Biomedical subjects

Stefan Hankemeier

Publications and source records attributed to Stefan Hankemeier.

10 recordsLinked to original sources

PubMed2006

[Arthroscopic partial meniscectomy].

OBJECTIVE: Excision of damaged meniscal tissue whereby the mechanical obstacles to joint movement are eliminated. As much functional, intact meniscal tissue should be retained as possible. Resection of only the bare minimum. INDICATIONS: Symptomatic, irreparable lesions of the meniscus due to trauma or degeneration. CONTRAINDICATIONS: Reparable lesions of the meniscus. Local skin affections. SURGICAL TECHNIQUE: Introduction of the arthroscope through an anterolateral or central portal. The instrument portal is positioned in accordance with the situation of the meniscal lesion to be treated. The tissue to be excised is either broken into fragments with different punches or resected en bloc. POSTOPERATIVE MANAGEMENT: Functional postoperative management without immobilization. Full loading on the leg. RESULTS: Very good and good clinical results can be achieved in the short and long term after arthroscopic partial meniscectomy. In a study by Burks et al., 88% of 146 patients with stable knee joints had a very good or good result 14.7 years after partial meniscectomy. 95% of 57 patients were satisfied or very satisfied with the result 12 years after partial medial meniscectomy. A degenerative meniscal tear, axial deformity, higher age, and anterior cruciate ligament insufficiency are factors associated with an increased rate of arthrosis in the long term.

Ambulatory Surgical Procedures↗

PubMed2006

Overdistraction of the fracture eases reduction in delayed femoral nailing: results of intraoperative force measurements.

BACKGROUND: (Initial) primary external fixation of femoral shaft fractures followed by secondary intramedullary nailing is a concept of damage control orthopedics. We hypothesized that external fixation with overdistraction of the fracture might reduce reduction forces and shorten reduction time during the secondary nailing. METHODS: An experimental study on seven patients with eight fractures of the femoral shaft was conducted. Intraoperative reduction forces were determined in all patients using a load cell. The amount of distraction was measured on the latest radiographs before nailing. The reduction time was recorded as an indirect indicator of the intricacy of reposition. Reduction forces and reduction times were compared between those fractures fixed with shortening (Group A) and those fixed in distraction (Group B). RESULTS: Three femurs showed some shortening and five femurs showed some distraction within the fracture. The maximum measured distraction force along the shaft axis was 396 N. On average the maximal force was 336 N (+/- 51.9 N) in Group A and 200 N (+/- 43.1 N) in Group B. This difference is statistically significant (p = 0.007). The average reduction time was 28.3 minutes (+/- 21.8 minutes) in Group A and 5.8 minutes (+/- 4.0 minutes) in Group B. This difference shows a trend toward significance (p = 0.056). CONCLUSION: Fracture shortening leads to higher restraining forces and consequently prolonged reduction time in delayed nailing. Overdistraction should be performed as soon as possible under careful soft-tissue monitoring.

Adult↗

PubMed2006

Differences in the mechanical properties of calcaneal artificial specimens, fresh frozen specimens, and embalmed specimens in experimental testing.

