Validity of the intelligent device for energy expenditure and activity accelerometry system for quantitative gait analysis in patients with hip osteoarthritis.

OBJECTIVE: To evaluate the concurrent validity of an accelerometry-based system (Intelligent Device for Energy Expenditure and Activity) with a criterion instrument (Gaitrite) for the evaluation of spatiotemporal gait variables in orthopedic patients. DESIGN: Validity study. SETTING: Research laboratory in an orthopedic hospital. PARTICIPANTS: Men with unilateral hip osteoarthritis (N=26; mean age ± SD, 54±9y). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Patients were asked to walk at normal and fast velocities while gait cycle, swing, double support, step length, cadence, and speed were concomitantly recorded with the 2 instruments. Concurrent criterion-related validity was examined using intraclass correlation coefficients and Bland-Altman limits of agreement. RESULTS: Intraclass correlation coefficients were acceptable for all gait parameters (range, .815-.997), except step length (.783). Limits of agreement were low for gait cycle, swing, and cadence, though relatively high for double support, step length, and speed. A significant bias between the 2 measuring instruments was consistently observed. CONCLUSIONS: In patients with hip osteoarthritis, quantitative gait analysis with the IDEEA accelerometry system was satisfactory for the main temporal gait parameters, while double support, step length, and walking speed quantifications were invalid. The IDEEA system should be used with caution, and modifications of the system are recommended for improved use in clinical practice and research.

The Oxford II medial unicompartmental knee arthroplasty: an independent 10-year survival study.

Unicompartmental knee arthroplasty (UKA) is being used increasingly. We report the outcome of a series of 48 Oxford II meniscal bearing UKAs carried out for osteoarthritis of the medial compartment (38 knees in 32 patients) and for spontaneous avascular necrosis of the medial femoral condyle (10 knees in 10 patients). Using the endpoint of revision for any cause, the outcome for every knee was established. Ten knees have been revised (20.8%). At ten years there were 215 knees still at risk and the cumulative survival rate was 77.7% (95% CI: 56.8 to 90.2). Our study reveals a higher failure rate than previous reports on this prosthesis. The technique of implantation of the Oxford knee is demanding; the learning curve is thus long and could explain, at least partially, our moderate results.

High revision rate at 5 years after hip resurfacing with the Durom implant.

BACKGROUND/RATIONALE: There is growing evidence that different resurfacing implants are associated with variable survival and revision rates. A registry analysis indicated the Durom resurfacing implant had high revision rates at 5 years, whereas three original studies reported low revision rates at short-term followups. Thus, the revision rates appear controversial. QUESTIONS/PURPOSES: We therefore assessed (1) the survivorship including differences between women and men at a mean of 5 years after resurfacing with the Durom implant, and (2) clinical scores and radiographic parameters. PATIENTS AND METHODS: We prospectively followed all 100 Durom hip resurfacings implanted in 91 patients (25 women and 66 men; mean age, 52 years) between 2003 and 2004. Survivorship analysis was performed with pending revision or revision for any reason as the endpoint. The minimum followup was 47 months (mean, 60 months; range, 47-72 months). RESULTS: At a mean of 5 years, 11 hips were revised for various reasons. Cumulative survival was 88.2% for all patients and 81.5% for women. The mean Oxford (OHS) and Harris hip (HHS) scores were 14.6 and 94.7, respectively. The mean UCLA activity level was 7.9. Sclerotic changes around the short femoral stem (pedestal sign) were detected in 40% of the hips. We observed considerable femoral neck thinning with component-to-neck ratios of 0.85 preoperatively and 0.82 at 5 years. CONCLUSIONS: Our study highlights a high revision rate 5 years after hip resurfacing with the Durom implant. This observation underlines previous findings from registry data and suggests that revision rates increase with time. LEVEL OF EVIDENCE: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Asymmetry in quadriceps rate of force development as a functional outcome measure in TKA.

