Polymethylmethacrylate (PMMA) bone cement is strong in compression, however it tends to fail under torsion. Sufficient pressurisation and subsequent interdigitation between cement and bone are critical for the mechanical interlock of cemented orthopaedic implants, and an irregular surface on the acetabular cup is necessary for reasonable fixation at the cup-cement interface. There is limited literature investigating discrepancies in the failure mechanisms of cemented all-polyethylene acetabular cups with and without cement spacers, under torsional loading. In vitro experimental comparison of three groups of polyethylene acetabular prosthesis (PAP) cemented into prepared sawbone hemipelvises:. * PAP without PMMA spacers maintaining an equal cement mantle circumferentially. (Group 1 n=3). * PAP without PMMA spacers cemented deliberately ‘bottoming-out’ the implant within the acetabulum. (Group 2 n=3). * PAP with PMMA spacers. (Group 3 n=3). The constructs were tested to torstional failure on a custom designed setup, and statistical analysis done by a one-way ANOVA and Tukey-Welsh test. Group 3 demonstrated superior torsional resistance with a statistically significant torque of 145Nm (SD±12Nm) at failure, compared to group 2 (109Nm, SD±7Nm) and group 1 (99Nm, SD±8Nm). Group 3 experienced failure predominantly at the bone-cement interface, in contrast, Groups 1 and 2 exhibited failure predominantly at the cup-cement interface. There was no significant difference between Group 1 and 2. Qualitative analysis of the failure mode indicates the efficient redistribution of stress throughout the cement mantle, consistent with the greater uniformity of cement. PMMA spacers increase the resistance to torsional failure at the implant-cement interface. Acetabular components without spacers (Groups 1 and 2) failed at the implant-cement interface before the cement-bone interface, at a statistically significantly lower level of torque to failure. Although the PMMA spacers may reduce cement interdigitation at the cement-bone interface the torsional forces required to fail are likely supraphysiological

Aims. Wrist arthroscopy is a standard procedure in hand surgery for diagnosis and treatment of wrist injuries. Even though not generally recommended for similar procedures, general administration of perioperative antibiotic prophylaxis (PAP) is still widely used in wrist arthroscopy. Methods. A clinical ambispective dual-centre study was performed to determine whether PAP reduces postoperative infection rates after soft tissue-only wrist arthroscopies. Retrospective and prospective data was collected at two hospitals with departments specialized in hand surgery. During the study period, 464 wrist arthroscopies were performed, of these 178 soft-tissue-only interventions met the study criteria and were included. Signs of postoperative infection and possible adverse drug effects (ADEs) of PAP were monitored. Additionally, risk factors for surgical site infection (SSIs), such as diabetes mellitus and BMI, were obtained. Results. The overall infection rate of SSI was zero. Neither in the PAP group (n = 69) nor in the control group (n = 109) were signs of postoperative infection observed. Observed symptoms of ADEs were three-times higher in the PAP group when compared to the control-group (16.3 vs 5.5%; p = 0.043). No major ADEs were observed, but one in ten patients in the PAP group reported mild to severe intestinal or hypersensitivity symptoms. Conclusion. We demonstrate that the number needed to treat (NNT) with PAP to prevent one postoperative infection in soft-tissue arthroscopies of the wrist is > 109. Conversely, symptoms of ADEs were reported by one out of ten patients given PAP. Considering the high NNT to prevent postoperative infection and the large number of ADEs caused by PAP, we recommend not to use PAP routinely in soft-tissue arthroscopies of the wrist. Subsequent large-scale studies should be conducted to substantiate these results. Cite this article: Bone Jt Open 2023;4(4):219–225

