Relationship between cutting errors and learning curve in computer-assisted total knee replacement

Digital TKA Alignment Training with a New Digital Simulation Tool (Knee-CAT) Improves Process Quality, Efficiency, and Confidence

Individual alignment techniques have been introduced to restore patients' unique anatomical variations during total knee arthroplasty. The transition from conventional mechanical alignment to individualised approaches, with the assistance of computer and/or robotic technologies, is challenging. The objective of this study was to develop a digital training platform with real patient data to educate and simulate various modern alignment philosophies. The aim was to evaluate the training effect of the tool by measuring the process quality and efficiency, as well as the post-training surgeon's confidence with new alignment philosophies. Based on 1000 data sets, a web-based interactive TKA computer navigation simulator (Knee-CAT) was developed. Quantitative decisions on bone cuts were linked to the extension and flexion gap values. Eleven different alignment workflows were introduced. A fully automatic evaluation system for each workflow, with a comparison function for all workflows, was implemented to increase the learning effect. The results of 40 surgeons with different experience levels using the platform were assessed. Initial data were analysed regarding process quality and efficiency and compared after two training courses. Process quality measured by the percentage of correct decisions was increased by the two training courses from 45% to 87.5%. The main reasons for failure were wrong decisions on the joint line, tibia slope, femoral rotation, and gap balancing. Efficiency was obtained with a reduction in time spent per exercise from 4 min 28 s to 2 min 35 s (42%) after the training courses. All volunteers rated the training tool as helpful or extremely helpful for learning new alignment philosophies. Separating the learning experience from OR performance was mentioned as one of the main advantages. A novel digital simulation tool for the case-based learning of various alignment philosophies in TKA surgery was developed and introduced. The simulation tool, together with the training courses, improved surgeon confidence and their ability to learn new alignment techniques in a stress-free out-of-theatre environment and to become more time efficient in making correct alignment decisions.

Computer-Assisted Surgery Enables Beginner Surgeons, Under Expert Guidance, to Achieve Long-Term Clinical Results not Inferior to Those of a Skilled Surgeon in Knee Arthroplasty

PURPOSE

The purpose of this study is to determine whether the use of a surgical navigation system in total knee replacement (TKR) enables beginner and intermediate surgeons to achieve clinical PROM outcomes as good as those conducted by expert surgeons in the long term.

METHODS

We enrolled 100 consecutive patients whose total navigated knee arthroplasty (TKA) was performed in our institution from 2008 to 2010. According to the principal surgeon's surgical experience, the patients were divided into three groups: (1) beginner surgeons, with no more than 30 previous knee replacement performances, (2) intermediate surgeons, with more than 30 but not more than 300, and (3) expert surgeons, with more than 300 knee replacements. Demographic data collected on the cohort included gender, laterality, age, and body mass index (BMI). The outcome measures assessed were Forgotten Joint Score (FJS), implant positioning, limb alignment, and prosthesis survival rate. A margin of equivalence of ± 18.5 points in the FJS scale was prespecified in terms of the minimal clinically important difference (MCID) to compare the FJS results obtained in the long period between the groups of interest.

RESULTS

The mean follow-up was 11.10 ± 0.78, 10.86 ± 0.66, and 11.30 ± 0.74 years, respectively, for each of the groups. The long-term FJS mean score was 80.86 ± 21.88, 81.36 ± 23.87, and 90.48 ± 14.65 for each group. The statistical analysis proved noninferiority and equivalence in terms of the FJS results reported in the long term by patients in Groups 1 or 2 compared to those in Group 3. More specifically, it has been proved that the mean difference between groups is within the interval of equivalence defined in terms of the MCID. The overall prostheses survival rate was 93.7%.

CONCLUSION

Navigated assisted TKA, under expert guidance, can be as effective when performed by beginner or intermediate surgeons as performed by senior surgeons regarding the accuracy of implant positioning, limb alignment, and long-term clinical outcome.

Osseous Morphological Differences in Knee Osteoarthritis

BACKGROUND

Improved understanding of the morphological characteristics of knees with osteoarthritis (OA) and various deformities can enable personalized implant positioning and balancing in total knee arthroplasty in an effort to continue improving clinical outcomes and optimizing procedural value. Therefore, the purpose of this study was to outline morphological differences in the medial and lateral distal femur and proximal tibia associated with varus and valgus deformities in knee OA.

METHODS

A large computed tomography (CT) database was used to identify 1,158 knees, which were divided into normal and osteoarthritic groups; the latter was further divided on the basis of deformity into neutral, varus, and valgus subgroups. Morphological measurements included the non-weight-bearing hip-knee-ankle angle (nwHKA), mechanical lateral distal femoral angle (mLDFA), medial proximal tibial angle (MPTA), rotation of the posterior condylar axis (PCA) relative to the surgical transepicondylar axis (sTEA), ratio of medial to lateral posterior condylar offset, ratio of medial to lateral condylar radius, medial posterior slope (MPS), lateral posterior slope (LPS), medial coronal slope (MCS), and lateral coronal slope (LCS).

RESULTS

Compared with the normal group, the OA group was in overall varus (nwHKA, -2.2° ± 5.0° compared with -0.2° ± 2.4°) and had a significantly smaller MPS (8.4° ± 4.0° compared with 9.2° ± 4.0°), larger LPS (9.2° ± 3.6° compared with 7.2° ± 3.3°), and smaller MCS (82.1° ± 4.3° compared with 83.9° ± 3.3°). Differences among the OA subgroups were also observed for the MCS and LCS. Compared with the normal group, the sTEA of the OA group was less externally rotated relative to the PCA (0.3° ± 1.5° compared with 1.2° ± 1.9°), and both the condylar offset ratio (1.01 ± 0.06 compared with 1.04 ± 0.07) and the condylar radius ratio (0.98 ± 0.07 compared with 1.03 ± 0.07) were smaller. Only the condylar radius ratio showed differences among the OA subgroups, with valgus deformity associated with a larger ratio.

CONCLUSIONS

An analysis of CT scans of 965 healthy and 193 osteoarthritic knees revealed significant differences in PCA, condylar offset, and condylar radius as well as tibial slope in both the sagittal and coronal planes.

CLINICAL RELEVANCE

There is a strong need to evolve toward a more personalized treatment for osteoarthritic knees that utilizes implants and technology to help tailor total knee arthroplasty on the basis of the patient's morphologic characteristics.

