Personalized alignment techniques better restore the native trochlear groove compared to systematic alignment techniques in total knee arthroplasty.

PURPOSE: The relationship between constitutional coronal alignment and implant positioning on trochlear groove restoration in total knee arthroplasty (TKA) is poorly understood. This study aimed to determine whether the choice of alignment philosophy significantly affects the restoration of the trochlea groove. METHODS: Sixty-one imageless robotic TKAs performed by a single orthopaedic surgeon were retrospectively reviewed. In each case, the entire native trochlea was digitized to generate the native femoral anatomy, and implants were planned according to a functional alignment (FA) technique. Final implant position was recorded using the validated bone resection planes from the navigation system. Simulated femoral component positions were generated according to previously described alignment techniques: mechanical alignment (MA), gap balancing (GB), kinematic alignment (KA), restricted kinematic alignment (rKA) and restricted inverse kinematic alignment (riKA). Trochlear angle (TA), trochlear under/overstuffing and mediolateral sulcus offset were compared between the six simulated alignment techniques, as well as the final implanted technique. Further analyses investigated the effect of preoperative coronal alignment on trochlear position. Comparisons were assessed with an analysis of variance and Welch's t-tests or Wilcoxon's rank-sum tests with Bonferroni corrections. RESULTS: The implanted and simulated techniques all resulted in greater TA valgus compared to the native groove (p < 0.001). The implanted technique, KA and rKA were closer to the native TA than GB, MA and riKA (p > 0.001). All alignment philosophies understuffed the native trochlea groove. KA and rKA understuffed less than all other techniques (p < 0.001), and GB understuffed more than all other techniques (p < 0.001). In extension, all techniques shifted the trochlear sulcus laterally, while in flexion, they medialized it. These effects were most prominent in GB and MA. CONCLUSION: Personalized alignment techniques such as KA and rKA, which consider variations in individual anatomy, best restore the native patellar groove compared to systematic alignment techniques when using a standardized femoral component. LEVEL OF EVIDENCE: Level III, retrospective review.

Dimensional accuracy of TKA cut surfaces with an active robotic system.

This is a study of the dimensional accuracy of the bone cut surfaces in robotic TKA. One surgeon performed robotic TKA on four cadaveric knees. A novel technique was developed for measuring the dimensional accuracy of both the femoral and tibial cut surfaces. CT scans were used to create a pre-operative plan and generate nominal cut surfaces on the 3D bone model. After TKA, the cut surfaces were then laser scanned. Two femoral components were also scanned and compared to nominal dimensions. Flatness was computed as the standard deviation between each of the cut surfaces and the best-fit plane. The angles between the five femoral best-fit planes were compared to the nominal values. The point-to-point distances between the femoral cut surfaces and the nominal cut planes were computed to estimate the bone-to-implant gap. The cut surfaces had an average flatness of 0.16 ± 0.06 mm with low variability between different cut planes. The femoral cut surfaces had average angular errors of 0.47 ± 0.39°, which are of similar magnitude as the errors found for the implants. The bone-to-implant gap was within ±1 mm for 97.9% of the surface on average. Using a novel methodology, the dimensional accuracy of an active robotic system for TKA was found to be very high for both the femoral and tibial bone cuts. Comparison studies are needed with other robotic systems as well as studies comparing manual and robotic techniques.

Learning curve for active robotic total knee arthroplasty.

