Impingement-free Range Of Motion Research Articles

Optimizing range of motion in reverse shoulder arthroplasty.

Optimal glenoid positioning in reverse shoulder arthroplasty (RSA) is crucial to provide impingement-free range of motion (ROM). Lateralization and inclination correction are not yet systematically used. Using planning software, we simulated the most used glenoid implant positions. The primary goal was to determine the configuration that delivers the best theoretical impingement-free ROM. With the use of a 3D planning software (Blueprint) for RSA, 41 shoulders in 41 consecutive patients (17 males and 24 females; means age 73 years (SD 7)) undergoing RSA were planned. For the same anteroposterior positioning and retroversion of the glenoid implant, four different glenoid baseplate configurations were used on each shoulder to compare ROM: 1) no correction of the RSA angle and no lateralization (C-L-); 2) correction of the RSA angle with medialization by inferior reaming (C+M+); 3) correction of the RSA angle without lateralization by superior compensation (C+L-); and 4) correction of the RSA angle and additional lateralization (C+L+). The same humeral inlay implant and positioning were used on the humeral side for the four different glenoid configurations with a 3 mm symmetric 135° inclined polyethylene liner. The configuration with lateralization and correction of the RSA angle (C+L+) led to better ROM in flexion, extension, adduction, and external rotation (p ≤ 0.001). Only internal rotation was not significantly different between groups (p = 0.388). The configuration where correction of the inclination was done by medialization (C+M+) led to the worst ROM in adduction, extension, abduction, flexion, and external rotation of the shoulder. Our software study shows that, when using a 135° inlay reversed humeral implant, correcting glenoid inclination (RSA angle 0°) and lateralizing the glenoid component by using an angled bony or metallic augment of 8 to 10 mm provides optimal impingement-free ROM.

Is there a role for acromioplasty and tuberoplasty in reverse shoulder arthroplasty to improve impingement-free range of motion?

Hypothesis and BackgroundLateralizing the center of rotation in reverse shoulder arthroplasty (RSA) decreases the risk of scapular notching due to inferior impingement but may limit range of motion (ROM) in abduction and forward flexion related to superior acromial impingement. Our primary hypothesis was that, using a 3-dimensional (3D) computer model, a virtual acromioplasty (with or without tuberoplasty) could improve abduction and forward flexion following RSA for cuff tear arthritis (CTA) or massive cuff tear. Our secondary hypothesis was that, based on the virtual planning, a surgical acromioplasty could be performed safely during RSA, without increasing the risk of postoperative acromial fracture. MethodsEighty seven patients with CTA scheduled for RSA were analyzed with a 3D software and impingement-free ROM was measured. After virtual prosthesis implantation, early acromio-humeral impingement (abduction ≤ 80° or forward flexion ≤ 120°) was observed in 25% of the cases (22/87). A virtual acromioplasty (with or without tuberoplasty) was then performed and glenohumeral ROM was measured again. Based on this 3D planning, a surgical acromioplasty (with or without tuberoplasty) was performed to improve ROM in the vertical plane in these 22 patients with early acromial impingement. Patients were followed with minimum 24 months of follow-up to assess final shoulder ROM and complications. ResultsAfter virtual acromioplasty alone (n = 11) or acromioplasty with tuberoplasty (n = 11), glenohumeral abduction significantly increased from 75° ± 6.9 before to 89.5° ± 23.4, and forward flexion from 119.3° ± 12 to 135.2° ± 10 (P < .001). After surgical acromioplasty/tuberoplasty, the final mean global forward flexion was 148° ± 5 and mean global abduction 150° ± 8 in these patients. At last follow-up, no acromial fracture was observed. ConclusionIn a 3D model, early acromial impingement may limit abduction (≤80°) or forward flexion (≤120°) after virtual RSA implantation for CTA or massive cuff tear. Virtual acromioplasty (with or without tuberoplasty) shows improved ROM in abduction and flexion. In patients with early impingement, a surgical acromioplasty can be performed safely during RSA, through a deltopectoral approach, without increasing the risk of postoperative acromial fracture.

Varus-valgus alignment of humeral short stem in reverse total shoulder arthroplasty: does it really matter?

