Improved design decreases wear in total knee arthroplasty with varus malalignment

Purpose

Controversy still exists whether coronal malalignment would influence the long-term survival of total knee arthroplasty (TKA). The hypothesis was that an improved design of the articular surface of modern TKA would prevent the increase in contact stresses and thus decrease the wear even when the implant was placed in a varus position. Two different designs of TKA were compared biomechanically and clinically.

Methods

The patients whose prosthesis was initially placed in a varus alignment by the postoperative long-leg radiographs were selected. Seventeen knees using the NexGen LPS and 16 knees using the MG I were examined. Changes in postoperative alignment and the thickness of the polyethylene insert in a follow-up period of approximately 7 years were evaluated. Additionally, an in vitro biomechanical testing was conducted to measure the contact stresses and the contact area at the tibiofemoral joint of the NexGen LPS and the MG I components mounted on a servohydraulic testing device.

Results

Although the long-leg alignment did not change in NexGen LPS, the varus alignment significantly progressed in MG I. The thickness of polyethylene insert in MG I decreased a significantly greater amount compared with that in NexGen LPS. Biomechanical test showed that the NexGen LPS had a larger contact area and lower mean and peak contact stresses than the MG I significantly.

Conclusion

These results suggest that comprehensive factors of modern prosthesis including improved implant designs could improve the durability of polyethylene insert and decrease implant failures due to component malalignment.     

Dynamic knee joint stiffness and contralateral knee joint loading during prolonged walking in patients with unilateral knee osteoarthritis

BackgroundLong duration walking, a commonly recommended treatment option for knee osteoarthritis (OA), may lead to increased knee joint loading.Research questionTo evaluate the effects of prolonged walking on dynamic knee joint stiffness and contralateral knee joint contact forces (KCFs) in individuals with unilateral symptomatic knee OA.MethodsTwenty-six older adults with knee OA completed a 45-minute bout of walking on a treadmill. Dynamic knee joint stiffness, estimated KCFs, measured ground reaction forces (GRFs), and simulated muscle forces were evaluated for both the symptomatic and asymptomatic limbs at 15-minute intervals using repeated measures, analysis of variance (ANOVA).ResultsDynamic knee joint stiffness during the early weight-acceptance phase of gait was significantly higher for the symptomatic limb throughout the 45-minute bout of walking. A significant increase in peak KCFs and simulated muscle forces were also observed during the weight-acceptance phase of gait for both limbs after 30 and 45 min of walking. Additionally, significantly elevated peak KCFs and muscle forces were observed during the late-stance phase of gait for the contralateral asymptomatic limb throughout the 45-minute bout of walking.SignificanceWalking durations of 30 min or greater lead to increased knee joint loading. Additionally, the elevated dynamic knee joint stiffness observed for the symptomatic knee during the weight acceptance phase of gait appears to be unrelated to the knee joint loading profile. Finally, the greater KCFs during the late-stance phase of gait observed for the asymptomatic limb are consistent with previously demonstrated risk factors for OA development and progression.     

Morphological analysis of the knee joint in patients with hip dysplasia

Purpose

The purpose of this study was to investigate the morphological changes of the knee in patients with untreated developmental dysplasia of the hip.

Methods

Morphological analysis of 150 knee joints in 75 patients with developmental dysplasia of the hip was performed by examining computed tomographic (CT) images. Of these patients, 36 had unilateral developmental dysplasia of the hip and 39 had bilateral developmental dysplasia of the hip. Therefore, 36 hips were normal, and 114 hips were dislocated. CT images ranged from the iliac crest to 2 cm inferior to the tibial tuberosity.

Results

Compared with the knees in patients with normal hips, the femoral condyles in patients with dislocated hips were smaller and exhibited greater medial and lateral condylar asymmetry. The anterior femoral condylar angle of the femur was increased, as was the groove angle, while the trochlear groove was shallower in patients with dislocated hips. Furthermore, the lateral patella shift was reduced and the patellar tilt angle was increased in patients with dislocated hips compared with patients with normal hips. The extent of changes in these variables differed with the degree of dislocation. However, the posterior condylar angle of the femur was not affected by the degree of dislocation.

