Robotic-assisted surgery has less soft tissue damage than traditional total knee arthroplasty, with better early recovery and prosthesis placement

Technical Summary: Robotic-Assisted vs. Conventional Total Knee Arthroplasty Using the Hong-Hu System

Problem Statement
Total knee arthroplasty (TKA) is the standard intervention for end-stage knee osteoarthritis (KOA), yet patient satisfaction rates plateau between 75% and 89%. Conventional TKA (CO-TKA) relies on manual cutting guides and anatomical landmarks, making the procedure heavily dependent on surgeon experience. This variability can lead to suboptimal osteotomy accuracy, iatrogenic soft tissue injury, and imperfect lower extremity alignment, which are critical determinants of prosthetic longevity and functional outcomes. While robotic-assisted TKA (RA-TKA) has emerged to address these limitations through enhanced precision and preoperative planning, clinical evidence regarding the specific efficacy of the Hong-Hu robotic system (a semi-active system by Suzhou MicroPort OrthoBot) remains limited.

Methodology
This retrospective cohort study evaluated 161 patients who underwent primary unilateral TKA between December 2022 and December 2023 at Gansu Provincial People's Hospital. Patients were allocated into two groups based on surgical approach:

• RA-TKA Group (n=76): Utilized the Hong-Hu robotic system. The workflow involved preoperative CT-based 3D modeling for surgical planning, intraoperative registration of the femur and tibia, and robotic-guided osteotomy using a semi-active arm that locks to guide the oscillating saw.
• CO-TKA Group (n=85): Performed using conventional instrumentation, intramedullary alignment rods, and manual cutting guides.

Key Metrics and Analysis:

• Intraoperative Parameters: Operative time, blood loss (measured directly and via hemoglobin decline using the Gross formula), incision length, and soft tissue injury severity (graded via the modified Hampp classification for the medial collateral ligament [MCL], lateral collateral ligament [LCL], and popliteal tendon).
• Radiographic Outcomes: Postoperative alignment measured by Hip-Knee-Ankle angle (HKA), mechanical lateral distal femoral angle (mLDFA), mechanical medial proximal tibial angle (mMPTA), and sagittal component angles (sTCA, sFCA). The Lower Extremity Alignment Correction (LEAC) rate was defined as achieving HKA within 3° of neutral.
• Clinical Outcomes: Functional scores (Oxford Knee Score [OKS], Knee Society Score [KSS], WOMAC) at 3 and 6 months. Daily Visual Analog Scale (VAS) pain scores and active knee range of motion (ROM) were recorded for the first 7 postoperative days.
• Statistical Approach: Continuous variables were analyzed using independent t-tests or Mann-Whitney U tests; categorical variables used chi-square tests; longitudinal data (VAS and ROM) were analyzed using repeated-measures ANOVA.

Key Results

• Surgical Efficiency and Safety: There was no significant difference in operative time between groups (72.5 vs. 75.6 minutes, P=0.30). However, the RA-TKA group exhibited significantly lower perioperative hemoglobin decline (10.2 vs. 15.5 g/L, P<0.001) and numerically lower intraoperative blood loss. The RA-TKA incision length was significantly longer (12.1 vs. 10.2 cm, P<0.001), attributed to the requirements of the robotic foot holder and tracker placement.
• Soft Tissue Preservation: RA-TKA resulted in significantly less severe soft tissue injury. Specifically, injury to the MCL (P=0.013) and popliteal tendon (P=0.003) was reduced in the robotic group compared to CO-TKA. No significant difference was found in LCL injury.
• Radiographic Accuracy: The RA-TKA group demonstrated superior accuracy in component positioning and osteotomy. Significant differences favored RA-TKA in HKA (P=0.027), mLDFA (P=0.015), mMPTA (P=0.046), sTCA (P=0.026), and sFCA (P=0.028). The LEAC rate was 97.4% for RA-TKA versus 92.9% for CO-TKA, though this difference was not statistically significant (P=0.35).
• Early Recovery: During the first postoperative week, the RA-TKA group reported significantly lower VAS pain scores (P<0.001) and greater active knee ROM (P<0.001) compared to the CO-TKA group.
• Functional Outcomes: At 3 months, no significant differences were observed in OKS, KSS, or WOMAC scores. At 6 months, the RA-TKA group achieved a significantly higher KSS-Knee score (95.2 vs. 89.8, P=0.03), while other functional scores remained comparable.
• Complications: Complication rates were low and comparable between groups. No prosthetic joint infections, loosening, or revision surgeries occurred. Transient femoral pain related to tracker pins occurred in 2.6% of RA-TKA patients.

Significance and Claims
The authors conclude that Hong-Hu robotic-assisted TKA offers distinct advantages over conventional techniques, specifically regarding reduced soft tissue trauma, improved osteotomy accuracy, and enhanced early postoperative recovery (pain control and mobility). The study suggests that the precision of the Hong-Hu system translates into tangible clinical benefits in the early to mid-term (6 months), evidenced by higher KSS-Knee scores.

The paper maintains a modest stance regarding long-term efficacy, noting that the 6-month follow-up is insufficient to determine long-term implant survival or functional superiority. The authors acknowledge limitations including the non-randomized design, the single-surgeon operator (which may limit generalizability to less experienced surgeons), and the short follow-up duration. They posit that while the Hong-Hu system demonstrates superior early outcomes, longer-term studies are required to validate its long-term efficacy.