Patient safety culture in an orthopaedic surgery centre in Denmark

INTRODUCTION

Measuring and developing patient safety culture (PSC) is a focal point in creating a highly reliable organisation, and patient safety is the cornerstone of quality healthcare. The purpose of this study was to describe PSC in an elective orthopaedic surgery centre in Denmark.

METHODS

A total of 445 healthcare workers were invited to participate. A cross-sectional study design using the Safety Attitudes Questionnaire (SAQ) was applied.

RESULTS

A total of 356 invitees (80%) answered the SAQ. The proportion of employees with a positive perception of the PSC was above the anticipated 60% threshold in five out of six dimensions. Perceptions of PSC varied by gender across four of six dimensions. Thus, significantly more female than male participants had a positive perception of the PSC. A significant variation was observed in the proportion of employees with a positive perception of PSC at the unit level except for teamwork climate and stress recognition.

CONCLUSIONS

This is the first Danish study of PSC in an elective orthopaedic surgical setting. Across dimensions, % positive were more favourable than reported in the international literature.

FUNDING

none.

TRIAL REGISTRATION

not relevant.

Inter-professional agreement and collaboration between extended scope physiotherapists and orthopaedic surgeons in an orthopaedic outpatient shoulder clinic - a mixed methods study

Background

Extended scope physiotherapists (ESP) are increasingly supplementing orthopaedic surgeons (OS) in diagnosing patients with musculoskeletal disorders. Studies have reported satisfactory diagnostic and treatment agreement between ESPs and OSs, but methodological study quality is generally low, and only few studies have evaluated inter-professional collaboration. Our aims were: 1) to evaluate agreement on diagnosis and treatment plan between ESPs and OSs examining patients with shoulder disorders, 2) to explore and evaluate their inter-professional collaboration.

Methods

In an orthopaedic outpatient shoulder clinic, 69 patients were examined independently twice on the same day by an ESP and an OS in random order. Primary and secondary diagnoses (nine categories) and treatment plan (five categories, combinations allowed) were registered by each professional and compared. Percentage of agreement and kappa-values were calculated.

Two semi-structured focus-group interviews were performed with ESPs and OSs, respectively. Interviews were based on the theoretical concept of Relational Coordination, encompassing seven dimensions of communication and relationship among professionals. A thematic analysis was conducted.

Results

Agreement on primary diagnosis was 62% (95% CI: [50; 73]). ESPs and OSs agreed on the combination of diagnoses in 79% (95% CI: [70; 89]) of the cases. Partial diagnostic agreement (one professional’s primary diagnosis was also registered as either primary or secondary diagnosis by the other) was 96% (95% CI: [91; 100]). Across treatment categories, agreement varied between 68% (95% CI: [57; 79]) and 100%. In 43% (95% CI: [31; 54]) of the cases, ESP and OS had full concordance between treatment categories chosen, while they agreed on at least one recommendation in 96% (95% CI: [91; 100]).

Positive statements of all dimensions of relational coordination were found. Three themes especially important in the inter-professional collaboration emerged: Close communication, equal and respectful relationship and professional skills.

Conclusions

In the majority of cases, the ESP and OS registered the same or partly the same diagnosis and treatment plan. Indications of a high relational coordination implying a good inter-professional collaboration were found. Our results support that ESPs and OSs can share the task of examining selected patients with shoulder disorders in an orthopaedic clinic.

Trial registration

ClinicalTrials.gov Identifier: NCT03343951. Registered 10 November 2017

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-020-03831-z.

Elbow Biomechanics, Radiocapitellar Joint Pressure, and Interosseous Membrane Strain Before and After Radial Head Arthroplasty

Complex radial head fracture and elbow instability can be treated with radial head arthroplasty. Good clinical results have been described after this surgical treatment. However, the revision and complication rate reported in the literature is concerning. This might be due to altered kinematics after radial head arthroplasty. Eight human native elbows were examined with dynamic radiostereometric analysis and compared with a radial head arthroplasty. Translations of the radial head in the x-, y-, and z-directions relative to the humerus and the ulna were measured. The radiocapitellar joint pressure was measured using a pressure sensor. The tension within the interosseous membrane was measured using a custom-made strain gauge. After radial head arthroplasty, the radial head was displaced approximately 1.8  mm medially and 1.4  mm distally at the starting point. During unloaded flexion motion the difference in all translations between the native radial head and the radial head arthroplasty was less than 1 mm (95% confidence interval [CI]  ±  0.5 mm) (p = 0.001). With loading the difference was less than 1.5  mm (95% CI  ± 1.5  mm) (p = 0.001). The mean difference in radiocapitellar joint contact pressure was less than 0.30 MPa (95% CI ± 0.40 MPa) (p = 0.001) during unloaded flexion motion. There were only submillimetre kinematic changes and small changes in joint pressure and interosseous membrane tension after the insertion of a radial head arthroplasty in an experimental setting. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:510-522, 2020.

High risk for revision after shoulder arthroplasty for failed osteosynthesis of proximal humeral fractures

Background and purpose - It is unclear whether previous osteosynthesis is a risk factor for inferior outcome following shoulder arthroplasty for a proximal humeral fracture. We used data from the Danish Shoulder Arthroplasty Registry (DSR) to examine this question. Patients and methods - All 285 patients treated with a shoulder arthroplasty after failed osteosynthesis of a proximal humeral fracture reported to DSR from 2006 to 2013 were included. Each case was matched with 2 controls (570) treated with a primary shoulder arthroplasty for an acute proximal humeral fracture. Patient reported outcome was assessed using the Western Ontario Osteoarthritis of the Shoulder index (WOOS) and the relative risk of revision was reported. Results - The mean WOOS was 46 (SD 25) for a shoulder arthroplasty after failed osteosynthesis and 52 (27) after a primary shoulder arthroplasty. The relative risk of revision for a shoulder arthroplasty after failed osteosynthesis was 2 with a primary arthroplasty for fracture as reference. In a separate analysis of patients treated by locking plate the mean WOOS was 46 (24), with a relative risk of revision at 1.5 with a primary arthroplasty as reference. Interpretation - Compared with primary arthroplasty for proximal humeral fracture, we found an inferior patient-reported outcome and a substantial risk of revision for patients treated with a shoulder arthroplasty after failed osteosynthesis for a proximal humeral fracture. The risk and burdens of additional surgery should be accounted for when deciding on the primary surgical procedure.

