Three hundred and nineteen patients who had chondromalacia
1. It is suggested that abruptness of the condylar ridges on the femur plays a major role in the etiology of chondromalacia
Objectives. To assess the effectiveness of a modified tibial tubercle osteotomy
as a treatment for arthroscopically diagnosed chondromalacia
1. The occurrence of bilateral double-layer
Full thickness samples of articular cartilage were removed from areas of chondromalacia on the medial and "odd" facets of the
Six cases of osteochondritis dissecans
Four methods of surgical treatment of chondromalacia
1 . Current theories of the etiology of chondromalacia
Minor degrees of malalignment of the patella and anatomical abnormalities including a flattened sulcus angle and an increased ratio between patellar tendon length and patellar length (PT:P) have been suggested as predisposing factors in the causation of chondromalacia
A new radiological technique is presented in which serial axial radiographs of the patellofemoral joints are taken under conditions in which the muscles about the knee and hip are contracted in a manner similar to that during weight-bearing. A form of analysis has been developed whereby patellar rotation can be measured in two planes and femoral rotation about its long axis inferred. A population of asymptomatic adults and children was investigated in this way and their results (regarded as normal) compared with those in fifteen children with idiopathic chondromalacia
This systematic review and meta-analysis aimed to compare the influence of patellar resurfacing following cruciate-retaining (CR) and posterior-stabilized (PS) total knee arthroplasty (TKA) on the incidence of anterior knee pain, knee-specific patient-reported outcome measures, complication rates, and reoperation rates. A systematic review of MEDLINE, PubMed, and Google Scholar was performed to identify randomized controlled trials (RCTs) according to search criteria. Search terms used included: arthroplasty, replacement, knee (Mesh), TKA, prosthesis, patella, patellar resurfacing, and patellar retaining. RCTs that compared patellar resurfacing versus unresurfaced in primary TKA were included for further analysis. Studies were evaluated using the Scottish Intercollegiate Guidelines Network assessment tool for quality and minimization of bias. Data were synthesized and meta-analysis performed.Aims
Methods
The use of cementless total knee arthroplasty (TKA) components has increased during the past decade. The initial design of cementless metal-backed patellar components had shown high failure rates due to many factors. The aim of this study was to evaluate the clinical results of a second-generation cementless, metal-backed patellar component of a modern design. This was a retrospective review of 707 primary TKAs in 590 patients from a single institution, using a cementless, metal-backed patellar component with a mean follow-up of 6.9 years (2 to 12). A total of 409 TKAs were performed in 338 females and 298 TKAs in 252 males. The mean age of the patients was 63 years (34 to 87) and their mean BMI was 34.3 kg/m2 (18.8 to 64.5). The patients were chosen to undergo a cementless procedure based on age and preoperative radiological and intraoperative bone quality. Outcome was assessed using the Knee Society knee and function scores and range of motion (ROM), complications, and revisions.Aims
Methods
1. Chondromalacia of the patella starts most frequently on the medial facet. 2. The anatomy of the medial femoral condyle is described, including the rim at its superior border, and the different arrangement at the upper border of the lateral femoral condyle. 3. Rubbing of the medial patellar facet on the rim at the upper border of the medial femoral condyle can explain in part the etiology of chondromalacia.
The articular cartilage of the patella was studied in 100 knees at necropsy. In twenty-one of these knees the cartilage changes were related to the trabecular architecture of the underlying bone. It would appear that the initiation and location of cartilage damage and its rate and degree of progression are related to the relative stiffness of the underlying cancellous bone. On the basis of our observations we suggest that the diagnosis "chondromalacia of the patella" should be reserved for patients with asymptomatic or transiently symptomatic fibrillation of the articular cartilage of the central medial patellar facet. Those patients with persistent patellofemoral pain should be considered to have some other syndrome.
The purpose of this prospective and randomized study was to objectively evaluate isokinetic strength, clinical, and radiographical outcome in bilateral TKA using the same prosthesis with and without patella resurfacing. Bilateral TKA, one with, one without patella resurfacing was performed in 22 osteoarthritic patients, mean age was 68 years using the Low-Contact-Stress prosthesis. Minimum Follow-up was one year. Evaluation included clinical investigation, specific patella scores, radiographic analysis and isokinetic strength measurement of both knee flexion and extension at 60 degrees per second (Biodex). surement at 60 degrees per second (Biodex). There was no significant clinical score difference, but mean isokinetic strength of knee extension was significantly (p<
.0001) stronger in the non-resurfaced patella TKA (40.5 Nm) compared with the resurfaced TKA (38,5 Nm). Flexion was also significantly stronger in the patella non-resurfaced group with 22.4 Nm versus 19.5 Nm in the resurfaced group. Mean lateral deviation was significantly (p<
.001) less ideal in the resurfaced group as was postoperative patellofemoral congruent contact (p<
.001). However, there was no correlation between lateral patella deviation or congruent contact and iso-kinetic strength. The results of this study indicate that mean isokinetic strength of both knee flexion and extension was significantly stronger in the non-resurfaced patella TKA. This study provides encouraging data for patella non-resurfacing. However, clinical scores or patient’s preference did not show any difference.
