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At least 163 records · Page 9Linked to original sources
PubMed2001

Biomechanics of the patella in total knee replacement.

An anatomical shape for the trochlea of the femoral component is an advantage in total knee design because in many cases the natural patella is preserved. The trochlea profile can be described as having a V-shape, with a wide angle and a circular base. In such cases the plastic patella should have the same profile, resulting in a generally conical shape. One of the questions regarding this design is whether the natural or artificial patella tilts in the femoral trochlea, producing wear and deformation of the plastic. We analysed the forces between the trochlea and the patella for various Q-angles and flexion angles. We found that the patella is fully stable and without tilting at all flexion angles, for a Q-angle of 14 degrees or less. Q-angles greater than this represent severe misalignment, and hence the cone-shaped patella is considered to be stable design.

Biomechanical Phenomena↗
PubMed1998

Modified Elmslie-Trillat procedure for instability of the patella.

The purpose of this study was to determine whether or not the modified medial transfer of the ligamentum patellae in case of objective instability of the patella is an adequate therapy and if it is possible to improve the patellar congruence angle by this method. Between October 1987 and April 1993, 41 operations were performed in 37 patients with medialization of the medial third of the ligamentum patellae with the corresponding part of the tibial tubercule. Four patients needed a bilateral operation; the two interventions were not performed at the same time. Thirty-six operated knees (88%) were examined at a median clinical and radiological follow-up of 62.8 months (+/- 15.8 SD). For evaluation, the objective and subjective Turba score was used, and pre- and postoperative X-rays were compared. The patients' average age at the time of intervention was 23.2 years (+/- 7 years SD). The operation was performed 39 times for recurrent dislocation or subluxation, for patella alta with cartilage tissue damage, and for first time traumatic dislocation. The only postoperative complication was a temporary peroneal paresis. There were no redislocations seen at the follow-up. One patient with repeated subluxations underwent an additional lateral release combined with a repair of the medial retinaculum. In all other cases, the Turba score showed good or excellent results (subjective 1.9; objective 0.8), the patellar congruence angle was significantly improved (P < 0.001), and there were no medial subluxations. We conclude that the transfer of the medial third of the ligamentum patellae for objective instability of the patella is a minimally invasive and adequate technique to improve significantly a pathological patellar congruence angle.

Adolescent↗
PubMed2006

The effect of patella resurfacing in total knee arthroplasty on functional range of movement measured by flexible electrogoniometry.

BACKGROUND: The need for patella resurfacing remains an area of considerable controversy in total knee replacement surgery. There would appear to be no reported evidence on the effect of patella resurfacing on knee function, as measured by functional range of movement used in a series of tasks, in patients undergoing knee replacement. The object of this study was to measure knee joint motion during functional activities both prior to and following total knee replacement in a randomised group of patients with and without patella resurfacing and to compare these patient groups with a group of normal age-matched subjects. METHODS: The study design was a double blinded, randomised, prospective, controlled trial. The knee joint functional ranges of movement of a group of patients (n=50, mean age=70 years) with knee osteoarthritis were investigated prior to and following total knee arthroplasty (4 months and 18-24 months) along with a group of normal subjects (n=20, mean age=67). Patients were randomly allocated into two groups, those who received patella resurfacing (n=25) and those who did not (n=25). Flexible electrogoniometry was used to measure the flexion-extension angle of the knees with respect to time in eleven functional activities. FINDINGS: No statistically significant differences (alpha level 0.05) in joint excursion of the affected knee were found between patients who received patella resurfacing and those who did not. INTERPRETATION: Routine patella resurfacing in a typical knee arthroplasty population does not result in an increase in the functional range of movement used after knee replacement.

Aged↗
PubMed2005

A review of sleeve fractures of the patella in children.

Patella fractures are rare in children and the sleeve fracture is a particular form of fracture that only occurs in children where it is the most common patella fracture. It is caused by rapid muscle contraction. Diagnosis may be difficult both clinically and on the X-ray which may look normal if there is no bony fragment. Patella alta is the best sign and ultrasound is very helpful. Awareness of the existence of the injury is all important. This fracture differs from straightforward avulsion because of the "sleeve" of periosteum which is pulled off the patella and will continue to form bone if not treated thus enlarging or even duplicating the patella. Treatment involves prompt reduction and, usually, internal fixation of the disrupted patella tendon.

