Dynamic activity dependence of in vivo normal knee kinematics

Dynamic knee kinematics were analyzed for normal knees in three activities, including two different types of maximum knee flexion. Continuous X-ray images of kneel, squat, and stair climb motions were taken using a large flat panel detector. CT-derived bone models were used for model registration-based 3D kinematic measurement. Three-dimensional joint kinematics and contact locations were determined using three methods: bone-fixed coordinate systems, interrogation of CT-based bone model surfaces, and interrogation of MR-based articular cartilage model surfaces. The femur exhibited gradual external rotation throughout the flexion range. Tibiofemoral contact exhibited external rotation, with contact locations translating posterior while maintaining 15 degrees to 20 degrees external rotation from 20 degrees to 80 degrees of flexion. From 80 degrees to maximum flexion, contact locations showed a medial pivot pattern. Kinematics based on bone-fixed coordinate systems differed from kinematics based on interrogation of CT and MR surfaces. Knee kinematics varied significantly by activity, especially in deep flexion. No posterior subluxation occurred for either femoral condyle in maximum knee flexion. Normal knees accommodate a range of motions during various activities while maintaining geometric joint congruency.

Can magnetic resonance imaging-derived bone models be used for accurate motion measurement with single-plane three-dimensional shape registration?

The purpose of this study was to compare three-dimensional (3D) kinematic measurements from single-plane radiographic projections using bone models created from magnetic resonance imaging (MRI) and computed tomography (CT). MRI is attractive because there is no ionizing radiation, but geometric field distortion and poor bone contrast degrade model fidelity compared to CT. We created knee bone models of three healthy volunteers from both MRI and CT and performed three quantitative comparisons. First, differences between MRI- and CT-derived bone model surfaces were measured. Second, shape matching motion measurements were done with bone models for X-ray image sequences of a squat activity. Third, synthetic X-ray images in known poses were created and shape matching was again performed. Differences in kinematic results were quantified in terms of root mean square (RMS) error. Mean differences between CT and MRI model surfaces for the femur and tibia were -0.08 mm and -0.14 mm, respectively. There were significant differences in three of six kinematic parameters comparing matching results from MRI-derived bone models and CT-derived bone models. RMS errors for tibiofemoral poses averaged 0.74 mm for sagittal translations, 2.0 mm for mediolateral translations, and 1.4 degrees for all rotations with MRI models. Average RMS errors were 0.53 mm for sagittal translations, 1.6 mm for mediolateral translations, and 0.54 degrees for all rotations with the CT models. Single-plane X-ray imaging with model-based shape matching provides kinematic measurements with sufficient accuracy to assess knee motions using either MRI- or CT-derived bone models. However, extra care should be taken when using MRI-derived bone models because model inaccuracies will affect the quality of the shape matching results.

Knee kinematics in medial osteoarthritis during in vivo weight-bearing activities

Dynamic knee kinematics were analyzed for medial osteoarthritic (OA) knees in three activities, including two types of maximum knee flexion. Continuous x-ray images of kneeling, squatting, and stair climbing motions were taken using a large flat panel detector. CT-derived bone models were used for the model registration-based 3D kinematic measurements. Three-dimensional joint kinematics and contact locations were determined using two methods: bone-fixed coordinate systems and by interrogation of CT-based bone model surfaces. The femur exhibited gradual external rotation with knee flexion for kneeling and squatting activities, and gradual internal rotation with knee extension for stair climbing. From 100 degrees to 120 degrees flexion, contact locations showed a medial pivot pattern similar to normal knees. However, knees with medial OA displayed a femoral internal rotation bias and less posterior translation when compared with normal knees. A classic screw-home movement was not observed in OA knees near extension. Decreased variability with both activities and methods of calculation were demonstrated for all three activities. In conclusion, the weight-bearing kinematics of patients with medial OA differs from normal knees. Pathological changes of the articulating surfaces and the ligaments correspond to observed abnormalities in knee kinematics.

Correlations between patient satisfaction and ability to perform daily activities after total knee arthroplasty: why aren't patients satisfied?

