Brian J. Harley

The Effect of Time to Definitive Treatment on the Rate of Nonunion and Infection in Open Fractures

Objectives To determine the association between time to definitive surgical management and the rates of nonunion and infection in open fractures resulting from blunt trauma. To determine the association of other clinical determinants with these same adverse events. Design Retrospective review of a consecutive series of open long bone fractures. Setting Referral trauma center with transport times often extending beyond eight hours from the time of injury. Patients A total of 227 skeletally mature patients with 241 open long bone fractures were treated between January 1996 and December 1998; 215 fractures were available for review at a minimum of twelve months postinjury. Intervention Medical charts of all patients were reviewed using a standardized data collection form. All available records and radiograph reports were inspected. All cases were followed to clinical and radiographic union of the fracture or until a definitive procedure for nonunion or deep infection was carried out. Main Outcome Measures Occurrence of deep infections or nonunions after fracture treatment. Results The mean time to definitive treatment was eight hours and twenty-five minutes (range 1 hour 35 minutes to 30 hours 40 minutes). Forty patients went on to nonunion, and twenty developed a deep infection. In the final multivariate regression model, time was not a significant factor in predicting either nonunion or infection (p > 0.05). The strongest determinants for nonunion were found to be presence of infection and grade of injury (p < 0.05). The strongest predictors for the development of a deep infection were fracture grade and a lower extremity fracture (p < 0.05). Conclusions The risk of developing an adverse outcome was not increased by aggressive debridement/lavage and definitive fixation up to thirteen hours from the time of injury when early prophylactic antibiotic administration and open fracture first aid were instituted.

Medial buttress versus lateral locked plating in a cadaver medial tibial plateau fracture model

Objective: To compare the mechanical stability of a medial tibial plateau fracture model secured with a lateral locking periarticular plate versus a medial buttress plate in cyclic testing and load to failure. Methods: Medial tibial plateau fractures were created in 6 matched pairs of fresh cadaveric tibias. In each pair of tibias, 1 side was randomly selected to be fixed with a lateral locking plate on 1 side and the contralateral limb to be fixed with a medial buttress plate. The fixated tibias then underwent cyclic testing followed by single-cycle failure compressive loading. Displacement of the medial tibial plateau was measured in both cyclic and failure testing. Results: Statistical analyses revealed relevant trends in fixation strength during cyclic testing, but neither the mean maximum displacement during nor mean residual displacement after cyclic testing were statistically different between the 2 fixation techniques. Statistically significant differences were observed for the mean forces to failure however. The medial buttress plate construct provided greater fixation strength with its failure force of 4136 ± 1469 N compared with the lateral locking plate mean failure force of 2895 ± 1237 N (P < 0.05). Conclusion: In the setting of a vertically oriented fracture in a medial tibial plateau without comminution, the medial buttress plate provides significantly greater stability in static loading, and a trend toward improved stability with cyclic loading. Clinical correlation is necessary to substantiate these findings.

4-Corner Arthrodesis and Proximal Row Carpectomy: A Biomechanical Comparison of Wrist Motion and Tendon Forces