PURPOSE: Total Knee Arthroplasty (TKA) procedures incorporate technology in an attempt to improve outcomes. The Active Robot (ARo) performs a TKA with automated resections of the tibia and femur in efforts to optimize bone cuts. Evaluating the Learning Curve (LC) is essential with a novel tool. The purpose of this study was to assess the associated LC of ARo for TKA. METHODS: A multi-center prospective FDA cohort study was conducted from 2017 to 2018 including 115 patients that underwent ARo. Surgical time of the ARo was defined as Operative time (OT), segmented as surgeon-dependent time (patient preparation and registration) and surgeon-independent time (autonomous bone resection by the ARo). An average LC for all surgeons was computed. Complication rates and patient-reported outcome (PRO) scores were recorded and examined to evaluate for any LC trends in these patient related factors. RESULTS: The OT for the cases 10-12 were significantly quicker than the OT time of cases 1-3 (p < 0.028), at 36.5 ± 7.4 down from 49.1 ± 17 min. CUSUM and confidence interval analysis of the surgeon-dependent time showed different LCs for each surgeon, ranging from 12 to 19 cases. There was no difference in device related complications or PRO scores over the study timeframe. CONCLUSION: Active Robotic total knee arthroplasty is associated with a short learning curve of 10-20 cases. The learning curve was associated with the surgical time dedicated to the robotic specific portion of the case. There was no learning curve-associated device-related complications, three-dimensional component position, or patient-reported outcome scores. LEVEL OF EVIDENCE: Level II.

Low dislocation rates with the use of patient specific "Safe zones" in total hip arthroplasty.

INTRODUCTION: The purpose of this study was to compare patient-specific acetabular cup target orientation using functional simulation to the Lewinnek Safe Zone (LSZ) and determine associated rates of postoperative dislocation. METHODS: A retrospective review of 1500 consecutive primary THAs was performed. Inclination, anteversion, pelvic tilt, pelvic incidence, lumbar flexion, and dislocation rates were recorded. RESULTS: 56% of dynamically planned cups were within LSZ (p < 0.05). 6/1500 (0.4%) of these cups dislocated at two year follow-up, and all were within LSZ. CONCLUSION: Optimal acetabular cup positioning using dynamic imaging differs significantly from historical target parameters but results in low rates of dislocation. LEVEL OF EVIDENCE: Level III: Retrospective.

Safe and effective use of active robotics for TKA: Early results of a multicenter study.

BACKGROUND: A novel active robotic system for total knee arthroplasty (TKA) performs automated milling of bone surfaces. Study objectives were to assess system safety and effectiveness in a US population. METHODS: A multicenter clinical trial was conducted, following 115 patients for at least 6-months. A pre-defined list of robot-related adverse events was used to evaluate safety. Efficacy was assessed radiographically comparing planned versus achieved coronal limb alignment. RESULTS: No pre-defined adverse events occurred and postoperative limb alignment more than ±3° from plan occurred in 11.2 % of cases. CONCLUSION: Active robotics for TKA is safe and effective as demonstrated in this trial.

Direct anterior approach total hip arthroplasty with an orthopedic traction table.

OBJECTIVE: Direct anterior approach total hip arthroplasty (DAA THA) has gained significant popularity in the last decade as it is a muscle-sparing procedure. Modern techniques for DAA THA utilize both a standard operating table and an orthopedic traction table. As the use of an orthopedic traction table shows technical ease and predictability, this article will focus on the use of the orthopedic table or table extension to facilitate DAA THA. INDICATIONS: Primary or secondary arthritis requiring THA; revision surgery-both acetabular and femoral. CONTRAINDICATIONS: Posterior wall hardware requiring removal; posterior mass (tumor) to be removed at surgery: large, overhanging pannus; need for gluteal tendon reconstruction; anterior skin envelope not conducive to DAA. SURGICAL TECHNIQUE: The incision is made over the tensor fascia latae. Capsulotomy is performed exposing the hip joint. After osteotomy of the femoral neck, traction is placed on the leg utilizing the orthopedic table and the head is removed. The acetabular cup is inserted. Traction, flexion, and internal reduction are used simultaneously while directing the femoral head into the acetabulum. RESULTS: In a meta-analysis, operative time (100 vs. 71 min), blood loss (531 vs. 382 ml), and intraoperative fracture rate (1.7 vs. 1.3%) were increased in the traction table cohort. All other complications and outcome measurements were the same. Traction-table related complications such as pudendal nerve palsy and ankle fractures were not found. An assessment of the senior author's initial 855 DAA THAs (2008-2014) showed a mean operative time of 65 min with a mean blood loss of 238 ml. Operative times decreased to average 56 min. Intraoperative fracture rate was 0.8%. Infection rate was 2.1%. Finally, 1.5% femoral implants did not osseointegrate and required revision after an average of 3.0 years.