Do Bone Graft and Cracking of the Sclerotic Cavity Improve Fixation of Titanium and Hydroxyapatite-coated Revision Implants in an Animal Model?

BACKGROUND

We previously introduced a manual surgical technique that makes small perforations (cracks) through the sclerotic bone shell that typically forms during the process of aseptic loosening ("crack" revision technique). Perforating just the shell (without violating the proximal cortex) can maintain overall bone continuity while allowing marrow and vascular elements to access the implant surface. Because many revisions require bone graft to fill defects, we wanted to determine if bone graft could further increase implant fixation beyond what we have experimentally shown with the crack technique alone. Also, because both titanium (Ti6Al4V) and hydroxyapatite (HA) implant surfaces are used in revisions, we also wanted to determine their relative effectiveness in this model.

QUESTIONS/PURPOSES

We hypothesized that both (1) allografted plasma-sprayed Ti6Al4V; and (2) allografted plasma-sprayed HA-coated implants inserted with a crack revision technique have better fixation compared with a noncrack revision technique in each case.

METHODS

Under approval from our Institutional Animal Care and Use Committee, a female canine animal model was used to evaluate the uncemented revision technique (crack, noncrack) using paired contralateral implants while implant surface (Ti6Al4V, HA) was qualitatively compared between the two (unpaired) series. All groups received bone allograft tightly packed around the implant. This revision model includes a cylindrical implant pistoning 500 μm in a 0.75-mm gap, with polyethylene particles, for 8 weeks. This engenders a bone and tissue response representative of the metaphyseal cancellous region of an aseptically loosened component. At 8 weeks, the original implants were revised and followed for an additional 4 weeks. Mechanical fixation was assessed by load, stiffness, and energy to failure when loaded in axial pushout. Histomorphometry was used to determine the amount and location of bone and fibrous tissue in the grafted gap.

RESULTS

The grafted crack revision improved mechanical shear strength, stiffness, and energy to failure (for Ti6Al4V 27- to 69-fold increase and HA twofold increases). The histomorphometric analysis demonstrated primarily fibrous membrane ongrowth and in the gap for the allografted Ti6Al4V noncrack revisions. For allografted HA noncrack revisions, bone ongrowth at the implant surface was observed, but fibrous tissue also was present in the inner gap. Although both Ti6Al4V and HA surfaces showed improved fixation with grafted crack revision, and Ti6Al4V achieved the highest percent gain, HA demonstrated the strongest overall fixation.

CONCLUSIONS

The results of this study suggest that novel osteoconductive or osteoinductive coatings and bone graft substitutes or tissue-engineered constructs may further improve bone-implant fixation with the crack revision technique but require evaluation in a rigorous model such as presented here.

CLINICAL RELEVANCE

This experimental study provides data on which to base clinical trials aimed to improve fixation of revision implants. Given the multifactorial nature of complex human revisions, such a protocoled clinical study is required to determine the clinical applicability of this approach.

Aarhus Regenerative Orthopaedics Symposium (AROS)

The combination of modern interventional and preventive medicine has led to an epidemic of ageing. While this phenomenon is a positive consequence of an improved lifestyle and achievements in a society, the longer life expectancy is often accompanied by decline in quality of life due to musculoskeletal pain and disability. The Aarhus Regenerative Orthopaedics Symposium (AROS) 2015 was motivated by the need to address regenerative challenges in an ageing population by engaging clinicians, basic scientists, and engineers. In this position paper, we review our contemporary understanding of societal, patient-related, and basic science-related challenges in order to provide a reasoned roadmap for the future to deal with this compelling and urgent healthcare problem.

The effect on implant fixation of soaking tricalcium phosphate granules in bisphosphonate

The use of bone grafting is a well-established way to enhance initial implant fixation in situations with reduced bone stock. Ceramic bone substitutes are inferior alternatives to autogenous or allogeneic bone graft. Improvement of bone graft substitutes is needed. We investigated whether biomechanical implant fixation and osseointegration of experimental implant grafted with β-TCP granules (Conduit) could be improved by soaking the β-TCP granules in bisphosphonate (zoledronate).

In 10 dogs, a pair of titanium coated implants surrounded by a 2.5 mm gap was inserted into the proximal part of each tibia. The gap was grafted with β-TCP granules either soaked with zoledronate or saline. At 12 weeks, the implants were evaluated with biomechanical push-out test and histomorphometrical analysis.

We found that bisphosphonate increased one of the three biomechanical parameters, but found no difference in the amount of new bone or β-TCP granules between the two treatment groups.

This study indicates that local treatment of β-TCP granules with zoledronate not only has the potential to increase implant fixation but also calls for further experimental research in order to optimize the dose of zoledronate.

Systemic intermittent parathyroid hormone treatment improves osseointegration of press-fit inserted implants in cancellous bone

BACKGROUND AND PURPOSE

Intermittent administration of parathyroid hormone (PTH) has an anabolic effect on bone, as confirmed in human osteoporosis studies, distraction osteogenesis, and fracture healing. PTH in rat models leads to improved fixation of implants in low-density bone or screw insertion transcortically.