PURPOSE Controversy exists as to whether a proximal row carpectomy (PRC) is a better procedure than scaphoid excision with 4-corner arthrodesis for preserving motion in the painful posttraumatic arthritic wrist. The purpose of this study was to determine how the kinematics and tendon forces of the wrist are altered after PRC and 4-corner arthrodesis. METHODS We tested 6 fresh cadaver forearms for the extremes of wrist motion and then used a wrist simulator to move them through 4 cyclic dynamic wrist motions, during which time we continuously recorded the tendon forces. We repeated the extremes of wrist motion measurements and the dynamic motions after scaphoid excision with 4-corner arthrodesis, and then again after PRC. We analyzed extremes of wrist motion and the peak tendon forces required for each dynamic motion using a repeated measures analysis of variance. RESULTS Wrist extremes of motion significantly decreased after both the PRC and 4-corner arthrodesis compared with the intact wrist. Wrist flexion decreased on average 13° after 4-corner arthrodesis and 12° after PRC. Extension decreased 20° after 4-corner arthrodesis and 12° after PRC. Four-corner arthrodesis significantly decreased wrist ulnar deviation from the intact wrist. Four-corner arthrodesis allowed more radial deviation but less ulnar deviation than the PRC. The average peak tendon force was significantly greater after 4-corner arthrodesis than after PRC for the extensor carpi ulnaris during wrist flexion-extension, circumduction, and dart throw motions. The peak forces were significantly greater after 4-corner arthrodesis than in the intact wrist for the extensor carpi ulnaris during the dart throw motion and for the flexor carpi ulnaris during the circumduction motion. The peak extensor carpi radialis brevis force after PRC was significantly less than in the intact wrist. CONCLUSIONS The measured wrist extremes of motion decreased after both 4-corner arthrodesis and PRC. Larger peak tendon forces were required to achieve identical wrist motions with the 4-corner arthrodesis compared with the intact wrist. We observed smaller forces for the PRC. CLINICAL RELEVANCE These results may help explain why PRC shows early clinical improvement, yet may lead to degenerative arthritis.

Wrist Tendon Forces With Respect to Forearm Rotation

PURPOSE Early motion therapy protocols are desirable to reduce wrist stiffness after carpal injuries and distal radius fractures. Based on our assumption that a reduction in wrist tendon forces will be associated with a reduction in radioulnar carpal joint reaction force, the goal of this study was to determine the forearm position at which the wrist tendon forces required to initiate wrist motion were the least. METHODS We tested 8 fresh-frozen cadaver forearms in a wrist and forearm motion simulator. In each specimen, we generated a wrist flexion-extension motion and a radioulnar deviation motion by pulling on the wrist flexor and extensor tendons with the forearm in supination, pronation, or neutral. We also performed a wrist flexion-extension motion during active forearm rotation. During each motion, we continuously recorded the forces in the 5 wrist tendons. We used repeated-measure analyses of variance to compare tendon forces. RESULTS During the wrist flexion-extension motion, the summed peak wrist extensor forces were significantly less with the wrist in forearm supination than with the forearm in neutral or during active forearm rotation. For the summed peak wrist flexor forces, flexor tendon forces were significantly less with the forearm in supination compared with active forearm rotation. The extensor carpi radialis longus and flexor carpi ulnaris forces were significantly less in supination than during active forearm motion. During wrist radioulnar deviation motion, peak extensor carpi ulnaris force was significantly less with the forearm in supination than in neutral, and peak flexor carpi radialis force was significantly less with the forearm in supination than in pronation. CONCLUSIONS Peak wrist tendon forces were least in the static forearm supinated position. CLINICAL RELEVANCE To reduce deforming forces on a fresh carpal injury or distal radial fracture, active rehabilitation appears to be best initiated with the forearm held in supination.

Core Decompression of the Distal Radius for the Treatment of Kienböck's Disease: A Biomechanical Study

PURPOSE The purpose of this study was to evaluate the biomechanical effect of core decompression of the distal radius for the treatment of Kienböcks disease. METHODS In 7 fresh cadaver upper extremities, axial loads were applied and the pressure in the radiocarpal joint measured using pressure-sensitive film before and after core decompression of the distal radius. RESULTS Biomechanically, the stiffness of the distal forearm statistically decreased significantly from 229.4 N/mm to 198.6 N/mm after core decompression. No or minimal changes in the distribution of the force in each radiocarpal fossa and ulnocarpal fossa, the area of contact in each fossa, and the location of the centroid of force were observed. CONCLUSIONS Core decompression of the distal radius in the setting of Kienböcks disease has been documented good clinical outcomes, yet the biomechanical analysis of this surgical technique does not demonstrate obvious unloading of the lunate.

