There are many reasons why a total knee replacement
(TKR) may fail and qualify for revision. Successful revision surgery
depends as much on accurate assessment of the problem TKR as it
does on revision implant design and surgical technique. Specific
modes of failure require specific surgical solutions. Causes of
failure are often presented as a list or catalogue, without a system
or process for making a decision. In addition, strict definitions
and consensus on modes of failure are lacking in published series
and registry data. How we approach the problem TKR is an essential
but neglected aspect of understanding knee replacement surgery.
It must be carried out systematically, comprehensively and efficiently.
Eight modes of failure are described: 1) sepsis; 2) extensor discontinuity;
3) stiffness; 4) tibial- femoral instability; 5) patellar tracking;
6) aseptic loosening and osteolysis; 7) periprosthetic fracture
and 8) component breakage. A ninth ‘category’, unexplained pain
is an indication for further investigation but not surgery. Cite this article:
We have reviewed the literature to establish the role of lateral retinacular release in the management of disorders of the extensor apparatus of the knee. The scientific evidence for intervention is explored and reports on outcome are discussed.
Substantial healthcare resources have been devoted
to computer navigation and patient-specific instrumentation systems
that improve the reproducibility with which neutral mechanical alignment
can be achieved following total knee replacement (TKR). This choice of
alignment is based on the long-held tenet that the alignment of
the limb post-operatively should be within 3° of a neutral mechanical
axis. Several recent studies have demonstrated no significant difference
in survivorship when comparing well aligned Review of the literature suggests that a neutral mechanical axis
remains the optimal guide to alignment. Cite this article:
Nail patella syndrome (NPS) is a skeletal dysplasia with patellofemoral
dysfunction as a key symptom. We present the first in-depth radiological
evaluation of the knee in a large series of NPS patients and describe
the typical malformations. Conventional radiological examination of 95 skeletally mature
patients with NPS was performed. Patellar morphology was classified
according to the Wiberg classification as modified by Baumgartl
and Ficat criteria, and trochlear shape was classified according
to the Dejour classification.Aim
Patients and Methods
During open orthopaedic surgery, joints may be exposed to air, potentially leading to cartilage drying and chondrocyte death, however, the long-term effects of joint drying The patellar groove of anaesthetised rats was exposed (sham-operated), or exposed and then subjected to laminar airflow (0.25m/s; 60 minutes) before wounds were sutured and animals recovered. Animals were monitored for up to eight weeks and then sacrificed. Cartilage and chondrocyte properties were studied by histology and confocal microscopy, respectively.Objectives
Methods
Excessive foot pronation has been considered to be related to anterior knee pain. We undertook a prospective study to test the hypothesis that exertional anterior knee pain is related to the static and dynamic parameters of foot pronation. Two weeks before beginning basic training lasting for 14 weeks, 473 infantry recruits were enrolled into the study and underwent two-dimensional measurement of their subtalar joint displacement angle during walking on a treadmill. Of the 405 soldiers who finished the training 61 (15%) developed exertional anterior knee pain. No consistent association was found between the incidence of anterior knee pain and any of the parameters of foot pronation. While a statistically significant association was found between anterior knee pain and pronation velocity (left foot, p = 0.05; right foot, p = 0.007), the relationship was contradictory for the right and left foot. Our study does not support the hypothesis that anterior knee pain is related to excessive foot pronation.
The August 2012 Knee Roundup360 looks at: meniscal defects and a polyurethane scaffold; which is best between a single or double bundle; OA of the knee; how to resolve anterior knee pain; whether yoga can be bad for your menisci; metal ions in the serum; whether ACI is any good; the ACL; whether hyaluronic acid delays collagen degradation; and hyaluronan and patellar tendinopathy.
As part of the national initiative to reduce
waiting times for joint replacement surgery in Wales, the Cardiff
and Vale NHS Trust referred 224 patients to the NHS Treatment Centre
in Weston-Super-Mare for total knee replacement (TKR). A total of
258 Kinemax TKRs were performed between November 2004 and August
2006. Of these, a total of 199 patients (232 TKRs, 90%) have been
followed up for five years. This cohort was compared with 258 consecutive
TKRs in 250 patients, performed at Cardiff and Vale Orthopaedic
Centre (CAVOC) over a similar time period. The five year cumulative
survival rate was 80.6% (95% confidence interval (CI) 74.0 to 86.0)
in the Weston-Super-Mare cohort and 95.0% (95% CI 90.2 to 98.2)
in the CAVOC cohort with revision for any reason as the endpoint.
