Unicompartmental knee arthroplasty: is the glass half full or half empty?

There is a large amount of evidence available about the relative merits of unicompartmental and total knee arthroplasty (UKA and TKA). Based on the same evidence, different people draw different conclusions and as a result, there is great variability in the usage of UKA. The revision rate of UKA is much higher than TKA and so some surgeons conclude that UKA should not be performed. Other surgeons believe that the main reason for the high revision rate is that UKA is easy to revise and, therefore, the threshold for revision is low. They also believe that UKA has many advantages over TKA such as a faster recovery, lower morbidity and mortality and better function. They therefore conclude that UKA should be undertaken whenever appropriate. The solution to this argument is to minimise the revision rate of UKA, thereby addressing the main disadvantage of UKA. The evidence suggests that this will be achieved if surgeons use UKA for at least 20% of their knee arthroplasties and use implants that are appropriate for these broad indications

Comparison of outcomes after UKA in patients with and without chondrocalcinosis: a matched cohort study

Purpose: Chondrocalcinosis can be associated with an inflammatory arthritis and aggressive joint destruction. There is uncertainty as to whether chondrocalcinosis represents a contraindication to unicompartmental knee arthroplasty (UKA). This study reports the outcome of a consecutive series of patients with chondrocalcinosis and medial compartment osteoarthritis treated with UKA matched to controls. Methods: Between 1998 and 2008, 88 patients with radiological chondrocalcinosis (R-CCK) and 67 patients with histological chondrocalcinosis (H-CCK) were treated for end-stage medial compartment arthritis with Oxford UKA. One-to-two matching was performed to controls, treated with UKA, but without evidence of chondrocalcinosis. Functional outcome and implant survival were assessed in each group. Results: The mean follow-up was 10 years. The mean Oxford Knee Score (OKS) at final follow-up was 43, 41 and 41 in H-CCK, R-CCK and control groups (change from baseline OKS was 21, 18 and 15, respectively). The change was significantly higher in H-CCK than in control but was not significantly different in R-CCK. Ten-year survival was 96 % in R-CCK, 86 % in H-CCK and 98 % in controls. Although the survival in H-CCK was significantly worse than in control, only one failure was due to disease progression. Conclusion: The presence of R-CCK does not influence functional outcome or survival following UKA. Pre-operative radiological evidence of CCK should not be considered to be a contraindication to UKA. H-CCK is associated with significantly improved clinical outcomes but also a higher revision rate compared with controls. Level of evidence: Case control study, Level III

The interaction of caseload and usage in determining outcomes of unicompartmental knee arthroplasty: A meta-analysis

Background: Outcomes following UKA are variable and influenced by surgical caseload (UKA/year) and usage (percentage of primary knee arthroplasty that are UKA), which relates to indications. This meta-analysis assesses the relative importance of these factors. Methods: MEDLINE (Ovid), Embase (Ovid) and the Web of Science (ISI) were searched for consecutive series of minimally invasive cemented Phase 3 Oxford medial UKA. The primary outcome measure was revision-rate/100 observed component years (%pa). Series were divided into groups according to caseload and usage. Results 46studies, including 12,520 knees, were identified. The annual revision-rate varied from 0%pa to 4.35%pa, mean 1.21%pa (95%CI 0.97-1.47). In series with mean follow-up of ten-years or more the revision-rate was 0.63%pa (95%CI 0.46-0.83), which equates to a ten-year survival of 94% (95%CI 92%-95%). Aseptic loosening, lateral arthritis, bearing dislocation, and unexplained pain were the predominant failure mechanisms with revision for patello-femoral problems and polyethylene wear exceedingly rare (<0.1%). Both increasing caseload (p=0.02) and usage (p<0.001) were associated with decreasing revision-rate. The lowest revision-rates were achieved with a caseload >24 UKA/year (0.88%pa, 95%CI 0.63-1.61) and usage >30% (0.69%pa, 95%CI 0.50-0.90). Usage was more important than caseload: with high-usage (≥20%) the revision-rate was low, whether the caseload was high (>12UKA/year) or low (≤12UKA/year), (0.94%pa (95%CI 0.69-1.23) and 0.85%pa (95%CI 0.65-1.08) respectively); whereas with low-usage (<20%) the revision-rate was high, whether the caseload was high or low (1.58%pa, 95%CI 0.57- 3.05 and 1.76%pa, 95%CI 1.21-2.41). Conclusion: To achieve optimum results with mobile-bearing UKA surgeons, whether high or low-caseload, should adhere to the recommended indications such that ≥20%, or ideally >30% of their knee replacements are UKA. If they do this then they can expect to achieve results similar to those of the long-term series, which all had high-usage (>20%) and an average ten-year survival of 94%

