Similar radiological results with accelerometer-based navigation versus conventional technique in total knee arthroplasty

An updated meta-analysis comparing complications, functional, clinically relevant and radiological outcomes of accelerometer based portable navigation and conventional technique of total knee arthroplasty

Introduction

Since previous studies, including small-scale meta-analyses comparing accelerometer-based portable navigation (APN-TKA) and conventional techniqueof total knee arthroplasty (CONV-TKA), have reported divergent results, there is a need for an updated meta-analysis to compare complications, functional outcomes, clinically relevant outcomes and radiographic alignment of components.

Methods

This meta-analysis was conducted as per PRISMA guidelines. Randomised controlled trials, and non-randomised comparative cohort studies in English language on primary TKA were included. The complications compared were Deep Vein Thrombosis (DVT), Pulmonary Embolism (PE), infection, manipulation under anaesthesia (MUA) for postoperative knee stiffness, re-operation and mortality. The functional outcomes compared were the Knee Society Knee Score, Knee Society Score function, Oxford Knee Score, Knee Injury and Osteoarthritis Outcome Score and Western Ontario and McMaster Universities Arthritis Index. The evaluated clinically relevant outcomes were surgical time, blood loss, drop in haematocrit, tourniquet time, postoperative knee flexion and complications). The number of radiological outliers; as well as the absolute values of the alignment of the overall prosthesis, femoral and tibial components in both coronal and sagittal planes, was assessed.

Results

Twenty-five studies were included. Both the groups were comparable in terms of preoperative demographic features. There was no difference in complications and functional outcomes. Operation time was longer in APN-TKA (p < 0.00001) but there was no difference in rest of the clinically relevant outcomes. Restoration of the lower limb mechanical axis (p = 0.003) and coronal femoral alignment angle (p = 0.0002) was better with APN. APN also significantly reduced the risk of the odds of outliers of lower limb mechanical axis (p < 0.0001), coronal femoral alignment (p = 0.03), coronal tibial alignment (p < 0.0001) and sagittal tibial alignment (p = 0.0001).

Conclusion

The improvement in the accuracy of implantation by the use of APN-TKA, as determined by the overall alignments of prosthesis, or femoral and tibial components, does not necessarily translate into lesser complications and better functional and clinical outcomes.

Level of evidence

Therapeutic study, Level II.

Accelerometer-Based Navigation versus Conventional Total Knee Arthroplasty for Posttraumatic Knee Osteoarthritis

BACKGROUND

Posttraumatic osteoarthritis (PTOA) frequently comprises femoral or tibial deformity, which makes it difficult to perform total knee arthroplasty (TKA). Accelerometer-based navigation (ABN) could be effective in restoring a neutral mechanical axis (MA) in TKA, but a limited number of studies have been reported in association with PTOA. Therefore, we aimed to compare the lower limb MA between ABN-assisted TKA (ABN-TKA) and conventional TKA in patients with PTOA.

METHODS

We conducted a retrospective analysis of 28 PTOA patients who underwent TKA using a conventional system (cTKA group, n = 16) and the ABN system (iTKA group, n = 12). Standing long-leg radiographs were assessed for MA and prosthesis alignment as primary outcomes. A postoperative MA deviating beyond ± 3° was defined as an outlier. Perioperative outcomes, Oxford Knee Score (OKS) at 2-year follow-up, and complications were also assessed.

RESULTS

The cTKA group and the iTKA group had a mean age of 63.07 years and 65.25 years, respectively. The iTKA group had significantly better MA accuracy when compared to the cTKA group (1.60° ± 2.09° vs. 3.59° ± 1.34°, p = 0.01). The iTKA group showed significantly less MA outlier than the cTKA group (78.6% vs. 25.0%, p = 0.02). The prosthesis alignment and OKS were comparable between the groups. There were 2 periprosthetic joint infections in the cTKA group and 1 periprosthetic fracture of the distal femur in the iTKA group.

CONCLUSIONS

For PTOA of the knee, both conventional TKA and ABN-TKA significantly improved the postoperative mechanical alignment and functional outcomes. The ABN-TKA seemed to offer higher accuracy and less MA outlier when compared to conventional TKA, and thus ABN could be a good alternative option.

Handheld computer-navigated constrained total knee arthroplasty for complex extra-articular deformities

INTRODUCTION

The present study aimed to assess the postoperative alignment and clinical outcomes of patients with complex extra-articular deformities (EADs) undergoing computer-assisted surgery (CAS) for constrained total knee arthroplasty (TKA) with modular stem extensions.

