Cadaveric Forearms Research Articles

The influence of partial union on the mechanical strength of scaphoid fractures: a finite element study.

Assessment of scaphoid fracture union on computed tomography scans is not currently standardized. We investigated the extent of scaphoid waist fracture union required to withstand physiological loads in a finite element model, based on a high-resolution CT scan of a cadaveric forearm. For simulations, the scaphoid waist was partially fused at the radial and ulnar sides. A physiological load of 100 N was transmitted to the scaphoid and the minimal amount of union to maintain biomechanical stability was recorded. The orientation of the fracture plane was varied to analyse the effect on biomechanical stability. The results indicate that the scaphoid is more prone to re-fracture when healing occurs on the ulnar side, where at least 60% union is required. Union occurring from the radial side can withstand loads with as little as 25% union. In fractures more parallel to the radial axis, the scaphoid seems less resistant on the radial side, as at least 50% union is required. A quantitative CT scan analysis with the proposed cut-off values and a consistently applied clinical examination will guide the clinician as to whether mid-waist scaphoid fractures can be considered as truly united.

Supplementary Fixation Improves Stability of Intra-Articular Distal Radius Fractures Managed With a Spanning Plate

Previous studies evaluating weight bearing of distal radius fractures treated through dorsal spanning bridge plates used extra-articular fracture models, and have not evaluated the role of supplementary fixation. We hypothesized that supplementary fixation with a spanning dorsal bridge plate for an intra-articular wrist fracture would decrease the displacement of individual articular pieces with cyclic axial loading and allow for walker or crutch weight bearing. Thirty cadaveric forearms were matched into 3 cohorts, controlling for age, sex, and bone mineral density. An intra-articular fracture model was fixed with the following 3 techniques: (1) cohort A with a dorsal bridge plate, (2) cohort B with a dorsal bridge plate and two 1.6-mm k-wires, and (3) cohort C with a dorsal bridge plate and a radial pin plate. Specimens were axially loaded cyclically with escalating weights consistent with walker and crutch weight-bearing with failure defined as 2-mm displacement. No specimens failed at 2- or 5-kg weights, but cohort A had significantly more displacement at these weights compared with cohort B. Cohort A had significantly more failure than cohort C. Both cohort A and cohort B had significantly more displacement at crutch weight bearing compared with cohort C. The supplementary fixation group had significantly lower displacement at crutch weight-bearing compared with cohort A in all gaps. Survival curves demonstrated the fixation cohort to survive higher loads than the nonfixation group. There was significantly less displacement and less failure of intra-articular distal radius fractures treated with a spanning dorsal bridge plate and supplementary fixation. Our model showed that either type of fixation was superior to the nonfixation group. When considering early weight-bearing for intra-articular distal radius fractures treated with a spanning dorsal bridge plate, supplementary fixation may be considered as an augmentation to prevent fracture displacement.

Bone Morphology and Vascular Supply of Pedicled Distal Radius Bone Using Nano-Computed Tomography.

The goal of this study was to use nano-computed tomography to describe the intraosseous vascularity and structural characteristics of commonly used distal radius vascularized bone grafts for treatment of scaphoid nonunion. We obtained 8 fresh frozen human cadaver forearm specimens for infusion of barium contrast. Specimens were scanned and segmented to quantify the vascular volume and trabecular density within 3 common graft regions, including 1, 2 intercompartmental supraretinacular artery (1,2 ICSRA), fourth extensor compartment artery (4 ECA), and volar carpal artery (VCA), as well as thirds of the scaphoid. Outcomes also included mean and maximum cortical thickness and number of cortical perforators. Single-specimen analyses were also performed comparing vascularity and trabecular density of each graft with scaphoid regions of a single specimen. Statistical analysis was performed using analysis of variance with post hoc Tukey testing when P value was less than .05. There was no significant difference between groups in the mean percent vascularity (P = .76). The ratio of trabecular bone in each graft to scaphoid thirds was less than 1. The mean cortical thickness (0.79 mm, 95% confidence interval [CI], 0.66-0.93 mm) and maximum cortical thickness (1.45 mm, 95% CI, 1.27-1.63 mm) of VCA grafts were both significantly greater than those of 4 ECA and 1,2 ICSRA (P < .001). There were no differences between vascular density of the 3 grafts and the scaphoid. Pedicled distal radius bone grafts have similar vascularity but morphometric differences such as cortical thickness and trabecular density which have unclear clinical implications.

