Applying models of care for total hip and knee arthroplasty: External validation of a published predictive model to identify extended stay risk prior to lower-limb arthroplasty.

OBJECTIVE: This study aimed to externally validate a reported model for identifying patients requiring extended stay following lower limb arthroplasty in a new setting. DESIGN: External validation of a previously reported prognostic model, using retrospective data. SETTING: Medium-sized hospital orthopaedic department, Australia. PARTICIPANTS: Electronic medical records were accessed for data collection between Sep-2019 and Feb-2020 and retrospective data extracted from 200 randomly selected total hip or knee arthroplasty patients. INTERVENTION: Participants received total hip or knee replacement between 2-Feb-16 and 4-Apr-19. This study was a non-interventional retrospective study. MAIN MEASURES: Model validation was assessed with discrimination, calibration on both original and adjusted forms of the candidate model. Decision curve analysis was conducted on the outputs of the adjusted model to determine net benefit at a predetermined decision threshold (0.5). RESULTS: The original model performed poorly, grossly overestimating length of stay with mean calibration of -3.6 (95% confidence interval -3.9 to -3.2) and calibration slope of 0.52. Performance improved following adjustment of the model intercept and model coefficients (mean calibration 0.48, 95% confidence interval 0.16 to 0.80 and slope of 1.0), but remained poorly calibrated at low and medium risk threshold and net benefit was modest (three additional patients per hundred identified as at-risk) at the a-priori risk threshold. CONCLUSIONS: External validation demonstrated poor performance when applied to a new patient population and would provide limited benefit for our institution. Implementation of predictive models for arthroplasty should include practical assessment of discrimination, calibration and net benefit at a clinically acceptable threshold.

Implementation of a day-stay joint replacement pathway in an Australian regional public hospital: A descriptive study.

OBJECTIVE: To describe the implementation, feasibility and safety of a day-stay joint replacement pathway in a regional public hospital in Australia. METHOD: Over a 12-month pilot period, a prospective descriptive analysis of consecutive patients undergoing total knee and hip arthroplasty was conducted. The number of eligible day-stay patients, proportion of successful same-day discharges and reasons for same-day failure to discharge were recorded. Outcome measures captured for all joint replacements across this period included length of stay (LoS), patient reported outcomes, complications and patient satisfaction. The implementation pathway as well as patient and staff identified success factors derived from interviews were outlined. RESULTS: Forty-one/246 (17%) patients booked for joint replacement surgery were eligible for day-stay and 21/41 (51%) achieved a successful same-day discharge. Unsuccessful same-day discharges were due to time of surgery too late in the day (7/20), no longer meeting same-day discharge criteria (11/20) and declined discharge same-day (2/20). Over the implementation period 65% (162/246) of all patients were discharged with a LoS of 2 days or less. Patient satisfaction for the day-stay pathway was high. Complication rates and patient-reported outcomes were equivalent across LoS groups. CONCLUSION: The day-stay joint replacement surgery pathway was feasible to implement, safe and acceptable to patients. Day-stay pathways have potential patient and system-level efficiency benefits.

Persistent knee extension deficits are common after anterior cruciate ligament reconstruction: a systematic review and meta-analysis of randomised controlled trials.

