Knee Prosthesis in the Computer Era

New materials and complications of prostheses in humans: situation in Spain

Prostheses or implantable medical devices (IMDs) are parts made of natural or artificial materials intended to replace a body structure and therefore must be well tolerated by living tissues. The types of IMDs currently available and usable are very varied and capable of replacing almost any human organ. A high but imprecise percentage of Spaniards are carriers of one or more IMDs to which they often owe their quality of life or survival. IMDs are constructed with different types of materials that are often combined in the same prosthesis. These materials must combine harmlessness to human tissues with high wear resistance. Their durability depends on many factors both on the host and the type of prosthesis, but the vast majority last for more than 10-15 years or remain in function for the lifetime of the patient. The most frequently implanted IMDs are placed in the heart or great vessels, joints, dental arches or breast and their most frequent complications are classified as non-infectious, particularly loosening or intolerance, and infectious. Complications, when they occur, lead to a significant increase in morbidity, their repair or replacement multiplies the health care cost and, on occasions, can cause the death of the patient. The fight against IMD complications is currently focused on the design of new materials that are more resistant to wear and infection and the use of antimicrobial substances that are released from these materials. Their production requires multidisciplinary technical teams, but also a willingness on the part of industry and health authorities that is not often found in Spain or in most European nations. Scientific production on prostheses and IMD in Spain is estimated to be less than 2% of the world total, and probably below what corresponds to our level of socio-economic development. The future of IMDs involves, among other factors, examining the potential role of Artificial Intelligence in their design, knowledge of tissue regeneration, greater efficiency in preventing infections and taking alternative treatments beyond antimicrobials, such as phage therapy. For these and other reasons, the Ramón Areces Foundation convened a series of experts in different fields related to prostheses and IMDs who answered and discussed a series of questions previously formulated by the Scientific Council. The following lines are the written testimony of these questions and the answers to them.

Real-Time Image-Guided Navigation in the Management of Alveolar Cleft Repair

Objectives: To present the use of dynamic navigation system in the repair of alveolar cleft. Patients and Participants: A total of three non-syndromic patients with unilateral alveolar cleft were involved in this study. Real-time computer-aided navigation were used to achieve restoration and reconstruction with standardized surgical technique. Methods: With the individual virtual 3-dimensional (3-D) modeling based on computed tomography (CT) data, preoperative planning and surgical simulation were carried out with the navigation system. During preoperative virtual planning, the defect volume or the quantity of graft is directly assessed at the surgical region. With the use of this system, the gingival periosteum flap incision can be tracked in real-time, and the bone graft can be navigated under the guidance of the 3-D views until it matches the preoperatively planned position. Results: Three patients with alveolar cleft were successfully performed under navigation guidance. Through the model alignment procedure, accurate matches between the actual intraoperative position and the CT images were achieved within the systematic error of 0.3 mm. The grafted bone was implanted according to the preoperative plan with the aid of instrument- and probe-based navigation. All the patients were healed well without serious complications. Conclusions: These findings suggest that image-guided surgical navigation, including preoperative planning, surgical simulation, postoperative assessment, and computer-assisted navigation was feasible and yielded good clinical outcomes. Clinical relevance: This dynamic navigation could be proved to be a valuable option for this complicated surgical procedure in the management of alveolar cleft repair.

Alignment analysis of Brainlab knee 3 navigation-guided total knee arthroplasty using the adjusted mechanical method

Purpose

With the application of navigation technology in Total Knee Arthroplasty (TKA), TKA procedures have become various. Studies have shown that navigation can improve the alignment of patients' lower limbs. To verify this conclusion, we collected the clinical data from patients who underwent Brainlab knee 3 navigation-guided TKA. Brainlab knee 3 is a completely new software that takes a different approach to address the current challenges of navigated TKA. During the procedure, we applied the Adjusted Mechanical Alignment (AMA) principle and took soft tissue balance as a priority. We aim to explore the patients’ lower limb alignment changes who underwent the Brainlab knee 3 navigation-guided TKA using the AMA method.

Methods

Fifty consecutive patients who underwent total knee arthroplasty using the Brainlab knee3 knee navigation system (Smith&Nephew) from January to August 2021 by the same doctor (Yunsu Chen) in the Department of Joint Surgery of the Shanghai Sixth People's Hospital were included. Hip-Knee-Ankle Angle (HKAA), anatomic Femur Tibia Angle (FTA), Lateral Distal Femoral Angle (LDFA), and medial proximal tibia angle (MPTA) were measured on preoperative and postoperative full-length lower-limbs x-ray films or weight-bearing anterior and lateral knee radiographs for observational and descriptive study. The preoperative and postoperative knee alignment changes were analyzed through paired t-test or nonparametric Wilcoxon test using SPSS 25.0 software

Results

Pre-operative and post-operative HKAA both obeyed normal distribution. The mean preoperative HKAA was 169.8° (154.9–178.7°) with a standard deviation of 5.41; the postoperative HKAA was 175.7° (168.4–180.0°) with a standard deviation of 2.81. Using the two-sample paired t-test to analyze, the result showed P = 0.000 < 0.05; a statistically significant difference exists. The preoperative and postoperative FTA obeyed normal distribution as well. The mean preoperative FTA was 174.7° (163.4–179.9°) with a standard deviation of 3.90; postoperative 175.6° (167.0–179.9°) with a standard deviation of 2.77. Using the two-sample paired t-test to analyze, the result showed P = 0.140 > 0.05, the difference was not statistically significant. The preoperative LDFA was normally distributed, while postoperative LDFA was not. The mean preoperative LDFA was 90.7° (83.5–99.6°) with a standard deviation of 3.83; the median of postoperative LDFA was 91.6° (86.0–103.2°) with an interquartile range of 2.93. Using the two-sample paired Wilcoxon test, the result showed P = 0.052 > 0.05; the difference was not statistically significant. Preoperative MPTA obeyed normal distribution, while postoperative MPTA did not. The mean preoperative MPTA was 83.5° (72.7–92.9°), with a standard deviation of 3.66; the median of postoperative MPTA was 89.3° (84.6–95.6°), with an interquartile range of 1.45. Using the two-sample paired Wilcoxon test, the result shows P = 0.000 < 0.05; a statistically significant difference exists.

