Prediction of ligament length and carpal diastasis during wrist flexion-extension and after simulated scapholunate instability.

PURPOSE: To determine the role of the carpal ligaments during wrist flexion-extension and to understand whether maintaining integrity of only the dorsal scapholunate ligament (SLL) is adequate for maintaining stability of the scapholunate joint. METHODS: This study combined motion analysis and manual digitization of ligament attachment regions to generate predictions of carpal ligament length and implied strain during wrist motion and length changes after simulated ligamentous injury. RESULTS: We modeled 13 ligaments and 22 ligament segments (subportions). We measured ligament length change with respect to wrist angle. A total of 11 segments had minimum stretch or elongation from neutral wrist position over the entire wrist range of motion for any ligament cut condition. The remaining 11 segments had more than 10% stretch in some portion of flexion-extension. In general, ligaments had increased stretch during wrist flexion and after cutting the entire SLL and the dorsal intercarpal ligaments off the scaphoid. CONCLUSIONS: Disruption of the membranous and palmar portions of the SLL and the dorsal intercarpal ligament off the scaphoid did not result in the development of an increased 3-dimensional scapholunate gap, as measured by differences in ligament length calculations between the scaphoid and lunate. This may indicate a predynamic instability condition (before clinical signs and x-ray findings) that is stabilized by the dorsal SLL, preventing the increase in the 3-dimensional scapholunate gap. This may also support surgical treatment recommendations, which suggest that repair of the dorsal component only of the SLL will be effective. Disruption of the dorsal intercarpal ligament off the scaphoid or lunate did not result in further significant changes. Therefore, the dorsal SLL has an important role in preventing scapholunate ligament instability. CLINICAL RELEVANCE: These results provide insight into the abnormal kinematics as various ligaments are compromised.

Wrist anatomy and biomechanics.

Anatomic and biomechanical research of the wrist has yielded a substantial amount of information that improves our basic knowledge of carpal morphology and function of the wrist and provides information to better assess and improve treatment(s) for various problems of the wrist joint. A precise knowledge of the anatomy and biomechanics of the wrist is useful not only for diagnosis of traumatic ligamentous injuries or degenerative change of the wrist joint but also for treatment for wrist dysfunction.

Thumb interphalangeal joint extension by the extensor pollicis brevis: association with a subcompartment and de Quervain's disease.

PURPOSE: First dorsal compartment anatomy was analyzed for the presence of a separate compartment for the extensor pollicis brevis (EPB) tendon and the ability of the EPB to extend the thumb interphalangeal (IP) joint in order to determine if these characteristics were associated with each other, and with de Quervain's disease. METHODS: Two groups were studied: (1) 90 cadaver wrists, 28 to 89 years, 38 male and 52 female specimens; and (2) 143 patient wrists, 21 to 82 years, 18 men and 125 women, in which the first dorsal compartment was released for treatment of de Quervain's disease. RESULTS: The EPB was in a separate compartment in 102 of 143 of the surgical group and 18 of 90 of the cadaver group. The EPB was able to extend the IP joint in 56 of 143 of the surgical group and 19 of 90 of the cadaver group. When the EPB was able to extend the IP joint, it was in a subcompartment in 49 of 56 of the surgical group and 9 of 19 of the cadaver group. When the EPB was able to produce IP extension in the cadaver group, it was inserted on the distal phalanx or the extensor hood. CONCLUSIONS: In a substantial number of people undergoing surgery for de Quervain's disease and in cadavers, the EPB can extend the thumb IP joint. When it does, particularly in patients with de Quervain's disease, it is likely to reside in a subcompartment of the first dorsal compartment. The incidences of a subcompartment for the EPB and the ability of the EPB to extend the thumb IP joint were higher in the de Quervain's patient population than in the cadaver group.

Three-dimensional computed tomography of the carpal ligaments.

