逆行筋膜骨瓣移植加桡骨茎突切除治疗腕舟骨骨不连

目的探索治疗腕舟骨骨不连的有效手术方法。方法对２５侧新鲜成人上肢标本进行显微解剖研究后，设计出逆行筋膜骨瓣移植加桡骨茎突切除的手术方法。１９８７以来，临床应用于２２例腕舟骨骨不连。结果术后１８例获得随访，随访时间为３～１０年，骨性愈合率达到１００％，愈合时间为２～３个月，腕关节功能完全恢复正常。结论该手术方法疗效好、副损伤小、操作简单、易于推广；为治疗腕舟骨骨不连的有效方法     

The use of vascularized grafts from the distal radius for the treatment of Preiser's disease

PURPOSE: To examine the outcome of vascularized bone grafts (VBGs) used for the treatment of Preiser's disease. METHODS: Over a 10-year period (1993-2003) 8 pedicled VBGs were performed as the primary treatment for Preiser's disease. All patients had preoperative magnetic resonance imaging (MRI) scans that confirmed the diagnosis of avascular necrosis of the scaphoid. Bone revascularization was evaluated by examining preoperative and postoperative MRIs. All patients had a reverse-flow pedicled VBG from the distal radius. The average patient age was 40 years and the mean follow-up period was 36 months. Postoperative evaluation included range of motion, grip strength, pain evaluation, and Mayo wrist scores. RESULTS: All MRIs showed evidence of revascularization, with improvement in T2 and/or T1 signal; however, a consistent finding on MRI was incomplete revascularization of the entire proximal pole. Wrist motion averaged 55% of the unaffected side after surgery. Grip strength remained stable. Seven patients had long-term improvement in pain. The average Mayo wrist score was 68, with 1 patient rated as excellent, 1 as good, 5 as fair, and 1 as poor. There was 1 reconstructive failure that resulted in a proximal row carpectomy less than 1 year after the surgery. CONCLUSIONS: In this series VBGs led to reduced pain levels and preserved the radiocarpal wrist motion in most patients. Inability to revascularize the proximal pole of the scaphoid and ongoing wrist arthritis appear to persist despite revascularization attempts. VBGs for Preiser's disease should be limited to patients with early stage disease (Herbert stages I or II) without evidence of radiocarpal arthritis and no evidence of carpal instability. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic, Level IV.     

Long-term assessment of proximal row carpectomy for chronic perilunate dislocations

Twelve patients with chronic stage III or stage IV perilunate dislocations were managed over the past 7 years by proximal row carpectomy. All dislocations were untreated or incompletely reduced for a minimum of 8 weeks after injury. The mean time from injury to definitive treatment was 15 weeks (range, 8 weeks to 6 months). Surgical management was inclusive of a dual dorsal and volar approach. Median nerve decompression, lunate excision, and capsuloligament repair was performed volarly and scaphoid and triquetrum carpectomy was accomplished dorsally. Temporary radio capitate K-wire fixation during early soft tissue healing was uniformly performed. All patients were evaluated at an average postoperative duration of 40 months (range, 28 months to 7 years). Marked relief of wrist pain and median nerve dysesthesias was routinely achieved. Effective wrist range of motion and grip strength were restored. Untreated stage III and IV chronic perilunate dislocation treated by proximal row carpectomy eliminates pain and restores function to a severely injured wrist.     

Vascularized bone graft from the iliac crest for the treatment of nonunion of the proximal part of the scaphoid with an avascular fragment.

