Functional and oncological outcomes of patients with proximal humerus osteosarcoma managed by limb salvage.

BACKGROUND: Osteosarcoma is the most common primary bone malignancy in skeletally immature patients. The proximal humerus is the third most common site of osteosarcoma. The literature shows a paucity of published data concerning the outcome of proximal humerus osteosarcoma managed by limb salvage. The purpose of this study was to answer the following questions: (1) do patients with proximal humerus osteosarcoma managed by limb salvage and neoadjuvant chemotherapy show good functional and oncological outcomes, and (2) are there any prognostic factors that are associated with better oncological and functional outcomes? MATERIALS AND METHODS: The study was a retrospective case series study assessing the overall outcome of 34 patients with proximal humerus osteosarcoma. Eighteen patients were males (53%) while 16 were females. Biological reconstruction was done in 15 patients (44%), while nonbiological reconstruction was done in 19 patients. Resections were mainly intraarticular (82%). Functional outcome was assessed using the Musculoskeletal Tumor Society (MSTS) score, while oncological outcome was assessed based on local recurrence and development of chest metastasis. Comparisons between quantitative variables were done using the nonparametric Mann-Whitney test. To compare categorical data, the chi-square (χ2) test was performed. The exact test was used instead when the expected frequency was less than 5. Correlations between quantitative variables were examined using the Spearman correlation coefficient. RESULTS: The mean MSTS score was 25.5 (range 23-29). A younger age was statistically correlated with a poorer MSTS score (P = 0.0016). Six patients out of 34 (17.6%) had local recurrence and four of them (67%) were treated by forequarter amputation. 41% of patients developed chest metastasis, and the majority of them were treated by chemotherapy (71%). In comparison with patients with osteosarcoma at other sites who were also managed in our institution, proximal humerus osteosarcoma patients showed higher incidence rates of local recurrence and chest metastasis along with lower 5-year patient and limb survivorships compared to distal femur, proximal tibia and proximal femur osteosarcoma patients. CONCLUSION: Treatment of osteosarcoma of the proximal humerus by limb salvage and chemotherapy yields a good functional outcome. The method of reconstruction does not impact the resultant function. The 5-year survivorship of these patients is 65%. Younger patients have a better oncological outcome and an inferior functional outcome. LEVEL OF EVIDENCE: Level IV therapeutic study.

Severe Hemodynamic Collapse During Humerus Stabilization with Photodynamic Implant: A Report of Two Cases.

CASE: We present 2 cases of severe hemodynamic collapse during prophylactic stabilization of impending pathologic humerus fractures using a photodynamic bone stabilization device. Both events occurred when the monomer was infused under pressure into a balloon catheter. CONCLUSION: We suspect that an increase in intramedullary pressure during balloon expansion may cause adverse systemic effects similar to fat embolism or bone cement implantation syndrome. Appropriate communication with the anesthesia team, invasive hemodynamic monitoring, and prophylactic vent hole creation may help mitigate or manage these adverse systemic effects.

[A multicenter clinical study on the treatment of lateral epicondylitis of humerus by manipulation].

