Dimensions of the trapezium bone: a cadaver and CT study

Computer-simulated TOUCH prosthesis cup malposition and solutions

INTRODUCTION

Total joint replacement has become significantly more common as a treatment for advanced trapeziometacarpal joint osteoarthritis in recent years. The latest generation of prostheses with dual-mobility designs leads to very good functional results and low rates of loosening and dislocation in the short and medium term. Biomechanical studies showed that central placement and parallel alignment of the cup with respect to the proximal articular surface of the trapezium are crucial for both cup stability and prevention of dislocation. Despite correct positioning of the guidewire, incorrect placement or tilting of the inserted cup may occur, requiring immediate intraoperative revision.

METHODS

The existing spherical and conical cup models in sizes 9 mm and 10 mm were transferred to a computer-aided design dataset. Depending on the intraoperative complication (tilting or incorrect placement), the revision options resulting from the various combinations of cup type and size were simulated and analyzed according to the resulting defect area and bony contact area.

RESULTS

In well centered cups, a size 9 conical cup could be replaced by a size 9 spherical cup and still be fixed by press-fit. Conversely, a size 9 spherical cup could not be replaced by a size 9 conical cup, but only by a size 10 cup, of whatever shape. When a size 9 conical cup was tilted up to 20°, the best revision option was to resect the sclerotic margin and insert a size 10 conical cup deeper into the cancellous bone, to achieve the largest contact area with the surrounding bone. When a size 9 cup of whatever shape was poorly centered (misplaced with respect to the dorsopalmar or radioulnar line of the trapezium), placement should be corrected using a size 10 cup, combined with autologous bone grafting of the defect. Again, the size 10 conical cup showed the largest bony contact area.

CONCLUSION

Our computer-based measurements suggested options for intraoperative cup revision depending on cup shape and size and on type of misalignment with resulting bone defects. These suggestions, however, need to be confirmed in anatomic specimens before introducing them into clinical practice.

Influence of the anatomy of the proximal articular surface of the trapezium (PAST) and the trapezoidal articular surface of the trapezium (TRAST) in cup placement during trapeziometacarpal arthroplasty

The influence of the anatomy of the proximal articular surface of the trapezium (PAST) and the trapezoidal articular surface of the trapezium (TRAST) on cup placement during trapeziometacarpal arthroplasty was retrospectively evaluated on 56 preoperative anteroposterior radiographs of patients who underwent surgery for trapeziometacarpal osteoarthritis. The percentage coverage of the prosthetic cup by the PAST and the available height of the trapezium were calculated. In 39% of cases, there was a significant difference (up to a mean 4.5 mm, p < 0.001) between the radial height of the trapezium (which is usually considered) and the available height of the trapezium. The anatomy of the PAST and the TRAST has an impact on the placement of the prosthetic cup when trapezium height is low. The results of the present study suggest that these considerations must be known by all operators performing trapeziometacarpal arthroplasty; that lateralization, implant suspension, or surgical alternatives should be considered to prevent several intra- and postoperative surgical complications. Level of evidence: IV.

Three-dimensional reconstruction of the hand from biplanar X-rays: Assessment of accuracy and reliability

BACKGROUND

Functional disorders of the hand are generally investigated first using conventional radiographic imaging. However, X-rays (two-dimensional (2D)) provide limited information and the information may be reduced by overlapping bones and projection bias. This work presents a three-dimensional (3D) hand reconstruction method from biplanar X-rays.

METHOD

This approach consists of the deformation of a generic hand model on biplanar X-rays by manual and automatic processes. The reference examination being the manual CT segmentation, the precision of the method was evaluated by a comparison between the reconstructions from biplanar X-rays and the corresponding reconstructions from the CT scan (0.3mm section thickness). To assess the reproducibility of the method, 6 healthy hands (6 subjects, 3 left, 3 men) were considered. Two operators repeated each reconstruction from biplanar X-rays three times to study inter- and intra-operator variability. Three anatomical parameters that could be calculated automatically from the reconstructions were considered from the bone surfaces: the length of the scaphoid, the depth of the distal end of the radius and the height of the trapezius.