BackgroundThe utilization of short humeral stems in reverse total shoulder arthroplasty (RTSA) has gained attention in recent times. However, concerns regarding the risk of misalignment during implant insertion are associated with their use. MethodsEight fresh-frozen cadaveric shoulders were prepared for dissection and biomechanical testing. A bespoke humeral implant was fabricated to facilitate assessment of neutral, varus, and valgus alignments using a single stem, and 10° was established as the maximum permissible angle for misalignments. Shift in humerus position and changes in deltoid length attributable to misalignments relative to the neutral position were evaluated using a Microscribe 3DLx system. The impingement-free range of motion (IFROM), encompassing abduction, adduction, internal rotation (IR), and external rotation (ER), was gauged using a digital goniometer. The capacity for abduction was evaluated at maximal abduction angles under successive loading on the middle deltoid. A specialized traction system coupled with a force transducer was employed to measure anterior dislocation forces. ResultsRelative to the neutral alignment, valgus alignment resulted in a more distal (10.5 ± 2.4 mm) and medial (8.3 ± 2.2 mm) translation of the humeral component, whereas the varus alignment resulted in the humerus shifting more superiorly (11.2 ± 1.3 mm) and laterally (9.9 ± 0.9 mm) at 0° abduction. The valgus alignment exhibited the highest abduction angle than neutral alignment (86.2°, P<0.001). Conversely, the varus alignment demonstrated significantly higher adduction (18.4±7.4°, P<0.001), IR (68.9±15.0°, P=0.014), and ER (45.2±10.5°, P=0.002) at 0° abduction compared to the neutral alignments. Anterior dislocation forces were considerably lower (23.8N) in the varus group compared to the neutral group at 0°ER (P=0.047). Additionally, abduction capability was markedly higher in varus alignment at low deltoid loads than the neutral alignment (5N, P=0.009; 7.5N, P=0.007). ConclusionsThe varus position enhances rotational ROM but increases instability, while the valgus position does not significantly impact ROM or instability compared to the neutral position.

Modification of Humeral Component Results in Increased Impingement Free Range of Motion in a Reverse Shoulder Arthroplasty Model.

Shoulder arthroplasties have been demonstrated to provide reliable pain relief as well as functional benefits. The advent of the reverse shoulder arthroplasty allowed for expanded indications for shoulder replacement. Several studies comparing the outcomes of anatomic and reverse total shoulder arthroplasties have demonstrated decreased range of motion in the reverse arthroplasty cohort, especially in internal rotation. The authors hypothesized that slight modifications to the humeral component of a reverse shoulder arthroplasty could result in increased impingement free range of motion without significant sacrifices to stability. A reverse shoulder arthroplasty model was fashioned to mimic a setting of anterior mechanical impingement after replacement. Sequential resections were taken from the anterior aspect of the polyethylene up to a resection of 10 mm. A solid modeling software was utilized to compare the experimental group to the control group with regard to impingement free motion. Finite element analysis was subsequently utilized to assess stability of the construct in comparison to the nonmodified polyethylene. Impingement free internal rotation increased minimally at 3 mm of resection but considerably at each further increase in resection. A resection of 10 mm resulted roughly 30% improvement in impingement free internal rotation. Instability in this model increased with modifications beyond 7 mm. Slight alterations to the geometry of the humeral tray and polyethene components can result in improvements in impingement-free internal rotation without substantial increased instability in this model. Further work is needed to determine in vivo implications of modifications to the humeral tray and polyethylene.

The role of bone morphology of the greater tuberosity and lateral acromion on subacromial space during scaption: a three-dimensional dynamic simulation analysis

BackgroundThe bone morphology of the greater tuberosity and lateral acromion plays a central role in subacromial impingement syndrome. The critical shoulder angle (CSA) and greater tuberosity angle (GTA) are two-dimensional measurement parameters that have been validated to evaluate it radiologically. These markers are, however, static and don’t consider the dynamic effect of glenohumeral motion.ObjectivesThis study aimed to better understand the biomechanics in subacromial impingement with a dynamic simulation based on a validated 3D biomechanical model coupling joint kinematics and 3D reconstructed computed tomography.Study design & methodsSixty-one patients were included in this study: a case group of 44 patients with degenerative rotator cuff tears involving only the supraspinatus, and a control group of 17 without a rotator cuff tear. Patients with previous surgeries, traumatic cuff tears, and cuff tear arthropathy were excluded. CSA, GTA, and impingement-free range of motion (IF-ROM) of the glenohumeral joint in scaption were calculated. Correlation tests were used to determine the relationship between ROM and CSA, GTA, and combined CSA and GTA values.ResultsCSA and GTA were significantly higher in the rotator cuff tear group (p = 0.001 and < 0.001), while IF-ROM was significantly higher in the control group (p = 0.001). There was no overall correlation between CSA and GTA (R = 0.02, p = 0.8). Individual correlation between both angles with IF-ROM was negatively weak for CSA (R = -0.4, p < 0.001) and negatively moderate for GTA and IF-ROM (R = -0.5, p < 0.001). However, combining both angles resulted in a negatively high correlation with IF-ROM (R = -0.7, p < 0.001).ConclusionSubacromial space narrowing during scaption is highly correlated to the cumulative values of GTA and CSA. These findings suggest that the combined bony morphology of the lateral acromion and greater tuberosity plays an important role in subacromial impingement.Level of evidenceIII

Preoperative Planning Software Does Not Accurately Predict Range of Motion in Reverse Total Shoulder Arthroplasty.

