Introduction. Flexion instability of the knee accounts for, up to, 22% of reported revisions following TKA. It can present in the early post-operative phase or present— secondary to a rupture of the PCL— in the late post-operative phase. While most reports of instability occur in conjunction with cruciate retaining implants, instability in a posterior-stabilized knee is not uncommon. Due to the prevalence of revision due to instability, the purpose of constructing the following techniques is to utilize intraoperative sensors to quantify flexion gap stability. Methods. 500 posterior cruciate-retaining TKAs were performed between September 2012 and April 2013, by four collaborating surgeons. All surgeons used the same implant system, compatible with a microelectronic tibial insert with which to receive real-time feedback of femoral contact points and joint kinetics. Intraoperative kinematic data, as reported on-screen by the VERASENSE™ knee application, displayed similar loading patterns consistent with identifiable sagittal plane abnormalities. These abnormalities were classified as: “Balanced Flexion Gap,” “Flexion Instability” and “Tight Flexion Gap.” All abnormalities were addressed with the techniques described herein. Results. Balanced Flexion Gap. Flexion balance was achieved when femoral contact points were within the mid-posterior third (Figure 1) of the tibial insert, symmetrical rollback was seen through ROM, intercompartmental loads were balanced, and central contact points displayed less than 10 mm of excursion across the bearing surface during a posterior drawer test. Flexion Instability. The femoral contact point tracking option dynamically displayed the relative motion of distal femur to the proximal tibia during the posterior drawer test, and through range of motion. Excessive excursion of the femoral contact points across the bearing surface, and femoral contact points translating through the anterior third of the tibial trial, was an indication of laxity in the PCL. Surgical correction requires use of a thicker tibial insert, anterior-constrained insert, or a posterior-stabilized knee design (Figure 2). Tight Flexion Gap. Excessive tension in the PCL was displayed during surgery via femoral contact points and excessive high pressures in the posterior compartment during flexion. When a posterior drawer test was applied no excursion of the femoral tibia contact point was seen. Excessively high loading in the posteromedial compartment was corrected through recession of the PCL using an 19 gauge needle or 11 blade. Additional tibial slope was added when excessive loads were seen in both compartments (Figure 3). Discussion. Flexion gap instability, or excessive PCL tension, is a common error resulting in poor patient outcomes and early revision surgery. The techniques described, utilized intraoperative sensor data to address sagittal plane abnormalities in a quantified manner. By using technology to guide the surgeon through appropriate sagittal plane correction, the subtleties in soft-tissue imbalance or suboptimal bone cuts can be accounted for, which otherwise may be overlooked by traditional methods of subjective surgeon “feel.” Longer clinical follow-up of these patients will be necessary to track the outcomes associated with quantifiable sagittal plane balance

The palpation of the controlateral iliac spinae remains a major hurdle to the success of navigation in lateral position. Several studies are seeking for alternative landmarks to compute the anterior pelvic plane (APP). Up to now, none of those methods have been used in clinical routine. Ultrasound navigation offers a great potential to identify new bony landmarks. The tubercles of the lower lumbar spine and the symphysis can easily be imaged. Those points define a sagittal plane, that can be used as a symmetry plane to compute a virtual controlateral spinae from the acquired colateral spinae. A virtual pelvic plane can then be computed. The objective of this study was to check the accuracy and reproducibility of this virtual anterior pelvic plane. 6 hips (3 left, 3 right) from 4 cadavers (mean BMI 22,6; range 19,5–26,7) embalmed with glycerol and alcohol were used for this study. All anatomic landmarks were acquired with the OrthoPilot® Ultrasound navigation system. One experienced surgeon acquired the reference APP with the cadavers lying supine. The cadavers were then placed in lateral position. Two experienced surgeons acquired 6 times following landmarks: 3 lower lumbar tubercles, 3 sacral tubercles (see Figure 1), the posterior spines, the symphysis and the colateral iliac spine. Several sagittal planes were computed using all points (least square plane) and all possible combinations between one symphysis point, one lower lumbar tubercle point (L5, L4 or L3), and one sacral tubercle point (S2 or S1). The angular error of the resulting virtual APP to the reference APP was computed. For each cadaver, an error map was computed to visualize the error of the virtual APP with respect to the height of the used sacral and lumbar tubercles along the spine. The reference APP was acquired with a good reproducibility: the deviation between each acquisition to the mean of all acquisitions was smaller than 1° (except for cadaver 2 right side, the deviation reached 2 ° in the frontal plane). As some sacral and lumbar points were mixed during the acquisition, the line joining the posterior spines was used to separate the sacral from the lumbar points. The mean errors and standard deviations were comparable between operators. The least square plane computed with all points strongly depended on the cadaver positioning : for the same cadaver, the mean error reached 0°on the left side and 8° on the right side. More constant results were obtained by using a combination of 3 points. 5 outliers were identified and removed as they clearly corresponded to erroneous acquisitions on bad quality images. After having removed those outliers, the mean error ranged between 2° and 5° and the standard deviation between 1° and 3°. The best combination of points was a point on the symphysis, the lowest sacral tubercle (S2) and the lowest lumbar tubercle (L5). This study shows that the symphysis, the lower lumbar and sacral tubercles can be used to define a sagittal plane and thereby define a virtual anterior pelvic plane. Outliers should be suppressed by taking special care to the image quality and by adding a guided ultrasound functionality: visualizing the resulting sagittal plane on the ultrasound picture would enable the surgeon to easily control the accuracy of his acquired plane. The next steps consist in checking the feasibility in a clinical set-up

