The John Insall Award: No Functional Benefit After Unicompartmental Knee Arthroplasty Performed With Patient-specific Instrumentation: A Randomized Trial

The efficacy and safety of patient-specific instrumentation versus conventional instrumentation for unicompartmental knee arthroplasty: Evidence from a meta-analysis

BACKGROUND

The aim of this study was to compare the efficacy and safety of patient-specific instrumentation (PSI) and conventional instrumentation (CI) for unicompartmental knee arthroplasty. Our hypothesis was that the PSI would be superior to CI in improving implant positioning and clinical function.

METHODS

We searched electronic databases (PubMed, Web of Science, Embase, and Cochrane) to identify relevant studies published before July 1, 2023 that met our inclusion criteria. The identified reports at least included one of the following outcome variables: coronal component alignment, sagittal component alignment, number of outliers, hip-knee-ankle angle, postoperative complications, operative time and knee joint functional evaluation. For dichotomous variables, we calculated the risk ratio and its 95% confidence interval (CI). For continuous variables, we calculated the mean difference (MD) and its 95% CI. Heterogeneity of the included studies was assessed using the standard chi-square test. Meta-analyses were performed using RevMan 5.4. software. The meta-analysis was registered with PROSPERO (No. CRD42023454160).

RESULTS

A total of 9 articles were included in the analysis, consisting of 4 randomized controlled trials and 5 cohort studies. The study population comprised 494 patients, with 262 in the PSI group and 232 in the CI group. Our findings demonstrate that the PSI group exhibits superior tibial component coronal alignment compared to the CI group (MD = -0.66, 95% CI: -1.21 to -0.12, P = .02). Conversely, the CI group demonstrates better femoral component coronal alignment than the PSI group (MD = 0.89, 95% CI: 0.17-1.60, P = .01). No significant between 2 groups differences were observed in tibial component sagittal alignment, femoral component sagittal alignment, tibial coronal axis outliers, tibial sagittal axis outliers, femoral coronal axis outliers, femoral sagittal axis outliers, postoperative complications, operative time, hip-knee-ankle angle, and postoperative knee joint function score.

CONCLUSIONS

Our study findings suggest that the PSI confer an advantage in achieving superior tibial component coronal alignment, whereas the CI associated with better femoral component coronal alignment. However, no significant differences were observed between the groups in terms of other parameters. Future studies with larger sample sizes are needed to validate these findings.

Computed tomography-based patient-specific cutting guides used for positioning of the femoral component of implants during unicompartmental knee arthroplasty: a cadaver study

BACKGROUND

To investigate whether patient-specific instrumentation (PSI) improves the femoral component positioning of implants during unicompartmental knee arthroplasty (UKA) using cadaver bone models.

METHODS

Fifty adult cadaveric femoral bone specimens collected from February 2016-2018, were randomized to receive medial UKA with a PSI guide (n = 25) or conventional instrumentation (CI) (n = 25). Standard anteroposterior and lateral view radiographs were obtained postoperatively to assess the coronal and sagittal positioning of the femoral prostheses, respectively. The osteotomy time was recorded to assess the convenience of PSI in guiding osteotomy.

RESULTS

Osteotomy time significantly shortened in the PSI group (3.12 ± 0.65 versus 4.33 ± 0.73 min, p < 0.001). There was a significant difference in the postoperative coronal alignment of the femoral component between the PSI and CI groups (varus/valgus angle: 1.43 ± 0.93° vs. 2.65 ± 1.50°, p = 0.001). The prevalence of outliers in coronal alignment was lower in the PSI than the CI group (2/25, 8% vs. 9/25, 36%). Sagittal posterior slope angle of the femoral component was significantly different between the two groups (8.80 ± 0.65° and 6.29 ± 1.88° in the CI and PSI groups, respectively, p < 0.001). The malalignment rate of the femoral component in the sagittal plane was 60% in the CI group, whereas no positioning deviation was observed in the PSI group.

CONCLUSION

This study used a cadaver model to support the fact that CT-based PSI shows an advantage over CI in optimizing implant positioning for UKAs.

Robotic Versus Conventional Unicompartmental Knee Surgery: A Comprehensive Systematic Review and Meta-Analysis

Robotic-assisted surgery is a computer-controlled technique that may improve the accuracy and outcomes of unicompartmental total knee arthroplasty (TKA), a partial knee replacement surgery. The purpose of a meta-analysis about robotic-assisted versus conventional surgery for unicompartmental TKA is to compare the effectiveness of these two methods based on the current evidence. Our meta-analysis can help inform clinical decisions and guidelines for surgeons and patients who are considering unicompartmental TKA as a treatment option. We searched four online databases for studies that compared the two methods until March 2023. We used RevMan software to combine the data from the studies. We calculated the mean difference (MD) and the 95% confidence interval (CI) for each outcome, which are statistical measures of the difference and the uncertainty between the two methods. We included 16 studies in our analysis. We found that robotic-assisted surgery had a better hip-knee-ankle angle, which is a measure of how well the knee is aligned, than conventional surgery (MD = 0.86, 95% CI = 0.16-1.56). We also found that robotic-assisted surgery had a better Oxford Knee score, which is a measure of how well the knee functions, than conventional surgery (MD = 3.03, 95% CI = 0.96-5.110). This study compared the results of conventional and robotic-assisted unicompartmental knee arthroplasty in 12 studies. We concluded that robotic-assisted surgery may have some benefits over conventional surgery in terms of alignment and function of the knee. However, we did not find any significant difference between the two methods in terms of other outcomes, such as pain, range of motion, health status, and joint awareness. Therefore, we suggest that more research is needed to confirm these results and evaluate the long-term effects and cost-effectiveness of robotic-assisted surgery.

Patient Specific Instruments and Patient Individual Implants—A Narrative Review

Joint arthroplasties are one of the most frequently performed standard operations worldwide. Patient individual instruments and patient individual implants represent an innovation that must prove its usefulness in further studies. However, promising results are emerging. Those implants seem to be a benefit especially in revision situations. Most experience is available in the field of knee and hip arthroplasty. Patient-specific instruments for the shoulder and upper ankle are much less common. Patient individual implants combine individual cutting blocks and implants, while patient individual instruments solely use individual cutting blocks in combination with off-the-shelf implants. This review summarizes the current data regarding the implantation of individual implants and the use of individual instruments.

Comparative efficacy of the different cutting guides in unicompartmental knee arthroplasty: A systematic-review and network meta-analysis

BACKGROUND

Several cutting guides including conventional, navigation, patient specific instrumentation (PSI) and robotic are currently used in unicompartmental knee arthroplasty (UKA). A network meta-analysis was conducted to compare the most widely used cutting guides regarding the improvement of radiological, functional outcomes and the rate of complications.

METHODS

Randomised controlled trials (RCTs) comparing UKA cutting guides were searched in electronic databases, major orthopaedics journals, and oral communications in major orthopaedics meetings, until May 1st, 2022. The primary outcomes were the rate of outliers for the tibial and femoral components in the frontal plane, KSS score and the complication rate.