PURPOSE: Knee extension deficits complicate recovery from ACL injury and reconstruction; however, the incidence of knee extension loss is not well defined. The aim of this review was to identify the incidence of loss of extension (LOE) following ACL rupture and reconstruction, explore the definitions of knee extension deficits reported and identify prognostic factors affecting LOE incidence. METHODS: A systematic search was conducted in Medline, Cochrane Library and PEDro for studies in publication up to November 2021, with no restrictions on publication year. References were screened and assessed for inclusion using predetermined eligibility criteria. Randomised controlled trials (RCTs) that quantified knee angle, loss of extension or incidence of extension deficit were included for quality assessment and data extraction. Statistical summaries were generated and meta-analyses performed in two parts to examine: (i) the probability of a datapoint being zero incidence compared to a nonzero incidence and (ii) the relationship between the predictors and nonzero LOE incidence. RESULTS: A sample of 15,494 studies were retrieved using the search criteria, with 53 studies meeting eligibility criteria. The pooled results from 4991 participants were included for analysis, with 4891 participants who had undergone ACLR. The proportion of included studies judged at an overall low risk of bias was small (7.8%). The observed group and study were the most important predictors for whether a datapoint reported an incidence of extension deficit. Time to follow-up (P < 0.001) and graft type (P = 0.02) were found to have a significant influence on nonzero LOE incidence (%). Covariate adjusted estimates of average LOE indicated 1 in 3 patients presenting with LOE at 12 month follow-up, reducing to 1 in 4 at 2 years. CONCLUSIONS: This review examined the definitions for the measurement and interpretation of postoperative knee extension and established the trajectory of knee extension deficit after ACL injury and reconstruction. While factors associated with loss of extension were identified, the exact trajectory of knee extension deficits was difficult to infer due to discrepancies in measurement techniques and patient variation. On average, 1 in 3 patients may present with loss of extension of at least 3 degrees at 12-month follow-up, decreasing to 1 in 4 at 2 years. These results may be used by clinicians as an upper threshold for acceptable complication rates following ACLR. Future work should focus on LOE as a clinically relevant complication of ACL injury and treatment with appropriate attention to standardisation of definitions, measurements and better understanding of natural history. PROSPERO REGISTRATION NUMBER: CRD42018092295. LEVEL OF EVIDENCE: Level I.

Implementation and quality assessment of a clinical orthopaedic registry in a public hospital department.

BACKGROUND: The aim of this study was to demonstrate a novel method of assessing data quality for an orthopaedic registry and its effects on data quality metrics. METHODS: A quality controlled clinical patient registry was implemented, comprising six observational cohorts of shoulder and knee pathologies. Data collection procedures were co-developed with clinicians and administrative staff in accordance with the relevant dataset and organised into the registry database software. Quality metrics included completeness, consistency and validity. Data were extracted at scheduled intervals (3 months) and quality metrics reported to stakeholders of the registry. RESULTS: The first patient was enrolled in July 2017 and the data extracted for analysis over 4 quarters, with the last audit in August 2018 (N = 189). Auditing revealed registry completeness was 100% after registry deficiencies were addressed. However, cohort completeness was less accurate, ranging from 12 to 13% for height & weight to 90-100% for operative variables such as operating surgeon, consulting surgeon and hospital. Consistency and internal validation improved to 100% after issues in registry processes were rectified. CONCLUSIONS: A novel method to assess data quality in a clinical orthopaedic registry identified process shortfalls and improved data quality over time. Real-time communication, a comprehensive data framework and an integrated feedback loop were necessary to ensure adequate quality assurance. This model can be replicated in other registries and serve as a useful quality control tool to improve registry quality and ensure applicability of the data to aid clinical decisions, especially in newly implemented registries. TRIAL REGISTRATION: ACTRN12617001161314; registration date 8/08/2017. Retrospectively registered.

Anatomical Variability of Intercondylar Fossa Geometry in Patients Diagnosed with Primary Anterior Cruciate Ligament Rupture.

The aims of this study were to (1) describe the three-dimensional characteristics and sources of anatomical variability in the geometry of the intercondylar fossa ("notch") in an anterior cruciate ligament (ACL)-injured sample and (2) assess the relationship between patient factors and anatomical variability of the fossa in the context of impingement risk. A retrospective analysis of preoperative magnetic resonance imaging (MRI) for 49 patients with ACL rupture was performed. Scans were examined in the axial plane using an online picture archiving and communication system (PACS) viewer and fossa width and angle assessed at multiple slices, as well as anteroposterior depth, fossa height, and calculated total volume. Principal component analysis was performed to prioritize the sources of variability. A multivariate linear regression was performed to assess relationships between different patient factors, controlling for imaging parameters and principal component loadings. Geometric properties were normally distributed for all but fossa volume, height, and distal angle. Three principal components (PCs) were identified explaining 80% of total variance, shape (PC1), size in the coronal plane (PC2), and size in the sagittal plane (PC3). Patient factors were significantly (P < 0.05) related to PC loadings; however, a substantial amount of variance in each model remained unexplained. Intercondylar fossa characteristics vary considerably within ACL-injury patients with shape and size in coronal and axial planes, explaining most of the variance. Although patient factors are associated with anatomical characteristics, further work is required to identify the correct combination of factors accurately predicting geometry of the fossa for planning ACL reconstruction. Clin. Anat. 33:610-618, 2020. © 2019 Wiley Periodicals, Inc.

