The Use of Knotless Suture Tape Construct vs Screw Fixation for Lisfranc Injuries: A Cadaveric Biomechanical Study.

BACKGROUND: Lisfranc injuries are often treated with open reduction and internal fixation using rigid fixation techniques. The use of flexible fixation to stabilize the Lisfranc joint is a newer technique. The purpose of this cadaveric study is to compare the amount of diastasis at the Lisfranc interval under diminished physiologic loads when treated with a knotless suture tape construct and a solid screw. METHODS: Ten cadavers (20 feet) had native motion at the intact Lisfranc interval assessed at multiple increasing loads (69, 138, and 207 N). The Lisfranc ligamentous complex was then disrupted, and testing repeated to evaluate the amount of diastasis. Randomization was performed to determine the type of fixation for each cadaver: solid screw or knotless suture tape construct. Once fixation was completed, specimens were cyclically loaded for 10 000 cycles at loads, and diastasis was quantified after each load cycle to compare the interventions. Diastasis was measured using motion tracking cameras and retroreflective marker sets. A non-inferiority statistical analysis was performed. RESULTS: Diastasis mean values were confirmed to be >2 mm for all load bearing conditions in the injury model. Posttreatment, diastasis was significantly reduced when compared to the sectioned conditions (P < .01) for both treatment options. Non-inferiority analyses showed that the knotless suture tape construct did not perform inferior to screw fixation for diastasis at the Lisfranc interval at any of the compared load states. CONCLUSION: Under the loads tested, there is no significant difference in diastasis at the Lisfranc interval when treating ligamentous Lisfranc injuries with a knotless suture tape construct or solid screws. Both reduced diastasis from the injured state and were not different from the intact state. CLINICAL RELEVANCE: In this cadaveric model with ligamentous Lisfranc injury, diastasis of a knotless suture tape construct is compared to solid screw fixation as tested.

Mini All-Suture Anchors for Repairing the Central Slip of the Extensor Tendon at the Proximal Interphalangeal Joint: A Biomechanical Investigation.

PURPOSE: This study evaluated 1.0-mm mini suture anchors for repairing the central slip of the extensor mechanism at the proximal interphalangeal joint. Studies have reported a requirement for central slip fixation to withstand 15 N during postoperative rehabilitation exercises and 59 N during forceful contraction. METHODS: Index and middle fingers from 10 matched pairs of cadaveric hands were prepared with 1.0-mm mini suture anchors with 2-0 sutures or threaded with 2-0 sutures through a bone tunnel (BTP). In total, 10 index fingers from unmatched hands were prepared with suture anchors and fixed to the extensor tendons to evaluate the tendon/suture interface response. Each distal phalanx was secured to a servohydraulic testing machine, and ramped tensile loads were applied to suture or tendon until failure. RESULTS: All anchors for the all-suture bone tests failed because of pullout from the bone (Mean failure force = 52.5+/-17.3 N). Three anchors from the tendon-suture pull out test failed by pullout from the bone and seven failed at the tendon/suture interface (Mean failure force = 49.0+/-10.1 N). CONCLUSIONS: The 1.0-mm mini suture anchor provides enough strength for early short-arc motion, but it may not be adequate for forceful contraction in the early postoperative rehabilitation stage. CLINICAL RELEVANCE: The site of fixation, the type of anchor, and the type of suture used are key factors to consider for early range of motion, after surgery.

A Biomechanical Analysis of the H-Taping Method Used by Rock Climbers as Prophylactic or Stabilizing Fixation of Partial A2 Pulley Tears.

