Primary resective shortening followed by distraction osteogenesis for limb reconstruction: a comparison with simple lengthening

Cysteine-rich matricellular protein improves callus regenerate in a rabbit trauma model

PURPOSE

Open fractures with severe soft-tissue trauma are predisposed to poor bone healing. The vital coupling between osteo- and angiogenesis is disturbed. Cysteine-rich protein 61 (CYR61) is an angiogenic inducer promoting vascularisation. However, little is known about the effect of CYR61 on the callus regenerate after acute musculoskeletal trauma. Therefore, our aim was to determine whether local administration of CYR61: (1) has an influence on callus formation and remodelling, (2) increases bone volume and (3) partially restores callus stability.

METHODS

A musculoskeletal trauma was created in 20 rabbits. To simulate fracture-site debridement, the limb was shortened. In the test group, a CYR61-coated collagen matrix was locally applied around the osteotomy. After ten days, gradual distraction was commenced (0.5 mm/12 h) to restore the original length. New bone formation was evaluated histomorphometrically, radiographically and biomechanically.

RESULTS

Osseus consolidation occured in all animals. Average maximum callus diameter was higher in the test group [1.39 mm; standard deviation (SD) = 0.078 vs 1.26 mm (SD = 0.14); p = 0.096]. In addition, bone volume was higher (p = 0.11) in the test group, with a mean value of 49.73 % (SD = 13.68) compared with 37.6 % (SD = 5.91). Torsional strength was significantly higher (p = 0.005) in the test group [105.43 % (SD = 31.68 %) vs. 52.57 % (SD = 24.39)]. Instead, stiffness of the newly reconstructed callus decreased (64.21 % (SD = 11.52) vs. 71.30 % (SD = 32.25) (p = 0.81)).

CONCLUSIONS

CYR61 positively influences callus regenerate after acute trauma, not only histologically and radiographically but also biomechanically, most probably by a CYR61-associated pathway.

A rabbit model for studying degeneration and regeneration properties of young striated muscle at different distraction rates

The present study evaluated the histological changes in the muscle tissue after limb lengthening in skeletally immature rabbits and assessed the effect of different lengthening rates on the regeneration and degeneration properties of striated muscle. Thirteen different lengthening protocols were applied on a total of 16 male domestic white rabbits divided into four groups. The histopathological changes were analysed by a semiquantitative method according to the scoring system of Lee et al. (1993). After evaluation of the five main degenerative parameters (muscle atrophy, internalisation of muscle nuclei, degeneration of the muscle fibre, perimysial and endomysial fibrosis, haematomas), it is evident that rabbits subjected to limb lengthening at a rate of 3.2 mm/day showed more degenerative changes than those limb-lengthened at 0.8 or 1.6 mm/day. Our study showed that the regenerative mechanisms were not endless. If the daily lengthening rate reached the 3.2 mm/day limit, the regenerating ability of the muscle decreased, and signs of degeneration increased significantly.

Local application of VEGF compensates callus deficiency after acute soft tissue trauma--results using a limb-shortening distraction procedure in rabbit tibia

Acute soft tissue trauma influences callus formation and fracture healing. Several studies showed a relationship between angiogenesis and bone formation during distraction osteogenesis. The purpose of this study was to investigate the influence of controlled release of vascular endothelial growth factor (VEGF) on callus formation in a limb-shortening distraction procedure after acute compartment syndrome. Acute soft tissue trauma with critical increased compartment pressure was generated in 22 rabbits, and the limb was shortened simulating fracture site debridement. In the test group (n=11), a VEGF-coated collagen matrix was locally applied around the fracture, while no collagen was applied in the control group (n=11). Following 10 days in limb shortening, a gradual distraction of 0.5 mm/12 h was performed using an external fixation device and followed up for 40 days. Osseous consolidation occurred in all animals. Average callus diameter (1.54 ± 0.8 vs. 1.27 ± 0.14 mm) and torsional strength (72% vs. 46% of normal) were significantly higher in the test versus the control group. Blood vessel formation increased with a significantly higher number of vessels (6.3 vs. 3.81/mm2 ) and larger cross-sectional area (>40 µm, 90.5% vs. 86%) in the test versus control group. The results showed that locally applied VEGF stimulates fracture healing after acute soft tissue trauma and might be an option for fracture treatment in cases with severe soft tissue damage.

