Aims

The use of technology to assess balance and alignment during total knee surgery can provide an overload of numerical data to the surgeon. Meanwhile, this quantification holds the potential to clarify and guide the surgeon through the surgical decision process when selecting the appropriate bone recut or soft tissue adjustment when balancing a total knee. Therefore, this paper evaluates the potential of deploying supervised machine learning (ML) models to select a surgical correction based on patient-specific intra-operative assessments.

Clinical outcomes of UKA procedures are sensitive to malalignment of the components, and thus show significant variability in the literature. This study evaluates the two year clinical results of a new surgical procedure designed to significantly increase the accuracy and precision of the alignment of the components, and thus increase postoperative functional outcomes.

A new UKA technique has been developed, which combines tactile guided robotic technology with image guided surgery. Three-dimensional planning of the implant positioning is followed by precise resection of the bony surfaces. To date, 73 (42 male, 31 female) patients (average age: 70±10yrs) are 2 years postoperative with all patients enrolled in an IRB approved outcomes registry. The tibial component was an allpoly inlay design.

At two year followup, all patients showed significant improvements, compared to pre-operative values, in Knee Society Knee (p< 0.0001) and Function (p< 0.0001) scores, sf-12 PCS scores (p< 0.0001), WOMAC total scores (p< 0.0001) and WOMAC pain (p< 0.0001), stiffness (p< 0.0001) and physical function (p< 0.0001) subscores. The tibial components of two patients have been revised to a standard metal backed onlay UKA for loosening.

This initial series of robotically guided UKA implantations provided significant improvement in the postoperative function of patients in every functional measurement with only two revisions to date, likely for improper patient selection. These patients were revised to standard UKA components. The introduction of new procedures and technologies in medicine is routinely fraught with issues associated with learning curves and unanticipated pitfalls. Because the explicit objectives of this novel technology are to optimize surgical procedures to provide more safe and more reliable outcomes, these favorable results provide the potential for significant improvements in orthopedic surgery.

Successful clinical outcomes following unicompartmental knee arthroplasty (UKA) depend on accurate component alignment, which can be difficult to achieve using manual instrumentation. A new technology has been developed using haptic robotics that replaces traditional UKA instrumentation. This study compares the accuracy of UKA component placement with traditional jig-based instrumentation versus robotic guidance.

85 UKAs performed using standard manual instrumentation were compared to 67 performed with a robotically guided implantation system without instrumentation. Each was performed using a minimally invasive surgical approach. The two groups were identical in terms of age, gender and BMI. The coronal and sagittal alignment of the tibial components were measured on pre-and post-operative AP and lateral radiographs. Postoperative tibial component alignment was compared to the pre-operative plan.

The RMS error of the tibial slope was 3.7° manually compared to 1.2° robotically. In addition, the variance using manual instruments was 9.8 times greater than the robotically guided implantations (p< 0.0001). In the coronal plane, the average error was 3.0 ± 2.2° more varus using manual instruments compared to 0.3 ± 1.9° when implanted robotically (p< 0.0001), while the varus/valgus RMS error was 3.7° manually compared to 1.8° robotically. The average depth of medial tibial plateau resection was significantly less with inlay tibial components (3.9 ± 0.9mm) relative to onlay tibial components (6.8 ± 0.9mm, p< 0.0001). In addition, a significantly higher percentage of robotic inlay patients went home the day of surgery (12% vs. 1%, p< 0.0001).

Tibial component alignment in UKA is significantly more accurate and less variable using robotic guidance compared to manual, jig-based instrumentation. By enhancing component alignment, this novel technique provides a potential method for improving outcomes in UKA patients.

Unicompartmental knee arthroplasty is realizing a resurgence due to factors such as improved alignment and sizing of components during surgery. This study compares the early results of two implantation techniques – robotic-assisted and standard manual alignment guides – to evaluate how a new technology developed to improve accuracy affects early patient outcomes.

For this study, we chose a prospective consecutive series of 20 patients in each group to receive a medial unicompartmental knee arthroplasty. The patients were evaluated clinically using standard outcomes measures (Knee Society, WOMAC and Oxford scores) as well as for modes of failure. Average follow-up for the manual onlay technique was 12 months and for the robotic-assisted inlay technique was and 10 months. Patients were not statistically different in terms of BMI, age, or diagnosis (p> 0.05).

Knee society score (p=0.65), total WOMAC score (p=0.75) and Oxford knee score (p=0.88) were not statistically different between the three groups. Five patients in the robotic-assisted inlay group complained of persistent tibial pain that resolved in four patients. There were no revisions for the manual onlay implant group and there was one revision for persistent tibial pain in the robotic-assisted inlay group, consisting of a conversion to a standard manual onlay UKA tibial component.

Patient outcomes were similar with inlay robotic-assisted unicompartmental knee arthroplasty compared with conventional manual onlay implant techniques. Roboticassisted inlay components resulted in slightly increased complaints of tibial pain and had one revision for tibial pain, however the revision was to a standard onlay UKA tibial component.

Bicompartmental arthritis involving the medial and patellofemoral compartments of the knee is a common pattern that has often been treated with total knee arthroplasty.

