Introduction and Objective

Guided Bone Regeneration (GBR) uses biodegradable collagen membranes of animal origin tissues (dermis and pericardium). Their barrier effect prevents soft tissues to interfere with the regeneration of alveolar bone. However, their xenogeneic origin involves heavy chemical treatments which impact their bioactivity. Wharton's Jelly (WJ) from the umbilical cord is a recoverable surgery waste. WJ is mostly made from collagen fibers, proteoglycans, hyaluronic acid, and growth factors. WJ with immunologically privileged status and bioactive properties lends credence to its use as an allograft. Nevertheless, low mechanical properties limit its use in bone regenerative strategies. Herein, our objective is to develop a crosslinked WJ-based membrane to improve its strength and thus its potential use as a GBR membrane.

Introduction and Objective

Found in bone-associated prosthesis, Cutibacterium acnes (C. acnes) is isolated in more than 50% of osteoarticular prosthesis infections, particularly those involving shoulder prostheses. Ongoing controversies exist concerning the origin of C. acnes infection. Few reports construct a reasonable hypothesis about probable contaminant displaced from the superficial skin into the surgical wound. Indeed, despite strict aseptic procedures, transecting the sebaceous glands after incision might result in C. acnes leakage into the surgical wound. More recently, the presence of commensal C. acnes in deep intra-articular tissues was reported. C. acnes was thus detected in the intracellular compartment of macrophages and stromal cells in 62.5% of the tested patients who did not undergo skin penetration. Among bone stromal cells, mesenchymal stem cells (MSCs) are predominantly found in bone marrow and periosteum. MSCs are the source of osteogenic lines of cells capable of forming bone matter. In this study, the pathogenicity of C. acnes in bone repair context was investigated.

Introduction

Studies have shown that increased implant conformity in total knee arthroplasty (TKA) has been linked to increased constraint and thus rotational torque at the bone/implant interface. Anterior stabilized (AS) tibial inserts were designed to compensate for excessive AP motion in less-conforming cruciate-retaining (CR) tibial inserts. However, increased constraint may affect implant loading. Therefore, the purpose of this study is to model rotational prosthesis constraint based on implant-specific data and to compare rotational torque and 3D contact forces in implants with CR-lipped and AS tibial inserts during normal gait.

Prosthetic Joint Infections (PJIs) are increasing with the use of orthopedic devices on an ageing population. Cutibacterium acnes is a commensal organism that plays an important role in the ecosystem healthy human skin, yet this species is also recognized as a pathogen in foreign body infection: endocarditis, prostatitis and specifically in PJIs. C. acnes is able to escape the immune system. This phenomenon could reflect two bacterial behaviour: the bacterial internalization by host cells and the biofilm formation. In this study, we studied different clinical strains of C. acnes. We noticed that C. acnes isolated from PJIs form 2 fold-more biofilm than the strains isolated from a normal skin in two models (Crystal violet staining and fluorescent microscopy (p=0.04 and p=0.02, respectively, Mann-Whitney test). We did not observe any difference in the internalization rate of those strains by osteoblasts. However, the quantity of biofilm formed by C. acnes before and after the internalization was compared. A significant increase in biofilm formation was observed for the strains isolated from the skin (x2.3±0.07; p=0.008, Mann-Whitney test). However, the hydrophobicity of the skin strains is significantly less important than for the PJIs strains (24.8±13% vs 56.6±12% respectively; p=0.003, Mann-Whitney test) but this did not change after internalization suggesting that there is no cell wall evolution. In conclusion, we studied for the first time the impact of bacterial internalization by osteoblasts on the virulent behaviour of C. acnes, which could explain the hided pathogenicity of this commensal bacterium.

Introduction

Preservation of the anterior cruciate ligament (ACL), along with the posterior cruciate ligament, is believed to improve functional outcomes in total knee replacement (TKR). The purpose of this study was to examine gait differences and muscle activation levels between ACL sacrificing (ACL-S) and bicruciate retaining (BCR) TKR subjects during level walking, downhill walking, and stair climbing.

The 3D interplay between femoral component placement on contact stresses and range of motion of hip resurfacing was investigated with a hip model. Pre- and post-operative contours of the bone geometry and the gluteus medius were obtained from grey-value CT-segmentations. The joint contact forces and stresses were simulated for variations in component placement during a normal gait. The effect of component placement on range of motion was determined with a collision model. The contact forces were not increased with optimal component placement due to the compensatory effect of the medialisation of the center of rotation. However, the total range of motion decreased by 33%. Accumulative displacements of the femoral and acetabular center of rotation could increase the contact stresses between 5–24%. Inclining and anteverting the socket further increased the contact stresses between 6–11%. Increased socket inclination and anteversion in combination with shortening of the neck were associated with extremely high contact stresses. The effect of femoral offset restoration on range of motion was significantly higher than the effect of socket positioning. In conclusion, displacement of the femoral center of rotation in the lateral direction is at least as important for failure of hip resurfacings as socket malpositioning.