Navigated Unicompartmental Knee Arthroplasty: A Different Perspective

Backgroud

Anteromedial osteoarthritis is a recognized indication for unicompartmental knee arthroplasty (UKA). Favorable postoperative outcomes largely depend on proper patient selection, correct implant positioning, and limb alignment. Computer navigation has a proven value over conventional systems in reducing mechanical errors in total knee arthroplasty (TKA). However, the lack of strong evidence impedes the universal use of computer navigation technology in UKA. Therefore, this study was proposed to investigate the accuracy of component positioning and limb alignment in computer navigated UKA and to observe the role of navigation in proper patient selection.

Methods

A total of 50 knees (38 patients) underwent computer navigated UKA between 2016 and 2018. All operations were performed by the senior surgeon using the same navigation system and implant type. The navigation system was used as a tool to aid patient selection: knees with preoperative residual varus > 5° on valgus stress and hyperextension > 10° were switched to navigated TKA. We measured the accuracy of component placement in sagittal and coronal planes on postoperative radiographs. Functional outcomes were also evaluated at the final follow-up (a minimum of 16 months).

Results

Nine patients had tibia vara and 14 patients had preoperative hyperextension deformity. We observed coronal outliers for the tibial component in 12% knees and for the femoral component in 10% knees. We also observed sagittal outliers for the tibial component in 14% knees and for the femoral component in 6% knees. There was a significant improvement in the functional score at the final follow-up. On multiple linear regression, no difference was found in functional scores of knees with or without tibia vara (p = 0.16) and with or without hyperextension (p = 0.25).

Conclusions

Our study further validates the role of computer navigation in desirable implant positioning and limb alignment. We encourage use of computer-assisted navigation as a tool for patient selection, as it allows intraoperative dynamic goniometry and provides real-time kinematic behavior of the knee to obviate pitfalls such as significant residual varus angulation and hyperextension that predispose early failure of UKA.

Outcomes of complex primary total knee arthroplasties performed with custom cutting guides

BACKGROUND

Total knee arthroplasty (TKA) is particularly challenging in patients with marked deformities or existing hardware due to the inability to use traditional instrumentation. One potential technique to mitigate this obstacle is the use of patient-specific cutting guides. The purpose of this study was to evaluate the use of custom cutting guides in complex primary TKAs.

METHODS

Twenty complex TKAs performed in 18 patients were identified. Of these, 11 were performed in patients with existing hardware, three in patients with dwarfism, three in patients with post-traumatic deformities, two in a patient with multiple epiphyseal dysplasia, and one in a patient with a large deformity from Blount's disease. All prior hardware was retained. One patient died from unrelated causes three months following surgery. The remaining patients were followed for a mean of 5.2 years (range: 1.2-9.7 years).

RESULTS

One patient sustained a non-displaced, medial tibial plateau fracture intra-operatively that was successfully treated with plating. Mean operative time was 112.1 ± 44.4 min, and mean hospital stay was 2.7 ± 1.6 days. Average deviation from the mechanical axis improved from 10.5° pre-operatively to 3.1° postoperatively (P < 0.001). Average Knee Society Scores improved from 48.1 to 77.4 points (P < 0.001). Mean extension improved from 5.9° to 1.4° (P = 0.049). Two patients subsequently required a manipulation under anesthesia, and one patient had delayed wound healing that resolved without surgery.

CONCLUSIONS

Custom cutting guides are a viable option in complex primary TKAs where the use of traditional instrumentation would be challenging.

A clinical review of robotic navigation in total knee arthroplasty: historical systems to modern design

Robotic-assisted total knee arthroplasty (RA-TKA) has shown improved reproducibility and precision in mechanical alignment restoration, with improvement in early functional outcomes and 90-day episode of care cost savings compared to conventional TKA in some studies. However, its value is still to be determined.Current studies of RA-TKA systems are limited by short-term follow-up and significant heterogeneity of the available systems.In today's paradigm shift towards an increased emphasis on quality of care while curtailing costs, providing value-based care is the primary goal for healthcare systems and clinicians. As robotic technology continues to develop, longer-term studies evaluating implant survivorship and complications will determine whether the initial capital is offset by improved outcomes.Future studies will have to determine the value of RA-TKA based on longer-term survivorships, patient-reported outcome measures, functional outcomes, and patient satisfaction measures. Cite this article: EFORT Open Rev 2021;6:252-269. DOI: 10.1302/2058-5241.6.200071.

Reliability of Imageless Computer-Assisted Navigation for Femoral Rotational Alignment in Total Knee Arthroplasty

Introduction:

The aim of this study was to evaluate the reliability of the femoral component rotation on intra-operative data recorded in a computer-assisted navigation system (CAN-FRA) compared with the post-operative femoral component rotation observed on computed tomography (CT-FRA).

Material and method:

Computer-assisted total knee arthroplasty (TKA) or primary osteoarthritis of the knee was performed in 51 knees in 36 patients with a mean age of 69.51 years. All procedures were performed by a single surgeon using the same implant design. The intraclass correlation coefficient (ICC) was used to compare the intra-operative CAN-FRA with the post-operative CT-FRA. The angle between the anatomical epicondylar axis and the posterior condylar axis of the implant (CT-FRA) was measured at two separate timepoints by three observers who were blinded to the intra-operative CAN-FRA. Internal rotation was defined as rotation in the negative direction, while external rotation was defined as positive.

Results:

The mean intra-operative CAN-FRA was 0.1° ± 2.8° (range -5.0° to 5.5°). The mean post-operative CT-FRA was -1.3° ± 2.1° (range -4.6° to 4.4°). The mean difference between the CAN-FRA and the CT-FRA was -1.3° ± 2.2° (range -7.9° to 2.4°). The respective ICC values for the three observers were 0.92, 0.94, and 0.93, while the respective intra-observer coefficients were 0.91, 0.85, and 0.90. The ICC for the intra-operative CAN-FRA versus the post-operative CT-FRA was 0.71.

Conclusion:

This study shows that using a computer-assisted navigation system in TKA achieves reliable results and helps to achieve optimal positioning of the femoral component and rotation alignment correction.

Does patient-specific instrumentation increase the risk of notching in the anterior femoral cortex in total knee arthroplasty? A comparative prospective trial

PURPOSE

Patient-specific instrumentation (PSI) was usually applied in total knee arthroplasty (TKA) to acquire a favourable alignment. We hypothesized that using PSI had a potential risk of notching in the anterior femoral cortex, because the femoral component may be placed in an overextension position due to the distal femoral sagittal anteversion. The aim of this study was to figure out the relationship between the notch and the distal femoral sagittal anteversion in PSI-assisted TKA.

