Abstract. Purpose. Intracanal rib head penetration is a well-known entity in dystrophic scoliotic curves in neurofibromatosis type 1. There is potential for spinal cord injury if this is not recognised and managed appropriately. No current CT-based classification system is currently in use to quantify rib head penetration. This study aims to propose and evaluate a novel CT-based classification for rib head penetration primarily for neurofibromatosis but which can also be utilised in other conditions of rib head penetration. Materials and methods. The grading was developed as four grades: normal rib head (RH) position—Grade 0, subluxed ext-racanal RH position—Grade 1, RH at pedicle—Grade 2, intracanal RH—Grade 3. Grade 3 was further classified depending on the head position in the canal divided into thirds. Rib head penetration into proximal third (from ipsilateral side)—Grade 3A, into the middle third—Grade 3B and into the distal third—Grade 3C. Seventy-five axial CT images of Neurofibromatosis Type 1 patients in the paediatric age group were reviewed by a radiologist and a spinal surgeon independently to assess interobserver and intraobserver agreement of the novel CT classification. Agreement analysis was performed using the weighted Kappa statistic. Results. There was substantial interobserver correlation with mean Kappa score (k = 0.8, 95% CI 0.7–0.9) and near perfect intraobserver Kappa of 1.0 (95% CI 0.9–1.0) and 0.9 (95% CI 0.9–1.0) for the two readers. Conclusion. The novel CT-based classification quantifies rib head penetration which aids in management planning

Purpose. Primary total hip arthroplasty (THA) has been a very successful surgical intervention for the management of end-stage arthritis in geriatric patients (> age 65). The mid- to long-term results have been less satisfactory however, in younger patients primarily due to the wear of the acetabular liner and loosening of the femoral component. The primary study purpose was to compare pain, function and stiffness over the first five years in a population less than 60 years of age who received either an alumina liner/alumina femoral head (alumina group) or a crossfire UHMWPE liner/alumina head (Poly group) following primary THA. Secondarily, we compared re-operation rates over five years between these two groups. Method. This was a randomized, controlled clinical trial of subjects with non-inflammatory OA who were booked for primary THA and consented to participate in the study. Subjects were evaluated pre-operatively and again at one and five years post-operatively by an evaluator who was blinded to group allocation. At each assessment, subjects completed the WOMAC Osteoarthritis Index (WOMAC); complications and re-operations were also recorded. All analyses were performed on an intention to treat basis. Results. 92 subjects were enrolled in the study. The mean age of subjects was 52.4 (SD 6.8) and 50 (54%) were male and was similar between groups (p>0.10). Baseline pain, function and stiffness as measured by the WOMAC were also similar between groups (p>0.48). Five-year follow-up data was available for 78 (85%) patients. Both groups showed substantial improvement in pain, function and stiffness within one year that was maintained out to five years post-operatively; there were no statistically significant differences between groups (p>0.50). Four subjects required re-operation within five years; no re-operation was related to liner type two cases were dislocation due to the malposition of the cup while the remaining two re-operations occurred in the immediate post-operative period for removal of hematoma. Conclusion. Our prospective randomized controlled trial showed substantial post-operative improvements in pain, stiffness, and function that were maintained out to five years, with no statistically significant differences seen between the two groups. No re-operations that were related to the liner type occurred in the first five post-operative years

Introduction. Total shoulder arthroplasty (TSA) is an effective treatment to restore shoulder function and alleviate pain in the case of glenohumeral arthritis [1]. Stress shielding, which occurs when bone stress is reduced due to the replacement of bone with a stiffer metallic implant, causes bone resorption of up to 9% of the humeral cortical thickness following TSA [2]. Shorter length stems and smaller overall geometries may reduce stress shielding [3], however the effect of humeral head backside contact with the resection plane has not yet been fully investigated on bone stress. Therefore, the purpose of this study was to quantify the effect of humeral head contact conditions on bone stresses following TSA. Methods. 3D models of eight male left cadaveric humeri (68±6 years) were generated from CT data using MIMICS. These were then virtually prepared for reconstruction by an orthopaedic surgeon to accept a short-stem humeral implant (Exactech Equinoxe® Preserve) that was optimally sized and placed centrally in the humeral canal. The humeral head was positioned in the inferior-medial position such that contact was achieved on the medial cortex, and no contact existed on the lateral cortex. Three different humeral head backside contact conditions were investigated (Figure 1); full backside contact (FULL), contact with only the inferior-medial half of the resection (INF), and contact with only the superior-lateral half of the resection (SUP). Cortical bone was assigned an elastic modulus of 20 GPa and a Poisson's ratio of 0.3. Trabecular bone was assigned varying stiffness based on CT attenuation [4]. A joint reaction force was then applied representing 45˚ and 75˚ of abduction [5]. Changes in bone stress, as well as the expected bone response based on change in strain energy density [6] was then compared between the intact and reconstructed states. Results. For cortical bone, the full backside contact altered bone stress by 28.9±5.5% compared to intact, which was significantly less than the superior (37.0±3.9%, P=0.022) and inferior (53.4±3.9%, P<0.001) backside contact conditions. Similar trends were observed for changes in trabecular bone stress relative to the intact state, where the full backside contact altered bone stress by 86.3±27.9% compared to intact, compared to the superior and inferior contact conditions, which altered bone stress by 115.2±45.0% (P=0.309) and 197.4±80.2% (P=0.024), respectively. In terms of expected bone response, both the superior and inferior contact resulted in an increase in bone volume with resorbing potential compared to the full contact (Figure 2). Discussion and Conclusions. The results of this study show that full humeral head backside contact with the humeral resection plane is preferable for short stem humeral TSA implants with the head in the inferior-medial position. As expected, the superior contact typically increased resorption potential in the medial quadrant due to the lack of load transfer, however interestingly the inferior contact increased resorption potential in both the lateral and medial quadrants. Analysis of implant micromotion showed that medial liftoff of the implant occurred, which resulted in a lack of load transfer in the most medial aspect of the resection plane. For any figures or tables, please contact the authors directly

