The medullary cavity morphology of the proximal femur influences the fixation pattern of the rectangular tapered short stem in total hip arthroplasty.

INTRODUCTION: This study aimed to evaluate differences in the pattern of fixation with a rectangular tapered short stem (Fitmore stem) due to proximal femoral medullary cavity morphology based on periprosthetic bone mineral density (BMD) and radiological findings. MATERIALS AND METHODS: We analyzed 105 consecutive patients (Dorr type A, 18; Dorr type B, 66; Dorr type C, 21) who underwent total hip arthroplasty using a Fitmore stem. Periprosthetic BMD was measured using dual-energy X-ray absorptiometry from 1 to 24 months postoperatively and radiological analysis was performed. Clinical outcomes were evaluated using the Harris hip score (HHS) and the University of California Los Angeles (UCLA) activity score preoperatively and 24 months postoperatively. RESULTS: At 24 months postoperatively, Dorr type C had significantly decreased BMD changes in Gruen zones 2, 6, and 7 compared to Dorr types A and B, and conversely, significantly increased BMD changes in zone 4 (p < 0.05). Dorr type C had significantly greater subsidence than the other types (p < 0.01) and significantly higher cortical hypertrophy in zone 3 (p < 0.01). Stress shielding was not significantly different between Dorr types. The preoperative and postoperative HHS and UCLA activity scores showed no significant differences between the Dorr types. CONCLUSIONS: In Dorr type C, BMD significantly decreased in the proximal femur with a rectangular tapered short stem, suggesting that the stem was fixed at the distal part. Careful observation of this prosthesis over time is needed in patients with Dorr type C.

Pre-milling technique improves the accuracy of posterior femoral condyle cut and reduces the tibial recut in Oxford unicompartmental knee arthroplasty.

BACKGROUND: Recuts are sometimes needed in UKA because of inadequate posterior tibial cut thickness. We investigated the efficacy of a pre-milling technique (the first milling is done prior to the posterior condylar cut) in Oxford unicompartmental knee arthroplasty to enhance bone cut thickness and to minimize tibial recuts. PATIENTS AND METHODS: Between January 2021 and January 2023, a posterior condyle cut was made before milling in 213 knees in 152 patients (conventional group), while the pre-milling technique was used in 198 knees in 140 patients (pre-milling group). The thickness of the posterior condyle and the rate of tibial recuts were compared between the groups. RESULTS: The bone cut thickness was thinner in the conventional group than in the pre-milling group in small-size (4.7 mm ± 0.6 mm and 5.0 mm ± 0.6 mm, P = 0.0001) and in medium-size (5.1 mm ± 0.5 mm and 5.4 mm ± 0.5 mm, 0.0001) femoral components, whereas there was no difference in large-size femoral components. However, the thickness was still less than the component thickness (5.17 mm for small, 5.57 mm for medium and 6.17 mm for large) in both groups. Tibial recuts were more prevalent in the conventional group than in the pre-milling group (14 knees, 7%, 3 knees 2%, P = 0.002). CONCLUSIONS: The pre-milling technique was found to increase the bone cut thickness in small and medium femoral components, reducing the need for tibial recuts. Further research is warranted to optimize the pre-milling technique and to investigate its long-term impact on patient outcomes.

Propensity of the tight mid-flexion and loose flexion gap despite the adjustment of extension and flexion gaps in Oxford unicompartmental knee arthroplasty: retrospective study.