Stiffness in total knee arthroplasty

Stiffness is a relatively uncommon complication after total knee arthroplasty. It has been defined as a painful limitation in the range of movement (ROM). Its pathogenesis is still unclear even if some risk factors have been identified. Patient-related conditions may be difficult to treat. Preoperative ROM is the most important risk factor, but an association with diabetes, reflex sympathetic dystrophy, and general pathologies such as juvenile rheumatoid arthritis and ankylosing spondylitis has been demonstrated. Moreover, previous surgery may be an additional cause of an ROM limitation. Postoperative factors include infections, arthrofibrosis, heterotrophic ossifications, and incorrect rehabilitation protocol. Infections represent a challenging problem for the orthopaedic surgeon, and treatment may require long periods of antibiotics administration. However, it is widely accepted that an aggressive rehabilitation protocol is mandatory for a proper ROM recovery and to avoid the onset of arthrofibrosis and heterotrophic ossifications. Finally, surgery-related factors represent the most common cause of stiffness; they include errors in soft-tissue balancing, component malpositioning, and incorrect component sizing. Although closed manipulation, arthroscopic and open arthrolysis have been proposed, they may lead to unpredictable results and incomplete ROM recovery. Revision surgery must be proposed in the case of well-documented surgical errors. These operations are technically demanding and may be associated with high risk of complications; therefore they should be accurately planned and properly performed

Unicompartmental Knee Arthroplasty: Mobile Magic

Unicompartmental knee arthroplasty has many advantages over total knee arthroplasty, including better function, restoration of normal kinematics, and less morbidity. This paper outlines the design features, indications, contraindications, principles of surgical technique, and long-term results of the Oxford Knee, a mobile-bearing unicompartmental knee arthroplasty. Approximately 1 in 3 patients requiring a knee replacement are appropriate for the Oxford knee. The Oxford Group believes that this is a definitive and not a pre-total knee arthroplasty option provided that appropriate indications and correct surgical technique are used. © 2011 Elsevier Inc

Cementless fixation in medial unicompartmental knee arthroplasty: a systematic review.

Purpose The aim of this study was to evaluate clinical outcome, failures, implant survival and complications encountered with cementless fixation in unicompartmental knee arthroplasty (UKA). Methods A systematic review of the literature on cementless fixation in UKA was performed according to the PRISMA guidelines. The following database were comprehensively searched: PubMed, Cochrane, MEDLINE, CINAHL, Embase, and Google Scholar. The keywords “unicompartmental”, “unicondylar”, “partial knee arthroplasty”, and “UKA” were combined with each of the keyword “uncemented”, “cementless” and “survival”, “complications”, “outcome”. The following data were extracted: demographics, clinical outcome, details of failures and revisions, cumulative survival and complications encountered. The risk of bias of each study was estimated with the MINORS score and a further scoring system based on the presence of the primary outcomes. Results From a cohort of 63 studies identified using the above methodology, ten papers (1199 knees) were included in the final review. The mean follow-up ranged from 2 to 11 years (median 5 years). The 5-year survival ranged from 90% to 99%, and the 10-year survival from 92 to 97%. There were 48 revisions with an overall revision rate of 0.8 per 100 observed component years. The most common cause of failure was progression of osteoarthritis in the retained compartment (0.9%). The cumulative incidence of complications and revisions was comparable to that reported in similar studies on cemented UKAs. The advantages of cementless fixation include faster surgical time, avoidance of cementation errors and lower incidence of radiolucent lines. Conclusions Cementless fixation is a safe and effective alternative to cementation in medial UKA. Clinical outcome, failures, reoperation rate and survival are similar to those reported for cemented implants with lower incidence of radiolucent lines.</p

Unicompartmental knee arthroplasty: is the glass half full or half empty?

