Capitate-based kinematics of the midcarpal joint during wrist radioulnar deviation: an in vivo three-dimensional motion analysis

PURPOSE: The purpose of this study was to obtain qualitative and quantitative information regarding in vivo 3-dimensional (3D) kinematics of the midcarpal joint during wrist radioulnar deviation (RUD). METHODS: We studied the in vivo kinematics of the midcarpal joint during wrist RUD in the right wrists of 10 volunteers by using a technology without radioactive exposure. The magnetic resonance images were acquired during RUD. The capitate was registered with the scaphoid, the lunate, and the triquetrum by using a volume registration technique. Animations of the relative motions of the midcarpal joint were created and accurate estimates of the relative orientations of the bones and axes of rotation (AORs) of each motion were obtained. RESULTS: The scaphoid, lunate, and triquetrum motions relative to the capitate during RUD were found to be similar, describing a rotational motion around the axis obliquely penetrating the head of the capitate in almost a radial extension/ulnoflexion plane of motion of the wrist. The AORs of the scaphoid, the lunate, and the triquetrum were located closely in space. In the axial plane the AORs of the scaphoid, lunate, and triquetrum formed a radially and palmarly opening angle of 43 degrees +/- 7 degrees, 41 degrees +/- 11 degrees, and 42 degrees +/- 14 degrees with the wrist flexion/extension axis, respectively. CONCLUSIONS: This study reports the in vivo 3D measurements of midcarpal motion relative to the capitate. Isolated midcarpal motion during RUD could be approximated to be a rotation in a plane of a radiodorsal/ulnopalmar rotation of the wrist, which may coincide with a motion plane of one of the most essential human wrist motions, known as the dart-throwing motion.     

Kinematics of the midcarpal and radiocarpal joint in flexion and extension: an in vitro study

PURPOSE: To apply carpal kinematic analysis using noninvasive medical imaging to investigate the midcarpal and radiocarpal contributions to wrist flexion and extension in a quasidynamic in vitro model. METHODS: Eight fresh-frozen cadaver wrists were scanned with computed tomography in neutral, full flexion, and full extension. Body-mass-based local coordinate systems were used to track motion of the capitate, lunate, and scaphoid with the radius as a fixed reference. Helical axis motion parameters and Euler angles were calculated for flexion and extension. RESULTS: Minimal out-of-plane carpal motion was noted with the exception of small amounts of ulnar deviation and supination in flexion. Overall wrist flexion was 68 degrees +/- 12 degrees and extension was 50 degrees +/- 12 degrees. In flexion, 75% of wrist motion occurred at the radioscaphoid joint, and 50% occurred at the radiolunate joint. In extension, 92% of wrist motion occurred at the radioscaphoid joint, and 52% occurred at the radiolunate joint. Midcarpal flexion/extension between the capitate and scaphoid was 0 degrees +/- 5 degrees in extension and 10 degrees +/- 13 degrees in flexion. Midcarpal flexion/extension between the capitate and lunate was larger, with 15 degrees +/- 11 degrees in extension and 22 degrees +/- 19 degrees in flexion. CONCLUSIONS: The capitate and scaphoid tend to move together. This results in greater flexion/extension for the scaphoid than the lunate at the radiocarpal joint. The lunate has greater midcarpal motion between it and the capitate than the scaphoid does with the capitate. The engagement between the scaphoid and capitate is particularly evident during wrist extension. Out-of-plane motion was primarily ulnar deviation at the radiocarpal joint during flexion. These results are clinically useful in understanding the consequences of isolated fusions in the treatment of wrist instability.     

Kinematics of the midcarpal and radiocarpal joints in radioulnar deviation: an in vitro study