MATERIALS AND METHODS

From May 2015 to July 2018, ten patients with EADs scheduled for constrained TKA were enrolled retrospectively. The preoperative average deviation from neutral (= 180°) mechanical axis was 15.3° (range of coronal alignment: 150.9° varus-202.9° valgus). Alignment was assessed using an accelerometer-based handheld CAS system. On long-leg films, the positions of the components and possible stems were analysed and templated preoperatively. The average follow-up was 3.3 years (range: 2.0-4.6 years).

RESULTS

The postoperative mechanical axis was within ± 3.0° from neutral in nine patients. In all patients, the Knee Society score (KSS) and range of motion improved significantly. A constrained condylar and a rotating hinge prosthesis were used in five patients each. In eight patients, the 100-mm cementless stem that was preferred by the authors was found to be unusable for the femur or the tibia in the planning stage. For the femur, a cementless 100-mm stem was used in three, and a cemented 30-mm stem in five patients; a femoral stem was not usable in two patients. For the tibia, a cementless 100-mm stem was used in six, and a cemented 30-mm stem in two patients; a monoblock rotating hinge tibia was used in two patients.

CONCLUSIONS

Complex EADs were excellently managed during constrained TKA implantation using the handheld CAS system. Templating allowed the possible stem lengths to be identified and prevented anatomical conflict with the CAS-configured mechanical alignment. Limb alignment and function improved significantly after surgery. No intra- or postoperative complications occurred.

LEVEL OF EVIDENCE

Level IV, retrospective study.

The accelerometer-based navigation system demonstrated superior radiological outcomes in restoring mechanical alignment and component sagittal positioning in total knee arthroplasty

Background

This study aimed to determine whether the accelerometer-based navigation (ABN) could improve the accuracy of restoring mechanical axis (MA), component positioning, and clinical outcomes compared to conventional (CON) total knee arthroplasty (TKA).

Methods

A total of 301 consecutive patients (ABN: 27, CON: 274) were included. A 1:4 propensity score matching (PSM) was performed between the two groups according to preoperative demographic and clinical parameters. The postoperative MA, femoral coronal angle (FCA), femoral sagittal angle (FSA), tibial coronal angle (TCA) and tibial sagittal angle (TSA) were compared. Absolute deviations of aforementioned angles were calculated as the absolute value of difference between the exact and ideal value and defined as norms if within 3°, otherwise regarded as outliers. Additional clinical parameters, including the Knee Society knee and function scores (KSKS and KSFS) and range of motion (ROM), were assessed at final follow-up (FU) (mean FU was 21.88 and 21.56 months respectively for ABN and CON group). A secondary subgroup analysis and comparison on clinical outcomes were conducted between norms and outliers in different radiological parameters.

Results

A total of 98 patients/102 knees were analyzed after the PSM (ABN: 21 patients/24 knees, CON: 77 patients/78 knees). In the ABN group, the mean MA, FCA and TSA were significantly improved (p = 0.019, 0.006, < 0.001, respectively). Proportions of TKAs within a ± 3°deviation were significantly improved in all the postoperative radiological variables except for TCA (p = 0.003, 0.021, 0.042, 0.013, respectively for MA, FCA, FSA, and TSA). The absolute deviations of FSA and TSA were also significantly lower in the ABN group (p = 0.020, 0.048, respectively). No significant differences were found in either mean value, absolute deviation or outlier ratio of TCA between two groups. On clinical outcomes, there were no significant differences between two groups, although KSKS, KSFS and ROM (p < 0.01, respectively) dramatically improved compared to baseline. The subgroup analysis also demonstrated no statistical difference on clinical outcomes between the outliers and norms in varied radiological parameters.

Conclusions

The ABN could improve the accuracy and precision of mechanical alignment and component positioning without significant improvement of clinical outcomes. Further high quality studies with long term FU are warranted to comprehensively evaluate the value of the ABN.

Usefulness of an accelerometer-based navigation system in bilateral one-stage total knee arthroplasty

Background

Bilateral one-stage total knee arthroplasty (BTKA) have increased because it provides a number of advantages. Recently, Accelerometer-based navigation (ABN) system which guide the cutting plane without intramedullary disturbance might result in less endothelial and microvascular damage. Therefore, we hypothesized that the ABN may reduce blood loss, reduce postoperative pain, and better restore BTKA alignment compared to conventional instruments.