The final alignment of Patient Specific Instrumentation (PSI) TKA relies on the accuracy and the correct placement of the 3-D moulds, precision of saw cuts, soft tissue balancing and cementing technique. We aimed to compare the predicted alignment between PSI and Articulated Surface Mounted (ASM) computer navigation. Eight consecutive patients underwent knee replacement using MRI based PSI (Zimmer) with planning of 0º femoral and tibial mechanical alignment. After placing the conventional cutting blocks over the pins (placed according to PSI), the predicted alignment of cuts was verified with ASM navigation. PSI technique was used regardless of navigation values and alignment was compared. Good correlation was found for tibial cuts (maximum variation: coronal plane – 1º, sagittal plane – 2º) and femoral cuts in the sagittal plane (maximum variation 2º). However, in two patients the coronal plane variation in femur was > 2º (3º and 4º respectively). Navigation predicted combined final alignment of 5º valgus and 4º valgus in these patients. However, long leg standing x-rays revealed neutral and 1º valgus alignment in those two patients respectively, matching closely with PSI prediction. Final alignment in long-leg standing x-rays were independently reported by a musculoskeletal radiologist. Six knees were in neutral mechanical alignment (including the 2 navigation predicted outliers). The remaining 2 knees had a maximum deviation of 2 degrees from neutral. We conclude that there was overall good correlation between PSI and navigation. Even in cases where navigation predicted more than 3º combined varus/valgus alignment, PSI prediction was more accurate on long leg views

The extension facet angle (EFA) of the medial compartment of the knee has been implicated as a potential mechanical cause for anteromedial knee osteoarthritis. We developed a novel sagittal plane flexion osteotomy of the medial tibiofemoral compartment. We then performed a cadaveric study to study the effect of the osteotomy on the intra-articular knee pressures under axial load mimicking the stance phase of gait. A Tekscan K400 pressure sensor was inserted submeniscally into the joint and 700N applied using an Instron machine. A topographical map of the pressure areas was then assessed pre- and post-osteotomy for the 10 cadaveric knees specimens. We found that the intra-articular pressures are greatest in the anteromedial compartment in the native knee and after the osteotomy the area of highest pressure moves posterolaterally spread over a greater surface area. We conclude that a flexion osteotomy of the medial compartment reduces intra-articular knee pressures concentrated anteromedially in full extension and may be beneficial in patients with an elevated EFA with anteromedial symptoms

Tibial plateau fracture reduction involves restoration of alignment and articular congruity. Restorations of sagittal alignment (tibial slope) of medial and lateral condyles of the tibial plateau are independent of each other in the fracture setting. Limited independent assessment of medial and lateral tibial plateau sagittal alignment has been performed to date. Our objective was to characterize medial and lateral tibial slopes using fluoroscopy and to correlate X-ray and CT findings. Phase One: Eight cadaveric knees were mounted in extension. C-arm fluoroscopy was used to acquire an AP image and the C-arm was adjusted in the sagittal plane from 15° of cephalad tilt to 15 ° of caudad tilt with images captured at 0.5° increments. The “perfect AP” angle, defined as the angle that most accurately profiled the articular surface, was determined for medial and lateral condyles of each tibia by five surgeons. Given that it was agreed across surgeons that more than one angle provided an adequate profile of each compartment, a range of AP angles corresponding to adequate images was recorded. Phase Two: Perfect AP angles from Phase One were projected onto sagittal CT images in Horos software in the mid-medial compartment and mid-lateral compartment to determine the precise tangent subchondral anatomic structures seen on CT to serve as dominant bony landmarks in a protocol generated for calculating medial and lateral tibial slopes on CT. Phase Three: 46 additional cadaveric knees were imaged with CT. Tibial slopes were determined in all 54 specimens. Phase One: Based on the perfect AP angle on X-ray, the mean medial slope was 4.2°+/-2.6° posterior and mean lateral slope was 5.0°+/-3.8° posterior in eight knees. A range of AP angles was noted to adequately profile each compartment in all specimens and was noted to be wider in the lateral (3.9°+/-3.8°) than medial compartment (1.8°+/-0.7° p=0.002). Phase Two: In plateaus with a concave shape, the perfect AP angle on X-ray corresponded with a line between the superiormost edges of the anterior and posterior lips of the plateau on CT. In plateaus with a flat or convex shape, the perfect AP angle aligned with a tangent to the subchondral surface extending from center to posterior plateau on CT. Phase Three: Based on the CT protocol created in Phase Two, mean medial slope (5.2°+/-2.3° posterior) was significantly less than lateral slope (7.5°+/-3.0° posterior) in 54 knees (p<0.001). In individual specimens, the difference between medial and lateral slopes was variable, ranging from 6.8° more laterally to 3.1° more medially. In a paired comparison of right and left knees from the same cadaver, no differences were noted between sides (medial p=0.43; lateral p=0.62). On average there is slightly more tibial slope in the lateral plateau than medial plateau (2° greater). However, individual patients may have substantially more lateral slope (up to 6.8°) or even more medial slope (up to 3.1°). Since tibial slope was similar between contralateral limbs, evaluating slope on the uninjured side provides a template for sagittal plane reduction of tibial plateau fractures

