Dissociation and Subsequent Stable Malrotation of Femoral Stem Within Sleeve After Sivash-Range of Motion Total Hip Arthroplasty: A Case Report.

CASE: A 78 year-old man fell 6 months after Sivash-range of motion (S-ROM) total hip arthroplasty (THA), after which he developed hip pain and external rotation deformity. Imaging showed stem malrotation in relative retroversion. Revision THA was delayed because of medical issues, occurring 1.5 years after the fall. No corrosion was observed intraoperatively at the stem-sleeve interface. His symptoms resolved after revision THA. CONCLUSION: We present a rare complication of S-ROM THA-dissociation of the femoral stem from the proximal sleeve, with subsequent re-engagement in static malrotation. No corrosion was observed, suggesting that the stem had stably reseated within the sleeve.

Prosthetic Joint Infections of the Hip and Knee Among the Elderly: A Retrospective Study.

BACKGROUND: As the population ages and demand for total joint arthroplasty increases, rates of periprosthetic joint infection are expected to increase in the geriatric population. Studies comparing prevalence of risk factors, etiology, management, and mortality of prosthetic joint infection in older patients are lacking. METHODS: We compared clinical characteristics, management, and mortality of patients <75 vs ≥75 years of age with first prosthetic joint infection of the hip or knee admitted to a tertiary medical center between September 2017 and December 2019. RESULTS: Ninety-eight patients (<75 years of age [n = 63]; ≥75 years of age (n = 35) were studied. Groups were similar in terms of etiology, culture-directed therapy, antibiotic suppression, and length of stay. There was no difference in surgical management, performed in almost 97% of cases in both groups. Arrhythmia and heart failure were more prevalent in those aged ≥75 years. Readmission related to prosthetic joint infection occurred less often in older individuals (P = .005). Deaths within 1 year of diagnosis were rare (n = 4; 4.1%), occurring in older patients and resulting mostly from sepsis. CONCLUSION: In our single-center study, patients with first prosthetic joint infection had similar management, regardless of age. We identified cardiac history as one of the host factors for prosthetic joint infection most seen in patients ≥75 years of age. Although deaths were rare, 1-year mortality was higher in patients aged ≥75. Prospective, multicenter studies are needed to explore risk factors and management strategies of prosthetic joint infection among elderly populations.

Acute Shortening Versus Bridging Plate for Highly Comminuted Olecranon Fractures.

Severely comminuted olecranon fractures, for which elbow stability becomes the main goal of surgery, remain a challenge for surgeons. We conducted a study to determine the percentage loss of articular surface at which a bridge plating (BP) construct becomes too unstable and an acute shortening (AS) construct is required. The olecranon process of 8 fresh-frozen cadaveric upper limbs was serially resected. At each resection, the simulated fracture was fixed first with BP and then with AS. Stability was tested by performing valgus and varus stress tests at various angles under fluoroscopy. As many as 6 serial resections were made on the cadaveric models. Maximum resection was 88%. The ulnohumeral joint remained stable to valgus and varus stress at all resections for both BP and AS. The elbow joint lost a significant amount of flexion with AS above 20% resection. The ulnohumeral joint can tolerate substantial loss of articular surface in the olecranon before becoming unstable. In this study, range of motion was preserved more with the BP construct than with the AS construct. The presented data may be considered when approaching a severely comminuted olecranon fracture in which the articular surface cannot be reconstructed.

A Call to Develop Course-Based Undergraduate Research Experiences (CUREs) for Nonmajors Courses.

Course-based undergraduate research experiences (CUREs) for non-science majors (nonmajors) are potentially distinct from CUREs for developing scientists in their goals, learning objectives, and assessment strategies. While national calls to improve science, technology, engineering, and mathematics education have led to an increase in research revealing the positive effects of CUREs for science majors, less work has specifically examined whether nonmajors are impacted in the same way. To address this gap in our understanding, a working group focused on nonmajors CUREs was convened to discuss the following questions: 1) What are our laboratory-learning goals for nonmajors? 2) What are our research priorities to determine best practices for nonmajors CUREs? 3) How can we collaborate to define and disseminate best practices for nonmajors in CUREs? We defined three broad student outcomes of prime importance to the nonmajors CURE: improvement of scientific literacy skills, proscience attitudes, and evidence-based decision making. We evaluated the state of knowledge of best practices for nonmajors, and identified research priorities for the future. The report that follows is a summary of the conclusions and future directions from our discussion.

