Covering of wound infection in hip arthroplasty with local cutaneous flaps

Total hip arthroplasty is a very common procedure to treat osteoarthritis. One of the complication is the infection which occurs in about 1% of the cases. The manifestation of infection can be poor wound healing with dehiscence and exposition of bone or prosthetic components. Hip arthroplasty infections are difficult to treat. It required an associated multidisciplinary approach with infectiology, orthopedic and plastic surgeries. The study included five patients with hip wound dehiscence after total hip arthroplasty. Coverage after orthopedic surgery was provided by local cutaneous flap. These cutaneous flaps were either a deep inferior epigastric perforator flap (DIEP) or a transposition flap. The orthopedic and the plastic treatment were done at the same time. Two deep inferior epigastric flaps were performed for patients with a deep defect with bone or prosthesis exposure. Four transposition flaps were done in three patients with wound dehiscence but without direct contact with the prosthesis. Three transposition flaps were done from the abdominal wall and one from the posterior thigh. The mean follow up was 18 months, ranging from 10 to 24months. After healing, there was no recurrence of the infection. In all cases, the coverage was obtained. The prosthesis was salvage and the gait was possible. Cutaneous flaps are easy and safe to cover the hip. They are reliable flaps even in patients with multiple co-morbidities. They do not cause sequelae on the recipient site. This study is the first about cutaneous flap for covering hip defects in hip arthroplasty infections.

Can a target zone safer than Lewinnek's safe zone be defined to prevent instability of total hip arthroplasties? Case-control study of 56 dislocated THA and 93 matched controls

BACKGROUND

Various factors contribute to instability of total hip arthroplasty (THA), with implant orientation being a major contributor. We performed a case-control study with computed tomography (CT) data to determine whether: 1) orientation contributes to THA instability and 2) a safer target zone for stability than Lewinnek's classic safe zone can be defined.

MATERIAL AND METHODS

We included prospectively 363 cases of THA dislocation that occurred during the calendar 2013 year in 24 participating hospitals. Of the 128 dislocations that occurred in patients who underwent THA at these centers, 56 (24 anterior, 32 posterior) had CT scans, thus were included in the analysis. The control group was matched 4:1 based on implant type, year of implantation, age, sex, bearing types and THA indication. Of the 428 matched control THA cases, 93 had CT scans. In all, the CT scans from 149 cases (56 unstable, 93 stable) were analyzed to determine the acetabular cup's inclination and anteversion, and the femoral stem's anteversion.

RESULTS

In the unstable THA group, cup inclination was 46.9°±7.4°, cup anteversion was 20.4°±10.8° and stem anteversion was 14.2°±9.9°. In the stable THA group, cup inclination was 44.9°±5.3° (P=0.057), cup anteversion was 22.1°±5.1° (P=0.009) and stem anteversion was 13.4°±4.4° (P=0.362). The optimal total anteversion (cup+stem) of 40-60° was achieved in 16.5% of unstable THA cases and 13.9% of stable THA cases, thus this parameter does not predict stability (odds ratio [OR] of 0.40, P=0.144). The cup was positioned in Lewinnek's safe zone in 44.6% of patients in the unstable group and 68.2% of those in the stable group (OR 3.74, P=0.003). A target zone defined as 40-50° inclination and 15-30° anteversion was better able to distinguish between unstable cases (23.2%) and stable cases (71.6%) resulting in an OR of 13.91 (P<0.001).

DISCUSSION

Implant positioning was the only risk factor for instability found in this study. Moreover, our findings reinforce the theory put forward by other authors that Lewinnek's safe zone is not specific enough to differentiate between stable and unstable THA implantations. The target zone for acetabular cups proposed here (40-50° inclination and 15°-30° anteversion) is related to a lower risk of instability. This orientation can be used as a guide, but must be combined with other technical elements to optimize stability. By balancing stability and biomechanics, the 40-50° inclination and 15°-30° anteversion target zone redefines the optimal positioning window.

LEVEL OF EVIDENCE

III case-control study.

Experimental validation of the GNRB® for measuring anterior tibial translation

INTRODUCTION

The objective of this study was to validate the technique used to measure anterior tibial translation in cadaver knees using the GNRB^® device by comparing it with the gold standard, the OrthoPilot^® navigation system.

HYPOTHESIS

Simultaneous measurement of anterior tibial translation by the GNRB^® and the OrthoPilot^® in the chosen experimental conditions will result in significant differences between devices.

MATERIAL AND METHODS

Five fresh frozen cadavers were used. The knee was placed in 20° flexion. Four calibrated posterior-anterior forces (134N to 250N) were applied. For each applied force, the anterior tibial translation was measured simultaneously by both devices. Two conditions were analyzed: anterior cruciate ligament (ACL) intact and ACL transected. The primary criterion was anterior tibial translation at 250N. The measurements were compared using a paired Student's t-test and the correlation coefficient was calculated. Agreement between the two methods was determined using Bland-Altman plots. Consistency of the measurements was determined by calculating the intraclass correlation coefficient.

RESULTS

For all applied forces and ligament conditions, the mean difference between the GNRB^® and the navigation system was 0.1±1.7mm (n.s). Out of the 80 measurements taken, the difference between devices was less than ±2mm in 66 cases (82%). There was a strong correlation, good agreement and high consistency between the two measurement methods.

DISCUSSION

The differences between the measurements taken by the GNRB^® and the navigation system were small and likely have no clinical impact. We recommend using the GNRB^® to evaluate anterior knee laxity.

LEVEL OF EVIDENCE

II controlled laboratory study.

Agreement between pre-operative and intra-operative bacteriological samples in 85 chronic peri-prosthetic infections

BACKGROUND

Whether pre-operative microbiological sampling contributes to the management of chronic peri-prosthetic infection remains controversial. We assessed agreement between the results of pre-operative and intra-operative samples in patients undergoing single-stage prosthesis exchange to treat chronic peri-prosthetic infection.

HYPOTHESIS

Agreement between pre-operative and intra-operative samples exceeds 75% in patients undergoing single-stage exchange of a hip or knee prosthesis to treat chronic peri-prosthetic infection.

MATERIAL AND METHODS

This single-centre retrospective study included 85 single-stage prosthesis exchange procedures in 82 patients with chronic peri-prosthetic infection at the hip or knee. Agreement between pre-operative and intra-operative sample results was evaluated. Changes to the initial antibiotic regimen made based on the intra-operative sample results were recorded.

RESULTS

Of 149 pre-operative samples, 109 yielded positive cultures, in 75/85 cases. Of 452 intra-operative samples, 354 yielded positive cultures, in 85/85 cases. Agreement was complete in 54 (63%) cases and partial in 9 (11%) cases; there was no agreement in the remaining 22 (26%) cases. The complete agreement rate was significantly lower than 75% (P=0.01). The initial antibiotic regimen was inadequate in a single case.

DISCUSSION

Pre-operative sampling may contribute to the diagnosis of peri-prosthetic infection but is neither necessary nor sufficient to confirm the diagnosis and identify the causative agent. The spectrum of the initial antibiotic regimen cannot be safely narrowed based on the pre-operative sample results. We suggest the routine prescription of a probabilistic broad-spectrum antibiotic regimen immediately after the prosthesis exchange, even when a pathogen was identified before surgery.

LEVEL OF EVIDENCE

IV, retrospective study.