MATERIAL AND METHODS

We examined the effect of human PTH (1-34) on the cancellous osseointegration of unloaded implants inserted press-fit in intact bone of higher animal species. 20 dogs were randomized to treatment with human PTH (1-34), 5 μg/kg/day subcutaneously, or placebo for 4 weeks starting on the day after insertion of a cylindrical porous coated plasma-sprayed titanium alloy implant in the proximal metaphyseal cancellous bone of tibia. Osseointegration was evaluated by histomorphometry and fixation by push-out test to failure.

RESULTS

Surface fraction of woven bone at the implant interface was statistically significantly higher in the PTH group by 1.4 fold with (median (interquartile range) 15% (13-18)) in the PTH group and 11% (7-13) in control. The fraction of lamellar bone was unaltered. No significant difference in bone or fibrous tissue was observed in the circumferential regions of 0-500, 500-1,000, and 1,000-2,000 μm around the implant. Mechanically, the implants treated with PTH showed no significant differences in total energy absorption, maximum shear stiffness, or maximum shear strength.

INTERPRETATION

Intermittent treatment with PTH (1-34) improved histological osseointegration of a prosthesis inserted press-fit at surgery in cancellous bone, with no additional improvement of the initial mechanical fixation at this time point.

The effect of adding an equine bone matrix protein lyophilisate on fixation and osseointegration of HA-coated Ti implants

Joint replacements should be firmly anchored in vital bone to avoid early implant subsidence and late aseptic loosening. We investigated whether the fixation of orthopedic implants could be improved by adding an osteoinductive extract of lyophilized equine bone matrix proteins (Colloss E, Ossacur AG, Germany), between the implant and the surrounding bone. Eighteen uncemented HA-coated implants were inserted pairwise in the proximal tibia of nine dogs. All implants were surrounded by a 2 mm concentric defect. In each dog, the intervention implant was added 20 mg protein lyophilisate. The contralateral control implant was inserted untreated. After four weeks, the treated HA-coated implants had better mechanical fixation than the untreated control implants. The treated implants were better osseointegrated, there was more newly formed bone around these implants, and fibrous tissue was eliminated. The mechanical implant fixation had a strong positive correlation to new bone formation on and around the implant, and a strong negative correlation to fibrous tissue encapsulation. The results suggest that bone protein extracts such as the Colloss E device may augment early implant fixation of even HA-coated Ti implants and thereby reduce the risk of long-term failure. This may be particularly useful in revision arthroplasty with bone loss.

Coralline hydroxyapatite granules inferior to morselized allograft around uncemented porous Ti implants: unchanged fixation by addition of concentrated autologous bone marrow aspirate

We compared early fixation of titanium implants grafted with impacted allograft bone or coralline hydroxyapatite (HA) granules (Pro Osteon 200) with and without the addition of concentrated bone marrow cells (BMC). Autologous bone marrow aspirate was centrifuged to increase the BMC concentration. Four nonloaded cylindrical, porous coated titanium implants with a circumferential gap of 2.3 mm were inserted in the proximal humeri of eight dogs. Coralline HA granules +/- BMC were impacted around the two implants on one side, and allograft +/- BMC was impacted around the contra lateral implants. Observation time was 4 weeks. The implants surrounded by allograft bone had a three-fold better fixation than the HA-grafted implants. The concentration of BMC after centrifugation was increased with a factor 2.1. The addition of BMC to either of the bone graft materials had no statistically significant effects on implant fixation. The allografted implants were well osseointegrated, whereas the HA-grafted implants were largely encapsulated in fibrous tissue. The addition of concentrated autologous BMCs to the graft material had no effect on implant fixation. The HA-grafted implants were poorly anchored compared with allografted implants, suggesting that coralline HA granules should be considered a bone graft extender rather than a bone graft substitute.

Parathyroid hormone treatment increases fixation of orthopedic implants with gap healing: a biomechanical and histomorphometric canine study of porous coated titanium alloy implants in cancellous bone

Parathyroid hormone (PTH) administered intermittently is a bone-building peptide. In joint replacements, implants are unavoidably surrounded by gaps despite meticulous surgical technique and osseointegration is challenging. We examined the effect of human PTH(1-34) on implant fixation in an experimental gap model. We inserted cylindrical (10 × 6 mm) porous coated titanium alloy implants in a concentric 1-mm gap in normal cancellous bone of proximal tibia in 20 canines. Animals were randomized to treatment with PTH(1-34) 5 μg/kg daily. After 4 weeks, fixation was evaluated by histomorphometry and push-out test. Bone volume was increased significantly in the gap. In the outer gap (500 μm), the bone volume fraction median (interquartile range) was 27% (20-37%) for PTH and 10% (6-14%) for control. In the inner gap, the bone volume fraction was 33% (26-36%) for PTH and 13% (11-18%) for control. At the implant interface, the bone fraction improved with 16% (11-20%) for PTH and 10% (7-12%) (P = 0.07) for control. Mechanical implant fixation was improved for implants exposed to PTH. For PTH, median (interquartile range) shear stiffness was significantly higher (PTH 17.4 [12.7-39.7] MPa/mm and control 8.8 [3.3-12.4] MPa/mm) (P < 0.05). Energy absorption was significantly enhanced for PTH (PTH 781 [595-1,198.5] J/m(2) and control 470 [189-596] J/m(2)). Increased shear strength was observed but was not significant (PTH 3.0 [2.6-4.9] and control 2.0 [0.9-3.0] MPa) (P = 0.08). Results show that PTH has a positive effect on implant fixation in regions where gaps exist in the surrounding bone. With further studies, PTH may potentially be used clinically to enhance tissue integration in these challenging environments.

