Is closed-suction drain necessary in unicompartmental knee replacement? A prospective randomised study

In a prospective randomised trial we evaluated the use of a post-operative closed-suction drain in unicompartmental knee replacement (UKR). Seventy-eight patients were divided into two groups: one without a post-operative closed-suction drain (Group A) and one with a drain (Group B). Both groups were matched for age, sex and pre-operative haemoglobin. In group A we observed a lower day one post-operative analgesic requirement, smaller knee circumference 3 days post-operatively and less local wound complications. Drain usage in UKR resulted in no significant advantage in post-operative pain, range of motion and hospital stay. Post-operative drainage does, however, increase the cost of the procedure both in labour and equipment expenditure. No deep infections occurred in either group during the follow-up period. We conclude that avoiding post-operative closed-suction drainage in UKR does not influence the outcome.     

Mobile bearing or fixed bearing? A meta-analysis of outcomes comparing mobile bearing and fixed bearing bilateral total knee replacements

BackgroundTo compare outcomes between mobile-bearing (MB) and fixed-bearing (FB) in bilateral total knee replacements.MethodsThe MEDLINE, EMBASE and Cochrane Library databases were searched. Randomized controlled trials of bilateral total knee arthroplasty with one of each design implanted were identified. Weighted mean differences (WMDs) and pooled risk ratios (RRs) were calculated using fixed- or random-effects models.ResultsTwelve studies were identified with a total of 807 patients and 1614 knees. All RCTs were of high quality with a low risk of bias. No statistical difference was found between MB and FB at 2- to 5-year follow-up in terms of America Knee Society score (WMD: − 1.29, 95% CI: − 5.65 to 3.06), pain score (WMD: − 3.26, 95% CI: − 10.45 to 3.93), range of motion (WMD: − 4.16, 95% CI: − 9.97 to 1.66), reoperation (RR: 1.00, 95% CI: 0.28 to 3.60), and radiolucent lines (RR: 1.51, 95% CI: 0.70 to 3.24). The results were similar at 1-, 5- to 8-, or > 8-year follow-up. Patient's satisfaction (RR: 0.85, 95% CI: 0.54 to 1.34), and complication (≤ 2-year, RR: 0.55, 95% CI: 0.29 to 1.04; > 2-year, RR: 1.0, 95% CI = 0.73 to 1.38) also showed no difference between two groups.ConclusionsBased on this meta-analysis we are unable to detect the superiority of MB as compared to FB. More randomized trials with a larger sample size and longer follow-up are needed to evaluate these two kinds of prosthesis.Level of evidenceTherapeutic Level II.     

Fixed bearing lateral unicompartmental knee arthroplasty—Short to midterm survivorship and knee scores for 101 prostheses

BackgroundIsolated unicompartmental knee arthritis is less common laterally than medially. Lateral unicompartmental knee arthroplasty (UKA) constitutes only 1% of all knee arthroplasty performed. Use of medial UKA is supported by several published series showing good long-term survivorship and patient satisfaction, in large patient cohorts. Results of lateral UKA however have been mixed. We present the short and mid-term survivorship and 5-year clinical outcome of 101 lateral UKAs using a single prosthesis.MethodsOver a 9 year period, 100 patients who satisfied inclusion criteria underwent a lateral fixed-bearing unicompartmental arthroplasty. American Knee Society (AKSS), Oxford Knee (OKS) and modified Western Ontario McMaster Universities Arthritis Index (WOMAC) scores were completed preoperatively and at 1, 2 and 5 years postoperatively. Kaplan–Meier survival analysis was used to determine the 2-year and 5-year survivorship, using revision for any cause as end point.ResultsSurvivorship was 98.7% and 95.5% at 2 and 5 years respectively. 1 knee was revised for subsidence of the tibial component and 1 knee for progression of medial compartment osteoarthritis. Of a possible 35 knees in situ at 5 year follow-up, 33 knees were fully scored. Median AKSS, OKS and modified WOMAC scores were 182, 41, and 16 respectively.ConclusionsThe mid-term survivorship and outcome scores at 5-years suggest that lateral unicompartmental knee arthroplasty provides a valuable alternative to total joint replacement in selected patients with isolated lateral tibio-femoral arthritis at mid-term follow-up.Level II evidence.     