The relative risk for revision at Weston-Super-Mare compared with
CAVOC was 3.88 (p <
0.001). For implants surviving five years,
the mean Oxford knee scores (OKS) and mean EuroQol (EQ-5D) scores
were similar (OKS: Weston-Super-Mare 29 (2 to 47) The results show a higher revision rate for patients operated
at Weston-Super-Mare Treatment Centre, with a reduction in functional
outcome and quality of life after revision. This further confirms
that patients moved from one area to another for joint replacement
surgery fare poorly.
The June 2014 Knee Roundup360 looks at: acute repair preferable in hamstring ruptures; osteoarthritis a given in ACL injury, even with reconstruction?; chicken and egg: patellofemoral dysfunction and hip weakness; meniscal root tears as bad as we thought; outcomes in the meniscus; topical NSAIDs have a measurable effect on synovitis; nailing for tibial peri-prosthetic fracture.
The low contact stress patellofemoral replacement consists of a trochlear component and a modular patellar component which has a metal-backed mobile polyethylene bearing. We present the early results of the use of this prosthesis for established isolated patellofemoral arthritis in 51 consecutive patellofemoral replacements in 35 patients. The mean follow-up was 25 months (5 to 60). The estimated survival rate at three years was 63% (95% confidence interval 47 to 80) with revision as the endpoint and 46% (95% confidence interval 30 to 63) with revision and ongoing moderate or severe pain as the endpoint. The early results of the use of the low contact stress patellofemoral replacement are disappointing with a high rate of revision. We cannot therefore recommend its use.
Although it is clear that opening-wedge high
tibial osteotomy (HTO) changes alignment in the coronal plane, which is
its objective, it is not clear how this procedure affects knee kinematics
throughout the range of joint movement and in other planes. Our research question was: how does opening-wedge HTO change
three-dimensional tibiofemoral and patellofemoral kinematics in
loaded flexion in patients with varus deformity?Three-dimensional
kinematics were assessed over 0° to 60° of loaded flexion using
an MRI method before and after opening-wedge HTO in a cohort of
13 men (14 knees). Results obtained from an iterative statistical
model found that at six and 12 months after operation, opening-wedge
HTO caused increased anterior translation of the tibia (mean 2.6
mm, p <
0.001), decreased proximal translation of the patella
(mean –2.2 mm, p <
0.001), decreased patellar spin (mean –1.4°,
p <
0.05), increased patellar tilt (mean 2.2°, p <
0.05) and
changed three other parameters. The mean Western Ontario and McMaster
Universities Arthritis Index improved significantly (p <
0.001)
from 49.6 (standard deviation ( The three-dimensional kinematic changes found may be important
in explaining inconsistency in clinical outcomes, and suggest that
measures in addition to coronal plane alignment should be considered. 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
This study used CT analysis to determine the rotational alignment of 39 painful and 26 painless fixed-bearing total knee replacements (TKRs) from a cohort of 740 NexGen Legacy posterior-stabilised and cruciate-retaining prostheses implanted between May 1996 and August 2003. The mean rotation of the tibial component was 4.3° of internal rotation (25.4° internal to 13.9° external rotation) in the painful group and 2.2° of external rotation (8.5° internal to 18.2° external rotation) in the painfree group (p = 0.024). In the painful group 17 tibial components were internally rotated more than 9° compared with none in the painfree group (p <
0.001). Additionally, six femoral components in the painful group were internally rotated more than 6° compared with none in the painfree group (p = 0.017). External rotational errors were not found to be associated with pain. Overall, 22 (56.4%) of the painful TKRs had internal rotational errors involving the femoral, the tibial or both components. It is estimated that at least 4.6% of all our TKRs have been implanted with significant internal rotational errors.
