Loss of reduction of the posterior pelvic ring after screw fixation in a child.
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Bone Screws↗
Biomedical subjects
D Pennig
Publications and source records attributed to D Pennig.
Antegrade femoral nailing: an anatomical determination of the correct entry point.
Operative problems in the application of femoral locking nails are frequently related to an unfavourable entry point at the greater trochanter. Especially in more distally located fractures the nail is forced to follow the cortex abutted medullary canal. A wrong defined entry point either in the medio-lateral or dorso-ventral direction inevitably leads to tension between nail and femur. Forceful insertion in this situation may cause disastrous iatrogenic comminution at the fracture side or additional fractures at the proximal femur. To avoid tension between nail and femur the best suited entry point must be defined according to the natural medullary cavity. In 16 human cadaver femora, the natural medullary cavity was opened and after cleaning filled with a radio-opaque substance (barium sulphate). Twelve radiographs where taken from each bone starting with the anterior-posterior view and then turning the bone axially in steps of 15 degrees. From these radiographs, the ideal entry point at the greater trochanter was calculated. In 88% of the specimen the ideal entry point for a straight nail was found constantly at the medial border of the greater trochanter overlaying the tendinous insertion of the piriformis muscle. The axis of the medullary cavity was in average 2.1cm anterior to the dorsal border of the greater trochanter. In a second step the ideal entry point for bend nails was calculated. According to this calculation a bend nail with a radius of 100 cm needs an entry point 0.7 mm anterior to the dorsal edge of the greater trochanter. Overlaying the hook like shape of the posterior part of the trochanter.
Bone Nails↗
[Presentation of a simple method of preoperative soft-tissue distraction in Dupuytren's contracture grade IV].
We describe a technique of continuous preoperative soft-tissue distraction in Dupuytren's contracture grade IV using an unilateral external fixator which is simple to apply. The operative technique and the result are demonstrated.
Dupuytren Contracture↗
[Narrowing of the third extensor tendon compartment in minimal displaced distal radius fractures with impending rupture of the EPL tendon].
Delayed ruptures of the extensor pollicis longus tendon (EPL) occur in about 0.7 percent following undisplaced distal radius fractures. Two possible mechanisms are mainly discussed in the literature: A mechanical irritation of the tendon caused by a sharp edge of the fractured bone and a direct microvascular compromise of the poorly vascularized tendon. In undisplaced fractures, however, a mechanical irritation seems less likely. In the cases here described we were able to demonstrate a fragment displacement in the area of Lister's tubercle suspected by the native X-ray and further evaluated by a CT scan. The use of CT scans even in minor displaced distal radius fractures involving Lister's tubercle may demonstrate a direct contact of the EPL tendon with a sharp edge of this fractured bone and make adequate surgery possible.
Bone Screws↗
[Distraction arthrolysis with humero-ulnar motion fixator].
Distraction arthroplasty in the treatment of elbow stiffness with an external fixator and subsequent fixator assisted mobilization is described. Joint distraction is employed to correct the shortened ligaments and capsule and permits the separation of articular surfaces. After intraoperative joint distraction, a phase of relaxation followed by fixator assisted mobilization is carried out. The use of the motion fixator is described and additional measures discussed. This technique is particularly valuable in joint subluxation or persistent joint dislocation and allows for reduction after distraction in order to secure joint congruity. Postoperative management is a key factor for the success of the management protocol.
Adult↗
Extraarticular external fixation in distal radius fractures pinplacement in osteoporotic bone.
External fixation is a well accepted treatment option in distal radial fractures. The fixator can be used in two different ways: joint bridging or extraarticular. The extraarticular technique presumes that the fracture does not involve the radio-carpal joint and that the distal fragment is broad enough to accommodate two fixator screws. Taking into account that the majority of distal radius fractures occur in elderly female patients the question arises whether osteoporotic bone is an obstacle to extraarticular external fixation. Bone slices of 2mm thickness were cut out of six human cadaver radii with a mean age of 76 years (from 65 to 94 years) in the saggital plane. A radiograph of each slice was digitized and the distribution of gray values measured. It was found that the radiographic density was highest at the palmar side of the distal radius in a triangular area built by the palmar lip of the radius. In this region, even in severe osteoporotic bone, strong trabeculae are visible running parallel to longitudinal axis of the radius. Fixator screws inserted into the distal radial fragment especially in an osteoporotic situation should be securely anchored in the palmar lip of the distal radius.
Adult↗
[Gradual wound closure by dermatotraction of the hand].
There are various treatments for skin defects. In our study we used a skin-stretching device for the closure of six skin defects of the hand and wrist (Sure-Closure System, Life Medical Sciences, Inc., Princeton, N.J.). Three defects were closed completely. The size of the other three wounds was reduced by 50 to 70%. We saw no complications. The skin-stretching device helped to close skin defects with local sensate tissue.
Adolescent↗
Fine thread versus coarse thread. A comparison of the maximum holding power.