BACKGROUND

Patient satisfaction has become an important parameter for assessing overall outcomes after total knee arthroplasty (TKA). The level of difficulty in performing activities of daily life that affects overall patient satisfaction is unknown. We therefore evaluated the influence of difficulty in performing activities of daily life on patient satisfaction and expectations.

METHODS

The 2011 Knee Society Knee Scoring System Questionnaire was mailed to patients who had undergone TKA with 375 patients completing and returning it. We evaluated the relationship between the ability to perform daily activities, as assessed via the questionnaire, and patient satisfaction and expectations of the same score in each patient using linear regression analysis. We also determined which activities affected patient satisfaction and expectations using multivariate linear regression analyses.

RESULTS

All patient-derived functional activities correlated significantly with the patient satisfaction score. In particular, "climbing up or down a flight of stairs" followed by "getting into or out of a car," "moving laterally (stepping to the side)" and "walking and standing" correlated strongly with patient satisfaction by linear regression analysis and were revealed to have significant contributions to patient satisfaction by multivariate linear regression analysis. Regarding expectations, all patient-derived functional activities correlated significantly with the patient expectation score, although none of the correlation coefficients was very high. "Squatting," followed by "walking and standing," contributed to the patient expectation score by multivariate linear regression analysis.

CONCLUSION

Activities related to walking and standing are some of the most basic movements and basic demands for patients. In addition, "climbing up or down a flight of stairs," "getting into and out of a car" and "squatting" are very important and distressing activities that significantly correlate with patient satisfaction after TKA.

Effect of Tibial Posterior Slope on Knee Kinematics, Quadriceps Force, and Patellofemoral Contact Force After Posterior-Stabilized Total Knee Arthroplasty

We used a musculoskeletal model validated with in vivo data to evaluate the effect of tibial posterior slope on knee kinematics, quadriceps force, and patellofemoral contact force after posterior-stabilized total knee arthroplasty. The maximum quadriceps force and patellofemoral contact force decreased with increasing posterior slope. Anterior sliding of the tibial component and anterior impingement of the anterior aspect of the tibial post were observed with tibial posterior slopes of at least 5° and 10°, respectively. Increased tibial posterior slope contributes to improved exercise efficiency during knee extension, however excessive tibial posterior slope should be avoided to prevent knee instability. Based on our computer simulation we recommend tibial posterior slopes of less than 5° in posterior-stabilized total knee arthroplasty.

Alignment factors affecting the medial meniscus extrusion increases the risk of osteoarthritis development

PURPOSE

Varus alignment is known as one of the major causes of medial compartment osteoarthritis (OA). Medial meniscus extrusion also plays a critical role in the in the development of OA. However, studies on the exact relationship between alignment parameters and medial meniscus extrusion are limited. Therefore, this study aimed to investigate this relationship in patients with knee OA.

METHODS

Based on a retrospective analysis of the outpatient magnetic resonance imaging (MRI) database, 190 knees were identified to be examined using weight-bearing, whole-leg radiographs and MRIs within 3 months from the first consultation. Subsequently, various parameters of lower leg alignment were measured, which affected the knee varus in radiographs. Finally, a statistical analysis was performed to assess the relationships between the OA grade, distance of medial meniscus extrusion (MME), and alignment parameters; hip-knee-ankle angle (HKAA), percentage of mechanical axis (% MA), medial proximal tibial angle (MPTA), and joint line convergence angle (JLCA). The subjects were divided according to the presence or absence of MME (Group A: MME distance below 3 mm, Group B: MME distance 3 mm and above) to assess the differences in each alignment parameter correlated with MME distance between the groups.

RESULTS

MME distance significantly increased with OA grade progression. HKAA, % MA, MPTA, and JLCA significantly correlated with medial meniscus extrusion distance (r = - 0.21, - 0.23, - 0.16, 0.3, respectively). Multiple regression analysis of each significant alignment combined with age, sex, and body mass index revealed that HKAA, % MA, MPTA, and JLCA were significant independent factors of MME distance (P = 0.008, 0.0026, 0.011, 0.0001, respectively). These significant findings were reinforced in group B. In contrast, the correlation between alignment parameters and medial meniscus extrusion distance was not significant in group A.

