Aims. The purpose of this investigation was to determine the relationship between height, weight, and sex with implant size in total knee arthroplasty (TKA) using a multivariate linear regression model and a Bayesian model. Methods. A retrospective review of an institutional registry was performed of primary TKAs performed between January 2005 and December 2016. Patient demographics including patient age, sex, height, weight, and body mass index (BMI) were obtained from registry and medical record review. In total, 8,100 primary TKAs were included. The mean age was 67.3 years (SD 9.5) with a mean BMI of 30.4 kg/m. 2. (SD 6.3). The TKAs were randomly split into a training cohort (n = 4,022) and a testing cohort (n = 4,078). A multivariate linear regression model was created on the training cohort and then applied to the testing cohort . A Bayesian model was created based on the frequencies of implant sizes in the training cohort. The model was then applied to the testing cohort to determine the accuracy of the model at 1%, 5%, and 10%
The surgical target for optimal implant positioning in robotic-assisted total knee arthroplasty remains the subject of ongoing discussion. One of the proposed targets is to recreate the knee’s functional behaviour as per its pre-diseased state. The aim of this study was to optimize implant positioning, starting from mechanical alignment (MA), toward restoring the pre-diseased status, including ligament strain and kinematic patterns, in a patient population. We used an active appearance model-based approach to segment the preoperative CT of 21 osteoarthritic patients, which identified the osteophyte-free surfaces and estimated cartilage from the segmented bones; these geometries were used to construct patient-specific musculoskeletal models of the pre-diseased knee. Subsequently, implantations were simulated using the MA method, and a previously developed optimization technique was employed to find the optimal implant position that minimized the root mean square deviation between pre-diseased and postoperative ligament strains and kinematics.Aims
Methods
Aims. Our aim was to compare kinematic with mechanical alignment in
total knee arthroplasty (TKA). Patients and Methods. We performed a prospective blinded randomised controlled trial
to compare the functional outcome of patients undergoing TKA in
mechanical alignment (MA) with those in kinematic alignment (KA).
A total of 71 patients undergoing TKA were randomised to either
kinematic (n = 36) or mechanical alignment (n = 35). Pre- and post-operative
hip-knee-ankle radiographs were analysed. The knee injury and osteoarthritis
outcome score (KOOS), American Knee Society Score, Short Form-36,
Euro-Qol (EQ-5D), range of movement (ROM), two minute walk, and timed
up and go tests were assessed pre-operatively and at six weeks,
three and six months and one year post-operatively. Results. A total of 78% of the kinematically aligned group (28 patients)
and 77% of the mechanically aligned group (27 patients) were within
3° of their pre-operative plan. There were no statistically significant
differences in the mean KOOS (difference 1.3, 95% confidence interval
(CI) -9.4 to 12.1, p = 0.80), EQ-5D (difference 0.8, 95% CI -7.9
to 9.6, p = 0.84), ROM (difference 0.1, 95% CI -6.0 to 6.1, p =
0.99), two minute distance
Single-stage revision total knee arthroplasty (rTKA) is gaining popularity in treating chronic periprosthetic joint infections (PJIs). We have introduced this approach to our clinical practice and sought to evaluate rates of reinfection and re-revision, along with predictors of failure of both single- and two-stage rTKA for chronic PJI. A retrospective comparative cohort study of all rTKAs for chronic PJI between 1 April 2003 and 31 December 2018 was undertaken using prospective databases. Patients with acute infections were excluded; rTKAs were classified as single-stage, stage 1, or stage 2 of two-stage revision. The primary outcome measure was failure to eradicate or recurrent infection. Variables evaluated for failure by regression analysis included age, BMI, American Society of Anesthesiologists grade, infecting organisms, and the presence of a sinus. Patient survivorship was also compared between the groups.Aims
