Considerable inter-individual variability of tibial geometric ratios renders bone-implant mismatch unavoidable using off-the-shelf total knee arthroplasty: a systematic review and meta-analysis

Comparison of the coverage and rotation of asymmetrical and symmetrical tibial components: a systematic review and meta-analysis

BACKGROUND

An optimized fit of the tibial component to the resection platform and correct rotational alignment are critical for successful total knee arthroplasty (TKA). However, there remains controversy regarding the superiority of symmetric tibial component versus asymmetric tibial component. The objective of this systematic review and meta-analysis was to evaluate the current evidence for comparing the coverage and rotation of asymmetrical and symmetrical tibial component.

METHODS

We searched potentially relevant studies form PubMed, Web of science, Embase, Cochrane Central Register of Controlled Trials (CENTRAL), and China National Knowledge Infrastructure (CNKI), up to 1 March 2023. Data extraction and quality assessment were performed by two independent reviewers. Meta-analysis was conducted using Review Manager 5.4.

RESULTS

Sixteen articles were identified. Compared to symmetric tibial component, asymmetric tibial component increased the coverage of the proximal tibial cut surface (MD, -2.87; 95%CI, -3.45 to -2.28; P < 0.00001), improved the prevalence of tibial baseplate underhang (OR, 0.16; 95%CI, 0.07 to 0.33; P < 0.00001) and malrotation (OR, 0.13; 95%CI, 0.02 to 0.90; P = 0.04), and reduced the degree of tibial component rotation (MD, -3.11; 95%CI, -5.76 to -0.47; P = 0.02). But there was no statistical significance for improving tibial baseplate overhang (OR, 0.58; 95%CI, 0.08 to 3.97; P = 0.58). Additionally, no revision had occurred for the two tibial components in the included studies.

CONCLUSION

The current evidence shows asymmetric tibial component offer advantages in terms of coverage and rotation compared with symmetric tibial component in TKA.

The posterior tibial slope affects the measurement reliability regarding the radiographic parameter of the knee

BACKGROUND

Posterior tibial slope (PTS) exhibits considerable variability among individuals and is anticipated to influence the accuracy of radiographic measurements related to the knee. Despite this potential impact, there is a lack of prior research investigating how PTS affects the accuracy of these measurements. Therefore, this study aimed to investigate the effect of PTS on the measurement reliability regarding the radiographic parameter of the knee.

METHODS

The medical records of patients who took full-length anteroposterior radiographs of the lower limb between January 2020 and June 2022 were evaluated retrospectively. Radiographic parameters related to the knee joint characteristics such as osteoarthritis grade, hip-knee-ankle angle, weight-bearing line ratio, medial proximal tibial angle (MPTA), lateral distal femoral angle, joint-line convergence angle (JLCA), and PTS were measured. Subjects were classified into 3 groups according to PTS (group A, PTS < 4°; group B, PTS ≥ 4° and < 8°; group C, PTS ≥ 8°), and the measurement reliability for the radiographic variables was compared between groups. The intra- and inter-observer agreements were assessed using the kappa coefficients, intra-class correlation coefficients (ICC), and Bland-Altman plots.

RESULTS

A total of 175 limbs (86 patients) were included in this study. As the intra- and inter-observer reliability for PTS ranged over 0.9, grouping was performed based on the average of the measured PTSs. The inter-observer reliability of the MPTA and JLCA decreased as the PTS increased (ICCs for MPTA in Groups A, B, and C: 0.889, 0.796, and 0.790, respectively; ICCs for JLCA in Groups A, B and C: 0.916, 0.859, and 0.843, respectively), whereas there were no remarkable differences in other variables. Similar trends were observed in the comparisons of intra-observer reliability and Bland-Altman plots also showed consistent results.

CONCLUSION

The larger the PTS, the lower the measurement reliability regarding the radiographic parameters of the knee that includes the joint line, such as MPTA and JLCA. Given the occasional challenge in accurately identifying the knee joint line in patients with a relatively large PTS, careful measurement of radiographic parameters is crucial and utilizing repetitive measurements for verification may contribute to minimizing measurement errors.

