Nano-Hydroxyapatite Bone Substitute Functionalized with Bone Active Molecules for Enhanced Cranial Bone Regeneration

The aim of this study was to synthesize and characterize a nano-hydroxyapatite (nHAP) and calcium sulfate bone substitute (NC) for cranioplasty. The NC was functionalized with low concentrations of bone morphogenetic protein-2 (BMP-2) and zoledronic acid (ZA) and characterized both in vitro and in vivo. In vitro studies included MTT, ALP assays, and fluorescent staining of Saos-2 (human osteoblasts) and MC3T3-E1 (murine preosteoblasts) cells cultured on NC. An in vivo study divided 20 male Wistar rats into four groups: control (defect only), NC, NC + ZA, and NC + ZA + rhBMP-2. The materials were implanted in an 8.5 mm critical size defect in the calvarium for 12 weeks. Micro-CT quantitative analysis was carried out in vivo at 8 weeks and ex vivo after 12 weeks. Mineralization was highest in the NC + ZA + rhBMP-2 group (13.0 ± 2.8 mm³) compared to the NC + ZA group (9.0 ± 3.2 mm³), NC group (6.4 ± 1.9 mm³), and control group (3.4 ± 1.0 mm³) after 12 weeks. Histological and spectroscopic analysis of the defect site provided a qualitative confirmation of neo-bone, which was in agreement with the micro-CT results. In conclusion, NC can be used as a carrier for bioactive molecules, and functionalization with rhBMP-2 and ZA in low doses enhances bone regeneration.

The masquelet induced membrane technique with BMP and a synthetic scaffold can heal a rat femoral critical size defect

Long bone defects can be managed by the induced membrane technique together with autologous bone graft. However, graft harvest is associated with donor site morbidity. This study investigates if a tricalcium phosphate hydroxyapatite scaffold can be used alone or in combination with bone active drugs to improve healing. Sprague Dawley rats (n = 40) were randomized into four groups. (A) scaffold, (B) BMP-7, (C) BMP-7 + scaffold, and (D) BMP-7 + scaffold + systemic bisphosphonate at 2 weeks. Locked femoral nailing was followed by 6 mm segment removal and implantation of an epoxy spacer. At 4 weeks, the spacers were removed and the defects grafted. Eleven weeks later, the bones were explanted for evaluation with radiography, manual assessment, micro-CT, histology, and Fourier Transform Infrared spectroscopy (FTIR). Isolated scaffolds (A) did not heal any defects, whereas the other treatments led to healing in 7/10 (B), 10/10 (C), and 9/10 (D) rats. Group D had greater volume of highly mineralized bone (p < 0.01) and higher bone volume fraction (p < 0.01) compared to all other groups. A synthetic scaffold + BMP-7 combined with a bisphosphonate improved the callus properties in a rat femoral critical size defect, compared to both BMP-7 and scaffold alone or the two combined.

Intermittent PTH(1-34) does not increase union rates in open rat femoral fractures and exhibits attenuated anabolic effects compared to closed fractures

