Improved accuracy of alignment with patient-specific positioning guides compared with manual instrumentation in TKA

Comparison between guide plate navigation and virtual fixtures in robot-assisted osteotomy

To verify the advantages of Virtual Fixtures (VFs) by comparing the result of guide plate navigation (GPN) and VFs in robot-assisted osteotomy. Robot-assisted surgery has been extensively applied in traditional orthopedic surgeries. It fundamentally improves surgeries' cutting accuracy. In addition, many key techniques have been applied in bone cutting to increase the procedure's safety in various ways. In this paper, two robot-assisted osteotomy methods are proposed. Three operators with no osteotomy experience performed plane cutting with the assistance of a robot. GPN and VFs were applied to assist the Sawbones cutting. Each operator has five attempts using each method to perform bone cutting, distance errors and angular errors were recorded. The advantage of Sawbones is that there is no influence from soft tissues and blood. It can give a more precise measurement. The results show that both methods have high accuracy with the robot's assistance. VFs have higher accuracy in comparison with GPN. With GPN, the mean distance and angular error of the three operators were 2.974 ± 0.282 mm and 4.737 ± 0.254°. With VFs, the mean range and angular error of the three operators were 1.857 ± 0.349 mm and 2.24 ± 0.123°, respectively. VFs limited the robot's end in the planned area, increasing the accuracy and safety of robot-assisted osteotomy.

Methodological Assessment of the 100 Most-Cited Articles in Total Knee Arthroplasty in the Last Decade Compared to the All-Time List

BACKGROUND

Recent advances in total knee arthroplasty (TKA) have been driven by a growing focus on evidence-based medicine. This transition is reflected in the critical appraisal of both, the quality of work and the potential impact on the orthopedic community. The purpose of our study was to (1) identify the top 100 most-cited articles in TKA in the last decade and from all-time, and (2) compare methodological rigor of the most-cited articles in TKA in the last decade to articles all-time by level of evidence.

METHODS

The top 100 cited articles were recorded for manuscripts from the last decade, January 1, 2012 to December 31, 2022, and manuscripts from all-time for TKA. We collected authors, year of publication, journal of the article, country of origin of authors, article type (basic science article, clinical research article), level of evidence, methodological index for non-randomized studies score, physiotherapy evidence database scale, and citation density (total citations/years published).

RESULTS

The largest number of studies for all-time TKA (53.0%) and decade TKA (42.0%) were Level III. The average methodological index for non-randomized studies score for comparative studies was 18.7 for all-time TKA and 20.7 for decade TKA (P < .001). The average physiotherapy evidence database score was 6.1 for all-time TKA and 8.1 for decade TKA (P > .05). The highest citation density for all-time TKA was 111 and for past decade was 63. The number of level II studies in TKA increased from 19.0% from all time to 38.0% from the last decade (P < .05).

CONCLUSIONS

Our findings of improved methodologies over time reflect positive steps toward evidence-based practice in TKA. A continued focus on producing methodologically sound studies may guide evidence-based clinical decision-making.

First long-term analysis of survival and clinical outcome in patient-specific instrumentation for total knee arthroplasty: follow-up of a prospective cohort study

Patient-specific instrumentation (PSI) was introduced to improve post-operative alignment, and consequently the revision rate and clinical results after total knee arthroplasty (TKA). Short- to mid-term data are conflicting regarding these theoretical advantages of PSI. The purpose of this retrospective analysis was to evaluate the survival rate and clinical outcome in PSI TKA 8.4 years after initial surgery. To our knowledge, no other study investigated long-term follow-up of TKA procedures using PSI. From a total cohort of 184 consecutive patients (200 TKA) 136 patients (144 TKA, 72%) were prospectively analysed at a mean follow-up of 8.4 years (±0.4). A survival analysis with all-cause revision of TKA as endpoint was performed. Patient-reported outcome measures (PROMs) were obtained preoperatively and after 1-, 2-, 5-, and 8.4-years of follow-up. Differences between these moments of follow-up were analysed. At final follow-up, 4 TKAs (2%) had undergone revision, all between 2-4 years after primary surgery. Reasons for revision were late infection, aseptic loosening, instability and polyethylene insert breakage. The median score of certain PROMs (WOMAC, VAS, EQ-index, EQ-VAS) decreased compared to previous follow-up scores but were significantly higher than preoperative scores. After 8.4 years of follow-up, no additional revision surgery was performed compared to 5-years postoperatively. Certain PROMs at 8.4-year follow-up decreased compared to earlier moments of follow-up, but all PROMs improved compared to preoperative PROMs.

Accuracy of Patient-Specific Instrument for Cylindrical Axis Implementation in Kinematically Aligned Total Knee Arthroplasty

Background

In kinematically aligned total knee arthroplasty (KA-TKA), the cylindrical axis (CA) is very important in restoring the native joint line and kinematics of the pre-arthritic knee. This study aimed to determine the accuracy of patient-specific instrument (PSI) for restoring the CA for femoral bone resection in KA-TKA.

Methods

Thirty KA-TKAs were performed using a computed tomography (CT)-based PSI system. Data from preoperative CT were reconstructed into three-dimensional (3D) models using 3D-planning software. The CA was created by connecting the centers of each virtual sphere to the medial and lateral femoral condyles using computer software. Femoral bone resection of the distal and posterior condyles was performed parallel to the sagittal planes of the CA. The thickness of the CA-referenced bone resection was determined based on the thickness necessary for the respective regions of the femoral component. The PSI was manufactured to locate the guide pin for a conventional cutting block. The accuracy of PSI for KA-TKA was evaluated as the absolute error between the preoperatively predicted thickness and the intraoperative measurements in each of the four regions, as well as the difference in error between distal-medial (DM) and posterior-medial (PM) and between distal-lateral (DL) and posterior-lateral (PL).

Results

The differences in thickness of bone cut in the DM, DL, PM, and PL were 0.79 ± 0.39 mm (range, -1.20 to 1.50), 0.70 ± 0.42 mm (range, -1.50 to 1.50), 0.80 ± 0.46 mm (range, -0.80 to 1.50), and 0.75 ± 0.47 mm (range, -2.10 to 1.40), respectively. There was no significant difference in the thickness error between DM and PM (p = 0.959) and between DL and PL (p = 0.812).

Conclusions

In KA-TKA, PSI was effective for accurate femoral bone resection based on virtually planned thickness.

The Role of 3D-Printed Patient-Specific Instrumentation in Total Knee Arthroplasty: A Literature Review

Total knee arthroplasty (TKA) is currently one of the most common orthopedic surgeries due to the ever-increasing average life expectancy. The constant need for effective and accurate techniques was contributed to the development of three-dimensional (3D) printing in that field, especially for patient-specific instrumentation (PSI) and custom-made implants fabrication. PSI may offer numerous benefits, such as resection accuracy, mechanical axis alignment, cost-effectiveness, and time economy. Nonetheless, the results of existing studies are controversial. For this purpose, a review article of the published articles was conducted to summarize the role of 3D-printed PSI in TKA.

3D-printed, patient-specific cutting guides improve femoral and tibial cut alignment in canine total knee replacement

OBJECTIVES

The purpose of this cadaveric study was to determine whether patient-specific guides (PSGs) improve the accuracy of tibial and femoral cut alignment in canine total knee replacement (TKR), as compared with generic cutting guides.

STUDY DESIGN

Original research.

ANIMALS

Sixteen pelvic limbs from skeletally mature medium- to large-breed canine cadavers.

METHODS

Specimens were randomly allocated to one of two groups (PSG or Generic; N = 8/group). In the Generic group, femoral and tibial ostectomies were made using the standard canine TKR femoral cutting blocks and tibial alignment guide. In the PSG group, the cuts were made using a series of custom 3D-printed cutting guides. "Planned" and "actual" tibial and femoral cut alignments were compared in the frontal and sagittal planes, and errors were calculated by subtracting actual from planned values.

RESULTS

Use of 3D-printed PSGs improved tibial cut alignment in the frontal plane but not the sagittal plane. PSGs also improved the alignment of the cranial and distal femoral ostectomies but did not impact varus-valgus alignment.

CONCLUSIONS

These findings support the use of PSGs for TKR in dogs. Clinical trials are now needed to determine whether the benefits of PSGs translate into measurable improvements in joint function and implant longevity.

CLINICAL SIGNIFICANCE

PSGs have the potential to improve femoral and tibial component alignment in canine TKR.

Patient-specific instrumentation in total knee arthroplasty: a review of the current literature

Total knee arthroplasty (TKA) is one of the most frequently performed interventions in the field of Orthopaedic surgery. Over the last decades the implantation technique has improved continuously. The majority of patients is satisfied with the clinical outcome of TKA. However in various clinical follow-ups, up to 20% of unsatisfied patients can be observed. Periprosthetic infection and aseptic loosening seem to be the most common reasons for failure. Malalignment has been discussed as a cause of aseptic loosening and often leads to revision surgery. In order to increase the precision of implant positioning and alignment, new technologies such as patient-specific instrumentation (PSI) have been developed. Since the introduction of PSI, multiple clinical studies have been performed analyzing the clinical and radiological outcome of TKA with PSI technique. This review covers the recent literature of PSI in respect to surgical accuracy, clinical outcome, time- and cost-effectiveness.

