Discovertebral lesion in ankylosing spondylitis: differential diagnosis with discitis by magnetic resonance imaging

Abstract  Ankylosing spondylitis (AS) is occasionally accompanied by erosive changes in the vertebral endplate at one or more restricted levels (Andersson lesions). The radiographic findings of this lesion are similar to those of bacterial discitis, and a differential diagnosis between them is often difficult. These diseases must be diagnosed correctly because they require different treatments. In order to evaluate the prevalence of Andersson lesions in the Japanese population, we examined 31 cases of AS which were treated in our department, and Andersson lesions were found in three (9.7%) of them. All these three cases developed Andersson lesions in the earlier phase of the AS, and differentiating the lesions from bacterial discitis was difficult. The details of these three cases are reviewed, and the importance of differentiating between Andersson lesions and bacterial discitis is discussed. Plain radiographs showed no clear difference between these conditions, but magnetic resonance imaging (MRI) was found to be more efficient.

Elevated cytokine responses to Vibrio harveyi infection in the Japanese pufferfish (Takifugu rubripes) treated with Lactobacillus paracasei spp. paracasei (06TCa22) isolated from the Mongolian dairy product

With the aim of evaluating the effect of a Mongolian dairy product derived Lactobacillus paracasei spp. paracasei (strain 06TCa22) (Lpp) on the cytokine-mediated immune responses to Vibrio harveyi infection, we examined 16 cytokine expressions in the Japanese pufferfish, Takifugu rubripes. Fish were orally treated with the heat-killed Lpp at 1 mg g(-1) body weight d(-1) for 3 days. At 24 h posttreatment, fish were infected by an intramuscular injection of 0.1 mL V. harveyi bacterial suspension (10(8) cfu mL(-1)). Additionally, superoxide anion production (SAP) and phagocytic activity (PA) of head kidney cells were assessed during 120 h postinfection period. Significant up-regulation of pro-inflammatory (IL-1β, IL-6, IL-17A/F-3, TNF-α and TNF-N), cell-mediated immune inducing (IL-12p35, IL-12p40 and IL-18), antiviral/intra-cellular pathogen killing (I-IFN-1 and IFN-γ), anti-inflammatory (IL-10) and lymphocyte agonistic (IL-2, IL-7, IL-15, IL-21 and TGF-β1) cytokines was observed in the treated fish compared to control ones during the pathogen infection. Furthermore, significantly increased SAP and PA (P < 0.01; 0.05) were recorded in the treated fish compared to untreated fish. These results suggest the beneficial role of Lpp in enhancement of cytokine-mediated immunity in the Japanese pufferfish against V. harveyi infection and application of this product as a potential fish immunostimulant.

Cytokine responses in the Japanese pufferfish (Takifugu rubripes) head kidney cells induced with heat-killed probiotics isolated from the Mongolian dairy products

Cytokine responses in the Japanese pufferfish (Takifugu rubripes) head kidney (HK) cells to heat-killed lactic acid bacteria probiotics isolated from the Mongolian dairy products were investigated by transcriptomic examination. The HK cells were incubated with two heat-killed bacteria, namely Lactobacillus paracasei spp. paracasei (strain 06TCa22) and L. plantarum (strain 06CC2) and the responses of 16 cytokine genes at 0 (control), 1, 4, 8, 12, 24 and 48 h post-stimulation were assayed by multiplex RT-PCR analysis (GenomeLab Genetic Analysis System, GeXPS; Beckman Coulter, Inc.). The 16 genes included in the assay were pro-inflammatory cytokines (IL-1β, IL-6, IL-17A/F-3, TNF-α and TNF-N), cell-mediated immune regulators (IL-12p35, IL-12p40 and IL-18), antiviral (I-IFN-1 and IFN-γ) and other regulatory (IL-2, IL-7, IL-15, IL-21, IL-10 and TGF-β1) cytokines. Despite the differences in the transcriptional profiles, expression of all the cytokines tested here was significantly elevated by both the probiotic bacterial stimulants compared with the unstimulated control. Therefore, this in vitro study has demonstrated the modulation of cytokine defense mechanisms in the HK cells by the two heat-killed probiotics indicating their potentiality as novel immunostimulants to fish. However, strain-dependent varied expression of important cytokines (cell-mediated immune regulators, antiviral and anti-inflammatory cytokines) suggests better efficacy of L. paracasei spp. paracasei strain as fish immunostimulant. Further in vivo studies to elucidate the cytokine regulation networks will validate our present observations. A careful evaluation of ant-inflammatory properties may be undertaken using single strain to affirm the immunostimulatory capability. Moreover, application timings and frequency to assess the longevity of immunostimulant effects and to make the application cost-effective need to be evaluated before any practical use in aquaculture.

