Gait analysis after total knee arthroplasty. Comparison of posterior cruciate retention and substitution

BioMAT: An Open-Source Biomechanics Multi-Activity Transformer for Joint Kinematic Predictions Using Wearable Sensors

Through wearable sensors and deep learning techniques, biomechanical analysis can reach beyond the lab for clinical and sporting applications. Transformers, a class of recent deep learning models, have become widely used in state-of-the-art artificial intelligence research due to their superior performance in various natural language processing and computer vision tasks. The performance of transformer models has not yet been investigated in biomechanics applications. In this study, we introduce a Biomechanical Multi-activity Transformer-based model, BioMAT, for the estimation of joint kinematics from streaming signals of multiple inertia measurement units (IMUs) using a publicly available dataset. This dataset includes IMU signals and the corresponding sagittal plane kinematics of the hip, knee, and ankle joints during multiple activities of daily living. We evaluated the model's performance and generalizability and compared it against a convolutional neural network long short-term model, a bidirectional long short-term model, and multi-linear regression across different ambulation tasks including level ground walking (LW), ramp ascent (RA), ramp descent (RD), stair ascent (SA), and stair descent (SD). To investigate the effect of different activity datasets on prediction accuracy, we compared the performance of a universal model trained on all activities against task-specific models trained on individual tasks. When the models were tested on three unseen subjects' data, BioMAT outperformed the benchmark models with an average root mean square error (RMSE) of 5.5 ± 0.5°, and normalized RMSE of 6.8 ± 0.3° across all three joints and all activities. A unified BioMAT model demonstrated superior performance compared to individual task-specific models across four of five activities. The RMSE values from the universal model for LW, RA, RD, SA, and SD activities were 5.0 ± 1.5°, 6.2 ± 1.1°, 5.8 ± 1.1°, 5.3 ± 1.6°, and 5.2 ± 0.7° while these values for task-specific models were, 5.3 ± 2.1°, 6.7 ± 2.0°, 6.9 ± 2.2°, 4.9 ± 1.4°, and 5.6 ± 1.3°, respectively. Overall, BioMAT accurately estimated joint kinematics relative to previous machine learning algorithms across different activities directly from the sequence of IMUs signals instead of time-normalized gait cycle data.

Spatiotemporal parameters of the operated and non-operated knees before and after unilateral total knee arthroplasty

BACKGROUND

Knee osteoarthritis is a common condition in various orthopedic clinics and hospitals. The aim of this study was to investigate the effects of unilateral total knee arthroplasty (TKA) application on short and long-term spatiotemporal gait parameters, maximum plantar pressure (MPP), and functional status in patients with knee osteoarthritis.

RESEARCH QUESTION

What is the change process in spatiotemporal parameters without any intervention before and after TKA surgery?

METHODS

This study is a prospective and cross-sectional study. Participants were assessed preoperatively at the 1st week (Pre1W), postoperative 1st month (Post1M) and 6th month (Post6M). Spatiotemporal parameters and MMP were assessed using the Win Track platform (Medicapteurs Technology, France) and functional states were assessed using the Western Ontario and McMaster Universities Arthritis Index (WOMAC) and the Lequesne Index.

RESULTS

Significant improvements were found in the WOMAC and Lequesne Index values in the Post1M and Post6M periods compared to the preoperative period. However, the improvement in WOMAC and Lequesne Index scores in the Post6M period was significant compared to the scores in the Post1M period (p < 0.01). Spatiotemporal parameters deteriorated in the Post1M period, while improvements were observed in the Post6M period. We observed that patients had worse gait parameters in the near postoperative period than before surgery. It was the period with the greatest improvements in long-term outcomes.

SIGNIFICANCE

In the light of our study results, we think that early gait disturbances in patients who underwent direct TKA may be caused by physiological processes. Therefore, we believe that there is no need for any intervention for gait disorders that occur in the early postoperative period.

Walking on a compliant surface does not enhance kinematic gait asymmetries after unilateral total knee arthroplasty

PURPOSE

To investigate gait asymmetries and the effect of walking on compliant surfaces in individuals with unilateral total knee arthroplasty (TKA), hypothesizing that asymmetries would increase as an effect of the compliant surface.

METHODS

Individuals with unilateral TKA ~19 months post-operative (n = 23, median age 59 years) recruited from one orthopaedic clinic and age- and gender-matched healthy individuals without knee complaints (n = 23, median age 56 years) walked at comfortable speed on a hard surface and on a compliant surface. 3D kinematic analyses were made for knee and hip angles in sagittal and frontal planes, stance time, step length, and gait velocity.

RESULTS

Shorter stance time (p < 0.01) and less peak knee flexion (p < 0.001) at weight bearing acceptance was found in the prosthetic side compared with the contralateral side. Larger knee (p < 0.01) and hip (p < 0.001) adduction was found compared with healthy controls. Neither asymmetries between the prosthetic and the contralateral side nor differences compared with healthy controls were enhanced when walking on compliant surfaces compared with hard surfaces.

CONCLUSION

The TKA group adapted their gait to compliant surfaces similarly to healthy controls. Gait asymmetries in the TKA group observed on hard surface were not enhanced, and adduction in hip and knee joints did not increase further as an effect of walking on compliant surfaces. Thus, unfavourable knee joint loading did not increase when walking on a compliant surface. This implies that recommendations for walking on soft surfaces to reduce knee joint loading are not counteracted by increased gait asymmetries and unfavourable joint loading configurations.

LEVEL OF EVIDENCE

III.

Long-term data of gait characteristics and moment-knee angle relations in female total knee arthroplasty patients

BACKGROUND

Despite the clinical success of total knee arthroplasty, impaired gait patterns and quadriceps and hamstring maximal voluntary force production might persist years post-surgery. Long-term data of gait patterns and quadriceps and hamstring maximal force production are rarely published with total knee arthroplasty patients. This work examined gait characteristics and the moment-knee angle relations of the knee extensors and flexors about 10 years post-total knee arthroplasty.

METHODS

About a decade post-surgery, 10 female total knee arthroplasty patients (64 years, mobile-bearing inlay) and 10 age-matched female controls were examined. Sagittal plane kinematics in the hip and knee joint during treadmill walking at 2 kilometres per hour were recorded using motion analysis. Spatiotemporal gait parameters were analyzed at self-selected walking speeds with a pressure-platform. The unilateral isometric moment-knee angle relations of the knee extensors and flexors and the electromyographic knee angle relation of the quadriceps were studied using dynamometry. Due to group differences for body mass index values, univariate analysis of variance (main effect: group, secondary effect: body mass index) was used for statistical analysis.

FINDINGS

Total knee arthroplasty patients demonstrated significant (P<0.05) gait deficits during constant and self-selected walking speeds and lower average absolute values in the moment-knee angle relations of the knee extensors and flexors. Significant (P<0.05) lower body-mass-normalized knee extension moments were detected at all knee joint positions for the patients.

INTERPRETATION

Long-term impairments of gait characteristics and maximal voluntary force production, especially for the knee extensors, might persist after total knee arthroplasty.

Retention versus sacrifice of the posterior cruciate ligament in total knee arthroplasty for treating osteoarthritis

BACKGROUND

The functional and clinical basis on which to choose whether or not to retain the posterior cruciate ligament during total knee arthroplasty surgery remained unclear after a Cochrane systematic review and meta-analysis in 2005, which contained eight clinical trials. Several new trials have been conducted since then. Hence, an update of the review was performed.

OBJECTIVES

Our aim was to assess the benefits and harms of retention compared to sacrifice of the posterior cruciate ligament in total knee arthroplasty in patients with osteoarthritis of the knee.

SEARCH METHODS

An extensive search was conducted in CENTRAL, MEDLINE (PubMed), EMBASE, Web of Science, CINAHL, Academic Search Premier, Current Contents Connect and Science Direct. All databases were searched, without any limitations, up to 6 December 2012. References of the articles were checked and citation tracking was performed.

SELECTION CRITERIA

Randomised and quasi-randomised controlled trials comparing retention with sacrifice of the posterior cruciate ligament in primary total knee arthroplasty in patients with osteoarthritis of the knee.

