Biomedical subjects

T Stähelin

Publications and source records attributed to T Stähelin.

5 recordsLinked to original sources

PubMed2006

[Abductor repair failure and nerve damage during hip replacement via the transgluteal approach. Why less invasive methods of joint replacement are needed, and some approaches to solving the problems].

BACKGROUND: When used for total hip replacement, the lateral approach is associated with two frequently iatrogenic, but virtually insoluble problems: limping attributable to abductor insufficiency and pain at the greater trochanter. They can result from injury to the inferior branch of the superior gluteal nerve and/or failure of the abductor repair. MATERIAL AND METHODS: These complications are due to the interruption of a voluminous abductor mass at the trochanter, which has to be done to allow undisturbed work on the femoral shaft and implantation of a straight femoral component while the leg is in the classic figure 4 position. When the lateral approach is used they cannot be avoided except by application of a technique that does not require the hip to be forced into flexion by the figure 4 position. This is possible with only slight detachment of anterior parts of the abductors, as described by Watson-Jones, and preparation of the femoral shaft as reported by Röttinger, with the hip in extension. RESULTS: In comparison with the Röttinger technique, in which the surgeon manages without detaching the abductors, the technique with the slight detachment lessens the traction on the abductors and lowers the risk of nerve damage in the interval between abductor and tensor. CONCLUSION: Whichever technique is ultimately selected, it is of decisive importance that in the case of an approach to the hip joint by way of an anterior capsulotomy with the abductors shifted in the posterior direction, the femoral shaft is prepared with the hip in extension.

Arthroplasty, Replacement, Hip↗

PubMed2004

[Incomplete, supracondylar femur osteotomy. A minimally invasive compression osteosynthesis with soft implant].

The aim of treatment of a valgus deformity and osteoarthrosis of the lateral compartment of the knee is to obtain axial correction of the misalignment of the extremity. Osteosynthesis of the osteotomized femur using internal fixation and a stiff implant has not been as successful as expected. We evaluated the accuracy of correction and the stability of fixation with a malleable plate after supracondylar osteotomy of the distal aspect of the femur that was performed to correct a valgus deformity of the knee. We performed an incomplete oblique closing-wedge osteotomy of the distal aspect of the femur in 32 consecutive patients (34 knees) and stabilized the osteotomy site with a malleable, semitubular plate, which was bent to form an angled plate, and lag screws. Postoperatively, the patients were immediately encouraged to walk, with partial weight bearing on the affected extremity. The mean age of the patients was 52 years, and the mean follow-up period was 4.4 years. In 32 knees, the osteosynthesis withstood the mechanical loading that occurred during the functional rehabilitation program. Due to pain or incorrect weight bearing, splinting was necessary to maintain the integrity of the osteosynthesis in three knees. The osteosynthesis failed in two knees. The mean deviation of the achieved tibiofemoral axis in the healed bone from the intended tibiofemoral axis was less than 2 degrees, and the maximal deviation less than 5 degrees. The Insall score was 21 points higher 4.4 years postoperatively than it had been preoperatively. Our method allows reliable correction of the tibiofemoral axis using intrinsic stability mechanisms to compress the congruently aligned cut ends of the cortical tubes. We believe that our technique provides an alternative to osteosynthesis using of a stiff implant such as a fixed-angle blade-plate device.

Bone Malalignment↗

PubMed2003

[Significance of axial rotation alignment of components of knee prostheses].

