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PubMed1995

[Postoperative low patella. Treatment by lengthening of the patellar tendon].

PURPOSE OF THE STUDY: Patella infera is a post operative complication that can be prevented in most cases. This study was undertaken to determine etiological factors and to determine the means to avoid patella infera following knee surgery. The authors describe a new surgical technic to correct this complication and describe prognostic factors for achieving good results. MATERIAL AND METHODS: From 1985 to 1991, 35 patellar tendon lengthenings were performed in 35 patients. There were 28 female and 7 male patients with an average age of 37 years (21 to 72). Follow-up averaged 27 months and all patients had radiographic follow-ups. All patients had previous knee surgery: 21 for patellar pain (= patellar pain), 9 ACL reconstructions, 5 traumatic lesions. The range of motion of the knee was between 5 and 120 degrees. Patients complained of a burning pain in the patellar region and the sensation that the knee was held in a vice. The average Insall index was 0.55 (0.3 to 0.87). 25 patients had osteoporosis of the patella and 31 patients had a typical "sunrise" aspect on axial radiographs in 30 degrees of flexion. The usual diagnosis was that of algodystrophy. All patients underwent patellar tendon lengthening. RESULTS: Intra operative findings showed transverse retractions leading to resection of the medial and lateral retinaculum. The patellar tendon was short but its histological structure was normal. 15 patients had excellent results with no residual pain and were able to resume sports activities. 11 had good results with residual pain in hyperflexion and 9 had poor functional results, however nocturnal pain disappeared. Range of motion was between 0 and 130 degrees. Radiographic results were excellent since the preoperative average Insall score of 0.55 increased to 1.02 at follow-up. DISCUSSION: Patella infera is caused by combination of two factors: patellar surgery (painful patellar syndrome, patellar instability, ACL reconstruction using the mid third of the patellar tendon) and painful post operative rehabilitation with no active quadriceps contractions. To avoid this complication, the knee should be braced in 20 degrees of flexion to tense the patellar tendon and rehabilitation should be undertaken with active quadriceps contractions. Patellar lengthening is a successful procedure with the results being dependent upon number of previous surgeries, cartilage damage and, most importantly, the patellar index: between 0.8 and 0.65 the results are uncertain, < 0.6, the results are usually good. CONCLUSION: Patella infera is not a frequent complication of knee surgery. It is important to diagnose it early in order to prevent it. For chronic cases, surgical criteria should be strict: sensation of burning pain, lack of motion, unstable flexed monopodal stance, "sunrise" aspect on axial radiographs and a patellar index < 0.6. Patella infera differs from algodystrophy and re operation by retinacular release is indicated if the delay from previous surgery is < 2 months. In older cases, patellar tendon lengthening should be undertaken.

Adult↗
PubMed1995

Patella of selected bats: patterns of occurrence or absence and associated modifications of the quadriceps femoris tendon.

BACKGROUND: Having observed the apparent absence of a bony patella in a Madagascar flying fox (Pteropus sp.), other species from the two suborders of bats (Megachiroptera and Microchiroptera) were examined to determine the presence or absence of a bony patella and the distribution of this feature among bats. METHODS: Gross, radiographic, and histologic examination of seven megachiropteran species representing four genera, as well as six microchiropteran species representing six genera, was performed. RESULTS: A bony patella was observed in all six microchiropteran and in three megachiropteran species. The tendon of the quadriceps femoris muscle in Microchiropteran species was composed mainly of dense regular connective tissue. The quadriceps tendon in Megachiropteran species with a patella contained an abundance of fibrocartilage and hyaline cartilage, unlike the quadriceps femoris tendon of the Microchiroptera or a laboratory mouse examined for comparison. CONCLUSIONS: Four species of the megachiropteran genus Pteropus lacking a bony patella displayed a similar occurrence and distribution of fibrocartilage and hyaline cartilage within the quadriceps tendon as seen in the other bats. In reference to this singular feature, Pteropus is unique among the representatives of megachiropteran and microchiropteran genera examined here.

