Mechanical, Anatomical, and Kinematic Axis in TKA: Concepts and Practical Applications. Curr Rev Musculoskelet Med. 2014;7:89-95. [PMID: 24671469 DOI: 10.1007/s12178-014-9218-y]

Optimal Implant Positioning Following Total Knee Arthroplasty Using Predictive Dynamic Simulation

In this paper, a novel method is proposed for the determination of the optimal subject-specific placement of knee implants based on predictive dynamic simulations of human movement following total knee arthroplasty (TKA). Two knee implant models are introduced. The first model is a comprehensive 12-degree-of-freedom (DoF) representation that incorporates volumetric contact between femoral and tibial implants, as well as patellofemoral contact. The second model employs a single-degree-of-freedom equivalent kinematic (SEK) approach for the knee joint. A cosimulation framework is proposed to leverage both knee models in our simulations. The knee model is calibrated and validated using patient-specific data, including knee kinematics and ground reaction forces. Additionally, quantitative indices are introduced to evaluate the optimality of implant positioning based on three criteria: balancing medial and lateral load distributions, ligament balancing, and varus/valgus alignment. The knee implant placement is optimized by minimizing the deviation of the indices from their user-defined desired values during predicted sit-to-stand motion. The method presented in this paper has the potential to enhance the results of knee arthroplasty and serve as a valuable instrument for surgeons when planning and performing this procedure.

Femoral and tibial phenotypes of varus alignment in a Southeast Asian arthritic population: a descriptive study

INTRODUCTION

Knowledge of femoral and tibial morphology is important for patient-specific surgery in both joint reconstruction and preservation procedures. Studies evaluating morphological variance in femoral and tibial alignments in Asian populations are scarce. This is the first descriptive study evaluating the femoral and tibial phenotypes of varus alignment in a Southeast Asian population.

METHODS

Long-leg coronal standing radiographs of 2021 limbs were obtained, and the hip-knee-ankle angle, mechanical lateral distal femoral angle, medial proximal tibial angle and joint line convergence angle were measured. Joint line obliquity was calculated, and the knees were classified according to the Coronal Plane Alignment of Knee (CPAK) classification. Descriptive analyses on alignment parameters and demographic data (age, gender, ethnicity and body mass index [BMI]) were performed and entered into a linear regression model.

RESULTS

The highest frequency of limb alignment in the population was found to be CPAK type I (52.71%, n = 1003). Tibial varus was the largest contributor of varus malignment. Of the varus knees (n = 1247), varus deformity was found solely in the tibia (68.60%), solely in the femur (2.07%) and was contributed by both the femur and the tibia (4.97%). In the linear regression model, BMI was found to be a strong determinant for femoral varus (P = 0.004) and joint line incongruence (P < 0.001).

CONCLUSION

The findings of this study will be important to surgeons during planning for joint preservation procedures (such as corrective osteotomies) and joint arthroplasties to restore alignment.

Developing a Computer Vision Model to Automate Quantitative Measurement of Hip-Knee-Ankle Angle in Total Hip and Knee Arthroplasty Patients

BACKGROUND

Increasing deformity of the lower extremities, as measured by the hip-knee-ankle angle (HKAA), is associated with poor patient outcomes after total hip and knee arthroplasty (THA, TKA). Automated calculation of HKAA is imperative to reduce the burden on orthopaedic surgeons. We proposed a detection-based deep learning (DL) model to calculate HKAA in THA and TKA patients and assessed the agreement between DL-derived HKAAs and manual measurement.

METHODS

We retrospectively identified 1,379 long-leg radiographs (LLRs) from patients scheduled for THA or TKA within an academic medical center. There were 1,221 LLRs used to develop the model (randomly split into 70% training, 20% validation, and 10% held-out test sets); 158 LLRs were considered "difficult," as the femoral head was difficult to distinguish from surrounding tissue. There were 2 raters who annotated the HKAA of both lower extremities, and inter-rater reliability was calculated to compare the DL-derived HKAAs with manual measurement within the test set.

RESULTS

The DL model achieved a mean average precision of 0.985 on the test set. The average HKAA of the operative leg was 173.05 ± 4.54°; the nonoperative leg was 175.55 ± 3.56°. The inter-rater reliability between manual and DL-derived HKAA measurements on the operative leg and nonoperative leg indicated excellent reliability (intraclass correlation (2,k) = 0.987 [0.96, 0.99], intraclass correlation (2, k) = 0.987 [0.98, 0.99, respectively]). The standard error of measurement for the DL-derived HKAA for the operative and nonoperative legs was 0.515° and 0.403°, respectively.

CONCLUSIONS

A detection-based DL algorithm can calculate the HKAA in LLRs and is comparable to that calculated by manual measurement. The algorithm can detect the bilateral femoral head, knee, and ankle joints with high precision, even in patients where the femoral head is difficult to visualize.

Systematic review and meta-analysis of long term outcomes and innovations in Total Knee Arthroplasty: KINEMATIC, PERSONALIZED KNEE vs. CONVENTIONAL

Background

Kinematic alignment is an emerging approach for total knee arthroplasty, with the aim to restore patient's individual pre-arthritic joint kinematics. In this systematic review and meta-analysis, we compared the kinematic alignment with the conventional mechanical alignment for total knee arthroplasty.

Methods

We searched PubMed, Web of Science, Cochrane Library, and Scopus on June 2, 2024. We screened the retrieved studies for eligibility. Then extracted the data from the included studies, and then pooled the data as mean difference (MD) or odds ratio (OR) with a 95% confidence interval using Review Manager Software (ver. 3.5).

Results

There was no significant difference between KA and MA in the different reported scores: combined KSS score at 6 months (P = 0.23) and 1 years (P = 0.60), KSS Patient satisfaction (P = 0.33), KSS function score (P = 0.07), Oxford score at 6 months (P = 0.45) and 2 years (P = 0.41), KOOS score (P = 0.26). Moreover, there was statistically significant difference in range of motion for flexion and extension at 1 and 2 years, incision length, the length of hospital stay, or the duration of surgery.

Conclusion

Although kinematic alignment showed slightly better clinical outcomes than mechanical alignment, the difference between the two techniques is not statistically significant.

Performance of Microsoft Azure Kinect DK as a tool for estimating human body segment lengths

The Microsoft Kinect depth sensor, with its built-in software that automatically captures joint coordinates without markers, could be a potential tool for ergonomic studies. This study investigates the performance of Kinect in limb segment lengths using dual-energy X-ray absorptiometry (DXA) as a reference. Healthy children and adults (n = 76) were recruited for limb length measurements by Kinect and DXA. The results showed consistent ratios of arm, forearm, thigh, and leg lengths to height, which were 0.16, 0.14, 0.23, and 0.22 respectively, for both age groups and methods. Kinect exhibited perfect correlation among all limb lengths, indicating fixed proportions assumed by its algorithm. Comparing the two methods, there was a strong correlation (R = 0.850-0.985) and good to excellent agreement (ICC = 0.829-0.977), except for the right leg in adults, where agreement was slightly lower but still moderate (ICC = 0.712). The measurement bias between the methods ranged from - 1.455 to 0.536 cm. In conclusion, Kinect yields outcomes similar to DXA, indicating its potential utility as a tool for ergonomic studies. However, the built-in algorithm of Kinect assumes fixed limb proportions for individuals, which may not be ideal for studies focusing on investigating limb discrepancies or anatomical differences.

Evaluating axial alignment and knee phenotypes in a young Indian population, using X-rays converted to three-dimensional bone models, and their relevance in total knee arthroplasty

PURPOSE

The standard principle of total knee arthroplasty (TKA) targeted by most orthopaedicians is the alignment of the lower limb in a neutral mechanical axis. However, for several patients the neutral mechanical alignment is not normal. Aligning these patients to a neutral mechanical axis may not result in desirable outcomes as it may feel unnatural. This study aimed to discover what percentage of the young healthy Indian population have a neutral hip-knee-ankle angle (HKA = 180°) and what percentage of this population have a deviation from the neutral HKA. We also studied the distribution of knee phenotypes in this non-arthritic population.

SUBJECTS AND METHODS

A total of 196 lower limbs were evaluated from 100 subjects, between the ages of 20 and 35 years, without any history of lower limb pathology, of which 50 were males and 50 were females. All volunteers were subjected to full-leg standing anteroposterior and lateral digital radiographs on which various alignment parameters were analysed. Three-dimensional bone models were generated using a validated software.

RESULTS

125 limbs (63.7%) from the total population lay in the range of 180 ± 3°; 7.14% (14/196) of the total limbs had an HKA angle of 180°; 29.5% (58/196) of the total population had a varus alignment, i.e., HKA angle of ≤176° and 6.6% (13/196) had knees in valgus alignment, i.e., HKA angle of ≥184°. Thirty-four percent (33/96) of limbs in men and 25% (25/100) of limbs in women had constitutional varus knees with an alignment of ≤176°; 5.2% (5) of limbs in men and 8% (8) of limbs in women had constitutional valgus knees with an alignment of ≥184°; 67/96 knees in males and 58 knees in females were in the range of 180 ± 3°.

CONCLUSIONS

A significant portion of the normal population had limbs that deviated from the neutral HKA. If these subjects were to need TKA in the future, it would not be desirable to restore their alignment to its neutral.

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.

Unicompartmental knee arthroplasty vs high tibial osteotomy for knee osteoarthritis: A comparison of clinical and radiological outcomes

BACKGROUND

Unicompartmental knee arthroplasty (UKA) and high tibial osteotomy (HTO) are well-established operative interventions in the treatment of knee osteoarthritis. However, which intervention is more beneficial to patients with knee osteoarthritis remains unknown and a topic of much debate. Simultaneously, there is a paucity of research assessing the relationship between radiographic parameters of knee joint alignment and patient-reported clinical outcomes, preoperatively and following HTO or UKA.

