T.D.V. Cooke

Association of Leg-Length Inequality With Knee Osteoarthritis: A Cohort Study

BACKGROUND Leg-length inequality is common in the general population and may accelerate development of knee osteoarthritis. OBJECTIVE To determine whether leg-length inequality is associated with prevalent, incident, and progressive knee osteoarthritis. DESIGN Prospective observational cohort study. SETTING Population samples from Birmingham, Alabama, and Iowa City, Iowa. PATIENTS 3026 participants aged 50 to 79 years with or at high risk for knee osteoarthritis. MEASUREMENTS The exposure was leg-length inequality, measured by full-limb radiography. The outcomes were prevalent, incident, and progressive knee osteoarthritis. Radiographic osteoarthritis was defined as Kellgren and Lawrence grade 2 or greater, and symptomatic osteoarthritis was defined as radiographic disease in a consistently painful knee. RESULTS Compared with leg-length inequality less than 1 cm, leg-length inequality of 1 cm or more was associated with prevalent radiographic (53% vs. 36%; odds ratio [OR], 1.9 [95% CI, 1.5 to 2.4]) and symptomatic (30% vs. 17%; OR, 2.0 [CI, 1.6 to 2.6]) osteoarthritis in the shorter leg, incident symptomatic osteoarthritis in the shorter leg (15% vs. 9%; OR, 1.7 [CI, 1.2 to 2.4]) and the longer leg (13% vs. 9%; OR, 1.5 [CI, 1.0 to 2.1]), and increased odds of progressive osteoarthritis in the shorter leg (29% vs. 24%; OR, 1.3 [CI, 1.0 to 1.7]). LIMITATIONS Duration of follow-up may not be long enough to adequately identify cases of incidence and progression. Measurements of leg length, including radiography, are subject to measurement error, which could result in misclassification. CONCLUSION Radiographic leg-length inequality was associated with prevalent, incident symptomatic, and progressive knee osteoarthritis. Leg-length inequality is a potentially modifiable risk factor for knee osteoarthritis. PRIMARY FUNDING SOURCE National Institute on Aging.

Does Measurement of the Anatomic Axis Consistently Predict Hip-Knee-Ankle Angle (HKA) for Knee Alignment Studies in Osteoarthritis? Analysis of long limb radiographs from the Multicenter Osteoarthritis (MOST) Study

OBJECTIVE Researchers commonly use the femoral shaft-tibial shaft angle (FS-TS) from knee radiographs to estimate the hip-knee-ankle angle (HKA) in studies examining risk factors for knee osteoarthritis (OA) incidence and progression. The objective of this study was to determine the relationship between HKA and FS-TS, depending on the method of calculating FS-TS and the direction and degree of knee deformity. METHODS 120 full-length digital radiographs were assigned, with 30 in each of four alignment groups (0.0°-4.9°, and ≥5.0° of varus and valgus), from a large cohort of persons with and at risk of knee OA. HKA and five measures of FS-TS (using progressively shorter shaft lengths) were obtained using Horizons Analysis Software, Orthopaedic Alignment & Imaging Systems Inc. (OAISYS). The offsets between HKA and the different versions of FS-TS were calculated, with 95% confidence intervals (CIs). Pearson correlations were calculated. RESULTS In varus limbs use of a shorter shaft length increased the offset between HKA and FS-TS from 5.1° to 7.0°. The opposite occurred with valgus limbs (from 5.0° to 3.7°). Correlations between HKA and FS-TS for the whole sample of 120 individuals were excellent (r range 1.00-0.88). However, correlations for individual alignment groups were low to moderate, especially for the shortest-shaft FS-TS (r range 0.41-0.66). CONCLUSIONS The offsets obtained using the shorter FS-TS measurements vary depending on direction and degree of knee deformity, and therefore may not provide reliable predictions for HKA We recommend that full-length radiographs be used whenever an accurate estimation of HKA is required, although broad categories of alignment can be estimated with FS-TS.

Universal bone cutting device for precision knee replacement arthroplasty and osteotomy

Since malplacement contributes most to loosening of total knee replacements (TKR), a jig was devised, aligned to and mounted on the tibia, with a 3 degrees of freedom sliding saw. A central distractor, attached to the jig, positions and aligns the knee at 0 degrees or 90 degrees. The femur is then rigidly linked to the jig for bone cutting. Resurfacing designs (Cloutier and Townley) have been regularly implanted, aligned +/- 1 degree. This precision should minimize loosening and improve function.

Can anatomic alignment measured from a knee radiograph substitute for mechanical alignment from full limb films

OBJECTIVES To examine whether categories of anatomic alignment (varus, neutral, valgus) measured from knee X-rays agree with similar categories of mechanical alignment from the full limb film and whether varus anatomic malalignment predicts medial joint space loss on knee X-rays as well as varus mechanical alignment. METHODS We used data from the Osteoarthritis Initiative (OAI) (full limb and flexed knee X-rays) to examine agreement of anatomic and mechanical alignment and data from Boston Osteoarthritis of the Knee Study (BOKS) to evaluate the association of full limb mechanical alignment vs knee X-ray anatomic alignment with joint space loss. A 4 degree offset was used to correct for the more valgus angulation of the anatomic alignment. RESULTS Of 143 subjects whose knee X-rays and full limb films were publicly released from the OAI, the agreement of varus, neutral and valgus alignment was only moderate (kappa=0.43, P<0.001). In BOKS, varus mechanical and anatomic alignments measured from full limb and knee X-rays respectively both predicted a high risk of medial joint space loss vs neutral alignment--for mechanical alignment, odds ratio (OR)=4.82 [95% confidence interval (CI) 1.93, 12.00] and for anatomic alignment OR=4.25 (95% CI 2.08, 8.72). CONCLUSIONS While agreement of alignment from knee X-ray to full limb film was only moderate, varus malalignment measured from a flexed knee predicted the likelihood of progression well. Flexed knee alignment may be more relevant to knee osteoarthritis (OA) risk than that of a fully extended knee, but a measurement of alignment from a short limb is an imperfect surrogate for full limb alignment.