This article details a current perspective and accurate anatomical three-dimensional descriptions of the ligaments of the wrist. The carpometacarpal ligaments, the intercarpal ligaments, and the radiocarpal ligaments are described and illustrated using a unique combination of detailed dissection, computed tomography, and a three-dimensional digitization technique. Detailed information is also provided about the ligamentous attachments of the carpometacarpal joints, the carpal bones, and the distal radius. This study improves knowledge and understanding of the normal anatomy and mechanics of the radiocarpal and intercarpal ligaments and the carpometacarpal joints, and it should help in the assessment of radiographic images and treatment of various injuries and degenerative changes seen in the wrist. The knowledge of the ligaments will further serve as a foundation for understanding the anatomy of the ligaments, the biomechanics of the wrist, and the function of the individual ligaments and their roles in joint motion and stability.

Arrow shaft injury of the wrist and hand: case report, management, and surgical technique.

A case of accidental, self-inflicted injury to the hand from a hollow carbon shaft arrow which broke in its midshaft while attempting to shoot the arrow from a compound bow is presented. Basic knowledge of low velocity gunshot wounds and arrow injuries was applied in the treatment of this injury along with a unique management technique. The outcome, including hand function was good without any functional loss.

Incidence of carpal boss and osseous coalition: an anatomic study.

PURPOSE: To determine the incidence of a clinically evident carpal boss (bony prominence on the dorsal aspect of the second and/or third carpometacarpal joint) and by means of dissection to determine the incidence of osseous coalitions and any abnormality or absence of associated ligament anatomy in the second through fifth carpometacarpal joints in a cadaver population. METHODS: The area of the second through fifth carpometacarpal joints was dissected in 202 cadaver wrists. RESULTS: Thirty-nine of the wrists had a bony prominence and partial osseous coalition between 2 or more of the capitate, trapezoid, second metacarpal, and third metacarpal bones. When an osseous coalition was present it was incomplete, located at the dorsal aspect of the joint, and there was an absence of the normal dorsal ligaments at that joint. Ten of the 87 pairs of wrists were found to have bilateral carpal bosses with partial dorsal osseous coalition. The most common location of the osseous partial coalition was between the second metacarpal and the trapezoid. There were no osseous coalitions or absence of the normal dorsal ligaments at the fourth and/or fifth carpometacarpal joints. CONCLUSIONS: This study showed that there was a high percentage of partial osseous coalitions with an associated prominence of the skeletal anatomy in the general cadaver population. The etiology of the carpal boss remains unclear.

Ulnar translation, a commonly overlooked, unrecognized deformity of distal radius fractures: techniques to correct the malalignment.

Distal radius fracture is one of the most common fractures, accounting for up to 15% of all bone injuries. Radial shortening, loss of palmar inclination, and/or radial tilt are commonly recognized and addressed components of radius fracture deformity. However, a common but typically overlooked and unrecognized component of distal radius fracture deformity is ulnar translation of the proximal radius metaphyseal/shaft. Several techniques to address ulnar translation deformity are presented.

Variations of capitate morphology in the wrist.

PURPOSE: This anatomical study details and categorizes variations in capitate morphology and associated structures in the human cadaveric wrist. METHODS: We dissected 107 cadaveric wrists. Capitate morphology, the presence of capitate and hamate ridges, the lunate types, and the width of the medial hamate facet of type II lunates and 4th carpometacarpal joint types were recorded. RESULTS: Three types of capitate were identified. The flat type (69/107, or 65%) was characterized by a horizontally oriented (radio-ulnar) lunate-capitate articulation and a longitudinally oriented (proximal-distal) scaphoid-capitate articulation. The flat type was associated with type I lunates or type II lunates with a smaller facet. The spherical type (23/107, or 22%) was associated with a concave articulation formed by the scaphoid and lunate articulations, with an indistinct border between the scaphoid and lunate facets. The width of the medial hamate facet of type II lunates in wrists with a spherical-type capitate was

Shrimp winch injuries.