Child↗
PubMed2005

Cutaneous stimulation from patella tape causes a differential increase in vasti muscle activity in people with patellofemoral pain.

Patella taping reduces pain in individuals with patellofemoral pain (PFP), although the mechanism remains unclear. One possibility is that patella taping modifies vasti muscle activity via stimulation of cutaneous afferents. The aim of this study was to investigate the effect of stretching the skin over the patella on vasti muscle activity in people with PFP. Electromyographic activity (EMG) of individual motor units in vastus medialis obliquus (VMO) was recorded via a needle electrode and from surface electrodes placed over VMO and vastus lateralis (VL). A tape was applied to the skin directly over the patella and stretch was applied via the tape in three directions, while subjects maintained a gentle isometric knee extension effort at constant force. Recordings were made from five separate motor units in each direction. Stretch applied to the skin over the patella increased VMO surface EMG and was greatest with lateral stretch. There was no change in VL surface EMG activity. While there was no net increase in motor unit firing rate, it was increased in the majority of motor units during lateral stretch. Application of stretch to the skin over VMO via the tape can increase VMO activity, suggesting that cutaneous stimulation may be one mechanism by which patella taping produces a clinical effect.

Adult↗
PubMed2002

Experimental investigation of the tension band in fractures of the patella.

We investigated the strain pattern developed in the anterior and posterior part of the fixed patella during knee motion. Eight fresh cadaver knees were used but two were excluded because of non reliable measurements due to misplacement of gauges. Two strain gauges were bonded in the midline of the anterior and two in the posterior surface of the patella. Threaded steel rods were cemented into the intramedullary femoral and tibial canals. The knee was placed on a special device. The quadriceps tendon was gripped and a 4.5 kg weight was attached to the tibial rod 16.5 cm distal to the joint line. Ten flexion/extension cycles were performed before testing. Initially the intact patella was tested. A transverse osteotomy was performed before being stabilized by the AO recommended tension band technique. The knee was retested again as above. Finally an additional circular wire was passed around the patella and the knee was tested again under the same loading configuration. The intact patella showed weak tensile strain on the anterior and compressive strain on the posterior surface through the range of knee motion. Tension band fixation produced weak tensile strains in the first few degrees of flexion and then weak compressive strains in the posterior surface. The presence of the additional circular wire significantly increased the compressive strain. The classical tension band is highly effective for the fixation of the fractured patella but is improved by an additional circular wire.

Biomechanical Phenomena↗
PubMed1998

Arthroscopic treatment of voluntary superior dislocation of the patella.

The patient, a 45-year-old woman who complained of crepitation and locking of her patella, had a voluntary superior dislocation of the patella and was arthroscopically treated. Radiography showed patella alta and osteoarthrosis in the patellofemoral joint. Fluoroscopy showed that, during active contraction of the quadriceps muscle, the tip of the osteophyte on the inferior edge of the patella was positioned at the same level as the osteophyte on the superior margin of the articular surface of the medial femoral condyle. The inferior edge of the patella could be made to catch on the femoral osteophyte by application of slight pressure to the patella. Arthroscopic resection of the osteophte was performed, and the postoperative course was uneventful. The patient reported no difficulty when she was last seen 1 year after the operation.

Arthroscopy↗
PubMed1989

Nonresurfaced patella in total knee arthroplasty.

Problems attributable to the patellofemoral joint are still the major cause of disability in contemporary knee arthroplasty. Patellar resurfacing does lead to further complications, such as loosening, wear, and malalignment. Two studies have been performed specifically to review experience with the nonresurfaced patella in total knee arthroplasty. The first study determined that patellofemoral symptoms occurred in 8% of the total group and the majority of these were due to patellar malalignment. The postoperative skyline views at 60 degrees and 90 degrees of flexion obtained routinely identified dynamic patellar maltracking responsible for anterior knee pain. The second study addressed long-term durability of the nonresurfaced patella. The tracking of the patella was maintained with only small shifts of patella position and the tendency to stabilize with time. Stress-induced bone remodelling, particularly of the lateral facet, occurred in 85% of patellae. No preoperative or postoperative radiologic variable was associated with anterior knee pain. The authors strongly recommend that accurate patellofemoral tracking be obtained at the time of knee arthroplasty by staged procedures, with removal of peripheral osteophytes, then proximal iliotibial tract release followed by lateral debulking to a marked degree to obtain neutral tracking. Only then will intracapsular lateral release be performed. The results presented support the use of the nonresurfaced patella, and patellar malalignment remains a major source of disability attributable to the patellofemoral joint following total knee arthroplasty.

