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.

Patient-reported outcomes of a short hospital stay after total knee replacement in a regional public hospital: a prospective cohort treated 2018-2019.

BACKGROUND: Patient-reported outcomes and satisfaction following short length of stay (LoS) after total knee arthroplasty (TKA) in the Australian regional context remain unexplored. This study reports complications, outcomes and satisfaction of patients discharged from an enhanced recovery protocol (ERP), 6 weeks after TKA in a regional hospital. METHODS: Prospective recruitment occurred between 2018 and 2019. Demographics, intraoperative data, complications and emergency department (ED) presentations were retrieved from hospital records. Complications were graded for severity using a published scale. Knee range of motion (ROM), timed up-and-go (TUG), 6-min walk test (6MWT) and Oxford Knee Scores (OKS) were assessed preoperatively and 6 weeks postoperatively. Patient satisfaction was assessed via questionnaire at the postoperative follow-up. RESULTS: One hundred patients/117 primary TKAs were prospectively included. Median LoS was 2 days (interquartile range 1-3 days) with 74.4% and 88.4% of patients satisfied with their knee and LoS, at 6 weeks respectively. Twenty-seven patients presented to the ED a total of 37 times with complication severity of Grade III or less, and 10 patients were readmitted. Significant improvements in objective and subjective outcomes were observed, however only change in median OKS exceeded the minimal clinically important difference (MCID) threshold. CONCLUSION: An enhanced recovery protocol after TKA in a regional hospital can achieve a median LoS of 2 days without compromising patient-reported outcomes and objective functional measures, whilst maintaining a high level of patient satisfaction with both the surgery and LoS. Further work is required to better optimize management of largely low-grade complications in this patient population.

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.

Towards a Dynamic Model of the Kangaroo Knee for Clinical Insights into Human Knee Pathology and Treatment: Establishing a Static Biomechanical Profile.

There is limited understanding of how patella realignment or patellectomy to surgically manage patellofemoral pain (PFP) affects knee biomechanics. By analysing marsupials like kangaroos that lack an ossified patella, actionable biomimetic insight for the management of end-stage PFP could be gained. This study aimed to provide the foundation of a multi-stage approach, by establishing a static biomechanical profile of the kangaroo stifle that informs the inputs and factors requiring consideration for future dynamic analyses. Volumetric CT and MRI sequences were obtained for four hindlimbs from two Macropus giganteus specimens, from which three-dimensional models of the stifles were created. Two limbs were dissected to visualise the insertion points, origins and lines of action of the quadriceps muscles and the knee extensor mechanism. Static measurements were obtained from the three-dimensional models to establish the biomechanical profile. The results confirmed structural differences in the kangaroo stifle with lack of an ossified patella, a prominent tuberosity and a shorter femur, which functionally affect the mechanical advantage and the torque-generating capability of the joint. The data reported in this study can be used to inform the inputs and constraints of future comparative analyses from which important lessons can be learned for the human knee.

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.

Factors affecting the incidence and management of fixed flexion deformity in total knee arthroplasty: A systematic review.

PURPOSE: This study aimed to systematically review the literature and identify factors which would contribute to the intraoperative correction of FFD to frame a potential surgical algorithm or predictive model to guide intraoperative decision-making. METHODS: Electronic searches of six databases were undertaken in April 2016 according to the PRISMA guidelines, and the reference lists of studies searched. Quality of studies was assessed using the STROBE checklist, and the Downs and Black Scores. RESULTS: Twenty-five studies investigating 10, 679 knees were found to satisfy the inclusion and exclusion criteria. These studies described a variety of pre-operative and intra-operative factors which contribute to the development or correction of post-operative FFD. The only patient predictor of post-operative FFD was pre-operative FFD. The intra-operative steps described to correct FFD were: distal femoral resection, soft-tissue balancing (in the posterior and medial compartments), sagittal component flexion and posterior condylar offset. However, no studies investigated these in an integrated model. CONCLUSION: This review has identified various pre-, intra- and post-operative factors predictive of post-operative FFD. In practice, these factors are likely to interact, and therefore further investigation in an integrated model is crucial to developing a statistically sound and reliable intraoperative algorithm for surgeons to follow when correcting fixed flexion deformity.