We have investigated the errors in the identification of the transepicondylar axis and the anteroposterior axis between a minimally-invasive and a conventional approach in four fresh-frozen cadaver knees. The errors in aligning the femoral prosthesis were compared with the reference transepicondylar axis as established by CT. The error in the identification of the transepicondylar axis was significantly higher in the minimal approach (4.5° of internal rotation,
Although it has been suggested that the outcome
after revision of a unicondylar knee replacement (UKR) to total knee
replacement (TKR) is better when the mechanism of failure is understood,
a comparative study on this subject has not been undertaken. A total of 30 patients (30 knees) who underwent revision of their
unsatisfactory UKR to TKR were included in the study: 15 patients
with unexplained pain comprised group A and 15 patients with a defined
cause for pain formed group B. The Oxford knee score (OKS), visual
analogue scale for pain (VAS) and patient satisfaction were assessed before
revision and at one year after revision, and compared between the
groups. The mean OKS improved from 19 (10 to 30) to 25 (11 to 41) in
group A and from 23 (11 to 45) to 38 (20 to 48) in group B. The
mean VAS improved from 7.7 (5 to 10) to 5.4 (1 to 8) in group A
and from 7.4 (2 to 9) to 1.7 (0 to 8) in group B. There was a statistically
significant difference between the mean improvements in each group
for both OKS (p = 0.022) and VAS (p = 0.002). Subgroup analysis
in group A, performed in order to define a patient factor that predicts
outcome of revision surgery in patients with unexplained pain, showed
no pre-operative differences between both subgroups. These results may be used to inform patients about what to expect
from revision surgery, highlighting that revision of UKR to TKR
for unexplained pain generally results in a less favourable outcome
than revision for a known cause of pain. Cite this article:
The advent of computer-assisted knee replacement surgery has focused interest on the alignment of the components. However, there is confusion at times between the alignment of the limb as a whole and that of the components. The interaction between them is discussed in this article. Alignment is expressed relative to some reference axis or plane and measurements will vary depending on what is selected as the reference. The validity of different reference axes is discussed. Varying prosthetic alignment has direct implications for surrounding soft-tissue tension. In this context the interaction between alignment and soft-tissue balance is explored and the current knowledge of the relationship between alignment and outcome is summarised.
One of the most controversial issues in total knee replacement is whether or not to resurface the patella. In order to determine the effects of different designs of femoral component on the conformity of the patellofemoral joint, five different knee prostheses were investigated. These were Low Contact Stress, the Miller-Galante II, the NexGen, the Porous-Coated Anatomic, and the Total Condylar prostheses. Three-dimensional models of the prostheses and a native patella were developed and assessed by computer. The conformity of the curvature of the five different prosthetic femoral components to their corresponding patellar implants and to the native patella at different angles of flexion was assessed by measuring the angles of intersection of tangential lines. The Total Condylar prosthesis had the lowest conformity with the native patella (mean 8.58°; 0.14° to 29.9°) and with its own patellar component (mean 11.36°; 0.55° to 39.19°). In the other four prostheses, the conformity was better (mean 2.25°; 0.02° to 10.52°) when articulated with the corresponding patellar component. The Porous-Coated Anatomic femoral component showed better conformity (mean 6.51°; 0.07° to 9.89°) than the Miller-Galante II prosthesis (mean 11.20°; 5.80° to 16.72°) when tested with the native patella. Although the Nexgen prosthesis had less conformity with the native patella at a low angle of flexion, this improved at mid (mean 3.57°; 1.40° to 4.56°) or high angles of flexion (mean 4.54°; 0.91° to 9.39°), respectively. The Low Contact Stress femoral component had the best conformity with the native patella (mean 2.39°; 0.04° to 4.56°). There was no significant difference (p >
0.208) between the conformity when tested with the native patella or its own patellar component at any angle of flexion. The geometry of the anterior flange of a femoral component affects the conformity of the patellofemoral joint when articulating with the native patella. A more anatomical design of femoral component is preferable if the surgeon decides not to resurface the patella at the time of operation.
Ensuring correct rotation of the femoral component
is a challenging aspect of patellofemoral replacement surgery. Rotation
equal to the epicondylar axis or marginally more external rotation
is acceptable. Internal rotation is associated with poor outcomes.
This paper comprises two studies evaluating the use of the medial
malleolus as a landmark to guide rotation. We used 100 lower-leg anteroposterior radiographs to evaluate
the reliability of the medial malleolus as a landmark. Assessment
was made of the angle between the tibial shaft and a line from the
intramedullary rod entry site to the medial malleolus. The femoral
cut was made in ten cadaver knees using the inferior tip of the
medial malleolus as a landmark for rotation. Rotation of the cut
relative to the anatomical epicondylar axis was assessed using CT.
The study of radiographs found the position of the medial malleolus
relative to the tibial axis is consistent. Using the inferior tip
of the medial malleolus in the cadaver study produced a mean external
rotation of 1.6° (0.1° to 3.7°) from the anatomical epicondylar
axis. Using the inferior tip of the medial malleolus to guide the
femoral cutting jig avoids internal rotation and introduces an acceptable
amount of external rotation of the femoral component.
Modern athletes are constantly susceptible to performance-threatening injury as they push their bodies to greater limits and endure higher physical stresses. Loss of performance and training time can adversely and permanently affect a sportsperson’s career. Now more than ever with advancing medical technology the answer may lie in biologic therapy. We have been using peripheral blood stem cells (PBSC) clinically and have been able to demonstrate that stem cells differentiate into target cells to enable regenerative repair. The potential of this technique as a regenerative agent can be seen in three broad applications: 1) articular cartilage, 2) bone and 3) soft tissue. This article highlights the successful cases, among many, in all three of these applications.