Revision of medial Oxford unicompartmental knee replacement to a total knee replacement: Similar to a primary?

Unicompartmental knee replacement (UKR) is an option for the treatment of isolated medial compartment osteoarthritis. A commonly perceived potential advantage is that revision of a UKR is straightforward. The purpose of this study was to determine the early outcomes and the level of complexity of revisions of Oxford UKRs performed at our hospital. A retrospective review of a prospective database of all phase III Oxford UKRs was undertaken. This identified 89 Oxford UKRs which were revised at our institution between 2002 and 2008. The median time from the primary procedure to revision was 19 months (interquartile range 2-73 months). Nine were revised to another UKR. Eighty were revised to a total knee replacement (TKR). Fifty-three were revised with primary TKR components. Twenty-seven were revised using stems and/or augments. The median overall tibial component thickness (including augments) was 15 mm. Forty-five knees had an overall tibial component thickness greater than 15 mm. A primary Oxford UKR bearing thickness of greater than 6mm was associated with an increased likelihood of requiring revision components. On the basis of this review, tibial bone defects were commonly encountered when revising UKRs. Reconstruction with either an augment and a stem, or thick polyethylene component was often required. We recommend that the potential complexity of revision for UKR failure should be borne in mind when considering a primary Oxford UKR.     

Does body mass index affect the outcome of unicompartmental knee replacement?

BackgroundObesity is considered to be a contraindication for unicompartmental knee replacement (UKR). The aim was to study the impact of BMI on failure rate and clinical outcome of the Oxford mobile bearing UKR.MethodTwo thousand four hundred and thirty-eight medial Oxford UKRs were studied prospectively and divided into groups: BMI < 25 (n = 378), BMI 25 to < 30 (n = 856), BMI 30 to < 35 (n = 712), BMI 35 to < 40 (n = 286), and BMI 40 to < 45 (n = 126) and BMI ≥ 45 (n = 80).ResultsThere was no significant difference in survival rate between groups. At a mean follow-up of 5 years (range 1–12 years) there was no significant difference in the Objective American Knee Society Score between groups. There was a significant (p < 0.01) trend with the Oxford Knee Score (OKS) and Functional American Knee Society Scores decreasing with increasing BMI. As there was an opposite trend (p < 0.01) in pre-operative OKS, the change in OKS increased with increasing BMI (p = 0.048). The mean age at surgery was significantly (p < 0.01) lower in patients with higher BMI.ConclusionsIncreasing BMI was not associated with an increasing failure rate. It was also not associated with a decreasing benefit from the operation. Therefore, a high BMI should not be considered a contra-indication to mobile bearing UKR.Level of evidenceIV     

Tibial component overhang following unicompartmental knee replacement—Does it matter?

As implants are made in incremental sizes and usually do not fit perfectly, surgeons have to decide if it is preferable to over or undersize the components. This is particularly important for unicompartmental knee replacement (UKR) tibial components, as overhang may cause irritation of soft tissues and pain, whereas underhang may cause loosening.One hundred and sixty Oxford UKRs were categorised according to whether they had minor (< 3 mm, 70%) or major (≥ 3 mm, 9%) tibial overhang, or tibial underhang (21%). One year post surgery, there was no significant difference in outcome between the groups. Five years after surgery, those with major overhang had significantly worse Oxford Knee Scores (OKS) (p = 0.001) and pain scores (p = 0.001) than the others. The difference in scores was substantial (OKS = 10 points). There was no difference between the ‘minor overhang’ and the ‘underhang’ group.We conclude that surgeons must avoid tibial component overhang of 3 mm or more, as this severely compromises the outcome. Although this study showed no difference between minor overhang or underhang, we would advise against significant underhang because of the theoretical risk of component subsidence and loosening.     

