Small deviations between planned and performed bone cuts using a CT-based robotic-arm-assisted total knee arthroplasty system.

PURPOSE: Computed tomography (CT)-based robotic system for total knee arthroplasty (TKA) has shown improved accuracy compared to conventional. This study was designed to (1) confirm the accuracy of the robotic system in achieving the plan and (2) establish the alignment and positioning deviation between final components and planning, by measuring the discrepancy between final implant alignment and the corresponding planned cut. METHODS: Ninety-six cementless robotic-arm assisted (RA) TKAs were assessed. Bone resections were performed using the haptically controlled robotic arm. Alignment in the coronal and sagittal plane and resection depth of the distal femoral and proximal tibial cuts were recorded with a navigation planar probe. After final components were impacted, the probe was positioned on each implant surface to determine its alignment and positioning. RESULTS: The mean tibial resections and implanted tibial component's positioning were 0.4 mm (standard deviation, SD: 0.6) and 0.9 mm (SD: 0.8), respectively, higher than planned (p < 0.01). The tibial sagittal cut had 19/96 cases (19.8%) of ±1° outliers from plan. In 40/96 cases (41.7%), the tibial component was more prominent than planned of more than 1 mm. The mean femoral resections and impacted femoral component's positioning was 0.1 mm (SD: 0.8) and 0.2 mm (SD: 0.7), respectively, higher than planned. In 23/96 cases (24.0%), the femoral sagittal cut and femoral component coronal alignment deviated more than ±1° from plan. CONCLUSIONS: The computed tomography-based robotic-assisted TKA system showed good accuracy regarding bone preparation and component's positioning relative to the planning. Cementless tibial component impaction resulted in the most deviation from plan, with a large proportion of cases resulting in being more prominent than planned. LEVEL OF EVIDENCE: Level III.

Robotic arm-assisted unicompartmental knee arthroplasty: high survivorship and good patient-related outcomes at a minimum five years of follow-up.

PURPOSE: Robotic arm-assisted unicompartmental knee arthroplasty (RA-UKA) has been shown to improve component placement, reduce intraoperative variability, increase patient satisfaction and improve short-term survivorship results. The aim of this retrospective study was to determine the incidence of revision and the clinical performance at a minimum of 5-year follow-up for a cohort of patients who received a medial RA-UKA. METHODS: Between April 2011 and July 2013, a total of 254 patients underwent medial RA-UKA at a single centre. Clinical performance was investigated using the Forgotten Joint Score-12 (FJS-12) and a 5-level Likert scale made of five items to assess joint perception and patient satisfaction. Kaplan-Meier implant survivorship was calculated and reasons for revision were collected. The effect of age, gender and body mass index (BMI) on the probability of reporting high FJS-12 and satisfaction were assessed. RESULTS: After considering exclusion criteria and loss to follow-up, a total of 216 patients (224 medial RA-UKAs) were assessed at a mean 5.9 years of follow-up. Five RA-UKAs underwent implant revision, resulting in an overall Kaplan-Meier survivorship of 97.8%. Unexplained knee pain (0.9%) was the most common reason for RA-UKA revision. Good-to-excellent FJS-12 scores and high satisfaction levels were reported at mid-term follow-up. Male patients had higher probability of having FJS-12 > 90 (p < 0.05) and high satisfaction levels (p < 0.05). CONCLUSIONS: RA-UKAs demonstrated high survivorship and good-to-excellent patient-reported outcome measures and satisfaction levels at minimum 5-year follow-up. Results for male patients had improved clinical performance when compared to female subjects. LEVEL OF EVIDENCE: IV.

Joint line is restored in robotic-arm-assisted total knee arthroplasty performed with a tibia-based functional alignment.