Quadriceps muscle strength is an important predictor of functional abilities in patients having TKA. However, because several daily activities are characterized by a limited time to generate force, it has been suggested that rate of force development (RFD) could better predict functional difficulties than maximal strength. We therefore hypothesized the side-to-side asymmetry would be larger for RFD than for maximal strength, and RFD asymmetry relates to subjective symptoms and/or functional daily living activities. We studied 31 subjects (17 women, 14 men) 6 +/- 1 months after undergoing TKA for unilateral osteoarthritis. Symptoms and limitations during activities of daily living were quantified using the knee outcome survey-activities of daily living scale (KOS-ADLS). Quadriceps maximal strength and RFD at different times (50 to 200 ms from contraction onset) were quantified during unilateral maximal voluntary isometric actions. Side-to-side asymmetries (involved versus uninvolved side) were larger for RFD (approximately 36%) than for maximal strength (approximately 24%). Subjective knee function related to all RFD asymmetry variables, but not to maximal strength asymmetry. In addition to maximal strength, quadriceps RFD in the first 100 to 200 ms from contraction onset provides an alternative functional outcome measure for individuals undergoing TKA.

Neuromuscular function after arthroscopic partial meniscectomy.

BACKGROUND: Quadriceps muscle strength, which is essential for the function and stability of the knee, has been found to be impaired even years after arthroscopic partial meniscectomy. However, the neuromuscular alterations that could account for such muscle weakness remain unclear. QUESTIONS/PURPOSES: We investigated (1) the side-to-side asymmetries in quadriceps muscle strength 6 months after arthroscopic partial meniscectomy, (2) the physiologic mechanisms (neural versus muscular) underlying muscle weakness, and (3) the impact of quadriceps weakness on muscle control at submaximal force levels. PATIENTS AND METHODS: We tested 14 volunteers (10 men, four women) with an average age of 44 +/- 9 years (range, 24-59 years) at 6 +/- 1 months after unilateral medial arthroscopic partial meniscectomy. We measured maximal voluntary strength and muscle activation during isometric, concentric, and eccentric contractions using isokinetic dynamometry and surface EMG, respectively. We assessed vastus lateralis muscle size and architecture using ultrasonography. We measured muscle control at submaximal force levels with a repositioning test (knee proprioception) and a low-force target-tracking task (steadiness, accuracy). RESULTS: Isometric and concentric quadriceps strength and vastus lateralis EMG activity were lower on the involved than on the uninvolved side. Muscle architecture and muscle control did not differ between the involved and uninvolved sides. CONCLUSIONS: Our results showed quadriceps weakness exists 6 months after arthroscopic partial meniscectomy. As suggested by the EMG results, this is likely attributable to neural impairments (activation failure) that affect muscle control at maximal but not submaximal force outputs. LEVEL OF EVIDENCE: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Five-year results of the Innex total knee arthroplasty system.

The clinical and radiographic results of 174 female and 86 male Innex (Zimmer, Warsaw, Indiana) mobile bearing total knee arthroplasty systems (245 patients) were evaluated, with particular emphasis on gender-related differences at five-year follow-up. Pre-operative Knee Society (KS) function and total scores were lower in women than in men. All KS scores showed a significant improvement at follow-up, but women still obtained lower KS function scores than men. Self-reported function was significantly better for male knees. No gender differences were observed for component alignment, while the occurrence of radiolucent lines, endosteal cavitations, and wear was significantly greater in male knees. Male Innex mobile bearing knees exhibited better clinical function and satisfaction than their female peers at five-year follow-up, despite inferior radiographic findings and higher revision rates.

Does hip resurfacing require larger acetabular cups than conventional THA?

