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

Improved Clinical Outcomes With Dynamic, Force-Controlled, Gap-Balancing in Posterior-Stabilized Total Knee Arthroplasty

BACKGROUND

Optimal soft-tissue management in total knee arthroplasty (TKA) may reduce symptomatic instability. We hypothesized that TKA outcomes using a computer-assisted dynamic ligament balancer that acquires medial and lateral gap sizes throughout the motion arc would show improved Knee Society Scores (KSS) compared to TKAs done with a traditional tensioner at 0 and 90°. We also sought to quantify the degree to which the planned femoral rotation chosen to optimize medio-lateral balance throughout the arc of motion deviated from the femoral rotation needed to achieve a rectangular flexion gap at 90° alone.

METHODS

Baseline demographics, clinical outcomes, KSSs, and femoral rotations were compared in 100 consecutive, computer-assisted TKAs done with the balancer (balancer group) to the immediately prior 100 consecutive computer-assisted TKAs done without the balancer (control group). Minimum follow-up was 13 months and all patients had osteoarthritis. Mean knee motion did not differ preoperatively (110.1 ± 13.6° balancer, 110.4 ± 12.5° control, P = .44) or postoperatively (119.1 ± 10.3° balancer, 118.8 ± 10.9° control, P = .42). Tourniquet times did not differ (93.1 ± 13.0 minutes balancer, 90.7 ± 13.0 minutes control, P = .13). Postoperative length of stay differed (40.2 ± 20.9 hours balancer, 49.0 ± 18.3 hours control, P = .0009). There were 14 readmissions (7 balancer, 7 control), 11 adverse events (4 balancer, 7 control), and 3 manipulations (1 balancer, 2 control). The cohorts were compared using Student's t-tests, Shapiro-Wilk normalities, Wilcoxon rank-sums, and multivariable logistic regression analyses.

RESULTS

Postoperative KSS improvements were higher in the balancer group (P < .0001). In multivariable regression analyses, the balancer group experienced 7 ± 2 point improvement in KSS Knee scores (P < .0001) and 4 ± 2 point improvement in KSS Function scores (P = .040) compared to the control group.

CONCLUSIONS

The statistically and clinically significant improvements in postoperative KSS demonstrated in the balancer cohort are likely driven by improved stability throughout the motion arc. Further study is warranted to evaluate replicability by non-design surgeons.

Spacer rotation technique allows precise evaluation of gap balance in total knee arthroplasty

The symmetry of the flexion and extension gap influences the functional and long-term outcome after total knee arthroplasty (TKA). Most surgeons check it by applying varus and valgus stress using spacers. This technique has limited accuracy and could be easily extended by rotational movement of the spacer. The objective was to determine the detection threshold and interobserver reliability of this technique. In an in vitro setting with a human cadaveric knee, gap asymmetries were simulated by different medially and laterally applied forces. Using an optical measurement system, the pivot point of the spacer was calculated as a function of the gap symmetry in the first part of the experiment. In the second part, the detection threshold and interobserver reliability of 4 surgeons were determined. For this purpose, gap asymmetries were adjusted to between 0 and 120N in a blinded trial. With a symmetrical gap, the centre of rotation of the spacer was located in the centre of the tibia. With increasing gap asymmetry, the centre of rotation of the spacer shifted to the tight side. This shift was approximately linearly dependent on the force difference. A perfectly balanced gap was detected by the examiners in 50% of the cases. From a force difference of 40N, all examiners identified the gap asymmetry in all cases (ICC = 1.0). The method of spacer rotation described is suitable for reliably detecting gap differences at ≥ 40N, independently of the examiner.

Patella scores are similar both with gap balancing and measured resection after total knee arthroplasty: a randomized single-centre study

PURPOSE

The purpose of this prospective study was to compare femoral component rotation (FCR) values when adjusted with 'gap balancing' (GB) and 'measured resection' (MR) techniques following total knee arthroplasty (TKA). The study hypothesis was that the GB technique would be better on FCR than MR in TKA.

METHODS

From a total of 93 unilateral TKAs performed between August 2019 and November 2020, the FCR values were adjusted by GB in 46 cases and MR in 47. Post-TKA magnetic resonance imaging (MRI) was applied for FCR assessment. Orthoroentgenograms and lateral knee radiographs were taken to determine the mechanical axis and posterior condylar offset (PCO) ratio, respectively. Both groups were compared radiologically. The Western Ontario and Mcmaster Universities Osteoarthritis Index (WOMAC), Knee Society Score (KSS), and Hospital for Special Surgery (HSS) patella scores were calculated and compared between the groups preoperatively and at the end of 6 months, and 1 and 2 years postoperatively.

RESULTS

There was no difference between the groups in respect of the demographic data. The mean HSS patella score was 86.4 ± 4.1 in the GB group and 84.6 ± 3.8 in the MR group in the 2nd year (p = 0.047). A higher degree of external rotation in the FC was determined in the GB group [2.2° (1.7°-4.3°)] compared to the MR group [1.7° (0.8°-3.0°)] (p = 0.009). The postoperative increase in PCO ratio was higher in the GB group (p = 0.005). All other variables were similar in both groups.

CONCLUSION

The results of this study showed that at the end of the 2nd year, the HSS patella scores were better, FCs were more externally rotated and PCO ratios were higher in TKAs using the GB technique. However, taking into account that the difference between the 2nd year HSS patella scores was too small to be considered clinically significant, it was shown that both the GB and MR techniques can be used for FCR in clinical practice without any hesitation.

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).

Optimizing Asymmetric Native Knee Flexion Gap Balance Promotes Superior Outcomes in Primary Total Knee Arthroplasty

INTRODUCTION

Replicating native knee kinematics remains the ultimate goal of total knee arthroplasty (TKA). Technology, such as robotics, provides robust intraoperative data; however, no evidence-based targets currently exist for improved clinical outcomes. Furthermore, some surgeons target a rectangular flexion space in TKA unlike the native knee. This study evaluated the effect of in vivo flexion gap asymmetry on patient-reported outcome measures (PROMs) in contemporary TKA.

METHODS

In vivo tibiofemoral joint space dimensions were measured during 129 TKAs using a calibrated tension device before and after complete posterior cruciate ligament resection. PROMs were compared based on the final dimensions and the change in flexion gap dimensions at 90° of flexion: (1) equal laxity, (2) lateral laxity, and (3) medial laxity. Groups did not differ by demographics ( P ≥ 0.347), clinical follow-up ( P = 0.134), tibiofemoral alignment ( P = 0.498), or preoperative PROMs ( P ≥ 0.093). Mean follow-up for the cohort was 1.5 years (range, 1-3).

RESULTS

Pain with climbing stairs, pain while standing upright, and knees "always feeling normal" scores were superior for patients with equal or lateral laxity compared with medial laxity ( P ≤ 0.064). Pain with level walking, University of California Los Angeles activity level, KOOS JR, and satisfaction scores also tended to be superior for patients with equal or lateral laxity, although it lacked statistical significance ( P ≥ 0.111).

DISCUSSION

Results of this study suggest that patients with either an equally tensioned rectangular flexion space or with later-flexion lateral laxity after posterior cruciate ligament resection may achieve superior PROMs. Findings support the clinical benefit of facilitating posterolateral femoral roll back in flexion, which mimics native knee kinematics and further helps define targets for advanced technology.

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.