No difference in torque load to failure between split anconeus fascia transfer and autograft palmaris longus tendon for reconstruction of the lateral ulnar collateral ligament.

Background: The split anconeus fascia transfer (SAFT) is an option for reconstruction of the lateral ulnar collateral ligament (LUCL) in chronic posterolateral rotatory instability (PLRI) of the elbow with potential advantages of using only local tissue within the surgical exposure and not requiring ulnar fixation. This study aimed to assess SAFT strength compared to a traditional free graft reconstruction in a PLRI biomechanical model. Methods: To measure biomechanical strength, eight cadaveric upper extremity pairs were utilized. Within each pair, one specimen was randomly assigned to LUCL reconstruction with autograft palmaris longus and the other to SAFT reconstruction. Torque load to failure was assessed on a load frame with the elbow in 30 degrees of flexion, 5 degrees of valgus, and 25 N axial load as the elbow was brought into external rotation. Torque load to failure was compared between the two reconstruction techniques. Results: No difference was found in the torque load to failure between SAFT specimens compared to palmaris longus autograft specimens (mean 14.6 ± 4.4 Nm vs. mean 11.3 ± 3.9 Nm; P = .16). Discussion: In this biomechanical study, the SAFT LUCL reconstruction provided torque load to failure similar to that of the traditional technique. These findings suggest that the SAFT technique warrants continued study as a biomechanically sound option for LUCL reconstruction in the setting of elbow PLRI.

The Relationship Between Hemihamate Graft Size and Proximal Interphalangeal Joint Flexion for Reconstruction of Fracture-Dislocations: A Biomechanical Study.

PURPOSE: The purpose of this study was to determine the relationship between hemihamate graft size and proximal interphalangeal (PIP) joint flexion in a biomechanical fracture-dislocation model. METHODS: We simulated middle finger PIP fracture-dislocations in 5 cadaver hands by resecting 50% of the palmar articular surface of the middle phalanx (P2) base. Fluoroscopy was used to confirm dorsal subluxation of the middle phalanx base after resection. A 10-mm osteochondral hamate graft was contoured to reconstruct the volar lip of the middle phalanx and was progressively downsized by 2-mm increments for each trial. A computer-controlled articulator and jig simulated active flexion and extension of the fingers. Maximum PIP flexion was measured at each graft size using fluoroscopy and digital imaging software. Clinically significant flexion block was defined as PIP flexion less than 90°. RESULTS: The actual mean size of the volar defect created was 52% (3.5 mm) of the middle phalanx articular surface, which created instability and dorsal subluxation in all tested fingers. After hemihamate reconstruction, all specimens were stable throughout flexion and extension for all graft sizes. A flexion block of 90° occurred at a mean graft size of 191% of the defect (6.5 mm). With regard to the volar lip of the P2, grafts that projected an average 0.8 mm past the native volar lip position had 98° (range, 84°-107°) maximum PIP flexion. Grafts that projected an average of 3.1 mm past the native volar lip position had 90° (range, 69°-100°) maximum PIP flexion. Linear regression modeling incorporating all of the results predicted flexion block to occur at a graft size as small as 166% of the 50% volar P2 defect. In this model, for every 50% (1.7-mm) increase in graft size relative to the defect, PIP flexion decreased by approximately 6°. CONCLUSIONS: Nonanatomical hemihamate grafts produce a PIP flexion block at extreme sizes, predicted to occur at greater than 166% of a 50% P2 base articular defect in our model. This suggests that relatively large grafts can be used for reconstruction of PIP fracture-dislocations without substantial biomechanical block to PIP flexion. We suggest sizing no larger than 3 mm past the native P2 volar lip position to avoid an important mechanical block to PIP flexion. CLINICAL RELEVANCE: The information from this study helps surgeons understand how large a hemihamate graft can be used for P2 volar base reconstruction before having a negative impact on PIP flexion.

Suture-Button Reconstruction of the Interosseous Membrane.

BACKGROUND: Reconstruction of the interosseous membrane (IOM) may play a role in the treatment of acute and chronic longitudinal forearm instability. Several reconstruction techniques have been proposed. Suture-button reconstruction is attractive because it obviates donor site morbidity and is relatively easy to perform. How this method compares to its alternatives, however, is unknown. MATERIALS AND METHODS: We review literature describing reconstruction of the forearm axis. We describe how we perform suture-button reconstruction of the IOM, summarize our previously published biomechanical data on the subject, and offer a case report. DESCRIPTION OF TECHNIQUE: A suture-button is implanted so as to approximate the course of the interosseous ligament. This may be accomplished percutaneously, or when grafting is desired, through an open approach. RESULTS: Data informing the choice of one reconstruction technique over another consist mostly of biomechanical studies and a small number of case reports. CONCLUSIONS: Suture-button reconstruction of the IOM may encourage anatomic healing of acute forearm axis injuries especially as an adjunct to radial head replacement or repair. Chronic injuries may benefit from a combination suture-button graft construct and ulnar shortening osteotomy.

The effect of operative technique on ulnar nerve strain following surgery for cubital tunnel syndrome.