Intermittent Parathyroid Hormone (PTH)((1-34)) has an established place in osteoporosis treatment, but also shows promising results in models of bone repair. Previous studies have been dominated by closed fracture models, where union is certain. One of the major clinical needs for anabolic therapies is the treatment of open and high energy fractures at risk of non-union. In the present study we therefore compared PTH((1-34)) treatment in models of both open and closed fractures. 108 male Wistar rats were randomly assigned to undergo standardized closed fractures or open osteotomies with periosteal stripping. 27 rats in each group were treated s.c. with PTH((1-34)) at a dose of 50 mug/kg 5 days a week, the other 27 receiving saline. Specimens were harvested at 6 weeks for mechanical testing (n=17) or histological analysis (n=10). In closed fractures, union by any definition was 100% in both PTH((1-34)) and saline groups at 6 weeks. In open fractures, the union rate was significantly lower (p<0.05), regardless of treatment. In open fractures the mechanically defined union rate was 10/16 (63%) in saline and 11/17 (65%) in PTH((1-34)) treated fractures. By histology, the union rate was 3/9 (33%) with saline and 5/10 (50%) with PTH((1-34)). Radiological union was seen in 13/25 (52%) for saline and 15/26 (58%) with PTH((1-34)). Open fractures were associated with decreases in bone mineral content (BMC) and volumetric bone mineral density (vBMD) on quantitative computerized tomography (QCT) analysis compared to closed fractures. PTH((1-34)) treatment in both models led to significant increases in callus BMC and volume as well as trabecular bone volume/total volume (BV/TV), as assessed histologically (p<0.01). In closed fractures, PTH((1-34)) had a robust effect on callus size and strength, with a 60% increase in peak torque (p<0.05). In the open fractures that united and could be tested, PTH((1-34)) treatment also increased peak torque by 49% compared to saline (p<0.05). In conclusion, intermittent PTH((1-34)) produced significant increases in callus size and strength in closed fractures, but failed to increase the rate of union in an open fracture model. In the open fractures that did unite, a muted response to PTH was seen compared to closed fractures. Further research is required to determine if PTH((1-34)) is an appropriate anabolic treatment for open fractures.

Open reduction and internal fixation compared to closed reduction and external fixation in distal radial fractures: a randomized study of 50 patients

BACKGROUND AND PURPOSE

In unstable distal radial fractures that are impossible to reduce or to maintain in reduced position, the treatment of choice is operation. The type of operation and the choice of implant, however, is a matter of discussion. Our aim was to investigate whether open reduction and internal fixation would produce a better result than traditional external fixation.

METHODS

50 patients with an unstable or comminute distal radius fracture were randomized to either closed reduction and bridging external fixation, or open reduction and internal fixation using the TriMed system. The primary outcome parameter was grip strength, but the patients were followed for 1 year with objective clinical assessment, subjective outcome using DASH, and radiographic examination.

RESULTS

At 1 year postoperatively, grip strength was 90% (SD 16) of the uninjured side in the internal fixation group and 78% (17) in the external fixation group. Pronation/supination was 150 degrees (15) in the internal fixation group and 136 degrees (20) in the external fixation group at 1 year. There were no differences in DASH scores or in radiographic parameters. 5 patients in the external fixation group were reoperated due to malunion, as compared to 1 in the internal fixation group. 7 other cases were classified as radiographic malunion: 5 in the external fixation group and 2 in the internal fixation group.

INTERPRETATION

Internal fixation gave better grip strength and a better range of motion at 1 year, and tended to have less malunions than external fixation. No difference could be found regarding subjective outcome.

Hemi-hamate osteochondral transplantation in proximal interphalangeal dorsal fracture dislocations: a minimum 4 year follow-up in eight patients

Fracture dislocations of the PIP joint are challenging to treat. In hemi-hamate arthroplasty, the palmar lip joint surface is reconstructed using an osteochondral graft from the hamate and the immediate stability permits early movement. In the long term, collapse of non-vascularized osteochondral grafts might lead to degenerative arthritis. We examined the radiographic result after a minimum of 4 years with special reference to the development of osteoarthritis and its relation to clinical symptoms in eight patients, mean age 49 (25-66) years. After a mean of 60 (48-69) months, the arc of motion was 67° (45°-95°) at the PIP joint and grip strength was 91% of the uninjured side. The visual analogue score for pain (0-100) was 10 (0-70) mm. Severe arthritis (grade IV) was found in two and mild arthritis (grade II) in another two patients, but only one of these four cases had troublesome pain. The hemi-hamate technique is an attractive alternative to other treatment options, but some cases develop osteoarthritis in the medium term.

The natural course of traumatic triangular fibrocartilage complex tears in distal radial fractures: a 13-15 year follow-up of arthroscopically diagnosed but untreated injuries

PURPOSE

To evaluate the long-term results of a prospective, longitudinal case series of untreated, traumatic triangular fibrocartilage complex (TFCC) tears found in displaced distal radial fractures.

