[Demonstration of 2 pathways for cholesterol synthesis in the mollusk: patella Patella vulgata L., (Gasteropoda, Prosobranches, Archeogasteropoda)].
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Acetates↗
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Patella or not?. (Is the patella component the 'Cinderella' of total knee arthroplasty?).
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Journal Article↗
Case of Accessory Patellae in the Human Subject, with Remarks on Emargination of the Patella.
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Journal Article↗
Patella baja and total knee arthroplasty (TKA): etiology, diagnosis, and management.
Patella baja, that can be divided into congenital, acquired, or a combination of the two, is commonly encountered in total knee arthroplasty (TKA). Congenital patella baja refers to a patella distal in relationship to the femoral trochlea and present since an early age. Acquired patella baja may occur secondary to distal positioning of the patella relative to the femoral trochlea or shortening of the patellar tendon, as a result of trauma or surgery. Patella baja also can occur postoperatively as a result of scarring and shortening of the patellar tendon, scarring of the patellar tendon to the anterior aspect of the tibia, or both. Another cause of acquired patella baja seen commonly in TKA is elevation of the joint line, referred to as pseudo-patella baja. The patella remains in a normal position relative to the femoral trochlea; however, the distance between the patella and tibia is narrowed. Pseudo-patella baja can be a result of tibial or femoral over-resection, which necessitates a large polyethylene insert. Alterations of the patello-tibial distance can occur during TKA by excessive soft-tissue release that requires elevation of the joint to regain stability and placement of the patellar polyethylene component distally on the patella. Prevention is the easiest way to avoid potential problems with patella baja during TKA; however, the surgeon is often confronted with this situation during total knee revisions. Failure to address patella baja can lead to decreased range of motion (ROM), a decreased lever arm, extensor lag, impingement of the patella against the tibial polyethylene or tibial plate, anterior knee pain, increased energy expenditure, and rupture of the patellar or quadriceps tendons. Treatment of patella baja first depends on determining the cause and distinguishing between patella baja and pseudo-patella baja. Five different methods to measure patella baja are reviewed and include: (1) Blumensaat's line, (2) Insall-Salvati ratio, (3) Modified Insall-Salvati ratio, (4) Blackburne-Peel, and (5) Caton-Deschamps. Corrective measures include reestablishing the joint line by use of distal femoral augments, tibial tubercle osteotomy with proximal displacement, lengthening of the patellar tendon, shaving of the anterior portion of the tibial polyethylene, and placement of the patellar implant in a cephalad position.
Aged↗
Commonsense design of patella implant: four years of clinical experience with 124 patients.
BACKGROUND: Patella resurfacing in Total knee Arthroplasty still is an issue of controversy, that results from the statistically poor performance of patella implants. Since the basic fault of conventional designs, in our opinion, is the inadequate thickness of the polyethylene, an innovative patella was designed and rules of technique were set to optimize the surgical procedure. METHODS: Since July 1998 we have employed the new patella in 124 consecutive patients undergoing total knee arthroplasty. They had the patella routinely resurfaced with an implant of a special design of a concave undersurface and a convex (dome) articulating surface. The thickness of the entire implant was uniform at all areas of contact. The bony patella was prepared with a concave reamer and shaped into a dome with a shallow central hole. Fixation with cement gave an optimally stable implant to shear forces and resistance to wear. RESULTS: All patients were studied prospectively and followed up to five years. Results were related specifically to performance of the patella as a part of the entire joint. Two patients died from unrelated causes. Four patients had delayed wound healing. One sustained a transverse fracture of the patella already healed with minimal displacement when she came to our attention. One sustained avulsion of the patella tendon from the tuberosity, which underwent surgical reattachment. Rest pain score (10-0) improved from 5.2 to 0.5. Activity pain score (10-0) improved from 9.0 to 1.4. Walking score (0-10) improved from 3.2 to 8.2. Stairs negotiation (0-10) improved from 2.8 to 8.0 and ADL Function (0-10) improved from 4.3 to 8.2. CONCLUSION: The special technique of resurfacing of the patella was developed during a short learning period. The new design of the patella implant, eight mm thick at any point of contact gave excellent and good results in 91%. There were no intra operative complications. During five years of follow up two complication were encountered and treated successfully: a minimally displaced transverse fracture and an avulsion of the patella tendon from the tuberosity. None of the patellae components required replacement. In our opinion the new design of bio-mechanically reliable patella implant will regain confidence of surgeons who presently refrain from patella resurfacing.
