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Biomedical subjects

A B Imhoff

Publications and source records attributed to A B Imhoff.

At least 19 recordsLinked to original sources
PubMed2007

[Primary stability of the capsule-labrum complex after reconstruction with the Mitek Bioknotless anchor system in human cadaver models].

BACKGROUND: This study examines the postoperative stability of the Mitek Bioknotless anchor system with biomechanical draw-out pulling in human cadaver shoulders. METHOD: With simulation of anterior shoulder dislocation a test group (n=10, Ø 45 years) was tested against a native group (n=8, Ø 47 years). All shoulders were dissected up to the passive stabilizers. In the test group an artificial Bankart lesion was created and repaired with three Mitek Bioknotless anchors. The humeri of both groups were fixed in 60 degrees glenohumeral abduction and 90 degrees external rotation and then dislocated in a ventral direction. For evaluation purposes the ultimate draw-out strength, mode of failure, translation of humeral head, capsular slope, and bone density in the test group were measured. RESULTS: In the test group the ultimate strength was a median of 937 N (min. 554 N, max. 1,294 N) with 28 bony anchor dislocations, 1 suture rupture, and 1 capsular rupture, and in the native group with 6 Bankart and 2 HAGL lesions it was 1,214 N (708 N, 1,471 N). The bone density showed a positive correlation to the draw-out strength regarding cortical density and total density. CONCLUSION: Regarding the high draw-out strength the Mitek Bioknotless anchor system provides enough stability for early functional treatment.

Cadaver↗
PubMed2006

Rotator cuff tears: assessment with MR arthrography in 275 patients with arthroscopic correlation.

We assessed the diagnostic performance of magnetic resonance (MR) arthrography in the diagnosis of articular-sided partial-thickness and full-thickness rotator cuff tears in a large symptomatic population. MR arthrograms obtained in 275 patients including a study group of 139 patients with rotator cuff tears proved by arthroscopy and a control group of 136 patients with arthroscopically intact rotator cuff tendons were reviewed in random order. MR imaging was performed on a 1.0 T system (Magnetom Expert, Siemens). MR arthrograms were analyzed by two radiologists in consensus for articular-sided partial-thickness and full-thickness tears of the supraspinatus, infraspinatus, and subscapularis tendons. At arthroscopy, 197 rotator cuff tears were diagnosed, including 105 partial-thickness (93 supraspinatus, nine infraspinatus, three subscapularis) and 92 full-thickness (43 supraspinatus, 20 infraspinatus, 29 subscapularis) tendon tears. For full-thickness tears, sensitivity, specificity, and accuracy were 96%, 99%, and 98%, respectively, and for partial tears 80%, 97%, and 95%, respectively. False negative and positive assessments in the diagnosis of articular-sided partial-thickness tears were predominantly [78% (35/45)] observed with small articular-sided (Ellman grade1) tendon tears. MR arthrography is highly accurate in the diagnosis of full-thickness rotator cuff tears and is accurate in the diagnosis of articular-sided partial-thickness tears. Limitations in the diagnosis of partial-thickness tears are mainly restricted to small articular-sided tears (Ellman grade 1) due to difficulties in differentiation between fiber tearing, tendinitis, synovitic changes, and superficial fraying at tendon margins.

Adolescent↗
PubMed2006

[Typical injuries seen in football players].

Injuries seen in football players mainly affect the knee and ankle joints and muscles. The causes include chronic overstrain and traumatization usually resulting from physical contact between opponent players. Torsional trauma of the joints results in excessive stressing of the capsular ligaments, potentially leading to rupture of the structures involved. Therapeutic options range from conservative measures to reconstructive or prosthetic surgery. While muscular injuries have a good prognosis with regard to the chances of continuing sports activities, injuries to ligaments often enforce a lengthy pause from sports. Extensive injuries to cartilages can terminate a player's sporting career. However, new procedures that take account of physiological biomechanics, together with the further development of surgical technologies now often allow players to regain their pre-injury level of fitness. Specific rehabilitation is a major therapeutic means of preventing further injury.

Ankle Injuries↗
PubMed2006

Positive effect of oral supplementation with glycosaminoglycans and antioxidants on the regeneration of osteochondral defects in the knee joint.