INTRODUCTION: Functional alignment (FA) in total knee arthroplasty (TKA) has been introduced to restore the native joint line obliquity, respect the joint line height and minimize the need of soft tissue releases. The purpose of this study was to assess the intraoperative joint line alignment and compare it with the preoperative epiphyseal orientation of the femur and tibia in patients undergoing robotic-arm-assisted (RA)-TKA using FA. MATERIALS AND METHODS: This retrospective study included a consecutive series of patients undergoing RA-TKA between February 2019 and February 2021. The joint line orientation of the femur and tibia in the three-dimensions was calculated and classified on preoperative CT-scans and compared with the intraoperative implant alignment. The tibial cut was performed according to the tibial preoperative anatomy. The femoral cuts were fine-tuned based on tensioned soft tissues, aiming for balanced medial and lateral gaps in flexion and extension. RESULTS: A total of 115 RA-TKAs were assessed. On average, the tibial component was placed at 1.8° varus (SD 1.3), while the femur was placed at 0.8° valgus (SD 2.2) and 0.6° external rotation (SD 2.6) relative to the surgical transepicondylar axis. Moderate to strong, statistically significant relationships were described between preoperative tibial coronal alignment and tibial cut orientation (r = 0.7, p < 0.0001), preoperative femoral orientation in the coronal and axial planes and intraoperative femoral cuts alignment (r = 0.7, p < 0.0001 and r = 0.5, p < 0.0001, respectively). One case (0.9%) of slight tibial component varus subsidence was reported 45-days post-operatively, but implant revision was not necessary. CONCLUSIONS: The proposed robotic-assisted functional technique for TKA alignment, with a restricted tibial component coronal alignment, based on the preoperative phenotype and femoral component positioning as dictated by the soft tissues, provided joint line respecting resections. Further studies are needed to assess long-term implant survivorship, patient satisfaction and alignment-related failures.

Clinical results and short-term survivorship of robotic-arm-assisted medial and lateral unicompartmental knee arthroplasty.

PURPOSE: The aim of this multicentre, retrospective, observational study was to determine the incidence of revision and clinical results of a large cohort of robotic-arm-assisted medial and lateral UKAs at short-term follow-up. It was hypothesized that patients who receive robotic-arm-assisted UKA will have high survivorship rates and satisfactory clinical results. METHODS: Between 2013 and 2016, 437 patients (470 knees) underwent robotic-arm-assisted medial and lateral UKAs at two centres. Knee Injury and Osteoarthritis Outcome Score (KOOS), Forgotten Joint Score 12 (FJS-12) and Short-Form Physical and Mental Health Summary Scales (SF-12) were administered to estimate patients' overall health status pre- and post-operatively. Results were dichotomized as 'excellent' and 'poor' if KOOS/FJS-12 were more than or equal to 90 and SF-12 was more or equal to 45. Associations between patients' demographic characteristics and clinical outcomes were investigated. Post-operative complications and pain persistence were recorded. RESULTS: Following exclusions and losses to follow-up, 338 medial and 67 lateral robotic-arm-assisted UKAs were assessed at a mean follow-up of 33.5 and 36.3 months, respectively. Three medial UKAs were revised, resulting in a survivorship of 99.0%. No lateral implants underwent revision (survivorship 100%). On average, significant improvement in all clinical scores was reported in both medial and lateral UKA patients. In medial UKA patients, male gender was associated with higher probability of better scores in overall KOOS, FJS-12 and in specific KOOS subscales. No other associations were reported between biometric parameters and outcome for either medial or lateral UKA. CONCLUSIONS: Robotic-assisted medial and lateral UKAs demonstrated satisfactory clinical outcomes and excellent survivorship at 3-year follow-up. Continued patient follow-up is needed to determine the long-term device performance and clinical satisfaction. LEVEL OF EVIDENCE: Retrospective cohort study, Level IV.

Robotic-Assisted versus Manually Implanted Total Hip Arthroplasty: A Clinical and Radiographic Comparison.

