New dynamic suture material for tendon transfer surgeries in the upper extremity - a biomechanical comparative analysis.

BACKGROUND: Early mobilization after tendon surgery is crucial to avoid commonly observed postoperative soft tissue adhesions. Recently, a new suture was introduced (DYNACORD; DC) with a salt-infused silicone core designed to minimize laxity and preserve consistent tissue approximation in order to avoid gap formation and allow early mobilization. AIMS: To compare the biomechanical competence of DC against a conventional high strength suture (FiberWire; FW) in a human cadaveric tendon transfer model with an early rehabilitation protocol. METHODS: Sixteen tendon transfers (flexor digitorum superficialis (FDS) IV to flexor pollicis longus (FPL)) were performed in 8 pairs human cadaveric forearms using either DC or FW. Markings were set 0.8 cm proximally and 0.7 cm distally to the level of the interweaving zone of the transfer. All specimens underwent repetitive thumb flexion against resistance in 9 intermittent series of 300 cycles each, simulating an aggressive postoperative rehabilitation protocol. After each series, the distance of the proximal marker to the interweaving zone (proximal), the length of the interweaving zone (intermediate) and the distance of the distal marker to the interweaving zone (distal) were measured. RESULTS: Pooled data over all nine series, normalized to the immediate postoperative status, demonstrated no significant differences between FW and DC (p ≥ 0.355) for the proximal and distal markers. However, at the intermediate zone, DC was associated with significant length shortening (p < 0.001) compared to FW without significant length changes (p = 0.351). Load to catastrophic failure demonstrated significant higher forces in FW (p = 0.011). Nevertheless, due to failure mainly proximal or distal of the transfer zone, these loads are not informative. CONCLUSION: From a biomechanical perspective, DC preserved tissue approximation and might be considered as a valid alternative to conventional high-strength sutures in tendon transfer surgery. DC might allow for a shorter interweaving zone and a more aggressive early postoperative rehabilitation program, possibly avoiding commonly observed postoperative soft tissue adhesions and stiffness.

Mid-term Clinical Outcome of Microvascular Gracilis Muscle Flaps for Defects of the Hand.

PURPOSE: Gracilis muscle flaps are useful to cover defects of the hand. However, there are currently no studies describing outcome measurements after covering soft tissue defects using free flaps in the hand. AIM: To analyze mid-term results of gracilis muscle flap coverage for defects on the hand, with regard to functional and esthetic integrity. METHODS: 16 patients aged 44.3 (range 20-70) years were re-examined after a mean follow-up of 23.6 (range 2-77) months. Mean defect size was 124 (range 52-300) cm2 located palmar (n = 9), dorsal (n = 6), or radial (n = 1). All flaps were performed as microvascular muscle flaps, covered by split thickness skin graft. RESULTS: Flaps survived in 15 patients. 6 patients required reoperations. Reasons for revisions were venous anastomosis failure with total flap loss (n = 1) requiring a second gracilis muscle flap; necrosis at the tip of the flap (n = 1) with renewed split thickness skin cover. A surplus of the flap (n = 2) required flap thinning and scar corrections were performed in 2 patients. Mean grip strength was 25% (range 33.3-96.4%) compared to the contralateral side and mean patient-reported satisfaction 1.4 (range 1-3) (1 = excellent; 4 = poor). CONCLUSIONS: Gracilis muscle flaps showed a survival rate of 94%. Patients showed good clinical outcomes with acceptable wrist movements and grip strength as well as high reported satisfaction rates. Compared to fasciocutaneous free flaps, pliability and thinness especially on the palmar aspect of the hand are advantageous. Hence, covering large defects of the hand with a gracilis muscle flap can be a very satisfactory procedure. LEVEL OF EVIDENCE: IV observational.

Digitally enhanced hands-on surgical training (DEHST) enhances the performance during freehand nail distal interlocking.