Reverse shoulder arthroplasty (RSA) has an increasing effective use in the treatment of patients with a variety of diagnoses, including rotator cuff deficiency, inflammatory arthritis, or failed shoulder prostheses. Glenoid bone loss is not uncommonly encountered in these cases due to the significant wear. Severe bone loss can compromise glenoid baseplate positioning and fixation, consequently increasing the risk for early component loosening, instability, and scapular notching. To manage severe glenoid bone deficiencies, bone grafts are commonly used. Although, many studies report outcome of bone grafting in revision RSA, the literature on humeral head autograft for glenoid bone loss in primary RSA is less robust. The purpose of this study is to evaluate the clinical and radiographic outcomes of primary RSA with humeral head autograft for glenoid bone loss at our institution. Institutional review board approval was obtained to retrospectively review the records of 22 consecutive primary RTSA surgeries in 21 patients with humeral head autograft for glenoid bone loss between January 2008 and December 2016. Five patients died during follow-up, three were unable to be contacted and one refused to participate, leaving a final study cohort of 12 patients with 13 shoulders that underwent RSA. All patients had a clinical evaluation including detailed ROM and clinical evaluation using the American Shoulder and Elbow Surgeons (ASES) Score, Constant Score, Western Ontario Osteoarthritis of the Shoulder Index (WOOS), and Short Form-12 (SF-12) questionnaires. Preoperative and postoperative plain radiographs and CT scans were assessed for component position, loosening, scapular notching, as well as graft incorporation, resorption, or collapse. There were 6 males and 6 females, with an average age of 74 ± 6.8 years. The average BMI was 31.7 ± 5.3, and the median ASA score was 3. Average follow-up was 3.4 ± 1.1 years. The average postoperative range of motion measurements for the operative arm are: flexion = 120 ± 37, abduction = 106 ± 23, external rotation = 14 ± 12, internal rotation at 90 degrees of abduction = 49 ± 7, external rotation at 90 degrees of abduction = 50 ± 28. Average functional scores are: ASES: 76.9 ± 19.2, WOOS: 456 ± 347, SF12 physical: 34.2 ± 8.2, SF12 mental: 54.1 ± 10.2, Constant Score: 64.6 ± 14. No evidence of hardware loosening or evidence of bone graft resorption were encountered. On CT, the average of pre operative B-angle was 79.3 ± 9.3 while the pre operative reverse shoulder angle was 101.4 ± 28. Glenoid retroversion average on CT was 13.3 ± 16.6. Post operative baseplate inclination average was 82 ± 7.4 while the baseplate version 7.8 ±10. The operative technique was able to achieve up to 30 degrees of inclination correction and up to 50 degrees of version correction. In conclusion, primary reverse shoulder arthroplasty with humeral head autograft for glenoid bone loss provides excellent ROM and functional outcomes at mid-term follow-up. This technique has a high rate of bone incorporation and small risk of bone resorption at mid term follow up

Fibular head avulsion fractures represent a significant injury to the posterolateral corner of the knee. There is a high rate of concomitant injuries including rupture of the cruciate ligaments. Surgical fixation is indicated to restore stability, protect repaired or reconstructed cruciate ligaments and possibly decrease the likelihood of degenerative change. The current presentation describes a novel technique which provides secure fixation to the fibular head, restoring integrity of the posterolateral ligament complex and facilitating early motion. We also present a case series of our experience by a single surgeon at our tertiary referral center. Twenty patients underwent open reduction and internal fixation between 2006 and 2016 using a large fragment cannulated screw and soft tissue washer inserted obliquely from the proximal fibula to tibia. Fixation was augmented with suture repair of the lateral collateral ligament and biceps tendon. The orientation of the fracture was assessed based on preoperative imaging. Repair / reconstruction of concomitant injuries was performed during the same procedure. Early range of motion was initiated at 2 weeks postoperatively under physical therapy guidance. All patients returned for clinical and radiographic assessment (average 3.5 years). All fractures went on to bony union. There were no reoperations for recurrent instability. All patients regained functional range of motion with mean extension of 0.94 degrees and mean flexion of 121.4 degrees. Two patients underwent hardware removal. One patient developed a late local infection, which occurred greater than 5 years after surgery. Eleven patients underwent postoperative varus stress radiographs which demonstrated less than 1 mm difference between the operated and contralateral side. Fracture morphology typically demonstrated an oblique pattern in the coronal plane and a transverse pattern in the sagittal plane. This study represents a novel surgical technique for the repair of fibular head avulsion fractures with a large fragment cannulated screw placed obliquely from the fibula to tibia. Fixation is augmented with a soft tissue washer and suture repair. Our results suggest that this technique allows for early range of motion with maintenance of reduction, high rates of union, and excellent postoperative stability