AIM

To compare UKAs and HTOs as interventions for medial-compartment knee osteoarthritis: Examining differences in clinical outcome and investigating the relationship of joint alignment with respect to this.

METHODS

This longitudinal observational study assessed a total of 42 patients that had undergone UKA (n = 23) and HTO (n = 19) to treat medial compartment knee osteoarthritis. Patient-reported outcome measures (PROMs) were collected to evaluate clinical outcome. These included two disease-specific (Knee Injury and Osteoarthritis Outcome Score, Oxford Knee Score) and two generic (EQ-5D-5L, Short Form-12) PROMs. The radiographic parameters of knee alignment assessed were the: Hip-knee-ankle angle, mechanical axis deviation and angle of Mikulicz line.

RESULTS

Statistical analyses demonstrated significant (P < 0.001), preoperative to postoperative, improvements in the PROM scores of both groups. There were, however, no significant inter-group differences in the postoperative PROM scores of the UKA and HTO group. Several significant correlations associated a more distolaterally angled Mikulicz line with worse knee function and overall health preoperatively (P < 0.05). Postoperatively, two clusters of significant correlations were observed between the disease-specific PROM scores and knee joint alignment parameters (hip-knee-ankle angle, mechanical axis deviation) within the HTO group; yet no such associations were observed within the UKA group.

CONCLUSION

UKAs and HTOs are both efficacious operations that provide a comparable degree of clinical benefit to patients with medial compartment knee osteoarthritis. Clinical outcome has a limited association with radiographic parameters of knee joint alignment postoperatively; however, a more distolaterally angled Mikulicz line appears associated with worse knee function/health-related quality of life preoperatively.

Total knee arthroplasty following lateral closing-wedge high tibial osteotomy versus primary total knee arthroplasty: a propensity score matching study

BACKGROUND

The disparity in patient-reported outcomes between total knee arthroplasty (TKA) following high tibial osteotomy (HTO) and primary TKA has yet to be fully comprehended. This study aims to compare the patient-reported outcomes, radiological parameters and complication rates between TKA following HTO and primary TKA.

METHODS

Sixty-five patients who underwent TKA following lateral closing-wedge HTO were compared to a matched group of primary TKA at postoperative 6-months and 1-year. Between-group confounders of age, gender, smoking status, Body Mass index, preoperative Numeric Rating Scale (NRS) pain in rest, Knee injury and Osteoarthritis Outcome Score-Physical function Shortform (KOOS-PS), EuroQol five-dimensional (EQ-5D) overall health score, and Oxford Knee Score (OKS) were balanced by propensity score matching. Patient-reported outcome measures were NRS pain in rest, KOOS-PS, EQ-5D overall health score, and OKS. Radiological parameters were femorotibial angle, medial proximal tibial angle, anatomical lateral distal femoral angle, posterior tibial slope, and patellar height assessed by Insall-Salvati ratio. The complication rates of TKA were compared between the two groups. The HTO survival time, the choice of staple removal before or during TKA in patients who underwent TKA following HTO patients, and the rate of patellar resurfacing were assessed. The p value < 0.0125 indicates statistical significance after Bonferroni correction.

RESULTS

After propensity score matching, no significant between-group differences in the patient-reported outcome measures, radiographical parameters and complication rates were found (p > 0.0125). In the TKA following HTO group, with an average HTO survival time of 8.7 years, staples were removed before TKA in 46 patients (71%) and during TKA in 19 patients, and 11 cases (17%) had patella resurfacing. In the primary TKA group, 15 cases (23%) had patella resurfacing.

CONCLUSION

The short-term assessment of TKA following HTO indicates outcomes similar to primary TKA. A previous HTO does not impact the early results of subsequent TKA, suggesting that the previous HTO has minimal influence on TKA outcomes.

LEVEL OF EVIDENCE

III, cohort study.

Comparison of Clinical and Radiological Outcomes of Total Knee Arthroplasty in Osteoarthritic Patients

Background The knee is the joint most commonly affected by osteoarthritis, more than any other. Osteoarthritis is a progressive, long-term condition that leads to the deterioration of joint tissue and cartilage, resulting in pain and impairment. Total knee arthroplasty (TKA) is a successful intervention that improves functional capability, decreases pain, and enhances quality of life. We conducted this study to evaluate whether radiological parameters following TKA influence the clinical outcomes of patients with knee osteoarthritis. Methods The study was conducted on patients treated for knee osteoarthritis at the Department of Orthopedics, Rajindra Hospital and Government Medical College, Patiala, Punjab, in collaboration with the Department of Radiology over a period of 1.5 years. A total of 152 patients diagnosed with knee osteoarthritis were included in the study; all underwent TKA. Patients underwent clinical evaluation and were graded using the Knee Society Score (KSS) during follow-up examinations. Pain was evaluated using the Visual Analog Scale (VAS). Postoperative X-rays were obtained, and various angles, including the distal femoral angle (DFA), the proximal tibial angle (PTA), and the posterior slope angle (PSA), were measured. Patient follow-up was conducted at three days, three months, and six months. Subsequently, a comparison of the clinical and radiological outcomes of TKA was performed. Results In this study, a total of 152 patients participated, with the majority falling into the 61-70 age group. Of these patients, 40.13% were female and 59.87% were male. The average medial DFA was 94.05°, the average medial PTA was 89.31°, and the PSA was 6.6°. Patients with a medial DFA of 94.05° (±3), a medial PTA of 89.31° (±3), and a PSA of 6.6° (±3) were categorized into the normal group. Conclusion Patients with DFA, PTA, and PSA in the normal range demonstrate improved KSS and clinical outcomes.

Severe genu varus deformity does not affect enhanced recovery after surgery total knee arthroplasty outcomes

INTRODUCTION

Enhanced recovery after surgery (ERAS) has been increasingly adopted in orthopaedic surgery. Although not an exclusion criterion, patients undergoing total knee arthroplasty (TKA) with preoperative severe varus deformity may be less likely to be enrolled for ERAS. This study aimed to compare the success of ERAS TKA between patients with severe preoperative varus deformities (≥ 15° varus) and the control group (< 15° varus to 14° valgus). Our secondary aim was to compare postoperative complications and functional outcomes between the two groups.

MATERIALS & METHODS

310 TKAs performed from August 2019 to February 2021 were analyzed with a follow-up of 6 months postoperatively. The primary outcome, ERAS TKA success, was defined as length of hospital stay of < 24 h. Other parameters included 30-day postoperative complications and clinical outcomes such as the original Oxford Knee Score (OKS), the Knee Society Knee (KSKS) and Function Score (KSFS), Visual Analog Scale for Pain (VAS-P), 36-Item Short-Form Health Survey (SF-36) Physical Component Summary (PCS) and SF-36 Mental Component Summary (MCS).

RESULTS

There were 119 patients in the severe deformity group and 191 patients in the control group. There were no significant differences in ERAS success between the severe deformity group and control group, with both groups achieving similarly high rates (> 90%) of ERAS success. There were also no differences in 30-day postoperative complications and 6-month postoperative clinical outcomes.

CONCLUSION

Patients with severe preoperative varus deformity undergoing ERAS TKA achieved high ERAS success rates (> 90%). Genu varum is not a contraindication for ERAS TKA.

Feasibility and Usability of Augmented Reality Technology in the Orthopaedic Operating Room

PURPOSE OF REVIEW

Augmented reality (AR) has gained popularity in various sectors, including gaming, entertainment, and healthcare. The desire for improved surgical navigation within orthopaedic surgery has led to the evaluation of the feasibility and usability of AR in the operating room (OR). However, the safe and effective use of AR technology in the OR necessitates a proper understanding of its capabilities and limitations. This review aims to describe the fundamental elements of AR, highlight limitations for use within the field of orthopaedic surgery, and discuss potential areas for development.

RECENT FINDINGS

To date, studies have demonstrated evidence that AR technology can be used to enhance navigation and performance in orthopaedic procedures. General hardware and software limitations of the technology include the registration process, ergonomics, and battery life. Other limitations are related to the human response factors such as inattentional blindness, which may lead to the inability to see complications within the surgical field. Furthermore, the prolonged use of AR can cause eye strain and headache due to phenomena such as the vergence-convergence conflict. AR technology may prove to be a better alternative to current orthopaedic surgery navigation systems. However, the current limitations should be mitigated to further improve the feasibility and usability of AR in the OR setting. It is important for both non-clinicians and clinicians to work in conjunction to guide the development of future iterations of AR technology and its implementation into the OR workflow.

Preoperative Joint Distraction Imaging and Planning Protocol for Total Knee Arthroplasty

BACKGROUND

Current preoperative total knee arthroplasty (TKA) planning strategies are bone-referencing and do not consider the ligamentous profile of the knee. This study assessed the mean Hip-Knee-Ankle (HKA) angle of the planned Distracted Alignment (DA), an alignment output using a joint distraction radiology and planning protocol, which incorporates preoperative evaluation of ligament laxity.

METHODS

A retrospective study of 144 knees undergoing TKA was performed. Each patient received a preoperative computer tomograph scan, a weight-bearing antero-posterior knee radiograph, and distracted knee radiographs in extension and flexion. The imaging was used to develop a preoperative DA plan aiming for medio-lateral and extension-flexion space balance. The mean DA, weight-bearing, and arithmetic HKA angles were compared to each other, and to the HKA of a healthy nonarthritic population.

