Interlocking intramedullary nailing of humeral fractures Progress
Author: Ji Quan Huang Gong-Yi Wang Qiang Zhang
【Key Words】 Fracture
Conservative therapy in the treatment of humeral fractures is still occupies an
important position, the majority of humeral fractures with non-surgical methods have
a good effect [1,2]. There is a certain indication of surgery, external fixation, dynamic compression plate (DCP), intramedullary nail fixation methods such as surgery have
been a classic style, interlocking intramedullary nail (intramedullary interlocking nail, IMN) generally applies to segment fractures, pathologic fractures and fractures associated with osteoporosis , suitable for surgical neck of humerus below the 2 cm
to 3 cm above the olecranon fossa within the fracture, pathological fracture or to be broken (impending fracture) is the most IMN good indication . Reported in the
(hereinafter referred to as RT nail), AO unreamed humeral company's interlocking nail (unreamed humeral nail, UHN nails), Seidel humeral locking nail and the medullary intramedullary nail (humeral locked nail, HLN).
1 IMN Biomechanics
Interlocking intramedullary nailing with closed nailing, bio-mechanics better
stability is conducive to early postoperative functional exercise. Interlocking intramedullary nail and dynamic compression plate fixation of the humerus, the physiological load of the bio-mechanical performance of similar, but the strength of interlocking intramedullary nails slightly more conducive to early upper limb functional training . In in vitro experiments, Seidel nail distal anti-rotation feature
somewhat less . Humerus fractures associated with osteoporosis in bio-mechanical
testing of its multiple breaks in the bone itself, but a normal bone mineral density in
humeral fractures are mostly from the screw itself began breaking .
Antegrade nailing and retrograde nailing in the treatment of unstable humeral fracture biomechanics are different. In the distal humerus fractures, retrograde nailing, and lateral direction before and after the anti-bending strength and anti-
rotation strength than that antegrade nailing is high; in proximal humerus fractures,
antegrade nailing is higher than the intensity of retrograde nail; in the the middle of fractures, both the intensity of approximation . Fracture short segment from the long segment into the nail to the cortex and intramedullary nail can be more fit,
enhance stability, better than in the opposite direction into the screw.
Different types of bio-mechanical strength of intramedullary nails may have some
difference. RT nail on each side of a nail, remote with a self-tapping screw-type locking,
locks are power sexual intercourse; UHN nails at both ends of each two locking nail. Blum et al  that the anti-RT nail bending and anti-rotation higher than before. Seidel
nail distal locking nail through the expansion of the self-locking, with the RT nail
compared to the biomechanical differences between the two is not, but the RT nail strength of the anti-rotation slightly. HLN compared with RT after fixation nail and Seidel nail biomechanics must be high .
2 IMN clinical application of
Although the treatment of humeral shaft fractures with IMN has for some time, in fact there are still a lot of controversy. Kropfl et al  followed by antegrade nailing of the 97 patients an average of 24.
2 months, the average healing time of fracture was 12.3 months, five cases of non-
union, 19 patients with limited shoulder range of activities, six cases of shoulder pain in a long-term, B super-display rotator cuff injury, 5 cases of patients with residual tail is
too long nails cause shoulder impingement syndrome, there are nine cases of preoperative radial nerve dysfunction, 8 patients on their own after about 4 months of rehabilitation, elbow function were in good condition. Authors believe that patients
should pay attention to nails embedded shoulder-length sleeves at the end of the repair,
postoperative limb may be an early functional exercise.
Due to various complications such as shoulder pain, delayed healing, nonunion,
iatrogenic fracture and reduction difficulties, there are authors  that the IMN in the treatment of humeral shaft fractures there is no great advantage, DCP is still the treatment of unstable humeral fractures One of the preferred methods; domestic applications found satisfactory effect . Cox et al  retrospective analysis of 37
cases of screw fixation of the humerus with the RT fracture, infection and 1 case of intraoperative fracture is not healing and delayed healing in patients with each of 4
cases, 1 case out because of shoulder impingement nails, three cases of limited because of shoulder joint function in patients with manipulation under anesthesia lysis OK, there are 6 cases of shoulder Constant score is low, and 2 cases of residual pain.