Conclusion

These findings suggest that developmental dysplasia of the hip is associated with morphological changes in the knee joint. These changes should be considered during hip and knee surgery.

Level of evidence

Prospective study, Level II.     

Arthroscopy of the knee in children and adolescents

A retrospective review was done of 69 children and adolescents (7-17 years old) who underwent 75 arthroscopies of the knee during a 5-year period. Girls were overrepresented (71%). Thirty-eight were children under the age of 16. Of 46 injuries, 34 (74%) happened during sports. Children and adolescents were divided into two age groups based on their presumed state of skeletal maturity (boys 9–15 and girls 7–14 in group I and boys 16–17 and girls 15–17 in group II); meniscal lesions were equally common in the two groups, whereas anterior cruciate ligament tears were more common in older children (NS). Eleven of 17 (65%) anterior cruciate ligament lesions were combined with other intra-articular pathology, most often meniscal tears (9/11). As in other studies, half of the prearthroscopic diagnoses were incorrect. A high frequency of incorrect prearthroscopic diagnoses and of combined lesions justifies arthroscopy as an important diagnostic tool in children and adolescents with a history of twisting knee injury or chronic nonspecific knee problems. Girls practising ball games seem to be especially prone to knee injuries leading to arthroscopy.     

Following the correction of varus deformity of the knee through total knee arthroplasty,significant compensatory changes occur not only at the ankle and subtalar joint,but also at the foot

Purpose

This study aimed to assess radiological changes of the ankle joint, subtalar joint and foot following the correction of varus deformity of the knee with total knee arthroplasty (TKA). It was hypothesized that following the correction of varus deformity by TKA, compensatory reactions would occur at the subtalar joint in accordance with the extent of the correction.

Methods

For this prospective study, 375 knees of patients who underwent TKA between 2011 and 2012 were enrolled. The varus angle of the knee, talar tilt of the ankle joint (TT), ground-talar dome angle of the foot (GD), anterior surface angle of the distal tibia and lateral surface angle of the distal tibia, heel alignment ratio (HR), heel alignment angle (HA), and heel alignment distance (HD) were measured on radiographs obtained pre-operatively and at post-operative 6 months.

Results

The mean correction angle in varus deformity of the knee was 10.8?±?4.1°. TT and GD changed significantly from 0.4?±?1.9° and 6.5?±?3.1° pre-operatively to 0.1?±?1.8° and 0.2?±?2.1°, respectively (p?=?0.007, p?<?0.001). No correlation was found between the preop–postop variance in mechanical axis of the lower extremity (MA) and TT, but there was a strong correlation between the preop–postop variance in MA and GD (r?=?0.701). HR, HA and HD also changed significantly post-operatively, and the preop–postop variance in MA showed correlations with the preop–postop variances in HR, HA and HD (r?=?0.206, ??0.348, and ??0.418). TT and the three indicators of hindfoot alignment all shifted to varus whereas GD was oriented in valgus.

Conclusion

Following the correction of varus deformity of the knee through TKA, significant compensatory changes occurred not only at the ankle and subtalar joints, but also at the foot. The findings of this study are useful in predicting the orientation of changes in the ankle and subtalar joints and the foot following TKA, and in determining the sequence of surgery when both the ankle and knee have a problem. In other words, changes in the parts of the lower extremity below the ankle joint following the correction of varus deformity of the knee must be considered when TKA is planned and performed. Patients who have problems at the ankle, subtalar, and foot joints in addition to varus deformity of the knee are recommended to undergo knee joint correction first.

Level of evidence

II.

