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Orthopaedic Proceedings
Vol. 105-B, Issue SUPP_7 | Pages 61 - 61
4 Apr 2023
Makaram N Al-Hourani K Nightingale J Ollivere B Ward J Tornetta III P Duckworth A
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The aim of this study was to perform a systematic review of the literature on Gustilo-Anderson (GA) type IIIB open tibial shaft (AO-42) injuries to determine the consistency of reporting in the literature. A search of PubMed, EMBASE and Cochrane Central Register of Controlled Trials was performed to identify relevant studies published from January 2000 to January 2021 using the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) statement. The study was registered using the PROSPERO International prospective register of systematic reviews. Patient/injury demographics, management and outcome reporting were recorded. There were 32 studies that met the inclusion criteria with a total of 1,947 patients (70.3% male, 29.7% female). There were 6 studies (18.8%) studies that reported on comorbidities and smoking, with mechanism of injury reported in 22 (68.8%). No studies reported on all operative criteria included, with only three studies (9.4%) reporting for time to antibiotics, 14 studies (43.8%) for time from injury to debridement and nine studies (28.1%) for time to definitive fixation. All studies reported on the rate of deep infection, with a high proportion documenting union rate (26/32, 81.3%). However, only two studies reported on mortality or on other post-operative complications (2/32, 6.3%). Only 12 studies (37.5%) provided any patient reported outcomes. This study has demonstrated a deficiency and a lack of standardized variable and outcome reporting in the orthopaedic literature for Gustilo-Anderson type IIIB open tibial shaft fractures. We propose a future international collaborative Delphi process is needed to standardize


Orthopaedic Proceedings
Vol. 105-B, Issue SUPP_7 | Pages 143 - 143
4 Apr 2023
Kröger I Pätzold R Brand A Wackerle H Klöpfer-Krämer I Augat P
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Tibial shaft fractures require surgical stabilization preferably by intramedullary nailing. However, patients often report functional limitations even years after the injury. This study investigates the influence of the surgical approach (transpatellar vs. parapatellar) on gait performance and patient reported outcome six months after surgery. Twenty-two patients with tibial shaft fractures treated by intramedullary nailing through a transpatellar approach (TP: n=15, age 41±15, BMI 24±3) or a parapatellar approach (PP: n=7, age 34±15, BMI 23±2) and healthy, matched controls (n=22, age 39±13, BMI 24±2) were assessed by instrumented motion analysis six months after intramedullary nailing. Short musculoskeletal function assessment questionnaire (SMFA) as well as kinematic and kinetic gait data were collected during level walking. Comparisons among approach methods and control group were performed by analysis of variance and Mann-Whitney test. Six months after surgery, knee kinetics in both groups differed significantly compared to controls (p <.04). The approach method affected gait speed (TP: p = .002; PP: p = .08) and knee kinematics in the early stance phase (TP: p = .011; PP: p = .082), with the parapatellar approach showing a more favorable outcome. However, the difference between patient groups was not significant for any of the assessed gait parameters (p > .2). Also, no differences could be found in the bother index (BI) or function index (FI) of SMFA between surgical approach methods (BI: TP: Mdn = 7.2, PP: Mdn = 9.4; FI: TP: Mdn = 10.3, PP: Mdn = 9.2, p > .7). Our study demonstrates, that six months after surgery for tibial shaft fractures functional limitations remain. These limitations appear not to be different for either a trans- or a parapatellar approach for the insertion of the intramedullary nail. The findings of this study are limited by the relatively short follow up time period and small number of patients. Future studies should investigate the source of the functional limitation after intramedullary nailing of tibial shaft fractures