METHODS

One hundred thirty-one patients who were to undergo total knee arthroplasty (TKA) were randomly divided into conventional instrumentation (CI) group and PSI group. The computed tomography (CT) data of lower extremities was collected and imported to the Mimics software to reconstruct the three-dimensional (3D) bone image of the femur. The angle between distal femoral anatomic axis (DFAA) and femoral mechanical axis (FMA) on sagittal plane was defined as distal femoral sagittal anteverted angle (DFSAA) and measured. The number of notch intra-operative and post-operative was recorded. Then, we calculated the incidence of the notch and analyzed its relationship with DFSAA.

RESULTS

The average DFSAA of 262 femurs is 2.5° ± 1.5° (range, 0.0°-5.7°). When DFSAA ≥ 3°, the incidence of notch was 7.10% in CI group and 33.30% in PSI group, respectively, which shows significant statistical difference in the two groups (P = 0.016 < 0.05). When DFSAA < 3°, the incidence of notch was 6.50% in CI group and 5.30% in PSI group, respectively, which shows no significant statistical difference in the two groups (P = 0.667 > 0.05).

CONCLUSION

DFSAA could be taken as an indicator to predict the notch when performing TKA assisted with PSI. Especially when the DFSAA ≥ 3°, the risk of notch could be markedly increased.

How should we evaluate robotics in the operating theatre?

The application of robotics in the operating theatre for knee arthroplasty remains controversial. As with all new technology, the introduction of new systems might be associated with a learning curve. However, guidelines on how to assess the introduction of robotics in the operating theatre are lacking. This systematic review aims to evaluate the current evidence on the learning curve of robot-assisted knee arthroplasty. An extensive literature search of PubMed, Medline, Embase, Web of Science, and Cochrane Library was conducted. Randomized controlled trials, comparative studies, and cohort studies were included. Outcomes assessed included: time required for surgery, stress levels of the surgical team, complications in regard to surgical experience level or time needed for surgery, size prediction of preoperative templating, and alignment according to the number of knee arthroplasties performed. A total of 11 studies met the inclusion criteria. Most were of medium to low quality. The operating time of robot-assisted total knee arthroplasty (TKA) and unicompartmental knee arthroplasty (UKA) is associated with a learning curve of between six to 20 cases and six to 36 cases respectively. Surgical team stress levels show a learning curve of seven cases in TKA and six cases for UKA. Experience with the robotic systems did not influence implant positioning, preoperative planning, and postoperative complications. Robot-assisted TKA and UKA is associated with a learning curve regarding operating time and surgical team stress levels. Future evaluation of robotics in the operating theatre should include detailed measurement of the various aspects of the total operating time, including total robotic time and time needed for preoperative planning. The prior experience of the surgical team should also be evaluated and reported.

Cite this article: Bone Joint J 2020;102-B(4):407–413.

Frequency, Cost, and Clinical Significance of Incidental Findings on Preoperative Planning Images for Computer-Assisted Total Joint Arthroplasty

BACKGROUND

The frequency of incidental findings with computer-assisted total joint arthroplasty (CA TJA) preoperative imaging and their clinical significance are currently unknown.

METHODS

We reviewed 573 patients who underwent primary CA TJA requiring planning imaging. Incidental findings were defined as reported findings excluding those related to the planned arthroplasty. Secondary outcomes were additional tests or a delay in surgery. Associated charges were obtained from our institution's website. Charge and incidence data were combined with TJA volumes obtained from the 2016 National Inpatient Sample to model costs to the healthcare system.

RESULTS

Overall, 262 patients (45.7%) had at least 1 incidental finding, 144 patients (25.1%) had 2, and 65 (11.3%) had 3. The most common finding types were musculoskeletal (MSK, 67.7%), digestive (19.5%), cardiovascular (4.9%), and reproductive (4.7%). Also, 9.3% of patients had at least 1 non-MSK incidental finding. Both MSK and non-MSK incidental findings were more common with total hip arthroplasty compared to total knee arthroplasty (67.9% vs 42.2%, P < .0001, and 15.4% vs 8.3%, P < .05, respectively). Further testing was required in 6 cases (1.0%); 1 case required delay in surgery (0.2%). Using the 2016 volume of TJA procedures and assuming a 10%, 15%, and 25%, utilization rate of image-based CA TJA, the annual cost of additional testing was $2.7 million (95% confidence interval, $1.1-$6.3 million), $4.1 million ($1.6-$9.5 million), and $6.9 million (95% confidence interval, $2.7-$15.8 million), respectively.

CONCLUSION

Incidental findings are relatively common on planning images. Stakeholders should be aware of the hidden costs of incidental findings given the increasing popularity of image-based CA TJA.

Computer-assisted surgery in total knee replacement: advantages, surgical procedure and review of the literature

Introduction: Total knee replacement (TKR) is one of the most frequent orthopaedic procedures performed every year. At the same time 20% of patients who underwent TKR are not satisfied with the outcome. The reasons are unknown; we think that a mechanical alignment beyond 3° of varus-valgus can represent the most important cause of failure of TKR and consequently patient dissatisfaction. Materials and Methods: Neutral mechanical alignment is the main goal in every TKR: this can be achieved through different tools, such as extramedullary and intramedullary guides, patient-specific instrumentation (PSI) and computer-assisted surgery (CAS). The aim of this review is to compare the different alignment techniques in TKR, to describe CAS procedure and CAS results in recent literature. Results: Regarding the intramedullary guide, there is an increased risk of fatty embolism; there are great limitations on its use, or even impossibility, in cases of bone deformity and sequelae of trauma. Regarding the extramedullary guide, it becomes more difficult to use in cases of great obesity or increased soft-tissue volume around the tibia. PSI for TKR has been introduced to improve alignment, reduce outliers, operation time and the risk of fatty embolism by avoidance of intramedullary canal violation. Recent randomized controlled trials and meta-analysis proved no advantage of PSI in improving mechanical axis and implant survivorship. Discussion: CAS has provided to be a useful tool in assisting the surgeon to achieve more accurate post-operative mechanical axis through precise and reproducible bone cuts and ligament balancing. Two meta-analyses definitively proved that CAS technique improves mechanical axis and implant survivorship and one recent meta-analysis demonstrated that CAS provides better mechanical alignment and higher functional scores at short-term follow-up. (www.actabiomedica.it)

Wire Placement in the Sustentaculum Tali Using a 2D Projection-Based Software Application for Mobile C-Arms: Cadaveric Study

BACKGROUND

Indirect screw fixation of the sustentaculum tali in the lateral-medial direction can be challenging due to the complex calcaneal anatomy. A novel 2-dimensional (2D) projection-based software application detects Kirschner wires (K-wires) and visualizes their intended direction as a colored trajectory. The aim of this prospectively randomized cadaver study was to investigate whether the software would facilitate the indirect K-wire placement in the sustentaculum tali.

