Treatment outcome of the Masquelet technique in 195 infected bone defects-A single-center, retrospective case series

BACKGROUND

The Masquelet technique is a surgical procedure for the reconstruction of bone defects. During the first step, an osteosynthetically stabilized defect is filled with a cement spacer. The spacer induces a foreign body membrane, called a Masquelet membrane. In a follow-up procedure, the spacer is replaced by a bone graft, which ossifies in the subsequent phase.

MATERIAL AND METHODS

A total of 171 patients with 195 septic bone defects on the extremities that had been treated with the Masquelet procedure at the BG Klinikum in Hamburg, Germany, from 2011 to 2021 were retrospectively analysed, comparing patients who reached full weight and load bearing on the affected extremity to those who failed to do so. Defect size and configuration, microbiological results and treatment methods as well as comorbidities and epidemiologic data were analysed for factors influencing the treatment outcome.

RESULTS

In all, 113[66%] of the patients were male, and 58[34%] were female, with an age distribution of 52 +/-16 years. Out of 171 patients, 24 patients had two defects. The number of patients that reached full weight bearing was 152[89%], the follow-up period was 2 +/-1 years (median +/- SD). Full weight bearing capability was negatively by the defect size as defects >62 mm tended to be less likely to reach full weight bearing than smaller defects. A secondary stabilization with an internal stabilization was applied in 58[34%] of all patients and positively influenced the attainment of full weight and load bearing.

DISCUSSION

With 171 patients and 195 septic bone defects treated at a single centre with the Masquelet Technique, this study represents a comparably large cohort. Demographics, defect characteristics and treatment outcomes did not differ from those of other cohorts described in the literature. Defects larger than 62 mm showed lower chances to reach full weight bearing and can be defined as "critical defect size" for the Masquelet technique based on our data.

Similar Clinical Outcome in Locking and Conventional Plate Osteosynthesis for the Treatment of AO 44-B2 Ankle Fractures

INTRODUCTION

Biomechanical studies have proved that locking plates have better primary stability besides versatility regarding fracture pattern while reducing bone contact and bridging the gap, whereas conventional nonlocking plates (plus lag screw) depend on bone-plate compression. The clinical benefit of locking plates over nonlocking plates remains unanswered, however. Therefore, this retrospective cohort study was set up to test the hypothesis that the use of locking plates for unstable ankle fractures will result in fewer re-displacements, superior bony healing, and functional and clinical outcomes better than observed in the nonlocking cohort.

METHODS

Bimalleolar ankle fractures (AO 44-B2) without syndesmotic injury treated with either a locking or a nonlocking plate were included. Groups were compared for complications, bone healing, secondary dislocation, progressions of osteoarthritis, and clinical outcome using patient-reported outcome measures.

RESULTS

Data revealed no clinical outcome differences (Olerud-Molander Ankle Score: nonlocking 88.2 ± 14.4, locking 88.8 ± 12.3, P = .69, robust two 1-sided test for equality (RTOST): P = .03; American Orthopaedic Foot and Ankle Score: nonlocking 91.2 ± 12.9, locking 91.8 ± 11.3, P = .96, RTOST: P = .04). Nevertheless, a significant postoperative progression of osteoarthritis was detected in both groups (P = .04). This was independent of implant (P = .16). Although difference was not significant, locking plates were preferred in older (P = .78) and sicker patients (P = .63) and in cases with severer osteoarthritis (P = .16), and were associated with a higher complication rate (P = .42) and secondary dislocation (nonlocking 9.4%, locking 18.2%; P = .42). Re-displacement, however, was not a compelling reason for revision.

CONCLUSIONS

The present study shows statistically significant equality of both types of implants. Contrary to our expectation, locking plates seemed to be associated with a higher risk for re-displacement. Overall, the use of either locking or nonlocking plates for unstable AO 44-B2 fractures is safe and successful despite significant progression of osteoarthritis.

LEVEL OF EVIDENCE

III, Retrospective observational cohort study.

[Removal of a bent femoral nail : Case report: treatment strategy of a complex femoral deformity with a bent femoral nail in situ since 36 years]

To remove a bent femoral nail is always a challenging task for a surgeon. In the last 20 years several case reports and descriptions of techniques are to be found in literature, the goal being to weaken the nail at the apex and then straightening it in situ in most cases. Those reports all have one parameter in common: the necessity to remove the nail relates to a refracture of the femur.We report the case of a patient who presented with the explicit wish to have a bent femoral nail removed and a femoral angulation corrected because of pain in the ipsilateral hip. A femoral fracture had been treated by a Küntscher nail in 1982. A refracture with severe bending of the nail had occurred a short time later, which was treated conservatively without a second surgical procedure.We can show that a planned removal of a bent and well-osseointegrated Küntscher nail can be achieved without complications and that thereby a multiplane angulation in the femur can be corrected, paving the way for a future arthroplasty in this specific case.

Percutaneous administration of allogeneic bone-forming cells for the treatment of delayed unions of fractures: a pilot study

Background

Overall, 5–10% of fractures result in delayed unions or non-unions, causing major disabilities and a huge socioeconomic burden. Since rescue surgery with autologous bone grafts can cause additional challenges, alternative treatment options have been developed to stimulate a deficient healing process. This study assessed the technical feasibility, safety and preliminary efficacy of local percutaneous implantation of allogeneic bone-forming cells in delayed unions of long bone fractures.

Methods

In this phase I/IIA open-label pilot trial, 22 adult patients with non-infected delayed unions of long bone fractures, which failed to consolidate after 3 to 7 months, received a percutaneous implantation of allogeneic bone-forming cells derived from bone marrow mesenchymal stem cells (ALLOB; Bone Therapeutics) into the fracture site (50 × 10⁶ to 100 × 10⁶ cells). Patients were monitored for adverse events and need for rescue surgery for 30 months. Fracture healing was monitored by Tomographic Union Score (TUS) and modified Radiographic Union Score. The health status was evaluated using the Global Disease Evaluation (GDE) score and pain at palpation using a visual analogue scale. The presence of reactive anti-human leukocyte antigen (HLA) antibodies was evaluated.

Results

During the 6-month follow-up, three serious treatment-emergent adverse events were reported in two patients, of which two were considered as possibly treatment-related. None of the 21 patients in the per-protocol efficacy population needed rescue surgery within 6 months, but 2/21 (9.5%) patients had rescue surgery within 30 months post-treatment. At 6 months post-treatment, an improvement of at least 2 points in TUS was reached in 76.2% of patients, the GDE score improved by a mean of 48%, and pain at palpation at the fracture site was reduced by an average of 61% compared to baseline. The proportion of blood samples containing donor-specific anti-HLA antibodies increased from 8/22 (36.4%) before treatment to 13/22 (59.1%) at 6 months post-treatment, but no treatment-mediated allogeneic immune reactions were observed.