Arthroplasty↗
PubMed2001

Atraumatic osteonecrosis of the patella.

Atraumatic secondary osteonecrosis of the patella is a rare entity and has been reported in only several case reports. The purpose of this study was to define the clinical and radiographic characteristics and outcome of this disease. Osteonecrosis of the patella was found in 25 knees in 19 patients. The mean age was 42 years (range, 21-63 years). Eighteen (95%) patients had greater than 2 g of lifetime corticosteroid exposure, and six (32%) patients had systemic lupus erythematosus. Osteonecrosis was found in the superior pole of the patella in all 23 knees (17 patients) that had magnetic resonance imaging. Osteonecrosis was apparent on plain radiographs in five knees (20%) in four patients, and only one knee (4%) in one patient had collapse of the posterior articulating surface of the patella. One (4%) patient presented with anterior knee pain localized to the patella. At a mean followup of 4 years (range, 2-18 years), none of the patients had an intervention that focused on treating the patellar lesion. Patellar osteonecrosis is characterized by patients with coincident lesions of the distal femur and the proximal tibia and lesions localized to the superior pole of the patella. It is a nonprogressive disease that does not warrant surgical exploration.

Adult↗
PubMed1999

Enlargement of remaining patella after partial patellectomy in rabbits.

PURPOSE: The purpose was to study the radiographic patellar tendon calcification and evaluate the histology of the healing interface between the patellar tendon and the remaining patella after partial patellectomy. METHODS: We removed the distal one-third of the patella in 24 rabbits. Specimens were harvested at 8, 12, and 24 wk postoperatively (N = 8 each). RESULTS: Histological observation demonstrated that healing interfaces between the patellar tendon and patella were structurally connected by scar tissue. The radiographic patellar tendon calcification next to the healing interface was in fact trabecular bone outgrowth histologically, resulting in an enlargement of the remaining patellar in length from 0.93+/-0.28 mm at week 8, 1.26+/-0.33 mm at week 12, to 2.5+/-1.12 mm at week 24. Metaplasia of the scar tissue observed next to the healing interface of the remaining patellar articular cartilage and the outgrowth of trabecular bone from the remaining patella with healing over time may increase the articular surface of the remaining patella after partial patellectomy. CONCLUSIONS: The remaining patella might be enlarged in length after partial patellectomy because of trabecular bone outgrowth and metaplasia with healing over time. Its theoretical advantages are an increased patellofemoral contact area and a diminished patellofemoral contact pressure following surgery.

Animals↗
PubMed1994

Detection and staging of chondromalacia patellae: relative efficacies of conventional MR imaging, MR arthrography, and CT arthrography.