Geometry of Proximal Humerus Locking Plates.

OBJECTIVES: Proximal humerus fractures are commonly treated with open reduction and internal fixation with periarticular locking plates. This study compared the geometry of proximal humerus locking plate's screw distribution, amount of bone-screw interface, and the volume the screws occupy within the humeral head, as well as how leaving the screws short of the articular surface affects these measures. METHODS: Locking plates from 7 manufacturers were applied to foam humerus models. The entry and exit hole of each screw trajectory was digitized using a 3-dimensional motion tracking system. A trajectory for each screw was modeled, as well as the volume enclosed by the screw trajectories. The following outcome metrics were calculated: the bone-screw interface, the volume enclosed by the screws, and the effect of leaving the screws short of the articular surface. RESULTS: Biomet had the most bone-screw interface (7259 mm), whereas Zimmer had the least (3982 mm). The original Synthes plate had the largest screw volume, occupying 31.5% of the humeral head, whereas Smith & Nephew and Zimmer had the lowest volumes, occupying 21.2% and 12.6%, respectively. Leaving the screws 15 mm short of the articular surface resulted in the most reduction in volume for the Depuy plate (50%) and the least reduction for the new version of the Synthes plate (29%). CONCLUSIONS: Many different manufactured periarticular locking plates exist to stabilize a proximal humeral fracture. Clinicians need to be familiar with the different plate configurations, screw lengths, and trajectories, which affect potential biomechanical performance and can optimize fracture site maintenance.

A better way to teach knot tying: a randomized controlled trial comparing the kinesthetic and traditional methods.

BACKGROUND: Knot tying is a fundamental and crucial surgical skill. We developed a kinesthetic pedagogical approach that increases precision and economy of motion by explicitly teaching suture-handling maneuvers and studied its effects on novice performance. METHODS: Seventy-four first-year medical students were randomized to learn knot tying via either the traditional or the novel "kinesthetic" method. After 1 week of independent practice, students were videotaped performing 4 tying tasks. Three raters scored deidentified videos using a validated visual analog scale. The groups were compared using analysis of covariance with practice knots as a covariate and visual analog scale score (range, 0 to 100) as the dependent variable. Partial eta-square was calculated to indicate effect size. RESULTS: Overall rater reliability was .92. The kinesthetic group scored significantly higher than the traditional group for individual tasks and overall, controlling for practice (all P < .004). The kinesthetic overall mean was 64.15 (standard deviation = 16.72) vs traditional 46.31 (standard deviation = 16.20; P < .001; effect size = .28). CONCLUSIONS: For novices, emphasizing kinesthetic suture handling substantively improved performance on knot tying. We believe this effect can be extrapolated to more complex surgical skills.

Mechanical behaviour of low-cost dynamic compression plates correlates with manufacturing quality standards.

PURPOSE: This study compares the mechanical properties of low-cost stainless steel dynamic compression plates (DCPs) from developing-world manufacturers, adhering to varying manufacturing quality standards, with those of high-cost DCPs manufactured for use in the developed world. METHODS: Standard-design ten-hole DCPs from six developing-world manufacturers and high-cost DCPs from two manufacturers in the developed world were studied. Nine plates from each manufacturer underwent mechanical testing: six in four-point monotonic bending to assess strength and stiffness and three in four-point bending fatigue. Statistical comparisons of the group means of monotonic bending test data were made, and a qualitative comparison was performed to assess failures in fatigue. RESULTS: Low-cost DCPs from manufacturers with at least one manufacturing quality standard had significantly higher bending strength and fewer failures in fatigue than did those from low-cost manufacturers with no recognised quality standards. High-cost DCPs demonstrated greater bending strength than did those in both low-cost groups. There were no differences in stiffness and fatigue failure between high-cost DCPs and those low-cost DCPs with quality standards. However, high-cost DCPs were significantly less stiff and had fewer fatigue failures than low-cost DCPs manufactured without such standards. CONCLUSION: Significant differences were found in the mechanical properties of ten-hole DCP plates from selected manufacturers in the developing and developed worlds. These differences correlated with reported quality certification in the manufacturing process. Mechanical analysis of low-cost implants may provide information useful in determining which manufacturers produce implants with the best potential for benefit relative to cost.