Arthroplasty, Replacement, Knee↗
Press-fit metal-backed rotating patella: seven- to 14-year followup.
A consecutive series of 80 patients with 110 press-fit metal-backed rotating platform patella resurfacing surgeries were reviewed at an average of 107 months followup (range, 84-167 months). Twenty-eight patients died before followup. Fifty-two patients (70 patellae) were available for clinical and radiographic followups. One patella was revised for failure of the patella component. Four patellae were revised along with revision of the knee replacement. One patella realignment procedure was done for recurrent subluxation of the patella. There were no patellar dislocations in this series, no patella fractures, and no disruption of the quadriceps tendon or infrapatellar ligament. Six patellae had subluxation seen on postoperative radiographs. The incidence of patellar tilt greater than 5 degrees was 13%. No patellae were considered radiographically loose. The incidence of radiolucencies was 37%. Subsidence of the component superiorly was identified in 39% of the patellae, and inferiorly in 36% of the patellae. Of the 49 patients (67 knees) returning for followup, 70% of the knees were rated as excellent, 10% were rated good, 15% were rated fair, and 5% were rated poor. Press-fit metal-backed patella provided good component durability with only one revision because of component failure. Radiographic analyses showed a high incidence of subsidence associated with good clinical results.
Aged↗
Congenital dislocation of the patella.
Congenital dislocation of the patella may occur as a persistent lateral dislocation of the patella that presents with a knee flexion contracture and the patella tethered lateral to the femoral condyles or as an intermittent dislocation of the patella. In the latter syndrome, the patella dislocates completely with each flexion and extension cycle of the knee and is best termed obligatory dislocation of the patella, because the patient has no control over the patella dislocating as he or she moves the knee. The first type of congenital dislocation, which is fixed, often is associated with syndromes such as arthrogryposis and should be corrected surgically by lateral release and realignment of the patella. Obligatory dislocation of the patella tends to be an isolated dysplastic anomaly and may be relatively well tolerated. Rebalancing of the patella usually is done at a later age because of less interference with function. The current author describes the natural history of patella femoral dysplasia, detailing the pathologic changes that are present, and recommends surgical techniques for correcting both types of congenital dislocation of the patella.
Child↗
Patella lead x-ray fluorescence measurements are independent of sample orientation.
In vivo x-ray fluorescence bone lead measurements assess long-term lead exposure. Tibia, calcaneus, and patella are the most commonly sampled bones. Patella measurements also include lead signals from the distal femur, proximal tibia, and synovium. It is therefore important to know whether the orientation of the patella relative to the measurement system substantially affects the measured patella lead concentrations and their measurement uncertainties. This study examined whether these parameters exhibited a dependence on the orientation of the patella with respect to the measurement system, a dependence that could arise from varying nonpatella contributions. There was no effect of orientation on measured patella lead concentration, but there was a highly significant effect of orientation on the measurement uncertainty. These data do not conclusively show that there are no nonpatella contributions to a patella lead measurement; rather, that any such contributions are not a function of measurement orientation over the range of orientations considered. Further study is required if the contribution of nonpatella tissues to a patella lead XRF-measured concentration is to be fully addressed. This study also filled a gap in the literature by quantifying the within-patella (29%) and between-patella (71%) variability of measured patella lead concentrations from replicate measures of nine patellae.
Adult↗
A comparative biomechanical study of the strength of the bony patella following dome cut or uniplanar cut in total knee arthroplasty.