Introduction. Total hip arthroplasty (THA) is a commonly performed procedure to relieve arthritis or traumatic injury. However, implant failure can occur from implant loosening or crevice corrosion as a result of inadequate seating of the femoral head onto the stem during implantation. There is no consensus—either by manufacturers or by the surgical community—on what head/stem assembly procedure should be used to maximize modular junction stability. Furthermore, the role of “off-axis” loads—loads not aligned with the stem taper axis—during assembly may significantly affect modular junction stability, but has not been sufficiently evaluated. Objective. The objective of this study was to measure the three-dimensional (3D) head/stem assembly loads considering material choice—metal or ceramic—and the surgeon experience level. Methods. A total of 29 surgeons of varying levels (Attending, Fellow, Resident) were recruited and asked to perform a benchtop, head/stem assembly using an instrumented apparatus simulating a procedure in the operating room (Figure 1). The apparatus comprised of a 12/14 stem taper attached to a 3D load sensor (9347C, Kistler® USA, Amherst, NY). Surgeons were randomly assigned a metal or ceramic femoral head and instructed to assemble the taper using their preferred surgical technique. This procedure was repeated five times. Surgeons were brought back to test the opposite material after four weeks. Output 3D load data was analyzed for differences in peak vertical load applied, angle of deviation from the stem axis—termed off-axis angle, variability between trials, and impaction location. Results. Preliminary results suggest no significant differences between the loads applied to the metal heads and the ceramic heads. Across the two materials tested, both attendings and residents applied greater loads than fellows (p=0.33; Residents=9.0 kN vs Fellow=7.2 kN: p=0.27; Attendings=8.9 kN vs 7.2 kN) with significantly less variability (Attendings: σ= 1.58; Fellows: σ= 3.26; Residents: σ= 2.86). Attending surgeons also exhibited applied loads at significantly lower off-axis angles compared to fellows (p=0.01; 4.6° vs Fellow=7.2°) (Figure 2). However, all of our clinicians assembled ceramic head tapers with a greater off-axis angle as compared to assembling metal heads. In addition, metal heads were impacted more on-axis for all surgeon experience levels (Figure 3). While the impaction load plots suggest that the first impact strike is the most crucial for head stability, it was determined that the number of strikes is not as important as the maximum impaction load applied. Conclusion. Differences in impaction load when assembling metal and ceramic femoral heads were not apparent; however, variability of technique and load was observed across the different surgical experience levels as well as within surgeons of the same level. Understanding assembly mechanics and surgical habits for THA will provide insight to the best assembly procedures for these implants. For any figures or tables, please contact authors directly

Introduction. Shoulder arthroplasty is used to treat several common pathologies of the shoulder, including osteoarthritis, post-traumatic arthritis, and avascular necrosis. In replacement of the humeral head, modular components allow for anatomical variations, including retroversion angle and head-neck angle. Surgical options include an anatomic cut or a guide-assisted cut at a fixed retroversion and head-neck angle, which can vary the dimensions of the cut humeral head (height, anteroposterior (AP), and superoinferior (SI) diameters) and lead to negative long term clinical results. This study measures the effect of guide-assisted osteotomies on humeral head dimensions compared to anatomic dimensions. Methods. Computed tomography (CT) scans from 20 cadaveric shoulder specimens (10 male, 10 female; 10 left) were converted to three-dimensional models using medical imaging software. An anatomic humeral head cut plane was placed at the anatomic head – neck junction of all shoulders by a fellowship trained shoulder surgeon. Cut planes were generated for each of the standard implant head-neck angles (125°, 130°, 135°, and 140°) and retroversion angles (20°, 30°, and 40°) in commercial cutting guides. Each cut plane was positioned to favour the anterior humeral head-neck junction while preserving the posterior cuff insertion. The humeral head height and diameter were measured in both the AP plane and the SI plane for the anatomic and guide-assisted osteotomy planes. Differences were compared using separate two-way repeated measures ANOVA for each dependent variable and deviations were shown using box plot and whisker diagrams. Results. Guide-assisted cuts tend to be smaller than the anatomic humeral head dimensions. Retroversion angle showed a significant effect on head height, AP, and SI diameters (p=0.002). The effect of head-neck angle was only significant for SI diameter (p<0.001). The largest dimensional deviation was observed at 20 degrees of retroversion and resulted in a 2.5mm decrease in humeral head height, averaged over the range of head-neck values. Conclusion. Where patient's natural anatomy falls outside the range of commercial cutting guides, resection according to the template may result in a deviation from the natural dimensions of the humeral head, which impacts the sizing of the implant head component. This has implications for both manufacturers to create a template that has a larger range of retroversion angles, as well as surgeons' choices in intra-operative planning

