Comparison of different distal radius dorsal and volar fracture fixation plates: a biomechanical study

PURPOSE: To compare the biomechanical properties of 6 dorsal and volar fracture fixation plate designs in a cadaver model. METHOD: Six different plating techniques were used on surgically simulated, unstable, extra-articular distal radius fractures in fresh-frozen cadavers. Specimens were tested to failure in axial compression with the Materials Testing System machine, and were analyzed with a motion analysis system. The 6 different fixation systems studied included an AO stainless steel Pi plate (group 1), an AO titanium Pi plate (group 2), a Forte plate (group 3), a dorsally placed Symmetry plate (group 4), a volarly placed Symmetry plate (group 5), and a volarly placed SCS/V plate (group 6). RESULTS: All dorsal plates (groups 1, 2, 3, 4) failed in apex dorsal angulation and all volar plates (groups 5, 6) failed in apex volar angulation. No group developed an average angular deformity greater than 5 degrees with a load of 100 N, which compares with the physiologic loads expected with active wrist motion. Only the volarly placed SCS/V plated specimens (group 6) resisted deformation of 5 degrees or more at loads up to 250 N, which compares with the physiologic loads expected with active finger motion, and was significantly stronger and more rigid than the other 5 plate groups. CONCLUSIONS: The SCS/V plate fixation system is the most rigid of the systems tested and may offer adequate stability for the treatment of the distal radius fracture in which the anterior and/or posterior metaphyseal cortex is comminuted severely.     

掌侧与背侧钢板固定关节外桡骨远端背侧粉碎性骨折的生物力学研究

目的 探讨掌侧与背侧钢板固定桡骨远端背侧粉碎性骨折时的抗压缩、抗扭转差异性.方法 将12侧新鲜成人尸体桡骨标本制成桡骨远端背侧粉碎性骨折模型,随机分为2个大组,分别进行掌侧与背侧钢板螺钉固定;再将每个大组分为2个亚组,分别进行轴向压缩试验和水平扭转试验.检测指标:轴向压缩强度、轴向压缩刚度、水平扭转强度和水平扭转刚度.结果 在轴向压缩试验中,掌、背侧两组之间轴向压缩强度差异有统计学意义(P＜0.05),背侧组大于掌侧组;在生理压缩载荷下,掌、背侧两组刚度值差异有统计学意义(P＜0.05),背侧组高于掌侧组.在水平扭转试验中,两组水平扭转强度与扭转刚度差异都没有统计学意义,但数据显示,掌侧组都略强于背侧组.结论 在抗压缩方面,两组的压缩强度以及压缩刚度差异均有统计学意义,背侧组要优于掌侧组;而在抗旋转方面,两组的扭转强度与扭转刚度差异均无统计学意义,但掌侧组在数据上均稍大于背侧组.     

Anatomic relationships in distal radius bridge plating: a cadaveric study

Background

Two separate approaches have been described for radiocarpal spanning internal fixation for high-energy distal radius fractures with metaphyseal extension. To our knowledge, relevant anatomic relationships and structures at risk for iatrogenic injury have not been identified in the literature.

Methods

Twelve fresh frozen cadaver arms were randomized to fixation with a dorsal radiocarpal spanning plate using one of two techniques: (1) index finger metacarpal fixation (index group) or (2) middle finger metacarpal fixation (middle group). Cadaveric dissection and relevant anatomic relationships were assessed in relation to the plate.

Results

Superficial branches of the radial sensory nerve were in contact with the index group plate in all specimens, while no contact occurred in the middle group specimens. No extensor digitorum comminus (EDC) middle extensor tendons contacted the plate in the index group; an average of 10 cm of plate contact was seen in the middle group. The extensor pollicis longus (EPL) tendon contacted the plate in both the index and middle groups for an average distance of 12.4 and 25.5 mm, respectively. One complication [EPL and extensor indicis proprius (EIP) entrapment] was observed in the middle finger metacarpal group.