PURPOSE: Rock climbing can lead to upper-extremity injuries, such as A2 pulley ruptures, leading to the bowstringing of the flexor tendons. Climbing finger positions are specific and can put undue stress on the pulley systems. This causes severe hand dysfunction and is a difficult problem to treat, and prevention is important. Using a cadaveric, experimental model, we evaluated the effectiveness of the H-taping method, commonly used by rock climbers, to prevent and treat A2 pulley tears. METHODS: Using fourteen matched pairs of fresh-frozen cadaveric hands with forearms, four experiments were conducted with 56 paired comparisons evaluating the failure force, fingertip force, and mode of failure (112 total tests). Comparisons were as follows: index fingers- intact versus 50% distal A2 pulley tears without H-taping (control); ring fingers- intact versus H-taping as a prophylactic for A2 pulley tears; little fingers- 50% distal A2 pulley tears with H-tape versus without tape; and middle fingers- H-taping as a prophylactic versus H-taping as a stabilizing treatment of torn pulleys. RESULTS: The mean index finger failure force was significantly higher in intact vs torn A2 pulleys (control). Failure force for intact H-taped fingers was significantly higher than torn H-taped fingers, but no other finger comparisons for failure force were significant. There were no significant findings in comparison of mean fingertip force values in any of the experiments. CONCLUSIONS: We found that H-taping is not effective as prophylaxis against A2 pulley ruptures or as a stabilizing treatment method for partially ruptured pulleys. CLINICAL RELEVANCE: While H-taping has not been recommended as prophylaxis for preventing A2 pulley ruptures, the climbing community has embraced this technique as a preventative measure. The present study provides biomechanical evidence against H-taping for this purpose. Furthermore, it does not appear to aid in increasing fingertip force after injury.

A Volar Locking Plate With Fossa Specific Fixation Provides Comparable Stability Between Articular and Nonarticular Cadaveric Models of Distal Radius Fracture.

BACKGROUND: Distal radius fractures often present with a 3-part articular fragmentation pattern, with separation of the dorsal and volar lunate fossa. The column concept of distal radius fixation addresses the importance of stabilizing both the scaphoid fossa lateral column and the lunate fossa intermediate column. Recent evidence strengthens the value of immediate postoperative mobilization. Satisfactory outcomes following these protocols are predicated on volar locking plates (VLPs) providing adequate stability to the fracture repair. We hypothesize that a VLP which individually supports both lateral and intermediate distal radius columns may provide comparable stability between articular and non-articular cadaveric fracture models under parameters meant to simulate postoperative loading. METHODS: Eleven cadaveric matched pair specimens were randomized to receive a simulated AO Type A2 non-articular distal radius fracture on one side with an AO Type C3 articular fracture on the contralateral side. Stiffness during cyclic loading was compared between fracture groups. A matched-paired Student t-test was used to determine statistical significance (P = .05). RESULTS: There were no significant differences (P = .35) in stiffness between the articular models (mean 370.0 N/mm, +/-93.5) and the non-articular models (360.4 N/mm, +/-60.0) of distal radius fracture. CONCLUSION: A VLP that individually supports the scaphoid and lunate fossa with fixed angle subchondral support may provide comparable fixation strength with resistance to displacement between articular and non-articular fracture patterns. The current results suggest that fossa-specific VLP fixation in articular fractures can maintain construct stability during postoperative loading.

Appropriately Matched Fixed-Angle Locking Plates Improve Stability in Volar Distal Radius Fixation.

Purpose: Size options for volar locking plates may provide value for distal radius fixation. We compared excessively narrow plates with plates that were appropriately matched in width for fixation of an multifragmented distal radius fracture model. Methods: Eighteen matched pairs (right and left wrists) of large, cadaveric male distal radii specimens, prepared with a simulated Arbeitsgemeinschaft für Osteosynthesefragen type C-3 distal radius fractures, were tested. One specimen from each matched pair was randomized to receive a plate that was appropriately matched in width to the distal radius. The contralateral limb received a narrow plate, which in all cases was undersized in width. Fixation stability was tested and compared to the contralateral matched specimen. Specimens were preloaded at 50 N for 30 seconds before cyclic loading from 50-250 N at 1 Hz for 5000 cycles then loaded to failure. Results: Loss of fixation under cyclic loading was significantly greater in the specimens fixed with excessively narrow plates compared with plates of appropriate width. When loaded to failure, the plates of appropriate width were stiffer, with higher force at failure and compressive strength than narrow plates. The primary mode of failure was displacement of the distal lunate facet fragment. Conclusions: These findings suggest that optimally matching the volar locking plate width to the radius may provide advantages for stability of the fixation construct and fragment capture. This may be due to reduced stress concentration from the distribution of forces across a larger surface area. Clinical relevance: Optimizing the plate width to the radial width may improve fracture stability and may carry additional importance in comminuted fractures, where narrow plates may not completely capture small bone fragments.

A Biomechanical Comparison of the LaPrade Technique Versus a Novel Technique for Reconstruction of Medial-Sided Knee Injuries.

