[Remote results of Camera's operation in habitual patellar luxation].
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Joint Dislocations↗
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In vitro measurement of patellar kinematics following reconstruction of the medial patellofemoral ligament.
This study compares the effects of two different techniques of medial patellofemoral ligament (MPFL) reconstruction, and proximal soft tissue realignment on patellar stabilization against lateral dislocation. Eight human cadaver knee specimens with no radiological pathomorpholgy on a straight lateral view, contributing to patellofemoral instability, were mounted in a kinematic knee simulator and isokinetic extension was simulated. Patellar kinematics were measured with an ultrasound positioning system (zebris) while a 100 N laterally directed force was applied to the patella. The kinematics were compared with intact knee conditions under MPFL deficient conditions, as well as following dynamic reconstruction of the MPFL using a distal transfer of the semitendinosus tendon, following static reconstruction by a semitendinosus autograft, and following proximal soft tissue realignment of the patella (Insall procedure). Dynamic reconstruction of the MPFL resulted in no significant alteration (P = 0.16) of patellar kinematics. Static reconstruction of the MPFL significantly medialized (P < 0.01) the patellar movement without, but restored intact knee kinematics under the laterally directed force. In contrast, following proximal soft tissue realignment, the patellar movement was constantly medialized and internally tilted (P = 0.04). Dynamic and static reconstruction of the MPFL create sufficient stabilization of the patella. Following proximal soft tissue realignment, the patellar position was over-medialized relative to intact knee conditions, which could lead to an overuse of the medial retropatellar cartilage.
Aged↗
[THE SURGICAL TREATMENT OF HABITUAL PATELLAR LUXATION].
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Humans↗
Patellofemoral malalignment: looking beyond the viewbox.
A clear understanding of the pathophysiology of anterior knee pain is inhibited by the use of imprecise, poorly defined, and often interchanged words, such as malalignment, patellar alignment, maltracking, subluxation, dislocation, and congruence. The literature is filled with articles regarding the diagnosis, "malalignment of the patella," most of which give no precise diagnosis. This article presents a definition of malalignment and a plea for rational descriptive and scientific analysis. Much of what is described is based on theory, not facts. These ideas are supported by clinical experience and logical analysis, but very little in the way of scientific data. Most of the data involve radiographic images, which present only one piece of the puzzle.
Humans↗
Prodromes of failure in total knee arthroplasty.
A total of 102 revision total knee arthroplasties (TKAs) were reviewed to determine the prodromal symptoms and radiographic findings associated with failure. Presenting symptoms included pain (84%); swelling (76%); progressive varus or valgus deformity (19%); instability (17%); stiffness (17%); clicking or grinding (7%); catching (4%); and patellar pain, subluxation, or clicking (4%). Radiographs were diagnostic in 91% of cases, demonstrating complete radiolucencies (80%), polyethylene wear (43%), component breakage (5%), metallic debris (3%), patellar subluxation or dislocation (4%), and osteolysis (4%). Gross intraoperative findings included polyethylene wear (72%), osteolysis (22%), metal-wear synovitis (9%), component breakage (6%), patellar wear and dissociation (4%), and occult sepsis (5%). The average duration of symptoms was 13 months; the interval between orthopedic evaluations averaged 23 months. Based on this information, we recommend that an annual questionnaire and weight-bearing radiographs be used to ensure adequate surveillance of TKA patients and avoid complications associated with delay in diagnosis of polyethylene wear or implant loosening.
Aged↗
[Habitual patellar luxation in a family].
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Knee Dislocation↗
Correction of ligament and bone defects in total arthroplasty of the severely valgus knee.
One hundred thirty-five knees with valgus deformity were treated with a minimally constrained, cementless total knee replacement using intramedullary alignment for the femur and tibia. Mean valgus angle before surgery was 16 degrees; mean valgus angle after surgery was 7 degrees. Neither alignment nor varus-valgus stability deteriorated during the six-year follow-up period, but the knees with greater than 25 degrees deformity had a tendency to increase posterior laxity. Severely deformed knees required bone grafting of the medial femoral and tibial surfaces. A technique was developed to resect the distal femur measured from the medial femoral condyle and to maintain joint line position. Patellar subluxation and dislocation occurred in fewer than 1% of the cases. Despite the absence of rotational constraint at the articular surface, there was no tendency for patellar stability to deteriorate over time.