The purpose of this study was to determine whether preoperative planning software (PPS) accurately predicts clinical range of motion (ROM) in patients with reverse total shoulder arthroplasty 1 year postoperatively with preoperative and postoperative computed tomography (CT) scans. This was a retrospective study of 16 reverse total shoulder arthroplasty patients with preoperative and postoperative (CT) scans obtained at least 1 year postoperatively. Clinical ROM was measured in abduction, external rotation at resting abduction, extension, and flexion at a minimum of 1 year postoperatively. All clinical measurements were obtained before generation of PPS ROM values. Using postoperative CT scans, the achieved implant component positions were quantified and then replicated in PPS on the preoperative CT scans. The preoperative predicted ROM was then recorded, both with and without osteophyte removal. Bland-Altman plots were generated within each motion comparing the differences between clinically measured motion and software-predicted motion. The variation in clinically measured ROM in abduction, external rotation at resting abduction, extension, and flexion were 118 ± 27 (65° to 180°), 33 ± 16 (10° to 75°), 56 ± 8 (50° to 65°), and 137 ± 25 (80° to 160°), respectively. Clinically measured motion differed greatly from PPS-predicted ROM, with mean differences of 33 ± 29 (-32 to 93) for abduction, 44 ± 25 (-38 to 57) for external rotation, 44 ± 25 (-35 to 65) for extension, and 54 ± 50 (-51 to 147) for flexion with no significant correlations between clinically measured and PPS-predicted ROM ( P > 0.05). With humeral or humeral and glenoid osteophyte resection, correlations for only flexion became significant ( P = 0.002 for both). The passive glenohumeral impingement-free ROM generated from PPS incompletely predicts clinically measured active humerothoracic ROM, possibly because of the unmeasured factors of soft-tissue tension, muscular strength, humeral torsion, resting scapular posture, and, most importantly, scapulothoracic motion. IV.

Comparative Analysis of Eccentric Glenosphere in Reverse Total Shoulder Arthroplasty: A Computer Simulation Study.

The aim was to evaluate the effects of different glenosphere eccentricities on impingement, range of motion (ROM), and muscle length during standard activities in reverse total shoulder arthroplasty (RSA). In this study, we utilized computational modeling techniques to create native shoulder and shoulder models undergoing RSA and simulate shoulder movements in all abduction-adduction, flexion-extension, and rotation. We tested a total of 36 different glenosphere configurations, which included three different inferior tilts (0°, +10°, +20°) and two different lateral offsets (0 mm and +4 mm), as well as six different glenosphere eccentricities (concentricity, inferior, posterior, anterior, anteroinferior, and posteroinferior). We evaluated the maximum impingement-free ROM, impingement sites, and muscle lengths. All glenosphere configurations exceeded 50% of native shoulder ROM in three planes and total global ROM. In abduction-adduction, there was no significant difference among the different glenosphere eccentricities (p > 0.05). In flexion-extension, the posteroinferior eccentricity had the maximum ROM among the different eccentricities, but no significant difference among the different glenosphere eccentricities (p > 0.05). In rotation, there was a significant difference overall, and anteroinferior eccentricity had a significant advantage over concentricity (p < 0.05). In total global ROM, anteroinferior eccentricity had a significant advantage over concentricity when lateral offset was 0 mm (p < 0.05). In all models of glenosphere eccentricities, only the elongation of the infraspinatus muscle was statistically significant (p < 0.05). Glenosphere eccentricity significantly influenced rotation, total global ROM, and the length of the subscapularis muscle. Among them, anteroinferior offset achieved the maximum ROM in abduction-adduction, rotation, and total global activities. Both anteroinferior and inferior glenoid eccentricity showed significant advantages over the concentricity in rotation and total global ROM. Basic Science Study; Computer Modeling.

