Kneeling difficulty is common following anterior cruciate ligament reconstruction with hamstring autograft and correlates with outcome measures.

INTRODUCTION: Patients frequently have discomfort or difficulty with kneeling following anterior cruciate ligament reconstruction (ACLR). This study aimed to report the prevalence of, and reasons for, kneeling difficulty after ACLR with a hamstring autograft; and to investigate the association between the degree of kneeling difficulty, presence of concurrent meniscal surgery, and clinical outcomes, including patient-reported outcome measures (PROMs) and functional tests. MATERIALS AND METHODS: A total of 104 patients undergoing ACLR with ipsilateral hamstring autograft were enrolled. Participants completed a kneeling difficulty questionnaire and other PROMs including the International Knee Documentation Committee (IKDC) questionnaire, the Knee Injury and Osteoarthritis Outcome Score (KOOS), the Cincinnati Knee Rating System (CKRS), the Lysholm Knee Scoring Scale (LKS), the Tegner Activity Scale (TAS), the 36-Item Short Form Health Survey (SF-36), and the Knee Outcome Survey (KOS). Patients were also assessed objectively via peak isokinetic knee extensor and flexor strength, range of movement (ROM), and functional hop tests. RESULTS: The prevalence of kneeling difficulty on the operated knee was 77% and 54% at 1 and 2 years after ACLR, respectively. Strong associations were observed between kneeling difficulty and PROMs, ranging from CKRS at 1 year of r = 0.403 (95% CI 0.228-0.553, p < 0.001) to KOS at 2 years of r = 0.724 (95% CI 0.618, 0.804, p < 0.001). No associations were observed with age, body mass index, or knee ROM measures. Weak-to-moderate associations were demonstrated with functional hop tests. The degree of kneeling difficulty did not differ with concurrent meniscal surgery. CONCLUSIONS: Kneeling difficulty occurs in as much as 77% of patients following ACLR with hamstring grafts at 1 year, and 54% at 2 years. This has a moderate-to-very strong association with patient-reported assessment of knee pain, symptoms, sport and recreation, and knee-related quality of life. There appears to be no association with patient age, BMI, time from injury to surgery, knee ROM, or concurrent meniscal surgery. LEVEL OF EVIDENCE: IV.

The kneeling test is a valid method of assessing kneeling tolerance.

PURPOSE: No quantitative test exists to reliably assess kneeling tolerance before and after surgery. The aim of this study was to validate a kneeling test, designed to quantify kneeling tolerance. METHOD: A total of 179 participants (324 knees) were enrolled into the study, including 124 asymptomatic knees, 98 with osteoarthritis (OA), 85 following total knee arthroplasty (TKA) and 17 following anterior cruciate ligament reconstruction (ACLR). Patients were asked to kneel on a custom-built platform on a soft, firm and hard surface, at both 90° and 110° of knee flexion. A kneeling score of 0-100 was established for 90° and 110° with 100 being a complete absence of pain or discomfort. A linear mixed model with random intercept was used to estimate differences between conditions (healthy, OA, ACLR and TKA). Pearson's correlation coefficient was used to test the strength of the association between the kneeling test and the forgotten joint score (FJS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score. Test-retest reliability was estimated by the intraclass correlation coefficient (ICC). RESULTS: The kneeling test demonstrated good discriminative validity with differences at 110° between asymptomatic knees and knees with OA (difference = - 42, p < 0.001), following ACLR (- 12, p = 0.013) and TKA (- 26, p < 0.001). Similar differences were observed at 90°. The kneeling test demonstrated construct validity, with a moderately strong correlation observed between the kneeling test and the FJS and the WOMAC at 90° (FJS 0.474 [95%CI: 0.357, 0.577], WOMAC - 0.503 [- 0.389, - 0.602]) and 110° (FJS 0.579 [95% CI: 0.479, 0.665], WOMAC - 0.648 [- 0.560, - 0.722]). The ICC for the kneeling test at 90° and 110° was 0.843 (95% CI: 0.745, 0.905) and 0.926 (95% CI: 0.877, 0.956), respectively. CONCLUSIONS: The kneeling test is a valid technique to quantitatively determine kneeling tolerance. It can aid in the assessment and modification of current surgical techniques to improve patient outcomes. LEVEL OF EVIDENCE: III.

Can Prophylactic Cables Stop Crack Propagation in Revision Arthroplasty: A Biomechanical Study.