METHODS

In 20 cadaver foot specimens, K-wires were placed indirectly in the sustentaculum tali by an experienced and an inexperienced surgeon, with and without using the application. Number of placement attempts, duration of procedure, fluoroscopy time, and number of individual fluoroscopy images were recorded. Each wire's position was analyzed in a 3-dimensional (3D) C-arm scan by an experienced blinded investigator.

RESULTS

Use of the software by the inexperienced surgeon significantly reduced the number of placement attempts from 3.2 to 1.2 ( P = .006). The application also reduced operating time, from 273 s to 199 s ( P = .15), and fluoroscopy time, from 41 s to 29 s ( P = .15). Using the software, the experienced surgeon had a longer operating time (139 s to 183 s; P = .30), longer fluoroscopy time (5.6 s to 9.2 s; P = .17), and more individual fluoroscopy images (11.6 to 14.8; P = .30). Wire position did not show significant differences in both cases.

CONCLUSION

During indirect K-wire placement in the sustentaculum tali, the software appeared to be a useful tool for the inexperienced surgeon. In our chosen study setting, the experienced surgeon did not benefit from the software.

CLINICAL RELEVANCE

Possible indications for the software would be fractures of the proximal femur, sacrum, sacroiliac instabilities, vertebral bodies, scaphoid, Lisfranc joint, talus and calcaneus.

Advances in Computer-Aided Technology for Total Knee Arthroplasty

Technology such as computer-assisted navigation systems, robotic-assisted systems, and patient-specific instrumentation has been increasingly explored during the past decade in an effort to optimize component alignment and improve clinical outcomes. Computer-assisted navigation accurately restores mechanical-axis alignment, but clinical outcome data are inconsistent. Computer-assisted navigation gap balancing has shown early promise in establishing mechanical-axis alignment with improved functional outcomes. Robotic-assisted systems more accurately restore component alignment when compared with computer-assisted navigation, but clinical outcomes have yet to be determined. Patient-specific instrumentation does not consistently improve alignment, accuracy, or patient outcomes. Studies demonstrating implant survivorship, cost-efficiency, and improved clinical outcomes and patient satisfaction are needed. [Orthopedics. 2017; 40(6):338-352.].

Encouraging treatment algorithm for computer-assisted navigated total knee arthroplasty (TKA): A retrospective cohort analysis

OBJECTIVE

Navigated computer-assisted total knee arthroplasty (TKA) shows inconclusive mid- to long-term outcome results and is limited by increased costs, surgery-time and an additional learning curve. We introduced a treatment algorithm preserving computer-assisted TKA for patients with adipositas-per-magna, posttraumatic leg-deformities, osteosynthetic material in-situ or reduced preoperative X-ray quality.

METHODS

237 primary unilateral TKA were allocated based on the treatment concept described above. A retrospective pre- and postoperative radiological analysis was performed.

RESULTS

222 TKA (93.7%) were within 3° varus/valgus of mechanical-lower-limb axis (mean absolute deviation: 1.8° ± 1.3°).

CONCLUSION

This algorithm showed an excellent postoperative implantation-accuracy based on an accurate preoperative surgery-planning.

Patient specific instrumentation versus conventional knee arthroplasty: comparative study

BACKGROUND

The key to a successful knee replacement is restoring normal kinematics with a neutral alignment, thus a hip-knee-ankle (HKA) angle of 180° (within 3° limits). Conventional TKR is proven to have excellent results but relies in extensive visual referencing of bony landmarks. Customised cutting blocks provide accurate bone cuts, also lowering the risk of fat embolism, blood loss and operating time.

METHOD

We share our experience comparing two different TKA techniques using patient specific instrumentation (PSI) with the Visionaire knee and conventional instrumentation (CVI) from the same system (Genesis II Smith&Nephew). A total number of 80 knees were divided into two equal groups, 40 PSI and 40 CVI respectively, operated between April 2013 and August 2014. One female patient had bilateral TKR during this period, at six months interval, both with the PSI.

RESULTS

All operated knees had varus deformity, with a mean HKA of 168° (PSI) vs 163° (CVI). We used tranexamic acid (double-dose scheme) and suction drains for 48 hours, with a mean blood drainage in the PSI group of 185 ml and Hb levels of 11.2 g/dl at three days post, compared to 260 ml and 10.7 g/dl in the CVI. Mean blood loss was 3.5 g/dl in PSI, and 4.2 g/dl in the CVI. On the long leg standing radiograph at six weeks, all knees were aligned in frontal plane, with simillar HKA values (178.9° PSI vs 178.6° CVI). Bone cuts measured intraoperatively proved to be accurate within a 1 mm limit.

CONCLUSIONS

We cannot recommend PSI-TKR for a better outcome. It is an alternative to conventional and computer-assisted TKR, but further studies are needed to evaluate weather surgical or economic benefits may be achieved by choosing customised instruments.

Navigated "small implants" in knee reconstruction

PURPOSE

At the beginning of this century, unprecedented interest in the concept of using less invasive approaches for the treatment of knee degenerative diseases was ignited. Initial interest in this approach was about navigated and non-navigated knee reconstruction using small implants and conventional total knee arthroplasty.

METHODS

To this end, a review of the published literature relating to less invasive compartmental arthroplasty of the knee using computer-based alignment techniques and on soft tissue-dedicated small implants is presented. The authors present and compare their personal results using these techniques with those reported in the current literature. These involved the use of a shorter incision and an emphasis sparing. However, nowadays most surgeons look at compartmental knee resurfacing with the use of small implants as the new customized approach for younger and higher-demand patients. The aim of this paper is to stimulate further debate.

RESULTS

Since the beginning of 2000, computer-assisted surgery has been applied to total knee arthroplasty (TKA) and later to compartmental knee arthroplasty. Recent studies in the literature have reported better implant survivorship for younger patients using navigation in TKA at longer-term follow-up. Only one published report was identified showing superior clinical outcomes at short-term follow-up using computer-assisted technology compared with conventional alignment techniques in small implant surgery. No studies were found in the literature that demonstrated similar clinical advantages with navigated small implants at long-term follow-up. Two published meta-analyses were identified reporting better implant and limb alignment and no increase in complications using a navigated unicompartmental knee arthroplasty. However, neither meta-analysis showed superior clinical outcomes or survivorship with the navigated techniques.

