INTRODUCTION. Component impingement in total hip arthroplasty (THA) can cause implant damage or dislocation. Dual mobility (DM) implants are thought to reduce dislocation risk, but impingement on metal acetabular bearings may cause femoral component notching. We studied the prevalence of (and risk factors for) femoral notching with DM across two institutions. METHODS. We identified 37 patients with minimum 1-year radiographic follow-up after primary (19), revision (16), or conversion (2) THA with 3 distinct DM devices between 2012 and 2017. Indications for DM included osteonecrosis, femoral neck fracture, concomitant spinal or neurologic pathology, revision or conversion surgery, and history of prosthetic hip dislocation. Most recent radiographs were reviewed and assessed for notching. Acetabular anteversion and abduction were calculated as per Widmer (2004). Records were reviewed for dislocations and reoperations. RESULTS. 2/37 of cases demonstrated femoral component notching, best seen on Dunn views (available in 7/37 cases). Notching was associated with increased mean acetabular anteversion (32.5° with notch, 19.6° without; p=.03). 2/5 patients with anteversion greater than 30° had notching, while no patients with less anteversion had notching (p=.01). Recurrent posterior instability was the indication for 6 revision THAs studied. Both cases of notching were in this group. Although not statistically associated with implant design, notching occurred in 2/18 MDM, 0/10 ADM and 0/9 G7 constructs. Dislocation occurred in 0/18 MDM, 0/10 ADM and 2/9 G7 constructs (p=.04), resulting in one revision to a constrained liner. We observed no significant differences in rate of notching or dislocation with respect to age, cup or head size, or component abduction. DISCUSSION AND CONCLUSION. Femoral notching was identified in 5% of DM cases, equal to the rate of dislocation. Dunn views are not routine after THA, so the incidence may be underestimated. Increasing acetabular anteversion to minimize posterior dislocation is a risk factor. Dislocation and notching incidence may vary between DM components based on design features. Further study is warranted to determine clinical significance. For any figures or tables, please contact authors directly

Background. Scapular notching causes glenoid bone loss after a reverse total shoulder arthroplasty (rTSA). The goal of this study was to assess the influence of prosthesis design on notching. Methods. Prospective, single surgeon cohort. Two different rTSA designs were consecutively implanted and compared: 25 Delta III rTSAs and 57 Delta Xtend rTSAs in 80 patients. Notching (Nerot 0–4) was assessed at 24 months follow-up. Patient dependent variables, surgical technique and implant geometry were assessed. Multivariate binary logistic regression was used to select the strongest independent predictors of notching. Results. The Delta III showed significantly more notching than the Delta Xtend: 72% and 23% respectively, p<0.001. The extent of notching was comparable. One patient (Delta III) needed revision for notching-associated glenoid loosening. Only 3 variables were significantly associated with notching in multivariate analysis: glenosphere overhang (R square 0.65), prosthesis-scapular neck angle (PSNA, R square 0.18) and humeral cup depth (R square 0.05), predicting 88% of notching cases. The corresponding odds ratios were 0.15 (95% CI 0.05–0.44) for 1 mm extra overhang, 8.4 (95% CI 2.0–35.6) for 10 degrees increase in PSNA and 7.6 (95% CI 1.3–43.3) for 1 mm extra cup depth. Surgical technique related variables, including peg-glenoid rim distance and PSNA, were comparable in both design groups. Conclusion. The key to prevent notching was to utilise the design features that maximise glenosphere overhang. Therefore, as a rule of thumb the baseplate should be positioned as inferior as possible. Minor contributions came from PSNA (patient anatomy/surgical technique) and polyethylene cup depth (also design). One patient required early revision for notching associated baseplate loosening. Long term follow-up is indicated to assess the effect of notching on prosthesis survival and outcome after revision

