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Determination of the Accuracy of Navigated Kinematic Unicompartmental Knee Arthroplasty: A 2-Year Follow-Up
Abstract
Background:
Unicompartmental knee arthroplasty (UKA) lacks history of patient satisfaction and research addressing technique validity. The aim of this study was to determine minimally invasive navigated kinematic UKA accuracy by comparing postoperative limb alignment with preoperative stress values.
Methods:
A single-center retrospective study was conducted on 53 consecutive patients (postoperative alignment: varus n = 51, valgus n = 2) who underwent computer navigation assisted UKA. Two patient groups (A and B) predetermined by joint deformity cut-off points (B included valgus deformity) underwent preoperative magnetic resonance imaging and x-ray evaluation to assess limb alignment and exclude lateral and patellofemoral osteoarthritis. Preoperative and postoperative joint alignment, stress value, and range of movement were recorded with navigation. Outcome measures include comparison of postoperative alignment to the preoperative stress values for varus and valgus postoperative alignment groups and preoperative and/or postoperative Western Ontario and McMaster Universities and Knee Society Score evaluations.
Results:
Minor systematic bias was found between stress value and postoperative alignment; however, the magnitude of difference was clinically acceptable. Score evaluations, prosthesis size or alignment didn't differ between groups. Furthermore, there was no significant increase in range of movement at 2 years. There was a high degree of agreement between stress value and postoperative alignment values suggesting strong validity for the surgical technique to determine optimal postoperative alignment.
Conclusion:
This study validates our surgical technique. Minimally invasive navigated UKA allows us to predict predisease alignment and recreates it with high accuracy. Our clinical results at 2 years are comparable with other published data.
... But at the same time, the risk of malpositioning components is higher because of the limited visualization of anatomical landmarks. The failure of precise component positioning could result in rapid loosening of the component, promoted process of osteoarthritis to the opposite side of the knee and increased revision rate [9][10][11][12][13]. Nowadays, the computer navigated system has been frequently used in UKA procedures [14]. ...
... By screening the titles and abstracts, 24 studies reaching the inclusion standards were reviewed for full-text screening. Posterior to the full-text eligibility evaluation, certain studies were excluded, as these researches focused on saw bones or cadaveric knees [25,26] with insufficient data [9,14,[27][28][29][30], and partial data were used in other reports [15,31]. Eventually, an overall 14 selected reports were described [7,10,12,13,15,17,20,21,[32][33][34][35][36][37]. ...
Background:
Though unicompartmental knee arthroplasty (UKA) is a useful procedure to treat knee osteoarthritis, it remains a great controversial point as to if navigated systems are able to achieve better accuracy of limb alignment and greater clinic results. Current meta-analysis was conducted to explore if better clinical outcomes and radiographic outcomes could be acquired in the navigated system when compared with conventional procedures.
Methods:
We identified studies in the online databases, including Medline, Embase, the Cochrane Library and Web of Science before May 2021. The PRISMA guidelines in this report were strictly followed. Our research was completed via Review Manager 5.4 software.
Results:
Fourteen articles were included, involving 852 knees. The present meta-analysis displayed that the navigated system had remarkably improved outcomes in inliers of mechanical axis (MA) (P < 0.01), MA in the Kennedy's central zone (Zone C) (P = 0.04), inliers of the coronal femoral component (P < 0.01), inliers of the coronal tibial component (P = 0.005), inliers of the sagittal femoral component (P = 0.03), inliers of the sagittal tibial component (P = 0.002) and Range Of Motion (ROM) (P = 0.04). No significant differences were observed in Oxford Knee Score (OKS) (P = 0.15), American Knee Society Knee Score (KSS score) (P = 0.61) and postoperative complications (P = 0.73) between these 2 groups. Regarding operating time, the navigated group was 10.63 min longer in contrast to the traditional group.
Conclusion:
Based on our research, the navigated system provided better radiographic outcomes and no significant difference in the risk of complications with longer surgical time than the conventional techniques. But no significant differences were found in functional outcomes. Because the included studies were small samples and short-term follow-up, high-quality RCTs with large patients and sufficient follow-up are required to identify the long-term effect of the navigated system.
... There have been a few studies of the navigation-based alignment of UKA that focused on varus alignment at knee extension. 10,11 Grant et al. 10 reported that clinical outcomes did not differ according to postoperative varus alignment at knee extension. However, whether varus alignment at knee flexion correlate with clinical outcomes has not yet been investigated. ...
... There have been a few studies of the navigation-based alignment of UKA that focused on varus alignment at knee extension. 10,11 Grant et al. 10 reported that clinical outcomes did not differ according to postoperative varus alignment at knee extension. However, whether varus alignment at knee flexion correlate with clinical outcomes has not yet been investigated. ...
Background:
The aim of the study was to investigate the effects of navigation-based varus or axial rotational alignment through knee flexion on patient reported outcomes or the maximum flexion angle of unicompartmental knee arthroplasty (UKA).
Methods:
Data were retrospectively collected from 46 knees that underwent UKA for medial unicompartmental knee osteoarthritis. An image-free knee navigation system was used in all cases, and intraoperative varus and axial rotational alignment at every knee flexion angle were recorded before and after implantation. All patients completed the Knee injury and Osteoarthritis Outcome Score (KOOS) at final follow-up. By varus or valgus at 0° knee flexion, the knees were subdivided into two groups (varus at 0° group, varus above the median value; neutral at 0° group, varus equal to or below the median value). By varus or valgus at 90° knee flexion, patients were similarly subdivided into two groups (varus at 90° group; neutral at 90° group). The maximum knee flexion angle was measured 3 months after surgery.
Results:
There were no differences in the KOOS between the neutral at 0° group and the varus at 0° group. However, the KOOS activity score (79 ± 17 vs 69 ± 16, p = 0.02) and the KOOS total score (72 ± 17 vs 65 ± 15, p = 0.03) of the neutral at 90° group were better than those of the varus at 90° group. The alignment and the maximum knee flexion angle 3 months after surgery were not correlated.