METHODS

Between 1995 and 1997, 51 patients (24 men, 27 women; age, 20-57 y) with a displaced distal radius fracture had wrist arthroscopy to identify associated injuries. Forty-three patients had complete or partial tears of the TFCC, which were not treated. All patients were contacted in 2010, 13-15 years after the injury. One patient had had a TFCC reattachment due to painful distal radioulnar joint instability and was excluded. Thirty-eight patients returned for a radiographic and clinical follow-up that recorded strength, distal radioulnar joint laxity, range of motion, pain scale score, and subjective and objective outcome scores.

RESULTS

After 13-15 years, 17/38 patients were lax in the distal radioulnar joint. The mean grip strength was worse in the patients with a lax distal radioulnar joint (83%, SD 15 of the contralateral side vs 103%, SD 33). The median Gartland and Werley score was 5 (good; range, 0-15) in the lax group compared to 1 (excellent; range, 0-9) in the non-lax group, and the median Disabilities of the Arm, Shoulder, and Hand scores were 14 (range, 0-59) and 5 (range, 0-70) respectively.

CONCLUSIONS

In this 13-15 year, prospective, longitudinal outcome study of the natural course of TFCC tears associated with distal radius fracture, only 1 patient had been operated on for painful instability since the injury. The subjective and objective results did not provide evidence that a TFCC injury would influence the long-term outcome. However, trends were found and, by speculation, the low number of patients in the series and the risk for a type II error could be the cause of absent statistically significance. Larger, preferably prospective, randomized studies are needed to find out whether a more aggressive treatment is beneficial.

TYPE OF STUDY/LEVEL OF EVIDENCE

Diagnostic I.

Osteotomy of distal radius fracture malunion using a fast remodeling bone substitute consisting of calcium sulphate and calcium phosphate

Malunion after a distal radius fracture can be treated with an osteotomy of the distal radius. Autologous iliac crest bone graft is often used to fill the gap, but the procedure is associated with donor site morbidity. In this study a novel fast resorbing biphasic bone substitute consisting of a mixture of calcium sulphate and calcium phosphate is used (Cerament BoneSupport AB, Sweden). Fifteen consecutive patients, with a mean age of 52 (27-71) years were included. All had a malunion after a distal radius fracture and underwent an osteotomy. A fragment specific fixation system, TriMed (TriMed, Valencia, CA), consisting of a Buttress Pin and a Radial Pin Plate were used for fixation and a calcium sulphate and calcium phosphate mixture as bone substitute. The patients were followed for 1 year. Grip strength increased from 61 (28-93)% of the contralateral hand to 85 (58-109)%, p < 0.001. DASH scores decreased from 37 (22-61) to 24 (2-49) p = 0.003. Radiographically all osteotomies healed. An increase of ulnar variance was noted during healing from 1.8 mm immediately postoperatively to 2.6 mm at final follow up. Osteotomy can increase grip strength and decease disability after a malunited fracture. In the present series the bone substitute was replaced by bone, but a minor loss of the achieved radiographic correction was noted in some patients during osteotomy healing. A more rigid fixation may improve the radiographic outcome with this kind of bone substitute.

Corroboration of mechanobiological simulations of tissue differentiation in an in vivo bone chamber using a lattice-modeling approach

It is well established that the mechanical environment modulates tissue differentiation, and a number of mechanoregulatory theories for describing the process have been proposed. In this study, simulations of an in vivo bone chamber experiment were performed that allowed direct comparison with experimental data. A mechanoregulation theory for mesenchymal stem cell differentiation based on a combination of fluid flow and shear strain (computed using finite element analysis) was implemented to predict tissue differentiation inside mechanically controlled bone chambers inserted into rat tibae. To simulate cell activity, a lattice approach with stochastic cell migration, proliferation, and selected differentiation was adopted; because of its stochastic nature, each run of the simulation gave a somewhat different result. Simulations predicted the load-dependency of the tissue differentiation inside the chamber and a qualitative agreement with histological data; however, the full variability found between specimens in the experiment could not be predicted by the mechanoregulation algorithm. This result raises the question whether tissue differentiation predictions can be linked to genetic variability in animal populations.