Introduction: Notching of the femoral neck during preparation of the femur during hip resurfacing has been associated with an increased risk of femoral neck fracture. We aimed to evaluate this with the use of a finite element model. Methods: A three dimensional femoral model was used and molded with a femoral component constructed from the dimensions of a Birmingham Hip Resurfacing. Multiple constructs were made with the component inferiorly translated in order to cause a notch in the superior femoral neck. The component angulation was kept constant. Once constructed the model was imported into the Ansys finite element model software for analysis. Elements within the femoral model were assigned different material properties depending on cortical and cancellous bone distributions. Von Misses stresses were evaluated near the notches and compared in each of the cases. Results: In the un-notched case the maximum Von Mises stress was only 40MPa. However, with the formation of a 1mm notch the stress rose to 144MPa and in the 4 mm notch the stress increased to 423MPa. These values demonstrated that a 1mm notch increased the maximum stress by 361% while a 4mm notch increased the maximum stress by 1061%. Discussion: This study demonstrated that causing a notch in the superior femoral neck dramatically increases the stress within the femoral neck. This may result in the weakening of the femoral neck and potentially predispose it to subsequent femoral neck fracture. The data suggests that even a small notch of 1mm may be detrimental in weakening the femoral neck by dramatically increasing the stress in the superior neck. This study suggests that any femoral neck notching should be avoided during hip resurfacing

Notching of the anterior femoral cortex during total knee arthroplasty is thought to be a possible risk factor for subsequent periprosthetic femoral fracture. Understanding the stress pattern caused by notching may help the orthopedic surgeon reduce the risk of fracture. A validated, three dimensional, finite element model of the femur using gait loads has been used to analyze the stress concentrations caused by anterior femoral cortex notching. Three factors that increase these stresses were identified. The notch depth, radius of curvature, and its proximity to the end of the femoral prosthesis influence the state of stress in the surrounding bone. The purpose of this study was to characterize the stress concentration caused by anterior femoral notching during total knee replacement (TKR) in order to determine when a patient is at risk for a periprosthetic fracture of the femur. We concluded that notches greater than 3 mm with sharp corners located directly at the proximal end of the femoral implant produced the highest stress concentrations and may lead to a significant risk of periprosthetic femur fracture. One complication that can occur during TKR is notching of the anterior femoral cortex which results in a stress concentration. It is important to characterize this stress riser in order to determine when a stemmed femoral component should be used to minimize the risk of fracture. Three factors that affected the stress concentration were identified. First, increasing the notch depth lead to significant increased stress concentrations. When the depth was greater than 3 mm, local stresses increased markedly. Second, the radius of curvature was found to be inversely related to stress concentration. As the radius decreased, the local stress increased. Third, the proximity of the notch to the prostheses affected the stress concentration. Notches that were 1 mm proximal to the implant resulted in much larger stresses than those that were 10 mm away. A validated, three dimensional finite element model of a femur subjected to a gait loading pattern was used to characterize the stress concentration caused by anterior femoral notching. The results compared well to previous work reported in the literature

Notching of the anterior femoral cortex during total knee arthroplasty is thought to be a possible risk factor for subsequent periprosthetic femoral fracture. Understanding the stress pattern caused by notching may help the orthopedic surgeon reduce the risk of fracture. A validated, three dimensional, finite element model of the femur using gait loads has been used to analyze the stress concentrations caused by anterior femoral cortex notching. Three factors that increase these stresses were identified. The notch depth, radius of curvature, and its proximity to the end of the femoral prosthesis influence the state of stress in the surrounding bone. The purpose of this study was to characterize the stress concentration caused by anterior femoral notching during total knee replacement (TKR) in order to determine when a patient is at risk for a periprosthetic fracture of the femur. We concluded that notches greater than 3 mm with sharp corners located directly at the proximal end of the femoral implant produced the highest stress concentrations and may lead to a significant risk of periprosthetic femur fracture. One complication that can occur during TKR is notching of the anterior femoral cortex which results in a stress concentration. It is important to characterize this stress riser in order to determine when a stemmed femoral component should be used to minimize the risk of fracture. Three factors that affected the stress concentration were identified. First, increasing the notch depth lead to significant increased stress concentrations. When the depth was greater than 3 mm, local stresses increased markedly. Second, the radius of curvature was found to be inversely related to stress concentration. As the radius decreased, the local stress increased. Third, the proximity of the notch to the prostheses affected the stress concentration. Notches that were 1 mm proximal to the implant resulted in much larger stresses than those that were 10 mm away. A validated, three dimensional finite element model of a femur subjected to a gait loading pattern was used to characterize the stress concentration caused by anterior femoral notching. The results compared well to previous work reported in the literature