The use of an anatomic tibial baseplate in total knee arthroplasty optimizes coverage without compromising rotation: A propensity-matched evaluation

BACKGROUND

The aims of this study were (1) to compare in vivo coverage and rotational alignment of 2 tibial component designs: anatomic and symmetrical; and (2) to determine if coronal deformity and tibial torsion were related to rotation and coverage.

METHODS

Postoperative CT scans of 200 propensity score-matched patients who underwent TKA with either an anatomic (ATC) or symmetrical tibia component (STC) were analyzed. Rotation was measured using four axes: surgical transepicondylar axis (sTEA), Berger's protocol, medio-lateral (ML) axis and posterior borders of the tibial plateau, while coverage was assessed by measuring fit and surface area. The relationship between coronal deformity, tibial torsion, rotation, and coverage was investigated.

RESULTS

Overall, STCs had more internal rotation when measured using the sTEA (-0.6° ± 3.5 vs 0.5° ± 3.6, p = 0.03), Berger's protocol (-21.6° ± 7.1 vs -17.9° ± 6.2, p = 0.000) and ML axes (2.9° ± 3.9 vs 8.1° ± 5.1, p = 0.000) compared to ATCs. STCs also had more posteromedial underhang (-3.3 mm ± 2.4 mm vs -1.7 mm ± 2.5 mm, p = 0.000) but smaller change in tibial torsion postoperatively (-18.4° ± 9.9° vs -13.1° ± 9.4°, p = 0.000). Tibial torsion was more pronounced in valgus than varus knees both preoperative (-25.4° ± 6.5° vs -20.2° ± 9.3°, p = 0.02) and postoperatively (-19.7° ± 7.2° vs -14.7° ± 10.3°, p = 0.04), but there was no difference in postoperative tibial torsion between ATCs and STCs in this subgroup.

CONCLUSION

The use of an anatomic tibial baseplate optimizes coverage by reducing posterolateral overhang and posteromedial underhang. It also achieved better rotational profiles compared to STCs. However, it resulted in a larger change in tibial torsion after TKA.

Satisfaction after total knee arthroplasty: a prospective matched-pair analysis of patients with customised individually made and off-the-shelf implants

PURPOSE

Customised individually made (CIM) total knee arthroplasty (TKA) was introduced to potentially improve patient satisfaction and other patient-reported outcome measures (PROMs). The purpose of this study was to compare PROMs, especially patient satisfaction, of patients with CIM and OTS TKA in a matched-pair analysis with a 2-year follow-up.

METHODS

This is a prospective cohort study with a propensity score matching of 85 CIM and 85 off-the-shelf (OTS) TKA. Follow-up was at 4 months, 1 year and 2 years. The primary outcome was patient satisfaction. Secondary outcomes were as follows: overall improvement, willingness to undergo the surgery again, Knee injury and Osteoarthritis Outcome Score (KOOS), Forgotten Joint Score (FJS-12), High-Activity Arthroplasty Score (HAAS), EQ-5D-3L, EQ-VAS, Knee Society Score (KSS) and surgeon satisfaction.

RESULTS

Patient satisfaction ranged from 86 to 90% and did not differ between CIM and OTS TKA. The EQ-VAS after 4 months and the HAAS after 1 year and 2 years were higher for CIM TKA. KOOS, FJS-12 and EQ-5D-3L were not different at follow-up. The changes in KOOS symptoms, pain and daily living were higher for OTS TKA. The KSS was higher for patients with CIM TKA. Surgeon satisfaction was high throughout both groups. Patients who were satisfied after 2 years did not differ preoperatively from those who were not satisfied. Postoperatively, all PROMs were better for satisfied patients. Patient satisfaction was not correlated with patient characteristics, implant or preoperative PROMs, and medium to strongly correlated with postoperative PROMs.

CONCLUSION

Patient satisfaction was high with no differences between patients with CIM and OTS TKA. Both implant systems improved function, pain and health-related quality of life. Patients with CIM TKA showed superior results in demanding activities as measured by the HAAS.