For osteosynthesis in the epiphyseal region of long bones, specialized screw types are available to achieve a better purchase in cancellous bone. Typically, the cancellous bone screw has a large outer thread diameter with a relatively small core diameter and a great pitch. Due to its dimensions, this screw type is not suited for the cancellous bone areas in hand and foot surgery, respectively. Fine machine screws are better adapted to the bone dimensions in this part of the skeleton. To compare the holding power of fine machine screws with the holding power of other screw types available in the market, a biomechanical study was undertaken. Different screw types were compared: 4 mm cancellous screw, 3.5 and 2.7 mm cortical screws and three different diameters of a fine machine screw (2.2, 1.6 and 1.2 mm). Both cortical screws were tested in pretapped and self-tapping version. Polyurethane foam and bovine cancellous bone were tested. The screws were applied according to the manufacturer's instructions and an axial extraction force was applied. The 4 mm cancellous bone screws were superior to all the other screws in both test materials (P<0.05). The 3.5 mm cortical screw showed a significant difference compared to the 2.7 mm cortical screw in both materials. A significant difference between the self-tapping and pretapped screws of the same diameter was only found in the 3.5 mm cortical screws in polyurethane foam (P<0.05). Interestingly, the maximum holding power of the 2.2 mm fine machine screws in homogeneous test material (polyurethane foam) was as high as the holding power of the 2.7 mm cortical screws (P<0.05). In natural bovine cancellous bone, the result was even more striking. There was no significant difference between the 2.2 mm fine machine screws and the 3.5 mm cortical screws (P<0.05). Relative to their thread diameter, the fine machine screws were superior to conventional cancellous and cortical screws in cancellous bone. The high holding power of this screw type is at least partly due to the impaction effect of the drilling debris between the thread and the abutting spongy bone structure.
Animals↗
The anatomical base of unilateral external fixation in the upper limb.
Unilateral external fixation requires an anatomically sound implantation of screws into the upper extremity. Detailed knowledge about the anatomical situation in the areas of pin implantation is of great importance. This paper focuses on relevant anatomical landmarks when implanting screws for external fixation in the humerus, the elbow, the forearm and the hand by studying anatomical specimen.
Arm↗
Transarticular fixation with the capacity for motion in fracture dislocations of the elbow.
Post-traumatic stiffness of the elbow joint is a frequent result of immobilisation leading to severe disability in the use of the upper extremity. Recognition of the tendency to stiffness leads to the assumption that the strong self-healing forces of the capsule and ligament apparatus converts the initial instability of the joint after ligament disrupture, into a high-grade undirected stability following immobilisation. Directed stability as it is produced by the natural ligament apparatus of the joint on the other hand produces a guided movement of the joint in one direction. These theoretical considerations lead to the idea that the self-healing forces of the ligament apparatus under continuous guided movement of the joint will result in a stable and movable joint to allow healing of the compromised soft tissue envelope and moreover to maintain free soft tissue access without compromising the stability. For this a unilateral fixator with motion capacity was developed. The joint bridging application approaches the humerus and ulna from the lateral side. The proximal pin group is inserted into the proximal region of the humerus respecting the radial nerve. The distal pin group is implanted from the dorsal side into the middle third of the ulna. The fixator has a hinge joint. The design of the fixator clamps, bars and the hinge joint allows simple alignment with the rotational axis of the elbow. Pro- and supination of the forearm is unhindered. Flexion and extension can be permitted according to the soft tissue situation.
Adult↗
Principles of external fixation and supplementary techniques in distal radius fractures.
External fixation for fractures of the distal radius has been used for almost 80 years. The main objective is to gain reduction and maintain the reduction throughout the treatment period. Several fixator concepts are available and selection is based on the complexity of the injury to be treated as well as the surgeon's experience. Periarticular application of the fixator with immediate use of the wrist joint is recommended whenever possible. For intra-articular fractures, transarticular application is advisable. External fixtion in complex fractures has to be supplemented by bone grafting, fixation wires and stabilization of the radioulnar joint. Associated injuries in distal radius fractures need to be identified and treated. The possible complications of external fixation and the means to prevent them are discussed. External fixation of the distal radius has found its place as an established method in treating certain types of this common fracture.
Adolescent↗
Corrective osteotomies in malunited distal radius fractures: external fixation as one stage and hemicallotasis procedures.
The correction of distal radius malunion was carried out using a radio-radial fixator. The two techniques used in 14 cases were one stage correction or gradual correction by hemicallotasis. The techniques are described and the patients treated were evaluated.
Adolescent↗
The use of minimally invasive fixation in fractures of the hand--the minifixator concept.
The minimally-invasive treatment of metacarpal and phalangeal fractures with a low profile external fixator is described. In most sites fixator pins are inserted percutaneously and closed reduction of the fracture is performed. Due to the special design bridging of adjacent joints in shaft, distal or proximal fractures is not necessary unless the fracture is intraarticular. The results of treatment are described. Advantages and disadvantages of a small external fixator in relation to conservative management and open reduction and internal fixation are discussed.
Bone Nails↗
[Minimally invasive management of metacarpal I fractures with a mini-fixateur].
