Fixed or mobile bearing unicompartmental knee replacement? A comparative cohort study

Unicompartmental knee replacement (UKR) for anteromedial osteoarthritis is a well-established technique. Numerous clinical outcome studies demonstrate good medium and long-term results. The aim of this prospective study was to compare the complications and short-term clinical outcome of the St. Georg Sled, a fixed bearing UKR, with the Oxford mobile bearing UKR. Outcome at 2 years was assessed using the Bristol knee score and the Oxford knee score; in addition, complications occurring since formal scoring at 2-year follow-up were recorded. A total of 47 Oxford UKRs and 57 St. Georg Sled UKRs were performed in 91 patients, none of whom were lost to follow-up. At 2 years, both outcome measures were better for the St. Georg Sled Group. The pain component of the Bristol knee score was significantly better for this group (p-value = 0.013). Three patients in the Oxford group had bearing dislocations and a further four patients required revision (mean time to revision 3.0 years). In the St. Georg Sled group, three patients required revisions (mean time to revision 3.4 years). These results demonstrate that in the short-term, the Oxford mobile bearing prosthesis has a higher re-operation rate and that the St. Georg Sled achieves better pain relief. The functional scores of the two groups were similar.     

A prospective randomised study comparing rotating platform and fixed bearing total knee arthroplasty in a cruciate substituting design — Outcomes at two year follow-up

BackgroundFixed bearing (FB) total knee replacement is a well established technique against which new techniques must be compared. Mobile bearing (MB) prostheses, in theory, reduce polyethylene wear but the literature is yet to provide evidence that they are superior in terms of function or long-term survivorship. In addition there has been no comparison of patella resurfacing on the outcome of either design. The aims of this randomised prospective study were firstly to determine whether a mobile bearing prosthesis produced better clinical outcome and range of motion at two year follow-up and secondly to assess the effect of patella resurfacing on the outcomes of both types of bearing design.MethodsThree hundred fifty-two patients were randomised into receiving either a PFC Sigma© cruciate sacrificing total knee arthroplasty either with a mobile bearing or a fixed bearing, with a sub-randomisation to either patella resurfacing or patella retention. All patients participated with standard clinical outcome measures and had their range of motion measured both pre-operatively and at follow-up.ResultsThe mobile bearing TKR design had no impact on range of motion; Oxford Knee Score and American Knee Society knee and function scores when compared to its fixed bearing equivalent.ConclusionsAt two year follow-up there was no difference between the PFC Sigma© fixed and mobile bearing designs. With no clinical difference between the cohorts, we cannot recommend one design over the other. Long term benefits, particularly with regards to polyethylene wear, may yet be demonstrated.Level of evidence — 1B.     

Does cruciate-retaining total knee arthroplasty enhance knee flexion in Western and East Asian patient populations? A meta-analysis

IntroductionThis study analyzed the published data to examine if CR TKAs can enhance the flexion and functional outcomes of the knee in the Western and East Asian populations using a meta-analysis approach.Materials and methodsA systematic review of literature published through Medline and EMBASE was conducted. The inclusion criteria were: primary TKA, follow up duration greater than one year, a fixed bearing CR prosthesis, and data for maximum pre- and post-operative flexion along with standard deviations or errors. We estimated the weighted mean differences between pre- and post-operative flexion, extension and knee scores (KSS and HSS) via a random effect model.ResultsSeventeen articles were selected and reviewed among 1229 studies that included 1090 knees of the Western and 516 knees of the East Asian. No significant difference was noted in maximal knee flexion pre- and post-operatively, when all the studies were pooled together (? 0.17°, p = 0.93, post-operative < pre-operative). The mean difference in flexion was ? 1.87° (p = 0.2) and 2.03° (p = 0.17), respectively in the both populations. However, the extension angle was significantly improved by ? 5.49° and ? 13.05° (p < 0.05), respectively. KSS scores were significantly improved by 46.39 and 51.63, and HSS scores by 36.65 and 30.67 (p < 0.05), respectively in the both populations.ConclusionThe meta-analysis indicated that contemporary CR TKAs have not been shown to enhance post-operative flexion capability in the Western and East Asian. The extension angles of the knee and the knee scores were significantly improved in both populations.     