PURPOSE: A well-balanced joint gap is necessary in Oxford unicompartmental knee arthroplasty (OUKA) to prevent mobile-bearing dislocation. While the gaps between 20° (extension) and 100° (flexion) are precisely adjusted using the incremental mill system, there has been insufficient evaluation of gaps in other angles. We hypothesized that the gap is not always the same in other angles. This retrospective study aimed to evaluate the gap in full-extension (0°), mid-flexion (60°) and deep flexion (130°) for comparison with those in extension and flexion gaps. METHODS: We evaluated 119 knees in 83 patients (51 females, 31 males, aged 71.9 years). The full-extension and mid-flexion gaps were compared with the extension gap, and the deep flexion gap was contrasted with the flexion gap. Each gap was classified into isometric, tight or loose, for evaluation of contributing factors. RESULTS: Although the full-extension gap tended to be isometric (45%), the mid-flexion tended to be tight (48%), whereas the deep-flexion was loose in most knees (84%) (P = 0.002). The tight mid-flexion and loose deep flexion gap pattern accounted for 44% of the total knees, especially so with smaller femoral components (P = 0.004). CONCLUSION: Our results highlight the propensity of tight mid-flexion and loose flexion gap despite the adjustment of extension and flexion gaps in OUKA. Although the effect of such a minor gap imbalance is still unknown, the pattern was more prevalent in patients with smaller-sized femoral components. Use of a larger femoral component may equalize the gap throughout the motion arc.

Trans patellar tendon sagittal tibial cut for lateral unicompartmental knee arthroplasty-location of the split- CT simulation study.

BACKGROUND: In lateral unicompartmental knee arthroplasty (UKA), a sagittal cut is often performed through the patellar tendon (PT). Although the approach is likely widely used, it has not been described in detail, especially regarding the site of the split. This study aimed to clarify where the split should be made. METHODS: This single-center retrospective cohort study included 49 consecutive patients and 51 knees with lateral osteoarthritis. Using preoperative computed tomography, we measured the distance from the medial edge of the PT to the intersection of the PT and the sagittal cutting line, defined as a line parallel to the Akagi's line and passing the tip of the lateral tibial spine. RESULTS: The sagittal cut line passed a mean of 45 ± 11% of the patellar tendon width from the PT medial edge. CONCLUSIONS: The tendon split should be made just medial to the center of the PT because it is where the sagittal cut line for lateral UKA passes.

Approximately 41% of knees have a looser gap in full extension than in 20° flexion after Oxford unicompartmental arthroplasty.

INTRODUCTION: In Oxford unicompartmental knee arthroplasty (OUKA), the flexion and extension gaps should be adjusted to prevent mobile-bearing dislocation. The extension gap is recommended to be evaluated in the 20° flexion position to avoid underestimation due to tension of the posterior capsule. However, we have become aware of a looser gap in full extension than in 20° flexion in some instances. MATERIALS AND METHODS: We retrospectively investigated 83 knees in 60 patients who underwent OUKA between January and June 2020. During surgery, the extension gaps were measured in both full extension and 20° flexion. The knees were classified into two groups: the gap was looser in full extension (0° group), and the gap was equal or looser in 20° flexion than in full extension (20° group). The hip-knee-ankle angle (HKAA), the lateral distal femoral angle (LDFA), the medial proximal tibia angle (MPTA), the posterior tibial slope angle (PTSA), and the last spigot size were also measured and compared between the groups. RESULTS: There was looseness in approximately 41% of knees (34 out of 83 knees) in full extension. In the knees in the 0° group, the last spigot size was significantly smaller (median 1 and 2, P < 0.01). However, there were no significant differences in the HKAA, MPTA, LDFA or PTSA between the groups. CONCLUSIONS: Approximately 41% of knees have a looser gap in full extension than in 20° flexion after OUKA. Further investigation is needed to better understand which extension gap should be used in such cases, and to find the contributing factors in loose full extension gap other than the size of the last spigot.

Short distance from the keel to the posterior tibial cortex is associated with fracture after cementless Oxford UKA in Asian patients.

