Aims

Research on hip biomechanics has analyzed femoroacetabular contact pressures and forces in distinct hip conditions, with different procedures, and used diverse loading and testing conditions. The aim of this scoping review was to identify and summarize the available evidence in the literature for hip contact pressures and force in cadaver and in vivo studies, and how joint loading, labral status, and femoral and acetabular morphology can affect these biomechanical parameters.

Aim

Diagnosing prosthetic joint infections(PJI) is sometimes difficult. Being able to identify the bacteria involved in intraoperative samples is an essential diagnostic criterion.

There are however some cases in which the traditional cultures are not capable of providing a definitive diagnosis. In this regard, implant sonication has emerged as a complementary test.

The aim of this study was to analyze the results of microbiological studies obtained with and without implants sonication, in order to understand its real contribution to diagnosis.

Aim

The aim of this study is to evaluate the value of inflammatory parameters normalization and/or increased time between stages necessary in predicting healing and preventing infection recurrence.

Aim

The purpose of this study is to evaluate the safety profile and impact on functional results of surgical debridement performed in the early postoperative by comparing them with patients that undergone uncomplicated total joint arthroplasty.

Primary tuberculous bursitis was a relatively frequent manifestation of the disease before the antituberculosis drug era. Nowadays, it is considered a rare condition; it accounts for 1–2% of all musculoskeletal tuberculosis. The diagnosis and treatment of tuberculous bursitis may be delayed because the paucity of symptoms, its indolent clinical course and a low clinical suspicion. A 50-year-old patient with tuberculous trochanteric bursitis is reported.

A 50-year-old woman was referred to our department to investigate a persistent pain in her left hip with 6 months duration. She was afebrile. The examination revealed a diffuse swelling from the buttock through the thigh, notable over the trochanter, but no sign of acute inflammation such as heat and redness. Her past medical and family histories revealed no previous tuberculosis.

Plain films of the left hip showed a partial destruction of the margin of the greater trochanter, lytic foci in the underlying bone and a small focus of calcification in the adjacent soft tissues. A computed tomogram showed a soft tissue mass and demonstrated the relationship with the trochanter. We performed a needle biopsy which revealed granulomatous tissue. The patient underwent complete excision of the bursa and curettage of the surface of the trochanter. The postoperative course was uneventful. Mycobacterium tuberculosis was isolated and definitive diagnosis of tuberculous bursitis was made. There was no evidence of concomitant tuberculosis at other musculoskeletal sites. The patient completed a treatment with rifampicin and etambutol for 6 months.

There has been a complete resolution of the symptoms after 3 months and no recurrence after 4 years of follow-up. On plain radiograph the remodeling of the bone structure is clearly visible.

Tuberculosis in the region of the greater trochanter is extremely rare. This rarity leads orthopedic surgeons to neglect this potential diagnosis, resulting in a delay in treatment. The pathogenesis of tuberculosis of the greater trochanteric area has not been well defined. The incidence of concomitant tuberculosis at other musculoskeletal sites, as well as the lung, is approximately 50%. Both hematogenous infection and propagation from other locations are reasonable explanations. Surgical intervention is mandatory for cure and the use of several antituberculosis agents is a standard approach.

We aim to describe the microbiological spectrum and relevant antibiotic susceptibility profile of PJI in our institution over a five-year period(2009–2013) and determine its evolution considering the preceding six years(2003–2008) thus evaluating the adequacy of our empirical antibiotic regimen.

We retrospectively reviewed the records of 96 consecutive PJI (51 hips:45 knees) treated from May 2009-December 2013. Demographics, microbial species and antibiotic susceptibility were recorded. These results were then compared to those previously obtained by studying the 2003–2008 time period.

Infections were polymicrobial in 27 cases(28.1%) and only two cases(2.1%) were culture-negative accounting for a total of 132 different culture results.

S.aureus grew in 37 samples(28.0%) being the most frequently isolated microorganism. Coagulase-negative staphylococci grew in 32 samples(24.2%) and gram negative bacteria in 35 samples(26.5%). Other Gram positive species (most commonly enterococci and streptococci) were isolated in 26 samples(19.7%).

Comparing 2009–2013 to 2003–2008, there was a significant increase of polymicrobial infections – 28% vs. 8%(OR=4.6, 95%CI [1.9–11.3]) and a significant decrease of culture-negative cases – 2% vs. 18%(OR=0.1, 95%CI [0.02–0.4]). It is also noteworthy that the prevalence of gram negative isolates was significantly increased – 26.5% vs. 13.3%(OR=1.3, 95%CI [1.1–1.6]).