RESULTS

The mean weight-bearing, arithmetic, and planned DA HKA angles were 4.8° (interquartile range [IQR] 6.5°) varus, 0.4° (IQR 4.5°) varus, and 2.2° (IQR 4.0°) varus, respectively. This compares to a healthy adult HKA angle of 1.3° varus. The difference between the planned DA and arithmetic HKA angles was greater than 3° for 36% of the patients in the study population.

CONCLUSIONS

The planned DA HKA angle was fundamentally different from the arithmetic HKA angle, but comparable to a healthy population. Considering both hard and soft tissue information of the knee, we believe the planned DA resulting from the joint distraction radiology protocol allows for optimized preoperative surgical planning in TKA. This protocol has been shown to be clinically viable.

Impact of postoperative femorotibial axis on functional outcomes in unicompartmental knee arthroplasty

OBJECTIVES

This study aimed to compare the functional outcomes of patients undergoing fixed-bearing medial unicompartmental knee arthroplasty (UKA) classified as either varus or neutral based on their postoperative femorotibial angle (FTA), with the goal of evaluating the impact of FTA on functional results.

PATIENTS AND METHODS

A total of 38 knees of 35 patients (27 females, 8 males; mean age: 63.6±7.1 years; range, 52 to 75 years) were included in this retrospective study. The data was collected between December 15, 2020, and January 15, 2021. Patients were categorized into two groups based on their postoperative FTA. The neutral group consisted of patients with an FTA range of 5.1° to 7.4°, while the varus group included patients with an FTA range of 0.1° to 4.8°. Knee Outcome Osteoarthritis Score (KOOS), Visual Analog Scale (VAS) scores, sit to stand test results, and six minute walk test data were analyzed.

RESULTS

The mean follow-up was 42.0±19.3 months. The postoperative VAS score for the varus group was 0.95±0.99, whereas the neutral group had a VAS score of 2.19±1.83 (p=0.021). The mean KOOS for the varus group was 88.01±7.88, whereas the neutral group had a mean KOOS score of 78.46±13.69 (p=0.006).

CONCLUSION

In patients undergoing UKA, mild varus alignment could yield superior early and midterm functional outcomes compared to a neutral femorotibial angle.

Navigating the Divide: A Comprehensive Review of the Mechanical and Anatomical Axis Approaches in Total Knee Replacement

This comprehensive review explores the mechanical and anatomical axis approaches in total knee replacement (TKR) surgery, addressing the ongoing debate within the orthopedic community. Emphasizing the significance of TKR in alleviating knee-related disorders, this review underscores the pivotal role of accurate alignment in achieving optimal surgical outcomes. The purpose is to navigate the divide between the well-established mechanical axis approach, focusing on a straight-line alignment, and the anatomical axis approach, aligning with natural knee landmarks. The analysis delves into the advantages, disadvantages, and clinical implications of each approach, offering a nuanced perspective on their efficacy. The conclusion emphasizes a patient-centric approach, recommending the adoption of hybrid strategies and the incorporation of emerging technologies for enhanced precision. The future of TKR aligns with personalized medicine, leveraging advancements in computer-assisted navigation, robotics, and patient-specific implants. Ongoing professional development and interdisciplinary collaboration are crucial for surgeons, and as the field evolves, innovations in artificial intelligence, imaging, and 3D printing are expected to shape the trajectory of TKR alignment approaches.

Fully Automated Analysis of the Anatomic and Mechanical Axes From Pediatric Standing Lower Limb Radiographs Using Convolutional Neural Networks

BACKGROUND

Lower limb alignment is the quantification of a set of parameters that are commonly measured radiographically to test for and track a wide range of skeletal pathologies. Determining limb alignment is a commonly performed yet laborious task in the pediatric orthopaedic setting and is therefore an interesting goal for automation.

METHODS

We employ a machine learning approach using convolutional neural networks (CNNs) to segment pediatric weight-bearing lower limb radiographs. The results are then used with custom Matlab code to extract anatomic landmarks and to determine lower limb alignment parameters.

RESULTS

Measurements obtained from the automated workflow proposed here were compared with manual measurements performed by orthopaedic surgery fellows. Mechanical axis deviation was determined within a mean of 2.02 mm. Lateral distal femoral angle and medial proximal tibial angle were determined with a mean deviation of 1.73 and 2.90 degrees, respectively. The calculation speed for the full set of mechanical and anatomic axis parameters was found to be ~2 seconds per radiograph.

CONCLUSIONS

The CNN-based approach proposed in this work was shown to produce results comparable to orthopaedic surgery fellows at fast calculation speed. Although further work is needed to validate these results against radiographs and measurements from other centers, we see this as a promising start and a functional path that can be employed in further research.

CLINICAL RELEVANCE

CNNs are a promising approach to automating commonly performed, repetitive tasks, especially those pertaining to image processing. The time savings are particularly important in clinical research applications where large sets of radiographs are routinely available and require analysis. With further development of these algorithms, we anticipate significantly improved agreement with expert-measured results and the calculation speed.

Appraisal of Clinical Improvement With Total Knee Arthroplasty in Valgus Knee Deformities: A Case Series

Introduction This case series explores the efficacy of unassisted total knee arthroplasty (TKA) in addressing valgus knee deformity secondary to osteoarthritis. The study aims to evaluate functional outcomes pre- and post-surgery using the Knee Society Score (KSS) and radiological assessments in short-term follow-up. Six patients underwent TKA and were evaluated retrospectively. Statistical analysis revealed significant improvements in the angle of deformity, KSS, and range of motion postoperatively. The study underscores the success of TKA in correcting valgus deformity, improving knee function, and enhancing patient satisfaction. TKA is a highly successful treatment for osteoarthritis, providing functional recovery and improved quality of life. However, valgus knee deformity presents a challenge in TKA, affecting approximately 10% of patients. This study aims to assess the functional outcomes of TKA for valgus deformity using KSS and radiological evaluation in short-term follow-up. Materials and methods A retrospective observational study was conducted from November 2022 to December 2023, involving six patients with valgus knee deformity secondary to osteoarthritis. TKA was performed with no technological assistance, and patients were assessed pre- and post-surgery using KSS and radiological measurements. Statistical analysis was performed using paired t-tests. Case description Six patients with grade two valgus deformity underwent technology-unassisted TKA. The postoperative assessment revealed significant improvements in the tibiofemoral angle, KSS, and range of motion. The medial parapatellar approach for TKA was utilized with a standard unconstrained primary TKA prosthesis, resulting in successful correction of deformity and improved knee alignment. Discussion TKA is a widely performed and reliable surgical intervention, with valgus knee deformity posing specific challenges. This study demonstrates the effectiveness of conventional TKA in correcting valgus deformity, improving knee function, and enhancing patient satisfaction in a very small case series. Comparison with previous studies supports the findings of the pre-existing literature, highlighting the importance of appropriate surgical approach and patient selection. Conclusion TKA utilizing a medial parapatellar approach proved effective in our small case series in correcting valgus deformity, improving knee function, and enhancing patient satisfaction. Short-term follow-up reveals significant improvements in stability, posture, and KSS scores. Further assessments and longer-term follow-up are warranted to confirm the long-term effectiveness of this approach.

Gender-based differences exist in the functional knee phenotypes classification of the osteoarthritic knee

PURPOSE

To identify gender differences in (1) the coronal alignment of functional knee phenotypes and (2) the JLCA (joint line convergence angle) in relation to the phenotype classification.

METHODS

This study is a retrospective data analysis, including 12,099 osteoarthritic knee computed tomography (5025 male, 7074 female) analysed by Medacta software for hip-knee-ankle angle (HKA), femoral mechanical angle (FMA), tibial mechanical angle (TMA) and JLCA. The data were grouped into genders and combined according to the Functional Knee Phenotypes Classification.

RESULTS

Out of 127 phenotypes for males and 131 for females, 17 common phenotypes were reported. The commonest four were similar for both genders with VARHKA177° NEUFMA93° NEUTMA87° (9.8% males, 9.50% females), followed by VARHKA174° NEUFMA93°VARTMA84° (7.1%) and VARHKA174°VARFMA90° NEUTMA87° (7.0%) for males and VARHKA174° NEUFMA93° NEUTMA87° (6.1%), VARHKA174° NEUFMA93°VARTMA84° (5.1%) for females. The commonest FMA and TMA (91.5° to 94.5° and 85.5° to 88.5°, respectively) were the same for both genders, however, the rest of the male population observed greater femoral varus than the female population (p < 0.001). JLCA values ranged from -28.4° to 8.2° in the overall study population. Males and females had a mean JLCA of -2.96° (±2.6° SD) and -2.66° (±2.8°7 SD), respectively, p < 0.001.

CONCLUSIONS

Gender differences exist within the osteoarthritic knee phenotype. The male varus phenotype is influenced by FMA, while TMA values are similar across genders. JLCA variations show similarities to both TMA and FMA, suggesting JLCA is influenced by bone morphology more than by gender. These differences inform surgical decision-making for the personalised approach to the primary TKA.

LEVEL OF EVIDENCE

Level III.