Infection recurrence factors in one- and two-stage total knee prosthesis exchanges

PURPOSE

Revision of infected total knee replacements (TKR) is usually delayed for a period in which the joint space is filled with an antibiotic-loaded acrylic spacer. In contrast, one-stage re-implantation supposes immediate re-implantation. Formal comparisons between the two methods are scarce. A retrospective multi-centre study was conducted to investigate the effects of surgery type (one-stage vs. two-stage) on cure rates. It was hypothesised that this parameter would not influence the results.

METHOD

All infected TKR, treated consecutively between 2005 and 2010 by senior surgeons working in six referral hospitals, were included retrospectively. Two hundred and eighty-five patients, undergoing one-stage or two-stage TKR, with more than 2-year follow-up (clinical and radiological) were eligible for data collection and analysis. Of them, 108 underwent one-stage and 177 received two-stage TKR. Failure was defined as infection recurrence or persistence of the same or unknown pathogens. Factors linked with infection recurrence were analysed by uni- and multi-variate logistic regression with random intercept.

RESULTS

Factors associated with infection recurrence were fistulae (odds ratio (OR) 3.4 [1.2-10.2], p = 0.03), infection by gram-negative bacteria (OR 3.3 [1.0-10.6], p = 0.05), and two-stage surgery with static spacers (OR 4.4 [1.1-17.9], p = 0.04). Gender and type of surgery interacted (p = 0.05). In men (133 patients), type of surgery showed no significant linkage with infection recurrence. In women (152 patients), two-stage surgery with static spacers was associated independently with infection recurrence (OR 5.9 [1.5-23.6], p = 0.01). Among patients without infection recurrence, International Knee Society scores were similar between those undergoing one-stage or two-stage exchanges.

CONCLUSION

Two-stage procedures offered less benefit to female patients. It suggests that one-stage procedures are preferable, because they offer greater comfort without increasing the risk of recurrence. Routine one-stage procedures may be a reasonable option in the treatment of infected TKR.

LEVEL OF EVIDENCE

III.

Can the presence of an infection be predicted before a revision total hip arthroplasty? Preliminary study to establish an infection score

INTRODUCTION

The diagnosis of periprosthetic joint infection can be challenging, in part because there is no universal diagnostic test. Current recommendations include several diagnostic criteria, and are mainly based on the results of deep microbiological samples; however, these only provide a diagnosis after surgery. A predictive infection score would improve the management of revision arthroplasty cases. The purpose of this study was to define a composite infection score using standard clinical, radiological and laboratory data that can be used to predict whether an infection is present before a total hip arthroplasty (THA) revision procedure.

HYPOTHESIS

The infection score will make it possible to differentiate correctly between infected and non-infected patients in 75% of cases.

MATERIAL AND METHODS

One hundred and four records from patients who underwent THA revision for any reason were analysed retrospectively: 43 with infection and 61 without infection. There were 54 men and 50 women with an average age of 70±12 years (range 30-90). A univariate analysis was performed to look for individual discriminating factors between the data in the medical records of infected and non-infected patients. A multivariate analysis subsequently integrated these factors together. A composite score was defined and its diagnostic effectiveness was evaluated as the percentage of correctly classified records, along with its sensitivity and specificity.

RESULTS

The score consisted of the following individually weighed factors: body mass index, presence of diabetes, mechanical complication, wound healing disturbance and fever. This composite infection score was able to distinguish correctly between the infected patients (positive score) and non-infected patients (negative score) in 78% of cases; the sensitivity was 57% and the specificity 93%.

DISCUSSION

Once this score is evaluated prospectively, it could be an important tool for defining the medical - surgical strategy during THA revision, no matter the reason for revision.

LEVEL OF EVIDENCE

Level IV - retrospective study.

May one-stage exchange for Candida albicans peri-prosthetic infection be successful?

Fungal infection of a total joint arthroplasty has a low incidence but is generally considered as more difficult to cure than bacterial infection. As for bacterial infection, two-stage exchange is considered as the gold standard of treatment. We report two cases of one-stage total joint exchange for fungal peri-prosthetic infection with Candida albicans, where the responsible pathogens was only identified on intraoperative samples. This situation can be considered as a one-stage exchange for fungal peri-prosthetic infection without preoperative identification of the responsible organism, which is considered as having a poor prognosis. Both cases were free of infection after two years. One-stage revision has several potential advantages over two-stage revision, including shorter hospital stay and rehabilitation, no interim period with significant functional impairment, shorter antibiotic treatment, better functional outcome and probably lower costs. We suggest that one-stage revision for C. albicans peri-prosthetic infection may be successful even without preoperative fungal identification.

LEVEL OF EVIDENCE

Level IV-Historical cases.

Validation of the French version of two on high-activity knee questionnaires

INTRODUCTION

Self-administered quality-of-life questionnaires are valuable evaluation tools in orthopedic surgery. The conventional questionnaires are limited by a substantial ceiling effect. We wished to validate a French translation of two English questionnaires for high-activity patients: the High-Activity Arthroplasty Score (HAAS) and the Activity Scale for Arthroplasty Patients (ASAP). One hundred patients operated on for knee replacement were selected. The answers to both questionnaires were analyzed and compared to the Oxford Knee Score (OKS) and to the scoring system of the American Knee Society (AKS).

HYPOTHESIS

There is no correlation between the results of both high-activity questionnaires and of the two conventional scoring systems.

RESULTS

All questions were easily understood. The mean scores of the HAAS and ASAP questionnaires were 8.2±3.0 and 30.7±9.6, respectively. The distributions were not considered normal. There was no floor effect, but there was a limited ceiling effect (0% and 14%, respectively). The internal coherence of both questionnaires was satisfactory. There was a significant correlation between the high-activity scores and the conventional scores.

DISCUSSION

Both high-activity questionnaires in our French translation can potentially measure the overall function of a patient after knee replacement as accurately as the index English version. It is self-administered, easy to use, can collect patients' answers by postage mailing, and involves no ceiling effect. All these points should allow its routine use for evaluation after knee replacement. The HAAS evaluation seems to be superior to the ASAP evaluation.

LEVEL OF EVIDENCE

Case-control study, level III.

Postoperative pain control by intra-articular local anesthesia versus femoral nerve block following total knee arthroplasty: impact on discharge

INTRODUCTION

The goal of this retrospective study was to compare pain control following total knee arthroplasty (TKA) on a perioperative protocol of local anesthesia (LA) versus the more classical femoral nerve block (FNB) technique.

HYPOTHESIS

Fitness for discharge would be achieved earlier using the LA protocol.

MATERIALS

Ninety-eight consecutive TKA patients operated on by a single surgeon were included with no selection criteria. In the study group (49 patients), 200 mL ropivacaine 5% was injected into the surgical wound and an intra-articular catheter was fitted to provide continuous infusion of 20 mL/h ropivacaine for 24h. The control group (49 patients) received ropivacaine FNB. Discharge fitness (independent walking, knee flexion>90°, quadricipital control, pain on VAS≤3) and hospital stay were assessed.

RESULTS

Discharge fitness was achieved significantly earlier in the study group (4.2±2.6 versus 6.7±3.2 days; P=0.0003), with significantly shorter mean hospital stay (6.1±3.4 versus 8.8±3.5 days; P=0.0002). The complications rate did not differ between study and control groups.

DISCUSSION

Although retrospective, this study indicates that the LA protocol improves management of post-TKA pain and accelerates rehabilitation, thereby, reducing hospital stay. The acceleration effect may be due to the absence of quadriceps inhibition.

LEVEL OF EVIDENCE

Level III - Case control study.

