Continuous Shoulder Activity Tracking after Open Reduction and Internal Fixation of Proximal Humerus Fractures.

Postoperative shoulder activity after proximal humerus fracture treatment could influence the outcomes of osteosynthesis and may depend on the rehabilitation protocol. This multi-centric prospective study aimed at evaluating the feasibility of continuous shoulder activity monitoring over the first six postoperative weeks, investigating potential differences between two different rehabilitation protocols. Shoulder activity was assessed with pairs of accelerometer-based trackers during the first six postoperative weeks in thirteen elderly patients having a complex proximal humerus fracture treated with a locking plate. Shoulder angles and elevation events were evaluated over time and compared between the two centers utilizing different standard rehabilitation protocols. The overall mean shoulder angle ranged from 11° to 23°, and the number of daily elevation events was between 547 and 5756. Average angles showed longitudinal change <5° over 31 ± 10 days. The number of events increased by 300% on average. Results of the two clinics exhibited no characteristic differences for shoulder angle, but the number of events increased only for the site utilizing immediate mobilization. In addition to considerable inter-patient variation, not the mean shoulder angle but the number of elevations events increased markedly over time. Differences between the two sites in number of daily events may be associated with the different rehabilitation protocols.

The anatomy and variation of the coracoid attachment of the subclavius muscle in humans.

The functions of the subclavius muscle (SM) are described as stabilization of the sternoclavicular joint (SCJ) and resisting elevation of the lateral end of the clavicle. During systematic cadaveric dissections, we observed additional fibrous structures, previously described as variants of the anatomy, extending from the SM and inserting into the coracoid process (CP). Due to the high incidence of these structures in our dissections, we hypothesized that the attachment at the CP is more common than appreciated and that, as a corollary, the function of the SM was (or has been) more complex than simply depressing the clavicle and generating stability at the SCJ. For our investigation, fifty-two upper extremities of 26 human cadavers were dissected. The SM was demonstrated from costal to clavicular attachment. We documented additional fibrous structures apparently derived from the SM inserting into the CP. Measurements of the length of the SM, the length of its attachment, and the length of the clavicle were taken in situ, with the specimens supine and the upper extremity in the anatomical position. Variations in the anatomy of the SM and its coracoidal attachment were recorded, and potential correlations were investigated. For documentation purposes photographs and video sequences of passive motion of the shoulder girdle of the specimens were taken. In 49 of the 52 specimens we found additional fibrous structures passing from the SM to the CP. We differentiated three types: (1) a strong cord-like structure; (2) a small or thin cord-like structure or structures; and (3) a planar twisted sheet-like structure. The SM and its extension to the CP appears to contribute to a 'functional scapular suspension system' together with the other muscles enveloped by the clavipectoral fascia (pectoralis minor, coracobrachialis and the short head of the biceps brachii). This system assists in the control of the position of the scapula in relation to the thorax, particularly in elevated positions of the upper extremity. We speculate that the differentiation of the fibrous structure depends on the functional demands of the individual. Level of Evidence: Basic science study.

Functional Shoulder Outcome and Quality of Life Following Modified Muscle-Sparing Pectoralis Major Flap Surgery.

BACKGROUND: The pedicled pectoralis major muscle flap (PMMF) is a well established flap for fistula prophylaxis after salvage laryngectomy. To reduce donor site morbidity, we established a modified muscle-sparing harvesting technique. We herein investigate postoperative shoulder function and health-related quality of life (HRQOL). METHODS: A chart review of patients receiving the modified muscle-sparing pectoralis major muscle flap between 2013-2020 was performed. Nineteen patients (male = 18, female = 1) were potentially eligible and six male patients were ultimately enrolled. Postoperative shoulder function was assessed on both sides (flap side versus non-flap side) using the Constant Murley Score and the Bak criteria. Health-related quality of life was assessed with the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire in cancer patients (EORTC QLQ-C30) and head and neck cancer patients (EORTC H&N35). RESULTS: No Constant Murley Score subscale was statistically significant (p ≥ 0.180). Bak criteria was overall rated "Good". Solely upper extremity adduction force was significantly altered on the flap side (p = 0.039). Median EORTC QLQ-C30 score was 82.2 (IQR 11.1) on the functional scale and 10.3 (IQR 2.6) on the symptomatic scale. Median quality of life score was 75.0 (IQR 33.3) and median EORTC QLQ-H&N35 was 20.6 (IQR 9.8). CONCLUSIONS: Postoperative shoulder function after modified muscle-sparing pectoralis major muscle flap surgery is comparable to function of the healthy side with a significant deficiency in adduction force not compromising daily life in this small study cohort.