PURPOSE: Freehand distal interlocking of intramedullary nails remains a challenging task. Recently, a new training device for digitally enhanced hands-on surgical training (DEHST) was introduced, potentially improving surgical skills needed for distal interlocking. AIM: To evaluate whether training with DEHST enhances the performance of novices (first-year residents without surgical experience in freehand distal nail interlocking). METHODS: Twenty novices were randomly assigned to two groups and performed distal interlocking of a tibia nail in mock operation under operation-room-like conditions. Participants in Group 1 were trained with DEHST (five distal interlocking attempts, 1 h of training), while those in Group 2 did not receive training. Time, number of X-rays shots, hole roundness in the X-rays projection and hit rates were compared between the groups. RESULTS: Time to complete the task [414.7 s (range 290-615)] and X-rays exposure [17.8 µGcm2 (range 9.8-26.4)] were significantly lower in Group 1 compared to Group 2 [623.4 s (range 339-1215), p = 0.041 and 32.6 µGcm2 (range 16.1-55.3), p = 0.003]. Hole projections were significantly rounder in Group 1 [95.0% (range 91.1-98.0) vs. 80.8% (range 70.1-88.9), p < 0.001]. In Group 1, 90% of the participants achieved successful completion of the task in contrast to a 60% success rate in Group 2. This difference was not statistically significant (p = 0.121). CONCLUSIONS: In a mock-operational setting, training with DEHST significantly enhanced the performance of novices without surgical experience in distal interlocking of intramedullary nails and hence carries potential to improve safety and efficacy of this important and demanding surgical task to steepen the learning curve without endangering patients. LEVEL OF EVIDENCE: II.

New generation of superior single plating vs. low-profile dual minifragment plating in diaphyseal clavicle fractures: a biomechanical comparative study.

BACKGROUND: Recently, a new generation of superior clavicle plates was developed featuring the variable-angle locking technology for enhanced screw positioning and a less prominent and optimized plate-to-bone fit design. On the other hand, minifragment plates in dual plating mode have demonstrated promising clinical results. The aim of the current study was to compare the biomechanical competence of single superior plating using the new-generation plate vs. dual plating using low-profile minifragment plates. METHODS: Sixteen paired human cadaveric clavicles were pairwise assigned to 2 groups for instrumentation with either a superior 2.7-mm variable-angle locking compression plate (group 1), or with one 2.5-mm anterior combined with one 2.0-mm superior matrix mandible plate (group 2). An unstable clavicle shaft fracture (AO/OTA 15.2C) was simulated by means of a 5-mm osteotomy gap. Specimens were cyclically tested to failure under craniocaudal cantilever bending, superimposed with bidirectional torsion around the shaft axis, and monitored via motion tracking. RESULTS: Initial construct stiffness was significantly higher in group 2 (9.28 ± 4.40 N/mm) compared to group 1 (3.68 ± 1.08 N/mm), P = .003. The amplitudes of interfragmentary motions in terms of axial and shear displacement, fracture gap opening and torsion, over the course of 12,500 cycles were significantly higher in group 1 compared to group 2, P ≤ .038. Cycles to 2 mm shear displacement were significantly lower in group 1 (22,792 ± 4346) compared to group 2 (27,437 ± 1877), P = .047. CONCLUSION: From a biomechanical perspective, low-profile 2.5/2.0-mm dual plates could be considered as a useful alternative for diaphyseal clavicle fracture fixation, especially in less common unstable fracture configurations.

Is augmented femoral lateral plating with helically shaped medial plates biomechanically advantageous over straight medial plates?

Dual plating of comminuted distal femoral fractures allows for early patient mobilization. An additional helically shaped medial plate avoids the medial vital structures of the thigh. The aim of this study is to investigate the biomechanical competence of an augmented lateral locking compression plate distal femur (LCP-DF) using an additional straight versus a helically shaped medial LCP of the same length. Ten pairs of human cadaveric femora were instrumented with a lateral anatomical 15-hole LCP-DF. Following, they were pairwise instrumented with either an additional medial straight 14-hole LCP (group 1) or a 90°-helical shape LCP (group 2). All specimens were biomechanically tested under quasi-static and progressively increasing combined cyclic axial and torsional loading until failure. Initial interfragmentary axial displacement and flexion under static compression were significantly smaller in group 1 (0.11 ± 0.12 mm and 0.21 ± 0.10°) versus group 2 (0.31 ± 0.14 mm and 0.68 ± 0.16°), p ≤ 0.007. Initial varus deformation under static compression remained not significantly different between group 1 (0.57 ± 0.23°) and group 2 (0.75 ± 0.34°), p = 0.085. Flexion movements during dynamic loading were significantly bigger in group 2 (2.51 ± 0.54°) versus group 1 (1.63 ± 1.28°), p = 0.015; however, no significant differences were observed in terms of varus, internal rotation, and axial and shear displacements between the groups, p ≥ 0.204. Cycles to failure and load at failure were higher in group 2 (25,172 ± 6376 and 3017 ± 638 N) compared to group 1 (22,277 ± 4576 and 2728 ± 458 N) with no significant differences between them, p = 0.195. From a biomechanical perspective, helical double plating may be considered a useful alternative to straight double plating, demonstrating ameliorated damping capacities during flexion deformation and safer application as the medial neurovascular structures of the thigh are avoided.

