Fragment-specific volar hook plate for volar marginal rim fractures.

The volar lunate facet/volar marginal rim fragment of distal radius fractures is a challenging problem for current volar plating systems to adequately maintain internal fixation. Fragment-specific wireforms and other constructs can be used to capture these difficult fragments but are difficult to place and have limited resistance to bending and axial load. Fixed-angle volar plates have limited distal translation without increasing the risk of flexor tendon rupture. Failure to reduce and maintain reduction of these volar ulnar intra-articular distal marginal rim fractures result in disastrous volar carpal subluxation. We present an alternative surgical technique using a low-profile volar hook plate designed specifically to address this fragment. The first 6 cases are presented here with no observed surgical complications to date.

Scapholunate ligament reconstruction using an acellular dermal matrix: a mechanical study.

PURPOSE: Numerous surgical techniques have been described for the treatment of chronic scapholunate ligament instability. We hypothesized that scapholunate ligament reconstruction using an acellular dermal matrix was biomechanically comparable to previously described surgical reconstructions. METHODS: The scaphoid and lunate with the entire scapholunate ligament were harvested from 15 cadaveric specimens. The scapholunate ligament was transected and reconstructed using an acellular dermal matrix (Arthroflex; LifeNet Health, Virginia Beach, VA) and 4 micro suture anchors in 10 specimens. Five specimens were kept with the native scapholunate ligament intact. Five other specimens were reconstructed using a 1.0-mm-thick dermal matrix, and a second cohort of 5 specimens was reconstructed using a 1.5-mm-thick matrix. Tensile testing of all specimens was performed using a servohydraulic material testing system and data acquisition software. The tensile test apparatus applied a distractive load of 10 mm/min (0.17 mm/s) until the specimens reached ultimate failure. Failure force, failure displacement, stiffness, and energy to failure were calculated. RESULTS: All 5 specimens in the intact group failed at the scapholunate ligament midsubstance. The mean ultimate failure force was 172 N, with mean stiffness of 74 N/mm. In the reconstruction group with 1.0-mm dermal matrices, the mode of failure was at the suture-matrix interface in all specimens, whereas the 1.5-mm dermal matrix reconstruction cohort all failed at the bone-suture anchor interface. In the 1.0-mm reconstruction group, the mean ultimate failure force was 77 N, with mean stiffness of 24 N/mm. In the 1.5-mm dermal matrix reconstruction cohort, the mean ultimate failure force was 111 N, with mean stiffness of 30 N/mm. CONCLUSIONS: Scapholunate ligament reconstruction using acellular dermal matrix and suture anchors demonstrated similar biomechanical properties to previously described reconstruction techniques. CLINICAL RELEVANCE: Scapholunate ligament reconstruction using acellular dermal matrix warrants clinical investigation as a potential treatment alternative for chronic scapholunate instability.

The reproducibility and repeatability of varus stress radiographs in the assessment of isolated fibular collateral ligament and grade-III posterolateral knee injuries. An in vitro biomechanical study.

BACKGROUND: Objective measures to quantitate the amount of lateral compartment opening for patients with lateral and posterolateral knee injuries have not been well documented. The purpose of the present study was to measure lateral compartment opening secondary to applied varus stresses following posterolateral corner structure sectioning and to develop radiographic guidelines to quantify the amount of lateral compartment gapping seen with these injuries. METHODS: Ten nonpaired fresh-frozen cadaver lower extremities were used. Two varus loads, a 12-Nm moment and a clinician-applied varus stress, were applied to the intact knees and after sequential sectioning of the fibular collateral ligament, popliteus tendon, popliteofibular ligament, and anterior and posterior cruciate ligaments to simulate degrees of posterolateral knee and associated combined cruciate ligament injuries. The shortest distance between the most distal subchondral bone surface of the lateral femoral condyle and the corresponding lateral tibial plateau was measured to quantify lateral compartment opening and was analyzed on digital radiographs. Three observers were used to determine interobserver reproducibility and intraobserver repeatability. RESULTS: In the intact knee, the mean lateral compartment gapping due to a 12-Nm moment and a clinician-applied varus stress was 8.9 and 9.7 mm, respectively. Lateral gapping significantly increased by 2.1 and 2.7 mm in association with sectioning of the fibular collateral ligament and by 3.4 and 4.0 mm in knees with a simulated posterolateral corner injury for each respective load-application technique (p < 0.0001 for all comparisons). Intraobserver repeatability was high, with all observers independently obtaining an intraclass correlation coefficient of 0.99, whereas the analysis of interobserver reproducibility demonstrated an intraclass correlation coefficient of 0.97. CONCLUSIONS: Measurements with use of current clinical digital imaging systems can be used to quantify the amount of lateral compartment knee opening. Clinicians should suspect an isolated fibular collateral ligament injury if opening on clinician-applied varus stress radiographs increases by approximately 2.7 mm and a grade-III posterolateral corner injury if values increase by approximately 4.0 mm. CLINICAL RELEVANCE: Varus stress radiographs appear to provide an objective and reproducible measure of lateral compartment gapping that should prove useful for the diagnosis, management, and postoperative follow-up of patients with fibular collateral ligament and posterolateral knee injuries.