Two distinct lesions affect the articular cartilage of the patella. Surface degeneration occurs particularly on the odd facet; it is age dependent, often present in youth and it becomes more frequent with increasing age. It probably does not occasion patello-femoral pain in youth, but may predispose to degenerative arthritis in that joint in later years and is regarded as a consequence of habitual disuse. The term "basal degeneration" is used to describe a lesion in which there is a fasciculation of collagen in the middle and deep zones of cartilage without, at first, affecting the surface. It was found astride the ridge separating the medial from the odd facet in twenty-three adolescents who had complained of prolonged patello-femoral pain. They were treated by excision of the disc of affected cartilage, with relief of pain in most cases. The pathogenesis of basal degeneration is related to the functional anatomy of the patella.
Lateralisation of the tuberosity tibia causes distal malalignment of the extensor mechanism of the knee and can lead to lateral tracking patella (LTP), resulting in anterior knee pain, or objective patellar instability (OPI), resulting in recurrent luxations. For a precise preoperative diagnosis the tuberositas tibia (TT) trochlear groove (TG) distance was measured on a CT scan. A distance of more than 15 mm was considered to be pathological. In a prospective study, the clinical results of a subtle, CT-guided medial tuberosity transfer for LTP and OPI were evaluated. 30 Consecutive patients with LTP and 30 patients with OPI and an increased TT TG were included. Outcomes were documented at 3, 12 and 24 months follow-up using the Lysholm scale, the Kujala score, and a visual analogue pain score. Postoperatively all but one patient reported good improvement in stability (no persistent subluxations or luxations). All patients had a marked improvement in pain and functional scores at follow up. Complications seem to be related to the peroperative technique. CT-guided TT transfer appears to be satisfactory and safe method for treating patients with an increased TT TG leading to either LTP or OPI.
Abstract. Objectives. The aim of this study was to develop an in vitro GAG-depleted patella model and assess the biomechanical effects following treatment with a SAP:CS self-assembling hydrogel. Methods. Porcine
Introduction. Patella implant research is often overlooked despite its importance as the third compartment in a total knee replacement. Wear and fracture of resurfaced
Abstract. Introduction. Osteoarthritis (OA) is one of the lead causes of pain and disability in adults. Bone marrow lesions (BMLs) are one feature of subchondral bone involvement in OA. MRI images suggest changes in tissue content and properties in the affected regions however, it is not known if this alters the mechanical behavior of the bone, which could in turn affect OA progression. The aim of this study was to characterize the mechanical properties of BMLs, using a combined experimental and computational approach. Methods. Six human cadaveric
Osteoarthritis (OA) is a disease that affects both bone and cartilage. Typically, this disease leads to cartilage degradation and subchondral bone sclerosis but the link between the two is unknown. Also, while OA was traditionally thought of as non-inflammatory condition, it now seems that low levels of inflammation may be involved in the link between these responses. This is particularly relevant in the case of Post-Traumatic OA (PTOA), where an initial phase of synovial inflammation occurs after injury. The inflammatory mediator interleukin 1 beta (IL-1B) is central to this response and contributes to cartilage degradation. However, whether there is a secondary effect of this mediator on subchondral bone, via bone-cartilage crosstalk, is not known. To address this question, we developed a novel patellar explant model, to study bone cartilage crosstalk which may be more suitable than commonly used femoral head explants. The specific aim of this study was to validate this novel patellar explant model by using IL-1B to stimulate the inflammatory response after joint injury and the subsequent development of PTOA. Female Sprague Dawley rats (n=48) were used to obtain patellar explants, under an institutional ethical approval license.