The presence of 3D printing in orthopedics: A clinical and material review

The field of additive manufacturing, 3D printing (3DP), has experienced an exponential growth over the past four decades, in part due to increased accessibility. Developments including computer-aided design and manufacturing, incorporation of more versatile materials, and improved printing techniques/equipment have stimulated growth of 3DP technologies within various industries, but most specifically the medical field. Alternatives to metals including ceramics and polymers have been garnering popularity due to their resorbable properties and physiologic similarity to extracellular matrix. 3DP has the capacity to utilize an assortment of materials and printing techniques for a multitude of indications, each with their own associated benefits. Within the field of medicine, advances in medical imaging have facilitated the integration of 3DP. In particular, the field of orthopedics has been one of the earliest medical specialties to implement 3DP. Current indications include education for patients, providers, and trainees, in addition to surgical planning. Moreover, further possibilities within orthopedic surgery continue to be explored, including the development of patient-specific implants. This review aims to highlight the use of current 3DP technology and materials by the orthopedic community, and includes comments on current trends and future direction(s) within the field.

Accuracy of a Three-Dimensional (3D)-Printed Patient-Specific (PS) Femoral Osteotomy Guide: A Computed Tomography (CT) Study

Femoral neck osteotomy creates a critical anatomical landmark for surgeons performing primary Total Hip Arthroplasty (THA); it affects the final height and position of the femoral component. Patient Specific Instrumentation (PSI) has been developed to guide the osteotomy. We aimed to assess the accuracy of a patient-specific (PS) femoral osteotomy guide in primary THA using three-dimensional (3D) computed tomography (CT) analysis. We included pre- and post-operative CT data of 103 THAs. All patients underwent 3D planning to define the optimal femoral neck osteotomy level. Our primary objective was to quantify the discrepancy between the achieved and planned osteotomy level; our secondary objective was to evaluate the clinical outcome. The median (Interquartile Range—IQR) discrepancy between the achieved and planned osteotomy level was 0.3 mm (−1 mm to 2 mm). We found a strong positive correlation between the planned and achieved osteotomy level (R2 = 0.9, p < 0.001). A satisfactory clinical outcome was recorded. Our findings suggest that surgeons can use 3D-printed PS guides to achieve a femoral neck osteotomy with a high level of accuracy to the plan.

3D-printed patient specific instruments for corrective osteotomies of the lower extremity

3D-printing has become a promising adjunct in orthopedic surgery over the past years. A significant drop in costs and increased availability of the required hardware and software needed for using the technique, have resulted in a relatively fast adaptation of 3D-printing techniques for various indications. In this review, the role of 3D-printing for deformity corrections of the lower extremity is described.

Minimum 5-Year Outcomes of a Multicenter, Prospective, Randomized Control Trial Assessing Clinical and Radiological Outcomes of Patient-Specific Instrumentation in Total Knee Arthroplasty

BACKGROUND

Patient-specific instrumentation (PSI) was developed to produce more accurate alignment of components and consequently improve clinical outcomes when used in total knee arthroplasty. We compare radiological accuracy and clinical outcomes at a minimum of 5-year follow-up between patients randomized to undergo total knee arthroplasty performed using PSI or traditional cutting block techniques.

METHODS

This multicenter, randomized control trial included patients blinded to the technique 1used. Outcome measures were coronal alignment measured radiologically, Euroqol-5D, Oxford knee score, and International Knee Society Score measured at 1- and 5-year follow-up.

RESULTS

At a minimum 5-year follow-up, there were 38 knees in the PSI group and 39 in the conventional instrumentation group for analysis. Baseline demographics and clinical outcome scores were matched between groups. Overall, there was no significant difference in the coronal femoral angle (P = .59), coronal tibial angle (P = .37), tibiofemoral angle (P = .99), sagittal femoral angle (P = .34), or the posterior tibia slope (P = .12) between knees implanted using PSI and those implanted with traditional cutting blocks. On the measurement of coronal alignment, intraobserver reliability tests demonstrated substantial agreement (k = 0.64). Clinical outcomes at both 1-year and 5-year follow-up demonstrated statistically significant and clinically relevant improvement in scores from baseline in both groups, but no difference could be detected between the Euroqol-5D (P = .78), Oxford knee score (P = .24), or International Knee Society Score (P = .86) between the 2 groups.

CONCLUSION

This study has shown no additional benefit to PSI in terms of improved alignment or functional outcomes at minimum 5-year follow-up over traditional techniques.

Varus alignment of the tibial component up to seven degrees is not associated with poor long-term outcomes in a neutrally aligned total knee arthroplasty

PURPOSE

The purpose of this retrospective study was to evaluate the effect of varus alignment of the tibial component on the outcomes with a minimum follow-up of 10 years. The hypothesis was that varus alignment of the tibial component might not affect the outcomes and survival of a neutrally aligned primary TKA.

METHODS

A matched case-control study was designed between 66 patients with varus alignment of the tibial component and 66 with neutral alignment with a minimum follow-up of 10 years. Functional outcome was assessed with the knee surgery scores (KSS) and reduced Western Ontario and MacMaster Universities questionnaire (WOMAC). Patient satisfaction was evaluated by a 0-10 visual analog scale. Radiological evaluation was performed at early postoperative and at final follow-up.

RESULTS

The mean follow-up was 11.9 (SD 2.6) years for both groups. The mean postoperative proximal tibial angle in the varus group was 85.0° (SD 0.9) and 88.8° (SD 0.9) in control group. At the final follow-up, there were no significant differences in KSS, WOMAC, range of motion or patient satisfaction. There were no differences in the coronal anatomical alignment of the TKA between groups. Revision of TKA was performed in four knees in the varus group, and one in control group, due to aseptic loosening of the tibial component in all cases. TKA survival at 10 years was not significantly different between groups.

CONCLUSION

The alignment of the tibial component up to 7° varus did not negatively affect implant survival, patient satisfaction, and function of a well-aligned TKA, with a minimum postoperative follow-up of 10 years.

LEVEL OF EVIDENCE

III.

Imageless Computer Navigation Reduces 5-Year All-Cause Revision Rates After Primary Total Knee Arthroplasty

BACKGROUND

The use of surgical navigation has been shown to reduce revision rates after total knee arthroplasty (TKA) in patients <65 years of age. It is unknown if this benefit extends to older patients. We hypothesized that the use of surgical navigation would reduce rates of all-cause revision in patients of all ages.

METHODS

In this cohort study, we queried the Truven MarketScan all-payer database to identify patients who underwent TKA from 2007 to 2015. Current Procedural Terminology codes were used to create 2 groups based on whether intraoperative navigation was used. Demographics, comorbidities, complications, and revision rates were determined. International Classification of Diseases codes were used to determine reasons for revision.

RESULTS

The conventional TKA cohort included 312,173 patients. The navigation cohort included 20,881 patients. There were not any clinically significant differences in demographics between the cohorts. All-cause revision rates were lower in the navigation cohort at 1 year (0.4% vs 0.5%, P = .04), 2 years (0.7% vs 0.9%, P = .003), and 5 years (0.9% vs 1.3%, P < .001) of follow-up. Revisions for mechanical loosening were more common in the conventional cohort (30.8% vs 21.9%, P = .009). Rates of revision for other causes, including infection, did not differ between groups, with the numbers available.

CONCLUSION

The use of surgical navigation yielded a 30.7% reduction in the all-cause revision rate at 5-year follow-up compared to conventional TKA. This benefit increased as follow-up duration increased. Increased usage of this inexpensive technology, from the current 6.3% in this US cohort, may reduce healthcare costs.

LEVEL OF EVIDENCE

III.

A Study of Surgical Accuracy with X-Ray-Based Patient-Specific Instrument (X3DPSI®) vs Conventional Instrument in Total Knee Arthroplasty Surgeries

INTRODUCTION

Patient-specific instruments (PSI) have been shown to be a good solution in getting accurate bone cuts in total knee arthroplasty (TKA) in many studies. However, the need for an extra CT/MRI makes the existing PSI method costly and unsafe. X-ray-based PSI can solve these problems, if proven to be accurate. The purpose of this study was to introduce a novel method to measure the performance of X-ray to 3D-based PSI (X3DPSI ^® ) in achieving planned bone cuts by comparing with conventional instruments (CI).

MATERIALS AND METHODS

This was a prospective study of a total of ten patients undergoing TKA surgery. Preoperative full length lower limb scanogram was done with specialized calibration strap-on marker to develop X3DPSI ^® which was used intraoperatively for the placement of guiding pins for the cutting jig. Similarly, intraoperative guide pins were placed using CI also. Calibrated intraoperative X-ray images, in AP and LAT view, were taken while the cutting-block guiding pins were placed on the distal femur and proximal tibia. These X-ray images were used to calculate the cutting plane alignments for femur and tibia and to simulate the postoperative hip-knee-ankle (HKA) angle and MAD (mechanical axis deviation), in a virtual Tabplan3D environment for both the methods.

RESULTS

The results showed that there was a significant difference between the two methods in terms of femoral cutting plane angles and in terms of the HKA angles and MAD. There was no significant difference in the tibial cutting plane angles in the coronal plane.

CONCLUSION

The mechanical axis alignment achieved based on the virtual cuts made using the X3DPSI ^® was significantly better than the alignment achieved based on the cuts made using the CI, in terms of both HKA and MAD. This novel method of X-ray-based PSI is a low-cost alternative to CT/MRI-based PSI if found to be accurate in future planned studies.