Does cement augmentation of the screws in angular stable plating for proximal humerus fractures influence the radiological outcome: a retrospective assessment.

BACKGROUND: Screw-tip augmentation in angular stable plating offers new possibilities for the treatment of complex proximal humerus fractures. This retrospective analysis was performed to evaluate the radiological outcome of proximal humerus fractures treated with angular stable plates and additional screw-tip cement augmentation in patients over the age of 60. MATERIALS AND METHODS: A retrospective single centre analysis was conducted from June 2013 to December 2016. The minimum follow-up time was set to 6 months after surgery. Anatomical reduction and fixation were evaluated in respect to reattached tuberosities to the head fragment and the adequate restoration of the calcar area not showing any valgus or varus malalignment. Complete fracture healing was determined 3 months after surgery. Any failures such as secondary displacement, primary screw perforation, intraarticular cement leakage and avascular necrosis of the humeral head with concomitant screw cut-out were assessed. RESULTS: In total, 24 patients (21 females; 3 males) at a median age of 77.5 (62-96) years were included. Five 2-part, twelve 3-part and seven 4-part fractures were detected. The measured median BMD value of 23 patients was 78.4 mg/cm3 (38.8-136.9 mg/cm3). Anatomical reduction was achieved in 50% of the patients. In most cases, the A level screws and the B1 screw were augmented with bone cement by a median of 7 (5-9) head screws used. Postoperative varus displacement was not detected in any of the patients. One patient (4.2%) sustained an early secondary displacement. Intraarticular cement leakage was detected in 3 patients (2 head-split fractures). Avascular necrosis of the humeral head was observed in 4 patients (16.7%). Revision surgery was necessary in four cases, using hemiarthroplasty twice and reverse shoulder arthroplasty the other two times. CONCLUSION: Screw-tip augmentation in angular stable plating for proximal humerus fracture treatment showed a low secondary displacement rate of 4.2% in patients suffering from poor bone quality. Nevertheless, the occurrence of avascular necrosis of the humeral head with mainly severe fracture patterns observed in this study was higher compared to previously reported results in the literature. Cement augmentation in head-split fractures is not recommended, considering the high risk of an intraarticular cement leakage.

Cement augmentation of the proximal humerus internal locking system in elderly patients: a multicenter randomized controlled trial.

INTRODUCTION: Cement augmentation of the proximal humerus internal locking system (PHILOS) screws might reduce complication rates in osteoporotic bones. This study compared the risk of mechanical failure during the first year after PHILOS™ treatment of proximal humerus fractures (PHF) without (control group) and with (augmented group) screw augmentation. Secondary objectives were to report shoulder functions, quality of life (QoL), adverse events (AEs), and reoperation rates. MATERIALS AND METHODS: This multicenter randomized trial enrolled patients aged ≥ 65 years with displaced/unstable PHF from eight European centers. Randomization was performed during surgery through sealed opaque envelopes. Mechanical failures were assessed by two independent reviewers via radiographs, shoulder function by Quick DASH, SPADI, and Constant Murley scores, and QoL by EQ-5D. Follow-ups were planned at postoperative 6 weeks, 3, 6, and 12 months. RESULTS: The preliminary analysis of 6-week radiographs of the first 59 enrolled patients suggested a mechanical failure rate lower than expected and the difference between groups was too small to be detected by the planned sample size of 144. The trial was prematurely terminated after 67 patients had been enrolled: 34 (27 eligible) in the control group and 33 (29 eligible) in the augmented group. Follow-ups were performed as planned. Nine patients had mechanical failures and the failure rates (95% CI) were: augmented group, 16.1% (5.5; 33.7); control group, 14.8% (4.2; 33.7); the relative risk (95% CI) for the augmented group was 1.09 (0.32; 3.65) compared to the control group (p = 1.000). No statistically significant differences in shoulder function, QoL, and AEs were observed between study groups at 1 year. Nine patients (15.8%) underwent a revision. CONCLUSIONS: Due to premature termination, the study was underpowered. A larger study will be necessary to determine if cement augmentation lowers the risk of mechanical failure rate.