INTRODUCTION: Component positioning during THA is one of the more critical surgeon-controlled factors as malposition has been associated with higher rates of hip dislocations, poor biomechanics, accelerated wear rates, leg length discrepancies (LLDs), and revision surgeries. In order to reduce the rates of component malposition and improve surgical accuracy, robotic-assisted THA has developed increased interest. The primary objective of this study was to compare patient outcomes following THA using the Mako Stryker robotic system (Stryker Orthopaedics, Mahwah, New Jersey) to outcomes in patients who underwent conventional instrumented THA. MATERIALS AND METHODS: Consecutive patients undergoing THA with a direct-lateral surgical approach from a single surgeon were reviewed. Patients were treated with either a robotic-arm assisted total hip arthroplasty (RTHA) or a conventional-instrumented total hip arthroplasty (CTHA). Minimum follow up was 16 months. RESULTS: Robotic-assisted THA significantly improved patient outcomes compared to conventional THA. No significant differences were observed in postoperative radiographic outcomes between the RTHA and CTHA cohorts. In our analysis, patients in the RTHA cohort compared to the CTHA cohort had significantly higher Western Ontario and McMaster Universities Arthritis Index (WOMAC) (P<0.001) and Harris Hip Scores (P<0.05) at final follow up. There were no significant differences between the RTHA cohort and CTHA cohorts in regard to cup inclination (°) (P=0.10), hip length difference (mm) (P=0.80), hip length discrepancy (mm) (P=0.10), and global offset difference (mm) (P=0.20). CONCLUSION: Further studies, particularly prospective randomized studies, are necessary to investigate the short- and long-term clinical outcomes, possible long-term complications, and cost-effectiveness of robotic-assisted THA in regard to improving outcomes and accuracy.

Evaluation of Native Femoral Neck Version and Final Stem Version Variability in Patients With Osteoarthritis Undergoing Robotically Implanted Total Hip Arthroplasty.

BACKGROUND: Combined anteversion in total hip arthroplasty influences both dislocation risk and range of motion. One of its components, stem version (SV), could be dictated by many factors, from native femoral anatomy to stem geometry and surgeon's choice. In the present multicenter study, robotic technology was used to assess the influence of native femoral version on final SV and combined anteversion using a straight, uncemented stem. METHODS: Three hundred sixty-two patients undergoing total hip arthroplasty were enrolled from 3 different orthopedic centers from 2012 and 2016. All patients underwent computed tomography planning with measurement of femoral neck version (FNV) and intraoperative measurement of stem version (SV), acetabular component version (AV), and combined version (CV) with robotic instrumentation. RESULTS: Mean FNV was 5.0° ± 9.6°, and SV was 6.4° ± 9.7°. The average difference between FNV and SV was 1.6° ± 9.8°. A moderate correlation was found between FNV and SV (R = 0.48, P < .001). SV was between 5° and 20° in 174 patients (48%). Mean CV was 28.2° ± 7.9°. A strong correlation was found between SV and CV (R = 0.89, P < .001). A significant difference in SV was found between the 3 centers (P < .001). CV was <25° in 109 patients (30.1%). Relative risk of CV < 25° was 8.6 times greater with SV < 5° (P < .001). CONCLUSION: With the use of an uncemented, single-wedge, straight stem, SV is highly variable. Despite being moderately correlated with native FNV, SV can be partially influenced by the surgeon. A low SV could be hardly corrected, bringing high risk of low CV.

Clinical outcome is not affected by total knee arthroplasty alignment.

