Mechanical advantage of the thumb muscles

The purpose of this study was to measure the moment arms of four extrinsic muscles (flexor pollicis longus, extensor pollicis longus, extensor pollicis brevis, and abductor pollicis longus) and four intrinsic muscles (flexor pollicis brevis, abductor pollicis brevis, adductor pollicis, and opponents pollicis) of the thumb at the interphalangeal, the metacarpophalangeal, and the carpometacarpal joints in the same cadaver specimens and to examine the specific role of each muscle. Measurements were made on seven fresh frozen cadaver hands. The moment arms were measured during flexion/extension of the interphalangeal joint, flexion/extension and adduction/abduction of the metacarpophalangeal joint, and flexion/extension and adduction/abduction of the carpometacarpal joint. Moment arms were computed using the slope of the tendon excursion joint angle relationship. The specific function of each muscle was determined by multiplying the measured moment arms by the maximum force that each muscle can generate. It was found that the flexor pollicis longus was a pure flexor while flexor pollicis brevis was an adductor as well as a flexor, the extensor pollicis longus was an extensor and an adductor, extensor pollicis brevis was an extensor and a mild abductor, the abductor pollicis longus was an extensor as well as an abductor, the abductor pollicis brevis was mainly an abductor, the adductor pollicis was a major flexor as well as an adductor, and the opponents pollicis was a flexor and an abductor.

The lunotriquetral joint: kinematic effects of sequential ligament sectioning, ligament repair, and arthrodesis

This experiment was conducted to study the effects of sequential sectioning of the ligaments of the lunotriquetral (LT) joint and the effects of simulated repair or arthodesis on kinematics of the wrist joint using an x-ray stereophotogrammetric technique. A 3-dimensional coordinate software program calculated relative motion between bodies as screw axis displacement and rotation about each axis. Sectioning of the proximal and dorsal component of the LT ligament had little effect on carpal kinematics, but sectioning of the proximal and palmar components of the ligament resulted in flexion of both the lunate and triquetrum, producing a volar intercalated segment instability (VISI) pattern. The triquetrum supinated away from the lunate after sectioning of the entire LT ligament. Greater VISI occurred after sectioning the dorsal radiotriquetral and scaphotriquetral ligaments. Progressive destabilization of the LT joint results in increasing kinematic alterations; however, these may not exactly mimic the clinical situation. Moving the wrist through 1,000 cycles increased the instability. Dorsal repair of the LT ligament realigned the lunate and triquetrum, and LT fusion corrected triquetral supination. The latter, however, resulted in overcorrection into extension, which prevented a full wrist extension. The repair used may be insufficient to restore the palmar ligamentous integrity. Lunotriquetral arthodesis was difficult to simulate, providing some insight into the cause of clinical nonunions. Severe VISI is not correctable by repair or arthrodesis and requires further study using reconstructive procedures not discussed here.

Axial loading induces rotation of the proximal carpal row bones around unique screw-displacement axes

The changes in carpal bone alignment secondary to the application of an axial compressive load through the major wrist motor tendons while the wrist is kept in neutral position (isometric loading) have been investigated on 13 fresh cadaver specimens using a biplanar radiographic method of kinematic analysis. The scaphoid, lunate and triquetrum rotate an average of 5.1, 4.2, and 3.8 degrees, respectively, around different screw displacement axes, all implying flexion, radial deviation and supination. Based on these findings, a new interpretation of the mechanism by which the wrist remains stable under physiologic loads is provided.

Melorheostosis in a patient with familial osteopoikilosis

We report on a 40-year-old woman with melorheostosis who also had radiographic findings of generalized osteopoikilosis. Three of her sibs have osteopoikilosis, but none of them have melorheostosis. Several cases of "mixed sclerosing bone dysplasia" have been described previously, and all have been sporadic. Isolated melorheostosis without osteopoikilosis is also generally a sporadic condition, but osteopoikilosis has been described as an autosomal-dominant trait. The finding of mixed sclerosing bone dysplasia in a family with osteopoikilosis suggests that the melorheostotic component of this disorder may be due to a second mutation at the same locus that causes isolated familial osteopoikilosis.