Propensity for hip dislocation in normal gait loading versus sit-to-stand maneuvers in posterior wall acetabular fractures.

Treatment of posterior wall (PW) fractures of the acetabulum is guided by the size of the broken wall fragment and by hip instability. Biomechanical testing of hip instability typically is done by simulating the single-leg-stance (SLS) phase of gait, but this does not represent daily activities, such as sit-to-stand (STS) motion. We conducted a study to examine and compare hip instability after PW fractures in SLS and STS loading. We hypothesized that wall fragment size and distance from the dome (DFD) of the acetabulum to the simulated fracture would correlate with hip instability and, in the presence of a PW fracture, the hip would be more unstable during STS loading than during SLS loading. Incremental PW osteotomies were made in 6 cadaveric acetabula. After each osteotomy, a 1200-N load was applied to the acetabulum to simulate SLS and STS loading until dislocation occurred. All hip joints in the cadaveric models were more unstable in STS loading than in SLS loading. PW fragments at time of dislocation were larger (P<.001) in SLS loading (85% ± 13%; range, 81%-100%) than in STS loading (40% ± 7%; range, 33%-52%). Mean (SD) DFD at time of dislocation was 15.0 (3.5) mm (range, 14.4-19.6 mm) in STS loading and 5.3 (4.3) mm (range, 0.1-10.0 mm) in SLS loading (P<.04). There was more hip instability in STS loading than in SLS loading. In STS loading, hips dislocated with a PW fracture size of 33% or more and a DFD of 20 mm or less.

Analysis of a knotless flexor tendon repair using a multifilament stainless steel cable-crimp system.

PURPOSE: To compare the biomechanical and technical properties of flexor tendon repairs using a 4-strand cruciate FiberWire (FW) repair and a 2-strand multifilament stainless steel (MFSS) single cross-lock cable-crimp system. METHODS: Eight tests were conducted for each type of repair using cadaver hand flexor digitorum profundus tendons. We measured the required surgical exposure, repair time, and force of flexion (friction) with a custom motor system with an inline load cell and measured ultimate tensile strength (UTS) and 2-mm gap force on a servo-hydraulic testing machine. RESULTS: Repair time averaged less than 7 minutes for the 2-strand MFSS cable crimp repairs and 12 minutes for the FW repairs. The FW repair was performed with 2 cm of exposure and removal of the C-1 and A-3 pulleys. The C-1 and A-3 pulleys were retained in each of the MFSS cable crimp repairs with less than 1 cm of exposure. Following the FW repair, the average increase in friction was 89% compared with an average of 53% for the MFSS repairs. Six of the 8 MFSS specimens achieved the UTS before any gap had occurred, whereas all of the FW repairs had more than 2 mm of gap before the UTS, indicating that the MFSS was a stiffer repair. The average UTS appeared similar for both groups. CONCLUSIONS: We describe a 2-strand multifilament stainless steel single cross-lock cable crimp flexor repair system. In our studies of this cable crimp system, we found that surgical exposure, average repair times, and friction were reduced compared to the traditional 4-strand cruciate FW repair. While demonstrating these benefits, the crimp repair also produced a stiff construct and high UTS and 2-mm gap force. CLINICAL RELEVANCE: A cable crimp flexor tendon repair may offer an attractive alternative to current repair methods. The benefits may be important especially for flexor tendon repair in zone 2 or for the repair of multiple tendons.

Biomechanical evaluation of a cable-crimp system designed for repair of tendons and ligaments in the hand.