A new concept for precise patella resection in total knee arthroplasty

We developed a new patella-cutting guide that simplifies proper alignment and enables resection of the correct thickness of bone. This guide consists of a central shaft, two support frames, and a ring. The ring consists of upper and lower disks, with a slot between the disks. The central shaft and the lower disk have holes for fixation pins. The distance from the distal end of the central shaft to the lowest level of the slot is 8 mm. Bone of the same thickness as that of the patellar component can be automatically resected using this guide. A feeler gauge is inserted through the slot, and the periarticular region is felt. This procedure enables the guide to be set at the correct angulation. A laboratory study using fresh-frozen cadaver patella specimens and a clinical study showed that proper alignment and proper resection were achieved using this guide.

Anteroposterior weight-bearing radiography of the knee with both knees in semiflexion, using new equipment

In order to obtain high reproducibility and sensitivity in the evaluation of joint space in osteoarthritic knees, we used new equipment, and established an anteroposterior weight-bearing radiograph with both knees in semiflexion taking into account our investigation of the posterior slope angle. We compared our method with the Rosenberg method, and the coefficient of variation of our method showed higher reproducibility than that of the Rosenberg method. The most essential issue is whether the bilateral leg loading radiograph can show the same sensitivity as the homolateral leg loading radiograph. We compared standing radiographs of the knee in 26 degrees flexion with those of 26 degrees flexion in both knees. We assessed the widths of the narrowest points of the joint spaces in the medial and lateral compartments, the condylar plateau angle, and the femorotibial angle, in 47 knees in 24 patients. The data were analyzed statistically by single regression and each correlation was of statistical significance. Our method has better reproducibility and is more comfortable for the subject than conventional methods.

Effect of femoral and tibial component position on patellar tracking following total knee arthroplasty: 10-year follow-up of Miller-Galante I knees

Rotational alignment of the femoral and tibial components using computed tomography (CT) was evaluated to establish if errors of alignment have a significant effect on patellofemoral complications. From 1987-1990, 54 knees in 39 patients were replaced with the Miller-Galante I knee system. Of these, 10 patients (13 knees) comprised this study. All patients had osteoarthritis. Mean patient age at surgery was 70.3 years. Mean follow-up was 10.3 years. On CT, rotational position of the femoral component relative to the epicondylar axis and the position of the tibial component relative to the tibial tubercle were evaluated. Patellar displacement and patellar tilt angle also were evaluated when the knee was flexed at 30 degrees. Mean rotation of the femoral component was 6.1 degrees of internal rotation (2.7 degrees-11.2 degrees). Mean rotation of the tibial component was 16.7 degrees of internal rotation (2.4 degrees-27.7 degrees). Mean lateral patellar tilt angle was 2.9 degrees (-6.0 degrees-11.9 degrees), and mean lateral displacement was 2.7 mm (-3.2-8.9 mm). Rotational position of both the femoral and tibial components showed a statistically significant correlation with the patellar tilt angle. This study showed the internally rotated femoral and tibial component were related to the patellar maltracking. This malalignment of the components, as well as nonanatomical patellar groove and metal-backed patellar component, could be one of the causes of the patellofemoral complications with the Miller-Galante I knee.

