T. Derek V. Cooke

Varus and valgus alignment and incident and progressive knee osteoarthritis

Objective Varus and valgus alignment increase medial and lateral tibiofemoral load. Alignment was associated with tibiofemoral osteoarthritis progression in previous studies; an effect on incident osteoarthritis risk is less certain. This study tested whether alignment influences the risk of incident and progressive radiographic tibiofemoral osteoarthritis. Methods In an observational, longitudinal study of the Multicenter Osteoarthritis Study cohort, full-limb x-rays to measure alignment were acquired at baseline and knee x-rays were acquired at baseline and knee x-rays at baseline and 30 months. Varus alignment was defined as ≤178° and valgus ≥182°. Using logistic regression and generalised estimating equations, the associations of baseline alignment and incident osteoarthritis at 30 months (in knees without baseline osteoarthritis) and alignment and osteoarthritis progression (in knees with osteoarthritis) were examined, adjusting. For age, gender, body mass index, injury, laxity and strength, with neutral knees as referent. Results 2958 knees (1752 participants) were without osteoarthritis at baseline. Varus (adjusted OR 1.49, 95% CI 1.06 to 2.10) but not valgus alignment was associated with incident osteoarthritis. 1307 knees (950 participants) had osteoarthritis at baseline. Varus alignment was associated with a greater risk of medial osteoarthritis progression (adjusted OR 3.59, 95% CI 2.62 to 4.92) and a reduced risk of lateral progression, and valgus with a greater risk of lateral progression (adjusted OR 4.85, 95% CI 3.17 to 7.42) and a reduced risk of medial progression. Conclusion Varus but not valgus alignment increased the risk of incident tibiofemoral osteoarthritis. In knees with osteoarthritis, varus and valgus alignment each increased the risk of progression in the biomechanically stressed compartment.

Valgus malalignment is a risk factor for lateral knee osteoarthritis incidence and progression: Findings from the multicenter osteoarthritis study and the osteoarthritis initiative

OBJECTIVE To study the effect of valgus malalignment on knee osteoarthritis (OA) incidence and progression. METHODS We measured the mechanical axis from long limb radiographs from the Multicenter Osteoarthritis Study (MOST) and the Osteoarthritis Initiative (OAI) to define limbs with valgus malalignment (mechanical axis of ≥1.1° valgus) and examined the effect of valgus alignment versus neutral alignment (neither varus nor valgus) on OA structural outcomes. Posteroanterior radiographs and knee magnetic resonance (MR) images were obtained at the time of the long limb radiograph and at followup examinations. Lateral progression was defined as an increase in joint space narrowing (on a semiquantitative scale) in knees with OA, and incidence was defined as new lateral narrowing in knees without radiographic OA. We defined lateral cartilage damage and progressive meniscal damage as increases in cartilage or meniscus scores at followup on the Whole-Organ Magnetic Resonance Imaging Score scale (for the MOST) or the Boston Leeds Osteoarthritis Knee Score scale (for the OAI). We used logistic regression with adjustment for age, sex, body mass index, and Kellgren/Lawrence grade, as well as generalized estimating equations, to evaluate the effect of valgus alignment versus neutral alignment on disease outcomes. We calculated odds ratios (ORs) and 95% confidence intervals (95% CIs). RESULTS We studied 5,053 knees (881 valgus) of subjects in the MOST cohort and 5,953 knees (1,358 valgus) of subjects in the OAI cohort. In both studies, all strata of valgus malalignment, including 1.1° to 3° valgus, were associated with an increased risk of lateral disease progression. In knees without radiographic OA, valgus alignment >3° was associated with incidence (e.g., in the MOST, adjusted OR 2.5 [95% CI 1.0-5.9]). Valgus alignment >3° was also associated with cartilage damage on MR imaging in knees without OA (e.g., in the OAI, adjusted OR 5.9 [95% CI 1.1-30.3]).We found a strong relationship of valgus malalignment with progressive lateral meniscal damage. CONCLUSION Valgus malalignment increases the risk of knee OA radiographic progression and incidence as well as the risk of lateral cartilage damage. It may cause these effects, in part, by increasing the risk of meniscal damage.

