Summary

In a rabbit model of early osteoarthritis, structural changes in femoral condyle cartilage were severer in the lateral compartment and preceded alterations in the underlying bone. In the medial compartment, altered bone properties occurred together with structural changes in cartilage.

Aims: Clinical methods do not provide direct quantitative information about cartilage functional properties. We have developed a novel handheld ultrasound indentation instrument for the diagnosis of articular cartilage degeneration. This study investigates the feasibility and reproducibility of the instrument to evaluate cartilage properties in situ. Methods: Osteochondral blocks (n=18) were prepared from lateral patellar groove (LPG), medial condyle (FMC) and medial tibial (MTP) of bovine knee. In ultrasound indentation, cartilage is indented with an ultrasound transducer. For the determination of cartilage dynamic modulus, tissue thickness and deformation are calculated using ultrasound and stress is measured with strain gauges. High-resolution material tester was used for reference mechanical tests. Cartilage glycosaminoglycan (GAG) content was determined using digital densitometry. Results: Cartilage dynamic modulus was efþciently detected with the novel instrument (r=0.913 with reference values). Dynamic modulus was signiþcantly (p< 0.05) higher at LPG (10.14±3.11 MPa) than at FMC (4.63±1.32 MPa) or MTP (2.92±1.38 MPa). Ultrasound reßection coeff. from the articular surface was signiþcantly smaller at MTP (2.04±0.73%) than at FMC (4.22±0.88%) or LPG(4.43±0.83%). Reproducibility (standardized coeff. of variation) was 3.0%, 5.2% and 1.7% for thickness, dynamic modulus and ultrasound reßection coeff. Cartilage GAG content correlated positively with dynamic modulus (r=0.678) but it was not related with the ultrasound reßection coeff. (r=0.294, p=0.24). Conclusions: Manual measurements were reproducible and the instrument can be used in situ to detect topographical variation of cartilage mechano-acoustic properties. This study establishes a step towards clinical arthroscopic use.

Aims: The aim of this prospective study was to measure changes of bone mineral density (BMD) in the proximal tibia after cemented total knee arthroplasty (TKA) in osteoarthrotic knee joints. Methods: Sixty-nine patients were scanned by dual-energy x-ray absorptiometry (DXA) within a week postoperatively, at 3, 6 and 12 months follow-up. Results:Medial metaphyseal measurement region on interest (ROI) showed a signiþcant decrease in BMD values in preoperatively varus knees joints (p < 0.0005). In preoperatively valgus knees there was a slight non-signiþcant increase in BMD (p=0.184). At the baseline the medial ROI BMD differed from each other signiþcantly in these alignment groups (p= 0.023, independent samples T-test). Alignment correction in the both groups showed bone remodeling towards similar actual BMD values. Finally medial and lateral BMD values were also more similar suggesting that the bone became equally strong on both compartments of metaphysis. We could not trace the effect of increasing AKS score values to the bone remodeling. Conclusions: We suggest that loading effect on bone may be a major profound bone remodeling factor. Its clinical value can not be ignored nor determined by other changes in knee joint status and function. These results conþrm the clinical importance of recreating the proper valgus alignment of the knee joint in TKA operation, which offers possibly better proof for the longevity of the tibial component.

Aim of the study: The aim of the study was to register and þnd out the longterm femoral bone response after insertion of femoral stem with or with-out cement. Materials and methods: Seventeen patients (7 men, 10 women) underwent cemented and 22 patients (14 men, 8 women) uncemented total hip arthroplasty (THA). The mean age in the cemented group was 69 (58–74) years and in the uncemented group 58 (46–68) years. Femoral bone mineral density (BMD) was measured using Lunar DPX or Lunar DPX-IQ densitometry according to zones by Gruen (ROI 1–7). BMD measurements were made preoperatively, and postoperatively over four to 14 days, and at 3, 6, 12, 24, and 36 months after THA. Postoperative BMD changes were calculated using the immediate postoperative BMD value as a reference, the change being expressed as a percent. Results: Peri-prosthetic BMD decreased signiþcantly almost in all ROIs during the þrst three months after both cemented (5–18%) and uncemented (3–14%) THA (p-values < 0.05 to p< 0.001). At the end of the þrst year the most remarkable decrease in BMD was found in the calcar (zone 7) in both groups (cemented 25%; uncemented 23%). Low preoperative bone loss predicted higher periprosthetic bone loss in both groups. From one to three year only small changes in periprosthetic BMD were detected after THA. Conclusions: The present study suggests that postoperative bone loss is equal after uncemented and cemented THA. The bone loss is most pronounced during the þrst six months after THA and mainly associated in proximal femoral bone. After the phase of acute bone loss, further loss is minimal after uncomplicated THA, reßecting merely the normal aging of bone. Patients with poor bone quality at baseline are at higher risk to lose bone around the prosthesis after THA.