Conclusion

This pilot study showed that the percutaneous implantation of allogeneic bone-forming cells was technically feasible and well tolerated in patients with delayed unions of long bone fractures. Preliminary efficacy evidence is supporting the further development of this treatment.

Trial registration

NCT02020590. Registered on 25 December 2013. ALLOB-DU1, A pilot Phase I/IIa, multicentre, open proof-of-concept study on the efficacy and safetyof allogeneic osteoblastic cells (ALLOB®) implantation in non-infected delayed-union fractures.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02432-4.

Evidence-Based Examination Techniques for the Shoulder Joint

OBJECTIVE

Digitalisation now almost covers all areas of medical student teaching. Teaching videos are a good way to help students learn practical skills. The existing evidence is a recognised aid for the classification of the respective technology.

METHOD

This video presents the usual examination techniques of the shoulder joint on a patient with an unstable shoulder. The respective techniques, if available, were backed up with appropriate evidence.

CONCLUSION

The examination techniques presented allow students to view them in a standardized manner on a patient. The evidence for the examination techniques can help with the classification of the respective technique.

Comparison of hamstring and quadriceps tendon autografts in anterior cruciate ligament reconstruction with gait analysis and surface electromyography

BACKGROUND

Anterior cruciate ligament (ACL) tear is the most frequent ligamentous injury of the knee joint. Autografts of hamstring (HS) or quadriceps tendons (QT) are used for primary ACL reconstruction. In this study, we planned to examine whether harvesting an HS graft is related to a deficit in dynamic knee stabilisation and strength revealed by dynamic valgus as compared with QT graft or the uninjured leg. Furthermore, if this deficit exists, is it compensated by higher neuromuscular activity of the quadriceps muscle?

MATERIALS AND METHODS

Adult patients who had undergone ACL reconstruction with QT or HS autografts were included in this two-armed cohort study. Clinical outcome was assessed by clinical data analysis, physical examination and the Lysholm Score and Knee Injury and Osteoarthritis Score (KOOS). In addition, gait analysis and non-invasive surface electromyography were performed.

RESULTS

A complete data set of 25 patients (QT: N = 8, HS: N = 17) was analysed. There was no significant demographic difference between the groups. Time between surgery and follow-up was significantly longer for the QT group. Significant differences regarding clinical outcome were not found between the treated and untreated leg or between the two groups, with excellent scores at the time of follow-up. Gait analysis revealed no significant differences of varus-valgus angles. Significant differences in surface electromyography were only found in the QT group with increased vastus medialis obliquus activity of the treated legs (p < 0.01).

CONCLUSIONS

Our results suggest that harvesting of HS grafts for primary ACL reconstruction will not lead to a medial collapse and consequently impaired medial stabilisation of the knee when compared with QT grafts.

LEVEL OF EVIDENCE

IV.

Evidence-Based Examination Techniques for the Knee

OBJECTIVE

Digitalisation now almost covers all areas of medical student teaching. Teaching videos are a good way to help students learn practical skills. The existing evidence is a recognised aid for the classification of the respective technology.

METHOD

This video presents the usual examination techniques of the knee joint on a patient with an unstable knee. The respective techniques, if available, were backed up with the appropriate evidence.

CONCLUSION

The examination techniques presented allow students to view the examination techniques in a standardised manner on a patient. The evidence for the examination techniques can help with the classification of the respective technique.

ZIELSETZUNG

Die Digitalisierung erfasst inzwischen alle Bereiche der studentischen Lehre. Um die Studierenden im Erlernen praktischer Fertigkeiten zu unterstützen, sind Lehrvideos eine gute Methode. Für die Einordnung der jeweiligen Technik ist die vorhandene Evidenz eine anerkannte Hilfestellung.

METHODE

Das hier vorliegende Video stellt die üblichen Untersuchungstechniken des Kniegelenkes an einer Patientin mit einem instabilen Knie dar. Die jeweiligen Techniken wurden, wenn vorhanden, mit der jeweiligen Evidenz unterlegt.

SCHLUSSFOLGERUNG

Die dargestellten Untersuchungstechniken ermöglichen es Studierenden, sich die Untersuchungstechniken standardisiert an einem Patienten anzuschauen. Die eingeblendete Evidenz für die Untersuchungstechniken kann hierbei eine Hilfestellung bei der Einordnung der jeweiligen Technik leisten.

Quality of life of persons with transfemoral amputation: Comparison of socket prostheses and osseointegrated prostheses

BACKGROUND

Until recently, no study had compared the quality of life of persons with transfemoral amputation treated with osseointegration to socket prosthesis users.

OBJECTIVES

Comparison of quality of life in two types of prostheses users: a cohort of patients with osseointegration and patients equipped with a socket prosthesis who were group-matched for age, body mass index and mobility grade.

STUDY DESIGN

A cross-sectional study that compared METHODS:: The quality of life of 39 participants (22 in the osseointegration group and 17 in the socket prosthesis group) was measured using the Questionnaire for Persons with Transfemoral Amputation (Q-TFA) and European Questionnaire 5-dimension 3-level (EQ-5D-3L) surveys.

RESULTS

Compared with the socket prosthesis group, the osseointegration group had a significantly higher 'Global' score (p = 0.022) and a significantly lower 'Problem' score (p < 0.001) of the Q-TFA. The 'Mobility' (p = 0.051) and 'Use' scores (p = 0.146) of the Q-TFA, the EQ-5D-3L index (p = 0.723), and EQ-5D visual analog scale (p = 0.497) showed no significant differences between groups.

CONCLUSIONS

Patients with osseointegration experienced less prosthesis-associated problems than socket prosthesis users and had a higher prosthesis-associated quality of life when assessed with the Q-TFA. General quality of life, as assessed with the EQ-5D-3L, was not different between groups.

Internship Experience in Orthopaedics and Traumatology and its Impact on Becoming a Specialist

INTRODUCTION

The German practical year is the last clinical placement period during Medical School. However, it remains unclear how medical students evaluate the practical year in orthopaedics and traumatology (Orthopädie und Unfallchirurgie; O & U) and whether it has an impact on becoming an O & U specialist.