RESULTS

Eighteen RCTs involving 1562 patients with 1564 UKA were included Regarding the prosthetic components' positions, we found a significant increase of the outliers rate using PSI for the femoral component, compared to robotic surgery (risk ratio 0.00 [95% CI 0.00 to 0.55]) and navigated surgery (risk ratio 305.1 [95% CI 1.50 to 1,27e + 07]). We didn't emphasize any difference regarding the tibial component's position, the KSS value at 24 months postoperatively, and the complication rate. Regarding secondary outcomes, robotics provided a better precision in bone cuts in the sagittal plane for the tibial component and the lower limb alignment. No other differences were observed.

CONCLUSION

In the light of these results, the robot seems to be the most precise cutting instrument to perform UKA. However, this did not demonstrate any difference in functional or clinical outcome. The cost of this technology can be a major economic brake, especially in surgical centers that do not have an exclusive prosthetic activity. Further outcome and survivorship data is needed to recommend one cutting instrument over the other.

Robot-assisted knee arthroplasty improves component positioning and alignment, but results are inconclusive on whether it improves clinical scores or reduces complications and revisions: a systematic overview of meta-analyses

PURPOSE

The purpose of this systematic overview was to identify, synthesise and critically appraise findings of meta-analyses on robot-assisted versus conventional unicompartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA). The hypothesis was that robotic assistance would reduce complications and revision rates, yield better clinical scores, and improve component positioning and alignment.

METHODS

Two researchers independently conducted a literature search using Embase^®, MEDLINE^®, Web of Science, Allied and Complementary Medicine™ and Cochrane Database of Systematic Reviews on 2 November 2020 for meta-analyses (Level I-IV) on robotic assistance in UKA and/or TKA. Outcomes were tabulated and reported as weighted mean difference (WMD), risk ratio (RR) or weighted odds ratio (WOR), and were considered statistically significant when p < 0.05.

RESULTS

A total of ten meta-analyses were identified; four on robot-assisted UKA (n, 1880 robot-assisted vs. 2352 conventional UKA; follow-up, 0 to 60 months), seven on robot-assisted TKA (n, 4567 robot-assisted vs. 5966 conventional TKA; follow-up, 0 to 132 months). Of the meta-analyses on UKA, one found that robotic assistance reduced complication rates (relative risk (RR), 0.62), one found that it improved clinical scores (weighted mean difference (WMD), 19.67), three found that it extended operation times (WMD, 15.7 to 17.1 min), and three found that it improved component positioning and alignment (WMD, - 1.30 to - 3.02 degrees). Of the meta-analyses on TKA, two found that robotic assistance improved clinical scores (WMD, 1.62-1.71), two found that that it extended surgery times (WMD, 21.5-24.26 min), and five found that it improved component positioning and alignment (WMD, - 0.50 to - 10.07 degrees). None of the meta-analyses reported differences in survivorship between robot-assisted versus conventional knee arthroplasty.

CONCLUSION

Robot-assisted knee arthroplasty enabled more accurate component positioning and placement within target zones, but extended operation time considerably. Although robotic assistance improved component positioning, its benefits regarding clinical scores, patient satisfaction and implant survivorship remains to be confirmed. Finally, this overview revealed that six of the ten meta-analyses were of 'critically low quality', calling for caution when interpreting results.

LEVEL OF EVIDENCE

IV.

The Use of Computerized Tomography Scans in Elective Knee and Hip Arthroplasty—What Do They Tell Us and at What Risk?

The average background radiation exposure in the United States has nearly doubled over the previous quarter century, with almost all the increase derived from medical imaging. Nearly 2% of all cancers in the United States may be attributable to radiation from computerized tomography (CT) scans. Given the nondiagnostic nature of CT scans that are used in elective knee and hip arthroplasty today, special consideration should be given to the inherent risk of radiation exposure with routine use of this technology. Methods to decrease radiation exposure including modulating the settings of the CT machine and using alternative non-CT-based systems can decrease patient exposure to radiation from CT scans. The rapid evolution of CT technology in arthroplasty has allowed for expanded clinical applications, the benefits of which remain controversial.

Advances in the Application of Three-dimensional Printing for the Clinical Treatment of Osteoarticular Defects

As a promising manufacturing technology, three-dimensional (3D) printing technology is widely used in the medical field. In the treatment of osteoarticular defects, the emergence of 3D printing technology provides a new option for the reconstruction of functional articular surfaces. At present, 3D printing technology has been used in clinical applications such as models, patient-specific instruments (PSIs), and customized implants to treat joint defects caused by trauma, sports injury, and tumors. This review summarizes the application status of 3D printing technology in the treatment of osteoarticular defects and discusses its advantages, disadvantages, and possible future research strategies.

Patient-specific guides in orthopedic surgery

The interest of patient-specific guides (PSGs) lies in reliable intraoperative achievement of preoperative planning goals. They are a form of instrumentation optimizing intraoperative precision and thus improving the safety and reproducibility of surgical procedures. Clinical superiority, however, has not been demonstrated. The various steps from design to implementation leave room for error, which needs to be known and controlled by the surgeon who is responsible for final outcome. Instituting large-scale patient-specific surgery requires management systems for guides and innovative implants which cannot be a simple extension of current practices. We shall approach the present state of knowledge regarding PSGs via 5 questions: (1) What is a PSG? Single-use instrumentation produced after preoperative planning, aiming exclusively to optimize procedural exactness. (2) How to use and assess PSGs in orthopedic surgery? Strict rules of use must be adhered to. Any deviation from the predefined objective is, necessarily, an error that must be identified as such. (3) Do PSGs provide greater surgical exactness? The contribution of PSGs varies greatly between procedures. Exactness is enhanced in the spine, in osteotomies around the knee and in bone-tumor surgery. In the shoulder, their contribution is seen only in complex cases. Data are sparse for hip replacement, and controversial for knee replacement. (4) What are the expected benefits of PSGs? As well as improving exactness, PSGs allow a lower radiation dose and shorter operating time. They also enable junior surgeons to train in techniques otherwise reserved to hyperspecialists. (5) How to include PSGs in everyday practice? As well as their potential clinical interest, PSGs involve deep changes in organization, equipment provision and economic model. LEVEL OF EVIDENCE: V; expert opinion.

