Little biomechanical information is available about kinematically aligned (KA) total knee arthroplasty (TKA). The purpose of this study was to simulate the kinematics and kinetics after KA TKA and mechanically aligned (MA) TKA with four different limb alignments. Bone models were constructed from one volunteer (normal) and three patients with three different knee deformities (slight, moderate and severe varus). A dynamic musculoskeletal modelling system was used to analyse the kinematics and the tibiofemoral contact force. The contact stress on the tibial insert, and the stress to the resection surface and medial tibial cortex were examined by using finite element analysis.Objectives
Materials and Methods
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:
Progressive degenerative changes in the medial
compartment of the knee following lateral unicompartmental arthroplasty
(UKA) remains a leading indication for revision surgery. The purpose
of this study is to evaluate changes in the congruence and joint
space width (JSW) of the medial compartment following lateral UKA.
The congruence of the medial compartment of 53 knees (24 men, 23
women, mean age 13.1 years; Our data suggest that a well conducted lateral UKA may improve
the congruence and normalise the JSW of the medial compartment,
potentially preventing progression of degenerative change. Cite this article:
The aim of this study was to compare the maximum
laxity conferred by the cruciate-retaining (CR) and posterior-stabilised
(PS) Triathlon single-radius total knee arthroplasty (TKA) for anterior
drawer, varus–valgus opening and rotation in eight cadaver knees
through a defined arc of flexion (0º to 110º). The null hypothesis
was that the limits of laxity of CR- and PS-TKAs are not significantly
different. The investigation was undertaken in eight loaded cadaver knees
undergoing subjective stress testing using a measurement rig. Firstly
the native knee was tested prior to preparation for CR-TKA and subsequently
for PS-TKA implantation. Surgical navigation was used to track maximal
displacements/rotations at 0º, 30º, 60º, 90º and 110° of flexion.
Mixed-effects modelling was used to define the behaviour of the
TKAs. The laxity measured for the CR- and PS-TKAs revealed no statistically
significant differences over the studied flexion arc for the two
versions of TKA. Compared with the native knee both TKAs exhibited
slightly increased anterior drawer and decreased varus-valgus and
internal-external roational laxities. We believe further study is required
to define the clinical states for which the additional constraint
offered by a PS-TKA implant may be beneficial. Cite this article:
Malrotation of the femoral component can result in post-operative complications in total knee arthroplasty (TKA), including patellar maltracking. Therefore, we used computational simulation to investigate the influence of femoral malrotation on contact stresses on the polyethylene (PE) insert and on the patellar button as well as on the forces on the collateral ligaments. Validated finite element (FE) models, for internal and external malrotations from 0° to 10° with regard to the neutral position, were developed to evaluate the effect of malrotation on the femoral component in TKA. Femoral malrotation in TKA on the knee joint was simulated in walking stance-phase gait and squat loading conditions.Objectives
Materials and Methods
Instability after total knee replacement (TKR)
accounts for 10% to 22% of revision procedures. All patients who
present for evaluation of instability require a thorough history to
be taken and physical examination, as well as appropriate imaging.
Deep periprosthetic infection must be ruled out by laboratory testing
and an aspiration of the knee must be carried out. The three main
categories of instability include flexion instability, extension instability
(symmetric and asymmetric), and genu recurvatum. Most recently,
the aetiologies contributing to, and surgical manoeuvres required
to correct, flexion instability have been elucidated. While implant
design and patient-related factors may certainly contribute to the
aetiology, surgical technique is also a significant factor in all
forms of post-operative instability. Cite this article:
Radiological evidence of post-traumatic osteoarthritis
(PTOA) after fracture of the tibial plateau is common but end-stage arthritis
which requires total knee arthroplasty is much rarer. The aim of this study was to examine the indications for, and
outcomes of, total knee arthroplasty after fracture of the tibial
plateau and to compare this with an age and gender-matched cohort
of TKAs carried out for primary osteoarthritis. Between 1997 and 2011, 31 consecutive patients (23 women, eight
men) with a mean age of 65 years (40 to 89) underwent TKA at a mean
of 24 months (2 to 124) after a fracture of the tibial plateau.
Of these, 24 had undergone ORIF and seven had been treated non-operatively.