The combined effect of parathyroid hormone and bone graft on implant fixation

Impaction allograft is an established method of securing initial stability of an implant in arthroplasty. Subsequent bone integration can be prolonged, and the volume of allograft may not be maintained. Intermittent administration of parathyroid hormone has an anabolic effect on bone and may therefore improve integration of an implant. Using a canine implant model we tested the hypothesis that administration of parathyroid hormone may improve osseointegration of implants surrounded by bone graft. In 20 dogs a cylindrical porous-coated titanium alloy implant was inserted into normal cancellous bone in the proximal humerus and surrounded by a circumferential gap of 2.5 mm. Morsellised allograft was impacted around the implant. Half of the animals were given daily injections of human parathyroid hormone (1-34) 5 μg/kg for four weeks and half received control injections. The two groups were compared by mechanical testing and histomorphometry. We observed a significant increase in new bone formation within the bone graft in the parathyroid hormone group. There were no significant differences in the volume of allograft, bone-implant contact or in the mechanical parameters. These findings suggest that parathyroid hormone improves new bone formation in impacted morsellised allograft around an implant and retains the graft volume without significant resorption. Fixation of the implant was neither improved nor compromised at the final follow-up of four weeks.

The effect on bone growth enhancement of implant coatings with hydroxyapatite and collagen deposited electrochemically and by plasma spray

Skeletal bone consists of hydroxyapatite (HA) [Ca(10)(PO(4))(6)(OH)(2)] and collagen type I, both of which are osseoconductive. The goal of osseointegration of orthopedic and dental implants is the rapid achievement of a mechanically stable long-lasting fixation between bone and an implant surface. In this study, we evaluated the mechanical fixation and tissue distribution surrounding implants coated with three surfaces: plasma-sprayed HA coating, thinner coating of electrochemical-assisted deposition of HA, and an identical thin coating with a top layer of mineralized collagen. Uncoated plasma-sprayed titanium (Ti-6Al-4V) served as negative control. The electrochemical-assisted deposition was performed near physiological conditions. We used a canine experimental joint replacement model with four cylindrical implants (one of each treatment group) inserted in the humeri cancellous metaphyseal bone in a 1 mm gap. Observation time was 4 weeks. The mechanical fixation was quantified by push-out test to failure, and the peri-implant tissue formation by histomorphometric evaluation. HA coatings deposited by plasma spray technique or electrochemically, increased the mechanical fixation and bone ongrowth, but there was no statistical difference between the individual HA applications. Addition of collagen to the mineralized phase of the coating to create a more bone natural surface did not improve the osseoconductive effect of HA.

Assessment of hip dysplasia and osteoarthritis: variability of different methods

BACKGROUND

Reliable assessment of hip dysplasia and osteoarthritis is crucial in young adults who may benefit from joint-preserving surgery.

PURPOSE

To investigate the variability of different methods for diagnostic assessment of hip dysplasia and osteoarthritis.

MATERIAL AND METHODS

By each of four observers, two assessments were done by vision and two by angle construction. For both methods, the intra- and interobserver variability of center-edge and acetabular index angle assessment were analyzed. The observers' ability to diagnose hip dysplasia and osteoarthritis were assessed. All measures were compared to those made on computed tomography scan.

RESULTS

Intra- and interobserver variability of angle assessment was less when angles were drawn compared with assessment by vision, and the observers' ability to diagnose hip dysplasia improved when angles were drawn. Assessment of osteoarthritis in general showed poor agreement with findings on computed tomography scan.

CONCLUSION

We recommend that angles always should be drawn for assessment of hip dysplasia on pelvic radiographs. Given the inherent variability of diagnostic assessment of hip dysplasia, a computed tomography scan could be considered in patients with relevant hip symptoms and a center-edge angle between 20 degrees and 30 degrees . Osteoarthritis should be assessed by measuring the joint space width or by classifying the Tönnis grade as either 0-1 or 2-3.

The effect of soaking allograft in bisphosphonate: a pilot dose-response study

BACKGROUND

Long-term survival of uncemented total joint replacements relies on osseointegration. With reduced bone stock impacted morselized allograft enhances early implant fixation but is subject to resorption.

PURPOSE

We therefore asked whether soaking morselized allograft in different concentrations of bisphosphonate before impaction would enhance fixation.

METHODS

In each of 10 dogs, we implanted four unloaded titanium implants surrounded by a 2.5-mm gap into the proximal humerus, two implants in each humerus. The gap was filled with impacted morselized allograft soaked in saline or a low-, middle-, or high-dose bisphosphonate solution (0.005, 0.05, or 0.5 mg zoledronate/mL). At 4 weeks, the implants were evaluated by histomorphometric analysis and mechanical pushout test.

RESULTS

The low dose of zoledronate increased new bone formation in the allograft but the high dose decreased new bone formation. The high dose of zoledronate resulted in the greatest inhibition of allograft resorption, whereas the low dose of zoledronate resulted in the lowest inhibition of allograft resorption. Implants surrounded allograft soaked in the low dose of zoledronate or saline had better fixation for all three mechanical parameters compared with implants surrounded by allograft soaked in the middle or high dose of zoledronate.

CONCLUSIONS

These data suggest bisphosphonate may enhance osseointegration of allografted implants and emphasize the need for preclinical testing of antiresorptive therapies.

Medium-term outcome of periacetabular osteotomy and predictors of conversion to total hip replacement

BACKGROUND

Little is known about medium or long-term results of periacetabular osteotomy and which factors predict a poor outcome in terms of conversion to total hip replacement. The aims of this study were to assess the medium-term outcome following periacetabular osteotomy and to analyze what radiographic and patient-related factors predict a poor outcome.