UNLABELLED: Hip resurfacing is femoral bone preserving, but there is controversy regarding the amount of bone removed at the acetabular side. We therefore compared the implanted acetabular cup sizes in primary THAs between two resurfacing devices and a conventional press-fit cup using a series of 2134 THAs (Allofit cup 1643 hips, Durom Hip Resurfacing 249 hips, and Birmingham Hip Resurfacing 242 hips). The effects of patient demographics and cup position in the horizontal plane also were assessed. After controlling for gender, patients were matched for height, weight, body mass index, and age. The mean size for Allofit cups was smaller than the sizes for Durom and Birmingham Hip Resurfacing cups in women (49.9 mm, 51.6 mm, 52.3 mm, respectively) and men (55.1 mm, 56.7 mm, 57.8 mm; respectively). Although patient height was associated with the implanted cup size, the cup position in the horizontal plane had no effect on the size used. Larger cups were used with hip resurfacing than for THA with a conventional press-fit cup. However, additional studies are needed to determine whether these small differences have any clinical implications in the long term. The association of cup size and patient height should be considered in future studies comparing component sizes among different implants. LEVEL OF EVIDENCE: Level III, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Outcome of hip resurfacing arthroplasty in patients with developmental hip dysplasia.

UNLABELLED: Patients with osteoarthritis secondary to developmental dysplasia of the hip (DDH) typically are young and active, which might affect functional ratings or failure rates after resurfacing arthroplasty. We therefore evaluated 24 patients (32 hips; mean age, 44.2 years) after hip resurfacing performed for osteoarthritis secondary to DDH. We used the Harris hip score (HHS), the University of California, Los Angeles (UCLA) activity scale, and a sports and activity questionnaire. A radiographic analysis also was performed. We followed patients a minimum of 28 months (mean, 43 months; range 28-60 months). The HHS improved from a mean of 54.7 to 97.3 and UCLA activity levels increased from a mean of 5.3 to 8.6. All patients returned to sports activity at a mean of 11 weeks after surface replacement. There were no major differences in preoperative and postoperative participation in the most common sports and activities. Two of the 32 replacements (6%) failed. We detected femoral radiolucencies in 10 of the remaining 30 hips. Despite satisfactory outcomes in clinical scores, return to sports, and hip biomechanics, the failure rate of 6% was disappointing. Additional followup is important to assess if failure rates increase in these young, active patients. LEVEL OF EVIDENCE: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Association of body mass index and clinical outcome 2 years after unicompartmental knee arthroplasty.

INTRODUCTION: Unicompartmental knee arthroplasty (UKA) has gained in popularity during the last years. However, the body mass index (BMI) of patients undergoing UKA is controversially discussed in the literature. There is, moreover, a paucity of information available concerning the association of BMI with early clinical outcomes after UKA. MATERIALS AND METHODS: We retrospectively reviewed the clinical data of 83 consecutive UKA, 2 years after surgery, and investigated the potential association of BMI and the outcome variables Knee Society Score (KSS), University of California at Los Angeles (UCLA) activity levels, anterior knee pain (AKP), range of motion, and implant failure. RESULTS: The KSS and UCLA significantly increased from 132 and 4.7 preoperatively to 187.5 and 7.1, respectively, after surgery. Knee flexion significantly improved from 123.7 to 128.4 degrees and the prevalence of extension deficiencies significantly decreased from 28.9 to 15.7%. Three knees (3.6%) failed and were converted to total knee arthroplasty. Failures were not associated with increased BMI (P = 0.387). The BMI had no significant association with KSS values, UCLA levels, and implant failure. We found a weak negative correlation between BMI and postoperative knee flexion (r = -0.285, P = 0.009) and a moderate positive correlation between BMI and the intensity of AKP (r = 0.525, P < 0.001). CONCLUSION: The results of the present study suggest that the BMI of patients undergoing UKA has no major impact on the early clinical outcome 2 years after surgery. There was, however, a definite correlation between the BMI and AKP. Longer follow-up is necessary to determine if overweight and obesity may increase revision rates after UKA.

Patellar height before and after unicompartmental knee arthroplasty: association with early clinical outcome?