Orthopaedic Proceedings
Vol. 105-B, Issue SUPP_16 | Pages 28 - 28
17 Nov 2023
Morris T Fouweather M Walshaw T Wei N Baldock T Eardley W
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Abstract. Objectives. The need to accurately forecast the injury burden has never been higher. With an aging, ever expanding trauma population and less than half of the beds available compared to 1990, the National Health Service (NHS) is stretched to breaking point1,2. Resultantly, we aimed to determine whether it is possible to predict the proportionality of injuries treated operatively within orthopaedic departments based on their number of Neck of Femur fracture (NOF) patients reported both in our study and the National Hip Fracture Database (NHFD). Methods. We utilised the ORthopaedic trauma hospital outcomes - Patient operative delays (ORTHOPOD) dataset of 22,585 trauma patients across the four countries of the United Kingdom (UK) admitted to 83 hospitals between 22/08/22 – 16/10/22. This dataset had two arms: arm one was assessing the caseload and theatre capacity, arm two assessed the patient, injury and management demographics. Results. Our results complied with the data reported to the NHFD in over 80% of cases for both the 2022 and five-year average reported numbers. More operations were performed for elderly hip fractures alone than for the combined totals of the next four most common fractures: ankle, distal radius, tibial shaft and forearm (6387 vs 5922). Conversely, 10 out of the 13 fracture types were not encountered by at least one hospital and 93% of hospitals encountered less than 2 fractures of a certain type.60% of trauma is treated within Trauma Units (TUs) however, per unit, Major Trauma Centres (MTCs) treat approximately 43% more patients. Similarly, 11 out of the 14 fracture types examined presented more frequently to a MTC however 3 of the most common fractures had a preponderance for TUs (elderly hip, distal radius and forearm fractures). After excluding NOF, lower limb fractures accounted for approximately 57% of fractures in all countries and ankle and distal radius fracture combined comprised more than 50% in 74% of regions. There were few outliers across the study regarding number of fractures treated by a hospital with tibial shaft fractures demonstrating the highest number of outliers with 4. Conclusions. The number of hip fractures seen on average by an individual unit remains relatively consistent as does the regional variation of any given fracture; resultantly, it is possible to predict injury proportionality based off a unit's hip fracture numbers. This powerful tool could transform both resource allocation and recruitment. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project


Orthopaedic Proceedings
Vol. 106-B, Issue SUPP_2 | Pages 100 - 100
2 Jan 2024
Morris T Fouweather F Walshaw T Baldock T Wei N Eardley W
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The need to accurately forecast the injury burden has never been higher. With an aging, ever expanding trauma population and less than half of the beds available compared to 1990, the National Health Service (NHS) is stretched to breaking point. 1,2. . We utilised a dataset of 22,585 trauma patients across the four countries of the United Kingdom (UK) admitted to 83 hospitals between 22/08/22 – 16/10/22 to determine whether it is possible to predict the proportionality of injuries treated operatively within orthopaedic departments based on their number of Neck of Femur fracture (NOF) patients. More operations were performed for elderly hip fractures alone than for the combined totals of the next four most common fractures: ankle, distal radius, tibial shaft and forearm (6387 vs 5922). Conversely, 10 out of the 13 fracture types were not encountered by at least one hospital and 93% of hospitals encountered less than 2 fractures of a certain type. 60% trauma is treated within Trauma Units (TUs) however, per unit, Major Trauma Centres (MTCs) treat approximately 43% more patients. After excluding NOF, lower limb fractures accounted for approximately 57% of fractures in all countries and ankle and distal radius fracture combined comprised more than 50% in 74% of regions. The number of hip fractures seen on average by an individual unit remains relatively consistent as does the regional variation of any given fracture; resultantly, it is possible to predict injury proportionality based off a unit's hip fracture numbers. This powerful tool could transform both resource allocation and recruitment


Orthopaedic Proceedings
Vol. 105-B, Issue SUPP_9 | Pages 15 - 15
17 Apr 2023
Inglis B Inacio J Dailey H
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Virtual mechanical testing is a method for measuring bone healing using finite element models built from computed tomography (CT) scans. Previously, we validated a dual-zone material model for ovine fracture callus that differentiates between mineralized woven bone and soft tissue based on radiodensity. 1. The objective of this study was to translate the dual-zone material model from sheep to two important clinical scenarios: human tibial fractures in early-stage healing and late-stage nonunions. CT scans for N = 19 tibial shaft fractures were obtained prospectively at 12 weeks post-op. A second group of N = 33 tibial nonunions with CT scans were retrospectively identified. The modeling techniques were based on our published method. 2. The dual-zone material model was implemented for humans by performing a cutoff sweep for both the 12-week and nonunion groups. Virtual torsional rigidity (VTR) was calculated as VTR = ML/φ [N-m. 2. /°], where M is the moment reaction, L is the diaphyseal segment length, and φ is the angle of twist. As the soft tissue cutoff was increased, the rigidity of the clinical fractures decreased and soft tissue located within the fracture gaps produced higher strains that are not predicted without the dual zone approach. The structural integrity of the nonunions varied, ranging from very low rigidities in atrophic cases to very high rigidities in highly calcified hypertrophic cases, even with dual-zone material modeling. Human fracture calluses are heterogeneous, comprising of woven bone and interstitial soft tissue. Use of a dual-zone callus material model may be instrumental in identifying delayed unions during early healing when callus formation is minimal and/or predominantly fibrous with little mineralization. ACKNOWLEDGEMENTS:. This work was supported by the National Science Foundation (NSF) grant CMMI-1943287