Application of Personalized Navigation Templates to Oxford Single Condylar Replacement in a Chinese Population

The purpose of this study is to develop and validate a novel patient-specific navigational template for unicompartmental knee arthroplasty (UKA). A total of 120 patients who underwent UKA were randomized and divided into the conventional method and navigational template groups. In the navigational template group, patient-specific navigational templates were designed and used intraoperatively to assist 60 patients with UKA. Information on operation time and blood loss was recorded by an independent operating room nurse. After surgery, the positions of the prostheses were evaluated using X-rays. All navigation templates were found to fit its corresponding biomodel appropriately without any free movement. The navigational template exhibited significantly better accuracy than the conventional method. Statistically significant differences in the femoral prosthesis flip angle, femoral prosthesis flexion angle, and tibial plateau varus and valgus angle were observed between the two groups (p = 0.022, 0.042, 0.043, respectively). In addition, the mean operation time was statistically and significantly lower in the navigational template group than in the conventional group (p = 0.035). This study introduces a novel navigational template to UKA, the accuracy of which is proven by clinical operation. This is a Level III, therapeutic study.

Robot-Assisted versus Conventional Total and Unicompartmental Knee Arthroplasty: A Meta-analysis of Radiological and Functional Outcomes

The study aims to provide an up-to-date systematic review and meta-analysis comparing radiological and functional outcomes of total knee arthroplasty (TKA) and unicompartmental knee arthroplasty (UKA) using either robotic assistance or conventional methods from the latest assemblage of evidence. This study was conducted according to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) and MOOSE (Meta-analysis of Observational Studies in Epidemiology) guidelines. All studies in PubMed, EMBASE, Medline, and Cochrane that reported radiological and functional outcomes after TKA or UKA with either robotic or conventional methods were included in the review. Selected endpoints for random effects, pairwise meta-analysis included operative details, radiological outcomes (mechanical axis, component angle deviation, and outliers), and functional outcomes (American Knee Society Score, Knee Society Function Score, revision and complication rate, range of motion (ROM), Hospital for Special Surgery score, and Western Ontario and McMaster Universities Osteoarthritis Index). A total of 23 studies comprising 2,765 knees were included from the initial search. Robot-assisted TKA and UKA were associated with significantly better component angle alignment accuracy (low-to-high quality evidence) at the cost of significantly greater operation time. Robot-assisted UKA was found to have significantly better short-term functional outcomes compared with conventional UKA (moderate-to-high quality evidence). Robot-assisted TKA, however, did not exhibit significantly better short- and midterm subjective knee outcome scores compared with its conventional counterpart (high-quality evidence). Robot-assisted TKA and UKA were associated with nonstatistically significant improved ROM and lesser rates of revision. Robot-assisted total and unicompartmental knee arthroplasty leads to better radiological outcomes, with no significant differences in mid- and long-term functional outcomes compared with conventional methods for the former. Larger prospective studies with mid- and long-term outcomes are required to further substantiate findings from the present study.

What is the evidence for clinical use of advanced technology in unicompartmental knee arthroplasty?

BACKGROUND

With an aim of improving prosthesis survivorship of unicompartmental knee arthroplasty (UKA), use of computer-assisted technologies (CATs) such as robotics, has been on the rise to reduce intraoperative errors in surgical technique. In light of recent influx of CATs in the UKA, a review of these innovations will help providers to understand their clinical utility.

METHOD

A systematic literature search was performed following Preferred Reporting Items for Systematic Review and Meta-Analysis guidelines.

RESULTS

Among 19 studies comparing robot-assisted UKA with conventional UKA, only 32% were randomized control trials, 47% reported minimum mean follow-up of 2 years, and 21% evaluated prosthesis survival. Similar results were obtained for navigation-assisted UKA and UKA performed with patient-specific instrumentation.

CONCLUSION

While CATs seem to reduce the surgical errors in UKA, the evidence on the efficacy of any of the studied CATs to improve survivorship remains limited and there are issues related to cost-effectiveness, learning curve, and increase in operating time.

Comparing clinical and radiographic outcomes of robotic-assisted, computer-navigated and conventional unicompartmental knee arthroplasty: A network meta-analysis of randomized controlled trials

Introduction

The purpose was to compare robotic assisted (RA), computer navigated (CN), and conventional UKA techniques.

Methods

Databases were queried for data on study characteristics, UKA systems, complications, and tibiofemoral alignment.

Results

Four RA and six CN RCTs were identified. No significant differences were found in operative time, tibiofemoral alignment, and reoperation rates when comparing RA or CN to conventional UKA. RA UKA resulted in a significantly lower risk of complications compared to conventional UKA.

Conclusions

RA UKA results in fewer complications than conventional UKA with a clinically significant increase in operative time. All groups were similar in remaining evaluated parameters.

[Focal femoral resurfacing and unicompartmental knee replacement : Between osteotomy and total knee replacement]

Unicompartmental knee arthroplasty, especially for both femorotibial compartments of the knee, is an established partly joint-saving treatment option for osteoarthritis of the knee if the disease is limited to one compartment. Even smaller implants or resurfacing of the patellofemoral joint have been shown-in smaller patient collectives-to have the potential to yield good clinical results.

Mid-term functional outcomes of patient-specific versus conventional instrumentation total knee arthroplasty: a prospective study

INTRODUCTION

Patient-specific instrumentation (PSI) utilizes three-dimensional imaging to produce total knee arthroplasty cutting jigs which matches patient's native anatomy. However, there are limited mid- to long-term studies examining its clinical efficacy. The aim of this study was to compare functional outcomes of PSI surgery versus conventional TKA surgery at 5-year follow-up.

MATERIALS AND METHODS

Sixty patients were prospectively recruited into either the MRI-based PSI or conventional TKA group. Functional outcomes were assessed using the Knee Society Function Score (KSFS), Knee Society Knee Score (KSKS) and Oxford Knee Score (OKS), while quality of life was evaluated with the Physical Component Score (PCS) and Mental Component Score (MCS) of Short-Form 36 and compared between the two groups at 5-year follow-up.

RESULTS

Although the PCS was 7 ± 3 points better in the PSI group preoperatively (p = 0.017), it became 5 ± 2 points worse than the conventional group at 5-year follow-up (p = 0.025). As compared to the PSI group, the conventional group showed a significantly greater improvement in PCS at 5 years as compared to before surgery (p = 0.003). There were no significant differences in KSFS, KSKS, OKS or MCS between the two groups.

CONCLUSIONS

PSI TKA did not result in improved functional outcomes or better quality of life when compared to conventional TKA. The additional costs and waiting time associated with PSI are not justifiable and therefore not recommended as an alternative to conventional TKA.

LEVEL OF EVIDENCE

II.

Lateral Unicompartmental Knee Arthroplasty

Lateral unicompartmental knee arthroplasty affords excellent functional results and implant survivorship for properly selected patients. More high-quality studies are necessary to determine whether expanded indications for medial unicompartmental knee arthroplasty also apply to lateral unicompartmental knee arthroplasty. Operative adjuncts such as robotics, custom implants, and navigation technology hold promise in minimizing the technical burden and unfamiliarity of lateral unicompartmental knee arthroplasty. Improvements in lateral-specific implants may translate to operational efficiency and improved outcomes, but few lateral-specific implants currently exist. Mobile-bearing devices have increased rates of failure due to bearing dislocation, and further studies are warranted to evaluate this complication with newer designs. Future registry and cohort studies should show medial unicompartmental knee arthroplasty and lateral unicompartmental knee arthroplasty separately to allow for better understanding of the nuances and technical differences between these uniquely different procedures.

