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Biomedical subjects

T Muellner

Publications and source records attributed to T Muellner.

At least 19 recordsLinked to original sources
PubMed2003

Shortening of the patellar tendon length does not influence the patellofemoral alignment in a cadaveric model.

INTRODUCTION: Anterior cruciate ligament (ACL) reconstruction with the use of autograft tissue represents the standard treatment. The use of a bone-patellar tendon-bone transplant for symptomatic ACL deficiency achieves good long-term results. The purpose of the study was to investigate in a cadaveric model whether reproducible patellar tendon shortening changes the patellofemoral alignment. MATERIALS AND METHODS: Using five cadaveric knees, an MRI investigation was performed with the patellar tendon left unchanged, shortened 5 mm and shortened 10 mm, respectively, in both 20 and 45 degrees of knee flexion. The lateral patellofemoral and the congruence angles were measured and compared using a one-way analysis of variance for repeated measurements. RESULTS: Shortening the patella tendon by approximately 20% did not significantly influence the patellofemoral alignment. CONCLUSION: Although anterior cruciate ligament-reconstruction using the patellar tendon has become a standard procedure, postoperative problems such as anterior knee pain, and patellofemoral osteoarthritis occur quite often. In this cadaver study we did not find a significant difference for the patellofemoral alignment, irrespective of the patellar tendon length.

Adult↗
PubMed2001

Inter- and intratester comparison of the Rolimeter knee tester: effect of tester's experience and the examination technique.

Clinical knee examination is imperative for the prognosis, follow-up, and scientific comparison of anterior cruciate ligament surgery results. A new device, the Rolimeter knee tester was studied in this study with respect to inter- and intratester reliability. We found no significant difference in the intratester evaluation, and data were reliable between repeated measurements and between different testers with the same examination technique. The tester's experience seems to play a role using use the Rolimeter knee tester, but even an inexperienced tester can use it and obtain data that are very close to the data obtained by an experienced tester when the same technique is used. Furthermore, it was found that the manual examination of anterior translation also provides a reliable measurement, at least in the hand of experienced testers. Further advantages are that the Rolimeter knee tester is cheap, can be sterilized, and is simple to use.

Adult↗
PubMed2001

Light and electron microscopic study of stress-shielding effects on rat patellar tendon.

In this second part of our study, the histomorphologic changes occurring in the patellar tendon (PT) of rats after sole stress-shielding were evaluated. In seven adult albino rats, both PTs were exposed by straight skin incision and then stress-shielded on one side by a cerclage, while the contralateral PT served as the sham-operated control. One animal died after the operation and was used as a negative control. After 10 weeks of otherwise unrestricted motion, the rats were killed, and the histomorphology of all PT specimen pairs compared by light and transmission electron microscopy. Light microscopy showed mid-portion thickening and irregularity of collagen bundles in the stress-shielded tendons. Intense remodelling was demonstrated by increased cellularity and vascularity, as well as by enrichment in acidic proteoglycans. Ultrastructural evaluation and morphometry revealed a predominance of large diameter (peak between 180 and 260 nm) collagen fibrils in the sham-operated controls, while in the stress-shielded tendons the number of apparently new, small-diameter (peak between 40 and 60 nm) collagen fibrils increased (up to 77% per cross-sectional field of view). The difference in peak diameters was statistically significant (p < 0.0005). This rat model demonstrated that sole stress-shielding not only causes biomechanical alterations, but also intense tissue remodelling and significant morphological changes in the collagen fibrils in the patellar tendon, comparable to so-called 'ligamentization' in experimental and clinical patellar tendon grafts for anterior cruciate ligament reconstruction.

Animals↗
PubMed2001

Accuracy of pressure and flow capacities of four arthroscopic fluid management systems.