     

Inexpensive footwear decreases joint loading in elderly women with knee osteoarthritis

Recent literature has highlighted that the flexibility of walking barefoot reduces overload in individuals with knee osteoarthritis (OA). As such, the aim of this study was to evaluate the effects of inexpensive, flexible, non-heeled footwear (Moleca^®) as compared with a modern heeled shoes and walking barefoot on the knee adduction moment (KAM) during gait in elderly women with and without knee OA. The gait of 45 elderly women between 60 and 70 years of age was evaluated. Twenty-one had knee OA graded 2 or 3 according to Kellgren and Lawrence's criteria, and 24 who had no OA comprised the control group (CG). The gait conditions were: barefoot, Moleca^®, and modern heeled shoes. Three-dimensional kinematics and ground reaction forces were measured to calculate KAM by inverse dynamics. For both groups, the Moleca^® provided peak KAM and KAM impulse similar to barefoot walking. For the OA group, the Moleca^® reduced KAM even more as compared to the barefoot condition during midstance. On the other hand, the modern heeled shoes increased this variable in both groups. Inexpensive, flexible, and non-heeled footwear provided loading on the knee joint similar to a barefoot gait and significant overload decreases in elderly women with and without knee OA, compared to modern heeled shoes. During midstance, the Moleca^® also allowed greater reduction in the knee joint loads as compared to barefoot gait in elderly women with knee OA, with the further advantage of providing external foot protection during gait.     

Torsion deformity and joint loading for medial knee osteoarthritis

PurposeThe consequences of lower limb torsion deformity on knee loading in knee osteoarthritis are poorly understood. The purpose of this study was to quantify the associations between the mechanical axis, tibial torsion and knee loading in subjects with medial knee OA and in controls.MethodsTwenty-four subjects: end-staged medial knee osteoarthritis (OA) with apparent torsion deformity (TKO, n = 6) and without torsion deformity (KOA, n = 8) and controls (CON, n = 10) were imaged using long standing lower extremity (LSLE) radiographs and computed tomography (CT). Medial knee loading was assessed using the internal knee varus moment determined by gait analysis. The LSLE mechanical axis, CT tibial torsion and the foot progression angle were used to predict medial knee loading.ResultsThe TKOs had significantly greater mechanical axis varus and knee varus moment compared to KOAs and CONs. The regression model predicting medial knee loading using the mechanical axis (β = 0.898), tibial torsion (β = 0.264) and foot progression angle (β = −0.369) showed a goodness of fit of 0.774.ConclusionsMedial knee loading was predicted by the mechanical axis and the foot progression angle. Future longitudinal studies are needed to assess the role of tibial intorsion during disease progression and following total knee replacement surgery.     

Nordic Walking does not reduce the loading of the knee joint

The use of Nordic Walking (NW) as a rehabilitation modality has increased considerably. NW (walking with poles) is advocated as a healthy physical activity that reduces the load on the knees. Few studies using the techniques of NW exist, and the findings are contradictory. The aim of this study was to investigate whether NW reduces the loadings upon the knee joint compared with walking without poles (NP). Seven experienced female NW instructors volunteered. Three-dimensional gait analyses were performed. Internal flexor and extensor joint moments were calculated using an inverse dynamics approach and the knee joint compressive forces were calculated. No differences in compression or shear forces between NW and NP were found. The peak knee flexion angles were larger during NW (−32.5±6.0°) compared with NP (−28.2±4.2°). The hip range of motion (ROM) was significantly increased during NW (64.4±10.2°) compared with NP (57.8±9.7°); no differences in the knee and ankle joint ROM were observed. The changes in the joint angles were not followed by changes in the joint dynamics. The present study does not support the statement that NW reduces the load on the knees.     

External loading of the knee joint during running and cutting maneuvers.

PURPOSE: To investigate the external loads applied to the knee joint during dynamic cutting tasks and assess the potential for ligament loading. METHODS: A 50-Hz VICON motion analysis system was used to determine the lower limb kinematics of 11 healthy male subjects during running, sidestepping, and crossover cut. A kinematic model was used in conjunction with force place data to calculate the three-dimensional loads at the knee joint during stance phase. RESULTS: External flexion/extension loads at the knee joint were similar across tasks; however, the varus/valgus and internal/external rotation moments applied to the knee during sidestepping and crossover cutting were considerably larger than those measured during normal running (P < 0.05). Sidestepping tasks elicited combined loads of flexion, valgus, and internal rotation, whereas crossover cutting tasks elicited combined loads of flexion, varus, and external rotation. CONCLUSION: Compared with running, the potential for increased ligament loading during sidestepping and crossover cutting maneuvers is a result of the large increase in varus/valgus and internal/external rotation moments rather than any change in the external flexion moment. The combined external moments applied to the knee joint during stance phase of the cutting tasks are believed to place the ACL and collateral ligaments at risk of injury, particularly at knee flexion angles between 0 degrees and 40 degrees, if appropriate muscle activation strategies are not used to counter these moments.     