Somatic versus sympathetic mediated chronic limb pain. Experience and treatment options

It has been helpful in our practice to separate somatic from sympathetic-mediated peripheral nerve pain. We would recommend application of the new nomenclature of type I complex regional pain (sympathetic dystrophy) and type II complex regional pain (causalgia) (see Table 1). We believe it is essential that both of these conditions be separated into their early and late phases and that the treatment alternatives be customized for the individual patient and the peripheral nerve involved. If a cast, pin, or external fixation apparatus is associated with peripheral nerve pain, the offending apparatus must be removed immediately and other forms of treatment initiated for the underlying injury. For acute injury and postsurgical pain, narcotic pain medications should be used no longer than 72 hours and careful patient re-examination must be performed if pain persists. Prescription of narcotic pain medications on a continuing basis is often the primary reason for the development of chronic pain syndromes. Physical therapy for the patient with chronic peripheral limb pain must be performed in a pain-free environment. "No pain, no gain" does not apply in the treatment of chronic limb pain-rather the reverse: "Only gain with no pain." In differentiating between sympathetic pain and somatic pain, the use of the reflex sympathetic dystrophy (RSD) score can be helpful (Table 4). If the pain is somatic, treatment options include: Somatic Pain: Treatment Isolated nerve block Continuous nerve block TENS (external) Direct electrical nerve stimulation (internal) Nerve ablation If the pain is sympathetic in origin, treatments to be considered are: Sympathetic Nerve Pain: Treatment Protection of limb (garment or splint) Combine with active use Sympathetic blocks single continuous Sympathectomy In addition, the treatment of each of those conditions must be directed at the primary condition. Once the two conditions are separated, a careful program of pain management is required. In patients who present with late pain dysfunction, the more commonly observed phenomenon at our institution, the combination of physician, surgeon, and anesthesiologist is essential. The role of physical therapist in restoring function to the injured limb must be discussed and planned carefully. Initial pain management is organized through a qualified anesthesiologist dedicated to this field. Physical therapy follows but only in a pain-free environment. The surgeon's role is to assist and direct the pain management program. Surgeons can be involved in the placement of percutaneous catheters, as well as isolated peripheral nerve blocks. Surgical intervention is limited to the release of compressive neuropathies, nerve transfers, and revascularization of the peripheral nerve bed. The surgeon occasionally may be involved in the manipulation and pinning of contracted joints, as well as release of muscle or joint contractures, followed by a supervised program of early range of motion. Finally, it is important that both physician and surgeon serve as patient advocates when questions of workers' compensation intervene that could deter proper treatment programs or when the patient needs the encouragement and guidance to continue with treatments that don't always initially appear to have immediate results. Finally, requests to the surgeon to find an operative cure must be resisted while continued psychological encouragement is provided.

Electrical stimulation and the treatment of complex regional pain syndromes of the upper extremity

Clinical, intractable pain in the upper extremity often results from neuroma, direct injury to a peripheral nerve, or repetitive operative insults to a peripheral nerve that has compressive neuropathy. Electrical stimulation applied directly to a single peripheral nerve can provide sufficient relief of pain, improve patient outlook, improve lasting sleep, release the individual from addictive narcotic pain medication, and restore a psychological sense of well-being.

Assessment of the ratio of carpal contents to carpal tunnel volume in patients with carpal tunnel syndrome: a preliminary report

An anatomic basis for carpal tunnel syndrome (CTS) has been proposed but not confirmed; both volumetric and area studies have been used to address this issue. The authors have demonstrated that the ratio of the carpal tunnel contents (CTC) to carpal tunnel volume (CTV) provides information regarding the relative free space in the carpal tunnel as compared with canal volume alone. This study was undertaken to determine whether the CTC/CTV ratio was higher for patients with CTS than for normal subjects. Seven asymptomatic volunteers and 7 patients with symptoms of CTS underwent magnetic resonance imaging (MRI) so that the CTC/CTV ratios could be determined. Standard radiographs were analyzed to identify plain radiographic variables that differed between patients with CTS and control subjects, and no differences were found. On MRIs, however, CTC/CTV ratios were noted to be higher for patients with CTS than for matched control subjects.

