Matthias Vanhees

Accuracy of placement of the glenoid component in reversed shoulder arthroplasty with and without navigation

HYPOTHESIS Navigation can improve accuracy of placement of the glenoid component in reversed shoulder arthroplasty. MATERIAL AND METHODS A glenoid component of a reversed shoulder prosthesis was implanted in 14 paired scapulohumeral cadaver specimens. Seven procedures with standard instrumentation were compared with 7 procedures using navigation. The intraoperative goal was to place the component centrally in the glenoid in the axial plane and 10° inferiorly tilted in the frontal plane. Glenoid component version and tilt and screw placement were studied using CT scan and macroscopic dissection. RESULTS The mean version of the glenoid component in the standard instrumentation group was 8.7° of anteversion, compared with 3.1° of anteversion in the navigated group. The mean tilt of the glenoid component was 0.9° in the standard group and 5.4° of inferior tilt in the navigated group. Using navigation, the range of error for version was 8° (SD 3.3°) compared to 12° (SD 4.1°) in controls. For tilt, the range of error was 8° (SD 3.6°) in navigated specimens and 16° (SD 6.0°) for controls. In the control group, there were no perforations of the central peg, but 1 inferior screw and 4 superior screws were malpositioned. In the navigation group, no central peg perforated, all inferior screws were correctly positioned, and 2 superior screws were malpositioned. CONCLUSION Computer navigation was more accurate and more precise than standard instrumentation in its placement of the glenoid component in reversed shoulder arthroplasty.

The Effect of Displacement on the Mechanical Properties of Human Cadaver Subsynovial Connective Tissue

The subsynovial connective tissue (SSCT) in the carpal tunnel may participate in the origin of carpal tunnel syndrome (CTS), yet material properties of the SSCT have not been well‐characterized. We investigated the response of the SSCT to repeated ramp stretch tests. Eight human cadaver wrists were used. The physiological excursion of the flexor digitorum superficialis of the third digit (FDS 3) was measured, starting from a neutral position to maximal flexion of the metacarpophalangeal and proximal interphalangeal joints. The FDS 3 tendon was pulled to 40%, 60%, 90%, and 120% of the physiological excursion. Two “ramp stretch” cycles were performed at every excursion level, except for 120% of excursion, where three cycles were performed. The ratio of energy absorbed between the second (E2) and first (E1) ramp stretch was 0.94 (SD = 0.07) for 60%, 0.84 (SD = 0.11) for 90%, and 0.68 (SD = 0.11) for 120% of the physiological excursion. A significant decrease occurred in energy absorbed after the first ramp stretch cycle at 90% and 120% of the physiological excursion, which was not seen at 60%. Our data are consistent with a stepwise damage occurring in the SSCT. Furthermore, the damage seems to initiate within the physiological range of tendon excursion. This finding may be important in understanding the pathophysiology of conditions that are associated with SSCT pathology, such as carpal tunnel syndrome.

The effect of low- and high-velocity tendon excursion on the mechanical properties of human cadaver subsynovial connective tissue

Fibrosis of the subsynovial connective tissue (SSCT) in the carpal tunnel is the most common histological finding in carpal tunnel syndrome (CTS). Fibrosis may result from damaged SSCT. Previous studies found that with low‐velocity (2 mm/s), tendon excursions can irreversibly damage the SSCT. We investigated the effect of tendon excursion velocity in the generation of SSCT damage. Nine human cadaver wrists were used. Three repeated cycles of ramp‐stretch testing were performed simulating 40%, 60%, 90%, and 120% of the middle finger flexor tendon superficialis physiological excursion with an excursion velocity of 60 mm/s. Energy and force were calculated and normalized by values obtained in the first cycle for each excursion level. Data were compared with low‐velocity excursion data. For high‐velocity excursions, a significant drop in the excursion energy ratio was first observed at an excursion level of 60% physiological excursion (p < 0.024) and that for low‐velocity excursions was first observed at 90% physiological excursion (p < 0.038). Furthermore, the energy ratio was lower at 60% for high velocities (p ≤ 0.039). Increasing velocity lowers the SSCT damage threshold. This finding may be relevant for understanding the pathogenesis of SSCT fibrosis, such as that accompanying CTS, and a relationship with occupational factors.