Computer navigation re-creates planned glenoid placement and reduces correction variability in total shoulder arthroplasty: an in vivo case-control study.

BACKGROUND: Accurate glenoid component placement is important to prevent glenoid component failure in total shoulder arthroplasty (TSA). Navigation may reduce the variability of glenoid component version and inclination; therefore, the aims of this study were to determine, in patients undergoing TSA, whether computer navigation improved the ability to achieve neutral postoperative version and inclination, as well as achieve the individualized preoperative plan. METHODS: Patients undergoing TSA using navigation (computer-assisted surgery [CAS], n = 33) or the conventional technique (n = 27) from January 2014 to July 2017 were recruited and compared. Preoperative and postoperative version and inclination, as well as postoperative inferior overhang, were measured using computed tomography scans. RESULTS: The CAS group had more than twice as many augmented glenoid components as the conventional group (45.5% vs. 19.2%). CAS significantly reduced the between-patient variability in postoperative version and led to a greater proportion of components positioned in "neutral" alignment for both inclination and version (P < .015). The incidence of neutral inclination or version postoperatively was significantly higher in the CAS group, and the glenoid was implanted within 5° of the surgical plan in more than 70% of cases, with more than 40% displaying no detectable difference. CONCLUSION: An integrated system of 3-dimensional surgical planning, augmented glenoid components, and intraoperative navigation may reduce the risk of glenoid placement outside of a neutral position in patients undergoing TSA compared with conventional methods. This study demonstrated the capacity for CAS to replicate the surgical plan in a majority of cases.

Role of intraoperative navigation in the fixation of the glenoid component in reverse total shoulder arthroplasty: a clinical case-control study.

BACKGROUND: Fixation of the glenoid baseplate in reverse total shoulder arthroplasty (rTSA) is an important factor in the success of the procedure. There is limited information available regarding the effect of navigation on fixation characteristics. Therefore, the aims of this study were to determine whether computed tomography-based computer navigation improved the glenoid base plate fixation by (1) increasing the length of screw purchase, (2) altering screw angulation, and (3) decreasing central cage perforation in patients undergoing rTSA. METHODS: Patients undergoing rTSAs using navigation (NAV, N = 27) and manual technique (MAN, N = 23) from January 2014 to July 2017 were analyzed in a case-control design. Screw purchase length and central cage perforation were assessed using multiplanar computed tomography. RESULTS: Median screw purchase length was significantly longer in the NAV group for both anterior (20 mm vs. 15 mm, P < .01) and posterior screws (20 mm vs. 13 mm, P < .01). In addition, the NAV group displayed significantly lower incidences of inadequate screw purchase (<22 mm) for the anterior (64.7% vs. 95.2%, P = .03) and posterior (70.6% vs. 100%, P = .01) screws. Significant differences in axial and coronal screw angulation were observed between groups. Similarly, the NAV group displayed significantly reduced incidence of central cage perforation (17.7% vs. 52.4%, P = .04). CONCLUSION: The use of computer-assisted navigated rTSA contributes to significant alterations in screw purchase length, screw angulation, and central cage perforation of the glenoid baseplate compared with non-navigated methods.

Gait adaptations following multiple-ligament knee reconstruction occur with altered knee kinematics during level walking.

PURPOSE: The biomechanical behaviour of the knee following multiple-ligament reconstruction (MLKR) may play a role in the pathogenesis of post-traumatic osteoarthritis. The aim of this study was to compare three-dimensional knee kinematics and gait characteristics of MLKR patients to healthy controls during level walking. METHODS: Three-dimensional optoelectronic motion capture during overground walking was performed on 16 patients with MLKR and a group of healthy controls matched individually to each patient for age, gender, height and weight. Three-dimensional knee angles were extracted from the weight acceptance and propulsion sub-phases of gait. Statistical analysis was performed using group-aggregated data, as well as for each patient-control pair using a single-case approach. RESULTS: Although group analysis detected few differences, single-case analysis revealed significant differences for a proportion of patients for all dependent variables during weight acceptance and propulsion sub-phases of stance. These kinematic differences occurred in the context of reduced gait velocity, step length and cadence, as well as increased time spent in double support. CONCLUSION: Patients with MLKR display abnormalities in knee kinematics during gait at an average of 4.5 years after surgery. The pattern of kinematic abnormalities appears individual specific and may not be related to differences in spatiotemporal gait characteristics. The current findings describe detailed functional outcomes of MLKR reconstruction at average medium-term follow-up that provide improved prognostic information for clinicians to counsel patients with these types of injuries.