Multiobjective optimization of cartilage stress for non-invasive, patient-specific recommendations of high tibial osteotomy correction angle - a novel method to investigate alignment correction.

Medial opening wedge high tibial osteotomy (MOWHTO) is a surgical procedure to treat knee osteoarthritis associated with varus deformity. However, the ideal final alignment of the Hip-Knee-Ankle (HKA) angle in the frontal plane, that maximizes procedural success and post-operative knee function, remains controversial. Therefore, the purpose of this study was to introduce a subject-specific modeling procedure in determining the biomechanical effects of MOWHTO alignment on tibiofemoral cartilage stress distribution. A 3D finite element knee model derived from magnetic resonance imaging of a healthy participant was manipulated in-silico to simulate a range of final HKA angles (i.e. 0.2°, 2.7°, 3.9° and 6.6° valgus). Loading and boundary conditions were assigned based on subject-specific kinematic and kinetic data from gait analysis. Multiobjective optimization was used to identify the final alignment that balanced compressive and shear forces between medial and lateral knee compartments. Peak stresses decreased in the medial and increased in the lateral compartment as the HKA was shifted into valgus, with balanced loading occurring at angles of 4.3° and 2.9° valgus for the femoral and tibial cartilage respectively. The concept introduced here provides a platform for non-invasive, patient-specific preoperative planning of the osteotomy for medial compartment knee osteoarthritis.

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.

Lack of agreement between computer navigation and post-operative 2-dimensional computed tomography (CT) measurements for component and limb alignment in total knee arthroplasty (TKA).

BACKGROUND: The purpose of this study was to assess the degree of mismatch between intraoperative navigation data using imageless computer navigation and post-operative CT scan measurements with respect to bone cuts, component and limb alignment during TKA. METHODS: Intraoperative navigation data including bone cut verification and overall limb alignment during TKA was compared to postoperative CT measurements of component and limb alignment according to the Perth protocol. The proportion of cases with mismatch between navigation and CT measurements at two and three degree thresholds was identified. RESULTS: In a total sample of 50 primary TKAs, 20% of cases showed a mismatch of more than two degrees between navigation and CT obtained measurements for coronal femoral alignment, 42% for femoral rotation, 16% for tibial component coronal alignment and 32% for overall limb alignment. CONCLUSION: Mismatch between intraoperative navigation data and postoperative CT measurements suggests that postoperative CT scan alignment data should be interpreted with caution. A surgeon should consider a multitude of factors when analysing component and limb alignment postoperatively.

Young men utilise limited neuromuscular preparation to regulate post-impact knee mechanics during step landing.

PURPOSE: The neuromuscular mechanisms determining the mechanical behaviour of the knee during landing impact remain poorly understood. It was hypothesised that neuromuscular preparation is subject-specific and ranges along a continuum from passive to active. METHODS: A group of healthy men (N=12) stepped-down from a knee-high platform for 60 consecutive trials. Surface EMG of the quadriceps and hamstrings was used to determine pre-impact onset timing, activation amplitude and cocontraction for each trial. Partial least squares regression was used to associate pre-impact preparation with post-impact knee stiffness and coordination. RESULTS: The group analysis revealed few significant changes in pre-impact preparation across trial blocks. Single-subject analyses revealed changes in muscle activity that varied in size and direction between individuals. Further, the association between pre-impact preparation and post-impact knee mechanics was subject-specific and ranged along a continuum of strategies. CONCLUSION: The findings suggest that neuromuscular preparation during step landing is subject-specific and its association to post-impact knee mechanics occurs along a continuum, ranging from passive to active control strategies. Further work should examine the implications of these strategies on the distribution of knee forces in vivo.

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.

Incidence and severity of complications due to femoral nerve blocks performed for knee surgery.