Conclusion:
Varus at 0° knee flexion and axial rotational alignment did not affect the clinical outcomes of UKA. Patient reported outcomes was better for the neutral knees with less varus at 90° knee flexion than for varus knees.
... Three-dimensional-to-2D video-fluoroscopy studies on patients implanted with UKA reveal similar kinematic features compared to healthy knees [9], in particular for what concern patterns of axial rotation and femoral condyle contact point posterior translation, with progressive femoral external rotation and posterior lateral condylar translation with knee flexion [33]. Navigation has demonstrated to be a useful tool for accurate implant positioning to predict pre-disease alignment and recreating it with high accuracy [34,35]. Simulator studies can mainly investigate the wear rate of the polyethylene, which informs the effects of the kinematics and femoral liftoff in several implant designs. ...
... Navigation has been introduced to improve accuracy in implant positioning and postoperative alignment in UKA as well as TKA. In several clinical studies, the accuracy of UKA implantations in relation to the coronal mechanical axis in a navigation group was significantly superior to that of conventional group, although clinical results, including ROM and Knee Society score, were equally good in both the groups [34,35]. ...
The biomechanics of the human knee joint has been a subject of speculation since the past century. Various theories as to how the tibia, the femur, and the patella articulate with respect to each other have developed as a result of researches involving cadavers and living subjects. The importance of the insight in replaced-knee kinematics in loading and unloading conditions has been demonstrated with the relation between joint motion and postoperative knee functioning. Different methods have been applied in order to study the functional kinematics of the human knee, taking into account how muscle activation, movement, and loading condition in different activities affect joint motion and bones’ relative positions. Differences have been reported relative to the kinematic behavior of the native, osteoarthritic, and implanted knee, in particular for what concern patterns of anterior-posterior displacement of the femoral condyles relative to the tibia and axial rotation. In the present chapter, the different approaches for knee kinematics investigation have been analyzed and described in the native joint, in knees with medial osteoarthritis and with unicompartmental arthroplasty.
... Loss of correction over the first year following MOW HTO was assessed by comparison of mHKA angles at 2 weeks post-operative, to each subsequent follow-up visit. The accuracy of the navigated, valgus stress technique for intraoperative prediction of the corrected limb alignment angle following surgery was confirmed by comparing the mHKA on A/P long-leg standing radiographs at 2 weeks post-operative to intraoperative stress HKA captured immediately after implantation using methods described previously [11]. ...
... Following assessment of skewness using Shapiro-Wilk test, a paired t test was used for comparison of changes in intraoperative parameters before and after surgery. Limits of agreement (LOA) were calculated between the navigated stress HKA values and 2 week post-operative mHKA angles, expressed using the Bland and Altman method and used to establish delimitations for assessing the accuracy of the navigated intraoperative alignment angles [11]. Kruskal-Wallis test was used to determine significance of changes in PROM scores following HTO, with Dunn's post hoc analysis to identify the location of differences between time points. ...
Background:
Accelerated rehabilitation protocols for medial opening wedge high tibial osteotomy (MOW HTO) using intraosseous implants have not previously been described. The present study provides early clinical and radiological outcomes of MOW HTO using a polyetheretherketone (PEEK) intraosseous system, in combination with an early weight-bearing protocol.
Methods:
Twenty consecutive knees (17 patients) underwent navigated MOW HTO using a PEEK implant with accelerated rehabilitation. Time to union and maintenance of correction were assessed radiographically for 12 months post-operative. Patient outcomes were monitored for a mean follow-up of 38 months (range 23-42) using standardised instruments (WOMAC, IKDC and Lysholm scores).
Results:
All knees were corrected to valgus. The mean time to unassisted weight-bearing was 55 days (SD 24, range 21-106). Bone union occurred in 95% of knees by 6 months, with correction maintained for 15 knees at 12 months post-operative. Knees for which correction was lost within 1 year of surgery had significantly greater preoperative varus alignment. Implant survivorship was 95% and 80% at 12 and 38 months post-operative, respectively. Significant improvements in patient-reported satisfaction, knee function and return to daily activities from preoperative to 38 months post-operative were reported (WOMAC 36 v 0; IKDC 35.6 v 96; Lysholm 44.5 v 100).
Conclusions:
Accelerated rehabilitation following MOW HTO with an intraosseous PEEK implant did not delay bone union, with significantly improved functional outcomes within 3 months post-operative. Early findings suggest that this approach may be suitable for a defined patient subset, with consideration for the extent of preoperative genu varum.
... Unstressed gaps were measured by applying a gravity-led opening of each compartment in extension and 90° flexion. Stressed gaps were measured in the same four positions whilst a varus or valgus force was applied across the joint as previously described [7]. Finally, the laxity in each compartment was measured and recorded at the completion of the surgery. ...
Purpose:
The decision on which technique to perform a total knee arthroplasty (TKA) has become more complicated over the last decade. Perceived limitations of mechanical alignment (MA) and kinematic alignment (KA) have led to the development of the functional alignment (FA) philosophy. This study aims to report the 2-year results of an initial patient cohort in terms of revision rate, PROMs and complications for Computer Aided Surgery (CAS) Navigated FA TKA.
Methods:
This paper reports a single surgeon's outcomes of 165 consecutive CAS FA TKAs. The final follow-up was 24 months. Pre-operative and post-operative patient-reported outcome measures, WOMAC and KSS, and intra-operative CAS data, including alignment, kinematic curves, and gaps, are reported. Stress kinematic curves were analysed for correlation with CAS final alignment and CAS final alignment with radiographic long-leg alignment. Pre- and post-operative CPAK and knee phenotypes were recorded. Three different types of prostheses from two manufacturers were used, and outcomes were compared. Soft tissue releases, revision and complication data are also reported.