Short stem hip arthroplasty via the minimally invasive direct anterior approach.

OBJECTIVE: Tissue-sparing, minimally invasive hip arthroplasty via the direct anterior approach (DAA) using a partially neck-preserving, calcar-guided short stem. INDICATIONS: Primary and secondary osteoarthritis of the hip due to developmental dysplasia, femoroacetabular impingement, femoral head necrosis or trauma sequelae. CONTRAINDICATIONS: Severe osteoporosis, active infection, American Society of Anesthesiologists (ASA) > III, large metaphyseal bone defects, severe metaphyseal deformities, Dorr type C femur. SURGICAL TECHNIQUE: Supine position on a standard operating table without extension device. Classic DAA skin incision or bikini incision distal to the inguinal fold. Blunt dissection entering the Hueter interval. Capsulotomy with capsule preservation or partial capsulectomy. Intraoperatively, it is crucial to adhere to the preoperatively planned angle and height of the femoral neck osteotomy. During femoral head removal and acetabular preparation, care must be taken to avoid iatrogenic damage to the remaining neck. After cup positioning, femoral access is achieved by release of superior capsular structures. During opening of the medullary canal and broaching, femoral torsion and axis have to be taken into account for correct rotational and axial alignment. Femoral broaches are inserted in an ascending series of sizes until the last broach is firmly lodged and is in direct contact with the antero-medial femoral neck cortex. Fluoroscopic control in two planes to check for femoral anatomic and overall offset and assess whether the implant is adequately seated with cortical support at the calcar, the distal lateral and the dorsal cortex. Implantation of the definitive implants, local infiltration analgesia and wound closure. RESULTS: Between 1/2011 and 12/2016 60 patients (24 female, 36 male; mean age 44 years) were treated with a partially neck-preserving short stem via the described approach. Seven patients underwent a bi-lateral procedure. Thus, 67 procedures were analysed in this retrospective cohort study. Mean follow-up was 70 months (range 28-93). The median Harris Hip Score was 48 (range 11-88) preoperatively and 98 (range 80-100) postoperatively. CONCLUSION: The minimally invasive implantation of a partially neck-preserving stem via DAA provides a safe technique with good to excellent clinical results in the mid-term.

Bilateral Total Hip Arthroplasty in the Setting of Developmental Dysplasia of the Hip and Extreme Hip Flexion Requirements due to Phocomelia.

Phocomelia is a rare congenital birth defect marked by hypoplastic or markedly absent limbs. Developmental dysplasia of the hip (DDH) is a congenital disorder with a failure of the native acetabulum to provide complete coverage over the femoral head. The secondary osteoarthritis that develops from DDH is technically challenging for orthopedic surgeons because of distorted anatomy. The present case describes the diagnosis of Crowe 3 DDH in a phocomelia patient with hyperflexion requirements who successfully underwent staged bilateral total hip arthroplasty via a direct anterior approach. It highlights the utility of preoperative computerized tomography and intraoperative computer navigation to assist in implant placement. Recognizing difficult arthroplasty cases in advance is imperative as these cases may require great expertise and more extensive surgical planning.

Active Robotic Total Knee Arthroplasty (TKA): Initial Experience with the TSolution One ® TKA System.