Angular shortening and delayed gradual distraction for the treatment of asymmetrical bone and soft tissue defects of tibia: a case series

BACKGROUND

Acute shortening is reported to be an effective method for the treatment of open fractures with bone and soft tissue defects. Little is known about primary skin closure with angulation to the side of the defect and distraction at the fracture site.

METHODS

We present a series of three cases treated for defective fractures of tibia by angular shortening and delayed gradual distraction with hinged circular external fixator. Two cases were type IIIB open fractures and one case was an infected nonunion. Bone and soft tissue defects were managed by adaptation of edges and primary skin closure with angulation to the side of the defect. Axial alignment was restored by gradual distraction after a 2 to 3 weeks interval. Residual limb length discrepancy was lengthened through a separate corticotomy in two cases.

RESULTS

Bone formation at both the fracture and corticotomy sites were sufficient to achieve union in all patients. Fixation time averaged 261 (182-392) days and average bone healing index was 42 days/cm. No further surgical intervention was necessary for soft tissue reconstruction after primary skin closure. Infection was eradicated in the case of infected nonunion.

CONCLUSIONS

Angular compression to the side of the defect is a safe and reliable method of treatment for asymmetrical bone or soft tissue defects of tibia. It eliminates the need for complex soft tissue reconstruction procedures. Unnecessary debridement of bone is prevented by angular adaptation of edges. Definitive treatment of complex injuries is possible with a circular external fixator.

Muscle strength quantification in small animals: a new transcutaneous technique in rabbits

The objective of this study was to develop a new, simple, and noninvasive technique to measure the force produced by dorsi-flexion of the foot in small animals. In addition, this study aimed to quantitatively describe changes in muscle and soft tissue structures using histomorphometry. The recovery of the dorsi-flexing muscles in the tibialis anterior compartment in New Zealand White rabbits was evaluated after musculoskeletal trauma by measuring isometric contractions after submaximal transcutaneous electrical stimulation of the peroneal nerve. The trauma included muscle and bone trauma that was treated with limb shortening followed by distraction osteogenesis. Muscle contractions were initiated at an amplitude of 5.1 mA for a duration of 2.56 ms at intervals of 50 ms. Based on consecutive measurements of the force on days 5, 10, 15, 20, 25, and 30 postsurgery, a positive trend in recovery of the stimulated force produced by dorsi-flexion of the foot was observed. The muscle strength at 30 days postsurgery was compared to that measured presurgery (baseline): 55% of the animals had dorsi-flexion strength that was 60% below that of the presurgery baseline muscle strength; 36% of the animals had dorsi-flexion strength that was greater than 60% of the baseline measure, indicating that there was a significant decrease in force produced by dorsi-flexion of the foot after trauma on all testing days (p < 0.01) and that a severe muscular injury was set with limited recovery. This technique provides a new option for examining muscle regeneration and rehabilitation in small animals.

Structural changes in the lengthened rabbit muscle

This study evaluated the histological changes in muscle tissue after limb lengthening in skeletally mature and immature rabbits and assessed the most vulnerable level of striated muscle. Twenty-three male domestic white rabbits, divided into six groups, were operated on and different lengthening protocols were used in the mature and immature rabbits. The histopathological changes were analysed by a semi-quantitative method according to the scoring system of Lee et al. (Acta Orthop Scand 64(6):688-692, 1993). After the evaluation of the five main degenerative parameters (muscle atrophy, muscle nuclei internalisation, degeneration of the muscle fibre, perimysial and endomysial fibrosis, haematomas), it is evident that the adults lengthened at a rate of 1.6 mm/day showed more degenerative changes than those lengthened at 0.8 mm/day. The adult 1.6 mm/day lengthened group presented significantly higher damage in the muscle and lower regenerative signs compared with the young 1.6 mm/day lengthened group, according to the summarised degenerative scores.