Methods
The primary aim of this study was to assess whether non-fatal postoperative venous thromboembolism (VTE) within six months of surgery influences the knee-specific functional outcome (Oxford Knee Score (OKS)) one year after total knee arthroplasty (TKA). Secondary aims were to assess whether non-fatal postoperative VTE influences generic health and patient satisfaction at this time. A study of 2,393 TKAs was performed in 2,393 patients. Patient demographics, comorbidities, OKS, EuroQol five-dimension score (EQ-5D), and Forgotten Joint Score (FJS) were collected preoperatively and one year postoperatively. Overall patient satisfaction with their TKA was assessed at one year. Patients with VTE within six months of surgery were identified retrospectively and compared with those without.Aims
Methods
The integrity of the soft tissue envelope is crucial for successful treatment of infected total knee arthroplasty (TKA). The purpose of this study was to evaluate the rate of limb salvage, infection control, and clinical function following microvascular free flap coverage for salvage of the infected TKA. We retrospectively reviewed 23 microvascular free tissue transfers for management of soft tissue defects in infected TKA. There were 16 men and seven women with a mean age of 61.2 years (39 to 81). The median number of procedures performed prior to soft tissue coverage was five (2 to 9) and all patients had failed at least one two-stage reimplantation procedure. Clinical outcomes were measured using the Knee Society Scoring system for pain and function.Aims
Methods
This aim of this study was to assess the feasibility of designing and introducing generic 3D-printed instrumentation for routine use in total knee arthroplasty. Instruments were designed to take advantage of 3D-printing technology, particularly ensuring that all parts were pre-assembled, to theoretically reduce the time and skill required during surgery. Concerning functionality, ranges of resection angle and distance were restricted within a safe zone, while accommodating either mechanical or anatomical alignment goals. To identify the most suitable biocompatible materials, typical instrument shapes and mating parts, such as dovetails and screws, were designed and produced.Aims
Materials and Methods
A retrospective study was conducted to measure short-term Nonweightbearing supine RSA exams were performed postoperatively and at six, 12, and 24 months. Weightbearing standing RSA exams were performed on select patients at 12 and 24 months. Wear was measured both linearly (joint space) and volumetrically (digital model overlap) at each available follow-up. Precision of both methods was assessed by comparing double RSA exams. Patient age, sex, body mass index, and Oxford Knee Scores were analyzed for any association with PE wear.Aims
Patients and Methods
The results of kinematic total knee arthroplasty (KTKA) have been reported in terms of limb and component alignment parameters but not in terms of gap laxities and differentials. In kinematic alignment (KA), balance should reflect the asymmetrical balance of the normal knee, not the classic rectangular flexion and extension gaps sought with gap-balanced mechanical axis total knee arthroplasty (MATKA). This paper aims to address the following questions: 1) what factors determine coronal joint congruence as measured on standing radiographs?; 2) is flexion gap asymmetry produced with KA?; 3) does lateral flexion gap laxity affect outcomes?; 4) is lateral flexion gap laxity associated with lateral extension gap laxity?; and 5) can consistent ligament balance be produced without releases? A total of 192 KTKAs completed by a single surgeon using a computer-assisted technique were followed for a mean of 3.5 years (2 to 5). There were 116 male patients (60%) and 76 female patients (40%) with a mean age of 65 years (48 to 88). Outcome measures included intraoperative gap laxity measurements and component positions, as well as joint angles from postoperative three-foot standing radiographs. Patient-reported outcome measures (PROMs) were analyzed in terms of alignment and balance: EuroQol (EQ)-5D visual analogue scale (VAS), Knee Injury and Osteoarthritis Outcome Score (KOOS), KOOS Joint Replacement (JR), and Oxford Knee Score (OKS).Aims