LEVEL OF EVIDENCE

II, prospective cohort study.

Definitions and consequences of current alignment techniques and phenotypes in total knee arthroplasty (TKA) - there is no winner yet

Dissatisfaction following total knee arthroplasty (TKA) has been extensively documented and it was attributed to numerous factors. In recent years, significant focus has been directed towards implant alignment and stability as potential causes and solutions to this issue. Surgeons are now exploring a more personalized approach to TKA, recognizing the importance of thoroughly understanding each individual patient's anatomy and functional morphology. A more comprehensive preoperative analysis of alignment and knee morphology is essential to address the unresolved questions in knee arthroplasty effectively. The crucial task of determining the most appropriate alignment strategy for each patient arises, given the substantial variability in bone resection resulting from the interplay of phenotype and the alignment strategy chosen. This review aims to comprehensively present the definitions of different alignment techniques in all planes and discuss the consequences dependent on knee phenotypes.Level of evidence V.

Inverse kinematic alignment accommodates native coronal knee alignment better in comparison to adjusted mechanical alignment and restricted kinematic alignment

PURPOSE

The purpose was to determine the proportion of native non-arthritic knees that fit within the target zones of adjusted mechanical alignment (aMA), restricted kinematic alignment (rKA), and inverse kinematic alignment (iKA), and to estimate adjustments in native coronal alignment to bring outlier knees within the respective target zones. The hypothesis was that the target zone of iKA, compared to the target zones of aMA and rKA, accommodates a higher proportion of native non-arthritic knees.

METHODS

The study used measurements obtained from a computed tomography (CT) scan database (SOMA, Stryker) of 972 healthy knees (Caucasian, 586; Asian, 386). Hip knee ankle (HKA) angle, medial proximal tibial angle (MPTA) and lateral distal femoral angle (LDFA) were used to estimate the proportions of knees within the patient-specific alignment target zones; and to estimate theoretical adjustments of MPTA, LDFA and soft tissue balance (HKA) to bring outlier knees within target zones. Theoretical adjustments to bring outlier knees within the alignment target zones of aMA, rKA and iKA were calculated by subtracting the native coronal alignment angles (MPTAnative, LDFAnative and HKAnative) from angles on the nearest target zone border (MPTAtarget, LDFAtarget and HKAtarget).

RESULTS

Patients were aged 59.8 ± 15.8 years with a BMI of 25.0 ± 4.4 kg/m2. The HKA angles were between 168° and 186°, MPTA between 78° and 98° and LDFA between 79° and 93°. Of the 972 knees, 81 (8%) were in the aMA target zone, 530 (55%) were in the rKA target zone, and 721 (74%) were in the iKA target zone. Adjustments of MPTA, LDFA and HKA angle to bring outlier knees within the target zones, were, respectively, 90, 91 and 28% for aMA, 45, 28 and 25% for rKA, and 25, 23 and 7% for iKA.

CONCLUSIONS

There is considerable variability in native knee coronal alignment that corresponds to different proportions of the restricted patient-specific alignment target zones for TKA. Although extension of the MPTA and LDFA target zones with rKA accommodate native knee alignment better than aMA, up to 25% would require adjustment of native HKA angle. By also extending the HKA angle target zone into varus, iKA accommodates a greater proportion (93%) of native limb alignment.

LEVEL OF EVIDENCE

IV.

Custom total knee arthroplasty combined with personalised alignment grants 94% patient satisfaction at minimum follow-up of 2 years

PURPOSE

The purpose was to report detailed patient-reported outcome measures (PROMs) and satisfaction rates for computed tomography (CT)-based custom TKA at minimum follow-up of 2 years. The hypothesis was that custom TKA combined with 'personalised alignment' would yield equivalent or better PROMs compared to values reported in systematic reviews and meta-analyses on off-the-shelf (OTS) TKA.