Aims: Fourier transform infrared imaging (FTIRI) is a new quantitative imaging technique for direct visualization of chemical constituents. Our goal was to investigate the suitability of FTIRI to characterize material properties of articular cartilage (AC) and its ability to indirectly determine biomechanical characteristics of AC. Methods: Cylindrical AC samples (dia.=3.7 mm, n=6) with different stages of osteoarthrosis (OA) were prepared from bovine patellae and mechanical properties of AC were determined with a highresolution material testing device to determine Youngñs modulus (stiffness) at equilibrium (E). After biomechanical testing, one piece of the sample was processed for the histological grading of OA and the other piece was processed for FTIRI. Measurements were conducted from air-dried cryosections. Degree of cartilage degeneration was characterized by the integrated area of amide I and II absorbance. Water content of the specimen was determined from the remaining tissue by measuring the wet and dry weight of the sample. Results: Histological Mankinñs grades of the samples ranged from 0 to 7 indicating that cartilage samples showed only mild to moderate OA. FTIRI absorption showed high correlations with histological grading (r=−0.928) and water content (r=−0.980). Also, average infrared absorption of AC correlated highly linearly with E (r=0.826). Conclusions: Present results show that FTIRI offers a new tool for structural evaluation of AC quality and chemical composition. FTIR correlated well with the histological and biomechanical þndings. Technique offers a new approach to optically determine cartilage constituents. In addition to in vitro research FTIR can be coupled to arthroscopic þber optic probe in order to diagnose cartilage structure and composition in vivo.

Aims: The purpose of this study was to investigate interactions of vitamin D receptor gene (VDR) polymorphisms and regular physical exercise on BMD in a four-year randomized, controlled intervention trial in Finnish middle-aged men. Methods: The TaqI, FokI, and ApaI RFLP-markers of the VDR gene were evaluated. BMDs of the lumbar spine (L2–L4), femoral neck, and total proximal femur were measured with a dual-energy X-ray absorptiometry (DXA). Results: In the entire study group, the subjects with the VDR gene TaqI Tt or tt genotype had a greater body height and higher femoral neck BMD values than the TT subjects (p=0.001, p=0.003, respectively). After adjustment the femoral neck BMD for body height, the association remained (p=0.021). There was no difference in BMD values between the reference and exercise groups during intervention. Conclusions: We suggest that the VDR gene TaqI polymorphism may be affecting bone mass through an influence on body growth. The present findings also suggest that the VDR polymorphisms do not modify the effect of regular aerobic exercise on BMD.

Aims: The objective of this study was to investigate the ability of ultrasound backscattering to detect degeneration of articular cartilage. For this aim, ultrasound B-mode images were acquired from the surfaces of normal and degenerated bovine cartilage samples. Methods: Cylindrical osteochondral samples (n=31) with different degenerative cartilage appearance were prepared from the bovine patellae. Subsequently, degenerative stages of the samples were quantiþed using the Mankin score method. Ultrasound B-mode images of the samples were obtained using a 20 MHz ultrasound instrument (CortexTech.,Denmark).Biomechanical reference measurements were conducted using a stress-relaxation protocol (10% prestrain, 10% strain, 2 mm/s ramp velocity) in unconþned compression geometry. Results: Average reßection coefþcient ( ARC) (r=0.58) and integrated reßection coefþcient ( IRC) (r=0.53) correlated positively with the cartilage dynamic modulus. Furthermore, moduli decreased as a function of Mankin score (r ≤ −0.68). Finally, strong linear correlations were established between the backscattering parameters and the Mankin score (r=−0.79 for the ARC and r =−0.78 for the IRC). Conclusions: Results of this study suggest that ultrasound backscattering from the articular surface is able to diagnose the degeneration of AC. Theoretically, it is also possible to evaluate changes in subchondral bone with the backscatter measurements. In conclusion, ultrasound backscattering, when applied arthroscopically in vivo, may signiþcantly beneþt clinical diagnostics of early osteoarthrosis as well as monitoring of tissue healing after cartilage repair surgery.