PURPOSE: This study aims to analyse the influence on total knee arthroplasty (TKA) clinical outcomes of biomechanical intra-operative computer-assisted surgery-measured parameters, together with radiographic and demographical data. METHODS: Between 2007 and 2009, 227 computer-assisted surgery (CAS) primary TKAs were performed in 219 consecutive patients. Information about gender, age and body mass index (BMI) was collected for each patient. Before knee replacement, all patients underwent a complete radiographic examination and passive flexion-extension range of motion was recorded. All TKAs were implanted using an image-free knee navigation system. Patients included in the study were evaluated at 3, 6 and 12 months of follow-up and then yearly. At each follow-up, subjects were asked to answer the validated Italian version of the Knee Injury and Osteoarthritis Outcome Score. RESULTS: One hundred and eighty patients (187 knees) had data available for analysis. Complications were reported in 13 patients (7.0 %). Intra-operative CAS-measured parameters, together with age, BMI, gender, pre- and post-operative radiographic alignment, did not influence TKA clinical results at a mean 2 years of follow-up. On the other hand, higher post-operative flexion arc of movement was suggestive of better clinical outcomes. CONCLUSION: TKA clinical outcome is influenced by post-operative knee flexion, other than neutral mechanical limb alignment. Therefore, it is recommended to prefer TKA designs that allow high flexion and to encourage early physical rehabilitation. LEVEL OF EVIDENCE: IV.

The Impact of Bone Deformity on Osteoarthritic Varus Knee Correctability.

BACKGROUND: Bone deformities in the varus osteoarthritic knee may influence soft-tissue balancing and therefore knee correctability. The hypothesis of the present study was that the grade of coronal plane knee deformity may influence directly knee correctability along the entire range of motion from 0° to 90°. Tibial and femoral epiphyseal bone deformities were also analyzed to determine which kind had the greater impact on knee correctability. METHODS: A coronal plane deformity radiographic assessment and an intraoperative correctability assessment using computer-assisted surgery were performed on 118 varus osteoarthritic knees undergoing total knee arthroplasty. Knees were divided into groups taking into account the kind of bone deformity (tibial, femoral, and combined). RESULTS: A significant inverse correlation was found between coronal plane deformity and knee correctability at every 10 degrees of flexion. Correlation was strong at 0° and progressively got weaker at further flexion angles. According to literature, knees with a varus deformity >10° were rarely correctable in full extension, but often correctable in flexion, whereas knees with varus deformity >15° showed to be almost never correctable. Combined deformity group had a significantly lower rate of correctability along the entire range of motion. CONCLUSION: The severity of varus knee malalignment always influenced knee correctability with the knee in full extension, in further flexion (20°-60°), correctability was mildly affected. Isolated tibial epiphyseal deformity and combined epiphyseal deformity have the greatest impact on knee correctability.

Design and kinematics in total knee arthroplasty.

PURPOSE: Posterior stabilised (PS) total knee arthroplasty (TKA) design development that focused on restoring normal knee kinematics was followed by the introduction of reason-guided motion designs. Although all PS fixed-bearing knee designs were thought to have similar kinematics, reports show they have differing incidences and magnitudes of posterior femoral rollback and axial rotation. In this retrospective comparative study between two guided-motion total knee systems, we hypothesised that kinematic pattern has an influence on clinical and functional outcomes. METHODS: This study represents the continuation of a previously reported clinical and kinematics analysis. We retrospectively reviewed 347 patients treated with two different TKA designs: Scorpio NRG (Stryker Orthopedics) and Journey Bi-Cruciate Stabilised (BCS) knee system (Smith & Nephew). Two hundred and eighty-one patients were assessed clinically. Patients were divided into groups according to implanted TKA. Clinical evaluation with the Knee Injury and Osteoarthritis Outcome Score (KOOS) questionnaire was performed. Fifteen Scorpio NRG and 16 Journey BCS patients underwent video fluoroscopy during stair climbing, chair rising/sitting and step up/down at six months of follow-up. RESULTS: At an average 29 months of clinical follow-up, patients with Journey BCS TKAs reported better clinical results. Stiffness was more frequently reported in the Journey group (5.2 % vs 1.2 %), whereas anterior knee pain was observed in the Scorpio NRG group (1.9 %) only. Both prosthetic models reported different posterior translation of the medial and lateral contact points (CP) in all analysed motor tasks during knee flexion (BCS 10-18 mm; NRG Scorpio 2-3 mm). Both designs produced progressive external rotation of the femoral component relative to the tibia during flexion. CONCLUSIONS: Journey BCS showed statistically significant better KOOS results. The higher posterior femoral rollback observed in the kinematic assessment of this design, associated with a better patellofemoral design, may be the reason for better clinical outcome. The reported cases of stiffness and anterolateral joint pain could be attributed to excessive medial and lateral tibiofemoral posterior translation. The NRG group demonstrated good axial rotation, but this was not coupled with physiological kinematic patterns. Patellofemoral pain can be explained by a less friendly femoral-groove design. TKA clinical-functional outcome and complications were highly influenced by the bearing geometry and kinematic pattern of prosthetic designs.