Optimization of the "Perth CT" Protocol for Preoperative Planning and Postoperative Evaluation in Total Knee Arthroplasty

Background and Objectives: Total knee arthroplasty (TKA) has become the treatment of choice for advanced osteoarthritis. The aim of this paper was to show the possibilities of optimizing the Perth CT protocol, which is highly effective for preoperative planning and postoperative assessment of alignment. Materials and Methods: The cross-sectional study comprised 16 patients for preoperative planning or postoperative evaluation of TKA. All patients were examined with the standard and optimized Perth CT protocol using advance techniques, including automatic exposure control (AEC), iterative image reconstruction (IR), as well as a single-energy projection-based metal artifact reduction algorithm for eliminating prosthesis artifacts. The effective radiation dose (E) was determined based on the dose report. Imaging quality is determined according to subjective and objective (values of signal to noise ratio (SdNR) and figure of merit (FOM)) criteria. Results: The effective radiation dose with the optimized protocol was significantly lower compared to the standard protocol (p < 0.001), while in patients with the knee prosthesis, E increased significantly less with the optimized protocol compared to the standard protocol. No significant difference was observed in the subjective evaluation of image quality between protocols (p > 0.05). Analyzing the objective criteria for image quality optimized protocols resulted in lower SdNR values and higher FOM values. No significant difference of image quality was determined using the SdNR and FOM as per the specified protocols and parts of extremities, and for the presence of prothesis. Conclusions: Retrospecting the ALARA ('As Low As Reasonably Achievable') principles, it is possible to optimize the Perth CT protocol by reducing the kV and mAs values and by changing the collimation and increasing the pitch factor. Advanced IR techniques were used in both protocols, and AEC was used in the optimized protocol. The effective dose of radiation can be reduced five times, and the image quality will be satisfactory.

Functional and Clinical Outcomes of Total Knee Arthroplasty: A Prospective Study

INTRODUCTION

A key to successful patient outcomes following knee procedures like total knee arthroplasty (TKA) is achieving normal knee alignment. Normal mechanical balance in the joints must be restored in order to lessen the failure rate of TKA, and precise assessment of lower extremity alignment and component location is thought to be the primary determinant of a good clinical outcome over the long term.

OBJECTIVE

The aim of this study was to assess the early functional and clinical outcomes of TKA by analyzing post-operative mechanical axis and Knee Society Score (KSS) data. The study also aimed to investigate the importance of achieving neutral mechanical alignment in TKA for long-term results.

METHODS

A prospective and retrospective observational study was conducted, involving 40 patients with primary osteoarthritis who underwent bilateral or unilateral TKA. Demographic information, pre-operative comorbidities, knee abnormalities, and radiographic assessment were collected. Post-operative mechanical axis and implant placement were evaluated using CT scanograms. Clinical and functional assessments were performed using the Knee Society Score at regular intervals. The KSS scores were obtained at six-month intervals following surgery. The scores were categorized as excellent, very good, good, fair, or poor based on predefined criteria.

RESULTS

A total of 47 knees from 40 patients were analyzed. The mean age of the study population was 65.6 years. Female patients accounted for 67.5% of the sample. The majority of patients (57.4%) achieved an excellent KSS score, followed by very good (25.5%) and good (17%) scores. The mean KSS score significantly improved from 177 points pre-surgery to 225 points post-surgery. The post-operative mechanical axis ranged from 1.1 degrees valgus to 9 degrees valgus, with a mean value of 3.5 degrees valgus. The range of motion improved from 10 to 90 degrees post-operatively, with a mean range of 0-110 degrees.

CONCLUSION

This study suggests that total knee replacement surgery resulted in positive outcomes, with most patients achieving excellent or very good scores on the Knee Society scale. Proper axial and rotational alignment of the components during TKA enhanced functional outcomes and contributed to long-term clinical success. Restoration of neutral mechanical alignment and optimal component placement may lead to lower revision rates and increased durability after TKA. Further studies with larger sample sizes are needed to validate these findings.

Functional knee phenotypes: A helpful classification tool for visualizing potential femoral varus in restricted kinematic alignment total knee arthroplasty in Japan

PURPOSE

Restricted kinematic alignment (rKA) is a modified technique of kinematically aligned total knee arthroplasty (TKA) within a safe alignment range for long-term implant survivorship. The purpose of this study was to clarify (1) the distribution of functional knee phenotypes in patients who underwent TKA in Japan and (2) whether the application of this classification results in anatomically neutral alignment after rKA TKA.

METHODS

Overall, 114 TKA surgeries (mechanical alignment [MA]: 49; rKA: 65) were performed. The joint line orientation angle (JLOA), hip-knee-ankle angle (HKA), femoral mechanical angle (FMA) and tibial mechanical angle (TMA) were obtained. The knees were categorized using a functional knee phenotype classification. Clinical evaluations, including the Knee Injury and Osteoarthritis Outcome, 12-question Forgotten Joint and Oxford Knee Scores, were performed 3 years postoperatively. Between-group comparisons were made.

RESULTS

The most common preoperative functional knee phenotype was VARHKA 3° + NEUFMA 0° + VARTMA 3° (11.4%). In the preoperative population, 51 knees (44.7%) had VARFMA  ≥ 3°. Postoperatively, the most common functional knee phenotype was NEUHKA 0° + VARFMA 3° + VALTMA 3° (14 knees, 28.6%) in the MA and NEUHKA 0° + NEUFMA 0° + NEUTMA 0° in the rKA group. The percentage of postoperative JLOA within ±3° from the floor was 27% and 72% in the MA and rKA groups, respectively (p < 0.001). The functional knee phenotype after rKA TKA was neutrally reproduced, and the joint line was more parallel to the ground in the standing position than that of MA. Between-group differences in clinical outcomes were not significant.

CONCLUSION

The application of functional knee phenotyping to knee osteoarthritis in Japan suggested the presence of racial morphological characteristics. This classification could help better visualize potential femoral varus, contributing to protocol deviation in applying restricted KA TKA.

LEVEL OF EVIDENCE

Level IV.

The use of virtual reality to assess the bony landmarks at the knee joint - The role of imaging modality and the assessor's experience

BACKGROUND

At present, extended reality technologies such as virtual reality (VR) have gained popularity in orthopedic surgery. The first aim of this study was to assess the precision of VR and other imaging modalities - computed tomography (CT), magnetic resonance imaging (MRI) - to localize bony landmarks near the knee joint. Secondly, the impact of the educational level of the assessor - medical master students, orthopedic residents, and orthopedic surgeons - on the precision with which landmarks near the knee joint could be localized was analyzed.

METHODS

We included a total of 77 participants: 62 medical master students, 10 orthopedic residents, and 5 orthopedic surgeons to analyze three cadaver legs. Every participant localized a series of sixteen bony landmarks on six different imaging modalities (CT, MRI, 3D-CT, 3D-MRI, VR-CT, VR-MRI).

RESULTS

Concerning the imaging modality, the inter- and intra-observer variability were lowest for 3D and VR, higher for MRI (respectively 7.6 mm and 6.9 mm), and highest for CT (respectively 9 mm and 8.7 m).Concerning the educational level of the assessor, inter- and intra-observer variability in VR were lowest for surgeons, (respectively 3.2 mm and 3.6 mm), higher for residents (respectively 5.9 mm and 6.5 mm) and medical students (respectively 5.9 mm and 5.8 mm).

CONCLUSIONS

VR can be considered a reliable imaging technique. Localization of landmarks tends to be more precise in VR and on 3D than on conventional CT and MRI images. Furthermore, orthopedic surgeons localize landmarks more precisely than orthopedic residents and medical students in VR.

Osteochondritis Dissecans of the Knee Associated With Mechanical Overload

BACKGROUND

Osteochondritis dissecans (OCD) of the knee is a rare but potentially incapacitating disorder in which subchondral bone detaches, leading to an osteochondral fragment that can become unstable and progress into a loose body. The exact cause is unknown, although several biological and mechanical factors have been described.

PURPOSE

To provide insight into epidemiological data of a large cohort of patients affected by OCD of the knee and to identify potential factors contributing to the cause of this disorder.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

A total of 236 patients (259 knees) affected by OCD were included in our Knee Registry (2005-2022) and retrospectively analyzed. Patient characteristics were extracted from the medical records. Location and International Cartilage Regeneration & Joint Preservation Society grade (1-4) of OCD were assessed using magnetic resonance imaging. If available, a full-leg standing radiograph was used to assess alignment. Additionally, a statistical scoring system for instability risk was created.

RESULTS

A total of 263 OCD lesions were identified in 259 knees, 66.2% on the medial femoral condyle (MFC), 26.6% on the lateral femoral condyle (LFC), 3.8% on the trochlea, 2.7% on the patella, and 0.8% on the lateral tibia plateau. Male patients made up 57.6% of the sample, which had a mean age of 21.8 years. A very high percentage of patients (77.1%; n = 182) practiced sports, of whom 67.6% (n = 123) were engaged in high-impact sports. The location of the OCD lesions and the leg alignment (n = 110) were significantly correlated: MFC lesions were associated with more varus than valgus alignment (47.5% vs 11.3%) and patients with LFC lesions had more valgus than varus alignment (46.7% vs 20.0%; P = .002). Based on age, smoking, sports activity, and preceding trauma, a multivariable scoring system (0-11 points) was created. An increased risk of lesion instability was associated with an increased score: 29.0% at 0 points and 97.0% at 11 points.

CONCLUSION

This study provides detailed epidemiological data for 236 patients affected by OCD of the knee. Older age, smoking, inactivity, and preceding trauma were predictive for instability of OCD lesions. There was an association between OCD of the MFC and varus malalignment and between OCD of the LFC and valgus malalignment. This finding, in combination with the high percentage of patients practicing high-impact sports, suggests an important role for mechanical overload in the pathogenesis of OCD.