Animals↗
PubMed1976

Structure and function of the human patella: the role of cancellous bone.

Total joint and other prosthesis often require the removal and replacement of considerable quantities of cancellous bone, and often are anchored in place by grouting into cancellous bone. Thus, a possible source of failure or loosening of many types of prostheses may be rooted in the lack of understanding of the structure, properties, and function of this material. In addition, as we have pointed out before, cancellous bone may play an important biomechanical role in the etiology of joint degeneration. With these considerations in mind, the architecture of the cancellous bone in the human patella was studied by serial sectioning and microradiography, using an improved technique developed in our laboratory. Volumes of cancellous bone with apparently different functional roles were identified. Stereological techniques were used to quantify the structural characteristics and geometrical relationships throughout the patella. These results led to a structural model for the cancellous bone of the patella, and a comprehensive picture of the internal architecture. The distribution of mechanical compliance and yield stress was also measured, as a function of location and orientation, by a specially constructed microcompression testing machine. The measurements reflected the distribution of trabecular architecture, and both the properties and architecture reflected the gross biomechanical function of the patella. Furthermore, a true structure-function relationship was derived. Patellar contact area studies were performed on fresh cadavers and mapped for various angles of flexion. The variation in contact areas and the spatial variations in stiffness are discussed relative to the biomechanics and clinical aspects of the patella.

Biomechanical Phenomena↗
PubMed2006

Comparison of conventional and highly crosslinked UHMWPE patellae evaluated by a new in vitro patellofemoral joint simulator.

A series of in vitro patella damage tests were developed using a knee simulator to investigate electron-beam-irradiated and -melted ultra-high molecular weight polyethylene and conventional ultra-high molecular weight polyethylene at the patellofemoral articulation. Three different simulations were created: (i) normal gait with optimal component alignment, (ii) stair climbing with optimal component alignment, and (iii) stair climbing with 4 degrees of femoral component internal rotation to simulate a component malalignment condition. In the last two simulations, all patellae were artificially aged. In normal gait, the unaged conventional and highly crosslinked patellae demonstrated similar behavior. In both stair climbing tests, unlike the aged highly crosslinked components, the aged conventional patellae developed cracks by 2 million cycles. These results demonstrate the potential advantage of highly crosslinked polyethylene for the patella.

Biocompatible Materials↗
PubMed1993

Are the nail-patella syndrome and the autosomal Goltz-like syndrome the phenotypic expressions of different alleles at the COL5A1 locus?

The COL5A1 gene, which encodes the pro alpha 1(V) chain, was recently mapped to 9q34.3 in the same region as the nail-patella locus. This was taken as an indication that the nail-patella syndrome may be an inherited connective tissue disorder. We demonstrate COL5A1 heterozygous deletion and fibroblast under-expression of alpha 1(V) chains in a girl with an unbalanced translocation resulting in 9q32-->qter monosomy. The patient presents dysplastic nails, a sign typical of nail-patella syndrome, but normal patella. Moreover, she has skin and bone disorders similar to those found in the Goltz syndrome. We suggest that monosomy for the COL5A1 gene is responsible for these connective tissue disorders. Accordingly, the nail-patella syndrome could be attributable to mutations inside the COL5A1 gene rather than to a deletion of it.

Alleles↗
PubMed1990

Paget's disease of the patella.

Five patients with Paget's disease involving the patella were evaluated for the following radiographic features: trabecular pattern, cortical integrity, density, and size of the affected patella. Radiographic appearances consisted of minimal trabecular coarsening in the patella of nearly normal size and progressed to considerable cortical thickening and osteoblastic remodeling in a dramatically enlarged patella. The radiologic features of Paget's disease of the patella are distinctive and should obviate biopsy.