Biomechanical evaluation of cable and suture cerclages for tuberosity reattachment in a 4-part proximal humeral fracture model treated with reverse shoulder arthroplasty.

BACKGROUND: Sufficient tuberosity fixation in proximal humeral fractures treated with shoulder arthroplasty is essential to gain a good clinical outcome. This biomechanical study evaluated the strength of the reattached tuberosities in reverse total shoulder arthroplasty fixed with cables or with sutures in a cerclage-like technique. Considering the mechanical advantages of flexible titanium alloy cables compared with conventional sutures for cerclage-like fixations, we hypothesized that titanium alloy cables would achieve higher fixation strengths of the tuberosities compared with heavy nonabsorbable sutures. METHODS: A 4-part fracture was created on 8-paired proximal human humeri. The tuberosities were reduced anatomically and fixed by 2 heavy nonabsorbable sutures (suture group) or by two 1-mm titanium alloy cables (cable group) in a cerclage-like technique around the neck of the prosthesis. The humeri were placed in a custom-made test setup enabling internal and external rotation. Cyclic loading with a stepwise increasing load magnitude was applied with a material testing machine, starting with 1 Nm and increasing the load by 0.25 Nm after each 100th cycle until failure of the fixation occurred (>15° rotation of the tuberosities). Any motion of the tuberosities was measured with a 3-dimensional ultrasound motion analysis system. RESULTS: Overall, the cable group reached 1414 ± 372 cycles, and the suture group reached 1257 ± 230 cycles until the fixations failed (P = .313). The suture group showed a significantly higher rotation of the lesser tuberosity relative to the humerus shaft axis after 200, 400, and 600 cycles compared with the cable group (P = .018-.043). CONCLUSIONS: Tuberosities reattached with cable cerclages showed higher fixation strength and therefore less rotation compared with suture cerclages in a 4-part proximal humeral fracture model treated with reverse total shoulder arthroplasty. Whether this higher fixation strength results in higher bony ingrowth rates of the tuberosities and thus leads to a better clinical outcome needs to be investigated in further clinical studies.

The female geriatric proximal humeral fracture: protagonist for straight antegrade nailing?

INTRODUCTION: Straight antegrade humeral nailing (SAHN) has become a standard technique for the surgical fixation of proximal humeral fractures, which predominantly affect elderly females. The nail's proximal anchoring point has been demonstrated to be critical to ensure reliable fixation in osteoporotic bone and to prevent iatrogenic damage to the superior rotator cuff bony insertion. Anatomical variations of the proximal humerus, however, may preclude satisfactory anchoring of the nail's proximal end and may bare the risk of rotator cuff violation, even though the nail is inserted as recommended. The aim of this study was to evaluate the anatomical suitability of proximal humeri of geriatric females aged 75 years and older for SAHN. Specifically, we sought to assess the proportion of humeri not anatomically amenable to SAHN for proximal humeral fracture. MATERIALS AND METHODS: A total of 303 proximal humeri of 241 females aged 75 years and older (mean age 84.5 ± 5.0 years; range 75-102 years) were analyzed for this study. Multiplanar two-dimensional reformations (true ap, true lateral, and axial) were reconstructed from shoulder computed tomography (CT) data sets. The straight antegrade nail's ideal entry point, "critical point" (CP), and critical distance (CD; distance between ideal entry point and CP) were determined. The rate of proximal humeri not anatomically suitable for SAHN (critical type) was assessed regarding proximal reaming diameters of currently available straight antegrade humeral nails. RESULTS: Overall, 35.6% (108/303) of all proximal humeri were found to be "critical types" (CD <8 mm) as to the recommended minimal proximal reaming diameter of 10 mm of straight antegrade nails currently in use. Moreover, 43.2% (131/303) of the humeri were considered "critical types" with regard to the alternatively used larger proximal reaming diameter of 11.5 mm. Mean CD was 9.0 ± 1.7 mm (range 3.5-13.5 mm) and did not correlate with age (r = -0.04, P = 0.54). No significant differences in CD and rate of "critical types" were found between left and right humeri as well as between females aged between 75 and 84 years (n = 151) and females aged 85 and older (n = 152). CONCLUSIONS: More than a third of proximal humeri of geriatric females are "critical types" as to SAHN and may, therefore, be at risk for procedure-related complications, such as rotator cuff violation, fixation failure, and potential malreduction. In view of this finding, we recommend to routinely analyze multiplanar CT reformations of the uninjured contralateral side prior to surgery to improve selection of patients for SAHN and to minimize foreseeable complications. For "critical type" humeri, an alternative surgical procedure should be considered.

