Outcomes of Humeral Allograft-Prosthetic Composites with Plate Fixation in Revision Total Elbow Arthroplasty.

Background: Traditionally, the reconstruction of severe distal humeral bone loss at the time of revision total elbow arthroplasty (TEA) has used allograft-prosthetic composites (APCs) stabilized with cerclage wires or cables. We have migrated to plate fixation when revision TEA using a humeral APC is performed. This study shows the outcomes of patients treated with a humeral APC with plate fixation during revision TEA. Methods: Between 2009 and 2019, 41 humeral APCs with plate fixation of distal humeral allograft to the native humerus were performed in the setting of revision TEA. There were 12 male patients (29%) and 29 female patients (71%), with a mean age of 63 years (range, 41 to 87 years). The mean allograft length was 12 cm. All elbows had a minimum follow-up of 2 years (mean follow-up, 3.3 years). Patients were evaluated for visual analog scale pain scores, range of motion, the ability to perform select activities of daily living, and the Mayo Elbow Performance Score (MEPS). Outcomes including reoperations, complications, and revisions were noted. The most recent radiographs were evaluated for union at the allograft-host interface, failure of the plate-and-screw construct, or component loosening. Results: The mean postoperative flexion was 124° (range, 60° to 150°) and the mean postoperative extension was 26° (range, 0° to 90°); the mean arc of motion was 99° (range, 30° to 150°). The mean MEPS was 58 points (range, 10 to 100 points). Two surgical procedures were complicated by neurologic deficits. The overall reoperation rate was 14 (34%) of 41. Of the 33 patients with complete radiographic follow-up, 12 (36%) had evidence of nonunion at the allograft-host interface with humeral component loosening, 1 (3%) had evidence of partial union, and 1 (3%) had ulnar stem loosening. Conclusions: Revision TEA with a humeral APC using compression plating was successful in approximately two-thirds of the elbows. Further refinement of surgical techniques is needed to improve union rates in these complex cases. Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Extended deltopectoral approach for revision total elbow arthroplasty requiring humeral allograft-prosthetic composites in patients with severely compromised proximal humerus bone stock.

Background: Severe humeral bone loss in the setting of failed total elbow arthroplasty (TEA) poses a particularly challenging reconstructive problem. The objective of this study was to review the rationale, indications, contraindications, and detailed surgical technique for using an extended anterior deltopectoral approach to perform a revision TEA when substantially long allografts are required in the presence of severely compromised proximal humerus bone stock. Methods: The authors developed this exposure and reconstructive strategy for failed elbow arthroplasties where the remaining segment of proximal humerus is extremely short, which makes adequate plate fixation of an allograft-prosthetic composite (APC) to the native bone extremely challenging. From an anterior deltopectoral approach, it is possible to use dedicated long, precontoured proximal humerus locking plates to maximize fixation in any remaining proximal humerus. This exposure still makes it possible to provide adequate access to the coupling mechanism of the humeral and ulnar components for implantation of a linked elbow arthroplasty. This exposure also allows for adequate judgment of humeral length and rotation. Pitfalls and Challenges: Crucial steps in the surgery include extending the dissection past the elbow flexion crease such that one can obtain circumferential exposure of the distal humerus. It is also important to couple the humeral and ulnar components prior to committing to the length of the APC. Special attention must be paid to gauge appropriate APC rotation and length for proper soft tissue tension. When performing fixation of the proximal humeral plate, screw purchase must be maximized in both the remaining native proximal humerus and the APC. Compression across the allograft-host interface is paramount for healing to occur. Conclusion: An extended anterior deltopectoral approach to perform a revision TEA when very long APCs are required is a viable option to restore humeral bone stock and regain humeral stem fixation in the setting of failed TEA with extensive humeral bone loss.

Evaluating the utility of inflammatory markers in the diagnosis of soft tissue abscesses of the forearm and hand.