Results:
Mean pre-operative WOMAC was 48.8 and 1.2 at the time of the final follow-up. KSS was 48.8 and 93.7, respectively. Pre- and post-operative range of motion was 118.6° and 120.1°, respectively. Pre-operative and final kinematic curve prediction had an accuracy of 91.8%. CAS data pre-operative stress alignment and final alignment strongly correlate in extension and flexion, r = 0.926 and 0.856, p < 0.001. No statistical outcome difference was detected between the types of prostheses. 14.5% of patients required soft tissue release, with the lateral release (50%) and posterior capsule (29%) being the most common.
Conclusion:
CAS FA TKA in this cohort proved to be a predictable, reliable, and reproducible technique with acceptable short-term revision rates and high PROMs. FA can account for extremes in individual patient bony morphology and achieve desired gap and kinematic targets with soft tissue releases required in only 14.5% of patients.
Level of evidence:
IV (retrospective case series review).
... After computer registration, alignment is assessed in extension (0 -10 ) and, importantly, at 90 flexion to determine the "neutral"/ nonstressed alignment. In addition, an opposing stress to the neutral alignment, varus in a valgus knee or valgus in a varus knee, is applied to the knee in extension and 90 flexion to evaluate ligamentous function or "stress alignment" and approximate the alignment kinematics of the "prearthritic" knee and the prearthritic alignment curve; via determining the extension and flexion alignment of the knee (Fig. 3) [8]. ...
The decision on which technique to use to perform a total knee arthroplasty has become much more complicated over the last decade. The shortfalls of mechanical alignment and kinematic alignment has led to the development of a new alignment philosophy, functional alignment. Functional alignment uses preoperative radiographic measurements, computer-aided surgery, and intraoperative assessment of balance, to leave the patient with the most “normal” knee kinematics achievable with minimal soft-tissue release. The purpose of this surgical technique article is to describe in detail the particular technique needed to achieve these alignment objectives.
Purpose
This study aimed to examine the accuracy of tibial implant alignment using an accelerometer-based portable navigation system in unicompartmental knee arthroplasty (UKA).
Methods
This retrospective matched case–control study reviewed 51 UKAs performed using an accelerometer-based portable navigation system, matched with 51 UKAs performed using conventional extramedullary rods. Coronal alignment and posterior slope of the tibial implant were measured on postoperative radiographs, and differences from preoperative planning were examined. Outliers and accuracy of tibial implant alignment were compared between the portable navigation and conventional groups using Fisher’s exact test and Mann–Whitney U test, respectively.
Results
In the portable navigation group, 100% of the implants were aligned within 3.0° of both target coronal and sagittal implant alignment. In the conventional group, 76.5% and 88.2% of the implants were within 3.0° of both target coronal and sagittal implant alignment. Statistical analysis revealed that outliers of coronal and sagittal alignment were significantly less in the portable navigation group than in the conventional group (P < 0.05). In addition, the absolute value difference between postoperative measurement and preoperative planning of both coronal and sagittal alignment was significantly smaller in the portable navigation group than in the conventional group (P < 0.05).
Conclusion
The portable navigation system improved the accuracy of tibial implant alignment in UKA. We found that 100% of the implants were aligned within 3.0° of both target coronal and sagittal implant alignment. The portable navigation system decreased the outliers of tibial coronal and sagittal alignment.
Level of evidence
Retrospective case–control study, Level III.
Despite the excellent success rates of modern implants,
unicompartmental knee arthroplasty (UKA) continues to
show relatively high failure and revision rates, especially
when compared with total knee arthroplasty (TKA).
These higher rates of failure and revision are mainly
observed during the early (< 5 years) post-operative
period and are often are due to incorrect indications and/
or surgical errors.
The correct clinical and radiological indications for UKA
have therefore been analysed and correlated as far as possible
with the principal mechanisms and timing of failures
of UKA.
Keywords: unicompartmental knee arthroplasty; polyethylene;
loosening; bearing dislocation; progression of osteoarthritis;
unexplained pain; early failure; revision
Unicompartmental knee arthroplasty (UKA) allows replacement of a single compartment in patients with limited disease. However, UKA is technically challenging and relies on accurate component positioning and restoration of natural knee kinematics. This study examined the accuracy of dynamic, real-time ligament balancing using a robotic-assisted UKA system. Surgical data obtained from the computer system were prospectively collected from 51 patients (52 knees) undergoing robotic-assisted medial UKA by a single surgeon. Dynamic ligament balancing of the knee was obtained under valgus stress prior to component implantation and then compared to final ligament balance with the components in place. Ligament balancing was accurate up to 0.53 mm compared to the preoperative plan, with 83% of cases within 1 mm at 0°, 30°, 60°, 90°, and 110° of flexion. Ligamentous laxity of 1.31 ± 0.13 mm at 30° of flexion was corrected successfully to 0.78 ± 0.17 mm (P < 0.05). Robotic-assisted UKA allows accurate and precise reproduction of a surgical balance plan using dynamic, real-time soft-tissue balancing to help restore natural knee kinematics, potentially improving implant survival and functional outcomes.
Most knee surgeons have believed during TKA neutral mechanical alignment should be restored. A number of patients may exist, however, for whom neutral mechanical alignment is abnormal. Patients with so-called "constitutional varus" knees have had varus alignment since they reached skeletal maturity. Restoring neutral alignment in these cases may in fact be abnormal and undesirable and would likely require some degree of medial soft tissue release to achieve neutral alignment.
We investigated what percentage of the normal population has constitutional varus knees and what are the contributing factors.
We recruited a cohort of 250 asymptomatic adult volunteers between 20 and 27 years old for this cross-sectional study. All volunteers had full-leg standing digital radiographs on which 19 alignment parameters were analyzed. The incidence of constitutional varus alignment was determined and contributing factors were analyzed using multivariate prediction models.