Menopausal syndrome in female patients with rheumatoid arthritis

Abstract This study was performed to assess the relationship between joint symptoms in rheumatoid arthritis (RA) and symptoms in menopausal syndrome. Detailed analyses of the clinical course, laboratory data, joint symptoms, and symptoms of menopausal syndrome were performed for five patients with stage I and monocyclic-type RA. The age when joint symptoms first appeared coincided with the age of menopause in all patients, and the mean age was 51.0 years. The mean period from menopause to this study was 5.4 years. All patients showed more than six menopausal syndrome symptoms. Two patients were confirmed gynecologically to have definite menopausal syndrome, and accordingly hormone replacement therapy (HRT) was given. In one patient, the polyarthralgia disappeared after she received HRT. All the American College of Rheumatology (ACR) criteria, with the exception of subcutaneous nodules, can be explained as symptoms related to estrogen deficiency in menopausal syndrome because estrogen regulates the production of inflammatory cytokines such as IL-1, IL-6, and TNFα, and these cytokines are produced in greater abundance in conditions of estrogen deficiency. Estrogen deficiency at the menopause influences joint symptoms and inflammatory parameters in rheumatoid arthritis. Estrogen deficiency in menopausal syndrome may induce joint symptoms resembling RA.

Factors affecting emotional instability in female rheumatoid arthritis outpatients with limited functional disorder

Abstract We attempted to identify which background factors were the most important indicators of such psychological problems as emotional instability, a feeling of hopelessness, and suicidal tendencies in female rheumatoid arthritis (RA) outpatients with limited functional disorder. Among female RA patients aged 20 years and older who visited the outpatient clinic, 101 class I and II patients were selected as subjects for the present study. An original questionnaire and a psychological test (CMI) were given to those subjects who had given their written consent to such testing, and an analysis was carried out on 85 patients who returned all the written forms. Their emotional instability was related to factors such as "not being able to understand the nature of RA disease and its treatment," "sense of value had changed after developing RA," "nonuse of drugs," and "duration of disease." A feeling of hopelessness was related to "smoking," and a suicidal tendency was related to "smoking" and "class I." We identified a characteristic correlation between emotional instability and background factors in this study. Paying close attention to these factors may thus be useful in preventing the appearance of psychological problems as well as in developing effective early treatment strategies.

Reductive dimerization of alkylidenemalonates using samarium(II) diiodide and 1H-NMR behavior of the dimers, 2,3-diaryl-1,1,4,4-butanetetracarboxylates

Alkylidenemalonates were readily dimerized in the presence of SmI2 to give 2,3-disubstituted 1,1,4,4-butanetetracarboxylates as mixtures of meso and racemic isomers in moderate to good yields. The structure of the less polar isomer of tetraethyl 2,3-diphenyl-1,1,4,4-butanetetracarboxylate was determined by X-ray crystallographic analysis to be the meso form. Characteristic 1H-NMR behavior of the meso and racemic isomers is also discussed.

Clinical features of multiple epiphyseal dysplasia expressed in the knee

The purpose of this study is to clarify the clinical features of the knee affected by multiple epiphyseal dysplasia. Thirty-one cases of multiple epiphyseal dysplasia were reviewed. Of the patients, 11 were male and 20 were female. The average age at onset of symptoms was 22.5 years. The average age at initial visit to the authors' hospital was 28.9 years. Radiographic findings showed epiphyseal abnormality of the knee in all but two (93%) cases. Irregularity, segmentation of the epiphysis, widening of the joint space, and genu valgum deformity were the dominant findings before epiphyseal closure. After epiphyseal closure, the most characteristic finding was a shallow femoral trochlear groove, which was observed in 56.5% of the cases. Other findings in adult patients included early onset osteoarthritic change, genu valgum, depression of the lateral tibial plateau, and multiple free bodies. However, there still is a possibility that multiple epiphyseal dysplasia exists, even if the patient lacks a shallow femoral trochlear groove. If genu valgum or varum, free bodies, and premature osteoarthritis are observed, one should evaluate other joints, keeping a diagnosis of multiple epiphyseal dysplasia in mind. Patients with knees that have a femoral trochlear groove of normal or near normal shape do exist, and premature osteoarthritic changes may develop in such patients.

