Combined medial and lateral plate fixation is recommended for complex tibial plateau fractures with medial fragments or no cortical bone contact. Although such fixation is adequate to resist forces ...during range of motion, it may be insufficient to support immediate postoperative weightbearing. Here, we analyzed displacement, stiffness, and fixation failure during simulated full weightbearing of bicondylar tibial plateau fractures treated with combined medial and lateral locking plate fixation.
We used 10 fresh-frozen adult human cadaveric tibias and mated femurs. Osteotomies were performed with an oscillating saw and cutting template to simulate an AO Foundation and Orthopaedic Trauma Association (AO/OTA) 41-C2 fracture (simple articular, multifragmentary metaphyseal fracture). Specimens were anatomically reduced and stabilized with combined medial and lateral locking plates (AxSOS, Stryker, Mahwah, NJ). Specimens were loaded axially to simulate 4 weeks of walking in a person weighing 70 kg. The specimens were cyclically loaded from 200 N to a maximum of 2800 N. Then, if no failure, loading continued for 200,000 cycles. We measured displacement of each bone fragment and defined fixation failure as ≥5 mm of displacement. Construct stiffness and load at failure were calculated. Categorical and continuous data were analyzed using Chi-squared and unpaired t-tests, respectively.
Mean total displacement values after 10,000 loading cycles were as follows: lateral, 0.4 ± 0.8 mm; proximal medial, 0.3 ± 0.7 mm; distal medial, 0.3 ± 0.6 mm; and central 0.4 ± 0.5 mm. Mean stiffness of the construct was 562 ± 164 N/mm. Fixation failure occurred in 6 of 10 specimens that reached 5 mm of plastic deformation before test completion. In the failure group, the mean load at failure was 2467 ± 532 N, and the mean number of cycles before failure was 53,155. After test completion, the greatest displacement was found at the distal medial fracture site (2.3 ± 1.4 mm) and lateral fracture site (2.2 ± 1.7 mm).
Although combined medial and lateral plate fixation of complex tibial plateau fractures provides adequate stability to allow early range of motion, immediate full weightbearing is not recommended.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
To investigate the effect of a dermal allograft superior capsule reconstruction (SCR) on kinematics and joint pressure biomechanics immediately after simulated superior irreparable rotator cuff tear.
...This controlled laboratory study tested 8 fresh-frozen cadaveric shoulders using a custom test frame. Balanced loading configuration centered the humeral head on the glenoid, and unbalanced load created a force pulling the head toward the acromion. Experimental conditions included the intact rotator cuff, irreparable supraspinatus tear (ISST), and dermal allograft SCR. A digital sensor measured glenohumeral and subacromial contact pressure maps, and a microscribe measured the acromion-humeral distance.
Glenohumeral contact pressure of ISST was 175% (295 ± 44 kPa; P = .018) of the intact rotator cuff value (169 ± 10 kPa) at 0° in the balanced condition and 176% (P = .048) of intact at 30°. SCR decreased glenohumeral contact pressure to 110% (185 ± 27 kPa; P = .044) of intact at 0° and to 95% (P = .034) at 30°. Unbalanced ISST contact pressure was 146% (365 ± 23 kPa; P = .009) of intact (250 ± 24 kPa) at 0° and 122% (P = .045) at 60°. SCR decreased contact pressures to 110% (274 ± 21 kPa; P = .039) of intact at 0° and to 89% (P = .003) at 60°. ISST increased superior migration of the humeral head, decreasing the acromion-humeral distance by 3.0 ± 0.6 mm (P = .006) in the unbalanced condition at 0°. SCR increased the acromion-humeral distance to a value similar to that of the intact cuff (P = .003). SCR significantly lowered subacromial pressures in the unbalanced condition.
In an irreparable supraspinatus tear model, the dermal allograft SCR showed competency in stabilizing the glenohumeral joint, decreasing glenohumeral and subacromial contact pressures, and increasing the acromion-humeral distance.
To compare flexor tendon repair strength and speed between a tendon coupler and a standard-core suture in a cadaver model.