Antibiotic susceptibilities study showed a 41.4% methicillin resistance among S.aureus and even higher among coagulase-negative staphylococci isolates(57.7%). This is a not quite significant decrease compared to the earlier period(p=0.10). We also found a high rate antibiotic resistance among gram negative: ampiciline(81.8%), amoxicilin/clavulanate(59.1%), ciprofloxacin(19.2%), aminoglycosides(17%), third generation cephalosporins(14.6%) and even carbapenems(13.6%).

These results show that our sampling protocol has improved considerably as the proportion of culture-negative cases has dramatically decreased. On the other hand this may also help explain the increase in polymicrobial infections. We have no clear explanation for the increase in gram negative bacteria.

Despite the downward trend we still face a very significant proportion of methicillin-resistant staphylococci infections. The antibiotic resistance profile among gram negative bacteria is also worrying. As such we believe a regimen consisting of vancomycin and gram-negative coverage such as aminoglycosides or a third generation cephalosporin is still warranted in our institution.

Evaluation of the effectiveness of biodegradable bone substitute with high doses of antibiotics in cavitary osteomyelitis and infected nonunions.

The authors evaluated 8 cases, 5 of them related to osteomyelitis with bone sequestration and other 3 regarding infected nonunions. All of them had in common the persistence of infection after antibiotic therapy.

All infections were confirmed by microbiological studies. In all cases the surgeons conducted a thorough surgical debridement and filling of bone defects with Herafill®. Later a tight clinical, analytical and imagiological control was performed.

Five of the cases were a success with simultaneous healing of the bone loss and treatment of the infection. These corresponded to the cases of cavitary osteomyelitis. In the remaining 3 cases, despite infection eradication, union was not achieved and additional surgical procedures were required for definitive treatment of nonunion.

In the treatment of bone infection, use of high doses of antibiotics at the site is a consensus as it allows eradication of the infection with lower systemic effects. With the emergence of biodegradable bone substitutes, the need for a new surgical intervention for their removal can be avoided. Properties of calcium sulfate and calcium carbonate stimulate osteogenesis at the site, allowing their absorption and replacement by bone matrix. These properties make them ideal to usage in cases of cavitary bone defects.

Our experience supports the idea that the use of high doses of antibiotics locally permits remission of the infection. However, when this is implemented through a bone substitute, it is possible to achieve osteogenesis in bony cavities. Nevertheless, when applied to infected nonunions, their role seems to be limited to the eradication of the infection.

The goals of the present study are to describe the prevalence of both methicillin sensitive and resistant S.aureus carriage among elective total hip and knee arthroplasty candidates and to evaluate the real impact of preoperatively treating carriers in preventing prosthetic joint infection.

Patients undergoing elective primary THA or TKA at a single institution were enrolled in a prospective randomized trial. S.aureus nasal carriage screening was performed in the outpatient setting and selected carriers underwent a 5-day preoperative treatment of nasal mupirocin and chlorhexidine bathing. All patients were followed regularly in the outpatient clinic. No patients were lost to follow-up at a minimum of one year after surgery. The main outcome of the study was the diagnosis of prosthetic joint infection occurring in the first year after surgery including all pathogens and a secondary outcome was defined as infections involving S.aureus bacteria only.

From January 2010 to December 2012, 1305 total joint arthroplasties were performed and 1028 of those were screened. We observed a 22.2% (228/1028) S.aureus colonization rate and only eight patients colonized with MRSA (0.8%). Twenty five cases of prosthetic joint infections were identified with an overall infection rate of 2.4%. S.aureus was involved in 14 cases. PJI rate in S.aureus carriers was 3.9% (9/228), which was not significantly higher than the 2.0% (16/800) found among non carriers. Treated and untreated carriers infection rate also showed no significant differences – 3.4% (3/89) vs. 4.3% (6/139). Multivariable analysis substantiates ASA≥ 3 (OR=3.42, 95% CI=1.51 – 7.74) and duration of surgery above the 75th percentile (OR=2.74, 95% CI=1.22 – 6.16) as independent predictors of PJI but not S.aureus carrier state. We obtained similar results when considering infection involving S.aureus bacteria only.

Of the 14 cases where S.aureus was present in PJI, only five were carriers preoperatively. Of those five cases, one was an untreated MSSA carrier that ultimately got an MRSA infection.

Our results show no clear benefit in screening and decolonizing S.aureus nasal carriers before total joint arthroplasty. There seems to be a lack of causal relation between nasal S.aureus and PJI pathogen as most of S.aureus PJI seems to have an exogenous source.