METHODS

One hundred and sixteen periacetabular osteotomies performed by the senior author from December 1998 to December 2002 were eligible for inclusion. Data were assessed through database inquiry and evaluation of radiographic material. The mean duration of follow-up was 6.8 years. At the time of follow-up, we conducted an interview, performed clinical and radiographic examinations, and asked the patients to complete the Western Ontario and McMaster Universities Osteoarthritis Index and the Short Form-36 questionnaires. We performed a Kaplan-Meier survival analysis, and we used a Cox proportional hazards model to identify factors predicting a poor outcome.

RESULTS

With conversion to total hip replacement as the end point, the Kaplan-Meier analysis showed a hip survival rate of 81.6% (95% confidence interval, 69.7% to 89.3%) at 9.2 years. At the time of follow-up, the median physical component score on the Short Form-36 was 48.31, the median mental component score on the Short Form-36 was 57.95, and the median Western Ontario and McMaster Universities Osteoarthritis Index total score was 84.44. The median pain score on the visual analog scale was 0 at rest and 1 after fifteen minutes of normal walking. When adjusting for preoperative osteoarthritis, we identified seven factors predicting conversion to total hip replacement. Preoperative predictive factors were severe dysplasia on conventional radiographs and computed tomographic scans, reduced acetabular anteversion angle on computed tomographic scans, and the presence of an os acetabuli (calcification of a detached labrum). Predictive factors identified on the immediate postoperative radiographs were a small width of the acetabular sclerotic zone and excessive lateral and proximal dislocation.

CONCLUSIONS

Periacetabular osteotomy can be performed with a good outcome at medium-term follow-up, suggesting that it may be applied by experienced surgeons with satisfactory results. To further improve the outcome, focus should be on the potential negative influence of parameters that are easily assessed, such as the preoperative grade of osteoarthritis, the presence of an os acetabuli, and severe acetabular dysplasia.

Effect of local TGF-beta1 and IGF-1 release on implant fixation: comparison with hydroxyapatite coating: a paired study in dogs

BACKGROUND AND PURPOSE

Hydroxyapatite (HA) coating stimulates the osseointegration of cementless orthopedic implants. Recently, locally released osteogenic growth factors have also been shown experimentally to stimulate osseointegration so that bone fills gaps around orthopedic implants. Here, we have compared the effect of local release of TGF-beta1 and IGF-1 with that of hydroxyapatite coating on implant fixation.

METHOD

Weight-bearing implants with a 0.75-mm surrounding gap were inserted bilaterally in the knees of 10 dogs. Growth factors were incorporated in a biodegradable poly(D,L-lactide) coating on porous coated titanium implants. Plasma-sprayed HA implants served as controls. The dogs were killed at 4 weeks and the implants were evaluated by mechanical push-out test and by histomorphometry.

RESULTS

There was no difference in any of the mechanical parameters. Bone ongrowth was 3-fold higher for HA-coated implants (p < 0.001). For growth factor-coated implants, bone volume was 26% higher in the inner half of the gap and 28% higher in the outer half compared to HA (p < 0.03).

INTERPRETATION

The mechanical fixation of porous-coated titanium implants with local growth factor release is comparable to that of HA coating. While HA mainly stimulated bone ongrowth, local release of TGF-beta1 and IGF-1 stimulated gap healing.

Fixation of hydroxyapatite-coated revision implants is improved by the surgical technique of cracking the sclerotic bone rim

Revision joint replacement has poorer outcomes that have been associated with poorer mechanical fixation. We investigate a new bone-sparing surgical technique that locally cracks the sclerotic bone rim formed during aseptic loosening. We inserted 16 hydroxyapatite-coated implants bilaterally in the distal femur of eight dogs, using a controlled weight-bearing experimental model that replicates important features of a typical revision setting. At 8 weeks, a control revision procedure and a crack revision procedure were performed on contralateral implants. The crack procedure used a splined tool to perform a systematic local perforation of the sclerotic bone rim of the revision cavity. After 4 weeks, the hydroxyapatite-coated implants were evaluated for mechanical fixation by a push-out test and for tissue distribution by histomorphometry. The cracking revision procedure resulted in significantly improved mechanical fixation, significantly more bone ongrowth and bone volume in the gap, and reduced fibrous tissue compared to the control revision procedure. The study demonstrates that the sclerotic bone rim prevents bone ingrowth and promotes fixation by fibrous tissue. The effect of the cracking technique may be due to improved access to the vascular compartment of the bone. The cracking technique is a simple surgical method that potentially can improve the fixation of revision implants in sclerotic regions important for obtaining the fixation critical for overall implant stability.

Local bisphosphonate treatment increases fixation of hydroxyapatite-coated implants inserted with bone compaction

It has been shown that fixation of primary cementless joint replacement can independently be enhanced by either: (1) use of hydroxyapatite (HA) coated implants, (2) compaction of the peri-implant bone, or (3) local application of bisphosphonate. We investigated whether the combined effect of HA coating and bone compaction can be further enhanced with the use of local bisphosphonate treatment. HA-coated implants were bilaterally inserted into the proximal tibiae of 10 dogs. On one side local bisphosphonate was applied prior to bone compaction. Saline was used as control on the contralateral side. Implants were evaluated with histomorphometry and biomechanical push-out test. We found that bisphosphonate increased the peri-implant bone volume fraction (1.3-fold), maximum shear strength (2.1-fold), and maximum shear stiffness (2.7-fold). No significant difference was found in bone-to-implant contact or total energy absorption. This study indicates that local alendronate treatment can further improve the fixation of porous-coated implants that have also undergone HA-surface coating and peri-implant bone compaction.