Factors affecting depression and anxiety in female Japanese patients with rheumatoid arthritis

OBJECTIVE

In this study, we attempted to identify which background factors were the most important indicators regarding such psychological problems as depression and anxiety in female rheumatoid arthritis (RA) patients.

METHODS

Among female RA patients aged 20 and older, who visited the outpatient clinic, and who met the Revised Criteria of the American Rheumatism Association for RA (ARA1987), 101 Class I and II patients were selected as subjects for the present study. Specially designed questionnaires and psychological tests were given to those subjects who had given their written consent for such testing, and a stepwise multiple logistic regression analysis was carried out on the 85 patients who returned all written forms. Those factors affecting psychological problems at a significance level of 5% or less were identified.

RESULTS

It was shown that among sociodemographic factors, "a decrease in the frequency of going out socially after having RA" and "a higher education" worked as significantly associated variables for depression, while "a decrease in the number of friends after having RA" served as a significantly associated variable for trait anxiety. Significantly associated variables for state anxiety included "a decrease in the frequency of going out socially after having RA" and "a willingness to join an RA study group".

CONCLUSION

The present study demonstrated that factors related to social interactions were significantly associated with depression and anxiety in Class I and II female RA outpatients.

Anatomic variations should be considered in total knee arthroplasty

The effect of anatomic variations on the operative techniques used in total knee arthroplasty (TKA) was assessed. In 133 Japanese patients with medial osteoarthritis (OA), six parameters were measured on anteroposterior radiographs of the lower extremities taken with the patients in the supine position. The results showed that the characteristics of the knees were bowing of the femoral shaft and proximal tibia vara, with lateral offset of the tibial shaft with respect to the center of the tibial plateau. The angle between a perpendicular to the mechanical axis and the tangent to the distal femoral condyles can be used in determining the external rotation of the femoral component. This angle was more than 3 degrees in 20% of the patients. The femoral component should therefore be externally rotated more than 3 degrees relative to the posterior condylar line in such patients. Because the center of the tibial plateau is located medial to the central line of the tibial shaft in knees with medial OA, the central point of the tibial articular surface should not be used for alignment of the tibial component. The medial offset stem of the tibial component may impinge against the medial wall. Anatomic variations should be evaluated before TKA is attempted.

Tibial tubercle malposition in patellar joint instability: a computed tomograpy study in full extension and at 30 degree flexion

We evaluated the tibial tubercle position in knees with patellar instability. CT in full extension and at 30 degree flexion was used in 18 knees with instability and 18 control knees. Scans were taken at the level of the femoral epicondyles, tibial tubercle and distal tibia. We found that in full extension, the tibial tubercle was in a more lateral position in the unstable than in the control knees. At 30 degree flexion, the tibial tubercle in the unstable knees rotated internally, but it was never within the normal range. CT scans taken in full extension and at 30 degree flexion seem to be of value for ascertaining the degree of tibial tubercle malposition during knee flexion in patellar instability.

Posterior tibial slope in the normal and varus knee

Posterior tibial slope was evaluated in 30 normal and 30 varus knees using magnetic resonance imaging. The mean tibial posterior slope in the medial plateau was 10.7 degrees (range: 5 degrees - 15.5 degrees) in the normal knees and 9.9 degrees (range: 1.5 degrees - 19 degrees) in the varus knees. The mean tibial posterior slope in the lateral plateau was 7.2 degrees (range: 0 degrees - 14.5 degrees) in the normal knees and 6 degrees (range: 1 degrees - 13 degrees) in the varus knees. Although these differences were not statistically significant, there was a large range in the posterior tibial slope in both groups. When 10-mm thickness of bone was resected in the middle of the lateral plateau in total knee arthroplasty, the thickness of the bone resection in the anterior and posterior part of the lateral plateau was measured. The presumed thickness of bone was 10.1 mm (range: 7.3-13.9 mm) in the anterior part and 7.5 mm (range: 5-10.3 mm) in the posterior part. A large range in the measured thickness of bone also was detected in the varus knees. These results suggest that the shape of the proximal tibia varies among individuals and that the cutting angle should be determined in each case to avoid any mismatch of the patient's posterior slope of the tibia after implantation.