Patients and Methods
The aim of this study was to determine the general postoperative opioid consumption and rate of appropriate disposal of excess opioid prescriptions in patients undergoing primary unilateral total knee arthroplasty (TKA). In total, 112 patients undergoing surgery with one of eight arthroplasty surgeons at a single specialty hospital were prospectively enrolled. Three patients were excluded for undergoing secondary procedures within six weeks. Daily pain levels and opioid consumption, quantity, and disposal patterns for leftover medications were collected for six weeks following surgery using a text-messaging platform.Aims
Patients and Methods
To evaluate the influence of discharge timing on 30-day complications following total knee arthroplasty (TKA). We identified patients aged 18 years or older who underwent TKA between 2005 and 2016 from the American College of Surgeons’ National Surgical Quality Improvement Program (NSQIP) database. We propensity score-matched length-of-stay (LOS) groups using all relevant covariables. We used multivariable regression to determine if the rate of complications and re-admissions differed depending on LOS.Aims
Patients and Methods
We sought to establish whether an oxidised zirconium (OxZr) femoral
component causes less loss of polyethylene volume than a cobalt
alloy (CoCr) femoral component in total knee arthroplasty. A total of 20 retrieved tibial inserts that had articulated with
OxZr components were matched with 20 inserts from CoCr articulations
for patient age, body mass index, length of implantation, and revision
diagnosis. Changes in dimensions of the articular surfaces were compared
with those of pristine inserts using laser scanning. The differences
in volume between the retrieved and pristine surfaces of the two
groups were calculated and compared.Aims
Materials and Methods
Patellofemoral arthroplasty (PFA) has experienced significant
improvements in implant survivorship with second generation designs.
This has renewed interest in PFA as an alternative to total knee
arthroplasty (TKA) for younger active patients with isolated patellofemoral
osteoarthritis (PF OA). We analysed the cost-effectiveness of PFA We used a Markov transition state model to compare cost-effectiveness
between PFA and TKA. Simulated patients were aged 60 (base case)
and 50 years. Lifetime costs (2015 United States dollars), quality-adjusted
life year (QALY) gains and incremental cost-effectiveness ratio
(ICER) were calculated from a healthcare payer perspective. Annual rates
of revision were derived from the National Joint Registry for England,
Wales, Northern Ireland and the Isle of Man. Deterministic and probabilistic
sensitivity analysis was performed for all parameters against a
$50 000/QALY willingness to pay. Aims
Patients and Methods
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 entry point of the alignment
jig and coronal entry-point position had significant effects on
the flexion/extension position. Pre-operative HKA angle had a significant
influence on posterior overhang of the femoral component. However,
there was no significant difference in American Knee Society scores
relative to the position of the femoral component.
While medial unicompartmental knee arthroplasty (UKA) is indicated
for patients with full-thickness cartilage loss, it is occasionally
used to treat those with partial-thickness loss. The aim of this
study was to investigate the five-year outcomes in a consecutive
series of UKAs used in patients with partial thickness cartilage
loss in the medial compartment of the knee. Between 2002 and 2014, 94 consecutive UKAs were undertaken in
90 patients with partial thickness cartilage loss and followed up
independently for a mean of six years (1 to 13). These patients
had partial thickness cartilage loss either on both femur and tibia
(13 knees), or on either the femur or the tibia, with full thickness
loss on the other surface of the joint (18 and 63 knees respectively).