Summary Statement

Bone stress fracture triggers a rapid increase in blood flow in association with mast cell production of inducible nitric oxide synthase (iNOS). NOS inhibition blocks the increase in blood flow and reduces woven bone formation needed for stress fracture healing.

Purpose of the study: Proximal fractures of the humerus account for 10% of fractures in persons aged over 65 years. There is no optimal treatment. The goal of surgery is to restore joint congruency, preserve vascular supply, and allow functional recovery. We describe the results obtained with a surgical technique designed to meet these goals.

Material and methods: Fifteen 3-fragment fractures of the proximal humerus were treated with transosseous suture. Mean age of patients was 58 years. Eighty-six percent of the patients were female. Follow-up was 18 months on average. The patients were placed in a lounge chair position for the deltopectoral or transdeltoid approach. For this type of fracture, the humeral head is displaced medially or laterally, so that care must be taken to ensure the realignment in the sagittal and coronal planes. The DASH and Constant scores were noted for the operated and non-operated shoulders. Signs of bone healing were noted on the plain x-rays.

Results: The mean DASH was 12, mean Constant score for the operated shoulder was 80 versus 90 for the other shoulder. The mean neck-shaft angle was 139°. There was one case of lost reduction but with a good final result. There was one case converted to arthroplasty.

Discussion: This technique is in line with the current trend for biological preservation minimising the aggression to the humeral head blood supply. There was no risk of migration with the fixation material used and no need to remove implants.

Conclusion: Transosseous suture of proximal fractures of the humerus is a mini-invasive method which provides good functional results avoiding voluminous metal implants, known to be costly and source of complications. The incidence of avascular necrosis of the humeral head is low, in agreement with the international literature.

Treatment of patellar instability in adolescents is controversial. Some investigators have advocated early repair of the medial structures, whereas others have treated this injury nonoperatively. The medial patellofemoral ligament, is a primary restrictor and stabilizer of the patella, and has acquired a significant role in the treatment of instability in children and adolescents.

The authors present a prospective study of 39 consecutive patients (45 knees), without physeal closure, who underwent plasty of the medial patellofemoral ligament for the treatment of symptomatic patellofemoral instability with autologous Gracilis tendon, according to Chassaing’s technique. There were 26 female and 13 male patients with an average age of 15, 9 years. Mean follow-up was 44 months (6–65). All patients presented with clinical evident patellar tilt. This population presented a TA-GT within a normal range (12+/− 5 mm), but presented in 80% of cases a trochlear dysplasia

Clinical functional results were evaluated using the Kujala scale. Arthroscopic evaluation was systematically performed searching for intra articular injuries or patellar tilt. Early rehabilitation protocols were used in all cases.

At the last follow up evaluation, 90% of the patients presented good or very good results. Kujala Score was 84, 5 +/−9,7 after surgery compared with 54,9+/−11,8 before surgery (p< 0,0001). There were 3 minor complications: 2 hematomas and 1 superficial infection that resolved without complications.

Four patients kept complaining of residual anterior knee pain as result of patellar chondropathy that was diagnosed intra operatively. Three patients complained of graft donor site pain. One patient presented with a patellar dislocation three years after the surgery, and two patients still present clinical instability two years after the procedure. There was no stiffness in the knee in any patient.

The technique presented in this study has allowed very good clinical results, with few complications, using a small incision to reconstruct in an isometric fashion, this important patellar stabilizer.

Osteoarthrosis (OA) is often considered to be due to “wear and tear”, aggravated by obesity. However, if developmental dysplasia of the hip (DDH) is treated incorrectly, osteoarthrosis can also occur at a very young age. We obtained cartilage from the femoral head a 23 year-old female after arthroplasty for DDH; from a 14 year-old male, resected for paralytic dislocation, and from OA and control patients. This provided a unique opportunity to compare the cellular and epigenetic features of OA in older patients with those in a young control as well as a DDH patient. We have recently defined the cellular and epigenetic features of idiopathic OA, in particular the association between induction of proteases and loss of DNA methylation in the respective promoter regions (Arthritis Rheum2005; 52: 3110–3124). We had shown that these proteases were silenced in normal articular chondrocytes, but “unsilenced” in OA chondrocytes. The present study determined whether the phenotypic changes of idiopathic OA also take place in juvenile OA and whether loss of DNA demethylation is also associated with the abnormal expression of proteases in juvenile OA. Paraffin sections were immunostained with antibodies to MMP-3, -9, and ADAMTS-4. DNA was extracted from freezer milled cartilage. The methylation status of specific CpG sites (at which methylation occurs) was established using methylation-sensitive restriction enzymes followed by PCR. From the 23 year old female, we only obtained a 1cm thick transverse slice of femur, taken near the femoral neck. However, this contained sufficient reasonably thick cartilage in the perimeter for histology and DNA extraction.