The role of varus and valgus alignment in the initial development of knee cartilage damage by MRI: the MOST study

Objective Varus and valgus alignment are associated with progression of knee osteoarthritis, but their role in incident disease is less certain. Radiographic measures of incident knee osteoarthritis may be capturing early progression rather than disease development. The authors tested the hypothesis: in knees with normal cartilage morphology by MRI, varus is associated with incident medial cartilage damage and valgus with incident lateral damage. Methods In MOST, a prospective study of persons at risk of or with knee osteoarthritis, baseline full-limb x-rays and baseline and 30-month MRI were acquired. In knees with normal baseline cartilage morphology in all tibiofemoral subregions, logistic regression was used with generalised estimating equations to examine the association between alignment and incident cartilage damage adjusting for age, gender, body mass index, laxity, meniscal tear and extrusion. Results Of 1881 knees, 293 from 256 persons met the criteria. Varus versus non-varus was associated with incident medial damage (adjusted OR 3.59, 95% CI 1.59 to 8.10), as was varus versus neutral, with evidence of a dose effect (adjusted OR 1.38/1° varus, 95% CI 1.19 to 1.59). The findings held even excluding knees with medial meniscal damage. Valgus was not associated with incident lateral damage. Varus and valgus were associated with a reduced risk of incident lateral and medial damage, respectively. Conclusion In knees with normal cartilage morphology, varus was associated with incident cartilage damage in the medial compartment, and varus and valgus with a reduced risk of incident damage in the less loaded compartment. These results support that varus increases the risk of the initial development of knee osteoarthritis.

Analysis of limb alignment in the pathogenesis of osteoarthritis: a comparison of Saudi Arabian and Canadian cases

Abstract A study was made of alignment abnormalities and bone deformities in Saudis with osteoarthritis (SOA). Data from standardized radiography of hips and knees were: hip-knee-ankle angle (HKA), condylar-hip angle (CH), tibial plateau-ankle angle (PA), and joint surface (condylar-plateau) angle (CP). Females dominated the <50 years SOA subgroup (1.8:1), having also early onset OA with severe bowlegged deformity (mean HKA –11°) and major shifts in CH, PA, and CP relative to normal parameters. In the females, links were noted between severe disease and osteomalacia or osteoporosis, requiring prospective studies. An association between femoral deformity (CH) and OA, first reported in Canadians with OA (COA), was confirmed in SOA (especially in males of all ages). The condition implies heightened mechanical risk of onset or progression at medial joint surfaces. Further, it calls for the fresh appraisal of surgical options based on biomechanical analysis of each case, including femoral osteotomy where necessary.

Optimizing Limb Position for Measuring Knee Anatomical Axis Alignment from Standing Knee Radiographs

There is abundant literature describing approaches to radiographic measurement of alignment of the lower limb and the knee. This is timely in the context of the current transition to digital imaging applications and software for taking and recording measurements1–9. It is obviously beneficial to move toward uniformity of methods for defining alignment, and we have supported approaches toward this end10. Yet, while touched on in these and other accounts10–13, limited emphasis has been placed on the importance of limb positioning for radiographic measurements. Limb positioning is prone to errors that often arise from a lack of standardization, most notably the poor control of limb rotation during patient set-up for imaging. These errors may be exacerbated in the presence of limb deformities, especially those that obscure reference bone landmarks useful in the control of rotation. Therefore, recognition of deformities and control of rotation in the context of both health and disease are important goals for reproducible radiography. Certainly, variations of limb position, especially rotation, significantly influence the alignment measures14,15. The purpose of our editorial is to discuss practical ways to minimize positional errors. This arises from our experience of measurements using a supporting frame to limit positioning variations, thereby improving imaging reliability. Using a positioning frame can limit measurement errors for angles, such as the hip-knee-ankle (HKA) angle, to less than 2° and, with parallax corrected, leg-length distances within 2 mm14. Long radiographic views of the whole limb in stance are ideal for measuring alignment of the knee, in terms of both the HKA angle and the other joint angles that may contribute to any deformity (Figure 1). In practice, femorotibial alignment is commonly assessed from short views of the knee (Figure 1, hatched … Address reprint requests to Dr. T.D.V. Cooke, 797 Princess Street, Suite 404, Kingston, Ontario K7L 1G1. E-mail: derek{at}cookes.ca

Prosthetic reconstruction of the arthritic knee: considerations for limb alignment, geometry and soft tissue reconstruction

Abstract The function of the replaced knee joint is influenced by many factors, including implant design, material properties, fixation and surgical techniques. General surgical approaches have changed in tandem with design developments, but within them various technical elements of knee surgery are strongly adhered to (conservation) whilst others are vigorously debated (variation). The merits of debate are beyond dispute, but it is problematic to surgical patients that variations in surgical technology can beget variations in the performance of knee implants. One can make a strong argument for standardisation of techniques to keep abreast of advances in the fundamental knowledge of the anatomy and kinematics of the human knee. This paper considers an approach to restore normal knee function and kinematics through resurfacing of bone parts, developed from an appreciation of the derangements induced by disease processes on limb alignment and soft tissue restraints. The location and orientation of the implanted parts, optimally sized, is based on the functional axes of the knee, an approach which uses the bony attachment points of the essential ligamentous structures as the principle guides.