Thirty-two percent of men and 17% of women had constitutional varus knees with a natural mechanical alignment of 3° varus or more. Constitutional varus was associated with increased sports activity during growth, increased femoral varus bowing, an increased varus femoral neck-shaft angle, and an increased femoral anatomic mechanical angle.
An important fraction of the normal population has a natural alignment at the end of growth of 3° varus or more. This might be a consequence of Hueter-Volkmann's law. Restoration of mechanical alignment to neutral in these cases may not be desirable and would be unnatural for them.
The consensus of opinion suggests that when assessing measurement agreement, the most appropriate statistic to report is the "95% limits of agreement". The precise form that this interval takes depends on whether a positive relation exists between the differences in measurement methods (errors) and the size of the measurements--that is, heteroscedastic errors. If a positive and significant relation exists, the recommended procedure is to report "the ratio limits of agreement" using log transformed measurements. This study assessed the prevalence of heteroscedastic errors when investigating measurement agreement of variables recorded on a ratio scale in sports medicine and sports science.
Measurement agreement (or repeatability) was assessed in 13 studies (providing 23 examples) conducted in the Centre for Sport and Exercise Sciences at Liverpool John Moores University over the past five years.
The correlation between the absolute differences and the mean was positive in all 23 examples (median r = 0.37), eight being significant (P < 0.05). In 21 of 23 examples analysed, the correlation was greater than the equivalent correlation using log transformed measurements (median r = 0.01). Based on a simple meta-analysis, the assumption that no relation exists between the measurement differences and the size of measurement must be rejected (P < 0.001).
When assessing measurement agreement of variables recorded on a ratio scale in sports medicine and sports science, this study (23 examples) provides strong evidence that heteroscedastic errors are the norm. If the correlation between the absolute measurement differences and the means is positive (but not necessarily significant) and greater than the equivalent correlation using log transformed measurements, the authors recommend reporting the "ratio limits of agreement".
Restoration of neutral alignment of the leg is an important factor affecting the long-term results of total knee arthroplasty (TKA). Recent developments in computer-assisted surgery have focused on systems for improving TKA. In a prospective study two groups of 80 patients undergoing TKA had operations using either a computer-assisted navigation system or a conventional technique. Alignment of the leg and the orientation of components were determined on post-operative long-leg coronal and lateral films. The mechanical axis of the leg was significantly better in the computer-assisted group (96%, within +/- 3 degrees varus/valgus) compared with the conventional group (78%, within +/- 3 degrees varus/valgus). The coronal alignment of the femoral component was also more accurate in the computer-assisted group. Computer-assisted TKA gives a better correction of alignment of the leg and orientation of the components compared with the conventional technique. Potential benefits in the long-term outcome and functional improvement require further investigation.
Spontaneous osteonecrosis of the knee (SONK) is a distinct clinical condition occurring in patients without any associated risk factors. There is controversy as to the best method of treatment, and the available literature would suggest that patients with SONK have a worse outcome than those with primary osteoarthrosis when arthroplasty is performed. We assessed the outcome of medial unicompartmental knee arthroplasty (UKA) using the Oxford prosthesis for end-stage focal spontaneous osteonecrosis of the knee (SONK; Ahlbäck grades III and IV).
We assessed 29 knees (27 patients) with spontaneous osteonecrosis of the knee using the Oxford Knee Score. 26 knees had osteonecrosis of the medial femoral condyle and 3 had osteonecrosis of the medial tibial plateau. All had been operated on using the Oxford Medial Unicompartmental Knee Arthroplasty (UKA). This group was compared to a similar group (28 knees, 26 patients) who had undergone the same arthroplasty, but because of primary osteoarthrosis. Patients were matched for age, sex and time since operation. The mean length of follow-up was 5 (1-13) years.
There were no implant failures in either group, but there was 1 death (from unrelated causes) 9 months after arthroplasty in the group with osteonecrosis. The mean Oxford Knee Score in the group with osteonecrosis was 38, and it was 40 in the group with osteoarthrosis.
Use of the Oxford Medial UKA for spontaneous focal osteonecrosis of the knee is reliable in the short to medium term, and gives results similar to those obtained when it is used for patients with primary osteoarthrosis.
In a prospective study, two groups of 20 unicompartmental knee replacements (UKR) each were operated either using a CT-free navigation system or the conventional minimal invasive technique. Radiographic assessment of postoperative alignment was performed by long-leg coronal and lateral radiographs. The results revealed a significant difference between the two groups in favor of navigation. In the computer-assisted group, 95% of UKRs were in a range of 4-0 degrees varus (mechanical axis) compared with 70% in the conventional group. The only inconvenience was a prolonged operation time (+19 min). Due to the limited exposure, the navigation system is helpful in achieving a more precise component orientation. The danger of overcorrection is diminished by real-time information about the leg axis at each step during the operation.
In a retrospective review of the cases of twenty-nine patients who had a revision of a failed unicondylar unicompartmental knee replacement, the cause of failure of the originial unicondylar arthroplasty was found to be loosening of one or both components in sixteen patients, progression of disease in the opposite compartment in nine, patellofemoral symptoms in two, ligamentous instability in one, and malposition of the tibial component in one. A technical error had been made in sixteen of the patients, and ten of the errors were associated with the ultimate failure of the original unicondylar procedure. Ninety-three per cent of the failed unicompartmental arthroplasties were revised using a posterior cruciate-sparing total knee replacement. Bone grafts, augmentation with screws and cement, a long-stem component, or a combination of these were used in half of the patients. The average follow-up after the revision arthroplasty was 4.6 years.