Accuracy of CT-Derived Patient-Specific Instrumentation for Total Ankle Arthroplasty: The Impact of the Severity of Preoperative Varus Ankle Deformity

BACKGROUND

Significant preoperative varus tibiotalar deformity was once believed to be a contraindication for total ankle arthroplasty (TAA). Our primary goal was to evaluate the influence of increasing preoperative varus tibiotalar deformity on the accuracy of final implant positioning using computed tomography (CT)-derived patient-specific guides for TAA.

METHODS

Thirty-two patients with varus ankle arthritis underwent TAA using CT-derived patient-specific guides. Patients were subcategorized into varying degrees of deformity based on preoperative tibiotalar angles (0°-5° neutral, 6°-10° mild, 11°-15° moderate, and >15° severe). Postoperative weightbearing radiographs were used to measure coronal plane alignment of the tibial implant relative to the target axis determined by the preoperative CT template. Average follow-up at the time of data collection was 36.8 months.

RESULTS

Average preoperative varus deformity was 6.06° (range: 0.66°-16.3°). Postoperatively, 96.9% (30/31) of patients demonstrated neutral implant alignment. Average postoperative tibial implant deviation was 1.54° (range: 0.17°-5.7°). Average coronal deviation relative to the target axis was 1.61° for the neutral group, 1.78° for the mild group, 0.94° for the moderate group, and 1.41° for the severe group (P = .256). Preoperative plans predicted 100% of tibial and talar implant sizes correctly within 1 size of actual implant size. Conclusion. Our study supports the claim that neutral postoperative TAA alignment can be obtained using CT-derived patient-specific instrumentation (PSI). Furthermore, final implant alignment accuracy with PSI does not appear to be impacted by worsening preoperative varus deformity. All but one patient (96.9%) achieved neutral postoperative alignment relative to the predicted target axis.

LEVEL OF EVIDENCE

Level IV, Clinical Case Series.

CT-based patient-specific instrumentation for total knee arthroplasty in over 700 cases: single-use instruments are as accurate as standard instruments

PURPOSE

Efforts in total knee arthroplasty are made to improve accuracy for a correct leg axis and reduce component malpositioning using patient-specific instruments. It was hypothesized that use of patient-specific instruments (vs. computer-navigated and conventional techniques) will reduce the number of outliers. Our second hypothesis was that single-use instrumentation will lead to the same accuracy compared to patient-specific instruments made of metal.

METHODS

708 primary total knee arthroplasties between 2014 and 2018 using computer tomography (CT)-based patient-specific cutting block technique and a preoperative planning protocol were retrospectively reviewed. Preoperative data [hip-knee-angle (HKA), lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), tibial slope, femoral component flexion] was compared to postoperative performed standard radiological follow-up X-rays. Differences of > 3° between measurements were defined as outliers.

RESULTS

Overall 500 prostheses using standard instrumentation and 208 prostheses using single-use instruments were implanted. Preoperative HKA axes (- 1.2°; p < 0.001), femoral component flexion (Δ 0.8°, p < 0.001), LDFA (Δ - 1.5°, p < 0.001), MPTA (Δ - 0.5°, p < 0.001) and tibial posterior slopes (Δ 0.5°, p < 0.001), respectively, were different from postoperative axes. More outliers occurred using standard (vs. single-use) instruments (p < 0.001) regarding postoperative HKA (ranges of standard- vs. single-use: instruments: HKA 178.0°-180.5° vs. 178.0°-180.5°, femoral component flexion 0.0°-6.0° vs. 0.0°-4.5°, LDFA 90.0°-91.0° vs. 90.0°-90.0°, MPTA 90.0°-90.0° vs. 90.0°-90.0°, tibial posterior slope - 10° to 10° vs. - 1° to 10°). No differences were seen for other angles measured. Comparing both systems, total number of outliers was higher using standard (8%) vs. single-use instruments (4.3%).

CONCLUSION

This study shows a high accuracy of CT-based patient-specific instrumentation concerning postoperative achieved knee angles and mechanical leg axes. Single-use instruments showed a similar accuracy.

LEVEL OF EVIDENCE

III.

Apparatus for In Vivo Knee Laxity Assessment Using High-Speed Stereo Radiography

Computational modeling is of growing importance in orthopedics and biomechanics as a tool to understand differences in pathology and predict outcomes from surgical interventions. However, the computational models of the knee have historically relied on in vitro data to create and calibrate model material properties due to the unavailability of accurate in vivo data. This work demonstrates the design and use of a custom device to quantify anterior-posterior (AP) and internal-external (IE) in vivo knee laxity, with an accuracy similar to existing in vitro methods. The device uses high-speed stereo radiography (HSSR) tracking techniques to accurately measure the resulting displacements of the femur, tibia, and patella bones during knee laxity assessment at multiple loads and knee flexion angles. The accuracy of the knee laxity apparatus was determined by comparing laxity data from two cadaveric specimens between the knee laxity apparatus and an existing in vitro robotic knee joint simulator. The accuracy of the knee laxity apparatus was within 1 mm (0.04 in.) for AP and 2.5 deg for IE. Additionally, two living subjects completed knee laxity testing to confirm the laboratory use of the novel apparatus. This work demonstrates the ability to use custom devices in HSSR to collect accurate data, in vivo, for calibration of computational models.

2D-3D reconstruction of distal forearm bone from actual X-ray images of the wrist using convolutional neural networks

The purpose of the study was to develop a deep learning network for estimating and constructing highly accurate 3D bone models directly from actual X-ray images and to verify its accuracy. The data used were 173 computed tomography (CT) images and 105 actual X-ray images of a healthy wrist joint. To compensate for the small size of the dataset, digitally reconstructed radiography (DRR) images generated from CT were used as training data instead of actual X-ray images. The DRR-like images were generated from actual X-ray images in the test and adapted to the network, and high-accuracy estimation of a 3D bone model from a small data set was possible. The 3D shape of the radius and ulna were estimated from actual X-ray images with accuracies of 1.05 ± 0.36 and 1.45 ± 0.41 mm, respectively.

Comparison of post-operative three-dimensional and two-dimensional evaluation of component position for total knee arthroplasty

PURPOSE

The purpose of this study was to evaluate the post-operative three-dimensional (3D) femoral and tibial component positions in total knee arthroplasty (TKA) by the same co-ordinates' system as for pre-operative planning and to compare it with a two-dimensional (2D) evaluation.

MATERIALS AND METHODS

Sixty-five primary TKAs due to osteoarthritis were included. A computed tomography (CT) scan of the femur and tibia was obtained and pre-operative 3D planning was performed. Then, 3D and 2D post-operative evaluations of the component positions were performed. KneeCAS (LEXI, Inc., Tokyo, Japan), a lower-extremity alignment assessment system, was used for the 3D post-operative evaluation. Standard short-knee radiographs were used for the 2D post-operative evaluation. Differences between the pre-operative planning and post-operative coronal and sagittal alignment of components were investigated and compared with the results of the 3D and 2D evaluations.

RESULTS

According to the 3D evaluation, the difference between the pre-operative planning and actual post-operative sagittal alignment of the femoral component and the coronal and sagittal alignments of the tibial component were 2.6° ± 1.8°, 2.2° ± 1.8° and 3.2° ± 2.4°, respectively. Using the 2D evaluation, they were 1.9° ± 1.5°, 1.3° ± 1.2° and 1.8° ± 1.4°, making the difference in 3D evaluation significantly higher (p = 0.013, = 0.003 and < 0.001). For the sagittal alignment of the femoral component and the coronal and sagittal alignment of the tibial component, the outlier (> ± 3°) ratio for the 3D evaluation was also significantly higher than that of the 2D evaluation (p < 0.001, = 0.009 and < 0.001).

CONCLUSIONS

The difference between the pre-operative planning and post-operative component alignment in the 3D evaluation is significantly higher than that of the 2D, even if the same cases have been evaluated. Two-dimensional evaluation may mask or underestimate the post-operative implant malposition. Three-dimensional evaluation using the same co-ordinates' system as for pre-operative planning is necessary to accurately evaluate the post-operative component position.

Establishing a point-of-care additive manufacturing workflow for clinical use

Additive manufacturing, or 3-Dimensional (3-D) Printing, is built with technology that utilizes layering techniques to build 3-D structures. Today, its use in medicine includes tissue and organ engineering, creation of prosthetics, the manufacturing of anatomical models for preoperative planning, education with high-fidelity simulations, and the production of surgical guides. Traditionally, these 3-D prints have been manufactured by commercial vendors. However, there are various limitations in the adaptability of these vendors to program-specific needs. Therefore, the implementation of a point-of-care in-house 3-D modeling and printing workflow that allows for customization of 3-D model production is desired. In this manuscript, we detail the process of additive manufacturing within the scope of medicine, focusing on the individual components to create a centralized in-house point-of-care manufacturing workflow. Finally, we highlight a myriad of clinical examples to demonstrate the impact that additive manufacturing brings to the field of medicine.

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.

