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PubMed2001

Orthopaedic measurements with computed radiography. Methodological development, accuracy, and radiation dose with special reference to the weight-bearing lower extremity and the dislocating patella.

The overall aim of this study was to develop and evaluate a measurement system for computed radiography (CR) and Picture Archiving and Communication Systems (PACS), permitting measurements of long distances and angles in and between related images. The developed measurement system, which was based on the QUESTOR Precision Radiography (QPR) system, was applied to the weight-bearing knee with special reference to the dislocating patella. The QPR system modified for CR fulfilled the criteria for measuring the weight-bearing knee. The special measuring assistance tools that were developed were important for the implementation of CR and PACS, particularly in workstations programmed for musculoskeletal radiology. The energy imparted to the patient was reduced by 98% at the lowest exposure of the CR-system, compared with our conventional analogue method, without loss of diagnostic accuracy. The CR technique creates a possibility, to an extent not previously feasible, to differentiate the exposure parametres (and thus minimise the radiation dose to the patient) by carefully considering the purpose of the examination. A radiographic method for measuring the rotation of the femur and the tibia, the Q-angle, and the patellar translation was developed and applied to healthy volunteers. The introduced patellar variables have yielded new insights into the complex sequence of motions between the femur, tibia, and patella. The patients with a dislocating patella were subdivided into one "clean" group of spontaneous dislocations and one group with various traumas in the history, which thus resulted in two groups with distinct radiographic differences. The Q-angle was decreased in knees that had suffered dislocations, and the traditional surgical treatment with a further reduction of the Q-angle must be challenged. The use of clinical measurements of the Q-angle was not an optimal way to evaluate the mechanical alignment in the patellofemoral joint under physiological conditions. In this study, we have proved that the developed method for CR and PACS is a useful technique for measurements in and between related images, and is superior to the conventional analogue technique.

Adolescent↗
PubMed2006

Thermal medial retinaculum shrinkage and lateral release for the treatment of recurrent patellar instability.

PURPOSE: To study a technique of medial retinacular thermal shrinkage and evaluate the clinical effectiveness of this technique. TYPE OF STUDY: Nonrandomized prospective case series. METHODS: A consecutive series of patients with recurrent patellar instability treated with arthroscopic lateral release and medial thermal retinaculum shrinkage using a monopolar radiofrequency probe was assessed subjectively by visual analog scale and both preoperatively and postoperatively by physical examination and Lysholm and Fulkerson knee scores. RESULTS: We evaluated 53 knees with an average follow-up of 53 months (range, 24 to 88 months). The mean Lysholm and Fulkerson scores improved from 45 and 41 to 81 and 82, respectively. Subjectively, 48 of 53 knees (90%) were reported as excellent or good. The average visual analog scale score was 8 out of 10. Five patients failed because of recurrent dislocation (9% recurrence). Additional stabilization procedures were performed in 4 patients. CONCLUSIONS: Medial shrinkage using monopolar thermal energy is effective in treating recurrent patellar instability. Our results were comparable with prior studies using suture plication. The technique avoids additional incisions and decreases operative time. LEVEL OF EVIDENCE: Level IV, therapeutic prospective cohort study.

Adolescent↗
PubMed1987

The patellar meniscus in total knee replacement.

Theoretically, because most patellar replacements are convex polyethylene structures subjected to high loads, considerable wear should occur. This has not been reported. A review of knee revisions had been carried out. The patella has been resurfaced on 12 occasions. It was revised on five occasions, and gross wear was seen in three of these cases, in all of which the patella had dislocated. The patella in all cases was surrounded by a meniscus of dense fibrous tissue. A small wear facet in the exposed area was present. This suggests that patellar articular surface geometry may not be critical as far as wear is concerned.

Humans↗
PubMed2006

International multi-centre survivorship analysis of mobile bearing total knee arthroplasty.

We retrospectively reviewed the experience of a large international multi-centre study of primary total knee arthroplasty with mobile bearing design and modifications of the tibial component to allow for bicruciate preservation, posterior cruciate retention, or sacrifice. Twenty-seven surgeons performed 4,743 total knee replacements between 1981 and 1997. Implants inserted were 324 that retained both cruciate ligaments, 2,165 that retained the posterior cruciate, and 2,254 that sacrificed both cruciates. The patella was resurfaced in 2,838 and unresurfaced in 1,905. With failure defined as revision or reoperation for any reason, the overall survivorship was 79% at 16 years' follow-up. Revision occurred in 259 (5.4%) knees out of the entire cohort. The risk adjusted rates of failure were higher in females, younger patients, osteoarthritis, post-traumatic arthritis, and in patients who had a meniscal bearing prosthesis or patellar resurfacing. The most common cause of revision was bearing-related issues including chronic instability, bearing subluxation, bearing dislocation, or bearing wear in 2.3%.

Arthroplasty, Replacement, Knee↗
PubMed1978

[Etiology of dislocation of the patella (author's transl)].

Using a new method for measuring the distal femoral torsion (Janssen a. Prüssner 1977) it is possible to determine the encreased medial torsion of the distal femur in most of the patients with dislocation of the patella. A group of patients with dislocated knee-cap was studied for this purpose. The characteristic clinical and x-ray features are listed and weighted according to their value. They throw a new light on the pathogenesis and pathomechanics of patellar luxation, and point to the need to reclassify the different types of luxations according to etiological aspects.