In 5 matched-pair fresh cadaver hands, we cut the flexor digitorum profundus ...tendon of each finger in zone 2 and assigned 20 tendons to both the coupler and the suture groups. Coupler repair was with low-profile stainless steel staple plates in each tendon stump, bridged by polyethylene thread. Suture repair was performed using an 8-strand locking-cruciate technique with 4-0 looped, multifilament, polyamide suture. One surgeon with the Subspecialty Certificate in Surgery of the Hand performed all repairs. Via a load generator, each flexor digitorum profundus was loaded at 5 to 10 N and cycled through flexion just short of tip-to-palm and full extension at 0.2 Hz for 2,000 cycles to simulate 6 weeks of rehabilitation. We recorded repair gapping at predetermined cycle intervals. Our primary outcome was repair gapping at 2,000 cycles. Tendons that had not catastrophically failed by 2,000 cycles were loaded to failure on a servohydraulic frame at 1 mm/s.
Tendon repair gapping was similar between coupled and sutured tendons at 2,000 cycles. Tendons repaired with the coupler had higher residual load to failure than sutured tendons. Mean coupler repair time was 4 times faster than suture repair.
Zone 2 flexor repair with a coupler withstood simulated early active motion in fresh cadavers. Residual load to failure and repair speed were better with the coupler.
This tendon coupler may eventually be an option for strong, reproducible, rapid flexor tendon repair.
Background:
This study evaluated whether the addition of a nitinol staple-plate to a single cannulated screw increased the mechanical stability for a talonavicular fixation construct.
Methods:
Twenty ...matched pairs of cadaveric feet were randomized to fusion with either a single 5.5-mm cannulated screw or a screw and a plate with 2 screws and a slot with an 18-mm nitinol staple. After in situ fusion procedure, the talonavicular joint complex was dissected free and the ends were embedded in epoxy. The specimens were then cyclically loaded on a servohydraulic load frame (1000 cycles at 20 N, increasing at intervals of 20 N until failure), half of them for cantilever bending and the other half for torsion.
Results:
In the bending arm of the study, the staple-plate group showed significantly higher stiffness, failure load, and cycles to failure. In the torsion arm of the study, the staple-plate group also had higher cycles to failure, stiffness in external rotation, and torque to failure. No significant difference was noted in stiffness in internal rotation.
Conclusion:
We found a significant increase in stability of the talonavicular joint when a nitinol staple-plate construct was placed to augment a single cannulated screw for the purpose of a talonavicular fusion.
Clinical Relevance:
This information may be helpful to surgeons in implant selection for this common arthrodesis procedure.
Background:
Tendon healing is a slow and complicated process that results in inferior structural and functional properties when compared to healthy tendon tissue. It may be possible to improve ...outcomes of tendon healing with enhancement of biological aspects of the repair including tissue structure, organization, and composition. The purpose of this study was to determine whether use of a stem cell-bearing suture improves Achilles tendon healing in a rat model.
Methods:
The Achilles tendon was transected in 108 bilateral hind limbs from 54 rats. Each limb was randomized to repair with suture only (SO), suture plus injection (SI) of mesenchymal stem cells (MSCs) at the repair site, or suture loaded with MSCs (suture with stem cells, SCS). One half of the animals were randomly sacrificed at 14 and 28 days after surgery and the Achilles tendon was harvested. From each repair group at each time point, 12 limbs were randomized to biomechanical testing and 6 to histologic analysis. Tendons were loaded using a 223-N load cell at 0.17 mm/s. A blinded pathologist scored the histology sections.
Results:
Ultimate failure strength (N/mm2) was significantly higher in the SI and SCS groups versus the SO group. In the SI group, ultimate failure strength decreased significantly at 28 days versus 14 days. Histology score in the SCS group was significantly lower (better) than in both other groups (P ≤ .001). Histology findings at day 28 were significantly higher versus day 14 for all groups (P = .01).
Conclusions:
Both the SI and the SCS groups had significantly higher ultimate failure strength versus the SO group, and strength was maintained at 28 days in the SCS group but not in the SI group. Histology in the SCS group was significantly better than in both other groups.
Clinical Relevance:
These findings in a rat model suggest that the use of stem cells enhances healing after Achilles repair and that embedding of stem cells directly into suture offers sustained early benefit to tendon healing.
