Unicompartmental knee arthroplasty (UKA) has
advantages over total knee arthroplasty but national joint registries report
a significantly higher revision rate for UKA. As a result, most
surgeons are highly selective, offering UKA only to a small proportion
(up to 5%) of patients requiring arthroplasty of the knee, and consequently
performing few each year. However, surgeons with large UKA practices
have the lowest rates of revision. The overall size of the practice
is often beyond the surgeon’s control, therefore case volume may
only be increased by broadening the indications for surgery, and
offering UKA to a greater proportion of patients requiring arthroplasty
of the knee. The aim of this study was to determine the optimal UKA usage
(defined as the percentage of knee arthroplasty practice comprised
by UKA) to minimise the rate of revision in a sample of 41 986 records
from the for National Joint Registry for England and Wales (NJR). UKA usage has a complex, non-linear relationship with the rate
of revision. Acceptable results are achieved with the use of 20%
or more. Optimal results are achieved with usage between 40% and
60%. Surgeons with the lowest usage (up to 5%) have the highest
rates of revision. With optimal usage, using the most commonly used
implant, five-year survival is 96% (95% confidence interval (CI)
94.9 to 96.0), compared with 90% (95% CI 88.4 to 91.6) with low
usage (5%) previously considered ideal. The rate of revision of UKA is highest with low usage, implying
the use of narrow, and perhaps inappropriate, indications. The widespread
use of broad indications, using appropriate implants, would give
patients the advantages of UKA, without the high rate of revision. Cite this article:
We compared patient-reported outcomes of the Kinemax fixed- and mobile-bearing total knee replacement in a multi-centre randomised controlled trial. Patients were randomised to the fixed- or the mobile-bearing prosthesis via a sealed envelope method after the bone cuts had been made in the operating theatre. Randomisation was stratified by centre and diagnosis. Patients were assessed pre-operatively and at eight to 12 weeks, one year and two years post-operatively. Validated questionnaires were used which included the Western Ontario MacMasters University, Short-Form 12, Mental Health Index-5, Knee Injury and Osteoarthritis Outcome Score for Knee-Related Quality of Life and Function in Sport and Recreation scales and a validated scale of satisfaction post-operatively. In total, 242 patients (250 knees) with a mean age of 68 years (40 to 80) were recruited from four NHS orthopaedic centres. Of these, 132 patients (54.5%) were women. No statistically significant differences could be identified in any of the patient-reported outcome scores between patients who received the fixed-bearing or the mobile-bearing knee up to two-years post-operatively.
As many as 25% to 40% of unicompartmental knee
replacement (UKR) revisions are performed for pain, a possible cause
of which is proximal tibial strain. The aim of this study was to
examine the effect of UKR implant design and material on cortical
and cancellous proximal tibial strain in a synthetic bone model.
Composite Sawbone tibiae were implanted with cemented UKR components
of different designs, either all-polyethylene or metal-backed. The tibiae
were subsequently loaded in 500 N increments to 2500 N, unloading
between increments. Cortical surface strain was measured using a
digital image correlation technique. Cancellous damage was measured
using acoustic emission, an engineering technique that detects sonic
waves (‘hits’) produced when damage occurs in material. Anteromedial cortical surface strain showed significant differences
between implants at 1500 N and 2500 N in the proximal 10 mm only
(p <
0.001), with relative strain shielding in metal-backed implants.
Acoustic emission showed significant differences in cancellous bone
damage between implants at all loads (p = 0.001). All-polyethylene implants
displayed 16.6 times the total number of cumulative acoustic emission
hits as controls. All-polyethylene implants also displayed more
hits than controls at all loads (p <
0.001), more than metal-backed
implants at loads ≥ 1500 N (p <
0.001), and greater acoustic
emission activity on unloading than controls (p = 0.01), reflecting
a lack of implant stiffness. All-polyethylene implants were associated
with a significant increase in damage at the microscopic level compared
with metal-backed implants, even at low loads. All-polyethylene
implants should be used with caution in patients who are likely
to impose large loads across their knee joint. Cite this article:
Our study aimed to examine if a mobile-bearing total knee replacement
(TKR) offered an advantage over fixed-bearing designs with respect
to rates of secondary resurfacing of the patella in knees in which
it was initially left unresurfaced. We examined the 11-year report of the New Zealand Joint Registry
and identified all primary TKR designs that had been implanted in
>
500 knees without primary resurfacing of the patella. We examined
how many of these were mobile-bearing, fixed-bearing cruciate-retaining
and fixed-bearing posterior-stabilised designs. We assessed the rates
of secondary resurfacing of the patella for each group and constructed
Kaplan-Meier survival curves.Objectives
Methods
We evaluated the rates of survival and cause
of revision of seven different brands of cemented primary total
knee replacement (TKR) in the Norwegian Arthroplasty Register during
the years 1994 to 2009. Revision for any cause, including resurfacing
of the patella, was the primary endpoint. Specific causes of revision