The goal of this study was to evaluate the biomechanical properties of an alternative method for connecting sutures using a crimp and to compare this method with a knot connection. Multifilament stainless steel suture (3-0 USP size) was connected by means of knot tying or crimp application and compared with FiberWire (3-0 USP size) connected by knot tying. Ultimate tensile strength (UTS) and stiffness were tested on a servohydraulic testing machine. The total UTS of the crimped constructs was significantly stronger and stiffer than the knotted groups, although the strength per strand was not statistically significant. Crimps offer an alternative method for connecting sutures. They have mechanical advantages over knot tying and allow the connection of multiple suture strands as well as the additional advantage of attaching both sides of the repair independently. This may provide precise pretensioning and potentially reduced surgical exposure.

A biomechanical comparison of ipsilateral and contralateral pedicle screw placement for modified triangular osteosynthesis in unstable pelvic fractures.

OBJECTIVES: Iliosacral fixation of unstable pelvic fractures does not produce enough stability to allow for immediate postoperative weight bearing. Triangular osteosynthesis creates additional resistance to vertical displacement and rotation. A disadvantage is the loss of the L5/S1 motion segment. We propose a modification of the standard triangular osteosynthesis construct in which the contralateral S1 pedicle is used. As the ipsilateral L5 pedicle is unavailable for fixation in a saw-bones composite pelvic model, we compared ipsilateral and contralateral S1 pedicle screw constructs. We hypothesized that ipsilateral and contralateral S1 pedicle screw constructs would demonstrate no difference in displacement or rotation. METHODS: Seven saw bones pelvic models were tested. A 5-mm vertical fracture gap was created through the left sacrum while the pubic symphysis was completely dissociated. Each pelvis was tested sequentially in 4 triangular osteosynthesis configurations: ipsilateral S1 screw with anterior plate, contralateral S1 screw with anterior plate, contralateral S1 screw without anterior plate, and ipsilateral S1 screw without anterior plate. Specimens were cyclically loaded from 100-200 N at 0.25 Hz for 25 cycles and then loaded up to 300 N at 10 mm/min while displacement and rotation at the sacral and pubic fracture sites were measured. RESULTS: There was no difference in any of the displacement measures between ipsilateral and contralateral constructs. When comparing rotation, the contralateral configuration experienced significantly less rotation than the ipsilateral configuration with and without the anterior plate applied. CONCLUSIONS: Within the limitations of the current model, contralateral S1 constructs for modified triangular osteosynthesis were biomechanically equal to ipsilateral constructs in preventing displacement and superior in preventing rotation.

Can a novel rectangular footplate provide higher resistance to subsidence than circular footplates? An ex vivo biomechanical study.

STUDY DESIGN: Ex vivo biomechanical evaluation using cadaveric vertebral bodies. OBJECTIVE: To compare the subsidence characteristics of a novel rectangular footplate design with a conventional circular footplate design. SUMMARY OF BACKGROUND DATA: Cage subsidence is a postoperative complication after reconstruction of corpectomy defects in the thoracolumbar spine and depends on factors, such as bone quality, adjunctive fixation, and the relationship between the footplate on the cage and the vertebral body endplate. METHODS: Twenty-four cadaveric vertebrae (T12-L5) were disarticulated, potted in a commercial resin, loaded with either a circular or a rectangular footplate, and tested in a servo hydraulic testing machine. Twelve vertebral bodies were loaded with a circular footplate, and after subsidence the same vertebral bodies were loaded with a rectangular footplate. The second set of 12 vertebral bodies was loaded with a rectangular footplate only. Force-displacement curves were developed for the 3 groups, and the ultimate load to failure and stiffness values were calculated. RESULTS: The ultimate load to failure with the circular footplate was 1310 N (SD, 482). The ultimate load to failure with a rectangular footplate with a central defect and without a central defect was 1636 N (SD, 513) and 2481 N (SD, 1191), respectively. The stiffness of the constructs with circular footplate was 473 N/mm (SD, 205). The stiffness of the constructs with a rectangular footplate with a central defect and without a central defect was 754 N/mm (SD, 217) and 1054 N/mm (SD, 329), respectively. CONCLUSION: A rectangular footplate design is more resistant to subsidence than a circular footplate design in an ex vivo biomechanical model. The new design had higher load to failure even in the presence of a central defect. These findings suggest that rectangular footplates may provide better subsidence resistance when used to reconstruct defects after thoracolumbar corpectomy.

Effect of mini-fragment fixation on the stabilization of medial malleolus fractures.