PURPOSE: The present study was conducted to evaluate 4 different fluid delivery systems: Arthrex AR-6450, Stryker 1.5L High Flow Pump, Arthro FMS 4, and Acufex InteliJet. Their flow and pressure capacity, as specified by the manufacturer, and their accuracy, as measured in a standardized fashion, were compared with directly measured pressure values. TYPE OF STUDY: Experimental study. METHODS: Two experiments were performed: (1) the achieved pressure was measured with the pressure sensor within a ball and compared with the preset pressure values. The pressure was increased constantly while the flow was kept constant. (2) maximum flow per minute was tested using a beaker and a stopwatch. RESULTS: The highest measured pressures for the Arthrex and the Stryker pumps were 115 mm Hg (46% of published maximum pressure) and 113 mm Hg (57% of published maximum pressure), respectively. The highest measured pressures for the Arthro FMS 4 and the InteliJet pumps were 251 mm Hg (101% of published pressure) and 132 mm Hg (88% of published maximum pressure), respectively. The maximal flow values for the Arthrex and Stryker pumps were 900 mL/min (56.3%) and 675 mL/min (48%), respectively. The Arthro FMS 4 and InteliJet pumps reached a maximal flow of 450 mL/min (56%) and 1,250 mL/min (62.5%). CONCLUSIONS: In the simpler pumps (Arthrex AR-6450 and Stryker 1.5L High Flow Pump), the pressure on the display must be set to higher values compared with the outflow-controlling pumps (Arthro FMS 4 and InteliJet) to achieve the same intra-articular pressure. All pumps were able to maintain a pressure of 60 mm Hg very accurately. Therefore, a surgeon can trust all of the pumps when the pressure is set below 60 mm Hg.

Arthroscopy↗
PubMed1999

The role of magnetic resonance imaging in routine decision making for meniscal surgery.

This clinical study evaluated factors affecting the decision for meniscal surgery in a patient population seen routinely at a trauma clinic. The study hypothesis was that patients who sustain a traumatic injury to the knee or have a long history of clinical symptoms are likelier to be operated on. We investigated 149 patients clinically and by magnetic resonance imaging (MRI). Group A (n = 62) underwent arthroscopic surgery and group B (n = 87) were treated conservatively. Multiple logistic regression analysis was used to examine correlations with regard to age, gender, injury pattern, period between the injury and first clinical examination, and MRI results. We found no significant difference between the two groups with regard to gender (P = 0.1), injury pattern (P = 0.44), or period between injury and first clinical examination (P = 0.5). Patients in group A were significantly older than those in group B (P = 0.044), and, as expected, MRI signal alterations were significantly higher in group A than in group B (P = 0.001). In acutely injured patients MRI helps to establish an accurate diagnosis, and in cases of positive MRI findings in a symptomatic patient, the surgeon should not wait 4-6 weeks but should immediately recommend surgery.

Acute Disease↗
PubMed1999

Cyclops and cyclopoid formation after anterior cruciate ligament reconstruction: clinical and histomorphological differences.

Prospectively, 119 patients were pursued clinically and by follow-up-arthroscopy for the occurrence of a "cyclops syndrome" after ACL reconstruction with a patellar tendon autograft, augmented by LAD. Twenty-one patients showed nodular formations. Ten of these (group 1) developed early clinical evidence of a "cyclops syndrome" with a mean extension deficit of 19 degrees before follow-up-arthroscopy, on average 5.9 months after the index operation. The nodular formations found and excised during débridement had a hard consistency. Histomorphological undecalcified microtome section evaluation of six specimens revealed fibrocartilagineous tissue with active bone formation in the center. The other 11 patients showed no clinical symptoms (group 2). A similar but soft nodulous scar formation was detected at follow-up-arthroscopy, on average 9.5 months after the index operation. Histomorphologically these so-called "cyclopoid" formations were only built-up fibrocartilagineous islands surrounded by granulation tissue. Neither remnants of tendon graft fibers nor old bone particles were found in specimens of either group. It can be concluded that both the hard cyclops and the soft "cyclopoid" are de novo scar formations.

Adolescent↗
PubMed1999

Anterior cruciate ligament reconstruction alters the patellar alignment.