THE LIGAMENTOUS CONTRIBUTION TO STABILITY AT THE DISTAL RADIOULNAR JOINT

The triangular fibrocartilage complex (TFCC) is a known stabiliser of the distal radioulnar joint (DRUJ). An injury to these structures can result in significant disability including pain, weakness and joint stiffness. The contribution each of its components makes to the stability of the TFCC is not well understood. This study was undertaken to investigate the role of the individual ligaments of the TFCC and their contribution to joint stability.The study was undertaken in two parts. 30 cadaveric forearms were studied in each group. The ligaments of the TFCC were progressively sectioned and the resulting effect on the stability of the DRUJ was measured. A custom jig was created to apply a 20N force through the distal radius, with the ulna fixed.Experiment one measured the effect on DRUJ translation after TFCC sectioning. Experiment two added the measurement of rotational instability.Part one of the study showed that complete sectioning of the TFCC caused a mean increase in translation of 6.09(±3) mm. Sectioning the palmar radioulnar ligament of the TFCC caused the most translation.Part two demonstrated a change in rotation with a mean of 18 (± 6) degrees following sectioning of the TFCC. There was a progressive increase in rotational instability until the palmar radioulnar ligament was also sectioned.Linear translation consistently increased after sectioning all of the TFCC ligaments, confirming its importance for DRUJ stability. Sectioning of the palmar radioulnar ligament most commonly caused the greatest degree of translation. This suggests injury to this ligament would more likely result in a greater degree of translational instability. The increase in rotation also suggests that this type of instability would be symptomatic in a TFCC injury.

Force-amplifying implant to improve key pinch strength in tendon transfer surgery: Cadaver modelproof-of-concept.

The brachioradialis (BR) to flexor pollicis longus (FPL) tendon transfer surgery is a common procedure used to restore key pinch grip for incomplete spinal cord injury patients. However, the procedure only restores 22% of the physiological grip strength, which is important for successfully grasping objects and minimizing fatigue. The purpose of this study was to evaluate the efficacy of using a novel force-amplifying pulley implant to modify the standard BR to FPL tendon transfer surgery to improve key pinch grip strength in a human cadaver forearm model. A total of eightcadaveric specimens were mounted onto a custom testbed where a torque-controlled motor actuated the BR tendon to produce key pinch grip. In each cadaver, two experimental groups were examined: a standard and an implant-modified BR to FPL tendon transfer surgery. A force sensor mounted to the thumb recorded isometric key pinch grip forces over a range of input BR forces (2 N-25 N) applied in a ramp-and-hold protocol. Across the range of input BR forces, the average improvement in key pinch grip strength in the implant-modified surgery compared to the standard surgery was 58 ± 7.1% (ranging from 41% to 64% improvement). Throughout the experiments, we observed that the implant did not hinder the movement of the BR or FPL tendons. These results suggest that a BR to FPL tendon transfer surgery utilizing a force-amplifying pulley implant to augment force transmission can provide additional functional strength restoration over the standard procedure that directly sutures two tendons together.

Anatomic relationship of extensor indicis propius and extensor digitorum communis: Implications for tendon transfer.