[New technologies (robotics, "custom-made") for unicondylar knee arthroplasty-contra]

BACKGROUND

Numerous long-term results for both medial and lateral unicondylar knee arthroplasty (UKA) demonstrate that UKA is a reliable and successful treatment for isolated anteromedial or lateral osteoarthritis of the knee when the correct indications are used. The relationship between operation volume and implant performance has clearly been established from recent studies and registry data. The use of novel technologies allows for an improvement in the accuracy of implant positioning with fewer outliers. However, evidence-based target zones for the positioning of available implants have not been sufficiently established.

INDIVIDUAL ENDOPROSTHETICS

Current data does not support the routine use of patient-specific instruments or custom-made implants.

ROBOTICS

Robot-assisted procedures must be interpreted as a very promising approach for the future. So far, there is insufficient evidence that robotically assisted surgical techniques improve implant performance or lead to better functional results from the patient's point of view.

Total knee arthroplasty: Latest robotics implantation techniques

The recent introduction of new robotic systems for total knee arthroplasty (TKA) has created somewhat of a craze. Nevertheless, we can ask ourselves whether it is justified to use these new but very costly technologies. The results and limitations of these robotic tools must be analyzed systematically before confirming their benefits. Most of the newest robotic systems are interactive ones. These systems can accurately restore the mechanical axis and can improve the ligament balance and implant positioning. Theoretically, this can lead to better survival, function and outcomes. Recent studies have shown that use of robotics for TKA implantation does not increase the surgery time and does not cause more complications. Nevertheless, the long-term advantages of robotics use in this context remains to be proven. This task will be more difficult since there is currently no consensus as to the ideal positioning of TKA implants for a given patient. The aim of this study is to summarize this topic by answering the following questions: What are the different types of robots that can be used for TKA implantation? Which steps of the TKA surgical procedure are done with robotic arm assistance? What are the outcomes of these new implantation techniques? What are the limitations of these new implantation techniques? LEVEL OF EVIDENCE: V; expert opinion.

Does static trunk motion analysis reflect its true position during daily activities in adolescent with idiopathic scoliosis?

INTRODUCTION

Adolescent idiopathic scoliosis is common condition in pediatric orthopedics that is generally analyzed with standard radiographs. However, the conditions under which the radiographs are made are completely different than the position that patients use during day-to-day activities. We hypothesized that the trunk's static position differs from its dynamic one. The aim of this study was to determine differences between the trunk's static and dynamic positions using motion analysis in adolescents with idiopathic scoliosis.

PATIENTS AND METHODS

This prospective, single-center study enrolled adolescents with idiopathic scoliosis who were scheduled to undergo surgical correction. The day before the surgery, radiographs were made and motion analysis was performed (static and dynamic acquisitions). Various parameters were measured on the radiographs and motion analysis, including the coronal vertical axis (CVA), sagittal vertical axis (SVA) and coronal shoulder tilt.

RESULTS

The study enrolled 62 patients with a mean age of 15.5 years. There was a significant correlation between the radiographic measurements and the static motion analysis results for most parameters. Conversely, dynamic measurements of CVA, SVA and coronal shoulder tilt were not correlated to their static measurements (R=0.229; 0.198 and -0.109 respectively, all p>0.05). The static coronal shoulder tilt was opposite to the one found during walking (-0.9° vs. 0.5°, p=0.031).

DISCUSSION

Our study is the first to compare the trunk's static position with its dynamic position during walking in a cohort of adolescents with idiopathic scoliosis. Motion analysis provides new information about the trunk's dynamic positions. Based on our findings, radiographic analysis only partially captures the spinal alignment and cannot be used to draw reliable conclusions about the trunk's dynamic balance.

Unicompartmental knee arthroplasty, an enigma, and the ten enigmas of medial UKA

Unicompartmental knee arthroplasty (UKA) is a bone- and ligament-sparing alternative to total knee arthroplasty in the patients with end-stage single-compartment degeneration of the knee. Despite being a successful procedure, the multiple advantages of UKA do not correlate with its usage, most likely due to the concerns regarding prosthesis survivability, patient selection, ideal bearing design, and judicious use of advanced technology among many others. Therefore, the purpose of this study is to review and summarize the debated literature and discuss the controversies as “Ten Enigmas of UKA.”

Patient-specific instrument for unicompartmental knee arthroplasty does not reduce the outliers in alignment or improve postoperative function: a meta-analysis and systematic review

BACKGROUND

Unsatisfactory alignment in unicompartmental knee arthroplasty (UKA) is one potential cause of postoperative failure. Patient-specific instruments (PSIs) are designed to improve the alignment of the prostheses, but the effect of PSIs on the alignment or clinical outcome is controversial and lacks validated evidence. We conducted a meta-analysis and systematic review to determine the effect of PSIs on UKA outcomes for the first time.

MATERIALS AND METHODS

A systematic literature search in MEDLINE, EMBASE, CNKI (Chinese database) and Cochrane Central Register of Controlled Trials (up to June 2019) was performed to collect studies that compared PSIs with conventional instruments. Two reviewers independently screened all the records on the basis of inclusion and exclusion criteria. Quality assessments with Cochrane's quality assessment tool or Newcastle-Ottawa scale (NOS) were conducted, the data were extracted, and statistical analyses were completed.

RESULTS

Ten studies with 444 knees were included. The meta-analysis confirmed that PSIs contributed to reduced errors in the alignment of the femoral compartment in the sagittal plane (mean difference = - 2.53, CI [- 3.14, - 1.99], P < 0.01) and the tibial compartment in both the coronal (mean difference = - 0.97, CI [- 1.44, - 0.49], P < 0.01) and the sagittal plane (mean difference = - 1.29, CI [- 1.81, - 0.76], P < 0.01). One study supported that PSIs reduced outliers in inexperienced surgeons; however, all studies investigating PSIs among experienced surgeons suggested that PSIs cannot reduce the percentage of outliers. There was no significant difference in the postoperative score (mean difference = - 0.06, CI [- 0.36, 0.23], P = 0.68) or rate of complications (RR = 1.02, CI [0.15, 6.79], P = 0.99) between PSIs and conventional instruments.

CONCLUSION

The findings of this study suggest PSIs could not reduce the percentage of outliers in UKA patients for experts, and postoperative scores and complication rates are not improved by PSIs, compared with conventional instruments. Based on this meta-analysis and systematic review, no practical benefit to UKAs in experts was detected in PSIs. The findings of this study also suggest that PSIs improved alignment of UKA and might be beneficial to inexperienced surgeons, but it is still unclear whether this improvement is clinically significant and the evidence of inexperienced surgeons is limited. Therefore, more high-quality RCTs are need to be carried out in the future.