Trispiral tomographic staging of Kienböck's disease

Trispiral tomography enhances the staging of Kienböck's disease and aids in surgical planning. The clinical records, plain x-rays, and trispiral tomograms of 105 patients with Kienböck's disease were reviewed. When tomograms were used, upward revision of the classification stage was indicated in 73% of patients with stage I or stage II disease and in 10% of those with stage III disease. On tomograms, 91% of patients had lunate fractures, compared with 55% on plain films. The most common lunate fracture seen on trispiral tomograms was a transverse shear fracture that represented lunate collapse; the next most common was a midcoronal fracture that may be displaced, causing fragment extrusion palmarly or dorsally. The most common instability pattern was nondissociative proximal row flexion, seen in stage III. Indices of carpal collapse and ulnar translation may be useful in following up patients, but values vary widely among patients.

Rupture of the triceps muscle at the musculotendinous junction: a case report

Rupture of the triceps brachii at the musculotendinous junction is reported in a patient with diabetes mellitus and hypertension. Successful reconstruction was achieved by delayed primary repair. V-Y advancement of the triceps, and a plantaris tendon graft.

En bloc resection of tumors of the distal end of the ulna

The operative treatment of malignant tumors and aggressive benign tumors involving the distal end of the ulna often necessitates en bloc resection. The oncological and functional results for eight patients in whom a neoplasm involving the distal end of the ulna had been treated with en bloc resection without reconstruction of the osseous defect were reviewed retrospectively at a mean of seventy-nine months (range, twenty-three to 271 months). Four patients had a giant-cell tumor; two, a low-grade osteogenic sarcoma; one, a hemangioendothelioma; and one, a soft-tissue epithelioid sarcoma with osseous involvement. The amount of bone that was removed from the distal end of the ulna ranged from 3.1 to 9.0 centimeters. In the four patients who had a malignant tumor, a minimum of 7.5 centimeters was removed in order to achieve an adequate wide margin proximally. In the patients who had a benign tumor, a maximum of 6.6 centimeters was resected. Extraperiosteal resection was performed in three of the patients who had a malignant tumor and in one of the patients who had an aggressive giant-cell tumor. Subperiosteal resection was performed in the three patients who had a benign tumor and in one patient who had a parosteal osteogenic sarcoma. None of the patients had local or systemic evidence of recurrence of the tumor. The functional result was excellent for six patients and good for two. Grip strength was reduced by a mean of 15 per cent compared with the strength on the contralateral side, and this reduction did not appear to be related directly to the amount of bone that had been resected. The findings of this study support the concept that routine reconstruction of the osseous defect is not necessary after en bloc resection of a neoplasm of the distal end of the ulna.

Biomechanical analysis of tension band fixation for olecranon fracture treatment

This study assessed the strength of various tension band fixation methods with wire and cable applied to simulated olecranon fractures to compare stability and potential failure or complications between the two. Transverse olecranon fractures were simulated by osteotomy. The fracture was anatomically reduced, and various tension band fixation techniques were applied with monofilament wire or multifilament cable. With a material testing machine load displacement curves were obtained and statistical relevance determined by analysis of variance. Two loading modes were tested: loading on the posterior surface of olecranon to simulate triceps pull and loading on the anterior olecranon tip to recreate a potential compressive loading on the fragment during the resistive flexion. All fixation methods were more resistant to posterior loading than to an anterior load. Individual comparative analysis for various loading conditions concluded that tension band fixation is more resilient to tensile forces exerted by the triceps than compressive forces on the anterior olecranon tip. Neither wire passage anterior to the K-wires nor the multifilament cable provided statistically significant increased stability.