Bone growth enhancement in vivo on press-fit titanium alloy implants with acid etched microtexture

Early bone ongrowth secures long-term fixation of primary implants inserted without cement. Implant surfaces roughened with a texture on the micrometer scale are known to be osseoconductive. The aim of this study was to evaluate the bone formation at the surface of acid etched implants modified on the micro-scale. We compared implants with a nonparticulate texture made by chemical milling (hydrofluoric acid, nitric acid) (control) with implants that had a dual acid etched (hydrofluoric acid, hydrochloric acid) microtexture surface superimposed on the primary chemically milled texture. We used an experimental joint replacement model with cylindrical titanium implants (Ti-6Al-4V) inserted paired and press-fit in cancellous tibia metaphyseal bone of eight canines for 4 weeks and evaluated by histomorphometric quantification. A significant twofold median increase was seen for bone ongrowth on the acid etched surface [median, 36.1% (interquartile range, 24.3-44.6%)] compared to the control [18.4% (15.6-20.4%)]. The percentage of fibrous tissue at the implant surface and adjacent bone was significantly less for dual acid textured implants compared with control implants. These results show that secondary roughening of titanium alloy implant surface by dual acid etching increases bone formation at the implant bone interface.

Comparison of the minimally invasive and ilioinguinal approaches for periacetabular osteotomy: 263 single-surgeon procedures in well-defined study groups

BACKGROUND AND PURPOSE

Periacetabular osteotomy is the treatment of choice in young adults with hip dysplasia. Patient morbidity and surgical outcome may depend on the choice of surgical approach. We compared the outcome of a new minimally invasive approach to that of the frequently used "classic" ilioinguinal approach.

PATIENTS AND METHODS

We retrospectively evaluated our experience with the ilioinguinal and minimally invasive approaches, which were used in successive time periods at our institution between December 1998 and February 2007 (n=263). Intraoperative and early postoperative outcome factors together with analysis of hip joint survival were compared in well-defined study groups.

RESULTS

In the minimally invasive and ilioinguinal groups respectively, the median (interquartile range) intraoperative blood loss was 250 (200-350) mL and 500 (350-700) mL (p<0.001), the mean (95% CI) hemoglobin reduction was 2.0 (1.9-2.1) mmol/L and 2.5 (2.4-2.7) mmol/L (p<0.001), transfusion was required following 4% and 18% of the procedures (p<0.001), and the median (interquartile range) duration of surgery was 70 (60-75) min and 100 (80-120) min (p<0.001). Median (interquartile range) postoperative center-edge and acetabular index angles were 33 (30-36) and 2 (0-6), respectively, in the minimally invasive group and 31 (25-35) and 9 (1-14) in the ilioinguinal group. There were no cases of moderate or severe complications in the minimally invasive group and 3 cases of arterial thrombosis in the ilioinguinal group (3%). At follow-up of 5 years, the hip joint survival rates were 97% in the minimally invasive group and 93% in the ilioinguinal group.

INTERPRETATION

Given the accumulated experience of the surgeon, the outcome of the minimally invasive approach compares favorably with that of the ilioinguinal approach, and the results support continued use of the minimally invasive approach for periacetabular osteotomy. Using this approach, we did not encounter any complications and acetabular reorientation was not compromized.

Ceramic bone graft substitute with equine bone protein extract is comparable to allograft in terms of implant fixation: a study in dogs

BACKGROUND AND PURPOSE

We studied whether osseointegration and fixation of plasma-sprayed titanium implants grafted with beta-TCP granules (Ossaplast) can be improved by adding an osteogenic signal (Colloss E). The results were compared to implants grafted with fresh frozen morselized allograft with and without the Colloss E device.

METHODS

4 porous-coated Ti implants were placed in the proximal humeri in each of 10 dogs. All implants were surrounded by a 2.5-mm defect, which was grafted with: (A) beta-TCP, (B) beta-TCP+20 mg Colloss E, (C) allograft, or (D) allograft+20 mg Colloss E. The observation time was 4 weeks.

RESULTS

Mechanical testing showed that the beta-TCP group with Colloss E was twice as well fixed as the control group grafted with beta-TCP granules alone, and comparable to both allograft groups. We found that every control implant in the beta-TCP grafted group was covered by a dense fibrous membrane. No fibrous tissue was seen in the beta-TCP group augmented with Colloss. These implants were well osseointegrated, with new bone covering 10-25% of the implant surface. Both treated groups had increased graft resorption compared to their respective control groups. Colloss E had no effect on new bone formation or fibrous tissue reduction around the allografted implants.

INTERPRETATION

The Colloss E device improved early osseointegration of implants grafted with beta-TCP granules and increased their mechanical implant fixation to the level of allografted implants. The experiment indicates that ceramic bone substitutes may be a viable alternative to allograft when combined with an osteogenic signal such as Colloss E.

Reliable angle assessment during periacetabular osteotomy with a novel device

We developed and assessed a measuring device for intraoperative assessment of the acetabular index and center edge angle during acetabular reorientation in periacetabular osteotomy. We asked whether reliable assessment of angles could be made using the device; to be reliable we presumed the variability of angle measurements should not exceed that of inherent variability when assessing angles on radiographs (+/- 5 degrees ). The device was mounted bilaterally on the pelvis, and using fluoroscopy, angle measurements were obtained with adjustable measuring discs. We conducted a cadaver study to assess intraobserver and interobserver variability of the device and to assess if pelvic positioning influenced variation of measurements. Intraoperative measurements of 35 consecutive patients were compared with measurements on postoperative radiographs. Intraoperatively obtained angle measurements differed less than +/- 5 degrees from measurements on postoperative radiographs and the intraobserver and interobserver variability of the device were confined within +/- 5 degrees . Positioning did not influence the variation of angle measurements beyond intraobserver variability of the device when applying arcs of tilt and rotation of +/- 12.5 degrees . We believe the device is a potentially helpful tool in the periacetabular osteotomy. It is simple to use and facilitates repeated reliable angle measurements during acetabular reorientation, making intraoperative radiographs unnecessary.