BACKGROUND: Intraoperative femur fractures are a common complication of revision hip arthroplasty. This study examined the use of a prophylactic cable in stopping a crack from propagating beyond the cable. METHODS: Seventy sheep femora were prepared. A 5-mm vertical incision was performed. Using a force-controlled materials testing machine, a Wagner shaft was advanced until a crack occurred. Cracks were visualized with green ink. In the first part, the control group without any cable (n = 10) was compared with polyethylene (n = 15) and single CoCr cable (n = 15) groups. The cables were positioned 15 mm distal to the osteotomy. In the second part, three different CoCr configurations were compared, single-wrapped (n = 15), double-wrapped (n = 125), and two separate cables at 10 and 15 mm distal to the osteotomy (n = 15). RESULTS: The polyethylene cable stopped only 3 of 15 cracks (20%), whereas the CoCr cable stopped 11 of 15 cracks (73%) (P = .009). The force needed to initiate the crack between the different groups was not significant. Twelve (80%) of 15 cracks were stopped at the level of the cable with two separate CoCr cables and 15 (100%) of 15 cracks with a double-wrapped cable (P = .11). CONCLUSION: This study demonstrated that an elastic cable is not suitable for preventive cabling. The force required to form a crack is not improved with the use of a prophylactic cable placed 10-15 mm below the osteotomy. While the results on the different configurations were not conclusive, the double-wrapped cable was able to stop all cracks from progressing distally.

Normative Values for the Forgotten Joint Score-12 for the US General Population.

BACKGROUND: The Forgotten Joint Score-12 (FJS-12) is a patient-reported outcome questionnaire of joint awareness in patients with hip and knee pathologies. To improve interpretability of values derived from this measure, we collected normative values for the US general population. METHODS: A sample of 2000 participants, representative of US general population, was sought via an online panel. Quota sampling was used to obtain age-specific and sex-specific groups of 200 participants each. The FJS-12 is a 12-item questionnaire assessing the ability to forget the hip or knee joint during activities of daily living. To match US national census data from 2010, raking was used for determining data weights. RESULTS: Normative data for the FJS-12 could be established based on a data set from 2017 respondents (50.1% men; mean age, 54.0 years; 66.3% white/Caucasian). Median FJS-12 scores in the total sample were 75.0 points for knees and 87.5 points for hips. In the age-specific and sex-specific groups, the lowest median score for knees was 54.2 points (men aged 18-39 years) and the highest median was 97.0 (men aged above 70 years). Similarly, median scores for hips were lowest in men aged 18-39 years (60.9 points) and highest in men aged above 70 years (100 points). CONCLUSION: Normative values have been established for the FJS-12 for hips and knees in US general population. Age-specific and sex-specific differences require relying on normative values from the respective groups when interpreting FJS-12 data.

The interaction between the vastus medialis and vastus intermedius and its influence on the extensor apparatus of the knee joint.

PURPOSE: Although the vastus medialis (VM) is closely associated with the vastus intermedius (VI), there is a lack of data regarding their functional relationship. The purpose of this study was to investigate the anatomical interaction between the VM and VI with regard to their origins, insertions, innervation and function within the extensor apparatus of the knee joint. METHODS: Eighteen human cadaveric lower limbs were investigated using macro-dissection techniques. Six limbs were cut transversely in the middle third of the thigh. The mode of origin, insertion and nerve supply of the extensor apparatus of the knee joint were studied. The architecture of the VM and VI was examined in detail, as was their anatomical interaction and connective tissue linkage to the adjacent anatomical structures. RESULTS: The VM originated medially from a broad hammock-like structure. The attachment site of the VM always spanned over a long distance between: (1) patella, (2) rectus femoris tendon and (3) aponeurosis of the VI, with the insertion into the VI being the largest. VM units were inserted twice-once on the anterior and once on the posterior side of the VI. The VI consists of a complex multi-layered structure. The layers of the medial VI aponeurosis fused with the aponeuroses of the tensor vastus intermedius and vastus lateralis. Together, they form the two-layered intermediate layer of the quadriceps tendon. The VM and medial parts of the VI were innervated by the same medial division of the femoral nerve. CONCLUSION: The VM consists of multiple muscle units inserting into the entire VI. Together, they build a potential functional muscular complex. Therefore, the VM acts as an indirect extensor of the knee joint regulating and adjusting the length of the extensor apparatus throughout the entire range of motion. It is of clinical importance that, besides the VM, substantial parts of the VI directly contribute to the medial pull on the patella and help to maintain medial tracking of the patella during knee extension. The interaction between the VM and VI, with responsibility for the extension of the knee joint and influence on the patellofemoral function, leads readily to an understanding of common clinical problems found at the knee joint as it attempts to meet contradictory demands for both mobility and stability. Surgery or trauma in the anteromedial aspect of the quadriceps muscle group might alter a delicate interplay between the VM and VI. This would affect the extensor apparatus as a whole.