Patient-specific instrumentation does not improve tibial component coronal alignment for medial UKA compared to conventional instrumentation

Background

Patient-specific instrumentation (PSI) may potentially improve unicompartmental knee arthroplasty (UKA) implant positioning and alignment. The purpose of this study was to compare early radiographic coronal alignment of medial UKA performed using PSI versus conventional instrumentation (CI) for tibial resections.

Methods

A consecutive series of 47 knees (47 patients) received medial UKA, with the tibial resections performed using CI (first 22 knees) or PSI (next 25 knees), while femoral resections were performed with CI in both groups. The target mechanical medial proximal tibial angle (mMPTA) was 87° ± 3°, and the target hip-knee-ankle (HKA) angle was 177° ± 2°. The postoperative mMPTA and HKA were evaluated from postoperative radiographs at a follow-up of 2 months.

Results

Differences in postoperative mMPTA (p = 0.509) and HKA (p = 0.298) between the two groups were not statistically significant. For the mMPTA target, 24% of knees in the PSI group (85.6° ± 2.1°) and 32% of the CI group (85.0° ± 3.6°) were outliers. For the HKA target, 44% of knees in the PSI group (176.3° ± 2.8°) and 18% of the CI group (177.1° ± 2.3°) were outliers. Considering the two criteria simultaneously, 60% of knees in the PSI group and 45% of knees in the CI group were outside the target zone (p = 0.324), whereas 28% of knees in the PSI group and 41% of knees in the CI group were outside the target zone by more than 1° (p = 0.357).

Conclusions

The results of the present study revealed no statistically significant difference in radiographic coronal alignment of UKA performed using PSI versus CI for tibial resections.

Curve location influences spinal balance in coronal and sagittal planes but not transversal trunk motion in adolescents with idiopathic scoliosis: a prospective observational study

PURPOSE

In adolescent idiopathic scoliosis (AIS), spinal deformity can be seen in the thoracic or in the lumbar area. Although differences according to curve location are well described on standard radiographs, dynamic consequences of such difference remain unclear. Our objective was to explore the differences in dynamic spinal balance according to curve location in AIS patients using gait analysis METHODS: We prospectively included 22 females with AIS planned for surgical correction (16.3 years old, 81% Risser ≥ 4). Patients were divided into two matched cohorts, according to major curve location [right thoracic (Lenke 1) or left lumbar (Lenke 5)]. Gait analysis was performed the day before surgery. Global balance was analyzed as the primary outcome. Local curves parameters (dynamic Cobb angles) were defined as the secondary outcome.

RESULTS

In coronal plane, Lenke 5 patients had a left trunk shift, whereas trunk was shifted to the right in Lenke 1 patients (- 20.7 vs 6.3, p = 0.001). In the sagittal plane, the main difference between the two groups was T12 position that remained over the pelvis during gait in Lenke 5 patients, whereas it was anterior to the pelvis in Lenke 1 patients. In the transversal plane, Lenke 5 and Lenke 1 patients presented the same gait abnormalities, with a global trunk rotation to the left (- 4.8 vs - 7.6, p = 0,165).

CONCLUSION

This is the first study to provide the results of a direct comparison between Lenke 1 and Lenke 5 patients during gait. Curve location influenced coronal and sagittal balance, but abnormalities of transversal trunk motion were the same, wherever the curve was located. These slides can be retrieved under Electronic Supplementary Material.

TRENDS IN UNICOMPARTMENTAL KNEE ARTHROPLASTY

Objective:

To evaluate trends in publications on unicompartmental knee arthroplasty (UKA) from the past to the present.

Methods:

As a web-based analysis, all UKA research articles, editorial letters, case reports, reviews and meeting abstracts published on the Thomson Reuters’ Web of Knowledge were evaluated. The period from the first publication in 1980 to January 2019 was divided into four decades and publications were evaluated. Research articles were grouped into headings according to the subjects.

Results:

A total of 1,658 publications were evaluated in this study. The most frequent term used in the publications title was “outcome,” with 260 items, followed by “biomechanics and kinematics,” with 99 items. Most reports have been published in the last decade, and the most common type of publication was postoperative follow-up and results.

Conclusion:

In parallel with technological advancements, publications related to UKA-especially patient-specific instrumentation, navigation, and robotic surgery-will increase in number and become more specific. Level of Evidence V, Expert Opinion.

A novel patient-specific instrument design can deliver robotic level accuracy in unicompartmental knee arthroplasty

BACKGROUND

A previous randomised controlled trial (RCT) by our group found that robotic assisted unicompartmental knee arthroplasty (UKA) surgery was significantly more accurate than conventional instrumentation. The aim of this study was to determine whether a low-cost novel PSI design could deliver the same level of accuracy as the robot in the same time efficient manner as conventional instruments.

METHODS

Thirty patients undergoing medial UKA took part. Tibial component position was planned using a low dose CT-scan, and compared to a day 1 postoperative CT-scan to determine the difference between the planned and achieved positions. Operations were performed by one expert surgeon using PSI (Embody, London, UK).

RESULTS

The mean absolute difference between planned and achieved tibial implant positions using PSI was 2.0° (SD 1.0°) in the coronal plane, 1.8° (SD 1.5) in the sagittal plane, and 4.5° (SD 3.3) in the axial plane. These results were not significantly different to the 13 historical robotic cases (mean difference 0.5°, 0.5°, and 1.7°, p = 0.1907, 0.2867 and 0.1049 respectively). PSI mean operating time was on average 62 min shorter than the robotic group (p < 0.0001) and 40 min shorter than the conventional instrument group (p < 0.0001). No complications were reported.

CONCLUSIONS

In conclusion, this clinical trial demonstrates that for tibial component positioning in UKA, a novel design PSI guide in the hands of an expert surgeon, can safely deliver comparable accuracy to a robotic system, whilst being significantly faster than conventional instruments. NIHR Clinical Research Network Reference: 16100.

Characterization of trunk motion in adolescents with right thoracic idiopathic scoliosis

BACKGROUND

Although standard radiography is currently used for deformity assessment in AIS patients, it is performed in a constrained position and probably not reflective of spinal balance during daily-life activities. Our main objective was to compare trunk motion in Lenke 1 and 2 AIS patients to healthy volunteers, using gait analysis.

MATERIAL AND METHODS

Lenke 1 or 2 AIS patients planned for surgery were included. The day before surgery, they underwent radiographic evaluation and gait analysis. Among the gait parameters, sagittal vertical axis (Dyn-SVA), shoulder line rotation (Dyn-SL rotation), pelvis rotation (Dyn-P rotation) and acromion pelvis angle (Dyn-APA) were measured. AIS patients were compared to 25 asymptomatic controls.

