As perioperative prophylaxis for major orthopedic operations 81 patients were given the fixed combination of ampicillin (1 g)/sulbactam (0.5 g) or cefotiam (2 g) as short infusions. The three beta-lactams were rapidly distributed into the different tissues and their pharmacokinetic profiles were found to be very similar. It was noteworthy that ampicillin, sulbactam and cefotiam penetrated within minutes, not only into skin, fat and muscles, but also into bone. Thus 0.25 h after starting the infusion the following mean concentrations were measured in bone: 21.8 +/- 10.5 mg/kg ampicillin, 4.9 +/- 2.2 mg/kg sulbactam and 19.4 +/- 10.6 mg/kg cefotiam. For a period of at least 2 h the concentrations measured in serum and in the different tissues affected by the operation (skin, fat, muscle, bone) were above the MICs for pathogens which are involved in postoperative wound infections. On the basis of pharmacokinetic data, ampicillin/sulbactam and cefotiam seem about equally suitable for perioperative prophylaxis in major orthopedic operations.

Adult↗

PubMedDate not supplied

[Water jet discotomy with microinvasive approach--in vitro testing and initial clinical aspects of a new procedure].

AIM: The difference in consistence of the nucleus pulposus and the annulus fibrosus allows the water jet to selectively remove the nucleus in a closed vertebral disc at a certain pressure range. The aim of the study was to investigate the use of water jet cutting in microinvasive spinal surgery. METHODS: A comparison in terms of efficiency between the water jet and those of the laser and APLD (automatic percutaneous lumbar discotomy) was achieved by plastic reconstruction of the resected spaces using the in-vitro-model of the spinal column of young pigs. The in-vitro-study was followed by a prospective clinical study with 21 patients. RESULTS: The in-vitro-employment of the three different methods showed that there were no significant differences in volume of the removed nucleus material. During the use of the hydro jet at 50 bar and simultaneous suction the intradiscal pressure measured in vitro remained below 1 bar. Clinical tests on the 21 patients showed good to very good results in 71% of the patients tested (mean follow-up 5.8 months). No complications were found. As working mechanism the pure mechanical effect and the influence on chemical processes within the nucleus remain points for discussion. CONCLUSION: The current studies results demonstrate that hydrojet spinal surgery might be a safe new method for surgery of disc protrusion and contained prolapse.

Adult↗

PubMedDate not supplied

[Use of a water jet for synovectomy: in vitro study of feasibility].

AIM: The selectivity of a water jet (WJ) is already used with clinical advantage in the surgery of liver, brain, kidney and herniated lumbar discs. The aim of the present study was to determine whether a WJ can be used for synovectomy without damaging the joint capsule and the cartilage. METHOD: 60 human cadaver knee specimens (67 +/- 14 years) were dissected into synovial and cartilage samples. They were randomly assessed to four pressure groups (pW = 3; 6; 9; 12 MPa) and three jet surface angles (beta = 30; 60; 90 degrees) The nozzle diameter was dD = 0.12 mm, the stand off distance of the jet was s = 10 mm with a feed rate of vV = 2 mm/s. The acquired parameters were depth of the cuts, histological layer, and change of the samples thickness. RESULT: There was a correlation of the cutting depth and the pressure (pW), whereas the jet-surface angle (beta) showed no correlation. The synovial layer of the cut likewise correlated with the pressure. At pW = 6 MPa the stratum subsynoviale could be cut selectively without damaging the fibrous capsule or the cartilage. The increase of the samples thickness was caused by an interstitial oedema. CONCLUSION: The different mechanical properties of the joint capsule and the stratum subsynoviale lead to the selective cutting of the water jet. Since the joint capsule was not damaged, the feasibility of WJ synovectomy has been proven. The device can be used for synovectomy in parts of the joint that are not visible as well as in very small joints.

Aged↗

PubMedDate not supplied

[Load shift-total hip replacement--numerical and clinical evaluation of a new concept of adaptive stem fixation].