Diagnostic accuracy of intra-articular C-reactive protein assay in periprosthetic knee joint infection--a preliminary study

BACKGROUND

Periprosthetic joint infection often raises diagnostic challenges, as the published criteria are heterogeneous. New markers for predicting periprosthetic infection have been evaluated. Here, we assessed one of these markers, C-reactive protein (CRP), in joint fluid.

HYPOTHESIS

We hypothesised that intra-articular CRP levels would perform better than serum CRP concentrations in diagnosing knee prosthesis infection.

PATIENTS AND METHODS

We prospectively included 30 patients including 10 with native-knee effusions, 11 with prosthetic-knee aseptic effusions, and 11 with prosthetic-knee infection defined using 2011 Musculoskeletal Society criteria. Serum CRP was assayed using turbidimetry or nephelometry and intra-articular CRP using nephelometry. Appropriate statistical tests were performed to compare the three groups; P values < 0.05 were considered significant.

RESULTS

Serum and intra-articular CRP levels were 5- to 16-fold higher in the group with periprosthetic infection than in the other two groups. Although the areas under the ROC curves were not significantly different, the likelihood ratios associated with the selected cut-offs suggested superiority of intra-articular CRP: a value > 2.78 mg/L suggested possible infection (100% sensitivity and 82% specificity) and a value > 5.37 mg/L probable infection (90% sensitivity and 91% specificity).

DISCUSSION

Our findings suggest a possible role for intra-articular CRP assay in diagnosing knee prosthesis infection and perhaps periprosthetic infection at any site.

LEVEL OF EVIDENCE

Level III, diagnostic study, development of a diagnostic criterion in consecutive patients comparatively to a reference standard.

Current concept in rotational laxity control and evaluation in ACL reconstruction

Rotation combined with translation; compose the three-dimensional motion of the knee subluxation in anterior cruciate ligament deficient knee. The worldwide scientists were focused initially on the translation part of this complex 3D motion, but since the beginning of the century there was a large interest on knee rotational laxity study. Lot of paper reported new devices and results with an explosion since the beginning of the decade. The purpose of this review is to provide an extensive critical analysis of the literature and clarify the knowledge on this topic. We will start with a dismemberment of different rotational laxities reported: the rotation coupled with translation in 2D tests such as Lachman test and anterior drawer test; the rotational envelope considering the maximum internal external rotation; and the "active rotation" occurring in 3D Pivot-shift (PS) test. Then we will analyze the knee kinematics and the role of different anterior cruciate ligament (ACL) bundle on rotation. A review of different mechanical and radiological devices used to assess the different rotations on ACL deficient knees will be presented. Two groups will be analyzed, dynamic and static conditions of tests. Navigation will be described precisely; it was the starter of this recent interest in rotation studies. Opto electronic and electromagnetic navigation systems will be presented and analyzed. We will conclude with the last generation of rotational laxity assessment devices, using accelerometers, which are very promising.

Validation of a French version of the Oxford knee questionnaire

INTRODUCTION

Self-administered quality-of-life questionnaires are a valuable evaluation tool in orthopedic surgery to determine patient satisfaction. The Oxford knee questionnaire has been validated for osteoarthritic patients. The aim of this study was to validate a French version of this English form. One hundred patients waiting for knee replacement were selected. The answers to the questionnaire were analysed and compared to the clinical and functional International Knee Society score (IKS).

HYPOTHESIS

There is negative correlation between the results of the Oxford knee questionnaire and the IKS score.

RESULTS

None of the patients had difficulty understanding the questions. The mean Oxford knee score was 43.7 (range 21-56, SD 6.9). The distribution was considered normal. There was no floor effect (0%); there was a limited ceiling effect (7%). The internal consistency of the questionnaire was excellent. There was a negative correlation between the Oxford knee score and the IKS knee score, functional score and global score.

DISCUSSION

Our results are very similar to the results from the normative English version of the knee questionnaire and to the results from translated questionnaires in other foreign languages. Our French adaptation of the Oxford knee questionnaire can be used to measure the global function of a patient before knee replacement as accurately as the original English version. It is self-administered, easy to use and patients can send their responses by post, which makes it a useful tool for the routine evaluation of patients before knee replacement.

Coronal plane knee laxity measurement: Is computer-assisted navigation useful?

INTRODUCTION

The goal of this observational study is to measure the physiological laxity of a knee, supposedly normal in the coronal plane, at 0 and 90° of flexion with a navigation system that can be used during total knee replacement.

HYPOTHESIS

The physiological laxity measured by this navigation system is different from the results already published using other measurement devices.

MATERIALS AND METHODS

Twenty patients consecutively operated on for an isolated anterior cruciate ligament injury were selected. Medial and lateral laxities at 0 and 90° of knee flexion were measured by the navigation system during cruciate replacement.

RESULTS

The mean medial laxity in extension was 3.6±1.2°. The mean lateral laxity in extension was 4.1±1.9°. The mean medial laxity at 90° of flexion was 2.1±1.2°. The mean lateral laxity at 90° of flexion was 3.7±1.2°. The medial and lateral laxities in extension were not asymmetric. The medial and lateral laxities at 90° of flexion were asymmetric. Medial laxities in extension and at 90° of flexion were asymmetric. Lateral laxities in extension and at 90° of flexion were not asymmetric.

DISCUSSION

The data collected in our study suggest, during total knee replacement, the following tolerable ligamentous balance: medial and lateral laxities in extension about 3°, medial laxity at 90° of flexion about 2°, and lateral laxity at 90° of flexion about 4°.

LEVEL OF EVIDENCE

Level IV. Prospective study.

[The history and development of computer assisted orthopaedic surgery]

Computer assisted orthopaedic surgery (CAOS) was developed to improve the accuracy of surgical procedures. It has improved dramatically over the last years, being transformed from an experimental, laboratory procedure into a routine procedure theoretically available to every orthopaedic surgeon. The first field of application of computer assistance was neurosurgery. After the application of computer guided spinal surgery, the navigation of total hip and knee joints became available. Currently, several applications for computer assisted surgery are available. At the beginning of navigation, a preoperative CT-scan or several fluoroscopic images were necessary. The imageless systems allow the surgeon to digitize patient anatomy at the beginning of surgery without any preoperative imaging. The future of CAOS remains unknown, but there is no doubt that its importance will grow in the next 10 years, and that this technology will probably modify the conventional practice of orthopaedic surgery.

[Knee septic arthritis]

The development of antibiotics and arthroscopic treatment have been two major turning points in the management of septic arthritis of the knee joint. We report a retrospective review of 78 patients managed in three surgery units and one rheumatology unit. Management practices varied between the units. Joint aspiration was proposed for all patients seen by rheumatologists. Certain surgeons proposed arthroscopy systematically at admission while others preferred a more selective approach. Arthroscopic wash-out was proposed as the first-line procedure for only 33 patients. All were given systemic antibiotics using a variety of protocols. The course under antibiotic treatment confirmed the potential gravity of septic arthritis of the knee joint since two patients died and 34 required surgery, half of which had more than one operation. The functional outcome at mean 19 months was rather poor. Only 65 knees were free of any implant and only 40 (62%) were pain free. Mean flexion was 116 degrees and 11 patients (17%) had significant flexion contracture. Factors of poor prognosis were initially high sedimentation rate, advanced stage according to Gächter, presence of specific germs (meti-R S. aureus, Gram-negative bacilli), and failure of first-line treatment. A management algorithm was proposed: initial aspiration for evacuation, medical treatment alone if there is no synovitis, and reduction synovectomy otherwise. The key to success is early well adapted treatment.