OBJECTIVE: To investigate clinical effect of tendons pulling,poking and kneading for the treatment of external humeral epicondylitis. METHODS: From January 2018 to December 2021,a multicenter randomized controlled study was performed to collect 192 patients with external humeral epicondylitis in Wangjing Hospital,Beijing Dianli Hospital,and Beijing Fengsheng Osteotraumatology Hospital,respectively,and they were divided into treatment group and control group by random number table method. There were 96 patients in treatment group,including 36 males and 60 females,aged from 28 to 60 years old with an average of (41.20±5.50) years old;the course of disease ranged from 1 to 14 days with an average of (5.24±1.35) days;they were treated once every other day for 2 weeks. There were 96 patients in control group ,including 33 males and 63 females,aged from 26 to 60 years old with an average of (43.35±7.75) years old;the course of disease ranged from 1 to 14 days with an average of (5.86±1.48) days;they were treated with topical voltaalin combined with elbow joint fixation for 2 weeks. Visual analogue scale (VAS) and Hospital for Surgery Scoring System (HSS) elbow pronation and supination angles,wrist metacarpal flexion and dorsal extension angles,elbow tenderness between two groups were compared before treatment and at 1,3,5,7,11 and 13 days after treatment;Hospital for Surgery Scoring System 2 (HSS2) was compared before treatment and the final treatment. RESULTS: All patients were followed up for 10 to 14 days with an average of (12±1.6) days. VAS between treatment group and control group before treatment were 6.83±1.36 and 6.79±1.58,respectively,and decreased to 1.49±1.09 and 2.11±1.81 after the final treatment. VAS of treatment group were significantly lower than those of control group at 1,3,5,7,9,11 and 13 days after treatment (P<0.05). HSS between two groups were 61.73±11.00 and 36.47±12.45 before treatment,respectively,and increased to 94.42±5.9 and 91.44±9.11 at the final treatment. HSS of treatment group were significantly higher than those of control group at 1,3,5,7,9,11 and 13 days after treatment (P<0.05). On the 5th day after treatment,the external and internal rotation angles of elbow in treatment group were (66.41±12.69) ° and (66.35±13.54) °,while those in control group were (62.08±16.03) ° and (61.77±16.35) °. On the 7th day after treatment,the external and internal rotation angles of elbow were (69.79±12.64) ° and (70.02±13.55) ° in treatment group,and (65.28±15.86) ° and (65.09±16.67) ° in control group. Elbow joint motion in treatment group was higher than that in control group (P<0.05). On the 5th day after treatment,angles of wrist dorsiflexion and palm flexion were (39.43±15.94) ° and (46.68±11.10) ° in treatment group,and (38.51±18.49) ° and (44.27±13.58) ° in control group. On the 7th day after treatment,angles of wrist dorsiflexion and palm flexion were (42.52±16.50) ° and (49.23±10.96) ° in treatment group,and (41.18±20.09) ° and (46.64±14.63) ° in control group. The motion of wrist joint in treatment group was higher than that in control group (P<0.05). On the 13th day after treatment,HSS2 in treatment group 93.61±6.32 were higher than those in control group 92.06±7.94(P<0.05). There was no significant difference in elbow tenderness between two groups at each time point (P>0.05). CONCLUSION: Voltaren external treatment combined with elbow fixation and tendons pulling,poking and kneading could effectively improve symptoms of external humeral epicondylitis. Compared with voltaren external treatment,tendons pulling,poking and kneading has advantages of longer analgesic time and better elbow function recovery.

Long-standing Nonunited Fracture Lateral Humeral Condyle in Children. Evaluating a Two-stage Surgical Treatment Strategy With Critical Review.

OBJECTIVE: This work aimed to evaluate the results of using a 2-stage surgical treatment strategy without doing anterior transposition of the ulnar nerve (ATUN) for cases with long-standing nonunited fracture lateral humeral condyle (LHC) in children, accompanied by a critical review. METHODS: A consecutive 12 children with a long-standing ">2 years" nonunited LHC with evident radiologic gross anatomic distortion of the elbow were included in this study. A 2-stage surgical treatment strategy was applied, wherein the first stage, open functional reduction, osteosynthesis, and iliac bone graft were done. Then after 6 months, the second stage surgery was carried out in the form of supracondylar humeral corrective osteotomy if the cubitus valgus angle was ≥20 degrees. ATUN was not done for any of the cases even with those having ulnar nerve dysfunction. RESULTS: Union took place in 11 out of the 12 cases after a mean follow-up period of 11 weeks (range: 8 to 14 wk; SD: 1.6). All the 7 cases showed preoperative ulnar nerve dysfunction and reported clinical recovery at the end of their follow-up. CONCLUSIONS: Two-stage surgical treatment strategy without ATUN is a convenient, reproducible, and successful line of treatment for children presented with longstanding nonunited LHC with anatomically distorted elbow. LEVEL OF EVIDENCE: Level IV-case series.

Time-elapsed microstructural imaging of failure of the reverse shoulder implant.

