The biomechanical evaluation of tendon repair with collagen-based scaffolds in rat model is a common method to determine the functional outcome of the tested material. We introduced a magnetic resonance imaging (MRI) approach to verify the biomechanical test data. In present study different collagen scaffolds for tendon repair were examined.

Two collagen test materials: based on bovine stabilized collagen, chemically cross-linked with oriented collagenous fibres (material 1) and based on porcine dermal extracellular matrix, with no cross-linking (material 2) were compared. The animal study was approved by the local review board. Surgery was performed on male Sprague-Dawley rats with a body weight of 400 ± 19 g. Each rat underwent a 5 mm transection of the right Achilles tendon. The M. plantaris tendon was removed. The remaining tendon ends were re-joined with a 5 mm scaffold of either the material 1 or 2. Each scaffold material was sutured into place with two single stiches (Vicryl 4–0, Ethicon) each end. A total of 16 rats (n= 8 each group) were observed for 28 days follow up. The animals were sacrificed and hind limbs were transected proximal to the knee joint. MRI was performed using a 7 Tesla scanner (BioSpec 70/30, Bruker). T2-weighted TurboRARE sequences with an in-plane resolution of 0.12 mm and a slice thickness of 0.7 mm were analysed. All soft and hard tissues were removed from the Achilles tendon-calcaneus-foot complex before biomechanical testing. Subsequently, the specimens were fixed in a materials testing machine (Z1.0, Zwick, Ulm, Germany) for tensile testing. All tendons were preloaded with 1 N and subsequently stretched at a rate of 1 mm/s until complete failure was observed. Non-operated tendons were used as a control (n=4).

After 28 postoperative days, MRI demonstrated that four scaffolds (material 1: n=2, material 2: n=2) were slightly dislocated in the proximal part of hind limb. In total five failures of reconstruction could be detected in the tendon repairs (material 1: n=3, material 2: n=2). Tendons augmented with the bovine material 1 showed a maximum tensile load of 57.9 ± 17.9 N and tendons with porcine scaffold material 2 of 63.1 ± 19.5 N. The native tendons demonstrated only slightly higher loads of 76.6 ± 11.6 N. Maximum failure load of the tendon-scaffold construct in both groups did not differ significantly (p < 0.05). Stiffness of the tendons treated with the bovine scaffold (9.9 ± 3.6 N/mm) and with the porcine scaffold (10.7 ± 2.7 N/mm) showed no differences. Stiffness of the native healthy tendon of the contralateral site was significantly higher (20.2 ± 6.6 N/mm, p < 0.05). No differences in the mechanical properties between samples of both scaffold groups could be detected, regardless of whether the repaired tendon defect has failed or the scaffold has been dislocated.

The results show that MRI is important as an auxiliary tool to verify the biomechanical outcome of tendon repair in animal models.

Purpose: To evaluate the effect of osteoporosis on healing time of long bone fractures.

Methods: Between January 2002 to January 2004 patients with femoral shaft fracture treated in our institution by locked reamed IM nailing were eligible for inclusion in this study. Patients were divided in two age groups; Group A, consisting of patients between 18 and 41 years of age and group B consisting of patients over 65 years old with radiological evidence of osteoporosis. Exclusion criteria were open fractures, pathological fractures, patients with head injuries and patients with systematic inflammatory diseases. In addition to the demographic details such parameters were documented as fracture classification, Injury Severity Score, mode of mobilization, time to clinical and radiological union, complications, and length of hospital stay. In all patients the Singh Index Score for osteoporosis was assigned. Following discharge from the hospital, all patients were followed up at regular intervals for clinical and radiological assessment in the trauma clinics. The minimum follow up was 12 months.

Results: Out of 112 patients, 90 met the inclusion criteria. Group A consisted of 48 and group B of 42 patients. The mean age in group A was 24.5 years (18 – 41) and in group B 78.3 years (65 – 93). The mean ISS was 13.3 (9 – 32) and 9.07 (9–10) respectively, (p> 0.05). According to OTA fracture classification in group A there were 16 type 32A, 19 type 32B and 13 type 32C fractures, whereas in group B there were 25 type 32A, 15 type 32B and 2 type 32C fractures respectively. In 96% of patients in group A, a Singh score of 5 or 6 was assigned, whereas 85.5% of group B patients had a Singh score of 4 or less, indicating the presence of installed osteoporosis. Overall, the incidence of complications was similar among the studied groups. Delayed union occurred in 6 patients of group B and in 1 patient of group A (P=0.113). All fractures eventually progressed to union without further intervention. In group A the mean time to union was 15.73±0.52 weeks (7–22) and in group B 19.45±1.5 weeks (10–52) from surgery (P=0.0156).

Conclusion and Significance: This study indicates that fracture healing of nailed femoral shaft fractures is significantly delayed in older osteoporotic patients. Further studies are mandatory to clarify the exact mechanism of osteoporosis in the fracture healing response and the possible future therapeutic strategies.

Failure of fixation is a common problem in the treatment of osteoporotic fractures around the hip. The reinforcement of bone stock or of fixation of the implant may be a solution. Our study assesses the existing evidence for the use of bone substitutes in the management of these fractures in osteoporotic patients. Relevant publications were retrieved through Medline research and further scrutinised. Of 411 studies identified, 22 met the inclusion criteria, comprising 12 experimental and ten clinical reports. The clinical studies were evaluated with regard to their level of evidence. Only four were prospective and randomised.

Polymethylmethacrylate and calcium-phosphate cements increased the primary stability of the implant-bone construct in all experimental and clinical studies, although there was considerable variation in the design of the studies. In randomised, controlled studies, augmentation of intracapsular fractures of the neck of the femur with calcium-phosphate cement was associated with poor long-term results. There was a lack of data on the long-term outcome for trochanteric fractures. Because there were only a few, randomised, controlled studies, there is currently poor evidence for the use of bone cement in the treatment of fractures of the hip.