This study was designed to investigate whether there is a difference in the strength of the bony patella following preparation either with a dome configuration or with a regular uniplanar cut in total knee arthroplasty. For each test 4 cadaveric patellae were used. Two of the 4 patellae were prepared with a regular uniplanar cut and 2 were prepared into a dome shape with a circumferential wall, using a concave reamer. The thickness of each patella after preparation was [figure 1 & 2: see text] 15 mm. The tests were performed using an impact drop weight apparatus. In the first two tests, which tested the resistance of the patella to tensile force and evaluated the strength of the patella by impact load while under tension, the soft tissues were torn, with no harm to the bony patella. In the third test, which evaluated the resistance of the patella without tension against impact load, the force required to fracture the dome-shaped patella was greater than for the traditional uniplanar cut (500 Kg vs 350 Kg). Dome shape with circumferential wall preparations of the bony patella in total knee arthroplasty were stronger in resisting external impact than the conventional uniplanar cut patella. This established the rationale for our use of the dome-shaped patella implant with a concave undersurface.
Arthroplasty, Replacement, Knee↗
Increased serum cartilage oligomeric matrix protein levels and decreased patellar bone mineral density in patients with chondromalacia patellae.
BACKGROUND: Chondromalacia patellae is a potentially disabling disorder characterised by features of patellar cartilage degradation. OBJECTIVE: To evaluate markers of cartilage and bone turnover in patients with chondromalacia patellae. METHODS: 18 patients with chondromalacia patellae were studied. Serum cartilage oligomeric matrix protein (s-COMP) and bone sialoprotein (s-BSP) levels were measured by enzyme linked immunosorbent assay (ELISA) and compared with those of age and sex matched healthy control subjects. Periarticular bone mineral density (BMD) of both knee joints was assessed by dual energy x ray absorptiometry (DXA). RESULTS: s-COMP levels were significantly raised in all patients with chondromalacia patellae compared with healthy control subjects (p=0.0001). s-BSP levels did not differ significantly between the groups (p=0.41). BMD of the patella was significantly reduced in patients with chondromalacia patellae compared with the control subjects (p=0.016). In patients with bilateral chondromalacia patellae, BMD of the patella was lower in the more symptomatic knee joint (p=0.005). Changes in periarticular BMD were localised to the patella and were not present in femoral regions. Neither s-COMP (p=0.18) nor s-BSP (p=0.40) levels correlated with patellar BMD. CONCLUSIONS: Increased s-COMP levels, reflecting cartilage degradation, and reduced BMD localised to the patella may represent clinically useful markers in the diagnosis and monitoring of patients with chondromalacia patellae. Measures of cartilage degradation did not correlate with loss of patellar bone density, suggesting dissociated pathophysiological mechanisms.
Absorptiometry, Photon↗
Intraosseous innervation of the human patella: a histologic study.
BACKGROUND: The soft tissue structures surrounding the human knee joint have been the subject of extensive anatomic study. The detailed histologic findings within the bone of the human patella, however, have not been systematically studied. While the nerves supplied to the periarticular soft tissues have been very well documented, the nerves supplied to the interior of the bony patella have never been described. HYPOTHESIS: This study tests the hypothesis that the patella contains an intraosseous nerve network. Further, the authors investigate the anatomic location of these intraosseous nerves to better understand their possible clinical relevance. STUDY DESIGN: Descriptive laboratory study. METHODS: Ten matched pairs of cadaveric patellae (left and right patellae from the same individual; 20 total) were prepared for evaluation by hematoxylin and eosin staining using a technique that allows the creation of complete, large histologic sections of individual patellae. The matched specimens were dissected free of soft tissue and then sectioned using a diamond-wafering saw into 3-mm sagittal (left patella) and transverse (right patella) sections. Sections were then decalcified and whole-mounted into paraffin blocks for further sectioning using a large-format microtome. All 20 specimens were prepared for evaluation. Age at death averaged 80 years (range, 64-91). All specimens demonstrated at least grade II chondromalacia. RESULTS: Nineteen of 20 (95%) specimens demonstrated intraosseous nerves. Of 248 sections studied, 116 (47%) demonstrated intraosseous nerves, with 227 individual nerves identified. The density of intraosseous nerves was greatest in the medial and central portions of the patella, with a significant paucity identified laterally. CONCLUSION: The primary intraosseous innervation of the patella derives from a medially based neurovascular bundle. CLINICAL RELEVANCE: A better understanding of the nerves within the human bony patella may improve understanding the patho-physiology of anterior knee pain syndromes.