BACKGROUND: Medial-sided knee injuries can lead to symptomatic valgus laxity or anteromedial rotatory instability and may require surgery, particularly in the setting of cruciate tears and tibial-sided medial collateral ligament (MCL) avulsions. The LaPrade (LP) technique utilizes 2 free grafts to reconstruct the superficial MCL (sMCL) and the posterior oblique ligament (POL). An alternative MCL reconstruction devised by the senior author comprises an anatomic single-bundle reconstruction using a free graft to reconstruct the sMCL with advancement and imbrication of the posteromedial capsule/POL (MCL anatomic reconstruction with capsular imbrication [MARCI] technique). These techniques have not been biomechanically compared with one another. PURPOSE: To identify if one of these reconstruction techniques better restores valgus and rotational medial knee stability throughout the range of motion. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 20 fresh-frozen, male (mean age, 43.7 years [range, 20-63 years]), midfemur-to-toe-matched cadaveric knees were utilized. All reconstructions were performed by a single fellowship-trained sports medicine surgeon. Left and right specimens within matched pairs were randomized to 1 of the 2 treatment groups: LP or MARCI. Each specimen was tested in 3 phases: (1) intact knee, (2) destabilized (MCL and POL completely severed), and (3) reconstructed (post-LP or post-MARCI reconstruction). We quantified valgus angulation defined by medial joint line opening, as well as internal and external tibial rotation at 0°, 20°, 30°, 60°, and 90° of knee flexion under applied external moments/torques at each phase. RESULTS: There were significant differences between the MARCI and LP reconstruction groups in valgus stability compared with the intact state (P = .021), with the MARCI reconstruction more closely approximating the intact knee. There was no overall difference between the MARCI and LP reconstruction techniques for internal rotation (P = .163), with both closely resembling the intact state. For external rotation, the effect of the reconstruction technique was dependent on the knee flexion angle (P < .001). At the highest angles, there were no differences between reconstructions; however, for lower knee flexion angles, the MARCI technique more closely resembled the intact state. CONCLUSION: Although both techniques improved knee stability compared with destabilized conditions, the MARCI technique better approximated intact stability during valgus at knee flexion angles from 0° to 90° and external rotation loads at knee flexion angles ≤30° in a cadaveric model. CLINICAL RELEVANCE: The MARCI technique provides an alternative option to improve valgus stability throughout the range of motion. It utilizes a POL advancement without the potential limitations seen in the LP technique, such as multiple tunnel complexity and collision, particularly in the multiple ligament-injured knee.

Ex Vivo Toxicity of Commonly Used Topical Antiseptics and Antibiotics on Human Chondrocytes.

Topical povidone-iodine, chlorhexidine, bacitracin, and vancomycin are commonly used antiseptic and antimicrobial agents to reduce risk and treat surgical site infections in numerous orthopedic procedures. Chondrocytes potentially may be exposed to these agents during operative procedures. The impact of these topical agents on chondrocyte viability is unclear. The goal of this study is to determine human chondrocyte viability ex vivo after exposure to commonly used concentrations of these topical antiseptic and antimicrobial agents. Human osteochondral plugs were harvested from the knee joint of a human decedent within 36 hours of death. Individual human osteochondral plugs were exposed to normal saline as a control; a range of concentrations of povidone-iodine (0.25%, 0.5%, and 1%), chlorhexidine (0.01% and 0.5%), and bacitracin (10,000 units/L, 50,000 units/L, and 100,000 units/L) for 1-minute lavage; or a 48-hour soak in vancomycin (0.16 mg/mL, 0.4 mg/mL, and 1.0 mg/mL) with nutrient media. Chondrocyte viability was evaluated with a live/dead viability assay at 0, 2, 4, and 6 days after exposure to bacitracin at 0, 3, and 6 days). Control subjects showed greater than 70% viability at all time points. Povidone-iodine, 0.5% chlorhexidine, and vancomycin showed significant cytotoxicity, with viability dropping to less than 40% by day 6. Chondrocytes exposed to 0.01% chlorhexidine maintained viability. Chondrocytes exposed to bacitracin showed viability until day 3, when there was a large drop in viability. Commonly used topical concentrations of povidone-iodine, vancomycin, and bacitracin are toxic to human chondrocytes ex vivo. A low concentration of chlorhexidine appears safe. Caution should be used when articular cartilage may be exposed to these agents during surgery. [Orthopedics. 2022;45(5):e263-e268.].

Additive Manufacturing: The Next Generation of Scapholunate Ligament Reconstruction.

