The effect of lunate position on range of motion after a four-corner arthrodesis: A biomechanical simulation study

Decreased Complication Rate Using Partially Threaded Compared With Fully Threaded Compression Screws in 4 Corner Arthrodesis: A Retrospective Study

BACKGROUND

Scapho-lunate advanced collapse (SLAC) and scaphoid nonunion advanced collapse (SNAC) of the wrist are the most common types of wrist arthritis. We compared the union rate and complication profile of patients with SLAC and SNAC wrist undergoing 4 corner arthrodesis with partially threaded or fully threaded headless compression screws.

METHODS

A single-center retrospective review was conducted to identify all patients treated for SLAC and SNAC with 4 corner fusion using headless compression screws from 2016 to 2021. A total of 33 patients undergoing surgery on 35 wrists were identified and included in the study. Demographics, comorbidities, complication profile, and radiographs were collected and compared between groups.

RESULTS

One hundred percent (16/16) of partially threaded and 84.2% (16/19) of fully threaded screws demonstrated union by minimum 10-week follow-up. The total complication rate (avascular necrosis of lunate, screw loosening, etc.) was 31.4%; 52.6% of wrists implanted with fully threaded screws experienced complications compared with a 6.3% complication rate with partially threaded screws. The difference was statistically significant between the 2 groups (P = .004).

CONCLUSIONS

Four corner arthrodesis using antegrade compression screws is an effective, reproducible method to achieve fusion in the wrist. The use of fully threaded screws was associated with more complications than with partially threaded screws, although union rate was not significantly different. Future studies with larger sample sizes would be useful to fully elucidate differences between these 2 constructs.

The effect of four-corner fusion and proximal row carpectomy on uniplanar and multiplanar wrist motion: A biomechanical study

Purpose

To compare changes in wrist kinematics after scaphoidectomy and four-corner fusion (4CF), and proximal row carpectomy (PRC).

Methods

Six cadaveric specimens underwent flexion-extension, radial-ulnar deviation and circumduction in an active motion wrist simulator. Native state, "anatomic 4CF", "radial 4CF", and PRC were compared.

Results

Radial 4CF reduced wrist extension, while PRC reduced radial deviation. Fusion groups had similar motion profiles. 44%, 41%, and 32% of native circumduction was maintained in PRC, anatomic, and radial 4CF.

Conclusions

Both fusion positions resulted in comparable motion outcomes. Anatomic 4CF was restricted in wrist extension compared to PRC but provided favourable radial deviation.

Mechanical performance comparison of two surgical constructs for wrist four-corner arthrodesis via dorsal and radial approaches

BACKGROUND

Four-corner arthrodesis, which involves fusing four carpal bones while removing the scaphoid bone, is a standard surgery for the treatment of advanced stages of wrist arthritis. Nowadays, it can be performed using a dorsal approach by fixing a plate to the bones and a new radial approach is in development. To date, there is no consensus on the biomechanically optimal and most reliable surgical construct for four-corner arthrodesis.

METHODS

To evaluate them biomechanically and thus assist the surgeon in choosing the best implant orientation, radial or dorsal, the two different four-corner arthrodesis surgical constructs were virtually simulated on a 3D finite element model representing all major structures of the wrist. Two different realistic load sets were applied to the model, representing common tasks for the elderly.

FINDINGS

Results consistency was assessed by comparing with the literature the force magnitude computed on the carpal bones. The Von Mises stress distribution in the radial and dorsal plates were calculated. Stress concentration was located at the plate-screw interface for both surgical constructs, with a maximum stress value of 413 MPa for the dorsal plate compared to 326 MPa for the radial plate, meaning that the stress levels are more unfavourable in the dorsal approach.

INTERPRETATION

Although some bending stress was found in one load case, the radial plate was mechanically more robust in the other load case. Despite some limitations, this study provides, for the first time, quantified evidence that the newly developed radial surgical construct is mechanically as efficient as the dorsal surgical construct.

Computational wrist analysis of functional restoration after scapholunate dissociation repair

The scapholunate ligament stabilizes the scaphoid and lunate of the proximal row in the wrist which allows for proper force transmission with the radius and ulna. Damage to this structure degenerates into arthritis and disability. Controversy exists over the best technique to restore function and reduce pain. A three-dimensional computational model of the wrist and hand was used to investigate the biomechanical effects of scapholunate ligament dissociation and its repair. The model replicated 3D bony anatomy, soft tissue structures, and muscle loading. The model predicted the increased instability caused by the injury, consistent with experimental and clinical evidence, and a return of more healthy kinematics with the repair. Changes to load transmission across the radiocarpal joints were noted with the injury, only some of which were mitigated by the repair. As better understanding of the biomechanics of the wrist joint is achieved, this model could prove to be an important tool to further investigate wrist mechanics and inform the effects of treatment options. Graphical abstract 3D computational model of all bones in the wrist/hand permitted simulation of five major motions-wrist flexion/extension, radial/ulnar deviation, and clenched fist. Shown are the array of tensile elements representing ligaments and capsule, as well as muscle force vectors for the desired motions. SL (scapholunate) separation (interval) predicted by the model for one motion compared well to an experimental study showing the instability induced by an injured (cut) SL ligament and returned stability by a clinical repair procedure, MBT (Modified Brunelli technique).

