Randomized Controlled Trial of Sensor-Guided Knee Balancing Compared to Standard Balancing Technique in Total Knee Arthroplasty

Enhancing soft tissue balance: Evaluating robotic-assisted functional positioning in varus knees across flexion and extension with quantitative sensor-guided technology

PURPOSE

Functional implant positioning (FIP) for total knee arthroplasty (TKA) is an evolution of kinematic alignment based on preoperative CT scan and robotic-assisted technology. This study aimed to assess the ligament balancing of image-based robotic-assisted TKA in extension, mid-flexion and flexion with an FIP using intraoperative sensor-guided technology. The hypothesis was that image-based robotic-assisted TKA performed by FIP would achieve ligament balancing all along the arc of knee flexion.

METHODS

This prospective monocentric study included 47 consecutive patients with varus knees undergoing image-based robotic-assisted TKA performed with FIP. After robotic-assisted bone cuts, trial components were inserted, and soft tissue balance was assessed using sensor-guided technology at 10°, 45° and 90° of knee flexion. A mediolateral balanced knee was defined by an intercompartmental pressure difference (ICPD) ≤ 15 lbf and medial and lateral compartment pressure ≤60 lbf. The mean age was 71.6 years old ±6.7, the mean BMI was 29.0 kg/m2 ± 4.9 and the mean preoperative HKA was 174° ± 5 [159; 183].

RESULTS

The mean postoperative knee alignment was 177.0° ± 2.2° [172; 181]. There were 93.6% of balanced knees (n = 44) at 10 and 90° of knee flexion versus 76.6% (n = 36) at 45° of knee flexion with a significant difference (p = 0.014). Median ICPD at 10, 45 and 90° of knee flexion were, respectively, 7.0 (interquartile range [IQR]: 9), 11.0 (IQR: 9.5) and 8.0 (IQR: 9.0). Pairwise analyses revealed differences for ICPD at 45° versus ICPD at 10° (p = 0.003) and ICPD at 90° versus ICPD at 45° (p = 0.007).

CONCLUSION

FIP with an image-based robotic-assisted system allowed the restoration of a well-balanced knee at 10° and 90° of flexion in varus knees. Nevertheless, some discrepancies occurred in midflexion, and more work is needed to understand ligament behaviour all along the arc of knee flexion.

LEVEL OF EVIDENCE

Level II.

SMART (self- monitoring analysis and reporting technology) and sensor based technology applications in trauma and orthopaedic surgery

Background

Innovations in implant designs and computer technology have led to the development of smart implants and prostheses in the field of orthopedics and trauma. Sensor-guided devices enable close monitoring of physical, chemical and biological environment around the implants, which has been purported to meliorate the intra-operative precision and post-operative surveillance of patients.

Objective

We evaluate the current applications of sensor-based technology in the management of patients with a spectrum of musculoskeletal conditions.

Material and methods

A thorough search of literature was performed on May 1, 2023, using the 5 databases (Embase, PubMed, Google Scholar, Cochrane Library and Web of Science) in order to identify suitable studies published between 2000 and 2023. All the studies which reported on SMART implants and Sensor based technology in the diverse sub-specialties of orthopedics like trauma, arthroplasty, spine surgery, infections, arthroscopy or sports medicine and paediatric orthopedics were considered. The keywords used for the search included 'Sensor technology', 'SMART implant' and "Orthopedics".

Results

Thirty articles were considered for this narrative review. A generation of SMART implants has been developed due to advancements in the microchip technology. Sensor based technology has been utilised in various subspecialties of arthroplasty (in assessing ligament balancing intra-operatively; or prosthetic loosening and gait analysis during follow-up), trauma surgery (as SMART instruments intra-operatively; or in the assessment of bone healing, distraction osteogenesis and functional recovery during follow-up), spine surgery (identification and protection of neural elements from iatrogenic injuries intra-operatively; and assessment of fusion across the instrumented levels during follow-up), paediatric orthopedics (compliance assessment for foot abduction orthosis in congenital talipes equinovarus), infection (monitoring of infection and biofilm formation), rehabilitation (gait analysis) and sports medicine (rotational stability and ligament compliance in patients with ligament injuries or reconstruction).

