A2 and A4 flexor pulley biomechanical analysis: comparison among gender and digit

A Biomechanical Analysis of the H-Taping Method Used by Rock Climbers as Prophylactic or Stabilizing Fixation of Partial A2 Pulley Tears

PURPOSE

Rock climbing can lead to upper-extremity injuries, such as A2 pulley ruptures, leading to the bowstringing of the flexor tendons. Climbing finger positions are specific and can put undue stress on the pulley systems. This causes severe hand dysfunction and is a difficult problem to treat, and prevention is important. Using a cadaveric, experimental model, we evaluated the effectiveness of the H-taping method, commonly used by rock climbers, to prevent and treat A2 pulley tears.

METHODS

Using fourteen matched pairs of fresh-frozen cadaveric hands with forearms, four experiments were conducted with 56 paired comparisons evaluating the failure force, fingertip force, and mode of failure (112 total tests). Comparisons were as follows: index fingers- intact versus 50% distal A2 pulley tears without H-taping (control); ring fingers- intact versus H-taping as a prophylactic for A2 pulley tears; little fingers- 50% distal A2 pulley tears with H-tape versus without tape; and middle fingers- H-taping as a prophylactic versus H-taping as a stabilizing treatment of torn pulleys.

RESULTS

The mean index finger failure force was significantly higher in intact vs torn A2 pulleys (control). Failure force for intact H-taped fingers was significantly higher than torn H-taped fingers, but no other finger comparisons for failure force were significant. There were no significant findings in comparison of mean fingertip force values in any of the experiments.

CONCLUSIONS

We found that H-taping is not effective as prophylaxis against A2 pulley ruptures or as a stabilizing treatment method for partially ruptured pulleys.

CLINICAL RELEVANCE

While H-taping has not been recommended as prophylaxis for preventing A2 pulley ruptures, the climbing community has embraced this technique as a preventative measure. The present study provides biomechanical evidence against H-taping for this purpose. Furthermore, it does not appear to aid in increasing fingertip force after injury.

A4 Pulley Reconstruction Using the Superficialis Oblique Flap and the Transverse Double Loop Techniques: A Biomechanical Evaluation Using a Chicken Model

BACKGROUND

The pulley system plays an important role in flexion mechanism. Reconstruction after trauma can be challenging. Numerous techniques have been described with several drawbacks. Herein, we describe the superficialis flap oblique technique for A4 pulley reconstruction using an animal model.

METHODS

Forty-two fresh legs of 21 eight-week-old chickens were used to evaluate the maximum flexion angle (MFA) and force at maximum flexion (FMF) in intact and sectioned A4 pulley equivalents of the third digit after reconstruction with the transverse double loop (TDL) technique and the superficialis oblique flap (SOF) technique. Biomechanical measurements were obtained in an exclusively designed instrument. Descriptive statistics were reported, and mean differences between the reconstructive techniques were analyzed.

RESULTS

Intact and severed A4 pulley equivalent average MFA were 96.50° ± 1.70° and 115.60° ± 1.50°, respectively. Average FMF were 8.16 ± 0.23 psi with the intact pulley and 6.92 ± 0.20 psi with the sectioned pulley (P < 0.001). After reconstruction with TDL and SOF techniques, the legs reached an average MFA at the distal interphalangeal joint of 98.13° ± 1.20° and 96.90° ± 1.30°, respectively. Mean MFA difference was 1.23° (P = 0.03). Force at maximum flexion was 8.12 psi and 8.10 psi for the TDL and SOF techniques (P = 0.6), respectively.

CONCLUSIONS

The authors believe that SOF technique for A4 pulley reconstruction can be used as first option when available, taking into account its theoretical advantages and its proven biomechanical characteristics. Long-term functional results should be assessed to translate these results into the clinical setting.

Morphological features of the chiasma tendinum and its relation with surface landmarks and pulleys: a cadaveric study

Aim

Chiasma tendinum (Camper’s chiasm) is of great importance in the delicate movements and stability of the fingers and takes place poorly in the literature. This study aims to reveal the morphometric details of the chiasma tendinum in relation with pulleys and other relevant structures.

Materials and methods

Palm and 2nd to 5th fingers of 10 (6 male, 4 female) formalin fixed cadavers were used bilaterally. After determining the superficial reference points on the fingers, the skin and the tendon sheath were incised, and then measurements of chiasma tendinum and related tendons were performed. The measurements were analyzed with respect to fingers, genders, and sides. Finally, the types of chiasma tendinum were identified and then grouped as symmetrical, asymmetrical, and pseudo chiasm.

