Introduction

Robotic-assisted total knee arthroplasty (TKA) has demonstrated significant benefits, including improved accuracy of component positioning compared to conventional jig-based TKA. However, previous studies have often failed to associate these findings with clinically significant improvements in patient-reported outcome measures (PROMs). Inertial measurement units (IMUs) provide a more nuanced assessment of a patient's functional recovery after TKA. This study aims to compare outcomes of patients undergoing robotic-assisted and conventional TKA in the early postoperative period using conventional PROMS and wearable sensors.

Introduction

Recent technological advancements have led to the introduction of robotic-assisted total knee arthroplasty to improve the accuracy and precision of bony resections and implant position. However, the in vivo accuracy is not widely reported. The primary objective of this study is to determine the accuracy and precision of a cut block positioning robotic arm.

Malnutrition is considered a risk factor for postoperative complications in total hip and knee arthroplasty, though prospective studies investigating this assumption are lacking. The aim of this study was to prospectively analyse the 90-day postoperative complications, postoperative length of stay (LOS) and readmission rates of patients undergoing primary total hip and total kneearthroplasty using albumin, total lymphocyte count (TLC) and transferrin as serum markers of potential malnutrition.

603 primary hip and 823 primary knee arthroplasties over a 3-year period from a single centre wereprospectively analysed. BMI, demographic and comorbidity data were recorded. Complications werecategorised as surgical site infection, venous thromboembolism (deep vein thrombosis andpulmonary embolus), implant related (such as dislocation), and non-implant related (such aspneumonia). Outcomes were compared between groups, with malnutrition defined as serumalbumin <3.5g/dL, transferrin <200 mg/dL, or TLC <1,500 cells/mm³.

Potential malnutrition was present in 9.3% of the study population. This group experienced a longeraverage LOS at 6.5 days compared to the normal albumin group at 5.0 days (p=0.003). Surgical siteinfection rate was higher in the malnourished group (12.5 vs 7.8%, p=0.02). There was no differencebetween the two groups in implant related complications (0.8 vs 1.0%, p=0.95) medicalcomplications (7.8 vs 13.3%, p=0.17), rate of venous thromboembolism (2.3 vs 2.7%) or 90-dayreadmission rate (14.1 vs 17.0%, p=0.56). TLC and transferrin were not predictive of any of theprimary outcomes measured (p<0.05). Pacific Island (p<0.001), Indian (p=0.02) and Asian (p=0.02) patients had lower albumin than NZ European.

This study demonstrates an association between low albumin levels and increased postoperativeLOS and surgical site infection in total joint arthroplasty, providing rationale for consideration ofpreoperative nutritional screening and optimisation.

The introduction of robotics for total knee arthroplasty (TKA) into the operating theatre is often associated with a learning curve and is potentially associated with additional complications. The purpose of this study was to determine the learning curve of robotic-assisted (RA) TKA within a multi-surgeon team.

This prospective cohort study included 83 consecutive conventional jig-based TKAs compared with 53 RA TKAs using the Robotic Surgical Assistant (ROSA) system (Zimmer Biomet, Warsaw, Indiana, USA) for knee osteoarthritis performed by three high-volume (> 100 TKA per year) orthopaedic surgeons. Baseline characteristics including age, BMI, sex and pre-operative Kellgren-Lawrence grade were well-matched between the conventional and RA TKA groups. Cumulative summation (CUSUM) analysis was used to assess learning curves for operative times for each surgeon. Peri-operative and delayed complications were reviewed.

The CUSUM analysis for operative time demonstrated an inflexion point after 5, 6 and 15 cases for each of the three surgeons, or 8.7 cases on average. There were no significant differences (p = 0.53) in operative times between the RA TKA learning (before inflexion point) and proficiency (after inflexion point) phases. Similarly, the operative times of the RA TKA group did not differ significantly (p = 0.92) from the conventional TKA group. There was no discernible learning curve for the accuracy of component planning using the RA TKA system. The average length of post-operative follow-up was 21.3 ± 9.0 months. There was no significant difference (p > 0.99) in post-operative complication rates between the groups.

