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Biomedical subjects

M S Kuster

Publications and source records attributed to M S Kuster.

15 recordsLinked to original sources
PubMed2006

[Knee ligament injuries].

Like no other joint of the human body the knee depends on intact ligaments. Knee instability due to ligament injuries will cause abnormal joint kinematics, and thereby is made responsible for secondary damage to other important knee joint structures. Diagnosis of knee ligament injuries is based on the detailed history with often typical injury patterns, as well as on the physical examination with specific knee ligament tests. In addition radiological evaluation is used. The range of knee ligament injuries is wide. Beginning with an isolated medial collateral ligament rupture which will heal with conservative treatment, they range to knee dislocation, a serious injury which needs emediate care and is associated with a high incidence of complications. Surgical procedures aim to reconstruct knee ligaments as anatomical as possible to provide for a long term stable knee joint.

Algorithms↗
PubMed2006

Tunnel placement in anterior cruciate ligament (ACL) reconstruction: quality control in a teaching hospital.

Correct placement of the femoral and tibial bone tunnels is decisive for a successful anterior cruciate ligament (ACL) reconstruction. Our method of tunnel placement was evaluated as part of quality control at a teaching hospital. The emphasis was placed mainly on investigating the influence of surgical experience on tunnel placement, and the effect of tunnel position on the clinical outcome. Seventeen surgeons with different levels of experience (between 0 and >150 ACL reconstructions) performed endoscopic ACL repair in uniform technique from August 2000 to August 2003 on 50 patients (18 women, 32 men, age range 18-43 years). The patients were available to clinical and radiological follow-up after an average of 19 months. The clinical outcome was classified according to the International Knee Documentation Committee (IKDC) standard evaluation form. The femoral tunnel was evaluated according to the quadrant method of Bernard and Hertel; the position of the tibial bone tunnel was assessed according to the criteria of Stäubli and Rauschnig. The IKDC score revealed 47 (94%) patients with a normal (A) or nearly normal (B) knee joint at follow-up. According to the quadrant method, the femoral canal was situated on average at 29% in the saggital plane. The tibial tunnel was situated on average at 43% of the a.p. diameter of the tibial condyle. Statistical analysis of our data showed no significant correlation between tunnel placement and surgical expertise. However, a highly significant correlation was found (alpha<0.01) between the femoral position of the tunnel in the sagittal plane and the IKDC score. The more anterior the femoral canal, the poorer the IKDC score. The method of tunnel placement in ACL reconstruction being investigated here only showed slight dependence on surgical experience, whereby good short-term clinical outcomes were achieved. Therefore, the method is suitable for application at a teaching hospital. A far too anterior femoral tunnel placement will probably lead to a decline in the clinical result.

Adult↗
PubMed2004

Influence of collateral ligament laxity on patient satisfaction after total knee arthroplasty: a comparative bilateral study.

INTRODUCTION: Correct ligamentous balancing is an important determinant of the clinical outcome in total knee arthroplasty (TKA). Many surgeons prefer a tight rather than a lax knee during implantation of a TKA. The hypothesis in this study was that patients with a slightly laxer knee joint might perform better than patients with a tight knee joint after implantation of a TKA. PATIENTS AND METHODS: Twenty-two patients with bilateral knee arthroplasties were clinically and radiologically evaluated at a mean follow-up of 4.5 years, ranging from 2 to 7 years. There were 12 women and 10 men with an average age of 68.9 years (range 32-82 years) at the time of surgery. A modified HSS score (excluding laxity), varus and valgus stress X-rays in 30 degrees of knee flexion, and the subjective outcome of both knees were compared. A knee was considered tight when it opened less than 4 degrees and lax if it opened 4 degrees or more on stress X-ray. RESULTS: There was a trend towards improved range of motion and HSS score for the laxer knee joints. However, the difference did not achieve statistical significance. Eleven of the 22 patients considered one side subjectively better than the other side. In 10 out of these 11 TKA, the slacker knee joint was the preferred side ( p<0.05). CONCLUSIONS: As the present study compared bilateral knee joints after TKA, the same patient could act as a control group, and subtle subjective differences were revealed which are not quantifiable. The results showed that patients with a preferred side felt significantly more comfortable on the laxer side, indicating that during intraoperative ligamentous tensioning, some varus and valgus laxity at 20-30 degrees of flexion might be preferable to an over-tight knee joint. Further biomechanical and prospective investigations will be necessary to establish the correct soft-tissue tensioning.

