In Vitro Testing and Clinical Handling of a Novel Implant Positioning Technology for Proximal Humeral Plating.

BACKGROUND AND OBJECTIVES: Fractures of the proximal humerus are common, particularly in elderly populations. Anatomical locking plates target stabilization with a multitude of screws spanning into the humeral head. Sound implant placement and screw length determination are key for a successful clinical outcome but are difficult to obtain from planar X-rays. A novel implant positioning technology for proximal humerus plating (Xin1) outputs screw lengths suggestions and plate position based on hole projections in conventional X-ray images. This study investigated the performance of a prototype Xin1 system in a postmortem (in vitro) experiment as well as in a clinical handling test. MATERIALS AND METHODS: For in vitro testing, twelve shoulders from six anatomical specimens were randomized into two groups to compare the Xin1 technique to the conventional operation in terms of surgical precision, procedure time and X-ray exposure. For the clinical trial, 11 patients undergoing plating of the proximal humerus were included. The aim was to investigate clinical handling of the Xin1 marker clip and to retrospectively evaluate the system performance in a real-life fracture situation. Image pairs before and after insertion of the proximal screws were retrospectively processed to investigate the influence of potential bone fragment shifts on the system output. RESULTS: In the postmortem experiment, the use of the system significantly improved the surgical precision (52% error reduction), procedure time (38% shorter) and radiation exposure (64% less X-rays). Clinical handling demonstrated seamless embedding of the marker clip into existing clinical workflows without adverse events reported. Retrospective X-ray analysis on six eligible patients revealed differences in the calculated screw lengths of ≤2 mm before and after screw insertion for five patients. In one patient, the screw lengths differed up to 8 mm, which might indicate displacement of the head fragment. CONCLUSIONS: Results suggest a strong potential of the Xin1 assistance technology to enhance the surgical procedure and patient outcomes in the rising incidence of osteoporotic humeral fractures. Robust performance in a real-life fracture situation was observed. In-depth validation of the system is, however, needed before placing it into clinical practice.

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.

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.

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.

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.

Validation of a novel biomechanical test bench for the knee joint with six degrees of freedom.

A novel biomechanical test bench has been developed for in-vitro evaluation of the knee joint. The test bench allows the kinematics of the knee joint to be studied in all six degrees of freedom. Flexion-extension knee movements are induced by quadriceps and hamstring muscle forces simulated by five pneumatic cylinders. The kinematics of the knee and the actively applied muscle forces are measured simultaneously. The aim of this study was to validate the sensitivity and reproducibility of this novel test bench. Four fresh frozen human knees were tested three times, each with seven flexion-extension cycles between 5° and 60°. After the native knees had been tested, the posterior cruciate ligament and then the lateral collateral ligament were dissected. The injured knees were tested in identical conditions [3×(7×5°-60°)] in order to evaluate whether the test bench is capable of detecting differences in knee kinematics between a native state and an injured one. With regard to reproducibility, the novel test bench showed almost perfect agreement for each specimen and for all states and flexion angles. In comparison with the native knees, the injured knees showed significant differences in knee kinematics. This validated novel test bench will make it possible to investigate various knee pathologies, as well as current and newly developed treatment options.