Hip movement pathomechanics of patients with hip osteoarthritis aim at reducing hip joint loading on the osteoarthritic side

This study aims at defining gait pathomechanics in patients with hip osteoarthritis (OA) and their effect on hip joint loading by combining analyses of hip kinematics, kinetics and contact forces during gait. Twenty patients with hip OA and 17 healthy volunteers matched for age and BMI performed three-dimensional gait analysis. Hip OA level was evaluated based on plane radiographs using the Tönnis classification. Hip joint kinematics, kinetics as well as hip contact forces were calculated. Waveforms were time normalized and compared between groups using statistical parametric mapping analysis. Patients walked with reduced hip adduction angle and reduced hip abduction and external rotation moments. The work generated by the hip abductors during the stance phase of gait was largely decreased. These changes resulted in a decrease and a more vertical and anterior orientation of the hip contact forces compared to healthy controls. This study documents alterations in hip kinematics and kinetics resulting in decreased hip loading in patients with hip OA. The results suggested that patients altered their gait to increase medio-lateral stability, thereby decreasing demand on the hip abductors. These findings support discharge of abductor muscles that may bear clinical relevance of tailored rehabilitation targeting hip abductor muscles strengthening and gait retraining.     

Radiographic measures of knee alignment in patients with varus gonarthrosis: effect of weightbearing status and associations with dynamic joint load

BACKGROUND: Radiographic measures of lower limb malalignment are used to indicate abnormal loading of the knee and to plan corrective procedures. HYPOTHESES: Weightbearing status during hip-to-ankle radiographs will significantly affect malalignment measures; malalignment in single-limb standing will be most highly correlated to the external knee adduction moment during gait, a proposed dynamic measure of functional knee joint load. STUDY DESIGN: Controlled laboratory study. METHODS: Mechanical axis angle was measured in 40 patients with varus gonarthrosis from hip-to-ankle radiographs taken with patients in single-limb standing, double-limb standing, and supine positions. Kinematic and kinetic data were collected during walking and used to calculate the peak adduction moment about the knee. RESULTS: Repeated-measures analysis of variance and Scheffé post hoc tests indicated that mechanical axis angle measured on single-limb standing radiographs (-8.7 degrees +/- 4.0 degrees) was significantly greater than on double-limb standing radiographs (-7.1 degrees +/- 3.8 degrees), which was significantly greater than on supine radiographs (-5.5 degrees +/- 2.8 degrees). The peak knee adduction moment (2.8 +/- 0.8 percentage body weight x height) was only moderately correlated with mechanical axis angle on single-limb standing (r = -0.46), double-limb standing (r = -0.45), and supine (r = -0.43) radiographs. CONCLUSION: Patient position significantly affects frontal plane knee alignment. However, the peak knee adduction moment is only moderately correlated to mechanical axis angle, regardless of weightbearing status. CLINICAL RELEVANCE: These findings are inconsistent with the hypothesis that mechanical axis angle measured in single-limb standing is more representative of dynamic joint load and further highlight the differences between static and dynamic measures. Results also underscore the importance of reporting patient position during radiographs and keeping positions consistent when evaluating patients over time.     

Bone scintigraphy of hip joint effusions in children

Thirty-eight children with hip pain of acute onset were studied by bone scintigraphy. Nine patients had diminished radiotracer deposition involving the entire proximal femoral ossification center. This could be related to infarction or compression of the blood supply by a tense joint effusion. Eight of these patients had joint aspiration confirming the presence of an effusion. Five patients had follow-up studies after aspiration, and femoral-head uptake reverted to normal in all but one which subsequently proved to be infarcted. A photopenic zone was seen on blood pool images in 10 patients, many of whom were also aspirated of fluid. Bone scintigraphy is useful in the diagnosis of joint effusions and can give information as to the state of perfusion of the femoral head. Follow-up studies after aspiration can differentiate infarction from reversible ischemia.