The extensor indicis proprius (EIP) tendon is a frequently used donor for a variety of tendon transfers, most commonly for reconstruction of the extensor pollicis longus (EPL). EIP is known to have frequent anatomic variants including split tendons and variations in tendon arrangement. To characterize the anatomy of the EIP at the level of the extensor retinaculum, where tendon harvest is often performed, and share our preferred technique for EIP to EPL transfer. Twenty-nine fresh-frozen cadaveric forearms without history of forearm or hand injury or surgery were dissected. Tendon circumference and relationship of the EIP and extensor digitorum communis to the index (EDCI) at the metacarpophalangeal (MCP) joint and the distal extensor retinaculum were recorded. Distance from the distal extensor retinaculum to the EIP myotendinous junction was measured. EIP was ulnar to the EDCI in 96.5% of specimens (28/29) at the distal edge of the extensor retinaculum. In the remaining specimen, EIP was volar to EDCI. Tendon circumference at the distal extensor retinaculum averaged (9.3 mm ± 1.7 mm) for EDCI and 11.1 mm (± 2.7 mm) for EIP (P = 0.0010). The tendon circumference at the index MCP joint averaged 11.0 mm (± 1.7 mm) for EDCI and 10.6 mm (± 2.1 mm) for EIP (P = 0.33). EIP had a greater circumference in 76% (22/29) of specimens at the distal extensor retinaculum whereas EIP had a greater circumference in only 31% (9/29) of specimens at the MCP joint. The EIP tendon is frequently ulnar to and greater in circumference than the EDCI at the distal extensor retinaculum, which can be taken into consideration for tendon transfers involving EIP.

Reliability of the Sigmoid Notch Classification of the Distal Radioulnar Joint.

Background The Tolat sigmoid notch classification is a commonly used classification to characterize the distal radioulnar joint (DRUJ). This classification was based on a limited assessment of the entire joint, which may lead to inaccuracies in sigmoid notch evaluation. Questions/Purposes The purpose of this study is to assess the reliability of the Tolat classification for sigmoid notch characterization. Methods The sigmoid notch of 52 models of cadaveric forearms was assessed by applying the Tolat classification to the three-dimensional (3D) modeled notch and then slices at the start of the notch (0 mm) and 4 mm more proximal. The inter- and intrarater agreement was assessed using Cohen's and Fleiss' kappa statistic. Results Agreement between iterations regardless of slices or surgeons/radiologists was moderate. Intrarater agreement between pairs of slices (0 vs 4 mm, 0 mm vs 3D, 4 mm vs 3D) was moderate, whereas agreement between all slices was slight. Agreement between surgeons and between radiologists was moderate, while agreement across all raters and slices was fair. Models described as "other" were more consistent in 3D classifications and were commonly classified as a reverse ski slope. Conclusions Classification using the Tolat scheme is fair to moderate at best. Classification of the sigmoid notch using an axial view of the distal radius may not accurately reflect the anatomy throughout the notch. Clinical Relevance The Tolat classification supplies a limited analysis of the sigmoid notch, and does not represent a comprehensive evaluation of the entire joint. Future classification systems should characterize the entire sigmoid notch.

Negative Ulnar Variance Lessens DRUJ Instability After DRUJ Disruption: A Biomechanical Analysis.

The purpose of this study was to perform a biomechanical investigation on the effect of ulnar variance (UV) on the stability of the distal radioulnar joint (DRUJ) prior to and after DRUJ sectioning. Ten cadaveric forearm specimens were included in the study and baseline UV was assessed radiographically. Radial motion relative to the ulna was evaluated using Intel real sense cameras and a custom developed program. The forearms were dissected, and a radial osteotomy was performed. Using a custom-made plate, radial stability was assessed with an UV of + 4, 0, and -4 mm by measuring the maximum and minimum radial position relative to the ulna during a simulated Shuck test. The volar radioulnar ligaments and triangular fibrocartilage complex (TFCC) were then sectioned, and testing was repeated at each UV state. Sectioning significantly increased radial translation at neutral (P = .008), +4 mm UV (P = .008), and -4 mm UV (P = .018). There were no significant differences in translation between the 3 UV groups with the DRUJ intact (P = .124). The ulnar negative (-4 mm) state had significantly lower translation compared to the positive (+4 mm) (P < .001) and the neutral (0 mm) (P = .026) UV states. There were no significant differences between the positive and neutral UV groups with the DRUJ sectioned. Fixating the radius in -4 mm of ulnar negativity significantly decreased radial translation after sectioning the volar radioulnar ligament and TFCC. Ulnar variance had no effect on stability with an intact DRUJ. Biomechanical Study.