PURPOSE: Tibial plateau fractures are serious complications of Oxford mobile-bearing unicompartmental knee arthroplasty (OUKA). This study examined where the fracture lines arises and evaluated the keel-cortex distances (KCDs) using three-dimensional computed tomography (3D-CT) and the effects of technical error (assessed by tibial component positions) and proximal tibial morphology on the KCDs. METHODS: This retrospective study included 217 OUKAs with cementless tibial components. Fifteen patients had tibial fractures after surgery. Anterior and posterior KCDs and fracture line origins were assessed using 3D-CT postoperatively. Proximal tibial morphology was assessed using the medial eminence line (MEL), which runs parallel to the tibial axis and passes through the tip of the medial intercondylar eminence of the tibia on long-leg anteroposterior radiograph. Knees had overhanging medial tibial condyle if the MEL passed medially to the medial tibial cortex. KCDs were compared between patients with/without fractures. Tibial component positions were evaluated, considering effects of tibial morphologies and component positions on fracture prevalence and KCDs. RESULTS: Fracture lines were found between the keel and posterior cortex in 12/15 patients. Posterior KCDs were significantly shorter in patients with fractures than in patients without (2.7 ± 1.6 mm vs 5.2 ± 1.7 mm, P < 0.001). Patients with medial overhanging condyles were more likely to have fracture (10/51 vs 5/166, P < 0.001) and had significantly shorter posterior KCD than those without (3.6 ± 1.5 mm vs 5.5 ± 1.8 mm, P < 0.001). Patients with tibial component that was set too medial, low, and valgus had higher rates of fracture than those without (7/39 vs 8/178, P = 0.008). Medial (r = 0.30, P < 0.001), low (r = -0.33, P < 0.001), and valgus implantations (r = 0.35, P < 0.001) of tibial components were related to shorter posterior KCDs. CONCLUSION: Short posterior KCD after OUKA is a risk factor for postoperative tibial fracture. Patients with either malposition of the tibial component (too medial, low, and valgus) and/or a medial overhanging condyle exhibit a shorter distance of posterior KCD and higher rate of fracture. LEVEL OF EVIDENCE: Level III.

Bearing Separation From the Lateral Wall of the Tibial Component Is a Risk of Anterior Dislocation of the Mobile Bearing in Oxford Unicompartmental Knee Arthroplasty.

BACKGROUND: Bearing dislocation is a serious complication after Oxford unicompartmental knee arthroplasty. Bearing separation from the lateral wall can cause it to spin (90° horizontal rotation) and eventually dislocate because there is just a 2 mm difference in height in both the lateral and medial sides from the bottom of the bearing, compared with the anterior (5 mm) and posterior (3 mm) sides. The details of this problem have not been previously examined. METHODS: Twenty-one dislocations in 12 patients were retrospectively analyzed. Bearing separation was defined as the bearing position being sufficiently distant from the lateral wall of the tibial component to allow spinning. We analyzed the incidence of separation, the direction and the recurrence of the dislocations, and their causes and treatments. RESULTS: Five of the 12 patients had separation. Of the total of 21 dislocations, 11 occurred in cases of separation (52%). Seven of 11 anterior dislocations were found to have separation, whereas nine of 13 posterior dislocations occurred without separation (P = .0237). Three of 5 patients with separation had recurrence of dislocation, and eventually 2 underwent revision to fixed-bearing unicompartmental knee arthroplasty. CONCLUSION: Bearing separation from the lateral wall of the tibial component can cause bearing dislocation, especially in an anterior direction. To prevent separation, the wall-bearing distance should be evaluated before the keel slot preparation, with manipulation as necessary. Conversely, posterior dislocation was predominant in our nonseparation cases.

Effectiveness of an accelerometer-based portable navigation for intraoperative adjustment of leg length discrepancy in total hip arthroplasty in the supine position.

BACKGROUND: This study aimed to examine the accuracy of the HipAlign® accelerometer-based portable navigation system by measuring the intraoperative leg length change of patients who underwent total hip arthroplasty (THA) and comparing the measured leg length discrepancy (LLD) determined by the navigation system and a freehand technique. METHODS: A total of 61 patients who underwent THA using the anterolateral approach in the supine position were included in this study and divided into two groups: those who underwent THA with navigation (Group N; N = 31) and with the freehand technique (Group F; N = 30). Statistical analyses were performed to compare the intraoperative leg length change, pre- and post-LLD, absolute values of post-LLD, and the number of patients with the postoperative LLD within 10 mm and 5 mm between the two groups. Additionally, we examined the correlation between the leg length change obtained through intraoperative navigation and measured from the radiographs. Moreover, to evaluate the navigation accuracy, we examined the correlation between the absolute error of leg length change and cup orientation. RESULTS: The postoperative LLD was significantly lower and the number of patients with the postoperative LLD within 5 mm was significantly higher in Group N, compared with Group F. Additionally, the amount of leg length change measured intraoperatively by the navigation system was strongly correlated with the values obtained by the postoperative radiographic measurement with a small absolute error and minimal wasted time. Moreover, a significant positive correlation was found between the absolute error of the leg length change and that of the cup inclination. CONCLUSIONS: Our study demonstrates that the accelerometer-based portable navigation system is useful for the intraoperative adjustment of leg length discrepancy during THA for patients in the supine position, as it provides good accuracy and minimizes required time for use.