Background:
We aimed to define reference lines on standard lateral ankle radiographs that could be used intraoperatively to minimize iatrogenic nerve injury risk in medial displacement calcaneal ...osteotomy.
Methods:
Forty cadaveric specimens were used. In 20 specimens, the sural, medial plantar (MP), and lateral plantar (LP) nerves were sutured to radiopaque wire, and a lateral ankle radiograph was obtained. On the radiograph, a line was drawn from the posterior superior apex of the calcaneal tuberosity to the origin of the plantar fascia and labeled as the “landmark line.” A parallel line was drawn 2 mm posterior to the most posterior nerve, and the area between these lines was defined as the safe zone. In 20 additional specimens, an osteotomy was performed 1 cm anterior to the landmark line using a percutaneous or open technique. Dissection was performed to assess for laceration of the sural, MP, LP, medial calcaneal (MC), or lateral calcaneal (LC) nerves.
Results:
The safe zone was determined to be within the area 11.2 ± 2.7 mm anterior to the landmark line. After open osteotomy, lacerations were found in 3 of 10 MC nerves and 3 of 10 LC nerves. After percutaneous osteotomy, lacerations were found in 2 of 10 MC nerves and 1 of 10 LC nerves. No lacerations of the sural, MP, or LP nerves were found with either osteotomy.
Conclusions:
The safe zone extended 11.2 ± 2.7 mm anterior to the described landmark line. The MC and LC nerves were always at risk during medial displacement calcaneal osteotomy.
Clinical Relevance:
Nerve injury to both major and minor sensory nerves is likely underrecognized as a source of morbidity after calcaneal osteotomy. The current study provides a ready intraoperative guideline for minimizing this risk.
Background:
Debate exists on the optimum fixation construct for large avulsion fractures of the fifth metatarsal base. We compared the biomechanical strength of 2 headless compression screws vs a ...hook plate for fixation of these fractures.
Methods:
Large avulsion fractures were simulated on 10 matched pairs of fresh-frozen cadaveric specimens. Specimens were assigned to receive two 2.5-mm headless compression screws or an anatomic fifth metatarsal hook plate, then cyclically loaded through the plantar fascia and metatarsal base. Specimens underwent 100 cycles at 50%, 75%, and 100% physiological load for a total of 300 cycles.
Results:
The hook plate group demonstrated a significantly higher number of cycles to failure compared with the screw group (270.7 ± 66.0 range 100-300 cycles vs 178.6 ± 95.7 range 24-300 cycles, respectively; P = .039). Seven of 10 hook plate specimens remained intact at the maximum 300 cycles compared with 2 of 10 screw specimens. Nine of 10 plate specimens survived at least 1 cycle at 100% physiologic load compared with 5 of 10 screw specimens.
Conclusion:
A hook plate construct was biomechanically superior to a headless compression screw construct for fixation of large avulsion fractures of the fifth metatarsal base.
Clinical Relevance:
Whether using hook plates or headless compression screws, surgeons should consider protecting patient weight-bearing after fixation of fifth metatarsal base large avulsion fracture until bony union has occurred.
To compare lag versus nonlag screw fixation for long oblique proximal phalanx (P1) fractures in a cadaveric model of finger motion via the flexor and extensor tendons.
We simulated long oblique P1 ...fractures with a 45° oblique cut in the index, middle, and ring fingers of 4 matched pairs of cadaveric hands for a total of 24 simulated fractures. Fractures were stabilized using 1 of 3 techniques: two 1.5-mm fully threaded bicortical screws using a lag technique, two 1.5-mm fully threaded bicortical nonlag screws, or 2 crossed 1.14-mm K-wires as a separate control. The fixation method was randomized for each of the 3 fractures per matched-pair hand, with each fixation being used in each hand and 8 total P1 fractures per fixation group. Hands were mounted to a custom frame where a computer-controlled, motor-driven, linear actuator powered movement of the flexor and extensor tendons. All fingers underwent 2,000 full flexion and extension cycles. Maximum interfragmentary displacement was continuously measured using a differential variable reluctance transducer. Our primary outcome was the difference in the mean P1 fragment displacement between lag and nonlag screw fixation at 2,000 cycles.