BACKGROUND: Artificial calcanei, fresh-frozen cadaver specimens, and embalmed cadaver specimens were compared in experimental testing under biocompatible loading to clarify the biocompatibility of artificial calcaneal specimens for implant testing. METHODS: Two different artificial calcaneal bone models (Sawbone, Pacific Research Laboratories, Vashon, WA, and Synbone, Synbone Inc., Davos, Switzerland), embalmed cadaver calcaneal specimens (bone density, 313.1 +/- 40.9 g/cm2; age, 43.8 +/- 7.9 years), and fresh-frozen cadaver calcanei (bone density, 238.5 +/- 30.0 g/cm2; age, 44.4 +/- 8.2 years) were used for testing. Seven specimens of each model or cadaver type were tested. A mechanical testing machine (Zwick Inc., Ulm, Germany) was used for loading and measurements. Cyclic loading (preload 20 N, load was increased every 100 cycles by 100 N from 1,000 to 2,500 N, 0.5 mm/s) and load to failure (0.5 mm/s) were performed. The loads were applied through an artificial talus in a physiological loading direction. The displacement of the posterior facet in the primary loading direction was measured. RESULTS: The four different specimen groups showed different stability and different displacement in the primary loading direction during cyclic loading. The variation of the maximal displacement in the primary loading direction for the entire cyclic loading was higher in artificial specimens than in the cadaver specimens. CONCLUSIONS: Artificial calcanei (Sawbone, Synbone) showed different biomechanical characteristics than cadaver bones (embalmed and fresh-frozen) in this experimental setup with biocompatible cyclic loading. These results do not support the use of artificial calcanei for biomechanical implant testing. Fresh-frozen and embalmed specimens seem to be equally adequate for mechanical testing. The low variation of mechanical strength in the unpaired cadaver specimens suggests that the use of PAIRED specimens is not necessary.

Adult↗

PubMed2005

Navigated intraoperative analysis of lower limb alignment.

INTRODUCTION: Accurate intraoperative assessment of lower limb alignment is crucial for the treatment of long bone fractures, implantation of knee arthroplasties and correction of deformities. During orthopaedic surgery, exact real time control of the mechanical axis is strongly desirable. The aim of this study was to compare conventional intraoperative analysis of the mechanical axis by the cable method with continuous, 3-dimensional imaging with a navigation system. MATERIALS AND METHODS: Twenty legs of fresh human cadaver were randomly assigned to conventional analysis with the cable method (n = 10) or navigated analysis with a fluoroscopy based navigation system (n = 10). The intersection of the mechanical axis with the tibia plateau was presented as percentage of the tibia plateau (beginning with 0% at the medial border and ending with 100% laterally). CT-scans were performed for all legs and the CT-values of the mechanical axis were compared to the measurements after cable method and navigation. Furthermore, the radiation time and dose area product of both groups for single analysis of the mechanical axis was compared. RESULTS: Conventional evaluation of the mechanical axis by the cable method showed 6.0+/-3.1% difference compared to the analysis by CT. In the navigated group the difference was 2.6+/-1.8% (P = 0.008). Radiation time and dose area product were highly significantly lower after conventional measurement. CONCLUSIONS: Navigated intraoperative evaluation of the mechanical axis offers increased accuracy compared to conventional intraoperative analysis. Furthermore, navigation provides continuous control not only of the mechanical axis, but also of the sagittal and transverse plane. Using the cable method, radiation exposure depends on the number of measurements and is lower compared to the navigation system for single intraoperative analysis of the mechanical axis, but may be higher in case of repeated intraoperative measurements.

Arthroplasty, Replacement, Knee↗

PubMed2005

Limb lengthening with the Intramedullary Skeletal Kinetic Distractor (ISKD).