INTRODUCTION: There is paucity of information available concerning the role of patellar height in unicompartmental knee arthroplasty (UKA). The present study was conducted to determine the patellar height before and after UKA and to assess possible effects on the early clinical outcome. MATERIALS AND METHODS: We measured the patellar height before and after UKA in 83 consecutive knees using the Blackburne-Peel (BP) index and Insall-Salvati (IS) ratio and investigated the impact of the patellar height on the clinical outcome 2 years after surgery. RESULTS: BP values significantly decreased from 0.81 before surgery to 0.76 postoperatively (P < 0.001). IS ratios did not significantly decrease from 1.02 to 1.01 (P = 0.108). Lower preoperative BP values were negatively correlated with the postoperative knee extension (r = -0.357, P = 0.026), while higher preoperative BP values were negatively associated with the postoperative Knee Society Score (r = -0.302, P = 0.046). Lower preoperative IS values were negatively correlated with postoperative Knee Scores (r = -0.394, P = 0.019). CONCLUSION: After UKA, the patellar height decreased significantly according to the BP index, but not significantly according to the IS ratio. We found only weak and inconsistent correlations between the patellar height and clinical outcome parameters. Hence, based on the present results, the patellar height seems not to be a strict separate patient-selection criterion for UKA.

Bleeding complications after systematic switch of routine thromboprophylaxis for major orthopaedic surgery.

The rate of bleeding complications after major orthopedic surgery approximates 2%. It is unclear whether a systematic switch of routine thromboprophylaxis has an impact on the rate of postoperative bleeding complications. We analyzed prospectively recorded postoperative bleeding complications and symptomatic venous thromboembolic events in 8,176 consecutive orthopedic patients at the Schulthess Clinic Zurich during a systematic switch of thromboprophylaxis from nadroparin to enoxaparin in the year 2004. Overall, 3,893 patients received nadroparin in the first nine-month observation period before the switch and 4,283 patients received enoxaparin in the second nine-month observation period after the switch. Overall, 96 (2.5%) patients in the first period and 70 (1.6%) patients in the second period suffered a postoperative bleeding complication requiring surgical revision, puncture, or transfusion (p < 0.01). Five objectively confirmed symptomatic venous thromboembolic events during hospitalization in the first period and three events in the second period were recorded. In conclusion, the switch of thromboprophylaxis in a large orthopedic clinic did not cause an increase of postoperative bleeding complications and therefore was accompanied by high patient safety.

Reconstruction of severe uncontained bone defects in revision total knee arthroplasty in a patient with rheumatoid arthritis.

We report on a 54-year-old rheumatoid arthritic female patient with uncontained type-III tibial and femoral bone defects at the time of revision total knee arthroplasty (TKA). The knee was reconstructed using a structural distal femoral allograft and a stemmed, semi-constrained knee prosthesis. We achieved the re-alignment of a severe preoperative valgus deformity of 40 degrees. Due to postoperative wound complications we had to perform a gastrocnemius muscle flap. At two-year follow-up the patient was free of pain and the Knee Society Score improved from 18 to 156 (p < 0.01). Radiographs revealed no loosening of the prosthetic components and progressive incorporation of the graft. Reconstruction of extensive uncontained bone defects in revision of TKA in rheumatoid arthritis can be managed by structural allografts; however, wound complications in those patients might necessitate soft tissue techniques.

[Closing-wedge high tibial osteotomy with a modified Weber technique]. / Modifizierte zuklappende tibiale Valgisationsosteotomie nach Weber.