BACKGROUND: The aim of this study is to compare the amount of strain on the ulnar nerve based on elbow position after in situ release, subcutaneous transposition, submuscular transposition, and medial epicondylectomy. METHODS: Six matched cadaver upper extremity pairs underwent ulnar nerve decompression, transposition in a sequential fashion, while five elbows underwent medial epicondylectomy. A differential variable reluctance transducer (DVRT) was placed in the ulnar nerve. An in situ release, a subcutaneous transposition, and a submuscular transposition were performed sequentially with the strain being measured after each procedure in neutral, full elbow flexion, and extension positions. The strain was then averaged and compared for each procedure. Five cadavers underwent medial epicondylectomy and were similarly tested. RESULTS: After the in situ release, there was no statistically significant change in strain in either flexion or extension. After a subcutaneous transposition, there was a statistically significant decrease in strain in full elbow flexion but not in extension. Similarly after a submuscular transposition, there was a statistically significant decrease in strain in full flexion but not in extension. There was not a statistically significant change in strain with medial epicondylectomy. CONCLUSION: An in situ release of the ulnar nerve at the elbow may relieve pressure on the nerve but does not address the problem of strain which may be the underlying pathology in many cases of ulnar neuropathy at the elbow (UNE). Transposition of the ulnar nerve anterior to the medial epicondyle addresses the problem of strain on the ulnar nerve. In addition, it does not create an increased strain on the ulnar nerve with elbow extension.

A biomechanical comparison of volar locked plating of intra-articular distal radius fractures: use of 4 versus 7 screws for distal fixation.

PURPOSE: To determine whether the number of distal locking screws significantly affects stability of a cadaveric simulated distal radius fracture fixed with a volar locking plate. METHODS: We created AO/ASIF type C2 fractures in 10 matched pairs of human fresh-frozen cadaveric wrists and then fixed them using volar locking plates. The number of distal locking screws used was 4 screws or 7 screws in each wrist of the matched pair. We loaded the stabilized fractures cyclically to simulate 6 weeks of postoperative stressing during a therapy protocol and then loaded them to failure. Failure was defined as 2 mm or more of displacement of any fracture fragment as recorded by differential variable reluctance transducers. RESULTS: No wrists failed during the cyclic loading portion for either the 4- or 7-screw construct. The average initial stiffness of the 7-screw construct was 69 N/mm (± 38) versus 48 N/mm (± 14) for the 4-screw construct. The average failure load for the 7-screw construct was 139 N (± 78) versus 108 N (± 18) for the 4-screw construct. Neither of these differences was statistically significant. CONCLUSIONS: Although there was a trend toward increased initial stiffness and higher failure load in fractures fixed distally with 7 locking screws, the results were not statistically significant compared with fractures fixed with only 4 screws. Both constructs can withstand forces likely encountered in early therapy protocols. CLINICAL RELEVANCE: The use of extra distal locking screws when fixing distal radius fractures increases expense and may increase the risk of complications, such as extensor tendon irritation or rupture.

Ulnar artery thrombosis associated with anomalous hypothenar muscle.

Ulnar artery thrombosis should be considered in patients presenting with cold intolerance or ischemia of the small and ring fingers, or a mass in the hypothenar area. Frequently this diagnosis is associated with a history of repetitive blunt trauma to the ulnar hand, thereby traumatizing the ulnar artery in Guyon's canal. This report presents a case of ulnar artery thrombosis associated with an abnormal muscle originating on the palmar antebrachial fascia, traversing volar to the ulnar artery and nerve, and inserting on the ulnar border of the abductor digiti minimi. This muscle is an abductor digiti minimi accessorius.

Cross-sectional anatomy of the bicipital tuberosity and biceps brachii tendon insertion: relevance to anatomic tendon repair.

This study evaluated the insertional anatomy and orientation of the biceps tuberosity and tendon to assess the anatomic validity of repairs made with 1 incision vs 2 incisions. Computed axial tomography was used to image 30 cadaver radii, and each tendon insertion was measured with a digital micrometer. Specimens were sectioned and imaged with Faxitron radiography (Faxitron X-Ray Corp, Wheeling, IL) to determine the angular orientation of the biceps tendon insertion relative to the tuberosity apex. The tuberosity axis of orientation averaged 65 degrees (range, 15 degrees -120 degrees ) of pronation from anterior, with angular orientation encompassing a mean 59 degrees (range, 15 degrees -100 degrees ) arc with the midpoint of the insertion averaging 50 degrees (range, -5 degrees to 105 degrees ). Most biceps tendons inserted on the anterior aspect of the apex of the tuberosity, with an average width of 7 mm and length of 22 mm. The biceps tuberosity is oriented in more pronation than is typically described, prohibiting anatomic reinsertion of the tendon in 35% of specimens with current single-incision techniques.

Lesions and tumors of the carpus.

Lesions and tumors of the carpus are usually identified radiographically during a routine workup for wrist pain. Although most of these entities are benign, a failure to appreciate their presence may delay diagnosis and treatment. More importantly, a small subset of these tumors may be quite aggressive, and early recognition can spare the patient the morbidity of late sequelae such as pathologic fracture, progressive wrist arthrosis, or even tumor metastasis. This article provides current information on how to identify, differentiate, and treat the varied lesions and tumors that may be discovered in the carpus.

Nerve tumors of the hand and upper extremity.

Tumors of peripheral nerve origin are usually slow growing and minimally symptomatic, making differentiation from other soft tissue neoplasms difficult. Yet failure to recognize a nerve tumor may result in irreversible loss of neurologic function. This article provides current information on the history, pathologic identification, and treatment of upper extremity nerve tumors. Other neoplastic and tumor-like lesions that occur within the peripheral nerve are also considered.