Aged↗
One-peg versus three-peg patella component fixation in total knee arthroplasty.
In many designs of total knee arthroplasty, the patella with one central peg has been replaced by a patella with three small pegs for cement fixation. There have been recent reports of failure of this design. This is a prospective, consecutive study of two types of patella component fixation in 228 posterior-stabilized knee arthroplasties done by one surgeon. A central peg all-polyethylene component was used for 84 consecutive knees in 63 patients (Group A) and a three-peg patella was used for the next 144 consecutive knees in 99 patients (Group B). The mean followup was 6.7 years (range, 2-10 years) for Group A and 3.5 years (range, 2-6 years) for Group B. Except for the patellar component fixation, all knees had the same posterior-stabilized prosthesis using a specific protocol for patellar resurfacing. No patient required reoperation for a patellofemoral complication. The prevalence of patella fracture was higher in Group A, 4.7% (four knees), compared with 2.1% (three knees) in Group B, but this difference was not statistically significant. The presence of anterior knee pain referable to the patella was 7.1% (five patients, six knees) in Group A (one patient with two knees had severe anterior knee pain) and 9% (13 knees in 13 patients) in Group B. There was no patella clunk syndrome, subluxation, or fracture of a fixation peg in either group. With this specific protocol for patella resurfacing, there was a higher rate of complications with the one central peg patella (4.7%) than with the three-peg patella (2.1%), but this did not reach statistical significance. The results do not support an increased risk of component failure with this three-peg patella design, but do not, at this length of followup, show any significant advantage of three-peg fixation.
Adult↗
[What influence do size and placement of patella resurfacing have on knee endoprosthesis?].
The aim of this study was to document the changes in retropatellar pressure, contact area and forces due to different sizes and placement of the patella resurfacing in knee arthroplasty. Six cadaver specimens (after Thiel fixation) were examined after the implantation of the total knee arthroplasty Genesis I. The patella sizes "small" and "medium" were placed as the "onlay" version, centered as well as off-centered by 0.4 cm in all four directions. Pressure and area measurements were done with Fuji pressure measuring film, which was placed between the patellar fascia of the femur and the patella in a defined position. The pressure was measured by applying a predetermined force for 5 s. The examinations were done with 60 degrees knee flexion and a force of 280 N. In our results there were no significant differences between, patella sizes. No significant differences for the medial, distal and proximal placement were found for the small patella. The lateral placement led to a significant decrease in the contact area (P = 0.0277), maximum pressure (P = 0.0422) and force (P = 0.0277). The average pressure did not change significantly (P = 0.1159). For the medium size patella there were no significant differences for medial or distal placement. The comparison of lateral and central placement revealed a significant decrease in the contact area (P = 0.0446). Comparing distal and proximal positioning, a significant increase in contact area and significant decrease in force were found (P = 0.0277 and P = 0.0277 respectively). In conclusion, the choice of small or medium patella resurfacing does not seem to have a significant influence. In comparison to the results without patella implants, the implantation of the small patella caused a significant decrease in the retropatellar contact area (P = 0.03) and force (P = 0.03). Average and maximum pressure did not change significantly (P = 0.6 and P = 0.35) even though pressure increased slightly. For the medium size, maximum pressure (P = 0.03) increased significantly and force decreased significantly (P = 0.0277) whereas contact area and average pressure increased slightly. The results of the different placements of the patella implant do not support the recommendation for a medial shift. However, at least the lateralized implantation led to a reduction of contact area and force as well as to a slight increase of pressure which is considered as unfavorable.