OBJECTIVE: Deceleration of the progression of medial gonarthritis via transfer of the mechanical load axis from the medial to the lateral femorotibial compartment and by reduction of compressive stresses in the medial compartment. INDICATIONS: Isolated early-stage unicompartmental medial gonarthritis. Symptomatic varus deformity. Adjustment of the mechanical load axis in reconstructive surgery such as autologous chondrocyte transplantation. Correction of posttraumatic varus deformities. CONTRAINDICATIONS: Concomitant patellofemoral arthritis, lateral femorotibial arthritis, or other painful conditions of the knee. Limited range of motion. Knee instabilities, since a rapid development of a tricompartmental gonarthritis is likely to occur. Advanced osteoporosis. Poor peripheral circulation with an absent foot pulse. Lateral meniscectomy. SURGICAL TECHNIQUE: Lateral approach. Subcapital osteotomy of the fibula. Preparation of the lateral tibial head. Partial osteotomy of the proximal one third of the tibial tuberosity. Marking of the joint line. A semitubular plate is placed over a guide wire parallel to the joint line, 1.5 cm distal to it, and is gently hammered into the tibial head with just the last hole seen outside. The lateral end of the plate is bent downward. Ascending osteotomy of the tibial head in an inferolateral to craniomedial direction. The osteotomy starts 2.5 cm distal to the plate and ends directly below the guide wire. The medial cortex remains intact. Excision of a lateral-based bone wedge according to the preoperative planning. The osteotomy is gently closed under valgus stress. A 4.5-mm cortical screw is aimed through the lateral hole of the plate into the distal fragment of the tibia and tightened until the osteotomy is brought under compression. POSTOPERATIVE MANAGEMENT: During hospitalization, there is a periodic treatment with continuous passive motion without any limitation of range of motion and isometric training is taken up. Mobilization is permitted with partial load of 15 kg with two crutches during 6 weeks postoperatively. Ambulatory physical training with active and passive motion exercises. After 6 weeks, the load can be increased stepwise depending on the consolidation as seen on the control radiographs. Full weight bearing is generally reached after 10 weeks. During this time, thromboembolism prophylaxis with low-molecular-weight heparin is necessary. RESULTS: A retrospective analysis of the own patients treated with the described surgical technique was performed. On the basis of Kaplan-Meier survival analysis, it could be demonstrated that there is a correlation between the patients' level of activity and the long-term survival rate 10-15 years after the osteotomy. Moreover, the extent of correction has a direct influence on the long-term result.

Sports after hip resurfacing arthroplasty.

BACKGROUND: No information is available concerning patients' sports activity after hip resurfacing arthroplasty. HYPOTHESIS: Patients treated by hip resurfacing arthroplasty will be able to achieve a high level of sports activity. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: We surveyed 112 patients by postal questionnaire to determine their sporting activities at a mean of 23.5 (range, 9-40) months after hip resurfacing surgery. Data were also analyzed separately for older and younger patients and women and men, respectively. RESULTS: Of 112 patients, 110 participated in an average of 4.6 sport disciplines after surgery, compared with 105 patients pre-operatively engaged in an average of 4.8 disciplines. About 26% performed sports 4 times per week or more--almost 60% for longer than 60 min at each session. A high proportion of our patients were still engaged in downhill skiing (51%) and in high-impact disciplines such as tennis (12%) or contact sports (22%). More than 50% of the patients commenced sports within the first 3 months after surgery. During activities, 70% were completely pain-free. The group of older patients (mean age, 60.2 years) participated in more different disciplines with a higher weekly frequency and longer session length than younger patients (mean age, 46.4 years). CONCLUSION: The present study reports for the first time on the detailed sports activity and activity extent after hip resurfacing arthroplasty. Our patients could return to a high level of sports participation after surgery. Age-related differences were found that have not yet been published. Nevertheless, further follow-up is necessary to assess the influence of high-level activity on loosening and revision rates after hip resurfacing arthroplasty.

Reliability of knee extension and flexion measurements using the Con-Trex isokinetic dynamometer.