355 non-cemented MOM arthroplasties, of a single surgeon, with a follow up of 3–16 years (avg. 7.5 years) were retrospectively reviewed for evidence of pseudotumor and aseptic mechanical failure. There were 186 with 28 mm heads, 126 with 34 mm heads, 47 with 38 mm heads, from a single manufacturer. There were 5 revisions of 38 mm heads for atraumatic painful “metalosis” 4–8 years after implantation (10.7%). There were 4 revisions of 34 mm heads for post-traumatic instability (dislocation) with secondary metalosis 4–7 years after implantation (3.1%). There were 2 revisions of 28 mm heads for post-traumatic instability (dislocation) with secondary metalosis 6–12 years after implantation (1.1%). There were 5 patients, all with 38 mm heads, with asymptomatic “psoas bursae” with elevated serum CR and Co levels (1.0–3.0). All of the failed THR's had acetabular components with lateral tilt <50 degrees (35–50), and anteversion angles <15 degrees (0–15). 2 of the 34 mm and both 28 mm instabilities were the consequence of injuries sustained in motor vehicle accidents. The remaining 2 instabilities with 34 mm implants were the result of mechanical falls. Particulate debris, whether secondary to polyethylene, ceramic or metal articulations has been well documented as a cause of synovitis and damage to bony and soft tissues adjacent to a THR. This debris appears to be the result of material wear and mechanical failure with use over time. Unlike native articular cartilage, these materials are incapable of self-lubrication. Therefore THR articulations are dependent upon the penetration of ambient synovial fluid to provide lubrication of the replacement surfaces. This study suggests that increase in head diameter may reduce penetration of synovial fluid between the articulating surfaces of a THR, compromising the lubrication of bearing surfaces; thereby contributing to accelerated wear and premature failure of larger MOM arthroplasties

Hemi shoulder arthroplasty is a rather successful procedure although revision surgery due to secondary glenoid erosion is reported in more than 25%. The downside of common shoulder arthroplasty is that in a deltopectoral approach the subscapularis tendon needs to be detached for exposure of the humeral head. Refixation of subscapularis tendon is associated with a retear rate of 4%, furthermore with progressing fatty muscle infiltration and loss of function. In case of revision surgery a second subscapularis tendon detachment is even more associated with worse function. Thus, arthroscopic humeral head resurfacing is an expedient alternative for minimal invasive humeral head arthroplasty without compromising subscapularis function. The purpose of this study was to report first clinical and subjective results after arthroscopic-assisted resurfacing of the humeral head. For this prospective case series, 24 patients (7 females, 17 males; mean age 59 years, range 42–73 years) undergoing arthroscopic-assisted partial shoulder resurfacing with the partial eclipse prosthesis were included in the study. Clinical conditions and subjective assessments were evaluated before surgery and annually thereafter using the Constant score (CS), active range of motion (ROM), visual analog scale (VAS) for pain, and the American Shoulder and Elbow Surgeons scale (ASES). Radiological outcomes and major complications were monitored. The mean CS for all patients improved significantly from 51 points preoperatively to 83 points 12 months after surgery (p=0.005). Trends towards increasing ROMs were detected. Subjective scores significantly improved from baseline to the 1-year follow-up (VAS: from 6.4 to 2.5, p=0.010; ASES: from 47 to 76, p=0.026). The majority of patients (88%) stated that they would undergo the procedure again. Revisions were indicated in 17% due to progression of osteoarthritis. Arthroscopic-assisted partial humeral head resurfacing as a minimal invasive procedure with the advantages of bone stock preservation and intact subscapularis tendon allowed immediate postoperative active mobilization and provided significant improvements in subjective outcome. In case of revision surgery a primary situation was encountered with postoperative results comparable to primary arthroplasty

A secure taper connection in shoulder arthroplasty is mandatory to avoid loosening and fretting. This study's objective was to determine the amount of in situ force used by surgeons to seat a humeral head and to determine the disengagement force of the taper connection. The influence of 1) material type, 2) head size, and 3) surgeon on the impaction force and the fixation (pulloff force) of the sample was examined. Methods. Impaction data was collected from experienced shoulder surgeons (n=5) during a cadaver lab. Testing groups (n=5 each) were: 1) small ceramic, 2) big ceramic, 3)small metal and 4) large metal. Twenty centric, anatomic humeral heads (DJO surgical, Vista, CA, TURONTM, material: CoCrMo or BIOLOX®delta, size: 38×14mm or 54×22mm) were paired with a corresponding humeral neck (TURON™, DJO surgical, type: neutral modular, material: CoCrMo). Each taper was always used with the same humeral head throughout testing. The impaction force sequence was recorded using an instrumented impactor (Piezo sensor, model 208 C05, PCB PIEZOTRONICSINC, Depew, NY, ±1%). The surgeons impacted all samples into the cadaver using their typical pattern of hammer strikes (Figure 1). The engaged humeral head and taper were removed by hand and then disengaged using an instrumented (U93, HBM, Darmstadt, Germany, load limit: 5kN) hand-held pulloff-device. Statistics and data analysis were performed in MATLAB (2014b, Mathworks, Natick, MA, α=0.05). Two-tailed, pearson's linear correlation coefficients are reported. Group differences were determined using Kruskal Wallis test. Pair-wise comparisons were performed using a Tukey correction. Results. Extremely high and variable impaction forces were measured (Table 1, Figure 2). The maximum force was nearly 27 kN; however, that value reduced to ∼18kN when the data from an outlier surgeon was removed. Maximum impaction forces were 12.45±4.36 kN, and the average was 10.47±3.63 kN. The pulloff force ranged from 0.94 kN to 5.54 kN with an average of 2.76±1.19 kN. Higher impaction forces required higher pulloff forces to disengage the taper connection (p<0.001, R>−0.608). Ceramic humeral heads showed a 24% higher fixation strength (p=0.004) under similar engagement conditions (p=0.18) in comparison to metal components. Head size does not appear to influence either the magnitude of the impaction force surgeons use (p>0.20) nor the force needed to disengage the taper (p=0.25). The surgeon performing the insertion had a significant influence on the impaction strike timing (p<0.001), number of strikes (p<0.001), and the impaction forces (p<0.03) and the pulloff force (p<0.001). Conclusions. Impaction forces were markedly larger than those recorded for taper engagement in hip arthroplasty. The ceramic humeral component showed greater fixation strength in comparison to the metal for similar impaction forces. Pulloff forces were approximately 25% of the impaction force. Potentially, this low taper efficiency resulted from the cadaver absorbing much of the energy rather than the taper connection. The influence of the patient and the clinical situation on the taper efficiency is unknown. Variations between surgeons greatly influenced the impaction and the fixation force. Therefore, individual surgeon practices may substantially influence clinical fixation strength of tapered shoulder implants