Guyon's canal revisited: an anatomic study of the carpal ulnar neurovascular space

The boundaries of the space through which the ulnar neurovascular bundle crosses the wrist have been reinvestigated. Using gross dissections, transverse and sagittal sections, and histologic study, we determined that the roof of Guyon's canal, the "carpal ulnar neurovascular space," does not directly connect to the hamate bone, as is currently accepted. The roof of this space extends radially to the hook of hamate and attaches to the flexor retinaculum. This anatomic arrangement allows the ulnar artery and sensory component of the ulnar nerve to course radially to the hook of hamate, where they lie on the flexor retinaculum (transverse carpal ligament). The roof and radial border have three segments: (1) a proximal segment that begins near the pisiform and extends distally to the level of the hook of hamate but does not attach directly to it, (2) a central segment that contains only adipose tissue, and (3) a distal fascial layer that includes the palmaris brevis muscle. The floor of the space consists of the muscles of the hypothenar eminence, their fibers of origin, and the flexor retinaculum (transverse carpal ligament). Guyon accurately described the proximal portion of the carpal ulnar neurovascular space, but his description has been misinterpreted; the hook of hamate does not serve as the radial boundary of Guyon's canal. The anatomic relationships of the "carpal ulnar neurovascular space" need to be appreciated to avoid complications during carpal tunnel surgery.

Kinematics of the trapeziometacarpal joint: a biomechanical analysis comparing tendon interposition arthroplasty and total-joint arthroplasty

The kinematics of the trapeziometacarpal joint were studied in 15 cadaver hands; normal joints were compared with simulated arthroplasties-either a total-joint arthroplasty of the ball-and-socket variety or a fibrous suspension arthroplasty of ligament reconstruction with tendon interposition. The motion of the thumb metacarpal was analyzed based on a trapezial coordinate system, using a magnetic tracking system. The pivot point (instantaneous center of rotation) for the thumb metacarpal changed during active and passive circumduction. Compared with normal trapeziometacarpal joint motion, the pivot point after ligament reconstruction with tendon interposition shifted significantly in palmar and ulnar directions in reference to the trapezial coordinate system, whereas after total-joint arthroplasty, the pivot point shifted slightly palmarly and radially. The axes of rotation were also compared for ligament reconstruction with tendon interposition and total-joint arthroplasty during thumb flexion-extension and abduction-adduction motions. After ligament reconstruction with tendon interposition, the center of flexion-extension shifted palmarly and the center of abduction-adduction shifted ulnarly. After total-joint arthroplasty, the center of rotation for flexion-extension shifted distally and palmarly and that for abduction-adduction shifted palmarly and proximally. In comparison with the normal joint, passive circumduction increased after tendon interposition arthroplasty but was less with total-joint arthroplasty. Changes in kinematics suggest a suspensory ligament function of ligament reconstruction with tendon interposition arthroplasty, whereas total-joint arthroplasty results in axes of rotation that reflect the joint replacement rather those of the normal joint.

Revision of failed bone grafting for nonunion of the scaphoid. Treatment options and results

Failure of bone grafting in scaphoid nonunion presents the hand surgeon a perplexing set of problems. Controversy remains as to the best course of treatment in this difficult situation. The authors have retrospectively reviewed during a 5-year period the patients treated at the Mayo Clinic who have gone on to a second nonunion after a failed initial bone grafting procedure. Twenty-five patients were identified, 19 of whom had a second bone grafting procedure. Depending on the preoperative evaluation, 4 types of bone grafting procedures were performed: conventional Russe procedure, 4; Maltese cross bone graft procedure, 6; interpositional wedge graft, 5; and vascularized pedicle bone graft, 4. Twenty-two of 25 united (88%). Average followup at 57 months (range, 25-90 months), shows satisfactory results (16% very satisfied and 8% moderately satisfied), but varying degrees of pain. Results using a modification of the Mayo Wrist Score are somewhat disappointing with 3 excellent, 5 good, 10 fair, and 7 poor. It must be remembered, however, these wrists have had at least 2 surgeries, multiple long periods of immobilization, and often a delay in treatment with a prolonged period of abnormal carpal mechanics. It is thought that a second bone grafting attempt should be strongly considered. The key to success is matching the type of bone graft procedure to the specific unique features of scaphoid shortening, carpal instability, and proximal pole vascularity that each patient's wrist displays. A treatment algorithm is presented to help decision making in this difficult problem.

