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At least 127 records · Page 7Linked to original sources
PubMed2002

The effect of malalignment on stresses in polyethylene component of total knee prostheses--a finite element analysis.

OBJECTIVE: To investigate the effects of malalignment on stresses in tibial polyethylene component of total knee prostheses. DESIGN: A three-dimensional finite element analysis was used to calculate the contact stress and von Mises stress in the tibial polyethylene component subjected to a compressive load, and the malalignment situations were simulated. BACKGROUND: Many biomechanical studies to investigate the stresses in tibial polyethylene component were assumed at the ideal contact alignment. The effect of malalignment on stresses in tibial polyethylene component was not investigated extensively. METHODS: Three-dimensional finite element models of the tibiofemoral joint of knee prostheses for three different designs were constructed. Three malalignment conditions including the medial translation (0.25, 0.5 and 1.0 mm), internal rotation (1 degree, 3 degree and 5 degree), and varus tilt (1 degree, 3 degree and 5 degree) of the femoral component relative to the tibial component were simulated. A compression load of 3000 N was applied to the tibiofemoral joint at 0 degree of flexion. The maximum contact stress and von Mises stress in the tibial component were compared to investigate the effects of malalignment. RESULTS: In comparing with the neutral position, the greatest increase of maximum contact stress were 67.6%, 14.3% and 145.9% and the greatest increase of maximum von Mises stress were 92.5%, 22.7% and 120.6% in maltranslation, internal rotation and varus tilt simulations, respectively. CONCLUSION: The greatest increase of contact stress and von Mises stress was occurred in the high conformity flat-on-flat design of knee prosthesis under the severest malalignment condition. The high conformity curve-on-curve design of knee prosthesis has the minimal risk of polyethylene wear under the malalignment conditions. RELEVANCE: This study revealed the importance of malalignment effect on stresses in tibial polyethylene component. Polyethylene wear in surface replacement total knees will be minimal when a high conformity curve-on-curve knee design is used and the rotational line between the femoral and tibial components has the least effect on polyethylene wear but varus/valgus malalignment, even with the best designed prosthesis will still accelerate wear.

Bone Malalignment↗
PubMed1994

Malalignment and degenerative arthropathy.

The axial relationship of the joints of the lower extremity reflects both alignment and orientation. Static considerations are useful for preoperative planning and deformity correction, but dynamic considerations including compensatory gait may be more relevant clinically. Laboratory animal models have been developed that simulate the deleterious effect of malalignment on articular cartilage. Malalignment disturbs the normal transmission of force across the knee, and altered stress distribution related to deformity has been demonstrated in cadaver models using pressure-sensitive film. No prospective data are available to document the natural history of malalignment, but several retrospective studies suggest the clinical course is one of gradual progression resulting in degenerative arthropathy. The long-term follow-up of fractures is less definitive, and difficult to interpret considering the bias inherent in patient selection. Although direct clinical evidence of a cause-and-effect relationship between malalignment and arthrosis has not been possible, substantial evidence from the orthopedic literature supports this hypothesis.

Animals↗
PubMed2006

Magnetic resonance imaging evaluation of patellofemoral malalignment.

PURPOSE: The purpose of this study was to determine the relationship between anterior knee pain secondary to suspected patellofemoral malalignment and tibial tubercle lateralization, patellar tilt, and patellar lateralization on magnetic resonance imaging. METHODS: We compared the bony relationships of the knee in patients with anterior knee pain and patients with nonspecific internal derangements of the knee. We measured the lateral deviation of the tibial tubercle and the patella from the trochlea, patellar tilt, and patellar and patellar tendon length. RESULTS: The symptomatic knees of patients with anterior knee pain had significantly (P < or = .01) greater lateralization of the tibial tubercle and lateral patellar tilt than did knees of the control group. Patella alta appears to be more common in subjects with anterior knee pain. CONCLUSIONS: Magnetic resonance imaging determination of tibial tubercle lateralization and patellar tilt correlates positively with the clinical diagnosis of anterior knee pain, suggesting that patellofemoral pain is caused by subtle malalignment. LEVEL OF EVIDENCE: Level III, development of diagnostic criteria on basis of nonconsecutive patients.