Knee stability in posterior cruciate ligament retaining total knee arthroplasty

Anteroposterior knee laxity was evaluated in 14 patients (19 knees) who had posterior cruciate ligament retaining total knee arthroplasty using the Miller Galante I prosthesis. The followup ranged from 87 to 118 months (average, 105.9 months), and the measurements were done using the KT-2000 arthrometer. The mean anteroposterior displacement with the knees with Miller Galante I prostheses was 10.1 mm at 30 degrees flexion and 8.1 mm at 75 degrees flexion. In the 15 knees with Miller Galante I prostheses with flexion greater than 90 degrees, seven had less stability at 75 degrees than at 30 degrees flexion. These knees were considered to have a nonfunctional posterior cruciate ligament, and they had a worse Knee Society score (81.1) than did the other eight knees with Miller Galante I prostheses (89.9). There were four knees in which the flexion was less than 90 degrees. In this study, approximately half of the knees with posterior cruciate ligament retaining total knee arthroplasty did not have good anteroposterior stability in flexion an average of 9 years after surgery.

Changes in knee alignment after total knee arthroplasty

Changes in limb alignment after total knee arthroplasty were evaluated in 20 knees replaced with the Miller Galante knee system. The mean follow-up period was 87.4 months. Seventeen of the 20 knees were in the varus position on the initial postoperative radiographs, but the alignment significantly changed to become even more aligned toward varus during the follow-up period. The thickness of the ultra-high-molecular-weight polyethylene (UHMWPE) also decreased significantly in the medial femorotibial joint. The wear of the UHMWPE possibly changed the alignment, and the postoperative alignment had a positive correlation with the wear rate. The components should be implanted so that the mechanical axis intersects the center of the components to prevent worsening of alignment as well as to minimize any such wear.

A new, all-inside technique for meniscus repair

A new method for arthroscopic meniscal repair using sutures with multiple knots was developed, and its mechanical strength was evaluated. Sutures are passed arthroscopically through the torn meniscus using a needle with a cleft in its tip, and when the needle is withdrawn, knots are placed both in the meniscus and the joint capsule. Our method does not require additional skin incisions and can be performed for repair of posterior tears. Furthermore, this all-inside technique minimizes the risk of popliteal neurovascular injury. Biomechanical analysis using bovine menisci showed that the maximum frictional force between the suture and meniscus was greater than the maximum strength of a suture itself. Our method is simple and rapid, making it easy to insert multiple sutures to achieve adequate stability.

Radiological assessment of the position of the tibial tuberosity by means of a marking wire in knees with patellofemoral arthritis

OBJECTIVE

To assess the usefulness of a new axial radiographic technique in knees with patellofemoral arthritis (PF-OA).

DESIGN AND PATIENTS

After a marking wire had been attached to the skin on the tibial tuberosity so that the wire matched the width of the patellar tendon, an axial radiograph was taken at 30 degrees of flexion in 16 normal knees and 14 PF-OA knees in which computed tomographic analysis had revealed a laterally positioned tibial tuberosity at 30 degrees of flexion. The distance of the marking wire from the lateral condyle and from the patellar groove was compared between the two groups.

RESULTS

The marking wire was located significantly laterally in PF-OA knees compared with normal knees.

CONCLUSION

An axial radiograph with a marking wire on the tibial tuberosity is useful for assessing the position of the tibial tuberosity in PF-OA knees.