BACKGROUND: It was hypothesized that nonunion of the proximal third of the scaphoid associated with avascular necrosis could be treated successfully with a free vascularized bone graft obtained from the iliac crest. METHODS: Fifteen patients who had a nonunion of the proximal part of the scaphoid that had been present for an average of two years and three months (range, nine months to seven years) were managed with use of a free vascularized bone graft obtained from the iliac crest. Avascularity of the scaphoid, as assessed on preoperative radiographs, was characterized by loss of trabecular structure, collapse of subchondral bone, and formation of bone cysts. The results of the procedure were assessed in terms of osseous union, pain, active motion of the wrist, and osteoarthritis. Postoperatively, vascularity of the scaphoid was evaluated with use of magnetic resonance imaging and color Doppler ultrasonography. The average duration of follow-up was six years and one month (range, two years and one month to eight years and one month). RESULTS: Preoperatively, one patient had had pain with any movement of the wrist and fourteen had had pain after strenuous manual labor or sports activity. The average pain score, derived with use of a 10-point visual analog scale, was 2.4 points (range, 1.0 to 6.7 points). Postoperatively, union was achieved in twelve patients; six were pain-free, and six had occasional pain during strenuous manual labor or sports activity, or both. The average pain score for these twelve patients was 1.1 points (range, 0.0 to 4.2 points) on the visual analog scale. Preoperatively, osteoarthritis was limited to the region between the radial styloid process and the distal part of the scaphoid in fourteen patients and to the radioscaphoid region in one patient. Postoperatively, the degree of osteoarthritis remained unchanged in seven of the twelve patients who had union and progressed to the radioscaphoid region in five. Vascularity, as seen on the imaging studies, was restored in all twelve patients who had union. The nonunion persisted in three patients, all of whom had progressive osteoarthritis leading to carpal collapse. CONCLUSIONS: The index procedure was successful in twelve of the fifteen patients who had a symptomatic nonunion of the proximal part of the scaphoid associated with avascular necrosis and osteoarthritis that was limited to the radioscaphoid joint.     

不同筋膜血管蒂骨瓣植入治疗舟状骨陈旧性骨折

目的介绍利用不同筋膜血管蒂桡骨茎突骨瓣植入治疗陈旧性腕舟状骨骨折的疗效。方法2002年9月-2010年5月,采用以桡动脉返支为蒂的骨瓣,或以骨间背动脉桡侧终末支的筋膜蒂骨瓣植入结合内固定治疗腕舟状骨陈旧性骨折41例。结果38例经6～27个月（平均19．3个月）的随访,X线片显示腕舟骨骨折均在术后4～6个月获得骨性愈合,愈合率达100％。腕关节活动度为4例腕掌屈60°背伸50°34例腕掌屈达70°-80°．背伸45°-55°。腕关节活动时无疼痛。腕关节功能按Krimmer评分表测定：总体疗效为优29例,良9例。结论采用带不同血管蒂桡骨茎突骨瓣植入治疗舟状骨陈旧性骨折疗效确切。     

Trans-scaphoid perilunate fracture dislocations: results of screw fixation of the scaphoid and lunotriquetral repair with a dorsal approach

PURPOSE: To review the clinical and radiographic outcome of dorsal trans-scaphoid perilunate fracture-dislocations treated with screw fixation of the scaphoid and repair of the lunotriquetral ligament with bone anchors. METHODS: Twenty-five patients treated over an 11-year period for dorsal trans-scaphoid perilunate fracture-dislocations were reviewed retrospectively at a mean of 44.3 months. The mean age of the patients was 28.6 years, and 22 patients were men. Delay to surgery was 3.5 days. Five scaphoids had bone grafting from the distal radius. Six patients developed carpal tunnel syndrome requiring release. The functional outcome was determined by comparing the range of motion of the injured extremity with the uninjured extremity, grip strength, ability to return to pre-injury employment, and overall patient satisfaction. Radiographic evaluation comprised time to scaphoid union, any changes in the lunotriquetral interval, development of a volar intercalated segmental instability pattern, and any development of arthritis over time. RESULTS: Total range of motion achieved was 91% of the uninjured wrist and grip strength was 80%. Average extension was 54 degrees with an average flexion of 60 degrees . Ulnar deviation was 23 degrees with radial deviation averaging 18 degrees . The average supination was 76 degrees and the average pronation was 76 degrees . All scaphoids united primarily. The average time to union of the scaphoid was 16 weeks. For those scaphoids with bone grafting the union time was an average of 18.4 weeks. The average postreduction lunotriquetral gap was 1.8 +/- 0.4 mm. The average lunotriquetral gap at the last follow-up evaluation was 1.9 +/- 0.6 mm. None of the patients developed a volar intercalated segmental instability deformity. All but 2 patients returned to their pre-injury occupation. All patients, however, returned to some type of employment. Complications included 1 superficial pin track infection that resolved with removal of the pin and a short course of oral antibiotics. CONCLUSIONS: A dorsal approach to the wrist provides adequate exposure for reduction of carpal bones, internal fixation of the scaphoid, and lunotriquetral repair. Although perilunate fracture-dislocations are challenging problems to treat, all of the patients had acceptable pain relief and achieved sufficient range of motion and strength to return to gainful employment.     