BACKGROUND: Shrimp winch injuries range from phalangeal injuries to life-threatening limb amputations. The injuries often result in significant morbidity, significant cost, and lengthy hospitalizations. There are usually insufficient or nonexistent safety mechanisms on the boats to prevent these injuries. No international, federal, or state agencies regulate safety in the shellfish industry. The injuries are relatively rare, but likely underreported. METHODS: We retrospectively reviewed 19 cases of injuries resulting from the use of shrimp winches in a 20-year period at our institution. In addition, people who use shrimp winches were interviewed and current regulations were researched. RESULTS: All patients were men with an average age of 46.5 years. There were 17 upper extremity injuries, ranging in severity from crushed finger tips to transhumeral amputations, and two lower extremity injuries. A classification system based on injury pathomechanics and severity is offered. During inspection of local shrimp boats, the winch system was often in poor condition. No International, federal, state, or local regulations guiding the shellfish industry were found. CONCLUSIONS: Injuries from the use of shrimp winches are rare, but may be underreported. However, they can be severe when they do occur. Stronger safety guidelines need to be put into practice to prevent these serious injuries.

Marginal excision of squamous cell carcinomas of the hand.

Squamous cell carcinoma is the most common malignant tumor of the hand. Most hand surgery texts recommend wide excision with 1- to 2-cm margins. During a 10-year period, 32 patients with 35 lesions were treated with marginal surgical excision for squamous cell carcinoma of the hand. Greater potential morbidity and functional loss associated with wide excision was avoided in these patients. No recurrences were found at a mean follow-up of 31 months. One case of possible metastasis was identified. Three (8%) tumors required further treatment due to positive surgical margins. Marginal excision of squamous cell carcinoma of the hand is associated with a low rate of recurrence and metastasis. In addition, the potential for improved cosmesis and diminished morbidity when compared to older more radical surgical methods supports marginal excision for squamous cell carcinoma of the hand as a viable treatment technique.

Carpal kinematics during simulated active and passive motion of the wrist.

PURPOSE: The purpose of this study was to investigate the effect of experimental control mechanisms, simulated active (tendon-driven) and passive (externally assisted), on carpal motion. METHODS: Kinematics of the carpal bones in five fresh-frozen cadaver upper extremities were studied using an optical motion analysis system. The wrist extensors and flexors were dissected and loaded. For passive motion, the tendons were loaded to simulate muscle tone while the investigator passively moved the wrist using a pin placed in the third metacarpal. To simulate active, patient-driven motion, the tendons were attached directly to guide bars while the investigator used a puppeteer mechanism to move the wrist. RESULTS: There were no significant differences in carpal motion (flexion-extension motion or radial-ulnar deviation) when the wrist was moved in simulated active motion through the extensor and flexor tendons or in passive motion, with a constant force applied to the tendons. Kinematics for simulated active motion, in general, was more difficult to control and was less smooth than the kinematics for passive motion. CONCLUSIONS: Carpal bone kinematics (excluding the pisiform) in a healthy normal joint are similar in both simulated active (tendon-driven) and passive (externally assisted) wrist motion because the carpal bones are passively moved during wrist motion (there are no direct tendon-to-muscle attachments to the proximal carpal bones and minimal attachments to the distal carpal bones).

Ultrasonographic examination of the synovial fold of the radiohumeral joint.

This report describes the anatomy of the synovial fold of the radiohumeral joint and assesses its visibility by ultrasonography. Forty-nine fresh cadaver radiohumeral joints were examined by ultrasonography before and after intraarticular saline injection and then dissected. Digital photos were taken before and after the joint capsule was excised. The relative coverage of the radial head by the fold was calculated. Synovial folds were observed in all specimens. Forty-three had anterior and posterior lobes. The synovial fold covered an average of 28% of the radiocapitellar joint surface of the radial head. The sensitivity of the ultrasonography was 81%, 46%, and 85% from the anterior, lateral, and posterior aspects of the radiohumeral joint, respectively. Intraarticular saline injection improved the sensitivity to 96%, 67%, and 94%, respectively. The synovial fold is a consistent anatomic structure, and ultrasonography can be a useful preoperative diagnostic tool.