Upper extremity abscesses frequently present to the acute care setting with inconclusive physical examination and imaging findings. We sought to investigate the diagnostic accuracy of inflammatory markers including white blood cell (WBC) count, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP). A retrospective cohort study was performed to identify subjects ≥ 18  years treated with surgical debridement of upper extremity abscesses at our institution between January 2012 and December 2015. In this study, 188 patients were screened, and 72 met the inclusion criteria. A confirmed abscess as defined by culture positivity was present in 67 (93.1 %) cases. The sensitivity of WBC, ESR, or CRP individually was 0.45, 0.71, and 0.81. The specificity of WBC, ESR, or CRP individually was 0.80, 0.80, and 0.40. In combination all three markers when positive had a sensitivity of 0.26 and specificity of 1.0. These values were similar among patients with diabetes and those with obesity. With the highest sensitivity and lowest specificity, CRP exhibited the most utility as a screening test (level IV).

Virtual surgical planning and mirrored, 3-dimensionally printed guides for corrective clavicle osteotomies in clavicle malunions and nonunions.

BACKGROUND: The objective of this study was to retrospectively review clinical and radiographic outcomes of patients who underwent corrective osteotomies for clavicle malunion and internal fixation for nonunion using a combination of virtual surgical planning, patient-specific 3-dimensional (3D)-printed clavicles, and 3D-printed cutting guides manufactured at the point of care. METHODS: Between 2015 and 2021, 18 patients underwent corrective osteotomy for a clavicle malunion (7 shoulders) or internal fixation for a clavicle nonunion (11 shoulders). There were 11 male and 7 female individuals with an average patient age of 43.9 (range 19-76) years. All patients underwent computed tomography evaluation of both clavicles. The DICOM files were manually segmented, virtual surgical planning was performed selectively using commercially available software, and a mirrored version of the normal clavicle was 3D printed along with a 3D-printed replica of the affected clavicle. Three-dimensionally printed mirrored clavicles were used in all cases to ensure adequate restoration of the shape and length of the clavicle and to precontour fixation plates. Virtual surgical planning and 3D-printed cutting guides for osteotomy were used in 4 of 18 (22%) patients. Either cancellous or structural intercalary bone grafting was used in 15 of 18 (83%) cases. Patients were contacted postoperatively to determine clinical outcome scores. Preoperative, early postoperative, and late postoperative radiographs were reviewed to assess for union and complications. The average follow-up time was 24.9 months. RESULTS: Radiographic evaluation at the most recent follow-up demonstrated adequate restoration of length and successful union for all shoulders. There were no complications or reoperations. Postoperative patient-reported outcomes could be obtained in 16 of 18 (88.9%) patients. At the most recent follow-up, the mean visual analog scale for pain was 2.38 points (range, 1-7), the mean shoulder American Shoulder and Elbow Surgeons score was 73.2 points (range, 25-100), and the mean Patient-Reported Outcome Measurement Information System Upper Extremity score was 26 points (range, 7-35). All (100%) the patients were satisfied with their outcome (9 very satisfied, 7 satisfied), and their mean subjective shoulder value was 73% (range, 10%-100%). However, 2 patients complained of hardware-related symptoms, and 1 patient had return of preoperative symptoms after an interim 2 years of pain relief. CONCLUSION: The use of mirrored 3D-printed clavicles combined with virtual surgical planning and patient-specific 3D guides provides a reliable technique for restoring native anatomy when performing corrective osteotomies for clavicle malunion or internal fixation for clavicle nonunion, with a high rate of satisfactory clinical and radiographic outcomes.

A bone-conserving revision stem for unstable intertrochanteric fractures of the geriatric osteoporotic population.