Rotational laxity and stiffness of the radiocarpal joint

OBJECTIVE: To investigate the constraint and potential mechanism of torque transmission across the wrist joint. DESIGN: In vitro experiment using human cadaveric specimens. BACKGROUND: Transmission of torque from the forearm to the hand requires rotational stability at the wrist. Better appriciation of the constraints would have applicability to several clinical problems where the stability is compromised. METHODS: Thirteen fresh-frozen cadaveric specimens were used in this experiment to investigate the rotational laxity and stiffness of the radiocarpal joint in unloaded and axially loaded (100 N) conditions, and three forearm orientations in a neutral, pronation (60 degrees ), or supination (60 degrees ) position. RESULTS: In pronation or supination, there was no difference between loaded and unloaded conditions in primary or total laxity at a maximum torque of 2.3 Nm. Unloaded specimens showed a mean total rotational laxity of 42.1 degrees. Supination or pronation of the forearm caused a decrease in laxity with respect to neutral forearm rotation (35 degrees and 41.6 degrees versus 49.6 degrees respectively). The primary rotational laxity accounted for half of the total laxity. With axial compression, total rotational laxity did not change, but primary laxity dropped to 50% of its unloaded value. The primary stiffness was very low -- approximately 11% of the secondary stiffness. CONCLUSION: The ligamentous structures and the joint articulation restricted excessive axial rotation of the wrist. However, a laxity of approximately 20 degrees was identified for normal wrists. RELEVANCE: This study demonstrated that the primary axial rotational laxity of the radiocarpal joint was approximately 20 degrees. In the mathematical model and implant design, muscular balance of the joint within such laxity should be considered.

Aetiology of work-related carpal tunnel syndrome: the role of lumbrical muscles and tool size on carpal tunnel pressures

A cadaveric study was undertaken to investigate the effect of tool size and lumbrical muscle incursion on carpal tunnel pressure during active grip. Active grip was simulated by securing the specimens on an apparatus and loading each of the eight finger flexor tendons with 1 kg each. Carpal tunnel pressures were measured with and without 1- and 2-in. tubing in the hand and before and after removing the lumbrical muscles. Both variables, tool size and lumbrical muscles, were found to have a statistically significant effect on carpal tunnel pressure. Higher pressure changes were found for the 2-in. tubing, compared with 1-in. tubing, but this difference was not statistically significant.

Golf-induced injuries of the wrist

Golf injuries of the wrist are rare, but when they occur they can be devastating for the avid golfer, competitive amateur golfer, or the professional golfer, as the hand and wrist are so integral to the game. The majority of golf injuries are overuse injuries of the wrist flexor or extensor tendons. The left wrist (in the right-handed golfer) is the most common location. Analysis of the golf swing finds excessive motion of the left wrist (in the right-handed golfer), along with a catapulting function, accounting for vulnerability of the left wrist to injury. Hyperextension and radial deviation of the right wrist may cause impingement syndrome and injury may also occur during impact of the swing phase. The majority of golf-induced overuse syndromes of the wrist are successfully treated nonoperatively, but may require restriction from golf for an extended period of time. Many of the wrist problems that we see can often be related to a strong grip (left hand positioned clockwise on the golf club handle), overgripping (too tight a grip) golf club grips in poor repair, or poor swing techniques. The most common bony injury of the wrist is fracture of the hook of the hamate. This injury is a source of chronic ulnar-sided wrist pain in the golfer and is often diagnosed late or left undiagnosed. Proper-fitting golf clubs, proper swing technique, and avoidance of obstacles may prevent this injury. Like any other sport, golf requires the use of proper equipment, proper technique, and conditioning to prevent injury.

Arthroscopic anatomy of the wrist

A good working knowledge of the intra-articular anatomy of the wrist is essential to perform arthroscopy. The authors present a detailed description of all pertinent structures that may be seen during a radiocarpal and midcarpal arthroscopic examination.