The influence of soft tissue trauma on bone regeneration after acute limb shortening

Reconstructing posttraumatic tibial defects is often challenging. Some authors recommend acute limb shortening. We determined whether soft tissue trauma affects the formation of regenerated bone after acute shortening and monofocal lengthening. Twenty-two rabbits were divided into two equal groups. In the test group, 90 minutes of ischemia and 30 minutes of tibialis anterior muscle contusion at 100 kPa induced substantially elevated pressure as an onset of compartment syndrome. The untreated hind limb acted as the paired control. An external fixator was applied and the limb was shortened 10 mm through bone resection. After a latency period, distraction was performed for 10 days until the natural length was restored. New bone formation was evaluated mechanically, radiographically, and histomorphometrically. Osseous consolidation occurred in all animals. Normalized mechanical values of the newly reconstructed tibia indicated torsional strength was lower in the trauma group than in controls (46% +/- 18.5% versus 64% +/- 16.7%). Average normalized callus diameters were smaller in the trauma group than in controls (1.27 +/- 0.14 versus 1.6 +/- 0.16), as were callus volumes (37% +/- 5.9% versus 44% +/- 10.3%). Although soft tissue trauma affected the formation of regenerated bone, our results suggest reconstruction of tibial defects using a monofocal technique is consistent, even in the presence of blunt trauma and elevated compartment pressure.

Response of rabbit skeletal muscle to tibial lengthening

BACKGROUND

Experimental and clinical studies have provided knowledge regarding osteogenesis during limb lengthening. However, response of skeletal muscle to limb lengthening is not fully understood, especially as concerns histogenesis. We studied the morphological response of rabbit skeletal muscle to limb lengthening. In this study, we investigated proliferation of satellite cells, responsible for generation of new myonuclei, during limb lengthening.

METHODS

Tibialis anterior muscles of young and adult rabbits were subjected to lengthening at a rate of 0.5 mm twice per day for 20 days. After lengthening, muscle wet weight was measured to assess skeletal muscle growth, then proliferating cell nuclear antigen was measured. Immunostaining was performed to analyze proliferating cells in the proximal, middle, and distal portions of the muscle belly and the musculotendinous junction.

RESULTS

Muscle wet weight increased significantly after lengthening both in adult (0.4 g) and young (0.1 g) rabbits. Satellite cells showed proliferation in response to lengthening. In adult rabbits, satellite cell proliferation increased along the entire lengthened muscle to a similar degree (from 7.1% in the middle portion to 8.6% in the musculotendinous junction). In young rabbits, proliferation was greater in the musculotendinous junction (4.8%) than that in other muscle portions (2.3% in the middle and distal portions, and 2.4% in the proximal portion). In adult rabbits, the rate of increase in satellite cell proliferation was 1780% in the middle portion to 2860% in the musculotendinous junction, whereas the rate was between 210% in the middle portion and 290% in the distal portion in young rabbit. The rate of increase in cell proliferation by lengthening was higher in adult muscle than that in young muscles as well as satellite cell proliferation.

CONCLUSION

These findings indicate that limb lengthening promotes muscle growth in both young and adult rabbits.