BACKGROUND: Reverse Shoulder Arthroplasties (RSA) have become a primary choice for improving shoulder function and pain. However, the biomechanical failure mechanism of the humeral component is still unclear. The present study reports a novel protocol for microstructural imaging of the entire humerus implant under load before and after fracture. METHODS: A humerus specimen was obtained from a 75-year-old male donor. An expert surgeon implanted the specimen with a commonly used RSA implant (Aequalis reversed II, Stryker Orthopaedics, USA) and surgical procedure. The physiological glenohumeral contact force that maximized the distal implant migration was selected from a public repository ( orthoload.com ). Imaging and concomitant mechanical testing were performed using a large-volume micro-CT scanner (Nikon XT H 225 ST) and a custom-made compressive stage. Both when intact and once implanted, the specimen was tested under a pre-load and by imposing a constant deformation causing a physiological reaction load (650 N, 10 degrees adducted). The deformation of the implanted specimen was then increased up to fracture, which was identified by a sudden drop of the reaction force, and the specimen was then re-scanned. RESULTS: The specimen's stiffness decreased from 874 N/mm to 464 N/mm after implantation, producing movements of the bone-implant interface consistent with the implant's long-term stability reported in the literature. The micro-CT images displayed fracture of the tuberosity, caused by a combined compression and circumferential tension, induced by the distal migration of the implant. CONCLUSION: The developed protocol offers detailed information on implant mechanics under load relative to intact conditions and fracture, providing insights into the failure mechanics of RSA implants. This protocol can be used to inform future implant design and surgical technique improvements.

The importance of interdigitating screw fixation of the trochlea in double plate osteosynthesis of low transcondylar distal humerus fractures: A biomechanical study.

OBJECTIVE: The trochlea is of great importance for the stability of the elbow and its fixation in low transcondylar fractures of the distal humerus is especially challenging. The aim of this study was to determine the optimal trochlea fixation in double plate osteosynthesis of intraarticular distal humerus fractures. METHODS: A low transcondylar, C3-type distal humerus fracture was created in 20 fresh-frozen human cadaveric humeri. The samples were then randomly divided into two groups of 10 specimens each. Double plate osteosynthesis was performed in both groups. In group A, the two most distal screws of the lateral plate were inserted into the trochlea fragment. In group B, these screws did not extend into the trochlea. Displacement under cyclic loading and ultimate failure loads were determined for all specimens. RESULTS: Group A showed significantly less displacement under cyclic loading in each measurement interval (0.92 mm vs. 1.53 mm after 100 cycles, p = 0 0.006; 1.10 mm vs. 1.84 mm after 1000 cycles, p = 0.007; 1.18 mm vs. 1.98 mm after 2000 cycles, p = 0.008). The ultimate failure load was significantly higher in group A than in group B (345.61 ± 120.389 N vs. 238.42 ± 131.61 N, p = 0.037). CONCLUSIONS: Fixation of the trochlea with interdigitating screws in double plate osteosynthesis of low-condylar type C distal humerus fractures results in superior construct stability. LEVEL OF EVIDENCE: not applicable (biomechanical).

Proximal Humerus Reconstruction for Bone Sarcomas: A Critical Analysis.

¼ The proximal humerus is a common location for primary bone tumors, and the goal of surgical care is to obtain a negative margin resection and subsequent reconstruction of the proximal humerus to allow for shoulder function.¼ The current evidence supports the use of reverse total shoulder arthroplasty over hemiarthroplasty when reconstructing the proximal humerus after resection of a bone sarcoma if the axillary nerve can be preserved.¼ There is a lack of high-quality data comparing allograft prosthetic composite (APC) with endoprosthetic reconstruction of the proximal humerus.¼ Reverse APC should be performed using an allograft with donor rotator cuff to allow for soft-tissue repair of the donor and host rotator cuff, leading to improvements in shoulder motion compared with an endoprosthesis.

Results of Allografts and Synthetic Grafts in Humeral Simple Bone Cysts.