Results

Pulley and chiasma tendinum positions were correlated with finger length (p < 0.01). Pulley lengths were significantly less in females. Asymmetrical chiasma tendinum types were found in 45% of the fingers. In most comparisons, values for fifth finger were significantly different than that of other fingers and chiasma tendinum types differed according to fingers and gender. The case of no fiber exchange was observed only in the 5th finger in 15%.

Conclusion

Findings related to the prediction of location of the pulleys and chiasma tendinum according to the superficial signs, awareness of cases where one of the two arms of the flexor digitorum superficialis is extremely thin and no fiber exchanges that may be risk factors for spontaneous tendon rupture may help provide more accurate approaches in relevant clinical applications.

Finger Flexor Pulley Injuries in Rock Climbers

Finger flexor pulley system injuries are the most common overuse injury in rock climbers. These injuries occur rarely outside of rock climbing, owing to the sport's unique biomechanical demands on the finger. As rock climbing continues to grow and earn recognition as a mainstream sport, an understanding of how to diagnose and treat these injuries also has become important. Our purpose is to describe current concepts in anatomy, biomechanics, clinical evaluation, imaging, prevention, and treatment strategies relating to finger flexor pulley system injuries. Our literature search was performed on PubMed with MeSH terms and keywords as subject headings to meet the objectives of this review. The "crimp grip" used in rock climbing is the mechanism for these injuries. The A2, A3, and A4 pulleys are at the highest risk of injury, especially when loaded eccentrically. Physical examination may reveal clinical "bowstringing," defined as the volar displacement of the flexor tendons from the phalanges; however, imaging is required for characterization of the underlying injury. Ultrasound is highly sensitive and specific for diagnosis and is recommended as the initial imaging technique of choice. Magnetic resonance imaging is recommended as an additional imaging study if ultrasound is inconclusive. Properly warming up increases the amount of physiologic bowstringing and is thought to prevent injury from occurring. Pulley injuries may be classified as grade I through IV. Conservative treatment, including immobilization, the H-tape method, and the use of a protective pulley splint, is recommended for grade I to III injuries. Surgical repair is reserved for grade IV injuries that are not amenable to conservative treatment.

Flexor tendon grafts for pulley reconstruction - Morphological aspects

BACKGROUND

Pulleys are crucial to convert flexor tendon excursion into angular motion at the metacarpophalangeal and interphalangeal joints. Loss of pulley function can lead to significant impairment of hand function and may require surgical reconstruction. This reconstruction can be achieved using different flexor tendons grafts, such as the intrasynovial flexor digitorum superficialis (FDS) or the extrasynovial palmaris longus (PL). However, there is limited knowledge on the micromorphology of human pulleys and the suitability of flexor tendon grafts for their reconstruction remains elusive.

METHODS

In the present cadaver study A2 and A4 pulleys were compared with FDS and PL tendons by means of scanning electron microscopy (SEM), histology and immunohistochemistry. Surface morphology, core structure and vascularization of the specimens were analyzed.

RESULTS

SEM imaging of the gliding surfaces revealed morphological differences between tendons and pulleys. Moreover, the core structure of FDS samples was characterized by bundles of individual collagen fibrils whereas PL tendons exhibited a less hierarchical microstructure. In contrast, pulleys consisted of lamellar sheets of densely packed collagen fibrils. Finally, immunohistochemical analyses revealed that the flexor tendons and pulleys contain similar numbers of CD31⁺ microvessels, indicating a comparable tissue vascularization.

CONCLUSION

This study provides novel SEM and immunohistochemical insights into the micromorphology of human pulleys and flexor tendon grafts. Intrasynovial flexor tendons may be particularly suitable for pulley reconstruction and preserving the paratenon may be crucial for graft revascularization.

Digital Pulley Reconstruction Using Pulley Allografts: A Comparison With Traditional Tendon-Based Techniques

BACKGROUND

The safety and feasibility of sterile, acellular pulley allografts in reconstruction has been previously demonstrated. Comparisons with tendon-based techniques for pulley reconstruction have not been reported. We hypothesized that the use of allograft pulleys would result in reduced procedural time and equivalent clinical outcomes as compared with traditional tendon-based reconstructive techniques.

METHODS

All cases of pulley reconstruction using either allograft pulleys or tendon-based pulley reconstruction between November 2013 and November 2015 were reviewed. Patients who underwent concomitant procedures were excluded. Patient demographics, comorbidities, operative details (tourniquet and total operative times, number of pulleys repaired), postoperative complications (surgical site infection, reoperation, stiffness, and persistent pain), disability of the arm, shoulder and hand scores, and follow-up data were recorded. A P value of <0.05 was considered significant.