Methods

We retrospectively compared 44 consecutive patients receiving ABN assisted BTKA (iBTKA) to 57 patients with conventional instruments (cBTKA). Identical pre- and post-operative care was utilized to all patients. The outcome measures assessed were hemoglobin (Hb), calculated blood loss (CBL), blood transfusion, VAS score for pain, morphine consumption, knee flexion angle, and length of stay (LOS). Radiographic assessment included mechanical axis (MA) and component positioning at 3–6 months of follow up.

Results

Both iBTKA and cTKA groups had equivalent demographic data. Postoperative Hb of the cBTKA group was significantly lower than those in the iBTKA group at 24 h (p = 0.02), but there was no significant difference in drain volume, CBL, and blood transfusion rate. For radiographic measures, the iBTKA group had more accurate MA and component orientation, and had a lower number of outliers than those in the cBTKA group (p ≤ 0.01), except for the sagittal femoral component angle.

Conclusion

The ABN assisted BTKA could not reduce blood loss or postoperative pain more than cBTKA, nor improve functional recovery. However, the ABN significantly improved the accuracy of MA and prostheses positioning.

Trial registration

The protocol of this study was registered in the Thai Clinical Trials Registry database No. TCTR20180731001# on 25 July 2018.

New Technologies in Knee Arthroplasty: Current Concepts

Total knee arthroplasty (TKA) is an effective treatment for severe osteoarthritis. Despite good survival rates, up to 20% of TKA patients remain dissatisfied. Recently, promising new technologies have been developed in knee arthroplasty, and could improve the functional outcomes. The aim of this paper was to present some new technologies in TKA, their current concepts, their advantages, and limitations. The patient-specific instrumentations can allow an improvement of implant positioning and limb alignment, but no difference is found for functional outcomes. The customized implants are conceived to reproduce the native knee anatomy and to reproduce its biomechanics. The sensors have to aim to give objective data on ligaments balancing during TKA. Few studies are published on the results at mid-term of these two devices currently. The accelerometers are smart tools developed to improve the TKA alignment. Their benefits remain yet controversial. The robotic-assisted systems allow an accurate and reproducible bone preparation due to a robotic interface, with a 3D surgical planning, based on preoperative 3D imaging or not. This promising system, nevertheless, has some limits. The new technologies in TKA are very attractive and have constantly evolved. Nevertheless, some limitations persist and could be improved by artificial intelligence and predictive modeling.

Accuracy of tibial component placement in unicompartmental knee arthroplasty performed using an accelerometer-based portable navigation system

PURPOSE

There is a need for new devices to improve the accuracy of implantation in unicompartmental knee arthroplasties (UKAs). The accelerometer-based portable navigation system is expected to improve this accuracy. This study aimed to compare the accuracy of UKAs performed by the portable navigation system with that of the conventional method, and to investigate whether the portable navigation system can complement the surgeon's experience.

METHODS

The study comprised of 80 Oxford UKAs. Knees were divided into two groups based on the method of tibial osteotomy: the conventional group (37 UKAs performed by an experienced surgeon using the extra-medullary guide) and the portable navigation group (43 UKAs performed by 2 unaccustomed surgeons using the navigation system). The absolute error from the target angle on the coronal and sagittal plane was measured on whole lower leg X-ray. The incidence of outliers (> 3°) was compared between the groups using Fisher's exact probability test.

RESULTS

The incidences of outliers on the coronal plane were 41.0% (15 of 37 knees) in the conventional group and 9.3% (4 of 43 knees) in the portable navigation group (p < 0.0001). The incidences of outliers on the sagittal plane were 13.5% (5 of 37 knees) in the conventional group and 14.0% (6 of 43 knees) in the portable navigation group (p = 0.3772).

CONCLUSION

This is the first report on the usefulness of an accelerometer-based portable navigation system in UKA. The use of this system improves the accuracy of implantation of the tibial component beyond the experience of the surgeon.

LEVEL OF EVIDENCE

Retrospective comparative study, Level III.

Comparison of early results of total knee replacement performed with Zimmer iASSIST versus conventional technique

Background:

Zimmer iASSIST knee is an accelerometer-based navigation system with the aim of achieving better alignment in total knee arthroplasty (TKA). We have started using this system since early 2016. This is a retrospective case–control study, which aims to compare the radiological alignment, operation time, and blood loss of TKAs performed using the iASSIST system and those using conventional techniques.