Using propensity score analysis, these patients were matched 1:2 based
on age, gender and pre-operative Oxford Knee Score (OKS) with knees
with full thickness loss on both the femur and tibia. The functional
outcomes, implant survival and incidence of re-operations were assessed
at one, two and five years post-operatively. A subgroup of 36 knees
in 36 patients with partial thickness cartilage loss, who had pre-operative
MRI scans, was assessed to identify whether there were any factors
identified on MRI that predicted the outcome.Aims
Patients and Methods
Early and accurate prediction of hospital length-of-stay
(LOS) in patients undergoing knee replacement is important for economic
and operational reasons. Few studies have systematically developed
a multivariable model to predict LOS. We performed a retrospective
cohort study of 1609 patients aged ≥ 50 years who underwent elective,
primary total or unicompartmental knee replacements. Pre-operative
candidate predictors included patient demographics, knee function,
self-reported measures, surgical factors and discharge plans. In
order to develop the model, multivariable regression with bootstrap
internal validation was used. The median LOS for the sample was
four days (interquartile range 4 to 5). Statistically significant
predictors of longer stay included older age, greater number of comorbidities,
less knee flexion range of movement, frequent feelings of being
down and depressed, greater walking aid support required, total
( Cite this article:
The Oxford Unicompartmental Knee replacement (UKR) was introduced as a design to reduce polyethylene wear. There has been one previous retrieval study involving this implant, which reported very low rates of wear in some specimens but abnormal patterns of wear in others. There has been no further investigation of these abnormal patterns. The bearings were retrieved from 47 patients who had received a medial Oxford UKR for anteromedial osteoarthritis of the knee. None had been studied previously. The mean time to revision was 8.4 years ( These results show that very low rates of polyethylene wear are possible if the device functions normally. However, if the bearing displays suboptimal function (extra-articular, intra-articular impingement or incongruous articulation) the rates of wear increase significantly.
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.
Pain, swelling and inflammation are expected
during the recovery from total knee arthroplasty (TKA) surgery.
The severity of these factors and how a patient copes with them
may determine the ultimate outcome of a TKA. Cryotherapy and compression
are frequently used modalities to mitigate these commonly experienced
sequelae. However, their effect on range of motion, functional testing,
and narcotic consumption has not been well-studied. A prospective, multi-center, randomised trial was conducted to
evaluate the effect of a cryopneumatic device on post-operative
TKA recovery. Patients were randomised to treatment with a cryopneumatic
device or ice with static compression. A total of 280 patients were
enrolled at 11 international sites. Both treatments were initiated
within three hours post-operation and used at least four times per
day for two weeks. The cryopneumatic device was titrated for cooling
and pressure by the patient to their comfort level. Patients were evaluated by physical therapists blinded to the
treatment arm. Range of motion (ROM), knee girth, six minute walk
test (6MWT) and timed up and go test (TUG) were measured pre-operatively,
two- and six-weeks post-operatively. A visual analog pain score
and narcotic consumption was also measured post-operatively. At two weeks post-operatively, both the treatment and control
groups had diminished ROM and function compared to pre-operatively.
Both groups had increased knee girth compared to pre- operatively.
There was no significant difference in ROM, 6MWT, TUG, or knee girth
between the 2 groups. We did find a significantly lower amount of
narcotic consumption (509 mg morphine equivalents) in the treatment
group compared with the control group (680 mg morphine equivalents)
at up to two weeks postop, when the cryopneumatic device was being
used (p <
0.05). Between two and six weeks, there was no difference
in the total amount of narcotics consumed between the two groups.
At six weeks, there was a trend toward a greater distance walked
in the 6MWT in the treatment group (29.4 meters A cryopneumatic device used after TKA appeared to decrease the
need for narcotic medication from hospital discharge to 2 weeks
post-operatively. There was also a trend toward a greater distance
walked in the 6MWT. Patient satisfaction with the cryopneumatic
cooling regimen was significantly higher than with the control treatment.
After obtaining informed consent, 80 patients were randomised to undergo a navigated or conventional total knee replacement. All received a cemented, unconstrained, cruciate-retaining implant with a rotating platform. Full-length standing and lateral radiographs and CT scans of the hip, knee and ankle joint were carried out five to seven days after operation. No notable differences were found between computer-assisted navigation and conventional implantation techniques as regards the rotational alignment of the femoral or tibial components. Although the deviation from the transepicondylar axis was relatively low, there was a considerable range of deviation for the tibial rotational alignment. There was no statistically significant difference regarding the occurrence pattern of outliers in mechanical malalignment but the number of outliers was reduced in the navigated group.