Knot holding capacity of two different high-strength sutures-a biomechanical analysis.

PURPOSE: The number of seven required throws per knot was previously reported as providing sufficient security against slippage. A novel high-strength suture featuring dynamic tightening may allow for throw number reduction without compromising stability. The aims of this study were to (1) investigate the influence of the throw number and the effect of different ambient conditions on the knot security of two different high-strength sutures, and (2) compare their biomechanical competence. METHODS: Two sutures (FiberWire (FW) and DynaCord (DC)) were considered for preparing alternating surgical knots. The specimens were stratified for exposure to different media during biomechanical testing-namely air (dry), saline solution (wet), and fat (fatty-wet). A monotonic tensile ramp loading to failure was applied in each test run. For each suture and ambient condition, seven specimens with three to seven throws each were tested (n = 7), evaluating their slippage and ultimate force to failure. The minimum number of throws preventing suture unraveling was determined for each suture type and condition. RESULTS: For each suture type and condition, failure occurred via rupture in all specimens for the following minimum number of throws: FW-dry-7, wet-7, fatty-wet-7; DC-dry-6, wet-4, fatty-wet-5. When applying seven throws, FW demonstrated significantly larger slippage (6.5 ± 2.2 mm) versus DC (3.5 ± 0.4 mm) in wet (p = 0.004) but not in dry and fatty-wet conditions (p ≥ 0.313). CONCLUSIONS: The lower number of throws providing knot security of DC versus FW in the more realistic wet and fatty-wet conditions indicates that the novel DC suture may allow to decrease the foreign body volume and save surgical time without compromising the biomechanical competence.

The Effect of Cerclage Banding Distally to a Clamshell Fracture Pattern in Total Hip Arthroplasty-A Biomechanical Study.

OBJECTIVES: As currently there is no existing biomechanical work on the topic of interest, the aim of the current study was to investigate the effect of cerclage banding distally to an intraoperatively occurring proximal periprosthetic femoral clamshell fracture versus a non-fractured femur after total hip arthroplasty. METHODS: A diaphyseal anchoring stem was implanted in twenty paired human cadaveric femora, assigned to a treatment and a control group. In the treatment group, each specimen was fitted with a cerclage band placed 3 mm distally to a clamshell fracture, created with an extent of 40% of the anchoring length of the stem. The resulting fragment was not treated further. The contralateral specimens were left with the stems without further fracture creation or treatment. All constructs were tested under progressively increasing cyclic axial loading until failure. Relative bone-implant movements were monitored by motion tracking. RESULTS: Number of cycles and the corresponding load at stem loosening, defined as 1 mm displacement of the stem along the shaft axis, were 31,417 ± 8870 and 3641.7 ± 887 N in the control group, and 26,944 ± 11,706 and 3194.4 ± 1170.6 N in the treatment group, respectively, with no significant differences between them, p = 0.106. CONCLUSION: From a biomechanical perspective, cerclage banding distally to an intraoperative clamshell fracture with an extent of 40% of the anchoring length of the stem demonstrated comparable resistance against hip stem loosening versus a non-fractured femur. It may therefore represent a valid treatment option to restore the full axial stability of a diaphyseal anchoring stem. In addition, it may be considered to keep the medial wall fragment unfixed, thus saving operative time and minimizing associated risks.

Helical Plating Compared with Straight Plating and Nailing for Treatment of Proximal Third Humeral Shaft Fractures-A Biomechanical Study.