Malunion deformity of the forearm: Three-dimensional length variation of interosseous membrane and bone collision.

It remains unclear to what extent the interosseous membrane (IOM) is affected through the whole range of motion (ROM) in posttraumatic deformities of the forearm. The purpose of this study is to describe the ligament- and bone-related factors involved in rotational deficit of the forearm. Through three-dimensional (3D) kinematic simulations on one cadaveric forearm, angular deformities of 5°in fourdirections (flexion, extension, valgus, varus) were produced at twolocations of the radius and the ulna (proximal and distal third). The occurrence of bone collision in pronation and the linear length variation of sixparts of the IOM through the whole ROM were compared between the 32 types of forearm deformities. Similar patterns could be observed among fourgroups: 12 types of deformity presented increased bone collision in pronation, 8presented an improvement of bone collision with an increase of the mean linear lengthening of the IOM in neutral rotation, 6had an increased linear lengthening of the IOM in supination with nearly unchanged bone collision in pronation and 6types presented nearly unchanged bone collision in pronation with a shortening of the mean linear length of IOM in supination or neutral rotation. This kinematic analysis provides a better understanding of the ligament- and bone-related factors expected to cause rotational deficit in forearm deformity and may help to refine the surgical indications of patient-specific corrective osteotomy.

HR-pQCT parameters of the distal radius correlate with the bending strength of the radial diaphysis.

High resolution, peripheral quantitative computed tomography (HR-pQCT) scanners can now characterize an individual's trabecular architecture, cortical structure, and volumetric bone mineral density at a nominal resolution of 61μm. While predictions of failure load of the distal radius and tibial diaphysis in compression by finite element analysis (FEA) of HR-pQCT scans have been validated against mechanical tests of cadaveric bones in compression, namely for images with nominal resolutions of 82μm and 165μm, the HR-pQCT parameters that best predict bending strength of cortical bone remain unknown. Therefore, we scanned cadaveric forearms from 31 elderly donors (Female: 72.8±8.8years and Male: 72.1±6.3years), and then loaded the radial diaphysis to failure in three-point bending after denuding each bone (38 in total). The cortical parameters had stronger correlations with ultimate moment than the trabecular parameters such that cortical area and estimated failure load of the distal radius had the highest Spearman correlation coefficients (r=0.89 and r=0.81, respectively, p<0.0001). Despite being a known determinant of bone strength, cortical porosity of the distal radius did not correlate with ultimate moment (p=0.8537). In multivariate linear regressions with section modulus (SM) of the radial diaphysis as one of two predictors of bending strength, cortical area and cortical thickness were each significant contributors to the prediction of ultimate moment. Their contribution was one-half and one-third, respectively, of the contribution from SM. None of the HR-pQCT parameters were strongly correlated with post-yield displacement, an indicator of bone brittleness. In support of HR-pQCT imaging of the distal radius to identify individuals with osteoporosis, the present study found that parameters of the cortex and failure load predictions by linear FEA are strongly related to the bending strength of cortical bone.