PURPOSE: Primary hemiarthroplasty is gaining popularity for the treatment of unstable intertrochanteric fractures in geriatric patients with severe osteoporosis. This study evaluated early clinical and radiographic outcomes by using a bone-conserving revision stem for unstable intertrochanteric fractures in the geriatric osteoporotic population. METHODS: A retrospective study involving 31 patients with unstable intertrochanteric fractures was conducted. The patients were aged 82.1 years on average. All patients underwent primary hemiarthroplasty using bone-conserving, fully porous-coated revision stem. The operative time, intraoperative blood loss, length of hospitalization, and need for blood transfusion were noted during the hospital stay. Postoperative complications, including dislocations, deep venous thrombosis, infections, peri-prosthetic fractures, and frontal thigh pain were also recorded. Koval's category was used to quantify activity level, and Harris hip score (HHS) was used for functional assessment. Radiographic outcomes, including osteolysis, bone ingrowth, subsidence of the femoral component, lower limb length discrepancy, and heterotopic ossification, were collected at each follow-up. RESULTS: The 31 patients were followed for an average time of 23 months postoperatively. The average operative time lasted for 74.2 min, while the mean intraoperative blood loss was 200.1 ml, with an average hemoglobin decrease of 11.1 g/L after the procedure. The mean visual analog scale (VAS) score for pain dropped from 7.4 preoperatively to 2.4 at the 4-week follow-up. At the latest follow-up, the mean Harris hip score was 82.1, and the VAS was 1.7. No intraoperative or postoperative peri-prosthetic fractures were noted. Postoperative complications included one case of thrombosis formation in the posterior tibial vein and one case of congestive heart failure. Both patients were discharged uneventfully after treatment. Radiographically, none of the hips had evidence of stem loosening or osteolysis. Within the follow-up period of 23 months, the mortality rate was 3.2% (1/31), and no revision surgeries were required. CONCLUSION: Primary hemiarthroplasty using a bone-conserving, cementless revision stem could serve as a reliable alternative for the treatment of unstable intertrochanteric fractures in the geriatric population with osteoporosis.

Unexpected high early failure rate of the Nexel total elbow arthroplasty.

Background: Aseptic loosening, polyethylene wear, and mechanical failure have limited the use of total elbow arthroplasty (TEA) in physically demanding patients. Newer implant designs have been introduced to improve mechanical performance. The purpose of this study was to report the results obtained after implantation of the Nexel TEA. Methods: Over a 3-year period, 2 surgeons implanted a total of 35 consecutive Nexel primary TEAs. The average patient age was 65 years, and standard TEA indications were utilized. Elbows were evaluated for pain, motion, the Mayo Elbow Performance Score, complications, and reoperations. Results: Twelve elbows underwent a revision surgery with removal of either a part of or all Nexel components at an average of 2.2 years. All revision surgeries performed at our institution revealed gross loosening of the component(s). Metallic debris and periprosthetic fractures were present in 45% and 50% of cases, respectively. Radiographic evaluation of existing components revealed humeral component loosening and periprosthetic fractures in 2 and 4 elbows, respectively. Overall, 17 of 35 (50%) elbows underwent reoperation, and 20 of 35 (60%) elbows sustained at least 1 postoperative complication. Conclusion: Primary TEA with implantation of this implant was associated with an unacceptably high rate of early implant loosening, periprosthetic fracture, and reoperation. We hypothesize that this early unexpected mechanical failure could be explained by both the utilization of a titanium-on-polyethylene bearing surface and a more posterior center of rotation causing premature anterior impingement with flexion leading to failure of the bonding interface, secondary titanium particle shedding, polyethylene wear, and osteolysis.

Effectiveness of a patient-specific guide for femoral stem implantation in primary total hip arthroplasty: a randomized control trial.

PURPOSE: The purpose of the present study was to evaluate the efficacy and feasibility of a novel CT-based patient-specific femoral alignment guide (PSG) as compared with conventional pre-operative planning during THA. METHODS: From March 2020 to September 2020, patients receiving unilateral primary THA were enrolled and randomly allocated to the conventional pre-operative planning group and the PSG group. Primary outcomes were radiographic measurements including lower limb length, femoral offset, femoral anteversion and stem varus/valgus angle, and post-operative perception of leg length discrepancy (LLD). Secondary outcomes were surgical time, intra-operative blood loss, total blood loss, visual analogue scale (VAS), and Harris Hip Score (HHS). The occurrence of post-operative complications was also recorded. RESULTS: Of the 104 patients screened, 80 cases were enrolled for analysis. The demographics of the two groups were similar. The PSG group illustrated significant improvements (p < 0.001) in lower limb length, femoral offset, femoral anteversion, and stem varus/valgus angle. Patients in the PSG group showed more favourable HHS (p < 0.001) at seven day, four week, andthree month (p = 0.003) follow-up. Perception of LLD was found significantly lower in the PSG group at three tmonth (p = 0.043), six month (p = 0.025), and 12-month (p = 0.048) follow-up. Utilization of the PSG had no significant increase in operative time, intra-operative blood loss, total blood loss, or VAS. No complication was noted in either group. CONCLUSION: Relative to conventional pre-operative planning, the application with the PSG could potentially provide a simple and reliable solution for improving femoral prosthesis orientation in THA with high accessibility and low healthcare costs. TRN: ChiCTR2000031043 Date of registration: 2020/3/21.