Arthritis↗
GUEPAR knee arthroplasty results and late complications.
One hundred eight GUEPAR knee arthroplasties have been studied with a follow-up of one year on 41; 2 years on 22 and 3 years on 45 knees. Overall results were 17% excellent, 44% good, 10% fair and 29% poor. Excellent results were comparatively fewer in rheumatoid arthritis. There was a deterioration in the quality of results of arthroplasty with longer follow-up. The incidence of deep infection was 11%. There was a significant correlation between early wound drainage and deep infection. More than half of the infected knees have not required intervenition as yet. One knee was revised and 3 had attempted arthrodesis with one successful fusion. Two patients died with septicemia. Axle migration occurred in 8 knees and femoral stem breakage in 2 knees. Loosening was found in 27% of the knees with progressive reduction in quality of the arthroplasty. Incomplete cementing predisposed to loosening. Patellar symptoms were present in 28% of the knees. Patellar subluxation and dislocation occurred in 49% of the knees. More than half of these were symptomatic. With normal patellofemoral alignment, pain was more common in the osteoarthritic knee. Use of a patellar implant with GUEPAR knee prostesis should be restricted to severely disabled patients with major fixed deformities. Mechanical failure can be minimized by proper positioning of the implant, correct alignment of the extensor mechanism and adequate cement around the entire stem.
Adolescent↗
Patellar thickness in total knee replacement.
The question of patellar thickness after total knee replacement (TKR) is an important issue. From November 1989 to June 1993, a total of 294 TKR were performed on 219 patients (34 males, 185 females) with an average age of 67 years. Tricon-M prostheses were used in TKRs performed before October 1992, and PCA prostheses were used after that date. In each TKR, all polyethylene patellar components used on patellar resurfacing were cemented in place. The average preoperative patellar thickness was 21.2 +/- 1.8 mm. The thickness was preserved in 106 knees, while for 53 knees, a slight increase in thickness (mean, 1.5 +/- 0.9 mm) was recorded, and for 120 knees, a slight decrease in thickness (mean, 1.5 +/- 0.8 mm) was recorded. Lateral retinacular release was performed in 96 knees (40%) of the 238 TKR with a Tricon-M prosthesis, but in only seven knees (17%) among the 41 TKR using the PCA prosthesis. Patellar subluxation and dislocation after TKR occurred in 13 knees of 11 patients (10 females, one male, mean body weight 63.5 kg) with the Tricon-M prosthesis. The mean time from arthroplasty to occurrence of patellar instability was eight months. Six knees were treated by proximal realignment procedure while seven knees were given conservative treatment, with good results and no recurrence reported. The use of a patellar cutting jig allows better control of patellar thickness when performing patellar resurfacing for small patella. No complications such as patellar fracture, infection or patellar component-loosening were encountered in the 294 TKRs performed.
Aged↗
The patellofemoral component of total knee arthroplasty.
Patellofemoral complications continue to form a large proportion (up to 50%) of total knee arthroplasty (TKA) complications. If adequate attention is paid intraoperatively to patellar tracking and component position, the incidence of subluxation, component loosening, and fracture should decrease. When treating patellar subluxation and dislocation, tibial tubercle transfer should be avoided because there is an unacceptably high incidence of complications. Care should be taken to treat the underlying cause of dislocation with either a soft tissue procedure or component revision. Fracture of the patella may be treated nonoperatively in 50% and 80% of patients. Cysts, if large, may be bone-grafted to avoid the potential complications of stress fracture and component loosening. Loosening of the patellar component is likely to be symptomatic and to require surgery in up to 75% of cases. A displaced patellar component may cause attritional wear of the quadriceps tendon or patellar ligament. All rheumatoid patellae should be resurfaced. The present trend in the osteoarthritic patella is toward resurfacing more often. With improved implant design and a predicted decrease in complications, resurfacing in the osteoarthritic patella may become routine. Osteoarthritic patellae that maintain good cartilage, normal anatomic shape, and congruent tracking need not be resurfaced.
Adult↗
Patellar instability: treatment by arthroscopic electrosurgical lateral release.