DATA COLLECTION AND ANALYSIS

Data were collected with a pre-developed form. Risk of bias was assessed independently by two authors (WV, LB). The level of evidence was graded using the GRADE approach. Meta-analysis was performed by pooling the results of the selected studies, when possible. Subgroup analyses were performed for posterior cruciate ligament retention versus sacrifice using the same total knee arthroplasty design, and for studies using a posterior cruciate ligament retaining or posterior stabilised design, and when sufficient studies were available subgroup analyses were performed for the same brand.

MAIN RESULTS

Seventeen randomised controlled trials (with 1810 patients and 2206 knees) were found, described in 18 articles. Ten of these were new studies compared to the previous Cochrane Review. One study from the original Cochrane review was excluded. Most new studies compared a posterior cruciate ligament retaining design with a posterior stabilised design, in which the posterior cruciate ligament is sacrificed (a posterior stabilised design has an insert with a central post which can engage on a femoral cam during flexion).The quality of evidence (graded with the GRADE approach) and the risk of bias were highly variable, ranging from moderate to low quality evidence and with unclear or low risk of bias for most domains, respectively.The performance outcome 'range of motion' was 2.4 ° higher in favour of posterior cruciate ligament sacrifice (118.3 ° versus 115.9 °; 95% confidence interval (CI) of the difference 0.13 to 4.67; P = 0.04), however the results were heterogeneous. On the item 'knee pain' as experienced by patients, meta-analysis could be performed on the Knee Society knee pain score; this score was 48.3 in both groups, yielding no difference between the groups. Implant survival rate could not be meta-analysed adequately since randomised controlled trials lack the longer term follow-up in order to evaluate implant survival. A total of four revisions in the cruciate-retention and four revisions in the cruciate-sacrifice group were found. The well-validated Western Ontario and McMaster Universities osteoarthritis index (WOMAC) total score was not statistically significantly different between the groups (16.6 points for cruciate-retention versus 15.0 points for cruciate-sacrifice). One study reported a patient satisfaction grade (7.7 points for cruciate-retention versus 7.9 points for cruciate-sacrifice on a scale from 0 to 10, 10 being completely satisfied) which did not differ statistically significantly. Complications were distributed equally between both groups. Only one study reported several re-operations other than revision surgery; that is patella luxations, surgical manipulation because of impaired flexion.The mean functional Knee Society Score was 2.3 points higher (81.2 versus 79.0 points; 95% CI of the difference 0.37 to 4.26; P = 0.02) in the posterior cruciate ligament sacrificing group. Results from the outcome Knee Society functional score were homogeneous. All other outcome measures (extension angle, knee pain, adverse effects, clinical questionnaire scores, Knee Society clinical scores, radiological rollback, radiolucencies, femorotibial angle and tibial slope) showed no statistically significant differences between the groups. In the subgroup analyses that allowed pooling of the results of the different studies, no homogeneous statistically significant differences were identified.

AUTHORS' CONCLUSIONS

The methodological quality and the quality of reporting of the studies were highly variable. With respect to range of motion, pain, clinical, and radiological outcomes, no clinically relevant differences were found between total knee arthroplasty with retention or sacrifice of the posterior cruciate ligament. Two statistically significant differences were found; range of motion was 2.4 ° higher in the posterior cruciate ligament sacrificing group, however results were heterogeneous; and the mean functional Knee Society Score was 2.3 points higher in the posterior cruciate ligament sacrificing group. These differences are clinically not relevant.

Comparison of the primary stability of different tibial baseplate concepts to retain both cruciate ligaments during total knee arthroplasty

BACKGROUND

A novel tibial baseplate design (Transversal Support Tibial Plateau) as a new treatment concept for bi-cruciate retaining total knee arthroplasty is evaluated for mechanical stability and compared to other tibial baseplate designs. This concept should provide better primary stability and thus, less subsidence, than implantation of two separate unicondylar tibial baseplates.

METHODS

Different baseplates were implanted into synthetic bone specimens (Sawbones® Pacific Research Laboratories, Inc., Washington, USA), all uncemented. Using a standardized experimental setup, subsidence was achieved, enabling comparison of the models regarding primary stability.

FINDINGS

Overall implant subsidence was significantly increased for the two separate unicondylar tibial baseplates versus the new Transversal Support Tibial Plateau concept, which showed comparable levels to a conventional tibial baseplate. Reduced subsidence results in better primary stability.

INTERPRETATION

Linking of two separate baseplates appears to provide increased primary stability in terms of bony fixation, comparable to that of a conventional single tibial baseplate.

Unicompartmental knee arthroplasty enables near normal gait at higher speeds, unlike total knee arthroplasty

Top walking speed (TWS) was used to compare UKA with TKA. Two groups of 23 patients, well matched for age, gender, height and weight and radiological severity were recruited based on high functional scores, more than twelve months post UKA or TKA. These were compared with 14 preop patients and 14 normal controls. Their gait was measured at increasing speeds on a treadmill instrumented with force plates. Both arthroplasty groups were significantly faster than the preop OA group. TKA patients walked substantially faster than any previously reported series of knee arthroplasties. UKA patients walked 10% faster than TKA, although not as fast as the normal controls. Stride length was 5% greater and stance time 7% shorter following UKA - both much closer to normal than TKA. Unlike TKA, UKA enables a near normal gait one year after surgery.

Lower limb biomechanics in individuals with knee osteoarthritis before and after total knee arthroplasty surgery

We investigated the biomechanical changes that occur in the lower limb following total knee arthroplasty (TKA). Lower limb joint kinematics and kinetics were evaluated in 32 patients before and 12 months following TKA and 28 age-matched controls. Analysis of variance with Bonferroni-adjusted post-hoc tests showed no significant changes in knee joint kinematics and kinetics following TKA despite significant improvements in pain and function. Significant increases in peak ankle plantarflexion and dorsiflexion moments and ankle power generation were observed which may be a compensatory response to impaired knee function to allow sufficient power generation for propulsion. Differences in knee gait parameters may arise as a result of the presence of osteoarthritis and mechanical changes associated with TKA as well as retention of the pre-surgery gait pattern.

Trunk muscle action compensates for reduced quadriceps force during walking after total knee arthroplasty

Patients with total knee arthroplasty (TKA) frequently exhibit changes in gait biomechanics post-surgery, including decreased ranges of joint motion and changes in joint loading; however, the actions of the lower-limb muscles in generating joint moments and accelerating the center of mass (COM) during walking are yet to be described. The aim of the present study was to evaluate differences in lower-limb joint kinematics, muscle-generated joint moments, and muscle contributions to COM accelerations in TKA patients and healthy age-matched controls when both groups walk at the same speed. Each TKA patient was fitted with a posterior-stabilized total knee replacement and underwent patellar resurfacing. Three-dimensional gait analysis and subject-specific musculoskeletal modeling were used to determine lower-limb and trunk muscle forces and muscle contributions to COM accelerations during the stance phase of gait. The TKA patients exhibited a 'quadriceps avoidance' gait pattern, with the vasti contributing significantly less to the extension moment developed about the knee during early stance (p=0.036). There was a significant decrease in the contribution of the vasti to the vertical acceleration (support) (p=0.022) and forward deceleration of the COM (braking) (p=0.049) during early stance; however, the TKA patients compensated for this deficiency by leaning their trunks forward. This significantly increased the contribution of the contralateral back extensor muscle (erector spinae) to support (p=0.030), and that of the contralateral back rotators (internal and external obliques) to braking (p=0.004). These findings provide insight into the biomechanical causes of post-operative gait adaptations such as 'quadriceps avoidance' observed in TKA patients.