Patients were assessed pre-operatively and at 6, 12 and >
60 months
using the Short Form-12, Oxford Knee Score and a patient satisfaction
score. Patients with instability or nonunion needed total knee arthroplasty
earlier (14 and 13.3 months post-injury) than those with intra-articular
malunion (50 months, p <
0.001). Primary cruciate-retaining implants
were used in 27 (87%) patients. Complication rates were higher in
the PTOA cohort and included wound complications (13% Total knee arthroplasty undertaken after fracture of the tibial
plateau has a higher rate of complications than that undertaken
for primary osteoarthritis, but patient-reported outcomes and satisfaction
are comparable. Cite this article:
The influence of identifiable pre-operative factors on the outcome
of eccentric rotational acetabular osteotomy (ERAO) is unknown.
We aimed to determine the factors that might influence the outcome,
in order to develop a scoring system for predicting the prognosis
for patients undergoing this procedure. We reviewed 700 consecutive ERAOs in 54 men and 646 women with
symptomatic acetabular dysplasia or early onset osteoarthritis (OA)
of the hip, which were undertaken between September 1989 and March
2013. The patients’ pre-operative background, clinical and radiological
findings were examined retrospectively. Multivariate Cox regression
analysis was performed using the time from the day of surgery to
a conversion to total hip arthroplasty (THA) as an endpoint. A risk
score was calculated to predict the prognosis for conversion to
THA, and its predictive capacity was investigated.Aims
Patients and Methods
One method of femoral head preservation following avascular necrosis
(AVN) is core decompression and insertion of a tantalum rod. However,
there may be a high failure rate associated with this procedure.
The purpose of this study was to document the clinical and radiological
outcomes following total hip arthroplasty (THA) subsequent to failed
tantalum rod insertion. A total of 37 failed tantalum rods requiring total hip arthroplasty
were identified from a prospective database. There were 21 hips
in 21 patients (12 men and nine women, mean age 37 years, 18 to
53) meeting minimum two year clinical and radiographic follow-up
whose THAs were carried out between November 2002 and April 2013
(mean time between tantalum rod implantation and conversion to a
THA was 26 months, 6 to 72). These were matched by age and gender
to individuals (12 men, nine women, mean age 40 years, 18 to 58)
receiving THA for AVN without prior tantalum rod insertion.Aims
Patients and Methods
We studied whether the presence of lateral osteophytes
on plain radiographs was a predictor for the quality of cartilage
in the lateral compartment of patients with varus osteoarthritic
of the knee (Kellgren and Lawrence grade 2 to 3). The baseline MRIs of 344 patients from the Osteoarthritis Initiative
(OAI) who had varus osteoarthritis (OA) of the knee on hip-knee-ankle
radiographs were reviewed. Patients were categorised using the Osteoarthritis
Research Society International (OARSI) osteophyte grading system
into 174 patients with grade 0 (no osteophytes), 128 grade 1 (mild
osteophytes), 28 grade 2 (moderate osteophytes) and 14 grade 3 (severe
osteophytes) in the lateral compartment (tibia). All patients had
Kellgren and Lawrence grade 2 or 3 arthritis of the medial compartment.
The thickness and volume of the lateral cartilage and the percentage
of full-thickness cartilage defects in the lateral compartment was
analysed. There was no difference in the cartilage thickness or cartilage
volume between knees with osteophyte grades 0 to 3. The percentage
of full-thickness cartilage defects on the tibial side increased
from <
2% for grade 0 and 1 to 10% for grade 3. The lateral compartment cartilage volume and thickness is not
influenced by the presence of lateral compartment osteophytes in
patients with varus OA of the knee. Large lateral compartment osteophytes
(grade 3) increase the likelihood of full-thickness cartilage defects
in the lateral compartment. Cite this article:
Moderate to severe hallux valgus is conventionally
treated by proximal metatarsal osteotomy. Several recent studies
have shown that the indications for distal metatarsal osteotomy
with a distal soft-tissue procedure could be extended to include
moderate to severe hallux valgus. The purpose of this prospective randomised controlled trial was
to compare the outcome of proximal and distal Chevron osteotomy
in patients undergoing simultaneous bilateral correction of moderate
to severe hallux valgus. The original study cohort consisted of 50 female patients (100
feet). Of these, four (8 feet) were excluded for lack of adequate
follow-up, leaving 46 female patients (92 feet) in the study. The
mean age of the patients was 53.8 years (30.1 to 62.1) and the mean
duration of follow-up 40.2 months (24.1 to 80.5). After randomisation,
patients underwent a proximal Chevron osteotomy on one foot and
a distal Chevron osteotomy on the other. At follow-up, the American Orthopedic Foot and Ankle Society
(AOFAS) hallux metatarsophalangeal interphalangeal (MTP-IP) score,
patient satisfaction, post-operative complications, hallux valgus
angle, first-second intermetatarsal angle, and tibial sesamoid position
were similar in each group. Both procedures gave similar good clinical
and radiological outcomes. This study suggests that distal Chevron osteotomy with a distal
soft-tissue procedure is as effective and reliable a means of correcting
moderate to severe hallux valgus as proximal Chevron osteotomy with
a distal soft-tissue procedure. Cite this article:
The traditional techniques involving an oblique
tunnel or triangular wedge resection to approach a central or mixed-type
physeal bar are hindered by poor visualisation of the bar. This
may be overcome by a complete transverse osteotomy at the metaphysis
near the growth plate or a direct vertical approach to the bar.