The effect of oral supplementation with glycosaminoglycans (GAG) and radical scavengers (vitamin E/selenium) on the regeneration of osteochondral defects was investigated in rabbits. After introduction of defined osteochondral defects in the knee joint, groups of ten animals were given a GAG/vitamin E/selenium mixture or a placebo (milk sugar) for 6 weeks. Following sacrifice, histological and histochemical analysis was performed. The amount of synovial fluid was increased in the placebo group, while the viscosity of the synovial fluid was significantly enhanced in the GAG group. The amount of sulfated GAG in the osteochondral regenerates (8.8 +/- 3.6 % vs. 6.0 +/- 5.6 %; p <0.03) was significantly higher in the GAG group. In both groups, the GAG amount in the cartilage of the operated knee was significantly higher than in the non-involved knee (p <0.05). Histological analysis of the regenerates in the GAG group was superior in comparison with the placebo group. For the first time, a biological effect following oral supplementation with GAG was demonstrated in healing of osteochondral defects in vivo. These findings support the known positive clinical results.

Administration, Oral↗
PubMed2005

Second generation of meniscus transplantation: in-vivo study with tissue engineered meniscus replacement.

INTRODUCTION: The options available after meniscus loss offer only limited chances for a long-term success. In the following experimental study, we investigated the effect of meniscus tissue engineering on properties of the collagen meniscus implant (CMI). METHODS: Autologous fibrochondrocytes, obtained per biopsy from adult Merino sheep (n=25), were released from the matrix, cultured in-vitro and seeded into CMI scaffolds (n=10, group 1). Following a 3-week in-vitro culture, the tissue engineered menisci were used for autologous transplantation. Macroscopical and histological evaluation were performed in comparison with non-seeded CMI controls (n=10, group 2) and with meniscus-resected controls (n=5, group 3) after 3 weeks (each 1 animal group 1 and 2) and 3 months. RESULTS: The lameness score did not show any difference between the groups. Meniscus tissue was found in seven knee joints (group 1), in five knee joints (group 2) and in two knee joints (group 3). The size of the transplants reduced from 25.9+/-4.5 to 20.1+/-10.8 mm (group 1) and from 25.9+/-1.5 to 14.4+/-12.5 mm (group 2). Histologically, enhanced vascularisation, accelerated scaffold re-modelling, higher content of extra-cellular matrix and lower cell number were noted in the pre-seeded menisci in comparison with non-seeded controls. Dense high-cellular fibrous scar tissue was found in two of five cases in the resection control group. CONCLUSION: Tissue engineering of meniscus with autologous fibrochondrocytes demonstrates a macroscopic and histological improvement of the transplants. However, further development of the methods, especially of the scaffold and of the cell-seeding procedure must prove the feasibility of this procedure for human applications.

Animals↗
PubMed2005

[A new minimally invasive arthroscopic technique for reconstruction of the acromioclavicular joint].

BACKGROUND: Over 100 techniques for acromioclavicular joint (ACJ) reconstruction have been described. Most of these techniques are invasive and are associated with a high complication rate. We therefore developed a new minimally invasive arthroscopic technique for reconstruction of the ACJ. METHODS: The new operation technique is described in detail. We operated 13 patients with Rockwood IV or V dislocations of the ACJ using this new technique. Intra- and postoperative complications were recorded. Each patient was evaluated after 3, 6, and 9 months using the Constant score for shoulder function and radiographs (anteroposterior, axillary, and Zanca views) of the operated and nonoperated shoulder for radiologic evaluation. The objective of this study was to evaluate the first clinical results and complication rates using this technique. RESULTS: The mean follow-up was 9 months. Of the 13 patients, 12 could be included in the study and we had 1 dropout. The mean Constant score was 97; all patients were satisfied with the postoperative shoulder function and cosmetics. Radiologically we observed ten patients with anatomic reduction and two with a subluxation between 2 and 4 mm compared to the nonoperated side. In one patient we determined coracoclavicular ossifications which were asymptomatic. There were no complications intra- and postoperatively. CONCLUSIONS: These first results suggest that this is a good and safe technique for ACJ reconstruction. Further randomized studies with more patients have to follow to confirm the results.

Acromioclavicular Joint↗
PubMed2004

Effect of high tibial flexion osteotomy on cartilage pressure and joint kinematics: a biomechanical study in human cadaveric knees. Winner of the AGA-DonJoy Award 2004.