Adult↗
PubMed1977

[The lateral splitting of the knee joint capsule for treatment of chondropathia patellae (author's transl)].

This is a report on the results of the lateral splitting of the knee-joint capsule for treatment of chondropathia patellae. The operative procedure is described. Pains relative to the patella syndrome, chondropathia patellae, forms of dysplasia of the patella and lateral dislocation of the patella are regarded as indications. 50 knee-joints were post-examined. 26% were without complaints, 54% showed improvement, 10% no change, 10% deteriorated. These results are comparable to those of other, more intensive surgery. Representing a comparatively minor operation, the lateral splitting of the capsule is therefore particularly recommended for young patients.

Adolescent↗
PubMed1994

Early development of patella infera after knee fractures.

The condition referred to as patella infera is characterized by a permanent shortening of the patellar ligament and is associated with a severely limited range of motion of the knee joint. Patella infera is a common complication of injury or surgery to the knee joint, and it is generally considered a condition that presents after a variable, albeit considerable time after injury. A review of the knee roentgenograms of patients with arthrofibrosis and patella infera showed this condition to be an immediate complication of knee fractures. Therefore, in order to better define the development of patella infera, the patellar height was studied during treatment of 146 knee joint fractures (46 supracondylar fractures, 50 patellar fractures and 50 tibial plateau fractures). Using the Caton-Deschamps method patella infera was detected in eight cases (17.39%) immediately after supracondylar fractures, in six cases (12%) after patellar fractures, and only in two cases (4%) after tibial plateau fractures. The patellar ratio remained unchanged or worsened further after treatment, and its incidence was unaffected by the type of treatment. These observations rule out etiologies such as inflammatory or algodystrophic phenomena and quadriceps inhibition, because the reduction of patellar height was evident immediately and persisted at follow-up examinations.

Adolescent↗
PubMed1997

The arterial blood supply of the human patella. Its clinical importance for the operating technique in vascularized knee joint transplantations.

The architecture of the arteries supplying the patellar rete was examined in 14 anatomic specimens in order to develop an optimized operating technique for knee joint transplantation. The specimens were fixed in Jores Solution and exarticulated from the hip joint. The lower limbs were injected with Berliner-Blau-Gelatin, and the arteries were dissected macroscopically. Five to six main arteries entered the patellar rete at 1, 3, 5, 7 and 11 o'clock forming an arterial circle. These arteries were the same main arteries which supply the distal end of the femur and the proximal part of the tibia. From an anatomic perspective, they provide the complete arterial blood supply to a whole knee joint being transplanted including the patella. Based on these anatomic results, we transplanted two allogenic vascularized human knee joints preserving the patella, the capsule, and the patellar ligament. Up to six months after surgery we demonstrated the perfusion and viability of all three transplanted bones, particularly the patella, by 99mTc DPD scintigraphy. We compared these findings with knee joint arthroscopy and with histologic results from biopsies taken from the patella. The postoperative examinations clearly indicated the viability of the transplanted patella employing this new operating technique. The results of the entire study demonstrate that it is technically feasible to transplant a whole knee joint which remains clinically viable.

Adult↗
PubMed1999

[Results of the Elmslie-Trillat procedure in cases of patella(sub)luxation related to chondral pathology].

Between May 1981 and December 1993, 120 patients (126 knee joints) were operated using the Elsmlie-Trillat procedure because of patella(sub)luxation. 79 patients were reviewed at an average follow up of 4.1 (1-13.6) years. 46 women and 33 men were operated with an average age at operation of 26.9 (14-59) years. The examination included Bentley's Score, radiological parameters (e. g. grading of patella dislocation), grading of chondromalacia and patient characteristics (e. g. age, pre-operative time). 64 knee joints (70. 3 %) were evaluated 'very good' and 'good', using the score of Bentley. There were significantly worse results in cases with higher grading of chondromalacia (p <0.0036), longer pre-operative time (p < 0.012) and older patients (p < 0.0023). The worst and most highly significant results were in these patients with prior knee surgery (p < 0.0001). A good patella relocation correlated with improved results (p < 0.001). There was no difference in cases with patella dislocation and/or patellasubluxation. In conclusion, the Elmslie-Trillat procedure should be carried out 'in the correct manner and at an early stage'. To optimise the therapy in cases of patella dislocation the high number of operation techniques should be analysed and used regarding risk groups.

