two hundred and sixty-five patients undergoing preoperative MRI for patient-specific jigs TKA were included in our study. The MRI data were then analysed via preoperative planning software, and values relating to WL, TEA, PCL and coronal axial alignment were generated. RESULTS: The mean age was 66.0 ± 8.7 years. There were 102 men and 163 women. The average mechanical axis (coronal deformity) was 4.2 ± 6.1 degrees of varus. TEA compared with WL was on average 92.6 ± 2.3 degrees. PCL was on average 2.3 ± 1.8 degrees internally rotated to the TEA. The PCL was more internally rotated in women (P < 0.01) and valgus (P < 0.001) knees. There was no significant relationship between age or varus knees when comparing TEA to WL (P > 0.1) and PCL to TEA (P > 0.1). CONCLUSIONS: Our study shows that the previously assumed values for rotational alignment of the femoral component may need to be reviewed. The use of advanced preoperative imaging (e.g. MRI) may aid to overcome this variability and assist surgeons in planning femoral component alignment in TKA.