Venothromboembolism following shoulder arthroscopy: a systematic review.

Background: Venous thromboembolic events (VTEs) following orthopedic surgery may lead to serious morbidity and mortality. Fortunately, VTEs following upper extremity procedures are uncommon. However, the true incidence is likely underreported. The aim of this study is to provide a systematic review, excluding large database studies, to report on the incidence of VTEs following shoulder arthroscopic procedures. Methods: Following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines, a systematic review of multiple databases was performed. A comprehensive search of several databases from inception to September 1, 2021, limited to English language and excluding animal studies, was designed and conducted. Studies were screened by 2 independent reviewers. A decision to exclude studies from large surgical or insurance claim databases was made to minimize the risk of including overlapping data points in this systematic review. Results: Thirteen studies met inclusion and exclusion criteria and form part of this systematic review. A total of 32,407 patients were included in this study. Among these patients, the deep vein thrombosis, pulmonary embolism, and overall VTE rates were 0.15%, 0.08%, and 0.21%, respectively. Among the patients specified to have undergone arthroscopic rotator cuff repair, the rate of deep vein thrombosis, pulmonary embolism, and overall VTE was 0.71%, 0.37%, and 1.04%, respectively. Conclusion: While symptomatic VTEs are rare following shoulder arthroscopic procedures, surgeons must be aware that they still account for a certain number of postoperative complications. Factors such as operative time, open procedures, obesity, and altitude may increase the risk of postoperative VTE although conflicting data exist. Current literature supports the idea that chemical antithrombotic prophylaxis likely provides no significant advantage over early mobilization in reducing VTEs following shoulder arthroscopy in low-risk patients.

Epidemiology of Pediatric Nonballistic Firearm Injuries to the Upper Extremity in the United States From 2000 to 2017.

Background: This study aimed to describe the epidemiology of pediatric upper extremity injury secondary to nonballistic firearms in the United States. Methods: The National Electronic Injury Surveillance Survey (NEISS) database was queried between 2000 and 2017 for injuries to the upper extremity from nonballistic firearms in patients aged ≤18 years. In total, 1502 unique cases were identified. Using input parameters intrinsic to the NEISS database, national weighted estimates were derived using Stata/IC 15.1 statistical software (StataCorp LLC, College Station, Texas), which yielded an estimate of 52 118 cases of nonballistic firearm trauma to the upper extremity who presented to US emergency departments over the study period. Descriptive statistics were performed using NEISS parameters. Results: An average of 2895 annual pediatric upper extremity nonballistic firearm injuries were identified between 2000 and 2017. Over 91% were sustained by men, and adolescents aged 12 to 18 were the most commonly injured (69.8%). Only 3.5% of all injuries required inpatient admission, and the most common sites of injury were the hand (41.1%), followed by fingers (35.9%). Conclusions: We conclude that nonballistic firearm injuries represent a significant burden of disease to adolescent men in the United States.

Chronic Nicotine Exposure Minimally Affects Rat Supraspinatus Tendon Properties and Bone Microstructure.

Cigarette smoking is the largest cause of preventable deaths, and a known risk factor for musculoskeletal issues including rotator cuff tendon tears. Tendon degeneration is believed to be due in part to changes in tendon cell health and collagen structure. Several studies have demonstrated that exposure to nicotine negatively impacts tendon healing, but surprisingly, nicotine exposure was shown to increase rat supraspinatus tendon stiffness. In order to address this seeming contradiction, the objective of this study was to comprehensively investigate the effects of long-term (18 weeks) exposure of nicotine on tendon-to-bone microstructural properties in a rat model. We hypothesized that long term subcutaneous nicotine delivery would lead to diminished tendon mechanical properties, decreased bone microstructure in the humeral head, and altered tendon cell morphology compared to age-matched control rats receiving saline. Results demonstrated a small decrease in tendon size and stiffness, with decreased cell density in the tendon midsubstance. However, no differences were found in the enthesis fibrocartilage or in the underlying subchondral or trabecular bone. In conclusion, our study revealed limited effects of nicotine on the homeostatic condition of the supraspinatus tendon, enthesis, and underlying bone. Future studies are needed to ascertain effects of other components of tobacco products.