METHODS

Of an initial cohort of 150 custom TKAs, four died (unrelated to surgery), one required a revision, and five refused participation, leaving 140 patients for analysis. Patients completed pre- and post-operative PROMs (Oxford Knee Score (OKS), Forgotten Joint Score (FJS), Knee injury and Osteoarthritis Outcome Score (KOOS), Western Ontario and McMaster osteoarthritis index (WOMAC)) as well as overall level of satisfaction. Proportions that attained a patient acceptable symptom state (PASS) were calculated for OKS and FJS. Clinical findings were compared to the average scores reported for PROMs in recent systematic reviews and/or meta-analyses on OTS TKA. Descriptive statistics were used to summarise the clinical findings as means, standard deviations (SD) and ranges, or numbers and percentages.

RESULTS

At mean follow-up 33.5 ± 4.5 months, 94% (135/143) were either satisfied or very satisfied. Proportions that achieved PASS were 89% for OKS (120/135), and 85% for FJS (118/139). Median OKS, WOMAC and KOOS Symptoms and Pain scores were all within the 4th quartile of medians reported in systematic reviews and/or meta-analyses.

CONCLUSIONS

At a minimum follow-up of two years following custom TKA combined with 'personalised alignment', 94% of patients were either satisfied or very satisfied, and the PASS criteria were achieved in 89% for OKS and 85% for FJS, all of which compare favourably to published outcomes of OTS TKA. Direct comparisons to the literature may not be appropriate, however, considering the heterogeneity of patient demographics and alignment techniques. Randomised controlled trials with sufficient statistical power are needed to corroborate these findings and generalise them to unselected TKA patients.

LEVEL OF EVIDENCE

IV, retrospective cohort study.

Insufficient evidence to confirm benefits of custom partial knee arthroplasty: a systematic review

PURPOSE

The purpose of this systematic review was to synthesise the available literature and critically appraise current evidence on the functional and radiographic outcomes as well as reoperation and revision rates of custom partial knee arthroplasty, i.e., unicompartmental knee arthroplasty (UKA), bicompartmental knee arthroplasty (BKA), and patellofemoral arthroplasty (PFA).

MATERIAL AND METHODS

This systematic review was performed in accordance with the guidelines of Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), and a protocol was registered with Prospero. On 25 May 2021, two authors independently searched and screened Level I-IV studies that reported on outcomes of custom partial knee arthroplasty using the databases of MEDLINE^®, EMBASE^®, and the Cochrane Library without restriction on date of publication. Findings from eligible articles were synthesised and tabulated, and quality assessments were done according to the guidelines of the Joanna Briggs Institute (JBI) Checklists.

RESULTS

Fifteen articles were eligible for data extraction, of which two comparative and four case series were on custom UKA (follow-up, 0-9 months), one comparative and five case series on custom BKA (follow-up, 0.25-72 months), and three case series on custom PFA (follow-up, 2-119 months). Three studies on custom UKA reported mean Knee Society Score (KSS) Knee of 86-94 and mean KSS Function of 94-95, and two studies on custom BKA reported mean KSS Knee of 90-94 and KSS function of 81, whereas one study on custom PFA reported KSS Knee of 91 and KSS Function of 89. Custom implants tended to have less bone-implant mismatch compared to off the shelf (OTS) implants. Revision rates were 3-25% for custom UKA (at 0-109 months), 3-5% for custom BKA (at 12-72 months), and 0-14% for custom PFA (at 2-119 months).

CONCLUSION

Due to the small number of comparative studies and lack of consistency in reported outcomes, it remains difficult to ascertain the benefits of custom partial knee arthroplasty. Anecdotal evidence suggests that, compared to OTS implants, custom implants result in less bone-implant mismatch and that 78-91% of patients are either satisfied or very satisfied after custom partial knee arthroplasty.

LEVEL OF EVIDENCE

IV.

Comparison of Anterior-Posterior Axis Versus Transepicondylar Axis in Patients Undergoing Simultaneous Bilateral Total Knee Arthroplasty: One Technique per Knee

BACKGROUND

In primary total knee arthroplasty (TKA), the preferred reference line for setting femoral component rotation is debatable. This study compared the anterior-posterior axis line (APAL) versus the transepicondylar axis line (TEAL) in patients undergoing simultaneous bilateral TKA using a measured resection technique where one reference line was randomized to each knee.

