Per Ludvigsen

High frequency distraction improves tissue adaptation during leg lengthening in humans

The present study investigates the effect of distraction frequency on the development of tensile force in the tissues during lengthening. Two patients with bilateral Ilizarov leg lengthening underwent distraction with high frequency in one leg and low frequency in the other. The clinical situation represented a unique model for investigating the effect of distraction frequency, as each individual served as its own control. Both patients had double level lengthening. Distraction frequency at the proximal lengthening zone was 0.25 mm × 4 in the first leg and 1/1440 mm once every minute in the other. Total diurnal distraction at the proximal metaphysis was 1 mm in both legs. In addition, a distal metaphyseal distraction of 0.25 mm × 3 daily was performed on each leg. The tissues mechanical response was monitored by measuring the tensile force at the proximal osteotomy. Both patients experienced a significant lower level of force during the high frequency lengthening. The lower level of force was concluded to be due to improved soft tissue adaptation, rather than reduced bone regeneration. Accordingly, high distraction frequency was considered favourable to low frequency, and is recommended in large lengthenings where high force levels are expected.

Tissue response during monofocal and bifocal leg lengthening in patients

The purpose of this investigation was to compare the tissue response during mono‐ and bifocal limb lengthening. The study includes four patients undergoing leg lengthening. All patients started out bifocally with a total diurnal distraction of 1.75 mm, but proceeded monofocally with a rate of 1 mm a day when the distal distraction was terminated due to contractures or pain. The tissue response was monitored by registration of axial force in the distraction rods. The force increased linearly during bifocal lengthening, but culminated or decreased in the period of monofocal lengthening. Average tissue stiffness, defined as the immediate force increase due to each 0.25 mm distraction increment, was significantly higher in the bifocal lengthening phase. The force decay between each distraction was significantly lower during bifocal lengthening, thus indicating decreased tissue accommodation. Details in the force registrations indicated that the soft tissue, not the regenerate, was the main contributor to the tensile force. Conclusively, the tissues at the two osteotomy sites do not lengthen independently. Bifocal lengthening exposes the entire soft tissue to large loads, resulting in increased tissue stiffness and reduced ability to adapt to the increased length. Accordingly, bifocal leg lengthening requires special attention to soft tissue adaptation.

Unchanged muscle function after bilateral femoral lengthening. A prospective study of 9 patients with a 2-year follow-up.

We performed pre- and 2-3.5-year postoperative isokinetic knee-testing to assess thigh muscle function in 9 patients undergoing bilateral femoral lengthening by callotasis. The median femoral lengthening was 17 (12-18) percent. The angular testing velocities were 60 degrees/sec (strength) and 180 degrees/sec (endurance). Only small changes in muscle strength were found postoperatively. Except for peak torque at 60 degrees/sec on the last-operated side (median 2 years follow-up), there were no differences between the pre- and postoperative isokinetic measurements. There were 3 major complications, 2 fractures and 1 varus deformity. 2 patients had problems with patellar pain. All patients achieved normal range of motion. They judged the final result as very good and underlined the psychological effect and the practical advantages of being taller.

External rotation — best isokinetic movement pattern for evaluation of muscle function in rotator tendinosis. A prospective study with a 2-year follow-up

We prospectively performed isokinetic shoulder testing III 31 patients with rotator tendinosis (Impingement, stage II), to evaluate which movement patterns these patients are able to fulfill both before and after treatment. The movement patterns used were externaIjinternal rotation and flexion/extension. The angular velocities were 60 0 /s and 180 0 /s and the patients were tested pre-treatment and after 6 and 24 months. Twenty-five of the patients (81 %) managed all three externaIjinternal rotation tests. In flexion/extension, however, only eight patients (26%) fulfilled all tests because of pain. Pre-treatment there was an average significant reduction of 25% (P < 0.001) in external rotation, while internal rotation only had a slight reduction of 10%. At 24 months both movement patterns had regained normal strength. Most patients fulfilled the externaIjinternal rotation tests and the performance was weakly correlated to pain compared to the flexion/extension pattern. This suggests that externaIjinternal rotation is the preferrable movement pattern for evaluation of muscle strength deficits per se in patients with rotator tendinosis.