[Difficulties and reproducibility of radiological measurement of the proximal tibial axis according to Lévigne]

PURPOSE OF THE STUDY

The angle between the anatomic axis of the tibia and the tangent to the superior borders of the tibial plateaus is, on average, tilted 3 degrees in the varus position. If there is no bone wear, this angle measures the constitutional epiphyseal axis of the proximal tibia. When degenerative joint disease modifies the aspect of the tibial plateaus, this angle measures the sum of the constitutional varus and the bone wear, without distinguishing between the two. It is known however that the respective contribution of these two deformations can have therapeutic implications, particularly when tibial osteotomy for valgus correction or implantation of a unicompartmental prosthesis is proposed. Lévigne proposed a radiographic measurement of the proximal tibial axis to distinguish between these two sources of tibial deformation. We studied the intra- and interobserver reproducibility of these measurements.

MATERIAL AND METHODS

Fifty volunteers free of knee disease were chosen at random among a population of patients undergoing upper limb surgery. All patients provided their informed consent for participation in the study. Full-limb radiographs of one lower limb (chosen at random) were obtained using a standardized technique. The proximal tibial axis was measured according to the Lévigne technique using a manual goniometer graduated in degrees. One operator performed two series of measures independently on the same films. Two other operators performed a series of measurements on each film. The intra- and inter-observer reproducibility was determined with the interclass coefficient of correlation (rho).

RESULTS

The proximal epiphyseal axis of the tibia could not be determined on 7 to 18 films, depending on the operator. All three operators were able to make the all measurements (four per film) for only 25 patients. The mean epiphyseal axis varied from 2.5 degrees to 4.7 degrees for the four series of measurements. Intra-observer reproducibility was considered good (rho=0.62). Inter-observer reproducibility was considered moderate (rho=0.41).

DISCUSSION

The Lévigne technique is to our knowledge the only method described in the literature distinguishing the relative contribution of constitutional varus and bone wear of the proximal tibia. According to the advocates of this method, the angle between the epiphyseal axis linking the center of the tibial plateaus and the center of the proximal growth cartilage scare, and the anatomic axis of the tibia is a measurement of constitutional varus. The average is 3 degrees . The angle between a line perpendicular to the epiphyseal axis and the tangent of the superior borders of the tibial plateaus measures the deformation related to bone wear. In the present work, we found that this technique enables acceptable intra-observer reproducibility but that inter-observer reproducibility is low. The differences observed are certainly related to uncertain identification of the growth cartilage scar. This illustrates the difficulty in generalizing this technique for measuring healthy knees. Such difficulties would be even greater for degenerative knees.

CONCLUSION

The Lévigne technique does not appear to be a reliable method for defining indications for different surgical procedures according to the morphology of the proximal tibia.

[Total hip replacement prosthesis infected by Mycobacterium tuberculous]

We examined the diagnostic and therapeutic approaches used for two patients with loosened total hip prostheses who developed Mycobacterium tuberculosis infection. Revision total hip arthroplasty (THA) was performed in one patient. The prosthesis was left in situ in the second patient due to lack of sufficient bone stock. Medical treatment was given. The diagnosis was established on direct examination of bacteriological samples and culture on specific media. Polymerase chain reaction identified the Mycobacterium tuberculosis complex. Non-specific granulomas were observed on the histology sections. For us, management of overt tuberculosis involving a THA depends on the quality of the fixation. If the prosthesis remains stable, medical treatment can be sufficient. If the prosthesis loosens, definitive ablation must be considered with possible revision THA later. Exceptionally, a loosened implant may be left in situ if the remaining bone stock is insufficient. Minimal duration of anti-tuberulosis treatment is six months.

[In vitro analysis of the continuous active patellofemoral kinematics of the normal and prosthetic knee]

PURPOSE OF THE STUDY

In vitro experiments are particularly useful for studying kinematic changes from the normal knee to experimental conditions simulating different disease states. We developed an experimental protocol allowing a kinematic analysis of the femorotibial and femoropatellar joints in the healthy knee and after implantation of a knee prosthesis, according to the central pivot during simulated active loaded movement from the standing to sitting position.

EXPERIMENTAL SETUP

An experimental device was designed to apply force to the femur of a cadaveric specimen including the femur, the patella and the tibia. The tibia was angled in the sagittal plane and the femur was free to move in space in response to the geometric movement of the knee joint, the capsuloligamentary structures, the quadriceps tendon and gravity. Variation in the length of the quadriceps tendon controlled the flexion-extension movement. The experimental setup included computer-controlled activation allowing continuous coordinated movement of the femur relative to the tibia and of the tibia relative to the ground. Standard activations simulated movement from the standing to the sitting position.

STUDY PROTOCOL

Five pairs of fresh-frozen cadaver specimens including the entire femur, patella, tibia and fibula, the capsuloligamentary and intra-articular structures of the knee, the superior and inferior tibiofibular ligaments and the quadriceps tendon were studied. The quadriceps tendon was connected to the computer-guided activation device. Reflectors were fixed onto the anterior aspect of the femur, the superior tibial epiphysis and the center of the patella. Anatomic landmarks on the femur, the tibia, and the patella were identified to determine the plane of movement of each bone in the three rotation axes and the three translation directions. Three infrared cameras recorded movements of the reflectors fixed on the bony segments and, by mathematical transformation, the movement of the corresponding bony segment, displayed in time-course curves.

RESULTS

The patella moved in continuous fashion over the femur, directly following the angle of knee flexion with a ratio of about 60%, which was constant for all knees studied and for all configurations. The patella of healthy knees and knees implanted with a unicompartmental prosthesis exhibited medial rotation during the first 30 degrees of flexion, with a movement of about of 10 degrees, then a lateral rotation of about 10 degrees to 20 degrees when the flexion reached 90 degrees; implantation of a total knee prosthesis led to a medial rotation which was continuous from 5 degrees to 15 degrees. There was a trend towards continuous abduction of about 10 degrees. The patella exhibited a continuous anterior translation of 10 to 20 mm from the tibia with increasing knee flexion, in both normal and prosthetic knees (unicompartmental prosthesis); knees implanted with a total knee prosthesis exhibited 5 to 10 mm anterior translation from 0 degrees to 50 degrees flexion, then an equivalent posterior translation for 50 degrees to 90 degrees flexion. The patella made a continuous 5 to 10 mm medial translation movement over the tibia in both normal and prosthetic (unicompartmental) knees; knees implanted with a total knee prosthesis exhibited 0 to 5 mm lateral translation starting after 50 degrees flexion. The patella also exhibited a continuous distal translation over the tibia of about 20 to 30 mm, for all configurations.

DISCUSSION

The experimental set up enables a comparison of the kinetics of a normal knee with the kinetics observed after implantation of a prosthesis on the same knee. Implantation of a unicompartmental medial prosthesis, leaving the posterior cruciate ligament intact and irrespective of the status of the anterior cruciate ligament, did not, in these experimental conditions, exhibit any significant difference in the femorotibial or femoropatellar kinetics compared with the same normal knee. Implantation of a total knee prosthesis had a significant effect on the femoropatellar kinematics, compared with the same knee before implantation. The main anomalies were related to the medial-lateral rotation of the patella which exhibited an abnormal lateral rotation, possibly favorable for subluxation; these changes were directly related to femorotibial rotation after implantation of the total prosthesis and appeared to be related to the symmetry of the femoral condyles of the prosthesis model studied, perturbing the normal automatic rotation of the knee. There is thus a strong relationship between femorotibial and femoropatellar kinetics in the total knee prosthesis.

