Scaphoid nonunions: a 3-dimensional analysis of patterns of deformity

We tested the hypothesis that the fracture location of scaphoid nonunions relates to the fracture displacement, development of dorsal intercalated segment instability (DISI) deformity, and changes in the contact area of the bones in the radiocarpal joint. Eleven patients with scaphoid nonunions were examined with 3-dimensional computed tomography and a new method of proximity mapping. Two different patterns of displacement of scaphoid nonunions were demonstrated, 1 volar and 1 dorsal. All patients with a volar pattern scaphoid nonunion had a DISI deformity. Only a few of the patients with a dorsal pattern scaphoid nonunion, mostly in longstanding nonunions, had a DISI deformity. The fracture line was generally distal to the dorsal apex of the ridge of the scaphoid in the volar-type fractures and proximal in the dorsal displaced fractures. The proximity map of the distal fragment of the scaphoid on the radius in the volar type shifts radial compared with normal; in the distal type it shifts dorsal. Neither of the patterns showed any significant changes of the proximity map in the radiocarpal joint at the proximal scaphoid fragment and the lunate. Whether the fracture line passes distal or proximal to the dorsal apex of the ridge of the scaphoid appears to determine the likelihood of subsequent fracture displacement, DISI deformity, and contact area of the bones in the radiocarpal joint.     

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.     

The silicone scaphoid: a biomechanical study

Five fresh cadaver upper extremities were studied by use of a static positioning frame, pressure-sensitive film, and a microcomputer-based videodigitizing system, to assess the load-bearing characteristics of a scaphoid silicone implant within the radioulnarcarpal joint. Specimens were studied in their "normal" condition, after resection of the scaphoid, after placement of a scaphoid implant, and with a scaphoid implant and a simulated capitate-lunate-triquetrum-hamate fusion. The scaphoid silicone implant bore significant, although less, load than the normal scaphoid. Decreasing the size of the scaphoid implant decreased the load born by the implant. Decreased load through the scaphoid implant was compensated by the lunate. The addition of a limited carpal fusion did not significantly decrease the load born by a scaphoid implant. Therefore, the silicone scaphoid implant is a load-bearing implant even when undersized or placed in association with a limited carpal fusion.     

Patterns of carpal deformity in scaphoid nonunion: a 3-dimensional and quantitative analysis

PURPOSE: To clarify quantitatively the 3-dimensional deformity of the carpus in scaphoid nonunion on the basis of fracture location. METHODS: Three-dimensional computed tomography was used to examine 20 patients with scaphoid nonunion. Displacements of the distal and proximal fragments of the scaphoid, lunate, triquetrum, and capitate were visualized and quantified using a 3-dimensional image-matching technology. Cases were categorized as distal fracture (16 cases) or proximal fracture (4 cases) based on the location of the fracture line relative to the dorsal apex of the scaphoid ridge where the dorsal scapholunate interosseous ligament is attached. RESULTS: The displayed distal scaphoid fractures showed that the proximal fragment of the scaphoid, lunate, and triquetrum rotated into extension and supination. The distal fragment of the scaphoid and capitate translated dorsally without notable rotation. The deformity in proximal fractures was less remarkable than that in distal fractures. Most distal scaphoid nonunions had dorsal intercalated segment instability deformity patterns, whereas a dorsal intercalated segment instability occurred in only 1 case of a proximal fracture. CONCLUSIONS: Whether the fracture line passes distal or proximal to the dorsal apex of the scaphoid determines the subsequent carpal deformity. Dorsal translation of the distal fragment might be one of the factors in the development of degenerative change at the radial styloid.     

Palmar lunate dislocation with a dorsal scaphoid fracture variant

A 20-year-old man had a dorsally displaced fracture of the proximal pole of the scaphoid and an ipsilateral palmar lunate dislocation--a rare combination of injuries that has not been previously reported. The most likely pathomechanics of this injury is a sheer fracture of the proximal pole of the scaphoid by the dorsal lip of the distal radius as the injury shifts from a dorsal perilunate to a palmar lunate pattern.     