Several recent advances, including the use of robotic devices, have been explored to improve outcomes in total knee arthroplasty (TKA). The TSolution One ® Total Knee Application (THINK Surgical, Inc., Fremont, CA, USA) introduces an active robotic device that supports an open implant platform and CT-based preoperative planning workflow, and requires minimal surgeon intervention for making bone cuts. Our experience was part of a multi-center, prospective, non-randomized trial assessing the safety and effectiveness of this active robotic system for TKA. Each patient underwent a preoperative CT-scan, which was uploaded to proprietary planning software. The surgeon reviewed the software-generated 3D digital model, selected the appropriate implants and generated a final preoperative plan. Intra-operatively, a standard medial parapatellar approach was used. The leg was then rigidly attached to the robot via fixation pins, and registration markers were placed in the tibia and femur. Landmark registration was performed to inform the robot of the knee's position in space and to confirm the robot's ability to execute the preoperative plan. Next, the robot performed femoral and tibial cuts using a cutter in a sequential fashion along a defined cut-path. The robot was then removed from the operative field and the surgeon completed the procedure by removing marginal bone and performing final balancing and implantation in the usual fashion. The TSolution One® Total Knee Application is a computer-assisted device that potentially allows a surgeon to make more accurate cuts and to determine optimal implant position based on the patient's specific anatomy. It is the only active robotic system currently available. In this manuscript, we describe the operative technique and workflow involved in performing this surgery and offer insight on optimizing safety and efficiency as we introduce new technologies to the operating theater. We also present two cases performed by the senior author to further demonstrate technical aspects of the procedure.

Computed Tomography Analysis of Postsurgery Femoral Component Rotation Based on a Force Sensing Device Method versus Hypothetical Rotational Alignment Based on Anatomical Landmark Methods: A Pilot Study.

Rotation of the femoral component is an important aspect of knee arthroplasty, due to its effects on postsurgery knee kinematics and associated functional outcomes. It is still debated which method for establishing rotational alignment is preferable in orthopedic surgery. We compared force sensing based femoral component rotation with traditional anatomic landmark methods to investigate which method is more accurate in terms of alignment to the true transepicondylar axis. Thirty-one patients underwent computer-navigated total knee arthroplasty for osteoarthritis with femoral rotation established via a force sensor. During surgery, three alternative hypothetical femoral rotational alignments were assessed, based on transepicondylar axis, anterior-posterior axis, or the utilization of a posterior condyles referencing jig. Postoperative computed tomography scans were obtained to investigate rotation characteristics. Significant differences in rotation characteristics were found between rotation according to DKB and other methods (P < 0.05). Soft tissue balancing resulted in smaller deviation from anatomical epicondylar axis than any other method. 77% of operated knees were within a range of ±3° of rotation. Only between 48% and 52% of knees would have been rotated appropriately using the other methods. The current results indicate that force sensors may be valuable for establishing correct femoral rotation.

Comparison of Patient-Reported Outcome from Neck-Preserving, Short-Stem Arthroplasty and Resurfacing Arthroplasty in Younger Osteoarthritis Patients.

Hip resurfacing has been considered a good treatment option for younger, active osteoarthritis patients. However, there are several identified issues concerning risk for neck fractures and issues related to current metal-on-metal implant designs. Neck-preserving short-stem implants have been discussed as a potential alternative, but it is yet unclear which method is better suited for younger adults. We compared hip disability and osteoarthritis outcome scores (HOOS) from a young group of patients (n = 52, age 48.9 ± 6.1 years) who had received hip resurfacing (HR) with a cohort of patients (n = 73, age 48.2 ± 6.6 years) who had received neck-preserving, short-stem implant total hip arthroplasty (THA). Additionally, durations for both types of surgery were compared. HOOS improved significantly preoperatively to last followup (>1 year) in both groups (p < 0.0001, η (2) = 0.69); there were no group effects or interactions. Surgery duration was significantly longer for resurfacing (104.4 min ± 17.8) than MiniHip surgery (62.5 min ± 14.8), U = 85.0, p < 0.0001, η (2) = 0.56. The neck-preserving short-stem approach may be preferable to resurfacing due to the less challenging surgery, similar outcome, and controversy regarding resurfacing implant designs.