Conclusion

SMART implants and Sensor based technology have applications in the surgical planning, intra-operative performance, post-operative monitoring and patient surveillance diverse subspecialties of orthopedics and trauma. Future research in newer designs, cost-effective SMART implants and refinement of Sensor based technology will enhance Patient Related Outcome Measures (PROMs).

An electronic force sensor accurately detects increased but not decreased soft tissue tension in total knee arthroplasty

BACKGROUND

Postoperative knee instability is a leading cause of revision total knee arthroplasty (TKA). This study used a commercially available insert-shaped electronic force sensor to measure joint loads and facilitate ligament balance adjustment, and assessed the ability of this sensor to detect increased or decreased soft tissue tension during primary TKA.

METHODS

Changes in medial and lateral tibiofemoral joint loads during knee flexion were evaluated with sensor thicknesses ranging from 10 to 16 mm using six varus osteoarthritis cadaver knees with intact medial collateral ligaments (MCLs), and the measurements were repeated after MCL resection. Correlations between joint loads and maximum knee extension angle were also evaluated. To validate the efficacy of the sensor, the values were compared with those obtained using a conventional tension device.

RESULTS

For MCL-intact knees in extension, the medial joint load increased with sensor thickness. The maximum knee extension angle decreased with sensor thickness (ρ = -0.4), resulting in extension restriction up to -20°. Knee flexion contracture was below 5° when the total tibiofemoral joint load was below a cut-off of 42 lb. After the MCL was resected, medial joint loads remained unchanged at low values, even with increased sensor thickness. In contrast, the tension device clearly detected an increased gap as the degree of tension decreased.

CONCLUSIONS

The electronic sensor identified increased joint loads associated with increased ligament tension, and could predict knee flexion contracture during TKA. However, unlike the tension device, it did not accurately detect excessively decreased ligament tension.

Collateral Ligament Tension and Balance Alone Does Not Ensure Improved Outcome after Total Knee Arthroplasty

BACKGROUND

It is hypothesized that suboptimal soft tissue and collateral ligament balance is a cause of patient dissatisfaction following total knee arthroplasty (TKA). This analysis examined the association between compartment pressures during TKA and patient reported outcome measurements (PROMs).

METHODS

This single-institution, retrospective cohort study of prospectively collected compartment pressure data measured during TKA comprised 145 patients who underwent surgery between 2015 and 2021 and completed 1-year follow-up PROMs. The primary outcome included pressures, in pounds (lbs), of the medial and lateral compartments in extension (5°), mid-flexion (45°), and flexion (90°), and associated PROMs. The difference been the 1-year and pre-operative PROMs was used to separate the top 25% from the bottom 75% performers. Pressures were compared using Student's T-tests and multivariate linear regressions, while controlling for preoperative deformity. A subgroup analysis of the most popular implant was performed.

RESULTS

Higher medial compartment pressures were seen in our total cohort (Knee Society Score (KSS) mid-flexion 24 vs 18lbs, P=.03, flexion 24 vs 17lbs p=.01) and within our subgroup analysis (Short form- Mental (SF-M) extension 32 vs 21lbs P=0.01, KSS mid-flexion 27 vs 16lbs P=.005, extension 31 vs 20lbs P=.003). This trend persisted in the subgroup analysis when controlling for pre-operative deformity (KSS extension +16.22lbs P=<.001, mid-flexion +17.6lbs. P=.001, and flexion +9.2lbs, P=.005).

CONCLUSION

Several groups demonstrated higher medial versus lateral pressures. However, this pattern was not consistent across PROMs, suggesting that compartment pressures at the time of TKA are an important factor, but not the sole predictor of patient satisfaction.

Verasense sensor-assisted total knee arthroplasty showed no difference in range of motion, reoperation rate or functional outcomes when compared to manually balanced total knee arthroplasty: a systematic review

PURPOSE

The aim of this systematic review was to investigate the clinical and functional knee outcomes after Verasense sensor-assisted total knee arthroplasty (VA TKA), and to compare these outcomes, where possible, with those from manually balanced total knee arthroplasty (MB TKA).