PURPOSE OF THE STUDY: Simple bone cysts (SBCs) are the most common benign bone lesions in childhood. There are many different methods in the treatment of SBCs. There is no consensus on which method to use in the treatment. In this study, we compared the results of allogeneic bone graft or synthetic bone graft in addition to fl exible intramedullary nail (FIN) for SBC located in the humerus. MATERIAL AND METHODS: This retrospective study comparing the data of 19 (group 1: 8 curettage, allograft and FIN; group 2: 11 curettage, synthetic graft and FIN) patients with a mean age of 11.4 (6 to 26; seven female, twelve male) who were surgically treated in our hospital for humeral SBC between April 2014 and January 2020. Patient data included age, sex, anatomical side, stage of the cyst, pathological fracture, previous treatments and complications. RESULTS: The mean follow-up period was 33.7 months (12 to 61). The average last follow-up Musculoskeletal Tumor Society functional scores for groups 1 and 2 were 27.8 (20 to 30) and 28.6 (21 to 30) (P > 0.05). Complete or signifi cant partial radiographic healing rates were achieved in group 1 (75%) compared with group 2 (81.9%). The reoperation rates for groups 1 and 2 were 62.5% (5/8; three for nails removed, two for recurrence) and 36.3% (4/11; two for nails removed, two for recurrence). One patient in group 2 had a 15° varus deformity due to recurrence. No other complications were observed. CONCLUSIONS: The combination of curettage-grafonage FIN is a common treatment method in recent years, as it provides early cyst healing and limb mobilization in SBCs located in the upper extremity. For defects after curettage of the bone cysts, allogeneic or synthetic grafts (granule b-tricalcium phospate) which have similar results in terms of healing can be used as an alternative to each other. KEY WORDS: allografts, bone cysts, bone nails, synthetic grafts, humerus.

Primary stability in locking plate fixation for proximal humeral fractures may be increased by using an additional nail osteosynthesis in combination with locking plate osteosynthesis-A biomechanical comparison.

BACKGROUND: Stability is regarded as an important factor for proper healing and avoiding secondary dislocation in osteoporotic fractures of the proximal humerus. Several surgical techniques have been proposed for treatment, including intramedullary nail osteosynthesis and locking plate fixation. This study introduces a novel approach that combines both techniques and compares its primary stability with conventional methods. METHODS: The study involved 25 osteoporotic humeri with two-part fracture models, which were randomly assigned to locking-plate fixation, intramedullary nailing, or a combination of both techniques. The specimens were subjected to sinusoidal loading at 250 N in 20° abduction for 5000 cycles and then to quasi-static loading until failure. Fracture movement, failure mode, and failure load were measured and compared among the groups. FINDINGS: The groups fixated with intramedullary nailing and the groups fixated with intramedullary nailing and locking plate fixation showed significantly lower fracture motion than the group using locking plate fixation only (p < 0.005) and significantly higher load to failure (p = 0.007 and p = 0.0062, respectively). There was no significant difference between the group using intramedullary nailing and the group using locking-plate fixation and intramedullary nailing in fracture movement or load-to-failure (p > 0.005). INTERPRETATION: The results indicate that locking plate fixation provides less primary stability than intramedullary nailing or the combined of both techniques. This combined approach may offer advantages as a treatment for complex proximal humeral fractures in osteoporotic bone, and specific implants should be developed to ensure optimal treatment.

Five-Year Follow-Up of Surgery vs Functional Bracing for Closed Displaced Humeral Shaft Fractures.

This study compares outcomes of surgery and functional bracing for closed humeral shaft fractures after 5 years of follow-up.

Outcomes of proximal humerus fractures in children: a retrospective cohort study.