BACKGROUND: Oblique fractures of the medial malleolus can arise from the application of axial force at various anatomic positions of the ankle, including supination-external rotation, pronation-external rotation, or pronation abduction. Although a variety of techniques exist to provide fixation of horizontal medial malleolus fractures, the optimal technique and pattern for internal fixation remains unclear. The aim of this study was to evaluate the mechanical properties of four different fixation methods for fractures of the medial malleolus. METHODS: Identical oblique osteotomies were created in synthetic distal tibiae using a jig. The specimens were divided into four fixation groups: contoured 2.0 mm mini-fragment T-plate, figure-of-eight tension band wire, construct two parallel 4.0 mm cancellous screws, and two divergent 4.0 mm cancellous screws. The specimens were tested using offset axial tension at 10 mm/min until 2 mm of joint line displacement. RESULTS: The average stiffness in tension and force at 2 mm of joint line displacement of the plate construct was significantly greater than any of the other constructs (p < 0.05), whereas the average stiffness in tension of the other three groups were not significantly different from each other (p > 0.05). CONCLUSION: Using a contoured 2.0 mm mini-fragment T-plate as the method of fixation resulted in an at least 25% stiffer construct during tension and required at least 24% more force for 2 mm of joint line displacement when compared with more traditional methods of fixation in an osteotomy model of an oblique medial malleolus fracture.

Propensity for hip dislocation in gait loading versus sit-to-stand maneuvers: implications for redefining the dome of the acetabulum needed for stability of the hip during activities of daily living.

INTRODUCTION: Current recommendations relating to the treatment of acetabular fractures are based on studies that evaluate the loading patterns associated with normal gait despite the fact that the forces on the acetabulum are significantly greater during sit-to-stand activities. We hypothesize that this increased force will lead to greater instability when an acetabular fracture occurs, and our goal was to compare cadaveric hip stability during single-leg-stance (SLS) and sit-to-stand (STS) maneuvers using a transverse acetabular fracture model. METHODS: Seven fresh-frozen cadaveric hemipelvic specimens with proximal femurs were dissected of all soft tissues. Transverse acetabular osteotomies were created in 5-mm increments from distal to proximal. The roof arc angle and decrease of articular surface area were measured after each osteotomy, and the specimens were tested in SLS and STS. A 1200-N load was applied and visible dislocation was recorded for each loading orientation. RESULTS: The average roof arc angle needed to dislocate in the SLS position was 46.1° in the anteroposterior, 71.9° in the iliac oblique, and 25.2° in the obturator oblique views compared with 90.9° in anteroposterior, 101.4° in iliac oblique, and 67.3° in obturator oblique views for the STS orientation (P < 0.003 for all radiographic views). The decrease in articular surface area needed to dislocate the hip was significantly less for the STS group (10.9%) than the SLS group (36.4%) (P = 0.003). CONCLUSIONS: There is significantly greater hip instability seen with STS loading of a transverse acetabular model than with simple SLS loading. This would suggest that some fractures previously deemed stable may show significant instability during common activities of daily living, and reassessment of nonoperative treatment may be indicated.

Comparison of a new multifilament stainless steel suture with frequently used sutures for flexor tendon repair.

PURPOSE: To investigate the mechanical properties of some common suture materials currently in use and compare them with a new multifilament stainless steel suture. METHODS: We investigated the mechanical properties of 3-0 and 4-0 Fiberwire, 3-0 Supramid, 3-0 Ethibond, and a new 3-0 and 4-0 multifilament stainless steel suture. All suture material was tested in a knotted configuration and all but the Supramid was tested in an unknotted configuration. We measured the load, elongation at failure, and stiffness during both tests. RESULTS: The 4-0 multifilament stainless steel showed the least elongation, whereas the 3-0 multifilament stainless steel withstood the highest load of any material in both the knotted and unknotted tests. There was no difference in stiffness between the 3-0 and 4-0 multifilament stainless steel when untied; however, the 3-0 multifilament stainless steel was stiffer when tied. Soaking in a saline solution had no significant effect on the ultimate load, elongation at failure, or stiffness of any of the sutures. The 3-0 Fiberwire and 3-0 Ethibond required at least 5 throws to resist untying. CONCLUSIONS: Multifilament stainless steel exhibited promising mechanical advantages over the other sutures tested. More research is needed to determine how this material will affect the clinical outcomes of primary flexor tendon repair. CLINICAL RELEVANCE: With a secure attachment to the tendon, the multifilament stainless steel's lower elongation and better knot-holding ability may result in a higher force to produce a 2-mm gap and a higher ultimate tensile strength in a tendon repair.