RESULTS

Double the root mean square error (2 Root Mean Square, 2RMS) at the point/area difference between biplanar X-rays and computed tomography reconstructions ranged from 0.46mm for the distal phalanges to 1.55mm for the bones of the distal carpals. The inter-intra-observer variability showed precision with a 95% confidence interval of less than 1.32mm for the anatomical parameters, and 2.12mm for the bone centroids.

DISCUSSION

The current method allows to obtain an accurate 3D reconstruction of the hand and wrist compared to the traditional segmented CT scan. By improving the automation of the method, objective information about the position of the bones in space could be obtained quickly. The value of this method lies in the early diagnosis of certain ligament pathologies (carpal instability) and it also has implications for surgical planning and personalized finite element modeling.

LEVEL OF PROOF

Basic sciences.

The Effect of Proximal Row Carpectomy and Trapeziectomy on First Ray Stability: A Cadaveric Study

PURPOSE

Wrist and thumb pathology can coexist leading to potential indications for proximal row carpectomy (PRC) and trapeziectomy. In this setting, the axial stability of the first ray is not known. We sought to evaluate axial subsidence of the first metacarpal in cadavers following trapeziectomy and trapeziectomy with PRC to determine the mechanical effects of the procedures performed concurrently.

METHODS

Eleven fresh-frozen cadaveric distal forearm specimens were used in this study. The specimens were fixed in cement and mounted to a material test system frame. A predetermined force (20 N) was applied to the thumb metacarpal to simulate forces observed with lateral pinch. Axial displacement of the thumb metacarpal was measured. The application of force was repeated following trapeziectomy on each hand and then again following PRC. Analysis was performed to compare thumb metacarpal subsidence of the 3 groups: native, trapeziectomy, and trapeziectomy with PRC.

RESULTS

Before trapeziectomy, native cadaver specimens had an average of 5.1 ± 1.9 mm of thumb metacarpal subsidence under the material test system load (20 N), compared to 16.2 ± 3.4 mm following trapeziectomy, and 25.0 ± 5.5 mm for trapeziectomy with PRC.

CONCLUSION

We observed a significant increase in thumb metacarpal subsidence following concurrent trapeziectomy with PRC when compared to trapeziectomy alone. Our results suggest that performing both operations together would lead to a substantial risk of first ray subsidence.

CLINICAL RELEVANCE

When treating concurrent basilar thumb and wrist arthritis, it may be more effective to stage the procedures or use a form of thumb metacarpal suspension or arthrodesis.

Anatomic Description of the Calcaneocuboid Joint: Implications for Staple Fixation

Understanding the anatomy of the calcaneocuboid (CCJ) remains essential when selecting staple fixation to optimize osseous purchase during rearfoot procedures. This anatomic study quantitatively describes the CCJ in relation to staple fixation sites. The calcaneus and cuboid from 10 cadavers were dissected. Widths at 5 mm and 10 mm increments away from the joint were measured in dorsal, midline, and plantar thirds of each bone. The widths between each position's 5 mm and 10 mm increments were compared using the Student's t test. The widths among the positions at both distances were compared using an ANOVA then post hoc testing. Statistical significance was set at p ≤ 0.05. The middle (23 ± 3 mm) and plantar third (18 ± 3 mm) of the calcaneus at the 10 mm interval was greater than the 5 mm interval (p = .04). At 5 mm distal to the CCJ, the dorsal third of the cuboid maintained a statistically significant greater width than the plantar third (p = .02). The 5 mm (p = .001) and 10 mm (p = .005) dorsal calcaneus widths as well as the 5 mm (p = .003) and 10 mm (p = .007) middle calcaneus widths were significantly greater than the plantar widths. This investigation supports the use of 20 mm staple 10 mm away from the CCJ in dorsal and midline orientations. Care should be taken when placing a plantar staple within 10 mm proximal to the CCJ as the legs may extend beyond the medial cortex compared to dorsal and midline placements.