Impact of constrained humeral liner on impingement-free range of motion and impingement type in reverse shoulder arthroplasty using a computer simulation

Dislocation is a major complication of reverse total shoulder arthroplasty (RSA). Humeral liner may be changed to the constrained type when stability doesn't improve by increasing glenosphere size or lateralization with implants, and patients, particularly women with obesity, have risks of periprosthetic instability that may be secondary to hinge adduction on the thorax, but there are few reports on its impact on the range of motion (ROM). This study aimed to determine the influence of humeral liner constraint on impingement-free ROM and impingement type utilizing an RSA computer simulation model. A virtual simulation model was created using 3D measurement software for conducting a simulation study. This study included twenty-five patients with rotator cuff tears and rotator cuff tear arthropathy. Impingement-free ROM and impingement patterns were measured during flexion, extension, abduction, adduction, external rotation, and internal rotation. Four different simulations of 2×2 were performed in each of the 25 cases, a total of 100 simulations: Glenosphere (38mm normal type vs. lateralized type) and humeral liner constraint (normal type vs. constrained type). There were four combinations: normal glenosphere and normal humeral liner, normal glenosphere and constrained humeral liner, lateralized glenosphere and normal humeral liner, and lateralized glenosphere and constrained humeral liner. Significant differences were found in all impingement-free ROM in one-way ANOVA (abduction: p=0.01, adduction: p<0.01, flexion: p=0.01, extension: p=0.02, external rotation: p<0.01, and internal rotation: p<0.01). Tukey's post-hoc tests showed that the impingement-free ROM was reduced during abduction, external rotation, and internal rotation with the combination of normal glenosphere and constrained humeral liner compared to the other combinations, and improved by glenoid lateralization compared to the combination of the lateralized glenosphere and constrained humeral liner. In the impingement pattern, Pearson's chi-squared test showed significantly greater proportion of impingement of the humeral liner into the superior part of the glenoid neck in abduction occurring in the combination of normal glenosphere and constrained humeral liner group compared to the other groups (p<0.01). Bonferroni post-hoc tests revealed that the combination of normal glenosphere and constrained humeral liner was significantly different from that of lateralized glenosphere and constrained humeral liner (p<0.01). Using constrained liners resulted in early impingement on the superior part of the glenoid neck in the normal glenosphere, whereas glenoid lateralization increased impingement-free ROM. This RSA computer simulation model demonstrated that constrained humeral liners led to decreased impingement-free ROM. However, using lateralized glenosphere improved abduction ROM.

Do hip resurfacing and short hip stem arthroplasties differ from conventional hip stem replacement regarding impingement-free range of motion?

Total hip joint replacement (THR)is clinically well-established. In this context, the resulting range of motion (ROM)is crucial for patient satisfaction when performing joint movements. However, the ROM for THR with different bone preserving strategies (short hip stem and hip resurfacing) raises the question of whether the ROM is comparable with conventional hip stems. Therefore, this computer-based study aimed to investigate the ROM and type of impingement for different implant systems. An established framework with computer-aided design3D models based on magnetic resonance imagingdata of 19 patients with hip osteoarthritis was used to analyse the ROM for three different implant systems (conventional hip stem vs. short hip stem vs. hip resurfacing) during typical joint movements. Our results revealed that all three designs led to mean maximum flexion higher than 110°. However, hip resurfacing showed less ROM (-5% against conventional and -6% against short hip stem). No significant differences were observed between the conventional and short hip stem during maximum flexion and internal rotation. Contrarily, a significant difference was detected between the conventional hip stem and hip resurfacing during internal rotation (p = 0.003). The ROM of the hip resurfacing was lower than the conventional and short hip stem during all three movements. Furthermore, hip resurfacing shifted the impingement type to implant-to-bone impingement compared with the other implant designs. The calculated ROMs of the implant systems achieved physiological levels during maximum flexion and internal rotation. However, bone impingement was more likely during internal rotation with increasing bone preservation. Despite the larger head diameter of hip resurfacing, the ROM examined was substantially lower than that of conventional and short hip stem.

A novel algorithm to efficiently calculate the impingement-free range of motion of irregularly-shaped total hip arthroplasty components.

There is great difficulty in quickly calculating the impingement-free range of motion (IFROM) of hip components with complex shapes after total hip arthroplasty. We have established a new algorithm to investigate the effect of different shapes of hip components on the IFROM and impingement-free safe zone (IFSZ). Then find the best combination of hip prosthesis and the optimal mounting position of the elevated-rim liner under different radiographic anteversion (RA) and radiographic inclination (RI) of the cup. We found the larger the opening angle of the beveled-rim liner and the smaller the cross-sectional area of the stem neck with an inverted teardrop cross-sectional shape, the greater the IFROM of the hip component. The beveled-rim liner in combination with the stem neck with an inverted teardrop-shaped cross-section could provide the greatest IFSZ (excluding the flat-rim liner). The optimal orientation of the elevated-rim liner was the posterior-inferior side (RI ≤ 37°), posterior-superior side (RI ≥ 45°), and posterior side (37° ≤ RI ≤ 45°). Our novel algorithm provides a solution to analyze the IFROM of any hip prosthesis with any complex shape. The shape and size of the cross-section of the stem neck, the orientation of the elevated rim, and the shape and opening angle of the liner are all critical factors for the quantitative calculation of the IFROM and mounting safe zone of the prosthesis. Stem necks with inverted teardrop cross-section and beveled-rim liner improved the IFSZ. The optimal direction of the elevated rim is not constant but varies with RI and RA.