[Validation of an experimental protocol of an optoelectronic analysis of continuous active knee kinematics in vitro]

PURPOSE OF THE STUDY

In vitro experiments are particularly useful for studying kinematic changes in the normal knee exposed to experimental conditions simulating different disease states. We developed an experimental protocol allowing a kinematic analysis of the femorotibial and femoropatellar joints in healthy knees and after implantation of a knee prosthesis, using a central pivot to simulate active loaded movement from the standing to sitting position.

EXPERIMENTAL SETUP

An experimental device was designed to apply force to the femur of a cadaveric specimen including the femur, the patella and the tibia. The tibia was angled in the sagittal plane and the femur was free to move in space in response to the geometric movement of the knee joint, the capsuloligamentary structures, the quadriceps tendon and gravity. Variation in the length of the quadriceps tendon controlled the flexion-extension movement. The experimental setup included computer-controlled activation allowing continuous coordinated movement of the femur relative to the tibia and of the tibia relative to the ground. Standard activations simulated movement from the standing to the sitting position.

STUDY PROTOCOL

Five pairs of fresh-frozen cadaver specimens including the entire femur, patella, tibia and fibula, the capsuloligamentary and intra-articular structures of the knee, the superior and inferior tibiofibular ligaments and the quadriceps tendon were studied. The quadriceps tendon was connected to the computer-guided activation device. Reflectors were fixed onto the anterior aspect of the femur, the superior tibial epiphysis and the center of the patella. Anatomic landmarks on the femur, the tibia, and the patella were identified to determine the plane of movement of each bone in the three rotation axes and the three translation directions. Three infrared cameras recorded movements of the reflectors fixed on the bony segments and, by mathematical transformation, the movement of the corresponding bony segment, displayed in time-course curves.

RESULTS

The precision of the measurements, evaluated in a previous study, was +/- 1.5 degrees for rotation and +/- 0.5 mm for translation movements. Three acquisitions were made for each experiment and produced results differing less than one degree. A qualitative analysis of femorotibial and femoropatellar kinematics was achieved for the normal knee. The automatic internal rotation of the femur during flexion was observed and the patellar kinematics were defined with six degrees of freedom.

DISCUSSION

This experimental setup enables a comparison of the kinetics of a normal knee with the kinetics observed after implantation of a prosthesis on the same knee. The kinetic analysis does not involve a succession of static states but rather a continuous movement generated by the action of the quadriceps that can be loaded, simulating partial weight bearing. Using the markers fixed directly on the bones, this in vitro study allowed remarkably precise and reproducible measurements. The movements simulated regularly encountered clinical situations. The quality of the movement recorded for a given prosthesis thus provides an accurate approach to the quality of the prosthesis. The goal is not to define the exact kinematics of the normal knee but rather to compare the kinematics of the normal knee with that of the same knee after prosthesis implantation allowing an accurate method for assessing prosthesis design and studying the influence of different parameters, particularly the ligaments. Concomitant study of femorotibial and femoropatellar kinematics provides further information rarely found in the literature.

Computer-assisted implantation of total knee prostheses: a case-control comparative study with classical instrumentation

A navigation system should improve the quality of a total knee prosthesis implantation in comparison to that obtained with the classical, surgeon-controlled operative technique. The authors implanted 30 total knee prostheses with an infrared navigation system (Orthopilot, Aesculap, Tuttlingen, Germany). The quality of implantation was studied on postoperative long-leg coronal and lateral X-rays, and compared to a control group of 30 matched-paired total knee prostheses of the same type (Search prosthesis, Aesculap, Tuttlingen, Germany) implanted with a classical, surgeon-controlled technique. An optimal mechanical femorotibial angle (177 to 183 degrees) was obtained in 25 cases in the study group and 21 cases in the control group (p > 0.05). Similar differences were seen for the coronal and sagittal orientations of both tibial and femoral components. Globally, 23 cases in the study group and 8 cases in the control group were implanted in an optimal manner for all studied criteria (p < 0.001). The navigation system used allows a significant improvement in the quality of implantation of a total knee prosthesis in comparison to that obtained with a classical, surgeon-controlled instrumentation, and long-term outcome could consequently be improved.

[Computer-assisted implantation of a total knee arthroplasty: a case-controlled study in comparison with classical instrumentation]

PURPOSE OF THE STUDY

The quality of total knee arthroplasty (TKA) implantation is an essential factor determining long-term outcome. Computer-assisted implantation could improve quality compared with conventional manual instrumentation.

MATERIAL AND METHODS

We studied the radiographic quality of TKA implantation in 100 patients with primary degenerative knee disease who underwent a computer-assisted procedure guided by an informatic navigation system without imagery (group A) or a conventional manual procedure (group B). The two groups were matched for age, sex, initial frontal mechanical tibiofemoral angle and severity of the degenerative lesions. Postoperative telemetry was used in accordance with the Knee Society guidelines to measure the frontal mechanical tibiofemoral angle and the frontal and sagittal tilt of the tibial and femoral components. The number of optimal implantations for the five measured criteria was chosen as the main study criterion. The two groups were compared using the chi-squared test with statistical significance set at 5% and power at 80%.

RESULTS

Globally, implantation of the prosthesis was considered to be optimal in 33 patients in group A and in 15 in group B (p<0.001). Mean angles were not different between the two groups, except for sagittal tilt of the femoral piece. The frontal mechanical tibiofemoral angle was considered optimal in 47 patients in group A and in 39 in group B (p<0.05). A significant improvement in the quality of the implantation was also found in group A for frontal tilt of the femoral piece (p=0.05), frontal tilt of the tibial piece (p<0.05) and sagittal tilt of the tibial piece (p<0.001). No particular peroperative difficulty or complication was related to the navigation system.

DISCUSSION AND CONCLUSION

The navigation system allowed a significant improvement in the quality of implantation of TKA compared with conventional instrumentation controlled by the surgeon's hand and eye. Only minimal changes in the operative technique are necessary and standard preoperative investigations remain unchanged. Long-term survival of prostheses implanted with this system could thus be improved compared with manually implanted TKA. The system used here does not involve preoperative imaging and allows a precision to the order of 1 degree for angles and 1 mm for lengths.

No drainage does not increase complication risk after total knee prosthesis implantation: a prospective, comparative, randomized study

Sixty patients were operated on for primary gonarthrosis by means of a cemented, posterior cruciate preserving total knee and were randomly allocated to postoperative drainage or nondrainage. The primary criterion was duration of hospital stay. Secondary criteria included serial evaluation of knee pain, knee flexion, knee circumference, calculated blood loss after 7 days, complications, reoperations, and the need for blood transfusions. There was no difference between the two groups in any of the criteria during the entire follow-up. There was a nonsignificant trend to a decreased calculated blood loss in the nondrained group and significantly less transfused blood units in the nondrained group. Lack of drainage does not increase complication risk after total knee prosthesis implantation. We therefore recommend using no routine drainage after this procedure.