were secondary outcomes. Three posterior cruciate-retaining (PCR) fixed modular-bearing
TKRs, two fixed non-modular bearing PCR TKRs and two mobile-bearing
posterior cruciate-sacrificing TKRs were investigated in a total
of 17 782 primary TKRs. The median follow-up for the implants ranged
from 1.8 to 6.9 years. Kaplan-Meier 10-year survival ranged from
89.5% to 95.3%. Cox’s relative risk (RR) was calculated relative
to the fixed modular-bearing Profix knee (the most frequently used
TKR in Norway), and ranged from 1.1 to 2.6. The risk of revision
for aseptic tibial loosening was higher in the mobile-bearing LCS
Classic (RR 6.8 (95% confidence interval (CI) 3.8 to 12.1)), the
LCS Complete (RR 7.7 (95% CI 4.1 to 14.4)), the fixed modular-bearing
Duracon (RR 4.5 (95% CI 1.8 to 11.1)) and the fixed non-modular
bearing AGC Universal TKR (RR 2.5 (95% CI 1.3 to 5.1)), compared
with the Profix. These implants (except AGC Universal) also had
an increased risk of revision for femoral loosening (RR 2.3
(95% CI 1.1 to 4.8), RR 3.7 (95% CI 1.6 to 8.9), and RR 3.4 (95%
CI 1.1 to 11.0), respectively). These results suggest that aseptic
loosening is related to design in TKR. Cite this article:
We performed a retrospective review of a consecutive
series of 178 Mobility total ankle replacements (TARs) performed
by three surgeons between January 2004 and June 2009, and analysed
radiological parameters and clinical outcomes in a subgroup of 129
patients. The mean follow-up was 4 years (2 to 6.3). A total of
ten revision procedures (5.6%) were undertaken. The mean Ankle Osteoarthritis
Scale (AOS) pain score was 17 (0 to 88) and 86% of patients were
clinically improved at follow-up. However, 18 patients (18 TARs,
14%) had a poor outcome with an AOS pain score of >
30. A worse
outcome was associated with a pre-operative diagnosis of post-traumatic degenerative
arthritis. However, no pre- or post-operative radiological parameters
were significantly associated with a poor outcome. Of the patients
with persistent pain, eight had predominantly medial-sided pain.
Thirty TARs (29%) had a radiolucency in at least one zone. The outcome of the Mobility TAR at a mean of four years is satisfactory
in >
85% of patients. However, there is a significant incidence
of persistent pain, particularly on the medial side, for which we
were unable to establish a cause. Cite this article:
We performed a systematic review and meta-analysis
of modern total ankle replacements (TARs) to determine the survivorship,
outcome, complications, radiological findings and range of movement,
in patients with end-stage osteoarthritis (OA) of the ankle who
undergo this procedure. We used the methodology of the Cochrane Collaboration,
which uses risk of bias profiling to assess the quality of papers
in favour of a domain-based approach. Continuous outcome scores
were pooled across studies using the generic inverse variance method
and the random-effects model was used to incorporate clinical and
methodological heterogeneity. We included 58 papers (7942 TARs)
with an interobserver reliability (Kappa) for selection, performance,
attrition, detection and reporting bias of between 0.83 and 0.98.
The overall survivorship was 89% at ten years with an annual failure
rate of 1.2% (95% confidence interval (CI) 0.7 to 1.6). The mean
American Orthopaedic Foot and Ankle Society score changed from 40 (95%
CI 36 to 43) pre-operatively to 80 (95% CI 76 to 84) at a mean follow-up
of 8.2 years (7 to 10) (p <
0.01). Radiolucencies were identified
in up to 23% of TARs after a mean of 4.4 years (2.3 to 9.6). The
mean total range of movement improved from 23° (95% CI 19 to 26)
to 34° (95% CI 26 to 41) (p = 0.01). Our study demonstrates that TAR has a positive impact on patients’
lives, with benefits lasting ten years, as judged by improvement
in pain and function, as well as improved gait and increased range
of movement. However, the quality of evidence is weak and fraught
with biases and high quality randomised controlled trials are required
to compare TAR with other forms of treatment such as fusion. Cite this article:
The lateral compartment is predominantly affected
in approximately 10% of patients with osteoarthritis of the knee. The
anatomy, kinematics and loading during movement differ considerably
between medial and lateral compartments of the knee. This in the
main explains the relative protection of the lateral compartment
compared with the medial compartment in the development of osteoarthritis.
The aetiology of lateral compartment osteoarthritis can be idiopathic,
usually affecting the femur, or secondary to trauma commonly affecting
the tibia. Surgical management of lateral compartment osteoarthritis
can include osteotomy, unicompartmental knee replacement and total
knee replacement. This review discusses the biomechanics, pathogenesis
and development of lateral compartment osteoarthritis and its management. Cite this article:
Current analysis of unicondylar knee replacements
(UKRs) by national registries is based on the pooled results of medial
and lateral implants. Consequently, little is known about the differential
performance of medial and lateral replacements and the influence
of each implant type within these pooled analyses. Using data from
the National Joint Registry for England and Wales (NJR) we aimed
to determine the proportion of UKRs implanted on the lateral side
of the knee, and their survival and reason for failure compared
with medial UKRs. By combining information on the side of operation
with component details held on the NJR, we were able to determine
implant laterality (medial
Patient-reported outcome measures (PROMs) are
increasingly being used to assess functional outcome and patient satisfaction.