Objective
To explore the outcome and surgical technique of minimally invasive unicompartmental knee arthroplasty (UKA) for spontaneous osteonecrosis of the knee.Methods
Twenty-seven patients with medial compartmental spontaneous osteonecrosis treated by minimally invasive Oxford phase 3 UKA from January 2009 to June 2013 were reviewed retrospectively. Twelve subjects were men and 15 women, with an average age of 64.6 ± 8.6 years (52–82 years). At the time of diagnosis, 11 patients had with grade III necrosis and 16 grade IV according to Mont's classification. Pain, range of motion (ROM) and Hospital for Special Surgery (HSS) knee scores were evaluated before and after UKA. Pre-and postoperative alignment of the lower limbs was measured and compared. Postoperative radiographic assessments were made according to the guidelines proposed by the Oxford group at the final follow-up.ResultsAll patients were followed for a mean time of 27.8 ± 15.9 months (6–59 months). There were no serious adverse events, such as infection, bearing dislocation, aseptic loosening, pulmonary embolism, deep venous thrombosis, cardio-cerebral vascular incident or psychological problems. One revision was required for unrelated causes (fracture of tibia plateau) 3 years after arthroplasty. One femoral component was tilted with a postoperative radiographic angle >10°. One radiolucent line was observed in a patient with spontaneous osteonecrosis of the knee. The two patients with implant failure had no symptoms at last follow-up. Visual analogue scale scores decreased from 6.9 ± 0.9 to 2.0 ± 1.1 (t = 19.27, P = 0.00). Pain was relieved in 96.3% of subjects (26/27). The mean post-operative ROM and femorotibial angle were 125.7° ± 9.6° and 177.7° ± 3.1°, respectively. HSS scores increased from 61.3 ± 9.7 to 93.0 ± 4.8 (t = 14.46, P = 0.00). Of the 27 patients, 26 (96.3%) were satisfied with the outcome of this surgical procedure.Conclusion
Minimally invasive UKA is an effective means of managing spontaneous osteonecrosis of the knee. The short-term outcome of UKA is encouraging.
Successful results of knee arthroplasty demand precise surgical technique, sound implant design, kinematics, appropriate materials and patient compliance with rehabilitation. The precision with which the implants are placed directly affects patient outcome as implant position and alignment influence the stability, durability and patellar tracking. Evaluating the alignment in total knee arthroplasty and functional outcome with respect to the alignment is the need of the hour. AIM AND OBJECTIVE OF THE STUDY: (1) To evaluate the accuracy of the overall limb alignment and component alignment in jig-assisted TKR. (2) To evaluate the functional outcome with respect to the alignment parameters.
This is a prospective study of 120 knees in 80 patients that underwent total knee replacement at Victoria and Bowring and Lady Curzon hospitals. Patients were selected according to the inclusion and exclusion criteria and evaluated using knee society score at regular follow-up. Preoperative and postoperative standing 'long-leg radiographs' and postoperative CT scans were taken from all the patients. In our study, we had 54 female patients and 26 male patients. Indications were OA in 72 and RA in 48 knees. The average follow-up period was 36 months.
Preoperatively, all the patients had moderate to severe pain. Mechanical and tibiofemoral axes were outside the acceptable range. Postoperatively, with respect to mechanical axis, the inliers had significantly better knee score (p = 0.026) compared to the outliers. But the functional score did not show any significant difference between these two groups (p = 0.2093). Inliers in tibiofemoral axis alignment parameter had extremely significant better knee score (p = 0.0001) and also functional score (p = 0.0082) compared to outliers group. Sagittal and rotational femoral component angles in all 120 cases were coming within the 'inliers group'. Similarly, the sagittal, the coronal and the rotational component angles of tibia were also coming under inliers group in all 120 replaced knees.
Aligning the mechanical axis, tibiofemoral angle within (0° ± 3°) and placement of prostheses within (0° ± 3°) to the normal alignment in all the three planes significantly produce excellent result with respect to functional outcome.
Unicompartmental knee arthroplasty (UKA) is a minimally invasive option reported to allow a more rapid recovery and better patient outcomes. However, whether these outcomes are related to selection bias has not been fully investigated. This study examines whether a bias existed in selection of UKA candidates. We compared outcomes of patients who were scheduled for UKA but had the plan changed intraoperatively to total knee arthroplasty (TKA) to two randomly selected contemporaneous control groups: 1) patients planned as UKA who received UKA and 2) patients planned as TKA who received TKA. Our results not only showed a selection bias existed, but also showed patients converted to TKA intraoperatively had similar clinical results to patients receiving UKAs and better results than patients originally scheduled for TKA.
Copyright © 2015. Published by Elsevier Inc.
Limb alignment after unicondylar knee arthroplasty (UKA) has a significant impact on outcomes. The literature lacks lateral UKA alignment studies, making our understanding of this issue based on medial UKA.
We evaluated limb alignment in 241 patients who underwent medial (229 knees) or lateral (37 knees) UKA. Alignment was measured pre and postoperatively in radiographs and intra-operatively using a navigation system. We compared the percentage of over-correction and the difference between post-operative alignment and navigation measurement.
Percentage of overcorrection was significantly higher in the lateral UKAs (11%) compared to the medial UKAs (4%). In medial UKAs, the mean difference between the intraoperative alignment and the post-operative was 1.33°. This was significantly lower than the mean 1.86° difference in the lateral UKAs.
Our data demonstrated an increased risk of "overcorrection," and greater difficulty in predicting postoperative alignment using computer navigation, when performing lateral UKAs compared to medial UKAs.
Copyright © 2015 Elsevier B.V. All rights reserved.