OBJECTIVE: Paediatric proximal humerus fractures (PHFs) have historically been treated non-operatively. However, the management of severely displaced PHFs in older children has been debated over the years, with contemporary studies advocating for surgery. The purpose of this study was to review the outcomes of a cohort of paediatric patients treated for a PHF to guide management of future paediatric PHFs. METHODS: The records of the Women's and Children's Hospital in South Australia were reviewed to identify paediatric PHFs occurring between 1 January 2010 and 1 June 2020. Participants completed the Quick Disabilities of the Arm, Shoulder and Hand (QuickDASH), the Shoulder Pain and Disability Index, and the Paediatric Outcomes Data Collection Instrument via phone interview. Participants' shoulder range-of-motion was assessed via telehealth using Zoom. Multivariable logistic regression was used to identify patient and clinical variables that were associated with a poorer outcome. RESULTS: Of 307 patients contacted, 125 participated. Forty-six patients met the definition of a poorer clinical outcome, defined as a QuickDASH score of ≥2. Fractures of greater severity were predictive of a poorer outcome, and patients aged ≥12 years old at the time of injury had higher total QuickDASH scores. The findings did not suggest that these subgroups of patients have superior outcomes if treated surgically. CONCLUSION: The majority of paediatric PHFs have an acceptable clinical outcome, irrespective of treatment methodology. Multicentre prospective studies are required to establish the indications for surgery for adolescent patients with severely displaced PHFs.

Bone deformity in sports-related elbow osteoarthritis: influence of osteochondritis dissecans of the capitellum-a cross-sectional study.

INTRODUCTION: Sports activity can cause elbow osteoarthritis, which subsequently induces bone deformity. Osteochondritis dissecans (OCD) of the capitellum develops defects of articular surfaces and can exacerbate bone deformity. This study aimed to investigate whether OCD exacerbates deformities in sports-related elbow osteoarthritis. MATERIALS AND METHODS: Twenty-one patients who underwent bilateral computed tomography preoperatively followed by surgery for sports-related elbow osteoarthritis were included. Patients were divided into two groups according to the presence or absence of an OCD history: OCD + (n = 6) and OCD- (n = 15). Bilateral three-dimensional bone models of the humerus, ulna, and radius were created using computed tomography data, and bone deformities were extracted by subtracting healthy mirror models from the affected models using a Boolean operation. Bone deformities were divided into 22 regions in the 3 bones. The volume of the deformity was estimated by correlating the anteroposterior and lateral diameters of the OCD and by comparing the two groups. RESULTS: The anteroposterior diameter of the OCD correlated with the articular surface of the medial trochlear notch, whereas the lateral diameter correlated with the whole ulna, medial gutter of the ulna, whole radius, and lateral side of the radial head. The deformities were 2.2 times larger in the whole humerus, 1.9 times larger in the whole ulna, and 3.0 times larger in the whole radius in the OCD + group than in the OCD- group. The deformities were significantly larger in the OCD + group than in the OCD- group in the radial fossa, posterior capitellum, medial gutter, and lateral gutter in the humerus, medial gutter in the ulna, and lateral, anterior, and posterior sides of the radial head. CONCLUSION: Larger OCD exacerbated deformity in elbow OA, and the presence of OCD exacerbated deformities in sports-related elbow OA. These results demonstrate the highlight of preventing OCD progression.

Complete resorption of the humerus in metastatic thyroid carcinoma: a case report.

BACKGROUND: Thyroid carcinoma is the most common endocrinological malignancy, but its spread to bone is rare. Particularly, bone metastases leading to complete resorption of the humerus are extremely uncommon. We aimed to explore factors affecting treatment decision in humeral metastasis by presenting a case and analyze the possible treatments via conducting a literature review. CASE PRESENTATION: We described a case of a 68-year-old woman experiencing chronic pain in her right upper arm for six years. Clinical, radiological, and pathological evaluations confirmed humeral metastasis from thyroid carcinoma. Surgical treatments like tumor removal or limb amputation were suggested for prolonging life and pain relief, but the patient refused them and pursued conservative managements such as herbal medicine, radioactive iodine (131I) therapy, and Levothyroxine Sodium(L-T4). The humeral destruction aggravated gradually, ultimately leading to complete resorption of her right humerus. The patient could not move her right shoulder, but her forearm motion was almost normal; thus, she could complete most of her daily living activities independently. Surgical treatments such as limb amputation were advised but she still refused them for preservation of the residual limb function and preferred conservative managements. CONCLUSION: A personalized multidisciplinary approach is important for patients with bone metastasis. The balance between limb amputation for life-prolonging and pain relief and limb salvage for preservation of residual function and social and psychological well-being should be considered. Our literature review revealed that some novel surgical treatments and techniques are available for bone metastases. This case adds to our current understanding of bone metastases and will contribute to future research and treatments.