Optimized Design of an Instrumented Spatial Linkage that Minimizes Errors in Locating the Rotational Axes of the Tibiofemoral Joint: A Computational Analysis

An accurate method to locate of the flexion-extension (F-E) axis and longitudinal rotation (LR) axis of the tibiofemoral joint is required to accurately characterize tibiofemoral kinematics. A method was recently developed to locate these axes using an instrumented spatial linkage (ISL) (2012, “On the Estimate of the Two Dominant Axes of the Knee Using an Instrumented Spatial Linkage,” J. Appl. Biomech., 28(2), pp. 200–209). However, a more comprehensive error analysis is needed to optimize the design and characterize the limitations of the device before using it experimentally. To better understand the errors in the use of an ISL in finding the F-E and LR axes, our objectives were to (1) develop a method to computationally determine the orientation and position errors in locating the F-E and LR axes due to transducer nonlinearity and hysteresis, ISL size and attachment position, and the pattern of applied tibiofemoral motion, (2) determine the optimal size and attachment position of an ISL to minimize these errors, (3) determine the best pattern of pattern of applied motion to minimize these errors, and (4) examine the sensitivity of the errors to range of flexion and internal-external (I-E) rotation. A mathematical model was created that consisted of a virtual “elbow-type” ISL that measured motion across a virtual tibiofemoral joint. Two orientation and two position errors were computed for each axis by simulating the axis-finding method for 200 iterations while adding transducer errors to the revolute joints of the virtual ISL. The ISL size and position that minimized these errors were determined from 1080 different combinations. The errors in locating the axes using the optimal ISL were calculated for each of three patterns of motion applied to the tibiofemoral joint, consisting of a sequential pattern of discrete tibiofemoral positions, a random pattern of discrete tibiofemoral positions, and a sequential pattern of continuous tibiofemoral positions. Finally, errors as a function of range of flexion and I-E rotation were determined using the optimal pattern of applied motion. An ISL that was attached to the anterior aspect of the knee with 300-mm link lengths had the lowest maximum error without colliding with the anatomy of the joint. A sequential pattern of discrete tibiofemoral positions limited the largest orientation or position error without displaying large bias error. Finally, the minimum range of applied motion that ensured all errors were below 1 deg or 1 mm was 30 deg flexion with ±15 deg I-E rotation. Thus a method for comprehensive analysis of error when using this axis-finding method has been established, and was used to determine the optimal ISL and range of applied motion; this method of analysis could be used to determine the errors for any ISL size and position, any applied motion, and potentially any anatomical joint.

Dynamic joint stiffness and co-contraction in subjects after total knee arthroplasty

BACKGROUND

Although total knee arthroplasty reduces pain and improves function, patients continue to walk with asymmetrical movement patterns, that may affect muscle activation and joint loading patterns. The purpose of this study was to evaluate the specific biomechanical abnormalities that persist after total knee arthroplasty and examine the neuromuscular mechanisms that may contribute to these asymmetries.

METHODS

Dynamic joint stiffness at the hip, knee and ankle, as well as co-contraction at the knee and ankle, were compared between the operated and non-operated limbs of 32 subjects who underwent total knee arthroplasty and 21 subjects without lower extremity impairment.

FINDINGS

Subjects after total knee arthroplasty demonstrated higher dynamic joint stiffness in the operated knee compared to the non-operated knee (0.056 (0.023) Nm/kg/m/deg vs. 0.043 (0.016) Nm/kg/m/deg, P=0.003) and the knees from a control group without lower extremity pathology (controls: 0.042 (0.015) Nm/kg/m/deg, P=0.017). No differences were found between limbs or groups for dynamic joint stiffness at the hip or ankle. There was no relationship between dynamic joint stiffness at the knee and ankle and the amount of co-contraction between antagonistic muscles at those joints.

INTERPRETATION

Patients after total knee arthroplasty walk with less knee joint excursion and greater knee stiffness, although no differences were found between groups for stiffness at the hip or ankle. Mechanisms other than co-contraction are likely the underlying cause of the altered knee mechanics. These findings are clinically relevant because the goal should be to create interventions to reduce these abnormalities and increase function.

Changes in varus-valgus laxity after total knee arthroplasty over time

PURPOSE

This randomized, prospective study was performed to evaluate changes in varus-valgus laxity over time and to evaluate the relationship between laxity and retention of the posterior cruciate ligament.

METHODS

Sixty knees of 60 patients with osteoarthritis received mobile-bearing prostheses. Thirty patients received posterior cruciate ligament-retaining prostheses (average follow-up, 75 months), and 30 patients received posterior cruciate ligament-sacrificing prostheses (average follow-up, 78 months). Varus-valgus laxity was measured with the knee in extension at 6 months, 1 and 2 years after surgery, and at final follow-up examination (average, 77 months).

RESULTS

Varus laxity measurements for patients with posterior cruciate ligament-retaining prostheses at 6 months, 1 year, 2 years, and final examination were 3.7° ± 1.2°, 4.0° ± 1.3°, 4.1° ± 1.7°, and 4.2° ± 1.3°, respectively; corresponding valgus laxity measurements were 3.5° ± 1.1°, 3.5° ± 1.3°, 3.5° ± 1.1°, and 3.6° ± 1.1°, respectively. Varus laxity measurements for patients with posterior cruciate ligament-sacrificing prostheses at 6 months, 1 year, 2 years, and final examination were 4.3° ± 1.9°, 4.3° ± 1.9°, 4.3° ± 1.8°, and 4.4° ± 1.7°, respectively; corresponding valgus laxity measurements were 3.7° ± 1.3°, 3.4° ± 1.3°, 3.5° ± 1.1°, and 3.6° ± 1.3°, respectively.

CONCLUSIONS

There were no significant differences in varus and valgus laxities between the two groups. This study demonstrates that coronal laxity does not change over time in either type of knee prostheses and that the posterior cruciate ligament does not affect coronal stability during varus-valgus stress.

LEVEL OF EVIDENCE

Prognostic study, See the Guidelines for Authors for a complete description of levels of evidence, Level I.

Gait analysis comparison of cruciate retaining and substituting TKA following PCL sacrifice

The role of the posterior cruciate ligament (PCL) remains controversial in total knee arthroplasty (TKA), with some surgeons who believe in PCL sacrifice and substitution and others who believe in PCL preservation for stability. Manufacturers have developed both cruciate-substituting/posterior stabilized (PS) implants typically used when the ligament is sacrificed and cruciate retaining (CR) implants designed for ligament preservation. However, studies demonstrate excellent clinical results with CR implants despite PCL sacrifice. This study sought to determine functional stability differences between PS and CR TKAs following PCL sacrifice. Eighteen (9 matched pairs) subjects with either a PS or CR TKA and sacrificed PCL and a normal contralateral knee were subjected to physical exam and gait analysis (walking, stair ascent and descent) using a staircase model, passive reflective arrays and an optoelectric system. No differences were detected between the two groups among any of the measured parameters (knee flexion angle, knee flexion moment, knee power absorption, pelvic tilt). PCL sacrifice in a well-balanced cruciate retaining TKA did not result in instability during stair descent based on gait parameters. The decision to use a posterior stabilized design when faced with an incompetent PCL intraoperatively should be based on factors other than anticipated instability.

Changes in lower extremity 3-dimensional load-bearing axes before and after mobile-bearing total knee arthroplasty

This study evaluated changes in the lower extremity 3-dimensional load-bearing mechanical axes in the anteroposterior and mediolateral directions before and at 3 weeks after mobile-bearing total knee arthroplasty. The effects of the degrees of anteroposterior constraint of the designs on the location of the load-bearing mechanical axis at the knee joint level were also assessed. We evaluated 151 knees from 134 patients with 74 knees receiving meniscal bearing-type and 77 knees receiving rotating platform-type prostheses. In the mediolateral direction, both designs showed significant improvements, whereas in the anteroposterior direction, they revealed no improvements postoperatively and were worsened significantly in meniscal bearing type. Differences in the degree of bone and soft tissue involvement for the correction of alignment may explain the findings.

The importance to including objective functional outcomes in the clinical follow up of total knee arthroplasty patients

In clinical practice, it is increasingly important to assess patients' daily functionality routinely and objectively. Acceleration-based gait analysis (AGA) has shown to be reliable and technically suitable for routine clinical use outside the laboratory. This study investigated the suitability of AGA for measuring function in orthopaedic patients with symptomatic gonarthrosis listed for total knee arthroplasty (TKA) by investigating (a) the ability of AGA to distinguish patients from healthy subjects, (b) the sensitivity to gait changes of AGA in assessing recovery following total knee arthroplasty in a subpopulation, and (c) correlations between AGA parameters and clinical scales. Gait was assessed using AGA in 24 patients with symptomatic gonarthrosis listed for TKA, and in 24 healthy subjects. AGA parameters (e.g. speed, asymmetry) and clinical scales (e.g. KSS) were used to monitor progress in 12 patients 3 months after TKA. The Mann-Whitney-U test, Receiver Operating Characteristic (ROC) curves, repeated measurement ANOVA and Pearson correlations were performed. AGA differentiated pathological from healthy gait. The area under the ROC curve, sensitivity and specificity values were high for speed, step frequency and step length. Different recovery profiles were found, with clinical scales showing faster recovery rates. None or only weak correlations were found between AGA and clinical scores. AGA was found to be of clinical relevance in identifying and monitoring patients with symptomatic gonarthrosis in orthopaedic practice, providing objective and additional information about function beyond clinical scales. This, together with the fact that AGA can be applied routinely, suggests the suitability of AGA for use in rehabilitation programs.