Background and Objectives: The surgical treatment of proximal humeral shaft fractures usually considers application of either long straight plates or intramedullary nails. By being able to spare the rotator cuff and avoid the radial nerve distally, the implementation of helical plates might overcome the downsides of common fixation methods. The aims of the current study were (1) to explore the biomechanical competence of different plate designs and (2) to compare their performance versus the alternative treatment option of using intramedullary nails. Materials and Methods: Twenty-four artificial humeri were assigned to the following four groups for simulation of an unstable proximal humeral shaft fracture and instrumentation: Group 1 (Straight-PHILOS), Group 2 (MULTILOC-Nail), Group 3 (45°-Helical-PHILOS), and Group 4 (90°-Helical-PHILOS). All specimens underwent non-destructive, quasi-static biomechanical testing under loading in axial compression, torsion in internal/external rotation, and pure bending in four directions, accompanied by motion tracking. Results: Axial stiffness/displacement in Group 2 was significantly higher/smaller than in all other groups (p ≤ 0.010). Torsional displacement in Group 2 was significantly bigger than in all other groups (p ≤ 0.017). Significantly smaller coronal plane displacement was identified in Group 2 versus all other groups (p < 0.001) and in Group 4 versus Group 1 (p = 0.022). Significantly bigger sagittal plane displacement was detected in Group 4 versus all other groups (p ≤ 0.024) and in Group 1 versus Group 2 (p < 0.001). Conclusions: Intramedullary nails demonstrated higher axial stiffness and smaller axial interfragmentary movements compared with all investigated plate designs. However, they were associated with bigger torsional movements at the fracture site. Although 90°-helical plates revealed bigger interfragmentary movements in the sagittal plane, they demonstrated improved resistance against displacements in the coronal plane when compared with straight lateral plates. In addition, 45°-helical plates manifested similar biomechanical competence to straight plates and may be considered a valid alternative to the latter from a biomechanical standpoint.

Relative lateral wall thickness is an improved predictor for postoperative lateral wall fracture after trochanteric femoral fracture osteosynthesis.

Lateral wall thickness is a known predictor for postoperative stability of trochanteric femoral fractures and occurrence of secondary lateral wall fractures. Currently, the AO/OTA classification relies on the absolute lateral wall thickness (aLWT) to distinguish between stable A1.3 and unstable A2.1 fractures that does not take interpersonal patient differences into account. Thus, a more individualized and accurate measure would be favorable. Therefore, we proposed and validated a new patient-specific measure-the relative lateral wall thickness (rLWT)-to consider individualized measures and hypothesized its higher sensitivity and specificity compared with aLWT. First, in 146 pelvic radiographs of patients without a trochanteric femoral fracture, the symmetry of both caput-collum-diaphyseal angle (CCD) and total trochanteric thickness (TTT) was assessed to determine whether the contralateral side can be used for rLWT determination. Then, data of 202 patients were re-evaluated to compare rLWT versus previously published aLWT. Bilateral symmetry was found for both CCD and TTT (p ≥ 0.827), implying that bone morphology and geometry of the contralateral intact side could be used to calculate rLWT. Validation revealed increased accuracy of the rLWT compared with the gold standard aLWT, with increased specificity by 3.5% (Number Needed to Treat = 64 patients) and sensitivity by 1% (Number Needed to Treat = 75 patients). The novel rLWT is a more accurate and individualized predictor of secondary lateral wall fractures compared with the standard aLWT. This study established the threshold of 50.5% rLWT as a reference value for predicting fracture stability in trochanteric femoral fractures.

Medial helical versus straight lateral plating of distal femoral fractures-a biomechanical comparative study.