Increased internal malrotation of the tibial and femoral components affects kinematics of the patellofemoral joint and the flexion gap. A combined tibial and femoral malrotation may lead to maltracking of the patella. Isolated internal malrotation of the femoral component results in an asymmetric flexion gap. Clinically, the patients suffer from either lateral instability or medial stiffness in flexion. Lateral flexion instability leads to medial tibial pain,difficulties standing up from a chair,or instability during descending stairs or walking downhill. Medial stiffness in flexion may lead to secondary arthrofibrosis. There are three methods for determining femoral rotation by bony landmarks: (1) posterior condyles with 3 degrees of external rotation, (2) anterior-posterior axis according to Whiteside, and (3) transepicondylar axis. The transepicondylar axis approximates the flexion axis of the knee. All three bony landmarks have the disadvantage that they will not create a symmetric flexion gap in all cases. The balanced flexion gap technique seeks to achieve a perfectly balanced extension gap first, and then aligns the femoral component parallel to the tibial resection plane when the knee is under symmetric distraction in 90 degrees of flexion. The soft tissue releases for varus or valgus contraction have to be performed in extension first until the mechanical axis passes through the center of the knee, the center of the femoral head, and the center of the ankle. Using these methods, both,extension and flexion gap will become rectangular. The balanced flexion gap method has the disadvantage that the femoral component will not be aligned parallel to the epicondylar axis in some cases. It is not known which of the two methods will produce better clinical results. Rotational positioning of the tibial component referenced on the tibial tuberosity represents the most reliable method. Placing the tibial component according to the femoral component using the floating technique may increase an internal malrotation problem of the femur if present.

Arthroplasty, Replacement, Knee↗

PubMed2000

Supracondylar osteotomy of the femur with use of compression. Osteosynthesis with a malleable implant.

BACKGROUND: The goal of treatment of a valgus deformity of the knee that is secondary to osteoarthritis of the lateral compartment is to obtain axial correction of the malalignment of the extremity. Osteosynthesis of the osteotomized femur with use of internal fixation and a stiff implant has not been as successful as expected. We evaluated the accuracy and maintenance of correction and the stability of fixation with a malleable plate after a supracondylar osteotomy of the distal aspect of the femur that was performed to correct a valgus deformity of the knee. METHODS: We performed an incomplete oblique osteotomy of the distal aspect of the femur in nineteen patients (twenty-one knees) and stabilized the osteotomy site with a malleable semitubular plate, which was bent to form an angled plate, and lag-screws. Postoperatively, the patients were immediately encouraged to walk, with partial weight-bearing on the affected extremity. The mean age of the patients was fifty-seven years (range, thirty-nine to seventy-one years), and the mean duration of follow-up was five years (range, two to twelve years). RESULTS: In seventeen knees, the osteosynthesis withstood the mechanical loading that occurred during the postoperative functional rehabilitation program. Prolonged use of crutches or immobilization, or both, was necessary after the operation in three knees. The osteosynthesis failed in one knee. The loss of correction in eighteen knees, after bone-healing, averaged 1.7 degrees (range, 0 to 4 degrees). CONCLUSIONS: Our method of achieving osteosynthesis is based on the concept that inherent endogenous stability mechanisms can be mobilized by circumferentially compressing the two cortical tubes with the cut ends congruently apposed to each other. We believe that our technique provides an alternative to osteosynthesis with use of a stiff implant such as a fixed-angle blade-plate device.

Activities of Daily Living↗

PubMed1997

A method to determine bone movement in the ankle joint complex in vitro.

An experimental set-up has been developed to quantify motion of bone structures in the ankle joint complex of human cadaver specimens under conditions approximating physiological joint loading. The device allows to load the foot/leg specimen along the axis of the tibia, and muscle forces can be simulated by clamping the extrinsic tendons of the foot. Additionally, an axial moment can be applied to the tibia. A variety of foot movements can be induced by rotating a foot plate around an arbitrary axis in the horizontal plane. The input force which produces the movement at the foot is applied to the entire sole of the foot. A forefoot fixation allows for the natural adaptation of the midfoot and hindfoot which occurs during loading of the specimen. Bone pins were placed in the tibia, talus, calcaneus and navicular, and three reflective markers were attached to each pin in order to record the bone movements with a video system. Intersegmental rotations in the talo-crural, talo-calcaneal, and talo-navicular joints were calculated in three dimensions, compared for different loading and ligament integrity conditions, and related to a functionally/anatomically described foot position. Repeated measurements of relative bone orientations indicated a reproducibility better than 2 degrees; the slope of the curves, representing the kinematic coupling, was virtually identical between repetitions. It is proposed that this method simulates multidirectional AJC compression similar to loading situations during locomotion.

Aged↗