Mobile or fixed unicompartmental knee prostheses? In-vitro wear assessments to solve this dilemma

The unicompartmental knee prosthesis is an attractive alternative to total knee arthroplasty. Current UKP devices can be subdivided into two groups based on different design principles: fixed bearing knees, where the ultra-high molecular weight polyethylene meniscal component snap or press fits into the tibial tray, and mobile bearing designs which facilitate movement of the insert relative to the tray. The present study was aimed at comparing the in-vitro wear behaviour of fixed and mobile unicompartmental knee menisci under two configurations: the femoral components were cemented into a custom-made metallic block or, as a novelty of the present study, into a synthetic femur (i.e. under conditions which should better reproduce the in-vivo behaviour). Analyses were performed using a displacement-control knee wear simulator with "three-plus-one" stations. All the kinematics tests were set in accordance with the ISO 14243-1,2,3. Fixed and mobile polyethylene menisci showed a different wear behaviour: the fixation-frame influenced directional load transfer through each component in a qualitative and quantitative way. In fact, gravimetric results showed that under the metal block holder fixation, mobile components worn more than fixed components (weight losses of 8.7±2.0 mg and 2.6±1.09 mg, respectively); on the other hand, under the synthetic femur configuration, differences in wear behaviour were less pronounced and mobile menisci underwent a slightly lower weight loss than fixed components (4.5±2.2 mg vs. 6.7±1.4 mg). This different trend was explained in relation to the kinematic schemes of the two fixation methods. Raman spectroscopy, used to evaluate the UHMWPE crystallinity changes induced by mechanical stress, showed that mobile menisci specimens were more affected than the fixed components in both their superior and inferior surfaces, independent of the fixation-frame. In conclusion, if tested under conditions which should better reproduce the in-vivo behaviour, mobile UKPs did not show a worse wear behaviour than fixed components in terms of weight losses, although UHMWPE changes at the molecular scale could be detrimental.     

Is a tourniquet beneficial in total knee replacement surgery?: A meta-analysis and systematic review

Proponents of tourniquets postulate that they optimise intra-operative visibility and reduce blood loss. This study compared the outcomes of tourniquet assisted to non-tourniquet assisted total knee replacement (TKR). A systematic review was undertaken of the electronic databases Medline, CINAHL, AMED and EMBASE, in addition to a review of unpublished material and a hand search of pertinent orthopaedic journals. The evidence-base was critically appraised using a tool from the Cochrane Bone, Joint and Muscle Trauma Group. Fifteen studies were identified evaluating 16 outcome measures and parameters of 1040 TKRs in 991 patients. There was a significantly greater intra-operative blood loss in non-tourniquet compared to tourniquet assisted surgery (p = 0.004). There was no significant difference between the groups for total blood loss or transfusion rate (p = 0.22; p = 0.48). There was a trend for greater complications in tourniquet compared to non-tourniquet patients. There was no difference between the groups for any other outcome measure assessed. In conclusion, this systematic review has found that there is no advantage to using a tourniquet in knee replacement surgery for reduction of transfusion requirements.     

Does arthroplasty type influence knee joint proprioception? A longitudinal prospective study comparing total and unicompartmental arthroplasty

Proprioception was assessed after knee replacement to compare total (TKA) to unicompartmental (UKA) knee arthroplasty. Thirty-four patients were recruited; seventeen patients underwent TKA and seventeen patients underwent UKA. The patient's age was similar in both groups. Two measures of proprioception, joint position sense (JPS) and postural sway (PS) were measured. Function was assessed using the Oxford Knee Score (OKS). Measurements were taken pre-operatively and 6 months post-operatively on both the operated and contralateral leg. Pre-operatively, no differences in JPS or PS were found between groups or between limbs in either group. Post-operatively, both groups had significant improvement of JPS in the operated limb only (20% increase). The improvement in JPS was similar in both groups. PS also improved significantly in both groups although the improvement of PS in the UKA group was twice that for the TKA group. The OKS improved by a similar amount in both groups. Both UKA and TKA result in a significant improvement in proprioception. Dynamic aspects of proprioception improve more after UKA than TKA, which may explain, in part, why UKA patients have superior functional outcome to that of TKA patients.     