Adult↗
PubMed2002

Lack of correlation between different measurements of proprioception in the knee.

Current methods of measurement of proprioceptive function depend on the ability to detect passive movement (kinaesthesia) or the awareness of joint position (joint position sense, JPS). However, reports of proprioceptive function in healthy and pathological joints are quite variable, which may be due to the different methods used. We have compared the validity of several frequently used methods to quantify proprioception. Thirty healthy subjects aged between 24 and 72 years underwent five established tests of proprioception. Two tests were used for the measurement of kinaesthesia (KT1 and KT2). Three tests were used for the measurement of JPS, a passive reproduction test (JPS1), a relative reproduction test (JPS2) and a visual estimation test (JPS3). There was no correlation between the tests for kinaesthesia and JPS or between the different JPS tests. There was, however, a significant correlation between the tests for kinaesthesia (r = 0.86). We conclude therefore that a subject with a given result in one test will not automatically obtain a similar result in another test for proprioception. Since they describe different functional proprioceptive attributes, proprioceptive ability cannot be inferred from independent tests of either kinaesthesia or JPS.

Adult↗
PubMed2002

Osteonecrosis of the humeral head after extracorporeal shock-wave lithotripsy.

A 59-year-old woman with calcific tendinitis in her right shoulder underwent extracorporeal shock-wave lithotripsy. Three years and four months later she presented with osteonecrosis of the head of the right humerus. It is known that shock waves in patients with urological disorders can damage blood vessels. A possible reason for the development of osteonecrosis in this patient may have been damage to the blood supply of the head of the humerus.

Female↗
PubMed2000

[Knee endoprosthesis: sports orthopedics possibilities and limitations].

Many patients would like to resume some sport activities after total knee replacement; however, most recommendations are based on subjective opinion rather than scientific evidence. The following paper presents a literature review of sports after total knee replacement and includes recommendations which are based on biomechanical laws. Most total knee designs show increased conformity near full extension. Beyond a certain knee flexion angle, the conformity ratio decreases due to a reduced femoral radius. Therefore, these designs accept higher loads near full extension than in flexion. In order to recommend suitable physical activities after total knee replacement, both the load and the knee flexion angle of the peak load must be considered. It has been shown that power walking and cycling produce the lowest polyethylene inlay stress of a total knee replacement and seem to be the least demanding endurance activities. Jogging and downhill walking show high inlay stress levels and should be avoided. Hence, for mountain hiking, patients are advised to avoid descents or at least use skipoles and walk slowly downhill to reduce the load on the knee joint. It must also be mentioned that any activity represents additional wear, which may affect the long-term results of total knee replacements. Further clinical studies are necessary to validate the biomechanical investigations.

Adolescent↗
PubMed2000

Arthroscopic management of septic arthritis: stages of infection and results.

Seventy-six patients with septic arthritis (78 affected joints) were treated with a combination of arthroscopic irrigation, debridement, and antibiotic therapy according to the tested bacterial sensitivity. There were 62 knee, 10 shoulder, 5 ankle joints, and 1 hip joint. No antibiotics were added to the irrigating solution. The arthroscopic and radiological stage of infection, treatment, and outcome in these patients was analyzed. The patients were classified into three groups according to initial stage of joint infection (stage I: 21 patients, 22 joints; stage II: 43 patients, 44 joints; stage III: 12 patients, 12 joints). Causes of infection were: hematogenous dissemination in 54%, postoperative wound infection in 28% (17% after open, 11% after arthroscopic procedures). Other causes were: 10% intra-articular steroid injections, 3% diagnostic punctures, and 3% open traumatic injury of the joint. In 78% of the infected joints the causative organism could be identified: Staphylococcus aureus was the most common organism found (42%), followed by streptococci (15%), pneumococci (6%), Escherichia coli (4%), Staphylococcus epidermidis (3%), Borrelia burgdorferi (3%), and others in 5%. In the stage I group only one patient needed repeated arthroscopic irrigation, in the stage II group 52%, and in the stage III group 75%. Open revision for eradication of the infection was necessary in one joint with stage II and in two joints with stage III infection (3%). Two joints of the stage III group needed additional surgery after successful treatment of the infection. The combination of arthroscopic irrigation and systemic antibiotic therapy was able to cure 91% of the affected joints. Open revision was necessary in 4% of joints. The number of arthroscopic procedures and the efficacy of treatment depended on the initial stage of the infection. It is concluded that an arthroscopic staging of the initial joint infection has prognostic and therapeutic consequences.

