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Biomechanical considerations on the anterior approach to the carpal scaphoid. Proposal of a new osteosynthesis system
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SESSION 12: FREE PAPERS Subchondral bone mineralisation: a key to load transmission through the carpus in the living R. Giunta, N. L6wer, K. Wilhelm, M. Miiller-Gerbl
Institute of Anatomy, Ludwig-Maximilians University, Munich, Germany Our most important ideas about the mechanism of load transmission through the radiocarpal joint have been acquired mostly from the study of specimens. Apart from this, however, it is possible to derive direct knowledge about the actual mechanical conditions of a joint from certain morphological parameters and in particular from an analysis of the subchondral mineralization. CT osteoabsorptiometry (CT-OAM) provides a research tool with which the distribution of the subchondral mineralization of the radiocarpal joint can be investigated non-invasively, making it suitable for the living subject. Seventeen wrist-joints were investigated in healthy young subjects by means of CT-OAM, and the results evaluated both topographically and quantitatively. In most cases two density maxima were found on the articular radial surface, one corresponding to the scaphoid and one to the lunate. These matched the positions of pressure peaks described in reports of research on mechanical models. The density maximum on the articular surface of the radius opposing the scaphoid is, however, dorsally placed, whereas that opposing the lunate lies on the palmar side of the radioulnar midline. This explains the transmission of forces to the forearm and the geometrical configuration of the joint components on kinematic grounds. On the other hand, our quantitative results do not confirm the existence of a generally greater degree of mineralization of either one of the joint compartments. We cannot therefore confirm theories attributing transmission of the main force through either the scaphoid or the lunate. We assume rather that the type of stress indicated by the predominantly monocentric density maxima on the scaphoid or the lunate surface of the radius, together with the equally balanced bicentric degree of mineralization, are to be regarded as physiological.
T H E J O U R N A L O F H A N D SURGERY VOL. 21B S U P P L E M E N T 1
cadaver limbs, focusing on the problems relating to the volar blood supply distribution and to the anterior ligament anatomy. A cannulated and self-threading version of the Herbert screw achieves compression of the fracture line by use of different pitch threads. The scaphoid was fractured at different levels to simulate both stable and unstable fracture; it was then fixed and harvested and submitted to anatomic and radiographic studies. A clinical trial followed the experimental study and includes: 15 fresh fractures (type B); 6 delayed unions (type C); 3 fibrous non-unions (type D1) and 6 sclerotic non-unions (type D2). Radiologic healing has been complete in 85% of cases. In the various groups the rate of radiologic healing has been: 93.5% in type B, 100% in type C, 100% in type D1, 50% in type D2. The main features demonstrated by the new screwing system can be summarized by the following points: 1. Compression is applied along the longitudinal axis of the scaphoid. Only after the scaphoid has been stabilized is the distal pole slightly elevated to expose the introduction point of the screw, moving the whole scaphoid without the risk of secondary displacement at the level of fracture or non-union site. 2. The screw can be introduced 'in line' and 'obliquely', maintaining the same points of application of the instrument on the distal and proximal poles. The new osteosynthesis system requires minimal mobilization of the distal pole, thus reducing the risk of jeopardizing the volar blood supply and stability. Furthermore, the possibility of introducing the screw obliquely avoids the risk of penetrating the anterior surface of the scaphoid or the eccentric positioning of the screw.
Pros and cons of conservative and operative treatment in fractures of the carpal scaphoid: results in 414 scaphoid fractures between 1984 and 1994 J. Ganser, M. Z i m m e r m a n n , E Horst, E Reill
Department of Hand Surgery, BG-Unfallklinik, Tuebingen, Germany Biomechanical considerations on the anterior approach to the carpal scaphoid. Proposal of a new osteosynthesis system E E Borelli*, C. Motta, R. Luchetti**, O. Soragni
*1st Department of Orthopaedic and Trauma Surgery, Ospedale Civile, Brescia, Italy and **Department of Orthopaedics, Trauma and Hand Surgery, (SOS Main) Ospedale di Stato, Republic of San Marino Since 1987, Herbert's system has undoubtedly been the most used device for osteosynthesis of fractures of the carpal scaphoid. However, some aspects of the method, relating to the anterior approach, have been criticized in literature: • the need to mobilize the distal pole generously " difficulty in applying the 'jig' at the level of the distal pole • difficulty in determining the introduction line of the screw in the sagittal plane. This has led us to study a new osteosynthesis technique. The new compression instrument has been tested on 14 fresh
In a retrospective study of 414 scaphoid fractures in 404 patients, treated within the first four weeks of injury, results of conservative and operative treatment were analysed. The outcome of fracture treatment was mainly influenced by: localisation of fracture in terms of Schernbergs and of Boehlers classification; amount of fracture-dislocation and kind of treatment in terms of conservative and operative treatment. Consistent with previous and well-known studies, the proximal scaphoid fracture did not heal by conservative management in more than 30% of cases. The operative regimen, used in 7 proximal scaphoid fractures, failed only once. In the middle third of the scaphoid, bony healing by conservative treatment was unsuccessful in nearly 20% of cases and in only 4 of 28 cases by operative treatment. In the distal, but not tuberculous, fracture-type the conservative method failed in 25% of cases as did the one operative ease. The healing rate was not significantly age-dependent, even young patients between 13 and 19 years did not have a better chance of fracture healing than older patients between 50 and 60 years. Bony consolidation of the fracture and range of motion in the wrist joint were analysed and categorized as good, fair and