Comparison of modified Kessler and Yotsumoto-Dona suture: A biomechanical study on porcine tendons

Abstract There is a need for a strong suture technique that allows early active mobilisation after repair of flexor tendons, but the best method has not yet been found. The aim of this study was to compare the modified Kessler suture biomechanically with a newer, two–strand suture. Eighteen porcine tendons were cut and repaired according to either the grasping modified Kessler suture or the combined side-locking loop technique (Yotsumoto) and interlocking horizontal mattress suture (Dona). The specimens were tested linearly to failure. The 2 mm gap force, yield force, ultimate force, stiffness, energy to yield, and energy to failure were all significantly higher (p value = 0.005, 0.003, <0.001, 0.001, 0.004, and 0.001, respectively) in the Yotsumoto-Dona group (median values (IQR): 30.9 (28.1-39.5) N, 82.7 (64.9-114.1) N, 82.7 (76.6-114.1) N, 12.5 (10-14.5) N/mm, 0.45 (0.2-0.5) J, and 0.45 (0.35-0.5) J) than in the modified Kessler group (25.8 (12.2-28.1) N, 35 (24.6-54.4) N, 50.9 (34.4-55.1) N, 7 (5.8-91) N/mm, 0.09 (0.06-0.18) J, and 0.21 (0.18-0.28) J). All Yotsumoto-Dona specimens had a yield force exceeding 35 N, while in the Kessler group only four did. The early yielding rate was 6/9 and 2/9 in the modified Kessler and the Yotsumoto-Dona groups, respectively (p = 0.15). Most of the core sutures failed by breakage, but three Yotsumoto knots loosened. All the simple running and six of the Dona epitendinous sutures failed predominantly by pulling-out, and by breakage at the intersections in three of the latter. The relatively easy two-strand Yotsumoto-Dona suture is likely to withstand the loads of active finger flexion, whereas the modified Kessler suture is probably not.

Differences in External and Internal Cortical Strain with Prosthesis in the Femur

The contact between a femoral stem prosthesis and the internal surface of the cortical bone with the stress in the interface is of crucial importance with respect to loosening. However, there are no reports of strain patterns at this site, and the main aim of the current study was to investigate differences of internal and external cortical strain in the proximal femur after insertion of a stem prosthesis. The external cortical strain of a human cadaveric femur was measured with strain gauges before and after implantation of a stem prosthesis. By use of optical fibres embedded longitudinally in the endosteal cortex, deformations at the implant–internal cortex interface could also be measured. The main external deformation during loading of the intact femur occurred as compression of the medial cortex; both at the proximal and distal levels. The direction of the principal strain on the medial and lateral aspects was close to the longitudinal axis of the bone. After resection of the femoral neck and insertion of a stem prosthesis, the changes in external strain values were greatest medially at the proximal level, where the magnitude of deformation in compression was reduced to about half the values measured on the intact specimen. Otherwise, there were rather small changes in external principal strain. However, by comparing vertical strain in the external and internal cortex of the proximal femur, there were great differences in values and patterns at all positions. The transcortical differences in strain varied from compression on one side to distraction on the other and vice versa in some of the positions with a correlation coefficient of 0.07. Our results show that differences exist between the external and internal cortical strain when loading a stem prosthesis. Hence, strain at the internal cortex does not correspond and can not be deducted from measured strain at the external cortex.

Biomechanical factors in the metaphyseal- and diaphyseal-lengthening osteotomy : an experimental and theoretic analysis in the ovine tibia

A post hoc comparison of the mechanical factors that affected the outcome of experimental metaphyseal- and diaphyseal-lengthening osteotomies in sheep tibiae was performed. The resulting motions between bone segments at the metaphyseal and diaphyseal levels were estimated using measured fixator stiffnesses, postural muscle activity, ground reaction forces, and calculated internal and external loads. Relative displacements of bone segments of up to 2.8 degrees were estimated in postural activities; displacements were up to 4.9 times larger at the metaphyseal than at the diaphyseal osteotomy level. The results suggest that due to these increased motions, mechanically inferior conditions for healing at the metaphyseal-lengthening osteotomy level may counteract any supposedly superior biologic healing potential that the metaphyseal region of the bone may have compared with the diaphyseal region. These results correlate well with the clinical findings of the earlier animal study.