Orthopaedic Proceedings
Vol. 103-B, Issue SUPP_4 | Pages 9 - 9
1 Mar 2021
To K Khan W
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The current standard of practice following knee arthroplasty is to demonstrate the appropriate alignment of knee replacements using knee radiographs. Recent studies have suggested that standard knee radiographs provide adequate accuracy for tibial prosthesis alignment assessment as compared with long knee view radiographs which are more technically demanding and carry greater radiation exposure. In this study, we aim to address whether alignment measured on standard knee radiographs are reliable and reproducible over time. We examined a cohort of 80 patients 37 male (46%), 43 females (54%), mean age = 68 years) who underwent total knee arthroplasty (TKA). Standard knee anteroposterior radiographs performed within 2 days following surgery were compared to standard knee anteroposterior radiographs taken 1 year following the surgery in patients with well-functioning prosthesis. Tibial prosthesis alignment angles between the longitude of the tibial shaft and the tibial baseplate were calculated using Centricity Enterprise Web V3.0 software. The data was examined using R software. In well-functioning primary knee arthroplasties, tibial prosthesis alignment angles measured in the 1-year follow-up standard view knee radiographs were found to deviate from measurements obtained with the same radiographic specifications in the immediate post-operative period. A significant mean percentage difference was found between the two radiographs. Long knee view radiographs may be required in order to accurately assess tibial prothesis alignment following total knee arthroplasty


Orthopaedic Proceedings
Vol. 103-B, Issue SUPP_2 | Pages 65 - 65
1 Mar 2021
Nicholson J
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Abstract. Objectives. Three-dimensional visualisation of sonographic callus has the potential to improve the accuracy and accessibility of ultrasound evaluation of fracture healing. The aim of this study was to establish a reliable method for producing three-dimensional reconstruction of sonographic callus. Methods. A prospective cohort of ten patients with a closed tibial shaft fracture managed with intramedullary nailing were recruited and underwent ultrasound scanning at 2-, 6- and 12-weeks post-surgery. Ultrasound B-mode capture was performed using infrared tracking technology to map each image to a three-dimensional lattice. Using echo intensity, semi-automated mapping was performed by two independent reviewers to produce an anatomic three-dimensional representation of the fracture. Agreement on the presence of sonographic bridging callus on three-dimensional reconstructions was assessed using the kappa coefficient. Results. Nine of the ten patients achieved union at six months. At six weeks, seven patients had bridging callus at ≥1 cortex on the three-dimensional reconstruction; when present all united. Compared to radiographs, no bridging callus was present in any patient. Of the three patients lacking sonographic bridging callus, one went onto a nonunion (77.8%-sensitive and 100%-specific to predict union). At twelve weeks, nine patients had bridging callus at ≥1 cortex on three-dimensional reconstruction and all united (100%-sensitive and 100%-specific to predict union). Compared to radiographs, seven of the nine patients that united had bridging callus. Three-dimensional reconstruction of the anteromedial and anterolateral tibial surface was achieved in all patients, and detection of sonographic bridging callus on the three-dimensional reconstruction demonstrated substantial inter-observer agreement (kappa=0.78, 95% confidence interval 0.29–1.0, p=0.011). Conclusions. Three-dimensional fracture reconstruction can be created using multiple ultrasound images in order to evaluate the presence of bridging callus. This imaging modality has the potential to identify impaired healing at an early stage in fracture management. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project


