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Biomedical subjects

K Knahr

Publications and source records attributed to K Knahr.

At least 19 recordsLinked to original sources
PubMed2005

Cementless total hip arthroplasty using a threaded cup and a rectangular tapered stem. Follow-up for ten to 17 years.

We carried out a clinical and radiological review of 103 cementless primary hip arthroplasties with a tapered rectangular grit-blasted titanium press-fit femoral component and a threaded conical titanium acetabular component at a mean follow-up of 14.4 years (10.2 to 17.1). The mean Harris hip score at the last follow-up was 89.2 (32 to 100). No early loosening and no fracture of the implant were found. One patient needed revision surgery because of a late deep infection. In 11 hips (10.7%), the reason for revision was progressive wear of the polyethylene liner. Exchange of the acetabular component because of aseptic loosening without detectable liner wear was carried out in three hips (2.9%). After 15 years the survivorship with aseptic loosening as the definition for failure was 95.6% for the acetabular component and 100% for the femoral component.

Adult↗
PubMed2005

Tribological considerations for a new hip system.

PURPOSE OF THE STUDY: This paper was initiated to evaluate a new total hip system based on cementless fixation and focusing options for different articulations within a single hip system. MATERIAL AND METHODS: 100 patients provided with the cementless Variall hip system were evaluated clinically and radiographically. The 59 female and 41 male patients were followed for a minimum of 3 years postoperative. They were clinically evaluated using the Harris Hip Score. Radiographic analysis was based on plain x-rays at the latest follow-up evaluation. RESULTS: The evaluated patients achieved an excellent clinical result with an average Harris Hip Score of 94,3 points after an average follow-up of 42 months. The radiographic evaluation of the threaded cup did not exhibit any migration of the implant nor could we find radiolucencies. All tapered stems were radiographically stable. Due to the modified proximal design and the macrostructure an improved stem bone interface was found during the follow-up period. DISCUSSION The new cementless cup with its cylindrical threads and the spherical floor achieves an anatomic fit within the acetabulum and provides excellent primary stability. The design of the gamma inlay offers the fixation of ceramic and metal articulations without polyethylene interface. Additionally, options for conventional and cross-linked polyethylenes are available. These facts make the cup a cost-effective device. The design of the new uncemented stem guarantees a high degree of primary stability and excellent rotational stability due its rectangular cross section. This pressfit is further enhanced by the proximal macrostructure of the implant, again ensuring an excellent bond between prosthesis and bone. CONCLUSION: Thanks to the versatility of all the components this comprehensive new total hip prosthesis offers many options for a long-term successful implant. Additionally, it is a cost-effective solution - an important fact of nowadays strained financial situation in public health care.

Adult↗
PubMed2004

Chevron osteotomy in hallux valgus. Ten-year results of 112 cases.

The Chevron osteotomy was described in 1976. There have, however, been only short- to mid-term follow-up reviews, often with small numbers of patients. We looked at 112 feet (73 patients) with a minimum follow-up of ten years following Chevron osteotomy with a distal soft-tissue procedure. Clinical evaluation was calculated using the hallux score of the American Orthopedic Foot and Ankle Society (AOFAS). For 47 feet (30 patients), the results were compared with those from an interim follow-up of 5.6 years. The AOFAS-score improved from a pre-operative mean of 46.5 points to a mean of 88.8 points after a mean of 12.7 years. The first metatarsophalangeal (MTP) angle showed a mean pre-operative value of 27.6 degrees and was improved to 14.0 degrees. The first intermetatarsal (IM) angle improved from a pre-operative mean value of 13.8 degrees to 8.7 degrees. The mean pre-operative grade of sesamoid subluxation was 1.7 on a scale from 0 to 3 and improved to 1.2. Measured on a scale from 0 to 3, arthritis of the first MTP joint progressed from a mean of 0.8 to 1.7. Comparing the results in patients younger and older than 50 years, the Chevron osteotomy performed equally in both age groups. Analysing the subgroup of 47 feet with a post-operative follow-up of both 5.6 and 12.7 years, the AOFAS pain and the overall score showed a further improvement between both follow-up evaluations. The MTP angle, first IM angle and sesamoid position remained unchanged. The progression of arthritis of the first MTP joint between 5.6 and 12.7 years post-operatively was statistically significant. Only one patient required a revision procedure due to painful recurrence of the deformity. Excellent clinical results following Chevron osteotomy not only proved to be consistent, but showed further improvement over a longer follow-up period. The mean radiographic angles were constant without recurrence of the deformity. So far, the statistically significant progression of first MTP joint arthritis has not affected the clinical result, but this needs further observation.

Adult↗
PubMed2002

Core decompression in early stages of femoral head osteonecrosis--an MRI-controlled study.