The Response of the Rabbit Subsynovial Connective Tissue to a Stress-Relaxation Test

The subsynovial connective tissue (SSCT) in the carpal tunnel may play a role in the etiology of carpal tunnel syndrome (CTS), yet the material properties of the SSCT remain unclear. Thus, we investigated the mechanical response of the SSCT in a rabbit model. Twenty‐four rabbit cadaver paws were used for mechanical testing; two paws were used for scanning electron microscopy (SEM) imaging. After testing normal tendon excursion, the divided third digit flexor digitorum superficialis (FDS) tendon was pulled to displacements of 2, 3.5, 5, or 8 mm, maintained at that position until force decay, and then the process was repeated. Normal excursion of the FDS averaged 4.8 mm. The ratio of the second peak force to the first peak force in the 2 mm group was 0.98 (SD = 0.16), which was significantly higher than the other groups (3.5 mm: 0.74, 5 mm, 0.63, and 8 mm: 0.59; p < 0.05). SEM showed ruptured fibrils in the displaced specimen. The declining force ratio with displacements >2 mm suggests damage to the SSCT within the physiological tendon excursion. These data may be useful in understanding SSCT mechanics in CTS, which is associated with SSCT fibrosis.

The effect of suture preloading on the force to failure and gap formation after flexor tendon repair.

PURPOSE Gap formation is a common and severe complication after flexor tendon repair that can affect the outcome and prolong tendon healing. The purpose of this study was to investigate the effect that a pretensional force applied to the suture during tendon repair has on the repair strength and force that causes gap formation. METHODS We used a total of 48 flexor digitorum profundus tendons from 12 human cadaver hands. We employed a core tendon suture, using the modified Pennington technique, and a running suture for flexor tendon repair. Before tying the knots of the core suture, we preloaded the sutures in each tendon end 0, 5, 10, or 15 N for 10 seconds to compare the effect of loading magnitude on repaired tendon peak force to failure and force causing gap formation. RESULTS The force to form a gap of 2 mm in the 15-N preload group was significantly increased compared with the 0-N and 5-N preload groups. At the 3-mm gap formation, the force of all preload groups was significantly higher than the nonpreload group. The peak force with a preload of 10 N and 15 N was significantly higher than 0-N preload. CONCLUSIONS These findings suggest that pretensioning with 10 to 15 N at the suture-tendon interface before tying the knot has a beneficial effect on both the tendon gap formation and the peak force to failure. CLINICAL RELEVANCE When the surgeons perform tendon repair, pretensioning at the suture-tendon conjunction will increase the repair strength.

Snapping triceps syndrome: a review of the literature

Snapping triceps syndrome is a rare and therefore often unknown cause of medial elbow pain. It is a condition in which the distal portion of the triceps dislocates over the medial epicondyle during flexion and extension of the elbow. It can occur, with or without ulnar neuropathy symptoms. The available literature on this subject is scarce and consists mainly of case reports. This report reviews the current literature and will provide guidance in diagnosis and treatment of this uncommon condition.

What Does the Transverse Carpal Ligament Contribute to Carpal Stability

Background The transverse carpal ligament is well known for its involvement in carpal tunnel syndrome, and sectioning of this ligament remains the definite treatment for this pathology. Some authors believe that the transverse carpal ligament is an important stabilizer of the carpal arch, whereas others do not consider it to be significant. Several studies have been performed, both in vivo and in in vitro. Sectioning of the transverse carpal ligament does not seem to have any effect on the width of the carpal arch in the unloaded condition. However, patients will load the arch during their activities of daily living. Materials and Methods A cadaveric study was done with distraction of the carpal bones before and after sectioning the transverse carpal ligament. Results With the transverse carpal ligament intact, the carpal arch is mobile, with distraction leading up to 50% widening of the arch. Sectioning of the transverse carpal ligament resulted in a significant widening of the carpal arch by a further 30%. Conclusions Loading of the carpal arch after sectioning of the transeverse carapal ligament leads to a significant increase in intracarpal mobility. This will inevitably influence carpal kinematics in the patient and might be responsible for some complications after simple carpal tunnel releases, such as pillar pain, palmar tenderness, and loss of grip strength.