METHODS

A systematic literature search following PRISMA guidelines was conducted on PubMed, Embase, Medline and Scopus from the beginning of January 2012 until the end of June 2022, to identify potentially relevant articles for this review. Selection was based on the following inclusion criteria: full text English- or German-language clinical studies, published in peer-reviewed journals, which assessed clinical and functional outcomes following VA TKA. Not original research, preprints, abstract-only papers, protocols, reviews, expert opinion papers, book chapters, surgical technique papers, and studies pertaining only to unicondylar knee arthroplasty (UKA) or patellofemoral arthroplasty (PFA) were excluded. Several scores (Knee Society Score [KSS], Oxford Knee Score [OKS], Western Ontario and McMaster Universities Osteoarthritis Index [WOMAC], Knee injury and Osteoarthritis Outcome Score-4 subscales [KOOS4] and Physical Function-Computerised Adaptive Testing [PF-CAT]), alongside postoperative measurements of range of motion [ROM], reoperation rates and the rate of manipulation under anaesthesia [MUA]) were used to evaluate clinical and functional outcomes. The quality of included papers, except randomised control trials (RCTs), was evaluated using the Methodological Index for Non-Randomised Studies (MINORS). For the assessment of included RCTs, the Jadad Scale was used.

RESULTS

The literature search identified 243 articles. After removing duplicates, 184 papers were included in the initial screening process. Fourteen of them met all the inclusion criteria following the selection process. Mean MINORS for non-comparative studies value was 11.5 (11-12), and for comparative studies 18.2 (13-21). Mean Jadad Scale score was 3.6 (2-5). Outcomes from a total number of 3633 patients were evaluated (mean age at surgery 68.5 years [32-88 years]). In terms of clinical outcomes, the overwhelming majority of studies observed an improvement after VA TKA, but no statistically significant difference in ROM and reoperation rate when compared to MB TKA. On the other hand, lower rates of MUA have been described in the VA TKA group. An increase in postoperative clinical and functional scores values, when compared to the preoperative ones, has been reported in both groups, although no statistically significant difference between them has been observed.

CONCLUSION

The use of Verasense pressure sensors in TKA leads to no significant improvement in ROM, reoperation rate or functional outcomes, when compared to the standard manually balancing technique. However, lower rates of MUA have been described in the VA TKA group. These findings highlight the importance of tools being able to measure ligament stresses or joint pressure for achieving an optimally balanced knee.

LEVEL OF EVIDENCE

III.

Custom total knee arthroplasty combined with personalised alignment grants 94% patient satisfaction at minimum follow-up of 2 years

PURPOSE

The purpose was to report detailed patient-reported outcome measures (PROMs) and satisfaction rates for computed tomography (CT)-based custom TKA at minimum follow-up of 2 years. The hypothesis was that custom TKA combined with 'personalised alignment' would yield equivalent or better PROMs compared to values reported in systematic reviews and meta-analyses on off-the-shelf (OTS) TKA.

METHODS

Of an initial cohort of 150 custom TKAs, four died (unrelated to surgery), one required a revision, and five refused participation, leaving 140 patients for analysis. Patients completed pre- and post-operative PROMs (Oxford Knee Score (OKS), Forgotten Joint Score (FJS), Knee injury and Osteoarthritis Outcome Score (KOOS), Western Ontario and McMaster osteoarthritis index (WOMAC)) as well as overall level of satisfaction. Proportions that attained a patient acceptable symptom state (PASS) were calculated for OKS and FJS. Clinical findings were compared to the average scores reported for PROMs in recent systematic reviews and/or meta-analyses on OTS TKA. Descriptive statistics were used to summarise the clinical findings as means, standard deviations (SD) and ranges, or numbers and percentages.

RESULTS

At mean follow-up 33.5 ± 4.5 months, 94% (135/143) were either satisfied or very satisfied. Proportions that achieved PASS were 89% for OKS (120/135), and 85% for FJS (118/139). Median OKS, WOMAC and KOOS Symptoms and Pain scores were all within the 4th quartile of medians reported in systematic reviews and/or meta-analyses.