RESULTS

A total of 57 patients were included in the study, with a mean Cobb angle of 55.4°. AIS patients had a lower Dyn-SVA when compared to controls (47.0 vs. 62.9 mm, p = 0.012). Dyn-APA and Dyn-SL rotation were negative in AIS patients, meaning that shoulder line was rotated towards the left (- 6.4 vs. 7.8° and - 7.5 vs. - 0.4°, p<0.001, respectively). On the other hand, Dyn-P rotation was positive, meaning that pelvis was rotated towards the right side during gait (1.1 vs. - 0.5, p = 0.026).

DISCUSSION

This is one of the largest series of gait analysis in AIS patients. We demonstrated that AIS patients have an abnormal gait pattern, with a decreased anterior tilt of the trunk and transverse plane abnormalities. We found that gait deviation was not related to radiographic measurements, pointing out that dynamic assessment provides new data about spinal posture. These slides can be retrieved under Electronic Supplementary Material.

Correlations linking static quantitative gait analysis parameters to radiographic parameters in adolescent idiopathic scoliosis

BACKGROUND

Radiography is the main tool used to assess spinal deformities in patients with adolescent idiopathic scoliosis (AIS) but requires repeated exposure to ionising radiation, potentially raising safety concerns. Consequently, new methods are needed. Among them, the acquisition of static parameters during quantitative gait analysis (QGA) has received attention in recent years. However, no data on correlations linking static QGA parameters to standard radiographic parameters are available. The objective of this study was to assess correlations between static QGA parameters and standard radiographic parameters in patients with AIS.

HYPOTHESIS

Spinal deformities in patients with AIS can be evaluated based on static QGA parameters.

PATIENTS AND METHODS

We studied patients scheduled for surgery to treat AIS. On the day before surgery, QGA was performed and antero-posterior and lateral radiographs obtained. QGA involved analysing the positions of 32 reflective markers, including 6 used to assess the spine. The coronal vertical axis (CVA), thoracic and lumbar Cobb angles, sagittal vertical axis (SVA), thoracic kyphosis, lumbar lordosis, and pelvic tilt were recorded and compared to the corresponding radiographic parameters.

RESULTS

The study included 57 patients, including 48 (84%) females, with a mean age of 15.2 years. Among them, 45 had Lenke 1 and 12 Lenke 5 scoliosis. The mean main Cobb angle was 51.9°. In the coronal plane, significant correlations with the corresponding radiographic parameters were found for the CVA (R=0.524, p<0.01) and thoracic Cobb angle (R=0.599, p<0.01). All the sagittal parameters correlated significantly with the corresponding radiographic parameters: SVA, R=0.313; pelvic tilt, R=0.342; thoracic kyphosis, R=0.575; and lumbar lordosis, R=0.360 (p<0.05 for all four parameters).

CONCLUSIONS

In this study, static QGA parameters accurately reflected the spinal deformities visualised radiographically. The lumbar deformity was more difficult to characterise, probably because it was mild in our population. Research efforts should focus on improving the performance of QGA, notably for detecting curve progression. Thus, QGA may allow a decrease in radiation exposure of patients with AIS.

LEVEL OF EVIDENCE

III.

A high rate of tibial plateau fractures after early experience with patient-specific instrumentation for unicompartmental knee arthroplasties

PURPOSE

Patient-specific instrumentation (PSI) for unicompartmental knee arthroplasty (UKA) has been available for a few years. However, limited literature is available on this subject. Hence, the aim of this cohort study is to evaluate the 2 years' results of our first experiences with the use of PSI in UKA. It is hypothesised that there is no advantage in rate of adverse events and in radiological and functional outcomes in comparison to literature on the conventional method.

METHODS

This cohort included 129 knees of 122 patients, operated by one surgeon. Outcome measures were the rate of adverse events (AEs); implant position as determined on radiographs; the accuracy of the default and approved planning of the implant sizes and the patient-reported outcome measures (PROMs) preoperatively, and at 3, 12 and 24 months, postoperatively.

RESULTS

A total of 6 (4.9%) AEs were observed in this study, with 4 (3.3%) tibial fractures being the main complication. The mean postoperative biomechanical axis was 176.4° and in the majority of cases, the radiographic criteria, as determined by the manufacturer, were met. The tibial component showed 20 (16.4%) outliers in the sagittal and 3 (2.5%) outliers in the frontal plane. There were no outliers of the femoral component. For the femoral and tibial components, respectively, in 125 (96.9%) and 79 (61.7%) cases, there was an agreement between approved planning and implanted component size. All PROMs improved significantly after surgery.

CONCLUSION

Tibial fracture was the most common AE, probably related to the transition from cemented to uncemented UKA. Perioperative modifications to the surgical technique were made in order to prevent this AE. Improvements should be made to the operation technique of the uncemented tibial plateau to obtain an adequate placement and at the same time reduce the risk for tibial fracture. The PSI technique was a reliable tool for the placement of the femoral component. Functional outcome was in line with literature on the conventional method. It is strongly recommended that the surgeon approves every preoperative plan, in order to optimise the accuracy during the PSI surgery.

LEVEL OF EVIDENCE

III.

Unicompartmental knee arthroplasty: Current indications, technical issues and results

An age younger than 60 years, a body weight of 180 lb (82 kg) or more, performing heavy work, having chondrocalcinosis and having exposed bone in the patellofemoral (PF) joint are not contraindications for unicompartmental knee arthroplasty (UKA).Severe wear of the lateral facet of the PF joint with bone loss and grooving is a contraindication for UKA.Medial UKA should only be performed in cases of severe osteoarthritis (OA) as shown in pre-operative X-rays, with medial bone-on-bone contact and a medial/lateral ratio of < 20%.The post-operative results of UKA are generally good. Medium-term and long-term studies have reported acceptable results at 10 years, with implant survival greater than 95% for UKAs performed for medial OA or osteonecrosis and for lateral UKA, especially when fixed-bearing implants are used.When all implant-related re-operations are considered, the 10-year survival rate is 94%, and the 15-year survival rate is 91%.Aseptic loosening is the principal failure mechanism in the first few years in mobile-bearing implants, whereas OA progression causes most failures in later years in fixed-bearing implants.The overall complication rate and the comprehensive re-operation rate are comparable in both mobile bearings and fixed bearings.The survival likelihood of the all-polyethylene UKA implant is similar to that of metal-backed modular designs for UKA.Notable cost savings of approximately 50% can be achieved with an outpatient UKA surgery protocol. Outpatient surgery for UKA is efficacious and safe, with satisfactory clinical results thus far. Cite this article: EFORT Open Rev 2018;3:363-373. DOI: 10.1302/2058-5241.3.170048.

3D printing and unicompartmental knee arthroplasty

In suitable patients, unicompartmental knee arthroplasty (UKA) offers a number of advantages compared with total knee arthroplasty. However, the procedure is technically demanding, with a small tolerance for error. Assistive technology has the potential to improve the accuracy of implant positioning.This review paper describes the concept of detailed UKA planning in 3D, and the 3D printing technology that enables a plan to be delivered intraoperatively using patient-specific instrumentation (PSI).The varying guide designs that enable accurate registration are discussed and described. The system accuracy is reported.Future studies need to ascertain whether accuracy for low-volume surgeons can be delivered in the operating theatre using PSI, and reflected in improved patient reported outcome measures, and lower revision rates. Cite this article: EFORT Open Rev 2018;3 DOI: 10.1302/2058-5241.3.180001.