PURPOSE: Carpal kinematics have been studied widely yet remain difficult to understand fully. The noninvasive measurement of carpal kinematics through medical imaging has become popular. Studies have shown that with radial deviation the scaphoid and lunate flex whereas the capitate moves radiodorsally relative to the lunate. This study investigated the midcarpal and radiocarpal contributions to radial and ulnar deviation of the wrist. This was accomplished through noninvasive characterization of the scaphoid, lunate, and capitate using 3-dimensional medical imaging of the wrist in radial and ulnar deviation. METHODS: Eight fresh-frozen and thawed cadaveric wrists were used in an experimental set-up that positioned the wrist through spring-scale actuation of the 4 wrist flexor and extensor tendon groups. The wrists were scanned by computed tomography in neutral and full radial and ulnar deviation. Body mass-based local coordinate systems were used to track the motion of the capitate, lunate, and scaphoid with the radius as a fixed reference. Helical axis motion and Euler angles were calculated from neutral to radial and ulnar deviation for the capitate relative to the radius, lunate, and scaphoid and for the lunate and scaphoid relative to the radius. RESULTS: The capitate, scaphoid, and lunate moved in a characteristic manner relative to the radius and to one another. Radial and ulnar deviation occurred primarily in the midcarpal joint. Midcarpal motion accounted for 60% of radial deviation and 86% of ulnar deviation. In radial deviation the proximal row flexed and the capitate extended; the converse was true in ulnar deviation. CONCLUSIONS: Radioulnar deviation (in-plane motion) occurred mostly through the midcarpal joint, with a lesser contribution from the radiocarpal joint. The results of our study agree with previous investigations that found the scaphoid and lunate flex in radial deviation (out-of-plane motion) relative to the radius whereas the capitate extends (out-of-plane motion) relative to the scaphoid/lunate (with the converse occurring in ulnar deviation). Our study shows how these out-of-plane motions combine to produce in-plane wrist radioulnar deviation. The use of 3-dimensional visualization greatly aids in the understanding of these motions. The results of our study may be useful clinically in understanding the consequences of isolated midcarpal fusions in the treatment of wrist instability.     

Ulnocarpal impaction syndrome restricts even midcarpal range of motion.

Ulnocarpal impaction syndrome is believed to be caused by abutment between the ulna and the ulnar carpus. We measured radiocarpal and midcarpal ranges of motion in 40 patients with ulnocarpal impaction syndrome by radiographic motion studies. The results showed that the radiocarpal and midcarpal ranges of motion were equally restricted in the affected wrist compared with the unaffected wrist. Therefore, motion of the radiocarpal joint and midcarpal joint contributed equally to total wrist motion bilaterally. No correlation between ulnar variance and the contribution of radiocarpal motion to overall wrist motion was found. Restriction of wrist motion in ulnocarpal impaction syndrome is not caused directly by abutment between the ulna and ulnar carpus, but a satisfactory explanation for restricted motion is still lacking.     

Avascular necrosis of the capitate

Although a large portion of the capitate is supplied by a single nutrient vessel, avascular necrosis of the capitatum is a rare condition. Its etiology is not clear, but a number of factors are linked to its pathogenesis including: repetitive trauma, dorsal instability of the carpus, Gaucher disease, systemic lupus erythematosus, gout, and steroid use. A 24-year-old woman presented with right wrist pain of 12 months duration. She reported no major trauma and reported that her pain had begun during the third month of her pregnancy. She had a history of hyperemesis gravidarum treated with 2 to 4 mg/daily of prednisone during her pregnancy for 6 weeks. She had 70° extension and 45° flexion of her wrist. Radiographs showed a hypodense area at the capitate head and midcarpal joint arthritis. Magnetic resonance imaging demonstrated avascular necrosis of the capitate and midcarpal collapse at the lunocapitate joint. Lunocapitate fusion with a partial scaphoidectomy was performed. At final follow-up 28 months postoperatively, she had 60° of volar flexion, and 50° of dorsiflexion. She was pain free in the majority of her activities of daily living. A small dose of steroid use during pregnancy, even in a short period of time, is a potential risk for avascular necrosis of the capitate and patients with a gradual onset of wrist pain during pregnancy may need to be investigated further if symptoms are not resolved with basic nonoperative measures within a reasonable time frame.     

Radioscapholunate Fusion Following Comminuted Fractures of the Distal Radius

Radioscapholunate (RSL) arthrodesis must be considered an appropriate procedure in painful radiocarpal arthrosis following comminuted fractures of the distal radius. Despite total wrist fusion, it offers the possibility to exclusively eliminate the destroyed articulation preserving a certain degree of motion in the midcarpal joint. Accordingly, 22 patients with painful posttraumatic arthrosis of the radiocarpal joint underwent RSL fusion between 1992 and 1998. Average follow-up was 18.7 months. Postoperatively, total range of wrist motion decreased by an average of 21° E-F and 6° U-R deviation. Average grip strength of the affected wrist improved from 31.9 to 51.1 kPa. There was a considerable decrease of pain during activity and at rest. Using the DASH questionnaire, an average of 25.7 points was reached. Radiologic examination revealed no major signs of arthritis at the midcarpal joint. In one patient, nonunion as well as reactivation of deep infection secondary to an infection sustained during surgical stabilization of the initial radial fracture were recorded. In our opinion, however, RSL fusion represents a good alternative to total wrist fusion, since valuable wrist motion is preserved.     

The development of a total wrist arthroplasty.