The digital human forearm and hand

How changes in anatomy affect joint biomechanics can be studied using musculoskeletal modelling, making it a valuable tool to explore joint function in healthy and pathological joints. However, gathering the anatomical, geometrical and physiological data necessary to create a model can be challenging. Very few integrated datasets exist and even less raw data is openly available to create new models. Therefore, the goal of the present study is to create an integrated digital forearm and make the raw data available via an open-access database. An un-embalmed cadaveric arm was digitized using 7T MRI and CT scans. 3D geometrical models of bones, cartilage, muscle and muscle pathways were created. After MRI and CT scanning, physiological muscle parameters (e.g. muscle volume, mass, length, pennation angle, physiological cross-sectional area, tendon length) were obtained via detailed dissection. After dissection, muscle biopsies were fixated and confocal microscopy was used to visualize and measure sarcomere lengths. This study provides an integrated anatomical dataset on which complete and accurate musculoskeletal models of the hand can be based. By creating a 3D digital human forearm, including all relevant anatomical parameters, a more realistic musculoskeletal model can be created. Furthermore, open access to the anatomical dataset makes it possible for other researchers to use these data in the development of a musculoskeletal model of the hand.

The Effect of Capitate Position on Coronal Plane Wrist Motion After Simulated 4-Corner Arthrodesis

PURPOSE

The objective of this study was to examine the effect of altering the capitolunate relationship on coronal-plane wrist motion after scaphoidectomy and simulated 4-corner arthrodesis. Two positions of different capitolunate alignments were compared: "anatomic" (unchanged from pre-fusion) and "lunate-covered" (capitate translated to cover the lunate). We hypothesized that wrist resting posture would be altered and radial-ulnar motion would diminish after 4-corner arthrodesis in the lunate-covered position when compared with normal wrists.

METHODS

Six human cadaveric limbs were disarticulated at the elbow and mounted on a custom jig. The resting position of the wrist was recorded with no load applied, followed by a load of 44 N applied to the flexor carpi radialis, extensor carpi radialis longus, and extensor carpi radialis brevis tendons to simulate radial deviation and to the flexor carpi ulnaris and extensor carpi ulnaris tendons to simulate ulnar deviation. Scaphoidectomy was performed and 2 methods of 4-corner arthrodesis with different capitolunate coronal alignments were studied in random order. Range of motion was compared using one-way analysis of variance and Bonferroni correction.

RESULTS

The "lunate covered" wrist demonstrated significantly greater radial resting posture than that of the preoperative wrist. Under a 44 N load, the lunate-covered position had significantly greater radial motion than the preoperative radial motion. Wrists fused in the "anatomic" position did not differ significantly from the preoperative wrists in posture or range of motion.

CONCLUSIONS

In this cadaveric model, complete covering of the capitate head by the lunate placed the wrist in increased radial deviation compared with the anatomic posture. Changes induced in the resting tension of the extrinsic wrist ligaments serve as a reasonable explanation for the increased radial posture and motion. In a clinical setting, these changes may affect postoperative wrist posture and function.

CLINICAL RELEVANCE

Maintaining anatomic lunate position leads to preservation of greater wrist motion and anatomic alignment in a patient undergoing 4-corner arthrodesis.

Decoupling the Wrist: A Cadaveric Experiment Examining Wrist Kinematics Following Midcarpal Fusion and Scaphoid Excision

At the wrist, kinematic coupling (the relationship between flexion-extension and radial-ulnar deviation) facilitates function. Although the midcarpal joint is critical for kinematic coupling, many surgeries, such as 4-corner fusion (4CF) and scaphoidexcision 4-corner fusion (SE4CF), modify the midcarpal joint. This study examines how 4CF and SE4CF influence kinematic coupling by quantifying wrist axes of rotation. Wrist axes of rotation were quantified in 8 cadaveric specimens using an optimization algorithm, which fit a 2-revolute joint model to experimental data. In each specimen, data measuring the motion of the third metacarpal relative to the radius was collected for 3 conditions (nonimpaired, 4CF, SE4CF). The calculated axes of rotation were compared using spherical statistics. The angle between the axes of rotation was used to assess coupling, as the nonimpaired wrist has skew axes (ie, angle between axes approximately 60°). Following 4CF and SE4CF, the axes are closer to orthogonal than those of the nonimpaired wrist. The mean angle (±95% confidence interval) between the axes was 92.6° ± 25.2° and 99.8° ± 22.0° for 4CF and SE4CF, respectively. The axes of rotation defined in this study can be used to define joint models, which will facilitate more accurate computational and experimental studies of these procedures.