Trauma & Orthopaedic Department, Bronglais Hospital & Hywel Dda University Health Board, Aberystwyth, UK. Auto-CAD study is done to observe the effects of head neck ratio (HNR) in joint replacements. Total hip replacement joints were reconstructed on CAD with increasing diameter of the head keeping neck diameter constant in 1997. Simulation was done and Range of Movement (ROM), impingement and stability of the hip joint was noted. A graph was plotted with HNR on X-axis and ROM on Y-axis. It was observed that as the HNR increases the ROM of the joint is increased, impingement is reduced and stability is also increased. It is also observed that diameter of the head and neck is more important than considering only head diameter of the hip joint. The graphical analysis confirms that different diameters of the head may have same HNR depending on the neck diameter. So even in smaller diameter head the HNR may be more due to smaller diameter neck and may be more advantages than larger diameter head with bigger neck having smaller HNR. We conclude that HNR is more important than the head diameter alone in hip replacements

Auto-CAD study is done to observe effects of head neck ratio (HNR) in hip replacements. Total hip replacement joints were reconstructed on CAD with increasing diameter of the head keeping neck diameter constant in 1997. Simulation was done and Range of Movement (ROM), impingement and stability of the hip joint was noted. A graph was plotted with Head Neck Ratio (HNR) on X-axis and ROM on Y-axis. It was observed that as the HNR increases the ROM of the joint is increased, impingement is reduced and stability is also increased. It is also observed that diameter of the head and neck is more important than considering only head diameter of the hip joint. The graphical analysis confirms that different diameters of the head may have same HNR depending on the neck diameter. So even in smaller diameter head the HNR may be more due to smaller diameter neck and may be more advantages than larger diameter head with bigger neck having smaller HNR. We conclude that HNR is more important than the head diameter alone in hip replacements

Background. Humeral version is the twist angle of the humeral head relative to the distal humerus. Pre-operatively, it is most commonly measured referencing the transepicondylar axis, although various techniques are described in literature (Matsumura et al. 2014, Edelson 1999, Boileau et al., 2008). Accurate estimation of the version angle is important for humeral head osteotomy in preparation for shoulder arthroplasty, as deviations from native version can result in prosthesis malalignment. Most humeral head osteotomy guides instruct the surgeon to reference the ulnar axis with the elbow flexed at 90°. Average version values have been reported at 17.6° relative to the transepicondylar axis and 28.8° relative to the ulnar axis (Hernigou, Duparc, and Hernigou 2014), although it is highly variable and has been reported to range from 10° to 55° (Pearl and Volk 1999). These studies used 2D CT images; however, 2D has been shown to be unreliable for many glenohumeral measurements (Terrier 2015, Jacxsens 2015, Budge 2011). Three-dimensional (3D) modeling is now widely available and may improve the accuracy of version measurements. This study evaluated the effects of sex and measurement system on 3D version measurements made using the transepicondylar and ulnar axis methods, and additionally a flexion-extension axis commonly used in biomechanics. Methods. Computed tomography (CT) scans of 51 cadaveric shoulders (26 male, 25 female; 32 left) were converted to 3D models using medical imaging software. The ulna was reduced to 90° flexion to replicate the arm position during intra-operative version measurement. Geometry was extracted to determine landmarks and co-ordinate systems for the humeral long axis, epicondylar axis, flexion-extension axis (centered through the capitellum and trochlear groove), and ulnar long axis. An anatomic humeral head cut plane was placed at the head-neck junction of all shoulders by a fellowship trained shoulder surgeon. Retroversion was measured with custom Matlab code that analysed the humeral head cut plane relative to a reference system based on the long axis of the humerus and each elbow axis. Effects of measurement systems were analyzed using separate 1-way RM ANOVAs for males and females. Sex differences were analyzed using unpaired t-tests for each measurement system. Results. Changing the measurement reference significantly affected version (p<0.001). The ulnar axis method consistently resulted in higher measured version than either flexion-extension axis (males 9±1°, females 14±1°, p<0.001) or epicondylar axis (males 8±1°, females 12±1°, p<0.001). See Figure 1. Version in males (38±11°) was 7° greater than females (31±12°) when referencing the flexion-extension axis (p=0.048). Conclusion. Different measurement systems produce different values of version. This is important for humeral osteotomies; if version is assessed using the epicondyles pre-operatively and subsequently by the ulna intra-operatively, then the osteotomy will be approximately 10° over-retroverted. For any figures or tables, please contact authors directly (see Info & Metrics tab above).