Effectiveness of Kinematic Alignment-Total Knee Arthroplasty in Treating Preoperative Varus and Valgus Deformities in Patients With Knee Osteoarthritis

Knee osteoarthritis (OA) is surgically treated with total knee arthroplasty (TKA). Traditionally, TKA has been performed using a mechanical alignment (MA) philosophy. However, due to significant patient dissatisfaction with surgical outcomes, an alternate alignment approach, kinematic alignment (KA), has gained popularity. KA-TKAs have improved functional patient outcomes by restoring the patient's native joint line orientation and minimizing soft tissue releases compared to neutral alignment in MA-TKAs. This review explores the postoperative effectiveness of utilizing KA-TKA to treat knee OA in patients with preoperative varus and valgus deformities. A comprehensive literature search was conducted on PubMed and Biomed Central databases, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The literature search focused on studies analyzing the postoperative TKA outcomes in knee OA patients with preoperative varus or valgus deformities whose surgeries followed a KA philosophy and those comparing KA-TKA with MA-TKA. The available clinical evidence indicates that KA-TKA can be a viable treatment option for individuals with knee OA. The alignment of phenotypes has little clinical significance concerning functional outcomes and implant survival rates following KA-TKA. Furthermore, surgery outcomes in patients with preoperative deformities who underwent KA-TKA were similar to those who underwent MA-TKA. KA-TKA produced significantly better functional outcomes than MA-TKA in certain aspects. However, studies with larger sample sizes and more extended follow-up periods that directly compare KA-TKA with MA-TKA in treating knee OA patients are needed to fully demonstrate the efficacy of each technique. Furthermore, further research into the effects of KA-TKA on implant survival rates will provide a better understanding of the benefits of this technique and ultimately lead to improved patient outcomes.

Functional alignment is associated with increased incidence of pre-balance, reduced soft-tissue release, and post-operative pain compared to mechanical alignment in patients undergoing simultaneous bilateral robotic-assisted TKA

This study aimed to compare two alignment strategies in the same patient undergoing simultaneous bilateral robotic-assisted TKA (SB-RATKA): mechanical alignment (MA), the gold-standard, and functional alignment (FA), a balance-driven, personalized alignment strategy. The outcome measures included quantitative assessment of soft-tissue release, incidence of knee balance, and post-operative pain. This was a prospective, self-controlled, randomized-controlled trial involving 72 patients who underwent SB-RATKA using the MAKO® robotic system with comparable grades of deformity and pain in both knees. 65 patients were finally included with one alignment strategy done per knee, with the patients blinded to the strategy used. The study recorded the additional soft-tissue releases required, incidence of pre-balance, and daily post-operative VAS pain scores. The mean age of the study population was 57.95 years, with a female preponderance (N = 53, 81.6%). MA group had significantly more medial compartment tightness in both flexion (MA-15.6 ± 1.8; FA-17 ± 1.3) and extension (MA-14.9 ± 1.9; FA-17 ± 1.1) (p < 0.0001) compared to the FA group after dynamic balancing. 66% of knees in the FA group (N = 43) achieved pre-balance compared to 32.3% in the MA group (N = 21) (p < 0.0001). VAS scores showed a significant reduction in pain in the FA group up to 72 h post-surgery (p < 0.0001). The requirement for posteromedial release (PM), posterior capsular (PC) release, tibial reduction osteotomy (TRO), and superficial MCL pie crusting (sMCL) were significantly lower in FA (PM-22, PC-13, TRO-8, sMCL-2) compared to MA (PM-44, PC-29, TRO-18, sMCL-8). Functional alignment strategy consistently resulted in a higher incidence of knee balance with a significant reduction in soft-tissue releases and immediate post-operative pain when compared to MA in the same patient undergoing SB-RATKA. Therapeutic Level 1.

Definitions and consequences of current alignment techniques and phenotypes in total knee arthroplasty (TKA) - there is no winner yet

Dissatisfaction following total knee arthroplasty (TKA) has been extensively documented and it was attributed to numerous factors. In recent years, significant focus has been directed towards implant alignment and stability as potential causes and solutions to this issue. Surgeons are now exploring a more personalized approach to TKA, recognizing the importance of thoroughly understanding each individual patient's anatomy and functional morphology. A more comprehensive preoperative analysis of alignment and knee morphology is essential to address the unresolved questions in knee arthroplasty effectively. The crucial task of determining the most appropriate alignment strategy for each patient arises, given the substantial variability in bone resection resulting from the interplay of phenotype and the alignment strategy chosen. This review aims to comprehensively present the definitions of different alignment techniques in all planes and discuss the consequences dependent on knee phenotypes.Level of evidence V.

Fostering Excellence in Knee Arthroplasty: Developing Optimal Patient Care Pathways and Inspiring Knowledge Transfer of Advanced Surgical Techniques

Osteoarthritis of the knee is common. Early sports trauma or cartilage defects are risk factors for osteoarthritis. If conservative treatment fails, partial or total joint replacement is often performed. A joint replacement aims to restore physiological biomechanics and the quality of life of affected patients. Total knee arthroplasty is one of the most performed surgeries in musculoskeletal medicine. Several developments have taken place over the last decades that have truly altered the way we look at knee arthroplasty today. Some of the fascinating aspects will be presented and discussed in the present narrative review.

[A multicenter randomized controlled trial of domestic robot-assisted and conventional total knee arthroplasty]

Objective

To investigate the accuracy, safety, and short-term effectiveness of a domestic robot-assisted system in total knee arthroplasty (TKA) by a multicenter randomized controlled trial.

Methods

Between December 2021 and February 2023, 138 patients with knee osteoarthritis who received TKA in 5 clinical centers were prospectively collected, and 134 patients met the inclusion criteria were randomly assigned to either a trial group ( n=68) or a control group ( n=66). Seven patients had lost follow-up and missing data, so they were excluded and the remaining 127 patients were included for analysis, including 66 patients in the trial group and 61 patients in the control group. There was no significant difference ( P>0.05) in gender, age, body mass index, side, duration of osteoarthritis, Kellgren-Lawrence grading, preoperative Knee Society Score (KSS) and Western Ontario and McMaster University Osteoarthritis Index (WOMAC) score between the two groups. The trial group completed the TKA by domestic robot-assisted osteotomy according to the preoperative CT-based surgical planning. The control group was performed by traditional osteotomy plate combined with soft tissue release. Total operation time, osteotomy time of femoral/tibial side, intraoperative blood loss, and postoperative complications were recorded and compared between the two groups. The radiographs were taken at 5 and 90 days after operation, and hip-knee-ankle angle (HKA), lateral distal angle of femur (LDFA), and posterior tibial slope (PTS) were measured. The difference between the measured values of the above indexes at two time points after operation and the preoperative planning target values was calculated, and the absolute value (absolute error) was taken for comparison between the two groups. The postoperative recovery of lower limb alignment was judged and the accuracy was calculated. KSS score and WOMAC score were used to evaluate the knee joint function of patients before operation and at 90 days after operation. The improvement rates of KSS score and WOMAC score were calculated. The function, stability, and convenience of the robot-assisted system were evaluated by the surgeons.

Results

The total operation time and femoral osteotomy time of the trial group were significantly longer than those of the control group ( P<0.05). There was no significant difference in the tibial osteotomy time and the amount of intraoperative blood loss between the two groups ( P>0.05). The incisions of both groups healed by first intention after operation, and there was no infection around the prosthesis. Nine patients in the trial group and 8 in the control group developed lower extremity vascular thrombosis, all of which were calf intermuscular venous thrombosis, and there was no significant difference in the incidence of complications ( P>0.05). All patients were followed up 90 days. There was no significant difference in KSS score and WOMAC score between the two groups at 90 days after operation ( P>0.05). There was significant difference in the improvement rate of KSS score between the two groups ( P<0.05), while there was no significant difference in the improvement rate of WOMAC score between the two groups ( P>0.05). Radiological results showed that the absolute errors of HKA and LDFA in the trial group were significantly smaller than those in the control group at 5 and 90 days after operation ( P<0.05), and the recovery accuracy of lower limb alignment was significantly higher than that in control group ( P<0.05). The absolute error of PTS in the trial group was significantly smaller than that in the control group at 5 days after operation ( P<0.05), but there was no significant difference at 90 days between the two groups ( P>0.05). The functional satisfaction rate of the robot-assisted system was 98.5% (65/66), and the satisfaction rates of stability and convenience were 100% (66/66).

Conclusion

Domestic robot-assisted TKA is a safe and effective surgical treatment for knee osteoarthritis, which can achieve favorable lower limb alignment reconstruction, precise implant of prosthesis, and satisfactory functional recovery.

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.

Human femur fracture by mechanical compression: Towards the repeatability of bone fracture acquisition

The increase in life expectancy combined with greater bone fragility over the years is causing a rise in the bone fracture cases. Femur fractures are the most important due to their high mortality rate. This multidisciplinary work is carried out in this context and focuses on the experimental reproduction of human femur fractures by compression. We describe a sequence of steps supervised by orthopaedic surgeons for the correct arrangement of specimens on the system set up to perform the experiment. The device applies force by compression until the human bone is fractured. All tests performed have been monitored and evaluated from different knowledge perspectives. The results obtained have demonstrated the repeatability of the fracture type in a controlled environment as well as identifying the main features involved in this process. In addition, the fractured bones have been digitized to analyze the fracture zone to recreate and evaluate future simulations.

A novel instrument for ligament balancing: a biomechanical study in human cadaveric knees

PURPOSE

Ligament balancing is a prerequisite for good function and survival in total knee arthroplasty (TKA). Various balancing techniques exist, but none have shown superior results. The pie-crusting technique by Bellemans of the medial collateral ligament is commonly utilized; however, it can be difficult to achieve repeatable ligament lengthening with this technique. Therefore, we invented a novel instrument to standardize the pie-crusting technique of the superficial and deep medial collateral ligament (hereafter MCL). The purpose was to examine if pie-crusting with the instrument could produce repeatable ligament lengthening.