Defining trapezial dysplasia - analysis of trapezial inclination in a normal population

We assess the distribution of trapezial inclination in a young population in order to propose a threshold for trapezial dysplasia. One hundred peritrapezial views were reconstructed from wrist computed tomography scan datasets to measure trapezial inclination. Seventy peritrapezial views were constructed from 10 datasets to assess the influence of radiograph rotation. Mean trapezial inclination in our population was 8° (range 0.2-17.9). Fifteen degrees of radiographic pronation or supination did not alter trapezial inclination significantly. Intra-rater consistency and absolute agreement had an interclass correlation (ICC) of 0.95. Inter-rater consistency and absolute agreement had an ICC of 0.88. Trapezial inclination is a reliable measurement for trapezial dysplasia with an excellent intra-rater and good inter-rater reliability and does not change significantly with 15° of radiographic pronation or supination. These normal values can be used to propose a threshold for trapezial dysplasia in the management of trapeziometacarpal joint instability in the younger population.Level of evidence: IV.

Total joint replacement for osteoarthritis of the carpometacarpal joint of the thumb: why and how?

Total joint replacement has certain advantages over other surgical treatment methods for osteoarthritis of the thumb carpometacarpal joint, including restoration of thumb length and alignment, good cosmetical result, fast recovery of hand function and prevention of iatrogenic complications at neighbouring joints. Disadvantages include the technical difficulty to perform this surgery and a possible higher complication rate. A meticulous surgical technique is mandatory. Combined with a cementless and modular ball-in-socket implant with a metal-on-polyethylene friction couple, a 10-year survival rate higher than 90% can be expected. Revision surgery is possible with implant exchange or conversion to trapeziectomy.

Intraoperative Load Tolerance of the Thumb Carpometacarpal Joint After Resection-Suspension-Interposition Arthroplasty

Purpose

The objective was to measure the intraoperative load tolerance of the thumb carpometacarpal (CMC) joint after trapeziectomy, tendon suspension, and interposition.

Methods

In this single-center prospective study, preoperative pinch grip, thumb mobility, and hypermobility of the thumb CMC joint were determined by 2 hand surgeons. Patients completed the brief Michigan Hand Outcomes Questionnaire. During surgery and upon removal of the trapezium, the surgeon subjectively rated the degree of thumb CMC load tolerance as “stable,” “medium stable,” or “unstable.” A measurement system with an integrated force sensor was used to measure intraoperative thumb CMC load tolerance. The thumb ray was displaced manually by 10 mm toward the scaphoid, and the counteracting force was measured over the entire displacement. The objective load tolerance was determined as the maximal measured force after trapezium resection, tendon suspension, and interposition. Analysis of variance was used to test for the differences in load tolerance between the surgical steps. Spearman’s coefficient was used to find correlations between load tolerance and clinical or patient-reported variables.

Results

Twenty-nine patients with a mean age of 70 years (SD, 8.1 years) were available for analysis. The measured intraoperative load tolerance after trapeziectomy was 15.5 N (SD, 5.4 N) and significantly increased to 18.7 N (SD, 5.5 N) after suspension. Load tolerance only slightly increased after tendon interposition, increasing the force to 20.3 N (SD, 6.7 N). Neither the surgeon’s subjective stability rating nor the clinical or patient-reported variables correlated with the measured load tolerance after trapeziectomy.

Conclusions

Our results show that tendon suspension leads to the highest increase in thumb CMC load tolerance during resection-suspension-interposition arthroplasty.

Clinical relevance

Tendon suspension appears to be the most important step in stabilizing the metacarpal base after trapeziectomy, whereas tendon interposition does not seem to have a relevant additional effect regarding load tolerance, at least immediately after surgery.