Adolescent↗
PubMed2005

Effects of lateral retinacular release on the lateral stability of the patella.

The objective of this cadaveric study was to evaluate quantitatively the effects of lateral retinacular release on the lateral stability of the patella. A materials testing machine was used to displace the patella of seven cadaveric specimens 10 mm laterally while measuring the required force, with 175 N quadriceps tension. The patella was connected via a ball-bearing patellar mounting 10 mm deep to the anterior surface to allow rotations. Patellar force--displacement behaviour was tested from 0 degrees to 60 degrees knee flexion. At 0 degrees , 10 degrees and 20 degrees flexion the mean force required to displace the patella 10 mm laterally was reduced significantly due to lateral retinacular release, by 16-19%. The average force required to displace the patella was also reduced for larger flexion angles, although this was not statistically significant. These findings suggest that lateral retinacular release may not be appropriate in treatment of patellar lateral instability.

Aged↗
PubMed2004

MRI criteria for patella alta and baja.

OBJECTIVE: To determine the range of the patellar tendon length to patellar length ratio on magnetic resonance imaging (MRI) of the knee in order to aid in the establishment of MRI criteria for patella alta and baja. PATIENTS: Two hundred and forty-five patients ages 6-85 (mean 44) years who went through 262 consecutive 1.5 MRI studies of the knee performed during November 2000 through February 2001 were evaluated, regardless of their clinical symptoms. DESIGN: Patellar length (PL) and patellar tendon length (TL) were measured by a single musculoskeletal radiologist on sagittal images by a line connecting the superior and inferior patellar poles and the shortest length of the inner margin of the tendon respectively. TL/PL ratio was subsequently calculated. The distribution of ratios was evaluated; the extreme 2.5% at each end of the distribution was defined as patella alta and baja. RESULTS: The TL/PL ratio ranged between 0.56 and 1.71 (mean 1.05). After plotting the ratios, we noted an asymmetric curve skewed to the left. Based upon calculation of the extreme 2.5% of the ratio at each end of the plot, we determined that the MRI definition of patella alta and baja is a ratio of TL/PL of more than 1.50 and less than 0.74 respectively. We found that females had significantly higher TL/PL ratio than males (1.0878 and 1.0032 respectively). Ratios defined for patella alta and baja were 1.52 and 0.79 respectively in females and 1.32 and 0.74 respectively in males ( p<0.0001). CONCLUSION: Patella alta and baja are determined as TL/PL of more than 1.50 and less than 0.74 respectively, somewhat different than traditionally quoted radiographic and previously described MRI criteria.

Adolescent↗
PubMed2005

The innervation of patella: anatomical and clinical study.

As much interest has been focused on afferent innervation of knee than that of patella, there are few articles about patellar innervation. But in clinical practice anterior knee pain due to patellar disorders is a quite frequent problem. Our aim was to review the innervation pattern of patella and to give the topographic anatomy of the nerves. We dissected 30 knees of 15 formaldehyde-fixed cadavers. Two nerves from vastus medialis and lateralis were found to reach patellar edge. Apart from these, we were unable to find any other neural structures around patellae. Mean distances between the tuberosity of the tibia and medial and lateral nerve entry points were 90.1(range 74-102) and 96.3 mm (range 76-109), respectively. The angles between lines which join the entry points of nerves and vertical line to the center point of patella were measured in frontal plane. It was approximately 60 degrees medially and 40 degrees laterally. To confirm that these nerves are patellar pain afferents, we performed a local anesthesia test in 32 knees of 20 patients with patellofemoral pain. Clinically, there was a significant difference between the visual analogue scale (VAS) scores before and after local anesthetic injections (p<0.01). Previous studies have emphasized especially the medial innervation. We found that both superomedial and superolateral nerves were important for patellar innervation. We described precisely the entry points of these nerves to patella for selective denervation.