Joint Mechanics After Total Knee Arthroplasty While Descending Stairs.

BACKGROUND: Modern knee designs do not fully restore the anatomy and kinematics of the natural knee. This study evaluates the kinematic and kinetic changes of well-functioning patients with total knee arthroplasty (TKA) in comparison to a healthy age-matched control group while descending stairs and level walking. The aim was to have a baseline for further investigations of TKA patients with problems. METHODS: Fifteen patients satisfied with TKA (8♀/7♂; 66.8 ± 7.4 years; body mass index (BMI) 25.9 ± 2.8 kg/m2; 2.1 ± 1.3 years postop, LCS Complete) and 17 healthy control subjects (7♀/10♂; 66.6 ± 6.8 years; BMI 25.0 ± 2.2 kg/m2) participated in the study. Kinematic (upper and lower body) and kinetic (lower body) data were collected during stair descending (step height 17 cm) and level walking, using an 8-camera Vicon system and 2 force plates. Parameters were compared using a Student t test. RESULTS: Patients after TKA showed significantly lower frontal knee moments and a more externally rotated hip during stance for both level walking and stair descent. There were 31% more significantly different parameters during level walking than during stair descent. CONCLUSION: The analysis of stair descending in addition to level walking for satisfied patients does not add additional information for the understanding of the kinematic and kinetic changes after TKA. It seems more important to include the kinematics and kinetics of the hip and ankle joint in all 3-dimensional planes.

Magnetic resonance imaging of the tensor vastus intermedius: A topographic study based on anatomical dissections.

The tensor of the vastus intermedius (TVI) is a newly described component of the extensor apparatus of the knee joint. The objective of this study was to evaluate the appearance of the TVI on magnetic resonance (MR) imaging and its association with the adjacent vastus lateralis (VL) and vastus intermedius (VI) muscles and to compare these findings with the corresponding anatomy. MR images were analyzed from a cadaveric thigh where the TVI, as part of the extensor apparatus of the knee joint, had been dissected. The course of the TVI in relation to the adjacent VL and VI was studied. The anatomic dissection and MR imaging revealed a multilayered organization of the lateral extensor apparatus of the knee joint. The TVI is an intervening muscle between the VL and VI that combined into a broad flat aponeurosis in the midthigh and merged into the quadriceps tendon. Dorsally, the muscle fibers of the TVI joined those of the VL and VI and blended into the attachment at the lateral lip of the linea aspera. In this area, distinguishing between these three muscles was not possible macroscopically or virtually by MR imaging. In the dorsal aspect, the onion-like muscle layers of the VL, TVI, and VI fuse to a hardly separable muscle mass indicating that these muscles work in conjunction to produce knee extension torque when knee joint action is performed. Clin. Anat. 30:1096-1102, 2017. © 2017 Wiley Periodicals, Inc.

Plate Positioning in Periprosthetic or Interprosthetic Femur Fractures With Stable Implants-A Biomechanical Study.

BACKGROUND: Angular stable plate fixation is a widely accepted treatment option for interprosthetic or periprosthetic femoral fractures with stable implants. This biomechanical study tries to establish a safe distance of the plate from the tip of a femoral prosthesis. METHODS: A total of 38 composite femurs were reamed to an inner diameter of 23 mm to create an osteoporotic bone model. A Weber hip stem was cemented into each and a distal femoral NCB plate applied with the distance to the stem varying from 8 cm apart to 6 cm overlap in 2-cm steps. Each specimen was tested in cyclic axial loading (400 N-1500 N) and then cyclic torsion (0.6 Nm-50 Nm). Peak strain on the femur around the tip of the plate was measured with a 3D image correlation system and averaged over 26 cycles (excluding the first 3 and the last cycles). Finally, each femur was axially loaded to failure. RESULTS: Strain increased with decreasing overlap or gap. Seven specimens failed early between 2-cm overlap and 2-cm gap. Results were divided into a far group with a distance of >4 cm and a close group of <4 cm. Strain was significantly higher in the close group for axial (P < .001) and torsional (P < .001) loading. Failure load was significantly lower in the close group (P = .002). CONCLUSION: A minimal gap and/or overlap of at least 6 cm is recommended in osteoporotic bone to avoid stress risers.

