Introduction

The Lunotriquetral Interosseus Ligament (LTIL) is one of the most important ligaments in maintaining carpal stability [ 1 ]. Injury to ligaments supporting the lunotriquetral joint is the second most common cause of carpal instability which mostly affects young athletes [ 2 ]. The anatomic configuration of LTIL is C-shaped consisting of volar (main part), dorsal, and membranous components. LTIL transaction can lead to wrist instability through lunate flexion [ 1 - 3 ]. Although LTIL injuries are rare, they can occur following trauma to the dorsal part of the wrist when in a flexed position [ 4 ]. These injuries may present with tenderness on the ulnar side of the wrist, reduced grip strength, pain during ulnar deviation, or as vaguely described dorsal wrist pain in chronic cases. In physical examination, the triquetrum compression, Kleinman, lunotriquetral ballottement, and Reagan tests can be positive in cases of LTIL injury [ 1 ]. The diagnosis is usually overlooked due to normal radiographic images; however, the injuries can be detected in magnetic resonance arthrography [ 5 ].

Since the diagnosis of this disease is dilemmatic, improper management of the condition is commonly encountered, leading to osteoarthritis and difficulty in performing daily activities [ 6 ]. If the wrist is generally stable, conservative management with immobilization can be a reasonable option. Corticosteroid injections are indicated in cases of persistent pain. Operative management should be considered if the joint is unstable, and the surgical options for this condition range from arthroscopic repair, closed reduction, and fixation using Kirschner wires, pins, or screws and capsulodesis [ 7 ]. However, no studies have compared the internal fixation of this joint using different orthopedic instruments in various configurations, likely due to the variability of this condition. The fixation of the lunotriquetral joint leads to high rates of complication. Arthroscopy management of LTIL injuries is the gold standard of treatment in developed countries. However, determining the best approach to prevent postoperative complications, such as osteoarthritis and malunion/nonunion, is crucial, particularly in resource-limited settings, in which proper surgical instruments and expertise may be lacking [ 8 ]. Consequently, the current study aimed to assess pin- and screw-fixation of lunotriquetral joints with different instrument directions using a three-dimensional model for better postoperative outcomes.

Material and Methods

In this computer simulation study, the Computed Tomography (CT) scan of the wrist joint in a normal subject was used to create a 3D model of the wrist joint. The CT scan (the 1.5 ulnar deviation with 0.98 mm thickness for the slices) of the wrist joint was exported to the Mimics software (Version 19, Materialise Company, Belgium) to create a 3D model, and the model of all bones in the wrist joint (the carpals, meta-carpals, ulnar, and radius) was produced. The 3D model of wrist joint bones was exported to 3 Mat software (version 11, Materialise Company, Belgium) for smoothing, re-meshing, and changing the format into STL. Moreover, pin fixation, screw fixation, and both fixation with screw and pin were done. It is important to note that in this study, the lunotriquetrum was fixed following the rupture of the Lunotriquetral Interosseous Ligament (LTIL) (Figure 1). The wrist joint complex bones were first exported to free CAD software to convert the models from STL format to parts. The final models were exported to Abaqus for further analysis, where the 3D models of the wrist joints were assembled. In the next step, the 3D models of the wrist joint bones were meshed, and the mechanical properties of the bones were applied to the structure . The supporting ligaments were modeled of spring elements. The stiffness of the supporting ligaments was obtained from the literature [ 11 , 12 ]. The force of the wrist joint extensors was applied to the model in Abaqus software. The force of the wrist and finger extensors was obtained from the output of OpenSIM software [ 13 ]. The distal end of the radius and ulnar was selected as a boundary condition in Abaqus software. Some parameters, such as the Maximum Value of Von Miss stress (MPAS), displacement of the lunate, and triquetrum bones in anteroposterior, mediolateral, and vertical directions, and angular displacement of the lunate bone were evaluated relative to the horizontal plane. The following conditions were assessed: normal condition with intact lunotriquetral interosseous ligament, pathological conditions with ruptured LTIL, pin fixation, screw fixation, and pin and screw fixation. This study was approved by the Ethics Committee of Shiraz University of Medical Sciences, Shiraz, Iran.