The Pronator Quadratus Muscle – its Morphology and Functions

Knowledge of the architecture and nerve supply of the human pronator quadratus muscle (MPQ) appears to be rather scarce and is insufficient for a surgical approach of the muscle. In older French and more recent clinical studies it is stated that the MPQ consists of two or even three parts, each of them with an individual nerve supply and function. Former studies have described a superficial part that is active during pronation, and a deeper part which acts during supination. Furthermore, other authors described that the MPQ regulates the tension of the capsular complex at the distal radio‐ulnar joint.We studied the existence of subdivisions of the MPQ and their pattern of nerve supply from the anterior interosseous nerve in 15 cadaver forearms (8 M, 7 F, mean age 80 years). The dissection was carried out using a surgical microscope. In all 15 forearms the MPQ consisted of three parts: a superficial (pars superficialis; PQs), a deep proximal (pars profunda proximalis; PQpp) and a deep distal part (pars profunda distalis; PQpd).Three primary nerve branches were identified (ramus proximalis, ramus intermedius and ramus distalis) as they originated from the anterior interosseous nerve and at entry of the individual parts of the MPQ.We have not been able to conclude whether the ramus proximalis or the ramus intermedius supplies the superficial (PQs) or the deep proximal (PQpp) part of the MPQ. However, it could be established that the ramus distalis goes to the deep distal (PQpd) part of the MPQ. We could also confirm that only fibers of the deep distal part insert into the distal radio‐ulnar joint.On the basis of the existing division of the MPQ in three different parts, functional considerations can be made with regard to the complex functions of MPQ, i.e. pronation by the superficial part of the MPQ, fine‐tuning of motion of the radius during pronation and supination by the deep proximal part and capsular tension (stabilization) of the distal radio‐ulnar joint by the deep distal part of the MPQ.

The intra-muscular course and distribution of the anterior interosseous nerve within pronator quadratus: An anatomical study

BackgroundThe anterior interosseous nerve (AIN) is a terminal motor branch of the median nerve innervating the following three muscles from proximal to distal: Flexor pollicis longus (FPL), the radial half of flexor digitorum profundus (FDP), and the pronator quadratus (PQ). The aim of this study was to define the course of the AIN within the PQ to aid surgeons performing distal radial procedures. MethodsTen embalmed cadaveric forearms were dissected to identify the path of the AIN within PQ. An en-bloc excision of the PQ with its supplying AIN and vasculature was performed to identify a safe zone where PQ can be elevated without damaging AIN. A scoping literature search was performed to identify other studies reporting the path of AIN through PQ. ResultsThe mean distance from the radial border of the radius perpendicular to the point at which the AIN enters the PQ was 22.3 mm (range 21–24 mm). The mean distance from the distal wrist crease to the AIN entering PQ was 74.3 mm (range 59–84 mm). The mean number of nerve branches to PQ was 5.2 (range 3–8). In all specimens, the AIN was found to lie on the radial side of the anterior interosseous artery (AIA). ConclusionsThe AIN courses on the deep surface of the PQ in a longitudinal proximal to distal direction. A ‘safe zone’ was identified within 20 mm of the radial border of the distal radius, which may be utilised by surgeons in a muscle-splitting approach to the distal radius.

Cadaveric and Ultrasound Validation of Percutaneous Electrolysis Approaches at the Arcade of Frohse: A Potential Treatment for Radial Tunnel Syndrome.

Entrapment of the radial nerve at the arcade of Frohse could contribute to symptoms in patients with lateral epicondylalgia or radial tunnel syndrome. Our aim was to determine the validity of applying percutaneous electrolysis, targeting the supinator muscle at the Frohse’s arcade with ultrasound imaging and in a Thiel-embalmed cadaver model (not ultrasound-guiding). Percutaneous electrolysis targeting the supinator muscle was conducted in five healthy volunteers (ultrasound study) and three Thiel-embalmed cadaver forearms. Two approaches, one with the forearm supinated and other with the forearm pronated were conducted. The needle was inserted until the tip reached the interphase of both bellies of the supinator muscle. Accurate needle penetration of the supinator muscle was observed in 100% in both US-imaging and cadaveric studies. No neurovascular bundle of the radial-nerve deep branch was pierced in any insertion. The distance from the tip of the needle to the neurovascular bundle was 15.3 ± 0.6 mm with the forearm supinated, and 11.2 ± 0.6 mm with the forearm pronated. The results of the current study support that percutaneous electrolysis can properly target the supinator muscle with either the forearm in supination or in pronation. In fact, penetration of the neurovascular bundle was not observed in any approach when percutaneous needling electrolysis was performed by an experienced clinician.