Background Ligament reconstruction, as a surgical method used to stabilize joints, requires significant strength and tissue anchoring to restore function. Historically, reconstructive materials have been fraught with problems from an inability to withstand normal physiological loads to difficulties in fabricating the complex organization structure of native tissue at the ligament-to-bone interface. In combination, these factors have prevented the successful realization of nonautograft reconstruction. Methods A review of recent improvements in additive manufacturing techniques and biomaterials highlight possible options for ligament replacement. Description of Technique In combination, three dimensional-printing and electrospinning have begun to provide for nonautograft options that can meet the physiological load and architectures of native tissues; however, a combination of manufacturing methods is needed to allow for bone-ligament enthesis. Hybrid biofabrication of bone-ligament tissue scaffolds, through the simultaneous deposition of disparate materials, offer significant advantages over fused manufacturing methods which lack efficient integration between bone and ligament materials. Results In this review, we discuss the important chemical and biological properties of ligament enthesis and describe recent advancements in additive manufacturing to meet mechanical and biological requirements for a successful bone-ligament-bone interface. Conclusions With continued advancement of additive manufacturing technologies and improved biomaterial properties, tissue engineered bone-ligament scaffolds may soon enter the clinical realm.

No Significant Difference Between Intramedullary and Extramedullary Button Fixation for Distal Biceps Brachii Tendon Rupture After Cyclic Loading in a Cadaver Model.

PURPOSE: To biomechanically compare intramedullary (IM) versus extramedullary (EM) distal biceps button fixation under cyclic loading conditions, which is most representative of postoperative physiologic status. METHODS: This controlled laboratory study used 13 fresh-frozen matched paired cadaver elbows. One specimen from each pair was randomized to either IM (unicortical) or EM (bicortical) distal biceps button fixation via onlay technique. A servohydraulic actuator was used to cycle each specimen from full extension to 90° of flexion at 0.5 Hz for 3,000 cycles. All specimens were subsequently loaded to failure to simulate an acute postoperative load. RESULTS: During cyclic loading, the mean change in force from cycle 5 to cycle 3000 was 2.1 ± 3.2 N for the IM group and 0.6 ± 4.2 N for the EM group (P = .19). The increase in tendon gap for the IM group was 1.02 mm and for the EM group was 1.83 mm (P = .37). During failure loading, the IM group had a mean failure load of 154.9 ± 44.5 N and the EM group a mean failure load of 191.1 ± 62.6 N (P = .16). CONCLUSIONS: No significant differences exist between the IM and EM techniques in loss of force and tendon gap formation under cyclic loading or load to failure conditions. Thus, IM fixation may adequately facilitate optimal bone-tendon apposition, with less risk of iatrogenic injury to the posterior interosseous nerve that can be seen with bicortical extramedullary fixation. CLINICAL RELEVANCE: The most common major complication following distal biceps repair is PIN palsy. IM fixation may be sufficient in facilitating optimal bone-tendon apposition and healing with onlay technique, while minimizing risk of iatrogenic PIN injury associated with EM fixation.

A Novel Approach for Assessing and Training the Drilling Skills of Orthopaedic Surgeons.

BACKGROUND: Although experiences in the operating room can help surgeons to learn simple bone-drilling techniques, outside training may be better suited for complex procedures. We adapted a rotary handpiece to evaluate the bone-drilling skills of orthopaedic resident physicians during the 2017 Southwest Orthopaedic Trauma Association (SWOTA) motor skills course. METHODS: Twenty-five postgraduate year (PGY)-1 orthopaedic residents from 7 institutions were asked to perform a bicortical drilling task 3 times both before and after attending a motor skills course. Kinetic and kinematic data were collected using force, acceleration, and visual sensors. RESULTS: Sixteen parameters were measured. The interdependence of these parameters (taken separately for precourse and postcourse performance) is presented. Evidence for motor skill acquisition across a short time scale is elucidated. Noteworthy correlations include overpenetration with force (0.65 mm), palmar-dorsal (P-D) toggle (0.65°), vibration in the P-D direction (0.53 m/s), time (-0.41 sec), and RPM (revolutions per minute; -0.36); time with both RPM (0.38) and P-D toggle (-0.40°); and force with both RPM (-0.41) and P-D toggle (0.32°). Differences in performance before and after the motor skills course include reduction in overpenetration (28.8 to 18.2 mm), reduction in skiving (22% to 6%), and reduction in preparation time (27.3 to 9.65 sec). Additionally, there were several differences in performance by institution that were significant (overpenetration, toggle in the P-D and radial-ulnar [R-U] directions, and both drilling force and drilling time). CONCLUSIONS: Understanding how performance and outcome parameters are correlated provides powerful insight into how surgical procedures can be best performed. In particular, we hope that these findings will inform new training paradigms. Variations in resident training from 1 institution to another are evidenced in surgical performance. Similarly, the methods used here to quantify changes in performance across the 3-day SWOTA training course allow a unique vehicle for optimization of these types of training opportunities outside of the operating room.

