Patellar instability most frequently presents
during adolescence. Congenital and infantile dislocation of the
patella is a distinct entity from adolescent instability and measurable
abnormalities may be present at birth. In the normal patellofemoral
joint an increase in quadriceps angle and patellar height are matched
by an increase in trochlear depth as the joint matures. Adolescent
instability may herald a lifelong condition leading to chronic disability
and arthritis. Restoring normal anatomy by trochleoplasty, tibial tubercle transfer
or medial patellofemoral ligament (MPFL) reconstruction in the young
adult prevents further instability. Although these techniques are
proven in the young adult, they may cause growth arrest and deformity
where the physis is open. A vigorous non-operative strategy may
permit delay of surgery until growth is complete. Where non-operative
treatment has failed a modified MPFL reconstruction may be performed
to maintain stability until physeal closure permits anatomical reconstruction.
If significant growth remains an extraosseous reconstruction of
the MPFL may impart the lowest risk to the physis. If minor growth
remains image intensifier guided placement of femoral intraosseous
fixation may impart a small, but acceptable, risk to the physis. This paper presents and discusses the literature relating to
adolescent instability and provides a framework for management of
these patients. Cite this article:
Disruption of the extensor mechanism in total
knee arthroplasty may occur by tubercle avulsion, patellar or quadriceps
tendon rupture, or patella fracture, and whether occurring intra-operatively
or post-operatively can be difficult to manage and is associated
with a significant rate of failure and associated complications.
This surgery is frequently performed in compromised tissues, and
repairs must frequently be protected with cerclage wiring and/or
augmentation with local tendon (semi-tendinosis, gracilis) which
may also be used to treat soft-tissue loss in the face of chronic
disruption. Quadriceps rupture may be treated with conservative
therapy if the patient retains active extension. Component loosening
or loss of active extension of 20° or greater are clear indications
for surgical treatment of patellar fracture. Acute patellar tendon
disruption may be treated by primary repair. Chronic extensor failure
is often complicated by tissue loss and retraction can be treated
with medial gastrocnemius flaps, achilles tendon allografts, and
complete extensor mechanism allografts. Attention to fixing the
graft in full extension is mandatory to prevent severe extensor
lag as the graft stretches out over time.
We compared extrusion of the allograft after
medial and lateral meniscal allograft transplantation and examined
the correlation between the extent of extrusion and the clinical
outcome. A total of 73 lateral and 26 medial meniscus allografts
were evaluated by MRI at a mean of 32 months (24 to 59) in 99 patients
(67 men, 32 women) with a mean age of 35 years (21 to 52). The absolute
values and the proportional widths of extruded menisci as a percentage were
measured in coronal images that showed maximum extrusion. Functional
assessments were performed using Lysholm scores. The mean extrusion
was 4.7 mm (1.8 to 7.7) for lateral menisci and 2.9 mm (1.2 to 6.5)
for medial menisci (p <
0.001), and the mean percentage extrusions
were 52.0% (23.8% to 81.8%) and 31.2% (11.6% to 63.4%), respectively
(p <
0.001). Mean Lysholm scores increased significantly from
49.0 (10 to 83) pre-operatively to 86.6 (33 to 99) at final follow-up
for lateral menisci (p = 0.001) and from 50.9 (15 to 88) to 88.3
(32 to 100) for medial menisci (p <
0.001). The final mean Lysholm
scores were similar in the two groups (p = 0.312). Furthermore,
Lysholm scores were not found to be correlated with degree of extrusion
(p = 0.242). Thus, transplanted lateral menisci extrude more significantly
than transplanted medial menisci. However, the clinical outcome
after meniscal transplantation was not found to be adversely affected
by extrusion of the allograft.
Between 1987 and 2006 we performed a modified Thompson’s quadricepsplasty on 40 fracture-related stiff knees and followed the patients for a mean of 7.9 years (2 to 11.1). The factors affecting the final gain of movement were investigated. A total of 15 knees required lengthening of the rectus femoris. The mean flexion gain was 70.2° (42.3° to 112.5°). According to Judet’s criteria, the results were excellent in 30 knees, good in seven, and fair in three. The range of movement which was achieved intra-operatively was related to the gain of knee flexion on univariate analysis. Five patients had complications: deep infection in one, recurrent patellar dislocation in one, and rupture of the extensor mechanism in three. This modified technique gives satisfactory results. Achieving maximum knee flexion intra-operatively seems to be the most important factor in enhancing the outcome in patients with stiffness of the knee following fracture.
We describe the influence of the angle of immobilisation during partial weight-bearing on the forces across the extensor mechanism of the knee. Gait analysis was performed on eight healthy male subjects with the right knee in an orthotic brace locked at 0°, 10°, 20° and 30°, with the brace unlocked and also without a brace. The ground reaction force, the angle of the knee and the net external flexion movement about the knee were measured and the extensor mechanism force was calculated. The results showed a direct non-linear relationship between the angle of knee flexion and the extensor mechanism force. When a brace was applied, the lowest forces occurred when the brace was locked at 0°. At 30° the forces approached the failure strength of some fixation devices. We recommend that for potentially unstable injuries of the extensor mechanism, when mobilising with partial weight-bearing, the knee should be flexed at no more than 10°.
The tensile strength of the medial patellofemoral ligament (MPFL), and of surgical procedures which reconstitute it, are unknown. Ten fresh cadaver knees were prepared by isolating the patella, leaving only the MPFL as its attachment to the medial femoral condyle. The MPFL was either repaired by using a Kessler suture or reconstructed using either bone anchors or one of two tendon grafting techniques. The tensile strength and the displacement to peak force of the MPFL were then measured using an Instron materials-testing machine. The MPFL was found to have a mean tensile strength of 208 N (SD 90) at 26 mm (SD 7) of displacement. The strengths of the other techniques were: sutures alone, 37 N (SD 27); bone