Adult↗
PubMedDate not supplied

Tibial osteotomy as a salvage procedure in the treatment of congenital talipes equinovarus.

Fourteen children (19 feet) ranging in age from 2.1 to 17.0 years (mean, 7.6 years) underwent tibial osteotomy for treatment of congenital talipes equinovarus (CTEV). The indications for tibial osteotomy were persistent or recurrent equinovarus deformity and internal rotation of the foot (medial malalignment syndrome), in most cases with severe distortion of the hindfoot joints resulting from previous operations. In 12 feet (9 children), bi- or triplanar supramalleolar osteotomy for the correction of all the elements of the deformity was performed. In the remaining cases, external rotation tibial osteotomy below the tuberosity in five feet (three children) and supramalleolar in two feet (two children) was performed. The follow-up ranged from 1 to 16 years (mean, 4.3 years). Partial or full improvement, concerning one or more elements of the equinovarus deformity, has been achieved in 11 feet (nine children). In eight feet (five children), tibial osteotomy did not improve the deformity. There are exceptionally rare indications for use of tibial osteotomy in the treatment of CTEV or medial malalignment syndrome after failed clubfoot surgery. They concern older children and adolescents with secondary osteoarthritis of the feet resulting from previous multiple operations.

Adolescent↗
PubMed2004

Patellofemoral relationships and cartilage breakdown.

We evaluated the association between patellofemoral relationships and cartilage lesions in patients (age range 15-49) with anterior knee pain without patellar dislocation (n = 24) and in patients with isolated meniscal rupture without a high energy trauma (n = 21). The position of the patella was assessed from knee radiographs, and cartilage lesion was graded and mapped at arthroscopy. In subjects with lateral patellar cartilage lesion the patella tilted laterally (p < 0.01) and was clearly laterally displaced (p < 0.001), compared to those without patellar cartilage lesion. In subjects with central patellar cartilage lesion the patella located high according to the Insall-Salvati index (p < 0.01) and was somewhat laterally displaced (p < 0.05). Compared to subjects without cartilage lesion in the femoral trochlea, the patella was laterally displaced in subjects with lesion in the lateral trochlea (p < 0.001). In conclusion, our results suggest that specific malalignments predispose to patellofemoral cartilage lesion, but prospective studies are needed to confirm the finding.

Adolescent↗
PubMed1994

Tibial osteotomy for genu varum. Indications, preoperative planning, and technique.

Valgus osteotomy of the proximal tibia remains the treatment of choice for the young active patient with a progressively symptomatic varus knee and mild to moderate secondary osteoarthritis. Although the natural history of the varus knee is not well established, it is widely accepted that patients with varus malalignment who develop meniscal injuries or progressive cartilage wear will inevitably develop more severe medial compartment osteoarthritis unless the abnormal mechanics of the knee are corrected.

Bone Malalignment↗
PubMed2003

[Rachitic knock knees in children].

Knee malpositions, for example valgus or varus deformations or flexion contractures, were often cited in the historical literature. In earlier times, clinical pictures such as rickets were often the reason for this kind of deformity. A causal therapy did not exist until the twentieth century. In most cases of rickets, genu valgum was reported as the typical knee deformation. The differential diagnosis for genu valgum caused by rickets was genu valgum traumaticum, paralyticum, and inflammatorium. The most important reports on the pathogenesis of valgus deformation can be found in publications by Hueter and von Mikulicz. The causal therapy of rickets was introduced at the beginning of the twentieth century.Vitamin therapy and UV phototherapy were developed during this period. Using these therapies, rickets decreased dramatically. Kurt Huldschinsky, a pediatrician from Berlin,was one of the main inventors of UV phototherapy in Germany. At the end of the nineteenth century, the operative correction of knee deformities increased while conservative treatment continued to be applied. Plaster casts,orthoses, and osteoclast therapy were the main noninvasive therapeutic possibilities. Positive aspects of the conservative techniques were mostly the good results and easy, timesaving technique compared with the operative treatment. The operative therapy increased with the knowledge of antisepsis and asepsis as well as advances in anesthetic procedures. Operative treatment modalities, for example tibial and femoral osteotomies, were more precise, but connected with multiple complications and greater time expenditure. Sufficient vitamin prophylaxis rendered knee deformations caused by rickets a rarity.

