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.

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.

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.

The Anatomy of the Articularis Genus Muscle and Its Relation to the Extensor Apparatus of the Knee.

BACKGROUND: The anatomy of the articularis genus muscle has prompted speculation that it elevates the suprapatellar bursa during extension of the knee joint. However, its architectural parameters indicate that this muscle is not capable of generating enough force to fulfill this function. The purpose of the present study was to investigate the anatomy of the articularis genus, with special emphasis on its relationship with the adjacent vastus intermedius and vastus medialis muscles. METHODS: The articularis genus muscle was investigated in 18 human cadaveric lower limbs with use of macrodissection techniques. All components of the quadriceps muscle group were traced from origin to insertion, and their affiliations were determined. Six limbs were cut transversely in the middle third of the thigh. The modes of origin and insertion of the articularis genus, its nerve supply, and its connections with the vastus intermedius and vastus medialis were studied. RESULTS: The muscle bundles of the articularis genus were organized into 3 main layers: superficial, intermediate, and deep. The bundles of the superficial layer and, in 60% of the specimens, the bundles of the intermediate layer originated from both the vastus intermedius and the anterior and anterolateral surfaces of the femur. The bundles of the deep layer and, in 40% of the specimens, the bundles of the intermediate layer arose solely from the anterior surface of the femur. The distal insertion sites included different levels of the suprapatellar bursa and the joint capsule. A number of connections between the articularis genus and the vastus intermedius were found. While the vastus medialis inserted into the whole length of the vastus intermedius aponeurosis, it included muscle fibers of the articularis genus, building an intricate muscle system supplied by nerve branches of the same medial deep division of the femoral nerve. CONCLUSIONS: The articularis genus, vastus medialis, and vastus intermedius have a complex, interacting architecture, suggesting that the articularis genus most likely does not act as an independent muscle. With support of the vastus intermedius and vastus medialis, the articularis genus might be able to function as a retractor of the suprapatellar bursa. The finding of likely interplay between the articularis genus, vastus intermedius, and vastus medialis is supported by their concurrent innervation. CLINICAL RELEVANCE: The association between the articularis genus, vastus medialis, and vastus intermedius may be more complex than previously believed, and this close anatomical connection could have functional implications for knee surgery. Dysfunction, scarring, or postoperative arthrofibrosis of the sophisticated interactive mechanism needs further investigation.

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.

Potential Risk to the Superior Gluteal Nerve During the Anterior Approach to the Hip Joint: An Anatomical Study.

BACKGROUND: The anterior approach to the hip joint is widely used in pediatric and adult orthopaedic surgery, including hip arthroplasty. Atrophy of the tensor fasciae latae muscle has been observed in some cases, despite the use of this internervous approach. We evaluated the nerve supply to the tensor fasciae latae and its potential risk for injury during the anterior approach to the hip joint. METHODS: Cadaveric hemipelves (n = 19) from twelve human specimens were dissected. The course of the nerve branch to the tensor fasciae latae muscle, as it derives from the superior gluteal nerve, was studied in relation to the ascending branch of the lateral circumflex femoral artery where it enters the tensor fasciae latae. RESULTS: The nerve supply to the tensor fasciae latae occurs in its proximal half by divisions of the inferior branch of the superior gluteal nerve. The nerve branches were regularly coursing in the deep surface on the medial border of the tensor fasciae latae muscle. In seventeen of nineteen cases, one or two nerve branches entered the tensor fasciae latae within 10 mm proximal to the entry point of the ascending branch of the lateral circumflex femoral artery. CONCLUSIONS: Coagulation of the ascending branch of the lateral circumflex femoral artery and the placement of retractors during the anterior approach to the hip joint carry the potential risk for injury to the motor nerve branches supplying the tensor fasciae latae. CLINICAL RELEVANCE: During the anterior approach, the ligation or coagulation of the ascending branch of the lateral circumflex femoral artery should not be performed too close to the point where it enters the tensor fasciae latae. The nerve branches to the tensor fasciae latae could also be compromised by the extensive use of retractors, broaching of the femur during hip arthroplasty, or the inappropriate proximal extension of the anterior approach.

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.

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.

Physical activity patterns and function 3 months after arthroscopic partial meniscectomy.

OBJECTIVES: To compare physical activity levels, subject-reported function, and knee strength in 21 arthroscopic partial meniscectomy (APM) patients (age 45.7 (6.06) years, BMI 27.3 (5.96) female 60%) 3 months post-surgery with 21 healthy controls (age 43.6 (5.71) years, BMI 24.5(4.2) female 60%) matched at the cohort level for age, gender and BMI. DESIGN: Case control study. METHODS: Physical activity intensity, number of steps, and minutes spent in activity were objectively quantified using an accelerometer-based activity monitor worn for 7 days. The Knee Injury and Osteoarthritis Outcome Score (KOOS) and concentric quadriceps strength were used to evaluate function post-surgery. Differences in activity levels and functional outcomes between the APM and control participants were assessed using t-tests, while multiple linear regression was used to quantify the best predictors of physical activity. RESULTS: APM patients engaged in a similar duration of activity to controls (469.0 (128.39)min vs. 497.1 (109.9)min), and take a similar number of steps per day (9227 (2977) vs. 10,383 (3501), but performed their activity at lower levels of intensity than controls. Time spent in moderate (r(2)=0.19) and hard (r(2)=0.145) intensity physical activity was best predicted by the Symptoms sub-scale of the KOOS for both controls and APM patients. CONCLUSIONS: APM patients participate in similar levels of activity at lower intensities, but with reduced activity at higher intensities which is related to the presence of symptoms of knee osteoarthritis.