Stem anteversion is not affected by proximal femur geometry in robotic-assisted total hip arthroplasty.

BACKGROUND: In the present study, the surgeon aimed to align the stem at 5° to 25° in anteversion. The robotic technology was used to measure stem anteversion with respect to proximal femur anteversion at different levels down the femur. METHODS: A total of 102 consecutive patients underwent robotic-arm-assisted total hip arthroplasty (RTHA). 3D CT-based preoperative planning was performed to determine femoral neck version (FNV), posterior cortex anteversion (PCA), anterior cortex anteversion (ACA), and femoral metaphyseal axis anteversion (MAA) at 3 different levels: D (10 mm above lesser trochanter), E (the midpoint of the planned neck resection line) and F (head-neck junction). The robotic system was used to define and measure stem anteversion during surgery. RESULTS: Mean FNV was 6.6° (SD: 8.8°) and the mean MAA was consistently significantly higher than FNV, growing progressively from proximal to distal. Mean SV was 16.4° (SD: 4.7°). There was no statistically significant difference (P = 0.16) between SV and MAA at the most distal measured level. In 96.1% cases, the stem was positioned inside the 5°-25° anteversion range. CONCLUSIONS: Femoral anteversion progressively increased from neck to proximal metaphysis. Aligning the stem close to femoral anteversion 10 mm above the lesser trochanter often led to the desired component anteversion.

Total knee arthroplasty in-vivo kinematics changes after insert replacement for posterior cruciate ligament deficiency: a case report.

In cruciate-retaining (CR) total knee arthroplasty (TKA) the preservation of the posterior cruciate ligament (PCL) provides joint stability and drives knee kinematics. No previous studies described in-vivo knee kinematics of PCL-deficient CR TKA. In the present case report it's described the in-vivo kinematic pattern change in a patient with post-operative PCL failure before and after insert replacement to a cruciate substituting (CS) design. In-vivo fluoroscopic analysis showed that PCL-deficient TKA showed more anterior translation of the lateral femoral condyle with respect to a cohort  of patients operated of CR-TKA with intact PCL, undergoing fluoroscopic analysis. The replacement to a CS design provided more external rotation of the femoral component and less anterior motion of the lateral condyle. The antero-posterior translation of the medial condyle was similar in PCL-deficient knee, CS TKA and controls. TKA with PCL deficiency showed more antero-posterior motion compared to TKAs with intact PCL and this can be source the of instability and a potential factor for patient's dissatisfaction. For this reason surgeons should attentively verify PCL integrity when performing a cruciate-sparing TKA.

Dislocation risk after robotic arm-assisted total hip arthroplasty: a comparison of anterior, lateral and posterolateral approaches.