Augmentation of autologous bone graft by a combination of bone morphogenic protein and bisphosphonate increased both callus volume and strength

BACKGROUND AND PURPOSE

Bone morphogenic proteins (BMPs) can be used in non-unions to replace autograft. BMPs induce osteoblasts and (less well known) also osteoclasts, which can in turn be controlled by a bisphosphonate. In the present study, our aim was to improve the biological effect of autologous bone graft by adding an anabolic BMP, with or without bisphosphonates, in an open-fracture model prone to non-union.

METHODS

Rat femurs were osteotomized and fixed with an intramedullary K-wire. Autograft was placed at the osteotomy, mixed with either saline or BMP-7. After 2 weeks, the rats had a single injection of saline or of a bisphosphonate (zoledronate). The rats were killed after 6 weeks and the femurs were evaluated by radiography, micro-CT, histology, and 3-point bending test.

RESULTS

All fractures healed. The callus volume was doubled in the BMP-treated femurs (p < 0.01) and increased almost 4-fold in the femurs treated with both BMP and systemic zoledronate (p < 0.01) compared to autograft. In mechanical testing, the autograft group reached approximately half the strength of the contralateral, non-osteotomized femur (p < 0.001). By adding BMP to the autograft, the strength was doubled (p < 0.001) and with both BMP and systemic zoledronate, the strength was increased 4-fold (p < 0.001) compared to autograft alone.

INTERPRETATION

The combination of BMP and bisphosphonate as an adjunct to autograft is superior to autograft alone or combined with BMP. The combination may prove valuable in the treatment of non-unions.

Nonoperative treatment of Achilles tendon rupture: 196 consecutive patients with a 7% re-rupture rate

BACKGROUND

The best treatment for acute Achilles tendon rupture is unknown.

PATIENTS AND METHODS

We assessed the outcome of nonoperative treatment in 196 consecutive individuals with an acute total Achilles tendon rupture who were followed until healing. The mean duration of treatment in cast or orthosis was 8 weeks. After 4 years, a questionnaire was sent to all patients who were still alive (182) to supplement and confirm the retrospective data. The questionnaire was completed by 176/182 patients (97%).

RESULTS

The re-rupture frequency was 7% (n = 14). 7 patients suffered other complications (7 deep venous thrombosis and 1 pulmonary embolism). At follow-up, 62% of the patients reported full recovery.

INTERPRETATION

The low re-rupture rate after nonoperative treatment challenges the claim in recent studies that acute rupture of the Achilles tendon should be operated.

A combination of bisphosphonate and BMP additives in impacted bone allografts

OP-1 increases bone ingrowth distance of new bone into allografts (Tägil et al. 2000), but the bone density after incorporation may be reduced by an increase in resorption (Höistner et al. 2000). Bisphosphonates inactivate osteoclasts and can be used to increase allograft bone density after incorporation (Aspenberg and Astrand 2002). A combination of locally-applied bisphosphonate and OP-1 in the graft could therefore be expected to increase both new bone ingrowth and density. We tested this by using a rat bone chamber model. OP-1 alone increased the ingrowth distance of bone. Clodronate increased final bone density greatly, but reduced the ingrowth distance of new bone into grafts that were extremely impacted. This reduction was improved by adding OP-1. Regardless of graft density, combinations of OP-1 and clodronate included a high final bone density, but the ingrowth distances were shorter than with OP-1 alone. These data indicate that new bone and tissue ingrowth into a compacted graft depends on resorption and that resorption is a prerequisite for the stimulating effect of OP-1 in this experimental set-up. Although the problems associated with the use of OP-1 in impaction grafting may be solved by adding a bisphosphonate, some of the benefits of OP-1 can be lost.

