Purpose: To determine the relationship between the in vivo indentation stiffness and indices of histopathological degeneration of human knee articular cartilage.

Materials and Methods: Cartilage compressive stiffness was measured in 98 patients during in vivo knee arthroscopies. The age of the patients ranged from 21 to 63 years (mean age 29 years). Male to female ratio of the patients was 37:61. The measurements were performed at eight standard sites. No chondropathic or grade I. chondropathic surfaces were measured. An indentation instrument, Artscan 1000, was used for in vivo measurements. Four plugs were harvested from each knee for histological analysis. The stage of cartilage degeneration was assessed according to Mankin histolopathology score. 16 measurements were performed after ACI.

Results: Lateral femoral condyle stiffness (mean + SD; 5.12 ±1.02N) was greater than all other sites and was significantly greater than mean values obtained for medial femoral condyle (4.8 ± 1.22N); medial and lateral trochlea (4.2 + 0.92, 4.6 + 1.27N), medial (3.1 ± 0.66N) and lateral patella (3.3 ± 1.01N); and medial and lateral tibial condyle for all subjects (2.4 ± 1.17N and 3.2 ± 1.16N).

The dynamic modulus of the normal or mildly degenerated cartilage correlated negatively with the Mankin score: r (Spearman) = −0.823, n =

348. All visually degenerated samples were softer (dynamic modulus < 2.9 Mpa) than the visually and histologically normal samples (dynamic modulus = 14.7 + 2.9 MPa). Stiffness at the repaired site was similar to normal cartilage at adjacent sites in the knee.

Conclusion: The high negative correlation between stiffness and the Mankin score suggests that the stage of cartilage degeneration can be quantitatively and indirectly assessed with a hand-held instrument during arthroscopy.

Purpose: To determine the relationship between the in vivo indentation stiffness and indices of histopathological degeneration of human knee articular cartilage.

Materials and Methods: Cartilage compressive stiffness was measured in 98 patients during in vivo knee arthroscopies. The age of the patients ranged from 21 to 63 years (mean age 29 years). Male to female ratio of the patients was 37:61. The measurements were performed at eight standard sites. No chondropathic or grade I. chondropathic surfaces were measured. An indentation instrument, Artscan 1000, was used for in vivo measurements. Four plugs were harvested from each knee for histological analysis. The stage of cartilage degeneration was assessed according to Mankin histolopathology score. 16 measurements were performed after ACI.

Results: Lateral femoral condyle stiffness (mean + SD; 5.12 ±1.02N) was greater than all other sites and was significantly greater than mean values obtained for medial femoral condyle (4.8 ± 1.22N); medial and lateral trochlea (4.2 + 0.92, 4.6 + 1.27N), medial (3.1 ± 0.66N) and lateral patella (3.3 ± 1.01N); and medial and lateral tibial condyle for all subjects (2.4 ± 1.17N and 3.2 ± 1.16N).

The dynamic modulus of the normal or mildly degenerated cartilage correlated negatively with the Mankin score: r (Spearman) = −0.823, n = 348. Stiffness at the repaired site was similar to normal cartilage at adjacent sites in the knee.

Conclusion: The high negative correlation between stiffness and the Mankin score suggests that the stage of cartilage degeneration can be quantitatively and indirectly assessed with a hand-held instrument during arthroscopy.

Purpose: Authors introduce short term results, hazards and solutions of 52 minimally invasive total knee replacement performed in their institute. Aspects of minimally invasive and minimalised exposures are detailed with differences in indication .

Methods: Starting in June 2004 52 minimally invasive total knee replacements were performed in authors institute. The technique is quadriceps sparing, the implants are placed in through a medial parapatellar MIS incision. Types of vastus medialis insertion are crucial in indication of MIS or minimalised total knee. Preparation of the surfaces needs careful preparation, precise instrumentation and skill. Following patellar resection alignment, ligament balance should be treated as important and accurate as with other techniques. No muscles and tendons are detached Neurovascular hazards, complications, difficulties with solutions are introduced. Indication is determined by pathoanatomy and weight of the patient. Malalignment shouldn’t exceed 10–15 degrees. Flexion contracture more than 10 degrees is contraindication of the technique.

Depending on the type of vastus insertion midvastus approach was used with good results in 8 cases .

Results: The operation performed on properly selected patients results in a good implantation with appropriate ligament balance and stability. Average flexion was 74 degrees in the first two post op days. Post operative pain was significantly reduced. Hospital stay was 3,1 days. There was no infection. Conversion to normal exposure was done in 3 cases. In 8 cases midvastus approach was preferred because of anatomy.

Conclusions: Minimally invasive total knee replacement is technically more demanding, requiring adequate training and knowledge. Appropriate indication is inevitable. Hospital stay and rehabilitation time is reduced also resulting in economic benefit, though never compromising good result of TKR.

Purpose: Authors introduce short term results, hazards and solutions of 250 two incision MIS hip replacement performed in their institute. Aspects of one incision techniques are detailed with differences in indication .

Methods: Between April 2003 and September 2004 250 two-incision minimally invasive total hip replacements were performed in authors institute. The cup and the stem is implanted through two incisions using physiological muscle route between m. sartorius and m. tensor fasciae latae and the m.rectus femoris and the m. gluteus medius. Preparation of the stem is done through an incision made above the greater trochanter through a gluteus maximus split straight done to the piriformis fossa. No muscles and tendons are detached Neurovascular hazards, complications with solutions are introduced. Indication is determined by pathoanatomy and weight of the patient. 115 osteoarthritis, 72 aseptic necrosis, 57 dysplastic and 6 posttraumatic patients were operated.