Fully hydroxyapatite-coated compaction broached and triple-tapered stem may reduce the risk of stress shielding after primary total hip arthroplasty.

PURPOSE: Changes in bone mineral density (BMD) around the fully hydroxyapatite (HA)-coated compaction broached and triple-tapered stem, namely, Polarstem, after total hip arthroplasty (THA) are currently unknown. Therefore, the aims of this study were to investigate clinical outcomes of Polarstem, mainly postoperative temporal changes in BMD around the stem for 2 years, and to compare them with those of HA-coated and non-HA-coated tapered-wedge stems. METHODS: This retrospective cohort study enrolled 100 consecutive patients who underwent THA using Polarstem (n = 38), HA-coated Anthology (n = 31), and non-HA-coated Anthology (n = 31). BMD was evaluated using dual-energy X-ray absorptiometry in seven regions according to the Gruen zones. Postoperatively, BMD around the stem was assessed within 2 months (baseline BMD) and at 6, 12, and 24 months. A change in BMD was defined as the value calculated by dividing each postoperative BMD value at 6, 12, and 24 months by the baseline BMD value. Changes in BMD and radiographic parameters such as stress shielding and spot welds were compared among the three stems. RESULTS: The incidence rate of stress shielding in the Polarstem group was significantly lower than those in the other two groups (p = 0.007). The change in BMD in Zone 7 of Polarstem was significantly more than that of the other two groups at 12 and 24 months postoperatively (p = 0.030 and p = 0.009, respectively). CONCLUSION: Polarstem, a fully HA-coated compaction broached and triple-tapered stem, maintained BMD around the femoral calcar until 2 years postoperatively and could reduce the risk of stress shielding compared with tapered-wedge stems.

Anterior Cruciate Ligament Deficiency is Not Always a Contraindication for Medial Unicompartmental Knee Arthroplasty: A Retrospective Study in Nondesigner's Japanese Hospital.

BACKGROUND: An intact anterior cruciate ligament (ACL) is thought to be prerequisite for successful unicompartmental knee arthroplasty (UKA), but recent studies reported successful midterm results of UKA in ACL-deficient (ACLD) knees. We hypothesized that ACLD is not always a contraindication for medial UKA when preoperative radiographs showed typical anteromedial knee patterns. METHODS: From April 2012 to March 2016, 401 Oxford mobile-bearing UKAs in 282 patients were retrospectively identified from our database. Patients whose ACL was severely damaged, but preoperative X-rays showed typical anteromedial osteoarthritis patterns, were categorized into the ACLD group. From intraoperative data, those whose ACL was intact were categorized into the ACL functional (ACLF) group. There were 32 and 369 knees in the ACLD and ACLF groups, respectively, and mean follow-up periods were 66.1 and 63.8 months for the ACLD and ACLF groups, respectively. We compared the postoperative clinical outcome and component survivorship, with an endpoint of component revision, between ACLD groups and ACLF groups. RESULTS: In both groups, the Oxford knee score, Knee Society score, Tegner activity score, and knee range of motion in extension were improved after surgery. The UKA component survival rate at five years was 100% in the ACLD group and 98.9% in the ACLF group. There were no significant differences between the groups. CONCLUSION: Mid-term clinical outcomes of Oxford mobile-bearing UKA in ACLD knees were similar to those in ACLF knees. ACL deficiency is not always a contraindication for medial unicompartmental knee arthroplasty in patients with typical anteromedial osteoarthritis radiographs.

Intraoperative pelvic movement is associated with the body mass index in patients undergoing total hip arthroplasty in the supine position.