The aim of this study was to evaluate the reliability of isokinetic and isometric assessments of the knee extensor and the flexor muscle function using the Con-Trex isokinetic dynamometer. Thirty healthy subjects (15 males, 15 females) were tested and retested 7 days later for maximal strength (isokinetic peak torque, work, power and angle of peak torque as well as isometric maximal voluntary contraction torque and rate of torque development) and fatigue (per cent loss and linear slope of torque and work across a series of 20 contractions). For both the knee extensor and the flexor muscle groups, all strength data - except angle of peak torque - demonstrated moderate-to-high reliability, with intraclass correlation coefficients (ICC) higher than 0.86. The highest reliability was observed for concentric peak torque of the knee extensor muscles (ICC = 0.99). Test-retest reliability of fatigue variables was moderate for the knee extensor (ICC range 0.84-0.89) and insufficient-to-moderate for the knee flexor muscles (ICC range 0.78-0.81). The more reliable index of muscle fatigue was the linear slope of the decline in work output. These findings establish the reliability of isokinetic and isometric measurements using the Con-Trex machine.

A multi-joint lower-limb tracking-trajectory test for the assessment of motor coordination.

This study aimed to determine whether a lower-limb trajectory-tracking task performed on a leg press machine, that is commonly adopted in both rehabilitation and resistance training settings, could yield reliable assessment of motor coordination in able-bodied individuals. Twenty-two female subjects allocated to two experimental groups were tested and retested after 48-72 h. Group A was fully familiarized with the experimental procedures before each test while group B received only verbal instructions. The unilateral coordination test consisted of target tracking during a simulated half squat including eccentric and concentric actions. In both groups, tracking error showed significant test-retest reliability with ICC values of 0.77-0.80 (p < 0.05). Significant group (A < B) and time (day 2 < day 1) main effects were found for tracking error, while there was no significant influence of action mode and dominance. Tracking error significantly decreased in the group A ( approximately 15%) but not in the group B on retest. Action mode (eccentric versus concentric), side dominance and familiarization on day 1 had no effect on tracking error. However, movement control significantly improved at day 2, thus confirming the occurrence of short-term motor learning and the sensitivity of the present trajectory-tracking test. For the first time, a simple test for the assessment of motor coordination during multi-joint closed-kinetic chain action of lower limb muscles has been proposed. Its uniqueness is represented by the specificity for rehabilitation and resistance training settings. Further studies with larger sample groups (e.g., male subjects and patients) and including neurophysiological measurements are needed.

Lesion of gluteal nerves and muscles in total hip arthroplasty through 3 surgical approaches. An electromyographically controlled study.

PURPOSE: Three surgical approaches in total hip arthroplasty (THA) were compared concerning: 1) clinical and radiological results; 2) innervation of the tensor fasciae latae and gluteal muscles; 3) clinical outcome of the nerve lesions; 4) sensitivity of the EMG analysis. METHODS: A total of 70 patients aged 39-79 years were evaluated clinically and electromyographically before and 3-9 months after THA in 2 centres using the anterolateral approach in 22, transgluteal approach in 33 and posterior approach in 15 patients, respectively. RESULTS: 1) Hip flexion, external rotation and Trendelenburg lurch were reduced and the centre of the rotation was higher after the anterolateral approach. 2) The inferior branch of the superior gluteal nerve of the tensor fasciae latae muscle was mostly damaged in the anterolateral approach (73% of lesions), whereas innervations of gluteus medius (9% of lesions) and maximus muscles (no lesion) were preserved. The transgluteal approach most often caused a partially denervated gluteus medius (81.8%) and the tensor fasciae latae (48%) and the gluteus maximus muscle only in 29%, respectively. After the posterior approach, partial denervation in the gluteus medius and maximus muscles were noted in 53.3% and 71.4%, respectively, whereas in the tensor fasciae latae muscle in only 14%. 3) The power of the abductors was not significantly reduced in partially denervated muscles. 4) The EMG examination is not sensitive enough to determine the relevant power of hip abductors. CONCLUSIONS: Despite some disadvantages associated with the anterolateral approach, the transgluteal and posterior approaches are often connected with a partial lesion of the gluteus medius and maximus muscles. In all approaches, clinical sequelae are not significant in primary THA.