AIMS: Dislocation is a major cause of early failure after THA and is highly influenced by surgical approach and component positioning. Robotic-arm assisted arthroplasty has been developed in an attempt to improve component positioning and reduce postoperative complications.The purpose of this study was to compare the rate of dislocation after robotic total hip arthroplasty through 3 different surgical approaches. MATERIALS AND METHODS: All patients who had undergone robotic arm-assisted THA at 3 centres between 2014 and 2019 were reviewed. After applying exclusion criteria, 1059 patients were included in the study. An anterior approach was used in 323 patients, a lateral approach in 394 and a posterior approach in 342 patients.Episodes of dislocation were recorded after 6 months follow-up. Stem anteversion, cup anteversion, cup inclination and combined anteversion were collected using the integrated navigation system.Cumulative incidence (CI), incidence rate (IR) and risk ratio (RR) were calculated with a confidence interval of 95%. RESULTS: 3 cases of dislocation (2 posterior approach, 1 anterior approach) were recorded, with a dislocation rate of 0.28% and an IR of 0.14%.The rate of placement of the cup in the Lewinnek safe zone was 82.2% for the posterior approach, 82.0% for the lateral approach and 95.4% for the anterior approach.The rate of placement in the combined version safe zone was 98.0% for the posterior approach, 73.0% for the lateral approach and 47.1% for the anterior approach.The incidence rate of dislocation was 0.30% for the anterior approach, 0.34% for the posterior approach and 0% for the lateral approach. CONCLUSIONS: The robotic arm-assisted technique is associated with a low risk of dislocation. The combined version technique appears to be a reliable way to reduce the risk of dislocation through the posterolateral approach but does not appear to be essential when using the lateral and anterior approaches.

Robotic Arm-Assisted Lateral Unicompartmental Knee Arthroplasty: How Are Components Aligned?

The purpose of this multicenter, retrospective, observational study was to investigate the association between intraoperative component positioning and soft tissue balancing, as reported by robotic technology for a cohort of patients who received robotic arm-assisted lateral unicompartmental knee arthroplasty (UKA) as well as short-term clinical follow-up of these patients. Between 2013 and 2016, 78 patients (79 knees) underwent robotic arm-assisted lateral UKAs at two centers. Pre- and postoperatively, patients were administered the Knee Injury and Osteoarthritis Score (KOOS) and the Forgotten Joint Score-12 (FJS-12). Clinical results were dichotomized based upon KOOS and FJS-12 scores into either excellent or fair outcome, considering excellent KOOS and FJS-12 to be greater than or equal to 90. Intraoperative, postimplantation robotic data relative to computed tomography-based components placement were collected and classified. Following exclusions and loss to follow-up, a total of 74 subjects (75 knees) who received robotic arm-assisted lateral UKAs were taken into account with an average follow-up of 36.3 months (range: 25.0-54.2 months) postoperative. Of these, 66 patients (67 knees) were included in the clinical outcome analysis. All postoperative clinical scores showed significant improvement compared with the preoperative evaluation. No association was reported between three-dimensional component positioning and soft tissue balancing throughout knee range of motion with overall KOOS, KOOS subscales, and FJS-12 scores. Lateral UKA three-dimensional placement does not seem to affect short-term clinical performance. However, precise boundaries for lateral UKA positioning and balancing should be taken into account. Robotic assistance allows surgeons to acquire real-time information regarding implant alignment and soft tissue balancing.

Mechanical alignment changes during flexion in total knee arthroplasty without affecting clinical outcomes.

BACKGROUND: Primary aim of this study is to investigate if Hip-Knee-Ankle angle, measured in the coronal plane, changes with knee flexion after total knee arthroplasty. The secondary aim is to assess the relationship between Hip-Knee-Ankle during knee flexion and clinical outcome at mid-term follow up. METHODS: 334 computer assisted total knee arthroplasties were retrospectively evaluated. A total of 233 patients were available for assessment of clinical outcomes at last follow up (mean 35 months). Hip-Knee-Ankle angle at different degrees of knee flexion and components' alignment were recorded intraoperatively. FINDINGS: Patients were stratified based on the preoperative alignment: 202 varus knees, 99 neutral knees, and 33 valgus knees. In the varus knee group, 146 patients (89%) maintained a neutral overall limb alignment when flexed to 20°, 118 (72%) remained neutrally aligned at 45° and 92 (54%) at 90°. In valgus knee group, 26 (90%) remained neutrally aligned at 20°, 22 (75%) at 45° and 16 (55%) at 90°. In neutrally-aligned knee group, 88 (96%) remained neutrally aligned at 20°, 73 (79%) at 45° and 61 (66%) at 90°. Femoral component external rotation was correlated with varus alignment in flexion. Good outcomes were reported in 181 (78%) cases, fair results in 28 (12%) cases, poor results in 24 (10%) of cases. Poor results were not correlated to Hip-Knee-Ankle angle at different knee flexion angles. INTERPRETATION: This study demonstrates that intraoperative Hip-Knee-Ankle angle changes as the knee moves into deeper flexion. However, neutral Hip-Knee-Ankle through the range of motion does not correlate with superior outcomes.