A patient-specific predictive model increases preoperative templating accuracy in hip arthroplasty.

Application of digital radiography during preoperative templating has shown potential to reduce complications in total hip arthroplasty. In this study, we aimed to further improve digital templating by using a predictive model built on patients' specific data. The model was significant in improving the accuracy of templating within ±1 size of acetabular component (χ(2)(1, N=468)=19.314, P<0.0001, Φ=0.604, and odds-ratio: 7.750 (95% CI 2.740-30.220)). We successfully achieved a 99% accuracy within ±2 of templated size. Additionally, patient demographics, such as height and weight, have shown significant effects on the predictive model. The outcome of this study may help reducing the costs of health care in the long term by minimizing implant inventory costs.

In vivo kinematics of a robot-assisted uni- and multi-compartmental knee arthroplasty.

BACKGROUND: There is great interest in providing reliable and durable treatments for one- and two-compartment arthritic degeneration of the cruciate-ligament intact knee. One approach is to resurface only the diseased compartments with discrete unicompartmental components, retaining the undamaged compartment(s). However, placing multiple small implants into the knee presents a greater surgical challenge than total knee arthroplasty, so it is not certain that the natural knee mechanics can be maintained or restored. The goal of this study was to determine whether near-normal knee kinematics can be obtained with a robot-assisted multi-compartmental knee arthroplasty. METHODS: Thirteen patients with 15 multi-compartmental knee arthroplasties using haptic robotic-assisted bone preparation were involved in this study. Nine subjects received a medial unicompartmental knee arthroplasty (UKA), three subjects received a medial UKA and patellofemoral (PF) arthroplasty, and three subjects received medial and lateral bi-unicondylar arthroplasty. Knee motions were recorded using video-fluoroscopy an average of 13 months (6-29 months) after surgery during stair and kneeling activities. The three-dimensional position and orientation of the implant components were determined using model-image registration techniques. RESULTS: Knee kinematics during maximum flexion kneeling showed femoral external rotation and posterior lateral condylar translation. All knees showed femoral external rotation and posterior condylar translation with flexion during the step activity. Knees with medial UKA and PF arthroplasty showed the most femoral external rotation and posterior translation, and knees with bicondylar UKA showed the least. CONCLUSIONS: Knees with accurately placed uni- or bi-compartmental arthroplasty exhibited stable knee kinematics consistent with intact and functioning cruciate ligaments. The patterns of tibiofemoral motion were more similar to natural knees than commonly has been observed in knees with total knee arthroplasty. Larger series are required to confirm these as general observations, but the present results demonstrate the potential to restore or maintain closer-to-normal knee kinematics by retaining intact structures and compartments.

Innovations in hip arthroplasty three-dimensional modeling and analytical technology (SOMA).

The modern generations of cementless hip arthroplasty implant designs are based on precise fit and fill of components within the native bony geometry of the proximal femur and the acetabulum for enhanced implant longevity. Variations exist based on a number of population demographics such as age, gender, body mass index, and ethnicity. Recently, establishment of comprehensive electronic computerized tomographic databases from a diverse population worldwide have been key innovations in the field of implant development. This technology provides a potential improvement compared to historical techniques of implant design and manufacturing which involved limited trials on cadavers. Segmentation of the computerized data to generate three-dimensional models allows precise and accurate measurements of anatomical structures and may provide better understanding of anthropometric variations that occur among individuals. Evidence-and population-based computational analyses may provide a better tool for designing orthopaedic implants that deliver an enhanced fit for a more diverse patient population. Moreover, these population-based databases can also verify new designs by means of virtual implantation and analysis on specific or large groups of bones within the database. The aim of this paper is to describe a three dimensional modeling and analytical technology and to review the various applications of this technology in relation to hip arthroplasty.