Bone Malalignment↗
PubMed2003

Effect of the foot on the mechanical alignment of the lower limbs.

The authors evaluated the effect of the foot on the loading axis of the lower limb measured from radiographs in 30 pediatric patients. Deviation at the knee was calculated for the hip-ankle (traditional) and the hip-foot lines (heel lined up with a metal wire). A trigonometric model of the limb loading axis was developed with predicted mechanical axis deviations at the knee. Statistics were based on the methods of Bland and Altman. Mechanical axis deviation at the knee in the frontal plane varies with foot height, foot-tibial angle, and genu valgum. The predicted trigonometric model was found to be in agreement with measured radiographic values. Including the foot in the radiographic measurement of limb alignment may increase validity of surgical planning for correction of malalignment and for evaluation of degenerative arthritis risk at the knee level.

Adolescent↗
PubMed2000

The mechanism of the effect of obesity in knee osteoarthritis: the mediating role of malalignment.

OBJECTIVE: Obesity is most strongly linked to osteoarthritis (OA) at the knee. Varus malalignment was examined as a possible local mediator that may increase the impact of body weight at the knee, versus the hip or ankle. Compartment load distribution is more equitable in valgus than in varus knees, and valgus knees may better tolerate obesity. We therefore tested whether 1) body mass index (BMI) is correlated with OA severity in varus knees, 2) the BMI-OA severity correlation is weaker in valgus than in varus knees, 3) BMI is correlated with the severity of varus malalignment, and 4) the BMI-medial tibiofemoral OA severity relationship is reduced after controlling for varus malalignment. METHODS: In 300 community-recruited patients with knee OA, 2 groups (varus and valgus) were identified based on dominant knee alignment on a full-limb radiograph, i.e., the angle formed by the intersection of the femoral and tibial mechanical axes. Severity of knee OA was assessed by measurement of the narrowest joint space width on radiographs of knees in a fluoroscopy-confirmed semiflexed position. RESULTS: Alignment direction was symmetric (or neutral in 1 limb) in 87% of patients. One hundred fifty-four patients had varus knees and 115 had valgus knees. BMI correlated with OA severity in the varus group (r = -0.29, P = 0.0009) but not in the valgus group (r = -0.13, P = 0.17). BMI correlated with malalignment in those with varus knees (r = 0.26) but not in those with valgus knees (r = 0.16). The partial correlation of BMI and OA severity, controlling for sex, was reduced from 0.24 (P = 0.002) to 0.04 (P = 0.42) when varus malalignment was added to the model. CONCLUSION: BMI was related to OA severity in those with varus knees but not in those with valgus knees. Much of the effect of BMI on the severity of medial tibiofemoral OA was explained by varus malalignment, after controlling for sex. Whether it precedes or follows the onset of disease, varus malalignment is one local factor that may contribute to rendering the knee most vulnerable to the effects of obesity.

Aged↗
PubMed1998

[Analysis of leg geometry--standard techniques and normal values].