Adult↗
PubMed2005

An anatomically based patient-specific finite element model of patella articulation: towards a diagnostic tool.

A 3D anatomically based patient-specific finite element (FE) model of patello-femoral (PF) articulation is presented to analyse the main features of patella biomechanics, namely, patella tracking (kinematics), quadriceps extensor forces, surface contact and internal patella stresses. The generic geometries are a subset from the model database of the International Union of Physiological Sciences (IUPS) (http://www.physiome.org.nz) Physiome Project with soft tissue derived from the widely used visible human dataset, and the bones digitised from an anatomically accurate physical model with muscle attachment information. The models are customised to patient magnetic resonance images using a variant of free-form deformation, called 'host-mesh' fitting. The continuum was solved using the governing equation of finite elasticity, with the multibody problem coupled through contact mechanics. Additional constraints such as tissue incompressibility are also imposed. Passive material properties are taken from the literature and implemented for deformable tissue with a non-linear micro-structurally based constitutive law. Bone and cartilage are implemented using a 'St-Venant Kirchoff' model suitable for rigid body rotations. The surface fibre directions have been estimated from anatomy images of cadaver muscle dissections and active muscle contraction was based on a steady-state calcium-tension relation. The 3D continuum model of muscle, tendon and bone is compared with experimental results from the literature, and surgical simulations performed to illustrate its clinical assessment capabilities (a Maquet procedure for reducing patella stresses and a vastus lateralis release for a bipartite patella). Finally, the model limitations, issues and future improvements are discussed.

Computer Simulation↗
PubMed1995

The biomechanics of the human patella during passive knee flexion.

The fundamental objectives of patello-femoral joint biomechanics include the determination of its kinematics and of its dynamics, as a function of given control parameters like knee flexion or applied muscle forces. On the one hand, patellar tracking provides quantitative information about the joint's stability under given loading conditions, whereas patellar force analyses can typically indicate pathological stress distributions associated for instance with abnormal tracking. The determination of this information becomes especially relevant when facing the problem of evaluating surgical procedures in terms of standard (i.e. non-pathological) knee functionality. Classical examples of such procedures include total knee replacement (TKR) and elevation of the tibial tubercle (Maquet's procedure). Following this perspective, the current study was oriented toward an accurate and reliable determination of the human patella biomechanics during passive knee flexion. To this end, a comprehensive three-dimensional computer model, based on the finite element method, was developed for analyzing articular biomechanics. Unlike previously published studies on patello-femoral biomechanics, this model simultaneously computed the joint's kinematics, associated tendinous and ligamentous forces, articular contact pressures and stresses occurring in the joint during its motion. The components constituting the joint (i.e. bone, cartilage, tendons) were modeled using objective forms of non-linear elastic materials laws. A unilateral contact law allowing for large slip between the patella and the femur was implemented using an augmented Lagrangian formulation. Patellar kinematics computed for two knee specimens were close to equivalent experimental ones (average deviations below 0.5 degrees for the rotations and below 0.5 mm for the translations) and provided validation of the model on a specimen by specimen basis. The ratio between the quadriceps pulling force and the patellar tendon force was less than unity throughout the considered knee flexion range (30-150 degrees), with a minimum near 90 degrees of flexion for both specimens. The contact patterns evolved from the distal part of the retropatellar articular surface to the proximal pole during progressive flexion. The lateral facet bore more pressure than the medial one, with corresponding higher stresses (hydrostatic) in the lateral compartment of the patella. The forces acting on the patella were part of the problem unknowns, thus leading to more realistic loadings for the stress analysis, which was especially important when considering the wide range of variations of the contact pressure acting on the patella during knee flexion.