CONCLUSION

In conclusion, we can assert that replacing just the damaged compartment and preserving the normal biomechanics will require not only new implant designs but also new technologies allowing the surgeon to make extremely precise adjustments to implant alignment and providing continuous feedback during surgery.

LEVEL OF EVIDENCE

IV.

Radiological and Functional Outcomes in Computer Assisted Total Knee Arthroplasty Between Consultants and Trainees - A Prospective Randomized Controlled Trial

Computer Aided Surgery has consistently shown superior alignment of components when compared to non-navigated jig based techniques. The aim of this study is to assess the mid-term clinical outcome of TKA performed by a consultant orthopedic surgeon, compared to trainee surgeons. Ninety-two patients were matched and randomly allocated to have CAS surgery performed by either a consultant or trainee and followed up prospectively for 5-years. Knee society scores, mechanical axis, tourniquet time and blood loss data were collected. Our study demonstrated that trainees were able to achieve equal coronal alignment (P=0.15), blood loss (P=0.45) and functional scores (P=0.15). The Consultant group had a significantly (P<0.001) shorter tourniquet time. We confirm that CAS can assist less experienced surgeons to reliably achieve good mid-term outcomes in TKA.

Accuracy of patient specific cutting blocks in total knee arthroplasty

Background. Long-term survival of total knee arthroplasty (TKA) is mainly determined by optimal positioning of the components and prosthesis alignment. Implant positioning can be optimized by computer assisted surgery (CAS). Patient specific cutting blocks (PSCB) seem to have the potential to improve component alignment compared to the conventional technique and to be comparable to CAS. Methods. 113 knees were selected for PSI and included in this study. Pre- and postoperative mechanical axis, represented by the hip-knee-angle (HKA), the proximal tibial angle (PTA), the distal femoral angle (DFA), and the tibial slope (TS) were measured and the deviation from expected ideal values was calculated. Results. With a margin of error of ±3°, success rates were 81.4% for HKA, 92.0% for TPA, and 94.7% for DFA. With the margin of error for alignments extended to ±4°, we obtained a success rate of 92.9% for the HKA, 98.2% for the PTA, and 99.1% for the DFA. The TS showed postoperative results of 2.86 ± 2.02° (mean change 1.76 ± 2.85°). Conclusion. PSCBs for TKA seem to restore the overall leg alignment. Our data suggest that each individual component can be implanted accurately and the results are comparable to the ones in CAS.

Navigated total knee arthroplasty: is it error-free?

PURPOSE

The aim of this study was to determine whether errors do occur in navigated total knee arthroplasty (TKAs) and to study whether errors in bone resection or implantation contribute to these errors.

METHODS

A series of 20 TKAs was studied using computer navigation. The coronal and sagittal alignments of the femoral and tibial cutting guides, the coronal and sagittal alignments of the final tibial implant and the coronal alignment of the final femoral implant were compared with that of the respective bone resections. To determine the post-implantation mechanical alignment of the limb, the coronal alignment of the femoral and tibial implants was combined.

RESULTS

The median deviation between the femoral cutting guide and bone resection was 0° (range -0.5° to +0.5°) in the coronal plane and 1.0° (range -2.0° to +1.0°) in the sagittal plane. The median deviation between the tibial cutting guide and bone resection was 0.5° (range -1.0° to +1.5°) in the coronal plane and 1.0° (range -1.0° to +3.5°) in the sagittal plane. The median deviation between the femoral bone resection and the final implant was 0.25° (range -2.0° to 3.0°) in the coronal plane. The median deviation between the tibial bone resection and the final implant was 0.75° (range -3.0° to +1.5°) in the coronal plane and 1.75° (range -4.0° to +2.0°) in the sagittal plane. The median post-implantation mechanical alignment of the limb was 0.25° (range -3.0° to +2.0°).

CONCLUSIONS

When navigation is used only to guide the positioning of the cutting jig, errors may arise in the manual, non-navigated steps of the procedure. Our study showed increased cutting errors in the sagittal plane for both the femur and the tibia, and following implantation, the greatest error was seen in the sagittal alignment of the tibial component. Computer navigation should be used not only to guide the positioning of the cutting jig, but also to check the bone resection and implant position during TKA.

LEVEL OF EVIDENCE

IV.

Impact of change of knee prosthesis on early clinical outcomes in a large volume arthroplasty centre

Introduction

The aim of our study was to investigate the effect of changing the default knee prosthesis in a high volume dedicated arthroplasty unit from DePuy’s PFC® Sigma® to Smith & Nephew’s Genesis™ II.

Methods

A retrospective analysis was performed of prospective data on primary total knee replacements (TKRs) from January 2009 until December 2011. This provided information on the operative time, length of stay, pain at mobilisation, radiography analysis, any complications, and readmission at 30 and 60 days.

Results

The total numbers of primary TKRs using the PFC® and Genesis™ II prostheses were 1,061 and 1,268 respectively. The results showed a slight increase (maximum of five minutes) in the operative time for all the surgeons except one surgeon, whose operative time reduced by an average of seven minutes. There was no significant adverse outcome after the change in the knee implant. There was no clinically significant increase in the length of stay, pain at mobilisation or complication rates. There was a twofold increase in the wastage of the implant in the Genesis™ II group in the initial learning period.

Conclusions

Through a competitive process of implant tendering, we have successfully introduced a new implant into a large elective orthopaedic unit. This has resulted in significant financial savings without adversely affecting our clinical practice or patient outcome.

Impact of change of knee prosthesis on early clinical outcomes in a large volume arthroplasty centre

INTRODUCTION

The aim of our study was to investigate the effect of changing the default knee prosthesis in a high volume dedicated arthroplasty unit from DePuy's PFC(®) Sigma(®) to Smith & Nephew's Genesis™ II.

METHODS

A retrospective analysis was performed of prospective data on primary total knee replacements (TKRs) from January 2009 until December 2011. This provided information on the operative time, length of stay, pain at mobilisation, radiography analysis, any complications, and readmission at 30 and 60 days.

RESULTS

The total numbers of primary TKRs using the PFC(®) and Genesis™ II prostheses were 1,061 and 1,268 respectively. The results showed a slight increase (maximum of five minutes) in the operative time for all the surgeons except one surgeon, whose operative time reduced by an average of seven minutes. There was no significant adverse outcome after the change in the knee implant. There was no clinically significant increase in the length of stay, pain at mobilisation or complication rates. There was a twofold increase in the wastage of the implant in the Genesis™ II group in the initial learning period.