BACKGROUNDS: There are very few reports on pelvic movement during total hip arthroplasty (THA) in the supine position. We investigated intraoperative pelvic motion in the sagittal and axial planes to determine if preoperative clinical factors, including body mass index (BMI) affect intraoperative pelvic motion. METHODS: Fifty-three patients with osteoarthritis undergoing THA in the supine position were included. Clinical factors, such as age, BMI, and pelvic tilt were assessed preoperatively. Intraoperative pelvic motion in the axial and sagittal planes was assessed using a portable navigation system. We assessed the change in pelvic tilt from registration to cup implantation as the pelvic tilt change; positive values indicated anterior pelvic tilt. We measured the values and absolute values of changes in axial rotation from registration to cup implantation to determine the axial rotation angle. The effects of patient factors on pelvic motion (pelvic tilt change and axial rotation angle) were analyzed using a Spearman's correlation analysis. RESULTS: Preoperative pelvic tilt was negatively correlated with pelvic tilt change (r = -0.57, p < 0.05) and the absolute axial rotation angle (r = -0.57, p < 0.05). BMI and absolute axial rotation angle were negatively correlated (r = -0.54, p < 0.05). Age was not correlated with change in the pelvic tilt and the axial rotation angle. CONCLUSIONS: Preoperative pelvic tilt and BMI are important factors to determine intraoperative pelvic motion in patients who undergo THA in the supine position. This can help surgeons to preoperatively identify patients with a higher risk of intraoperative pelvic motion.

Evaluation of the accuracy of acetabular cup orientation using the accelerometer-based portable navigation system.

BACKGROUND: Accurate orientation of acetabular and femoral components is important during total hip arthroplasty (THA). In recent years, several navigation systems have been developed. However, these navigation systems for THA are unpopular worldwide because of their high cost. We assessed the orientation accuracy of cups inserted using a disposable accelerometer-based portable navigation system for THAs. METHODS: This was a prospective cohort study. We analyzed 63 hips with navigation prospectively and 30 hips without navigation retrospectively as historical control. The patients underwent THA via the mini anterolateral approach in the supine position using an accelerometer-based portable navigation system. We compared the preoperative target angles, intraoperative cup angles using navigation records, postoperative angles using postoperative CT data, measurement errors of cup angles, and clinical parameters such as sex, treated side, age at surgery, and body mass index (BMI). RESULTS: The average absolute error (postoperative CT-navigation record) was 2.7 ± 2.1° (inclination) and 2.7 ± 1.8° (anteversion), and the absolute error (postoperative CT-preoperative target angle) was 2.6 ± 1.9° (inclination) and 2.7 ± 2.2° (anteversion). The absolute error between postoperative CT and target angle with navigation was significantly lower than the error without navigation (inclination; p = 0.025, anteversion; p = 0.005). Cup malalignment (absolute difference of inclination or anteversion between postoperative CT and preoperative target angle of over 5°) was significantly associated with BMI value (OR: 1.3, 95% CI: 1.1-1.7). The absolute measurement error of cup inclination and anteversion was significantly correlated with patients' BMI (inclination error: correlation coefficient = 0.53, p < 0.001, anteversion error: correlation coefficient = 0.58, p < 0.001). CONCLUSIONS: The clinical accuracy of accelerometer-based portable navigation is precise for the orientation of cup placement, although accurate cup placement was affected by high BMI. This is the first study to report the accuracy of accelerometer-based portable navigation for THA in the supine position.

The tibial lateral axis is a novel extraarticular landmark for detection of the tibial anteroposterior axis.