Three-dimensional Technologies in Orthopedics

New 3-dimensional digital technologies are revolutionizing orthopedic clinical practice, allowing structures of any complexity to be manufactured in just hours. Such technologies can make surgery for complex cases more precise, more cost-effective, and possibly easier to perform. Applications include pre-operative planning, surgical simulation, patient-specific instrumentation and implants, bioprinting, prosthetics, and orthotics. The basic principles of 3- dimensional technologies, including imaging, design, numerical simulation, and printing, and their current applications in orthopedics are reviewed. [Orthopedics. 2018; 41(1):12-20.].

Do patient-specific instruments (PSI) for UKA allow non-expert surgeons to achieve the same saw cut accuracy as expert surgeons?

INTRODUCTION

High-volume unicompartmental knee arthroplasty (UKA) surgeons have lower revision rates, in part due to improved intra-operative component alignment. This study set out to determine whether PSI might allow non-expert surgeons to achieve the same level of accuracy as expert surgeons.

MATERIALS AND METHODS

Thirty-four surgical trainees with no prior experience of UKA, and four high-volume UKA surgeons were asked to perform the tibial saw cuts for a medial UKA in a sawbone model using both conventional and patient-specific instrumentation (PSI) with the aim of achieving a specified pre-operative plan. Half the participants in each group started with conventional instrumentation, and half with PSI. CT scans of the 76 cut sawbones were then segmented and reliably orientated in space, before saw cut position in the sagittal, coronal and axial planes was measured, and compared to the pre-operative plan.

RESULTS

The compound error (absolute error in the coronal, sagittal and axial planes combined) for experts using conventional instruments was significantly less than that of the trainees (11.6°±4.0° v 7.7° ±2.3º, p = 0.029). PSI improved trainee accuracy to the same level as experts using conventional instruments (compound error 5.5° ±3.4º v 7.7° ±2.3º, p = 0.396) and patient-specific instruments (compound error 5.5° ±3.4º v 7.3° ±4.1º, p = 0.3). PSI did not improve the accuracy of high-volume surgeons (p = 0.3).

CONCLUSIONS

In a sawbone model, PSI allowed inexperienced surgeons to achieve more accurate saw cuts, equivalent to expert surgeons, and thus has the potential to reduce revision rates. The next test will be to determine whether these results can be replicated in a clinical trial.

The impact of patient-specific instrumentation on unicompartmental knee arthroplasty: a prospective randomised controlled study

PURPOSE

Patient-specific instrumentation (PSI) has been proposed as a means of improving surgical accuracy and ease of implantation during technically challenging procedures such as unicompartmental knee arthroplasty (UKA). The purpose of this prospective randomised controlled trial was to compare the accuracy of implantation and functional outcome of mobile-bearing medial UKAs implanted with and without PSI by experienced UKA surgeons.

METHODS

Mobile-bearing medial UKAs were implanted in 43 patients using either PSI guides or conventional instrumentation. Intra-operative measurements, meniscal bearing size implanted, and post-operative radiographic analyses were performed to assess component positioning. Functional outcome was determined using the Oxford Knee Score (OKS).

RESULTS

PSI guides could not be used in three cases due to concerns regarding accuracy and registration onto native anatomy, particularly on the tibial side. In general, similar component alignment and positioning was achieved using the two systems (n.s. for coronal/sagittal alignment and tibial coverage). The PSI group had greater tibial slope (p = 0.029). The control group had a higher number of optimum size meniscal bearing inserted (95 vs 52%; p = 0.001). There were no differences in OKS improvements (n.s).

CONCLUSION

Component positioning for the two groups was similar for the femur but less accurate on the tibial side using PSI, often with some unnecessarily deep resections of the tibial plateau. Although PSI was comparable to conventional instrumentation based on OKS improvements at 12 months, we continue to use conventional instrumentation for UKA at our institution until further improvements to the PSI guides can be demonstrated.

LEVEL OF EVIDENCE

Therapeutic, Level I.

Knee function after limb salvage surgery for malignant bone tumor: comparison of megaprosthesis and distal femur allograft with epiphysis sparing

PURPOSE

Limb salvage surgery is increasingly used for the treatment of distal femur bone sarcomas. Total knee replacement using megaprosthesis and epiphysis-sparing biologic reconstruction using an allograft are widely used in order to preserve joint motion. We aimed to compare the results of these procedures using gait analysis in patients undergoing limb salvage surgery.

METHODS

Fifteen patients were included, nine undergoing allograft with epiphysis sparing (Allograft group) and six undergoing megaprosthesis (Megaprosthesis group). Every patient underwent a gait analysis using the Plug-in-Gait protocol. Spatiotemporal parameters, knee kinematics, and kinetics were compared between the two groups and a cohort of ten asymptomatic subjects. Knee function was assessed by the Gait Deviation Index (GDI) and the Gilette Gait Index (GGI).

RESULTS

Both treatment groups showed decreased knee flexion during the loading response phase. Megaprosthesis patients showed a decreased knee flexion all along stance phase. There was no difference in gait pattern between the treatment groups. GDI was significantly lower in Megaprosthesis and Allograft patients when compared to controls (86.4 and 84.3 vs 94, all p < 0.05). This difference was not clinically relevant.

CONCLUSION

Our study reveals that Megaprosthesis and Allograft patients did not show differences in gait patterns and global function. Even though Allograft and Megaprosthesis patients have significant changes in gait pattern, knee function is acceptable with effective gait mechanisms. Changes occur during stance phase and are due to the quadriceps weakness. The particular pattern of gait in Megaprosthesis patients could be a concern for prosthesis wear and should be investigated on this specific aspect.

LEVEL OF EVIDENCE

4.

Patient-specific positioning guides do not consistently achieve the planned implant position in UKA

PURPOSE

To investigate whether the intended preoperative planning corresponded with the postoperative component position after medial UKA using patient-specific positioning guides (PSPGs).

METHODS

Twenty-five consecutive UKAs performed with the PSPG technique (Signature™) were included. Two independent observers performed postoperative CT measurements. The preoperative angles for the femoral component were defined in the frontal plane as 0°. In the first eight cases, a femoral component with single peg was inserted, and the flexion of the femoral component was set to 5°. In the last 17 cases, a twin-peg component was used and flexion set to 10°. In the axial plane, the femoral component was on average set at 2.5° internal rotation. The preoperative tibial component angles in the frontal and axial plane were defined as 0° and in the sagittal plane as 4° in flexion.