Materials and Methods:

42 TKAs using Zimmer iASSIST and 44 TKAs using conventional instrumentation were recruited. The overall coronal alignment and the coronal and sagittal alignment of the femoral and tibial component were compared. For coronal alignment, additional analysis of the absolute deviation from neutral mechanical axis was performed to avoid canceling out of varus/valgus deviation. The number of outliers, operation time, and blood loss in terms of maximal hemoglobin drop were also compared.

Results:

When comparing the alignment of the iASSIST group with the conventional group, there were no significant differences ( p > 0.05) in the number of outliers, mean coronal alignments, mean deviation from neutral coronal mechanical axis (2.9° vs. 2.9°), and femoral component flexion angle (4.9° vs. 4.7°). The difference in the mean tibial component posterior slope was significant (5.7° vs. 7.1°, p < 0.05). The mean operation time was significantly longer by 13 min ( p < 0.05) in the iASSIST group. There were no significant differences in the mean hemoglobin drop between the two groups.

Conclusion:

The results demonstrated no significant differences in terms of coronal radiological alignment, femoral flexion angle, outliers, and blood loss between iASSIST and conventional technique. There was a small but statistically significant difference in tibial posterior slope. The iASSIST group needed a longer operation time.

Usefulness of an Accelerometer-Based Portable Navigation System for Total Knee Arthroplasty: A Multicenter Prospective Randomized Controlled Trial

BACKGROUND

An accelerometer-based portable navigation system was recently introduced to improve prosthetic alignment during total knee arthroplasty (TKA). The purpose of this multicenter prospective randomized controlled trial (RCT) was to evaluate the effects of this accelerometer-based portable navigation system for achieving more accurate alignment during TKA in the clinical setting.

METHODS

One hundred patients with primary varus osteoarthritis of the knee were enrolled in this prospective RCT conducted in 5 hospitals. A navigation system was utilized in 50 patients (navigation group), and a conventional intramedullary femoral guide and an extramedullary tibial guide were utilized in 50 patients (conventional group). At 6 months postoperatively, weight-bearing radiographs were obtained of the whole operative leg. An experienced surgeon who was blinded to the treatment assignments then measured the alignment to 1 decimal place with use of computer software. Power analysis showed that 41 knees were required in each group.

RESULTS

There were no complications as a result of the use of the accelerometer-based portable navigation system. Postoperative radiographs were obtained in 45 patients from each group. There were no significant differences in sex, age, height, body weight, body mass index, preoperative femorotibial angle, and operative time between groups. The absolute differences of the femoral prosthesis (p = 0.01), tibial prosthesis (p < 0.01), and hip-knee-ankle angle (p < 0.01) from a neutral mechanical axis were less in the navigation group compared with those in the conventional group. Alignment outliers (>2° away from the neutral mechanical axis) of the tibial prosthesis and hip-knee-ankle angle were less in the navigation group (9% and 27%, respectively) compared with those in the conventional group (31% and 49%; p = 0.01 and p = 0.04, respectively).

CONCLUSIONS

To our knowledge, this is the first multicenter prospective RCT to evaluate an accelerometer-based portable navigation system. An accelerometer-based portable navigation system provides more accurate prosthetic and limb alignment in the coronal plane than conventional techniques, without extended operative time or an increased rate of complications. The results of this study may help orthopaedic surgeons decide whether or not to use an accelerometer-based portable navigation system.

LEVEL OF EVIDENCE

Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

The use of accelerometer-based navigation for coronal TKA alignment: a prospective, single surgeon comparative study

INTRODUCTION

There is the need for a device that can be used to accurately position components during total knee arthroplasty (TKA) with minimal impact on procedure time, workflow and cost. This study aimed to investigate the accuracy and time efficiency of a novel, accelerometer-based navigation system (ABN).

METHODS

This prospective, single surgeon study of patients undergoing TKA for osteoarthritis over a 5 year period involved a total of 138 patients: 110 using the ABN system and 28 without. The ABN system consists of two coupled inertial pods that are secured to resection guides, providing a body-fixed 3D coordinate system for limb segments. Post-operative coronal alignment was measured from standardised long-leg AP radiographs. Deviation of the femur and tibia from the neutral coronal mechanical axis was recorded. Intra-observer repeatability was performed on three independent blinded data sets. The BMI and the surgical time (skin to skin) were recorded for all patients.

RESULTS

The mean BMI was 34 in the ABN group and 33 in the control group (p = 0.92). The skin-to-skin time was also similar between the groups; 105 min in the navigation group and 100 min in the control group (p = 0.297). The use of navigation resulted in significantly fewer outliers as defined by < 3º deviation from the target angle. 3 of 110 navigated patients recorded an AP femur angle of more than 3º from the target of 90º, where 5 of 28 control patients fell outside of the ± 3º window (p = 0.009, Fig. 1).