Navigational predictors in determining the necessity for collateral ligament release in total knee replacement

The requirement for release of collateral ligaments to achieve a stable, balanced total knee replacement has been reported to arise in about 50% to 100% of procedures. This wide range reflects a lack of standardised quantitative indicators to determine the necessity for a release. Using recent advances in computerised navigation, we describe two navigational predictors which provide quantitative measures that can be used to identify the need for release. The first was the ability to restore the mechanical axis before any bone resection was performed and the second was the discrepancy in the measured medial and lateral joint spaces after the tibial osteotomy, but before any femoral resection.

These predictors showed a significant association with the need for collateral ligament release (p < 0.001). The first predictor using the knee stress test in extension showed a sensitivity of 100% and a specificity of 98% and the second, the difference between medial and lateral gaps in millimetres, a sensitivity of 83% and a specificity of 95%. The use of the two navigational predictors meant that only ten of the 93 patients required collateral ligament release to achieve a stable, neutral knee.

Design and evaluation of a new general-purpose device for calibrating instrumented spatial linkages

Because instrumented spatial linkages (ISLs) have been commonly used in measuring joint rotations and must be calibrated before using the device in confidence, a calibration device design and associated method for quantifying calibration device error would be useful. The objectives of the work reported by this paper were to (1) design an ISL calibration device and demonstrate the design for a specific application, (2) describe a new method for calibrating the device that minimizes measurement error, and (3) quantify measurement error of the device using the new method. Relative translations and orientations of the device were calculated via a series of transformation matrices containing inherent fixed and variable parameters. These translations and orientations were verified with a coordinate measurement machine, which served as a gold standard. Inherent fixed parameters of the device were optimized to minimize measurement error. After parameter optimization, accuracy was determined. The root mean squared error (RMSE) was 0.175 deg for orientation and 0.587 mm for position. All RMSE values were less than 0.8% of their respective full-scale ranges. These errors are comparable to published measurement errors of ISLs for positions and lower by at least a factor of 2 for orientations. These errors are in spite of the many steps taken in design and manufacturing to achieve high accuracy. Because it is challenging to achieve the accuracy required for a custom calibration device to serve as a viable gold standard, it is important to verify that a calibration device provides sufficient precision to calibrate an ISL.

Is gait normal after total knee arthroplasty? Systematic review of the literature

BACKGROUND

Development or retention of abnormal gait patterns after total knee arthroplasty may be related to the predictable pattern of further deterioration of other lower extremity joints. The purpose of this study was to determine whether gait mechanics are abnormal after total knee arthroplasty by conducting a systematic review of the literature.

METHODS

Articles were identified by searching the following electronic databases: PubMed, Cinahl, Web of Science: 221 references were retrieved. The titles and abstracts were reviewed to identify studies that potentially met the inclusion criteria. These articles were retrieved for further assessment. Ten articles met the inclusion criteria and were included in the review.

RESULTS

There was a lack of common variables across the studies. Studies indicated smaller peak knee flexion during weight acceptance and less knee flexion excursion in total knee arthroplasty subjects compared to controls. Knee angle at foot strike was generally similar in arthroplasty groups compared to controls. Maximum external knee flexion moment was generally lower in arthroplasty groups compared to controls. Conflicting results were found for other knee moments. Several other stance phase variables were reported by individual studies only.

CONCLUSIONS

Peak knee flexion and knee flexion excursion during weight acceptance are smaller in the operated knee following total knee arthroplasty compared to healthy controls. There may also be a smaller peak knee flexion moment after arthroplasty compared to controls. Knee mechanics in the operated knee are not normal after total knee arthroplasty. Abnormal gait mechanics may predispose the individual to further joint degeneration, particularly in the nonoperated knee. Further research should focus on the effects of unilateral total knee arthroplasty on the nonoperated knee.

The application of support vector machines for detecting recovery from knee replacement surgery using spatio-temporal gait parameters

Knee osteoarthritis (OA) is one of the leading causes of disability among the elderly which, depending on severity, may require surgical intervention. Knee replacement surgery provides pain relief and improves physical function including gait. However gait dysfunction such as altered spatio-temporal measures may persist after the surgery. In this paper, we investigated the application of support vector machines (SVM) to classify gait patterns indicative of knee OA before surgery based on 12 spatio-temporal gait parameters and investigated whether SVMs could be used to predict gait improvement 2 and 12 months following knee replacement surgery. Test results for the pre-operative data indicated that the SVM could successfully identify individuals with OA gait from the healthy using all of the spatio-temporal parameters with a maximum leave one out accuracy of 100% for the training set and 88.89% for the test set. Findings indicated that three patients still had altered gait patterns 2 months post-knee replacement surgery, but all individuals showed improvement in gait 12 months following surgery. Consequently, the SVM detected improvement in gait function due to surgical intervention at 2 and 12 months following knee replacement which coincided with clinical assessment of the knee. This suggests that spatio-temporal parameters contain important discriminative information which may be used for the identification of pathological gait using an SVM classifier.

Knee range of motion during the first two years after use of posterior cruciate-stabilizing or posterior cruciate-retaining total knee prostheses. A randomized clinical trial

BACKGROUND

The impact of posterior cruciate ligament-substituting and posterior cruciate ligament-retaining devices on the range of motion of the knee following primary total knee arthroplasty is unclear. The primary objective of our study was to compare the range of motion of the knee over the first two postoperative years between subjects who had received the ligament-substituting design and those who had received the ligament-retaining design. Secondarily, pain, function, and health-related quality of life were compared between the two groups.

METHODS

We undertook a prospective randomized study of 100 patients with noninflammatory osteoarthritis who were undergoing primary total knee arthroplasty. Patients were randomized at the time of surgery to receive one of the two study prosthesis designs. They were evaluated preoperatively, at the time of hospital discharge, at three months postoperatively, and at up to two years postoperatively by a physical therapist who was blinded to the group allocation. Active knee flexion and extension, measured with a goniometer, were the primary outcome measures. Self-reported pain, function, and health-related quality of life were measured with the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and the RAND 36-Item Health Survey (RAND-36). Complications and revision rates were determined through hospital record review and at each patient evaluation.

RESULTS

Eighty percent (seventy-eight) of the ninety-eight available patients returned for the final assessment. At two years postoperatively, the mean difference between the groups with regard to knee flexion was 0.03 degrees (95% confidence interval, -5.9 degrees to 6.0 degrees ) and the mean difference in knee extension was 1.0 degrees (95% confidence interval, -0.36 degrees to 2.4 degrees ). Ninety-one (93%) of the ninety-eight available patients completed questionnaires at the time of the final assessment. The two treatment groups had similar pain, function, and quality-of-life scores and complication rates. One subject in the cruciate-retaining group required revision, secondary to a deep joint infection, and one subject in the cruciate-substituting group required manipulation to address poor knee flexion.

CONCLUSIONS

Overall, the two treatment groups had a similar range of motion of the knee over the initial two-year postoperative time period. A satisfactory range of motion was achieved by three months postoperatively and was maintained at the final assessment.

Evaluation of joint laxity against distal traction force upon flexion in cruciate-retaining and posterior-stabilized total knee arthroplasty

BACKGROUND

Several studies have reported varus-valgus stability in the extension position after total knee arthroplasty (TKA). However, few studies have evaluated joint laxity in the flexion position postoperatively. The purpose of the study was to evaluate joint laxity against distal traction force on flexion after cruciate-retaining and posterior-stabilized total knee arthroplasties.