OBJECTIVE: Callus distraction of the femur or tibia with an intramedullary distractor, which lengthens mechanically through alternating rotations of at least 3 degrees. INDICATIONS: Femoral or tibial shortening between 20 and 80 mm. Angular and rotational deformities can be corrected at the osteotomy site. CONTRAINDICATIONS: Open epiphyses. Small medullary canal (after intramedullary reaming femoral diameter < 14.5 mm, tibial diameter < 12.5 mm). Severe deformities. Insufficient compliance. Osteitis. Soft-tissue infections. SURGICAL TECHNIQUE: Supine position. Femoral shaft osteotomy at the proximal or middle third by multiple drill holes completed with a chisel. For lengthening of the tibia, osteotomy with a Gigli saw is preferred. Control of the rotation by two parallel 3.0-mm Kirschner wires. Correction of angular or rotational deformities. Via stab incision reaming of the medullary canal with a flexible reamer. The femur is overreamed 2.0 mm and the tibia 1.5 mm above the desired implant diameter. Insertion of the Intramedullary Skeletal Kinetic Distractor (ISKD) into the medullary canal and distal locking in freehand technique. Control of the rotation and of the osteotomy gap. Proximal locking with an aiming device. For femoral lengthening 3 days and for tibial lengthening 5 days postoperatively the distraction is begun by increasing mobilization with partial weight bearing, to achieve daily distraction of 1 mm. In case of insufficient distraction, additional rotations are performed by the patient while checking the external monitor that displays the daily and total distraction length. RESULTS: Intramedullary lengthening with the ISKD was performed in four patients having an average age of 29 years (18-36 years). Two femoral shortenings were combined with complex rotational and angular deformities. The average lengthening of three femora and one tibia was 31 mm (26-40 mm). The average intraoperative blood loss was 230 ml (110-320 ml), the mean surgical time 108 min (90-145 min). The average daily distraction amounted to 1.2 mm (0.9-1.8 mm). Full weight bearing was permitted after 10 weeks (7-14 weeks), return to regular work after 11 weeks (7-16 weeks). At follow-up examination of an average of 2.3 years postoperatively the knee range of motion was full. Consolidation was noted 80 days (51-111 days) postoperatively with an average consolidation index of 2.9 days/mm (1.8-4.1 days/mm). No complications were observed. According to the Paley Score all patients had an excellent outcome.

Adolescent↗

PubMed2004

Improved comfort in lower limb lengthening with the intramedullary skeletal kinetic distractor. Principles and preliminary clinical experiences.

INTRODUCTION: Limb lengthening by external fixators is associated with many problems such as pain at the pin tracts, muscle transfixation, pin tract infections, reduced joint motion, and prolonged fixation time. The intramedullary skeletal kinetic distractor (ISKD) is a new internal, mechanically activated implant, which distracts by mild rotations of 3 degrees. MATERIAL AND METHODS: In a prospective clinical study, four patients with an mean age of 29 years (18-36 years) underwent intramedullary lengthening via ISKD. The average lengthening of three femora and one tibia was 31 mm (26-40 mm). RESULTS: All patients performed the rotations for the distraction themselves without any significant problems. One patient took mild analgesics during the first days of distraction, whereas three patients did not require any analgesics. The average patient discharge occurred 10 days (8-11 days) postoperatively with no complications during the hospital stay. The planned length of distraction was achieved in all patients with normal alignment and normal joint orientation. Full weight bearing was performed on average after 10 weeks (7-14 weeks). Consolidation was noted 80 days (51-111 days) postoperatively with an average consolidation index of 2.9 days/mm. No complications were observed during the follow-up period of 14 months. The Enneking score was 26.8 points, and according to the classification of Paley all patients had an excellent result. CONCLUSIONS: From these preliminary results we conclude that the comfort of limb lengthening with the ISKD is increased by the elimination of fixator-associated complications and by the simple distraction mechanism, which is well tolerated by the patients. Further advantages of the ISKD are early full weight bearing and excellent limb function.

Adolescent↗

PubMed2004

Computer aided high tibial open wedge osteotomy.

High tibial osteotomy is a widely accepted treatment of medial compartment osteoarthritis as well as other lower extremity deformities. However, it is a technically demanding procedure. The lack of exact intraoperative real time control of the mechanical axis often results in postoperative malalignments, which is one reason for poor long term results. These problems can be addressed with the use of a surgical navigation system. Following exposure, dynamic reference bases (DRBs) are attached to the femur, and the proximal and the distal part of the tibia. After intraoperative measurement of the deformities and correction planning, the osteotomy is performed under navigational guidance. The wedge size, joint line orientation, and tibial plateau slope are monitored during correction. The in vitro evaluation with a plastic bone model suggests that the error of deformity correction is less than 1.7 degrees (95% confidence limits) in the frontal, and less than 2.3 degrees (95% confidence limits) in the sagittal plane, respectively. On a cadaver study of 13 legs, the mechanical axis intersected the Fujisawa line in 80.7% (range 77.5-85.8%). The preliminary clinical experience confirms these results. A novel computer tomography free navigation system for high tibial osteotomy has been developed that holds the promise of improving the accuracy, reliability, and safety of this kind of approach.