Aim. Duration of perioperative antimicrobial prophylaxis (PAP) remains controversial in prevention of fracture-related infection (FRI) – with rates up to 30% - in open fracture (OF) management. Objectives were to investigate the impact of the PAP duration exclusively in or related to long bone OF trauma patients and the influence of augmented renal clearance (ARC), a known phenomenon in trauma patients, as PAP consists of predominantly renally eliminated antibiotics. Method. Trauma patients with operatively treated OF, admitted between January 2003 and January 2017 at the University Hospitals Leuven, were retrospectively evaluated. FRI was defined following the criteria of the consensus definition of FRI. A logistic regression model was conducted with FRI as outcome. Results were considered statistically significant when p< 0.05. Results. Forty (8%) from the 502 patients developed a FRI, with 20% FRIs in Gustilo-Anderson (GA) III OFs. Higher GA grade and polytrauma were independently associated with the occurrence of FRI. The heterogeneity in OF management, especially with regard to the applied PAP regimens and duration, was striking and consequently hampering the investigation on the impact of PAP duration. To overcome this issue, a subgroup analysis was performed in patients treated with the two PAP regimens as defined in the hospitals' guidelines – i.e. cefazolin, with metronidazole and tobramycine when extensive contamination was present -, revealing flap coverage and relative duration of augmented renal ARC as independently associated factors. Conclusions. For the first time, a definition based on diagnostic criteria was used to objectively include patients with a FRI. In order to support clinicians in establishing strategies to prevent FRI in long bone OFs, further prospective large randomized controlled trials with clearly predefined PAP regimens are needed to provide reliable recommendations regarding the impact of duration of PAP and ARC

Aim. Open fractures still have a high risk for fracture-related Infection (FRI). The optimal duration of perioperative antibiotic prophylaxis (PAP) for open fractures remains controversial due to heterogeneous guidelines and highly variable prophylactic regimens in clinical practice. In order to provide further evidence with which to support the selection of antibiotic duration for open fracture care, we performed a preclinical evaluation in a contaminated rabbit fracture model. Method. A complete humeral osteotomy in 18 rabbits was fixed with a 7-hole-LCP and inoculated with Staphylococcus aureus (2×106 colony forming units, CFU per inoculum). This inoculum was previously shown to result in a 100% infection rate in the absence of any antibiotic prophylaxis. Cefuroxime was administered intravenously in a weight adjusted dosage equivalent to human medicine (18.75 mg/kg) as a single shot only, for 24 hours (every 8 hours) and for 72 hours (every 8 hours) in separate groups of rabbits (n=6 per group). Infection rate per group was assessed after two weeks by quantitative bacteriological evaluation of soft tissue, bone and implants. Blood samples were taken from rabbits preoperatively and on days 3, 7 and 14 after surgery to measure white blood cell count (WBC) and C-reactive protein (CRP) levels. Results. Duration of PAP had a significant impact on the success of antibiotic prophylaxis. The single shot regimen completely failed to prevent infection. All samples (soft tissue, implant and bone) from this group displayed high numbers of bacteria. Additionally, abscesses were present in two of six rabbits. The 24-hour regimen showed a reduced infection rate (1 out of 6 rabbits infected), but only the 72-hour course was able to prevent FRI in all animals in our model. After an initial postoperative peak on day three, CRP levels then decreased to baseline (approx. 30 µg/ml) in the 24h-group and 72h-group, but remained significantly higher in the single shot group at day 7 and 14 (p<0.05). Conclusions. When contamination with high bacterial loads is likely (e.g. in an open fracture situation), a 72-hour course of intravenous cefuroxime appears to be superior in preventing FRI compared to a single shot or 24-hour antibiotic regimen. Acknowledgements. This work was funded by AOTrauma

Aims

Tissue responses to debris formed by abrasion of polymethylmethacrylate (PMMA) spacers at two-stage revision arthroplasty for prosthetic joint infection are not well described. We hypothesised that PMMA debris induces immunomodulation in periprosthetic tissues.

The April 2015 Knee Roundup360 looks at: Genetic determinants of ACL strength; TKA outcomes influenced by prosthesis; Single- or two-stage revision for infected TKA?; Arthroscopic meniscectomy: a problem that just won’t go away!; Failure in arthroscopic ACL reconstruction; ACL reconstruction in the over 50s?; Knee arthroplasty for early osteoarthritis; All inside meniscal repair; Steroids, thrombogenic markers and TKA

Loss of proprioception following an anterior cruciate ligament (ACL) injury has been well documented. We evaluated proprioception in both the injured and the uninjured limb in 25 patients with ACL injury and in 25 healthy controls, as assessed by joint position sense (JPS), the threshold for the detection of passive movement (TDPM) and postural sway during single-limb stance on a force plate. There were significant proprioceptive deficits in both ACL-deficient and uninjured knees compared with control knees, as assessed by the angle reproduction test (on JPS) and postural sway on single limb stance. The degree of loss of proprioception in the ACL-deficient knee and the unaffected contralateral knee joint in the same patient was similar. The TDPM in the injured knee was significantly higher than that of controls at 30° and 70° of flexion. The TDPM of the contralateral knee joint was not significantly different from that in controls.