Force Variations in the Distal Radius and Ulna: Effect of Ulnar Variance and Forearm Motion

PURPOSE To better define normal wrist joint forces during wrist motion and forearm motion at specific wrist and forearm positions and to see if there is a relationship between these forces and the amount of ulnar variance. A secondary purpose was to determine the relationship between the thickness of the articular disk of the triangular fibrocartilage complex and the amount of force transmitted through the distal ulna. METHODS Multi-axis load cells were attached to the distal radius and ulna of 9 fresh cadaver forearms. The axial radial and ulnar compressive forces were recorded while each wrist was moved through wrist and forearm motions using a modified wrist joint simulator. During each motion, the tendon forces required to cause each motion were recorded. The ulnar variance and triangular fibrocartilage complex articular disc thickness were measured. RESULTS The axial force through the distal ulna and the wrist extensor forces were greatest with the forearm in pronation. No relationship was found between the amount of force through the distal ulna and the amount of ulnar variance. A strong inverse relationship was found between the triangular fibrocartilage complex thickness and the ulnar variance. CONCLUSIONS Wrists with positive ulnar variance have generally been thought to transmit greater loads across the distal ulna, which has been felt to predispose these wrists to the development of ulnar impaction. The results of this study appear to show that all wrists have similar loading across the distal ulna regardless of ulnar variance. By comparison, pronation relatively increases loading across the distal ulna. CLINICAL RELEVANCE Because these results suggest that within reasonable ranges of ulnar variance loading across the distal ulna is independent of ulnar variance, the clinically observed incidence of ulnar impaction is more likely the result of increased wear on a thinner and less durable triangular fibrocartilage complex than due to increased distal ulna loading in ulnar positive variant wrists.

Force in the Scapholunate Interosseous Ligament During Active Wrist Motion.

PURPOSE To examine the force experienced by the scapholunate interosseous ligament (SLIL) during movements of the wrist. METHODS Six fresh-frozen cadaveric wrists were freed of soft tissue and tested in a computer controlled, servohydraulic simulator. Each wrist was tested cyclically through simulated active arcs of flexion-extension and dart throw motion. Tensile forces were recorded across the scapholunate joint with the SLIL cut through a cable placed through the scaphoid to the lunate and fixed to a force transducer external to the wrist. RESULTS The average recorded maximal tensile force across the scapholunate joint during all tested motions was 20 N. During wrist flexion-extension and the dart throw motion, SLIL force was greater at maximum extension than at maximum flexion. No significant differences among the different motions at maximum flexion or extension or for maximal force during motion were found. CONCLUSIONS Forces during the flexion-extension and dart throw motions were significantly higher in extension than in flexion. However, during simple unresisted wrist motions, the force did not exceed 20 N. CLINICAL RELEVANCE This information can be used to evaluate surgical methods used for SLIL repairs and thus provide better outcomes for patients.

Anatomy and biomechanics of the forearm interosseous membrane.

PURPOSE To examine the anatomy and function of the forearm interosseous membrane by exploring the anatomical insertions of the central band (CB) on the radius and the ulna and by quantifying the length of the intact ligament and replacement grafts located at the original CB attachment sites and alternative locations. METHODS Eight fresh cadaver forearms were supinated and pronated and the wrist was extended and flexed while the motion between the distal radius and ulna were recorded. The length of the CB was computed for the intact CB as well for several alternative graft orientations and positions. RESULTS The maximum length of the CB did not significantly change among different wrist motions. However, with the wrist in a static neutral position, the CB length was significantly shorter in forearm supination than in neutral. During active forearm rotation when CB replacement grafts were positioned distal or proximal to the original CB site, yet still parallel to it, each had a similar trend to be longer in neutral than in supination. If a graft was more transversely oriented, the computed CB length would be 1.6 mm shorter in supination than in neutral. CONCLUSIONS These results support tensioning a CB graft with the forearm in supination if the goal is to maximize graft tension and to maintain the native 22° angle for a CB graft between the radius and ulna. The results also suggest that the CB graft can probably be located slightly distal or slightly proximal to its original attachment sites. CLINICAL RELEVANCE Reconstruction of the interosseous membrane has been hampered by a lack of understanding of its length changes with forearm or wrist motion. These results provide a starting point in helping clinicians understand how to more precisely reconstruct this ligament in an anatomical manner.

Effect of Pisiform Excision or Pisotriquetral Arthrodesis as a Treatment for Pisotriquetral Arthritis: A Biomechanical Study

PURPOSE To determine whether flexor carpi ulnaris (FCU) forces and tendon displacements change after pisotriquetral arthrodesis or after pisiform excision. METHODS Nine cadaver wrists were moved through 4 variations of a dart throw motion, each having an oblique plane of motion, but with different ranges of motion and different antagonistic forces. The FCU tendon force and movement were measured in the intact wrist, following pisotriquetral arthrodesis, and following pisiform excision. Changes in force and tendon movement were compared using a repeated measures analysis of variance. RESULTS After excision of the pisiform, a significantly greater FCU force was required during the 2 variations of the dart throw motion having a larger range of motion and during the smaller motion having a larger antagonistic force. Pisotriquetral arthrodesis did not cause a significant increase in the peak FCU force. Excision of the pisiform caused the FCU tendon to significantly retract during all wrist motions as compared to the intact wrist or after pisotriquetral arthrodesis. CONCLUSIONS Greater FCU forces are required to move the wrist when the pisiform with its moment arm function has been removed. This occurs during large oblique plane wrist motions and also in a smaller motion when greater antagonistic forces are applied. Excision of the pisiform also allows the FCU to move proximally, again because its moment arm function has been eliminated. CLINICAL RELEVANCE Excision of the pisiform requires greater FCU forces during large wrist motions and during motions that include large gripping forces such that excision may be a concern in high-demand patients with pisotriquetral arthritis. Although pisotriquetral arthrodesis does not alter the mechanical advantage of the FCU, its use in high-demand patients with pisotriquetral osteoarthritis cannot yet be recommended until the effects of that arthrodesis on midcarpal kinematics are further clarified.

Structural Properties of 6 Forearm Ligaments

PURPOSE To first determine the structural properties of 6 forearm ligaments and then to create linear and nonlinear analytical models of each ligament from these properties. METHODS We nondestructively tested the annular ligament, dorsal and palmar radioulnar ligaments, and the distal, central, and proximal bands of the interosseous ligament from 7 fresh cadaver forearms in a servohydraulic testing apparatus. We performed testing with the bone-ligament-bone constructs positioned corresponding to neutral forearm rotation as well as in 45° of supination and 45° of pronation. Based on a mechanical creep test of each ligament, we computed a linear and nonlinear ligament stiffness value for each ligament. We then compared these computed analytical responses to loading with loading data when each ligament was tested at 1.0 and 0.05 mm/s. We analyzed differences among ligaments and forearm positions using 1-way and 2-way analyses of variance. RESULTS The stiffnesses for the distal band and the dorsal radioulnar ligament were statistically less when the constructs were positioned in supination compared with neutral forearm rotation. At all forearm positions, the linear stiffness of the central band was greater than that for the distal band of the interosseous ligament, the proximal band of the interosseous ligament, and the dorsal radioulnar and palmar radioulnar ligaments. In neutral forearm rotation, the linear stiffness of the central band was statistically greater than the annular ligament. The experimental loading behavior of each ligament was better modeled by a nonlinear stiffness than a linear one. CONCLUSIONS The central band of the interosseous membrane is the stiffest stabilizing structure of the forearm. Any structure used to replace the central band or other forearm ligaments should demonstrate a nonlinear response to loading. CLINICAL RELEVANCE In considering a reconstruction for the forearm, the graft used should have a nonlinear response to loading and be one that is similar to the normal, original ligament.