Figure 1. The models used in this study, (a) Normal model, (b) fixation with screw, (c) fixation with pin, (d) fixation with pin and screw

Results

This study compared the results of three different surgical methods for lunotriquetral fusion: using a pin, a screw, or both a pin and a screw. The current study also looked at how much the bones moved after surgery and the amount of stress placed on them, and compared these results to normal and abnormal (pathological) wrists to understand how well each surgical method worked.

The post-operative outcomes of lunotriquetral fusion regarding the lunate bone are summarized in Table 1. In normal conditions, the lunate bone was displaced for 0.32, 0.64, and 5.00 mm in the anteroposterior, mediolateral, and vertical planes. When the LTIL was completely torn, the lunate bone moved more freely from side to side, but its up-and-down movement was limited to about 4.10 millimeters. In the three surgical methods for lunotriquetral fusion, pin-fixation showed the least mobility of this bone in the anteroposterior direction (1.65 mm), which was the closest to the normal anatomic condition, with a significant difference among the three options. Moreover, the fixation of the lunotriquetral joint using a pin (1.47 mm) showed more resemblance to the normal condition compared to the screw fixation and double-instrument fixation (3.97 mm and 3.10 mm, respectively). The amount that the lunate bone moved up and down was very similar after the three different fusion surgeries. None of the methods were significantly better or worse than the others, and all were close to the normal movement of about 5 millimeters.

The stress imposed on the lunate bone was also assessed in the current study. In the normal condition, 453 MPas was imposed to the lunate bone, which was increased to 513 MPas in total LTIL tear. However, the use of a pin in the lunotriquetral fusion decreased the stress significantly (360 MPas); screw-fixation and double-instrument operation significantly increased the stress on the lunate bone predisposing the joint to arthrosis. Moreover, the pin-fixation method showed the least amount of stress imposed on the surgical instrument. As for the angular motion of the lunate bone after the surgery, the angular motion was significantly limited in all three methods. However, the use of two instruments was superior to the other approaches, which might provide the patients with more range of motion.

Table 2 presents the mechanistic parameters of the triquetrum bone after its fixation with the lunate bone in different surgical approaches. The triquetrum bone could move for 3.07 mm, 0.94 mm, and 4.60 mm in the anteroposterior, mediolateral, and vertical directions, respectively. When the LTIL was completely torn, the bone could move in the mediolateral plane more freely (1.55 mm). However, its motion in anteroposterior and vertical directions was rather limited (2.24 mm and 3.99 mm, respectively). Screw-fixation and double-instruments significantly decreased the triquetral motion in the anteroposterior aspect (0.20 mm and 1.25 mm, respectively), but fusion with a pin was relatively similar to the normal individual in this respect (3.27 mm). Fusion of the lunate and triquetrum bones increased the triquetral motion in the mediolateral direction even further than the total pathologic condition, and the difference was not clinically significant. Pin-fixation also showed superior results in the vertical motion of the triquetrum bone compared to other surgical approaches. The maximal stress imposed on the triquetrum bone was significantly lower in the pin-fixation method (109 MPas) compared to the screw-fixation (701 MPas) and double instrumentation (867 MPas).

Discussion

In this study, after 3D modeling of a normal wrist joint, the lunotriquetral ligament was completely torn to induce wrist instability. Then, in the model, lunotriquetral fixation was achieved using a pin, a screw, and one pin along with one screw. The current study measured how much the lunate and triquetrum bones moved, the amount of force on each bone, and how much the lunate bone rotated. We also measured the force on the pins and screws used in each surgery.

The amount the lunate bone movement from front to back, showing that tearing the ligament didn’t affect its movement, but fixing the joint with surgery actually caused it to move more than normal or injured wrists. A pin and a screw led to the most movement in this direction.

As for the side-to-side movement of the lunate bone, using a screw or a pin and a screw together caused the bone to move more than just using a pin. However, the amount of bone moved up and down, and all three surgical methods were similar to normal wrists. Also, none of the methods limited the bone’s rotation, and the force on the implants and bone was low. Based on these results, fixing the lunotriquetral ligament injury with just a pin seems to be the best option when focusing on the lunate bone’s health (Table 1).

