Surgeon-Applied Stress and a Ligament Tensor Instrument Provide a Similar Assessment of Preresection Flexion Laxity During Robotic Total Knee Arthroplasty.

Background: Robotic-assisted total knee arthroplasty (RA-TKA) allows surgeons to perform intraoperative soft tissue laxity assessments prior to bone resections and is used to alter resections to achieve gap balance. This study compared 2 techniques for flexion gap laxity assessment during RA-TKA. Methods: A prospective study of 50 primary RA-TKAs performed by a single surgeon was conducted between February and October 2023. Following full exposure, anterior tibial dislocation, and osteophyte removal, maximal medial and lateral compartment flexion laxity was quantified to the nearest 0.5 mm by the robotic system using a dynamic, surgeon-applied stress (SURGEON). This data was used to plan a balanced flexion gap by adjusting the femoral component size, rotation, and anterior-posterior translation. Flexion laxity was quantified again after distal femoral and proximal tibial resections using a ligament tensor instrument (TENSOR). These new data were used to plan for the same desired flexion gap using the same variables. Paired-samples t-tests and a simple linear regression were used for analysis. Results: Both methods produced near-identical recommendations for femoral component sizing (mean deviation 0.06 sizes, range -1 to +1 size; P = .569), rotation (deviation mean 1.0°, range -3.0° to +3.0°; P = .741), and anterior-posterior translation (deviation mean 0.13 mm, range -0.5 to +0.5 mm, P = .785). SURGEON femoral component rotation predicted TENSOR rotation (R2 = 0.157; 95% confidence interval = 0.124, 0.633; P = .004). Conclusions: Assessing flexion laxity with a surgeon-applied stress vs a ligament tensor produced near-identical laxity data in RA-TKA, suggesting surgeons may comfortably choose either technique as a reliable method. Level of Evidence: Level III.

Does Lack of Initial Collar-Calcar Contact Influence Performance of Collared Cementless Femoral Stems?

Background: Initial stability of cementless stems is important to minimize the risk of subsidence, pain, and periprosthetic fracture after total hip arthroplasty (THA). Collared stems improve initial component stability when contacting the femoral calcar. Direct contact is not always achieved, and collared stem performance has not been studied in this context. We hypothesized that collared stems achieving direct contact would demonstrate reduced subsidence. Methods: A single-surgeon retrospective study of 482 consecutive primary THAs implanted between February 2020 and May 2023 using collared cementless stems was performed. The 2 cohorts included stems with initial collar-calcar contact vs stems without. Subsidence was evaluated by comparing intraoperative fluoroscopy to postoperative 8-week radiographs. Binary logistic regression identified independent risk factors for subsidence. Chi-square tests were used for categorical variables and t-tests for continuous variables. Results: Of stems, 63.9% achieved initial collar-calcar contact, while 36.1% did not. The rate (1.3% vs 19.0%; P < .001) and magnitude (0.02 mm, range 0-3 mm vs 0.35 mm, range 0-3 mm; P < .001) of subsidence were significantly higher among stems without initial contact. Stems without initial collar-calcar contact (P < .001) and male gender (P = .007) were independent risk factors for subsidence. Two patients with initial contact had nondisplaced calcar cracks and <3 mm of subsidence at 4 weeks, which healed with protected weight-bearing. Stem survivorship was 100% in both groups, with all achieving osteointegration and none needing revision. Conclusions: Excellent performance of collared cementless stems was observed at 8 weeks after primary THA. Initial collar-calcar contact lowered the risk and magnitude of minor subsidence but did not affect survivorship or fracture risk. Level of Evidence: Level III.

How are Oral Antibiotics Being Used in Total Joint Arthroplasty? A Review of the Literature.

While the role and benefit of perioperative intravenous (IV) antibiotics in patients undergoing total joint arthroplasty (TJA) is well-established, oral antibiotic use in TJA remains a controversial topic with wide variations in practice patterns. With this review, we aimed to better educate the orthopedic surgeon on when and how oral antibiotics may be used most effectively in TJA patients, and to identify gaps in the literature that could be clarified with targeted research. Extended oral antibiotic prophylaxis (EOAP) use in high-risk primary, aseptic revision, and exchange TJA for infection may be useful in decreasing periprosthetic joint infection (PJI) rates. When prescribing oral antibiotics either as EOAP or for draining wounds, patient factors, type of surgery, and type of infectious organisms should be considered in order to optimally prevent and treat PJI. It is important to maintain antibiotic stewardship by administering the proper duration, dose, and type of antibiotics and by consulting infectious disease when necessary.

Robotic Total Knee Arthroplasty is Associated with Earlier Return of Postoperative Range of Motion.