Computed tomography-based prediction of the straight antegrade humeral nail's entry point and exposure of "critical types": truth or fiction?

BACKGROUND: Straight antegrade intramedullary nailing of proximal humerus fractures has shown promising clinical results. However, up to 36% of all humeri seem to be "critical types" in terms of the potential violation of the supraspinatus (SSP) tendon footprint by the nail's insertion zone. The aims of this study were to evaluate if a computed tomography (CT) scan could reliably predict the nail's entry point on the humeral head and if it would be possible to preoperatively estimate the individual risk of iatrogenic violation of the SSP tendon footprint by evaluating the uninjured contralateral humerus. METHODS: Twenty matched pairs of human cadaveric shoulders underwent CT scans, and the entry point for an antegrade nail as well as measurements regarding critical distances between the entry point and the rotator cuff were determined. Next, gross anatomic measurements of the same data were performed and compared. Furthermore, specimens were reviewed for critical types. RESULTS: Overall, 42.5% of all specimens were found to be critical types. The CT measurements exhibited excellent intra-rater and inter-rater reliability (intraclass correlation coefficients >0.90). Similarly, excellent agreement between the CT scan and gross anatomic measurements in contralateral shoulders (intraclass correlation coefficients >0.88) was found. CONCLUSION: Assessing the uninjured contralateral side, CT can reliably predict the entry point in antegrade humeral nailing and preoperatively identify critical types of humeral heads at risk of iatrogenic implantation damage to the SSP tendon footprint. This study may help surgeons in the decision-making processon which surgical technique should be used without putting the patient at risk for iatrogenic, implant-related damage to the rotator cuff.

A Simple Method for Measurement of Femoral Anteversion-Validation and Assessment of Reproducibility.

OBJECTIVES: To propose a simple method for measurement of femoral anteversion (AV) with a conventional fluoroscope, to evaluate the interobserver and intraobserver reliability of this method on the basis of human cadaver femurs, and to validate such method on the basis of computed tomography (CT). METHODS: Fourteen human cadavers with 28 intact femurs were included in the study. Three blinded observers measured femoral AV of the specimen with a fluoroscope. The session was repeated 8 weeks later and CT of the femurs were performed. Mean AV values and the difference between single and mean AV values were calculated. Interobserver/intraobserver reliability of the proposed method was assessed. Correlation between AV values measured with fluoroscope and CT was calculated. RESULTS: Mean AV was 18.1° when measured with fluoroscope and 19.2° when measured with CT. Mean differences between single AV values were 2.2° with fluoroscope and 2.5° with CT. The mean maximum observer variation per specimen was 8.8°. Interobserver reliability was excellent (intraclass correlation coefficient: 0.853) and intraobserver reliability was good (intraclass correlation coefficient: 0.682). A high correlation was found between AV values measured with fluoroscope and CT (rho = 0.739, P < 0.01). CONCLUSION: The presented technique allows reliable and simple measurement of femoral AV with a conventional fluoroscope. The mean interobserver variation is comparable to what has been reported for CT. Maximum interobserver variation was <15° in all specimens. A clinical study will be necessary to prove the value of this technique for intraoperative adjustment of femoral AV according to the intact contralateral side.

The relevance of neutral arm positioning for true ap-view X-ray to provide true projection of the humeral head shaft angle.