Is patellar resurfacing superior than nonresurfacing in total knee arthroplasty? A meta-analysis of randomized trials

Conflicting results from abundant studies have made it unclear whether the patella should be resurfaced during total knee replacement. A meta-analysis was undertaken to pool the results of randomized controlled studies (RCTs) and to compare the outcomes and postoperative complications after total knee arthroplasty with patellar resurfacing or nonresurfacing. Sixteen RCTs including 3034 knees between 1966 and December 2009 were analyzed. Reoperation for patellofemoral problems was significantly more likely in the nonresurfacing group (P = 0.03). There was no difference between the two groups in terms of anterior knee pain rate, knee pain score, knee society score and knee function score. The results indicate that patellar resurfacing would reduce the risk of reoperation after total knee replacement, but it seems that the benefits are limited on other aspects, and the analysis of high-quality studies shows no advantage of resurfacing over nonresurfacoing group, even in the aspect of reoperation risk. More carefully and scientifically designed RCTs are beneficial and necessary to further prove the results.     

Length of stay and short-term functional outcomes after total knee arthroplasty: Can we predict them?

Background

To identify variables influencing length of stay (LOS) and short-term functional outcome in patients undergoing total knee arthroplasty (TKA). A secondary aim was to verify the effect of the same variables on blood management and the rate of postoperative infection.

Staged total knee arthroplasty for bilateral complex knee deformities from Kashin–Beck disease and skeletal dysplasia

This study reported two cases of patients with Grade III Kashin–Beck disease (KBD) with skeletal dysplasia concomitant with complex knee deformity and functional limitation treated by staged total knee arthroplasty (TKA). Detailed pre-operative planning, bone resection, and soft tissue balancing in affected knees were performed in the surgeries in this report. The results demonstrated that TKA could correct lower limb alignment, alleviate knee pain, improve function, and provide good quality of life in people with KBD. Surgical efficacy is still lower compared with treatment for osteoarthritis; contributing factors include weak muscle strength, severe deformity and unequal length of the lower limb, weak extensor apparatus of the knee, and patient-specific factors.     

Synthetic mesh vs. allograft extensor mechanism reconstruction in total knee arthroplasty — A systematic review of the literature and meta-analysis

Background: Extensor mechanism disruption after total knee arthroplasty (TKA) is a devastating complication. Reconstruction with allograft and synthetic mesh has been described. However, these reports have typically been small case series, and controversy exists with regard to which reconstruction technique is optimal.Methods: The authors performed a systematic review using PUBMED, MEDLINE, EMBASE, BIOSIS, Clinicaltrials.gov, and Cochrane Database of Systematic Reviews identifying 14 articles meeting inclusion criteria and producing 204 knees for comparison. Studies with repairs performed under full knee extension were included. Case reports and non-English studies were excluded. Available demographics and clinical outcome data were collected from each study. Appropriate statistical analysis was performed to compare the variables.Results: Baseline demographics and patient complexity were similar between the two cohorts. Reconstruction success rates (76% allograft vs. 74% mesh), average time to diagnosis/treatment, Knee Society Scores (KSS), knee range of motion/extensor lag, and complication rates yielded no statistical difference. Synthetic mesh was used more frequently with concomitant revision of components.Discussion: This systematic review shows equivalent success of allograft and synthetic mesh with approximately 25% failure rate in both groups. Periprosthetic joint infection remains a common and significant complication and reason for failure in both groups. Overall, synthetic mesh showed equivalent extensor mechanism reconstruction success as allograft but with much lower cost, near universal availability, lack of disease transmission, and potential for diminishing graft stretch-out. Future research in larger case series or comparative study is needed to help aid in management of this largely unsolved problem in total knee reconstruction.     