METHODS

This prospective study compared the two reference lines using posterior knee referencing with a cemented posterior stabilized knee. The study included 32 patients with osteoarthritis with both knees having similar varus knee deformities. All patients had the same surgical procedure with the only change being the selected femoral rotation axis line. Patients were followed up for a minimum of two years.

RESULTS

There was no significant difference in any of the measured radiographic, operative, and clinical parameters, except for a postoperative radiographic limb alignment (APAL 179.7° vs TEAL 180.1° P = .04). The mean femoral external rotation relative to the posterior condylar axis line (PCAL) was 3.0 degrees (0-7 degrees) using the APAL and 3.3 degrees (2-7 degrees) using the TEAL (P = .46). Two-year knee flexion and revised Oxford Knee Scores showed no difference. Seventy-five percent of patients stated no preference for either knee technique.

CONCLUSION

When using a measured resection, a posterior referencing technique, we found no difference in knee function and scores when setting femoral component rotation using the APAL versus TEAL.

LEVEL OF EVIDENCE

2, Randomized prospective study.

Robotics versus personalized 3D preoperative planning in total knee arthroplasty: a propensity score-matched analysis

Purpose

Lower limb alignment is crucial in total knee arthroplasty (TKA). Previous studies have shown that robotics and personalized three-dimensional (3D) preoperative planning could improve postoperative alignment accuracy compared with conventional TKA, but comparison between the above two techniques has never been reported. The authors hypothesized that robotics may be superior to personalized 3D preoperative planning in terms of postoperative alignment in primary TKA, with similar patient-reported outcome measures (PROMs) but higher cost and longer operative time.

Methods

A consecutive series of patients who received TKA in our center from September 2020 to January 2021 were enrolled retrospectively. After 1:2 matching, 52 and 104 patients were included and divided into study group for robotics and control group for personalized 3D preoperative planning, respectively. Multiple postoperative alignment angles were measured, and clinical features such as operation and tourniquet time, length of hospital stay and hemoglobin (Hb) were recorded. Knee Society Score (KSS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) were used to evaluate clinical results.

Results

Compared with control group, robotics group had significantly lower frontal femoral component angle (FFC) and frontal tibial component angle (FTC) absolute deviation (P < 0.05). It also had less outliers in hip–knee–ankle angle (HKA), FTC, lateral femoral component angle (LFC) and lateral tibial component angle (LTC) (P < 0.05). Hb loss of robotics group was significantly lower than control group (P < 0.001), while the operation and tourniquet time were longer (P < 0.001). There was no significant difference in KSS and WOMAC scores between two groups.

Conclusion

Compared with control group, patients in robotics group had significantly less malalignment, malposition, Hb loss, but similar PROMs. The operations in robotics group spent longer operation time and cost more compared with control group.

Trial registration: The Chinese Clinical Trial Registry, ChiCTR2000036235. Registered 22 August 2020, http://www.chictr.org.cn/showproj.aspx?proj=59300.

Level of evidence

III.

The Morphology of a Kinematically Aligned Distal Femoral Osteotomy Is Different from That Obtained with Mechanical Alignment and Could Have Implications for the Design of Total Knee Arthroplasty

Background: Kinematically aligned total knee arthroplasty (KA-TKA) may lead to a different pattern of osteotomy from mechanically aligned total knee arthroplasty (MA-TKA). This paper aims to analyze the effects of KA and MA on the morphology of the distal femoral osteotomy surface. Methods: Computed tomography scans of 80 TKA candidates were reconstructed into 3D models. The measurement of bone morphology was performed after the distal femur cut according to two different alignment techniques. The aspect ratio, trapezoidicity ratio, and asymmetry ratio of the distal femur were assessed. Results: The aspect ratio and the asymmetry ratio in the KA group was significantly lower than that in the MA group in the general population (p < 0.001). The trapezoidicity ratio in the KA group was significantly higher than that in the MA group in the general population (p < 0.001). Conclusions: It was found that KA-TKA and MA-TKA presented different morphologies of the distal femoral osteotomy surface, and this difference was also influenced by gender. The surgery pattern of KA-TKA and MA-TKA and gender should be considered when surgeons choose femoral prostheses.