Outcomes of proximal interphalangeal joint pyrocarbon implants

PURPOSE

To prospectively register and report the hand function and occupational performance of patients with proximal interphalangeal joint-pyrocarbon arthroplasty, using both objective tests and subjective outcome instruments.

METHODS

From 2004 to 2008, 53 joints in 43 patients were reconstructed with a proximal interphalangeal joint-pyrocarbon prosthesis. The patients underwent a rehabilitation program allowing early motion with an extension stop to limit hyperextension. Range of motion, grip strength, and pain (Visual Analog Scale [VAS]) were recorded and the subjective outcome was evaluated using Canadian Occupational Performance Measure (COPM) and Disabilities of the Arm, Shoulder, and Hand score.

RESULTS

Seven patients were reoperated on (2 infections, 2 arthrodesis, 2 tenolysis, and 1 hyperextension). Pain (VAS) at rest improved from 3.1 cm preoperatively to 0.4 cm (p < .001) and pain (VAS) at activity from 6.2 to 2.0 cm (p < .001) at the latest follow-up (mean, 24 months; minimum, 12 months [+/- 2 weeks]). Disabilities of the Arm, Shoulder, and Hand score improved from a median of 39 to 29 (p = .026). The COPM subjective measurement of occupational performance, improved from a median of 4.6 preoperatively to 5.9 (p = .013) at the latest follow-up, and the COPM, measurement of satisfaction improved from a median of 3.8 to 5.9 (p = .002). Range of motion and grip strength were unchanged.

CONCLUSIONS

All patients reported decreased pain, and although we found no improvement in range of motion and grip strength, one third of patients reported a clinically significant improvement in occupational performance and satisfaction. A total of 13% of the joints required a secondary surgical procedure.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Swanson versus APL arthroplasty in the treatment of osteoarthritis of the trapeziometacarpal joint: a prospective and randomized study in 26 patients

Twenty-six patients were operated because of osteo-arthritis of the trapeziometacarpal joint. After excision of the trapezium, they were randomized to receive either a Swanson silicone trapezium implant or a tendon interposition arthroplasty using a strip of the abductor pollicis longus tendon (APL). No infection or clinical silicone synovitis occurred and no major radiographic cyst formation was found. Two endoprostheses dislocated early. All 13 patients in the Swanson group and 11 of the 13 in the APL group were subjectively satisfied at 2-5 year (mean, 43 months) follow-up. All patients were free of pain at rest and at light work, but half of the patients in each group still experienced pain with heavy work. Thumb pinch strength and range of motion were not significantly different in the two groups. The trapezial space decreased both with load and length of follow-up in both groups. Five endoprostheses subluxed during stressed pinch. In conclusion, both methods gave good, but not complete, pain relief and neither produced better results than the other in the short term.

Characterising bone material composition and structure in the ovariectomized (OVX) rat model of osteoporosis

The ovariectomized (OVX) rat model is well established in investigations of osteoporosis and osteoporotic therapies. Advent of techniques such as Fourier-transform infrared (FTIR) spectroscopy and small angle X-ray scattering (SAXS) facilitate characterization of bone composition and mineral structure, respectively, which are key determinants of bone strength. Limited publications exist on the implementation of these techniques in the OVX rat model. At 12 weeks of age, female Sprague-Dawley rats were either sham-operated (n = 6) or ovariectomized (n = 6) and sacrificed 18 weeks later. L2 lumbar vertebrae and proximal tibiae were assessed by µCT, FTIR and SAXS. Presence of extensive trabecular deterioration in the µCT data confirmed the onset of osteoporosis. FTIR compositional parameters were determined including measures of degree of mineralization, crystallinity, collagen maturity and acid phosphate content. Mineral crystal thickness was determined from the SAXS data using two approaches available in literature. Compositionally, a decline in the heterogeneity of acid phosphate content was observed while measures of crystallinity and collagen maturity remained unaltered. Using an iterative curve fitting method, OVX-induced increases in the mineral crystal thickness of 3.8 and 7.8 % (p < 0.05) were noted in the trabecular of the vertebra and tibia, respectively. In conclusion, implementation of FTIR and SAXS techniques in the OVX rat model, identified no significant compositional changes while substantiating thickening of the mineral crystals as a general structural feature of OVX-induced osteoporosis in rats.