PURPOSE: Although the tibial rotation axis is significant in knee arthroplasty, no reliable extraarticular landmark has been proposed. We hypothesized that the tibial lateral axis (TLA), a tangential line of the lateral tibial surface, is perpendicular to the surgical epicondylar axis (SEA) and compared it to other existing landmarks by 3D-CT. METHODS: Fifty legs in 25 consecutive patients were studied. Using their preoperative CT, the TLAs were identified on slices at 10-50% of the total length of the tibia and the measured differences of angles against the line perpendicular to the SEA (the tibial AP axis) were calculated. The differences between the SEA and the femoral and tibial posterior condylar axis, Akagi's line and the line between the medial intercondylar spine and the medial border of the patellar tendon (sAP line)(intraarticular), the ankle axis, and the transmalleolar axis (extraarticular) were also calculated and compared. RESULTS: The mean values of TLA at 10%, 20%, 30% were virtually parallel to the SEA (0.97° ± 4.84°, 0.02° ± 4.61°, 1.10° ± 4.97°, respectively). They were equivalent to existing intraarticular landmarks and superior to existing extraarticular landmarks, and these levels corresponded to the tip to the lower end of the tibial tubercle (at 10.8% and 17.0% of total tibial length). CONCLUSION: The proximal TLAs can be an extraarticular bony landmark that indicates the line perpendicular to the SEA. A prospective study is needed to prove the validity and accuracy of the axes clinically.

A subcutaneous arthroscopic portal closure technique without thread exposure.

We present a simple new suture technique for an arthroscopic portal that enables a secured subcutaneous suture without thread exposure. A curved suture needle is inserted through the skin at approximately 1 cm from the wound edge. The needle penetrates the subcutaneous tissue and exits through the skin on the opposite side of the wound edge. The needle and suture are pulled from just underneath the skin layer. The thread is collected within the wound, and the other end of the thread is pulled from the wound. The needle is inserted at just beneath the skin layer, penetrates the subcutaneous tissue, and pierces the opposite side of the skin. The needle is retrieved along with the thread at approximately 1 cm from the other side of the wound edge. After removing the needle from the thread, the thread passing in the wound is located and the needle side of the thread is retrieved from the wound. The ends of the thread are tied under the appropriate tension. From our findings, we recommend this method for suturing of all arthroscopic portals, as well as other small incisions that need water-tight suture.

Effect of tibial component position on short-term clinical outcome in Oxford mobile bearing unicompartmental knee arthroplasty.

BACKGROUND: Malposition of the tibial components is a well-known complication of unicompartmental knee arthroplasty. In this study, we aimed to ascertain the relationship between the tibial component position and clinical outcomes of unicompartmental knee arthroplasty. We focused on the tibial component height and obliquity in the coronal plane. METHODS: Patients with anteromedial osteoarthritis who underwent Oxford mobile-bearing unicompartmental knee arthroplasty (n = 45) were included, and their Oxford knee score was assessed prior to and 1 and 2 years following surgery. We also assessed the postoperative tibial component position in the coronal plane using radiography, measuring the tibial component height and obliquity. We analyzed the sequential change in both clinical scores using repeated measures analysis of variance (p < 0.05). The effects of tibial component position on the clinical outcomes were analyzed using linear regression analysis (p < 0.05). RESULTS: The Oxford knee score significantly improved 1 year after surgery. The tibial component height and obliquity had a significantly negative correlation with the 2-year postoperative Oxford knee score. They were also correlated significantly with Oxford knee score recovery after unicompartmental knee arthroplasty. CONCLUSION: The 2-year postoperative outcomes of Oxford unicompartmental knee arthroplasty depended on the tibial component position. We observed poorer outcomes when the tibial component was placed at a lower level relative to the lateral compartment and when there was an excessive valgus angle relative to the lower limb axis.

Ideal screw positions for multiple screw fixation in femoral neck fractures - Study of proximal femur morphology in a Japanese population.

BACKGROUND: Despite the fact that multiple screw fixation is a common option of surgical treatment for femoral neck fractures, there is a paucity of precise morphological study of the femoral neck. To identify appropriate positions and spacing of hip screws for multiple-screw femoral neck fracture fixation, proximal femur morphology in Japanese patients was studied. METHOD: One hundred hips in fifty knee arthroplasty candidates were studied. Following full limb CT, defined slices were created and anatomical variables measured. RESULT: The average neck-shaft angle was 126.5° and the distance from the subcapital line to the subchondral bone on a line parallel to the femoral neck axis (FNA) was approximately 25 mm at the superior and inferior; borders of the femoral neck. The FNA was shown to run anterior to the femoral axis (FA). The cross section of the femoral neck forms a reverse right triangle. The height and width of the neck medullary canal were equal (approximately 25 mm), with the posterior wall closer to the femoral axis than the anterior wall. CONCLUSION: Based on these data, the anterior screw positioned just above the calcar femorale, 16 mm proximal and 27° anterior to the FA, and the posterior screw positioned 12 mm proximal and 5 mm posterior to the FA is recommended. For screws inserted with a fixed angle side-plate, ≤130° is recommended.