SESSION 12: FREE PAPERS Subchondral bone mineralisation: a key to load transmission through the carpus in the living R. Giunta, N. L6wer, K. Wilhelm, M. Miiller-Gerbl
Institute of Anatomy, Ludwig-Maximilians University, Munich, Germany Our most important ideas about the mechanism of load transmission through the radiocarpal joint have been acquired mostly from the study of specimens. Apart from this, however, it is possible to derive direct knowledge about the actual mechanical conditions of a joint from certain morphological parameters and in particular from an analysis of the subchondral mineralization. CT osteoabsorptiometry (CT-OAM) provides a research tool with which the distribution of the subchondral mineralization of the radiocarpal joint can be investigated non-invasively, making it suitable for the living subject. Seventeen wrist-joints were investigated in healthy young subjects by means of CT-OAM, and the results evaluated both topographically and quantitatively. In most cases two density maxima were found on the articular radial surface, one corresponding to the scaphoid and one to the lunate. These matched the positions of pressure peaks described in reports of research on mechanical models. The density maximum on the articular surface of the radius opposing the scaphoid is, however, dorsally placed, whereas that opposing the lunate lies on the palmar side of the radioulnar midline. This explains the transmission of forces to the forearm and the geometrical configuration of the joint components on kinematic grounds. On the other hand, our quantitative results do not confirm the existence of a generally greater degree of mineralization of either one of the joint compartments. We cannot therefore confirm theories attributing transmission of the main force through either the scaphoid or the lunate. We assume rather that the type of stress indicated by the predominantly monocentric density maxima on the scaphoid or the lunate surface of the radius, together with the equally balanced bicentric degree of mineralization, are to be regarded as physiological.
T H E J O U R N A L O F H A N D SURGERY VOL. 21B S U P P L E M E N T 1
cadaver limbs, focusing on the problems relating to the volar blood supply distribution and to the anterior ligament anatomy. A cannulated and self-threading version of the Herbert screw achieves compression of the fracture line by use of different pitch threads. The scaphoid was fractured at different levels to simulate both stable and unstable fracture; it was then fixed and harvested and submitted to anatomic and radiographic studies. A clinical trial followed the experimental study and includes: 15 fresh fractures (type B); 6 delayed unions (type C); 3 fibrous non-unions (type D1) and 6 sclerotic non-unions (type D2). Radiologic healing has been complete in 85% of cases. In the various groups the rate of radiologic healing has been: 93.5% in type B, 100% in type C, 100% in type D1, 50% in type D2. The main features demonstrated by the new screwing system can be summarized by the following points: 1. Compression is applied along the longitudinal axis of the scaphoid. Only after the scaphoid has been stabilized is the distal pole slightly elevated to expose the introduction point of the screw, moving the whole scaphoid without the risk of secondary displacement at the level of fracture or non-union site. 2. The screw can be introduced 'in line' and 'obliquely', maintaining the same points of application of the instrument on the distal and proximal poles. The new osteosynthesis system requires minimal mobilization of the distal pole, thus reducing the risk of jeopardizing the volar blood supply and stability. Furthermore, the possibility of introducing the screw obliquely avoids the risk of penetrating the anterior surface of the scaphoid or the eccentric positioning of the screw.
Pros and cons of conservative and operative treatment in fractures of the carpal scaphoid: results in 414 scaphoid fractures between 1984 and 1994 J. Ganser, M. Z i m m e r m a n n , E Horst, E Reill
Department of Hand Surgery, BG-Unfallklinik, Tuebingen, Germany Biomechanical considerations on the anterior approach to the carpal scaphoid. Proposal of a new osteosynthesis system E E Borelli*, C. Motta, R. Luchetti**, O. Soragni
*1st Department of Orthopaedic and Trauma Surgery, Ospedale Civile, Brescia, Italy and **Department of Orthopaedics, Trauma and Hand Surgery, (SOS Main) Ospedale di Stato, Republic of San Marino Since 1987, Herbert's system has undoubtedly been the most used device for osteosynthesis of fractures of the carpal scaphoid. However, some aspects of the method, relating to the anterior approach, have been criticized in literature: • the need to mobilize the distal pole generously " difficulty in applying the 'jig' at the level of the distal pole • difficulty in determining the introduction line of the screw in the sagittal plane. This has led us to study a new osteosynthesis technique. The new compression instrument has been tested on 14 fresh
In a retrospective study of 414 scaphoid fractures in 404 patients, treated within the first four weeks of injury, results of conservative and operative treatment were analysed. The outcome of fracture treatment was mainly influenced by: localisation of fracture in terms of Schernbergs and of Boehlers classification; amount of fracture-dislocation and kind of treatment in terms of conservative and operative treatment. Consistent with previous and well-known studies, the proximal scaphoid fracture did not heal by conservative management in more than 30% of cases. The operative regimen, used in 7 proximal scaphoid fractures, failed only once. In the middle third of the scaphoid, bony healing by conservative treatment was unsuccessful in nearly 20% of cases and in only 4 of 28 cases by operative treatment. In the distal, but not tuberculous, fracture-type the conservative method failed in 25% of cases as did the one operative ease. The healing rate was not significantly age-dependent, even young patients between 13 and 19 years did not have a better chance of fracture healing than older patients between 50 and 60 years. Bony consolidation of the fracture and range of motion in the wrist joint were analysed and categorized as good, fair and