BACKGROUND: Distal femoral fractures are commonly treated with lateral straight plates. However, the lateral approach may not always be desirable, and 180°-helical plates may be an alternative. AIM: To investigate the biomechanical competence of 180°-helical plating versus standard straight lateral plating of unstable fractures at the distal femur. METHODS: Twelve left artificial femora were instrumented with a 15-hole Locking Compression Plate-Distal Femur, using either 180°-helical plates (group 1) or conventional straight lateral plates (group 2). An unstable distal femoral fracture AO/OTA 33-A3.3 was simulated. All specimens were biomechanically tested under quasi-static and progressively increasing combined cyclic axial and torsional loading in internal rotation until failure. FINDINGS: Initial axial stiffness (N/mm) was significantly higher in group 1 (185.6 ± 50.1) compared to group 2 (56.0 ± 14.4), p < 0.001. Group 1 demonstrated significantly higher initial interfragmentary flexion (°) and significantly lower initial varus/valgus deformation (°) under 500 N static axial compression versus group 2 (2.76 ± 1.02 versus 0.87 ± 0.77 and 4.08 ± 1.49 versus 6.60 ± 0.47), p ≤ 0.005. Shear displacement (mm) under 6 Nm static torsion was significantly higher in group 1 versus group 2 in both internal (1.23 ± 0.28 versus 0.40 ± 0.42) and external (1.21 ± 0.40 versus 0.57 ± 0.33) rotation, p ≤ 0.013. Cycles to failure and failure load (N) (clinical/catastrophic) were significantly higher in group 1 (12,484 ± 2116/13,752 ± 1518 and 1748.4 ± 211.6/1875.2 ± 151.8) compared to group 2 (7853 ± 1262/9727 ± 836 and 1285.3 ± 126.2/1472.7 ± 83.6), p ≤ 0.001. INTERPRETATION: Although 180°-helical plating using a pre-contoured standard straight lateral plate was associated with higher shear and flexion movements, it demonstrated improved initial axial stability and resistance against varus/valgus deformation compared to straight lateral plating. Moreover, the helical plates were associated with significantly higher endurance to failure. From a biomechanical perspective, 180°-helical plating may be considered as a valuable alternative to standard straight lateral plating of unstable distal femoral fractures.

Is a Washer a Mandatory Component in Young Trauma Patients with S1-S2 Iliosacral Screw Fixation of Posterior Pelvis Ring Injuries? A Biomechanical Study.

Background and purpose: Cannulated screws are standard implants for percutaneous fixa-tion of posterior pelvis ring injuries. The choice of whether to use these screws in combination with a washer is still undecided. The aim of this study was to evaluate the biomechanical competence of S1-S2 sacroiliac (SI) screw fixation with and without using a washer across three different screw designs. Material and Methods: Twenty-four composite pelvises were used and an SI joint injury type APC III according to the Young and Burgess classification was simulated. Fixation of the posterior pelvis ring was performed using either partially threaded short screws, fully threaded short screws, or fully threaded long transsacral screws. Biomechanical testing was performed under progressively increasing cyclic loading until failure, with monitoring of the intersegmental and bone-implant movements via motion tracking. Results: The number of cycles to failure and the corresponding load at failure (N) were significantly higher for the fully threaded short screws with a washer (3972 ± 600/398.6 ± 30.0) versus its counterpart without a washer (2993 ± 527/349.7 ± 26.4), p = 0.026. In contrast, these two parameters did not reveal any significant differences when comparing fixations with and without a washer using either partially threaded short of fully threaded long transsacral screws, p ≥ 0.359. Conclusions: From a biomechanical perspective, a washer could be optional when using partially threaded short or fully threaded long transsacral S1-S2 screws for treatment of posterior pelvis ring injuries in young trauma patients. Yet, the omission of the washer in fully threaded short screws could lead to a significant diminished biomechanical stability.

Quality of Life and Working Conditions of Hand Surgeons-A National Survey.

Background and Objectives: Providing high-quality care for patients in hand surgery is an everyday endeavor. However, the quality of life (QoL) and working conditions of hand surgeons ensuring these high-quality services need to be investigated. The aim of this study was to evaluate the QoL and working conditions of Swiss hand surgeons. Materials and Methods: A national survey with Swiss hand surgeons was conducted. Standardized questionnaires were completed anonymously online. Core topics included working conditions, QoL, satisfaction with the profession, and aspects of private life. Results: A total of 250 hand surgeons were invited to participate, of which 110 (44.0%) completed the questionnaire. Among all participants, 43.6% stated that they are on call 4-7 days per month, versus 8.2% never being on call. Overall, 84.0% of the residents, 50.0% of the senior physicians, 27.6% of the physicians in leading positions, and 40.6% of the senior consultants/practice owners, as well as 55.1% of the female and 44.3% of the male respondents, felt stressed by their job, even during holidays and leisure time. Out of all participants, 85.4% felt that work affects private relationships negatively. Despite the reported stress, 89.1% would choose hand surgery as a profession again. Less on-call duty (29.1%) and better pay (26.4%) are the most prioritized factors for attractiveness of a position at a hospital. Conclusions: The QoL of Swiss hand surgeons is negatively affected by their workload and working hours. Residents, senior physicians and female surgeons suffer significantly more often from depression, burnout or chronic fatigue in comparison to leading positions, senior consultants/practice owners and male surgeons. Better pay or less on-call duty would make the work more attractive in acute care hospitals.