INTRODUCTION: Textbooks commonly recommend using the true anterior-posterior (ap)-view with the patient's arm in a sling and therefore in internal rotation (IR) for radiologic diagnostic assessment of the proximal humerus after trauma. However, IR or external rotation (ER) may affect the projection of the head shaft angle (HSA) and therefore bias the diagnostic conclusion significantly. We hypothesized that neutral rotation (NR) of the arm is mandatory for true ap-view to provide true projection of the HSA. MATERIALS AND METHODS: A simplified geometrical model of the proximal humerus was used to examine the influence of different arm positions and angulations of the central ray in relation to the projection of the HSA. RESULTS: Both ER and IR misleadingly suggested an increased valgus angle. Simulating the true ap-view with the central ray in cranio-caudal direction, IR changed the projection of the HSA substantially. CONCLUSION: In conclusion, standard fixation of the patient's arm in a shoulder sling in IR for true ap-view may result in an oblique projection, potentially leading to incorrect surgical implications. To prevent misdiagnosed valgus or varus angulation, NR of the arm should be obeyed when performing true ap-view X-ray. We, therefore, highly recommend to overcome the traditionally arm position, ensuring the true amount of dislocation to assure correct surgical implications and comparable follow-up examinations.

Trabecular bone strength is not an independent predictive factor for dynamic hip screw migration--A prospective multicenter cohort study.

This study assessed whether mechanically measured trabecular bone strength is an independent predictor of dynamic hip screw (DHS) stability, i.e., DHS migration (DHSM) after the fixation of proximal femoral fractures. One-hundred and seven patients older than 50 years with proximal femoral fractures were included. During fracture fixation, a mechanical probe (DensiProbe™ Hip) was inserted at the site where the DHS tip would ultimately be positioned. Peak torque to breakaway the trabecular bone was measured. Fracture reduction, primary implant position and postoperative DHSM were assessed by radiographs taken postoperatively, at 6 and 12 weeks after surgery. Univariate regression analysis revealed no association between peak torque and DHSM (R(2) = 0.025, p = 0.135). DHSM correlated with the primary DHS position, i.e., the distance between the DHS and (i) the central femoral neck axis (CNFAD, R(2) = 0.230; p < 0.0001) and (ii) the apex of the femoral head (R(2) = 0.110; p = 0.001). DHSM did not correlate with areal BMD of the contralateral proximal femur. Multivariable regression modeling revealed the CFNAD as predictive factor for screw migration. The primary implant position measured by the CFNAD, rather than DensiProbe™ Hip measured bone strength, is an independent predictor of DHSM.

Allogenic bone grafting for augmentation in two-part proximal humeral fracture fixation in a high-risk patient population.

INTRODUCTION: The surgical fixation of unstable, varus displaced two-part fractures of the proximal humerus remains challenging. MATERIALS AND METHODS: In a case series of 10 non-compliant, high-risk patients (median age 63 years; range 52-78), a cancellous allograft was used to augment plate fixation of the fractures. RESULTS: After a median follow-up of 28.5 months, all but one fracture were healed, with the bony allografts incorporated without any systemic or local complications. No significant loss of reduction or evidence of avascular necrosis of the humeral head was seen. The median Constant-Murley Score was 72.0 (range 45-86). Median pain on a visual analog scale was 1 (range 0-7). Median values for the range of motion were flexion: 155° (range 90-170), abduction: 168° (range 95-180) and external rotation: 43° (range: 30-50). Compared to the uninjured contralateral side, flexion was impaired by 13 %, abduction by 14 %, and external rotation by 15 %. Median abduction power was 64 % of the uninjured side. The median varus displacement was 51° (range 45-59) preoperatively, 4° (range -5 to 19) intraoperatively, and 13° (range 1-18) at the time of the final follow-up, relating to an improvement of 38° compared to the preoperative status. CONCLUSIONS: The augmentation of proximal humeral fracture fixation using a cancellous allograft might be a viable and reliable alternative to prevent early varus failure and to, moreover, lead to bony union in a non-compliant or high-risk patient population.

Mechanical torque measurement for in vivo quantification of bone strength in the proximal femur.