Authors found that humeral fractures in elderly patients with non-union rate and a
higher rate of delayed healing, but also the efficacy of a conservative approach compared to intramedullary nails have an advantage, antegrade nailing right shoulder joint function relatively large, to a certain extent partially offset its advantages, so interlocking intramedullary nails require attention to the indication of certainty.
Retrograde and antegrade IMN excellent efficacy of As everyone is inconclusive.
Ajmal et al  In a group of 33 cases of humeral shaft fractures in all patients with antegrade nailing in 18 cases (56%) patients with postoperative pain in the shoulder joint or a fracture, 41% of patients had poor shoulder function Only 51% of patients
satisfactory surgical results. Author believes that this method of non-healing rate was
higher postoperative shoulder function of the affected their efficacy inaccurate. Blum et al , multi-center prospective study of retrograde and antegrade nail (UHN system,
57 cases of retrograde nailing, 27 patients with antegrade nail) differences. Intraoperative complication rate was similar to group 3 cases of retrograde nail entry point of crack fracture and 1 case of humeral shaft fractures, only the retrograde group
of 5 patients required reoperation because they do not heal, but the authors think that more and operating technology-related ; fracture healing after the feature is not
significant differences. Retrograde than antegrade nailing nail surgical techniques
require a higher entrance point must be carefully prepared before being to avoid complications such as fractures. Crates, etc.  a group of concurrent humeral fractures in multiple trauma patients, 90% of patients with shoulder functional recovery, 96% of patients with good function of the elbow. Authors believe that antegrade nailing of the credibility of the efficacy of multiple trauma patients.
3 IMN treatment of humeral fractures in some of the problems
3.1 The anatomical characteristics of the humerus
Humerus unique anatomical structure, blood circulation, stress type and direction as well as the neighboring joints are related to differ materially from the femur and tibia. IMN in the efficacy of lower limb fractures is very good, but these experiences
and principles can not be applied directly humerus. In 80% of the length of the proximal humerus within the framework of the medullary cavity of tubular, and its distal 20% of the change bian, and a comma-shaped lateral bias extends to the top of
the lateral condyle, and the humerus itself has a slight forward curvature of the often tends to highlight the nail back. Humeral medullary cavity of the characteristics that make it difficult to fit closely with the intramedullary nail and accordingly it was
suggested that using only static-type locking nail. Humerus is not a typical weight-
bearing bone, so humeral fractures with intramedullary nail without reaming o'clock, but the meticulous fixation of the intramedullary nail may lead to unstable Ershi
nonunion. Comminuted fracture with intramedullary nailing there can not be separated so as to avoid displacement of delayed healing.
3.2 into the nails and nail the direction of
Intramedullary nail can be inserted antegrade or retrograde medullary cavity, there
are authors believe that the short segment from the fracture of a long segment to insert nails better, this would reduce the instability of the initial fixed-time increase in fixation
strength . Antegrade nail into the nail is generally close to the inside of large nodules, pay attention to the end of embedded nails. When the proximal nail the top of the lock from the outside in, without the bottom when placed in the humeral head more easily
lead to subacromial impingement. Remote locking nail is preferred before or after the anterior direction bit in order to avoid nerve injury. Antegrade nailing front-end from
the olecranon fossa is about 1.5 ~ 2 cm, nail tail generally buried about 5 mm under the
humeral head . Retrograde nail tip can only be inserted just inside the humeral head can not be too deep, you can reduce the rotator cuff and subacromial tissue damage, but there may be some impact on the elbow, so the way into surviving in the different
views. Retrograde hits the nail entrance point when sufficient length in order to avoid fracture, which is a nail diameter and eccentricity of the distal humerus. The eccentricity of distal humerus