However, the success of unicompartmental and patellofemoral arthroplasty for unicompartmental arthritis, as well as an interest in bone and ligament conservation for earlier stages of arthritis, has led to an interest in bicompartmental arthroplasty. The purpose of this study is to review the clinical, functional, and radiographic results of modular bicompartmental arthroplasty.

Twelve consecutive modular bicompartmental arthroplasties, using separate contemporary unicompartmental tibiofemoral and patellofemoral prostheses, were performed by the senior author. Clinical and functional data including range of motion (ROM), WOMAC and Knee Society (KS) scores were collected pre-operatively and post-operatively at 6 weeks, 12 weeks and annually. Radiographs were taken preoperatively and at the 6 week and annual postoperative visits. The average patient age at the time of surgery was 63 (range, 47 to 72); seven patients were women.

At most recent follow-up, the mean knee ROM improved from 100 degrees of flexion pre-operatively (range, 90 to 110) to a mean of 126 degrees of flexion (range, 115 to 130) (p < 0.0001). Improvements in WOMAC scores were statistically significant (p = 0.02). Statistically significant improvements in Knee Society scores were also observed (p = 0.03). No radiographs showed evidence of loosening, polyethylene wear or progressive lateral compartment degenerative arthritis. There were no complications in the peri-operative period.

Modular bicompartmental arthroplasty is an effective method for treating arthritis of the knee restricted to the medial and patellofemoral compartments. Early results using contemporary prostheses are encouraging and should prompt further mid-and long-term study.

Introduction: It is generally agreed that the function of the knee after total knee arthroplasty needs to be improved to meet the expectations of younger and more active patients. However, little objective information consists to quantify the frequency and importance of activities that place increased biomechanical demand on the knee. This study was performed to asses which specific “high-demand” activities are actually performed by patients after knee replacement, and which activities are of greatest personal importance to the patient.

Methods: An initial group of 243 patients (47% male; 53% female, average age: 70 years; range: (45–91 yrs)) were enrolled in this study with Institutional approval. All were at least 1 year post knee replacement and resided in the Houston area. All participants completed a validated, self-administered knee function questionnaire consisting of 55 scaled multiple choice questions regarding each respondent’s physical activities, limitations, and level of importance for those activities. Participants were also asked to assess the personal importance of each activity and the severity of any symptoms experienced when each activity was performed. An expanded version of the Knee Function Questionnaire was completed by a second group of 101 patients from 5 centres in the United States and Canada. This instrument addressed 120 physical, vocational and recreational activities involving the knee. Fifty-four of these activities were considered “highly demanding” and were drawn from a wide variety of water and team sports, martial arts, running/biking, exercise, weight-lifting and fitness training.

Results: The initial study demonstrated that TKR patients participate in a wide range of “high demand” activities. Most commonly, activities requiring increased knee flexion were gardening (58% participation), kneeling (64%), and squatting (39%). Moderate to severe difficulty was reported by 39% (squatting) to 64% (kneeling) of respondents performing these activities. The most common activity which placed increased loads on the affected joint was carrying loaded shopping bags (47% participation), which provoked Significant symptoms in 23% of patients. The expanded nation-wide study showed that after TKR, few patients actually perform high impact competitive sports although many patients perform individual exercise routines which potentially place Significant demands on the knee. The most common of these “high demand” activities were still squatting and kneeling, but also included participation in gym and exercise activities, typically leg extensions (59%), leg curls (35%) and leg press exercises (33%).

Conclusions:

Kneeling and squatting are the most common “high-demand” activities actually performed on a routine basis by patients after TKR

Summary: Intraoperative assessment of knee kinematics during passive flexion and extension of the unloaded knee fails to adequately replicate the kinematics of the loaded knee during a functional activity.

Introduction: Intraoperatively, the alignment and stability of the prosthetic knee are assessed by observing the motion of the articular surfaces during passive flexion/extension. However, this examination is performed via a medial arthrotomy with limited visibility of the articular surfaces and with the joint unloaded. In view of these limitations of the intraoperative exam, this study was conducted to determine whether unloaded knee motion observed on the operating table is predictive of the motion of the knee during a loaded functional activity.

Methods: Six cadaveric knees were tested:

in a simulator which reproduced the manual intraoperative manipulation of the knee during unloaded passive range of motion (PROM), and

Standard 14cm midvastus medial arthrotomies were performed on each knee, and the PROM and squatting simulations were repeated. A laser scanner was used in conjunction with CT models to recreate the three-dimensional position of the knee and allow calculation of medial and lateral femoral rollback and tibial rotation.

Results: With PROM, the femoral condyles translated posteriorly (medial: 6.8±2.2mm, lateral: 15.2±1.3mm) and the tibia rotated internally (13.8±2.0°). A similar motion pattern was observed during squatting with slightly less medial (5.2±0.7mm; p=0.57), and lateral (12.8±0.9mm; p=0.06) rollback and rotation (10.7±1.54°; p=0.30). Interestingly, paradoxical anterior translation of the femur (> 2mm) and external rotation of the tibia (> 2°) were observed in 30% of knees during a loaded squat; however, this motion was not predicted by the PROM test.

Discussion: Similar knee kinematics are observed during unloaded flexion/extension and a physiologic squatting activity. However, the unloaded intraoperative test was unable to predict the occurrence of paradoxical motion during functional loading. Therefore, passive intraoperative testing of the knee is of limited value as a predictor of functional knee biomechanics.