Direct anterior approach to total hip arthroplasty using computer navigation.

UNLABELLED: The incorporation of computer navigation in total hip arthroplasty (THA) has been much slower than for total knee arthroplasty (TKA). One reason for this is that a majority of THAs are performed with the patient in the lateral position through a posterior or lateral approach, making the tracker placement and the registration process cumbersome. In the direct anterior approach, the patient is in the supine position, which accommodates pelvic tracker placement and markedly facilitates the registration process. At our institution, we use the direct anterior approach and computer navigation on all of our primary THAs. We hypothesized that computer navigation improves cup placement without increasing operative time. MATERIALS AND METHODS: This was a retrospective study comparing a consecutive series of 150 computer navigated THAs to a consecutive series of 150 non-navigated hips. The two groups were similarly matched by age, gender, and body mass index. Postoperative anteroposterior pelvic radiographs and operative times were analyzed. RESULTS: The navigation group mean cup inclination was 41° (range, 32° to 54°), compared to 36° (range, 19° to 52°) for the non-navigated group. The mean surgical time for the navigation group was 56 minutes (range, 34 to 91 minutes) and 61 minutes (range, 33 to 119 minutes) for the non-navigated group. CONCLUSION: The results suggest that computer navigation is easy to incorporate when utilizing a direct anterior approach and in our series shortens the operative time. The accuracy and precision of cup angle placement is comparable to our non-navigated method but appears to be slightly improved with computer navigation. Although more work is needed for progress with this promising technology, we believe that incorporating computer navigation for hip arthroplasties in the supine position is straightforward and of great value.

Direct anterior approach for hip resurfacing: surgical technique and complications.

BACKGROUND: The direct anterior approach (DAA) for hip resurfacing arthroplasty is a technically difficult approach but theoretically reduces the soft tissue trauma to the hip because it does not require muscle detachments from the bone. Furthermore, the patient is in the supine position facilitating fluoroscopy to control component placement. However, the complications associated with the learning curve and functional outcome scores are not well defined in the literature. QUESTIONS/PURPOSES: We therefore asked how our first 57 operations using the anterior approach and special table extension compared with that in the literature with regard to (1) complication rate; (2) functional outcome scores; (3) component placement; and (4) length of stay. METHODS: We retrospectively reviewed 51 patients who underwent 57 hip resurfacing procedures using a DAA. There were 45 men and six women with an average age of 51 years (range, 31-63 years) and a body mass index of 28.7 kg/m(2) (range, 19.7-42.0 kg/m(2)). The minimum followup was 0.3 months (mean, 8.7 months; range, 0.3-24.9 months). RESULTS: There were three atraumatic (5%) and one posttraumatic (1.8%) femoral neck fractures. Average HOOS scores were equal to or better than averages reported for total hip arthroplasty. Average cup inclination was 36.5° (range, 25°-48°). The average length of stay was 2.11 days (range, 1-4 days). CONCLUSIONS: The surgical approach for anterior hip resurfacing is technically difficult but may have some clinical benefits. Surgeons interested in using the DAA for hip resurfacing should be very familiar with the DAA for total hip arthroplasty and with hip resurfacing.

Bicompartmental knee arthroplasty: a bone-sparing, ligament-sparing, and minimally invasive alternative for active patients.

In the past, treatment of knee osteoarthritis has been limited to unicompartmental knee replacement or total knee arthroplasty (TKA). Neither option is well suited for the active patient with midstage osteoarthritis of the medial and patellofemoral compartments. Now an alternative treatment is available that targets the diseased area without sacrifice of normal bone or both the cruciate ligaments. Minimally invasive surgical techniques are easily used, which reduces tissue trauma and results in a quicker recovery than TKA. Bicompartmental replacement offers decreased pain, stability through normal ligament structure, and the retention of normal bone for patients with medial and patellofemoral osteoarthritis.