[Beta risk: an unrecognized risk of statistical error]

Data collected in a medical study should, from a methodological point of view, be considered as a sample taken from a larger population. The purpose of the statistical analysis is to check whether the differences in the experimental results observed in different subgroups are related to chance or not. The risks of error must be known to assess the validity of the conclusions. The first order risk, also called the alpha risk, is the risk of announcing a wrongly positive conclusion, that is to conclude that there is a significant difference that in reality does not exist. By convention, an alpha risk of 5 p. 100 is generally accepted. This means that it is acceptable to announce a statistically positive test when no difference exists in at most 5 p. 100 of the cases. After recording and processing the data, the statistical analysis produces a value called p that is the exact value of the first order risk in the given situation. If p is less than or equal to the alpha risk accepted before the study, it can be concluded that the observed difference is statistically significant at the chosen alpha level and that the p value represents the risk of first order risk in the given situation. If p is greater than the initially accepted alpha, the observed difference is not considered to be significant at the alpha level. But the assertion that two samples are equivalent, also involves a second order risk, also called the beta risk, that must be known. The beta risk is the risk of announcing wrongly negative results, that is to conclude that two samples are equivalent while in reality they are different. The number of elements in each sample necessary to demonstrate a difference becomes greater as the size of the difference becomes smaller. The beta risk increases as the alpha risk decreases, the number of cases becomes smaller, and the difference to detect becomes smaller. If a difference is not statistically significant at the chosen alpha level, the beta risk of an erroneous conclusion of equivalence is generally less than or equal to 20 p. 100. In most cases, the beta risk is not determined before the study but after, being calculated from the alpha risk, the sample size, and the non-significant difference observed. If the beta risk is found to be greater than 20 p. 100, no conclusion can be drawn and the study data are useless. It is therefore preferable to define both the alpha and beta risk and the smallest clinically pertinent difference, and to calculate the necessary sample size, before initiating the study. Let us take a numerical example where two different treatments, A and B, are given to two groups of 100 patients each. Treatment A produced success in 70 cases and treatment B in 80 cases. The chi-squared test yields a p value of 0.10. The observed difference is thus not statistically significant at an alpha level of 5 p. 100. In this case, the calculated beta risk is 54 p. 100. With 200 patients and a beta risk of 20 p. 100, a difference of 20 p. 100 in the success rates between the two groups cannot be detected. If it is accepted that a difference of 10 p. 100 between the success rates is clinically pertinent, to have an acceptable beta risk of 20 p. 100 and detect the difference, the study would have to include 500 patients instead of 200. In conclusion, when a comparative study concludes that there is no significant difference between two groups, one cannot deduct that these two groups are identical unless the beta risk is less than 20 p. 100. If the beta risk is greater than 20 p. 100, or if it is not mentioned, one cannot conclude that the two groups are equivalent.

[Navigated implantation of total knee endoprostheses--a comparative study with conventional instrumentation]

OBJECTIVE

A navigation system should improve the quality of a total knee prosthesis implantation in comparison to the classical, surgeon-controlled operative technique.

METHODS

The authors have implanted 40 knee total prostheses with an optical infrared navigation system (Orthopilot AESCULAP, Tuttlingen--group A). The quality of implantation was studied on postoperative long leg AP and lateral X-rays, and compared to a control group of 40 computer-paired total knee prostheses o the same model (Search Prosthesis, AESCULAP, Tuttlingen) implanted with a classical, surgeon-controlled technique (group B).

RESULTS

An optimal mechanical femorotibial angle (3 degrees valgus to 3 degrees varus) was obtained by 33 cases in group A and 31 cases in group B (p > 0.05). Better results were seen for the coronal and sagittal orientation of both tibial and femoral components in group A. Globally, 26 cases of the group A and 12 cases of the group B were implanted in an optimal manner for all studied criteria (p < 0.01).

CONCLUSIONS

The used navigation system allows a significant improvement of the quality of implantation of a knee total prosthesis in comparison to a classical, surgeon-controlled instrumentation. Long-term outcome could be consequently improved.

Type of screw does not influence holding power in the femoral head: a cadaver study with shearing test

We studied the holding power during cut-out tests of 4 different screw fixation devices of the femoral head, correlated to head size and bone density, on 48 paired deep frozen proximal femurs of fresh gross specimens. We found no significant effect of the device on the holding power. There was a significantly higher maximal load at failure in large and dense heads. It seems then unnecessary to advocate more sophisticated but also more expensive devices to fix femoral neck fractures.

[C-reactive protein and transthyretin in early diagnosis of infection after open fractures of the lower limbs (a preliminary study)]

PURPOSE OF THE STUDY

The authors investigated the value of C-reactive protein (CRP) and transthyretin (TTR) in the early diagnosis of infection after open fractures of the lower limb in an open, prospective study.

MATERIAL AND METHODS

Eighty patients were treated with acute debridement and bone fixation. Follow-up included clinical, radiological, bacteriological and biological assessment: white cell blood count (WBC), erythrocyte sedimentation rate (ESR), CRP and TTR. Diagnosis of infection was based on macroscopic presence of pus.

RESULTS

Post-operative reference biological profiles were defined in 74 cases without infection. Reference profiles of WBC and ESR showed unreliable interindividual variations and could not be considered for the diagnosis of infection. Reference profiles of CRP and TTR showed a respective increase (for CRP) and decrease (for TTR) in the early post-operative course, with return to normal values after 12 days. In 6 infected patients, CRP concentrations were suddenly increased and TTR concentrations decreased at the time (3 cases) or even before (3 cases) clinical diagnosis of infection. These variations were mostly simultaneous. No unusual profile was found. The ratio of CRP/TTR concentrations experienced also a sudden increase in infected cases.

DISCUSSION

Because of not specifical and unreliable variations in the post-operative outcome of non infected patients, WBC and ESR cannot be considered for the early diagnosis of infection. CRP and TTR concentrations with a respective cut-off value of 100 mg/L and 120 mg/L were found efficient for the early diagnosis of infection, and preceded clinical diagnosis in three of them. A CRP/TTR ratio over 60 p. 100, 8 days or more after initial surgery was found to be very specific (93 p. 100) and sensitive (100 p. 100) for the diagnosis of infection.

CONCLUSION

Serial quantifications of CRP and TTR should be performed every four days during the follow-up of open fractures in order to early diagnose a post-operative infection. Comparison of both CRP and TTR could allow a higher accuracy, because of the possible lack of variation of one the two markers.

Preservation of anterior cruciate ligament in total knee arthroplasty

Few prostheses allow preservation of the anterior cruciate ligament (ACL) during total knee replacement. We report a short-term, prospective, open study of 32 ACL-retaining and 93 ACL-replacing total knee replacements and compare the respective outcomes of both prosthesis types with a follow-up time of 2-3 years. Mean operative time, complication or revision rates did not differ, nor did the early and late clinical and radiological evaluations. This study does not support the suggestion that technical difficulties increase for ACL preservation. The clinical and functional results were neither improved nor worsened for ACL-retaining prostheses. There is thus no advantage, but also no inconvenience, in retaining the ACL according to short- to mid-term results of a gliding posterior cruciate ligament (PCL)-retaining prosthesis with ACL-replacement design. The possibility of an improved long-term outcome of an ACL-retaining prosthesis should be investigated further.

[Long-term survival rate of tibial osteotomies for valgus gonarthrosis]

PURPOSE OF THE STUDY

High tibial osteotomy (HTO) is a routine procedure for medial gonarthrosis. Mid-term results are known to be satisfactory, but they deteriorate with longer follow-up. The authors present a long term survival analysis of 109 out of 111 consecutive HTO with a minimal potential follow-up of ten years.