When considering the triquetrum bone, pin-fixation of the joint mostly resembles the normal anatomy in the anteroposterior displacement of the bone, while screw-fixation significantly limits the anteroposterior motion of the triquetrum bone. There wasn’t a big difference in how much the triquetrum bone moved from side to side with the three surgical methods, but a pin and screw together was slightly better. However, using a pin alone was significantly better at preventing up-and-down movement of the triquetrum bone, and it also put the least amount of stress on the implant (Table 2).

In a study by Nelson et al. [ 8 ] the authors compared lunotriquetral using Kirschner wires and concomitant use of K-wires and screws. They found that in cases of using K-wires alone 60% of the procedures ended in proper fusion of the bones; in the patients who needed a revision arthrodesis, the fusion was completely successful though. In cases of screws in lunotriquetral fusion, the rate of success was 91%. In this study, the long-term fusion of the bones was not assessed, and only the results of surgery immediately after the operation were evaluated; however, since non-union has a multifactorial etiology consisting of post-op bone motility and stress, finding the best approach in this matter can predict the long-term effects as well.

Further, Sennwald et al. [ 14 ] performed lunotriquetral fusion on 23 patients using screws and showed that about 57% developed pseudoarthrosis; however, the mean period of follow-up of the patients was not available. Accordingly, lunotriquetral fusion might not be clinically acceptable due to high rates of complication. In the current study, lunotriquetral fixation using screws was relatively inferior to fixation with a pin or concomitant use of a pin and a screw. Thus, lunotriquetral fixation with a revised method using pins might show clinical potential for the treatment of patients with LTIL injury.

In another study by Vandesande et al. [ 15 ], 44.8% of the patients undergoing lunotriquetral fusion experienced nonunion. The range of motion of the patients who had non-union and successful operations did not differ. With regard to different surgical methods, patients who underwent screw-fixation had higher fusion rates compared to K-wire fixation. The study did not include any patients who had undergone lunotriquetral fusion using pins. Given our findings that pin fixation yielded better postoperative outcomes compared to screw fixation, this surgical technique may warrant further investigation for LTIL injuries.

Lunotriquetral fusion was performed with the addition of a cancellous bone graft [ 16 ]. This approach resulted in impressive outcomes, including over 80% pain reduction and a complete fusion rate within 50 days.

More novel methods, mostly using arthroscopic approaches, have been introduced for better management of LTIL injuries. For example, dorsal ligamentocapsulodes was proposed by Özçelik et al. which resulted in a pain-free status in most of the patients [ 17 ]. In low-resource settings, where access to skilled surgeons and advanced equipment is limited, exploring effective traditional surgical methods is crucial. Furthermore, in well-resourced environments, comparing pin fixation to arthroscopic techniques in future studies would be beneficial. It’s important to note that 3D modeling doesn’t fully capture the complexities of real-world surgeries, including potential complications. Therefore, additional clinical trials are necessary for a comprehensive understanding of this issue.

Conclusion

Lunotriquetral fusion for lunotriquetral interosseous ligament injuries can be achieved through various surgical approaches. However, a pin for bone fixation can be superior to screws or double instrumentation, particularly in low-resource setting.

Authors’ Contribution

MA. Mahdiyar, MT. Karimi participated in writing process. The first author in H. Namazi. MT. Karimi wrote the method and materials and did the data analysis. Both MA. Mahdiyar and HN. Namazi collected data. H. Namazi wrote the result. All the authors read, modified, and approved the final version of the manuscript.

Ethical Approval

This study has been approved by the Committee of ethics in Biomedical Studies of Shiraz University of Medical Sciences with ethical code: IR.SUMS.MED.REC.1402.295.

Informed Consent

This article does not involve any human or animal participants and is based on existing literature or research. However, the CT scan which were used for computer simulation was obtained from PACS image system.

Funding

This study has not been funded by any company or individual.