Introduction. The aim of the study is to evaluate the results of using Ilizarov technique for correcting the post traumatic lower limb deformities. Materials and Methods. This prospective study included 25 femurs (Group A) and 65 tibias (Group B) underwent correction with Ilizarov technique and frame. Both groups had moderate and complex deformed segments. Outcomes were Ilizarov correction time, distraction index (DI), consolidation index (CI), Ilizarov index (II) and complications. Results. Within group A, mean correction of frontal plane deformity was 15°, sagittal plane was 10° rotational deformity was 20°. In group B, mean correction of frontal plane deformity was 19°, sagittal plane was 12° and rotational deformity was 10°. Conclusions. Ilizarov provided easy, accurate and excellent lower limb deformity correction and lengthening

Robotic-assisted technology in total knee arthroplasty (TKA) aims to increase implantation accuracy, with real-time data being used to estimate intraoperative component alignment. Postoperatively, Perth computed tomography (CT) protocol is a valid measurement technique in determining both femoral and tibial component alignments. The aim of this study was to evaluate the accuracy of intraoperative component alignment by robotic-assisted TKA through CT validation. A total of 33 patients underwent TKA using the MAKO robotic-assisted TKA system. Intraoperative measurements of both femoral and tibial component placements, as well as limb alignment as determined by the MAKO software were recorded. Independent postoperative Perth CT protocol was obtained (n.29) and compared with intraoperative values. Mean absolute difference between intraoperative and postoperative measurements for the femoral component were 1.17 degrees (1.10) in the coronal plane, 1.79 degrees (1.12) in the sagittal plane, and 1.90 degrees (1.88) in the transverse plane. Mean absolute difference between intraoperative and postoperative measurements for the tibial component were 1.03 degrees (0.76) in the coronal plane and 1.78 degrees (1.20) in the sagittal plane. Mean absolute difference of limb alignment was 1.29 degrees (1.25), with 93.10% of measurements within 3 degrees of postoperative CT measurements. Overall, intraoperatively measured component alignment as estimated by the MAKO robotic-assisted TKA system is comparable to CT-based measurements

Femoral shaft fractures are fairly common injuries in paediatric age group. The treatment protocols are clear in patients of age less than 4 years and greater than 6 years. The real dilemma lies in the age group of 4–6 years. The aim of this study is to find whether a conservative line should be followed, or a more aggressive surgical intervention can provide significantly better results in these injuries. This study was conducted in a tertiary care hospital in Bhubaneswar, India from January 2020 to March 2021. A total of 40 patients with femur shaft fractures were included and randomly divided in two treatment groups. Group A were treated with a TENS nail while group B were treated with skin traction followed by spica cast. They were regularly followed up with clinical and radiological examination to look out for signs of healing and any complications. TENS was removed at 4–9 months’ time in all Group A patients. Group A patients had a statistically significant less hospital stay, immobilisation period, time to full weight bearing and radiological union. Rotational malunions were significantly lower in Group A (p-value 0.0379) while there was no statistically significant difference in angular malunion in coronal and sagittal plane at final follow up. Complications unique to group A were skin necrosis and infection. We conclude that TENS is better modality for treatment of shaft of femur fractures in patients of 4–6 years age as they significantly reduce the hospital stay, immobilization period and rotational malalignment