CONCLUSIONS

At a minimum follow-up of two years following custom TKA combined with 'personalised alignment', 94% of patients were either satisfied or very satisfied, and the PASS criteria were achieved in 89% for OKS and 85% for FJS, all of which compare favourably to published outcomes of OTS TKA. Direct comparisons to the literature may not be appropriate, however, considering the heterogeneity of patient demographics and alignment techniques. Randomised controlled trials with sufficient statistical power are needed to corroborate these findings and generalise them to unselected TKA patients.

LEVEL OF EVIDENCE

IV, retrospective cohort study.

Robust Randomized Controlled Data Is Lacking in Total Joint Arthroplasty

INTRODUCTION

 Randomized controlled trials (RCTs)are regarded as highest level of scientific evidence. There is belief that while prospective randomized control trials (PRCTs) are the gold standard for evaluating efficacy of interventions, there are very few conducted on lower extremity joint arthroplasty. However, there was a more than adequate amount (n=197) of published RCTs in knee arthroplasty during the 2021 calendar year. Therefore, we studied RCTs on knee arthroplasties for 2021 and assessed them for overall study topic reasons (i.e., devices as well as prostheses, rehabilitation, pain control, blood loss [tranexamic acid], and other), which were then subcategorized by: (1) country of origin; (2) sample size; and (3)whether or not they were follow-up studies. After this, we specifically focused on the studies (n=26) concerning devices or prostheses.

METHODS

 A search of PubMed on "knee arthroplasty" specifying "RCT" using their search function and dates between January 1, 2021 to December 24, 2021 resulted in the analyzed reports. A total of 17.3% reports analyzed rehabilitation methods while 28.4% studied pain control. A total of 20.3% examined blood loss topics and 20.8% investigated other topics.

RESULTS

 We found that 26 studies (13.2%) involved prosthetic design and implantation. Overall, only 15% knee arthroplasty RCTs were conducted in the United States, the mean total final sample size was 133±146 patients, and 7% were follow-up studies. None of the prostheses studies were performed in the United States, and the mean total final sample size of all of these studies was 86±54 patients, and 23% were follow-up studies. Total knee arthroplasty prospective RCTs were not performed in the United States.

CONCLUSION

 The authors believe that other study designs, such as database or registry analyses, are also appropriate in this rapidly advancing field of joint arthroplasty for the continuing evaluation and approval of new prostheses and techniques, while we await more PRCTs in our field.

No Benefit to Sensor-guided Balancing Compared With Freehand Balancing in TKA: A Randomized Controlled Trial

BACKGROUND

Soft tissue balancing in TKA has traditionally relied on surgeons' subjective tactile feedback. Although sensor-guided balancing devices have been proposed to provide more objective feedback, it is unclear whether their use improves patient outcomes.

QUESTIONS/PURPOSES

We conducted a randomized controlled trial (RCT) comparing freehand balancing with the use of a sensor-guided balancing device and evaluated (1) knee ROM, (2) patient-reported outcome measures (PROMs) (SF-12, WOMAC, and Knee Society Functional Scores [KSFS]), and (3) various surgical and hospital parameters (such as operative time, length of stay [LOS], and surgical complications) at a minimum of 2 years of follow-up.