Introduction: In most of the reported series, scapular notching in inverse shoulder arthroplasty has been identified as a major problem. Therefore, a novel concept has been developed in order to minimize the incidence and the evolution (pathophysiology) of scapular notching. The current cohort study is now large enough to examine the results with special attention on notching. Methods: A dual peg design of the metaglene with CaP coating provides high primary and secondary stability. “Geometrical” notching is reduced by inferior (eccentric) fixation of the glenosphere on the metaglene, beveling of the medial part of the humeral inlay, and by the choice of three different sizes of the glenosphere (36, 39 and 42). “Biological” notching is addressed by inversion of the components: the epiphysis – as the mobile part – is metallic. Its contact to the scapula, should this occur, cannot lead to polyethylene wear. This study is a prospective multicentric study on Affinis Inverse and Affinis Fracture Inverse shoulder prosthesis (Mathys Ltd Bettlach, Switzerland), which is running in 7 European hospitals since December 2007. All cases but two (lost to follow-up) are included. Preoperative and all postoperative radiographs were reviewed. Notching has been graded 0 to 4, on a scale adapted after Sirveaux. Results: At submission deadline for the abstract, 163 cases were included. Grade 1 notching was detected in 8 cases (4.9%), and grade 2 notching in one. In those cases, notching developed early, but was not progressive over time. There were no cases of grade 3 or 4. In 17 cases, the X-rays were not assessable and therefore it was impossible to definitively rule out a possible grade 1 notching. None of the Affinis Fracture Inverse prostheses produced any notching. New bone apposition on the inferior aspect of the scapula was detected in 15 cases. We postulate this to be a metaplasia of the long head of the triceps due to local periosteal stimulation. Conclusions: The present design leads to a very low rate of scapular notching. Even in the 9 cases where notching was present, it appears that the epiphysis only created the space it needed, without any ongoing osteolytic process beyond this. Specific prosthetic design improves both quantity and quality of scapular notching

Aims

This study aimed to investigate the optimal sagittal positioning of the uncemented femoral component in total knee arthroplasty to minimize the risk of aseptic loosening and periprosthetic fracture.

Scapular notching is of concern in reverse shoulder arthroplasty and has been suggested as a cause of glenoid loosening. Our purpose was to analyze in a large series the characteristics and the consequences of the notch and then to enlighten the causes in order to seek some solutions to avoid it. 430 consecutive patients (457 shoulders) were treated by a reverse prosthesis for various etiologies between 1991 and 2003 and analyzed for this retrospective multicenter study. Adequate evaluation of the notch was available in 337 shoulders with a follow-up of 47 months (range, 24–120 months). The notch has been diagnosed in 62% cases at the last follow-up. Intermediate reviews show that the notch is already visible within the first postoperative year in 82% of these cases. Frequency and grade extension of the notch increase significantly with follow-up (p< 0.0001) but notch, when present, is not always evolutive. At this point of follow-up, scapular notch is not correlated with clinical outcome. There is a correlation with humeral radiolucent lines, particularly in metaphyseal zones (p=0.005) and with glenoid radiolucent lines around the fixation screws (p=0.006). Significant preoperative factors are: cuff tear arthropathy (p=0.0004), muscular fatty infiltration of infraspinatus (p=0.01), narrowing of acromio-humeral distance (p< 0.0001) and superior erosion of the glenoid (p=0.006). It was more frequent with superolateral approach than with deltopectoral approach (p< 0.0001) and with standard cup than with lateralized cup (p=0.02). We conclude that scapular notching is frequent, early and sometimes evolutive but not unavoidable. Preoperative superior glenoid erosion is significantly associated with a scapular notch, possibly due to the surgical tendency to position the baseplate with superior tilt and/or in high position which has been demonstrated to be an impingement factor. Preoperative radiographic planning and adapted glenoid preparation are of concern.

Introduction

The clinical impact of scapular notching is controversial. Some reports suggest it has no impact while others have demonstrated it does negatively impact clinical outcomes. The goal of this clinical study is to analyze the pre- and post-operative outcomes of 415 patients who received rTSA with one specific prosthesis (Equinoxe; Exactech, Inc).

Purpose of the study: During resurfacing arthroplasty, excessive valgus of the femoral neck or an insufficient surgical technique can lead to formation of a notch in the femoral head. Although the mechanisms weakening the femoral neck and subsequent fractures are well described, the effects of altered blood supply via the retinacular vessels on potential ischemia of the femoral head are largely unknown. The purpose of our study was to assess blood supply to the femoral head when a notch occurred in the femoral neck during total hip replacement surgery and to deduct possible implications concerning the resurfacing procedure.