CONCLUSION

Varus alignment factors are related to MME distance especially in extruded meniscus knees, as the OA grade progressed. Therefore, the coexistence of varus alignment and MME can be the risk factors for OA progression. As the low MPTA was an independent alignment factor for generating varus alignment, patients with osteoarthritis of the knee with both, low MPTA and MME could be the appropriate candidates for early intervention by high tibial osteotomy.

LEVEL OF EVIDENCE

III.

Influence of the posterior tibial slope on the flexion gap in total knee arthroplasty

BACKGROUND

Adjusting the joint gap length to be equal in both extension and flexion is an important issue in total knee arthroplasty (TKA). It is generally acknowledged that posterior tibial slope affects the flexion gap; however, the extent to which changes in the tibial slope angle directly affect the flexion gap remains unclear. This study aimed to clarify the influence of tibial slope changes on the flexion gap in cruciate-retaining (CR) or posterior-stabilizing (PS) TKA.

METHODS

The flexion gap was measured using a tensor device with the femoral trial component in 20 cases each of CR- and PS-TKA. A wedge plate with a 5° inclination was placed on the tibial cut surface by switching its front-back direction to increase or decrease the tibial slope by 5°. The flexion gap after changing the tibial slope was compared to that of the neutral slope measured with a flat plate that had the same thickness as that of the wedge plate center.

RESULTS

When the tibial slope decreased or increased by 5°, the flexion gap decreased or increased by 1.9 ± 0.6mm or 1.8 ± 0.4mm, respectively, with CR-TKA and 1.2 ± 0.4mm or 1.1 ± 0.3mm, respectively, with PS-TKA.

CONCLUSIONS

The influence of changing the tibial slope by 5° on the flexion gap was approximately 2mm with CR-TKA and 1mm with PS-TKA.

CLINICAL RELEVANCE

This information is useful when considering the effect of manipulating the tibial slope on the flexion gap when performing CR- or PS-TKA.

Vertebral strength changes in rheumatoid arthritis patients treated with alendronate, as assessed by finite element analysis of clinical computed tomography scans: a prospective randomized clinical trial

OBJECTIVE

Finite element analysis of clinical computed tomography (CT) scans provides a noninvasive means of assessing vertebral strength that is superior to dual x-ray absorptiometry (DXA)-measured areal bone mineral density. The present study was undertaken to compare strength changes, measured using this newer method, in rheumatoid arthritis (RA) patients who were treated with alendronate (ALN) versus those who were not.

METHODS

Thirty female RA patients without radiologic signs of L3 compression fractures or a history of osteoporosis medication were enrolled in a prospective randomized clinical trial. Patients were randomly assigned to the ALN group (5 mg orally, once daily) or the control group not receiving antiresorptive treatment. All patients were evaluated by DXA and quantitative CT at baseline and reevaluated after a mean of 12.2 months. Nonlinear finite element analysis was performed on the CT scans (n = 29 available for analysis) to compute an estimate of vertebral compressive strength and to assess strength changes associated with changes in the trabecular compartment and the outer 2 mm of bone (peripheral compartment).

RESULTS

On average, vertebral strength was significantly decreased from baseline in the control group (n = 15) (median change -10.6%; P = 0.008) but was maintained in the ALN group (n = 14) (median change +0.4%; P = 0.55), with a significant difference between the 2 groups (P < 0.01). Strength decreased more rapidly within the trabecular bone, and ALN treatment was much more effective in the peripheral than the trabecular compartment.

CONCLUSION

Our results indicate that patients with RA can lose a substantial amount of vertebral strength over a relatively short period of time, and this loss can be prevented by ALN, primarily via its positive effect on the outer 2 mm of vertebral bone.

Extension gap needs more than 1-mm laxity after implantation to avoid post-operative flexion contracture in total knee arthroplasty

PURPOSE

In total knee arthroplasty (TKA), a high soft-tissue tension in extension at the time of operation would cause a post-operative flexion contracture. However, how tight the extension gap should be during surgery to avoid a post-operative flexion contracture remains unclear. The hypothesis is that some laxity in the intraoperative extension gap is necessary to avoid the post-operative flexion contracture.