RESULTS

The postoperative femoral component angles were on average 0.8° of valgus (SD 3.2, range 12.2° valgus to 5.1° varus, n.s., CI -2.1 to 0.6), 5.0° of flexion (SD 3.9, range 10.2° flexion to 6.0° extension, p = 0.001, CI -5.3 to -1.5) and 4.0° of internal rotation (SD 1.7, range 1.4° to 6.9° int.rot., p < 0.001, CI -4.7 to -3.4). The tibial component angles were on average 3.0° of varus (SD 1.9, range 1.3° valgus to 6.8° varus, p < 0.001, CI 2.2 to 3.8), 3.2° of flexion (SD 2.4°, 6.7° flex to 1.8° ext, n.s., CI -0.2 to 1.7) and 2.7° of internal rotation (SD 7.0, range 16.6° int.rot. to 10.7° ext.rot., n.s., CI -5.6 to 0.2).

CONCLUSION

This study showed no agreement between preoperative planning and postoperative component alignment (p < 0.05) for the femoral component angle in sagittal and axial plane and for the tibial component angle in the coronal plane. Although the results did not show significant difference for the tibial component angle in the axial plane, a considerable range of the component angles was found varying from 17° internal to 11° external rotation. This study suggests that the use of PSPGs for UKA does not lead to consistent component position.

LEVEL OF EVIDENCE

IV.

[Custom-fit kinematic alignment in total knee arthroplasty using PSI. The story of ShapeMatch technology]

BACKGROUND

The story of ShapeMatch® custom-fit cutting guides for primary total knee arthroplasty (TKA) is special compared to other available techniques. First, it was the first such patient-specific instrument (PSI) on the market. Second, the underlying philosophy of kinematic alignment is unique compared to other competitors. Finally, it is the only PSI technique that has been withdrawn from the market.

OBJECTIVES AND METHODS

The objective of this paper is to summarize the history of the ShapeMatch® technology and to review the current literature regarding clinical evidence for kinematically aligned TKA.

RESULTS AND CONCLUSIONS

In the recent literature, faster rehabilitation, better knee function and higher patient satisfaction are described for kinematically aligned TKA compared to conventional alignment. However, there is also evidence for inaccuracies by using the PSI technology as a possible cause of treatment failures. Due to those problems, this technology was recalled from the market. As an alternative method to achieve kinematic alignment in TKA, manual as well as computer-assisted techniques are currently under development and are discussed here.

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.

Patient specific instrumentation in total knee arthroplasty: a state of the art

Patient specific instrumentation (PSI) is a modern technique in total knee arthroplasty (TKA) aiming to facilitate the implant of the prosthesis. The customized cutting blocks of the PSI are generated from pre-operative three-dimensional model, using computed tomography (CT) or magnetic resonance imaging (MRI). A correct surgical plan is mandatory for a good surgical implant. The PSI guide takes into account any slight deformities or osteophytes and applies preoperative planning for bone resection, using the pre-determined implant size, position, and rotation. The apparent benefits of this technology are that neutral postoperative alignment is more reproducible, surgical time is decreased, and the entire procedure results more efficient and cost-effective. The use of PSI is indicated when advanced osteoarthritis, severe pain, and limited function/walking ability are present, such as in a standard instrumentation TKA. In addition to that, PSI finds its indication when intra-medullary guides cannot be used. For example, when there is a post-traumatic femoral deformity. Large debates have taken place about this topic during the last years and, at the moment, there is no consensus in literature regarding the accuracy and reliability of PSI as many studies have shown controversial and inconsistent results. Literature does not suggest PSI techniques as a gold standard in TKA, and therefore it cannot be recommended as a standard technique in standard, not complicated primary TKA. Moreover, literature does not underline any improvement in components alignment, surgical time, blood loss or functional outcomes. Nevertheless, many patients who underwent TKA suffered a previous trauma. In case of deformities, like femoral or tibial fractures healed with a malalignment, preoperative planning may result difficult, and some intra-operative technical difficulties can occur, such as the use of intra-medullar rod. In these selected cases, PSIs may be very useful to avoid errors in alignment and planning.

[Total and unicompartmental knee replacement. Patient-specific Instrumentation]

BACKGROUND

The objective of patient-specific instrumentation (PSI Zimmer®) technology is to optimize positioning and selection of components as well as surgical procedure in uni- and bicompartimental knee replacement. The article contains a description of the planning and surgical technique and evaluates the method based on own results and literature.

METHODS

Using MRI or CT scans a virtual 3D model of the joint is created in order to simulate and plan the implant positioning. According to these data, pin placement and/or cutting guides are produced, which enable the surgeon to transfer the planning to the surgical procedure. In a prospective comparative study 88 patients (44 per each of the two techniques) were operated by one surgeon receiving the same TKA using either MRI-based PSI or a conventional technique. The number of surgical trays, operating time, intraoperative changes and frontal alignment using a full leg x‑ray (70 cases) were compared. In 17 patients the method was applied with unicondylar knee replacement.

RESULTS

Anatomical abnormalities could be detected preoperatively and considered during the operation. With PSI the number of trays could be reduced and predictability of the component size was more precise. Intraoperative changes became necessary only for distal femoral (25 %) and proximal tibial (36 %) resection and tibial rotation (40 %). Alignment was more precise in the PSI cases

DISCUSSION

PSI using the applied technique proved to be practicable and reliable. The advantages of precise planning became obvious. Results concerning alignment are inconsistent in the literature. Soft tissue balancing has only been included in the technique to a limited degree so far. PSI is still in an early stage of development and further development opportunities should be exploited before final assessment.

Unicompartmental knee arthroplasty: long-term results

Unicompartmental knee arthroplasty has been controversial since its introduction in the early 1970s. Some initial reports suggested that medial compartment replacement did not yield good enough early results to be a viable long-term option, although lateral compartment replacement seemed to be promising. By the early 1980s, however, good initial results were being published for medial and lateral replacements and enthusiasm for the procedure began to increase. Refinements were made in patient selection, surgical technique, and prosthetic design. Ten-year followup studies were reported that showed survivorship was slightly less than that reported for total knee arthroplasty but acceptable considering the theoretically conservative nature of unicompartmental surgery. Unicompartmental knee arthroplasty now can be characterized as a procedure with a reliable 8- to 10-year outcome in properly selected patients with osteoarthritis who receive a skillfully implanted proper design. Unicondylar knee arthroplasty can be an attractive alternative to osteotomy or total knee arthroplasty especially some middle-aged women. Approximately all studies with followups of 10 years or greater show that unicompartmental knee arthroplasty will have inferior survivorship to total knee arthroplasty whether from loosening, prosthetic wear, or secondary degeneration of the opposite compartment in the second decade. Recently published 10-year results from two centers (one using a mobile-bearing design, the other using a fixed-bearing design) are comparable with those of total knee arthroplasty. This suggests that enhanced second-decade survivorship and therefore an expansion of the indications for unicompartmental knee arthroplasty are possibilities.