Adolescent↗
PubMed2000

The effects of conformity and load in total knee replacement.

The effects of different conformity ratios and loads on the ultrahigh molecular weight polyethylene stress levels acting on knee implants were examined using a nonlinear, finite element analysis. The contact condition between a rigid cylinder with a radius of 30 mm and a polyethylene plate was modeled. Nonlinear behavior of polyethylene was assumed. The polyethylene plate was constructed with varying radii, with a minimal thickness of 6 mm and with a width of 40 mm. The ratio of the cylinder radius to the radius of the polyethylene plate was defined as the conformity ratio; a conformity ratio of 0 represented a flat tibial inlay, whereas the highest ratio modeled of 0.99 was nearly conforming. The conformity ratios modeled were 0, 0.2, 0.4, 0.6, 0.7, 0.8, 0.9, 0.95, and 0.99. The loads applied were 1000 N, 2000 N, 3000 N, 4000 N, 5000 N, and 6000 N. The effects of different conformity ratios and loads on the contact area (mm2), the compressive surface stress (MPa), the shear stress (MPa), and the von Mises stress (MPa) were investigated. It was found that all of these parameters were affected by changes to the conformity ratio and to a lesser extent by load changes. That is, increasing the load from 3000 N to 6000 N resulted in a surface and shear stress increase lower than the increase in stress caused by the small change of the conformity ratio from 0.99 to 0.95. The effect of an increasing conformity ratio on the reduction in stress was more pronounced for conformity ratios above 0.8. In addition, the effect of a load increase for a flat tibial inlay was two times greater than for one with near full conformity.

Biomechanical Phenomena↗
PubMed2000

Endurance sports after total knee replacement: a biomechanical investigation.

PURPOSE: No biomechanical evaluation of total knee designs exists for loads occurring during sports activities. It was the purpose of the present study to evaluate the contact stress distribution and contact area of different knee joint designs for loads that occur during four common recreational endurance activities. METHODS: Three different total knee designs were evaluated for loads occurring during cycling (1.2 body weight (BW) at 80 degrees of knee flexion), power walking (4 BW at 20 degrees), hiking (8 BW at 40 degrees), and jogging (9 BW at 50 degrees) using Fuji pressure-sensitive film. The designs consisted of a flat tibial inlay, a curved inlay, and an inlay with mobile bearings. Five measurements were conducted for each load. The pressure sensitive films were scanned and analyzed using an image analysis program. RESULTS: During cycling, the area with stress levels above the yield point of polyethylene (overloaded area) was below 15 mm2 for each design. During power walking, the mobile bearing design showed no overloaded area, whereas it was below 50 mm2 for the flat and curved design. During downhill walking and jogging, more than 140 mm2 were overloaded for each design. CONCLUSIONS: It was concluded that patients after total knee replacement should alternate activities such as power walking and cycling. For mountain hiking, patients are advised to avoid descents or at least use ski poles. Jogging or sports involving running should be discouraged after total knee replacement.

Biomechanical Phenomena↗
PubMed1999

The benefits of wearing a compression sleeve after ACL reconstruction.

PURPOSE: It was the purpose of the present study to examine the possibility of increased muscle coordination after anterior cruciate ligament (ACL) reconstruction through the wearing of a compression sleeve. METHODS: Thirty-six patients were studied who had undergone unilateral ACL reconstruction at least 12 months previously. All subjects were required to perform a 10-cm standing drop jump from an elevated platform onto a force plate, to land on one leg, and thereafter maintain a one-legged balance for 25 s. This task was repeated three times without and three times with an elastic compression sleeve worn on the reconstructed limb. For analysis, the task was partitioned into a landing phase (150 ms), an adjusting phase (10s), and a balancing phase (10s). The peak impact loadings were measured in each direction (Fx, Fy, and Fz) during landing, while force-time integrals (intFz, intFy, and intFz) and root mean square (RMS) error of these forces were calculated for the adjusting and balancing phases. The path length and RMS of the center of pressure coordinates (Ax and Ay) were obtained for the adjusting and balancing phases combined. RESULTS: Drop landings with the bandage produced significantly larger (P < 0.001) peak ground reaction forces in the vertical and anteroposterior direction, suggesting increased subject confidence in their knee. Wearing the knee bandage also enabled the patients to reduce all measured parameters in the anteroposterior direction (rmsFx, intFx, rmsAx) during both the adjusting and balancing phases (P < 0.001 ). A significant reduction in the center of pressure path length further indicated an enhanced steadiness during the one-legged stance. CONCLUSIONS: It was concluded that a compression sleeve improved the total integration of the balance control system and muscle coordination.