Adolescent↗
PubMedDate not supplied

[Patellar fracture after reconstruction of the anterior cruciate ligament--case report].

INTRODUCTION: The most frequent procedure in treatment of acute or chronic anterior cruciate ligament (ACL) rupture is the so called bone-tendon-bone reconstruction. A transverse dislocated patella fracture is a rare complication of this procedure with an incidence of 0.23%-2.3%. In a five year period, (1998-2002), 407 arthroscopic reconstructions of the anterior cruciate ligaments were done at our Clinic, and there was only one case of patella fracture. CASE REPORT: An 18-year-old female patient, a handball player, suffered an acute rupture of anterior cruciate ligament of the left knee, so arthroscopic bone-tendon-bone reconstruction of the anterior cruciate ligament was performed. After adequate skin incision, a bone graft was taken from the patella and upper part of trapezoid tibia, which was 25 mm long, 10 mm wide and 5 mm thick, together with a part of patellar ligament. After the remains of the anterior cruciate ligament had been arthroscopically removed, tunnels were made in tibia and femur and a graft was inserted and fixed with two metal interference screws. Knee stability was tested, and drainage was put in the knee joint. The wound was closed by layers. The quadriceps exercises and passive knee movements started immediately. Full range of movements was accomplished six weeks later when the patient started to walk with full weight-bearing on her operated leg. Three weeks later, (nine weeks after the operation), the patient has accidentally lost her balance and fell. A transverse, dislocated fracture of the left patella was diagnosed and osteosynthesis of the fractured patella with two Kirschner wires and a metallic loop was performed. Postoperatively, full range of movement was allowed. Six months later, the patient felt no pain, there was no swelling, full range of knee movement was achieved, while the Lachman Test was identical in both knees and the pivot shift test was negative. DISCUSSION: Fracture of patella after ACL reconstruction is due to several reasons: size and shape of the graft, technique of its taking, disturbed patellar blood supply, incomplete filling of patella defect after graft taking, and inappropriate postoperative rehabilitation. If a patellar fracture occurs after anterior cruciate ligament reconstruction, the best treatment is firm osteosynthesis, which enables bone healing and immediate continuation of the previously resumed rehabilitation program. However, this complication prolongs the rehabilitation period and slows down return to sports.

Adolescent↗
PubMed1980

Congenital dislocation of the patella.

This is a report of 2 rare, neglected congenital irreducible complete lateral dislocations of the patella. The patients were boys, 10 and 13 years old. The dislocations were designated irreducible because closed manipulative effects were invariably failures and the dislocations are permanent because they persist from birth until openly reduced. The deformity was neglected for years (one patient through childhood, the other into adolescence) during which time the anomalous defects were exacerbated by adverse growth changes. The propitious time (late infancy or early childhood) for open reduction and patellar stabilization with an excellent prognosis had long since passed by the time the patients were first seen by an orthopedic surgeon. Neglect had not only caused them to grow up as cripples, but had also rendered their patellae more difficult to reduce surgically. Neglect also increased the challenge to their surgeon to stabilize their patellae and to cope with their needless and preventable secondary deformities by multiple surgical interventions with decreased prospects of emerging free of residual problems and disabilities. In the growing child with active proximal tibial epiphyseal cartilage, interference with growth was avoided by patellar stabilization using the W. T. Green technique for quadricepsplasty. In the adolescent boy, who was closer to skeletal maturity, patellar stabilization was effectually accomplished by transplanting the tibial tuberosity medially and distally with relative impunity and reinforcing it with a Campbell sling. Angular and linear limb deformities were treated by epiphysiodeses. Prolonged dislocations result in loss of normal articular contours, and nonuse of articular cartilages has a morbid effect; both predispose the joint to early degenerative arthritis. Early diagnosis and early referral for orthopedic care are imperative because delay vitiates the ultimate result.

Adolescent↗
PubMed1994

Effects of patella alta and patella infera on patellofemoral contact forces.

The relationship between patella alta and patellar subluxation may, in part, reflect the relationship between the height of the patella above the tibiofemoral joint line and the patellofemoral contact force. This study reports on the direct in vitro measurement of the patellofemoral contact force, and its point of application on the patella, as a function of patellar height. The contact force was measured by a specially designed six-degree-of-freedom force transducer under loading simulating rising from a chair. The magnitude of the resultant contact force increased significantly with superior displacement of the patella. The magnitude of the resultant contact force changed as much as 3% per millimeter of change in patellar height. The details of this response varied among the knees tested and depended on the original anatomical patellar height. For a high-riding patella, the onset of tendofemoral contact is delayed and the magnitude of the patellofemoral contact continues to increase with increasing flexion angle. Early onset of tendofemoral contact associated with a low-riding patella results in a concomitant reduction in the magnitude of the contact force. The medially directed component of the contact force acting on the patella resists lateral subluxation of the patella. This force component increased with superior displacement of the patella. This may explain in part the tendency for a high-riding patella to sublux. For all seven specimens tested the point of application of the resultant contact force migrated superiorly with inferior displacement of the patella.

Aged↗