Reduced invasive approach for Oxford II medial unicompartmental knee replacement — a preliminary study

Nineteen patients (20 knees) who underwent consecutive Oxford Phase II unicompartmental arthroplasty for anteromedial osteo-arthritis were prospectively evaluated to determine whether performing the operation with a reduced exposure improved their functional recovery as compared to the traditional midline skin incision and lateral dislocation of the patella. Alternative knees underwent either approach. In 10 knees, a reduced medial arthrotomy incision was used without dislocations of the patella. In the other 10, a standard paramedial arthrotomy incision was employed with dislocation and eversion of the patella. In the former group post-operative recovery of straight leg raising, flexion to 90° and ability to climb stairs was achieved approximately 3 days earlier than in the second group. No complications occurred and, 3 months after surgery, the two groups had achieved similar recovery. There was no radiological evidence of impaired cementation or orientation of the prostheses implanted through the smaller incision.     

Unusual mechanical complications of unicompartmental low contact stress mobile bearing patellofemoral arthroplasty: A cause for concern?

The Low Contact Stress Patellofemoral Arthroplasty (LCS PFA) is a newer design belonging to the second generation of inlay type implants, addressing the problems encountered in the first generation models (Lubinus & Richard's). The cemented mobile bearing metal backed patellar component in this system is “modular”; allowing interchangeable usage with either the trochlear component in a PFA or the femoral component of a total knee arthroplasty, thus obviating the need for patellar revision during conversion of PFA to TKA. The younger active patient with a PFA may exert extreme joint reaction forces on their patellar implant, rendering early loosening of the patellar implant. The endurance of this implant with repeated flexion beyond 90° is also a concern. We describe a series of three unusual mechanical failures associated with this particular design of metal backed patellar component of the unicompartmental LCS patellofemoral arthroplasty.     

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.

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.     

Medium to long‐term results of the UNIX uncemented unicompartmental knee replacement

IntroductionWe report the first non-designer study of the Unix uncemented unicompartmental knee prosthesis.Materials and methodsEighty-five consecutive UKRs were carried out with sixty-five available for follow-up. Oxford Knee Scores, WOMAC questionnaire and radiological assessment were completed.ResultsThe mean Oxford Knee Score was thirty-eight and WOMAC Score was twenty. Overall Kaplan Meier survival estimate is 76% (95% confidence interval 60%–97%) at 12 years and 88% (95% confidence interval 76–100%) with aseptic loosening as the endpoint. Radiographic assessment showed lysis in the tibia in 6% of patients with no lysis evident around the central fin.DiscussionSurvivorship is comparable to other published series of UKRs. We suggest the central fin design is key to dissipating large forces throughout the proximal tibia, resulting in low levels of tibial loosening.Level of evidence IV.     

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.     

Does 99mTc-MDP bone scintigraphy add to the investigation of patients with symptomatic unicompartmental knee replacement?

AimThe purpose of this study was to determine whether nuclear medicine ^99mTc-Methyl diphosphonate bone scintigraphy (^99mTc-MDP bone scintigraphy) added information over plain radiographs loosening infection in symptomatic unicompartmental knee replacements (UKRs).Methods and materialsA cohort of 39 patients who presented with knee pain following UKR was retrospectively reviewed. All had undergone nuclear medicine bone scans for possible loosening or infection of the prosthesis. The findings of the bone scintigraphy were compared to subsequent operative findings during diagnostic arthroscopic investigation or revision surgery for those patients who had undergone these procedures.ResultsOf the 39 patients with painful knees following UKR, surgical findings confirmed that 11 had either loose (n = 9) or infected (n = 2) implants. Logistic regression analysis demonstrated no statistically significant combination of features on nuclear medicine or radiographs associated with failure of the prosthesis due to infection or loosening (p > 0.05).Classification of a satisfactory position of the UKR on plain radiography exhibited a high negative predictive value (96% for infections, and 80% for loosening). However, plain radiograph was not sensitive for loosening (50%) or infection (37%) of the UKR with very low positive predictive values (9.1% for infection and 27.3% for loosening).ConclusionThis study provides no evidence to support the routine use of ^99mTc-MDP bone scintigraphy in the clinical decision-making for patients with a painful UKR.Level of evidence: level 4.     

Can knee position save blood following total knee replacement?