The Use of Smart Glasses for Surgical Video Streaming.

Observation of surgical procedures performed by experts is extremely important for acquisition and improvement of surgical skills. Smart glasses are small computers, which comprise a head-mounted monitor and video camera, and can be connected to the internet. They can be used for remote observation of surgeries by video streaming. Although Google Glass is the most commonly used smart glasses for medical purposes, it is still unavailable commercially and has some limitations. This article reports the use of a different type of smart glasses, InfoLinker, for surgical video streaming. InfoLinker has been commercially available in Japan for industrial purposes for more than 2 years. It is connected to a video server via wireless internet directly, and streaming video can be seen anywhere an internet connection is available. We have attempted live video streaming of knee arthroplasty operations that were viewed at several different locations, including foreign countries, on a common web browser. Although the quality of video images depended on the resolution and dynamic range of the video camera, speed of internet connection, and the wearer's attention to minimize image shaking, video streaming could be easily performed throughout the procedure. The wearer could confirm the quality of the video as the video was being shot by the head-mounted display. The time and cost for observation of surgical procedures can be reduced by InfoLinker, and further improvement of hardware as well as the wearer's video shooting technique is expected. We believe that this can be used in other medical settings.

Additional Visualization via Smart Glasses Improves Accuracy of Wire Insertion in Fracture Surgery.

BACKGROUND: Smart glasses (SG) are a wearable device consisting of a small computer built into a head-mounted monitor (HMM) that can display various kinds of information. Lateral side visualization is displayed on the HMM of SG so the operator may also see it and the anteroposterior (AP) direction simultaneously. The present pilot study aimed to investigate the usefulness of SG in wire insertion for bone fracture. METHODS: We marked both the front and lateral sides of the shaft of an artificial femur bone. From the tip of the greater trochanter, we inserted a 2.4-mm Kirschner wire (K-wire) so that it could be directed toward the marks in both planes. Three surgeons enrolled in the study each performed 10 trials, both with SG (SG arm) and without (direct vision arm). We defined the error angle as the angle between the K-wire and the line connecting the marking point from the insertion point in both the front and lateral view images. We also measured the time it took to insert the K-wire in both arms. RESULTS: The SG had a significantly reduced (mean = 3.2°) error angle ( P = .02) when compared to the direct vision group (mean = 4.8°). However, no significant difference was found between direct vision (mean = 17.5 seconds) and SG arms (mean = 14.9 seconds) in the insertion time. CONCLUSION: While keeping the AP image view in primary focus, simultaneously viewing the lateral side of the surgical field using SG helps achieve more accurate wire insertion in surgery.

The effect of acetabular and femoral component version on dislocation in primary total hip arthroplasty.

PURPOSE: The purpose of the present study was to: (1) investigate the variation of both acetabular and femoral component version in a large series of consecutive primary THA patients, and (2) to better define the associations of acetabular and femoral component alignment and clinical factors with subsequent hip dislocation in those patients. METHODS: We analyzed CT scans of 1,555 consecutive primary THAs and measured version of the components. We also documented the frequency and direction of subsequent dislocation as well as femoral head size, posterior tissue repair, any history of previous hip surgery, and gender. RESULTS: The dislocation rate after THA was 3.22 %. The dislocation risk was 1.9 times higher if cup anteversion was not between 10° and 30°. Compared to hips that did not dislocate, those that experienced anterior dislocation had a significantly greater combined anteversion; those that dislocated posteriorly had a significantly smaller combined anteversion. Hips with previous rotational acetabular osteotomy or head size smaller than 28 mm correlated with an increased dislocation rate. CONCLUSION: The dislocation risk could be higher if cup anteversion was not between 10° and 30°. Greater combined anteversion could be a risk factor of anterior dislocation, and posterior dislocation could be more common in smaller combined anteversion.