METHODS

A total of 152 patients scheduled for primary TKA were recruited and provided informed consent to participate in this this study. Of these, 22 patients were excluded preoperatively, intraoperatively, or postoperatively due to patient request, surgery cancellation, anatomical exclusion criteria determined during surgery, technical issues with the sensor device, or loss to follow-up. After the minimum 2-year follow-up was accounted for, there were 63 sensor-guided and 67 freehand patients, for a total of 130 patients undergoing primary TKA for osteoarthritis. The procedures were performed by one of three fellowship-trained arthroplasty surgeons (RPS, HJC, JAG) and were randomized to either soft tissue balancing via a freehand technique or with a sensor-guided balancing device at one institution from December 2017 to December 2018. There was no difference in the mean age (72 ± 8 years versus 70 ± 9 years, mean difference 2; p = 0.11), BMI (30 ± 6 kg/m 2 versus 29 ± 6 kg/m 2 , mean difference 1; p = 0.83), gender (79% women versus 70% women; p = 0.22), and American Society of Anesthesiology score (2 ± 1 versus 2 ± 1, mean difference 0; p = 0.92) between the sensor-guided and freehand groups, respectively. For both groups, soft tissue balancing was performed after all bony cuts were completed and trial components inserted, with the primary difference in technique being the ability to quantify the intercompartmental balance using the trial tibial insert embedded with a wireless sensor in the sensor-guided cohort. Implant manufacturers were not standardized. Primary outcomes were knee ROM and PROMs at 3 months, 1 year, and 2 years. Secondary outcomes included pain level evaluated by the VAS, opioid consumption, inpatient physical therapy performance, LOS, discharge disposition, surgical complications, and reoperations.

RESULTS

There was no difference in the mean knee ROM at 3 months, 1 year, and 2 years postoperatively between the sensor-guided cohort (113° ± 11°, 119° ± 13°, and 116° ± 12°, respectively) and the freehand cohort (116° ± 13° [p = 0.36], 117° ± 13° [p = 0.41], and 117° ± 12° [p = 0.87], respectively). There was no difference in SF-12 physical, SF-12 mental, WOMAC pain, WOMAC stiffness, WOMAC function, and KSFS scores between the cohorts at 3 months, 1 year, and 2 years postoperatively. The mean operative time in the sensor-guided cohort was longer than that in the freehand cohort (107 ± 0.02 versus 84 ± 0.04 minutes, mean difference = 23 minutes; p = 0.008), but there were no differences in LOS, physical therapy performance, VAS pain scores, opioid consumption, discharge disposition, surgical complications, or percentages of patients in each group who underwent reoperation.

CONCLUSION

This RCT demonstrated that at 2 years postoperatively, the use of a sensor-balancing device for soft tissue balancing in TKA did not confer any additional benefit in terms of knee ROM, PROMs, and clinical outcomes. Given the significantly increased operative time and costs associated with the use of a sensor-balancing device, we recommend against its routine use in clinical practice by experienced surgeons.

LEVEL OF EVIDENCE

Level I, therapeutic study.

Tibial component rotation alters soft tissue balance in a cruciate retaining total knee arthroplasty

Our aim was to understand whether using different landmarks for tibial component rotation influenced articular contact pressures in a balanced total knee arthroplasty (TKA). Twelve patients underwent TKA (Triathlon CR, Stryker Inc., Mahwah, NJ) and contact pressures were assessed using a wireless sensor. Robotic arm assisted TKA using a functional alignment technique was performed, with balanced gaps between medial and lateral compartments. Compartment pressures were measured with the trial tibial component rotated to Akagi's line and to Insall's axis respectively. Rotating the tibial component to Akagi's line resulted in a significantly greater proportion of knees being balanced and lower contact pressures than when the tibial component was rotated to Insall's axis at 10°, 45° and 90° of flexion (p < 0.05). Medial compartment pressures were significantly increased in 10° of flexion, as were lateral compartment pressures in all positions when the tibial component was aligned to Insall's axis (p < 0.05). The mean difference in rotation observed with the two landmarks was 6.9° (range 4.1-9.1°). Rotational alignment of the tibial component using Akagi's line reduced contact pressures, improved balance and reduced the need for soft tissue release when compared with Insall's axis in robotic arm assisted TKA.

Intraoperative pressure sensors improve soft-tissue balance but not clinical outcomes in total knee arthroplasty: a multicentre randomized controlled trial

AIMS

Intraoperative pressure sensors allow surgeons to quantify soft-tissue balance during total knee arthroplasty (TKA). The aim of this study was to determine whether using sensors to achieve soft-tissue balance was more effective than manual balancing in improving outcomes in TKA.

