Hermann J. Bail

Hamstring Tendon Fixation Using Interference Screws: A Biomechanical Study in Calf Tibial Bone

It has recently been shown that graft fixation close to the ACL insertion site is optimal in order to increase anterior knee stability. Hamstring tendon fixation using interference screws offers this possibility and a round threaded titanium interference screw has been previously developed. The use of a round threaded biodegradable interference screw may be equivalent. In addition, to increase initial fixation strength, graft harvest with a distally attached bone plug may be advantageous, but biomechanical data do not exist. This study compares the initial pullout force, stiffness of fixation, and failure modes of three strand semitendinosus grafts in 36 proximal calf tibiae using either biodegradable poly-(D,L-lactide) (Sysorb; Sulzer Orthopaedics Ltd, Münsingen, Switzerland) or round threaded titanium (RCI; Smith & Nephew DonJoy, Carlsbad, CA) interference screws, harvested either without (biodegradable: group I, titanium III) or with (biodegradable: group II, titanium: group IV) attached tibial bone plugs. Maximum pullout force in group I (507 +/- 93 N) was significantly higher than in group III (419 +/- 77 N). Pullout force of bone plug fixation was significantly higher than that of direct tendon fixation (717 +/- 90 N in group II and 602 +/- 117 N in group IV). Pullout force of biodegradable fixation was significantly higher in both settings. These results indicate that initial pullout force of hamstring-tendon graft interference screw fixation can be increased by using a biodegradable interference screw. In addition, initial pullout force of hamstring-tendon graft fixation with an interference screw can be greatly increased by harvesting the graft with its distally attached tibial bone plug.

The new proximal femoral nail antirotation (PFNA®) in daily practice: Results of a multicentre clinical study

The treatment of unstable trochanteric femoral fractures is still challenging. The ideal implant should be easy to handle, allow for immediate full weight-bearing postoperatively and should have sufficient purchase in the femoral head/neck-fragment to limit cut-outs due to varus-deviation and rotation. The proximal femoral nail antirotation (PFNA), designed by AO, is an intramedullary device with a helical blade rather than a screw for better purchase in the femoral head and was tested in a clinical study. Consecutive patients with unstable trochanteric fractures (AO-classification 31.A.2 and A.3 only) were included and followed for 1 year. Primary objectives were assessment of operative and postoperative complications, whereas secondary objectives included surgical details, general complications and final outcome measurements. In 11 European clinics, 315 patients were included and treated with a PFNA. Almost all fractures healed within 6 months. Fifty-six percent of the patients regained the pre-trauma mobility and 18% died within the follow-up period. Forty-six implant-related complications--leading to 28 unplanned re-operations--were recorded, with four acetabular penetrations (three of which were after a new fall on that hip) and seven ipsilateral femoral shaft fractures as the most serious ones. As the joint-penetrations did not resemble the cut-out seen with other implants it is concluded that the PFNA--due to its helical blade--possibly limits the effects of early rotation of the head/neck-fragment in unstable trochanteric fractures and therefore seems currently to be the optimal implant for the treatment of these fractures especially in osteoporotic bone.

Local application of growth factors (insulin-like growth factor-1 and transforming growth factor-β1) from a biodegradable poly(d,l-lactide) coating of osteosynthetic implants accelerates fracture healing in rats