Three-dimensional analysis of the ligamentous attachments of the second through fifth carpometacarpal joints.

The purpose of this study is to clarify, measure, and show the anatomic locations and areas of specific ligamentous attachments and paths of the second through fifth carpometacarpal (CMC) joints on a three-dimensional (3D) surface model. Ten fresh-frozen cadaver wrists were used to dissect and identify the second through fifth CMC ligaments. Their ligamentous attachments and whole bone surfaces were digitized three-dimensionally and their areas calculated. The attachments of each ligament were represented in a model combining CT surfaces overlaid by a digitized 3D surface, and were also visually demonstrated with a specific color on 3D images of the bones. Nine dorsal and 11 palmar CMC ligaments and one CMC interosseous ligament were identified in the second through fifth CMC joints. An intra-articular ligament between the third metacarpal (MC), the fourth MC, capitate, and hamate was also identified. Five dorsal and five palmar intermetacarpal ligaments and three intermetacarpal interosseous ligaments were also identified in the second through fifth intermetacarpal joints. A previously undescribed palmar intermetacarpal ligament was located between the third, fourth, and fifth MC bases. The anatomic 3D attachment sites of the second through fifth CMC ligaments were visually depicted qualitatively, and their areas quantified. This 3D information will not only afford a better understanding of the anatomy and mechanics of the second through fifth CMC joints, but will also assist in the assessment of radiographic images and treatment of various injuries.

A new modification of corrective osteotomy for treatment of distal radius malunion.

A new modification of corrective osteotomy for distal radius malunion, which minimizes the need for bone grafting and addresses the constraining aspect of the extensor retinaculum, is described. This new modification uses a volar and dorsal approach to perform an angled step-cut osteotomy, release of the extensor retinaculum, and volar plating. The typically dorsally extruded comminuted fracture fragments from the distal, dorsal compression fracture component of the distal radius fracture is mobilized with the distal fragment and acts as a dorsal strut graft to span the opening wedge, corrective osteotomy. Therefore, this new modification facilitates and improves the realignment of the malunited radius, while minimizing or eliminating the need for bone grafting.

The effect of radial shortening on wrist joint mechanics in cadaver specimens with inherent differences in ulnar variance.

PURPOSE: To assess load changes in the wrist and forearm resulting from surgically-induced radial shortening in wrists with inherent differences in ulnar variance. METHODS: Eleven fresh cadaver upper extremities, 4 with ulnar-plus variance of 2 mm or greater and 7 with ulnar-minus variance of 2 mm or greater were used. The radius and ulna of each specimen were instrumented with load cells, a 15-mm segment of the radius was resected and replaced with aluminum blocks of various sizes, and the specimens were loaded with 143 N (32 lb) at 1-mm differences of radial length. The load distribution between the radius and ulna was measured. RESULTS: The load distribution in the specimens with an ulnar-plus variance averaged 69% through the radius and 31% through the ulna. In the wrists with ulnar-minus variance, the load distribution averaged 94% through the radius and 6% through the ulna. The mean force in the ulna increased and the mean force in the radius decreased with incremental shortening of the distal end of the radius. The mean force through the ulna in the ulnar-plus-variance group was always higher than that of the ulnar-minus-variance group. When compared not by the number of millimeters of radial shortening but by the adjusted ulnar variance, there was no difference between the ulnar-plus-variance and the ulnar-minus-variance groups. CONCLUSIONS: Wrists with ulnar-minus variance could accommodate radial shortening without as much increase in the ulna load as wrists with ulnar-plus variance. The clinical relevance is that a patient with an ulnar-minus variance may accommodate more radial shortening after a wrist fracture without developing an ulnar impaction syndrome than a patient with an ulnar-plus-variant wrist.

Three-dimensional imaging of the carpal ligaments.