Ilizarov external fixation using small wires allows firm fixation
of the short physis-bearing fragment, and can also correct an associated angular
deformity and permit limb lengthening. We accurately approached and successfully excised ten central-
or mixed-type bars; six in the distal femur, two in the proximal
tibia and two in the distal tibia, without damaging the uninvolved
physis, and corrected the associated angular deformity and leg-length
discrepancy. Callus formation was slightly delayed because of periosteal
elevation and stretching during resection of the bar. The resultant
resection of the bar was satisfactory in seven patients and fair
in three as assessed using a by a modified Williamson–Staheli classification. Cite this article:
We report the outcome of 39 patients who underwent
a modified Pauwels’ intertrochanteric osteotomy for nonunion of
a femoral neck fracture following failed osteosynthesis. There were
31 men and eight women with a mean age of 47.2 years (34 to 59).
By Pauwels’ classification, there were 11 Type II fractures and
28 Type III fractures. The mean follow-up was 7.9 years (2 to 19).
In the 11 patients whose initial treatment had been osteotomy, union was
achieved in nine (81.8%). In 28 patients whose initial treatment
had been with a lag screw or a dynamic hip screw, union was achieved
in 27 (96.4%). Limb lengths were equalised in 14 of 16 patients
(87.5%) with pre-operative shortening. The mean neck-shaft angle
improved significantly from 100.5° (80° to 120°) to 131.6° (120°
to 155°) (p = 0.004). The mean modified Harris hip score was 85.6
points (70 to 97) and the mean modified Merle d’Aubigné score was
14.3 (11 to 18). Good to excellent functional outcomes were achieved
in 32 patients (88.8%). A modified Pauwels’ intertrochanteric osteotomy
is a reliable method of treating ununited fractures of the femoral neck
following failed osteosynthesis: coxa vara and shortening can also
simultaneously be addressed. Cite this article
The April 2014 Knee Roundup360 looks at: mobile compression as good as chemical thromboprophylaxis; patellar injury with MIS knee surgery; tibial plateau fracture results not as good as we thought; back and knee pain; metaphyseal sleeves may be the answer in revision knee replacement; oral tranexamic acid; gentamycin alone in antibiotic spacers; and whether the jury is still out on unloader braces.
Tibial nonunion represents a spectrum of conditions
which are challenging to treat, and optimal management remains unclear
despite its high rate of incidence. We present 44 consecutive patients
with 46 stiff tibial nonunions, treated with hexapod external fixators
and distraction to achieve union and gradual deformity correction.
There were 31 men and 13 women with a mean age of 35 years (18 to
68) and a mean follow-up of 12 months (6 to 40). No tibial osteotomies
or bone graft procedures were performed. Bony union was achieved
after the initial surgery in 41 (89.1%) tibias. Four persistent
nonunions united after repeat treatment with closed hexapod distraction,
resulting in bony union in 45 (97.8%) patients. The mean time to
union was 23 weeks (11 to 49). Leg-length was restored to within
1 cm of the contralateral side in all tibias. Mechanical alignment
was restored to within 5° of normal in 42 (91.3%) tibias. Closed
distraction of stiff tibial nonunions can predictably lead to union
without further surgery or bone graft. In addition to generating
the required distraction to achieve union, hexapod circular external
fixators can accurately correct concurrent deformities and limb-length
discrepancies. Cite this article:
Instability in flexion after total knee replacement
(TKR) typically occurs as a result of mismatched flexion and extension
gaps. The goals of this study were to identify factors leading to
instability in flexion, the degree of correction, determined radiologically,
required at revision surgery, and the subsequent clinical outcomes.