Material and methods: Blood supply to the femoral head was measured with laser Doppler fluorometry in 14 hips undergoing total hip replacement for osteoarthritis via a lateral approach with anterior dislocation. An optical laser probe for the fluorometry (Moor Instruments, Wilmington Delewar, 20 mW laser, probe length 780 nm) was introduced via a 3.5 mm hole drilled in the antrolaeral quadrant of the femoral head (leg in neutral position). The position of the probe was checked on the x-ray of the femoral head after resection. A notch was simulated in the lateral posterior portion of the femoral neck using a bone gouge.

Results: Mean patient age was 65 years (range 48–77 years). There were eight men and six women. Two measurements were made: one after dislocation of the hip and the second after simulating the notch. A significant decrease in blood supply measured at more than 50% was observed in all but four hips after simulating the notch. The median decrease in blood flow was 76% (4.4–90.4, p< 0.001).

Conclusion: The retinacular vessels appear to be equally important for the blood supply for osteoarthritic and non-osteoarthritic femoral heads. A notch occurring during hip resurfacing would not only weaken the mechanical resistance of the neck but would also increase the risk of osteonecrosis and subsequent loosening of the femoral component. Consequently, approaches compromising retinacular blood supply (for example the posterior approach) would add a supplementary danger for the integrity and viability of the femoral head.

Background

There has been increased focus on understanding the risk factors associated with scapular notching in reverse shoulder arthroplasty (RSA). The purpose of this study is to evaluate the effect of scapular morphology and surgical technique on the occurrence of scapular notching using the notching index as a comprehensive predictive tool.

Introduction: A unique failure mode of hip resurfacing is femoral neck fracture. These tend to occur early after surgery during normal activities. One theory regarding fracture occurrence includes the introduction of stress magnifiers in the form of notches on the superior neck. The presence of a notch can arise from reaming or from removal of osteophytes during surgery. The aim of the present study was to investigate the effect of notching the femoral neck, following resurfacing by using a finite element (FE) model.

Methods: A physiological load case was simulated in the FE model of a femur, implanted with a cemented hip resurfacing system. Twelve implant alignments were modelled: an ideal implant alignment with no notch, and a 1 mm, 3 mm, 5 mm and 7 mm superior notch; 5° anteversion, 5° and 10° degrees retroversion; 5° and 10° degrees in varus and valgus. These models were compared to that of an intact femur for baseline analysis.

The intact femur geometry was derived from a CT dataset of a cadaveric femur and CT numbers were converted into a realistic distribution of material properties. The FE intact mesh was based on an experimentally validated mesh of a human femur. The femur was segmented into 22 neck sections.

The loading condition was modelled to represent an instant at 10% of gait where all muscle forces were included. The femoral neck regions were compared between the models to evaluate the effect of notch sizes on stress distribution. Maximum tensile stresses were compared to the ultimate tensile stress (UTS) of cortical and cancellous bone.

Results: As the notch size increased the peak and average 1st (tensile) and 3rd (compressive) principal stress increased along the superior portion of the femoral neck. For the 5 mm superior notch, the maximum 1st principal stress increased by 283% and 154% when compared to that of the ideally aligned implant and the intact femur respectively. The largest increase of tensile stress was observed when the implant was mal-aligned in 10° of varus; this resulted in a 768% increase in stress compared to the ideally implanted model.

Discussion: The introduction of a superior notch causes a stress concentration on the femoral neck. Although the stress concentration is pronounced, a notch on the superior aspect of the femoral neck may not lead to fracture following resurfacing; the UTS of cortical bone is 100MPa, and the UTS of cancellous bone is between 2MPa and 20MPa. Peak stresses in the model are well below the UTS of cortical bone, and for damage to accumulate in cancellous bone, energy absorption in the ‘honey-comb’ structure of trabecular bone must be considered. Varus mal-alignment resulted in the largest increase in tensile stress on the superior aspect of the neck, and has been associated with femoral neck fracture; this type of mal-alignment may be critical when considering femoral neck fractures.