CONCLUSIONS

Through a competitive process of implant tendering, we have successfully introduced a new implant into a large elective orthopaedic unit. This has resulted in significant financial savings without adversely affecting our clinical practice or patient outcome.

No difference between computer-assisted and conventional total knee arthroplasty: five-year results of a prospective randomised study

PURPOSE

The use of computer-assisted surgery (CAS) in total knee arthroplasty (TKA) results in better limb and implant alignment compared to conventional TKA; however, it is unclear whether this translates to better mid- to long-term clinical outcome. This prospective randomised study comparing CAS and conventional TKA reports the functional and patient perceived outcomes at a follow-up of 5 years. The hypothesis was that there would be a difference in functional outcome or quality of life after mid-term follow-up.

METHODS

Sixty-seven patients were available for physical and radiological examination at 5 years. The Knee Society Score (KSS) was used to describe functional outcome and the Euroquol questionnaire for quality of life.

RESULTS

The mean total KSS for the CAS group improved from 91.1 (SD 22.3) points preoperatively to 157.4 (SD 21.9) and 150.2 (SD 30.4) points at 2 and 5 years, respectively. In the conventional group, the mean total KSS was 99.6 (SD 18.6) points preoperatively and 151.1 (SD 26.0) and 149.0 (SD 28.0) points at 2 and 5 years, respectively. The mean quality of life score improved from 48.2 (SD 16.5) points preoperatively to 67.4 (SD 16.3) and 66.8 (SD 22.2) points at 2 and 5 years in the CAS group, and from 52.2 (SD 17.1) points preoperatively to 65.6 (SD 14.6) and 61.7 (SD 19.3) points at 2 and 5 years, respectively, in the conventional TKA group. These differences were not statistically significant. There were radiolucent lines up to 2 mm in 11 knees (four CAS, seven conventional), but there were no changes in implant position.

CONCLUSIONS

There were no significant differences in functional or patient perceived outcome after mid-term follow-up in this study.

LEVEL OF EVIDENCE

I.

Navigation-Assisted Total Knee Arthroplasty for Osteoarthritis with Extra-Articular Femoral Deformity and/or Retained Hardware

Total knee arthroplasty (TKA) for osteoarthritis (OA) patients with extra-articular deformity is still challenging because angular deformity, canal sclerosis, or the retained hardware that precludes the use of the traditional intramedullary guide. In addition, atypical bone cut for intra-articular correction leads to imbalanced soft tissue gap. Furthermore, corrective osteotomy should be considered for severe deformity or para-articular deformity cases. Recently, navigation-assisted TKA has been reported to increase the accuracy of prosthetic positioning and limb alignment. This system can calculate mechanical axis regardless of extra-articular deformity, canal sclerosis, or retained hardware. Accordingly, navigation surgery has been considered to be a powerful option especially in TKAs with extra-articular deformity cases. Here, we report 3 successful navigation-assisted TKAs for osteoarthritis with extra-articular deformities and/or retained hardware. Navigation-assisted TKA is an effective and reliable alternative for patients with extra-articular deformities.

Computer-assisted surgery: a teacher of TKAs

INTRODUCTION

The hypothesis of this study is that computer-aided navigation experience could improve the ability to better place components in the coronal plane and to improve visual/spatial awareness based on the ability of navigation to provide instant feedback. The purpose of this study is to demonstrate the educational role of the navigation system to obtain a better alignment of the prosthetic components with standard instrumentation after a computer-aided navigation experience.

MATERIALS AND METHODS

One hundred fifty patients were operated by the same surgeon, with more than 5 years experience with TKA. They were equally divided in three groups: group A (operated with non-navigated technique by surgeon without computer-assisted experience); group B (operated with computer-assisted surgery by the same surgeon); group C (operated with non-navigated technique by the same surgeon after the computer-navigated experience). We evaluated by full-length weight-bearing radiographs the overall alignment of the lower limb in the coronal plane. The optimum placement of the components was considered when the angle was within the limits of ±3° varus/valgus on the coronal x-rays. Comparison between groups was done using one-way ANOVA followed by post hoc Bonferroni test and Pearson chi-square statistics for proportions of optimum placement (P<0.05).

RESULTS

In the group A 34 patients (68%) had the optimum placement on the coronal x-rays; in the group B they were 46 (92%) and in the group 41 (82%). The difference is statistically significant in comparing group A and Group B (<0.001), group A and group C (P=0.04), but not for group B and C (P=0.2).

CONCLUSION

We believe that the navigation system has an educational role to improve the ability of surgeon of positioning prosthetic components precisely in the coronal plane.

Perioperative complications and learning curve of the Mobility Total Ankle System

BACKGROUND

Only 2 articles related to the recently developed Mobility Total Ankle System (Johnson & Johnson Medical/DePuy International, Leeds, UK) have been published to date. The purpose of this study was to determine the perioperative complications associated with the Mobility Total Ankle System and whether a learning curve exists for this system.

MATERIALS AND METHODS

We recruited 60 consecutive patients undergoing total ankle arthroplasty using the Mobility Total Ankle System for advanced osteoarthritis and rheumatoid arthritis between May 2008 and June 2010. Group A included the initial 30 patients who underwent surgery, and group B included the next 30 patients. Reporting of adverse perioperative events, including wound healing problems, fracture, aseptic loosening, tendinitis, component malposition, neuroma, and bony impingement, was limited to the first 3 months after the surgery.

RESULTS

Eleven of the 30 patients in group A developed complications (36.7%), and 1 died of an unknown cause 6 months after leaving the hospital. The complications in this group included medial malleolar fracture in 6 patients, lateral malleolar fracture in 1, wound healing problems in 2, and varus deformity in 2. Five of the 30 patients in group B developed complications (16.7%). The complications in this group included medial malleolar fracture in 1 patient, medial impingement in 2, Achilles tendon rupture in 1, and wound problems in 1. There was no statistically significant difference (P = .08) between the 2 groups in the incidence of complications after total ankle replacement arthroplasty. There was also no significant difference between the 2 groups in the types of complications seen.

CONCLUSIONS

Perioperative complications associated with total ankle replacement arthroplasty using the Mobility Total Ankle System were seen in 16 of 60 patients. Group A had a higher incidence of perioperative complications than did group B. However, the difference was not statistically significant. Either the expertise of the surgeon or the simplicity of the total ankle system can affect the learning curve, although these things were not specifically quantified in this study.

LEVEL OF EVIDENCE

Level III, comparative case series.