Advantages of patient-specific cutting guides with disposable instrumentation in total knee arthroplasty: a case control study

Background

Total knee arthroplasty (TKA) is most frequently planned using conventional two-dimensional weight-bearing lower limb radiographs and is performed with conventional femoral and tibial cutting guides. Questions have been raised about the accuracy of conventional TKA instrumentation and planning for an anatomically standard or complex joint. Use of computed tomography (CT)-based three-dimensional (3D) templating and patient-specific cutting guides printed in 3D has shown improved postoperative lower limb alignment parameters. This case-control study compared costs and operative times of using CT-based, patient-specific, single-use instruments versus conventional metal instruments for TKA.

Methods

In this case-control, retrospective chart review, all TKAs were performed by one senior surgeon, using the F.I.R.S.T. posterior-stabilised knee prosthesis (Symbios, CH), with a similar protocol and identical operating room setup. Group A included 51 TKAs performed with patient-specific cutting guides and conventional metal instruments. Group B included 49 TKAs performed with patient-specific cutting guides and patient-specific, single-use instrumentation. Operation duration, number of instrumentation trays and sterilisation costs were evaluated.

Results

The groups were similar for age, body mass index, hip-knee-ankle angle and operation duration. The mean number of instrumentation trays was 8.0 ± 0.8 for group A (controls) and 5.1 ± 0.9 for group B (p<0.001). The mean sterilisation costs were 380 ± 47 Swiss Francs (CHF) for group A and 243 ± 55 CHF for group B (p<0.001), for a mean cost reduction of 130.50 CHF per intervention in group B. The time interval between two consecutive surgeries was 24 min for group A and 18 min for group B. There were no adverse events or complications, instrument-related or otherwise.

Conclusion

Compared to conventional instrumentation, use of patient-specific, single-use instruments for TKA reduced the number of instrumentation trays by more than one-third and saved 36% in sterilisation costs. If fabrication costs of single-use instruments are included by the company, the total cost is significantly diminished. There was no operative time advantage for single-use instrumentation.

Using standard X-ray images to create 3D digital bone models and patient-matched guides for aiding implant positioning and sizing in total knee arthroplasty

X-Atlas™ is a new imaging technology intended to advance the state of the art in patient-specific instrumentation. It uses standard AP and lateral radiographs instead of CT or MRI scans to create 3D bone models, which can be used to perform pre-operative surgical planning and fabricate TKA personalized guides. The aim of this study was to validate X-Atlas™ and evaluate the accuracy of personalized guides created with this imaging technology. Its ability to predict implant size was also determined. The accuracy of the X-Atlas™ imaging technology was evaluated by comparing the landmarks of X-Atlas™ 3D Bone models to MRI-reconstructed bone models. The accuracy of PSI guides created with X-Atlas™ (X-PSI™ guides) was evaluated during a validation study (16 specimen knees) and a clinical study (50 patients; Health Canada #CSU2015-12K). Optical navigation was used to measure positioning accuracy. In addition, the ability of X-Atlas™ to predict implant size was assessed. The accuracy of the X-Atlas™ imaging technology was below 0.87 and 1.28 mm for the femoral and tibial landmarks, respectively. The accuracy of X-PSI™ guides to reproduce the pre-operative planned HKA was within ± 3° in 100% and 86.1% of cases, for the laboratory and clinical study respectively, which was significantly better than historical data for conventional instrumentation. X-Atlas™ was able to predict implant size to ± 1 size in 95.6% and 100%, for the femur and tibia component respectively. The X-Atlas™ imaging technology demonstrated excellent accuracy for reconstructing a 3D bone model. The results show that PSI guides created with X-Atlas™ (X-PSI™ guides) provide greater implant positioning accuracy than conventional instrumentation, without the requirement of advanced imaging. Furthermore, the X-Atlas™ imaging technology could effectively predict implant sizing, potentially reducing the number of instrument trays and improving surgical efficiency.

Limb Lengthening after Primary Total Knee Arthroplasty: Customized Patient-Specific Instrumentation Does Not Affect Expected Limb Lengthening

Introduction

Expectations for limb length differences after TKA are important for patient perception and outcomes. Limb length discrepancies may occur due to postoperative leg length increases, which can lead to decreased patient functionality and satisfaction and even possible litigation. The purpose of this study is to examine the frequency and extent of limb lengthening among various preoperative deformities and between two different implant systems.

Methods

Preoperative and postoperative full-length standing radiographs were obtained between August 2018 and August 2019 to measure mechanical axis and limb length of operative limbs. Demographic information such as age, sex, and BMI was also collected. Patients were grouped into categories for pre- and postoperative subgroup analysis: valgus, varus, customized implant, and conventional implant. Regression analysis was performed to evaluate significant relationships.

Results

Of the 121 primary TKAs analyzed, 62% of the knees showed an increase in limb length after TKA, with an average lengthening of 5.32 mm. Preoperative varus alignment was associated with a mean lengthening of 3.14 mm, while preoperative valgus alignment was associated with a mean lengthening of 16.2 mm. Overall, there were no statistically significant differences in limb lengths pre- and postoperatively (p = 0.23) and no significant changes in limb length for any subgroup. Further, no variables were associated with limb length changes (p = 0.49), including the use of customized implants (p = 0.2).

Conclusions

Limb lengthening after TKA is common and, on average, occurs more significantly in valgus knees. No significant difference in limb lengthening could be demonstrated using customized over conventional implants. Preoperative counseling is important to manage patient expectations.

Interobserver and intraobserver agreement for Letournel acetabular fracture classification system using 3-dimensional printed solid models

BACKGROUND

Acetabular fractures pose diagnostic and surgical challenges. They are classified using the Judet-Letournel system, which is based solely on X-ray. However, computed tomography (CT) imaging is now more widely utilized in diagnosing these injuries. The emergence of 3-dimensional (3-D) printing technology in varying orthopedic fields has provided surgeons a solid model that improves their spatial understanding of complex fractures and ability to plan pre-operatively.

AIM

To evaluate the reliability of the Judet-Letournel classification system of acetabular fractures, when using either CT imaging or 3-D printed models.

METHODS

Seven patients with acetabular fractures underwent pelvic CT imaging, which was then used to create solid, 3-D printed models. Eighteen orthopaedic trauma surgeons responded to questionnaires regarding fracture classification and preferred surgical approach. The same questionnaire was completed using only CT imaging, and two weeks later, using only 3-D printed models. The inter- and intra-observer agreement rates were then analyzed.

RESULTS

Inter-observer agreement rates based on CT imaging or 3-D printed models were moderate for fracture classification: κ = 0.44, κ = 0.55, respectively (P < 0.001) and fair for preferred surgical approach: κ = 0.34, κ = 0.29, respectively (P < 0.005). Intra-observer agreement rates for fracture classification and preferred surgical approach comparing CT imaging or 3-D printed models were moderate: κ = 0.48, κ = 0.41, respectively. No significant difference in intra-observer agreement was detected when comparing orthopedic pelvic specialists to general orthopedic traumatologists.

CONCLUSION

The Judet-Letournel classification demonstrated only moderate rates of agreement. The use of 3-D printed models increased the inter-observer agreement rates with respect to fracture classification, but decreased it with respect to the preferred surgical approach. This study highlights the role of 3-D printed models in acetabular fractures by improving spatial understanding of these complex injuries, thus providing more reliable fracture diagnoses and alternative viewpoints for pre-operative planning.

Distal femoral valgus cut angles unreliable in total knee arthroplasty

We hypothesized that valgus distal femoral cut angle made using a conventional cutting guide would be reproducible in a Sawbone model, regardless of training level. 3°, 5°, or 7° valgus cuts were made on lower extremity Sawbone specimens and were measured with radiographic imaging. 66 patient radiographs were also analyzed to compare pre and post-operative femoral cut angles, and VR12 measurements from each patient were collected. All femoral cuts deviated significantly from target cuts. Also, pre-TKA valgus angles showed no correlation with the angles post-TKA, and final cut angle did not correlate with functional outcomes at 1 year post-surgery.

Three-dimensional-printed custom guides for bipolar coxofemoral osteochondral allograft in dogs

The objective of this experimental study was to develop and evaluate a three-dimensionally printed custom surgical guide system for performing bipolar coxofemoral osteochondral allograft transplantation in dogs. Five cadaver dogs, weighing 20–38 kg were used in the study. Custom surgical guides were designed and three-dimensionally printed to facilitate accurate execution of a surgical plan for bipolar coxofemoral osteochondral allograft transplantation. Guide-assisted technique was compared to freehand technique in each cadaver. Surgical time was recorded and postoperative computed tomography and three-dimensional segmentation was performed. Femoral version and inclination angles, femoral neck length, and gap present at the femoral and acetabular donor-recipient interface was compared between the virtual surgical plan and postoperative outcome for both techniques. One-tailed paired t-test (P < .05) was used for statistical analysis. When compared to free-hand preparation, mean donor femoral preparation time was 10 minutes longer and mean recipient preparation time was 2 minutes longer when using guides (p = 0.011 and p = 0.001, respectively). No difference in acetabular preparation time was noted between groups. Gap volume at the acetabular and femoral donor-recipient interface was not different between groups. Mean difference between the planned and postoperative version angle was 6.2° lower for the guide group when compared to the freehand group (p = 0.025). Mean femoral neck length was 2 mm closer to the plan when using guides than when performing surgery freehand (p = 0.037). Accuracy for femoral angle of inclination was not different between groups. Custom surgical guides warrants consideration in developing bipolar coxofemoral osteochondral allograft transplantation as an alternative surgical technique for managing hip disorders in dogs.