Summary sentence

The bowing of the femur defines a curvature plane to which the proximal and distal femoral anatomic landmarks have a predictable interrelationship. This plane can be a helpful adjunct for computer navigation to define the pre-operative, non-diseased anatomy of the femur and more particularly the rotational alignment of the femoral component in total knee arthroplasty (TKA).

We report the outcome at a minimum of 10 years follow-up for 80 polished tapered stems performed in 53 patients less than 35-years-old with a high risk profile for aseptic loosening. Forty-six prosthesis were inserted for inflammatory hip arthritis and 34 for avascular necrosis. The mean age at surgery was 28 years in the inflammatory arthritis (17–35) and 27 years in the avascular necrosis (15–35) patients. At a mean follow-up of 14.5 years in the inflammatory arthritis group and 14 years in the avascular necrosis group respectively, survivorship of the 80 stems with revision of the femoral component for any reason as an endpoint was 100 % (95 % CI). Re-operation was because of failure of four metal-backed cups, 3 all polyethylene cups and one cementless cup. None of the stems were radiographically loose. All but two femoral components subsided within the cement mantle to a mean of 1.2 mm (0 tot 2.5) at final follow-up. Periarticular osteolysis was noted in 4 femurs in zone 7. This finding was associated with polyethylene wear and was only seen in those hips that needed revision for a metal backed cup loosening. Our findings show that the polished tapered stem has excellent medium-term results when implanted in young patients with high risk factors for aseptic loosening.

The Exeter stem is a polished cemented stem that has been associated with an excellent survivorship. However, this wedge shaped stem has also been associated with a relative higher risk for a peri-periprosthetic fracture due to the wedge-shaped configuration that can lead to a Vancouver type B2 fracture when the stem is being driven downwards inside the femoral canal by a traumatic blast. Traditionally, these fractures should be treated with a revision stem because the stem has become loosened in the fractured cement mantle. We present a case series of 5 cases where our treatment algorithm was to first let the non-displaced fracture to consolidate by 6 weeks of limited weight bearing as tolerated in order to conduct a second stage in-cement revision. This would simplify the revision procedure dramatically. However, all patients are currently pain free and do not require revision surgery although they are being monitored very closely.

We conclude that non-displaced Vancouver type B2 fractures can be approached by a 2 stage treatment algorithm where the initial step is to let the fracture consolidate with limited weight bearing.

Introduction

It was the purpose to evaluate the biomechanical changes that occur after optimal and non-optimal component placement of a hip resurfacing (SRA) by using a subject specific musculoskeletal model based on CT-scan data.

Purpose: Precise biomechanical reconstruction of the hip joint by a hip arthroplasty is essential for the success of this procedure. With the increasing use of surface replacement arthroplasty (SRA), there is a need for better understanding of the key factors that influence the anatomical and the biomechanical parameters of the resurfaced hip joint. The goal of this study was to examine the influence of SRA on the vertical and horizontal offset of the hip.

Method: Twenty-one hips from 12 embalmed cadavers were resurfaced with a Birmingham Hip resurfacing. The thickness of the acetabular bone was measured pre- and post-reaming in 6 acetabular zones. Radiographs were taken before and after the procedure with a scaling marker. For statistical analysis, the paired Student’s T-test with a confidence interval of 95% and a significant p-value of p< 0.05 was used.

Results: The mean acetabular bone loss was 3.8 mm, 5.9 mm, 9.3 mm, 10.6 mm, 8.5 mm and 3.6 mm in zones 1 to 6. The “polar length loss” is the cumulative displacement of the femoral and the acetabular articulating surface in zones 2 to 5. This displacement indicates a shortening of the neck plus a medio-cranial displacement of the acetabular articulating surface and was 4.3 mm, 7.5 mm, 9.4 mm and 7.7 mm (zone 2–5). The radiographic center of rotation (COR) was significantly medialised (mean 6.2 mm) and displaced in the cranial direction (mean 6.9 mm) (p< 0.00001). The mean total (femoral plus acetabular) horizontal and vertical offset change was 6.4 mm and 9.5 mm respectively (p< 0.00001). There was a significantly higher vertical offset change in the acetabulum than in the femur (p=0.0006). This resulted in a significantly larger change in vertical than in horizontal offset (p=0,04).