No difference in patient-reported satisfaction after 12 months between customised individually made and off-the-shelf total knee arthroplasty

PURPOSE

A subset of patients is usually not satisfied after a total knee arthroplasty (TKA). Customised individually made (CIM) TKA are deemed to overcome drawbacks of classical off-the-shelf (OTS) TKA, but evidence is still sparse. The aim of this study was to compare satisfaction of patients with CIM and OTS TKA.

METHODS

This prospective cohort study compared clinical and patient-reported outcome measures (PROM) between patients with CIM and OTS TKA. The primary outcome was patient satisfaction after 12 months. Secondary outcomes were the Knee Society Score (KSS), the Knee injury and Osteoarthritis Outcome Score (KOOS), the Forgotten Joint Score (FJS-12) and the EQ-5D-3L after 4 and 12 months.

RESULTS

Data were analysed from 74 CIM TKA and 169 OTS TKA between January 2017 and September 2020. Patients with CIM TKA were slightly younger, more often male, had a lower body mass index, a lower KSS and partially higher preoperative PROMs. Patient satisfaction after 12 months was high and comparable (CIM 87%, OTS 89%). All PROMs improved for both groups (p < 0.001) and did not differ after 12 months (p > 0.063). The majority of patients improved above the minimal important difference (range 65 to 89%) and reported a clear overall improvement (CIM 86%, OTS 87%). The postoperative KSS, notably regarding knee stability, was higher for CIM TKA (p < 0.001).

CONCLUSION

No difference was found in patient satisfaction between CIM and OTS TKA after 12 months. In both groups, patient satisfaction was high and PROMs improved considerably.

LEVEL OF EVIDENCE

II, prospective cohort study.

No significant difference in early clinical outcomes of custom versus off-the-shelf total knee arthroplasty: a systematic review and meta-analysis

PURPOSE

The purpose of this systematic review and meta-analysis was to collect, synthesise and critically appraise findings of clinical studies that report outcomes of custom total knee arthroplasty (TKA). The hypothesis was that, compared to off-the-shelf (OTS) TKA, custom TKA would yield better surgical, clinical and radiographic outcomes.

METHODS

This systematic review and meta-analysis was performed in accordance with the guidelines of Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). On 8 February 2021, two authors independently searched and screened articles using MEDLINE®, Embase® and the Cochrane Library without restriction on date of publication. Findings from eligible articles were narratively synthesised and tabulated, and when ≥ 3 comparative studies reported the same outcome, results were pooled and summarised in forest plots. Quality assessments of the studies were done according to the guidelines of the Joanna Briggs Institute (JBI) Checklists.

RESULTS

A total of 15 articles were eligible for data extraction, of which 9 were case-control studies reporting on 929 custom versus 998 OTS TKA, 5 were case series reporting on results of 587 custom TKA, and 1 was a cross-sectional study reporting on results of 44 custom versus 132 OTS TKA. Five studies that compared early revision rates found the overall effect in favour of OTS TKA (odds ratio (OR), 0.4; p = n.s.) but the result did not reach statistical significance. Four studies found no statistically significant difference in KSS knee (standardised mean difference (SMD), - 0.10; p = n.s.) and function (SMD, 0.03; p = n.s.), and five studies found no statistically significant difference in range of motion (SMD, 0.02; p = n.s.). One study that compared bone-implant fit between custom and three OTS tibial components found no overhang but revealed under-coverage of up to 18% in knees with custom tibial baseplates.

CONCLUSION

Custom TKA demonstrated no significant benefits compared to OTS TKA in terms of pooled clinical outcomes, but had considerably higher early revision rates. The findings of the present systematic review and meta-analysis suggest the need for studies with better comparable groups and standardisation of reporting outcomes amongst studies, that could increase the quality of evidence and enable pooling of results in future meta-analyses.

LEVEL OF EVIDENCE

Level IV.