In vitro and in vivo studies have demonstrated an osteoinductive effect of growth factors such as insulin-like growth factor-1 (IGF-1) and transforming growth factor-beta1 (TGF-beta1). However, for therapeutic use in fracture treatment, questions remain with regard to the local application of these proteins. A controlled, local release of growth factors from a biodegradable polylactide coating of osteosynthetic implants may have a stimulating effect on fracture healing. Such implants could stabilize the fracture and their bioactive surface could function simultaneously as a local drug-delivery system. Previous studies have demonstrated the high mechanical stability of an approximately 10-14-microm-thick poly(D,L-lactide) (PDLLA) coating on metallic implants, which can even withstand the process of intramedullary insertion. Following an initial peak, 80% of incorporated growth factors IGF-1 and TGF-beta1 were continuously released within 42 days. The effect of locally applied IGF-1 and TGF-beta1 from a biodegradable PDLLA coating of intramedullary implants on fracture healing was investigated in a rat model. Midshaft fractures of the right tibia of 5-month-old female Sprague-Dawley rats (n = 127) were stabilized with coated vs. uncoated titanium Kirschner wires. X-ray examinations and blood analyses were performed, and body weight and body temperature measurements were taken throughout the experimental period. After 28 and 42 days, respectively, tibiae were dissected for mechanical torsional testing and histomorphometrical analyses. X-rays demonstrated an almost completely consolidated fracture, biomechanical testing showed a significantly higher maximum load and torsional stiffness, and histological and histomorphometric analyses demonstrated progressed remodeling after 28 and 42 days in the group treated with growth factors as compared with controls. Interestingly, the PDLLA coating itself revealed a positive effect on fracture healing even without incorporated growth factors. No systemic changes of serum parameters, including IGF-1 and IGF binding proteins, and no differences in body weight and body temperature were observed within and between groups. These findings suggest that the local application of growth factors from a biodegradable PDLLA coating of osteosynthetic implants accelerates fracture healing significantly without systemic side effects.

Where should implants be anchored in the humeral head

To determine histomorphometric and bone strength distribution of the proximal humerus, analyses were done on 24 freshly harvested human cadaveric humeri. Median ages of 46 and 69 years were recorded respectively for the male group (n = 11; minimum, 34 years; maximum, 76 years) and the female group (n = 13; minimum, 46 years; maximum, 90 years). The humeral head was sliced into four equal horizontal levels (Levels 1–4). Five regions of interest were defined in each cutting plane: anterior, posterior, lateral, medial, and central. Histomorphometric analyses evaluated structural parameters (tissue volume to bone volume ratio, trabecular thickness), connectivity (number of nodes, node to node length), and trabecular orientation (mean bone length). The peak values of histomorphometric parameters and bone strength were identified for the cranial section and decreased caudally. The medial and dorsal aspects of the proximal humeral head were found to be the areas of highest bone strength. The trabecular network formed a pattern that connected the center of the gleaned cavity. The structural and connectivity parameters, bone strength, and trabecular orientation showed region- and level-related characteristics. Knowledge of distribution, microstructure, and quality of bone in the humeral head allows the remaining bone stock to be used effectively, even in elderly patients, with a minimally invasive approach and maximum mechanical stability.

Improvement of fracture healing by systemic administration of growth hormone and local application of insulin-like growth factor-1 and transforming growth factor-β1

Fracture healing is influenced by numerous hormones, growth factors, and cytokines. The systemic administration of growth hormone (GH) has shown to accelerate bone regeneration. Local application of growth factors, such as insulin-like growth factor-1 (IGF-1) and transforming growth factor-beta-1 (TGF-beta1), are known to stimulate bone metabolism. Until now, the exact local and systemic mechanisms that lead to improved bone regeneration remain unclear. In addition, the effect of systemic administration of GH as compared with locally delivered growth factors on fracture healing in rats is not known. A midshaft fracture of the right tibia of 5-month-old female Sprague-Dawley rats (n = 80) was intramedullary stabilized with IGF-1 and TGF-beta1 coated vs. uncoated titanium K-wires. The growth factors were incorporated in a poly(D,L-lactide) (PDLLA) coating and released continuously throughout the experiment. Recombinant species-specific (rat) GH was applied systemically (2 mg/kg body weight) by daily subcutaneous injection and compared with a placebo group. The healing process was radiologically monitored. Twenty-eight days after fracture biomechanical torsional testing was performed. The consolidation and callus composition, including quantification of cartilage and mineralized tissue, was traced in histomorphometrical investigations using an image analysis system. Both methods, the systemic administration of GH and the local application of growth factors, showed significant biomechanical and histological effects on fracture healing. The local growth factor application showed a stronger effect on fracture healing than the systemic GH injection. The combined application of both methods did not accelerate the effect on bone healing compared with the single application. It is therefore concluded that combining local and systemic stimulating methods does not provide further additive effects with regard to fracture healing.