Spontaneous bone regeneration in surgically induced bone defects in young rabbits

Defects of the femoral shaft (15%, 20%, 25%, and 30% of the femoral length) with intact periosteum were made in young rabbits to investigate differences in union time. The mean union time was 7.3, 7.1, 7.4, and 7.0 weeks, respectively and there was no significant difference ( >0.05) between the groups. The mean healing indices were 6.7, 4.6, 3.9, and 3.1 weeks/cm, respectively and these were significantly different ( <0.05) between the 15% bone defect group and the other bone defect groups. These results suggested that union time was not affected by the amount of bone defect. Femoral lengthening of 20% was performed to compare the quality of callus with those of the femoral defect of 20%. The mean healing indices of defect and lengthening were 4.6 and 5.7, respectively and the difference was significant ( = 0.004). The callus stiffness of femoral defect was higher ( = 0.02) than that after femoral lengthening whereas the bone mineral density of the callus showed no significant difference ( = 0.37) between two groups. The method of filling bone defect with callus generated from the intact periosteum may be a new therapeutic option for the reconstruction of large bone defects in children when other treatments are not available.

Callus stimulation in distraction osteogenesis

Distraction osteogenesis has been described as in vivo tissue engineering. The ability to stimulate this process for the repair of bony defects or lengthening of congenitally shortened facial structures is likely to significantly impact the field of craniofacial surgery. The purpose of this study was to determine whether mechanical stimulation of the distracted rabbit mandible would accelerate the maturation of the bony callus when applied during the early consolidation period. Twenty adult New Zealand White rabbits underwent unilateral mandibular osteotomy. A uni-directional internal distractor device (Synthes, Paoli, Pa.) was positioned along a plane perpendicular to the line of osteotomy. After a 7-day latency period, distraction was commenced at a rate of 1.0 mm/day for 12 days in all animals. In a control group of 10 rabbits, a consolidation period of 8 weeks was observed before they were killed. In the experimental group of 10 rabbits, daily alternate compression and distraction of 1 mm (sequential compression and distraction) was performed for 3 weeks followed by a 5-week period of rigid fixation. Each animal received a dose of a fluorescent label at three different time points during the study: at the end of the distraction period, 3 weeks after the completion of the distraction phase, and 3 days before it was killed. All animals were killed 8 weeks after the completion of the distraction phase. Undecalcified histologic analysis and 3-point bending tests to failure were performed on the extracted mandibles. The results of the experimental and control groups were compared. Four animals in the control group and three animals in the experimental group were excluded from the study because of screw loosening resulting in distractor dislodgment or because of infection. On histologic analysis, cortical thickness at the center of the callus was found to be significantly greater in the experimental group compared with the control group when normalized to the contralateral hemimandible (83 percent versus 49 percent, respectively; p < 0.007). The ratio of cortical to cancellous bone in the distracted callus was uniformly found to be greater in the experimental specimens. The mineral apposition rate was calculated by using fluorescence microscopy and found to be significantly greater in the experimental group both during the period of sequential compression and distraction (3.2 microm/day versus 2.1 microm/day, p = 0.02) and after the period of sequential compression and distraction (1.4 microm/day versus 1.1 microm/day, p = 0.006). Mechanical testing revealed no significant differences in bending strength or stiffness between experimental or control groups (p = 0.54 and 0.47, respectively). This study has demonstrated that daily alternating compression and distraction of 1 mm amplitude during the early consolidation period has a stimulatory impact on callus formation with respect to osteoblastic activity, remodeling, and maturation of bone. Optimal timing and amplitude of sequential movement, long-term biomechanical differences, and molecular pathways have yet to be elucidated.

Distraction osteogenesis for reconstruction after mandibular segmental resection

Distraction osteogenesis with the shortening and lengthening method is a well-established procedure for repairing extremities. We used this technique for reconstruction after mandibular segmental resection. A 74-year-old woman underwent distraction osteogenesis with an intraoral device, initially shortening the mandible after a 20-mm-long segmental resection, followed by lengthening at a rate of 0.8 mm per day for 21 days. Eight weeks after the distraction, the device was removed and a dental implant was placed at the site of distraction. Radiographic observation showed new bone formation, and the implant was completely osseointegrated. Although the follow-up period is relatively short, the clinical course was uneventful. Distraction osteogenesis with the shortening and lengthening method seems to be a feasible option for reconstruction after segmental resection of the mandible.