New Technologies in Knee Arthroplasty: Current Concepts

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

Reconstruction of Bony Defects after Tumor Resection with 3D-Printed Anatomically Conforming Pelvic Prostheses through a Novel Treatment Strategy

There has been an increasing interest and enormous applications in three-dimensional (3D) printing technology and its prosthesis, driving many orthopaedic surgeons to solve the difficult problem of bony defects and explore new ways in surgery approach. However, the most urgent problem is without an effective prosthesis and standard treatment strategy. In order to resolve these problems, this study was performed to explore the use of a 3D-printed anatomically conforming pelvic prosthesis for bony defect reconstruction following tumor resection and to describe a detailed treatment flowchart and the selection of a surgical approach. Six patients aged 48-69 years who had undergone pelvic tumor resection underwent reconstruction using 3D-printed anatomically conforming pelvic prostheses according to individualized bony defects between March 2016 and June 2018. According to the Enneking and Dunham classification, two patients with region I+II tumor involvement underwent reconstruction using the pubic tubercle-anterior superior iliac spine approach and the lateral auxiliary approach and one patient with region II+III and three patients with region I+II+III tumor involvement underwent reconstruction using the pubic tubercle-posterior superior iliac spine approach. The diagnoses were chondrosarcoma and massive osteolysis. After a mean follow-up duration of 30.33 ± 9.89 months (range, 18-42), all patients were alive, without evidence of local recurrence or distant metastases. The average blood loss and blood transfusion volumes during surgery were 2500.00 ± 1461.51 ml (range, 1200-5000) and 2220.00 ± 1277.62 ml (range, 800-4080), respectively. During follow-up, the mean visual analogue scale (VAS) score decreased, and the mean Harris hip score increased. There were no signs of hip dislocation, prosthetic loosening, delayed wound healing, or periprosthetic infection. This preliminary study suggests the clinical effectiveness of 3D-printed anatomically conforming pelvic prostheses to reconstruct bony defects and provide anatomical support for pelvic organs. A new surgical approach that can be used to expose and facilitate the installation of 3D-printed prostheses and a new treatment strategy are presented. Further studies with a longer follow-up duration and larger sample size are needed to confirm these encouraging results.

Systematic effects of femoral component rotation and tibial slope on the medial and lateral tibiofemoral flexion gaps in total knee arthroplasty

Purpose

To quantify the effects of the systematic internal and external femoral component rotations and tibial slope on the medial and lateral tibiofemoral gaps in total knee endoprostheses.

Methods

Nineteen knee cadaver specimens with an intact ligament apparatus were fixed in a custom frame, facilitating physiological flexion motion. Virtual total knee arthroplasty (TKA) was performed on three-dimensional models obtained from computed tomography ​scans (0° and 90° flexions) with systematically altered femur rotations and tibial slopes.

Results

Both the femur rotation and the tibial slope influenced the medial and lateral tibiofemoral flexion gaps (p ​< ​0.001), and the effects differed between the medial and lateral sides (p ​< ​0.001). The medial tibiofemoral flexion gap increased by 2.90 ​± ​0.34 ​mm and decreased by 2.66 ​± ​0.26 ​mm for 7° external and internal femur component rotations, respectively (both with p ​< ​0.001). The lateral tibiofemoral flexion gap decreased by 3.11 ​± ​0.31 ​mm and increased by 3.29 ​± ​0.33 ​mm for 7° external and internal femur component rotations, respectively (both with p ​< ​0.001).

Conclusion

For established surgical methods, we recommend a neutral femur rotation for a 0° tibial slope and a 3° external femur rotation for a tibial slope of 9–10°. The translational potential of this research shows that while the rotation of the femoral component in extension has no effect on the gap size, owing to the axis of rotation being perpendicular to the gap, for a 90° flexion, we not only observe differences in the gap size between the medial and lateral ​but also unequal differences on either side depending on the inward or outward rotation. The main reason for this is the position of the axis of rotation, which is not precisely half way between the lateral and medial contact points. The results show that rotation of the femoral component always creates an unbalanced flexion gap.

The translational potential of this article

The article points out the differences in the tibiofemoral gap in total knee endoprostheses due to the systematic internal and external femoral component rotation. While in lower leg extension there are no differences seen, in 90° knee-flexion there are unequal differences within the medial and lateral compartment that show a mathematical relationship towards the femoral compartment rotation which needs to be intraoperatively considered.

A double-blind randomized controlled trial of total knee replacement using patient-specific cutting block instrumentation versus standard instrumentation

Background

Patient-specific cutting blocks in total knee arthroplasty have been promoted to improve mechanical alignment, reduce alignment outliers and improve patient outcomes. The aim of this study was to compare the efficacy of patient-specific instrumentation (PSI) and conventional instrumentation (CI) in achieving neutral alignment and accurate component positioning in total knee arthroplasty.

Methods

We conducted a double-blinded randomized controlled trial in which patients were randomly assigned to treatment with either PSI or CI.

Results

Fifty-four patients were included in the study. No relevant improvement in coronal alignment was found between the PSI and CI groups with post-hoc power of 0.91. Tibial slope was found to be more accurately reproduced to the preoperative target of 3° with PSI than with CI (3.8°± 3.1° v. 7.7°± 3.6°, respectively, p < 0.001). There were no differences found in patient-reported outcome measures, surgical time or length of hospital stay.

Conclusion

Given the added cost of the PSI technique, its use is difficult to justify given the small improvement in only a single alignment parameter.

Clinical trial registration

Clinicaltrials.gov, no. NCT03416946

CT-based TruMatch® Personal Solutions for knee replacement Surgery … Does it really match?

Objective

Patient-specific templates promises to be able to increase alignment while decreasing operative time, increasing patient throughput, decreasing instrumentation, reducing risk of fat embolism and intraoperative bleeding, decreasing tissue loss, shortening recovery, reducing post-operative pain and decreasing incidence of infection. However, multiple studies have shown conflicting results regarding these potential benefits. This study serves to critically evaluate the potential advantages and disadvantages of using a patient-specific templating technique through a single-surgeon study.

Methods

All patients who underwent primary total knee arthroplasty (TKA) for osteoarthritis of the knee using TruMatch® Personal Solutions total knee replacement by a single surgeon were identified. An age-, gender-, side-, diagnosis- and surgeon-matched cohort who underwent conventional primary TKAs was randomly identified for comparison.

Results

The average distal medial femur (p < 0.001), distal lateral femur (p < 0.001), posteromedial femur (p < 0.001), posterolateral femur (p < 0.001), medial tibial (p < 0.001) and lateral tibial (p = 0.12) predicted cuts showed significant difference from the actual corresponding cuts. Three knees also required the need to freehand. There was no significant difference in mechanical (p = 0.96) and anatomical alignments (p = 0.26), as well as the changes in mechanical (p = 0.06) and anatomical (p = 0.39) alignments between the two groups. Duration of surgery (p = 0.26), length of inpatient stay (p = 0.06) and incidence of wound infection (p = 1.00) were similar. Additionally, patients in the TruMatch® Personal Solutions group had a greater decrease drop in hemoglobin levels (p = 0.02), with five transfusions needed while only one patient in the conventional group required transfusion (p = 0.09).

Conclusion

Our early experience and results with the CT-based TruMatch® Personal Solutions templates for TKA has not been promising. Despite promised, there were no demonstrable benefits with the technology. Moreover, the disadvantage of having increased blood loss was identified. Further studies are required to recommend the use of this technology.

MRI-based or CT-based patient-specific instrumentation in Total knee Arthroplasty: How do the two systems compare?

Background

Patient-specific instrumentation (PSI) has been introduced into total knee arthroplasty (TKA) to improve accuracy in restoration of alignment. PSI in TKA refers to custom-made cutting jigs manufactured according to anatomic configuration of the patient’s bone based on preoperative magnetic resonance imaging (MRI) or computed tomography (CT) scans. The purpose of this study was to compare the MRI- or CT-based PSI to see if they could reproduce accurate bone resection and postoperative outcomes.

Methods

Seventy-one patients who received elective TKA using a PSI system for primary osteoarthritis with varus deformity were prospectively enrolled for this study. We randomly allocated those patients to MRI-based PSI group (36 patients) and CT-based PSI group (35 patients). The actual resection thickness and planned resection thickness by preoperative PSI electronic program were compared between the two groups. Radiographic findings of the postoperative limb alignment, three-dimensional position of the implants, and related complications were also evaluated. Clinical evaluation was also performed before and 2 years after the surgery.

Results

There were no significant differences in the resection thickness in femur and tibia between actual resection and planned resection in both groups. Furthermore, there were no significant differences between two groups in terms of coronal, sagittal and rotational alignment of the components. All clinical assessments revealed no differences between two groups 2 years after the operation. No specific complication related to PSI was observed.

Conclusions

Although MRI allows for visualization of cartilage, MRI-based PSI system did not show better accuracy in predicting the thickness of bone resection than CT-based PSI. Moreover, there were no differences in radiographic and clinical outcomes between the two groups.