Changes in total knee arthroplasty design affect in-vivo kinematics in a redesigned total knee system: A fluoroscopy study.

BACKGROUND: Journey II Bi-Cruciate-Stabilized knee system was designed to overcome the complications of Journey Bi-Cruciate-Stabilized, including ilio-tibial band inflammation and episodes of dislocation. The purpose of this study was to assess differences in knee kinematics between the first and second-generation design by means of video-fluoroscopy. Re-designed prosthesis in-vivo kinematics was analyzed during activities of daily living and results were eventually compared with those of the previous system, as reported in a previously published study. It was hypothesized that changes in components' design influences replaced knee's kinematic patterns. METHODS: Sixteen patients (3 males, 13 females) implanted with the redesigned prosthesis were assessed by video-fluoroscopy during stair-climbing, chair-rising and leg-extension at 8 months of follow-up. Patterns of axial rotation and antero-posterior motion of the medial and lateral femoral condyles were obtained. Range of Motion and International Knee Society Score were recorded pre- and post-operatively. Student t-tests were applied to compare the mean of each interesting variables. FINDINGS: The comparison of the kinematics of the two designs revealed similar patterns of axial rotation, with progressive femoral external rotation in flexion and reduced absolute values of displacement for the new system. Reduced posterior displacements of the medial and lateral condyles were observed in Journey II patients. In terms of absolute location, the lateral condyle in the redesigned prosthesis showed a more anterior position on the tibial-baseplate embedded coordinate system at maximal flexion. INTERPRETATION: Design changes in the recently-introduced total knee system contributed to modify its in-vivo knee kinematics as demonstrated by video-fluoroscopy.

Robotic-arm assisted partial knee arthroplasty: a single centre experience.

BACKGROUND AND AIM OF THE WORK: UKA has proven to be an effective surgical procedure, but its survivorship is still negatively affected by inaccuracy in component component positioning, implant and limb alignment. Robotic surgery has been introduced in order to minimize such technical errors. The aim of the present paper was to evaluate clinical and surgical outcomes after a 3 years' experience of robotic assisted UKA with the Mako Robotic Arm. METHODS: Seventy-three patients undergoing  UKA with robotic instrumentation (65 medial UKAs, 8 lateral UKAs) and with a clinical follow-up of 3 -37 months were included in the present study. A complete clinical evaluation with KOOS, FJS-12 and SF-12 was administered to all patients pre and post operatively. Post-operative HKA angle and surgical time were also recorded. RESULTS: Mean post-operative KOOS score was 81.32 (SD 17.19), while the mean FJS-12 score was 75.51 (SD 30.12) and the mean SF-12 Physical Score 42.25 (SD 9.97). 91% to 88% of post-operative results were considered satisfactory. Only 1 UKA failure was reported (1.3%) caused by peri-prosthetic infection. In medial UKAs mean postoperative HKA angle in extension was 3.9° varus (SD 2.5°), with no case of overcorrection; in lateral UKAs mean postoperative HKA angle in extension was 1.9° valgus (SD 1.9°) with 1 case (13%) of overcorrection. Mean skin to skin surgical time decreased from 83.2 minutes (SD 13.0) to 70.0 minutes (SD 10.9) along the learning curve. CONCLUSIONS: Robotic UKA has provided an improvement both in clinical and technical results, determining satisfactory clinical outcomes and a low risk of post-operative complications.