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Orthopaedic Proceedings
Vol. 95-B, Issue SUPP_34 | Pages 4 - 4
1 Dec 2013
Andriacchi T
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Answering the question of what the patient can teach us about the future of joint replacement starts with a look to the past. The modern era of total joint replacement began in the late 1950's with the pioneering work of John Charnley that established the fundamental structure of a total joint replacement with a metal component bearing against polyethylene and provided many disabled patients with a substantial improvement in function. As the application of joint replacement expanded to a broader patient population it became apparent that a better understanding of the mechanics of patient function was needed to provide more rigorous design criteria and objective assessment of design changes. This presentation will examine how improvements in total knee replacement has been aided by objective measures of ambulatory function and the potential for future improvements in joint replacement that can be based on information from testing patients.

Specifically, from a historical viewpoint one of the major problems limiting the use of total knee replacement in the 1970's was tibial component loosening. The problem of tibial component loosening could be related to the load imbalance between the medial and lateral surface of the tibia. The load asymmetry at the knee resulting from the adduction moment during gait provided a strong rationale for maintaining proper limb alignment following total knee arthroplasty. The analysis clearly showed that knees with a varus alignment of the mechanical axis were more likely to have a substantial load imbalance creating the type of stresses that would eventually lead to tibial component loosening. When the information from gait studies was combined with both clinical and biomechanical studies, tibial component designs were modified using metal backing of the polyethylene articulating surface and instrumentation was modified to allow for proper alignment of the mechanical axis and avoid residual varus deformity following total knee replacement.

Similarly, knee kinematics and moments have been used to differentiate the functional characteristics of different types of designs during stair climbing. Patients with cruciate-sacrificing knee replacements had a tendency to reduce the moment sustained by the quadriceps by leaning forward during the portion of the support phase of ascending stairs when the quadriceps moment would reach a peak value, while patients with a posterior cruciate retaining design were able to sustain normal quadriceps function. The functional differences between the PCL-retaining and sacrificing designs were associated with the normal posterior movement of the femur on the tibia (rollback), with flexion. This finding indicated that TKR design must permit rollback in the early phases of knee flexion to sustain normal stair climbing.

This presentation will conclude with a review of the functional performance of patients with an anterior cruciate deficient knee as a basis for addressing the future needs of a knee replacement to permit natural knee movement. Specifically the role of the anterior cruciate ligament will be discussed in the context of the interaction of the curvature of the articulating surfaces in maintaining a functional envelope of movement that is consistent with retaining both cruciate ligaments.


Orthopaedic Proceedings
Vol. 95-B, Issue SUPP_34 | Pages 587 - 587
1 Dec 2013
Wimmer M Knowlton C Pourzal R McEwen P Andriacchi T
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Introduction:

Many variables contribute to aseptic loosening, and the release of wear particles is a predominant source of late failure. It has been difficult to measure TKA wear quantitatively from retrieved devices; hence, there is a relative paucity of clinically observed TKA wear rates in the literature. Additionally, little is known about patient factors influencing wear rates. This study (a) establishes a clinically relevant TKA wear rate for a cruciate retaining TKA design and (b) relate those wear readings to gait measures of their hosts.

Methods:

34 revision- and 11 postmortem-retrieved MG II tibial PE-components were included in the analysis. Wear scars on the articulating surface of the insert were digitized under light microscopy. The geometry of the surfaces was mapped at 100×100 μm using a low-incidence laser. Autonomous mathematical reconstruction of the original surface was used [1], and linear penetration on the medial and lateral surfaces and total wear volume were calculated (Fig-1).

For five implants, gait data recorded during 1.5 years after surgery were available. Gait studies were performed using a three-dimensional optoelectronic system for motion capture. Joint kinematics and kinetics were calculated using a six-marker model of the lower extremity [2]. All knee moments are reported in Nm, acting externally at the tibia. Potential linear relationships between wear and moment characteristics were investigated.


Orthopaedic Proceedings
Vol. 84-B, Issue SUPP_I | Pages - 24
1 Mar 2002
Hulet C Hurwitz D Andriacchi T Galante J Vielpeau C
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Purpose of the study: This prospective study was conducted to analyze the mechanisms of gait compensation in patients with painful hip and to search for correlations with preoperative clinical and radiographic findings.

Material and methods: Optoelectronic and multicomponent force-plate datas were used to calculate joint motion, moments and intersegmental forces for 26 patients with unilateral hip pain and 20 normal age and sex-matched patients. Height was similar in the two groups but mean weight in the study group (83 kg) was greater than in the controls (68 kg). The preoperative Harris score was 53 in the study group and 16 patients had a permanent flexion contracture of the knee (mean 15°, range 5–30°). Radiographically, there were 22 cases of osteoarthritis hip disease and 4 cases of necrosis.

Results: Gait analysis showed a significant 0.66 ± 0.06 m (12 p. 100) reduction in step length. Patients who had severe hip pain walked with a decreased dynamic range of motion (18 ± 5°, p < 0.0001) with a curve reversal as they extended the hip. They also reduced dynamic range of motion of the knee and ankle. Patients who presented a reversal in their dynamic hip range of motion had a greater passive flexion contracture and a greater loss in range of motion during gait than those with a smooth regular pattern (p < 0.0001). Patients with hip pain walked with significantly decreased external extension, adduction, and internal and external rotation moments (p < 0.0001). They also unloaded the ipsilateral knee and ankle. The decreased hip extension moment was significantly correlated with an increased level of pain (p < 0.0001). There was no correlation with radiological findings.

Discussion: Reversal of dynamic hip range of motion was interpreted as a mechanism to increase effective hip extension during stance phase through increased anterior pelvic tilt and lumbar lordosis.

Conclusion: Patients with painful hip walked with a manner that was asymmetric. These gait modifications were related to hip limitation in passive motion and pain. Patients with flexion contracture adopted a compensatory gait mechanism. This study confirms relation between hip pain and forces across the hip joint.