Conclusion

In our study, AMA alignment was applied in Brainlab Knee3 computer navigation-assisted total knee arthroplasty. The femoral and tibial osteotomy angles were minimally adjusted according to soft tissue situations to reduce soft tissue release. We found AMA alignment provides good control of knee alignment in the coronal plane of the lower limbs, which is a reliable technique.

Implication of Changes in the Imaging Measurements after Mechanically Aligned Total Knee Arthroplasty

OBJECTIVE

Imaging measurements allow assessment of the mechanical alignment before and after total knee arthroplasty (TKA). The changes in radiographic parameters in each period of time within 1 year after TKA has been poorly understood. The purpose of this study was to examine the timing and causes of imaging changes in lower extremity force lines after total knee arthroplasty with mechanical alignment.

METHODS

A total of 93 mechanically-aligned TKA were radiographically examined before, 3 days, 3 months, and 1 year after surgery. Radiographic parameters included hip-knee angle (HKA), lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), knee joint line orientation (KJLO), ankle joint line orientation (AJLO), the knee joint line relative to ankle joint line angle (KJLTA) and midpoints of the ankle distance (MAD). Paired t-test were used to analyze the changes of these imaging parameters, By establishing a simple tibial model, the time points of changes in the imaging parameters after TKA was determined, with an attempt to understand the post-TKA changes in these imaging parameters.

RESULTS

Statistically significant differences were found between the preoperative data and the data measured 3 days after surgery in HKA, LDFA, MPTA, MAD, KJLTA, AJLO (P < 0.05) while KJLO exhibited no significant difference (P = 0.089). There existed significant differences between the data measured 3 days and the measurements taken 3 months after operation in HKA, MPTA, KJLTA, KJLO, AJLO (P < 0.05), whereas LDFA and MAD showed no significant difference (P > 0.05). Significant differences were revealed between the data measured 3 months and those collected 1 year after surgery in LDFA, MPTA, AJLO, KJLTA (P < 0.05) but HKA, KJLO, AJLO showed no significant differences (P > 0.05). The tibial model was made to look into the changes in postoperative imaging parameters. ΔMAD and postoperative AJLO were calculated to verify the model and hypothesis.

CONCLUSIONS

Postoperative changes in radiographic parameters and tibial models showed that the lower extremities were in an unnatural state within 1 year after TKA. The changes in the lower extremities force line were the results of the gradual adaptation of the lower extremities to TKA and the lateral swing of the extremities (3°) after surgery. Imaging data 1 year after surgery should be taken into account in the explanation of post-TKA changes in lower limb force lines.

The Comparison between Mini-Subvastus Approach and Medial Parapatellar Approach in TKA: A Prospective Double-Blinded Randomized Controlled Trial

Objective

Minimal invasive approach has been increasingly used in total knee arthroplasty (TKA) and more is expected of early rehabilitation in terms of pain release and recovery of knee function. The approach type is one of the major factors that determines the early rehabilitation after TKA. The purpose of this study is to determine whether mini‐subvastus approach (MSVA) is superior to the traditional medial parapatellar approach (MPA) in TKA.

Methods

From 2018 to 2019, a randomized double‐blinded prospective study was conducted on 58 patients who underwent simultaneous bilateral TKA. The subjects included eight men and 50 women, with an average age of 65 years. One side was randomized using MSVA and the other side using MPA. Visual analog scale (VAS), operative duration, recovery time to straight leg raising (SLR), range of motion (ROM), HSS score, release rate of lateral retinaculum, satisfaction rate were recorded and compared. Paired‐samples T test were used for quantitative data and chi‐square test for qualitative data.

Results

There was no statistical difference in the ratio of left and right sides, preoperative ROM, VAS, HSS score, muscular strength of lower limbs, KL grade, operative order, and operative duration between the two groups. The average ROM (118.91 ± 8.21 vs. 107.60 ± 7.99, t = 14.320, p = 0.0000) and HSS score (72.03 ± 4.55 vs. 61.22 ± 4.36, t = 13.095, p = 0.0000) on POD 3, VAS in rest and motion on POD 1 and 3, the recovery time to SLR (1.17 ± 0.38 vs. 3.09 ± 0.76, t = 19.902, p = 0.0000), and the satisfaction rate on POD 1 (96.55% vs. 74.14%, χ² = 9.9251, p = 0.0016) were superior in the MSVA group over MPA group. ROM in rest and motion and HSS score on POD 30 had no difference. The release rate of lateral retinaculum was less in the MSVA group than in the MPA group. The mean value of HKA, FFC, and FTC and the proportion of outliers did not differ significantly between the two groups.

Conclusions

Compared with MPA, MSVA can make ROM of knee and SLR recover earlier, reduce postoperative pain after TKA, improve the early postoperative satisfaction and reduce the lateral release rate. MSVA can be used as a favorable measure in the concept of enhanced recovery after surgery (ERAS).