The 'anvil' osteophyte-a primary cause of fixed flexion of the knee?

Three cases are reported in which clinical presentation was with arthritic symptoms and inability to straighten the knee. An unusually prominent anterior tibial osteophyte, whose shape is remarkably suggestive of a blacksmith's anvil, appeared to be a contributory factor through its apparent impingement with the femoral trochlea at the limit of extension. The osteophyte was radically removed arthroscopically in each case as an isolated gesture, and the patients were followed up with particular emphasis on fixed flexion deformity. At clinical review, after a mean follow-up period of 5.3 years, it was concluded that there had not been a convincing or sustained improvement in knee function, although the fixed flexion deformities had not increased significantly. Our conclusion is that the 'anvil' osteophyte may simply be a part of a more diffuse degenerative process and that it was probably not, in itself, the primary cause of fixed flexion deformity in these cases.     

LCS mobile bearing total knee arthroplasty without patellar resurfacing. Does the unresurfaced patella affect outcome? Survivorship at a minimum 10-year follow-up

BackgroundPatellar resurfacing during total knee arthroplasty (TKA) remains controversial. The aim of this study was to evaluate the long-term outcomes of a mobile-bearing TKA without patellar resurfacing.MethodsWe assessed the outcomes in 503 patients (600 knees) who had cemented LCS (low contact stress) mobile bearing TKA without patellar resurfacing at a minimum follow-up of 10 years. Clinical outcome scores and radiological assessment were used.ResultsFour knees were revised, two had bearing dislocation and nine patients (1.5%) had secondary resurfacing for anterior knee pain. There were no radiolucent lines or osteolytic defects on radiographic evaluation.The overall survivorship was 97.8% with re-operation for any reason as the endpoint.ConclusionNon-resurfacing of the patella does not adversely affect the outcome of the LCS mobile bearing TKA at minimum 10 years follow-up.     

Short term patient outcomes after total knee arthroplasty: Does the implant matter?

BackgroundNewer implants for total knee arthroplasty (TKA) often gain market share at higher cost with little patient-reported and long-term clinical data. We compared outcomes after TKA using two different implants: DePuy PFC Sigma and Attune.MethodsUsing a prospective data repository from an academic tertiary medical center, we analyzed 2116 TKAs (1603 Sigma and 513 Attune) from April 2011 through July 2016. Outcomes included length of surgery, length of stay, facility discharge, 90-day reoperation, range of motion (ROM) change, and patient-reported physical function (PCS).ResultsThere was no difference in length of surgery (Attune ? 2.87 min, P = 0.143). Implant type was not associated with extended LOS (> 3 days) (OR 0.80, P = 0.439). There was no difference in facility discharge (OR 0.65, P = 0.103). Unadjusted 90-day reoperations were 0.3% for Sigma and 1.0% for Attune cohorts (P = 0.158). Sigma implants were associated with more ROM improvement in unadjusted analyses (+ 2.1 degree improvement P = 0.031). Fifty nine percent of the Sigma cohort and 49% of the Attune cohort achieved the minimal clinically important (MCID) change for PCS improvement, although there was no adjusted difference in achieving MCID (Attune OR 0.84, P = 0.435). There was no adjusted difference in absolute PCS improvement (Attune + 0.12 score, P = 0.864).ConclusionsOur data show no difference in physical function and most outcomes between Sigma and Attune. Attune implants had shorter absolute LOS, but there were no differences in extended LOS.     

Retain or sacrifice the posterior cruciate ligament in total knee arthroplasty? A histopathological study of the cruciate ligament in osteoarthritic and rheumatoid disease