We reviewed the results of arthroscopic lateral release using electrosurgery in 39 patients (45 knees) with a history of recurrent patellar subluxation or dislocation. The average follow-up time was 28 months (range, 24-36). At follow-up, the patients had decreased swelling, instability, and pain. There was an improvement in flexion activities, sports participation, and overall functional ability. Only 20% of the knees had completely normal physical findings: 11.1% of the knees were rated as excellent; 64.4% were improved; and 24.5% were poor. Dislocators had more frequent poor results. The complication rate was 4.4%. There were no postoperative hemathroses. One patient was considered a surgical failure. The technique yields results comparable with those of open extensor realignment procedures and avoids the complications inherent to lateral release in general. The place for this procedure in patellar instability is well-documented.
Adult↗
Impact of patellofemoral design on patellofemoral forces and polyethylene stresses.
BACKGROUND: The patellofemoral joint is a complex articulation because it relies mainly on soft-tissue constraints for stable tracking. The presence of a functioning posterior cruciate ligament and the design parameters of a total knee arthroplasty, such as trochlear groove alignment and cam-post configuration, can have a major effect on patellar biomechanics. METHODS: A finite element model of a knee implanted with femoral, tibial, and patellar components was generated. The model was validated by experimental testing of three cadaver knees implanted with a total knee prosthesis and a patellar force transducer. Two femoral component designs with different valgus angles of the trochlear groove (0 degrees and 7 degrees ) were studied. The effects of femoral rollback, rotation of the femoral component, medialization of the patellar implant, and alignment of the trochlear groove on patellar forces were then analyzed. RESULTS: A consistent reduction of up to 7% in patellofemoral forces was seen with progressive magnitudes of femoral rollback. The 0 degrees -aligned trochlear groove generated some lateral patellofemoral shear force throughout knee flexion. The 7 degrees -aligned trochlear groove generated medial shear force at flexion angles of <20 degrees and lateral shear force at flexion angles of >20 degrees. A more medial patellar component position reduced peak lateral shear forces by up to 10 to 15 N. However, a corresponding increase in medial shear forces was seen. CONCLUSIONS: This model predicted substantial reduction in patellofemoral lateral shear forces with a medialized patellar component or with external rotation of the femur. The model supported the hypothesis that femoral rollback reduces patellofemoral forces by improving the efficiency of the extensor mechanism. CLINICAL RELEVANCE: Patellofemoral complications after total knee arthroplasty include anterior knee pain, patellar subluxation and dislocation, abnormal polyethylene wear and damage, and loosening. There is a wide variation in the design features of current total knee prostheses, such as the sagittal radius, depth, and orientation of the trochlear groove of the femur and the geometry of the patellar component surface. The finite element model used in the present study can provide insight into the effects of design parameters on patellofemoral forces and on local contact stresses.
Arthroplasty, Replacement, Knee↗
Distal realignment of the patellar tendon to correct abnormal patellar tracking.
Between January 1980 and January 1994, 31 knees required distal realignment of the extensor mechanism to treat lateral patellar subluxation that could not be corrected with lateral patellar release and vastus medialis advancement during total knee arthroplasty. Fifteen had a preoperative valgus angle of more than 12 degrees, and 16 were undergoing revision total knee arthroplasty. Ten knees had a modified Roux-Goldthwait procedure, 18 had medial tibial tubercle transfer, and three had medial transfer of the medial 1/2 of the patellar tendon. The length of followup ranged from 2 to 16 years. No late patellar subluxations or dislocations have occurred in any of these cases. Three cases of medial tibial tubercle transfer had hematomas develop, with two requiring surgical evacuation; one of these developed a late infection. No fractures or displacements of the tubercle fragment have occurred. No significant patellar complications have occurred in those patients who underwent the modified Roux-Goldthwait procedure or the medial transfer of the medial 1/2 of the patellar tendon. One year after surgery, the mean knee flexion was 113 degrees, four knees had a flexion contracture of 5 degrees, and none had a quadriceps lag.
Arthroplasty, Replacement, Knee↗
The anteroposterior axis for femoral rotational alignment in valgus total knee arthroplasty.