Reliability of the anteroposterior axis and the posterior condylar axis for determining rotational alignment of the femoral component in total knee arthroplasty

We examined the reliability of the anteroposterior and posterior condylar axes for determining rotational alignment of the femoral component in total knee arthroplasty (TKA). A computed tomography scan was taken at the level of the femoral epicondyle in 84 knees (27 varus knees with medial femorotibial arthritis (FT-OA) in 26 patients, 17 knees with patellofemoral arthritis in 14 patients, and 40 normal knees in 40 volunteers). On the image, an anteroposterior axis, a line perpendicular to the anteroposterior axis, an epicondylar axis and a posterior condylar axis were drawn, and the relationship between the three axes was assessed. The mean values for the 84 knees were evaluated, and the posterior condylar axis was 6.0 degrees +/- 2.4 degrees internally rotated relative to the epicondylar axis, while the line perpendicular to the anteroposterior axis was 1.4 degrees +/- 3.3 degrees internally rotated relative to the epicondylar axis. The internal rotation angle of the posterior condylar axis relative to the epicondylar axis was 6.2 degrees +/- 1.9 degrees in the knees with medial femorotibial arthritis, 6.4 degrees +/- 2.4 degrees in the knees with patellofemoral arthritis, and 5.8 degrees +/- 2.7 degrees in the normal knees, showing consistent values in normal and osteoarthritic knees. The internal rotation angle of the line perpendicular to the anteroposterior axis relative to the epicondylar axis was 0.1 degrees +/- 3.3 degrees, 1.3 degrees +/- 3. 3 degrees, and 2.3 degrees +/- 3.1 degrees in the three groups, respectively (i.e., there were significant differences between the medial FT-OA knees and the normal knees). The results demonstrated that the anteroposterior axis was rotated externally to a significant degree in medial FT-OA knees and was less reliable than the posterior condylar axis for use in alignment for TKA on medial FT-OA knees.

Malposition of the tibial tubercle during flexion in knees with patellofemoral arthritis

OBJECTIVE

To assess the mechanisms contributing to the induction of patellofemoral arthritis (PF-OA).

DESIGN AND PATIENTS

A computed tomography scan was taken at three levels of the lower extremity in full extension and at 30 degrees of flexion. The cuts were superimposed and 12 parameters were compared in 17 PF-OA knees and 27 normal knees to assess the rotation angle of the tibial tubercle.

RESULTS

Although the tibial tubercle was in almost the same position in full extension in the normal and PF-OA knees, it was positioned significantly laterally at 30 degrees of flexion in PF-OA knees. Also the articular surface of the lateral femoral condyle was significantly narrower or steeper in PF-OA knees.

CONCLUSION

Anatomic variations and mechanical abnormalities were identified in the PF-OA knees.

Is patellar height really lower after high tibial osteotomy?

It has been reported that patellar position becomes lower after the high tibial osteotomy. However, the most commonly used methods for determining patellar height, namely, the Insall-Salvati and Blackburne-Peel methods, use a reference point on the tibia. Therefore, when a surgery is performed on the proximal tibia, the point of reference itself shifts, which may generate spurious values indicating a change when nothing has occurred. We developed a new method for measuring the change in patellar height in relation to the femur under the condition that the patella articulates with the femur, and not with the tibia. Contrary to published reports, we found that the patella height is unchanged or moves slightly proximal in relation to the femur following high tibial osteotomy.

Effect of medial displacement of the tibial tubercle on patellar position after rotational malposition of the femoral component in total knee arthroplasty

A large Q angle induced by technical error such as an internally rotated femoral component causes patellar failure after total knee arthroplasty. The effect of medial displacement of the tibial tubercle to decrease the Q angle for patellar tracking was studied by evaluating the patellar position relative to the patellar groove on the femoral component in cadaver specimens. A 5 degrees internally rotated femoral component caused the patella to shift medially about 5 mm, and also caused the tibia to rotate internally about 3 degrees at full extension. With a 5 degrees externally rotated femoral component, normal patellar tracking occurred. The distance of medial displacement was determined so that the patellar tendon was parallel to the longitudinal axis of the tibia at full extension. This allowed the quadriceps tendon, the patella, and the patellar tendon to form a straight line. The average distance of medial transposition of the tibial tubercle was 9.32 mm. Medialization of the tibial tubercle caused the patella to shift about 2 mm medially from the patellar groove. The transfer also caused an external rotation of the tibia (2 degrees-5 degrees). Medial transfer of the tibial tubercle changes patellar kinematics and corrects the tendency toward lateral patellar dislocation caused by internally rotating the femoral component; however, it also creates minor patellar and tibial kinematic changes that may have a clinical effect.

