Progressive patterns of degenerative arthritis in scaphoid nonunion demonstrated by three-dimensional computed tomography

Current Management of Scaphoid Nonunion Based on the Biomechanical Study

Scaphoid nonunion causes abnormal wrist kinematics and typically leads to carpal collapse and subsequent degenerative arthritis of the wrist. However, the natural history, including carpal collapse and degenerative arthritis of scaphoid nonunion, may vary at different fracture locations. This article reviews recent biomechanical studies related to the natural history of scaphoid nonunion. In the distal-type fractures (type B2 in Herbert classification), where the fracture located distal to the scaphoid apex, the proximal scaphoid fragment and lunate, which are connected through the dorsal scapholunate interosseous ligament (DSLIL) and dorsal intercarpal ligament (DIC), extend together, and the distal fragment of the scaphoid flexes individually. Therefore, untreated type B2 fractures normally show the humpback deformity, resulting in dorsal intercalated segment instability deformity relatively earlier after the injury. In the proximal-type fractures (type B1), where the fracture is located proximal to the scaphoid apex, the connection between the distal fragment and lunate is preserved through the DSLIL and DIC so that the scaphoid-lunate complex remains stable and the carpal collapse is less severe than that in distal-type fractures. The fracture location relative to the apex of the dorsal scaphoid ridge is a reliable landmark in the determination of the natural history of scaphoid nonunion.

Three-dimensional analysis of osteophyte formation on distal radius following scaphoid nonunion

BACKGROUND

The purposes of this study were to quantitatively analyze osteophyte formation of the distal radius following scaphoid nonunion and to investigate how fracture locations relate to osteophyte formation patterns.

METHODS

Three-dimensional surface models of the scaphoid and distal radius were constructed from computed tomographic images of both the wrists of 17 patients' with scaphoid nonunion. The scaphoid nonunions were classified into 3 types according to the location of the fracture line: distal extra-articular (n = 6); distal intra-articular (n = 5); and proximal (n = 6). The osteophyte models of the radius were created by subtracting the mirror image of the contralateral radius model from the affected radius model using a Boolean operation. The osteophyte locations on the radius were divided into 5 areas: styloid process, dorsal scaphoid fossa, volar scaphoid fossa, dorsal lunate fossa, and volar lunate fossa. Osteophyte volumes were compared among the areas and types of nonunion. The presence or absence of dorsal intercalated segment instability (DISI) deformity was also determined.

RESULTS

The distal intra-articular type exhibited significantly larger osteophytes in the styloid process than the distal extra-articular type. Furthermore, the proximal type exhibited significantly larger osteophytes in the dorsal scaphoid fossa than the distal extra-articular type. Finally, the distal intra- and extra-articular types were more associated with DISI deformity and tended to have larger osteophytes in the lunate fossa than the proximal type.

CONCLUSION

The pattern of osteophyte formation in the distal radius determined using three-dimensional computed tomography imaging varied among the different types of scaphoid nonunion (distal extra-articular, distal intra-articular, and proximal). The results of this study are clinically useful in determining whether additional resection of osteophytes or radial styloid is necessary or not during the treatment of the scaphoid nonunion.

Analysis of deformity in scaphoid non-unions using two- and three-dimensional imaging

Pre-operative assessment of the deformity in scaphoid non-unions influences surgical decision-making. To characterize deformity, we used three-dimensional computed tomographic modelling in 28 scaphoid non-unions, and quantified bone loss, dorsal osteophyte volume and flexion deformity. We further related these three-dimensional parameters to the intrascaphoid and capitate-lunate angles, and stage of scaphoid non-union advanced collapse assessed on conventional two-dimensional images and to the chosen surgical procedure. Three-dimensional flexion deformity (mean 26°) did not correlate with intrascaphoid and capitate-lunate angles. Osteophyte volume was positively correlated with bone loss and stage of scaphoid non-union advanced collapse. Osteophyte volume and bone loss increased over time. Three-dimensional modelling enables the quantification of bone loss and osteophyte volume, which may be valuable parameters in the characterization of deformity and subsequent decision-making about treatment, when taken in addition to the clinical aspects and level of osteoarthritis.

TYPE OF STUDY/LEVEL OF EVIDENCE

Level IV.

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.

MDCT and radiography of wrist fractures: radiographic sensitivity and fracture patterns

OBJECTIVE

The purpose of our study was to determine which wrist fractures are not prospectively diagnosed at radiography using CT as a gold standard and to identify specific fracture patterns.