Although there are many articles dealing with anterior cruciate ligament (ACL) reconstruction, there are none dealing with the possibility of changes of the patellofemoral alignment after these procedures. Forty-six patients were evaluated preoperatively and 1 year postoperatively, after undergoing intra-articular ACL reconstruction, for changes of the patellofemoral alignment. Patella-tilt and congruence angles were measured on tangential view radiographs that were taken in the supine position. Analysis of covariance was performed and revealed a significant change of the congruence angle 1 year postoperatively. The patella-tilt did not change. One year postoperatively, the patella shifted on average 5 degrees medially after ACL grafting. It can be deduced that anterior knee pain after ACL reconstruction could be caused by distinct changes in the patellofemoral alignment.

Adult↗
PubMed1999

New instrument that uses near-infrared spectroscopy for the monitoring of human muscle oxygenation.

BACKGROUND: Early detection of vascular impairments after free tissue transfers are essential to prevent flap failure. Near-infrared spectroscopy showed good promise to monitor flaps at deep levels successfully without being invasive. The purpose of this study was to test whether the INVOS 3100 cerebral oxymeter is capable of detecting circulatory impairments. METHODS: In 10 healthy adults, near-infrared spectroscopy was used to measure regional saturation values during tourniquet ischemia and venous outflow restriction, in two test cycles. The probe, containing an infrared-light-emitting source and two infrared-light sensors, was placed below the elbow above the brachioradialis muscle. Statistical comparison of the data was performed using the Friedman test and the Wilcoxon-Wilcox test. RESULTS: Venous and arterial occlusions were characterized by an instantaneous fall of the regional saturation. Arterial occlusion showed a mean decrease of the saturation values down to 28+/-9%, whereas venous occlusion showed a mean fall of saturation values down to 51+/-12%. These falls were significant after 3 minutes of occlusion compared with baseline values (74+/-6%). The differences between arterial and venous occlusions were statistically significant. CONCLUSION: This study, designed to test less-expensive equipment, was able to measure absolute values, and was not prone to interference caused by probe movement, providing information on the oxygenation profile accurately and noninvasively, and distinguishing between arterial and venous occlusion.

Adult↗
PubMed1999

Recommendations for the diagnosis of traumatic meniscal injuries in athletes.

It has always been difficult to develop a method of correctly evaluating knee injuries and, in turn, to devise the appropriate rehabilitation programme. Flawless diagnosis of meniscal injury is necessary, considering the diverse consequences of this injury for patients, and even more so in relation to athletes, bearing in mind the intensified physical demands on their bodies. There is no doubt that an accurate and concise clinical evaluation of patients with injuries to the knee is the basis for an exact diagnosis and successful treatment. The use of noninvasive methods, such as magnetic resonance imaging, in addition to clinical evaluation is recommended because of their high accuracy and negative predictive value. The use of invasive methods, such as arthroscopic operations, should be restricted to treatment, and not be used for diagnosis.

Adolescent↗
PubMed1998

No benefit of bracing on the early outcome after anterior cruciate ligament reconstruction.

Forty patients were prospectively investigated to evaluate the effects of bandaging after reconstructive surgery of the anterior cruciate ligament (ACL). For the 6 weeks of the postoperative course, the operated knee was bandaged in 20 patients (group A) and braced in the other 20 patients (group B). The isokinetic torque for extension and flexion (Cybex) and the range of motion (ROM) were investigated after 6, 12, 24 and 52 weeks postoperatively. At 24 weeks and 1 year postoperatively the stability of the knee joint (KT-1000) as well as the clinical outcome ('Orthopädische Arbeitsgemeinschaft Knie') were evaluated. No statistically significant differences between the two groups were found for the extension and flexion strengths. Free ROM was achieved significantly earlier in group A than in group B. No statistically significant differences regarding the stability of the operated knee joint nor the early outcome were found between the two groups. This study demonstrated that the renunciation of using a brace had no adverse effect on the early outcome with respect to stability and function. On the contrary, bracing seems not to be mandatory after ACL reconstruction when the central third of the patellar tendon is used.