For many individuals the preservation of wrist motion is essential for augmentation of fine motor control of the hand and fingers. When significant functional disability exists at the wrist, currently available surgical treatment includes soft tissue arthroplasty, carpectomy, or arthrodesis. A total wrist joint arthroplasty offers the patient the potential of a pain-free, stable, and mobile wrist. Based upon the principles of total joint replacement as applied to the hip and knee, the prosthesis is secured to the carpus and radius with methylmethacrylate cement, following removal of the navicular, lunate, and head of the capitate. The design of the prosthesis provides for the two planes of motion normally seen at the wrist; 90 degrees of flexion and extension and 50 degrees of radial ulnar deviation are permitted by the design. Candidates for total wrist arthroplasty are patients who exhibit far-advanced disease at the wrist and who might be considered as candidates for arthrodesis, but in whom the permanent loss of motion would represent a significant handicap. To date 17 arthroplasties have been performed in 14 patients. The longest follow-up is 14 months. All but 2 patients have gained a useful range of motion. All patients have noted dramatic relief of pain and deformity, permitting them to perform tasks which were preoperatively impossible.     

Operative technique of a new decompression procedure for Kienböck disease: partial capitate shortening

A new decompression procedure for Kienb?ck disease, namely "partial capitate shortening," was developed. Patients in Lichtman stages 2 and 3A, independent of the ulnar variance, are candidates for this procedure. This procedure can dramatically reduce compressive forces on the lunate almost as much as a traditional decompression procedure of the capitate (capitate shortening combined with capitate-hamate fusion) and much more than the decompression procedure of the forearm bone such as radial shortening. We surmise that our procedure will allow better lunate revascularization. Although the scaphoid progressively adopts an abnormal palmarflexed position after capitate shortening combined with capitate-hamate fusion, partial capitate shortening can maintain normal carpal alignment, resulting in better joint congruency around the scaphoid and range of motion of the wrist. Moreover, partial capitate shortening allows minimal invasion and is an easy technique without bone grafting. Both operating and immobilizing time are shortened, and there are no secondary problems in the distal radioulnar and/or ulnocarpal joint often seen after radial osteotomy procedures.     

Four-corner fusion and scaphoid excision using headless compression screws for SLAC and SNAC wrist deformities

Scapholunate advanced collapse and scaphoid nonunion advanced collapse wrist deformities are the most common causes of traumatic arthritis of the wrist. Four-corner fusion and scaphoid excision has proven to be an effective procedure for relieving pain and preserving range of motion in the wrist joint. Several methods for providing fixation of the midcarpal joint during fusion have been used, including K-wires, staples, and the Spider plate. K-wire fixation has proven effective, but requires a period of cast immobilization to protect the fusion mass. The Spider plate was promising, but has not been without complications. The development and improvements in cannulated headless compression screws has resulted in increased indications for their use, including fixation for 4-corner fusion. We review the technique and tips developed by the senior author over the last several years using headless compression screws for fixation of the midcarpal joint. Acutrak 2 Standard implants were used. This technique has allowed for early range of motion with reliable fusion rates.     

Der posttraumatische karpale Kollaps Verlauf und Therapiekonzept

Significant progress has been made in the understanding of carpal kinematics and posttraumatic disorders of the wrist. The importance of stabilization of the scaphoid is well known. More and more ligament injuries of the proximal carpal row have been diagnosed in cases of severe arthrotic changes. Long-standing scaphoid nounion or scapholunate ligament injuries can lead to progressive carpal collapse due to a break of the continuity of the proximal carpal row. SLAC-wrist (scapholunate advanced collapse) and SNAC-wrist (scaphoid nonunion advanced collapse) after missed fusion of scaphoid fractures should be differentiated. Severity of degenerative changes is classified into three stages. Salvage procedures preserving wrist mobility, like midcarpal fusion, are preferable to total wrist fusion because of the functional benefit. With complete excision of the scaphoid and fusion of the midcarpal joint, all arthritic joint surfaces are eliminated and motion is preserved in the radiolunate joint which is usually spared of degenerative changes.     

Chronic transscaphoid,transcapitate perilunate fracture dislocation of the wrist: Fenton's syndrome

The authors report about chronic Fenton's syndrome. This rare injury of the wrist is characterized by scapho-capitate fracture accompanied by 180° rotation of the head of capitate and associated perilunate dislocation. Two patients suffering from chronic Fenton's syndrome were treated with pyrocarbon capitate resurfacing prosthesis. Patients were evaluated according to the wrist range of motion, Mayo modified wrist and DASH scores. In conclusion, prosthetic surgery may achieve satisfactory results for this rare and diagnostically challenging syndrome.     

