Finite element analysis of the performance of additively manufactured scaffolds for scapholunate ligament reconstruction

Rupture of the scapholunate interosseous ligament can cause the dissociation of scaphoid and lunate bones, resulting in impaired wrist function. Current treatments (e.g., tendon-based surgical reconstruction, screw-based fixation, fusion, or carpectomy) may restore wrist stability, but do not address regeneration of the ruptured ligament, and may result in wrist functional limitations and osteoarthritis. Recently a novel multiphasic bone-ligament-bone scaffold was proposed, which aims to reconstruct the ruptured ligament, and which can be 3D-printed using medical-grade polycaprolactone. This scaffold is composed of a central ligament-scaffold section and features a bone attachment terminal at either end. Since the ligament-scaffold is the primary load bearing structure during physiological wrist motion, its geometry, mechanical properties, and the surgical placement of the scaffold are critical for performance optimisation. This study presents a patient-specific computational biomechanical evaluation of the effect of scaffold length, and positioning of the bone attachment sites. Through segmentation and image processing of medical image data for natural wrist motion, detailed 3D geometries as well as patient-specific physiological wrist motion could be derived. This data formed the input for detailed finite element analysis, enabling computational of scaffold stress and strain distributions, which are key predictors of scaffold structural integrity. The computational analysis demonstrated that longer scaffolds present reduced peak scaffold stresses and a more homogeneous stress state compared to shorter scaffolds. Furthermore, it was found that scaffolds attached at proximal sites experience lower stresses than those attached at distal sites. However, scaffold length, rather than bone terminal location, most strongly influences peak stress. For each scaffold terminal placement configuration, a basic metric was computed indicative of bone fracture risk. This metric was the minimum distance from the bone surface to the internal scaffold bone terminal. Analysis of this minimum bone thickness data confirmed further optimisation of terminal locations is warranted.

Feasibility of MRI for the evaluation of interosseous ligament vertical segment via subtalar arthroscopy correlation: comparison of 2D and 3D MR images

Background Interosseous ligament vertical segment (IOLV) and calcaneofibular ligament (CFL) have been reported to be important in stabilizing the subtalar joint. Unlike CFL, there is not much information regarding the comparison of MRI results with surgical evaluation of IOLV and the comparison between 2D and 3D MRI on IOLV evaluation. The feasibility of MRI in IOLV evaluation has yet to be reported. The purpose of this study was to evaluate the validity and reliability of MRI in IOLV tear detection via correlation with arthroscopic results. We also compared the diagnostic performance of 2D and 3D MR images. Methods In this retrospective study, 52 patients who underwent subtalar arthroscopy after ankle MRI were enrolled. Arthroscopic results confirmed IOLV tear in 25 cases and intact IOLV in 27 cases. Two radiologists independently evaluated the IOLV tears using only conventional 2D images, followed by isotropic 3D images, and comparison with arthroscopic results. Results Only the 2D sequences interpreted by two readers showed a sensitivity of 64.0–96.0%, a specificity of 29.6–44.4%, a positive predictive value of 51.6–56.4%, and a negative predictive value of 57.1–88.9%. Addition of isotropic 3D sequences changed the sensitivity to 60.0–80.0%, specificity to 63.0–77.8%, positive predictive value to 64.3–76.9%, and negative predictive value to 66.7–80.8%. The overall diagnostic performance of isotropic 3D sequences (AUC values: 0.679–0.816) was higher than that of 2D sequences (AUC values: 0.568–0.647). Inter-observer and intra-observer agreement between the two readers was moderate-to-good for both 2D and 3D sequences. The diagnostic accuracy in 19 patients with tarsal sinus fat obliteration tended to increase from 26.3–42.1% to 57.9–73.7% with isotropic 3D sequences compared with 2D sequences. Conclusions Isotropic 3D MRI was feasible for the assessment of IOLV tear prior to subtalar arthroscopy. Additional 3D sequences showed higher diagnostic accuracy compared with conventional 2D sequences in IOLV evaluation. Isotropic 3D sequences may be more valuable in detecting IOLV tear in case of tarsal sinus fat obliteration.

Dynadesis for Treatment of Dynamic Scaphoid Instability with 20-Year Results

Background Even though the scapholunate interosseous ligament is the most common wrist ligament injury, its treatment remains a challenge for hand surgeons. We report on a surgical treatment (Dynadesis) for dynamic scaphoid instability (DSI) with a 20-year follow-up period. Description of Technique Dynadesis utilizes antagonist forearm muscles in order to synergistically provide dynamic stabilization to the scaphoid when the wrist is loaded. It is a tendon-to-tendon transfer with the following two components: 1) Dorsal—The extensor carpi radialis longus (ECRL) is passed through a hole in the reduced, distal scaphoid, providing the scaphoid with an independent extension force. 2) Volar—A dynamic checkrein is created by tension-locking the ECRL tendon around the flexor carpi radialis (FCR) tendon. The portion of the FCR distal to the scaphoid tethers and tightens with contracture of the ECRL and FCR muscles. Patients and Methods Twenty patients (21 wrists) were treated with Dynadesis and reevaluated 20 years later (range: 20–27 years). Results Average grip strength improved by 8 kg. The average wrist flexion-extension arc decreased by 3°. Wrist X-rays showed no radiocarpal arthritis. On the Mayo wrist score, 81% reported excellent to good results (average: 89). Pain levels improved by 90%, with 76% of patients reporting no pain. All patients (100%) were satisfied with their results and would recommend the procedure. Conclusions Dynadesis is specifically designed for the treatment of DSI. It avoids the eventual complication of osteoarthritis and does not sacrifice wrist motion. A predictable and satisfactory long-term result is obtainable with correct patient selection based on clinical staging and arthroscopic findings.