Percutaneous, Transtrapezial Fixation without Bone Graft Leads to Consolidation in Selected Cases of Delayed Union of the Scaphoid Waist

Purpose We evaluated clinical and radiographic outcome of percutaneous transtrapezial fixation of the scaphoid delayed union or nonunion using a headless bone screw without bone grafting. Methods Sixteen patients with delayed union or nonunion of the scaphoid were included in this retrospective study between 2006 and 2011. All patients had a delayed presentation of scaphoid fracture, and none of them was treated conservatively elsewhere. Patients with bone graft, sclerotic bone debridement, or displacement of the fragment at the nonunion site were excluded. A percutaneous transtrapezial fixation technique was used in all cases. Patients were reviewed until clinical and radiographic union was observed. At the final follow‐up, DASH (Disabilities of the Arm, Shoulder and Hand) and PRWHE (Patient‐Rated Wrist and Hand Evaluation) outcome scores were completed. Results Radiographic union was obtained in 15 out of 16 patients (94%) at an average follow‐up of 36 months (range: 12‐98 months). No complications from the percutaneous technique were noted. The average DASH score was 6 (range: 0‐39) and the average PRWHE score was 10 (range: 0‐56). No statistical significant difference in range of motion and grip strength was found between the operated side and the contralateral side. Conclusion Percutaneous transtrapezial screw fixation for delayed or nonunion of selected scaphoid fractures without bone grafting is promising. At a mean of 4 months, 94% union was obtained with good functional results when there was no sclerosis, minimal osteolysis, and no displacement at the scaphoid nonunion site. Type of Study Therapeutic study. Level of Evidence IV.

Transforming growth factor-β (TGF-β) expression is increased in the subsynovial connective tissue in a rabbit model of carpal tunnel syndrome.

Carpal tunnel syndrome (CTS) is an idiopathic disease that results from increased fibrosis of the subsynovial connective tissue (SSCT). A recent study found overexpression of both transforming growth factor-β (TGF-β) and connective tissue growth factor (CTGF) in the SSCT of CTS patients. This study investigated TGF-β and CTGF expression in a rabbit model of CTS, in which SSCT fibrosis is induced by a surgical injury. Levels of TGF-β1 and CTGF at 6, 12, 24 weeks after injury were determined by immunohistochemistry A significant increase in TGF-β1 and a concomitant significant increase in CTGF were found at 6 weeks, in addition to higher cell density compared to normal (all p<0.05), Interestingly, CTGF expression was reduced at 12 and 24 weeks, suggesting that an initial insult results in a time limited response. We conclude that this rabbit model mimics the fibrosis found in human CTS, and may be useful to study pathogenetic mechanisms of CTS in vivo.

Anthropometric Study of the Radiocapitellar Joint

PURPOSE There is scant knowledge about the relationship between the size of the radial head and the size of the capitellum. Also, no data exist comparing the size of the capitellum between the left and the right elbow. METHODS Eight pairs of elbows and 12 single elbows from fresh-frozen cadavers were obtained for this study. The vertical height and anterior width of the capitellum were measured with digital calipers. Four different measurements were performed at the radial head: longest outer diameter, shortest outer diameter, the long dish diameter, and short dish diameter. The Pearson intrarater intraclass correlation coefficients were obtained for all measurements. RESULTS For the paired elbows, the correlations ranged between 0.95 and 0.96 for the capitellar dimensions and 0.77 and 0.98 for the radial head dimensions. The correlations between the long outer diameter of the radial head with the vertical height and the anterior width of the capitellum were 0.8 and 0.9, respectively. CONCLUSIONS There is a high correlation between the long outer diameter of the radial head and the vertical height of the capitellum as well its anterior width. There is also a high correlation between the left and the right elbow. CLINICAL RELEVANCE These findings are relevant to radiocapitellar arthroplasty and may be useful for radiocapitellar prosthetic design as well as in the preoperative planning of cases in which the radial head and/or the capitellum is destroyed.