Distal femoral resection in conventional total knee arthroplasty (TKA) utilizes an intramedullary guide to determine coronal alignment, commonly planned for 5° of valgus. However, a standard 5° resection angle may contribute to malalignment in patients with variability in the femoral anatomical and mechanical axis angle. The purpose of the study was to leverage deep learning (DL) to measure the femoral mechanical-anatomical axis angle (FMAA) in a heterogeneous cohort. Patients with full-limb radiographs from the Osteoarthritis Initiative were included. A DL workflow was created to measure the FMAA and validated against human measurements. To reflect potential intramedullary guide placement during manual TKA, two different FMAAs were calculated either using a line approximating the entire diaphyseal shaft, and a line connecting the apex of the femoral intercondylar sulcus to the centre of the diaphysis. The proportion of FMAAs outside a range of 5.0° (SD 2.0°) was calculated for both definitions, and FMAA was compared using univariate analyses across sex, BMI, knee alignment, and femur length.Aims
Methods
Aseptic loosening is the most common cause of failure following cemented total knee arthroplasty (TKA), and has been linked to poor cementation technique. We aimed to develop a consensus on the optimal technique for component cementation in TKA. A UK-based, three-round, online modified Delphi Expert Consensus Study was completed focusing on cementation technique in TKA. Experts were identified as having a minimum of five years’ consultant experience in the NHS and fulfilling any one of the following criteria: a ‘high volume’ knee arthroplasty practice (> 150 TKAs per annum) as identified from the National joint Registry of England, Wales, Northern Ireland and the Isle of Man; a senior author of at least five peer reviewed articles related to TKA in the previous five years; a surgeon who is named trainer for a post-certificate of comletion of training fellowship in TKA.Aims
Methods
This study aimed to evaluate the association between the sagittal alignment of the femoral component in total knee arthroplasty (TKA) and new Knee Society Score (2011KSS), under the hypothesis that outliers such as the excessive extended or flexed femoral component were related to worse clinical outcomes. A group of 156 knees (134 F:22 M) in 133 patients with a mean age 75.8 years (SD 6.4) who underwent TKA with the cruciate-substituting Bi-Surface Knee prosthesis were retrospectively enrolled. On lateral radiographs, γ angle (the angle between the distal femoral axis and the line perpendicular to the distal rear surface of the femoral component) was measured, and the patients were divided into four groups according to the γ angle. The 2011KSSs among groups were compared using the Kruskal-Wallis test. A secondary regression analysis was used to investigate the association between the 2011KSS and γ angle.Aims
Methods
Graft-tunnel mismatch of the bone-patellar tendon-bone
(BPTB) graft is a major concern during anatomical anterior cruciate
ligament (ACL) reconstruction if the femoral tunnel is positioned
using a far medial portal technique, as the femoral tunnel tends
to be shorter compared with that positioned using a transtibial
portal technique. This study describes an accurate method of calculating
the ideal length of bone plugs of a BPTB graft required to avoid
graft–tunnel mismatch during anatomical ACL reconstruction using
a far medial portal technique of femoral tunnel positioning. Based on data obtained intra-operatively from 60 anatomical ACL
reconstruction procedures, we calculated the length of bone plugs
required in the BPTB graft to avoid graft–tunnel mismatch. When
this was prevented in all the 60 cases, we found that the mean length
of femoral bone plug that remained in contact with the interference
screw within the femoral tunnel was 14 mm (12 to 22) and the mean
length of tibial bone plug that remained in contact with the interference
screw within the tibial tunnel was 23 mm (18 to 28). These results
were used to validate theoretical formulae developed to predict
the required length of bone plugs in BPTB graft during anatomical
ACL reconstruction using a far medial portal technique. Cite this article:
A soft-tissue defect over an infected total knee
replacement (TKR) presents a difficult technical problem that can
be treated with a gastrocnemius flap, which is rotated over the
defect during the first-stage of a revision procedure. This facilitates
wound healing and the safe introduction of a prosthesis at the second
stage. We describe the outcome at a mean follow-up of 4.5 years
(1 to 10) in 24 patients with an infected TKR who underwent this procedure.
A total of 22 (92%) eventually obtained a satisfactory result. The
mean Knee Society score improved from 53 pre-operatively to 103
at the latest follow-up (p <
0.001). The mean Western Ontario
and McMaster Universities osteoarthritis index and Short-Form 12
score also improved significantly (p <
0.001). This form of treatment can be used reliably and safely to treat
many of these complex cases where control of infection, retention
of the components and acceptable functional recovery are the primary
goals. Cite this article:
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.