Cervical spinal arthrodesis is the standard of care for the treatment of spinal diseases induced neck pain. However, adjacent segment disease (ASD) is the primary postoperative complication, which draws great concerns. At present, controversy still exists for the etiology of ASD. Knowledge of cervical spinal loading pattern after cervical spinal arthrodesis is proposed to be the key to answer these questions. Musculoskeletal (MSK) multi-body dynamics (MBD) models have an opportunity to obtain spinal loading that is very difficult to directly measure in vivo. In present study, a previously validated cervical spine MSK MBD model was developed for simulating cervical spine after single-level anterior arthrodesis at C5-C6 disc level. In this cervical spine model, postoperative sagittal alignment and spine rhythms of each disc level, different from normal healthy subject, were both taken into account. Moreover, the biomechanical properties of facet joints of adjacent levels after anterior arthrodesis were modified according to the experimental results. Dynamic full range of motion (ROM) flexion/extension simulation was performed, where the motion data after arthrodesis was derived from published in-vivo kinematic observations. Meanwhile, the full ROM flexion/extension of normal subject was also simulated by the generic cervical spine model for comparative purpose. The intervertebral compressive and shear forces and loading-sharing distribution (the proportions of intervertebral compressive and shear force and facet joint force) at adjacent levels (C3-C4, C4-C5 and C6-C7 disc levels) were then predicted. By comparison, arthrodesis led to a significant increase of adjacent intervertebral compressive force during the head extension movement. Postoperative intervertebral compressive forces at adjacent levels increased by approximate 20% at the later stage of the head extension movement. However, there was no obvious alteration in adjacent intervertebral compressive force, during the head flexion movement. For the intervertebral shear forces in the anterior-posterior direction, no significant differences were found between the arthrodesis subject and normal subject, during the head flexion/extension movement. Meanwhile, cervical spinal loading-sharing distribution after anterior arthrodesis was altered compared with the normal subject's distribution, during the head extension movement. In the postoperative loading-sharing distribution, the percentage of intervertebral disc forces was further increased as the motion angle increased, compared with normal subject. In conclusion, cervical spinal loading after anterior arthrodesis was significantly increased at adjacent levels, during the head extension movement. Cervical spine musculoskeletal MBD model provides an attempt to comprehend postoperative ASD after anterior arthrodesis from a biomechanical perspective

INTRODUCTION:. Recreating the natural head center of the hip joint during hip arthroplasty is important for restoring biomechanics in order to minimize leg length discrepancies, improve soft-tissue tension, and mitigate impingement [1,2]. New tools have been developed that allow anatomical measurements and analysis of three-dimensional digital femura geometry based on CT scans [3]. The purpose of this study is to analyze the head center location of various fit-and-fill hip stem designs in relation to the natural bone head center location using a novel technique. METHODS:. 556 computer tomography (CT) images (SOMA™) of left femora were used in this study. The acetate templates of five fit-and-fill stem designs (Design 1: Secur-Fit Advanced, Stryker; Design 2: Secur-Fit Max, Stryker; Design 3: Summit, Depuy; Design 4: Synergy, Smith & Nephew; Design 5: Zimmer, VerSys Epoch FullCoat) were compared to each other to correlate stem sizes between different systems. The appropriate stem body size for each of the CT bones was established based on the medial offset of the bone 20 mm above the lesser trochanter (MO+20) and the stem medial offset at the medial resection point. Utilizing the commercially available offset heads for each design, the bone head centers and the stem head centers were plotted, aligning the central axis of the bone/stem as well as the MO+20 of the bone with the stem medial resection point. The percent of bone head centers within 1,2,3,4,&5 mm of a stem/head offset data point was calculated for all designs. Additionally, the distance from the bone head center to the closest stem/head offset data point and the average head offset used were calculated. RESULTS:. Each of the five designs except for the VerSys Epoch FullCoat exhibits similar results for the percent of stem head centers within 3,4,&5 mm of the natural bone head centers (see Figure 2). However, Designs 1 & 2 are able to reconstruct the natural head center within 1 mm and 2 mm with a higher percentage than Designs 3,4,&5. Additionally, the average distances from the bone head centers to the closest stem/head offset data points are similar between all five designs, but the average head offset used for each design does vary (see Figure 3). DISCUSSION:. This novel technique of using CT scans to analyze stem head center locations shows that Designs 1 & 2 are able to reconstruct the natural head center within 1 mm and 2 mm with a higher percentage compared to Designs 3,4, & 5. Further, less ‘plus’ offset heads may be used for Designs 1,3,4, & 5 to reconstruct the natural head center compared to Design 2, and subsequently, less skirted heads may be used for Designs 1,3,4,&5. In this study, the neck resection level was held constant. Preoperative templating is important to allow appropriate adjustment of the neck resection in order to properly reconstruct the natural bone head centers. This novel technique may allow for optimizing the head center position for hip designs in order to more closely reproduce the native femur head centers