Effects of distal radius fracture malunion on wrist joint mechanics

An experimental model using a static positioning frame, pressure-sensitive film (Fuji), and a microcomputer-based videodigitizing system was used to measure contact areas and pressures in the wrist. Contact areas and pressures were compared in a group of wrists between the normal state and with simulated distal radius fracture malunions of varying degrees. In simulated malunions, radial shortening to any degree slightly increased the total contact area in the lunate fossa, and was significant at 2 mm of shortening. By angulating the distal radius more than 20 degrees either palmar or dorsal, there was a dorsal shift in the scaphoid and lunate high pressure areas, and the loads were more concentrated, but there was no change in the load distribution between the scaphoid and lunate. Decreasing the radial inclination shifted the load distribution so that there was more load in the lunate fossa and less load in the scaphoid fossa.     

晚期月骨无菌性坏死舟骨环形征的解剖学及生物力学研究

目的明确稳定舟骨近极的韧带及断裂后桡腕关节面应力的改变,阐明舟骨环形征的临床意义. 方法实验分为两部分,分别通过5侧上肢标本的解剖学观察,确定稳定舟骨近极的韧带;通过桡侧、尺侧屈腕肌腱及桡侧、尺侧伸腕肌腱,垂直加载12 kg负荷5分钟,应用压敏薄膜及FPD-305E、FPD-306E系统,分别测量腕关节中立、掌屈、背伸、尺偏及桡偏时,正常及韧带断裂后舟骨窝、月骨窝应力的变化. 结果解剖学观察发现,稳定舟骨近极的韧带为:桡舟头韧带、长桡月韧带及舟月骨间韧带,其中长桡月韧带和舟月骨间韧带起到限制舟骨近极向背侧移位的作用.生物力学研究结果表明,在稳定舟骨近极的韧带断裂后,背伸位时,舟骨窝桡侧亚区应力(0.90±0.43)与正常(0.85±0.15)无差异,但掌侧(0.59±0.20)、尺侧(0.52±0.05)及背侧亚区(0.58±0.23)应力较正常(相对应力为0.77±0.13、0.75±0.08、0.68±0.09)减小;中立、掌屈、桡偏及尺偏位时,舟骨窝内各亚区应力与正常相比增大或无差异;而月骨窝在中立位时,各亚区的应力增大;掌屈、背伸、桡偏及尺偏位时,各亚区的应力减小或无差异. 结论在月骨无菌性坏死ⅢB期,舟骨窝承受的负荷增加,在治疗方法的选择上,应注意矫正舟骨的旋转半脱位,防止后期出现桡舟关节创伤性关节炎.     

Management of chronic rotary subluxation of the scaphoid by scapho-trapezio-trapezoid arthrodesis. Rationale for the technique, postoperative changes in biomechanics, and results

In cases of static or symptomatic dynamic scapholunate instability, reduction of the scaphoid proximal pole into the scaphoid fossa of the radius and stabilization of the relationship of the scaphoid and lunate by distal arthrodesis to the trapezium and trapezoid will significantly alter carpal mechanics; however, elimination of pain, preservation of a functional arc of motion, and restoration of the ability to pursue routine activities (including heavy labor) all suggest that the planes of radiocarpal and intercarpal motion following distal scaphoid arthrodesis are compatible with long-term physiologic function without late loss of reduction.     

Effects of radioulnar instability on the radiocarpal joint: a biomechanical study

Five fresh cadaver upper extremities were studied with use of a static positioning frame, pressure-sensitive film and a microcomputer-based videodigitizing system to assess the effect of increasing radioulnar instability on the load distribution within the proximal carpal joint. Three stages of radioulnar instability were studied: (1) an avulsion fracture at the base of the ulna styloid; (2) an avulsion fracture at the base of the ulna styloid plus disruption of the dorsal portion of the distal radioulnar joint capsule; and (3) an avulsion fracture at the base of the ulna styloid, disruption of the dorsal portion of the distal radioulnar joint capsule, and disruption of the radioulnar interosseous membrane. All stages of radioulnar instability demonstrated a decrease in the lunate contact area in positions with the forearm in supination. In stage 3 instability there was also less lunate contact area in positions with the forearm in neutral pronation/supination. In stage 3 instability the lunate high pressure area centroid was abnormally palmar in all positions and the scaphoid high pressure area centroid was abnormally palmar in positions with the forearm in pronation or supination.     