Aged↗
The relationship between patella position and length of the iliotibial band as assessed using Ober's test.
The purpose of the study was to investigate the relationship between length of the iliotibial band (ITB) and the medio-lateral position patella. Eighty subjects (37 male, 43 female) were examined for patella position and ITB length. All subjects were physically active, asymptomatic and aged between 18 and 34 years (mean 21.5 years). ITB length was assessed using the Ober's test and modified Ober's test, with hip adduction angle being measured using a fluid goniometer. Patella position was assessed using the method first described by McConnell [The management of chondromalacia patellae: a long term solution. Australian Journal of Physiotherapy 1986;32:215-22]. Patella position had a weak correlation (r=0.28) with modified Ober's (extended knee) test and a poor correlation with Ober's (knee flexed) test (r=0.1). In the group of 47 subjects with laterally displaced patellae, patella position had a moderate statistically significant correlation to ITB length measured by modified Ober's test (r=0.34, P=0.012). Only a poor relationship existed between Ober's test and patella position in the laterally displaced group. The results of this study only partially support the hypothesis that there is a relationship between ITB length and lateral patella displacement. The relationship was not strong enough to confirm ITB length as the only cause of lateral patella displacement.
Adolescent↗
[Ultrasound in the early diagnosis of congenital dislocation of the patella].
INTRODUCTION: Congenital dislocation of the patella is defined as lateral dislocation of the patella present at birth, impossibility of closed reduction and diagnosis before the age of 10 years. We report about a rare case of a bilateral congenital dislocation of the patella. CASE REPORT: Physical examination of an eight-month- old boy showed bilateral knee flexion contractures associated with moderate genu varum. On both sides the patella could not be palpated easily. Radiographic diagnosis could not show the patella as the patella normally ossifies later. Ultrasound examination located the patella lateral to the lateral femoral condyle on both sides. Closed reduction was impossible. An open reduction with division of the lateral soft tissues, lateral release, and derotation of the quadriceps femoris and refining of the medial structures was performed. After cast removal the patellae were both located in the intercondylar grooves as confirmed by clinical and ultrasound examinations of both knees. Active and passive exercises were started. CONCLUSION: Failure of internal rotation of the myotome which contains the quadriceps femoris and the patella is the etiology of congenital dislocation of the patella. The quadriceps acts as flexor, exerting a valgus stress on the knee, causing external rotation of the tibia. Diagnosis is often delayed because of the lack of pathological findings on plain radiographs. Early diagnosis is enabled by ultrasonography. Surgical treatment is necessary and results are good, as long as there are no secondary changes.
Contracture↗
Comparison between patella cartilage volume and radiological assessment of the patellofemoral joint.
OBJECTIVES: There is no information on how patella cartilage relates to the radiological grade of individual features of patellofemoral osteoarthritis (osteophytes or joint space narrowing) which have been used in most epidemiological and clinical studies. In this study we compared patella cartilage volume as measured by magnetic resonance imaging (MRI) with radiological assessment of the patellofemoral joint. METHODS: 157 subjects with specific features of patellofemoral osteoarthritis (osteophytes and joint space narrowing) ranging from grade 0-3 were examined (age 62 +/- 10 years, 62% female). Each subject had skyline and lateral patellofemoral radiographs performed. Patella cartilage volume was determined by processing images acquired in the sagittal plane using T1-weighted fat saturated MRI at an independent work station. RESULTS: Grade of joint space narrowing (JSN) as measured on skyline and lateral patellofemoral radiographs was inversely associated with patella cartilage volume. After adjusting for age, gender and body mass index, for every increase in grade of skyline JSN (0-3), the patella cartilage volume was reduced by 411 mm3. For every increase in lateral patellofemoral JSN grade (0-3), the adjusted patella cartilage volume was reduced by 125 mm3. The relationship was stronger for patella cartilage volume and skyline JSN (r = -0.54, p < 0.001) than for lateral patellofemoral JSN (r = -0.16, p = 0.015). There was no significant association between patella cartilage volume and osteophytes measured on skyline or lateral radiographs. CONCLUSIONS: There is a significant negative association between patella cartilage volume and JSN, but not osteophytes. This association was strongest for the skyline rather than lateral radiographs. Longitudinal studies will be needed to determine the role of patella cartilage measurement in assessing progression of patellofemoral osteoarthritis.