We treated 45 hips with idiopathic necrosis of the femoral head stages I-III with core decompression. Average age of patients was 41 (27-68) years and average follow-up 68.9 (31-120) months. In 30 hip joints in stage I, 29 showed no radiographic progression and a complete remission of the changes consistent with necrosis on MRI at the last follow-up. In 27 patients the clinical result based on the Harris Hip Score (HHS) assessment--was excellent (average HHS 91.9 points). Of nine hips in stage II, four had received a total hip arthroplasty, one had deteriorated to stage IV, and four were still classified as stage II (average HHS 95 points). Of six hips in stage III, three had received a total hip arthroplasty and three had deteriorated to stage IV (average HHS 73 points).

Adult↗
PubMed2002

Adverse tissue reactions to wear particles from Co-alloy articulations, increased by alumina-blasting particle contamination from cementless Ti-based total hip implants. A report of seven revisions with early failure.

We revised seven alumina-blasted cementless hip prostheses (Ti-alloy stems, cp Ti threaded sockets) with low- or high-carbon Co-alloy bearings at a mean of 20.1 months after implantation because of pain and loosening. Histological examination of the retrieved periprosthetic tissues from two cases in which the implant was stable and three in which the socket was loose showed macrophages with basophilic granules containing metal and alumina wear particles and lymph-cell infiltrates. In one of the two cases of stem loosening the thickened neocapsule also contained definite lymphatic follicles and gross lymphocyte/plasma-cell infiltrates. Spectrometric determination of the concentration of elements in periprosthetic tissues from six cases was compared with that of joint capsules from five control patients undergoing primary hip surgery. In the revisions the mean concentration of implant-relevant elements was 693.85 microg/g dry tissue. In addition to Cr (15.2%), Co (4.3%), and Ti (10.3%), Al was predominant (68.1%) and all concentrations were significantly higher (p < 0.001) than those in the control tissues. The annual rates of linear wear were calculated for six implants. The mean value was 11.1 microm (heads 6.25 microm, inserts 4.82 microm). SEM/EDXA showed numerous fine scratches and deep furrows containing alumina particles in loosened sockets, and stems showed contamination with adhering or impacted alumina particles of between 2 and 50 microm in size.

Aged↗
PubMed2002

Intertrochanteric osteotomy for avascular necrosis of the head of the femur. Survival probability of two different methods.

We have compared different types of intertrochanteric osteotomy for avascular necrosis of the hip and evaluated their performance in the light of improving outcome after total hip arthroplasty (THA). During a period of 14 years we performed 63 flexion osteotomies (partly combined with varus or valgus displacement), 29 rotational osteotomies, 13 varus osteotomies, eight medialising osteotomies and two extension osteotomies. The mean period of follow-up for all 115 operations was 7.3 years (maximum 24.6). At follow-up, 27 of 29 patients with a rotational osteotomy had already undergone a THA, compared with 36 of 63 after flexion osteotomy. A high incidence of complications (55.2%) was seen early after rotational osteotomy, compared with 17.5% after flexion osteotomy. For all osteotomies there was a high correlation between the size of the necrotic area and the incidence of failure, which also correlated with the preoperative Ficat and Steinberg stages. Using Kaplan-Meier survivorship analysis, Sugioka's rotational osteotomy showed a survival probability after five years of 0.26 (95% confidence interval 0.49 to 0.14), and after ten years of 0.15 (CI 0.36 to 0.06). The survival probability for flexion osteotomy was 0.70 (CI 0.83 to 0.59) after five years and 0.50 (CI 0.65 to 0.38) after ten years. The subgroup of flexion osteotomy with a necrotic sector of less than 180 degrees achieved the best survival probability of 0.90 (CI 1.00 to 0.80) after five years and 0.61 (CI 0.84 to 0.45) after ten years. The indications for intertrochanteric osteotomy for avascular necrosis of the hip have to be addressed critically. Even flexion osteotomy in cases with small areas of necrosis provides only temporary benefit. Rotational osteotomy was associated with a high incidence of complications.

Adult↗
PubMed2001

Surgery for hallux valgus. The expectations of patients and surgeons.

Two-hundred patients who had undergone surgery for hallux valgus were interviewed in an attempt to study the different variables which may have contributed to the success of their surgery. These data were compared to the results obtained by using clinically applied scores. To obtain data on surgeons' expectations, 186 members of two national orthopaedic foot societies were interviewed in order to quantify the importance and value of these variables in prognosis. The main interest of the patients is a painless great toe which, when wearing conventional shoes, gives no problems. They also wish to have their bursitis and bunion treated in order to regain their ability to walk as much as they wish. Surgeons are not only specially interested in pain and shoe problems but also in restoring an adequate range of motion in the metatarsophalangeal joint (MTP), removal of the bunion and the treatment of tender callosities. We found that the correction of footwear problems, alleviation of pain and restoration of adequate walking are the most important factors influencing the outcome of surgery. It was surprising that these expectations are only partly revealed by using clinical foot scores.