Introduction. Experimental wear simulation of an all-polymer knee implant has shown an equivalent rate of wear of UHMWPE tibial components against PEEK-OPTIMA™ and cobalt chrome femoral components of a similar initial geometry and surface topography. However, when the patella is resurfaced with an UHMWPE patella button, it is important to also ascertain the wear of the patella. Wear debris from the patella contributes to the total volume of wear debris produced by the implant which should be minimised to reduce the potential for osteolysis and subsequent implant loosening. The aim of this study was to investigate the wear of the patellofemoral joint in an all-polymer knee implant. The wear of UHMWPE
Abstract. Background. Accurate analysis of the patellar resurfacing is essential to better understand the etiology of patella-femoral problems and dissatisfaction following total knee arthroplasty (TKA). In the current published literature patellar resurfacing is analysed using 2D radiographs. With use of radiographs there is potential for error due to differences in limb positioning, projection, anatomic variability and difficulties in appreciating the cement-bone interface. So, we have developed a CT Scan based 3D modelled technique for accurate evaluation of patellar resurfacing. Methods. This technique for analyses of patellar resurfacing is based on the pre-operative and pos-operative CT Scan data of the patients who underwent TKA with patellar resurfacing. In the first step, accurately landmarked 3D models of pre-op
Introduction and Objective. Traditionally, osteoarthritis (OA) has been associated mostly with degradation of cartilage only. More recently, it has been established that other joint tissues, in particular bone, are also centrally involved. However, the link between these two tissues remains unclear. This relationship is particularly evident in post-traumatic OA (PTOA), where bone marrow lesions (BMLs), as well as fluctuating levels of inflammation, are present long before cartilage degradation begins. The process of bone-cartilage crosstalk has been challenging to study due to its multi-tissue complexity. Thus, the use of explant model systems have been crucial in advancing our knowledge. Thus, we developed a novel patellar explant model, to study bone cartilage crosstalk, in particular related to subchondral bone damage, as an alternative to traditional femoral head explants or cylindrical core specimens. The commonly used osteochondral explant models are limited, for our application, since they involve bone damage during harvest. The specifics aim of this study was to validate this novel patellar explant model by using IL-1B to stimulate the inflammatory response and mechanical stimulation to determine the subsequent developments of PTOA. Materials and Methods. Lewis rats (n=48) were used to obtain patellar and femoral head explants which were harvested under an institutional ethical approval license. Explants were maintained in high glucose media (containing supplements), under sterile culture conditions. Initially, we characterised undamaged patellar explants and compared them with the commonly used femoral head. First, tissue viability was assessed using an assay of metabolic activity and cell damage. Second, we created chemical and mechanical damage in the form of IL-1B treatment, and mechanical stimulation, to replicate damage. Standard biochemical assays, histological assays and microstructural assays were used to evaluate responses. For chemical damage, explants were exposed to 10ng/ml of IL-1B for 24 hours at 0, 1, 3 and 7 days after harvesting. For mechanical damage, tissues were exposed to mechanical compression at 0.5 Hz, 10 % strain for 10 cycles, for 7 days. Contralateral
Introduction. The trochlea of a typical patellofemoral replacement or anterior flange of a total knee replacement usually extends past the natural trochlea and continues onto the femoral anterior cortex. One reason for this is that it allows a simple patella button to be permanently engaged in the trochlea groove in an attempt to ensure stability. On the natural patella, the apex helps to guide it into the trochlea groove as the knee moves from full extension into flexion. The aim is to study whether a generalised patella can be created that is close in form to a healthy patella. Method. MRI scans were taken of 30
Joint registries suggest a downward trend in the use of uncemented Total Knee Replacements (TKR) since 2003, largely related to reports of early failures of uncemented tibial and patella components. Advancements in uncemented design such as trabecular metal may improve outcomes, but there is a scarcity of high-quality data from randomised trials. 319 patients <75 years of age were randomised to either cemented or uncemented TKR implanted using computer navigation.