Surgical outcome of scaphoid nonunions in heavy manual workers

The management of scaphoid nonunion in heavy manual workers is challenging. Symptoms appear earlier and manual labor-related stress at the operated nonunion site may worsen the postoperative outcome. This study involved 16 heavy manual workers with scaphoid nonunion (11 cases involving the dominant hand) treated by internal fixation and autologous bone grafting. The nonunion was in 12 patients in the waist, in 3 patients in the proximal, and in 1 patient in the distal pole of the scaphoid. Clinical and radiographic evaluation of union was done according to the criteria of Bynum et al. and Fernandez and Eggli. Pain, wrist motion, and grip strength were evaluated and compared to the contralateral side. At a mean follow-up of 24 months (range, 10 months to 6 years), the mean range of motion and the grip strength compared to the contralateral hand were 95% and 91%, respectively. Overall hand function was excellent in 13 patients, good in 2 patients, and fair in 1 patient. All except one patient were pain free and returned to their work without or with minimal complaints at an average of 3.4 months (range, 2-6 months), postoperatively. In 15 patients, scaphoid nonunions healed at a mean time of 64 days. One patient had a reoperation, and union was observed at 90 days after the second operation. In all patients, the radiolunate angle was restored to normal. One patient developed complex regional pain syndrome that resolved completely after 2 months with adequate intensive physical therapy. Clinical symptoms of scaphoid nonunions are more severe and appear earlier in heavy manual workers; in this group of patients, surgical treatment is necessary. The double-threaded screw provides adequate stabilization for union. Autologous cancellous bone graft, because of its plasticity and malleability to exactly fill the scaphoid defect, is recommended.     

Distal scaphoid resection arthroplasty for the treatment of degenerative arthritis secondary to scaphoid nonunion

Nineteen patients with chronic scaphoid nonunion and associated degenerative arthritis between the distal fragment and the radial styloid were treated by resection of the distal fragment. All patients had a dorsal intercalated segment instability wrist collapse pattern with an average radiolunate angle of -32 degrees and a 10% reduction in the carpal height, both of which changed minimally during the follow-up period. The duration of the nonunion averaged 12 years and the follow-up period averaged 49 months. Range of motion improved 85% and grip improved 134%. Thirteen of the patients experienced complete pain relief. One patient required additional surgery and elected wrist arthrodesis. Resection of the distal fragment is not recommended for patients with capitolunate arthritis. Two of the 4 patients with capitolunate arthritis had persistent symptoms; 3 had progressive degenerative changes.     

Dorsal perilunate dislocations and fracture-dislocations: questionnaire, clinical, and radiographic evaluation

Twenty-two consecutive patients (23 wrists) underwent open reduction internal fixation of dorsal perilunate dislocations and fracture-dislocations through combined dorsal and volar approaches. One of 5 experienced wrist surgeons performed these procedures within an average of 3 days of injury (range, 0-26 days) and intercarpal fixation was kept within the proximal carpal row. Motion was instituted an average of 10 weeks (range, 5-16 weeks) after injury. All patients were males. The average age at the time of injury was 32 years (range, 16-60 years). The average follow-up period was 37 months (range, 13-65 months). Average flexion-extension motion arc and grip strength in the injured wrist were 57% and 73%, respectively, compared with the contralateral wrist. The scapholunate angle increased and the revised carpal height ratio decreased over time, which was statistically significant for both measurements. Three patients (3 wrists) required wrist arthrodesis and a fourth patient had an immediate scaphoid excision and 4-corner arthrodesis secondary to an irreparable scaphoid fracture. One patient required a proximal row carpectomy to treat septic arthritis. Nine of the remaining 18 wrists had radiographic evidence of arthritis, most often at the capitolunate or scaphocapitate articulations. Short form-36 mental summary scores were significantly greater than age- and gender-matched US population values; physical summary scores were significantly less. The disabilities of arm, shoulder, and hand evaluation, Mayo wrist score, and patient-rated wrist evaluation all reflected loss of function. Seventy-three percent of all patients had returned to full duties in their usual occupations and a total of 82% were employed.     