INTRODUCTION: Bone strength determines fracture risk and fixation strength of osteosynthesis implants. In vivo, bone strength is currently measured indirectly by quantifying bone mineral density (BMD) which is however only one determinant of the bone's biomechanical competence besides the bone's macro- and micro-architecture and tissue related parameters. We have developed a measurement principle (DensiProbe™ Hip) for direct, mechanical quantification of bone strength within the proximal femur upon hip fracture fixation. Previous cadaver tests indicated a close correlation between DensiProbe™ Hip measurements, 3D micro-CT analysis and biomechanical indicators of bone strength. The goal of this study was to correlate DensiProbe™ Hip measurements with areal bone mineral density (BMD). METHODS: Forty-three hip fracture patients were included in this study. Intraoperatively, DensiProbe™ Hip was inserted to the subsequent hip screw tip position within the femoral head. Peak torque to breakaway of local cancellous bone was registered. Thirty-seven patients underwent areal BMD measurements of the contralateral proximal femur. Failure of fixation was assessed radio graphically 6 and 12 weeks postoperatively. RESULTS: Peak torque and femoral neck BMD showed significant correlations (R=0.60, P=0.0001). In regression analysis, areal BMD explained 46% of femoral neck BMD variance in a quadratic relationship. Throughout the 12-week follow-up period, no failure of fixation was observed. CONCLUSIONS: DensiProbe™ Hip may capture variations of bone strength beyond areal BMD which are currently difficult to measure in vivo. A multicenter study will clarify if peak torque predicts fixation failure.

Functional and clinical outcome of total shoulder arthroplasty with oversized glenoid.

BACKGROUND: The Epoca-Reconstruction-(Reco)®-Glenoid has been developed to treat patients with cuff-tear-arthropathy. The glenoid component of this system has a hemispheric shape that canopies the humeral head. This design is believed to provide a stable fulcrum and restore normal deltoid function. The purpose of this study was to analyse strengths and disadvantages of the Epoca-Reco®-Glenoid in cuff-tear-arthropathy patients. Changes in functional outcome using Constant-Murley-Scoring(CMS), CMS sub-scoring parameters and radiological outcome were analysed. For this purpose, a classification for radiologic lucency was proposed. Diverging results, influencing factors and alternative treatment options have been discussed to analyse weaknesses and enhance future development of this arthroplastic model. MATERIALS AND METHODS: 23 patients aged 68 ± 8.4 years with irreparable cuff-tear-arthropathy refractory to physiotherapeutic treatment were treated with Reco-Glenoid Total-Shoulder-Arthroplasty (TSA). Pre-operative standardized evaluations included history, physical examination, radiographs, computer tomography and clinical scorings. The post-operative controls included physical examination with CMS, video documentation and radiological evaluation. RESULTS: After a median follow-up time of 38 ± 18 months, the CMS had been significantly improved (p < 0.001) from (17.4 ± 5.8) to (43.2 ± 19.2) points. Significant improvement in pain, activities of daily life, range of motion (p < 0.001) and power (p = 0.006) was achieved. Significantly, inferior results in functional outcome and higher lucency rates were observed in female patients and in patients treated with small glenoid components. The follow-up rate was 100 %. CONCLUSION: The semi-constraint reconstruction glenoid prosthesis model in cuff-tear-arthropathy patients significantly improves shoulder function, however, it yields controversial results, with satisfactory results in male and poor results in female patients. Revision rate of the female cohort and loosening of the glenoid component in this short-term follow-up is of concern. Further investigations taking BMD, osteopenic conditions and influence of surface area in smaller individuals into consideration are recommended, to determine whether this is the underlying cause of the inferior results in females.

Preoperative assessment of the cancellous bone mineral density of the proximal humerus using CT data.