桡骨远端楔形截骨术治疗腕舟状骨不愈合及月骨坏死

目的评价桡骨远端楔形截骨术治疗腕舟状骨不愈合和月骨坏死的效果。方法应用桡骨远端楔形截骨术治疗腕舟状骨不愈合123例和月骨坏死32例。术中第一截骨线在桡骨茎突近端1.5 cm处,截骨方向与桡骨远端关节面平行;第二截骨线位于第一截骨线近端0.5~1.0 cm处,截骨方向与桡骨纵轴垂直;两截骨线在下尺桡关节中心会合。取出楔形骨块,桡偏使楔形截骨处对合,用1或2枚克氏针固定。结果术后平均随访25(6~60)个月。腕舟状骨折均愈合,平均愈合时间10(8~14)周。32例月骨坏死者中,13例硬化骨重新成活,余无明显改善。术后腕关节疼痛VAS评分、腕关节活动度及握力均较术前明显改善(P0.05);术后患侧腕关节活动度与握力与健侧比较无统计学差异(P0.05)。99例手功能正常,56例有轻微功能障碍。腕关节功能按Krimmer评分:优99例,良56例。结论桡骨远端楔形截骨术治疗腕舟状骨不愈合及月骨坏死的效果确切,操作简单,是值得推荐的一种有效方法 。     

Giant cell tumor of the capitate

A case of giant cell tumor of the capitate is presented. Its recurrence and the problem of reconstruction after resection are discussed. Recommended treatment of this tumor if it occurs within the carpals is resection of the carpus with intercarpal arthrodesis if the distal row is involved or proximal row carpectomy if the scaphoid or lunate is involved.     

Partial excision of scaphoid: is it ever indicated?

The carpal scaphoid cannot be partially or totally excised without paying a functional penalty, usually in the form of carpal instability. In selected conditions, however, a partial scaphoidectomy may be preferred over other less reliable alternatives. These include excision of a small fragment of a fractured proximal pole when there is no injury to the scapholunate ligaments; excision of the distal fragment of a nonunited, arthritic distal-third scaphoid fracture; resection-arthroplasty of isolated STT osteoarthritis; and distal scaphoid excision to improve midcarpal function after a radioscapholunate fusion. In this article, both the pathomechanics and clinical results of such techniques are discussed.     

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.     

Load transfer characteristics of the wrist. Part II. Perilunate instability

An experimental model with a static positioning frame, pressure-sensitive film (Fuji), and a microcomputer-based video digitizing system, previously developed by the two senior authors, was used in this study to examine the effects of increasing perilunate instability on the load transfer characteristics of the wrist. These effects included a significant dorsal ulnar shift of the scaphoid centroid with increasing perilunate instability together with a less dramatic palmar ulnar shift of the lunate centroid. Overall, the scaphoid contact area was found to decrease as the stage of perilunate instability increased, even in ulnar deviation and/or extension, which in the normal wrist was found to be the positions that had the greatest scaphoid contact area. Average pressures in the high pressure zones were found to significantly increase in wrists with a stage III instability compared with normal wrists. An increase in the intercentroid (scaphoid/lunate) distance was most evident with the wrist in 20 degrees extension, neutral radioulnar deviation, and 90 degrees supination.     

Treatment of Scaphoid Nonunions with Closed-Wedge Osteotomy of the Distal Radius: Report of Six Cases