Background:. The axis of the fibula in the sagittal plane are known as a landmark for the extramedullary guide in order to minimize posterior tibial slope measurement error in the conventional total knee arthroplasty (TKA). However, there are few anatomic studies about them. We also wondered if the fibula in the coronal plane could be reliable landmark for the alignment of the tibia. This study was conducted to confirm whether the fibula is reliable landmark in coronal and sagittal plane. Methods:. We evaluated 60 osteoarthritic knees after TKA using Athena Knee (SoftCube Co, Ltd, Osaka, Japan) 3-D image-matching software. Angle between the axis of the fibula (FA) and the mechanical axis (MA) in the coronal and sagittal plane were measured. Results:. The mean angle between the FA and MA was 0.86 ± 2.0° of varus in the coronal plane (range 6.0° of varus to 4.2° of valgus) and 2.6 ± 2.3° of posterior inclination in the sagittal plane (range 6.8° of posterior inclination to 2.8 of anterior inclination), respectively. The percentage of subjects in which FA was within 3° of the MA was 77% in the coronal plane and 58% in the sagittal plane, respectively. Conclusions:. The FA used as a landmark for the alignment of the tibia in the conventional TKA differed from MA relatively in this study, and not be used safely if the differences are considered

The Lisfranc fracture dislocation of the tarsometatarsal joint (TMTJ) is a complex injury with a reported incidence of 9.2 to 14/100,000 person-years. Lisfranc fixation involves dorsal bridge plating, transarticular screws, combination or primary arthrodesis. We aimed to identify predictors of poor patient reported outcome measures at long term follow up after operative intervention. 127 patients underwent Lisfranc fixation at our Level One Trauma Centre between November 2007 and July 2013. At mean follow-up of 10.7 years (8.0-13.9), 85 patients (66.92%) were successfully contacted. Epidemiological data including age, gender and mechanism of injury and fracture characteristics such as number of columns injured, direction of subluxation/dislocation and classification based on those proposed by Hardcastle and Lau were recorded. Descriptive analysis was performed to compare our primary outcomes (AOFAS and FFI scores). Univariate analysis and multivariate regression analysis was done adjusted for age and sex to compare the entirety of our data set. P<0.05 was considered significant. The primary outcomes were the American Orthopaedic Foot and Ankle Society (AOFAS) Midfoot Score and the Foot Function Index (FFI). The number of columns involved in the injury best predicts functional outcomes (FFI, P <0.05, AOFAS, P<0.05) with more columns involved resulting in poorer outcomes. Functional outcomes were not significantly associated with any of the fixation groups (FFI, P = 0.21, AOFAS, P = 0.14). Injury type by Myerson classification systems (FFI, P = 0.17, AOFAS, P = 0.58) or open versus closed status (FFI, P = 0.29, AOFAS, P = 0.20) was also not significantly associated with any fixation group. We concluded that 10 years post-surgery, patients generally had a good functional outcome with minimal complications. Prognosis of functional outcomes is based on number of columns involved and injured. Sagittal plane disruption, mechanism and fracture type does not seem to make a difference in outcomes

Malalignment is a common complication following tibial surgery, occurring in 10% of fractures. This is associated with prolonged healing time and non-union. It occurs due to inability to maintain a satisfactory reduction. A reduction device, such as the Staffordshire Orthopaedic Reduction Machine (STORM), permits the surgeon to manipulate the fracture and hold it reduced. A retrospective parallel case series was undertaken of all patients undergoing tibial nails over a six-year period from 2014 to 2021. Patient demographics were obtained from medical records. Operative times obtained from the theatre IT system and included the time patient entered theatre and surgical start and finish times for each case. Anteroposterior and lateral long leg post-operative radiographs were reviewed. Angulation was measured in both coronal and sagittal planes, by two separate orthopaedic surgeons. A reduction was classified to be ‘mal-aligned’ if the angle measured was greater than 5 degrees. One tailed unpaired t-test was used to compare alignment in each plane. Bony union was assessed on subsequent radiographs and was determined according to the Radiographic Union Score for Tibial Fractures. 31 patients underwent tibial nail during the time period. 8 patients were lost to follow up and were excluded. Of the remaining 23 patients, the STORM device was utilised in 11. The overall mean alignment was acceptable across all groups at 2.17° in the coronal plane and 2.56° in the saggital plane. Analysing each group individually demonstrated an improved alignment when STORM was utilised: 1.7° (1°–3°) vs 2.54° (0°–5°) for the coronal plane and 1.6° (0°–3°) vs 3.31° (0°–9°) in the saggital plane. This difference was significant in saggital alignment (p=0.03) and showed a positive trend in coronal alignment, although was not significant (p=0.08). The time in theatre was shorter in the control group with a mean of 113 minutes (65 to 219) in comparison to STORM with a mean of 140 minutes (105 to 180), an increased theatre time of 27 minutes (p=0.04). This study demonstrates that STORM can be used in the surgical treatment of tibial fractures resulting in improved fracture alignment with a modest increase in theatre time