Force and pressure transmission through the normal wrist. A theoretical two-dimensional study in the posteroanterior plane

Force transmission through the wrist in the normal population was investigated using the rigid body spring modeling (RBSM) technique (assuming carpal bones are rigid bodies interposed by series of springs simulating articulating cartilage and constraining ligaments). One-hundred and twenty normal wrist posteroanterior X-rays of adults (evenly divided to represent both genders and two age groups) provided the anatomical data. Reaction forces between the carpal bones were modeled using a system of compression linear springs, representing cartilage and subchondral bone, and of tensile linear springs, representing ligaments. The spring constants were determined based on the material properties of wrist cartilage and ligaments. Assumed axial loads were applied along the metacarpals to simulate a grasp strength of 10 N with active stabilization of the wrist in neutral position. The force transmission ratio at the radio-ulno-carpal joint was 55% through the radio-scaphoid and 35% through the radio-lunate joints. The remaining 10% of the load was passing through the triangular fibrocartilage with minor differences between genders. Among the intercarpal joints, a large percentage of the load of the wrist was transmitted to the scaphoid. The peak pressure was highest at the proximal pole of the radio-scaphoid, with a radio-scaphoid versus radio-lunate peak pressure ratio of 1.6. The most important ligaments in terms of load transmission were those opposing ulnar translation of the carpus. The wrist morphology had little influence on the magnitude and pattern of load distribution. There was no effect of age on wrist force distribution.

The use of topographical landmarks to improve the outcome of Agee endoscopic carpal tunnel release

A modified approach to endoscopic carpal tunnel release has been developed and tested in 60 cadaveric specimens by three surgeons using the Agee endoscopic carpal tunnel release system. The modified approach, which includes specific localization of the hook of the hamate, flexor retinaculum, and the superficial palmar arch utilizing topographical landmarks, avoids entry into Guyon's canal and injury to the ulnar artery and nerve, median nerve, and common digital nerves. Use of the anatomic approach resulted in significantly superior results. There were fewer incomplete releases, and fewer surgical passes were required, for the inexperienced surgeons. When these anatomic considerations were not included, the learning curve was much steeper. For surgeons planning endoscopic surgical release of the transverse carpal ligament, the described topographical approach improves the technical competence with the procedure and reduces the number of complications and learning curve associated with new procedures. We recommend the use of topographical landmarks and other anatomic considerations during endoscopic carpal tunnel release.

Pressure dynamics of the carpal tunnel and flexor compartment of the forearm

Although carpal tunnel pressures have been observed to increase as a result of repetitive flexion and extension of the wrist, and forearm compartment pressures have been shown to rise during and after muscle activity, the relationship between those two observations has not been studied. The flexor compartments of five cadavers were perfused with saline to determine whether elevated pressure in the flexor compartment of the forearm is transmitted to the carpal tunnel. The pressure in the carpal tunnel after the infusion was significantly different from the pressure in the flexor compartment of the forearm. Furthermore, pressures recorded in the carpal tunnel at the conclusion of the study were not statistically different from the preinfusion pressures. While the carpal tunnel may appear to be an open compartment anatomically, it functions as a relatively closed compartment with respect to transfer of pressure from the flexor compartment of the forearm under conditions that mimic elevated tissue pressure.

Rotational stability of the carpus relative to the forearm

To perform rotational tasks adequately, the rotational laxity between the radius and the carpus must be constrained within a certain limit. The contribution of nine individual capsuloligamentous structures to the rotational stability of the radiocarpal joint was studied using 14 fresh-frozen human cadaveric specimens. Torque-rotation curves, with sequential section of the soft-tissue structures, were used to calculate the percentage contribution of each individual structure. The primary pronation constraint was the palmar radioscaphocapitate ligament. The contributions to supination constraint were more complex; the dorsal radiotriquetral ligament was dominant, assisted by the palmar ulnolunate ligament. Structures originating from the ulna changed their major constraint contribution with forearm orientation, whereas those with a radial origin had a constant contribution independent of forearm rotation. Injury of these structures may lead to rotational instability at the radiocarpal level and should be considered when treating carpal instabilities.