METHODS

A multicentre randomized trial compared the outcomes of sensor balancing (SB) with manual balancing (MB) in 250 patients (285 TKAs). The primary outcome measure was the mean difference in the four Knee injury and Osteoarthritis Outcome Score subscales (ΔKOOS₄) in the two groups, comparing the preoperative and two-year scores. Secondary outcomes included intraoperative balance data, additional patient-reported outcome measures (PROMs), and functional measures.

RESULTS

There was no significant difference in ΔKOOS₄ between the two groups at two years (mean difference 0.4 points (95% confidence interval (CI) -4.6 to 5.4); p = 0.869), and multiple regression found that SB was not associated with a significant ΔKOOS₄ (0.2-point increase (95% CI -5.1 to 4.6); p = 0.924). There were no significant differences between groups in other PROMs. Six-minute walking distance was significantly increased in the SB group (mean difference 29 metres; p = 0.015). Four-times as many TKAs were unbalanced in the MB group (36.8% MB vs 9.4% SB; p < 0.001). Irrespective of group assignment, no differences were found in any PROM when increasing ICPD thresholds defined balance.

CONCLUSION

Despite improved quantitative soft-tissue balance, the use of sensors intraoperatively did not differentially improve the clinical or functional outcomes two years after TKA. These results question whether a more precisely balanced TKA that is guided by sensor data, and often achieved by more balancing interventions, will ultimately have a significant effect on clinical outcomes. Cite this article: Bone Joint J 2022;104-B(5):604-612.

Sensor-guided gap balance versus manual gap balance in primary total knee arthroplasty: a meta-analysis

Background

Despite Vast improvements in technology and surgical technique in total knee arthroplasty (TKA), approximately 15–25% TKAs, have suboptimal subjective clinical outcomes. Our study sought to evaluate if sensor-guided balancing improves postoperative clinical outcomes compared to a conventional gap balancing technique.

Methods

We searched Web of Science, Embase, PubMed, Cochrane Controlled Trials Register, Cochrane Library, Highwire, CBM, CNKI, VIP, and Wanfang database in March 2022 to identify studies involving sensor-guided balancing versus conventional gap balancing technique in TKA. Finally, we identified 2147 knees assessed in nine studies.

Results

Compared with manual gap balancing, Sensor-guided gap balancing resulted in less rate of Manipulation under anesthesia (MUA) (P = 0.02), however more rate of intraoperative additional procedures (P = 0.0003). There were no significant differences in terms of KSS (P = 0.21), KSS Function score (P = 0.36), OKS (P = 0.61), KOOS (P = 0.78), operative time (P = 0.17), Mechanical axis (P = 0.69) and rate of reoperation between two groups.

Conclusion

Compared with conventional manual gap balancing techniques, sensors have more balancing procedures being performed. However, it did result in a reduction in the rate of MUA. More extensive, high-quality RCTs are required to verify our findings further.

Total Knee Arthroplasty and Intra-Articular Pressure Sensors: Can They Assist Surgeons with Intra-Operative Decisions?

PURPOSE OF REVIEW

Soft tissue imbalance, presenting as instability or stiffness, is an important cause of revision total knee arthroplasty (TKA). Traditional methods of determining soft tissue balance of the knee lack precision and are not reliable between operators. Use of intra-operative pressure sensors offers the potential to identify and avoid soft tissue imbalance following TKA. This review aims to summarise the literature supporting the clinical indication for the use of intra-articular pressure sensors during TKA.

RECENT FINDINGS

Analytical validation studies suggest that intra-operative pressure sensors demonstrate 'moderate' to 'good' intra-observer reliability and 'good' to 'excellent' interobserver reliability throughout the flexion arc. However, there are important errors associated with measurements when devices are used out-with the stated guidelines and clinicians should be aware of the limitations of these devices in isolation. Current evidence regarding patient benefit is conflicting. Despite positive early results, several prospective studies have subsequently failed to demonstrate significant differences in overall survival, satisfaction, and patient-reported outcome measures within 1 year of surgery. Surgeon-defined soft tissue stability appears to be significantly different from the absolute pressures measured by the intra-operative sensor. Whilst it could be argued that this confirms the need for intra-articular sensor guidance in TKA; the optimal 'target' balance remains unclear and the relationship with outcome in patients is not determined. Future research should (1) identify a suitable reference standard for comparison; (2) improve the accuracy of the sensor outputs; and (3) demonstrate that sensor-assisted TKA leads to patient benefit in patient-reported outcome measures and/or enhanced implant survival.