Hip resurfacing has many advantages such as proximal bone conservation and easy revision including conversion to total hip arthroplasty. The major complication in the hip resurfacing is notching at the lateral cortical bone and fracture of the neck. In this research, we simulated the range of direction of reaming without causing notch.

One left femur model was used for the simulation. The femoral head was fitted by a sphere and the origin of Cartesian coordinate was set at the center of the sphere. The simulation was made by imposing a cylindrical cut to the femoral head in varying direction and location. The existence of notching was decided comparing the maximum distance from reaming axis to neck section contour and the radius of cylindrical cut. If the maximum distance is bigger than the radius of cut, the notching exists and vice versa. We simulated existence of notching by varying inclination(α) from 20 to 70 degrees, anteversion(β) from 0 to 30 degree and depth passing through the head center(d) from 0 to 5mm. The implant used for the simulation was Durom^®, Zimmer^©. We selected the implant size that is close to the fitted sphere of femoral head.

No notching was made for any direction when the depth d was less than 2mm. When the depth was 3mm, notching did not generate in the range of α from 43 degrees to 60 degrees and β from 0 to 25 degrees. When the range of depth was from 4mm to 5mm, notching did not generate in ranges of α from 41 degrees to 60 degrees and β from 0 to 29 degrees. The no-notching angle range had tendency increasing slightly when the depth was increased. The angle between the stem of the implant and the neck shaft axis without notching can be calculated from the angle α. When the depth was from 4mm to 5mm, the corresponding angle between stem of implant and the shaft axis was from 120 degrees to 139 degrees.

Introduction: It has been suggested that notching of the femoral neck during hip resurfacing weakens the proximal femur and predisposes to femoral neck fracture. We aimed to examine the effect of neck notching during hip resurfacing on the strength of the proximal femur.

Methods: 3^rd generation composite femurs that have been shown to replicate the biomechanical properties of human bone were utilised. The bone was secured in a position of single leg stance and tested with an Instron mechanical tester. Imageless computer navigation was used to position the initial guide wire during head preparation. Six specimens were prepared without a superior notch being made in the neck of the femur, six were prepared in an inferiorly translated position to cause a 2mm notch in the superior femoral neck and six were prepared with a 5mm notch. The femoral component was then cemented in place. All specimens had radiographs taken to ensure that the stem shaft angle was kept constant. The specimens were then loaded to failure in the axial direction.

Results: The 2mm notched group (mean load to failure 4034N) were significantly weaker than the un-notched group (mean load to failure 5302N) when tested to failure (p=0.017). The 5mm notched group (mean load to failure 3121N) were also significantly weaker than the un-notched group (p=0.0003) and the 2mm notched group (p=0.046). All fractures initiated at the superior aspect of the neck, at the component bone interface. All components were positioned in the same coronal alignment +/−2 degrees.

Discussion: A superior notch of 2mm in the femoral neck weakens the proximal femur by 24% and a 5mm notch weakens it by 41%. This study provides biomechanical evidence that notching of the femoral neck may lead to an increased risk of femoral neck fracture following hip resurfacing.

Fourteen hips with osteoarthritis had femoral head blood flow measured with laser Doppler flowmeter while undergoing during total hip replacement through a modified lateral approach. Mean age sixty-five years (48–77); eight males & six females. Two measurements were taken within the femoral head one after anterior hip dislocation and one after simulated notching of the femoral neck. All hips had a significant decrease in blood flow with a median percentage decrease of 76% (range 4.4–90.4). During surface arthroplasty of the hip, notching of the femoral neck may not only mechanically weaken the bone but also put the femoral head at risk of osteonecrosis.

To evaluate femoral head blood supply in patients with osteoarthrtis of the hip undergoing simulated notching of the femoral neck during total hip replacement and its potential implications in hip resurfacing.

During surface arthroplasty of the hip, notching of the femoral neck may not only mechanically weaken the femoral neck but also put the femoral head at risk of osteonecrosis and subsequent femoral loosening.

It would appear that the retinacular vessels (extraosseous blood supply) are as important in the arthritic femoral head as they are in the nonarthritic state, contradicting the notion that arthritic femoral heads in humans rely mainly on an intraosseous blood supply.