Functional outcomes of nonunion scaphoid fracture treated by pronator quadratus pedicled bone graft

Between 1998 and 2007, a pronator quadratus pedicled bone graft was performed for 45 patients of ununited scaphoid fracture. One of them had bilateral ununited scaphoid fracture. There were 29 men and 16 women with a median age at operation of 24 (16-32) years. The affected side was the right side (dominant hand) in 32 patients whereas 13 patients had fracture of the nondominant left side. There had been 32 proximal pseudoarthrosis (through or proximal to the junction of the proximal and middle thirds of the bone) and 14 of the middle third of the scaphoid. The original fractures were caused by motor cycle accidents in 23 patients, falling on outstretched hand in 15 patients, and sport injuries in the remaining 7 patients. Surgery was indicated from 5 months to 6 years after injury (average 43 months) because of complaints of pain on heavy work. The fracture has been missed at the initial examination in 23 patients whereas cast immobilization was done for 6 weeks and 3 months in 15 and 7 cases, respectively, that had failed to result in union. There were no preoperative osteoarthritic changes, but in 25 cases, there were avascular necrosis of the proximal fragment of the scaphoid. Forty-three patients showed radiographic union after an average of 14 weeks (12-16 weeks). One patient had dislodgement of the graft and refused to do it again. The average range of movement of wrist improved after operation. Taken as a percentage of the normal range, dorsiflexion increased from 69% to 80%, palmar flexion from 66% to 76%, radial deviation from 45% to 70%, and ulnar deviation from 67% to 84%. Grip strength improved from 82% to 92% of normal. All the patients have been able to return to their former activities with no pain.     

Scaphoid morphology and clinical outcomes in scaphoid reconstructions

Scaphoid malunion and carpal malalignment can result after scaphoid reconstruction, if the two fragments are not properly reduced before fixation. However, currently there is no information about which degree of deformity or malalignment can be tolerated without impairing clinical function. The purpose of this study was to investigate the influence of the scaphoid morphology and carpal alignment on clinical outcomes after scaphoid reconstruction. A total of 65 patients with an average age of 29 years were followed-up after a mean period of 45 months. In all patients, osseous union after a first-time scaphoid reconstruction in the middle third had been confirmed. Scapholunate (SL) and radiolunate (RL) angles were obtained on plain radiographs as were intrascaphoid (ISA) and dorsal cortical (DCA) angles and the height/length (H/L) ratio of the reconstructed scaphoid on computed tomography (CT) scans. These parameters were correlated with clinical outcome measures. RL angles correlated significantly with wrist range of motion, grip strength and pain levels, whilst SL angles, ISA, DCA and H/L ratio failed to show significant correlations. Our data suggest that clinical outcome is correlated with correct restoration of bone morphology and carpal alignment. After reconstruction, the RL angle should not exceed 10°.     

Rotatory subluxation of the scaphoid in Kienböck's disease is not a cause of scapholunate advanced collapse (SLAC) in the wrist

We have examined whether the rotatory subluxation of the scaphoid which is seen in patients with advanced Kienb?ck's disease is associated with scapholunate advanced collapse (SLAC) wrist. We studied 16 patients (11 men, 5 women) who had stage-IV Kienb?ck's disease with chronic subluxation of the scaphoid. All had received conservative treatment. The mean period of affection with Kienb?ck's disease was 30 years (14 to 49). No wrist had SLAC. In eight patients, 24 years or more after the onset of the disease, the articular surface of the radius had been remodelled by the subluxed scaphoid with maintenance of the joint space. The wrists of six patients were considered to be excellent, nine good, and one fair according to the clinical criteria of Dornan. Our findings have shown that rotatory subluxation of the scaphoid in Kienb?ck's disease is not a cause of SLAC wrist and therefore that scaphotrapeziotrapezoid arthrodesis is not required for the management of these patients.     