OBJECTIVE: Chondromalacia patellae is a condition characterized by softening, fraying, and ulceration of patellar articular cartilage. We compare the sensitivity, specificity, and accuracy of conventional MR imaging, MR arthrography, and CT arthrography in detecting and staging this abnormality. SUBJECTS AND METHODS: Twenty-seven patients with pain in the anterior part of the knee were prospectively examined with MR imaging, including T1-weighted (650/16), proton density-weighted (2000/20), T2-weighted (2000/80), and spoiled two-dimensional gradient-recalled acquisition in the steady state (SPGR/)/35 degrees (51/10) with fat saturation pulse sequences. All were also examined with T1-weighted MR imaging after intraarticular injection of dilute gadopentetate dimeglumine and with double-contrast CT arthrography. Each imaging technique was evaluated independently by two observers, who reached a consensus interpretation. The signal characteristics of cartilage on MR images and contour abnormalities noted with all imaging techniques were evaluated and graded according to a modification of the classification of Shahriaree. Twenty-six of the 54 facets examined had chondromalacia shown by arthroscopy, which was used as the standard of reference. The sensitivity, specificity, and accuracy of each imaging technique in the diagnosis of each stage of chondromalacia patellae were determined and compared by using the McNemar two-tailed analysis. RESULTS: Arthroscopy showed that 28 facets were normal. Grade 1 chondromalacia patellae was diagnosed only with MR and CT arthrography in two (29%) of seven facets. Intermediate (grade 2 or 3) chondromalacia patellae was detected in two (13%) of 15 facets with T1-weighted and SPGR MR imaging, in three (20%) of 15 facets with proton density-weighted MR imaging, in seven (47%) of 15 facets with T2-weighted MR imaging, in 11 (73%) of 15 facets with CT arthrography, and in 12 (80%) of 15 facets with MR arthrography. Grade 4 was detected in three (75%) of four facets with T1-, proton density-, and T2-weighted MR imaging, two (50%) of four facets with SPGR MR imaging, and four (100%) of four facets with MR and CT arthrography. Thus, all imaging techniques were insensitive to grade 1 lesions and highly sensitive to grade 4 lesions, so that no significant difference among the techniques could be shown. CONCLUSION: All imaging techniques studied had high specificity and accuracy in the detection and grading of chondromalacia patella; however, both MR arthrography and CT arthrography were more sensitive than T1-weighted, proton density-weighted, and SPGR with fat saturation MR imaging for showing intermediate grades of chondromalacia patellae. Although the arthrographic techniques were not significantly better than T2-weighted imaging, the number of false-positive diagnoses was greatest with T2-weighted MR imaging.

Adult↗
PubMed2002

Vertical position of the patella in the stifle joint of clinically normal large-breed dogs.

OBJECTIVE: To define the vertical position of the patella in clinically normal large-breed dogs. SAMPLE POPULATION: Cadavers of 13 clinically normal large-breed dog. PROCEDURE: Both hind limbs were harvested with intact stifle joints and mounted on a positioning device that allowed full range of motion of the stifle joint. Lateral radiographic views were obtained with the stifle joints positioned at each of 5 angles (148 degrees, 130 degrees, 113 degrees, 96 degrees, and 75 degrees). Vertical position of the patella through a range of motion was depicted on a graph of mean stifle angle versus corresponding mean proximal patellar position (PPP) and distal patellar position (DPP) relative to the femoral trochlea for each dog. Ratio of length of the patellar ligament to length of the patella (L:P) was determined for each dog. Overall mean, SD, and 95% confidence intervals for L:P were calculated for all dogs. RESULTS: Evaluation of vertical position of the patella through a range of motion revealed a nearly linear relationship between joint angle and PPP and joint angle and DPPF Evaluation of L:P results did not reveal significant differences between limbs (left or right) or among joint angles. Overall mean +/- SD L:P for all dogs was 1.68 +/- 0.18 (95% confidence interval, 1.33 to 2.03). CONCLUSIONS AND CLINICAL RELEVANCE: The L:P proved to be a repeatable measurement of vertical patellar position, which is independent of stifle angles from 75 degrees to 148 degrees. This measurement could be used as a quantitative method for diagnosing patella alta and patella baja in large-breed dogs.

Animals↗
PubMed1982

Intraosseous pressure in the patella in relation to simulated joint effusion and knee position: an experimental study in puppies.

Simultaneous pressure measurements were carried out in the patella, juxtaarticular epiphyses and the knee joint cavity of six mongrel puppies. The mean intraosseous pressure in the patella was 12.2 mmHg, range 8-15 mmHg. An increase in intraarticular pressure in turn caused an increase in the intraosseous pressure of the patella and juxtaarticular epiphyses. The pressure increase in the patella was the most pronounced. During extension of the knee joint, a significant rise in intraosseous pressure of the tibial epiphysis and patella was observed, whereas during flexion femoral epiphyseal pressure and patellar pressure increased significantly. The introduction of moderate intraarticular effusion amplified intraosseous pressure responses during flexion of the knee joint. The intraosseous pressure changes during knee movement could not be explained solely by the corresponding changes in intraarticular pressure. Intraosseous phlebography revealed a venous drainage system largely parallel to the arterial blood supply. The contrast clearance time was decreased during moderate elevation of the intraarticular pressure, suggesting increased bone blood flow of the patella.