The diagnosis of malalignments of the lower extremities includes analysis of the geometry of the whole leg. The first step in the diagnostic process is a standardized physical examination. It provides valuable background information for an effective radiological diagnosis. Even with a thorough standardized physical examination it is not possible to define exactly the deformity or decide on an operative procedure. The diagnosis of axis deviations in the frontal plane can be measured on a conventional plain X-ray of the whole leg. In this view it is very important that the knee joints are in a true a.p. view independent on torsional deformities of the lower legs. Today the gold standard to measure the torsion and length of the lower extremities is the CT scan. However, the multitude of analytical methods for CT measurements described in the literature do not lend themselves readily to comparison; thus, it is difficult to identify a clear method of choice. Not every CT measurement is better than a physical examination. Evidence of reproducibility and accuracy is a prerequisite for useful interpretation of the results. Up to this point in the literature there are only reference values for the Ulm CT Method. One alternative is the MR scan, which avoids radiological risks, but the reproducibility and accuracy of the MRI method are not as good as for the CT method. Another alternative is ultrasound, where recent advances in the measurement of torsion and length of the lower extremities have proven competitive with or superior to the accuracy of MRI. The three-dimensional determination of the torsion and length of the lower extremities by ultrasound has now assumed a leading role in the non-radiological diagnosis of malalignments of the lower extremities in children and adolescents. This method furthermore is increasingly being used in preoperative planning of leg deformities in adults.

Adolescent↗
PubMed2004

Factors affecting the outcome of distal realignment for patellofemoral disorders of the knee.

This study correlated the risk factors with the clinical outcome of distal realignment for patellofemoral disorders in 48 patients with 53 knees with 25 to 96 months follow-up. The indications for surgery included pain and disability due to patellofemoral disorders with failure of at least 6 months of conservative treatments. The evaluations included pain scores, Lysholm functional scores and radiographs of the knee. The overall results were satisfactory in 47 knees (88.7%) and unsatisfactory in six knees (11.3%). There was no correlation of the clinical results with age, sex, body weight and body height, preoperative pain scores and Lysholm scores. However, the clinical outcome correlated with the severity of articular damage and the correction of patellar malalignment. Error in patient selection and inadequate surgical technique were attributable to poor outcomes.

Adolescent↗
PubMedDate not supplied

High tibial osteotomy.

High tibial osteotomy is effective for managing a variety of knee conditions, including gonarthrosis with varus or valgus malalignment, osteochondritis dissecans, osteonecrosis, posterolateral instability, and chondral resurfacing. The fundamental goals of the procedure are to unload diseased articular surfaces and to correct angular deformity at the tibiofemoral articulation. Although the clinical success of total knee arthroplasty has resulted in fewer high tibial osteotomies being done during the past decade, the procedure remains useful in appropriately selected patients with unicompartmental knee disease. Renewed interest in high tibial osteotomy has occurred for a number of reasons. These include the prevalence of physiologically young active patients presenting with medial compartment osteoarthritis; the advent of new techniques for performing the procedure (ie, improved instrumentation and fixation plates for medial opening wedge osteotomy, dynamic external fixation for medial opening wedge osteotomy, and improved instrumentation for lateral closing wedge osteotomy); and the need to concomitantly correct malalignment when performing chondral resurfacing procedures (ie, autologous chondrocyte transplantation, mosaicplasty, and microfracture).

Arthritis↗
PubMed1994

Failed meniscus transplantation. A report of three cases.

Treatment of patients with an established disabling compartment arthrosis after total meniscectomy is an important clinical problem. Meniscal transplantation may be an alternative method of treatment. Between 1989 and 1992, 25 cryopreserved nontissue antigen matched meniscal transplantations were performed. In three patients with a medial meniscus, the transplantation failed because of partial loosening of the meniscus. The donor meniscus was removed in one case after 12 months and in the other two cases after 20 and 24 months. In two cases, there was a varus malalignment of the knee. In the third case, the knee was unstable because of an insufficient anterior and posterior cruciate ligament. The retrieved menisci were stained with enzyme and immunohistochemical reactions. Focal areas of degeneration were noted, with vital cells around the microvascular supply and at the synovial side. The growth potential of vital parts of the grafts, as shown by proliferation markers, seemed to be virtually nil. The success of meniscal transplantation seems to depend on factors responsible for vascularization. Malalignment and instability of the joint, causing abnormal pressure on the graft, may be responsible for vascular damage leading to degeneration and loosening of the graft.