In this study, the enhancement on 4-chloronitrobenzene (4-CNB) reduction was investigated in a dual-bioelectrochemical system with the cathode seeded by enriched 4-CNB degradation inoculums. We demonstrated that the biocathode had the ability to promote 4-CNB reduction and avoid more reluctant byproducts production. At room temperature, when initial 4-CNB concentration was 20 mg/L with 0.5 V external voltage, the 4-CNB removal efficiency reached 93.7%, while in the abiotic reactor and anaerobic bioreactor reduction rate were 62.9% and 88.4%, respectively. The 4-CNB was mainly converted to 4-CAN (para-chloroaniline). Some of the 4-CAN could be dechlorinated and form aniline (AN), which was more degradable by microorganism. The biodiversity was richer based on the result of scanning electron microscope. Results also showed that the present used reactor was feasible to simplify pollutant transformation and improve transformation efficiency compared with the single abiotic cathode and anaerobic reactor. The bioelectrochemical reactor cathode provided a promising condition for pollutants reduction.
Purpose
The aim of this study was to compare the functional outcome of patients following unicompartmental knee replacement (UKR) using the Oxford domed lateral UKR to patients who underwent cruciate-retaining total knee replacement (TKR) for isolated osteoarthritis in the lateral compartment.
Methods
With the help of our institutional database, we retrospectively identified 22 matched pairs with regards to age, gender and body mass index (BMI). Functional outcome was measured using the Oxford Knee Score (OKS) and range of motion (ROM). Complications and revisions were recorded.
Results
The mean follow-up was 22 (UKR) and 19 (TKR) months, respectively. Patients following UKR had a statistically significant higher mean postoperative OKS and ROM: mean OKS was 43 [standard deviation (SD) 4] for UKR and 37 (SD 9) for TKR, respectively (p = 0.023); ROM was 127° (SD 13) for UKR and 107° (SD 17) for TKR (p
We compared lower limb coronal alignment measurements obtained pre- and post-operatively with long-leg radiographs and computer navigation in patients undergoing primary total knee replacement (TKR). A series of 185 patients had their pre- and post-implant radiological and computer-navigation system measurements of coronal alignment compared using the Bland-Altman method. The study included 81 men and 104 women with a mean age of 68.5 years (32 to 87) and a mean body mass index of 31.7 kg/m ² (19 to 49). Pre-implant Bland–Altman limits of agreement were -9.4° to 8.6° with a repeatability coefficient of 9.0°. The Bland–Altman plot showed a tendency for the radiological measurement to indicate a higher level of pre-operative deformity than the corresponding navigation measurement. Post-implant limits of agreement were -5.0° to 5.4° with a repeatability coefficient of 5.2°. The tendency for valgus knees to have greater deformity on the radiograph was still seen, but was weaker for varus knees.
The alignment seen or measured intra-operatively during TKR is not necessarily the same as the deformity seen on a standing long-leg radiograph either pre- or post-operatively. Further investigation into the effect of weight-bearing and surgical exposure of the joint on the mechanical femorotibial angle is required to enable the most appropriate intra-operative alignment to be selected.
Background:
This study originated from a symposium held by the French Hip and Knee Society (Société française de la hanche et du genou [SFHG]) and was carried out to better assess the distribution of causes of unicompartmental knee arthroplasty (UKA) failures, as well as cause-specific delay to onset.
Hypothesis:
Our working hypothesis was that most failures were traceable to wear occurring over a period of many years.
Materials and methods:
A multicentre retrospective study (25 centres) was conducted in 418 failed UKAs performed between 1978 and 2009. We determined the prevalence and time to onset of the main reasons for revision surgery based upon available preoperative findings. Additional intraoperative findings were analysed. The results were compared to those of nation wide registries to evaluate the representativeness of our study population.
Results:
Times to revision surgery were short: 19% of revisions occurred within the first year and 48.5% within the first 5 years. Loosening was the main reason for failure (45%), followed by osteoarthritis progression (15%) and, finally, by wear (12%). Other reasons were technical problems in 11.5% of cases, unexplained pain in 5.5%, and failure of the supporting bone in 3.6%. The infection rate was 1.9%. Our results were consistent with those of Swedish and Australian registries.
Discussion:
Our hypothesis was not confirmed. The short time to failure in most cases suggests a major role for surgical technique issues. Morbidity related to the implant per se may be seen as moderate and not greater than with total knee prostheses. The good agreement between our data and those of nationwide registries indicates that our population was representative. A finer analysis is needed, indicating that the establishment of a French registry would be of interest.
Whilst various studies have examined lower extremity joint kinematics during running, there is limited investigation on joint kinematics at steady-state running and at intensities close to exhaustion. Subsequently, the purpose of this study was to determine whether the reliability of kinematics in the lower extremity and thorax is affected by varying the running speeds during a running economy test. 14 trained and moderately trained runners undertook 2 running economy tests with each test incorporating 3 intensity stages: 70-, 90- and 110% of the second ventilatory threshold, respectively. The participants ran for 10 min during each of the first 2 stages and to exhaustion during the last stage. Kinematics of the ankle, knee, hip, pelvis and thorax were recorded using a 3-dimensional motion analysis system. Intra-class correlation coefficient (ICC), limits of agreement (LOA) and coefficient of variation (CV) were used to calculate reliability. The ICC, LOA and CV of the lower extremity and thoracic kinematic variables ranged from 0.33-0.97, 1.03-1.39 and 2.0-18.6, respectively. Whilst the reliability did vary between the kinematic variables, the majority of results showed minimal within-subject variation and moderate to high reliability. In conclusion, examining thoracic and lower extremity kinematics is useful in determining whether running kinematics is altered with varying running intensities.