METHOD

We analysed data of 146 medical students (46,7% female) who completed the placement in O & U. From the evaluation, 37 items were included in the analyses. Participants who could imagine becoming an O & U specialist (O & U-Ja) following graduation were statistically compared to those who could not (O & U-Nein).

RESULTS

Overall 123 (83.7%) trainees indicated that they would like to become an O & U specialist (O & U-Ja), 18 (12.8%) negated (O & U-Nein) and 6 (4.1%) were undecided. Groups did not differ for sex and age (sex: Chi² = 2.50, p = 0.114; age: F [1.93] < 1, p = 0.764). Group differences were found for practical orientation, independency, acquisition of anamnesis and diagnostics skills and problem-solving expertise with students who could imagine becoming an O & U specialist (O & U-Ja) giving the highest ratings.

DISCUSSION

Evaluations of the last medical year are essential in order to continuously improve the internship experience and to attract students towards a certain medical field and, moreover, to post-graduate specialist training. Clinics and institutions who already emphasize on the factors derived from this evaluation, or are continuously working on improvement, might be more able to attract young professionals, since personnel acquisition is starting early in the medical field.

Checklist Focused on Patients for Making of Teaching Videos in Orthopedic Surgery

INTRODUCTION

The focus of medical-didactic research is the improvement of clinical-practical training. One way to support practical skills training in a time- and resource-saving way is to provide instructional videos. Often the freely available instructional videos do not meet didactic or content requirements. Creating your own videos can therefore be a useful alternative for teachers. There are a variety of instructions on the Internet for shooting instruction videos. To date, this does not include any concrete instructions/assistance for the production of medical instructional videos. However, the presentation of medical learning content in particular can contain many hurdles. The aim of this work was to design a checklist for the creation of instructional videos, which can be used as a guide.

METHODS

As a first step, a systematic literature search was carried out to identify works that deal with the creation and not the use of medical instructional videos. To date, corresponding publications do not exist. In a workshop, the participants, who already gained experience in creating this type of video, exchanged ideas. These were critically discussed and analyzed. As a result, a checklist was created. In a subsequent multi-step review process, the checklist was reviewed with regard to applicability, comprehensibility, completeness and quality of the items.

RESULTS

Four phases in the creation of an instructional video could be differentiated: preliminary reflections, preparation, day of filming, post-production. The checklist is structured accordingly and should be actively processed phase by phase. The checklist is created in such a way that it can be used and edited without reading this text. Particular focus is placed on the patient and his needs.

CONCLUSION

The checklist created provides useful help in the creation of medical instructional videos and can for the first time serve as a guide especially for orthopedic and accident surgical instructional videos.

Autologous Iliac Bone Graft Compared with Biphasic Hydroxyapatite and Calcium Sulfate Cement for the Treatment of Bone Defects in Tibial Plateau Fractures: A Prospective, Randomized, Open-Label, Multicenter Study

BACKGROUND

Bone-graft substitutes are commonly used for the augmentation of traumatic bone defects in tibial plateau fractures. However, their clinical performance compared with that of autologous bone-grafting, the gold standard in bone defect reconstruction, still remains under debate. This study investigates the differences in quality of life, pain, and radiographic outcomes in the treatment of tibial plateau fracture-associated bone defects with either autologous bone grafts or a bioresorbable hydroxyapatite and calcium sulfate cement (CERAMENT BONE VOID FILLER [CBVF]; BONESUPPORT).

METHODS

In this study, 135 patients with acute depression and split-depression fractures of the proximal part of the tibia (OTA/AO types 41-B2 and 41-B3) were enrolled in a prospective, controlled, randomized, multicenter trial including 20 hospitals in Germany. Patients were randomized to receive either autologous iliac bone graft or CBVF for reconstruction of the bone defect. The primary outcome measures were the Short Form (SF)-12 version 2 Physical Component Summary (PCS) score at week 26 (the study was designed to show noninferiority of the CBVF with regard to the PCS with a prespecified margin of -5 points) and the pain level at 26 weeks postoperatively measured by a visual analog scale (VAS). The secondary outcomes were the SF-12 version 2 Mental Component Summary (MCS) and SF-12 PCS scores at weeks 1, 6, and 12 and bone-healing on radiographs.

RESULTS

Age, sex, fixation methods, and fracture pattern were comparable in both groups. There were no significant differences (p > 0.05) in the SF-12 PCS or VAS scores at postoperative week 26. There was a significant reduction of blood loss (p = 0.007) and pain levels (p = 0.008) at postoperative day 1 in the CBVF group. The rates of fracture-healing, defect remodeling, and articular subsidence were not significantly different (p > 0.05) in both groups.

CONCLUSIONS

Bioresorbable CBVF was noninferior to autologous bone graft with regard to both patient-reported and radiographic outcomes in tibial plateau fractures of OTA/AO types 41-B2 and 41-B3.

LEVEL OF EVIDENCE

Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

Complications during removal of conventional versus locked compression plates: is there a difference?

BACKGROUND

Osteosynthesis plate removal is one of the most commonly performed procedures in orthopaedic surgery. Due to technological advances and the quality of increasing osteosynthesis material, more and more locked plates have been implanted over the last 20 years. The aim of this study was to determine whether the complication rate during plate removal differs between conventional and locked plates.

MATERIAL AND METHODS

In this retrospective cohort study, 620 patients were included and divided into two groups based on the type of plate (locked and conventional). Technical complications during implant removal included screw breakage, destroyed screw head, implant breakage, remaining implant material, refracture, bony or soft tissue overgrowth. The following plate-associated complications were identified: osteosynthesis plate not detachable, plate bent or broken, necessity of special tools or plate loosened. Three types of screw-related complications were observed: screw not detachable, screw broken or screw dislocated.

RESULTS

Overall, complications related to the plate or screws were documented in 110 of the 620 cases. These complications occurred in 48 of the 382 cases involving conventional osteosynthesis (7.7% of all removals, 12.6% of all conventional removals) and in 62 of the 238 cases involving locked plate osteosynthesis (10.0% of all removals, 26.1% of all locked plate removals). The statistical analysis showed a significantly higher implant-related complication rate with locked plates compared to the conventional plates (p < 0.01).

CONCLUSIONS

Hardware removal can be a complication-afflicted operation, especially cases involving locked-plate removal should only be performed if a strong indication is evident. Possible benefits of the procedure should be considered carefully, taking the cost-benefit ratio into account.