Comparison of preoperative continuation and discontinuation of aspirin in patients undergoing total hip or knee arthroplasty.

INTRODUCTION: Preoperative discontinuation of aspirin (acetylsalicylic acid) can reduce bleeding risk but may increase the risk of perioperative cardiovascular events. MATERIALS AND METHODS: We retrospectively assessed the impact of preoperative continuation versus discontinuation of aspirin compared with a control group in a cohort of 739 consecutive patients undergoing total hip (THA) (n = 396) or knee arthroplasty (TKA) (n = 343) at a tertiary hospital. Bleeding risk, local complications, orthopaedic outcome, and cardiac and cerebral complications were assessed. RESULTS: Four hundred and sixty-five patients did not receive antithrombotic or full-dose anticoagulant medication, 175 patients were taking low-dose aspirin, 99 vitamin K antagonists, clopidogrel, or a combination of these drugs. Of the patients taking aspirin, 139 discontinued and 36 continued aspirin. Blood loss and local bleeding complications were comparable in these two groups. TKA patients who continued aspirin more frequently showed marked knee swelling after 1 week than those discontinuing aspirin (35.1 vs. 81.3 %; p = 0.001). However, orthopaedic outcome did not differ significantly between the two groups. There was a trend towards an increased risk of cardiac complications in patients who discontinued aspirin (6.5 vs. 0.0 %; p = 0.107). CONCLUSIONS: Continuation or discontinuation of aspirin did not show a statistically significant difference in the risk of relevant perioperative bleeding complications in our study. Continuation of aspirin was associated with a transitory increase in knee swelling, but had no effect on orthopaedic outcome. Continuation of aspirin may be associated with a favourable perioperative cardiac outcome. Our data support perioperative continuation of aspirin intake in patients undergoing THA or TKA.

Limitations of the Vastus Lateralis Muscle as a Substitute for Lost Abductor Muscle Function: An Anatomical Study.

Abductor insufficiency after hip arthroplasty resulting from an impaired gluteus medius and minimus remains an unsolved problem in orthopaedic surgery. The vastus lateralis (VL) was described as a functional substitute for abductor insufficiency in 2004. We carried out a macrodissection of twelve cadaveric hemipelvises to investigate the innervation of the VL and adjacent muscles to assess the extent the VL can be safely transferred. Results showed that direct muscle branches to proximal portions of the VL are too short to allow a significant shift; the shift may be as small as 13 mm. Nerves that supply the VL also extend to the vastus intermedius. This innervation pattern makes it impossible to shift the VL significantly without damaging branches to both.

Polyaxial locking and compression screws improve construct stiffness of acetabular cup fixation: a biomechanical study.

Bone ingrowth into uncemented acetabular components requires intimate cup-bone contact and rigid fixation, which can be difficult to achieve in revision hip arthroplasty. This study compares polyaxial compression locking screws with non-locked and cancellous screw constructs for acetabular cup fixation. An acetabular cup modified with screw holes to provide both compression and angular stability was implanted into a bone substitute. Coronal lever out, axial torsion and push-out tests were performed with an Instron testing machine, measuring load versus displacement. Polyaxial locking compression screws significantly improved construct stiffness compared with non-locked or cancellous screws. This increased construct stiffness will likely reduce interfacial micromotion. Further research is required to determine whether this will improve bone ingrowth in vivo and reduce cup failure.

Can plate osteosynthesis of periprosthethic femoral fractures cause cement mantle failure around a stable hip stem? A biomechanical analysis.

Periprosthetic femoral fractures (PFF) are a serious complication after total hip arthroplasty. Plate fixation with screws perforating the cement mantle is a common treatment option. The study objective was to investigate hip stem stability and cement mantle integrity under dynamic loading. A cemented hip stem was implanted in 17 composite femur models. Nine bone models were osteotomised just distal to the stem and fixed with a polyaxial locking plate the other eight constructs served as the control group. All specimens were tested in a bi-axial material testing machine (100000 cycles). There were no statistically significant differences in axial nor in medial (varus) stem migration. No cement cracks were detected in both groups. Plate fixation of a PFF with a stable, cemented prosthesis did not lead to cement mantle failure in this in vitro study.

Association of psychological status and patient-reported physical outcome measures in joint arthroplasty: a lack of divergent validity.