The aim of our study was to compare the use of the Orthopilot Navigation system with conventional non-navigation technique for medial UKA with respect to the intraoperative mechanical limb alignment measurements and correlation with the postoperative radiological measurements. The postoperative mechanical limb alignment axes of 51 consecutive medial unicompartmental knee arthroplasty performed by a single surgeon over a 12-month period were measured. The cases were randomly assigned to two groups of which 21 cases were performed using conventional non-navigation based technique and 30 cases were performed using the Orthopilot Navigation System. Computed tomography (CT) scanogram was performed for all cases within the same hospitalization stay to assess the postoperative mechanical limb alignment. Our results showed that the non-navigated group had a more neutral mechanical axis with a narrower range compared to the navigation assisted group. The difference in the mean mechanical axis between the two groups was statistically not significant. There was poor correlation between the intraoperative navigation system measurements and the postoperative radiological measurements. In conclusion, the use of computer navigation in UKA is not as well validated as compared to TKA. We did not demonstrate any improvement in postoperative axial limb alignment measurement in using a computer navigation system compared to conventional non-navigation technique.
Unicompartmental arthroplasty using the Marmor Modular knee was performed in 27 knees of 24 patients--three men and 21 women--aged 51-82 years (average age 68.9 years). The disease was osteoarthritis in 19 knees, steroid arthropathy in two knees, Charcot joint in three knees, and rheumatoid arthritis in three knees. Medial replacement was done in 24 knees and lateral replacement in three knees. Follow-up was from 2-7 years (average 4 years 9 months). Post-operatively, 14 knees were reported to be free of pain and 11 only occasionally mildly painful. Walking distance improved to more than 1 km in 17 patients. The knee score improved from 40.4 to 72.2 points (p less than 0.01). Complications included two knees with loosening due to postoperative limb malalignment; there were no instances of infection or fracture.
Thirty-two unicondylar knee replacements in thirty patients were done between 1972 and 1974. Ten patients were lost to follow-up because of death or other reasons. The remaining twenty-two knees (seventeen medial and five lateral compartments replaced) had a follow-up ranging from five to seven years, with an average of six years. Although the quality and result of these unicondylar arthroplasties were initially considered good, they have subsequently shown a marked deterioration. At the time of this report only one knee was rated as excellent; seven knees, as good; four knees, as fair; and ten knees, as poor. Seven knees (28 per cent) have been converted to a bicondylar prosthesis. The lateral replacements did much better than the medial replacements.
A synthetic femur and tibia were used to create a model resurfacing total knee arthroplasty. The femoral component was placed in 7 degrees valgus; the tibial component was placed in 2 degrees varus with a 5 degrees posterior slope. The overall anatomic alignment was 5 degrees valgus. A series of radiographs were taken on 14 inch x 17 inch plates, in full extension and 10 degrees flexion, with the limb rotated, in 5 degree increments, from 20 degrees external rotation to 25 degrees internal rotation. Seven orthopaedic surgeons independently measured the tibiofemoral angle and tibial alignment for each series of radiographs; interobserver variability was insignificant. Average radiographic anatomic alignment ranged from 2.29 degrees valgus in 20 degrees external rotation and 10 degrees flexion, to 6.73 degrees valgus in 25 degrees internal rotation and 10 degrees flexion. Limb rotation and knee flexion of 10 degrees, either alone or in combination, had a highly statistically significant effect on measured values of the anatomic alignment. Tibial alignment ranged from 5 degrees varus in 20 degrees external rotation to 3 degrees valgus in 25 degrees internal rotation, with the knee flexed 10 degrees. The variability associated with changes in rotation was statistically significant. Changes associated with rotation, when the knee was flexed 10 degrees, were not significantly different than those measured with the knee fully extended. Even in a well aligned total knee arthroplasty, limb positioning at the time of radiographic assessment will alter the apparent alignment indices, making objective evaluation difficult.
Retrieval studies have shown that the use of fully congruent meniscal bearings reduces wear in knee replacements. We report the outcome of 143 knees with anteromedial osteoarthritis and normal anterior cruciate ligaments treated by unicompartmental arthroplasty using fully congruous mobile polyethylene bearings. At review, 34 knees were in patients who had died and 109 were in those who were still living. The mean elapsed time since operation was 7.6 years (maximum 13.8). We established the status of all but one knee.
There had been five revision operations giving a cumulative prosthetic survival rate at ten years (33 knees at risk) of 98% (95% CI 93% to 100%). Considering the knee lost to follow-up as a failure, the ‘worst-case’ survival rate was 97%. No failures were due to polyethylene wear or aseptic loosening of the tibial component. One bearing which dislocated at four years was reduced by closed manipulation.
The ten-year survival rate is the best of those reported for unicompartmental arthroplasty and not significantly different from the best rates for total knee replacement.
Sixty-two consecutive cemented modular unicompartmental knee arthroplasties in 51 patients were studied prospectively. At surgery, the other compartments had at most Grade 2 chondromalacia. The average age of the patients at arthroplasty was 68 years (range, 51-84 years). One patient was lost to followup and 10 died with less than 6 years followup. The average followup of the remaining 51 knees was 7.5 years (range, 6-10 years). The preoperative Hospital for Special Surgery knee score of 55 points (range, 30-79 points) improved to 92 points (range, 60-100 points) at followup; 78% (40 knees) had excellent and 20% (10 knees) had good results. The mean range of motion at followup was 120 degrees with 26 knees (51%) having range of motion greater than 120 degrees. One patient underwent revision surgery for retained cement, one patient underwent knee manipulation, and one patient underwent revision surgery at 7 years for opposite compartment degeneration and pain. Radiographically, 26 knees (51%) had at least one partial radiolucency. There were no complete femoral radiolucencies, but there were three complete tibial radiolucencies, all less than 2 mm. No component was loose as seen on radiographs. At final followup, five of the opposite compartments (10%) and three of the patellofemoral joints (6%) had some progressive radiographic joint space loss; this was less than a 25% loss in all but one knee component that was revised. At 6- to 10-years followup, cemented unicompartmental knee arthroplasty yielded excellent clinical and radiographic results. The 10-year survival using radiographic loosening or revision as the end point was 98%. Using stringent selection criteria, unicompartmental knee replacement can yield excellent results and represents a superb alternative to total knee replacement.