Shoulder arthroplasty is used to treat osteoarthritis, post-traumatic arthritis, and avascular necrosis. Modular components allow for natural variability in shoulder anatomy, including retroversion and head-neck angles. Surgical options include anatomic or guide-assisted cut at a fixed retroversion and head-neck angle. The purpose of this study was to determine the variability between head height (HH) and anteroposterior (AP) and superoinferior (SI) diameters using anatomic and guide-assisted humeral head cuts. Computed tomography scans of 10 cadaveric shoulder specimens (5 male, 5 female) were converted to 3D models. An anatomic humeral head cut plane was placed at the anatomic head–neck junction maintaining the posterior cuff insertion for all shoulders by a fellowship trained shoulder surgeon. Cut planes were generated for standard implant head neck angles (125°,130°,135°, and 140°) and retroversion angles (20°,30°, and 40°) in commercial cutting guides, for a combination of 12 repeated cut conditions per specimen. The humeral HH and the head diameter were measured in the AP and the SI planes for anatomic and guide-assisted osteotomy planes. Differences were compared using a separate two-way repeated measures ANOVA for each dependent variable. Guide-assisted cuts showed no significant effect on HH due to head-neck (p=0.205) or retroversion angles (p=0.190). These results persisted by gender (male: head-neck p=0.659 and retroversion p=0.386; female: head-neck p=0.204 and retroversion p=0.190). SI diameter increased by 1.3 mm with increasing head-neck angle (p<0.001), but there was no effect due to retroversion (p=0.148). A head-neck angle of 125° caused the greatest decrease in SI diameter of −2.8 mm compared to the anatomic cut, averaged over the retroversion range. The greatest reduction of SI diameter, −3.4 mm compared to anatomic, occurred with 125° head-neck angle and 20° retroversion. By gender, males showed a significant effect from head-neck angle (p=0.008), but females did not (p=0.077). There was no significant difference from retroversion in either gender group (male p=0.792; female p=0.057). There was no significant difference in AP diameter by head-neck (p=0.192) or retroversion angles (p=0.168). These results persisted in the males (head-neck p=0.420 and retroversion p=0.780). In females, there was no effect from head-neck angle (p=0.232); however, retroversion angle trended toward significance (p=0.050). For patients whose natural anatomy falls outside the range of the commercial cut guides, templated resection may result in deviation from natural humeral head dimensions. Due to the large variability in anatomic retroversion and head-neck angles in the subjects of this study, further study with a larger sample size is needed to investigate observed trends. These preliminary results have implications for manufacturers to create guides to represent a larger segment of the population, and surgeons' intra-operative choice

Introduction. Modern ceramic-on-ceramic bearings have become attractive alternatives to conventional polyethylene due to their low wear and minimal particle production. However, ceramic-on-ceramic implants have been associated with ceramic fracture and squeaking. To address these issues, large ceramic heads with a titanium-alloy sleeve have been introduced although limited data are available on their clinical outcomes. The purpose of this study was to report the midterm results of primary total hip arthroplasty using a 32mm with a titanium-alloy sleeve. Materials & Methods. We reviewed 245 patients who had 274 total hip arthroplasties with a 32 mm ceramic head with a titanium-alloy sleeve and had been followed for more than 5 years (average, 6.5 years; range, 5–9 years). The mean patient age at the time of surgery was 55.1 years (range, 16–82 years). All operations were performed at a single center. All of the ceramic implants were hot isostatic pressed, laser-marked, proof-tested third-generation alumina (Fig. 1). We determined the implant survival, Harris hip scores, incidence of ceramic fracture or noisy hips, and presence of osteolysis. Results. The survival rate of ceramic-on-ceramic bearings in primary total hip arthroplasty using 32 mm ceramic head with titanium-alloy sleeve was 97.5% at 9 years (Fig. 2). The Harris hip score improved from mean of 47 preoperatively to 93 at last follow-up. One ceramic head fractured at 6 years postoperatively. No ceramic liners were seen to fracture. Audible hip noise was identified in five hips (1.8%); clicking in four and squeaking in one. Osteolysis was detected in four hips (1.5%), but all had no symptom (Fig. 3). Other complications included three deep infections, two dislocations, and one peroneal nerve palsy. Conclusions. Primary ceramic-on-ceramic total hip arthroplasty using a 32 mm ceramic head with a titanium-alloy sleeve has a high survival rate of 97.5% at a 9-year follow-up. Nevertheless, surgeons should be aware of the potential risks of ceramic fracture, noise, and osteolysis associated with the use of ceramic head with a titanium-alloy sleeve

Introduction:. Ceramic head with titanium-alloy sleeve offers a modular ceramic head solution for the damaged taper in revision total hip arthroplasty (THA). It can also be used in primary THA to reduce the risk of ceramic head fracture. The purpose of the present study was to report the intermediate-term outcomes of primary ceramic-on-ceramic THA with use of ceramic head with titanium-alloy sleeve. Materials & Methods:. We evaluated 244 patients (271 hips) who had undergone primary ceramic-on-ceramic THA with use of BIOLOX® forte 32 mm ceramic head with titanium-alloy sleeve between November 2005 and August 2009. There were 158 males (175 hips) and 86 female (96 hips) patients with a mean age of 55.5 years. Clinical and radiographic evaluation was performed at a mean of 4.6 years (range, 2–7 years) postoperatively. Results:. Mean Harris hip score improved from 46 points (range, 7–77 points) preoperatively to 91 points (range, 45–100 points) postoperatively. One (0.4%) ceramic heads fractured at 6 years postoperatively, which was treated with isolated cup revision and ceramic head exchange. Periprosthetic osteolysis was detected in 3 hips (1.1%), but not symptomatic in all patients. One patient (0.4%) complained of clicking in his operated hip. There was no aseptic loosening of the acetabular cup. Two (0.7%) out of 271 hips sustained aseptic loosening of the femoral stem (both were 14×9 mm small stem). Other complications included 3 (1.1%) deep infections, 2 (0.7%) dislocations, and 1 (0.4%) periprosthetic femoral fracture. Conclusions:. The intermediate-term outcomes of primary ceramic-on-ceramic THA with use of BIOLOX® forte 32 mm head with titanium-alloy sleeve was encouraging. However, it is concerning that ceramic head fractures still occur, even in a very low incidence rate (0.4%). Additionally, long-term observation is required for periprosthetic osteolysis whether it comes from corrosion/fretting between taper and sleeve