Introduction. The metal-backed patella was originally designed to address shortcomings found with cemented, all-polyethylene
Total knee replacements are being more commonly performed in active younger and obese patients. Fifteen-year survivorship studies demonstrate that cemented total knee replacements have excellent survivorship, with reports of 85 to 97%. Cemented knee arthroplasties are doomed to failure due to loss of cement-bone interlock over time. Inferior survivorship occurs in younger patients and obese patients who would be expected to place increased stress on the bone-cement interfaces. Roentgen stereophotogrammetric analysis (RSA) studies have indicated that cementless fixation should perform better than cemented fixation. However, cementless fixation for total knee replacement has not gained widespread utilization due to the plethora of poor results reported in early series. The poor initial results with cementless total knee replacement have occurred due to poor implant designs such as cobalt chrome porous interfaces, poor initial tibial component stability, lack of continuous porous coating, poor polyethylene, and use of metal-backed
Total knee replacements (TKRs) are being more commonly performed in active younger and obese patients. Fifteen year survivorship studies demonstrate that cemented total knee replacements have excellent survivorship, with reports of 85% to 97%. However, inferior survivorship occurs in younger patients and obese patients who would be expected to place increased stress on the bone cement interfaces. Cementless fixation for total knee replacement has not gained widespread utilization due to the plethora of poor results reported in early series. These poor results do not reflect that cementless fixation is not obtainable, since an almost universal acceptance of cementless fixation for total hip replacement has shown. A Cochrane database study of total knees with roentgen stereophotogrammetric analysis (RSA) demonstrated that the risk of future aseptic loosening should be 50% less with cementless fixation. The poor initial results with cementless total knee replacement have occurred due to poor implant designs such as cobalt chrome porous interfaces, poor initial tibial component fixation, lack of continuous porous coating, poor polyethylene, and use of metal-backed
Patients ≤ 55 years have a high primary TKA revision rate compared to patients >55 years. Guided motion knee devices are commonly used in younger patients yet outcomes remain unknown. In this sub-group analysis of a large multicenter study, 254 TKAs with a second-generation guided motion knee implant were performed between 2011–2017 in 202 patients ≤ 55 years at seven US and three European sites. Revision rates were compared with Australian Joint Registry (AOANJRR) 2017 data. Average age 49.7 (range 18–54); 56.4% females; average BMI 34 kg/m2; 67.1% obese;
A high proportion of complications following TKR occur at the patellofemoral articulation secondary to delami-nation and adhesive/abrasive wear. Electron beam cross-linking and melting has been shown to substantially reduce delamination and adhesive/abrasive wear in polyethylene tibial inserts. A series of in-vitro patella wear and fatigue tests were developed to explore the benefits of this material at the patellofemoral articulation.
Resurfacing the patella is performed the majority of the time in the United States and in many regions it is considered standard practice. In many countries, however, the patella is left un-resurfaced an equal amount of the time or even rarely ever resurfaced. Patella resurfacing is not a simple or benign procedure. There are numerous negative sequelae of resurfacing including loosening, fragmentation, avascular necrosis, lateral facet pain, stress fracture, acute fracture, late fracture, and restricted motion. In a study by Berend, Ritter, et al, failures of the patella component were reported 4.2% of the time at an average of only 2.6 years. A study was undertaken at Washington University in recent years to determine rather more clinical problems were observed following total knee replacement with or without patella resurfacing. Records were maintained on all problem total knees cases with well localised anterior knee pain. The referral area for this clinic is St. Louis which is among the largest American cities, with the highest percentage of total knees that are performed without patella resurfacing. During 4 years of referrals of total knee patients with anterior knee pain, 47 cases were identified of which 36 had a resurfaced patella and 11 had a non-resurfaced patella. Eight of 36 resurfaced
Introduction: Patellar complications after total knee arthroplasty (TKA) remain a common reason for failure. Fully congruent patellar components, with larger contact areas and a polyethylene articular surface that is free to rotate in the frontal plane (LCS design), were designed to accommodate patellar mechanics and decrease wear. However, it remains to be determined whether the perceived advantages of a mobile-bearing, fully congruent patella design are realized in-vivo. The purpose of this study is correlate wear patterns on congruent mobile-bearing patellar components with patellar mechanics that existed after TKA. Methods: Uncemented metal-backed patellar components were retrieved at revision surgery from 26 knees with meniscal bearing (23 knees) and rotating platform (3 knees) LCS mobile bearing prostheses (DePuy Orthopaedics). Mean patient age and time in-situ was 75+11 years and 11+4 years, respectively. Revision reasons included bearing wear (11), patella wear (7), instability (2), pain (3), loosening (1), osteolysis (1), and unknown (1). Polyethylene damage was assessed using optical microscopy. Articular wear area was measured using digital image analysis and the % area, location and incidence of each damage mode was calculated. Results: The average damage area on the retrieved patella occupied 69%+15% of the surface. Burnishing, delamination and scratching modes occupied the largest areas. Delamination was noted on 58% of the retrieved