Conclusion

Mounting the dorsal bridge plate to the index finger metacarpal places the superficial branches of the radial sensory nerve at risk during dissection, while mounting the plate to the middle finger metacarpal leads to a greater degree of tendon-plate contact.     

Nailing versus plating for comminuted fractures of the distal femur: a comparative biomechanical in vitro study of three implants

Purpose

The purpose of our study was to determine the biomechanical properties of three different implants utilized for internal fixation of a supracondylar femur fracture. The retrograde supracondylar nail (SCN), the less invasive stabilization system plate (LISS) and the distal femoral nail (DFN) were tested and their biomechanical properties compared.

Methods

Twenty pairs of fresh-frozen human femura were used. Each femur was osteotomised to simulate a comminuted supracondylar fracture (AO/OTA 33.A3) and then randomized to fracture fixation with either SCN (n=9) or LISS (n=9). Each contralateral femur was stabilized with DFN as a control (n=18). Two femur pairs were spent on pretesting. All femura were subjected to axial (10–500 N) and torsional (0.1–14 Nm) loading.

Results

Eighteen matched femur pairs were analyzed. The post-loading median residual values were 49.78, 41.25 and 33.51% of the axial stiffness of the intact femur and 59.04, 62.37 and 46.72% of the torsional stiffness of the intact femur in the SCN, LISS and DFN groups. There were no significant differences between the three implants concerning axial and torsional stiffness.

Conclusions

All implants had sufficient biomechanical stability under physiological torsional and axial loading. All three implants have different mechanisms for distal locking. The SCN nail with the four-screw distal interlocking had the best combined axial and torsional stiffness whereas the LISS plate had the highest torsional stiffness.     

Dorsal plating for distal radius fractures

A dorsal approach to the distal radius for comminuted intra-articular fractures affords excellent exposure of the joint surface. Dorsal plating can reliably buttress the joint, leading to low rates of arthrosis, but at the expense of wrist stiffness and high rates of extensor tendon problems. New, smaller implants may prove capable of supporting the joint with lower rates of extensor irritation.     

Volar fixation for dorsally angulated extra-articular fractures of the distal radius: a biomechanical study

PURPOSE: To compare the biomechanical properties of 10 volar plate-fixation designs in 2 fracture models (dorsal wedge osteotomy, segmental resection osteotomy models). METHODS: Forty-eight radiuses were used in this study including 8 pairs. In 40 specimens a 15-mm dorsally based wedge osteotomy was performed and the volar cortex was fractured manually. They were arranged into 10 fixation groups with 5 different fixation designs (test 1). In the contralateral specimens of 8 paired radiuses a 10-mm segment of bone was excised (test 2). Four of the 10 fixation systems were chosen for these specimens. Cadaver hands and the proximal radiuses were potted in polymethylmethacrylate and tested with a servohydraulic materials testing machine with 300 N of axial compression load at 1 N/s initially and after each 1,000 cycles up to 5,000 cycles. After cyclic loading the specimens were loaded to failure in axial compression at 2 mm/min. The stiffness, failure peak load, and failure mode of each specimen were recorded. RESULTS: In test 1 in the wedge osteotomy specimens the T plate was the stiffest and the Synthes titanium plate was the least stiff; however, all specimens completed the 5,000 cycles of loading with no failures. There was no significant difference between the 10 fixation groups in failure peak load and only 7 of 40 failed at the distal portion of the hardware in the final load to failure testing. In test 2 the resection osteotomy specimens were less stiff and failed at a lower failure peak load compared with the wedge osteotomy specimens. Failure at the distal portion of the fixation system was seen in 7 of 8 specimens; nonlocking screws loosened and tines compressed the surrounding bone, resulting in tine-hole enlargement. CONCLUSIONS: All of the plate-fixation systems delivered sufficient stability to permit the simulated postoperative regimen of 1 week of immobilization followed by 5 weeks of early mobilization until expected union at 6 weeks after surgery. Based on these results a preferable volar fixation system would appear to benefit from the following: (1) sufficient plate strength to support the distal fragment from the volar side, (2) a locking system with sufficient strength to remain locked during the healing process, and (3) a distal design that does not affect the bone adversely. The anatomic reduction of the volar cortex in the wedge osteotomy specimens added stability to the construct.     