Accuracy of Blueprint in Predicting Range of Motion One Year After Reverse Total Shoulder Arthroplasty.

/hypothesis: Blueprint 3D CT software has a functionality that predicts impingement-free range of motion with the limits of range of motion determined at which bone and/or prosthetic impingement occurs. To the best of knowledge, there is only one previously published study that assessed the ability for the Blueprint software to predict actual postoperative range of motion after reverse total shoulder arthroplasty. The hypothesis of this study was that 1) mean Blueprint predicted impingement-free range of motion will be statistically similar to the mean actual range of motion one year after reverse total shoulder arthroplasty and 2) there will be a correlation between Blueprint predicted impingement-free range of motion and the actual range of motion one year after reverse total shoulder arthroplasty. A retrospective review of patients that had Blueprint planning prior to undergoing reverse total shoulder arthroplasty from March 2017 through May 2021 was reviewed. At one-year follow-up. flexion, external rotation at the side, abduction, abduction / external rotation, abduction / internal rotation, and internal rotation behind the back were measured. The preoperatively predicted flexion, extension, abduction, external rotation, and internal rotation were recorded from the Blueprint software. Group 1 analysis examined the predicted vs actual range of motion for all 127 patients regardless if intraoperative component modifications were made. Group 2 examined the predicted vs actual range of motion of only the patients that did not have intraoperative changes that would affect the preoperative range of motion prediction (n=97). Group 3 examined the predicted vs actual range of motion of Group 2 combined with the 30 patients that had post-hoc Blueprint planning modifications to account for the changes made intraoperatively (combined sample size = 127). One-hundred-twenty-seven patients of the 141 patients (90%) were available for one year follow-up. When examining the mean of all three groups, the actual range of motion and predicted range of motion was statistically significantly different (p<0.0001) for flexion, external rotation, abduction, abduction/ external rotation, and abduction / internal rotation. In Group 1, a very weak or poor correlation was found between predicted internal rotation and actual abducted/internal rotation (r=0.19; p=0.04). For all other range of motion metrics in Groups 1, 2, and 3, there were no correlations between predicted and actual range of motion (p >.07). In its current state, preoperative Blueprint 3D CT planning software is unable to accurately predict range of motion one year after reverse total shoulder arthroplasty.

DYNAMIC 3D ANIMATION OPTIMIZING GLENOSPHERE CONFIGURATION IN REVERSE SHOULDER ARTHROPLASTY

Scapular notching is a common problem following reverse shoulder arthroplasty (RSA). This is due to impingement between the humeral polyethylene cup and scapular neck in adduction and external rotation. Various glenoid component strategies have been described to combat scapular notching and enhance impingement-free range of motion (ROM). There is limited data available detailing optimal glenosphere position in RSA with an onlay configuration. The purpose of this study was to determine which glenosphere configurations would maximise impingement free ROM using an onlay RSA prosthesis.A three-dimensional (3D) computed tomography (CT) scan of a shoulder with Walch A1, Favard E0 glenoid morphology was segmented using validated software. An onlay RSA prosthesis was implanted and a computer model simulated external rotation and adduction motion of the virtual RSA prosthesis. Four glenosphere parameters were tested; diameter (36mm, 41mm), lateralization (0mm, 3mm, 6mm), inferior tilt (neutral, 5 degrees, 10 degrees), and inferior eccentric positioning (0.5mm, 1.5mm. 2.5mm, 3.5mm, 4.5mm). Eighty-four combinations were simulated. For each simulation, the humeral neck-shaft angle was 147 degrees and retroversion was 30 degrees.The largest increase in impingement-free range of motion resulted from increasing inferior eccentric positioning, gaining 15.0 degrees for external rotation and 18.8 degrees for adduction. Glenosphere lateralization increased external rotation motion by 13. 6 degrees and adduction by 4.3 degrees. Implanting larger diameter glenospheres increased external rotation and adduction by 9.4 and 10.1 degrees respectively. Glenosphere tilt had a negligible effect on impingement-free ROM.Maximizing inferior glenosphere eccentricity, lateralizing the glenosphere, and implanting larger glenosphere diameters improves impingement-free range of motion, in particular external rotation, of an onlay RSA prosthesis. Surgeons’ awareness of these trends can help optimize glenoid component position to maximise impingement-free ROM for RSA. Further studies are required to validate these findings in the context of scapulothoracic motion and soft tissue constraints.