INTRODUCTION: Following Total Knee Arthroplasties, patellofemoral complications have shown to be responsible for approximately 50% of re-operations. Contemporary patellar designs employ both “onlay” and “inset” configurations. The latter promotes ease of placement, reduced bone removal and a heralded theoretic advantage of increased strength at the fixation interface. However, to date, no reports have compared the disassociation strengths of these two patellar component modes of fixation. The purpose of this study is to quantify the shear disassociation strength for both onlay and inset patellar fixation techniques. METHODS: Two sets of synthetic solid foam
Resurfacing the patella is performed the majority of the time in the US and in many regions it is considered standard practice. In many countries, however, the patella is left unresurfaced an equal amount of the time or even rarely ever resurfaced. Patella resurfacing is not a simple or benign procedure. There are numerous negative sequelae of resurfacing including loosening, fragmentation, avascular necrosis, lateral facet pain, stress fracture, acute fracture, late fracture, and restricted motion. In a study by Berend, Ritter, et al, failures of the patella component were reported 4.2% of the time at an average of only 2.6 years. A study was undertaken at Washington University in recent years to determine whether more clinical problems were observed following total knee replacement with or without patella resurfacing. Records were maintained on all problem total knees cases with well localised anterior knee pain. The referral area for this clinic is St. Louis which is among the largest American cities, with the highest percentage of total knees that are performed without patella resurfacing. During 4 years of referrals of total knee patients with anterior knee pain, 47 cases were identified of which 36 had a resurfaced patella and 11 had a non-resurfaced patella. Eight of 36 resurfaced
Graft choices for revision anterior cruciate ligament (ACL) reconstruction and complex ligament reconstructions of the knee are controversial. The aim of our study was to analyze the biomechanical effect of harvesting bone plugs from both the distal and proximal poles of the patella, to simulate a simultaneous harvesting of a Bone – Patellar Tendon – Bone and Quadriceps Tendon – Bone grafts, in a transverse stress environment. Sixty Bovine
Rotational mal-alignment of the patella-femoral interface will result in increased wear. Highly cross-linked polyethylene will decrease wear even if mal-aligned. A biomechanical model based on high load and flexion was used to measure wear of rotationally aligned and mal-aligned all-polyethylene
The purpose of this study was to characterise accurately, the extent and geometry, and produce representative rigid resin models of full thickness articular cartilage lesions of various types, shapes and sizes on the articular surface of pig
Introduction. Management of the patellofemoral surface in total knee arthroplasty (TKA) remains a topic of debate. Incidence of anterior knee pain and incidence of repeat operation have been the focus of several recent meta-analyses, however there is little recent data regarding patients” subjective ability to kneel effectively after TKA. The purpose of this study was to compare patient reported outcomes, including reported ability to kneel, after total knee arthroplasty with and without patellar resurfacing. Methods. Retrospective chart review of 84 consecutive patients who underwent primary TKA with patella resurfacing (56 knees) or without patella resurfacing (28 knees) having a minimum of 2.5 year follow up was performed. Oxford knee scores (OKS), visual analog pain scores (VAS), and questionnaires regarding ability to kneel were evaluated from both groups. Inability to kneel was defined as patients reporting inability or extreme difficulty with kneeling. Shapiro-Wilk test was used to determine normality of data. Mann Whitney U test was used to compare the OKS and VAS between groups. Chi square test was used to compare kneeling ability between groups. Statistical analysis was performed with SPSS version 23 (IBM, Aramonk, NY). Results. The 84 patients included 26 males and 58 females with average age 66.5 (range 46–91). Average follow up was 51 months (range 30–85). There was no significant difference in the percentage of female patients (64% vs 79%), age (67.8 vs 63.8), or reoperation rate (4% vs 7%) between the resurfaced and non-resurfaced groups. There was significantly longer follow up in the non-resurfaced group (57 vs 48 months). There was no statistically significant difference between the resurfacing and non-resurfacing group in terms of OKS (39 vs 38) or VAS (2.5 vs 3.0). However, those patients who did not have their patellofemoral joint resurfaced were more likely to report ability to kneel when compared to the resurfacing group (64% vs 39%, p=0.035). Kneeling ability was not correlated with duration of follow up, patient age or VAS. Kneeling ability was higher in female patients (57%) than males (27%), p=0.017. Discussion. There is concern for increased anterior knee pain and reoperation in patients whose