Investigating the synergistic efficacy of BMP-7 and zoledronate on bone allografts using an open rat osteotomy model

Bone grafts are well-established in the treatment of fracture non-unions but union is still not always achieved. Harvesting autograft is associated with donor site morbidity and the available amount of bone is limited. Allograft is more easily obtained and available in greater quantities but lacks the osteoinductive characteristics of autograft. We have previously shown a synergistic effect of bone morphogenetic protein (BMP-7), systemic bisphosphonates and autograft. In the present study we hypothesized that the combination of allograft+BMP-7+systemic ZA is more effective than autograft alone, which is currently the most frequently used aid in augmenting fracture and non-union healing. Femoral osteotomies were performed on 82 male Sprague Dawley rats and fixed with intramedullary K-wires. The rats were randomized into 7 groups: (i) saline, (ii) autograft, (iii) allograft, (iv) allograft+BMP-7, (v) autograft+zoledronate (ZA), (vi) allograft+ZA and (vii) allograft+BMP-7+ZA. Autografts were harvested from the contralateral tibia. Allografts were obtained from donor rats and frozen. BMP-7 was administered locally in the form of a putty placed circumferentially around the osteotomy. At 2 weeks, the rats were injected with a single dose of either saline or ZA. The rats were sacrificed at 6 weeks and the femurs were evaluated using radiography, histology, μCT and three-point bending tests. Complete radiological healing was seen in all rats in the BMP-7 groups. The callus volume was larger and the calluses were denser with allograft+BMP-7+ZA than in all other groups (μCT, p<0.001). Mechanical testing yielded a substantially higher peak force with the allograft+BMP-7+ZA combination than all other groups (p<0.01, p<0.001). This was further reinforced in the 59% increase in the peak force observed in the osteotomized femurs of the allograft+BMP-7+ZA group compared to the control femurs (p<0.01), whereas significant decreases of 22-27% were observed in the saline or bone-graft alone groups (p<0.01, p<0.05). Thus our results suggest that allograft combined with the anabolic effect of BMP-7 and the anti-catabolic effect of zoledronate is more efficient than autograft alone.

Cartilage induction by controlled mechanical stimulation in vivo

To study mechanical control of tissue differentiation, we designed a new version of the previously described bone conduction chamber. The bone conduction chamber consists of a cylindrical titanium chamber for implantation in the rat tibia. It has tissue ingrowth openings at one end, located subcortically, and the other end protrudes into the subcutis. The newly developed load chamber has a mobile piston so that an external compressive load can be transferred to the tissue within the chamber. Sprague-Dawley rats had a regular bone conduction chamber implanted in one tibia and a load chamber implanted in the other. Mesenchymal tissue was allowed to grow into the chamber for 3 weeks before the mechanical loading was started. Thereafter, twice a day, 20 cycles of compressive load were applied with a frequency of 0.17 Hz to the load chamber. This was estimated to produce a compressive hydrostatic stress of 2 MPa. The chambers, harvested after 7 weeks of loading, all contained newly formed bone. The bone ingrowth distance into the chamber was decreased in the loaded specimens compared with the contralateral unloaded controls (p = 0.01). Instead, cartilage was found in the loaded chambers next to the piston. Beneath the cartilage was a dense bone plate under which a marrow cavity had formed. No cartilage was found in the unloaded controls, but the architecture of the bone and marrow cavity was similar to that of the loaded specimens. We conclude that this model allows load to be transmitted onto the ingrowing tissue and that the load parameters used cause this tissue to differentiate into cartilage close to the piston.