MATERIAL AND METHODS

111 patients were consecutively operated on for isolated primary varus gonarthrosis between 1977 and 1985: 57 men and 54 women, with a mean age of 53 years (range, 27 to 79 years). X-ray measurements were done on stance, hip-ankle view. Global axial deformation was defined as the angle between mechanical axes of femur and tibia. The respective part of congenital and degenerative tibial deformation was assessed according to Dejour. The angle between femoral and tibial bicondylar lines, representing lateral instability, was added to the tibial degenerative deformation to represent the total degenerative deformation. The goal of correction was a 3 to 7 degree mechanical valgus angulation. At the time of bone healing, 82 patients (74 per cent) had an optimal correction. Two patients were excluded from the follow-up study because of a severe complication (1 bacterial arthritis and 1 tibia non union) which could interfere with the long term result. The 109 remaining patients were followed for a minimal period of 1 year (mean: 8.4 years). GUEPAR pain grading and the occurrence of a revision were prospectively analyzed. 57 non reoperated patients could be re-examined at a mean maximal follow-up of 13.5 years (range, 10 to 18 years). Failure was defined as either the occurrence of a grade 2 or 3. GUEPAR pain during the whole follow-up, or a clinical or functional Knee Society score < 80 points at final follow-up, or revision. Failure and revision rates were calculated according to Kaplan and Meier.

RESULTS

11 patients were reoperated on before final examination (10 per cent): 2 medial unicondylar and 9 total knee prostheses. At final follow-up, the mean clinical and functional scores were respectively 87.0 points (range, 24 to 100 points) and 86.3 (range, 45 to 100 points). The cumulative failure rate was 33 per cent after 10 years and 54 per cent after 15 years; the respective revision rates were 9 per cent and 19 per cent. A pre-operative total degenerative deformation superior to 3 degrees led to a 3.5 fold increased failure rate (p < 0.000,1). A pre-operative medial joint space narrowing over the half of the normal, lateral one led to a 2.2 fold increased failure rate (p = 0.014). An optimal post-operative correction led to a 3.2 fold decreased failure rate (p = 0.000,1). For a given total degenerative deformation, patients with a congenital deformation superior to 5 degrees had a significant lower failure rate (p < 0.000,1). No factor significantly influenced the revision rate.

DISCUSSION

Ideal patients for HTO, with an expected survival rate of 100 per cent after 13 years, have moderate degenerative changes and a congenital deformation superior to 5 degrees. Patients with advanced degenerative changes and no congenital deformation experienced a 35 per cent failure rate after 10 years. In this population, unicondylar replacement should be considered as a valuable alternative.

[Proximal tibial meniscal slope: a comparison with the bone slope]

PURPOSE OF THE STUDY

X-ray measurements of the proximal tibial slope only study bony structures, without considering cartilage and meniscil thickness. It is well known that the posterior horn of the meniscil is thicker than the anterior one, and this could decrease the bony postero-distal slope. The aim of this study was to measure the meniscal slope, including cartilage and meniscil, and to compare it to the usual bony slope.

MATERIAL AND METHODS

19 knee cadaver specimens without meniscal or chondral lesions were studied. Four metallic clamps were inserted at the most anterior or posterior part of the medial or lateral meniscosynovial border. Lateral plain X-ray was taken for each knee. The bony proximal tibial slope and the medial and lateral meniscal slopes were measured and compared for each knee. Paired Wilcoxon T-test and correlations were calculated with a 5 per cent significant limit.

RESULTS

The mean paired difference between bony slope and medial or lateral meniscal slope was -6 degrees: the actual meniscal slope was less oblique than the bony slope, and it was almost perpendicular to the proximal tibial axis. There was a very significant correlation between bony and medial meniscal slopes. There was no correlation between bony and lateral meniscal slopes, nor between medial and lateral meniscal slopes.

DISCUSSION

These results suggest that the proximal tibial meniscal slope, which is the mechanically active one, is less oblique than the usually measured bony slope. Medial meniscal slope and bony slopes are very strongly correlated for one given knee. But medial and lateral meniscal slopes can be very different for one given knee.

CONCLUSION

These results could have an influence on the design of total or unicondylar knee replacements: the polyethylene slope of the tibial surface, which should reconstruct the natural articular design, should reproduce the meniscal, and not the bony slope. The medial and lateral slopes, should perhaps be individually reconstructed.

Incomplete or absent acute phase response in some postoperative patients

In a prospective study, 74 patients were admitted for an open fracture of the lower limb and treated by osteosynthesis. None of them presented infectious complication during the postoperative period. Among them, 67 exhibited a classical acute phase response. In 5 patients, the response was apparently incomplete since no serum C-reactive protein (CRP) rise was observed after the injury; i.e. CRP concentrations remained inferior to the detection limit of the assay used; in contrast, serum alpha-1 acid glycoprotein (AAG) concentrations were temporarily increased, a variation associated with a concomitant decrease of transthyretin (TTR) concentration. In 2 other patients, CRP and AAG levels were not significantly modified. The 7 patients did not suffer hepatic insufficiency or protein malnutrition. In our series, incomplete or absent acute phase response was not rare (prevalence 9%) and was not related to an increased risk of postoperative infection. In contrast to CRP, the TTR response, i.e. a transitory decrease, was observed in all the 7 patients.

Diagnostic value of C-reactive protein and transthyretin in bone infections of the lower limb

In a prospective study, white and red blood cell counts, hematocrit, erythrocyte sedimentation rate (ESR), albumin, alpha-1 acid glycoprotein, C-reactive protein (CRP), and transthyretin (TTR) values were determined by serial measurements during 23 days in 80 patients with an open fracture of the lower limb. Postoperative reference profiles were defined in 74 patients without septic complications. In the six remaining patients, serum CRP and TTR concentrations were found efficient for the early diagnosis of postoperative infections: a CRP/TTR mass concentration ratio higher than 0.6 from the 8th day after surgery was sensitive (100%) and specific (93%). Variations of CRP and TTR concentrations often preceded the clinical diagnosis in patients with early infection. ESR was found unreliable with regard to postoperative infection because of its high dependence with respect to red blood cell count.

Elevation of the tibial tubercle for patellofemoral pain syndrome. An 8- to 15-year follow-up

One hundred patients were operated on by the Maquet procedure for chondromalacia patellae. All of them were first re-examined after a mean follow-up of 4 years, and 65 of them re-examined after a mean follow-up of 11 years (range, 8-15 years). The pain score improved significantly after the operation and remained unchanged with longer follow-up. The success rate was only 62% at both follow-ups. Outerbridge grade IV chondral lesions at the time of surgery were associated with a significant improvement of the pain score at the 4-year follow-up and a success rate of 69%. The Maquet procedure should only be proposed for chronic retropatellar pain with grade IV chondral lesions, after conservative treatment has proven unsuccessful, as the expected failure rate is about 30%.