Comparison of completely knotless and hybrid double-row fixation systems: a biomechanical study.

PURPOSE: The purpose of this study was to compare the biomechanical performance of a completely knotless double-row repair system (SutureCross Knotless Anatomic Fixation System; KFx Medical, Carlsbad, CA) with 2 commonly used hybrid double-row repair (medial knot-tying, lateral knotless) systems (Bio-Corkscrew/PushLock [Arthrex, Naples, FL] and Spiralok/Versalok [DePuy Mitek, Raynham, MA]). METHODS: Fourteen pairs of fresh-frozen cadaveric shoulders were harvested, the supraspinatus tendons were isolated, and full-thickness supraspinatus tears were created. One of each pair was repaired with the completely knotless system, and the contralateral side was repaired with either of the hybrid systems. The repairs were then subjected to cyclic loading followed by load to failure. Conditioning elongation, peak-to-peak elongation, ultimate load, and mechanism of failure were recorded and compared by use of paired t tests. Seven additional shoulders were tested to determine the effect of refrigeration storage on the completely knotless system by use of the same mechanical testing protocol. RESULTS: For the completely knotless repair group, 11 of 14 paired specimens failed during the cyclic loading period. Only 1 of 14 hybrid repair systems had failures during cyclic loading, and both hybrid repair systems had statistically lower conditioning elongation than the completely knotless repair group. The mean ultimate load of the SutureCross group was 166 ± 87 N, which was significantly lower than that in the Corkscrew/PushLock (310 ± 82 N) and Spiralok/Versalok (337 ± 44 N) groups. There was an effect of refrigeration storage on the peak-to-peak elongation and stiffness of the SutureCross group; however, there was no difference in ultimate tensile load or conditioning elongation. CONCLUSIONS: The completely knotless repair system has lower time-zero biomechanical properties than the other 2 hybrid systems. CLINICAL RELEVANCE: The SutureCross system has lower time-zero biomechanical properties when compared with other hybrid repair systems. Clinical outcome studies are needed to determine the significance.

Tibial plateau fracture repairs augmented with calcium phosphate cement have higher in situ fatigue strength than those with autograft.

OBJECTIVES: This study compared the biomechanical fatigue strength of calcium phosphate augmented repairs versus autogenous bone graft (ABG) repairs in lateral tibia plateau fractures. METHODS: Eight matched pairs of tibias (six male, two female; age, 75 ± 14 years) were harvested from fresh-frozen cadavers. Reproducible split-depression fractures were simulated and repaired by an orthopaedic traumatologist using a lateral tibial plateau plate. One tibia from each donor was randomly assigned to either calcium phosphate (Callos; Acumed, Hillsboro, OR) or ABG as augmentation. The femoral component of a hemitotal knee arthroplasty was attached to the actuator of a servohydraulic press and centered above the repair site. Cyclic, physiological compression loads were applied at 4Hz starting with a maximum load of 15% body weight and increasing by 15% body weight every 70,000 cycles. Loading conditions were determined from calculations of weight distribution, joint contact area, and gait characterization from existing literature. Repair site depression and stiffness were measured at regular intervals. Specimens were then loaded to failure at 1 mm/min. RESULTS: Calcium phosphate augmented repairs subsided less and were more stiff during the fatigue loading than were ABG repairs at the 70,000, 140,000, and 210,000 cycle intervals (P < 0.03) All repairs survived to 210,000 cycles. The average ultimate load of the calcium phosphate repairs was 2241 ± 455 N (N = 6) and 1717 ± 508 N (N = 8) for ABG repairs (P = 0.02). CONCLUSION: Calcium phosphate repairs have significantly higher fatigue strength and ultimate load than ABG repairs and may increase the immediate weightbearing capabilities of the repaired knee.