Matrix-Associated Autologous Chondrocyte Implantation: A Clinical Follow-Up at 15 Years

INTRODUCTION

A prospective clinical investigation was carried out in order to clarify whether Matrix-associated autologous chondrocyte implantation (MACI) results in clinical improvement at long-term follow-up.

HYPOTHESIS

MACI will result in clinical improvement at long-term follow-up.

STUDY DESIGN

Case series; level of evidence, 4.

METHODS

Thirty-eight patients were treated with MACI. These patients were evaluated for up to a mean of 16 years (range 15-17 years) after the intervention. Three different scores (Lysholm-Gilquist score, International Cartilage Repair Society score, and Tegner score) formed the basis of this study. Overall, we were able to obtain valid preoperative and postoperative results from 18 (47%) of 38 patients. In 1 patient, both knees were treated. In 4 patients, an arthroplasty was implanted over the course of time; thus they were excluded from this case series. In conclusion, follow-up of 15 knees was performed in the recent series.

RESULTS

In subjective rating, 12 out of 14 patients (86%) rated the function of their knee as much better or better than before the index procedure. All numerical outcome scores showed significant improvement compared to the preoperative value (preoperative/postoperative at 5 years/postoperative at 15 years): Lysholm score 59.6 (±24.6)/78.6 (±21.5)/82.7 (±11.3), International Knee Documentation Committee score 50.6 (±22.7)/64.7 (±21.6)/69.7 (±18.7), Tegner score 3.0 (±2.2)/3.6 (±1.5)/5.2 (±1.7).

CONCLUSION

The significantly improved results on 3 scores after 15 years suggest that MACI represents a suitable treatment of local cartilage defects in the knee.

Complications in Treatment of 31-A Fractures with Trochanteric Gamma Nail (TGN) Versus Gamma3 Nail (G3N) - A Review of 217 Cases

INTRODUCTION

The aim of this study was to clinically evaluate two generations of intramedullary gamma-nail used in the treatment of 31-A femur fractures.

MATERIALS AND METHODS

In two consecutive series, 117 trochanteric gamma nails (TGN) and 100 Gamma3 nails (G3N) were implanted for the treatment of inter- and subtrochanteric fractures between 2009 and 2011. Clinical and radiological follow-up examinations were assessed. An analysis of surgical time, hemoglobin drop and complications were performed.

RESULTS

Average surgical time, fluoroscopy time, haemoglobin drop and length-of-stay (LOS) were similar in both groups. No significant differences were found in surgery-related complications like wound hematomas (p=0,59), abscesses (p=0,38), wound infections (p=0,69) and Cut-outs (p=0,69) between the two groups. The cumulative surgery-related complication rate was higher in the TGN group compared to the G3N group (13,68% vs. 8%) but this did not reach statistical significance (p=0,2).

CONCLUSION

Our findings suggest that both TGN and G3N allow adequate treatment of trochanteric fractures with an acceptable complication rate.

Treatment of femoral neck fracture with a minimal invasive surgical approach for hemiarthroplasty - clinical and radiological results in 180 geriatric patients

Purpose :

The Direct Anterior Approach (DAA) is well established as a minimal access approach in elective orthopaedic hip surgery. For the growing number of elderly patients with femoral neck fractures treated with Bipolar Hip Hemiarthroplasty (BHH), only a few results do exist. The study shows the clinical and radiological outcome for 180 patients treated by a modified DAA with BHH.

Materials and Methods :

The data of 180 geriatric patients with medial femoral neck fractures were evaluated retrospectively. The general and surgical complications, mobilisation using the Timed Up and Go test (TUG), the social environment pre- and postoperative and the radiological results have been compared with established approaches for geriatric hip surgery.

Results :

After joint replacement, 18 (10%) patients were developed pneumonia, of which 3 (1.7%) died during hospitalisation. In 7 cases (4%), surgical revision had to be carried out: three times (1.7%) because of a seroma, three times (1.7%) because of subcutaneous infection, and one time (0.6%) because the BHH was removed, owing to deep wound infection. One dislocation (0.6%) occurred, as well as one femoral nerve lesion (0.6%) occured. 88.3% of patients were mobilised on walkers or crutches; the Timed Up and Go Test showed a significant improvement during inpatient rehabilitation. 83% were discharged to their usual social environment, 10% were transferred to a short-term care facility and 7% were relocated permanently to a nursing home. 3/4 of patients had a cemented stem alignment in the range between -5° and 5°, while 2/3 of patients had a maximum difference of 1 cm in leg length.

Conclusion :

Using the modified DAA, a high patient satisfaction is achieved after implantation of a BHH. The rate of major complications is just as low as in conventional approaches, and rapid mobilisation is possible.

An economic analysis of aseptic revision hip arthroplasty: calculation of partial hospital costs in relation to reimbursement

INTRODUCTION

Aseptic loosening is one of the most common intermediate and long-term complications after total hip replacement (THR). These complications cause suffering and require expensive revision surgery. Little concrete data on direct costs are available from the hospital's, moreover operating department's perspective. We here provide a detailed analysis of the costs of THR revision and relate them to reimbursement underlying the German diagnosis-related groups (DRG) system.

MATERIALS AND METHODS

Major cost parameters were identified using for orientation the cost matrix of the German Institute for Hospital Reimbursement (InEK GmbH). We then retrospectively analysed the major direct costs of aseptic revision THR in terms of contribution margins I and II. The analysis included a total of 114 patients who underwent aseptic revision from 1 January 2009 to 31 March 2012. Data were retrieved from the hospital information system and patient records. All costs of surgery, diagnostic tests, and other treatments were calculated as purchase prices in EUR. The comparative analysis of direct costs and reimbursements was done for DRG I46A and I46B from the hospital's, especially treating department's rather than the society or healthcare insurance's perspective.

RESULTS

The average direct cost incurred by the hospital for a THR revision was <euro>4,380.0. The largest share was accounted for surgical costs (62.7 % of total). Implant and staff costs were identified as the most important factors that can be influenced. The proportion of the daily contribution margin that was left to cover the hospital's indirect cost decreased with the relative cost weight of the DRG to which a patient was assigned.

CONCLUSION

Our study for the first time provides a detailed analysis of the major direct case costs of THR revision for aseptic loosening from the provider's perspective. Our findings suggest that these revision operations could be performed cost-beneficially by the operating unit. From an economic perspective, cases with higher cost weights are more favorable for a hospital. These results need to be confirmed in multicenter studies.