Orthopaedic Proceedings
Vol. 103-B, Issue SUPP_4 | Pages 11 - 11
1 Mar 2021
Barcik J Ernst M Balligand M Dlaska CE Drenchev L Todorov S Gueorguiev B Skulev H Zeiter S Epari D Windolf M
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The course of secondary fracture healing typically consists of four major phases including inflammation, soft and hard callus formation, and bone remodeling. Callus formation is promoted by mechanical stimulation, yet little is known about the healing tissue response to strain stimuli over shorter timeframes on hourly and daily basis. The aim of this study was to explore the hourly, daily and weekly variations in bone healing progression and to analyze the short-term response of the repair tissue to well-controlled mechanical stimulation. A system for continuous monitoring of fracture healing was designed for implantation in sheep tibia. The experimental model was adapted from Tufekci et al. 2018 and consisted of 3 mm transverse osteotomy and 30 mm bone defect resulting in an intermediate mobile bone fragment in the tibial shaft. Whereas the distal and proximal parts of the tibia were fixed with external fixator, the mobile fragment was connected to the proximal part via a second, active fixator. A linear actuator embedded in the active fixator moved the mobile fragment axially, thus stimulating mechanically the tissue in the osteotomy gap via well-controlled displacement being independent from the sheep's functional weightbearing. A load sensor was integrated in the active fixation to measure the force acting in the osteotomy gap. During each stimulation cycle the displacement and force magnitudes were recorded to determine in vivo fracture stiffness. Following approval of the local ethics committee, experiments were conducted on four skeletally mature sheep. Starting from the first day after surgery, the daily stimulation protocols consisted of 1000 loading events equally distributed over 12 hours from 9:00 to 21:00 resulting in a single loading event every 44 seconds. No stimulation was performed overnight. One animal had to be excluded due to inconsistencies in the load sensor data. The onset of tissue stiffening was detected around the eleventh day post-op. However, on a daily basis, the stiffness was not steadily increasing, but instead, an abrupt drop was observed in the beginning of the daily stimulations. Following this initial drop, the stiffness increased until the last stimulation cycle of the day. The continuous measurements enabled resolving the tissue response to strain stimuli over hours and days. The presented data contributes to the understanding of the influence of patient activity on daily variations in tissue stiffness and can serve to optimize rehabilitation protocols post fractures


Orthopaedic Proceedings
Vol. 96-B, Issue SUPP_11 | Pages 335 - 335
1 Jul 2014
Tai T Lai K
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Summary Statement. We present a simple and useful geometrical equation system to carry out the pre-operative planning and intra-operative assessments for total knee arthroplasty. These methods are extremely helpful in severely deformed lower limbs. Introduction. Total knee arthroplasty is a highly successful surgery for most of the patients with knee osteoarthritis. With commercial instruments and jigs, most surgeons can correct the deformity and provided satisfactory results. However, in cases with severe extra-articular deformity, the instruments may mislead surgeons in making judgment of the true mechanical axis. We developed a geometrical equation system for pre-operative planning and intra-operative measurement to perform correct bony cuts and achieve good post-operative axis. Patients & Methods. From 2008 to 2012, twenty-four patients with severe extra-articular deformities of low limbs underwent total knee arthroplasties for osteoarthritis. The deformities included malunion of femoral or tibial shafts with angulation, non-union of femoral supracondylar fractures, failed high tibia osteotomies, severe bowing of femurs, and other post-traumatic sequelae. The intra-medullary or extra-medullary guide devices were not possible to provide correct axis in these cases. For pre-operative planning, we analyzed the deformities on triple-film scanography and standing anterior-posterior and lateral X-ray films. The angles needed to be corrected in coronal and sagittal planes were measured. A geometrical equation system was applied to calculate the thickness of the proximal tibia cut and distal femoral cut. If the flexion contracture was presented, the degree of necessary elevation of joint line was also calculated. Intra-operatively, the degree of rotation of anterior and posterior femoral cuts was assessed after proximal tibial and distal femoral cuts. The sizes of prosthesis were judged according to the balance between flexion and extension gaps. A 3-in-1 jig was used for chamfering of the femur. After fine-tuning of bony cuts and balancing of soft tissue, the prostheses were cemented. The conventional intra-medullary and extra-medullary guiding devices were not used during the whole procedure. Results. All of the patients achieved satisfactory results in the aspect of pain relief and functional outcomes. All patients had good post-operative axis in coronal plane (varus or valgus deformity < 3 degrees). Twenty-two patients (92%) achieved good sagittal alignments (deformity < 3 degrees). The results were compatible with those in the patient population without those severe deformities. There was no major complication among these patients. Discussion/Conclusion. In this series, we present a simple and useful geometrical equation system to carry out the pre-operative planning and intra-operative assessments for total knee arthroplasty. These methods are extremely helpful in severely deformed lower limbs. Optimal post-operative alignments were achieved in this series and no major complication was found