Based on these findings, the effect of proprioceptive training of the contralateral uninjured knee should be explored.

Cite this article: Bone Joint J 2013;95-B:188–91.

Graded limb lengthening by callus distraction is a widely used surgical procedure to correct tubular bone deformities and can result in dramatic functional improvements in children. We used a model of tibial lengthening in rabbits to study the postoperative pain pattern during limb lengthening and morphological changes in the dorsal root ganglia (DRG), including alteration of substance P (SP) expression. Four groups of animals (naïve; OG: osteotomised only; SDG/FDG: slow/fast distraction with 1mm/3mm lengthening a day) were used. Signs of increasing postoperative pain were detected till the10th postoperative day in all groups; then it decreased in OG, whereas remained higher in SDG/FDG until the distraction finished. This suggests that pain response is based mainly on surgical trauma until the 10th day: the lengthening extended its duration and increased its intensity. The only morphological change observed in the DRGs was the presence of large vacuoles in large neurons of all operated groups. Although osteotomy was conducted in OG/SDG/FDG groups, significant de novo SP-expression in the large DRG cells appeared only in OG and significant decrease in the number of SP-immunoreactive small DRG neurons was detected solely in the SDG/FDG groups. Faster and larger distraction resulted in more severe pain sensation and lowered further the number of SP-positive small cells. Our data suggest that down-regulation of SP in the small cells in lengthened animals is associated with the stretch nerve injury, whereas de novo expression of the peptide in the large cells in OG is likely to correspond to the undergoing regeneration.

Problem: The displacement of the rotation centre of the humeral head in relation to the shaft axis strongly varies individually. In order to measure the position of the pivot points of the head, the Affinis shoulder prosthesis has a double eccentric adjustment possibility that permits to adapt the head to the medial and dorsal offset. So far, such examinations took place exclusively on the anatomical preparation. This raises the question of whether the need for such a prosthetic system can be derived from the anatomical variation of the pivot points.

Method: In 126 patients with an Affinis shoulder prosthesis, we calculated the individual rotation centres of the head from the position of the adjustable prosthetic cone and the eccentric position of the head. In addition, we used the Constant Score to record the clinical function.

Results: We found great variation of the rotational centres. Therefore we needed the entire setting range of 12mm mediolateral and 6mm dorsoventral. The examination showed that none of the found anatomic head centres could have been reconstructed exactly with a conventional prosthesis. Prosthesis with a single eccentricity would allow correct adjustment in only 22 cases, as the adjustable rotational centres of the head are situated on a circle, which limits the setting possibilities. The Constant Score of the total group improved from 29% preoperatively to 94% after 2 years.

Conclusions: The high variation of the head centres indicates the necessity of a freely adjustable system, such as in a double eccentric bearing. This is the only way that permits an optimal reconstruction of the anatomical conditions – it prevents an increased tension of the rotator cuff, reduces the eccentric loading of the glenoid and creates the prerequisites for the anatomical kinematics. The good clinical results speak for the need to observe bony balancing.

Purpose: The objective of this study is to investigate the effects of the Reamer-Irrigator-Aspirator (RIA) on fat embolism outcome, as compared to the standard AO reamer, utilizing physiologic parameters as outcome measures. Methods: All animal procedures were approved by the Animal Care Committee. Fifteen animal experiments were completed. Following anesthesia, each pig was intubated and ventilated. Initial blood samples were analyzed for proper ventilation and acceptable baseline conditions (PaCO2 between 35–40 mm Hg). One third of the pig’s blood volume was withdrawn to simulate hemorrhagic shock. Each animal was kept in a state of hypovolemia for an hour before transfusion and resuscitation. Each pig underwent alternate assignment into either the RIA or AO group. The distal femur was exposed and reamed in a retrograde fashion, followed by cement pressurization with methylmethacrylate. Physiologic measurements included mean arterial pressure (MAP), pulmonary arterial pressure (PAP), partial pressure of arterial oxygen (PaO2), and cardiac output. Upon completion, the animals were euthanized. The data was analyzed using the SPSS statistical program. Results: One animal in the AO group expired after cement pressurization associated with profound hypotension, pulmonary hypertension and eventual cardiac arrest. There was a statistically significant difference for PaO2 (P = 0.004), cardiac output (P = 0.002), and PAP (P = 0.005) between the AO and RIA groups. That is, by the completion of the experiment the RIA group had higher PaO2, lower PAP, and higher cardiac output measurements as compared to the AO group. There was no statistical significance between the two groups with respect to MAP (P = 0.468). Conclusions: Using established physiologic parameters, there appears to be a difference between the standard AO reamer and the RIA in terms of fat embolism outcome. The RIA showed a more favorable outcome with respect to PAP, PaO2, and cardiac output. With its simultaneous irrigation and aspiration, the RIA may result in less intramedullary fat displacement into the systemic circulation