A new minimally invasive transsartorial approach for periacetabular osteotomy

BACKGROUND

A new minimally invasive transsartorial approach for the Bernese periacetabular osteotomy was developed. We investigated whether this technique was safe and successful with regard to minimizing tissue trauma and, more importantly, whether it was possible to obtain optimal reorientation of the acetabulum.

METHODS

Our experience with this approach was retrospectively assessed by means of database inquiry and the evaluation of radiographs. We assessed ninety-four procedures performed between April 2003 and August 2005 to determine perioperative and early postoperative outcome measures, the achieved acetabular reorientation, and hip joint survival.

RESULTS

The mean duration of surgery was 73.1 minutes, the median perioperative blood loss was 250 mL, and the mean reduction in the hemoglobin level was 33 g/L. Blood transfusion was required following 3% of the procedures. No injuries to the great vessels or nerves, arterial thromboses, unintended extension of the osteotomy, or deep infections occurred. The postoperative acetabular reorientation was assessed by measuring the center-edge and acetabular index angles, the medians of which were 34 degrees and 3 degrees , respectively. With total hip arthroplasty as the end point, the hip joint survival rate was estimated to be 98% at 4.3 years.

CONCLUSIONS

Osteotomy with use of this minimally invasive transsartorial approach appears to be a safe, relatively short surgical procedure associated with a relatively small amount of blood loss and minimal transfusion requirements. Optimal acetabular reorientation can be achieved with this technique.

Soaking morselized allograft in bisphosphonate can impair implant fixation

The use of impacted, morselized allograft is a well-established way to provide initial stability of revision joint replacements. We investigated whether rinsing morselized allograft in bisphosphonate and subsequently impacting it around experimental titanium-coated implants would further facilitate biomechanical implant fixation and graft incorporation. In 10 dogs, a pair of titanium implants surrounded by a 2.5-mm gap was inserted into the proximal part of each humerus during two separate surgeries to allow two observation periods. The gap was filled with impacted, morselized allograft soaked in either bisphosphonate (alendronate, 2 mg/mL) or saline (control). Unbound alendronate was not rinsed away. During the first surgery, one pair of implants (alendronate and control) was inserted into one humerus. Eight weeks later, a second pair of implants was inserted into the contralateral humerus. The first pair of implants was observed for 12 weeks and the second pair for 4 weeks. Implants were evaluated by histomorphometry and biomechanical pushout test. We found substantially decreased biomechanical implant fixation for all implants surrounded by impacted, morselized allograft that had been soaked in alendronate. Furthermore, the alendronate treatment blocked formation of new bone and inhibited resorption of the graft material. Although limited by the specific dose of alendronate used and the omission of rinsing away excess bisphosphonate, this study warrants caution and calls for further experimental research before impacting alendronate-soaked morselized allograft around clinical joint replacements.

Local alendronate increases fixation of implants inserted with bone compaction: 12-week canine study

Bone compaction has been shown to increase initial implant fixation. Furthermore, bone compaction creates a peri-implant zone of autograft that exerts osteoconductive properties. We have previously shown that locally applied bisphosphonate (alendronate) at 4-week observation can preserve the autograft generated by bone compaction. We now investigate whether the increased amount of autograft, seen at 4 weeks, can increase implant osseointegration and biomechanical fixation. Porous-coated titanium implants were bilaterally inserted with bone compaction into the proximal part of tibia of 10 dogs. On the right side, local bisphosphonate was injected into the bone cavity prior to bone compaction immediately prior to implant insertion. On the left side, saline was used as control. Observation period was 12 weeks. Locally applied bisphosphonate significantly increased biomechanical implant fixation (approximately twofold), bone-to-implant contact (1.2-fold), and peri-implant bone volume fraction (2.3-fold). This study indicates that local alendronate treatment can increase early implant osseointegration and biomechanical fixation of implants inserted by use of bone compaction. Long term effects remain unknown.

Locally delivered TGF-beta1 and IGF-1 enhance the fixation of titanium implants: a study in dogs

BACKGROUND

Osteogenic growth factors have been suggested to enhance the fixation of implants used in joint replacement. We examined the effect of locally delivered transforming growth factor-beta1 and insulin-like growth factor-1 in a biodegradable poly (D, L-lactide) coating.

MATERIAL AND METHODS

In a paired study using 9 dogs, unloaded titanium implants surrounded by a 1-mm gap were inserted into the proximal humerus. The growth factors were incorporated in a poly (D, L-lactide) coating at a 1% (w/w) ratio of TGF-beta1 and a 5% (w/w) ratio of IGF-1. Control implants were uncoated. After 4 weeks, the implants were evaluated by mechanical push-out test and by histomorphometry.

RESULTS

A twofold increase was seen in mechanical fixation (strength, stiffness, energy absorption) for the growth factor-treated implants (p = 0.04). Similar results were seen in histomorphometry, as bone ongrowth was 2.5 times higher (p = 0.02), and gap healing was 30-110% higher (p = 0.04) for the growth factor-treated implants than for the control implants. Ongrowth of fibrous tissue was eliminated by the treatment.

INTERPRETATION

TGF-beta-1 and IGF-1, locally delivered in a biodegradable poly(D,L-lactide) coating, enhance the mechanical fixation and osseointegration of titanium implants in cancellous bone, and no fibrous tissue is produced in the growth factor treated implants.

The bovine bone protein lyophilisate Colloss improves fixation of allografted implants--an experimental study in dogs

BACKGROUND

Impacted morselized bone allograft is a well-established way of giving joint arthroplasties additional support in situations where there is insufficient bone stock. For long-term survival of the implant, early implant fixation is important. We hypothesized that Col-loss, a bone protein lyophilisate, might improve early implant fixation of allografted implants.