Stereoradiogrammetric technique for estimating alignment of the joints in the hand and wrist.

A method and apparatus for quantitative measurement of the alignment and motion of the joints of the hand in three dimensions has been developed using stereoradiogrammetric principles. Alignment in planes of flexion-extension and radial-ulnar deviation can be determined to within 2.5 degrees; rotation about the long axis of the metacarpals or phalanges is more difficult to determine, and can be measured to within 7 degrees. Stereo views subtending angles in the range of 40 degrees were found to optimize the total system accuracy.

Validity and sensitivity to change of three scales for the radiographic assessment of knee osteoarthritis using images from the Multicenter Osteoarthritis Study (MOST)

OBJECTIVES The purpose of this study was to assess the concurrent validity and sensitivity to change of three knee osteoarthritis (OA) grading scales. The Kellgren-Lawrence (KL) and the Osteoarthritis Research Society International (OARSI) joint space narrowing (JSN) grading scales are well-established. The third scale, the compartmental grading scale for OA (CG) is a novel scale which grades JSN, femoral osteophytes, tibial erosion and subluxation to create a total score. METHODS One sample of 72 posteroanterior (PA) fixed-flexion radiographs displaying mild to moderate knee OA was selected from the Multicenter Osteoarthritis Study (MOST) to study validity. A second sample of 75 radiograph pairs, which showed an increase in OA severity over 30 months, was selected to study sensitivity to change. The three radiographic grading scales were applied to each radiograph in both samples. Spearmans rank correlation coefficients were used to correlate the radiographic grades and the change in grades over 30 months with a Whole-organ Magnetic Resonance Imaging Score (WORMS)-based composite score which included five articular features of knee OA. RESULTS Correlations between the KL, OARSI JSN and CG grading scales and the magnetic resonance image (MRI)-based score were 0.836, 0.840 and 0.773 (P < 0.0001) respectively while correlations between change in the radiographic grading scales and change in the MRI-based score were 0.501, 0.525 and 0.492 (P < 0.0001). CONCLUSIONS All three radiographic grading scales showed high validity and are suitable to assess knee OA severity. They showed moderate sensitivity to change; therefore caution should be taken when using ordinal radiographic grading scales to monitor knee OA over time.

Alignment of the first metatarsal-phalangeal joint: important criteria for a new joint replacement

Joint replacement is one of many options for the treatment of the first metatarsophalangeal (MTP) joint. Studies of the geometry of that joint have shown that it consists of two distinct articulations, the metatarsophalangeal and the MT-sesamoidal. Both are important, but the MT-sesamoidal tolerates only small deviations from an ideal alignment. The aim of this study was to investigate the alignment of the first MTP joint of a potential patient population, in order to design an optimal surface replacement. One measurement, the extension angle between the MT and the proximal phalanx was found to be the most important alignment criterion for the successful design of an implant and the necessary instruments. This angle controls the delicate interplay between the metatarsal head and the sesamoids and tolerates only small deviations from the normal range before the chance of sesamoidal subluxation increases significantly. The pre-operative knowledge of this and other alignment criteria is important for the ideal placement of an anatomical implant.

393 IS THE FEMORAL SHAFT-TIBIAL SHAFT ANGLE A RELIABLE SUBSTITUTE FOR THE HIP-KNEE-ANKLE ANGLE IN KNEE OSTEOARTHRITIS?

eralization. The fact that these changes exist within the BMEL regions but not in adjacent regions (also from an osteoarthritic joint) imply a localized imbalance in bone formation and mineralization specific to the BMEL region. These results suggest that BMEL may be implicated in abnormal bone turnover in regions underlying cartilage defects, and therefore may be a therapeutic target and prognostic marker of OA progression.

Application of Bench-Mounted Saws for Precision Replacement Arthroplasty of the Arthritic Knee — The Questor Systems

Prosthetic replacement arthroplasty has revolutionised surgical treatment for arthritis of hip and knee joints, but as time passes, the number of failures, (mainly) due to loosening of the implant, increases. Although poor design and material features have a recognised importance in loosening, a malpositioned prosthesis must carry the greatest responsibility [1–4]. The precision involved in the manufacturing process of the implant is set to a level of tolerance ±0. 2 mm. This is, in all likelihood, a factor of over ten times greater precision than current bone cutting/placement techniques. The geometric accuracy employed in the construction of the implants sets a standard to be emulated in the orientation and accurate placement of the prosthesis; it recommends a comparably high level of placemealignment accuracy for the bone cuts.

The physiological basis for a flexible condylar tibial plateau design.

Knee resurfacing is a successful treatment for osteo- and rheumatoid arthritis in elderly patients. The application of this treatment to younger more active and obese persons has the potential to produce premature wear, loosening, and undesirable bone remodelling. A new generation of more physiologically compatible components is required for these situations. This paper discusses the design and analysis of a prototype tibial base plate aimed at physiological load transfer. Incorporated in the design are mechanisms to alleviate lift-off phenomena, bone stress concentrations, stress shielding, and micromotion at the bone-implant interface. The design requires viable cancellous bone stock, so that the bone may respond by remodelling to the dynamic loading during normal ambulatory activities.