The response of the muscle is critical in determining the functional outcome of limb lengthening. We hypothesised that muscle response would vary with age and therefore studied the response of the muscles during tibial lengthening in ten young and ten mature rabbits. A bromodeoxyuridine technique was used to identify the dividing cells.

The young rabbits demonstrated a significantly greater proliferative response to the distraction stimulus than the mature ones. This was particularly pronounced at the myotendinous junction, but was also evident within the muscle belly.

Younger muscle adapted better to lengthening, suggesting that in patients in whom a large degree of muscle lengthening is required it may be beneficial to carry out this procedure when they are young, in order to achieve the optimal functional result.

Introduction: In the evaluation of the major joints, self assessment tools have become wide spread aiming at a more precise quantification of joint function. Different tools have been developed for the elbow joint. However, there are only few data on the relationship between subjective self-assessment of joint function and objective measures.

We developed a comprehensive assessment set for the evaluation of subjective elbow function and objective clinical findings and investigate long-term results after implantation of GSB III Elbow arthroplasties in a first study. The PREE-G was cross-culturally adapted, following the recommendations of the American Association of Orthopedic Surgeons.

Material and Methods: 79 patients (56 female, 23 male, mean age 64 years) after elbow arthroplasty between 1984 and 1996 due to rheumatoid (59) or posttraumatic (20) arthritis underwent an assessment of the joint function using the PREE, the Short Form 36 (SF-36), the Disabilities of Arm, Shoulder, Hand (DASH)) and the modified American Shoulder and Elbow Surgeons (mASES) for a clinical evaluation. In 62 patients implantation was performed unilaterally and in 17 patients bilaterally, resulting in 96 elbow joints altogether. The mean follow up time was 11,2 years

Results: In the SF-36 score, the mean physical component scale (PCS) was worse (37,2 vs 41,7, p=0,004), the mean mental component scale (MCS) better (52,3 vs 50,3, p=0,092) than normative values of a German population. Subjective assessment by the PREE revealed a mean of 66,8, by the mASES of 63,1 and by the DASH of 56,5 points. Clinical examination resulted in a mean mASES score of 71,6 points. Comparison between the patients self assessment and the objective score revealed a significant correlation between the DASH (r=0,46, p< 0,001), PREE (p=0,54, p< 0,001) and mASES (r=0,60, p< 0,001) with the clinical mASES. In contrast, no significant correlation was found between the physical component scale (PCS) and mental component scale (MCS) of SF-36 and the clinical mASES. Also the patients assessment scores DASH, PREE and mASES showed a strong significant correlation among one another (r=0,74–0,92, p< 0,001) and (PCS) (r=0,58–0,75, p< 0,001) but not with the (MCS) of SF-36.

Conclusion: Assessment of long term results after elbow arthroplasty yielded favourable clinical and subjective results. The clinical outcome tended to be higher than results of the patient self-rated scores. Hereby, the newly developed assessment set proved to be a feasible tool for a comprehensive assessment of elbow function. In addition to clinical outcome assessment, with this set it is possible to gain important and new insights on the relationship between objective measures and subjective patients-assessment of elbow disorders and postoperative conditions.