Introduction. The Oxford Unicompartmental Knee Replacement (OUKA) is the most popular unicompartmental knee replacement (UKR) in the New Zealand Joint Registry with the majority utilising cementless fixation. We report the 10-year radiological outcomes. Methods. This is a prospective observational study. All patients undergoing a cementless OUKA between May 2005 and April 2011 were enrolled. There were no exclusions due to age, gender, body mass index or reduced bone density. All knees underwent fluoroscopic screening achieving true anteroposterior (AP) and lateral images for radiographic assessment. AP assessment for the presence of radiolucent lines and coronal alignment of the tibial and femoral components used Inteliviewer radiographic software. The lateral view was assessed for lucencies as well as sagittal alignment. Results. 687 OUKAs were performed in 641 patients. Mean age at surgery was 66 years (39–90yrs), 382 in males and 194 right sided. 413 radiographs were available for analysis; 92 patients had died, 30 UKRs had been revised and 19 radiographs were too rotated to be analysed the remainder were lost to follow-up. Mean radiograph to surgery interval was 10.2 years (7.1–16.2yrs). RLLs were identified in zone 1 (3 knees), zone 2 (2 knees), zone 3 (3 knees), zone 5 (3 knees), zone 6 (2 knees) and zone 7 (42 knees). No RLL had progressed, and no case had any osteolysis or prosthesis subsidence. Alignment in the coronal plane: mean 2.90° varus (9.30° varus - 4.49° valgus) of the tibial component to the tibial anatomic axis and the femoral component in mean 4.57° varus (17.02° varus - 9.3° valgus). Sagittal plane posterior tibial slope was a mean 6.30° (0.44° -13.60° degrees) and mean femoral component flexion of 8.11° (23.70° flexion – 16.43° extension). Conclusion. The cementless OUKA demonstrates stable fixation with low revision rates at our centre supporting results earlier published by the design centre

Total joint arthroplasty is an extremely high quality medical intervention with measured benefit to individual patients and society as a whole. However, nearly 20% of patients following total knee arthroplasty (TKA) may report some level of dissatisfaction following surgery. Weight-bearing-in-flexion activities such as squatting and ascending/descending stairs are those activities with which patients most frequently report dissatisfaction. It is assumed that optimal functioning following TKA requires proper femoral and tibial implant positioning in all planes (sagittal, coronal, and axial), proper femoral-tibial balance in the coronal and sagittal plane and durable fixation irrespective of implant design and the manner in which the surgery is executed. Posterior stabilised (PS) and cruciate retaining (CR) TKA designs are the most predominant implants utilised yet their kinematics are infrequently close to normal. In addition, there is little clinical evidence that one design is superior to another. Alternative designs such as bi-cruciate and medially stabilised designs are much less frequently used and much less frequently studied. However, in both cases, isolated centers with relatively small volumes of patients studied have reported outcomes superior to PS and CR designs depending on the metric assessed. With respect to kinematics, bi-cruciate and medially stabilised designs have displayed certain patterns of behavior that more closely mimic the native knee both in-vitro and in-vivo. Normal knee kinematics, as described by Freeman and Pinskerova, includes lateral sided femoral rollback with progressive knee flexion (alternatively thought of as internal tibial rotation with flexion) and sagittal plane stability achieved through the medial compartment. In theory, both optimal sagittal plane stability and internal tibial rotation with progressive flexion (consistent with normal dynamic changes in tibial tubercle – trochlear groove distance) following TKA should optimise weight-bearing-in-flexion kinematics and load transfer. Patient-related satisfaction with such activities might thus reasonably improve and may help explain the separate findings of Pritchett and Hossain regarding outcomes following medially stabilised TKA. Medially stabilised TKA affords sagittal plane stability in mid-flexion and internal tibial rotation with flexion without the complexity and unique failure modes seen following bi-cruciate TKA. The work flow of performing medially stabilised TKA is similar to PS and CR surgical techniques and the surgeon need not climb a steep learning curve. In addition, similar to PS TKA, medial stabilised TKA is applicable to any primary state in which coronal plane balance can be achieved. Further investigation in well-designed trials is necessary to fully develop an understanding of how different contemporary TKA designs might impact patient reported outcome. Larger registry populations of medially stabilised TKA over time are also necessary to best assess survivorship compared to other contemporary designs