METHODS

A total of 44 knees (22 knees cruciate-retaining, 22 knees posterior-stabilized) in 40 patients with osteoarthritis were tested in this study. The subjects were seated at a table and their knee joints were fixed at 80 degrees of flexion to avoid overlapping images of condyles and the femoral shaft. Tibial shafts were adjusted to be parallel to the radiographic films, and posteroanterior radiographs were obtained. Flexion stress tests were performed with a distal traction of 100 N at a neutral foot position. Radiographs were obtained at neutral and traction positions. The distance from the perpendicular line of the top of the polyethylene insert to the midpoint on the tangential line of the femoral condyle was measured (joint space distance) at each side.

RESULTS

In the flexion-neutral position, average joint space distances were 0.1 +/- 0.2 mm in cruciate-retaining (CR) TKA knees and 0.2 +/- 0.3 mm in posterior-stabilized (PS) TKA knees. With flexion-traction stress tests, the average joint space distances were 0.5 +/- 0. 5 mm in CR TKA knees 2.4 +/- 1.2 mm in PS TKA knees. Average changes of joint space distances between the two positions were 0.3 +/- 0.4 mm (CR TKA) and 2.2 +/- 1.5 mm (PS TKA). The changes in joint space distances between neutral and traction positions of PS TKA knees were significantly larger than those of CR TKA knees in flexion stress tests (P < 0.01).

CONCLUSION

The posterior cruciate ligament acted as a stabilizer against distal traction force in the CR-TKA knees. However, the laxity of PS-TKA knees against distal force differed among individual cases.

Support Vector Machines for detecting recovery from knee replacement surgery using quantitative gait measures

Knee osteoarthritis (OA) is one of the leading causes of disability among the elderly which, depending on severity, may require surgical intervention. Knee replacement surgery provides pain relief and improves physical function including gait. Gait dysfunction such as altered spatio-temporal measures and gait asymmetry both pre- and post-surgery, however, may still persist after the surgery. In this paper, we investigated the application of Support Vector Machines (SVM) to classify gait patterns pertaining to knee OA before surgery based on spatio-temporal gait parameters and to investigate whether SVM can assess gait improvement at 2 months following knee replacement surgery. Test results indicate that the SVM can identify the OA gait from the healthy ones with a max leave one out (LOO) accuracy of 94.2%. When feature selection technique was applied, the accuracy improved to 97.1% using only 2 symmetry index features. Further, the post surgery test results by the SVM indicated 4 patients still had altered gait. This suggests that subject gait symmetry should be monitored closely after surgery to assess treatment outcomes and recovery.

Gait analysis of patients following total knee replacement: a systematic review

Gait analysis has been used to objectively measure patients' function following total knee replacement (TKR). Whilst the findings of this research may have important implications for the understanding of the outcomes of TKR, the methodology of existing research appears to be diverse and many of the results inconsistent. The objective of this systematic review was to synthesise reported findings and to summarise the methods used by researchers in this field. Eleven articles published in the medical literature that used gait analysis to compare patients following TKR with controls were identified for inclusion in this review. Each article was assessed for methodologic quality and data was compared across studies through the calculation of effect sizes. Consistently large effect sizes showed that patients following TKR walk with less total knee motion during gait and with less knee flexion during swing than controls. Kinetic discrepancies between patients and controls were also identified. The substantial methodologic differences between studies may contribute to the inconsistencies in reported findings for many gait outcomes. Future research is needed to determine the clinical relevance of these findings.

Design and demonstration of a new instrumented spatial linkage for use in a dynamic environment: application to measurement of ankle rotations during snowboarding

Joint injuries during sporting activities might be reduced by understanding the extent of the dynamic motion of joints prone to injury during maneuvers performed in the field. Because instrumented spatial linkages (ISLs) have been widely used to measure joint motion, it would be useful to extend the functionality of an ISL to measure joint motion in a dynamic environment. The objectives of the work reported by this paper were to (i) design and construct an ISL that will measure dynamic joint motion in a field environment, (ii) calibrate the ISL and quantify its static measurement error, (iii) quantify dynamic measurement error due to external acceleration, and (iv) measure ankle joint complex rotation during snowboarding maneuvers performed on a snow slope. An "elbow-type" ISL was designed to measure ankle joint complex rotation throughout its range (+/-30 deg for flexion/extension, +/-15 deg for internal/external rotation, and +/-15 deg for inversion/eversion). The ISL was calibrated with a custom six degree-of-freedom calibration device generally useful for calibrating ISLs, and static measurement errors of the ISL also were evaluated. Root-mean-squared errors (RMSEs) were 0.59 deg for orientation (1.7% full scale) and 1.00 mm for position (1.7% full scale). A custom dynamic fixture allowed external accelerations (5 g, 0-50 Hz) to be applied to the ISL in each of three linear directions. Maximum measurement deviations due to external acceleration were 0.05 deg in orientation and 0.10 mm in position, which were negligible in comparison to the static errors. The full functionality of the ISL for measuring joint motion in a field environment was demonstrated by measuring rotations of the ankle joint complex during snowboarding maneuvers performed on a snow slope.

Three-dimensional kinematics and kinetics of total knee arthroplasty during level walking using single plane video-fluoroscopy and force plates: a pilot study

The goal of the study was to simultaneously obtain accurate kinematic and kinetic data from a total knee arthroplasty (TKA) during level walking, by coupling force plate data with the kinematics of TKA measured by a movable video-fluoroscopic system. Kinematic and kinetic information of a TKA is crucial for the improvement of implant designs and for the increased longevity of the implant components. Instrumented gait analysis, with skin mounted marker tracking and force plates, is a well-established method for the acquisition of kinematic and kinetic data of TKA in vivo and for non-invasive estimation of joint function. However, resultant moments at the knee joint are inaccurate with this method, due to skin movement artifacts. Video-fluoroscopy reduces these inaccuracies by means of the direct tracking of the implant components with X-ray. However this measuring technique carries disadvantages: it provides only kinematic data, and the image intensifier covers a limited field of view. This paper presents a newly developed measuring technique, which enables a more accurate resultant moments calculation for level walking than could be achieved by conventional instrumented gait analysis.

Three-dimensional knee motion before and after high tibial osteotomy for medial knee osteoarthritis

BACKGROUND

High tibial osteotomy (HTO) is an established surgical option for treating medial knee osteoarthritis. HTO moves the mechanical load on the knee joint from the medial compartment to the lateral compartment by changing the leg alignment, but the effects of the operation remain unclear. The purpose of this study was to evaluate the change in three-dimensional knee motion before and after HTO, focusing on lateral thrust and screw home movement, and to investigate the relationship between the change in knee motion and the clinical results.

METHODS

A series of 19 patients with medial knee osteoarthritis who had undergone HTO were evaluated. We performed a clinical assessment, radiological evaluation, and motion analysis at 2.4 years postoperatively. The clinical assessment was performed using the Japanese Orthopaedic Association knee score.

RESULTS

The score was significantly improved in all patients after operation. Motion analysis revealed that lateral thrust, which was observed in 18 of the 20 knees before operation, was reduced to 7 knees after operation. Regarding active terminal extension of the knee, three patterns of rotational movement were observed before operation: screw home movement (external rotation), reverse screw home movement (internal rotation), and no rotation. By contrast, after operation, only reverse screw home movement and no rotation were observed; the screw home movement disappeared in all patients. In the knees with reverse screw home movement after operation, the preoperative score was significantly lower than those in the knees with no rotation after operation.

CONCLUSIONS

Kinetically, HTO was useful for suppressing lateral thrust in medial knee osteoarthritis, although the rotational movement of the knee joint was unchanged.

Status of physiotherapy rehabilitation after total knee replacement in Australia

BACKGROUND AND PURPOSE

Owing to a scarcity of clinical research, evidence-based clinical guidelines are not available to guide physiotherapy rehabilitation after total knee replacement surgery. This is despite the fact that, annually, over 20000 patients in Australia, over 300 000 patients in North America and 36 000 patients in the UK potentially require rehabilitation at this time to regain functional independence and to resume recreational and work-related physical activities. This survey of clinicians aimed to describe standard (usual) care after total knee replacement in Australia and to provide possible explanations for practice variance, if such variation exists.