The cartilage of the 14-year old showed high cellularity and absence of immunostaining for all proteases investigated. Apart from the higher cellularity, this was similar to the ‘control’ cartilage obtained from patients with a fracture of the femoral neck. We had previously shown that, as OA progresses, more chondrocytes become immunopositive for the degradative enzymes and these cells divide so that in the typical clones of OA all cells synthesize the proteases. The cartilage from the 23-year old DDH patient showed extensive loss of proteoglycans from the superficial zone and fibrous repair tissue covered some areas. Nearly all chondrocytes produced the proteases and clones had formed, as in idiopathic OA. Since these sample were from the base of the femoral neck, where in idiopathic OA good cartilage often remains even in severe OA, the disease process must have reached an early end-stage in this young patient. The findings indicate that severe OA, as defined by the presence of clones that produce degradative enzymes, can develop very quickly. Interestingly, the expression and synthesis of degradative enzymes by OA chondrocytes was the same in juvenile and old-age OA. and their abnormal expression was associated with “unsilencing” via DNA demethylation in both juvenile and old-age OA. The results thus suggest that age per se is not a major determinant of OA progression.

Background: Metal-metal bearings are frequently implanted in young, active patients. The relationship between patient activity and Co and Cr ion levels has not been scientifically investigated.

Methods: Seven patient subjects with well-functioning metal-metal bearing hip prostheses and one control subject (no implants), all with normal renal function, were monitored during a two-week long activity protocol. Lower extremity activity was continuously assessed by a computerized, two-dimensional accelerometer (Step Activity Monitor; SAM). During the first week, subjects were requested to limit physical activity. Subjects then completed an hour-long treadmill test followed by a week where they were encouraged to be as physically active as possible. Serum Co and Cr ion levels and urine Cr levels were assessed at 10 different time points during these two weeks.

Results: Regardless of activity, the serum ion levels for a given patient were essentially constant and there was no correlation between patient activity and serum or urine ion levels. A mean increase in activity of 28% (95% CI, 13 to 43%; SE, 6%) during the high-intensity activity week resulted in a mean decrease of 2.6% (95% CI, −14.2 to 8.9%; SE, 4.7%) in serum Co and a mean increase of 2.0% (95% CI, −5.3 to 9.3%; SE, 3.0%) in serum Cr. During the treadmill test, a mean activity increase of 1,621% (16-fold) (95% CI, 972 to 2,271%; SE, 265%) resulted in a mean increase of 3.0% (95% CI, −5.7 to 11.7%; SE, 3.6%) in serum Co and a mean increase of 0.8% (95% CI, −3.5 to 5.0%; SE, 1.7%) in serum Cr. This effectively constitutes no change in serum ion levels for these changes in activity because the differences are within the variability for the measurement accuracy of these tests.

Conclusions: In patients with normal renal function and a well-functioning metal-metal bearing, ion levels are not affected by patient activity. Periodic measurements of serum ion levels can be used to monitor the tribologic performance of prosthesis with a metal-metal bearing without adjusting for patient activity.

Introduction: The Step Activity Monitor (SAM) is a microprocessor worn on the ankle that measures ambulatory activity in real time.

Methods: Activity magnitudes, speed parameters and activity patterns were analyzed in 31 patients with 37 primary total hips. Wear was measured from digitized radiographs using a validated two-dimensional, edge detection-based computer algorithm.

Results: On average, patients walked 5.6 hours per day (range: 1.9–9.8); averaging 5,266 gait cycles (range: 1,737–11,805), at 20 cycles/minute (range: 12.7–32.8) with a maximum speed of 63 cycles/minute (range: 45.0–88.0). Fast and very fast walking (30–49 and > 50 cycles/minute) accounted for 9.4% and 4.4% of total walking time. Patients started and stopped walking about 66 times per day (range: 34–113), with about 81 cycles between stops (range: 28.1-200.1) in average active intervals of 5.3 minutes (range: 3.3–10.3).