Robotic biomechanical evaluation of six different reverse shoulder implants

BackgroundThe reverse total shoulder arthroplasty is a popular surgical treatment for a degenerative shoulder with a nonfunctional rotator cuff. Currently, more than 36 different brands with small different features are available. This creates choice stress among many surgeons, who no longer know which parameters and surgical factors are important to optimize the placement of the implant. PurposeThe first purpose of this pilot study was to compare the passive range of motion (ROM) of 6 different implant designs implanted following the manufacturer’s guidelines. The second goal was to identify the impingements after implantation which determines the maximal ROM. The last goal of the study was to link the different parameters of an implant with the ROM. MethodsSix implant systems were implanted on identical sawbones. The procedure was repeated 3 times on a different sawbone to objectify the surgical repeatability of the procedures. A Stäubli TX-90 robot was used to perform and control the humerus' kinematic movement. An optical tracking system was used to perform the system's calibrations, track the humerus and scapula in space, and compute the center of rotation. ResultsThere was a wide ROM in the scapular plane (44.8°-105.5°) while the minimal elevation (adduction) varied between −4.8° and 35.6°. The rotational movements were limited by contact of the superior humeral polyethylene inlay and the inferior scapular neck. The adduction in the coronal and scapular plane was limited by inferior scapular impingement, whereas the maximal abduction was limited either by bony contact between the humerus and acromion or by contact between the humeral polyethylene inlay and the superior glenoid cavity. A bigger radius of the glenosphere resulted in a larger passive humeroscapular ROM (P < .001). A larger Neck-Shaft-Angle results in a better abduction (P < .001) but compromised adduction (P < .001). The localization of the center of rotation has a significant impact on the ROM. The medialized designs have larger abduction and rotational angles (P < .001). ConclusionThere is a wide variation in the measured glenohumeral ROM between the 6 frequently implanted prostheses. The most important factor to optimize the impingement-free ROM in all types of prostheses is the creation of the prosthetic overhang of the glenosphere to the bone. Too much lateralization of the center of the glenosphere with or without lateralization of the humeral stem can create a subacromial and/or subcoracoidal impingement.

Therapieentscheidung bei Kombinationspathologien Dysplasie – FAI – Fehlrotation

Hip dysplasia, FAI and femoral malrotation often occur together, resulting in mixed symptoms and severe biomechanical limitations of the hip. To report on the current recommendations for the best possible diagnosis and treatment strategies of combination pathologies in hip-preserving surgery. Review and discussion of the relevant literature with consideration of own experience in the treatment of complex combined pathomorphologies of the hip. Patient history and athorough clinical examination are key for determining the predominant pathomorphologies causing the symptoms. Standardized conventional ap pelvic and axial images of the hip are the basis for the radiological assessment of the hip, supplemented with MRI, CT and animations of the hip, depending on the case. As the pathologies influence each other functionally, astepwise approach to treatment is recommended. The functionally most relevant pathology is treated first, followed by further corrections as needed. The primary goal is to achieve astable hip with normal acetabular coverage, followed by an impingement-free range of motion and normalized musculoskeletal function. Care must be taken in the choice of surgical method to ensure that all pathologies can be adequately treated. Complex, combined pathologies of the hip can be treated sufficiently with hip-preserving surgery. Athorough diagnosis is important in order to recognize the functional interaction of the different pathologies. The goal of the surgical therapy is acorrectly covered, stable hip with anormal range of motion.

Which Safe Zone Is Safe in Total Hip Arthroplasty? The Effect of Bony Impingement

“Safe zones” for cup position are currently being investigated in total hip arthroplasty (THA). This study aimed to evaluate the impact of bony impingement on the safe zone and provide recommendations for cup position in THA. CT scans were performed on 123 patients who underwent a cementless THA. Using the implant data and bone morphology from the CT scans, an impingement detection algorithm simulating range of motion (ROM) determined the presence of prosthetic and/or bony impingement. An impingement-free zone of motion was determined for each patient. These zones were then compared across all patients to establish an optimized impingement-free “safe zone”. Bony impingement reduced the impingement-free zone of motion in 49.6% (61/123) of patients. A mean reduction of 23.4% in safe zone size was observed in relation to periprosthetic impingement. The superposition of the safe zones showed the highest probability of impingement-free ROM with cup position angles within 40–50° of inclination and 20–30° of anteversion in relation to the applied cup and stem design of this study. Virtual ROM simulations identified bony impingement at the anterosuperior acetabular rim for internal rotation at 90° of flexion and at the posteroinferior rim for adduction as the main reasons for bony impingement.