Antecubital Fossa Perforator Flaps for Soft-Tissue Defect Repair of the Anterior Elbow: Anatomical Study and Clinical Application.

The antecubital fossa is a main perforator cluster region located beside the anterior elbow defect, rendering it crucial to harvest the perforator pedicled flaps for the anterior elbow defects. A total of 30 preserved cadaveric forearms were dissected in order to describe the perforator anatomy in the antecubital fossa. For each perforator, the number, the site of origin, the diameter at its origin, and the trajectory were recorded. In addition, all the patients treated for anterior elbow defects using inferior cubital artery (ICA) perforator pedicled flaps between June 2013 and June 2018 were reviewed in this retrospective study. A total of 85 perforators were dissected in the antecubital fossa area from the 30 specimens. Among these, 65 perforators originated from the radial artery, 6 from the recurrent radial artery, 13 from the brachial artery, and 1 from the ulnar artery. Each forearm specimen had a constant and large ICA perforator. All perforators originated from source vessels 2-5cm distal from the interepicondylar line and could be harvested as perforator pedicled flap for anterior elbow reconstruction. In the clinical study, 11 patients with anterior elbow defects were treated with ICA perforator pedicled flaps with satisfactory functional and aesthetic outcomes. The antecubital fossa has a constant and dominant ICA perforator and many other perforators. The pedicled antecubital fossa perforator flaps could be harvested flexibly with a reliable blood supply for anterior elbow reconstruction.

Cortical bone thickness of the distal radius predicts the local bone mineral density.

AimsThe distal radius is a major site of osteoporotic bone loss resulting in a high risk of fragility fracture. This study evaluated the capability of a cortical index (CI) at the distal radius to predict the local bone mineral density (BMD).MethodsA total of 54 human cadaver forearms (ten singles, 22 pairs) (19 to 90 years) were systematically assessed by clinical radiograph (XR), dual-energy X-ray absorptiometry (DXA), CT, as well as high-resolution peripheral quantitative CT (HR-pQCT). Cortical bone thickness (CBT) of the distal radius was measured on XR and CT scans, and two cortical indices mean average (CBTavg) and gauge (CBTg) were determined. These cortical indices were compared to the BMD of the distal radius determined by DXA (areal BMD (aBMD)) and HR-pQCT (volumetric BMD (vBMD)). Pearson correlation coefficient (r) and intraclass correlation coefficient (ICC) were used to compare the results and degree of reliability.ResultsThe CBT could accurately be determined on XRs and highly correlated to those determined on CT scans (r = 0.87 to 0.93). The CBTavg index of the XRs significantly correlated with the BMD measured by DXA (r = 0.78) and HR-pQCT (r = 0.63), as did the CBTg index with the DXA (r = 0.55) and HR-pQCT (r = 0.64) (all p < 0.001). A high correlation of the BMD and CBT was observed between paired specimens (r = 0.79 to 0.96). The intra- and inter-rater reliability was excellent (ICC 0.79 to 0.92).ConclusionThe cortical index (CBTavg) at the distal radius shows a close correlation to the local BMD. It thus can serve as an initial screening tool to estimate the local bone quality if quantitative BMD measurements are unavailable, and enhance decision-making in acute settings on fracture management or further osteoporosis screening.Cite this article: Bone Joint Res 2021;10(12):820–829.