Adult↗
PubMed2000

[The value of core decompression in treatment of femur head necrosis].

Core decompression of the necrotic area for treatment of idiopathic osteonecrosis of the femoral head was developed and published by Ficat and Arlet in 1962 within the scope of their "Functional exploration of bone". The mode of action is attributed to a reduction of the intramedullary pressure in the bony compartment of the femoral head. The possibilities of repair and bone regeneration following core decompression are still discussed controversially. Core decompression is a common but not generally accepted procedure in the treatment of idiopathic osteonecrosis of the femoral head. After first publications of positive mid- and long-term effects, some subsequent studies judged it as an ineffective and high-risk method. Analysis of the literature shows that the effectiveness of core decompression depends on the stage of osteonecrosis at the time of surgical intervention. Prognosis is influenced by the extent and location of the necrotic area, the presence and amount of head depression, and continued risk factors--mainly corticoid medication. The best prognosis can be given for patients with a small, medial-centrally located necrosis without head depression. The classification according to Ficat appears to be insufficient, as the extent and localization of the necrotic area are not assessed. Magnetic resonance imaging has become a diagnostic gold standard, as radiographic diagnosis showed poor sensitivity and specificity, especially in the early stages of the disease. As an essential part, MRI was integrated into the new classification of the "Association Internationale de Recherche sur la Circulation Osseuse" (ARCO). On account of the literature and our own experience, treatment by core decompression can be recommended in cases of reversible early stages of osteonecrosis (ARCO 1), as well as in those cases of irreversible early stages (ARCO 2) that show a medial or central location of the necrosis with an extent of less than 30% of the femoral head. Once the disease reaches the irreversible early stage, complete recovery cannot be expected. In these cases only reduction of pain and retardation of the natural course of the osteonecrosis are possible to gain time until total hip replacement is unavoidable.

Decompression, Surgical↗
PubMed2000

Chemonucleolysis and automated percutaneous discectomy--a prospective randomized comparison.

In this prospective study 22 patients with painful disc herniations were randomized either to chemonucleolysis (CN) or automated percutaneous discectomy (APD) Preoperatively the Oswestry score was 44 points in the CN group and 41 points in the APD group. Except for a longer duration of preoperative leg pain in the APD group, clinical data were approximately the similar same in the two groups. In the APD group there was one intra-operative complication. Open revision surgery in the same segment was performed once in the CN group and twice in the APD group. Improvement of neurologic deficits and of Owestry score was significant in both groups. At 2 years after surgery the CN treated patients were significantly better with respect to Oswestry score, back pain and leg pain recurrence.

Adult↗
PubMed2000

Haglund's syndrome: disappointing results following surgery -- a clinical and radiographic analysis.

Clinical and radiographic data were analyzed for 49 surgical interventions of painful heel syndrome with a mean follow-up of 4 years and 7 months. In all patients the surgical procedure consisted of a triangular shaped resection of the posterosuperior portion of the calcaneus. The clinical evaluation showed disappointing results with complete relief of complaints in only 34 procedures (69.4%), and 7 patients (14.3%) with even a worsening of their symptoms. The time course of rehabilitation was long with an average of 6 months of functionally significant pain after surgery, reducing the willingness to undergo this operation again. Formerly published angular thresholds of radiographic calcaneal angles could not be confirmed to be predictors for the preoperative symptoms or the postoperative outcome. There was no accumulation of pathologic clinical foot shapes, only a slight increased calcaneal pitch in patients with isolated pain on the posterosuperior lateral part of the calcaneus. According to Haglund's description of painful heel syndrome, the clinical picture of our patients included affections of bone, tendon, peritendon, bursae, soft tissue and skin in different combinations. Based on this evaluation, we advise to be cautious to indicate the operation. All possibilities of conservative treatment should be performed prior to surgery.

Adolescent↗
PubMed1999

Loss of correction after lateral closing wedge high tibial osteotomy--a human cadaver study.