Meniscal translation during knee flexion: what do we really know?

PURPOSE: Translation during knee flexion is a key function of the menisci. The amount of translation displayed by the medial and lateral meniscus during knee flexion, particularly while loadbearing, remains relatively unknown. To address this lack of knowledge, a systematic review of the relevant literature was performed. METHODS: We performed a literature search for studies in which a primary aim was to report the anterior-posterior translation of the menisci during knee flexion. Data were collected on the characteristics of the sample, the imaging approach, measurement and analysis techniques, and outcome variables. We scored the quality of studies and their reporting using a modified Coleman methodology score with ten criteria, with a maximum possible score of 100. RESULTS: Twelve full-text studies were retrieved that met the inclusion criteria. Of these, the in vitro studies (N = 4) scored the lowest for methodology (median 44.5), with in vivo studies of healthy knees (N = 4) (median 60) and in vivo comparative studies (N = 4) scoring highest (median 74.5). The evidence from studies with the highest methodology scores (>65) (N = 4) indicate that the lateral meniscus translates more posteriorly than the medial meniscus during flexion. In addition, meniscal translation is influenced by loading, particularly in knee rotation, but not by ACL deficiency, despite greater posterior translation of the medial femoral condyle during flexion. CONCLUSIONS: The generally low methodological quality of studies suggests that caution is required when interpreting meniscal translation during knee flexion reported in the literature. While the methods for assessing meniscal translation in vivo continue to improve and provide opportunity for clinical implementation, there remains a lack of robust evidence regarding meniscal translation in the healthy knee for comparative purposes. A number of recommendations are made for future studies to address key limitations identified in previous investigations. Additional studies of high methodological quality are required to quantify the relationships between joint loading, joint pathology and meniscal translation during knee flexion. LEVEL OF EVIDENCE: III.

Patient-specific instrumentation for total knee arthroplasty does not match the pre-operative plan as assessed by intra-operative computer-assisted navigation.

PURPOSE: The introduction of patient-specific instruments (PSI) for guiding bone cuts could increase the incidence of malalignment in primary total knee arthroplasty. The purpose of this study was to assess the agreement between one type of patient-specific instrumentation (Zimmer PSI) and the pre-operative plan with respect to bone cuts and component alignment during TKR using imageless computer navigation. METHODS: A consecutive series of 30 femoral and tibial guides were assessed in-theatre by the same surgeon using computer navigation. Following surgical exposure, the PSI cutting guides were placed on the joint surface and alignment assessed using the navigation tracker. The difference between in-theatre data and the pre-operative plan was recorded and analysed. RESULTS: The error between in-theatre measurements and pre-operative plan for the femoral and tibial components exceeded 3° for 3 and 17% of the sample, respectively, while the error for total coronal alignment exceeded 3° for 27% of the sample. CONCLUSION: The present results indicate that alignment with Zimmer PSI cutting blocks, assessed by imageless navigation, does not match the pre-operative plan in a proportion of cases. To prevent unnecessary increases in the incidence of malalignment in primary TKR, it is recommended that these devices should not be used without objective verification of alignment, either in real-time or with post-operative imaging. Further work is required to identify the source of discrepancies and validate these devices prior to routine use. LEVEL OF EVIDENCE: II.

A physiotherapy-led review of guideline-based care for community-dwelling older people presenting to a metropolitan hospital with accidental falls.

OBJECTIVE(S): Several guidelines exist to inform best-practice management of community-dwelling fallers. This study aimed to outline a pragmatic approach to developing an audit tool for guideline-based care of falls and provide an overview of current practice. METHODS: An audit tool to determine compliance with guideline-based care was developed with an allied health and physiotherapy focus, utilising the Australian Commission on Safety and Quality in Health-Care Guidelines for Preventing Falls and Harm from Falls in Older People (2009) and Queensland State Government 'Stay on your Feet' guidelines. A retrospective audit of medical records was completed in July 2020 of community-dwelling people aged 65 years and over with a fall-related emergency department (ED) presentation in a medium-sized metropolitan hospital in Australia. Data were compared between patients admitted to hospital and those discharged home from the ED. RESULTS: Ninety-three patients were included: 68 were discharged home from ED and 25 were admitted to hospital. There was a significant difference in receiving an allied health review (p < .001) between admitted patients (96%) and those who discharged home from ED (68%). The Clinical Frailty Scale was only completed for 23% of patients. Physiotherapy quality-of-care (n = 46 patients) was variable, with poor completion of physical outcome measures (7%) and fall education (4%). However, assessment of mobility was routinely completed (94%), and most patients were referred to an appropriate community service (66%). CONCLUSIONS: Adherence to guideline-based care of community-dwelling fallers is inconsistent. Improvements are required in the consistency of risk stratification, comprehensive physical assessment and patient education.

