Manual Stress Mismatched With Tensioner Forces in Robotic Knee Surgery
Manual Stress Mismatched With Tensioner Forces in Robotic Knee Surgery
A study analyzing 55 bi-cruciate-stabilized total knee arthroplasty procedures found significant divergence between joint laxity measurements obtained via manual varus-valgus stress and those measured using standardized distraction forces. Published in the journal Arthroplasty, the research indicates that the relationship between these methods is not uniform across the knee, varying by compartment and flexion angle. Conducted between May 2024 and August 2025 with patients undergoing surgery using the CORI system by Smith and Nephew, the investigation revealed that manual stress can underestimate or overestimate joint laxity depending on specific conditions, particularly in the lateral compartment at mid-flexion angles. The findings underscore the need for standardized evaluation methods to ensure accurate soft-tissue balance assessment during robot-assisted procedures.
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The study provides empirical evidence of discrepancies between manual stress and force-controlled tensioner measurements in robotic knee surgery, highlighting variability by compartment and flexion angle that impacts soft-tissue balance assessment.
What the source reports
Publisher-reported claims, with original evidence. These results have not been independently verified by RoboSignal.
Reported numbers
distraction force
80
View original evidence
ciate ligaments were resected, and the patella was resurfaced in all cases. Femoral and tibial alignments were established using the robotic system, with specific angles set relative to the mechanical axis. The extension and flexion gaps were initially measured using a force-controlled compartment-specific ligament tensioner with a distraction force of 80 Newtons for each compartment. This initial measurement guided
Open source S7distraction force
60
View original evidence
the bone resection to ensure medial stability, while femoral rotation was aligned parallel to the surgical epicondylar axis to allow for residual lateral ligamentous laxity. After the implantation of the final prosthetic components, joint laxity was evaluated using two distinct methods. First, the component gaps were measured using the force-controlled tensioner at distraction forces of 60 and 80 Newtons. These measu
Open source S8inter-observer error
4
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producibility of the manual stress technique. The results showed that interobserver variability was greater in the lateral compartment than in the medial compartment, especially at higher flexion angles. The absolute error values in the lateral compartment were significantly larger at 30, 60, and 90 degrees of flexion compared to the medial compartment. A maximum inter-observer error of 4.0 millimeters was observed a
Open source S14intraclass correlation (medial)
0.46–0.77
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t 90 degrees of flexion in the lateral compartment, indicating that manual stress measurements can be highly variable between different surgeons. The study utilized intraclass correlation coefficient and Bland-Altman analysis to quantify the agreement between the senior surgeon and the assistants. In the medial compartment, the intraclass correlation values ranged from 0.46 to 0.77 across the different flexion angles
Open source S15patient count
51
View original evidence
balance, a critical factor for achieving successful clinical outcomes following knee replacement. The findings indicate that the relationship between manual stress and force-controlled tensioner measurements is not uniform across the knee, varying significantly by compartment and flexion angle. The study was conducted between May 2024 and August 2025, involving 51 patients who underwent 55 primary bi-cruciate-stabili
Open source S3
- paper: not_reported
Source excerpts and review record
Automatically extracted; no manual editorial approval recorded.
balance, a critical factor for achieving successful clinical outcomes following knee replacement. The findings indicate that the relationship between manual stress and force-controlled tensioner measurements is not uniform across the knee, varying significantly by compartment and flexion angle. The study was conducted between May 2024 and August 2025, involving 51 patients who underwent 55 primary bi-cruciate-stabili
Open source S3
ciate ligaments were resected, and the patella was resurfaced in all cases. Femoral and tibial alignments were established using the robotic system, with specific angles set relative to the mechanical axis. The extension and flexion gaps were initially measured using a force-controlled compartment-specific ligament tensioner with a distraction force of 80 Newtons for each compartment. This initial measurement guided
Open source S7
the bone resection to ensure medial stability, while femoral rotation was aligned parallel to the surgical epicondylar axis to allow for residual lateral ligamentous laxity. After the implantation of the final prosthetic components, joint laxity was evaluated using two distinct methods. First, the component gaps were measured using the force-controlled tensioner at distraction forces of 60 and 80 Newtons. These measu
Open source S8
producibility of the manual stress technique. The results showed that interobserver variability was greater in the lateral compartment than in the medial compartment, especially at higher flexion angles. The absolute error values in the lateral compartment were significantly larger at 30, 60, and 90 degrees of flexion compared to the medial compartment. A maximum inter-observer error of 4.0 millimeters was observed a
Open source S14
t 90 degrees of flexion in the lateral compartment, indicating that manual stress measurements can be highly variable between different surgeons. The study utilized intraclass correlation coefficient and Bland-Altman analysis to quantify the agreement between the senior surgeon and the assistants. In the medial compartment, the intraclass correlation values ranged from 0.46 to 0.77 across the different flexion angles
Open source S15
, while in the lateral compartment, they ranged from 0.66 to 0.84. The Bland-Altman analysis revealed mean biases and limits of agreement that were wider in the lateral compartment, particularly at 90 degrees of flexion, where the limits of agreement extended from -2.08 to 3.03 millimeters. These statistical measures underscore the limited reproducibility of lateral gap measurements in flexion, a finding consistent w
Open source S16
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