Conclusion: The displacement of the acetabular COR was responsible for 60% of the total vertical and 99% of the total horizontal offset change. The femoral side did not compensate for this displacement. SRA did not restore the biomechanics of the native hip.

Purpose: Plate and cable alone constructs to treat periprosthetic fractures around a well-fixed femoral stem in total hip replacements, have been reported with high failure rates. The aim of this study was to evaluate the results of our surgical treatment algorithm to reliably use lateral plate and cable constructs in these fractures.

Method: One hundred and six periprosthetic fractures in 102 patients were treated between 1996 and 2006. Forty-five fractures were pre-operatively assessed as Vancouver type B1 fractures. The joint was always dislocated and stability of the implant was meticulously evaluated. This led to the identification of nine (20%) unstable stems leaving 36 fractures to be real B1-type fractures. The fracture was considered to be suitable for lateral plate and cable alone fixation if the medial cortex was not comminuted and an anatomical reduction of the medial cortex could be achieved. Twenty-nine B1- and 5 C-type fractures had been treated with a single lateral plate and cable construct. The mean length of follow-up was 43.2 months. The paired Student’s T-test with a confidence interval of 95% and a significant p-value of p< 0.05 was used to compare the pre- and postoperative UCLA hip scores.

Results: Four (12%) patients died within one month from surgery leaving 30 patients for follow-up. Twenty-nine fractures united at a mean of 6.4 months. One B1-type construct failed due to inappropriate proximal fixation. Two fractures united uneventfully with a mean of 8° of varus alignment of the proximal fragment. One patient with a C-type fracture sustained a fracture distal to the tip of the plate. There were three plate infections (8.8%). There was no significant difference between the pre- and post-operative UCLA hip scores (25 versus 23 resp.).

Conclusion: These fractures represent a difficult problem with a high complication rate of 30%. The presented treatment algorithm contributed significantly to the 97% union rate with plate and cable alone constructs that was comparable to the union rates achieved with combined plate and strut graft fixation.

Aim: Component positioning may be adversely affected by minimally invasive approach in total hip replacement due to restricted visualization. Problems with proper alignement are suggested to concern anteversion more than inclination and occur particulary in the lateral position.

Method: 53 patients were enrolled prospectively randomised to each group. First group (standard group, n= 30pts) underwent conventional total hip replacement in supine position and transgluteal approach and second group (MIS group, n= 23pts) underwent THR using minimally invasive anterior approach in lateral decubitus position Every group was operated on by two experienced senior surgeons. Desired cup position was 40°–45°inclination and 15–20° anteversion for the MIS group and 45°inclination and 15 ° anteversion for standard group. Postoperatively all patients had pelvic CT scan. Inclination and anteversion were determined by an independent observer using a 3-D model and planning software, the operative definition was used according to Murray.

Results: Mean inclination/anteversion in the MIS group was 39°(26°–50°)/25°(10°–47°), and 44°(29°–57°)/22°(1°–53°) within the standard group. Standard deviation for inclination was 7° for both groups, and 10° (MIS group) vs 14° (standard group) for anteversion.

The difference in the mean values regarding inclination was greater than would be expected by chance; there was a statistically significant difference (P = 0,010).

Discussion: In general cup positioning in both groups was less steep and more anteverted as presumed. The standard deviation for inclination was the same in both groups, but the standard deviation for anteversion was less in MIS group, that means less outliers regarding anteversion. Cup positioning in minimally invasive total hip replacement is safe compared to traditional approach.

Navigation technique was discussed to equalize the drawback of MIS. However, tools like imageless navigation may further improve the cup position even in traditional approach.

Introduction: The Birmingham Hip Resurfacing (BHR) is the most commonly used hip resurfacing for the treatment of hip osteoarthritis. The goal of this study was to evaluate how the surgeon could influence the biomechanical features of the navigated and non-navigated resurfaced proximal femur. METHODS 20 Cadaver hips were resurfaced with a BHR using femoral navigation. The native anteversion and neck shaft angle as indicated by the navigation system were used as a reference. The non-navigated femoral component jig was first placed in the “ideal” position aiming for 10° of valgus and neutral anteversion. The jig was then displaced 5mm in 4 directions. The anteversion and stem shaft angle (SSA) angle were measured for each position using the navigation system. A scaled XR was taken pre- and post-operatively. For statistical analysis, the paired Student’s T-test with a confidence interval of 95% and a significant p-value of p< 0.05 was used.