There was no difference in the average number of gait cycles between females and males. However, polyethylene wear per million cycles was significantly higher in males (p=0.006). Even after adjustment for greater height and weight in males, their wear rate was still significantly higher (p< 0.01). Males walked at a higher average speed (p=0.07), spent 33.9% more time walking fast or very fast, had 4% more starts/stops per day, with 13% less strides between stops. The percentage of time spent walking slow (5–9 cycles/minute) was negatively correlated to wear (p< 0.05).

Discussion and Conclusion: The SAM allows assessment of patterns and intensity of joint use. Similar to a set of automobile tires, polyethylene wear is a function of the amount and type of use; faster walking with more frequents starting and stopping is associated with a higher polyethylene wear rate. As the clinical performance of crosslinked polyethylenes is being monitored, it is critical to consider the influence of the amount and type of patient activity on wear.

Introduction: Recent in vivo studies of flexor tendon midsubstance healing have indicated that during the first 10 days after injury and repair there is no increase in ultimate tensile force. In contrast, there is an increase of approximately 170% in the rigidity (stiffness) of the repair site and a decrease of more than 45% in the repair-site strain at 20 N force. The basis for the increase in rigidity during the early stages of tendon healing is not known, but may be due to either biological or mechanical factors. In particular, cyclic loading of the tendon repair site during post-operative rehabilitation may have a mechanical conditioning effect that increases the stiffness of the repair site independent of repair-site healing. Our objective was to determine whether or not cyclic loading of repaired flexor tendons causes an in increase in repair-site rigidity and whether or not this increase depends on the level of applied force. We simulated 10 days of passive motion rehabilitation by applying 6000 loading cycles to repaired flexor tendons ex vivo at force levels generated during passive motion rehabilitation. We then evaluated the tensile mechanical properties. We hypothesized that cyclic loading causes an increase in repair-site rigidity and a decrease in repair-site strain.

Materials and Methods Forty-eight flexor digitorum profundus (FDP) tendons with attached distal phalanges were obtained from twelve hindlimbs of six adult mongrel dogs. Specimens were randomly assigned to one of three groups: control (no loading), low-force (5 N) cyclic loading or high force (17 N) cyclic loading. Tendons were transected in Zone II, 4 cm proximal to the insertion site. They were repaired using a four-strand modified Kessler technique with double-stranded 4-0 Supramid suture (S. Jackson) supplemented with a running peripheral suture of 6-0 Prolene (Ethicon). For cyclic loading, the distal phalanx and proximal tendon stump were placed in custom clamps attached to a materials testing machine (Instron 8500R). Tendons in the low-force and high-force groups were loaded for 6000 cycles at 2 Hz from 0.5 N to peak forces of 5 and 17 N, respectively. The force levels were chosen to match the peak tendon forces that were measured in vivo for low- and high-force passive motion rehabilitation protocols of the canine forelimb; 6000 cycles were used to simulate the number of cycles applied during a 10-day period of rehabilitation (600 cycles/day). Specimens in the control group were sham loaded for an equivalent period of time (50 minutes). After cyclic loading, specimens were allowed to recover for 1 hour and then tested to failure in tension. From plots of force versus repair-site strain we determined ultimate (maximum) force (N), repair-site rigidity (N/[mm/mm]) and repair-site strain (%) at 20 N force. One-way analysis of variance was used to determine the effect of loading on tensile properties.

Results: Specimens subjected to high-force cyclic loading had significantly increased rigidity compared to specimens in the low-force and control groups. Rigidity in the high-force group was increased by 100% compared to control. Similarly, repair-site strain at 20 N was decreased by 50% in the high-force group compared to control group. Ultimate force was increased in the high force group compared to control (p = 0.02; Table), but the magnitude of the increase was only 13%. There were no significant differences between the low-force and control groups (p > 0.05).

Discussion: Based on our findings, we conclude: 1) Repair-site rigidity is increased by 100% and repair-site strain decreased by 50% following 6000 cycles of high-force (17 N) loading. In contrast, ultimate force is changed only slightly (13%) by high-force loading. 2) Mechanical conditioning of the repair site by repetitive forces applied during rehabilitation may have a consequence that has not been noted previously, i.e. it leads to increases in rigidity and decreases in strain. This effect may explain in part the changes in tensile properties observed after only 10 days of healing in vivo. 3) The lack of effect of low-force (5 N) loading on repair-site rigidity and strain is in contrast to the previous in vivo findings in which rigidity increased in the low-force rehabilitation group. This discrepancy suggests that the observed in vivo changes can not be explained entirely by mechanical conditioning effects. 4) Therefore, both biological and mechanical factors are likely to play an important role in the rapid changes in repair-site mechanical properties that occur following flexor tendon injury and repair.