[Rare Compression Syndrome of the Median Nerve due to a Supracondylar Humeral Process and a Ligament of Struthers]. / Seltenes Kompressionssyndrom des N. medianus durch den Processus supracondylaris und das Struthers-Ligament.

INTRODUCTION: A supracondylar process is a bony spur on the distal anteromedial surface of the humerus, and it is considered an anatomical variant with a prevalence of 0.4-2.7% according to anatomical studies. In almost all cases, it is associated with a fibrous, sometimes ossified ligament, which extends from the supracondylar process to the medial epicondyle. This ligament is known in the literature as the ligament of Struthers, named after the Scottish anatomist who first described it in detail in 1854. In rare cases, the supracondylar process can be a clinically relevant finding as a cause of nerve compression syndrome. The median and ulnar nerve can be trapped by the ring-shaped structure formed by the ligament of Struthers and the supracondylar process. CASE REPORT: A 59-year-old patient with symptoms of a cubital tunnel syndrome and additional ipsilateral sensory deficits in his thumb was referred to our clinic. Electroneurography showed no signs of an additional carpal tunnel syndrome. Preoperative x-ray and CT scans of the upper arm revealed a supracondylar process, which led us to suspect an associated entrapment of the median nerve. An MRI scan of the upper arm showed a ligament of Struthers and signs of a related median nerve compression as we initially assumed. We performed a surgical decompression of the median nerve in the distal upper arm and of the ulnar nerve in the cubital tunnel. Intraoperatively, there was evidence of compression of the median nerve due to the supracondylar process and the ligament of Struthers. The latter was cleaved and then resected along with the supracondylar process. Three months after surgery, the patient had no motor or sensory deficits. SUMMARY: The ring-shaped structure formed by the supracondylar process and ligament of Struthers represents a rare cause of compression syndrome of the median and ulnar nerve. Its incidence remains unknown so far. This anatomical variant should be considered a differential diagnosis in case of possibly related nerve entrapment symptoms after ruling out other, more frequent nerve compression causes. Moreover, the supracondylar process should be completely resected including the periosteum during surgery to minimise the risk of recurrence.

Kirschner Wire Prying and Leverage Technique: a new closed reduction method in treatment of pediatric "Irreducible Supracondylar Humerus Fractures".

BACKGROUND: This study employs an innovative closed reduction approach to treat pediatric "Irreducible Supracondylar Humerus Fractures" with the goal of demonstrating its practical application compared to conventional methods. METHODS: This study sampled 146 surgically treated cases of "Irreducible Supracondylar Humerus Fractures" in our department. After applying inclusion and exclusion criteria, 120 children were selected and divided into two groups based on treatment methods. Group 1 underwent Closed Reduction and Percutaneous Pinning (CRPP), while Group 2 received treatment using the Kirschner Wire Prying and Leverage Technique alongside CRPP. The relevant data to the study were collected and assessed during the follow-up period. RESULTS: Results indicate that Group 2 demonstrated significantly shorter operative times and fewer instances of intraoperative fluoroscopy compared to Group 1. Furthermore, the percentage of cases requiring open reduction was notably higher in Group 1 than in Group 2. The analysis also identified age, BMI, time from injury to surgery, and the initial deviation of the distal fragment as independent risk factors associated with the failure of closed reduction. The integration of CRPP with the Kirschner Wire Prying and Leverage Technique emerges as a safe and effective strategy for managing "Irreducible Supracondylar Humerus Fractures." This innovative approach not only reduces operative time and intraoperative fluoroscopy needs but also diminishes the reliance on open reduction without compromising safety.

Poor clinical outcomes and high rates of dislocation after modular reverse shoulder arthroplasty for proximal humeral oncologic resection.