[Experiences with arthroplasty of the basal joint of the thumb : The"mini-hip" gains ground]

The complex kinematics of the saddle joint has been a challenge in the development of trapeziometacarpal prostheses. The introduction of the dual-mobility design increases the range of motion and limits strains on the cup fixation. Therefore, rates of loosening and dislocation have been markedly reduced. Furthermore, several studies showed a similar relief of pain, range of movement and grip strength compared to the results of resection arthroplasty. The preservation of the length of the first ray as well as the more stable and functional joint can be favourable in younger and active patients. Further investigation is needed to determine whether or not those higher demands affect long-term survivorship. The high grade of patient satisfaction, the shorter recovery time and the safe surgical technique motivates considering the implantation of a total endoprosthesis with a dual-mobility cup as an attractive alternative to resection arthroplasty in the operative treatment for trapeziometacarpal osteoarthritis.

Assessment of trapezial prosthetic cup migration: A biomechanical study

We performed a biomechanical study using 60 Sawbones® rigid foam blocks of two simulated densities (osteoporotic, n = 30 and non-osteoporotic, n = 30) and 10 cadaveric trapezium bones from fresh-frozen, unembalmed adult cadaver hands to assess the trapezial prosthetic cup migration with progressively greater compression loads (10-40 kg). Two cups from the Touch® prosthesis were compared: 9-mm conical cup and 9-mm spherical cup. Uniaxial compression tests were carried out using an MTS Criterion® Series 40 Electromechanical Testing System. Cup migration was measured in millimeters (mm) at 10, 20, and 40 kg of compression load. Median cup migration values were similar in the cadaveric trapezium bones and Sawbones® non-osteoporotic blocks, and higher in the Sawbones® osteoporotic blocks. In the cadaveric trapezium bones and the Sawbones® non-osteoporotic blocks, migration values were less than or equal to 0.1 mm for 10 and 20 kg loads; it was 0.2 mm for 40 kg load. In the Sawbones® osteoporotic blocks, migration values were less than or equal to 0.3 mm for 10 and 20 kg loads; it was 0.4-0.5 mm for 40 kg load. There was no significant difference between the two cup shapes in both cadaveric trapezium bones and Sawbones® non-osteoporotic blocks. In Sawbones® osteoporotic blocks, the largest difference between the two cup shapes was 0.1 mm for loads up to 40 kg, which corresponded to our measurement accuracy. Our findings indicate that the trapezial component of total trapeziometacarpal joint arthroplasty undergoes very weak migration for axial compression loads up to 40 kg, presumably below the threshold of clinical relevance. The cup shape did not have an obvious influence; however, low bone mineral density may result in greater cup migration.

Comparison of two radiographic landmarks for centering the trapezial component in total trapeziometacarpal arthroplasty

We performed a retrospective review of standard anteroposterior and lateral radiographs of the thumb in 80 patients, to compare two radiographic landmarks, in terms of mediolateral bone support, for centering the trapezial component in total joint arthroplasty. On anteroposterior view, we identified the distal articular surface of the trapezium and trapezium width, and defined the two midpoints as radiographic landmarks for positioning a 9-mm trapezial cup. Mean trapezium width was significantly greater than the distal articular surface of the trapezium, and the midpoints did not match. Thus, after positioning simulated 9-mm prosthetic cups centered on each landmark, the residual radial bone distance was significantly greater using the landmark based on trapezium width. The mean value was 33% greater with this landmark, and the minimum value was 2.1 mm, compared to 0.2 mm using the landmark based on the distal articular surface. Our study thus suggested that the midpoint of the trapezium width is the more relevant radiographic landmark for centering the trapezial prosthetic cup in total joint arthroplasty, by preserving better bone stock on the radial side without depleting the ulnar side. On an intraoperative anteroposterior fluoroscopic view, this landmark could be used to check cup positioning.