Fourteen hips with a diagnosis of degenerative arthritis had femoral head blood flow measured with laser Doppler flowmeter while undergoing during total hip replacement through a modified lateral approach. With the femoral head exposed and leg in neutral position, a 3.5mm drill hole was made into the anterior lateral quadrant and the fiber optic probe of the laser Doppler flowmeter (Moor Instruments, Wilmington Delaware, 20mW laser, wavelength 780nm) was inserted. Mean age was sixty-five years (48–77). Eight males and six females. Two measurements were taken one after anterior hip dislocation and one after simulated notching of the femoral neck. All but four hips had a significant decrease of more than 50% in blood flow after neck notching with a median percentage change of 76% (range 4.4–90.4), p< 0.001.

This study was designed to determine the risk of femoral neck fracture after anterior or posterior notching of the femoral neck. The anterior femoral neck is under tensile forces during gait similarly to the superior neck [6].

Method: Fortyseven 4th generation synthetic femora were implanted with Birmingham Hip Resurfacing pros-theses (Smith & Nephew Inc. Memphis, USA). Implant preparation was performed using imageless computer navigation (VectorVision SR 1.0, BrainLAB, Germany). The prosthesis was initially planned for neutral version and translated anterior, or posterior, to create a femoral neck notch. The femora were fixed in a single-leg stance and tested with axial compression. This method enabled comparison with previously published data. The synthetic femora were prepared in 8 experimental groups: 2mm and 5mm anterior notches, 2mm and 5mm posterior notches, neutral alignment with no notching (control), 5mm superior notch, 5mm anterior notch tested with the femur in 25° flexion and 5mm posterior notch tested with the femur in 25° extension

We tested the femora flexed at 25° flexion to simulate loading as seen during stair ascent. [3] The posterior 5mm notched femoral necks were tested in extension to simulate sporting activities like running. The results were compared to the control group in neutral alignment using a one- way ANOVA:

Results: Testing Group Mean load to failure Significance

Neutral (Control) 4303.09 ± 911.04N

The anterior 5mm notch tested in single-leg stance and anterior notch in flexion displayed lower compressive loads to failure (3374.64N and 3048.11N). The mean load to failure value for the posterior 5mm notches in extension was 3104.62N compared to 4303.09N for the control group.

Our data suggests that anterior and posterior 2mm notches are not significantly weaker in axial compression. The anterior 5mm notches was not significant in axial compression (p=0.38), but trended towards significance in flexion (p=0.087). A 5mm posterior notch was not significant. (p=0.995, p=0.117). The 5mm superior notch group was significantly weaker with axial compression supporting previous published data (p=0.003).

Conclusion: We conclude that anterior and posterior 2mm notching of the femoral neck has no clinical implications, however a 5mm anterior femoral neck notch may lead to fracture. The fracture is more likely to occur with stair ascent rather than normal walking given the reduction in strength noted after testing in flexion. Posterior 5mm notches are not likely to fracture. Hip resurfacing is commonly performed on active patients and 5mm notching of anterior cortex has clinically important implications.

INTRODUCTION: The reverse DELTA III shoulder prosthesis can successfully relieve pain and restore function in cuff tear arthropathy. The most frequently reported complication is inferior scapular notching. The purpose of this study was to evaluate the clinical relevance of notching and to determine the anatomic and radiographic parameters that predispose to its occurrence.

STUDY PROTOCOL: Seventy-seven consecutive shoulders of 76 patients of an average age of 71 years with an irreparable rotator cuff deficiency were treated with a reverse DELTA III shoulder arthroplasty and followed clinically and radiographically under fluoroscopic control for a minimum of 24 months (mean: 44, range: 24 to 96). The effect of glenoid cranial caudal component positioning and of the prosthesis–scapular neck angle on the development of inferior scapular notching and clinical outcome was assessed.

RESULTS: All shoulders which developed notching did so in the first fourteen months. Forty-four percent of the shoulders had inferior scapular notching, 30% had posterior notching and anterior notching (8%) was rare. Osteophytes along the inferior scapula occurred in 27% of the shoulders. The angle between the glénosphère and the scapular neck (r=+0.677)) as well as the craniocaudal position of the glénosphère (r=+0.654) were highly correlated with inferior notching (p< 0.001). A notching index (notching index = height of prosthesis + (prosthesis scapular neck angle x 0.13) was calculated using the height of implantation of the glénosphère and the postoperative prosthesis scapular neck angle: This allowed a prediction of the occurrence of notching with a sensitivity of 91% and specificity of 88%. The height of implantation of the glenosphere had a greater influence on inferior notching than the prosthesis scapular neck angle by a factor of approximately 1:8. Inferior scapular notching was associated with a significantly poorer clinical outcome than absence of inferior notching: At final follow-up, the respective average subjective shoulder values were 62% and 71% (p=0.032), relative Constant scores were 72% and 83% (p=0.028), abduction strength was 4.3 versus 8.7 kilograms (p< 0.001), active abduction was 102° versus 118° (p=0.033) and flexion averaged 110° versus 127° (p=0.004).