Relationship Between Wrist Motion and Capitolunate Reduction in Four-Corner Arthrodesis

The authors retrospectively studied 36 patients with degenerative changes associated with scaphoid nonunion and scapholunate advanced collapse treated with circular plate fixation and bone graft. The goals of the study were to review the incidence of dorsal impingement, nonunion of arthrodesis, loose hardware, broken screws, and limitation in wrist motion associated with correct or incorrect surgical capitolunate reduction. Surgical indications were scapholunate advanced collapse (3 patients), scaphoid nonunion advanced collapse (32 patients), and sequelae of irreducible perilunate dislocation (1 patient). All of the patients were men, with a mean age of 48 years (range, 35-68 years). Average follow-up was 56 months (range, 12-108 months). Functional outcomes evaluated were pain with the visual analog scale, range of motion, grip strength, Disabilities of the Arm, Shoulder and Hand (DASH) score, satisfaction, and time to union. Mean visual analog scale score was 7 (range, 5-9) preoperatively and 1 (range, 0-2) postoperatively. Average wrist range of motion was 42° in extension, 36° in flexion, 15° in ulnar deviation, and 12° in radial deviation. Mean grip strength was 34 kg preoperatively, 50 kg postoperatively, and 56 kg contralaterally. Thirty-five of the 36 patients achieved union at 6 months. Degenerative changes at the radiolunate articulation were present in 1 patient 62 months after surgery, but he was asymptomatic. Mean capitolunate angle was 38º preoperatively and 9º postoperatively. Poor correlation was found between the measured capitate-lunate angle and subsequent flexion and extension (r=0.32 and r=0.17, respectively) using the Pearson correlation coefficient. The authors noted 1 or 2 broken screws in 3 cases (8.3%) and hardware dorsal impingement in the plate in 6 cases (16.6%). Mean DASH score was 24 of 100. Overall patient satisfaction was 70%.

Wrist salvage procedures alter moment arms of the primary wrist muscles

BACKGROUND

Proximal row carpectomy and scaphoid-excision four-corner fusion are salvage procedures that relieve pain by removing arthritic joint surfaces. While numerous studies have examined how these procedures affect joint motion, few have examined how they influence muscle mechanical actions. This study examines whether muscle moment arms change after these procedures.

METHODS

Moment arms of primary wrist muscles were measured in 8 cadaveric specimens using the tendon excursion method. In each specimen, moment arms were measured for two degrees of freedom (flexion-extension and radial-ulnar deviation) and three conditions (nonimpaired, scaphoid-excision four-corner fusion, and proximal row carpectomy). For each muscle and degree of freedom, moment arm versus joint angle curves for the three conditions were statistically compared.

FINDINGS

Wrist salvage procedures significantly alter moment arms of the primary wrist muscles. Proximal row carpectomy primarily alters flexion-extension moment arms, while scaphoid-excision four-corner fusion primarily alters radial-ulnar deviation moment arms. Both procedures also alter the balance between agonist and antagonist wrist muscles. Following proximal row carpectomy, wrist extensors have smaller moment arms in extended postures. Following scaphoid-excision four-corner fusion, radial deviators have larger moment arms throughout radial-ulnar deviation.

INTERPRETATION

Different moment arms indicate that different forces are required to complete the same tasks in nonimpaired and surgically altered wrists. The altered muscle moment arms likely contribute to post-operative impairments. Understanding how salvage procedures alter muscle mechanical actions is a critical first step toward identifying the cause of post-operative impairments and is necessary to develop effective interventions to augment deficient muscles and improve overall function.

Dynamic in vivo evaluation of radiocarpal contact after a 4-corner arthrodesis

PURPOSE

To understand the mechanisms that preserve joint integrity after 4-corner arthrodesis (FCA).

METHODS

We investigated the long-term changes of the radiolunate articulation after an FCA for different motions of the wrist in a cross-sectional study that included wrists of 10 healthy participants and both operated and nonoperated wrists of 8 individuals who had undergone FCA on 1 side. The average postoperative follow-up period of the FCA group was 5.7 years. The radiolunate articulation was assessed from dynamic 3-dimensional distance maps during wrist motion. Contact surface area, centroid position of the articular area, and distance between radiolunate articular surfaces were measured and compared between healthy subjects and operated and nonoperated wrists of FCA patients.

RESULTS

The total radiolunate articulation area was larger in patients with FCA. The average radiolunate joint space thickness was preserved in the operated FCA wrists. The centroid of the articulation area was shifted radially and dorsally in FCA wrists.