Current role of intraoperative sensing technology in total knee arthroplasty

PURPOSE

Sensors have been introduced within the last 10 years to quantify soft tissue balancing during total knee arthroplasty (TKA) and to give the surgeon objective data. These devices are fairly new and their impact on patient outcome remains uncertain. The aim of this systematic review was to summarize all the relevant surgical and clinical results of sensors for TKA.

METHODS

A PRISMA systematic review was conducted using five databases (PubMed, EMBASE, MEDLINE, GOOGLE SCHOLAR, and the COCHRANE LIBRARY) to identify all available literature that described the surgical and clinical results of sensors for TKA between 2000 and 2021. The main investigated outcome criteria were intraoperative data, postoperative functional and clinical outcome, knee range of motion, complications and revision rates.

RESULTS

Twenty-seven articles were finally included. The maximum reported follow-up was 26 months. A balanced knee with sensor corresponded to a mediolateral difference inferior to 15 lb and a stable posterior drawer test. The standard assessment of knee balance was a poor predictor of the true soft tissue balance when compared to sensor data. At least 60% of TKA needed an additional rebalancing procedure with the sensor, after conventional gap balancing. Achieving a quantitatively balanced knee resulted in a significantly higher patient satisfaction score. But the prospective comparative studies found no demonstrable improvement in clinical outcome, range of motion or complication rate at one year postoperatively for patients undergoing TKA using sensor-guided balancing compared with routine techniques.

CONCLUSION

Even though the use of the intraoperative sensing technology was not related to an improvement in clinical outcome, the current studies showed that using sensors facilitates the reproduction of natural joint stability, and improves the rate of achieving a balanced knee. Sensor use in complex cases could be particularly valuable, but their use in standard practice remains to be defined.

Kinetic Sensors for Ligament Balance and Kinematic Evaluation in Anatomic Bi-Cruciate Stabilized Total Knee Arthroplasty

Sensor technology was introduced to intraoperatively analyse the differential pressure between the medial and lateral compartments of the knee during primary TKA using a sensor to assess if further balancing procedures are needed to achieve a “balanced” knee. The prognostic role of epidemiological and radiological parameters was also analysed. A consecutive series of 21 patients with primary knee osteoarthritis were enrolled and programmed for TKA in our unit between 1 September 2020 and 31 March 2021. The VERASENSE Knee System (OrthoSensor Inc., Dania Beach, FL, USA) has been proposed as an instrument that quantifies the differential pressure between the compartments of the knee intraoperatively throughout the full range of motion during primary TKA, designed with a J-curve anatomical femoral design and a PS “medially congruent” polyethylene insert. Thirteen patients (61.90%) showed a “balanced” knee, and eight patients (38.10%) showed an intra-operative “unbalanced” knee and required additional procedures. A total of 13 additional balancing procedures were performed. At the end of surgical knee procedures, a quantitatively balanced knee was obtained in all patients. In addition, a correlation was found between the compartment pressure of phase I and phase II at 10° of flexion and higher absolute pressures were found in the medial compartment than in the lateral compartment in each ROM degree investigated. Moreover, those pressure values showed a trend to decrease with the increase in flexion degrees in both compartments. The “Kinetic Tracking” function displays the knee’s dynamic motion through the full ROM to evaluate joint kinetics. The obtained kinetic traces reproduced the knee’s medial pivot and femoral rollback, mimicking natural knee biomechanics. Moreover, we reported a statistically significant correlation between the need for soft tissue or bone resection rebalancing and severity of the initial coronal deformity (>10°) and a preoperative JLCA value >2°. The use of quantitative sensor-guided pressure evaluation during TKA leads to a more reproducible “balanced” knee. The surgeon, evaluating radiological parameters before surgery, may anticipate difficulties in knee balance and require those devices to achieve the desired result objectively.