Imageless navigation system (Naviswiss) provides accurate component position in total hip arthroplasty with lateral decubitus position for end-stage hip osteoarthritis: a prospective cohort study with CT-validation.

AIMS: The Naviswiss system (Naviswiss AG, Brugg, Switzerland) is a handheld imageless navigation device used to improve the accuracy of implant positioning in total hip arthroplasty (THA). However, clinical data for leg length discrepancy and femoral offset is lacking, and the validity of the system has not been reported for patients undergoing THA in the lateral decubitus position. This study aimed to report the accuracy of the device in this patient population. METHODS: Patients underwent THA in the lateral decubitus position performed by a single surgeon. Component position measured by the device intraoperatively was compared to postoperative measurements on computed tomography (CT) scans. Agreement between the navigation system and postoperative measurements was reported for acetabular cup inclination, acetabular cup version, femoral offset, and leg length discrepancy. RESULTS: Thirty-three patients were included in the analysis. The mean difference between intraoperative and postoperative CT measurements was within 2° for angular measurements and 2 mm for leg length. Absolute differences in the two indices were up to 4° and 3 mm. The mean bias was 1°-2° overestimation for cup orientation and up to 2 mm overestimation for leg length change. However, 95% limits of agreement did not exceed absolute thresholds of 10° and 10 mm, especially after correction for bias. One case (3%) was declared intraoperatively for issues with fixation on the greater trochanter. CONCLUSIONS: The accuracy of the Naviswiss system falls within clinically acceptable recommendations for acetabular cup placement, femoral offset, and leg length for total hip arthroplasty with a anterolateral approach in lateral decubitus position. The system could be further improved with regression-based bias correction.

In vivo assessment of weight-bearing knee flexion reveals compartment-specific alterations in meniscal slope.

PURPOSE: The purpose of this study was to determine the effects of flexion angle on meniscal slope during partial weight-bearing knee flexion. METHODS: Forty-eight sagittal sequences were performed on 12 patients (6 male patients, 6 female patients; 25.7 ± 10.5 years) during partial weight bearing in an open magnetic resonance imaging (MRI) scanner at full extension, 60°, 90°, and maximum knee flexion. A previously published method was used to measure the meniscal slope for each compartment using manual digitalization. A general linear model was used to test for effects of compartment and flexion angle on meniscal slope. RESULTS: The mean maximum flexion angle achieved was 125° ± 10.5°. A significant main effect of compartment (P < .01) and flexion angle (P < .01) on meniscal slope was observed. A significant interaction between compartment and angle was also detected (P < .01). Specifically, the lateral meniscal slope was significantly more horizontal than the medial meniscus slope at full extension (P = .017) but significantly more posterior at all other angles. In addition, the lateral meniscus displayed a greater change in posterior slope across the range of motion compared with the medial meniscus. Significant correlations were found in medial meniscal slope at full extension and at maximum knee flexion (P = .031). CONCLUSIONS: The results showed that meniscal slope in healthy knees increased significantly with knee flexion for both menisci, with significantly greater changes in the lateral meniscus. Furthermore, a lack of correlation was observed between the meniscal slope in extension and the meniscal slope at increasing flexion angles, questioning the efficacy of measuring the meniscal slope only in extension as commonly described. Overall, this study has provided valuable insight into how meniscal slope changes with knee motion.

Influence of soft tissues on the proximal bony tibial slope measured with two-dimensional MRI.