METHOD

A nationwide postal survey involving public and privately funded hospital physiotherapy departments was conducted. Purposive sampling was used to randomly select hospitals from the National Joint Replacement Registry. A series of closed and open-ended protocol-based questions were asked.

RESULTS

A response rate of 65% (65/100) was obtained. Elements of consistency and diversity across the acute and post-acute phases were evident. Consistent findings included the provision of gait retraining and exercise prescription in the acute period, the requirement for independent ambulation as a criterion for discharge from acute care and the routine referral to ongoing outpatient or community-based physiotherapy. Less consistency was reported for the use of continuous passive motion and cryotherapy in the acute phase, the modes of ongoing rehabilitation, discharge from rehabilitation criteria and the tools for measuring outcomes. Both institutional and non-institutional factors appeared to explain the demonstrated practice variation.

CONCLUSIONS

In order to propagate evidence-based practice guidelines and uniformity in care, well-designed clinical trials are required to identify cost-effective rehabilitation programmes after total knee replacement.

Retention versus removal of the posterior cruciate ligament in total knee replacement: a systematic literature review within the Cochrane framework

BACKGROUND

There is no consensus as to whether to use a posterior cruciate ligament (PCL) retaining design or a posterior-stabilized design for total knee arthroplasty. The objective of this study was to establish the difference in functional, clinical, and radiological outcome between retention and removal of the PCL.

METHODS

We conducted a search in Medline, EMBASE, the Cochrane database, and Current Contents, along with reference checks and citation tracking. Randomized controlled trials were selected and methodological quality was assessed with the van Tulder and Jadad checklists by 2 independent reviewers.

RESULTS

We found 8 randomized controlled trials. 2 treatment options were compared against PCL retention: PCL removal without post and cam mechanism (2 studies), and posterior-stabilized design (5 studies). 1 study included all 3 options. Range of motion was found to be 8 degrees higher (105 degrees vs. 113 degrees ) in the posterior-stabilized group compared to the PCL retention group (p = 0.01, 95% CI (1.7, 15)).

INTERPRETATION

These results should be interpreted with caution, as the methodological quality of the studies was highly variable. Suggestions are given to improve future research on this specific aspect of knee arthroplasty.

Retention versus sacrifice of the posterior cruciate ligament in total knee replacement for treatment of osteoarthritis and rheumatoid arthritis

BACKGROUND

The functional and clinical results to support the choice whether or not to retain the posterior cruciate ligament (PCL) during total knee arthroplasty have not been gathered and analysed so far. There are at least some trials showing no difference.

OBJECTIVES

To identify the difference in functional, clinical, and radiological outcome between retention and sacrifice of the PCL in total knee arthroplasty in patients with osteoarthrosis and other non-traumatic diseases.

SEARCH STRATEGY

A search was conducted in MEDLINE(Through PubMed; 1966 - March 2004), EMBASE (1980 - March 2004), Cochrane Central Register of Controlled Trials (CENTRAL Issue 2004 - 1), and Current Contents (1996 - March 2004). Also, references of selected articles were checked and citation tracking on the articles selected was performed.

SELECTION CRITERIA

Randomised controlled trials comparing retention to sacrifice of the PCL during total knee arthroplasty with regard to functional, radiological and clinical outcome in patients with osteoarthritis and other non-traumatic diseases were selected by two independent reviewers.

DATA COLLECTION AND ANALYSIS

Methodological quality was assessed with the checklist by van Tulder and the Jadad list. Data was collected with a predeveloped form. Meta-analysis was performed with subgroup analyses on age, gender, disease severity, and follow-up time, if allowed by adequate power.

MAIN RESULTS

Eight randomised controlled trials were found. Two treatment options were compared against PCL retention: PCL sacrifice without additional stabilisation (post and cam mechanism) (2 studies), and PCL sacrifice with posterior stabilized design (5 studies). One study included all three options. Range of motion was found to be 8.1 degrees higher in the posterior stabilized group compared to the PCL retention group (p=0.01, 95% confidence interval [1.7, 14.5]), although the heterogeneity was high (I(2 )= 66.3%). PCL resection without substituting the PCL with a posterior stabilised prosthesis showed no difference compared to PCL retention (p=0.31, I(2) = 83.2%). On clinical scores, only Hospital for Special Surgery score revealed a significant difference of 1.6 points (p=0.03, 95% confidence interval [-3.1, -0.1]) between PCL retention versus PCL sacrifice and substitution combined favouring the latter group. The necessary subgroup analyses could not be performed for the clinical scores.

AUTHORS' CONCLUSIONS

These results should be interpreted with caution as the methodological quality of the studies was highly variable. We conclude that there is, so far, no solid base for the decision to either retain or sacrifice the PCL with or without use of a posterior stabilized design during total knee arthroplasty. The technique of PCL retention is difficult because the normal configuration and tension need to be reproduced with ligament tensioners. Knowledge of the technique needs to be improved before it can yield superior results compared to the more straightforward techniques of PCL sacrifice or use of a posterior stabilized design. Also, studies evaluating the effect of both techniques should address the right outcome parameters such as range of motion, contact position, and anterior-posterior stability. Suggestions are given to improve future research on this specific topic of knee arthroplasty.

Primary total knee arthroplasty using the Genesis I total knee prosthesis: a 5- to 10-year follow-up study

This study analyzed the data from 82 primary total knee arthroplasties performed in 74 patients using the Genesis Total Knee Arthroplasty System. Ten men and 64 women with a mean age of 78 years were evaluated at a mean follow-up of 7 years. Seventy procedures used cemented femoral and tibial components, and 12 used cementless femoral and tibial components. The preoperative mean HSS score was 39. At the most recent follow-up, the mean HSS score increased to 92. The mean preoperative range of motion was 82 degrees and increased to 108 at the most recent follow-up. Clinically, there were 63 excellent (77%), 14 good (17%), 4 fair (5%), and 1 poor (1%) result.

Effect of soft tissue tension on measurements of coronal laxity in mobile-bearing total knee arthroplasty

BACKGROUND

The purpose of this study was to determine the effect of intraoperative coronal laxity in total knee arthroplasty on the postoperative condition.

METHODS

We conducted stress arthrometric studies using a Telos arthrometer on 40 knees in 36 patients. Both posterior cruciate ligament-retaining (PCLR) prostheses and posterior cruciate-sacrificing (PCLS) prostheses were placed in 20 knees respectively. All of the TKA procedures were judged clinically successful (Hospital for Special Surgery scores: PCLR 92 +/- 3 points, PCLS 91 +/- 4 points). Laxities were measured under spinal anesthesia (immediately postoperatively) and 6 months postoperatively.

RESULTS

PCLR prostheses had an average of 2.9 degrees +/- 1.8 degrees and 3.0 degrees +/- 1.2 degrees in abduction and 4.4 degrees +/- 2.8 degrees and 3.6 degrees +/- 1.5 degrees in adduction under anesthesia and the postoperative condition. PCLS prostheses had average laxities of 3.8 degrees +/- 1.4 degrees and 3.5 degrees +/- 0.9 degrees in abduction and 4.6 degrees +/- 3.8 degrees and 4.0 degrees +/- 1.7 degrees in adduction. There were no significant differences between them.

CONCLUSIONS

The findings suggest that surgeons should emphasize the achievement of suitable laxity under anesthesia to ensure the success of total knee arthroplasty.

Sagittal laxity in vivo after total knee arthroplasty

INTRODUCTION

A stress arthrometry study of 77 knees undergoing total knee arthroplasty was performed to determine the difference in anteroposterior (AP) laxity between posterior cruciate ligament (PCL)-retaining (PCLR) and PCL-substituting (PCLS) prostheses using the Genesis I TKA.

MATERIALS AND METHODS

Fifty-three knees had PCLR and 24 had PCLS prostheses. The selected patients had successful arthroplasties after a minimum follow-up of 5 years. AP laxity was measured with a KT-2000 arthrometer (Medmetric, San Diego, CA, USA) using standard protocols.