Age Factors↗
Patella resurfacing in total knee arthroplasty using metal-backed rotating bearing components: a 2- to 10-year follow-up evaluation.
Management of the patella in total knee arthroplasty (TKA) has become an important issue. Patella-related complications remain a major concern and have frequently been the reason for secondary intervention, whether resurfaced or not. Common modes of failures are increased polyethylene (PE) wear, PE fractures, component dissociation (loosening or PE spinout), and patella fractures. This study evaluated 235 cases of low contact stress (LCS) TKA using a metal-backed rotating PE bearing. The setting was a large joint replacement center which has performed more than 2750 cases of LCS TKA since 1988. Cases with a follow-up shorter than 2 years were not calculated for statistical analysis but were included in postoperative complications. The mean follow-up was 4.2 years (range 2-10 years). Of the 105 cases 94.7% scored excellent or good results on a modified 100-point Hospital for Special Surgery score. Patellofemoral tracking was analyzed on axial radiographs in all cases and revealed perfect tracking in 96%. Revision surgery related to patella complications was required in 7 of 235 cases (3%), including two of PE bearing spinout and one each of infection, patella necrosis, PE break-age, patella maltracking, and traumatic patella component loosening. Four patella complications (1.7%) were related to patellofemoral maltracking, excluding the infected, traumatic, and patella necrosis cases. These results are similar to or better than those reported in the literature and complications appear to occur more frequently in cases with non-ideal patellofemoral maltracking.
Adult↗
Q-angle undervalued? The relationship between Q-angle and medio-lateral position of the patella.
BACKGROUND: For an accurate quadriceps angle measurement, the patella must be centralised in the femoral trochlear groove, numerous authors have described lateral displacement of the patella in patellofemoral pain patients, this leads to the intriguing possibility that the Q-angle might be undervalued within patellofemoral pain patients who have laterally displaced patella. METHOD: 109 asymptomatic subjects (51 male, 58 female) were assessed. Medio-lateral patella position was measured using a previous validated method and Q-angle was measured in standing with the quadriceps relaxed. FINDINGS: Mean Q-angle was 11.6 degrees (SD 5.2) left knee, 11.3 degrees (SD 4.9) right knee in the male subjects and 14.4 degrees (SD 5.2) left knee, 13.3 degrees (SD 5.5) right knee for female subjects. 40 females and 28 males had laterally displaced patellae. 13 subjects had centrally placed patellae (7 females, 6 males) with 28 subjects having medially displaced patellae (11 females, 17 males). Recalculation of Q-angle for the laterally displaced group brought about a statistically significant increase in angle. In the medial displaced group failed to produce a statistically significant decrease. INTERPRETATION: The adjusted Q-angle values for medially and neutral placed patellae brought the values very much into the centre of the reported ranges for Q-angles. After adjustment for lateral patella displacement, Q-angle values were towards the under end of values reported as normal, especially female values which were close to the previously reported pathological cut off point. Because of the inverse relationship between quadriceps strength and the magnitude of Q-angle and quadriceps crucial role in the aetiology of patellofemoral pain, any method which improves the reliability and applicability of Q-angle measurement could prove useful in investigations into the aetiology of and outcome from treatment of patellofemoral pain syndrome.
Adolescent↗