Adult↗
PubMed2006

Management of lower extremity malalignment during running with neuromuscular retraining of the proximal stabilizers.

This case report presents a high-level female runner with a history of more than 25 years of recurrent lower extremity (LE) injuries and LE malalignment problems during running. Due to her LE malalignment, she has been unable to run for the past 3 years. A definitive diagnosis was not found for her inability to run so by exclusion we diagnosed dysfunction of the hip, spine, and pelvic stabilizers that resulted in her in LE malalignment. To treat this muscle weakness, we designed a Pilates-evolved functional movement intervention to improve the control and strength of the proximal stabilizers and regain normal LE alignment. The Pilates-evolved treatment approach involved a series of functional and progressive resistance exercises designed to dynamically stabilize the spine, pelvis, and hip through all planes of motion. After 1 year of Pilates-evolved training, the athlete's disabling movement pattern resolved and she has returned to a regular running program. The purpose of this case report is to describe a Pilates-evolved functional movement intervention that resolved this runner's LE malalignment and returned her to running when other traditional treatment approaches were not effective in doing so.

Athletic Injuries↗
PubMed1994

Dynamics of knee malalignment.

The dynamics of malalignment are based on the combination of the static limb alignment and the dynamics of loading at the knee during walking and other activities of daily living. Dynamic loading at the knee can be influenced by subconscious control of limb position such as foot placement, active muscle contraction, passive soft-tissue stability, as well as the speed of walking. The loads that are generated during these dynamic activities are substantially greater than the loads that can be generated during static postures. Therefore, limb alignment based on static radiographic measurements provides one component to the complete analysis of the factors influencing loading at the knee joint. Loading at the knee joint is an important consideration in the progression of degenerative processes at the knee, as well as in the planning and selection of certain treatment modalities. Dynamic malalignment that occurs during activities such as gait should be considered in evaluating the progression of disease processes as well as the selection of appropriate treatment modalities.

Adaptation, Physiological↗
PubMed1994

[Unreduced congenital hip dislocation in adults].

Thirty-four cases of unreduced congenital dislocation of the hip were reviewed. The hips were completely dislocated and rode high with the femoral head supported by gluteal muscles, but not by a false acetabulum. The mean Harris hip score was 64 points. Twenty-four patients (80%) had mild or severe low backache, and this was associated with increased lumbar lordosis or functional scoliosis. Seven patients (20%) had valgus malalignment and dysfunction of the knee joint. In older patients over 50 years old, there were many significant problems in the hip, lumbar spine and knee.

Adult↗
PubMed2003

[Tibial malalignment of mobile-bearing prostheses--a simulator study].

Total knee replacement requires exact implantation in order to avoid long-term failure. Longitudinal in vivo studies of malaligned prostheses are problematic for ethical reasons. To assess the critical angle of tibial (varus/valgus) malalignment of knee prostheses in vitro, a simulator investigation was performed. Mobile-bearing prostheses were implanted in a simulator with 1-3 degrees valgus and varus malalignment as well as in a neutral position. More extreme malalignment caused unacceptable forces in the simulator. After each 500,000 cycles (ca. 0.5 years of walking) the replicas of the polyethylene inlay were examined and the extent of the tribocontact areas was measured until 1,500,000 total cycles. Finally the original polyethylene was examined with a scanning electron microscope. The polyethylene showed only abrasive wear without any fatigue effect. Tribocontact areas of 900-1500 mm(2) were observed under malalignment of mobile-bearing prostheses according to the manufacturer's specifications. With 1-3 degrees of malalignment, tribocontact areas were located at atypical polyethylene zones, but still showed abrasive wear only. Increasing malalignment due to a lift off of the femoral part of the prostheses with a strong torsional strength of the polyethylene made more extreme simulation impossible. Malalignment of 3 degrees could be suggested as maximum in vivo tolerability; perfect alignment with ideal implantation should be the goal. Soft tissue was given less consideration in this simulator study.

Bone Malalignment↗