Algorithms↗
PubMed2005

Anatomic dimensions of the patella measured during total knee arthroplasty.

The anatomic measurements of 92 patellae with normal underlying bony structure were studied during total knee arthroplasty before and after resection of the articular surface. The articular surface of the patella was found to have an oval shape with a width-to-height ratio (46 x 36 mm) of 1.30. The dome was 4.8 mm high and displaced medially 3.6 mm. The medial facet was slightly thicker than the lateral facet (18 vs 17 mm). The lateral facet is 25% wider than the medial facet. Coverage provided by oval patellar prostheses was significantly better than with round prostheses. The patellae in women were significantly smaller than in men. Size differences and deformity need to be taken into account when the patella is prepared for resurfacing. It is recommended that the bony resection should be no greater than one third of the maximum patellar thickness to avoid alteration of normal bony structure. Key words: patella, total knee arthroplasty, anatomy.

Aged↗
PubMed2004

Patella kinematics and patello-femoral contact areas in patients with genu varum and mild osteoarthritis.

BACKGROUND: Patients with genu varum of the knee and moderate to severe osteoarthritis often suffer from additional symptoms of the patello-femoral joint. These patients have a poor prognosis following high tibial osteotomy. It is unclear whether varus knees with only mild femoro-tibial osteoarthritis are also associated with alterations of patella biomechanics, and affect the prognosis of intended high tibial osteotomy. METHODS: Fifteen patients with genu varum and mild osteoarthritis and 15 healthy volunteers were assessed in an open MRI-scanner. 3D-GRE sequences of the knee were obtained in 0 degrees, 30 degrees and 90 degrees with and without activity of the extensor muscles. After segmentation of patella, femur, tibia and the adjacent cartilage, a patella-based local coordinate system was established. Femoral and tibial reference points allowed definition of the spatial position of the patella. Contact areas were defined by intersection of opposing cartilage volumes. FINDINGS: No significant differences in patella kinematics and patello-femoral contact areas could be found (P > 0.05) between varus knees with mild osteoarthritis and healthy knees either at different flexion angles or under extending muscle activity. INTERPRETATION: In knees with genu varum and mild medial osteoarthritis we could detect no alterations in patello-femoral kinematics. Since the alterations of patients with genu varum and mild osteoarthritis are restricted to the medial femoro-tibial joint high tibial osteotomy might be successful.

Adult↗
PubMed2005

Influence of patella alta on knee extensor mechanics.

The purpose of this study was to compare the knee extensor mechanics in persons with and without patella alta. Thirteen subjects with patella alta and 14 subjects with normal patellar position participated in the study. Sagittal and axial MR images of the knee were acquired at 0 degrees , 20 degrees , 40 degrees , and 60 degrees of knee flexion. Measurements of actual moment arm, patellar ligament/quadriceps tendon force ratio, quadriceps effective moment arm, and joint reaction force/quadriceps force ratio were obtained. There were no differences between groups in terms of actual moment arm. However, subjects with patella alta had significantly larger patellar ligament/quadriceps tendon force ratios (1.04+/-0.02 vs. 0.92+/-0.02) and quadriceps effective moment arms (4.40+/-0.09 vs. 4.00+/-0.09 cm) when averaged across the range of knee flexion angles tested. There was no difference in the joint reaction force/quadriceps force ratio between groups. The observed differences in knee extensor mechanics suggest that individuals with patella alta have a more efficient knee extensor mechanism and would be expected to generate similar joint reaction forces per unit quadriceps force compared to subjects with normal patellar position. Therefore, persons with patella alta may experience less patellofemoral joint reaction force to overcome the same knee flexion moment in the range of 0 degrees -60 degrees of knee flexion.

Adult↗