Does accelerometer-based portable navigation provide more accurate and precise cup orientation without prosthetic impingement than conventional total hip arthroplasty? A randomized controlled study

This prospective randomized controlled study examined whether accelerometer-based navigation resulted in more accurate or precise cup orientation than a conventional mechanical guide. We used a simulation to evaluate how cup orientation affected potential hip range of motion (RoM) and freedom from prosthetic impingement. Sixty hips were randomly allocated 1:1 to accelerometer-based portable navigation or conventional guidance. Procedures were performed through a standard posterolateral approach and combined anteversion technique. Cup inclination, cup anteversion, and stem anteversion were measured using computed tomography (CT). Using CT-based simulation, we evaluated impingement-free potential RoM and the proportion of hips with potential RoM required for daily activities. Absolute cup inclination and anteversion error averaged 4.3° ± 3.2° and 4.4° ± 2.9° for the navigation cohort and 5.6° ± 3.7° and 5.7° ± 4.2° for the conventional cohort, with no significant differences. Navigation resulted in significantly less variation in anteversion error than the conventional guide (p = .0049). Flexion, internal rotation (IR) at 90° of flexion, extension, and external rotation (ER) averaged 123° ± 12°, 46° ± 13°, 50° ± 10°, and 73° ± 23°, respectively, in the navigation cohort and 127° ± 10°, 52° ± 14°, 45° ± 10°, and 63° ± 12°, respectively, in the conventional cohort (p = .15, .15, .03, and .03, respectively). Flexion > 110°, IR > 30° at 90° of flexion, extension > 30°, and ER > 30° were achieved by 93%, 90%, 100%, and 100% of hips, respectively, in the navigation cohort and 97%, 93%, 97%, and 100% of hips, respectively, in the conventional cohort, with no significant differences. Cup anteversion with the navigation system was more precise, but not more accurate, than with the conventional guide. The navigation cohort exhibited greater potential extension and ER than the conventional cohort, but no significant difference in impingement within the potential RoM required for daily activities. 29036. Date of registration: November 14, 2017.

The accuracy of restoration of femoral head centre of rotation in the anteroposterior plane after uncemented total hip arthroplasty

AimsHip arthroplasty aims to accurately recreate joint biomechanics. Considerable attention has been paid to vertical and horizontal offset, but femoral head centre in the anteroposterior (AP) plane has received little attention. This study investigates the accuracy of restoration of joint centre of rotation in the AP plane.MethodsPostoperative CT scans of 40 patients who underwent unilateral uncemented total hip arthroplasty were analyzed. Anteroposterior offset (APO) and femoral anteversion were measured on both the operated and non-operated sides. Sagittal tilt of the femoral stem was also measured. APO measured on axial slices was defined as the perpendicular distance between a line drawn from the anterior most point of the proximal femur (anterior reference line) to the centre of the femoral head. The anterior reference line was made parallel to the posterior condylar axis of the knee to correct for rotation.ResultsOverall, 26/40 hips had a centre of rotation displaced posteriorly compared to the contralateral hip, increasing to 33/40 once corrected for sagittal tilt, with a mean posterior displacement of 7 mm. Linear regression analysis indicated that stem anteversion needed to be increased by 10.8° to recreate the head centre in the AP plane. Merely matching the native version would result in a 12 mm posterior displacement.ConclusionThis study demonstrates the significant incidence of posterior displacement of the head centre in uncemented hip arthroplasty. Effects of such displacement include a reduction in impingement free range of motion, potential alterations in muscle force vectors and lever arms, and impaired proprioception due to muscle fibre reorientation.Cite this article: Bone Joint Res 2022;11(3):180–188.

Development of a framework to assess the biomechanical impact of reverse shoulder arthroplasty placement modifications.

Reverse shoulder arthroplasty biomechanics can be improved by modifying the placement of prosthesis. Biomechanical studies have quantified the impact of placement modifications on the mobility and stability of the reverse shoulder. While these studies have provided detailed insights, direct comparisons between their finding are obfuscated by their use of differing methodologies. The aim of our study was to develop an assessment framework which used musculoskeletal simulations to consistently evaluate the biomechanics of various placement modifications. We conducted musculoskeletal simulations of humeral elevations and rotations using 15 reverse shoulder models. For each model, these simulations were conducted for a reference configuration of the prosthesis, established using surgical guidelines, and 34 modified configurations, which were based on commonplace adaptations to the placement of the glenosphere and humeral tray. The effect of each modified configuration on deltoid elongation, deltoid moment arm (DMA), joint stability, and impingement-free range of motion (IFROM) was determined relative to the reference configuration. We found that 16 of the 34 modified placements had an overall beneficial impact on reverse shoulder biomechanics. Within this subset, we identified two biomechanical trade-offs. First, there is an antagonistic relationship between IFROM and both the DMA and joint stability. Second, functional requirements differ between humeral elevations and rotations. Furthermore, we found that posteromedial translation of the humeral tray had the most beneficial impact on joint stability and inferior translation of the glenosphere had the most beneficial impact on IFROM and DMA.