Open reduction and internal fixation of acute displaced scaphoid waist fractures

Fourteen consecutive patients with acute displaced scaphoid waist fractures were treated with open reduction and internal fixation. The operative technique consisted of anatomic reduction of the displaced scaphoid waist fracture, correction of carpal instability, radial bone grafting for comminution, and internal fixation with K-wires or Herbert screw. The patients were evaluated an average of 26 months (range, 4-48 months) after surgery. Thirteen of the 14 (93%) fractures united. The average time to union was 11.5 weeks (range, 8-20 weeks). Fracture union was confirmed with trispiral tomography. Final radiographic assessment consistently revealed a healed scaphoid fracture, restored intrascaphoid alignment, and no evidence of carpal instability. All patients regained functional wrist range of motion (wrist extension, 57 degrees; wrist flexion, 52 degrees ) and grip strength. Open reduction and internal fixation of acute displaced scaphoid waist fractures restores scaphoid alignment and leads to predictable union. Early operative intervention avoids malunion and carpal instability that often occurs with closed management of these complex fractures.     

Operative Behandlungsmöglichkeiten bei fortgeschrittenem karpalen Kollaps (SNAC/SLAC wrist)

Longstanding and untreated scaphoid fractures and scapholunate dissociations lead to painful destruction of the wrist with carpal collapse. The severity of degenerative arthrosis is classified in three stages and can be treated adequate operatively. SNAC wrist (scaphoid nonunion advanced collapse) after failed fusion of the scaphoid and SLAC wrist (scapholunate advanced collapse) after scapholunate dissociation should be differentiated. The reconstruction of the scaphoid or scapholunate ligament in stage II and III is no reasonable option. Motion preserving procedures such as proximal row carpectomy or midcarpal arthrodesis are preferable in this situation. Thirty-one male patients (average 41 years) were treated for SNAC or SLAC wrist with midcarpal arthrodesis. All patients were reexamined, the mean follow-up was 15 months. Grip strength was measured with the Dexter-System, pain was evaluated by a visual analogue scale (VAS 0-100). Patients' daily activities and general quality of life were estimated with the DASH-questionnaire. Pain was reduced to 50% compared to the preoperative situation. Grip strength improved to 60% of the opposite side. Active range of motion reached 50% of the contralateral wrist. Total DASH-score reached 39.0. Nonunion at the fusion site necessitated additional surgery in four patients resulting in total wrist arthrodesis. 80% of the patients returned to their original occupation. Midcarpal fusion is a reliable procedure for treating the difficult condition of advanced carpal collapse if proper realignment of the carpus is performed. The DASH-score reflects the subjective impressions of the patients in daily life and justifies the choice of a salvage procedure preserving wrist mobility. Total wrist fusion represents the last line of defense.     

Reevaluation of the cause of the wrist ganglion

The cause of the wrist ganglion is uncertain. We reviewed our experience with rotary subluxation of the scaphoid after ganglion excision. Seventeen patients had triscaphe arthrodesis for treatment of rotary subluxation of the scaphoid at an average of 35 months (range, 6 to 130 months) after ganglion excision. In addition, dynamic or static rotary subluxation of the scaphoid was found in 8 of 10 patients who were examined at an average of 16 years (range, 11 to 19 years) after excision of a ganglion. These patients had no symptoms at the time of review. Only single case reports of rotary subluxation of the scaphoid after ganglion excision have been previously reported. We believe our data supports a hypothesis that the ganglion is a secondary manifestation of underlying periscaphoid ligamentous injury. Persistent symptoms after ganglion excision should lead one to suspect underlying scaphoid instability.     