INTRODUCTION: Postoperative range of motion (ROM) is an important measure for the functional outcome and overall success after total knee arthroplasty (TKA). While robotic knee systems have been shown to reduce pain and improve early function, the return of postoperative ROM specifically has not been adequately studied. The purpose of this study was to compare postoperative ROM in robotic and conventional TKA. We hypothesized that robotic TKA leads to an improvement in postoperative ROM. MATERIALS AND METHODS: A retrospective cohort study of 674 primary TKAs by a single surgeon between January 2018 and February 2023 was completed. Patients that did not have both a two-week follow up and eight-week follow up were excluded. Revision/conversion TKAs were excluded. The population was divided into two cohorts based on technique utilized: robotic versus conventional. Preoperative extension/flexion data, postoperative extension/flexion data at two-week and eight-week follow ups, and manipulation under anesthesia data were collected. ROM was defined as flexion minus extension. Chi-square tests were used to examine for differences between categorical variables and t-tests for continuous variables. RESULTS: A total of 307 robotic and 265 conventional knees were included. There were no differences in demographics, mean follow up, or preoperative ROM between groups. The robotic group had significantly more flexion (99.20° vs. 96.98°; p=0.034) and ROM (97.81° vs. 95.56°; p=0.047) at the two-week follow up. The loss in ROM at the two-week follow up from preoperative ROM was significantly less for the robotic group (-11.21° vs. -14.16°; p=0.031). There were no significant differences in extension at either follow up, in flexion at the eight-week follow up, or in ROM at the eight-week follow up. CONCLUSION: Robotic TKA leads to an improvement in postoperative flexion and ROM when compared to preoperative ROM at two-week follow up. These findings could partially explain the quicker recovery associated with robotic TKA.

Is It Necessary to Wake Patients for Overnight Vital Signs Following Total Joint Arthroplasty?

Benefits of sleep are well-established in postoperative recovery; however, patients undergoing total joint arthroplasty (TJA) often experience poor sleep during hospitalization. While multifactorial, among the major reasons are the frequent and ritualized overnight vital sign checks. In the absence of data in support of or against this practice, we asked whether it remains necessary. We retrospectively analyzed a cohort of 419 primary TJA patients. Demographics, comorbidities, operative, and vital sign data were collected through postoperative Day 3. Correlation between daytime (6:00 a.m. to 10:00 p.m.) and nighttime (10:01 p.m. to 5:59 a.m.) vitals was examined. The vast majority of nighttime vitals fell within normal ranges, including O2 saturation (O2; 99.4%), temperature (TEMP; 97.8%), heart rate (HR; 87.5%), systolic blood pressure (SBP; 85.8%), and diastolic blood pressure (DBP; 84.4%). Predictors of abnormal nighttime vitals included American Society of Anesthesiologists (ASA) score (abnormal SBP; odds ratio [OR] 1.64, p = .045), obesity (abnormal DBP; OR: 0.37, p = .011), and smoking status (elevated temperature; OR: 2.79, p = .042). Estimated blood loss was predictive of an abnormal nighttime TEMP (OR: 1.002; p < .001). Postoperatively, there were several correlations between abnormal daytime and nighttime vitals, including SBP (OR: 6.23, p < .001), DBP (OR: 4.31, p < .001), and HR (OR: 10.35; p < .001). Of the 419 patients, only 9 (2.1%) received any intervention based on abnormal nighttime vitals. Each exhibited daytime vital sign abnormalities prior to the abnormal nighttime readings. Patients with abnormal nighttime vitals can be predicted on the basis of medical comorbidities and abnormal daytime vitals. These findings suggest that healthy post-TJA patients with normal daytime vitals may not need to be routinely woken at night.

Registration of Bony Landmarks and Soft Tissue Laxity during Robotic Total Knee Arthroplasty is Highly Reproducible.

INTRODUCTION: There is growing interest and enthusiasm for robotic total knee arthroplasty (TKA). Many robotic systems require registration of bony landmarks as well as a dynamic soft tissue evaluation to plan femoral and tibial resections. Variability in this user-driven registration can introduce error and undermine the purported precision and accuracy offered by robotics. The purpose of this study was to evaluate inter- and intrarater reliability in robotic registration with a new robotic system (ROSA®; Zimmer-Biomet, Warsaw, IN). METHODS: Two unpaired cadaveric knee specimens were exposed, and optical arrays were placed into the femur and tibia. Three separate evaluators conducted repeated trials of anatomic registration and assessment of soft tissue laxity, as well as coronal alignment, sagittal alignment, femoral size, and maximum opening in the medial and lateral compartments in both flexion and extension. Repeated trials were conducted using these specimens with and without preoperative imaging for landmarking (image-based and image-free workflows). An Intraclass Correlation Coefficient (ICC) was calculated for each observer and across observers to determine intra-and interrater reliability, respectively, in robotic registration. RESULTS: There was good to excellent reliability for all conditions, and all correlation coefficients were >0.767. On average, ICCs for intrarater reliability were excellent for Doctor 1 (0.952), Doctor 2 (0.975), and Doctor 3 (0.925). On average, the ICCs for interrater reliability were excellent for both the "Registration + Gap Assessment" condition (0.961) and the "Gap Assessment" condition (0.994). CONCLUSION: Our results show a high repeatability of registration of anatomic landmarks and gap assessment among observers using this robotic system for both image-based and image-free software.