To evaluate the impact of a knee prosthesis on the soft-tissue envelope or knee kinematics, cadaveric lower extremities are often mounted in a custom test rig, e.g. Oxford knee rig. Using such test rig, the knee is tested while performing a squatting motion. However, such motion is of limited daily-life relevance and clinical practices has shown that squatting commonly causes problems for knee patients. As a result, a new test rig was developed that allows a random, controlled movement of the ankle relative to the hip in the sagittal plane. Mounting the specimen in the test rig, restricts five degrees of freedom (DOF) at the hip; only the rotation in the sagittal plane is not restrained (Figure 1). On the other hand, at the ankle, only two degrees of freedom are restrained, namely the movement in the sagittal plane. The ankle has thus three rotational degrees of freedom, all rotation axis intersect in a single point: the center of the ankle. In addition, the out-of-plane translational movement of the ankle remains free. This is achieved by means of a linear bearing. The other translational degrees of freedom, in the sagittal plane, are controlled by two actuators. As a result, the knee has five degrees of freedom left; flexion-extension is controlled. This represents typical closed chain applications, such as cycling. In a first step, the knee kinematics have been evaluated under un-loaded conditions (no quadriceps or hamstring forces applied). To evaluate the knee kinematics, an infrared camera system (OptiTrack, NaturalPoint Inc, USA) is used. Therefore, three infrared markers are placed on the femur and tibia respectively. In addition, markers are placed on the test rig itself, to evaluate the accuracy of the applied motion. All markers are tracked using eight infrared cameras. At the ankle, a 2D circular motion with a radius of 100 mm was applied. Based on the 3D motion analysis, it was demonstrated that the control system has an accuracy of ± 0.5 mm. The evaluation of the knee kinematics in accordance to Grood and Suntay (J. of Biomechanical Engineering, 1983), additionally requires the evaluation of the knee anatomy. To that extent, the cadaveric specimen has been visualized using a CT scan, with the infrared markers in place. From these CT images, a 3D reconstruction has been created (Mimics, Materialise, Belgium). Subsequently, custom software has been developed that combines the CT data with the motion analysis data (Matlab, The MathWorks Inc., USA). As a result, knee motion is visualized in 3D (Figure 2.a) and clinical relevant kinematic parameters can be derived (Figure 2.b). In conclusion, the presented test rig and analysis framework is ready to evaluate more complex knee kinematics with reasonable accuracy and stability of the control loops. Future research will however primarily focus on the evaluation and validation of the impact of forces applied onto the specimen

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. Methods. Based on a clinical series of 479 primary total knees and 1,305 associated surgical decisions, various ML models were developed. These models identified the indicated surgical decision based on available, intra-operative alignment, and tibiofemoral load data. Results. With an associated area under the receiver-operator curve ranging between 0.75 and 0.98, the optimized ML models resulted in good to excellent predictions. The best performing model used a random forest approach while considering both alignment and intra-articular load readings. Conclusion. The presented model has the potential to make experience available to surgeons adopting new technology, bringing expert opinion in their operating theatre, but also provides insight in the surgical decision process. More specifically, these promising outcomes indicated the relevance of considering the overall limb alignment in the coronal and sagittal plane to identify the appropriate surgical decision

Introduction. Acquired chronic radial head (RH) dislocations present a significant surgical challenge. Co-existing deformity, length discrepancy and RH dysplasia, in multiply operated patients often preclude acute correction. This study reports the clinical and radiological outcomes in children, treated with circular frames for gradual RH reduction. Materials and Methods. Patient cohort from a prospective database was reviewed to identity all circular frames for RH dislocations between 2000–2021. Patient demographics, clinical range and radiographic parameters were recorded. Results. From a cohort of 127 UL frames, 30 chronic RH dislocations (14 anterior, 16 posterior) were identified. Mean age at surgery was 10yrs (5–17). Six pathologies were reported (14 post-traumatic, 11 HME, 2 Nail-Patella, 1 Olliers, OI, Rickets). 70% had a congruent RH reduction at final follow-up. Three cases re-dislocated and 6 had some mild persistent incongruency. Average follow up duration was 4.1yrs (9mnths-11.5yrs). Mean radiographic correction achieved in coronal plane 9. o. , sagittal plane 7. o. and carrying angle 12. o. Mean ulna length gained was 7mm and final ulnar variance was 7mm negative (congenital). All cases achieved bony union with 2 requiring bone grafting. Mean frame duration was 166 days. Mean final range of motion was 64. o. supination, 54 . o. pronation, 2. o. to 138. o. flexion. 5 complications and 7 further operations were reported. Conclusions. The majority of children having frame correction achieve complete correction or minor subluxation, which is well tolerated clinically. Frame assisted reduction is an effective tool for selective complex cases irrespective of the pathology driving the RH dislocation

