Isolated and combined tears of the subscapularis tendon.

BACKGROUND: Isolated and combined subscapularis tendon tears are rare and are described in the literature only in small numbers. HYPOTHESIS: The outcome of surgical intervention for isolated and combined subscapularis tendon tears may be influenced by the tear pattern of the anterior rotator cuff and the period of time between trauma and surgical procedure. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Between 1994 and 1999, 34 shoulders with isolated traumatic tears (16 shoulders) or subscapularis tendon rupture combined with a supraspinatus tendon tear were treated operatively. The average patient age was 51 years, and the mean follow-up period was 37 months. For statistical analyses, the Friedman and Mann-Whitney tests were used. RESULTS: In patients with isolated tears, the Constant score rose from an average of 43.9 to 88.7 points (P < .01), and in patients with combined tears, it rose from an average of 40.6 to 74.7 points (P <.01). Isolated tears improved 14 points more than combined tears (P <.05). The delay between trauma and surgical intervention was inversely proportional to the improvement in the Constant score. The Spearman coefficient of correlation was -0.97 in isolated tears and -0.89 in combined tears. CONCLUSIONS: Young patients with isolated traumatic tears of the subscapularis tendon and immediate repair have the best prognostic factors for treatment. Accuracy in the trauma history and the clinical and radiographic examination is demanded.

Complications following the treatment of trochanteric fractures with the gamma nail.

INTRODUCTION: The treatment of trochanteric fractures with the use of gamma nails has become an established method. Despite the good and reliable results, some typical failures and complications may occur. It was our purpose to analyse the most common complications and their treatment options. MATERIALS AND METHODS: A total of 498 patients were treated with a gamma nail from January 1992 until December 2001. There were 77% pertrochanteric, 10% subtrochanteric, 11% reversed pertrochanteric and 2% lateral femoral neck fractures. The patients' mean age was 78.6 years (ranging from 29 to 98 years). RESULTS: There were a total of 78 general complications (16%) and implant-related complications in 8% (n=42). The most common complication was trochanteric pain necessitating removal of the gamma nail (n=30). Four patients fell after removal of the nail and sustained a neck fracture on the same side. Cut-out of the screw occurred in 19 patients. Sixteen of them had to be converted to a total hip replacement. Another 5 patients were converted to a total hip replacement because of pseudoarthrosis. During conversion to total hip replacements, the trochanter major refixation and length adjustment were the most problematic steps (intra- or postoperative dislocations necessitating anti-dislocation rings in three cases). Furthermore, cement extrusion at the femur and acetabulum occurred in 13 cases. Infections occurred in 3 patients. Five patients with a short gamma nail needed a conversion to a long gamma nail due to pseudoarthrosis (n=2) or femur fracture at the distal interlocking bolt (n=3). In addition, 7 patients sustained a distal femur fracture through the distal bolt, necessitating a plate osteosynthesis. CONCLUSION: Most complications after gamma nail fixation can be prevented by following certain rules. The other inevitable problems can be dealt with either through a conversion to a total hip replacement, a re-osteosynthesis with a long gamma nail or an additional condylar plate. Conversion to total hip replacement may be a demanding operation with a higher than normal complication rate. Removal of the gamma nail should be performed cautiously as re-fractures can occur.

Oblique screws at the plate ends increase the fixation strength in synthetic bone test medium.

OBJECTIVE: To test the hypothesis that oblique screws at the ends of a plate provide increased strength of fixation as compared to standard screw insertion. DESIGN: Biomechanical laboratory study in synthetic bone test medium. METHODS: Narrow 4.5-mm stainless steel low-contoured dynamic compression plates were anchored with cortical screws to blocks of polyurethane foam. The fixation strength in cantilever bending (gap closing mode) and torsion was quantified using a material testing system. Different constructs were tested to investigate the effect of the screw orientation at the end of the plate (straight versus oblique at 30 degrees), the plate, and bridging length as well as the number of screws. RESULTS: An oblique screw at the plate end produced an increased strength of fixation in all tests; however, the difference was more significant in shorter plates and in constructs with no screw omission adjacent to the fracture site. Both longer plates and increased bridging length produced a significantly stronger construct able to withstand higher compression loads. Under torsional loading, the fixation strength was mainly dependent on the number of screws. CONCLUSIONS: The current data suggest that when using a conventional plating technique, plate length is the most important factor in withstanding forces in cantilever bending. With regard to resisting torsional load, the number of screws is the most important factor. Furthermore, oblique screws at the ends of a plate increase fixation strength.

Biomechanical testing of the LCP--how can stability in locked internal fixators be controlled?

New plating techniques, such as non-contact plates, have been introduced in acknowledgment of the importance of biological factors in internal fixation. Knowledge of the fixation stability provided by these new plates is very limited and clarification is still necessary to determine how the mechanical stability, e.g. fracture motion, and the risk of implant failure can best be controlled. The results of a study based on in vitro experiments with composite bone cylinders and finite element analysis using the Locking Compression Plate (LCP) for diaphyseal fractures are presented and recommendations for clinical practice are given. Several factors were shown to influence stability both in compression and torsion. Axial stiffness and torsional rigidity was mainly influenced by the working length, e.g. the distance of the first screw to the fracture site. By omitting one screw hole on either side of the fracture, the construct became almost twice as flexible in both compression and torsion. The number of screws also significantly affected the stability, however, more than three screws per fragment did little to increase axial stiffness; nor did four screws increase torsional rigidity. The position of the third screw in the fragment significantly affected axial stiffness, but not torsional rigidity. The closer an additional screw is positioned towards the fracture gap, the stiffer the construct becomes under compression. The rigidity under torsional load was determined by the number of screws only. Another factor affecting construct stability was the distance of the plate to the bone. Increasing this distance resulted in decreased construct stability. Finally, a shorter plate with an equal number of screws caused a reduction in axial stiffness but not in torsional rigidity. Static compression tests showed that increasing the working length, e.g. omitting the screws immediately adjacent to the fracture on both sides, significantly diminished the load causing plastic deformation of the plate. If bone contact was not present at the fracture site due to comminution, a greater working length also led to earlier failure in dynamic loading tests. For simple fractures with a small fracture gap and bone contact under dynamic load, the number of cycles until failure was greater than one million for all tested constructs. Plate failures invariably occurred through the DCP hole where the highest von Mises stresses were found in the finite element analysis (FEA). This stress was reduced in constructions with bone contact by increasing the bridging length. On the other hand, additional screws increased the implant stress since higher loads were needed to achieve bone contact. Based on the present results, the following clinical recommendations can be made for the locked internal fixator in bridging technique as part of a minimally invasive percutaneous osteosynthesis (MIPO): for fractures of the lower extremity, two or three screws on either side of the fracture should be sufficient. For fractures of the humerus or forearm, three to four screws on either side should be used as rotational forces predominate in these bones. In simple fractures with a small interfragmentary gap, one or two holes should be omitted on each side of the fracture to initiate spontaneous fracture healing, including the generation of callus formations. In fractures with a large fracture gap such as comminuted fractures, we advise placement of the innermost screws as close as practicable to the fracture. Furthermore, the distance between the plate and the bone ought to be kept small and long plates should be used to provide sufficient axial stiffness.