Mid- to long-term clinical and radiological results of anatomic total shoulder arthroplasty in patients with B2 glenoids.

Background: Eccentric biconcave (B2) glenoid erosion in primary glenohumeral arthritis is common. There are serious concerns regarding the longevity of fixation of cemented glenoids if anatomic total shoulder arthroplasties (aTSAs) are used in B2 glenoid. The purpose of this study is to analyze the mid- to long-term results of aTSA with B2 glenoids. Methods: This is a retrospective study of a single center experience. Thirty patients (32 shoulders) at an average of 9.2 years (range, 5.0-16.6, ±3.2) after primary TSA were evaluated. Clinical and radiographic outcomes were analyzed. Results: The mean preoperative intermediate glenoid version was -14° ± 7° (range, -2° to -29°) and the mean humeral subluxation according to the plane of the scapula was 67% ± 9% (range, 49%-87%). There was a significant improvement for all the postoperative clinical outcome parameters including the mean absolute and relative Constant Score, subjective shoulder value, active elevation, external rotation, abduction, internal rotation, pain scores, and strength (P < .001). The complication rate was 15.6% and the revision rate was 12.5% at a mean follow-up of 9.2 years (range, 5.0-16.6, ±3.2). The estimated survivorship without revision was 94% at 5 years and 85% at 10 years (12.1-14.7 years). The survival rate without advanced glenoid component loosening (defined as Lazarus grade ≥ 4 or modified Molé scores ≥ 6) was 91% at 5 years and 84% at 10 years (12.2-15.8 years). Conclusion: In this case series, aTSA with asymmetric reaming for the treatment of shoulder osteoarthritis with milder forms of B2 glenoid is a viable option with good to excellent clinical results and an 85% prosthetic survivorship at 10 years.

Simulated full weight bearing following posterior column acetabular fracture fixation: a biomechanical comparability study.

PURPOSE: The incidence of acetabular fractures (AFs) is increasing in all industrial nations, with posterior column fractures (PCFs) accounting for 18.5-22% of these cases. Treating displaced AFs in elderly patients is a known challenge. The optimal surgical strategy implementing open reduction and internal fixation (ORIF), total hip arthroplasty (THA), or percutaneous screw fixation (SF), remains debated. Additionally, with either of these treatment methods, the post-surgical weight bearing protocols are also ambiguous. The aim of this biomechanical study was to evaluate construct stiffness and failure load following a PCF fixation with either standard plate osteosynthesis, SF, or using a screwable cup for THA under full weight bearing conditions. METHODS: Twelve composite osteoporotic pelvises were used. A PCF according to the Letournel Classification was created in 24 hemi-pelvis constructs stratified into three groups (n = 8) as follows: (i) posterior column fracture with plate fixation (PCPF); (ii) posterior column fracture with SF (PCSF); (iii) posterior column fracture with screwable cup fixation (PCSC). All specimens were biomechanically tested under progressively increasing cyclic loading until failure, with monitoring of the interfragmentary movements via motion tracking. RESULTS: Initial construct stiffness (N/mm) was 154.8 ± 68.3 for PCPF, 107.3 ± 41.0 for PCSF, and 133.3 ± 27.5 for PCSC, with no significant differences among the groups, p = 0.173. Cycles to failure and failure load were 7822 ± 2281 and 982.2 ± 428.1 N for PCPF, 3662 ± 1664 and 566.2 ± 366.4 N for PCSF, and 5989 ± 3440 and 798.9 ± 544.0 N for PCSC, being significantly higher for PCPF versus PCSF, p = 0.012. CONCLUSION: Standard ORIF of PCF with either plate osteosynthesis or using a screwable cup for THA demonstrated encouraging results for application of a post-surgical treatment concept with a full weight bearing approach. Further biomechanical cadaveric studies with larger sample size should be initiated for a better understanding of AF treatment with full weight bearing and its potential as a concept for PCF fixation.