Outcomes Following Surgical Treatment of Hamate Arthrosis Lunotriquetral Ligament Injuries

Background: An institutional review board–approved study of the functional outcomes of patients after surgical treatment of hamate arthrosis lunotriquetral ligament tear (HALT) lesions was conducted. Methods: In all, 21 wrists in 19 patients underwent arthroscopic, open, or combined treatment of HALT lesions. Seven patients underwent isolated hamate debridement and 14 had concomitant procedures to address lunotriquetral pathology. Nineteen wrists underwent procedures to address additional pathology, including triangular fibrocartilage complex, ulnotriquetral ligament split, and scapholunate ligament injuries. Results: Mayo wrist scores increased from 54 to 71. Sixteen patients had no or mild pain postoperatively, compared with none preoperatively. When stratified by lunotriquetral interosseous ligament management, 75% of the limited treatment group (none or debridement) and 78% of the additional treatment group reported improved pain. Three patients underwent additional surgeries for persistent pain. Conclusion: Resection of the proximal pole of the hamate can improve pain and function for patients with ulnar-sided wrist pain secondary to a HALT lesion. Concomitant wrist pathologies should be considered when determining treatment plans.

The treatment of scaphoid non-unions with partial and total scaphoid in titanium custom-made 3D-printed prostheses and reconstruction of scapholunate interosseous ligament: a preliminary study

ABSTRACTThe treatment of sequelae of scaphoid fractures is still one of the unsolved problems of hand surgery. Between January 2019 and July 2020 in the Hand Surgery Department of San Paolo’s Hospital in Savona (Italy) 9 partial scaphoid in titanium custom-made 3D-printed prosthesis have performed in 9 patients (all men) with an average age of 27.5 years (minimum 18-maximum 37 years). The aim of the study is to evaluate over time the clinical-functional and radiographic results of the wrists treated with partial and total scaphoid titanium custom-made 3D-printed prostheses and reconstruction of SLIL.

Treatment Recommendations for Suspected Scapholunate Ligament Pathology

Background The diagnosis and treatment of scapholunate interosseous ligament (SLIL) pathology is debated and notably variable. This study assessed the influence of diagnostic arthroscopy on treatment recommendations and the interobserver reliability of the arthroscopic classification of SLIL pathology. Methods The influence of diagnostic arthroscopy on treatment recommendations and the reliability of the arthroscopic classification of SLIL pathology were tested in a survey-based experiment. Seventy-seven surgeons evaluated 16 scenarios of people with wrist pain with variation in symptoms, scaphoid shift, time of symptom onset, and MRI appearance of the SLIL. Participants were randomized to view or not to view diagnostic wrist arthroscopy. Factors associated with recommendation for repair, capsulodesis, or tenodesis were analyzed. Results Viewing arthroscopic videos was associated with both offering surgery and a more reconstructive option. Other factors independently associated with recommendation for surgery included greater pain intensity and activity intolerance, women surgeons, an asymmetric scaphoid shift, and a recent onset of symptoms. The interobserver reliability of SLIL classification was slight. Conclusions Diagnostic arthroscopy leads to more surgery, and more invasive surgery, in spite of unreliable assessment of pathology. Clinical Relevance This points to the need to measure the potential benefits and harms of diagnostic wrist arthroscopy among people with wrist pain and no clear diagnosis on interview, examination, and radiographs. Level of Evidence Not applicable.

Radiocarpal Contact Pressures Are Not Altered after Scapholunate Ligament Tears

Background The scapholunate interosseous ligament (SLIL) couples the scaphoid and lunate, preventing motion and instability. Prior studies suggest that damage to the SLIL may significantly alter contact pressures of the radiocarpal joint. Questions/Purposes The purpose of this study was to investigate the contact pressure and contact area in the scaphoid and lunate fossae of the radius prior to and after sectioning the SLIL. Methods Ten cadaveric forearms were dissected distal to 1-cm proximal to the radiocarpal joint and a Tekscan sensor was placed in the radiocarpal joint. The potted specimen was mounted and an axial load of 200 N was applied over 60 seconds. Results Sectioning of the SLIL did neither significantly alter mean contact pressure at the lunate fossa (p = 0.842) nor scaphoid fossa (p = 0.760). Peak pressures were similar between both states at the lunate and scaphoid fossae (p = 0.301–0.959). Contact areas were similar at the lunate fossa (p = 0.508) but trended toward an increase in the SLIL sectioned state in the scaphoid fossa (p = 0.055). No significant differences in the distribution of contact pressure (p = 0.799), peak pressure (p = 0.445), and contact area (p = 0.203) between the scaphoid and lunate fossae after sectioning were observed. Conclusion Complete sectioning of the SLIL in isolation may not be sufficient to alter the contact pressures of the wrist. Clinical Relevance Injury to the secondary stabilizers of the SL joint, in addition to complete sectioning of the SLIL, may be needed to induce altered biomechanics and ultimately degenerative changes of the radiocarpal joint.