INTRODUCTION: Valgus high tibial osteotomy is an established treatment for unicompartmental varus osteoarthritis. However, only little is known about the effect of osteotomy in the sagittal plane on biomechanical parameters such as cartilage pressure and joint kinematics. This study investigated the effects of high tibial flexion osteotomy in a human cadaver model. MATERIALS AND METHODS: Seven fresh human cadaveric knees underwent an opening wedge osteotomy of the proximal tibia in the sagittal plane. The osteotomy was opened anteriorly, and the tibial slope of the specimen was increased gradually. An isokinetic flexion-extension motion was simulated in a kinematic knee simulator. The contact pressure and topographic pressure distribution in the medial joint space was recorded using an electronic pressure-sensitive film. Simultaneously the motion of the tibial plateau was analyzed three-dimensionally by an ultrasonic tracking system. The traction force to the quadriceps tendon which was applied by the simulator for extension of the joint was continuously measured. The experiments were carried out with intact ligaments and then after successively cutting the posterior and anterior cruciate ligaments. RESULTS: The results demonstrate that tibial flexion osteotomy leads to a significant alteration in pressure distribution on the tibial plateau. The tibiofemoral contact area and contact pressure was shifted anteriorly, which led to decompression of the posterior half of the plateau. Moreover, the increase in the slope resulted in a significant anterior and superior translation of the tibial plateau with respect to the femoral condyles. Posterior subluxation of the tibial head after cutting the posterior cruciate ligament was completely neutralized by the osteotomy. The increase in slope resulted in a significant higher quadriceps strength which was necessary for full knee extension. CONCLUSIONS: We conclude from these results that changes in tibial slope have a strong effect on cartilage pressure and kinematics of the knee. Therapeutically a flexion osteotomy may be used for decompression of the degenerated cartilage in the posterior part of the plateau, for example, after arthroscopic partial posterior meniscectomy. If a valgus osteotomy is combined with a flexion component of the proximal tibia, complex knee pathologies consisting of posteromedial cartilage damage and posterior and posterolateral instability can be addressed in one procedure, which facilitates a quicker rehabilitation of these patients.

Aged↗
PubMed2004

[Refixation of complete tendon ruptures of proximal ischio-crural muscles].

Complete ruptures of the proximal hamstring muscles at the ischial tuberosity are rare injuries in sports. The trigger is usually an indirect trauma with overstretching of the ischiocrural muscles. In 8 patients, the ruptured tendons were anatomically refixed using a suture anchor system. 6 patients were treated within 3 weeks after trauma, while 2 patients were operated after delayed diagnosis of more than 2 months. The follow-up was on average 25.8 (5-52) months. After rehabilitation, five patients returned to their preinjury sports level within 9-15 months on average. Indeed, 2 patients (1 primary and 1 delayed operative management) also participated in sports activities in this period of time, but could not reach their preinjury sports level completely. 1 elite athlete was still in the rehabilitation program at 5 months of individual follow-up. A postoperative complication was 1 revision because of a suture anchor dislocation after improper use of the orthosis. In four patients, incisional pain and discomfort lasting up to 2 years were noticed. In case of early diagnosis, operative treatment especially in athletically ambitious patients is the gold standard for complete ruptures of the proximal hamstring tendons. The use of a suture anchor system represents an elegant and effective technique for the treatment of ruptures of the proximal hamstring tendon complex.

Adult↗
PubMed2004

[Corrective osteotomy in primary varus, double varus and triple varus knee instability with cruciate ligament replacement].

Osteochondral lesions and osteoarthritis in young patients are often caused by chronic knee instability in varus malaligned knees. We present the indication, operative technique, and results of 57 patients treated by simultaneous high tibial osteotomy and cruciate ligament reconstruction. The indication for simultaneous high tibial valgus osteotomy and ACL reconstruction is chronic anterior knee instability in varus knees of patients under 40 years of age. In these patients, medial meniscus deficiency secondary to prior injuries and/or chronic knee instability have frequently led to unicompartmental (medial) tibiofemoral degenerative changes. The average correction angle of the osteotomy was 7 degrees (4-10). Subjectively, all patients reported an improvement of preoperative swelling, pain, and instability. Additional cartilage surgery or meniscus implantation did not significantly alter the clinical score values. Complications occurred in four patients. Unstable varus malangulated knees can be sufficiently treated by osteotomy and cruciate ligament plasty and is suggested as cost-effective therapy with good short-term results. Performing both operations in one procedure facilitates early rehabilitation and return of the patients back to the activities of daily living and sports.