PURPOSE: Despite increasing interest in the functional anatomy of the menisci, little information is available regarding the relationship between the tibial slope and the menisci. It was hypothesized that the meniscus would reduce the differences in slope between the medial and lateral compartments and would mitigate the effects of age and gender on the tibial slope. METHODS: MRI sagittal images from 101 patients were used in this study. The angle between a line tangent to the medial and lateral tibial bony slope and the proximal tibial anatomical axis was measured on sagittal MRI images (bony slope). The angle between the tangent line to the highest point of the anterior and posterior horn of the meniscus and the proximal tibial anatomical axis was also determined (soft tissue slope). The measurements were carried out twice by two observers. The influence of gender and age on these parameters was analysed. RESULTS: Repeated measures analysis of variance showed good inter- and intra-observer reliability for both bony and soft tissue slope (ICC (0.87-0.93) and (0.91-0.97) for inter- and intra-observer reliability, respectively). In both compartments, the soft tissue significantly reduced the tibial slope towards the horizontal plane. In addition, the soft tissue slope was significantly more horizontal in the lateral compartment compared to the medial compartment (p < 0.01). These differences were not influenced by age or gender. CONCLUSION: The menisci of the knee generate a more horizontal tibial slope when measured on MRI. The soft tissue slope is more horizontal in the lateral compartment of the knee compared to the medial compartment. LEVEL OF EVIDENCE: Diagnostic, Level III.

Intraoperative computer navigation parameters are poor predictors of function 1 year after total knee arthroplasty.

Intraoperative navigation data were collected prospectively for 134 knees undergoing cemented, posterior-stabilized total knee arthroplasty. Partial least squares regression analysis was used to test the association between patient demographics and intraoperative data collected with a computer-assisted navigation system (coronal alignment, ligament balance, range of motion, external tibiofemoral rotation) with 1-year outcomes (36-item Short-Form Health Survey, Oxford Knee Score, range of motion). Age at surgery displayed the largest coefficients of any other predictor. In contrast, navigation coefficients were variable in the strength and direction of their association with the outcome variables. Static knee alignment data obtained intraoperatively have limited capacity to explain the variance in functional outcome at 1 year. Although alignment and component position can be precisely measured intraoperatively, intrinsic patient factors remain dominant in determining the outcome.

Unsatisfactory accuracy as determined by computer navigation of VISIONAIRE patient-specific instrumentation for total knee arthroplasty.

This investigation evaluated the Smith and Nephew VISIONAIRE patient-specific cutting block (PSCB) system for total knee arthroplasty. A consecutive series of 60 patients was recruited. Intraoperative computer navigation was used to evaluate the accuracy of the cutting blocks in the coronal and sagittal planes for the tibia, as well as rotational plane for the femur. The PSCB would have placed 79.3% of the sample within ±3° of the preoperative plan in the coronal plane, while the rotational and sagittal alignment results within ±3° were 77.2% and 54.5% respectively. The VISIONAIRE PSCB system achieved unacceptable accuracy when assessed by computer navigation. There might be many sources of error, but caution is recommended before using this system routinely without objective verification of alignment.

CT validation of intraoperative imageless navigation (Naviswiss) for component positioning accuracy in primary total hip arthroplasty in supine patient position: a prospective observational cohort study in a single-surgeon practice.

BACKGROUND: The aim of this study was to report on the validity of the Naviswiss handheld image-free navigation device for accurate intraoperative measurement of THA component positioning, in comparison with the three-dimensional (3D) reconstruction of computed tomography (CT) images as the gold standard. METHODS: A series of patients presenting to a single-surgeon clinic with end-stage hip osteoarthritis received primary hip arthroplasty with the anterolateral muscle-sparing surgical approach in the supine position. Imageless navigation was applied during the procedure with bone-mounted trackers applied to the greater trochanter and ASIS. Patients underwent routine CT scans before and after surgery and these were analyzed by using three-dimensional reconstruction to generate cup orientation, offset and leg length changes, which were compared to the intraoperative measurements provided by the navigation system. Estimates of agreement between the intraoperative and image-derived measurements were assessed with and without correction for bias and declared cases with potential measurement issues. RESULTS: The mean difference between intraoperative and postoperative CT measurements was within 2° for angular measurements and 2 mm for leg length. Absolute differences for the two indices were between 5° and 4 mm. Mean bias was 1.9°-3.6° underestimation for cup orientation and up to 2 mm overestimation for leg length change, but absolute thresholds of 10° and 10 mm were not exceeded by 95% limits of agreement (LOA), especially after correction for bias. Four cases (12%) were declared intraoperatively for issues with fixation on the greater trochanter. Inclusion of these cases generated acceptable accuracy overall and their omission failed to improve between-case variability in accuracy or LOA for both offset and leg length. CONCLUSIONS: The accuracy of the Naviswiss system applied during primary THA in a supine position and anterolateral surgical approach falls within clinically acceptable recommendations for acetabular cup placement, femoral offset, and length. With refinements to surgical technique to adapt to the navigation hardware, the system could be further improved with regression-based bias correction. TRIAL REGISTRATION: Registered with the Australian New Zealand Clinical Trials Registry (ACTRN12618000317291).