Previous research showed knee flexion at 70 degrees for 6 h following total knee replacements (TKR) reduced wound drainage by 30%. However, wound drainage may not represent total blood loss and obstruction of the drain in flexion or the relative elevation of the knee could have caused the reduction in drainage. We wished to confirm that this simple, cheap method not only reduced wound drainage but also total haemoglobin loss and determine what part elevation or drain obstruction may play. Sixty consecutive TKR patients were randomly allocated to three groups. Group 1-knee extended and level with bed. Group 2-leg elevated 35 degrees at the hip with knee flexed to 70 degrees for 6 h post-operatively. Group 3-leg elevated 35 degrees at the hip with knee extended for 6 h post-operatively. We assessed wound drainage over 48 h, calculated haemoglobin loss, total blood transfusion, pain, arc of motion, swelling, length of hospital stay and complications. We found knee flexion and knee elevation in extension reduced haemoglobin loss by 25%. Compromise to tissue oxygenation has been reported with knee flexion. We recommend elevation of the leg at 35 degrees from the hip with the knee extended. This offers a simple, safe and effective way to reduce total blood loss by 25%.     

Central or local incident reporting? A comparative study in Dutch GP out-of-hours services

Background

Centralised incident reporting in a Dutch collaboration of nine out-of-hours services yielded very few incident reports. To improve incident reporting and the awareness of primary caregivers about patient safety issues, a local incident-reporting procedure was implemented.

Aim

To compare the number and nature of incident reports collected in a local incident-reporting procedure (intervention) versus the currently used centralised incident-reporting procedure.

Design of study

Quasi experiment.

Setting

Three GPs'' out-of-hours services (OHSs) in the centre of the Netherlands participated over 2 years before and 2 years after the intervention.

Method

A local incident-reporting procedure was implemented in OHS1, in which participants were encouraged to report all occurring incidents. A local committee with peers analysed the reported incidents fortnightly in order to initiate improvements if necessary. In OHS2 and OHS3, the current centralised incident-reporting procedure was continued, where incidents were reported to an advisory committee of the board of directors of the OHSs collaboration and were assessed every 2 months. The main outcome measures were the number and nature of incidents reported.

Results

At baseline, participants reported fewer than 10 incidents per year each. In the follow-up period, the number of incidents reported in OHS1 increased 16-fold compared with the controls. The type of incidents reported did not alter. In the local incident-reporting procedure, improvements were implemented in a shorter time frame, but reports in the centralised incident-reporting procedure led to a more systematic addressing of general and recurring safety problems.

Conclusion

It is likely that a local incident-reporting procedure increases the willingness to report and facilitates faster implementation of improvements. In contrast, the central procedure, by collating reports from many settings, seems better at addressing generic and recurring safety issues. The advantages of both approaches should be combined.     

Fixed bearing,all-polyethylene tibia,lateral unicompartmental arthroplasty – A final outcome study with up to 28 year follow-up of a single implant

BackgroundLateral unicompartmental arthroplasty (UKA) constitutes only 5–10% of all unicompartmental replacements performed. Whilst the short and medium term benefits are well documented, there remains concern regarding the higher revision rate when compared with total knee replacement. We report the long term clinical outcome and survivorship of a large series of lateral UKA.Patients and MethodsBetween 1974 and 1994, 71 patients (82 knees) underwent a lateral fixed-bearing St Georg Sled UKA. Prospective data was collected pre-operatively and at regular intervals post-operatively using the Bristol Knee Score (BKS), with later introduction of the Oxford Knee (OKS) and Western Ontario MacMaster (WOMAC) scores. Kaplan Meier survival analysis was used, with revision, or need for revision, as end point. 85% of the patients were female. No patients were lost to follow-up.ResultsFunctional knee scores improved post-operatively up to 10 years, at which point they demonstrated a steady decline. Survivorship was 72% at 15 years, and 68% at 20 and 25 years. Nineteen knees were revised, with progression of disease in another compartment the commonest reason. There were two revisions due to implant fracture. In patients aged over 70 years at time of index procedure, 81% died with a functioning prosthesis in situ.ConclusionThis represents the longest follow-up of a large series of lateral UKA. Results of this early design of fixed bearing UKA demonstrate satisfactory long term survivorship. In elderly patients, further intervention is rarely required. More contemporary designs or techniques may show improved long term survivorship in time.     

The St. Leger total knee replacement. A false economy?