Radiographic evaluation of vascularity in scaphoid nonunions: A review.

Scaphoid fractures, particularly those that occur more proximally, are unreliable in achieving union due to the retrograde blood supply of the scaphoid bone. Vascular compromise is associated with the development of nonunions and avascular necrosis of the proximal pole. Due to the tenuous blood supply of the scaphoid, it is imperative that the vascularity be assessed when creating diagnostic and treatment strategies. Early detection of vascular compromise via imaging may signal impending nonunion and allow clinicians to perform interventions that aid in restoring perfusion to the scaphoid. Vascular compromise in the scaphoid presents a diagnostic challenge, in part due to the non-specific findings on plain radiographs and computed tomography. Magnetic resonance imaging techniques have dramatically improved our ability to assess the blood supply to the scaphoid and improve time to intervention. This review aims to summarize these advances and highlights the importance of imaging in assessing vascular compromise in scaphoid nonunion and in reperfusion following surgical intervention.

American Society for Surgery of the Hand (ASSH) Presidential Address Themes, 1964-2018: Revisiting Our History as We Move Forward.

The American Society for Surgery of the Hand (ASSH) was established in 1946. Since then, important advances have been made in the diagnosis and treatment of conditions affecting the upper extremity. However, there has been little documentation regarding how the largest and oldest society dedicated to hand surgery has evolved over time. Furthermore, an understanding of the history of the ASSH and the specialty of hand surgery should be emphasized in resident and fellow education. The authors aim to provide a historical overview of the ASSH through the speeches of ASSH past presidents that sheds light on future directions and long-term goals. Presidential addresses from 1961 to 2018 (courtesy of ASSH Chase Library historical archives) were reviewed. The overall percentage of ASSH presidents by specialty was 67% orthopedic, 25% plastic surgery, and 8% general surgery. The most common speech theme overall was how to be a good hand surgeon (31%). The most common speech themes were, by decade: the 1960s, history and the current state of ASSH; the 1970s and 1980s, assessments of how to be a good surgeon and goals for ASSH; the 1990s, health care and governmental regulation; the 2000s, how to be a better hand surgeon; and the 2010s goals for ASSH. In earlier years, there was more of a focus on education and technical skill development in the ASSH. Work-life balance, introduced in the 1990s, has become more of a focus in the past 20 years. Revisiting the history of the ASSH and its goals allows us to reflect on progress made while recognizing what is important as we look into the future. Furthermore, as we strive to make progress in the field of hand surgery during the current pandemic, valuable tools surface that will allow the specialty to strengthen its education, research, and patient care delivery in the future.

Epidemiology of Fireworks-Related Injuries to the Upper Extremity in the United States From 2011 to 2017.

Purpose: Fireworks may result in a wide spectrum of injury to the upper extremity ranging from mild burns to amputation. In this cross-sectional study, we describe the epidemiology of upper-extremity injuries in the United States associated with fireworks using the Consumer Product Safety Commission's National Electronic Injury Surveillance System (NEISS). Methods: The NEISS database was queried between 2011 and 2017 for all injuries of the upper extremity (from shoulder to fingertip) associated with fireworks. There were 806 unique cases, yielding a total weighted estimate of 31,430 national cases presenting to emergency departments in the United States during this time frame. National estimates, standard errors, and 95% confidence intervals were calculated using parameters provided by the NEISS database. Significance of trends was determined using adjusted Wald tests, for which P values less than .05 were considered significant. Results: The weighted estimate was 4,490 yearly cases from 2011 until 2017. Trend analysis did not show a significant change in the number of yearly cases during that time frame. Most injuries (62%) occurred around June 27 until July 11. Nearly 50% of those injured were aged 10 to 29 years and were male. Fireworks with low pyrotechnic content such as sparklers, snakes, and poppers resulted in 26% of injuries. Although 83% of patients were treated and released from the emergency department, other injuries were more severe, with a 4.5% rate of amputation, 7% rate of hospital admission, and 8% rate of transfer to another hospital. Conclusions: Fireworks injuries to the hand and upper extremity continue to represent a serious burden of disease to the United States population and the health care system. Increased awareness, legislation, and targeted public education about the dangers of fireworks should be considered ways to reduce the incidence of these injuries. Type of study/level of evidence: Prognostic III.