MATERIALS AND METHODS

Through a search of radiology records from January 1 to December 31, 2005, 103 consecutive patients were identified as having radiographic and CT examinations of the wrist. After excluding incomplete or nondiagnostic examinations and those with a greater than 6-week interval between imaging studies, the final study group consisted of 61 wrist examinations in 60 patients. Two musculoskeletal radiologists and one emergency radiologist blindly reviewed CT examinations, and each bone (scaphoid, lunate, triquetrum, pisiform, trapezium, trapezoid, capitate, hamate, metacarpals, distal radius, distal ulna) was categorized as normal or fractured, with agreement reached by consensus. Each prospective radiographic report was categorized as either normal or fracture/equivocal for each osseous structure. Results were compared using the chi-square and Fisher's exact tests.

RESULTS

In the proximal carpal row, lunate and triquetrum fractures were often radiographically occult (0% and 20%, respectively, detected at radiography); whereas in the distal carpal row, trapezoid, capitate, and hamate fractures were often occult (0%, 0%, and 40% detected at radiography, respectively). Hamate fractures were significantly associated with metacarpal fractures, and distal radius fractures were associated with scaphoid and ulna fractures.

CONCLUSION

Thirty percent of wrist fractures were not prospectively diagnosed on radiography, suggesting that CT should be considered after a negative radiographic finding if clinically warranted. The location of a dorsal scaphoid avulsion fracture emphasizes the need for specific radiographic views or cross-sectional imaging for diagnosis.

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.

Comparison of sagittal computed tomography and plain film radiography in a scaphoid fracture model

PURPOSE

To compare computed tomography (CT) in the sagittal plane and plain film radiography in the diagnosis of scaphoid fracture and displacement.

METHODS

Three groups of scaphoids (no fracture, undisplaced fractures, fractures with displacement > 1 mm) from 11 cadaver wrists were prepared. Each wrist then was imaged by using sagittal plane CT scans in the long axis of the scaphoid and plain film imaging using 6 standard scaphoid views. Eight readers from 3 specialties read each group of images. The sensitivity and specificity for the presence of fracture and fracture displacement were calculated in addition to interobserver and intraobserver reliabilities for each.

RESULTS

Both x-ray and CT scans showed a high sensitivity and specificity in detecting the presence of a fracture with no interspecialty differences. The sensitivity for displacement greater than 1 mm was lower for both modalities with no inter-specialty differences. The specificities for x-ray and CT for detecting displacement greater than 1 mm were 84% and 89%, respectively. The poor sensitivity for detecting displacement was explained by the low sensitivity of CT in the diagnosis of radial/ulnar displacement compared with x-ray and the low sensitivity of x-ray in the diagnosis of volar/dorsal displacement compared with CT scans. When fellowship-trained hand surgeons reviewed CT scans and plain films together the sensitivity and specificity for fracture displacement increased significantly. Intraobserver and interobserver reliability for both x-ray and CT scans was excellent except for the reading of CT scans among emergency physicians and for the reading of plain x-rays among senior house staff, representing moderate agreement.

CONCLUSIONS

Based on these results both CT scans in the sagittal plane and plain films accurately detect fractures with a high degree of interobserver and intraobserver reliability, but they fall short in detecting displacement greater than 1 mm.

Does three-dimensional computer simulation improve results of scaphoid nonunion surgery?

The purpose of this study was to clarify the effectiveness of the three-dimensional computer simulations in scaphoid nonunion surgery. Seven consecutive clinical patients with scaphoid nonunion at the middle third comprised the study group. Surface models of the scaphoid were constructed on the computer using computed tomography data of the bilateral wrists in neutral position. The distal and proximal fragments of the nonunion model were matched to the mirror image of the contralateral scaphoid model. The rotation of the distal fragment relative to the proximal fragment was calculated, and reduction of the displaced fragment of the scaphoid nonunion was simulated. Similarly, the estimated bone defect and the appropriate site and direction of the screw insertion were simulated. Full-sized hard models of the bone, including a model with simulated reduction and screw insertion, then were made using stereolithography based on the computer data. In the actual surgery, reduction, bone grafting, and screw insertion were achieved using the hard models as guides. All the patients obtained solid bone fusion and substantial clinical improvement with normalized scapholunate and radiolunate angles after surgery. Three-dimensional computer simulations were found as useful for accurate correction of scaphoid nonunions and proper screw placement, which consequently leads to good clinical results.

The use of medical imaging-based kinematic analysis in the evaluation of wrist function and outcome

The authors developed a 3D CT technique to analyze in vivo variations in carpal bone position based on 3D reconstruction of transverse CT data in 5 wrist positions. The subject groups analyzed consisted of 40 asymptomatic volunteers and 30 patients with various wrist disorders (fractures, instabilities). In 11 anatomic specimens, this kinematic analysis was completed by a radiographic morphologic study and an investigation of capsular ligament anatomy. Clinical applications showed that carpal bone motion in the injured wrist was not significantly different from contralateral, asymptomatic wrist motion. In both wrists of patients with unilateral pathology, however, significant differences were observed as compared with asymptomatic volunteers. Scaphoid motion was bilaterally altered, suggesting the existence of anatomic or kinematic factors predisposing to certain carpal pathologies.