METHODS

A posterior-stabilized TKA was performed for 75 osteoarthritic knees with a varus deformity. The intraoperative extension gap was measured using a tensor device that provides the gap length and the angle between the femoral component and the tibial cut surface. The medial component gap was defined as the gap calculated by subtracting the selected thickness of the tibial component, including the polyethylene liner, from the extension gap at the medial side. Then, the patients were divided into three groups according to the medial component gap, and post-operative extension angle measured 1 year after the surgery was compared between each groups.

RESULTS

One year post-operatively, a flexion contracture of more than 5° was found in 0/34 patients when the medial component gap was more than 1 mm, in 2/26 (8%) patients when the gap was between 0 and 1 mm, and in 3/15 (20%) patients when the gap was <0 mm. Three factors were associated significantly with the post-operative extension angle: age, preoperative extension angle, and medial component gap.

CONCLUSION

The intraoperative extension gap is related to the post-operative extension angle. Surgeons should leave more than 1-mm laxity after the implantation to avoid the post-operative flexion contracture. As a clinical relevance, this study clarified the optimal extension gap to avoid the post-operative flexion contracture.

LEVEL OF EVIDENCE

Prospective comparative study, Level II.

In vivo knee kinematics during stair and deep flexion activities in patients with bicruciate substituting total knee arthroplasty

Orthopedic surgeons and their patients continue to seek better functional outcomes after total knee arthroplasty. The bicruciate substituting (BCS) total knee arthroplasty design has been introduced to achieve more natural knee mechanics. The purpose of this study was to characterize kinematics in knees with BCS arthroplasty during deep flexion and stair activities using fluoroscopy and model-image registration. In 20 patients with 25 BCS knees, we observed average implant flexion of 128° during kneeling and consistent posterior condylar translations with knee flexion. Tibial rotations were qualitatively similar to those observed in the arthritic natural knee. Knee kinematics with BCS arthroplasty were qualitatively more similar to arthritic natural knees than knees with either posterior cruciate-retaining or posterior-stabilized arthroplasty.

Remodelling of femoral head-neck junction in slipped capital femoral epiphysis: a multicentre study

PURPOSE

We examined the remodelling of the femoral head-neck junction in patients with slipped capital femoral epiphysis (SCFE) and the frequency of residual cam deformities.

METHODS

We reviewed 69 hips in 56 patients with stable SCFE who had undergone in situ pinning. Mean age at slip was 11.7 years and the follow-up period 63.4 months. Cam deformity was evaluated using the anterior offset alpha (α) angle and head-neck offset ratio (HNOR).

RESULTS

The average α angle and HNOR significantly improved from 76.2° to 51.3° and 0.086 to 0.135, respectively; 25 hips (36.2%) still had an α angle greater than 50°, and 32 hips (46.4%) had an HNOR of under 0.145. A multivariate analysis selected age at onset and slip angle as risk factors for cam deformity, with cutoff values 11.1 years and 21.0°, respectively.

CONCLUSIONS

Although most hips had remodelling of the head-neck junction, 29.4 % had residual cam deformities that may be susceptible to femoroacetabular impingement.

Late dislocation is associated with recurrence after total hip arthroplasty

PURPOSE

This study was conducted to examine the risk factors for recurrent dislocation after total hip arthroplasty (THA) and test the hypothesis that late dislocations are associated with recurrence.

METHODS

A total of 1,250 hips in 1,017 patients were retrospectively reviewed. All operations were performed through the posterolateral approach with posterior soft tissue repair. An early or late dislocation was defined as a dislocation occurring before or after one year postoperatively, respectively.

RESULTS

Dislocation occurred in 36 hips (2.9 %) and 20 of them experienced recurrence. Recurrent dislocations were observed in ten out of 25 hips (40.0 %) with early dislocation; however, ten out of 11 hips (90.9 %) with late dislocation experienced recurrence (p = 0.0046). Multivariate analysis revealed that late dislocation was significantly associated with recurrence with odds ratio of 5.94 per year. Seven in 20 hips with recurrent dislocation required surgical treatment.

CONCLUSION

Late dislocation significantly contributed to the development of recurrent dislocations.