Capitolunate arthrodesis with scaphoid and triquetrum excision

A retrospective two-center outcome study was designed to evaluate the results of capitolunate arthrodesis with scaphoid and triquetrum excision mainly for scapholunate advanced collapse patterns of arthritis. Fourteen wrists in 14 patients were evaluated objectively by standard parameters and subjectively by the Short Musculoskeletal Functional Assessment at an average of 28 months after surgery (range, 14-51 months). All patients were men between the ages of 20 and 70 years (average, 49 years). Two patients had a painful nonunion and one had persistent pain despite conversion to a solid wrist arthrodesis. One patient had x-ray evidence of progressive radiolunate narrowing, but only occasional pain. Postoperative wrist flexion-extension arc was 53 degrees and radioulnar deviation arc was 18 degrees. Grip and pinch strengths were 71% and 75%, respectively, of the normal contralateral wrist. The results of our study indicate that capitolunate arthrodesis with scaphoid and triquetrum excision is comparable to other motion-preserving operative procedures for scapholunate advance collapse.     

经皮腕背入路DTJ空心螺钉内固定治疗舟骨骨折

目的 总结经皮腕背人路DTJ空心螺钉内固定治疗舟骨骨折的经验.方法 利用经皮腕背人路DTJ空心螺钉内固定治疗舟骨骨折患者12例,男10例,女2例;年龄16~39岁,平均25岁.根据改良Herbert舟骨骨折分型:A2型3例,82型5例,83型2例,D1型2例.10例新鲜骨折患者自受伤至就诊时间为1~12d,平均3.5d;2例纤维愈合患者自受伤至就诊时间分别为76d和68d.结果 骨愈合时间为术后6.5~9.5周,平均8.5周.除1例患者行体力劳动后自觉有轻度腕痛外,其余11例患者术后疼痛均消失.患者均获得随访,随访时间6~26个月,平均14个月.12例患者术后患手握力恢复至健侧的平均86.4%(82%~93%),患侧腕关节屈伸活动度恢复至健侧的平均87.5%(83%~100%).除1例患者体力劳动后自觉有轻度腕痛改变原工作外,6例患者于术后平均5.5周(4.5~8周)返回原工作岗位,5例学生患者于术后平均4.5个月(3~6个月)恢复体育运动.所有患者腕背小切口均一期愈合,无感染等并发症发生.结论 经皮腕背入路DTJ空心螺钉内固定是一种微创、骨折愈合率高、并发症相对较少的舟骨骨折的有效治疗方法.     

Resection of the distal pole of the scaphoid for scaphoid nonunion with radioscaphoid and intercarpal arthritis

PURPOSE: The treatment of scaphoid nonunion with degenerative arthritis poses a clinical problem that is particularly challenging in cases of associated dorsal intercalated segmental instability collapse, radiocarpal and intercarpal degenerative changes, and poor scaphoid bone quality. The purpose of this study was to report our clinical experience performing a distal scaphoid resection for symptomatic scaphoid nonunion in patients with either radioscaphoid or intercarpal arthritis who have had multiple surgeries. METHODS: Nine patients with recalcitrant scaphoid nonunion and associated degenerative arthritis treated by resection of the distal scaphoid fragment were evaluated both clinically and radiographically. Eight patients were male and one patient was female; the average follow-up period was 28.6 months (range, 12-52 mo). RESULTS: Seven patients reported pain with daily use and the remaining 2 patients reported mild pain with light work before surgery, whereas after surgery 4 of the 9 patients had no wrist pain and the remaining 5 patients had only mild pain with strenuous activity. The wrist range of motion improved from 70 degrees (51.4% of the opposite wrist) to 140 degrees (94% of the opposite wrist) and grip strength improved from 18 kg (40% of the opposite wrist) to 30 kg (77% of the opposite wrist). Clinical results were excellent in 6 patients and good in 3 patients based on a modified Mayo wrist-scoring chart. Radiographically neither additional degeneration nor progress of degenerative changes was noted after surgery in 8 patients. Newly developed degenerative arthritis occurred at the proximal scapholunate capitate articulation in the remaining patient who has a type II lunate, which had a facet (medial facet) articulation with the hamate. CONCLUSIONS: The results of this study showed that distal scaphoid resection produces a satisfactory clinical outcome, requires only a short period of immobilization, and should be considered one of the surgical options for long-standing scaphoid nonunion with either radioscaphoid or intercarpal degenerative arthritis. Nevertheless care must be taken in performing this procedure on patients whose preoperative radiograph show a type II lunate.     

In vivo radiocarpal kinematics and the dart thrower's motion

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.