Minifragment plating for fractures of the distal radius

Twelve patients with fracture of the distal radius were treated by open reduction and internal fixation with titanium minifragment plates. There were 8 women and 3 men, with a mean age of 42 years. The mean follow-up was 18 months. According to the score of Gartland and Werley, 11 patients had an excellent result and one patient had a good result. All patients reported no pain in their activities of daily living and were satisfied with the result. All workers returned to work. One patient developed reflex sympathetic dystrophy which resolved with treatment. No patients needed plate removal because of irritation of the tendons. The results obtained with this technique appear promising, although more cases are needed to achieve a definitive conclusion.     

Dynamic biomechanical study of a new osteosynthesis system for distal radius fractures

The aim of this study was to evaluate the stability in compression of a new implant for fractures of the distal radius. Of all the displacements found with this fracture, shortening is the one most difficult to maintain by osteosynthesis. We tested the properties of a central-medullary steel nail 9 cm length, of diameter 5 mm, curvilinear, introduced at the radial styloid, combining proximal unicortical and distal bicortical locking. The biomechanical laboratory tests were carried out on 10 human radii taken from 5 male anatomical subjects of ages ranging from 48 to 88 years. A wedge-shaped defect in the metaphyseal zone was created to reproduce posterior shortening in these Pouteau-Colles' fractures. The same anatomical subject received the two types of osteosynthesis: an intramedullary nail and a styloid pinning. The force-displacement curves showed that intramedullary osteosynthesis with this interlocking nail is an assembly three times more resistant to compression than bi-styloid pinning. Stabilization of this fracture in porotic bone has to rely on distal screw purchase in the subchondral bone, which seems to us to be the only element able to resist compressive forces. This new implant should make it possible to restore and preserve the length of the radius whilst maintaining reduction in all three dimensions. Given its good biomechanical results, this nail constitutes a viable possibility for minimally invasive internal fixation of these fractures and warrants a clinical trial.     

Rehabilitation of distal radius fractures: a biomechanical guide

Fracture healing and surgical decision making are not always predictable. The suggested protocols are intended to be flexible rather than rigid to be responsive to patient progress and the fracture site stability. A methodologic approach to the rehabilitation following a distal radius fracture, based on a knowledge of the biology of fracture healing and biomechanics of fixation, may preempt some of the pitfalls associated with distal radius fracture healing.     

Stacked plating for metadiaphyseal fractures of the distal radius: a technique report

Combined injuries of the distal radius and shaft are rare, are usually caused by high energy, and pose a surgical dilemma. Surgical tactics and implants that are routinely used either for isolated fractures of the distal radius or for fractures of the radial shaft are often not applicable for this combined injury. We describe a technique of dual-stacked plating for these metadiaphyseal fractures and its use in two patients.     

Volar fixed-angle plating of the distal radius

The treatment of unstable distal radius fractures continues to improve as better methods of skeletal fixation and soft-tissue management are developed. Apart from closed reduction and percutaneous pinning of simpler fracture patterns, the three main methods of management are external fixation, dorsal plating, and volar fixed-angle plating. Specific advantages of volar fixed-angle plating include stable fixed-angle support that permits early active wrist rehabilitation, direct fracture reduction, and fewer soft-tissue and tendon problems. Volar fixed-angle plating also avoids the complications often associated with external fixation and dorsal plating. Biomechanical data indicate that, when loaded to failure, volar fixed-angle plates have significant strength advantages over dorsal plating. Volar fixed-angle plating is advantageous in elderly osteopenic patients and for high-energy comminuted fractures and malunions requiring osteotomy.     