Kinematic analysis of kneeling in cruciate-retaining and posterior-stabilized total knee arthroplasties

Kneeling is an important function of the knee for many activities of daily living. In this study, we evaluated the in vivo kinematics of kneeling after total knee arthroplasty (TKA) using radiographic based image-matching techniques. Kneeling from 90 to 120 degrees of knee flexion produced a posterior femoral rollback after both cruciate-retaining and posterior-stabilized TKA. It could be assumed that the posterior cruciate ligament and the post-cam mechanism were functioning. The posterior-stabilized TKA design had contact regions located far posterior on the tibial insert in comparison to the cruciate-retaining TKA. Specifically, the lateral femoral condyle in posterior-stabilized TKA translated to the posterior edge of the tibial surface, although there was no finding of subluxation. After posterior-stabilized TKA, the contact position of the post-cam translated to the posterior medial corner of the post with external rotation of the femoral component. Because edge loading can induce accelerated polyethylene wear, the configuration of the post-cam mechanism should be designed to provide a larger contact area when the femoral component rotates.

Effect of sagittal pelvic tilt on joint stress distribution in hip dysplasia: A finite element analysis

BACKGROUND

Physiologic pelvic tilt can change acetabular orientation and coverage in patients with hip dysplasia. In this study, we aimed to clarify the impact of change in sagittal pelvic tilt on joint stress distribution in dysplastic hips.

METHODS

We developed patient-specific finite element models of 21 dysplastic hips and 21 normal hips. The joint contact area, contact pressure, and equivalent stress of the acetabular cartilage were assessed at three pelvic tilt positions relative to the functional pelvic plane: 10° anterior tilt, no tilt, and 10° posterior tilt.

FINDINGS

The mean contact area was 0.6-0.7 times smaller, the mean maximum contact pressure was 1.8-1.9 times higher, and the mean maximum equivalent stress was 1.3-2.8 times higher in dysplastic hips than in normal hips at all three pelvic positions. As the pelvis tilted from 10° anterior to 10° posterior, the mean contact area decreased, and the mean maximum contact pressure and median maximum equivalent stress increased. The latter two changes were more significant in dysplastic hips than in normal hips (total increment was 1.3 MPa vs. 0.4 MPa, P = 0.001, and 3.6 MPa vs. 0.4 MPa, P < 0.001, respectively). The mean equivalent stress increased in the anterosuperior acetabulum during posterior pelvic tilt in dysplastic and normal hips, while the change was not significant in the superior and posterosuperior acetabulum in both groups.

INTERPRETATION

Sagittal pelvic tilt alters the loading environment and joint stress distribution of the hip joint and may impact the degeneration process in dysplastic hips.

Comparison of static and dynamic knee kinematics during squatting

BACKGROUND

there long has been debate whether static knee kinematics measured using magnetic resonance imaging are the same as knee kinematics in dynamic weight-bearing motion. Magnetic resonance imaging provides excellent volumetric detail but is static. Fluoroscopic imaging provides for dynamic observation of knee kinematics but provides no direct observation of the soft-tissue structures. We attempted to answer the question 'Are knee kinematics the same during static and dynamic squatting?'

METHODS

knee kinematics data from two previously reported studies of healthy knee kinematics during squatting from 0° to 120° were obtained. The results of the dynamic fluoroscopic study were reformatted to perform a direct comparison of femoral anteroposterior translation and internal-external rotation with the static magnetic resonance imaging study.

FINDINGS

comparison of internal-external rotations and lateral femoral condyle anteroposterior translations did not reveal significant differences between static and dynamic data. The medial femoral condyle demonstrated 0 (SD=3) mm posterior translation during dynamic squatting from 0° to 120° flexion compared to 5 (SD=3) mm posterior translation during static squatting (P=0.01, Cohen's d=1.7).

INTERPRETATION

for squatting types of motions, static and dynamic study protocols appear to produce equivalent knee kinematics with no functionally important differences. Differences in medial condyle translations can be attributed to differences in foot position during the study. Investigators can choose the modality that best fits their goals and resources with the knowledge that the results for squatting activities are comparable.