METHODS

The MCL was isolated in 16 human cadaveric knees, and subjected to axial tension. The instrument was composed of a specific grid of holes in rows, used to guide sequential pie-crusting puncturing of the MCL with a Ø1.6 mm end-cutting cannula. Ligament lengthening was measured after each row of punctures. Regression analysis was performed on the results.

RESULTS

Mean lengthening ± SD in human cadaveric MCL for puncturing of row 1 in the instrument was 0.06 ± 0.09 mm, 0.06 ± 0.04 mm for row 2, 0.09 ± 0.08 mm for row 3, 0.06 ± 0.05 mm for row 4 and 0.06 ± 0.04 mm for row 5, giving a mean total lengthening of 0.33 ± 0.20 mm. Linear regression revealed that MCLs were repeatably lengthened by 0.07 mm per row when punctured using the instrument.

CONCLUSIONS

MCLs showed linear lengthening in human cadavers for subsequent use of the instrument. Our instrument shows promising results for repeatable ligament lengthening.

Shear's role in non-union. Measuring mean angle of long bone multi-fragmentary non-unions

INTRODUCTION

Both mechanical and biological theories have been proposed in the development of non-union. The mechanical theory suggests that a high strain environment in a fracture will predispose it to non-union. While in simple fractures and wedge fractures there are only one and two primary fracture planes respectively, in multi-fragmentary fractures there are many and a non-union may form along any of the original fracture lines, however the plane which experiences the highest strain is at 45O - the shear plane. We hypothesise that in multi-fragmentary fractures the initial fracture line that most often fails to unite will tend towards the plane with the highest strain.

OBJECTIVES

1) Define the mean non-union angle in a cohort of multi-fragmentary tibial and femoral fractures. 2) In wedge-like fractures within the cohort, define and compare the mean angle of initial fracture planes which go on to form a non-union to those that unite 3) In comminuted fractures within the cohort, define the mean non-union angle DESIGN: Retrospective cohort study SETTING: Level-1 trauma centre METHODOLOGY: Fractures were categorised into wedge-like and comminuted. A published technique was utilised to measure fracture and non-union angles. In wedge-like fractures, united and non-united initial planes were compared. In comminuted fractures only the mean non-union angle was defined. Demographic patient data was also collected.

RESULTS

183 non-unions were screened, 68 patients were included. The mean non-union angle was 56°(SD 18) across all fractures. In wedge-like fractures the mean non-union angle was 59°(SD 18). In comminuted fractures the mean non-union angle was 50°(SD 19). Non-united initial fracture planes in wedge-like fractures showed a peaked distribution about a mean of 58° while united fracture planes were distributed at the extremities of the range.

CONCLUSIONS

In patients with multi-fragmentary fractures resulting in non-union, the mean tibial non-union angle was 52° while the mean femoral non-union angle was 65°. In wedge-like fractures, non-unions occurred more commonly than appropriate union in fractures between 41°-80°. The non-union angle is closer to 45° in comminuted fractures than in wedge-like fractures. These results support the mechanical theory that strain from the shear plane is an important factor in the formation of non-unions.

LEVEL OF EVIDENCE

Prognostic level 3.

Anatomical variations of the equine femur and tibia using statistical shape modeling

The objective of this study was to provide an overarching description of the inter-subject variability of the equine femur and tibia morphology using statistical shape modeling. Fifteen femora and fourteen tibiae were used for building the femur and tibia statistical shape models, respectively. Geometric variations in each mode were explained by biometrics measured on ±3 standard deviation instances generated by the shape models. Approximately 95% of shape variations within the population were described by 6 and 3 modes in the femur and tibia shape models, respectively. In the femur shape model, the first mode of variation was scaling, followed by notable variation in the femoral mechanical-anatomical angle and femoral neck angle in mode 2. Orientation of the femoral trochlear tubercle and femoral version angle were described in mode 3 and mode 4, respectively. In the tibia shape model, the main mode of variation was also scaling. In mode 2 and mode 3, the angles of the coronal tibial plateau and the medial and lateral caudal tibial slope were described, showing the lateral caudal tibial slope angle being significantly larger than the medial. The presented femur and tibia shape models with quantified biometrics, such as femoral version angle and posterior tibial slope, could serve as a baseline for future investigations on correlation between the equine stifle morphology and joint disorders due to altered biomechanics, as well as facilitate the development of novel surgical treatment and implant design. By generating instances matching patient-specific femorotibial joint anatomy with radiographs, the shape model could assist virtual surgical planning and provide clinicians with opportunities to practice on 3D printed models.

Accuracy of Intraoperative Mechanical Axis Alignment to Long-Leg Radiographs following Robotic-Arm-Assisted Unicompartmental Knee Arthroplasty

Improper alignment and implant positioning following unicompartmental knee arthroplasty (UKA) has been shown to lead to postoperative pain and increase the incidence of revision procedures. The use of robotic-arm assistance for UKA (RAUKA) has become an area of interest to help overcome these challenges. The accuracy of intraoperative alignment compared with standing long-leg X-rays postoperatively following medial RAUKA has been in question. Therefore, the purpose of this study was to (1) determine final mean intraoperative coronal alignment in extension utilizing an image based intraoperative navigation system, and (2) compare final intraoperative alignment to 6-week weight-bearing (WB) long-leg X-rays. Patients who underwent RAUKA for medial compartmental osteoarthritis were identified from January 1, 2018, to August 31, 2019, through our institution's joint registry. The query yielded 136 (72 right and 64 left) patients with a mean age of 72.02 years and mean body mass index (BMI) of 28.65 kg/m2 who underwent RAUKA. Final intraoperative alignment was compared with WB long leg X-rays 6 weeks postoperatively by measuring the mechanical alignment. Statistical analysis was primarily descriptive. Pearson's correlation coefficient was used to determine the relationship between intraoperative alignment to 6-week alignment. A p-value of <0.05 was considered statistically significant. Mean intraoperative coronal alignment after resections and trialing was 4.39 varus ± 2.40 degrees for the right knee, and 4.81 varus ± 2.29 degrees for the left knee. WB long-leg X-rays 6 weeks postoperatively demonstrated mechanical axis alignment for the right and left knees to be 3.01 varus ± 2.10 and 3.7 varus ± 2.38 degrees, respectively. This resulted in a change in alignment of 1.36 ± 1.76 and 1.12 ± 1.84 degrees for the right and left knees, respectively (p < 0.05). Pearson's correlation coefficient demonstrated a correlation of 0.69 between intraoperative to long-leg-X-ray alignment. RAUKA demonstrates excellent consistency when comparing postoperative WB long-leg X-rays to final intraoperative image-based non-WB alignment.

Coronal alignment in total knee arthroplasty: a review

Total knee arthroplasty (TKA) alignment has recently become a hot topic in the orthopedics arthroplasty literature. Coronal plane alignment especially has gained increasing attention since it is considered a cornerstone for improved clinical outcomes. Various alignment techniques have been described, but none proved to be optimal and there is a lack of general consensus on which alignment provides best results. The aim of this narrative review is to describe the different types of coronal alignments in TKA, correctly defining the main principles and terms.

Combined Femoral Osteotomy and Contralateral Hip Arthroplasty to Correct Limb Alignment and Arthritis in a Scoliosis and Polio Patient: A Case Report

We describe the first case of a 62-year-old female symptomatic patient with multiple comorbidities presenting with coronal limb malalignment due to scoliosis and osteoarthritis who underwent a combined total hip arthroplasty and biplane opening wedge osteotomy of the distal femur in one procedure. It is essential to realize that in patients who present with multiple comorbidities, combining different established procedures should be considered as a therapeutic option. We detail the operative procedure, preoperative considerations, and postoperative rehabilitation. By reviewing the literature on operative techniques, we highlight how our findings can be applied to similar cases with multiple comorbidities. Our report underscores the importance of considering combined procedures as a viable therapeutic option for patients with complex medical histories.

Pre-Planning the Surgical Target for Optimal Implant Positioning in Robotic-Assisted Total Knee Arthroplasty

Robotic-assisted total knee arthroplasty can attain highly accurate implantation. However, the target for optimal positioning of the components remains debatable. One of the proposed targets is to recreate the functional status of the pre-diseased knee. The aim of this study was to demonstrate the feasibility of reproducing the pre-diseased kinematics and strains of the ligaments and, subsequently, use that information to optimize the position of the femoral and tibial components. For this purpose, we segmented the pre-operative computed tomography of one patient with knee osteoarthritis using an image-based statistical shape model and built a patient-specific musculoskeletal model of the pre-diseased knee. This model was initially implanted with a cruciate-retaining total knee system according to mechanical alignment principles; and an optimization algorithm was then configured seeking the optimal position of the components that minimized the root-mean-square deviation between the pre-diseased and post-operative kinematics and/or ligament strains. With concurrent optimization for kinematics and ligament strains, we managed to reduce the deviations from 2.4 ± 1.4 mm (translations) and 2.7 ± 0.7° (rotations) with mechanical alignment to 1.1 ± 0.5 mm and 1.1 ± 0.6°, and the strains from 6.5% to lower than 3.2% over all the ligaments. These findings confirm that adjusting the implant position from the initial plan allows for a closer match with the pre-diseased biomechanical situation, which can be utilized to optimize the pre-planning of robotic-assisted surgery.