Image guidance shortens the learning curve for K-wire placement - an experimental study

BACKGROUND

Computer assisted systems in orthopaedic trauma depend in most cases on fixed reference markers. This work evaluated a reference-free image-based guidance system. Outcome parameters were the number of trials needed to achieve an optimal wire position, the radiation and procedure time, and the learning curve.

METHODS

Forty artificial proximal femora covered in polyurethane foam were used and randomized in two groups. Each bone was equipped with a target marker at the fovea capitis femoris. Two surgeons each inserted 20 K-wires, 10 with and 10 without assistance from the guidance system. The aim was to bring the tips of the K-wires as close as possible to the target marker. Both procedures were performed under fluoroscopic control. The new guidance system is based on 2D-C-arm images. Following the procedure the result was determined using computed tomography.

RESULTS

The same accuracy (P = 0.34) was achieved with less time (P = 0.0008) and less radiation (P = 0.0002) with the guidance system. However, use of the guidance system did shorten the learning curve of both surgeons, leading to a reduced number of trials (P <0.0001). The learning curve of both surgeons was strongly correlated. From the first trial, the performance of both surgeons while using the guidance system, improved over their performance without the guidance system.

CONCLUSIONS

The guidance system helped to achieve an optimal K-wire position with less radiation and less time. The major advantage is the ability of the guidance system to be integrated into the workflow and the short and flat learning curve.

Computer-assisted total knee arthroplasty is currently of no proven clinical benefit: a systematic review

BACKGROUND

Navigated total knee arthroplasty (TKA) may improve coronal alignment outliers; however, it is unclear whether navigated TKA improves the long-term clinical results of TKA.

QUESTIONS/PURPOSES

Does the literature contain evidence of better long-term function and lower revision rates with navigated TKA compared with conventional TKA?

METHODS

A systematic literature review was conducted of navigated TKA reviewing articles related to coronal alignment, clinical knee and function scores, cost, patient satisfaction, component rotation, anteroposterior and mediolateral stability, complications, and longer-term reports.

RESULTS

Coronal plane alignment is improved with navigated TKA with fewer radiographic outliers. We found limited evidence of improvements in any other variable, and function was not improved. The duration of surgery is increased and there are unique complications related to navigated TKA. The long-term benefits of additional increase in accuracy of alignment are not supported by any current evidence.

CONCLUSIONS

The findings in reports of navigated TKA should be interpreted with caution. There are few short- and medium- and no long-term studies demonstrating improved clinical outcomes using navigated TKA. Despite substantial research, contradictory findings coupled with reservations about the cost and efficacy of the technology have contributed to the failure of computer navigation to become the accepted standard in TKA. Longer-term studies demonstrating improved function, lower revision rates, and acceptable costs are required before navigated TKA may be widely adopted. In the future, with improvements in study design, methodology, imaging, navigation technology, newer functional outcome tools, and longer-term followup studies, we suspect that navigated TKA may demonstrate yet unrecognized benefits.

The limits of precision in conventionally instrumented computer-navigated total knee arthroplasty

PURPOSE

Computer-navigated total knee arthroplasty (TKA) improves the accuracy of component implantation. However, the final implant alignment may not match planned alignment. The hypothesis of this study is that although computer navigation improves alignment, imprecision may not be completely eliminated. The aim of the study was to establish the incidence and sources of imprecision during TKA using computer navigation to measure deviations from planned alignment.

METHODS

Computer navigation was used to quantify changes in planned alignment at four steps during 136 TKA's: application of cutting blocks, addition of definitive pin fixation, bone cuts and after prosthesis application. Mean changes in alignment deviation at each step in each plane were measured and the number of significant outliers (>3° from the planned resection plane) were assessed in each plane.

RESULTS

Overall changes in planned alignment were small and non-cumulative between steps but the incidence of outliers (cuts measured as >3° from planned alignment at each step) increased through the steps, with 21.3 % (n = 29) of final implants outlying in the tibial sagittal plane, which was the least precise plane. The highest number of outliers occurred after bone resection and the addition of pins to cutting blocks was also identified as a source of imprecision.

CONCLUSION

Despite improved accuracy of bone resection with computer-navigated TKA, the precision of bone cuts may be affected at several steps of the procedure. Cutting block application, bone resection and prosthesis application may all affect accuracy. Bone cuts should be made with meticulous care, whether navigated or not, and navigated cuts should be checked and corrected, particularly in the tibial sagittal plane.

LEVEL OF EVIDENCE

IV.

Computer-assisted total knee arthroplasty after prior femoral fracture without hardware removal

This study presents a consecutive series of patients who underwent total knee arthroplasty (TKA) after prior distal femoral fracture without hardware removal. The purpose of this study was to determine the effectiveness of computer-assisted TKA in patients with posttraumatic arthritis, specifically those with retained hardware after prior distal femoral fracture. The study group included a consecutive series of 16 patients who had developed posttraumatic knee arthritis after a distal femoral fracture with retention of hardware (group A). Patients in the study group were matched with patients who had undergone a computer-assisted TKA using the same implant and software (group B). The indication for TKA in all group B patients was atraumatic arthritis, and surgery was performed during the same period as that in the study group. Patients were matched for age, sex, preoperative range of motion, preoperative severity of arthritis, type and grade of deformity, and implant features. No statistically significant differences existed between the 2 study groups in terms of operative time, duration of hospital stay, or intra- and postoperative complications. At last follow-up, no statistically significant differences existed in Knee Society Scores and Western Ontario and McMaster Universities Arthritis Index scores. Implant alignment and radiological parameters were similar in both groups. This study demonstrated that posttraumatic knee arthritis after prior distal femoral fracture can be safely managed using a computer-assisted TKA without hardware removal. Comparison between the study group and a matched group with atraumatic arthritis showed similar postoperative results and complication rates.

Adjustable cutting blocks improve alignment and surgical time in computer-assisted total knee replacement

PURPOSE

Computer navigation increases accuracy and precision of component alignment in total knee arthroplasty (TKA) compared to the manual technique, but is often associated with increases in surgical time. In a previous cadaver study, we demonstrated a significant improvement in guide positioning precision, final bone cut precision, and procedure length when using adjustable cutting blocks (ACB) compared to conventional cutting blocks (CCB) in computer-navigated TKA. The aim of this study was to evaluate the use of ACB in vivo.

METHODS

We radiographically compared component alignment and mechanical leg alignment, as well as tourniquet time, in 94 patients who underwent TKA using either ACB (N = 30) or CCB (N = 64).

