Comparison of Suture-Based Anchors and Traditional Bioabsorbable Anchors in Foot and Ankle Surgery.

We compared the pullout strength of a suture-based anchor versus a bioabsorbable anchor in the distal fibula and calcaneus and evaluated the relationship between bone mineral density and peak load to failure. Eight paired cadaveric specimens underwent a modified Broström procedure and Achilles tendon reattachment. The fibula and calcaneus in the paired specimens received either a suture-based anchor or a bioabsorbable suture anchor. The fibular and calcaneal specimens were loaded to failure, defined as a substantial decrease in the applied load or pullout from the bone. In the fibula, the peak load to failure was significantly greater with the suture-based versus the bioabsorbable anchors (133.3 ± 41.8 N versus 76.8 ± 35.3 N; p = .002). No significant difference in load with 5 mm of displacement was found between the 2 groups. In the calcaneus, no difference in the peak load to failure was found between the 2 groups, and the peak load to failure with 5 mm of displacement was significantly lower with the suture-based than with the bioabsorbable anchors (52.2 ± 9.8 N versus 75.9 ± 12.4 N; p = .003). Bone mineral density and peak load to failure were significantly correlated in the fibula with the suture-based anchor. An innovative suture-based anchor had a greater peak load to failure compared with a bioabsorbable anchor in the fibula. In the calcaneus, the load at 5 mm of displacement was significantly lower in the suture-based than in the bioabsorbable group. The correlation findings might indicate the need for a cortical bone shelf with the suture-based anchor. Suture-based anchors could be a viable alternative to bioabsorbable anchors for certain foot and ankle procedures.

Biomechanical characteristics of hemi-hamate reconstruction versus volar plate arthroplasty in the treatment of dorsal fracture dislocations of the proximal interphalangeal joint.

PURPOSE: To compare stability and range of motion after hemi-hamate reconstruction versus volar plate arthroplasty in a biomechanical proximal interphalangeal (PIP) joint fracture-dislocation model. METHODS: Eighteen digits from 6 cadaver hands were tested. We created defects of 40%, 60%, and 80% in the palmar base of each digit's middle phalanx, simulating an acute PIP joint fracture-dislocation. Each defect scenario was reconstructed with a hemi-hamate arthroplasty followed by a volar plate arthroplasty. A computer-controlled mechanism was used to bring each digit's PIP joint from full extension to full flexion via the digital tendons in each testing state, and in the intact state. During each testing scenario we collected PIP joint cinedata in a true lateral projection using mini-fluoroscopy. A digital radiography program was used to measure the amount of middle phalanx dorsal translation (subluxation) in full PIP joint extension. We recorded the angle at which subluxation, if present, occurred during each testing scenario. RESULTS: Average dorsal displacement of the middle phalanx in relation to the proximal phalanx was 0.01 mm for the hemi-hamate reconstructed joints and -0.03 mm for the volar plate arthroplasty, compared with the intact state. Flexion contractures were noted in each of the specimens reconstructed with volar plate arthroplasty. Degree of contracture was directly correlated with defect size, averaging 20° for 40% defects, 35° for 60% defects, and 60° for 80% defects. We observed no flexion contractures in the hemi-hamate reconstructions. CONCLUSIONS: Surgeons can use both hemi-hamate and volar plate arthroplasty to restore PIP joint stability following a fracture dislocation with a large middle phalanx palmar base defect. Use of volar plate arthroplasty led to an increasing flexion contracture as the middle phalanx palmar base defect increased. CLINICAL RELEVANCE: Clinicians can use the information from this study to help with surgical decision-making and patient education.

Stability of acute dorsal fracture dislocations of the proximal interphalangeal joint: a biomechanical study.

PURPOSE: We performed a cadaveric biomechanical study to characterize proximal interphalangeal joint stability after an injury to different amounts of the volar articular base of the middle phalanx (intact, 20%, 40%, 60%, and 80% volar defects). METHODS: Eighteen digits on 6 hands were tested through full proximal interphalangeal joint range of motion using computer-controlled flexion and extension via the digital tendons. We collected proximal interphalangeal joint kinematic cine data in a true lateral projection with mini-fluoroscopy. We measured the amount of dorsal middle phalanx translation in full proximal interphalangeal joint extension. As we cycled the joint from full flexion into extension, we recorded the angle at which subluxation occurred. RESULTS: No specimens with 20% volar bony defect subluxated. All specimens in the 60% and 80% groups subluxated at an average flexion angle of 67° (range, 10° to 90°) in the 60% group and at all degrees of flexion in the 80% group. In the 40% group, 28% of specimens demonstrated subluxation at an average flexion angle of 14° (range, 4° to 40°). Mean dorsal translation of the middle phalanx in relation to the proximal phalanx at full digital extension was 0.2 mm in the 20% group, 0.8 mm in the 40% group, 3.2 mm in the 60% group, and 3.1 mm in the 80% group. CONCLUSIONS: Simulated volar articular bony defects of 20% were stable, whereas those with 60% and 80% defects were unstable during digital motion. Stability in the 40% group was variable and appeared to be the threshold for stability. CLINICAL RELEVANCE: Knowledge of the typical amount of middle phalanx defect and degree of proximal interphalangeal joint extension that can lead to joint instability may improve management of mechanically important proximal interphalangeal joint fracture dislocations.