A Novel Implant for Superior Pubic Ramus Fracture Fixation-Development and a Biomechanical Feasibility Study.

Background and Objectives: Pubic ramus fractures are common in compound pelvic injuries known to have an increased rate of morbidity and mortality along with recurrent and chronic pain, impeding a patient's quality of life. The current standard treatment of these fractures is percutaneous screw fixation due to its reduced risk of blood loss and shorter surgery times. However, this is an intricate surgical technique associated with high failure rates of up to 15%, related to implant failure and loss of reduction. Therefore, the aim of this biomechanical feasibility study was to develop and test a novel intramedullary splinting implant for fixation of superior pubic ramus fractures (SPRF), and to evaluate its biomechanical viability in comparison with established fixation methods using conventional partially or fully threaded cannulated screws. Materials and Methods: A type II superior pubic ramus fracture according to the Nakatani classification was created in 18 composite hemi-pelvises via a vertical osteotomy with an additional osteotomy in the inferior pubic ramus to isolate the testing of three SPRF fixation techniques performed in 6 semi-pelvises each using either (1) a novel ramus intramedullary splint, (2) a partially threaded ramus screw, or (3) a fully threaded ramus screw. Results: No significant differences were detected among the fixation techniques in terms of initial construct stiffness and number of cycles to failure, p ≥ 0.213. Conclusion: The novel ramus intramedullary splint can be used as an alternative option for treatment of pubic ramus fractures and has the potential to decrease the rate of implant failures due to its minimally invasive implantation procedure.

Anterior variable-angle locked plating versus tension band wiring of simple and complex patella fractures - a biomechanical investigation.

BACKGROUND: The aim of this study was to investigate the biomechanical performance of novel anterior variable-angle locking plates versus tension band wiring used for fixation of simple and complex patella fractures. METHODS: Sixteen pairs of human cadaveric knees were used to simulate two-part simple transverse AO/OTA 34-C1 and five-part complex AO/OTA 34-C3 patella fractures. The complex fracture pattern was characterized with a medial and a lateral proximal fragment, together with an inferomedial, an inferolateral and an inferior fragment mimicking comminution around the distal patella pole. Eight pairs with simple fractures were split for fixation via either tension band wiring (TBW) through two parallel cannulated screws or anterior variable-angle locked plating, whereas other eight pairs with complex fractures were split for either TBW through two parallel cannulated screws plus circumferential cerclage wiring, or anterior variable-angle locked plating using a cortical caudo-cranial polar screw. Each specimen was tested over 5000 cycles with a range of motion from 90° flexion to full extension by pulling on the quadriceps tendon. Interfragmentary movements were captured by motion tracking. RESULTS: For both fracture types, the longitudinal and shear articular displacements, measured between the proximal and distal fragments at the central patella aspect between 1000 and 5000 cycles, together with the relative rotations of these fragments around the mediolateral axis were all significantly smaller following anterior variable-angle locked plating versus TBW, p ≤ 0.01. CONCLUSIONS: From a biomechanical perspective, anterior locked plating of both simple and complex patella fractures resulted in less interfragmentary displacement under extended cyclic loading.

Biomechanical analysis of helical versus straight plating of proximal third humeral shaft fractures.