Volar plating of dorsally comminuted fractures of the distal radius: a 6-year study

This article describes a 6-year study of use of volar plating in treating unstable dorsally comminuted distal radius fractures. Forty-six fractures treated with volar plating were reviewed. All cases were followed for at least 6 months; 35 were followed for more than 1 year. Fractures treated with adjunctive protruding pins were excluded. Bone graft was used in 4 cases. Anatomical results were rated excellent or good in 39 cases (85%). Subsidence occurred in 9 fractures, 4 of which malunited. Flexor pollicis longus tendon attrition occurred in 2 cases. Mean operative time was less than 1 hour (range, 30-90 minutes). Study results support continued use of volar plating in treating selected unstable dorsally displaced fractures of the distal radius. Prominent plates and sharp-edged screws may imperil deep flexor tendons and should be removed. More liberal use of bone graft and improvements in plate design should reduce complications.     

Low-profile dorsal plating for dorsally angulated distal radius fractures: an outcomes study

PURPOSE: Controversy exists surrounding the effectiveness and complications associated with dorsal plating for distal radius fractures. This study evaluated the functional outcome of dorsal plating for dorsally angulated distal radius fractures at a single institution. METHODS: Thirty patients formed the study cohort. All plates were low profile and stainless steel. Radiographic parameters, range of motion, and strength compared with the uninjured side were recorded. The functional outcome was evaluated by the Disabilities of the Arm, Shoulder, and Hand questionnaire and the Gartland and Werley scoring system. RESULTS: The median patient age at surgery was 59 years. The median follow-up period was 18 months. According to the AO classification system, there were 4 type A fractures, 5 type B fractures, and 21 type C fractures. The median preoperative dorsal angulation was 30 degrees, and the median postoperative angulation was -4 degrees volar. Sixteen patients with fractures had an intra-articular step-off or gap, which were all corrected to neutral by the procedure. Seven patients with the fractures showed positive ulnar variance, all corrected to neutral at time of follow-up evaluation. Compared with the contralateral side, the mean extension and flexion were 88% and 81%, respectively; pronation and supination were 89% and 87%, respectively; and grip strength and thumb pinch were 78% and 94%, respectively. The mean postoperative Disabilities of the Arm, Shoulder, and Hand questionnaire score was 15 points, and 28 patients had Gartland and Werley scores of good or excellent. No patients needed to have their plates removed, and no extensor tendon rupture was reported. One patient lost reduction, 1 patient needed a tenolysis of the extensor pollicis longus tendon, and 2 patients required the removal of a single metaphyseal screw. CONCLUSIONS: Results from this study show that patients can expect to have 80% of their range of motion and strength after dorsal plating for distal radius fractures. Moreover, 93% of the patients will have good to excellent functional outcomes. Complications from dorsal plating may be caused by the specific plate used, rather than by the technique itself, supporting a dorsal approach for dorsally angulated distal radius fractures.     

Palmar plating for dorsally displaced fractures of the distal radius

Extensor tendon rupture and irritation caused by implants or surgical intervention are serious complications in the treatment of fracture of the distal radius when a dorsal approach is used. To prevent complications, the dorsally displaced fracture of the distal radius was treated using a palmar approach. The subjects were 18 men and 15 women with a mean age of 54 years at the time of the injury (range, 23-75 years). All the patients had internal fixation with a plate and screws using the palmar approach. Union was achieved in all patients. Radiographic parameters, including the palmar tilt, radial inclination, radial length, and ulnar variance have been maintained since the operation. According to the rating scale of Gartland and Werley, there were 12 excellent, 20 good, and one fair result. There were no extensor tendon injuries that occurred during use of the palmar approach in this small series of patients. Palmar plating can be safe and effective for treatment of a dorsally displaced fracture of the distal radius.