Displaced perarticular fractures of the first metacarpal are mainly treated operatively due to the importance of the first ray for hand function. Open reduction and internal fixation as well as minimal-invasive techniques using minifixator systems may be employed. We use a minifixator, which allows pin-positioning even in small perarticular fragments eliminating the necessity of bridging joints. The anatomical basis, operative technique, and data of seven patients treated according to this method and results are presented. Range of motion according to the neutral-zero-method, tendon gliding, five-second-holding power, and force grip were equal compared to the uninjured contralateral side. The use of a minifixator to stabilize perarticular fractures of the first metacarpal includes the advantages of a minimal invasive procedure, respects the advantages of conservative fracture treatment, and permits secure fracture fixation after reduction.
Adult↗
External fixation in the distal forearm: its use in fractures and malunions.
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Adolescent↗
[Radio-radial external fixation for correction of malunited distal radius fracture].
For correction of malunited distal radius fractures, the use of the external fixator in radio-radial application was assessed. The device has been used for one-stage correction with corticocancellous bone blocks as well as with hemicallotasis for correction of dorsal angulation. The technical application is described and the use of the external fixator defined. Fourteen patients were treated with radio-radial application, seven of those were corrected with callus distraction. The mechanical possibilities of the fixator allowed complete correction of the malunion.
Adolescent↗
[External stabilization of the metacarpal bones II to V. Anatomic-clinical study].
The four ulnar metacarpal bones are connected to each other at their proximal and distal ends by strong ligaments. The second and fifth metacarpal bones are the frame of the metacarpus. Surgically, this is of great importance. A fracture of these two bones often requires stabilization, whereas a fracture of the third and fourth metacarpal bones with intact ligaments seldom requires surgery except in cases of severe fragment dislocation. Using external fixation for these purposes it seems to be of utmost interest to define secure pintracks through the soft tissue. In an anatomical study using formalin fixed specimen it clearly could be demonstrated that the second and fifth metacarpal bones are best suited for external fixation. The second metacarpal bone should always be fixed from the radial side because the fixator pins can be inserted within a wide range of angles without the risk of violating the extensor tendons. Variations of tendons and ligaments are seldom located on the radial side of the second metacarpal bone and therefore, finger movement is unhindered after pin application. A similar consideration is true for the fifth metacarpal bone which should be fixed from the ulnar side. With respect to the extensor tendon which covers the entire dorsal surface of the fifth metacarpal bone, the angle of the pins should be 40 to 90 degrees from the dorsal side. For the third metacarpal bone, fixation from the radial side is preferable taking topographical and biomechanical considerations into account. The radial corridor to the fourth metacarpal bone is smaller than the ulnar corridor, but there is much less morphological variability of the extensor tendons than on the ulnar side where strong fibres often cross the fourth intermetacarpal space. Because in the proximal fourth of the metacarpal bones the tendons are located very close to each other, a small skin incision and preparation to the bone surface is advisable to exclude violation of the tendons when inserting fixator screws into the third and fourth metacarpal bones. Using formalin-alcohol fixed cadaver specimens for the research gives an idea of the anatomical situation in the dorsal metacarpus but cannot answer the question whether the tendons in the lax subcutaneous tissue of the living will automatically slip aside when the fixator pin approaches. This should be item to subsequent studies in fresh frozen specimens and follow-up studies in a larger amount of patients treated with external fixation.
External Fixators↗
[Changes in the form of the interosseous hood during extension and flexion of the metacarpophalangeal joint].
Finger flexion initiated at the distal and proximal interphalangeal joint level forces the extensor tendon to move distally. Therefore, the interosseous hood fixed to the extensor apparatus moves distally, too. The proximal part of the hood which is located at the level of the metacarpal head during extension of the finger slides distally along the basis of the proximal phalanx. Due to the much smaller cross-section of the phalanx compared to the metacarpal head, the palmar border of the interosseous hood is shifted palmarly. This produces a two-fold effect concerning the metacarpophalangeal joint. First, it leads to an increasing flexion moment of the intrinsic muscles during flexion of the metacarpophalangeal joint. Second, the same mechanism improves the ability of abduction and adduction in the metacarpophalangeal joint during extension of the finger. In this position, the proximal part of the interosseous hood covers the metacarpal head and the strong palmar bundles of the hood are pushed to the ulnar and radial sides resulting in a greater distance to the abduction/adduction axis of the MP-joint. The other effect concerns the proximal interphalangeal joint. The described transformation of the interosseous hood during flexion especially of its proximal part causes a curved deformation of the strong palmar border of the interosseous hood. The power of the intrinsic muscles inserting at the interosseous hood is passed along this smooth curve on its way to the dorsal side of the proximal interphalangeal joint thus allowing a continuous extension of the proximal interphalangeal joint in all flexion phases of the MP-joint. The typical transformation of the interosseous hood is regulated by the form of the underlying bone and ligament apparatus and can be understood as a passive mechanism effecting in a senseful change of muscle function as the active element during finger flexion and extension. These not yet described morphological data concerning the transformation of the interosseous hood during finger flexion and the functional interpretation complete the former described mechanism of flexion by Landsmeer (1955) and Landsmeer and Long (1965).
Biomechanical Phenomena↗