Postoperative mechanical alignment analysis of total knee replacement patients operated with 3D printed patient specific instruments: A Prospective Cohort Study

Objective

Total knee replacement (TKR) is a surgical treatment for final stage gonarthrosis. The lifespan of the prosthetic implants used in TKR surgery is a major interest for the orthopaedic research community.Previously, proper implant alignment of the implants has been advocated for longevity of the TKR surgery. Recently, patient-specific (PSI) instruments have been proposed to improve the mechanical alignment of the TKR by permitting better implant positioning over conventional TKR surgery. The aim of this study is to compare the mechanical alignment results of patients operated with PSIs and conventional instruments.

Methods

Two groups of 20 patients chosen in a quasi-random manner have been compared in this study. In the first group femoral distal and tibial osteotomies were made by a PSI which was produced by the patients' computed tomography scans. All osteotomies in the control group were made with the TKR set's routine instruments by conventional means. Patients' preoperative and postoperative mechanical femorotibal angles (mFTA), femoral coronal angles (FCA), tibial coronal angles (TCA) were measured and the number of outliers which showed more than 3° of malalignment were counted in both groups for comparison.

Results

The average postoperative mFTA was found to be 2.09° for the PSI group and in was found to be 2.84° for the control which was not statistically significant. The comparison of postoperative FCA and TCA also did not show significant difference between the groups. The number of outliers showing more than 3° of malalignment per group were found to be 1 out of 20 (5%) for the PSI group and 7 out of 20 (35%) for the control which was statistically significant.

Conclusion

In this study patient-specific instrumentation provided significantly better mechanical alignment compared to conventional TKR for the frequency of outlier cases with malalignment beyond 3°. PSI proved no significant difference when the groups were compared for mFTA, FCA and TCA. Our findings support that PSI may improve TKR alignment by improving the ratio of the outlier patients with marked malalignment.

Level of Evidence

Level III, Therapeutic Study.

Individual resection and reconstruction of pelvic tumor with three-dimensional printed customized hemi-pelvic prosthesis: A case report

RATIONALE

Pelvic tumor had great impact on patients' quality of life. After tumor resection, how to accurately fill bone defect remained challenging for orthopedic surgeons. Due to lack of individual design, high incidence of prosthetic mismatching, and loosening were reported in pelvic reconstruction surgery with conventional modular prostheses. Nowadays, with rapid development of three-dimensional (3D) print technology, pelvic prostheses could be designed according to patients' own anatomy. The objective of this study was to describe the application of 3D printed customized hemi-pelvic prosthesis for patients with pelvic tumor.

PATIENT CONCERNS

A 62-year-old female had developed severe right joint pain without obvious inducement from 5 months before she sought medical advice. Pain, swelling, and limited range of motion of right joint were founded during physical examination.

DIAGNOSIS

The patients were diagnosed as "right acetabulum metastatic carcinoma" INTERVENTION:: 3D printed titanium alloy hemi-pelvic prosthesis was designed according the morphology of unaffected side hemi-pelvis and subsequently implanted in surgery to reconstruct the pelvis. 3D printed osteotomy guide and pelvic model were also manufactured and applied to improve accuracy of osteotomy and reduce operation time. X-Ray of pelvis, Harris score, musculoskeletal tumor society score (MSTS) and The MOS item short from health survey (SF-36) were recorded during the period of preoperation, 1, 3, 6, 12 months follow-up after operation.

OUTCOMES

3D printed hemi-pelvic prosthesis matched precisely with pelvis and implanted successfully. There was no sign of prosthetic loosening within 12 months' follow-up. No sign of peri-prosthetic infection from laboratory examination. Harris score, MSTS, and SF-36 were gradually increasing during follow-up period.

LESSONS

Satisfactory effect of pelvic reconstruction could be achieved by 3D printed hemi-pelvic prostheses. It also provided a promising way to the treatment of pelvic tumor in similar cases.

Prospective Validation of a Demographically Based Primary Total Knee Arthroplasty Size Calculator

BACKGROUND

Preoperative planning for total knee arthroplasty (TKA) is essential for streamlining operating room efficiency and reducing costs. Digital templating and patient-specific instrumentation have shown some value in TKA but require additional costs and resources. The purpose of this study was to validate a previously published algorithm that uses only demographic variables to accurately predict TKA tibial and femoral component sizes.

METHODS

Four hundred seventy-four consecutive patients undergoing elective primary TKA were prospectively enrolled. Four surgeons were included, three of which were unaffiliated with the retrospective cohort study. Patient sex, height, and weight were entered into our published Arthroplasty Size Prediction mobile application. Accuracy of the algorithm was compared with the actual sizes of the implanted femoral and tibial components from 5 different implant systems. Multivariate regression analysis was used to identify independent risk factors for inaccurate outliers for our model.

RESULTS

When assessing accuracy to within ±1 size, the accuracies of tibial and femoral components were 87% (412/474) and 76% (360/474). When assessing accuracy to within ±2 sizes of predicted, the tibial accuracy was 97% (461/474), and the femoral accuracy was 95% (450/474). Risk factors for the actual components falling outside of 2 predicted sizes include weight less than 70 kg (odds ratio = 2.47, 95% confidence interval [1.21-5.06], P = .01) and use of an implant system with <2.5 mm incremental changes between femoral sizes (odds ratio = 5.50, 95% confidence interval [3.33-9.11], P < .001).

CONCLUSIONS

This prospective series of patients validates a simple algorithm to predict component sizing for TKA with high accuracy based on demographic variables alone. Surgeons can use this algorithm to simplify the preoperative planning process by reducing unnecessary trays, trials, and implant storage, particularly in the community or outpatient setting where resources are limited. Further assessment of components with less than 2.5-mm differences between femoral sizes is required in the future to make this algorithm more applicable worldwide.

Patient-specific instrumentation in total knee arthroplasty

INTRODUCTION

Total knee arthroplasty (TKA) is one of the most commonly performed orthopedic procedures. During the past decade, patient-specific instrumentation (PSI) has been commercially introduced in order to simplify and make TKA surgery more effective, precise and efficient than conventional mechanical instrumentation (CI) and computer-assisted surgery (CAS). Nevertheless, there are critical arguments against PSI for routine use. The aim of the current manuscript is to describe advantages and limitations of PSI for primary TKA.

AREAS COVERED

By means of a description of the available literature different aspects are discussed (accuracy, clinical and functional outcomes, operative time, blood loss, efficiency and costs).

EXPERT OPINION

Most publications do not claim a significant increase in PSI accuracy over CI, but they also do not postulate PSIs accuracy is worse either. Regarding clinical aspects, PSI did not appear to give any advantage over standard techniques although, equally, it did not appear to show any disadvantages. PSI seems to reduce operative time, could reduce perioperative blood loss and provides logistical benefits in the operation room. Further studies will be required to more thoroughly assess all the advantages and disadvantages of this promising technology as an alternative to CI and CAS.

Accuracy of patient-specific instrumentation in total ankle arthroplasty: A comparative study

BACKGROUND

Patient-specific instrumentation (PSI) for TAA is a novel technology with several potential benefits. The primary goal of this study was to compare the use of PSI with the standard referencing guide (SRG) in regards to accuracy of tibial implant positioning. Operative time, fluoroscopy time and accuracy of PSI preoperative reports were also evaluated.

METHODS

A retrospective analysis of 99 patients who underwent a primary TAA with the INFINITY prosthesis (Wright Medical, Memphis, TN) was performed. Patients were divided in two groups based on the type of instrumentation used during the TAA (75 in the PSI group vs 24 in the SRG group). There was no significant difference between groups in regards to age at the time of surgery (P=0.122), sex (P=0.138), number of concomitant procedures performed during surgery (P=0.567) and etiology (P=0.841). However, preoperative deformity was significantly smaller in the PSI group (P=0.002).

RESULTS

Tibial implant positioning was similar between groups. In the coronal plane, the absolute deviation of the tibial implant from the intended alignment was 1.7±1.4° for the SRG and 1.6±1.2° for PSI (P=0.710). In the sagittal plane, the absolute alignment deviation of the tibial implant was 1.8±1.4° for the SRG and 1.9±1.5° for PSI (P=0.675). Operative time (167 vs 190min, P=0.040) and fluoroscopy time (85 vs 158s, P<0.001) were significantly decreased in the PSI group. The PSI preoperative plan report correctly predicted the implant size in 73% of cases for the tibial component and in 51% of cases for the talar component.

CONCLUSIONS

PSI provided similar tibial component alignment as standard instrumentation. Additionally, PSI preoperative plan reports were poor predictors of implant sizing. Therefore, the final decision should always be based on surgeon's experience in order to prevent errors in implant sizing and positioning.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Single-use, patient-specific instrumentation technology in knee arthroplasty: a comparative study between standard instrumentation and PSI efficiency system

Patient-specific instrumentation is a surgical technique that was created to improve the accuracy of implantation, surgical time and workflow in total knee arthroplasty. This study is a single-center, single-surgeon randomized clinical trial. The aim of this work was to evaluate clinical efficacy of PSI versus standard surgical instrumentation in malalignment risk and blood loss reduction. From April 2015 to September 2016, 40 patients for a total of 40 knees were included in the randomization process. Each patient underwent CT scan of the lower limb including hip, knee and ankle joint with the realization of the PSI system and the TKA with Medacta GMK Primary^®. Patients were evaluated 1 month after surgery with X-ray and after 2 months with clinical examination and assessment by Knee Society Score (KSS). Blood loss was detected by adding the values calculated in the operative room and the blood loss in the vacuum systems. In the study group, mean value of KSS was 85.2 (IC 95% 81.2-88.5), mean blood loss was 657 ml (IC 95% 580.6-735.4), and mean value of femorotibial angle was 178.8° (IC 95% 178.5-179.3). In the control group, mean value of KSS was 87.2 (IC 95% 85.3-89.4), mean blood loss was 866.5 ml (IC 95% 763.3-972.5), and mean value of femorotibial angle was 178.9°(IC 95% 177.6-180.3). The Student t test detected a significant difference in blood loss between groups (p < 0.05), and no differences were found between KSS. The single-use instrumentation should improve precision, operative time, turnover time, sterilization and maintenance costs and could help to reduce infection risks. Our results confirm only the improvement on reducing blood loss. In our opinion, this technique should be used in selected patients when the surgeon could have some difficulties to perform femoral cuts on coronal plane or when patients need to have a very little blood loss due to other conditions.