The biomechanical stability of salvage procedures for distal radioulnar joint arthritis.

PURPOSE: To test distal forearm stability after 3 surgical procedures for distal radioulnar joint (DRUJ) arthritis. METHODS: We tested 11 cadaver limbs with the DRUJ intact, after distal ulna-matched hemiresection, after Darrach distal ulna resection, and after unlinked total DRUJ arthroplasty. We evaluated distal forearm stability in neutral rotation, full pronation, and full supination in unweighted and 1-kg-weighted conditions. We measured dorsal/palmar translation and convergence/divergence of the distal radius relative to the ulna. RESULTS: Under neutral rotation, whether weighted or unweighted, matched hemiresection and Darrach specimens demonstrated significant radioulnar convergence relative to intact specimens. Weighted and unweighted, DRUJ arthroplasty demonstrated similar radioulnar convergence to intact. Weighted and unweighted, only Darrach specimens showed significant radius-palmar translation compared with intact, hemiresected, and DRUJ arthroplasty. In pronation, no testing scenario, either weighted or unweighted, demonstrated statistically significant radioulnar convergence relative to intact state. In unweighted pronation, palmar translation of the radius was significantly different from the intact state for all surgical scenarios and the Darrach was significantly worse than the other procedures. In weighted pronation, palmar translation of the radius was significantly different from the intact state for all surgical scenarios and the matched hemiresection was significantly better than the other procedures. In supination, weighted and unweighted, Darrach specimens had significant radioulnar convergence relative to intact. Either weighted or unweighted, the hemiresection and arthroplasty groups demonstrated similar radioulnar convergence relative to intact. Unweighted, all scenarios demonstrated similar dorsal translation of the radius. Weighted, the Darrach group showed significant radius-dorsal translation relative to intact specimens. CONCLUSIONS: For tested procedures, DRUJ arthroplasty overall was biomechanically superior to the other conditions except that we found greater stability in the hemiresected group in weighted pronation. CLINICAL RELEVANCE: Knowledge of baseline biomechanical characteristics of DRUJ arthritis procedures will aid surgical decision-making and patient counseling.

The effect of distal radius translation in the coronal plane on forearm rotation: a cadaveric study of distal radius fractures.

PURPOSE: To determine the effect of lateral translation of the distal radius in the coronal plane on forearm rotation after distal radius fracture. METHODS: Ten fresh cadaveric limbs underwent distal radius osteotomy just proximal to the distal radial-ulnar joint to simulate an extra-articular distal radius fracture. We used an Agee Wrist Jack external fixator to create increasing magnitudes of distal fragment lateral translation in 2-mm increments. Forearm rotation was measured using a 3-dimensional camera at each magnitude of lateral translation. RESULTS: Total forearm rotation for the intact specimen and 2, 4, 6, and 8 mm (maximal) radial translations was 186° ± 53°, 188° ± 54°, 189° ± 55°, 190° ± 57°, and 193° ± 59°, respectively. There was no significant difference for any magnitude of radial translation. The average maximal radial translation possible before radioulnar abutment was 8 ± 0.5 mm. CONCLUSIONS: In this cadaveric model, translation of the distal radius fragment in the lateral direction had no effect on forearm rotation. CLINICAL RELEVANCE: At the level of the proximal border of the distal radioulnar joint, isolated distal radius translation does not significantly affect forearm rotation.

Distribution of Subchondral Bone Puncture Strength in the Talus and Tibial Plafond: A Biomechanical Study.

We investigated talus and tibial plafond subchondral bone puncture strength based on surface location. Puncture tests of the subchondral bone were performed in 9 equal zones on the articular surface of 12 cadaver specimens aged 49.1 years (range, 36-56 years). Compressive load was applied through a microfracture awl at 2 mm/min. Puncture strength was defined as the first load drop in load-deflection curves. In the talus, zone 1 (215 ± 91 N) and zone 2, the anterior medial and anterior middle zones, had significantly greater puncture strength than zones 7, 8, and 9, the posterior medial, middle, and lateral zones (104 ± 43 N, 115 ± 43 N, and 102 ± 35 N, respectively; P < .001). In the tibial plafond, zone 3, the anterior-lateral zone, and zone 7, the posterior medial zone, had significantly greater strength than zone 8, the posterior middle zone (202 ± 72 N, 206 ± 121 N, and 112 ± 65 N, respectively; P < .001) These results suggest that the subchondral bone is significantly weaker to penetrative force in the posterior region than in the anterior region of the talar dome and of the tibial plafond. These findings may have implications for microfracture awl design and for understanding the complex anatomy and physiology of the ankle joint. LEVELS OF EVIDENCE: Controlled laboratory study.