Refixation of osteochondral fractures by ultrasound-activated, resorbable pins: An ovine in vivo study

Objectives

Osteochondral injuries, if not treated adequately, often lead to severe osteoarthritis. Possible treatment options include refixation of the fragment or replacement therapies such as Pridie drilling, microfracture or osteochondral grafts, all of which have certain disadvantages. Only refixation of the fragment can produce a smooth and resilient joint surface. The aim of this study was the evaluation of an ultrasound-activated bioresorbable pin for the refixation of osteochondral fragments under physiological conditions.

Methods

In 16 Merino sheep, specific osteochondral fragments of the medial femoral condyle were produced and refixed with one of conventional bioresorbable pins, titanium screws or ultrasound-activated pins. Macro- and microscopic scoring was undertaken after three months.

Results

The healing ratio with ultrasound-activated pins was higher than with conventional pins. No negative heat effect on cartilage has been shown.

Conclusion

As the material is bioresorbable, no further surgery is required to remove the implant. MRI imaging is not compromised, as it is with implanted screws. The use of bioresorbable pins using ultrasound is a promising technology for the refixation of osteochondral fractures.

Marginal contribution of UKS- versus TKA in varus arthritis of the knee

BACKGROUND

In recent years, decisions regarding the treatment of individual patients have increasingly been affected by economic considerations. The G-DRG system reimburses sledge endoprosthetic implantations at a much lower rate than surface replacements and at significantly different cost weights (CW). Therefore, when only G-DRG payments are considered, TKA produces higher gains. Taking only these revenues alone into consideration, however, does not provide the basis of an economically sound decision-making process. The target of this research was to present a comparison between variable costs of the two procedures.

METHODS

The mean cost and performance data of 28 Endo-Modell (Link company) sledge implantations (UKS) and of 85 NexGen CR surface replacement total knee arthroplasties (TKA; Zimmer company) were compared in 2007.

RESULTS

From the perspective of the hospital, UKS treatment is of greater economic advantage when the medical indication is given. In preferring UKS marginal contribution can be improved, and although the relative weighting is comparatively low, the costs are significantly lower than in a comparative analysis of TKA. Based on the length of stay required for each procedure the average daily CW for UKS can be calculated as 0.1728, while being 0.1955 for TKA. The earlier release of the first patient results in another patient being admitted 1.5 days earlier and thus an increase in case mix. Meanwhile, the case-mix index and the costs of care per case decrease ceteris paribus.

CONCLUSION

Assuming the correct medical indication, the hospital seeking to maximize its marginal contribution would be wise to select sledge endoprosthesis implantation. Considering the economic perspective of gains and costs, the assumption that TKA is advantageous could not be confirmed in the present study.

Medium-term results after total clavicle resection in cases of osteitis: a consecutive case series of five patients

PURPOSE

Claviculectomy is a rare and poorly described event in the surgical therapy of diseases of the clavicle. We present a case series and functional results of patients who underwent total claviculectomy.

METHODS

From 1995 to 2006 a total of 26 patients diagnosed with osteitis of the clavicle underwent surgery in our unit. Of these, five patients (all female) needed a total resection of the clavicle in order to ensure permanent healing from infection. The data collection was prospective. The data gathered preoperatively and at follow-up included clinical examinations, laboratory findings, radiographs and the Constant shoulder scores. The mean follow-up period was 7.5 months.

RESULTS

The surgical concept described was able to eliminate infection in all cases studied within an average hospital stay of 13.4 days (8-18 days). Only one patient showed complications; suffering from chronic pain syndrome requiring surgical revision. After total resection of the clavicle four of five patients showed very good functional results. The average Constant score showed a significant increase from 82 before surgery to 95 at follow-up.

CONCLUSIONS

The surgical technique described for total claviculectomy, along with the insertion of local antibiotic beads, was able to eliminate infection in every case. Good functional results and a low complication rates were observed. For good functional results and the permanent elimination of infection, adjacent joints have to be addressed, the periosteal tube should be preserved and early functional treatment is essential.

[Sledge versus bicondylar surface treatment in the endoprosthetic therapy for unicompartmental knee arthrtitis--a comparative cost analysis]

BACKGROUND

The G-DRG system reimburses sledge endoprosthetic implantations (UKA) at a much lower rate than surface replacements (TKA), at significantly different cost weights (CW). Therefore, when only G-DRG payments are considered, the complete endoprosthesis implantation produces higher gains. An orientation on these revenues alone, however, does not provide the basis for an economically sound decision-making process. The aim of this study is to present a comparison of the variable costs of the two procedures.

MATERIAL AND METHODS

The mean cost and performance data of 28 Endo-Model UKA implantations and of 85 NexGen CR TKA replacements were compared with each other in 2007.

RESULTS

From the perspective of the hospital, when the correct medical indication is present, UKA treatment is of greater economic advantage. In this way the total unit contribution margin can be improved, and although the relative weighting is comparatively low, the costs are significantly lower than in a comparative analysis of the TKA.

CONCLUSION

For the desired maximisation of the unit contribution margin, assuming that it is the proper medical indication, the recommendation for the hospital would be implantation of the UKA. Considered from the economic perspective of gains and costs, the assumption that a TKA would be advantageous could not be confirmed in the present study.

Mid-term results after operative treatment of rockwood grade III-V acromioclavicular joint dislocations with an AC-hook-plate

Acromioclavicular joint dislocations often occur in athletic, young patients after blunt force to the shoulder. Several static and dynamic operative procedures with or without primary ligament replacement have been described. Between February 2003 and March 2009 we treated 313 patients suffering from Rockwood III-V lesions of the AC joint with an AC-hook plate. 225 (72 %) of these patients could be followed up. Mean operation time was 42 minutes in the conventional group and 47 minutes in the minimal invasive group. The postoperative pain on a scale from 1 to 10 (VAS-scale) was rated 2.7 in the conventional group and 2.2 in the minimal invasive group. Taft score showed very good and good results in 189 patients (84%). Constant score showed an average of 92.4 of 100 possible points with 89 % excellent and good results and 11 % satisfying results. All patients had some degree of pain or discomfort with the hook-plate in place. These symptoms were relieved after removal of the plate. The overall complication rate was 10.6 %. There were 6 superficial soft tissue infections, 1 fracture of the acromion, 7 redislocations after removal of the hook-plate. We observed 4 broken hooks which could be removed at the time of plate removal, 4 seromas and 2 cases of lateral clavicle bone infection, which required early removal of the plate. We can conclude that clavicle hook plate is a convenient device for the surgical treatment of Rockwood Grade III-V dislocations, giving good mid-term results with a low overall complication rate compared to the literature. Early functional therapy is possible and can avoid limitations in postoperative shoulder function.