CONCLUSIONS

Changes of the motion pattern of the lunate during radioulnar deviation and flexion-extension of the wrist after FCA can explain the shift of the centroid radially and dorsally.

TYPE OF STUDY/LEVEL OF EVIDENCE

Diagnostic IV.

Bicolumnar intercarpal arthrodesis: minimum 2-year follow-up

PURPOSE

To determine greater than 2-year outcomes for combined lunate-capitate and triquetrum-hamate arthrodeses.

METHODS

We identified 16 patients who underwent scaphoid excision and combined arthrodeses of the lunate-capitate and triquetrum-hamate joints (bicolumnar arthrodesis) from 2007 to 2010. Eleven patients returned for follow-up evaluation, which included measurement of operative and contralateral control wrist flexion, extension, and grip strength, and completion of a patient-reported outcomes questionnaire, visual analog scale pain assessment, and Disabilities of the Arm, Shoulder, and Hand questionnaire. Radiographs of each patient were reviewed for evidence of union. Complications including nonunion and hardware migration were recorded.

RESULTS

Wrist flexion-extension in the operative wrist was 68% of the contralateral control wrist. Grip strength of the operative wrist was 97% of the contralateral wrist. All 11 patients had radiographic bicolumnar union; 8 patients had spontaneous radiographic fusion of the capitohamate joint. One patient required capitolunate screw removal for migration despite having evidence of union.

CONCLUSIONS

Results from scaphoid excision and bicolumnar intercarpal arthrodesis are comparable to those reported for traditional scaphoid excision and 4-corner arthrodesis, with a similar loss of wrist range of motion and with possible preservation of better grip strength in the operative wrist. Advantages of this modification include preservation of the normal lunate-triquetrum and capitate-hamate anatomic relationships and simplification of operative technique.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Early motion following 4-corner arthrodesis using cannulated compression screws: a biomechanical study

PURPOSE

To assess the ability of headless compression screws to maintain immobile bony contact throughout wrist cycling following simulated 4-corner arthrodesis. Our hypothesis was that the screw constructs would not permit displacement of the carpal bones and, therefore, could tolerate early postoperative range of motion in vivo.

METHODS

Using 6 matched-paired cadaveric arms, 4-corner arthrodesis was performed using an all-cannulated compression screw construct (capitolunate, lunotriquetral, and triquetrohamate screws) or a partial compression screw combined with partial K-wire construct (2 crossing capitolunate screws with the lunotriquetral and triquetrohamate interfaces immobilized with 2 K-wires). Wrists were mounted and cycled 5,000 times. Intercarpal distances were measured at 0, 100, 1,000, and 5,000 cycles at fixed points of passive flexion. Because previously published studies considered intercarpal distances of greater than 1 mm as significant, we defined fixation failure as greater than 0.5 mm gapping.

RESULTS

Neither screw construct showed any significant intercarpal gapping at any point during the experimental cycling (largest average intercarpal gapping was 0.2 mm). There were no significant differences between the constructs regarding gapping at any point.

CONCLUSIONS

In this biomechanical model, cannulated compression screws effectively resist significant intercarpal gapping during early motion after 4-corner arthrodesis. This may allow for immediate postoperative range of motion.

CLINICAL RELEVANCE

Early gentle range of motion may be possible immediately following 4-corner arthrodesis using a construct consisting of headless compression screws.

Orientations of wrist axes of rotation influence torque required to hold the hand against gravity: a simulation study of the nonimpaired and surgically salvaged wrist

The wrist is a complex kinematic link connecting the forearm and hand. The kinematic design of the wrist is permanently altered during surgical salvage procedures, such as proximal row carpectomy (PRC) and scaphoid-excision four-corner fusion (SE4CF), which have the unintended consequence of long-term functional impairments to both the wrist and hand. We developed simulations of the nonimpaired, PRC, and SE4CF wrists to evaluate if surgically altered wrist kinematics contribute to functional impairments. Specifically, as a step toward understanding the connection between kinematics and function, we examined the torque necessary to statically maintain functional postures. All simulations included only bone geometry and joint kinematics; soft tissues were excluded. Our simulations demonstrate that the torque necessary to maintain a functional posture is influenced by the orientations of the flexion and deviation axes of rotation relative to each other and the anatomical planes of the radius. The magnitude of torque required to hold the hand against gravity decreased in simulations of the PRC wrist compared to the nonimpaired wrist. In contrast, the torque required increased relative to the nonimpaired wrist in simulations of the SE4CF wrist. These divergent results are directly related to how motion is coupled between the flexion-extension and deviation axes of rotation. This study highlights that, even without considering the effects of soft tissues, changing the kinematic design of the wrist influences function; therefore, kinematics should be considered when surgically redesigning the wrist.