Closed-leg standing long leg radiographs can be a useful tool to assess whether the joint line is parallel to the ground in restricted kinematic alignment total knee arthroplasty

PURPOSE

Restricted kinematic alignment (rKA) is a modified technique of kinematic alignment (KA) total knee arthroplasty (TKA) for patients with an outlier or atypical knee anatomy, striving to preserve the native knee joint line parallel to the ground in a bipedal stance. This study aimed to evaluate the accuracy of rKA TKA with a computed tomography (CT)-based patient-specific instrument (PSI) to achieve the preoperative plan with the joint line parallel to the ground level.

METHODS

Using a CT-based PSI, 74 closed-leg standing long-leg radiographs were obtained before and after rKA TKA. The hip-knee-ankle angle (HKA), joint line orientation angle (JLOA), lateral distal femoral angle (LDFA), and medial proximal tibial angle (MPTA) were measured. Bone resection accuracy was evaluated by postoperative HKA deviations from the planned alignment and joint line by postoperative JLOA deviations from the ground level.

RESULTS

The mean postoperative JLOA and HKA were 2.1° valgus (range, standard deviation: 6.0° valgus to 3.0° varus, 2.0) and 2.6° varus (3.5° valgus to 12.5° varus, 3.2), respectively. Postoperative JLOA and HKA were within ± 3° of the planned alignment for 69% and 86% of cases, respectively.

CONCLUSIONS

Despite a static verification, we clarified how the joint line after rKA TKA was reproduced in the closed-leg long leg radiographs to mimic the limb position during gait. However, this imaging method is not well-established, and lack of long-term survivorship and the relationship between joint line inclination and clinical outcomes represented limitations of this study.

LEVEL OF EVIDENCE

Level IV.

Achieving functional alignment in total knee arthroplasty: early experience using a second-generation imageless semi-autonomous handheld robotic sculpting system

PURPOSE

In order to minimize errors during achieving the targeted alignment of the total knee arthroplasty (TKA) components, robotic-assisted surgery has been introduced with the aim to help surgeons to improve implant survival, clinical outcomes, and patient satisfaction. The primary goal of this paper is to highlight surgical tips and tricks on how to achieve functional alignment (FA) through intra-operative boney mapping, numeric gap, and alignment data, using the next generation of imageless robotic surgical systems.

METHOD

This retrospective case-series contains planned and achieved data on the FA and joint gap data obtained from 526 patients captured and assessed with use of a semi-autonomous imageless handheld robotic sculpting systems. All patients were operated upon by two experienced TKA surgeons.

RESULTS

The mean difference between planned and achieved alignment was 1.46° (≥ 7° varus group), 1.02° (< 7° varus group), 1.16° (< 7° valgus group), and 1.43° (≥ 7° valgus group). The mean observed planned and achieved extension and flexion gaps were below 1.47 mm for medial extension gaps, 1.12 mm for the lateral extension gaps, 1.4 mm for the medial flexion gaps, and 1.16 mm for the lateral flexion gaps.

CONCLUSION

Analysis of these first cases highlights the capability of the next generation of imageless robotic-assisted total knee replacement using a semi-autonomous handheld robotic sculpting to maintain accuracy of the desired alignment. The system allows the surgeon to choose freely their own alignment philosophy while maintaining efficiency.

Prevalence of extra-articular tibia valga morphology in valgus knees and its implications for primary total knee arthroplasty

INTRODUCTION

Tibia valga, an extra-articular valgus deformity of the tibia, is common in valgus knees and can result in component misplacement and early total knee arthroplasty (TKA) failure. However, the prevalence and importance of tibia valga in TKA have been seldom reported. This study aims to describe the prevalence and characteristics of tibia valga morphology in valgus knees and describe implications for surgical planning in primary TKA.

METHODS

We prospectively examined pre-operative weightbearing whole-body EOS digital radiographs of patients with knee osteoarthritis listed for TKA between December 2018 and December 2020. Hip-knee-ankle angle (HKA), mechanical lateral distal femoral angle (mLDFA), mechanical medial proximal tibial angle (mMPTA), joint line convergence angle (JLCA) and tibial morphology with centre of rotation of angulation of tibia (CORA-tibia) were measured and analysed.

RESULTS

In 830 knees, 253 (30%) and 577 (70%) were classified as valgus and varus, respectively. In valgus knees, 89 knees (35%) had tibia valga. Median CORA-tibia was 2.8° (range 0.2°-10.9°). Tibia valga knees had no difference in mLDFA, higher HKA (5.0^o versus 3.0°, p = 0.002) and mMPTA (89.6° versus 88.1°, p < 0.01), and lower JLCA (2.1° versus 2.3°, p < 0.01) compared to non-tibia valga knees. Tibia valga deformity was weakly positively correlated with valgus HKA (ρ = 0.23, p < 0.001) and mMPTA (ρ = 0.38, p < 0.001). In varus knees, there were 52 cases of tibia valga (9%) with median CORA-tibia of 3.0° (range 0.5°-5.5°). Tibia valga knees had higher mMPTA (87.0° versus 85.2°, p < 0.05) and no difference in HKA, mLDFA and JLCA. CORA-tibia was weakly positively correlated with mMPTA.

CONCLUSIONS

Valgus knees may have an extra-articular deformity of the tibia which might be the primary contributor of the overall valgus HKA deformity rather than the distal femoral anatomy. To detect the deformity, full leg-length radiographs should be acquired pre-operatively. Intramedullary instrumentation should be used cautiously in knees with tibia valga when performing TKA.

Functional knee apparatus for the evaluation of ligamentous tensions on contact loads

BACKGROUND

Soft tissue balancing is integral in providing stability following total knee arthroplasty (TKA). Although intraoperative contact load sensors are providing insights into the effects of soft tissue balancing, there is still a lack of understanding of the relationship between the knee's ligamentous tensions and joint surface contact loads. This study reports on the development of a multifunctional testing apparatus that can quantify the effects of ligamentous tension on joint contact loads in a controlled repeatable environment.

METHODS

The functional knee apparatus was constructed to act as an anatomical substitute for the benchtop assessment of intraoperative soft tissue balancing. The system was calibrated through reproduction of results from a cadaveric study that employed intraoperative load sensors. Experimentation was then conducted to quantify the effects of tensile pretension variation on measured contact loads throughout the full range of flexion.

RESULTS

A linear relationship between the ligamentous tensions and contact loads was observed, with ligaments contributing to 74-80% of the measured contact loads. Ligamentous tensions could be approximated from measured contact loads to within ± 23 N.

CONCLUSION

The proposed apparatus can prove to be a valuable tool in the continued exploration of currently undocumented effects (e.g. surgical alteration) in soft tissue balancing. In addition to quantifying the relationship between ligamentous tensions and joint contact loads, soft tissue loading conditions where bicondylar contact was lost (i.e. known sign of kinematic instability) were identified. As a corollary, this system may be able to provide insights on soft tissue balancing standards predictive of patient outcomes.

Accelerometer-Based Navigation versus Conventional Total Knee Arthroplasty for Posttraumatic Knee Osteoarthritis

BACKGROUND

Posttraumatic osteoarthritis (PTOA) frequently comprises femoral or tibial deformity, which makes it difficult to perform total knee arthroplasty (TKA). Accelerometer-based navigation (ABN) could be effective in restoring a neutral mechanical axis (MA) in TKA, but a limited number of studies have been reported in association with PTOA. Therefore, we aimed to compare the lower limb MA between ABN-assisted TKA (ABN-TKA) and conventional TKA in patients with PTOA.

METHODS

We conducted a retrospective analysis of 28 PTOA patients who underwent TKA using a conventional system (cTKA group, n = 16) and the ABN system (iTKA group, n = 12). Standing long-leg radiographs were assessed for MA and prosthesis alignment as primary outcomes. A postoperative MA deviating beyond ± 3° was defined as an outlier. Perioperative outcomes, Oxford Knee Score (OKS) at 2-year follow-up, and complications were also assessed.

RESULTS

The cTKA group and the iTKA group had a mean age of 63.07 years and 65.25 years, respectively. The iTKA group had significantly better MA accuracy when compared to the cTKA group (1.60° ± 2.09° vs. 3.59° ± 1.34°, p = 0.01). The iTKA group showed significantly less MA outlier than the cTKA group (78.6% vs. 25.0%, p = 0.02). The prosthesis alignment and OKS were comparable between the groups. There were 2 periprosthetic joint infections in the cTKA group and 1 periprosthetic fracture of the distal femur in the iTKA group.

CONCLUSIONS

For PTOA of the knee, both conventional TKA and ABN-TKA significantly improved the postoperative mechanical alignment and functional outcomes. The ABN-TKA seemed to offer higher accuracy and less MA outlier when compared to conventional TKA, and thus ABN could be a good alternative option.

Comparison of Clinical Outcomes for Patients Treated With Gradually Reducing Radius Versus Single-Radius Total Knee Arthroplasty Systems

The choice of implant used for primary total knee arthroplasty (TKA) may have an impact on clinical outcomes. Clinical outcomes after TKA with gradually reducing radius implants (group G) vs single-radius implants (group S) were evaluated among Asian patients. This study included 541 patients (754 knees) in group G and 187 patients (275 knees) in group S. Range of motion (ROM), flexion contracture, American Knee Society Knee and American Knee Society Function scores (KSKS and KSFS, respectively), and mechanical and anatomic tibiofemoral angles (MTFA and ATFA, respectively) were evaluated with electronic medical records. In univariate analysis, improvements in ROM, KSKS, and KSFS were significantly better in group G compared with group S at 1-year follow-up. Multivariable analyses showed greater ROM (4.52°, P=.002), decreased flexion contracture (-2.80°, P=.011), and improved KSKS (15.57, P<.001) at 1 year for group G vs group S. No significant differences in KSFS, MTFA, or ATFA were observed. Implant-related complications and radiologic loosening were not identified in either group at 2-year follow-up. The TKA implants with a gradually reducing radius showed greater 1-year improvements in ROM, flexion contracture, KSKS, and similar implant-related safety outcomes compared with a single-radius system. [Orthopedics. 2022;45(6):367-372.].