METHOD

We inserted 4 porous-coated Ti implants in the distal femurs of 16 dogs. All implants were surrounded by a 2.5-mm gap, which was impacted with morselized allograft with or without Colloss. In each dog, the implants were treated with no Collos or low-, middle- or high-dose (0, 10, 20 and 40 mg) Colloss per cm3 allograft. The observation time was 4 weeks.

RESULTS

Mechanical implant fixation was improved for all 3 groups with Colloss-treated implants (p < 0.05). The best anchorage was seen in the middle-dose group, where fixation was improved by 100%. We saw a dramatic reduction in fibrous tissue on the surface of the Colloss-treated implants (p < 0.001). The Colloss groups showed increased ongrowth of new bone (p < 0.01) and accelerated gap remodeling (p < 0.05).

INTERPRETATION

Colloss can improve early osseointegration and fixation of allografted implants.

Effect of topical alendronate treatment on fixation of implants inserted with bone compaction

Bone compaction has been shown to enhance the critical initial implant stability that is important for secure long-term fixation. We investigated whether topical bisphosphonate treatment improves fixation of implants inserted with bone compaction. Porous-coated titanium implants were inserted with bone compaction into the knees of eight dogs. In the right knee, topical bisphosphonate treatment was applied before bone compaction. Saline was used as a control in the left knee. The knees were observed for 4 weeks. We found an increase in total bone-to-implant contact and total bone density around the implants in the bisphosphonate-treated group. These were results of increased nonvital bone-to-implant contact and increased nonvital periimplant bone density. No change in biomechanical fixation was found. Studies with a longer followup are needed to investigate whether the preservative effect of alendronate on nonvital bone might enhance implant fixation by osteoconduction.

In vivo study of the effect of RGD treatment on bone ongrowth on press-fit titanium alloy implants

Early bone ongrowth is known to increase primary implant fixation and reduce the risk of early implant failure. Arg-Gly-Asp (RGD) peptide has been identified as playing a key role in osteoblast adhesion and proliferation on various surfaces. The aim for this study is to evaluate the effect of RGD peptide coating on the bony fixation of orthopaedic implants, to justify its further evaluation in clinical applications. Sixteen unloaded cylindrical plasma sprayed Ti6Al4V implants coated with cyclic RGD peptide were inserted as press-fit in the proximal tibia of 8 mongrel dogs for 4 weeks. Uncoated control implants were inserted in the contralateral tibia. Results were evaluated by histomorphometry and mechanical push-out test. A significant two-fold increase was observed in bone ongrowth for RGD-coated implants. Also, fibrous tissue ongrowth was significantly reduced for RGD-coated implants. Bone volume was significantly increased in a 0-100 microm zone around the implant. The increased bony anchorage resulted in moderate increases in mechanical fixation as apparent shear stiffness was significantly higher for RGD-coated implants. Increases in median ultimate shear strength and energy to failure were also observed. This study demonstrates that cyclic RGD coating increases early bony fixation of unloaded press-fit titanium implants.

Fixation of revision implants is improved by a surgical technique to crack the sclerotic bone rim

Revision joint replacement has poorer outcomes compared with primary joint replacement, and these poor outcomes have been associated with poorer fixation. We investigated a surgical technique done during the revision operation to improve access from the marrow space to the implant interface by locally cracking the sclerotic bone rim that forms during aseptic loosening. Sixteen implants were inserted bilaterally by distal femur articulation of the knee joint of eight dogs, using our controlled experimental model that replicates the revision setting (sclerotic bone rim, dense fibrous tissue, macrophages, elevated cytokines) by pistoning a loaded 6.0-mm implant 500 microm into the distal femur with particulate PE. At 8 weeks, one of two revision procedures was done. Both revision procedures included complete removal of the membrane, scraping, lavaging, and inserting a revision plasma-spray Ti implant. The crack revision procedure also used a splined tool to circumferentially locally perforate the sclerotic bone rim before insertion of an identical revision implant. Superior fixation was achieved with the cracking procedure in this experimental model. Revision implants inserted with the rim cracking procedure had a significantly higher pushout strength (fivefold median increase) and energy to failure (sixfold median increase), compared with the control revision procedure. Additional evaluation is needed of local perforation of sclerotic bone rim as a simple bone-sparing means to improve revision implant fixation and thereby increase revision implant longevity.

In vivo effects of RGD-coated titanium implants inserted in two bone-gap models

RGD (Arg-Gly-Asp) coating has been suggested to enhance implant fixation by facilitating the adhesion of osteogenic cells to implant surfaces. Orthopedic implants are unavoidably surrounded partly by gaps, and these regions represent a challenging environment for osseointegration. We examined the effects of cyclic RGD-coated implants on tissue integration and implant fixation in two cancellous bone-gap models. In canines, we inserted loaded RGD-coated implants with 0.75-mm gap (n = 8) and unloaded RGD-coated implants with 1.5-mm gap (n = 8) into the distal femur and proximal tibia, respectively. Control gap implants without RGD were inserted contralaterally. The titanium alloy (Ti-6Al-4V) implants were plasma sprayed and cylindrical. The observation period was 4 weeks and the fixation was evaluated by push-out test and histomorphometry. Mechanical implant fixation was improved for RGD-coated implants. Unloaded RGD-coated implants showed a significant increase in bone whereas both loaded and unloaded implants showed a significant reduction in fibrous tissue anchorage. The results are encouraging, because RGD had an overall positive effect on the fixation of titanium implants in regions where gaps exist with the surrounding bone. RGD peptide coatings can potentially be used to enhance tissue integration in these challenging environments.