RESULTS

At 30 degrees of flexion, there was no statistical difference in anterior (PCLR: 4.7 mm, PCLS: 4.5 mm), posterior (PCLR: 1.1 mm, PCLS: 0.7 mm), or total (PCLR: 5.8 mm, PCLS: 5.3 mm) displacement. At 75 degrees , significant differences were seen in both anterior (PCLR: 3.3 mm, PCLS: 2.3 mm) and total (PCLR: 4.8 mm, PCLS: 3.4 mm) displacement (p=0.001 and p=0.009, respectively), although there was no statistical difference in posterior displacement (PCLR: 1.5 mm, PCLS: 1.1 mm).

CONCLUSION

The above values are considered the suitable degree of AP laxity in total knee arthroplasty for a satisfactory clinical outcome 5-9 years after surgery. The PCL in a PCLR prosthesis and the central tibial spine and femoral cam in a PCLS prosthesis might play comparable roles in determining the laxity in the posterior direction in these prostheses.

Changed gait pattern in patients with total knee arthroplasty but minimal influence of tibial insert design: gait analysis during level walking in 39 TKR patients and 18 healthy controls

INTRODUCTION

Previous radiostereometric studies have revealed abnormal anterior-posterior translation of the femur in patients operated with AMK (DePuy, Johnson and Johnson, Leeds, UK) total knee arthroplasty (TKA). Based on these observations, we hypothesized that patients with TKA have an abnormal gait pattern, and that there are differences in kinematics depending on the design of the tibial joint area.

METHOD

We used a gait analysis system to evaluate the influence of joint area design on the kinematics of the hip and knee during level walking. 39 TKA patients (42 knees) and 18 healthy age-matched controls were studied. Patients with 5 degrees varus/valgus alignment or less were randomized to receive either a relatively flat or a concave tibial insert with retention of the posterior cruciate ligament. Patients who had more than 5 degrees varus-valgus alignment and/or extension defect of 10 degrees or more were randomized to receive the concave or a posterior-stabilized tibial component with resection of the posterior cruciate ligament.

RESULTS

Patients with TKA tended to have less hip and knee extension and decreased knee and hip extension moment than controls. They also tended to walk more slowly. TKA altered the gait pattern, but choice of implant design had little influence.

INTERPRETATION

In patients with a similar degree of degenerative joint disease and within the limits of the constraints offered by the prostheses under study, the choice of joint area constraint has little influence on the gait pattern.

Gait and clinical measurements in patients with knee osteoarthritis after surgery: a prospective 5-year follow-up study

The aim of this prospective follow-up study was to determine if gait measurements and/or clinical measurements could detect differences in treatment outcome between two surgical interventions in patients with knee osteoarthritis (OA). The patients were followed for 5 years after surgery. Forty patients, 55-70 years of age, with unilateral knee OA were included. The patients were treated either with a high tibial osteotomy (HTO) (n=18) or a unicompartmental knee arthroplasty (UKA) (n=22). Clinical outcome measures were the British Orthopaedic Association (BOA) score, pain during walking, passive range of knee motion (PROM) and patients' subjective opinion. The gait variables were free walking speed, step frequency, step length and single and double-stance phase for each leg. The patients were examined before surgery and 3 months, 1 year and 5 years after surgery. The time-distance variables of gait could detect differences in treatment outcome, 3 months after surgery, while the clinical outcome measures, as given here, could not detect any differences between the two groups of patients. Measurements of free walking speed could be recommended for clinical evaluation, after surgical interventions, in patients with knee OA.

Bilateral total knee arthroplasty increases the propensity to trip on an obstacle

Tripping over an obstacle is the most frequent cause of falls. We examined the effects of total knee arthroplasty on obstacle avoidance success rates in older adults. Obstacle avoidance success rates, body mass index, visual acuity, contrast sensitivity, depth perception, and single-leg stance duration were evaluated in 29 subjects who had bilateral total knee arthroplasties (age range, 72.6 +/- 5.4 years) and 27 age-matched healthy control subjects (age range, 70.6 +/- 5.5 years). The patients who had total knee arthroplasties had a lower obstacle avoidance success rate, lower single-leg stance duration, and greater body mass index than control subjects. Age, contrast sensitivity, and depth perception were not different between patients who had total knee arthroplasties and control subjects. Obstacle avoidance success rates decreased linearly as single-leg stance duration decreased in the control group and across all groups, but not in the group that had total knee arthroplasties. Linear relationships between obstacle avoidance success rates and body mass index existed for all subjects but not for the group that had total knee arthroplasties or the control group individually. Total knee arthroplasty reduces obstacle avoidance success rate, suggesting that persons who have total knee arthroplasties have an increased propensity to trip on an obstacle and fall. Increased body mass index and decreased single-leg stance duration in patients who have total knee arthroplasties are associated with a decreased obstacle avoidance success rate.

Differences in articular track area of posterior-stabilized and cruciate-retaining retrieved total knee implants

Press-fit condylar total knee arthroplasties removed at revision surgery from 27 knees were examined. Fourteen of the implants were posterior-stabilized press-fit condylar systems and 13 were cruciate-retaining press-fit condylar systems. The articular track areas were examined using a digital camera and manual measurements. Findings revealed the track area in posterior-stabilized implants (93%) was larger than in cruciate-retaining implants (59%). Mean posterior distance ratio of the articular track from the posterior limit of the polyethylene was 2% (.08 cm) for posterior-stabilized implants versus 23% (.97 cm) for cruciate-retaining implants. No differences in wear rating were noted. The pattern of articular contact in cruciate-retaining knees demonstrated little migration of the femoral contact surface across the tibial polyethylene plateau.

Tibiofemoral kinematic analysis of kneeling after total knee arthroplasty

Some surgeons warn against kneeling after total knee arthroplasty (TKA), because limited clinical data exist. We describe the tibiofemoral contact position of TKA components during kneeling in vivo. Ten posterior-substituting (PS) and 10 cruciate-retaining (CR) designs were examined using a radiographic image-matching technique. Movement from standing to kneeling at 90 degrees produced different responses. CR knees translated anteriorly (medial, 4 +/- 4 mm; lateral, 2 +/- 6 mm). PS knees underwent little posterior translation (medial, 0.2 +/- 3 mm; lateral, 1 +/- 4 mm). Movement from 90 degrees to maximum flexion produced femoral posterior translation (CR medial, 5 +/- 4 mm; CR lateral, 5 +/- 4 mm; PS medial, 6 +/- 4 mm; PS lateral, 6 +/- 3 mm). The relationship between tibiofemoral contact position and flexion angle was more variable for CR (r2=.38) than for PS (r2=.64). Knee kinematics was similar to other deep-flexion weight-bearing activities.

The stability of the cemented tibial component of total knee arthroplasty: posterior cruciate-retaining versus posterior-stabilized design

Micromotion of the tibial component in 40 knee arthroplasties for gonarthrosis was studied using Roentgen stereophotogrammetric analysis. The stability of this component was assessed for 2 years' postoperatively. In all arthroplasties, an attempt was made to reconstruct the preoperative posterior slope. Posterior cruciate-retaining (CR) and posterior-stabilized (PS) components showed at 2 years a maximum total point motion of 0.6 +/- 0.4 mm and 0.7 +/- 0.5 mm, respectively. Whereas 92.5% of the implants were determined to be stable, 1 of the CR group and 2 of the PS group displayed migration between the first and the second year of at least 0.2 mm. A negative correlation between subsidence of the tibial component at 2 years of follow-up and the difference between preoperative and postoperative tibial slope was found. Consequently, we suggest that restoring the original posterior slope of the tibial plateau must be a goal of tibial component implantation.

Total knee replacement influences both knee and hip joint kinematics during stair climbing

A gait analysis system was used to evaluate the kinematics of the hip and knee during stair ascending and descending after operation with total knee replacement. Patients with 5 degrees varus/valgus alignment or less were selected randomly to receive either a flat or a concave tibial component with retention of the posterior cruciate ligament. Patients who had more than 5 degrees varus/valgus alignment and/or an extension defect of 10 degrees or more were selected randomly to receive the concave or posterior-stabilized tibial component with resection of the posterior cruciate ligament. Twenty patients and 17 controls were studied 1-2 years after the operation. Patients had abnormal kinematics during stair ascending and descend-ing. Both knee extension and flexion were reduced. Hip extension tended to decrease, and decreased hip extension moment was noted.