DISCUSSION: Inferior scapular notching after reverse total shoulder arthroplasty adversely affects midterm clinical outcome. It can be prevented by optimal positioning of the glenoid component.

Despite the high success rates of Reverse Shoulder replacements, complications of instability & scapular notching are a concern. Factors reducing relative motion of implant to underlying bone which include lateral offset to centre of rotation, screw & central peg insertion angle and early osteo-integration are maximized in the Trabecular Metal Reverse total shoulder system. We present clinico-radiological outcomes over 72 months.

Analysis of a single surgeon series of 140 Reverse total shoulder replacements in 135 patients was done. Mean age was 72(range 58– 87 yrs); 81 females: 54 males. Indications were Rotator cuff arthropathy {n= 88} (63%); Osteo-arthritis with dysfunctional cuff {n= 22}(15%); post-trauma{n=23} (15%); revision from hemiarthroplasty {n=3} (2.4%) and from surface replacement {n=4} (2.8%)

All patients were assessed using pre-operative Constants and Oxford scores and clinical & radiographic reviews with standard X-Rays at 6 weeks, 3, 6,12 months and yearly thereafter. X rays included an AP view in 45 degrees of external rotation and modified axillary view. Inferior Scapular notching using the Nerot-Sirveaux grades and Peg Glenoid Rim Distance were looked into by a consultant musculoskeletal radiologist/ Orthopaedic surgeon/ Senior Fellow (post CCT) or a specialist Trainee (ST4 and above). Pain on the visual analogue scale decreased by 98% (9.1 to 0.8) (p<0.01). Constant score improved by 81.8% (12.4 to 68.1) (p<0.05), Oxford shoulder score by 76.7% (56 to 13) (p<0.05). 95.6% of Humeral stems had no radiolucent lines and 4.4% had < 2mm of lucency. Scapular notching was calculated using Sirveaux grades with Peg scapular base angle distance (PSBA) measurements on PACS with Siemens calibration (grade 1= 4 (2.8%); grade 2 =1; grade 3 =0; grade 4=0). 3.57% showed radiographic signs of scapular notching at 72 months. Range of Peg Glenoid Rim Distance was 1.66 to 2.31 cm. Power analysis showed 65 patients were needed to have an 80% power to detect relation of Peg Glenoid Rim Distance to Scapular notching. A likelihood ratio test from Logistic regression model to check correlation of Peg Glenoid Rim Distance to Scapular notching gave a p value of 0.0005. A likelihood ratio from Logistic regression gave a p value of 0.0004 for Infraglenoid Scapular spurs. Highest incidence of spurring was seen in Reverse Total Shoulder Replacements done for Trauma and lowest in patients who got the procedure for Osteoarthritis. Complications included two glenosphere revisions; two stitch abscesses and two Acromial fractures in patients who had a fall two years after the procedure. Improved surgical outcomes can be attributed to surgical technique and implant characteristics. Trabacular metal promotes early osteointegration which resists shearing action of Deltoid on Glenoid component. This allows early mobilisation. Deltoid split approach preserves integrity of Subscapularis and Acromial osteotomy and lateral clavicle excision improve exposure and prevent Acromion fracture. Positioning the Glenoid component inferiorly on the Glenoid decreases incidence of Scapular notching.

Our mid-term validated outcomes are promising with only 3.57% Grade I/II radiographic signs of scapular notching. Long term studies (10 year follow ups) are necessary to confirm its efficacy.

Introduction: We aimed to examine the effect of neck notching during hip resurfacing on the strength of the proximal femur.