AIM: The new load-shift fixation concept pursues the goal of an adaptive change of geometrical characteristics of the in-situ hip replacement. In this study a preclinical and clinical evaluation was performed. METHODS: By three-dimensional, dynamic finite element calculation the biomechanical properties of the prosthesis were analyzed in the early postoperative and long-term configuration. By clinical (20 +/- 10 months) and radiological (18 +/- 10 months) follow-up of a first series of implants (n = 20) the primary functional status of the prosthesis was examined in vivo. RESULTS: The preclinical results revealed that the metaphyseal micromotions are reduced significantly with the diaphyseal fit of the stem postoperatively. By absorption of a biodegradable element (spreader) integrated into the tip of the stem a change of stem geometry associated with loss of the diaphyseal fit occurs. This results in a complete shifting of load transmission into the metaphyseal area. In the clinical situation the postoperative Harris hip score averaged 92.9 +/- 10.5 points. Only in two patients did reversible episodes of thigh pain occur. The radiological analysis of bone remodeling phenomena pointed to a physiological load transmission. There was no evidence of loosening or osteolysis. On radiology, stem tapering could be demonstrated. CONCLUSION: On the basis of these promising preclinical and early clinical results the innovative load-shift prosthesis should now be further evaluated in prospective long-term studies.

Aged↗

PubMedDate not supplied

[Significance of the splitting of the lateral patellar retinaculum and the mediopatellar synovial fold in the surgical therapy of patellar chondromalacia].

Using strain gauges we investigated proximal-distal and lateral-medial strain of the dorsum patellae before and after cutting of the lateral retinaculum and the plica mediopatellaris under flexion. Lateral-medial strain was abolished by the lateral release for the larger part and by cutting of the plica for a smaller part. Proximal-distal strain was not changed in any case. Therefore we conclude that the operation will only lead to a medial positioning, but not to a loosening of the extension apparat of the knee.

Biomechanical Phenomena↗

PubMedDate not supplied

[The mobile segment above fusion].

The question is, if a possible concentration of stress in the segment adjacent to the fusion level might result in disc degeneration. Two series of patients have been evaluated: One group of 70 patients underwent a posterolateral fusion without instruments and the other group of 69 patients underwent a posterolateral instrumented fusion. The follow-up was in average 5.7 years resp. 4.6 years. The operations were divided in monosegmental, floating and polysegmental fusions. In the total group, 10% of the non-instrumented and 28% of the instrumented patients had an osteoarthritis of the facet joints, 10% resp. 23% were unstable and in 9% resp. 1% a disc resorption occurred. There have been no statistical differences in the both polysegemental groups, but this was the case for all osteoarthritis and instabilities in the monosegmental fusions. It is supposed that the changes in kinematics together with material related alterations of elasticity led to higher stress concentration in case of instrumentation.

Biomechanical Phenomena↗

PubMedDate not supplied

[Compartment pressure of the anterior tibial area in jogging].

31 healthy persons had to run on a treadmill under defined conditions at a constant speed of 8 km/h. Pressure in the anterior flexor-muscles compartment was measured regulary in time before, during and after running; the size of the compartment was documented by sonography. The measured pressure was attached to the respective compartment size. The runners were divided into three groups based on characteristic pressure-courses: the normal-type with average values below 50 mmHg, the indifference-type with a distinctly higher pressure than 50 mmHg and the risk-type with values more than 70 mmHg. A correlation between exercise-pressure and time of post-exercising decrease of pressure was found. While the normal type reached the starting pressure within 6 minutes the indifference and risk type didn't succeed in decreasing after this period of time. No change of compartmental size was measured while the pressure increased on exertion.

Adolescent↗

PubMedDate not supplied

[Determination of contact surfaces of the femoropatellar joint with reference to the localization of chondromalacia].

At 13 post-mortem-knees we investigated the patello-femoral contact area in different degrees of function, referring to the localization of chondromalacia. We found that the localization of chondromalacia didn't accord to the contact area in 50% of all cases. Possible other causes are discussed.

Adolescent↗

PubMedDate not supplied

[Meniscectomy--total, partial, open or closed operation?].

The importance of the menisci for stability of the knee joint is pointed out. Because of its mechanical importance in the knee a more conservative behaviour for treatment is recommended. Even the degenerated meniscus can play his role sufficiently. For each type of lesion individual surgery is applied, especially if there is locking impingement linked with mechanically induced arthritis. Out of the clinical results follows that arthroscopic partial meniscectomy is superior to conventional open meniscectomy, especially in the early postoperative period.

Follow-Up Studies↗