This study evaluated a technique using the anteroposterior axis of the distal femur, rather than the transepicondylar or posterior femoral condylar axis, to establish rotational alignment of the femoral component in valgus knees. The anteroposterior axis of the distal femur was defined by a line through the deepest part of the patellar groove anteriorly and the center of the intercondylar notch posteriorly. Total knee arthroplasty was done in 46 valgus knees between 1980 and 1986 using the posterior femoral condyles as landmarks for rotational alignment. From January 1986 through January 1992 total knee arthroplasty was done in 107 valgus knees using the anteroposterior axis for rotational alignment of the femoral component. In the group of knees using the posterior condylar axis, medial tibial tubercle transfer was needed intra-operatively in 8 knees to prevent lateral dislocation of the patella. In the first 2 postoperative years, 4 knees had recurrent patellar dislocation or subluxation that required surgical correction. In the group of knees using the anteroposterior axis, patellar tracking problems that required realignment were significantly reduced. One knee required medial tibial tubercle transfer to correct a Q angle > 20 degrees. In the remaining knees, the Q angle was < 10 degrees, and patellar tracking was acceptable. Two years after surgery, no knees had patellar instability.
Aged↗
A modified system of stress radiography for patellofemoral instability.
Axial radiographs were obtained under valgus and external rotation stress at 45 degrees of knee flexion with and without contraction of the quadriceps muscle in order to assess the dynamics of patellar subluxation or dislocation. The radiography was performed on 82 knees in 61 patients with patellofemoral instability, and on 44 normal knees. The lateral patellofemoral angle and the congruence angle were measured and compared with the conventional Merchant views. Both parameters showed greater differences between symptomatic and normal knees on the stress radiographs obtained without quadriceps contraction. There was a major difference in the lateral patellofemoral angles between the groups, which clearly distinguished symptomatic knees from normal controls. Congruence angles on stress radiography had a significant correlation with the functional scores obtained after a period of conservative treatment and a positive correlation with the frequency of patellar subluxation. When the quadriceps contracted, two patterns of patellar shift were observed. While the patella reduced into the trochlear groove in all normal knees and about 70% of the symptomatic knees, contraction of the quadriceps caused further subluxation of the patella in the remaining symptomatic knees. All the knee joints which showed this displacement failed to respond to conservative treatment and eventually required surgical treatment. Thus, this technique of stress radiography is a simple, cost-effective and useful method of evaluating patellar instability and predicting the prognosis.
Adolescent↗
Lateral patellar instability: treatment with a combined open-arthroscopic approach.
Lateral patellar maltracking, subluxation, and dislocation could arguably be grouped together as varying degrees of lateral patellar instability. Besides common anatomical etiological factors, such as genu valgum, patella alta, tibial rotation, and others, the author has found that many of these patients exhibit patellar hypermobility, a seldom mentioned physical finding. Lateral retinacular release fails to address the hypermobility, whereas traditional, more extensive open operations often carry significant postoperative morbidity and disability. This article suggests a surgical approach that combines open medial tethering of the patellar tendon with arthroscopic lateral release. The procedure addresses both etiological factors of anatomical peculiarity and patellar hypermobility, with a relatively benign postoperative course. In a series of 29 cases with follow-up of 4-8 years, results appear encouraging so far.
Adolescent↗
Distal patellar pole fractures. A proposed common mechanism of injury.
A variety of names has been given to disorders of the inferior pole of the patella occurring in young athletic individuals and several different causes have been proposed for these disorders. Occasionally a direct blow will cause fracture of the inferior pole of the patella, but the only other mechanism which seems to be responsible is subluxation or dislocation. Ten cases of distal patellar pole fracture secondary to dislocation or subluxation of the patella are reported. From these cases and an extensive review of the literature it is concluded that patellar subluxation or dislocation is the usual common mechanism of distal patellar pole fractures in young, active individuals and that adequate treatment of this problem must address the patellar instability as well as the fracture.
Adolescent↗
ICLH knee arthroplasty. A consecutive study of 108 knees with uncemented tibial component fixation.
One hundred eight ICLH knee arthroplasties with cementless tibial component fixation were performed from 1978 through 1982 in Gothenburg, Sweden. The patients were followed for 2-8 years (mean, 4 years) with clinical and radiographic examinations at regular intervals, and the data were computer-analyzed. Patellar subluxation-dislocation, often accompanied by pain, occurred in 50% of the knees. Eleven arthroplasties failed due to aseptic loosening. Survival rate analysis performed using three different definitions of failure resulted in cumulative success rates after 8 years of 86%, 78%, and 72%. Most failures occurred between 2 and 5 years after surgery. Patients with bilateral arthritis were overrepresented among the failures. There was a significant correlation between failure and poor bone sclerosis around the polyethylene pegs. Most patients can be treated with cementless fixation, but other types of fixation should be considered for elderly patients and patients with severe bilateral disease.
Aged↗