BACKGROUND: The ideal treatment of nonunion of the scaphoid remains unresolved and controversial. It was hypothesized that scaphoid nonunion could be treated successfully using a closed-wedge osteotomy of the distal radius which reduces the inclination of the joint surface and decreases the pressure between the radial and scaphoid surfaces with a reduction of the force applied by the styloid process. We present a preliminary report in six patients with nonunion of the carpal scaphoid using this procedure. The main objective of the osteotomy is to achieve fusion, alleviate pain, and improve function. MATERIALS AND METHODS: Six closed-wedge osteotomies to reduce the inclination of the distal radial surface were performed in patients with scaphoid waist nonunion and a viable proximal pole, without posttrauma osteoarthritis or with moderate posttraumatic osteoarthritis confined to the radio-scaphoid joint. The present series of six patients (all men) were followed for at least 8 months (mean follow-up 14.2 months, range 8-21 months). RESULTS: Solid union was achieved in five patients. Postoperatively, three patients were pain-free, two presented mild pain for heavy work, and one had moderate pain. This type of osteotomy reduced the inclination of the joint surface (radial angulation) 6.2 degrees on average. There was an improvement in joint flexion from a preoperative mean of 40 degrees to 52.5 degrees at last follow-up, in extension from 40.8 degrees to 66.7 degrees , in radial deviation from 15 degrees to 22.5 degrees , and in ulnar deviation from 30.8 degrees to 41.7 degrees . CONCLUSIONS: This preliminary study suggests that a closed-wedge osteotomy of the distal radius could be an alternative approach for patients with scaphoid waist nonunion and a viable proximal pole, without posttrauma osteoarthritis or with moderate posttraumatic osteoarthritis confined to the radio-scaphoid joint. The number of cases was small; however, further studies with a much larger series are needed before routine use of wedge osteotomy in scaphoid nonunion can be recommended.     

Pressure distribution in the wrist joint

We performed a study to determine pressure distribution properties of the normal radio-carpal joint. A system was developed for measurement of the contact pressure within the wrist joint surfaces. The transducer was based on Fuji pressure-sensitive paper, which was inserted into the joint space through a dorsal capsular incision. The hand was then positioned using a jig that permitted free axial loading of the joint. Each of five specimens was tested in 36 positions combining flexion/extension with radio/ulnar deviation and supination/pronation. The transducers were analyzed for contact area, scapho-lunate contact area ratio, pressure, and centroid locations using a microcomputer-based video-imaging system. The scaphoid and lunate contact areas on the radius and triangular fibrocartilage were separate and distinct in all wrist positions. Together these contact areas accounted for a relatively small fraction of the total joint surface area (average contact area/total joint area = 0.206, SD = 0.0495). For an applied 103 Newton compressive load, the high pressure averaged 3.17 MPa (SD = 0.83 MPa). Overall, the scaphoid contact area was 1.47 times that of the lunate, although variations occurred with position, as in flexion, in which the scaphoid/lunate area ratio was 0.83. The high-pressure centroids of both scaphoid and lunate contact areas shifted palmarly from 20 degrees of flexion to 20 degrees of extension and then dorsally with further extension. The scaphoid-lunate intercentroid distance averaged 14.91 mm with a range of 10-20 mm.     

Central placement of the screw in simulated fractures of the scaphoid waist: a biomechanical study

BACKGROUND: Recent reports on internal fixation of acute fractures of the scaphoid waist have demonstrated higher rates of central placement of the screw when cannulated screws were used than when noncannulated screws were used. This cadaveric study was designed to determine whether central placement in the proximal fragment of the scaphoid offers a biomechanical advantage. METHODS: Eleven matched pairs of scaphoids were removed from fresh cadaveric wrists. Each scaphoid was placed in a custom manufactured jig that was used to create reproducible central and eccentric positioning of the guidewire. Then a linear osteotomy was made followed by placement of a Herbert-Whipple cannulated screw to fix the osteotomy. The specimen was then potted in a holder with use of polymethylmethacrylate with a Kirschner wire passed through the proximal end of the scaphoid and placed into a fixture with a pneumatically driven plunger resting on the surface of the distal pole. The load acting through the plunger was measured with use of a load-cell, and its excursion was measured with use of a linear variable differential transformer. Stiffness, load at 2 mm of displacement, load at failure, and mechanism of failure were measured, and the two groups were compared with regard to stiffness and strength. RESULTS: Central placement of the screw in the proximal fragment of the scaphoid had superior results compared with those after eccentric positioning of the screw. Fixation with central placement of the screw demonstrated 43% greater stiffness (12.7 N per mm compared with 8.9 N per mm; p < 0.01), 113% greater load at 2 mm of displacement (126 N compared with 59.1 N; p < 0.01), and 39% greater load at failure (712 N compared with 513 N; p > 0.05). CONCLUSIONS AND CLINICAL RELEVANCE: Central placement of the screw in the proximal fragment of the scaphoid offers a biomechanical advantage in the internal fixation of an osteotomy of the scaphoid waist. Clinical efforts and techniques that facilitate central placement of the screw in the fixation of fractures of the scaphoid waist should be encouraged.     