Unicompartmental arthroplasty is a treatment alternative when only one compartment of the knee is affected with arthritis, but the reported results of this procedure have been variable. The purpose of the present study was to evaluate the results of a modern unicompartmental knee arthroplasty performed with use of a cemented metal-backed prosthesis and surgical instrumentation comparable with that used for total knee replacement.
The indications for the procedure were osteonecrosis or osteoarthritis associated with full-thickness loss of cartilage that was limited to one tibiofemoral compartment as evaluated on standing and stress radiographs. One hundred and sixty consecutive cemented metal-backed Miller-Galante prostheses in 147 patients were evaluated after a mean duration of follow-up of sixty-six months (range, thirty-six to 112 months). The mean age of the patients at the time of the index procedure was sixty-six years.
Three knees were revised because of progression of osteoarthritis in the patellofemoral joint (two knees) or the lateral tibiofemoral compartment (one knee). Two knees had revision of the polyethylene liner. The average Hospital for Special Surgery knee score improved from 59 points preoperatively to 96 points at the time of the review. According to Kaplan-Meier analysis, the ten-year survival rate (with twenty-nine knees at risk) was 94% +/- 3% with revision for any reason or radiographic loosening as the end point.
A modern unicompartmental knee arthroplasty is a valid alternative for patients with unicompartmental tibiofemoral noninflammatory disease. The patient selection must be strict with regard to the status of the patellofemoral joint. The preoperative planning includes stress radiographs to assess the correction of the deformity and the status of the uninvolved compartment. Continued long-term follow-up is necessary to evaluate long-term polyethylene wear.
We describe postoperative functional outcome and accuracy of implant position in 38 cases after unicompartmental knee arthroplasty with the Oxford knee prosthesis with a standard open approach compared with 30 cases with a minimally invasive approach. Patients with the minimally invasive approach had significantly better functional results, with an average Hospital for Special Surgery scores of 92 (range, 81-98) compared with 78 (range, 24-99). Range of motion 1 year postoperatively was better in the minimally invasive group (113 degrees vs 107 degrees ), but the results were not statistically significant. The number of patients with extension lag was significantly higher after the open approach. The minimal invasive approach had no negative effect on positioning of the prosthesis. In our opinion, minimally invasive implantation is the method of choice for the treatment of anteromedial osteoarthritis by unicompartmental knee arthroplasty.
We describe the outcome of a series of 66 consecutive porous coated low contact stress (LCS) unicompartmental knee arthroplasty (UKA) cases performed in 52 patients for osteoarthritis (OA) by a single surgeon. Both survival, using the endpoint of revision for any cause, and knee function, using the Oxford knee score (OKS) as a validated outcome measure, were established in a retrospective review. At an average postoperative follow-up period of 5.9 years (range 5.1-6.6), there were 8 knees in patients who had died and 58 knees in those who were still living. We established the status of all knees, and prosthesis survival at 5 years was 89.7% (95% confidence interval, 81.6% to 97.7%). Technical errors were responsible for four of six failures and included progression of lateral compartment OA due to overcorrection, a medial tibial stress fracture due to poor pin placement, and a case where cement was required and poor cementing technique lead to early tibial component loosening. In the remaining 52 knees, the average preoperative OKS had improved significantly (p<0.0001) from 37.0 (range, 17-49) to a postoperative score of 20.5 (range, 13-32). We conclude that the functional results following UKA compare favourably to total knee arthropasty (TKA); however, the survivorship of this series does not match that of published reports of TKA. The introduction of a new system of UKA includes the risk of early failures due to surgeon error, even when a surgeon is competent in UKA, warranting careful surveillance during this period.
We reviewed the outcome of 30 consecutive primary unicompartmental knee arthroplasties (UKAs) performed by a single surgeon over a 26-month period. All operations were performed to treat osteoarthritis of the medial compartment of the knee. Fifteen Allegretto (Sulzer, Winterthur, Switzerland) UKAs were implanted without computer navigation whereas 15 EIUS (Stryker-Howmedica, Allendale, NJ) UKAs were implanted using navigation. The patients were assessed clinically using the Oxford knee score and radiologically using long-leg weight-bearing films and non-weight-bearing computed tomography leg alignment films. No patients operated on were lost to follow-up. Unicompartmental knee arthroplasty performed with computer-assisted surgical navigation resulted in a more accurate and reproducible limb alignment than UKA performed without surgical navigation.
Tibial articular cartilage wear was assessed intraoperatively in 100 consecutive patients with varus osteoarthritis undergoing total knee arthroplasty. Severity of deformity on radiographs, integrity of the anterior cruciate ligament (ACL) at surgery, and body mass index were recorded. Posterior half of the medial tibial plateau was more commonly involved in knees with ACL deficiency; there was predominantly anteromedial involvement with an intact ACL. Varus deformity was significantly greater in knees with a deficient ACL than with an intact ACL. Severity of deformity did not alter the wear pattern, irrespective of the ACL integrity. The functional status of ACL in an osteoarthritic knee can be corroborated with the wear pattern on the tibial plateau articular cartilage.
Minimally invasive surgery vs conventional exposure using the Miller-Galante unicompartmental knee arthroplasty: a randomised radiostereometric study
- L V Carlsson
- Bej Alberktsson
- L R Regner
Carlsson LV, Alberktsson BEJ, Regner LR. Minimally invasive surgery vs conventional exposure using the Miller-Galante unicompartmental knee arthroplasty: a randomised radiostereometric study. J Arthroplasty 2006;21(2):999.
Kinematic alignment in total knee arthroplasty. Definition, history, principle, surgical technique, and results of an alignment option for TKA
- S M Howell
- J D Roth
- M L Hull
Howell SM, Roth JD, Hull ML. Kinematic alignment in total knee arthroplasty.
Definition, history, principle, surgical technique, and results of an alignment
option for TKA. Arthropaedia 2014;1:44.