CONCLUSION

The use of the ABN system significantly improved accuracy of implant position and alignment without increasing surgical time.

Handheld, accelerometer-based navigation versus conventional instrumentation in total knee arthroplasty: a meta-analysis

BACKGROUND

Precise and accurate alignments in total knee arthroplasty are important predictors for survivorship and functional outcomes. We aim to compare accelerometer-based navigation (ABN) to conventional instrumentation (CONV), patient-specific instrumentation (PSI) and computer-assisted surgery (CAS) in published literature.

METHODS

A systematic search of publications from databases (MEDLINE, EMBASE and Cochrane) was obtained from inception to 15 August 2018. A random-effects meta-analysis was used to pool odd ratios for outliers greater than 3° for the hip-knee-ankle, coronal and sagittal femoral and tibial angles (CFA, CTA, SFA, STA). Secondary outcomes included procedural characteristics and functional outcomes.

RESULTS

Thirteen studies, involving 1566 patients, met inclusion that compared ABN (50.2%) to CONV (49.8%) and five comparing ABN to CAS/PSI. The pooled odds ratios for percent outliers of greater than 3° from the mechanical axis for the hip-knee-ankle (relative risk 0.58, P = <0.05) and CFA (relative risk 0.42, P = 0.02) was significantly lower for ABN compared to CONV. The pooled odds ratios for CTA, SFA and STA were not significantly different. No differences were identified in comparison to PSI/CAS. There was no statistically significant difference in procedural characteristics and functional outcomes.

CONCLUSIONS

The use ABN in total knee arthroplasty is a successful method of increased precision and accuracy for the restoration of the mechanical axis. In addition, there is no significant compromise in procedural or functional outcomes.

Comparison of iASSIST Navigation System with Conventional Techniques in Total Knee Arthroplasty: A Systematic Review and Meta-Analysis of Radiographic and Clinical Outcomes

The iASSIST navigation system is a handheld accelerometer‐based navigation system that has been applied in clinical practice in recent five years. This meta‐analysis aimed to compare the radiographic and clinical outcomes of iASSIST navigation with conventional surgical techniques for patients undergoing total knee arthroplasty (TKA) and to compare the surgery time between an iASSIST group and a conventional treatment group. This systematic review and meta‐analysis included all comparative prospective and retrospective studies published in Pubmed, Embase, the Cochrane Central Register of Controlled Trials, the Web of Science and the CNKI databases over the past 20 years. Inclusion criteria were studies that compared the iASSIST navigation system with conventional TKA. The primary outcomes were mechanical axis (MA) and outliers, which means postoperative MA varus or valgus of more than 3°. Secondary outcomes were coronal femoral angle (CFA) and coronal tibial angle (CTA). Knee Society Score (KSS) was used to evaluate functional outcome. The Newcastle–Ottawa Scale (NOS) was used to assess the methodological quality of included studies. Eight studies involving 558 knees were included in this meta‐analysis. Of these, 275 patients used the iASSIST navigation system and 283 used conventional surgical techniques. A total of 5 studies were considered high quality and the other 3 were considered to be of moderate quality. The occurrence of malalignment of >3° in the iASSIST group was 13.3%, compared with 29.04% in the conventional group. Postoperative MA of the iASSIST group was significantly better than that of the conventional group (I² = 19%, OR = −0.92, 95% CI = −1.09 to −0.75, P < 0.00001). The iASSIST navigation system provided significantly increased accuracy in the coronal femoral angle (I² = 79%, OR = −0.88, 95% CI = −1.21 to −0.54, P < 0.00001) and the coronal tibial angle (I² = 34%, OR = 0.39, 95% CI = −0.48 to −0.30, P < 0.00001) compared with conventional techniques. However, the duration of surgery using the iASSIST procedure was longer and there was no significant difference in the short‐term KSS in the iASSIST group compared with the conventional group. We found that when pooling the data of included studies, the number of outliers was fewer in the iASSIST group, and compared with conventional TKA techniques, the iASSIST system significantly improved the accuracy of lower limb alignment but the duration of surgery was prolonged in addition to there being no apparent advantage in terms of short‐term functional score.