Recombinant Growth Hormone Accelerates Bone Regenerate Consolidation in Distraction Osteogenesis

The purpose of the present study was to prove whether homologous GH has a stimulating effect on bone healing. Therefore, left tibiae of 30 micropigs were osteomized and distracted over an external fixator at the rate of 2 mm/day on each of 10 consecutive days. Animals were killed after a healing period of another 10 days. The treatment group received 100 microg of recombinant porcine growth hormone (rpGH) per kilogram of body weight per day. Serial torsional nondestructive biomechanical tests were performed in vivo using a newly developed measurement device. After killing, destructive torsional strength testing of the sites of distraction was performed. To determine the endocrine response to the administration of rpGH, serum levels of insulin-like growth factor-I (IGF-I) were determined. Nondestructive in vivo testing showed that torsional stiffness of the regenerate was significantly higher in the treatment group than in the control group. Final regenerate torsional failure load was 131% higher and ultimate torsional stiffness was 231% higher in the treatment group than in the control group. The mean serum level of IGF-I increased to 440% of preoperative basal level in the treatment group and remained unchanged in the control group. Our data indicate that systemic administration of recombinant homologous growth hormone greatly accelerates ossification of bone regenerate in distraction osteogenesis.

Differential regulation of blood vessel formation between standard and delayed bone healing

Blood vessel formation is a prerequisite for bone healing. In this study, we tested the hypothesis that a delay in bone healing is associated with an altered regulation of blood vessel formation. A tibial osteotomy was performed in two groups of sheep and stabilized with either a rigid external fixator leading to standard healing or with a highly rotationally unstable one leading to delayed healing. At days 4, 7, 9, 11, 14, 21, and 42 after surgery, total RNA was extracted from the callus. Gene expressions of vWF, an endothelial cell marker, and of several molecules related to blood vessel formation were studied by qPCR. Furthermore, histology was performed on fracture hematoma and callus sections. Histologically, the first blood vessels were detected at day 7 in both groups. mRNA expression levels of vWF, Ang1, Ang2, VEGF, CYR61, FGF2, MMP2, and TIMP1 were distinctly lower in the delayed compared to the standard healing group at several time points. Based on differential expression patterns, days 7 and 21 postoperatively were revealed to be essential time points for vascularization of the ovine fracture callus. This work demonstrates for the first time a differential regulation of blood vessel formation between standard and mechanically induced delayed healing in a sheep osteotomy model.

Insulin-like growth factor-1 and transforming growth factor-β1 accelerates osteotomy healing using polylactide-coated implants as a delivery system: a biomechanical and histological study in minipigs

Stimulation of bone healing and bone formation through local application of growth factors from implants may improve the clinical outcome in fracture treatment. Previous studies demonstrated a high mechanical stability of a thin poly(D,L-lactide) (PDLLA) coating on metallic implants that can withstand the process of intramedullary insertion. Following an initial peak, 80% of incorporated insulin-like growth factor-1 (IGF-1) and transforming growth factor-beta1 (TGF-beta1) were released continuously, within 42 days. The goal of the present study is evaluation of the coated implants on fracture healing in a large animal model. A midshaft osteotomy (1 mm gap) of the right tibia of Yucatan minipigs was stabilized with uncoated vs. coated titanium interlocking nails (5 mm). X-ray examinations and blood analyses (including IGF-1 and IGF-binding proteins) were performed, and body weight and body temperature were taken throughout the experiment. After 28 days, both tibiae were dissected for mechanical torsional testing and histomorphometric analyses. No differences were found in the blood analyses, body weight, or temperature due to the coating or the incorporated growth factors between the groups. X-ray examinations revealed a faster consolidation of the osteotomy in the growth factor-treated group. Biomechanical testing showed a significantly higher torsional stiffness and maximum load. Progressive remodeling was observed in the histological and histomorphometric analyses with a larger callus volume in the growth factor group compared with the control groups. We conclude that local application of growth factors from a biodegradable PDLLA coating of intramedullary implants accelerates bone healing in a large animal model without systemic side effects.