They provide a framework for comparisons between surgical units,
and individual surgeons for benchmarking and financial remuneration.
Better performance may bring the reward of more customers as patients and
commissioners seek out high performers for their elective procedures.
Using National Joint Registry (NJR) data linked to PROMs we identified
22 691 primary total knee replacements (TKRs) undertaken for osteoarthritis
in England and Wales between August 2008 and February 2011, and
identified the surgical factors that influenced the improvements
in the Oxford knee score (OKS) and EuroQol-5D (EQ-5D) assessment
using multiple regression analysis. After correction for patient
factors the only surgical factors that influenced PROMs were implant
brand and hospital type (both p <
0.001). However, the effects
of surgical factors upon the PROMs were modest compared with patient
factors. For both the OKS and the EQ-5D the most important factors
influencing the improvement in PROMs were the corresponding pre-operative
score and the patient’s general health status. Despite having only
a small effect on PROMs, this study has shown that both implant
brand and hospital type do influence reported subjective functional
scores following TKR. In the current climate of financial austerity,
proposed performance-based remuneration and wider patient choice,
it would seem unwise to ignore these effects and the influence of
a range of additional patient factors.
Between April 2004 and July 2007, we performed 241 primary total knee replacements in 204 patients using the e.motion posterior cruciate-retaining, multidirectional mobile-bearing prosthesis. Of these, 100 were carried out using an image-free navigation system, and the remaining 141 with the conventional technique. We conducted a retrospective study from the prospectively collected data of these patients to assess the early results of this new mobile-bearing design. At a mean follow-up of 49 months (32 to 71), 18 knees (7.5%) had mechanical complications of which 13 required revision. Three of these had a peri-prosthetic fracture, and were removed from the study. The indication for revision in the remaining ten was loosening of the femoral component in two, tibiofemoral dislocation in three, disassociation of the polyethylene liner in four, and a broken polyethyene liner in one. There were eight further mechanically unstable knees which presented with recurrent disassociation of the polyethylene liner. There was no significant difference in the incidence of mechanical instability between the navigation-assisted procedures (8 of 99, 8.1%) and the conventionally implanted knees (10 of 139, 7.2%). In our view, the relatively high rate of mechanical complications and revision within 30 months precludes the further use of new design of knee replacement.
We have examined the results obtained with 72 NexGen legacy posterior stabilised-flex fixed total knee replacements in 47 patients implanted by a single surgeon between March 2003 and September 2004. Aseptic loosening of the femoral component was found in 27 (38%) of the replacements at a mean follow-up of 32 months (30 to 48) and 15 knees (21%) required revision at a mean of 23 months (11 to 45). We compared the radiologically-loose and revised knees with those which had remained well-fixed to identify the factors which had contributed to this high rate of aseptic loosening. Post-operatively, the mean maximum flexion was 136° (110° to 140°) in the loosened group and 125° (95° to 140°) in the well-fixed group (independent These implants allowed a high degree of flexion, but showed a marked rate of early loosening of the femoral component, which was associated with weight-bearing in maximum flexion.
Twenty patients underwent simultaneous bilateral medial unicompartmental knee arthroplasty. Pre-operative hip-knee-ankle alignment and valgus stress radiographs were used to plan the desired post-operative alignment of the limb in accordance with established principles for unicompartmental arthroplasty. In each patient the planned alignment was the same for both knees. Overall, the mean planned post-operative alignment was to 2.3° of varus (0° to 5°). The side and starting order of surgery were randomised, using conventional instrumentation for one knee and computer-assisted surgery for the opposite side. The mean variation between the pre-operative plan and the achieved correction in the navigated and the non-navigated limb was 0.9° ( Assessment of lower limb alignment in the non-navigated group revealed that 12 (60%) were within ± 2° of the pre-operative plan, compared to 17 (87%) of the navigated cases. Computer-assisted surgery significantly improves the post-operative alignment of medial unicompartmental knee arthroplasty compared to conventional techniques in patients undergoing bilateral simultaneous arthroplasty. Improved alignment after arthroplasty is associated with better function and increased longevity.
Mobile-bearing posterior-stabilised knee replacements have been developed as an alternative to the standard fixed- and mobile-bearing designs. However, little is known about the We conclude that mobile-bearing posterior-stabilised knee replacements reproduce internal rotation of the tibia more closely during flexion than fixed-bearing posterior-stabilised designs. Furthermore, mobile-bearing posterior-stabilised knee replacements demonstrate a unidirectional movement which occurs at the upper and lower sides of the mobile insert. The femur moves in an anteroposterior direction on the upper surface of the insert, whereas the movement at the lower surface is pure rotation. Such unidirectional movement may lead to less wear when compared with the multidirectional movement seen in fixed-bearing posterior-stabilised knee replacements, and should be associated with more evenly applied cam-post stresses.