Three-Dimensional Magnetic Resonance Imaging Bone Models of the Hip Joint Using Deep Learning: Dynamic Simulation of Hip Impingement for Diagnosis of Intra- and Extra-articular Hip Impingement.

Background:Dynamic 3-dimensional (3D) simulation of hip impingement enables better understanding of complex hip deformities in young adult patients with femoroacetabular impingement (FAI). Deep learning algorithms may improve magnetic resonance imaging (MRI) segmentation.Purpose:(1) To evaluate the accuracy of 3D models created using convolutional neural networks (CNNs) for fully automatic MRI bone segmentation of the hip joint, (2) to correlate hip range of motion (ROM) between manual and automatic segmentation, and (3) to compare location of hip impingement in 3D models created using automatic bone segmentation in patients with FAI.Study Design:Cohort study (diagnosis); Level of evidence, 3.Methods:The authors retrospectively reviewed 31 hip MRI scans from 26 symptomatic patients (mean age, 27 years) with hip pain due to FAI. All patients had matched computed tomography (CT) and MRI scans of the pelvis and the knee. CT- and MRI-based osseous 3D models of the hip joint of the same patients were compared (MRI: T1 volumetric interpolated breath-hold examination high-resolution sequence; 0.8 mm3 isovoxel). CNNs were used to develop fully automatic bone segmentation of the hip joint, and the 3D models created using this method were compared with manual segmentation of CT- and MRI-based 3D models. Impingement-free ROM and location of hip impingement were calculated using previously validated collision detection software.Results:The difference between the CT- and MRI-based 3D models was <1 mm, and the difference between fully automatic and manual segmentation of MRI-based 3D models was <1 mm. The correlation of automatic and manual MRI-based 3D models was excellent and significant for impingement-free ROM (r = 0.995; P < .001), flexion (r = 0.953; P < .001), and internal rotation at 90° of flexion (r = 0.982; P < .001). The correlation for impingement-free flexion between automatic MRI-based 3D models and CT-based 3D models was 0.953 (P < .001). The location of impingement was not significantly different between manual and automatic segmentation of MRI-based 3D models, and the location of extra-articular hip impingement was not different between CT- and MRI-based 3D models.Conclusion:CNN can potentially be used in clinical practice to provide rapid and accurate 3D MRI hip joint models for young patients. The created models can be used for simulation of impingement during diagnosis of intra- and extra-articular hip impingement to enable radiation-free and patient-specific surgical planning for hip arthroscopy and open hip preservation surgery.

The impact of functional combined anteversion on hip range of motion: a new optimal zone to reduce risk of impingement in total hip arthroplasty.

AimsPelvic tilt (PT) can significantly change the functional orientation of the acetabular component and may differ markedly between patients undergoing total hip arthroplasty (THA). Patients with stiff spines who have little change in PT are considered at high risk for instability following THA. Femoral component position also contributes to the limits of impingement-free range of motion (ROM), but has been less studied. Little is known about the impact of combined anteversion on risk of impingement with changing pelvic position.MethodsWe used a virtual hip ROM (vROM) tool to investigate whether there is an ideal functional combined anteversion for reduced risk of hip impingement. We collected PT information from functional lateral radiographs (standing and sitting) and a supine CT scan, which was then input into the vROM tool. We developed a novel vROM scoring system, considering both seated flexion and standing extension manoeuvres, to quantify whether hips had limited ROM and then correlated the vROM score to component position.ResultsThe vast majority of THA planned with standing combined anteversion between 30° to 50° and sitting combined anteversion between 45° to 65° had a vROM score > 99%, while the majority of vROM scores less than 99% were outside of this zone. The range of PT in supine, standing, and sitting positions varied widely between patients. Patients who had little change in PT from standing to sitting positions had decreased hip vROM.ConclusionIt has been shown previously that an individual’s unique spinopelvic alignment influences functional cup anteversion. But functional combined anteversion, which also considers stem position, should be used to identify an ideal THA position for impingement-free ROM. We found a functional combined anteversion zone for THA that may be used moving forward to place total hip components.Cite this article: Bone Jt Open 2021;2(10):834–841.