舟月骨间韧带在腕尺桡偏时舟月骨三维运动中的作用

目的 观察在腕关节尺桡偏运动时,舟月骨间韧带(scapholunate interosseous ligament,SLIL)及其各亚区分级切断后对舟骨与月骨三维运动的影响,从亚区水平对SLIL在舟月骨三维运动中的作用进行研究.方法 取12例新鲜冰冻成人上肢标本(左、右侧各6例),共分为正常对照组、断SLIL近侧组、断SLIL近+背侧组、断SLIL近+掌侧组、SLIL全断组(每组6例).采用三维激光扫描及图像重建技术,测定在腕关节尺桡偏时舟骨与月骨的三维运动数据,并进行统计学处理.结果 在正常腕关节做尺桡偏运动时,舟、月骨同时也做尺桡偏运动,但还伴有明显的屈伸方向上的运动;与此同时,舟、月骨还做一定的旋前、旋后活动.在切断近+掌和近+背侧亚区组,舟月骨的活动受到影响.全切断SLIL会导致舟骨掌屈度增加,月骨掌屈活动减弱.结论 采用三维激光扫描及图像重建技术可准确测定腕舟月骨的三维活动度,从SLIL亚区水平上进行的研究表明,部分或全部切断SLIL后会对舟月骨的掌屈程度产生明显影响,但SLIL近侧亚区在控制舟、月骨的活动上不起主要作用.     

舟月骨间韧带在腕尺桡偏时舟月骨三维运动中的作用

目的 观察在腕关节尺桡偏运动时,舟月骨间韧带(scapholunate interosseous ligament,SLIL)及其各亚区分级切断后对舟骨与月骨三维运动的影响,从亚区水平对SLIL在舟月骨三维运动中的作用进行研究.方法 取12例新鲜冰冻成人上肢标本(左、右侧各6例),共分为正常对照组、断SLIL近侧组、断SLIL近+背侧组、断SLIL近+掌侧组、SLIL全断组(每组6例).采用三维激光扫描及图像重建技术,测定在腕关节尺桡偏时舟骨与月骨的三维运动数据,并进行统计学处理.结果 在正常腕关节做尺桡偏运动时,舟、月骨同时也做尺桡偏运动,但还伴有明显的屈伸方向上的运动;与此同时,舟、月骨还做一定的旋前、旋后活动.在切断近+掌和近+背侧亚区组,舟月骨的活动受到影响.全切断SLIL会导致舟骨掌屈度增加,月骨掌屈活动减弱.结论 采用三维激光扫描及图像重建技术可准确测定腕舟月骨的三维活动度,从SLIL亚区水平上进行的研究表明,部分或全部切断SLIL后会对舟月骨的掌屈程度产生明显影响,但SLIL近侧亚区在控制舟、月骨的活动上不起主要作用.     

舟月骨间韧带在腕尺桡偏时舟月骨三维运动中的作用

目的 观察在腕关节尺桡偏运动时,舟月骨间韧带(scapholunate interosseous ligament,SLIL)及其各亚区分级切断后对舟骨与月骨三维运动的影响,从亚区水平对SLIL在舟月骨三维运动中的作用进行研究.方法 取12例新鲜冰冻成人上肢标本(左、右侧各6例),共分为正常对照组、断SLIL近侧组、断SLIL近+背侧组、断SLIL近+掌侧组、SLIL全断组(每组6例).采用三维激光扫描及图像重建技术,测定在腕关节尺桡偏时舟骨与月骨的三维运动数据,并进行统计学处理.结果 在正常腕关节做尺桡偏运动时,舟、月骨同时也做尺桡偏运动,但还伴有明显的屈伸方向上的运动;与此同时,舟、月骨还做一定的旋前、旋后活动.在切断近+掌和近+背侧亚区组,舟月骨的活动受到影响.全切断SLIL会导致舟骨掌屈度增加,月骨掌屈活动减弱.结论 采用三维激光扫描及图像重建技术可准确测定腕舟月骨的三维活动度,从SLIL亚区水平上进行的研究表明,部分或全部切断SLIL后会对舟月骨的掌屈程度产生明显影响,但SLIL近侧亚区在控制舟、月骨的活动上不起主要作用.