The composite of hydroxyapatite and calcium sulphate: a review of preclinical evaluation and clinical applications

Recent publications have shown that the combination of α-calcium sulfate hemihydrate, the densest form of hydrates and hydroxyapatite (HA) particles gives good clinical outcome in various applications. It has large potential as bone substitute since the material transforms to bone throughout the entire volume and not only by creeping substitution, from the surface toward the inside. Release of important proteins for osteogenesis has been observed around implanted material and is speculated to be due to fast dissolution of the calcium sulfate phase in combination with the osteoconductive and bioactive nature of HA. In diabetic foot infection, the osteoconductive HA/calcium sulfate material has been successfully used loaded with antibiotics and since it is injectable, the application is minimally invasive, easy and precise. It is a bone substitute for the future.

A facile one-stage treatment of critical bone defects using a calcium sulfate/hydroxyapatite biomaterial providing spatiotemporal delivery of bone morphogenic protein-2 and zoledronic acid

Bone morphogenic proteins (BMPs) are the only true osteoinductive molecules. Despite being tremendously potent, their clinical use has been limited for reasons including supraphysiological doses, suboptimal delivery systems, and the pro-osteoclast effect of BMPs. Efforts to achieve spatially controlled bone formation using BMPs are being made. We demonstrate that a carrier consisting of a powder of calcium sulfate/hydroxyapatite (CaS/HA) mixed with bone active molecules provides an efficient drug delivery platform for critical femoral defect healing in rats. The bone-active molecules were composed of osteoinductive rhBMP-2 and the bisphosphonate, and zoledronic acid (ZA) was chosen to overcome BMP-2-induced bone resorption. It was demonstrated that delivery of rhBMP-2 was necessary for critical defect healing and restoration of mechanical properties, but codelivery of BMP-2 and ZA led to denser and stronger fracture calluses. Together, the CaS/HA biomaterial with rhBMP-2 and/or ZA can potentially be used as an off-the-shelf alternative to autograft bone.

Fibrous tissue armoring increases the mechanical strength of an impacted bone graft

Impacted, morselized bone allografts are used with good clinical results in revision of hip prostheses with loosening and osteolysis. The impacted bone graft appears radiographically to remodel, but histological analyses have shown a heterogeneous picture with a mixture of living and dead bone. Thus, complete remodeling of the graft may be neither a prerequisite nor a cause of the good clinical results. The present study concerns the mechanical effect of the mere armoring of the bone graft by ingrowing fibrous tissue. We compared the compression strength of freshly-impacted grafts to grafts that had been inserted into a bone chamber and thus were penetrated by fibrous tissue growing in between the graft trabeculae. The compressive strength was doubled after 4 weeks of fibrous ingrowth. We conclude that the mechanical properties of an impacted graft are enhanced by armoring with ingrowing fibrous tissue. Strengthening of the parts of the impacted grafts which have not yet remodeled, would be clinically relevant for the outcome of the operation, since these parts are at high stress during the whole remodeling period. Complete osseous remodeling may not be necessary to obtain a good clinical result with a morselized impacted graft.

The natural course of spontaneous osteonecrosis of the knee (SPONK): a 1- to 27-year follow-up of 40 patients

BACKGROUND AND PURPOSE

Spontaneous osteonecrosis of the knee (SPONK) is a painful lesion in the elderly, frequently leading to osteoarthritis and subsequent knee surgery. We evaluated the natural course and long-term consequences of SPONK in terms of need for major knee surgery.

METHODS

Between 1982 and 1988, 40 consecutive patients were diagnosed with SPONK. The short-term outcome has been reported previously (1991). After 1-7 years, 10 patients had a good radiographic outcome and 30 were considered failures, developing osteoarthritis. In 2012, all 40 of the patients were matched with the Swedish Knee Arthroplasty Register (SKAR) and their medical records were reviewed to evaluate the long-term need for major knee surgery.