[Introduction to statistical methodology]

Statistical analysis does not absolutely need very large samples to draw a valuable conclusion. It is not only calculation, but above all reflexion about methodology, and calculation itself is only a small part of it. It is the way to get the best information from the available data.The basic question is the following: what is the probability of drawing a given number of white balls from a box with 50 white and 50 black balls ? In 95% of the cases, this number will be between 2 and 8: this is the confidence interval with a 5% error level, which is the common significance level. This interval will be closer if the number of balls drawn increases: that is why large numbers of subjects are interesting on the statistical point of view.On the contrary, if 4 white and 6 black balls are drawn from a 100 ball box, can the proportion of white balls in this box be estimated ? With a 5% error level, the proportion will be between 10 and 70%: this is the confidence interval with a 5% error level. As before, this interval will be closer if the number of balls drawn increases.The common question is the comparison of two or more results: it follows the same but repeated principle. From a first 1.000 ball box are drawn 40 white and 60 black balls; from a second 1.000 ball box 60 white and 40 black balls are drawn: are the proportion of white balls different in both boxes? The confidence interval with a 5% error level for the first box is between 30 and 50%; the confidence interval with a 5% error level for the second box is between 50 and 70%. As these intervals have a common value, it is impossible to simply conclude a difference in composition. Statistical tests (Chi2 test) allow detection of more subtle differences: in this example the Chi2 test compares the result of a mathematical calculation to a theoretical value: the difference is significant (with a 5% error level) if the calculated value is over the theoretical one, then it can be concluded that the proportion of white balls are different in both boxes. It is important to notice that the statistical tests not only study means or percentages, but the actual number for each studied subject: as before, the test will detect a more subtle difference if the number of subjects increases.There are two risks of error during statistical calculations. a is the risk of drawing a false-positive conclusion: it is always under 5%. b is the risk of not finding an actual difference: it is the false-negative risk. Both risks are related to the number of subjects studied and to the smallest difference by a mathematical calculation. On the contrary this calculation let us know how many subjects have to be studied with given a and b risks. It is important to understand that the results of a statistical test only give a relation, that is an association between two observed results, but not always a correlation, that is a consequence of the observed results. The correlation can only be studied if the studied groups are comparable.Statistical calculation is only one step of the whole statistical methodology, which involves seven steps: to ask the question precisely, to define the accepted error level and the nescessary number of subjects; to define the study design, and to obtain comparability between the different subgroups: this can be better done by randomisation, which allows separation of prognostic factors at random in all subgroups studied; to choose the criteria for results; to collect the data; to choose the appropriate statistical test: each test has precise conditions of application, which have to be respected; to apply the test and to perform the mathematical calculation; to draw the conclusion.These basic principles have to be respected for a confident statistical study: - the methodology is the most important point and shoud be perfect; - the study must be designed before starting; - the computer and software are only helpful but do not work alone; - the correlation can only be studied if the subgroups are comparable; - the comparability is better controlled by randomisation.

Infection after reamed intramedullary nailing of lower limb fractures. A review of 1,464 cases over 15 years

We studied 1,464 consecutive immediately-reamed intramedullary locked nailings of tibial or femoral fractures. There was an increase in postoperative infection if the tibial fracture was open; the relative risk increased with the severity of the soft tissue lesion. There was a marginal increase in the postoperative infection rate for open femoral fractures. A comparison of these figures with those in other methods of treatment and the mechanical and clinical advantages of nailing leads us to propose this method of treatment for Grades I and II open fractures of the femur or tibia.

A comparison of pre-operative evaluation of anterior knee laxity by dynamic X-rays and by the arthrometer KT 1000

The comparison of bilateral dynamic X-rays in passive anterior and posterior drawer with a load of 9 kg, and the arthrometer KT 1000 measurements obtained from 100 patients before anterior cruciate ligament reconstruction, confirms the good diagnostic efficiency of the following methods: (1) radiological measurement of the anterior translation of the medial compartment, as an absolute value and especially as a differential value in relation to the opposite, uninjured knee, the normal value limits being respectively 5 and 2 mm; and (2) arthrometric measurement of the maximal manual translation, also as absolute and differential values, the normal value limits being 10 and 2 mm respectively. These two measurements have a predictive value of 90%. No numerical equivalency exists between the radiological and arthrometric values, but their variations in relation to each other are statistically correlated. The arthrometer, simple to use and totally innocuous, is an excellent test device for consultation, while dynamic X-rays allow separate studies of each compartment to look for lesions of the posteromedial or posterolateral corners.

[Total prosthesis after ankylosis of the hip joint. Report of 22 cases]

Between 1968 and 1987 we carried out a total replacement arthroplasty on 22 hips which were either ankylosed or had previously undergone arthrodesis. The hips were revised because of pain due to pseudoarthrosis or malposition, pain in the other joints such as the lumbar spine, the ipsilateral knee or the contralateral hip, fractures about the hip, or professional disability. Significant functional and subjective improvement was obtained. The revised hips were painfree, stable and had an average range of flexion of 70 degrees. Pain in other joints was improved if their degenerative changes were moderate, but many required further procedures. Revision of a hip arthrodesis to a replacement arthroplasty is a worthwhile procedure in suitable cases.

[Intermediate results of the replacement of the anterior cruciate ligament with 3 types of dacron prostheses]

We have replaced the anterior cruciate ligament in 92 patients using Dacron prostheses. There were 52 Stryker implants, 25 Leeds-Keio and 15 Proflex. The majority of the patients were active sportsmen. A similar operative technique and postoperative programme was used in each patient. Seventy patients have been re-examined, and a further 9 answered a postal questionnaire. Forty Stryker ligament repairs have been followed up for an average of 28 months; 15 had broken or were otherwise inadequate. Ten patients had symptoms and there were 4 re-operations. Of the Leeds-Keio repairs 20 have been reviewed, of which 7 were either ruptured or mechanically inadequate. Three patients had symptoms and 1 had undergone further operation. Of 14 Proflex ligaments, 1 had failed, but the patient was asymptomatic. The authors consider that the Stryker and Leeds-Keio ligaments should not be used, and that the Proflex prosthesis shows promise but requires long term assessment.

[Phlebography of the femoral head following femoral neck fracture]

The incidence of avascular necrosis (AVN) of the head of the femur after transcervical fracture is 30-60%, depending on the diagnostic methods used. A poor outcome in AVN is not inevitable, since early diagnosis and treatment with prolonged non-weightbearing can produce satisfactory revascularisation without deformity. Nineteen patients with fractures of the femoral neck treated with internal fixation were assessed after operation by per-osseous phlebography. Weightbearing was allowed, irrespective of the state of union of the fracture, only if this test was positive. Of 13 patients who were allowed to bear weight after consolidation of the fracture, only one developed avascular necrosis. A further six patients were treated by non-weightbearing for up to eight months. Only one, in whom the fracture did not unite, developed avascular necrosis. The average time to union was 3.2 months, and the time to weightbearing was 4.1 months. This small difference, taking into account the low incidence of AVN (2 out of 19 or 10.5%, has led us to suggest a fresh approach to fractures of the femur neck in which the indications for immediate arthroplasty are restricted if the patient can tolerate prolonged non-weightbearing. Revascularisation may be assessed with phlebography and weightbearing allowed when this becomes positive. This approach should diminish the incidence of advanced AVN of the femoral head, and widen the indications for internal fixation.

[Management of combination injuries of the femur shaft and femoral neck fractures with a locking nail. Multicenter study of 26 cases from 4 trauma clinics]

Twenty-six patients with femoral shaft- and ipsilateral neck-fracture, treated in four different hospitals, have been analysed. The majority of these fractures was treated by a distally locked dynamic nail and fixation of the femoral neck by two or three lag-screws. In some cases a "contralateral" nail with a proximal locking screw in the femoral neck was used. Results are excellent without non-union or mal-union. Only one case of avascular necrosis occurred in an 68 years old patient. Interlocking intramedullary nailing certainly has its place in the treatment of associated femoral shaft- and neck-fractures. This closed method presents a stable fixation and permits early mobilisation and joint-function.

[Value of ceftriaxone (Rocephine) within the framework of preventive antibiotic therapy in digestive surgery]

The authors report their experience with prophylactic antibiotic therapy by Ceftriaxone in 30 cases of digestive surgery, the advantage of this new 3rd generation cephalosporin is that only one injection every 24 hours is quite efficient.