Factors Associated With Severity of Intra-articular Lesions in Patients With Severe Hip Dysplasia

PURPOSE

To identify demographic and morphologic factors associated with the severity of intra-articular lesions in patients with severe hip dysplasia.

METHODS

One hundred twenty-one patients (134 hips) with symptomatic hip dysplasia were retrospectively reviewed. The cartilage and labral lesions were scored according to the Outerbridge and the original classification systems, respectively. The association of the cartilage and labrum scores with patient demographics (age, gender, body mass index, bilateral hip dysplasia, and treatment history for developmental hip dislocation) and morphologic factors (the lateral center-edge angle, Sharp angle, acetabular index, acetabular head index, acetabular depth ratio, Shenton line disruption, roundness index of the femoral head, and femoral neck shaft angle) were determined using a multiple linear regression analysis.

RESULTS

The cartilage and labral scores were significantly associated with radiographic osteoarthritis; however, these scores showed wide distribution among hips with equivalent degrees of radiographic osteoarthritis. Age (38.4 ± 12.8 years) (P < .001), lateral center-edge angle (0.2 ± 9.0°) (P = .014), acetabular head index (54.4 ± 9.1%) (P = .001), and the roundness index of the femoral head (55.6 ± 4.6%) (P = .022) were identified as independent factors associated with the cartilage score. Age (P < .001), having a medical history of developmental hip dislocation (P = .002), acetabular index (27.8 ± 6.8°) (P = .011), and the roundness index of the femoral head (P = .022) were identified as independent factors associated with the labral score.

CONCLUSIONS

Our findings suggest that the morphologic factors responsible for severe intra-articular lesions differ for cartilage degeneration and labral tears in patients with severe hip dysplasia. Decreased acetabular coverage of the femoral head was responsible for cartilage degeneration severity, whereas an increased acetabular index was responsible for labral tear severity.

LEVEL OF EVIDENCE

Level III, diagnostic study.

Continuous sagittal radiological evaluation of stair-climbing in cruciate-retaining and posterior-stabilized total knee arthroplasties using image-matching techniques

In this study, we evaluated the in vivo kinematics of stair-climbing after posterior stabilized (PS) and cruciate retaining (CR) total knee arthroplasty (TKA) using radiographic-based image-matching techniques. Mid-flexion anteroposterior stability was demonstrated in all knees after CR TKA. However, paradoxical femoral translation at low flexion angles was seen in both designs. The post-cam mechanism did not function after PS TKA. Larger posterior tibial slope in PS TKA was linked to forward sliding of the femur at mid-flexion and unintended anterior tibial post impingement at knee extension. CR TKA is more sagittally stable in mid-flexion during stair climbing and attention must be given to minimize posterior tibial slope when using late cam-post engaging PS TKA designs.

In vivo kinematics of healthy male knees during squat and golf swing using image-matching techniques

PURPOSE

Participation in specific activities requires complex ranges of knee movements and activity-dependent kinematics. The purpose of this study was to investigate dynamic knee kinematics during squat and golf swing using image-matching techniques.

METHODS

Five healthy males performed squats and golf swings under periodic X-ray images at 10 frames per second. We analyzed the in vivo three-dimensional kinematic parameters of subjects' knees, namely the tibiofemoral flexion angle, anteroposterior (AP) translation, and internal-external rotation, using serial X-ray images and computed tomography-derived, digitally reconstructed radiographs.

RESULTS

During squat from 0° to 140° of flexion, the femur moved about 25 mm posteriorly and rotated 19° externally relative to the tibia. Screw-home movement near extension, bicondylar rollback between 20° and 120° of flexion, and medial pivot motion at further flexion were observed. During golf swing, the leading and trailing knees (the left and right knees respectively in the right-handed golfer) showed approximately five millimeters and four millimeters of AP translation with 18° and 26° of axial rotation, respectively. A central pivot motion from set-up to top of the backswing, lateral pivot motion from top to ball impact, and medial pivot motion from impact to the end of follow-through were observed.

CONCLUSIONS

The medial pivot motion was not always recognized during both activities, but a large range of axial rotation with bilateral condylar AP translations occurs during golf swing. This finding has important implications regarding the amount of acceptable AP translation and axial rotation at low flexion in replaced knees.