Early Clinical Outcomes and Complications of Transfibular Total Ankle Arthroplasty: The Australian Experience.

BACKGROUND: We report the short-term outcomes of a retrospective cohort of Trabecular Metal total ankle arthroplasties (TAAs) via a transfibular approach from a single, nondesigner surgeon in Australia. METHODS: This was a retrospective cohort study. Demographic, clinical, and patient-reported outcome measures (PROMs) were collected. The primary outcome was the Foot and Ankle Outcome Score (FAOS), and secondary outcomes included patient satisfaction, the EuroQol-5 Dimension (EQ5D), and complications including revision rates. RESULTS: Between 2016 and 2019, 84 trabecular metal prostheses were implanted in 84 patients. Mean age (SD) at time of surgery was 68 (7.8) years, and 46 (55%) were male. Mean follow-up (SD) was 26.1 (13) months. There were significant (P < .001) improvements in the FAOS in the subscales of pain (47.9 to 79.1), activities of daily living (59.5 to 83.7), and quality of life (25.5 to 60.2) and EQ-5D (0.55 to 0.75) (P < .001), and overall satisfaction was 69.6%. The commonest complications were wound infection or breakdown (11.9%, n=10), fibular nonunion (3.5%), plate irritation (3.5%), and tibial nerve neuropathy (3.5%). There were no thromboembolic complications. Implant survivorship was 100%, with Trabecular Metal components retained in all patients. Two patients developed deep infection, with 1 requiring debridement and polyethylene exchange. No patients experienced implant loosening. CONCLUSION: Our results demonstrate that the trabecular metal survival rates are comparable with other total ankle implants in the Australian Orthopaedic Association National Joint Replacement Registry and as published in other international literature. Overall patient satisfaction was high, as were PROMs. However, the data highlight potential complications uniquely associated with this implant. The authors believe that these figures support TAA via a transfibular approach as a viable option in the treatment of ankle arthritis. LEVEL OF EVIDENCE: Level IV, retrospective cohort study.

Is femoral component rotation in a TKA reliably guided by the functional flexion axis?

BACKGROUND: The position of the femoral component in a TKA in the axial plane influences patellar tracking and flexion gap symmetry. Errors in femoral component rotation have been implicated in the need for early revision surgery. Methods of guiding femoral component rotation at the time of implantation typically are derived from the mean position of the flexion-extension axis across experimental subjects. The functional flexion axis (FFA) of the knee is kinematically derived and therefore a patient-specific reference axis that can be determined intraoperatively by a computer navigation system as an alternative method of guiding femoral component rotation. However, it is unclear whether the FFA is reliable and how it compares with traditional methods. QUESTION/PURPOSES: We asked if the FFA could be measured reproducibly at different stages of the operative procedure; (2) where it lies in relation to a CT-derived gold standard; and (3) how it compares with more traditional methods of judging femoral component rotation. METHODS: Thirty-seven patients undergoing elective TKAs were recruited to the study. Preoperative CT scans were obtained and the transepicondylar axis (TEA) was identified. The TKA then was performed using computer navigation. The FFA was derived before incision and again after the surgical approach and osseous registration. The navigation system was used to register the surgical TEA. The FFA and surgical TEA then were compared with the CT-derived TEA. RESULTS: The mean preincision FFA was similar to the intraoperative FFA and therefore deemed reproducible. We observed no differences in variability between surgical TEA and preincision FFA. The FFA was different from the CT-TEA and judged similar in accuracy to the surgical TEA. CONCLUSION: The reliability and accuracy of the FFA were similar to those of other intraoperative methods. Further evaluation is required to ascertain whether the FFA improves on currently available methods for determining the ideal rotation of the femoral component during TKA.