Adult↗
PubMed1998

Shape of wear particles found in human knee joints and their relationship to osteoarthritis.

OBJECTIVE: To analyse and compare the shape of wear particles found in healthy and osteoarthritic human knee joints for monitoring the progress of osteoarthritis, the long-term prognosis and to evaluate therapeutic regimens. METHOD: Joint particles from seven patients with normal cartilage in all compartments of the knee joint, 12 patients with fibrillation of less than half the cartilage thickness (grade 1), seven patients with fibrillation of more than half the cartilage thickness (grade 2) and four patients with erosions down to bone (grade 3) were analysed. A total of 565 particles were extracted from synovial fluid samples by ferrography and analysed in a scanning electron microscope. A number of numerical descriptors, i.e. boundary fractal dimension, shape factor, convexity and elongation, were calculated for each particle image and correlated to the degree of osteoarthritis using non-parametric tests. RESULTS: Experiments demonstrated that there were significant differences between the numerical descriptors calculated for wear particles from healthy and osteoarthritic knee joints (P < 0.01), suggesting that the particle shape can be used as an indicator of the joint condition. In particular, the fractal dimension of the particle boundary was shown to correlate directly with the degree of osteoarthritis. CONCLUSION: Numerical analysis of the shape of wear particles found in human knee joints may provide a reliable means for the assessment of cartilage repair after surgical or conservative treatment of osteoarthritis.

Adolescent↗
PubMed1997

Joint load considerations in total knee replacement.

Estimates of knee joint loadings were calculated for 12 normal subjects from kinematic and kinetic measures obtained during both level and downhill walking. The maximum tibiofemoral compressive force reached an average load of 3.9 times body-weight (BW) for level walking and 8 times BW for downhill walking, in each instance during the early stance phase. Muscle forces contributed 80% of the maximum bone-on-bone force during downhill walking and 70% during level walking whereas the ground reaction forces contributed only 20% and 30% respectively. Most total knee designs provide a tibiofemoral contact area of 100 to 300 mm2. The yield point of these polyethylene inlays will therefore be exceeded with each step during downhill walking. Future evaluation of total knee designs should be based on a tibiofemoral joint load of 3.5 times BW at 20 degrees knee flexion, 8 times BW at 40 degrees and 6 times BW at 60 degrees.

Adult↗
PubMedDate not supplied

The effects of arthroscopic acromioplasty on the acromioclavicular joint.

Thirty patients with 31 shoulders underwent clinical and radiologic evaluation 5 to 6 years after arthroscopic acromioplasty. The mean age was 51 years. The acromioclavicular (AC) joint was assessed for tenderness on palpation and pain on horizontal adduction of the shoulder. All patients underwent a radiologic examination consisting of an anteroposterior view of the AC joint and bilateral stress views. No patient had superior translation or widening of more than 1 mm of the AC joint on stress views on the unoperated side. On the operated side 12 (38%) shoulders showed signs of instability consisting of a superior translation of the clavicle of 2 to 3 mm, distraction on weight bearing view, or both. No severely osteoarthritic AC joint (grade 3 or 4) was unstable. The degree of osteoarthritis did not differ for both shoulders, suggesting that arthroscopic acromioplasty does not accelerate osteoarthritic change in the AC joint but can induce instability. Nine patients had tenderness over the AC joint and instability on stress views. They had a significantly reduced University of California Los Angeles score of 25 +/- 5 compared with the other patients (29.5 +/- 7). We conclude that preservation of the inferior capsule during arthroscopic acromioplasty is important for the integrity of the AC joint in patients without severe osteoarthritic changes.

Acromioclavicular Joint↗
PubMedDate not supplied

[Extracorporeal shock-wave lithotripsy for the treatment of calcific tendonitis of the glutaeus maximus tendon].

Calcific tendinitis at the femoral insertion of the glutaeus maximus tendon is an unusual but well-described location for an ossifying enthesopathy. Extracorporeal shock-wave lithotripsy has become a standard therapy for various pathologies in orthopaedics. We report a case of a 50-year-old man with painful calcific tendinitis at the femoral insertion of the glutaeus maximus tendon who successfully underwent extracorporeal shock-wave treatment.

Adult↗