There is a large amount of evidence available about the relative merits of unicompartmental and total knee arthroplasty (UKA and TKA). Based on the same evidence, different people draw different conclusions and as a result, there is great variability in the usage of UKA. The revision rate of UKA is much higher than TKA and so some surgeons conclude that UKA should not be performed. Other surgeons believe that the main reason for the high revision rate is that UKA is easy to revise and, therefore, the threshold for revision is low. They also believe that UKA has many advantages over TKA such as a faster recovery, lower morbidity and mortality and better function. They therefore conclude that UKA should be undertaken whenever appropriate. The solution to this argument is to minimise the revision rate of UKA, thereby addressing the main disadvantage of UKA. The evidence suggests that this will be achieved if surgeons use UKA for at least 20% of their knee arthroplasties and use implants that are appropriate for these broad indications

Gait and electromyographic analysis of anterior cruciate ligament deficient subjects

Some anterior cruciate ligament deficient (ACLD) patients can overcome passive sagittal joint laxity and maintain dynamic stability of the knee joint. Gait analysis with electromyographic (EMG) support was used in an attempt to identify mechanisms whereby ACLD individuals achieve this functional stability. A group of 18 patients with arthroscopically proven, unilateral, chronic (&gt; 6 months) ACLD had their gait assessed using a three-dimensional VICON gait analysis system. Simultaneous quadriceps, hamstrings and gastrocnemius muscle activity was recorded using surface electromyography. Values of minimum knee flexion angle and activity duration of leg musculature were calculated for each section of stance phase and compared to a group of nine matched controls. The minimum flexion angle at heel contact and mid-stance was larger for the ACLD group than in controls. Throughout stance phase, the ACLD patients had increased hamstrings activity duration compared to the controls. Quadriceps activity duration was similar in both groups. It was found that the duration of hamstring activity correlated with the flexion angle at foot contact. The similarity in quadriceps activity between groups implies that the previously reported net increase in internal flexion moment observed in ACLD patients during stance phase may not necessarily be due to decreased activity of the quadriceps. Net increase in internal flexion moment may be achieved by the observed increase in hamstrings activity. Mechanisms and reasons why ACLD patients maintain increased knee flexion angles in stance phase are discussed

Most unicompartmental knee replacement revisions could be avoided: a radiographic evaluation of revised Oxford knees in the National Joint Registry

Purpose The purpose of this study was to understand why the revision rate of unicompartmental knee replacement (UKR) in the National Joint Registry (NJR) is so high. Using radiographs, the appropriateness of patient selection for primary surgery, surgical technique, and indications for revision were determined. In addition, the alignment of the radiographs was assessed. Methods Oxford UKR registered with the NJR between 2006 and 2010 and subsequently revised were identified by the NJR. A blinded review was undertaken of pre-primary, post-primary, and pre-revision anteroposterior and lateral radiographs of a sample of 107 cases from multiple centres. Results The recommended indications were satisfied in 70%, with 29% not demonstrating bone-on-bone arthritis. Major technical errors, likely leading to revision, were seen in 6%. Pre-revision radiographs were malaligned and, therefore, difficult to interpret in 53%. No reason for revision was seen in 67%. Reasons for revision included lateral compartment arthritis (10%), tibial loosening (7%), bearing dislocation (7%), infection (6%), femoral loosening (3%), and peri-prosthetic fracture (2%, one femoral, one tibial). Conclusions Only 20% of the revised UKR were implanted for the recommended indications, using appropriate surgical technique and had a mechanical problem necessitating revision. One-third of primary surgeries were undertaken in patients with early arthritis, which is contraindicated. Two-thirds were presumably revised for unexplained pain, which is not advised as it tends not to help the pain. This study suggests that variable and inappropriate indications for primary and revision surgery are responsible for the high rates of revision seen in registries. Level of evidence III, Therapeutic study