Comparison of a ceiling-mounted 3D flat panel detector vs. conventional intraoperative 2D fluoroscopy in plate osteosynthesis of distal radius fractures with volar locking plate systems

ObjectivesTo compare intraoperative 3D fluoroscopy with a ceiling-mounted flat panel detector in plate osteosynthesis of distal radius fractures (AO/OTA 2R3C1.2) with volar locking plate systems to conventional 2D fluoroscopy for detection of insufficient fracture reduction, plate misplacement and protruding screws.MethodsUsing a common volar approach on 12 cadaver forearms, total intraarticular distal radius fractures were induced, manually reduced and internally fixated with a 2.4 distal radius locking compression plate. 2D (anterior-posterior and lateral) and 3D (rotational) fluoroscopic images were taken as well as computed tomographies. Fluoroscopic images, Cone Beam CT (CBCT), 360° rotating sequences (so called “Movies”) and CT scans were co-evaluated by a specialist orthopedic surgeon and a specialist radiologist regarding quality of fracture reduction, position of plate, position of the three distal locking screws and position of the three diaphyseal screws. In reference to gold standard CT, sensitivity and specifity were analyzed.Results“Movie” showed highest sensitivity for detection of insufficient fracture reduction (88%). Sensitivity for detection of incorrect position of plate was 100% for CBCT and 90% for “Movie.” For intraarticular position of screws, 2D fluoroscopy and CBCT showed highest sensitivity and specifity (100 and 91%, respectively). Regarding detection of only marginal intraarticular position of screws, sensitivity and specifity of 2D fluoroscopy reached 100% (CBCT: 100 and 83%). “Movie” showed highest sensitivity for detection of overlapping position of screws (100%). When it comes to specifity, CBCT achieved 100%. Regarding detection of only marginal overlapping position of screws, 2D fluoroscopy and “Movie” showed highest sensitivity (100%). CBCT achieved highest specifity (100%).ConclusionAs for assessment of quality of fracture reduction and detection of incorrect position of plate as well as overlapping position of the three diaphyseal screws CBCT and “Movie” are comparable to CT – especially when combined. Particularly sensitivity is high compared to standard 2D fluoroscopy.

A quantitative measurement of trapeziometacarpal joint pressure using a cadaveric model of lateral pinch.

Trapeziectomy is performed for trapeziometacarpal (TMC) arthritis but decreased lateral pinch strength is a major source of discomfort after the surgery. The magnitude of the decrease is unclear, however, and how the pressure changes in the TMC joint is unknown. To investigate this relationship, we designed a cadaveric study to measure TMC joint pressure using a lateral pinch model, and quantitatively evaluated the effect of trapeziectomy on the pressure measurements. For 10 cadaveric forearms, physiologic forces were applied across the thumb TMC joint by loading five tendons, thereby simulating lateral pinch. Using pressure sensors, we measured the lateral pinch pressure and TMC joint pressure, which averaged 10.1 (range, 4.2-16.2) kg/cm2 and 2.0 (range, 0.8-4.4) kg/cm2 , respectively. A significant correlation between the measurements was found, with an average ratio of 19% (range, 10%-27%). After trapeziectomy and interposition of the tendon ball using flexor carpi radialis, the pressure measurements were repeated under the same conditions. Significant changes were found, which averaged 5.1 (range, 1.7-10.7) kg/cm2 for lateral pinch pressure and 15.0 (range, 5.6-25.6) kg/cm2 for TMC joint pressure. In conclusion, TMC joint pressure could be measured as the ratio relative to lateral pinch pressure using a cadaveric model. After trapeziectomy, the lateral pinch strength decreased, whereas the TMC joint pressure increased.

Carpal Tunnel Surgery Using a Wireless Endoscopic Visualization Instrument: A Cadaveric Study.