Clinical and functional comparison of bicondylar sledge prostheses retaining all ligaments and constrained total knee replacement

OBJECTIVE

Comparison of different total knee replacements regarding clinical and functional differences with respect to gait and electromyographic analyses.

DESIGN

Retrospective, comparative, clinical and functional study.

METHODS

Three groups (control group of 11 healthy subjects, 15 patients with bicondylar sledge prostheses retaining all ligaments (cemented unicondylar prostheses in both the medial and lateral compartment), 15 patients with constrained total knee replacement sacrificing all cruciate and collateral ligaments (cemented total knee prosthesis with intramedullary stems and a large intercondylar tibial post) were compared by clinical evaluation using a number of clinical evaluation scores, a pain scale, surface electromyographic examinations of the lower limb, and gait analysis.

RESULTS

Clinical scores revealed significantly worse results for patients with constrained prostheses. Both patient groups had significantly lower clinical scores compared to the control group. Gait analysis and electromyographic parameters revealed no significant differences between both patient groups. Compared to the control group, patients revealed significantly impaired parameters. Electromyography also demonstrated significant differences between patients and controls: mean electromyographic activities were reduced in vastus medialis and lateralis, semitendinosus, tibialis anterior and gastrocnemius. Peak activities were reduced in all muscles but rectus femoris.

CONCLUSION

Clinical scores demonstrated significantly better results in bicondylar sledge than in constrained prostheses. Nevertheless, gait and electromyographic analyses did not reveal significant differences.

RELEVANCE

Retaining of ligaments in bicondylar sledge prostheses apparently improved the activities of daily living but is not reflected in gait and electromyographic parameters.

In vivo laxity of low contact stress mobile-bearing prostheses

A stress arthrometric study was done on 60 knees in 54 patients with total knee arthroplasties using a Telos arthrometer, to determine anteroposterior and abduction and adduction laxity and to evaluate the relationship between laxity and retention of the posterior cruciate ligament using low contact stress mobile-bearing prostheses. Thirty knees had posterior cruciate ligament-retaining and 30 had posterior cruciate ligament-sacrificing prostheses. The selected patients had successful knee arthroplasty 6 months previously. Anteroposterior displacement was measured at 30 degree and 90 degree flexion; there were no statistically significant differences between the posterior cruciate ligament-retaining (10.5 mm at 30 degree, 9.3 mm at 90 degree) and posterior cuciate ligament-sacrificing (9.8 mm at 30 degree, 9.7 mm at 90 degree) groups. Abduction and adduction were between 0 degree and 20 degree flexion, there were no significant differences between the two groups. Because all the patients in this study had good clinical results, approximately 10 mm anteroposterior displacement and 4 degree laxity in the coronal direction are considered favorable in low contact stress mobile-bearing prostheses of both designs.

Coronal laxity in extension in vivo after total knee arthroplasty

We performed stress arthrometric studies on 77 knees (71 patients) with total knee arthroplasty to determine the presence and magnitude of femoral abduction and adduction in knee extension. A total of 53 knees (49 patients) had posterior cruciate ligament-retaining (PCLR) prostheses, and 24 (22 patients) had PCL-substituting (PCLS) prostheses. The selected patients had successful arthroplasties with no clinical complications a minimum of 5 years after primary surgery. Each patient was subjected to a successive abduction and adduction stress test at 0 degrees -20 degrees of flexion using a Telos arthrometer. The mean values for abduction and adduction were 4.8 degrees and 4.5 degrees with a PCLR prosthesis, respectively, and 4.6 degrees and 4.0 degrees with a PCLS prosthesis. There were no statistical differences between PCLR and PCLS knees. The results suggest that approximately 4 degrees of laxity in these directions is suitable in total knee arthroplasty for a satisfactory clinical outcome 5-9 years after surgery.

Quantitative gait analysis after medial unicompartmental knee arthroplasty for osteoarthritis

This study characterized the footstep pattern and knee kinematics during walking in 12 patients who had undergone unicompartmental knee arthroplasty for unilateral medial compartment osteoarthritis. Patients had all achieved a successful recovery and were tested at least 1 year after surgery. Gait analysis was conducted during self-selected comfortable and fast walking conditions using a 3-dimensional motion analysis system and electronic walkway. Results showed that patients were able to increase their walking speed by 28% by increasing both stride length and cadence. All but one patient showed a biphasic pattern of flexion-extension motion about the treated knee. In 8 of 12 patients, significant increases in knee flexion were seen in the treated limb compared with the contralateral limb, the cause and ramifications of which are yet to be determined.

Kinematics of three variations of the Freeman-Samuelson total knee prosthesis

The effect of changes in the articulating surfaces on the kinematics of the Freeman-Samuelson total knee replacement was evaluated. Twenty-two patients (22 knees) (median age, 69 years) were randomized to a standard design with a fixed polyethylene bearing, a design with a mobile bearing, or a new design with a spherical medial femoral condyle with a fixed bearing. The patients were studied with radiostereometry and film-exchangers at 0 degrees nonweightbearing and during active weightbearing extension from 45 degrees to 15 degrees. The center of the tibial tray with a mobile-bearing prosthesis occupied a more anterior position than observed in the designs with a fixed bearing. The medial femoral condyle center had a more posterior position in the standard design than in the design with a spherical medial condyle. From a distally displaced position at 45 degrees, the medial condylar center displaced a mean of 1.8 mm proximally during extension in the standard design and had a constant position in the meniscal design. In the spherical design the medial condyle was displaced proximally at 45 degrees and displaced a mean of 1.6 mm distally during extension. The reduced anteroposterior and proximodistal translations in the meniscal design are compatible with improved congruency between the components. The design with a spherical medial condyle stabilized anteroposterior motions, but showed more pronounced proximodistal displacement medially than did the other two designs.

Intraoperative measurements of knee motion in total knee arthroplasty

A photostereometric technology-based knee motion analysis system was developed and intraoperative kinematics during total knee arthroplasty (TKA) was investigated. Ten knees were evaluated and two different types of posterior-cruciate-retaining TKA (Genesis-I and Genesis-II) were used. Both TKA showed posterior translation of the medial and lateral femoral condyle with knee flexion. The motion pattern of the estimated contact point of Genesis-II was small initial rollback followed by sliding motion, then rollback again more than 60 degrees. In Genesis-II, the amount of translation of the medial condyle was significantly larger than that of the lateral, suggesting that the lateral condyle acted as a rotational pivot. Our developed knee motion analysis system was non-contact, high resolution and can evaluate both kinematics and estimated contact pattern. The results of this study suggest that intraoperative measurement using this analysis system has advantages for the investigation of in-vivo kinematics and contact condition in TKA.

Six degrees-of-freedom kinematics of ACL deficient knees during locomotion-compensatory mechanism

The purpose of the study was to investigate six degrees-of-freedom (DOF) kinematic changes in anterior cruciate ligament ACL-deficient knees during locomotion and the possible compensatory mechanism involved. Compared with healthy subjects, ACL-deficient patients walked with increased tibial external rotation throughout most of the stride and increased tibial abduction at the heel contact, and the tibia was more anterior during swing phase (P<0.05). Considering tibial external rotation and abduction unload the ACL, the kinematic changes indicated compensatory mechanism developed by patients to avoid unstable knee positions due to the loss of the ACL or to avoid stretching a partially torn ACL.

A practical guide to gait analysis

The act of walking involves the complex interaction of muscle forces on bones, rotations through multiple joints, and physical forces that act on the body. Walking also requires motor control and motor coordination. Many orthopaedic surgical procedures are designed to improve ambulation by optimizing joint forces, thereby alleviating or preventing pain and improving energy conservation. Gait analysis, accomplished by either simple observation or three-dimensional analysis with measurement of joint angles (kinematics), joint forces (kinetics), muscular activity, foot pressure, and energetics (measurement of energy utilized during an activity), allows the physician to design procedures tailored to the individual needs of patients. Motion analysis, in particular gait analysis, provides objective preoperative and postoperative data for outcome assessment. Including gait analysis data in treatment plans has resulted in changes in surgical recommendations and in postoperative treatment. Use of these data also has contributed to the development of orthotics and new surgical techniques.