A Biomechanical Comparison of the Arciero and LaPrade Reconstruction for Posterolateral Corner Knee Injuries.

BACKGROUND: Injury to the posterolateral corner (PLC) of the knee requires reconstruction to restore coronal and rotary stability. Two commonly used procedures are the Arciero reconstruction technique (ART) and the LaPrade reconstruction technique (LRT). To the authors' knowledge, these techniques have not been biomechanically compared against one another. PURPOSE: To identify if one of these reconstruction techniques better restores stability to a PLC-deficient knee and if concomitant injury to the proximal tibiofibular joint or anterior cruciate ligament affects these results. STUDY DESIGN: Controlled laboratory study. METHODS: Eight matched-paired cadaveric specimens from the midfemur to toes were used. Each specimen was tested in 4 phases: intact PLC (phase 1), PLC sectioned (phase 2), PLC reconstructed (ART or LRT) (phase 3), and tibiofibular (phase 4A) or anterior cruciate ligament (phase 4B) sectioning with PLC reconstructed. Varus angulation and external rotation at 0º, 20º, 30º, 60º, and 90º of knee flexion were quantified at each phase. RESULTS: In phase 3, both reconstructions were effective at restoring laxity back to the intact state. However, in phase 4A, both reconstructions were ineffective at stabilizing the joint owing to tibiofibular instability. In phase 4B, both reconstructions had the potential to restrict varus angulation motion. There were no statistically significant differences found between reconstruction techniques for varus angulation or external rotation at any degree of flexion in phase 3 or 4. CONCLUSION: The LRT and ART are equally effective at restoring stability to knees with PLC injuries. Neither reconstruction technique fully restores stability to knees with combined PLC and proximal tibiofibular joint injuries. CLINICAL RELEVANCE: Given these findings, surgeons may select their reconstruction technique based on their experience and training and the specific needs of their patients.

Design for Transtibial Modifiable Socket for Immediate Postoperative Prosthesis.

Amputations are long-standing surgical procedures that have been performed for centuries; however, very little attention and urgency have been given to immediate restoration of movement and return to a normal lifestyle. In many cases, the time between amputation and prosthetic fitting can pause recovery and development of new routines. To increase recovery, immediate postoperative prostheses (IPOPs) have been developed yet these are under-utilized because of concerns for wound healing and complications with vascular diseases. Subsequently, we designed a transtibial IPOP that utilizes an ergonomic modifiable socket that allows for examination, wound care, and in situ edema control. Additionally, the IPOP facilitates early weight bearing and protects the amputated limb from external trauma postoperatively. Our purpose is to introduce this technology and describe how its unique design will serve to provide potential benefits and positive effects on patients who have undergone amputations.

Damage in a Distal Radius Fracture Model Treated With Locked Volar Plating After Simulated Postoperative Loading.

PURPOSE: "Damage" is an engineering term defining a period between a state of material perfection and the onset of crack initiation. Clinically, it is a loss of fixation due to microstructural breakdown, indirectly measured as a reduction of stiffness of the bone-implant construct, normalized by the cross-sectional area and length of the bone. The purpose of this study was to characterize damage in a cadaver model of extra-articular distal radius fracture with dorsal comminution treated using 2-column volar distal radius plates. METHODS: Ten matched distal radii were randomly divided into 2 groups: group I specimens were treated with a volar distal radius plate with an independent, 2-tiered scaffold design; group II specimens (contralateral limbs) were treated with a volar plate with a single-head design for enhanced ulnar buttressing. Specimens were cyclically loaded to simulate a 6-month postoperative load-bearing period. We report damage after a defined protocol of cyclical loading and load to failure simulating a fall on an outstretched hand. RESULTS: Group II specimens experienced more damage under cyclic loading conditions than group I specimens. Group I specimens were stiffer than group II specimens under load-to-failure conditions. Ultimate force at failure in group I and group II specimens was not different. Specimens failed by plate bending (group I, n = 6/10; group II, n = 2/10) and fracture of the lunate facet (group I, n = 4/10; group II, n = 8/10). CONCLUSIONS: Group I specimens had less screw cutout at the lunate facet than group II specimens under cyclic loading as indicated by lower damage measures and fewer facet fractures during load-to-failure testing. The overall strength of the construct is not affected by plate design. CLINICAL RELEVANCE: Microstructural damage or a loss of fixation due to an overly rigid volar plate design may cause malunion or nonunion of fracture fragments and lead to bone-implant instability.

