The Parallelogram Effect: The Association Between Central Band and Positive Ulnar Variance.

PURPOSE: Ulnar impaction syndrome is a poorly understood degenerative wrist condition characterized by symptoms of pain thought to be caused by increased loads between the ulnar head and the carpals. Radiographic evaluation often reveals an ulnar-positive wrist. We hypothesize that progressive elongation of the central band of the forearm interosseous ligaments changes the longitudinal radial-ulnar relationships, resulting in an ulnar-positive wrist. The objective of the study was to identify a relationship between the loss of integrity of the forearm interosseous ligaments and increased ulnar variance. METHODS: Six cadaveric human forearms were used to measure displacement of the radius relative to the ulna during axial loading of the lunate fossa of the radius. Radial heights were measured in supination and pronation under a 5-lbF (22-N) preload. Gradual axial loads were applied up to 50 lbF (222N); the resultant axial displacement was measured in supination and pronation. All measurements were evaluated with the interosseous ligament intact and repeated with the central band cut. RESULTS: With an applied 5-lbF preload, cutting the central band increased ulnar variance by 3.02 ± 0.80 mm in supination and by 2.15 ± 0.79 mm in pronation. In supination, when the loads were increased from the 5-lbF preload to 50 lbF, the radius displaced 2.1 times further after the central band was cut (3.00 mm) compared with the group with the intact forearm construct (1.41 mm). In pronation, when the loads were increased from the 5-lbF preload to 50 lbF, the radius displaced 1.8 times further when the central band was cut (2.84 mm) than with the intact forearm construct (1.57 mm). CONCLUSIONS: Because of a parallelogram effect, the radius shifted proximally under a 5-lbF preload, creating an ulnar-positive wrist relationship. Dynamic loading of the forearm after ligament excision resulted in significant additional radial displacement relative to the intact forearm. CLINICAL RELEVANCE: Deficiency in the ligamentous restraints of the central band leads to positive ulnar variance, which could be a factor (among others) that contributes to idiopathic ulnar impaction syndrome.

Surgical Management of Acute on Chronic Distal Radius Fractures: Correcting Malunion Deformities Through the Secondary Fracture Plane.

It is challenging to restore the clinically acceptable alignment of the distal radius after an acute on chronic fracture or after a secondary fracture occurring after malunion of a primary distal radius fracture. In cases of insignificant primary deformity, restoration to the primary deformity may suffice to obtain a successful clinical result. A borderline acceptable primary radial deformity can be unacceptable after the second injury, resulting in functional disability. If surgery is indicated, the surgeon must contend with both primary and secondary deformities to restore proper distal radius anatomy. We present our technique to correct both primary and secondary distal radius deformities through the new or secondary fracture plane.

Prevent Collapse and Salvage Failures of the Volar Rim of the Distal Radius.

Background Articular fractures of the distal radius may include a small fragment from the volar margin of the lunate fossa: volar marginal fragments (VMFs); these fragments are prone to loss of fixation and avascular necrosis, and often result in wrist subluxation. We present our experience managing acute and delayed VMFs. The first is treated using a hook plate extension to a volar locking plate and the latter using a volar opening wedge osteotomy to redistribute loads on the remaining articular surface. Materials and Methods We retrospectively reviewed the records of all patients treated at our facility with a hook plate extension for a VMF and for patients treated with a volar opening wedge osteotomy. Medical charts were examined for complications and functional results. Technique A hook plate extension was used to fix the VMF when plate buttressing was insufficient. For patients who presented a collapsed and reabsorbed VMF, a volar opening wedge osteotomy was used to reorient the articular surface, restoring joint stability. Results The hook plate extension was successful in managing 19 of the 21 acute VMFs. The volar opening wedge osteotomy provided concentric reduction and improved pain and motion in all treated patients. Conclusion We demonstrated that hook plate fixation of the VMF is an effective means of fixing the acute VMF and that a volar opening wedge osteotomy can be used to salvage a distal radius fracture with a collapsed VMF.

The EFCR Approach and the Radial Septum-Understanding the Anatomy and Improving Volar Exposure for Distal Radius Fractures: Imagine What You Could Do With an Extra Inch.

Locked volar plating is the most common surgical procedure to address distal radius fractures. The extended flexor carpi radialis approach continues to be an excellent method for visualizing distal radius fractures and applying a volar plate. A new understanding of the anatomy allows for better visualization and reduction of the many different distal radius fracture patterns surgeons commonly see. Within the extended flexor carpi radialis approach, we describe the radial septum in further detail including the anatomy which comprises the radial septum triangle. Knowledge of this area allows for better visualization, more anatomic reductions, and fewer complications.

Regional Differential Genetic Response of Human Articular Cartilage to Impact Injury.

OBJECTIVE: Normal physiological movement creates different weightbearing zones within a human knee: the medial condyle bearing the highest and the trochlea bearing the lowest weight. Adaptation to different physiological loading conditions results in different tissue and cellular properties within a knee. The objective of this study was to use microarray analysis to examine gene expression differences among three anatomical regions of human knee articular cartilage at baseline and following induction of an acute impact injury. DESIGN: Cartilage explants were harvested from 7 cadaveric knees (12 plugs per knee). A drop tower was utilized to introduce injury. Plugs were examined 24 hours after impact for gene expression using microarray. The primary analysis is the comparison of baseline versus impacted samples within each region separately. In addition, pairwise comparisons among the three regions were performed at baseline and after impact. False discovery rate (FDR) was used to evaluate significance of differential gene expression. RESULTS: In the comparison of before and after injury, the trochlear had 130 differentially expressed genes (FDR ≤ 0.05) while the condyles had none. In the comparison among regions, smaller sets of differentially expressed genes (n ≤ 21) were found, with trochlea being more different than the condyles. Most of more frequently expressed genes in trochlea are developmental genes. CONCLUSIONS: Within the experimental setup of this study, only the trochlea was displaying an acute genetic response on injury. Our data demonstrated the regional-specific response to injury in human articular cartilage.