BACKGROUND: While single shot femoral nerve blocks and indwelling femoral nerve catheters provide significant peri-operative analgesia, there are small but serious risks of neurovascular complications. We aimed to determine the incidence and characterise the nature of neural complications arising from femoral nerve blocks performed for knee surgery. METHODS: One thousand eight hundred and two patients receiving a femoral nerve block for knee surgery during the study period were screened. Patients with possible neurological symptoms were evaluated with a detailed physical examination and self-report questionnaires. Also measures of depression, anxiety and tension/stress were collected. RESULTS: In the patients screened, an incidence of 1.94% was found. Of the 24 patients available for testing, 4 had bilateral symptoms following bilateral nerve blocks. All had sensory abnormalities in the distribution of the femoral nerve. The incidence was significantly higher in females (females=2.5%, males=0.83% p=0.01) and in patients receiving a single shot block (single shot=2.66%, femoral catheter=0.93, p=0.01). CONCLUSIONS: The incidence of neurological complication after FNB was higher in this series than typically reported and the symptoms significantly influenced the quality of life in the affected cases. The decision to include a femoral nerve block in the peri-operative analgesic regimen should be made on an individual basis considering the risks and benefits.

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.

Single-subject analysis reveals variation in knee mechanics during step landing.

PURPOSE: Evidence concerning the alteration of knee function during landing suffers from a lack of consensus. This uncertainty can be attributed to methodological flaws, particularly in relation to the statistical analysis of variable human movement data. The aim of this study was to compare single-subject and group analyses in detecting changes in knee stiffness and coordination during step landing that occur independent of an experimental intervention. METHODS: A group of healthy men (N=12) stepped-down from a knee-high platform for 60 consecutive trials, each trial separated by a 1-minute rest. The magnitude and within-participant variability of sagittal stiffness and coordination of the landing knee were evaluated with both group and single-subject analyses. RESULTS: The group analysis detected significant changes in knee coordination. However, the single-subject analyses detected changes in all dependent variables, which included increases in variability with task repetition. Between-individual variation was also present in the timing, size and direction of alterations. CONCLUSION: The results have important implications for the interpretation of existing information regarding the adaptation of knee mechanics to interventions such as fatigue, footwear or landing height. It is proposed that a participant's natural variation in knee mechanics should be analysed prior to an intervention in future experiments.

Is femoral nerve block necessary during total knee arthroplasty?: a randomized controlled trial.

There remains a lack of randomized controlled trials comparing methods of perioperative analgesia for total knee arthroplasty. To address this deficiency, a blinded, randomized controlled trial was conducted to compare the use of femoral nerve block (group F) and local anesthetic (group L). A sample of 55 patients who met the inclusion criteria were randomized to either group. No significant differences in the most severe pain score or 36-Item Short Form Health Survey, The Western Ontario and McMaster Universities Arthritis Index (WOMAC), or Oxford scores were observed between groups. However, the Knee Society score was significantly higher in group F. In addition, group F used significantly fewer micrograms of intravenous fentanyl in the first 24 hours. Balancing the risks of femoral nerve block with those of increased systemic narcotic delivery should be performed on a case-by-case basis.

Sagittal placement of the femoral component in total knee arthroplasty predicts knee flexion contracture at one-year follow-up.

PURPOSE: Flexion contracture has been shown to impair function and reduce satisfaction following total knee arthroplasty (TKA). The aim of this study was to identify modifiable intra-operative variables that predict post-TKA knee extension. METHODS: Data was collected prospectively on 95 patients undergoing total knee arthroplasty, including pre-operative assessment, intra-operative computer assisted surgery (CAS) measurements and functional outcome including range of motion at one year. Patients were divided into two groups: those with mild flexion contracture (> 5°) at the one-year follow-up and those achieving full extension. RESULTS: The sagittal orientation of the distal femoral cut differed significantly between groups at the one-year follow-up (p = 0.014). Sagittal alignment of greater than 3.5° from the mechanical axis was shown to increase the relative risk of a mild flexion contracture at one-year follow-up by 2.9 times, independent of other variables. CONCLUSION: Increasing the sagittal alignment of the distal femoral cut more than 3.5° from the mechanical axis is an independent risk factor for clinically detectable flexion contracture one year from index procedure.