Cadaveric Investigation of Active Finger Range of Motion for Detection of Intratendinous Needle Placement.

BACKGROUND: The authors' purpose was to determine if investigators can predict whether a needle is within a finger's flexor tendon by postinsertion tactile and visualization evaluation in an active range-of-motion cadaver model. METHODS: In 48 cadaver fingers, a 25-gauge needle, with a 1-cc syringe attached, was placed into one of three randomly assigned positions at the A2 pulley level: within the flexor digitorum profundus, within the flexor digitorum superficialis, or outside both flexors and the sheath. Each finger was cycled through full active range of motion as three hand surgeons, blinded to each other's responses and needle position, recorded whether they thought the needle was intratendinous. The initial investigator confirmed needle position after each surgeon's assessment. RESULTS: Active cadaver finger range of motion did not allow surgeons to accurately determine whether a needle was in a flexor tendon. There was no statistically significant agreement among the surgeons about whether the needle was intratendinous. CONCLUSION: Because of poor interobserver agreement, sensitivity, and negative predictive value, we conclude that finger range of motion is not a reliable test to detect intratendinous needle placement in this cadaver model.

Olecranon tip osteoarticular autograft transfer for irreparable coronoid process fracture: a biomechanical study.

BACKGROUND: We hypothesized that transfer of the olecranon tip for simulated type III coronoid fracture would restore posterior ulnohumeral translation to a level not different from that in the intact state. METHODS: The collateral ligaments were left intact in 12 fresh-frozen cadaveric elbows, and all other soft tissues were removed. The entire coronoid process was osteotomized flush with the ventral aspect of the ulna and was reconstructed using the tip of the olecranon process. Specimens were tested with an axial load of 100 N at 0.25 mm/s in 15° increments from 15 to 120° of flexion. Intact, osteotomized, and reconstructed posterior ulnohumeral displacement was measured. RESULTS: The bony reconstruction did not obstruct range of motion of the elbow. Intact translation (mean ± SD) ranged from 0.3 ± 0.1 to 1.1 ± 0.6 mm, and translation in the osteotomized state ranged from 1.3 ± 1.0 to 2.0 ± 1.0 mm. Resection of the coronoid resulted in a significant increase in posterior ulnar translation compared with intact at all flexion angles (p < 0.05) except at 75°. Reconstruction decreased translation versus the osteotomized state at all flexion angles, significantly at 60 and 120°. No significant difference in translation was found between reconstructed and intact states at five of eight positions tested. CONCLUSIONS: In this biomechanical study of irreparable coronoid fracture, autograft olecranon tip transfer restored posterior elbow stability to a level not significantly different from the intact elbow in five of eight elbow positions tested.

Glenohumeral pressure with surface replacement arthroplasty versus hemiarthroplasty.

It is not known whether significant differences in the glenohumeral center of pressure and contact pressure exist between surface replacement arthroplasty and hemiarthroplasty compared with the native joint. Twelve fresh-frozen cadaveric shoulders were dissected free of soft tissue, and the joint capsule was removed. The scapula was potted with the glenoid parallel to the ground. A pressure-sensitive sensor was placed in the glenohumeral joint, and each specimen was tested in sequence: intact, surface replacement, and hemiarthroplasty. Loading was done with a 440-N compression load at 0.5 Hz with the shoulder in 4 different positions. The center of pressure and contact pressure were measured at each position. The glenohumeral contact pressure with surface replacement was not different from intact pressure in 2 arm positions. Pressure with hemiarthroplasty was significantly different compared with the intact shoulder at all 4 arm positions and compared with the surface replacement group at 2 arm positions (P≤.05). Change in the anterior-posterior center of pressure from intact was significantly smaller with surface replacement compared with hemiarthroplasty with the humerus at 0° flexion/0° abduction and at 0° flexion/90° abduction (1.11±0.89 mm vs 2.38±1.62 mm, P=.02, and 0.68±0.50 mm vs 2.37±2.0 mm, P=.01, respectively). Change in the superior-inferior center of pressure was significantly smaller with surface replacement vs hemiarthroplasty at 0° flexion/0° abduction and at 90° flexion/90° abduction (0.98±1.16 mm vs 2.33±1.38 mm, P=.02, and 1.50±1.28 mm vs 2.90±1.92 mm, P=.04, respectively). Compared with hemiarthroplasty, surface replacement arthroplasty more closely replicated the contact pressure and center of pressure in the intact glenohumeral joint.