BACKGROUND: The decision whether to retain or resect the posterior cruciate ligament in total knee arthroplasty is at present determined clinically by preoperative radiological variables focusing upon the amount of joint destruction, and subsequent soft tissue contractures. However, these variables give only indirect information on the histological integrity and proprioceptive properties of the posterior cruciate ligament. METHODS: Twenty posterior cruciate ligaments, obtained during total knee arthroplasty, were evaluated histologically to study the relation between the degree of preoperative radiological joint destruction, structural integrity of the posterior cruciate ligament and the neurological integrity of the targeted tissue. Eleven patients had osteoarthritis and nine patients rheumatoid arthritis. Haematoxylin and eosin, Alcian blue (mucoid degeneration), elastica von Gieson, Gomori (elastic fibres and collagen), and immunohistochemical staining for neural structures were used. RESULTS: In all but one of the posterior cruciate ligaments, morphologically intact neural tissue was present in the peritendineum of the ligaments. Structural integrity of the collagen framework was present in only seven posterior cruciate ligaments. These cases all had grade three or four radiological joint destruction. In 13 of the specimens a certain degree of mucoid degeneration of collagen was present. All patients with grade five radiological knee joint destruction displayed mucoid degeneration and irregularity of the posterior cruciate ligament fibres. CONCLUSION: Because of the extensive architectural and probably functional damage of the posterior cruciate ligament in patients who have grade five radiological knee joint destruction, retention of the posterior cruciate ligament in knee prosthesis should not be advocated.     

Mobile bearing medial unicompartmental knee arthroplasty in patients whose lifestyles involve high degrees of knee flexion: A 10–14 year follow-up study

Background

Because Asian populations have different lifestyles, such as squatting and sitting on the floor, from those of Western populations, it is possible that the clinical results and survival rate of unicompartmental knee arthroplasty (UKA) for Asian patients may be different. This study described outcomes of mobile bearing medial UKA for Korean patients.

Radiographic assessment of knee–ankle alignment after total knee arthroplasty for varus and valgus knee osteoarthritis

Background

There are unanswered questions about knee–ankle alignment after total knee arthroplasty (TKA) for varus and valgus osteoarthritis (OA) of the knee. The aim of this retrospective study was to assess knee–ankle alignment after TKA.

A case for one-stage revision in infected total knee arthroplasty?

Infection in total knee replacement is a rare but devastating complication. The current literature tends to support a two-stage revision as definitive treatment of established deep infection. Despite the fact that single stage revision is a well recognised treatment for the infected hip replacement, it has not gained the same level of support in the knee.This article reviews the literature of two-stage and single stage revision and reports the senior author's experience with the latter.     

Preoperative or postoperative self-efficacy: Which is a better predictor of outcome after total hip or knee arthroplasty?

OBJECTIVE: Self-efficacy is considered an important determinant of outcome after total hip or knee arthroplasty. Aim of this study is to evaluate the contributions of preoperative and short-term postoperative self-efficacy in predicting long-term outcome. METHODS: Self-efficacy was determined in 103 total hip and knee arthroplasty patients preoperatively and 6 weeks postoperatively with the Self-Efficacy for Rehabilitation Outcome Scale (SER). The 6-month outcome was assessed with a disease-specific and a generic self-report questionnaire and an objective measure of function (walking speed). Multiple linear regression analyses were used to examine the value of preoperative and short-term postoperative self-efficacy in predicting 6-month outcomes. RESULTS: Preoperative self-efficacy was only a significant predictor of long-term postoperative walking speed, with higher self-efficacy resulting in faster walking speed at the long-term measurement (R(2)=0.47). Short-term postoperative self-efficacy was a significant predictor of the long-term postoperative generic outcome measure (physical functioning: R(2)=0.30; mental health: R(2)=0.53) and of walking speed (R(2)=0.66), with higher self-efficacy resulting in a better long-term outcome. CONCLUSION: Short-term postoperative self-efficacy seems a better predictor of long-term outcome after total hip or knee arthroplasty than preoperative self-efficacy. PRACTICE IMPLICATIONS: Interventions should focus on enhancing short-term postoperative rather than preoperative self-efficacy.     

Does overstuffing of the patellofemoral joint in total knee arthroplasty have a significant effect on postoperative outcomes?

Background

There is ongoing debate in the literature as to whether or not patellofemoral joint overstuffing has a clinically significant effect on postoperative outcomes following total knee arthroplasty (TKA). This study investigates the effect of patellofemoral joint overstuffing on patient-reported outcomes using novel methods of radiographic measurement.