Long-term Outcomes of Partial Trapeziectomy With Capsular Interposition Arthroplasty for Osteoarthritis of the Thumb Basal Joint.

The purpose of this study was to describe long-term outcomes of partial trapeziectomy with capsular interposition (PTCI) arthroplasty for patients with osteoarthritis of the basal joint of the thumb. A total of 27 patients (20 women, 7 men; 32 thumbs) with a mean age of 61 years (range, 47-74 years) agreed to return for follow-up and were included in the study. Mean postoperative follow-up was 64.3 months (range, 28-112 months). Evaluation included tests for grip and pinch strength; range of motion of the metacarpophalangeal joint; measurement of the first web space; completion of the Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire; visual analog scale (VAS) measurements; and radiographic examination of the hand. A paired, 2-tailed t test was used to determine statistical significance (P<.05) of pre- and postoperative values. Postoperative values for grip strength were significantly increased from preoperative values. No significant loss of pinch strength was noted. Excessive hyperextension of the metacarpophalangeal joint did not occur, and the first web space was maintained. The mean DASH questionnaire and VAS scores were 5.06 (range, 0-26.5) and 0.32, respectively. Use of PTCI arthroplasty resulted in minimal loss in thumb height (7%) and significantly reduced thumb metacarpal subluxation (13%). There were no reported complications. The low DASH questionnaire and VAS scores compare well with other studies and indicate good functional outcomes. In treating thumb basal joint osteoarthritis, use of PTCI arthroplasty may result in improved thumb stability and grip strength, minimal subsidence of the thumb metacarpal, and reduced joint subluxation. [Orthopedics. 2018; 41(2):e228-e233.].

Objective Evaluation of Motor Skills for Orthopedic Residents Using a Motion Tracking Drill System: Outcomes of an ABOS Approved Surgical Skills Training Program.

BACKGROUND: Orthopedics is a motor skills-demanding surgical specialty requiring surgical skills training outside of the operating room. Unfortunately, limited quantitative techniques exist to determine the effectiveness of these surgical skills training programs. Using a variety of drill, surgeon, and specimen mounted sensors, we evaluated orthopedic surgery residents during a surgical skills training course approved by the American Board of Orthopaedic Surgeons (ABOS). This evaluation consisted of quantitative measures of various kinematic and kinetic parameters with the goal of relating these to clinically-significant outcomes. METHODS: Seven experienced surgeons and 22 surgical residents participated in this study, each performing 5 surgical drilling trials, pre- and post-training. Utilizing arm and tool kinematics, applied force, tool and bone vibration, and drill RPM were measured using a combination of force, acceleration, and optical tracking sensors. Post hoc screw pullout testing and resident survey data were also evaluated. Overall, 25 measured parameters were expressed as scalars and their covariance calculated. RESULTS: Non-trivial direct correlations whose magnitude exceeded 0.5 were: maximum penetration distance with applied force, drill toggle with drill roll angle, and drill RPM with force. Surgeons applying a high drill RPM also yielded a large force which in turn gave an increase in tendency for over-penetration. As a whole, the differences between experienced and novice surgeons measured in these trials were not statistically significant. However, when looking at specific performance criterion individually (maintaining steady force, minimizing over-penetration, minimizing both the major and minor axis diameters, minimizing toggle and drill vibration), experienced surgeons tended to outperform their novice counterparts. CONCLUSIONS: Objective assessment of surgical skills using sensor based technologies may help elucidate differences between novice and experienced surgeons for improved out-of-the-OR training methodologies.

A Biomechanical Comparison Of Pin Configurations Used For Percutaneous Pinning Of Distal Tibia Fractures In Children.