The effects of incremental ulnar styloid osteotomies on distal radioulnar joint stability: a biomechanical cadaveric study.

The purpose of this study was to systematically quantify distal radioulnar joint stability with a cadaveric model, using radiographic and joint contact force measurements. Six fresh-frozen cadavers underwent sequential ulnar styloid osteotomies. Posteroanterior and lateral stress radiographs were obtained and joint contact forces and areas were measured. Posteroanterior radiographs showed a significant increase in the distal radioulnar joint gap after osteotomy of the base of the ulnar styloid. Contact force and contact area measurements were not significantly different. We conclude that fractures that involve the ulnar styloid base should be considered for operative fixation when carrying out open reduction and internal fixation of fractures of the distal radius.

Nicotine impairs intra-substance tendon healing after full thickness injury in a rat model.

Nicotine is harmful to many bodily systems; however, the effects of nicotine on intra-substance tendon healing remain largely unexplored. The purpose of this study was to examine the functional, structural, and biomechanical effects of nicotine on the healing of Achilles tendons in rats after an acute full-thickness injury. Sixty Sprague-Dawley rats were enrolled in this study. Half were exposed to 0.9% saline and half to 61 ng/mL of nicotine for 3 months via subcutaneous osmotic pumps. At 3 months, all rats underwent blunt full thickness transection of the left Achilles tendon and were immobilized for one week in plantarflexion. In-vivo assays were conducted prior to injury, at 21 days, and at 42 days post-injury and included the following: Functional limb assessment, passive joint mechanics, and vascular evaluation. Rats were sacrificed at 21 and 42 days for biomechanical testing and histologic evaluation. Rats exposed to nicotine demonstrated decreased vascularity, greater alteration in gait mechanics, and increased passive ROM of the ankle joint. Biomechanically, the nicotine tendons failed at lower maximum loads, were less stiff, had smaller cross-sectional areas and had altered viscoelastic properties. Histologically, nicotine tendons demonstrated decreased vessel density at the injury site. This study demonstrates that nicotine leads to worse functional outcomes and biomechanical properties in tendons. The decreased vascularity in the nicotine group may suggest an underlying mechanism for inferior tendon healing. Patients should be counseled that using nicotine products increase their risk of poor tendon healing and may predispose them to tendon re-rupture. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

The Effect of Computed Tomography Scans Oriented Along the Longitudinal Scaphoid Axis on Measurements of Deformity and Displacement in Scaphoid Fractures.

PURPOSE: Reformatting computed tomography (CT) scans along the scaphoid longitudinal axis improves the ability to detect scaphoid fractures compared with reformats along the wrist axis. However, it remains unclear whether scaphoid axis reformats affect measurements of displacement or deformity, which are factors that drive the clinical decision to perform open reduction internal fixation. Our null hypothesis was that reformatting CT scans along the scaphoid axis does not affect measurements of fracture displacement and deformity. METHODS: Thirty patients with CT scans demonstrating scaphoid fractures (4 proximal pole, 17 midwaist fractures, and 9 distal) were identified and reformatted along 2 axes: the longitudinal axis of the scaphoid and the longitudinal axis of the wrist. The reformatted scans were sent to 2 musculoskeletal radiologists and 2 orthopedic hand surgeons who made the following measurements: (1) fracture gap, (2) displacement of the articular surface, (3) intrascaphoid angle, and (4) height to length (H:L) ratio. RESULTS: The reliability of each of the measurements cited above was compared for all raters between the 2 axes using intraclass correlation coefficients. Measurement of fracture gap and articular displacement trended toward more reliability in the wrist axis, whereas measurement of H:L ratio and intrascaphoid angle trended toward more reliability in the scaphoid axis. However, no differences in measurements between the 2 axes were statistically significant. CONCLUSIONS: This study demonstrates that reformatting CT scans in line with the axis of the scaphoid does not result in more reliable measurements of displacement or deformity. CLINICAL RELEVANCE: Measurements of displacement and deformity in scaphoid fractures can be made in the wrist axis with comparative reliability to those in the longitudinal scaphoid axis.