Background: Endoscopic carpal tunnel release is a common treatment for moderate to severe carpal tunnel syndrome. Recently there have been various new techniques which offer improved accuracy and decreased recovery time. In this study, orthopedic surgeons and biomedical engineers from the Faculty of Medicine and Faculty of Engineering, Prince of Songkla University, designed a wireless endoscopic carpal tunnel release with a single portal technique and tested the efficacy and safety of the new technique in a cadaveric study. Methods: Ten fresh cadaveric forearms were used in the study. The surgical technique began with a surgical incision 15-20 mm above the wrist crease on the line between the middle finger and ring finger. The palmaris longus aponeurosis was retracted by Senn retractors. A visual enhancer was inserted to improve the internal visual field in order to see the flexor retinaculum clearly. The flexor retinaculum was cut distally to create an entry and the flexor retinaculum was cut by the scalpel. The flexor retinaculum length was observed until the release was completed. The median nerve was observed. Results: Each flexor retinaculum was cut completely. All of the median nerves were carefully observed during the operation and none were injured. This technique showed the effectiveness and safety of minimally invasive carpal tunnel surgery. Conclusions: The study found that the new device using this technique is effective for carpal tunnel syndrome (CTS) surgery in terms of minimally invasive endoscopic carpal tunnel surgery.

Biomechanical Analysis of Abductor Pollicis Longus Lasso Suspensionplasty for Trapeziectomy

Multiple methods of ligament reconstruction and tendon interposition (LRTI) or suspension have been described to prevent first metacarpal subsidence following trapeziectomy. An abductor pollicis longus (APL) lasso is a newly described technique of suspensionplasty, which aims to obviate concerns regarding previously described methods. The purpose of this study was to compare subsidence between the APL lasso and 2 other common methods, APL sling and flexor carpi radialis LRTI, after trapeziectomy in cadaveric forearms. Ten cadaveric forearms were prepared on a custom-made plinth to recreate pinch grip upon the loading of previously identified muscles. A sequence of procedures was performed, with radiographs taken after each to assess the subsidence. The APL lasso was superior to simple trapeziectomy and flexor carpi radialis LRTI in preventing subsidence. The APL lasso was superior to simple trapeziectomy and flexor carpi radialis LRTI in preventing subsidence, and it may be a viable alternative when considering suspension methods after trapeziectomy. The APL lasso may be considered when trying to prevent subsidence after trapeziectomy.

Is the Dorsal Fiber-Splitting Approach to the Wrist Safe? A Kinematic Analysis and Introduction of the “Window” Approach

To compare the kinematic effects of the dorsal fiber-splitting approach for scapholunate ligament repair to a dorsal "window" approach that spares all ligaments. We randomized 24 fresh-frozen paired cadaveric forearms to either the dorsal fiber-splitting capsulotomy approach (FSC) or the dorsal window approach (window) following scapholunate interosseous ligament(SLIL) division. Loaded fluoroscopic radiographs were obtained after each of the 4 testing conditions following cyclic loading (200 cycles; 71 N): (1) intact SLIL, (2) SLIL-division, (3) surgical approach, and (4) closure. FSC specimens were randomly allocated to 2 subgroups for closure with either a suture anchor (n= 6) or a simple running suture closure (n= 6). Radiographic parameter measurements included the scapholunate gap, radiolunate angle, scapholunate angle, and dorsal scaphoid translation. Following the FSC, there were significant alterations in all radiographic parameters when compared with the intact and SLIL-division conditions. The window approach did not result in significant changes in any radiographic parameter. When compared to the window approach, all radiographic parameters of the FSC approach were significantly altered. Following closure with suture anchors in the FSC group, radiographic parameters improved, whereas with standard closure they failed to do so. Despite anchor closure, dorsal scaphoid translation, radiolunate angle, and scapholunate angle all remained elevated compared with scapholunate-divided wrists. The FSC produced significant changes in carpal posture under load, including scapholunate diastasis, dorsal intercalated segment instability, and dorsal scaphoid translation in SLIL-deficient wrists. The window approach preserved the critical dorsal ligament stabilizers and did not produce changes in carpal posture. The FSC may create iatrogenic changes in carpal posture that cannot be fully corrected with standard or anchor closure. The window approach does not alter carpal posture and should be considered when performing surgical procedures on the scaphoid or lunate.