Biopolymer augmentation of the lag screw in the treatment of femoral neck fractures--a biomechanical in-vitro study

The cut-out of the sliding screw is one of the most common complications in the treatment of intertrochanteric fractures. The reasons for the cut-out are: a suboptimal position of the hip-screw in the femoral head, the type of fracture and poor bone quality. The aim of this study was to reproduce the cut-out event biomechanically and to evaluate the possible prevention of this event by the use of a biopolymer augmentation of the hip screw. Concerning the density and compression force of osteoporotic femoral bone polyurethane foam according to the terms of the Association for Standard Testing Material (ASTMF 1839-97) was used as test material. The polyurethane foam Lumoltan 200 with a compression force of 3.3 Mpa and a density of 0.192 g/cm(3) was used to reproduce the osteoporotic bone of the femoral fragment (density 12 lbm/ft(3)). A cylinder of 50 mm of length and 50 mm of width was produced by a rotary splint raising procedure with planar contact. The axial load of the system was performed by a hydraulic force cylinder of a universal test machine type Zwick 1455, Ulm, Germany. The CCD-angle of the used TGN-System was preset at 130 degrees. The migration pattern of the hip screw in the polyurethane foam was measured and expressed as a curve of the distance in millimeter (mm) against the applied load in Newton (N) up to the cut-out point. During the tests the implants reached a critical changing point from stable to unstable with an increased load progression of steps of 50 Newton. This unstable point was characterized by an increased migration speed in millimeters and higher descending gradient in the migration curve. This peak of the migration curve served as an indicator for the change of the hip screw position in the simulated bone material. The applied load in the non-augmented implant showed that in this group for a density degree of 12 (0,192 g/cm(3)) the mean force at the failure point was 1431 Newton (+/- 52 Newton). In the augmented implant we found that the mean force at the failure point was 1987 Newton (+/- 84 Newton). This difference was statistically significant. In conclusion, the bone density is a significant factor for the stability of the hip screw implant. The osteosynthesis with screws in material with low density increases the chance for cut-out. A biopolymer augmented hip screw could significantly improve the stability of the fixation. The use of augmentation with a fast hardening bone replacement material containing polymer-ceramic changes the point of failure under axial load in the osteoporotic bone model and could significantly improve the failure point. Our study results indicate, that a decrease of failure in terms of cut-out can be achieved with polymer augmentation of hip screws in osteoporotic bones.

Posttraumatic severe infection of the ankle joint - long term results of the treatment with resection arthrodesis in 133 cases

Although there is a clear trend toward internal fixation for ankle arthrodesis, there is general consensus that external fixation is required for cases of posttraumatic infection. We retrospectively evaluated the technique and clinical long term results of external fixation in a triangular frame for cases of posttraumatic infection of the ankle. From 1993 to 2006 a consecutive series of 155 patients with an infection of the ankle was included in our study. 133 cases of the advanced "Gächter" stage III and IV were treated with arthrodesis. We treated the patients with a two step treatment plan. After radical debridement and sequestrectomy the malleoli and the joint surfaces were resected. An AO fixator was applied with two Steinmann-nails inserted in the tibia and in the calcaneus and the gap was temporary filled with gentamicin beads as the first step. In the second step we performed an autologous bone graft after a period of four weeks. The case notes were evaluated regarding trauma history, medical complaints, further injuries and illnesses, walking and pain status and occupational issues. Mean age at the index procedure was 49.7 years (18-82), 104 patients were male (67,1%). Follow up examination after mean 4.5 years included a standardised questionnaire and a clinical examination including the criteria of the AO-FAS-Score and radiographs. 92,7% of the cases lead to a stable arthrodesis. In 5 patients the arthrodesis was found partly-stable. In six patients (4,5%) the infection was not controllable during the treatment process. These patients had to be treated with a below knee amputation. The mean AOFAS score at follow up was 63,7 (53-92). Overall there is a high degree of remaining disability. The complication rate and the reduced patient comfort reserve this method mainly for infection. Joint salvage is possible in the majority of cases with an earlier stage I and II infection.

Hook plate for medial clavicle fracture

Medial clavicle fractures are the least common type of clavicular fractures. Although rare, such injuries deserve rapid diagnosis and effective treatment to avoid future complications. An optimal, standardized operative treatment has not been yet established. We report a case of medial clavicle fracture, where primary operative treatment was indicated due to gross dislocation. An open reduction and osteosynthesis with a modified hook plate was performed, leading to an excellent postoperative outcome after a sixteen-month follow-up. The hook plate seems to be a promising approach for the operative treatment of medial clavicle fractures.

Arthroscopic treatment of multidirectional glenohumeral instability in young overhead athletes

Purpose:

This prospective case series evaluates the outcome, and the return to sports of young overhead athletes with a persistent, symptomatic multidirectional instability (MDI) with hyperlaxity type Gerber B5 treated with an arthroscopic anteroposteroinferior capsular plication and rotator interval closure.

Methods:

9 young overhead athletes (10 shoulders) with the rare diagnosis of MDI (Gerber B5) and an indication for operative treatment, after a failed physiotherapy program were physically examined 3, 6 and 12 months postoperatively by a physical examination, and got a final phone interview after median 39 months.

Results:

At the final follow-up all patients were satisfied; Rowe Score showed 7 “excellent” and “good” results; Constant Score was “excellent” and “good” in 6, and “fair” in 1 patient. 7/9 returned to their previous sports, 3/9 at a reduced level.

Conclusion:

Symptomatic MDI requires an individual indication for surgical treatment after a primary conservative treatment. The described arthroscopic technique stabilizes glenohumeral joint. A return to overhead sports is possible but often at a reduced level; returning to high-performance sports cannot be recommended because of the high risk of reinstability.

