The aim of this study was to examine the loading
of the other joints of the lower limb in patients with unilateral osteoarthritis
(OA) of the knee. We recruited 20 patients with no other symptoms
or deformity in the lower limbs from a consecutive cohort of patients
awaiting knee replacement. Gait analysis and electromyographic recordings were
performed to determine moments at both knees and hips, and contraction
patterns in the medial and lateral quadriceps and hamstrings bilaterally.
The speed of gait was reduced in the group with OA compared with
the controls, but there were only minor differences in stance times
between the limbs. Patients with OA of the knee had significant
increases in adduction moment impulse at both knees and the contralateral
hip (adjusted p-values: affected knee: p <
0.01, unaffected knee
p = 0.048, contralateral hip p = 0.03), and significantly increased
muscular co-contraction bilaterally compared with controls (all
comparisons for co-contraction, p <
0.01). The other major weight-bearing joints are at risk from abnormal
biomechanics in patients with unilateral OA of the knee. Cite this article:
Stems improve the mechanical stability of tibial
components in total knee replacement (TKR), but come at a cost of stress
shielding along their length. Their advantages include resistance
to shear, reduced tibial lift-off and increased stability by reducing
micromotion. Longer stems may have disadvantages including stress
shielding along the length of the stem with associated reduction
in bone density and a theoretical risk of subsidence and loosening, peri-prosthetic
fracture and end-of-stem pain. These features make long stems unattractive
in the primary TKR setting, but often desirable in revision surgery
with bone loss and instability. In the revision scenario, stems
are beneficial in order to convey structural stability to the construct
and protect the reconstruction of bony defects. Cemented and uncemented
long stemmed implants have different roles depending on the nature
of the bone loss involved. This review discusses the biomechanics of the design of tibial
components and stems to inform the selection of the component and
the technique of implantation.
In arthritis of the varus knee, a high tibial
osteotomy (HTO) redistributes load from the diseased medial compartment
to the unaffected lateral compartment. We report the outcome of 36 patients (33 men and three women)
with 42 varus, arthritic knees who underwent HTO and dynamic correction
using a Garches external fixator until they felt that normal alignment
had been restored. The mean age of the patients was 54.11 years
(34 to 68). Normal alignment was achieved at a mean 5.5 weeks (3
to 10) post-operatively. Radiographs, gait analysis and visual analogue
scores for pain were measured pre- and post-operatively, at one
year and at medium-term follow-up (mean six years; 2 to 10). Failure
was defined as conversion to knee arthroplasty. Pre-operative gait analysis divided the 42 knees into two equal
groups with high (17 patients) or low (19 patients) adductor moments.
After correction, a statistically significant (p <
0.001, At final follow-up, after a mean of 15.9 years (12 to 20), there
was a survivorship of 59% (95% CI 59.6 to 68.9) irrespective of
adductor moment group, with a mean time to conversion to knee arthroplasty
of 9.5 years (3 to 18; 95% confidence interval ± 2.5). HTO remains a useful option in the medium-term for the treatment
of medial compartment osteoarthritis of the knee but does not last
in the long-term. Cite this article:
Primary total knee arthroplasty (TKA) is a reliable
procedure with reproducible long-term results. Nevertheless, there
are conditions related to the type of patient or local conditions
of the knee that can make it a difficult procedure. The most common
scenarios that make it difficult are discussed in this review. These
include patients with many previous operations and incisions, and
those with severe coronal deformities, genu recurvatum, a stiff knee,
extra-articular deformities and those who have previously undergone
osteotomy around the knee and those with chronic dislocation of
the patella. Each condition is analysed according to the characteristics of
the patient, the pre-operative planning and the reported outcomes. When approaching the difficult primary TKA surgeons should use
a systematic approach, which begins with the review of the existing
literature for each specific clinical situation. Cite this article:
