Biomedical subjects
Publications and source records attributed to Scott W Wolfe.
The motion of the eight carpal bones is extremely complex, and their accurate measurement has been hampered by their multiplanar rotations and translations, the irregularity of their shape, and the small magnitudes of movements. However, an accurate three-dimensional understanding of carpal motion is critical for academic and clinical purposes, and may play an important role in assessing surgical procedures or rehabilitation protocols.
PURPOSE: To investigate the elongation of the palmar and dorsal subregions of the scapholunate interosseous ligament (SLIL) in healthy human subjects throughout a complete range of wrist motion. METHODS: The 3-dimensional in vivo kinematics of the scaphoid and lunate were determined in both wrists of 13 female and 13 male volunteers from computed tomography volume images. For each wrist the palmar and dorsal insertions of the SLIL were identified on reconstructed surface models of the scaphoid and lunate. The interbone distances between the palmar and dorsal sites were calculated for the neutral wrist position. Elongations were then calculated after applying the 3-dimensional kinematics to the scaphoid and lunate. A multiple linear regression model was used to determine if elongations varied significantly as a function of wrist flexion/extension and radioulnar deviation. RESULTS: From pure wrist extension to pure wrist flexion, the fibers of the SLIL at the palmar insertion site increased significantly, from 29% shortening to 27% elongation, and the dorsal insertion decreased from 26% to 4% shortening with respect to the fiber lengths in the neutral position. From pure radial deviation to pure ulnar deviation, the elongation of the palmar insertion significantly decreased from 9% elongation to 21% shortening. There was no notable change in dorsal elongation with wrist radioulnar deviation. The multiple linear regression model predicted that there would be minimal elongation of the palmar and dorsal fibers at the wrist position along the dart thrower's path from radial extension to ulnar flexion. CONCLUSIONS: In vivo elongation of the palmar and dorsal fibers of the SLIL varied with wrist position. The palmar fibers lengthened and the dorsal fibers shortened with wrist flexion and the opposite occurred with wrist extension. Scapholunate interosseous ligament elongation was minimal as the wrist was positioned along the dart thrower's path.
Atypical hand infections with Mycobacterium species are uncommon, and Mycobacterium scrofulaceum infections are rare. We present a case of flexor tenosynovitis caused by M scrofulaceum in a 66-year-old man with hypertension and diabetes.
The incidental finding of an aberrant wrist flexor is reported. This anomalous muscle was identified during surgical reconstruction for a distal radius fracture malunion. Distal and proximal dissection showed an independent, well-formed muscle belly with no interconnections to adjacent structures. A review of the literature yielded a report of these findings in cadaveric specimens; here we give a description in a living person.
Kinematic analysis has shown a near-stationary proximal carpal row during the dart-thrower's motion, which is believed to provide a stable platform for the generation of force and accuracy during certain power and precision grip activities. This finding is consistent with evidence in the human hand of adaptations that enabled effective manipulation of stones, cylindric wood, and bone tools for throwing and clubbing. There are at least two possible explanations for the observed human proximal carpal row kinematics. One is that it is retained from a previous common ancestor with great apes and previously adapted to some form of foraging or locomotor behavior involving the hands, but was recruited for tool use after we diverged from the apes. The second is that it evolved after our divergence from apes, in synchrony with adaptations in the human hand to the manipulation of tools, and central to the development of the human's unique ability to aim and accelerate tools and weapons.
Brachial plexus injuries are devastating and usually result from high-energy trauma in young patients. Clinicians treating brachial plexus injuries need to recognize the pattern of injury presenting in each patient. Most injuries can be described as either supraclavicular or infraclavicular. The specific injury is determined by means ofa precise workup, including careful physical examination, electrodiagnostic studies, and imaging studies; a thorough workup is essential for successful preoperative planning. Priorities need to be identified and matched with available resources in each patient. A growing number of good treatment alternatives are available. Finally,counseling patients toward realistic expectations isa critical component of preparation for surgery.
Many of the principles of flexor tendon repair and rehabilitation can be applied to zones III-V. Injuries in zones III-V are rarely isolated and neurovascular involvement is common. Because of the often extensive and unknown degree of injury, there should be a low threshold for surgical wound exploration. Primary repair of injured tendons and neurovascular structures is recommended by way of a systematic approach. Good to excellent outcomes in range of motion and tendon function can be expected; however, functional outcomes of associated nerve injuries are varied, with younger patients generally demonstrating the best results (Fig. 2E).
PURPOSE: The use of intraoperative fluoroscopy in hand surgery is common. Two types of fluoroscopic units are available: the mini C-arm and the standard C-arm. There is little literature on the radiation exposure from the mini C-arm, therefore, the primary goal of this study was to quantify and compare the amount of radiation exposure to members of the surgical team (surgeon, first assistant, nurse, anesthesiologist) using both standard and mini C-arms in a simulated wrist surgery setup. Mini C-arm positioning was also examined to determine the safest configuration to minimize radiation exposure to surgeons. METHODS: Radiation dosimeters were used to test 2 commercially available fluoroscopy units in a simulated wrist surgery setup with a cadaveric upper extremity. Several different configurations of the C-arms were tested to determine radiation exposure rates to surgeons and the operating room staff. RESULTS: The mean in-beam radiation exposures with the use of the mini and standard C-arms were 3,720 mR/h and 6,540 mR/h, respectively. The mini C-arm had universally less radiation exposure than the standard C-arm in the clinical configurations tested. The safest configuration of mini C-arm use to minimize radiation exposure was with the surgeon standing on the image intensifier side of the unit as compared with the source side. Mini C-arm radiation exposure to the hands, groin, chest, and thyroid of the operating surgeons were well below the National Council of Radiation Protection and Measurement's annual dose limits. CONCLUSIONS: In the clinical configurations tested in this study the mini C-arm had lower radiation exposures than the standard C-arm. To reduce radiation exposure maximally surgeons should stand behind the lead-encased image intensifier and should use techniques to reduce exposure.
BACKGROUND: Wrist motion is dependent on the complex articulations of the scaphoid and lunate at the radiocarpal joint. However, much of what is known about the radiocarpal joint is limited to the anatomically defined motions of flexion, extension, radial deviation, and ulnar deviation. The purpose of the present study was to determine the three-dimensional in vivo kinematics of the scaphoid and lunate throughout the entire range of wrist motion, with special focus on the dart thrower's wrist motion, from radial extension to ulnar flexion. METHODS: The three-dimensional kinematics of the capitate, scaphoid, and lunate were calculated from serial computed tomography scans of both wrists of fourteen healthy male subjects (average age, 25.6 years; range, twenty-two to thirty-four years) and fourteen healthy female subjects (average age, 23.6 years; range, twenty-one to twenty-eight years), which yielded data on a total of 504 distinct wrist positions. RESULTS: The scaphoid and lunate primarily flexed or extended in all directions of wrist motion, and their rotation varied linearly with the direction of wrist motion (R2= 0.90 and 0.82, respectively). Scaphoid and lunate motion was significantly less along the path of the dart thrower's motion than in any other direction of wrist motion (p < 0.01 for both carpal bones). The scaphoid and lunate translated radially (2 to 4 mm) when extended, but they did not translate appreciably when flexed. CONCLUSIONS: The dart thrower's path defined the transition between flexion and extension rotation of the scaphoid and lunate, and it identified wrist positions at which scaphoid and lunate motion approached zero. These findings indicate that this path of wrist motion confers a unique degree of radiocarpal stability and suggests that this direction, rather than the anatomical directions of wrist flexion-extension and radioulnar deviation, is the primary functional direction of the radiocarpal joint.
Surgical indications for the treatment of distal radial fractures are evolving. It is important to identify the various articular fragments and their significance to facilitate optimal surgical treatment of these fragments from the standpoint of both internal and external fixation. New techniques in the visualization and stabilization of the articular surface and the treatment of defects in the metaphysis, including the use of cement to buttress the articular surface, have been brought to the forefront. A treatment algorithm for associated injuries to the distal radioulnar joint is also helpful.
PURPOSE: The recent ability to measure 3-dimensional in vivo carpal kinematics has facilitated the noninvasive study of complex carpal bone motion. METHODS: In this study we examined the flexion/extension carpal kinematics of both wrists in 8 patients with unilateral scapholunate interosseous ligament (SLIL) tears by using computed tomographic (CT) imaging and a markerless bone registration technique. Carpal bone neutral posture and flexion/extension motion of both wrists of the injured patients were compared with the same parameters in wrists of 10 uninjured male and female volunteers (normals). RESULTS: The neutral posture of the injured scaphoid and lunate were significantly more extended than those of normals. In these patients, however, the postures of the scaphoid and lunate in the contralateral uninjured wrists also were abnormal and were similar to those of the injured wrist. In addition, extension of the lunate and flexion of the scaphoid in both the injured and uninjured wrist were significantly different from normal but not different from each other. CONCLUSIONS: This study was unable to attribute altered carpal posture and motion to SLIL tears because abnormalities were found in both wrists of patients with unilateral injury. The etiology of abnormal wrist kinematics in the asymptomatic wrist of patients with unilateral tears of the scapholunate ligament is not known.
PURPOSE: To report the functional and radiographic outcomes of a cohort of patients treated for ulnar impaction syndrome with a single technique of ulnar shortening osteotomy. METHOD: We performed ulnar shortening osteotomy on 18 consecutive patients over a 10-year period by using an oblique osteotomy and compression plating technique with an AO compression device (Synthes, Paoli, PA). There were 11 men and 7 women in the series, with an average age of 32.7 years. All patients were graded before and after surgery with the modified wrist grading system of Chun and Palmer. RESULTS: All 18 osteotomies healed over an average of 6-8 weeks. There were significant improvements in pain, function, strength, and range of motion at an average follow-up of 3 years. Thirteen wrists were graded excellent, 3 good, and 2 fair. There were no postoperative complications, however, 8 patients ultimately required plate removal for local discomfort. CONCLUSIONS: This study showed that ulnar shortening osteotomy using an oblique osteotomy and an AO compression device is easy to execute and is associated with satisfactory outcomes. Healing time is rapid and postoperative cast immobilization is not required.
PURPOSE: Previous studies have hypothesized unequal load sharing between peripheral and core sutures in flexor tendon repairs. Most commonly peripheral sutures are placed very near the repair site and characteristically fail before the core strands. We hypothesized that placement of the peripheral sutures farther from the repair site would better optimize load sharing and resist suture pullout, yielding a stronger overall repair. METHODS: To test the hypothesis we developed a mathematical model of the load sharing between core and peripheral sutures. By using this model we predicted that placement of peripheral sutures 2 mm from the repair site would optimize the balance of load between core and peripheral sutures. We then divided and repaired 27 flexor digitorum profundus tendons in 6 ways (core plus peripheral or peripheral sutures only at 1 mm, 2 mm, or 3 mm from the repair site). Tendons were clamped to a custom-built linear loading machine and distracted to failure. RESULTS: There was a clinically and statistically significant increase in strength with an increased distance of the peripheral suture from the repair site showing that core sutures augmented by a 2-mm peripheral repair were stronger than those performed with 1-mm peripheral repairs (50.8 vs 37.1 N). CONCLUSIONS: A peripheral stitch placement approximately 2 mm from the repair site represents a simple modification that can significantly increase the ultimate strength of flexor tendon repairs.
A case of a young patient with a severely comminuted intra-articular distal radius fracture dislocation and severe injury of the distal radioulnar joint is presented. Early reconstruction of the sigmoid notch and radioulnar ligaments was performed using the remaining scaphoid facet of the distal radius articular surface, an autogenous tendon graft for ligament reconstruction, and radioscapholunate arthrodesis. The patient was able to return to his manual work without limitations. We present additional information on the comparative anatomy of the sigmoid notch and scaphoid facet that may guide surgeons in treating this severe injury.
We conducted a systematic quantitative meta-review of the literature to provide evidence-based suggestions for the treatment of scaphoid nonunion. This search identified 1,121 articles of which 36 met eligibility requirements. In unstable nonunions, screw fixation with grafting at 94% union was superior to K-wires and wedge grafting (77% union). Immediate mobilization versus 6 weeks or more of casting showed the same union rate of 74%. For avascular necrosis of the proximal fragment, union was achieved in 88% of those patients with a vascularized graft versus 47% with screw and wedge fixation. These results suggest that established unstable nonunions should be treated with screw fixation and wedge grafting. There is not evidence supporting the need for postoperative immobilization in patients with solid screw fixation. A vascularized graft may be preferable for patients with avascular necrosis of the proximal fragment or with a previously failed surgery.
The biomechanical stability of an internal fixation system that uses low-profile modular implants to stabilize individual fracture components was studied in a validated cadaver fracture model that incorporated physiologic muscle forces and wrist motion. Fragment-specific fixation with immediate range of motion was compared with static augmented external fixation in simulated, unstable 3- and 4-part intra-articular distal radius fractures (n = 20). Fixation was applied and specimens were loaded via their major wrist tendons. Because the wrist joint was not constrained in the internal fixation group, full wrist motion occurred during load application in these specimens. A 3-dimensional motion tracking system calculated individual fracture fragment motion in both groups. In the 3-part fracture pattern fragment-specific fixation showed comparable stability to static augmented external fixation despite the full wrist range of motion that occurred during application of load in these specimens. In the 4-part fracture pattern fragment-specific fixation was shown to be significantly more stable when compared with static augmented external fixation in 4 of 6 axes of motion. Our findings confirm the stability of this low-profile plating system and support the consideration of early wrist motion when treating complex, intra-articular distal radius fractures with fragment-specific fixation.
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