Animals↗
PubMed2002

[Recurrent dislocation of the patella--arthroscopic therapy].

PURPOSE OF THE STUDY: The authors present results of the surgical treatment of the recurring patella dislocation. They use the surgical technique of medial percutaneous raphe by absorbable PDS suture and lateral release with arthroscopis assistance. MATERIAL: The operation was performed for recurring dislocation in 19 cases in 16 patients. Three patients underwent a surgery on both knees. The average age of patients was 22 years (range, 14-29 years). The average period after the surgery was 22 months (range, 12-45 months). Minimal number of dislocations prior to operation was 3, maximal more than 20. METHOD: The surgical technique consists in medial raphe by percutaneously inserted absorbable PDS suture with arthroscopic assistance and in performing a lateral release in the "closed manner" under the check of the arthroscope. After-care consists in the application of a rigid orthesis which is starting from the first postoperative day removed for physiotherapy by CPM. After two weeks a hinged orthesis is used with a gradual increase of the range of motion. After 6 weeks the patient starts full weightbearing without any fixation. The authors evaluated the results of the operation after Bentley. They also followed the duration of turniquet of the operated on limb, the duration of hospitalization and the period necessary for the achievement of the full range of motion. Radiograph was used for the determination of the shape of patella after Baumgartl and Wiberg, the angle of the femoral sulcus, the height of patella after the Insall-Salvati index and lateral shift of patella. Arthroscopic examination focused on the evaluation of the patellar and femoral chondromalacy and its classification after Outerbridge. Clinically, Q angle was measured, the axis of the limb, anxiosity test was made and the presence of crepitation was checked. RESULTS: Ninety per cent of the patients evaluated the condition after the surgery as very good or good, twice as poor. In one patient there occurred one recurrence of dislocation after the surgery. In the second patient after the surgery pain aggravated in connection with a severe degenerative damage of the femoropatellar joint. Neither avascular necrosis of the patella nor any more extensive bleeding was encountered. There was no infectious complication in the group of patients. Chondral lesion was recorded in 80% of patients. The degree of the damage increased with the number of dislocations. A frequent complication was a recurring knee effusion with the necessity of its evacuation. The relation between the number of dislocations and the final outcome of the surgery was proved. No patient with the number of dislocations 10 and more was evaluated as excellent. DISCUSSION: AS release and medial raphe is a surgical technique which brings very good and good results in a high number of patients. Independently performed raphe or release do not have comparable good results in the therapy of recurring dislocation. The authors' results do not differ from data in specialised literature. CONCLUSION: Arthroscopically performed lateral release and medial raphe by percutaneously inserted suture and with AS assistance has a number of unquestionable benefits. The performance is associated with only minimum complications. It reduces the duration of hospitalization, immobilization of the limb, duration of physiotherapy as well as the total duration of the incapacity to work. The cosmetic result is good. It is possible to operate on also on young patients prior to the final ossification in the area of the tibial tubercle. A prerequisite of a good result is an accurate performance of the operation and subsequent physical therapy. Contraindications include marked degenerative changes in the femoropatellar joint, instability of the knee, patella dislocation in TKR. Q angle exceeding 30 degrees and valgus deformity of the limb exceeding 15 degrees. A high number of dislocations and the resulting more severe damage to the cartilage reduce the potential for achieving excellent results.

Adolescent↗
PubMed1992

The Elmslie-Trillat procedure for recurrent subluxation of the patella. One to five year follow-up.