Operative Treatment and Soft Tissue Management of Open Distal Tibial Fractures - Pitfalls and Results

Open tibial fractures usually result from high-energy trauma. Severe soft-tissue injuries are often combined with open fractures of the distal tibia. A consecutive series of 42 patients with open extraarticular distal tibial fractures (Gustilo I-IIIc) operated on between July 2006 and February 2009 were included in the study reported here. We performed open reduction and internal fixation for the Gustilo I cases. Soft tissue was closed directly after antibiotic beads had been temporarily applied. For the Gustilo II and III cases, our treatment protocol included soft-tissue debridement of all devitalized soft tissue and bone fragments, pulsatile jet irrigation, and external stabilization. Soft tissue was temporarily closed with Epigard_ after the application of antibiotic beads. A second-look operation was scheduled after 3-5 days. Gustilo II patients needed an average of 1.1 (0-3) revisions until wound closure, compared to the average of 2.1 revisions necessary for the Gustilo III patients. It took 5.6 (0-16) days to obtain definitive wound closure in the Gustilo II patients and 9.9 (3-28) days in the Gustilo III patients. Skin grafting was sufficient for definitive softtissue closure in ten cases, local flaps in eight cases, and free musculocutaneous flaps were needed in six cases. Gustilo II patients with primary wound closure remained hospitalized for 11 days, while patients with secondary wound closure stayed in hospital for an average of 20 days. Our early results concerning infection rate, number of reoperations, and time to bony consolidation can be compared with other studies. Functional results will have to be evaluated at clinical follow-up.

[Single bundle anterior cruciate ligament reconstruction using quadriceps tendon autografts]

AIM

The purpose of this study was to evaluate postoperative outcome and functional scores after single bundle anterior cruciate ligament (ACL) reconstruction with the use of quadriceps tendon autografts after a 16 (12-24) month follow-up.

METHOD

54 patients (9 women, 45 men, body mass index [BMI] 25.3 [18.1-36.3 kg/m (2)]) were included in this prospective series, treated between January 2004 and December 2005. Ligament stability was assessed with the Lachmann and pivot-shift tests and a KT 1000 arthrometer. Tegner index, Lysholm-Gilquist score and the International Knee Documentation Committee (IKDC) were employed to evaluate the functional outcomes. In addition, the single leg hop test was performed.

RESULTS

Ligament arthrometry using the KT 1000 arthrometer demonstrated a mean side-to-side difference of 1.53 mm (0.2-4.1 mm). Regarding the Lachmann test, 17 patients (32%) showed 1+ laxity and no patient had an abnormal pivot-shift. The mean Tegner activity score was 4.22 (1-10), the mean Lysholm score was 80.8 (20-100) and the mean IKDC score 68.1 (29-87). Results of the single leg hop test revealed a mean decline of the treated leg to 87.7% (70-100%) of the contralateral side. The mean extension was reduced by 1.7 degrees (0-10 degrees) on the treated knee and the flexion by 2.1 degrees (0-10 degrees), compared to the contralateral knee.

CONCLUSION

Single bundle anterior cruciate ligament reconstruction using quadriceps tendon demonstrates highly satisfactory results. Due to a moderate donor site morbidity and preservation of the medial stabilizing structures of the knee a wider use in primary cruciate ligament reconstruction may arise in the future.

Early Weight Bearing of Calcaneal Fractures Treated by Intraoperative 3D-Fluoroscopy and Locked-Screw Plate Fixation

Operative therapy of intraarticular fractures of the calcaneus is an established surgical standard. The aim is an accurate reduction of the fracture with reconstruction of Boehler’s angle, length, axis and subtalar joint surface. Intraoperative 3D-fluoroscopy with the Siremobil Iso-C 3D® mobile C-arm system is a valuable assistant for accurate reconstruction of these anatomical structures. Remaining incongruities can be recognized and corrected intraoperatively. The achieved reduction can be fixed by the advantages of an internal fixator (locked-screw plate interface). In the period of October 2002 until April 2007 we operated 136 patients with intraarticular fractures of the calcaneus by means of anatomical reduction, and internal plate fixator under intraoperative control of 3D-fluoroscopy. All patients were supplied with an orthesis after the operation which allowed weight bearing of 10 kg for 12 weeks for the patients operated between October 2002 and October 2004 (Group A). Transient local osteoporosis was observed in all X-Rays at follow-up after an average of 8,6 months. Therefore we changed our postoperative treatment plan for the patients operated between November 2004 and April 2007 (Group B). Weight bearing started with 20 KG after 6 weeks, was increased to 40 KG after 8 weeks and full weight bearing was allowed after 10 weeks for these patients. In no case a secondary dislocation of the fracture was seen. No bone graft was used. At follow up the average American Foot and Ankle Society Score (AOFAS) were 81 for Group_A, compared to 84 for Group B, treated with earlier weight bearing. Autologous bone graft was not necessary even if weight bearing was started after a period of six weeks postoperatively. The combination of 3D-fluoroscopy with locked internal fixation showed promising results. If the rate of patients developing subtalar arthrosis will decrease by this management will have to be shown in long term follow up.

Acoustic monitoring (RFM) of total hip arthroplasty - Results of a cadaver study

Introduction

At present there are no reliable non-traumatic and non-invasive methods to analyse the healing process and loosening status after total hip replacement. Therefore early as well as late loosening of prosthesis and interface component problems are difficult to be found or diagnosed at any time.

Methods

In a cadaver study the potential application of Resonance Frequency Monitoring (RFM) will be evaluated as a non-invasive and non-traumatic method to monitor loosening and interface problems in hip replacement. In a 65 year old female cadaver different stability scenarios for a total hip replacement (shaft, head/modular head and cup, ESKA, Luebeck, Germany) are simulated in cemented and cement less prosthesis and then analysed with RFM. The types of stability vary from secure/press-fit to interface-shaft disruption.

Results

The RFM shows in cemented as well as cement less prosthesis significant intra-individual differences in the spectral measurements with a high dynamic (20 dB difference corresponding to the factor 100 (10000%)), regarding the simulated status of stability in the prosthesis system.

Conclusion

The results of the study demonstrate RFM as a highly sensitive non-invasive and non-traumatic method to support the application of RFM as a hip prosthesis monitoring procedure. The data obtained shows the possibility to use RFM for osteointegration surveillance and early detection of interface problems, but will require further evaluation in clinical and experimental studies.

Initial results of the s3-humerus plate

Fractures of the humeral head account for 5% of all fractures and incidence increases with age. Depending on fracture form and patients age a wide variety of therapeutical options exist. Stable fractures can be treated conservatively, while the majority of unstable and displaced fractures require surgical treatment. Many different surgical options are available; open reduction and internal fixation are widely preferred. The S3 Proximal Humerus Plate is a contoured plate to match the complex shape of the proximal humerus. It is designed to be positioned distal to the greater tuberosity preventing subacromial impingement.

Between august 1 and 30, 2007, 5 patients meeting the inclusion criteria (that is primary operative stabilization within 7 days after trauma in a standardized way and minimal follow up period of 3 month) with acute fractures of the proximal humerus were treated with S3 Proximal Humerus Plate. Follow up was performed using the Constant Score. The mean age was 59.0 years. According to the Neer classification fractures were rated as Neer 2,3 and 4. A mean Constant score of 72.3 (57-86) points was obtained.