The introduction of the RA TKA system was associated with a learning curve for operative time of 8.7 cases. Operative times between the RA TKA and conventional TKA group were similar. The short learning curve implies this RA TKA system can be adopted relatively quickly into a surgical team with minimal risks to patients.

Excessive postoperative opioid prescribing is a significant contributor to the opioid crisis. Prescribing in orthopaedic surgery is often further complicated by high use of opioid-based preoperative analgesia. ‘Opioid PrEscRiptions and usage After Surgery’ (OPERAS) is an international multicentre prospective student- and trainee-led collaborative study which aims to quantify the amount of opioids prescribed at discharge after common orthopaedic surgeries against what is consumed by patients at 7-days, and assess the impact of opioids on patient-reported outcomes.

Data is being collected over 6 14-day periods on consecutive adult patients undergoing shoulder arthroplasty, rotator cuff repair, shoulder labral repair, anterior cruciate ligament repair, hip arthroplasty, and knee arthroplasty, with follow-up via telephone call at 7-days after discharge. The primary outcome is the proportion of oral morphine equivalents (OME) of prescribed opioids versus consumed opioids at 7-days post-discharge.

This ongoing study is actively recruiting in over 20 countries. Globally, 65 centres are collecting orthopaedic, including 10 New Zealand centres and 17 Australian centres. To date, 284 orthopaedic patients have been prospectively enrolled with complete data (mean age 59.6 ± 16.7 years; 51.6% female). Overall, 77% and 89% of patients were prescribed opioids on discharge in New Zealand and Australia respectively. On average, 60% of prescribed opioids were consumed at 7-days post-discharge globally (150 OME (75-500) vs. 90 OME (15-200); p<0.01). In New Zealand and Australia, 42.1% (285 OME (150-584) vs. 120 OME (6-210); p<0.01) and 63.3% (150 OME (86-503) vs. 95 OME (28-221); p<0.01) of prescribed opioids were consumed at 7-days, respectively.

OPERAS will provide the first high-quality global data on opioid prescription and consumption patterns with patient perspectives. These data can inform prescribing practice and inform guidelines. The growing interest in New Zealand and Australia in student- and trainee-led orthopaedic collaborative research, as evidenced by this study should be actively encouraged and fostered.

Patient-reported outcome measures (PROMs) have failed to highlight differences in function or outcome when comparing knee replacement designs and implantation techniques. Ankle-worn inertial measurement units (IMUs) can be used to remotely measure and monitor the bi-lateral impact load of patients, augmenting traditional PROMs with objective data. The aim of this study was to compare IMU-based impact loads with PROMs in patients who had undergone conventional total knee arthroplasty (TKA), unicompartmental knee arthroplasty (UKA), and robotic-assisted TKA (RA-TKA).

77 patients undergoing primary knee arthroplasty (29 RA-TKA, 37 TKA, and 11 UKA) for osteoarthritis were prospectively enrolled. Remote patient monitoring was performed pre-operatively, then weekly from post-operative weeks two to six using ankle-worn IMUs and PROMs. IMU-based outcomes included: cumulative impact load, bone stimulus, and impact load asymmetry. PROMs scores included: Oxford Knee Score (OKS), EuroQol Five-dimension with EuroQol visual analogue scale, and the Forgotten Joint Score.

On average, patients showed improved impact load asymmetry by 67% (p=0.001), bone stimulus by 41% (p<0.001), and cumulative impact load by 121% (p=0.035) between post-operative week two and six. Differences in IMU-based outcomes were observed in the initial six weeks post-operatively between surgical procedures. The mean change scores for OKS were 7.5 (RA-TKA), 11.4 (TKA), and 11.2 (UKA) over the early post-operative period (p=0.144). Improvements in OKS were consistent with IMU outcomes in the RA-TKA group, however, conventional TKA and UKA groups did not reflect the same trend in improvement as OKS, demonstrating a functional decline.

Our data illustrate that PROMs do not necessarily align with patient function, with some patients reporting good PROMs, yet show a decline in cumulative impact load or load asymmetry. These data also provide evidence for a difference in the functional outcome of TKA and UKA patients that might be overlooked by using PROMs alone.