LEVEL OF EVIDENCE

IV.

Evaluation of impingement of the anterior tibial post during gait in a posteriorly-stabilised total knee replacement

Mechanical failure because of wear or fracture of the polyethylene tibial post in posteriorly-stabilised total knee replacements has been extensively described. In this study of 12 patients with a clinically and radiologically successful NexGen LPS posteriorly-stabilised prosthesis impingement of the anterior tibial post was evaluated in vivo in three dimensions during gait using radiologically-based image-matching techniques. Impingement was observed in all images of the patients during the stance phase, although the NexGen LPS was designed to accommodate 14 degrees of hyperextension of the component before impingement occurred. Impingement arises as a result of posterior translation of the femur during the stance phase. Further attention must therefore be given to the configuration of the anterior portion of the femoral component and the polyethylene post when designing posteriorly-stabilised total knee replacements.

Pelvic tilt and movement during total hip arthroplasty in the lateral decubitus position

OBJECTIVES

Total hip arthroplasty (THA) is often performed in the lateral decubitus (lateral) position. In this position, the pelvis may have various degrees of tilt leading to implant malposition. We sought to quantify the pelvic tilt in lateral position and further pelvic movement during surgery.

METHODS

In 95 cases with primary THA, three-dimensional pelvic tilts were quantified by superimposing images reconstructed from CT data onto antero-posterior radiographs taken in lateral position at set-up and after cup placement. Pelvises were fixed with a device compressing anterior superior iliac spines and sacrum.

RESULTS

Various degrees of pelvic tilt occurred compared to the supine position; sagittal: -3.1° (-25.5° to 10.2°), axial: 3.9° (-8.4° to 17°), coronal: 0.9° (-11.9° to 13.2°). Absolute changes more than 5° were observed 43%, 47%, and 12% in the sagittal, axial, and coronal planes, respectively. The more preoperative posterior pelvic tilt resulted in the more change in the sagittal plane. Further pelvic movement of about 3° in three planes were observed ranging from -11° to 20° after cup placement.

CONCLUSION

This study showed various pelvic tilt and movement during THA. As pelvic tilt directly alters the cup orientation, its changes should be well understood. Improved tools for positioning and holding the pelvis are required.

Patient-reported outcomes after primary or revision total hip arthroplasty: A propensity score-matched Asian cohort study

BACKGROUND

Few studies have compared patient-reported outcome measures (PROMs) between primary and revision total hip arthroplasty (THA). We investigated and compared PROMs between propensity score-matched primary and revision THA in an Asian cohort.

METHODS

The Oxford Hip Score (OHS) and University of California-Los Angeles (UCLA) activity score, satisfaction score, and Short Form-12 Health Survey (SF-12) were compared between 110 primary and 110 revision THAs after propensity score matching. Multivariate analyses were performed to determine which factors, including patients' demographics, indication for revision, and pre-operative PROMs, were associated with post-operative PROMs in the revision THA cohort.

RESULTS

The revision THA cohort demonstrated significantly lower post-operative OHS, UCLA activity score, and satisfaction score (10% decrease on average) than those in the primary THA cohort (P < .05). The difference in SF-12 mental component summary measure (MCS) between the two cohorts was statistically insignificant (P = .24). In multivariate analysis for the revision THA cohort, lower post-operative UCLA activity score was significantly associated with higher BMI and lower pre-operative UCLA activity score (P < .05).

CONCLUSION

Revision THA was associated with a modest but significant decrease in physical PROMs as compared with primary THA. Pre-operative UCLA activity score significantly affected the post-operative physical outcome measures in the revision THA cohort. However, post-operative SF-12 MCS was comparable between the primary and revision THA cohorts.