RESULTS

At the 2012 review, 33 of the 40 patients had died. The mean follow-up time from diagnosis to surgery, death, or end of study was 9 (1-27) years. 17 of 40 patients had had major knee surgery with either arthroplasty (15) or osteotomy (2). All operated patients but 1 were in the radiographic failure group and had developed osteoarthritis in the study from 1991. 6 of 7 patients with large lesions (> 40% of the AP radiographic view of the condyle) at the time of the diagnosis were operated. None of the 10 patients with a lesion of less than 20% were ever operated.

INTERPRETATION

It appears that the size of the osteonecrotic lesion can be used to predict the outcome. Patients showing early signs of osteoarthritis or with a large osteonecrosis have a high risk of later major knee surgery.

Arthroscopically diagnosed scapholunate ligament injuries associated with distal radial fractures: a 13- to 15-year follow-up

PURPOSE

To evaluate the natural history of untreated complete or partial scapholunate (SL) ligament tears associated with displaced distal radius fractures.

METHODS

Between 1995 and 1997, 51 consecutive patients aged < 60 years with displaced distal radius fractures were examined arthroscopically to assess for concomitant soft tissue injuries. Thirty-two of 51 patients had an SL ligament tear, 10 had a complete tear (Lindau grade 3), and 22 had a partial tear (Lindau grades 1 and 2). Thirty-two patients had AO type-C fractures, 3 had type-B fractures, and 16 had type-A fractures. In 2010, 47 of the 51 patients were still alive, and they were invited for an interview, clinical examination, and radiography.

RESULTS

Thirty-eight of the 51 original patients participated in the long-term follow-up. Mean grip strength was 83% relative to the contralateral hand in patients with a complete tear, as compared with 92% in patients with partial or no SL tears (nonsignificant). Median Disabilities of the Arm, Shoulder, and Hand questionnaire score was 2 (range, 0‒55) for complete SL tears, compared with 9 (range, 0‒70) for the others (nonsignificant). No differences were found regarding visual analog scale pain or wrist motion/forearm rotation. None of the patients developed a static SL dissociation or a SL advanced collapse wrist.

CONCLUSIONS

No major differences were found in the subjective, objective, or radiographic outcome after a complete (grade 3) or partial (grade 1 or 2) SL untreated tear associated with displaced distal radius fracture. It should be noted that none of the patients had a grade 4 SL tear, which may have a different outcome.

TYPE OF STUDY/LEVEL OF EVIDENCE

Prognostic II.

Reduced expression of BMP-3 due to mechanical loading: a link between mechanical stimuli and tissue differentiation

Mechanical signaling and BMP expression appear to be involved in controlling the differentiation of cartilage in fracture repair, but the connection between mechanics and BMP signaling is not known. In this study of rats, we used a bone chamber to see how BMP gene expression was changed by a mechanical loading regime that induces cartilage formation in this model. We compared the still undifferentiated tissue in loaded and unloaded chambers in the same rat regarding the expression of TGFbeta-1, BMP-2, 3, 4, 5, 6, 7, CDMP-1, 2 and ALK-2 and 3 by using RT-PCR normalized against GAPDH. We found expression of TGFbeta-1, BMP-2 and 4 in all specimens, and BMP 5-7 and CDMPs in none. 1 week after loading started, BMP-3 was strongly expressed in the unloaded control specimens in 7 of 8 animals, but detectable in only I of the contralateral loaded ones. After 2 weeks of loading, the BMP-3 expression pattern was less clear, but with both time groups taken together, there was still less BMP-3 expression on the loaded side in 9 rats, more in 1 and no difference in 5 (p = 0.01). ALK-2 at 1 week was expressed in all specimens expressing BMP-3 and in none of the others. At 2 weeks, ALK-2 was expressed in all specimens. Thus, a loading regime, known to induce cartilage in this model, caused down-regulation of BMP-3 and ALK-2. The results are consistent with the view that BMP-3 inhibits differentiation, as recently described. This role appears to be linked to the ALK-2 receptor. Most importantly, the results indicate a link between mechanical signaling and BMP expression such that mechanically-induced down-regulation of the inhibiting BMP-3 enabled the induction of cartilage.