The purpose of this study was to measure the
radiological parameters of femoral component alignment of the Oxford
Phase 3 unicompartmental knee replacement (UKR), and evaluate their
effect on clinical outcome. Multiple regression analysis was used
to examine the relative contributions of the radiological assessment
of femoral component alignment in 189 consecutive UKRs performed
by a single surgeon. The American Knee Society scores were compared
between groups, defined as being within or outside recommended tolerances
of the position of the femoral component. For the flexion/extension
position 21 UKRs (11.1%) lay outside the recommended limits, and for
posterior overhang of the femoral component nine (4.8%) lay outside
the range. The pre-operative hip/knee/ankle (HKA) angle, narrowest
canal distance from the distal femoral
Our aim was to assess the use of intra-operative fluoroscopy
in the assessment of the position of the tibial tunnel during reconstruction
of the anterior cruciate ligament (ACL). Between January and June 2009 a total of 31 arthroscopic hamstring
ACL reconstructions were performed. Intra-operative fluoroscopy
was introduced (when available) to verify the position of the guidewire
before tunnel reaming. It was only available for use in 20 cases,
due to other demands on the radiology department. The tourniquet
times were compared between the two groups and all cases where radiological
images lead to re-positioning of the guide wire were recorded. The
secondary outcome involved assessing the tibial interference screw
position measured on post-operative radiographs and comparing with
the known tunnel position as shown on intra-operative fluoroscopic
images.Objectives
Methods
Intra-articular resection of bone with soft-tissue balancing and total knee replacement (TKR) has been described for the treatment of patients with severe osteoarthritis of the knee associated with an ipsilateral malunited femoral fracture. However, the extent to which deformity in the sagittal plane can be corrected has not been addressed. We treated 12 patients with severe arthritis of the knee and an extra-articular malunion of the femur by TKR with intra-articular resection of bone and soft-tissue balancing. The femora had a mean varus deformity of 16° (8° to 23°) in the coronal plane. There were seven recurvatum deformities with a mean angulation of 11° (6° to 15°) and five antecurvatum deformities with a mean angulation of 12° (6° to 15°). The mean follow-up was 93 months (30 to 155). The median Knee Society knee and function scores improved from 18.7 (0 to 49) and 24.5 (10 to 50) points pre-operatively to 93 (83 to 100) and 90 (70 to 100) points at the time of the last follow-up, respectively. The mean mechanical axis of the knee improved from 22.6° of varus (15° to 27° pre-operatively to 1.5° of varus (3° of varus to 2° of valgus) at the last follow-up. The recurvatum deformities improved from a mean of 11° (6° to 15°) pre-operatively to 3° (0° to 6°) at the last follow-up. The antecurvatum deformities in the sagittal plane improved from a mean of 12° (6° to 16°) pre-operatively to 4.4° (0° to 8°) at the last follow-up. Apart from varus deformities, TKR with intra-articular bone resection effectively corrected the extra-articular deformity of the femur in the presence of antecurvatum of up to 16° and recurvatum of up to 15°.
Mechanical failure because of wear or fracture of the polyethylene tibial post in posteriorly-stabilised total knee replacements has been extensively described. In this study of 12 patients with a clinically and radiologically successful NexGen LPS posteriorly-stabilised prosthesis impingement of the anterior tibial post was evaluated in vivo in three dimensions during gait using radiologically-based image-matching techniques. Impingement was observed in all images of the patients during the stance phase, although the NexGen LPS was designed to accommodate 14° of hyperextension of the component before impingement occurred. Impingement arises as a result of posterior translation of the femur during the stance phase. Further attention must therefore be given to the configuration of the anterior portion of the femoral component and the polyethylene post when designing posteriorly-stabilised total knee replacements.
We compared the alignment of 39 total knee replacements implanted using the conventional alignment guide system with 37 implanted using a CT-based navigation system, performed by a single surgeon. The knees were evaluated using full-length weight-bearing anteroposterior radiographs, lateral radiographs and CT scans. The mean hip-knee-ankle angle, coronal femoral component angle and coronal tibial component angle were 181.8° (174.2° to 188.3°), 88.5° (84.0° to 91.8°) and 89.7° (86.3° to 95.1°), respectively for the conventional group and 180.8° (178.2° to 185.1°), 89.3° (85.8° to 92.0°) and 89.9° (88.0° to 93.0°), respectively for the navigated group. The mean sagittal femoral component angle was 85.5° (80.6° to 92.8°) for the conventional group and 89.6° (85.5° to 94.0°) for the navigated group. The mean rotational femoral and tibial component angles were −0.7° (−8.8° to 9.8°) and −3.3° (−16.8° to 5.8°) for the conventional group and −0.6° (−3.5° to 3.0°) and 0.3° (−5.3° to 7.7°) for the navigated group. The ideal angles of all alignments in the navigated group were obtained at significantly higher rates than in the conventional group. Our results demonstrated significant improvements in component positioning with a CT-based navigation system, especially with respect to rotational alignment.
Osteonecrosis of the knee comprises two separate disorders, primary spontaneous osteonecrosis which is often a self-limiting condition and secondary osteonecrosis which is associated with risk factors and a poor prognosis. In a series of 61 knees (38 patients) we analysed secondary osteonecrosis of the knee treated by a new technique using multiple small percutaneous 3 mm drillings. Total knee replacement was avoided in 59 knees (97%) at a mean follow-up of 3 years (2 to 4). Of the 61 knees, 56 (92%) had a successful clinical outcome, defined as a Knee Society score greater than 80 points. The procedure was successful in all 24 knees with small lesions compared with 32 of 37 knees (86%) with large lesions. All the procedures were performed as day cases and there were no complications. This technique appears to have a low morbidity, relieves symptoms and delays more invasive surgery.