Immune Regulation of Collagenase Secretion in Rheumatoid and Osteoarthritic Synovial Cell Cultures

Primary cultures of synovial cells were obtained by proteolytic dispersion of synovial tissue from patients with rheumatoid arthritis (n = 19), psoriatic arthritis (n = 2), osteoarthritis (n = 13) and other joint problems (n = 3). The levels of endogenously secreted collagenase were variable from patient to patient but did not differ significantly between rheumatoid arthritis and osteoarthritis. The endogenous collagenase secretion was likely a consequence of mononuclear cell factor (MCF) release from monocytes/macrophages which have been shown to be present among the heterogeneous primary rheumatoid synovial cell population (Dayer et al., 1976). As also demonstrated by these investigators, medium containing MCF can be generated from peripheral blood mononuclear cells in a T lymphocyte-dependent process by the addition of phytohemagglutinin (PHA). The addition of such medium stimulated collagenase secretion from all our synovial cell cultures regardless of the endogenous level. Protein synthesis but not synovial cell proliferation was required for MCF stimulation of collagenase secretion. The direct addition of PHA to primary synovial cell cultures stimulated collagenase secretion in some but not all cases indicating the presence of T lymphocytes in these positively-responding cultures. In some of these primary synovial cell cultures in which the addition of PHA stimulated collagenase secretion, secretion was also stimulated by the addition of collagen peptides, native collagen, proteoglycan or purified protein derivative of tuberculin. We propose that, in these instances, MCF release is mediated by antigen-sensitized lymphocytes. Antigen-responsive cultures were not restricted to the rheumatoid population. Our data are compatible with the idea that infiltrated lymphocytes in inflamed synovial tissue become sensitized to cartilage and joint capsule components released during tissue degradation and contribute to matrix destruction by mediating MCF release with consequent stimulation of collagenase synthesis and secretion from synovial cells.

Conceptual Design for Condylar Guiding Features of a Total Knee Replacement

This study investigates the design requirements for guiding features that can be incorporated into the shapes of the femoral condyles and the tibial component geometry of a knee replacement system without occupying the intercondylar space of the joint so that the cruciates can be spared and still produce more physiological motions. A conceptual design for a surface-guided knee is introduced to induce effective guiding both in flexion and extension by novel features incorporated in the shape of the lateral condyle. This design can accommodate preservation of either of the cruciates while deficiencies in the functions of the other are compensated by contributions of the articular geometry in guiding the motion and stabilizing the joint. The preliminary kinematic tests on a prototype demonstrated viability of the features in guiding motion under compression.

A multiple-bundle model to characterize the mechanical behavior of the cruciate ligaments

Measurements of elongations of the cruciate ligaments have been used to study the behaviors of these ligaments in-vitro and in-vivo, mostly based on simplified two-bundle models of the cruciates. The complex fiber anatomy of the cruciates may suggest a complex deformation behavior across the continuum of their substance that cannot be captured by only two measurement points. In this study, a new methodology was introduced to include more detailed fiber anatomy and to take into consideration the wrapping of the PCL around the intercondylar notch of the femur in deep flexion. The method was used in comparison to the conventional two-bundle models on three sample cadaver knees that underwent a passive flexion up to 150°. The elongation ratios of the bundles were measured as the ratio of change in the length of the bundles over their lengths at 0° flexion. The multiple-bundle models showed ranges of variations across the attachment sites of the cruciates which at all flexion angles were significantly larger than those observed from the conventional two-bundle models. When expressed in percentages, at 150° flexion the ranges of variations in the elongation ratio of the bundles were 32.7%±31.9% and 34%±8.6% for the ACL and PCL, respectively. Results of this study showed that important variations of elongation across the body of the cruciates can be obscured to the conventional two-bundle model of the cruciates, and therefore a more detailed bundle configuration is suggested for the purpose of studying elongation behaviors of these ligaments.

Principles of Alignment in Primary and Revision Knee Replacement

Most agree that current knee replacement surgery is directed toward the resurfacing of the joint with reconstitution of physiological features, and most current designs employ anatomically shaped femoral components. All systems are geared toward the restoration of the load-bearing axis (LBA) as a line of force (body weight) passing through the hip to the ankle through the centre of the knee. Most procedures are aimed to reconstitute the joint line but opinions differ on the coronal orientation of the joint [1–3]. Most systems also advocate balance of the soft tissues [1, 3, 4].