We did not observe any complications like humeral head necroses, loss of reduction, deep infection or breakage of the plate.

["Basketball Foot"--long-time prognosis after peritalar dislocation]

Subtalar dislocation is considered a severe injury but occurs rarely and studies generally refer to relatively small patient collectives. We investigated the functional outcome in 22 cases to determine the long-term prognosis. Since associated foot injury is common, we compared the outcome for 12 cases of isolated subtalar luxation with 10 cases of collateral fractures of the adjacent bones of the hind foot and Talus. 19 cases of complex, partially open injuries after high energy trauma have got excluded because of the apparently poor long-term results. The Kitaoka-hind-foot-Score (AOFAS) after mean follow up of 8.3 years indicated a significantly better outcome for isolated luxation. Nearly 50 % of isolated luxations had a excellent outcome (73 %, mean score 89), luxations with associated fractures had mainly good and fair results (73 %, mean score 74). Analysis of the gait pattern by dynamic plantar pressure measurement demonstrated lower pressures in the isolated luxation group and higher pressures in the group with associated fractures in the lateral region of the forefoot with shorter phases of weight bearing.

Determination of optimal non-invasive patient fixation methods for use in robotic hip replacement surgery--an in vitro study

BACKGROUND

A robotic system for the implantation of a total hip arthroplasty (THA) is currently under development. One of the goals of this system is non-invasive patient fixation, aiding the robotic system by an infrared tracking system. To determine the extent of fixation that can be achieved by non-invasive methods, an in vitro study was performed.

METHODS

In cadaver testing, different non-invasive fixation methods (Arthrex leg holder with tourniquet mechanism; arthroscopic leg holder with disposable foam inserts; gynaecological leg holder; Goepel knee crutch) were evaluated under load in different directions.

RESULTS

Deviation was measured in the range 0.33-18.1 mm with up to 20 N load. The testing showed the pneumatic leg holder system to provide the highest stability, followed by an arthroscopic leg holder system with foam inserts.

CONCLUSIONS

Use of a leg holder with foam inserts produced a stability that should enable tracking of the remaining deviation by the navigation system. We will therefore use this method in our future development of the robotic milling tool.

Robotic systems in total hip arthroplasty--is the time ripe for a new approach?

The technical aspects of manual total hip arthroplasty are briefly described. The development, technique and technical problems of previous robotic systems in total hip arthroplasty are described with special details of the Robodoc--System. Recent advances regarding the minimally invasive technique of total-hip implantation and navigation are described. The current development of a robotic assisted system for total hip arthroplasty is presented. This project aims to combine the advantages of minimally invasive techniques and navigational systems with the accuracy that robotic assisted bone milling can provide. The project-name is RomEo (Robotic minimally invasive Endoprosthetics), the main project partners are the Helmut-Schmidt-University/Hamburg and the Department of Trauma and Orthopaedics of the BG Trauma Hospital Hamburg.

Physical evaluation of a new technique for X-ray dose reduction: Measurement of signal-to-noise ratio and modulation transfer function in an animal model

Aim of this study was to record objective changes in image quality of optically re-exposed, radiation-reduced X-ray images in comparison to a normally exposed reference image in an animal model. Under investigation is the question if optical re-exposure of conventional, radiation-reduced X-ray images partially or even fully compensates the loss of information caused by underexposure. Dose-reduced, underexposed images were prepared by reducing the mAs product to 50% with constant anode voltage. Reproduction of the image was performed with a 52% decrease in the radiation dose. Comparing different re-exposure times, the optimal time was found to be 60s. These underexposed X-rays were then optically re-exposed for a defined period of time before development. In all X-ray images of the animal model, different osseous structures were defined as regions of interest (ROI) for evaluation of the objective changes in image quality. The density curves were plotted with the two-beamed densitometer. The contrast transfer factors as the function of local frequency were determined from this, which served as the basis for calculating the modulation transfer factor. To establish if X-ray sensitisation by optical re-exposure leads to a change in the sensitometric gradation, the sensitometric curves were determined using a standardized aluminum scale and thermal luminescence dosimetry. In the comparison the lowest correlation with the standard technique film (X-ray 1) was seen in the purely dose-reduced X-ray. In the range of 1.6-3.4Lp/mm, both SNR curves have an identical course. Despite a 52% dose reduction in the re-exposed image, both densitometry curves of the conventional and re-exposed X-ray show an almost identical distribution of the transmittance levels. In conclusion film sensitisation provides a technically simple and inexpensive procedure, which is easily integrated into previous film development processes and considerably reduces the patient radiation exposure as well as clearly improving the image quality.

Locked vs. unlocked plate osteosynthesis of the proximal humerus - a biomechanical study

BACKGROUND

Locked plates (internal fixators) have been found to be an optimal method for the fixation in proximal humeral fractures. In a biomechanical cadaver study the difference between locked and non-locked osteosyntheses was investigated.

METHODS

Paired humeri were harvested, bone density measured. Locked internal fixators were mounted on one specimen; identical plate-screw-systems without locking mechanism applied to the contralateral specimen for comparison. After that, a transverse subcapital osteotomy was performed. With 7 pairs of humeri static tests with increasing axial loads and with 5 pairs dynamic tests with 10 N preload and 80 N maximal axial load for up to 1 million cycles were performed.

RESULTS

In the static experiments the elastic stiffness of the construct was 74% higher in the locked group (median 80 N/mm, quartile range 77-86 N/mm) compared with the non-locked group (46 N/mm, 35.5-56.5 N/mm). The difference was statistically significant (Wilcoxon test for paired samples, P<0.05). Similarly, the linear range until failure was definitely extended in the locked group by 64% (92 N, 89-98 N vs. 56 N, 36.5-73.5 N, P<0.05). Under dynamic loading the non-locked group showed fixation failures between 97,000 and 500,000 cycles. In the locked group no failure was observed until the end of the experiment at 1 million cycles (P<0.0.5). The final deformation was found to be 1 mm (median, quartil range 1.0-1.2 mm) in the non-locked group and 0.3 mm (0.2-0.3 mm) in the locked group (P<0.05). The differences were found equally in lower as well as in higher bone density specimen.

INTERPRETATION

Because of the optimal load transfer between implant and cancellous bone, a locked screw plate interface will reduce fixation failure in proximal humeral fractures.