Results: The centre of rotation (COR) of the navigated resurfaced femur was 3,5 mm significantly (p=0,0006) more distal in the femoral neck than the native COR. This resulted in a 2.1 mm vertical caudal drop (vertical offset) and an average 2.7 mm lateral displacement of the COR (horizontal offset). The same measurements were done with 5° increments of the SSA from 120° to 140°. The vertical offset loss increased non-significantly (1.7 to 2.6 mm). The horizontal offset loss decreased non-significantly (3 to 2.2 mm). The native vertical and horizontal offset could be restored if 5 mm less bone was taken off the femur. The offset loss was significantly increased if 5 mm more bone than the normal reaming had been taken off (p< 0.0001). The “ideal” jig position on the lateral femoral cortex led to an average 137° SSA. Five millimetres of jig displacement on the lateral cortex in either direction did not lead to significant changes in the SSA or anteversion angles relative to the “ideal” position (all p> 0,13). Five millimetres of posterior displacement resulted in an average 139° SSA and 5,8° of anteversion in 95% of hips.

Conclusion: Surgical interventions can significantly change the biomechanics of the hip. Increasing the SSA with a fixed femoral head entry point, as often is done with navigation, does not significantly change the femoral offset. If the surgeon decides to take less bone off the femur, then the offset could be restored and even increased to 1 mm more than the native femur. If due to pathologic changes the bone loss would be increased to 5mm more than the “normal” bone loss, a significant offset loss of > 5 mm could be expected which might lead to detrimental biomechanical effects. The positioning of the jig is subject to surgical errors. The effect of a 5 mm error in either direction does not lead to significant changes in anteversion or SSA. Posterior displacement led to the most reproducible component positioning.

Highly cross-linked polyethylene (XLPE) has been introduced in total hip arthroplasty in an effort to reduce polyethylene wear and the associated periprohetic osteolysis. Cross-linking is a procedure in which irradiation and subsequent heating stabilize the internal structure of PE. Most of the conventional PE’s used, are gamma irradiated in air or an inert environment with a dose level of no more than 25 to 50 kGy. By irradiating PE at a higher dose, optimally around 95–100 kGy, a definite reduction in wear rate has been achieved. History already provided us some mixed in vivo results regarding altered PE. Therefore, present time surgeons are cautious when it comes down to using a new PE.

Some short follow up in vivo studies already suggested reduced wear rates with XLPE in comparison to conventional PE. Our aim was to demonstrate these reduced wear rates in a 2-dimensional head penetration model using the DICOMeasure™ computerized edge detection method (GreyStone, France) and to perform a clinical comparison of both groups using the Harris Hip Score and SF-36 questionnaire.

Sixty hips with a Trilogy XLPE liner (Zimmer Co.) were age and BMI matched with a control group of twenty conventional Trilogy PE liners (Zimmer Co.).

No differences in clinical performance were seen, but a statistically significant reduction of 67% in steady state wear rate was observed in the XLPE group.

It is clear that, due to the reduction and stabilization of free radicals in polyethylene, a reduction in annual wear can be achieved.

Background: Flail or unstable elbow presents a difficult challenge for the elbow surgeon. This study reports the medium-term follow-up of 30 elbows in 25 patients, treated with two different designs of sloppy-hinged prosthesis: the Coonrad-Morrey and the snap-fit Souter-Strathclyde.

Methods: All patients treated over a 12 year period by a single surgeon were identified and reviewed. This included a detailed history of indications, complications, and subjective assessment (including Mayo Elbow Performance Scores, subjective satisfaction score, and SF-12 mental and physical disability questionnaire), as well as examination and radiographic review of preoperative and most recent xrays.

Results: 30 elbows in 25 surviving patients were assessed at an average postoperative period of 5.7 years. 17 Coonrad-Morrey and 13 snap-fit Souter-Strathclyde prostheses were implanted. 4 elbows (13.3%) have been revised. Average Mayo Elbow Performance score was 78.8 out of a top score of 100, with 15 classed as excellent, 5 good, 4 fair and 6 poor. Average subjective satisfaction with the operation was 4.5 out of a top score of 5. There was an average flexion arc of 104.7°, with 18 elbows ≥100°. 3 of the 17 Coonrad-Morrey elbows (17.6%) and 3 of the 13 snap-fit Souter-Strathclyde elbows (23.1%) demonstrated at least Grade 3 humeral radiolucency at the bone-cement interface. In the ulna, these figures were 6 out of 17 (35.3%) for Coonrad-Morrey elbows and 2 out of 13 (15.4%) for snap-fit Souter-Strathclyde elbows.

Conclusions: Sloppy-hinged elbow replacement is a safe procedure with a high subjective satisfaction level. Its main indication is as a salvage operation in patients with a functionally useless elbow due to failed primary replacement or non-union of distal humeral fracture.