Does Accelerometer-based Navigation Have Any Clinical Benefit Compared with Conventional TKA? A Systematic Review

BACKGROUND

Accelerometer-based navigation is a handheld navigation tool that was introduced to offer a simpler technique compared with more-cumbersome computer-assisted surgery (CAS). Considering the increasing number of adopters, it seems important to evaluate the potential clinical benefits of this technology compared with conventional TKA.

QUESTIONS/PURPOSES

In this systematic review, we asked: (1) Is accelerometer-based navigation more accurate than conventional TKA? (2) Does accelerometer-based navigation provide better functional outcome than conventional TKA? (3) Does accelerometer-based navigation increase surgical time or decrease the risk of complications or reoperations compared with conventional TKA?

METHODS

This systematic review included all comparative prospective and retrospective studies published in the MEDLINE/PubMed and Cochrane libraries over the last 10 years. Inclusion criteria were all studies in English that compared accelerometer-based navigation with conventional TKA. Eleven studies met these criteria with 621 knees in accelerometer-based navigation group and 677 knees in conventional TKA group. Results related to alignment, objective and subjective functional scores, duration of surgery, complications and reoperations were extracted and compared between accelerometer-based-navigation and conventional TKA. Methodological quality was assessed using Methodological Index for Non-Randomized Studies (MINORS) tool (for nonrandomized control trials) and Cochrane Risk of Bias (for randomized control trials (RCTs). All studies with fair or better quality were included. Four RCTs and six nonrandomized studies comparing accelerometer-based navigation to conventional TKA were found.

RESULTS

Inconsistent evidence on mechanical axis alignment was found, with five of nine studies slightly favoring the accelerometer-based navigation group, and the other four showing no differences between the groups. Only two of eight studies favored accelerometer-based navigation in terms of tibial component alignment in the coronal plane; the other six found no between-group differences. Similarly, mixed results were found regarding other metrics related to component alignment; a minority of studies favored accelerometer-based navigation by a small margin, and most studies found no between-group differences. Only three studies evaluated functional outcome and none of them showed a difference in range of motion or patient-reported outcomes. Most studies, six of seven, found no between-group differences concerning surgical time; one study demonstrated a slight increase in time with accelerometer-based navigation. There were no between-group differences in terms of the risk of complications, which generally were uncommon in both groups, and no reoperations or revisions were reported in either group.

CONCLUSIONS

We found conflicting evidence about whether accelerometer-based navigation reduces the number of coronal-plane outliers or improves alignment to a clinically important degree, and we found no evidence that it improves patient-reported outcomes or reduces the risk of complications or reoperations. Accelerometer-based navigation may increase surgical time. The overall quality of the evidence was low, which suggested that any observed benefits were overestimated. Given the absence of higher-quality evidence demonstrating compelling benefits of this accelerometer-based navigation technology, it should not be widely adopted.

LEVEL OF EVIDENCE

Level III, therapeutic study.

No definite advantage of a portable accelerometer-based navigation system over conventional technique in total knee arthroplasty: A systematic review and meta-analysis

BACKGROUND

Precise implant alignment is a crucial prognostic factor in total knee arthroplasty (TKA). Portable navigation systems (PN-TKA) were reported to be better than the conventional technique (CON-TKA). We hypothesized that PN-TKA offered greater radiologic precision than CON-TKA in mechanically aligning components. We investigated whether (1) it improved global mechanical alignment, and (2) optimized component placement with respect to the tibial and femoral mechanical axes.

PATIENTS AND METHODS

A systematic literature review compared PN-TKA versus CON-TKA. PubMed, Web of Science and Cochrane Library search retrieved ten studies. Their data were pooled using RevMan 5.3. Odds ratios (OR) for dichotomous data were calculated with 95% confidence intervals (CIs) for each outcome. Statistical heterogeneity was assessed as I² using a standard χ² test. I²>50% denoted significant heterogeneity requiring a random effects model; otherwise, a fixed effects model was applied.

RESULTS

There were significantly fewer outliers for mechanical axis (I²=24%, OR=0.62, 95% CI=0.42-0.91, p=0.02) and coronal femoral component angle (I²=58%, OR=0.31, 95% CI=0.13-0.73, p=0.007) using PN-TKA; however, no significant difference was observed for coronal tibial component angle outliers (I²=0%, OR=0.66, 95% CI=0.38-1.15, p=0.14).

DISCUSSION

Although PN-TKA appeared to improve global alignment, it had no effect on coronal tibial alignment, which is a key factor in predicting the long-term success of component fixation. There thus appeared to be no definite advantage of PN-TKA over CON-TKA.

LEVEL OF EVIDENCE

III.