Adult↗
PubMed2004

Inducible nonviral gene expression in the treatment of osteochondral defects.

OBJECTIVE: The repair of osteochondral defects with chondrocytes genetically modified to express desired growth factors promises great potential in orthopaedic therapy. Controlled expression of the transgenes is required in many instances. The objective of the present study was to demonstrate the inducibility of tetracycline-responsive transgene expression in osteochondral defects in the knee joint filled with genetically modified chondrocyte implants. METHODS: An expression plasmid containing the lacZ gene under the control of the minimal CMV promoter fused to the Tet-responsible element (TRE) as well as the reverse transactivator (rtTA2s-M2) was constructed and used to transfect isolated articular chondrocytes from New Zealand white rabbits. rtTA2s-M2 binds to the TRE in the presence of tetracycline and leads to the transcription of the transgene. Different concentrations of DNA and various DNA:lipid ratios were tested to determine best transfection conditions. Transfection efficiency and inducibility were analysed by histochemical analysis and flow-cytometry. To evaluate the system in vivo, collagen-sponges were seeded with transfected autologous chondrocytes and implanted in osteochondral defects in the knees of NZW-rabbits. Gene expression was induced by doxycycline and 3 weeks later, LacZ-expression in isolated knee joints was evaluated in histological sections by X-gal staining. RESULTS: In vitro 13.5% (+/-1.32) of induced primary chondrocytes were LacZ-positive, while non-induced controls showed a background-staining in 0.6% (+/-0.2). In vivo, upon doxycycline treatment, induction of lacZ-gene-expression could be demonstrated in chondrocytes in 3-week-old, well-integrated implants. CONCLUSION: For the first time, tetracycline-inducible gene expression is demonstrated to work in the treatment of osteochondral defects. This demonstrates the feasibility for a gene therapy-assisted approach using controlled expression of therapeutic growth factors from transplanted genetically modified chondrocytes.

3T3 Cells↗
PubMed2003

[Refixation of the meniscus with the SD meniscal staple: a comparative biomechanical study on cadaver knees].

GOAL: The failure load of the SD meniscal staple was compared with the 2-0 Etibond meniscus suture in a dynamic test without isolating the meniscus. METHODS: In eight knee joint pairs, a standardized lesion of the posterior part of the medial meniscus was repaired by either three staples (7 mm) or three 2-0 Etibond sutures. After resection of the cruciate ligaments and 15 degrees external rotation, 45 degrees flexion, and 70 kg of axial loading, a tibial translation was exerted on the knee joint. The test was documented on a way force diagram, demonstrating the failure of the device at a sudden load of force. RESULTS: The average load before failure of the meniscus staple was 591.2 N (540-690 N), that of the sutures 850 N (600-1350 N). We did not find any statistical correlation to age,weight, or height of the specimens. The suture migrated, but never ruptured. In two cases the suture caused a radial meniscus lesion. Failure of the staple was detachment of the inferior part in all cases, but no migration. CONCLUSION: This test is based on the dynamic forces of the knee joint on the meniscus. Our measurements show lower failure loads of the staple compared to those of the sutures, but compared to other tests a stable method of meniscus repair.

Absorbable Implants↗
PubMed2003

[Normal anatomical variants of the superior labrum biceps tendon anchor complex. Anatomical and magnetic resonance findings].

There are difficulties in diagnosing pathologies of the labrum-biceps tendon complex (LBTC) because of the great individual variability of this structure. Anatomical variations, such as the sublabral recess, are frequently found and can also be misinterpreted as Andrews or SLAP II lesions. The etiology and mechanisms of creating such a sublabral recess are not exactly known. The examination of 31 cadaveric shoulder specimens from an age group between 49.3 and 83.6 years showed a sublabral recess in 63.6-85%. This high frequency of sublabral detachment of the labrum in older patients indicates that according to the high range of motion of the humeral head and therefore the changing angle of the long biceps tendon (LBS) a certain mobility of the superior LBTC is physiological and should not necessarily be seen as a sign of instability. Besides mobility-increasing factors such as overhead professions and sports with high repetitive maximal abduction and external rotation and the individual age, the type of insertion of the LBT at the glenoid influences the development of sublabral recess. Accordingly, posterior oriented insertion types of the LBT determine deeper and more posterior oriented sublabral recesses whereas in cases of anterior directed types of insertions no or less deep recesses can be found. Anamnestic aspects, such as the mechanism of injury and overhead activities, these macroscopic and functional associations in MR arthrography and arthroscopic inspection have to be considered in order to differentiate between physiological and traumatic changes of the labrum-biceps tendon complex.