Previosuly, Komistek et al. have shown that the kinematics of the patellofemoral joint is altered after a TKA surgery. Specifically the implanted patella experiences significantly less rotation than the natural patella. Also, in early flexion, the patellofemoral contact positions differed significantly between implanted and non-implanted
The aim of this study was to assess the outcome of patients who underwent ElmslieTrillat antero-medial tibial tubercle transfer for treatment of persistent symptomatic anterior knee pain due to chondromalacia
The October 2012 Knee Roundup. 360. looks at: autologous chondrocytes and chondromalacia
Whereas thermography has already been used as an assessment of disease activity in some kinds of inflammatory arthritis, it is a new method for objektive pain evaluation in patients with joint prosthesis. To our knowledge, no study has tested the correlation between increase of temperature and anterior knee pain with total knee prosthesis yet. Thirteen patients were included in this study who suffered from anterior knee pain of the retinaculum
Introduction. Patients ≤ 55 years have a high primary TKA revision rate compared to patients >55 years. Guided motion knee devices are commonly used in younger patients yet outcomes remain unknown. Materials and Methods. In this sub-group analysis of a large multicenter study, 254 TKAs with a second-generation guided motion knee implant (Journey II Bi-Cruciate Stabilized Knee System, Smith & Nephew, Inc., Memphis) were performed between 2011–2017 in 202 patients ≤ 55 years at seven US and three European sites. Revision rates were compared with Australian Joint Registry (AOANJRR) 2017 data. Results. Average age 49.7 (range 18–54); 56.4% females; average BMI 34 kg/m. 2. ; 67.1% obese;
Purpose: Patellar bracing is a common, mechanical-based treatment strategy for patellofemoral osteoarthritis (OA). It is thought that the brace corrects patellar tracking, however, this correction has not been quantified in the OA population. Through advances in magnetic resonance imaging (MRI), we can now assess patellar tracking in three-dimensions. Method: We assessed three-dimensional patellar tracking in ten subjects with symptomatic radiographic patellofemoral knee OA using a validated, quasi-static, MRI-based method. Four conditions were studied:. no knee brace, no load,. no knee brace, 15% bodyweight (BW) load,. knee brace, no load,. knee brace, 15% BW load. Patellar tracking (flexion, spin and tilt; proximal, lateral and anterior translation) was assessed. Comparisons were made at 1° increments over the coincidental range of knee flexion between the no-brace and brace conditions, at no load and 15% BW load, using a paired t-test with Bonferroni correction. Results: All subjects (7 female, 3 male, 60.9±1.3 yrs, 89.5±19.3 kg) had radiographic lateral patellofemoral OA and seven had concomitant tibiofemoral OA (KL grade≥2). Under no load, the brace extended (mean=2.7°, CI=[2.4°, 2.9°], P<
0.001) and medially tilted (mean=−1.4°, CI=[−1.6°, −1.2°], P<
0.001) the
Introduction A biomechanical model was developed to measure wear of all-polyethylene patellar components as it relates to femoral component mal-rotation. The model, based on high load and flexion activities such as stair climbing, was used to differentiate the effects of femoral mal-rotation and differing materials on a single patellar design. Methods The patellar components (Scorpio®, Stryker-Howmedica-Osteonics) were cemented onto metal fixtures and articulated against “aligned” and “mal-aligned” (six degrees internally rotated) femoral components. The patellar components were subjected to a constant force and articulated against femoral components flexing from 600 to 1200.
Purpose of the study: The stability of the patella over the femur depends on several factors, one being the rotatory freedom of the tibia. Femorotibial rotatory laxity of a total knee arthroplasty (TKA) can be:. dictated by the congruence of the polyethylene in an ultracongruent plateau;. completely free, depending solely on the ligament structures in a self-aligning prosthesis;. the consequence of a compromise between the two, using a semi-constrained prosthesis. With the OMNIA system, the unique femoral piece can be combined with a Wallaby ultracongruent plateau (WUC), a self-aligning mobile plateau (SAL), or a semiconstrained plateau with preservation of the posterior cruciate ligament (Wallaby 1, W1). A comparative study of these three prostheses was performed to evaluate the influence of femorotibial rotatory constraint on patellar stability. Material and methods: The series included 157 TKA: 68 SAL,44 WUC and 45 W1. The same surgeon operated all patients in three successive series. The operative technique was the same using the same instrument set. The femoral piece was inserted first with an automatic rotation systematically set at 5° with the posterior condyles. The knees were varus (71%), valgus (20%) and perfectly aligned (9%). A patellar prosthesis was used in only 10.8% due to excessive wear as assessed intraoperatively. A medial approach was used for the varus knees and a lateral approach for the valgus knees greater than 10°, independently of preoperative patellar stability. Radiological outcome was assessed on the 30° femoro-patellar views.