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_XVIII | Pages 62 - 62
1 May 2012
Chan K Wong J Thompson N
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INTRODUCTION. Intramedullary nail fixation has been used for successful treatment of long bone fracture such as humerus, tibia and femur. We look at the experience of our trauma unit in treating long bone fracture using the AO approved Expert femoral/tibial nail and proximal femoral nail antirotation (PFNA). We look at the union and complication rates in patients treated with AO approved nailing system for pertrochanteric, femoral and tibial shaft fracture. METHODS. We carried out retrospective case notes review of patients that underwent femoral and tibial nailing during the period of study- October 2007 to August 2009. All patients were treated using the AO approved nailing system. We identified all trauma patients that underwent femoral and tibial nailing through the trauma register. Further information was then obtained by going through medical notes and reviewing all followed-up X-rays stored within the online radiology system. RESULTS. 149 patients, 85 male and 64 female were included into the study. 150 procedures were carried out during period of study as 1 patient underwent conversion of lateral entry femoral nail to PFNA due to refracture. Patients' age ranged from 14-96 with mean of 55. 140 patients had isolated long bone fracture (either femur or tibia) compared to 9 patients with multiple bone fractures. Our unit performed 64 Expert tibial nail, 36 PFNA, 31 Expert lateral entry femoral nail and 19 Expert retrograde femoral nail during period of study. 13 patients treated with intramedullary nail sustained open fracture, 9 of them were compound tibial fracture compared to 4 compound femoral fractures. All patients were followed-up between 2 to 24 months or until death. 9 out of 17 patients that died in this study had diagnosis of tumour. Complication rates were 17% for Expert tibial nail (1 patient with valgus deformity, peroneal nerve palsy and delayed union, 3 with delayed union, 4 with broken locking screw, 2 with wound infection and 1 with abscess over wound site), 4% for lateral/retrograde femoral nail (1 each for pulmonary embolism and broken locking screw) and 4% for PFNA (1 each for delayed union and deep vein thrombosis). The overall complication rates were 10% from this study. DISCUSSION & CONCLUSIONS. We conclude that the AO approved nailing system used for treating pertrochanteric, femoral and tibial fractures were effective with high union rate. The overall complication rates were 10% from this study. Complication rates for tibial nail were as high as 17% compared to 4% for femoral nail or PFNA. The complication rates for PFNA in our study were lower compared to 29% in PFN that was reported in one literature


Orthopaedic Proceedings
Vol. 100-B, Issue SUPP_4 | Pages 1 - 1
1 Apr 2018
Graziani G Carnevale G Pisciotta A Bertoni L Boi M Gambardella A Berni M Marchiori G Russo A De Pol A Bianchi M
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Fabrication of biogenic coatings with suitable mechanical properties is a key goal in orthopedics, to overcome the limitations of currently available coatings and improve the clinical results of coated implants compared to uncoated ones. In this paper, biological-like apatite coatings were deposited from a natural bone-apatite source by a pulsed electron deposition technique (PED). Bone apatite-like (BAL) films were deposited directly from bone targets, obtained by standard deproteinization of bovine tibial cortical shafts and compared to films deposited by sintered stoichiometric-hydroxyapatite targets (HA). Deposition was performed at room temperature by PED in the Ionized Jet Deposition (IJD) version. Half of the samples was annealed at 400°C for 1h (BAL_400 and HA_400). As-deposited and annealed coatings were characterized in terms of composition and crystallinity (XRD, FT-IR), microstructure and morphology (SEM-EDS, AFM) and mechanical properties (nanoindentation and micro-scratch). For the biological tests, human dental pulp stem cells (hDPSCs) were isolated from dental pulp from patients undergoing a routine tooth extraction, plated on the samples (2500 cells/cm2) and cultured for 3 weeks, when the expression of typical osteogenic markers Runx-2, osteopontin, Osx and Osteocalcin in hDPSCs was evaluated. Results showed that deposition by PED allows for a close transfer of the targets” composition. As-deposited coatings exhibited low cristallinity, that was significantly increased by post-deposition annealing, up to resembling that of biogenic apatite target. As a result of annealing, mechanical properties increased up to values comparable to those of commercial plasma-sprayed HA-coatings. In vitro biological tests indicated that BAL_400 promotes hDPSCs proliferation to a higher extent compared to non-annealed bone coating and HA-references. Furher, immunofluorescence and western blot analyses revealed that the typical osteogenic markers were expressed, indicating that BAL_400 alone can efficiently promote the osteogenic commitment of the cells, even in absence of an osteogenic medium. In conclusion, bone-like apatite coatings were deposited by PED, which closely resembled composition and structure of natural-apatite. Upon annealing at 400°C, the coatings exhibited satisfactory mechanical properties and were capable of providing a suitable microenvironment for hDPSCs adherence and proliferation and for them to reach osteogenic commitment. These results suggest that bone apatite-like thin films obtained by biogenic source may represent an innovative platform to boost bone regeneration in the orthopedic, maxillofacial and odontoiatric field