RESULTS

Fifteen pulleys in 10 patients were reconstructed: 5 tendon-based and 5 with allograft. Average length of follow-up was 12.5 ± 2.9 months. There was no difference in patient demographic factors or comorbidities between groups. The most common indication for surgery was trauma. Four of 5 patients in the allograft group had multiple pulleys reconstructed versus 1 in the tendon-based group. One patient in the tendon-based group required reoperation versus 0 in the allograft group. Total operative and tourniquet times were significantly reduced in the allograft group (46 ± 5.5 vs 89 ± 12.9 minutes and 34 ± 6.8 vs 63 ± 5.3 minutes; P = 0.015 and 0.014). Postoperative disability of the arm, shoulder and hand scores were lower in the allograft group (56.8 vs 3.6, P = 0.11). There was no significant difference in postoperative range of motion between groups.

CONCLUSION

Pulley reconstruction with allograft is an efficient, technically feasible, reconstructive technique that adheres to the principle of replacing like with like, while eliminating donor site morbidity. Overall operative and tourniquet times were significantly shorter using allograft pulleys for pulley reconstruction.

Acute A4 Pulley Reconstruction with a First Extensor Compartment Onlay Graft

Background:

The integrity of the flexor tendon pulley apparatus is crucial for unimpaired function of the digits. Although secondary reconstruction is an established procedure in multi-pulley injuries, acute reconstruction of isolated, closed pulley ruptures is a rare occurrence. There are 3 factors influencing the functional outcome of a reconstruction: gapping distance between tendon and bone (E-space), bulkiness of the reconstruction, and stability. As direct repair is rarely done, grafts are used to reinforce the pulley. An advantage of the first extensor retinaculum graft is the synovial coating providing the possibility to be used both as a direct graft with synovial coating or as an onlay graft after removal of the synovia when the native synovial layer is present.

Methods:

A graft from the first dorsal extensor compartment is used as an onlay graft to reinforce the sutured A4 pulley. This technique allows reconstruction of the original dimensions of the pulley system while stability is ensured by anchoring the onlay graft to the bony insertions of the pulley.

Results:

Anatomical reconstruction can be achieved with this method. The measured E-space remained 0 mm throughout the recovery, while the graft incorporated as a slim reinforcement of the pulley, displaying no bulkiness.

Conclusions:

The ideal reconstruction should provide synovial coating and sufficient strength with minimal bulk. Early reconstruction using an onlay graft offers these options. The native synovial lining is preserved and the graft is used to reinforce the pulley.

Recovery of rock climbing performance after surgical reconstruction of finger pulleys

This study evaluated recovery of sport performance and correction of bowstringing after surgical reconstruction of closed finger pulley rupture in high-level rock climbers. A total of 38 patients treated with an extensor retinaculum graft were assessed. The mean follow-up time was 85 months, and 30 patients returned to their previous climbing level. The mean total active motion score was 96% of the opposite side. All patients had an excellent Buck-Gramcko score. There was no significant difference in grip strength and tip pinch strength in the crimp position between the injured side and the opposite side. A total of 31 patients were examined with ultrasonography. In 18, flexor bowstringing effects had returned to near-normal values. There was an association between rock climbing level recovery and the flexor bowstringing correction (odds ratio, 6.9; 95% confidence interval, 1.1-42.8). If flexor bowstringing was corrected, patients were more likely to regain their preinjury sport performance. The ultrasonography measurement was a useful tool for predicting functional recovery.

LEVEL OF EVIDENCE

4.

Rock Climbing Injuries: Acute and Chronic Repetitive Trauma

Rock climbing has increased in popularity as a sport, and specific injuries related to its practice are becoming more common. Chronic repetitive injuries are more common than acute injuries, although acute injuries tend to be more severe. We review both acute and chronic upper and lower extremity injuries. Understanding the injury pattern in rock climbers is important for accurate diagnosis.

Flexor pulley system: anatomy, injury, and management

Flexor pulley injuries are most commonly seen in avid rock climbers; however, reports of pulley ruptures in nonclimbers are increasing. In addition to traumatic disruption, corticosteroid-induced pulley rupture has been reported as a complication of treating stenosing tenosynovitis. Over the last decade, there have been 2 new developments in the way hand surgeons think about the flexor pulley system. First, the thumb pulley system has been shown to have 4 component constituents, in contrast to the classic teaching of 3 pulleys. Second, in cases of zone II flexor tendon injury, the intentional partial A2 and/or A4 pulley excision or venting is emerging as a component for successful treatment. This is challenging the once-held dogma that preserving the integrity of the entire A2 and A4 pulleys is indispensable for normal digit function.