BACKGROUND: Patient-reported outcome measures have become a well-recognised part of outcome assessment in orthopaedic surgery. These questionnaires claim to measure joint-specific dimensions like pain, function in activities of daily living, joint awareness or stiffness. Interference of the patient's psychological status with these orthopaedic questionnaires however may make accurate interpretation difficult. METHODS: We recruited 356 patients after unilateral, primary THA or TKA and performed a postal survey including the Brief Symptom Inventory (psychological distress measure), the Catastrophising Scale (from the Coping Strategies Questionnaire), the WOMAC score (Western Ontario and McMaster Universities Osteoarthritis Index) and the Forgotten Joint Score--12 (FJS-12). Associations between the different questionnaires were determined calculating Pearson correlation coefficients. Two multiple linear regression models were used to investigate the impact of socio-demographic variables, clinical variables and of the psychological scales (BSI and Catastrophising Scale) separately for the WOMAC score and the FJS-12. RESULTS: WOMAC-Total score showed strong correlation to Catastrophising (r = 0.79), BSI-Somatisation (r = 0.63) and BSI-GSI (r = 0.54). The FJS-12 demonstrated modest to strong correlation with Catastrophising (r = -0.60), BSI-Somatisation (r = -0.49) and the BSI-GSI (Global Severity Index) (r = -0.44). BSI-GSI and Catastrophising explained 54.3% of variance in a multivariate regression model for the WOMAC score. The same two scales explained 30.0% of variance for the FJS-12. CONCLUSIONS: There is a strong relationship between psychological status and orthopaedic outcome. The scale names of orthopaedic outcome measures suggest to measure specific dimensions like pain, stiffness, function or joint awareness. In fact they largely include patient's psychological status indicating poor divergent validity.

Development of a computer-adaptive version of the forgotten joint score.

Patient-reported outcomes (PROs) are an important endpoint in orthopedics providing comprehensive information about patients' perspectives on treatment outcome. Computer-adaptive test (CAT) measures are an advanced method for assessing PROs using item sets that are tailored to the individual patient. This provides increased measurement precision and reduces the number of items. We developed a CAT version of the Forgotten Joint Score (FJS), a measure of joint awareness in everyday life. CAT development was based on FJS data from 580 patients after THA or TKA (808 assessments). The CAT version reduced the number of items by half at comparable measurement precision. In a feasibility study we administered the newly developed CAT measure on tablet PCs and found that patients actually preferred electronic questionnaires over paper-pencil questionnaires.

Does Far Cortical Locking Improve Fracture Healing in Distal Femur Fractures: A Randomised, Controlled, Prospective Multicentre Study.

(1) Background: Bone healing is influenced by various mechanical factors, such as stability, interfragmentary motion, strain rate, and direction of loading. Far cortical locking (FCL) is a novel screw design that promotes bone healing through controlled fracture motion. (2) Methods: This study compared the outcome of distal femur fractures treated with FCL or SL (standard locking) screws and an NCB plate in a randomised controlled prospective multicentre trial. The radiographic union scale (RUST) and healing time was used to quantify bone healing on follow-up imaging. (3) Results: The study included 21 patients with distal femur fractures, 7 treated with SL and 14 treated with FCL screws. The mean working length for patients with SL screws was 6.1, whereas for FCL screws, it was 3.9. The mean RUST score at 6 months post fracture was 8.0 for patients with SL plates and 7.3 for patients with FCL plates (p value > 0.05). The mean healing time was 6.5 months for patients with SL plates and 9.9 months for patients with FCL plates (p value < 0.05). (4) Conclusions: Fractures fixed with SL plates had longer working lengths and faster healing times when compared to FCL constructs, suggesting that an adequate working length is important for fracture healing regardless of screw choice.

Kneeling tolerance following intramedullary nailing or plate fixation of uncomplicated distal tibia fractures.