This article provides a new perspective and detailed anatomic description of the attachments of the carpometacarpal (CMC) ligaments, intercarpal ligaments, and radiocarpal ligaments, which are described and illustrated using a unique combination of detailed dissection, CT imaging, and three-dimensional digitization. Detailed information is also provided about the ligamentous attachments of the CMC joints, carpal bones, and distal radius. This information advances the current knowledge and understanding of the normal anatomy and its impact on the mechanics of the radiocarpal intercarpal ligaments and the CMC joints, and should help surgeons to assess and treat injuries and degenerative changes seen in the wrist and CMC joints. Furthermore, this additional knowledge of the ligaments will help to further understand wrist kinematics and, more precisely, the function of the individual ligaments and their roles in joint motion and stability and injuries.

Intrinsic muscle contribution to the metacarpophalangeal joint flexion moment of the middle, ring, and small fingers.

PURPOSE: To analyze the relative contribution of the intrinsic muscles to the flexion moment potential of the metacarpophalangeal (MCP) joints of the middle, ring, and small fingers and to calculate the moment potential loss occurring with deep motor branch, low, or high ulnar nerve palsy or low median nerve palsy. METHODS: Eleven fresh cadaver hands were used. A small wire sutured to each tendon was connected to an excursion transducer containing a constant-tension spring. The tendon excursion and the MCP joint rotation were measured simultaneously during 10 to 16 cycles of passive flexion/extension cyclic motion. The moment arm was calculated from the tendon excursion-joint rotation curve as the derivative of the curve. The flexion moment potential was calculated by multiplying the moment arm with the known tension fractions of the muscles. RESULTS: When the MCP joint was at 0 degrees of flexion the relative moment potential contributions of the intrinsic muscles to MCP joint flexion were 8%, 13%, and 28% in the middle, ring, and small fingers, respectively. Moment potential losses were 7%, 13%, and 6% in the middle, ring, and small fingers, respectively, in deep motor branch ulnar nerve palsy. In low ulnar nerve palsy the losses were 7%, 13%, and 28%, respectively. In high ulnar nerve palsy they were 7%, 64%, and 82%, respectively. Low median nerve palsy, however, resulted in a moment potential loss at the middle finger MCP joint of less than 2%. CONCLUSIONS: The relative contribution of the intrinsic muscles to the total flexion moment at the MCP joint was different for each finger. The small finger had a large intrinsic contribution, primarily because of the larger moment arms of the hypothenar muscles.

Three-dimensional analysis of the ligamentous attachments of the first carpometacarpal joint.

PURPOSE: To show the ligamentous locations and attachments of the first carpometacarpal (CMC) joint on a 3-dimensional (3-D) surface model. METHODS: Ten fresh-frozen cadaver wrists were used to dissect and identify the first CMC ligaments. Their ligamentous attachments and whole bone surfaces were digitized 3-dimensionally and their areas were calculated. The attachments of each ligament were represented in a model combining 3-D computed tomography surfaces overlaid by a digitized 3-D surface and also were shown visually by a specific color on 3-D bone images. The superimposed outlines of the ligamentous attachments on both the radial and ulnar base of the first metacarpal (MC) also are described. RESULTS: Seven ligaments of the first CMC joint were identified: the dorsoradial ligament, the posterior oblique ligament, the superficial anterior oblique ligament, the deep anterior oblique ligament, the ulnar collateral ligament, the dorsal first MC ulnar base-second MC radial base intermetacarpal ligament, and the volar first MC ulnar base-second MC radial base intermetacarpal ligament. The detailed locations and areas of the ligamentous attachments of the first CMC joint were determined. The average locations of the centroid of the ligamentous attachments of the ulnar collateral and the dorsoradial ligaments were located ulnovolar and dorsoradial on the first MC base, respectively. CONCLUSIONS: The anatomic 3-D attachment sites of the first CMC ligaments were shown qualitatively and their areas were quantified. The results of this study improve the knowledge and understanding of the normal anatomy and its impact on the mechanics of the first CMC joint. This should help in making an accurate assessment of radiographic images and treating injuries and degenerative changes in the first CMC joint by ligament reconstruction, repair, and arthroscopy.