BACKGROUND: Percutaneous pin fixation is often used in conjunction with closed-reduction and cast immobilization to treat pediatric distal tibia fractures. The goal of this procedure is to maintain reduction and provide improved stabilization, in effort to facilitate a more anatomic union. We conducted a biomechanical study of the torsional and bending stability of three commonly used pin configurations in distal tibia fracture fixation. METHODS: A transverse fracture was simulated at the metaphyseal/diaphyseal junction in 15 synthetic tibias. Each fracture was reduced and fixed with two Kirschner wires, arranged in one of three pin configurations: parallel, retrograde, medial to lateral pins entering at the medial malleolus distal to the fracture (group A); parallel, antegrade, medial to lateral pins entering at the medial diaphysis proximal to the fracture (group B); or a cross-pin configuration with one retrograde, medial to lateral pin entering the medial malleolus distal to the fracture and the second an antegrade, medial to lateral pin entering at the medial diaphysis proximal to the fracture (group C). Stability of each construct was assessed by resistance to torsion and bending. RESULTS: Resistance to external rotation stress was significantly higher in group A than group B (P = 0.044). Resistance to internal rotation stress was significantly higher in group C than group B (P = 0.003). There was no significant difference in torsional stiffness when comparing group A with group C. Under a medial-directed load, group B and C specimens were significantly stiffer than those in group A (28 N/mm and 24 N/mm vs. 14 N/mm for A; P = 0.001 and P = 0.009, respectively). CONCLUSIONS: None of the three pin configurations produced superior results with respect to all variables studied. Group A configuration provided the highest resistance to external rotation forces, which is the most clinically relevant variable under short-cast immobilization. Parallel, retrograde, medial to lateral pins entering at the medial malleolus provide the greatest resistance to external rotation of the foot while minimizing the potential for iatrogenic injury to soft tissue structures.

Thumb Metacarpal Subsidence After Partial Trapeziectomy With Capsular Interposition Arthroplasty: A Biomechanical Study.

Background: In a cadaveric model, we evaluated thumb metacarpal subsidence, indicated by a decreased metacarpal-to-scaphoid distance, after 2 surgical procedures used to treat thumb carpometacarpal (CMC) osteoarthritis (OA): partial trapeziectomy with capsular interposition (PTCI), which involves removal of 2 mm of both the distal trapezium and base of the metacarpal; and total trapeziectomy with capsular interposition (TTCI). Methods: Nine matched pairs of cadaveric hands were randomly assigned to undergo either PTCI or TTCI. Preoperatively, physiologic forces were applied across the thumb CMC joint by loading 6 tendons, simulating lateral pinch. Anteroposterior radiographs were obtained, and the metacarpal-to-scaphoid distance on each image was estimated independently by 3 separate readers using customized software. A hand surgeon then performed the PTCI and TTCI procedures, and the measurements under loading were repeated. The results were assessed for interrater reliability. Mean values for metacarpal-to-scaphoid distance before and after the surgical procedures were compared. Results: Preoperatively, the metacarpal-to-scaphoid distance in the PTCI and TTCI groups was not significantly different. Postoperatively, metacarpal subsidence was significantly less in the PTCI group (17% compared with 34% for TTCI; P = .05). Conclusions: Metacarpal subsidence occurred after both PTCI and TTCI, but significantly less subsidence was observed after PTCI; thus, thumb length was better preserved. Previous research has shown an inverse correlation between maintenance of thumb length and overall Disabilities of the Arm, Shoulder, and Hand (DASH) score. A procedure for treating thumb CMC OA that preserves thumb length and minimizes disruption of stabilizing joint tissue may provide enhanced maintenance of thumb stability and improved patient outcomes.

Structures at Risk During Volar Percutaneous Fixation of Scaphoid Fractures: A Cadaver Study.