Humeral head necrosis rate at mid-term follow-up after open reduction and angular stable plate fixation for proximal humeral fractures

INTRODUCTION Short-term follow-up of angular stable fixation for proximal humeral fractures has been well documented in the literature. Longer follow-up series are difficult to find. However, especially regarding the risk of avascular humeral head necrosis longer follow-up series are high of clinical relevance. METHODS Forty-eight patients with a mean age of 66 years and treated with open reduction and angular stable internal fixation for proximal humeral fractures were followed up for a mean of 45 months. The clinical and radiographic follow-up (Constant Score (CS), age and gender related Constant Score (agCS), Constant Score in comparison to the contralateral side (%CS) and shoulder anterior-posterior and lateral view and axial view X-rays) was performed postoperatively. RESULTS Clinical results after 45 months showed a mean CS of 66.2+/-15.4 points with a mean agCS of 90.0+/-23.1%. Evaluation of the %CS showed 77.7+/-17.8%. %CS results showed no significant differences after 45 months in comparison to those obtained after 12 months. However, incidence of avascular necrosis of the humeral head doubled over the follow-up period from 4 cases at 12 months follow-up to 9 cases at final follow-up. CONCLUSION Results of open reduction and internal fixation with angular stable implants for proximal humeral fractures are reliable, however long-term complications such as avascular necrosis of the humeral head need to be evaluated further on since its incidence increases over the time.

Initial Fixation Strength of Modified Patellar Tendon Grafts for Anatomic Fixation in Anterior Cruciate Ligament Reconstruction

Recently it has been shown that anatomic tibial graft fixation in anterior cruciate ligament (ACL) reconstruction is preferable in order to increase isometry and knee stability. To facilitate anatomic patellar tendon graft fixation, customized graft length shortening is necessary. The purpose of this study was to compare the initial fixation strength of four different shortened patellar tendon grafts including three bone plug flip techniques and direct patellar tendon-to-bone interference fit fixation in a model with standardized bone density. Ninety calf tibial plateaus (22 to 24 weeks old) with adjacent patella and extensor ligaments were used. Tendon grafts were shortened by flipping the bone plug over the tendon leaving a tendon-tendon-bone (TTB) construct and, as the first modification in the opposite direction resulting in a tendon-bone-tendon (TBT) construct. The second modification consisted of the TBT construct with interference screw position at the lateral aspect of the bone plug (TBTlat). As the fourth modification the tendon graft was directly fixed (Tdirect) with an interference screw. In addition, a round-threaded titanium (RCI; Smith & Nephew DonJoy, Carlsbad, CA), a round-threaded biodegradable screw (Sysorb; Sulzer Orthopedics, Münsingen, Switzerland), and a conventional titanium interference screw (Arthrex Inc, Naples, FL) were compared. We found that TTB (mean 441 N for biodegradable screw, 357 N for RCI screw, 384 N for conventional screw) and TBT (mean 407 N for biodegradable screw, 204 N for RCI screw, 392 N for conventional screw) construct fixation achieves comparable fixation strength, although failure in the TTB was due to tendon strip off at its ligamentous insertion. The highest failure load was found in TBTlat fixation (mean 610 N for biodegradable screw, 479 N for RCI screw). Therefore, this technique should be recommended when using a tendon flip technique. The failure load for Tdirect fixation (mean 437 N for biodegradable screw, 364 N for RCI screw) was similar to that of TTB and TBT fixation, which may indicate that a patellar-tendon graft harvested without its patellar bone plug and directly fixed with an interference screw is equivalent to a flipped graft. This may additionally reduce harvest site morbidity and eliminates the risk of patellar fracture. The fixation strength of round-threaded biodegradable and conventional titanium interference screws was similar, whereas that of round-threaded titanium screws was significantly lower in the patellar tendon flip-techniques. However, it should be taken into consideration that round-threaded titanium screws are proposed for direct tendon-to-bone fixation.