Patellofemoral arthroplasty (PFA) has higher revision rates than total knee arthroplasty (TKA) [Van der List, 2015; Dy, 2011]. Some indications for revision include mechanical failure, patellar mal-tracking, implant malalignment, disease progression and persistent pain or stiffness [Dy, 2011; Turktas, 2015]. Implant mal-positioning can lead to decreased patient satisfaction and increased revision rates [Turktas, 2015]. Morphological variability may increase the likelihood of implant mal-positioning. This study quantifies the morphological variability of the anterior-posterior (AP) and medial-lateral (ML) aspects of the patellofemoral compartment using a database of computed tomography (CT) scans. The analysis presented here used the custom CT based program SOMA (SOMA V.4.3.3, Stryker, Mahwah, NJ). SOMA contains a large database of 3D models created from CT scans. Anatomic analysis and implant fitting tools are also integrated into SOMA to perform morphometric analyses. A coordinate system is established from the femoral head center, the intercondylar notch, and a morphological flexion axis (MFA). The MFA is created by iteratively fitting circles to the posterior condyles and creating and axis through the circles' centers. The sagittal plane is created normal to this axis and through the notch. A coronal plane is created from the femoral head center and the flexion axis. The AP measurement is taken normal to the coronal plane from the anterior cortex sulcus to the intercondylar notch (Figure 1). A 5°-flexed anterior resection is created to run-out at the anterior cortex sulcus. The ML measurement is taken normal to the sagittal plane from the most medial to the most lateral points of the anterior resection (Figure 1). The ML measurements are broken down into medial and lateral components divided by a sagittal plane through the trochlea. Means and standard deviations of the AP and ML measurements are calculated. The mean and standard deviation for the AP measurement are 24.9mm and 2.8mm, respectively. The data predicts that 99.7% of the population will have an AP measurement between 16.5mm and 33.3mm. The mean and standard deviation for the ML measurement are 54.6 mm and 5.5mm, respectively. The data predicts that 99.7% of the population will have an ML measurement between 38.1mm and 71.1mm A Pearson Correlation value of 0.134 was calculated for AP/ML indicating a very weak positive correlation between the measures. The correlation value and the large measurement ranges indicate that there is high variability between the AP and ML measurements. A scatterplot was created to graphically represent the high variability between the AP and ML width measurements (Figure 2). A Pearson Correlation value of −0.649 was calculated for the medial and lateral components of ML (Figure 3). The results of this study suggest that patellofemoral morphology is highly variable with respect to the AP and ML dimensions. This variability may impact implant fit and positioning and should be taken into consideration in the design and use of prostheses for PFA. For any figures or tables, please contact authors directly (see Info & Metrics tab above).

Introduction. In total knee arthroplasty extramedullary tibial guides could not to be as accurate as requested in obtaining proper alignment perpendicular to the mechanical axis. The aim of this study was to determine the accuracy of an accelerometer-based system (KneeAlign 2; OrthAlign Inc, Aliso Viejo, California) as evaluated by post-op X-rays analysis. Methods. Between March 2012 and May 2012 thirty consecutive patients with primary gonarthrosis were selected for unilateral total knee arthroplasty (TKA) using a handheld surgical navigation system to perform the tibial resection. Navigation procedure: The entire system is provisionally secured to the tibia using a spring placed around the leg and is fixed to the proximal aspect of the tibia using 2-headed pins. Before fixing the system proximally, an aiming arm is used to align the top of the device with the anterior cruciate ligament footprint and the medial one third of the tibial tubercle. Distally, a footplate connected to the tibial jig is used to keep the EM jig a set distance off of the tibial surface. A gyrometer within the navigation unit is then able to calculate the posterior slope of the tibial jig. Subsequent anatomical landmarkings of both the lateral and medial malleoli are identified using the distal aspect of the EM jig to establish the tibia's mechanical axis. Similarly, the gyrometer within the navigation unit is able to calculate the varus or valgus alignment of the tibial jig relative to the tibia's established mechanical axis. Once anatomical registration has been performed, the tibial cutting block is placed at the proximal aspect of the device, and real-time feedback is provided by the navigation unit to the surgeon, who is then able to set the cutting block's varus/valgus and posterior slope alignment before performing the tibial resection. Postoperatively, standing anteroposterior hip-to-ankle radiographs and lateral knee-to-ankle radiographs were performed to determine the varus/valgus alignment and the posterior slope of the tibial components relative to the mechanical axis in both the coronal and sagittal planes. The difference between the intraoperative reading of the tibial varus/valgus alignment and posterior slope provided by the system was compared to the radiographic measurements obtained postoperatively for each respective case. Differences were analysed via standard t test. The critical level of significance was set at P <0.05. Results. Intraoperatively, the average reading provided by the system with regard to varus/valgus alignment before performing the tibial resection was 0.3° ± 0.3° relative to the mechanical axis and 5.4° ± 0.9° in the sagittal plane. The average tibial component alignment postoperatively in the knees with was 0.6° ± 0.3° in the coronal plane (P=0.07) and 4.7° ± 0.9° in the sagittal plane (P=0.07). In no case a difference > 2° from the planned resection was detected in both coronal and sagittal plane. Conclusions. The handheld surgical navigation system combines the accuracy of computer-assisted surgery systems with the ease of use and familiarity of conventional instrument. The system might improve the accuracy of the tibial resection and subsequent tibial component alignment in TKA