Effect of rotational malposition of the femoral component on knee stability kinematics after total knee arthroplasty

Excessive external rotation of the femoral component can cause an abnormally tight popliteus tendon complex, which induces loss of rotational laxity of the knee in the late phase of knee flexion after total knee arthroplasty. This study evaluated the effect of popliteus tendon release on rotational and varus-valgus laxity of implanted knees with an excessively externally rotated femoral component. Rotational and varus-valgus laxity was measured with a knee kinematics testing device before and after total knee arthroplasty. External rotational positions of the femoral component of 5 degrees and 8 degrees were compared, and the effects of popliteus tendon release on rotational and varus-valgus laxity were evaluated. To further investigate this question, the effect of a conforming articular design was compared with that of a flat tibial surface. External rotational position of 5 degrees did not change rotational or varus-valgus laxity of the knee. With an 8 degrees external rotational position, however, external rotational laxity significantly decreased in knees with a conforming surface at angles of 30 degrees, 45 degrees, 60 degrees, and 90 degrees. After popliteus tendon release, external rotational laxity significantly improved at 90 degrees flexion and was identical to that of the normal knee. Internal rotational range was similar before and after popliteus tendon release. Popliteus tendon release did not affect the varus-valgus laxity (stability) with either articular surface.

Patellar tracking measurement in the normal knee

Eleven fresh frozen cadaveric knee specimens were mounted in a knee kinematics test device, and normal patellar movements were evaluated with use of an external device for direct measurement of patellar movements. The effects of four different measurement conditions were assessed through alteration of one condition and determination of its effect on patellar kinematics with the use of six specimens. The four conditions included (a) change of the measuring axis from an axis parallel to the central axis of the femur (femoral axis) to one parallel to the central axis of the tibia (tibial axis), (b) rotation of the femoral axis internally 6 degrees, (c) change of the direction of the quadriceps force from parallel to the mechanical line of the lower extremity to a direction parallel to the femoral shaft, and (d) increase of the magnitude of the quadriceps force from 111 to 500 N. During knee flexion, the patella shifted laterally after a slight initial medial shift, tilted laterally from midflexion to 90 degrees, and gradually rotated medially. The patellar shift relative to the tibial axis appeared to be more medial than the shift measured relative to the femoral axis; the discrepancy was caused by the valgus position of the tibia relative to the femur. Changing the rotational angle of the femoral axis artificially changed the patellar position. Varying the direction of the quadriceps within the narrow range and increasing the quadriceps force did not affect patellar movements.(ABSTRACT TRUNCATED AT 250 WORDS)

Patellar tracking after total knee arthroplasty. The effect of tibial tray malrotation and articular surface configuration

The effect of total knee arthroplasty (TKA) with neutrally aligned and malrotated tibial trays was studied in five fresh anatomic specimen knees. Patellar shift, tilt, and rotation, and the rotational position of the tibia were measured in normal knees and after TKA with the Ortholoc Modular knee system. Both semiconstrained and unconstrained articular surfaces were assessed in the neutral position and at anatomic, 15 degrees internal, and 15 degrees external rotation of the tibial tray. After TKA, the patellae shifted slightly medially in the early phase of knee flexion because the anterior lateral flange of the femoral component was longer than the lateral trochlea of the femur and because the tibia rotated internally. The raised lateral flange on the femoral component tilted the patella medially at full extension after TKA. The semiconstrained tray allowed minimal tibial rotation because of its articular configuration. As much as 15 degrees malrotation of the unconstrained tibial tray did not affect patellar tracking. The semiconstrained tibial tray in the neutral position had almost the same patellar tracking as the unconstrained tray, but at 15 degrees external rotation, the semiconstrained tray internally rotated the tibia, leading to medial shift of the patella. Although 15 degrees internal rotation caused external rotation of the tibia, the patella did not shift as much laterally, despite the increase in the Q angle.