BACKGROUND: Osteoporotic fractures of the proximal humerus show an increasing incidence. Osteoporosis not only influences the fracture risk after low-energy trauma, but also affects the mechanical stability of internal fixation. Preoperative assessment of the local bone quality may be useful in the surgical treatment of patients sustaining these injuries. The aim of the present study was to present a method for the preoperative assessment of the local cancellous bone mineral density (BMD) of the proximal humerus using CT data. METHODS: In the first part of the study, CT scans of 30 patients with unilateral fractures of the proximal humerus after low-energy trauma were used. The local BMD was assessed on the contralateral uninjured side. All 30 patients additionally underwent dual-emission X-ray absorptiometry (DXA) of the lumbar spine, proximal femur, and forearm of the side of the uninjured proximal humerus within 6 weeks after trauma. Three independent trauma surgeons performed measurements on the uninjured proximal humerus twice with a time interval of 4 weeks in order to assess the inter- and intraobserver reliability of the method. In the second part of the study, the local BMD of 507 patients with either proximal humerus fractures or chronic shoulder instability was assessed by a single trauma surgeon. In both parts, the average HU values in standardized ROIs of the humeral head were automatically calculated after correcting for HU values below the water equivalent. A linear calibration equation was computed for the calculation from HU to BMD using a calibration device (EFP). RESULTS: The intra- and interobserver reliability was high (ICC > 0.95). Correlation coefficients between the local BMD of the proximal humerus and other anatomical sites were between 0.35 (lumbar spine) and 0.64 (forearm). We found a high correlation between the local BMD and age. The BMD in the fracture group was significantly lower than in the instability group. These patients were significantly older and more likely to be female. CONCLUSION: Our method may provide a preoperative tool for the assessment of the local bone quality of the proximal humerus using CT data. Therapeutic adjustments such as augmentation or primary arthroplasty may be considered in patients with very low local BMD.

Predicting failure after surgical fixation of proximal humerus fractures.

BACKGROUND: Several studies reported high failures rates after internal fixation of proximal humerus fractures. Loss of reduction and screw cut-out are the most common reasons for revision surgery. Several risk factors for failure have been described in the literature. The aim of the present study was to assess risk factors for failure after surgical fixation of unstable proximal humerus fractures in a multivariate setup. METHODS: Two different surgical techniques (PHILOS locking plate and Humerusblock) were used. In the PHILOS group, every kind of postoperative relative movement between the implant and the humeral head or shaft was defined as failure. In the Humerusblock group, postoperative movement between the humeral head and the shaft in terms of angulation or translational displacement was defined as failure. The following parameters were assessed: age, gender, cancellous bone mineral density (BMD) of the humeral head, fracture type, medial metaphyseal comminution, medial metaphyseal head extension, initial angulation of the humeral head in the frontal plane, initial anteversion of the humeral head, medial hinge displacement, maximum displacement of the tuberosities with respect to the head, surgical technique, anatomic reconstruction and restoration of the medial cortical support. RESULTS: The following parameters were found to have a significant influence on the failure rate: age, local BMD, anatomic reduction, and restoration of the medial cortical support. The failure rate significantly increased with the number of risk factors. CONCLUSION: Preoperative assessment of the local BMD and the patients' biological age as well as intraoperative anatomic reduction and restoration of the medial cortical support are the essentials for successful surgical fixation of proximal humerus fractures. Multifragmentary fracture patterns in old patients with low local BMD are prone for fixation failure. If the surgeon is not able to achieve anatomic reduction and restoration of the medial cortical support intraoperatively in this situation, adjustments such as augmentation or primary arthroplasty should be considered.

Trabecular bone analysis in CT and X-ray images of the proximal femur for the assessment of local bone quality.

Currently, conventional X-ray and CT images as well as invasive methods performed during the surgical intervention are used to judge the local quality of a fractured proximal femur. However, these approaches are either dependent on the surgeon's experience or cannot assist diagnostic and planning tasks preoperatively. Therefore, in this work a method for the individual analysis of local bone quality in the proximal femur based on model-based analysis of CT- and X-ray images of femur specimen will be proposed. A combined representation of shape and spatial intensity distribution of an object and different statistical approaches for dimensionality reduction are used to create a statistical appearance model in order to assess the local bone quality in CT and X-ray images. The developed algorithms are tested and evaluated on 28 femur specimen. It will be shown that the tools and algorithms presented herein are highly adequate to automatically and objectively predict bone mineral density values as well as a biomechanical parameter of the bone that can be measured intraoperatively.

Prediction of biomechanical parameters of the proximal femur using statistical appearance models and support vector regression.

Fractures of the proximal femur are one of the principal causes of mortality among elderly persons. Traditional methods for the determination of femoral fracture risk use methods for measuring bone mineral density. However, BMD alone is not sufficient to predict bone failure load for an individual patient and additional parameters have to be determined for this purpose. In this work an approach that uses statistical models of appearance to identify relevant regions and parameters for the prediction of biomechanical properties of the proximal femur will be presented. By using Support Vector Regression the proposed model based approach is capable of predicting two different biomechanical parameters accurately and fully automatically in two different testing scenarios.