Three-dimensional knee joint kinematics during golf swing and stationary cycling after total knee arthroplasty

The expectation of returning to sports activities after total knee arthroplasty (TKA) has become more important to patients than ever. To our knowledge, no studies have been published evaluating the three-dimensional knee joint kinematics during sports activity after TKA. Continuous X-ray images of the golf swing and stationary cycling were taken using a large flat panel detector for four and eight post-arthroplasty knees, respectively. The implant flexion and axial rotation angles were determined using a radiographic-based, image-matching technique. Both the golf swing from the set-up position to the top of the backswing, and the stationary cycling from the top position of the crank to the bottom position of the crank, produced progressive axial rotational motions (p = 0.73). However, the golf swing from the top of the backswing to the end of the follow-through produced significantly larger magnitudes of rotational motions in comparison to stationary cycling (p < 0.01). Excessive internal-external rotations generated from the top of the backswing to the end of the follow-through could contribute to accelerated polyethylene wear. However, gradual rotational movements were consistently demonstrated during the stationary cycling. Therefore, stationary cycling is recommended rather than playing golf for patients following a TKA who wish to remain physically active.

Sports Participation in Patients After Total Hip Arthroplasty vs Periacetabular Osteotomy: A Propensity Score-Matched Asian Cohort Study

BACKGROUND

No studies have compared sports participation between total hip arthroplasty (THA) and periacetabular osteotomy (PAO) in matched Asian cohorts. We investigated sports participation and activity levels in Asian THA cohort, and compared them between THA and PAO cohorts.

METHODS

Multivariate analyses were applied to determine which factors were associated with postoperative sports participation and University of California-Los Angeles (UCLA) activity score in (1) 524 THA patients and (2) 487 acetabular dysplasia patients (295 THA patients and 192 PAO patients). In addition, postoperative sports participation and UCLA score were compared between 62 THA and 62 PAO patients after adjusting for baseline characteristics with propensity score matching.

RESULTS

Sports participation and UCLA score significantly increased after THA (P < .001 in both analyses). Preoperative sports participation was the factor most associated with both postoperative sports participation and UCLA score in both 524 THA patients and 487 acetabular dysplasia patients (P < .001 in all analyses). Multivariate analysis in 487 acetabular dysplasia patients demonstrated that THA, compared with PAO, was negatively associated with postoperative sports participation (P < .001), but not postoperative UCLA score (P = .22). THA patients showed significantly lower rate of postoperative sports participation (32.3% and 51.6%, respectively, P = .046), but not postoperative UCLA score (5.0 ± 1.6 and 5.2 ± 1.9, respectively, P = .47) compared with matched PAO patients.

CONCLUSION

THA significantly increased both sports participation and activity levels. Both multivariate and propensity score-matched analyses showed that postoperative activity levels were comparable between THA and PAO cohorts.

Does knee stability in the coronal plane in extension affect function and outcome after total knee arthroplasty?

PURPOSE

The aim of the present study was to clarify whether varus-valgus laxities under static stress in extension, femoral condylar lift-off during walking, and patient-reported outcomes after total knee arthroplasty (TKA) were correlated with each other.

METHODS

Ninety-four knees, which had undergone posterior-stabilized TKA, were analysed. The varus-valgus laxity during knee extension was measured using a stress radiograph. New Knee Society Score (KSS) questionnaires were mailed to all patients. Correlations between the values of stress radiographs and KSS were analysed. Additionally, continuous radiological images were taken of 15 patients while each walked on a treadmill to determine condylar lift-off from the tibial tray using a 3D-to-2D image-to-model registration technique. Correlations between the amount of lift-off and either the stress radiograph or the KSS were also analyzed.

RESULTS

The mean angle measured was 5.9 ± 2.7° with varus stress and 5.0 ± 1.6° with valgus stress. The difference between them was 0.9 ± 2.8°. Varus-valgus laxities, or the differences between them, did not show any statistically significant correlation with either component of the KSS (p > 0.05). The average amount of femoral condylar lift-off during walking was 1.4 ± 0.8 mm (medial side) and 1.3 ± 0.6 mm (lateral side). The amount of lift-off did not correlate with either varus-valgus laxities or the KSS (p > 0.05).

CONCLUSIONS

No correlations were found among varus-valgus laxities under static stress in extension, femoral condylar lift-off during walking, or patient-reported outcomes after well-aligned TKA. This study suggests that small variations in coronal laxities do not influence lift-off during walking and the patient-reported outcomes.

LEVEL OF EVIDENCE

IV.