PURPOSE: The shoulder is the most common site for upper extremity tumors. The aim of the study was to analyze the outcomes and the complications of modular reverse shoulder arthroplasty (RSA) after proximal humerus resection. METHODS: We retrospectively included 15 consecutive patients who underwent a modular MUTARS™ RSA reconstruction after proximal humerus tumour resection between 2017 and 2020. The mean age was 52 years. Their clinical outcomes were assessed using the Constant-Murley score and the MSTS shoulder. Radiological outcomes were assessed based on the presence of loosening, osteolysis, and scapular notching. Complications such as dislocation, oncological recurrence, and infection were assessed. Mean follow-up time was 32.9 months (24 to 45). RESULTS: The mean adjusted Constant score was 50.7% (min 22, max 81), and the mean MSTS score was 15.6 (min 4, max 26). We had no loosening, osteolysis, or scapular notching on the radiographs at last follow-up. We had a high complication rate of 53%: one infection, one oncological recurrence, and six dislocations (40%), of which five were re-operated. CONCLUSION: In our experience, the MUTARS™ Implantcast™ modular RSA has poor functional results and a high rate of dislocation in the case of large proximal humerus resections below the distal insertion of the deltoid.

Developing and Validating a Model of Humeral Stem Primary Stability, Intended for In Silico Clinical Trials.

In silico clinical trials (ISCT) can contribute to demonstrating a device's performance via credible computational models applied on virtual cohorts. Our purpose was to establish the credibility of a model for assessing the risk of humeral stem loosening in total shoulder arthroplasty, based on a twofold validation scheme involving both benchtop and clinical validation activities, for ISCT applications. A finite element model computing bone-implant micromotion (benchtop model) was quantitatively compared to a bone foam micromotion test (benchtop comparator) to ensure that the physics of the system was captured correctly. The model was expanded to a population-based approach (clinical model) and qualitatively evaluated based on its ability to replicate findings from a published clinical study (clinical comparator), namely that grit-blasted stems are at a significantly higher risk of loosening than porous-coated stems, to ensure that clinical performance of the stem can be predicted appropriately. Model form sensitivities pertaining to surgical variation and implant design were evaluated. The model replicated benchtop micromotion measurements (52.1 ± 4.3 µm), without a significant impact of the press-fit ("Press-fit": 54.0 ± 8.5 µm, "No press-fit": 56.0 ± 12.0 µm). Applied to a virtual population, the grit-blasted stems (227 ± 78µm) experienced significantly larger micromotions than porous-coated stems (162 ± 69µm), in accordance with the findings of the clinical comparator. This work provides a concrete example for evaluating the credibility of an ISCT study. By validating the modeling approach against both benchtop and clinical data, model credibility is established for an ISCT application aiming to enrich clinical data in a regulatory submission.

3D printing assisted MIPO for treatment of complex middle-proximal humeral shaft fractures.

BACKGROUND: This study was designed to explore the clinical efficacy of 3-dimensional (3D) printing assisted minimally invasive percutaneous plate osteosynthesis (MIPO) technique by comparing the clinical outcomes with traditional open reduction and internal plating fixation (ORIF) for treating complex middle-proximal humerus fractures (AO 12C fracture type). MATERIALS AND METHODS: The data of 42 participants who received a complicated middle-proximal humerus fracture from the beginning of 2018 to the end of 2022 were retrospectively analyzed. All patients were assigned to two groups: MIPO with detailed preoperative planning assisted by 3D printing technique (MIPO group), and traditional ORIF (ORIF group). RESULTS: This study included 21 patients in the ORIF group and 21 patients in the MIPO group. All patients were followed-up for at least one year (mean: 16.12 ± 4.13 months), and no difference was observed in the range of shoulder joint motion (ROM), Quick Disabilities of the Arm, Shoulder and Hand (QuickDASH) scores and Constant scores between the two groups. However, the occurrence of complications (surgical incision site infection, implant loosening, bone nonunion and radial nerve palsy) in ORIF group was remarkably higher compared to the MIPO group. All the cases achieved bone union within the MIPO group. Significant differences were found in surgical time, intraoperative blood loss and fracture healing time between the two groups. CONCLUSION: Preoperative 3D printing assisted MIPO technique exhibits obvious advantages in high operational efficiency and low occurrence of complications, which is worthy of clinical application for treating complex middle-proximal humeral shaft fractures.