Scaphoid nonunion and distal fragment resection: analysis with three-dimensional rigid body spring model

Background  Distal fragment resection is one of the salvage procedures for scaphoid nonunion with osteoarthritis. Despite being reported as a simple procedure with favorable midterm outcomes, further arthritic changes remain a concern in the long term. Scaphoid waist fracture is classified into volar or dorsal types according to the displacement pattern, but the indications for distal fragment resection have never been discussed for these fracture types. Method  We reconstructed a normal wrist model from computed tomography images and performed theoretical analysis utilizing a three-dimensional rigid body spring model. Two types of scaphoid fracture nonunion followed by distal fragment resection were simulated. Results  With volar-type nonunion, the force transmission ratio of the radiolunate joint increased, and the pressure concentration was observed in the dorsal part of the scaphoid fossa and volar part of the lunate fossa of the radius; no deterioration was seen in the midcarpal joint. In the distal fragment resection simulation for volar-type nonunion, pressure concentrations of the radiocarpal joint resolved. With dorsal-type nonunion, force transmission ratio in the radiocarpal joint resembled that of the normal joint model. Pressure concentrations were observed in the dorsoulnar part of the scaphoid fossa and radial styloid. The pressure concentration in the dorsoulnar part of the scaphoid fossa disappeared in the resection model, whereas the concentration in the radial styloid remained. In the midcarpal joint, pressure was concentrated around the capitate head in the nonunion model and became aggravated in the resection model. Conclusions  With volar-type scaphoid nonunion, distal fragment resection seems to represent a reasonable treatment option. With dorsal-type nonunion, however, pressure concentration around the capitate head was aggravated with the simulated distal fragment resection, indicating a potential risk of worsening any preexisting lunocapitate arthritis.     

Analysis of radiocarpal and midcarpal motion in stable and unstable rheumatoid wrists using 3-dimensional computed tomography

PURPOSE: The kinematic evaluation of carpal motion, especially midcarpal motion, in rheumatoid arthritis (RA) has been extremely difficult because of limited imaging techniques previously available. The purpose of this study was to evaluate the amount of radiocarpal and midcarpal motion in the flexion-extension plane in both stable and unstable rheumatoid wrists using three-dimensional computed tomography. METHODS: We acquired in vivo kinematic data on 30 wrists with RA by three-dimensional computed tomography with the wrist in 3 positions: neutral, maximum flexion, and maximum extension. All cases were radiographically classified into 1 of 2 subtypes, the stable form or unstable form, according to the classification by Flury et al. We evaluated the precise range of radiocarpal and midcarpal motion using a markerless bone registration technique and calculated the individual contributions to the total amount of wrist motion in the flexion-extension plane in the different radiographic subtypes of RA. RESULTS: The average range of motion of radiocarpal and midcarpal joint was 27 degrees +/-15 and 32 degrees +/-17, respectively. The average contribution of midcarpal motion to the total amount of wrist motion was 54%. The average contribution of midcarpal motion in the unstable form was 67%, which was significantly higher than 47% (p< .05) in the stable form. CONCLUSIONS: Midcarpal motion of rheumatoid wrists in the flexion-extension plane was better preserved than previously thought. The contribution of midcarpal motion to the total amount of wrist motion was significantly greater (p< .05) in the unstable form than in the stable form of RA.     

The rheumatoid wrist

Wrist involvement is common in patients with rheumatoid arthritis. Individual patient assessment is important in determining functional deficits and treatment goals. Patients with persistent disease despite aggressive medical management are candidates for surgery. Soft-tissue procedures offer good symptomatic relief and functional improvement in the short term. Extensor and flexor tendons may rupture because of synovial infiltration and bony irritation. When rupture occurs, direct repair usually is not possible. However, when joints that are motored by the ruptured tendon are still functional, tendon transfer or grafting may be considered. Because of the progressive nature of the disease, dislocation and end-stage arthritis often require stabilization with bony procedures. The distal radioulnar joint is usually affected first and is commonly treated with either the Darrach or the Sauvé-Kapandji procedure. Partial wrist fusion offers a compromise between achieving stability of the affected radiocarpal joint and maintaining motion at the midcarpal joint. For pancarpal arthritis, total wrist fusion offers reliable pain relief at the cost of motion. Total wrist arthroplasty is an alternative that preserves motion; however, the outcomes of total wrist replacement are still being evaluated.     