BACKGROUND: Fracture of the scaphoid bone can be treated with cast immobilization or surgery. Historically, surgery was reserved for displaced fractures. However, because weeks of cast immobilization may result in stiffness, loss of strength, loss of bone density and an inability to work or participate in recreational activities for a prolonged period, operative treatment of non-displaced fractures has become increasingly common. Several surgical techniques for fixation have been described, but their risks and benefits have not yet been clearly elucidated. In a study in cadavers, we investigated whether one approach--volar percutaneous fixation--might pose a risk of injury to surrounding structures. METHODS: In 15 cadaver upper limbs with the wrist structures intact, a K-wire was inserted in a volar percutaneous manner under fluoroscopic guidance, distal to proximal and through the scaphoid waist into the center-center position. The volar aspect of the wrist and hand were then dissected around the K-wire, with isolation of surrounding structures. The distance between the K-wire and several individual structures was then measured with use of a digital caliper. RESULTS: The K-wire was at least 4 mm from the superficial radial nerve, the first dorsal extensor compartment, the recurrent motor branch of the median nerve, and the radial artery (RA) in all specimens. However, the K-wire had penetrated die flexor carpi radialis (FCR) tendon in four specimens and was directly adjacent to it in another four. In one specimen, the K-wire was directly adjacent to the superficial volar branch of die RA. CONCLUSIONS: The K-wire may penetrate the FCR tendon and the superficial volar branch of the radial artery during volar percutaneous scaphoid fixation. The possible long-term clinical implications of this finding require investigation. CLINICAL RELEVANCE: Our findings indicate that modification of the volar percutaneous approach to scaphoid fixation may be advisable to avoid damage to adjacent structures. We suggest use of a "mini-open" percutaneous procedure.

Titanium mesh as a low-profile alternative for tension-band augmentation in patella fracture fixation: A biomechanical study.

OBJECTIVES: We performed a simple biomechanical study to compare the fixation strength of titanium mesh with traditional tension-band augmentation, which is a standard treatment for transverse patella fractures. We hypothesised that titanium mesh augmentation is not inferior in fixation strength to the standard treatment. METHODS: Twenty-four synthetic patellae were tested. Twelve were fixed with stainless steel wire and parallel cannulated screws. Twelve were fixed with parallel cannulated screws, augmented with anterior titanium mesh and four screws. A custom test fixture was developed to simulate a knee flexed to 90°. A uniaxial force was applied to the simulated extensor mechanism at this angle. A non-inferiority study design was used to evaluate ultimate force required for failure of each construct as a measure of fixation strength. Stiffness of the bone/implant construct, fracture gap immediately prior to failure, and modes of failure are also reported. RESULTS: The mean difference in force at failure was -23.0 N (95% CI: -123.6 to 77.6N) between mesh and wire constructs, well within the pre-defined non-inferiority margin of -260 N. Mean stiffness of the mesh and wire constructs were 19.42 N/mm (95% CI: 18.57-20.27 N/mm) and 19.49 N/mm (95% CI: 18.64-20.35 N/mm), respectively. Mean gap distance for the mesh constructs immediately prior to failure was 2.11 mm (95% CI: 1.35-2.88 mm) and 3.87 mm (95% CI: 2.60-5.13 mm) for wire constructs. CONCLUSIONS: Titanium mesh augmentation is not inferior to tension-band wire augmentation when comparing ultimate force required for failure in this simplified biomechanical model. Results also indicate that stiffness of the two constructs is similar but that the mesh maintains a smaller fracture gap prior to failure. The results of this study indicate that the use of titanium mesh plating augmentation as a low-profile alternative to tension-band wiring for fixation of transverse patella fractures warrants further investigation.

Quantitative computed tomography-based finite element analysis predictions of femoral strength and stiffness depend on computed tomography settings.

The aim of the present study was to compare proximal femur strength and stiffness obtained experimentally with estimations from Finite Element Analysis (FEA) models derived from Quantitative Computed Tomography (QCT) scans acquired at two different scanner settings. QCT/FEA models could potentially aid in diagnosis and treatment of osteoporosis but several drawbacks still limit their predictive ability. One potential reason is that the models are still sensitive to scanner settings which could lead to changes in assigned material properties, thus limiting their results accuracy and clinical effectiveness. To find the mechanical properties we fracture tested 44 proximal femora in a sideways fall-on-the-hip configuration. Before testing, we CT scanned all femora twice, first at high resolution scanner settings, and second at low resolution scanner settings and built 88 QCT/FEA models of femoral strength and stiffness. The femoral set neck bone mineral density, as measured by DXA, uniformly covered the range from osteoporotic to normal. This study showed that the femoral strength and stiffness values predicted from high and low resolution scans were significantly different (p<0.0001). Strength estimated from high resolution QCT scans was larger for osteoporotic, but smaller for normal and osteopenic femora when compared to low resolution scans. In addition, stiffness estimated from high resolution scans was consistently larger than stiffness obtained from low resolution scans over the entire femoral dataset. While QCT/FEA techniques hold promise for use in clinical settings we provided evidence that further improvements are required to increase robustness in their predictive power under different scanner settings and modeling assumptions.