Adolescent↗
PubMed1998

Rotational instability and integrity of the interosseous membrane in cadaveric ulnar shaft fractures.

The stability of isolated ulnar shaft fractures required further investigation because no data were available for fractures in the middle third or on the effect on rotational stability. Ten intact cadaveric arms were used to study the pathomechanics of fractures of the middle ulna. In all of them a transverse osteotomy was performed (A), then in five of them, an additional osteotomy was done in order to create a third fragment (B). The interosseous membrane was subsequently divided for 2 cm on either side of the osteotomy (A-->C, C-->D). On radiographs the displacement was recorded in pronation and supination, and the rotational displacement was calculated. Rotational instability occurred in all fractures studied, even in the so-called stable ones. Also, dissection of the interosseous membrane was not followed by a displacement of more than 50%, and shortening of the ulna should also be considered in fractures with less than 50% displacement as a sign of instability.

Adult↗
PubMed1998

Twisting of patellar tendon grafts does not reduce their mechanical properties.

The purpose of this study was to investigate whether the twisting of a patellar tendon (PT) graft improves or reduces its mechanical properties. Twenty-seven pairs of 10 mm cadaveric PT grafts were tested at a strain rate of 10% min(-1). For each pair, the left specimen served as an unmanipulated control while the right specimen was either left untwisted, twisted + 90 degrees, or twisted - 90 degrees. All avulsion failures were excluded from the data analysis, focusing only on pure in-substance tendon ruptures. Higher ultimate load values than previously reported were obtained for both the twisted and untwisted specimens, without a statistical significant difference between the two. The values obtained for the left and right specimens from Group A were 4014+/-319 and 3973+/-245 N, from Group B 3613+/-207 and 3891+/-14 N, and from Group C 3997+/-278 and 4415+/-507 N, respectively. Stiffness and failure strain were not influenced by the twisting. Neither the presence of a twist, nor the direction of the twist were found to increase the ultimate load of the 10 mm cadaveric patellar tendon graft. Therefore, recommendation for twisting cannot be assessed to its mechanical properties.

Adult↗
PubMed1998

Shortening of the patellar tendon after anterior cruciate ligament reconstruction.

In this prospective study, patellar height changes were investigated after anterior cruciate ligament (ACL) reconstruction with a mean follow-up of 22.4 months. A total of 114 patients were included. Fifty-two patients (group A) were treated by multiple suture repair, 27 patients (group B) underwent acute ACL reconstruction, and 35 patients (group C) underwent ACL reconstruction > or =6 weeks after injury with a patellar tendon graft. The patellar vertical height ratios (VHR) were evaluated preoperatively (VHR 1), 6 months postoperatively (VHR 2), and at follow-up (VHR 3). For the studied questions, the following answers were obtained: (1) The change of the patella height was the same in all three groups (i.e., disregarding the different surgical procedures). (2) The time elapsed between injury and ACL reconstruction did not influence the shortening of the patellar tendon. (3) Women showed a more pronounced shortening of the patellar tendon than did men. (4) A significant shortening of the patellar tendon occurred in 30% of our patients, and the process of shortening was finished 6 months postoperatively. (5) Anterior knee pain was present in 27.2% of our patients and occurred significantly more often after patellar tendon graftings. (6) Age had no influence on the changes of the patellar height.

Adult↗
PubMed1998

Epidermoid cyst after arthroscopic knee surgery.

Eleven years after an arthroscopic procedure, a benign tumor of the knee located beneath the scar where the outflow canula was placed was excised. Histomorphological evaluation determined the diagnosis of an epidermoid cyst. This is the first case reported in the literature of an epidermoid cyst occurring after an arthroscopic operation. The previous epidermoid cysts reported were found after trauma or after dermal grafting for epithelium implantation.