RESULTS

Postoperative mechanical alignment variability was significantly less in the ACB group (SD = 1.7°) than in the CCB group (SD = 2.7°). Tourniquet time was significantly reduced by 14.8 min in the ACB group compared to the CCB. Differences in component alignment were not significant.

CONCLUSION

ACB for TKA significantly reduced postoperative mechanical alignment variability and tourniquet time compared to conventional navigated instrumentation, while providing equal or better component alignment.

LEVEL OF EVIDENCE

III.

Displays mounted on cutting blocks reduce the learning curve in navigated total knee arthroplasty

The use of computer navigation in total knee arthroplasty (TKA) improves the implant alignment but increases the operation time. Studies have shown that the operation time is further prolonged due to the surgeon's learning curve, and longer operation times have been associated with higher morbidity risks. It has been our hypothesis that an improvement in the human-machine interface might reduce the time required during the learning curve. Accordingly, we asked whether the use of navigation devices with a display fixed on the surgical instruments would reduce the operation time in navigated TKAs performed by navigation beginners. Thirty medical students were randomized and used two navigation devices in rotation: these were the Kolibri® device with an external display and the Dash® device with a display that was fixed on the cutting blocks. The time for adjustment of the tibial and femoral cutting blocks on knee models while using these devices was measured. A significant time reduction was demonstration when the Dash® device was used: The time reduction was 21% for the tibial block (p = 0.007), 40% for the femoral block (p < 0.001), and 32% for the whole procedure (p < 0.001). The integrated display, fixed on surgical instruments in a manner similar to a spirit level, seems to be more user-friendly for navigation beginners. Hence, unproductive time losses during the learning curve may be diminished.

Do residents perform TKAs using computer navigation as accurately as consultants?

The implantation of a total knee arthroplasty (TKA) is a milestone in a resident's surgical training. Studies demonstrate higher loosening rates after TKA by inexperienced surgeons. Alignment outliers should be avoided to achieve a long implant survival. Therefore, our study questioned whether residents implant knee prostheses using computer navigation as accurately as experienced consultants. The data for 662 consecutive TKAs were analyzed retrospectively. The operations were performed by 4 consultants (n=555) and 5 residents under supervision by a consultant (n=107). Cutting errors were recorded from the navigation data. The postoperative mechanical axis and operation time were recorded. Operation time was significantly prolonged if residents performed the operation vs consultants (139 vs 122 minutes, respectively). The analysis of cutting errors within each surgeon's first 20 navigated operations resulted in no significant difference between residents and consultants. During the subsequent operations, a trend toward a more accurate placement of the prosthesis was detected for consultants. The rate of outliers with a mechanical axis deviation >2° was low and did not significantly differ between residents and consultants (3.7% vs 2.3%, respectively). Our study shows that residents implant their first TKA using computer navigation as accurately as experienced consultants. However, the residents' operations take longer and therefore incur additional costs for the teaching clinic.

The effect of pelvic movement on the accuracy of hip centre location acquired using an imageless navigation system

OBJECTIVE

The aim of this study was to assess the accuracy of an imageless navigation system in localising the hip centre and to evaluate the effect of pelvic movement on the accuracy of hip centre acquisition.

MATERIAL AND METHODS

A phantom leg was constructed to simulate the hip joint and upper femur. A 3D measurement device was used to measure precisely the co-ordinates of hip centre. A limber link simulated hip motion as used when defining the hip centre during computer-assisted surgery. The data generated by the 3D measurement device and the image-free navigation system was compared with increasing amounts of simulated pelvic movement.

RESULTS

For moderate pelvic movement (5 mm) the mean error of the hip centre ranged between 1.5 mm and 3.9 mm with a corresponding angular error of between 0.25° and 0.64°. In conditions of excessive pelvic movement (15 mm) the mean error was 11.7 mm corresponding to an angular error of 1.9°.

CONCLUSION

This in vitro study showed accurate acquisition of the centre of hip with a surgical navigation system. These data suggest that during TKA using this computer assisted navigation system, the accuracy of insertion will not be significantly affected by moderate pelvic movement during data acquisition.

NAVIGATION IN TOTAL KNEE ARTHROPLASTY

Navigation was the most significant advance in instrumentation for total knee arthroplasty over the last decade. It provides surgeons with a precision tool for carrying out surgery, with the possibility of intraoperative simulation and objective control over various anatomical and surgical parameters and references. Since the first systems, which were basically used to control the alignment of bone cutting referenced to the mechanical axis of the lower limb, many other surgical steps have been incorporated, such as component rotation, ligament balancing and arranging the symmetry of flexion and extension spaces, among others. Its efficacy as a precision tool with an effective capacity for promoting better alignment of the lower-limb axis has been widely proven in the literature, but the real value of optimized alignment and the impact of navigation on clinical results and the longevity of arthroplasty have yet to be established.

Imageless navigation system does not improve component rotational alignment in total knee arthroplasty

BACKGROUND

The aim of computer-assisted surgery is to improve accuracy and limit the range of surgical variability. However, a worldwide debate exists regarding the importance and usefulness of computer-assisted navigation for total knee arthroplasty (TKA). The main purpose of this study is to summarize and compare the radiographic outcomes of TKA performed using imageless computer-assisted navigation compared with conventional techniques.

MATERIALS AND METHODS

An electronic search of PubMed, EMBASE, Web of Science, and Cochrane library databases was made, in addition to manual search of major orthopedic journals. A meta-analysis of 29 quasi-randomized/randomized controlled trials (quasi-RCTs/RCTs) and 11 prospective comparative studies was conducted through a random effects model. Additional a priori sources of clinical heterogeneity were evaluated by subgroup analysis with regard to radiographic methods.

RESULTS

When the outlier cut-off value of lower limb axis was defined as ±2° or ±3° from the neutral, the postoperative full-length radiographs demonstrated that the risk ratio was 0.54 or 0.39, respectively, which were in favor of the navigated group. When the cut-off value used for the alignment in the coronal and sagittal plane was 2° or 3°, imageless navigation significantly reduced the outlier rate of the femoral and tibial components compared with the conventional group. Notably, computed tomography scans demonstrated no statistically significant differences between the two groups regarding the outliers in the rotational alignment of the femoral and tibial components; however, there was strong statistical heterogeneity.

CONCLUSIONS

Our results indicated that imageless computer-assisted navigation systems improve lower limb axis and component orientation in the coronal and sagittal planes, but not the rotational alignment in TKA. Further multiple-center clinical trials with long-term follow-up are needed to determine differences in the clinical and functional outcomes of knee arthroplasties performed using computer-assisted techniques.