A randomized controlled trial investigating the value of patient-specific instrumentation for total knee arthroplasty in the Canadian healthcare system

Aims

The purpose of the present study was to compare patient-specific instrumentation (PSI) and conventional surgical instrumentation (CSI) for total knee arthroplasty (TKA) in terms of early implant migration, alignment, surgical resources, patient outcomes, and costs.

Patients and Methods

The study was a prospective, randomized controlled trial of 50 patients undergoing TKA. There were 25 patients in each of the PSI and CSI groups. There were 12 male patients in the PSI group and seven male patients in the CSI group. The patients had a mean age of 69.0 years (sd 8.4) in the PSI group and 69.4 years (sd 8.4) in the CSI group. All patients received the same TKA implant. Intraoperative surgical resources and any surgical waste generated were recorded. Patients underwent radiostereometric analysis (RSA) studies to measure femoral and tibial component migration over two years. Outcome measures were recorded pre- and postoperatively. Overall costs were calculated for each group.

Results

There were no differences (p > 0.05) in any measurement of migration at two years for either the tibial or femoral components. Movement between one and two years was < 0.2 mm, indicating stable fixation. There were no differences in coronal or sagittal alignment between the two groups. The PSI group took a mean 6.1 minutes longer (p = 0.04) and used a mean 3.4 less trays (p < 0.0001). Total waste generated was similar (10 kg) between the two groups. The PSI group cost a mean CAD$1787 more per case (p < 0.01).

Conclusion

RSA criteria suggest that both groups will have revision rates of approximately 3% at five years. The advantages of PSI were minimal or absent for surgical resources used and waste eliminated, and for meeting target alignment, yet had significantly greater costs. Therefore, we conclude that PSI may not offer any advantage over CSI for routine primary TKA cases. Cite this article: Bone Joint J 2019;101-B:565–572.

No correlation between rotation of femoral components in the transverse plane and clinical outcome after total knee arthroplasty

PURPOSE

It was hypothesized that malrotation of femoral component in total knee arthroplasty (TKA) will significantly impact clinical outcome.

METHODS

Eighty-eight consecutive patients with primary osteoarthritis of the knee were prospectively evaluated. They received a cemented posterior stabilized TKA (NexGen, Zimmer/Biomet^® Inc., Warsaw, IN, USA). The femoral component was placed in 3° of external rotation referenced to the posterior condylar line. Postoperatively, a CT scan was performed to evaluate rotation of femoral component in the transverse plane. SF-36, KSS, and WOMAC, as well as their range of motion was assessed prior to surgery, after 6 and 24 months. Data are presented as mean and standard deviation (SD), as well as range if applicable. Correlation analysis was performed between the placement of the femoral component in the transverse plane and the clinical outcome.

RESULTS

Femoral component placement was on average 0.1° [SD 2.5°, range - 6.5° to + 6.5°] referenced to the surgical transepicondylar line showing a wide range between the two landmarks after surgery. After 6 months, WOMAC category 'physical function' correlated significantly with femoral component rotation (r = - 0.28, p = 0.007). After 24 months, WOMAC categories 'physical function' and 'pain' correlated significantly with femoral rotation (r = - 0.41, p < 0.001; and r = - 0.33, p = 0.001). No significant correlations were found between femoral component rotation and range of motion (r = 0.04), WOMAC category "stiffness", KSS, as well as SF-36 questionnaires. These reported formally significant correlations were without any clinical relevance.

DISCUSSION

The study showed that there is a significant patients specific femoral component placement in the transverse plane. Internal or external malrotation of the femoral component does not correlate automatically with poor knee function. The lack of correlation between femoral component position and clinical as well as functional outcome underlines complexity and significant individuality of each patient. The surgeon should be aware of the finding and attention should be paid during surgery when significant divergency is seen between the two landmarks. Soft tissue balancing might be very crucial in these specific patients, which needs to be studied in depth in the future.

LEVEL OF EVIDENCE

II.

Accuracy of tibial cuts with patient-specific instrumentation is not influenced by the surgeon's level of experience

PURPOSE

It was hypothesized that surgeon's experience as well as bone density play a significant role in achieving accurate cuts with patient-specific instrumentation (PSI). The aim of this study was to compare the accuracy of the tibial cuts in different bone densities made by a highly experienced orthopedic surgeon on one hand and a less experienced orthopedic surgeon on the other.

METHODS

Tibial models from three different sawbone densities were developed for this study. Each surgeon performed 21 cuts. A coordinate measuring machine was used to analyse the cuts. The K-Cohen test was performed to evaluate the results. The analyzed parameters were guide positioning and deviation from the guide cut to the tibial cut, including varus/valgus angle, the tibial slope, cut height, planarity (mm²), and rugosity (mm).

RESULTS

There was a significant difference in the positioning of the tibial cut guide between the two surgeons for the tibial slope (p < 0.05), while no difference was observed for the varus/valgus angle (n.s.) and the cut height (n.s.). No significant difference in the tibial cut was observed between the surgeons for the tibial slope angle (n.s.), varus/valgus angle (n.s.), planarity (n.s.), and rugosity (n.s.). In the different bone types, no significant difference was observed for the tibial slope (n.s.) and varus/valgus angle (n.s.), while planarity and rugosity showed significant differences (p < 0.05). Our study showed no significant difference in the tibial cuts for the tibial slope, varus/valgus angle, planarity, and rugosity between the two surgeons.

CONCLUSIONS

In the present study, it could be demonstrated that accuracy of the cuts is ensured by PSI not depending on the surgeon's experience and the bone mineral density. This speaks to its clinical significance: PSI might be suited for less experienced surgeons to reduce outliers in total knee arthroplasty (TKA).

No difference in mid-term survival and clinical outcome between patient-specific and conventional instrumented total knee arthroplasty: a randomized controlled trial

PURPOSE

The purpose of this multicentre prospective randomized controlled trial was to compare the survival rate and clinical outcome in total knee arthroplasty (TKA) after MRI-based patient-specific instruments (PSI) and conventional instruments 5 years after initial surgery.

METHODS

At a mean follow-up of 5.1 years (0.4), 163 patients (90.6%) with a mean age of 71.8 years (8.7) were analysed. A survival analysis with revision of the TKA as endpoint was performed. The Knee Society Score (KSS), evaluations on plain radiographs and patient-reported outcome measures (PROMs) were obtained preoperatively and at each FU.

RESULTS

At final follow-up, one TKA in the PSI- (1.2%) and 3 TKAs in the conventional group (3.8%) had undergone revision surgery (n.s.). No radiological abnormalities were noted at any time point. Postoperatively, the KSS and PROMs significantly improved within each group compared with the preoperative values. There were no clinically relevant differences for the KSS [PSI: 77.4, 9.8 (95% CI 75.0-79.7) vs. conventional: 77.3 10.5 (95% CI 74.9-79.8)] and the PROMs between both groups (n.s.) at 5 years follow-up.

CONCLUSION

There is still a lack of reliable data on the survival of TKA and clinical evidence, when using PSI for TKA. Longer follow-up studies are, therefore, needed.

LEVEL OF EVIDENCE

I.

Impact of Image-Derived Instrumentation on Total Knee Arthroplasty Revision Rates: An Analysis of 83,823 Procedures from the Australian Orthopaedic Association National Joint Replacement Registry

BACKGROUND

Computer navigation and image-derived instrumentation (IDI) are technology-based methods developed to improve outcomes and potentially reduce revision total knee arthroplasty (TKA). IDI refers to the use of manufactured, patient-specific surgical jigs. Conflicting reports exist on IDI-associated improvements in outcomes. The primary aim of the current study was to compare the rates of revision among TKA cases in which components were initially implanted with use of IDI, computer navigation, or neither of these methods ("other" TKA). The secondary aim was to determine whether the outcomes of IDI differed for specific subgroups.

METHODS

Data were obtained from the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) for the 3 TKA groups: IDI, computer-navigated, and other TKA. The study period was from the first IDI procedure recorded by the AOANJRR (April 2010) to December 31, 2016. The analysis was restricted to primary TKA cases undertaken for osteoarthritis and involving patellar resurfacing and the use of a cross-linked polyethylene insert. Subanalyses were performed to evaluate the effects of age, sex, implantation method, IDI manufacturer, prosthetic design, and prosthesis type on the rates of revision. Kaplan-Meier estimates of survivorship described the time to first revision. Hazard ratios (HRs, Cox proportional hazards models) with adjustment for age and sex were used to compare revision rates.

RESULTS

IDI was used in 5,486 primary TKA procedures. There was no significant difference among the groups in the cumulative percent revision (CPR) at 5 years: 3.3% (95% confidence interval [CI], 2.4% to 4.6%) for IDI, 2.4% (95% CI, 2.2% to 2.7%) for the computer-navigated group, and 2.5% (95% CI, 2.3% to 2.7%) for other TKA. Posterior-stabilized TKA with use of the IDI method had a significantly higher rate of revision at >3 months (HR, 1.45 [95% CI, 1.02 to 2.04]; p = 0.036), as did IDI TKA in the ≤65-year-old patient cohort (HR, 1.52 [95% CI, 1.10 to 2.09]; p = 0.010), compared with computer-navigated TKA. Patellar revision was significantly more likely in the IDI group.

CONCLUSIONS

IDI TKA demonstrated no overall difference in early to mid-term revision rates compared with standard implantation methods. However, elevated rates of revision were seen with posterior-stabilized TKA, in patients ≤65 years of age, and for patellar revision, meaning that this method should be used with some caution and requires further study.

LEVEL OF EVIDENCE

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

Fixed Distal Femoral Cut of 6° Valgus in Total Knee Arthroplasty: A Radiographic Review of 788 Consecutive Cases

BACKGROUND

In place of the mechanical axis (MA), the use of the variable tibiofemoral angle is frequently used to plan measured resection bony cuts during total knee arthroplasty (TKA). This angle, coupled with operator-dependent variability of intramedullary distal femoral cutting guides, has the potential for catastrophic outcomes. Therefore, a simpler, fixed femoral cut of 6° valgus may be more appropriate when direct measurement of the MA is not possible.

METHODS

This was a retrospective study of 788 consecutive TKAs, in which the distal femoral cut was set to 6° valgus. The preoperative and 6-week postoperative MA were measured on hip-to-ankle radiographs. Data were evaluated as a group as well as grouped by preoperative deformity (MA < -3°, -3° < MA < 3°, 3° < MA).

RESULTS

Following TKA, MA alignment for all patients was 0.0° ± 2.3° (range, -7.0° to 8.0°). When grouped by pre-TKA alignment, 548 patients were considered varus (MA < -3°), 137 were neutral (-3° < MA < 3°), and 103 patients were valgus (3° < MA). When evaluating the post-TKA alignment achieved in the 3 groups, neutral alignment (-3° < MA < 3°) was established in 86.5% of varus patients, 86.1% of neutral patients, and 82.5% of valgus patients.

CONCLUSION

A standard distal femoral cut of 6° resulted in a neutral MA in 86% of patients. While no single technique will be correct for all deformities, in the absence of sophisticated preoperative planning aids, this simple technique could provide a more reliable surgical technique than the measured tibiofemoral angle.

Patient-specific Guides Using 3-dimensional Reconstruction Provide Accuracy and Reproducibility in Reverse Total Shoulder Arthroplasty

Background

We aimed to evaluate whether the use of our novel patient-specific guide (PSG) with 3-dimensional reconstruction in reverse total shoulder arthroplasty (RTSA) would allow accurate and reliable implantation of the glenoid and humeral components.

Methods

20 fresh-frozen cadaveric shoulders were used. The PSG group (n=10) and conventional group (n=10) was evaluated the accuracy and reproducibility of implant positioning between before and after surgery on the computed tomography image.

Results

The superoinferior and anteroposterior offset in the glenoid component were 0.42 ± 0.07, 0.50 ± 0.08 in the conventional group and 0.45 ± 0.03, 0.46 ± 0.02 in the PSG group. The inclination and version angles were -1.93° ± 4.31°, 2.27° ± 5.91° and 0.46° ± 0.02°, 3.38° ± 2.79°. The standard deviation showed a smaller difference in the PSG group. The anteroposterior and lateromedial humeral canal center offset in the humeral component were 0.45 ± 0.12, 0.48 ± 0.15 in the conventional group and 0.46 ± 0.59 (p=0.794), 0.46 ± 0.06 (p=0.702) in the PSG group. The PSG showed significantly better humeral stem alignment.

Conclusions

The use of PSGs with 3-dimensional reconstruction reduces variabilities in glenoid and humerus component positions and prevents extreme positioning errors in RTSA.

The Accuracy of Alignment Determined by Patient-Specific Instrumentation System in Total Knee Arthroplasty

Purpose

The aim of this study is to assess the accuracy of alignment determined by patient-specific instrumentation system in total knee arthroplasty (TKA).

Materials and Methods

Twenty-seven TKAs using patient-specific instrument were reviewed. The intraoperative pin location determined by the patient-specific guide was recorded using imageless navigation software. Data recorded included tibial coronal alignment and posterior slope, femoral coronal alignment and sagittal alignment, and transepicondylar axis. A discrepancy within ±3° in each plane was considered an acceptable result.

Results

On the tibia, an acceptable alignment was obtained in 24 (88.1%) in the coronal plane and 21 (77.8%) in the sagittal plane. On the femur, a satisfactory alignment was obtained in 25 (92.6%) in the coronal plane and 24 (88.1%) in the sagittal plane. Based on the transepicondylar axis, a satisfactory alignment was obtained in 23 (85.1%).

Conclusions

Satisfactory alignment was obtained in more than 85% of each plane of the femur and in the coronal plane of the tibia and relative to the transepicondylar axis. Sufficeint experience and precise preoperative planning are required to improve the accuracy of sagittal alignment of the tibia.

Patient-specific instrumentation improved axial alignment of the femoral component, operative time and perioperative blood loss after total knee arthroplasty

PURPOSE

The purpose of the present study was to compare patient-specific instrumentation (PSI) with standard instrumentation (SI) in patients undergoing total knee arthroplasty (TKA). PSI is hypothesized to have advantages with respect to component alignment; number of outliers (defined as alignment > 3° from the target alignment); operative time; perioperative blood loss; and length of hospital stay. This new surgical technique is expected to exhibit superior performance.

METHODS

A total of 23 randomized controlled trials (RCTs) involving 2058 knees that compared the clinical outcomes of TKA between PSI and SI were included in the present analysis; these RCTs were identified via a literature search of the PubMed, Embase, and Cochrane Library databases through March 1, 2018. The outcomes of interest included coronal, sagittal and axial component alignment (presented as the angle of deviation from the transcondylar line); number of outliers; operative time; perioperative blood loss; and length of hospital stay.

RESULTS

There was a significant difference in postoperative femoral axial alignment between PSI and SI patients (95% CI - 0.71 to - 0.21, p = 0.0004, I² = 48%). PSI resulted in approximately 0.4° less deviation from the transcondylar line than SI. Based on our results, PSI reduced operative time by a mean of 7 min compared with SI (95% CI - 10.95 to - 3.75, p < 0.0001, I² = 78%). According to the included literature, PSI reduced perioperative blood loss by approximately 90 ml compared with SI (95% CI - 146.65 to - 20.18, p = 0.01, I² = 74%). We did not find any differences between PSI and SI with respect to any other parameters.

CONCLUSIONS

PSI has advantages in axial alignment of the femoral component, operative time, and perioperative blood loss relative to SI. No significant differences were found between PSI and SI with respect to alignment of the remaining components, number of outliers, or length of hospital stay.

LEVEL OF EVIDENCE

Therapeutic study (systematic review and meta-analysis), Level I.

Computer navigation for total knee arthroplasty achieves better postoperative alignment compared to conventional and patient-specific instrumentation in a low-volume setting

BACKGROUND

Procedure volume is an important determinant of total knee arthroplasty (TKA) outcomes. We aimed to determine whether computer navigation or patient-specific instrumentation (PSI) would improve postoperative alignment in a low-volume setting.

HYPOTHESIS

PSI for TKA achieves better limb and implant alignment compared to conventional TKA and to computer navigated TKA.

MATERIALS AND METHODS

This is a retrospective cohort study of 385 primary TKAs (Women=59%. Mean age=67years. Mean BMI=30.1kg/m²), which were performed using conventional instrumentation (n=117; 30%), computer navigation (n=209; 54%), or patient-specific instrumentation (n=59; 15%) in a low-volume center (<50 TKAs/year). The risk of postoperative leg and implant mechanical alignment outliers in the coronal plane (>3° from neutral), average alignment and operation time were assessed.

RESULTS

The risk of postoperative mechanical alignment outliers (>3°) was reduced by 89% in the navigated group (4% outliers) compared to the conventional group (35%) (RR=0.11; p<0.0001). No significant improvement was observed in the PSI group (27%) (RR=0.91; p=0.772). The risk of postoperative femoral component coronal alignment outliers was reduced by 63% in the navigated group (11%) compared to the conventional group (31%) (RR=0.37; p=0.018). No significant reduction in outliers was observed in the PSI group (32%) (RR=1.08; p=0.816). There was a reduction in the risk of tibial component coronal malalignment of 66% in the navigated group (5%) compared to the conventional group (13%) (RR=0.33; p=0.070). There was a two-fold increase in the risk of tibial component alignment outliers in the PSI group (29%) (RR=1.94; p=0.110).

DISCUSSION

Computer navigation improved postoperative alignment in TKA. No evidence of improved alignment was seen with patient-specific instrumentation. The routine use of patient-specific instrumentation in low-volume centers is not supported by the currently available data.

TYPE OF STUDY

Retrospective cohort study. Level IV.