Adult↗

PubMed2004

Femoral nail removal should be restricted in asymptomatic patients.

Femoral nail removal has been suggested as a routine procedure for symptomatic and asymptomatic patients. The aim of this study was to evaluate whether asymptomatic patients have long-term complaints after femoral nail removal. Additionally, factors that might extend operation time and effect soft tissue healing negatively were analyzed. A retrospective study on the removal of 164 femoral nails after fracture consolidation was done. A review of the patient charts and radiographs was done. Neither the interval between nail implantation and nail removal or the use of an end-cap significantly influenced the operation time. The surgeon's qualification and nail depth were the only variables that influenced operation time. Neither operation time, nail depth, surgeon's qualification, nor the grade of heterotopic ossification significantly influenced the incidence of wound healing problems. One hundred nine patients (73%) were available for the followup interview. Preoperatively, 58 patients (53%) had local complaints. Of these 58 patients, 78% reported improvement and 7% reported an aggravation of their local complaints. Of the 51 patients who were asymptomatic before surgery, 20% reported long-term complaints at followup. Only symptomatic patients should be considered for femoral nail removal.

Adolescent↗

PubMedDate not supplied

Modulation of proliferation and differentiation of human bone marrow stromal cells by fibroblast growth factor 2: potential implications for tissue engineering of tendons and ligaments.

Bone marrow stromal cells (BMSCs) play a central role in the repair and regeneration of mesenchymal tissues. For tissue engineering of ligaments and tendons, both stimulation of cell proliferation and differentiation with increased expression of essential extracellular matrix proteins and cytoskeletal elements are desirable. This study analyzes the effect of low-dose (3 ng/mL) fibroblast growth factor 2 (FGF-2) and high-dose FGF-2 (30 ng/mL) on proliferation (bromodeoxyuridine content, spectrophotometry), differentiation (transcription of collagen I, collagen III, fibronectin, elastin, alpha-smooth muscle actin, and vimentin, reverse transcription-polymerase chain reaction, and cell density and apoptosis (annexin V, fluorescence-activated cell sorting) of human BMSCs, and compares the results with those of a control group without FGF-2. Low-dose FGF-2 triggered a biphasic BMSC response: on day 7, cell proliferation reached its maximum and was significantly higher compared with the other groups. On days 14 or 28, collagen I, collagen III, fibronectin, and alpha- smooth muscle actin mRNA expression was significantly enhanced in the presence of low-dose FGF-2. In contrast, high-dose FGF-2 did not stimulate differentiation or proliferation. Vimentin mRNA was expressed only in cultures with low-dose and high-dose FGF-2 after 14 and 28 days. Cell density was significantly higher in cultures with low-dose FGF-2 compared with the group with high-dose FGF-2 on days 7, 14, and 28. The apoptosis rate remained stable, at a rather high level, in all groups. Microscopic investigation of the cell cultures with low-dose FGF-2 showed more homogeneous, dense, fibroblast-like, spindle-shaped cells with long cell processes compared with cultures with high-dose, or no FGF-2. Low-dose FGF-2 may be useful for tissue engineering of ligaments and tendons by increasing BMSC proliferation and stimulating mRNA expression of specific extracellular matrix proteins and cytoskeletal elements.

Bone Marrow Cells↗

PubMedDate not supplied

Minimally invasive exchange tibial nailing for a broken solid nail: case report and description of a new technique.

We present a minimally invasive technique for the removal of a broken solid tibial nail. A special device was invented that minimizes the extraction difficulties. After minimal over-reaming, the device is slid in an antegrade fashion over the nail and locked. Retraction is safe and easy. This article is an illustrative case-presentation describing the device and the surgical technique.

Adult↗