Fixed 6° distal femoral cut consistently achieves neutral alignment for Asians, Caucasians, and Native Hawaiian/Pacific Islanders

BACKGROUND

Restoration of a neutral mechanical axis (MA) is important to the success of total knee arthroplasty (TKA). While known differences are present between Asians and Caucasians regarding native knee alignment, it is unknown whether such differences exist amongst Native Hawaiian/Other Pacific Islanders (NHPI) or if utilizing a fixed distal femoral cut of 6° can consistently achieve a neutral MA in these minority racial groups. This study examines the preoperative deformities presented by Asians, Caucasians, and NHPI, and the resulting knee alignment achieved following TKA when a fixed 6° distal femoral cut is targeted for all patients.

METHODS

Preoperative and postoperative MA was measured from 835 Asian, 447 Caucasian, and 163 NHPI hip-to-ankle radiographs. All patients underwent TKA in which a standard distal femoral cut of 6° valgus was targeted for all patients. Data were evaluated as continuous variables and by groupings of varus (MA < - 3°), valgus (MA > 3°), and neutral (- 3° ≤ MA ≤ 3°) alignment.

RESULTS

Preoperative deformity ranged from 38° varus to 29° valgus. The proportion of Asian and NHPI presenting with varus alignment prior to surgery was significantly greater than Caucasian patients in both males (Asians: 80.6%; Caucasians: 67.0%; NHPI: 79.0%, p = 0.001) and females (Asians: 66.1%; Caucasians: 45.7%; NHPI: 63.2%, p < 0.001). There was no difference in the proportion of patients (72-79%) achieving a neutral MA amongst all three racial groups.

CONCLUSION

NHPI appear to have similar preoperative deformities to Asians with both groups having significantly more varus alignment than Caucasians. Despite a wide range of preoperative deformity, application of a fixed distal femoral cut of 6° valgus successfully established a neutral MA equally in the majority of patients across all three racial groups.

Surgical principles for complex primary total knee arthroplasty in the presence of extra-articular deformity

Background

Accurate restoration of alignment is vital to the success of a total knee arthroplasty (TKA) procedure. Deformities, whether these are intra-articular and/or extra-articular AND/OR whether these are uniplanar/multiplanar/complex, can impose varying technical challenges in surgical planning and execution. Literature on performing TKA in presence of limb deformity is limited, especially for extra-articular deformities.

Objectives

The objectives of this narrative review are twofold. Firstly, we analyse the existing English literature for studies focussed on TKA and deformity correction and summarise the important points about deformity pathomechanics, clinical and radiological assessment, pre-operative planning and surgical techniques. The second objective is to provide the readers with a simplistic and wholistic management algorithm to assist surgeons in meticulous planning to tackle the technical challenges imposed by lower limb deformities while performing a TKA.

Discussion

Approach to each patient must be holistic and customised on an individual basis according to patient characteristics, deformity characteristics and surgeon experience. The three main options available are: (1) Primary TKA (symmetric cuts/asymmetric cuts with/without computer navigation assistance) (2) Single stage corrective osteotomy and TKA and (3) Two-staged deformity correction and TKA. A multi-disciplinary team approach is required and a knee surgeon well-versed in revision arthroplasty and a limb reconstruction surgeon specialising in deformity correction, should be involved from the outset. The use of computer navigation technology, particularly for deformity correction and TKA, has increased over the last couple of decades and is recommended by the authors for these challenging cases.

Robot-assisted total knee arthroplasty improves mechanical alignment and accuracy of component positioning compared to the conventional technique

Purpose

The purpose of this study was to compare the mechanical axis, accuracy of component positioning, and polyethylene liner thickness between robot-assisted total knee arthroplasty (TKA) and conventional TKA.

Methods

From July 2020 to December 2020, 154 TKAs were performed in 110 patients with Kellgren-Lawrence grade IV varus knees using a robot-assisted system (MAKO group). Additionally, 110 propensity score-matched patients who had undergone primary conventional TKA were chosen in a one-to-one ratio for the conventional group. Post-operative radiographs were used to evaluate mechanical axis and component coronal and sagittal positioning. The polyethylene liner thickness was investigated. The respective mean error values and outliers were obtained for the two study groups and were compared to determine the mechanical axis and the accuracy of the postoperative component positioning.

Results

Patients in the MAKO group achieved better accuracy than those in the conventional group in terms of postoperative mean mechanical axis (1.9˚ vs. 2.8˚, p < 0.05), femur coronal inclination (91.2˚ vs. 91.8˚, p < 0.05), tibia coronal inclination (90.8˚ vs. 91.1˚, p < 0.05), and tibia sagittal inclination (90.7˚ vs. 91.7˚, p < 0.05). However, there was no difference between the two groups in polyethylene liner thickness.

Conclusions

Robot-assisted TKA showed improved mechanical axis and higher accuracy of component positioning compared to the conventional TKA technique, with no significant difference in polyethylene liner thickness between the two groups. Long-term follow-up studies are needed to compare the clinical outcomes of robot-assisted TKA.

Level of evidence

IV.

Cadaveric Biomechanical Evaluation of Capsular Constraint and Microinstability After Hip Capsulotomy and Repair

Background:

It remains unclear if capsular management contributes to iatrogenic instability (microinstability) after hip arthroscopy.

Purpose:

To evaluate changes in torque, stiffness, and femoral head displacement after capsulotomy and repair in a cadaveric model.

Study Design:

Controlled laboratory study.

Methods:

A biomechanical analysis was performed using 10 cadaveric hip specimens. Each specimen was tested under the following conditions: (1) intact, (2) portals, (3) interportal capsulotomy (IPC), (4) IPC repair, (5) T-capsulotomy (T-cap), (6) partial T-cap repair, and (7) T-cap repair. Each capsular state was tested in neutral (0°) and then 30°, 60°, and 90° of flexion, with forces applied to achieve the displacement-controlled baseline limit of external rotation (ER), internal rotation (IR), abduction, and adduction. The resultant end-range torques and displacement were recorded.

Results:

For ER, capsulotomies significantly reduced torque and stiffness at 0°, 30°, and 60° and reduced stiffness at 90°; capsular repairs failed to restore torque and stiffness at 0°; and IPC repair failed to restore stiffness at 30° (P < .05 for all). For IR, capsulotomies significantly reduced torque and stiffness at 0°, 30°, and 60° and reduced stiffness at 90°; and capsular repairs failed to restore torque or stiffness at 0°, 30°, and 60° and failed to restore stiffness at 90° (P < .05 for all). For abduction, IPC significantly decreased torque at 60° and 90° and decreased stiffness at all positions; T-cap reduced torque and stiffness at all positions; IPC repair failed to restore stiffness at 0° and 90°; and T-cap repair failed at 0°, 60°, and 90° (P < .05 for all). For adduction, IPC significantly reduced torque at 0° and reduced stiffness at 0° and 30°; T-cap reduced torque at 0° and 90° and reduced stiffness at all positions; IPC repair failed to restore stiffness at 0° and 90°; and T-cap repair failed at 0°, 60°, and 90° (P < .05 for all). There were no statistically significant femoral head translations observed in any testing configurations.

Conclusion:

Complete capsular repair did not always restore intact kinematics, most notably at 0° and 30°. Despite this, there were no significant joint translations to corroborate concerns of microinstability.

Clinical Relevance:

Caution should be employed when applying rotational torques in lower levels of flexion (0° and 30°).

Correlation between component alignment and short-term clinical outcomes after total knee arthroplasty

OBJECTIVE

This study aimed to investigate the correlation between component alignment and short-term clinical outcomes after total knee arthroplasty (TKA).

METHODS

50 TKA patients from a regional hospital were enrolled in the study. The following component alignments were measured from radiological data acquired within 1 week after surgery: hip-knee-ankle angle (HKA), medial distal femoral angle (MDFA), medial proximal tibial angle (MPTA), femoral flexion-extension angle (FEA), tibial slope angle (TSA), femoral rotational angle (FRA) and tibial rotational angle (TRA). The Hospital for Special Surgery (HSS) knee scoring system was used to assess clinical outcomes after 1 year, with patients being divided into three groups (excellent, good and not good) according to the HSS scores. Difference analysis and linear correlation analysis were used for the statistical analysis.

RESULTS

The results showed significant differences in MDFA (p = 0.050) and FEA (p = 0.001) among the three patient groups. It was also found that the total HSS had only a moderate correlation with FEA (r = 0.572, p < 0.001), but FEA had a positive linear correlation with pain scores (r = 0.347, p = 0.013), function scores (r = 0.535, p = 0.000), ROM scores (r = 0.368, p = 0.009), muscle scores (r = 0.354, p = 0.012) and stability scores (r = 0.312, p = 0.028). A larger MDFA was associated with lower FE deformity scores (r = -0.289, p = 0.042) and the TSA had a positive influence on the ROM (r = 0.436, p = 0.002). Also, changes in FRA produced a consequent change in the FE deformity score (r = 0.312, p = 0.027), and the muscle strength scores increased as TRA increased (r = 0.402, p = 0.004).

CONCLUSION

The results show that the FEA plays a significant role in clinical outcomes after TKA. Surgical techniques and tools may need to be improved to accurately adjust the FEA to improve joint functionality and patient satisfaction.