Introduction Polymethylmethacrylate (PMMA) has been widely used in orthopaedic procedures for fixation of joint replacements or enhancing the fixation of implants. However, the use of PMMA has been associated with cardiovascular deterioration and even death. More recently, PMMA has also been used for augmenting osteoporotic vertebral bodies which have fractured or are at risk of fracture. The main complication is PMMA leakage into adjacent structures. Transient hypotension and fatal fat embolism (FE) have also been reported. The pathomechanism of cardiovascular deterioration after the injection of PMMA (i.e. FE) remains a highly controversial subject. The exact role of PMMA in the development of FE remains unclear. The aim of the present study was to elucidate the acute effects of injecting PMMA compared with bone wax into vertebral bodies on the cardiovascular system using an established animal model for vertebroplasty (VP) (Aebli, N, et al. Spine. 2002). Methods In 8 skeletally mature mixed-bred ewes (2–4 years) 6.0ml PMMA (CMW3-Depuy) or bone wax (Bone Wax, Ethicon) were injected unilaterally, through an open approach into the L1 & L2 pedicles. Blood pressure, heart rate, and cardiac output were measured. Results The major difference between the cardiovascular response of the PMMA and that of the bone wax group was the recovery in Pulmonary Artery Pressure (PAP) and Pulmonary Vascular Resistance (PVR). Three minutes post-injection, PAP had fully recovered to baseline values in the wax group. However in the PMMA group, PAP had only recovered by 52% after 3 min and fully recovered after 10 min. Discussion The augmentation of vertebral bodies resulted in transient cardiovascular changes regardless of the material used. However, the recovery of PAP and PVR values took significantly longer with the PMMA group. The peak response was a result of pulmonary vasoconstriction triggered by a reflex reaction to the embolisation of bone marrow particles or by vasoactive cytokines. The peak response was therefore mainly associated with the increase in intraosseous pressure during the augmentation causing release of bone marrow contents into the and not the cement monomer. The cement monomer however plays a role in the cardiovascular complications during FE. The delayed recovery of PAP and PVR in the PMMA group may be due to a vasoconstriction effect of the cement monomer on the pulmonary vascular system. Potentially serious cardiovascular complications may occur during VP regardless of the material used. The injection of PMMA may cause prolonged pulmonary hypertension during vertebro- and also arthroplasty. Continuous invasive cardiovascular monitoring may be required in patients with impaired cardiovascular and pulmonary function

We assessed proprioception using threshold levels for the perception of knee movement at slow angular velocities (0.1°/s to 0.85°/s) in 20 patients with unilateral tears of the anterior cruciate ligament (ACL) and 15 age-related control subjects. Failure to detect movement was also analysed.

The threshold levels of detection did not differ between the damaged and undamaged knees in the patients or between the patients and the control group. Failure to appreciate movement, however, was significantly greater in knees with ACL loss compared with the undamaged knees of patients and the control group.

Our findings show a proprioceptive deficit in the absence of the ACL. Measurements of threshold levels of detection of passive movement alone are not suitable for the evaluation of proprioceptive loss in ACL deficiency; assessment of failure to appreciate movement is essential.

We examined the roles of methylmethacrylate (MMA) monomer and cementing technique in the formation, and haemodynamic outcome, of pulmonary fat emboli. The preparation of the femoral canal and the cementing technique were studied in four groups of adult dogs as follows: control (no preparation); lavage; cement pressurisation; and cement pressurisation after lavage. We measured the intramedullary pressure, pulmonary artery pressure (PAP), pulmonary capillary wedge pressure and bilateral femoral vein levels of triglyceride, cholesterol and MMA monomer at rest and after reaming, lavage, and cementing. Femoral vein triglyceride and cholesterol levels did not vary significantly from resting levels despite significant elevations in intramedullary pressure with reaming, lavage and cementing (p = 0.001). PAP was seen to rise significantly with reaming (p = 0.0038), lavage (p = 0.0031), cementing (p = 0.0024) and cementing after lavage (p = 0.0028) while the pulmonary capillary wedge pressure remained unchanged. MMA monomer was detected in femoral vein samples when cement pressurisation was used. Intramedullary lavage before cementing had no significant effect on the MMA level. Haemodynamic evidence of pulmonary embolism was noted with reaming and intramedullary canal preparation, irrespective of the presence of MMA monomer. We found no relationship between MMA monomer level and intramedullary pressure, PAP or pulmonary capillary wedge pressure. Our findings suggest that the presence of MMA monomer in femoral venous blood has no effect on the formation of fat emboli or their pulmonary haemodynamic outcome during cemented hip arthroplasty