BACKGROUND: Proximal humeral shaft fractures are surgically challenging and plate osteosynthesis with a long straight plate is one operative treatment option in these patients although endangering the radial nerve distally. Helical plates potentially avoid the radial nerve by twisting around the humeral shaft. Aim of the study was to investigate in a human cadaveric model the biomechanical competence of helical plates versus straight lateral plates used for fixation of proximal third comminuted humeral shaft fractures. METHODS: Eight pairs of humeral cadaveric humeri were instrumented using either a long 90°-helical plate (Group1) or a straight long PHILOS plate (Group2). An unstable proximal humeral shaft fracture was simulated by means of a 5 cm osteotomy gap. All specimens were tested under quasi-static loading in axial compression, internal and external rotation, and bending in four directions. Subsequently, progressively increasing cyclic loading in internal rotation until failure was applied and interfragmentary movements were monitored by motion tracking. RESULTS: During static testing flexion/extension deformation in Group1 was significantly higher, however, varus/valgus deformation as well as shear and torsional displacement under torsional load remained statistically indifferent between both groups. During cyclic testing shear and torsional displacements were both significantly higher in Group1 compared to Group 2. However, cycles to catastrophic failure remained statistically indifferent between the groups. CONCLUSIONS: From a biomechanical perspective, although 90°-helical plating is associated with higher initial stability against varus/valgus collapse and comparable endurance under dynamic loading, it demonstrates lower resistance to flexion/extension and internal rotation with bigger shear interfragmentary displacements versus straight lateral plating and, therefore, cannot be considered as its real alternative. Alternative helical plate designs should be investigated in the future.

Statistical Morphology and Fragment Mapping of Complex Proximal Humeral Fractures.

Background and Objectives: Proximal humerus fractures (PHFs) are common in the elderly, but the treatment results are often poor. A clear understanding of fracture morphology and distribution of cortical bone loss is important for improved surgical decision making, operative considerations, and new implant designs. The aim of this study was to develop a 3D segmentation fracture mapping technique to create a statistical description of the spatial pattern and cortical bone loss of complex PHFs. Materials and Methods: Fifty clinical computed tomography (CT) scans of complex PHFs and their contralateral intact shoulders were collected. In-house software was developed for semi-automated segmentation and fracture line detection and was combined with manual fracture reduction to the contralateral template in a commercial software. A statistical mean model of these cases was built and used to describe probability maps of the fracture lines and cortical fragments. Results: The fracture lines predominantly passed through the surgical neck and between the tuberosities and tendon insertions. The superior aspects of the tuberosities were constant fragments where comminution was less likely. Some fracture lines passed through the bicipital sulcus, but predominantly at its edges and curving around the tuberosities proximally and distally. Conclusions: A comprehensive and systematic approach was developed for processing clinical CT images of complex fractures into fracture morphology and fragment probability maps and applied on PHFs. This information creates an important basis for better understanding of fracture morphology that could be utilized in future studies for surgical training and implant design.

Getting Cartilage Thickness Measurements Right: A Systematic Inter-Method Comparison Using MRI Data from the Osteoarthritis Initiative.

OBJECTIVE: Magnetic resonance imaging is the standard imaging modality to assess articular cartilage. As the imaging surrogate of degenerative joint disease, cartilage thickness is commonly quantified after tissue segmentation. In lack of a standard method, this study systematically compared five methods for automatic cartilage thickness measurements across the knee joint and as a function of region and sub-region: 3D mesh normals (3D-MN), 3D nearest neighbors (3D-NN), 3D ray tracing (3D-RT), 2D centerline normals (2D-CN), and 2D surface normals (2D-SN). DESIGN: Based on the manually segmented femoral and tibial cartilage of 507 human knee joints, mean cartilage thickness was computed for the entire femorotibial joint, 4 joint regions, and 20 subregions using these methods. Inter-method comparisons of mean cartilage thickness and computation times were performed by one-way analysis of variance (ANOVA), Bland-Altman analyses and Lin's concordance correlation coefficient (CCC). RESULTS: Mean inter-method differences in cartilage thickness were significant in nearly all subregions (P < 0.001). By trend, mean differences were smallest between 3D-MN and 2D-SN in most (sub)regions, which is also reflected by highest quantitative inter-method agreement and CCCs. 3D-RT was prone to severe overestimation of up to 2.5 mm. 3D-MN, 3D-NN, and 2D-SN required mean processing times of ≤5.3 s per joint and were thus similarly efficient, whereas the time demand of 2D-CN and 3D-RT was much larger at 133 ± 29 and 351 ± 10 s per joint (P < 0.001). CONCLUSIONS: In automatic cartilage thickness determination, quantification accuracy and computational burden are largely affected by the underlying method. Mesh and surface normals or nearest neighbor searches should be used because they accurately capture variable geometries while being time-efficient.