We reviewed the outcome of 53 primary St. Leger total knee replacement (TKR) implanted into 47 patients over a 2-year period from March 1995 and compared the outcome with age and sex matched controls with the Kinemax Plus TKR. All operations were performed to treat osteoarthritis of the knee. The St. Leger replacements were done in a Teaching Hospital by a Consultant surgeon while the Kinemax Plus replacements were done in the same hospital by two other surgical teams. During the period of review, 13 patients (13 knees) with St. Legers died or were too demented to participate, and 4 were lost to follow up. Eleven patients (13 knees) with the Kinemax died or were too demented to cooperate, and 2 patients (2 knees) were lost to follow up. The St. Leger group had inferior Oxford Knee Scores to the Kinemax group but this was not significant. The St. Leger group had significantly worse survivorship of the prosthesis. The St. Leger prosthesis was cheaper (Pound sterling 650) than the Kinemax (Pound sterling 1150). The initial saving was dwarfed by the ultimate cost of revision procedures.     

Does resurfacing of asymptomatic full-thickness localized articular defects of the trochlea influence the outcome following unicompartmental knee arthroplasty of the medial compartment?: A retrospective cohort study with minimum seven-year follow-up

BackgroundPatellofemoral joint (PFJ) degeneration has been found not to affect outcome following medial unicompartmental knee arthroplasty (UKA). However, PFJ disease occasionally presents as isolated trochlear cartilage lesions, with little available evidence regarding treatment options or necessity. We evaluated the effectiveness of concomitant trochlear resurfacing in patients undergoing medial UKA with asymptomatic trochlear lesions.MethodsWe included 60 patients undergoing medial UKA with an associated full thickness lesion of the trochlea. A fixed bearing UKA implant (PKR™, Stryker, Warsaw, IND) was used in all cases. In 30 patients, trochlear lesions were resurfaced with a HemiCAP® PF Classic (HemiCAP® PFC) implant (Arthrosurface, Franklin, MA). Outcome measures included VAS-, KOOS-, WOMAC-, SF-36 scores and radiological assessment.ResultsAverage length of follow-up was 97.4 months (range: 88–106 months). Both groups showed significant improvement for all clinical scores post-operatively compared to pre-operatively (p < 0.001 for all). The UKA group showed a better VAS score at all follow-up moments (p < 0.01 for all), but no differences were found between both groups at all time points for other outcome measures. None of the HemiCAP® PFC implants needed to be revised within the timeframe of the study.ConclusionsIn this retrospective cohort study, we found a 100% survivorship of the HemiCAP® PFC implant at an average eight-year follow-up. However, no clinical benefits were found in performing trochlear resurfacing in conjunction with medial UKA for asymptomatic end-stage trochlear cartilage lesions. Therefore, these lesions can be safely ignored when performing a medial UKA.     

Femoral fixation pattern in cemented Oxford unicompartmental knee arthroplasty — An experimental cadaver study

Femoral component loosening is a rare but serious complication in cemented Oxford unicompartmental knee arthroplasty (OUKA). In a cadaver study, OUKA was performed in 24 knees to evaluate the femoral fixation pattern. Due to the geometry of bone and implant, three different zones were identified. Complete cement mantles and good interdigitation were found in the spherical part of the implant (zone 1) and around the peg (zone 3), which implies that these are most important for implant fixation. The posterior plane facet (zone 2) is the weak point of the interface due to incompleteness of the cement mantle and a lack of interdigitation. This study suggests that the cancellous bone in zone 2 and the drill holes in sclerotic bone areas should be filled with cement and pressurised prior to component seating.     

Is routine splintage following primary total knee replacement necessary? A prospective randomised trial

It was hypothesised that routine splintage following primary total knee replacement has no affect on flexion deformity and offers no benefit over simple wool and crepe. Fifty-five patients undergoing primary total knee replacement were entered into a prospective study. The patients were randomly assigned to two groups: The first group was rehabilitated without a splint and the second received an adjustable semi-rigid extension splint (Richards splint) for the first 48 h after surgery. Range of motion measurements were recorded pre-operatively and at 2 days, 1 week and 3 months post-operation by a research nurse blinded to the allocation. No statistically significant difference in flexion deformity was found at any stage (P>0.5). No difference was found in general or wound complications, or requirement for blood transfusion, and the post-operative stay was equal in the two groups. We conclude that routine use of a semi-rigid splint following primary total knee replacement has no advantage over simple wound dressings.