Malorientation of the acetabular cup in Total Hip replacement (THR) may contribute to premature failure of the joint through instability (impingement, subluxation or dislocation), runaway wear in metal-metal bearings when the edge of the contact patch encroaches on the edge of the bearing surface, squeaking of ceramic-ceramic bearings and excess wear of polyethylene bearing surfaces leading to osteolysis. However as component malorientation often only occurs in functional positions it has been difficult to demonstrate and often is unremarkable on standard (usually supine) pelvic radiographs. The effects of spinal pathology as well as hip pathology can cause large rotations of the pelvis in the sagittal plane, again usually not recognized on standard pelvic views. While Posterior pelvic rotation with sitting increases the functional arc of the hip and is protective of a THR in regards to both edge loading and risk of dislocation, conversely Anterior rotation with sitting is potentially hazardous. We developed a protocol using three functional positions – standing, supine and flexed seated (posture at “seat-off” from a standard chair). Lateral radiographs were used to define the pelvic tilt in the standing and flexed seated positions. Pelvic tilt was defined as the angle between a vertical reference line and the anterior pelvic plane. Supine pelvic tilt was measured from computed tomography. Proprietary software (Optimized Ortho, Sydney) based on Rigid Body Dynamics then modelled the patients’ dynamics through their functional range producing a patient-specific simulation which also calculates the magnitude and direction of the dynamic force at the hip and traces the contact area between prosthetic head/liner onto a polar plot of the articulating surface. Given prosthesis specific information edge-loading can then be predicted based on the measured distance of the edge of the contact patch to the edge of the acetabular bearing. Results and conclusions. The position of the pelvis in the sagittal plane changes significantly between functional activities. The extent of change is specific to each patient. Spinal pathology can be an insidious “driver” of pelvic rotation, in some cases causing sagittal plane spinal imbalance or changes in orientation of previously well oriented acetabular components. Squeaking of ceramic on ceramic bearings appears to be multi factorial, usually involving some damage to the bearing but also usually occurring in the presence of anterior or posterior edge loading. Often these components will appear well oriented on standard views [Fig 1]. Runaway wear in hip resurfacing or large head metal-metal THR may be caused by poor component design or manufacture or component malorientation. Again we have seen multiple cases where no such malorientation can be seen on standard pelvic radiographs but functional studies demonstrate edge loading which is likely to be the cause of failure [Fig 2]. Clinical examples of all of these will be shown

Achieving optimal acetabular cup orientation in Total Hip Replacement (THR) remains one of the most difficult challenges in THR surgery (AAOR 2013) but very little has been added to useful understanding since Lewinnek published recommendations in 1978. This is largely due to difficulties of analysis in functional positions. The pelvis is not a static reference but rotates especially in the sagittal plane depending upon the activity being performed. These dynamic changes in pelvic rotation have a substantial effect on the functional orientation of the acetabulum, not appreciated on standard radiographs [Fig1]. Studies of groups of individuals have found the mean pelvic rotation in the sagittal plane is small but large individual variations commonly occur. Posterior rotation, with sitting, increases the functional arc of the hip and is protective of a THR in regards to both edge loading and risk of dislocation. Conversely Anterior rotation, with sitting, is potentially hazardous. We developed a protocol using three functional positions – standing, supine and flexed seated (posture at “seat-off” from a standard chair). Lateral radiographs were used to define the pelvic tilt in the standing and flexed seated positions. Pelvic tilt was defined as the angle between a vertical reference line and the anterior pelvic plane (defined by the line joining both anterior superior iliac spines and the pubic symphysis). In the supine position pelvic tilt was defined as the angle between a horizontal reference line and the anterior pelvic plane. Supine pelvic tilt was measured from computed tomography. Proprietary software (Optimized Ortho, Sydney) based on Rigid Body Dynamics then modelled the patients’ dynamics through their functional range producing a patient-specific simulation which also calculates the magnitude and direction of the dynamic force at the hip and traces the contact area between prosthetic head/liner onto a polar plot of the articulating surface, Fig 2. Given prosthesis specific information edge-loading can then be predicted based on the measured distance of the contact patch to the edge of the acetabular liner. Delivery of desired orientation at surgery is facilitated by use of a solid 3D printed model of the acetabulum along with a patient specific guide which fits the model and the intra-operative acetabulum (with cartilage but not osteophytes removed) - an incorporated laser pointer then marks a reference point for the reamer and cup inserter to replicate the chosen orientation. Results and conclusions. The position of the pelvis in the sagittal plane changes significantly between functional activities. The extent of change is specific to each patient. Spinal pathology is a potent “driver” of pelvic sagittal rotation, usually unrecognised on standard radiographs. Pre-operative patient assessment can identify potential orientation problems and even suitability for hard on hard bearings. Optimal cup orientation is likely patient-specific and requires an evaluation of functional pelvic dynamics to pre-operatively determine the target angles. Post-operatively this technique can identify patient and implant factors likely to be causing edge loading leading to early failure in metal on metal bearings or squeaking in ceramic on ceramic bearings