Aged↗
PubMed2003

[MR imaging of variants of the superior labral-bicipital complex and SLAP lesions].

In the detection of SLAP (superior labral anterior to posterior) lesions of the shoulder MR arthrography shows a significantly higher sensitivity compared with conventional MR techniques and therefore, represents the method of choice in diagnostic imaging of the superior labral-bicipital complex. On the basis of morphological criteria it mostly allows distinction of traumatic lesions and anatomic variants of the superior labrum and the biceps anchor as well as classification of detected SLAP lesions (types 1-4 according to Snyder). However, the differentiation of a SLAP type 2 lesion and a sublabral recess can be very difficult, even if all distinction criteria are considered.

Cartilage, Articular↗
PubMed2003

[SLAP lesions as a cause of posterior instability].

SLAP lesions disrupt the perilabral architecture, but so far there have been no reports about posterior instability due to SLAP lesions. In a prospective study of 30 patients with recurrent posterior instability, we found SLAP lesions as a reason for instability in three cases. The purpose of this study is to point out that SLAP lesions can be a cause of posterior instability. Thirty patients with clinical posterior shoulder instability underwent diagnostic arthroscopy before operative stabilization procedures, three of whom (three males, aged 29-51 years) showed a SLAP lesion (once case each of types II, III, and IV) as a cause of posterior instability. All three patients had a history of a fall on the outstretched arm. All patients underwent arthroscopic refixation of the labrum. After arthroscopic refixation of the SLAP lesions, two patients were completely stable (SLAP II and III), whereas one patient (SLAP IV) reported microinstability during overhead activity but complete stability during activity of daily living. The same patient complained about moderate pain in extreme external-flexion rotation with slightly reduced range of motion in external-flexion position. All other patients were free of pain and showed free range of motion. Our results demonstrate that SLAP lesions can be a cause for posterior shoulder instability. In our cases, posterior shoulder instability caused by SLAP lesions was successfully treated by arthroscopic refixation of the torn biceps anchor. When treating posterior shoulder instability, SLAP lesions should be taken into account.

Adult↗
PubMed2003

[The arthroscopic SLAP refixation].

Lesions of the superior glenoid labrum and the insertion of the biceps tendon are a common cause for shoulder pain in patients performing overhead sports. The therapeutic management depends on the type of lesion, and should be carried out using an arthroscopic procedure. While type I SLAP lesions should be treated conservatively or with simple debridement, SLAP II, IV, and V lesions, with a detachment of the labrumanchor- complex, should be refixed with suture anchors. Only in cases of type III lesions with a bucket handle-like lesion of the labrum, but stable insertion of the biceps tendon, a simple debridement can be performed. From the biomechanical point of view, large type III lesions should also be reconstructed. To improve the arthroscopic view for preparation of the glenoid neck, an intraarticular loop ("Imhoff-suspension sling") can prevent the posterosuperior labrum from falling into the joint. The arthroscopic SLAP refixation is a technically highly demanding procedure which provides good clinical results for the patient.

Adult↗
PubMed2002

[Mega-OATS. Technique and outcome].

Big osteochondral defects in the weight-bearing zone of the medial respectively the lateral femoral condyle are still an unsolved problem especially in younger patients. The transfer of the posterior aspect of the femoral condyle was described as a salvage procedure. Mega-OATS is a technical improvement of the transfer of the posterior condyle-procedure. Essential advantages of the conventional OATS-technique are integrated in the Mega-OATS procedure, so that iatrogenic lesions of the transferred cartilage by press-fit-fixation and secondary hardware removal can be avoided. However, the Mega-OATS procedure itself remains a salvage procedure and should only be reserved for younger patients. The results of the first series of 17 patients (average follow-up 12 (5-19) months) showed an improvement of quality of life and a significant (p = 0.003) increase in the Lysholm-score.

Adult↗