The observed differences in mean displacement between lag and nonlag screw fixation were not statistically significant throughout all time points. A two one-sided test procedure for paired samples confirmed statistical equivalence in the fragment displacement between these fixation methods at all time points, including the primary end point of 2,000 cycles.
Nonlag screws provided equivalent biomechanical stability to lag screws for simulated long oblique P1 fractures during cyclic testing in this cadaveric model.
Fixation of long oblique P1 fractures with nonlag screws has the potential to simplify treatment without sacrificing fracture stability during immediate postoperative range of motion.
Background:
The bicipital aponeurosis, or lacertus fibrosus, can potentially be used as a reconstruction graft in chronic distal biceps tendon tears.
Purpose:
To evaluate construct stiffness, load to ...failure, and failure mechanism with lacertus fibrosus versus Achilles allograft for distal biceps tendon reconstruction.
Study Design:
Controlled laboratory study.
Methods:
Ten fresh-frozen matched cadaveric pairs of elbows were used. Three centimeters of the distal biceps tendon was resected. Specimens were randomized to the lacertus fibrosus or Achilles tendon group. In one group, the lacertus fibrosus was released from its distal attachment and then tubularized and repaired intraosseously to the radius. In the other group, an Achilles tendon graft was sutured to the biceps muscle and repaired to the ulna. The prepared radii were rigidly mounted at a 45° angle on a load frame. The proximal biceps muscle was secured in a custom-fabricated cryogenic grip. Displacement was measured using a differential variable reluctance transducer mounted at the radius–soft tissue junction and in the muscle- or muscle allograft–tissue junction proximal to the repair. Specimens were loaded at 20 mm/min until failure, defined as a 3-mm displacement at the radius–soft tissue junction.
Results:
No significant difference was found in mean load to failure between the lacertus fibrosus and Achilles tendon group (mean ± SD, 20.2 ± 5.5 N vs 16.89 ± 4.54 N; P = .18). Stiffness also did not differ significantly between the lacertus fibrosus and Achilles tendon group (12.3 ± 7.1 kPa vs 10.5 ± 5.7 kPa; P = .34). The primary mode of failure in the lacertus fibrosus group was suture pullout from the tissue at the musculotendinous junction (7 of 10). In the Achilles group, failures were observed at the muscle-allograft interface (3) and the allograft-bone (radial tuberosity) interface (3), and 3 suture failures were observed. The button fixation did not fail in any specimens.
Conclusion:
The mean stiffness and load-to-failure values were not significantly different between a lacertus fibrosus construct and Achilles tendon allograft.
Clinical Relevance:
Use of the lacertus fibrosus may be a potential alternative to Achilles tendon allograft reconstruction of chronic distal biceps tears when primary repair is not possible.
Background:
Arthroscopic criteria for identifying syndesmotic disruption have been variable and subjective. We aimed to quantify syndesmotic disruption arthroscopically using a standardized ...measurement device.
Methods:
Ten cadaveric lower extremity specimens were tested in intact state and after serial sectioning of the syndesmotic structures (anterior inferior tibiofibular ligament AiTFL, interosseous ligament IOL, posterior inferior tibiofibular ligament PiTFL, deltoid). Diagnostic ankle arthroscopy was performed after each sectioning. Manual external rotational stress was applied across the tibiofibular joint. Custom-manufactured spherical balls of increasing diameter mounted on the end of an arthroscopic probe were inserted into the tibiofibular space to determine the degree of diastasis of the tibiofibular joint under each condition.
Results:
A ball 3 mm in diameter reliably indicated a high likelihood of combined disruption of the AiTFL and IOL. Disruption of the AiTFL alone could not be reliably distinguished from the intact state.
Conclusion:
Use of a spherical probe placed into the tibiofibular space during manual external rotation of the ankle provided an objective measure of syndesmotic instability. Passage of a 2.5-mm probe indicated some disruption of the syndesmosis, but the test had poor negative predictive value. Passage of a 3.0-mm spherical probe indicated very high likelihood of disruption of both the AiTFL and the IOL.
Clinical Relevance:
The findings challenge the previously used but unsupported standard of a 2-mm diastasis of the tibiofibular articulation for diagnosis of subtle syndesmotic instability.
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