Adult↗
PubMed1998

Patients with increased intracranial pressure cannot be monitored using near infrared spectroscopy.

The hypothesis of this study was that with near infrared spectroscopy a decrease of the regional cerebral saturation would be detectable in patients with increased intracranial pressure. For this purpose, two study groups were compared: (A) eight healthy volunteers and (B) eight heart beating organ donors with brain stem herniation. The regional cerebral saturation was measured according to the developer's suggestions. Mean arterial pressure and peripheral pulse oximetry were recorded. The statistical comparison, using the unpaired t-test, revealed no significant differences for the regional cerebral saturation (p = 0.97) or for the mean arterial pressure or peripheral pulse oximetry between the groups. In both of the studied situations, no differences in the regional cerebral situation were detectable, even though the patient situations were completely antagonistic. Therefore, it is reasonable to discourage the use of the INVOS 3100 Cerebral Oxymeter to monitor patients with increased intracranial pressure indirectly.

Adult↗
PubMed1998

Patellar alignment evaluated by MRI.

We analyzed the congruence of the articular cartilage surfaces and the corresponding subchondral bone in the patellar joint. 20 volunteers underwent MRI investigations of the right patellar joint in 20 degree and 45 degree flexion in the axial plane. The sulcus, congruence, and lateral patellofemoral angles, measured on MRI slices centered through the midtransverse patella, were recorded. In 20 degree and 45 degree knee flexion, the bony sulcus and lateral patellofemoral angles were significantly different from the respective cartilagineous angle. We conclude that 1) measurement of the bony sulcus and lateral patellofemoral angles does not allow conclusions about the articular cartilage surface and its thickness, 2) the bony congruence angle corresponds well to the articular cartilage surface as an indicator of patellar centralization.

Anthropometry↗
PubMed1997

Economic considerations for the diagnosis and therapy of meniscal lesions: can magnetic resonance imaging help reduce the expense?

With magnetic resonance imaging (MRI) the surgeon has such an effective diagnostic tool in the diagnosis of a meniscal lesion that the times of diagnostic arthroscopy should be in the past. A total of 823 patients with clinically diagnosed meniscal lesions were divided into two groups: group A, 143 patients underwent MRI and 75 of those arthroscopy; group B, 680 patients, 201 (30%) of whom were operated after being only clinically examined. MRI was done on a Siemens Medical System Magnetom 1.5 Tesla with a 256 x 256 matrix. Spinal echo and gradient echo images were performed with slices of 2 to 4 mm thickness. All meniscal tears were graded according to Reicher and Crues, respectively. Grades III and IV were judged to be positive for a meniscal lesion. Arthroscopy was carried out under general anesthesia and the usual technique. The MRI revealed the following results: Medial meniscus: accuracy 95%, positive predictive value (PPV) 92%, negative predictive value (NPV) 95%, sensitivity 98%, and specificity 82%, lateral meniscus: accuracy 97%, PPV 92%, NPV 98%, sensitivity 94%, and specificity 98%. The overall values for MRI of the medial and lateral menisci combined were: accuracy 96%, PPV 93%, NPV 98%, sensitivity 96%, and specificity 90%. The clinical examination often failed to diagnose a meniscal lesion: accuracy 64%, PPV 59%, NPV 89%, sensitivity 96%, and specificity 33% for the medial meniscus. For the lateral meniscus the accuracy was 91%, PPV 61%, NPV 98%, sensitivity 89%, and specificity 91%. The overall values for the clinical investigation of the medial and lateral menisci combined were: accuracy 78%, PPV 60%, NPV 94%, sensitivity 93%, and specificity 62%. Investigation of all 201 patients operated from group B with MRI would have cost $160,800. The cost of 30% fewer arthroscopies would have been $562,800--in total $723,600. The operation of all 201 patients cost $804,000. Hence about $80,000 could have been saved by scanning all 201 patients and therefore reduce the rate of diagnostic arthroscopies.

Adolescent↗