Conflict of Interest

None

References

1. Wilson MS. Diagnosis and Management of Lunotriquetral Ligament Injuries. Curr Rev Musculoskelet Med. 2023; 16(2):55-59. Publisher Full Text | DOI | PubMed [ PMC Free Article ]
2. Berger RA. The anatomy of the ligaments of the wrist and distal radioulnar joints. Clin Orthop Relat Res. 2001; 383:32-40. DOI | PubMed
3. Weiss LE, Taras JS, Sweet S, Osterman AL. Lunotriquetral injuries in the athlete. Hand Clin. 2000; 16(3):433-8. PubMed
4. Mayfield JK, Johnson RP, Kilcoyne RK. Carpal dislocations: pathomechanics and progressive perilunar instability. J Hand Surg Am. 1980; 5(3):226-41. DOI | PubMed
5. Asaad AM, Andronic A, Newby MP, Harrison JWK. Diagnostic accuracy of single-compartment magnetic resonance arthrography in detecting common causes of chronic wrist pain. J Hand Surg Eur Vol. 2017; 42(6):580-5. DOI | PubMed
6. Van De Grift TC, Ritt MJ. Management of lunotriquetral instability: a review of the literature. J Hand Surg Eur Vol. 2016; 41(1):72-85. DOI | PubMed
7. Nicoson MC, Moran SL. Diagnosis and Treatment of Acute Lunotriquetral Ligament Injuries. Hand Clin. 2015; 31(3):467-76. DOI | PubMed
8. Nelson DL, Manske PR, Pruitt DL, Gilula LA, Martin RA. Lunotriquetral arthrodesis. J Hand Surg Am. 1993; 18(6):1113-20. DOI | PubMed
9. Anderson DD, Deshpande BR, Daniel TE, Baratz ME. A three-dimensional finite element model of the radiocarpal joint: distal radius fracture step-off and stress transfer. Iowa Orthop J. 2005; 25:108-17. Publisher Full Text | PubMed [ PMC Free Article ]
10. Bajuri MN, Abdul Kadir MR, Murali MR, Kamarul T. Biomechanical analysis of the wrist arthroplasty in rheumatoid arthritis: a finite element analysis. Med Biol Eng Comput. 2013; 51(1-2):175-86. DOI | PubMed
11. Ledoux P, Lamblin D, Wuilbaut A, Schuind F. A finite-element analysis of Kienbock’s disease. J Hand Surg Eur Vol. 2008; 33(3):286-91. DOI | PubMed
12. Ramlee MH, Beng GK, Bajuri N, Abdul Kadir MR. Finite element analysis of the wrist in stroke patients: the effects of hand grip. Med Biol Eng Comput. 2018; 56(7):1161-71. DOI | PubMed
13. Namazi H, Ghaedi E, Karimi MT. Comparison of Biomechanical Results about the Effect of Three Surgery Methods in Decompression of Lunate Bone. J Wrist Surg. 2021; 10(4):296-302. Publisher Full Text | DOI | PubMed [ PMC Free Article ]
14. Sennwald GR, Fischer M, Mondi P. Lunotriquetral arthrodesis. A controversial procedure. J Hand Surg Br 1995; 20(6):755-60. DOI | PubMed
15. Vandesande W, De Smet L, Van Ransbeeck H. Lunotriquetral arthrodesis, a procedure with a high failure rate. Acta Orthop Belg. 2001; 67(4):361-7. PubMed
16. Guidera PM, Watson HK, Dwyer TA, Orlando G, Zeppieri J, Yasuda M. Lunotriquetral arthrodesis using cancellous bone graft. J Hand Surg Am. 2001; 26(3):422-7. DOI | PubMed
17. Özçelik İB, Ayik Ö, Demirel M, Yildirim T, Uğurlar M. Arthroscopic Dorsal Ligamentocapsulodesis in the Treatment of Isolated Lunotriquetral Interosseous Ligamentous Injury: A Retrospective Case Series of 22 Patients. J Hand Surg Asian Pac Vol. 2022; 27(3):480-90. DOI | PubMed