Bone & Joint Research
Vol. 2, Issue 6 | Pages 102 - 111
1 Jun 2013
Patel RA Wilson RF Patel PA Palmer RM

Objectives

To review the systemic impact of smoking on bone healing as evidenced within the orthopaedic literature.

Methods

A protocol was established and studies were sourced from five electronic databases. Screening, data abstraction and quality assessment was conducted by two review authors. Prospective and retrospective clinical studies were included. The primary outcome measures were based on clinical and/or radiological indicators of bone healing. This review specifically focused on non-spinal orthopaedic studies.


The Journal of Bone & Joint Surgery British Volume
Vol. 87-B, Issue 3 | Pages 426 - 432
1 Mar 2005
Mueller CA Eingartner C Schreitmueller E Rupp S Goldhahn J Schuler F Weise K Pfister U Suedkamp NP

The treatment of fractures of the proximal tibia is complex and makes great demands on the implants used. Our study aimed to identify what levels of primary stability could be achieved with various forms of osteosynthesis in the treatment of diaphyseal fractures of the proximal tibia. Pairs of human tibiae were investigated. An unstable fracture was simulated by creating a defect at the metaphyseal-diaphyseal junction. Six implants were tested in a uniaxial testing device (Instron) using the quasi-static and displacement-controlled modes and the force-displacement curve was recorded. The movements of each fragment and of the implant were recorded video-optically (MacReflex, Qualysis). Axial deviations were evaluated at 300 N.

The results show that the nailing systems tolerated the highest forces. The lowest axial deviations in varus and valgus were also found for the nailing systems; the highest axial deviations were recorded for the buttress plate and the less invasive stabilising system (LISS). In terms of rotational displacement the LISS was better than the buttress plate.

In summary, it was found that higher loads were better tolerated by centrally placed load carriers than by eccentrically placed ones. In the case of the latter, it appears advantageous to use additive procedures for medial buttressing in the early phase.


The Journal of Bone & Joint Surgery British Volume
Vol. 89-B, Issue 11 | Pages 1528 - 1533
1 Nov 2007
Jeffcote B Nicholls R Schirm A Kuster MS

Achieving deep flexion after total knee replacement remains a challenge. In this study we compared the soft-tissue tension and tibiofemoral force in a mobile-bearing posterior cruciate ligament-sacrificing total knee replacement, using equal flexion and extension gaps, and with the gaps increased by 2 mm each. The tests were conducted during passive movement in five cadaver knees, and measurements of strain were made simultaneously in the collateral ligaments. The tibiofemoral force was measured using a customised mini-force plate in the tibial tray. Measurements of collateral ligament strain were not very sensitive to changes in the gap ratio, but tibiofemoral force measurements were. Tibiofemoral force was decreased by a mean of 40% (sd 10.7) after 90° of knee flexion when the flexion gap was increased by 2 mm. Increasing the extension gap by 2 mm affected the force only in full extension. Because increasing the range of flexion after total knee replacement beyond 110° is a widely-held goal, small increases in the flexion gap warrant further investigation.