David B. Spenciner

Biomechanical comparison of single-row arthroscopic rotator cuff repair technique versus transosseous repair technique.

This study determined the effect of tear size on gap formation of single-row simple-suture arthroscopic rotator cuff repair (ARCR) vs transosseous Mason-Allen suture open RCR (ORCR) in 13 pairs of human cadaveric shoulders. A massive tear was created in 6 pairs and a large tear in 7. Repairs were cyclically tested in low-load and high-load conditions, with no significant difference in gap formation. Under low-load, gapping was greater in massive tears. Under high-load, there was a trend toward increased gap with ARCR for large tears. All repairs of massive tears failed in high-load. Gapping was greater posteriorly in massive tears for both techniques. Gap formation of a modeled RCR depends upon the tear size. ARCR of larger tears may have higher failure rates than ORCR, and the posterior aspect appears to be the site of maximum gapping. Specific attention should be directed toward maximizing initial fixation of larger rotator cuff tears, especially at the posterior aspect.

In Vitro Evaluation of the Effect Lateral Process Talar Excision on Ankle and Subtalar Joint Stability

Background: Recent literature reflects a substantial increase in interest surrounding lateral talar process fractures. Previous anatomic investigations discovered that excision of a 1 cm3 fracture fragment from the lateral talar process involves approximately 100% of the lateral talocalcaneal ligament origin and 10% to 15% of both the posterior and anterior talofibular ligament insertions. The objective of this study was to determine the effect that excision of this 1 cm3 fragment has on ankle and subtalar joint stability. Methods: Ten fresh-frozen cadaver lower limbs were thawed before testing and placed in a clinical stress apparatus (Model SE 20, Telos, Marburg, Germany). Radiographs were taken before and after application of a 150 N of force. Three views (lateral, anteroposterior, 30-degree Bróden) were used to asses anterior tibiotalar translation (AT), talar tilt (TT), medial talocalcaneal motion (TCM), and talocalcaneal tilt (TCT) before and after excision of the 1 cm3 fragment the lateral talar process. Results: The mean increases in AT, TT, TCM and TCT after excision of the 1 cm3 fragment were: AT = 1.0 mm ± 0.94 mm (p = 0.0085); TT = 0.4 ± 0.52 degrees (p = 0.0368); TCM = 1.0 mm ± 1.25 mm (p = 0.0319); TCT = 1.2 ± 1.32 degrees (p = 0.0181). Conclusions: Since it has been generally accepted that a 3 mm increase in AT, 3-degree increase in TT, 5-mm increase in TCM, more than 5-degree increase in TCT define instability of the ankle and subtalar joints, respectively. These results suggest that excision of a 1 cm3 fragment causes neither ankle nor subtalar instability as defined by radiographic stress examination.

Proximity of the Lateral Talar Process to the Lateral Stabilizing Ligaments of the Ankle and Subtalar Joint

Background: Fractures of the lateral process of the talus have become more frequent as the sport of snowboarding has gained popularity. The anatomy of the ligamentous attachments to the process has been described, but ligament proximity to the lateral talar process has never been specified. The objective of this cadaver study was to measure the proximity of the lateral talar process to the various lateral stabilizing ligaments of the ankle and subtalar joint: the anterior talofibular ligament, lateral talocalcaneal ligament, posterior talofibular ligament, interosseous ligament, cervical ligament, and lateral root of the extensor retinaculum. Methods: After thawing, all musculotendinous structures from 10 fresh-frozen cadaver lower limbs were carefully removed and the distal fibula was reflected to enable adequate exposure of the lateral talar process and ligamentous attachments. The apex of the lateral process was defined. Subsequently, the distance from the apex to the nearest edge and center of these surrounding ligaments was independently measured by two examiners. Results: The average apex-edge distances were 9.3 mm (posterior talofibular); 8.7 mm (anterior talofibular), 3.4 mm (lateral talocalcaneal), 13.9 mm (interosseous), 19.1 mm (cervical), and 13.0 mm (lateral root of extensor retinaculum). The average apex-center distances for those ligaments found to actually insert on the lateral talar process were 18.0 mm (posterior talofibular), 15.7 mm (anterior talofibular), and 6.2 mm (lateral talocalcaneal). Conclusions: Contrary to previous reports, our cadaver dissections identified that only three ligaments attach to the lateral process of the talus: lateral talocalcaneal, anterior talofibular, and posterior talofibular. Clinical Relevance: Familiarity with these anatomic relationships may help guide the clinical treatment of lateral talar process fractures.

Cyclic Biomechanical Testing of Biocomposite Lateral Row Knotless Anchors in a Human Cadaveric Model

PURPOSE The purpose of this study was to assess the mechanical performance of biocomposite knotless lateral row anchors based on both anchor design and the direction of pull. METHODS Two lateral row greater tuberosity insertion sites (anterior and posterior) were identified in matched pairs of fresh-frozen human cadaveric shoulders DEXA (dual energy X-ray absorptiometry) scanned to verify comparability. The humeri were stripped of all soft tissue and 3 different biocomposite knotless lateral row anchors: HEALIX Knotless BR (DePuy Mitek, Raynham MA), BioComposite PushLock (Arthrex, Naples, FL), and Bio-SwiveLock (Arthrex). Fifty-two anchors were distributed among the insertion locations and tested them with either an anatomic or axial pull. A fixed-gauge loop (15 mm) of 2 high-strength sutures from each anchor was created. After a 10-Nm preload, anchors were cycled from 10 to 45 Nm at 0.5 Hz for 200 cycles and tested to failure at 4.23 mm/second. The load to reach 3 mm and 5 mm displacement, ultimate failure load, displacement at ultimate failure, and failure mode were recorded. RESULTS Threaded anchors (Bio-SwiveLock, P = .03; HEALIX Knotless, P = .014) showed less displacement with anatomic testing than did the nonthreaded anchor (BioComposite PushLock), and the HEALIX Knotless showed less overall displacement than did the other 2 anchors. The Bio-SwiveLock exhibited greater failure loads than did the other 2 anchors (P < .05). Comparison of axial and anatomic loading showed no maximum load differences for all anchors as a whole (P = .1084). Yet, anatomic pulling produced higher failure loads than did axial pulling for the Bio-SwiveLock but not for the BioComposite PushLock or the HEALIX Knotless. The nonthreaded anchor (BioComposite PushLock) displayed lower failure loads than did both threaded anchors with axial pulling. CONCLUSIONS Threaded biocomposite anchors (HEALIX Knotless BR and Bio-SwiveLock) show less anatomic loading displacement and higher axial failure loads than do the nonthreaded (BioComposite PushLock) anchor. The HEALIX Knotless BR anchor showed less displacement than did the BioComposite PushLock and Bio-SwiveLock anchors. Neither axial nor anatomic loading had an effect on overall anchor displacement. CLINICAL RELEVANCE Because of the strength profiles exhibited, this study supports the use of biocomposite anchors, which have definite advantages over polyetheretherketone (PEEK) and metal products. However, the nonthreaded BioComposite PushLock anchor cannot be recommended.