Thirty-four patients who had undergone the Elmslie-Trillat procedure from 1985 to 1989 were examined in order to evaluate the effectiveness of this operation in the treatment of recurrent subluxation of the patella. The result of an increased Q angle accompanied by patella alta, femoral sulcus dysplasia, or vastus medialus obliquus dysplasia was also studied. Only those patients with recurrent subluxation of the patella took part in this study; cases of habitual or permanent dislocation, potential instability, traumatic dislocation, and degenerative arthritis were excluded. The patients were reviewed both clinically and radiographically, and the A.R.P.E.G.E. scoring system was used to evaluate the results. The follow-up period ranged from 1 year to 5 years and 4 months, with an average of 3 years. The overall results were excellent or good in 77% of the cases, as was the subjective knee stability rating in 87% of the cases and the pain rating in 82% of the cases. Recurrence of the subluxation was observed in only one instance. The results were not significantly different when the groups of patients with patella alta and type 1 femoral sulcus dysplasia were considered separately. The results were also excellent in the patients who underwent the Elmslie-Trillat procedure with reconstruction of the vastus medialis obliquus. In conclusion, surgical realignment of the anterior tibial tubercle confirmed its reliability in the treatment of recurrent subluxation of the patella. In cases of patella alta, the authors recommend lowering the anterior tibial tubercle only when the Insall-Burstein index is greater than 1.3. Femoral sulcus-plasty should be performed in cases of type 3 sulcus dysplasia.

Adolescent↗
PubMed1991

[An experimental study on the etiology of chondromalacia patellae].

Chondromalacia patellae is one of the common causes of patellofemoral disorders in young subjects. It frequently occurs in patients with lateral subluxation of the patella. However, the etiology of this disease is still obscure. The purpose of this study was to elucidate the histological changes of articular cartilage and bone in chondromalacia patellae. Lateral subluxations of the patellae were produced experimentally in forty New Zealand white rabbits. The mean tilting angle of the patellae was 14.2 degrees just after surgery, 10.7 degrees after 6 weeks, and 7.1 degrees after 12 weeks respectively. Contact pressure was lower on the medial facets than on the lateral facets and both facets of the controls. Macroscopic changes on the patellar cartilage did not appear until 12 weeks postoperatively. On the other hand, histological changes such as vascular invasion of the calcified layer, irregularity of tidemark and a decrease in the number of chondrocytes in the deep layer of the cartilage were observed on the medial facet about 4 weeks postoperatively. The degeneration of chondrocytes and matrix gradually progressed from the deep layer to the superficial layer. Twelve weeks after, a depressed area was shown in the medial facet macroscopically. Repairing process was substantiated such as the proliferation of synovial tissue, the cluster formation of chondrocytes and the recurrence of the tidemark about 30 weeks postoperatively. From the results mentioned above, it is suggested that cartilaginous and bony degeneration were caused by a decrease in contact pressure on the articular cartilage. The histological features of the chondromalacia patellae would be eventually developed by degenerative changes and restorative reaction.

Animals↗
PubMed1977

[Operative treatment of fractures of the patella (author's transl)].

Relative incongruance and great pressure in the femoro-patella joint are, besides the primary traumatic damage of the cartilage, responsible for frequent posttraumatic arthrosis and posttraumatic chondropathy of the patella after patellafracture. An operative reconstruction with a smooth joint surface of the patella is necessary. The only reliable method to fulfil these demands is the tension wire osteosynthesis by Pauwels, which, according to the type of fracture, can be combined with Kirschner wires and small fragment screws. The best access to the patella is established by diagonal incision. Open fractures must and closed fractures should be operated immediately. In comminuted fractures with devitalised cartilagefragments there is no indication to preserve the patella. Primary patellectomy has better results as late patellectomy. According to stability the after-treatment requires 4 to 6 weeks rest in a plaster cast. Although the operation can be performed with technical skill, arthrosis and chondropathy of the patella cannot always be avoided.

Aftercare↗
PubMed1984

[A radiological study of the patella and the facies patellaris of the femur].

Fifty-eight patellae and femora of cadaveric knees were studied. Radiological measurement of the osseous projection and cartilaginous projection, aided by contrast medium, revealed several morphological characteristics of the patella and the facies patellaris of the femur as follows. Depth index, facet angle, facet ratio of the patella and median ridge index which indicates position of the median ridge, showed almost the same value as reported by many authors previously. There were configurational rules in the axial view and the lateral view of the patella. Imaging of the configuration of the articular surface of the patella was therefore possible when osseous projection was measured. Regardless of the positioning to take radiograph, depth index and sulcus angle of the trochlea showed almost the same value, but the facet ratio varied considerably. There were good correlations between facet angle of the patella and sulcus angle of the trochlea both in osseous and cartilagenous projections. The depth index and facet ratio, on the other hand, were shown to have correlation in cartilagenous projection only.

Adult↗