We report a case of fatal heart failure caused by cobalt intoxication after revision THR in the patient who successfully underwent re-revision THR. 53-year old male presented to emergency room in our hospital with progressive shortness of breath. Symptom was started about 6 months ago so he visited local hospital. He worked up for worsening dyspnea. Simple chest radiograph and enhanced heart MRI study were performed and they showed bilateral pericardial and pleural effusion. There was no evidence of ischemic change. Transthoracic echocardiogram showed the evidence of heart failure, left ventricular ejection fraction(EF) was 40%. He was admitted at local hospital and started on vasopressors but urine output was decreased and follow-up echocardiogram showed a 25% of EF. Patient recommended heart transplantation and transferred our hospital emergency room. He underwent sequential bilateral total hip arthroplasties using CoP bearing surfaces. At 12 years postoperatively, he presented to the other hospital with acute onset of left hip pain. He was diagnosed ceramic head fracture on his left hip. Head and liner change revision surgery was performed using Cobalt-Chrome alloy 28mm metal head and Protruded cross-linked polyethylene liners. In our hospital, the patient admitted cardiovascular department of internal medicine. Patient complained nonspecific fatigue and general weakness but had no other symptoms such as visual and hearing loss, cognitive dysfuction. During work-up, patient presented progressive left hip pain and complaint of discomfort for the mass on the left groin. He also complained Left leg weakness and numbness. Simple radiograph and enhanced CT study was done. Simple radiograph image shows radiodense area around the hip joint and radiologist suspected heterotopic ossification. The cardiovascular department consulted orthopedic department. In the image findings showed huge mass combined hemorrhagic component lining acetabular component extending psoas compartment and eccentric wear on cobalt-chrome alloy metal head. Also highly radiodense material was seen around neck inferor portion and severly deformed metal head was seen. It was highly suspected that metal related granuloma, which means severe metallosis. Performed heavy metals screen, cobalt levels were 397,800 μg/Land chrome levels were 236,000 μg/L suggesting cobalt toxicity. Hip joint aspiration was done for decompression as radiologic intervention and EDTA (ethylenediamine tetraacetate) chelation therapy started immediately. After 10 cycle chelating therapy, metal level was lowered cobalt levels by 255.2μg/L and chrome levels by 39.5 μg/L. When hospital day after 134, Medical condition of the patient was getting improved, we underwent revision surgery using ceramic on ceramic bearing surface. The patient discharged postoperative 79 days. Final heavy metals screen results were 27.79μg/L on cobalt and 22.17μg/L on chrome. Although there were also reported a good clinical result of revision surgery using MoP bearing, and some surgeons reluctant to use CoC articulation because of concerns about re-fracture of ceramic. But take into account like this devastating complication after cobalt-chrome wear caused by remained ceramic particles, we should carefully select which bearing is safer

In shoulder arthroplasty, humeral resurfacing or short stem devices rely on the proximal humeral bone for fixation and load transfer. For resurfacing designs, the fixation takes place above the anatomical neck, whilst for short stem designs the resection is made at the anatomical neck and fixation is achieved in the bone distal to that resection. The aim of the study is to investigate the bone density in these proximal areas to provide information for implant design and guidance on appropriate positions to place implant fixation entities. CT scans of healthy humeri were used to map bone density distribution in the humeral head. CT scans were manually segmented and a solid model of the proximal humerus was discretised into 1mm tetrahedral elements. Each element centroid was then assigned an apparent bone density based on CT scan Grey values. Matlab was used to sort data in spatial groups according to element centroid position to map bone density distribution. The humeral head was divided into twenty 2mm thick slices parallel to the humeral neck starting from the most proximal region of the humeral head to distal regions beneath epiphyseal plate (Fig 1a). Each slice was then radially divided into 30 concentric circles and each circle was angularly divided into 12 regions (Fig 1b). The bone density for each of these regions was calculated by averaging density values of element centroid residing in each region. Average bone density in each slice indicates that bone density decreases from proximal region to distal regions below the epiphyseal plate and higher bone density was measured proximal to the anatomical neck of the humerus (Fig2). Figure 3 shows that, both above and below the anatomical neck, bone density increases from central to peripheral regions where eventually cortical bone occupies the space. This trend is more pronounced in regions below the anatomical neck and above the epiphyseal plate. In distal slices below the anatomical neck, a higher bone density distribution in inferior (calcar) regions was also observed. Current generation short stem designs require a resection at the anatomical neck of the humerus and a cruciform keel to fix the implant in the distal bone. In the example in Figure 3, the anatomical neck resection corresponds to the 18 mm slice, with the central cruciform keel engaging between slices 18 mm and 27 mm. The data indicates that this keel should make use of the denser bone by the calcar for fixation, suggesting a crucifix orientation as highlighted in Figure 3. The current generation of proximally fixed humeral components are less invasive than conventional long-stemmed designs, but the disadvantage is that they must achieve fixation over a smaller surface area and with a less advantageous lever arm down the shaft of the humerus. By presenting a spatial density map of the proximal humerus, the current study may help improve fixation of proximally fixed designs, with a simple modification of implant rotational orientation to make use of the denser bone in the calcar region for fixation and load transfer