A titanium plasma-sprayed cup with and without hydroxyapatite-coating: a randomised radiostereometric study of stability and osseointegration.

We present a prospective, two-centre radiostereometric analysis (RSA) regarding the stability of a flattened pole titanium press-fit cup (EP-FIT PLUS), and whether additional hydroxyapatite coating leads to faster bone ingrowth into the porous coating. Forty-two postmenopausal female patients (44 hips) undergoing total hip arthroplasty for primary osteoarthritis, selected to avoid hormonal factors influencing bone metabolism, were randomised to receive this cup with a titanium-plasma-sprayed surface with or without an additional hydroxyapatite coating. RSA was used to measure cup translation and rotation along three cardinal axes with respect to the host bone at the following time points: immediately postoperatively, at 6 weeks, and at 3, 6, 12, and 24 months. The most pronounced translation was proximal (0.11 mm) and posterior tilt (-0.27°). No difference in translation and rotation could be detected between the two groups. With the exception of one cup with an isolated radiolucent line <2 mm in zone 1, all cups showed complete osseointegration on conventional radiographs. The flattened pole cup provided excellent early stability and no advantage could be detected with additional hydroxyapatite coating.

Prospective study of gait function before and 2 years after total knee arthroplasty.

PURPOSE: To perform a prospective evaluation of gait before and 2 years after total knee arthroplasty (TKA) and examine the influence of comorbidity and other joint problems on gait characteristics and their improvement after TKA. METHODS: One hundred and eleven patients scheduled for TKA took part (34 men, 65 ± 10 y; 77 women, age 68 ± 9 y). Gait velocity, cadence, and ground reaction force parameters were measured before and 2 years after surgery. Patients completed a questionnaire to rate their pain and other joint problems. Comorbidity was measured with the American Society of Anaesthesiologists (ASA) score. RESULTS: Two years after TKA there were significant improvements (each p<0.05) in gait velocity and cadence and most of the ground reaction parameters, though forces during loading/unloading remained lower for the operated leg than for the contralateral leg. Higher comorbidity and other painful joints of the lower extremities/spine had a consistent, negative influence (p<0.05) on the absolute values achieved for the gait parameters although their improvement compared with baseline was independent of these factors. CONCLUSIONS: Comorbidity and other joint problems negatively influenced gait performance. These confounders should be taken into account when setting realistic patient expectations and when interpreting the success of TKA in the individual patient. Improvement in gait is however still possible, within the bounds of concomitant comorbidity.

A seven-zone rating system for assessing bone mineral density after hip resurfacing using implants with metaphyseal femoral stems.

The seven Gruen zones are widely accepted for the assessment of periprosthestic bone mineral density (BMD) following traditional total hip arthroplasty, but no comparable rating system exists for hip resurfacing arthroplasty (HRA).We describe a seven-zone rating system around the femoral component of a typical HRA implant with a short metaphyseal stem and its intra- and inter-observer reliability.A cohort of 23 selected male patients underwent bone mineral density (BMD) measurements by dual energy X-ray absorptiometry (DEXA) two years after HRA. After development of the new seven-zone rating system, reliability was assessed using intraclass correlation coefficients (ICC). The coefficient of variation was also determined. The new rating-system proved high reliability with ICCs for the intra and inter-observer reliability ranging from 0.92 to 1.0. The coefficient of variation ranged from 1.4% to 3.3%. Mean BMD values were highest in the medial zones 5 to 7 and lowest in the lateral zones 1 to 3 and below the stem tip, corresponding to zone 4. We observed that BMD after HRA can be measured reliably in seven zones around the femoral component. The use of this easily applicable method in future investigations might enhance the comparability of study results. However, the rating system described may have limitations in HRA implants with very short metaphyseal femoral stems.