Volar radial wrist–forearm primary and recurrent ganglia of the flexor carpi radialis tendon secondary to pathology isolated to the trapezial fibro-osseous synovial sheath tunnel: A case series report

Surgical treatment of primary and recurrent volar radial wrist–forearm ganglia has yielded higher recurrence rates of ganglia when compared to surgical treatment of dorsal wrist ganglia. The published surgical literature hypothesizes that the variability in etiology of volar radial wrist–forearm ganglia may account for the higher surgical recurrence rates of these ganglia. Currently, the literature states that volar radial wrist–forearm ganglia may be secondary to arthritic intercarpal joints, carpal interosseous ganglia, or by mechanical stress within tendon sheaths, joint capsules, and ligaments. The literature has not reported pathology isolated to the flexor carpi radialis tendon and its tendon sheath at the volar trapezial fibro-osseous synovial sheath tunnel as a cause of volar radial wrist–forearm ganglia. This case series reports findings of pathology isolated to the flexor carpi radialis tendon at the trapezial fibro-osseous synovial sheath tunnel that caused primary and recurrent volar radial wrist–forearm ganglia. The pathology identified in this case series hypothesizes an additional etiologic factor in development of volar radial wrist–forearm ganglia. Surgeon awareness of potential pathology of the flexor carpi radialis tendon at the trapezial fibro-osseous synovial sheath tunnel may reduce recurrence rates of volar radial wrist–forearm ganglia treated by surgical intervention.

[Applied anatomy research of the uncovertebral joint for design of uncovertebral joint fusion cage]

OBJECTIVE

To measure anatomical parameters related to cervical uncovertebral joint and provide data support for the design of uncovertebral joint fusion cage.

METHODS

According to the inclusion and exclusion criteria, raw DICOM data of cervical CT scan in 60 patients (30 males and 30 females, aged 39-60 years) were obtained, then the three-dimensional cervical spine model was reconstructed for anatomical measurement by using the Mimics19.0 software. The height of the uncinate process, the length of the uncinate process, the width of the uncinate process, and the length of the uncovertebral joint in the intervertebral foramen region were measured bilaterally from C3 to C7. The anterior and posterior distances between the uncinate processes were measured from C3 to C7. The height of the uncovertebral joint space, the central height of the intervertebral disc space, and the depth of the intervertebral disc space were also measured from C2, 3 to C6, 7. The mean, standard deviation, maximum, and minimum were calculated by using the SPSS22.0 statistical software for the design of uncovertebral joint fusion cage.

RESULTS

The height of the uncinate process, the length of the uncinate process, the width of the uncinate process, and the length of the uncovertebral joint in the intervertebral foramen region of C3-C7 and the height of the uncovertebral joint space of C2, 3-C6, 7 showed no significant difference between two sides (P>0.05). The height of the uncovertebral joint space also had no significant difference between females and males (P>0.05). The anterior distances between the uncinate processes of C3-C7 were significantly larger than the posterior distances between the uncinate processes (P<0.05), the uncovertebral joint presented a posterior cohesive shape. The central height of the intervertebral disc space in male group was slightly higher than that in female group, and the differences were significant (P<0.05) at C2, 3 and C5, 6; the depth of the intervertebral disc space in male group was significantly higher than that in female group (P<0.05). The central height of the intervertebral disc space was (4.94±0.49) mm (range, 3.81-5.90 mm), the depth of the intervertebral disc space was (15.78±1.23) mm (range, 12.94-18.85 mm), the anterior and posterior distances between the uncinate processes were (17.19±2.39) mm (range, 13.39-24.63 mm) and (10.84±2.12) mm (range, 7.19-16.64 mm), respectively. According to the results of the anatomical research, the height of the uncovertebral joint fusion cage was designed as 5, 6, 7, and 8 mm; the depth of the uncovertebral joint fusion cage was designed as 12, 13, 14, 15, and 16 mm; the width of the uncovertebral joint fusion cage was designed as 14-18 mm; and the two wings are designed as arc-shape with 2 and 3 mm in width.

CONCLUSION

There are certain differences in the anatomical parameters of the uncovertebral joint between different segments. The uncovertebral joint fusion cage that designed based on the results of anatomical research is suitable for most patients.