Between 2000 and 2010, 60 TKRs in 60 patients underwent revision
for instability in flexion associated with well-fixed components.
There were 33 women (55%) and 27 men (45%); their mean age was 65
years (43 to 82). Radiological measurements and the Knee Society
score (KSS) were used to assess outcome after revision surgery.
The mean follow-up was 3.6 years (2 to 9.8). Decreased condylar
offset (p <
0.001), distalisation of the joint line (p <
0.001)
and increased posterior tibial slope (p <
0.001) contributed
to instability in flexion and required correction at revision to regain
stability. The combined mean correction of posterior condylar offset
and joint line resection was 9.5 mm, and a mean of 5° of posterior
tibial slope was removed. At the most recent follow-up, there was
a significant improvement in the mean KSS for the knee and function
(both p <
0.001), no patient reported instability and no patient
underwent further surgery for instability. The following step-wise approach is recommended: reduction of
tibial slope, correction of malalignment, and improvement of condylar
offset. Additional joint line elevation is needed if the above steps
do not equalise the flexion and extension gaps. Cite this article:
We present the clinical and radiographic outcome of 81 children
with Gartland type I to III supracondylar humeral fractures at a
minimum follow-up of ten years (mean 12.1 years; 10.3 to 16.1) following
injury. The clinical and functional outcomes are compared with normal
age- and gender-matched individuals. The population-based study
setting was first identified from the institutional registries;
the rate of participation was 76%. Controls were randomly selected
from Finnish National Population Registry.Aims
Patients and Methods
In total hip arthroplasty (THA), the cementless, tapered-wedge stem design contributes to achieving initial stability and providing optimal load transfer in the proximal femur. However, loading conditions on the femur following THA are also influenced by femoral structure. Therefore, we determined the effects of tapered-wedge stems on the load distribution of the femur using subject-specific finite element models of femurs with various canal shapes. We studied 20 femurs, including seven champagne flute-type femurs, five stovepipe-type femurs, and eight intermediate-type femurs, in patients who had undergone cementless THA using the Accolade TMZF stem at our institution. Subject–specific finite element (FE) models of pre- and post-operative femurs with stems were constructed and used to perform FE analyses (FEAs) to simulate single-leg stance. FEA predictions were compared with changes in bone mineral density (BMD) measured for each patient during the first post-operative year.Objectives
Patients and Methods
Mechanical alignment has been a fundamental tenet of total knee arthroplasty (TKA) since modern knee replacement surgery was developed in the 1970s. The objective of mechanical alignment was to infer the greatest biomechanical advantage to the implant to prevent early loosening and failure. Over the last 40 years a great deal of innovation in TKA technology has been focusing on how to more accurately achieve mechanical alignment. Recently the concept of mechanical alignment has been challenged, and other alignment philosophies are being explored with the intention of trying to improve patient outcomes following TKA. This article examines the evolution of the mechanical alignment concept and whether there are any viable alternatives.
Flexor digitorum longus transfer and medial displacement
calcaneal osteotomy is a well-recognised form of treatment for stage
II posterior tibial tendon dysfunction. Although excellent short-
and medium-term results have been reported, the long-term outcome
is unknown. We reviewed the clinical outcome of 31 patients with
a symptomatic flexible flat-foot deformity who underwent this procedure
between 1994 and 1996. There were 21 women and ten men with a mean
age of 54.3 years (42 to 70). The mean follow-up was 15.2 years
(11.4 to 16.5). All scores improved significantly (p <
0.001).
The mean American Orthopedic Foot and Ankle Society (AOFAS) score improved
from 48.4 pre-operatively to 90.3 (54 to 100) at the final follow-up.
The mean pain component improved from 12.3 to 35.2 (20 to 40). The
mean function score improved from 35.2 to 45.6 (30 to 50). The mean
visual analogue score for pain improved from 7.3 to 1.3 (0 to 6).
The mean Short Form-36 physical component score was 40.6 ( Cite this article: