Custom TKA: what to expect and where do we stand today?

Robotic-assisted differential total knee arthroplasty with patient-specific implants: surgical techniques and preliminary results

OBJECTIVE

In total knee arthroplasty (TKA), achieving soft-tissue balance while retaining acceptable lower limb alignment is sometimes difficult and may lead to patient dissatisfaction. Theoretically, patient-specific implants can bring great benefits, while the lack of precise surgical tools may hinder the improvement of outcomes. The objective of this study was to illustrate surgical techniques and evaluate kinematics and early clinical outcomes of robotic-assisted TKA using patient-specific implants.

METHODS

Based on preoperative CT scan, femoral and tibial components were 3D printed. Medial and lateral tibial liners were separate with different thicknesses, posterior slopes and conformity. TiRobot Recon Robot was used for surgery, and was armed with smart tools that quantify gap, force and femoral-tibial track. We collected data on demographics, intraoperative gap balance and femoral-tibial motion. In the follow-up, we evaluated the range of motion, Visual Analogue Scale (VAS), forgotten joint score (FJS), Knee injury and Osteoarthritis Outcome Score, Joint Replacement (KOOS, JR) score. Radiological data were also harvested.

RESULTS

Fifteen patients (17 knees) were enrolled with a mean age of 64.6 ± 6.4 (53-76) years. In 5 knees, we used symmetric tibial liners, the rest were asymmetric. After surgery, the average alignment was 1.6 ± 2.0 (-3-5) degrees varus. The average follow-up lasted 6.7 ± 4.2 (1-14) months. The mean visual analogue scale was 0.8 ± 0.7 (0-2), FJS was 62.4 ± 25.3 (0-87), KOOS was 86.5 ± 9.4 (57-97). 11 patients were "very satisfied", 3 were "satisfied" with the result, and one patient was neutral due to restricted extension and unsatisfactory rehabilitation at five months' follow-up.

CONCLUSIONS

With patient-specific implants and robotics, TKA could be performed by a mathematical way, which was dubbed a "differential" TKA. Intraoperative kinematics was excellent in terms of gap-force balancing and femoral-tibial relative motion. Preliminary clinical outcomes were overall satisfactory.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

LEVEL OF EVIDENCE

II, prospective cohort study.

Customized-individually-made origin® implants in total knee arthroplasty allow a reliable solution for accurate reproduction of planned implant positioning

PURPOSE

To evaluate the accuracy and reproducibility of a patient-specific, customized individually made (CIM) total knee replacement (TKR) using the ORIGIN® prosthesis.

METHODS

This was a prospective study conducted at a University Hospital from January 15, 2019, to April 30, 2021. The study included patients planned for an ORIGIN® CIM TKR procedure. Exclusion criteria included revision surgery, severe deformity, stiffness, or laxity. Evaluations were carried out using computed tomography scans performed 8 weeks preoperatively and 6 weeks postoperatively. The primary outcome measurements were the preoperative, planned, and postoperative CT scan alignment measurements including the Hip-Knee-Ankle (HKA) angle, mechanical Medial Distal Femoral articular surface Angle (mMDFA, distal alpha angle), Posterior Distal femoral articular surface angle (PDFA, posterior alpha angle), mechanical Medial Proximal Tibial articular surface Angle (mMPTA, beta angle) and posterior proximal tibial angle (PPTA). Secondary outcomes included the accuracy of implant positioning with percentage of outliers at 2° and 3° RESULTS: The study encompassed 51 knees from 50 patients with mean age of 68.1 (SD = 8.89). The overall HKA angle deviated by -0.93° [95% CI: -1.45; -0.43], and the PDFA angle by -0.61° [95% CI: -1.07; -0.15], while the mMPTA exceeded planned values by 1.00° [95% CI: 0.57; 1.43]. The 3° outliers rate ranged from 3.9% for the mMPTA to 7.8% for the HKA alignment, with no outliers in mMDFA and PPTA. Similarly, the 2° outliers rate ranged from 15.7% for both the PDFA angle and mMPTA to 19.6% for the HKA alignment. The Bland-Altman plots further emphasized the precision of planned and post-operative angles across all measurements.

CONCLUSION

The CIM TKR showed high accuracy and reproducibility, closely matching preoperative planning. The weakest accuracy at 3°-outliers is in the reproduction of the HKA alignment at 92.2% (range for all angle: 92.2-100%). Similarly, the weakest accuracy at 2°-outliers is in the reproduction of the HKA alignment at 80.4% (range for all angles: 80.4-92.2%).

Improved Knee Function with Customized vs. Off-the-Shelf TKA Implants-Results of a Single-Surgeon, Single-Center, Single-Blinded Study

BACKGROUND

Recent studies have been able to show certain benefits of Customized, Individually Made (CIM) compared to Off-the-Shelf (OTS) total knee arthroplasties (TKAs), but evidence is still lacking regarding the benefits of these implant systems. This study aimed to find differences in scores and functional outcome by comparing CIM and OTS implants, using Patient-Reported Outcome Measures (PROMs) and functional tests for activities of daily living in a single-surgeon setup.

METHODS

A total of 48 patients (16 CIM vs. 32 OTS) were consecutively enrolled and blindly examined. Functional testing was performed using four timed functional tests (TUG, WALK, TUDS, and BBS) and the VAS for pain. The Aggregated Locomotor Function (ALF) score was then calculated based on the addition of the average times of the three functional tests.

RESULTS

The CIM group showed significantly faster times in all functional tests and significantly better ALF scores. There were remarkable differences in the assessment of maximum pain sensation between the two groups, with superiority in the CIM group. The PROMs analysis revealed a higher proportion of excellent and good ratings for the items objective and function (KSS) in the CIM group.

CONCLUSION

The study showed that time-limited activities of daily living (ADLs) can be completed significantly faster with a CIM prosthesis and that a significantly higher percentage in this group reports freedom from pain during certain loads. Partial aspects of the PROM scores are also better in this group; however, this superiority could not be shown with regard to most PROM scores collected in this study.

Current Trends in Knee Arthroplasty: Are Italian Surgeons Doing What Is Expected?

Objectives: The purpose of this study is to evaluate Italian surgeons’ behavior during knee arthroplasty. Materials and Methods: All orthopedic surgeons who specialized in knee replacement surgeries and were members of the Italian Society of Knee, Arthroscopy, Sport, Cartilage and Orthopedic Technologies (SIGASCOT) between January 2019 and August 2019 were asked to complete a survey on the management of knee arthroplasty. Data were collected, analyzed, and presented as frequencies and percentages. Results: One-hundred and seventy-seven surgeons completed the survey and were included in the study. Ninety-five (53.7%) surgeons were under 40 years of age. Eighty-five surgeons (48%) worked in public hospitals and 112 (63.3%) were considered “high volume surgeons”, with more than 100 knee implants per year. Postero-stabilized total knee arthroplasty was the most commonly used, implanted with a fully cemented technique by 162 (91.5%) surgeons. Unicompartmental knee arthroplasty (UKA) was a rarer procedure compared to TKA, with 77% of surgeons performing less than 30% of UKAs. Most common TKA pre-operative radiological planning included complete antero-posterior (AP) weight-bearing lower limb radiographs, lateral view and patellofemoral view (used by 91%, 98.9% and 70.6% of surgeons, respectively). Pre-operative UKA radiological images included Rosenberg or Schuss views, patellofemoral view and magnetic resonance imaging (66.1%, 71.8% and 46.3% of surgeons, respectively). One hundred and thirty-two surgeons (74.6%) included an AP weight-bearing lower limb X-ray one year after surgery in the post-operative radiological follow-up. Furthermore, 119 surgeons (67.2%) did not perform a post-operative patellofemoral view because it was not considered useful for radiological follow-up. There was no uniformity in the timing and features of post-operative follow-up, with 13 different combinations. Conclusions: Italian surgeons perform TKA more commonly than UKA. Pre-operative TKA planning is quite uniform rather than UKA planning. Despite literature evidence, there is no agreement on follow-up. It may be useful to create a uniform checklist, including correct timing and exams needed. This analysis is also part of a society surgical educational project for training doctor.

Finite Element Analysis for Pre-Clinical Testing of Custom-Made Knee Implants for Complex Reconstruction Surgery

In severe cases of total knee arthroplasty, where off-the-shelf implants are not suitable or available anymore (i.e., in cases with extended bone defects or periprosthetic fractures), custom-made knee implants represent one of the few remaining treatment options. Design verification and validation of such custom-made implants is very challenging. The aim of this study is to support surgeons and engineers in their decision on whether a developed design is suitable for the specific case. A novel method for the pre-clinical testing of custom-made knee implants is suggested, which relies on the biomechanical test and finite element analysis (FEA) of a comparable reference implant. The method comprises six steps: (1) identification of the main potential failure mechanism and its corresponding FEA quantity of interest, (2) reproduction of the biomechanical test of the reference implant via FEA, (3) identification of the maximum value of the corresponding FEA quantity of interest at the required load level, (4) definition of this value as the acceptance criterion for the FEA of the custom-made implant, (5) reproduction of the biomechanical test with the custom-made implant via FEA, (6) conclusion, whether the acceptance criterion is fulfilled or not. Two exemplary cases of custom-made knee implants were evaluated with this method. The FEA acceptance criterion derived from the reference implants was fulfilled in both custom-made implants. Subsequent biomechanical tests verified the FEA results. The suggested method allows a quantitative evaluation of the biomechanical properties of a custom-made knee implant without performing a biomechanical test with it. This represents an important contribution in the pre-clinical testing of custom-made implants in order to achieve a sustainable treatment of complex revision total knee arthroplasty patients in a timely manner.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

LEVEL OF EVIDENCE

II, prospective cohort study.