Methods: Third generation composite femurs that have been shown to replicate the biomechanical properties of human bone were utilised. Imageless computer navigation was used to position the initial guide wire during head preparation. Six specimens were prepared without a superior notch being made in the neck of the femur, six were prepared in an inferiorly translated position to cause a 2mm notch in the superior femoral neck and six were prepared with a 5mm notch. All specimens had radiographs taken to ensure that the stem shaft angle was kept constant. The specimens were then loaded to failure in the axial direction with an Instron mechanical tester.

A three dimensional femoral finite element model was constructed and molded with a femoral component constructed from the dimensions of a Birmingham Hip Resurfacing. The model was created with a superior femoral neck notch of increasing depths.

Results: The 2mm notched group (mean load to failure 4034N) were significantly weaker than the un-notched group (mean load to failure 5302N) when tested to failure (p=0.017). The 5mm notched group (mean load to failure 3121N) were also significantly weaker than the un-notched group (p=0.0003) and the 2mm notched group (p=0.046). All fractures initiated at the superior aspect of the neck, at the component bone interface. The finite element model revealed increasing Von Mises stresses with increasing notch depth.

Discussion: A superior notch of 2mm in the femoral neck weakens the proximal femur by 24% and a 5mm notch weakens it by 41%. This study provides biomechanical evidence that notching of the femoral neck may lead to an increased risk of femoral neck fracture following hip resurfacing due to increasing stresses in the region of the notch.

Surgeons performing hip resurfacing ante-vert and translate the femoral component anterior to maximize head/neck offset and educe impingement. The anterior femoral neck is under tensile forces during gait similarly to the superior neck [6]. This study was esigned to determine the risk of femoral neck fracture after anterior or posterior notching of the femoral neck.

Method: Fortyseven 4th generation synthetic femora were implanted with Birmingham Hip Resurfacing pros-theses (Smith & Nephew Inc. emphis, USA). Implant preparation was performed using imageless computer navigation (VectorVision SR 1.0, BrainLAB, Grmany). The virtual prosthesis was initially planned for neutral version and translated anterior, or posterior, to create the notch. The femora were fixed in a single-leg stance and tested with axial compression using a mechanical testing machine. This method enabled comparison with previously published data. The synthetic femora were prepared in 8 experimental groups:2mm and 5mm anterior notches, 2mm and 5mm posterior notches, neutral alignment with no notching (control), 5mm superior notch, 5mm anterior notch tested with the femur in 25° flexion and 5mm posterior notch tested with the femur in 25° extension We tested the femora flexed at 25° flex-ion to simulate loading as seen during stair ascent. [3] The posterior 5mm notched femoral necks were tested in extension to simulate sporting activities like running. The results were compared to the control group in neutral alignment using a one-way ANOVA:

Results: Testing Group Mean load to failure Significance Neutral (Control) 4303.09 ± 911.04N Anterior 2mm 3926.62 ± 894.17N p=0.985 Anterior 5mm 3374.64 ± 345.65N p=0.379 Posterior 2mm 4208.09 ± 1079.81N p=1.0 Posterior 5mm 3988.07 ± 728.59N p=0.995 Superior 5mm 2423.07 ± 424.16N p=0.003 Anterior 5mm in 25° flexion 3048.11 ±509.24N p=0.087 Posterior 5mm in 25° extension 3104.61±592.67N p=0.117 Both the anterior 5mm notch tested in single-leg stance and anterior notch in flexion displayed lower compressive loads to failure (3374.64N and 3048.11N). The mean load to failure value for the posterior 5mm notches in extension was 3104.62N compared to 4303.09N for the control group. Our data suggests that anterior and posterior 2mm notches are not statistically significantly weaker in axial compression. The anterior 5mm notches tend towards significance in axial compression (p=0.38) and bordered significance in flexion (p=0.087). The 5mm posterior notches were not significantly weakened in axial compression (p=0.995), but tended towards significance in extension (p=0.117). The 5mm superior notch group was significantly weaker with axial compression supporting previous data published (p=0.003). We are currently assessing offset and other variables that may reduce data spread.

Conclusion: We conclude that anterior and posterior 2mm notching of the femoral neck has no clinical implications, however 5mm anterior notches may lead to fracture. The fracture is more likely to occur with stair ascent rather than normal walking. Posterior 5mm notches are not likely to fracture with normal gait, but may fracture with higher impact activities that promote weight bearing in extension. Hip resurfacing is commonly performed on active patients and ultimately 5mm notching in the anterior or posterior cortices has clinically important implications.