Fibulo-scapho-lunate arthrodesis as a motion-preserving procedure after tumour resection of the distal radius

Free microvascular fibula transfer is an established method for reconstruction of the distal radius following tumour resection. If the radial articular surface is resected, fixation of the fibula to the carpus is either performed as a complete wrist fusion, or the fibular head is transferred together with the shaft to replace the radial joint surface, thus allowing some wrist mobility but providing only limited wrist stability. Fibulo-scapho-lunate fusion represents an alternative. This reconstruction in two patients provided excellent wrist stability and a functional range of midcarpal motion.     

Treatment of radiocarpal degenerative osteoarthritis by radioscapholunate arthrodesis and distal scaphoidectomy

PURPOSE: The purpose of this study was to assess wrist pain, range of motion, and the presence of radiographic midcarpal degenerative joint disease (DJD) in patients who had a distal scaphoidectomy in association to a radioscapholunate (RSL) arthrodesis and to compare these findings with prior studies of patients with only an RSL fusion. METHODS: Sixteen patients with radiocarpal DJD treated by RSL arthrodesis and distal scaphoidectomy were evaluated retrospectively for pain relief and range of motion at an average follow-up period of 37 months (range, 12-84 mo). Radiographs were assessed for the presence of secondary radiographic midcarpal DJD. RESULTS: Complete pain relief was obtained in 10 patients, 3 patients complained of slight pain during strenuous loading, and 3 patients had occasional pain with regular activities. The average postoperative ranges of motion were 32 degrees of flexion, 35 degrees of extension, 14 degrees of radial deviation, and 19 degrees of ulnar deviation. Two patients exhibited secondary midcarpal DJD. These results are significantly better compared with those previously published about RSL arthrodesis alone in terms of residual pain and decrease of wrist radial deviation and flexion. CONCLUSIONS: Patients who require an RSL arthrodesis for the treatment of severe localized radiocarpal DJD appear to have less pain and to retain more flexion and radial deviation if the distal scaphoid is excised concomitantly. This associated procedure also may help prevent secondary midcarpal DJD.     

Partial Fusion of the wrist - an alternative procedure to the total wrist arthrodesis

Despite the important observations that have been made concerning biomechanics and function of the wrist joint in recent years, the surgeon is still confronted with a huge number of delayed posttraumatic disorders of this joint. In the past, total wrist fusion was the leading salvage procedure, whereas today several salvage procedures are available to solve these problems. Partial wrist fusions are supposed to stabilize the carpus, immobilize destroyed articulating surfaces while allowing motion in the unharmed parts of the wrist. Acknowledging pathobiomechanical laws, they have been used for a growing number of indications with a large benefit. The patients profit of better functional results than can be observed in patients with total arthrodesis of the wrist. Furthermore, partial wrist fusion provides a more stable situation and the absence of pain for a longer period of time. However, further studies evaluating the clinical outcome of these salvage procedures are necessary and to be expected in the near future.     

Distal scaphoid excision after radioscaphoid arthrodesis

Radioscaphoid and radioscapholunate arthrodeses are effective surgical procedures for the treatment of nonsalvageable and isolated radiocarpal arthritis. These procedures, however, limit wrist motion significantly as the immobile scaphoid bridges the remaining midcarpal joint. A cadaver study of radioscaphoid arthrodesis followed by distal scaphoid excision was undertaken. Range of motion after radioscaphoid K-wire fixation alone demonstrated a 58% decrease in the preoperative flexion-extension arc to 60 degrees. After distal scaphoid excision (with the radioscaphoid pins still in place) the flexion-extension arc increased to 122 degrees or 86% of the preoperative range of motion; most of the increase in motion occurred at the midcarpal joint. Distal scaphoid excision releases the midcarpal joint following radioscaphoid fixation and results in a significantly greater wrist motion. If the results of this cadaver study are extrapolated to clinical practice the addition of this step to the previously described procedures of radioscaphoid or radioscapholunate arthrodesis addresses their major limitation, restricted motion.     

Radioscapholunate arthrodesis

Although RSL fusion is a viable option for isolated radiocarpal arthritis, the enthusiasm for this procedure should be tempered with the reality that kinematics of the wrist is not entirely suited for independent midcarpal flexion and extension [10]. Limited wrist flexion and extension is expected following a successful RSL arthrodesis. The effects of imposed abnormal kinematics are further shown by the high incidence of RSL nonunions, occurrence of scaphoid fractures, and postoperative deterioration of the midcarpal joint [15,22]. In a young patient with posttraumatic arthritis or rheumatoid arthritis limited to the radiocarpal joint, however, RSL arthrodesis remains a viable alternative to complete wrist arthrodesis if the midcarpal joint is normal. Internal fixation with plates and screws and distal scaphoid excision are technical alternatives to consider when an RSL arthrodesis is performed.