INTRODUCTION: Distal tibia fractures often occur in younger, high demand patients, though the literature surrounding management remains contentious. This study sought to quantitatively determine differences in kneeling ability and self-reported knee function in patients managed with either intramedullary nailing (IMN) or open reduction internal fixation (ORIF) with compression plating following distal tibia fracture to assist in the preoperative consent process. HYPOTHESIS: There is no difference in kneeling tolerance following either tibial nailing or plate fixation of distal tibia fractures. MATERIAL AND METHODS: Retrospective sampling of public hospital data with outpatient prospective functional testing were completed. The primary outcome measure was the Kneeling Test (KT). Secondary outcome measures were The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and the Forgotten Joint Score (FJS) for the knee joint. There were 28 patients recruited (18 IMN and 10 ORIF) with a mean age of 44years. Mean overall follow-up was 13.3months (range 8-25, SD 3.6). All fractures had completely healed without postoperative complication. RESULTS: The IMN affected limb had a significantly worse overall kneeling function than their non-affected limb (mean KT: 70.4 vs. 94.9 respectively, p<0.005) Additionally, the IMN group performed significantly worse when compared to the ORIF group (mean KT 70.4 vs. 92.5 respectively, p<0.005). No significant differences (p>0.05) in kneeling function existed for the ORIF group when comparing affected to non-affected limbs. Secondary outcome analysis showed significantly worse overall WOMAC and FJS in the IMN group compared to the ORIF group (mean WOMAC 19.3 vs. 6.9 respectively, p=0.040; mean FJS 38.3 vs. 75.9 respectively, p=0.005). DISCUSSION: The use of intramedullary nailing for the treatment of distal tibia fracture results in a mean reduction of 20% in kneeling tolerance in comparison to ORIF. The resulting kneeling tolerance is comparable to that of patients post-total knee arthroplasty. The present findings should assist in the consent process for patients with high kneeling demands in sportive, professional or cultural pastimes. LEVEL OF EVIDENCE: IV; retrospective cohort study with quantitative outcome measurement.

Augmentative Plating versus Exchange Intramedullary Nailing for the Treatment of Aseptic Non-Unions of the Femoral Shaft-A Biomechanical Study in a SawboneTM Model.

BACKGROUND: Non-unions after intramedullary nailing of femoral shaft fractures are a significant problem. Treatment options such as augmenting with plates or exchange nailing have been proposed. The ideal treatment remains controversial. METHODS: Augmentative plating using a 4.5 mm LCP or a 3.2 mm LCP leaving the nail in situ was tested biomechanically and compared to exchange intramedullary nailing in a SawboneTM model of a femoral shaft non-union. RESULTS: The difference of fracture gap motion in axial testing was small. In rotational testing, the exchange nail allowed for the largest amount of motion. The 4.5 mm augmentative plate was the most stable construct in all loading conditions. CONCLUSIONS: Augmentative plating using a 4.5 mm LCP plate while leaving the nail in situ is biomechanically superior to exchange intramedullary nailing. A small fragment 3.2 mm LCP is undersized and does not reduce fracture motion sufficiently in a femoral shaft non-union.

The "forgotten joint" as the ultimate goal in joint arthroplasty: validation of a new patient-reported outcome measure.

With improving patient outcome after joint arthroplasty, new assessment tools with increased discriminatory power especially in well-performing patients are desirable. The goal of the present study was to develop and validate a new score ("Forgotten Joint Score," or FJS) introducing a new aspect of patient-reported outcome: the patient's ability to forget the artificial joint in everyday life. After a pilot study, the FJS was validated and showed high internal consistency (Cronbach α = .95). Ceiling effects were considerably lower for the FJS (9.2%) compared with the Western Ontario and McMaster Universities subscales (16.7%-46.7%). Known-group comparisons proved the FJS to be highly discriminative in a validation sample of 243 patients. The FJS not only reflects differences between "good" and "bad" but also between "good," "very good," and "excellent" outcomes. This concise score is appealing for its more adequate measurement range and because it measures the new, promising concept of the "forgotten joint."

Recurrent hemarthrosis after total knee arthroplasty.

This report describes a case of spontaneous recurrent hemarthrosis of the knee that presented 4 weeks after total knee arthroplasty. Femoral arteriography showed a false aneurysm of a branch of the inferior lateral geniculate artery. Therapeutic embolization of the arterial branch was performed using three platinum coils with good clinical result and good knee joint function. Hemarthrosis has not recurred since embolization.

The treatment of periprosthetic fractures with locking plates: effect of drill and screw type on cement mantles: a biomechanical analysis.

INTRODUCTION: Periprosthetic fractures after cemented hip replacement are a challenging problem to manage. Biomechanical studies have suggested the benefit of using locking screws for plate fixation, but there are concerns whether screws damage the cement mantle and promote crack propagation leading to construct failure. METHOD: In this biomechanical study, different screw types were implanted into the cement mantle after pre-drilling holes of different sizes, in unicortical and bicortical configuration. The presence of cracks and the pull-out resistance of these screws were then evaluated. RESULTS: No unicortical screw induced cracks. Screws with a shortened tip, smaller flutes and double threads were significantly better for pull-out resistance. Bicortical screws were associated with a risk of local cement mantle damage, but also with a significantly greater holding power. By increasing the drill diameter, the onset of cracks decreased, but so does the pull-out resistance.