Results: The operation performed on properly selected patients results in increased primary stability, because of preserving structures like the iliotibial tract, muscles and the iliofemoral ligament, causing minimal soft tissue damage. There was no dislocation. Radiological analysis revealed more than 3 degrees malalignment in 3,7 % for stem and in 5,1% for cup. Fluoroscopy and OP time was reduced to av. 6 secs. Average flexion was 76 degrees in the first two post op days. Post operative pain was significantly reduced. Hospital stay was 3,2 days. There was no infection, nor heterotopic ossification. In 5 cases the femur fractured and wiring was necessary through the anterior incision. 1 revision for cemented stem was necessary because of stem migration due to extreme size of femur . Conversion to lateral exposure was done in one case.

Conclusions: Two incision minimally invasive total hip replacement is technically more demanding, requiring adequate training and knowledge. Appropriate indication is inevitable. Hospital stay and rehabilitation time is reduced also resulting in economic benefit, though not compromising good result of THR.

Introduction: Adequate congruency and primary stability are vital for good long-term results after mosaicplasty. The strength of press-fit stability of the grafts depends upon the length and diameter of the graft, extent of dilation and bone quality. The aim of our study was to quantify the effect of graft diameter and dilation length on the primary stability of single osteochondral grafts against compression and compare the stability of single and multiple osteochondral grafts in an in vitro biomechanical animal model.

Methods: In the single graft series one osteochondral graft was transplanted from the trochlea of porcine femurs to the weight-bearing area of the lateral femoral condyle, while in the multiple graft series three grafts were transplanted in a row or in circular fashion in the same position. We used the MosaicPlasty instruments (Acufex, Smith & Nephew Inc. MA, USA). The specimen was installed on a testing machine (Computer controlled ZWICK FR005TH type tensile machine, Zwick GmbH Ulm, Germany) and the graft was first pushed in level with the surrounding cartilage surface, then it was pushed 3 mm deeper. The push-in forces were measured and the compression curve was registered.

Results: In the case of single 4.5-mm grafts, the mean level push-in force was 43.5 N, pushing 3 mm deeper needed a mean of 92.5 N (n=13). In the case of single 6.5-mm grafts, level push-in needed a mean of 76.2 N, while for pushing 3 mm deeper a mean of 122.2 N force had to be used (n=14). The length of the drill-hole and the dilation were both 20 mm in each setting. When using 20 mm long drill-holes and 15 mm dilation length, the values above were found to be 36.6 N and 122.5 N in the case of 4.5-mm grafts (n=12).

In case of multiple grafting level push-in needed a mean force of 31.8 N in the row series, while pushing 3 mm deeper needed a mean of 52.17 N (n=7). In the circle series level push-in needed a mean of 30.44 N, while for pushing 3 mm deeper a mean of 54.33 N force had to be used (n=9).

Conclusions: These results suggest that grafts of greater diameter are more stable in absolute values and the stability may be increased by shorter dilation length, while level push-in forces do not increase significantly. Multiple grafts may not be as stable as single grafts after transplantation and transplantation in a row or in circular fashion does not influence stability.

Aims: The relationship between the structural and histological changes of articular hyaline cartilage and the stiffness of this tissue was evaluated. Methods: Artscan 1000, an articular stiffness tester was used for in vivo measurements during arthroscopy indicated on orthopaedic or trauma disorders. 100 patients were involved in the study. Measurements were performed at eight standard sites: medial and lateral femoral condyles, medial and lateral tibial condyles, medial and lateral facet of the patellofemoral joint and medial and lateral facet of the patella. Standard 10N predefined loading force was applied during the measurements. The indenter force produced by the deformed cartilage tissue is used as the indicator of cartilage stiffness. Results: Clinical measurements revealed a topographical variation of the stiffness of normal cartilage. In general, the femoral cartilage is stiffer than tibial or patellar one. The stiffest cartilage was measured at the lateral femoral condyle. Conclusions: Changes of articular cartilage structure can be indirectly observed during arthroscopy as an alteration in cartilage stiffness.

Aim: The purpose of this paper was to describe the biological reaction imposed by a prosthetic ligament.

Materials-Methods: Polyester-carbon synthetic matrices were implanted into 29 rabbits. The implants were transected centrally and reconstructed with resorbable suture material. At regular intervals from 4th day to 29 weeks, tissue samples from the ingrown implants were obtained for histology and mechanical testing. Light microscopy, DNA cytometry, immunohistochemical analysis of the collagen types, transmission and scanning electron microscopy were carried out. Ultimate tensile strength (UTL), elongation to failure (EF) and structural stiffness (SS) were determined at intervals of 8, 16 and 29 weeks.

Results: The ingrowth of tissue into the scaffold provided a significant increase in tensile strength, which improved with time. The UTL significantly increased from 18.86 N ±14.69 at 8 weeks to 51.4 N ±14.64 at 29 weeks. Light microscopy showed no infl ammation or foreign body reaction. At 4th day the first fibroblast cells settled on the matrix. The DNA cytometry showed an increase of the number of the fibroblast cell mitoses up to 16 days. After 2 weeks a mesh of connective tissue was formed around the scaffold, but the number of fibroblast cells remained constant. At 4 weeks the connective tissue started to infiltrate in between the artificial fibres. Type I, III and V collagens were identified. Electron microscopically the collagen weave was irregular with a mean fibril diameter of 28.4 ± 5.2 nm of a monophasic distribution. Collagen type I accumulated progressively and more and more dense collagenous fascicles appeared in the mesh in the proximity of the artificial fibres.

Conclusion: The subcutaneous tissue may act as a bio-reactor and the skin fibroblast seeding of a synthetic matrix appears to be transformed a dense connective tissue during the first 4 weeks, providing tensile strength improvement to the tissue envelope with time.