In 12 human cadaver tibiae, osteotomies were carried out at two levels (2 and 3 cm from the distal joint line) with three different wedges (5 degrees, 10 degrees, 15 degrees) to evaluate the influence of displacement of the osteotomy fragments on areas of cortical contact. In undisplaced osteotomies (medical cortical edges superposed) cortical contact areas formed 28% (level 2 cm) and 40.5% (level 3 cm) of the cortical circumference of the proximal fragments (NS). Wedge angles and levels of osteotomy displayed no statistical differences. In displaced osteotomies cortical contact decreased significantly (P < 0.05). Displacing the distal fragment laterally, medial cortical contact is lost, and weight-bearing leads to revarisation as cancellous bone sustains only 3 MPa, and the measured compressive stresses at the medial edge amounted to 6 MPa on average. Displacing the distal fragment medially leads to a decrease of total cortical contact, too, but at the medial edge of the osteotomy cortical contact areas are still present. As a result of the study, postoperative weight-bearing without additional plaster cast fixation is recommended only in cases with undisplaced fragments.

Cadaver↗
PubMed1998

Uncemented Miller-Galante total knee replacement. The influence of alignment on clinical and radiological outcome in a 5 to 8-year follow-up.

Sixty-one primary uncemented Miller-Galante total knee replacements were implanted in 55 patients between June 1988 and December 1990. The results of routine radiological and clinical follow up carried out at an average of 1.3 years and 6.2 years after operation were used for evaluation. The Knee Society clinical score improved from 47.8 points before operation to 83.3 points one year after, and had progressed further to 87.6 points at the recent follow-up. The functional score improved from 45 points before operation to 75.23 points at early follow up, and 81.3 points at the recent review. Although radiological analysis showed that the femoral and tibial components overall were placed perpendicular to the mechanical axis of the limb, sufficient correction of the mechanical axis was not achieved to within +/- 10 mm deviation from the centre of the knee in 22 cases, with varus or valgus deformity remaining. No early or late infection occurred in this series. The uncemented Miller-Galante total knee replacement shows good biological fixation of both components. Wear of the metal-backed patellar and tibial polyethylene lead to a revision rate of 19% after 5 years.

Activities of Daily Living↗
PubMed1998

Metatarsophalangeal and intermetatarsal angle: different values and interpretation of postoperative results dependent on the technique of measurement.

For measurement of the first metatarsophalangeal angle and intermetatarsal angle I-II, five different methods for drawing the axis of the first metatarsal have been published. This study aimed to evaluate differences in the resulting angles that depend on the method of drawing this axis. Using pre- and postoperative radiographs of 20 patients who had surgery on the hallux (chevron procedure), highly significant differences were found: mean values for the preoperative metatarsophalangeal angle ranged from 27.3 degrees to 31.9 degrees; the mean postoperative values were calculated at 8.6 degrees to 20.3 degrees. The preoperative mean of intermetatarsal angle I-II showed values from 13.0 degrees to 17.6 degrees; the postoperative mean ranged from 5.2 degrees to 16.7 degrees. These differences--especially in the postoperative evaluation--resulted in a postoperative improvement between 11.6 degrees and 20.8 degrees for the metatarsophalangeal angle and between 0.9 degrees and 10.0 degrees for the intermetatarsal angle. These wide differences seem to be unacceptable for angles as a criterion of success in surgery on the hallux. The reason for these discrepancies can be found in the different relations of the points of reference to the anatomical outline of the metatarsal and the site of osteotomy. As a consequence of this study, defining the axis of the first metatarsal as a line connecting the center of the articular surface of the metatarsal head and the center of the proximal articulation can be recommended as the most appropriate method. The resulting angles are independent of the type of surgery performed on the hallux.

Evaluation Studies as Topic↗
PubMed1998

Scoring in forefoot surgery: a statistical evaluation of single variables and rating systems.

We assessed 13 scores for forefoot surgery and their single parameters in 200 cases of hallux surgery. Outcome expressed in descriptive terms from excellent to poor, as well as calculated as a numerical value differed to a great extent. The rank correlation between different scores showed poor conformity, in some combinations even slight negative correlations. The rank correlation between single parameters and the overall outcome gave good values for some variables included in most scores, e.g., walking distance, general activity, problems on uneven surfaces, shoe wear, cosmetics and pain. Little, if any, correlation was found for joint instability, range of motion of the MTP- and IP-joints, the use of walking aids and medication. We find a need for a generally accepted score, with parameters of high clinical relevance.

Activities of Daily Living↗
PubMed1996

Antibiotic-associated colitis in orthopaedic patients.

Antibiotic-associated colitis was diagnosed in 23 orthopaedic patients: 17 had abdominal symptoms, 3 had a fever and the remaining 3 had no symptoms but increasing C-reactive protein values or white blood count. The antibiotic was clindamycin in 19, cephalosporins in 3 and a combination of vancomycin and fusidic acid intravenously in one. The antibiotics were stopped in 12, changed in 5 and continued in the remaining 5. Oral treatment for colitis was given in 21 patients, and in one patient the only treatment was stopping the antibiotics. One patient died after a myocardial infarct; the remaining 22 were discharged after successful treatment of their primary condition and the colitis.

Adult↗