Sensitivity of knee soft-tissues to surgical technique in total knee arthroplasty.

Restricted range of motion and excessive laxity are both potential complications of total knee arthroplasty (TKA). During TKA surgery, the surgeon is frequently faced with the question of how tightly to implant the prosthesis. The most common method of altering implantation tightness is to vary the thickness of the polyethylene inlay after the bone cuts have been made and the trial components inserted. We have sought to quantify how altering the polyethylene thickness may affect post-operative soft tissue tension for a range of prosthetic designs. Four different prosthetic designs were implanted into fresh-frozen cadaveric knee joints. All four designs were implanted in the standard manner, with a 100 Newton distraction force used to set soft tissue balance. The tibiofemoral force was then recorded at 15° intervals throughout the passive flexion range. After the standard implantation of each prosthesis, the tibial component was raised or lowered to mimic increasing and decreasing the polyethylene thickness by 2mm and the force measurements repeated. Tibiofemoral force in extension correlated with implantation tightness for all prosthesis designs. Between 15° and 90° of knee flexion, all four designs were insensitive to changes in implantation tightness. Beyond 90° the effect was more notable in rotating platform mobile-bearing and cruciate-retaining prostheses than in posterior-stabilised mobile-bearing designs. The findings of this research may be useful in assisting surgical decision-making during the implantation of TKA prostheses.

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.

Assessment of isometricity before and after total knee arthroplasty: a cadaver study.

Total knee arthroplasty (TKA) relies on soft tissue to regulate joint stability after surgery. In practice, the exact balance of the gaps can be difficult to measure, and various methods including intra-operative spreaders or distraction devices have been proposed. While individual ligament strain patterns have been measured, no data exist on the isometricity of the soft tissue envelope as a whole. In this study, a novel device was developed and validated to compare isometricity in the entire soft tissue envelope for both the intact and TKA knee. A spring-loaded rod was inserted in six cadaver knee joints between the tibial shaft and the tibial plateau or tibial tray after removing a 7 mm slice of bone. The displacement of the rod during passive flexion represented variation in tissue tension around the joint. The rod position in the intact knee remained within 1 mm of its initial position between 15 degrees and 135 degrees of flexion, and within 2 mm (+/-1.2 mm) throughout the entire range of motion (0-150 degrees). After insertion of a mobile-bearing TKA, the rod was displaced a mean of 6 mm at 150 degrees (p<0.001). The results were validated using a force transducer implanted in the tibial baseplate of the TKA, which showed increased tibiofemoral force in the parts of the flexion range where the rod was most displaced. The force measurements were highly correlated with the displacement pattern of the spring-loaded rod (r=-0.338; p=0.006). A simple device has been validated to measure isometricity in the soft tissue envelope around the knee joint. Isometricity measurements may be used in the future to improve implantation techniques during TKA surgery.

Patella intraosseous blood flow disturbance during a medial or lateral arthrotomy in total knee arthroplasty: a laser Doppler flowmetry study.

Patella complications are recognized sequelae of total knee arthroplasty (TKA). Disruption of blood flow to the patella and adjacent soft tissues during surgery may contribute to reduced viability of the bone and patella ligament tissue. The effect on genicular blood flow to the medial and lateral patella was compared for a medial (MA) and lateral arthrotomy (LA) during TKA. Laser Doppler flowmetry was used to measure both baseline and postarthrotomy flow in vivo for 16 primary TKA patients. Flow in the lateral patella was reduced approximately 20% for both MA and LA. Conversely, the use of MA resulted in substantial reduction in flow to the medial patella (53%) compared to the lateral approach (27%). A large standard deviation of scores was evident in all cases. Although there was a tendency for LA to disturb the patellar blood flow less, the difference was not significant. It was concluded that neither approach is superior regarding the blood flow preservation to the patella. Hence, a lateral approach might only have an advantage in knee joints that are likely to need a lateral release in combination with an MA-e.g., a valgus deformity or preoperative patella maltracking.

Massive wear of an incompatible metal-on-metal articulation in total hip arthroplasty.

We report on a case of massive wear because of an incompatible metal-on-metal combination. In a 62-year-old man, a cobalt-chromium (CoCr) inlay and a stainless steel head were paired by accident. Because of persistent pain, revision surgery was performed 7 months later. Histologic analysis of the surrounding tissue revealed massive metallosis. The wear volume was increased by a factor of 18 for the head and 2 for the cup compared with normal metal-on-metal articulation. The serum concentrations of chromium and cobalt were increased by a factor of 20 and 4 over levels of a healthy population, respectively. Incompatible metal-on-metal combinations should be revised immediately. In case of delayed diagnosis, no metal-on-metal articulation should be implanted because of the high volume of metal in the human body.